Nature’s Fantastical Palette: Color From Structure

Nature’s Fantastical Palette: Color From Structure

Peacock Feathers

Source: STRUCTURAL COLORATION IN NATURE

Key Terms

  • Iridescence
  • Nanostructures
  • Color from Pigments
  • Color from Structures
  • Smart Pigments
  • Material Science
  • Color from Bioluminescence
  • Color Change
  • Photonics
  • Biomimicry
  • Non Iridescent Colors
  • Iridescent Colors
  • Photonic Crystals (PhC)
  • Diffraction Grating
  • Specular Reflection
  • Braggs Diffraction
  • 1D Grating
  • 2D and 3D Photonic Crystals
  • Optical Nanotechnology
  • Multilayer Filters
  • Biomimetics
  • Peacock
  • Morpho Butterflies
  • Interference
  • Colloidal Crystals
  • Colloidal Amorphous Array
  • Microfluidics
  • Photonic Pigments
  • Reflective Displays (E-Ink)
  • Colloidal Assembly
  • Photonic Glass (PG)
  • Plasmonic Films
  • Inverse-Opals
  • Braggs Stacks
  • Dielectric Structural Colors
  • Plasmonic Structural Colors
  • Amorphous Photonic Structures
  • Melanin
  • Dopamine
  • Poly Dopamine
  • Plasmonic Metasurfaces

Source: GOLD BUGS AND BEYOND: A REVIEW OF IRIDESCENCE AND STRUCTURAL COLOUR MECHANISMS IN BEETLES (COLEOPTERA)

Source: GOLD BUGS AND BEYOND: A REVIEW OF IRIDESCENCE AND STRUCTURAL COLOUR MECHANISMS IN BEETLES (COLEOPTERA)

Source: Structural color and its interaction with other color-producing elements: perspectives from spiders

Color Vision

Source: Structural Color and Odors: Towards a Photonic Crystal Nose Platform

Color Sources

  • From Pigments
  • From Bioluminescenece
  • From Structure

Source: Chromic Phenomena: Technological Applications of Colour Chemistry

Source: Chromic Phenomena: Technological Applications of Colour Chemistry

Structural Color in Nature

  • Peacock
  • Butterflies
  • Beetles
  • Parrots
  • Birds
  • Moth

Peacock Colors

Feathers of Peacock

Source: Structural colors: from natural to artificial systems

Colors of Marpho Butterfly

Closeup of Marpho Butterfly

Structure and Color

  • Iridescent – (Colloidal Crystals)- Angle Dependent – Regular Structure
  • Non Iridescent – (Colloidal Amorphous Arrays) – Angle Independent – Irregular Structure

Optics of Structural Colors

  • Interference
  • Diffraction Gratings
  • Scattering
  • Reflection

Nano Structures Responsible for Colors

Source: Structural color and its interaction with other color-producing elements: perspectives from spiders

  • Christmas Tree
  • Multilayer – 1 D Periodicity
  • Photonic Crystals – 2 D and 3 D
  • Diffraction Grating
  • Quasi Ordered Photonic Crystal
  • Disorder Structure

Source: BIO-INSPIRED VARIABLE STRUCTURAL COLOR MATERIALS

  • 1 D Gratings
  • 1 D Periodicity Multilayers
  • 1 D Discrete Periodicity
  • 2 D Gratings
  • 2 D Periodicity
  • Closed Packed Spheres of Solid Materials
  • Inverse Opal Analogoues

Source: STRUCTURAL COLORATION IN NATURE

  • Thin Film Interference
  • Multi Film Interference
  • Diffraction Gratings
  • Coherent Scattering
  • Incoherent Scattering
  • 1 D Photonic Crystals
  • 2 D Photonic Crystals
  • 3 D Photonic Crystals

Source: Structural Color and Odors: Towards a Photonic Crystal Nose Platform

Source: PHYSICS OF STRUCTURAL COLORS

Source: PHOTOPHYSICS OF STRUCTURAL COLOR IN THE MORPHO BUTTERFLIES

Source: Gold bugs and beyond: a review of iridescence and structural colour mechanisms in beetles (Coleoptera)

  • Cuticular Multilayer Reflector
  • Epicuticular Reflector
  • Exocuticular Reflector
  • Endocuticular Reflector

Source: Gold bugs and beyond: a review of iridescence and structural colour mechanisms in beetles (Coleoptera)

  • Multilayer Reflectors
  • Diffraction Gratings
  • 3 D Photonic Crystals

Multilayer reflectors in beetles have also been described as ‘thin-layer stacks’, ‘one-dimensional photonic crystals’ and ‘thin-film reflectors’ (e.g. Parker 1998, 2002; Vigneron et al. 2006). The vocabulary used to describe these structures is somewhat dispersive, as the variously intersecting disciplines of entomology, physics and applied optics (e.g. laser technology, fibre-optic data transmission, telescopes and microscopy) have all developed slightly different suites of terminology. Other synonyms for ‘multilayer reflector’ include multilayer stack, quarter wave stack, interference reflector and dielectric mirror.

We propose that the term multilayer reflector be applied to such structures in Coleoptera; this describes the multilayered nature of cuticular chitin lamellae (which are not true films) and the reflective mechanism by which colour is produced.

The terms ‘metallic colours’ or ‘metallic iridescence’ can be used to distinguish multilayer effects from those produced by other optical structures. Multilayer reflectance can typically be diagnosed as such by its limited palette (usually one or two apparent hues per reflector), blue shift with decreased observation angle and fixed position on the cuticle surface.

Source: Gold bugs and beyond: a review of iridescence and structural colour mechanisms in beetles (Coleoptera)

Three-dimensional crystalline structures producing scintillating, gem-like reflectance were described by Parker et al. (2003) in the entimine weevil Metapocyrtus sp. (initially misidentified as Pachyrrhynchus argus); by Welch et al. (2007) in Pachyrrhynchus congestus, and recently in another entimine weevil, Lamprocyphus augustus, by Galusha et al. (2008). The photonic crystals found in the scales of pachyrrhynchine weevils (Pachyrrhynchus and Metapocyrtus) have a close-packed hexagonal arrangement analogous to (mineral) opal, while the photonic crystal of Lamprocyphus has a diamond-based lattice (i.e. a face-centred cubic system rather than a hexagonal one).

Although the term ‘photonic crystal’ applies to any ordered subwavelength structure that affects the propagation of specific wavelengths of light (Parker & Townley 2007), it is the three-dimensionally ordered structures to which the term is most commonly applied. We recommend use of the term ‘three-dimensional photonic crystal’, which distinguishes these structures from the one-dimensional periodicity of multilayer reflectors or Bragg gratings. The terms ‘opal’ and ‘diamond based’ have been used to describe iridescence in weevil scales, but refer to phenomena that are relatively similar from an organismal perspective; it is important to note that these terms refer to crystalline lattice morphology and not the appearance of the scales themselves. Maldovan & Thomas (2004) provided an excellent overview of diamond-based lattice morphology (as observed in Lamprocyphus) in photonic crystals; Yablonovitch (1993) provided a thorough introduction to the photonic band-gap mechanism by which colours are produced in three-dimensional photonic crystals.

Source: Gold bugs and beyond: a review of iridescence and structural colour mechanisms in beetles (Coleoptera)

A diffraction grating is any nanoscale array of parallel ridges or slits that disperses white light into its constituent wavelengths (figure 8a shows a grating in cross section). Because white light consists of many different wavelengths, it diffracts into full spectra, creating the rainbow-like reflectance shown in figures 1a,b, 8c and 9b,d. While man-made diffraction gratings can disperse light via reflection or transmission, all beetle gratings are strictly reflection mechanisms.

Source: Gold bugs and beyond: a review of iridescence and structural colour mechanisms in beetles (Coleoptera)

http://photobiology.info/Ball.html

Nature’s Fantastical Palette: Color from Structure

Philip Ball
18 Hillcourt Road
East Dulwich
London SE22 0PE, UK
p.ball@btinternet.com

The changing hues of a peacock’s splendid tail feathers have always captivated the curious mind (Figure 1). The seventeenth-century English scientist Robert Hooke called them ‘fantastical’ because the colors could be made to disappear by wetting the feathers (Hooke, 1665). Using the newly invented microscope, Hooke looked at peacock feathers and saw that they were covered with tiny ridges, which he figured might be the origin of the colors. 

Figure 1

Figure 1. The shifting colors of the peacock’s tail have had metaphorical interpretations for centuries.

Hooke was on the right track. The bright, often iridescent colors of bird plumage, insect cuticle and butterfly wings are ‘structural’; produced not by light absorption by pigments, but light scattering from a regular array of objects just a few hundreds of nanometers (millionths of a millimeter) in size (Vukusic & Sambles, 2003; Vukusic, 2004; Wolpert, 2009). This scattering favors particular wavelengths depending on the size and spacing of the scatterers, and so it picks out specific colors from the full spectrum of sunlight. Because the precise hue may depend also on the viewing angle, structural colors are often iridescent, changing from blue to green or orange to yellow. And because they involve reflection rather than absorption, these colors can be startlingly brilliant. The Blue Morpho butterflies of South and Central America are visible from a quarter of a mile away, seeming almost to shine when sunlight penetrates the tropical forest canopy and bounces off their wings. 

Structural colors are just one example of how living organisms manipulate and channel light using delicately arranged micro- and nanostructures. These biological designs offer inspiration to engineers seeking to control light in optical technologies, and could lead to more brilliant visual displays, new chemical sensors, and better storage, transmission and processing of information. To make effective use of such tricks, we need to understand how nature creates and deploys these tiny optical structures; indeed, we must learn a new language of color production and mixing. 

Rather little is known about how many of these biological structures are put together, how they evolved, and how evolution has made creative use of the color and light effects they offer. But one thing is clear; nature doesn’t have the sophisticated patterning technologies, such as drilling with electron beams, that microengineers can use to laboriously carve such structures from solid blocks. Ingenuity is used instead of finesse; these biological structures must make themselves from the component parts. 

If we can master that art, we might develop new, cheap technologies to make such things as materials that change color or appearance, like the camouflage skins of some fish and squid, or fibres that guide and channel light with virtually no leakage, or chemically controlled light shutters. Here I look at some of nature’s tricks for turning structure into color; and the ways they are being exploited in artificial materials and devices (Ball, 2012). 

Layers

Although the ridges seen by Hooke on butterfly wing scales do scatter light, the bright colors of the reflected light generally come from invisible structures beneath the surface. In the natural world, they offer a robust way of generating color that is not hostage to the fate of delicate, light-sensitive organic pigments. 

The colored scales and feathers of birds, fish and butterflies typically contain organized microscopic layers or rods of a dense light-scattering material embedded in a matrix of a different substance. Because the distance between the scatterers is roughly the same as the wavelengths of visible light, the stacks cause the wave phenomenon of diffraction, in which reflected waves interfere with one another. Depending on the angle of reflection, light rays of a certain wavelength interfere constructively when they bounce off successive layers in the stack, boosting the corresponding color in the reflected light (Vukusic and Sambles, 2003; Vukusic, 2004; Wolpert, 2009). It is much the same process that elicits the chromatic spectrum in light glancing off a tilted CD. 

In butterfly wing scales the reflecting stacks are made of cuticle; a hard material containing the natural polymer chitin, separated by air-filled voids. In bird feathers, the stacks are platelets or rods of the dark pigment melanin; sometimes hollow, as in the Black Inca hummingbird, Coeligena prunellei, embedded in keratin, the protein from which our hair and fingernails are made (Figure 2). Analogous diffraction gratings made from alternating ultrathin layers of two materials are widely used in optical technologies to select and reflect light of a single color. For example, mirrors made from multiple layers of semiconductors are used as reflectors and color filters in devices ranging from astronomical telescopes to solid-state lasers and spectrometers. 

Figure 2

Figure 2. The iridescent blues and greens in the feathers of hummingbirds such as this Black Inca (left; part of blue iridescence highlighted with white box) are created by platelets of melanin pigment punctuated with air holes (right), which act as a photonic crystal to reflect light of a particular wavelength. K=keratin, A=air, M=melanin. (From Shawkey et al., 2009)

The male bird of paradise Lawes’ parotia (Parotia lawesii) has a particularly neat twist on this trick (Figure 3). The barbules (hair-like structures on the feather barbs) of its breast feathers contain layers of melanin spaced at a distance that creates bright orange-yellow reflection. But, as Stavenga and colleagues have recently discovered, each barbule has a V-shaped or boomerang cross-section, with sloping surfaces that also act as reflectors of blue light (Stavenga et al., 2011). Slight movements of the feathers during the bird’s courtship ritual can switch the color abruptly between yellow-orange and blue-green; guaranteed to catch a female’s eye. Stavenga suspects that technologists will want to use this trick for producing dramatic chromatic shifts. “I suspect the fashion or automobile industries will in due time make bent structures or flakes that will exploit these angular color changes”, he says. 

Figure 3a
Figure 3b

Figure 3. A striking color change in the feathers of the male Lawes’ parotia, from yellow-orange (a) to blue-green (b), is caused by the presence of two mirror-like reflectors in the feather barbules (c): layers of melanin rods reflect yellow light, while the sloping faces of the boomerang-shaped barbule cross-section reflect blue at oblique angles. Scale bar in b: 1 cm. (From Stavenga et al., 2011)

Christmas Trees

The butterflies Morpho didius and Morpho rhetenor obtain their dazzling blue color not from simple multilayer’s but from more complex nanostructures in the wing scales: arrays of ornate chitin ‘Christmas Trees’ that sprout at the surface (Vukusic & Sambles, 2003) (Figure 4). Each ‘tree’ presents a stack of disk-like layers to the incoming light, which acts as another kind of diffraction grating. These arrays may reflect up to 80 percent of the incident blue light. And because they are not flat, they can reflect a single color over a range of viewing angles, somewhat reducing the iridescence; organisms don’t always want to change color or get dimmer when seen from different directions. 

Figure 4

Figure 4. The butterfly Morpho didius (left) obtains its dazzling blue color from delicate ‘Christmas Tree’ light-scattering structures (right), made from chitin, that sprout within the wing scales. (Left, courtesy of Peter Vukusic. Right (micrograph) from Vukusic and Sambles, 2003.)

The precise color reflected depends on the refractive index contrast between the nanostructures and the surrounding medium. This is usually air, but as Robert Hooke observed, wetting such surfaces alters the refractive index contrast, and changes the color in a way that is closely linked to the wetting liquid’s refractive index. For that reason, artificial Morpho-like structures carved into solids using microlithographic techniques are being developed by researchers at GE Global Research in New York, in collaboration with others at the State University of New York at Albany and butterfly-wing expert Pete Vukusic at the University of Exeter in England, as color-change chemical sensors that can identify a range of different liquids (Potyrailo, 2011). These might find applications for sensing emissions at power plants, monitoring of food safety, and testing of water purity. 

Reflecting Bowls

The bright green color of the Emerald Swallowtail butterfly (Papilio palinurus), found widely in southeast Asia, is not produced by green light at all. The wing scales are covered with a honeycomb array of tiny bowl-shaped depressions just a few micrometers across, lined with alternating layers of chitin cuticle and air which act as reflective mirrors. Light bouncing off the bottoms of the bowls is preferentially reflected in the yellow part of the spectrum. But from the sides it is reflected twice before bouncing back, and this selects blue. Our eyes can’t resolve these yellow spots and blue rings, which merge to create the perception of green (Vukusic & Sambles, 2003). 

Figure 5

Figure 5. The green of the Emerald Swallowtail butterfly (left) comes from the optical mixing of blue and yellow reflections from tiny bowl-like depressions in the wing scales (right). (Right figure, courtesy of Christopher Summers, Georgia Institute of Technology) 

This way of making color has been copied by Summers and coworkers (Crne et al., 2011). To create the tiny bowls, they let water vapour condense as microscopic droplets, called breath figures, on the surface of a polymer dissolved in a volatile solvent. The solvent gradually evaporates to form a solid polymer film, while the water droplets pack together on the surface of the drying solution much like greengrocers’ oranges and apples in crates, sinking into the setting film to imprint an array of holes. By pulling off the top part of the film, Summers and colleagues were left with a surface with hemispherical bowl-like dimples. They then used this structure as a template on which they deposited alternating thin layers of titania and alumina to make a multilayer reflector, like that lining the bowls of the butterfly wing scales (Figure 6). 

Figure 6

Figure 6. An artificial micro-structured surface that mimics the green color of the Emerald Swallowtail. Scale bar: 5 µm. (Courtesy of Christopher Summers, Georgia Institute of Technology)

Because each reflection changes the polarization of the light, under crossed polarizing filters the yellow light bouncing back from a single reflection at the bowl centers disappears, while the twice-reflected blue-green light from the rims remains. This could offer a distinctive authentification mark on bank and credit cards. Apparently just a simple green reflective coating, such a material would in fact carry a hidden polarized signature in the reflected blue and yellow light that would be hard to counterfeit. But Summers’ collaborator Mohan Srinivasarao admits that the main reason for seeking to replicate the butterfly’s green color was that “it’s beautiful in its own right”. 

Ordered Nanosponges

Scattering by regular arrays of microscopic objects can, for some arrangements, totally exclude light within a particular band of wavelengths, called the photonic band gap (Vukusic, 2004). These so-called photonic crystals occur naturally, for example, in opal, a biogenic form of silica in which the scatterers are tiny mineral spheres. Artificial photonic crystals can be used to confine light within narrow channels, creating waveguides that might be deployed to guide light around on silicon chips for optical information technology. 

Nature has already got there first. Under the electron microscope, the wing scales the Emerald Patched Cattleheart Butterfly (Parides sesostris) display zigzagging, herring-bone arrays: patches of an orderly sponge made from chitin with holes a hundred nanometers or so across. Each patch is a photonic crystal seen from a different alignment. Stavenga and Michielsen have found that these labyrinths in the wing-scales of P. sesostris and some species of papilionid and lycaenid butterflies have a structure known to mathematicians as a gyroid (Michielsen & Stavenga, 2008). In P. sesostris the structure has a photonic band gap that enables it to reflect light within the green part of the spectrum over a wide range of incident angles (Figure 7). Some weevils and other beetles also derive their iridescent color from three-dimensional photonic crystals made of chitin. 

Figure 7

Figure 7. The wing scales of P. sesostris (top left, and close-up, top right) contain photonic crystals of chitin (bottom, middle and right) Scale bars: left, 100 µm; middle, 2 µm; right, 2 µm. (Bottom figure, from Saranathan et al., 2010)

Richard Prum and coworkers have figured out how these photonic crystals grow (Saranathan et al., 2010). The molecules in the soft membranes that template the deposition of chitin during wing-scale growth become spontaneously organized into the ‘crystalline sponge’. Biological membranes are made up of long, tadpole-like molecules called lipids, which have a water-soluble head and an oily tail. To shield the tails from water, they cluster side by side into sheets with the heads pointing outwards; the sheets then sit back to back in bilayer membranes. Pores in these membrane induce curvature, partly exposing the lipid tails and therefore incurring a cost in energy. For this reason, the pores in effect repel one another, and this can force them to become arranged in a regular way, an equal distance apart. Periodic membrane structures have been found in the cells of many different organisms, from bacteria to rats (Hyde et al., 1997). 

In P. sesostris wing-scale progenitor cells, the outer ‘plasma membrane’ and the folded membrane of the inner compartments called the endoplasmic reticulum, where lipids and other molecules are made, come together to form a so-called double-gyroid structure (Figure 8, left), in which two interweaving sets of channels divide up space into three networks that interpenetrate, but are isolated from one another. One of these is then filled with chitin, which hardens into a robust form while the cell dies and the rest of the material is degraded, leaving behind the single gyroid phase (Saranathan et al., 2010). 

It has been suggested that these natural nanostructures might be used as the templates for making artificial ones, for example, by filling the empty space around the chitin with a polymer or an inorganic solid, and then dissolving away the chitin (Saranathan et al., 2010). But it is also possible to mimic the structures from scratch. For instance, artificial bilayer membranes made from lipid-like molecules called surfactants will also form orderly sponges, and so will so-called block copolymers, in which the chain-like molecules consist of two stretches with different chemical composition (Hyde et al., 1997). Ulrich Wiesner and coworkers (Stefik et al., 2012) have mixed liquid block copolymers with nanoparticles of niobium and titanium oxide, and let the polymers form into gyroid and other ordered ‘nanosponge’ structures that usher the nanoparticles into the same arrays. When this composite is heated, the polymer is burnt away while the mineral nanoparticles coalesce into continuous networks (Figure 8, center). 

These porous solids could find a wide range of uses. Thin porous films of titanium dioxide nanoparticles coated in light-absorbing dyes are already used in low-cost solar cells. These orderly gyroid networks can offer improvements, partly because the solid material through which light-excited electrons are harvested is continuously connected rather than relying on random electrical contacts between nanoparticles. And the researchers have calculated that double-gyroid nanosponges made from metals such as silver or aluminum, which might similarly be assembled from nanoparticles guided by block copolymers, could have the weird property of a negative refractive index, meaning that they would bend light ‘the wrong way’ (Hur et al., 2011). Such materials could be used to make so-called superlenses for optical microscopes that can image objects smaller than the wavelength of light; something that isn’t possible with conventional lenses. 

Inspired by the butterfly structures, Mark Turner and colleagues (Turner et al., 2011) have used laser beams to ‘write’ these intricate three-dimensional photonic crystals directly into a commercial light-polymerizable ‘photoresist’ material (Figure 8, right). Being somewhat ‘scaled-up’ versions of the natural nanostructures, these had photonic band gaps in the infrared part of the spectrum. Current telecommunications operates mostly at infrared wavelengths, and these structures could find uses there; some, for example, have a corkscrew lattice that make them respond differently to circularly polarized light with a left- or right-handed twist. 

Figure 8

Figure 8. The gyroid phase (left), and structures mimicking the ‘butterfly gyroid’: (middle) a network of titania organized by self-assembly of a block copolymer, and (right) a larger-scale lattice made by setting a light-sensitive polymer with laser beams (scale bar: 10 µm). (Left figure, courtesy of Matthias Weber, Indiana University. Middle figure, from Stefik et al., 2012. Right figure, from Turner et al., 2011)

Photonic Crystal Fibers

The spines of some marine polychaete worms, such as Aphrodita (the sea mouse) and Pherusa, are tubular structures containing hexagonally packed hollow cylindrical channels a few hundred nanometers across and made from chitin. These arrays act as two-dimensional photonic crystals that reflect light strongly in the long-wavelength part of the spectrum, which gives the Aphrodite spine a deep, iridescent red color (Figure 9) (Parker et al., 2001; Trzeciak & Vukusic, 2009). 

Figure 9a
Figure 9b
Figure 9c

Figure 9. The tiny spines of polychaete worms such as the sea mouse (Polychaeta: Aphroditidae; top left) are natural photonic crystals. Seen close up in cross section, they consist of regularly packed hollow channels with walls of chitin. Middle left: cross-section from Pherusa (scale bar: 2 µm); center: side view of channels from Aphrodita; right: the red color of light passing through a spine of Aphrodita. Artificial photonic fibres like this can easily be made by heating and drawing out bundles of glass capillaries (bottom). They can confine light within the ‘solid’ channels even around tight bends. (Note the solid ‘defect’ in the central channel.) (Top, middle center and middle right, courtesy of Andrew Parker, University of Oxford. Middle left, from Trzeciak & Vukusic, 2009. Bottom, from Russell, 2003)

It is not clear if the optical properties of the polychaete spines have any biological function. But there are certainly uses for such light-manipulating fibres in optical technology. For example, Philip Russell and collaborators (Russell, 2003) have made them by stacking glass capillaries into hexagonally packed bundles and drawing them out under heat into narrow fibers laced through with holes. If ‘defects’ are introduced into the array of tubular channels, either by including a wider capillary or a solid rod in the bundle, light can pass along the defect while being excluded from the photonic crystal, creating an optical fiber with a cladding that is essentially impermeable to light of wavelengths within the band gap. Photonic crystal fibers like this can guide light around tighter bends than is usually possible with conventional fibers, where the light is confined less reliably by internal reflection at the fibre surface. As a result, these fibers would work better for guiding light in tightly confined spaces, such as on optical microchips. And because photonic crystal fibers are in general less ‘leaky’ than conventional ones, they could be replace them in optical telecommunications networks, requiring less power, and obviating the need for amplifiers to boost signals sent over long distances.  

Disordered Nanosponges

The splendid blue and green plumage of many birds, while also being physical rather than pigmented colors, lacks the iridescence of the hummingbird or the peacock. Instead, they have the same color viewed from any angle. They scatter light from sponge-like keratin nanostructures; but because these structures are disordered, the scattering is diffuse, like the blue of the sky, rather than mirror-like and iridescent (Dufresne et al., 2009). 

In the blue-and-yellow macaw, Ara ararauna, (Figure 10), and the black-capped kingfisher Halcyon pileata, the empty spaces in the keratin matrix of the feather barbs form tortuous channels about 100 nm wide. A similar random network of filaments in the cuticle of the Cyphochilus beetle gives it a dazzlingly bright white shell. In some other birds, such as the blue-crowned manakin, Lepidothrix coronata, the air holes are instead little spherical bubbles connected by tiny cavities. 

Figure 10a
Figure 10b

Figure 10. The blue feathers of the blue-and-yellow macaw contain sponge-like labyrinths of air and keratin (bottom left), which scatter blue light strongly in all directions. Some other feathers derive similar colors from spherical ‘bubble-like’ air holes in the keratin matrix (bottom right). Scale bars: 500 nm. (Bottom figure, from Dufresne et al., 2009)

It is believed that both of these structures are formed as keratin separates out spontaneously from the fluid cytoplasm of feather-forming cells, like oil from water (Dufresne et al., 2009). In liquid mixtures, such as solidifying molten metal alloys or polymers, such phase separation creates different structures in different conditions. If the mixture is intrinsically unstable, the components separate into disorderly, interwoven channels in a process called spinodal decomposition. But if the mixture is metastable (provisionally stable), like water supersaturated with dissolved gas, then the separating phase will form discrete blobs or bubbles that grow from very tiny ‘seeds’ or nuclei. Prum thinks that either of these processes may happen as bird feathers develop, and that birds have evolved a way of controlling the rate of keratin phase separation so that they can arrest the nanostructure at a certain size. Once the cells have died and dried, this size determines the wavelength of scattered light, and thus the feather’s color. 

This kind of diffuse light-scattering has been used for centuries as a way of making colors in technology. In milk, microscopic droplets of fat with a wide range of sizes cause scattering of all visible wavelengths, and give the liquid its opaque whiteness. Michael Faraday discovered in the nineteenth century that light scattering from nanoscale particles of gold suspended in water can create a deep reddish-purple color with a precise hue that depends on the size of the particles. Glassmakers had been using alchemical recipes to precipitate nanoscale gold particles in molten silica to make ruby glass ever since ancient times. 

Today, engineers are looking at how these random networks and particle arrays can give rise to strongly colored and high-opacity materials. Pete Vukusic and colleagues (Hallam et al., 2009) have mimicked the cuticle of Cyphochilus beetles in random porous networks made from interconnected filaments of the minerals calcium carbonate and titanium dioxide mixed with a polymer and oil liquid binders and left to dry. Guided by the size and density of filaments in the beetle shell, they were able to make thin coatings with brilliant whiteness. Meanwhile Prum, his colleague Eric Dufresne and their coworkers at Yale University (Forster et al., 2010) have mimicked the disordered sponges of bird feathers by creating films of randomly packed microscopic polymer beads, which have blue-green colors (Figure 11). 

Figure 11

Figure 11. This thin film of randomly arrayed polymer microspheres mimics the keratin matrix in the blue feathers of the blue-crowned manakin. (From Forster et al., 2010)

Color Change

One of the most enviable optical tricks in nature is to produce reversible color changes. The reflective, protean colors in the skins of squid such as the Loligidinae family are produced by a protein called reflectin, arranged into plate-like stacks in cells called iridophores, which again act as color-selective reflectors (Figure 12). The color changes are thought to be involved in both camouflage and communication between squid for mating and displays of aggression. 

Figure 12

Figure 12. Stacked plates of the reflectin protein (left) in iridophore cells (center) create tunable reflective colors in squid (right). (Center figure, courtesy of Daniel Morse, University of California at Santa Barbara)

Daniel Morse and colleagues have recently figured out how the color changes of iridophores are achieved (Tao et al., 2010). The reflectin proteins crumple up into nanoparticles, which pack together into dense arrays that make up the flat layers. These layers are sandwiched between deep folds of the cell membrane. The color change can be triggered by neurotransmitter lipid molecules called acetylcholine, which activate a biochemical process that fixes electrically charged phosphate chemical groups onto the reflectin protein. These groups largely neutralize the proteins’ intrinsic charge and allow them to pack more closely together, increasing the reflectivity of the layers. At the same time, this compaction squeezes water from between the protein particles and out of the cell, and enables the reflectin layers to sit closer together. 

Morse and colleagues (Holt et al., 2010) think that it should be possible to copy some of these tricks in optical devices, perhaps even using reflectins themselves. They have inserted the gene encoding a reflectin protein from the long-finned squid Loligo pealeii into Escherichia colibacteria. When expressed, the protein spontaneously collapses into nanoparticles (Tao et al., 2010). The size of these particles can be tuned by controlling the interactions between charged groups on the proteins using salt. Held between stacks of permeable membranes, these materials might therefore swell and contract, altering the reflected wavelengths, in response to chemical triggers. Morse and colleagues have also taken inspiration from reflectins to develop a light switch based on a wholly synthetic light-sensitive polymer. They use an electric field both to change the refractive index of the polymer and to pull salt into the polymer film to swell it. As with iridophores, this combination of effects alters the material’s response to light dramatically, switching it from transparent to opaque; all without moving parts or high-tech manufacturing methods. The team are currently working with Raytheon Vision Systems, an optics company in Goleta, California, to use this system in fast shutters for infrared cameras. 

The Art and Science of Natural Color Mixing

Many of the optical effects found in nature are not purely due to structural colors, but arise from their combination with absorbing pigments (Shawkey et al., 2009). In squid, a thin pigment layer above the reflective layer acts as a filter that can modify the appearance, for example, making it mottled; reflective and absorbing to different degrees in different places. In bird feathers, the physical colors resulting from melanin nanostructures embedded in a keratin protein matrix can be tuned by light-absorbing filters of pigments, such as carotenoids, which absorb red and yellow light. The characteristic green plumage of parrots seems to be produced by laying a yellow pigment over a blue reflective layer of melanin and keratin (Figure 13). And the purple wing tips of Purple Tip butterflies come from red pigments beneath a blue iridescent surface. 

Figure 13

Figure 13. Green is a characteristic color of parrots, but their plumage contains no green pigment, nor is it purely a structural color. Rather, it results from ‘structural blue’ overlaid with a filter of yellow pigment.

Chameleons display perhaps the most advanced mastery of these mixing tricks. Their spectacular color changes are produced by three separate systems for modifying the reflected light, stacked one atop the other. The first layer consists of cells containing red and yellow light-absorbing pigment particles, the location of which within the cell determines the color intensity. Below these are iridophores like those of squid, from which blue and white light may be selectively reflected by crystalline layers of the molecule guanine (also a component of DNA). Finally there is a layer of cells containing the dark pigment melanin, which act like the colored ‘ground’ layers of Old Master paintings to modify the reflection of light that penetrates through the first two layers. This combination of reflection and absorption enables the chameleon to adapt its skin color across a wide, albeit species-specific, range to signal warning, for mating displays, and for camouflage (Forbes, 2009). 

How pigments alter and adjust the reflected light in such cases is still imperfectly understood. One problem is that the combinations are so diverse; more than 20 different arrangements of melanin, keratin and air have been identified in the plumage of birds. Moreover, melanin is itself a light absorber, creating colors ranging from yellow to black. The bright white markings on the blue wings of the Morpho cypris butterfly are produced by simply removing the melanin from reflective multilayer structures; the mirrors remain, but the pigments do not. 

In such ways, evolution has made creative use of the limited range of materials at its disposal to generate a riot of profuse coloration and markings. A better understanding of how this is achieved could give painters and visual artists access to entirely new ways of making colors based on iridescent and pearlescent pigments, whose use has so far been largely restricted to less sophisticated applications in the automobile and cosmetic industries (Schenk & Parker, 2011). 

Painter Franziska Schenk has been exploring the mixing of structural and pigmented color during her stay as artist-in-residence in the Department of Biosciences at the University of Birmingham in the UK (Schenk, 2009). With iridescent particles, says Schenk, “the established methods of easel painting no longer apply. Their conversion to painting requires something truly innovative.” 

Schenk used iridescent particles to reproduce the starting blue of the Morpho wing in a series of paintings that change color when lit or viewed from different angles (Figure 14). The background color on which the particles are placed is central to the effect. On white, the light not reflected from the blue particles passes through and bounces off the base. This means that when not seen face-on, the blue quickly fades and is replaced by a muted yellow. But on a black background, all non-blue light is absorbed, and the blue is more pure and intense. 

Figure 14

Figure 14. Painting of a Morpho butterfly wing by Franziska Schenk, using blue pearlescent pigments. The color changes depending on the angle of illumination, as well as on the nature of the background color. (Courtesy of Franziska Schenk)

Although the brilliance of these colors doesn’t approach that of butterfly wings, it takes advantage of recent improvements in synthetic pearlescent particles. The first of these were made by coating mica flakes with multilayers of metal oxides to generate the diffraction grating. But because the mica surfaces were not perfectly smooth and the grain sizes varied, there was always a range in the precise colors and intensities of the particles. Schenk has used pigments in which the mica substrate is replaced by a transparent borosilicate glass, which is smoother and gives a purer hue. She believes that “iridescent technology is destined to introduce a previously unimaginable level of intensity and depth, thus adding beauty, luster and a dynamic dimension to art”. Schenk’s Studies of Cuttlefish (Figure 15) is a painting that uses iridescent flakes mixed with beads and wax. 

Figure 15

Figure 15. “Studies of Cuttlefish” by Franziska Schenk, using iridescent flakes mixed with beads and wax. (Courtesy of Franziska Schenk)

Another series of cuttlefish, “Mantle of Many Colours” (Figure 16), was made with iridescent paint that differs in appearance depending on the conditions and angle of lighting, which results in a compelling chameleon effect that traditional paints simply cannot create. The colors change from greens to purples as the viewing angle shifts. “Still images, together with any attempt to verbally describe the effect, are pretty limiting”, Schenk admits; you have to see these things in the flesh to appreciate their full impact. 

Figure 16

Figure 16. “Mantle of Many Colours” by Franziska Schenk, which uses iridescent paint, as seen from different angles. (Courtesy of Franziska Schenk)

Conclusion

“Every day you play with the light of the universe”, wrote the Chilean poet Pablo Neruda, but he had no idea how literally true this would become. Our technologies for transmitting, manipulating and displaying information, whether for work or play, depend increasingly on our ability to control light; to harness and transform color. Some of nature’s most stunning sights depend on such a facility too, and often they show us that beauty can be inextricably linked to utility. We are impressed by plumage, by markings and animal displays, that are specifically designed by evolution to make such an impression. And nature has found ways to make this chromatic exuberance robust, changeable, responsive, and cheap and reliable to manufacture. In shaping color without the chemical contingency of pigments, there seems to be little we can dream up that nature has not already anticipated, exploiting its capacity to fashion intricate fabrics and structures on the tiniest scales. We can only learn, and admire. 

References

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05/30/12 

Technology of Nanostructures

Colloidal Self Assembly for fabrication of Photonic nanostructures including

  • Colloidal crystals
  • Composite and Inverse Opals
  • Photonic Glasses

Applications

  • Displays
  • Optical Devices
  • Photochemistry
  • Biological Sensors

Source: Self-assembled colloidal structures for photonics

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(73) Assignee:SNUR&DBFoundation,Seoul(KR)

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NATURE | VOL 396 | 5 NOVEMBER 1998

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Structural color

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https://manoharan.seas.harvard.edu/structural-color

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https://pubmed.ncbi.nlm.nih.gov/16015669/

Mechanisms of structural colour in the Morpho butterfly: cooperation of regularity and irregularity in an iridescent scale.

Shuichi KinoshitaShinya Yoshioka, and  Kenji Kawagoe

Proc Biol Sci. 2002 Jul 22;269(1499):1417-21.

https://pubmed.ncbi.nlm.nih.gov/12137569/

Structural Colours in Feathers

Nature volume 112, page243(1923)

https://www.nature.com/articles/112243a0


Angle-independent Structural Coloured Materials inspired by Blue Feather Barbs

Yukikazu TAKEOKA
NIPPON GOMU KYOKAISHI (2014)

Stimuli-responsive opals: colloidal crystals and colloidal amorphous arrays for use in functional structurally colored materials

Yukikazu Takeoka
Journal of Materials Chemistry C (2013)

Angle-independent structural coloured amorphous arrays

Yukikazu Takeoka
Journal of Materials Chemistry (2012)

Full-Spectrum Photonic Pigments with Non-iridescent Structural Colors through Colloidal Assembly

Jin-Gyu Park, Shin-Hyun Kim, Sofia Magkiriadou, Tae Min Choi, Young-Seok Kim, Vinothan N. Manoharan*

Angewandte Chemie International Edition 53(11): 2899 (2014)

https://dash.harvard.edu/bitstream/handle/1/24873725/submitted_version-postprint.pdf?sequence=1

Amorphous Photonic Structures with Brilliant and Noniridescent Colors via Polymer-Assisted Colloidal Assembly

Yang Hu, Dongpeng Yang,* and Shaoming Huang*

ACS Omega 2019, 4, 18771−18779

https://pubs.acs.org/doi/pdf/10.1021/acsomega.9b02734

Viburnum tinus Fruits Use Lipids to Produce Metallic Blue Structural Color

Rox Middleton,1,8,10 Miranda Sinnott-Armstrong,2,9,10 Yu Ogawa,3 Gianni Jacucci,1 Edwige Moyroud,4,5 Paula J. Rudall,6 Chrissie Prychid,6 Maria Conejero,6 Beverley J. Glover,7 Michael J. Donoghue,2 and Silvia Vignolini

In-Plane Direct-Write Assembly of Iridescent Colloidal Crystals

Alvin T. L. Tan, Sara Nagelberg, Elizabeth Chang-Davidson, Joel Tan, Joel K. W. Yang, Mathias Kolle, and A. John Hart

Fabrication of non-iridescent structural color on silk surface by rapid T polymerization of dopamine

Xiaowei Zhu, Biaobiao Yan, Xiaojie Yan, Tianchen Wei, Hongli Yao, Md Shipan Mia, Tieling Xing*, Guoqiang Chen

Bioinspired Stimuli-Responsive Color-Changing Systems

Golnaz Isapour and Marco Lattuada

Advanced Materials 30(19): 1707069

Plasmonic films based on colloidal lithography

Bin Ai a, Ye Yu a, Helmuth Möhwald b, Gang Zhang a,⁎, Bai Yang

Advances in Colloid and Interface Science

Printing a Wide Gamut of Saturated Structural Colors Using Binary Mixtures, With Applications in Anti-Counterfeiting

March 2020

ACS Applied Materials & Interfaces 

https://www.researchgate.net/publication/340326621_Printing_a_Wide_Gamut_of_Saturated_Structural_Colors_Using_Binary_Mixtures_With_Applications_in_Anti-Counterfeiting

Template Synthesis for Stimuli-Responsive Angle Independent Structural Colored Smart Materials

Mohammad Harun-Ur-Rashid1, Abu Bin Imran1, Takahiro Seki1, Yukikazu Takeoka1*, Masahiko Ishii2 and Hiroshi Nakamura2

https://www.jstage.jst.go.jp/article/tmrsj/34/2/34_333/_pdf

Optical Characterization of the Photonic Ball as a Structurally Colored Pigment

Ryosuke Ohnuki,* Miki Sakai, Yukikazu Takeoka, and Shinya Yoshioka

2020

HIGHLY DIFFRACTING, COLORSHIFTING, POLYMERIZED CRYSTALLINE COLLODAL ARRAYS OF HIGHILY CHARGED POLYMER SPHERES, PAINTS AND COATINGS AND PROCESSES FOR MAKING THE SAME

Matti Ben-Moshe, Reut(IL);

Sanford A. Asher, Pitsburgh, PA(US);

Justin J.Bohn, Pitsburgh, PA(US)

US7,902,272B2 /2011

Structural colors: from natural to artificial systems

Yulan Fu,1 Cary A. Tippets,2 Eugenii U. Donev3 and Rene Lopez

WIREs Nanomed Nanobiotechnol 2016

Structural color and its interaction with other color-producing elements: perspectives from spiders

Bor-Kai Hsiung*, Todd A Blackledge, and Matthew D Shawkey
Department of Biology and Integrated Bioscience Program, The University of Akron, Akron, Ohio

Self-assembled colloidal structures for photonics

Shin-Hyun Kim1, Su Yeon Lee2, Seung-Man Yang2* and Gi-Ra Yi3*

Harvard University, USA, KAIST and Chungbuk National University, Korea

Chameleon-Inspired Strain-Accommodating Smart Skin

Yixiao Dong,† Alisina Bazrafshan,† Anastassia Pokutta,‡ Fatiesa Sulejmani,‡ Wei Sun,‡ J. Dale Combs,† Kimberly C. Clarke,† and Khalid Salaita

ACS Nano XXXX, XXX, XXX−XXX

A composite hydrogels-based photonic crystal multi-sensor

Cheng Chen1, Zhigang Zhu1, Xiangrong Zhu1, Wei Yu1, Mingju Liu1, Qiaoqiao Ge1 and Wei-Heng Shih2

Published 16 April 2015 • 
Materials Research ExpressVolume 2Number 4

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Template Synthesis for Stimuli-Responsive Angle Independent Structural Colored Smart Materials

Article in Transactions of the Materials Research Society of Japan

February 2009

PATTERNED SILK INVERSE OPAL PHOTONIC CRYSTALS WITH TUNABLE, GEOMETRICALLY DEFINED STRUCTURAL COLOR

US Patent US2019/018731A1

Fiorenzo G.Omenetto, Lexington,MA (US);

YuWang, Medford, MA (US)

Bioinspired colloidal materials with special optical, mechanical, and cell-mimetic functions

Taiji Zhang, Yurong Ma and Limin Qi*

J. Mater. Chem. B, 2013, 1, 251

DYNAMICALLY TUNABLE PLASMONIC STRUCTURAL COLOR

DANIEL FRANKLIN

PhD Thesis 2018

Wetting in Color: Colorimetric Differentiation of Organic Liquids with High Selectivity

Ian B. Burgess,†,* Natalie Koay,‡,§, Kevin P. Raymond,‡,§, Mathias Kolle,† Marko Loncar,† and Joanna Aizenberg†,‡,^,*

Biologically inspired LED lens from cuticular nanostructures of firefly lantern

Jae-Jun Kima, Youngseop Leea, Ha Gon Kimb, Ki-Ju Choic, Hee-Seok Kweonc, Seongchong Parkd, and Ki-Hun Jeong

PNAS | November 13, 2012 | vol. 109 | no. 46

Functional Micro–Nano Structure with Variable Colour: Applications for Anti-Counterfeiting

Hailu Liu , Dong Xie, Huayan Shen, Fayong Li, and Junjia Chen

Hindawi
Advances in Polymer Technology
Volume 2019, Article ID 6519018, 26 pages

REVIEW ARTICLE
515 million years of structural colour

Andrew Richard Parker

J. Opt. A: Pure Appl. Opt. (2000) R15–R28

Colloidal Crystals from Microfluidics

Feika Bian, Lingyu Sun, Lijun Cai, Yu Wang, Yuetong Wang, and Yuanjin Zhao

Small 2019, 1903931

Nanochemistry Chapter 1

Mimicking the colourful wing scale structure of the Papilio blumei butterfly

Mathias Kolle1,2, Pedro M. Salgard-Cunha1, Maik R. J. Scherer1, Fumin Huang1, Pete Vukusic3, Sumeet Mahajan1, Jeremy J. Baumberg1 & Ullrich Steiner

Cambridge Univ

Nature Nanotechnology, 2010, (5) 511-515

Bioinspired bright noniridescent photonic melanin supraballs

Ming Xiao,1* Ziying Hu,2,3* Zhao Wang,4 Yiwen Li,5 Alejandro Diaz Tormo,6 Nicolas Le Thomas,6 Boxiang Wang,7 Nathan C. Gianneschi,2,3,4† Matthew D. Shawkey,8,9† Ali Dhinojwala

Sci. Adv. 2017;3:e1701151 15 September 2017

Structural Color and Odors: Towards a Photonic Crystal Nose Platform

Leonardo da Silva Bonifacio

PhD Thesis 2010

The Self-Assembly of Cellulose Nanocrystals: Hierarchical Design of Visual Appearance

Richard M. Parker, Giulia Guidetti, Cyan A. Williams, Tianheng Zhao, Aurimas Narkevicius, Silvia Vignolini,* and Bruno Frka-Petesic

Adv. Mater. 201830, 1704477

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.201704477

Bio-inspired design of multiscale structures for function integration

Kesong Liua, Lei Jiang

A ROBUST SMART FILM :REVERSIBLY SWITCHING FROM HIGH TRANSPARENCY TO ANGLE-INDEPENDENT STRUCTURAL COLOR DISPLAY

US Patent 2018

US2018/024876A1

Inventors:Shu YANG, BlueBel, PA(US);

Deng teng GE, Shanzhai(CN);

Elaine LEE,Brooklyn,NY (US)

Click to access US20180244876A1.pdf

Optimization of sharp and viewing-angle-independent structural color

Chia Wei Hsu,1,2,∗ Owen D. Miller,3 Steven G. Johnson,3 and Marin Soljacˇic ́1

Bioinspired living structural color hydrogels

Fanfan Fu, Luoran Shang, Zhuoyue Chen, Yunru Yu, Yuanjin Zhao

SCIENCE ROBOTICS

Measuring and specifying goniochromatic colors

Alejandro Ferrero1, Joaquín Campos1, Esther Perales2, Ana M. Rabal1, Francisco Martínez-Verdú2, Alicia Pons1, Elisabet Chorro2 and M. Luisa Hernanz

Bio-Inspired Photonic Structures: Prototypes, Fabrications and Devices

By Feng Liu, Biqin Dong and Xiaohan Liu

Submitted: November 5th 2011Reviewed: May 28th 2012Published: September 19th 2012

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Photobiology

The Science of Light and Life
  • Lars Olof Björn

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“Guanigma”: The Revised Structure of Biogenic Anhydrous Guanine 

Anna Hirsch,† Dvir Gur,‡ Iryna Polishchuk,§ Davide Levy,§ Boaz Pokroy,§ Aurora J. Cruz-Cabeza,∥ Lia Addadi,*,‡ Leeor Kronik,*,† and Leslie Leiserowitz*,†

Natural photonics 

Pate Vukusic

Stimuli-Responsive Structurally Colored Films from Bioinspired Synthetic Melanin Nanoparticles

Ming Xiao,†,# Yiwen Li,‡,#,○ Jiuzhou Zhao,† Zhao Wang,‡ Min Gao,§ Nathan C. Gianneschi,*,‡ Ali Dhinojwala,*,† and Matthew D. Shawkey

Chem. Mater. 2016, 28, 5516−5521

A Microfluidic Chip with Integrated Colloidal Crystal for Online Optical Analysis

Siew-Kit Hoi, Xiao Chen, Vanga Sudheer Kumar, Sureerat Homhuan, Chorng-Haur Sow, and Andrew A. Bettiol*

Highly monodisperse zwitterion functionalized non-spherical polymer particles with tunable iridescence

Vivek Arjunan Vasantha*aWendy RusliaChen JunhuiaZhao WenguangaKandammathe Valiyaveedu SreekanthbcRanjan Singhbc and Anbanandam Parthiban*a 

 RSC Adv., 2019, 9, 27199-27207

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Stimuli-responsive opals: colloidal crystals and colloidal amorphous arrays for use in functional structurally colored materials

Yukikazu Takeoka

J. Mater. Chem. C, 2013, 1, 6059

Biomimetic and Bioinspired Photonic Structures

Wu Yi, Ding-Bang Xiong * and Di Zhang

Nano Adv., 2016, 1, 62–70.

Bio-inspired photonic crystal patterns

Pingping Wu,abJingxia Wang *abc  and  Lei Jiang

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Stretchable and reflective displays: materials, technologies and strategies

Nano Convergence volume 6, Article number: 21 (2019)

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Colloidal Lithography

By Ye Yu and Gang Zhang

2013

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Structure and mechanical properties of beetle wings: a review 

Jiyu Sun and Bharat Bhushan

RSC Advances, 2012, 2, 12606–12623

A highly conspicuous mineralized composite photonic architecture in the translucent shell of the blue-rayed limpet

Ling LiStefan KolleJames C. WeaverChristine OrtizJoanna Aizenberg & Mathias Kolle 

Nature Communications volume 6, Article number: 6322 (2015) 

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Fabrication of 3D polymeric photonic arrays and related applications 

A. Yadav a, *, A. Kaushik b, Y. Mishra c, V. Agrawal d, A. Ahmadivan e, K. Maliutina f, Y. Liu g, Z. Ouyang h, W. Dong a, **, G.J. Cheng

Materials Today Chemistry, https://doi.org/10.1016/j.mtchem.2019.100208

Reversible Design of Dynamic Assemblies at Small Scales

Fernando Soto, Jie Wang, Shreya Deshmukh, and Utkan Demirci

Adv. Intell. Syst. 2020, 2000193

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Biological composites— complex structures for functional diversity.

Eder, M., Shahrouz, A., & Fratzl, P. (2018).

Science, 362(6414), 543-547.

Stimuli-Responsive Optical Nanomaterials

Zhiwei Li, and Yadong Yin

https://onlinelibrary.wiley.com/doi/am-pdf/10.1002/adma.201807061

Bio-Inspired Structural Colors Produced via Self-Assembly of Synthetic Melanin Nanoparticles

Ming Xiao,†,^ Yiwen Li,‡,^ Michael C. Allen,§ Dimitri D. Deheyn,§ Xiujun Yue,‡ Jiuzhou Zhao,† Nathan C. Gianneschi,*,‡ Matthew D. Shawkey,*, and Ali Dhinojwala

ACS Nano 2015

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Pigments Based on Colloidal Photonic Crystals

Carlos Israel Aguirre Vélez

PhD Thesis 2010

Structural Colors in Nature: The Role of Regularity and Irregularity in the Structure

Shuichi Kinoshita* and Shinya Yoshioka

ChemPhysChem 2005, 6, 1442 – 1459

Flexible mechanochromic photonic crystals: routes to visual sensors and their mechanical properties

Rui Zhang, Qing Wang  and Xu Zheng

J. Mater. Chem. C, 2018, 6, 3182

Designing visual appearance using a structured surface

VILLADS EGEDE JOHANSEN,1,* LASSE HØJLUND THAMDRUP,2 KRISTIAN SMISTRUP,2 THEODOR NIELSEN,2 OLE SIGMUND,1 AND PETER VUKUSIC

Vol. 2, No. 3 / March 2015 / Optica

Subwavelength nanocavity for flexible structural transmissive color generation with a wide viewing angle

KYU-TAE LEE,1 JI-YUN JANG,2 SANG JIN PARK,2 UJWAL KUMAR THAKUR,2 CHENGANG JI,1 L. JAY GUO,1 AND HUI JOON PARK

Vol. 3, No. 12 / December 2016 / Optica

Color and Texture Morphing with Colloids on Multilayered Surfaces

Ziguang Chen,†,‡,⊥ Shumin Li,†,‡,⊥ Andrew Arkebauer,§ George Gogos,† and Li Tan

ACS Appl. Mater. Interfaces 2015, 7, 10125−10131

https://pubs.acs.org/doi/pdf/10.1021/am5087215

Electrodeposition of Large Area, Angle-Insensitive Multilayered Structural Colors

Chengang Ji,1,† Saurabh Acharya,1,† Kaito Yamada,2 Stephen Maldonado,2,3,* and L. Jay Guo

https://par.nsf.gov/servlets/purl/10111165

Bright and Vivid Diffractive-Plasmonic Structural Colors

Emerson G. Melo,†,‡,§ Ana L. A. Ribeiro,†,‡ Rodrigo S. Benevides,†,‡ Antonio A. G. V. Zuben,†,‡ Marcos V. P. Santos,† Alexandre A. Silva,¶ Gustavo S. Wiederhecker,†,‡ and Thiago P. M. Alegre

2019

Biomimetic photonic structures for optical sensing

Raúl J. Martín-Palmaa, Mathias Kolle

Optics and Laser Technology 109

2019

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Colloidal Self-Assembly Concepts for Plasmonic Metasurfaces

Martin Mayer, Max J. Schnepf, Tobias A. F. König,* and Andreas Fery

Adv. Optical Mater. 20197, 1800564

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Flourishing Smart Flexible Membranes Beyond Paper

Anal. Chem. 2019, 91, 7, 4224–4234

Publication Date:March 18, 2019

https://doi.org/10.1021/acs.analchem.9b00743

https://pubs.acs.org/doi/full/10.1021/acs.analchem.9b00743

Biological vs. Electronic Adaptive Coloration: How Can One Inform the Other?

Eric Kreit1, Lydia M. Mäthger2, Roger T. Hanlon2, Patrick B. Dennis3, Rajesh R. Naik3, Eric Forsythe4 and Jason Heikenfeld1*

Dynamic plasmonic color generation enabled by functional materials

  1. Frank Neubrech
  2. Xiaoyang Duan
  3. Na Liu

Science Advances  04 Sep 2020:
Vol. 6, no. 36, eabc2709
DOI: 10.1126/sciadv.abc2709

https://advances.sciencemag.org/content/6/36/eabc2709

The New Generation of Physical Effect Colorants

Faiz Rahman and Nigel P. Johnson

Optics and Photonics News

2008

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The Japanese jewel beetle: a painter’s challenge

Franziska Schenk1, Bodo D Wiltsand Doekele G Stavenga2

Bioinspir. Biomim. (2013) 045002 (10pp)

Gold bugs and beyond: a review of iridescence and structural colour mechanisms in beetles (Coleoptera)

Ainsley E. Seago1,*, Parrish Brady2, Jean-Pol Vigneron3 and Tom D. Schultz4

Iridescence as Camouflage

Karin Kjernsmo,1,4,* Heather M. Whitney,1 Nicholas E. Scott-Samuel,2 Joanna R. Hall,2 Henry Knowles,1 Laszlo Talas,2,3 and Innes C. Cuthill1

Current Biology

VOLUME 30, ISSUE 3, P551-555.E3, FEBRUARY 03, 2020

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Chromic Phenomena: Technological Applications of Colour Chemistry

Peter Bamfield

Book, Royal Society of Chemistry 2018 edition

Amorphous diamond-structured photonic crystal in the feather barbs of the scarlet macaw

Haiwei Yina,1, Biqin Donga,1, Xiaohan Liua, Tianrong Zhana, Lei Shia, Jian Zia,2, and Eli Yablonovitchb,2

PNAS | July 24, 2012 | vol. 109 | no. 30

Amorphous Photonic Crystals with Only Short-Range Order

Lei Shi, Yafeng Zhang, Biqin Dong, Tianrong Zhan, Xiaohan Liu,* and Jian Zi

Adv. Mater. 201325, 5314–5320

Diamond-structured photonic crystals

Nature Materials  volume 3, pages593–600(2004)

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Nano-Optics in the Biological World: Beetles, Butterflies, Birds, and Moths

Mohan Srinivasarao*

Fiber and Polymer Science Program, North Carolina State University, Raleigh, North Carolina 27695-8301

Chem. Rev. 1999, 99, 1935−1961

515 million years of structural colour

Andrew Richard Parker

Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK

E-mail: andrew.parker@zoo.ox.ac.uk

J. Opt. A: Pure Appl. Opt. (2000) R15–R28

Photophysics of Structural Color in the Morpho Butterflies

Shuichi KINOSHITA1,2*, Shinya YOSHIOKA1,2, Yasuhiro FUJII2 and Naoko OKAMOTO

Forma17, 103–121, 2002

Photonic structures in biology

  • October 2004

Peter Vukusic

https://www.researchgate.net/publication/235888153_Photonic_structures_in_biology

Physics of structural colors

S Kinoshita, S Yoshioka and J Miyazaki

Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan

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Rep. Prog. Phys. 71 (2008) 076401 (30pp)

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Coloration strategies in peacock feathers

Jian Zi*, Xindi Yu, Yizhou Li, Xinhua Hu, Chun Xu, Xingjun Wang, Xiaohan Liu*, and Rongtang Fu

A Review of Electronic Paper Display Technologies from the Standpoint of SID Symposium Digests

Tatsumi Takahashi

Review of Paper-Like Display Technologies

Peng Fei Bai1, Robert A. Hayes1, Ming Liang Jin1, Ling Ling Shui1, Zi Chuan Yi1, L. Wang1, Xiao Zhang1, and Guo Fu Zhou1, 2

Progress In Electromagnetics Research, Vol. 147, 95–116, 2014

Stretchable and reflective displays: materials, technologies and strategies

Nano Convergence volume 6, Article number: 21 (2019)

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Review Paper: A critical review of the present and future prospects for electronic paper

Jason Heikenfeld (SID Senior Member) Paul Drzaic (SID Fellow)
Jong-Souk Yeo (SID Member)
Tim Koch (SID Member)

Journal of the SID 19/2, 2011

Biological versus electronic adaptive coloration: how can one inform the other?

Eric Kreit1, Lydia M. Ma ̈thger2, Roger T. Hanlon2, Patrick B. Dennis3, Rajesh R. Naik3, Eric Forsythe4 and Jason Heikenfeld1

J R Soc Interface 10: 20120601.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsif.2012.0601

Transmissive/Reflective Structural Color Filters: Theory and Applications


Yan Yu,1,2 Long Wen,2 Shichao Song,2 and Qin Chen

Volume 2014 |Article ID 212637 | https://doi.org/10.1155/2014/212637

https://www.hindawi.com/journals/jnm/2014/212637/

Interferometric modulator display

https://en.wikipedia.org/wiki/Interferometric_modulator_display

Qualcomm resurrects Mirasol reflective displays with new 576 ppi smartphone panel

https://www.theverge.com/2013/5/22/4354642/high-res-mirasol-display-for-smartphones-demonstrated

Iridescence-controlled and flexibly tunable retroreflective structural color film for smart displays

  • Wen Fan
  • Jing Zeng
  • Qiaoqiang Gan
  • Dengxin Ji
  • Haomin Song
  • Wenzhe Liu
  • Lei Shi
  • Limin Wu

Science Advances  09 Aug 2019:
Vol. 5, no. 8, eaaw8755
DOI: 10.1126/sciadv.aaw8755

Click to access eaaw8755.full.pdf

Artificial Structural Color Pixels: A Review 

by Yuqian Zhao 1Yong Zhao 1,*Sheng Hu 1Jiangtao Lv 1Yu Ying 2Gediminas Gervinskas 3 and Guangyuan Si 

Materials 201710(8), 944; https://doi.org/10.3390/ma10080944

https://www.mdpi.com/1996-1944/10/8/944/htm

Dynamically Tunable Plasmonic Structural Color

Daniel Franklin
University of Central Florida 2018

PHD Thesis

Colors with plasmonic nanostructures: A full-spectrum review 

Applied Physics Reviews 6, 041308 (2019); https://doi.org/10.1063/1.5110051

https://aip.scitation.org/doi/abs/10.1063/1.5110051?journalCode=are

Dynamic plasmonic color generation enabled by functional materials

Frank Neubrech1,2, Xiaoyang Duan1,2, Na Liu3,4*

Bright and Vivid Diffractive–Plasmonic Reflective Filters for Color Generation

  • Emerson G. Melo, 
  • Ana L. A. Ribeiro, 
  • Rodrigo S. Benevides, 
  • Antonio A. G. V. Zuben, 
  • Marcos V. Puydinger dos Santos, 
  • Alexandre A. Silva, 
  • Gustavo S. Wiederhecker, and 
  • Thiago P. M. Alegre*

ACS Appl. Nano Mater. 2020, 3, 2, 1111–1117Publication Date:December 31, 2019 https://doi.org/10.1021/acsanm.9b02508

https://pubs.acs.org/doi/full/10.1021/acsanm.9b02508

Active control of plasmonic colors: emerging display technologies

Kunli Xiong, Daniel Tordera, Magnus Jonsson and Andreas B. Dahlin

Rep Prog Phys. 2019 Feb;82(2):024501.

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Self-assembled plasmonics for angle-independent structural color displays with actively addressed black states

Daniel Franklina,b, Ziqian Hec, Pamela Mastranzo Ortegab, Alireza Safaeia,b, Pablo Cencillo-Abadb, Shin-Tson Wuc, and Debashis Chandaa,b,c,1

https://www.pnas.org/content/117/24/13350

Bio-inspired intelligent structural color materials

Luoran Shang, Weixia Zhang, Ke Xuc and Yuanjin Zhao

Mater. Horiz., 2019,6, 945-958 

https://pubs.rsc.org/en/content/articlelanding/2019/mh/c9mh00101h#!divAbstract

Advanced Plasmonic Materials for Dynamic Color Display

DOI: 10.1002/adma.201704338

https://www.researchgate.net/publication/320997060_Advanced_Plasmonic_Materials_for_Dynamic_Color_Display

Polarization-independent actively tunable colour generation on imprinted plasmonic surfaces

Nature Communications volume 6, Article number: 7337 (2015)

https://www.nature.com/articles/ncomms8337

Tunable plasmonic color filter 

Rosanna Mastria, Karl Jonas Riisnaes, Monica Craciun, and Saverio Russo

Frontiers in Optics / Laser Science OSA Technical Digest (Optical Society of America, 2020),paper JTh4B.7•

https://doi.org/10.1364/FIO.2020.JTh4B.7

https://www.osapublishing.org/abstract.cfm?uri=FiO-2020-JTh4B.7

Optics of Metallic and Pearlescent Colors

Optics of Metallic and Pearlescent Colors

Source: A GENERAL FRAMEWORK FOR PEARLESCENT MATERIALS

Key Terms

  • Pearlescent
  • Metallic
  • Luster Pigment
  • Color Travel Pigment
  • Interference Pigment
  • Angle Dependent Colors
  • Structural Colors
  • Effect Pigments
  • Goniochromatic
  • Iridescence
  • Refraction
  • Reflection
  • Transmittance
  • Gloss
  • Diffraction
  • Interference
  • Refractive Index
  • Isotropic
  • Anisotropic
  • Illuminating and viewing geometries
  • Bidirectional Reflectance Distribution Function (BRDF)
  • Bidirectional Scatter Distribution Function (BSDF)
  • CIE tristimulus values
  • Multiangle spectrophotometers
  • D65, A, and F11 illuminants
  • CIEDE2000 color differences
  • CAM02-SCD
  • CIELAB color differences
  • Illuminating and viewing geometries
  • Color appearance of metallic coatings
  • Aluminum-flake pigments
  • Spectral radiance factors
  • Spectro Goniophotometers
  • Goniospectrometers
  • Thin Film Interference
  • Flop Control Agent
  • Specular Reflection

Source: Pearlescent Pigments

https://encyclopedia.pub/805#1._Introduction

4. Layered Pearlescent Pigments

The dominant class of Pearlescent Pigments is represented by natural mica coated with thin films of different metal oxides[2]Mica based pigments were firstly developed in the 1970s and got accelerated until 1990s when multilayer systems on mica were successfully realized. Natural muscovite mica is a rather inexpensive crystal and it can be easily cleaved to thinner flakes of typically 250 nm. These advantages made mica-based pigments quickly monopolize the special effect pigment market, until reaching 90% of the whole market. This pigment is easily produced by the deposition of metal oxide layers on the mica surface[2]. TiO2 or iron oxide covered mica pigments can be easily produced with a high thickness control, but sometimes they show limited optical properties[10]. Mica-based pigments with multilayers show pronounced angle dependence, but they are heavier respect to other pearlescent pigment types, thus leading to a higher pigment content required to reach a certain colour strength[11][12][13]. There are many emerging substrate-based pigments, different from the ones based on mica substrates, that show interesting optical properties. Pigments based on silica flakes (SiO2) are easily produced in a very controlled and uniform thickness by the web-coating process[5]. The thickness of silica flakes is in the order of 400 nm, comparable to that of mica particles, and it can be tailored be so narrow to become itself an optical layer. These pigments allow obtaining a high chromatic strength and special colour travel effects, useful for automotive applications, decorative plastics and security inks[14]Alumina (Al2O3) based pigments represent another type of emerging pearlescent pigment[5]. This pigment type has got strong pearlescent effect respect to mica-based pigments mainly due to its high aspect ratio and narrow thickness distribution, as it happens for silica-based pigments.  In addition to that, alumina-based pigments exhibit unique crystal-like effect (sparkle effect), mainly due to their smooth surface and chemical purity, thus being interesting for high-duty decorative purposes, such as car paints[2]. The study recently published by our group study the effect of the addition of alumina-based pigments on the durability of powder coatings. The pearlescent pigments taken under consideration were supplied by Merck S.p.A (Darmstadt, Germany). Figure 2 shows an SEM image of one of the pigments used in this study. 

In order to be complete, it necessary to mention the presence of other substrate-based pigments such as pigments based on glass flakes and aluminium flakes. Pigments based on glass substrates play a minor role in the market because they are very thick and show limited optical properties, apart from special applications. Pigments base on aluminium flakes are produced via CVD processes and show an interesting angle-dependent colour changing, but the variety of colours available is limited to gold, orange and reddish metal-like colours.

Source: EFFECT PIGMENTS FOR INDUSTRY

Source: Photo-realistic Rendering of Metallic Car Paint from Image-Based Measurements

Source: QCV Korea

Source: QCV Korea

Source: QCV Korea

Source: QCV Korea

Source: CCM System for Metallic and Pearlescent Colors

Types of Metallic and Pearlescent Pigments

( Composition Based)

Source: Effect pigments—past, present and future

Effect pigments without a layer structure—substrate-free pigments
  • Metal effect pigments
    • Flakes or lamellae of
      • aluminum (“aluminum bronzes”)
      • copper
      • copper-zinc alloys (“gold bronzes”)
      • zinc
      • other metals
  • Natural pearl essence
  • Basic lead carbonate
  • Bismuth oxychloride
  • Micaceous iron oxide
  • Titanium dioxide flakes
  • Flaky organic pigments
  • Pigments based on liquid crystal polymers

Substrate based, Pearlescent Pigments, Layered
  • Mica Based
  • Alumina Based
  • Silica Flakes based
  • Glass Flakes Based
  • Iron Oxide Flakes Based
  • Graphite Flakes Based
  • Aluminum Flakes Based
Multilayer structures of the Fabry–Perot type

Structural arrangements consisting of alternating thin metal and dielectric layers can be used to achieve strong angle-dependent optical effects, e.g., in form of so-called optically variable pigments (OVP) [5,12]. Different color shifts can be produced by precisely controlled thickness of the multilayers. The metal layers consist in most cases of chromium (semitransparent absorber layers on the top and the bottom of a five-layer system) and of aluminum (opaque reflector layer in the center of the layer structure). The dielectric layers in between the chromium and aluminum layers consist mostly of magnesium fluoride or silicon dioxide. Such layer systems are the basis for an optical interference phenomenon called Fabry–Perot effect, which is different from interference effects of transparent layer systems because of the complete reflection of the light at the opaque reflector layer. Symmetrical arrangements of at least five layers are necessary to achieve strong color-shifting effects. In the case of pigments, only the five-layer systems play a role for practical use.

Effect pigments—past, present and future

Source: Industrial Inorganic Pigments / Edited by G. Buxbaum and G. Pfaff

Source: Industrial Inorganic Pigments / Edited by G. Buxbaum and G. Pfaff

Types based on Optics

  • Multiple Reflection
  • Refractive Pigments
  • Interference Pigments
  • Diffraction Pigments
  • Holographic Pigments

Source: Fascinating displays of colour
Effect pigments – A successful interplay of chemistry and physics

Source: Ceramic Coatings for Pigments

Special Effects Pigments

( Luster Pigments)

  • Pearl luster pigments
    • Pearlescent pigments
    • Nacreous pigments
    • Interference pigments
  • Metal effect pigments.

All these pigments consist of small thin platelets that show strong lustrous effects when oriented in parallel alignment in application systems (e.g. in paints, plastics, printing inks, cosmetic formulations).

Source: Inorganic Pigments/Gerhard Pfaff

Source: Pearlescent PIGMENTS in Coatings A Primer

Source: Pearlescent PIGMENTS in Coatings A Primer

Source: Pearlescent PIGMENTS in Coatings A Primer

Source: Pearlescent PIGMENTS in Coatings A Primer

Source: Pearlescent PIGMENTS in Coatings A Primer

Effect Pigments Producers

  • Altana AG 
  • BASF SE 
  • Cabot Corporation 
  • Carlfors Burk AB 
  • Clariant AG 
  • Dainichiseika Color & Chemicals Mfg. Co. Ltd 
  • Dayglo Color Corp. 
  • Dic Corporation 
  • E.I. Du Pont De Nemours and Company 
  • Ferro Corporation 
  • Flint Group Pigments 
  • Geotech International B.V. 
  • Huntsman Corporation 
  • Kobo Products Inc. 
  • Kolortek Co., Ltd 
  • Merck KGaA 
  • Mono Pigment Developments Ltd. 
  • Nemoto & Co., Ltd. 
  • Sensient Industrial Colors 
  • Siberline Manufacturing Co. Inc 
  • Special Effects & Coatings 
  • Sudarshan Chemical Industries 
  • The Chemours Company 
  • Toyal Europe
  • Toyocolor Co., Ltd.

GeoTech Pearlescent Pigments

Industrial Application of Effect Pigments

Source: https://www.emdgroup.com/en/company.html

  • Coatings and Paints
  • Printing
  • Arts and Crafts
  • Plastics
  • Cosmetics
  • Food
  • Pharma
  • Architecture
  • Automotives
  • Ceramics and Glass

Decorative Papers

  • Pearlescent Effect
  • Metallic Effect
  • Shimmer Effect
  • Texture (Linen) Effect

Pearlescent Effect

Source: Amazon Germany

Pearlescent Effect

Source: Amazon Germany

Metalic Effect

Source: Amazon Germany

Metallic Effect

Source: Amazon Germany

Shimmer Effect

Source: Amazon Germany

Linen Effect

Source: Amazon Germany

List of some commercially available papers

Brands:

Source: https://netuno.pl/en/130-metalizowane-perlowe

  • Majestic – Italian papermills -Favini
  • Sirio Pearl – Italian papermills – Fedrigoni
  • Cocktail
  • Constellation Jade
  • Galaxy
  • Curious Matallics
  • Astrosilver
  • Stardream
  • Aster Metallic

Source: AMAZON Germany

  • Sirio Pearl A4 Paper with Metallic Effect, 125 g, Ideal for Weddings, Christmas, Greeting Cards
  • 10 x A4 Gold Peregrina Real Gold Pearlescent Effect Paper 120gsm Double Sided Suitable for Inkjet and Laser Printers
  • 20 x A4 QUARZO Pale Ivory Flower Heart Majestic Double-Sided Pearlescent Paper 120 g/m² for Inkjet and Laser Printers
  • 20 x A4 QUARZO Pale Ivory Flower Heart Majestic Double-Sided Pearlescent Paper 120 g/m² for Inkjet and Laser Printers
  • Syntego A4 Rose Gold Pearlescent Decorative 120gsm Double Sided Paper
  • Syntego A4 Gold Pearlescent Single Sided Card 300gsm Purple (10 Sheets)
  • Syntego 10 Sheets Ivory A4 Card with Pink Pearlescent Shimmer Decorative Single Sided 300gsm
  • A4 Pink Pearlescent Gold Card 300gsm Rose
  • 10 x A4 Petals Pink Peregrina Majestic Pearlescent Shimmer Paper Double Sided 120gsm Suitable for Inkjet and Laser Printers
  • Synthetic Ego Peregrina Pearlescent Paper, A4, 120 g/m², suitable for inkjet/Laser Printers – Blue (Pack of 10)
  • Synthetic Ego 20 Sheets of A4 Baby Pink and Baby Blue Pearlescent Card Double Sided 120 g/m² for Inkjet and Laser Printers Pack of 10)
  • A4 Paper Sea Blue Pearlescent Paper 100 g/m² for Inkjet and Laser Printers
  • 10 x A4 Fresh Mint Green Peregrina Majestic Pearlescent Shimmer Paper Double Sided 120gsm Suitable for Inkjet and Laser Printers
  • 10 x A4 Nightclub Purple Peregrina Majestic Pearlescent Shimmer Paper Double Sided 120gsm Suitable for Inkjet and Laser Printers
  • Syntego A4 Gold Pearlescent Single Sided Card 300gsm Magenta 10 Sheets
  • Sirio Pearl A4 Paper with Metallic Effect, 125 g, Ideal for Weddings, Christmas, Greeting Cards
  • Netuno x Sheets Pearlescent Azure Blue A4 210 x 297 mm Majestic Damask Blue
  • Netuno x Sheets Pearlescent Silver Paper DIN A4 210 x 297 mm Majestic Moonlight Silver
  • Sirio Pearl Red Fever 10 x Sheets of Pearlescent Red 300 g Paper DIN A4 210 x 297 mm Ideal for Weddings, Birthdays, Christmas, Invitations, Diplomas,…
  • 10 Sheets of Mother of Pearl Gold 290 g Cardboard DIN A4 210 x 297 mm Cocktail Mai Tai, Ideal for Wedding, Birthday, Christmas, Invitations, Diplomas, Arts…
  • 10 x A4 Frost White Pearlescent Shimmer Paper 120gsm Suitable for Inkjet and Laser Printers (PIA4-5)
  • A4 Pink Pearlescent Gold Card 300gsm Rose
  • Netuno x Sheets Pearlescent Dark Blue Paper DIN A4 210 x 297 mm Majestic Kings Blue
  • Nettuno Oltremare, 10 sheets, blue cardboard, 215 g, felt marked on both sides, with line structure, DIN A4, 210 x 297 mm, ideal for wedding, birthday,…
  • 25 Sheets Light Green Coloured Card DIN A4 210 x 297 mm 210 g Sirio Colour Lime, Ideal for Weddings, Birthdays, Christmas, Invitations, Diplomas, Business Cards, Scrapbooking, Crafts and Decorating
  • 10 x A4 Pearlescent Intense Shine Mellow Gold Paper 120 g/m² Double Sided For Inkjet and Laser Printers
  • A4 Paper Sea Blue Pearlescent Paper 100 g/m² for Inkjet and Laser Printers
  • 20 Sheets A4 Maya Blue Pearlescent Paper 100gsm for Inkjet and Laser Printers
  • 20 x A4 Printer Paper Damask Majestic Light Blue Double-sided Peregrina Pearl 120 g/m², suitable for inkjet and laser printers
  • Syntego 10 Sheets Pale Purple Pearlescent Double Sided A4 Decorative Card 300gsm
  • 10 x A4 Frost White Pearlescent Shimmer Paper 120gsm Suitable for Inkjet and Laser Printers (PIA4-5)
  • A4 Pearlised Purple Periwinkle Paper 100 g/m² for Inkjet and Laser Printers
  • 10 x A4 Nightclub Purple Peregrina Majestic Pearlescent Shimmer Paper Double Sided 120gsm Suitable for Inkjet and Laser Printers
  • Syntego A4 Gold Pearlescent Single Sided Card 300gsm Magenta 10 Sheets
  • 10 x A4 Gold Peregrina Real Gold Pearlescent Effect Paper 120gsm Double Sided Suitable for Inkjet and Laser Printers

Cosmetics

Source: Merck KGaA

  • Black Color Pigments
  • Color Luster Pigments
  • Color Travel Pigments
  • Gold Pigments
  • Interference Pigments
  • Metallic Color Luster Pigments
  • Silverwhite Pigments

Automotive Paints

Automotive Coatings: Creating Excitement with Effect Pigments

By Cynthia Challener, CoatingsTech Contributing Writer

Regardless of the end-use application, special effect pigments provide a differentiated appearance. That is certainly true in the automotive industry, where they are used in coatings applied to both the interior and exterior of vehicles. Shifts in customer color and appearance preferences drive the use and development of effect pigments, as do developments in coatings technology and application processes. High sparkle finishes and intensely chromatic colors on car bodies and mirror-like finishes on interior components are increasing in popularity and driving the use of glass flakes, colored aluminums, and aluminum pigments with a much finer particle size. Pigments also need to provide the same appearance in coatings with thinner and/or fewer layers while exhibiting increased durability.

Creating a Unique Look

Coatings formulators work directly with pigment suppliers to develop and commercialize new specialty effect pigments to generate exciting color spaces that accentuate the bodylines of new vehicles. Effect pigments are the fastest growing segment of the high performance pigment market, and in 2015 were present in 70% and 65% of automotive colors for new builds in the Americas and Europe, respectively, according to Jane Harrington, manager of color styling with PPG Automotive OEM Coatings. “While neutral colors such as white, black, and silvers still dominate most of the automotive color palette, deep, rich, highly chromatic blues, greens, oranges, and reds have begun to find their place in the automotive world as well,” says Jason Kuhla, manager of technical service & product application with Silberline Manufacturing. “Special effect pigments that provide brilliance and ‘pop’ can help to create a look that stands out among the sea of color monotony, and appeal to those consumers who wish to stand apart from the crowd,” he adds. Allen Brown, advanced development and mastering manager in the Color and Material Design group of Ford Motor Company, agrees that while there will always be niche colors for special applications, overall there seems to be a balancing of colors to round out a complete selection, with a shift away from achromatic colors to a more sophisticated, balanced palette. For some applications, designers are seeking to create a value-added appearance by increasing the brilliance and reflectivity of metallic finishes while maintaining a smooth, non-sparkling appearance, according to Michael T. Venturini, global marketing manager, Coatings, Sun Chemical Performance Pigments.

Effect pigments are the fastest growing segment
of the high performance pigment market, and in 2015
were present in 70% and 65% of automotive colors
for new builds in the Americas and Europe . . . .

To achieve the desired appearance, most pigment flakes must be oriented in a specific manner within the coating. Their particle size also impacts the way they interact with light; larger particles provide more sparkle and iridescence, but the dimensions are limited to avoid impacts on gloss and other appearance properties. The industry is pushing the limits in this area, according to Paul Czornij, technical manager with the Color Excellence Group of BASF Coatings, and is seeking as much coarseness as the color can allow yet still providing a smooth and glossy look. The rheology of effect pigments, particularly in high solids, solvent-based systems, also influences their final appearance properties. On the other hand, there is a desire for smoother glass-like finishes, which has led to greater use of finer particle sizes to help deliver a quality liquid appearance in many colors, according to Brown. However, smoother finishes that give strong travel (bright face and dark side-tone) are difficult to achieve with electrostatic bell application (preferred for its greater transfer efficiency), which tends to make flakes stand up and give a more granular appearance, according to John Book, product line manager with Viavi. “Smaller particle sizes and size distributions also have a negative impact on color capability and metallic orientation, so such advances are far from simple,” asserts Frank Maimone, manager of pigment and color technology for the Color Development group of PPG Automotive OEM Coatings.

The shape of the vehicle has a significant impact on which effect pigments are used. For instance, fine/bright effect pigments that give coatings brightness with higher travel are preferred for vehicles that have a more interesting, free-flowing form, while for trucks, which are more slab-sided, coatings with more sparkle are frequently used, according to Jerry Koenigsmark,* who was manager of technical color design for PPG Automotive Coatings in North America. “For many of the new car designs targeting a younger consumer base, there is a push towards highly chromatic colors that employ colored aluminum pigments, mica pigments, glass flakes, and interference pigments,” says Kuhla. He also notes a shift in the wheel coatings market, where black is becoming more popular at the expense of traditional silvers.

Fast sports car moving with blur

For car interior trim parts, chrome-like coatings are used to create a value-added look and add haptic properties to simple plastic and other components. Auto parts and accessories (APA) also tend to be dominated by silvers, and many of these coatings contain pigments manufactured using physical vapor deposition (PVD) processes. In addition, many interior coatings are intended to provide attractive haptic properties. Because they are often single-layer systems, the effect pigments must have high resistance to body oils, perspiration, lotions, cosmetics, and other chemicals, according to Jörg Krames, vice president for global key account management with Eckart. He also notes, in these applications, liquid coatings compete with powder coatings and alternative technologies such as in-mold decoration with foils.

Finding Functional and Sustainable Solutions

Numerous other factors influence the choice of effect coatings beyond the appearance a designer wishes to create. In addition to provoking an emotional response in car buyers, effect pigments are often expected to serve multiple additional functions, according to Krames. The functional performance will be dictated by the type of coating and coating application systems. For external coatings, the compact application processes (primerless coating systems, three-coat/one-bake, integrated processes) widely used today on exterior car bodies involve the application of only a basecoat and topcoat over the e-coat. “Effect pigments in these systems must provide hiding power and exhibit high chemical-, moisture-, and UV-resistance properties in order to protect the e-coat,” he says. In addition, coating formulations now have higher pigment concentrations in smaller volumes, and the coating layers are either thinner or the flash times are eliminated. “Both scenarios have a negative impact on coating appearance and require extensive reformulation of coatings to meet end-use expectations,” notes Thomas A. Cook, global manager for color and process technologies with PPG Automotive OEM Coatings.

The trend towards thinner coatings has driven the development of new low-aspect-ratio effect pigment particles like colored, thin silver-dollar aluminum pigments that deliver brilliant metallic luster in high-chroma hues with good hiding and gloss. Generally, the use of smaller particle sizes will provide a smoother appearance with good gloss. However, to achieve the most chromatic colored effects and good flop behavior, manufacturers must consistently deliver highly optimized particle size distributions, comments Mike Crosby, market segment manager for BASF’s Global Automotive/OEM Pigments Business Unit. New lightweight substrates have surface-roughness and adhesion issues that also require coating reformulation, according to Bill Eibon, director of technology acquisitions for PPG Automotive OEM Coatings. On a positive note, Brown points out that ultra-smooth primers have helped to achieve a better glass-like appearance by creating a smoother base on which to paint.

APR16_iStock_48622668_WEB

Such integrated processes are just one response by the automotive industry to improve sustainability, reduce the use of hazardous materials and its carbon footprint, and meet increasing governmental regulatory requirements—all while ensuring outstanding value and consumer satisfaction, according to Czornij. “These imperatives are driving innovation and change, and even as formulations and applications change, effect pigments must continue to afford durable coatings that are aesthetically pleasing and in alignment with trends in color popularity,” he asserts. The ongoing switch to water-based coatings is another key driver of effect pigment development. The goal has been to achieve highly brilliant products with identical optical properties as those of solvent-based and nontreated pigments, according to Mark Stoll, global head of marketing & technical service with Eckart. Although stability issues with aluminum pigments in waterborne formulations have, in general, been resolved with silica encapsulation technology, Venturini notes that the increasing adoption of waterborne coatings continues to drive pigment innovation as producers seek more efficient ways to better stabilize their pigments and make them easier to use.

Additional important trends noted by Book include the incorporation of effect pigments in the clearcoat, where historically they have only been used in the basecoat. This application is commonly referred to as tinted clearcoats. “Increased color saturation and depth are achieved when effect pigments are present in the basecoat and finely milled organic pigments are added to the clearcoat,” he says. The effect is enhanced when new nanoscale pigments with increased dispersion saturation are used in the tinted clearcoats, according to Brown. “These systems have allowed us to achieve color spaces not obtainable in the past, such as our Ruby Red on the Ford Fusion and Burgundy Velvet on the Lincoln MKZ. Both colors were created using ANDARO® effect pigments from PPG. However, as with other recent development, these finishes are not easily applied or repaired, and OEMs are looking for alternative two-coat solutions that can replicate this look,” according to Book. PPG color experts would like to see durable dye-like systems with ultra-high transparency for use in both solvent-based and water-based coatings, as well as thinner flakes to minimize the number of clearcoat layers needed to bury the finish. Book does note that new colored aluminum pigments can create a tinted clearcoat appearance that is much easier to apply and repair.

Advances in Pigment Technology

In addition to the development of effect pigments already mentioned, pigment manufacturers have responded to changing coatings formulation and application trends and technologies with a variety of technology advances of their own. Dieter Marquardt, manager of color matching, Europe, with PPG Automotive OEM Coatings notes two key advances. The first is process improvements in the manufacturing of synthetic micas that make them more affordable and will drive a shift away from natural micas and lead to the development of more chromatic colors and improved appearance. The second is new processes to generate colored aluminums based on inorganic layers and brighter aluminum feedstocks that offer stylists higher chroma and color saturation. Thin, silver-dollar colored aluminum pigments are producing new and attractive color spaces with dramatic chroma and travel characteristics. Colored aluminum pigments also enable styling of rich, chromatic colors at a lower pigment loading than a combination of traditional silver aluminum silver dollars with absorption pigments. They can therefore deliver good hiding with excellent gloss, even in thin-film automotive coatings, according to Crosby. Meanwhile, the process of depositing different layering systems on pigment cores has driven the introduction of more dramatic effects such as better color travel and more sparkle, according to Gareth Hughes, director of Americas Technology for PPG Automotive Refinish. “The use of multiple layer stacks to optimize light travel and interference in pearlescent pigments is a major contributor to the new high-impact colors you see today,” Crosby agrees.

OLYMPUS DIGITAL CAMERA

Kuhla sums it up best: “High chroma, multilayer effect pigments, newer shades of colored aluminum flake, and glass flake pigments have given color formulators the tools they need to achieve head-turning color shades that excite consumers and inspire pigment research to dig even deeper into what variations of these new technologies can yield. From the high-sparkle glitz of glass flakes to the eye-appealing, high opacity of colored aluminums, recent developments are giving formulators the ability to make colors that dazzle.”

It should also be noted that for many of the challenges facing automotive coating formulators working with effect pigments, effective solutions are often achieved with the use of additives. “At Eckart, we have found it hugely beneficial to have direct access to additive technologies through Altana’s BYK division. Cooperative development of effect pigments and additives makes it possible to develop higher-performance products,” Krames remarks.

There are limitations of effect technology that pigment manufacturers, coating formulators, and car makers continue to work to address. Many are related to the coating application process. “We are challenged by the effect on flake orientation from bell application, and there is a need for improvement in aluminum travel through equipment, formulation, and flake technology,” says Maimone. There is also a need for an alternative to vacuum metalized aluminum pigments that can produce a liquid metal effect or highly brilliant mirror-like finish using conventional application technology, according to Venturini. “Even with vacuum metalized pigments, specific low-solids paint technology and a highly specialized, skilled application process must be used to achieve the desired appearance,” he adds. As a result, the number and types of end-use applications are limited—chrome-like wheel finishes are one example. “Simplification of the process would open the door to a wider range of applications,” asserts Venturini. Ford would like to see one-layer specialty “liquid” and anodized coatings that meet all specifications without the need for a clearcoat, according to Brown.

High chroma, multilayer effect pigments, newer shades of colored aluminum flake, and glass flake pigments have given color formulators the tools they need to achieve head-turning color shades that excite consumers and inspire pigment research to dig even deeper into what variations of these new technologies can yield.

Mike Jones, paint material engineer with Ford’s Vehicle Operations unit, notes that, in general, coatings with effect pigments can be more difficult to apply than coatings with traditional pigments, but the process is manageable. Color-shifting pigments pose the greatest challenge. “The color changes at different angles, and it can be difficult to achieve the same type of changes on all components of a vehicle, largely due to vehicle geometry and the use of different application equipment and/or process conditions at the different component suppliers,” he explains. There is, in fact, a general need to be more consistent with application processes for all coatings that contain effect pigments, according to Jones. “These coatings are not as forgiving as paints containing traditional pigments,” he says. Jones has also seen issues with the application of coatings containing aluminum pigments created using PVD. Krames adds that the ability to combine PVD with electrostatic spray application is a major focus of research for the automotive industry.

There are, in fact, a number of fascinating new effect technologies under development with potential for use in the automotive industry in the distant future. Pigments that have switchable functionality or that incorporate photocatalytic TiO2 are just two of the innovations Eckart is investigating. Eckart is also developing effect pigments for improved heat insulation and better corrosion protection, as well as pigments that have multiple functionality. Viavi, meanwhile, is developing a new pigment effect that draws inspiration from the natural surface of a moth’s eye. This very fine structure creates a blue-green glow when viewed in retro-reflection, according to Book.

Ford is paying close attention to potential legislation related to infrared (IR) requirements in California and a few other states. “The California Air Resource Board (CARB) rules may require specification of the amount of IR energy absorbed by a vehicle in order to help regulate the temperature in the interior and thus reduce the size of the air-conditioning unit and increase mileage,” Brown explains. There is also interest in the use of effect pigments in marketing strategies. Book raises the concept of paid colors. “Premium colors have been available in the luxury segment for some time. OEM’s are also now more frequently offering modestly priced special option colors on economy cars. As a result, it is becoming an increasingly difficult challenge to maintain an appearance difference for luxury cars, leading to more innovation in pigment and coating technologies,” he notes. Brown is also interested in specialty pigments that are tailored to represent a specific brand.
Whatever the driving forces, continued development of interesting effect pigment technologies can be expected going forward. “PPG receives a lot of unique special-effects requests from young automotive designers, so I think there will be some exciting things happening in the future in exterior auto paints, according to Koenigsmark.”*

*Jerry Koenigsmark, who was Manager of Technical Color Design for PPG Automotive OEM Coatings in North America, passed away in December 2015 after a brief battle with pancreatic cancer. He had worked for PPG for over 30 years. Jerry’s color expertise, creativity and passion for cars will be missed by the global automotive industry, and his impact on automotive color design will live on in future model years.

Measurement and Testing of Metallic and Pearlescent Colors

Source: Photonics Measures the Quality of Automotive Paint

The automotive industry has not yet chosen standards for the angles for these measurements, but several manufacturers produce multiangle color-measuring instruments:

• Konica Minolta Business Solutions USA Inc. of Ramsey, N.J., makes the CM-512m3 spectrophotometer for the measurement of metallic colors. It illuminates a painted surface at angles of 25°, 45° and 75° to the normal, and observes at a fixed 0° angle. The portable instrument measures the surface temperature at the same time as the color, because many paints change color with temperature, an effect called thermochromism.

• X-Rite Inc. of Grandville, Mich., offers the MA68II multiangle spectrophotometer. The device has a fixed angle of illumination at 45° to the surface normal and five angles of observation: Relative to the angle of specular reflection and moving toward the angle of incidence, the viewing angles are 15°, 25°, 45°, 75° and 110°.

• Standox GmbH of Wuppertal, Germany, produces a five-angle spectrophotometer called Genius+ to measure the color of metallic and pearlescent paints. Software assists in the selection of matching paint formulations.

• GretagMacbeth AG of Regensdorf, Switzerland, and New Windsor, N.Y., makes a series of instruments with fixed 45° illumination and four angles of observation. The Auto-Eye 640 measures light reflected at 15° to the specular, and at 45°, 75° and 110°, and the 641 uses 20° in place of 15° (Figure 6). The 642 uses 25°. These portable multiangle spectrophotometers cope with slightly curved surfaces by means of a large aperture (the 642 illuminates a 14-mm-diameter circle) and three contact sensors that ensure that the instrument is normal to the surface at the center of the sensors. The device is primed for measurement when all the sensors make contact.

• Datacolor of Lawrenceville, N.J., offers a meter with 10 sets of illumination and viewing geometries. The Datacolor FX10 measures the light reflected at 10-nm intervals through the visible spectrum and has bi-directional measurement geometry.

Source: CCM System for Metallic and Pearlescent Colors

Source: CCM System for Metallic and Pearlescent Colors

Source: CCM System for Metallic and Pearlescent Colors

Source: CCM System for Metallic and Pearlescent Colors

Modelling and Prediction of Colors of Metallic and Pearlescent Coatings

It is very difficult to model appearance of metallic and pearlescent colors. Some attempts have been made but it is still an active area of research.

Some models have been developed for paint layers.

Some rendering models have been developed in computer graphics area using BRDF and BTF.

Source: Modeling the appearance of special effect pigment coatings

Source: Modeling the appearance of special effect pigment coatings

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Key Sources of Research

THE CHEMISTRY & PHYSICS OF
SPECIAL EFFECT PIGMENTS & COLORANTS

A. NURHAN BECIDYAN

President
UNITED MINERAL & CHEMICAL CORPORATION

Pearlescent pigments in printing

  • April 2018
  • Conference: Innovations in Publishing, Printing and Multimedia Technologies

Authors:

Ivana Tomic

Sandra Dedijer

Ivan Pintier

https://www.researchgate.net/publication/325896991_Pearlescent_pigments_in_printing

Effect pigments—past, present and future

F. J. MaileG. PfaffP. Reynders

Published 2005

Progress in Organic Coatings

Pearlescent Pigments: history, properties and application in powder coatings

Francesca Russo
Published 2020

https://www.semanticscholar.org/paper/Pearlescent-Pigments%3A-history%2C-properties-and-in-Russo/6a93b0d68ef42510f975cbc0c4565add3e2b55e5

Colorimetric and spectral evaluation of the optical anisotropy of metallic and pearlescent samples

https://www.researchgate.net/publication/238961530_Colorimetric_and_spectral_evaluation_of_the_optical_anisotropy_of_metallic_and_pearlescent_samples

Use of effect pigments for quality enhancement of offset printed specialty papers

M. DebeljakA. Hladnik, +1 author D. Gregor-Svetec

Published 2013

Color Research and Application

Review of instrumental inter‐agreement study of spectral and colorimetric data of commercial multiangle spectrophotometers

E. PeralesBàrbara Micó-Vicent, +3 authors Yuta Yamanoi

Published 2019

Color Research and Application

https://www.semanticscholar.org/paper/Review-of-instrumental-inter%E2%80%90agreement-study-of-and-Perales-Micó-Vicent/1855ced4cabffe1a464b348c37ce432aef236530

On Visual Attractiveness of Anisotropic Effect Coatings

J. Filip, M. Kolafová

Method and matrix for measuring the colour gamut of a gonio-apparent coating

https://patents.google.com/patent/WO2015092097A1/en

A General Framework for Pearlescent Materials

IBÓN GUILLÉN, Universidad de Zaragoza – I3A
JULIO MARCO, Universidad de Zaragoza – I3A
DIEGO GUTIERREZ, Universidad de Zaragoza – I3A
WENZEL JAKOB, École Polytechnique Fédérale de Lausanne
ADRIAN JARABO, Universidad de Zaragoza – I3A and Centro Universitario de la Defensa Zaragoza

ACM Trans. Graph., Vol. 39, No. 6, Article 253. Publication date: December 2020.

EFFECT PIGMENTS

https://www.emdgroup.com/en/expertise/effect-pigments.html

A Physically‐based Appearance Model for Special Effect Pigments

J. GuoYanjun Chen, +1 author Jingui Pan

Published 2018

Computer Graphics Forum

https://www.semanticscholar.org/paper/A-Physically%E2%80%90based-Appearance-Model-for-Special-Guo-Chen/310c2366615573db0bd5fd54d9c4a520ec07ef20

Influence of pearlescent pigments on light-fastness of water-based flexographic inks

Warsaw University of Technology, Faculty of Production Engineering, Institute of Mechanics and Printing, Department of Printing Technology, 2 Konwiktorska Street, 00-217, Warsaw, Poland

Dyes and Pigments
Volume 138, March 2017, Pages 119-128

https://www.sciencedirect.com/science/article/abs/pii/S0143720816311202?via%3Dihub

Iridescent Color: From Nature to the Painter’s Palette

Franziska Schenk and Andrew Parker
Posted Online April 11, 2011
Leonardo

Volume 44 | Issue 2 | April 2011 
p.108-115

Recent advances in the biomimicry of structural colours.

A. DumanlıT. Savin

Published 2016

Chemical Society reviews

Biomimetics, color, and the arts

F. Schenk

Published in Smart Structures 2015

https://www.semanticscholar.org/paper/Biomimetics%2C-color%2C-and-the-arts-Schenk/fb7633a363fe50d3ce7dbf38c2ef83392664f309

Goniospectrometric space curve for coatings with special effect pigments.

N. RogeljM. K. Gunde

Published 2016

Applied optics

https://www.semanticscholar.org/paper/Goniospectrometric-space-curve-for-coatings-with-Rogelj-Gunde/7b240347788ce822b18b789e5ac43dbc3ad8861f

Color changing effects with anisotropic halftone prints on metal

P. PjanicR. Hersch

Published 2015

ACM Trans. Graph.

https://www.semanticscholar.org/paper/Color-changing-effects-with-anisotropic-halftone-on-Pjanic-Hersch/f5c71d7c4d8c73266535fbef08a71c43db8a5746

Color representation and interpretation of special effect coatings.

A. FerreroE. Perales, +4 authors A. Pons

Published 2014

Journal of the Optical Society of America. A,

https://www.semanticscholar.org/paper/Color-representation-and-interpretation-of-special-Ferrero-Perales/c3c9b111beab2a607385880733296ad1d6d90027

Evolution of the Automotive Body Coating Process—A Review

Nelson K. AkafuahSadegh Poozesh, +3 authors K. Saito

Published 2016

THE Coatings

Color prediction of metallic coatings from measurements at common geometries in portable multiangle spectrophotometers

Heng FengHaisong Xu, +1 author Zhehong Wang

Published 2018

Journal of Coatings Technology and Research

https://www.semanticscholar.org/paper/Color-prediction-of-metallic-coatings-from-at-in-Feng-Xu/c7b9b9960b74f3d4183ffbf8938b0e709c9de0f1

https://www.springerprofessional.de/en/color-prediction-of-metallic-coatings-from-measurements-at-commo/15469696

Properties and application of luster pigments

W. OstertagN. Mronga

Published 1995

https://www.semanticscholar.org/paper/Properties-and-application-of-luster-pigments-Ostertag-Mronga/41a1f3022da57fb022d72161255b26c1ee281416

Pigments, Inorganic, 6. Luster Pigments

G. PfaffK. Franz, +2 authors R. Besold

Published 2009

Materials Science

https://www.semanticscholar.org/paper/Pigments%2C-Inorganic%2C-6.-Luster-Pigments-Pfaff-Franz/384fa8894d59511f42b13837adf631e325af4c5c

PEARLESCENT PIGMENTS IN PRINTING 

Tomić, I., Dedijer, S., Pinćjer, I.

University of Novi Sad

https://www.researchgate.net/publication/325896991_Pearlescent_pigments_in_printing

INKJET PRINTING OF PEARLESCENT AND METALLIC COLOURS

US10,173,449B2 DeMondt

Date of Patent: Jan.8,2019

(71) Aplicant:AGFAGRAPHICSNV,Mortsel(BE)

(72) Inventor: Roel DeMondt, Mortsel(BE)
(73) Asigne:AGFANV,Mortsel(BE)

Geotech Special Effects Pigments

https://www.geotech.nl/en/

Color characterization of coatings with diffraction pigments 

A. Ferrero, B. Bernad, J. Campos, E. Perales, J. L. Velázquez, and F. M. Martínez-Verdú

Journal of the Optical Society of America AVol. 33,Issue 10,pp. 1978-1988(2016)

https://www.osapublishing.org/josaa/abstract.cfm?uri=josaa-33-10-1978

Global color estimation of special-effect coatings from measurements by commercially available portable multiangle spectrophotometers

A. Ferrero,1,* J. Campos,1 E. Perales,2 F. M. Martínez-Verdú,2 I. van der Lans,3 and E. Kirchner3

Received September 2, 2014; accepted October 29, 2014;
posted November 7, 2014 (Doc. ID 220195); published December 3, 2014

Vol. 32, No. 1 / January 2015 / J. Opt. Soc. Am. A

Measuring and specifying goniochromatic colors

Alejandro Ferrero1, Joaquín Campos1, Esther Perales2, Ana M. Rabal1, Francisco Martínez-Verdú2, Alicia Pons1, Elisabet Chorro2 and M. Luisa Hernanz1

1Instituto de Optica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas, C/. Serrano, 144. 28006 Madrid. Spain

2Grupo de Visión y Color. Departamento de Óptica, Farmacología y Anatomía. Universidad de Alicante. Carretera de San Vicente del Raspeig s/n, 03690 Alicante. Spain

Goniocolorimetry: from measurement to representation in the CIELAB color space

Lionel Simonot

Mathieu Hébert

Damien Dupraz
STIL SA, 595 rue Pierre Berthier, Domaine de St Hilaire, F-13855 Aix en Provence Cedex 3, France

Automotive Coatings: Creating Excitement with Effect Pigments

Observation and Measurement of the Appearance of Metallic Materials. Part I. Macro Appearance

C. S. McCamy

Color measurements for pearlescent coatings

Maria E. Nadal Edward A. Early

First published: 11 December 2003

https://onlinelibrary.wiley.com/doi/abs/10.1002/col.10210

Coatings with metallic effect pigments for antimicrobial and conductive coating of textiles with electromagnetic shielding properties

How Auto Body Shops Can Address the Color Measurement Challenges of Pearlescent Paint

Posted on  May 16, 2016 by Ken Phillips

Pearlescent Pigments in Coatings – a Primer

https://www.pcimag.com/articles/105225-pearlescent-pigments-in-coatings-a-primer

Measuring Effect Pigments

https://www.pcimag.com/articles/83900-measuring-effect-pigments

Color representation and interpretation of special effect coatings 

A. Ferrero, E. Perales, A. M. Rabal, J. Campos, F. M. Martínez-Verdú, E. Chorro, and A. Pons

https://www.osapublishing.org/josaa/abstract.cfm?uri=josaa-31-2-436

Effect Pigments Market Share, Size Global Current and Future Plans, Future Growth, Regional Trend, Leading Players Updates, Industry Demand by Forecast to 2025

https://www.wicz.com/story/42834984/effect-pigments-market-share-size-global-current-and-future-plans-future-growth-regional-trend-leading-players-updates-industry-demand-by-forecast-to

APPLICATIONS, CHARACTERISTICS AND INFORMATION OF PEARL PIGMENTS

Pearlescent glass pigment

https://patents.google.com/patent/US6045914A/en

Iridescent magnetic effect pigments comprising a ferrite layer

https://patents.google.com/patent/US7678449B2/en

METALLIC (PEARLESCENT)

https://netuno.pl/en/130-metalizowane-perlowe

Effect pigments—past, present and future

Frank J.Maile Gerhard Pfaff Peter Reynders

Progress in Organic Coatings
Volume 54, Issue 3, 1 November 2005, Pages 150-163

https://www.sciencedirect.com/science/article/pii/S0300944005001608

Modeling Material Reflection with BRDFLab 

Adrià Forés1,2, Sumanta N. Pattanaik2, Carles Bosch1, Xavier Pueyo1

1 ViRVIG – Universitat de Girona 

2 University of Central Florida

Visual appearance measurement of surfaces containing pearl flakes

Ye Seul Baek, Youngshin Kwak, and Seungjoon Yang

Journal of the Optical Society of America A

Vol. 32,Issue 5,pp. 934-942(2015)

https://www.osapublishing.org/josaa/abstract.cfm?uri=josaa-32-5-934

Effect pigments for textile coating: a review of the broad range of advantageous functionalization

Journal of Coatings Technology and Research volume 14, pages35–55(2017)

https://link.springer.com/article/10.1007/s11998-016-9854-9

https://www.semanticscholar.org/paper/Effect-pigments-for-textile-coating%3A-a-review-of-of-Mahltig-Zhang/00c1c15d8da44a00fe4f78ea239cf01423dc2183

Application of the Transfer Matrix Method to Anti-reflective Coating Rendering

Benamira A., Pattanaik S. (2020)

In: Magnenat-Thalmann N. et al. (eds) Advances in Computer Graphics. CGI 2020. Lecture Notes in Computer Science, vol 12221. Springer, Cham.

https://link.springer.com/chapter/10.1007/978-3-030-61864-3_8#citeas

Angle Resolved Light Scattering in Turbid Media

Analysis and Applications

Magnus Neuman

Licentiate Thesis No. 56 Ha ̈rno ̈sand, Sweden 2011

Geometry Related Inter-Instrument Differences in Spectrophotometric Measurements

Edström, Per
Neuman, Magnus
Avramidis, Stefanos
Andersson, Mattias

DOI: 10.3183/NPPRJ-2010-25-02-p221-232

https://www.researchgate.net/publication/228470650_Geometry_Related_Inter-Instrument_Differences_in_Spectrophotometric_Measurements

Global Special Effect Pigments (Metallic, Pearlescent) Market, 2022 – Focus on Plastics, Paints & Coatings, Printing Inks, & Cosmetics

https://www.prnewswire.com/news-releases/global-special-effect-pigments-metallic-pearlescent-market-2022—focus-on-plastics-paints–coatings-printing-inks–cosmetics-300481356.html

Ceramic application of mica titania pearlescent pigments

Patrícia M. Tenório Cavalcante1, Michele Dondi2, Guia Guarini2, Fernanda M. Barros1, Adão Benvindo da Luz

Dyes and Pigments, 74 (2007) 1–7

Colorimetric characterization of pearlescent coatings

Maria E. NadalThomas A. Germer

Proceedings Volume 4421, 9th Congress of the International Colour Association; (2002)

https://doi.org/10.1117/12.464577
Event: 9th Congress of the International Color Association, 2001, Rochester, NY, United States

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/4421/0000/Colorimetric-characterization-of-pearlescent-coatings/10.1117/12.464577.short?SSO=1

Characterization of gonio-apparent colours

F. Leloup, P. Hanselaer, M. Pointer*, and J. Versluys

Laboratory for Optical Measurements and Lighting Technology

KaHo Sint-Lieven, Gebr. Desmetstraat 1,

B-9000 Gent (BELGIUM)

* National Physical Laboratory, Teddington, TW11 0LW (UK)

Modeling the appearance of special effect pigment coatings

Thomas A. Germer and Maria E. Nadal

Optical Technology Division National Institute of Standards and Technology Gaithersburg, Maryland 20899

Published in Surface Scattering and Diffraction for Advanced Metrology,

Zu-Han Gu and Alexei A. Maradudin, Eds. Proc. SPIE 4447, 77–86 (2001).

Angle-Dependent Optical Effects Deriving from Submicron Structures of Films and Pigments

Chem. Rev. 1999, 99, 7, 1963–1982

Publication Date:June 11, 1999

https://pubs.acs.org/doi/10.1021/cr970075u

Use of effect pigments for quality enhancement of offset printed specialty papers

Mirica Debeljak Aleš Hladnik Lidija Černe Diana Gregor‐Svetec

First published: 22 February 2012

Color Research and Application

Volume 38, Issue3
June 2013
Pages 168-176

https://onlinelibrary.wiley.com/doi/10.1002/col.20753

Pearlescent Pigments

https://encyclopedia.pub/805#1._Introduction

The Chemistry and Physics of Special-Effect Pigments and Colorants for Inks and Coatings

Paints and Coatings Industry

https://www.pcimag.com/articles/85016-the-chemistry-and-physics-of-special-effect-pigments-and-colorants-for-inks-and-coatings?

Fascinating displays of colour

Effect pigments – A successful interplay of chemistry and physics

Prof. Dr Gerhard Pfaff, Merck KGaA Darmstadt, Germany

Pearlescent Pigments – The Science of Optics

https://www.spmorell.com/newsletters/pearlescent_pigments/pearlescent_pigments.html

The New Generation of Physical Effect Colorants

Faiz Rahman and Nigel P. Johnson

February 2008  Optics and Photonics

https://www.osa-opn.org/home/articles/volume_19/issue_2/features/the_new_generation_of_physical_effect_colorants/

Ceramic Coatings for Pigments

  • February 2012
  • In book: Ceramic Coatings – Applications in Engineering

Alireza Mirhabibi

https://www.researchgate.net/publication/221925909_Ceramic_Coatings_for_Pigments

Optical analysis of coatings including diffractive pigments using a high-resolution gonioreflectometer

Jiří Filip, Radomír Vávra & Frank J. Maile

Journal of Coatings Technology and Research

https://doi.org/10.1007/s11998-018-0137-5

“Anisotropic reflectance from turbid media. I. Theory,”

M. Neuman and P. Edstro ̈m,

J. Opt. Soc. Am. A 27, 1032–1039 (2010).

“Anisotropic reflectance from turbid media. II. Measurements,”

M. Neuman and P. Edstro ̈m,

J. Opt. Soc. Am. A 27, 1040–1045 (2010).

“Geometry related inter-instrument differences in spectrophotometric measurements,”

P. Edstro ̈m, M. Neuman, S. Avramidis, and M. Andersson,

Nord. Pulp Pap. Res. J. 25, 221–232 (2010).

“Angular variations of color in turbid media – the influence of bulk scattering on goniochromism in paper,”

M. Neuman, P. Edstro ̈m, M. Andersson, L. Coppel, and O. Norberg,

in Proc. of 5th European Confer- ence on Colour in Graphics, Imaging and Vision, (Joensuu, Finland, 2010), pp. 407–413.

“Point spreading in turbid media with anisotropic single scattering,”

M. Neuman, L. G. Coppel, and P. Edstro ̈m,

Opt. Express 19, 1915–1920 (2011).

Special Effects Pigments

Gerhard Pfaff

Chapter in Book

High Performance Pigments

Edited by
Edwin B. Faulkner and Russell J. Schwartz

Special Effects Pigments

Technical Basics and Applications

Book by Gerhard Pfaff published in 2008

Special Effects Pigments

Book Chapter by Gerhard Pfaff

In Industrial Inorganic Pigments

Edited by G. Buxbaum and G. Pfaff

Inorganic Pigments

Book by Gerhard Pfaff, PhD

2017

Degruyter

Measuring Metallic and Special Effect Automotive Finishes

https://www.xrite.com/learning-color-education/using-our-solutions/measuring-effect-finishes-paint

Pearlescent PIGMENTS in Coatings A Primer

http://www.pcizone.com/details.php?id=6890

Photonics Measures the Quality of Automotive Paint

https://www.photonics.com/Articles/Photonics_Measures_the_Quality_of_Automotive_Paint/a23155

Measuring special effect: Comparison of Spectrophotometers

Multiangle Spectrophotometer Technology

https://www.konicaminolta.com/about/research/instruments/instrument_001.html

Rendering Pearlescent Appearance Based On Paint-Composition Modelling

Sergey Ershov , Konstantin Kolchin and Karol Myszkowski

Photo-realistic Rendering of Metallic Car Paint from Image-Based Measurements

Martin Rump, Gero Müller, Ralf Sarlette, Dirk Koch and Reinhard Klein Institute for Computer Science II, University of Bonn †

CCM system for Metallic and Pearlescent Colors

Applied Multi-Angle Image and Spectrum

Masayuki Osumi

Effect Pigments for Industry

CQV Korea

Special effect pigments in cosmetic applications

An amazing development for a bright future

Gerhard Pfaff

A General Micro-flake Model for Predicting the Appearance of Car Paint

S. Ergun1 and S. Önel2 and A. Ozturk

Eurographics Symposium on Rendering – Experimental Ideas & Implementations (2016) E. Eisemann and E. Fiume (Editors)

Efficient representation of bidirectional reflectance distribution functions for metallic paints considering manufacturing parameters

DOI: 10.1117/1.3529429

Myoung Kook Seo

Kang Yeon Kim

Duck Bong Kim

Hiu Kwan Lee

https://www.researchgate.net/publication/253321753_Efficient_representation_of_bidirectional_reflectance_distribution_functions_for_metallic_paints_considering_manufacturing_parameters

Essentials of Effect Pigments (infographic)

Effect pigments for textile coating: a review of the broad range of advantageous functionalization

Boris Mahltig, 17 November 2016

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Color Change: In Biology and Smart Pigments Technology

  • Color change due to Pigment
  • Color change due to Structure

This post is on color change due to pigments.

In a future post, I will research structural colors.

Key Words

  • Color Change in Biology
  • Color Change using Technology
  • Smart Pigments
  • Thermochromic property
  • Photochromic property
  • Piezochromic property
  • Solvatochromic property
  • Chimiochromic property
  • Electrochromism
  • Smart Textiles
  • Smart Plastics
  • Smart Paper
  • Smart Inks
  • Smart Food Packaging
  • Color Science
  • Material Science
  • Color Fading
  • Color Fastness
  • Color Metamerism
  • Chromatophores
  • Iridophores
  • Leucophores
  • Chlorophyll
  • Anthrocyanins
  • Flavonols
  • Flavonoids

Color Change and Technology

Chromic phenomena in dyes and pigments

Some of the major companies are

  • LCR Hallcrest LLC
  • Hali Pigment Co. Ltd
  • Chromatic Technologies Inc.
  • QCR Solutions Corp.
  • OliKrom
  • SFXC
  • MICI
  • RPM International Inc.
  • Good Life Innovations Ltd
  • FX Pigments Pvt. Ltd
  • Smarol Industry Co. Ltd
  • Kolortek Co. Ltd
  • Kolorjet Chemicals Pvt. Ltd
  • Colourchange

Source: OliKrom

Smart Hybrid Pigments

The solutions developed by OliKrom involve a new generation of hybrid pigments that combines the proven strength of the metal ions and the flexibility of the molecular material. The change in the structure allow to control the color change as a function of :

  • Temperature (thermochromic property),
  • Light (photochromic property),
  • Pressure (piezochromic property),
  • A solvent (solvatochromic property),
  • A gas (chimiochromic property),

The expertise of OliKrom allows for each of these properties:

  • To adjust the request colors,
  • To obtain reversible and/or irreversible color-shifting,
  • To modulate the speed of the color change,
  • To control the issues of fatigability.
  • To insert these adaptive pigments in a formulation (paint, ink, masterbatch, …) without altering the properties!
  • To produce on an industrial scale paintings, inks, master batches, …

Applications

SAFETY
  • Threshold temperature indicators / industrial pipes, thermal mapping.
  • Display: visual aid in the detection of ice.
  • Indicator of “health matter”, gauge effort, shock detection (Aeronautic & Navy).
  • Control: Temperature Indicator for monitoring sensitive products: cold chain, transport & medical vaccines or blood products.
  • Sterilization indicator: labels or inks.
  • Adhesives: indicator of adhesion, optimum drying.
  • Food Packaging: temperature indicator for the consumption of a product: beer, wine, vodka, champagne, cans and bottles, hot and cold drinks, baby food.
TRACEABILITY / INFRINGEMENT
  • Irreversible overheat indicator of industrial processes.
  • Security inks: offset ink for ticketing, games, secure access badges.
  • Infringement Indicator: branded article, banknote.
DECORATION / MARKETING / ADVERTISING
  • Plastic toys: decor with changing color, labels, packaging, paper / plastic promotional, “dynamic” advertising inserts.
  • Cosmetics: Bottles & Jars of cosmetic or perfume.
  • Smart Textiles: comfort indicator, clarification of the textile with temperature.

Fluorescent Pigments and Phosphorescent Pigments

Source: PHOTOLUMINESCENTS: FLUORESCENT AND PHOSPHORESCENT INKS AND PAINTS / OliKrom

Photochromic Pigments

Piezochromic Pigments

Thermochromic

Type

  • Reversible Thermochromic Material
  • Irreversible Thermochromic Material

Material

  • Liquid Crystal
  • Leuco Dyes
  • Pigment
  • Other Materials

Application

  • Roof Coatings
  • Printing
  • Food Packaging
  • Cosmetics
  • Other Applications

Solvachromes and Chemochromes

Color Change in Biology

Animals
  • Chameleon
  • Golden Tortoise Beetle
  • Mimic Octopus
  • Pacific Tree Frog
  • Sea Horses
  • Flounders
  • Cuttlefish
  • Crab Spiders
  • Squid
  • Cyanea Octopus

Mechanisms for Color Change

  • Chromatophores
  • Leucophores
  • Iridophores

Source: Adaptive camouflage helps blend into the environment 

Cephalopods such as cuttlefish often use use adaptive camouflage to blend in with their surroundings. They are able to match colors and surface textures of their surrounding environments by adjusting the pigment and iridescence of their skin.

On the skin surface, chromatophores (tiny sacs filled with red, yellow, or brown pigment) ab­sorb light of various wavelengths. Once vis­ual input is processed, the cephalopod sends a signal to a nerve fiber, which is connected to a muscle. That muscle relaxes and contracts to change the size and shape of the chromato­phore. Each color chromatophore is controlled by a different nerve, and when the attached muscle contracts, it flattens and stretches the pigment sack outward, expanding the color on the skin. When that muscle relaxes, the chro­matophore closes back up, and the color dis­appears. As many as two hundred of these may fill a patch of skin the size of a pencil eraser, like a shimmering pixel display.

The innermost layer of skin, composed of leuc­ophores, reflects ambient light. These broadband light reflectors give the cephalopods a ‘base coat’ that helps them match their surroundings.

Between the colorful chromatophores and the light-scattering leucophores is a reflective lay­er of skin made up of iridophores. These reflect light to create pink, yellow, green, blue, or silver coloration, while the reflector cells (found only in octopuses) reflect blue or green.

Source: https://www.worldatlas.com/articles/10-animals-that-can-change-colors.html

10 Animals That Can Change Colors

The mimic octopus changes their skin tone and body shape to copy other sea creatures.
The mimic octopus changes their skin tone and body shape to copy other sea creatures. 

There are a few animals that have the unique ability to change colors. The ability to change colors can help animals protect themselves against their predators because it allows them to blend into their natural environment. Here is a list of 10 color changing animals.

10. Chameleon

A chameleon is a unique species of lizard famous for changing its skin color. It does so to camouflage with its surrounding. Sometimes chameleons change their color when they are angry or fearful. To change its color, the chameleon adjusts a layer of specialized cells underlying its skin. Others change color in response to humidity, light, and temperature. Chameleons never stop growing. They keep shedding their skin from time to time. Furthermore, chameleons have excellent eyesight characterized by a 360-degree arc vision. Although chameleons do not hear, their bodies detect sound within the surrounding.

9. Golden Tortoise Beetle

The golden tortoise beetle is an insect that can change its color. The species with this ability include Charidotella sexpunctata and Charidotella egregia. The tortoise beetles change color due to particular events that occur in their environment. Such events include meeting a willing mate and being touched by a curious human being. Hence, when they are mating or agitated, the tortoise beetles change their color from gold to a bright red color. The change of color occurs due to a process referred to as optical illusion.

8. Mimic Octopus

Mimic octopus, scientifically known as Thaumoctopus mimicus, change their color and they can also mimic other sea creatures such as a lionfish, jellyfish, stingrays, and sea snakes. The mimic octopus can pick the color of the sea creature that they intend to mimic. The mimic octopuses change their body shape to avoid potential predators. The change of skin color helps them to adapt to their surrounding. Mimic octopuses can change color and mimic shapes due to their skin which is very responsive to the environment.

7. Pacific Tree Frog

The Pacific Tree Frog inhabits North America. One of its common features is the sticky toe pads. The sticky toe pads enable them to climb trees and plants. The Pacific Tree Frog changes its color to blend in with its surroundings. The change of color is a defense mechanism against predators such as raccoons, bullfrogs, snakes, heron, and many others. Pacific Tree Frogs also change their color based on the seasons and temperature. When the temperatures are high, they turn into a shade of yellow. An example of Pacific Tree Frog species that changes color is Hyla regilla. The process of color change in Pacific Tree Frogs takes 1-2 minutes.

6. Seahorses

Seahorses, such as the thorny seahorse, are among the marine animals that have mastered changing their color. The purpose of changing their skin color is to camouflage, frighten predators, communicate their emotions, and for courtship. Complex interactions between the brain, nervous system, hormones, and organelles make it possible for the seahorses to change their color. The organelles responsible for these color changes are known as chromatophores. Regarding the speed at which the skin color changes, this depends on the stimulus. For instance, in a life or death situation such as involving a predator, the color changes quickly. But whenever the seahorse is courting a mate, the change takes place slowly.

5. Flounders

Flounders are naturally brown. However, they can change color to suit their surroundings. A flounder uses its vision and specialized cells inside the skin to change color. The cells, in turn, have color pigments and are linked to the eyes of the flounders. When a flounder moves to a new environment, the retina in the eyes captures the new color. Consequently, the color seen by the eyes are transmitted to the cells. The cells adjust the pigmentation to match the surface color. Scientists have discovered that flounders depend entirely on their vision to change color. When their eyes are damaged, then they have difficulties in camouflaging to their surrounding. An example of flounder species that changes color is the peacock flounder.

4. Cuttlefish

Cuttlefish are cephalopods that change color to feed on prey and avoid predators craftily. They have three mechanisms by which they can change color. Firstly, the cuttlefish skin contains papillae that alter the tone of the fish. The papillae cause the skin to become smooth or rough depending on the environment. Secondly, camouflaging is possible because of the chromatophores in their skin. The chromatophores are sacs of color pigments. To change color, these sacs receive color-changing instructions from the brain and act accordingly. Lastly, cuttlefish have reflecting plates called leucophores and iridophores. The plates enable the fish to change its color.

3. Crab Spiders

Spiders called flower spiders (or crab spiders) change their color. They usually change color to hide from their prey. Consequently, the spiders change color to resemble the flower surface on which they sit through the reflection of light. Some spiders release a yellow pigment that enhances their color changing process. An example of a species of spider with such color changing features is Misumenoides formosipes and Misumena vatia. The color change from white to yellow takes 10-25 days. Hence, the flower spiders patiently wait for the completion of the process before they can attack their prey.

2. Squid

Squids are marine cephalopods. They possess two long tentacles and eight arms. An interesting fact about the squids is that their blood is blue. Furthermore, they have three hearts instead of one like other fish. The squids are uniquely beautiful and able to change color. They change color using chromatophores engraved in their skin. The purpose of changing color is to match the surface they are on so that they can avoid predators. The camouflage also acts as a hunting tactic since it enables them to hide away from their prey.

1. Cyanea Octopus

Known as the big blue octopus or the day octopus, octopus cyabea is found in the waters of the Indo-Pacific. It is known as the day octopus as it is most active during the daytime in contrast to most other octopus species. The cyanea octopus is especially adept at camouflage, able to not only frequently change the color of their skin, but also recreate patterns and textures. On the hunt for crabs, molluscs, shrimp, and fish, the cyanea octopus is able to quickly adapt its appearance to its surroundings, even mimicking moving shadows such as overhead clouds.

Color Change in Plants And Flowers

Color change in Leaves and Flowers

  • Chlorophyll – Green
  • Cartenoids – Xanthophylls – Yellow as in Corn
  • Cartenoids – Carotenes – Orange as in Carrots
  • Anthrocyanins – Blueberries and Cherries – Blue, purple, red, pink
  • Flavonols – Pale yellows and whites

Plants change colors

  • Change in Heat
  • Change in pH
  • During the Fall
  • During the day

Color Fading and Color Metamerism are also important problems but are not discussed in this post.

Source: The science behind why leaves change color in autumn

A rainbow of autumn colors

The green color of chlorophyll is so strong that it masks any other pigment. The absence of green in the fall lets the other colors come through. Leaves also contain the pigments called carotenoids; xanthophylls are yellow (such as in corn) and carotenes are orange (like in carrots). Anthocyanins (also found in blueberries, cherries) are pigments that are only produced in the fall when it is bright and cold. Because the trees cut off most contact with their leaves at this point, the trapped sugar in the leaves’ veins promotes the formation of anthocyanins, which are used for plant defense and create reddish colors.

However, trees in the fall aren’t just yellow and red: they are brown, golden bronze, golden yellow, purple-red, light tan, crimson, and orange-red. Different trees have different proportions of these pigments; the amount of chlorophyll left and the proportions of other pigments determine a leaf’s color. A combination of anthocyanin and chlorophyll makes a brown color, while anthocyanins plus carotenoids create orange leaves.

Source: The science behind why leaves change color in autumn

Source:https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-turning-different-color.htm

Can Hibiscus Change Color: Reasons For Hibiscus Turning A Different Color

07/20/20

Can hibiscus change color? The Confederate Rose (Hibiscus mutabilis) is famous for its dramatic color changes, with flowers that can go from white to pink to deep red within one day. But almost all hibiscus varieties produce flowers that can change colors under certain circumstances. Read on to learn more.

Reasons for Color Changing in Hibiscus

If you’ve ever noticed the flowers on your hibiscus turning a different color, you’ve probably wondered what was behind the change. To understand why this happens, we need to look at what creates flower colors in the first place.

Three groups of pigments create the vibrant color displays of hibiscus flowers. Anthocyanins produce blue, purple, red, and pink colors, depending on the individual pigment molecule and the pH it is exposed to. Flavonols are responsible for pale yellow or white colors. Carotenoids create colors on the “warm” side of the spectrum – yellows, oranges, and reds.

Each hibiscus variety has its own genetics that determine what pigments, and what range of colors it can produce. However, within that range, temperature, sunlight, pH, and nutrition can all affect the levels of different pigments in a flower and what color they appear.

The blue- and red-colored anthocyanins are water-soluble pigments carried in plant sap. Meanwhile, the red, orange and yellow carotenoids are fat-soluble pigments created and stored in the plastids (compartments in plant cells similar to the chloroplasts that carry out photosynthesis). Therefore, anthocyanins are less protected and more sensitive to environmental changes, while carotenoids are more stable. This difference helps explain the color changes in hibiscus.

Anthocyanins exposed to hot conditions will often break down, causing flower colors to fade, while carotenoid-based colors hold up well in the heat. High temperatures and bright sunlight also enhance carotenoid production, leading to bright reds and oranges.

On the other hand, plants produce more anthocyanins in cold weather, and the anthocyanins they produce tend to be more red- and pink-colored as opposed to blue or purple. For this reason, some anthocyanin dependent hibiscus flowers will produce brilliant color displays during cool weather or in partial shade, but will fade in bright, hot sunlight.

Similarly, flavonols exposed to high temperatures will fade from yellow to white, while cold weather will cause an increase in production and a deepening of yellow flower colors.

Other Factors in Hibiscus Color Change

Some anthocyanin pigments will change color depending on the pH they’re exposed to within the flower. The pH doesn’t usually change over time within a hibiscus flower because it is determined genetically, but patches of different pH levels can lead to multiple colors occurring within one flower.

Nutrition is also a factor in color changes. Adequate sugar and protein in the sap are required for anthocyanin production. Making sure your plant has enough fertility and nutrients is important for vibrant colors in anthocyanin dependent flowers.

So, depending on its variety, your hibiscus changed color because of some combination of temperature, sunlight, nutrition, or pH has taken place. Can gardeners control this hibiscus color change? Yes, indirectly – by controlling the plant’s environment: shade or sun, good fertility, and protection from hot or cold weather.

Source: https://www.loc.gov/everyday-mysteries/botany/item/what-causes-flowers-to-have-different-colors/

What causes flowers to have different colors?

Answer

Anthocyanins and carotenoids… plus some other things.

Flowers come in all shapes and sizes, but what makes them truly stand apart from each other is their vibrant colors.  These colors are made up of pigments and, generally speaking, the fewer the pigments, the lighter the color.  The most common pigments in flowers come in the form of anthocyanins.  These pigments range in color from white to red to blue to yellow to purple and even black and brown.  A different kind of pigment class is made up of the carotenoids.  Carotenoids are responsible for some yellows, oranges, and reds.  (These little guys are what cause the brilliant colors of autumn leaves!)  While many flowers get their colors from either anthocyanins or carotenoids, there are some that can get their colors from a combination of both.

Anthocyanins and carotenoids are the main sources of flower coloration, but there are other factors that can affect how colors present themselves.  The amount of light flowers receive while they grow, the temperature of the environment around them, even the pH level of the soil in which they grow can affect their coloration.  Another factor is stress from the environment.  This stress can include a drought or a flood or even a lack of nutrition in the soil, all of which can dampen the coloration of flowers.  And then, of course, there is the visual that the eye and brain form together: humans can, for the most part, view all colors in the visible spectrum, BUT every human perceives color differently, so a red rose may appear more vibrant to one person while it appears more muted to another.  Beauty (and color!) is in the eye of the beholder.

My Related Posts

Digital Color and Imaging

Color and Imaging in Digital Video and Cinema

On Light, Vision, Appearance, Color and Imaging

On Luminescence: Fluorescence, Phosphorescence, and Bioluminescence

Key Sources of ResearCH

Photochromic and Thermochromic Colorants in Textile Applications

M. A. Chowdhury, M. Joshi and B. S. Butola

https://journals.sagepub.com/doi/pdf/10.1177/155892501400900113

THE CHEMISTRY & PHYSICS OF
SPECIAL EFFECT PIGMENTS & COLORANTS

A. NURHAN BECIDYAN

President
UNITED MINERAL & CHEMICAL CORPORATION

PHOTOLUMINESCENTS: FLUORESCENT AND PHOSPHORESCENT INKS AND PAINTS

Structural colour and iridescence in plants: the poorly studied relations of pigment colour

Beverley J. Glover1,* and  Heather M. Whitney2

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2850791/

Analysing photonic structures in plants 

Silvia Vignolini1,2, Edwige Moyroud3, Beverley J. Glover3 and Ullrich Steiner1

1Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK 2Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK 3Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK

The Mechanism of Color Change in the Neon Tetra Fish: a Light‐Induced Tunable Photonic Crystal Array

Dvir Gur 1 , Benjamin A Palmer 1 , Ben Leshem 2 , Dan Oron 2 , Peter Fratzl 3 , Steve Weiner 1 , Lia Addadi 4

First published: 27 April 2015

https://pubmed.ncbi.nlm.nih.gov/25914222/

10 Animals that can Change Colors

https://www.worldatlas.com/articles/10-animals-that-can-change-colors.html

How Octopuses and Squids Change Color

https://ocean.si.edu/ocean-life/invertebrates/how-octopuses-and-squids-change-color

Why color-changing animals alter their appearance

By Zach Fitzner

Earth.com staff writer

Iridophores and their interactions with other chromatophores are required for stripe formation in zebrafish

Hans Georg Frohnhöfer, Jana Krauss, Hans-Martin Maischein, Christiane Nüsslein-Volhard

Development  2013  140: 2997-3007;  doi: 10.1242/dev.096719

https://dev.biologists.org/content/140/14/2997.article-info

Magic Traits in Magic Fish: Understanding Color Pattern Evolution Using Reef Fish

Author links open overlay panelPaulineSalis1ThibaultLorin2VincentLaudet1BrunoFrédérich3

https://www.sciencedirect.com/science/article/abs/pii/S0168952519300162

Developmental and comparative transcriptomic identification of iridophore contribution to white barring in clownfish. 

https://www.x-mol.com/paper/959131

Rapid integumental color changes due to novel iridophores in the chameleon sand tilefish Hoplolatilus chlupatyi

Makoto Goda

First published: 13 February 2017 https://doi.org/10.1111/pcmr.12581

https://onlinelibrary.wiley.com/doi/abs/10.1111/pcmr.12581

Flashing Tilefish’s Color Changing Skin is Unique in the Animal World

Top 10 Colour Changing Animals Around the World

Chameleon-Inspired Variable Coloration Enabled by a Highly Flexible Photonic Cellulose Film

  • Ze-Lian Zhang, 
  • Xiu Dong, 
  • Yi-Ning Fan, 
  • Lu-Ming Yang, 
  • Lu He, 
  • Fei Song*
  • Xiu-Li Wang, and 
  • Yu-Zhong Wang*

Cite this: ACS Appl. Mater. Interfaces 2020, 12, 41, 46710–46718Publication Date:September 23, 2020

https://pubs.acs.org/doi/10.1021/acsami.0c13551

The secret to chameleon color change: Tiny crystals

By Robert F. ServiceMar. 10, 2015 

https://www.sciencemag.org/news/2015/03/secret-chameleon-color-change-tiny-crystals

Amazing Octopus Color Transformation | National Geographic

How do Octopuses Change Color?

Here’s everything you ever wanted to know about chromatophores.

Study demonstrates that octopus’s skin possesses same cellular mechanism for detecting light as its eyes do

by  University of California – Santa Barbara

https://phys.org/news/2015-05-octopus-skin-cellular-mechanism-eyes.html

Progress and Opportunities in Soft Photonics and Biologically Inspired Optics

Mathias KolleSeungwoo Lee

First published: 23 October 2017

https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.201702669

https://pubmed.ncbi.nlm.nih.gov/29057519/

https://onlinelibrary.wiley.com/doi/am-pdf/10.1002/adma.201702669

Bioinspired living structural color hydrogels

Fanfan Fu, Luoran Shang, Zhuoyue Chen, Yunru Yu, Yuanjin Zhao

Smart pigments with reactive nanocolors printed on paper and flexibles

2009 International Conference on Nanotechnology for the Forest Products Industry

Click to access 09nan23.pdf

Thermochromic Material

https://www.sciencedirect.com/topics/engineering/thermochromic-material

Color Changing Plastics for Food Packaging

By

Lizanel Feliciano
Ohio State University, Columbus, Ohio

Smart dyes for medical and other textiles

  • February 2007

DOI: 10.1533/9781845692933.1.123

Tatjana Rijavec, Sabina Bračko

University of Ljubljana

https://www.researchgate.net/publication/288402591_Smart_dyes_for_medical_and_other_textiles

Thermochromic colors in textiles

S. Periyasamy, Gaurav Khanna

https://www.fibre2fashion.com/industry-article/3059/thermochromic-colors-in-textiles

“Smart” fluorescent dyes change color in different solid states

Aug 21st, 2018

https://www.laserfocusworld.com/lasers-sources/article/16571232/smart-fluorescent-dyes-change-color-in-different-solid-states

Materials that Change Color

Smart Materials, Intelligent Design
  • Marinella Ferrara
  • Murat Bengisu

https://link.springer.com/book/10.1007%2F978-3-319-00290-3#about

Switching Colors with Electricity

BY  ROGER J. MORTIMER

American Scientist

JANUARY-FEBRUARY 2013

VOLUME 101, NUMBER 1

https://www.americanscientist.org/article/switching-colors-with-electricity

Smart textiles change colour on demand


Friday, 13 May 2016

https://portal.engineersaustralia.org.au/news/smart-textiles-change-colour-demand

Design Concepts for a Temperature-sensitive Environment Using Thermochromic Colour Change

Robert M Christie, Sara Robertson and Sarah Taylor

Colour: Design & Creativity (2007) 1 (1): 5, 1–11

Smart responsive phosphorescent materials for data recording and security protection

Huibin Sun1,2,􏰀, Shujuan Liu1,􏰀, Wenpeng Lin1, Kenneth Yin Zhang1, Wen Lv1, Xiao Huang2, Fengwei Huo2, Huiran Yang1, Gareth Jenkins1,2, Qiang Zhao1 & Wei Huang1,2

Received 21 Oct 2013 | Accepted 10 Mar 2014 | Published 7 April 2014

NATURE COMMUNICATIONS 

https://www.nature.com/articles/ncomms4601.pdf?origin=ppub

Anthocyanin food colorant and its application in pH-responsive color change indicator films

Swarup Roy & Jong-Whan Rhim (2020)

Critical Reviews in Food Science and Nutrition,

DOI: 10.1080/10408398.2020.1776211

Smart monitoring of gas/temperature changes within food packaging based on natural colorants

COMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY

2020;19:2885–2931.

DOI: 10.1111/1541-4337.12635

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/1541-4337.12635

Smart textiles: an overview of recent progress on chromic textiles

Heloisa Ramlow Karina Luzia Andrade  & Ana Paula Serafini Immich 

Pages 152-171 | Received 20 Feb 2019, Accepted 24 Oct 2019, Published online: 29 Jun 2020

The Journal of The Textile Institute Volume 112, 2021 – Issue 1

https://www.tandfonline.com/doi/abs/10.1080/00405000.2020.1785071

Anthocyanin – A Natural Dye for Smart Food Packaging Systems

Suman Singh1, Kirtiraj K. Gaikwad2, and Youn Suk Lee3*

https://www.semanticscholar.org/paper/Anthocyanin-–-A-Natural-Dye-for-Smart-Food-Systems-Singh-Forestry/4f41ec48d77d61bc05decd7738a672f414f9b2db?p2df

Critical Review on Smart Chromic Clothing

Esraa El-Khodary1, Bahira Gebaly2, Eman Rafaat2, Ahmed AlSalmawy2

Colorimetric properties of reversible thermochromic printing inks

Rahela Kulcar a, Mojca Friskovec b, Nina Hauptman c, Alenka Vesel d, Marta Klanjsek Gunde

Dyes and Pigments 86 (2010) 271e277

Designing Smart Textiles Prints with Interactive Capability

Prof. Hoda Abdel Rahman Mohamed El-Hadi 1 ,Prof. Sherif Hassan Abdel Salam 2 Eng. Kholoud Hassan Mohamed Mahmoud

Smart Chromic Colorants Draw Wide Attention for the Growth of Future Intelligent Textile Materials

Amit Sengupta#& Jagadananda Behera

Wool Research Association, Thane, India

LEUCO DYE-BASED THERMOCHROMIC INKS: RECIPES AS A GUIDE FOR DESIGNING TEXTILE SURFACES

MARJAN KOOROSHNIA Swedish School of Textiles

Relation between colour- and phase changes of a leuco dye-based thermochromic composite

Scientific Reports volume 8, Article number: 5511 (2018)

https://www.nature.com/articles/s41598-018-23789-2

The Chemistry and Physics of Special-Effect Pigments and Colorants for Inks and Coatings

Paints and Coatings

2003

https://www.pcimag.com/articles/85016-the-chemistry-and-physics-of-special-effect-pigments-and-colorants-for-inks-and-coatings

THERMOCHROMIC MATERIAL MARKET

https://www.mordorintelligence.com/industry-reports/thermochromic-material-market

QCR Solutions Corp

OliKrom

The Effective Use of Interference and Polychromatic Colorants

https://www.pcimag.com/articles/102445-the-effective-use-of-interference-and-polychromatic-colorants

White reflection from cuttlefish skin leucophores

Cephalopod Camouflage: Cells and Organs of the Skin

https://www.nature.com/scitable/topicpage/cephalopod-camouflage-cells-and-organs-of-the-144048968/

Chromatophore Organs, Reflector Cells, Iridocytes and Leucophores in Cephalopods

RICHARD A. CLONEY AND STEVEN L. BROCCO

Mechanisms and behavioural functions of structural coloration in cephalopods

Lydia M. Ma ̈thger1,2,3,*,†, Eric J. Denton3,‡, N. Justin Marshall2 and Roger T. Hanlon1

J. R. Soc. Interface (2009) 6, S149–S163

Cephalopod Camouflage: Cells and Organs of the Skin

https://www.nature.com/scitable/topicpage/cephalopod-camouflage-cells-and-organs-of-the-144048968/

Chromatophore

https://en.wikipedia.org/wiki/Chromatophore

Leucophores are similar to xanthophores in their specification and differentiation processes in medaka

https://www.researchgate.net/publication/262111984_Leucophores_are_similar_to_xanthophores_in_their_specification_and_differentiation_processes_in_medaka

Identification and Characterization of Highly Fluorescent Pigment Cells in Embryos of the Arabian Killifish (Aphanius Dispar)

On leucophores and the chromatic unit of Octopus vulgaris

D. Froesch1J. B. Messenger2

https://zslpublications.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-7998.1978.tb03363.x

Adaptive camouflage helps blend into the environment 

Cuttlefish

https://asknature.org/strategy/adaptive-camouflage-helps-blend-into-the-environment/

Identification of kit-ligand a as the Gene Responsible for the Medaka Pigment Cell Mutant few melanophore

THE SECRET OF A SQUID’S ABILITY TO CHANGE COLORS MAY LIE IN AN UNEXPECTED SPARKLE ON ITS SKIN

INVISIBILITY IS (ALMOST) POSSIBLE WHEN HUMAN CELLS ARE MERGED WITH SQUID GENES

https://www.syfy.com/syfywire/human-cells-merged-with-squid-invisibility-trait

How Cephalopods Change Color

By Dr. James Wood and Kelsie Jackson

ELECTRONIC PAPER DISPLAYS: Kindles and cuttlefish: Biomimetics informs e-paper displays

https://www.laserfocusworld.com/detectors-imaging/article/16549524/electronic-paper-displays-kindles-and-cuttlefish-biomimetics-informs-epaper-displays

Skin paterning in Octopus vulgaris and its importance for camouflage

Iridophores and Not Carotenoids Account for Chromatic Variation of Carotenoid-Based Coloration in Common Lizards ( Lacerta vivipara ).

Biological vs. Electronic Adaptive Coloration: How Can One Inform the Other?

Eric Kreit1, Lydia M. Mäthger2, Roger T. Hanlon2, Patrick B. Dennis3, Rajesh R. Naik3, Eric Forsythe4 and Jason Heikenfeld1*

The Chemistry of Biological Camouflage

https://www.chemistryislife.com/the-chemistry-of-biological-camouflage

Mechanisms and behavioural functions of structural coloration in cephalopods

https://espace.library.uq.edu.au/view/UQ:170626

Sepiida algorithm for solving optimal reactive power problem

Are You Ready for Plants That Change Color?

Why Leaves Change Color

https://www.esf.edu/pubprog/brochure/leaves/leaves.htm

Can Hibiscus Change Color: Reasons For Hibiscus Turning A Different Color

https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-turning-different-color.htm

What causes flowers to have different colors?

https://www.loc.gov/everyday-mysteries/botany/item/what-causes-flowers-to-have-different-colors/

The science behind why leaves change color in autumn

Why has my plant’s flower changed colour?

Why Does Cannabis Change Colors?

https://cannabis.net/blog/strains/why-does-cannabis-change-colors

A cyborg plant with color-changing leaves? Scientists just rose to the challenge.

https://www.washingtonpost.com/news/speaking-of-science/wp/2015/11/23/a-cyborg-plant-with-color-changing-leaves-scientists-just-rose-to-the-occasion/

Color-changing plants detect pollutants and explosives

https://newatlas.com/color-changing-plants-detect-pollutants-and-explosives/17915/

The Color Genes of Speciation in Plants

Daniel Ortiz-Barrientos1

Genetics. 2013 May; 194(1): 39–42.
doi: 10.1534/genetics.113.150466

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3632479/

Guide to Fall Colors in Upstate New York

Donald J. Leopold
Chair, Department of Environmental and Forest Biology and Distinguished Teaching Professor
SUNY-ESF, Syracuse

The plants that change colour through the seasons

https://www.stuff.co.nz/life-style/home-property/nz-gardener/76979012/the-plants-that-change-colour-through-the-seasons

Colours of plants and animals

https://www.itp.uni-hannover.de/fileadmin/arbeitsgruppen/zawischa/static_html/botzooE.html

On Luminescence: Fluorescence, Phosphorescence, and Bioluminescence

Key Words

  • Photoluminescence
  • Fluorescence
  • Phosphorescence
  • Chemiluminescence
  • Luminescence
  • Incandescence
  • Spectrophotometer
  • Spectrofluorophotometer
  • Bioluminescence
  • Chemluminescence
  • Mechnoluminescence
  • Thermoluminescnce
  • Sonoluminescence
  • Electroluminescence
  • Daylight Fluorescent dyes
  • UV Fluorescent Dyes
  • Angle dependent Pigments in coatings
  • Optical Effects
  • Opalescence
  • Iridescence
  • Pearlescence
  • Adularescence
  • Labradorescence
  • Aventurescence
  • GonioSpectrometers
  • Multi Angle Spectrophotometers

There are many forms of energy which selected luminescent pigments can absorb and convert to luminescence, e.g. radioactive (radioluminescence); X-ray (Roentgenoluminescence); cathode ray (cathodoluminescence); mechanical (triboluminescence); electrical (electroluminescence); heat -after previous storage of energy (thermoluminescence); and Ultraviolet (UV) visible and Infrared (IR) (photoluminescence).

Luminescence Vs Incandescence

  • Incandescence
  • Luminescence
    • Bioluminescence
    • Photoluminescence
      • Fluorescence
      • Phosphorescence

Source:

Source:

Source: Introduction/Molecular Fluorescence: Principles and Application

Source: FLUORESCENCE AND PHOSPHORESCENCE

Source: Introduction/Molecular Fluorescence: Principles and Application

Bioluminescence

Please see references listed below for examples of bioluminescence.

  • In plants
    • Reviewing the relevance of fluorescence in biological systems
    • PLANTS WITH SELF-SUSTAINED LUMINESCENCE
  • In ocean Life
    • BIOLUMINESCENCE IN THE SEA
  • Fireflies
    • RESURRECTING THE ANCIENT GLOW OF THE FIREFLIES

Photoluminescence

  • Fluorescence
  • Phasphorescence

Source: Fluorescence and Phosphorescence

Jablonski Diagram – Molecular States

Source: Fluorescence and Phosphorescence

Source: Fluorescence and Phosphorescence

Fluorescence

Types of Fluorescence

  • Daylight
  • UV

Fluorescent Dyes and Pigments

Source: Fluorescent Dyes and Pigments

1.Introduction
2.Naphthalimide Dyes
3.Coumarin Dyes
4.Xanthene Dyes
5.Thioxanthene and Benzoxanthene Dyes
6.Naphtholactam, Hydrazam Dyes and Homologues
7.Azlactone Dyes
8.Methine Dyes
9.Oxazine and Thiazine Dyes
10.Miscellaneous Fluorescent Dyes
11.UV Fluorescent Chromophores with No or Low Body Color
12.Special Uses
13.Daylight Fluorescent Pigments
13.1.Production
13.1.1.Dyes for Daylight Fluorescent Pigments
13.1.2.Pigment Matrices
13.1.3.Formaldehyde‐Free and Solvent Resistant Fluorescent Pigments
13.1.4.Sunlight Sensors
13.1.5.Fluorescent Modifications with Covalently Bound Dyes
13.1.6.More ‐ Not Resinated ‐ Solid‐State Fluorescent Pigments
13.2.Quality Specifications of Fluorescent Pigments
13.3.Applications of Fluorescent Pigments
13.4.Toxicology

Industrial Applications of Fluorescence

  • Paper
  • Plastics
  • Paints
  • Textiles
  • Printing Inks
  • Laudary Detergent

In Paper Industry

  • Disulfonated OBA – used in wetend of paper machines
  • Tetrasulfonated OBA – surface coating in size press for standard whiteness
  • Hexasulfonated OBA- for high whiteness

Optical brightening agents in paper

Posted on April 6, 2018 by admin

Optical brightening agents are additives which are used in the paper industries to enhance whitening effects of papers. These chemical compounds absorb light in the ultraviolet and violet region (usually 340-370nm) and re-emit light in the blue region (typically 420-470 nm). It gives a fluorescent effect that masks the inherent yellowness of the fiber and enhances the brightness of the paper product. They not only used in paper but also used in plastics, textiles, laundry detergents. They are also known as optical brighteners, artificial whiteners. It is one kind of coating agent.

The optical brighteners can be applied in either the wet end or dry end or both end. If you want to internal brightness then you have to add them to the stock in wet end. Many paper manufactures use them in dry end at the size press or calender stack as surface coating. The dry end application is more economical compare to the wet end because in the dry end the chemical are used on the outer surface fiber in lieu of whole fiber content for reflects the ultraviolet light. However some manufacturers use a combination treatment; they use both the wet and dry end. 

Types of optical brightening agents

The optical brighteners that are used in paper industries can be sort into three types based on the sulfonic groups. All of them contain stilbene structure.

Disulfonated OBAs

This OBAs contains two sulphonic groups. They are hydrophobic and have a very good affinity. The solubility is very low. Normally it is used in wet end.

Tetrasulfonated types

This OBAs contains four sulphonic groups. It has medium affinity and good solubility so ideal for paper industries both in wet end and dry end. They are suitable for neutral or alkaline pH medium. It is most common type of OBAs that are used in paper and paper board.

Hexasulfonated OBAs

hexasulfonated OBAs contains six sulphonic groups. It is special type of brightener which has excellent solubility. Mostly it is used in those papers where high brightness is required such as photographic paper. They are used in dry end as coating.

Optical brightener’s chemistry

We know that optical brightening agents are stilbene derivatives. The stilbene is a diphenylethene which consist two stereo-isomer – trans-isomer and cis-isomer. Between these two configurations, the trans-isomer can exhibits strong fluorescence whereas the cis-isomer does not exhibit fluorescence. The trans configuration is more stable than cis configuration but when the uv light applied on the trans configuration then it become electronically exited and converted into cis configuration. Consequently the fluorescence phenomenon occurs in. The visible blue light effectively neutralizes the cream color or yellowish hue of the paper fiber.

Disadvantage

All the optical brightening agents are dyestuffs. As like most of the other colorants they also degraded by oxygen in air slowly. So after several years or months, the increasing brightness of the paper with optical brighteners will decrease. As a result the printed paper will not look good. Thus some people does not like print on the paper with artificial brightness. Similarly it is not useful in photographic or art applications. On the other hand in some places or some printers the OBAs would not work. Therefore the paper will appear its normal brightness. This is the reason why some printed papers have a yellowish hue. Although the OBAs are efficient on bleached chemical pulps but it is ineffective on unbleached pulp due to lignin is also an ultraviolet absorbing agent.

Finally

Normally the consumers expect higher brightness paper and paper boards. But all the time the brightness of pulp and fillers cannot fulfill the targeted brightness. Therefore the manufactures use different type of optical brightening agents. Most of the paper manufacturers add these chemicals in order to make paper appear brighter.

Source: The issues of Optical Brightening Agents in paper and ink

Industrial Testing and Measurements

Source: Fluorescence and Phosphorescence

Source: Fluorescence and Phosphorescence

Source: Fluorescence and Phosphorescence

Source: Fluorescence and Phosphorescence

Fluorescence Prediction and Control

Please see my post related to Color and Fluorescence Meaurement, Prediction and Control.

On Light, Vision, Appearance, Color and Imaging

There are also several references in the list below which describe fluorescence measurement, prediction, and control in more detail. Papers by LG Coppel describe fluorescence modelling. Papers by Tarja Shakespeare describe fluorescence modeling and control online on paper machines.

My Related Posts

Digital Color and Imaging

Color and Imaging in Digital Video and Cinema

On Light, Vision, Appearance, Color and Imaging

Key Sources of Research

Constructing Models to Explain Photoluminescence

Fluorescence, Phosphorescence, and Chemiluminescence

Noureen Siraj,† Bilal El-Zahab,‡ Suzana Hamdan,† Tony E. Karam,† Louis H. Haber,† Min Li,§
Sayo O. Fakayode,∥ Susmita Das,⊥ Bertha Valle,⊗ Robert M. Strongin,○ Gabor Patonay,#
Herman O. Sintim,× Gary A. Baker,$ Aleeta Powe,¶ Mark Lowry,○ Jan O. Karolin,& Chris D. Geddes,& and Isiah M. Warner*,†

Anal. Chem. 2016, 88, 170−202

Reviewing the relevance of fluorescence in biological systems

https://pubs.rsc.org/en/content/getauthorversionpdf/c5pp00122f

Pigments, dyes and fluorescent brightening agents for plastics: An overview

Robert M. Christie

First published: August 1994

https://onlinelibrary.wiley.com/doi/abs/10.1002/pi.1994.210340401

FLUORESCENT DYES FOR PAPER DYEING

Inventor: Helmut-MartinMeier,Ratingen(DE)

Assignee: KemiraGermanyGmbH,Leverkusen (DE)

Photochromic and Thermochromic Colorants in Textile Applications

M. A. Chowdhury, M. Joshi and B. S. Butola

https://journals.sagepub.com/doi/pdf/10.1177/155892501400900113

THE CHEMISTRY & PHYSICS OF
SPECIAL EFFECT PIGMENTS & COLORANTS

A. NURHAN BECIDYAN

President
UNITED MINERAL & CHEMICAL CORPORATION

Luminescence Phenomena: An Introduction

K.V.R. Murthy

Hardev Singh Virk

https://www.researchgate.net/publication/271866484_Luminescence_Phenomena_An_Introduction

Introduction

Molecular Fluorescence: Principles and Applications, Second Edition. Bernard Valeur,
Mário Nuno Berberan-Santos.
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA. Published 2013 by Wiley-VCH Verlag GmbH & Co. KGaA.

A Brief History of Fluorescence and Phosphorescence before the Emergence of Quantum Theory

Bernard Valeur*,† and Mario N. Berberan-Santos*,‡

Plants with self-sustained luminescence

Tatiana Mitiouchkina et all

Bioluminescence in the Sea

Steven H.D. Haddock,1 Mark A. Moline,2 and James F. Case3

Resurrecting the ancient glow of the fireflies

PHOTOLUMINESCENTS: FLUORESCENT AND PHOSPHORESCENT INKS AND PAINTS

An Introduction to Fluorescence Spectroscopy

Fluorescence Spectroscopy

Molecular Fluorescence, Phosphorescence, and Chemiluminescence Spectrometry

https://pubs.acs.org/doi/pdf/10.1021/ac00084a016

Molecular Luminescence Spectrometry

Molecular Fluorescence, Phosphorescence, and Chemiluminescence Spectrometry

Anal Chem. 2006 Jun 15; 78(12): 4047–4068.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2662353/

Fluorescence and phosphorescence

Fluorescence and Phosphorescence

Practical Capture and Reproduction of Phosphorescent Appearance

O. Nalbach1, H.-P. Seidel1 and T. Ritschel2

1Max-Planck Institut für Informatik, Germany 2University College London, United Kingdom

Fluorescent Dyes and Pigments

Rami Ismael Hansrudolf Schwander Paul Hendrix

Dyes, optical brightening agents

Permanency of paper and board

Structural colour and iridescence in plants: the poorly studied relations of pigment colour

Beverley J. Glover1,* and  Heather M. Whitney2

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2850791/

Analysing photonic structures in plants 

Silvia Vignolini1,2, Edwige Moyroud3, Beverley J. Glover3 and Ullrich Steiner1

1Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK 2Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK 3Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK

The Mechanism of Color Change in the Neon Tetra Fish: a Light‐Induced Tunable Photonic Crystal Array

Dvir Gur 1 , Benjamin A Palmer 1 , Ben Leshem 2 , Dan Oron 2 , Peter Fratzl 3 , Steve Weiner 1 , Lia Addadi 4

First published: 27 April 2015

https://pubmed.ncbi.nlm.nih.gov/25914222/

Colour measurement in the paper industry

https://www.erx50.com/en/anwendungen/papier-obsolete

Print Quality Control Management for Papers Containing Optical Brightening Agents

Roberto Pasic, Ivo Kuzmanov, Svetlana Mijakovska

The issues of Optical Brightening Agents in paper and ink

http://the-print-guide.blogspot.com/2009/03/issues-of-optical-brightening-agents-in.html

Optical Brightening Agents in Manufacturing

Posted July 20, 2015 by Greg Stehn

https://www.xrite.com/blog/controlling-obas-in-manufacturing

SUCCESSFUL COLOR MANAGEMENT OF PAPERS WITH OPTICAL BRIGHTENERS

Effect of Optical Brightening Agents and UV Protective Coating on Print Stability of Fine Art Substrates for Ink Jet

Veronika Chovancova-Lovell* and Paul D. Fleming III**

*Daniel J Carlick Technical Center Sun Chemical Corporation

**Department of Paper Engineering, Chemical Engineering and Imaging, Center for Ink and Printability Western Michigan University

OPTICAL BRIGHTENING AGENTS

A Visual Examination of the Solubility of Brighteners in Paper after Aqueous Treatment

Emily H. Cohen

December 17, 2014

Color & Perception Roemich

To Brighten or Not to Brighten

Scientifically examining the controversy over OBA inkjet media additives.

SIGN & DIGITAL GRAPHICS • July 2009

Substitution of Optical Brightener Agents in Industrial Textiles

MUDP report October 2018

Denmark

Chemistry of optical brighteners and uses in textile industries

by Mr. Anwer Tiki, Afreen Amin and Azeema Kanwal, AVM Chemical Industries.

Archroma Introduces Leucophor® MT, A New Cost-Effective Optical Brightening Agent For High Whiteness Surface Applications

Reinach, Switzerland – 20/02/2018

https://www.archroma.com/press/releases/archroma-introduces-leucophor-mt-a-new-cost-effective-optical-brightening-agent-for-high-whiteness-surface-applications

Whiteness indices and UV standards

Konica Minolta

https://www5.konicaminolta.eu/ru/measuring-instruments/learning-centre/colour-measurement/colour/the-colour-of-white.html

The Effect of Optical Brightening Agent (OBA) in Paper and Illumination Intensity on Perceptibility of Printed Colors

Changlong Yu 2014

RIT MS Thesis

Demystifying Three Key Paper Properties

Whiteness, Brightness and Shade

Xerox

The Evolution of Tinting Dyes and Optical Brighteners in White Papers

Mark Crable

Greenville Colorants

Addressing the Challenges of Optical Brightening Agents in Paper Color Measurement

Posted on  December 4, 2015 by Ken Phillips

Hunter Lab

Adding optical brightening agents to high-yield pulp at the pulp mill

Review: Use of optical brightening agents (OBAs) in the production of paper containing high-yield pulps

Shi, H., Liu, H., Ni, Y., Yuan, Z., Zou, X., and Zhou, Y. (2012). 

BioRes. 7(2), 2582-2591.

FLUORESCENT WHITENING AGENTS IN LAUNDRY DETERGENT & PAPER

https://www.sas.upenn.edu/~kimg/mcephome/chem507/spec6.html

A summary of ultra-violet fluorescent materials relevant to Conservation


AICCM National Newsletter No 137 March 2017

Danielle Measday, Museums Victoria

Efficiency of Fluorescent Whitening Agents in Pigment Coatings

Zaeem Aman 2012

Master Thesis
Master of Science in Chemical Engineering

Karlstads universitet (KAU) 651 88 Karlstad

Colour Chemistry 2nd edition

Robert M Christie

School of Textiles & Design, Heriot-Watt University, UK and Department of Chemistry, King Abdulaziz University, Saudi Arabia

Email: r.m.christie@hw.ac.uk

Colour and the Optical Properties of Materials

An Exploration of the Relationship Between Light, the Optical Properties of Materials and Colour

PROFESSOR RICHARD J. D. TILLEY

Emeritus Professor, University of Cardiff, UK

2011 John Wiley & Sons, Ltd

FLUORESCENCE AND PHOSPHORESCENCE

Andrew Glassner

Rendering of fluorescent materials using spectral path tracing : Niixtracer, a custom rendering engine

Nolan MESTRES

2018

Spectral Mollification for Bidirectional Fluorescence

A. Jung1, J. Hanika1 and C. Dachsbacher1 1Karlsruhe Institute of Technology

Assessment of whiteness and tint of fluorescent substrates with good inter-instrument correlation

Rolf Griesser

1994 Williamsburg Conference on Colorimetry of Fluorescent Materials“; English first publication in Color Res. Appl. 19 (1994), 6, p. 446-460

CIE whiteness and tint : possible improvements

R. Griesser

„AIC Interim Meeting ’95 Colorimetry”, Berlin, 4. – 6. September 1995;

first publication (Engl.) Appita 49 (1996), 2, p. 105-112;

https://www.semanticscholar.org/paper/CIE-whiteness-and-tint-%3A-possible-improvements-Griesser/d2a1df7fb5b7b489fecd344c1f6b8025b3a84165?p2df

WHITENESS DETERMINATION OF OPTICALLY BRIGHTENED TEXTILES

R. Hirschler, D.F. Oliveira and A.F. Azevedo

WHITENESS ASSESSMENT OF PAPER SAMPLES AT THE VICINITY OF THE UPPER CIE WHITENESS LIMIT

Coppel L., Lindberg, S., and Rydefalk, S.

STFI-Packforsk, Stockholm, Sweden

Limitations in the efficiency of fluorescent whitening agents in uncoated paper

Ludovic G. Coppel, Mattias Andersson, Per Edström and Jussi Kinnunen

WHITENESS EVALUATIONS ON TINTED AND FWA ADDED PAPERS

Burak Aksoy, Paul D. Fleming* and Margaret K. Joyce

Department of Paper Engineering, Chemical Engineering and Imaging Center for Coating Development
Western Michigan University
Kalamazoo, MI 49008

Comparative Study of Brightness/Whiteness Using Various Analytical Methods on Coated Papers Containing Colorants

Burak Aksoy, Margaret K. Joyce and Paul D. Fleming
Department of Paper and Printing Science and Engineering, Western Michigan University, Kalamazoo, MI, 49008

https://www.researchgate.net/publication/250763960_Comparative_Study_of_BrightnessWhiteness_Using_Various_Analytical_Methods_on_Coated_Papers_Containing_Colorants

Using Optical Brightening Agents (OBA) for Improving the Optical Properties of HYP-Containing Paper Sheets

H. ZhangZ. HeY. Zhou

Published 2009 Materials Science

https://www.semanticscholar.org/paper/Using-Optical-Brightening-Agents-%28OBA%29-for-the-of-Zhang-He/665b2e9c5e7749d54f8904624370945c2e723dd1?p2df

Whiteness and Fluorescence in Layered Paper and Board

Perception and Optical Modelling

L G Coppel

PhD Thesis 2012 Sweden

Influence of SPD on Whiteness value of FWA treated samples

Michal VIK, Martina VIKOVÁ, Aravin Prince PERIYASAMY

https://dspace.vutbr.cz/bitstream/handle/11012/51679/257-vik.pdf?sequence=1

Fluorescence model for multi-layer papers using conventional spectrophotometers

L. G. Coppel, M. Andersson, M. Neuman and P. Edström

https://www.researchgate.net/publication/258551824_Fluorescence_model_for_multi-layer_papers_using_conventional_spectrophotometers

Factors affecting the whiteness of optically brightened material

Juan Lin 1Renzo ShameyDavid Hinks

J Opt Soc Am . 2012 Nov 1; 29 (11): 2289-99.

https://pubmed.ncbi.nlm.nih.gov/23201789/

FLUORESCENCE AND THE PAPER APPEARANCE – CHALLENGES IN PAPER COLORING

Dr. Tarja Shakespeare1, Dr. John Shakespeare

  • June 2009
  • Conference: Papermaking Research Symposium, PRS2009
  • At: Kuopio, Finland

https://www.researchgate.net/publication/328873894_FLUORESCENCE_AND_THE_PAPER_APPEARANCE-CHALLENGES_IN_PAPER_COLORING

A fluorescent extension to the Kubelka–Munk model

Tarja Shakespeare John Shakespeare

First published: 30 December 2002

Col Res Appl, 28, 4–14, 2003

https://onlinelibrary.wiley.com/doi/abs/10.1002/col.10109

Problems in colour measurement of fluorescent paper grades

Tarja Shakespeare John Shakespeare

Analytica Chimica Acta
Volume 380, Issues 2–3, 2 February 1999, Pages 227-242

https://www.sciencedirect.com/science/article/abs/pii/S0003267098004838

Colorant modelling for on-line paper coloring: Evaluations of models and an extension to Kubelka-Munk model 

Show affiliations

  • Shakespeare, Tarja Tuulikki
  • Thesis (PhD). TAMPEREEN TEKNILLINEN KORKEAKOULU (FINLAND), Source DAI-B 61/11, p. 6074, May 2001, 147 pages.

https://www.researchgate.net/publication/234289229_Colorant_modelling_for_on-line_paper_coloring_Evaluations_of_models_and_an_extension_to_Kubelka-Munk_model

Kubelka Munk Model in Paper Optics: Successes, Limitations and Improvements

L. Yang

Progress in Paper Physics Seminar 2011

Conference Proceedings

Editor U. Hirn

Radiative properties of optically thick fluorescent turbid media

Alexander A. Kokhanovsky

Journal of the Optical Society of America A

Vol. 26,Issue 8,pp. 1896-1900(2009)•

https://www.osapublishing.org/josaa/abstract.cfm?uri=josaa-26-8-1896

Fluorescent Transfer of Light in Dyed Materials

S. D. Howison and R. J. Lawrence


Read More: https://epubs.siam.org/doi/abs/10.1137/0153026

SIAM J. Appl. Math., 53(2), 447–458. (12 pages)

https://epubs.siam.org/doi/abs/10.1137/0153026

Extension of the Stokes equation for layered constructions to fluorescent turbid media

Ludovic G. Coppel,1,2 Magnus Neuman,2 and Per Edström

1Innventia AB, Box 5604, SE-11486 Stockholm, Sweden

2Department of Natural Sciences, Engineering and Mathematics, Mid Sweden University, SE-87188 Härnösand, Sweden

https://www.researchgate.net/publication/223985363_Extension_of_the_Stokes_equation_for_layered_constructions_to_fluorescent_turbid_media

Influence of Deinked Pulp on Paper Colour and its Susceptibility to Ageing

Ewa Drzewińska

Whiteness Assessment: A Primer

Concepts, Determination and Control of Perceived Whiteness

Dr. Claudio Puebla Axiphos GmbH Germany

The Chemistry and Physics of Special-Effect Pigments and Colorants for Inks and Coatings

Paints and Coatings Industry

2003

https://www.pcimag.com/articles/85016-the-chemistry-and-physics-of-special-effect-pigments-and-colorants-for-inks-and-coatings