Tag Archives: jewel beetles

Cambridge University wants to take its flexible opals to market

Structural colour due to nanoscale structures such as those found on Morpho butterfly wings, jewel beetles, opals, and elsewhere is fascinating to me (Feb. 7, 2013 posting). It would seem many scientists share my fascination  including these groups at the UK’s University of Cambridge and Germany’s Fraunhofer Institute, from the May 30, 2013 University of Cambridge news release (also on EurekAlert),

Instead of through pigments, these ‘polymer opals’ get their colour from their internal structure alone, resulting in pure colour which does not run or fade. The materials could be used to replace the toxic dyes used in the textile industry, or as a security application, making banknotes harder to forge. Additionally, the thin, flexible material changes colour when force is exerted on it, which could have potential use in sensing applications by indicating the amount of strain placed on the material.

The most intense colours in nature – such as those in butterfly wings, peacock feathers and opals – result from structural colour. While most of nature gets its colour through pigments, items displaying structural colour reflect light very strongly at certain wavelengths, resulting in colours which do not fade over time.

In collaboration with the DKI (now Fraunhofer Institute for Structural Durability and System Reliability) in Germany, researchers from the University of Cambridge have developed a synthetic material which has the same intensity of colour as a hard opal, but in a thin, flexible film.

Here’s what the researchers’ synthetic opal looks like,

Polymer Opals Credit: Nick Saffel [downloaded from http://www.cam.ac.uk/research/news/flexible-opals]

Polymer Opals Credit: Nick Saffel [downloaded from http://www.cam.ac.uk/research/news/flexible-opals]

The news release provides a brief description of naturally occurring opals and contrasts them with the researchers’ polymer opals,

Naturally-occurring opals are formed of silica spheres suspended in water. As the water evaporates, the spheres settle into layers, resulting in a hard, shiny stone. The polymer opals are formed using a similar principle, but instead of silica, they are constructed of spherical nanoparticles bonded to a rubber-like outer shell. When the nanoparticles are bent around a curve, they are pushed into the correct position to make structural colour possible. The shell material forms an elastic matrix and the hard spheres become ordered into a durable, impact-resistant photonic crystal.

“Unlike natural opals, which appear multi-coloured as a result of silica spheres not settling in identical layers, the polymer opals consist of one preferred layer structure and so have a uniform colour,” said Professor Jeremy Baumberg of the Nanophotonics Group at the University’s Cavendish Laboratory, who is leading the development of the material.

Like natural opals, the internal structure of polymer opals causes diffraction of light, resulting in strong structural colour. The exact colour of the material is determined by the size of the spheres. And since the material has a rubbery consistency, when it is twisted and stretched, the spacing between spheres changes, changing the colour of the material. When stretched, the material shifts into the blue range of the spectrum, and when compressed, the colour shifts towards red. When released, the material will return to its original colour.

I find the potential for use in the textile industry a little more interesting than the anti-counterfeiting application. (There’s a Canadian company, Nanotech Security Corp., a spinoff from Simon Fraser University, which capitalizes on the Blue Morpho butterfly wing’s nanoscale structures for an anti-counterfeiting application as per my first posting about the company on Jan. 17, 2011.) There has been at least one other attempt to create a textile that exploits structural colour. Unfortunately Teijin Fibres has stopped production of its morphotex, as per my April 12, 2012 posting.

Here’s what the news release has to say about textiles and the potential importance of structural colour,

The technology could also have important uses in the textile industry. “The World Bank estimates that between 17 and 20 per cent of industrial waste water comes from the textile industry, which uses highly toxic chemicals to produce colour,” said Professor Baumberg. “So other avenues to make colour is something worth exploring.” The polymer opals can be bonded to a polyurethane layer and then onto any fabric. The material can be cut, laminated, welded, stitched, etched, embossed and perforated.

The researchers have recently developed a new method of constructing the material, which offers localised control and potentially different colours in the same material by creating the structure only over defined areas. In the new work, electric fields in a print head are used to line the nanoparticles up forming the opal, and are fixed in position with UV light. The researchers have shown that different colours can be printed from a single ink by changing this electric field strength to change the lattice spacing.

As for wanting to take this research to market, from the news release,

Cambridge Enterprise, the University’s commercialisation arm, is currently looking for a manufacturing partner to further develop the technology and take polymer opal films to market.

For more information, please contact sarah.collins@admin.cam.ac.uk.

The reference to opals reminded me of yet another Canadian company exploring the uses of structural colour, Opalux, as per my Jan. 31, 2011 posting.

It’s a bird. It’s a plane. No, it’s a laser!

I couldn’t resist the Superman reference although it really should have been a Morpho butterfly or a jewel beetle reference since these are two other animals/insects that also display unusual optical properties courtesy of nanoscale structures.

Top: Male eastern bluebird (Sialia sialis, Turdidae). Credit: Ken Thomas (image in public domain). Published in Soft Matter, 2009, 5, 1792-1795. E.R. Dufresne et al., “Self-assembly of amorphous biophotonic nanostructures by phase separation.” Royal Society of Chemistry. http://dx.doi.org/10.1039/B902775K

According to the Oct. 12, 2011 news item on Nanowerk,

Researchers at Yale University are studying how two types of nanoscale structures on the feathers of birds produce brilliant and distinctive colors. The researchers are hoping that by borrowing these nanoscale tricks from nature they will be able to produce new types of lasers—ones that can assemble themselves by natural processes. The team will present their findings at the Optical Society’s (OSA) Annual Meeting, Frontiers in Optics (FiO) 2011, taking place in San Jose, Calif. next week. [It starts Sunday, Oct. 16, 2011.]

Devin Powell, in a May 13, 2011 article for Science News provides some additional detail,

The barbs of these feathers [from bluebirds, blue jays, and parrots] contain tiny pockets of air. Light striking the tightly packed air bubbles scatters, bringing out deep shades of blues and ultraviolet (which birds can see but humans can’t).

“Birds use these structures to create colors that they can’t make in other ways,” says Richard Prum, an  ornithologist at Yale University who discovered the mechanism behind this color.

To make a two-dimensional imitation of a bird feather, Yale physicist Hui Cao and her colleagues punched holes into a thin slice of gallium arsenide semiconductor. The holes were arranged like people in a crowd — somewhat haphazardly but with small-scale patterns that dictate roughly how far each hole is from its neighbor.

“The lesson we learned from nature is that we don’t need something perfect to get control,” says Cao, whose team describes their laser in the May 6 [2011] Physical Review Letters.

The latest work being presented is described this way in an Oct. 2011 news release (why aren’t people putting dates on their news releases????) from the Optical Society of America,

Inspired by feathers, the Yale physicists created two lasers that use this short-range order to control light. One model is based on feathers with tiny spherical air cavities packed in a protein called beta-keratin. The laser based on this model consists of a semiconductor membrane full of tiny air holes that trap light at certain frequencies. Quantum dots embedded between the holes amplify the light and produce the coherent beam that is the hallmark of a laser. The researchers also built a network laser using a series of interconnecting nano-channels, based on their observations of feathers whose beta-keratin takes the form of interconnecting channels in “tortuous and twisting forms.” The network laser produces its emission by blocking certain colors of light while allowing others to propagate. In both cases, researchers can manipulate the lasers’ colors by changing the width of the nano-channels or the spacing between the nano-holes.

What makes these short-range-ordered, bio-inspired structures different from traditional lasers is that, in principle, they can self-assemble, through natural processes similar to the formation of gas bubbles in a liquid. This means that engineers would not have to worry about the nanofabrication of the large-scale structure of the materials they design, resulting in cheaper, faster, and easier production of lasers and light-emitting devices.

Here’s an image of a ‘feather-based laser’,

Top: A laser based on feathers with the sphere-type nanostructure. This laser consists of tiny air holes (black) in a semiconductor membrane; each hole is about 77 nanometers across. (Scale bar = 5 micrometers.) Credit: Hui Cao Research Laboratory / Yale University.

As for the Morpho butterfly and jewel beetle, I last posted about gaining inspiration from these insects (biomimicry) in my May 20, 2011 posting in the context of some anti-counterfeiting strategies.

I first came across some of this work on the optical properties of nanostructures in nature in a notice about a 2008 conference on iridescence at Arizona State University. Here’s the stated purpose for the conference (from the conference page),

A unique, integrative 4–day conference on iridescent colors in nature, Iridescence: More than Meets the Eye is a graduate student proposed and organized conference supported by the Frontiers in Life Sciences program in Arizona State University’s School of Life Sciences. This conference intends to connect diverse groups of researchers to catalyze synthetic cross–disciplinary discussions regarding iridescent coloration in nature, identify new avenues of research, and explore the potential for these stunning natural phenomena to provide novel insights in fields as divergent as materials science, sexual selection and primary science education.

Marc Rembold’s nanotechnological colours at Jacana Gallery in Vancouver

Jacana Gallery (2435 Granville St., Vancouver, Canada) is displaying a piece described by a Swiss artist as (from the Marc Rembold webpage on the Jacana Gallery website)

Using high tech nanotechnological colours, materials and instruments I have the possibility to create more real (nearer to the liquid space) and strong colours. It allows me to define and create colours in a contemporary manner instead of using traditional pigments. In the series  LIQUIDS there is no use of pigments in oil or acrylic, no painterly technique, and no other ordinary processes to create colours is involved.

From there, the colours in their visible forms are treated manually and finally the polymethylmethacrylat process brings to the colors a final optical effect, giving them the visual quality of liquid precious stones.

Using high tech nanotechnological colours, materials and instruments I have the possibility to create more real (nearer to the liquid space) and strong colours. It allows me to define and create colours in a contemporary manner instead of using traditional pigments. In the series < LIQUIDS there is no use of pigments in oil or acrylic, no painterly technique, and no other ordinary processes to create colours is involved.

From there, the colours in their visible forms are treated manually and finally the polymethylmethacrylat process brings to the colors a final optical effect, giving them the visual quality of liquid precious stones.

The concept behind my work is the materialisation of light. Through electronic instrumentation and contemporary imaging processes, I bring the invisible realm of light’s colour spectrum to our eyes. I explore ways to manifest the beauty of something immaterial into vibrant, pure liquid-like colour.

Here’s Marc Rembold’s Welly, the work being featured at Jacana,

Welly by Marc Rembold (downloaded from the Jacana Gallery website)

I’m not sure how these colours are nanotechnological but they are certainly stunning. This reminds me of the work that’s based on Morpho butterfly wings, opals, jewel beetles, and other naturally iridescent animals and objects. All of it has to do with mimicking nanoscale structures in order to obtain certain optical properties. My May 20, 2011 posting is the latest on mimicking those optical properties.