Tag Archives: Jeremy Baumberg

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 [email protected].

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.

Mechanics of quantum kissing

“It is as if you can kiss without quite touching lips,” says Professor Jeremy Baumberg from the University of Cambridge Cavendish Laboratory in the University of Cambridge’s Nov. 7, 2012 news release about quantum electron jumps,

Even empty gaps have a colour. Now scientists have shown that quantum jumps of electrons can change the colour of gaps between nano-sized balls of gold. The new results, published today in the journal Nature, set a fundamental quantum limit on how tightly light can be trapped.

The team from the Universities of Cambridge, the Basque Country and Paris have combined tour de force experiments with advanced theories to show how light interacts with matter at nanometre sizes. The work shows how they can literally see quantum mechanics in action in air at room temperature.

As for the kissing, it all starts with metal and jumping electrons,

Because electrons in a metal move easily, shining light onto a tiny crack pushes electric charges onto and off each crack face in turn, at optical frequencies. The oscillating charge across the gap produces a ‘plasmonic’ colour for the ghostly region in-between, but only when the gap is small enough.

Team leader Professor Jeremy Baumberg from the University of Cambridge Cavendish Laboratory suggests we think of this like the tension building between a flirtatious couple staring into each other’s eyes. As their faces get closer the tension mounts, and only a kiss discharges this energy.

H/T to the Nov. 7, 2012 news item on ScienceDaily where I first learned of quantum kissing,

In the new experiments, the gap is shrunk below 1nm (1 billionth of a metre) which strongly reddens the gap colour as the charge builds up. However because electrons can jump across the gap by quantum tunnelling, the charge can drain away when the gap is below 0.35nm, seen as a blue-shifting of the colour. …

Prof Javier Aizpurua, leader of the theoretical team from San Sebastian complains: “Trying to model so many electrons oscillating inside the gold just cannot be done with existing theories.” He has had to fuse classical and quantum views of the world to even predict the colour shifts seen in experiment.

The new insights from this work suggest ways to measure the world down to the scale of single atoms and molecules, and strategies to make useful tiny devices.

Something to think about the next time you kiss.