Silkworms and squid inspire smart materials

Wed May 2, 2012 6:57am EDT

Silkworm cocoons are seen at a silk museum in Bsous village in Mount Lebanon August 17, 2011. REUTERS/Jamal Saidi

Silkworm cocoons are seen at a silk museum in Bsous village in Mount Lebanon August 17, 2011.

Credit: Reuters/Jamal Saidi

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(Reuters) - Car panels made of silkworm cocoons, clothing that can camouflage the wearer at the flick of a switch and a "smart" shirt with a phone and power source embedded in the fabric.

Scientists, some with funding from the U.S. Air Force, have made breakthroughs that could eventually make all this reality.

Research published on Wednesday reveals advances in materials science that could transform industries struggling with the rising cost and scarcity of raw materials and save lives in post-conflict countries still clearing minefields.

In a study published in the Royal Society journal Interface, Oxford University researchers David Porter and Fujia Chen examine the structure of silkworm cocoons, which are extremely light and tough, with properties that could inspire advanced materials for use in protective helmets and light-weight armor.

"Silkworm cocoons have evolved a remarkable range of optimal structures and properties to protect moth pupae from many different natural threats," Porter and Chen said in their paper. These structures are lightweight, strong and porous and therefore "ideal for the development of bio-inspired composite materials."

Their research could lead to lightweight armor that dissipates rather than deflects the particular components of a blast that do the most damage to the human body - much like crumple zones in modern cars or sound-absorbing sonar tiles that make submarines harder to detect.

Even more tantalizing from an economic standpoint, Porter and Chen's research, which was funded by a grant from the U.S. Air Force, could point to a new material for fabricating car panels in some of the fastest-growing car markets - China and India.

Fritz Vollrath, who heads the Oxford research group, said supplies of cocoons are plentiful. "Present raw silk market production globally is half a million tons annually."

Most of that is boiled and unraveled for textiles, but Vollrath says there are potential applications for the cocoons themselves, particularly in the developing world and potentially in car panels that are very tough and totally sustainable.

The researchers are working on carbon footprint calculations but Vollrath notes that the production process is probably carbon neutral, involving a mulberry bush and worms that, unlike cattle, don't emit any methane.

Further research is needed. Porter said the next stage will be to find a way to replicate the structures found in the cocoons or use them as a base material impregnated with gels as a way of developing a scalable production process.

There are plenty of precedents for the commercial exploitation of structures found in the natural world. One of the best known is the so-called ‘lotus effect', the properties of the lotus leaf that keeps them extremely clear of dust and dirt. Researchers found tiny nodules on the surface of the leaf that stops water from settling on them. Droplets form and simply roll off, gathering any dirt as they go.

It was this research that eventually led to the development of self-cleaning windows and advanced exterior paints.

Velcro was developed after Swiss engineer George de Mestral observed the way the flowers of the mountain thistle stuck to his trousers after a walk in the countryside.

NOW YOU SEE ME, NOW YOU DON'T

Scientists have also created artificial muscles in the laboratory that mimic the color-changing ability of squid and zebrafish and could eventually be used in camouflaging ‘smart clothes'.

Researchers at the University of Bristol in the UK created soft and stretchy artificial muscles based on specialist cells called ‘chromatophores' that are found in some fish and reptiles. They contain pigments which give these animals the ability to change color.

"We have taken inspiration from nature's designs and exploited the same methods to turn our artificial muscles into striking visual effects," said Jonathan Rossiter, lead author of the study, which was published on Wednesday in the Institute of Physics journal Bioinspiration and Biomimetics.

The Bristol scientists say their camouflaging technology could also be used to regulate the temperature of the wearer at the flick of a switch.

Zebrafish can pump pigmented fluid from under their skin to the skin's surface - a process Rossiter and his colleagues have been able to mimic in artificial muscles in the lab.

"The application of this biomimetic pumping action to thermoregulation is most easily understood by considering smart clothing or a 'second skin' which contains heat-emitting fluid," Rossiter told Reuters. "When the wearer is cold, the fluid is kept close to the skin. When the wearer becomes hot, the fluid is translocated to the outside of the 'second skin' where the heat energy is radiated away from the body."

Rossiter said his group will be looking for more potential applications, from artificial skins for human-interacting robots, to new electronic devices.

"We are keen to move from laboratory prototypes to commercial products, and this is expected to be through industrial partnerships," he said.

WIRED FOR SOUND

High-tech clothing is an area that researchers from the University of Exeter hope to exploit with findings unveiled in the last week in the journal Advanced Materials. They have made the "most transparent, lightweight and flexible material ever for conducting electricity".

The material, which is based on the revolutionary substance graphene, a form of carbon just one atom thick but 100 times stronger than steel, could accelerate the creation of clothing with embedded devices like mobile phones and MP3 players.

The Exeter group, led by engineer Dr Monica Craciun, is now working on a spray-on version of the transparent material, which they have dubbed ‘GraphExeter', that could be applied to ‘smart' tee-shirts, or windows to turn them into solar panels that are 30 percent more efficient than those in use today.

Currently, the main electrical conductor used in electronics is indium tin oxide, which is not flexible and is a finite resource that could run out in five years or so and is rapidly getting more expensive. Until now, the Exeter researchers say, no one has been able to come up with a viable alternative to do the job when the world's reserves of indium run out.

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Comments (1)
rick_short wrote:
Full disclosure: I am employed at The Indium Corporation (www.indium.com):

Your poorly-researched claim that indium-tin oxide “could run out” is preposterous!

Quoting from a recent position paper we published:

“There has been concern expressed that the world may face an indium shortage given the rising price environment experienced this year. The Indium Corporation believes that the temporary imbalance between supply and demand will be corrected and that sufficient indium is available to meet forecasted demand.

In 1934 the Indium Corporation began extracting, refining, purifying and fabricating indium. Seventy years later indium is still “Our Product, Our Symbol, Our Name.” Over the years we have significantly increased our refining and recycling capacity which has ultimately increased the global supply.

Short-term shortages have periodically occurred because global production and usage are so finely balanced. However, these shortages have historically been corrected by increasing refining capacity and, ultimately, supply.

The documents below contain data from the U.S. Geological Survey. The data shows that indium is available. Indium exists in the earth’s crust in quantities approximately three times that of silver (which is currently extracted at 60x the rate of indium). While extraction efficiency is greater for silver, the relative abundance and current extraction rates of indium versus silver are still a telling story.

According to the U.S. Geological Survey statistics, the worldwide output of indium metal has increased 7X since 1980. We believe that this trend will continue and supply will expand to meet demand.

The indium supply has been bolstered by continued improvement in recycling programs. In the rapidly growing LCD market, greater than 85% of non-deposited indium is reclaimed and returned to the supply chain.

We believe the currently-observed price fluctuations are primarily due to a time lag between emerging demand and available supply. As has been observed in previous cycles, the Indium Corporation believes higher prices will draw forward additional supplies which will alleviate any scarcity.

Indium metal’s unique properties make it a critical component for many products, and the Indium Corporation is committed to, and confident of, meeting the indium needs of its partners.

Read more: http://www.indium.com/supply.php#ixzz1tixzy8O3

May 02, 2012 10:54am EDT  --  Report as abuse
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