japan: TECHNOLOGY - NEXT, THE FEELING MATERIAL. - Self-diagnosing, self-repairing, smart materials which will know when they've had enough could be on their way from Japan, writes Pallab Ghosh.

Last Updated: 31 Aug 2010

Self-diagnosing, self-repairing, smart materials which will know when they've had enough could be on their way from Japan, writes Pallab Ghosh.

Nature's designs are subtle, complex and, in engineering terms, flawless. Designers have in the past borrowed ideas extensively from the living world, but the practice seems to be falling into disuse with engineering research now focused on taming the abstract sub- atomic realm. However, as the Japanese well know, only the foolish forsake a wise teacher. They have recently embarked on a research programme which, if successful, could change forever the way in which engineers think about design.

Good engineers know intimately the properties of the materials they use: their strengths, weaknesses and their quirks. From this knowledge everything else flows. But for all the diversity of natural and artificial materials, they still limit the engineer's imagination. How often do they stifle pleas for materials that are lighter, stronger or more robust, before settling for what they have? For that is the lot, and indeed the art of an engineer.

But that frustration may soon end with the advent of a new class of materials. The Japanese government has given the go-ahead for a research programme aimed at developing new materials with properties similar to living tissue. These so-called smart materials, once developed, will be able to adapt to their environment, discover where they have been damaged and repair themselves.

At present, engineers assume the worst of their designs. A structure, such as a bridge or an aeroplane, is only as safe as its weakest component. And while regular maintenance can extend its life time, it must eventually be scrapped when irreplaceable components approach the end of their life.

The thresholds set by regulatory bodies are rightly high, so expensive plant is usually scrapped before its time. Materials able to diagnose their own health and so set their own retirement date would therefore be a great boon.

The US aerospace industry has for some years been experimenting with planes whose skins are embedded with sensors. They monitor the skin's temperature and vibration and look for any cracks that develop. The sensors are linked by optical fibre to the plane's on-board computer which alerts the crew to any problems that might develop. But a sensitive material is not necessarily smart. Smart materials are able to adapt to the situation they find themselves in. A smart aircraft skin extends its lifetime by eliminating vibration by vibrating in anti-phase to the engine and air turbulence. Smart vibration control can also be used to reduce noise in the aircraft and to make it invisible to radar. It is a technique already used in some advanced fighter aircraft. The US stealth fighter, used to deadly effect in the Gulf war, probably has one of the smartest artificial skins on the planet.

Japan's aim is to transfer smart materials technology to the civil sector. Vibration control lends itself readily to applications in the motor industry. One Japanese company is said to be close to developing a car that is as smooth and quiet as a Jaguar but as cheap as an Escort.

Japanese civil engineering companies have also taken a lead in the technology in developing smart buildings. Tokyo already has two earthquake-proof buildings that use smart materials. Sensors on the floors of the buildings detect vibration and a central computer instructs the steel structure of the building to shake in anti-phase to the earthquake.

But vibration control gives only a hint of what the technology can offer. The aim is to develop materials which are able to repair themselves. There are already prototype self-healing plastics available that bleed and clot. Perhaps the most exciting breakthrough is the development of a material that behaves like a muscle. Researchers at Ibaraki University near Tokyo have developed a plastic that contracts when an electric charge is applied to it. It opens up the possibility of self-focusing contact lenses and implants within the body that release drugs at pre-set times.

Japanese companies are experimenting with the material to use it as an alternative to servo-motors in electronic devices. The material has no moving parts, and so is more reliable - and is 40% more efficient than the most efficient motor available.

This year will see the emergence of smart materials as a key technology in Europe and the US. The University of Strathclyde in Scotland has already set up the country's first smart materials institute. Others will follow. So will the emergence of ever smarter and exotic materials. Never has it been so much fun to be a designer.

Pallab Ghosh is a science and technology writer.

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