AN aircraft begins to lose height as sudden ice formation increases the load on Its wings. An in built sensor on the wings signals a microcomputer to change the configuration of the aircraft for more 11ft.

Walls of an office building begin to develop stress due to a hurricane but the in built sensors Immediately activate braces to prevent the walls from swaying.

A room gets overheated by sunlight and immediately the window glass changes colour to reflect sunlight bringing the room temperature down.

These are the Intelligent or smart materials that respond to their environment just as a chameleon's skin adapts to its surroundings or like a tree leaf curling protectively In a drought.

Man s increasing ability to create new materials by manipulating the atoms of molecules of existing ones Is revolutionizing our world. But todays materials — natural and man-made — have one drawback : they are unable to warn of problems or impending failure of the structure built with those materials.

All over the world scientists are trying to produce "Smart" materials that have In-built Intelligence not only to sense the Impending failure but also to take corrective action.

Photochromatic glass is one such smart material. It darkens in bright sunlight to lessen the glare in spectacle lense than clears quickly when the wearer moves out of the sun.

Another class of Intelligent materials Is the shape memory alloy (SMA) so called because tt can be deformed or distorted In any fashion but remembers Its original shape to which It reverts when heated to a right temperature.

The Japanese have Invented a brassiere reinforced with frame of shape memory alloy that would collapse while the garment was being laundered but regain 11s precise shape and size before It was worn a©Un.

Already in market are heat shrinkable plastic sleeves made through the process of irradiation. These sfccVcs arc ideal for insulating electrical and telephone cables because they shrink when exposed to heat tightening the grip on the wires and providing an excellent seal.

A nickel-tltanium alloy called NITINOL Is the most commercially Important SMA. The ability of this alloy lo revert to original shape when healed to right temperature is exploited to create a variety of products like nails, suture clips, splints (used in bone surgery) and self-spreading satellite antenna.

The shape memory effect remained a curiosity since 1932 until 1969 when an American company under a military contract developed the pipe connectors for F-14 combat aircraft using SMA containing nickel and titanium.

A Japanese company has introduced heat detection springs made of SMA. These springs Installed In air condi-

tioning ducts are designed to detect heal and to shut off ducts to prevent smoke, flame, and poisonous gases from reaching other rooms.

Applications of SMA arc several. Clamps made of SMA can open and close without any mechanical strains. Plane surface could be covered with bumps and indcnlattons. Straight wires can take spiral shapes.

In the biomedical sector, especially in orthodontal field, the super elastic effect of SMA Is already In use for making arches.

The SMAs are also expected to bring about radical changes In the field of constructions, aeronautics, space and optics. Even the art world is taking an interest in these remarkable materials.

The French firm "Sourian" which has been actively concerned with SMA since 1983 in now trying to develop copper based memory alloys. Another firm "Cezus" which makes 20 kg to 50 kg ingots of SMA is now planning to manu facture semi-finished goods : bars, wires, sections, plates, sheets and pipes.

Of late the shape memory effect has been discovered In resins and rubber.

Four Japanese companies have developed a shape memory resin called “ASMER". At room temperature it behaves like a resin while at temperatures above 60 degree (C) it behaves as a rubber.

The companies anticipate a wide range of commercial applications for asmer from acoustic insulation and vibra-

tion control lo shoe padding and artificial flowers.

In India the Surana Udyog group of industries has cstab lishcd a new unit In Hyderabad for Indigenous manufacture ol heal shrinkable cable Jointing kits and plastic wire conncc-tors.

Other SMAs are yet to attract Indian Industry but they have already been develop'd at the Bhabha Atomic Research Centre (BARC) and lh National Metallurgical laboratory In Calcutta.

At BARC work is going on to develop Nitinol SMA hydraulic pipe coupling and fasteners using SMA. BARC scientists have also produced a rotary shape memory heal engine general Ing up to 70 rotations per minute.

Scientist have also developed a line of intelligent poly mere or gels that could prow useful in a range of appllca tions from self focusing contact lenses to miniature systems for delivering drugs lo specific parts of Ihe body.

The latest gel developed at the Massachusetts Institute of Technology in the United Stales is unique. Il shrinks to one thousandth of its original size when exposed lo visible light from a laser and then swells back once the light is removed. Scientists say the gel could contribute to Ihe field of elcctro-optics In novel switching or memory devices or might form the basis of artificial muscle.

Scientists arc talking about next generation of materials that will have built tn "software". These Intelligent

materials will be able to delect changes in their environmental conditions (sensor func tlon) make their own Judg mcnls (processor function) and give instructions or take actions themselves (effector function).

For example, an intelligent structural material will sell diagnose a defect, indicate the defect by a colour change or noise emission before a serious accident occurs, and may even al tempt self recovery by rcctf fying Hie defect itself.

If such materials can be produced, it is expected that epoch- making technical innovations will occur In the fields of electronics, medical treatment. biotechnology and safely engineering.

Japan has established the Intelligent Material Forum and launched a five-year research programme aimed at "the creation and production of structural materials with intelligent functions."

In Britain, a Smart Structures Research Institute has been set up at Strathclyde University in Glasgow. It is expected Ihat all new bridges to be built in Europe and the United States will Incorporate smart structure techniques making It possible to monitor them remotely and receive automatic warning of impending structural failure. The smart structure technology also has promising applications in the field of pipelines for waler. oil uid gas.

Dr K S Jayaraman is PPI St fence Editor based in Netu Delhi.