New forms of plastic that conduct electricity, already used in a few commercial applications, may soon find a host of novel uses in which they outperform copper, the most common conductor, specialists in the field said.

Sometimes called synthetic metals, conductive plastics were invented in the 1970s but have not found many uses because they were more expensive than copper and carried far less current for a given thickness of wire.

This is changing. Alan G. McDiarmid, a pioneer in the field at the University of Pennsylvania, writing in the February Scientific American, said recent advances suggest conductive plastics may someday be made better conductors than silver, the best known conductor at room temperature. Because the plastics are lighter than metal, they could replace copper wiring, the second best conducting metal, in airplanes.

The Japanese have come out with a coin-sized rechargeable battery that has plastic electrodes. Its capacity is three times that of conventional lithium rechargeables.

Other potential applications include:

Heat-sensing devices that rely on the fact that heat alters the conductivity of some conductive plastics.

Sandwiches of conductive plastic film in windows whose tinting can be adjusted at will.

Drug-dispensing plastic pellets impregnated with a drug that can be implanted in the body. Because the plastic responds to an electromagnetic field by changing its molecular structure, which alters the rate at which the drug is released, doses of the drug can be regulated by an external electromagnetic field.