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A knee sleeve that provides feedback to athletes about their knee movements; a bra that adjusts support in response to breast movement; and a stretch cotton T-shirt that keeps track of heart rate, body temperature, and other vital signs are just a few possible applications of new types of cloth known as electro-textiles.

Also known as intelligent polymers, electro-textiles have plastic strands that can carry electricity woven or knitted into natural or synthetic fabrics. These conductive fibers alter their conductivity in response to stretching, temperature, or moisture.

Polymers that conduct electricity aren't a new idea. Back in the 1970s, U.S. and Japanese researchers found that plastic—normally an insulator of electricity—could act as a conductor under certain circumstances.

In the case of the knee sleeve, polymer strands woven into the sleeve send signals to a detachable buzzer when the fabric is stretched, warning the wearer of an incorrect knee movement. Developed in Australia through a collaboration between the University of Wollongong and
Commonwealth Scientific and Industrial Research Organization (CSIRO) Textile and Fibre Technology center, the "intelligent knee sleeve" was tested during the Geelong football team's preseason training sessions.

Players of Australian football—an amalgam of soccer, rugby, and American football—are prone to knee injuries from all the running, cutting, jumping, and kicking. Without interfering with normal movements, the knee sleeve "tells" the athlete through audio tones when he is developing bad knee habits that could lead to anterior cruciate ligament damage.

The developers believe the technology used to design the intelligent knee sleeve can be applied to other sports in which consistency of movement is important, like tennis, golf, baseball, and track and field. It could also help patients rehabilitating after an injury to repeat the exercises prescribed to them in a physical therapist's office.

But electro-textiles aren't confined to the sports arena. The clothing industry is very interested in possible applications. Some of the ideas bandied around include bed sheets and T-shirts that monitor vital signs, outdoor clothing that changes insulation based on temperature, and clothes that power phones and music devices.

A few years ago, scientists at the University of Wollongong started developing a "smart bra" that changes its properties in response to breast movement. Using polymer sensors, the bra tightens and loosens its straps, or stiffens and relaxes its cups in response to the movements of the wearer.