Designer Logic Comes to E-Textiles

Sew cool!
Connected polymer threads create transistors that are linked into a logic circuit.

M. Hamedi et al., Nature Materials, published online 1 April 2007.

E=mc2 t-shirts are no longer the latest in geek chic. By intertwining polymer threads, researchers have woven transistors and other simple logic circuitry into the very warp and weft of textiles. Such computing fabrics may one day track the medical conditions of patients or sense chemical weapons for soldiers.

Computing fabrics have been around for more than a decade. In 1996, for example, researchers at Georgia Institute of Technology in Atlanta created a shirt studded with sensors capable of monitoring a patient's heartbeat, temperature, and breathing. Other researchers have added tiny silicon chips to their textiles to create rudimentary computation. But such devices must be sewn on or attached by some other means that creates added expense and often makes them more susceptible to failure.

So Olle Inganäs, a chemist at Linköping University in Sweden, and his colleagues decided to see if they could make their electronic circuitry out of a textile's own threads. They started by coating nylon threads with a conducting polymer combo abbreviated PEDOT/PSS. Where two threads crossed, they dabbed a bit of a conductive liquid polymer electrolyte, which dried and hardened into an electrical connection between the two conducting threads. The crossed fibers then acted as a transistor, so that when a voltage was applied to one of the conducting threads, current began to flow through the crossing thread, the researchers reported online yesterday in Nature Materials. They even wove their threads into a conventional textile and created patterns of connections that formed two types of circuits common in digital logic--an inverter and a multiplexer. Whether such fabrics will hold up to the punishment of a washing machine isn't yet known, but Inganäs says the fibers and transistors are waterproof.

The new approach could be a boon for incorporating various types of circuitry into textiles, says Barry DeCristofano, a chemical engineer and electrical textiles expert at the U.S. Army Natick Soldier Research, Development, and Engineering Center in Massachusetts. "Having the conducting fibers woven into your fabric would allow you to pattern those connections in a lot of different ways," DeCristofano says.

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