A period of the 90's fashion craze focussed on clothing which changed colour with body heat - based on a time temperature ink. It died out as these fashion trends naturally do and when people realised that it wasn't so great to show where you were sweating.
But now with the emerging range of nanotechnologies are useful applications of wearable electronics, such as clothing which dispense medication based on sensed need (iontophoresis), shirts with radios and music payers embedded into them, suits for camouflage and coats with displays carrying weather forecasts.
In July 2004 France Telecom incorporated a wireless display slipped into the chest pockets of garments created by a fashion designer. In a promotional video shoot, a woman smiles as the display in her chest pocket carries a flashing red heart.
Maggie Orth at International Fashion Machines produces textiles that are screens. Their 'Electric Plaid' is a weave of conductive and resistive material coated with ink that changes color based on its temperature (like the clothing mentioned above). As low voltages are passed through the fibres, they are warmed and the colour changes. Orth says they are working on a woven touch sensor which will be ready this year.
For more information see International Fashion Machines.
Building transistors directly onto fibers
Vivek Subramanian from the University of California Berkeley has demonstrated building transistors onto fibers. The transistors were formed at the cross section of fibers using an additive process (i.e. not etching away patterns). The textile could be curved to the equivalent of a 15 centimeter cylinder, and using a more flexible organic insulator would allow more flexibility.