A lightweight, comfortable jacket that can generate the power to light up a jogger at night may sound futuristic, but materials scientist Trisha Andrew at the University of Massachusetts Amherst could make one today. In a new paper this month, she and colleagues outline how they have invented a way to apply breathable, pliable, metal-free electrodes to fabric and off-the-shelf clothing so it feels good to the touch and also transports enough electricity to power small electronics.
Generating small electric currents through relative movement of layers is called triboelectric charging, explains Andrew, who trained as a polymer chemist and electrical engineer. Materials can become electrically charged as they create friction by moving against a different material, like rubbing a comb on a sweater. "By sandwiching layers of differently materials between two conducting electrodes, a few microwatts of power can be generated when we move," she adds.
In the current early online edition of Advanced Functional Materials, she and postdoctoral researcher Lu Shuai Zhang in her lab describe the vapor deposition method they use to coat fabrics with a conducting polymer, poly(3,4-ethylenedioxytiophene) also known as PEDOT, to make plain-woven, conducting fabrics that are resistant to stretching and wear and remain stable after washing and ironing. The thickest coating they put down is about 500 nanometers, or about 1/10 the diameter of a human hair, which retains a fabric's hand feel.
Until recently, she and Zhang point out, textile scientists have tended not to use vapor deposition because of technical difficulties and high cost of scaling up from the laboratory. But over the last 10 years, industries such as carpet manufacturers and mechanical component makers have shown that the technology can be scaled up and remain cost-effective. The researchers say their invention also overcomes the obstacle of power-generating electronics mounted on plastic or cladded, veneer-like fibers that make garments heavier and/or less flexible than off-the-shelf clothing "no matter how thin or flexible these device arrays are."