Working up a sweat could recharge the environment

RESEARCH: Team shows perspiration can be power source for wearable devices

A new generation of wearable devices could be powered by human sweat instead of conventional, environmentally-unfriendly batteries, according to Scottish scientists.

Engineers at Glasgow University say working up a sweat could be enough to generate power for exercise monitors and other electronic devices in the future.

They have developed a new type of flexible supercapacitor which replaces the electrolytes found in conventional batteries with sweat. It can be fully charged with as little as 20 microlitres of fluid and is robust enough to survive 4,000 cycles of the types of flexes and bends it might encounter in realworld use.

It works by coating polyester cellulose cloth in a thin layer of a polymer known aspoly(3,4-e thy len edioxyt hi op he ne) polystyrene sulfonate – or Pedot:pss.

The team chose the polyester cellulose cloth because it is particularly absorbent, and Pedot:pss because it offers a useful combination of flexibility, high conductivity and environmental friendliness. The Pedot:pss acts as the supercapacitor’s electrode.

As the cloth absorbs its wearer’s sweat, the positive and negative ions in the sweat interact with the polymer’s surface, creating an electrochemical reaction which generates energy.

The researchers tested the

“Human sweat provides a real opportunity to do away with... toxic materials. PROF RAVINDER DAHIYA, GLASGOW UNIVERSITY

effectiveness of their tech by having volunteers run outdoors and on a treadmill while wearing a 2cm x 2cm cell version of the device. The runner sweated enough to allow the device to generate about 10 milliwatts of power – about enough to power a small bank of LEDS – which kept it going until the runner stopped.

The research was led by Professor Ravinder Dahiya, head of the Bendable Electronics and Sensing Technologies (Bestt) group at the university’s James Watt School of Engineering, who said yesterday: “Conventional batteries are cheaper and more plentiful than ever before, but they are often built using unsustainable materials which are harmful to the environment.

“What we’ve been able to do for the first time is show human sweat provides a real opportunity to do away with those toxic materials, with excellent charging and discharging performance.”