flexible supercapacitor, which stores energy, replacing 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 use.

The device works by coating polyester cellulose cloth in a thin layer of a polymer, which 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.