Engineers at University of Illinois at Urbana-Champaign have built the world's smallest working fuel cell, at 9 cubic millimeters — 3mm, or 1/8th of an inch, per side — and it could mean fewer batteries for you to buy and throw out to power your favorite gadgets.
They achieved the micro-size cell by getting rid of the pump, pressure sensor and electronics typically used in fuel cells. This new design has just four components: a water reservoir on top, a metal hydride chamber below, a thin membrane that separates them, and an assembly of electrodes to conduct the electricity.
Tiny holes in the membrane allow the water molecules to reach the adjacent metal-hydride chamber as vapor. There, it reacts to form hydrogen, which fills the chamber and pushes the membrane upwards, blocking the flow of water. The hydrogen is then gradually depleted, though, as it reacts at the electrodes beneath the chamber to create electricity.
The fuel cell generates 0.7 volts and a current of 0.1 milliamps for 30 hours before it runs out of fuel, but the engineers say the latest designs give currents of around 1 milliamp at a similar voltage.