A researcher at Lawrence Berkeley National Laboratories has demonstrated a fuel cell measuring just 200 nanometers across that potentially can be integrated on-chip to supply power from a hydrogen reservoir for decades. Today, there are only two ways to power remote sensors and similar devices that require little power over years of unattended use. For devices with lifetimes of less than 10 years, the solution is expensive, bulky lithium batteries. For longer lifetimes, the answer is batteries that draw energy from radioactive isotopes. While experimenting with making metallic nanowires at the University of Wisconsin, Madison, Kenneth Lux hit upon a way to build three-dimensional electrodes porous enough for nano fuel cells. By making a nanowire alloy of two metals, he found it was possible to remove the atoms of one metal in the alloy, leaving behind a densely porous 3-D structure that increased the surface area of the electrode by orders of magnitude. Lux discovered the best way to make porous 3-D platinum electrodes: soak copper-platinum alloy nanowires in nitric acid, removing their copper. Later, they found, they could create nano fuel cells by merely laying them out lithographically so their anode and cathode electrodes protruded from the same side, with a liquid electrolyte reservoir that bent to chemically connect them. With concept proven, Lux is trying to replace the liquid electrolyte with a solid-state version, enabling future remote sensor chips to potentially integrate all the components but fuel for arrays of on-chip fuel cells.