Firefighters entering burning buildings, athletes competing in the broiling sun and workers in foundries may eventually be able to carry their own, lightweight cooling units with them, thanks to a nanowire array that cools, according to Penn State materials researchers. "Most electrocaloric ceramic materials contain lead," said Qing Wang, professor of materials science and engineering. "We try not to use lead. Conventional cooling systems use coolants that can be environmentally problematic as well. Our nanowire array can cool without these problems." Electrocaloric materials are nanostructured materials that show a reversible temperature change under an applied electric field. Previously available electrocaloric materials were single crystals, bulk ceramics or ceramic thin films that could cool, but are limited because they are rigid, fragile and have poor processability. Ferroelectric polymers also can cool, but the electric field needed to induce cooling is above the safety limit for humans. Wang and his team looked at creating a nanowire material that was flexible, easily manufactured and environmentally friendly and could cool with an electric field safe for human use. Such a material might one day be incorporated into firefighting gear, athletic uniforms or other wearables.