New York, April 29 (IANS): Firefighters entering burning buildings, athletes competing in the broiling sun and workers in foundries may soon be able to carry their own, lightweight cooling units with them, thanks to a nanowire array that cools, say researchers.

The 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.

The vertically aligned nanowire array that the researchers created can cool about 5.5 degrees Fahrenheit (-14.7 degree Celsius) using 36 volts, an electric field level safe for humans. 

A 500 gram battery pack about the size of an iPad could power the material for about two hours.

"This low voltage is good enough for modest exercise and the material is flexible," said Qing Wang, professor of materials science and engineering at Pennsylvania State University in the US.

The findings appeared in the journal Advanced Materials.

Such a material might one day be incorporated into firefighting gear, athletic uniforms or other wearables. 

"Now we need to design a system that can cool a person and remove the heat generated in cooling from the immediate area," Wang noted.

The researchers grew the material in two stages. First, titanium dioxide nanowires were grown on fluorine doped tin oxide coated glass. 

The researchers used a template so all the nanowires grow perpendicular to the glass surface and to the same height. Then they infused barium and strontium ions into the titanium dioxide nanowires.

The researchers applied a nanosheet of silver to the array to serve as an electrode.

It is possible to move this nanowire forest from the glass substrate to any substrate they want -- including clothing fabric -- using a sticky tape, the researchers said.

"Conventional cooling systems use coolants that can be environmentally problematic as well. Our nanowire array can cool without these problems," Wang said.