Fabric flips from green to brown when a voltage is applied

Scientists are closer to producing outfits for the armed forces that change colour to match surroundings when soldiers move from a forest to a desert.

Clothing that adapts quickly to camouflage troops in different places would protect them against visual detection. Sunglasses, anti-glare mirrors and electronic display devices all use conducting polymers to change colour. Now, Wei Huang and Hong Meng at Nanjing Tech University, and their team in China, have designed an organic polymer that is green in the reduced state but oxidises and turns a sandy-brown when a low voltage is applied.

‘The alkoxy side chains of our polymer play an important role fine tuning the colors,’ explains Meng. The polymer takes 1–1.5 seconds to change colour and maintains its activity after 1000 repetitions. The polymer also absorbs IR radiation, so could conceal body heat too, and it is super-hydrophobic so would not wash out of clothing.

The structure of the polymer’s sidechain influence the material’s colour

The team used conductive fabric as an electrode to confirm the polymers application in clothing.  To make it, they sprayed the conductive fabric with a mixture of the polymer and toluene.

Luca Beverina, an expert in conducting materials at the University of Milano-Bicocca, Italy, says ‘a working device on conducting fabric is successfully demonstrated and my experience is that the industrial interest in such products could be relatively high, and not just restricted to the military sector’.