The device, developed by Feng ZHOU at CAS Lanzhou Institute of Chemical Physics, is based on polydimethylsiloxane decorated with a hydroresponsive polyelectrolygte brush. Upon increasing the humidity or immersing in water, the brush swells and the resulting lateral pressure leads to a bending movement of the rubber within a fraction of a second. When the environmental humidity is repeatedly cycled up and down, the small device walks on a surface with a roughness gradient.

CAS news release, July 3, 2015