Researchers from the Institute of Chemistry in Beijing have developed a new material that can repel or absorb water and may be used to guide flowing liquids.
Their paper, “Reversible Super-hydrophobicity to Super-hydrophilicity Transition of Aligned ZnO Nanorod Films”, in the Journal of the American Chemical Society reports on a coating of nanosized columns of zinc oxide that is normally water-resistant but becomes water absorbing when exposed to ultraviolet light. When in the water repelling state liquid droplets roll off the surface and when water absorbing the droplets flatten into a smooth film and soak into the surface. The material becomes repellent again after seven days in the dark.
If the researchers can reduce the transition time, the coating could be used to control the movement of liquids. One application is the movement of liquids around a 'laboratory on a chip' which will allow researchers to perform detailed chemical analyses of very small samples.