Novel technique makes liquid droplets run uphill

The mechanism, which mechanical engineers from the City University of Hong Kong (CityU) describe in Nature Materials, can transport droplets of liquid against gravity and even for the first time along a vertical surface. Prof Wang Zuankai of CityU collaborated with Prof Xu Deng of the University of Electronic Science and Technology of China and Prof Hans-Jürgen Butt of the Max Planck Institute for Polymer Research in Germany on the work, key to which is manipulation of surface charge via liquid contact.

The researchers developed a superamphiphobic (water- and oil-repellent) surface and dropped a chain of water droplets onto it. On impact, the droplets immediately spread out, retracted, and rebounded from the surface. This resulted in electron separating from the droplets and creating a negative charge on the surface.

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