Excellent Fog-Droplets Collector via Integrative Janus Membrane and Conical Spine with Micro/Nanostructures

Inspired by a cactus spine and trichomes integrated fog collection system, a strategy is presented to design a micro/nanostructured conical spine and Janus membrane integrative system (MNCS+JM). In this strategy, the surface of conical spine can be covered with rough micro and nanostructure (MNCS), so that the tiny fog-droplets can be captured, coalesced, and transported. Janus membrane (JM) with inside hydrophobic surface and outside hydrophilic surface is further used to control the water collection in process of droplet transport when the Janus membrane is vertically placed with different positions on the MNCS, thus MNCS+JM propel the droplet continuously for transport–coalescence–transport in a circle of droplet transport and collection. It is demonstrated that a higher fog collection rate can be achieved effectively, which is attributed to a cooperation effect between the Laplace pressure in difference and the released surface energy in droplet coalescence, in addition to wettability force of superhydrophobic–hydrophilic difference in the Janus membrane. This strategy of MNCS+JM offers an insight into the surface of materials to control the droplet transport for water collection in efficiency, which is significant to be extended into the realms of applications such as high-efficiency water collection systems, microfluidics devices, and others.