Lossless and Directional Transport of Droplets on Multi-bioinspired Superwetting V-shape Rails

Lossless and directional droplet transport is desirable in biological processes as well as in technical applications such as targeted drug therapies, bioassays, and microfluidics. Conventional methods that use surface energy and Laplace pressure gradients to achieve spontaneous droplet transport often suffer from droplet destruction and loss. Herein, an efficient strategy is reported based on a V-shaped underwater superoleophobic rail and a V-shaped superhydrophobic rail that delivers lossless and directional oil and water droplet transport, respectively. The V-shaped rail not only converts the kinetic energy of the impacting droplets into planar motion but also seriously deforms the droplet to create a 3D Laplace pressure difference that directionally moves the droplet. The superoleophobic and superhydrophobic wettability of a copper rod surface is crucial for achieving lossless water and oil droplet transport, which is attributable to low adhesive forces acting on the droplets. The V-shaped rail can also feasibly be used in droplet sensors, microchemical reactions, droplet-based electricity generators, and water/oil separation applications, thereby significantly expanding the applications of lossless and directional droplet transport.

Automated summary

This study reports an efficient strategy for lossless and directional oil and water droplet transport using a V-shaped underwater superoleophobic rail and a V-shaped superhydrophobic rail. The kinetic energy of impacting droplets is converted into planar motion by the V-shaped rail, while the droplet deformation creates a 3D Laplace pressure difference for directional droplet movement. The superoleophobic and superhydrophobic wettability of a copper rod surface is crucial for achieving lossless droplet transport due to low adhesive forces. The applications of this V-shaped rail extend to droplet sensors, microchemical reactions, droplet-based electricity generators, and water/oil separation.