Interlaced wetting surfaces with switchable wettability for manipulating underwater oil droplets

Biomimetic surfaces that can manipulate droplets have attracted intense attention because of their application prospects in the fields of drug detection, cell sorting, bio-sensor, etc. Although many promising advances have been made, it is still a challenge to achieve lossless, no cross-contamination and on-demand controllable manipulation of underwater oil droplets without external energy input. Herein, SHI & SLIP interlaced wetting smart surfaces were fabricated by a simple strategy for manipulating underwater oil droplets. Depending on the switchable wettability and reasonable alternating wetting, the lubricant-infused area and superhydrophilic area can be on-demand controlled on the same surface. Numerical calculation and theoretical analysis reveal that the energy barrier between different interfaces is an important factor to realize underwater oil droplet manipulation. By the rational design of the interlaced wetting pattern, the capture, lossless transfer, fusion and directional transportation of underwater oil droplets were realized. Besides, the as-prepared surface has cross-contamination resistance, stable wettability and rewritability, which expands the application field and improves the potential value. We expect this work to open new avenues for flexible and controllable manipulation of underwater oil droplets and promote the development of smart microfluidic platform. It is also expected to be used in unpowered delivery systems, micro-reactions and energy transfer.