Peristome‐Mimetic Curved Surface for Spontaneous and Directional Separation of Micro Water‐in‐Oil Drops

Abstract

AbstractSeparation of micro‐scaled water‐in‐oil droplets is important in environmental protection, bioassays, and saving functional inks. So far, bulk oil–water separation has been achieved by membrane separation and sponge absorption, but micro‐drop separation still remains a challenge. Herein we report that instead of the “plug‐and‐go” separation model, tiny water‐in‐oil droplets can be separated into pure water and oil droplets through “go‐in‐opposite ways” on curved peristome‐mimetic surfaces, in milliseconds, without energy input. More importantly, this overflow controlled method can be applied to handle oil‐in‐oil droplets with surface tension differences as low as 14.7 mN m−1 and viscous liquids with viscosities as high as hundreds centipoises, which markedly increases the range of applicable liquids for micro‐scaled separation. Furthermore, the curved peristome‐mimetic surface guides the separated drops in different directions with high efficiency.