Single-Side Etching for On-Demand and Versatile Liquid Diodes with Opposite Wettability in Multiple Systems

Abstract

Materials with opposite wettability to achieve one-way liquid transportation, that is, liquid diode, have been widely used in liquid capture, rapid elimination of sweat and blood, separation of immiscible liquids and so on. Current work has been mainly bent on the fabrication of asymmetric wettability in single phase such as air or water, which inevitably hindered their utilization in multiple systems. Till now, it has been terribly challenging to achieve ubiquitously opposite wettability for on-demand liquid diode in various systems. Herein, a two-step single-side etching strategy was adopted to develop CuC 2 O 4 nanorod and copper coating on reverse sides of single-layered meshes. Opposite wettability formed not only in air but also under various liquids such as water and oil to realize unidirectional liquid penetration in these systems. More importantly, varied thickness of lyophobic layer was found to be crucial in liquid transportation in different systems, which was further demonstrated by the analysis of Laplace pressure on various meshes. Besides, such single-layered liquid diodes were also competent in fog collection, liquid capture and water/oil separation, exhibiting great versatility. Thus, the findings here not only proposed on-demand and versatile liquid diodes but could also enlighten further study in smart valves in different systems.

Keywords: single-side, liquid diode, opposite wettability, multiple systems, single-layered