A printable asymmetrical surface pattern for responsive directional liquid transport

Abstract

Long-distance directional liquid surface transport is of great importance not only for many biologic functionalities of living organisms, but also for broad applications of open-channel microfluidics, microreactors, heat transfer, water harvesting, and chemo/bioanalysis. However, relevant studies have long concentrated on asymmetric 3D arrays produced by complicated microfabrication techniques. Also, it remains challenging to switch the liquid surface transport direction on demand in a specific system. Herein, we showed that directional liquid transport could be controlled easily on printable asymmetric surface patterns via anisotropic interactions between the topographical barriers and the liquid. Due to the unbalanced motion resistance and Laplace pressure, liquids showed different directional transport modes according to their surface tension. When patterned on elastic substrates, mechanical stretching could change their characteristic geometric parameters and thereby switch the direction of liquid transport. Thus, this study may not only offer an affordable and ingenious surface that can achieve liquid directional steering dictated by its inherent properties, but also pose an endurable and simple method for intelligent liquid transport control. The responsiveness to liquids and strains offered extra flexibility of switching liquid transport directions essential in liquid droplet separation and open-channel microfluidics.