Dynamically adjustable wet ridge for directional liquid movement and controllable coating distribution

Abstract

Controllable wettability on the surface is widely used in architecture coating, energy transfer, microfluidics, etc. Much progress has been focused on liquid wetting state transition of the artificial surface by external induction, while it is still difficult to realize in situ reversible and controllable transformation of the wetting state in real-time to meet the requirement for complex practical applications. Herein, inspired by the unique functions of the superhydrophobic self-cleaning lotus leaf and long-term preservation of rose petal resulting from special wetting states, we achieve the real-time unidirectional movement of droplet on superhydrophobic ZnO nanoarrays surface via the dynamically adjustable wet ridge. By changing the height of the nanorod and the wetting direction of the solvent, the dynamic wet ridge occurs and controls the existence of air in nanostructure, that is, symmetrical wet ridge can realize in situ reversible wetting state transition, while asymmetrical wet ridge can drive water droplet to move. Based on this, the strategy can be used to effectively adjust wettability of coating solution on superhydrophobic surface and to further obtain controllable coating distribution. This work offers an available strategy to achieve real-time droplet movement and controllable complex coating even on structurally challenging substrate, so as to provide opportunities and positive effects for designing functional materials and devices.