Anisotropic Stick-Slip Behavior of Aqueous Drops on Lubricated Chemically Heterogeneous Slippery Surfaces

TL;DR

This paper introduces a novel chemically heterogeneous surface design that enables controlled anisotropic drop motion, including stick-slip behavior, by leveraging differential wetting properties on lubricated stripes, offering a cost-effective alternative to topographic methods.

Contribution

The study presents a new approach using chemically patterned lubricated surfaces to achieve directional drop control and anisotropic stick-slip behavior, improving efficiency over previous topographic strategies.

Findings

Drops exhibit anisotropic sliding behavior along and across stripes.

A phase diagram categorizes different drop dynamic states.

The method enables directional control of aqueous drops on lubricated surfaces.

Abstract

Conventional slippery surfaces show isotropic drop mobility in all directions, but many applications require directional drop motion along a particular path only. In previous studies, researchers used topographic substrates, together with different external stimuli, to demonstrate anisotropic drop motion, which is not very efficient and cost-effective. Herein, we report a novel approach to smartly control drop motion on lubricating fluid coated chemically heterogeneous surfaces composed of alternating hydrophobic and hydrophilic stripes. Upon depositing an aqueous drop on such a surface, the underneath lubricating fluid dewets from the hydrophilic regions but remains intact on the hydrophobic ones, providing sticky and slippery areas for the drop. This results in remarkable anisotropic drop sliding behavior, from uniform motion along parallel to stripes to stick-slip motion along the perpendicular to them. Furthermore, we also demonstrate a phase diagram summarizing different dynamic situations exhibited by drops, sticking, or moving in one or both directions.