Programmable Droplet Transport Using Mechanically Adaptive Chemical Gradients with Anisotropic Microtopography

Abstract

The effect of anisotropic surface roughness on the spontaneous transport of droplets on chemical wettability gradients has not been investigated. Understanding the details of this process has the potential to unlock new fluid handling functionality critical to the development of next‐generation surfaces with intelligent control capabilities. Herein, the fabrication of chemical gradients with mechanically tunable anisotropic microtopography (microwrinkles with directional roughness) is described and the use of these surfaces in programable microdroplet transport is reported. In particular, the interplay between chemical gradient intensity, microwrinkle orientation, and droplet velocity/trajectory was investigated, enabling the rational synthesis of surface fluidic systems capable of mechanically programmable 2D droplet manipulations, vertical droplet transport, and droplet combination. These findings highlight the sophisticated capabilities of mechanically switchable droplet handling systems and demonstrate new avenues for designing intelligent materials with programable transport properties for potential use in surface/microfluidics, water harvesting, energy generation, bioanalysis, and microreactor design.