Tunable Wettability with Stretchable Microstructured Surfaces

Abstract

Analyzing the wettability of stretchable microstructured surfaces is crucial in applications like soft robotics, wearable biosensors, stretchable electronics, and electronic skin (e‐skin). However, it remains unclear how stretching affects the surface free energy (SFE) of these stretchable surfaces. In this article, stretchable microstructured surfaces are designed and fabricated, enabling liquid droplets to stay on top of the surface gaps. The corresponding SFE values are quantified as a function of both micropillar geometry and strain. It is observed that stretching could significantly affect their SFE and wettability. For instance, for the microstructured surface with pillar and gap dimensions of 10 μm, increasing the strain from 0% to 50% causes a sevenfold increase in the effective SFE. Interestingly, reversible decreasing of the strain decreases SFE to its original value, suggesting that the SFE remains unchanged after a complete stretching and releasing cycle. This trend agrees with the measurement of apparent contact angle (CA) as a function of strain. The results demonstrate stretching's capacity to significantly increase the wettability of microstructured surfaces, leading to a decrease in the CA and an increase in SFE. These findings further shed light on understanding the tunable wettability of microstructured surfaces under various deformation conditions.