Role of wide tip of mushroom-like micropillar arrays to make the Cassie state on superrepellent surfaces

Abstract

In this study, we have demonstrated a structural advantage of mushroom-like micropillar arrays for making superrepellent surfaces. We derived and plotted theoretical graphs based on the Cassie–Baxter equation to find out optimal conditions in order to repel liquid droplets with a wide range of surface tensions on desirable surfaces. Superrepellency experiments were carried out using two types of microstructure, namely, a mushroom-like shape and a cylindrical shape, for comparison with the theoretical analysis. The results show that only mushroom-like arrays can maintain the metastable Cassie state even with a liquid droplet of low surface tension such as ethanol, owing to the structural advantage of their wide-tip shape. As a result, we identified the smart function of the wide-tip structure by theoretical and experimental approaches for designing superrepellent surfaces that can be used for various potential applications.