Robust liquid repellency by stepwise wetting resistance

Abstract

Maintaining both high static liquid repellency and large dynamic pressure resistance is highly preferred for a myriad of applications, such as energy conversion, anti-icing, and antifouling. However, these two merits are mutually exclusive in conventional surface design: Sparse structures with reduced solid-liquid contact area yield high static liquid repellency, which in turn inevitably suffer from poor dynamic wetting properties as exemplified by low wetting resistance and easy Cassie-to-Wenzel transition. Here, we circumvent this trade-off by designing a springtail cuticle-inspired surface consisting of multilayered, doubly reentrant posts with increasing diameter from top to bottom, which simultaneously imparts high static wetting and multiple energy barriers for the gradual liquid penetration in a stepwise mode. Particularly, the synergy between the doubly reentrant structure, which increases the breakthrough pressure, and the multilayered architecture sustains a robust liquid repellency in a broad range of conditions otherwise challenging on conventional structures. Our findings provide an important insight for the rational design of robust superliquid-repellent surfaces.