Monostable Super Antiwettability

TL;DR

This paper demonstrates the existence of a monostable region in super-antiwettability, enabling reversible transitions between wetting states on rough surfaces, which is crucial for designing durable super-antiwetting materials.

Contribution

It introduces the concept of a monostable region allowing reversible Wenzel-Cassie transitions, supported by experimental validation and a predictive transition criterion.

Findings

Identified a monostable region in phase space for super-antiwetting.

Established a simple criterion for Wenzel-to-Cassie transitions.

Experimental validation across different liquids and substrates.

Abstract

Super-antiwettability is an extreme situation of wetting where liquids stay at the tops of rough surfaces, in the so-called Cassie state1. Owing to the dramatic reduction of solid/liquid contact, it has many applications, such as antifouling2,3, droplet manipulation4,5, and self-cleaning6-9. However, super-antiwettability is often destroyed by impalement transitions caused by environmental disturbances10-16 while inverse transitions without energy input have never been observed12,17-21. Here we show through controlled experiments that there is a "monostable" region in the phase space of the receding contact angle and roughness parameters where transitions between (impaled) Wenzel and Cassie states can be reversible. We describe the transition mechanism and establish a simple criterion that predicts the experimentally observed Wenzel-to-Cassie transitions for different liquids placed on micropost-patterned substrates. These results can guide for designing and engineering robust super-antiwetting surfaces.