# Drop Impact on Two-Tier Monostable Superrepellent Surfaces

## TL;DR

This study investigates how drops impact two-tier superhydrophobic surfaces, revealing a reversible wetting state transition that enhances self-cleaning and condensation, offering new insights for designing durable superrepellent materials.

## Contribution

It uncovers a repeated Cassie-Wenzel-Cassie transition during drop impact on two-tier surfaces, contrasting with traditional irreversible wetting breakdowns, and quantifies the influence of material parameters.

## Key findings

- Reversible Cassie-Wenzel-Cassie transition observed during drop impact.
- Impact dynamics influenced by material parameters.
- Enhanced self-cleaning and condensation due to transition.

## Abstract

Superrepellency is a favorable non-wetting situation featured by a dramatically reduced solid/liquid contact region with extremely low adhesion. However, drop impact often brings out a notable extension of the contact region associated with rather enhanced water affinity, such renders irreversible breakdowns of superhydrophobicity. Here, we report an alternative outcome, a repeated Cassie-Wenzel-Cassie (CWC) wetting state transition in the microscale occurs when a drop impacts a two-tier superhydrophobic surface, which exhibits a striking contrast to the conventional perspective. Influences of material parameters on the impact dynamics are quantified. We demonstrate that self-cleaning and dropwise condensation significantly benefit from this outcome - dirt particles or small droplets in deep textures can be taken away through the transition. The results reported in this study allows us to promote the strategy to design functional superrepellency materials.

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Source: https://tomesphere.com/paper/1906.07894