Texture and Wettability of Metallic Lotus Leaves

TL;DR

This paper demonstrates that hydrophilic metallic surfaces can be made superrepellent to water through chemical texturing, mimicking lotus leaves, which could enable scalable manufacturing of superhydrophobic surfaces without coatings.

Contribution

It introduces a stochastic chemical texturing method to create superrepellent metallic surfaces, expanding the design space beyond deterministic structuring and coatings.

Findings

Hydrophilic metals can be made superrepellent via chemical texturing.

A mechanistic model links surface roughness to wettability and repellency.

The method enables scalable, robust manufacturing of superhydrophobic surfaces.

Abstract

Superhydrophobic surfaces with the self-cleaning behavior of lotus leaves are sought for drag reduction and phase change heat transfer applications. These superrepellent surfaces have traditionally been fabricated by random or deterministic texturing of a hydrophobic material. Recently, superrepellent surfaces have also been made from hydrophilic materials, by deterministic texturing using photolithography, without low-surface energy coating. Here, we show that hydrophilic materials can also be made superrepellent to water by chemical texturing, a stochastic rather than deterministic process. These metallic surfaces are the first analog of lotus leaves, in terms of wettability, texture and repellency. A mechanistic model is also proposed to describe the influence of multiple tiers of roughness on wettability and repellency. This demonstrated ability to make hydrophilic materials superrepellent without deterministic structuring or additional coatings opens the way to large scale and robust manufacturing of superrepellent surfaces.