# Effect of Surfactants on Longevity of Submerged Superhydrophobic Surfaces

## TL;DR

This study shows how surfactants can either extend or shorten the lifespan of superhydrophobic surfaces underwater, depending on their concentration.

## Contribution

The novel contribution is the experimental demonstration of surfactant effects on SHS longevity across multiple surfactant types and surface geometries.

## Key findings

- High surfactant concentrations cause sudden wetting transitions, reducing SHS longevity.
- Low surfactant concentrations increase SHS longevity by reducing mass transfer.
- The effect was consistent across four surfactants and three surface geometries.

## Abstract

The gas trapped on a submerged superhydrophobic surface
(SHS) could
diffuse into the surrounding liquid, reducing the SHS longevity. Although
surfactants are known to inhibit mass transfer between gas and liquid
phases, their influence on SHS longevity remains unclear. In this
work, we experimentally investigate the effect of surfactants on the
mass transfer from the SHS to the surrounding liquid and the resulting
SHS longevity. Four surfactants, 1-pentanol, Triton X-100, 2-propanol,
and methanol, were tested over a range of concentrations and on three
types of SHS texture geometries: microholes, microposts, and a randomly
roughed texture. We found that at sufficiently high surfactant concentrations,
the SHS longevity decreased significantly due to a sudden wetting
transition triggered probably by surface energy minimization. In contrast,
at low surfactant concentrations, the SHS longevity was larger than
that in pure water and increased with an increasing surfactant concentration.
This extended SHS longevity was observed for all four surfactants
and across all three texture geometries. Our results demonstrate the
universal role of surfactants in reducing the mass transfer coefficient
and highlight the importance of accounting for surfactants when assessing
the SHS longevity in real-world applications.