# From Hydrophilic to Superhydrophobic: Tuning Surface Wettability through Salvinia-Inspired Topographies

## TL;DR

This paper shows how to make hydrophilic surfaces superhydrophobic using only structural design, inspired by the Salvinia plant, without chemical coatings.

## Contribution

A novel method using two-photon polymerization to create superhydrophobic surfaces through structural design alone.

## Key findings

- Salvinia-inspired microstructures achieved contact angles above 160° without chemical modification.
- Surface architecture significantly affects wettability, with design parameters like arm number and spacing being critical.
- Fabrication resolution impacts surface quality and droplet behavior, as shown by power spectral density and 3D topography analysis.

## Abstract

The development of superhydrophobic surfaces traditionally
relies
on combining surface roughness with low-surface-energy coatings. In
contrast, this work demonstrates the use of two-photon polymerization
to induce superhydrophobicity on hydrophilic substrates solely through
structural design. A comprehensive set of Salvinia-inspired microstructures
was fabricated with precise control over geometrical features such
as the number of arms, arm diameter, fill configuration, spacing,
and height. Static contact angle measurements revealed that surface
architecture plays a pivotal role in modulating wettability, with
optimized structures achieving contact angles above 160° without
any chemical modification. The study further investigates how morphological
fidelity, governed by two-photon polymerization (TPP) printing parametersspecifically
slicing distance and hatching distanceinfluences surface quality,
roughness, and droplet behavior. Power spectral density analysis and
3D surface topography confirm that fabrication resolution critically
impacts the performance of designed features. Finally, fabrication
efficiency was evaluated in terms of areal fabrication rate, highlighting
trade-offs among design complexity, printing resolution, and throughput.
The results establish a set of design principles for achieving superhydrophobicity
on hydrophilic materials and provide a scalable framework for future
applications in microfluidics, biomimetics, and surface engineering
where chemical-free wettability control is desired.