Probing superhydrophobic surface topography using droplet adhesion

TL;DR

This paper investigates how microscopic surface structures influence droplet adhesion on superhydrophobic surfaces, revealing that adhesion forces depend logarithmically on pillar area and that tensile force measurements better characterize surface features.

Contribution

The study introduces a validated expression linking adhesion force to pillar area fraction and demonstrates that tensile force measurements are more reliable for surface characterization.

Findings

Adhesion force increases logarithmically with pillar area fraction.

Tensile force measurements are more reliable indicators of surface structure.

Numerical simulations and experiments confirm the relationship between forces and microstructure.

Abstract

Understanding contact line dynamics on superhydrophobic surfaces with microscopic structures is essential for designing materials with reduced drag, anti-icing, self-cleaning, and anti-fouling properties. Using numerical simulations, we demonstrate that forces on droplets receding over structured surfaces are governed by microscale deformations near the contact line. We present and experimentally validate an expression demonstrating that adhesion force increases logarithmically with pillar area fraction at constant droplet volume and pillar surface chemistry. Furthermore, we establish that the average tensile force measured in direct force measurements provides a more reliable indicator of surface structure than the commonly used maximum force. This newfound insight enables precise quantification of superhydrophobic surface structure using a droplet probe.