Internal advection dynamics in sessile droplets depend on the curvature of superhydrophobic surfaces

TL;DR

This study investigates how the curvature of superhydrophobic surfaces influences internal flow patterns in sessile droplets, revealing that convexity reduces and concavity enhances internal circulation velocities, with implications for microscale thermofluidics.

Contribution

It introduces a curvature-dependent scaling model and experimental validation for internal advection dynamics in sessile droplets on superhydrophobic surfaces.

Findings

Convex surfaces decrease internal circulation velocity.

Concave surfaces increase internal circulation velocity.

Experimental velocities align with model predictions.

Abstract

The article demonstrates that the internal circulation velocity and patterns in sessile droplets on superhydrophobic surfaces is governed by the surface curvature. Particle Image Velocimetry reveals that increasing convexity deteriorates the advection velocity whereas concavity augments it. A scaling model based on the effective curvature modulated change in wettability can predict the phenomenon, but weakly. Potential flow theory is appealed to and the curvatures are approximated as wedges with the rested droplet engulfing them partly. The spatially averaged experimental velocities are found to conform to predictions. The study may have strong implications in thermofluidics transport phenomena at the microscale.