Phase Separation in Wetting Ridges of Sliding Drops on Soft and Swollen Surfaces

TL;DR

This study investigates how drops on swollen elastomeric surfaces induce phase separation in wetting ridges, revealing the dynamics of oil migration during steady sliding and the influence of transport timescales.

Contribution

It demonstrates the visualization of phase separation in wetting ridges during drop sliding and links separation rates to transport timescales in swollen networks.

Findings

Inverse relationship between oil tip height and sliding speed

Separation rates comparable to diffusion in pure melts

Visualization of phase separation during steady-state sliding

Abstract

Drops in contact with swollen, elastomeric substrates can induce a capillary-mediated phase separation in wetting ridges. Using laser scanning confocal microscopy, we visualize phase separation of oligomeric silicone oil from a crosslinked silicone network during steady-state sliding of water drops. We find an inverse relationship between the oil tip height and the drop sliding speed, which is rationalized by competing transport timescales of oil molecules: separation rate and drop-advection speed. Separation rates in highly swollen networks are as fast as diffusion in pure melts.