De-pinning of contact line of droplets on rough surfaces

TL;DR

This study investigates how droplet patterns form on PDMS-coated DVD surfaces under alcohol vapors, revealing that pattern formation depends on alcohol type and contact line depinning, with implications for surface patterning.

Contribution

It demonstrates the influence of alcohol vapor type on droplet pattern formation and links pattern distortion to contact line depinning on rough surfaces.

Findings

Pattern forms with methanol and ethanol vapors but not with 2-propanol and n-butanol.

Pattern distortion is caused by contact line depinning.

Pattern formation is influenced by alcohol chain length and hydrophobic groups.

Abstract

The present study reports the formation of self-assembled droplet pattern on the PDMS polymer coated over grooved side of DVD under saturated vapours of alcohols. Comparison of the results with breath figures formed over unconstrained side of DVD is made. Four different environments namely methanol, ethanol, 2-propanol and n-butanol are used for the analysis. It is observed that the pattern formation occurs with methanol and ethanol vapours and not with 2-propanol and n-butanol. The difference is pattern formation with different alcohols is attributed to the variation in chain length and the presence of hydrophobic groups in alcohols, as given by Traube's rule. The distortion of patterns over constrained surface is attributed to the depinning of contact lines.