Controlling breath figure patterns on PDMS by concentration variation of ethanol-methanol binary vapors

TL;DR

This study demonstrates how varying ethanol-methanol vapor concentrations can control the self-assembly of droplet patterns on PDMS, resulting in ordered porous structures with tunable features and high hydrophobicity.

Contribution

It reveals the role of binary vapor atmospheres in pattern formation on PDMS and explores the effects of constraints on droplet self-assembly, without using additives.

Findings

Hexagonally ordered pore arrays achieved without additives

Pore size and shape influenced by vapor composition and constraints

Patterned surfaces exhibit high hydrophobicity and water adhesion

Abstract

In this paper, the self-assembly of condensed droplets on smooth and constrained surfaces under saturated vapor atmosphere of ethanol and methanol binary system is reported. Hexagonally ordered array of pores are obtained on smooth surfaces with saturated vapors of binary liquids without the assistance of any additives. The results show that the addition of small amount of ethanol to methanol plays a role very similar to that of surface active agents in inducing the formation of regular droplet array. The effect of constraints on self-assembled droplet pattern such as movement of contact line and depinning of contact line is also investigated. It is observed that the pore size, pore shape, pore depth and ring diameter are influenced by the atmosphere of binary vapors in addition to the commonly held attribution to the surface tension of the solvent. Contact angle studies of the patterned substrates showed hydrophobicity with very high adhesiveness to water and Wenzel's state of wetting.