Controlled uniform coating from the interplay of Marangoni flows and surface-adsorbed macromolecules

TL;DR

This paper demonstrates how the interplay of Marangoni flows and surface-adsorbed macromolecules can be used to achieve uniform coatings in droplet evaporation processes, offering new control strategies for surface patterning.

Contribution

It introduces a novel approach combining multiple Marangoni flows and surface-adsorbed polymers to control uniform particle coatings in binary solutions.

Findings

Sequential Marangoni flows prevent non-uniform particle distribution

Small concentrations of surfactant and polymer achieve uniform deposits

Surface-adsorbed macromolecules influence coating uniformity

Abstract

Surface coatings and patterning technologies are essential for various physicochemical applications. In this Letter, we describe key parameters to achieve uniform particle coatings from binary solutions: First, multiple sequential Marangoni flows, set by solute and surfactant simultaneously, prevent non-uniform particle distributions and continuously mix suspended materials during droplet evaporation. Second, we show the importance of particle-surface interactions that can be established by surface-adsorbed macromolecules. To achieve a uniform deposit in a binary mixture, a small concentration of surfactant and surface-adsorbed polymer (0.05 wt% each) is sufficient, which offers a new physicochemical avenue for control of coatings.