Dynamic Control of Particle Deposition in Evaporating Droplets by an External Point Source of Vapor

TL;DR

This paper demonstrates real-time, deterministic control of internal flows in evaporating droplets using an external vapor source, enabling precise patterning of particles on surfaces for applications like printing and self-assembly.

Contribution

It introduces a novel method to actively control Marangoni flows in evaporating droplets through an external vapor source, allowing dynamic patterning.

Findings

External vapor source modulates internal droplet flows.

Flow patterns can be controlled in space and time.

Particle deposition patterns are tunable via flow control.

Abstract

The deposition of particles on a surface by an evaporating sessile droplet is important for phenomena as diverse as printing, thin-film deposition and self-assembly. The shape of the final deposit depends on the flows within the droplet during evaporation. These flows are typically determined at the onset of the process by the intrinsic physical, chemical and geometrical properties of the droplet and its environment. Here, we demonstrate deterministic emergence and real-time control of Marangoni flows within the evaporating droplet by an external point-source of vapor. By varying the source location, we can modulate these flows in space and time to pattern colloids on surfaces in a controllable manner.