Water under the Ridge: Evaporation, Translation, Crumpling and Encapsulation of a Water Droplet atop a Liquid Polymeric Film

TL;DR

This paper investigates the complex interplay of evaporation, motion, crumpling, and encapsulation in a water droplet on a viscoelastic polymer film, revealing new phenomena with potential applications in microfluidics and drug delivery.

Contribution

It introduces an analytical model explaining the self-propulsion, crumpling, and encapsulation phenomena in a water-polymer system, a process not previously reported.

Findings

Self-propulsion of water droplet observed due to evaporation dynamics.

Crumpling of the polymer film occurs as a result of droplet motion.

Encapsulation of water droplet by polymer achieved without complex fabrication.

Abstract

The intriguing dynamics of a compound liquid-system comprising of water and (uncured) poly-dimethylsiloxane is explored in the present work. The viscoelastic nature of the film, coupled with the dynamics of evaporation, triggered a self-propulsion in the droplet, which gradually segued into the crumpling of the film, and finally culminated in the encapsulation of the water droplet by the polymer. The physics of the hitherto unreported phenomena has been explained via the development of an analytical model, by taking into account all the germane forces. It is conjectured that this symbiotic and self-sustained dynamics, aided with the non-requirement of any complex fabrication procedures, would pave the path for the development of precision drug-delivery, unmediated flow-focusing, self-mixed microreactors, the study of micro-swimmers, surface encapsulation, and photonics, to name a few.