Vertical-supercooling-controlled interfacial instability for a spreading liquid film

TL;DR

This paper investigates how vertical supercooling influences interfacial instability in spreading liquid films, revealing a thermo-viscous mechanism that can be controlled through structure design for applications in microfluidics and advanced materials.

Contribution

It uncovers the correlation between supercooling-induced solidification and fingering instability, demonstrating control via structure design and highlighting a thermo-viscous mechanism.

Findings

Onset timescale of instability correlates with vertical solidification.

Control of fingering instability achieved through structure design.

Viscous fingering driven by increased viscosity during solidification.

Abstract

Thermal effect is essential to regulate the interfacial instabilities for diverse technology applications. Here we report the fingering instability at the propagation front for a spreading liquid film subjected to the supercooling at the vertical direction. We find the onset timescale of hydrodynamic instability is strongly correlated with that of the vertical solidification process. This correlation is further validated in a non-uniform geometry, demonstrating the capability of controlling fingering instability by structure design. We attribute the identified interfacial instability to a pronounced thermo-viscous effect, since the rapidly increased viscosity of propagation front undergoing solidification can significantly enhance the mobility contrast locally in the vicinity of the spreading front, consequently producing the instability analogous to viscous fingering. This work offers another valuable dimension by gating the vertical temperature to exploit the interfacial stabilities and steer liquid flow, consequently shedding light on the microfluidic cooling for electronics, and the advanced functional fibers and fabrics.