Electric field Induced Patterns in Soft Visco-elastic films: From Long Waves of Viscous Liquids to Short Waves of Elastic Solids

TL;DR

This paper investigates electric field-induced surface instabilities in visco-elastic films, revealing two regimes: liquid-like long waves and solid-like short waves, with distinct scaling laws and threshold behaviors.

Contribution

It identifies and characterizes two distinct regimes of surface instability in visco-elastic films under electric fields, detailing their different wavelength scaling and threshold conditions.

Findings

Long wavelength instability governed by voltage and surface tension in liquid-like regime.

Short wavelength instability with a fixed scale of about four times the film thickness in solid-like regime.

Transition zone where storage modulus influences wavelength behavior.

Abstract

We show that the electric field driven surface instability of visco-elastic films has two distinct regimes: (1) The visco-elastic films behaving like a liquid display long wavelengths governed by applied voltage and surface tension, independent of its elastic storage and viscous loss moduli, and (2) the films behaving like a solid require a threshold voltage for the instability whose wavelength always scales as ~ 4 x film thickness, independent of its surface tension, applied voltage, loss and storage moduli. Wavelength in a narrow transition zone between these regimes depends on the storage modulus.