Capillary Thinning of Elastic and Viscoelastic Threads: from Elastocapillarity to Phase Separation

TL;DR

This paper investigates the transition from viscoelastic to elastic behavior in filament thinning, revealing a universal similarity solution and phase separation phenomena through experiments on biopolymer materials.

Contribution

It connects the dynamics of viscoelastic liquids and elastic solids by demonstrating a common similarity solution and identifying phase separation-driven instabilities.

Findings

Interface shapes follow a universal similarity solution at low viscosity and high elasticity.

A second filament instability occurs due to dynamical phase separation.

Bridges the understanding between fluid and solid filament behaviors.

Abstract

The formation and destabilisation of viscoelastic filaments are of importance in many industrial and biological processes. Filament instabilities have been observed for viscoelastic fluids but recently also for soft elastic solids. In this work, we address the central question how to connect the dynamical behavior of viscoelastic liquids to that of soft elastic solids. We take advantage of a biopolymer material whose viscoelastic properties can be tuned over a very large range by its pH, and study the destabilization and ensuing instabilities in uniaxial extensional deformation. In agreement with very recent theory, we find that the interface shapes dictated by the instabilities converge to an identical similarity solution for low-viscosity viscoelastic fluids and highly elastic gels. We thereby bridge the gap between very fluid and strongly elastic materials. In addition, we provide direct evidence that at late times an additional filament instability occurs due to a dynamical phase separation.