Shear-Induced Collective Shape Oscillations in Dense Soft Suspensions

TL;DR

This paper demonstrates that dense soft suspensions under shear can spontaneously develop collective shape oscillations due to particle deformation and neighbor exchanges, revealing a generic mechanism for dynamic behavior in such systems.

Contribution

The study introduces a multi-phase field model and a minimal theoretical model to explain shear-induced collective oscillations in dense soft suspensions, highlighting a universal mechanism.

Findings

Shear induces ordered states with shape oscillations.

Oscillations originate from neighbor exchange cycles.

A minimal model captures the oscillatory limit cycle.

Abstract

Dense suspensions of deformable particles can exhibit rich nonequilibrium dynamics arising from complex flow-structure coupling. Using a multi-phase field model, we show that steady shear drives an initially disordered, dense, soft suspension into a positionally and orientationally ordered state, within which particles undergo robust self-sustained shape oscillations. These oscillations originate from repeated T1 neighbor exchanges that force the ordered particle lattice to cyclically traverse different ordered configurations, coupling particle deformation to evolving lattice topology. By identifying the lattice angle as a key variable, we construct a minimal one-degree-of-freedom model that quantitatively captures the limit cycle oscillation. Because these mechanisms rely only on deformability, packing, and shear, they provide a generic route to collective time-dependent behavior in dense soft suspensions.