Bridging particle deformability and collective response in soft solids

TL;DR

This study uses numerical simulations to explore how particle deformability influences the collective mechanical behavior of soft solids, revealing unique vibrational modes and transitions that differ from rigid particle packings.

Contribution

It introduces a detailed analysis of deformable particles in jammed packings, highlighting the impact of shape degrees of freedom on stability and response, which was previously not well understood.

Findings

Deformable particles exhibit low-frequency quartic vibrational modes.

Adding intra-particle constraints can cause buckling and shape transitions.

Deformability significantly alters the mechanical response compared to rigid particles.

Abstract

Soft, amorphous solids such as tissues, foams, and emulsions are composed of deformable particles. However, the effect of single-particle deformability on the collective behavior of soft solids is still poorly understood. We perform numerical simulations of two-dimensional jammed packings of explicitly deformable particles to study the mechanical response of model soft solids. We find that jammed packings of deformable particles with excess shape degrees of freedom possess low-frequency quartic vibrational modes that stabilize the packings even though they possess fewer interparticle contacts than the nominal isostatic value. Adding intra-particle constraints can rigidify the particles, but these particles undergo a buckling transition and gain an effective shape degree of freedom when their preferred perimeter is above a threshold value. We find that the mechanical response of jammed packings of deformable particles with shape degrees of freedom differs significantly from that of jammed packings of rigid-shape particles, which emphasizes the importance of particle deformability in modelling soft solids.