Visualizing the strain field in semiflexible polymer networks: strain fluctuations and nonlinear rheology of F-actin gels

TL;DR

This paper visualizes local strain fields in F-actin gels under shear, revealing how microscopic strain uniformity correlates with nonlinear elasticity, influenced by polymer length and crosslink density.

Contribution

It provides direct imaging and measurement of strain fluctuations in semiflexible polymer networks, linking microscale strain nonaffineness to bulk nonlinear rheology.

Findings

Nonaffine strain depends on polymer length and crosslink density.

Microscale strain uniformity correlates with nonlinear elasticity.

Strain fluctuations are measurable at scales of 2-100 microns.

Abstract

We image semi-flexible polymer networks under shear at the micrometer scale. By tracking embedded probe particles, we determine the local strain field, and directly measure its uniformity, or degree of affineness, on scales of 2-100 micron. The degree of nonaffine strain depends on polymer length and crosslink density, consistent with theoretical predictions. We also find a direct correspondence between the uniformity of the microscale strain and the nonlinear elasticity of the networks in the bulk.