Spinning elastic beads: a route for simultaneous measurements of shear modulus and interfacial energy of soft materials

TL;DR

This study introduces a method to simultaneously measure the shear modulus and interfacial energy of soft elastic materials by analyzing the equilibrium shapes of spinning hydrogel beads, combining theory, simulation, and experiments.

Contribution

It demonstrates that equilibrium shapes of spinning elastic beads can be used to concurrently determine elastic modulus and surface energy, supporting the surface energy-tension equivalence in polymer gels.

Findings

Elastic modulus and surface energy can be deduced from bead shapes.

Theoretical and experimental results are in good agreement.

Supports the surface energy equals surface tension scenario for polymer gels.

Abstract

Large deformations of soft elastic beads spinning at high angular velocity in a denser background fluid are investigated theoretically, numerically, and experimentally using millimeter-size polyacrylamide hydrogel particles introduced in a spinning drop tensiometer. We determine the equilibrium shapes of the beads from the competition between the centrifugal force and the restoring elastic and surface forces. Considering the beads as neo-Hookean up to large deformations, we show that their elastic modulus and surface energy constant can be simultaneously deduced from their equilibrium shape. Also, our results provide further support to the scenario in which surface energy and surface tension coincide for amorphous polymer gels.