Thermophoretically induced large-scale deformations around microscopic heat centers

TL;DR

This paper combines theory and experiments to show that heating microscopic particles in elastic matrices causes large-scale, long-range displacements, with elasticity playing a key role in these deformations.

Contribution

It provides a macroscopic hydrodynamic two-fluid model that explains long-range displacements around heat centers, confirming experimental observations.

Findings

Elasticity causes large-scale displacements.

Finite sample size affects displacement decay.

Theoretical model matches experimental results.

Abstract

Selectively heating a microscopic colloidal particle embedded in a soft elastic matrix is a situation of high practical relevance. For instance, during hyperthermic cancer treatment, cell tissue surrounding heated magnetic colloidal particles is destroyed. Experiments on soft elastic polymeric matrices suggest a very long-ranged, non-decaying radial component of the thermophoretically induced displacement fields around the microscopic heat centers. We theoretically confirm this conjecture using a macroscopic hydrodynamic two-fluid description. Both, thermophoretic and elastic effects are included in this theory. Indeed, we find that the elasticity of the environment can cause the experimentally observed large-scale radial displacements in the embedding matrix. Additional experiments confirm the central role of elasticity. Finally, a linearly decaying radial component of the displacement field in the experiments is attributed to the finite size of the experimental sample. Similar results are obtained from our theoretical analysis under modified boundary conditions.