Rotating spherical particle in a continuous viscoelastic medium -- a microrheological example situation

TL;DR

This paper analytically examines the rotational dynamics of a spherical particle in a viscoelastic medium, linking theoretical response functions to microrheological applications involving magnetic particles.

Contribution

It provides a detailed analytical framework for understanding how a rigid sphere behaves under torque in viscoelastic environments, including response functions relevant to microrheology.

Findings

Characterized long-term rotational behavior in viscoelastic media.

Derived response functions applicable to microrheological measurements.

Connected theoretical results to experimental techniques using magnetic particles.

Abstract

Using analytical calculations, we characterize the rotational behavior of a rigid spherical particle when subject to a net external torque in a continuous viscoelastic environment. On long time scales, the embedding medium can either feature a net terminal flow, like a fluid, or damped reversible dynamics, like an elastic solid. The coupling of the sphere to its environment together with the therein induced deformations and flows are taken into account explicitly. In reality, using magnetically anisotropic particles, the torque can, for instance, be applied via magnetic fields. We calculate corresponding response functions. This connects our study to evaluations of microrheological investigations.