Stochastic force dynamics of the model microswimmer Chlamydomonas reinhardtii: Active forces and energetics

TL;DR

This study combines experimental, theoretical, and numerical methods to analyze the stochastic force dynamics and energetics of the microswimmer Chlamydomonas reinhardtii, revealing complex oscillatory forces and high power dissipation.

Contribution

It introduces direct force measurements of a microswimmer using optical trapping and models its energetics with stochastic thermodynamics, advancing understanding of active matter forces.

Findings

Detected complex oscillatory force dynamics

Measured power dissipation around 10^6 k_B T/sec

Validated active matter models with experimental data

Abstract

We study the stochastic force dynamics of a model microswimmer (Chlamydomonas reinhardtii), using a combined experimental, theoretical, and numerical approach. While swimming dynamics have been extensively studied using hydrodynamic approaches, which infer forces from the viscous flow field, we directly measure the stochastic forces generated by the microswimmer using an optical trap via the photon momentum method. We analyze the force dynamics by modeling the microswimmer as a self-propelled particle, a la active matter, and analyze it's energetics using methods from stochastic thermodynamics. We find complex oscillatory force dynamics and power dissipation on the order of $10^6$ $k_B T / s$ ($\sim$ fW)