Oscillatory Flows Induced by Microorganisms Swimming in Two-dimensions

TL;DR

This study provides the first detailed measurements of oscillatory flow fields generated by swimming microorganisms, revealing complex time-dependent structures and quantifying the power and energy dissipation involved.

Contribution

It introduces a novel experimental approach to measure time-resolved flow fields around microorganisms in two dimensions, uncovering new insights into their oscillatory swimming dynamics.

Findings

Flow structures are complex and time-dependent.

Velocity fields scale inversely with distance.

Power peaks at 15 femtowatts, with dissipation over four times higher than steady swimming.

Abstract

We present the first time-resolved measurements of the oscillatory velocity field induced by swimming unicellular microorganisms. Confinement of the green alga C. reinhardtii in stabilized thin liquid films allows simultaneous tracking of cells and tracer particles. The measured velocity field reveals complex time-dependent flow structures, and scales inversely with distance. The instantaneous mechanical power generated by the cells is measured from the velocity fields and peaks at 15 fW. The dissipation per cycle is more than four times what steady swimming would require.