Light control of the flow of phototactic microswimmer suspensions

TL;DR

This paper demonstrates how light can be used to control the movement and concentration of phototactic micro-algae in flow, with potential applications in bio-concentration and pollutant detection.

Contribution

It introduces a method to manipulate micro-algae flow using light, combining phototaxis with flow dynamics for targeted concentration control.

Findings

Algae concentrate around the flow center under light control

Intermittent light exposure reveals reversible dynamics

Potential applications in bio-concentration and pollutant detection

Abstract

Some micro-algae are sensitive to light intensity gradients. This property is known as phototaxis: the algae swim toward a light source (positive phototaxis). We use this property to control the motion of micro-algae within a Poiseuille flow using light. The combination of flow vorticity and phototaxis results in a concentration of algae around the center of the flow. Intermittent light exposure allows analysis of the dynamics of this phenomenon and its reversibility. With this phenomenon, we hope to pave the way toward new algae concentration techniques (a bottleneck challenge in hydrogen algal production) and toward the improvement of pollutant bio-detector technology.