Controlling cell motion and microscale flow with polarized light fields

TL;DR

This study explores how polarized light fields influence the movement of photo-responsive algae, revealing control over cell motion and microscale flow through light polarization patterns, with potential applications in bio-robotics and fluid manipulation.

Contribution

It demonstrates that light polarization can direct cell motion and generate fluid flow, supported by a quantitative active Brownian particle model.

Findings

Cells swim perpendicular to polarization in uniform fields.

Spatially varying polarization modulates cell motion and distribution.

Ordered swimming induces directed fluid flow.

Abstract

We investigate how light polarization affects the motion of photo-responsive algae, \textit{Euglena gracilis}. In a uniformly polarized field, cells swim approximately perpendicular to the polarization direction and form a nematic state with zero mean velocity. When light polarization varies spatially, cell motion is modulated by local polarization. In such light fields, cells exhibit complex spatial distribution and motion patterns which are controlled by topological properties of the underlying fields; we further show that ordered cell swimming can generate directed transporting fluid flow. Experimental results are quantitatively reproduced by an active Brownian particle model in which particle motion direction is nematically coupled to local light polarization.