title: Microalga propels along vorticity direction in a shear flow.
abstract: Using high-speed digital holographic microscopy and microfluidics, we discover that, when encountering fluid flow shear above a threshold, unicellular green alga Dunaliella primolecta migrates unambiguously in the cross-stream direction that is normal to the plane of shear and coincides with the local fluid flow vorticity. The flow shear drives motile microalgae to collectively migrate in a thin two-dimensional horizontal plane and consequently alters the spatial distribution of microalgal cells within a given suspension. This shear-induced algal migration differs substantially from periodic rotational motion of passive ellipsoids, known as Jeffery orbits, as well as gyrotaxis by bottom-heavy swimming microalgae in a shear flow due to the subtle interplay between torques generated by gravity and viscous shear. Our findings could facilitate mechanistic solutions for modeling planktonic thin layers and sustainable cultivation of microalgae for human nutrition and bioenergy feedstock.
authors.affiliation: St. Anthony Falls Laboratory, Department of Civil Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: Anwar
authors.initials: A
authors.lastname: Chengala
authors.forename: Miki
authors.initials: M
authors.lastname: Hondzo
authors.forename: Jian
authors.initials: J
authors.lastname: Sheng
mesh_terms: D002465:Cell Movement / Q000502:physiology*; D003198:Computer Simulation; D058086:Microalgae / Q000502:physiology*; D008954:Models, Biological; D012212:Rheology / Q000379:methods*; D033081:Shear Strength