Sedimenting chiral swimmers*

The squirmer model is a theoretical model introduced to study microorganisms like algae and bacteria [1].
The presence of walls can strongly modify the motion of microorganisms [2]. On the other hand, the gravity force represents another factor that can affect the motion of microorganisms [3].
We combine all of these features studying the dynamics of a sedimenting squirmer under the effect of the gravity force, near a solid boundary taking into account its chirality [4].
Neutral squirmers and pullers sediment to the bottom wall, stop their motion and reorient perpendicular to the wall. Pushers, instead, exhibit continuous motion with tilted direction. When the chirality is introduced, it causes a deviation from the straight path in circular trajectories whose radius of curvature strongly depends on its magnitude.
References
[1] M.J. Lighthill, Commun. Pure Appl. Math. 5, 109 (1952); J.R. Blake, J. Fluid Mech. 46, 199 (1971).
[2] E. Lauga, W. R. DiLuzio, G.M. Whitesides and H.A. Stone, Biophys. J. 90, 400 (2006).
[3] F. Ruhle, J.Blaschke, J.-T.Kuhr and H.Stark, New J. Phys. 20, 025003 (2018).
[4] E. Lauga, Annu. Rev. Fluid Mech. 48, 105 (2016).