Experimental characterization of helical swimming trajectories in circular channels

Official URL: http://dx.doi.org/10.1007/s10404-017-1973-9

Trajectories of microorganisms and artificial helical swimmers in confinements are important in biology and for controlled swimming in medical applications. Numerical studies on the locomotion of model microorganisms and spherical particles are reported in the literature. Here, we report experimental results on the trajectories and velocities of artificial helical swimmers in circular channels. Trajectories are recorded by a digital camera and images are processed to obtain the radial position and the orientation of the swimmer. Tail length, channel diameter, rotation frequency and the rate of the Poiseuille flow are varied in the experiments. Experimental results demonstrate that confinement and flow affect the orientation of swimmer and the swimming performance. Swimmers follow stable helical trajectories in the forward direction when the tail pushes the swimmer. However, when the tail pulls the swimmer in the backward direction trajectories converge to a straight line in the narrow channel, whereas helical trajectories are observed for pullers as well in the wide channel.