Propulsion kinematics of achiral microswimmers in viscous fluids

Abstract

Here we investigate the dynamic behavior of self-assembling achiral swimmers in viscous media. The response of magnetically actuated swimmers of two differing geometries is explored under various uniform rotational field frequencies and amplitudes. Kinematic characteristics obtained from tracked swimming motion, including speed, precession angle (wobbling angle), and re-orientation time (turning rate), are determined and reveal nonlinear relationships between the dynamic response of the achiral swimmers and fluid viscosity, which induces drag forces that reduce the speed of propulsion and turning rates. We also find distinct regimes of swimmer motion that are dependent on both fluid viscosity and swimmer geometry. Similar viscosity and geometric dependence is observed for turning rates of swimmers when undergoing rapid changes in field orientation. The characteristic results obtained for microswimmer motion in viscous fluids will contribute to the development of control strategies for propelling other simple swimmers with two or more planes of symmetry. Characterized propulsion kinematics will aid in the optimization of swimmer designs and actuation approaches, critical for future low Reynolds number applications.