Abstract

This talk will present three classes of active particles: i) Liquid crystal skyrmions activated by time-periodic electric fields, with the skyrmion velocity tuneable by the field amplitude and frequency. A collective variable model of the skyrmion dynamics will be discuss. The model relates the skyrmion motion to the reorientation dynamics of the far-field director and dynamics of the width of the twist wall around the skyrmion core. ii) A chemical nanoswimmer moving in a ratchet potential will be considered, where the ratchet potential is additionally “rocked” in the transverse direction. As a result of the mechanochemical coupling, the self-propulsion velocity probes the potential energy landscape and particle trajectories are rectified in the direction of the ratchet modulation. The magnitude and direction of the net current depend upon both the rocking amplitude and the frequency. iii) Finally, the dynamics of gold microplates with twisted star shape ( symmetry) moving within the nodal plane of a uniform acoustic field will be presented. The relationship between the particle shape and its rotational motion is quantified by varying the shape of these spinners. The experimental observations are explained by a hydrodynamic model that describes the steady streaming flows and particle motions induced by ultrasonic actuation.