(588i) Directed Motion of Metallodielectric Particles By Contact Charge Electrophoresis

Active colloidal particles harness energy from their environment to power directed motions relative to their fluid surroundings. This talk will describe a mechanism for colloidal propulsion based on contact charge electrophoresis (CCEP) of metallodielectric Janus particles between two parallel electrodes. CCEP uses a constant voltage to repeatedly charge and actuate conductive particles within a dielectric fluid, resulting in rapid oscillatory motion. In addition to particle oscillations, micrometer-scale Janus particles move perpendicular to the field at high speeds (up to 600 μm/s) and over large distances. We characterize these directed motions and propose a mechanism based on the rotation-induced translation of the particle following charge transfer at the electrode surface. The propulsion mechanism is supported both by experiments with fluorescent particles that reveal their rotational motions and by simulations of CCEP dynamics that capture the relevant electrostatics and hydrodynamics. We also show that interactions among multiple particles can lead to repulsion, attraction, and/or cooperative motions depending on the position and phase of the respective particle oscillators. Our results demonstrate how particle asymmetries can be used to direct the motions of active colloids powered by CCEP. By expanding the repertoire of active colloids, we aim to discover new dynamical behaviors and enable applications such as cargo delivery.