Directed Motion of Metallodielectric Particles by Contact Charge Electrophoresis

Abstract

We investigate the dynamics of metallodielectric Janus particles moving via contact charge electrophoresis (CCEP) 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 between the electrodes. In addition to particle oscillations, we find that micrometer-scale Janus particles move perpendicular to the field at high speeds (up to 600 μm/s) and over large distances. We characterize particle 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.

Emergence of traveling waves in linear arrays of electromechanical oscillators

“…4b). In contrast to previous strategies for rectifying CCEP motions based on ratcheted channels 22 or asymmetric particles 16 , the present approach relies on the self-organization of multiple particles working in concert.…”

“…To achieve scalable mechanisms of pattern formation, the processes that drive oscillations should scale in the same way as those used to couple neighboring oscillators. In this context, electromechanical oscillators based on contact charge electrophoresis (CCEP) 13,14 can provide a useful model on length scales spanning millimeters 15 to microns 16 (perhaps even nanometers 17,18 ).…”

Recent Advances in Motion Control of Micro/Nanomotors

“…[78] Dou et al fabricated an Au-SiO 2 Janus micromotor (JM) moving in mineral oil between two parallel electrodes; the micromotor exhibited a rapid oscillatory motion between the two electrodes, and each single moving process toward one electrode is propelled by the ICEP. [79] In addition, the asymmetric EDL could also be generated by the asymmetric shapes of these micro/nanomotors. Ni et al developed special hybrid clusters linked with microspheres of different materials using sequential capillarity-assisted particle assembly (sCAPA).…”

Fabrication of Self‐Propelled Micro‐ and Nanomotors Based on Janus Structures

“…[16,56] In general, SiO 2 microparticles were dispersed on the pretreated wafer to form am onolayer and dried under vacuum. AuÀSiO 2 Janus micromotors have been studied widely.…”

“…AuÀSiO 2 Janus micromotors have been studied widely. [16,56] In general, SiO 2 microparticles were dispersed on the pretreated wafer to form am onolayer and dried under vacuum. The Au layer was half-coated throughc onventional PVD, followed by ultrasonic treatment and centrifugation.…”