Contact Charge Electrophoresis: Experiment and Theory

Abstract

Contact charge electrophoresis (CCEP) uses steady electric fields to drive the continuous, oscillatory motion of conductive particles and droplets between two or more electrodes. These rapid oscillations can be rectified to direct the motion of objects within microfluidic environments using low-power, dc voltage. Here, we compare high precision experimental measurements of CCEP within a microfluidic system to equally detailed theoretical predictions on the motion of a conductive particle between parallel electrodes. We use a simple, capillary microfluidic platform that combines high-speed imaging with precision electrical measurements to enable the synchronized acquisition of both the particle location and the electric current due to particle motion. The experimental results are compared to those of a theoretical model, which relies on a Stokesian dynamics approach to accurately describe both the electrostatic and hydrodynamic problems governing particle motion. We find remarkable agreement between theory and experiment, suggesting that particle motion can be accurately captured by a combination of classical electrostatics and low-Reynolds number hydrodynamics. Building on this agreement, we offer new insight into the charge transfer process that occurs when the particle nears contact with an electrode surface. In particular, we find that the particle does not make mechanical contact with the electrode but rather that charge transfer occurs at finite surface separations of >0.1 μm by means of an electric discharge through a thin lubricating film. We discuss the implications of these findings on the charging of the particle and its subsequent dynamics.

Perspective: Outstanding theoretical questions in polymer-nanoparticle hybrids

“…10. [260][261][262][263] Bishop and his coworkers, for example, considered conducting NPs in an insulating liquid in a DC field. The contact electrification of a single NP leads it to execute oscillatory motion between the two plates.…”

Metallic nanowires and mesoscopic networks on a free surface of superfluid helium and charge-shuttling across the liquid–gas interface

“…[23][24][25][26][27] The phenomenon is referred to as a contact charge electrophoresis 27,28 or a charge-shuttling 23 …”

Contact Charging and Electrphoresis of a Glassy Carbon Microsphere

“…에서 활발히 연구되고 있다 [1][2][3][4][5][6][7][8][9][10][11][12]. 액적 접촉충전 현상 기반의 미세 유체 기술은 개별 액적을 전기를 이용해 다루는 디지털 미세유체 기 술의 한 분야로 [13,14], 채널 내 액적을 다루는 액적 미세유체 (Droplet Microfluidics) [15,16] 기술과는 다르며 기존 미세유체 기술 들의 단점을 극복할 수 있어 새로운 대안 기술로 제시되고 있는 신 기술 이다 [17,18].…”