Fabrication and electrokinetic motion of electrically anisotropic Janus droplets in microchannels

Abstract

This paper presents experimental investigations of the fabrication and the motion of electrically anisotropic Janus droplets in a microchannel under externally applied direct current (DC) electrical field. The fabrication method of the Janus droplets is presented first. To begin, oil droplets are coated uniformly with positively charged nanoparticles in the aluminum oxide nanoparticle suspension. The electrically anisotropic Janus droplets are formed when the nanoparticles are accumulated to one side of the droplets in response to externally applied DC electric field. The surface coverage of the Janus droplets by nanoparticles can be adjusted by controlling the concentration of the nanoparticle suspension. The flow fields around the Janus droplets moving in a microchannel were observed with tracing particles. Finally, the electrokinetic velocity of the Janus droplets in a microchannel was measured. The effects of the strength of the electrical field, the surface coverage of the Janus droplets by nanoparticles, the size of the droplets as well as the electrolyte concentration on the electrokinetic velocity of the Janus droplets were studied.