Electric Field-Induced Arrangement of Colloidal Materials in Microfluidic Devices

Abstract

In this chapter, colloidal materials arrangement by microfluidic approach utilizing an electric field-induced interfacial flow is presented. A microfluidic platform is suitable for precise control of behavior of colloidal particles. Electrokinetics in the platform has been growing owing to its versatility and simplicity in fabrication, implementation and handling. Alternating-current electroosmosis (ACEO), which is nonlinear electrokinetic phenomena resulting in advent motion of fluid generated by an interaction between AC electric field and an induced diffuse charge layer on the electrode surface, has a potential for a particle control in a microfluidic channel. The arrangement of the colloidal particles is achieved by the ACEO flow in a microfluidic device with a parallel double-gap electrode. The experimental results show that concentrated particles exist on the electrode surface within 5 μm, and that three-dimensional concentration of particle with the concentration factor as large as 700 is attained. As a result, total concentration efficiency was 98.4 % for all the particles in the fluidic device. Also, this approach can be used for nanoparticle concentration. Examples of gold nanoparticles collection from 20 to 100 nm are presented here. The ACEO-based arrangement technique provides us to ensure the novel functionality for colloidal materials.