Abstract

Diffusion-based Separation Using Bidirectional Electroosmotic Flow

Moran Bercovici, Assistant Professor, Technion – Israel Institute of Technology

We present a microscale separation method that leverages bidirectional flow, generated by an array of alternate-current field-effect electrodes, to electroosmotically tune the dispersion regime of molecules and particles. Under bidirectional flow the relative motion of species due to differences in their molecular diffusivity can be significantly enhanced.  The system can be configured so that low diffusivity species experience a ballistic transport regime and are advected through the chamber, whereas high diffusivity species experience a diffusion dominated regime with zero average velocity and are retained in the chamber.  We experimentally demonstrate the separation of particles, antibodies, and dyes, and present a theoretical analysis of the system, providing engineering guidelines for its optimal design and operation. This method provides means for leveraging molecular diffusivity for analysis and sample preparation applications, particularly for sub-microliter sample volumes that are not compatible with standard separation techniques.