Non-orthogonal micro-free flow electrophoresis: from theory to design concept

Micro-free flow electrophoresis (microFFE) is a technique that facilitates continuous separation of molecules in a shallow channel with a hydrodynamic flow and an electric field at an angle to the flow. We recently developed a general theory of microFFE that suggested that an electric field non-orthogonal to the flow could improve resolution. Here, we used computer modeling to study resolution as a function of the electric field strength and the angle between the electric field and the hydrodynamic flow. In addition we used our general theory of microFFE to investigate other important influences on resolution, which include the velocity of the hydrodynamic flow, the height of the separation channel, and the magnitude and direction of the electroosmotic flow. Finally, we propose four designs that could be used to generate non-orthogonal electric fields and discuss their relative merits.