Continuous Particle Separation In Complex Microchannel Via Direct Current Dielectrophoresis

A key procedure in biochemical analyses is the separation of synthetic or biological particles from a mixture in a microchannel. Among various separation technologies, Dielectrophoresis(DEP) was becoming a hot spot due to its advantages of diversified separation designs, simplified fabrications, low cost in experiments, and outstanding performance in a continuous way, etc. To date, electrode DEP(DEP generated through metal electrode array on chip) and insulator DEP(DEP generated through insulator obstacle between electrodes) are two main techniques, and have been both widely applied on lab-on-a-chip(LOC) devices. Comparing to chip-based separation devices, the newly designed twisted capillary-based microchannel has advantages of lower cost and higher throughput. With a series cross-sectional clamping of a capillary from rotatory 90 degree directions, a 3D twisted capillary-based microchannel can be generated. As a key requirement applying DC insulator DEP technology, a spatial non-uniform electric field can be conveniently established through the 3D twisted capillary-based microchannel by applying a voltage difference between the inlet and the outlet. With the apparent DEP force exerted on the particles that moving through the microchannel, a radial shift occurs to the particles towards the central line of the 3D capillary-based microchannel. Hence separation is achieved by collecting particles at different radii at the outlet. 3D numerical models are constructed to eventually calculate the particle trajectory through the microchannel. The electroosmotic(EOF) forces, the electrophoretic(EP) forces and the DEP forces are analyzed. The effect of applied voltage and the effect of mobility ratio are also investigated. Particles with size interval of 1μm are theoretically separated under optimized condition, and corresponding separation threshhold voltages of 8μm, 9μm, 10μm, 11μm, and 12μm diameter particles are 180 V, 150 V, 120 V, 95 V, 85 V. Separation trajectories are compared between 2D saw-tooth chip-based microchannels and our 3D capillary-based microchannels. It is shown that under the same conditions, the particle trajectory’s radial shift in 2D microchannel is more significant. However, the separation precisions are better, the particle’s average velocities are faster, and the separation throughputs are larger in our 3D microchannel.