Particle separation and alignment technique in microchannel flow by dielectrophoretic force using boxcar-type electrode

Abstract

We have developed a technique which can control the particle interval (spacing), velocity and timing in microchannel flow by exerting dielectrophoretic (DEP) force on the particles periodically over time and space using the boxcar electrode. Controlling the interval of the particles to align with even space in the microchannel can improve the performance of the sensor, sorter, and encapsulation system for particles and cells in the microfluidic devices. One of the concerns about this technique is whether we can align the particles when several particles are located in the same periodic area. In the present study, we conducted numerical simulations and measurements for the motion of 12μm polystyrene particles flowing in the boxcar electrode region to evaluate how the particles separate when they are located in the same periodic area, and understand their motion characteristics during the separation process. The result showed that the two particles approach each other, change their position, and separate due to the DEP forces, flow velocity distribution, and collision between the particles. The particle located in the downstream side then moves to the upstream periodic region in a repetitive manner until it fits in a vacant region. We measured the frequency distribution of the number of particles in the periodic area at the inlet and outlet of the boxcar electrode and observed only 0 and 1 particle in each periodic area at the outlet. This represents that particles entering the boxcar electrode region with random interval separate and align with even interval by the time they reach the outlet.

Keywords

• particle alignment
• dielectrophoretic force
• boxcar-type electrode
• microchannel flow
• periodic force