Tunable Manipulation and Separation of Microtarget by Microdroplet‐Based DC‐DEP

A novel DC-dielectrophoresis (DEP) method employing a tunable insulating microdroplet for the continuous sorting of microtargets is presented in this article. To induce the dielectrophoretic effect, a DC electric voltage is applied via the microdroplet through the microchannel to induce the gradient of the inhomogeneous electric field. When passing through the gap between the microdroplet and the channel where there is the strongest nonuniformity of the electric field, the microparticles experience the DEP effects, and their trajectories shift. The effects of the gap spacing and the applied voltage on the distribution of the electric field gradient and the effect of the flow rate on the particle trajectory were analyzed numerically. On the basis of theoretical analysis, a tunable microdroplet-based microfluidic chip was fabricated, and the experimental system platform centered on the tunable droplet chip was constructed. Experiments were conducted to demonstrate the sorting of 5 and 10 µm polystyrene microparticles by adjusting the joint gap distance, flow rate, and applied voltage. The experimental results were in good agreement with the numerical simulation, which proved the feasibility of using microdroplet to serve as tunable insulator for the manipulation and separation of microtargets.