Utilizing a Coil to Realize 3D Electrodes for Dielectrophoresis-Based Particle Concentration

In this paper a novel technique is presented to fabricate a coil of insulated and uninsulated wires placed in a polydimethylsiloxane (PDMS) channel. The design introduces 3D dielectrophoresis-based particle concentration using a coil for the first time. The wires were wound around a 3D printed acrylonitrile butadiene styrene (ABS) rod and embedded in the PDMS. The ABS then dissolved in acetone to create the channel surrounded by wires. Electric field is attained by applying 180 degrees phase-shifted electric potentials to the uninsulated wires, acting as electrodes. Hence, the insulated wires only serve as insulators between the electrodes to prevent them from electrical shorting. This configuration produces a gradient in the electric field with its maximum near the channel walls (electrodes) and its minimum at the centre of the channel. Thus, under proper electric field frequency, negative dielectrophoresis force focuses particles by pushing them to the central area of the channel while the fluid flow carries them to the outlet. Proof-of-concept simulations and experiments were conducted. Polystyrene particles, with a diameter of 6 mu m, were used in the experiments. To find the concentration performance under different conditions, the variations in the frequency and amplitude of the electric potential and the flow rate of the solution were examined. The results confirmed the capability of the coil to efficiently focus the polystyrene particles under optimum conditions. A comprehensive set of COMSOL simulations demonstrate the underlying principles. In addition, polystyrene particles with diameters of 6 mu m and 15 mu m were simulated under different conditions. Under the same conditions, the larger particles can be focused more efficient than the smaller particles.