Author(s): D F Chen, H Du, W H Li
This paper presents a microfluidic system comprising a three-dimensional microelectrode structure for accumulation and separation of micro-sized particles based on the combination of negative dielectrophoresis (DEP) and hydrodynamic force. The paired electrode array is constructed by aligning two layers of microelectrode structure face to face on the top and bottom sides of the microchannel. Dielectrophoretic gates are generated between the top and bottom electrodes with high-frequency ac voltage. These gates are designed to study the behavior of microparticles such as polystyrene beads or cells carried by a laminar flow past the electrodes. Depending on the relative strength of the DEP force and hydrodynamic force acting on the particles, the particles can either penetrate the gates or settle by the gates. The threshold velocity at which the particles begin to penetrate the gates depends on a number of parameters such as channel height, particle size, dielectric properties, electrode width and local heating, etc. A wide range of these parameters give rise to approaches of accumulating and separating microparticles. For this purpose, a microfluidic device with the paired microelectrode array sitting on the channel has been designed and fabricated using microfabrication techniques. Polystyrene beads were used to study the performance of the device and particle behavior. Using a proper range of flow rates, particle accumulation and separation are successfully achieved with the microsystem.