High-throughput electrokinetic bioparticle focusing based on a travelling-wave dielectrophoretic field

This study presents a sheathless and portable microfluidic chip that is capable of high-throughput focusing bioparticles based on 3D travelling-wave dielectrophoresis (twDEP). High-throughput focusing is achieved by sustaining a centralized twDEP field normal to the continuous through-flow direction. Two twDEP electrode arrays are formed from upper and lower walls of the microchannel and extend to its center, which induce twDEP forces to provide the lateral displacements in two directions for focusing the bioparticles. Bioparticles can be focused to the center of the microchannel effectively by twDEP conveyance when the characteristic time due to twDEP conveying in the y direction is shorter than the residence time of the particles within twDEP electrode array. Red blood cells can be effectively focused into a narrow particle stream (similar to 10 mu m) below a critical flow rate of 10 mu l/min (linear flow velocity similar to 5 mm/s), when under a voltage of 14 Vp-p at a frequency of 500 kHz is applied. Approximately 90% focusing efficiency for red blood cells can be achieved within two 6-mm-long electrode arrays when the flow rate is below 12 mu l/min. Blood cells and Candida cells were also focused and sorted successfully based on their different twDEP mobilities. Compared to conventional 3D-paired DEP focusing, velocity is enhanced nearly four folds of magnitude. 3D twDEP provides the lateral displacements of particles and long residence time for migrating particles in a high-speed continuous flow, which breaks through the limitation of many electrokinetic cell manipulation techniques.