Virtual Filter Membranes in a Microfluidic System for Sorting and Separating Size-Based Micro Polystyrene Beads by Illumination Intensity Design in Optically Induced Dielectrophoresis (ODEP)

In biomedical diagnosis, the efficient separation and purification of specific targets from clinical samples is the desired first step. Herein, the concept of virtual filter membranes based on optically-induced dielectrophoresis (ODEP) manipulation in a microfluidic channel is proposed as a light screening membrane for the separation of polystyrene (PS) microparticles with three different diameters of 15.8, 10.8 and 5.8 µm. The ODEP manipulation velocity of three types of PS microparticles reacted with the color brightness setting was investigated to determine the light intensity to induce an ODEP force higher than the drag force of fluid speed. The color brightness of the light bar in three areas of the light screening membrane was selected as 60%, 70% and 100% to isolate PS microparticles with diameters of 15.8, 10.8 and 5.8 µm, respectively. With a double light bar and a flow rate of 3 µL/min, the recovery rate and isolation purity was improved by 95.1~100% and 94.4~98.6% from the mixture of three types of PS microparticles within 2 min, respectively. This proposed light screening membrane could be a candidate for the separation of small-volume and rare biomedical samples, including circulating tumor cells (CTCs) and bacteria in the blood.