(441c) DC Dielectrophoresis: Separation of Fluorescent Polystyrene Particles

This research describes a lab-on-a-chip device for the separation of microparticles by size via Direct Current Dielectrophoresis (DC-DEP). The separation was achieved by using a rectangular insulating obstacle in a 200 micron channel to create non-uniformities in field density. Particles travel into one of four exit channels based on their deflection from the insulating obstacle. The device and insulating obstacle were fabricated with PDMS device by soft-photolithography process. The PDMS device was sealed to glass slide by various techniques. A baseline EOF was established by current monitoring method for the devices sealed by these techniques: 1) IPA treated glass slide with heat at 65 deg C 2) UV/Ozone treated PDMS device with DI water washed glass slide 3) electrostatic seal with no treatment. The DC-DEP particle flow behaviors were investigated with three different sizes of fluorescent polystyrene particles- 2.28 µm, 5.49 µm and 15.68 µm. 0.14 M phosphate buffer saline was used as a dilution buffer for all experiments. Field dependency studies were carried out at 3.42, 6.85 and 10.27 V/cm. Reproducibility was tested by repeating experiments at least 5 times or until the standard deviation was within 5% of the mean. An Axiovision CCD camera was used to record fluorescent images at 5 mS interval for 2 minutes. The data analysis was carried out by taking fluorescent intensity profiles at locations prior to and just past the insulating obstacle. These intensity profiles identify particle flow events in the channel and each position is recorded with time. The total intensity for all the events in the 2-minute experiment at a particular Y position were plotted to determine the trajectory of the particle. This work is an essential first step in using DC-DEP for particle sorting in a continuous flow lab on a chip device.