500 μl glass syringe

The device was designed to allow cells suspended in DEP buffer to flow through the channels and be attracted to the BPE tips in pDEP mode. AC voltage to drive the DEP response was applied to the driving electrodes (outer rows of electrodes) using a Tektronix AFG3011C waveform generator (Tektronix, Beaverton, OR) and Trek model 2205 amplifier (Trek, Lockport, NY). The AC frequency was maintained at 70 kHz to ensure the MDA-MB-231 cells experienced strong pDEP, based on crossover frequencies (25-50 kHz) reported by Shim et al.^{21 (link)} and corroborated by our previous work.^{22 (link)} The devices were imaged using a Nikon AZ100 microscope (Nikon, Tokyo, Japan). Flow was induced using a Pico Plus Elite syringe pump (Harvard Apparatus, Holliston, MA) paired with a 500 μL glass syringe (Hamilton Company, Reno, NV) in withdrawal mode. Cell counting was assisted through labeling of a cell surface antigen (EpCAM) with a phycoerythrin-linked antibody (PE/anti-EpCAM). The resolution of these fluorescence images, obtained over the entire array, is too low to determine cell volume. Higher resolution micrographs were obtained during DEP capture for limited sections of the array. Since cell volume influences the total quantity of enzyme contained in each cell, strategies for rapidly and accurately determining cell volume through imaging will be pursued in our future work.