Digital microfluidic platform for dielectrophoretic patterning of cells encapsulated in hydrogel droplets

In this article, we present a method for cell culture on a digital microfluidic (DMF) platform. Dielectrophoresis is used for trapping and patterning cells encapsulated within a 3D gelatin methacrylate (GelMA) hydrogel. In this method, planar traps are patterned within the electrodes on the DMF chip. Dispersed HEK 293 cells in GelMA solution are used to show negative dielectrophoresis when subject to a voltage at 20 kHz. The effects of the cell concentration, trap area, and trap spacing are analyzed. The rise time for patterning cells is shown to be rapid, from 8.5 seconds to 198.3 seconds for 50 mm and 500 mm diameter traps, respectively. The number of cells trapped was significantly influenced by the trap diameter and cell concentration. Live/dead assayed cells under a fluorescence microscope indicated that clusters of HEK 293 cells are 66% viable after 4 days of culturing. Certain trap designs were 78% viable on average after 4 days. This platform can be applied to execute quantitative, automated cell behavior studies and drug tests on the array of cells in vitro.