Dielectrophoretic isolation of cells using 3D microelectrodes featuring castellated blocks

We present 3D microelectrodes featuring castellated blocks for dielectrophoretically isolating cells. These electrodes provide a more effective dielectrophoretic force field than thin-film surface electrodes and yet immobilize cells near stagnation points across a parabolic flow profile for enhanced cell viability and separation efficiency. Unlike known volumetric electrodes with linear profiles, the electrodes with structural variations introduced along their depth scale are versatile for constructing monolithic structures with readily integrated fluidic paths. This is exemplified here in the design of an interdigitated comb array wherein electrodes with castellated surfaces serve as building blocks and form digits with an array of fluidic pores. Activation of the design with low-voltage oscillations (+/- 5 V-p, 400 kHz) is found adequate for retaining most viable cells (90.2% +/- 3.5%) while removing nonviable cells (88.5% +/- 5%) at an increased throughput (5 x 10(5) cells h(-1)). The electrodes, despite their intricate profile, are structured into single-crystal silicon through a self-aligned etching process without a precision layer-by-layer assembly.