Design and fabrication of a micromachined planar patch-clamp substrate with integrated microfluidics for single-cell measurements

We have designed, fabricated, tested, and integrated microfabricated planar patch-clamp substrates and poly(dimethylsiloxane) (PDMS) microfluidic components. Substrates with cell-patch-site aperture diameters ranging from 300nm to 12 μm were produced using standard MEMS-fabrication techniques. The resistance of the cell-patch sites and substrate capacitance were measured using impedance spectroscopy. The resistance of the microfabricated apertures ranged from 200 kΩ to 47 MΩ for apertures ranging from 12 μm to 750 nm, respectively. The substrate capacitance was 17.2 pF per mm² of fluid contact area for substrates with a 2-μm-thick layer of silicon dioxide. In addition, the ability of the planar patch-clamp substrates to form high-resistance seals in excess of 1 GΩ has been confirmed using Chinese hamster ovary cells (CHO-K1). Testing shows that the microfluidic components are appropriate for driving human embryonic kidney cells (HEK 293) to patch apertures, for trapping cells on patch apertures, and for exchanging the extracellular fluid environment.