A CMOS capacitance sensor for cell adhesion characterization

We describe a CMOS capacitance sensor for measuring the capacitive coupling between living cells and the underlying substrate, a quantity that can be used to characterize cell adhesion strength and cell health. The capacitance sensor operates on the charge sharing principle, mapping sensed capacitance values to voltages. The sensor has been fabricated in a commercially available 0.5 /spl mu/m, 2-poly 3-metal CMOS technology. Experimental results are presented for bench tests using a micropositioned electrode and in vitro tests with cells cultured directly on the chip surface. The sensor achieves an empirical distance resolution of 3 nm and capacitance resolution of 135 aF. The sensors have been successfully used for long term monitoring of cell viability in vitro.