Integrated 0.35 pm CMOS capacitance sensor with atto-farad sensitivity for single cell analysis

Differential 3-stage and 5-stage, ring oscillator based capacitance sensors were designed and integrated using 0.35 μm CMOS technology. The sensor operates at 0.7 GHz and 1.4 GHz and achieves ~14 aF capacitive sensitivity. The use of CMOS technology makes the integration of the sensing circuit, and the detection microelectrodes on chip possible. A hybrid system was developed where a Plexiglas microfluidic system was mounted on top of the CMOS chip. This created a complete Lab-on-Chip cytometer sensor that was used to detect individual polystyrene spheres (10-15 μm) and Chinese hamster ovary (CHO) cells. The integration of sensing circuitry with the microfluidic parts reduces the sensor size and weight significantly when compared with previous designs.