A 6.5/17.5-GHz Dual-Channel Interferometer-based Capacitive Sensor in 65-nm CMOS for High-Speed Flow Cytometry

In this paper, a dual-channel interferometer-based capacitive sensor with high sensitivity is implemented in 65nm CMOS. Such architecture facilitates high throughput flow cytometry applications using intrinsic EM signatures of biological cells. To enhance SNR, injection-locked oscillator is utilized to perform phase amplification with regard to capacitance-induced frequency shift. Noise from on-chip QVCO is further reduced through I/Q interpolation. Measurements show that the sensor achieves better than 1.5 aF of sensitivity at 250-kHz equivalent noise-bandwidth. With the aid of 3D hydrodynamic focusing, flow cytometry is tested with polystyrene beads. The proposed dual-channel sensor consumes 30 mW under 1 V supply.