An 8 GHz CMOS near field bio-sensor array for imaging spatial permittivity distribution of biomaterials

In this paper a CMOS biosensor array operating around 8 GHz is presented, for characterizing biomaterials by imaging the spatial distribution of permittivity. The sensor is fabricated in standard 250 nm SiGe BiCMOS process. The sensor operation is based on the frequency shift of cross-coupled oscillator circuit due to capacitance change of the core LC tank. Non-uniform four finger interdigitated capacitor is used as the sensor unit. A four element sensor array system is used in this work for the proof of concept of spatial dielectric imaging. Measured sensitivity is observed to be 22 MHz per unit permittivity change. After first sensitivity tests, the spatial discrimination capability of the array is shown by further testing the array with biomaterials of different permittivity on different sensor units, showing unique frequency shift for individual sensors.