Design and Characterization of a 16×16 CMOS Capacitive DNA Sensor Array

The charge carried by biomolecules immobilized on the electrode surface causes a direct change in the electrode capacitance, enabling capacitive sensors to provide label-free real-time biodetection for point-of-care diagnostic applications. Capacitive sensors are easier to design and implement than other field effect transistor (FET)-based label-free biosensing devices. This work presents a $16\times16$ capacitive sensor array implemented in a 0.35- $\mu \text{m}$ complementary metal oxide semiconductor (CMOS) process. The signal-to-noise ratio of ON-chip switched-capacitor readout benefits from the reduced parasitic capacitance through monolithic integration. The interdigitated sensing electrodes have an area of $30\times 30\,\,\mu \text{m}^{{2}}$ and a measured capacitance of 57.3 fF in air. The pH measurement exhibited a capacitive sensitivity of 151 fF/pH. The deoxyribonucleic acid (DNA) measurements showed a capacitive sensitivity of 94 fF/log10[DNA] from 10 aM to 100 pM at a clock frequency of 2 MHz.