Detection of DNA Hybridization Beyond the Debye Screening Length by CMOS Capacitive Sensors

Capacitive sensors are very promising to provide label-free and real-time biological detection for point-of-care diagnostic applications. However, the Debye charge screening effect severely hinders the detection under high ionic strength condition, such as in human serum. Therefore, most measurements are made indirectly in diluted solutions. To solve this problem, electric field modulation between the interdigitated sensing electrodes is applied in this study to increase the Debye length. For DNA (deoxyribonucleic acid) measurements, the two designs operating around 90 and 40 MHz exhibited sensitivities of 2.6 fF/log[DNA] and 10.8 fF/log[DNA] up to 100 fM and a response time of 12 minutes.