CMOS Capacitive Sensor for DNA Detection in Undiluted Ionic Solution

Capacitive detection of affinity-bound biomolecules enables rapid and label-free bioassays suitable for point-of-care diagnostic applications. However, direct detection at high ionic strengths is severely limited by the Debye charge-screening effect of the electric double layer on the sensor surface, leading most studies to be performed at diluted ionic strengths. In this study, probe–target deoxyribonucleic acid (DNA) hybridization was successfully measured by modulating the electric field of the interdigitated sensing electrodes to reduce charge screening. The developed 8 × 8 complementary metal–oxide–semiconductor (CMOS) capacitive sensor array exhibited a sensitivity of 150 fF/log ₁₀ [DNA] measured at 15 MHz from 10 aM to 100 pM with a response time of approximately 400 s. The array also exhibited a pH sensitivity of 354 fF/pH.