An alternating current-driven control for biomolecule detection

A biosensor with an alternating current-driven control is realized for label-free detection of biomolecule. This sensor precisely measures the capacitive changes in the electrode-electrolyte interface after hybridization with complementary DNA targets. Conventional capacitive biosensors generally use the excitation method with double current-sources. However these sensors have limitations due to performance-based issues of the DC potential drift and offsets, as well as weakness against common-mode noises. In this paper, the proposed device includes differential electrode pairs that are located in a single current-source line with sensing circuits, which results in the elimination of the effect due to the current mismatch. The device also shows an improved signal-to-noise ratio. Additionally, the individual control of the switch controller in this device offers robust and reproducible measurement capabilities independent of the duty asymmetry and pre-charged initial offset voltage. The device is a hybrid sensor that has both working electrodes and readout circuitry in one-chip using a CMOS process. The prototype successfully demonstrated the specific detection of oligonucleotide sequences. The device consumes 2.34mW from a 3.3 V supply in a 0.35 μm CMOS process.