CMOS electrochemical measurement circuit for biomolecular detection

This paper presents a three-electrode potentiostat transducer circuit for electrochemical sensing system designed for biomolecular detection. Melatonin has been found to be used as a significant index of potential breast cancer risk. The proposed chip automatically measures the redox current which depends on the concentration of melatonin in the analyte solution. Moreover, a current-to-time converter is designed to convert the sensed current into the proportional digitized time signal for back-end signal processing. Cyclic voltammetry and molecularly imprinted polymers were used in the experiments. The sensing electrodes were coated with a thin film imprinted with the target molecule. Fabricated in the TSMC CMOS 0.18 μm 1P6M technology, the proposed chip has a core chip size of 0.083 mm² and a power consumption of 1.143 mW with a 1.8 V supply voltage. This chip can measure the sensed current from ±15 to ±1500 µA with a linearity of R² = 0.999. In the cyclic voltammetry measurement, this chip has an error of less than 0.7%. The urine measurement results of the proposed chip were compared with that of enzyme-linked immune sorbent assay. Verified by melatonin concentration measurement, the proposed chip with high sensitivity demonstrates the feasibility of melatonin concentration detection, which contributes to the examination of breast cancer.