CMOS capacitive biosensor with enhanced sensitivity for label-free DNA detection

Silicon devices based on impedance measurements offer label-free and direct electrical detection when used to quantify the hybridization of DNA molecules. They show rapid, robust, and inexpensive measurement and compatibility with commercial microfabrication technology. The real-time measurement of the impedance does not require the use of labeling molecules attached to the target DNA in optical and magnetic technology [1,2]. It also has the advantage of miniaturization for point-of-care (PoC) or on-site sensing applications, unlike the 3-electrode topology in electrochemical sensors [3]. Several studies have proposed capacitive biosensors that utilize a nonfaradaic process, which refers to transient currents charging a geometrical capacitor in an electrolyte-electrode interface [4]. Conventional capacitive biosensors using the excitation of the bidirectional current [5,6] can be implemented with a compact design, but they have several issues that degrade the sensitivity of the sensor, such as DC drift in the electrode caused by a charge imbalance, the electrolysis generated by DC voltage across the electrodes, the offset generated by pre-charged initial values, and weakness against common-mode noise. As a solution, we report a fully integrated capacitance-based biosensor that locates two electrodes differentially in a single current source.