Calibration-free CMOS capacitive sensor for life science applications

Tabrizi, Hamed Osouli and Forouhi, Saghi and Farhanieh, Omid and Bozkurt, Ayhan and Magierowski, Sebastian and Ghafar-Zadeh, Ebrahim (2021) Calibration-free CMOS capacitive sensor for life science applications. IEEE Transactions on Instrumentation and Measurement, 70 . ISSN 0018-9456 (Print) 1557-9662 (Online)

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CMOS capacitive sensors reported for high-accuracy cellular molecular measurements typically suffer from significant parasitic capacitance changes caused by remnants and sediments during the experiment with several biological and chemical reactions. In this article, we propose a novel calibration-free capacitive sensing system that addresses this problem. The proposed CMOS capacitive sensor includes interdigitated electrodes (IDEs), a capacitance-to-current converter with a wide input dynamic range (IDR), a variable reference capacitor, and an oscillator-based analog-to-digital converter (ADC) which has been fabricated using 0.35 μm AMS CMOS process. Sweeping the value of the variable reference capacitor from 0.1 fF up to 1.27 pF with a step of 10 fF and repeating the sweep each second during the experiment allows the creation of time-resolved three-dimensional (3-D) fingerprints for the measurement of capacitance variations of the sample-electrode interface resulted from both the target material as well as non-target parasitic capacitances. We have tested the sensor using three different chemical solvents. The four different categories of curves that constitute the fingerprints of the chemicals showed a match with the post-layout simulation results. Capacitance change in the range of 0.416 fF up-1.27 pF can practically be monitored. The electrode area of 110 by 220 μm and the micrometer chamber size allows for placing tiny droplets of a few microliters. The generated fingerprint is valid for the chemicals with a conductivity of up to 5 mS/cm.
Item Type: Article
Uncontrolled Keywords: CMOS capacitive sensor; life science applications; time-resolved capacitance monitoring
Divisions: Faculty of Engineering and Natural Sciences
Depositing User: Ayhan Bozkurt
Date Deposited: 28 Aug 2022 12:51
Last Modified: 28 Aug 2022 12:51

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