IEEE Trans Biomed Circuits Syst. 2021 Apr;15(2):339-350. doi: 10.1109/TBCAS.2021.3075348. Epub 2021 May 25.
This paper presents a new fully integrated CMOS capacitance sensor chip with a wider input dynamic range (IDR) compared to the state-of-the-art, suitable for a variety of life science applications. With the novel differential capacitance to current conversion topology, it achieves an IDR of about seven times higher compared to the previous charge based capacitive measurement (CBCM) circuits and about three times higher compared to the CBCM with cascode current mirrors. It also features a calibration circuitry consisting of an array of switched capacitors, interdigitated electrodes (IDEs) realized on the topmost metal layer, a current-controlled 300 MHz oscillator, and a counter-serializer to create digital output. The proposed sensor, fabricated in AMS 0.35 μm CMOS technology, enables a high-resolution measurement, equal to 416 aF, of physiochemical changes in the IDE with up to 1.27 pF input offset adjustment range (IOAR). With a measurement speed of 15 μs, this sensor is among the fast CMOS capacitive sensors in the literature. In this paper, we demonstrate its functionality and applicability and present the experimental results for monitoring 2 μL evaporating droplets of chemical solvents. By using samples of solvents with different conductivity and relative permittivity, a wide range of capacitance and resistance variations in the sample-IDE interface electric equivalent model can be created. In addition, the evaporating droplet test has inherently fast dynamic changes. Based on the results, our proposed device addresses the challenge of detecting small capacitance changes despite large parasitic elements caused by the ions in the solution or by remnants deposited on the electrode.
本文提出了一种新的全集成 CMOS 电容传感器芯片,与现有技术相比,具有更宽的输入动态范围 (IDR),适用于各种生命科学应用。通过新颖的差分电容到电流转换拓扑结构,与基于电荷的电容测量 (CBCM) 电路相比,它实现了大约 7 倍的 IDR 提升,与具有级联电流镜的 CBCM 相比,实现了大约 3 倍的 IDR 提升。它还具有一个校准电路,由一个开关电容器阵列、顶层金属层上实现的叉指电极 (IDE)、一个电流控制的 300MHz 振荡器以及一个计数器-串器组成,以创建数字输出。该传感器采用 AMS 0.35μm CMOS 技术制造,能够以 416aF 的高分辨率测量 IDE 中的物理化学变化,输入失调调整范围 (IOAR) 高达 1.27pF。测量速度为 15μs,是文献中最快的 CMOS 电容传感器之一。在本文中,我们演示了其功能和适用性,并展示了用于监测 2μL 化学溶剂蒸发液滴的实验结果。通过使用具有不同电导率和相对介电常数的溶剂样本,可以在样品-IDE 界面的等效模型中创建广泛的电容和电阻变化。此外,蒸发液滴测试具有固有快速的动态变化。基于这些结果,我们提出的器件解决了检测小电容变化的挑战,尽管溶液中的离子或沉积在电极上的残留物会导致寄生元件很大。