IEEE Trans Biomed Circuits Syst. 2021 Dec;15(6):1174-1185. doi: 10.1109/TBCAS.2022.3141553. Epub 2022 Feb 17.
This paper presents ISFET array based pH-sensing system-on-ultra-thin-chip (SoUTC) designed and fabricated in 350 nm CMOS technology. The SoUTC with the proposed current-mode active-pixel ISFET circuit array is desined to operate at 2 V and consumes 6.28 μW per-pixel. The presented SoUTC exhibits low sensitivity to process, voltage, temperature and strain-induced (PVTS) variations. The silicon area occupancy of each active-pixel is 44.9 × 33.5 µm with an ion-sensing area of 576 µm. The design of presented ISFET device is analysed with finite element modeling in COMSOL Multiphysics using compact model parameters of MOSFET in 350 nm CMOS technology. Owing to thin (∼30 µm) Si-substrate the presented SoUTC can conform to curvilinear surfaces, allowing intimate contact necessary for reliable data for monitoring of analytes in body fluids such as sweat. Further, it can operate either in a rolling shutter fashion or in a pseudo-random pixel selection mode allowing the simultaneous detection of pH from different skin regions. Finally, the circuits have been tested in aqueous Dulbecco's Modified Eagle Medium (DMEM) culture media with 5-9 pH values, which mimics cellular environments, to demonstrate their potential use for continuous monitoring of body-fluids pH.
本文提出了一种基于 ISFET 阵列的 pH 传感系统-on-ultra-thin-chip（SoUTC），该系统采用 350nm CMOS 技术设计和制造。SoUTC 采用所提出的电流模式有源像素 ISFET 电路阵列设计，工作电压为 2V，每个像素消耗 6.28μW。所提出的 SoUTC 对工艺、电压、温度和应变引起的（PVTS）变化具有低灵敏度。每个有源像素的硅面积占用为 44.9×33.5μm，离子感应面积为 576μm。所提出的 ISFET 器件的设计采用 COMSOL Multiphysics 中的有限元建模进行分析，使用 350nm CMOS 技术中的 MOSFET 紧凑模型参数。由于采用了较薄的（约 30μm）硅衬底，所提出的 SoUTC 可以贴合弯曲表面，允许进行可靠数据监测所需的紧密接触，从而用于监测体液中的分析物，如汗液。此外，它可以以滚动快门模式或伪随机像素选择模式运行，允许同时检测来自不同皮肤区域的 pH 值。最后，这些电路已经在含有 5-9 pH 值的水性 Dulbecco's Modified Eagle Medium（DMEM）培养基中进行了测试，该培养基模拟了细胞环境，证明了它们在连续监测体液 pH 值方面的潜在用途。
