Kim Ji Hyun, Park Seong Jun, Han Jin-Woo, Ahn Jae-Hyuk
Department of Electronic Engineering, Kwangwoon University, Seoul 01897, Korea.
Center for Nanotechnology, NASA Ames Research Center, Mountain View, CA 94035, USA.
Sensors (Basel). 2021 Mar 10;21(6):1939. doi: 10.3390/s21061939.
Field-effect transistor (FET)-based biosensors have garnered significant attention for their label-free electrical detection of charged biomolecules. Whereas conventional output parameters such as threshold voltage and channel current have been widely used for the detection and quantitation of analytes of interest, they require bulky instruments and specialized readout circuits, which often limit point-of-care testing applications. In this study, we demonstrate a simple conversion method that transforms the surface potential into an oscillating signal as an output of the FET-based biosensor. The oscillation frequency is proposed as a parameter for FET-based biosensors owing to its intrinsic advantages of simple and compact implementation of readout circuits as well as high compatibility with neuromorphic applications. An extended-gate biosensor comprising an AlO-deposited sensing electrode and a readout transistor is connected to a ring oscillator that generates surface potential-controlled oscillation for pH sensing. Electrical measurement of the oscillation frequency as a function of pH reveals that the oscillation frequency can be used as a sensitive and reliable output parameter in FET-based biosensors for the detection of chemical and biological species. We confirmed that the oscillation frequency is directly correlated with the threshold voltage. For signal amplification, the effects of circuit parameters on pH sensitivity are investigated using different methods, including electrical measurements, analytical calculations, and circuit simulations. An Arduino board to measure the oscillation frequency is integrated with the proposed sensor to enable portable and real-time pH measurement for point-of-care testing applications.
基于场效应晶体管（FET）的生物传感器因其对带电生物分子的无标记电学检测而备受关注。虽然传统的输出参数如阈值电压和沟道电流已被广泛用于检测和定量感兴趣的分析物，但它们需要庞大的仪器和专门的读出电路，这常常限制了即时检测应用。在本研究中，我们展示了一种简单的转换方法，该方法将表面电位转换为振荡信号，作为基于FET的生物传感器的输出。由于其在读出电路的实现上具有简单紧凑的固有优势以及与神经形态应用的高度兼容性，振荡频率被提议作为基于FET的生物传感器的一个参数。一个包括沉积有AlO的传感电极和读出晶体管的扩展栅生物传感器连接到一个环形振荡器，该振荡器产生用于pH传感的表面电位控制振荡。作为pH函数的振荡频率的电学测量表明，振荡频率可以用作基于FET的生物传感器中用于检测化学和生物物种的灵敏且可靠的输出参数。我们证实振荡频率与阈值电压直接相关。为了进行信号放大，使用不同方法研究了电路参数对pH灵敏度的影响，包括电学测量、分析计算和电路模拟。一个用于测量振荡频率的Arduino板与所提出的传感器集成在一起，以实现用于即时检测应用的便携式实时pH测量。
