In this paper, a novel fully autonomous and integrated power management interface circuit is introduced for energy harvesting using thermoelectric generators (TEGs) to supply power to IoT nodes. The circuit consists of a self-starting DC-DC converter based on a dual-phase charge pump with LC-tank oscillator, a digital MPPT unit, and a 1-V LDO regulator. The novel MPPT algorithm avoids open-circuit state, and accommodates varying input power and ultra-low voltage conditions. Validation data from the fabricated test-chip in 180nm standard CMOS technology indicates the circuit start-up voltage is as low as 170 mV. The maximum output power capacity is 0.5 mW, which is the highest noted in the literature for a fully integrated solution. The high output power at low cost is achieved with a peak system efficiency of 30%. The relatively low efficiency is expected, since the focus of the design is high power capacity at low cost. The MPPT algorithm reaches 98% maximum accuracy for a source output resistance of 40 Ω, which is typical for wearable TEG modules.

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.

This article introduces a new foundry-based ion-sensitive field-effect transistor named open-gate junction field-effect transistor (OG-JFET), which is intended to be used for chemical and biological sensing applications. OG-JFET can be realized by removing the n-type gate in a p-type JFET to open the space for electrolyte gating. The new configuration enables applying a bias voltage via back-gate that results in more efficient channel current control. Accordingly, a $1.6 ~{\mu }\text{m}$ thick p-type conductive layer has been epitaxially grown on a $450 ~{\mu }\text{m}$ thick n-type silicon layer based on a standard foundry process. The design promotes a large sensing area including seven p-type conduction channels with dimensions of $1000\,\, {\mu }\text{m}\,\,{\times }\,\,100\,\, {\mu }\text{m}$ (W ${\times }$ L) and depth of $1.6 ~{\mu }\text{m}$ . All the necessary transfer characteristics required for biosensing/ion-sensing of OG-JFET have been derived. Furthermore, we have conducted a COMSOL Multiphysics simulation on OG-JFET to verify the operation of the sensor, which helps to comprehend the functionality of the sensor in different biasing conditions. The COMSOL semiconductor simulation results showed good consistency with experimental results that make the simulations a reliable reference for optimization and customizing the chip for specific applications. OG-JFET showed a sensitivity of 55.29 mV/pH, a hysteresis of 16 mV, and drift of $3 ~{\mu }\text{A}$ /hours which are in the order of standard ISFET sensors in the literature. The simulation and experimental results in this paper, for the first time, put forward the OG-JFET as a new foundry-process-based, mass-producible ion-sensitive FET sensor for chemical and biological applications.

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 paper, 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 (3D) 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 to 1.27 pF can practically be monitored. The electrode area of 110 μm 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.

This paper presents a fully integrated complementary metal-oxide-semiconductor (CMOS) capacitive sensor array for life science applications. This sensing device consists of an array of 16 × 16 interdigitated electrodes (IDEs) integrated with a charge-based readout and multiplexing circuitries on the same chip. This chip was implemented in 0.35 µm AMS CMOS process. This sensing device has a wide input capacitance range (ICR) of about 100 fF and a resolution of 150 aF, and the capability of temporal, spatial, and dielectric sensing. It makes it possible to develop a low-cost, multimodal, calibration-free sensing platform for life science applications. Here, we demonstrate and discuss the functionality and applicability of the proposed sensing device by introducing various chemical solvents including ethanol, methanol, and pure water. The simulation and experimental results achieved in this work have taken us one step closer to a fully automated calibration-free multimodal capacitive sensing platform for high-throughput drug development and other purposes.

This paper presents a portable impedimetric biosensor for detecting infectious diseases such as SARS-CoV-2 Infections. A bio-ready sensing electrode functionalized with SARS-CoV-2 nucleocapsid antibody was employed to quantitatively convert the concentration of nucleocapsid protein (N-protein) into impedance changes. In this paper, we proposed a readout system with a dynamic input range of 200 Ω to 1 MΩ magnitude and 0 to 180° phase. The resolution of this device is 1% and 6.5° for measuring the magnitude and phase, respectively. Herein we demonstrate and discuss the proposed system’s functionality, sensitivity, and selectivity using the clinical swab samples. As per these results, this readout system is suitable for the detection of N-protein ranging up to 10,000 pg/mL with a resolution of 56 fg/mL. The proposed impedimetric sensing system can be adopted for the detection of infectious diseases in the future. This low-cost (<$80) device using off-the-shelf is a unique candidate for batch production purposes during urgent pandemic situations.