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Bottom-gate bottom contact amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) were fabricated using solution processing. The nonpassivated a-IGZO-TFTs exhibited a significant threshold voltage shift, large hysteresis in the current–voltage characteristics, and degradation in the subthreshold swing. TFTs’ performance degradation is due to the interaction of its back channel with adsorbed oxygen and water molecules in the ambient air. The hydroxy-phenyl zinc porphyrin (ZnP) self-assembled monolayer (SAM) was formed on TFTs’ back channel using a low-cost solution-based approach to passivate TFTs back channel. The passivated a-IGZO-TFTs exhibited enhanced electrical characteristics and improved stability compared with nonpassivated TFTs. Passivated TFTs presented significantly reduced hysteresis up to 87% and subthreshold slope degradation up to 71%. The passivated TFTs showed excellent stability under positive (20 V) and negative (−20 V) bias stress conducted for 5000 s.

This article discusses a novel RF energy-harvesting system for available power as low as 500 nW. The system includes a main RF rectenna (antenna followed by rectifier) for energy harvesting, an auxiliary RF rectenna for power detection, and a boost converter along with its control circuit. For maximum power point tracking (MPPT), a particular reference voltage ${V_{\text {ref}}}$ for a range of received RF power (from −11 to 3 dBm) is used to harvest maximum available power from the main rectenna by regulating its output voltage with the help of the boost converter. ${V_{\text {ref}}}$ for MPPT is provided by the auxiliary RF rectenna and the power-detector circuit and depends on the RF power. The complete system is designed, simulated, fabricated, and tested in the 180-nm mixed-mode CMOS technology. Measured results show that the boost converter can track the maximum power point for the input available power ranging from 500 nW to 1 mW. The efficiency of the boost converter is a function of the available input power and the equivalent source resistance of the RF energy harvester. For an equivalent source resistance of ${1~\text {k}\Omega }$ , the maximum efficiency of the boost converter is 91.6% at ${165~\mu \text {W}}$ of the available input power. As a potential application, a ${\Delta \Sigma }$ modulator designed in the 180-nm mixed-mode CMOS technology is powered by the proposed energy-harvesting system. The efficiency of the boost converter is approximately 76.6% while powering the ${\Delta \Sigma }$ modulator and 78.5% while powering the dc load at the RF power of ${-7\,\,\text {dBm}}$ .

This letter presents a methodology to model the effect of electromagnetic interference (EMI) on the wireline communication channels. The proposed simulation methodology incorporates the effect of EMI on the circuit during the design phase in EMI-sensitive applications. It allows simple and faster EMI simulations at the SPICE level which minimizes the post-fabrication failures. A TEM (transverse electromagnetic) cell is used to emulate the effect of EMI on the test circuit as provided in the standard IEC-62132. An analytical model is presented to quantify the effect of induced voltage and current on a transmission line placed in the TEM cell. The developed model is experimentally verified for a frequency range of 1 MHz to 1 GHz. As an experimental study, the proposed model is used to validate the effect of EMI on the wireline communication channel transmitting a pseudorandom binary sequence (PRBS) data generated from an FPGA board at 1 Gbps data rate for a wide range of EMI powers and frequencies.

This work presents high resolution and adaptable frequency measurement techniques for relaxation oscillator based capacitive sensors. The techniques rely on extremely simple hardware such as a 1-bit coarse voltage quantizer to generate a 1-bit data stream and subsequently determine frequencies with resolutions greater than 20 bits from the 1-bit data stream. The proposed readouts are based on two types of 1-bit hardware approaches with Nyquist sampling in one approach and oversampling in the other. The first approach employs a Nyquist rate sampled 1-bit comparator while the second approach relies on an oversampled 1-bit quantizer based delta-sigma modulator (DSM) as a hardware to generate the bit stream. High resolution frequency is estimated from the 1-bit data stream using parametric, non-parametric and compressed sensing approaches. We provide detailed study and measurement results comparing the performance of the proposed techniques for test inputs with different frequencies and amplitudes and multiple signal shapes including sine, square, triangular and sawtooth. We show that the 1-bit comparator along with the CS approach provides the best performance across all input amplitude, frequency and shapes. A capacitive water level sensor was implemented in a PCB and embedded in a conventional square wave relaxation oscillator to verify the proposed technique. Measurement results show that incremental SNRs can be achieved only by increasing the 1-bit data stream length without any change in the hardware thereby demonstrating the adaptability of the technique based on an application requirement.

Micro-Electro-Mechanical-System (MEMS) cantilevers are sensitive to minute changes in environmental parameters. MEMS cantilevers possess a single readout transduction mechanism like stress to frequency, resistive and capacitive changes. Here, we demonstrate a novel dual readout MEMS cantilever for sensing applications with high optical and resistive sensitivities. The proposed work focuses on the design, fabrication and characterization of an L-shaped 2D photonic crystals (PhC) waveguide piezoresistive MEMS cantilever and its use in a sensor platform. We integrated a 2D PhC waveguide on top of the cantilever along with a piezoresistor element embedded within the cantilever and attained a synergistic combination of both optical and resistive sensing. When the cantilever deflects in the ‘Z’ direction, it is perceived that it leads to stress in the cantilever and the corresponding change in resistance and the optical property is measured. Thus, a unique L-shaped cantilever is designed for reliable coupling of the light inside the 2D PhC waveguide using optical fiber. An orthogonal measurement setup is developed to demonstrate the cantilevers dual readout feature. We achieved excellent piezoresistive and optical sensitivities of ~0.0072 (( $\Delta \text{R}$ /R)/ $\mu \text{m}$ ), and ~0.046 (( $\Delta \text{P}$ /P)/ $\mu \text{m}$ ), respectively. The fabricated cantilever is tested with the VOC and measurements show that it provides two distinct signatures i.e., $\Delta \text{R}$ /R and $\Delta \text{P}$ /P for the same target analyte. Therefore, the miniaturized MEMS cantilever is unique because of its dual readout feature and it can be vital in high detection accuracy applications.

In this article, the power gating (PG) technique is analyzed using nano-electro-mechanical switches (NEMS), FinFETs, and nanowire field-effect transistors (NWFETs). We have used detailed circuit level simulations using well-calibrated models to obtain the conditions for net energy saving with thermal effects. We demonstrate that for a benchmark 17-stage buffer chain circuit, the NEMS PG will be superior to sub-10-nm FinFETs and NWFETs-based gating when the $ {T}_{ \text{on}}/ {T}_{ \text{off}}$ ratio is less than 0.1 at room temperature. The ratio increases as temperature increases. Circuit simulations show that the energy gain ( $ {T}_{\text {on}}/ {T}_{ \text{off}} = {10}^{-{4}}$ ) due to NEMS gating increases by 3.6 times with reference to NWFETs and 7.3 times as compared to FinFETs-based gating when the temperature increases from 30 °C to 80 °C. NWFETs require a longer breakeven cycle for PG to become more energy-efficient than FinFETs due to its better gate control over the channel.

In this article, for the first time, we present the improvement in efficiency in a low-voltage dc–dc boost converter for the energy-harvesting applications using the experimentally demonstrated sub-50-mV nano electro-mechanical switch (NEMS). As per the measurement results, the sub-50-mV NEMS having a small air gap of only 100 nm exhibits very low hysteresis ( $\text{V}\cdot \mu \text{m}$ ). This study explores a discontinuous-conduction mode (DCM) boost converter with specifications suitable for energy-harvesting applications using the NEMS-based design. The results are compared with the corresponding design using the MOSFET switches in 0.18- $\mu \text{m}$ CMOS technology. This work illustrates that the NEMS-based DCM boost converter design has an improvement in the efficiency of around 30% at a switching frequency of 10 kHz over CMOS for the same ON-state resistance. This is because the proposed fabricated NEMS has extreme low pull-in voltage (50 mV) and low parasitic capacitances (~3.3 fF/ $\mu \text{m}$ ).

Metal oxide semiconductors proved their usability in environmental monitoring applications and are considered successful in detecting ionizing radiation. This work reports the feasibility of solution-processed metal oxide semiconductor thin-film transistors for radiation sensing for the first time. In particular, the effects of a wide range of gamma radiation (100Gy to 10kGy) on the performance of solution-processed amorphous Indium-Gallium-Zinc-Oxide (a-IGZO) transistors are investigated. The current-voltage (IV) characterization (both output and transfer characteristics) of IGZO-TFTs before and after irradiation are obtained to study different parameters. The radiation-induced changes in TFT are mainly observed in the threshold voltage shift ( $\sf \Delta ~\text{V}_{th}$ ) and the increase of subthreshold swing. It is observed that up to a total dose of 1kGy, threshold voltage increases negatively ( $\sf \Delta \,\,\text{V}_{th}= -1.8\text{V}$ at 1 kGy), and beyond 1 kGy, threshold voltage increases positively ( $\Delta \,\,\text{V}_{\text{th}} =0.8\text{V}$ at 10 kGy). The XRD and AFM data of IGZO thin-film suggests minor structural and morphological changes after exposure to gamma irradiation. The corresponding sensitivity obtained with gamma irradiation is 27.78 mV/Gy (100Gy-1kGy), expressed in the threshold voltage shift. The effects of radiation-induced changes in TFTs are completely removed after storing irradiated TFTs in the vacuum at room temperature for 6 months.

This paper presents a hybrid pattern recognition with temperature compensation (HPR-TC) used within an E-Nose system. HPR-TC with E-nose has the novelty, amongst MEMS sensor platforms, of having two modes of operation i.e., rapid mode of detection to be used in time-critical conditions and comprehensive analysis mode for improved detection accuracy. Two modes of operations in HPR-TC are possible because of the implementation of hybrid PR featuring a combination of two different data analysis techniques for explosive sensing. The first part of the hybrid PR is the binary PR based on threshold-based detection and the second one is the analog PR based on PCA and K-mean. The E-Nose system with proposed HPR-TC is validated with two different highly sensitive MEMS sensor types, i.e., SU8 and Si3Nx piezo-resistive cantilever. These MEMS sensors are coated with surface receptors, 4-MBA, 6-MNA and 4-ATP, to improve the selectivity. The E-Nose system can detect explosive compounds such as TNT, RDX, and PETN, in a controlled environment at a concentration as low as 16ppb of TNT, 56ppb of RDX and 134ppb of PETN. Furthermore, measurements show that E-Nose with temperature compensated binary PR can detect the explosives with a detection accuracy higher than 74% as true positives and higher than 79% as true negatives in a short time, within initial 17 seconds of the experiment. However, the temperature compensated analog PR gives a detailed classification of explosives with a higher detection accuracy of 80% as true positives and 86% as true negatives after approximately 95 seconds.

There is an increasing demand for the development of various tools for diagnosis and control of plant infections. The early diagnosis of plant disease serves as a vital element to improve crop productivity and meet demands of the ever-growing world population. The traditional methods of plant disease detection are time consuming, laborious and require 3-5 days to estimate the disease incidence. In this review, we focus on the advances in the detection techniques, mainly the miniaturized systems that has developed in the last decade. The analytical techniques for plant pathogen detection have been classified as direct and indirect detection methods. The direct methods involving laboratory techniques such as polymerase chain reaction, enzyme-linked immune-sorbent assays, and immunofluorescence and their recent advances have been discussed. Similarly, indirect methods which rely on sensing the plant stress indicators to detect plant diseases have been categorized and reviewed. In the last decade, various detection platforms with high sensitivity and selectivity have been developed and commercialized into handheld devices and products for on-field plant disease detection. This review focusses on the transition from the gold standard techniques to the advanced on-field biosensors to detect plant diseases with higher accuracy, cost-effective and making timely diagnosis possible. A growing trend for pathogen detection based on biosensors has been highlighted and further categorized into electrochemical, optical, and mass-based sensors. These innovative advancements in plant pathogen detection systems help to make the agricultural sector more safe, reliable, and sustainable for the ever-growing population.

In this article, we demonstrate a double-clamped nano-electromechanical switch (NEMS) with low stand-by power as an effective solution to the leakage issues in scaled CMOS-based power gating (PG) in logic circuits. The proposed NEMS structure is achieved to have a low pull-in (~1.2 V), low hysteresis ( ${T}_{\text{ON}}/{T}_{\text{OFF}} as compared to the sub 10-nm CMOS based PG.

A capacitive approach is employed to find moisture of the soil at various depths (4.5–20 cm). The sensor probe having dimensions 22 × 4 × 0.5 cm3, embedded with a series of five microsensors (scala...

In many applications such as gravimetric sensing, there is a need to rapidly estimate the center resonant frequency of the sensor system. This paper proposes and compares different quantized analog compressive sensing approaches for rapid frequency estimation. In particular, we discuss (a) Atomic norm Soft Thresholding - Semidefinite Programming (AST-SDP), (b) Atomic norm Soft Thresholding - Alternating Direction Method of Multipliers (AST-ADMM) and (c) Superfast Line Spectral Estimation (LSE) algorithms. As a result of this comparison we report that Superfast LSE achieves a good trade-off between computational speed, quantization, and error in frequency estimation among the three approaches. We further compare the compressive sensing approaches to several classical methods such as the Prony’s algorithm and the Pisarenko’s algorithm and show that compressive sensing based approaches remain robust to higher quantization errors. Finally, experimental results are shown for a quartz crystal and a MEMS based gravimetric sensor. Frequency measurement results with the quartz crystal show that a resolution of 0.1 ppm RMSE is achieved with the compressed sensing approach.

This article presents Switched-Capacitor assisted Power Gating (SwCap PG) for reducing the leakage currents of large digital circuits. For the first time, PG switch is biased in the super turn-off and the super turn-on mode during the off-state and the on-state, respectively. A simple switched-capacitor network reconfigures and biases the PG switch in four different possible states with low area and power overhead. During the super turn-off, voltage stress is avoided in the PG switch when the circuit load uses supply voltage equal to the nominal $\text{V}_{\mathbf {DD}}$ in a given technology, and maximum possible leakage current reduction is achieved by the optimal biasing of the gate voltage. The proposed SwCap PG is experimentally validated in the 180nm CMOS technology. Measurement results of CMOS SwCap PG show that leakage current and $\text{R}_{\mathbf {ON}}$ reduce by 186- $226\times $ and 18% respectively, as compared to the conventional PG. An alternate solution for SwCap network using MEMS devices as the switching elements is implemented for additional benefits. Measurement results of MEMS SwCap PG show that leakage current and $\text{R}_{\mathbf {ON}}$ reduce by $172\times $ and 26% respectively, compared to the conventional PG. Finally, the applicability of the SwCap PG in the nano-scale CMOS technologies is addressed.

Most of the resistive sensors have a large baseline resistor and a relatively small incremental change in the resistor value due to the measurand. A half-bridge-based versatile $\Delta R/R_{s}$ measurement system for a wide range of resistive sensors is reported in this article. A four-phase auto-calibration-based differential and ratiometric operation is used to compensate for the baseline resistance of the sensor and the mismatches due to the non-ideal circuit parameters. A low-noise application-specific current generator and low noise, high CMRR current-mode instrumentation amplifier is designed and fabricated in UMC 180-nm technology. A prototype board of the $\Delta R/R_{s}$ measurement system is developed and tested. The experimental results show that the proposed system is able to detect even smaller ppm level of about 72 ppm of $\Delta R/R_{s}$ for the base resistor $R_{s}$ value as high as 0.5 $\text{M}\Omega $ with a relative error of less than ±1%. The effect of the parasitic capacitors on the sensor response is also tested experimentally. Finally, the proposed system is tested with an in-house fabricated displacement sensor.

In this article, we propose an autonulling-based multimode impedance-to-voltage converter (AN-Z2V) signal conditioning circuit for resistive–capacitive (R-C) sensors. The proposed technique takes advantage of the reuse of the phase tracking and autonulling modules to extract the in-phase and quadrature components of the sensors. The circuit is designed for three sensing modes: 1) Mode-C for capacitive sensors with leakage resistor; 2) Mode-R for resistive sensors with parasitic shunt capacitor; and 3) Mode-Z for impedance R-C sensor. A novel autotuning quadrature phase generator circuit is designed and implemented for the generation of reference 90° phase-shifted signal for the leaky capacitive sensors. A prototype of the proposed circuit is fabricated and tested. Measurement results show that AN-Z2V provides the measurement range with low relative error compared with the reported systems. The system is tested for a range of 10–760 pF and 56 $\text{k}\Omega $ –6.5 $\text{M}\Omega $ for mode-C and mode-R, respectively. The accuracy of the proposed circuit is found to be ±0.11% and ±0.07% for mode-C and mode-R, respectively. The capacitance and resistance of the impedance R-C sensor are simultaneously measured in mode-Z for a range of 33–528 pF and 100 $\text{k}\Omega $ –7.8 $\text{M}\Omega $ , respectively.

This paper presents the experimental, analytical and numerical dynamic analysis of SU-8 polymer MEMS mass-spring systems using two different attachment beams, dual and quad. Beam thicknesses of $4.48~\mu \text{m}$ and $8.21~\mu \text{m}$ produce two different sets of prototypes using dual-beam attachments. Those using quad-beam are only $8.21~\mu \text{m}$ thick. Using Lazer Doppler Vibrometer (LDV), dynamic characterization is performed to measure respective resonance frequencies of 1325 Hz and 1813 Hz for dual and quad-beam attachments having a thickness of $8.21~\mu \text{m}$ . Numerical and analytical dynamic analysis are performed to investigate the frequency response of systems using both attachment structures. Using measured key geometric dimensions, numerical and analytical resonance frequencies are evaluated. Theoretical and experimental values are in good agreement with maximum errors of 16% and 12% for dual and quad-beam structures, respectively. The low-cost microfabrication process can be used to incorporate a piezoresistive material/nanomaterial in locations of maximum stress on the beams producing dual and quad-beam MEMS piezoresistive sensors. Numerical analysis is performed to show that the resonance frequency is not affected which proves that the developed dynamic analysis stays valid.

This article presents a portable and programmable frequency measurement system (PrO-FMS) with 0.1-ppm RMSE resolution over a measurement time interval of 33.2 s for bulk-acoustic resonator applications. PrO-FMS has a feature of choosing a frequency estimation method and accordingly the sampling frequency, which is programmable. Five frequency estimation methods, Candan, Djukanovic, Prony, M-Pisarenko, and zero crossing interpolation methods, are reviewed for high-resolution frequency measurement. PrO-FMS can also be reconfigured to select a particular resonance mode over a range of 1–10 MHz. Measurement results are provided for two different commercial quartz crystals and a microfabricated in-plane bulk acoustic resonator in two different modes of resonance. The results of these estimation methods are compared with a standard commercial tabletop frequency counter. Measurement results show that PrO-FMS can achieve a resolution of 0.1 ppm RMSE. For the same gate time, PrO-FMS provides better resolution than standard tabletop frequency counter. This article also provides a study on the behavior of the five different frequency estimation methods for short- and long-term measurements for quartz crystals and bulk acoustic resonator in two different modes.