A Glucose Biosensor Using CMOS Potentiostat and Vertically Aligned Carbon Nanofibers

A Multimodality Electrochemical and Impedance Spectroscopy System-on-a-Chip With Temperature Sensing and Impedance-Boosting Techniques

This article presents a multimodal electrochemical sensing system-on-chip (SoC), including the functions of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and temperature sensing. CV readout circuitry achieves an adaptive readout current range of 145.5 dB through an automatic range adjustment and resolution scaling technique. EIS has an impedance resolution of 9.2 m Ω/√ Hz at a sweep frequency of 10 kHz and an output current of up to 120 μA. With an impedance boost mechanism, the maximum detectable load impedance is extended to 22.95 k Ω, while the total harmonic distortion is less than 1%. A resistor-based temperature sensor using a swing-boosted relaxation oscillator can achieve a resolution of 31 mK in 0-85 °C. The design is implemented in a 0.18 μm CMOS process. The total power consumption is 1 mW.

A Power-Harvesting CGM Chiplet Featuring Silicon-Based Enzymatic Glucose Sensor

Diabetes has become a leading cause of death and disability in the past decades. Continuous glucose monitoring (CGM) is a prevailing technique to determine the glucose level and provide in-time treatment. However, conventional CGM systems combine an electrochemical sensor with a CMOS chip, suffering from bulky size and interface issues. Integrating the CGM sensor on silicon is potential to miniaturize the CGM system and reduce the cost, while the recent silicon-based sensors show limited detection range and sensitivity. In this work, we present a silicon-based CGM chip let with wireless power transfer (WPT) and real-time wireless telemetry. Fabricated on a single silicon substrate, the chiplet consists of a silicon-based CGM sensor, a power-harvesting wireless-telemetry chip, and a silicon-based antenna. Measured results show that the chip let achieves a sensitivity of 4 μA.mM.cm-2 and a linear detection range of 0-10 mM. Based on WPT and backscattering communication, the chip let consumes 18.8 μ W power in glucose telemetry.

Wireless Multimodality Sensing System-on-a-Chip With Time-Based Resolution Scaling Technique and Analog Waveform Generator in 0.18 μm CMOS for Chronic Wound Care

Multimodal sensing can provide a comprehensive and accurate diagnosis of biological information. This paper presents a fully integrated wireless multimodal sensing chip with voltammetric electrochemical sensing at a scanning rate range of 0.08-400 V/s, temperature monitoring, and bi-phasic electrical stimulation for wound healing progress monitoring. The time-based readout circuitry can achieve a 1-20X scalable resolution through dynamic threshold voltage adjustment. A low-noise analog waveform generator is designed using current reducer techniques to eliminate the large passive components. The chip is fabricated via a 0.18 μm CMOS process. The design achieves R² linearity of 0.995 over a wide current detection range (2 pA-12 μA) while consuming 49 μW at 1.2 V supply. The temperature sensing circuit achieves a 43 mK resolution from 20 to 80 degrees. The current stimulator provides an output current ranging from 8 μA to 1 mA in an impedance range of up to 3 kΩ. A wakeup receiver with data correlators is used to control the operation modes. The sensing data are wirelessly transmitted to the external readers. The proposed sensing IC is verified for measuring critical biomarkers, including C-reactive protein, uric acid, and temperature.

Towards Development of a Non-Intrusive and Label-Free THz Sensor for Rapid Detection of Aqueous Bio-Samples Using Microfluidic Approach

As most of the bio-molecules sizes are comparable to the terahertz (THz) wavelength, this frequency range has spurred great attention for bio-medical and bio-sensing applications. Utilizing such capabilities of THz electromagnetic wave, this paper presents the design and analysis of a new non-intrusive and label-free THz bio-sensor for aqueous bio-samples using the microfluidic approach with real-time monitoring. The proposed THz sensor unit utilizes the highly confined feature of the localized spoof surface plasmon (LSSP) resonator to get high sensitivity for any minute change in the dielectric value near it's surface. The proposed sensor, which is designed at 1 THz, exploits the reflection behavior (S₁₁) of the LSSP resonator as the sensing response. The proposed sensor has been designed with a high-quality factor of 192 to obtain a high sensitivity of 13.5 MHz/mgml^-1. To validate the proposed concept, a similar sensor unit has been designed and implemented at microwave frequency owing to the geometry dependent characteristics of the LSSP. The developed sensor has got a highly sensitive response at microwave frequency with a sensitivity of 1.2771e-4 MHz/mgml^-1. A customized read-out circuitry is also designed and developed to get the sensor response in terms of DC-voltage and to provide a proof of concept for the low-cost point of care (PoC) detection solution using the proposed sensor. It is anticipated that the proposed design of highly sensitive sensor will pave a path to develop lab-on-chip systems for bio-sensing applications.

A Compact Low-Power Current-to-Digital Readout Circuit for Amperometric Electrochemical Sensors

This paper introduces a novel compact low-power amperometric instrumentation design with current-to-digital output for electrochemical sensors. By incorporating the double layer capacitance of an electrochemical sensor's impedance model, our new design can maintain performance while dramatically reducing circuit complexity and size. Electrochemical experiments with potassium ferricyanide, show that the circuit output is in good agreement with results obtained using commercial amperometric instrumentation. A high level of linearity (R² = 0.991) between the circuit output and the concentration of potassium ferricyanide was also demonstrated. Furthermore, we show that a CMOS implementation of the presented architecture could save 25.3% of area, and 47.6% of power compared to a traditional amperometric instrumentation structure. Thus, this new circuit structure is ideally suited for portable/wireless electrochemical sensing applications.

A Microwatt Dual-Mode Electrochemical Sensing Current Readout With Current-Reducer Ramp Waveform Generation

An electrochemical sensing chip with an integrated current-reducer pattern generator and a current-mirror based low-noise chopper-stabilization potentiostat circuit is presented. The pattern generator, utilizing the current reducer technique and pseudo resistors, creates a sub-Hz ramp signal for the cyclic voltammetric (CV) measurement without large-size passive components. The proposed design adopts the chopper-stabilization and low-noise biasing technique for the potentiostat and a counter-based time-to-digital converter to reduce the amplitude noise effects and to convert the sensing current signal to digital codes for further data processing. The design is fabricated using a 0.18-μm CMOS process and achieves a 41 pA current resolution in the current range of ±5 μA while maintaining the R² linearity of 0.998. The system consumes 16 μW from a 1.2 V supply when a 5 μA sensing current is detected. The power efficiency of the readout interface is 0.31, and the sensing current dynamic range is 108 dB. The design is fully integrated into a single chip and is successfully tested in the dual-mode (CA/CV) measurements with commercial gold electrodes in a potassium ferricyanide solution in sub-millimolar concentrations.

Golf ball-like MoS2 nanosheet arrays anchored onto carbon nanofibers for electrochemical detection of dopamine

Arrays of molybdenum(IV) disulfide nanosheets resembling the shape of golf balls (MoS₂ NSBs) were deposited on carbon nanofibers (CNFs), which are shown to enable superior electrochemical detection of dopamine without any interference by uric acid. The MoS₂ NSBs have a diameter of ∼ 2 μm and are made up of numerous bent nanosheets. MoS₂ NSBs are connected by the CNFs through the center of the balls. Figures of merit for the resulting electrode include (a) a sensitivity of 6.24 μA·μM^-1·cm^-2, (b) a low working voltage (+0.17 V vs. Ag/AgCl), and (c) a low limit of detection (36 nM at S/N = 3). The electrode is selective over uric acid, reproducible and stable. It was applied to the determination of dopamine in spiked urine samples. The recoveries at levels of 10, 20 and 40 μM of DA are 101.6, 99.8 and 107.8%. Graphical abstract Schematic presentation of the golf ball-like MoS₂ nanosheet balls/carbon nanofibers (MoS₂ NSB/CNFs) by electrospining and hydrothermal process to detect dopamine (DA).

CMOS Interfaces for Internet-of-Wearables Electrochemical Sensors: Trends and Challenges

Smart wearables, among immediate future IoT devices, are creating a huge and fast growing market that will encompass all of the next decade by merging the user with the Cloud in a easy and natural way. Biological fluids, such as sweat, tears, saliva and urine offer the possibility to access molecular-level dynamics of the body in a non-invasive way and in real time, disclosing a wide range of applications: from sports tracking to military enhancement, from healthcare to safety at work, from body hacking to augmented social interactions. The term Internet of Wearables (IoW) is coined here to describe IoT devices composed by flexible smart transducers conformed around the human body and able to communicate wirelessly. In addition the biochemical transducer, an IoW-ready sensor must include a paired electronic interface, which should implement specific stimulation/acquisition cycles while being extremely compact and drain power in the microwatts range. Development of an effective readout interface is a key element for the success of an IoW device and application. This review focuses on the latest efforts in the field of Complementary Metal–Oxide–Semiconductor (CMOS) interfaces for electrochemical sensors, and analyses them under the light of the challenges of the IoW: cost, portability, integrability and connectivity.

EGFET-Based Sensors for Bioanalytical Applications: A Review

Since the 1970s, a great deal of attention has been paid to the development of semiconductor-based biosensors because of the numerous advantages they offer, including high sensitivity, faster response time, miniaturization, and low-cost manufacturing for quick biospecific analysis with reusable features. Commercial biosensors have become highly desirable in the fields of medicine, food, and environmental monitoring as well as military applications, whereas increasing concerns about food safety and health issues have resulted in the introduction of novel legislative standards for these sensors. Numerous devices have been developed for monitoring biological processes such as nucleic acid hybridization, protein–protein interaction, antigen–antibody bonds, and substrate–enzyme reactions, just to name a few. Since the 1980s, scientific interest moved to the development of semiconductor-based devices, which also include integrated front-end electronics, such as the extended-gate field-effect transistor (EGFET) biosensor, one of the first miniaturized chemical sensors. This work is intended to be a review of the state of the art focused on the development of biosensors and chemosensors based on extended-gate field-effect transistor within the field of bioanalytical applications, which will highlight the most recent research reported in the literature. Moreover, a comparison among the diverse EGFET devices will be presented, giving particular attention to the materials and technologies.

Heterogeneous Integration of CMOS Sensors and Fluidic Networks Using Wafer-Level Molding

Direct sensing in liquids using CMOS-integrated optical and electrical sensors is attractive for lab-on-chip applications, where close physical proximity between sample and sensor can obviate optical lenses, enhance electrical sensitivity, and decrease noise due to parasitics. However, controlled delivery of fluid samples to the chip surface presents an ongoing challenge for lab-on-CMOS development, where traditional wire-bond packaging prevents integration of planar microfluidics. In this paper, we present a method for scalable heterogeneous integration of microfluidic channels and silicon-integrated circuit substrates using a commercial fan-out wafer-level packaging approach. The planar surface supports multiple approaches for fluidic integration; we present both a stacked laser-cut fluidic assembly and the fabrication of monolithic SU-8 microchannels over the IC surface. As a proof-of-principle, both electrical and fluidic routing are provided to a custom 0.18-m CMOS optical sensor IC, and optical transmission and fluorescence measurement experiments are demonstrated.

A Differential Electrochemical Readout ASIC With Heterogeneous Integration of Bio-Nano Sensors for Amperometric Sensing

A monolithic biosensing platform is presented for miniaturized amperometric electrochemical sensing in CMOS. The system consists of a fully integrated current readout circuit for differential current measurement as well as on-die sensors developed by growing platinum nanostructures (Pt-nanoS) on top of electrodes implemented with the top metal layer. The circuit is based on the switch-capacitor technique and includes pseudodifferential integrators for concurrent sampling of the differential sensor currents. The circuit further includes a differential to single converter and a programmable gain amplifier prior to an ADC. The system is fabricated in [Formula: see text] technology and measures current within [Formula: see text] with minimum input-referred noise of [Formula: see text] and consumes [Formula: see text] from a [Formula: see text] supply. Differential sensing for nanostructured sensors is proposed to build highly sensitive and offset-free sensors for metabolite detection. This is successfully tested for bio-nano-sensors for the measurement of glucose in submilli molar concentrations with the proposed readout IC. The on-die electrodes are nanostructured and cyclic voltammetry run successfully through the readout IC to demonstrate detection of [Formula: see text].