Explore the vast range of titles available.

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.

The demand for miniaturized point‐of‐care chemical/biochemical sensors has driven the development of field‐effect transistors (FETs) based pH sensors over the last 50 years. This paper aims to review the fabrication technologies, device structures, sensing film materials, and modeling techniques utilized for FET‐based pH sensors. We present the governing principles of potentiometric sensors, with major focus on the working principles of ion‐sensitive FETs (ISFETs). We extensively review different sensing film materials deposited by various techniques, which is critical to the sensing performance of ISFETs. The popular fabrication technologies have been presented, with special emphasis on state‐of‐the‐art silicon‐on‐insulator based technology, which can achieve high sensitivity by utilizing the dual‐gate effect. Furthermore, recent advancements in nano‐ISFETs has been elucidated. We also discuss the adoption of unmodified complementary metal‐oxide semiconductor (CMOS) ISFETs using standard CMOS processes, which has enabled the fabrication of integrated ISFET arrays, which are especially suited for ion‐imaging applications. Moreover, recent developments in extended‐gate FETs has been discussed, which have gained lot of attention due to their design flexibility and ease of fabrication, which is desirable for wearable sensing applications. In addition, recently there have been efforts to utilize nonsilicon channel materials for pH‐sensing application to obtain superior performance and various channel materials have been reviewed. Finally, we have extensively reviewed the ISFET device modeling and simulation techniques using various computer‐aided design tools, which aid in sensor design and characterization.

The seminal importance of DNA sequencing to the life sciences, biotechnology and medicine has driven the search for more scalable and lower-cost solutions. Here we describe a DNA sequencing technology in which scalable, low-cost semiconductor manufacturing techniques are used to make an integrated circuit able to directly perform non-optical DNA sequencing of genomes. Sequence data are obtained by directly sensing the ions produced by template-directed DNA polymerase synthesis using all-natural nucleotides on this massively parallel semiconductor-sensing device or ion chip. The ion chip contains ion-sensitive, field-effect transistor-based sensors in perfect register with 1.2 million wells, which provide confinement and allow parallel, simultaneous detection of independent sequencing reactions. Use of the most widely used technology for constructing integrated circuits, the complementary metal-oxide semiconductor (CMOS) process, allows for low-cost, large-scale production and scaling of the device to higher densities and larger array sizes. We show the performance of the system by sequencing three bacterial genomes, its robustness and scalability by producing ion chips with up to 10 times as many sensors and sequencing a human genome. 'Post-light' genome sequencing chips Progress towards cheaper and more compact DNA sequencing devices is limited by a number of factors, including the need for imaging technology. A new DNA sequencing technology that does away with optical readout, instead gathering sequence data by directly sensing hydrogen ions produced by template-directed DNA synthesis, offers a route to low cost and scalable sequencing on a massively parallel semiconductor-sensing device or ion chip. The reactions are performed using all natural nucleotides, and the individual ion-sensitive chips are disposable and inexpensive. The system has been used to sequence three bacterial genomes and a human genome: that of Gordon Moore of Moore's law fame.

Ion‐sensitive field effect transistor (ISFET) sensor is a hot topic these years, playing the combined roles of signal recognizer and converter for (bio)chemical analytes. In this review article, the basic concept, origination, and history of the ISFET sensor are presented. In addition, the common fabrication processes, the most‐used working principle (potentiometric, amperometric, and impedancemetric), and the techniques of gate functionality (physical, chemical, and biological) are discussed introducing the afterward signal transfer processes from ISFET to the terminals through different types of circuits. At last, the development and recent progress (until 2021) of ions and biomolecules (DNA molecules, antibodies, enzymatic substrates, and cell‐related secretions or metabolism) were introduced together with the outlook and facing obstacles (Debye screening, the wearability of ISFET, the multiplexed detections) before the commercialization of ISFET. This review article emphasizes the advantages of the developed ISFET sensors as miniaturization, low‐cost, all‐solid, highly sensitive, and easy operation for portable and multiplexed detections. ISFET sensing system for biochemical detection of different analytes and applications of miniaturization and wearability

As promising biochemical sensors, ion-sensitive field-effect transistors (ISFETs) are used widely in the growing field of biochemical sensing applications. Recently, a new type of field-effect transistor gated by ionic electrolytes has attracted intense attention due to the extremely strong electric-double-layer (EDL) gating effect. In such devices, the carrier density of the semiconductor channel can be effectively modulated by an ion-induced EDL capacitance at the semiconductor/electrolyte interface. With advantages of large specific capacitance, low operating voltage and sensitive interfacial properties, various EDL-based transistor (EDLT) devices have been developed for ultrasensitive portable sensing applications. In this article, we will review the recent progress of EDLT-based biochemical sensors. Starting with a brief introduction of the concepts of EDL capacitance and EDLT, we describe the material compositions and the working principle of EDLT devices. Moreover, the biochemical sensing performances of several important EDLTs are discussed in detail, including organic-based EDLTs, oxide-based EDLTs, nanomaterial-based EDLTs and neuromorphic EDLTs. Finally, the main challenges and development prospects of EDLT-based biochemical sensors are listed.

Methodology of electrical characterization of ISFETs has been described. It is based on a three-stage approach. First, electrical measurements of ISFET-like MOSFETs and extraction of basic parameters of the MOSFET compact model are performed. Next, mapping of the ISFET channel conductances and a number of other characteristic parameters is carried out using a semi-automatic testing setup. Finally, ISFET sensitivity to solution pH is evaluated. The methodology is applied to characterize ISFETs fabricated in the Institute of Electron Technology (IET).

The ISFET sensing membrane is in direct contact with the electrolyte solution, determining the starting sensitivity of these devices. A SiO2 gate dielectric shows a low response sensitivity and poor stability. This paper proposes a comprehensive identification of different high-k materials which can be used for this purpose, rather than SiO2. The Gouy-Chapman and Gouy-Chapman-Stern models were combined with the Site-binding model, based on surface potential sensitivity, to achieve the work objectives. Five materials, namely Al2O3, Ta2O5, Hfo2, Zro2 and SN2O3, which are commonly considered for micro-electronic applications, were compared. This study has identified that Ta2O5 have a high surface potential response at around 59mV/pH, and also exhibits high stability in different electrolyte concentrations. The models used have been validated with real experimental data, which achieved excellent agreement. The insights gained from this study may be of assistance to determine the suitability of different materials before progressing to expensive real ISFET fabrication.

An ion-sensitive field-effect transistor (ISFET) is widely used in environmental and biomedical applications due to its rapid response, miniaturization, and cost-effectiveness. In this study, a numerical model of an Al₂O₃-gated ISFET was developed to detect pH levels. The effects of gate dielectric thickness, doping concentration, and temperature on ISFET’s performance were evaluated using I DS –V DS characteristics. An eXtreme Gradient Boosting (XGBoost) regression model was employed to predict pH levels using data obtained from I DS –V DS characteristics. Further, Hyperparameter optimization was performed to tune critical XGBoost-hyperparameters such as maximum depth, minimum child weight, estimators, learning rate, α, and λ. The optimization strategies such as random search, grid search and Bayesian optimization were utilized to improve the efficacy of regressor by minimizing errors and maximizing accuracy in prediction. A stacking ensemble learning approach was also implemented to integrate multiple models, enhancing prediction accuracy and thereby capturing additional information. The XGBoost regressor achieved superior results with R 2  = 0.9846, MSE = 0.2342, and MAE = 0.2317, compared to other regressor models. Therefore, the use of XGBoost regressors with hyperparameter optimization and stacking ensemble learning approach is found to be highly effective for pH prediction from ISFET under various operating conditions.

This paper proposes a numerical simulation approach to study the electrolyte pH change of ion-sensitive field effect transistor (ISFET) structures using Silvaco technology computer-aided design (TCAD) tools. This paper examines the ISFET device's electrical response to electrolyte pH change. The modeling method is exploited by changing the potential surface charge depending on the electrolyte pH change and investigating how will it cause threshold voltage shift of ISFET device and other transfer characteristic parameters. The properties of a user-defined material offered by Silvaco are exploited to simulate the electrolyte behavior. The parameters of silicon semiconductor material (i.e., energy bandgap, permittivity, affinity, and density of states) are set to reconstruct an electrolyte solution. The electrostatic solution of the electrolyte area is investigated by giving a numerical solution for the semiconductor equation inside this area. Results show excellent agreement between theoretical model and self-consistency TCAD model. Additionally, transfer characteristics of a conventional ISFET device are simulated. The ID current as a function of the reference voltage VRef. and drain voltage VD for different pH scale and ID current as a function of VDS for different VRef. values for specific pH value are simulated. The proposed model allows accurate and efficient ISFET modeling by trying different designs and further optimization with commercial Silvaco TCAD tools rather than expensive fabrication.

Ion-sensitive field-effect transistors (ISFETs) are used as elementary devices to build many types of chemical sensors and biosensors. Organic thin-film transistor (OTFT) ISFETs use either small molecules or polymers as semiconductors together with an additive manufacturing process of much lower cost than standard silicon sensors and have the additional advantage of being environmentally friendly. OTFT ISFETs’ drawbacks include limited sensitivity and higher variability. In this paper, we propose a novel design technique for integrating extended-gate OTFT ISFETs (OTFT EG-ISFETs) together with dual-gate OTFT multiplexers (MUXs) made in the same process. The achieved results show that our OTFT ISFET sensors are of the state of the art of the literature. Our microsystem architecture enables switching between the different ISFETs implemented in the chip. In the case of sensors with the same gain, we have a fault-tolerant architecture since we are able to replace the faulty sensor with a fault-free one on the chip. For a chip including sensors with different gains, an external processor can select the sensor with the required sensitivity.