Field-effect transistor (FET) biosensors have been intensively researched toward label-free biomolecule sensing for different disease screening applications. High sensitivity, incredible miniaturization capability, promising extremely low minimum limit of detection (LoD) at the molecular level, integration with complementary metal oxide semiconductor (CMOS) technology and last but not least label-free operation were amongst the predominant motives for highlighting these sensors in the biosensor community. Although there are various diseases targeted by FET sensors for detection, infectious diseases are still the most demanding sector that needs higher precision in detection and integration for the realization of the diagnosis at the point of care (PoC). The COVID-19 pandemic, nevertheless, was an example of the escalated situation in terms of worldwide desperate need for fast, specific and reliable home test PoC devices for the timely screening of huge numbers of people to restrict the disease from further spread. This need spawned a wave of innovative approaches for early detection of COVID-19 antibodies in human swab or blood amongst which the FET biosensing gained much more attention due to their extraordinary LoD down to femtomolar (fM) with the comparatively faster response time. As the FET sensors are promising novel PoC devices with application in early diagnosis of various diseases and especially infectious diseases, in this research, we have reviewed the recent progress on developing FET sensors for infectious diseases diagnosis accompanied with a thorough discussion on the structure of Chem/BioFET sensors and the readout circuitry for output signal processing. This approach would help engineers and biologists to gain enough knowledge to initiate their design for accelerated innovations in response to the need for more efficient management of infectious diseases like COVID-19.

Field-effect transistors (FETs) have gained significant interest and hold great potential as groundbreaking sensing technology in the fields of biosensing and life science research

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.

This paper presents a new field-effect sensor called open-gate junction gate field-effect transistor (OG-JFET) for biosensing applications. The OG-JFET consists of a p-type channel on top of an n-type layer in which the p-type serves as the sensing conductive layer between two ohmic contacted sources and drain electrodes. The structure is novel as it is based on a junction field-effect transistor with a subtle difference in that the top gate (n-type contact) has been removed to open the space for introducing the biomaterial and solution. The channel can be controlled through a back gate, enabling the sensor’s operation without a bulky electrode inside the solution. In this research, in order to demonstrate the sensor’s functionality for chemical and biosensing, we tested OG-JFET with varying pH solutions, cell adhesion (human oral neutrophils), human exhalation, and DNA molecules. Moreover, the sensor was simulated with COMSOL Multiphysics to gain insight into the sensor operation and its ion-sensitive capability. The complete simulation procedures and the physics of pH modeling is presented here, being numerically solved in COMSOL Multiphysics software. The outcome of the current study puts forward OG-JFET as a new platform for biosensing applications.

This paper presents a novel hybrid microfluidic electronic sensing platform, featuring an electronic sensor incorporated with a microfluidic structure for life science applications. This sensor with a large sensing area of 0.7 mm² is implemented through a foundry process called Open-Gate Junction FET (OG-JFET). The proposed OG-JFET sensor with a back gate enables the charge by directly introducing the biological and chemical samples on the top of the device. This paper puts forward the design and implementation of a PDMS microfluidic structure integrated with an OG-JFET chip to direct the samples toward the sensing site. At the same time, the sensor’s gain is controlled with a back gate electrical voltage. Herein, we demonstrate and discuss the functionality and applicability of the proposed sensing platform using a chemical solution with different pH values. Additionally, we introduce a mathematical model to describe the charge sensitivity of the OG-JFET sensor. Based on the results, the maximum value of transconductance gain of the sensor is ~1 mA/V at Vgs = 0, which is decreased to ~0.42 mA/V at Vgs = 1, all in Vds = 5. Furthermore, the variation of the back-gate voltage from 1.0 V to 0.0 V increases the sensitivity from ~40 mV/pH to ~55 mV/pH. As per the experimental and simulation results and discussions in this paper, the proposed hybrid microfluidic OG-JFET sensor is a reliable and high-precision measurement platform for various life science and industrial applications.

This article presents a novel open gate junction field-effect transistor (OG-JFET)-based sensor that can be used for various life science applications including deoxyribonucleic acid (DNA) storage monitoring. We put forward the design, modeling, implementation, and characterization of OG-JFET sensor using a foundry process through CMC Microsystems. We also demonstrate and discuss the functionality and applicability of the proposed sensor for monitoring DNA samples suitable for DNA storage applications. Synthetic storage has emerged as an intriguing data storage solution with high density and long-term preservation potential. Most common modalities include the conversion of digital data into synthesized nucleotides, the physical storage of DNA materials, and reading out the data via sequencing and other computational processes. Among these, this article tackles the challenge of physical storage monitoring of DNA materials by developing a sensor for measurement of DNA samples in dry conditions. The proposed sensor reveals a linear response of sensor toward DNA concentration in ultra-pure water. Across a 0.7 mm ² sensing area, a DNA mass concentration from approximately 100–400 ng/ $\mu \text{L}$ has been detected using OG-JFET demonstrating a sensitivity of 30 $\mu \text{A}$ /(ng/ $\mu \text{L}$ ). These performance quantities imply a promising role for OG-JFETs in emerging biotechnology applications including DNA storage monitoring.