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.

Wearable technologies have established novel strategies for continuous electrocardiogram (ECG) monitoring, exploiting recent developments in sensors and integrated circuit technology. Advances in dry electrodes fabrication improved the growth of wearable devices. Herein, we present an on-chip integrated ECG signal acquisition system along with dry electrodes for wearable and long-term monitoring. Custom electrodes are fabricated using multi-walled carbon nanotube (MWCNT) and Polydimethylsiloxane (PDMS) composite on a flexible substrate. A1.5 μW fully-differential operational transconductance amplifier (OTA) with a capacitive-resistive feedback network is designed in 130 nm CMOS process achieving a mid-band gain of 43.09 dB and an input-referred noise of 2.81 μVrms in the range from 0.175 Hz to 1.636 kHz. Reconfigurability of the lower cut-off frequency is achieved by controlling the bias voltage of the triple-well nMOS transistors acting as the feedback pseudoresistor. Electrodes with different surface area and MWCNT concentrations were investigated in a real-time ECG measurement scenario. The recorded signals achieve a high signal-to-noise ratio which spans from 35.7 dB to 38.6 dB with the increasing MWCNT concentration. Experimental results demonstrate that the proposed system allows for high performance and low-power ECG signal recording for the long-term and wearable applications.

Extended-gate field-effect transistor (EGFET) is an electronic interface originally developed as a substitute for an ion-sensitive field-effect transistor (ISFET). Although the literature shows that commercial off-the-shelf components are widely used for biosensor fabrication, studies on electronic interfaces are still scarce (e.g., noise processes, scaling). Therefore, the incorporation of a custom EGFET can lead to biosensors with optimized performance. In this paper, the design and characterization of a transistor association (TA)-based EGFET was investigated. Prototypes were manufactured using a 130 nm standard complementary metal-oxide semiconductor (CMOS) process and compared with devices presented in recent literature. A DC equivalence with the counterpart involving a single equivalent transistor was observed. Experimental results showed a power consumption of 24.99 mW at 1.2 V supply voltage with a minimum die area of 0.685 × 1.2 mm². The higher aspect ratio devices required a proportionally increased die area and power consumption. Conversely, the input-referred noise showed an opposite trend with a minimum of 176.4 nV_rms over the 0.1 to 10 Hz frequency band for a higher aspect ratio. EGFET as a pH sensor presented further validation of the design with an average voltage sensitivity of 50.3 mV/pH, a maximum current sensitivity of 15.71 mA^1/2/pH, a linearity higher than 99.9%, and the possibility of operating at a lower noise level with a compact design and a low complexity.

Since 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, environmental monitoring as well as military applications (e.g., Hoffmann–La Roche, Abbott Point of Care, Orion High technologies, etc.), whereas increasing concerns on the food safety and health issues have resulted in the introduction of novel legislative standards for these sensors. Numerous devices have been developed for monitoring of biological–processes such as nucleic–acid hybridization, protein–protein interaction, antigen–antibody bonds and substrate–enzyme reactions, just to name a few. Since 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 biosensor which is 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 based extended–gate–field–effect–transistor within the field of bioanalytical applications, which will highlight the most recent research works reported in the literature. Moreover, a comparison among the diverse EGFET devices will be presented giving particular attention to the materials and technologies.

This paper presents a power-efficient complementary metal-oxide-semiconductor (CMOS) neural signal-recording read-out circuit for multichannel neuromodulation implants. The system includes a neural amplifier and a successive approximation register analog-to-digital converter (SAR-ADC) for recording and digitizing neural signal data to transmit to a remote receiver. The synthetic neural signal is generated using a LabVIEW myDAQ device and processed through a LabVIEW GUI. The read-out circuit is designed and fabricated in the standard 0.5 μ$\mathsf{\mu }$m CMOS process. The proposed amplifier uses a fully differential two-stage topology with a reconfigurable capacitive-resistive feedback network. The amplifier achieves 49.26 dB and 60.53 dB gain within the frequency bandwidth of 0.57–301 Hz and 0.27–12.9 kHz to record the local field potentials (LFPs) and the action potentials (APs), respectively. The amplifier maintains a noise–power tradeoff by reducing the noise efficiency factor (NEF) to 2.53. The capacitors are manually laid out using the common-centroid placement technique, which increases the linearity of the ADC. The SAR-ADC achieves a signal-to-noise ratio (SNR) of 45.8 dB, with a resolution of 8 bits. The ADC exhibits an effective number of bits of 7.32 at a low sampling rate of 10 ksamples/s. The total power consumption of the chip is 26.02 μ$\mathsf{\mu }$W, which makes it highly suitable for a multi-channel neural signal recording system.

This paper presents a motion-sensing device with the capability of harvesting energy from low-frequency motion activities. Based on the high surface area reverse electrowetting-on-dielectric (REWOD) energy harvesting technique, mechanical modulation of the liquid generates an AC signal, which is modeled analytically and implemented in Matlab and COMSOL. A constant DC voltage is produced by using a rectifier and a DC–DC converter to power up the motion-sensing read-out circuit. A charge amplifier converts the generated charge into a proportional output voltage, which is transmitted wirelessly to a remote receiver. The harvested DC voltage after the rectifier and DC–DC converter is found to be 3.3 V, having a measured power conversion efficiency (PCE) of the rectifier as high as 40.26% at 5 Hz frequency. The energy harvester demonstrates a linear relationship between the frequency of motion and the generated output power, making it highly suitable as a self-powered wearable motion sensor.