Field effect-based biosensors (BioFETs) stand out among other biosensing technologies due to their unique features such as real time screening, ultrasensitive detection, low cost, and amenability to extreme device miniaturization due to the convenient utilization of nanoscale materials. Nanodevices pave the way for the detection of tiny biomolecules and minute concentrations of analytes as they are ultrasensitive to surface charge modulation, allowing for better point-of-care screening of various life-threatening infectious diseases. Semiconducting carbon nanotubes (sc-CNTs) are exceptionally promising for FET-channel integration to replace bulky silicon technology beyond the dimensions of the short channel effects for their 1D ultrathin structure, superior electronic features, and biocompatibility. However, performance of CNTFET biosensors is influenced by the inhomogeneous interface between sc-CNTs and metallic source and drain electrodes. This article reviews recent studies on CNTFET biosensors, morphology of these devices and the cause-and-effect of the interface issues between sc-CNTs and metallic electrodes. Finally, future outlook on suggested technology to improve the performance of such CNTFET devices is presented.

Exhaled breath acetone has been identified as a diabetes biomarker for non-invasive diagnosis. Its detection using biosensors features many advantages over the conventional means. This paper reviews recent literature on the detection of exhaled breath acetone and acetone vapour for diabetic interest. The biosensors have been classified based on their transduction methods. Performance characteristics of the biosensors have been explored for comparison. The future trends are also highlighted.

Chemicals and pesticides contamination in the food, drinking water, and environment ecosystem have become one of the most serious problems for human public health in the world due to their large amount used and wide application in the agriculture industry. Therefore, the detection and analysis of contamination in the food and drinking water by using techniques that are simple and suitable for fast screening are important. This review gives an overview of the last trends and recent advances biosensors for chemicals and pesticides detection based on electrochemical, optical and mechanical transducers strategies. Furthermore, the biosensors are classified according to their immobilized biorecognition elements including aptamer, antibodies, enzymes, and molecularly imprinted polymers. The implementation of nanomaterials such as graphene, carbon nanotubes, and metals nanoparticles are also emphasized and discussed in this review, these nanomaterials provides remarkable features to the biosensors such highly sensitive and accurate which allowing efficient pesticides detection. In addition to highlighting and summarizing various novel sensors, this review also provided some drawbacks, challenging, prospects as well as the current efforts to enhanced optical sensors.

This paper reports on the fabrication and characterization of a Complementary Metal Oxide Semiconductor-Microelectromechanical System (CMOS-MEMS) device with embedded microheater operated at relatively elevated temperatures (40 °C to 80 °C) for the purpose of relative humidity measurement. The sensing principle is based on the change in amplitude of the device due to adsorption or desorption of humidity on the active material layer of titanium dioxide (TiO₂) nanoparticles deposited on the moving plate, which results in changes in the mass of the device. The sensor has been designed and fabricated through a standard 0.35 µm CMOS process technology and post-CMOS micromachining technique has been successfully implemented to release the MEMS structures. The sensor is operated in the dynamic mode using electrothermal actuation and the output signal measured using a piezoresistive (PZR) sensor connected in a Wheatstone bridge circuit. The output voltage of the humidity sensor increases from 0.585 mV to 30.580 mV as the humidity increases from 35% RH to 95% RH. The output voltage is found to be linear from 0.585 mV to 3.250 mV as the humidity increased from 35% RH to 60% RH, with sensitivity of 0.107 mV/% RH; and again linear from 3.250 mV to 30.580 mV as the humidity level increases from 60% RH to 95% RH, with higher sensitivity of 0.781 mV/% RH. On the other hand, the sensitivity of the humidity sensor increases linearly from 0.102 mV/% RH to 0.501 mV/% RH with increase in the temperature from 40 °C to 80 °C and a maximum hysteresis of 0.87% RH is found at a relative humidity of 80%. The sensitivity is also frequency dependent, increasing from 0.500 mV/% RH at 2 Hz to reach a maximum value of 1.634 mV/% RH at a frequency of 12 Hz, then decreasing to 1.110 mV/% RH at a frequency of 20 Hz. Finally, the CMOS-MEMS humidity sensor showed comparable response, recovery, and repeatability of measurements in three cycles as compared to a standard sensor that directly measures humidity in % RH.

Acetone vapor sensing is important for environmental monitoring and non-invasive screening of diabetes mellitus (DM). Inhaling higher than 176 parts per million (ppm) acetone concentrations affects the respiratory system, while acetone in exhaled breath correlates with blood glucose and exhaling more than 1.8 ppm indicates the person is in danger of DM. DM is currently diagnosed invasively by measuring glucose level in blood, which is painful, and therefore inconvenient. This paper reports MEMS sensor device functionalized with blend of Chitosan/Polyethylene glycol polymers for acetone vapor sensing for possible non-invasive screening of diabetes. The sensor was experimentally tested using synthetic acetone vapor, and found to give linear response for 0.05-5 ppm acetone in air, with a sensitivity of 21 mV/ppm, good repeatability, response, and reversibility. Cross-sensitivity for 2-propanol and methanol was examined, where the responses of the sensor to 1 ppm concentration in air of these two analytes were found to be 24% and 33%, respectively, less compared to its response to the same concentration of acetone.

This work describes the fabrication and characterization of a Micro-Electro-Mechanical System (MEMS) sensor for gas sensing applications. The sensor is based on standard PolyMUMPs (Polysilicon Multi-Users MEMS Process) technology to control the temperature over the sensing layer. Due to its compact size and low power consumption, micro-structures enable a well-designed gas-sensing-layer interaction, resulting in higher sensitivity compared to the ordinary materials. The aim of conducting the characterization is to compare the measured and calculated resistance values of the micro-heater and the temperature sensor. The temperature coefficient of resistance (TCR) of the temperature sensor has been estimated by raising and dropping the temperature throughout a 25–110 °C range. The sensitivity of these sensors is dependent on the TCR value. The temperature sensor resistance was observed to rise alongside the rising environmental temperatures or increasing voltages given to the micro-heater, with a correlation value of 0.99. When compared to the TCR reported in the literature for the gold material 0.0034 °C${}^{-1}$, the average TCR was determined to be 0.00325 °C${}^{-1}$ and 0.0035 °C${}^{-1}$, respectively, indicating inaccuracies of 4.6% and 2.9%, respectively. The variation between observed and reported values is assumed to be caused by the fabrication tolerances of the design dimensions or material characteristics.