Flexible transistors are the next generation sensing technology, due to multiparametric analysis, reduced complexity, biocompatibility, lightweight with tunable optoelectronic properties. We summarize multitude of applications realized with OFETs.

The successful development of modern gas sensing technologies requires high sensitivity and selectivity coupled to cost effectiveness, which implies the necessity to miniaturize devices while reducing the amount of sensing material. The appealing alternative of integrating nanoparticles of a porous metal–organic framework (MOF) onto capacitive sensors based on interdigitated electrode (IDE) chips is presented. We report the deposition of MIL-96­(Al) MOF thin films via the Langmuir–Blodgett (LB) method on the IDE chips, which allowed the study of their gas/vapor sensing properties. First, sorption studies of several organic vapors like methanol, toluene, chloroform, etc. were conducted on bulk MOF. The sorption data revealed that MIL-96­(Al) presents high affinity toward water and methanol. Later on, ordered LB monolayer films of MIL-96­(Al) particles of ∼200 nm were successfully deposited onto IDE chips with homogeneous coverage of the surface in comparison to conventional thin film fabrication techniques such as drop-casting. The sensing tests showed that MOF LB films were selective for water and methanol, and short response/recovery times were achieved. Finally, chemical vapor deposition (CVD) of a porous thin film of Parylene C (thickness ∼250–300 nm) was performed on top of the MOF LB films to fabricate a thin selective layer. The sensing results showed an increase in the water selectivity and sensitivity, while those of methanol showed a huge decrease. These results prove the feasibility of the LB technique for the fabrication of ordered MOF thin films onto IDE chips using very small MOF quantities.

Organic field effect transistors (OFETs) have been the focus of sensing application research over the last two decades. In comparison to their inorganic counterparts, OFETs have multiple advantages, such as low-cost manufacturing, large area coverage, flexibility and readily tunable electronic material properties. To date, various organic semiconductors (OSCs), both polymers and small molecules, have been extensively researched for the purpose of developing the active channel layers in OFETs, enhancing their sensitivity and selectivity. However, OFET devices still need to be optimized to demonstrate reliable performance at the device level and in sensing applications. This review begins with an introduction of the OFETs with an emphasis on their geometry, materials (OSCs), fabrication process, and data analysis. After this, multiple applications are discussed and the progress regarding sensing elements and precisions is highlighted. In the end, the challenges and possible future directions of OFET arrays in embedded sensing platforms are presented.

MXenes are a promising class of two-dimensional materials with several potential applications, including energy storage, catalysis, electromagnetic interference shielding, transparent electronics, and sensors. Here, we report a novel Mo2CTx MXene sensor for the successful detection of volatile organic compounds (VOCs). The proposed sensor is a chemi-resistive device fabricated on a Si/SiO2 substrate using photolithography. The impact of various MXene process conditions on the performance of the sensor is evaluated. The VOCs toluene, benzene, ethanol, methanol, and acetone are studied at room temperature with varying concentrations. Under optimized conditions, the sensor demonstrates a detection limit of 220 ppb and a sensitivity of 0.0366 Ohm/ppm at a toluene concentration of 140 ppm. It exhibits an excellent selectivity toward toluene against the other VOCs. Ab initio simulations demonstrate selectivity toward toluene in line with the experimental results.