Comparison of the Extended Gate Field-Effect Transistor with Direct Potentiometric Sensing for Super-Nernstian InN/InGaN Quantum Dots

Molecularly imprinted polymer-based extended-gate field-effect transistor chemosensors for selective determination of antiepileptic drug

Ultrathin molecularly imprinted polymer (MIP) films were deposited on the surfaces of ZnO nanorods (ZNRs) and nanosheets (ZNSs) by electropolymerization to afford extended-gate field-effect transistor sensors for detecting phenytoin (PHT) in plasma. Molecular imprinting efficiency was optimized by controlling the contents of functional monomers and the template in the precursor solution. PHT sensing was performed in plasma solutions with various concentrations by monitoring the drain current as a function of drain voltage under an applied gate voltage of 1.5 V. The reliability and reproducibility of the fabricated sensors were evaluated through a solution treatment process for complete PHT removal and PHT adsorption-removal cycling, while selectivity was examined by analyzing responses to chemicals with structures analogous to that of PHT. Compared with the ZNS/extracted-MIP sensor and sensors with non-imprinted polymer (NIP) films, the ZNR/extracted-MIP sensor showed superior responses to PHT-containing plasma due to selective PHT adsorption, achieving an imprinting factor of 4.23, detection limit of 12.9 ng/mL, quantitation limit of 53.0 ng/mL, and selectivity coefficients of 3-4 (against tramadol) and ~ 5 (against diphenhydramine). Therefore, we believe that the MIP-based ZNR sensing platform is promising for the practical detection of PHT and other drugs and evaluation of their proper dosages.

Nonenzymatic Potentiometric Detection of Ascorbic Acid with Porphyrin/ZnO-Functionalized Laser-Induced Graphene as an Electrode of EGFET Sensors

Laser-induced graphene (LIG) has emerged as a highly versatile material with significant potential in the development of electrochemical sensors. In this paper, we investigate the use of LIG and LIG functionalized with ZnO and porphyrins-ZnO as the gate electrodes of the extended gate field effect transistors (EGFETs). The resultant sensors exhibit remarkable sensitivity and selectivity, particularly toward ascorbic acid. The intrinsic sensitivity of LIG undergoes a notable enhancement through the incorporation of hybrid organic-inorganic materials. Among the variations tested, the LIG electrode coated with zinc tetraphenylporphyrin-capped ZnO nanoparticles demonstrates superior performance, reaching a limit of detection of approximately 3 nM. Furthermore, the signal ratio for 5 μM ascorbic acid relative to the same concentration of dopamine exceeds 250. The practical applicability of these sensors is demonstrated through the detection of ascorbic acid in real-world samples, specifically in a commercially available food supplement containing l-arginine. Notably, formulations with added vitamin C exhibit signals at least 25 times larger than those without, underscoring the sensors' capability to discern and quantify the presence of ascorbic acid in complex matrices. This research not only highlights the enhanced performance of LIG-based sensors through functionalization but also underscores their potential for practical applications in the analysis of vitamin-rich supplements.

Recent Advances in Tactile Sensory Systems: Mechanisms, Fabrication, and Applications

Flexible electronics is a cutting-edge field that has paved the way for artificial tactile systems that mimic biological functions of sensing mechanical stimuli. These systems have an immense potential to enhance human-machine interactions (HMIs). However, tactile sensing still faces formidable challenges in delivering precise and nuanced feedback, such as achieving a high sensitivity to emulate human touch, coping with environmental variability, and devising algorithms that can effectively interpret tactile data for meaningful interactions in diverse contexts. In this review, we summarize the recent advances of tactile sensory systems, such as piezoresistive, capacitive, piezoelectric, and triboelectric tactile sensors. We also review the state-of-the-art fabrication techniques for artificial tactile sensors. Next, we focus on the potential applications of HMIs, such as intelligent robotics, wearable devices, prosthetics, and medical healthcare. Finally, we conclude with the challenges and future development trends of tactile sensors.

Self-powered freestanding multifunctional microneedle-based extended gate device for personalized health monitoring

Online monitoring of prognostic biomarkers is critically important when diagnosing disorders and assessing individuals' health, especially for chronic and infectious diseases. Despite this, current diagnosis techniques are time-consuming, labor-intensive, and performed offline. In this context, developing wearable devices for continuous measurements of multiple biomarkers from body fluids has considerable advantages including availability, rapidity, convenience, and minimal invasiveness over the conventional painful and time-consuming tools. However, there is still a significant challenge in powering these devices over an extended period, especially for applications that require continuous and long-term health monitoring. Herein, a new freestanding, wearable, multifunctional microneedle-based extended gate field effect transistor biosensor is fabricated for online detection of multiple biomarkers from the interstitial fluid including sodium, calcium, potassium, and pH along with excellent electrical response, reversibility, and precision. In addition, a hybrid powering system of triboelectric nanogenerator and solar cell was developed for creating a freestanding, closed-loop platform for continuous charging of the device's battery and integrated with an Internet of Things technology to broadcast the measurements online, suggesting a stand-alone, stable multifunctional tool which paves the way for advanced practical personalized health monitoring and diagnosis.

Nano-Brush Structure for Rapid Label-Free Differentiation of Alzheimer's Disease Stages and Direct Capture of Neuron-Derived Exosomes from Human Blood Plasma

The measurement of the neurofilament light chain (NFL) in human blood plasma/serum is a promising liquid biopsy for Alzheimer's disease (AD) diagnosis, offering advantages over conventional neuroimaging techniques recommended in clinical guidelines. Here, a controllable nano-brush structure comprising upstanding silicon nanowires coated with indium tin oxide was employed as the sensing substrate. This nano-brush structure was modified with an NFL antibody (NFLAb) via silane coupling and then further connected as the extended gate in a field-effect transistor (EGFET). Notable signal differences emerged within a 2 min timeframe, enabling the label-free differentiation in human blood plasmas among four distinct cohorts: healthy controls, subjective cognitive decline, mild cognitive impairment, and dementia due to AD. Our study indicates that achieving a surface roughness exceeding 400 nm on the modified nano-brush structure enables the effective electrical sensing in our EGFETs. These distinct electrical responses measured via the NFLAb-modified nano-brush EGFETs can be attributed to the combined effects of the captured NFLs and NFL-specific neuron-derived exosomes (NDEs) found in dementia patients, as confirmed by electron spectroscopy for chemical analysis, atomic force microscopy, and scanning electron microscopy. Finally, the potential of quantitatively detecting NDEs on the NFLAb-modified nano-brush structure was demonstrated using spiked solutions containing NFL-specific NDEs from IMR-32 neuroblast cells, wherein concentration-dependent changes were observed in the EGFETs output signal. Our findings show that the NFLAb-modified nano-brush EGFET enables rapid, label-free differentiation between healthy individuals and patients at varying stages of AD.

Light-Activated Interface Charge-Alternating Interaction on an Extended Gate Photoelectrode: A New Sensing Strategy for EGFET-Based Photoelectrochemical Sensors

Integration of extended gate field-effect transistors (EGFET) and photoelectrochemical (PEC) measurement to construct highly sensitive sensors is an innovative research field that was proven feasible by our previous work. However, it remains a challenge on how to adjust the interaction between the extended gate and the analyte and study its influence on EGFET-based PEC sensors. Herein, a new sensing strategy was proposed by a mutual electrostatic interaction. Three-dimensional TiO₂ and g-C₃N₄ core-shell heterojunction on flexible carbon cloth (TCN) was designed as the extended sensing gate. Tetracycline (TC) was also used as a model analyte, and it contains electron-donating groups (-NH₂ and -OH) with negative charge. The designed TCN-extended sensing gate was negatively charged in the dark by introducing carbon vacancies with oxygen doping in the g-C₃N₄ shell, while it was positively charged under illustration due to the aggregation of photogenerated holes on the surface. Therefore, a light-activated PEC sensing platform for the sensitive and selective determination of tetracycline (TC) was demonstrated. Such a PEC sensor exhibited wide linear ranges within 100 pM to 1 μM and 1-100 μM with a low detection limit of 0.42 pM. Furthermore, the sensing platform possessed excellent selectivity, good reproducibility, and stability. The proposed sensing strategy in this work can expand the paradigm for developing a light-regulated FET-based PEC sensor by mutual electrostatic interaction, and we believe that this work will offer a new perspective for the design of interface interaction in PEC devices.

A Wearable Microneedle-Based Extended Gate Transistor for Real-Time Detection of Sodium in Interstitial Fluids

Sodium is a prominent prognostic biomarker for assessing health status, such as dysnatremia. As of now, detection and monitoring of sodium levels in the human body is carried out by means of laborious and bulky laboratory equipmentand/or by offline analysis of various body fluids. Herein, an innovative stretchable, skin-conformal and fast-response microneedle extended-gate FET biosensor is reported for real-time detection of sodium in interstitial fluids for minimally invasive health monitoring along with high sensitivity, low limit of detection, excellent biocompatibility, and on-body mechanical stability. The integration of the reported device with a wireless-data transmitter and the Internet-of-Things cloud for real-time monitoring and long-term analysis is reported and discussed. This platform would eventually help bringing unlimited possibilities for effecient medical care and accurate clinical decision-making.

InN/InGaN Quantum Dot Abiotic One-Compartment Glucose Photofuel Cell: Power Supply and Sensing

InN/InGaN quantum dots (QDs) are introduced as an efficient photoanode for a novel abiotic one-compartment photofuel cell (PFC) with a Pt cathode and glucose as a biofuel. Due to the high catalytic activity and selectivity of the InN/InGaN QDs toward oxidation reactions, the PFC operates without a membrane under physiologically mild conditions at medium to low glucose concentrations with a noble-metal-free photoanode. A relatively high short-circuit photocurrent density of 0.56 mA/cm² and a peak output power density of 0.22 mW/cm² are achieved under 1 sun illumination for a 0.1 M glucose concentration with optimized InN/InGaN QDs of the right size. The super-linear dependence of the short-circuit photocurrent density and the output power density as a function of the logarithmic glucose concentration makes the PFC well suited for sensing, covering the 4-6 mM range of glucose concentration in blood under normal conditions with good selectivity. No degradation of the PFC operation over time is observed.

Fabrication of a Mesoporous Multimetallic Oxide-based Ion-Sensitive Field Effect Transistor for pH Sensing

Sensitive and reliable noninvasive sensors are in demand to cope with an increasing need for robust working conditions and fast results. One of the leading potential technologies is field-effect transistor (FET)-based sensors to improve response time, sensitivity, and stability. Here, a sol-gel method fabricates an ion-sensitive field-effect transistor with a high current and output sensitivity for electrochemical sensing, solving binary device design, component regulating, and long-term stability, while maintaining the promoted sensitivity. Metal oxide-based devices with single and binary contents are fabricated and characterized for monitoring pH changes, with performance fitted to a Nernst-Poisson model. After detecting the performance, the result was compared with devices in different components and ratios to obtain excellent performance and high stability. In addition, these extended gate FETs with multimetallic oxide promise efficiency and stability optimization in terms of a flexible component design, demonstrating the feasibility of the novel sol-gel fabrication method to achieve efficient and reliable FET sensors.

A NOVEL pH SENSITIVITY OF SnO2 THIN FILM BASED EGFET PREPARED USING CHEMICAL BATH METHOD

Nanocrystalline (NC) tin dioxide (SnO2) thin film has been prepared using chemical bath method at low working temperature onto SiO2/Si substrates. The structural and morphological properties were studied through X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The as-deposited thin film appeared with tetragonal rutile structure. The crystallization of SnO2 film was achieved when the film was exposed to anneal at [Formula: see text]C. NC SnO2 thin film was successfully utilized as an extended gate field-effect transistor (EGFET) pH sensing. NC SnO2 film based pH-EGFET sensor displayed a notable pH sensing performance, where the sensitivity and the linearity values are equal to 25.7 (mV/pH) and 0.8489 within 2–12 range consecutive. The NC SnO2 thin film sensor has shown good pH sensor stability and reliability; thus it can be considered the best choice for flexible and disposable biosensors.