Response Time Of Sensor Research Articles

Gas Permeable Protection Caps for Wafer Level Chip Scale Packaging (WLCSP) of MEMS Environmental Sensors

This work presents new porous environmental protection caps designed for wafer level chip scale packaging (WLCSP) of MEMS environmental sensors. The caps consist of gaspermeable microstructures formed from loose aluminum oxide powder solidified by a ceramic thin film, grown using atomic layer deposition (ALD). For the first time, the full process flow of the proposed approach is demonstrated by manufacture of the cap wafer followed by substrate bonding using glass-frit technology. By analyzing the influence of the caps on the response time of MEMS humidity sensors, this study proves the viability of the proposed packaging technology. In addition, the ability to further functionalize the porous caps is demonstrated by the deposition of a superhydrophobic polymer thin film by chemical vapor deposition.

Design of ammonia sensor based on ZnO for analyzing hazards at critical infrastructure

A gas sensor based on ZnO has been designed, which demonstrates sensitivity to NH3 under standard conditions (temperature, 25 °С; pressure, 101.3 kPa). The experimental sample was manufactured by magnetron sputtering at direct current. A VUP-5M vacuum unit with an original material-saving magnetron was used to produce ZnO films. To analyze the efficiency of the gas sensor to ammonia (NH3) under standard conditions, its operating characteristics were studied. The concentration of NH3 for investigating operating characteristics was chosen at the level of 25 ppm. To determine the resistivity of the contacts of the instrument structure, the current-voltage characteristics of the gas sensor were examined in the voltage range between −100 and +100 V. Based on the results of investigating the current-voltage characteristics, which have a linear character, the resistivity of the contacts was confirmed. To study the sensitivity of the gas sensor to the target gas, the change in resistance of the sensitive layer of the gas sensor under the influence of NH3 with a concentration of 25 ppm under standard conditions was explored. The study results demonstrated the high sensitivity of the gas sensor to the target gas – at the level of 229 relative units. The investigation of the response and recovery time of the gas sensor showed that the ZnO-based gas sensor has a response and recovery time of 20 and 26 s, respectively. The selectivity of the ZnO-based gas sensor was studied. The selectivity study was carried out by determining the sensitivity of the gas sensor in the presence of vapors of various gases, namely methanol, ethanol, acetone. The study results showed that the reaction to ammonia is selective compared to the reaction to other gases. The results of examining the working characteristics of the ammonia gas sensor demonstrate the high efficiency of its application under standard conditions and a low concentration of the target gas

Non-contact humidity monitoring: Boosting the performance of all-printed humidity sensor using PDDA-modified Ti3C2Tx nanoribbons

Non-contact humidity monitoring can provide us with rich information about our bodies in a non-invasive way. However, this concept is hindered by the low sensitivity and slow response time of conventional humidity sensors. Herein, we employed two strategies, structural design and surface modification of MXene materials, to improve the sensitivity of MXene-based humidity sensors. A 3D porous structure was formed by the alkalinization treatment MXene, which facilitated rapid diffusion of water molecules along interlayer nanochannels and fast electron transport. Furthermore, the charged positively poly (diallyldimethylammonium chloride) (PDDA) was adsorbed onto the surface of the 3D skeleton through self-assembly to prepare a novel composite material KPMX. The loaded PDDA enhanced the interaction between MXene and water molecules, reducing the oxidation sensitivity of MXene. Additionally, the material was further formulated as inks with suitable viscosity and successfully used to produce a paper-based flexible humidity sensor through screen printing. Consequently, the KPMX sensor exhibited impressive potential in humidity sensing with high sensitivity (48813 %), rapid response/recovery time (8.794/2.656 s), and excellent stability. This work provided a practical strategy for non-contact humidity monitoring, including detecting the proximity of fingertips and changes in humidity in breathing patterns.

Modeling analysis and experimental study on epoxy packaged FBG sensor for cryogenic temperature measurement

The Fiber Bragg grating (FBG) is a kind of temperature-sensitive optical device that has irreplaceable advantages for cryogenic measurement. In this work, a model-driven FBG temperature sensor packaging method was proposed to improve the sensor’s sensitivity and linearity and predict the sensor's response time in cryogenic. The numerical model explores the relationship between the sensor’s size and performance. The packaging method can prepare high-precision samples of multiple sizes and provide experimental support for this study. The accuracy of the model is verified by comparing the calculated results with the results of a warming-up experiment and a liquid nitrogen experiment. The results show an improvement in sensitivity and linearity, and the model can also be used to predict the characteristics of FBG coated with epoxy resins at cryogenic temperature. The sensor with a thickness of 0.2 mm has a sensitivity and linearity of 26.6 pm/K and 0.997, respectively, in the range of 80 K-270 K.

Skin temperature influence on transcutaneous carbon dioxide (CO2) conductivity and skin blood flow in healthy human subjects at the arm and wrist.

Objective: present transcutaneous carbon dioxide (CO2)-tcpCO2-monitors suffer from limitations which hamper their widespread use, and call for a new tcpCO2 measurement technique. However, the progress in this area is hindered by the lack of knowledge in transcutaneous CO2 diffusion. To address this knowledge gap, this study focuses on investigating the influence of skin temperature on two key skin properties: CO2 permeability and skin blood flow. Methods: a monocentric prospective exploratory study including 40 healthy adults was undertaken. Each subject experienced a 90 min visit split into five 18 min sessions at different skin temperatures-Non-Heated (NH), 35, 38, 41, and 44°C. At each temperature, custom sensors measured transcutaneous CO2 conductivity and exhalation rate at the arm and wrist, while Laser Doppler Flowmetry (LDF) assessed skin blood flow at the arm. Results: the three studied metrics sharply increased with rising skin temperature. Mean values increased from the NH situation up to 44°C from 4.03 up to 8.88 and from 2.94 up to 8.11 m·s-1 for skin conductivity, and from 80.4 up to 177.5 and from 58.7 up to 162.3 cm3·m-2·h-1 for exhalation rate at the arm and wrist, respectively. Likewise, skin blood flow increased elevenfold for the same temperature increase. Of note, all metrics already augmented significantly in the 35-38°C skin temperature range, which may be reached without active heating-i.e. only using a warm clothing. Conclusion: these results are extremely encouraging for the development of next-generation tcpCO2 sensors. Indeed, the moderate increase (× 2) in skin conductivity from NH to 44°C tends to indicate that heating the skin is not critical from a response time point of view, i.e. little to no skin heating would only result in a doubled sensor response time in the worst case, compared to a maximal heating at 44°C. Crucially, a skin temperature within the 35-38°C range already sharply increases the skin blood flow, suggesting that tcpCO2 correlates well with the arterial paCO2 even at such low skin temperatures. These two conclusions further strengthen the viability of non-heated tcpCO2 sensors, thereby paving the way for the development of wearable transcutaneous capnometers.

Optical fiber gas sensor with multi-parameter sensing and environmental anti-interference performance

Formic acid finds widespread applications in numerous fields, including the petrochemicals production, rubber industry, and leather tanning process, in which the operational environments are complex and diverse. The corresponding industrial systems are often intricate and highly integrated. Indeed, formic acid gas is insidious and poses a hazard to both operating personnel and industrial equipment. The existing detection technologies for formic acid gas suffer from inherent technical limitations, making it challenging to effectively shield against industrial interference in complex environments while accurately conveying information. Furthermore, the simultaneous transmission of essential environmental data alongside formic acid gas concentration remains a formidable challenge, which is crucial for facilitating the integration and simplification of industrial system. In response to the aforementioned challenges, this research firstly employs an optical fiber structure (SNS: single mode fiber-no-core fiber-single mode fiber) with natural resistance to electromagnetic interference as the substrate. Subsequently, considering the characteristics of spectral variations and the response mechanism of formic acid gas, and addressing the issue of humidity interference of the current-stage sensors based on sensitive material, the chitosan and chitosan@PDMS are chosen as sensitive membranes. Finally, a correction formula was introduced to address the temperature and humidity coupling issue of the sensor, resulting in the successful development of two formic acid gas sensors. The chitosan-based sensor has a detection sensitivity of up to 7.7 pm/ppm, whose dual parameter detection performance for temperature and formic acid gas has been experimentally demonstrated. It can also correct the humidity-induced detection error in real-time by the correction formula. The chitosan@PDMS-based sensor was fabricated by plating a hydrophobic and breathable PDMS membrane on the surface of the chitosan-based sensor. In addition to maintaining the performance compared to the original sensor (response and recovery time was increased), the latter sensor can effectively resist the humidity interference from the environment. Furthermore, the new capability has been complemented for the simultaneous detection of temperature and humidity. That is, it realizes the dual parametric detection for formic acid gas and humidity, meanwhile providing the compensation ability for temperature change. The proposed sensors have the outstanding sensitivity, selectivity, immunity, and safety. This research not only effectively resolves the interference problem in formic acid gas detection, but also provides a new idea for equipment simplification and information integration in complex industrial systems.

Reduction of response time of fire detection and containment systems in compartments

Bench tests were performed on promising sensors used in fire safety systems in compartments. Activation delay times of fire sensors and systems were analyzed during the thermal decomposition and suppression of burning construction and interior design materials typical of compartments: wood, particle board, fiberboard, linoleum, cardboard, different types of wallpaper, paper and plastic. The thermal decomposition and ignition characteristics were identified using commercially available fire detectors of different types and designs (thermal, smoke and flame detectors), contact and non-contact temperature measurement instruments, a gas detection system and video recording equipment. Devices with the highest efficiency in terms of response time and detection reliability were determined that are necessary and sufficient to identify the thermal decomposition of construction and interior design materials at an early stage of fire. When generalizing the experimental data, mathematical equations were derived to predict the integral characteristics of the processes under study. Promising methods of reducing the response time of fire sensors and systems in general were determined. Guidelines were proposed on upgrading the existing systems of fire prevention in buildings and developing new automatic ones to significantly accelerate the detection of fires in buildings and optimize their containment and suppression.

High performance microheater-based catalytic hydrogen sensors fabricated on porous anodic alumina substrates

Catalytic combustion-type gas sensors are widely used in industry and everyday life for detecting flammable gases. However, high power consumption is one of the main drawbacks of the catalytic sensors. Replacing the platinum wire heating element with a thin-film microheater can significantly reduce power consumption, but maintaining high sensitivity and long-term stability of such devices is a challenge. Here we developed microheater-type catalytic hydrogen sensors based on porous anodic aluminium oxide served simultaneously as a substrate for platinum microheater and as a carrier for a catalyst. The fabricated sensors have a high sensitivity of 76 mV/vol% hydrogen. The deviation of the sensor response during continuous operation for 14 days is less than 4%. The relative humidity of the ambient atmosphere does not affect the sensor response. The fast sensor response time (0.4 s) makes it possible to use the pulsed power supply mode to reduce the power consumption to 3.2 mW without sacrificing the measurement accuracy. The performance of the developed catalytic hydrogen sensors promotes the high competitiveness in the market and the prospects for industrial applications.

Bamboo-like carbon nanotube composites containing cobalt nanoparticles combined with imidazole-based ionic liquids enhance the performance of oxygen sensors

In this study, BMIMPF6 was modified by adding BCNT/Co to it. The BCNT/Co + BMIMPF6 electrolyte system reduced the sensor response time to 16 s and showed good linearity in the range of 0–60% oxygen concentration.

Fabrication and characterization of chemiresistive CuO sensors sensitized by Ca-doping for detection of sweat electrolyte concentration

Intense electrolyte loss as a result of excessive sweating can disrupt the electrolyte balance in the body and cause damage to many organs, as well as potentially fatal disturbances in even brain functions. There are commercial sensors developed to monitor users' physical activity, however, few of them can provide information on users' health status through sweat analysis. Herein we report a chemiresistive sensor to monitor the sweat electrolyte concentration level. Metal oxide semiconducting CuO films were deposited on Au electrodes as sensing layers. Ca2+ ions were doped into the CuO lattice as sensitizer. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and UV–Vis spectroscopy were used to characterize the films. Sensors produced with pure and Ca-doped CuO films were tested against different concentrations of artificial sweat. The sensors responded well to sweat electrolyte concentration with a linear detection range of 20–80 mM. Detection limits between 6.64 and 9.86 mM were estimated using standard deviation methods. Average sensor response times were found to be 12 s.

Thermal-assisted resistive sensor based on the PdCr alloy thin film for sensitive detection of hydrogen isotopes in helium atmosphere

The detection of hydrogen isotopes is not only the premise of ensuring safety of hydrogen energy, but also has very important application value and scientific significance in the field of fusion energy. Therefore, it is imperative to develop efficient and reliable hydrogen isotope sensors. Herein, a thermal-assisted resistive sensor is constructed based on the hydrogen isotope effect of PdCr alloy thin film for sensitive detection of hydrogen isotopes in helium atmosphere. The permeation of hydrogen isotopes in palladium lattice is facilitated through thermal effect to improve the dynamic response capability of sensor. The research results show that the response time of sensor to hydrogen and deuterium is reduced from 192 s to 113 s–17 s and 10 s respectively. However, the sensitivity deteriorated by about 40% at 110 °C compared with room temperature. Meanwhile, the PdCr alloy thin film resistive sensor represents a remarkable linear response in a range of 0.1%–4% hydrogen and deuterium, with correlation coefficients of 0.9971 and 0.9998 respectively. And the response difference of hydrogen and deuterium may be utilized to discriminate hydrogen isotopes. Furthermore, the sensor exhibits prominent selectivity, extraordinary working stability and a wide range of 100ppm-100%. Therefore, this work presents a feasible approach to design high-performance resistive hydrogen isotope sensors for the development of hydrogen energy and fusion energy.

A smart sensor for monitoring antimicrobial interventions in wound infections

Effective therapeutic monitoring of wound infections is crucial for wound care. We explore a novel approach using a previously described 3D-printed, colourimetric indicator to non-invasively monitor antimicrobial interventions in wound infection. The indicator contains a pH-sensitive dye which detects carbon dioxide production from wound pathogens by changing colour from blue to yellow. The sensor accurately reported the minimum inhibitory concentration of antibiotic against Pseudomonas aeruginosa in a sealed 96-well plate. Subinhibitory antibiotic concentrations resulted in the sensor changing colour, whilst remaining blue for inhibitory concentrations. The sensor was applied to a porcine skin wound model with Pseudomonas aeruginosa biofilms, testing several antimicrobial treatments: antibiotic monotherapy, phage monotherapy, and a combination of both. After treatment, the sensor, sealed with the wound, enabled visual monitoring of antimicrobial efficacy. Through comparing post-treatment bioburden and sensor response, greater log-fold reductions in P. aeruginosa following antimicrobial treatment correlated with longer sensor response times. Sensors monitoring unsuccessfully treated biofilms changed colour, while those treated at or above the minimum biofilm eradication concentration elicited no colour change, indicating P. aeruginosa eradication. This sensor holds promise for monitoring wound infection treatment efficacy, improving patient outcomes, and promoting undisturbed wound healing as a non-invasive point-of-care tool.

Evaluation and optimization of the performance characteristics of fast response fiber optic oxygen gas probes

Even though many different designs for currently available, fluorescence-based fiber optic sensors for measuring oxygen concentration (O2) are well known (and indeed some are commercially available), they often are limited by their response time and long-term stability. This will cause problems in the important industrial applications of fiber optic sensors of this type that are developing, with limitations that are evident, for example, in physiology and other fields where rapid sensor responses are required. Research by a number of groups has discussed various new designs of fiber optical sensors, which have been developed in recent years where the key features of such probes to achieve the performance required are, for example, optimization of design features such as tip shape and coating layer thickness. The research reported in this paper represents an evaluation of such key factors to allow the design of better fiber optic-based sensors for oxygen measurement, where the optimized performance of a new, specially tapered tip O2 sensor designed has been compared with the output of conventional and commercially available probe designs. The performance of a group of such sensors has been analyzed and cross-compared, examining the key features of such a probe including sensor accuracy, response time and overall long-term stability, as well as cross-sensitivity to any temperature changes which may occur in ‘real’ measurement situations.

A double‐dynamic‐bond crosslinked multifunctional conductive hydrogel with self‐adhesive, remoldability, and rapid self‐healing properties for wearable sensing

AbstractIn recent years, conductive hydrogels have been designed as flexible sensors with broad application prospects in the field of smart wearable devices. However, the coordination of the mechanical properties, self‐healing capability, and conductivity of hydrogels has always been a challenge. In this work, a multifunctional conductive hydrogel with self‐adhesive, re‐shapeable, and rapid self‐healing abilities (PB‐PACS‐PM3 (self‐healing efficiency) = 98.8% in 15 s) was prepared by incorporating protocatechualdehyde modified carboxymethyl chitosan (PA@o‐CMCS) and PDA‐modified MXene (PDA@MXene) into the interchain of polyvinyl alcohol through dynamic borate ester crosslinking. The dynamic Schiff base reaction not only effectively introduced o‐CMCS as a mechanical enhancer but also improved the viscoelasticity and self‐healing capability of the hydrogel through the dual dynamic bond crosslinking structure. The PDA@MXene nanosheets are uniformly distributed in the hydrogel, providing the composite system with excellent conductivity (the conductivity of PB‐PACS‐PM3 hydrogel is 1.5 S/m) and strain sensitivity (the response time and recovery time of the hydrogel sensor are 230 and 260 ms, respectively), while the tensile strength of the hydrogel is improved to 0.035 MPa. Due to all these advantages, this conductive hydrogel can be assembled into flexible wearable sensors for rapid and accurate monitoring of various physiological activities of the human body, such as finger, wrist, elbow, and knee bending vibrations, among others.

Characteristic of graphene-based thick film gas sensor for ethanol and acetone vapor detection at room temperature

<p>Ethanol and acetone are volatile organic compound gases widely used in food processing. Health problems such as irritation of the eyes, nose, and throat can affect human health if exposed to these gases. Two graphene gas sensors were fabricated using a screen-printing technique onto a glass substrate to compare their performance to the acetone and ethanol vapors at room temperature. The graphene paste was prepared by mixing 95 wt.% of the binder with 5 wt.% of graphene nanoflakes. A silver paste was used asthe interdigitated electrode of the gas sensor and becamethe first layer of the gas sensor. The silver paste was deposited on the glass substrate using a screen-printing technique and fired at 150°C for 15 minutes. Next, the graphene paste was depositedonto the interdigitated electrode using a screen-printing technique and becamethe second layer of the gas sensor. The graphene was annealed at 200°C for 30 minutes. Both graphene gas sensors responded well to ethanol and acetone vapor with an n-typed gas sensor at room temperature. As a comparison, the graphene gas sensor showed better characteristics in terms of response and recovery characteristicsto ethanol vapor than acetone vapor at room temperature. The response and response time of the graphene-based thick film gas sensor to ethanol were approximately 21.89 and 24.08, respectively.</p>

Drift Characteristics of Sea-Bird Dissolved Oxygen Optode Sensors

Abstract The Sea-Bird 63 dissolved oxygen optode sensors used on various oceanographic platforms are known to drift over time. Corrections for drift are necessary for accurate dissolved oxygen measurements on the time scale of months to years. Here, drift on 14 Sea-Bird 63 dissolved oxygen optode sensors deployed on Spray underwater gliders over 5 years is described. The gliders with oxygen sensors were deployed regularly for 100-day missions as part of the California Underwater Glider Network (CUGN). A laboratory two-point calibration was performed on the oxygen sensor before and after glider deployment. Sensor drift during 100-day deployments was larger than during 100-day storage periods. Sensor behavior is modeled with a gain that asymptotically approaches 1.090 ± 0.005 with an e-folding time scale of 3.70 ± 0.361 years. At zero oxygen concentration, the sensor consistently reads around 3 μmol kg−1; a negative offset term is used in addition to the gain to correct the sensor oxygen. The correction procedure removes the error due to long time drift, one of the major sources of error, with an uncertainty of 0.5% (0.9% including outliers) or 0.5 μmol kg−1 depending on concentration, which improves the accuracy of the Sea-Bird 63 although uncertainty from other sources of error including the initial factory calibration and the sensor response time remain. Suggested procedures for implementing a two-point calibration procedure in the laboratory are discussed. Calibrations must be considered starting 6 months after initial factory calibration to keep error from sensor time drift under 1%. Significance Statement Dissolved oxygen measurements are widely used in oceanography. The optode sensors used to measure dissolved oxygen are known to drift over time. Here, the characteristics of drift for the oxygen optode sensor from Sea-Bird Scientific are described using a two-point calibration at zero and full saturation. The calibration procedure can be applied to oxygen optode sensors deployed on a variety of platforms when it is impractical to complete a multipoint calibration.

Exploring the design and performance of a tellurium optical sensor utilizing a plasticizer-free polymer inclusion membrane

A highly responsive, discerning, and uncomplicated technique has been devised for immobilizing reagents onto a plasticizer-free optical sensor membrane, employing polymer inclusion membranes (PIMs). This procedural strategy relies on a physical immobilization approach, specifically encapsulation, resulting in the creation of an optical sensing membrane. The responsive PIM is composed of poly(vinyl chloride) (PVC) as the fundamental polymer, Aliquat 336 as an extractant, and 4-(4 -chlorobenzylideneimino)-3-methyl-5-mercapto-1,2,4-triazole (CBIMMT) as the reagent. The optimized sensor demonstrates a linear range of 6.00–156 ng/mL for Te(IV), along with detection and quantification limits of 1.75 and 5.60 ng/mL, respectively. The sensor response time is 3.0 min, confirming its reproducibility. Effective regeneration of the sensor is achieved using a 0.2 mol/L HCl solution. The sensor membrane's selectivity is evaluated against various interfering ions, underscoring minimal interference. The sensor membrane efficacy is demonstrated through successful applications in quantifying Te(IV) levels, including natural water, chalcogenides, milk, vegetables, and soil samples.

Multiple source tracking and identifications in urban regions with unstable wind flows: Particle swarm optimization methodologies and their benchmark solutions

The prompt and accurate identification of transient pollution sources in urban regions is imperative for effective pollutant control and the mitigation to public health risks. Depending on sparse concentration distributions, multiple pollution sources identification is inherently complex and difficult, particularly when the pollutant sources exhibit time-varying release rates and are located in urban environments subject to dynamic wind flows. In this research, two niche-based Particle Swarm Optimization (PSO) algorithms, Niche-DPSO (niche pso for dynamic systems) and RSNM-DPSO (ranged subgroup pso with nelder mead for dynamic systems), were simultaneously proposed, aiming to localize multiple pollution sources under the background of unsteady wind flow fields. The MUST experiment, characterized by its complex layout replete with densely arranged obstacles, was adopted as the application scenario. Computational Fluid Dynamics (CFD) was employed to simulate the release of pollutant concentration at (−25.8 m, 0 m, 1.6 m) and (24.2 m, 41.6 m, 1.6 m), with flow velocities ranges from 1.8 to 7.6 m/s. Representative performance-influencing factors, including niche radius, population size, sensor response time, and sensor errors, were systematically evaluated. The results suggested that both Niche-DPSO and RSNM-DPSO algorithms were generally effective in positioning multiple pollution sources. Comparative analysis revealed that Niche-DPSO consistently outperformed RSNM-DPSO in terms of localization success rates, achieving a peak performance of approximately 98 %. Furthermore, Niche-DPSO could maintain its robust performance even under time-spatial-varying environmental and operational conditions, albeit at the expense of requiring more search steps and longer CPU processing time.

Advances in electrochemical biosensor design for the detection of the stress biomarker cortisol.

The monitoring of stress levels in humans has become increasingly relevant, given the recent incline of stress-related mental health disorders, lifestyle impacts, and chronic physiological diseases. Long-term exposure to stress can induce anxiety and depression, heart disease, and risky behaviors, such as drug and alcohol abuse. Biomarker molecules can be quantified in biological fluids to study human stress. Cortisol, specifically, is a hormone biomarker produced in the adrenal glands with biofluid concentrations that directly correlate to stress levels in humans. The rapid, real-time detection of cortisol is necessary for stress management and predicting the onset of psychological and physical ailments. Current methods, including mass spectrometry and immunoassays, are effective for sensitive cortisol quantification. However, these techniques provide only single measurements which pose challenges in the continuous monitoring of stress levels. Additionally, these analytical methods often require trained personnel to operate expensive instrumentation. Alternatively, low-cost electrochemical biosensors enable the real-time detection and continuous monitoring of cortisol levels while also providing adequate analytical figures of merit (e.g., sensitivity, selectivity, sensor response times, detection limits, and reproducibility) in a simple design platform. This review discusses the recent developments in electrochemical biosensor design for the detection of cortisol in human biofluids. Special emphasis is given to biosensor recognition elements, including antibodies, molecularly imprinted polymers (MIPs), and aptamers, as critical components of electrochemical biosensors for cortisol detection. Furthermore, the advantages and limiting factors of various electrochemical techniques and sensing in complex biofluid matrices are overviewed. Remarks on the current challenges and future perspectives regarding electrochemical biosensors for stress monitoring are provided, including matrix effects (pH dependence and biological interferences), wearability, and large-scale production.

Non-enzymatic glucose detection with screen-printed chemiresistive sensor using green synthesised silver nanoparticle and multi-walled carbon nanotubes-zinc oxide nanofibers

Non-enzymatic screen-printed chemiresistive interdigitated electrodes (SPCIE) were designed and fabricated using a low-cost screen-printing method for detection of the glucose. The interdigitated electrodes (IDE) pattern was printed using conductive graphene ink on the glossy surface of the photo paper. The proposed glossy photo paper-based SPCIE are functionalized with multi-walled carbon nanotubes-zinc oxide (MWCNTs-ZnO) nanofibers to create the chemiresistive matrix. Further, to bind these nanofibers with the graphene electrode surface, we have used the green synthesized silver nanoparticles (AgNPs) with banana flower stem fluid (BFSF) as a binder solution. AgNPs with BFSF form the conductive porous natural binder layer (CPNBL). It does not allow to increase the resistivity of the deposited material on graphene electrodes and also keeps the nanofibers intact with paper-based SPCIE. The synthesized material of MWCNT-ZnO nanofibers and green synthesized AgNPs with BFSF as a binder were characterized by Ultraviolet-visible spectroscopy (UV–vis), scanning electron microscope (SEM), x-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The amperometric measurements were performed on the proposed SPCIE sensor to detect the glucose sample directly. The innovative paper-based SPCIE glucose sensor exhibits a linear corelation between current measurements and glucose concentration in the range between 45.22 μm and 20 mm, with a regression coefficient (R 2) of 0.9902 and a lower limit of detection (LoD) of 45.22 μm (n = 5). The sensitivity of the developed SPCIE sensor was 2178.57 μAmM−1cm−2, and the sensor’s response time determined was approximately equal to 18 s. The proposed sensor was also tested for real blood serum sample, and relative standard deviation (RSD) was found equal to 2.95%.