Changes In Resistance Research Articles

Method for Underground Motion Using Vibration-Induced Ground Resistance Changes for Planetary Exploration

Exploration rovers have difficulty moving underground because the drag force from the ground restricts their movement; this hinders underground exploration. This study aimed to address this challenge. We posit a hypothesis that the rover can move underground by imparting vibration to the ground and changing the drag force. To validate this hypothesis, a testbed that moves underground was developed, and the drag force when imparting vibration was investigated. The results revealed that the drag force while imparting vibration is smaller than that after imparting vibration, and we accordingly devised the operation for moving underground. The proposed operation causes bias of the drag force by imparting vibration to make the testbed move in the direction of the small drag force. The effectiveness of the proposed method was assessed through an experiment wherein the testbed was set to move underground. The experimental results demonstrate the superiority of the proposed method, as the movement distance achieved with vibration is considerably greater than that without vibration. The findings validate the hypothesis that using vibration for underground motion is effective in improving mobility and provides valuable insights into the design of robots for underground motion.

Humidity Sensing Properties of Different Atomic Layers of Graphene on the SiO2/Si Substrate.

Graphene has great potential to be used for humidity sensing due to its ultrahigh surface area and conductivity. However, the impact of different atomic layers of graphene on the SiO2/Si substrate on humidity sensing has not been studied yet. In this paper, we fabricated three types of humidity sensors on the SiO2/Si substrate based on one to three atomic layers of graphene, in which the sensing areas of graphene are 75 μm × 72 μm and 45 μm × 72 μm, respectively. We studied the impact of both the number of atomic layers of graphene and the sensing areas of graphene on the responsivity and response/recovery time of the prepared graphene-based humidity sensors. We found that the relative resistance change of the prepared devices decreased with the increase of number of atomic layers of graphene under the same change of relative humidity. Further, devices based on tri-layer graphene showed the fastest response/recovery time, while devices based on double-layer graphene showed the slowest response/recovery time. Finally, we chose devices based on double-layer graphene that have relatively good responsivity and stability for application in respiration monitoring and contact-free finger monitoring.

Mechanoluminescent/Electric Dual-Mode Sensors Enabled by Trace Carbon Nanotubes.

Mechanoluminescence (ML)-based sensors are emerging as promising wearable devices, attracting attention for their self-powered visualization of mechanical stimuli. However, challenges such as weak brightness, high activation threshold, and intermittent signal output have hindered their development. Here, a mechanoluminescent/electric dual-mode strain sensor is presented that offers enhanced ML sensing and reliable electrical sensing simultaneously. The strain sensor is fabricated via an optimized dip-coating method, featuring a sandwich structure with a single-walled carbon nanotube (SWNT) interlayer and two polydimethylsiloxane (PDMS)/ZnS:Cu luminescence layers. The integral mechanical reinforcement framework provided by the SWNT interlayer improves the ML intensity of the SWNT/PDMS/ZnS:Cu composite film. Compared to conventional nanoparticle fillers, the ML intensity is enhanced nearly tenfold with a trace amount of SWNT (only 0.01wt.%). In addition, the excellent electrical conductivity of SWNT forms a conductive network, ensuring continuous and stable electrical sensing. These strain sensors enable comprehensive and precise monitoring of human behavior through both electrical (relative resistance change) and optical (ML intensity) methods, paving the way for the development of advanced visual sensing and smart wearable electronics in the future.

Structural health monitoring of scarf bonded repaired glass/epoxy laminates interleaved with carbon non-woven veil

Bonded repair patches/joints often introduce vulnerabilities in composite laminates, making them prime candidates for structural health monitoring (SHM). In this study, stepped-scarf bonded joints were manufactured using glass fibre-reinforced epoxy laminates as representative repair patches, and a novel SHM approach through the electrical resistance change method was applied. To establish an electrically conductive path within the stepped-scarf joint, non-woven carbon fibre veils with areal weights of 10 g/m² and 20 g/m² were interlaid along the stepped bondline. Two types of tensile tests were performed. In the first set of tests, the stepped-scarf joints underwent monotonic quasi-static tensile loading until the bondline was completely fractured (catastrophic failure) and the change in electrical resistance was continuously monitored. The failure stress of the joint with a 10 g/ m² carbon veil was only marginally decreased (∼2 %) in comparison with that of the joints without a carbon veil, while the failure stress of the joint with a 20 g/m² carbon non-woven veil was considerably decreased (by ∼9 %). However, the joints with 10 g/m² and 20 g/m² carbon veils exhibited a significant change in electrical resistance (∼200 % and ∼1000 %, up to full failure, respectively). Simultaneously, the change in electrical resistance was used for the detection of damage initiation and progression, supported by digital images taken during the tests. In the second set of tests, the joints were subjected to a cyclic tensile loading/unloading regime and the change in electrical resistance was monitored. A significant amount of permanent change in resistance during the unloading phases (up to 120 % in the bondline with a 20 g/m² veil) was observed, providing insights into the laminate and bondline damage evolution. In addition, thermal images obtained with the joule heating method in the cyclic tensile tests were used to confirm the damage detected with the electrical resistance change method. Moreover, the micrographs from the fracture surfaces indicated that the variations in electrical resistance change are largely caused by damage occurring within or near the carbon veils. In conclusion, the results demonstrate that the presented SHM approach, which incorporates carbon non-woven fibre veils within non-conductive laminate composites, holds promise for monitoring damage initiation and propagation in repaired composite laminates as well as adhesively bonded composite laminate joints, without adversely influencing the structural integrity of the bondline.

IDENTIFICATION OF AQUIFERS BASED ON THE VERTICAL ELECTRICAL SOUNDING (VES) METHOD SCHLUMBERGER CONFIGURATION CASE STUDY: PULAU BAAI KAMPUNG MELAYU SUB-DISTRICT, BENGKULU CITY, INDONESIA

Investigation of the groundwater potential in the Pulau Baai area, Kampung Melayu Sub-district, Bengkulu City, must be carried out in such a way that the activities and needs of the people in the area can be fulfilled and the needs of the population in the area can be met. This study aims to determine the status of groundwater using the Schlumberger configuration geoelectric method. Measurements were made using a resistivity meter, and the results for each configuration depended on changes in resistivity. Measurements for each configuration depend on changes in resistivity at depth, the vertical direction (sounding), and the lateral direction (mapping), so hydrogeological analysis in this activity aims to get the maximum use of groundwater / underground water in aquifers for raw water needs. The dominant rock structures in the study area are clay, alluvium, siltstone, and sandstone, as well as some rocks with suitable porosity and permeability as water carriers, such as sand and gravel. However, what appears to have considerable potential is that groundwater is found at depths of 4-53 meters in VES 1, VES 2, VES 3, VES 5, and VES 10. The results of the analysis show that the location of the Pulau Baai, Kampung Melayu Sub-district, Bengkulu City Priority Utilization Area is within the groundwater storage area, so it can be used to meet the raw water needs of the study area.

Conductive Framework Materials for Chemiresistive Detection and Differentiation of Toxic Gases.

ConspectusSensing complex gaseous mixtures and identifying their composition and concentration have the potential to achieve unprecedented improvements in environmental monitoring, medical diagnostics, industrial safety, and the food/agriculture industry. Electronically transduced chemical sensors capable of recognizing and differentiating specific target gases and transducing these chemical stimuli in a portable electronic device offer an opportunity for impact by bridging the utility of chemical information with global wireless connectivity. Among electronically transduced chemical sensors, chemiresistors stand out as particularly promising due to combined features of low-power requirements, room temperature operation, non-line-of-sight detection, high portability, and exceptional modularity. Relying on changes in resistance of a functional material triggered by variations in the surrounding chemical environment, these devices have achieved part-per-billion sensitivities of analytes by employing conductive polymers, graphene, carbon nanotubes (CNTs), metal oxides, metal nanoparticles, metal dichalcogenides, or MXenes as sensing materials. Despite these tremendous developments, the need for stable, selective, and sensitive chemiresistors demands continued innovation in material design in order to operate in complex mixtures with interferents as well as variations in humidity and temperature.To fill existing gaps in sensing capabilities, conductive metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have recently emerged as a promising class of materials for chemiresistive sensing. In contrast to previously reported chemiresistors, these materials offer at least three unique features for gas sensing applications: (i) bottom-up synthesis from molecularly precise precursors that allows for strategic control of material-analyte interactions, (ii) intrinsic conductivity that simultaneously facilitates charge transport and signal transduction under low power requirements, and (iii) high surface area that enables the accessibility of abundant active sites and decontamination of gas streams by coordinating to and, sometimes, detoxifying harmful analytes. Through an emphasis on molecular engineering of structure-property relationships in conductive MOFs and COFs, combined with strategic innovations in device integration strategies and device form factor (i.e., the physical dimensions and design of device components), our group has paved the way to demonstrating the multifunctional utility of these materials in the chemiresistive detection of gases and vapors. Backed by spectroscopic assessment of material-analyte interactions, we illustrated how molecular-level features lead to device performance in detection, filtration, and detoxification of gaseous analytes. By merging the bottom-up synthesis of these materials with device integration, we show the versatility and scalability of using these materials in low-power electronic sensing devices. Taken together, our achievements, combined with the progress spearheaded on this class of materials by other researchers, establish conductive MOFs and COFs as promising multifunctional materials for applications in electronically transduced, portable, low-power sensing devices.

Damage monitoring on inter-lamination of GFRP via the resistance change of the MWCNT@GF sensor

The paper aimed to investigate the performance of multi-walled carbon nanotube-coated GF (MWCNT@GF) sensors on interlayer shear damage monitoring and sensing capability of glass fiber-reinforced polymers (GFRPs) based on the resistance change under short beam shear (SBS) load. The MWCNT@GF sensor, manufactured by physical vapor deposition (PVD), was embedded into the neutral layer of laminates to form an in-situ sensing network in different directions and positions. “The MWCNT@GF sensor, manufactured by physical vapor deposition (PVD), was embedded into the neutral layer of laminates to form an in-situ sensing network.” “With the help of Keithley 2700 programmable electrometer and the 3D-digital image correlation(3D-DIC), monotonic and cyclic tests were carried out.” The monotonic test found that the off-axis sensor is more sensitive to shear failure than the on-axis sensor because of its lower shear strength. In addition, the qualitative relationship between shear damage and relative resistance was established by selecting crucial moments. In the cyclical test, the relative resistance of off-axis sensors presented a cyclic mode under cyclic load. Furthermore, the relative resistance under the first 20 cyclic loads was similar to that under monotonic loads. “Furthermore, the relative resistance under the first 20 cyclic loads was similar to that under monotonic loads, which shows that the sensor has superior sensing ability. Finally, the quantitative relation between shear damage and relative resistance was established.” “That means MWCNT@GF sensors can be used to reasonably evaluate the damage state and further evaluate the service performance, reliability and remaining life of the structure.”

Exploring the mechanisms of benzanilide crystal growth and morphology: Crystal surface structure, solvent diffusion and solvent-interface interactions

Flaky crystals are fragile, rendering them unsuitable for various applications including use, processing, storage and transportation. This work investigates the growth and morphology regulation mechanisms of flaky crystals using benzanilide as a model material. Initially, block-like crystals are prepared by solvent screening and cooling crystallization with its morphology greatly improved. Subsequently, growth kinetics of (111), (1–10) and (020) faces are established with crystal growth experiments. The crystal growth of (001) face is also determined to follow a two-dimensional nucleation model with the microscopic surface analysis using atomic force microscopy. The changes of the surface integration resistance and the growth step height are regarded as kinetic mechanisms of the growth behavior and crystal morphology modulation by solvent and supersaturation. Finally, the molecular mechanism of the modulation of the solvent in crystal morphology is revealed base on crystal surface structure analysis and molecular dynamics simulations. The weak solvent-interface polar interactions facilitate the incorporation of benzanilide molecules into the weak polarity (001) face, leading to the surface roughening and increased crystal thickness when employing strongly polar solvents such as acetonitrile. Unlike the former, the relatively weak hydrogen bonding interactions between solvents and strong polarity (020) face, and the higher diffusion ability of molecules promote the rapid growth and disappearance of (020) face in ethanol and acetonitrile with strong hydrogen bond formation ability. This study can contribute to a deeper understanding of the solvent effect on crystal morphology and provide guidance for optimizing crystallization conditions to obtain shape-tailored crystal products.

Development and properties of cost-effective self-sensing Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) incorporating steel slags

This study examined the electrical and self-sensing capacities of ultra-high performance fiber-reinforced concrete （UHPFRC） with and without steel slag powder. The inclusion of steel slags provides a reliable way to enhance the electrically conductive and self-sensing capabilities of UHPFRC, which is composed of cement, silica fume, and steel fiber. The conductibility of UHPFRC and its response to external loading were investigated. Additionally, through 3D analysis of fiber structure and pore distribution, the conductive mechanisms were revealed. The results show that the addition of steel slags powder (SSP) can improve both mechanical properties and flowability. The maximum fractional change in electrical resistivity under compressive and flexural loads reached 37.6 % and 54.1 %, respectively. However, the conductive model under compressive loading differs from that under flexural loading. Furthermore, an analysis of carbon emissions and material costs revealed that using SSP reduced carbon emissions by 45.2–96.4 % and lowered costs by 41.8–88.8 %, making this approach both economically and environmentally advantageous.

The triglyceride-glucose index dynamic trajectory reveals the association between the clinical subphenotype of insulin resistance and mortality in patients with sepsis

BackgroundThe relationship between the dynamic changes in insulin resistance (IR) and the prognosis of septic patients remains unclear. This study aims to investigate the correlation between the clinical subphenotype of IR represented by the triglyceride-glucose (TyG) index trajectory and the mortality rate among patients with sepsis.MethodsIn this retrospective cohort study, we utilized data from septic patients within the Medical Information Mart for Intensive Care (MIMIC)-IV database version 2.0 to construct trajectories of the TyG index over 72 h. Subsequently, we computed the similarity among various TyG index trajectories with the dynamic time warping (DTW) algorithm and utilized the hierarchical clustering (HC) algorithm to demarcate distinct cluster and identified subphenotypes according to the trajectory trend. Subsequently, we assessed the mortality risk between different subphenotypes using analyses such as survival analysis and validated the robustness of the results through propensity score matching (PSM) and various models.ResultsA total of 2350 patients were included in the study. Two trajectory trends: TyG index decreasing (n = 926) and TyG index increasing (n = 1424) were identified, which indicated corresponding to the clinical subphenotype of increased and alleviative IR respectively. The 28-day and in-hospital mortality for the increased IR group was 28.51% and 25.49% respectively. In comparison, patients in the alleviative IR group with a 28-day mortality of 23.54% and an in-hospital mortality of 21.60%. These subphenotypes exhibited distinct prognosis, time dependent Cox model showed the increased IR group with a higher 28-day mortality [hazard ratio (HR): 1.07, 95% confidence interval (CI): 1.02–1.12, P = 0.01] and in-hospital mortality [HR: 1.05, 95% CI: 1.00–1.11, P = 0.045] compared to the alleviative IR group. Sensitivity analyses with various models further validated the robustness of our findings.ConclusionDynamic increase in the TyG index trajectory is associated with elevated mortality risk among patients with sepsis, which suggests that dynamic increased IR exacerbates the risk of poor outcomes in patients.

Absolute coronary flow and microvascular resistance before and after transcatheter aortic valve implantation.

Severe aortic stenosis (AS) is associated with left ventricular (LV) remodelling, likely causing alterations in coronary blood flow and microvascular resistance. We aimed to evaluate changes in absolute coronary flow and microvascular resistance in patients with AS undergoing transcatheter aortic valve implantation (TAVI). Consecutive patients with AS undergoing TAVI with non-obstructive coronary artery disease in the left anterior descending artery (LAD) were included. Absolute coronary flow (Q) and microvascular resistance (Rμ) were measured in the LAD using continuous intracoronary thermodilution at rest and during hyperaemia before and after TAVI, and at 6-month follow-up. Total myocardial mass and LAD-specific mass were quantified by echocardiography and cardiac computed tomography. Regional myocardial perfusion (QN) was calculated by dividing absolute flow by the subtended myocardial mass. In 51 patients, Q and R were measured at rest and during hyperaemia before and after TAVI; in 20 (39%) patients, measurements were also obtained 6 months after TAVI. No changes occurred in resting and hyperaemic flow and resistance before and after TAVI nor after 6 months. However, at 6-month follow-up, a notable reverse LV remodelling resulted in a significant increase in hyperaemic perfusion (QN,hyper: 0.86 [interquartile range {IQR} 0.691.06] vs 1.20 [IQR 0.99-1.32] mL/min/g; p=0.008; pre-TAVI and follow-up, respectively) but not in resting perfusion (QN,rest: 0.34 [IQR 0.30-0.48] vs 0.47 [IQR 0.36-0.67] mL/min/g; p=0.06). Immediately after TAVI, no changes occurred in absolute coronary flow or coronary flow reserve. Over time, the remodelling of the left ventricle is associated with increased hyperaemic perfusion.

Intermittent compared with continuous calorie restriction for treatment of metabolic dysfunction-associated steatotic liver disease: a randomized clinical trial

BackgroundCalorie restriction has been demonstrated to be effective in treating metabolic dysfunction-associated steatotic liver disease (MASLD). However, it has been limited by poor long-term adherence. ObjectivesThis study aimed to compare intermittent calorie restriction (ICR) with traditional continuous calorie restriction (CCR) for the treatment of MASLD. MethodsWe conducted a 12-wk, parallel-arm, randomized controlled trial that included 60 adults with MASLD and abnormal glucose metabolism. The participants were randomly assigned to either the ICR group (2 successive days of fasting [∼500 kcal/d] and 5 d of recovery per week) or the CCR group. The primary outcome was liver fat content (LFC) measured by 1H-proton magnetic resonance spectroscopy. The secondary and exploratory outcomes included weight, body composition, glucose, insulin, lipids, and liver stiffness. ResultsThe mean reduction in LFC was −20.5% [95% confidence interval (CI): −25.0, −15.9%] in the ICR group and −15.5% (95% CI: −20.3, −10.8%) in the CCR group. Changes in LFC were not significantly different between the 2 groups (P = 0.15), and were homogeneous among different liver segments. The analysis of exploratory endpoints provided clues that the ICR was associated with greater reductions in fat mass and glycosylated hemoglobin. There were no significant differences in changes of weight, lean mass, insulin resistance, triglyceride, and liver stiffness between the 2 groups. Participants showed high adherence to both the ICR and CCR schemes. ConclusionsThe ICR and CCR schemes had similar effects on reducing LFC, suggesting that the ICR 5:2 diet can be an effective alternative for treating MASLD with high adherence. Trial registration numberThis trial was registered at clinicaltrials.gov as NCT04283942.

Changes in the Antimicrobial Resistance and Bacterial Epidemiology of Moraxella catarrhalis from Pediatric Community-Acquired Pneumonia Patients During the COVID-19 Pandemic: A 5-Year Study at a Tertiary Hospital of Southwest China.

This study aimed to assess the impact of the COVID-19 pandemic on Moraxella catarrhalis infections in pediatric patients hospitalized with community-acquired pneumonia (CAP). The epidemiological features and antimicrobial resistance (AMR) patterns of M. catarrhalis were compared between the pre-pandemic period (2018-2019) and during the pandemic (2020-2022). The results revealed a marked increase in the positivity rate of M. catarrhalis in 2020 and 2021 compared with the pre-pandemic years. The median age of the patients increased significantly in 2021 and 2022, while the proportion of male patients decreased substantially from 2019 to 2021. In addition, there were notable changes in the co-infections of Haemophilus influenzae, parainfluenza virus, and respiratory syncytial virus during the COVID-19 pandemic. The AMR profile of M. catarrhalis also changed significantly, showing increased resistance to ampicillin, but decreased resistance to trimethoprim-sulfamethoxazole and ofloxacin, and a lower proportion of multidrug-resistant isolates. Notably, ampicillin resistance increased among β-lactamase-producing isolates. Before the pandemic, the number and detection rate of isolates, along with resistance to ampicillin and trimethoprim-sulfamethoxazole, were seasonally distributed, peaking in autumn and winter. However, coinciding with local COVID-19 outbreaks, these indices sharply fell in February 2020, and the number of isolates did not recover during the autumn and winter of 2022. These findings indicate that the COVID-19 pandemic has significantly altered the infection landscape of M. catarrhalis in pediatric CAP patients, as evidenced by shifts in the detection rate, demographic characteristics, respiratory co-infections, AMR profiles, and seasonal patterns.

Electrical stimulation of biofidelic engineered muscle enhances myotube size, force, fatigue resistance, and induces a fast-to-slow-phenotype shift.

Therapeutic development for skeletal muscle diseases is challenged by a lack of exvivo models that recapitulate human muscle physiology. Here, we engineered 3D human skeletal muscle tissue in the Biowire II platform that could be maintained and electrically stimulated long-term. Increasing differentiation time enhanced myotube formation, modulated myogenic gene expression, and increased twitch and tetanic forces. When we mimicked exercise training by applying chronic electrical stimulation, the "exercised" skeletal muscle tissues showed increased myotube size and a contractility profile, fatigue resistance, and gene expression changes comparable to invivo models of exercise training. Additionally, tissues also responded with expected physiological changes to known pharmacological treatment. To our knowledge, this is the first evidence of a human engineered 3D skeletal muscle tissue that recapitulates invivo models of exercise. By recapitulating key features of human skeletal muscle, we demonstrated that the Biowire II platform may be used by the pharmaceutical industry as a model for identifying and optimizing therapeutic drug candidates that modulate skeletal muscle function.

Study on the suppression of secondary electron emission characteristics based on TiN

Abstract With the continuous development of satellite communications, the problem of high-frequency high-power multipactor caused by the miniaturization of microwave passive components in the aerospace field has become more and more serious. In this paper, for the problem of multipactor suppression of load passive devices, we carried out research on the preparation of TiN thin films based on PEALD and put forward a new method for suppressing SEE with good suppression effect, high consistency, low surface resistance, and other aspects of the unity of the multipactor effect. The use of 20nm TiN coating can make the silver-plated surface secondary electron emission coefficient down to 1.59. The RF surface resistance change rate is less than 3%. In the field of communication, satellite and navigation and other fields have a wide range of application prospects.

The development and characterisation of 3D-printed multi-material thermistor

This paper introduces a multi-material, low-cost, and highly sensitive thermistor concept developed for body temperature monitoring. The designed thermistor employs poly(3,4-ethylenedioxythophene):poly(4-styrenesulfonate) (PEDOT:PSS) for the temperature sensing layer, silver (Ag) for the contact electrodes, and polycarbonate (PC) as the substrate. In contrast to traditional printed electronics substrates used in thermistor development, the utilisation of Material Extrusion via Fused Deposition Modelling (FDM) for the manufacture of PC substrates is the distinct feature of the work. For the manufacture of multi-material thermistors two different Additive Manufacturing (AM) methods: FDM for substrates and micro dispensing for PEDOT:PSS sensing layer and Ag electrodes, were utilised. Two thermistors with varying sensing areas, namely D1 and D2, were designed and fabricated. The thermistors demonstrated a high degree of linearity and repeatability within the temperature range of 25–45°C with a viable hysteresis maximum around 3%. The measurement sensitivity of thermistors was assessed based on Temperature Coefficient of Resistance (TCR) values, which were –0.68 ±0.057% and –0.49 ±0.078% per °C for the D1 design and –0.53 ±0.078% and –0.40 ±0.069% per °C for the D2 design, during heating and cooling, respectively. Comparable average response and recovery times to the literature were also acquired, which were 31.47 ±1.02 and 54.42 ±0.70seconds for D1 and 27.38 ±0.96 and 48.45 ±1.69seconds for D2, during heating and cooling, respectively. It was evident that the sensing area had an impact on thermistor TCR as well as response and recovery times, where higher TCR and faster response and recovery times were recorded with the small sensing area. It was also observed that humidity had a significant impact on thermistor reliability, exhibiting a normalised resistance change of ∼12% and ∼9% of the initial measurement at 50 and 75% RH, respectively. When compared to PEDOT:PSS-based thermistors reported in the literature, the obtained results in this research have demonstrated that our multi-material thermistor concept is a promising candidate for the low-cost and highly sensitive multi-material thermistor that can be manufactured in a fully additive manner using AM technologies.

Ultra-thin V2O5 nanowires: synthesis and gas sensing characteristics

This study presents the synthesis of vanadium oxide nanowires via a simple hydrothermal method and explores their potential as high-performance sensors for monitoring harmful gases, with a particular focus on NO2. The microstructure and morphology of the nanowires were characterized using scanning electron microscopy, powder x-ray diffraction, and Raman spectroscopy. The vanadium oxide nanowire material demonstrates outstanding NO2 gas sensing capabilities, detecting 5 ppm with a rapid response and high sensitivity at an optimal working temperature of 150 °C. It exhibits a relative resistance change of 70%, showcasing a sub-ppm detection limit. The V2O5 nanowires exhibited good stability and high gas selectivity for NO2 over other interfering gases (H2S, NH3, C2H4, and CO). The ultrathin structure of the nanowires holds promise for practical applications in developing NO2 gas sensors. The study sheds light on the superior sensitivity of the V2O5 gas sensor toward NO2 at low temperatures, emphasizing the influence of the 1D structure on the sensing mechanism.

A ZnO-nanorod/PEDOT:PSS nanocomposite functionalized bridge-like membrane type nanomechanical sensing device for ultrasensitive blood lead detection

Lead (Pb) ion detection poses a critical problem, particularly in environmental monitoring, industrial operations, and public health, especially for young children and expecting women. Determining lead levels in blood early on is essential to minimizing the long-term consequences of lead exposure. Several sophisticated detection instruments, such as mass spectrometers which perform with high sensitivity, specificity and accuracy, but require a lab-based setting, multi-step sample preparation, expensive payment and professional operation. It is evident that a highly sensitive, portable, low-cost, quick sample-to-result, blood lead detection device that can be tested at the point-of-care is necessary. Consequently, we developed a unique ZnO/PEDOT:PSS nanocomposite layer integrated with a CMOS MEMS-based bridge-like membrane-type (BM) nanomechanical sensor for detecting lead levels in blood. PEDOT:PSS was combined with ZnO nanorods to increase lead ion binding. The sensor responds seven times better to lead ions using nanorods in the detecting layer. A linear resistance change rate response was found from 0.005 to 10 ppm, with the limit of detection (LOD) of 0.12 ppb. Similarly, our BM nanomechanical sensor can correctly assess Pb2+ in human serum with recovery rates of 86.25-150%. Measurements of human blood samples from patients with varying lead ion concentrations validated by the standard AAS show a good linear connection with the BM nanomechanical sensors' concentration, with a regression coefficient of 0.92. This describes the first micromachined nanoachanical sensing system for detection of Pb2+ in only 5 μL of human serum sample. The device achieves a time-to-result of less than 10 min. The system is designed to be very sensitive and offers affordable, disposable sensing chips together with a portable signal acquisition platform.

Comparison of gas-sensitive properties of Pb, Pd and Pt metal-doped Ti3C2X2 for aqueous zinc ion battery H2 gas

This work aims to provide early warning of uncontrolled reactions in aqueous zinc-ion batteries by timely and effectively detecting H2 gas. The large specific surface area and rich pore structure of Ti3C2X2 (X = F, O, and OH) make it a good gas-sensitive sensing material, and the gas-sensitive properties of the material can be improved by metal doping. Therefore, in this paper, the gas-sensitive response properties of Pb, Pd and Pt metal-doped Ti3C2X2 (M-Ti3C2X2) to H2 are compared based on density functional theory (DFT) calculations. The adsorption mechanism was analyzed by structure optimization, density of states, frontier molecular orbital theory and differential charge density, and the results were in high agreement. Doping of three metals, Pb, Pd and Pt, improved the adsorption capacity of Ti3C2X2 for H2 gas to different degrees. The simulation results show that the energy gap of Pb-Ti3C2(OH)2 adsorbed gas changes most obviously, and the maximum change value of energy gap (Eg) is 297.56 %. And Pt-Ti3C2F2 and Pt-Ti3C2O2 adsorbed H2 with large adsorption energies and large charge transfers indicating that they can be used as H2 removers. The energy gaps after the adsorption of H2 by M-Ti3C2O2 are 0.109 eV, 0.163 eV, and 0.082 eV, and the change of Eg is 24.77 %, 16.56 %, and 67.07 %, respectively. The change of Eg for the adsorption of H2 by Pt-Ti3C2O2 adsorbed H2 with a resistivity change of 67.07 %. This is caused by the irreversibility of adsorption due to too strong adsorption resulting in elongation of Pt-O bond length after adsorption. For the detection of H2, the properties of several doped materials were ranked as follows: Pb-Ti3C2(OH)2 > Pt-Ti3C2O2 > Pb-Ti3C2F2 > Pb-Ti3C2O2 > Pd-Ti3C2O2 > Pd-Ti3C2(OH)2 > Pt-Ti3C2F2 > Pt-Ti3C2(OH)2 > Pd-Ti3C2F2. In summary, it is shown that Ti3C2X2 doped with Pb, Pd and Pt metals is a potential H2 gas-sensitive material that can be a new material for online monitoring of fault gas content in aqueous zinc-metal energy storage batteries.

High-quality VO2 thin films sputter-deposited on borosilicate glass substrates for modulating solar transmission and thermal emission

M1-phase VO2 exhibits a reversible phase transition between the insulating and metallic states at T = ∼341 K, and VO2-based smart windows have been extensively studied. The smart window application requires the growth of high-quality VO2 films with a large resistivity change and small hysteresis width (ΔT) on glass substrates using a scalable deposition method such as sputtering. However, the polymorphic nature of VO2 makes it challenging to obtain high-quality VO2 films on ordinary window glasses (borosilicate and soda-lime glasses). Thus far, VO2 films sputtered on glass substrates have exhibited resistivity changes of 1.5–2 orders of magnitude and ΔT = 3–19 °C. In this study, we show that high-quality VO2 films with a resistivity change of 2.5−3.0 orders of magnitude and ΔT = 2 °C can be grown on borosilicate glass substrates via radio-frequency sputtering followed by thermal annealing. The simultaneous achievement of such a large resistivity change and small hysteresis width is highly encouraging not only for smart windows but also for other applications. With respect to the modulation of solar transmission and thermal emission with temperature, the performance levels of the produced VO2 films were 70−75 % of those expected from pure M1-phase VO2 films.