Change In Electrical Resistance Research Articles

Potentially probiotic Limosilactobacillus reuteri from human milk strengthens the gut barrier in T84 cells and a murine enteroid model.

At conception, the infant gut barrier is immature, gradually developing with regular intake of maternal milk. This study addressed whether the barrier-strengthening effect of breast feeding might be attributable, at least in part, to autochthonous beneficial human milk bacteria. Twelve bacterial strains from the breast milk of Pakistani mothers who underwent cesarean delivery (NPL-88, NPL-157, NPL-179, NPL-181, NPL-388 (Limosilactobacillus reuteri), NPL-76, NPL-495, NPL-504 (Limosilactobacillus fermentum), NPL-415 (Lactobacillus pentosus), NPL-412, NPL-416 (Lactiplantibacilllus plantarum) and NPL-374 (Bifidobacterium longum) were shortlisted based on their tolerance to acidic pH (2.8-4.2) and bile (0.1-0.3%). The effect of these bacteria on gut barrier function in the presence and absence of pathogens was assessed as changes in transepithelial electrical resistance (TEER) in the human T84 colonic epithelial cell line and in murine enteroid-derived monolayers (EDMs). The TEER of T84 cells monolayers rose in the presence of most of the human milk strains, being most pronounced in case of L. reuteri NPL-88 (34% within five h), exceeding the effect of the well-known probiotic L. acidophilus (20%). qRT-PCR, western blot and immunofluorescent staining associated the increase in TEER with enhanced expression of tight junction proteins. Pretreatment of murine EDMs with NPL-88 also largely prevented the ability of the pathogen, Salmonella, to decrease TEER (87±1.50%; P<0.0001, n=4). Human milk lactic acid bacteria are potential probiotics that can strengthen gut barrier function and protect breastfed neonates against enteric infections.

Integration of conductive silver sensors on zirconia ceramics by screen-printing for monitoring strain under applied load

There is a growing interest in zirconia ceramics due to their high flexural strength, excellent corrosion resistance and good biocompatibility. The assembly of advanced zirconia material with functions of sensing, actuation and controlling to solve the problems that may arise during its use is critical to ensure long-term service and performance. Within this context, the objective of this work is to analyse the structural health of zirconia samples by screen-printing silver-based conductive ink on the surface subjected to maximum load under flexural testing. In doing so, silver conductive ink was formulated using silver nanoparticles where polyvinyl pyrrolidone acted as the capping agent. Silver ink was then screen-printed onto zirconia samples and sintered at 200 °C. The resistance of the sensors was measured and the sensing capabilities of printed conductive patterns were investigated using the four-point probe method. Experimental findings displayed a reproducible direct correlation between electrical resistance change and strain resulting from surface displacement under applied load in four-point bending.

Acrylonitrile butadiene styrene – carbon nanotubes nanocomposites for 3D printing of health monitoring components

In this paper self-sensing nanocomposite formulations made of acrylonitrile butadiene styrene and different loading (3, 5 and 10 wt%) of multi-walled carbon nanotubes have been produced and 3D printed via fused filament fabrication. The nanocomposites have been characterized from a rheological, mechanical, thermal and electrical point of view to assess the strain-sensing properties. All the samples show a piezoresistive behaviour and the electrical resistance changes when a stress is applied. The gauge factor, measure of the sensitivity, for ABS 3CNT, ABS 5CNT and ABS 10CNT are 11.36, 3.21 and 1.62, respectively. The ABS 3CNT samples have shown the best self-sensing performances with high sensitivity and this formulation has been used for producing a health-monitoring 3D-printed smart structure where the active material is placed locally in the structure. The 3D-printed structure itself is able to monitor the strain and hence the stress level to which is subjected with a gauge factor of 1.5. A finite element analysis helps to explain the reason for reduced sensitivity namely the placement of the sensing layer.

Changes in the Specific Electrical Resistivity of Rocks at Different Depths of the Geoelectric Section and Their Comparison with Seismicity

Changes in the Specific Electrical Resistivity of Rocks at Different Depths of the Geoelectric Section and Their Comparison with Seismicity

Non-destructive micro analysis of electromigration failures in solder microbumps using 3D X-ray computed tomography

Three-dimensional (3D) X-ray was employed to characterize the electromigration (EM) induced failures (voids, cracks, and necking) in 30 μm Cu/Sn/Ni/Cu solder joints. The 3D X-ray is capable of mapping the positions and evolution of voids and morphology change in the solder joints caused by EM. Such an approach offers an alternatively non-destructive assessment for the reliability of large-area solder arrays. The EM-induced failures of hundreds of solder joints could be captured and characterized. The results show that large voids mostly formed near the entrance of electron flow. Two-step change of solder electrical resistance was found: a gradual increase (10.6% after 5.1 h) at the beginning EM stage due to slow nucleation of newly individual voids and a sharp increase (10.6% to 22.2% within 0.8 h) caused by the significant growth and coalescence of multiple voids and necking. We found that the total number of solder joints with obvious voids in plan-view CT images was larger than that in side-view micrographs indicating their better practical implementation. Additionally, we found that the total contact area of the solder joints gradually decreased due to solder necking after EM tests. It further expanded and merged with neighboring voids to generate cracks near solder edges. • 3D X-ray was used to map the positions of EM-induced voids and necking. • SEM was also employed to verify such EM-induced failures mapped by 3D X-ray. • EM-induced failures of hundreds of solder joints could be captured and characterized. • Voids formed at electron entrance, and the contact area gradually reduced due to solder necking. • It further expanded and merged with neighboring voids to generate cracks near solder edges.

Possibilities of Using the Method of Median Gradients to Reveal Changes in Apparent Electrical Resistivity during the Nucleation of Earthquakes

Possibilities of Using the Method of Median Gradients to Reveal Changes in Apparent Electrical Resistivity during the Nucleation of Earthquakes

Histone deacetylase activity is a novel target for epithelial barrier defects in patients with eosinophilic chronic rhinosinusitis with nasal polyps.

Studies have independently indicated that eosinophils and histone deacetylases (HDACs) may compromise the integrity of the epithelial barrier in nasal polyps; however, the underlying mechanisms are not clear. In this study, we aimed to investigate the role of eosinophilia and HDACs in regulation of tight junctions (TJs) and nasal epithelial barrier integrity in chronic rhinosinusitis with nasal polyps (CRSwNP) patients. Expression of mRNAs and proteins of TJs and HDACs of biopsy specimens and air-liquid interface (ALI) human nasal epithelial cell cultures (HNECs) from eosinophilic and noneosinophilic CRSwNP patients and healthy controls was assessed. The ALI HNECs were also assessed for changes in transepithelial electrical resistance (TER) and paracellular flux of fluorescein isothiocyanate (FITC)-labelled dextran. Meanwhile, the assessments for the effect of HDAC inhibitor in eosinophilic nasal polyps were also conducted. Decreased TER and increased paracellular flux of FITC-labelled dextran in the ALI cultures were found in both eosinophilic and noneosinophilic CRSwNP, along with irregular, patchy and reduced expression of claudin-1, 4, 7, occludin, zonula occludens (ZO)-1 and ZO-2 and increased expression of HDAC1, 9 and SIRT7 for both ALI culture cells and biopsy specimens, especially for the eosinophilic CRSwNP group. Treatment of eosinophilic CRSwNP ALI-HNECs with an HDAC inhibitor improved the TJs expression and epithelial barrier integrity. Our data suggest that eosinophilia and HDACs influence epithelial barrier function in CRSwNP patients by regulating TJ protein expression. Targeting HDACs with specific inhibitors may be a potential treatment option for patients with eosinophilic CRSwNP.

Combined effects of residual stress and microstructure on degradation of Cu thin films on Si

In this paper, combined effects of residual stress and microstructure on degradation of Cu thin films on Si have been investigated. Magnetron sputtering with different processing parameters produced cracked and non-cracked Cu films with various grain sizes and residual stresses. Phase transformation and the change in electrical resistance of the Cu thin films have been analyzed for different annealing conditions. It has been revealed that non-cracked and large-grained (25.2±8.9nm) Cu films with high tensile residual stress (186 MPa) result in the most significant degradation (sheet resistance increase of 894%) upon annealing at 300°C. Specimens with smaller grains (17.3±6.4 nm) and low residual stress (41.6 MPa) or cracks showed no increase in sheet resistance after annealing at 300°C. The microstructural evaluation showed that residual stress of Cu affects the grain growth rate during annealing, which is closely related to the Cu/Si interdiffusion behavior.

Evolution of short-range order and its effects on the plastic deformation behavior of single crystals of the equiatomic Cr-Co-Ni medium-entropy alloy

Short-range ordering (SRO), its evolution in the equiatomic Cr-Co-Ni medium-entropy alloy (MEA), and its effects on mechanical properties were investigated by, respectively, electrical resistivity measurements and tension and compression tests on single crystal specimens at room temperature and liquid nitrogen temperature. SRO below 973 K can be monitored by changes in electrical resistivity, which increases gradually with time to a saturation value during isothermal annealing in the temperature range of 673–973 K. While the time required to reach saturation is shorter at higher temperatures, the saturation resistivity is higher at lower temperatures, indicating a higher degree of SRO at lower temperature although it takes longer to reach saturation because of slower kinetics. No significant change in the plastic deformation behavior is found at room temperature and 77 K for different degrees of SRO. The yield stress as well as the slip localization behavior are basically the same after SRO, and the magnitude of yield drop does not correlate with the degree of SRO. Tensile stress-strain curves are not much affected by SRO up to high strain levels, resulting in identical shear stresses for the onset of deformation twinning at room temperature regardless of the degree of SRO. The dislocation structure, variations in dislocation dissociation width, and stacking fault energy are all essentially unchanged.

Structural performance of reinforced concrete beams with 3D printed cement-based sensor embedded and self-sensing cementitious composites

Cementitious composites containing conductive functional fillers can achieve self-sensing and continuous monitoring of the damages and cracks through piezoresistive characteristics defined as the electrical resistivity change under external deformation. Previous studies developed two types of self-sensing cementitious composites expressing superior piezoresistive characteristics, as well as good linearity, repeatability, and sensitivity. This research further investigates the flexural damage sensing capability of the developed self-sensing cementitious composites by applying them to reinforced concrete beams. The 3D printed self-sensing cementitious composites containing carbon fibre (CF) at 0.7 wt% and activated carbon powder (ACP) at 0.25 wt% were tested as the embedded sensors in this study. Mould cast self-sensing cementitious composites developed by 100 wt% of magnetite aggregate (MA), 0.3 wt% of CF, and 0.05 wt% of carbon nanotube (CNT) were examined in bulk form. The corresponding fractional change in resistivity (FCR) was attained on the tension face of the reinforced concrete beams when subjected to flexural loading. Experimental findings suggest that the embedded 3D printed cement-based sensors in beam elements can contribute to the load-carrying capacity of the reinforced concrete beam, achieving an average load of yielding at 88.65 kN and a maximum loading capacity of 111.09 kN, which is 10% and 12% higher compared with the controlled reinforced concrete beam, respectively. In terms of sensing performance, both 3D printed self-sensing cementitious composites in sensor form and mould cast self-sensing cementitious composites in bulk form could reflect stress and strain changes and detect crack formation in reinforced concrete beams, which demonstrate gage factors at 318 and 527, respectively. However, 3D printed cementitious sensors are more effective when reinforced concrete beams are severely damaged. In terms of self-sensing cementitious composites in bulk form, the randomly distributed CF and CNT could provide a more pronounced crack and damage sensing capability, with fluctuations that can be observed at both low and high levels of damage.

Hydrogen diffusion and its electrical properties variation as a function of the IGZO stacking structure

The oxygen vacancies and hydrogen in oxide semiconductors are regarded as the primary sources of charge carriers and various studies have investigated the effect of hydrogen on the properties of oxide semiconductors. However, the carrier generation mechanism between hydrogen and oxygen vacancies in an a-IGZO semiconductor has not yet been clearly examined. In this study we investigated the effect of hydrogen and the variation mechanisms of electrical properties of a thin film supplied with hydrogen from the passivation layer. SiOx and SiNx, which are used as passivation or gate insulator layers in the semiconductor process, respectively, were placed on the top or bottom of an a-IGZO semiconductor to determine the amount of hydrogen penetrating the a-IGZO active layer. The hydrogen diffusion depth was sufficiently deep to affect the entire thin semiconductor layer. A large amount of hydrogen in SiNx directly affects the electrical resistivity of a-IGZO semiconductor, whereas in SiOx, it induces a different behavior from that in SiNx, such as inducing an oxygen reaction and O–H bond behavior change at the interface of an a-IGZO semiconductor. Moreover, the change in electrical resistivity owing to the contribution of free electrons could be varied based on the bonding method of hydrogen and oxygen.

Soft Multifunctional Porous Sponge Sensor for Pressure and Strain Using Liquid Metal/Polydimethylsiloxane with Silver-Nanowire-Coated Composite.

Compression and tension sensors with a porous structure have attracted attention recently. Porous sponge sensors have the advantage of a wide deformation range owing to their structural characteristics. In this study, a porous sponge structure was prepared by absorbing polydimethylsiloxane (PDMS) into the matrix of porous commercial sugar cubes. A conductive network was formed by coating the outside of the sponge skeleton with silver nanowires (AgNWs), which have a high aspect ratio. In addition, a liquid metal (LM), which does not directly form an electrical network but changes from zero-dimensional to one-dimensional under an external force was introduced into this porous sponge structure. The effects of the LM on the sensor sensitivity to pressure and strain were analyzed by comparing the electrical resistance changes of PDMS/AgNW and LM/PDMS/AgNW sponge sensors under tension and pressure. This study shows that the use of a porous structure and an LM may be useful for future wearable sensor design.

Design and Fabrication of a Gas Sensor Based on a Polypyrrole/Silver Nanoparticle Film for the Detection of Ammonia in Exhaled Breath of COVID-19 Patients Suffering from Acute Kidney Injury.

One of the serious complications of COVID-19 is acute kidney injury (AKI), leading to a decrease in kidney function and even death. The concentration of ammonia (NH3) in the exhaled breath (EB) of COVID-19 patients suffering from AKI symptoms will be significantly increased. In this work, the detection of breath NH3 was performed at gold interdigital electrodes modified with a soluble polypyrrole microparticle and silver nanoparticle film (Au-IDEs/S-PPyMPs/AgNPs) as a noninvasive chemiresistor gas sensor. The response behavior of unmodified and modified gas sensors toward NH3 and other interfering compounds was studied. The Au-IDEs/S-PPyMPs/AgNPs exhibited NH3 detection in the linear dynamic range of 1.00-19.23 ppm, with a limit of detection of 0.12 ppm. Finally, the fabricated gas sensor was used to monitor the NH3 concentration in the EB of COVID-19 patients suffering from AKI symptoms. For this purpose, the gas sensor was validated in 19 EB samples (seven COVID-19-positive patients, four COVID-19-negative patients, and eight post-COVID-19 patients). The gas sensor was directly exposed to the EB samples, followed by recording the changes in electrical resistance via a low-cost digital multimeter. The sensing mechanism was explained as the interaction between breath NH3 and sensing materials. The breath NH3 concentrations have a desirable correlation (R2 = 0.8463) with the estimated glomerular filtration rate (eGFR) values in COVID-19-positive patients. The fabricated gas sensor can distinguish COVID-19-positive patients suffering from AKI symptoms from COVID-19-negative patients and post-COVID-19 patients. The present work can pave the way for the development of a simple and efficient analytical approach for COVID-19 patients with AKI without the need for sample pretreatment.

Recent Advances in Gas Sensing Technology Using Non-Oxide II-VI Semiconductors CdS, CdSe, and CdTe

In recent years, there has been an increasing need and demand for gas sensors to detect hazardous gases in the atmosphere, as they are indispensable for environmental monitoring. Typical hazardous gas sensors that have been widely put to practical use include conductometric gas sensors, such as semiconductor gas sensors that use the change in electrical resistance of metal oxide semiconductors, catalytic combustion gas sensors, and electrochemical gas sensors. However, there is a growing demand for gas sensors that perform better and more safely, while also being smaller, lighter, less energy-demanding, and less costly. Therefore, new gas sensor materials are being explored, as well as optical gas sensor technology that expresses gas detection not electrically but optically. Cadmium sulfide (CdS), cadmium selenide (CdSe), and cadmium telluride (CdTe) are typical group II-VI non-oxide semiconductors that have been used as, for example, electronic materials. Recently, they have attracted attention as new gas sensor materials. In this article, recent advances in conductometric and optical gas sensing technologies using CdS, CdSe, and CdTe are reviewed.

SUBSTITUTIONAL MODEL OF THE SOIL BASED ON ARTIFICAL NEURAL NETWORKS

This paper presents an interpretation of the results of measurement of specific soil resistivity by means of artificial neural networks. The model based on artificial neural networks replaces the soil which can be physically considered a two-layer medium with a vertical change of the specific electric resistivity and a horizontal boundary line between the layers. Learning of the neural network was performed under supervision using the input dataset obtained by means of a very accurate theoretical model of the double-layer soil. The proposed algorithm that approximates non-linear soil properties using the artificial neural network is reliable in assessment of the soil parameters and specific electric soil resistivity. Application of the substitutional model of the soil based on neural networks is demonstrated by a realistic example, determination of parameters of the double-layer soil from the measured data obtained by the Wenner technique for measuring the specific soil resistivity. For simplicity of presentation and model comparability, the current probes (poles) are replaced by the ball electrodes, i.e. spot fi eld sources. The results obtained are analytically and graphically presented and discussed.

Structural Health Monitoring of Repairs in Carbon-Fiber-Reinforced Polymer Composites by MWCNT-Based Multiscale Sensors

The precision maintenance of delaminated carbon-fiber-reinforced polymer composites calls for the high demand of continuous, in situ monitoring of the damage-repair process along with the in-service status of the repaired region. Moreover, the repaired region faces a high risk of re-damage; therefore, in-service monitoring is highly desired. However, the current repair process lacks the in situ monitoring function, leading to the mechanism and evaluation of the repair approach being unclear. Here, we implanted multi-wall carbon nanotubes (MWCNTs) at the interface between the carbon fiber and resin matrix of the damaged region to achieve in situ monitoring of the repair, compression, and seawater-immersion processes. By depositing both the coupling agent and MWCNTs at the interfaces, a high recovery efficiency of 85% was achieved, which was independent of the delamination pattern shapes. The electric resistance changes of MWCNT-modified panels could effectively identify the resin permeation and solidification processes and could be used to in situ monitor the structural health of the repair region when it is subjected to the compression and seawater immersion tests. This strategy, combining high-efficient repair and precision maintenance, demonstrates potential in the structural applications of carbon-fiber-reinforced polymer composites.

First-principles predictions of stable structure of AuAl2 under high pressure

Pressure-induced phase transformation of AuAl2 had been theoretically investigated by using crystal structure searching technique combined with first-principles calculations. The predicted orthorhombic Pbnm structure possesses a larger structural stability with pressure larger than 17 GPa, and transition pressure is consistent with experimental value. The simulated x-ray diffraction patterns of Pbnm structure are in satisfactory agreement with the experimental data. The specific density of states indicate that there are discontinuous changes of electrical resistance accompanying with phase transition, and these are in accordance with experimental observations. Moreover, phonon dispersions and elastic constants reveal that Pbnm structure has dynamical and mechanical stabilities. The directional dependence of Young's modulus was analyzed and Pbnm phase has a larger elastic anisotropy.

The Effect of Multi-Walled Carbon Nanotubes on the Heat-Release Properties of Elastic Nanocomposites

Of great importance in materials science is the design of effective functional materials that can be used in various technological fields. Nanomodified materials, which have fundamentally new properties and provide previously unrealized properties, have acquired particular importance. When creating heating elements and materials for deformation measurement, it is necessary to understand the patterns of heat release under conditions of mechanical deformation of the material, as this expands the potential applications of such materials. A study of elastomers modified with multi-walled carbon nanotubes (MWCNTs) has been carried at the MWCNTs concentration of 1–8 wt.%. The modes of heat release of nanomodified elastomers at a voltage of 50 V at different levels of tension are reported. The increment of the MWCNTs concentration to 7 wt.% leads to an increment in the power of heat emissions. It is worth noting the possibility of using the obtained elastomer samples with MNT as sensitive elements of strain sensors, which will allow obtaining information about physical and chemical parameters following the principles of measuring the change in electrical resistance that occurs during stretching and torsion. The changes in conductivity and heat emission under different conditions have been studied in parallel with Raman mapping and infrared thermography. The reported studies allow to make the next step to develop flexible functional materials for the field of electric heating and deformation measurement based on elastic matrices and nanoscale conductive fillers.

Resistive type NO2 gas sensing in polymer-dispersed liquid crystals with functionalized-carbon nanotubes dopant at room temperature

The embedding of liquid crystal (LC) droplets into polymer matrices yields polymer-dispersed liquid crystals (PDLCs), which play an important role in the formation of mechanically resistant films for flexible photonic devices. Despite the fact that PDLCs respond to a variety of physical and chemical stimuli, LCs have had limited success in detecting environmental pollutants due to a lack of reactive functional groups in their structures. In this work, we execute the idea of integrating functionalized carbon nanotubes (f-CNTs) into PDLCs to accelerate the absorption of gas molecules at room temperature (RT). The proposed f-CNT-PDLC sensor device was prepared by depositing the composite mixture onto an interdigitated electrode substrate and carrying out phase separation under UV light exposure. Compared to the pure PDLC device, the proposed device exhibited a response of ~12.9 % and 1 % for 100 and 5 ppm of NO 2 gas, and a linear relationship was obtained with gas concentrations. Furthermore, this device displayed a good reproducibility over five cycles, exhibiting an excellent selectivity against other interfering gases, such as H 2 S, CO, H 2 , and NH 3 . The boosted response was attributed to charge transport between the NO 2 gas molecules and the f-CNTs, which was detected by measuring the change in electrical resistance caused by the f-CNTs, in addition to the orientational phase modulation of the f-CNTs and the LCs within a droplet. Our experimental results revealed that the proposed f-CNT-doped PDLCs are promising candidates for sensing various physical and chemical stimuli. • An f-CNT-doped PDLC sensor device was developed for NO 2 gas detection. • The f-CNT dopant significantly improved the sensing performance of the PDLC device. • A difference in the droplet configuration was identified with NO 2 gas molecules. • A fast and specific sensing response was achieved with proposed f-CNT-PDLC sensor.

Kirigami inspired shape programmable and reconfigurable multifunctional nanocomposites for 3D structures

The ability to shape and program remotely and contactlessly from two-dimensional (2D) flat multilayer materials into three-dimensional (3D) structures and functional devices could be ideal for applications like space missions, environmental remediation and minimally invasive surgery. However, achieving a fast and accurate deployment of complex 3D shapes contaclessly at low energy consumption, while embedding a number of physical propertiesand functionalities, remains very challenging. Herein, a strategy to widen the complexity space of 3D shapes and functions achievable is demonstrated, by enabling a controlled sequential folding while incorporating nano-reinforcements. Sequential folding was successfully achieved and a honeycomb structurewas developed by designing multilayer polymer films with different kirigami patterns - each responding at a different rate upon heating. A finite element method (FEM) model was developed to better understand the main underlying physical mechanism as well as to feedback into materials and structure design. Moreover, a shape-programmed CNT veil-based honeycomb structure was developed, triggered remotely by thermal stimuli, with capability to self-sense the folding state through the electrical resistance change (ΔR/R0 = 100–300 %). Overall, it was demonstrated that designing layered nanocomposites with different 2D patterns allows an accurate sequential folding into 3D structures, with bespoke physical properties and integrated sensing–actuating functionalities.