Changes In Electrical Conductivity Research Articles

Preparation of carbon-coated Fe2 O3 @Ti3 C2 Tx composites by mussel-like modifications as high-performance anodes for lithium-ion batteries.

Fe2 O3 with high theoretical capacity (1007 mA h g-1 ) and low cost is a potential anode material for lithium-ion batteries (LIBs), but its practical application is restricted by its low electrical conductivity and large volume changes during lithiation/delithiation. To solve these problems, Fe2 O3 @Ti3 C2 Tx composites were synthesized by a mussel-like modification method, which relies on the self-polymerization of dopamine under mild conditions. During polymerization, the electronegative group (-OH) on dopamine can easily coordinate with Fe3+ ions as well as form hydrogen bonds with the -OH terminal group on the surface of Ti3 C2 Tx , which induces a uniform distribution of Fe2 O3 on the Ti3 C2 Tx surface and mitigates self-accumulation of MXene nanosheets. In addition, the polydopamine-derived carbon layer protects Ti3 C2 Tx from oxidation during the hydrothermal process, which can further improve the electrical conductivity of the composites and buffer the volume expansion and particle agglomeration of Fe2 O3 . As a result, Fe2 O3 @Ti3 C2 Tx anodes exhibit ~100 % capacity retention with almost no capacity loss at 0.5 A g-1 after 250 cycles, and a stable capacity of 430 mA h g-1 at 2 A g-1 after 500 cycles. The unique structural design of this work provides new ideas for the development of MXene-based composites in energy storage applications.

Ab. No. 162 Autonomic Tone (Galvanic Skin Response) During Vertical Height Tolerance (VHT) Using Stairs in Young Adults: A Cross-Sectional Study

Introduction: Autonomic tone influences segmental dissociation, balance strategies and the control of the centre of gravity during activities of daily living (ADL). Stair climbing is a common ADL which has been noted to be challenging and linked to fear avoidance. It is vital to understand the activity of the autonomic nervous system (ANS) during stair climbing in the normal population, to optimize therapies for the patient population. The GSR is an objective measure of the ANS that detects changes in electrical conductivity of the skin due to increased sweat gland activity, seen in fearful individuals. The study aims to understand the changes in the autonomic tone measured by galvanic skin response (GSR) during VHT using stairs in young adults. Methods: 34 young adults (18 to 25 years) were recruited based on the eligibility criteria using convenience sampling. A cross-sectional study was performed. Baseline GSR was recorded for 20 seconds in both sitting and standing positions. Participants were then required to stand at the edge of 4 steps with uniform height increments. GSR values were recorded on each step with eyes open and eyes closed for 20 seconds each. Result: ANOVA showed statistically significant difference between each task position (χ 2=175, p<0.001). Statistically significant difference was seen in DSCF Pairwise comparisons between baseline sitting & all positions (p<0.001), step 1 & step 3 (w=4.8, p<0.003) and step 1 & step 4 (w=5.9, p<0.001). Conclusion: VHI using stairs generates significant changes in the autonomic tone in young adults. Implications: Understanding the sensitivity of the GSR response during ADLs such as stair climbing in normal populations may help optimize treatment techniques in the patient population having a fear of falls

Self-indicating polymers: a pathway to intelligent materials.

Self-indicating polymers have emerged as a promising class of smart materials that possess the unique ability to undergo detectable variations in their physical or chemical properties in response to various stimuli. This article presents an overview of the most important mechanisms through which these materials exhibit self-indication, including aggregation, phase transition, covalent and non-covalent bond cleavage, isomerization, charge transfer, and energy transfer. Aggregation is a prevalent mechanism observed in self-indicating polymers, where changes in the degree of molecular organization result in variations in optical or electrical properties. Phase transition-induced self-indication relies on the transformation between different phases, such as liquid-to-solid or crystalline-to-amorphous transitions, leading to observable changes in color or conductivity. Covalent bond cleavage-based self-indicating polymers undergo controlled degradation or fragmentation upon exposure to specific triggers, resulting in noticeable variations in their structural or mechanical properties. Isomerization is another crucial mechanism exploited in self-indicating polymers, where the reversible transformation between the different isomeric forms induces detectable changes in fluorescence or absorption spectra. Charge transfer-based self-indicating polymers rely on the modulation of electron or hole transfer within the polymer backbone, manifesting as changes in electrical conductivity or redox properties. Energy transfer is an essential mechanism utilized by certain self-indicating polymers, where energy transfer between chromophores or fluorophores leads to variations in the emission characteristics. Furthermore, this review article highlights the diverse range of applications for self-indicating polymers. These materials find particular use in sensing and monitoring applications, where their responsive nature enables them to act as sensors for specific analytes, environmental parameters, or mechanical stress. Self-indicating polymers have also been used in the development of smart materials, including stimuli-responsive coatings, drug delivery systems, food sensors, wearable devices, and molecular switches. The unique combination of tunable properties and responsiveness makes self-indicating polymers highly promising for future advancements in the fields of biotechnology, materials science, and electronics.

Electronic and elastic properties of metastable Zr3N4: a joint experimental and theoretical study.

The electronic structures and elastic properties of metastable Zr3N4 phases have been investigated using the first-principles calculations with the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional, in comparison with those of the stable ZrN phase. All three metastable Zr3N4 phases (including orthorhombic, spinel and Th3P4-type phases) are found to be semiconducting with bandgaps of 1.72-1.94 eV. In particular, the computationally indirect bandgap of 1.72 eV of orthorhombic Zr3N4 is consistent with the experimental value of 1.8 eV. The detailed analyses of the electronic structures reveal that the change of electrical conductivity from metallic ZrN to semiconducting Zr3N4 is mainly due to the electron transfer from Zr to N atoms, which weakens the Zr-Zr interactions and reduces the proportion of metallic bonding. In addition, the elastic properties of Zr3N4 and ZrN phases have been calculated. The theoretical hardness values of ZrN and orthorhombic Zr3N4 are 18.06 and 6.98 GPa, respectively, agreeing well with the experimental values of 19.26 and 7.90 GPa. This work may further promote the understanding of the promising Zr-N material system.

Study of electrical conductivity of fluorine-conducting solid electrolytes based on lead fluoride

Samples of solid electrolytes based on β-Pb F2 doped with ScF3 were synthesized. The dependence lg σT has been studied from 1/Т the samples received. Significant changes in electrical conductivity and enthalpy are observed at an impurity concentration of 0,05±0,02. It has been established that as the content of SсF3 molecules in a solid solution increases, the number of defective regions increases and at a certain impurity concentration their spatial overlap occurs. The formation of a closed three-dimensional network of the defect phase corresponds to percolation and is accompanied by a change (often sharp) in the conductivity and other properties of solid solutions.

Assessment of Physicochemical Properties and Heavy Metal Content of Floriculture Soil in Amhara Region of Northwest Ethiopia.

Floriculture is a new and rapidly expanding sector in Ethiopia that aids economic growth but has also come under blame for pollution of the surrounding soil. The purpose of this study was to assess the soil physicochemical properties and heavy metal contents in floriculture in the Amhara Region of Northwest Ethiopia. Soil samples were collected from seven different greenhouses (2ABC, 4DEF, 5ABC, 7DEF, 8ABC, 9DEF, and 11DEF), and a control soil sample was taken on the 15-cm depth from a nearby agricultural area. They were analyzed for soil physicochemical parameters and heavy metal compositions. Soil texture showed a significant difference between the soils sampled from the greenhouses and the control group. The highest average clay, silt, and sand contents were recorded in the control group, 4DEF, and 9DEF, respectively. The lower clay content was at 9 DEF, silt at 11 DEF, and sand in the control group. Clay was positively correlated to soil pH (r = 0.66) and TN (r = 0.38) but showed significant negative correlation with the sand fraction (r = -0.96). The average bulk density (BD) values of the soils from the greenhouses were within acceptable ranges; however, the mean BD value of 7DEF was relatively highest (1.34 g/cm3). There were significant (P < 0.05) changes in soil pH and electrical conductivity, with pH values ranging from 5.8 to 7.17 and EC from 0.08 to 1.72 mScm-1. Soil organic carbon, available phosphorus, total nitrogen, and carbon-to-nitrogen ratio of the soil samples from the greenhouses and the control group were significantly different. There were also significant differences in soil exchangeable aluminum and acidity between greenhouse soil samples and the control group. Soil contents of some of the heavy metals (Pb, Cd, Mn, and Cu) in the floriculture soil were above the permissible limits, while Cr, Zn, and Ni contents were below. The soil in floriculture showed low quality compared to the control group and international standards, indicating the need for improved soil quality management. This study recommends reducing agrochemical use, increasing bio-fertilizers, using botanicals, and transitioning to organic farming. Further studies are needed to assess soil microbial diversity and abundance for soil fixation.

Removal of Crystal Violet Dye by Electrocoagulation – Analysis of Electrode and Solution Changes

This study investigates the changes at the electrodes and in the solution during crystal violet dye removal by electrocoagulation at different current densities (0.016, 0.024, and 0.032 A cm&amp;lt;sup&amp;gt;–2&amp;lt;/sup&amp;gt;) and initial pH values (3.2, 5.5, and 7.0). The electrocoagulation process, which lasted 50 min, revealed changes in pH, temperature, electrical conductivity, and concentration of the crystal violet dye in the solution. The results demonstrate complete removal of crystal violet dye at the highest current density (achieved after 40 min) and an initial pH of 5.5 (complete removal after 30 min). During the electrocoagulation process, both the anodic and cathodic electrode materials were consumed. The consumption of electrode material increased with higher current density and solution pH, the influence of current density being more pronounced. Examination of the electrode surfaces under a light microscope revealed that the anodes dissolved uniformly and locally during the electrocoagulation process, while the cathodes mostly underwent uniform corrosion.

Stochastic wave propagation in magneto-thermoelastic materials subjected to the change in electrical and thermal conductivity

This paper presents the results of an investigation that focuses on the stochastic wave propagation that occurs within an elastic medium when the thermoelectric properties are taken into consideration. It has been found that there is a clear association between the characteristics of electrical conductivity and thermal conductivity. As a result, the current topic focuses on the influence a magnetic field has on the variable thermal conductivity and electrical conductivity that exists within a material. This is done within the context of dual phase lag thermoelasticity. Several parameters are incorporated into the governing equations, which exhibit coupling. Thermal shock has been applied to the boundary of the medium that represents the non-traction barrier. At the border of the problem, stochasticity is imposed in order to make the problem appear more realistic. Within the boundary conditions, it is presumed that the white-noise function is present. Utilizing the Laplace transform method is the approach that is taken to address the issue. It is possible to determine the inverse transformations using numerical approximation approaches. Both graphical and visual analyses are performed on the dataset. In conclusion, graphical representations are utilized in order to make comparisons between the deterministic and stochastic solutions of all physical fields.

Electrical properties of PbO–Bi2O3–Ga2O3 glasses with addition of Ag2O and Sb2O3

Formation of Ag nanoparticles in the PbO–Bi2O3–Ga2O3 heavy metal oxide glasses modified by addition of Ag2O and Sb2O3 was monitored using electrical and optical measurements. Electrical measurements are suitable for this purpose as they are very sensitive to any changes in the arrangement of the material structure. The formed spherical silver nanoparticles were studied by a high-resolution transmission electron microscopy (HRTEM), their nature was confirmed by selected area electron diffraction analysis (SAED) and x-ray photoelectron spectroscopy (XPS). We demonstrated and documented that the samples containing Ag/Sb change during additional heating (in the investigated temperature range of 240–290 °C) – the electrical conductivity changes and also the relaxation time as established by electrical modulus measurements changes. The behaviour of the base glass without Ag/Sb addition remains practically unaffected by the same additional heating. TEM confirmed an increased number of spherical nanoparticles as a consequence of heat treatment. The indexes of the SAED pattern match the fcc-Ag crystalline phase, HRTEM identified the periodical arrangement in these particles to correspond to d-spacing of (111) planes in Ag and the elemental state of the present Ag in the heat-treated sample was confirmed also by XPS.

Using Magnetic Field Analysis for Localizing Defects of Fuel Cell & Electrolyzer Components

Production capacities of electrolysis and fuel cell technologies are expected to increase significantly in the upcoming years, reducing costs of stack components through numbering-up. To ensure reliability and durability and reduce costs along the manufacturing process, developing suitable in-line non-destructive diagnostic methods for quality control becomes essential for their industrialization.In both fuel cell and electrolyzer stacks, the main components' electrical resistance and current density distribution greatly influence stack efficiency and longevity. Here, the flowing electric current generates a magnetic field depending on its strength and direction. Potential defects caused by the manufacturing process, including cracks, defective welding spots, coating adhesion issues, delamination, and contamination, influence the components' electric conductivity and current density distribution and hence the magnetic field distribution.This work investigates non-destructive diagnostic methods using magnetic field analysis (MFA) to identify changes in the magnetic field distribution and, thus, local electrical resistance and current density distributions of fuel cell and electrolyzer components. The methods used are magnetic field imaging (MFI) and Eddy Current Testing (ECT). MFI analyzes the magnetic field distribution in all three spatial directions to trace electrical currents and identify electrical defects, creating a magnetic field signature that can potentially distinguish between functional and non-functional components along the manufacturing process. ECT measures variations in local conductivity by inducing eddy currents in the sample through an alternating magnetic field generated by a sender coil. These eddy currents create a detectable magnetic field in a receiver and are affected by defects and changes in electrical conductivity. Therefore, the method can characterize sheet resistance and material homogeneity through electrical anisotropy in electrically conductive components.In initial experiments, ECT measurements on coated and uncoated hollow embossed stainless steel bipolar half plates showed systematic differences depending on quality characteristics resulting in unique patterns and inhomogeneities which require further investigation. Furthermore, experiments with both methods on other stack components will be presented and discussed. In addition, their in-line capability will be assessed and evaluated. However, these first promising results imply that MFA is potentially useful as an in-line, non-destructive diagnostic method for quality control.

A Discolorable Flexible Synaptic Transistor for Wearable Health Monitoring.

Multifunctional intelligent wearable electronics, providing integrated physiological signal analysis, storage, and display for real-time and on-site health status diagnosis, have great potential to revolutionize health monitoring technologies. Advanced wearable systems combine isolated digital processor, memory, and display modules for function integration; however, they suffer from compatibility and reliability issues. Here, we introduce a flexible multifunctional electrolyte-gated transistor (EGT) that integrates synaptic learning, memory, and autonomous discoloration functionalities for intelligent wearable application. This device exhibits synergistic light absorption coefficient changes during voltage-gated ion doping that modulate the electrical conductance changes for synaptic function implementation. By adaptively changing color, the EGT can differentiate voltage pulse inputs with different frequency, amplitude, and duration parameters, exhibiting excellent reversibility and reliability. We developed a smart wearable monitoring system that incorporates EGT devices and sensors for respiratory and electrocardiogram signal analysis, providing health warnings through real-time and on-site discoloration. This study represents a significant step toward smart wearable technologies for health management, offering health evaluation through intelligent displays.

Theoretical and Experimental Studies of Molecular Interactions between Engineered Graphene and Phosphate Ions for Graphene-Based Phosphate Sensing.

Fundamental understanding of the interactions of nanoscale materials with molecules of interest is essential for the development of electronic devices, such as sensors. In particular, structures and molecular interaction properties of engineered graphenes are still largely unexplored, despite these materials' great potential to be used as molecular sensors. As an example of end user application, the detection of phosphorus in the form of phosphate in a soil environment is important for soil fertility and plant growth. However, due to the lack of an affordable technology, it is currently hard to measure the amount of phosphate directly in the soil; therefore, suitable sensor technologies need to be developed for phosphate sensors. In this work, pristine graphene and several modified graphene materials (oxygenated graphene, graphene with vacancies, and curved graphene) were studied as candidates for phosphate sensor materials using density functional theory (DFT) calculations. Our calculations showed that both pristine graphene and functionalized graphene were able to adsorb phosphate species strongly. In addition, these graphene nanomaterials showed selectivity of adsorption of phosphate with respect to nitrate, with stronger adsorption energies for phosphate. Furthermore, our calculations showed significant changes in electrical conductivities of pristine graphene and functionalized graphenes after phosphate species adsorption, in particular, on graphene with oxygen (hydroxyl and epoxide) functional groups. Experimental measurements of electrical resistivity of graphene before and after adsorption of dihydrogen phosphate showed an increase in resistivity upon adsorption of phosphate, consistent with the theoretical predictions. Our results recommend graphene and functionalized graphene-based nanomaterials as good candidates for the development of phosphate sensors.

Metal-organic framework-derived self-grown core-shell V2O5 for high-performance zinc ion storage

The nanostructure designing strategy is one of the most effective methods to carry out the optimization of cathode materials for aqueous zinc ion batteries (ARZIBs). The design and synthesis of materials with stable nanostructure and short ion/electron transport paths are expected to alleviate the dilemma faced by vanadium-based materials, such as poor electrical conductivity and structural changes. Ostwald ripening is a promising option in the design and fabrication of special nanostructures such as hollow and core shells. Selecting vanadium-based metal-organic frameworks (V-MOF) as reactants, we successfully obtained vanadium oxide precursors with self-growing core-shell structures in one-step. As the reaction time increases, the vanadium oxide precursors undergo the process of microspheres → core-shell → yolk shell, which is thought to be the result of Ostwald ripening. After annealing, the vanadium oxide precursor becomes a "core-shell" structure vanadium pentoxide (core-shell V2O5). The ARZIBs assembled with core-shell V2O5 cathodes showed superior capacity (309.4 mAh/g at 0.1 A/g) and cycling stability (91.4 % capacity retention after 4000 cycles at 3A/g). Hence, we successfully realized the self-growth of vanadium oxide with core-shell structure in one step but also revealed the crystallization process based on Ostwald ripening and its zinc storage mechanism, which provides new possibilities for the facile synthesis of special nanostructured ARZIB cathode materials.

Facile and Cost-Effective Fabrication of Highly Sensitive, Fast-Response Flexible Humidity Sensors Enabled by Laser-Induced Graphene.

The need to simplify fabrication processes and reduce costs for high-performance humidity sensors is increasingly vital, especially in fields such as healthcare and agriculture. This study introduces a simple and cost-effective approach using laser-induced graphene (LIG) on a polyimide film to create highly sensitive and fast-response flexible humidity sensors. The LIG acts as the electrode, while the porous polyimide between the interdigital LIG electrodes serves as the humidity sensing material, showing changes in electrical conductivity based on the humidity levels. The LIG humidity sensor, an ionic-conduction type, exhibits remarkable sensitivity, with a 28,231-fold increase in current as relative humidity changes from 26.1 to 90.2%. It also boasts of ultrashort response/recovery times (less than 0.5/7 s), providing significant advantages in detecting rapid and subtle humidity variations compared to a commercially available MEMS humidity sensor. We successfully demonstrated the LIG humidity sensor's capabilities in ultrafast breathing monitoring (≈174 times per minute), moisture detection of grains, and detection of sudden water pipe leakage. Due to its straightforward and cost-effective fabrication process, the LIG humidity sensor holds immense practical value for affordable, widespread use across various applications.

High sensitive humidity sensor based on PEDOT:PSS/CMC-Na coated polyester fabric with directional moisture transport performance

Flexible humidity sensors with excellent flexibility and sensitivity have been widely used in various fields such as human and plant health monitoring and management, non-contact human-machine interaction, smart e-textiles, and industrial and agricultural production. However, many sensors are limited their application due to the problems of unbreathable and poor wear comfort. Herein, a highly sensitive humidity sensor based on flexible polyester fabric with directional moisture transport is proposed. The facile method of coating is conducted by the preparation of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) and sodium carboxymethylcellulose (CMC-Na) paste with adjustable content and applied to the polyester fabric. The difference of hydrophilicity between the two sides of the fabric caused by the coating helps to directional moisture transport, thus giving rapid sensitivity, while using PEDOT: PSS can obtain the changes of electrical conductivity coming from the humidity. and the addition of CMC-Na not only helps the coating, but also provides hydrophilic groups, which is conducive to humidity sensing and directional moisture transport. The combination of this moisture-sensitive coating and directional moisture transport gives the sensor a fast humidity response time of 0.35 s, a wide humidity detection range (0‐100%(0–100% RH) and sensitivity of 4.15. Furthermore, the sensor can maintain the humidity response time in milliseconds even after being subjected to water washing and friction, indicating its excellent durability and stability.

The effects of physical treatment on physicochemical and biological properties of water and aqueous solutions

Objectives. Changes to the properties of water caused by factors such as pressure or temperature, can only be explained by its structural changes. Scientists study changes to the properties of water due to various physical stimuli only without the addition of any substances. Examples of stimuli are acoustic exposure, thermal exposure, pressure variation, shaking, intensive vibration treatment followed by dilutions, vortexing, bubble generation, inter alia.The aim of the present review article is to summarize the available data on how the above processes affect the physicochemical and biological properties of water and aqueous solutions.Results. It has been shown that heating makes water less compressible and decreases air solubility in water, while cooling enhances its viscosity. Acoustic exposure makes the structure of water become coarse-grained, followed by an increase the number of large clusters, pH and temperature inside a cavitation bubble. High pressure enhances the viscosity, self-diffusion, and compressibility of water. For bubble processed water, there are changes in the spin-spin and spin-lattice relaxation times. Reactive oxygen species are formed, as well as increased solubility of gases in liquids and reduced friction. Vortex process technology causes an increase of electrical conductivity of water and reduced viscosity. Intensive vibration treatment and dilution processes result in changes in electrical conductivity of water, dissolved gas concentration, ultrasonic wave velocity, рН, surface tension, dielectric constant, and spectral response. There is also data to support the biological effects of different types of physical treatment of solutions.Conclusions. This review shows that physical treatment of water can induce changes both in physicochemical and biological properties of water and aqueous solutions.

Optimization of water repellency in soils for geotechnical applications

ABSTRACT Applying organo-silanes (OS) as water-repellent additives can enhance soil properties, crucial for use as moisture barriers in infrastructures like roads, landfills, and tunnels. This study used four soil samples and glass beads, treated with three OS products at dosages from 1:1 to 1:1000. Laboratory tests included contact angle, water drop penetration, and breakthrough pressure on 216 samples. Results showed increased hydrophobicity with higher OS dosages, with contact angles over 110° and Water Drop Penetration Test times above 3600s. However, effectiveness plateaued at certain dosages, indicated by electrical conductivity and pH changes. The primary factors (94.6% influence) were soil type, OS product, dosage, and drying condition, while reaction time, and leaching/washing had a minor impact (5.4%). Treated soils could sustain a hydrostatic head of up to 17 kPa. These insights aid in optimizing water-repellency treatments for soil performance and infrastructure durability in geotechnical applications.

Surface adsorption of adenine on pristine and B/N/O/P-doped coronene as a biosensing substrate for DNA detection- DFT study

Nucleobase detection is crucial for the exploration of specific nucleotide sequences. Inspired by the recent realization of two dimensional nanomaterials as DNA detectors as well as sensors, the interactions of pristine and B/N/O/P-doped coronenes with adenine nucleobase have been studied on the basis of Density Functional Theory. Optimal configurations, the corresponding adsorption energies, charge transfer and electrical properties have been calculated for each complex. The adsorption strength and charge transfer in doped coronene have been found larger than that in the pristine coronene. AIM-RDG study suggests that non-covalent interactions existing in the associated interactive region are responsible for the stability of the complexes. The change in electrical conductivity of coronenes after the adsorption indicates its sensitivity towards DNA bases. The predicted energy gap and the prolonged recovery time for adenine-coronene configurations imply that pristine/doped coronene has potential applications in DNA detection.

The effects of humidity on the electrical properties and carrier mobility of semiconducting polymers anion-exchange doped with hygroscopic salts

To improve their electrical conductivity for various applications, semiconducting polymer films are often chemically doped to increase their equilibrium charge carrier density. Recently, a novel doping method involving anion exchange has provided control over the identity of the counterions that reside in such films, leading to increased stability under ambient conditions. In this work, however, we show that by ion-exchanging 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane-doped poly(3-hexylthiophene-2,5-diyl) films with hygroscopic salts like bis(trifluoromethane)sulfonimide lithium or LiPF6, the doped film's electrical conductivity drops significantly when exposed to ambient humidity. The change in electrical conductivity depends directly on the degree of hygroscopicity of the counterion and can be over 50% with relatively modest changes in relative humidity (RH), and up to a factor of four between ambient and completely dry conditions. The film's humidity response is entirely reversible when adsorbed water is removed, potentially allowing the doped semiconducting polymer films to function as humidity sensors. Hall effect measurements show that the cause of the drop in conductivity with increasing RH is due to a decrease in carrier mobility and not due to de-doping. Our results emphasize that it is important to control the sample environment when making electrical measurements on anion-exchange doped semiconducting polymer films.

A review of self-sensing ultra-high performance concrete: Towards next-generation smart structural materials

Today, the desired intelligent civil engineering structures urge the development of high-performance smart structural materials. Self-sensing ultra-high performance concrete (UHPC) emerged in 2014 based on the observation that the concrete structures rendered with randomly distributed conductive additives exhibit electromechanical effects under external loading, and the demand of UHPC from high-strength to sustainable, intelligent, and multifunctional. This smart structural material has since grown greatly and has been considered as one of the potential alternatives to ordinary self-sensing concrete. This paper presents a state-of-the-art review of self-sensing UHPC in terms of its raw materials, mixture design, manufacturing approaches, microstructural characteristics, mechanical properties, electrical resistivity, electromechanical properties, and applications, with a particular focus on stress-deformation/damage behaviour and changes in electrical conduction under external compression, tension, and bending. The novel uncertainties regarding electromechanical effects are thoroughly discussed from the perspective of the continuity of conductive network. Compared with ordinary self-sensing concrete, self-sensing UHPC exhibits significantly reduced porosity, exceptional strength, marginally lower stress/strain sensitivity, heightened damage sensitivity, insensitivity to humidity, and delayed cracking behaviour. In the end, this paper identifies research gaps, challenges, and recommendations in three aspects: (1) scale fabrication and cost control, (2) satisfactory and reliable properties, and (3) from smart structural materials to integrated components to civil engineering structures.