Search Results (453)

A flexible piezoresistive material based on vulcanized natural rubber (VNR) and multiwalled carbon nanotubes (MWCNTs) was developed and systematically investigated for strain sensing applications. The nanocomposites were prepared by melting and vulcanizing MWCNT, while keeping the rubber composition constant to isolate the effect of the conductive nanofiller. By scanning electron microscopy, morphological analyses indicated that MWCNTs were dispersed throughout the rubber matrix, with localized agglomerations becoming more evident at higher loadings. In mechanical tests, MWCNT incorporation increases the tensile strength of VNR, increasing the stress at break from 8.84 MPa for neat VNR to approximately 10.5 MPa at low MWCNT loadings. According to the electrical characterization, VNR-MWCNT nanocomposite exhibits a strong insulator–conductor transition, with the electrical percolation threshold occurring between 2 and 4 phr. The dc electrical conductivity increased sharply from values on the order of 10⁻¹⁴ S·m⁻¹ for neat VNR to approximately 10⁻³ S·m⁻¹ for nanocomposites containing 7 phr of MWCNT. Impedance spectroscopy revealed frequency-independent conductivity plateaus above the percolation threshold, indicating continuous conductive pathways, while dielectric analysis revealed strong interfacial polarization effects at the MWCNT–VNR interfaces. The piezoresistive response of samples containing MWCNT exhibited a stable, reversible, and nearly linear response under cyclic tensile deformation (10% strain). VNR/MWCNT nanocomposites demonstrate mechanical compliance and tunable electrical sensitivity, making them promising candidates for flexible and low-cost piezoresistive sensors. Full article

The development of flexible and self-powered electronic systems requires triboelectric materials that combine high charge retention, mechanical compliance, and stable dielectric properties. Here, we report a redox reaction approach to prepare liquid metal particle-reduced graphene oxide (LMP@rGO) core–shell structures and introduce into a poly(acrylic acid) (PAA) hydrogel to create a high-performance triboelectric layer. The spontaneous interfacial reaction between gallium oxide of LMP and graphene oxide produces a conformal rGO shell while simultaneously removing the native insulating oxide layer onto the LMP surface, resulting in enhanced colloidal stability and a controllable semiconductive bandgap of 2.7 (0.01 wt%), 2.9 (0.005 wt%) and 3.2 eV (0.001 wt%). Increasing the GO content promotes more complete core–shell formation, leading to higher zeta potentials, stronger interfacial polarization, and higher electrical performance. After embedding in PAA, the LMP@rGO structures form hydrogen-bonding networks with the hydrogel nature, improving both dielectric constant and charge retention while notably preserving soft mechanical compliance. The resulting LMP@rGO/PAA hydrogels show enhanced triboelectric output, with the 2.0 wt/vol% composite generating sufficient power to illuminate more than half of 504 series-connected LEDs. All the results demonstrate the potential of LMP@rGO hydrogel composites as promising triboelectric layer materials for next-generation wearable and self-powered electronic systems. Full article

Electric-field-sensitive dielectrics play a crucial role in electric field induction sensing and related capacitive conversion, with interfacial polarization and charge accumulation largely determining the signal output. This paper introduces graphene/transition metal dichalcogenide (TMD) (MoSe₂, MoS₂, and WS₂) heterojunctions as functional fillers to enhance the dielectric response and electric-field-induced voltage output of flexible polydimethylsiloxane (PDMS) composites. Density functional theory (DFT) calculations were used to evaluate the stability of the heterojunctions and interfacial electronic modulation, including binding behavior, charge redistribution, and Fermi level-referenced band structure/total density of states (TDOS) characteristics. The calculations show that the graphene/TMD interface is primarily controlled by van der Waals forces, exhibiting negative binding energy and significant interfacial charge rearrangement. Based on these theoretical results, graphene/TMD heterojunction powders were synthesized and incorporated into polydimethylsiloxane (PDMS). Structural characterization confirmed the presence of face-to-face interfacial contacts and consistent elemental co-localization within the heterojunction filler. Dielectric spectroscopy analysis revealed an overall improvement in the dielectric constant of the composite materials while maintaining a stable loss trend within the studied frequency range. More importantly, calibrated electric field induction tests (based on pure PDMS) showed a significant enhancement in the voltage response of all heterojunction composite materials, with the WS₂-G/PDMS system exhibiting the best performance, exhibiting an electric-field-induced voltage amplitude 7.607% higher than that of pure PDMS. This work establishes a microscopic-to-macroscopic correlation between interfacial electronic modulation and electric-field-sensitive dielectric properties, providing a feasible interface engineering strategy for high-performance flexible dielectric sensing materials. Full article

This study examines the effects of temperature, relative humidity, moisture content, and density on the dielectric constant (ε′) and dielectric loss tangent (tan δ) of oak wood lamellae within a frequency range of 0.079 MHz to 25.1 MHz. The hypothesis tested was that increased temperature and moisture content enhance both dielectric polarization and loss, while density acts as a dominant structural determinant of dielectric behaviour. Oak lamellas were conditioned above saturated salt solutions at 20 °C and measured using an Agilent 4285A LCR meter according to ASTM D150-22. Multiple linear regression was used to demonstrate the statistically significant influence of temperature, relative humidity, moisture content, and density on the tested electrical properties of the lamellas. The results showed that the dielectric properties increase with higher sample density and higher air humidity. Temperature also had an influence, but it was significantly smaller, though still statistically significant (p < 0.05). Changes in dielectric properties were most pronounced at frequencies below 1 MHz, suggesting that dipolar and interfacial polarization are greater at lower frequencies. The findings in this paper provide a basis for optimizing the high frequency/dielectric heating process for heating before bending of oak and other similar hardwoods. Full article

Polyhydroxybutyrate (PHB) is considered a coating material capable of limiting the corrosion of biodegradable metallic implants due to its biocompatibility and ability to form a physical barrier. In this study, PHB was deposited on commercial AZ91D magnesium alloy using the spin coating technique. To improve adhesion at the polymer–substrate interface, the magnesium substrates were subjected to atmospheric pressure plasma treatment for different exposure times (5, 10, or 15 min) before coating. The optimal treatment time of 5 min significantly increased substrate wettability and surface free energy, facilitating stronger PHB adhesion. In addition, the PHB coatings were subjected to atmospheric pressure plasma treatment for 5, 10, or 15 s to evaluate potential surface modifications. Corrosion behavior under simulated physiological conditions was assessed via potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in HANK’s solution at 37 °C. Pull-off tests were used to evaluate the adhesion strength between the coating and the substrate under each treatment condition. The results showed a significant decrease in the corrosion rate (V_corr), from 4.083 mm/year for bare Mg-AZ91D to 0.001 mm/year when both the substrate and the polymer received plasma treatment. This indicates that the treatment modifies surfaces and improves interfacial bonding, enhancing polymer–metal interaction and producing durable, biocompatible coatings for medical implants. Full article

We report the synthesis and multifunctional characterization of copper-reinforced Ba_0.85Sr_0.15TiO₃ (BST) ceramic composites with Cu contents ranging from 0 to 40 wt%, prepared by a sol–gel route and densified using spark plasma sintering (SPS). X-ray diffraction and FT-IR analyses confirm the coexistence of cubic and tetragonal BST phases, while Cu remains as a chemically separate metallic phase without detectable interfacial reaction products. Microstructural observations reveal abnormal grain growth induced by localized liquid-phase-assisted sintering and progressive Cu agglomeration at higher loadings. Scanning electron microscopy reveals abnormal grain growth, with the average BST grain size increasing from approximately 3.1 µm in pure BST to about 5.2 µm in BST–Cu40% composites. Optical measurements show a continuous reduction in the effective optical bandgap (apparent absorption edge) from 3.10 eV for pure BST to 2.01 eV for BST–Cu40%, attributed to interfacial electronic states, defect-related absorption, and enhanced scattering rather than Cu lattice substitution. Electrical characterization reveals a percolation threshold at approximately 30 wt% Cu, where AC conductivity and dielectric permittivity reach their maximum values. Impedance spectroscopy and equivalent-circuit analysis demonstrate strong Maxwell–Wagner interfacial polarization, yielding a maximum permittivity of ~1.2 × 10⁵ at 1 kHz for BST–Cu30%. At higher Cu contents, conductivity and permittivity decrease due to disrupted Cu connectivity and increased porosity. These findings establish BST–Cu composites as tunable ceramic–metal systems with enhanced dielectric and optical responses, demonstrating potential for specialized high-capacitance decoupling applications where giant permittivity is prioritized over low dielectric loss. Full article

Composite materials are increasingly required to operate in cryogenic environments, including liquid hydrogen and oxygen storage, deep-space structures, and polar infrastructures, where long-term strength, toughness, and reliability are essential. This review provides a unique contribution by systematically integrating recent advances in understanding cryogenic behaviour into a unified multi-scale framework. This framework synthesises four critical and interconnected aspects: constituent response, composite performance, enhancement mechanisms, and modelling strategies. At the constituent level, fibres retain stiffness, polymer matrices stiffen but embrittle, and nanoparticles offer tunable thermal and mechanical functions, which collectively define the system-level performance where thermal expansion mismatch, matrix embrittlement, and interfacial degradation dominate failure. The review further details toughening strategies achieved through nano-addition, hybrid fibre architectures, and thin-ply laminates. Modelling strategies, from molecular dynamics to multiscale finite element analysis, are discussed as predictive tools that link these scales, supported by the critical need for in situ experimental validation. The primary objective of this synthesis is to establish a coherent perspective that bridges fundamental material behaviour to structural reliability. Despite these advances, remaining challenges include consistent property characterisation at low temperature, physics-informed interface and damage models, and standardised testing protocols. Future progress will depend on integrated frameworks linking high-fidelity data, cross-scale modelling, and validation to enable safe deployment of next-generation cryogenic composites. Full article

ABO₃ perovskite oxides are a versatile class of materials whose surfaces and interfaces play essential roles in sustainable energy technologies, including catalysis, solid oxide fuel and electrolysis cells, thermoelectrics, and energy-relevant oxide electronics. The interplay between point defects and surface reconstructions strongly affects interfacial stability, charge transport, and catalytic activity under operating conditions. This review summarizes recent progress in understanding how oxygen vacancies, cation nonstoichiometry, and electronic defects couple to atomic-scale surface rearrangements in representative perovskite systems. We first revisit Tasker’s classification of ionic surfaces and clarify how defect chemistry provides compensation mechanisms that stabilize otherwise polar or metastable terminations. We then discuss experimental and theoretical insights into defect-mediated reconstructions on perovskite surfaces and how they influence the performance of energy conversion devices. Finally, we conclude with a perspective on design strategies that leverage defect engineering and surface control to enhance functionality in energy applications, aiming to connect fundamental surface science with practical materials solutions for the transition to sustainable energy. Full article

Electrokinetics has established itself as a central pillar in microfluidic research, offering a powerful, non-mechanical means to manipulate fluids and analytes. Mechanisms such as electroosmotic flow (EOF), electrophoresis (EP), and dielectrophoresis (DEP) re-main central to the field, once more layers of complexity emerge heterogeneous interfaces, viscoelastic liquids, or anisotropic droplets are introduced. Five research directions have become prominent. Field-driven manipulation of droplets and emulsions—most strikingly Janus droplets—demonstrates how asymmetric interfacial structures generate unconventional transport modes. Electrokinetic injection techniques follow as a second focus, because sharply defined sample plugs are essential for high-resolution separations and for maintaining analytical accuracy. Control of EOF is then framed as an integrated design challenge that involves tuning surface chemistry, engineering zeta potential, implementing nanoscale patterning, and navigating non-Newtonian flow behavior. Next, electrokinetic instabilities and electrically driven micromixing are examined through the lens of vortex-mediated perturbations that break diffusion limits in low-Reynolds-number flows. Finally, electrokinetic enrichment strategies—ranging from ion concentration polarization focusing to stacking-based preconcentration—demonstrate how trace analytes can be selectively accumulated to achieve detection sensitivity. Ultimately, electrokinetics is converging towards sophisticated integrated platforms and hybrid powering schemes, promising to expand microfluidic capabilities into previously inaccessible domains for analytical chemistry and diagnostics. Full article

In the context of global energy demands, the efficient demulsification of highly stable heavy crude oil emulsions remains a critical challenge. This study systematically investigated the demulsification mechanisms of two demulsifiers (P1# and P2#) through multi-dimensional characterisation and performance evaluation. The results indicated that asphaltenes and resins can strengthen the oil–water interfacial film and stabilise the emulsion due to their unique structural properties. FTIR and ¹HNMR analyses showed that both demulsifiers contained polar groups and alkyl chains; however, P1# exhibited higher viscosity and lower surface tension, which favored its rapid adsorption at the interface. Demulsification tests at 60 °C demonstrated that P1# achieved superior efficiency (92.44% demulsification efficiency (DE) in 120 min versus 82.31% for P2#), attributable to its enhanced ability to displace asphaltene/resin at the oil-water interface. Turbiscan stability analysis and microscopic observations confirmed that P1#-treated emulsions underwent faster droplet coalescence and significant interfacial film disruption. Mechanistic studies indicated that the demulsifiers competitively adsorb at the interface, thereby weakening film cohesion through steric hindrance and charge redistribution. XRD and FTIR analyses suggested that interactions between the demulsifier and the asphaltene/resin increased interlayer spacing and reduced crystallinity. Zeta potential and interfacial tension measurements further highlighted P1#’s ability to neutralize negative charges (from −14.52 mV to +8.3 mV) and reduce the IFT (from 28.5 mN/m to 12.1 mN/m), thereby promoting droplet aggregation. This study helps elucidate the mechanism of emulsion phase transition induced by demulsifiers and provides theoretical support for improving the demulsification efficiency of crude oil emulsions. Full article

Self-powered sensors, leveraging their integrated energy harvesting–signal sensing capability, effectively overcome the bottlenecks of traditional sensors, including reliance on external power resources, high maintenance costs, and challenges in large-scale distributed deployment. As a result, they have become a major research focus in fields such as flexible electronics, smart healthcare, and human–machine interaction. This paper reviews the core technical paths of six major types of self-powered sensors developed in recent years, with particular emphasis on the working principles and innovative material applications associated with frictional charge transfer and electrostatic induction, pyroelectric polarization dynamics, hydrovoltaic interfacial streaming potentials, piezoelectric constitutive behavior, battery integration mechanism, and photovoltaic effect. By comparing representative achievements in fields closely related to self-powered sensors, it summarizes breakthroughs in key performance indicators such as sensitivity, detection range, response speed, cyclic stability, self-powering methods, and energy conversion efficiency. The applications discussed herein mainly cover several critical domains, including wearable medical and health monitoring systems, intelligent robotics and human–machine interaction, biomedical and implantable devices, as well as safety and ecological supervision. Finally, the current challenges facing self-powered sensors are outlined and future development directions are proposed, providing a reference for the technological iteration and industrial application of self-powered sensors. Full article

To address the issue of inefficient interfacial diffusion between virgin asphalt and the aged asphalt in Reclaimed Asphalt Pavement (RAP), this study investigates how a rejuvenator improves the interfacial blending behavior and restores the functional properties of aged asphalt. Molecular dynamics (MD) simulations were employed to construct aged asphalt–rejuvenator models with varying rejuvenator contents and to establish a bilayer dynamic model of the virgin-aged asphalt–rejuvenator diffusion system. The kinetic characteristics of the diffusion process were analyzed based on system density and relative concentration profiles, while the mean square displacement (MSD) and diffusion coefficients were calculated to elucidate the diffusion mechanism. The accuracy of the MD simulation results was validated using Fourier Transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC), and the regulatory mechanism of the rejuvenator on the interfacial diffusion between virgin and aged asphalt was revealed at the microscopic scale. The results demonstrated that the addition of the rejuvenator effectively promotes the blending and diffusion at the virgin-aged asphalt interface. Specifically, a 6% rejuvenator significantly improved the diffusion efficiency at elevated temperatures, optimized system density toward virgin asphalt properties, and achieved the most uniform molecular distribution, thereby facilitating balanced intermolecular interactions. Meanwhile, the regenerant effectively restored the aromatic fraction content, reduced polar functional groups such as sulfoxide, and significantly lowered the glass transition temperature (Tg), thereby enhancing the low-temperature crack resistance and overall mechanical performance of RAP. Full article

In this study, Fe₃O₄-chopped carbon fiber (CF) fillers with varying CF:Fe₃O₄ weight ratios (1:0.5, 1:0.75, and 1:1) were fabricated using the wet chemical reduction method. Different weight percentages (1, 3, 7 wt.%) of the CF/Fe₃O₄ fillers were used to fabricate lightweight, flexible, and porous thermoplastic polyurethane (p-TPU) composites for electromagnetic interference (EMI) shielding applications. Due to its poor electrical and magnetic properties, the TPU matrix alone exhibited negligible shielding effectiveness. The electromagnetic interference (EMI) performance of TPU composites is greatly affected by the amount of filler materials, the CF/Fe₃O₄ ratio, and the porous structure, which in turn influence the interfacial interactions between filler and p-TPU matrix. Effective electromagnetic attenuation is achieved by conductive CF network, interfacial polarization at CF/Fe₃O₄/TPU interfaces, and multiple internal reflections promoted by microstructural heterogeneity and porosity. A maximum EMI shielding effectiveness (SE_T) of 22.28 dB was achieved for a CF/Fe₃O₄/p-TPU composite with a filler load of 7 wt.%, a CF:Fe₃O₄ ratio of 1:1, and a porosity of 15%. Full article

Measuring spin polarization (P) of materials is essential for understanding their fundamental properties and for their application in spintronics. Point contact Andreev reflection (PCAR) spectroscopy is a straightforward yet powerful technique for measuring P. However, conventional analysis methods depend on iterative fitting procedures that are time-consuming, subjective, and often lead to non-unique solutions. This complexity arises from the interplay of multiple physical parameters with pressure, including temperature, superconducting gap, and interfacial barrier strength. Here, we present a machine learning (ML) approach that utilizes convolutional neural networks (CNNs) to facilitate the rapid and automated extraction of P from PCAR spectra. We validate the ML model by analyzing experimental PCAR spectra from various materials reported in the literature. The predicted parameters by the CNN model show excellent agreement with the literature values, demonstrating its robust performance across a wide range of materials and parameter sets. This approach significantly reduces analysis time while maintaining accuracy, providing a practical tool for material characterization, thus accelerating materials discovery for spintronics. Full article

This review critically examines photoresponsive supercapacitors based on TiO₂/graphene hybrids, with a particular focus on their emerging dual role as energy-storage devices and environmental sensors. We first provide a concise overview of the electronic structure of TiO₂ and the key attributes of graphene and related nanocarbons that enable efficient charge separation, transport, and interfacial engineering. We then summarize and compare reported device architectures and electrode designs, highlighting how morphology, graphene integration strategies, and illumination conditions govern specific capacitance, cycling stability, rate capability, and light-induced enhancement in performance. Particular attention is given to the underlying mechanisms of photo-induced capacitance enhancement—including photocarrier generation, interfacial polarization, and photodoping—and to how these processes can be exploited to embed sensing functionality in working supercapacitors. We review representative studies in which TiO₂/graphene systems operate as capacitive sensors for humidity, gases, and volatile organic compounds, emphasizing quantitative figures of merit such as sensitivity, response/recovery times, and stability under repeated cycling. Finally, we outline current challenges in materials integration, device reliability, and benchmarking, and propose future research directions toward scalable, multifunctional TiO₂/graphene platforms for self-powered and environmentally aware electronics. This work is intended as a state-of-the-art summary and critical guide for researchers developing next-generation photoresponsive supercapacitors with integrated sensing capability. Full article