Search Results (4,173)

This study reports a simple, high-performance, and cost-effective hydrovoltaic power generator driven by natural seawater. The device combines 3D porous non-woven fabrics with asymmetric copper–aluminum electrodes, offering flexible design and excellent environmental adaptability. The stochastic network of the non-woven fabric acts as an efficient ion-transport highway, accelerating electrolyte infiltration via its large surface area and strong capillary wicking. Leveraging the high ionic strength of seawater compresses the electrical double layers and minimizes internal resistance, boosting the short-circuit current by 25 times compared with deionized water. Short-circuit currents of ~60 μA and open-circuit voltages of ~650 mV were each maintained for over 1200 s. Systematic optimization shows that a 1 mm electrode spacing balances ionic transport and parasitic losses, delivering a peak power of 12.5 μW. Scalability is demonstrated by integrating multiple units: three parallel units scale the current to 173 μA, while three series units increase the voltage to 1500 mV, providing a practical strategy for sustaining low-power electronics. This work establishes non-woven fabric-based generators as a robust platform for harvesting energy from naturally abundant seawater, offering a practical and scalable design for next-generation self-powered small-scale devices. Full article

Additive-free methylammonium lead bromide (MAPbBr₃) electrodes were fabricated by electrophoretic deposition (EPD) directly on Cu foil to investigate Li-storage kinetics while minimizing electrochemical and interfacial contributions associated with polymer binders and conductive carbon additives. The EPD-derived film formed a porous particulate coating and exhibited an optical band gap of approximately 2.24 eV, confirming the retention of MAPbBr₃ after deposition. Peak-resolved electrochemical analysis showed that Li storage does not proceed through a single intercalation pathway. The low-voltage cathodic peak showed mixed diffusion/interfacial behavior. In contrast, other redox peaks were mainly diffusion-controlled, with b-values close to 0.5. After cycling, energy dispersive spectroscopy revealed decreased N, Br, and Pb contents and increased F, P, and O signals, indicating MAPbBr₃ reconstruction and electrolyte-derived interphase formation. Electrochemical impedance spectroscopy results showed that charge-transfer resistance decreased during discharge, suggesting kinetic activation of the reconstructed interface. This work establishes additive-free EPD as a powerful platform for revealing cycling-induced interfacial reconstruction and multistep Li-storage kinetics in MAPbBr₃ perovskite electrodes. Full article

Microneedling has found various applications in dermatology recently. However, many problems still need to be solved in the fabrication of high-aspect-ratio polymeric microneedles with good mechanical strength, dimensional accuracy and thermal conductivity for energy-assisted treatments. Herein, a low-shrinkage photocurable resin specifically designed for high-precision additive manufacturing was developed in this work to enable the rapid and reproducible fabrication of ultra-long microneedle arrays through photopolymerisation-based 3D printing. Moreover, an even and uninterrupted layer of silver was added to the surface at room temperature via electroless plating. The resulting microneedle arrays have good structural integrity and high mechanical strength, and the thermal conductivity of them has been increased by a factor of 37 compared to that of uncoated polymeric materials. Mechanical tests showed that the compressive strength was high enough, and simulated skin and ex vivo porcine skin penetration experiments also demonstrated a low insertion force and stable microchannel formation. The in vitro cytotoxicity tests showed good cell compatibility both before and after silver coating. Such work has successfully developed an all-purpose and manufacturable microneedle platform that connects high-precision additive manufacturing with energy-based dermatological therapy, which provided a scalable strategy for expanding the application of polymeric microneedles in medical aesthetics and related clinical fields. The complete route from the digital model to the finished silver-coated array takes about 2.5 h and requires no mould, master or dedicated tooling. The arrays are intended to serve as low-cost, single-use and geometrically customisable needle-electrode cartridges for energy-assisted dermatological treatment and in particular for fractional radiofrequency (RF) microneedling. Full article

This work presents a numerical investigation of an asymmetric Pt/HfSiON/Ti metal–insulator–metal (MIM) tunnel diode for long-wave infrared (LWIR) rectenna applications at 28.3 THz (10.6 μm). HfSiON is investigated as the tunneling dielectric owing to its favorable electronic properties, thermal stability, and compatibility with nanoscale device fabrication. The electrical transport and rectification characteristics are evaluated using the full Simmons quantum-mechanical tunneling model implemented in MATLAB release 2025b. The analysis encompasses the current density–voltage (J–V) and current–voltage (I–V) characteristics, zero-bias dynamic resistance, current asymmetry, nonlinearity, responsivity, and temperature dependence. Under AC excitation, the Pt/HfSiON/Ti diode exhibits a calculated rectified current density of 1.78 × 10² A/cm² at zero DC bias, while a current density of 6.32 × 10⁵ A/cm² is obtained at an applied voltage amplitude of ±0.5 V. The asymmetric electrode configuration, arising from the difference in the work functions of Pt and Ti, results in a calculated asymmetry of 2.5 × 10⁴. At zero DC bias, the diode exhibits a zero-bias dynamic resistance of 3.85 × 10⁵ Ω and a zero-bias responsivity of approximately 10 V⁻¹. The calculated rectification characteristics show only weak sensitivity to temperature over the investigated range, indicating that the transport response is predominantly governed by quantum-mechanical tunneling rather than thermally activated processes. These results demonstrate the potential of HfSiON as a tunneling dielectric for nanoscale MIM rectifiers and indicate that the asymmetric Pt/HfSiON/Ti architecture provides strong nonlinear rectification and favorable zero-bias response for LWIR rectenna and energy-harvesting applications. Full article

Maintaining low leakage current with high capacitance density in metal–insulator–metal (MIM) capacitors is essential for next-generation dynamic random-access memory (DRAM) scaling. Rutile TiO₂ is a promising high-k dielectric; however, its narrow bandgap causes high leakage, while defect-free stabilization in ultrathin films remains challenging. RuO₂/TiO₂/Ru MIM capacitors were fabricated using a reactive direct current (DC)-sputtered RuO₂ bottom electrode, followed by TiO₂ growth by direct plasma atomic layer deposition (DP-ALD) or remote plasma atomic layer deposition (RP-ALD) and rapid thermal annealing in O₂ to reduce defects. Rutile TiO₂ was deposited directly on highly crystalline RuO₂ under both plasma modes, suggesting that RuO₂ crystallinity governs TiO₂ phase evolution. The RP-ALD film replicated the RuO₂ grain morphology, yielding higher roughness than that of the DP-ALD film. Moreover, the RP-ALD film exhibited lower oxygen-vacancy density and improved stoichiometric stability. The RP-ALD-fabricated capacitors exhibited a higher dielectric constant and lower leakage current density at 0.8 V than the DP-ALD-fabricated capacitors (~100 and ~1.76 × 10⁻⁶ A/cm² vs. ~97 and ~1.41 × 10⁻⁴ A/cm², respectively). Ion bombardment during DP-ALD likely promoted oxygen-vacancy-related defect formation, whereas RP-ALD mitigated such damage, improving leakage characteristics. This work highlights the potential of RP-ALD-based RuO₂/TiO₂/Ru MIM capacitors for next-generation DRAM. Full article

Polyimide-based composites with graphene nanoplatelet (GNP) fillers are investigated as multifunctional materials for potential space-compatible biomedical monitoring. These composites are designed to combine the intrinsic high thermal and chemical stability of polyimides, as well as their well-established radiation resistance reported in the literature, with the electrical functionality of graphene. PI/GNP membranes are fabricated by casting dispersions of graphene nanoplatelets within the polyimide solution, using a green and bio-based solvent (dimethyl isosorbide), followed by thermal treatment in vacuum. The effect of UV-C irradiation is investigated as a sterilization-relevant stress condition, showing that the PI/GNP composites retain their main chemical and surface characteristics after exposure. In addition, irradiation is associated with an improvement in the electrical response, suggesting that the conductive network formed by graphene nanoplatelets remains effective after treatment. Overall, this study highlights the PI/GNP composites as robust and electrically functional candidate materials for dry electrode applications in harsh environments. By combining chemical stability, thermal resistance, a stable surface and electrical conductivity, these membranes emerge as promising candidates for future health monitoring applications on Earth and during long-term missions in space. Full article

Developing efficient, non-enzymatic glucose sensors is crucial for overcoming the stability and environmental limitations of conventional enzymatic devices. In this work, a series of ruthenium-based bimetallic microstructures (Ru–Ir, Ru–Pt, Ru–Au DMF, and Ru–Au NPs) were successfully fabricated on glass substrates using a mask-free, two-stage laser-induced chemical liquid-phase deposition (LCLD) technique. Among the prepared materials, the binder-free Ru–Ir electrode exhibited the highest electrocatalytic activity toward glucose oxidation in an alkaline medium. Characterization by SEM, EDX, and XRD revealed a highly developed hierarchical surface morphology with distinct metallic phases. Chronoamperometric measurements performed at an operating potential of 0.45 V (vs. Ag/AgCl) demonstrated that the Ru–Ir sensor possesses a dual-range linear calibration—0.5–3000 μM and 3000–12,500 μM—with sensitivities of 0.027 and 0.014 μA μM⁻¹ cm⁻², respectively. The limit of detection was determined to be 58.1 nM. This improved performance and dual-range linearity are highly likely attributed to the abundance of electroactive sites provided by the hierarchical architecture and a synergetic effect between Ru and Ir that accelerates surface-controlled glucose dehydrogenation. Furthermore, the Ru–Ir sensor demonstrated negligible cross-sensitivity toward common interferents, an electrode-to-electrode RSD of 2.33% (n = 5), and remarkable long-term stability, retaining over 85% of its initial response after 30 days. Overall, the two-stage LCLD procedure provides a mask-free, binder-free, and direct-write route for fabricating bimetallic electrodes under ambient conditions. Full article

Graphene nanoplatelets (GNPs)-reinforced AlSi10Mg composites were fabricated by selective laser melting (SLM), and their corrosion resistance was systematically investigated as a function of GNPs content (0, 0.1, 0.3, and 0.5 wt.%) and corrosion duration. In the short term (≤30 days), the corrosion resistance followed the order: 0.1 wt.% GNPs/AlSi10Mg > 0.3 wt.% GNPs/AlSi10Mg > 0.5 wt.% GNPs/AlSi10Mg > AlSi10Mg. The 0.1 wt.% composite exhibited the best performance, attributed to the uniform dispersion of GNPs that filled micropores and microcracks to form a physical barrier against corrosive ions, along with favorable interfacial bonding that hindered crack growth and reduced corrosion pathways. After 60 days of exposure, however, the ranking reversed to: AlSi10Mg > 0.1 wt.% GNPs/AlSi10Mg > 0.3 wt.% GNPs/AlSi10Mg > 0.5 wt.% GNPs/AlSi10Mg. EIS analysis revealed a porous electrode behavior in the low-frequency response, captured by the constant phase element in the equivalent circuit. The long-term deterioration arose from the gradual penetration of corrosive media through micropores and microcracks, which triggered galvanic corrosion between GNPs and the matrix and rendered the barrier effect ineffective. These findings demonstrate that GNPs addition increases both the number and the total area of cathodic sites in the matrix alloy, thereby accelerating corrosion under prolonged exposure. In essence, GNPs serve as a protective barrier in the short term but transition to corrosion accelerators under long-term exposure. Full article

This work presents the design and experimental demonstration of a micromachined edge reflection thin-film surface acoustic wave (SAW) resonator on an X-cut LiNbO₃-on-SiC platform. Unlike conventional Bragg reflection resonators (BRRs), the demonstrated device employs etched free edges adjacent to the interdigital transducer (IDT) to provide lateral acoustic confinement without additional reflector arrays. Edge half electrodes are further used to tailor the lateral phase condition and suppress spurious modes. The representative Design I resonator exhibits an electromechanical coupling coefficient (k_t²) of 37.6% and a maximum Bode-Q of 712 at 4.64 GHz, corresponding to a figure of merit (FoM) of 267.7. Compared with BRR counterparts fabricated in the same batch, the ERR reduces the effective resonator footprint by approximately 27–37% while maintaining a comparable k_t². Measurements further show that the ERR exhibits a higher Q in most paired designs, thereby yielding an improved FoM. These results establish micromachined edge boundary engineering as an effective route toward reflector-less thin-film SAW resonators with reduced effective resonator footprints and high-Q coupling performance while also clarifying the fabrication-related trade-offs associated with etched free edge confinement. Full article

In this study, an electrochemical sensor based on a graphitized carboxylated multi-walled carbon nanotube/polyaniline (G-COOH-MWCNTs/PANI) composite was developed for the highly sensitive detection of Pb²⁺ in seawater. A G-COOH-MWCNTs/PANI composite dispersion was prepared via a solution blending method and subsequently drop-cast onto a glassy carbon electrode (GCE) to fabricate the modified electrode. Differential pulse anodic stripping voltammetry (DPASV) was employed for the quantitative determination of Pb²⁺. The morphology of the composite was characterized by scanning electron microscopy (SEM), while the electrochemical behavior of the modified electrode was investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Critical experimental parameters, including the type and pH of the supporting electrolyte, deposition potential, deposition time, and loading amount of the composite film, were systematically optimized. In addition, the optimal concentration ratio of G-COOH-MWCNTs to PANI was determined using an orthogonal experimental design. Under the optimized experimental conditions, the proposed sensor exhibited a linear response toward Pb²⁺ over the concentration range of 25–220 μg/L, with the regression equation Ip = 2.757C + 4.316 (R² = 0.997). The limit of detection (LOD), calculated at a signal-to-noise ratio (S/N) of 3, was 0.0337 μg/L. The sensor also demonstrated excellent reproducibility (relative standard deviation, RSD = 1.7%), satisfactory anti-interference capability, and good long-term stability, retaining 94.1% of its initial response after 35 days of storage. Spike recovery experiments using real seawater samples yielded recoveries ranging from 96.73% to 99.73%, with RSD values below 3%, indicating excellent accuracy and precision in complex seawater matrices. These results demonstrate that the proposed sensor enables accurate determination of Pb²⁺ in seawater without complicated sample pretreatment and exhibits considerable potential for applications in marine environmental monitoring of heavy metal contamination. Full article

Lignin-derived carbon nanofibers (LCF) with hierarchical micro–mesoporous architecture featuring unusually high mesopore preservation were fabricated by electrospinning. The process used a lignin/poly(ethylene oxide) precursor in an alkaline medium (sodium hydroxide, NaOH), followed by carbonization and selective HCl washing. During electrospinning, sodium species were incorporated from the alkaline spinning solution and, upon subsequent thermal treatment, converted in situ into sodium-containing domains that acted as transient porogens, enabling the development of a highly accessible pore network without conventional activation. The resulting free-standing carbon nanofiber mats exhibited a hierarchical micro–mesoporous architecture, in which 84% of the specific surface area arose from micropores accompanied by a well-defined 8–12 nm mesopore population that is expected to facilitate ion transport, maximizing the utilization of the microporous surface for charge storage. Raman analysis further revealed a defect-rich, edge-abundant sp² carbon network (I_D/I_G = 1.05). As self-supported supercapacitor electrodes in 3 M potassium hydroxide (KOH), the materials delivered a specific capacitance of ≈275 F g⁻¹ at 0.25 A g⁻¹, retained ≈87% of this value at 2.5 A g⁻¹, and exhibited outstanding cycling stability, with 117% capacitance retention and 99.9% coulombic efficiency after 10,000 charge–discharge cycles. This simple, low-cost, and low-waste strategy demonstrates that in situ sodium templating effectively engineers hierarchical pore architectures in lignin-derived carbon nanofibers without aggressive chemical activation, providing a sustainable platform for high-performance energy-storage electrodes. Full article

Salvianolic acid B is an important bioactive biomarker in traditional Chinese medicines (TCMs). Current methods for its quantitation are time- and cost-consuming; a rapid and reliable method is urgently needed. In this work, we have developed a simple and sensitive electrochemical (EC) sensor on screen-printed carbon electrode (SPCE) that was modified with three-dimensional hierarchical Au–Pt nanostructured film. This highly conductive structure facilitates direct electron transfer when the sample solution containing salvianolic acid B is dropped, thereby amplifying its generated current response. Under optimized conditions, the fabricated label-free EC sensor exhibited a wide linear range (4–500 μg/mL) with excellent conductivity and a detection limit as low as 3.76 μg/mL for salvianolic acid B, as well as high reproducibility and outstanding stability. Furthermore, the practical applicability was validated by satisfactory spiked recovery rates (97.5–101.4%) in complex Salvia miltiorrhiza matrices. These findings indicated that the Au–Pt nanostructure-modified SPCE could achieve reliable and stable quantitation of salvianolic acid B. The developed EC sensor provided an economical, efficient, user-friendly, and reliable on-site strategy for accurate determination of salvianolic acid B and other components in more TCMs. Full article

A piezoelectric cantilever with a longitudinal slit splits one bending resonance into two closely spaced peaks. This is attractive for two-frequency sources. However, existing models fit, rather than predict, the resonances. We develop a predictive branched-beam model where the harvester consists of a full-width root splitting into two prongs with independent tip masses. The two resonances are the roots of a closed-form characteristic equation without fitted parameters, the anti-resonance is the transmission zero of the same branched model, and the formulation reduces to the classical cantilever in the no-slit limit. The second (anti-symmetric) mode is weakly tunable and is located near 45 Hz; the inversion leaves the first resonance free and pins the second effectively. It is predictive and inverted to size the tip masses. Three-dimensional finite-element analysis, which tracks 27.2 → 22.3 Hz (against a finite-element 28.9 → 23.5 Hz as the mass doubles) within about 6%, and the prong kinematics, confirm the tip-mass trend. The anti-resonance is called the charge cancellation effect and can be controlled by wiring the electrodes. For a two-line source (25/45 Hz), the design, tuned to the two lines, yields up to about 1.9× the power of a size-matched single-peak beam with two matched lines (1.6× when the second dominates, ≈1× for broadband), with the second peak being intrinsically smaller. A Monte-Carlo study shows a power coefficient of variation of about 72% with manufacturing and damping scatter, the two layer thicknesses accounting for about 83% of the variance, motivating post-fabrication tip-mass trimming. The model is rigorously validated against three-dimensional electromechanical finite-element analysis; experimental validation on a physical prototype is identified as the essential next step. This work transforms the slitted harvester into a designable monolithic dual-frequency device. Full article

Wearable electronics, particularly dry epidermal electrodes, provide human-connected interfaces for recording biopotential signals. However, their practical utility is often hindered by their limited operational longevity and the resulting environmental burden of electronic waste, as most conventional electrodes are discarded after a single use because of performance degradation. Herein, a reusable, soft, and conductive epidermal electrode is reported, fabricated through the precise incorporation of functional additives. By intentionally modulating the polymer chain architecture, a homogeneous composite is developed that exhibits exceptional flexibility, high conductivity (~100 S/cm), softness (~649 kPa), and stretchability (~234%). This molecular-level design promotes strong intermolecular interactions at the skin–electrode interface, facilitating persistent adhesion and conformability to challenging surfaces, including wet, wrinkled, and stretched skin. These properties enable reliable electrocardiography acquisition through 50 repeated attachment and detachment cycles, over which a commercial Ag/AgCl gel electrode became unmeasurable after 20. The applicability of the electrode to human–machine interfaces is further demonstrated by capturing clear electromyography signals of muscle activity during a rock–paper–scissors game. This low-modulus electrode platform offers a route towards repeated-use wearable healthcare systems and soft-robotics applications, with the potential to reduce the waste associated with single-use electrodes. Full article

The increasing demand for miniaturized, flexible and wearable electronics has accelerated the development of printed electrochemical energy-storage devices capable of combining high performance with scalable and cost-effective manufacturing. Among emerging electrode materials, MXenes have attracted significant attention owing to their exceptional electrical conductivity, hydrophilic surface chemistry, tunable interlayer structure and excellent solution processability, making them particularly suitable for jet printing technologies. In particular, inkjet printing (IJP) and aerosol jet printing (AJP) enable maskless, high-resolution and material-efficient fabrication of micro-scale energy-storage devices while offering excellent compatibility with flexible substrates. This review provides a comprehensive overview of the use of MXene-based inks in jet-printed energy-storage devices, emphasizing the relationships between MXene physicochemical properties, ink formulation, printing processes and electrochemical performance. First, the structural characteristics, synthesis strategies and electrochemical charge-storage mechanisms of MXenes are discussed, together with the rheological, colloidal and stability requirements governing ink printability. The fundamental principles of IJP and AJP are then critically analyzed, highlighting the influence of solvent systems, printability criteria, processing parameters and deposition conditions. Recent advances in jet-printed MXene-based supercapacitors and micro-supercapacitors are comprehensively and critically reviewed, with particular attention to how material design, ink formulation, and printing strategies affect device performance. Battery-related studies, which remain comparatively limited, are discussed as an emerging application area highlighting the broader potential of jet-printed MXenes for electrochemical energy storage. Finally, the major challenges hindering the large-scale implementation of MXene-based printed energy-storage systems, including oxidation stability, restacking, ink shelf life, and manufacturing scalability, are critically discussed. Full article