Wearable temperature sensors are becoming increasingly important for continuous health monitoring, personalized healthcare, and biointegrated electronic systems. However, conventional temperature-sensing platforms often suffer from limited thermal sensitivity, insufficient mechanical compliance, and unstable performance under repeated deformation, making it difficult to detect subtle physiological temperature variations in real time. Here, this tutorial status report presents a fabrication strategy for highly sensitive wearable temperature sensors based on gold-doped crystalline silicon nanomembranes. Gold diffusion into crystalline silicon introduces deep-level impurity states that modulate the Fermi level and shift the freeze-out region toward the physiological temperature range, enabling an ultrahigh negative temperature coefficient of resistance. By integrating the gold-doped silicon nanomembrane with a polyimide-supported ultrathin platform, neutral mechanical plane design, and serpentine mesh interconnects, the resulting device can provide high thermal sensitivity, fast response, conformal skin attachment, and stable operation under mechanical deformation. This fabrication approach is expected to broaden the use of impurity-engineered silicon nanomembranes in next-generation wearable sensors, flexible bioelectronics, and multifunctional healthcare monitoring systems.
This review offers a critical overview of recent developments in lead-free piezoelectric materials and flexible device architectures for self-powered wearable and Internet of Things systems. It examines the scientific and technological rationale for replacing conventional battery-dependent power sources with ambient mechanical energy harvesters, and it evaluates the relative merits of inorganic ceramics, organic polymers, and composite systems in achieving efficient electromechanical conversion under practical operating conditions. The discussion further considers compositional tuning, phase boundary engineering, microstructural optimization, and device-level integration as key strategies for improving piezoelectric output, mechanical compliance, durability, and manufacturability. By connecting fundamental materials design with application-driven device requirements, the review identifies the principal challenges and emerging directions necessary for the realization of reliable, scalable, and sustainable electronic platforms.
Renewable energy harvesting technologies, which convert ambient resources such as wind into electrical energy, have attracted significant attention as sustainable power sources for self-powered systems. However, the long-term applicability of wind energy harvesters in remote or extreme environments has not yet been fully discussed, particularly in terms of structural robustness and environmental adaptability. In this study, we designed a double-clamped flutter-type triboelectric generator (DFTEG) for efficient wind energy harvesting and evaluated its output performance under various simulated outdoor conditions. The DFTEG features a modular acrylic frame with a magnet-based assembly for easy maintenance and film replacement, utilizing PTFE films and aluminum electrodes to maximize the charge density difference according to the triboelectric series. Structural optimization revealed that a single-film configuration with a length of 110 mm produced the most stable flutter vibration and a large effective contact area, achieving a maximum open-circuit voltage of 42.28 V and a short-circuit current of 2.89 μA. Furthermore, performance evaluations under various environmental variables, including relative humidity, temperature, and sand particles interference, confirmed consistent electrical output across diverse environmental conditions. These results demonstrate the potential of the proposed DFTEG as an environmentadaptive independent power source capable of stable operation under complex environmental factors.
The expansion of smart healthcare and wearable electronics has intensified the need for fabric-based sensors that integrate conformally with the human body for continuous bio signal monitoring. However, the heavy reliance of conventional devices on external batteries remains a major obstacle to commercialization, necessitating the development of flexible piezoelectric energy harvesters that convert biomechanical energy into sustainable power. Here, we present a highly flexible and wearable piezoelectric energy harvester (PEH) fabricated by a screen-printing of BaTiO3 nanoparticlePDMS composites onto a fabric substrate. An optimized piezo-ceramic filler concentration of 70 wt% yielded a peak output voltage of 0.52 V and a current of 40 nA under the mechanical bending deformations. The fabricated PEH demonstrated exceptional mechanical and electrical stability, showing no performance degradation of over 5,000 repetitive bending cycles. These results indicate that a PEH can function as a stable self-powered source within complex clothing environments, offering a promising pathway for next-generation autonomous wearable sensor systems.
This paper proposes a circular sequential lighting control method to reduce current imbalance and luminance deviation among multiple LED modules in AC-powered LED lighting systems. Conventional fixed-sequence lighting control repeatedly prioritizes the same LED modules in every rectified voltage cycle, which leads to unequal current distribution, luminance non-uniformity, and the accelerated degradation of specific modules during long-term operation. To address these limitations, a circular sequential lighting strategy is introduced, in which the lighting order is cyclically rotated at every rectified cycle, ensuring that all LED modules experience equal lighting opportunities. A prototype AC-LED lighting system consisting of four series-connected LED modules was implemented and experimentally evaluated. The results demonstrate that, while the conventional fixed-sequence method produces a maximum average current deviation of up to 1.6 mA among modules, the proposed method equalizes the average current across all modules to approximately 17.1 mA. Furthermore, the flicker index remains at 0.13, which is comparable to that of the conventional method, indicating that luminance uniformity is improved without degradation of optical performance. The proposed circular sequential lighting control effectively distributes electrical stress, enhances luminance uniformity, and improves long-term reliability, making it a practical and efficient solution for high-quality AC-LED lighting applications.
Metamaterials, as artificially engineered structures with unconventional mechanical and acoustic properties, have recently emerged as a transformative platform for enhancing the capabilities of triboelectric nanogenerator (TENG) systems. Since the invention of TENG devices, extensive efforts have been devoted to improving charge density, output stability, and overall performance. Conventional performance optimization strategies mainly rely on device-level improvements such as surface chemistry modification, microstructuring, and nanopatterning. However, limited emphasis has been given to system-level development of smart self-powered intelligent systems. The integration of metamaterials into TENG devices opens a new era by enabling frequency-selective localization, mechanical impedance matching, and controllable deformation pathways. These engineered mechanical structures not only improve energy harvesting efficiency but also introduce new functionalities into the system. This review systematically summarizes recent advances in metamaterial-integrated TENG systems across four major application domains: (i) energy harvesting, (ii) acoustic telecommunication and acoustic-to-electric conversion, (iii) self-powered sensing, and (iv) vibration suppression and monitoring. Overall, the integration of metamaterials into TENG systems will pave the way for next-generation sustainable, intelligent, self-powered devices with diverse functionalities.
Long lifetime, low power consumption, and environmental friendliness have enabled light-emitting diode (LED) lighting to rapidly replace conventional light sources such as incandescent and fluorescent lamps. In particular, AC-LED lighting systems can be directly powered by commercial alternating current (AC) sources; however, they suffer from significant luminance deviation caused by uneven current distribution among LED light-emitting modules. This paper proposes a lighting control method that improves flicker performance while maintaining lamp brightness and effectively reduces luminance deviation in AC-LED lighting. The proposed method reduces luminance deviation by controlling the lighting order of multiple LED light-emitting modules. Among four LED modules, only the required number of modules is continuously turned on, and the lighting priority alternates between rectification cycles. Specifically, during odd rectification cycles, LED modules are activated sequentially in ascending order (11→12→13→14), whereas during even rectification cycles, they are activated in descending order (14→13→12→11). By alternately applying continuous lighting control with opposite activation orders, the proposed reverse alternating lighting control method equalizes the current distribution among LED modules. As a result, luminance uniformity is improved, electrical stress concentration on specific modules is reduced, and the operational lifetime of the LED modules is extended compared with the conventional fixed-sequence lighting control method.
Neuromorphic computing, which mimics the energy-efficient parallel processing capabilities of the human brain, has emerged as an alternative to traditional von Neumann architectures that struggle with high power consumption in the era of artificial intelligence (AI). Despite the potential of Si-based neuromorphic chips, they often face fundamental limitations in integration density and biological compatibility, necessitating the development of next-generation devices that can better emulate the ionic signaling of biological systems. This review provides a comprehensive analysis of the recent research trends in artificial synapses and neurons based on organic electrochemical transistors (OECTs), highlighting their unique ability to achieve high transconductance and mixed ionic-electronic conduction at ultra-low operating voltages. We discuss how OECTs successfully replicate diverse synaptic plasticities and complex neuronal spiking behaviors through advanced material engineering and structural optimizations such as vertical architectures. Furthermore, this review discusses the implementation of high-order neural functions, including associative learning and logic operations, which are facilitated by the inherent electrochemical dynamics of organic semiconductors. Finally, overcoming current challenges in reliability and scalability will establish OECTs as a pivotal platform for low-power neuromorphic hardware and bio-integrated electronics.
Breakdown strength is an essential parameter for evaluating the electrical performance and degradation behavior of cable insulation and IEC 60243 also emphasizes its importance for detecting changes in insulation characteristics due to aging. However, the current IEC standards are mainly limited to specifying electrode configurations and test voltage conditions for breakdown tests, while the influence of insulating oil, is not clearly addressed. In this study, the breakdown strength of a 66 kV wet-type submarine cable was experimentally evaluated using insulating oils with different kinematic viscosities of 10, 100, 500, and 1,000 cSt in order to achieve reliable and reproducible breakdown measurements. The experimental results show that the measured breakdown strength decreases by up to approximately 20% depending on the oil viscosity. This indicates that the viscosity of the insulating oil has a significant influence on the measured breakdown strength during breakdown test. Therefore, it is necessary to perform breakdown strength measurements under identical test conditions, including the physical properties of the insulating oil, to ensure reliable comparison and accurate assessment of insulation performance and degradation characteristics.
The increasing global demand for renewable energy has accelerated the deployment of offshore wind farms, thereby highlighting the need for advanced development and performance assessment techniques for dynamic submarine cables used in floating offshore wind systems. These cables are continuously subjected to combined thermal, electrical, and mechanical stresses, with mechanical loading playing a particularly dominant role. As a result, dynamic submarine cables exhibit degradation behaviors that differ significantly from those of conventional fixed submarine cables. This paper presents the design and implementation of a comprehensive evaluation system capable of applying combined thermal, electrical, and mechanical stresses to dynamic submarine cables. The system was validated using a 66 kV wet type submarine cable through commissioning tests and insulation performance measurements. Electrical stress of 72 kV, thermal stress exceeding 95°C, and mechanical stress corresponding to a bending radius of 20 times the cable diameter over 20 cycles were applied to verify system reliability. The subsequent insulation assessments quantitatively confirmed performance variations induced by the combined stresses. The results demonstrate that the proposed platform is the first system capable of simultaneously applying thermal, electrical, and mechanical stresses to dynamic submarine cables, and its operational performance has been successfully validated. This platform enables realistic reliability evaluation of dynamic cables used in floating offshore wind farms and is expected to improve the overall operational reliability of offshore wind power systems.
The rapid proliferation of artificial intelligence (AI) servers and high-performance computing systems has significantly elevated the technical and reliability requirements for multilayer ceramic capacitors (MLCCs). In such systems, MLCCs are critical passive components that must deliver high capacitance, fast transient response, and robust insulation performance under high temperature, voltage, and current density. This review examines the material, structural, and process innovations that underpin MLCC performance in AI applications. Key topics include the development of ultrathin dielectric layers (<0.5 μm), rare-earth doped BaTiO₃-based dielectrics with enhanced DC bias stability, and core-shell microstructures designed for temperature and field resilience. The paper also explores insulation degradation mechanisms―such as vacancydriven conduction and demixing―and advanced reliability assessment methodologies, including HALT, TSDC, and the tipping point framework. Comparisons with automotive-grade MLCCs highlight the unique requirements of AI systems, such as ultraminiaturization, high volumetric efficiency, and ppm-level field failure rates. Finally, the review discusses emerging trends in MLCC technology, including particle engineering, interface stabilization, and advanced lamination techniques, and provides insight into the future direction of capacitor development tailored to AI data center environments.
The quench behavior of wires for superconducting fault current limiters at DC faults was simulated, with a focus on the effect of capacitor discharge on the quench. The behavior was also expressed in mathematical forms to facilitate a better understanding of the simulation results and for rough analytical estimations of the wire length suitable for the circuit voltage and capacitance. The quench resistance development behavior for various wire lengths and circuit capacitances was simulated using the model developed in the previous work. The quench behavior was expressed in mathematical forms, reflecting the concept of heat balance. During the quench, the wire temperature increased more slowly for longer wires, but was found to increase in a similar pattern. The wire length estimated by the mathematical formula was close to the one obtained by the simulation, with an error range of a few %. The calculations will be used to estimate effectively the length of wires needed to build superconducting fault current limiters for applications in DC power systems.
Flexible and wearable electronics, which require stable operation under mechanical deformation, are increasingly utilizing Eutectic Gallium-Indium (EGaIn) for their conductive components. This study presents a systematic approach to fabricating highly reliable, deformable electrodes via a direct-ink-writing (DIW) 3D printing process using EGaIn as the functional ink. We conducted a thorough optimization of key printing parameters, specifically the extrusion pressure and printing speed, to achieve stable and uniform conductive lines. Through this optimization, we successfully established an optimal process window, achieving a stable line width of approximately 130 μm at an extrusion pressure of 300 kPa and a printing speed of 16 mm/s. The fabricated flexible electrodes exhibited exceptional electromechanical stability, maintaining negligible resistance change (< 0.82%) both under severe bending (3 mm radius) and after 100 repetitive bending cycles. This work demonstrates that the 3D printing of EGaIn is a viable and effective method for creating robust, high-performance electrodes for the next generation of deformable and wearable electronic devices.
Perovskite light-emitting diodes (PELEDs) are emerging as promising candidates for next-generation displays, thanks to their narrow full width at half maximum and low-cost solution processing capabilities. Blue PeLEDs are essential for achieving a full-color gamut; however, efficiency and stability challenges limit their practical use. A primary bottleneck arises from interfacial issues between the perovskite emissive and charge transport layers. This review summarizes the key interfacial challenges hindering the performance of blue PeLEDs and highlights recent advances in interfacial engineering strategies. By focusing on interfacial engineering between the hole-transport layer and perovskite, this review compares different strategies and outlines future directions for developing high-performance blue light-emitting devices.
Nozzle-printing dispensers, which utilize air pulsation as a dispensing principle, operate by transmitting air pressure to the liquid to push a constant amount of liquid. Nozzle printers have the advantage of precisely controlling energy based on liquid properties, such as viscosity and surface tension, enabling the precise application of liquid at specific locations and quantities. This study introduces a printing process sequence using a nozzle printer equipped with a high-resolution vision alignment system. It compares printing patterns according to key process variables (jet pressure, tip height, and travel speed) that affect coating quality. Experimental results showed that a coating standard deviation of 2.14 μm was achieved at a moving speed of 20 mm/s and a nozzle height of 0.2 mm, resulting in the most stable and uniform coating quality. Through these experiments, optimal conditions were identified based on factors such as coating width, uniformity, and presence of discontinuity, and the effects of these conditions on the precision manufacturing process are discussed.
Quantum dots (QDs) offer size-dependent tunability across the infrared to ultraviolet range with narrow emission linewidths and high color purity, making them highly attractive for next-generation light-emitting devices. Quantum dot lightemitting diodes (QLEDs) further combine precise spectral control with scalable, low-cost solution processing, positioning them as strong candidates for wearable, stretchable, and AR/VR display technologies. However, conventional single-emission QLEDs suffer from charge imbalance, efficiency roll-off, and limited operational lifetime, necessitating new device architectures. Tandem QLEDs, which vertically stack multiple emissive layers (EMLs) connected by charge generation layers (CGLs), provide a compelling solution by enabling higher luminance, improved charge balance, and longer lifetime at equivalent current density. The CGL serves as the interfacial region mediating charge injection and generation between adjacent EMLs, directly determining device efficiency and stability. This review highlights recent progress in CGL engineering, categorizing representative designs into planar heterojunction, inorganic-based, and dipole-based configurations. Comparative analysis of their formation mechanisms, material systems, and process compatibilities reveals evolving charge-control strategies that extend beyond material selection. These insights establish design principles for next-generation tandem QLEDs with enhanced efficiency, durability, and manufacturability.
Thermal batteries are designed to activate at high temperatures (~500℃), therefore, the electrodes used in these systems are typically made into pellet form using compression molding techniques that do not involve polymer binders. However, the compression molding technique poses limitations in scaling up the electrode area without increasing thickness for high-power properties. Additionally, the tape casting method has been studied as a way to solve with, but too low a loading level is still an obstacle to practical use. This study fabricated a film cathode of high loading level (35.79 mAh·cm-2) using the tape casting method for these problem. As utilized fabricated cathode, it investigated the influence of electrode thickness and density on electrochemical performance. Furthermore, a film cathode with a larger area but the same amount of active material as the pellet was fabricated, enabling the design of high-power cells with the same energy density. We expect that the fabricated film cathode with a high loading level and scalable area will enable the development of various thermal battery designs.
The rapid evolution of wearable technology has driven a surge in demand for sustainable, self-powered electronic devices. Flexible thermoelectric materials, capable of converting body heat into electricity, have emerged as a promising solution for powering next-generation wearables. This review comprehensively examines recent progress in organic (polymer-based) and hybrid thermoelectric materials, focusing on their design, fabrication, and integration into flexible architectures suitable for conformal contact with human skin. Key developments include advanced doping strategies, post-treatment techniques, and composite engineering, particularly in conductive polymers such as PEDOT: PSS and P3HT, which have significantly enhanced power factors and mechanical flexibility. Additionally, the integration of high-performance inorganic materials into stretchable systems has further elevated device efficiency and durability. The review highlights breakthroughs, ongoing challenges, and future opportunities in realizing practical, scalable, and high-efficiency wearable thermoelectric generators for sustainable energy harvesting applications.
Abstract In this study, to develop composition ceramics for energy harvesting devices, Pb(Ni1/3Nb2/3)O₃-Pb(Zr Ti)O₃ system ceramics substituted with Pb(Mg1/2W1/2)O₃ were manufactured by conventional mixed oxide method using Li₂CO₃ and Na₂CO₃ (LNCO) as sintering aids. Their microstructure and piezoelectric properties were also investigated. At the specimen sintered at 930℃, high values of piezoelectric properties appeared: the dielectric constant (εr) of 2,522 planar electromechanical coupling factor kp of 0.602, and k31 of 0.385, d31 = 229 [pC/N], g31 = 10.13 [mV.m/N], Qm of 70, respectively. These values were suitable for the application of devices such as energy harvesting devices and ultrasonic devices.
Cathodoluminescence (CL) spectroscopy provides valuable insights into the optical and electronic properties of materials by analyzing photon emission induced by electron beam excitation. In this study, we present a novel CL detection system integrated into a transmission electron microscope (TEM) specimen stage, enabling high-resolution optical analysis of internal microstructures. The system features a parabolic mirror, a focusing lens, and a UV-VIS range optical fiber to maximize light collection and transmission efficiency, with performance further enhanced by a liquid nitrogen cooling setup. Using this system, we successfully performed CL mapping of InGaN/GaN multiple quantum wells (MQWs) and GaN thin films. The results revealed that threading dislocations act as non-radiative centers in GaN and locally increase the bandgap energy in InGaN MQWs, causing a blue-shift in CL emission. These findings support a model in which dislocations induce carrier delocalization, preserving high radiative efficiency despite high dislocation densities. This work demonstrates the effectiveness of the TEM-integrated CL system for nanoscale optical characterization, offering a new pathway for studying defect-related phenomena in semiconductor materials.
Porous polymeric structures with piezoelectric properties have attracted considerable attention in the fields of biomaterials and tissue engineering due to their ability to convert mechanical stimuli into electrical signals. However, conventional fabrication methods for porous structures often face limitations in controlling pore architecture, maintaining structural uniformity, and achieving process reproducibility, in addition to requiring complex processing conditions. To address these issues, we propose a facile and reproducible fabrication method for porous poly (vinylidene fluoride) (PVDF) piezoelectric sponges using molded sugar cubes as sacrificial pore templates. By adjusting the particle size of the sugar templates, the pore size and distribution of the sponges could be effectively controlled, and a uniform open-pore network was achieved. The fabricated sponges were evaluated with a focus on pore morphology, mechanical behavior, and piezoelectric performance depending on the sugar particle size, and these evaluations confirmed the structural properties and functional efficacy. This study presents a simple and reproducible fabrication strategy along with a quantitative analysis method for porous structures, which is expected to enhance process accessibility and practical applicability in the development of piezoelectric polymer-based biomaterial platforms.
Conductive inks are essential for developing flexible and wearable electronic devices, where printability and electrical performance must be finely balanced. However, achieving high conductivity while minimizing costly silver filler content remains a key challenge in ink formulation. In this work, we demonstrate that a simple ball-milling process transforms spherical silver particles into platelet-shaped fillers, dramatically enhancing conductivity at equivalent filler loading. The resulting inks show a reduction in sheet resistance from ~180 Ω/□ to ~ 0.57 Ω/□ at 70 wt% filler content, with improved performance attributed to surface-to-surface contact between platelets. Moreover, we show that filler content influences not only electrical conductivity but also ink viscosity, with the 53.8 wt% formulation achieving a practical balance between conductivity, processability, and cost. This morphology- and composition-controlled ink design offers a scalable strategy for manufacturing high-performance, cost-effective conductive inks suitable for next-generation printed electronics.
This study aimed to elucidate factors limiting power conversion efficiency (PCE) in GaN-based micro-light-emitting diodes (μ-LEDs). To this end, we investigated the effects of operating temperature and chip-size of μ-LEDs on their efficiency. For the investigation, 460 nm-emitting μ-LEDs with various chip-sizes were fabricated; then their characteristics were carefully measured from 100 to 400 K. As the chip-size decreases and the operating temperature increases, their PCE and external quantum efficiency (EQE) decrease, while voltage efficiency (VE) increases. This indicates that the EQE plays a more important role than the VE in determining the PCE of μ-LEDs. Particularly, for a chip-size of 20 × 20 μm2, the EQE was very lower and the ideality factor was unexpectedly higher compared to the others for all operating temperatures, which is believed to be due to the critical plasma damage at the sidewall during dry-etching process for the chip-size < 20 × 20 μm2.
We have proposed and demonstrated a fiber optic magnetic field sensor using a FBG (fiber bragg grating) attached on a Terfenol-D bar. The volume of Terfenol-D is changed by the applied magnetic field due to the magnetostriction effect, as a result, the grating period of FBG varies with the intensity of the magnetic field and the Bragg wavelength of FBG is shifted. The temperature sensitivity of the sensor was measured with and without the magnetic field. The temperature sensitivity of the sensor was measured to be 0.02 nm/℃. We observed that the sensitivity of the fabricated device to magnetic field intensity was decreased with the environment temperature.
Ceramic powder is an important material used for various purposes in advanced industries, and the fundamental properties of ceramic powder such as particle size, particle size distribution, and flow properties play a decisive role in determining the quality and performance of the final product. In general, these properties have been evaluated through particle size and shape analysis. However, these methods have limitations in providing a comprehensive understanding phenomena related to powder flow, coagulation, and wear. Consequently, performance evaluation based on the analysis of powder flow properties has been increasingly adopted. Previously, flow properties were primarily assessed using funnel-based methods. However, these methods have limitations, as they are challenging to apply to powders smaller than a few micrometers or those with strong coagulation tendencies, and they also suffer from low reliability. To address these issues, this paper introduces a novel piece of equipment that measures flow properties using image analysis and presents various parameters for static and dynamic flow behavior based on this technique. The proposed equipment offers exceptional versatility, as it can be applied to all types of ceramic powders regardless of their size or shape. The principles and measurement methods of the equipment are demonstrated through static and dynamic image analysis of ceramic powders with varying sizes and shapes used as examples.
This review examines the principles, limitations, and recent advancements in elastic modulus measurement using nanoindentation. The importance of accurate contact area prediction is discussed, along with the Oliver-Pharr method and its limitations. The Continuous Stiffness Measurement (CSM) technique is presented as a significant improvement, allowing continuous measurement of mechanical properties throughout the indentation process. For ultra-thin films, the Li and Vlassak method, which incorporates Yu's solution and the concept of effective thickness, is highlighted as a means to correct for substrate effects. Recent developments in artificial neural network-based models for elastic modulus prediction are also explored. These advancements have greatly expanded the applicability of nanoindentation in semiconductor and MEMS device reliability assessment.
Neuromorphic computing, inspired by the biological mechanisms of neural signal transmission, has emerged as a promising technology for efficient and parallel data processing with minimal power consumption. In this study, we developed floating-gate organic thin-film transistors (OTFTs) with self-assembled monolayer (SAM)-based tunneling layers to mimic the characteristics of artificial synapses. The tunneling layers were formed using mixed phosphonic acid SAMs with varying ratios of octadecylphosphonic acid (ODPA) and 12-pentafluorophenoxydodecylphosphonic acid (PFPA). The influence of these ratios on the memory and neuromorphic characteristics of the devices was systematically evaluated. Our results revealed that the ODPA ratio significantly impacts the hysteresis window, with higher ODPA content yielding improved memory characteristics. Conversely, the PFPA : ODPA ratio of 2:1 exhibited the lowest non-linearity (NL = 0.48), demonstrating the potential for highly accurate weight updates in neuromorphic devices. Additionally, pulse width modulation studies showed that a pulse width of 100 ms optimized the linearity and stability of long-term potentiation (LTP) and depression (LTD) characteristics. The combination of sol-gel processed AlOx as a floating-gate layer and tailored SAM-based tunneling layers allowed for precise control of device performance. These findings highlight the importance of molecular engineering in designing SAM layers to balance memory retention and neuromorphic functionality. This study provides a pathway for advancing organic floating-gate transistors as a core component in next-generation neuromorphic computing systems.
With the extensive industrial growth driven by the Fourth Industrial Revolution and the excessive use of fossil fuels, greenhouse gas emissions have accelerated global warming. Energy harvesting technologies have garnered significant attention as a potential solution to this issue. Among them, triboelectric nanogenerators (TENGs) have emerged as promising candidates for energy collection and conversion. However, TENGs typically face limitations in providing an efficient energy supply due to their high output voltage and low output current. To overcome these challenges, numerous studies have explored various methods to enhance the output performance by increasing the surface area of the triboelectric materials. Herein, we report a high-output TENG fabricated through a simple scratch process. By utilizing sandpaper, typically used for abrasion or polishing, the surface roughness of the triboelectric material PFA was increased through surface scratching. The surface-engineered TENG, prepared through this simple and rapid process, demonstrated enhanced output characteristics with a voltage of 276 V and a current of 72 μA, showing a 21% increase in voltage and a 41% increase in current compared to the non-engineered counterpart, providing sufficient energy to power an LED. These results indicate that the scratch-based surface modification process using sandpaper offers an effective solution for improving triboelectric output performance, establishing TENGs as a key contributor to sustainable energy supply.
The quench behavior of coated conductors (CCs) was simulated with a focus on the initial stage of quenches, and the current limiting behavior of superconducting fault current limiters (SFCLs) at DC faults was calculated. Since the fault current reaches the peak in several ms in DC lines due to capacitor discharge, it is necessary to understand the initial quench behavior well. Considered in the simulation are characteristics of CCs in the flux-flow state, current sharing, non-uniform critical current distribution in CCs, and heat transfer to surroundings. The simulation fit data well. Using the CC model developed in the simulation, the current limiting behavior of SFCLs made of CCs at DC faults was calculated. Critical current distribution and heat transfer were found to affect the current limiting behavior of SFCLs less at DC faults. The calculation will contribute to the effective design of SFCLs for applications in DC lines.
The printed and bifacial organic photovoltaics (OPVs) using a semi-transparent electrode structure to enhance light management were investigated. To optimize energy-band alignment for bifacial device structure, a cathode interlayer of ZnO nanoparticles with a low work function of 3.9 eV combined with a polyethyleneimine (PEI) layer was employed. Photon distribution simulations revealed the influence of structural parameters on device conductivity, light absorption, and surface morphology. The dispensing strength, adjusted via applied voltage during printing, significantly impacted device performance. At 13 V and 17 V, J-V characteristics were consistent; however, at 20 V, line width increased by approximately 100%, resulting in a 50% reduction in PCE. These findings highlight the critical relationship between spraying strength, line width, and efficiency, offering valuable insights for advancing printed OPV technologies.
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