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.
Lead-free bismuth sodium titanate (BNT)-based ceramics have attracted strong attention as environmentally benign dielectric materials for high-efficiency electrostatic energy-storage capacitors. A key challenge is that pristine BNT typically exhibits large hysteresis, high remnant polarization, and limited dielectric reliability, which restrict recoverable energy storage and efficiency under practical electric fields. Here, we present a focused mini-review of recent studies to clarify how composition design, phase boundary tuning, defect chemistry, and microstructural control collectively enable slim or pinched polarization-electric field (P-E) behavior and improved energy-storage functionality in BNT-related bulk ceramics. The reviewed outcomes consistently show that stabilizing relaxor states governed by polar nanoregions (PNRs), often via solid-solution engineering and secondary relaxor/antiferroelectric-like incorporation, suppresses irreversible switching and reduces hysteresis loss, while densification and grain-size control enhance electrical homogeneity and breakdown strength. In addition, defect-mediated tuning of oxygen vacancy-related complexes is highlighted as an independent lever to control relaxor ergodicity and polarization reversibility, providing a complementary route to slim-loop optimization. These insights are expected to guide integrated design strategies that couple phase/relaxor-state engineering with defect and microstructure optimization, accelerating the development of reliable, temperature-robust, lead-free dielectric capacitors based on BNT-related ceramics.
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Progress and outlook of dielectric energy storage characteristics of Lead–free (K,Na)NbO3 based bulk ceramics/composite films for capacitors Twinkle, Varun Kamboj, Chetna, Arun Kumar Singh, Gurpreet Singh, Sanjeev Kumar Current Opinion in Solid State and Materials Science.2026; 44: 101297. CrossRef
Structural Stability and Electromechanical Response of Lead-Free (Bi1/2Na1/2)TiO3‒SrTiO3 Ceramics Under A-Site Strontium Non-Stoichiometry Yubin Kang, Trang An Duong, Gwang-Hwi Jeong, Chang Won Ahn, Yong-Jai Kwon, Hyoung-Su Han Journal of Electrical and Electronic Materials.2026; 39(5): 549. CrossRef
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.
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Fabrication and performance of integrated self-powered PAAM hydrogel flexible pressure sensors Huaikuan Zang, Chao Hu, Pan Niu, Yong Zhang Materials Science in Semiconductor Processing.2026; 214: 110899. CrossRef
This paper reviews the energy yield enhancement characteristics of bifacial photovoltaic systems combined with solar tracking, focusing on their performance relative to conventional monofacial fixed-tilt configurations. The fundamental mechanisms of yield improvement are summarized, highlighting the largely additive contributions of solar tracking, which increases front-side irradiance, and bifacial modules, which utilize rear-side reflected and diffuse radiation. Reported results from previous studies indicate that bifacial systems with single-axis tracking typically achieve 25–35% higher annual energy yield compared with standard monofacial fixed-tilt systems, with variations depending on environmental and design conditions. Key design and environmental considerations influencing system performance are discussed to provide practical insights for the application of bifacial tracking systems in utilityscale photovoltaic installations.
The ability to manipulate and probe biomolecules at the single-molecule level has become an essential approach for understanding molecular interactions, conformational dynamics, and nanoscale transport phenomena. Advances in experimental techniques have enabled precise control of individual molecules with high spatial resolution and piconewton-level force sensitivity. These developments have significantly expanded the capability of studying biomolecular mechanics and dynamics beyond conventional ensemble measurements. A variety of physical strategies have been developed for single-molecule manipulation, including mechanical-force-based approaches, electric-field-driven methods, and nanoscale structural confinement techniques. Mechanical-force-based methods, such as optical tweezers, magnetic tweezers, and atomic force microscopy, enable direct measurement of molecular mechanical responses. Electric-field-based manipulation, represented by dielectrophoresis, allows noncontact control of particles and biomolecules through polarization effects in non-uniform electric fields. In addition, nanopore-based systems employ nanoscale confinement to regulate molecular transport and residence behavior. This review provides an overview of representative single-molecule manipulation techniques based on mechanical, electrical, and structural control and discusses their fundamental principles and implementation strategies.
Quantum dots (QDs) are semiconductor nanocrystals with sizes on the order of several nanometers, whose bandgaps can be tuned by controlling the particle size. Owing to this bandgap tunability, QDs can absorb near-infrared (NIR) and short-wave infrared (SWIR) light, spectral regions that are difficult to access with conventional silicon-based devices. However, colloidal QDbased infrared photodetectors still suffer from intrinsically high dark current, trap-induced noise, and limited response speed. As a result, they exhibit fundamental performance gaps in terms of detectivity and speed–bandwidth product compared to epitaxial infrared detectors, highlighting the need for structural and architectural design strategies to overcome these limitations. In this review, we discuss recent advances in enhancing the spectral selectivity and sensitivity of infrared photodetectors through three-dimensional optical architectures, including metasurfaces and metamaterials. We focus in particular on design strategies and the underlying mechanisms responsible for performance enhancement, and we outline how structural approaches can be leveraged to effectively control the sensitivity and wavelength selectivity of QD-based infrared detectors.
As technologies such as artificial intelligence, autonomous driving, the Internet of Things, wearable electronics, and edge computing continue to spread in the era of the Fourth Industrial Revolution, the importance of hardware security for the safe storage, transmission, and processing of large volumes of data has grown substantially. One of the key components of such security systems is the true random number generator (TRNG), which produces unpredictable random numbers for cryptographic use. In recent years, research on TRNGs has increasingly moved beyond conventional CMOS-based approaches toward semiconductor devices built from emerging materials. These material-based TRNGs offer several advantages, including high integration density, low power consumption, compact form factors, and strong suitability for next-generation edge and IoT environments, because they can directly exploit the intrinsic stochasticity of the device itself as an entropy source. In this review, recent studies on TRNGs based on emerging material-based semiconductor devices are examined from the perspectives of entropy sources, device structures, randomness validation, and wearable/flexible extensions. By bringing together the key physical mechanisms, device platforms, evaluation criteria, and prospects for wearable and flexible electronics in edge and IoT environments, this review aims to provide a useful framework for future research on hardware security devices.
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.
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Reliability enhancement in Dy-doped BaTiO3 nanoceramics: from core–shell structure to phase-field modeling Shuyan Huang, Xinjie Wang, Mengjian Xiao, Xu Cheng, Xiaohui Wang Journal of Materials Science.2026; 61(37): 27665. CrossRef
Key factors determining high-temperature operating lifetime of multilayer ceramic capacitors (MLCCs) Yuto Tomura, Tzu-han Weng, Yusuke Oba, Tomohiro Kajita, Daiki Ishii Japanese Journal of Applied Physics.2026; 65(16): 16SP05. CrossRef
Effect of BaZrO3 Addition on the Frequency and Temperature Dependent Dielectric Properties of BaTiO3-Based Ceramics Won-Su Lee, Jong Kyu Lee, Moon-Taek Cho, Jung Rag Yoon Journal of Electrical and Electronic Materials.2026; 39(5): 478. CrossRef
Manufacturing Process Optimization of Oxide-Based Multilayer Ceramic Batteries Using Multilayer Ceramic Processing Technologies Won-Su Lee, Jong Kyu Lee, Jung Rag Yoon Journal of Electrical and Electronic Materials.2026; 39(5): 519. CrossRef
The effects of BaZrO₃ addition on the structural and electrical properties of BaTiO₃-based base-metal-electrode (BME) multilayer ceramic capacitor (MLCC) ceramics were investigated. Dielectric compositions containing 0–9 wt% BaZrO₃ were fabricated using a conventional MLCC process, and their crystal structure, dielectric behavior, temperature stability, frequency stability, and insulation resistance were evaluated. X-ray diffraction and Rietveld refinement confirmed the formation of a single-phase perovskite structure for all compositions. Increasing BaZrO₃ content resulted in a systematic shift of diffraction peaks toward lower angles and an increase in unit-cell volume from 64.61 to 66.05 ų, indicating successful Zr incorporation into the BaTiO₃ lattice. The dielectric permittivity increased with BaZrO₃ addition and reached a maximum value of approximately 2,110 at 6 wt%, while dielectric loss decreased significantly. Capacitance stability against temperature and frequency variations was markedly improved with increasing BaZrO₃ content. In addition, insulation resistance increased substantially over the investigated temperature range, demonstrating enhanced electrical reliability.
This study investigates the effect of dielectric layer thickness on the electrical and reliability characteristics of BaTiO₃- based X8R multilayer ceramic capacitors (MLCCs) for automotive applications. MLCCs with 30 dielectric layers and thicknesses ranging from 5 to 30 μm were fabricated, and key parameters―including capacitance, equivalent series resistance (ESR), insulation resistance (IR), breakdown voltage (BDV), DC-bias characteristics, temperature coefficient of capacitance (TCC), and ripple current-induced heating―were evaluated. The dielectric constant (~2,000) and sintering shrinkage (~-25%) were nearly independent of thickness, confirming stable microstructure formation. ESR increased with thickness, while normalized BDV (V/μm) decreased due to defect accumulation. IR improved with increasing thickness but dropped sharply above 125℃. Dielectrics thinner than 10 μm exhibited significant capacitance degradation under DC-bias and temperature variation, reflecting strong internal field effects. Ripple-induced heating correlated directly with ESR. These results indicate that, although thinner layers enhance capacitance density, reducing the thickness below 10 μm compromises bias stability and thermal reliability. A minimum dielectric thickness of 10 μm is therefore recommended to achieve an optimal balance between electrical performance and durability in high-reliability X8R MLCCs.
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Structural Analysis of Electric Field-Induced Polarization and Strain in Ferroelectric BaTiO3 Jae Hwan Park Journal of Electrical and Electronic Materials.2026; 39(4): 374. CrossRef
X-ray photon correlation spectroscopy (XPCS) provides access to nanoscale dynamics, yet practical approaches for interpreting its data remain limited. This tutorial presents a systematic framework for XPCS data analysis, illustrated using measurements performed at the NSLS-II CHX beamline. The fundamental concepts of speckle pattern and the intensity autocorrelation function are introduced, followed by ferroelectric case studies demonstrating how polarization switching and phase transition dynamics can be extracted from XPCS measurements. The influence of the probed q-range experimental conditions such as X-ray transmittance is examined for data interpretation. These elements are consolidated into practical guidelines for the reliable analysis of XPCS data.
The search for sustainable and efficient energy conversion technologies is becoming increasingly critical in response to global energy and environmental challenges. Traditional lead-based piezoelectric materials, such as lead zirconate titanate (PZT), have high piezoelectric constant but present significant health problems and environmental risks due to their hazardous metal contaminants. This study addresses these concerns by investigating barium titanate (BTO), a lead-free alternative, and enhancing its performance using anisotropic nanowires (NWs) structures. BTO NWs were synthesized via a two-step hydrothermal method and incorporated into a poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] matrix to fabricate a piezoelectric composite film. The resulting device demonstrated a notable increase in electrical output compared to devices based on isotropic morphology of BTO nanoparticles, exhibiting enhanced performance. These findings suggest that BTO NWs hold significant promise for applications in flexible and wearable electronics, paving the way for further advancements in sustainable energy technology.
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Interphase engineering in carbon black–reinforced piezoelectric nanocomposites: A combined experimental and micromechanical modeling study Ziwen Zhao, Masoumeh Khamehchi, Mohammad J. Mahmoodi, Zhenjin Wang, Fumio Narita Materials & Design.2026; 268: 116391. CrossRef
MXene-reinforced ultrasensitive piezoelectric pressure sensors based on P(VDF-TrFE) nanofibers with hybrid nanofillers Jingyi Yang, Jianqiao Wang, Zike Guo, Shuai Liu, Yaohua Dong, Peng Zhou, Tianjin Zhang, Yajun Qi Journal of Alloys and Compounds.2026; 1079: 189867. CrossRef
Layer-engineered BNBT–polymer films for multifunctional applications M. Vijatovic Petrovic, A. Dzunuzovic, J. Bobic, Z. Despotovic, F. Cordero, E. Mercadelli, Z. Radovanovic, F. Craciun Journal of Alloys and Compounds.2026; 1079: 189972. CrossRef
Piezoionic sensor devices of integrated gradient electrolyte gels Yi Fang, Hongbing Li, Taeuk Eom, Chang Kyu Jeong, Yong Zhang Chemical Engineering Journal.2026; 540: 177542. CrossRef
Interfacial polarization triggered by low-k fillers boosts piezoelectricity of MMT/PT composites for intelligent health monitoring Yong Ao, Junjun Yuan, Wenqi Yu, Rui Yuan, Boling Lan, Shenglong Wang, Tingting Zhou, Guicen Liu, Wei Zhao, Zhiyuan Gao, Xiaofei Jiang, Weili Deng, Long Jin, Weiqing Yang Journal of Materials Chemistry A.2026;[Epub] CrossRef
Interfacial Engineering
of Composite Piezoelectric
Fibers Via an Anchor-Chain Architecture Jun Liu, Qiao Zhou, Pengcheng Zhang, Shuying Hu, Fang Zhou, Shuangshuang Ren, Ting Guo, Leiying Miao ACS Applied Engineering
Materials.2026; 4(8): 4367. CrossRef
The 0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr0.5Ti0.5)O3 (0.2PZN-0.8PZT) ceramic system exhibits excellent piezoelectric properties; however, its high sintering temperature (~1,250°C) causes severe PbO volatilization, increases processing cost, and limits co-firing with low-melting-point electrodes in multilayer devices. In this study, LiBiO2 was introduced as a sintering aid to enable lowtemperature densification of 0.2PZN–0.8PZT ceramics. The optimal composition of x = 0.3 mol% sintered at 1,050°C achieved d33 = 367 pC/N, kp = 0.54, and εT33/ε0 = 1,643. The Curie temperature was also enhanced to 347.8°C, compared with 297.2°C for the reference specimen sintered at 1,250°C. These results demonstrate that LiBiO2 addition enables a 200°C reduction in sintering temperature while maintaining piezoelectric performance and improving thermal stability.
Dye adsorption is one of the most time-consuming processes in the fabrication of dye-sensitized solar cells (DSSCs), typically requiring approximately 24 h at room temperature. In this study, the effect of adsorption temperature and time on photovoltaic performance of DSSCs was investigated in order to reduce processing time and improve device productivity. Nanoporous TiO2 photoelectrodes were immersed in N719 dye solution at 60°C for 3 h, 10 h, 17 h, and 24 h, and their performance was compared with that of cells sensitized at room temperature for 24 h. Photovoltaic characterization under AM 1.5 illumination showed that DSSCs sensitized at 60°C exhibited improved performance compared to those sensitized at room temperature. The device sensitized at 60°C for 3 h showed comparable or higher conversion efficiency than the reference cell sensitized for 24 h at room temperature. The improvement in device performance is attributed to enhanced dye adsorption kinetics resulting from increased reaction rate between the carboxyl groups of N719 dye molecules and hydroxyl groups on the TiO2 surface. Electrochemical impedance spectroscopy analysis revealed reduced recombination resistance at the TiO2/dye/electrolyte interface for cells sensitized at elevated temperature. UV–Vis absorption analysis confirmed increased dye loading on the TiO2 surface for the 60°C condition. These results demonstrate that elevated temperature dye adsorption significantly reduces processing time while maintaining photovoltaic performance, providing an effective strategy for improving manufacturing efficiency of DSSCs.
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Enhanced charge transport characteristics of hydrothermally grown rutile TiO2 nanorod arrays for dye-sensitized solar cells Kyu Seop Choi, Hyung Jin Kim, Byungyou Hong Surfaces and Interfaces.2026; 98: 110402. CrossRef
The phase transition of Li3PO4 solid electrolyte for secondary batteries in vacuum has been studied by using real-time synchrotron X-ray scattering. According to the vacuum heating results, the crystal β-Li3PO4 phase was stable only from room temperature to 400°C. The crystal γ-Li3PO4 phase appeared at 410°C and the crystal β-Li3PO4 phase completely disappeared at 430°C. The transition from the β-Li3PO4 to the γ-Li3PO4 phases occurred primarily at 410°C, which is 40°C lower than the transition temperature of 450°C in air. The decrease in the phase transition temperature in vacuum, compared to that in air, is attributed to a relatively high concentration of oxygen vacancies. As the isothermal annealing time at 390°C was increased to 8 hours, the β-Li3PO4 phase was completely transitioned into the γ-Li3PO4 phase. Our study revealed the detailed transition behavior from the β-Li3PO4 to the γ-Li3PO4 phases during real-time annealing in vacuum.
Two-dimensional van der Waals (2D vdW) magnets have attracted enormous attention as an emerging material platform for magnetism, spintronics, and multifunctional applications. Their single-crystalline layered structures, layer-number controllability, and unique 2D properties provide unique opportunities that are difficult to achieve in conventional magnetic materials. However, the discovery and development of new 2D magnetic compounds require considerable time and effort, and only a limited number of these materials have been reported to be suitable for practical use. Therefore, materials engineering based on already established 2D vdW magnets has become an important research direction to explore new characteristics and find a practical route for device applications. This review summarizes recent materials engineering pathways for 2D vdW magnets. The main contents focus on the engineering strategy through electrostatic, chemical, lattice, symmetry, and heterostructure ways. These approaches provide practical design routes for tailoring magnetic properties beyond intrinsic 2D vdW magnets. Further progress will require broader application to various types of materials and delicate optimization that connects expanding fundamental magnetism with electromagnetic device applications.
The direct utilization of steelmaking by-product gases in solid oxide fuel cells (SOFCs) offers a promising pathway to improve energy efficiency and reduce carbon emissions in the steel industry. In this study, a Sr-deficient and Ni-doped double perovskite oxide, Sr1.95Fe1.35Ni0.15Mo0.5O6-δ (SFNM), was investigated as an anode material for direct Linz-Donawitz converter gas (LDG)-fueled SOFCs. A single-phase double perovskite structure was successfully obtained after calcination at 1,200°C for 12 h, while exsolved metallic Ni nanoparticles were generated on the SFNM surface after reduction at 800°C. Electrochemical performance was evaluated using H2, simulated-LDG, and CO/CO2 (85:15) fuels at 800°C. The maximum power densities achieved were 1.23, 0.70, and 0.40 W cm-2 for H2, simulated-LDG, and CO/CO2 fuels, respectively. Although CO-containing fuels exhibited lower opencircuit voltages and power outputs than H2, the SFNM anode maintained stable operation and appreciable performance under direct simulated-LDG utilization. Impedance analysis revealed that the increased polarization resistance in simulated-LDG and CO/CO2 atmospheres was mainly associated with fuel adsorption/desorption and gas diffusion, while interfacial charge-transfer resistance remained relatively small. The superior performance obtained with simulated-LDG compared to the CO/CO2 mixture was attributed to the presence of a small amount of H2, which facilitated anode reaction kinetics. These results demonstrate that SFNM is a promising mixed ionic-electronic conductor anode for the direct electrochemical conversion of CO-rich steelmaking by-product gases into electricity.
Multilayer ceramic batteries (MLCBs) have attracted increasing attention as compact all-solid-state energy-storage devices that can be manufactured using multilayer ceramic processing technologies. In this study, an MLCC-compatible fabrication process for oxide-based MLCBs was developed using Li₁₊ₓAlₓTi₂₋ₓ(PO₄)₃ (LATP) solid electrolytes, Li₃V₂(PO₄)₃ (LVP) cathodes, and Cu current collectors. Commercial LATP powders were evaluated in terms of particle-size distribution, phase purity, thermal stability, and ionic conductivity. The selected LATP powder was subsequently employed for tape-cast green-sheet fabrication, and the effects of polyvinyl butyral (PVB) binder content on slurry rheology and sheet microstructure were investigated. An optimized binder composition containing 11 wt% PVB (BM-2/BH-3 = 3:7) provided improved processability and microstructural uniformity. Drying conditions during sequential electrode printing were also optimized to suppress sheet warpage and improve multilayer registration. Thermogravimetric and differential thermal analyses (TG–DTA) were used to establish an optimized two-step debinding and co-firing process under a controlled reducing atmosphere. The resulting multilayer structures exhibited uniform densification without significant blistering, delamination, or interfacial defects. Charge–discharge measurements confirmed that electrochemical functionality was retained after the complete manufacturing process, yielding a discharge capacity of approximately 2.5–2.7 μAh.
Energy harvesting technology offers an innovative solution for providing self-sustaining power to wearable and implantable electronic devices. However, traditional energy harvesters face limitations in operating within electrolytic environments or at low motion speeds. To overcome these challenges, a mechano-electrochemical energy harvester using carbon nanotubes has been developed. This technology relies on electrochemical ion movement to induce changes in electrochemical double-layer capacitance, enabling operation within electrolytes and optimizing performance at low deformation speeds. This environmentally friendly and sustainable energy solution is expected to play a crucial role in the advancement of future smart systems and wearable technologies.
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Fabrication and performance of integrated self-powered PAAM hydrogel flexible pressure sensors Huaikuan Zang, Chao Hu, Pan Niu, Yong Zhang Materials Science in Semiconductor Processing.2026; 214: 110899. CrossRef
Piezoionic sensor devices of integrated gradient electrolyte gels Yi Fang, Hongbing Li, Taeuk Eom, Chang Kyu Jeong, Yong Zhang Chemical Engineering Journal.2026; 540: 177542. CrossRef
Covalent Interfacial Anchoring of 1D‐2D Hybrid Nanofillers to Poly(Vinyl Alcohol) Networks Enables High‐Strength, High‐Stiffness Hydrogel Fibers Dong Yeop Lee, Ji Hwan Moon, Hocheol Gwac, Gyu Hyeon Song, Hyunsoo Kim, Yongwoo Jang, Changsoon Choi, Seon Jeong Kim Advanced Materials.2026;[Epub] CrossRef
Mechano-Electrochemical Sensor Using CNT/SEBS Bilayer Seokkan Ki, Junyoung Lee, Hyeon Jun Sim Journal of Electrical and Electronic Materials.2026; 39(5): 532. CrossRef
Hierarchically Chiral Self‐Plied Yarn for Torsional Stability and Self‐Recovery, and Its Application to Direction‐Selective, Low‐Frequency, Wide‐Range Mechano‐Electrochemical Torsional Sensor Hyunsoo Kim, Youngkun Hong, Seonghyun Kim, Wonkyeong Son, Jae Myeong Lee, Ha Eun Cho, Jeongyun Kim, Jae Sang Hyeon, Yongwoo Jang, Jeyeong Kim, Seongjae Oh, Shi Hyeong Kim, Seon Jeong Kim, Changsoon Choi, Young‐Jin Kim, Hyeon Jun Sim Advanced Functional Materials.2026;[Epub] CrossRef
Polymer nanocomposites incorporating inorganic nanofillers have emerged as highly promising electromagnetic interference (EMI) shielding materials, combining mechanical compliance with robust conductive percolation networks. Carbon nanotubes (CNTs) are particularly attractive as conductive fillers because their high aspect ratio facilitates percolation at low loadings. Also, CNTs offer superior mechanical durability under deformation compared to rigid, fracture-prone metal nanowires. For EMI shielding, high electrical conductivity is critical as it enhances both reflection and absorption through efficient charge dissipation and conduction losses. However, achieving highly aligned conductive pathways without degrading the intrinsic electrical properties of CNTs remains a significant challenge. Here, we demonstrate a non-destructive magnetic surface-functionalization and alignment strategy. Using a polydopamine (PDA)-mediated route, pristine multiwalled CNTs are uniformly decorated with Fe3O4 nanoparticles (FMWCNTs). This enables highly effective magnetic field-driven alignment at fields as low as 10 mT, promoting the strategic formation of percolation networks. By optimizing the Fe₃O₄/MWCNT ratio for high saturation magnetization and uniform coverage, the aligned FMWCNTs exhibit significant electrical anisotropy, delivering a 10.7-fold higher electrical conductivity in the parallel configuration compared to the vertical configuration. These findings present a scalable, room-temperature platform for engineering directionally enhanced conductivity in polymer nanocomposites, with broad applicability in advanced EMI shielding, flexible electronics, and advanced packaging technologies.
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Interfacial Engineering
of Composite Piezoelectric
Fibers Via an Anchor-Chain Architecture Jun Liu, Qiao Zhou, Pengcheng Zhang, Shuying Hu, Fang Zhou, Shuangshuang Ren, Ting Guo, Leiying Miao ACS Applied Engineering
Materials.2026; 4(8): 4367. CrossRef
This study examined the crystallinity and potential of BaTiO₃ powder, prepared by hydrothermal synthesis at 60 nm, as a dielectric material for automotive MLCCs under varying heat treatment temperatures. At temperatures above 850℃, the powder exhibited an orthorhombic structure, with crystallinity and particle size increasing as the temperature rose. In the range of 850~900℃, the powder displayed a uniform particle size distribution and minimal agglomeration, with particles ranging between 150~200 nm. Additionally, it was confirmed that the heat treatment temperature significantly impacts the properties of BaTiO₃ powder, which are critical for the dielectric performance required in X7R MLCCs used in automotive applications. Specifically, high-temperature treatment (above 850℃) was essential for enhancing the powder's crystallinity and forming a stable core-shell structure, which is crucial for achieving stable TCC (Temperature Coefficient of Capacitance) characteristics. It was confirmed that increased crystallinity at temperatures above 850℃ facilitated the development of the core-shell structure through interactions with additives, thereby achieving the necessary characteristics required for highly reliable automotive MLCCs.
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[100]-Oriented BaTiO₃ via reaction-mediated texturing with SrTiO₃ templates Nu-Ri Ko, Jinsung Chun, Kutak Lee, Chang Kyu Jeong, Wook Jo Journal of the Korean Ceramic Society.2026; 63(4): 574. CrossRef
Effect of BaZrO3 Addition on the Frequency and Temperature Dependent Dielectric Properties of BaTiO3-Based Ceramics Won-Su Lee, Jong Kyu Lee, Moon-Taek Cho, Jung Rag Yoon Journal of Electrical and Electronic Materials.2026; 39(5): 478. CrossRef
Enhanced dielectric performance in BaTiO3 ceramics by diffusion-controlled core-shell structuring with 2D Ca2Nb3O10 nanosheets Tae Yeong Song, Junwon Lee, Nayeon Kwon, Do-Kyun Kwon Journal of the Korean Ceramic Society.2026; 63(5): 1194. CrossRef
In this study, we systematically investigated the effects of thermal atomic layer deposition (ALD) conditions on the electrical characteristics of conductive-filament-based volatile threshold switching memristors with a Pt/Al₂O₃/Ag structure. Although volatile threshold switching memristors have attracted significant attention for neuromorphic computing applications such as spiking neural networks, the impact of dielectric deposition conditions on their switching behavior remains relatively unexplored. The number of ALD cycles was varied from 40 to 200, and the deposition temperature was varied from 50 to 250°C to evaluate their effects on threshold voltage (Vth), off-state resistance (Roff), and device yield. Devices fabricated using 75–150 ALD cycles showed clear volatile threshold switching behavior with relatively high device yield, whereas excessively low or high cycle numbers resulted in short-type and open-type failures, respectively. In addition, Vth and Roff tended to increase at higher deposition temperatures, while the device yield significantly degraded above 150°C. These results indicate that the number of ALD cycles and the deposition temperature define a critical process window for achieving volatile threshold switching while suppressing both short-type and open-type failures. This study provides practical guidelines for optimizing dielectric ALD conditions in conductive-filament-based volatile threshold switching memristors for future neuromorphic hardware applications.
Metal sacrificial-layer-assisted transfer is a promising strategy for transferring thermally annealed thin films onto flexible polymer substrates without exposing the receiver substrate to thermal damage. However, stable release of the annealed thin-film stack remains challenging because high-temperature annealing can alter the etching behavior of the sacrificial metal layer and the protective oxide layer. In this study, we propose a thin-film transfer process using a Ni metal sacrificial layer and etch access holes, in which an SU-8/Ti/SiO2 transferable stack was fabricated on a rigid sapphire donor substrate, annealed at 400–700°C, selectively released by Ni etching, and transferred onto a flexible PET receiver substrate. As the annealing temperature increased from 400 to 700°C, the SiO2 etch rate decreased from 6.8–6.96 to 2.61–3.83 nm/s, while the Ni release time increased from 72–77 to 82–95 min; nevertheless, the transferable stack was successfully transferred under all process conditions with image-based transfer yields of 58.81–82.76%, with the highest yield obtained for the 200 nm Ni sacrificial layer annealed at 550°C. These results demonstrate the process feasibility of the proposed metal sacrificial-layer and etch-access-hole-based transfer approach for transferring thermally annealed thin-film structures from rigid donor substrates to flexible receiver substrates.
Dye-sensitized solar cells (DSSCs) suffer from efficiency limitations due to interfacial charge recombination at the TiO₂/dye/electrolyte interface. In this study, aminopropyltrimethoxysilane (APS) was introduced onto nanoporous TiO₂ photoelectrodes via a dip-coating process with controlled coating times to investigate the effect of silanization time on interfacial charge transport behavior. Unlike concentration-driven structural modification, this work focuses on the evolution of the APS-modified interface governed by reaction time. The DSSC with 30 min APS treatment exhibited the highest power conversion efficiency of 5.34%, representing a 19% enhancement compared to the untreated device (4.49%), mainly due to increased short-circuit current density and open-circuit voltage. However, prolonged coating times (2 h and 24 h) resulted in a significant decrease in photocurrent density, leading to reduced device performance despite partial improvement in recombination resistance. These results are attributed to the time-dependent evolution of the APS interfacial layer. At moderate coating time, APS provides effective surface functionalization, enhancing dye adsorption and suppressing interfacial recombination. In contrast, prolonged coating is expected to induce increased surface coverage and silane condensation, which can hinder electron injection and increase charge transport resistance. Therefore, the photovoltaic performance is governed by a trade-off between recombination suppression and charge injection efficiency, controlled by the silanization time. This study highlights the critical role of interfacial reaction kinetics in determining charge transport behavior and provides an effective strategy for optimizing DSSC performance through time-dependent interface engineering.
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Enhanced charge transport characteristics of hydrothermally grown rutile TiO2 nanorod arrays for dye-sensitized solar cells Kyu Seop Choi, Hyung Jin Kim, Byungyou Hong Surfaces and Interfaces.2026; 98: 110402. CrossRef
We investigated the potential of IO:H thin films and hydrogen doping to improve current density and fill factor for enhancing the performance of silicon heterojunction solar cells. We revealed that a transmittance of 86.7% and work function of 5.4 eV could be achieved by injecting 3 sccm of hydrogen gas. The lattice constant of 1.037 nm at the AB site indicates an anion antibonding tendency, and the work function increases as the Fermi level shifts to the valence band. Based on these findings, we fabricated a silicon heterojunction solar cell and achieved an efficiency of 18.53%, while computer simulation confirmed a conversion efficiency of 24.65%, an open-circuit voltage of 724 mV, and a fill factor of 82.72% at a current density of 41.15 mA/㎠.
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A Review on Energy Yield Enhancement Characteristics of Bifacial Photovoltaic Systems Combined with Solar Tracking Hyeong Gi Park Journal of Electrical and Electronic Materials.2026; 39(4): 309. CrossRef
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.
The growing demand for thinner, lighter, and more energy-efficient electronic systems has driven the development of acoustic technologies toward compact and flexible sound generation platforms. Despite significant progress, conventional electromagnetic speakers remain limited by bulky structures, energy losses, and poor compatibility with modern ultrathin devices. In this review, recent advancements in piezoelectric acoustic systems are presented, demonstrating a new generation of speakers capable of producing high-fidelity sound from ultra-slim, lightweight, and mechanically compliant designs. Through refined structural configurations and efficient electromechanical coupling, these piezoelectric exciters achieve strong acoustic output, fast response, and wide frequency operation while drastically reducing component thickness. These exciters also show their suitability for seamless integration into flexible displays, wearable devices, and automotive panels, offering enhanced spatial audio practicality and multifunctional operation, including demonstrative output and sensing. This advancement marks a step toward the convergence of acoustic, haptic, and interactive technologies, for the realization of sustainable and immersive humanmachine interfaces in future electronic and automotive systems.
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Flexible piezoelectric cross-bar array sensors for upper-limb kinesthetic sensing via muscle dynamics Junki Lee, Jihun Choi, Hyunseung Kim, Min Gon Son, Dong Yeol Hyeon, Jung Hwan Park, Andris Šutka, Chang Kyu Jeong Journal of the Korean Ceramic Society.2026;[Epub] CrossRef
The dielectric and piezoelectric properties of the ferroelectric BaTiO3 were measured and analyzed using both strong and weak electric field conditions. To measure the electric field induced polarizations and strains, a high voltage source and the measuring circuit were used and the dielectric constants were measured with an impedance analyzer. The spontaneous polarization of BaTiO3 at room temperature was calculated as 17 μC/cm2 based on the lattice structure and internal ion location, which is in good agreement with the experimental results. The polarization and strain hysteresis curve according to the electric field were analyzed in terms of lattice structure and ion position. The magnitude of remanent polarization is proportional to the offset distance of Ti4+ ion from the lattice center. The magnitude of dielectric permittivity is proportional to the degree to which Ti4+ ion can move freely inside the lattice. The magnitude of piezoelectric constant d33 is proportional to how much Ti4+ ion distorts the lattice as it moves inside the lattice.
There is an increasing demand for freeform stretchable display technologies capable of overcoming spatial limitations in next-generation platforms such as augmented reality (AR) and virtual reality (VR). To realize such stretchable displays, all constituent materials—including semiconductors, electrodes, insulators, and substrates—must exhibit sufficient mechanical elasticity. To date, stretchable gate insulators have primarily relied on organic polymers such as poly(4-vinylphenol-co-methyl methacrylate) (PVP-co-PMMA). However, their practical application is significantly limited by poor electrical properties, including low dielectric constant and instability. In this work, we propose a novel gate insulator structure that minimizes the use of solution-based processes, which often suffer from poor uniformity and may damage underlying layers during fabrication. The proposed structure integrates the advantages of both organic and inorganic materials by employing a hybrid configuration. Specifically, high-k HfO2 thin films are deposited on both the top and bottom of an organic layer composed of PVP-co-PMMA, poly(melamine-co-formaldehyde) (PMF) as a crosslinking agent, and propylene glycol monomethyl ether acetate (PGMEA) as a solvent. This inorganic–organic–inorganic structure effectively compensates for the inherent electrical limitations of organic materials. As a result, the fabricated thin-film transistors (TFTs) exhibit improved electrical performance and reliability compared to devices employing a single organic gate insulator.
Lead-free (Bi1/2Na1/2)TiO3 (BNT)-based incipient piezoelectrics are highly promising for high strain actuators, but the high electric fields (4 ~ 6 kV/mm) required for activation limit practical device integration. In the current literature, large strains are frequently attributed to local structural variations like microscopic core-shell architectures. This work systematically investigates an alternative pathway by introducing A-site Strontium (Sr) excess non-stoichiometry into 0.74(Bi1/2Na1/2)TiO3‒0.26SrTiO3 (BNST26) ceramics. Microstructural and X-ray diffraction analyses reveal highly dense, uniform matrices completely devoid of micro-scale core-shell boundaries or macroscopic symmetry distortions, revealing that Sr non-stoichiometry diverges from typical Bi-excess mechanisms. Interestingly, despite negligible variations in overall macro-scale strain behavior across the composition series, a peak normalized strain (Smax/Emax) of approximately 804 pm/V is achieved at a low driving field of 2 kV/mm for the 1 mol% Sr-excess specimen (x = 0.010). These results indicate that while Sr non-stoichiometry weakly influences nanoscale stability, it can be inferred that subtle modifications of local defect configurations optimize switching energy barriers, enabling high-strain, low-drive-field performance in lead-free relaxors.
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