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.

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.

Smart electronic skin (E-skin) is an emerging technology that integrates electronic devices with human skin, enhancing human-machine interactions. One critical challenge in its development is effective thermal management to ensure device reliability, longevity, and user comfort. This review highlights passive cooling techniques - thermal conduction, convection, radiation, and phase-change materials - as key strategies to address this challenge without additional power consumption. These integrated mechanisms have demonstrated the ability to efficiently dissipate heat, preventing thermal buildup and maintaining optimal performance in E-skin devices. Recent advancements indicate that combining these methods can significantly enhance the thermal management of flexible electronics. Future research should focus on refining these materials and techniques to overcome challenges related to cost, durability, and environmental stability, thereby advancing the practical application of E-skin technology.

In this study, the electrical properties of zinc oxide (ZnO) thin-film transistors (TFTs) based on oxide semiconductors were analyzed. As interest in next-generation transparent and flexible displays grows, ZnO, which offers high field-effect mobility and transparency, has emerged as a promising material to overcome the limitations of amorphous silicon (a-Si)-based TFTs. ZnO has a wide bandgap and optical transparency and can be deposited on various substrates at low temperatures, making it a suitable channel material for future display devices. In this study, ZnO TFTs were fabricated with an inverted staggered structure using a p⁺⁺ Si wafer coated with SiO₂ as the substrate. The ZnO channel layer was deposited by RF magnetron sputtering, and the ITO source/drain electrodes were formed using an e-beam evaporator. The electrical characteristics was evaluated using Keithley 4200A-SCS parameter analyzer. Mobility, On/Off ratio, and subthreshold swing (SS) were calculated from the measurements.

This study investigates the effects of chemical etching for anti-glare (AG) treatment and the subsequent deposition of a TiZrO₂/SiO₂ double-layer anti-reflection (AR) coating on glass surfaces. The AG treatment was performed using ammonium fluoride in gel form via screen printing, followed by electron beam deposition of SiO₂/TiZrO₂ layers. The surface roughness, optical transmittance, and refractive index were analyzed. The results revealed that while the surface roughness increased with larger screen patterns during the AG treatment, it was reduced by the deposition of the AR layers. Additionally, the gloss caused by external light was higher with lower surface roughness, but it was effectively reduced by the AR coating. The optical reflectance showed minimal changes during the AG treatment, remaining similar to that of bare glass substrates. However, the AR coating significantly decreased reflectance. The combination of AG treatment and AR coating improved optical transmittance and reduced gloss, making this method beneficial for enhancing visibility in automotive displays. The findings suggest that this approach can mitigate the impact of external light and improve the clarity of displayed information, making it suitable for automotive display applications.

Cu₂O metal oxide was synthesized using NaBH₄ as a reducing agent in this study. The transformation of Cu composite with the pH adjustment was investigated, and the conditions for Cu₂O synthesis were analyzed. As pH of the solution was changed, the synthesized Cu composite evolved into Cu/Cu₂O and Cu/Cu₂O/CuO composites. The Cu₂O composite synthesized under conditions closest to pure Cu₂O was heat-treated at 200℃. The remaining minor Cu metal was oxidized, resulting in pure Cu₂O particles with enhanced crystallinity. The synthesized Cu₂O exhibited various morphology with particle sizes of about 160~720 nm, and the shape and size of the Cu₂O particles remained significantly unchanged after heat treatment. Surface analysis was conducted to compare the changes before and after heat treatment. No significant changes were observed, except for those attributed to water evaporation. The Cu₂O synthesized via this simple chemical reduction method can be utilized in various application fields, including catalysts, optical devices, and sensors.

This paper presents a comparative analysis of the fire detection characteristics between conventional fire detector sensors and an Si-based color sensor. With the rapid industrial development in modern society, the concentration of urban populations and the expansion of building sizes have accelerated, leading to an increased frequency of large-scale fires. As a result, the importance of fire detection technologies has been emphasized. However, conventional detectors continue to experience issues such as false alarms and malfunctions. To address these challenges, a novel fire detection technology utilizing an Si-based color sensor, which is effective for fire detection, is proposed. To evaluate the fire detection performance of each sensor, a fire detection test apparatus was developed, and experiments were conducted separately under smoke and flame conditions to analyze the fire detection capabilities of the Si-based color sensor, temperature sensor, and flame detection sensor. The experimental results demonstrated that detection speed and sensor values varied depending on the type of combustible material. Specifically, in the smoke and flame tests, the Si-based color sensor detected fires 26.7 and 43.7 seconds faster than the temperature sensor, and 26.6 and 15.4 seconds faster than the flame detection sensor, respectively. Therefore, it was confirmed that the Si-based color sensor proposed in this study is an effective detection technology that is expected to provide improved performance compared to conventional fire detectors.

Al-Mo thin films were fabricated using combinatorial sputtering system to realize highly sensitive surface acoustic wave (SAW) devices. The Al-Mo sample library was grown with various chemical compositions and electrical resistivities, which provided important information for selecting the most suitable materials for SAW devices. As the SAWs generated from piezoelectric materials are significantly affected by the resistivity and density of the interdigital transducer (IDT) electrodes, three types of Al-Mo thin films with different Al contents were fabricated. The thickness of the Al-Mo thin film used in the SAW-IDT electrode was fixed at 150 nm. As the Al content of the Al-Mo thin film decreased from 81.2 to 30.3 at%, the resistivity decreased slightly from 5.43±0.15 to 4.87±0.1×10^-5 Ω-cm, whereas the calculated density increased significantly from 4.1 to 7.9 g/㎤. The SAW device composed of Al-Mo IDT electrodes resonated at 143 MHz without frequency shifts; however, the selectivity of the resonant frequency and insertion loss deteriorated as the Al content decreased. This suggest that the resonant characteristics of the SAW devices fabricated with Al-Mo thin films were more strongly influenced by the material density rather than the electrical properties of the IDT electrodes.

In this study, the effect of thickness on the Sn-doped β-Ga₂O₃ thin films was investigated. β-Ga₂O₃ is a next-generation material for power semiconductors and optoelectronics owing to its remarkable properties, such as an ultra-wide bandgap, excellent thermal and chemical stability, and large breakdown voltage. However, its inherently low conductivity can be limiting in applications that require high conductivity; therefore, improving the conductivity of β-Ga₂O₃ is important. In this study, Sn-doped β-Ga₂O₃ thin films with various thicknesses were deposited on β-Ga₂O₃ substrates. All the fabricated samples exhibited β-phase with a uniform and dense surface and transmittance of above 80% in the visible region. In particular, the 100 nm samples showed the highest carrier concentration and mobility and the lowest resistivity. Thus, these findings are expected to play an important role in improving the performance of devices by controlling the thickness of thin films.

4H-Silicon carbide (4H-SiC) is a promising material for power and harsh environment devices owing to its superior material properties, including wide bandgap, high critical electric field, and high thermal conductivity. However, despite the advantages of 4H-SiC, its channel mobility is reduced due to the high interface defect density between SiC and the oxide film, leading to increased device switching loss. Therefore, it is necessary to develop new fabrication methods to improve the quality of the SiO₂/4H-SiC interface. According to recent research, the effect of high-temperature (1,250~1,300℃) nitric oxide (NO) annealing on the interface states of SiO₂/4H-SiC and the channel mobility of 4H-SiC metal-oxide-semiconductor-field-effect transistors (MOSFETs) were investigated. Previous studies have optimized the NO post-oxidation annealing (POA) process, using N₂ diluted NO at 1,300℃ to reduce the high SiO₂/4H-SiC interface trap density (D_it). This paper focuses on high-temperature (1,250℃) 10% NO annealing to reduce interface defects by integrating nitrogen atoms into the oxide layer near the SiC interface, potentially increasing the channel mobility. Electrical properties such as D_it, threshold voltage (V_th), field-effect mobility (μ_FE), and specific on-resistance (R_on,sp) were assessed through capacitance-voltage (C-V) and current-voltage (I-V) measurements. It has been confirmed that the interface defect density of the gate oxide film was effectively improved under the POA conditions of 10% NO for 1 hour at 1,250℃.

Hazardous gas leakage incidents rank among the most serious safety accidents, leading to significant loss of life, extensive property damage, and severe environmental pollution. This paper describes an innovative IoT-based Assembly Double Pipe System (IADPS) designed for the prevention, early detection, and automated isolation of toxic gas leaks. The proposed system features a double-layered pipe design, with nitrogen charged between the inner and outer pipes, and gas detectors installed at strategic locations. This configuration is intended to prevent pipe corrosion, suppress ignition caused by escaping gas, and facilitate the early detection of gas leaks, thereby mitigating the risk of safety accidents. Furthermore, the system includes a comprehensive real-time monitoring system for pipe integrity and gas leakage, as well as an automated gas leakage detection and isolation system to quickly respond to any incidents.

Iron oxide nanoparticles (NPs) have gained significant attention for their broad applicability in biomedical imaging, soft robotics, and catalysis owing to their exceptional magnetic properties and biocompatibility. A key challenge in maximizing their functionality lies in achieving a uniform size distribution and dispersity, alongside strong interfacial affinity with the surrounding medium that are essential for optimizing magnetic behavior and processibility. In this study, we present a facile solvothermal synthesis of monodisperse iron oxide NPs with tunable size and controllable surface hydrophobicity by varying precursors, capping agents, and solvents. By varying these synthesis parameters, we demonstrate a clear correlation between NP size, dispersity, and key magnetic properties, including saturation magnetization (MS) and coercivity (HC). This advancement in synthesis methodology offers a reliable, efficient approach for producing high-quality iron oxide NPs, which makes possible for practical use of them across a range of technological and biomedical applications.

As the importance of eco-friendly technologies increases, hydrogen vehicles are gaining significant attention as a key component of future mobility. However, the sensor technology required to accurately measure the concentration of high-purity hydrogen gas, which serves as the fuel for hydrogen vehicles, currently lacks the sensitivity needed for commercialization and remains at a demonstrative stage. This study aims to enhance the detection performance of hydrogen sensors by optimizing the fabrication process of a membrane electrode assembly (MEA) with a Pt-based electrode-electrolyte-electrode structure, where the proton-conducting electrolyte is sandwiched between upper and lower Pt electrodes. The MEA was fabricated using a hot press method, and the process was optimized by adjusting pressure, temperature, and time parameters to improve both the physical and electrical properties of the MEA. The hydrogen sensor produced using the optimized MEA showed improved sensitivity. This enhancement enables the effective monitoring of high-purity hydrogen gas used in hydrogen vehicles, thereby improving the fuel efficiency of these vehicles.

The 4H-SiC VDMOSFET demonstrates a high reverse breakdown voltage (BV) due to the JFET region but experiences relatively high on-resistance (R_on). A widely adopted method to reduce the R_on is to uniformly increase the doping concentration of the JFET region, which results in a trade-off that reduces the BV. This study proposes a method to optimize the segmentation of the JFET region by selectively increasing the doping concentration using ‘total doping’, ‘half-doping’, and ‘quarter-doping’. The optimized quarter segment with a specific doping concentration slightly reduces BV, but the sharp decrease in specific on-resistance (R_on,sp) results in a 105% improvement in the performance index, Baliga’s Figure of Merit (BFOM). This research suggests the potential for electrically superior designs by modifying the doping concentration in the JFET region of conventional VDMOSFET structures.

Recent studies have focused on enhancing the efficiency of triboelectric nanogenerators (TENGs) using aluminum (Al) and polydimethylsiloxane (PDMS). This research investigates how surface morphology and material structure affect energy generation. By layering PDMS/Al and creating pyramid-shaped patterns, the study found that increasing the number of PDMS/Al layers significantly boosts the output voltage, reaching over 234 mV with three layers. Additionally, increasing the number of pyramid structures from 1 to 36 on PDMS surfaces, while maintaining the same contact area, led to a notable rise in generated voltage due to charge concentration at the pyramid tips. Higher pyramid angles also amplified this effect. These results highlight the importance of structural optimization in maximizing the energy output of TENGs, offering a promising route for more efficient energy harvesting.

In this study, Pb(Ni_1/3Nb_2/3)O₃-Pb(Zr,Ti)O₃ ceramics substituted with Pb(Mg_1/2W_1/2)O₃ were fabricated with the variation of CuO for application to ultrasonic cleaning of removable orthodontic appliances (ROA). And their piezoelectric and dielectric properties were investigated. At the 0.12 wt% CuO added ceramics sintered at 930℃, the excellent values of dielectric constant=2,519, density=7.82 g/㎤, kp=0.64, d₃₃=536 pC/N, Qm=57 were obtained, respectively. These values were suitable for application to ultrasonic cleaning of ROA.