Yoonkap Kim

Digital printing technologies—including inkjet printing, aerosol jet printing, and electrohydrodynamic jet printing—have emerged as promising strategies for next-generation electronic devices. However, the weak adhesion between printed electrodes and substrates can lead to electrode delamination, thereby compromising device reliability and lifetime. In this study, a dielectric interlayer was introduced to improve the adhesion of silver (Ag) mesh electrodes on glass, polyethersulfone film, and polyimide film substrates. The optimized electrode on PES film achieved an optical transmittance of 83% at 550 nm and line resistance of 0.3 Ω, confirming its suitability as a transparent electrode. The incorporation of the interlayer also enhanced the adhesion and mechanical flexibility across all substrates. Moreover, the printed electrodes exhibited uniform surface heating under an applied bias (≤DC 3 V), and their feasibility as low-power flexible transparent heaters was experimentally demonstrated. These findings present a simple and effective printing strategy for fabricating robust and multifunctional electrodes, offering enormous potential for the realization of future flexible and transparent electronic systems.

Heaters fabricated via printing conductive ink or paste on various flexible substrates have been extensively investigated. However, flexible/wearable heaters wherein all the functional structures (heater substrate, heating element, and cover layer) are fabricated via printing have not been reported. In this study, fully printed see-through conductors are fabricated using conductive Ag ink and dielectric ink and their potential for use as wearable see-through heaters is demonstrated. The relationship between the heater performance and the resistance of a printed Ag micromesh structure (which serves as the heating element) is analyzed. In addition, three types of printed heaters are fabricated based on different embedding configurations (three-sides open, one-side open, and fully embedded) of the Ag mesh electrodes, and their mechanical flexibilities are compared. The flexible heater based on the fully embedded Ag mesh structures exhibits remarkable mechanical flexibility. The rapid thermal response and high reliability of the printed flexible heaters are confirmed through Joule heating performance analysis. These results indicate the excellent potential of the proposed inkjet printing technology for the development of all-printed optoelectronics.

This study presents an inkjet-printed, single-step double layer electrode with an acrylate adhesion layer on PES to enhance Ag adhesion. The electrode offers strong mechanical stability and a simplified solution for flexible device applications.

Flexible transparent electrodes (FTEs) with an embedded metal meshes play an indispensable role in many high-performance optoelectronic devices due to their excellent mechanical stability and low-surface roughness. However, great challenges remain for achieving simple, cost-effective, and environmentally friendly manufacturing of FTEs with embedded metal mesh. In this work, a vacuum-free, mask-free, and plating-free fabrication technique is proposed for FTEs with embedded silver (Ag) mesh by combining an ink-jet printing technique and a newly developed eco-friendly polymer (polyvinyl alcohol) solution-assisted metal transfer process that does not use organic solvents. The fabricated FTEs exhibit excellent optoelectronic performance with an electrical resistance of ~ 1.6 Ω and an optical transmittance at 550 nm of ~ 85.98%. The FTEs with embedded Ag mesh show strong adhesion to the substrate due to their morphology features. The proposed technique offers a promising fabrication strategy with a cost-effective and environmentally friendly process for high-performance printed flexible electronics. Graphical abstract

We used capacitance–voltage (C–V), conductance–voltage (G–V), and noise measurements to examine the carrier trap mechanisms at the surface/core of an AlGaN/GaN nanowire wrap-gate transistor (WGT). When the frequency is increased, the predicted surface trap density promptly drops, with values ranging from 9.1 × 10¹³ eV⁻¹∙cm⁻² at 1 kHz to 1.2 × 10¹¹ eV⁻¹∙cm⁻² at 1 MHz. The power spectral density exhibits 1/f-noise behavior in the barrier accumulation area and rises with gate bias, according to the 1/f-noise features. At lower frequencies, the device exhibits 1/f-noise behavior, while beyond 1 kHz, it exhibits 1/f²-noise behavior. Additionally, when the fabricated device governs in the deep-subthreshold regime, the cutoff frequency for the 1/f²-noise features moves to the subordinated frequency (~10² Hz) side.

n-TOPCon solar cells have been the subject of extensive research by various groups in order to overcome the limitations on efficiency of p-PERC solar cells. The passivated contacts formed on the rear side of wafers for the production of n-TOPCon solar cells are deposited using LPCVD or PECVD, however, wrap-around of heavily doped polysilicon is inevitable and results in optical loss and increased shunt resistance. Therefore, post-etching process of wrap-around is necessary and detection of wrap-around after the etching process is also required. In this study, we report on the development of a machine vision system based on a digital microscope equipped with a high-magnification zoom lens and controlled by operation software to minimize human intervention as much as possible. Although further optimization of the machine vision system is needed, we expect to achieve meaningful results after optimization.

Graphene oxide (GO) is one of the interesting ink materials owing to its fascinating properties, such as high dissolubility in water and high controllable electric properties. For versatile printing application, the viscosity of GO colloids should be controlled in order to meet the specific process requirements. Here, we report on the relatively rapid fabrication of viscosity-increased GO (VIGO) colloids mixed with electrophoretically deposited GO sheets (EPD-GO). As the GO colloid concentration, applied voltage, and deposition time increase, the viscosity of the GO colloids becomes high. The reason for the improved viscosity of GO colloids is because EPD-GO has parallel stacked GO sheets. The GO and VIGO colloids are compared and characterized using various chemical and structural analyzers. Consequently, our simple and fast method for the fabrication of GO colloids with enhanced viscosity can be used for producing inks for flexible and printed electronics.

Background: The risk of displaced and comminuted midshaft clavicle fractures is increased in high-energy traumas such as sport injuries and traffic accidents. Open reduction and plate fixation have been widely used for midshaft clavicle fractures. Among various plates for clavicle shaft fractures, superior locking compression plates (LCPs) have been mostly used. In plate fixation, nonunion caused by implant failure is the most difficult complication. The most common reasons for metal plate failure are excessive stress and stress concentration caused by cantilever bending. These causes were easily addressed using a locking screw cap (LSC). Methods: The clavicle 3-dimensional image was made from a computed tomography scan, and the clavicle midshaft fracture model was generated with a 10-mm interval. The fracture model was fixed with a superior LCP, and finite element analysis was conducted between the presence (with LSC model) and absence (without LSC model) of an LSC on the site of the fracture. The stresses of screw holes in models with and without LSCs were measured under 3 forces: 100 N cantilever bending force, 100 N axial compression force, and 1 N·m axial torsion force. After the finite element analysis, a validation test was conducted on the cantilever bending force known as the greatest force applied to superior locking plates. Results: The mean greatest stress under the cantilever bending force was significantly greater than other loading forces. The highest stress site was the screw hole edge on the fracture site in both models under the cantilever bending and axial compression forces. Under the axial torsional force, the maximum stress point was the lateral first screw hole edge. The ultimate plate stress of the with LSC model is completely lower than that of the without LSC model. According to the validation test, the stiffness, ultimate load, and yield load of the with LSC model were higher than those of the without LSC model. Conclusions: Therefore, inserting an LSC into an empty screw hole in the fracture area reduces the maximum stress on an LCP and improves biomechanical stability.

Thickness-controlled transparent conducting films (TCFs) were fabricated by transfer printing a 100 nm thick Cu micromesh structure onto poly(vinyl alcohol) (PVA) substrates of different thicknesses (~ 50, ~ 80, and ~ 120 μm) to develop a lightweight transparent wearable heater with short response time. The Cu mesh-based TCF fabricated on a ~ 50 µm thick PVA substrate exhibited excellent optical and electrical properties with a light transmittance of 86.7% at 550 nm, sheet resistance of ~ 10.8 Ω/sq, and figure-of-merit of approximately 236, which are comparable to commercial indium tin oxide film-based transparent conductors. The remarkable flexibility of the Cu mesh-based TCF was demonstrated through cyclic mechanical bending tests. In addition, the Cu mesh-based TCF with ~ 50 μm thick PVA substrate demonstrated a fast Joule heating performance with a thermal response time of ~ 18.0 s and a ramping rate of ~ 3.0 ℃/s under a driving voltage of 2.5 V. Lastly, the reliable response and recovery characteristics of the Cu mesh/PVA film-based transparent heater were confirmed through the cyclic power test. We believe that the results of this study is useful in the development of flexible transparent heaters, including lightweight deicing/defogging films, wearable sensors/actuators, and medical thermotherapy pads.