With the advancement of microstructure manufacturing technology, an array of functional surfaces based on micro/nano structures have been developed. Recently, there has been active research in the development of functional surfaces using composite materials that combine the properties of two different materials. One notable area of research is the creation of functional surfaces that utilize magnetic force to actuate microstructures. Typically, these surfaces are produced using a composite material that blends a flexible, easily deformable material with iron particles that respond to magnetic force. However, the inclusion of iron particles in the flexible material can increase its Young’s modulus, making it more challenging to effectively actuate the microstructures. To address this issue, our paper presents a fabrication method that allows for the effective actuation of microstructures by removing the residual layer of the composite material. This method enables the arrangement of iron particles at the end of the microstructure, maximizing the bending of the microstructure when magnetic force is applied. Furthermore, we conducted experiments to actuate microstructures with varying ratios of iron particles, confirming the effectiveness of this fabrication method.

This study examines the efficiency of chitosan microbeads in manufacturing and their effectiveness as a disinfectant. The microbeads are developed using a solvent-assisted extraction process. The manufacturing process involves crosslinking chitosan through an emulsion-based method, with the help of a crosslinker. This leads to an increase in particle size while maintaining homogeneity and dispersion. The solvent-assisted method, which utilizes acetone, effectively extracts the crosslinked beads into the aqueous phase. This extraction process ensures the structural stability of the beads, with an average particle size of 40±3.94 ㎛. By incorporating the disinfectant agent into the chitosan beads, antiviral effects against the Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) were observed. These effects were found to be effective at dilutions estimated to be between 1 : 1 and 1 : 100. The findings of this study demonstrate the inherent antiviral capabilities of chitosan beads and the enhanced impact when combined with the disinfectant. This suggests a synergistic approach to managing viral infections in livestock environments.

In recent years, significant progress has been made in functional soft materials, alongside advances in nano/micromanufacturing techniques, driving the evolution of soft grippers to the forefront of robotics innovation. Compared to their traditional rigid counterparts, soft grippers offer unparalleled adaptability, effortlessly conforming to objects of varying sizes and shapes. This comprehensive review explores the latest trends shaping the landscape of soft robotic grippers, providing insights into their diverse functionalities and applications. The exploration begins with an examination of the various actuation mechanisms utilized by soft grippers, including cable or tendon-driven, pneumatic, electroactive, and thermoactive systems. Additionally, the review delves into the intricacies of grasping and manipulating mechanisms, spanning from multi-finger configurations to innovative approaches, such as jamming, suction, and adhesion grasping. Notably, hybrid grippers, which integrate multiple actuation and grasping mechanisms, are of particular interest, thereby enhancing the range of functionalities offered by these grippers. Finally, the review briefly addresses current limitations and future directions in the field.

We demonstrate a practical and efficient hybrid triboelectric-piezoelectric energy harvesting structure that consists of a nanopatterned and/or metal-deposited polymer film and a piezoelectric elastomeric sponge. When a polymer (here, polycarbonate (PC)) and an elastomer (here, polydimethylsiloxane (PDMS)) make contact with and detach from each other, triboelectric energy can be harvested. In this case, the PC surface can be nanopatterned by continuous dynamic nanoinscribing and/or coated by a metal (here, Cu) layer for enhanced performance. When a piezoelectric material (here, lead zirconate titanate (PZT)) and sugar powder are mixed with PDMS, and the sugar is later dissolved, a porous piezoelectric elastomeric sponge (PES) can be fabricated. When a PC film and a PES make contact with and detach from each other, both triboelectric and piezoelectric energies can be simultaneously harvested. We systematically study the effect of PES and Cu thicknesses and dynamic nanoinscribed nanopattern on the energy harvesting performance of the hybrid triboelectric–piezoelectric nanogenerator (HTPENG). The performance of the HTPENG can be improved by using the PES of optimal thickness, and by applying the nanopattern and Cu layer. The HTPENG can be utilized in many systems where wireless self-powering is desired, such as wearable devices, flexible sensors, and skin electronics.

For the commercialization of polymer electrolyte membrane fuel cells (PEMFCs), it is essential to achieve high performance while improving the durability of the membrane electrode assembly. In particular, the durability of PEMFCs can be improved by adding radical scavengers, such as CeO2 (ceria), to the membrane. Though it is desirable to insert the ceria at the interface between the membrane and electrode, where the generated radical attack initiates, this increases interfacial resistance and ionic resistance, thereby inducing a probable reduction in initial performance, compared to that of a conventional membrane. Here, we developed modified Nafion electrolyte membranes with a spatially located patterned ceria containing Nafion ionomer to improve durability while minimizing performance degradation. The fabrication process includes an etching process to pattern the electrolyte membrane, and the ceria nanoparticle layer is selectively deposited by spray coating onto the membrane. The synergetic effect of the structural modification of the electrolyte membranes and the introduction of the functional ceria layer exhibited improved chemical durability, while maintaining the initial performance of the PEMFC.

Recent advancements in additive manufacturing (AM) have made it possible to create compact heat exchangers (HXs) with complex geometries. This study introduces a new approach that uses Triply Periodic Minimal Surface (TPMS)-based designs for HXs. Mathematical filtering techniques are incorporated to optimize the local morphology changes. The goal of the proposed mathematical filtering method is to improve the flow characteristics and heat exchange capability of TPMS HXs by modifying the structure’s morphology at the inlet and outlet regions. This modification facilitates flow selection and reduces pressure drop. The HX design includes cylindrical flow domains at the inlet and outlet regions. Three different HX designs with varying inlet/outlet domains (through-hole, half-hole, and taper-hole) were fabricated using polymer AM and DLP 3D printing. These designs were then tested for pressure drop. Among the three designs, the taper-hole configuration showed the best flow characteristics, with a 50% reduction in pressure drop compared to previous studies. The taper-hole design was then replicated using metal AM technology, resulting in a 70-125% improvement in heat exchange capacity compared to previous studies.

Additive manufacturing (AM) technology, also known as 3D printing, is a highly promising technology that can drive innovation in various industrial areas, including the nuclear industry. Although the nuclear industry is traditionally conservative when it comes to adopting new technologies, it is crucial that AM technology is eventually applied for a variety of reasons. To overcome the barriers that currently hinder the adoption of AM in the nuclear industry, it is essential to ensure the reliability of AM products. One key factor is ensuring that AM products have mechanical properties equivalent to those of traditionally manufactured products. This paper presents the results of mechanical property tests conducted on additive manufactured specimens of stainless steel 316 L after heat treatment. We performed tensile tests, hardness tests, and microstructure analysis on specimens produced using two types of metal AM technologies: powder bed fusion (PBF) and directed energy deposition (DED). The results of the tests indicate that certain weaknesses, such as anisotropy and brittleness, in AM products can be improved through three types of heat treatments. In particular, AM products produced using the PBF method and subjected to heat treatments show potential for application in the nuclear industry in terms of materials.

Varicose vein treatments range from conventional surgical ligation and sclerotherapy to venous closure using biological adhesives. However, considering ease of procedure, recovery time, and cosmetic outcomes like minimal scarring, minimally invasive techniques employing lasers or radiofrequency are preferred. The efficacy of these methods heavily relies on clinician expertise and ultrasound imaging, with manual catheter retraction during cauterization presenting challenges, such as overlapping or untreated areas, especially in long vessels exceeding 1 meter, leading to increased procedure time and operator fatigue. To address these issues, we propose an automated catheter procedure for varicose veins. This system features a handpiece for energy generation control (laser, radiofrequency) operated near the clinician for convenience. We designed a pullback system that enables constant speed rotation and forward/backward movements of the catheter without moving the handpiece. Through handpiece operation, the catheter rotates at a set speed, and a roller-driven pullback action occurs as it winds on a reel, expanding the diameter of the reel for retraction while remaining stationary. Conversely, reducing the diameter of the reel facilitates forward movement. The length adjustment of the catheter based on winding turns on the reel makes it adaptable for various vascular procedures, enhancing the procedural accuracy and operator convenience.

This paper presents an integrated thermo-mechanical model for analyzing angular contact ball bearings (ACBBs) operating under oil-jet lubrication. The proposed approach enables a comprehensive analysis of both the mechanical and thermal behavior of the ACBB system. The proposed formulation employs a quasi-static approach to accurately calculate contact loads and heat generation, taking into careful consideration variations in internal clearance resulting from factors such as surface pressure, centrifugal forces, and thermal expansion. For the thermal analysis, a refined thermal network model is utilized. The proposed thermal model incorporates a newly derived correlation for the drag coefficient under oil-jet lubrication, which is obtained through high-fidelity computational fluid dynamics simulations. The validity of the proposed model is confirmed through comparison with experimental data. Furthermore, extensive simulations are conducted to investigate the impact of bearing fit-up and thermal variations on the performance of ACBBs.

The use of reflective optical systems is essential to acquiring high-resolution image quality in aerospace applications that observe distant objects. The geometric shapes of large-aperture reflective optical systems can be deformed depending on various operating and space environments, which deformation consequently affects optical performance. In this study, we predict the image quality of a reflective aerospace optical system according to various environmental changes. In particular, the shape deformation due to vibration and heat generated from the launch vehicle was mainly observed, and the effect on gravity was also considered. The variations of image quality, such as Modulation Transfer Function (MTF) and wave-front error (WFE), were also observed by importing the deformed shapes into the optical simulation tool. This study is intended to provide approaches to reduce the cost and lead time to develop aerospace optical systems.