Microphysiological systems (MPS) are advanced platforms that mimic the functions of human tissues and organs, aiding in drug development and disease modeling. Traditional MPS fabrication mainly depends on silicon-based microfabrication techniques, which are complex, time-consuming, and costly. In contrast, 3D printing technologies have emerged as a promising alternative, allowing for the rapid and precise creation of intricate three-dimensional structures, thereby opening new avenues for MPS research. This review examines the principles, characteristics, advantages, and limitations of key 3D printing techniques, including fused deposition modeling (FDM), stereolithography (SLA)/digital light processing (DLP), inkjet 3D printing, extrusion-based bioprinting, and laser-assisted bioprinting. Additionally, we discuss how these technologies are applied in MPS fabrication and their impact on MPS research, along with future prospects for advancements in the field.

Bioengineered skeletal muscle constructs that replicate the architectural, metabolic, and contractile characteristics of native tissue are becoming essential platforms for disease modeling and advancing regenerative medicine. The creation of these constructs relies heavily on cell-mediated gel compaction, a crucial process for facilitating tissue maturation. To ensure myotube alignment, muscle cell-laden hydrogels are typically embedded in 3D-printed molds with anchor structures. However, structural detachment or rupture often occurs during culture, which undermines the stability and functional differentiation of the engineered tissue. To address these challenges, we developed an improved anchor-type mold through a series of structural optimizations. We first compared two anchor geometries—linear and mushroom-shaped pillars—within rectangular frames, finding that the mushroom-shaped design provided better structural retention. However, the rectangular frames led to excessive gel compaction, causing detachment and disrupting cellular alignment, especially in central regions. To alleviate these issues, we introduced a dumbbell-shaped mold with a narrowed midsection to better distribute mechanical stress. This new mold effectively promoted aligned myotube formation, long-term construct maintenance, and functional maturation. Our findings underscore the benefits of structurally optimized molds in creating stable engineered muscle, with significant implications for regenerative therapies and preclinical testing platforms.

Dental implant surgery usually takes over 6 to 9 months, with 3 to 6 months specifically allocated for osseointegration between the implant and the surrounding bone. To expedite this process, we developed an innovative hybrid composite structure and a bioreactor. This hybrid structure features an assembly-type implant combined with a 3D-printed polycaprolactone (PCL) scaffold. The implant was redesigned in a modular format to enable the insertion of a scaffold between components, facilitating bone-to-bone contact instead of metal-to-bone contact, which enhances osseointegration. The PCL scaffold was coated with polydopamine (PDA) to improve cell adhesion. Additionally, a bioink that mimics bone composition, consisting of type I collagen and nano-hydroxyapatite (nHA), was incorporated into the scaffold. To support cell maturation within the scaffold, we developed a hydrostatic pressure bioreactor system that applies uniform compressive stress to complex 3D structures. We assessed cell viability in the scaffold using the CCK-8 assay, and SEM imaging confirmed the effectiveness of the PDA coating. Furthermore, we evaluated osteogenic differentiation through ALP activity and calcium quantification assays under both static and dynamic stimulation conditions.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder marked by the progressive degeneration of motor neurons and muscle atrophy. Despite extensive clinical research, effective treatments remain scarce due to the complexity of the disease's mechanisms and the inadequacy of current preclinical models. Recent advancements in microphysiological systems (MPS) present promising alternatives to traditional animal models for studying ALS pathogenesis and evaluating potential therapies. This review outlines the latest developments in ALS MPS, including co-culture membrane-based systems, microfluidic compartmentalization, microarray platforms, and modular assembly approaches. We also discuss key studies that replicate ALS-specific pathologies, such as TDP-43 aggregation, neuromuscular dysfunction, and alterations in astroglial mitochondria. Additionally, we identify significant challenges that need to be addressed for more physiologically relevant ALS modeling: replicating neural fluid flow, incorporating immune responses, reconstructing the extracellular matrix, and mimicking the pathological microenvironment. Finally, we emphasize the potential of ALS MPS as valuable tools for preclinical screening, mechanistic studies, and personalized medicine applications.

The rise of electric vehicles (EVs) has led to a reduction in engine noise, making suspension and road noise more noticeable. However, most assessments focus only on air-conducted (AC) pathways and overlook bone-conducted (BC) transmission. This study identifies key sources of vehicle noise and implements a finite-element simulation to replicate real-world driving conditions. A 12-degree-of-freedom (DOF) human body model quantifies how vibrations transmit from the vehicle structure to the head. Additionally, a detailed finite-element model of the human head evaluates basilar-membrane (BM) vibrations for both AC and BC inputs. The results indicate that BC dominates below 10 Hz, producing BM velocities up to 50 dB greater than AC. Above 10 Hz, AC prevails, showing a difference of approximately 40 dB. Notably, at frequencies of 33, 46, 67, and 80 Hz, the AC–BC difference narrows to below 10 dB, highlighting significant BC effects even at higher frequencies. These findings reveal that neglecting bone-conduction pathways can lead to an underestimation of occupant exposure to low-frequency vibrations. Therefore, comprehensive evaluations and control methods for vehicle noise should consider both AC and BC transmission mechanisms to accurately reflect human perception

ERCP (Endoscopic Retrograde Cholangiopancreatography) is a common procedure used to diagnose and treat biliary and pancreatic diseases. However, the repeated exposure to X-ray radiation during these procedures poses health risks to surgeons. Teleoperation systems can help reduce this exposure, but they face challenges such as the lack of force feedback and differences between the master device's mechanisms and the movements of surgical tools, which can diminish surgical precision. This study aimed to develop a master device with force feedback specifically for teleoperated ERCP guidewire insertion, drawing inspiration from the natural hand movements of surgeons. The device includes a ring-shaped translation control handle and a rotation control handle, both designed to allow unlimited movement, thereby intuitively replicating the operation of the guidewire. A force feedback system was incorporated to enable collision detection and prevent potential injuries during procedures. Experimental results showed that the proposed system enhances control precision, reduces handling inertia, and provides effective force feedback. These advancements ensure safer and more accurate guidewire manipulation, addressing key limitations of existing teleoperation systems. Ultimately, this device not only minimizes radiation exposure for surgeons but also facilitates intuitive and precise teleoperated ERCP procedures.

A study investigated hydrogen permeability in sulfur-cured NBR composites filled with carbon black (CB) and silica, using volumetric analysis across pressures ranging from 1.2 to 92.6 MPa. Both pure NBR and MT CB- and silica-filled NBR exhibited a single sorption mechanism that followed Henry’s law, indicating hydrogen absorption into the polymer chains. In contrast, HAF CB-filled NBR displayed dual sorption behavior, adhering to both Henry’s law and the Langmuir model, which suggests additional hydrogen adsorption at the filler interface. Hydrogen diffusivity in NBR followed Knudsen diffusion at low pressures and bulk diffusion at high pressures. In HAF CB-filled NBR, permeability decreased exponentially with increasing density, while in MT CB- and silica-filled NBR, it declined linearly. The strong polymer-filler interactions in HAF CB significantly influenced permeability. Permeability trends closely correlated with hardness, tensile strength, and density, allowing for the establishment of quantitative relationships between these physical and mechanical properties. These findings indicate that analyzing these properties can predict hydrogen permeability, positioning NBR composites as promising sealing materials for high-pressure hydrogen storage in refueling stations and fuel cell vehicles.

This study introduces a highway secondary accident prevention system that employs Fast Fourier Transform (FFT) analysis of vehicle collision sounds. The system is designed to identify abnormal acoustic patterns produced during collisions and skidding events, enabling faster and more accurate accident detection than traditional methods. When a crash is detected, visual warning signals are instantly sent to nearby vehicles using LED devices powered by a photovoltaic panel and an energy storage system (ESS). Experimental results showed 100% detection accuracy during independent playback of collision, skidding, and driving sounds, and 80% accuracy during simultaneous playback. These results confirm the system's ability to effectively differentiate accident-related sounds and deliver timely alerts. This research offers an innovative and environmentally sustainable approach to enhancing highway safety and reducing the societal and economic consequences of secondary accidents.

This study quantitatively examines the impact of ultraviolet (UV) intensity and energy on the formation of high aspect ratio (HAR) microstructures using the Self-Propagating Photopolymer Waveguide (SPPW) process. This mechanism relies on the self-focusing of UV light within a refractive index gradient, allowing the light to propagate and polymerize vertically beyond the initial exposure zone. Experiments were performed at UV intensities of 7.5, 12.5, and 17.5 mW/cm², with energy levels ranging from 0.0375 to 13.5 J/cm². The results indicated that a lower UV intensity of 7.5 mW/cm² produced uniform and vertically elongated structures, achieving a maximum aspect ratio of 12.26 at 0.9 J/cm². In contrast, higher UV intensities led to lateral over-curing, base expansion, and shape distortion, primarily due to rapid polymerization and the oxygen inhibition effect. These findings emphasize the importance of precisely controlling both UV intensity and energy to produce uniform, vertically aligned HAR microstructures, offering valuable insights for optimizing the SPPW process in future microfabrication applications.

Centrifugal compressor is a device that converts kinetic energy to increase the air pressure. It rotates at a high speed of up to 200,000 RPM and directly affects aerodynamic noise. Various studies have already been conducted, but the direct calculation method of acoustics based on the unsteady solution is inefficient because it requires a lot of resources and time. Therefore, flow characteristics and numerical comparison according to various aerodynamic factors predicted as a cause of noise generation were analyzed in this study based on the steady solution. High-frequency noise was calculated locally near the asymmetric flow properties. Vortex and turbulent kinetic energy were generated at similar locations. Among static components, a large-sized vortex of 3.48×10⁷ s^-1 was distributed at the location where the rotational flow around the compressor wheel combined with the inlet suction flow. In addition, a locally high vortex of 8.16×10⁵ s^-1 was distributed around the balancing cutting configurations that cause asymmetric flow characteristics. Analysis of these factors and causes that directly affect noise can be efficiently improved in the pre-design stage. Therefore, the efficient design methodology for centrifugal compressors that considers both performance and noise is expected based on the results of this study.