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.

The rapid growth of semiconductor and display manufacturing highlights the demand for fast, precise motion stages. Advanced systems such as lithography and bio-stages require accuracy at the μm and nm levels, but linear motor stages face challenges from disturbances, model uncertainties, and measurement noise. Disturbances and uncertainties cause deviations from models, while noise limits control gains and performance. Disturbance Observers (DOBs) enhance performance by compensating for these effects using input–output data and a nominal inverse model. However, widening the disturbance estimation bandwidth increases noise sensitivity. Conversely, the Kalman Filter (KF) estimates system states from noisy measurements, reducing noise in position feedback, but it does not treat disturbances as states, limiting compensation. To address this, we propose an Augmented Kalman Filter (AKF)–based position control for linear motor stages. The system was modeled and identified through frequency response analysis, and DOB and AKF were implemented with a PIV servo filter. Experimental validation showed reduced following error, jitter, and control effort, demonstrating the improved control performance of the AKF approach over conventional methods.

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.

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.

Propulsion motors are vital components in marine propulsion systems and industrial machinery, where high torque and operational reliability are paramount. During operation, high-power propulsion motors generate considerable heat, which can adversely affect efficiency, durability, and stability. Therefore, an effective thermal management system is necessary to maintain optimal performance and ensure long-term reliability. Cooling technologies, such as water jackets, are commonly employed to regulate temperature distribution, prevent localized overheating, and preserve insulation integrity under high-power conditions. This paper examines the cooling performance of water jackets for high-power propulsion motors through numerical analysis. We evaluated the effects of three different cooling pipe locations and varying coolant flow rates on thermal balance and cooling efficiency. Additionally, we analyzed temperature variations in the windings and key heat-generating components to determine if a specific cooling flow rate and pipe configuration can effectively keep the winding insulation (Class H) within its 180^oC limit. The findings of this study highlight the significance of optimized cooling system design and contribute to the development of efficient thermal management technologies, ultimately enhancing motor reliability, operational stability, and energy efficiency.

Currently, advanced countries such as the US and the UK are researching laser-based weapons and communication systems. The application of Fast Steering Mirror (FSM) is crucial in laser systems to control internal optical paths and compensate for disturbances, including atmospheric fluctuations and mechanical vibrations. Additionally, research is underway to enhance image clarity in surveillance and reconnaissance systems, such as Electro-Optical/Infrared (EO/IR) systems, by applying FSM technology. Consequently, the demand for FSMs is rising, necessitating the development of small, lightweight, and high-performance solutions. In this study, we designed a compact and lightweight FSM with a diameter of 25 mm, and its performance was validated through rigorous testing. Furthermore, we developed a piezoelectric actuator using single crystal piezoelectric material to ensure a wide operating bandwidth and rapid response speed for the FSM. Before manufacturing the designed FSM, we conducted modeling and simulation (M&S) to analyze its performance and confirm that it met the required specifications. Subsequently, a prototype of the FSM was produced, and its operating range, bandwidth, and accuracy were evaluated through performance tests.

The polymer electrolyte membrane fuel cell (PEMFC) generates electrical energy through electrochemical reactions and is a key technology for sustainable energy. The electrolyte membrane significantly affects performance under varying conditions. This study examines the impact of membrane thickness and relative humidity (RH) on PEMFC performance using j-V curves and electrochemical impedance spectroscopy (EIS). Experiments were conducted with membrane thicknesses of 30, 15, and 5 μm under RH conditions of 100%-100% and 100%-0%. Under RH 100%-100%, performance improved as the membrane thickness decreased, with values of 954, 1050, and 1235 mW/cm² for the 30, 15, and 5 μm membranes, respectively. The 5 μm membrane demonstrated a 23% performance improvement over the 30 μm membrane. Under RH 100%-0%, performances were 422, 642, and 852 mW/cm², with degradation rates of 55.8%, 39.0%, and 32.1%. The 5 μm membrane exhibited the lowest degradation rate, indicating superior performance under low humidity. These results suggest that thinner membranes generally enhance performance and maintain efficiency even in dry conditions.

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.