The need for large-area cross-sectional analysis with nanometer precision is rapidly growing in various advanced manufacturing sectors. Traditional focused ion beam (FIB) techniques are too slow for milling millimeter-scale volumes. They often introduce ion implantation, redeposition, and curtaining effect, which ultimately prevent effective large-area processing and analysis. To overcome these limitations, we developed a hybrid machining process integrating femtosecond laser micromachining for rapid roughing with FIB milling for precision finishing. Angle of incidence (AOI) control during laser machining was employed to minimize the taper angle of laser-ablated sidewalls, thereby significantly reducing subsequent FIB milling volume. Using a 1030 nm, 350 fs laser, we achieved nearly vertical sidewalls (taper angle: ~2.5° vs. ~28° without AOI control) in silicon. Raman spectroscopy revealed a laser-affected zone extending about 2 μm perpendicular to the sidewall, indicating the need for further FIB milling besides laser-tapered regions to remove laser-induced damage. On multilayer ceramic capacitors and micropillar fabrication, the hybrid laser-FIB method achieved efficient large-area cross sections with preserved microscale details. We present the development of an integrated triple-beam system combining laser, plasma FIB, and SEM, capable of fast volume removal and nanoscale imaging in one equipment. This approach can markedly improve throughput for large-area cross-sectional analysis.

Since sCO₂ (Supercritical Carbon Dioxide) turbomachinery are generally small and operate at high rotational speed, the bearings remain a significant challenge to the design of the turbomachinery for the sCO₂ power cycles. However, a fluid induced instability similar to the oil whirl may occur even with the magnetic bearing under high pressure and high speed conditions of the sCO₂ turbomachinery. This paper presents experimental investigation on the instability of a sCO₂ compressor supported by the magnetic bearing. First, we introduce the sCO₂ compressor supported by the magnetic bearing. The procedure to guarantee the rotordynamic performance of the sCO₂ compressor supported by the magnetic bearing is provided. Then, the effects of the working condition such as the pressure and rotating speed on the fluid induced instability are investigated experimentally. Finally, a strategy to resolve the fluid-induced instability with conventional PID control is proposed and experimentally verified.

In this study, aluminum, used throughout the industry and actively studied for surface modification, is selected as the test subject. Micro-structured through acid etching, nano-structured through alkali treatment to maximize surface roughness, and the superhydrophilic surfaces were fabricated by forming the surface chemicals into aluminum hydroxide (Al(OH)₃). The superhydrophobic surfaces were fabricated through the self-assembled monolayer coating on the surface, and the surface structure and components were analyzed. The superhydrophilicity and superhydrophobicity were applied on the aluminum surface at the bottom of the low speed water vehicle. For the superhydrophilic and superhydrophobic surfaces, the reasons for the drag reduction performance on the bare surface and the difference in the amount of reduction were analyzed. A coating material that strong bonds with the surface are selected for anti-corrosive performance under NaCl solution. To verify that, the contact angle was measured by exposing each prepared aluminum surface to a 3.5% NaCl solution for 14 days. Additionally, we analyzed why the superhydrophobic surfaces were robust against the NaCl solution.

In this study, experiments were performed to determine if the pattern fabricated by the UV nano imprint process could be modified using additional processes such as surface treatment. We wanted to confirm the fabrication possibility of a special pattern such as the reverse trapezoidal shape difficult to produce because of the releasing problem. The UV ozone treatment (Hydrophilic Treatment) and OTS coating (Water Repellent Treatment) were used and shape modification occurred under controlled treatment time. As a result of performing the UV ozone treatment for 30 minutes or more on a micro pattern manufactured by UV curing resin of PUA series, the contraction phenomenon of the micro structure occurred and the shrinkage was dependent on treatment time. When the OTS treatment was performed, the surface of the microscale pattern could be roughened. When the nanoscale pattern was treated, the pattern change could be induced. It was possible to partially cure the resin by adjusting the UV absorption using dye material, and the deformation of the pattern was made by an additional pressing process. As a result of the experiment of the various methods causing the shape change of the cured pattern, the possibility of the methods was verified.

In today’s manufacturing industries, the demand for light non-ferrous materials is considerable due to the need to improve productivity and manufacturability. Since the surface roughness of a material is important for improving the functionality of machined parts, various techniques for surface treatments have been developed to obtain non-ferrous materials with low roughness. A superfinishing method utilizing polishing films is generally applied to the anodized surface of Al7075 in order to improve its roughness. The objective of this research is to determine through experiment the parameters that facilitate the shortest processing time, using a superfinishing method, for reaching a roughness of Ra 0.2㎛. This objective is met by applying the Taguchi method in the experiments. Through the experiments of superfinishing, the effectiveness of the parameters adopted for the surface treatment is demonstrated.

Recently, concerns about the environment are becoming more important because of global warming and the exhaustion of earth’s resources. In the aviation and automobile industries, the application of light materials is increasingly important for eco-friendly and effective. Carbon Fiber Reinforced Plastics is a composite material which great formability and the high strength of carbon fiber. CFRP, which is both light and strong, is hard to manufacture. In addition, CFRP machining has a high chance of defects. This research discusses the development of a manufacturing system package for CFRP machining. It involving CFRP Drilling/Water-jet Manufacturing Machines, Inspection/Post-processing Systems, CNC platform for an EtherCAT servo Communication, Flexible Manufacturing Systems and CFRP machining Processes.

In this study, experiments were conducted for micro pattern printing to combine solution atomization process and stencil printing based on electrospray deposition. The stencil mask fabricated by etching the photosensitive glass placed below 0.3 mm distance to substrate has 100 um line width. The process parameters of electrospray deposition system for the atomization of the solution are applied voltage and supply flow rate of the solution. Meniscus angle of cone-jet was optimized by varying the supply flow rate from 0.3 ml/hr to 0.7 ml/hr. Voltage condition was verified having symmetric cone-jet angle and no pulsation at 8.5 kV applied voltage. In addition, a number of micro patterns are printed using a single 1 step process by solution atomization process. Variable line width of approximate 100 um was confirmed by changing conditions of solution atomization regardless of the pattern size of stencil mask.

EHD (electro-hydro-dynamics) patterning was performed under atmospheric pressure at room temperature in a single step. The drop diameter smaller than nozzle diameter and applied high viscosity conductive ink in EHD patterning method provide a clear advantage over the piezo and thermal inkjet printing techniques. The micro electrode pattern was printed by continuous EHD patterning method using 3-type control parameters (input voltage, patterning speed, nozzle pressure). High viscosity (1000cps) conductive ink with 75wt% of silver nanoparticles was used. EHD cone type nozzle having an internal diameter of 50μm was used for experimentation. EHD jetting mode by input voltage and applied 1st order linear regression in stable jet mode was analyzed. The stable jet was achieved at the amplitude of 1.4~1.8 kV. 10μm micro electrode pattern was created at optimized parameters (input voltage 1.6kV, patterning speed 25mm/sec and nozzle pressure -2.3kPa).

The aim of this study was to develop and verify gait training system for post-stroke hemiplegia patients with step length asymmetry. Most post-stroke hemiplegic patients show gait asymmetry and weight shifting training has been suggested as a useful method for improving the walking ability. However, verbal cue by physical therapist may be not effective. Therefore, our weight shift training system was designed to give a feedback to patients through precise plantar pressure and center of pressure (COP) measurement. This weight shifting biofeedback training system is composed of F-Scan plantar pressure measurement system and software development kit (SDK) for Windows operating system. Two post-stroke patients with step length asymmetry were enrolled in this study. After training for six weeks, the weight shift score and step length ratio of two all patients were improved and approached to them of non-disabled. This system developed in this study may improve the step length asymmetry, and therefore this system is also expected to improve a walking ability in hemiplegic patients.

The Electrostatic Inkjet system has many applications in cost and time effective manufacturing of printed electronics like RFIDs, OLEDs and flexible displays etc. This paper presents pneumatic ink supply system for an electrohydrodynamic deposition (EHD) setup for the precise pressure control to produce a small amount of discharge at the end of the capillary. The meniscus shape depends upon the applied pneumatic pressure to the ink supply system. Furthermore, this paper also compares meniscus shapes at different applied pneumatic pressures. It is concluded that patterning of constant line-width can be achieved better by controlling the meniscus shape using this technique.

MEMS and LIGA technologies have been used for fabricating microstructures, but their shape is not 3D because of difficulty for preparation of many masks. To fabricate 3D microstructures, micro stereo lithography technology based on Digital Micromirror Device(DMD™) was introduced. It has no need of masks and is capable of fabricating high aspect ratio microstructures. In this technology, STL file is the standard format as the same of conventional rapid prototyping system, and 3D parts are fabricated by layer-by-layer according to 2D section sliced from STL file. The UV light source is illuminated to DMD which makes bitmap images of2D section, and they are transferred and focused on resin surface. In this paper, we addressed optical design of microstereolithography system in consideration of light path according to DMD operation and image-forming on the resin surface using optical design program. To verify the performance of implemented microstereolithography system, 3D microstructures with complexity and high aspect ratio were fabricated.

Digital 3D Real Object Duplication System (RODS) consists of 3D Scanner and Solid Freeform Fabrication System (SFFS). It is a device to make three-dimensional objects directly from the drawing or the scanning data. In this research, we developed an office type SFFS based on Three Dimensional Printing Process and an industrial SFFS using Dual Laser. An office type SFFS applied sliding mode control with sliding perturbation observer (SMCSPO) algorithm for control of this system. And we measured process variables about droplet diameter measurement and powder bed formation etc. through experiments. In case of industrial type SFFS, in order to develop more elaborate and speedy system for large objects than existing SLS process, this study applies a new Selective Dual-Laser Sintering (SDLS) process and 3-axis Dynamic Focusing Scanner for scanning large area instead of the existing f lens. In this process, the temperature has a great influence on sintering of the polymer. Also the laser parameters are considered like that laser beam power, scan speed, and scan spacing. Now, this study is in progress to evaluate the effect of experimental parameters on the sintering process.

Recently, it has been reported that frictional behavior at nanometer scale can be different from that at macro scale. In this article, friction and wear tests were conducted using an AFM to investigate the effect of real contact area on the coefficient of friction and wear property. SiO₂, Mica, and SiGe were used in friction test and the AFM tip was Si₃N₄.The real contact area between an AFM tip and flat surface was calculated by the Johnson-Kendall-Roberts (JKR) theory. Wear specimen was Mica, and the diamond tip was used. We found that the coefficient of friction is constant below a critical area, but it is degraded over the area. Moreover, it is found that wear depth increased rapidly from a certain load and was degraded as a function of the number of the scanning cycles. Also, the range of scanning velocity used in this study had little effect on the wear depth.