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Manufacturing Technology: 19
A Novel Porous Structure with High Mechanical Performance for Additive Manufacturing
Biomimetic design based on bone biomechanics
A novel three-dimensional (3D) printed porous structure with high mechanical performance is designed biomimetically based on the insights of bone biomechanics. The resulting structure might be lightweight and mechanically isotropic with suppressed fracture progression and high energy absorption.
In general, porous structures with repeating units, such as diamond lattices, suffer from mechanical issues, such as fracture development, low energy absorption, and mechanical anisotropy due to these repeating units. To address these issues, we develop a novel porous structure with high mechanical performance for additive manufacturing. The structure is designed biomimetically based on the insights of bone biomechanics. It has a framework made up of 3D isotropically interconnected beams. Here, the beam lengths and bifurcation counts are arbitrarily determined using probability distributions without any repeated units. Furthermore, the structure can be manufactured through the powder bed fusion of a laser beam using metal powders and material extrusion using plastic filaments. Additionally, compression tests revealed that the structure exhibited suppressed fracture progress after the initial fracture and increased energy absorption. Moreover, the fracture behavior of the structure was found to be independent of the compression direction because of its structural isotropy.Satoshi Yamada Assistant ProfessorPhDDivision of Mechanical and Aerospace Engineering, Faculty of Engineering
Automatic Recognition System for Symmetry and Regularity of Shapes
Exhaustive extraction of face-symmetric, axisymmetric, and regular arrangement patterns from 3D mesh models, measured point clouds, FEM meshes, etc.
This software extracts symmetrical subregions and regularly arranged grid or radial regions from 3D measurement data of lasers and X-ray CT scans fully automatically.
It is useful for reverse engineering and the generation of 3D-CAD data and FEM meshes.
This software can automatically and comprehensively extract the symmetry and regularity of shape patterns that appear on the surface of 3D mesh models measured by laser/X-ray CT scanning, 3D measurement point groups, FEM finite element meshes, etc. None of these functions are available with conventional commercial software. This software has a wide range of applications, including automatic reference surface generation and model shaping of 3D-CAD data for reverse engineering, generation of reduced element size models (1/4 models, etc.) and shaping of element boundaries in FEM preprocessors, as well as quantitative symmetry inspection of manufactured products. It is also possible to automatically extract various shapes of regular array (rectangular, radial, etc.) that correspond to pattern features in 3D-CAD data. It can also be applied to the generation of BIM (Building Information Model) from laser measurements.
Development of a Non-destructive CT-XRD Coupling Method and Its Application
Visualization of the microstructure of hardened cement
To develop innovative cement-hardening materials, we are devising a non-destructive integrated CT-XRD method, a novel measurement method combining the CT method to obtain geometric and spatial information on microstructures inside concrete with an accuracy of several microns, and a diffraction method to investigate hydrates and alterations in the region of interest.
Concrete is structurally hardened by binding rock (aggregate) through a hydration reaction between cement and water. As a structural material, concrete is intended to withstand loading and certain weather/environmental conditions, but these may cause cracking of the concrete, which may progressively deteriorate due to strong acids and other chemical reactions caused by erosion and materials from the atmosphere, seawater and groundwater that come in contact with it. To stably use the social infrastructure for a long period of time, it is important to be able to see inside the internal structure of concrete with “bug eyes” and find any abnormalities that have occurred.
With the pioneering “non-destructive integrated CT-XRD method,” the sample is irradiated with high-intensity X-rays from synchrotron radiation to selectively visualize 3D structures from transmitted monochromatic X-rays at 25 keV. Energy-dispersive X-ray diffraction is also performed in specific regions of interest through multiple slit operations to identify hydrates (portlandite, calcite, etc.), their alteration and aggregate minerals.
Development of Rolled Gauze for Aspiration Prevention
Aiming at patient safety
Rolled cotton is frequently used in dental treatment, but aspiration accidents continue to occur. Therefore, we are developing an anti-aspiration rolled gauze that can be used as an alternative to rolled cotton currently in use, and to further reduce the cost.
Dental rolls are routinely used in dental treatment to absorb moisture and apply pressure, but accidents due to aspiration are often reported, and in some unfortunate cases it has resulted in the death of patients.
Therefore, to make rolled cotton safer to use and reduce the number of accidents caused by aspiration, we decided to thread it. Since it is difficult to sew thread on conventional cotton rolls due to the processing, and there is a risk of the thread coming off, we developed aspiration prevention rolled gauze. In addition to preventing aspiration, this gauze roll has the advantage of preventing misplacement and making it easier to remove. It also has the same water absorbency and absorption speed as conventional rolled cotton.
Development of Technology for Generation and Measurement of Topological Light Waves
Topological light waves, such as optical vortices, are expected to be applied to the microfabrication of materials, large-capacity information communication, and super-resolution microscopy thanks to their unique properties. In our laboratory, we are currently developing light sources and measurement techniques for the application of topological light waves.
As shown in Fig. 1, optical vortices have a helical phase distribution and a donut-shaped intensity distribution in the beam cross-section. These properties can be used to realize microscopes demonstrating performance that far exceeds the spatial resolution of conventional optical microscopes and nanometer-order microfabrication. In our laboratory, we are conducting research and development to enable further new applications by combining this kind of light with ultrashort optical pulses, which are extremely short in duration (10-12 to -15 seconds). We have succeeded in generating ultrashort optical vortex pulses that can computer-control the helical phase and has a peak power of several tens of GW. We have also succeeded in developing a completely new method for instantaneous measurement of the helical phase (Fig. 2). We are now applying these originally developed fundamental technologies to material processing and communication technologies.
Gel that is Stronger Than Steel
Soft and tough composite material
By conjugating glass fiber and self-healing gel, we have achieved a gel that is stronger than carbon fiber-reinforced plastic (CFRP). Since the base material is a gel, it is as flexible as rubber against bending, but tougher than CFRP against tearing, making it difficult to break.
The glass fiber composite gel we have developed exhibits unbreakable, untearable and tear-resistant properties. Generally speaking, CFRP and glass fiber reinforced plastic (GFRP) are widely used as composite materials. Similar to these fiber-reinforced plastics, fiber-reinforced gels are hard and resistant to tension because of the characteristics of the fibers, while being soft and flexible on bending because of the characteristics of the gel. The self-healing polyampholyte (PA) gel used as the base material is also strong as such thanks to its ability to dissipate a large amount of energy against deformation. Since the gel is flexible, when it is combined with fiber, local distortions can be transmitted through the fiber to the distant base material, resulting in large energy dissipation of the entire material, meaning that it is remarkably strong.
Iodine Reduction in Edible Dried Kelp
Technology to reduce iodine in dried kelp by the competitive adsorption method
We have developed technology that can remove approximately 90% of iodine from kelp by simply circulating and distributing an extraction solvent containing monosaccharides and calcium through a column filled with dried kelp and adsorbents.
Iodine is an essential element for humans, but excessive intake of iodine can cause thyroid function problems. The Ministry of Health, Labour and Welfare (MHLW) has set the maximum tolerable dose of iodine at 2.2 mg/day, but only 1 g of kelp (Fig. 1) is enough to reach the maximum tolerable dose, due to its high iodine content. Technology for recovering iodine from seaweed has been available for many years, but there has been no research on developing technology for removing iodine from seaweed for consumption. Figure 2 shows the iodine removal rate (○) and mass loss rate (●) of kelp after circulating and distributing an extraction solvent (100 L) containing monosaccharide and calcium for 20 minutes in a column filled with dried kelp (5 kg) and adsorbent (1.5 kg). Although the extraction solvent was used four times to reduce the cost, an iodine removal rate of 90% or more was maintained.
Liquid Atomization Technology Using Ultrasound and Microbubbles
Toward active control of the amount of liquid atomization
When ultrasonic waves are irradiated from the liquid to the liquid surface, atomization of the liquid occurs at the liquid surface. In recent years, it has become clear that microbubbles near the liquid surface are responsible for this phenomenon. We are aiming to control the amount of liquid atomization by ultrasound.
When ultrasonic waves are emitted from inside a liquid to the surface, the liquid is atomized. The atomized liquid becomes small droplets with a diameter of several micrometers. This liquid atomization technology can produce uniform fine droplets in an energy saving manner and is still widely used in our daily life. Although the mechanism of liquid atomization is still not completely understood, based on our previous research, it has become clear that microbubbles in the vicinity of the liquid surface promote atomization. In this study, we focus on the number of microbubbles in a liquid and aim to control the amount of liquid atomization by ultrasound. By adjusting the number of microbubbles appropriately, we aim to atomize liquids that could not be atomized by ultrasound and to further increase the amount of liquid atomization.
To clarify the coupled phenomena of electromagnetism, heat, fluid, and structure
We simulate multiphysics phenomena such as electromagnetism, heat, fluid, and structure. We conduct comprehensive research that covers aspects from mesh generation to the execution of simulations and visualization of the results. By observing invisible phenomena, we aim to contribute to the manufacturing field.
We are developing our own simulation tools to analyze multi-physics phenomena such as heat, fluid, and structure, which cannot be analyzed by commercial simulation software, with a focus on electromagnetism. We carefully select the most suitable analysis method for each phenomenon, and conduct comprehensive research on mesh generation, speeding up, enlargement, and visualization (drawing) of the analysis results. We aim to apply these methods to everything from equipment performance evaluation to design. Furthermore, advanced design techniques are also possible by using the tools together with optimization algorithms and game theory.
New Developments in Combustion Reaction Fluid Simulation
Proposal of a highly efficient analysis method that enables the application of detailed reaction mechanisms
We are proposing a numerical analysis technique to efficiently incorporate detailed large-scale reaction mechanisms, such as those of hydrocarbon fuels that consist of hundreds of chemical species and thousands of chemical reaction orders, into thermo-fluid simulations.
Until now, chemical reaction phenomena in thermo-fluid (CFD) analysis have been modeled simply by assuming an infinitely fast reaction or an overall reaction model consisting of a few chemical species and reaction equations due to computational load and lack of analysis techniques. On the other hand, when the interaction between chemical reactions and fluid phenomena is important, such as in the case of unsteady phenomenon prediction like the ignition timing of automobile engines or ultra-dilute combustion under extreme conditions, it is difficult to apply simple models. Our research group has solved the problem of applying detailed reaction mechanisms to CFD analysis. The proposed method consists of a time integration method (ERENA) that can significantly reduce the calculation time of chemical reaction equations, and a species bundling technique that combines similar chemical species. Depending on the conditions, the proposed method can be tens to hundreds of times faster than the conventionally used methods while maintaining equivalent accuracy.
Nonlinear Compensator That Can Be Implemented Without Sensors
Nonlinear compensator that can easily be added to PID control systems
Currently, PID control is used as the main control method in industry, but the PID control technique has a problem that the control accuracy deteriorates due to the influence of nonlinear terms such as friction and gravity. We have proposed a nonlinear compensator that can easily be added to PID controllers.
Digital acceleration control (DAC) is a robust control technique for systems with nonlinear terms and modeling errors that are difficult to model. DAC is a very effective controller, but it cannot perform position control by itself because it controls the target acceleration value. Therefore, we have combined DAC with a general PID control system. This PID-DAC combined control system allows both robust position control and acceleration control. In addition, as a new nonlinear compensator that can easily be added to PID controllers without sensors, we propose two controllers: the PID-DA0 control system, which sets the target acceleration value of the control object to zero, and the PID-DJ0 control system, which sets the target acceleration value to zero. Both controllers can easily be added to existing PID controllers without additional sensors, so they have the great advantage of improving system performance sensorless.
Observation of the 3D Structure of Soft Matter and the Microrheological Measurement Method
Relationship between structure formation and viscoelasticity in non-equilibrium complex fluids
Since soft matter is literally soft, its structure tends to change depending on the external fields, and at that time its physical properties will also change considerably. We are developing methods to investigate the 3D structure and physical properties of soft matter to apply these to functional materials.
It is known that the apparent viscosity of certain blends of two mutually incompatible polymers is reversibly increased by applying an electric field (electrorheological effect). In general, when two polymers are mixed, one of them becomes a droplet and is dispersed in the other. Under shear flow, the droplet structure in Figure 1(a) is observed, but when an electric field is applied to it, it changes to the network structure in (b), and the viscosity increases accordingly. The relationship between this structure and rheology has been clarified for the first time using this newly developed system. This system has made it possible to clearly observe the phase separation caused by shear flow in actin solutions of biological materials. As shown in Fig. 2, when shear is applied, regions with large velocity gradients appear in the upper and lower positions, and these regions widen as the shear rate increases.
Optimal Design of Advanced Composite Materials
New functional composite materials with free fiber shape
Advanced composites (carbon fiber-reinforced composites) have come to be widely used as structural materials, but their anisotropic properties have not yet efficiently been exploited. In our laboratory, we are developing a method to optimally design the fiber orientation (linear or curved) of composites.
Advanced composites (carbon fiber composites, carbon fiber reinforced plastics (CFRP)) are widely used as structural materials due to their high specific strength and stiffness. The development of fiber orientation technology has made it possible to arrange fibers not only in straight but also curved lines. Compared with straight fibers, design flexibility is greatly improved, and it is thus possible to produce CFRP components for specific part shapes and uses. In our laboratory, we have been producing composite specimens with curved fibers using a fiber stitching machine (Fig. 1), which is based on embroidery machine technology, to evaluate the mechanical properties of specimens and develop a unique method to optimize fiber shapes. For example, Figure 2 shows the optimum fiber shape to reduce the strain concentration around the holes in a wing model with multiple circular holes, and the strain distribution is shown in Fig. 3. It has been found that the strain concentration is reduced more than with straight fibers.
Portable Liquid Chromatograph
Battery-powered, ultra-light, ultra-compact chemical analyzer
Using proprietary technology, we have miniaturized the pump, column and detector, all key components of liquid chromatography, realizing a compact, B5 size, lightweight and portable liquid chromatograph weighing 2 kg. This allows us to instantly obtain analysis results on the spot.
The pump we have developed for liquid chromatography is based on electroosmotic phenomena and can operate for a long time on dry batteries. Since there is no mechanical drive, it is extremely compact and lightweight, and does not generate pulsating flow. Using microfabrication technology, the column and (electrochemical and UV) detectors are mounted on small amounts of substrate, the size of a business card. Conventional packing materials are used for the column, so the same analysis conditions as before can be applied directly without modification. The electrochemical detector uses a uniquely developed comb-shaped electrode. Although small in size, it has comparable sensitivity as conventional detectors. Liquid chromatographs currently used as the main instrument for chemical analysis are large and heavy, limiting their use to specific locations in the laboratory, but the instrument we have developed can easily be used anywhere. The amount of solvent used can also be reduced to 1/100 to 1/1000 of conventional detectors.
Semiconductor Precision Processing Technology
Low-damage and controllable semiconductor etching technology using electrochemical reactions
A semiconductor etching technique using electrochemical reactions was developed to reduce damage and achieve precise processing control in the depth direction compared with conventional methods, and was applied to the gate recess processing of AlGaN/GaN heterostructure transistors to realize normally-off transistors.
The etching process of semiconductor surfaces is one of the essential steps in the fabrication of semiconductor devices such as transistors. In this laboratory, we have developed an etching method that is superior to conventional dry etching methods in terms of both depth control and damage suppression, by utilizing electrochemical oxidation and dissolution reactions on semiconductor surfaces. As a result of applying the method to AlGaN/GaN heterostructures, which are considered to be promising power transistor materials, it was revealed that the etching process can be self-stopped at the desired processing depth by optimizing the electrochemical conditions, thus eliminating the need for an etching stop layer, which had been essential in prior technologies, and enabling precise control of the transistor threshold in a simpler way. In addition, the etched surface by this method has less processing damage than the dry-etched surface, and is expected to be a promising method for improving transistor performance.Taketomo Sato Associate Professor
Steam/Water Mixture Spray Cleaning Method with an Ultra-low Impact on the Environment
An ultraprecise and safe cleaning method making use of the physical action of steam and water and no chemicals.
We have developed an innovative cleaning method using a completely new vapor-water multiphase spray method, whereby water and steam are mixed and sprayed at high speed from a nozzle. This method is especially notable for not using any chemicals and minimizing the burden on the environment.
We have confirmed that the specified performance can be achieved with ultra-precision cleaning during semiconductor manufacturing processes, etc.
Based on our previous research results, we have discovered that when a droplet hits a solid surface in a condensable gas (not air), splashing is suppressed and a thin liquid film (lamella) spreads on the solid surface at high speed. Since the high-speed lamellae may generate a strong fluid shear force, it seemed possible to use a mixed jet of steam and water to realize an environmentally friendly cleaning method.
Based on our previous research results, we have confirmed that this cleaning method, which uses only water and steam, can achieve the specified cleaning performance for ultra-precision cleaning required in the manufacturing processes of semiconductors, LEDs, and solar cells. This cleaning method is also safe both for the human body and the environment, because it uses only water and steam instead of detergents or other chemicals that are harmful to the human body.
Super-hierarchical Structure Imaging Through the Combined Use of Neutrons and X-rays
Non-destructive imaging of unknown information over a wide range of scales using multi-quantum beams
Pulsed neutron transmission spectroscopy imaging is attracting attention as a method of non-destructive visualization of information that cannot be seen with other microscopic methods, and when it is combined with other quantum beams such as X-rays, it is possible to visualize information that cannot be seen with images alone.
Hokkaido University’s laboratory facilities, where small accelerators are used, have a history of nearly half a century, and are attracting worldwide attention as pioneering facilities. We mainly produce pulsed neutron beams, and the transmission spectra obtained using these beams enable us to map information on crystal structure, microstructure, internal stress and temperature on a two-dimensional real image as a distribution map of the entire sample. We also use X-ray CT which can measure the three-dimensional structure of the inside of an object, and analyze the combined results from neutrons and X-ray studies to synergistically understand the interior information of an object. In the figure, shown as synergistic imaging based on information from neutrons and X-rays, information on elements that cannot be individually obtained is mapped on the inside structure shown on the X-ray CT image. X-ray CT shows the presence of wires in an Al cylinder, but when neutron information is added, we can see that each wire is a different material.
Use of Lignin, a Wood Component, as an Electronic Device Material
Molding of lignin and its conversion to a functional material
Lignin is second only to cellulose in availability, but the only way to effectively use lignin at present is to burn it for energy production. We are currently working on molding lignin into fibers and films for use as electrodes and separators in electric double-layer capacitors (EDLCs).
EDLCs are electronic devices that are attracting attention as next-generation storage batteries that can replace rechargeable batteries such as Li-ion batteries. The parts called electrodes and separators in EDLCs are made from polymeric materials, so we are conducting research on replacing these polymers with lignin, a major component of woody biomass. By forming lignin into microfibers through electrospinning and converting them into active carbon fibers, we have succeeded in producing the large surface area required for electrode materials. This has led to the production of electrodes with high energy and power densities. In addition, by converting lignin into a flexible polyester film, it became possible to prepare a material that exhibits the same performance as conventional separators. We are currently endeavoring to further improve the performance.
Vibration Measurement Technology Using a Non-contact Laser Excitation System
Development of high-frequency vibration measurement and high-sensitivity damage detection technology
We have developed a technique to apply an ideal impulse excitation force using laser ablation generated on a structural surface by high-power pulsed laser irradiation. This technology enables non-contact, high-precision vibration measurement in the high-frequency range, which had previously been impossible.
As in Fig. 1, which shows the principle of laser-induced excitation force generation, the laser-induced excitation force is caused by laser ablation. Figure 2 shows an example of the application of this technology, a vacuum environmental excitation measurement system for a membrane structure. This system consists of a YAG-pulsed laser, dielectric multilayer mirror, collecting lens, membrane structure, LDV and vacuum chamber. The membrane structure is fixed inside the vacuum chamber, allowing us to conduct the experiment by adjusting the air pressure inside the chamber from the atmospheric to the vacuum environment. Figure 3 shows the measured frequency response of the membrane. As shown in Fig. 3, with an increase in the vacuum level, the resonance frequency of the membrane becomes higher and at the same time the resonant response level increases. In this way, this technology enables the extraction of both mass effect and damping effect caused by the air on the membrane surface. We have conducted experiments to verify the effectiveness of this technology in a vacuum chamber, which assumes a space environment.