Hydrogen is widely used in fuel cell vehicles and spacecrafts, and is deemed as the next-generation energy carrier. On the other hand, hydrogen leakage is anticipated in various occasions ranging from production to consumption. Because system degradation and human error are inevitable and also hydrogen can be easily ignited even by weak magnitude of static electricity, quick, flexible and reliable sensing techniques of leaked hydrogen are required. Previously, we proposed a new wireless high-speed continuous sensing system with a semiconductor-type hydrogen sensor installed on a quadrotor drone [1]. In this study, the effects of the attitude angle and blade rotation on hydrogen sensing are investigated from the view point of the rotor wakes. As a result, we obtained encouraging results regarding the present approach for measuring leaked hydrogen.

This paper reports experimental results of underwater shock wave phenomena in a tube made of materials with different acoustic impedance for an establishment of a new shock wave pressure control method related to the shock wave medical and biomedical application. In this study, underwater shock wave was generated by an explosion of micro-explosive (a 10 mg silver aide pellet) in a metal tube as a closed space. The process of underwater shock wave generation phenomena from a metal tube was visualized by the shadowgraph method and recorded by high-speed framing camera. The pressure history of generated shock wave was measured simultaneously by a needle hydrophone. The peak overpressure of induced underwater shock wave from a metal tube in the case of stainless steel was larger and faster than that in the case of aluminum due to differences in acoustic impedance value.

This paper reports on the visualization results of the attachment phenomenon of microbubble to the burrs of micro order in the tip of medical implant and of the interaction between the underwater explosion induced by the electrical discharge and the implant attached with microbubbles. The attachment of microbubbles to the implant was directly visualized by the magnified photographing with the microscope attached to the camera. The interaction of underwater explosion caused by the electrical discharge was visualized by the shadowgraph method with suppressing light emission intensity of electrical discharge. The visualization results indicated that the implant was attached with the bubbles combined with at least two microbubbles. It was found form the visualization images that not only the underwater shock wave and but also the motion of primary bubble induced by the electrical discharge interfered with the bubbles attached to the implant, resulting in the motion of the bubbles on the burrs of implant.

This paper reports that the effect of cumulative number of discharge shot on the pit of gelatin simulating biomaterial attached with microbubbles subjected to the underwater shock wave loading generated by the electrical discharge. The height distributions of gelatin surface attached without and with microbubbles loaded by the underwater shock wave were measured by the 3-D microscope. The diameter and depth of pits in the surface were measured from the results of height distributions. The results indicated that the diameter and depth of pits in the gelatin were increased as the number of discharge shot increased and as the microbubble diameter attaching the gelatin was increased.

In drug discovery research, an in vitro tubule model is necessary as an alternative method of animal experiments for drug toxicity assays. Kidney-derived cells are cultured on a microporous membrane in culture inserts and evaluated with a Transepithelial Electrical Resistance (TEER) measurement which is a well-established method for quantitative observation of kinetics and monitoring tight junctions of cells in conventional methods. However, it is difficult that the in vitro tubule models with culture inserts reproduce its physiological functionality. Microfluidics is a promising technology to reproduce physiological environments and functionality on cultured cells. In this study, we have developed a microfluidic device which is capable of measuring TEER of cultured cells on a microporous membrane. Electrodes for TEER measurement have been integrated with a microfluidic device which has a culture part with a microporous membrane. To validate functions of the device, TEER value of renal cells cultured in the device has been measured. We confirmed that the TEER value increase with their proliferation. Then, the device has been used for kidney toxicity assays using model chemicals, cisplatin and cimetidine. As a result, we conclude that the device may be a powerful tool which can be applied to drug discovery researches.

We aim to develop a microdevice that measures material permeation via epithelial tight junction (TJ) to evaluate its barrier function. A microdevice is equipped with square pillar microchamber filled with collagen gel. Thus, when epithelial cells are cultured on its surface, cells do not invade into the microchamber, so that a flat epithelial sheet is formed. If the inner space of the microchamber is closed by a cell sheet, the inflow and outflow of the matter is restricted. If the permeability of TJ is increased by drugs, the target substance concentration in the microchamber changes due to the diffusion. In this study, the mass transfer of fluorescent dextran, a model substance, between the chamber and the bulk space was measured, in correlation to the morphology of MDCK cells on the microchamber device, using a confocal laser scanning microscope (CLSM). On the first day of cell culture, it was confirmed that the cells did not enter the microchamber and adhered on the collagen gel, and the leakage of fluorescent dextran was suppressed. However, after the second day of cell culture, cells invaded into collagen gel. The development of TJ requires about 3 days of culture, so we will study the concentration and hardness of collagen gel to develop a device that can measure substance permeation under long-term culture conditions.

Cell rolling on the vascular endothelium is an initial phenomenon of allergy, arteriosclerosis, or cancer metastasis and detailed understanding of this phenomenon would help the development of innovative treatments for these diseases. In this study, we observed the rolling behaviors of leukocytes on E-selectin-coated microchannel walls with various flow rate and different E-selectin density. As a result, we found that the rolling motion can be sorted into two modes from a perspective of the instantaneous cell migration. The first mode (Mode 1) is characterized by rather intensive rolling with low probability, whereas the second one (Mode 2) is characterized by mild rolling with high probability. We also found that thresholds of the mode are determined by both the wall shear stress exerted on the cells and the density of E- selectin on the wall. Furthermore, it was implied that the force to untether the adhesion molecules bonds by the flow is larger in Mode 2 than in Mode 1.

Renal proximal tubule epithelial cells (RPTECs) have reabsorptive and secretory functions involved in membrane transporters, and the cells are cultured in a microphysiological system for the observation of drug-induced nephrotoxicity. However, even today an effective method to recapitulate RPTEC functions in vitro has not been fully established. Since RPTECs are exposed to the flow of urine in vivo, we developed a microphysiological system in this study for the application of flow shear stress and the screening of nephrotoxicity. Micro-volumetric flow rates of a peristaltic pump were controlled through pulse-width modulation generated by a micro-computer. The cell culture device contained a tubule channel and a vascular channel, and a micro-pore membrane was sandwiched between the two layers. In this study, RPTECs were cultured on the membrane and exposed to flow shear stress at a physiological level for different time periods after pre-culture. After shear stress exposure for 3 days, cell membrane transporter MATE2-K was up-regulated, and mRNA levels of transporters OCT2, MATE1, MATE2 and P-gp increased prominently with 5-day exposure. Since nephrotoxicity is commonly elicited by injuring RPTECs, which is mediated by membrane transporters, enhanced expression of membrane transporters by flow shear stress may lead to high sensitivity of the microphysiological system.

The composite material composed of the hydroxyapatite (HAp) particles and poly-lactic acid (PLA) is one of the candidates of the scaffold materials for bone regeneration. Previously, we had proposed the hybrid interface control method, where the HAp particles are efficiently coated with pectin and chitosan utilizing the electrostatic interaction and the reaction process control, for HAp/PLA composite materials, resulting in the improvement of their fracture properties. In this study, we aimed to evaluate the effect of the molecular weight of the modification polymers on the tensile strength of the hybrid-interface-controlled HAp/PLA composites. As a result, the lower molecular weight of chitosan improved the tensile strength before the hydrolysis. In addition, the lower molecular weight of chitosan accelerated the degradation in the tensile strength. Its mechanism was discussed based on the interfacial microstructural viewpoint, suggesting the possibility of the control of the hydrolysis property by the change of the molecular weight of the modification polymers.

Cancer cells are known to lead human death, but they are difficult to treat. The reason is that the mechanism of metastasis has not been elucidated. Since cancer cells are known to induce the hardening and moving surrounding tissues i.e. extracellular matrix (ECM), this study aimed to increase the elastic modulus of ECM without changing the density of collagen fibers. The crosslinking agent (EDCNHS) was used for this purpose. By making collagen gel with administering the crosslinking agent, it was succeeded to increase the elastic modulus of ECM up to 5 times approximately than the case without crosslinking agent. Based on this result, it is possible to observe the infiltration behavior of cancer cells with the difference of elastic modulus under three-dimensional culture by enclosing cancer cells in the collagen gel.

In tissue engineering developed by Langer and Vacanti, it is known that lost tissues and organs can be regenerated artificially. Tissue engineering requires three elements, i.e., cell, growth factor, and biological material for cell scaffold, and these elements interact with each other. Thereby, the original regeneration ability of organisms can be enhanced. The surface properties have been considered to affect to material and cell interaction because a cell contacts directly with the surface of a biomaterial. Therefore, in this study, the change of the surface state of the material by plasma surface treatment and the influence on the cell adhesiveness were investigated. Since PET has been employed as cell scaffold, its adhesiveness to the surface of PET plate in vortex flow was investigated. Although the surface of PET temporarily became hydrophilic by the plasma surface treatment, the contact angle changed with time and reached to the same value as that of the control material after about 9 days. After plasma treatment, the surface chemistry by XPS measurement was found that the surface was oxidized. The surface analysis by AFM images showed that the surface roughness increased. In this study, it was suggested that the decrease in the contact angle by the plasma treatment affected to the cell adhesiveness to PET plate.

Microfabrication processes have widely used as a method modifying the surface of materials. The surface processing is expected to use for the prevention of adhesions of marine organisms as a way without killing actions. In the developments of antifouling materials, it is important to achieve the quantitative evaluations of the adhesion characteristics between organisms and material surfaces. In this study, adhesion experiments were planned by using native species mussels on the surface-treated resin substrates located in an aquarium. And adhesive properties of the mussels were evaluated in the measurements of adhesion strength of byssus under tensile loading and observing the morphology of byssus. The effect of loading direction was investigated in the vertical and the shearing directions. Although the measured values of adhesion strength showed little differences in the surface conditions, the force on the shear direction tended to exceed the vertical direction in all substrate conditions. Adhesion marks of the byssus were found on the substrate surface after the tests. And, it was confirmed that the amount of the adhesion marks was different depending on the surface condition. The evaluation of adhesion was achieved in the loading experiments of byssus and in observations of the morphology of byssus.

Bone calcification occurs in response to mechanical loading, and is an essential factor in bone maturation. However, how mechanical loading applied to the bone tissue stimulates calcification is largely unknown. In this study, we observed calcification process of immature bone tissue cultured under static stretch to examine its relationship to collagen fiber alignment and amount. Bone thin specimens were obtained from the tibia of 0~2-day-old chicks by cutting the tibia perpendicularly to the bone axis, and calcification process was observed up to 24 h while they were stretched in the direction parallel to the slice. It was found that there are two different modes in calcification process: In ‘mode 1’, calcification proceeds from the specimen circumference to center region, while in ‘mode 2’, calcification radially spreads from the center region to the specimen circumference. There was no significant increase in mode 1 calcification in response to tissue stretch, while mode 2 calcification was observed only in the stretched specimens. Mode 2 calcification might be dominant in bone tissue response to mechanical loading. These differences in calcification might have something to do with collagen fiber alignment and amount in uncalcified area of bone tissue.

Titanium has been widely used in biomaterial fields owing to its excellent corrosion resistance, superior tissue compatibility; however, titanium shows poor resistance. Conventional nitriding can improve the tribological properties, but decreased the strength and corrosion resistance. The purpose of this study is to improve various properties of commercially pure titanium with high corrosion resistance by the formation of three-dimensional nitrogen diffusion phases using powder metallurgy. Gas nitriding was performed at 550 or 600 oC to form a nitrided layer at the surface of powders, and nitrided powders were consolidated by spark plasma sintering at 800, 1000, 1200 and 1400 oC. Nitrogen concentration of sintered compacts tended to increase with the nitriding temperature. Grain size of sintered compacts became large as the nitriding and sintering temperature increased. Tensile tests were performed for sintered compacts fabricated from nitrided powder in air. Ultimate tensile strength of CP titanium with three-dimensional nitrogen diffused phase was higher than that of the un-nitrided one. Furthermore, the ultimate tensile strength and ductility of sintered compacts tended to increase with decreasing the nitriding temperature. Fatigue tests were also performed in air under four-point bending. Fatigue properties of sintered compact fabricated from nitrided powder tended to be improved with decreasing the nitriding temperature.

Recently, carburization has attracted extensive attention as surface stiffening processing of titanium. In this research, the influence of processing temperature of pure titanium by carburization was examined. As a result of the examination, the surface hardness was approximately increased firstly and then decreased with the processing temperature increasing. And the hardness of the diffusion layer reached to the maximum value was about 1052 HV when the processing temperature at 850°C. The wear depth and wear width reached the minimum value at 850°C. At different carburizing temperatures, the content of wear width and wear depth were 262 μm and 2.76 μm respectively. In summary, when the processing temperature at 850°C, the carburization of pure titanium can improve the comprehensive properties.

This study focused on the shape memory alloy used for the structural material of self-expanding stents and examined their effects on deformation by finite element method (FEM) analysis. Though the NiTi alloy is widely used for the selfexpanding stent, the research of the alternative material is being carried out, due to Ni having strong toxicity and may cause metal allergy. In this study, deformation analysis of self-expanding stents using Fe alloy, Cu alloy and Ti alloy without Ni were carried out, and the applicability of those materials to the self-expanding stent was examined. It was found that CuAlMn alloy and TiNbZr alloy can be a sufficient substitute for NiTi considering advantages such as low cost and safety.

Fiber-reinforced thermoplastics (FRTP) have better specific strength and specific modulus than metal and ceramics. In recent years, improvement of mechanical properties of FRTP due to addition have been considered for weight reduction of FRTP. In this study, CNT dispersion effects on weld strength of injection molded fiber reinforced thermoplastic were investigated. It was found that the addition of CNTs can increase the weld strength. It was found that the addition of CNTs can increase the weld strength. It is suggested that this effect is manifested the increase of elastic modulus of base materials and interaction force generated at the interface with resin and fiber by the addition of CNT. In addition, the interaction force between resin and fiber was found to be dependent on the injection temperature.

One way to meet the needs of materials is to mix two or more polymer materials, which is called as polymer blends. It is known that this largely changes mechanical properties depending on molding conditions, compatibility, form and the like. The injection molding temperature dependences of mechanical properties of PS/SEBS polymer blends with different styrene content were investigated. The mechanical properties were evaluated using a 3-point bending test, and the morphology observation was evaluated using a digital microscope and AFM. The negative correlation obtained between styrene contents of SEBS and injection molding temperature, and flexural yield strain was considered to be due to the increase of Poisson's ratio. The yield conditions of PS/SEBS polymer blends were craze which is a local shear yielding phenomenon regardless of the compatibility between PS and SEBS. The difference between the experimental value and the theoretical value of yield stress was considered to thermal residual strain. It was found that the injection molding temperature dependence on the mechanical properties of PS/SEBS polymer blends needs to take into account both Poisson’s ratio and residual strain.

Carbon fiber, which has high strength, high rigidity and low thermal expansion, would be a candidate for improving the high temperature properties of aluminum. In this study, carbon fiber preforms were formed using a water glass binder for reducing the cost of the forming. Cast aluminum alloy was used for the matrix, and the fiber-reinforced composites were fabricated by the squeeze casting. Microstructure and properties of the composites were compared with the composites using the conventional silica binder. The carbon fibers were planar-dimensionally random arrangement in the composites, and the reaction at the carbon fiber-aluminum interface was not recognized. The thermal expansion coefficient of the composite was decreased only in the direction horizontal to the pressed surface in the squeeze casting, and the value was similar to that of the composite using the silica binder. The compressive strength was equivalent to that of the composite using the silica binder. Based on these results, the water glass can be used as a substitute binder for the silica sol.

The flower of the Stylidium has stamens and a style fused into a single column. When the flower is stimulated, the column flips rapidly through an angle of 270–300 degrees in 10–30 ms, depending on species. After this high-speed rotation called "firing", the column slowly resets to its original position in 200–600 s. More than forty years ago, a mechanical model of the Stylidium's column was proposed in which "firing" was caused by changing turgor pressure, but this model could not explain the movement of ions in the bending part of the column. We focused on a oscillatory movement of the column whose laballum had been removed. In this study, how the contact between the column and the labellum plays a role in the firing movement was investigated by blocking this contact with alminum foil and the others. From the results of these experiments, we attempted to explore the mechanism of the high-speed rotation of the column by proposing a new mechanical model of the column. Furthermore, we observed the surface of the column and the labellum by using SEM (Scanning Electron Microscope) to find out some evidence of adherence in the column which was shown in the blocking experiments.

Pressure ulcer occurs by prolonged external force on bone prominence. The external force consists of compressive force and shear force. Many studies have been done for the effect of the compressive force because this is a primary cause of pressure ulcer. The effect of shear force has also been studied as a combination with the compressive force. The purpose of this study is to evaluate the shear deformation behavior of a layer of synthetic rubber, which is a gel-like material, in a mat with a polyurethane foam layer. Monotonic and cyclic shear were applied to the rubber material with a constant compressive strain. Under the cyclic shear and a constant compressive strain, stable hysteresis loops were obtained. The mean shear modulus was about 1 kPa which was close to the reported value in the literature. The mat with the polyurethane foam obtained a low resistance to shear with an addition of a synthetic rubber layer.

Anterior Cruciate Ligament (ACL) plays an important role in controlling tibial anterior translation and tibial internal rotation. But knee rotational instability does not improve after ACL Reconstruction (ACLR) for ACL Injury. Therefore, there is surgery to perform ACLR and Anterolateral Ligament Reconstruction (ALLR) at the same time. Anterolateral Ligament(ALL) controls tibial internal rotation. However, It has been reported that the reconstruction position of ALL affects tibial internal rotation. In this study, we first made a 3D knee joint model consisting of the femur, tibia, and fibula. Next, in the knee joint model which ALL, ACL, Posterior Cruciate Ligament (PCL), Lateral collateral ligament (LCL), and Medial collateral ligament (MCL) were attached, the effect of the attachment position of ALL on the internal rotation control function was evaluated by the finite element method (FEM). Using a 3D digitizer, we performed 3D scanning while rotating the right knee model by 20 °. The ligament model was made with a linear spring. When an anterior drawer force of 135 N was applied to the tibia, there was no difference in the tibial anterior translation amount with and without ALL. On the other hand, when an internal rotation torque of 5 N·m was applied, there was a difference in the tibial internal rotation amount with or without ALL.

In general, as the materials for the catheter used in the surgery, a certain degree of rigidity and responsiveness is required for bringing the tip of the catheter to the target location. In the present study, using the catheters made of soft nylon resin reinforced with thin stainless wires, the creep deformation behaviors under three stage step stress for uniaxial tension or torsion load are investigated. It is presumed that the Young's modulus of matrix decreases and the braids become easy to peel off due to the water contained. Moreover, it is considered that the loading histories for tension and torsion affect the creep deformation behavior under water containing condition. Therefore, as a preliminary step to verify them, experiments are conducted under the proportional loading state with changing the ratio of tension and torsion, and the creep behaviors obtained under water containing condition are compared with non-water containing condition.

This study aims at observing the effects of loading conditions in loosening behavior of acetabular cup using Finite Element Analysis (FEA). Number of total hip replacement (THR) has been increasing in super-aging society like Japan. Service lives of hip joints are limited by loosening behavior and loosening occurs by either, biological, chemical and mechanical factors. However, it is very difficult to identify the contributions of each factor in the loosening behavior in vivo, and then FEA was applied to simulate the loosening behavior owing only to mechanical loading. 3-dimensional FEA model was developed and the effect of bonding conditions between acetabular cup and bone was considered. Only in the case of shear stress breaking bonding, the contact was partially broken, which led to large displacement of 100 μm. Such the relative displacement at the interface can be a critical factor of worsening the value of loosening.

Intramedullary nail fixation is one of the useful treatments for subtrochanteric fracture. In many cases, long type of intramedullary nail is applied to treatment of subtrochanteric fractures. A middle intramedullary nail, which has an intermediate length between long type and short type, was developed because of the viewpoint of minimally invasive. It is important to examine biomechanical influences on length and diameter of the intramedullary nail systems subjected to various loads. The aim of this study was to investigate the influence of length and diameter of intramedullary nail for subtrochanteric fracture models with Seinsheimer classification IIB using finite element analysis (FEA). Four types of intramedullary nail were considered: nail diameter 10mm and 12mm in long type, and nail diameter 10mm and 12mm in middle type. Subtrochanteric fracture finite element (FE) models with fracture type IIB that each nail was implanted were developed. A 1-mm-thick callus layer was set in the gap between bone fragments of the femur. As a result of FE analysis, the effectiveness of nail diameter increase was indicated from the viewpoint of bone union.

Ti alloy and Co-Cr alloy are authorized as implant materials. These alloys are utilized by machining and heat treatment. The manufacturing process will generate residual stresses that influence in destruction and deformation of materials. X-Ray Diffraction (XRD) is one of methods to estimate residual stresses. However, X-ray stress constants K of some alloys have never been reported before. So when residual stresses of some alloys are measured, stress constants of pure metal are used. This case isn’t clear for evaluation of residual stresses. In this study, system to measure X-ray stress constants of alloys were constructed. Specifically, we designed and fabricated a measurement system that can irradiate X-ray to materials under load. It was confirmed that the load was uniformly applied to the test piece. So the result of loading test showed that it is possible to use this apparatus. Next, we thought about a test piece for measuring residual stress with stress constants calculated by the constructed system. Vacuum annealing was performed on the pure titanium powder and the procedure for producing test pieces in a stress-free (strained) state was confirmed.

Para Ice Hockey is an adaptive form of ice hockey used for athletes who have a disability which could be from limb loss, spinal cord injury, or a condition such as cerebral palsy. Athletes use a special sled called a ‘sledge’ to play Para Ice Hockey. Because Para Ice Hockey is a very physical sport, a sledge needs strength and stiffness. Foreign-made sledge is heavy and bad handling for Japanese athletes so there is a necessity of their weight saving. Therefore, Mg alloy sledge was manufactured because of weight saving. However, there were some problems about strength and stiffness for Mg alloy sledge. The purpose of this study is to evaluate strength of frame shape for Mg alloy sledge using finite element (FE) analysis. Based on the drawing, CAD models of Mg alloy prototype sledge were created, and their FE models were constructed. From FEA result on frontal impact, several high stress values were found in the sledge frame.

Recently, there is a growing demand for orthopedic implant which can fit to the patient’s individual skeleton shape. Then, it is expected the application of custom-made implant made by electron beam melting method (EBM) which is one of additive manufacturing (AM). EBM method is capable of modeling complex shapes freely but remains internal defects like pores. We previously reported its defect reduces fatigue property, however, it has not been clarified that effect of defect location and size on torsional fatigue property. In this study, we introduced an artificial micro defect on the surface that becomes fracture origin, and examined the effect of defect location and size on the degradation of torsional fatigue property of Ti-6Al-4V alloy manufactured by EBM. From the result of torsional fatigue test, it was revealed artificial defect does not reduce torsional fatigue property. Therefore, it is suggested that the fracture mechanism is different between surface-initiated fracture and in-interior fracture.

In order to obtain the fatigue strength characteristics under varying stress amplitude condition of IN100, the experiment was carried out by conducting two-step stress test on IN100 that is Ni-based super alloy. In the two-step multiple test, the high and low stress amplitude values were set to across the Kth. As a result, it was confirmed that the fatigue crack progressed at low stress level even if it is below in the fatigue limit by conducting the test mentioned above. Also, the evaluation of strain distribution around the fatigue crack by EBSD observation was conducted. According to this approach, strain distribution is increased after loading high stress amplitude, however, it is recovered after loading low stress amplitude which is below in fatigue limit.

Since the operating condition of thermal power plants has become harsher for minimizing the emission of CO2, Ni-based superalloys, such as Alloy 617 and 625, have been used in the plants to replace the conventional ferritic materials. Unfortunately, its higher coefficient of thermal expansion compared with conventional steels is a concern of the increase in thermal stress during operation. In addition, Ni-based superalloys have to suffer creep-fatigue random loading because thermal power plants have to compensate the random output of various renewable energies. It was found that the lifetime of Ni-based superalloys under creep-fatigue loading was much shorter than that under simple fatigue or creep loading. Thus, it has become very important to clarify the mechanism and establish the quantitative theory for estimating their lifetime under various loading conditions at elevated temperatures. Thus, the elucidation of the initial damage mechanism of Alloy 625 under various loading is indispensable. In this study, the initial cracking mechanism of Alloy 625 at grain boundaries under creep loading was investigated experimentally. It was found that the local accumulation of dislocations at the cracked grain boundaries caused the initial cracks at those grain boundaries. The initiation of cracks appeared clearly between two grains which had difference of KAM (Kernel Average Misorientation) values larger than 0.2. Therefore, dislocations were accumulated at one side of the grain boundary. By measuring the KAM values near grain boundaries, the appearance of initial cracks can be predicted approximately.