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Local adhesion strength of the interface between Cu line and SiN cap layer in a Cu damascene interconnect structure of LSI has a significant fluctuation when evaluated with in-plane dimensions of 1 × 1 μm specimens, which was 4.78 ± 1.63 J/m2. The reproducibility of the evaluation technique was investigated by evaluating the strength of the Cu/SiN interface for the specimens fabricated on a plate of Cu single crystal, where the interface strength was measured as 0.62 ± 0.02 J/m2. The relative standard deviation of interface strength distribution in LSI interconnect structure was 34% which was more than ten times larger than the value 2.5% for the specimens fabricated on the plate of Cu single crystal. The significant fluctuation of interface strength was induced clearly not by the random error of the evaluation technique, but by the inhomogeneous grain structure of Cu line with various crystal orientations and grain boundaries. By means of elastic-plastic interface crack extension simulations, it was revealed that the difference in the amount of energy dissipated in plastic deformation of Cu layer mainly leads to a significant fluctuation of the apparent strength. Plastic deformation of Cu layer plays a dominant role on the local strength of interface Cu/SiN in LSI interconnects.

Local adhesion strength of the interface composed of a single copper grain and SiN insulation layer was evaluated by using subgrain-scale specimens fabricated on a damascene interconnect structure. Crystallographic information was also surveyed at the fracture sites of the specimens in view of possible correlations between the strength and the crystal orientation of copper. Evaluated strength distributed on the crystal orientation map with a wide range of scatter, which indicates that copper crystal orientation plays an important role on adhesion strength. In addition, the relationship between the evaluated adhesion strength and the crystal orientation of copper grain suggests the significant contribution of the energy to be dissipated to plastic deformation. The result of this fundamental evaluation supports the possible variation of local interface adhesion strength in damascene interconnects which consist of polycrystalline copper and the insulation layer.

The local interfacial strength is a key factor in designing and fabricating advanced three-dimensional large-scale integration interconnect structures. In this paper, both local fracture tests and three-dimensional elastic–plastic crack propagation analysis for a 10 μm × 10 μm specimen were performed, and the local interfacial adhesion between a Cu interconnect and a SiN cap layer were evaluated. The three-dimensional elastic–plastic crack propagation simulation was developed to evaluate the interfacial adhesion that eliminated the effect of progressive plastic dissipation energy during crack propagation. The results show that the average interfacial adhesion for Cu/SiN is 4.46 ± 0.17 J/m2. The crack propagation behavior and fracture pattern depend on the interfacial adhesion, and these differences are due to the plastic yielding of the side edge of the specimen. The critical interfacial adhesion for the onset of shear fracture is 4.92 J/m2, which is the upper bound of the interfacial adhesion evaluation for the 10 μm × 10 μm specimen.

The effects of alloy type and heat treatment on crater size, ejecta fragment mass, and ejecta fragment size were examined for polycarbonate spheres striking thick aluminum alloy targets at very high velocities. The diameter and depth of the craters were compared with those obtained through an empirical equation. The size and mass of the ejecta fragments collected from the test chamber were also measured. The ejecta fragment mass was proportional to the impact energy of the projectiles, and the ejecta fragment size was proportional to the cubic root of the impact energy. The calculated characteristic lengths, cross-sectional areas, and mass-to-area ratios were compared with those from the NASA breakup model and Hata's model. The ejecta ring diameter obtained from the witness plates decreased with increasing impact velocity.

The adhesion strength distribution at the interface between damascene copper lines and the cap layers covering the lines was explored. A novel system composed of a dual-beam SEM/FIB equipped with a nanoindenter and an EBSD camera enabled successful evaluation with a resolution of the order of 300 nm, which is the scale of crystal grains. The adhesion strength was found to scatter in a range spanning roughly half to double the average value. Although no clear correlation was observed with the geometry of the copper line, the impact of the copper grain structure beneath the specimens was rather distinct, where the adhesion strength of specimens with grain boundary junctions observed on their footprints was significantly lower than that of specimens without junctions. This result suggests that the microscopic structure of deposited materials may strongly influence the strength of adhesion to neighboring layers. Therefore, the evaluation of local adhesion is important from an engineering point of view as a means for avoiding unexpected fractures at possible weak points and assessing the mechanical reliability of the layered systems.

Thrombus formation in blood pumps is a major problem. It has been reported that the shear rate is closely related to thrombus formation in blood pumps; however, the mechanism of blood coagulation in a shear flow field is not yet fully understood. The purpose of this study is to evaluate the effect of shear loading on the reaction of blood coagulation factors quantitatively. Human blood and porcine blood were used as test blood and sheared at 2,880 s-1 for 3 h using a rheometer. After shear loading to the test blood, the activated partial thromboplastin time (APTT) and prothrombin time (PT) of sample plasma were measured using an automated coagulation analyzer. The APTT and PT of mixed plasma containing human blood coagulation factor-deficient plasma and sample plasma were also measured. The APTT and PT of mixed plasma reflected the reaction of the particular blood coagulation factor. Results show that shear loading prolonged the APTT and PT of human sample plasma. Accordingly, the APTT and PT of mixed plasma containing human blood coagulation factor V-deficient plasma and human sample plasma were prolonged after shear loading. Thus, the reaction of human blood coagulation factors was inhibited by specific inhibition of the reaction of human blood coagulation factor V in the shear flow field. The reaction time of porcine blood coagulation factors after shear loading differed from that of human blood coagulation factors. The result suggest the evaluation difficulty of animal blood coagulation reaction, that is, porcine blood coagulation reaction did not fully proceed with clinical reagents due to species specificity.

A long-term durability test was conducted on a newly developed axial-flow ventricular assist device (VAD) with hydrodynamic bearings. The mock circulatory loop consisted of a diaphragm pump with a mechanical heart valve, a reservoir, a compliance tank, a resistance valve, and flow paths made of polymer or titanium. The VAD was installed behind the diaphragm pump. The blood analog fluid was a saline solution with added glycerin at a temperature of 37 °C. A pulsatile flow was introduced into the VAD over a range of flow rates to realize a positive flow rate and a positive pressure head at a given impeller rotational speed, yielding a flow rate of 5 L/min and a pressure of 100 mmHg. Pulsatile flow conditions were achieved with the diastolic and systolic flow rates of ~0 and 9.5 L/min, respectively, and an average flow rate of ~5 L/min at a pulse rate of 72 bpm. The VAD operation was judged by not only the rotational speed of the impeller, but also the diastolic, systolic, and average flow rates and the average pressure head of the VAD. The conditions of the mock circulatory loop, including the pulse rate of the diaphragm pump, the fluid temperature, and the fluid viscosity were maintained. Eight VADs were tested with testing periods of 2 years, during which they were continuously in operation. The VAD performance factors, including the power consumption and the vibration characteristics, were kept almost constant. The long-term durability of the developed VAD was successfully demonstrated.

An impeller the same geometry as the impeller of a commercial monopivot cardiopulmonary bypass pump was manufactured using 3D printing. The 3D-printed impeller was integrated into the pump casing of the commercially available pump to form a 3D-printed pump model. The surface roughness of the impeller, the hydraulic performance, the axial displacement of the rotating impeller, and the hemolytic properties of the 3D-printed model were measured and compared with those of the commercially available model. Although the surface roughness of the 3D-printed model was significantly larger than that of the commercially available model, the hydraulic performance of the two models almost coincided. The hemolysis level of the 3D-printed model roughly coincided with that of the commercially available model under low-pressure head conditions, but increased greatly under high-pressure head conditions, as a result of the narrow gap between the rotating impeller and the pump casing. The gap became narrow under high-pressure head conditions, because the axial thrust applied to the impeller increased with increasing impeller rotational speed. Moreover, the axial displacement of the rotating impeller was twice that of the commercially available model, confirming that the elastic deformation of the 3D-printed impeller was larger than that of the commercially available impeller. These results suggest that trial models manufactured by 3D printing can reproduce the hydraulic performance of the commercial product. However, both the surface roughness and the deformation of the trial models must be considered to precisely evaluate the hemolytic properties of the model.

The purpose of the present study is to investigate a bearing gap adjustment for improvement of levitation performance in a hydrodynamically levitated centrifugal blood pump to realize a blood pump with a low hemolysis level. The impeller levitates axially by balancing a gravitational force, buoyancy, a magnetic force, and hydrodynamic forces on the top and bottom sides of the impeller. To adjust the levitation position of the impeller, the balance of acting forces on the impeller was adjusted by changing the shroud area on the bottom impeller. Three pumps having various shroud area were prepared as tested models: 817 mm(2) (HH-S), 875 mm(2) (HH-M) and 931 mm(2) (HH-L). First, for evaluating the bearing gap adjustment, the bearing gap was estimated by calculating a balancing position of the acting forces on the impeller. We actually measured the gravitational force, buoyancy and the magnetic force, and numerically analyzed hydrodynamic forces on the top and bottom sides of the impeller. Second, to verify accuracy of the estimated bearing gap, the measurement test of the bearing gap was performed. Finally, an in-vitro hemolysis test was performed to evaluate a hemolysis level of the pump. As a result, bottom bearing gaps were estimated as 40 μm (HH-S), 60 μm (HH-M) and 238 μm (HH-L). In the measurement test, bottom bearing gaps were measured as 63 μm (HH-S), 219 μm (HH-M), and 231 μm (HH-L). The estimated bearing gaps had positively correlated with the measured bearing gaps in relation to the shroud area on the impeller. In the hemolysis test, hemolysis level in every model was almost equivalent to that of BPX-80, when the bearing gap was adjusted greater than 60 μm. We could adjust the bearing gap by changing the shroud area on the impeller for improvement of levitation performance to realize a blood pump with a low hemolysis level.

Heart failure is a condition in which the heart cannot pump sufficiently because its contractile force has deteriorated. Patients with heart failure can sometimes undergo heart transplantation, but in number these patients comprise less than 10 % of patients actually requiring heart transplantation. Thus, mechanical circulatory assistance plays an important role in substituting for heart transplantation wherein the pump function of the heart is assisted by an artificial blood pump called a ventricular assist device. On the other hand, cardiopulmonary bypass is a form of extracorporeal circulation that temporarily takes over the function of the heart and lungs to maintain the circulation of blood and the oxygen content of the body during surgery for heart failure and aneurysms of the thoracic aorta. This chapter describes the vascular engineering of circulatory assist devices. Particular emphasis is placed on recent progress in ventricular assist devices and cardiopulmonary bypass pumps. These important medical devices assist with human circulation at either the chronic or the acute phase. Because these devices are derived from an industrial pump, a great many studies have been conducted not only from the medical perspective but also from industrial and engineering perspectives. In this chapter, current ventricular assist devices and cardiopulmonary bypass pumps, their specifications, their classifications, and methods for their design and evaluating are presented, including flow analysis inside the pump to optimize the geometry.

The effects of the additive amount of a chain extender, with a weight ratio of 3–5 %, on stress-strain curves of poly(lactic acid) (PCL) and poly(butylene succinate-co-l-lactate) (PBSL) polymer blends were examined with a mixing ratio of PLA to PBSL of 70/30. The additive increased the elongation at break, and the strain rate decreased elongation at break.

The MERA monopivot centrifugal pump has been developed for use in open-heart surgery, circulatory support, and bridge-to-decision for up to 4 weeks. The pump has a closed-type, 50-mm diameter impeller with four straight paths. The impeller is supported by a monopivot bearing and is driven by a radial-flux magnet-coupling motor. Because flow visualization experiments have clarified sufficient pivot wash and stagnation at the sharp corner of the pivot support was suggested, sharp corners were removed in the design stage. The index of hemolysis of the pump operating at more than 200 mm Hg was found to be lower than that of a commercial pump. Four-week animal tests were then conducted two times; improvement of thrombus formation was seen in the female pivot through modification of female pivot geometry. Overall antithrombogenicity was also recorded. Finally, to assure mid-term use, an additional 4-week durability test revealed that the rate of the axial pivot wear was as small as 1.1 µm/day. The present in vitro and in vivo studies revealed that the MERA monopivot centrifugal pump has sufficient hemocompatibility and durability for up to 4 weeks.

The influence of temperature on crater formation and ejecta composition in thick aluminum alloy targets were investigated for impact velocities ranging from approximately 1.5 to 3.5 km/s using a two-stage light-gas gun. The diameter and depth of the crater increased with increasing temperature. The ejecta size at low temperature was slightly smaller than that at high temperature and room temperature. Temperature did not affect the size ratio of ejecta. The scatter diameter of the ejecta at high temperature was slightly smaller than those at low and room temperatures.

Plasma skimming is a phenomenon in which discharge hematocrit is lower than feed hematocrit in microvessels. Plasma skimming has been investigated at a bearing gap in a spiral groove bearing (SGB), as this has the potential to prevent hemolysis in the SGB of a blood pump. However, it is not clear whether plasma skimming occurs in a blood pump with the SGB, because the hematocrit has not been obtained. The purpose of this study is to verify plasma skimming in an SGB of a centrifugal blood pump by developing a hematocrit measurement method in an SGB. Erythrocyte observation using a high-speed microscope and a bearing gap measurement using a laser confocal displacement meter was performed five times. In these tests, bovine blood as a working fluid was diluted with autologous plasma to adjust the hematocrit to 1.0%. A resistor was adjusted to achieve a pressure head of 100 mm Hg and a flow rate of 5.0 L/min at a rotational speed of 2800 rpm. Hematocrit on the ridge region in the SGB was measured using an image analysis based on motion image of erythrocytes, mean corpuscular volume, the measured bearing gap, and a cross-sectional area of erythrocyte. Mean hematocrit on the ridge region in the SGB was linearly reduced from 0.97 to 0.07% with the decreasing mean bearing gap from 38 to 21 μm when the rotational speed was changed from 2250 to 3000 rpm. A maximum plasma skimming efficiency of 93% was obtained with a gap of 21 μm. In conclusion, we succeeded in measuring the hematocrit on the ridge region in the SGB of the blood pump. Hematocrit decreased on the ridge region in the SGB and plasma skimming occurred with a bearing gap of less than 30 μm in the hydrodynamically levitated centrifugal blood pump.

In order to monitor the condition of patients with implantable left ventricular assist systems (LVAS), it is important to measure pump flow rate continuously and noninvasively. However, it is difficult to measure the pump flow rate, especially in an implantable axial flow blood pump, because the power consumption has neither linearity nor uniqueness with regard to the pump flow rate. In this study, a miniaturized mass-flow meter for discharged patients with an implantable axial blood pump was developed on the basis of computational analysis, and was evaluated in in-vitro tests. The mass-flow meter makes use of centrifugal force produced by the mass-flow rate around a curved cannula. An optimized design was investigated by use of computational fluid dynamics (CFD) analysis. On the basis of the computational analysis, a miniaturized mass-flow meter made of titanium alloy was developed. A strain gauge was adopted as a sensor element. The first strain gauge, attached to the curved area, measured both static pressure and centrifugal force. The second strain gauge, attached to the straight area, measured static pressure. By subtracting the output of the second strain gauge from the output of the first strain gauge, the mass-flow rate was determined. In in-vitro tests using a model circulation loop, the mass-flow meter was compared with a conventional flow meter. Measurement error was less than ±0.5 L/min and average time delay was 0.14 s. We confirmed that the miniaturized mass-flow meter could accurately measure the mass-flow rate continuously and noninvasively.

The dynamic behavior of granular media subjected to projectile impact was numerically investigated using a discrete element method (DEM). Specifically, the effects of the impact angle on the dynamic phenomena of projectile and granular media were examined. In general, after impact, a projectile either penetrates, rebounds, or moves horizontally depending on the impact angle of the projectile. The velocity histories of projectiles after impact for penetration and rebound differed. The impact angle did not affect drag force histories. The drag force histories of projectiles had ƒ-0.4 and ƒ-2.7 spectra. We have presented the probability distribution of the scattered velocity of granular media. When projectiles rebounded from granular media, the angle distribution of scattered granular media in the horizontal plane was butterfly-like. The impact angle did not affect the angle distribution of scattered granular media in the vertical plane. The granular media scattered in an elevation angle region of 40-60° regardless of the impact angle.

Stress-strain curves of the polyamid11, which is one of bio-based plastics (plant-derived plastics), were measured over a wide range of strain rates from 10-4 s-1 to 103 s-1, using a quasi-static compression testing machine and a split Hopkinson pressure bar (SHPB) method. Young's modulus and flow stress were increased with increasing strain rate, as is commonly seen in most machine materials. We confirmed the effects of water absorption and temperature from 5 °C to 65 °C on flow stress. The specimens were soaked in distilled water at 35°C. After 30 days, water absorption in the specimens did not increase much and the percentage of water absorption was 1% of their weight. The flow stress was decreased with increasing water absorption. Young's modulus and flow stress were decreased with increasing temperature, as is commonly seen in most engineering plastics.

The dynamic behavior of projectiles upon impact with granular media was recorded using two high-speed video cameras for capturing different angles. We used steel, brass, tungsten carbide spheres, and alumina ceramic spheres with diameters in the range of 6-20 mm as the projectiles and poly- styrene beads (6 mm in diameter) and glass beads (1.7 mm in diameter) as the granular media. Upon impact, the projec- tiles penetrated the media, rebounded from the media, or were deflected such that their resulting motion was in a horizontal direction. Post-impact motion of the projectiles depended on the impact angles of the projectiles, the density ratio (bulk density/projectile density), and the diameter ratio (granular diameter/projectile diameter) and not on the impact veloc- ity. The post-impact motion of the projectiles did not fol- low a clear trend in terms of the transient angle; instead, we observed the existence of a transient region. On the basis of the area of the transient regions, an empirical equation was derived for determining the critical angle of projectiles (the angle at which they can penetrate the granular media) as a function of the density ratio and the diameter ratio.

The dynamic response of a two-dimensional ordered particle packing composed of nylon-66 spheres 6.35 mm in diameter impacted by a spherical projectile was investigated both experimentally and numerically using the discrete element method (DEM). First, the influence of the number of layers in the particle packing on wave propa- gation and post-impact movement were examined. As the number of layers increased, the contact forces reaching the base plate decreased together with the rebound velocity of the projectiles. Next, the effects of dissimilar material lay- ers were examined. The spheres in one or two layers of the particle packing were replaced with spheres made of dissim- ilar materials, that is, alumina ceramic (Al2O3) or steel, and it was found that the scattering of the nylon spheres above the dissimilar material layers increased. The experimental results obtained using force sensors at the base plate showed that the dissimilar material layers reduced the contact forces at the base plate. Furthermore, as the mass of the dissimi- lar material spheres increased, the magnitude of the contact forces at the base plate decreased, and the rebound velocity of the projectile increased.

The first global interoperability experiment of GMPLS controlled Ethernet with VLAN tag swapping between two different implementations is successfully demonstrated. High definition video streaming is realized through a newly established Layer 2 Label Switched Path (L2-LSP). The results of this experiment can be applied to designing reliable Layer 2 networks.

We developed a simple in vitro antithrombogenic testing method using a mock circulation system as used in the hemolysis tests to evaluate the antithrombogenicity of centrifugal blood pumps. This method was not designed to substitute for animal experiments but was intended to be a screening test method for selecting pumps robust enough to operate properly during animal experiments. In this study, we were able to maintain an almost constant activated clotting time for test blood for 10 hours by using both trisodium citrate and calcium chloride. We carried out the in vitro antithrombogenic testing of monopivot type centrifugal blood pumps (models DD3 and DD6) and hydrodynamic bearing pumps (models HH2 and HH7), which were developed at Advanced Industrial Science and Technology. Thrombus formation was not observed in the DD3 or DD6 pumps but occurred in the HH2 and HH7 pumps. The HH2 pump generated thrombi during a 1.5-hour ex vivo test, and the test was terminated. We expect this in vitro testing method to be useful for undertaking evaluations before animal experiments.

The hemocompatibility of a newly developed monopivot circulatory assist pump was evaluated by the computational fluid dynamic (CFD) analyses with the particle tracking velocimetry measurement. Results were compared with those of the hemolysis test and in vitro antithrombogenic test to prevent hemolysis and thrombus formation inside the pump. The results of the CFD analysis and the particle tracking velocimetry had a good agreement with each other. The flow distributions by the CFD analysis indicated that the radial jet out of the impeller was adequately weak so that the wall shear stress was lower than 300 Pa on the volute casing wall. It corresponded with the hemolysis tests results, indicating that the hemolysis level was lower than that of the commercially available pump. However, the flow distributions also indicated that the pivot that was easy to stagnate was washed out, not only by the secondary flow through the back gap of the impeller, but also by the vortices generated by the secondary vanes. It corresponded with the in vitro antithrombogenic test results, indicating that thrombus formation could be removed only by redesigning the geometry of the secondary vanes.

For studying the generation of space debris, we experimentally investigated the penetration of steel projectiles into thick targets made of aluminum alloy 5056 and the subsequent crater formation in the velocity range from 0.7 to 1.9 km/s using a two-stage light gas gun. We added 1- and 2-mm-thick pure nickel plates and 2-mm-thick aluminum alloy plates to the thick targets, and examined the effects of plate addition, plate material, and plate thickness on the crater shape (depth, diameter, depth/diameter ratio) and lip formation. The plate addition suppressed the formation of crater lips and changed the crater shape. In particular, addition of nickel plates decreased the crater diameter, depth, and depth/diameter ratio. Furthermore, component analyses by scanning electron microscopy indicated the presence of Ni-Al alloy near the crater wall and Ni-Fe alloy in the post-impact projectile when nickel plates were used.