Biomedical subjects

Toru Masuzawa

Publications and source records attributed to Toru Masuzawa.

7 recordsLinked to original sources

PubMed2006

Hemolysis resulting from surface roughness under shear flow conditions using a rotational shear stressor.

The degree of hemolysis as a function of surface roughness value and roughened area under shear flow conditions was investigated using a rotational shear stressor. The shearing portion of the stressor is cone shaped in its upper and lower positions, with a cylindrical central section. Surface roughness was applied to the cylindrical section. Bovine blood was sheared for 30 min over a set of roughened surfaces of between arithmetic mean roughness (Ra) 0.1 and 0.8 mm covering 10% of the surface area of the cylindrical section (equivalent to 1.8% of the whole blood contact area) at a shear rate of 3750/s. The threshold value thus obtained for rapid increase in hemolysis was between Ra 0.6 and 0.8 mm. When sheared with a roughened surface of Ra 0.8 mm applied to the cylindrical surface at areas between 0 and 100% (equivalent to between 0 and 18% of the whole blood-contacting area), the hemolysis level did not increase from 10 to 100%, but a significant difference was obtained between 0 and 10%. This suggests that red blood cells were destroyed not by fatigue failure caused by rolling on the roughened surface, but due to the high shear stress generated by surface roughness. Moreover, it appears that the shear stress was generated over the entire cylindrical section, regardless of the area of surface roughness.

Animals↗

PubMed2005

Hemolysis caused by surface roughness under shear flow.

In this study, the relationship between the degree of roughness of blood contact surfaces under laminar shear flow conditions and the level of hemolysis resulting from this roughness was investigated using a rotational shear stressor. Unlike previous in vitro experiments that used a pumped circuit, the level of hemolysis was directly evaluated under a constant shear flow. In total, 1.8% of the blood contact area was roughened to an arithmetic mean roughness (Ra) value of between 0.4 and 9.2 microm by machine processing and a shear load was applied for 30 min at a shear flow rate of 3750 s(-1). As a result, the threshold Ra value for the induction of hemolysis was found to be between 0.4 and 0.8 microm. In addition, the results of this experiment suggested that the high shear stress resulting from surface roughness plays a major role in determining the level of hemolysis caused by surface roughness.

Animals↗

PubMed2003

Axial type self-bearing motor for axial flow blood pump.

An axial self-bearing motor is proposed which can drive an axial blood pump without physical contact. It is a functional combination of the bi-directional disc motor and the axial active magnetic bearing, where it actively controls single degree-of-freedom motion, while other motions such as lateral vibration are passively stable. For application to a blood pump, the proposed self-bearing motor has the advantages of simple structure and small size. Through the finite element method (FEM) analysis and the experimental test, its good feasibility is verified. Finally, the axial flow pump is fabricated using the developed magnetically suspended motor. The pump test is carried out and the results are discussed in detail.

Equipment Design↗

PubMed2003

Magnetically suspended centrifugal blood pump with an axially levitated motor.

The longevity of a rotary blood pump is mainly determined by the durability of its wearing mechanical parts such as bearings and seals. Magnetic suspension techniques can be used to eliminate these mechanical parts altogether. This article describes a magnetically suspended centrifugal blood pump using an axially levitated motor. The motor comprises an upper stator, a bottom stator, and a levitated rotor-impeller between the stators. The upper stator has permanent magnets to generate an attractive axial bias force on the rotor and electric magnets to control the inclination of the rotor. The bottom stator has electric magnets to generate attractive forces and rotating torque to control the axial displacement and rotation of the rotor. The radial displacement of the rotor is restricted by passive stability. A shrouded impeller is integrated within the rotor. The performance of the magnetic suspension and pump were evaluated in a closed mock loop circuit filled with water. The maximum amplitude of the rotor displacement in the axial direction was only 0.06 mm. The maximum possible rotational speed during levitation was 1,600 rpm. The maximum pressure head and flow rate were 120 mm Hg and 7 L/min, respectively. The pump shows promise as a ventricular assist device.

Biomedical Engineering↗

PubMedDate not supplied

Fractural characteristic evaluation of a microcapsule suspension using a rotational shear stressor.

We are developing microcapsule suspensions to evaluate the absolute hemolytic properties of centrifugal blood pumps. Four types of microcapsule suspensions, with maximum diameters of 100 microm or 10 microm, and membranes of polyurethane or melamine resin, were exposed to fluid dynamic shear up to 15,000 s(-1) with a rotating shear stressor developed in our laboratory. As a result, destruction was observed of only the 100 microm microcapsules. The microcapsules with polyurethane membranes broke at a high shear velocity range over 11,250 s(-1), a tendency similar to that observed using bovine blood. The microcapsules with melamine resin ruptured at approximately 7,500 s(-1). These observations could lead to determination of absolute hemolysis from shear stress occurring in centrifugal blood pumps.

Biomechanical Phenomena↗

PubMedDate not supplied

Magnetically suspended centrifugal blood pump with a self bearing motor.

A magnetically suspended centrifugal blood pump with a self bearing motor has been developed for long-term ventricular assistance. A rotor of the self bearing motor is actively suspended and rotated by an electromagnetic field without mechanical bearings. Radial position of the rotor is controlled actively, and axial position of the rotor is passively stable within the thin rotor structure. An open impeller and a semiopened impeller were examined to determine the best impeller structure. The outer diameter and height of the impeller are 63 and 34 mm, respectively. Both the impellers indicated similar pump performance. Single volute and double volute structures were also tested to confirm the performance of the double volute. Power consumption for levitation and radial displacement of the impeller with a rotational speed of 1,500 rpm were 0.7 W and 0.04 mm in the double volute, while those in the single volute were 1.3 W and 0.07 mm, respectively. The stator of the self bearing motor was redesigned to avoid magnetic saturation and improve motor performance. Maximum flow rate and pressure head were 9 L/min and 250 mm Hg, respectively. The developed magnetically suspended centrifugal blood pump is a candidate for an implantable left ventricular assist device.

Centrifugation↗

PubMedDate not supplied

Novel maglev pump with a combined magnetic bearing.

The newly developed pump is a magnetically levitated centrifugal blood pump in which active and passive magnetic bearings are integrated to construct a durable ventricular assist device. The developed maglev centrifugal pump consists of an active magnetic bearing, a passive magnetic bearing, a levitated impeller, and a motor stator. The impeller is set between the active magnetic bearing and the motor stator. The active magnetic bearing uses four electromagnets to control the tilt and the axial position of the impeller. The radial movement of the levitated impeller is restricted with the passive stability dependent upon the top stator and the passive permanent magnetic bearing to reduce the energy consumption and the control system complexity. The top stator was designed based upon a magnetic field analysis to develop the maglev pump with sufficient passive stability in the radial direction. By implementing this analysis design, the oscillating amplitude of the impeller in the radial direction was cut in half when compared with the simple shape stator. This study concluded that the newly developed maglev centrifugal pump displayed excellent levitation performance and sufficient pump performance as a ventricular assist device.

Biomedical Engineering↗