| Co-Investigator(Kenkyū-buntansha) |
OHMURA Shoji Makabe Giken Co. Ltd., Research development manager, 研究開発部長(研究職)
LI Jing-feng Graduate School of Eng., Tohoku Univ., Asoc. Prof, 大学院・工学研究科, 助教授 (50241542)
WATANABE Ryuzo Graduate School of Eng., Tohoku Univ., Professor, 大学院・工学研究科, 教授 (20005341)
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| Budget Amount *help |
¥8,700,000 (Direct Cost: ¥8,700,000)
Fiscal Year 1999: ¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 1998: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1997: ¥4,300,000 (Direct Cost: ¥4,300,000)
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| Research Abstract |
Small particles having the same size, often called as monosized powder, have now been finding increased needs in a number of scientific fields. They are very interesting in several medical applications, such as starting materials for the elaboration of resolvable bone substitutes, resolvable systems for sustained drugs delivery, or supports for differentiated mammalian cell cultures. For biomedical applications, it would be desirable to dispose of monodisperse spherical particles in the size range of 0.05〜0.5mm. Depending on the application, either dense solid particles, hollow spheres, or porous spheres with controlled porosity would be preferable. The particles may consist of tricalcium phosphate (TCP), hydroxyl apatite (HAp) or mixtures there of, depending on the desired bioresorvability of the material. In any case, a key issue is to shape the starting calcium phosphate powders into spheres with the desired size distribution. Given the relatively high cost of medical-grade powders,
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a method allowing to prepare monodisperse spherical granules would be highly appealing. Already well established techniques exist for the preparation of particles in the micrometer rage (sol-gel, controlled precipitation) and in the millimeter range (paste extrusion, spheronization) but none of them is able to work properly in the 0.05〜0.5mm range.
In this study, monosized spherical particles of tricalcium phosphate (β-TCP) with porous and hollow structure have been successfully prepared by pulsated orifice ejection method in the 200〜500μm range. The apparatus was devised for ejecting suspensions of calcium-phosphate ceramics from a small orifice by a clipping action of a pressure transmitting diaphragm by a piezoelectric actuator. Each pulse pressure produced one liquid droplet having a size almost equal to the orifice diameter. Ceramic suspensions have been developed, which can be processed with the apparatus; for mulations have been optimized with respect to powder characteristics (granulometry, degree of agglomeration, solid/liquid ratio, nature and concentration of dispersants, theological additives and binders). Less
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