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Biomedical Porous Shape Memory Alloys for Hard-Tissue Replacement Materials

by Bin Yuan 1,2, Min Zhu 1,2,* and Chi Yuen Chung 3
School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China
Key Laboratory of Advanced Energy Storage Materials of Guangdong Province, Guangzhou 510640, China
Department of Physics & Materials Science, City University of Hong Kong, Kowloon, Hong Kong, China
Author to whom correspondence should be addressed.
Materials 2018, 11(9), 1716;
Received: 29 July 2018 / Revised: 3 September 2018 / Accepted: 5 September 2018 / Published: 13 September 2018
Porous shape memory alloys (SMAs), including NiTi and Ni-free Ti-based alloys, are unusual materials for hard-tissue replacements because of their unique superelasticity (SE), good biocompatibility, and low elastic modulus. However, the Ni ion releasing for porous NiTi SMAs in physiological conditions and relatively low SE for porous Ni-free SMAs have delayed their clinic applications as implantable materials. The present article reviews recent research progresses on porous NiTi and Ni-free SMAs for hard-tissue replacements, focusing on two specific topics: (i) synthesis of porous SMAs with optimal porous structure, microstructure, mechanical, and biological properties; and, (ii) surface modifications that are designed to create bio-inert or bio-active surfaces with low Ni releasing and high biocompatibility for porous NiTi SMAs. With the advances of preparation technique, the porous SMAs can be tailored to satisfied porous structure with porosity ranging from 30% to 85% and different pore sizes. In addition, they can exhibit an elastic modulus of 0.4–15 GPa and SE of more than 2.5%, as well as good cell and tissue biocompatibility. As a result, porous SMAs had already been used in maxillofacial repairing, teeth root replacement, and cervical and lumbar vertebral implantation. Based on current research progresses, possible future directions are discussed for “property-pore structure” relationship and surface modification investigations, which could lead to optimized porous biomedical SMAs. We believe that porous SMAs with optimal porous structure and a bioactive surface layer are the most competitive candidate for short-term and long-term hard-tissue replacement materials. View Full-Text
Keywords: shape memory alloy; NiTi; β type Ni-free Ti alloy; porous material; surface modification; biocompatibility shape memory alloy; NiTi; β type Ni-free Ti alloy; porous material; surface modification; biocompatibility
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Yuan, B.; Zhu, M.; Chung, C.Y. Biomedical Porous Shape Memory Alloys for Hard-Tissue Replacement Materials. Materials 2018, 11, 1716.

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