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Shape Memory Alloys for Biomedical Aplications Ni-Ti alloys β-Ti alloys Prof. dr. ir. Jan Van Humbeeck Dep. MTM-KU Leuven SHAPE MEMORY ALLOYS Ed. Hiroyazu Funakubo, Gordon and Breach, 1987 by OPA ISBN 2-88124-136-0 ENGINEERING ASPECTS OF SHAPE MEMORY ALLOYS Ed. T.W. Duerig, K.N. Melton, D. Stôckel, C.M. Wayman, ISBN 0-750-61009-3 Buttherworth-Heinemann Ltd, 1990 THE APPLICATION OF SHAPE MEMORYALLOYS IN MEDICINE J.P. Lipscomb and L.D. Nokes, Ed. Anthony Row ltd, 1996 ISBN 0852989563 SHAPE MEMORY MATERIALS K.Ostsuka and C.M. Wayman Cambridge University Press, 1999 ISBN 052144487X DELAY LAW AND NEW CLASS OF MATERIALS AND IMPLANTS IN MEDICINE Ed by E. Gunther, Northampton , MA 2000, STT2000 ISBN 9702353-0-5 (printed in Russia) SHAPE MEMORY IMPLANTS Ed. L. Yahia, Springer 2000 ISBN 3-540-67229-X Books on Shape Memory Alloys SHAPE MEMORY ALLOYS:MODELING AND ENGINEERING APPLICATIONS Ed. C. Lagoudas Springer 2008 THIN FILM SHAPE MEMORY ALLOYS FUNDAMENTALS AND DEVICE APPLICATIONS Ed. S. Miyazaki, Yong Qing Fu and Wei Min Huang Cambridge University Press 2009 ISBN 978-0-521-88576-8 SHAPE MEMORY ALLOYS FOR BIOMEDICAL APPLICATIONS Ed. T. Yoneyama and S. Miyazaki, Woodhead Publ., CRC, 2009 ISBN 978-1-84569-344-2 SHAPE MEMORY ALLOYS Ed. C. Cismasiu Published by Siyo (Croatia), 2010 ISBN 978-953-307-106-0 SHAPE MEMORY AND SUPERELASTIC ALLOYS/ TECHNOLOGIES AND APPLICATIONS Ed. By K. Yamauchi, I. Ohkata, K. Tsuchiya, S. Miyazaki, Woodhead publ. Cie, 2011 ISBN 978-1-84569-705-5 SHAPE MEMORY MICROACTUATORS M. Kohl, Springer 2004 ISBN 3-540-20635-3 SHAPE MEMORY ALLOYS-PROCESSING? CHARCTERISATION AND APPLICATIONS Ed. By F.M. Braz Fernandez Publ. by In Tech (Croatia), March 2013 ISBN 978-953-51-1084-2 PHYSICAL METALLURGY OF NiTi BASED SHAPE MEMORY ALLOYS K. Otsuka and X. Ren Progress in materials Science 50(200() pp. 511-678 SHAPE MEMORY ALLOYS HANDBOOK Christan Lexcellent ISBN: 978-1-84821-434-7 Wiley-ISTE, March 2013 2 Important properties of Biomaterials • Biocompatibilty – Ion-exchange, – Toxicity, – Corrosion (passivation) • Surface properties: – Roughness – Surface energy • Mechanocompatibility – E-modulus – Fatigue – Wear • Manufacturability (machinability) Requirements for Medical Implants (biomaterials) • The reliability of the mechanical functions and functional properties • The chemical reliability (the resistance to deterioration of their properties in a biological medium, the resistance to expansion, dissolution, corrosion) • Biological reliability-biological compatibility, lack of toxicity and carcenogenicity, resistance to the formation of thrombus and antigens. NiTi alloys 5 NiTi shape memory alloys (Nitinol) • Ni50Ti50 is an intermetallic compound which exhibits a thermoelastic martensitic transformation around room temperature • The hot phase is called beta, the cold phase is called martensite. • This transformation is characterized by its transformation temperatures. • The martensitic variants can reorient through deformation of the martensite or induced in the beta phase under loading. • This special deformation mode forms the basis of the functional properties: shape memory effect, pseudo-elasticity and damping. • NiTi-shape memory alloys are very biocompatible : - intermetallic compound (strong bounds between Ni and Ti) - passivation by Ti02 –surface layer 6 Influence of the composition on the transformation temperatures (TT): 400°C and 500°C give the TT after cold deformation and recovery annealing at those temperatures 7 NiTi-alloys The transformation temperatures of those alloys are controlled by • • • • Composition Impurities Degree of cold deformation Recovery annealing temperature (controls precipitates and defects concentrations and distributions) 8 Alloying of NiTi • To decrease the hysteresis (Cu) or to increase (Nb) • To decrease the TT (Fe, Cr, Co, Al), i.e. Ni39,8Ti49,8Cu10Cr0,4 • To increase the TT (Hf, Zr, Pd, Pt, Au) • To increase the strength of the matrix (Mo, W, O, C) 9 Properties of NiTi SMA 10 Biocompatibility of NiTi • NiTi is bio-inert (osteopermissive) – intermetallic compound – Ti02 passivation • Deviation of stoechiometry (more or less than 2% Ni) decreases slightly the corrosion resistance • Alloying with elements of the Pt-group (Ru, Rh, Os, Ir, Pd, Pt) or Mo improves the corrosion resistance. TiNi-Mo has a better passivation. • Alloying with Cu, Fe, Mn, Al decreases the corrosion resistance 11 Table 3 12 Corrosion resistance 13 Influence of sterilisation techniques on Ni-release 14 Difference due to variable Ni surface concentrations reported on NiTi wires (0.4-15at%) High-temperature treatments, which promote the formation of a thicker external Ti-oxide layer, result in Ni accumulation in the internal surface layers. S. Shabalovskaya and J. Van Humbeeck, “Biocompatibility for biomedical applications”, Chapter 9, SHAPE MEMORY ALLOYS FOR BIOMEDICAL APPLICATIONS Ed. T. Yoneyama and S. Miyazaki,Woodhead Publ., CRC, 2009, ISBN 978-1-84569-344-2 a:TEM image of a cross section of the microwire. b: Schematic of the average Ni and Ti contents at different spot locations in the wire as determined by EDXS. H. Tian,1 D. Schryvers, S. Shabalovskaya, and J. Van Humbeeck “Microstructure of Surface and Subsurface Layers of a Ni-Ti Shape Memory Microwire” Microsc. Microanal. 15, 62–70, 2009 Beta-Ti alloys • Ti melts at 1668°C and exhibits during further cooling an allotropic solid state transformation from the bcc (β) to the hcp (α) phase at 882,5°C. • Depending on the alloying elements, one defines α, α+β or β alloys related to the microstructure at room temperature. • The most important alloys used as biomaterials are Cp-Titanium (α -alloy) (commercial pure) (ASTM F67), Ti-6Al-4V (α+β ) (ASTM F136) and TMA (β) (ASTM 1713). • Ti-alloys are sensitive to hydrogen brittleness. • Ti-alloys are passivated by a TiO2 ( 10 nm) surface layer which forms spontaneously in air. • Ti-alloys have a very high pitting corrosion potential and are few sensitive to galvanic and stress corrosion. • Titanium is also interesting due to its low density (4.51 ton/m3) and low Emodulus (order of 100 GPa) and very good fatigue properties. • Titanium and its alloys exhibit a poor wear resistance. 17 Beta-Ti alloys • β (bcc)-stabilizing elements to be added. α(hcp)/α+β border decreases with increasing concentration of the alloying element. • Quenching of β leads to martensite formation (α’ or α”. • α”-martensite (orthorombic) is required. α’martensite (hexagonal) does not show SME. • α”-martensite is favoured by higher alloying content and higher quenching rate. • ω phase has to be avoided. 18 19 Ti-alloys 20 Compositions and electron/atom ratios of the α’/ α” boundary in some Ti-TM binary alloys “The Physical Metallurgy of Titanium Alloys”, E.W. Collings, ASME ISBN 0-87170-181-2, 1984 21 How to obtain α’’-martensite 22 Biocompatibility of beta-Ti alloys? • E. Eisenbarth et al., “Biocompatibility of betastabilizing elements of Titanium alloys”, Biomaterials 25 (2004) 5705-5713 – Decreasing biocompatibility: Nb-Ta-Ti-Zr-Al-316LMo – Al: potentially necrotic – Mo: cytotoxic effects, moderate toxic, – Nb, Ta, Ti, Zr: inertness Compositions of beta-Ti alloys for biomedical applications • Ti-(10-12)Mo-(2,8-4)Al-(0-2)Cr-(0-2)V-(0-4)Nb US Patent 6,258,182 BI, July 10, 2001 • Ti-10V-2Fe-3Al-0.2N • Ti-(20-30)Nb-(2-15)Zr-(2-12)Sn-(0-2)Al • Ti-30nb-(8-10)Ta-5Zr • Ti-(8-10)Mo-(2.8-6)Al-2V-4Nb • …………. Summary and a future direction Ti-Nb superelastic alloy + Zr: increases transformation strain but accelerate the formation of w phase. + Sn(Al) : suppresses formation of w phase and increases transformation strain. + O, N: create nano-domains and increase critical stress for slip deformation. Ti-Nb-Zr-(Sn, Al)-(O,N) alloys Further improvement by thermomechanical treatment and texture control. More than 6% of superelastic recovery. Stress (MPa) 600 Ti-Nb-Zr-Sn 400 200 0 0 1 2 3 4 5 6 7 8 9 10 11 12 Strain (%) Slide obtained from prof. S. Miyazaki Biomedical Applications • • • • • • • • Orthodontic devices Guidewires Non-invasive surgical instruments Orthopaedic implants Stents Filters Exo-prosthesis … Securing the Human Body 28 Applications of SMA as biomaterials 29 Orthodontic 30 Compare the stored energy of a stainless steel wire and a pseudoelastic NiTi. Moreover during the tooth movement the stress in NiTi will remain constant for along time while for SS the stress decreases fast. The frequency of correction is thus lower for NiTi alloys . 31 Orthodontic wires 32 Medical instruments A 1-mm-diam urological grasper (Bacher, Tuttlingen, Germany) demonstrates kink resistance. The shaft comprises a nitinol wire concentrically placed in a nitinol tube; the distal end is a hinged, stainless-steel grasper, which opens to an approximately 90° included angle. A Simon filter, shown in longitudinal and transverse views of the deployed state 33 Guidewires: -high flexibility and high kink resistance Superelastic NiTi endodontic files for root canal surgery •Steerable biliary guidewire (Director) 34 Stents • Self expanding stents on the basis of the pseudo-elastic property. • Balloon-expandable stents • Expansion on the basis of the shape memory effect • “Drug delivery” stents • (Removable stents as long the stent is not encapsulated.) 35 Stents produced by laser cutting of a tube Self expandable (Angiomed) Wire-stent 36 Mounting a stent trough balloon dilatation A self expanding stent pushed out of the catheter 37 NDC “Stents” Amplatzer 39 Bone grafts Fracture recovery by applying special NiTi grafts After the operation After one month 41 Biorthex porous NiTi for bone reconstruction 42 Porous structures by “3D-printing” Biomedical porosity Generating Test Samples 3D printing Evaluating Performance 43 From design to biomedical application NiTi; Porous Acetabular Cup; Cellular Gyroid Generating Porous Architecture Biomedical component 44 Market prospects: 14,24% growth 2013-2018 • Global Shape Memory Alloy Market 20142018 – Published: July 2014 – 58 pages – Price: 1953 EURO • Global Shape Memory Material Market Research Report – Publish Date: 28 Sep 2014 – Next Update Date: 28 Dec 2014 – Price: 3425 EURO You do not have to ask questions, but if you feel a need for it please do so. Thank you https://www.uantwerpen.be/en/conferences/esomat-2015/newsletter/ Keynote speakers: Ryosuke Kainuma (TU, Japan) “martensitic transformations at low T in high Ni-content alloys” Francesca Caballero (CENIM, Spain) “martensite and bainite in nanostructured steels” Hanus Seiner (CTU, Czech Rep.) “mobile interfacial microstructures in SMAs” Elisabeth Gautier (CNRS, France) “diffusionless transformations in Ti alloys“: Yinong Liu (UWA, Australia) “new directions for SMAs in composite systems” Richard James (UMN, USA) “future directions in martensitic and multi-ferroic systems”