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

SHAPE MEMORY MICROACTUATORS

M. Kohl,

Springer 2004

ISBN 3-540-20635-3

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: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 ALLOYS-PROCESSING? CHARCTERISATION AND

APPLICATIONS

Ed. By F.M. Braz Fernandez

Publ. by In Tech (Croatia), March 2013

ISBN 978-953-51-1084-2

SHAPE MEMORY ALLOYS HANDBOOK

Christan Lexcellent

ISBN: 978-1-84821-434-7

Wiley-ISTE, March 2013

Books on Shape Memory Alloys

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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.

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NiTi alloys

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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

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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

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NiTi-alloys

• Composition

• Impurities

• Degree of cold deformation

• Recovery annealing temperature (controls

precipitates and defects concentrations and distributions)

The transformation temperatures of those alloys

are controlled by

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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)

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Properties of NiTi SMA

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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

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Table 3

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Corrosion resistance

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Influence of sterilisation techniques on Ni-release

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

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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 E-

modulus (order of 100 GPa) and very good fatigue properties. • Titanium and its alloys exhibit a poor wear resistance.

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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.

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Ti-alloys

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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

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How to obtain α’’-martensite

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Biocompatibility of beta-Ti alloys?

• E. Eisenbarth et al., “Biocompatibility of beta-stabilizing elements of Titanium alloys”, Biomaterials 25 (2004) 5705-5713

– Decreasing biocompatibility: Nb-Ta-Ti-Zr-Al-316L-Mo

– 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.

1 2 30 5 6 74 9 10 118 12

600

400

200

0

Str

ess

(MP

a)

Strain (%)

Ti-Nb-Zr-Sn

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

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Applications of SMA as biomaterials

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Orthodontic

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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

.

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Orthodontic wires

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A Simon filter,

shown in longitudinal and transverse views of the deployed state

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.

Medical instruments

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•Steerable biliary guidewire (Director)

Guidewires:

-high flexibility and high kink resistance

Superelastic NiTi endodontic files for root canal surgery

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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.)

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Stents produced by laser cutting of a tube

Wire-stent

Self expandable (Angiomed)

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Mounting a stent trough

balloon dilatation

A self expanding stent pushed out

of the catheter

NDC

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“Stents”

Amplatzer

Bone grafts

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Fracture recovery by applying

special NiTi grafts

After the

operation After one

month

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Biorthex porous NiTi for bone reconstruction

Porous structures by “3D-printing”

Generating Test

Samples

3D printing

Evaluating Performance

Biomedical porosity

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From design to biomedical application

NiTi; Porous Acetabular Cup; Cellular Gyroid

Generating Porous

Architecture

Biomedical component

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Market prospects: 14,24% growth 2013-2018

• Global Shape Memory Alloy Market 2014-2018

– 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/

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”

Keynote speakers: