White Papers
As perennial students of nitinol, we have for many years authored peer-reviewed articles in respected medical, trade and nitinol-specific journals.
We undertake the writing of white papers with the goal of offering insight on key issues facing the advanced materials industry, and hope they will become useful resources for our fellow professionals.
The following white papers were authored or co-authored by Memry team members. Click on any of the links below to download a PDF of that document.
Comparison of Optical and SEM-BEI Inclusion Analyses of VIM-VAR Nickel-Titanium Alloy
Frank Sczerzenie, Graeme W. Paul, Clarence Belden, and Audrey Fasching
(Submitted May 11, 2010; in revised form July 28, 2010)
The ASTM Standard for NiTi alloys does not specify the method to be used for the analysis of inclusions. Quantitative analysis is generally done by optical metallography with a computer program to measure size and area fraction. This study gives a comparison of quantitative analyses of inclusions by scanning electron microscopy using backscattered electron imaging (SEM-BEI) and quantitative analyses by optical metal- lography. Seven samples of 6.3-mm hot-rolled NiTi were evaluated. The coil samples were selected to exhibit a wide range of inclusion content. Each sample had a different Ni to Ti ratio corresponding to a different transformation temperature range (TTR) from As = 225 °C (Ni = 50.79 a/o) to As = +95 °C (Ni = 49.63 a/o). Quantitative analyses by optical and by SEM-BEI are in reasonable good agreement for maximum particle size and maximum area fraction. Both methods of analysis show that carbide and intermetallic oxide inclusion populations in VIM-VAR hot-rolled coil vary significantly in the amount and size of inclusions with the alloy transformation temperature. Therefore, an analysis of a larger number of samples at each TTR is needed to develop statistically precise data. All carbide inclusions were less than 12.5 lm and less than 1.0% area fraction in all the samples. Maximum size and area fraction of carbides decreased as TTR increased. Intermetallic oxide size and area fraction increased with increasing TTR Intermetallic oxides are fractured and separated from the matrix during hot working. However, stringering is very limited. The fracturing appears to happen in high TTR alloys but not in low TTR alloys. This dependence on TTR suggests that chemistry in or around the oxides affects their fracture behavior. Download the Full Article here.
Fracture of Polymer Coated Nitinol during Gamma Sterilization
Dennis. W. Norwich, P.E. Memry Corporation, Bethel, Connecticut, USA
After gamma sterilization of a packaged medical device, fractures were discovered in the superelastic Nitinol wire used as part of the assembly. The Nitinol wire was encased in FEP (fluorinated ethylene propylene) shrink tube. The only fractures occurred where the encased wire was held under strain during gamma sterilization. A study was conducted to determine the susceptibility of Nitinol to this type of failure. The variables studied included wire diameter, wire surface finish, wire oxide layer, quantity of wires encased, type of tubing, and strain level during gamma sterilization. The greatest susceptibility to fracture occurred to single wire samples with a light oxide layer held under high strain in FEP shrink tube. Gamma sterilization experiments were conducted to isolate and confirm this failure mechanism. Scanning Electron Microscopy (SEM) was used to analyze the fractured samples. Chemical analysis was performed in an attempt to detect trace elements to determine the root cause of the failures. Stress Corrosion Cracking (SCC) caused by the liberation of Fluorine due to the degradation of the polymer during gamma sterilization is suspected. Download the entire paper.
A Study of the Properties of a High Temperature Binary Alloy Above and Below its Martensite To Austenite Transformation Temperature
Dennis W. Norwich, P.E.; SAES Memry Corporation, Bethel, CT; SMST-2010, Pacific Grove, California, 2010.
High temperature Nitinol alloys provide a challenge to end users of the material because they are martensitic and soft at room temperature. These are commonly referred to as Shape Memory alloys as they revert to their superelastic (pseudoelastic) form and austenitic structure at a temperature above ambient. For this study, a NiTi wire, Ti-55.3 wt %Ni in composition (Alloy-B) and heat treated to an Af _ 60°C was used. Tensile testing was performed to fully characterize the performance of the material at a series of temperatures above and below its transformation temperature. This paper will summarize the properties of the material along with the affects of multiple strains on key material performance characteristics…. Download the entire paper.
An Evaluation of NiTiCo Alloy and its Suitability for Medical Device Applications
Audrey A. Fasching, Memry Corporation, Bethel, CT. Presentation delivered at SMST-2010, Pacific Grove, California, 2010.
Comparison of basic mechanical and physical properties between a binary NiTi alloy and a ternary NiTiCo alloy for medical device applications…. Download the entire paper.
Study on Thermomechanical Treatment, Mechanical Properties and Fatigue of Nitinol Superelastic Thin Sheet
Matthias Mertmann and Wolfgang Oswald; Memry GmbH, Weil am Rhein, Germany; Rainer Steegmüller and Andreas Schüssler, Admedes Schuessler GmbH, Pforzheim, Germany. Presented at SMST-2010, Pacific Grove, California.
Paper investigates the effect of thermomechanical treatments on the properties (mechanical, thermal, fatigue) of Nitinol thin sheet. Special emphasis is put on the effect of sheet anisotropy on mechanical properties…. Download the entire paper.
A Study of the Effect of Diameter on the Fatigue Properties of NiTi Wire
Dennis W. Norwich and Audrey Fasching; Memry Corporation, Bethel, CT. Accepted for Publication, SMST-2008, Stresa, Italy, 2008.
It is a generally held belief that controlled strain fatigue life is independent of wire diameter. This has led to the widespread use of general S-N curves for Engineering metals. Independence of wire diameter on fatigue life may not hold true for Nitinol. If so care must be used when applying generic Nitinol S-N curves to product design. To provide a more comprehensive understanding of this issue, a comparison study was conducted on the fatigue properties of various diameters of NiTi (Ti-55.8/55.9 wt%Ni) wire drawn from the same starting material… Download the entire paper.
Functional Characterization of SMA Wires in Actuation Conditions.
Luca Toia, Alberta Coda, Giorgio Vergani and Andrea Mangioni, SAES Getters, Lainate, Italy; A. Tuissi, P. Bassani, CNR-IENI, Lecco, Italy; 2006.
Actuation is one of the most promising fields for industrial application of Shape Memory Alloys (SMA). Since most of the present industrial applications are in the medical field, there is a lack of standardization in the characterization of SMA for actuators. SmartFlex is a wire specifically developed by SAES for actuation…. Read the entire poster.
A Study of the Effects of Surface Modifications and Process on the Fatigue Properties of NiTi Wire
Mark A. Polinsky, Dennis W. Norwich, Ming H. Wu; Memry Corporation, Bethel, CT. Proceedings, SMST-2006, Pacific Grove, California.
Several studies on the processing effects on NiTi fatigue were published in the recent past. However, there were disagreements and debates with respect to the interpretation on these results. In hope to provide a more comprehensive understanding of this issue, a study on the fatigue properties of NiTi wires, Ti-55.8/55.9 wt %Ni in composition, comparing the various effects of surface finishes and heat treatments was conducted using a rotating beam test method in a 37oC water bath…. Download the entire paper.
Comparative performance of Nitinol surfaces in protein absorption and platelet adhesion. Preliminary results
S. Shabalovskaya; Institute for Physical Research and Technology, Ames Laboratory, Ames, IA; K. Hauch; University of Washington, Seattle WA; J. Anderegg; Institute for Physical Research and Technology, Ames Laboratory, Ames, IA; and P. Poncet; Memry Corporation, Bethel CT; 2004.
Nitinol superelasticity can be favorably used to design self-expending medical devices that can reduce the level of vessel injury associated with neointimal proliferation and thrombosis. This study was performed to compare the relative thrombogenicity of Nitinol surfaces prepared using various protocols (polished 600 grit and 1 μm finish, chemically-etched, heat treated and electropolished in two different electrolytes)…. Download the entire paper.
Consideration of the ASTM Standards for Ni-Ti Alloys.
Frank Sczerzenie, Special Metals Corporation. Published in SMST 2004: Proceedings of the Second European Conference on Shape Memory and Superelastic Technologies, edited by Meertman and Fisscher, Baden Baden, October, 2004.
ASTM Standards F2004, F2005, F2063 and F2082 have been issues for binary Ni-Ti alloy raw materials for use in medical devices. Thermal analysis and chemistry data are presented on nine binary alloys ranging in nickel content from 54.8 to 56.1 weight percent nickel…. Read the entire paper.
The Effect of Alloy Formulation on the Transformation Temperature Range of Ni-Ti Shape Memory Alloys.
Frank Sczerzenie and Subhash Gupta, Special Metals Corporation, 2004.
Thermal analysis data and statistics are presented on nine binary Ni-Ti alloys ranging from As = +95ºC down to As = -50ºC. The material was made by vacuum induction melting (VIM) followed by vacuum arc remelting (VAR). The VIM pieces are bundled to make the electrodes for VAR. Analysis of differential scanning colorimetry data shows that the standard deviation of transformation temperature parameters, Mf, Mp, Ms, As, Ap and Af are affected by the alloy formulation…. Read the entire paper.
Fabrication Process and Characterization of NiTi Wires for Actuators.
Authors: Ausonio Tuissi and Paola Bassani, National Research Council, Institute for Energetics and Interphases, CNR-IENI Leccom Lecco, Italy; Andrea Mangioni and Luca Toia, SAES Getters, Lainate (Mi), Italy; Francesco Butera, Centro Ricerche FIAT, Orbassano (To), Italy; 2004.
A production route of NiTi wire with shape memory effect has been experimented on laboratory equipment and transferred to pilot scale. Technological aspects of vacuum induction melting, hot and cold working operations have been reported. The material has been characterized throughout the production steps by DSC, stress-strain, fatigue and thermo-mechanical measurements.
The process has been optimized for long life applications with particular focus on stabilization of functional properties over lifetime. Preliminary characterization of actuators using shape memory alloy wires deriving from the experimented production route have been carried out…. Read the entire paper.
Effects of Nitinol surface treatments and Ethylene oxide sterilization on human lymphocyte proliferation
S. Shabalovskayal and J. Anderegg; Institute for Physical Research and Technology, Ames Laboratory, Ames, IA; J. Wataha, Medical College of Georgia School of Dentistry, Augusta, GA; P. Poncet. Memry Corporation, Bethel CT; J. Cunnick, Dept. of Animal Science, Iowa State University, Ames IA. Published in Journal Biomedical Materials Research, 2003.
Surface treatment and sterilization are those critical protocols in the manufacturing of implant devices that can eventually predetermine the outcome of implantation. Biological performance of well characterized Nitinol surfaces (mechanically polished, chemically etched, aged in boiling water, heat treated, and electropolished) was evaluated using human peripheral blood lymphocyte proliferation test…. Download the entire paper.
Issues in the Further Development of Nitinol Properties And Processing for Medical Device Applications
L. McD. Schetky and M.H. Wu; Memry Corporation, Bethel, CT. Published in Proceedings, ASM Materials & Processes for Medical Devices Conference, Anaheim, p.271, 2003.
Binary Nickel-Titanium is currently a material of choice for many medical devices but there are challenges in fabricating the alloy to the required shape and surface finish. In addition, the properties of the binary are in need of improvement, particularly in the area of radiopacity, superelastic performance and fatigue strength. Alloy developments as well as new approaches to improve properties and fabrication techniques will be discussed as they relate to a variety of devices. The emerging field of MEMS will be reviewed with thoughts on future applications in implantable drug delivery systems…. Download the entire paper.
The Role Of Alkaline Cleaning Solutions And CL-Containing Lubricants On Pitting Corrosion In NiTi Alloys
P.H. Adler, S. Herreria, G. Kostur, S. Carpenter, P. Poncet, M.Wu; Memry Corporation, Bethel, CT; W. DiScipio; PercuSurge, Inc., Sunnyvale, CA. Published in Proceedings, SMST-2003, Pacific Grove, California, p.385, 2003.
Alkaline cleaning agents are found to react with remnant manufacturing lubricants trapped in surface defects of a NiTi alloy to form Cl-based salts. These sub-surface “reservoirs” may act as nucleation sites for pitting corrosion either latent under ambient conditions, or on exposure to a limited range of high temperatures used to impart pseudoelastic properties in these alloys as part of normal processing…. Download the entire paper.
A Closed Loop Implantable Artificial Pancreas Using Thin Film Nitinol MEMS Pumps
L. McD. Schetky, Memry Corporation; Peter Jardine, Shape Change Technologies LLC; Francis Moussy, University of South Florida. Published in Proceedings, SMST-2003, Pacific Grove, California, p.555 (2003).
To prevent the onset of serious pathologies diabetics must maintain extremely close control over their glucose levels which requires as many as eight blood samplings a day, an onerous task. A long sought solution is to have glucose monitored by an implantable sensor which is coupled to an implanted insulin pump which would deliver insulin in response to the monitor signal. The paper describes the elements of such a closed loop system…. Download the entire paper.
Fabrication of Nitinol Materials and Components
NiTiNb Plugs for Sealing High Pressure Fuel Passage in Fuel Injector Applications
Tony Wu, Diesel Technology Company, Kentwood, Michigan; Ming H. Wu, Memry Corporation, Brookfield, CT. Proceedings, International Conference on Shape Memory and Superelastic Technologies (SMST-2000), Pacific Grove, California, p.235, 2000.
A typical heavy-duty diesel fuel injector comprises of a solenoid control valve, a plunger cylinder and a fuel passage linking the first two elements…. Conventional sealing [of the fuel passage] method utilizing a brazed steel plug often fails under prolonged exposure to extreme cyclical pressures. The present paper describes an alternate sealing method utilizing a heat-to-recover NiTiNb plug that offers a more reliable seal and can be installed at much lower temperatures than a brazed steel plug…. Download the entire paper.
Industrial Applications for Shape Memory Alloys
Ming H. Wu and L. McD. Schetky, Memry Corporation, Brookfield, CT. Published in Proceedings, SMST-2000, Pacific Grove, California, p.171, 2000.
Although medical applications for shape memory alloys (SMA) now dominate in today’s market, there are many applications in the industrial sector which have reached large volume production that far surpass the material usage in the medical fields. In the early growth of shape memory alloy technology the most important applications were for fasteners and couplings, mainly in the military sector. With the maturing of the technology, and the broader availability of alloys, industrial applications appear in a wide spectrum of commerce…. Download the entire paper.
Nitinol Medical Device Design Considerations
Philippe P. Poncet; MEMRY Corporation, Menlo Park, CA. Published in Proceedings, SMST-2000, Pacific Grove, California, p.441, 2000.
Since the late 1980’s, Nitinol has been increasingly utilized in a variety of medical devices and, in some cases, has become one of the materials of choice for many designers and engineers. From surgical devices to endoluminal stents and other prosthesis, the material’s thermo-mechanical characteristics and its biocompatibility has allowed its use across many medical and surgical specialties both on the diagnostics and therapeutics sides. Nitinol’s non-linear behavior and thermal dependency are presenting a variety of design challenges that are further enhanced by the material processing complexity. Clear definitions and understanding of the final medical product performance requirements will assist the designers in selecting the right material condition for the application but also in defining the right testing and validation protocols. This paper lists a few design and processing guidelines when it comes to evaluating nitinol as a material candidate for a medical device application…. Download the entire paper.
Applications of Superelastic Nitinol Tubing
Phillipe P. Poncet, MEMRY Corporation, Menlo Park, CA. Proceedings, SMST-94, Pacific Grove, California, (1994).
The first pieces of Nitinol tubing were manufactured by Raychem Corporation of Menlo Park, California and made their first commercial appearance in 1991 in a laparoscopic set of steerable medical devices co-developed by Raychem and U.S surgical (AutoSuture Endo-Roticulators). Since then, the applications have replicated and have reached unprecedented levels that are still increasing today. By a large majority and due to its unique properties and biocompatibility, nitinol tubing has seen its strongest proponents among the designers of less invasive medical devices as its elevated price tag has limited its entry in mainstream industrial or commercial applications…. Download the entire paper.
Applications of Superelastic Ni-Ti in Laparoscopy
Phillipe P. Poncet, MEMRY Corporation, Menlo Park, CA. Proceedings, SMST-94, Pacific Grove, California, (1994).
The first pieces of Nitinol tubing were manufactured by Raychem Corporation of Menlo Park, California and made their first commercial appearance in 1991 in a laparoscopic set of steerable medical devices co-developed by Raychem and U.S surgical (AutoSuture Endo-Roticulators). Since then, the applications have replicated and have reached unprecedented levels that are still increasing today. By a large majority and due to its unique properties and biocompatibility, nitinol tubing has seen its strongest proponents among the designers of less invasive medical devices as its elevated price tag has limited its entry in mainstream industrial or commercial applications…. Download the entire paper.
Additional White Papers Published by Memry
The following is a list of white papers that have been published or presented by Memry professionals working at our manufacturing facility in Germany:
M. Mertmann, S. Kautz, W. Brown:
Design Principles and New Actuator Applications with NiTi Straight Wire Actuators, Proc. Actuator 2002, 8th International Conference on New Actuators, 10 – 12 June 2002, Bremen, S. 85 – 90.
M. Mertmann, E. Hornbogen, A. Bracke:
Development of a Roboitic Gripper Based on a NiTi-Silicone Composite Material with Integrated Sensing Functions, Proc. of the Int. Symp. on Shape Memory Materials SMM 94, Beijing, China (1994), S. 556-560.
M. Mertmann, E. Hornbogen, A. Bracke:
Influence of Thermal Treatment on the Stability of Partially Constrained Recovery of NiTi Actuator Wire, Journal de Physique IV, Coll. C8, supplément au Journal de Physique III, Vol. 5 (1995), C8-1259-1264.
M. Mertmann (V), K. Escher, E. Hornbogen:
Entwicklung eines Greifmechanismus aus neuen Verbundwerkstoffen mit Zweiweg-Formgedächtnis, Vorträge/Rheinisch-Westfälische Akademie der Wissenschaften (Düsseldorf): Natur-, Ingenieur- und Wirtschaftswissenschaften; N 418; Westdeutscher Verlag GmbH Opladen (1996).
M. Mertmann, E. Hornbogen, R. Pittschellis, M. Mertmann:
Optimization of NiTiCu-Actuator Wire for Use in Micron-sized Grippers, Proc. of 2nd Int. Conf. on Shape Memory and Superelastic Technologies: Engineering and Biomediccal Applications, Asilomar Conference Center, Pacific Grove, CA (USA), 3.-7. März 1997, 549-554.
M. Mertmann:
NiTi-Formgedächtnislegierungen für Aktoren der Greifertechnik - Funktionelle Eigenschaften und Optimierung, VDI-Fortschrittbericht, Reihe 5, Nr. 469, VDI-Verlag, Düsseldorf, 1997.
M. Mertmann, E. Hornbogen:
Grippers for the Micro Assembly Containing Shape Memory Actuators and Sensors, Journal de Physique IV, supplément au Journal de Physique III, No. 11, Coll. C5, 621- 626.
W. Siegert, M. Mertmann, K. Neuking, G. Eggeler:
Influence of Nb Content and Processing Conditions on Microstructure and Functional Properties of NiTiNb Shape Memory Alloys, SMST 2001, Kunming, China, to be published in: Materials Science Forum by Trans Tech Publications Ltd.
W. Siegert, M. Mertmann, K. Neuking, G. Eggeler:
Einfluß der thermomechanischen Behandlung auf eine iTiNb Formgedächtnislegierung für den Einsatz in Kopplungsmechanismen, in: Materialwissenschaft und Werkstofftechnik 31, 9, (2000) S. 822-824.
W. Siegert, K. Neuking, M. Mertmann, G. Eggeler:
Einfluß thermomechanischer Behandlung auf das Formgedächtnisverhalten von NiTiNb-Legierungen, DPG-Frühjahrstagung 2001, Hamburg.
E. Hornbogen, M. Mertmann:
Intelligent Materials, Composites and Systems, Proc. MATEH 96, Opatija, Kroatien (1996), 1-11.
W. Siegert, M. Mertmann, K. Neuking:
Charakterisierung einer NiTiNb-Formgedächtnislegierung für den Einsatz in (Ent-) Kopplungsmechanismen, DPG-Frühjahrstagung 2000, Regensburg.
K. Weinert, M. Buschka, F. Mach, M. Mertmann:
Herstellung von Rohrverbindungshülsen aus einer NiTiNb-Formgedächtnislegierung, in: VDI-Z, Spezial Werkzeuge, Mai 2001, S. 42-46.
A.Schuster, H. Voggenreiter, M. Mertmann:
Mechanical Decoupling Elements for Satellites based on Shape Memory Alloys, Adaptronik-Congress 2000, Potsdam, S. 71-76.
H. Voggenreiter, A. Schuster, M. Mertmann, M. Reindl, M. Roth, H. Vorbrugg:
Shape Memory Based Release Mechanism for Satellite Devices, Proc. 33rd Aerospace Mechanisms Symposium, Ed. Ed Boesiger et.al., Pasadena CA, USA (1999), S. 169-174.
A. Schuster, M.-C. Berger, H. Voggenreiter, M. Mertmann, et. al.:
“Marforming” NiTi for Solar Panel Release Mechanisms, Proc. 1st Europ. Conf. on Shape Memory and Superelastic Technologies, SMST99, Antwerp Zoo, Belgien, 1999, S. 300-306.
H. Voggenreiter, M. Mertmann, K. Johansen, A. Schuster, et. al.:
Eine neue SMA-Legierung für Satellitenentkopplungsmechanismen, Proc. Werkstoffwoche 98, Ed. Reiner Kopp et. al., Bd. VI, Symp. 8, Wiley-VCH Verlagsgesellschaft, Weinheim (1999), S. 701-706.
A. Wichelhaus, M. Mertmann:
Heat Treatment and Force Characteristics of NiTi Orthodontic Wires, Proc. 1st Europ. Conf. on Shape Memory and Superelastic Technologies, SMST99, Antwerp Zoo, Belgien, 1999, S. 220-225.
H. Voggenreiter, A. Schuster, V. Thuet, M. Mertmann, A. Jargo:
A Release Mechanism Based on SMA-Strips for the Satellite Instrument SCIAMACHY, Proc. EUROMAT99, 27.-30. September 1999, München (im Druck).
E. Hornbogen, M. Mertmann:
Intelligente Werkstoffe, Verbunde, Systeme. Tagungsband zur Hauptversammlung der Deutschen Gesellschaft für Materialkunde DGM, Stuttgart 1996, im Druck.
E. Hornbogen, M. Mertmann:
“Intelligente: Werkstoffe, Verbunde, Systeme, Metall 50 (1996) Nr. 12, 809-814.
J. Hesselbach, R. Pittschellis, E. Hornbogen, M. Mertmann:
Shape Memory Alloys for Use in Miniature Grippers, Proc. of 2nd Int. Conf. on Shape Memory and Superelastic Technologies: Engineering and Biomediccal Applications, Asilomar Conference Center, Pacific Grove, CA (USA), 3.-7. März 1997, 251-256.
K. Escher, E. Hornbogen, M. Mertmann:
The Two-Way Effect in Homogeneous Alloys and Composites for Robotic Applications, Proc. Int. Conference on Martensitic Transformations ICOMAT-92, Monterey CA, USA (1992), S. 1289-1294.
K. Escher, M. Mertmann, Ch. Haastert:
Entwicklung eines Greifmechanismus aus Formgedächtnis-Silicon-Verbundwerkstoffen, Metall 47 (1993) 7, S. 644 - 647.
K. Escher, C. Haastert, E. Hornbogen, M. Mertmann:
A Gripper Based on NiTi-Silicone-Composite Materials With Reversible Shape Memory Effect, Proc. Trans. Mat. Res. Soc. Jpn., Vol. 18B (1994), S. 1167 - 1170.
J. Hesselbach, R. Pittschellis, H. Stork, E. Hornbogen, M. Mertmann:
Optimization and Control of Electrically Heated Shape Memory Actuators, Proc. 4th Int. Conf. on New Actuators, ACTUATOR94, AXON Technologie Consult GmbH, Bremen, 15.-17. Juni 1994, S. 337 - 340.
G. Kubla, M. Mertmann, D. Treppmann:
Legierungen mit Formgedächtnis - Entwicklungsstand und Perspektiven in Deutschland
Metall 49 (1995), S. 180 - 186.