Shape Memory and Superelasticity: From Scientific Curiosity to Life Saving Technology
Dieter Stoeckel, Nitinol Devices and Components, Inc.
Friday, April 22, 2011
This seminar is part of the Jones Seminars on Science, Technology, and Society series
Shape Memory and Superelasticity are effects associated with the thermo-elastic martensitic transformation in equi-atomic or near equi-atomic Titanium-Nickel intermetallic compounds, commonly called Nitinol. While the term shape memory is used to describe the phenomenon of restoring a predetermined shape through heating, after having "plastically" deformed that shape, the term superelasticity refers to the enormous elasticity of the material. During the past 20 years Nitinol has evolved from a scientific curiosity into the material of choice for medical devices and implants. Its unusual properties allow the miniaturization and functionality of instruments for minimally invasive therapies, and its pronounced stress hysteresis makes implants biomechanically compatible with the body's structures. Nitinol also exhibits excellent corrosion resistance, biocompatibility and MR compatibility. It has found particularly wide spread use in the treatment of cardiovascular disease, where it is used for self-expanding stents, filters, occlusion devices, heart valve frames, and various other devices. The presentation will focus on the engineering aspects of shape memory and superelasticity, as well as the material specific properties of Nitinol medical devices, like biased and temperature dependent stiffness, kink resistance, durability and fatigue.
About the Speaker
Dr. Dieter Stoeckel has been involved in the development and commercialization of advanced materials for over 40 years. He became interested in the shape memory effect during the late 1970s while researching alternatives for thermostatic bimetals. Ever since, he directed material research, process development and product innovation with shape memory and superelastic alloys, specifically Nitinol. He is currently Senior Advisor and a Member of the Board of Directors of NDC (Nitinol Devices & Components, Inc.), Fremont, CA, whose medical materials and components business he started in 1993, and where he served as president from 1995 until 1997, when the company was acquired by Johnson & Johnson. While at Johnson & Johnson, he was instrumental in the development and production of the market leading self-expanding Nitinol stents and filters for the Cordis franchise. In 2008 he co-lead the management buy-out for J&J's Nitinol business, which is now privately owned again. Dr. Stoeckel is also co-founder of Euroflex GmbH (1993, a Nitinol semi-finished materials manufacturer) and Admedes GmbH (1996, a producer of Nitinol medical components) in Germany. Prior to NDC, he worked at Raychem Corp. in Menlo Park, CA, an early pioneer in Nitinol technology, and at G. RAU in Pforzheim, Germany, a diversified metals producer. Dr. Stoeckel received an M.S. and Ph.D. in Physical Metallurgy from the University in Stuttgart (Max Planck Institute for Metals Research), Germany, in 1969 and 1972, respectively.