SMA - Smart materials for medical applications

The paper presents Nitinol, a Nickel-Titanium shape memory alloy, as a smart material for medical implants and devices. The atomistic nature of shape memory and superelasticity of Nitinol and the associated unique changes in mechanical properties are described. The smartness of the material is exemplified by its use for self-expanding stents. Caused by the stress hysteresis of superelastic Nitinol, these devices exhibit a biased stiffness behavior, i.e. they exert a low chronic outward force on the vessel wall, but resist external deformation with much higher forces. Some recent developments of thin film Nitinol stents and filters are also discussed.