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.
