Laser-cut nitinol stent. Nitinol is an alloy of nickel and?titanium. It is a so-called memory metal, which resumes its original shape after compression. Stents are implants used to expand blocked blood vessels. They are inserted via a catheter that delivers the compressed stent to the blockage site. When the catheter is withdrawn the stent opens up (as seen here) to widen and support the blood vessel.