From its earliest use in orthodontic arch wires to its more-recent dominant role in cardiovascular implants such as stents, endografts, and filters, nitinol possesses unique properties that have made it the material of choice for a variety of medical applications. The vast majority of medical applications take advantage of nitinol’s unusual superelastic properties.

While conventional engineering materials typically have an elastic limit much less than 1% strain, nitinol can experience fully recoverable strains up to 8%. This capability allows a properly designed nitinol component to radically transform its shape during service, fueling the trend toward minimally invasive procedures. For example, a nitinol stent may be designed to be delivered through a 2-mm sheath and expand to support a 10-mm vessel. Similarly, an endoscopic instrument may be delivered through a 15-mm instrument, expand to 60 mm to retrieve a specimen, and then collapse to exit through a similarly sized port.

In short, if a medical component must be delivered in a compressed state and then become an expanded shape, nitinol is likely to offer design advantages unavailable with other materials.