Nickel Titanium (NiTiNOL)

Nickel Titanium (NiTiNOL) is a metal alloy that has the unique ability to change shape (up to 8% strain) and still fully recover back to its original geometry. Consisting of near equal amounts of nickel and titanium, this mechanically active alloy gets its name from the location of its initial discovery, the Naval Ordinal Laboratory, in 1959.

NiTiNOL derives its unique shape-changing behavior from its atomic structure that can undergo a phase transformation when deformed. Depending upon the composition and temperature, NiTiNOL can display either shape memory or pseudoelastic properties. NiTiNOL exhibits shape memory when it can be deformed easily and maintain that deformed shape at room temperature. Upon heating to a certain temperature (i.e. body temperature in biomedical applications), shape memory NiTiNOL will recover back to its original “memorized” shape. For clinical applications, this activation temperature can be tailored to body temperature to allow for shape change inside the body. In contrast, superelastic NiTiNOL can be deformed and automatically recover back to its original shape (no activation temperature needed) at large strains up to 10X more than traditional metals. If constrained while deformed, pseudoelastic NiTiNOL can apply significant recovery forces as it tries to return to its original shape¹.

Due to the inherent difficulty in machining NiTiNOL, the designs of most NiTiNOL biomedical devices have been limited to simple 2-dimensonal geometries cut from wire or sheet stock. However, Enovis™ with its proprietary processing, allows for 3-dimensional, more complex geometries.