Many diverse applications have been developed for “memory metal” and other “smart” materials. These uses include eyeglass frames, coffee pot thermostats , electrical connectors, deicing system, heat pipes, clamps, and sculptures.
Research is underway on using shape memory alloys to deploy solar arrays and antennae on satellites and to control the balance on helicopter rotor blades.
The biocompatibility of NiTi allows its use in many medical applications such as: vascular stents, anchors for attaching tendons to bone, medical guidewires, medical guidepins, root canal files, bendable surgical tools, and devices for closing holes in the heart.
Another important attribute of nitinol in medicine is its superelasticity.
Other shape memory materials include gold cadmium, copper-aluminum-nickel, copper-zinc-aluminum, and iron-manganese-silicon alloys.
Other Examples of Memory Metal
Cumulative dust deposition is measured by rotating a quartz cover from a solar cell on the Sojourner rover (nearest corner in the photograph). Electrical heating of a 3-cm NiTi wire decreases its length by 5% to overcome a conventional return spring. Dust accumulated linearly at 0.28% per day, having implications for solar power production.
(Mars Pathfinder, July 5, 1997, http://photojournal.jpl.nasa.gov
JPL image PIA01551)
Top view schematic of the solar cell with removable cover.
The archwire of these braces used in orthodontia is made of memory metal to apply pressure uniformly to the teeth.
Flexible eyeglass frames.
Bending the memory metal eyeglass frames converts the metal from the rigid austenite structure to the more flexible martensite structure. When this mechanical stress is removed, the frames return to their original shape and austenite structure. See this exact pair of frames distort when exposed to liquid nitrogen.
Radius vascular stents
A company called NanoMuscle marketed a small actuator. These actuators are aimed at the toy market as reported in “Toy Story: Materials Engineering at Play“.