According to a portion of that article: Demonstration model heat engines have been built which use nitinol wire to produce mechanical energy from hot and cold heat sources. A prototype commercial engine developed in the 1970s by engineer Ridgway Banks at Lawrence Berkeley National Laboratory, was named the Banks Engine.
However, the applications are not limited to just energy production. The article continues…
“There are four commonly used types of applications for nitinol.
- Free Recovery: nitinol is deformed at a low temperature, and heated to recover its original shape.
- Constrained Recovery: The same, except that recovery is rigidly prevented, and thus a stress is generated.
- Work Production: Here the alloy is allowed to recover, but to do so it must act against a force (thus doing work).
- Superelasticity: As discussed above, here the nitinol acts as a super spring.
In 1989 a survey was conducted in the United States and Canada that involved seven organizations. The survey focused on predicting the future technology, market, and applications of SMAs. The companies predicted the following uses of nitinol in a decreasing order of importance: (1) Couplings, (2) Biomedical and medical, (3) Toys, demonstration, novelty items, (4) Actuators, (5) Heat Engines, (6) Sensors, (7) Cryogenically activated die and bubble memory sockets, and finally (8) lifting devices.
- Nitinol is also popular in extremely resilient glasses frames. It is also used in some mechanical watch springs.
- It can be used as a temperature control system; as it changes shape, it can activate a switch or a variable resistor to control the temperature.
- It is used in cell-phone technology as a retractable antenna, or microphone boom, due to its highly flexible and mechanical memory nature.
- It is used in some novelty products, such as self-bending spoons which can be used by amateur and stage magicians to demonstrate “psychic” powers or as a practical joke, as the spoon will bend itself when used to stir tea, coffee, or any other warm liquid.
- It can also be used as wires which are used to locate and mark breast tumours so that the following surgery can be more exact.
- Due to the fact it can change shapes it is also used as a golf club insert.
- Nickel titanium can be used to make the underwires for underwire bras.
- Nitinol is highly biocompatible and has properties suitable for use in orthopaedic implants. Due to Nitinol’s unique properties it has seen a large demand for use in less invasive medical devices. Nitinol tubing is commonly used in catheters, stents, and superelastic needles.
- In colorectal surgery.
, the material is used in devices for reconnecting the intestine after removing the pathology.
- In dentistry, the material is used in orthodontics brackets and wires connecting the teeth. Suresmile is one example of an orthodontic application. Once the SMA wire is placed in the mouth its temperature rises to ambient body temperature. This causes the nitinol to contract back to its original shape, applying a constant force to move the teeth. These SMA wires do not need to be re-tightened as often as other wires because they can contract as the teeth move unlike conventional stainless steel wires. Additionally, nitinol can be used in endodontics, where nitinol files are used to clean and shape the root canals during the procedure. Because of the high fatigue tolerance and flexibility of nitinol, it greatly decreases the possibility of an endodontic file breaking inside the tooth during root canal treatment, thus improving safety for the patient.
- Another significant application of nitinol in medicine is in stents: a collapsed stent can be inserted into an artery or vein, where body temperature warms the stent and the stent returns to its original expanded shape following removal of a constraining sheath; the stent then helps support the artery or vein to improve blood flow. It is also used as a replacement for sutures – nitinol wire can be weaved through two structures then allowed to transform into its preformed shape, which should hold the structures in place.”