Editing Shape-memory alloy (section)

=== Medicine ===
Shape-memory alloys are applied in medicine, for example, as fixation devices for [[osteotomy|osteotomies]] in [[orthopaedic surgery]], as the [[actuator]] in surgical tools; active steerable surgical needles for minimally invasive [[percutaneous]] cancer interventions in the surgical procedures such as [[biopsy]] and [[brachytherapy]],<ref>{{cite book |doi=10.1115/DMD2019-3307 |chapter=3D Steerable Active Surgical Needle |title=2019 Design of Medical Devices Conference |year=2019 |last1=Karimi |first1=Saeed |last2=Konh |first2=Bardia |isbn=978-0-7918-4103-7 |s2cid=200136206 }}</ref>  in [[dental braces]] to exert constant tooth-moving forces on the teeth, in [[Capsule Endoscopy]] they can be used as a trigger for biopsy action.

The late 1980s saw the commercial introduction of [[Nitinol]] as an enabling technology in a number of minimally invasive endovascular medical applications. While more costly than stainless steel, the self expanding properties of Nitinol alloys manufactured to BTR (Body Temperature Response), have provided an attractive alternative to balloon expandable devices in [[stent graft]]s where it gives the ability to adapt to the shape of certain blood vessels when exposed to body temperature. On average, {{val|50|s=%}} of all peripheral vascular [[stent]]s currently available on the worldwide market are manufactured with Nitinol.

==== Optometry ====
[[Glasses|Eyeglass frames]] made from titanium-containing SMAs are marketed under the trademarks [[Flexon]] and TITANflex. These frames are usually made out of shape-memory alloys that have their transition temperature set below the expected room temperature. This allows the frames to undergo large deformation under stress, yet regain their intended shape once the metal is unloaded again. The very large apparently elastic strains are due to the stress-induced martensitic effect, where the crystal structure can transform under loading, allowing the shape to change temporarily under load. This means that eyeglasses made of shape-memory alloys are more robust against being accidentally damaged.

==== Orthopedic surgery ====

Memory metal has been utilized in [[orthopedic surgery]] as a fixation-compression device for [[osteotomy|osteotomies]], typically for lower extremity procedures. The device, usually in the form of a large staple, is stored in a refrigerator in its malleable form and is implanted into pre-drilled holes in the bone across an osteotomy. As the staple warms it returns to its non-malleable state and compresses the bony surfaces together to promote bone union.<ref>{{cite journal |last1=Mereau |first1=Trinity M. |last2=Ford |first2=Timothy C. |title=Nitinol Compression Staples for Bone Fixation in Foot Surgery |journal=Journal of the American Podiatric Medical Association |date=March 2006 |volume=96 |issue=2 |pages=102–106 |doi=10.7547/0960102 |pmid=16546946 |s2cid=29604863 }}</ref>

==== Dentistry ====
The range of applications for SMAs has grown over the years, a major area of development being dentistry. One example is the prevalence of [[dental braces]] using SMA technology to exert constant tooth-moving forces on the teeth; the nitinol [[archwire]] was developed in 1972 by [[Orthodontics|orthodontist]] [[George Andreasen]].<ref>[https://www.nytimes.com/1989/08/15/obituaries/george-andreasen-55-orthodontics-inventor.html Obituary of Dr. Andreasen]. New York Times (1989-08-15). Retrieved in 2016.</ref> This revolutionized clinical orthodontics. Andreasen's alloy has a patterned shape memory, expanding and contracting within given temperature ranges because of its geometric programming.

[[Harmeet D. Walia]] later utilized the alloy in the manufacture of root canal files for [[endodontics]].

==== Essential tremor ====
Traditional active cancellation techniques for tremor reduction use electrical, hydraulic, or pneumatic systems to actuate an object in the direction opposite to the disturbance. However, these systems are limited due to the large infrastructure required to produce large amplitudes of power at human tremor frequencies. SMAs have proven to be an effective method of actuation in hand-held applications, and have enabled a new class active tremor cancellation devices.<ref>{{cite thesis |last1=Pathak |first1=Anupam |year=2010 |title=The Development of an Antagonistic SMA Actuation Technology for the Active Cancellation of Human Tremor |hdl=2027.42/76010 }}</ref> One recent example of such device is the [[Liftware]] spoon, developed by [[Verily Life Sciences]] subsidiary [[Lift Labs]].