Editing Shape-memory alloy (section)

== Applications ==

=== Industrial ===

==== Aircraft and spacecraft ====
[[Boeing]], [[General Electric Aircraft Engines]], [[Goodrich Corporation]], [[NASA]], [[Texas A&M University]] and [[All Nippon Airways]] developed the Variable Geometry Chevron using a NiTi SMA. Such a variable area fan nozzle (VAFN) design would allow for quieter and more efficient jet engines in the future. In 2005 and 2006, Boeing conducted successful flight testing of this technology.<ref name=Mabe>{{Cite book | doi = 10.1117/12.776816| chapter = Variable area jet nozzle using shape memory alloy actuators in an antagonistic design| title = Industrial and Commercial Applications of Smart Structures Technologies 2008| volume = 6930| pages = 69300T| year = 2008| last1 = Mabe | first1 = J. H. | last2 = Calkins | first2 = F. T. | last3 = Alkislar | first3 = M. B. | s2cid = 111594060| editor3-first = M. Brett| editor3-last = McMickell| editor2-first = Benjamin K| editor2-last = Henderson| editor1-first = L. Porter| editor1-last = Davis}}</ref>

SMAs are being explored as vibration dampers for launch vehicles and commercial jet engines. The large amount of [[hysteresis]] observed during the superelastic effect allow SMAs to dissipate energy and dampen vibrations. These materials show promise for reducing the high vibration loads on payloads during launch as well as on fan blades in commercial jet engines, allowing for more lightweight and efficient designs.<ref name=Hartl>{{Cite journal | doi = 10.1243/09544100jaero211| title = Aerospace applications of shape memory alloys| journal = Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering| volume = 221| issue = 4| pages = 535| year = 2007| last1 = Lagoudas | first1 = D. C. | last2 = Hartl | first2 = D. J. | doi-access = free}}</ref> SMAs also exhibit potential for other high shock applications such as ball bearings and landing gear.<ref name=DellaCorte>DellaCorte, C. (2014) [https://ntrs.nasa.gov/search.jsp?R=20140010477 Novel Super-Elastic Materials for Advanced Bearing Applications].</ref>

There is also strong interest in using SMAs for a variety of actuator applications in commercial jet engines, which would significantly reduce their weight and boost efficiency.<ref name=Webster>{{Cite book | doi = 10.1117/12.669027| chapter = High integrity adaptive SMA components for gas turbine applications| title = Smart Structures and Materials 2006: Industrial and Commercial Applications of Smart Structures Technologies| volume = 6171| pages = 61710F| year = 2006| last1 = Webster | first1 = J. | s2cid = 108583552| editor1-first = Edward V| editor1-last = White}}</ref> Further research needs to be conducted in this area, however, to increase the transformation temperatures and improve the mechanical properties of these materials before they can be successfully implemented. A review of recent advances in high-temperature shape-memory alloys (HTSMAs) is presented by Ma et al.<ref name=Ma />

A variety of wing-morphing technologies are also being explored.<ref name=Hartl />

==== Automotive ====
The first high-volume product (> 5Mio actuators / year) is an automotive valve used to control low pressure [[pneumatic]] bladders in a [[car seat]] that adjust the contour of the lumbar support / bolsters. The overall benefits of SMA over traditionally-used solenoids in this application (lower noise/EMC/weight/form factor/power consumption) were the crucial factor in the decision to replace the old standard technology with SMA.

The 2014 Chevrolet Corvette became the first vehicle to incorporate SMA actuators, which replaced heavier motorized actuators to open and close the hatch vent that releases air from the trunk, making it easier to close. A variety of other applications are also being targeted, including electric generators to generate electricity from exhaust heat and on-demand air dams to optimize aerodynamics at various speeds.

==== Robotics ====
There have also been limited studies on using these materials in [[robotics]], for example the hobbyist robot [[Stiquito]] (and "Roboterfrau Lara"<ref>[http://www.lararobot.de/ The Lara Project – G1 and G2]. Lararobot.de. Retrieved on 2011-12-04.</ref>), as they make it possible to create very lightweight robots. Recently, a prosthetic hand was introduced by Loh et al. that can almost replicate the motions of a human hand [Loh2005]. Other biomimetic applications are also being explored. Weak points of the technology are energy inefficiency, [[#Response time and response symmetry|slow response times]], and large [[hysteresis]].

==== Valves ====
SMAs are also used for actuating [[valves]].<ref>{{cite web |url=https://www.gesundheitsindustrie-bw.de/en/article/news/ultra-compact-valves-shape-memory-actuators |title = Ultra-compact: valves with shape memory actuators - Healthcare industry| date=24 March 2021 }}</ref> The SMA valves are particularly compact in design.

==== Bio-engineered robotic hand ====
There is some SMA-based prototypes of robotic hand that using shape memory effect (SME) to move fingers.<ref>{{Citation|last1=Duerig|first1=T.W.|title=Wide Hysteresis Shape Memory Alloys|date=1990|work=Engineering Aspects of Shape Memory Alloys|pages=130–136|publisher=Elsevier|isbn=9780750610094|last2=Melton|first2=K.N.|last3=Proft|first3=J.L.|doi=10.1016/b978-0-7506-1009-4.50015-9}}</ref>

==== Civil structures ====
SMAs find a variety of applications in civil structures such as bridges and buildings. In the form of rebars or plates, they can be used for flexural, shear and seismic strengthening of concrete and steel structures. Another application is Intelligent Reinforced Concrete (IRC), which incorporates SMA wires embedded within the concrete. These wires can sense cracks and contract to heal micro-sized cracks. Also the active tuning of structural natural frequency using SMA wires to dampen vibrations is possible, as well as the usage of SMA fibers in concrete.<ref name=Song>{{Cite journal | doi = 10.1016/j.engstruct.2005.12.010| title = Applications of shape memory alloys in civil structures| journal = Engineering Structures| volume = 28| issue = 9| pages = 1266| year = 2006| last1 = Song | first1 = G.| last2 = Ma | first2 = N.| last3 = Li | first3 = H. -N. | bibcode = 2006EngSt..28.1266S}}</ref>

==== Piping ====
The first consumer commercial application  was  a [[shape-memory coupling]] for piping, e.g. oil pipe lines, for industrial applications, water pipes and similar types of piping for consumer/commercial applications.

=== Consumer electronics ===
==== Smartphone cameras ====
Several smartphone companies have released handsets with [[Image stabilization|optical image stabilisation]] (OIS) modules incorporating SMA actuators, manufactured under licence from Cambridge Mechatronics.

=== 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]].

=== Engines ===
Experimental solid state heat engines, operating from the relatively small temperature differences in cold and hot water reservoirs, have been developed since the 1970s, including the Banks Engine, developed by [[Ridgway Banks]].

=== Crafts ===
Sold in small round lengths for use in affixment-free bracelets.

=== Heating and cooling ===

German scientists at [[Saarland University]] have produced a prototype machine that transfers heat using a nickel-titanium ("nitinol") alloy wire wrapped around a rotating cylinder.  As the cylinder rotates, heat is absorbed on one side and released on the other, as the wire changes from its "superelastic" state to its unloaded state.  According to a 2019 article released by Saarland University, the efficiency by which the heat is transferred appears to be higher than that of a typical heat pump or air conditioner.<ref>{{cite web |author=Saarland University |date=March 13, 2019 |title=Research team uses artificial muscles to develop an air conditioner for the future |url=https://phys.org/news/2019-03-team-artificial-muscles-air-conditioner.html |website=phys.org }}</ref>

Almost all air conditioners and [[heat pumps]] in use today employ vapor-compression of [[refrigerants]].  Over time, some of the refrigerants used in these systems leak into the atmosphere and contribute to [[global warming]].  If the new technology, which uses no refrigerants, proves economical and practical, it might offer a significant breakthrough in the effort to reduce climate change.{{citation needed|date=December 2019}}

=== Clamping Systems ===
Shape memory alloys (SMAs), such as [[Nickel titanium|nickel-titanium (Nitinol)]], are used in clamping systems due to their unique thermo-responsive behavior.<ref>{{cite web |url=https://www.refractorymetal.org/nitinol-spring/ |title=NT0404 Nitinol Spring (Nickel Titanium) |website=Advanced Refractory Metals |access-date=Sep 7, 2024}}</ref> The clamps made from SMA are used in the dentofacial surgery to heal [[mandibular fractures]].<ref>{{cite journal |last1=Drugacz |first1=J |last2=Lekston |first2=Z |year=1995 |title=Use of TiNiCo shape-memory clamps in the surgical treatment of [[mandibular fractures]] |journal=J Oral Maxillofac Surg |volume=53 |issue=6 |pages=665-71 |doi=10.1016/0278-2391(95)90166-3 |pmid=7776049}}</ref>