Shape memory alloys (SMAs) are able to remember and recover their original shape after undergoing significant physical deformation. The "training" that forms part of their formation dictates the exact shape that the alloy will "remember" and return to once heated. It’s quite magical to watch a paper clip reform itself. Watch HERE.
The concept of shape memory alloys can be traced back to the 1930s when Swedish chemist Arne Ölander observed unusual properties in certain gold-cadmium alloys. However, it was not until the 1960s that significant advancements were made in this field, when researchers at the United States Naval Ordnance Laboratory, including William J. Buehler, Frederick Wang, and Bernard S. Needleman discovered the unique shape memory effect in nickel-titanium (Ni-Ti) alloys aka “nitinol”, a word derived from its composition and its place of discovery: Nickel Titanium-Naval Ordnance Laboratory.
The discovery that nitinol objects could undergo significant deformation and return to their original shape upon heating has led to various applications across multiple industries, ranging from aerospace and automotive to biomedical and consumer electronics, e.g. SMAs are extensively used in orthodontics, where they are employed in dental braces to apply constant, gentle force to reposition teeth. They are also used in stents for treating blocked arteries (set to reform at body temperature), as well as in various surgical tools and implants.
SMA applications are many and varied. You can use heat applied to a coil to mechanically lift weight, and even use temperature differentials along with wires or springs to power motors.
The applications for interplanetary travel are especially interesting, e.g. the NASA Glenn Research Center in Cleveland has developed a new tire for future Mars rovers. It is made of a mesh of wires of Nitinol, allowing the tire to return to its original shape after undergoing deformation by the uneven Martian surface.
Yet another reinvention of the wheel.
Story Idea: Remo Giuffré
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References
wikipedia.org/wiki/Shape-memory_alloy
wikipedia.org/wiki/Nickel_titanium
Images
1. Nitinol
2. Video: WTF Paperclip!? by Andy Elliott Craft & Creations
3. William James Buehler (1923–2014)
4. Paper clip: before and after
5. Nitinol stent
6. Heated coil lifts the weight
7. Nitinol mesh wire tire for future Mars rovers
8. Video: How a metal with a memory will shape our future on Mars, Verge Science
