Phase changing wire - NITINOL

Phase changing wire - NITINOL


The Background

Like many of the world’s greatest inventions, William J. Buehler along with Frederick Wang, discovered the properties of Nitinol by accident. Having established that a 1:1 alloy of nickel and titanium would be an optimum solution for a stronger and more resistant missile nose cone, he presented the prototype to colleagues. One of them applied heat to it and to everyone’s surprise the folded strips began to stretch and unfold into its previous flat shape.


The Material

Nickel titanium, also known as Nitinol, is a metal alloy of nickel and titanium, where the two elements are present in roughly equal percentages. Nitinol alloys exhibit two unique properties: shape memory and superelasticity. Shape memory is the ability that Nitinol has to be deformed and manipulated at one temperature, but then recovers its original shape when heated above its "transformation temperature". Superelasticity occurs at a narrow temperature range, just above its transformation temperature. No further heating is necessary for the shape to recover. The material exhibits enormous elasticity, some 10-30 times that of ordinary metal. Crucial to Nitinol properties are two key characteristics. First is that the transformation is "reversible" and second, that the transformation in both directions is instantaneous. Nitinol is available in various forms including wires, tubes, sheets and springs. 



The Advantage

Unlike plastics, metals, and traditional alloys, shape-memory alloys like Nitinol are strong and flexible, easy to sterilize, and corrosion-resistant too. Being lightweight, tough, and capable of operating at high temperatures, they're widely used in aerospace components. Its properties have also been applied in interactive product design as well as to create smart, heat reactive facades.


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