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Invention and innovation: An introduction
Invention and innovation: An introduction

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10.9.1 New materials

The discovery of new materials, exploration of their properties and the invention of new industrial processes is a huge field of study in its own right. The potential rewards for a company discovering a successful application of a new material are great.

An example of this is shape memory alloys (SMAs). SMAs are mixtures of metals that, after being stress treated, can be deformed significantly but then triggered to return to their original shape. Some display unusual elastic properties and immediately spring back into shape, others recover their shape when heated. Originally made from an equal combination of nickel and titanium – still the most common SMA – further experiments have led to many more SMAs combining two or more different metals. These remarkable memory properties have been applied to an increasing number of new or improved products. One of the most visible applications is in superelastic spectacles that can regain their shape after you've sat on them.

There are currently dozens of other applications, particularly in the area of medical instruments. A stent is a tiny wire mesh tube used to reinforce weak arteries or to widen arteries narrowed by coronary heart disease (Figure 36). These are delivered to the heart in a catheter on the end of a wire usually inserted into an artery in the groin. Once in place they are expanded to their full size by inflating a balloon positioned inside the stent. However stents can now be made from SMAs and are stressed into a smaller diameter. When delivered by the catheter the stent expands to its intended size due to the heat of the body.

Figure 36
Figure 36 SMA stent that expands to its intended size when subjected to body temperature. These are predicted to replace stainless steel stents expanded with a balloon (Source: Nitinol Devices & Components Inc)