In the early days of TiNi SMA good material such as fine-gage wire was not available, and this impeded work for many researchers. At the present time there is available not only excellent material but how-to instructions enabling the unfamiliar user to build successful prototypes. There are several toys and novelties. A Monarch butterfly, shown in Figure 3, moves its wings gracefully in response to pulses of electricity. TiNi actuated butterfly.
Several designs exist for steerable catheters used in medicine.
Braille and tactile devices have been developed. The resistivity of TiNi is approximately 80 microhm cm, and is suitable for Joule heating which provides a simple means of actuation. However, for macroscopic devices this is generally impractical for two reasons. Thermodynamic efficiency is low because of the small temperature difference in which the transition takes place, and removal of heat is slow. SMA wire has not replaced electric motors for many applications.