In our experience the 0.5mm diameter nitinol offers the best in terms of ease of manipulation
The properties of Nitinol (pronounced "night-in-all") were discovered by William J. Buehler and Frederick Wang at the Naval Ordinance Laboratory in 1959. Its name is derived from its composition of nickel and titanium, as well as its place of discover at the Naval Ordinance Laboratory. At the time, Beuhler was trying to create a better nose cone for missiles, and during a presentation the folded up piece of nitinol came into contact with a lighter. Much to the surprise of everyone in attendance, the material retook its previous shape.
The nitinol alloy exhibits two unique, related properties: shape memory, and superelasticity. With its shape memory, nitinol is capable of undergoing deformation at one temperature, and when exposed to a heat supply above its transformation temperature, it will recover is original, undeformed shape. Its superelasticity occurs in a narrow temperature range just above the transformation temperature, wherein it exhibits enormous elastic capacity, in the range of 10-30x that of ordinary metal.
It is an excellent demonstration and teaching tool for both physics and chemistry classes, as it can be used as an educational aid for shape memory, superelasticity, and states of matter. In addition to its educational uses, it is prominently featured in several real-world applications. Examples include items such as the self-bending spoon, inserts in golf clubs, and in glasses frames, mechanical watch springs, ect.