Fig. 3.
Force–strain characteristics of the material (15 V, 1 A). a 30 following cycles of loading to 60 N (blocked force; cylindrical specimen; diameter 15.1 mm, length 40 mm; weight 6 g). b Detailed view of three cycles in a. c Blocked force at various elongations for constrained cylindrical actuation; error bar relates to s.d. Specimen diameter 11.1 mm, length 25 mm; weight 2 g. Note that the actuation depends on heating and cooling rates