Use of a thermoset shape memory material in a thread-like variable stiffness device and thread-like variable stiffness device

A thread-like variable stiffness device comprising an elongate shaft, the shaft comprising a polymeric material, and a heat conducting device configured to exchange heat with the polymeric material to cause a phase transition of the polymeric material conferring a variable stiffness to the thread-like device, the polymeric material being a thermoset shape memory material, wherein the thermoset shape memory material is a mercaptoester polyurethane.