A surgical instrument has a tip section with several degrees of freedom of articulation and at least one link that may be too long for insertion through an entry guide that follows a curved path. Each long link is made of a shape memory alloy or another material having a state in which the link is sufficiently flexible to bend as needed to pass through the entry guide. Once through the entry guide, the material of the link makes a transition to a state in which the link returns to a desired shape and is sufficiently rigid for precise controlled movement against external forces and for actuation using tendons.
