Towards Clinically-Relevant Shape Memory Alloy Actuated Active Steerable Needle

Abstract

Abstract The targeting error with surgical needles in percutaneous procedures is the major factor that undermines their efficacy. The limitations in trajectory correction to reduce this error during the insertion have motivated researchers to develop actuation mechanisms in needles. The study of shape memory alloy (SMA) wire actuators in needles has gathered significant interest in the past decade because of high strain density, shape memory effect and biocompatibility. An active steerable needle design with an active stylet and a compliant collet is presented. The stylet tip bends by actuating the SMA wire installed on the bending region of the stylet. The bending region is composed of polytetrafluoroethylene (PTFE) polymer attached to the machined portion of the stylet. PTFE has low stiffness and high thermal and electrical insulation that are suitable for active needle applications. The finite element analysis of the actuation of a 3.25 mm diameter active needle model showed 18% greater tip deflection in the air compared to the prototype. By improving the SMA attachment region in the prototype, increased tip deflection as well as reduced needle diameter of 2 mm (14 gauge), which is a medically applicable scale, could be achieved.