Towards a Nitinol Actuator for an Active Surgical Needle

Surgical needles, for safe and accurate percutaneaous interventions, need to be navigated accurately through the tissue and placed precisely at the targets. A novel active needle, using Nitinol wires as actuators, has been proposed to navigate the needle within the tissue. In this design, when temperature of Nitinol wire was increased by Joule heating, the material undergoes a phase transformation that produces relatively large actuating forces and strains. Using both experimental and numerical simulations, the force-temperature response of the Nitinol wires were characterized. The results indicate that increasing the applied current decreases the response time to reach maximum force, but increases the maximum temperature reached. Therefore, the chosen applied current should be high enough to produce sufficient actuation force and shorter response time, but not too high such that the lower actuator temperatures are maintained to minimize tissue damage.