Needle-Size Bending Actuators Based on Controlled Nitinol Curvatures and Elastic Structures

Surgical navigation of small lumens during surgery is a challenging task, requiring expert knowledge and dexterity. The challenge pertains to the manipulation of the distal tip (inside the patient) from the proximal end (outside the patient). Limitations in down-scaling tendon-based manipulation have led our group to investigate shape-memory-alloy, curvature-based actuation for small lumen navigation. We demonstrate two prototype designs with different approaches and characterize the deflection angles for use in surgical navigation. Nitinol wire was shape trained to memorize a particular curvature and assembled without using micro-fabrication techniques. By varying actuation voltage and control signal pulse width, we show controlled deflections ranging between 5 deg and 22 deg, which applies to surgical navigation. This concept improves distal control and makes the actuation of surgical actuators easier and safer. By varying voltage between 5.7 V to 6.3 V, we show the temperature generated ranging between 37 °C and 43 °C, the force generated ranging between 0.015 N and 0.021 N experimentally and 0.01 N and 0.028 N theoretically.