A multi-segmented shape memory alloy-based actuator system for endoscopic applications26 Sep 2019 00:00
This paper describes the design, fabrication and testing of a shape memory alloy based actuator system to provide three degrees of freedom bending with high flexibility and repeated use capability without any performance loss for minimally invasive surgery. The flexibility, long-term endurance and thermal characteristics of this system were studied. The system consisted of 3 segments, front, middle and back. Thermal simulations showed an increase in temperature of 1–2 °C at the segment nearest to the activated segment and a temperature increase of 1 °C at the segment furthest from the activated segment. Transformation strain simulations showed that the 8 mm width design has the lowest strain (2%). The average maximum bending angle was above 30° across most actuator segments but a reformation angle of only 50% of the maximum angle. The endurance test showed that all actuators can operate for 7000 actuation cycles with a standard deviation of 0.6154, 0.8293 and 0.0364 mm for sections A, B and C, respectively. The system was capable of high angle of bending across all segments and capable of continuous long-term use with little performance deviation. The system will allow surgeons to have more flexibility during surgery and thus enable reaching difficult regions in minimally invasive surgery.
Actuators for minimally invasive surgery (MIS) have gone through several developments to solve some of the fundamental problems in performing MIS procedures. These problems include low flexibility and the accuracy needed to navigate through the internal passages of the human body. This is due to the nature of MIS, which is done through a small incision in the patient and causes the surgeon to lose three-dimensional visual feedback and disturbs the surgeon's eye-hand coordination. To address these problems, we propose the usage of the super-elastic backbone in combination with the shape memory alloy actuators in order to better facilitate the bending of the instrument as the super-elastic backbone would provide ample stiffness to push the instrument back to its original shape but would still allow for the bending of the instrument.