Pneumatic Soft Arm Based on Spiral Balloon Weaving and Shape Memory Polymer Backbone

Abstract

This paper presents a novel design of soft arm with triplet spiral balloons weaving and a shape memory polymer (SMP) backbone mechanism, which enables dexterous actuation and an additional variable stiffness function. The soft arm is aimed for assisting minimally invasive surgery (MIS). The triplet spiral balloons, which are actuated by pressure air, are woven helically around the SMP backbone, covered by a rubber sheath. This structure gives the soft arm a wide range of actuation, which allows it to reach the target without damaging surrounding tissues blocking its way. The SMP backbone, whose stiffness changes with the temperature, gives the arm the ability of shape holding. Temperature control of the SMP backbone is realized by the electric wire and cooling channels. A prototype is manufactured and a set of experiments is conducted with the aim of assessing the performance of variable stiffness and actuation. The effects of different loads and pressures on trajectory of the arm are evaluated together with the force-deflection curves. The prototype has also been validated with abdominal phantom, demonstrating the potential clinical value of the system.