Design optimization of a shape memory alloy–actuated robotic catheter

In this article, we present a method for optimizing the design of a shape memory alloy–actuated robotic catheter. Highly maneuverable robotic catheters have the potential to revolutionize the treatment of cardiac diseases such as atrial fibrillation. To operate effectively, the catheter must navigate within the confined spaces of the heart, motivating the need for a tight bending radius. The design process is complicated by the shape memory alloy’s hysteretic relationships between strain, stress, and temperature. This article addresses the modeling and optimization of both a single-tendon and antagonistic tendon robotic catheter using COMSOL Multiphysics Modeling and Simulation software. Several design variables that affect the actuator behavior are considered; these include the shape memory alloy tendon radius and its prestrain, the shape memory alloy tendon offset from the neutral axis of the flexible beam, the flexible beam radius and elastic modulus, and the thermal boundary condition between the shape memory alloy tendon and the beam. A genetic algorithm is used to optimize the radius of curvature of the two catheter designs. Both a single-crystal and polycrystalline models are implemented in COMSOL and are experimentally validated.