Submillimeter-scale Flexible Micro-catheters Driven by Shape Memory Alloys for Vascular Interventions

A novel design of an active micro-catheter, as well as its fabrication and assembly processes, for active navigation in vascular interventions is proposed in this work. A prototype of such micro-catheters consisted of a silicone rubber catheter and the guide tip or actuator developed via embedding the U-shape SMA wires into the silicone rubber base. The U-shaped part of the SMA wire was detwinned to retain the residual strain for the performance of the guide actuator, and the demolding process was optimized by using a tensile device to obtain the guide actuator, followed by in-situ characterization using the infrared camera. Moreover, a catheter feeding mechanism enabling automatic control of such micro-catheters was proposed in the work, which could provide both axial and circumferential feed motions. A micro-clamp based on piezoelectric ceramic was then introduced into the mechanism to ensure stable clamping of the micro-catheter. The performance of the guide actuators was dominated by the residual stress and shape memory effects of the biased SMA wires. As a result, a bending angle of approximately 100° was realized by the guide actuator, suggesting its great potential for active and efficient navigation in narrow blood vessels.