Development of the Forward-Looking Active Micro-Catheter Actuated by Ti-Ni Shape Memory Alloy Springs

This paper describes fabrication, characterization, and demonstration of a novel active micro-catheter with Ti-Ni shape memory alloy (SMA) actuators for wide range of forward-looking area to remedy diseased area inside a blood vessel. The developed active micro-catheter consists of eight Ti-Ni SMA spring actuators for catheter actuation, an ultrasonic piezoelectric transducer for forward-looking, a guide wire, a polyurethane tube for catheter coating, and spiral wirings for various flexure motions of catheter by Ti-Ni SMA actuators. The size of the catheter is 3.5 mm in diameter and 60 mm in length of the sum of transducer and actuator sections. Ti-Ni SMA springs were fabricated from a Ti-50at.% Ni sheet by electrochemical etching with a mixed solution of ethanol and lithium chloride. The micro-catheter was assembled by hand under a stereomicroscope. The tip of the produced micro-catheter was able to bend toward at least eight directions by controlling an applied current to Ti-Ni SMA springs. We have demonstrated the effectiveness of the active micro-catheter by carrying out experiments on blood vessels in a small animal.