Batch fabricated flat meandering shape memory alloy actuator for active catheter

Abstract

We have developed a new batch fabrication process of a shape memory alloy (SMA) sheet based on electrochemical pulse etching with a sacrificial dummy metal layer. The method has realized a throughout micromachining of the SMA sheet. Using the new batch fabrication process, flat meandering S-shape SMA actuators of 38 μm in thickness have been developed. The actuators whose widths were narrower than 290 μm could generate the forces over 75 mN. The batch fabrication process was also applied to a micromachining of NiTi super elastic alloy (SEA) helical coils. A small outer diameter active catheter was developed by using the flat meandering SMA actuators of 290 μm in width and the SEA helical coil of about 460 μm in outer diameter. The outer diameter of the catheter without an outer tube was 0.8 mm. A silicon rubber outer tube of 75 μm in wall thickness was put on the catheter, nevertheless, the outer diameter was smaller than 1 mm. The bending angle of the developed active catheter without the outer tube was about 50°at heating current of 60 mA. The bending angle tended to be lower after the outer tube was put on, however, the catheter with outer tube could be bent to the angle of 35°.