University Honors

Shape memory alloys (SMA), such as nitinol, have great potential as smart actuationmaterials when implemented in cardiac catheters. The muscle-like flexibility of nitinol makesSMA catheters particularly useful when negotiating delicate environments such as vasculaturesand heart chambers, and the compliant nature of nitinol minimizes damage to surroundingtissues. These characteristics are an invaluable attribute for a catheter being used in proceduressuch as radiofrequency ablation. Despite such an advantage, constructing a catheter with nitinolpresents one primary challenge: creating a robust mechanism capable of bidirectional movementwith minimal rigid components. To accomplish this challenge, the catheter presented in thisreport leverages a single nitinol wire alongside elastic material to enable bidirectional steering.Nitinol's shape memory properties are harnessed by training the wire into a 3D curve, with theelastic serving as an antagonistic recovery force. The implementation of an elastic recovery forcein conjunction with nitinol wire is novel, so multiple engineering tests were conducted tovalidate the catheter's design and determine its capabilities. These tests included surfacetemperature evaluation and bend angle measurements, where the effect of different currents onthe catheter's surface temperature and range of motion were characterized. Additionally, a fatiguetest was executed where the change in the catheter's bend angle over a period of 150 cycles wasused to examine the catheter's useful life. In future works, the diameter of the catheter will befurther decreased, and the implementation of functionalities such as a working channel, microcamera, or feedback control steering system will be introduced, with the eventual goal ofproducing a functioning surgical tool.