Nitinol is a shape memory alloy that demonstrates ideal characteristics suitable for the Biomedical Engineering Field. The rise in popularity of Nitinol has opened exploration in research for its use in medical procedures. This research will focus mainly on the use of focused and unfocused ultrasound waves commonly used in medical applications in junction with nitinol wire to noninvasively insert inside the human body and heat the wire above the activation energy threshold without causing any damage to the surrounding human tissue.
The qualities that Nitinol exhibits are ideal because of its biocompatibility, corrosion resistance, and "shape memory" properties. The challenge that arises while using Nitinol wire has been heating the wire above 46.0 degrees Celsius without causing damage to surrounding human tissue. By incorporating MRgFUS (Magnetic Resonance-guided focused ultrasound surgery) to precisely and noninvasively heat the alloy to above its memory temperature threshold. To show the memory effect of the wire, first it must be strained at room temperature (25 degrees Celsius), wrapped tightly around a rod in a coil shape in order to be inserted into a ballistic gelatin that mimics human tissue. Using the focused ultrasound transducer (with frequencies from 500 kHz to 1.8 MHz) the wire is heated inside of the ballistic gelatin recipient until it returns to its conditioned shape memory state. Thermocouples will measure the temperature of the gelatin to verify that it is within safe temperatures for human tissue. The experiment will run multiple lengths and diameters of Nitinol wire ranging from 1.0mm to 3.0mm for diameter that have activation temperatures between 30-50 degrees Celsius. Additional data will be collected using a commercially available, non-focused ultrasound transducer (frequency range= 1.3 MHz) which generates a more diffused heat region.