Investigating the Feasibility of Focused Ultrasound Actuation of Shape Memory Alloy

Abstract Nitinol, a shape memory alloy, has shown immense promise and utility in biomedical engineering with its remarkable biocompatibility and corrosion resistance. Most biomedical applications rely on Nitinol’s superelasticity rather than its hysteretic properties, otherwise known as its shape memory. The aim of this research is to determine if local heating from focused ultrasound could be used to induce the shape memory effect of Nitinol safely and non-invasively for biomedical applications deep within the body. Specifically, Nitinol’s shape memory properties and focused ultrasound’s precise and localized heating in deep tissues could be utilized for non-invasive actuation and slow deployment of stents in the treatment of peripheral artery disease, which affects approximately 21 million Americans today. This approach could reduce the risk of in-stent restenosis, a consequence of injury to arterial walls caused by the traditionally rapid deployment of stents. The current study investigates whether focused ultrasound can actuate a tight coil of Nitinol (representing a simple stent) under experimental conditions that mimic in vivo conditions. Results demonstrate that focused ultrasound-induced actuation of Nitinol stents in deep vessels under physiological conditions is a possibility. Precise positioning and control of the stent and ultrasound transducer will be necessary to achieve stent actuation at power levels that prevent thermal damage to surrounding healthy tissues.