Percutaneous transluminal angioplasty is a surgical procedure conducted on the lesions as a solution to resolve stenosis or narrowing of blood vessels. This procedure uses an inflatable balloon to expand the narrowed arteries and restore the blood flow using stent. Unfortunately, re-narrowing or restenosis is known to reoccur in long-term following this procedure. Moreover, commercial stents are unable to monitor the re-occurrence of stenosis without undergoing medical diagnosis such as angiography or intravascular ultrasound.
We present a novel shape memory alloy nitinol type active stent for non-invasive restenosis treatment, which operates using a radiofrequency (RF) electro-thermo-mechanical actuation technique for wireless revascularization. The stent is equipped with sensing capability for in-artery blood pressure measurement and can provide multiple expansion to restore the blood flow. The device design, working principle, fabrication, and characterization of the nitinol active stent are reported in this article. The wireless monitoring feature is achieved via peak shifting in the reflection coefficient of the S11 parameter. The active stent with initial diameter and resonant frequency of 2 mm and 315 MHz, respectively, is expanded uniformly in stages up to 4.2 mm in diameter when excited with an RF power of ~30 W. The active stent is delivered and deployed ex vivo inside the left coronary artery of a cervine heart. The stented cervine heart before and after wireless actuation is inspected via penetration of X-rays. Endoscopic images reveal the expansion of the stent strut profile within the lumen of the stented artery. The active stent expands in stages up to 3.7 mm in diameter to scaffold the cervine coronary artery after excited with an RF power of 46.7 W. The achievable wireless revascularization capability eradicates the necessity of reintervention and repeat stenting procedure, whereas real-time wireless monitoring provides rapid indication of in-artery re-narrowing occurrence.