Micromachined shape memory alloy active stent with wireless monitoring and re-expansion features

Abstract

This paper reports a novel shape memory alloy (SMA) active stent for non-invasive restenosis treatment which operates using radiofrequency (RF) wireless electro-thermo-mechanical actuation technique for re-expansion. The developed stent is equipped with capacitive pressure sensor for in-artery blood pressure measurement and is able to provide multiple expansion to restore the blood pressure flow. The device design, working principle, fabrication and characterization of the SMA active stent are reported in this work. The wireless monitoring feature is achieved via peak shifting in return loss of S 11 parameter. An SMA stent with initial diameter and resonant frequency of 2 mm and 315 MHz is expanded uniformly in stages up to 4.2 mm diameter when excited with RF power of ~30 W for 320 s. The achievable re-expansion capability eradicates the necessity of revascularization and repeat stenting procedure whereas real-time wireless monitoring provides rapid indication of in-artery re-narrowing occurrence.