An Implantable, Stretchable Microflow Sensor Integrated with a Thin-Film Nitinol Stent

Recent advances for the treatment of a cerebral aneurysm include a neurovascular flow diverter which can cover the entire length of the aneurysm inside the vessel. The flow diverter reduces blood flow that enters the aneurysmal sac without any adverse effects on the normal directional flow in the vessel. However, existing neurovascular flow diverters show a lengthy curing rate of the sac, which requires follow-up monitoring using invasive, expensive angiograms or MRIs. Here, we introduce a stretchable microflow sensor package that is integrated with a microstructured thin-film nitinol (TFN) stent for a 'smart' flow diverter to monitor cerebral aneurysm hemodynamics over the course of treatment. The stretchable sensors are made of a set of biocompatible materials including gold nanomembrane and polyimide, together encapsulated with a silicone elastomer for electrically safe, long-term implementation. Computational and experimental studies establish the fundamental aspects of the bending and stretching mechanics of the TFN flow diverter (with negligible strain up to 500 percent in radial stretching and up to 180 degrees in bending). We develop a capacitive microflow sensor and demonstrate the functionality via in vitro study using an aneurysm model for monitoring of a blood flow. The detection sensitivity of the sensor shows 0.04 m/s of flow rate, which is capable of measuring the mean velocity flow at the neck region of the aneurysm.