Development of a Smart Guidewire for Intravascular Sensing

This study presents a smart guidewire developed to measure the pressure inside blood vessels during minimally invasive surgery. The use of pressure sensor guidewires enables the medical doctor to make a judgement of the stent insertion procedure by precisely measuring coronary pressure. A pressure sensor is embedded inside the guidewire to measure the coronary lesion's vascular pressure to determine the clogging's severity. Pressure sensors inside the guidewires require high sensitivity, good linearity, and huge size reduction. The pressure sensor needs to be packaged inside a 350 µm diameter catheter. Size constraints and mechanical reliability requirements are extremely high. We describe the design and manufacture of the micro-scaled pressure sensor and the packaging process of the guidewire. To improve sensor sensitivity and reduce nonlinearity, we employed a finite element analysis to optimize the design for the membrane. The sensor fabrication process employs a cavity-first process for ultrathin sensor design. Additionally, we built a measurement system that records the sensor signal in air pressure. The results showed that the air pressure ranged up to 7.2 psi. We developed a systematic setup for assembling the ultraminiature pressure sensor inside the 800 µm guidewire. The packaging procedure includes the preparation of the electric wires, sensor placement, sensor to wire alignment, soldering, and finally, wired sensor placement inside the medical tubing.