Fabrication of a flexible wireless pressure sensor for intravascular blood pressure monitoring

This work presents the development of a wireless passive pressure sensor for cardiovascular pressure monitoring. The device is designed to be inserted into a stent that can be deployed within a blood vessel using a catheter-based delivery system. By utilizing micromachining techniques, a variable capacitor and an inductor were implemented in the sensor as an L-C resonator for wireless pressure sensing and signal retrieving. The sensor employs biocompatible polymeric material, parylene-C, as the substrate material. The pressure responses of the sensor, such as the sensitivity, linearity, and hysteresis, were measured and discussed. The sensitivity was approximately 6.19 x 10(-2)/kPa (8.25 x 10(-3)/mmHg), and the linearity over the ranges of 0-6 kPa (0-50 mmHg) and 6-33 kPa (50-250 mmHg) were approximately 91.5% and 87.6%, respectively. The wireless pressure sensing performance of the sensor was evaluated using the phase-dip technique. Additionally, the measured results indicate that the resonant frequency of the resonator shifted from 211 MHz to 182 MHz, as the pressure varied from 0 to 33 kPa (250 mmHg). The maximum standard error of the mean is 0.86 MHz. Finally, the influence of coil thickness on the wireless readout performance was investigated.