Blood Flow Detection Using Piezoelectric Sensors

This study introduces an innovative method for noninvasively monitoring blood flow, utilizing piezoelectric materials. These materials generate electric fields under mechanical stress, making them ideal for sensing. This study presents a novel method for estimating the radius of blood vessels using two identical piezoelectric sensors. The approach leverages the relationship between the output voltage of piezoelectric sensors and the mechanical stress induced by blood flow within vessels. A mathematical model is developed to correlate blood viscosity, velocity, and vessel radius with sensor output signals. Key steps in the method include calculating time delays between signals, determining flow velocity, and estimating vessel radius by rearranging relevant equations. The system demonstrated consistent sensor performance across multiple measurements on human arms and legs. The maximum output voltage recorded was 50 mV (peak-to-peak), corresponding to a stress-induced hysteresis change of 0.6 nC/cm2. Time delay measurements ( $\Delta {t}$ ) between sensors were 0.035 s for the arm and 0.069 s for the leg, with corresponding blood velocities of 0.113 and 0.115 m/s, respectively. Blood flow rates were estimated at 3.63 L/min in the arm and 0.070 L/min in the leg, with a significant reduction in flow observed when external pressure was applied, simulating clot formation. Additionally, pulse wave velocity (PWV) was measured and found to align with conventional Doppler-based measurements. The proposed method shows promise for noninvasive blood vessel monitoring, with potential applications in detecting vascular obstructions such as clots.