A Wearable Doppler Ultrasound Patch for Continuous Blood Flow Monitoring

With the acceleration of the modern social pace and the evolution of lifestyles, cardiovascular diseases have become a major global health threat. Continuous blood flow monitoring is crucial for the diagnosis and prevention of cardiovascular diseases. However, commercially available Doppler ultrasound probes are limited by their rigid design, large size, and the need for manual operation and calibration, making them unsuitable for daily use. To address these limitations, this study proposes a wearable Doppler ultrasound patch for continuous blood flow monitoring. The patch integrates six three-layer ultrasonic transducer elements with a center frequency of 5 MHz and vertical interconnect channels. Its innovation lies in the preparation of an Ecoflex flexible substrate through 3D printing molds, providing a 30° inclined installation surface for the transducers, and the use of laser-cut serpentine electrodes and packaging technology to ensure the overall flexibility and durability of the device. To verify its performance, we built an in vitro flow field experimental platform and measured constant and pulsatile flow fields using the pulsed-wave Doppler mode. The results show that the fabricated transducer has a resonant frequency of 4.85 MHz, a pulse-echo response center frequency of 5.05 MHz, and a -6 dB bandwidth of 42.58%, which can accurately measure constant and variable flow fluids, demonstrating its excellent measurement accuracy and stability.