An RFID-Based Sensor for Vascular Flow Monitoring

This work demonstrates a batteryless, implantable blood-flow sensor with RFID readout. This flexible sensor system was developed specifically for surgical implantation around blood vessels, without contacting blood to improve sensor stability. An RFID data/power antenna was implemented using a split-double helix antenna (DHA) to enable surgical placement around a tubular structure in the body, e.g. a natural or synthetic blood vessel. A flexible pulsation sensor (FPS) was developed from a piezoresistive carbon black-polydimethylsiloxane (PDMS) nanocomposite, which enabled measurement of vascular distension caused by blood flow. A commercial RFID chip enabled sensor readout to an external transceiver in real time with a sample rate of 12 Hz and reading distance of 3.5 cm. DHAs with diameter of 3-8 mm were fabricated and had modest quality factors of 9 - 23. Prototype implantable DHA antennas were developed to wrap around vessels of 3 to 8 mm. Validation experiments on a vascular phantom with simulated stenosis demonstrated blood flow rate monitoring from 200 - 400 mL/min with the capacity to distinguish flow changes as low as 10 mL/min.