A Flexible Near-Field Biosensor for Multisite Arterial Blood Flow Detection

Area of Science:

• Biomedical Engineering
• Radio Frequency Engineering
• Wearable Technology

Background:

• Current wearable devices have limitations in conforming to variable human anatomy for accurate vital sign detection.
• Flexible radio frequency (RF) resonators offer conformable bio-interfaces for diverse anatomical locations.

Purpose of the Study:

• To develop a compact wearable RF biosensor for detecting multisite hemodynamic events via noninvasive tissue-electromagnetic field interaction.
• To assess the sensor's capability in monitoring cardiovascular health indicators at clinically significant locations.

Main Methods:

• Development of a skin patch spiral resonator and a wearable transceiver for RF biosensing.
• Utilizing strong capacitive coupling and impedance matching for sensitive detection of dielectric variations in tissues.
• Employing a direct digital synthesizer and a demodulator unit (resistive bridge, envelope detector, filter, amplifier) for signal transduction.

Main Results:

• The sensor was tested at the radial artery, thorax, carotid artery, and supraorbital locations on a healthy subject.
• The carrier frequency was tuned to the spiral resonator's resonance at 34.5 ± 1.5 MHz.
• Transient waveforms detected systolic upstroke, systolic peak, dicrotic notch, and diastolic downstroke, confirming hemodynamic event detection.

Conclusions:

• The developed wearable RF biosensor successfully detects multisite hemodynamic events noninvasively.
• This platform demonstrates potential for improved cardiovascular health monitoring through flexible, conformable sensing.