An Adjustable Smart Ring to Monitor Pulse Rate and Peripheral Blood Oxygen Saturation
Martina Montenegro1, Andrea Aliverti1, Alessandra Angelucci2
1Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy.
Annals of Biomedical Engineering
|December 10, 2025
Summary
This study developed an adjustable smart ring for accurate pulse rate (PR) and blood oxygen (SpO₂) monitoring. The wearable device shows strong agreement for PR during static and dynamic activities, validating its potential for physiological tracking.
Area of Science:
- Biomedical Engineering
- Wearable Technology
- Physiological Monitoring
Background:
- Smart rings offer compact physiological monitoring but lack adjustability and validation during motion.
- Existing literature has a gap in validating wearable sensors during dynamic activities.
Purpose of the Study:
- To design, develop, and validate an adjustable, research-grade smart ring for pulse rate (PR) and peripheral blood oxygen saturation (SpO₂) monitoring.
- To assess the smart ring's performance under static and controlled-motion conditions.
Main Methods:
- A rigid-flex printed circuit board (PCB) was engineered for adaptable finger placement and sensor accuracy.
- Data was transmitted via ANT protocol for real-time mobile application visualization.
- 30 healthy volunteers participated in experiments including breathing variations and physical activity, comparing measurements to a gold-standard pulse oximeter.
Main Results:
- Strong agreement was found for pulse rate (PR) measurements in both static and dynamic conditions (r=0.91, p<0.001).
- Peripheral blood oxygen saturation (SpO₂) measurements showed a slight overestimation (mean bias=1.04%).
Conclusions:
- An adjustable, research-grade smart ring utilizing a rigid-flex PCB is feasible for finger-based PR and SpO₂ monitoring.
- The device demonstrates good agreement with clinical-grade oximeters in healthy adults during various conditions.
- The platform is designed for reusability across sizes, with future work focusing on signal processing algorithms.
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