FuSenseRing: An Open-Source Platform for Robust Cuffless Blood Pressure Monitoring via Multimodal Sensor Fusion and Temperature-Adaptive Attention

Reliable, frequent blood pressure (BP) monitoring outside clinical settings is crucial for cardiovascular health management, yet current wearable solutions often fail to deliver clinically accurate measurements in real-world conditions. A key limitation stems from the common reliance, particularly in convenient ring form factors, on photoplethysmography (PPG) sensing alone. PPG signals acquired from the finger are highly susceptible to physiological and environmental noise; notably, finger skin temperature fluctuations induce errors exceeding 10 mmHg due to vascular changes, while sensor-skin contact pressure further distorts the signal. This inherent sensitivity of PPG, when uncompensated, prevents many devices from consistently meeting clinical accuracy standards. We introduce FuSenseRing , an open-source smart ring engineered to overcome these issues through synergistic hardware-software co-design. FuSenseRing integrates a multimodal sensor suite (PPG, ECG, skin temperature, contact force) on a custom flexible PCB within a low-cost form factor, approximately $94.9 per unit at retail (batch of 5) and approximately $28.72 per unit at wholesale (batch of 500), while remaining lightweight (4.6 g) to ensure optimal signal acquisition during BP measurements. Our core algorithmic innovation is a Temperature-Adaptive Attention (TAA) mechanism that dynamically fuses PPG/ECG features and recalibrates their contributions using real-time temperature context to specifically mitigate thermal drift. Efficient personalization via transfer learning requires only 5-10 normal-temperature calibration samples. Through rigorous evaluations involving total 60 participants across diverse laboratory-controlled temperatures (17 °C to 40 °C skin temp) and challenging real-world ambulatory conditions (-10 °C to 24.4 °C ambient temp), we demonstrate FuSenseRing's effectiveness. Our system maintains high accuracy across the full temperature range (Overall SBP/DBP ME±STD: -0.09 ± 7.67 / 0.42 ± 5.74 mmHg), satisfying the stringent accuracy criteria of the FDA-recognized AAMI/ISO 81060-2 standard. Furthermore, FuSenseRing significantly outperformed three popular commercial BP rings in the real-world study.