H ygieia : A Wearable Metamaterial Patch for Calibration-free Carotid Hemodynamics Monitoring

Long-term, continuous cardiac monitoring is essential for early detection and risk prediction of cardiovascular diseases. Recently, electromagnetic-based monitoring methods have gained attention because they are not affected by skin tone or contact force compared to optical or pressure-based methods. While existing systems perform well, they typically rely on professional-grade RF transceivers or require subject-specific impedance tuning based on tissue composition, leading to high cost and per-user calibration that severely limit scalability in large-scale deployments. In this paper, we present H ygieia , a wearable, calibration-free, and low-cost electromagnetic patch that supports continuous, high-accuracy hemodynamic monitoring. H ygieia introduces an air-gap cavity sensing method that converts carotid-induced skin vibrations into resonant frequency shifts, effectively decoupling the hemodynamic measurement from individual differences. In addition, H ygieia combines spectral shaping with morphology-aware feature extraction to reconstruct fine-grained hemodynamic waveforms from noise and adaptively high-accuracy estimate hemodynamic indicators across heterogeneous users. We design and fabricate the H ygieia patch and readout hardware using commodity components at low cost, and validate the system through extensive experiments with 110 participants. H ygieia achieves 96.14% waveform similarity to medical-grade equipment and mean absolute errors below 0.04 s for time-based indicators on average, demonstrating high accuracy and robustness and continuous potential for practical monitoring.