Highly Penetrative Chest-Worn Metasurface for Multi-Angle RADAR-Based Vital Sign Monitoring.

This paper presents a novel chest-worn, highly penetrative reflectionless metasurface designed to significantly enhance radar-based vital sign monitoring by addressing key challenges in electromagnetic (EM) wave transmission through biological tissues. Operating at 60 GHz, the metasurface achieves excellent penetration across different body compositions and orientations. Unlike prior works, this study emphasizes practical applicability by integrating the metasurface into a wearable form factor and validating performance using realistic human tissue models and multi-angle configurations. The radar system demonstrates exceptional accuracy in heart rate monitoring, with measurements closely aligning with electrocardiogram (ECG) benchmarks (bias < 0.01 Hz), even under challenging conditions. This wearable metasurface bridges the gap between laboratory designs and real-world applications, offering a robust, non-invasive solution for continuous health monitoring. These findings highlight the potential of reflectionless metasurfaces to transform wearable biomedical technologies by enabling precise and reliable monitoring in dynamic, real-life scenarios.