A Wearable Chest Band Based on a 3-D-Printed FBG Sensor for Cardiorespiratory Monitoring

Continuous monitoring of respiratory rate (RR) and heart rate (HR) is essential for the early detection and management of critical cardiorespiratory conditions. Deviations from normal RR and HR values can indicate the onset of acute respiratory or cardiac failure. However, conventional clinical approaches, such as electrocardiography (ECG) and impedance pneumography, are typically limited to controlled environments and short timeframes, potentially overlooking transient pathological events. Wearable systems represent a promising solution to enable long-term and unobtrusive monitoring of vital signs. Among emerging technologies, fiber Bragg gratings (FBGs) have gained attention for their compactness, excellent metrological properties, biocompatibility, and immunity to electromagnetic interference. When combined with 3-D printing, FBGs can be integrated into highly customizable, skin-conformal devices suitable for wearable applications. This study presents a wearable chest band (WCB) incorporating a single FBG embedded in a 3-D-printed thermoplastic polyurethane (TPU) matrix. A custom-designed adjustment system and fiber protection box were developed to improve wearability, usability, and durability. Seven healthy volunteers participated in a protocol involving different postures (i.e., standing, sitting, and supine) and breathing conditions (i.e., normal and fast). The system showed high accuracy in RR detection across all conditions, and reliable HR estimation, demonstrating its potential as a wearable tool for continuous cardiorespiratory monitoring.