Optimization and characterization of a 3D-printed wearable strain sensor for respiration and heartbeat measurements

Recently, the healthcare scenario recognized the advantages of embedding fiber Bragg gratings (FBGs) into 3D-printed structures for biomedical purposes. Material extrusion is considered a next-generation method to develop sensors based on FBG with exciting characteristics (e.g., low cost, lightweight, and fast prototyping with customized designs). The aim of this study is to combine the FBG and material extrusion benefits for proposing a novel sensor for strain sensing application in respiration and heartbeat measurements from chest wall deformations. A finite-element analysis guided the sensor design to maximize the strain localization in the sensor area. The bonding at the fiber - encapsulation material interface was discussed by analyzing the spectral response and microstructural imaging. The sensor response was investigated by applying mechanical and thermal inputs. Finally, the skin-mountable system was used in a pilot test for estimating respiratory and heart rates, showing promising results in human physiological monitoring.