Low-cost plastic optical fiber integrated with smartphone for human physiological monitoring

Human physiological signal monitoring is a key factor in diagnosing health conditions, such as monitoring heart rate and respiration. To meet the increasing monitoring requirements, such as safety, economy, and equipment miniaturization, it is necessary to optimize and improve the monitoring device. Polymer optical fiber sensor has great potential in human physiological monitoring because of their inherent safety, compactness, electrical isolation, and flexibility. In this paper, we report the integration of low-cost plastic optical fibers in smartphones for the measurement of respiratory rate and heart rate in human physiological monitoring. The performance of the plastic optical fiber (POF) sensor with different sensitivity zone is analyzed. With three sensitivity zones, the respiratory rate and heart rate can be displayed in the power spectral density simultaneously. For improving the POF sensor performance, the shutter speed of the smartphone is also optimized to 30 s−1. Finally, the POF sensor is tested under different motion states indicate that the sensor can monitor the heart rate and breathing rate under different postures (running, walking, standing, squatting and lying), where the spectral energy is 2.8 ± 0.11 × 108 pt during running and is 1.4 ± 0.55 × 107 pt in the supine state. And it also can be used to assess the dynamic posture, which is important for some potential sensory applications in clinical and home settings.