Development of respiratory monitoring and actions recognition based on a pressure sensor with multi-arch structures

In this paper, a method of greatly improving the voltage or charge output of the pressure sensor fabricated by polyvinylidene fluoride (PVDF) film through making the film into a multi-arch structure is presented, and is also introduced into wearable medical monitoring system together with other technologies, such as flexible printed circuit (FPC). Results of analysis and experiments revealed that the curvature (k) of the sensor's structure was one of the main factors influencing the voltage output performance of PVDF piezoelectric film. The proposed multi-arch-structure pressure sensor (MASP sensor) with a radius of 5 mm (the curature is 200 m(-1)) increased the detection signal amplitude of the measurements by 141% compared with the counterpart of planar type, and it had the highest signal-noise ratio (SNR) among the three manufactured sensors with the radii of 5 mm, 2 mm, 0 mm, respectively. What's more, we optimized the target sensor by combining the physiological characteristics of human respiration and design standards of wearable devices, and then fabricated it into a flexible belt. With the help of belt monitoring system, the characteristics and frequency ranges of human actions during sleep including turning around, coughing, and speaking were recognized before sleep monitoring. In addition, multiple sets of experiments involved multiple subjects showed that the belt respiratory monitoring system could obtain the wearers' respiratory signals conveniently and real-time in various occasions including sleeping, working (sitting for paperwork) and post-exercise (standing up). The proposed wearable belt system for respiration provides the possibility of implementation for remote diagnoses and home care treatments of some certain respiratory diseases. (C) 2019 Elsevier B.V. All rights reserved.