A universal respiration sensing platform utilizing surface water condensation

Abstract

Respiration is one of the most vital physiological activities of the human body. Abnormalities in the respiratory rates and patterns can ascertain the condition of the human body, such as sleeping, exercising, anaerobic threshold during athletic activity, etc. However, current respiratory sensor materials are often complicated in system and cumbersome in technology. This paper proposes a simple model breathing sensor preparation scheme that only requires electrodes to be attached to common insulating materials used in daily life. The basic working principle is: (a) conductive layer formation (the conductivity of hydrogen bonding induced water layer is mainly due to the proton transition), (b) signal acquisition and (c) health-status-feedback. The effects of the chemical and physical properties of different insulating materials on the respiratory detection caused by surface water condensation were studied for the first time. The different response mechanisms of several types of materials were studied in detail, and the selection criteria for sensing materials were given, which has great reference value for further research and industrial production. Considering the requirements of comfort, long-term hygiene (antibacterial) and excellent performance, etc., a complete human respiratory monitoring system specifically based on nitrile rubber films (NRFs) as wearable respiration sensors is constructed. This sensor achieved a good balance of several parameters. The signal changes by 3 orders of magnitude in cycles of inhalation and exhalation maximally. This universal patterning design scheme for respiratory sensors will be a significant reference for application and industrialization, and will have a profound impact on further fundamental research.