Long Term Monitoring of Respiration and CO2 using Flexible Printed Sensors

Long term unobtrusive monitoring of respiration and environmental conditions is critical for tracking the health and psychophysiological state of astronauts. Wearable, flexible sensors provide increased comfort and improved human factors. Recent advances in additive manufacturing, such as printed electronics, allow miniaturization of sensors and implementation onto flexible, unobtrusive substrates. We developed a low power, flexible, sensor platform with wireless Bluetooth Low Energy (BLE) interface. The platform integrates 9 Degrees of Freedom (DOF) inertial sensor, ambient sensor (temperature, humidity, and Carbon Dioxide/Volatile Organic Compounds - CO2/VOC sensor), and prototyping area for printed sensors. In this paper we present an implementation of a printed co-doped barium titanate capacitive sensor that is highly sensitive to water vapor as an unobtrusive breathing sensor. The 2×4mm sensor is highly sensitive to changes during breathing, even at distances of more than 20cm. Synergy of information from on-platform and printed sensors allows long term user monitoring both as wearable and ambient sensor. We demonstrate the results of sensor validation using 9 subjects. Average change of capacitance of the sensor during breathing at the distance of 7.5 cm was 6.2±3.5 pF. Our sensors represent very good option for low-power, wearable, and unobtrusive monitoring.