A New Low-Power MEMS Sensor for Atmospheric CO2 Measurements

75232S Low power, low cost carbon dioxide (CO2) sensors are needed to monitor the global carbon cycle, in particular for the exchange of carbon from man-made and natural sources. The sensors must be small and lightweight in order to be compatible with flight in balloonsondes. This project will develop prototype sensor systems with MEMS (microelectromechanical systems) microcapacitor sensor arrays that can monitor atmospheric CO2 concentrations with 1 ppm sensitivity. The measurement will be accomplished by filling the sensors with chemoselective sol-gels whose electric permittivity changes when exposed to CO2. The sensor systems will be battery operated, portable, and remotely operated, and will be able to compensate for changes in humidity, temperature, and pressure. In Phase I, MEMS capacitor sensors were demonstrated to have the necessary sensitivity (1ppm) to CO2 in a background of high humidity. Detection of CO2 ¿ from 0 to 500 ppm, in ambient temperatures ranging from +40 C to -10 C, and in humidity ranges from 0to 80% ¿ was demonstrated. In Phase II, a manufacturable process will be developed for the sol-gel technology. Software algorithms will be developed to mitigate interference form other gases and from humidity effects. Prototype systems will be built and tested. Commercial Applications and Other Benefits as described by the awardee: In addition to their application for atmospheric monitoring, these lightweight, low cost, low power CO2 monitors should find applications in HVAC monitoring, industrial process control, and industrial health and safety.