Low Power Consumption CO2 Gas Sensor Using Ionic Liquid

Tuesday, May 13, 2014
Grand Foyer, Lobby Level (Hilton Orlando Bonnet Creek)
M. Honda (NMEMS Technology Research Organization), T. Itoh, and R. Maeda (National Institute of Advanced Industrial Science and Technology)
Recently, various gas sensors are investigated. Specially, CO2 gas sensor is worthy of the notice, because monitoring of CO2 gas concentration is important for energy-saving. For example CO2 gas concentration is required for 1000 ppm or less in space, such as office buildings, a building management method, a production plant, and an IT-related server room. An exhaust gas periodically compulsory in order to make the present condition and CO2 gas concentration below into a steady value. By minimizing the displacement volume of the air which is carrying out air-conditioning management using CO2 sensor, an air-conditioning system carries out efficient operation, and it aims at development of CO2 sensor corresponding to the low consumption power high integration interlocked with a sensor network system efficiently. However the conventional CO2 gas sensors have the following problems, 1) large power consumption, 2) large size and 3) long detection time. These problems are mainly caused by usage of a light source and heater. We are interested in the ionic liquids because the ionic liquids are 1) the conductivity is high at room temperature, 2) thermal and chemical property is high stable, 3) volatility is high and 4) adsorb polarity molecule gases as like CO2, NH3, SO2, and NO2. Therefore we develop CO2 sensor which converted CO2 concentration into ionic liquid which adsorbed CO2 specifically by impedance. Our sensor feature is that it isn't used light source and heater, it is used ionic response. It compares with conventional CO2 sensor, 1) low consumption power, 2) miniaturization, 3) high-speed response and 4) low consumption CO2 gas sensor using ionic liquids. We use ionic liquids of imidazolium salts, EMIMBF4, EMIMTFSI and DEMEBF4. The impedance of ionic liquids decreases along with increase of CO2 gas concentration. By measuring the impedance of ionic liquids, we can estimate CO2 gas concentration of the atmosphere. From the experiment, measurement resolution of CO2 gas concentration was 100 ppm. The power consumption of our proposed CO2 gas sensor is several tens of microwatts, and this value is 1/1000 smaller compared with conventional CO2 gas sensors (NDIR and Solid state electrolyte cell).