Solid State Carbon Dioxide (CO2) Sensor

The technology is a solid state, Carbon Dioxide (CO2) sensor configured for sensitive detection of CO2 having a concentration within the range of about 100 Parts per Million (ppm) and 10,000 ppm in both dry conditions and high humidity conditions (e.g., > 80% relative humidity). The solid state CO2 sensor achieves detection of high concentrations of CO2 without saturation and in both dynamic flow mode and static diffusion mode conditions. The composite sensing material comprises Oxidized Multi-Walled Carbon Nanotubes (O-MWCNT) and a metal oxide, for example O-MWCNT and iron oxide (Fe2O3) nanoparticles. The composite sensing material has an inherent resistance and corresponding conductivity that is chemically modulated as the level of CO2 increases. The CO2 gas molecules absorbed into the carbon nanotube composites cause charge-transfer and changes in the conductive pathway such that the conductivity of the composite sensing material is changed. This change in conductivity provides a sensor response for the CO2 detection. The solid state CO2 sensor is well suited for automated manufacturing using robotics and software controlled operations. The solid state CO2 sensor does not utilize consumable components or materials and does not require calibration as often as conventional CO2 sensors. Since the technology can be easily integrated into existing programmable electronic systems or hardware systems, the calibration of the CO2 sensor can be automated. Detection of Carbon Dioxide (CO2) is very important for environmental, health, safety and space applications. CO2 is a harmful pollutant at higher concentrations due to its ability to displace oxygen in large concentrations. Current commercial sensors for CO2 have issues and shortcomings particular with precision at different temperatures, pressures and high humidity levels. NASA Ames has developed a novel solid state, CO2 sensor configured for sensitive detection of CO2 having a concentration within the range of about 100 Parts Per Million (ppm) and 10,000 ppm in both dry conditions and high humidity conditions. The composite sensing material comprises Oxidized Multi-Walled Carbon Nanotubes (O-MWCNT) and a metal oxide. The composite sensing material has an inherent resistance and corresponding conductivity that is chemically modulated as the level of CO2 increases. The CO2 sensor can be easily integrated into existing electronic circuitry and hardware configurations, including the hardware of a mobile computing device, such as a smart phone or tablet device.