We propose to develop a stable, low-cost, low power CO2 sensor module that meets the requirements of the ARPA-E SENSORS FOA, namely, 30 ppm precision over a dynamic range of 400 ppm to 2000 ppm with 10 ppm drift per year. Existing optical non-dispersive infrared (NDIR) CO2 sensors simply cannot scale to the cost and power requirements of the FOA. We therefore propose a solid state architecture that leverages scalable semiconductor manufacturing processes. This approach will easily meet, and in fact surpass the size, cost and power requirements described in the FOA. The trick to developing any solid state gas sensor is to come up with a receptor material. This material must be designed to selectively absorb the molecule of interest (CO2), desorb the molecule when the concentration decreases, and respond relatively quickly (10s). Our secret sauce for such a receptor material is a new class of porous, crystalline materials known as metal-organic frameworks (MOFs). MOFs are a transformative class of materials with unparalleled gas uptake properties, uptake selectivity, and high stability. Our sensor architecture is a MEMS resonant mass transducer that we coat with a MOF thin film. As the MOF absorbs and desorbs CO2, the transducer detects the change in mass. We expect our sensor to scale to $5 price, 50 mJoules/measurement (can be battery operated), 5 year lifetime, self-calibrating, and 10 ppm/year drift. We propose to develop a solid state CO2 sensor using advanced porous materials, metal-organic frameworks (MOFs), as the receptor material. We will design a MOF structure that selectively absorbs and desorbs CO2. The material will be applied to a MEMS resonant mass transducer in the form of a thin film coating. The CO2 loading of the material, which varies with CO2 partial pressure (i.e., concentration), will lead to a signal reported by the sensor.
