A miniaturized amperometric electro-chemical (solid electrolyte) carbon dioxide (CO2) sensor using a novel and robust sensor design has been developed and demonstrated. Semiconductor microfabrication techniques were used in the sensor fabrication, and the sensor is fabricated for robust operation in a range of environments. The sensing area is 1.0 × 1.1 mm. The sensor is operated by applying voltage across the electrodes and measuring the resultant current flow at temperatures from 450 to 600 °C. Linear responses were achieved to the CO2 concentrations from 1% to 4%, and to the natural logrithmic concentrations of the CO2 from 0.02% to 1%. This CO2 sensor has the advantage of being simple to batch-fabricate, small in size, low in power consumption, easy to use, and fast with response time.
The fabrication of carbon dioxide sensors includes three steps: (1) deposition of platinum interdigitated finger electrodes on alumina substrates, (2) deposition of solid electrolyte called NASICON (Na3Zr2Si2PO12) in between the finger electrodes, and (3) deposition of auxiliary electrolyte sodium carbonate and barium carbonate (Na2CO3/BaCO3,1:1.7 in molar ratio) on top of the electrodes.
The resulting miniature CO2 sensor can be integrated into a sensor array with other sensors and electronics, power, and telemetry on a stamp-sized package. Like a postage stamp, the complete system (“lick-and-stick” technology) could be placed at a number of locations, including some hidden areas, to give a full-field understanding of what is occurring in an environment.