A miniaturized carbon dioxide gas sensor based on sensing of pH-sensitive hydrogel swelling with a pressure sensor. Biomedical microdevices

Abstract. A measurement concept has been realized for the detec-tion of carbon dioxide, where the CO2 induced pressure generation by an enclosed pH-sensitive hydrogel is measured with a micro pres-sure sensor. The application of the sensor is the quantification of the partial pressure of CO2 (Pco2) in the stomach as diagnosis for gas-trointestinal ischemia. The principle is put to the proof by examining the sensor response to changes in Pco2. Furthermore, the response time, temperature-sensitivity and resolution are determined. The sensor responds well to changes in Pco2 with a maximum pressure generation of 0.29 × 105 Pa at 20 kPa CO2. The 90 % response time varies between 1.5 and 4.5 minutes at 37◦C. The sensor shows a linear temperature-sensitivity which can easily be compensated for, and enables detection of Pco2 changes as small as 0.5 kPa CO2