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

A measurement concept has been realized for the detection of carbon dioxide, where the CO2 induced pressure generation by an enclosed pH-sensitive hydrogel is measured with a micro pressure sensor. The application of the sensor is the quantification of the partial pressure of CO2 (Pco(2)) in the stomach as diagnosis for gastrointestinal ischemia. The principle is put to the proof by examining the sensor response to changes in Pco(2). Furthermore, the response time, temperature-sensitivity and resolution are determined. The sensor responds well to changes in Pco(2) with a maximum pressure generation of 0.29x 10(5) Pa at 20 kPa CO2. The 90% response time varies between 1.5 and 4.5 minutes at 37 degrees C. The sensor shows a linear temperature-sensitivity which can easily be compensated for, and enables detection of Pco(2) changes as small as 0.5 kPa CO2.