A swelling hydrogel-based PCO2 sensor

This paper reports the exploration of hydrogel as sensor material for the detection of carbon dioxide (CO2). Hydrogel microspheres, which swell or shrink in response to a change in pH, were specifically prepared for this purpose and placed on a pressure sensor membrane. Subsequently, a porous metal screen was placed on top to fix the volume and position of the microspheres. The newly created sensor was placed in a sodium bicarbonate solution and CO2 was led through the solution to decrease the pH. In response, the hydrogel microspheres deswell and consequently, the measured pressure decreases. The main advantage of this sensor principle is the lack of a reference electrode as required for potentiometric sensors. (C) 2003 Elsevier Science B.V. All rights reserved.