An integrated module for sensing pO2, pCO2, and pH Original Research Article

An integrated sensing module for monitoring pO2, pCO2, and pH was fabricated. Electrode patterns were formed on a glass substrate and the containers for corresponding electrolyte solutions were formed by anisotropically etching a silicon substrate. The Clark-type oxygen electrode and the Severinghaus-type pCO2 electrode were used for sensing pO2 and pCO2, respectively. An iridium oxide indicator electrode was used for the sensing element of the pCO2 electrode and the pH electrode. The pH electrode was a combination electrode with an on-chip liquid-junction reference electrode. Distinct responses were observed for each of these electrodes. The linear relationships between the output current of the oxygen electrode and pO2, and between the potential of the carbon dioxide electrode and logarithm of pCO2 were confirmed. The output potential of the pH electrode was compared using the on-chip liquid-junction reference electrode and a macroscopic commercial reference electrode. No substantial difference was observed. Simultaneous operation of the three electrodes was confirmed.