Development of a Clark Microsensor for Low Concentration Dissolved Oxygen Monitoring

This paper reports on a geometrically optimized implantable three-electrode Clark microsensor for measuring dissolved oxygen concentration. The sensor is based on a conventional concentric three electrode structure. In order to maximize the current between the working and counter electrode, sensor structures with different reference electrode sizes and shapes are simulated. Results show that the highest current is achieved for a half crescent electrode with a surface area half of the conventional full crescent reference electrode. The optimized microsensor structure is fabricated using silicon-based microtechnology. Electrochemical measurements performed with the sensor show that the sensor responds to different concentration of dissolved oxygen (DO2). A measured current of 0.87 µA between working and counter electrodes is reported for 96% of DO2 concentrations. The sensor shows a sensitivity of −0.0094 μA/%DO2 and an accuracy of 1.98% DO2 in measurement. A measurable output current at 2% DO2 of the microsensor demonstrates that the microsensor can have potential for low DO2 concentration measurement.