Needle-type dissolved oxygen microelectrode array sensors for in situ measurements

Dissolved oxygen is a critical indicator in a variety of biomedical and environmental processes. This work describes the development of a new needle-type microelectrode array (MEA) sensor for in situ measurements of dissolved oxygen (DO) using microfabrication technologies. A dynamic etching technique was used to fabricate 10 mm long sensor probes and sharpen them to micrometer dimensions. The sensors utilized a gold sensing electrode inside a recess fabricated at the tip of each microelectrode. Electrochemical performance of these DO MEA sensors was fully characterized by measuring the oxygen concentration of saline solutions with a Ag/AgCl reference electrode. The DO MEA exhibited a rapid 15 s linear response in the 0–9 mg/L (0–21% O2) range. The DO microelectrode array sensor was successfully applied to evaluation of DO microprofiles in a multi-species aerobic bacterial film. The developed new sensors are able to penetrate samples in order to perform DO measurements, and will enable in situ analysis in many biological applications.