Profiling of oxygen in biofilms using individually addressable disk microelectrodes on a microfabricated needle

Abstract

A novel microelectrode array sensor was fabricated using MEMS technology on a needle, and then applied to real-time measurement of dissolved oxygen (DO) inside biofilms. The sensor consists of eleven gold disk microelectrodes and a rectangular auxiliary electrode along them and an external & internal reference electrode. Three kinds of sensors were designed and their responses were characterized and evaluated under various environmental conditions. The arrays exhibit a linear response to DO in the 0 - 8 mg L-1 concentration range in water, high sensitivity, repeatability, and low limits of detection (< 0.11 mg L-1) and quantification (0.38 mg L-1). The sensors were then validated against a commercial Clark-type microelectrode and applied to profiling of DO in a heterotrophic biofilm cultivated in a flat-plate bioreactor. It is shown that the sensor array can provide a multipoint, simultaneous snapshot profile of DO inside a biofilm with high spatial resolution due to its micrometric dimensions. We conclude that this new sensor array represents a powerful tool for sensing of DO biofilms and in numerous bioprocesses.