Modeling a micromanufactured open recess-tip oxygen microelectrode

Abstract

The authors' interest is to micromanufacture an oxygen microelectrode capable of measuring oxygen in a volume (on the order of a cubic micron or less). The open-tipped needle electrode is intended for measuring oxygen tension in biological media where it may be inserted into a biological system such as heart or brain with minimal disturbance to the specimen. The prototype design is based on an etched glass needle and is the result of a study of several possible manufacturing methods using different micromanufacturing technologies available at the Institute for Micromanufacturing at Louisiana Tech. University. Guiding the design are species mass transport and electrical system models. These help quantify the critical dimensions necessary to minimize oxygen depletion in the tissue region of the electrode and stabilize the polarization voltage at it's catalytic surface. The models also lead the authors to electrode design parameters which will help minimize response time while maximizing output of the electrode. The multi-region species mass transport model of the oxygen transport includes both the tissue and the recess region of the electrode while the electrical model is a study the effects of the electrode instrumentation design on the electrode and its output. Modeling efforts have demonstrated the importance of design of the electrode in achieving reliable oxygen measurements and also demonstrating the sensitivity of the design to small changes in the critical dimensions of recess length and radius. Also, the characteristics of the tip potential, which is known to influence the performance of other types of glass electrodes, is suggested to have an influence on the performance of this type of electrode.