Research Abstracts Online
January - December 2011
University of Minnesota Twin Cities
College of Science and Engineering
PI: Philippe Buhlmann
Solving the Reference Problem of Implantable Electrochemical Sensors
In ion-selective potentiometry, the concentration of a chemical species of interest is determined from the electrical potential difference between an ion-selective electrode (ISE) and a reference electrode whose potential is sample-independent. In hospitals this approach is used billions of times annually. Unfortunately, the use of ISEs is severely limited by the salt bridge, which separates the conventional reference electrode from the sample. Salt bridges become easily contaminated and cease to function properly when their salt content is depleted due to diffusion into samples. This project will replace salt bridges with water-immiscible receptor-doped polymeric membranes. The uncontrolled loss of bridge electrolyte into the sample will be substituted by controlled release of ions into the sample with a current pulse prior to potentiometric measurements. After measurements, reference electrodes will be completely regenerated with pulses of opposite current. This project sets the foundation for long-term implantation of ISEs into the human body. It requires the use of the software COMSOL to predict the potential responses of these pulse-operated reference electrodes during and following voltage and current pulses. COMSOL will permit the prediction of concentration gradients, ion fluxes, and voltage drops.
Xu Y. Zou, Graduate Student