TRANSIENT GAS SENSORS

THE CONVENTIONAL CLARK-TYPE OXYGEN SENSOR NEEDS FREQUENT RECALIBRATION WHEN IMPLANTED IN VIVO DUE TO MEMBRANE FOULING, ELECTROLYTE THICKNESS CHANGES RESULTING FROM PRESSURE VARIATIONS, AND THE FLUCTUATING FLOW RATE OF BLOOD. AN IMPROVED OXYGEN SENSOR IS PLANNED THAT REDUCES ORELIMINATES MANY OF THESE PROBLEMS. THIS SENSOR, WHICH IS A MODIFIED CLARK SENSOR, USES THE FOLLOWING APPROACHES: (1) A MEASURING PULSE BASED ON THE ESTABLISHMENT OF A TRANSIENT DIFFUSIONAL CONCENTRATION GRADIENT; (2) AN ELECTRICAL WAVEFORM FOR IN SITU CONDITIONING (REACTIVATING) OF THE SENSOR ELECTRODE; (3) ALL NOBLE-METAL, NONCONTAMINATING ELECTRODES IN A NONCHLORIDE, ACIDIC ELECTROLYTE; AND (4) SENSING ELECTRODE GEOMETRIES THAT ENHANCE THE SIGNAL-TO-NOISE RATIO. DURING PHASE I, THE OPTIMUM MATERIAL AND ELECTRICAL PARAMETERS WILL BE CHOSEN BASED EXCLUSIVELY ON IN VITRO LABORATORY TESTING OF A MACROSENSOR. WORK DURING PHASE II WILL CONCENTRATE ON TRANSLATING THIS TECHNOLOGY INTO AN IMPLANTABLE SENSOR FOR BLOOD AND/OR TISSUE OXYGEN MEASUREMENTS AND ON CARRYING OUT AN EXTENSIVE IN VIVO TESTING PROGRAM AIMED AT VERIFYING THE APPROACH AND AT OPTIMIZATION OF THE SENSOR.