FLEXIBLE CONDUCTIMETRIC SENSOR

A flexible sensor constructed in a sandwich configuration with a hydrophilic poly(tetrafluoroethylene) membrane placed between two gold deposited layers was evaluated for use as a conductimetric sensor in biologic fluids. The conductivity was measured using the device at frequencies ranging from 100 Hz to 100 kHz, and the device was calibrated at 100 kHz against sodium chloride solutions over the range of 0.1-50.0 g/L, which includes physiologic ion concentrations. Attached to a contact lens, the flexible conductimetric sensor can be placed directly onto the surface of the rabbit eye to monitor the electrical conductivity of tear fluids. Osmolarity obtained from the sensor data was consistently lower than previously reported values, perhaps indicating the effects of protein and lipid deposition. Tear flow with a mean turnover rate of 64.9%/min was elicited by eye drops of high concentration sodium chloride and distilled water.