A Self-Powered, Biodegradable Dissolved Oxygen Microsensor

We report a biodegradable, self-powered sensor for measurement of dissolved oxygen in the body. The principle of operation is the competition of an oxygen reduction reaction against the ordinarily dominant hydrogen reduction reaction at the cathode of a corroding electrochemical couple. Because the relative contribution of the oxygen reduction reaction to the overall electrochemical reaction depends on the local oxygen concentration, the output voltage of the couple is also dependent on local oxygen concentration. The sensor is formed by embedding the biodegradable metals magnesium and molybdenum within a biodegradable poly(lactic acid) substrate using lamination; external physiological solution is utilized as the electrolyte. The output voltage of the sensor (i.e., the voltage generated across the corroding couple) was measured as a function of oxygen concentration over typical physiological oxygen concentration ranges of 0-60% that of atmospheric oxygen. A linear output voltage response of approximately 6 mV per percentage point oxygen concentration was observed; oxygen concentrations above this range resulted in sensor saturation.