A wearable oxygen sensor for transcutaneous blood gas monitoring at the conjunctiva

A thinner and flexible oxygen sensor as one of the Soft-MEMS devices was developed in order to monitor transcutaneous oxygen tension from conjunctiva. The wearable oxygen sensor with membrane structure was constructed by pouching KCl electrolyte solution by nonpermeable membrane and gas-permeable membrane with Pt- and Ag/AgCl electrode patterned by using photolithography and sputtering methods. The wearable oxygen sensor (width: 3 mm, thickness: 84 mu m) was applied to the electrochemical measurement with a fixed potential of -550 mV versus Ag/AgCl, thus obtaining the calibration range to dissolved oxygen from 0.01 to 8.0 mg/l. The sensor was also evaluated in gas phase by purging with 10% oxygen gas and the response time to reach 90% of the steady current after purging was approximately 45 s, sensor outputs and responses were stable during repeated measurements at 3.66% of the coefficient of variance. As the physiological application, the wearable sensor was placed onto a conjunctiva of a Japanese white rabbit without any thermoregulation. As an experiment, the rabbit inhaled standard air and high concentration oxygen (60 and 90%). As the result, sensor output increased and decreased synchronously with high concentration oxygen and standard air inhaling, respectively. This suggests that the sensor can be a new transcutaneous oxygen sensor. (c) 2005 Elsevier B.V. All rights reserved.