Flexible electronics for skin wearable pH sensor

Abstract

INTRODUCTION: Recent advances in soft, flexible, hybrid electronics allow to develop a novel wearable platform for direct sweat collection and analysis in real-time. The unobtrusive and mechanically compliant system can provide a gentle, conformal integration onto the skin and offer the comfortable, long-term and continuous monitoring of sweat that overcomes the limitations of conventional technologies. In order to develop such system, however, a number of biosensors are essential that can be miniaturized and are mechanically compatible while providing reliable and accurate measurements. As the first step, we have successfully developed a IrOx based solid state pH sensor. It was built on ultrathin metal wires, which can be bendable with minimal forces. 1% nafion membrane and 1mM 6-merceptohexanol (MCH) were applied on IrOx electroplated working electrode and/or Ag/AgCl reference electrode to significantly improve the response time, stability, and reliability of the sensor. As a result, the long-term test demonstrated that the pH sensor provides accurate readings with a super-Nernstian response of -68.4±2.3 mV/pH for extended periods of time.