High-Performance and Flexible Sodium Ion-Based Electrochemical Devices Toward Self-Powered Wearable Volatile Organic Compounds Sensing System

Abstract

Self-powered wearable electronic systems consider an ideal solution to realize ubiquitous Internet-of-Things (IoT), personalized healthcare, and point-to-care diagnosis. Here, we demonstrate the integration of a high-performance and ultra-stable sodium ion-based micro-supercapacitor (MSC) and a high-sensitive sensor for self-powered wearable VOC sensing systems. It is found that a sodium-based solid electrolyte exhibited high ionic conductivity, reaching 2.4 mS cm-1 at 70 °C. Further, the capacitance of sodium ion-based MSC can be enhanced about 2.25 times by virtue of TiO2 NPs acting as additives in solid electrolyte. PDMS-encapsulated MSC showed ultra-stability of capacitance retention (approximately 98.8%) after 50,000 cycles while also achieving a high flexibility of 1000 cycles with a minimal capacitance change. As a proof-of-concept of a self-powered wearable sensor, it is demonstrated that an integrated polymer electrolyte-based VOC sensor powered by a charged-MSC can continuously operate for more than 4000 s (over 1.1 h) in the ethanol/nitrogen gas chamber. Therefore, we believe that our integration of sodium ion-based electrochemical storage and VOC sensor capabilities will pave a way to revolutionize the approach of wearable electronic applications toward self-powered systems.

Keywords: polymer electrolyte, gas sensor, supercapacitor, self-powered, wearable device