Hydrodynamics-engineered polyaniline nanofibers on graphene nanosheets for high-performance pH sensors

Abstract

Real-time sweat monitoring in the human body using wearable sensors is promising for noninvasive and continuous healthcare applications. For reliable and accurate sweat analysis, further improvement in the response time and long-term stability of sensors is required. This paper reports an electrochemical pH sensor based on polyaniline/graphene (PANi-Gr) with rapid electron and ion transfer. The implementation of the Taylor–Couette flow approach allowed the efficient exfoliation of graphite into Gr nanosheets and the rapid polymerization of aniline monomers on the Gr surface, resulting in nanofiber PANi-deposited Gr nanocomposites. PANi-Gr had a large surface area and porous structure, which are favorable for rapid and stable electrochemical reactions. The screen-printed PANi-Gr-based pH sensor exhibited a Nernstian sensitivity of 61.91 mV/pH, rapid response time of <1 s, and long-term stability upon monitoring with minimal potential drift (0.04 mV h−1) under strong acidic and basic conditions. Furthermore, the on-body performance of the wearable pH sensor integrated with a wireless electronic device was analyzed via the noninvasive real-time monitoring of human sweat pH during stationary cycling. The developed sensor can be used in wearable real-time sweat monitoring devices for medical and healthcare applications.