Graphene Oxide-Poly(vinyl alcohol) Hydrogel-Coated Solid-Contact Ion-Selective Electrodes for Wearable Sweat
Siyi Liu1, Lijie Zhong1, Yitian Tang1
1Center for Advanced Analytical Science, Guangzhou Key Laboratory of Sensing Materials and Devices, Guangdong Engineering Technology Research Center for Photoelectric Sensing Materials and Devices, Key Laboratory of Optoelectronic Materials and Sensors in Guangdong Provincial Universities, School of Chemistry and Chemical Engineering, Guangzhou University, Guangzhou, Guangdong 510006, China.
Abstract:
Solid-contact ion-selective electrodes (SC-ISEs) with ionophore-based polymer-sensitive membranes have been the major devices in wearable sweat sensors toward electrolyte analysis. However, the toxicity of ionophores in ion-selective membranes (ISMs), for example, valinomycin (K+ ion carrier), is a significant challenge, since the ISM directly contacts the skin during the tests. Herein, we report coating a hydrogel of graphene oxide-poly(vinyl alcohol) (GO-PVA) on the ISM to fabricate hydrogel-based SC-ISEs. The hydrogen bond interaction between GO sheets and PVA chains could enhance the mechanical strength through the formation of a cross-linking network. Comprehensive electrochemical tests have demonstrated that hydrogel-coated K+-SC-ISE maintains Nernstian response sensitivity, high selectivity, and anti-interference ability compared with uncoated K+-SC-ISE. A flexible hydrogel-based K+ sensing device was further fabricated with the integration of a solid-contact reference electrode, which has realized the monitoring of sweat K+ in real time. This work highlights the possibility of hydrogel coating for fabricating biocompatible wearable potentiometric sweat electrolyte sensors.
