Lattice Proton Intercalation to Regulate WO3‐Based Solid‐Contact Wearable pH Sensor for Sweat Analysis

Abstract

AbstractSweat pH monitoring is a routine indicator in wearable biotechnology. The state‐of‐the‐art wearable pH sensors mostly rely on organic materials but face the risk of biological toxicity. WO3 is a typical H+‐sensitive inorganic material with chemical stability, biocompatibility, and low cost but low sensitivity and slow response. Lattice H+ intercalation is herein proposed as an efficient approach that can greatly improve the sensitivity and selectivity of WO3‐based pH sensors. Specifically, lattice H+ intercalation can promote WO3 from the monoclinic phase to cubic phase, which enhances the ion exchange capacity between WO3 and H+. The resistance decreases more than two orders of magnitudes, which improves the interfacial charge transport. The occupancy of lattice H+ leads to ion exchange only with H+, thus increasing the H+ recognition. The intercalated HxWO3 exhibits much improved sensitivity, reversibility, and response time. Additionally, the HxWO3 is integrated with a solid reference electrode on a miniaturized chip for wearable sweat pH monitoring. The pH sensor exhibits good potential response even at curving over 270°. On‐body sweat pH measurments show high accuracy compared with ex situ analyses. This work emphasizes the concept of lattice proton intercalation to regulate the H+ recognition of solid contacts.