Lattice Proton Intercalation to Regulate WO<sub>3</sub>‐Based Solid‐Contact Wearable pH Sensor for Sweat Analysis
Yitian Tang, Shiyu Gan, Lijie Zhong, Zhonghui Sun, Longbin Xu, Chunxian Liao, Kanglong Lin, Xiaoqing Cui, Dequan He, Yingming Ma, Wei Wang, Li Niu
Abstract
Abstract Sweat 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. WO 3 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 WO 3 ‐based pH sensors. Specifically, lattice H + intercalation can promote WO 3 from the monoclinic phase to cubic phase, which enhances the ion exchange capacity between WO 3 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 H x WO 3 exhibits much improved sensitivity, reversibility, and response time. Additionally, the H x WO 3 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.