Tendon-inspired robust ionic conductive hydrogels with multi-hierarchical structures towards asthmatic patients’ medication monitoring

Abstract

Conductive hydrogels have shown substantial potential in the field of medication monitoring due to their exceptional flexibility and biocompatibility. However, some challenges such as low ionic conductivity, restricted mechanical properties, and limited sensitivity have hindered their further development. Inspired by fiber-like aligned tendon tissues, robust and conductive hydrogels with multi-hierarchical structures via constructing cellulose-reinforced polyvinyl alcohol (PVA) networks using a directional freeze-casting technique combined with Zn²⁺/Li⁺ bimetallic ion coordination were developed. As a result, high mechanical properties (σ = 1.5 MPa, ε = 1020%), a high conductivity of 3.5 S m⁻¹ and a low strain detection limit of 0.5% of the hydrogels were simultaneously achieved, ascribed to the multi-hierarchical structure interactions such as polymer chain orientation, formation of nanocrystalline domains, and ionic coordination effects. Interestingly, the conductive hydrogel showed great potential as an electrolyte of flexible zinc-ion batteries. More importantly, for the first time, a strong correlation between varying wind forces and the relative resistance of the hydrogel was created and therefore an intelligent real-time medication monitoring system was then well designed utilizing the ionic hydrogels as a flexible sensor, which can be used to monitor the drug-intake for infant or elder asthmatic patients. This work provides a green and biomimetic strategy to construct ionic conductive hydrogels for medical monitoring.