The dual transportation channel of ionic strain sensor constructed by amorphous polymer chains and two-dimensional nanoplatelets

A large amount of ions favors high ionic-conductivity, but remarkably reduces the sensitivity of hydrogel-based wearable sensors, which severely limits their advanced applications. Herein, this contradiction is successfully overcome by the strategy of constructing the dual-ion transportation channels (DITC) in hydrogels. Specifically, using an anti-freezing CaCl2, an amorphous polymer network is created in freeze-thawed polyvinyl alcohol (PVA) hydrogel, which induces the enlarged spacing between PVA chains and thus promotes the transportation of ions as the first channel. Secondly, the two-dimensional nanoplatelets-bentonite (BT) with electrostatic interaction with PVA chains construct a second layer of ion transportation channel, which is capable of reversibly transforming between the dense and loose distribution under external force and thus further improves the ionic sensitivity of hydrogel sensors. Contributed by this particular amorphous crosslinked network and DITC, the ultimate hydrogels represent excellent flexibility, stretchability, self-adhesion, freezing-tolerance, long-term stability, and the most important strain sensitivity even with high ion concentration, which can monitor both subtle and complicated movements (e.g., finger bending and hand writing). Therefore, the DITC strategy extends the design principle for highly sensitive ionic-hydrogel sensors and provides excellent potential for stretchable electronic sensors and intelligent detection of human motions.