Metal cation-ligand interaction modulated mono-network ionic conductive hydrogel for wearable strain sensor

Ionic cross-linked hydrogels with flexibility, self-recovery and conductivity have attracted extensive attention for the diverse applications in flexible and wearable sensors as ionic conductive hydrogels. However, the hydrogels need to trade off the ionic conductivity for the mechanical property due to the significant decrease in ionic bond strength at high salt concentration. It remains a challenge to find a feasible strategy to realize both excellent mechanical property and ionic conductivity in ionic cross-linked hydrogels. Herein, hydrogels with high extensibility, fatigue, toughness resistance and ionic conductivity are prepared by the incorporating of trivalent metal cations as cross-linker in one-pot reaction. The improved mechanical property of Al3+ cross-linked hydrogel can be attributed to the labile ligand substitution of Al3+ compared with that of Cr3+, resulting in the rapid self-recovery of ionic bonds. Meanwhile, the hydrogels exhibit a high ionic conductivity, sensibility and stability as strain sensors. The hydrogel sensors can detect the motion of multiple body parts and distinguish different electrical signals. Our study will unfold the crucial role of the metal cation-ligand interaction in the design of soft materials with excellent mechanical performance.

Automated summary

In this study, hydrogels with high extensibility, fatigue, toughness resistance, and ionic conductivity were prepared by incorporating trivalent metal cations as cross-linkers. The improved mechanical property of Al3+ cross-linked hydrogel is attributed to the labile ligand substitution of Al3+ compared with Cr3+, leading to rapid self-recovery of ionic bonds. The hydrogel sensors exhibit high ionic conductivity, sensitivity, and stability as strain sensors, capable of detecting motion of multiple body parts and distinguishing different electrical signals.