A Mechanoluminescence-Based Stress Sensing Hydrogel for Intelligent Artificial Ligament

Robust and biocompatible hydrogels are recognized as promising biomimetic soft materials to improve human life quality. To ensure their stable, reliable, and safe service, the hydrogels are further required to have non-contact and wireless stress sensing ability. Herein, a mechanoluminescence (ML) based micellar hydrogel is developed, in which the surface-modified BaSi₂O₂N₂: Eu²⁺ (M-BSON) particles are chemically incorporated into the cross-linked polyacrylamide/polymethyl acrylate (PAM/PMA) network structure. Because of the interactions between the M-BSON particles and the PMA micelles, the as-fabricated composite hydrogel exhibits enhanced mechanical properties with a mechanical strength of 2.73 MPa and a toughness of 3.40 MJ m⁻³, respectively. The chemical wrapping of the M-BSON particles by the hydrophobic PMA micelles further protects the ML properties from water quenching, leading to remarkable stress-induced luminescence under the water environment of hydrogel. Because of its desirable mechanical performance, attractive stress-light responsiveness, and good biocompatibility, the M-BSON incorporated hydrogel has the potential to be applied as an intelligent artificial ligament for stress self-monitoring and failure warning. This work addresses the inhomogeneous dispersion and water quenching issues of the ML particles in hydrogel structure, which significantly promote ML applications in bionic engineering.