Robust and ultra-fast self-healing elastomers with hierarchically anisotropic structures and used for wearable sensors

• Hierarchically anisotropic, real-time self-healing elastomer was established. • The obtained elastomer exhibited high mechanical strength. • Hierarchical CNT layer can be easily obtained by spray-coating. • Outstanding healing speed (0.1 s) in electrical property was achieved. • Hierarchical conductive layer endowed wearable sensor with high gauge factor. Fabrication of self-healing elastomers with high strength and real-time (<30 s) self-healing capability is still a huge challenge. It is well documented that biological tissues with hierarchically anisotropic structures possess excellent self-healing and mechanical properties. Self-healing elastomer with similar hierarchically anisotropic structures as biological tissues has, however, not been reported yet. Herein, we highlight a facile strategy to fabricate self-healing elastomers with hierarchically anisotropic structures similar to tendons and ligaments by drying precursor hydrogels under fixed strains. Elastomers obtained by drying at 200% strain exhibit a high strength (8.4 MPa) and ultrafast self-healing ability (86% recovery after 10 s) under ambient conditions. Besides, elastomers with a surface CNT coating layer can be easily prepared by directly spraying the CNT suspension onto the surface of precursor hydrogel before drying under strain. Benefiting from the hierarchical structure of the surface CNT layer, the elastomer can be used as a sensor to detect minute human motions. This study provides a novel strategy for fabricating hierarchically anisotropic self-healing elastomers and simultaneously achieving high strength and real-time self-healing ability.