Bioinspired Mechano-Tunable and Healable Materials for Self-Adaptive Intelligent Devices

Mechanically adaptive materials responsive to environmental stimuli through changing mechanical properties are highly attractive in intelligent devices. However, it remains a great challenge for most mechanically adaptive materials to facilely regulate and repair their mechanical properties in a broad spectrum ranging from high strength to extreme toughness in a single body. Here, inspired by reversible nanofibrils network structure of skeletal muscle to achieve muscle strength regulation, we present a mechano-tunable silk fibroin (SF) composite through regulating metal-ligand coordination bonds and the β-sheet secondary structure by using water molecules as competitive regulators. Effective hydrogen bonds and two-dimensional nanosheets skeleton network endow the SF composite with high mechanical strength and self-healing ability. The resulted composite exhibits 837-fold change in Young's modulus (5.77 GPa to 6.89 MPa) after vapour triggering, robust mechanical properties (72.5 MPa), and excellent self-healing efficiency (nearly 100%). The proof-of-concept ultra-conformable iontronic skin and robust actuators are demonstrated, thereby providing a direction for future self-adaptive intelligent device applications.