Dual Physically Crosslinked Silk Fibroin Ionoelastomer with Ultrahigh Stretchability and Low Hysteresis

Innovations in ionotronics have greatly facilitated the development of ultraflexible devices, displays, and machines. However, ionotronics often suffer from an inherent trade-off between stretchability and elasticity due to their viscous nature. Here, we overcome this limitation by incorporating dimension-and-content-confined nanocrystalline crosslinks into amorphous and molecularly entangled silk fibroin (SF) ionotronics. The welding-entanglement network exhibited a 34-fold increase in Young's modulus, a 14-fold increase in tensile strength, and a 9-fold increase in toughness compared to the same SF material without the nanocrystal crosslinks. The welding-entanglement network also gained recoverable hysteretic energy dissipation with hysteresis as low as 22%. The stretchability and low hysteresis exhibited by these SF ionoelastomers far exceed those of previously reported ionotronics and bioelastomers. These mechanical merits, together with the inherent advantages of SF ionoelastomers, including their multiprocessability, sustainability, biocompatibility, and degradability, promote their applications in human-machine interfaces and bio-functional devices.