Tough and Temperature‐Resistant Material Based on <i>Bombyx mori</i> Silk Fibroin

Extreme temperatures present significant challenges for materials in polar and extraterrestrial exploration. Inspired by Bombyx mori spinning, we propose a biomimetic "Hydration-Crystallization Locking" (HCL) strategy. By precisely controlling the composition and distribution of hydrophilic domains and hydrophobic crystals in silk fibroin (SF), we developed a flexible fibroin membrane (FFM) exhibiting high tensile strength (∼50.5 ± 3.2 MPa), toughness (∼16.4 ± 1.2 MJ/m³), and >95% shape retention under large deformations at -196°C and 70°C. The HCL strategy was confirmed to promote the formation and retention of hydrophilic Silk I structure, with its conformational signature type II β-turn retained from 30.8% to 14.6%, while partially transitioning to the hydrophobic Silk II structure. Silk I captured immobile water via serine, forming orderly hydrated structures that enhanced chain plasticization; uniformly dispersed Silk II crystalline domains acted as hydrophobic and thermal barriers, preventing water escape and freezing. FFM served as a multifunctional platform in extreme environments for flexible photovoltaics, polar equipment, and a lightweight electromagnetic interference shielding shell. Additionally, FFM was recyclable under mild conditions. The HCL strategy enables renewable SF to replace petroleum-based polymers for balancing mechanical properties and temperature resistance. It provides a sustainable framework for designing high-performance biomass polymers for extraterrestrial exploration and low-temperature systems.