Tough and Temperature‐Resistant Material Based on Bombyx mori Silk Fibroin

ABSTRACT 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/m 3 ), 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.