Spider-Silk-Like Alginate Fibers with Outstanding Photomodulating Mechanical Properties upon Molecular Motion

Spider silks exhibit extraordinary mechanical performances by combining strength and toughness together. However, spider-silk-like materials hardly achieve great modulation of mechanical properties under the trigger of external stimuli. Herein, a molecular designing strategy for synthesizing spider silk-like fibers is developed by cross-linking alginate molecules with the designed merocyanine-containing ammonium surfactant as flexible contact points. Through establishing an electrostatic complexation between alginate and surfactant, the noncovalent cohesive network imparts the fibers with an outstanding strength of 1.54 GPa and a toughness of 121.12 MJ/m³. Assisted by the isomerization of merocyanine, the strength and toughness of such fibers could be light-modulated to be 0.67 GPa and 16.87 MJ/m³. The spider silk-like and photoresponsive mechanical properties, reversible color change, and good resistance to various conditions could support the use of such alginate fibers in wide-application scenarios. This study provides a new design strategy for fabricating smart biomaterials with high mechanical performances.