Vapor-responsive Shape Memory Material based on Carbon Nanotube Sponge dominated by Pressure-induced Structural transformation of Spidroin

Abstract Over decades, the confliction between excellent performances i.e. outstanding strength, elasticity, biocompatibility, and limited yields of the spider silks has become a severe challenge. Almost all the practical applications involve with the recombination of spidroin then the fabrication of artificial spider silks. Various attempts have been conducted to reveal both the components and the structures, while it remains insufficient to understand and copy the structural transition process of spidroin in practical applications. Herein by systematical experimental results, we feature that only a small hydrostatic pressure (several mega pascals) can induce the secondary structural transition of spidroin from α-helix to β-sheet, showing a tunable structural elasticity. Based on our understanding, we design and fabricated a vapor-responsive shape memory material by compositing both spidroin and carbon nanotube sponges (CNTS). The appearance of hydrostatic pressure can induce the secondary structural transition which terminates the elasticity of the CNTS and will recover under a simple solvent vapor annealing at ambient atmosphere, indicating a reversible “shape-memory” effect with the recovery efficiency close to 100 %. Our observations not only provide a promising shape-memory material with unique temperature-independent character, but reveal a crucial mechanism on the structural transformation of spidroin molecules under a confined environment, which will pave the way toward the design and fabrication of outstanding artificial spider silk-based products.