Make the dream fibre, Artificial Spider Silk, become a reality

Among many unqiue properties, exatraordinary toughness and smart behavior of spider silks such as supercontraction and water collection are particularly attractive. However, unlike silkworm to make silk, spiders cannot be farmed due to their cannibalistic nature. This limits the supply of spider silks in their natural form for real world applications. Thus, man-made spider silk has long been a dream of many scientists and companies. The extraordinary properties of spider silks are due to their hiearchical structures, particularly nanostructures; beta sheet crystals, elastic spinglike coils and amorphous domains from proein gene sequence. The understanding of the molecular and morphological structure of silks has inspired research in biomimic, novel and high performance materials by genetic engineering and chemical methods. This talk will present the recent develolment by the spakers’ team of biomimetic fibrous fibers with shape memory/supercontraction, supertoughness and directional water collection by both genetic and chemical engineering approach. First of all, a spider-silk-mimicking (molecular structure and spinning) strategy was reported for preparing a scalable supertough fiber from chemical synthesis route. Supertoughness (~387 MJ m-3) and high tensile strength (~100 MPa) are achieved by introducing hierarchical hydrogen-bonding structure (urethane, urea, α-helix, β-sheet) in an easily prepared peptide-polyurethane/urea. The toughness of this fiber is more than twice the reported value of a normal spider dragline silk, and comparable with the toughest spider silk, aciniform silk of Argiope trifasciata. The widely available feedstocks and facile preparation make it possible for large-scale applications. A spider web collects water by its capture-silk for recovering the daytime-distorted shape during night through water-sensitive suoercontraction. Different from using synthetic materials, an all silk-protein fiber (ASPF) with periodic knots endows extremely high volume-to-mass water collection capability. This fiber has a main body of B. mori degummed silk coated with recombinant eMaSp2 of spider dragline silk. It is 252 times lighter than synthetic polymer coated nylon fibers that once was reported to have the highest water collection performance. The ASPF collected a volume of 6.6 µL of water and has 100 times higher water collection efficiency compared to existing best water collection artificial fibers in terms of volume-to-mass index (VTMI) at the shortest length (0.8 mm) of three phase contact line (TCL). Since silkworm silks are available abundantly, effective use of recombinant spidroins tandemly shows great potential for scalability. Spider dragline silk features a supercontraction with its great sensitivity to moisture/water. Enlightened by this phenomenon, thus thirdly, we put forward an understanding of spider silk supercontration as a shape memory behaviour and first time realised this unique behaviour with our genetically engineered major ampullate spidroin 2 (eMaSp2) fiber, which has abundant polyalanine and proline motif. Interestingly, at ̴75% relative humidity (RH), eMaSp2 fibre demonstrated a moisture-triggered shape memory behavior with excellent shape fixity and recovery ratio of 82.1 ± 2.1% and 98.5 ± 0.4%, respectively. Apart from that, an impressive recovery stress of eMaSp2 fibre was determined with a maximum value of 19.1 MPa, outperforming almost all shape memory polymers or even most shape memory composites reported to date.