石墨烯诱导水凝胶成核的高强韧人造蛛丝

Graphene-Oxide Seeds Nucleate Strong and Tough Hydrogel-Based Artificial Spider Silk

天然蜘蛛丝是由β-sheet交联的蛛丝蛋白溶剂流入S-型导管后经牵引拉伸形成,它显示了高强度与高韧性的完美结合。其优异的力学性质主要源于它的多级结构:交联、线性排列的纳米组装体以及核壳结构。受此启发,我们合成了一种交联的水凝胶,通过牵引拉丝的方法,制备了交联的、含有取向排列的纳米组装体结构以及核壳结构的凝胶纤维,并通过少量引入二维纳米材料—氧化石墨烯(0.01%),进一步调控纳米组装体的取向和尺寸,实现了蜘蛛丝般优异的力学性能(断裂强度560 MPa,断裂韧性200 MJ∙m^(−3),缓冲能94%)。这种纤维可以用于高速下落物体的能量耗散和降低冲击力。

Natural spider silk is composed of spun spidroin protein containing beta-sheet crosslinking sites drawn from an S-shaped spinning duct.It exhibits an excellent combination of strength(1150±200 MPa)and toughness(165±30 MJ∙m^(−3))that originates from its hierarchical structure,including crosslinking sites,highly aligned nano-aggregates,and a sheath-core structure.In this work,we prepared a hydrogel fiber that contains crosslinking sites,highly aligned nano-aggregates,and a sheath-core structure,by draw-spinning a bulk hydrogel composed of polyacrylic acid crosslinked with vinyl-functionalized silica nanoparticles(SNVs).The core-sheath structure was prepared by the water-evaporation-controlled self-assembly of the polyacrylic hydrogel,while nanometer-sized aggregates were formed by the self-assembly of polyacrylic acid chains.The addition of a tiny amount of graphene oxide(GO:0.01%),a 2D nanomaterial,enhanced the mechanical properties of the fiber(breaking strength:560 MPa;fracture toughness:200 MJ∙m^(−3);damping capacity:94%).In addition,we investigated the factors responsible for the mechanical properties of the gel fibers,including fiber diameter,drying time in air,relative air humidity,and stretching speed.A higher breaking strength and a lower fracture strain was obtained by decreasing the fiber diameter,increasing the drying time,or increasing the stretching speed,while a lower fracture strain and higher breaking strength were obtained by increasing the relative air humidity.Polarized optical and SEM images revealed that the GO-seeded material is better aligned and contains smaller nano-aggregates,with GO seeding found to play a key role in the formation of nano-aggregates and polymer-chain alignment.The prepared fiber exhibited excellent mechanical properties compared to gel fibers prepared by other methods(e.g.,electro-,wet,dry,and microfluidic spinning,as well as templating,and 3D printing,etc.).Repeated mechanical testing involving stretch-release cycles to 70%strain at 20%relative humidity revealed that the fibers have an energy-damping capacity of 93.6%,which exceeds that of natural spider silk and many types of artificial fiber.The relaxed stretched fiber recovered its initial length when exposed to 80%relative humidity,while the fiber recovered its initial mechanical properties when stored for 2 h at room temperature.A yarn composed of three hundred of the prepared gel fibers was shown to lift a 3 kg object without breaking;the prepared fiber was also shown to absorb dynamic energy and lower the impact force of a falling object.