羧基化与季铵盐细菌纤维素共同构筑仿墨鱼骨结构材料

天然材料中不同的基本结构间存在显著的力学协同作用，构成的整体结构对于提升损伤容限具有重要意义。例如，墨鱼骨具有刚性空腔-隔板的整体结构，能够承受来自深海的巨大水压。在外部载荷作用下，隔板可以分散应力，刚性空腔通过充分破碎吸能，显著提高材料的损伤容限和能量吸收性能，有效避免材料的灾难性破坏。然而，如何调控微纳构筑基元的有序排布，实现仿生结构材料中不同基本结构的整体同步组装极具挑战性。受天然墨鱼骨“刚性空腔-隔板”有序层状结构的启发，本工作报道了一种预设异种结构水凝胶进行组装的新策略，实现了仿墨鱼骨结构材料的跨尺度一体化构筑。具体而言，采用自下而上的方法，通过表面氨基化的绢云母微米片与羧基化纤维素纳米纤维构筑砖泥结构作为隔板层；采用硼硅酸盐空心玻璃微球和聚乙烯醇、季铵化纤维素纳米纤维进行组装，构筑致密空腔结构作为刚性空腔层。将具有不同微结构的水凝胶进行层层交叠组装，在外力诱导组装脱水成型过程中，被包裹在纤维素纳米纤维网络中的绢云母微米片发生致密化组装堆叠，实现具有砖泥结构的隔板层制备；与此同时，被包裹在聚乙烯醇/纤维素纳米纤维基质网络的玻璃微珠发生致密堆积，实现了刚性空腔层的制备。所得仿墨鱼骨结构材料具有显著的抗裂纹扩展作用，可促使刚性空腔结构充分破碎吸能，失效行为与天然墨鱼骨相似，具有优于传统吸能材料的比强度和比能量吸收性能。

Significant mechanical synergistic effects exist between distinct basic structures in natural materials, and the overall integrated structure plays a critical role in enhancing damage tolerance. For instance, cuttlefish bone features an integrated rigid cavity-septum structure that can withstand the extreme hydrostatic pressure of the deep sea. Under external loads, the septa disperse stress, while the rigid cavities fully fracture to absorb energy, significantly improving the material's damage tolerance and energy absorption capacity and effectively preventing catastrophic failure. However, regulating the ordered arrangement of micro-nano building blocks to achieve the synchronous integrated assembly of different basic structures in biomimetic structural materials remains highly challenging.

Inspired by the ordered layered "rigid cavity-septum" structure of natural cuttlefish bone, this work reports a novel strategy for assembling preset heterogeneous structural hydrogels, enabling the cross-scale integrated fabrication of cuttlefish bone-mimetic structural materials. Specifically, a bottom-up approach was employed: surface-aminated sericite microflakes and carboxylated cellulose nanofibers were used to construct a brick-and-mortar structure as the septum layer; borosilicate hollow glass microspheres, polyvinyl alcohol (PVA) and quaternized cellulose nanofibers were assembled to form a dense cavity structure as the rigid cavity layer.

The hydrogels with distinct microstructures were assembled via layer-by-layer overlapping. During the external force-induced assembly, dehydration and molding process, the sericite microflakes encapsulated within the cellulose nanofiber network underwent densified assembly and stacking, facilitating the preparation of the septum layer with a brick-and-mortar structure. Meanwhile, the glass microspheres encapsulated in the polyvinyl alcohol/cellulose nanofiber matrix network underwent densified packing, enabling the fabrication of the rigid cavity layer.

The resulting cuttlefish bone-mimetic structural material exhibits remarkable crack propagation resistance, can promote the full fracture of the rigid cavity structure for energy absorption, displays a failure behavior analogous to that of natural cuttlefish bone, and outperforms traditional energy-absorbing materials in terms of specific strength and specific energy absorption performance.