Department of Materials Science and Engineering , Stanford University , Stanford , California 94305-2205 , United States.
RISE Bioeconomy , P.O. Box 5604, SE-114 86 Stockholm , Sweden.
ACS Nano. 2018 Jul 24;12(7):6378-6388. doi: 10.1021/acsnano.8b01084. Epub 2018 May 9.
Nanoscale building blocks of many materials exhibit extraordinary mechanical properties due to their defect-free molecular structure. Translation of these high mechanical properties to macroscopic materials represents a difficult materials engineering challenge due to the necessity to organize these building blocks into multiscale patterns and mitigate defects emerging at larger scales. Cellulose nanofibrils (CNFs), the most abundant structural element in living systems, has impressively high strength and stiffness, but natural or artificial cellulose composites are 3-15 times weaker than the CNFs. Here, we report the flow-assisted organization of CNFs into macroscale fibers with nearly perfect unidirectional alignment. Efficient stress transfer from macroscale to individual CNF due to cross-linking and high degree of order enables their Young's modulus to reach up to 86 GPa and a tensile strength of 1.57 GPa, exceeding the mechanical properties of known natural or synthetic biopolymeric materials. The specific strength of our CNF fibers engineered at multiscale also exceeds that of metals, alloys, and glass fibers, enhancing the potential of sustainable lightweight high-performance materials with multiscale self-organization.
由于其无缺陷的分子结构，许多材料的纳米级构建块表现出非凡的机械性能。由于需要将这些构建块组织成多尺度图案并减轻较大尺度上出现的缺陷，将这些高机械性能转化为宏观材料代表了一项具有挑战性的材料工程任务。纤维素纳米纤维（CNF）是生命系统中最丰富的结构元素，具有令人印象深刻的高强度和刚度，但天然或人工纤维素复合材料的强度比 CNF 低 3-15 倍。在这里，我们报告了 CNF 借助流动辅助作用组织成具有近乎完美单向排列的宏观纤维。由于交联和高度有序，宏观尺度到单个 CNF 的有效应力传递使它们的杨氏模量达到 86 GPa，拉伸强度达到 1.57 GPa，超过了已知天然或合成生物聚合物材料的机械性能。我们在多尺度上设计的 CNF 纤维的比强度也超过了金属、合金和玻璃纤维，增强了具有多尺度自组织的可持续轻质高性能材料的潜力。
