Nanofibrillar materials, such as cellulose, chitin and silk, are highly ordered architectures, formed through the self-assembly of repetitive building blocks into higher-order structures, which are stabilized by non-covalent interactions. This hierarchical building principle endows many biological materials with remarkable mechanical strength, anisotropy, flexibility and optical properties, such as structural colour. These features make nanofibrillar biopolymers interesting candidates for the development of strong, sustainable and biocompatible materials for environmental, energy, optical and biomedical applications. However, recreating their architecture is challenging from an engineering perspective. Rational design approaches, applying a combination of theoretical and experimental protocols, have enabled the design of biopolymer-based materials through mimicking nature's multiscale assembly approach. In this Review, we summarize hierarchical design strategies of cellulose, silk and chitin, focusing on nanoconfinement, fibrillar orientation and alignment in 2D and 3D structures. These multiscale architectures are discussed in the context of mechanical and optical properties, and different fabrication strategies for the manufacturing of biopolymer nanofibril-based materials are investigated. We highlight the contribution of rational material design strategies to the development of mechanically anisotropic and responsive materials and examine the future of the material-by-design paradigm.

纳米原纤维材料（例如纤维素，甲壳质和丝绸）是高度有序的体系结构，是通过将重复的结构单元自组装为高阶结构而形成的，这些结构通过非共价相互作用而得以稳定。这种分层的构造原理使许多生物材料具有出色的机械强度，各向异性，柔韧性和光学特性，例如结构颜色​​。这些特性使纳米原纤维生物聚合物成为开发用于环境，能源，光学和生物医学应用的坚固，可持续和生物相容性材料的有趣候选者。但是，从工程角度来看，重新创建其体系结构具有挑战性。合理的设计方法，结合了理论和实验方案，通过模仿自然界的多尺度组装方法，实现了基于生物聚合物的材料的设计。在这篇综述中，我们总结了纤维素，丝绸和几丁质的分层设计策略，重点是纳米约束，原纤维取向和2D和3D结构中的对齐方式。在机械和光学特性的背景下讨论了这些多尺度体系结构，并研究了用于制造基于生物聚合物纳米原纤维的材料的不同制造策略。我们重点介绍了合理的材料设计策略对机械各向异性和响应性材料开发的贡献，并探讨了“按设计设计”材料范式的未来。丝和几丁质，着眼于纳米约束，2D和3D结构中的原纤维取向和排列。在机械和光学特性的背景下讨论了这些多尺度体系结构，并研究了用于制造基于生物聚合物纳米原纤维的材料的不同制造策略。我们重点介绍了合理的材料设计策略对机械各向异性和响应性材料开发的贡献，并探讨了“按设计设计”材料范式的未来。丝和几丁质，着眼于纳米约束，2D和3D结构中的原纤维取向和排列。在机械和光学特性的背景下讨论了这些多尺度体系结构，并研究了用于制造基于生物聚合物纳米原纤维的材料的不同制造策略。我们重点介绍了合理的材料设计策略对机械各向异性和响应性材料开发的贡献，并探讨了“按设计设计”材料范式的未来。