Natural Bouligand structures are formed by the unidirectional assembly of nanofibers into layers that then spiral-stack, endowing various biological materials with exceptional mechanical properties. A profound understanding of the structure-property relationship of Bouligand structures and the transcription of this knowledge into artificial systems holds promise for advancing the development of fiber-based structural materials.
Recently, a team led by Academician Shuhong Yu from the University of Science and Technology of China (USTC) addressed the issue of weak interfaces in fiber-based materials. They conducted a systematic study on the multi-level reconfigurable fiber interface design of biomimetic Bouligand structures based on the concept of moderately ordered mechanical design of network-state nanofibers. They proposed the concept of bionic moderately ordered Bouligand structures and constructed high-performance biomimetic Bouligand structure materials with dynamically reconfigurable fiber interfaces. Their research findings were published in Science Advances.
Dr. Siming Chen, the first author of the paper and an associate researcher at USTC, explained that unlike traditional chemical cross-linking for biomimetic interfaces, the fiber bridging interlocking structure and three-dimensional hydrogen bond network created by this moderately ordered fiber design can dynamically adapt to external loads through fiber sliding and hydrogen bond rupture-reconstruction, thereby achieving the purpose of dissipating energy extensively. The unique biomimetic interface and moderately ordered structural design will provide new insights and guidance for the high-performance assembly and application of network-state nanofibers.
The spatial orientation of nanofibers is crucial in determining their arrangement. Rational design of fiber spatial arrangement to regulate molecular-scale interactions between fibers helps optimize interface deformation modes and load transfer capabilities, thereby enabling the bottom-up design of biomimetic fiber-based structural materials with excellent macroscopic mechanical properties. Researchers used network-state bacterial cellulose nanofibers as model units, uniaxially stretching their gel films to induce nanofiber spatial orientation. However, it was difficult experimentally to determine the effect of orientation on the microscale mechanical behavior of fiber networks. Based on this, researchers conducted large-scale molecular dynamics simulations based on fiber models with different orientation angles. The results showed that moderately ordered structures can optimize the dimension of the hydrogen bond network and facilitate the bridging interlocking of cellulose molecular chains on the model cross-section, demonstrating a more robust toughness section than a completely ordered structure.
Researchers used scanning electron microscopy, graph theory analysis, and polarized light-microloading techniques to conduct imaging studies, confirming the network characteristics of nanofibers within the membrane layer and the derived fiber bridging interlocking and three-dimensional hydrogen bond network interfaces significantly promote fiber micro-motion, stress transfer, and energy dissipation. Furthermore, combining spiral stacking and hot pressing densification, researchers can transfer the behavior of nanofiber interfaces within the membrane layer to the macroscopic scale, producing biomimetic moderately ordered Bouligand structure materials. Systematic investigations of mechanical properties showed that the constructed biomimetic materials exhibit outstanding mechanical performance and dimensional stability, with promising prospects in fields such as the repair and replacement of energy-dissipating fibrous cartilage in the biomedical field.
According to Siming Chen, overall, the bionic moderately ordered Bouligand structure mediated by fiber bridging interlocking and three-dimensional hydrogen bond networks will provide important insights for the mechanical enhancement design of nanocellulose materials and promote the assembly, high-performance, and application of network-state nanofibers.
Related Paper Information: https://doi.org/10.1126/sciadv.adl1884
