New progress in research on biomechanics and biomimetic materials of the Institute of Metals, Chinese Academy of Sciences

Although biomaterials are assembled from relatively simple components with relatively poor performance under relatively mild conditions, they exhibit excellent overall mechanical properties and functional properties, which are mainly due to their complex and ingenious organization spanning different scales. Structure, especially the unique deformation and fracture mechanism and toughening mechanism brought about by this.

Recently, Dr. Liu Zenggan, Ph.D., Biomechanics and Biomimetic Materials Research Group, Materials Fatigue and Fracture Laboratory, Institute of Metal Research, Chinese Academy of Sciences, led the research team under the “Introduction of Excellent Scholars” project of the Institute of Metals, based on the idea of ​​“Knowing Nature – Understanding Nature – Learning Nature” From the perspective of materials science, it reveals the structure of typical biomaterials in nature and the key mechanism that gives them excellent performance. It refines the optimal design principles of the commonality between natural and man-made materials, and then applies them to man-made material systems to realize man-made materials through bionic design. Performance is optimized to improve and enhance its ability to withstand fatigue fracture.

On the basis of systematically expounding the form and principle of gradient design of natural biomaterials and their functions and mechanisms, the research group first proposed the concept and design principle of new material structure structure orientation gradient, and established the organizational structure orientation and deformation process. The systematic quantitative relationship between structural reorientation and mechanical properties of materials occurs, clarifies the optimization mechanism of gradient structure orientation and reorientation on mechanical properties, and refines the new idea of ​​bionic design to improve the comprehensive mechanical properties of materials, namely by controlling microstructure. The structural orientation achieves the optimal distribution and matching of the local stiffness, strength and toughness of the material, thereby improving the overall mechanical properties of the material. At the same time, the research team found for the first time that the reorientation of the structure of the material during the loading process can not only improve its deformability, but also provide an effective way to achieve the improvement of comprehensive mechanical properties, as shown in Figure 1. By adjusting the orientation relationship between its own structure and the external force, the stiffness and strength of the material under tension are gradually increased, and the crack propagation path gradually deviates from the direction of the maximum normal stress, so the fracture toughness is simultaneously enhanced; Under the conditions, the mechanical stability and splitting toughness of the material also show a trend of increasing simultaneously. Therefore, the material can achieve an overall improvement in stiffness, strength, stability and fracture toughness with limited deformation, and these properties themselves often exhibit a mutually constrained relationship.

In addition, the research group elucidated its main types, forms and organizational structure characteristics for the natural biological materials mainly used as weapons in the long-term "arms race" of nature. From the perspective of material science and mechanics, it reveals its simultaneous attack and protection. The performance optimization mechanism of the effect, and refine the common bionic material design principles, including macroscopic shape and size to multi-scale design of micro-nano-structure, spatial gradient design matching local stress state, adaptive and self-repair function design , as well as supporting and supporting system design. In particular, the study found that, as a typical natural weapon material, giant panda enamel, which is mainly composed of inorganic minerals, can undergo significant automatic recovery at the micro-nano scale after deformation and damage, mainly due to its high density and richness. The microscopic interface of organic matter and the ingenious structure design, that is, the inorganic mineral units constituting the enamel are regularly arranged along the occlusion direction at the micro-nano scale, and the interface between the minerals is filled with natural organic matter, as shown in Fig. 2. The deformation, damage and auto-recovery of enamel are realized by the interface medium. Water molecules can significantly promote the self-repairing effect, which is mainly attributed to the natural organic matter in the enamel interface under hydration conditions. The swelling, the flexibility of the polymer chain, and the decrease in the glass transition temperature occur.

The above research results can provide useful enlightenment and guidance for the design of new high-performance artificial bionic materials. At present, the research team is working on the design and development of new biomimetic materials by using the above principles, and has made new progress in human tooth matching bionic composite denture materials, high-strength and high-conductivity contact materials, and is expected to significantly improve the performance and use of materials. To better meet the needs of practical applications.