For the first time, researchers have discovered a self-healing mechanism for giant panda teeth

giant panda is a typical representative of the animal world's fangs, 99% of its food is bamboo, strong teeth are giant pandas eat bamboo. Recently, a team led by Liu Zengqian, Ph.D., Material Fatigue and Fracture Laboratory, Institute of Metals, Chinese Academy of Sciences, found that giant panda tooth enamel can respond significantly at the micron nanoscale after deformation and damage. The findings were published in the Journal of Biological Materials on 11 January 2019, 28 September 2018 and Advanced Materials on 5 June 2018.
Speaking about the discovery, Liu said the main benefits are the high density of organic-rich micro-interfaces and clever tissue design of giant panda tooth enamel, where inorganic mineral units that make up tooth enamel are arranged at micron scales along the bite direction, while the interface between minerals is filled with natural organic matter. The deformation, damage and automatic reply of tooth enamel are realized by interface as medium, and water molecules can promote self-healing effect significantly, which is mainly due to the change of natural organic matter in tooth enamel interface under hydration conditions, such as swelling, increase of polymer chain flexibility, and decrease of glass transition temperature.
Liu Zengqian research team, on the basis of systematically clarifying the form, principle and function and mechanism of natural biological material gradient design, first put forward the concept and design principle of the orientation gradient of the new material structure, and expounded the gradient structure orientation and re orientation to the aesthetics. The optimization of performance, and the improvement of material mechanical properties of bionic design of new ideas, that is, by controlling the orientation of micro-organizational structure to achieve the material's local stiffness, strength and toughness of the optimal distribution and matching, so as to improve the overall mechanical properties of the material.
same time, the research team found for the first time that the re orientation of the structure of the material during loading can not only improve its deformation ability, but also provide an effective way to improve the comprehensive performance of science. By adjusting the orientation relationship between its own organizational structure and the external forces, the stiffness and strength of the material gradually increase under stretch conditions, while the crack expansion path gradually deviates from the direction of maximum positive stress, so that fracture toughness can be enhanced simultaneously, while under compression conditions, the mechanical stability and crack toughness of the material also show a trend of increasing synchronously. Therefore, the material can use limited deformation to achieve its stiffness, strength, stability and fracture toughness of the overall improvement, and these properties themselves often reflect the relationship between mutual constraints.
In addition, in response to the natural biological materials that have been mainly used as weapons in the long-term "arms race" in nature, the research team also clarified its main types, forms and organizational characteristics, and revealed the performance optimization mechanism of its simultaneous realization of attack and protection effects from the perspective of materials science and aesthetics. The principles of common bionic material design are refined, including multi-scale design from macro-shape and size to micro-nano-organizational structure, spatial gradient design to match local stress state, adaptive and self-healing function design, and supporting system design.
Currently, the research team is working to use the above principles to design and develop new bionic materials, and has made new progress in human teeth matching bionic composite denture materials, high-strength high-conductive contact materials, etc., and is expected to significantly improve the performance and use of materials to better meet the needs of practical applications. (Source: Science Network Shen Chunlei)
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