Study On Mechanical Properties And Preparation Of Hydrogels With Directional Structure Based On Natural Cartilage Structure

Articular cartilage as an important part of human joints which has low elastic modulus,high deformability,and excellent lubrication and wear resistance can effectively dampen any impact and absorb shocks.Since the joint is the biological friction pair that the human body bears the largest load,the articular cartilage must withstand the constant friction caused by movement throughout life.Therefore,the articular cartilage will continue to wear and degrade,which leads to the occurrence of osteoarthritis.Finally,the function of joints can only be rebuilt by artificial joint replacement.But the contact forms of artificial implants are mainly"hard-hard"and"hard-soft",which cause poor wear resistance.It is urgent to carry out systematic research on"hard-soft"contact pair of articular cartilage to construct biomimetic articular cartilage material.Therefore,based on a systematic study of the multi-layer structure and mechanical properties of articular cartilage,bionic articular cartilage materials with directional structure are constructed,which is significant for improving the quality of life of joint replacements and promoting the development of the implant prosthesis manufacturing industry in China.The main research contents are as follows:In this paper,the cartilage of the bovine knee joint is taken as the research object,and the static mechanics,dynamic mechanics and bio-tribological properties are studied.The friction and lubrication mechanism of the"hard-soft"contact interface is analyzed.The relationship between the multilayer structure and the loading capacity is explored.The results show that the strain rate and the strain variable of articular cartilage is greater with the load increasing.The friction coefficient shows a trend of decreasing first,then increasing and decreasing again with the load increasing,which is because there is a mechanism of consumption and self-replenishment of the phospholipid bilayer in the surface amorphous layer.Under"hard-soft"contact conditions,the greater the loading speed is,the larger the deformation rate is.When the loading speed is0.3mm/s,the deformation rate of the superficial layer can reach 80%under the compression condition of articular cartilage.At the same loading speed,the deformation rate of different layers of articular cartilage is different.The superficial layer is the largest,the middle layer is the second largest,and the deep layer is the smallest.Compared with the unconfined cyclic compression test,the deformation rate of each layer of articular cartilage during confined compression test is large,and the deformation discontinuity during deformation process directly indicates that the articular cartilage has a hierarchical structure.Based on a systematic study of the layered structure of natural articular cartilage,bionic articular cartilage materials with directional structures was constructed to investigate the effect of directional distribution of nanoparticles on the static and dynamic mechanical properties of bionic articular cartilage materials.The results show that when nanoparticles are distributed vertically or horizontally in bionic articular cartilage material,the lower the Fe₃O₄ nanoparticle content is,the higher the tensile strength is,up to 2.209MPa,the lower the compressive elastic modulus is,and the larger the creep variable is.For the same Fe₃O₄ nanoparticle content,the compression elastic modulus of the bionic articular cartilage material with the nanoparticles distributed vertically is higher than that with horizontal distribution,and the tensile strength and creep variables are lower than those with horizontal distribution.When the content of Fe₃O₄ nanoparticles is the same,the deformation rate of the bionic articular cartilage material with the horizontal distribution of nanoparticles is the largest,Up to 45%,followed by the random distribution,and the deformation rate of the vertical distribution of Fe₃O₄ nanoparticles is the smallest.When the distribution direction of Fe₃O₄ nanoparticles is the same,the higher the content is,the smaller the deformation rate is.Compared with unconfined compression,the deformation rate of bionic articular cartilage materials is greater during confined compression,and the deformation is continuous.This shows that Fe₃O₄ nanoparticles distributed vertically have a supporting effect to resist deformation.