Research On Synthesis And Bio-tribology Of Multi-layer Bionic Artificial Joint Material

Artificial joint replacement has become one of the important methods to treat joint diseases,but the wear and failure of artificial joints restrict their life.The contact surface of natural joints is covered with cartilage tissue,so that it can be effectively less impact and decrese worn during friction.Based on the structure of natural joints,we design a multi-layer bionic cartilage material.It has good properties on bio-tribology,which can reduce the friction and wear of the artificial joint,reduce the aseptic failure due to wear debris and improve the life of the artificial joints.We use polyvinyl alcohol(PVA),hydroxyapatite(HA)and polyacrylic acid(PAA)to prepare multi-layer bionic cartilage.Then we use chemical grafting on the surface of a hard-ultra-high molecular weight polyethylene(UHMWPE)substrate to construct a multi-layer biomimetic cartilage material.Multi-layer bionic cartilage has a porous three-dimensional network structure,and its interface is closely combined.Its internal crystallinity is high and there are many hydrogen bonds.It shows good swelling properties in both deionized water and bovine serum solutions.Multi-layer bionic cartilage exhibits good mechanical properties.The fracture strength of multi-layer bionic cartilage is 38.9 MPa,elongation at break is 545%,and elastic modulus is 1.75 MPa,and both performances are significantly higher than that of a single-layer hydrogel.Multi-layer bionic cartilage has better recovery property and can withstand multiple repeating stretches.The elasticity compressive modulus of multi-layer bionic cartilage material is about 4.47 MPa,which is much better than that of single layer of hydrogels.And multi-layer bionic cartilage is less deformable when subjected to external forces.Both the stress relaxation rate and the stress recovery of the multi-layer bionic cartilage increase with the increase of the strain.In terms of creep performance,the axial strain of multi-layer bionic cartilage material gradually increases with time,which fully complies with the three-term Voigt-Kelvin model.In dynamic rheological properties,the storage modulus is higher than the loss modulus under the change of frequency and temperature.The loss factor increases with the increase of frequency and remains stable with the increase of temperature.The storage modulus decreases with the increase of strain,and the loss modulus shows the opposite property,and its loss factor shows a nonlinear growth trend with the increase of strain.Compared with single-layer hydrogels,multi-layer bionic cartilage exhibits better static and dynamic properties.The sliding friction properties between multi-layer bionic cartilage material and Co Cr Mo ball and the natural cartilage under different loads,sliding speeds,and friction pairs.When coupled with the Co Cr Mo ball,the sliding friction coefficient increases with the increase of the load,and with the natural cartilage pair,it tends to decrease at first and then increase with the increase of the load.Under both pairs of fittings,their sliding friction coefficient shows a trend of rising first and then decreasing with increasing sliding speed.Under the same sliding conditions,the friction coefficient of multi-layer bionic cartilage material is better than that of single layer hydrogel and is close to that of natural cartilage.And by comparing the finite element modles to simulate the contact loads and deformations under different contact forms,we can see that soft-soft contact can effectively reduce the phenomenon of stress concentration,thereby reducing wear.