Study On Friction Characteristics Of Water Lubricated PAM-PAM/SA Double Layer Hydrogel For Biomimetic Cartilage

As a repair material of articular cartilage,excellent friction properties are particularly important.Researchers often ignore the friction properties when pursuing high mechanical properties,and lack of systematic research on the friction and wear properties of hydrogels.Therefore,this paper is inspired by the natural articular cartilage layered structure to prepare double-layer hydrogel,in order to achieve high load and low friction performance,and even reach the level of natural articular cartilage.In this paper,polyacrylamide single network（PAM）hydrogel,polyacrylamide/sodium alginate semi-interpenetrating（Semi-IPNPAM/SA）network hydrogel and Ca²⁺crosslinked sodium alginate/polyacrylamide（PAM/SA）double network hydrogel were prepared.The microstructure of hydrogel was observed by scanning electron microscope（SEM）.It was found that the two networks of PAM and SA did not form chemical bonds,but the two networks formed interpenetrating network（IPN）hydrogel by entanglement.Through the test of the mechanical properties of PAM/SA double network hydrogel,the compression strength of PAM/SA hydrogel is up to1.65MPa,which is more than 2 times that of single network hydrogel,the elongation at break can reach 1800%,the tensile strength can reach 0.75MPa,and has high toughness.Secondly,by simulating the layered structure of natural articular cartilage,the double-layer hydrogel was prepared by means of the low friction of PAM hydrogel and the high load-carrying capacity of PAM/SA double-network hydrogel（the upper layer is single-network PAM hydrogel and the lower layer is PAM/SA double-network hydrogel）.With the help of the viscosity and interfacial force of PAM hydrogel,the bilayer structure with solid and stable interface can be obtained.First of all,the mechanical properties of PAM-PAM/SA double-layer hydrogel are tested.The compressive strength of PAM-PAM/SA double-layer hydrogel can reach 1MPa,and the compression modulus can reach 0.22MPa,which shows good mechanical properties.Secondly,the friction and wear properties of PAM-PAM/SA double-layer hydrogels were studied,and the effects of different pressures,speeds and other conditions on the friction and wear properties of hydrogels were studied.The results show that the friction coefficient can be as low as 0.032,and compared with the single-layer structure,it can achieve low friction under large load.Finally,the self-bending properties and interfacial strength of PAM-PAM/SA bilayer hydrogel were investigated.The results show that it has a good application prospect as a cartilage repair material.