Research On The Structure And Properties Of Graded Micro-nanofiber Structure Hydrogels Imitated Octopus Tentacles

In the modern society with the continuous progress of science and technology,human beings pursue a more efficient and comfortable way of life.with the emergence and research of a variety of flexible materials,the application of flexible materials has begun to infiltrate into people’s daily production and life,such as software robot field,automobile field,hydraulic engineering and so on.The main characteristic of flexible material is that it can withstand a certain external force,produce stretching,bending and torsion deformation without being destroyed,and can maintain the performance.Compared with the traditional rigid structure,it can achieve good interaction with the complex environment.From this point of view,excellent mechanical properties are very important for flexible materials,and the strengthening and toughening of flexible materials is an important prerequisite for its application value.As a kind of material with high water content and soft properties,hydrogel has a good application prospect,but the traditional hydrogel has low mechanical strength and poor toughness,which greatly limits the application of hydrogel in many fields.The muscle fiber structure with hierarchical and directional arrangement of octopus tentacles in nature gives us inspiration.The biomimetic structure is introduced into the microstructure of flexible materials to improve the mechanical properties of flexible materials.In this paper,two works have been done to improve the strength and toughness of hydrogel flexible materials.In the first work,we selected sodium alginate（SA）and polyvinyl alcohol（PVA）as raw materials for hydrogel synthesis.By adjusting the traditional interpenetrating network PVA/SA hydrogel molding process and introducing the limited drying method,we prepared PVA/SA composite hydrogel with octopus tentacle graded micro/nanofiber structure.The PVA/SA hydrogel with biomimetic structure shows obvious mechanical anisotropy,and the maximum tensile stress,elastic modulus and fracture energy are about 4.87,7.74,5.23 times that of the traditional PVA/SA hydrogel.And the biomimetic structure PVA/SA hydrogel has good recycling ability and self-recovery properties,and the mechanical properties have been greatly improved.In order to further establish the application of hydrogel as a flexible material in the field of intelligent materials,the second work was carried out.On the basis of the graded micro-nanofiber structure PVA/SA hydrogel,Fe₃O₄magnetic particles were introduced into the hydrogel network by in-situ deposition method to prepare Fe₃O₄-PVA/SA magnetic composite hydrogel.The axial tensile mechanical experiments,cyclic loading-unloading experiments,equilibrium swelling properties and magnetic properties of magnetic hydrogels were investigated under the preparation conditions of different total iron ions(Fe²⁺and Fe³⁺)and Na OH concentrations.The change rules of magnetic hydrogels under different preparation conditions were obtained by analyzing the experimental data.When the total amount of iron ions(Fe²⁺and Fe³⁺)is 2 M,the maximum tensile strength is 15.227MPa.With the increase of Na OH concentration,the tensile strength,elastic modulus and fracture energy of magnetic hydrogels increased gradually.Under different conditions,the magnetization of Fe₃O₄-PVA/SA magnetic hydrogels increases with the increase of external magnetic field,the maximum saturation magnetization（Ms）is about 1.571 emu/g at 2 M Na OH,and the maximum saturation magnetization（Ms）is about 1.614 emu/g at 2 M iron ion concentration,which shows superparamagnetism.It lays a good foundation for the application of hydrogel flexible materials in the field of intelligence.