The Research On Specific Adhesion Mechanics Of Media

Specific adhesion of cell-cell and cell-extracellular is a ubiquitous biological phenomenon in biological systems.Specific adhesion is caused by the formation of non-covalent bonds between transmembrane receptor molecules and ligand molecules on the extracellular matrix,it is targeted.Specific adhesion involves the coupling of random response(open or closed)of molecular bonds and deformation of elastic body,and plays an important role in many biological processes and functions,including embryonic development,tissue metabolism and injury treatment.Experiments and theories have shown that the cell is a complex dynamic structure,mainly composed of the cell membrane,cytoplasm and nucleus.It not only exhibits elasticity,but also exhibits creep and relaxation,and increasing modulus under large deformation,which have a great influence on specific adhesion.Currently,most of the researches on specific adhesion consider the half-space geometric model and linear elastic constitutive model,few researchers have considered the effect of elastic media size and nonlinear properties of materials on specific adhesion.Therefore,the paper proposed a specific adhesion model between finite size elastic bodies to characterize specific adhesion behavior occurred in the biology.Through theoretical analysis or finite element method,it is concluded that there is an optimal elastomer size there is an optimal elastomer size that corresponds to the maximum adhesion strength between elastomers;the increase of loading rate and viscosity coefficient is helpful to improve the adhesion strength between elastomers,The slower the loading rate the more obvious the creep effect of molecular bonds,thus reducing the adhesion strength between interfaces;the hardening behavior of the fiber structure in the elastic body can improve the pull off force,while the inclination of the fiber orientation is one of the reasons for the migration of the elastomers.The following main research contents were included:Firstly,the specific adhesion model between finite sized elastic bodies was established to characterize specific adhesion behavior of elastic body.By using the solution method of cantilever beam under arbitrary load in elasticity theory,the differential-integral governing equation of molecular bond displacement at adhesion interface under external force is given,and the numerical solution was obtained under the steady state or dynamic state.The influence of size,stiffness of elastic body and the loading rate on specific adhesion behavior was quantitatively analyzed.In addition,the finite element method was also used to solve the same adhesion problem under the steady state and the results obtained by the two methods are consistent.The finite element method can be used to implement a wide range of material constitutive equations and to study cell adhesion.Secondly,considering the characteristric of the fiber orientation and the hardening behavior of the skeleton in cells and large deformation of cell.First of all,based on the framework of continuum mechanics,the paper studies how to implement the hyperelastic constitutive theory by the finite element method and derived the tangential stiffness matrix of hyperelastic materials and developed user subroutine of approximately incompressible hyperelastic constitutive model as well as verified the effectiveness of the subroutine through the numerical example.Then,the transverse isotropic superelastic constitutive model was applied to elastic body,and the specific adhesion model between hyperelastic body and elastomer was established.The effects of fiber performance and fiber orientation in the cellon the specific adhesion behavior between elastomers were studied.Finally,in view of the creep and relaxation behavior of cells,the finite element implementation process of viscoelastic and visco-hyperelastic constitutive model is analyzed and derived in detail,and the reliability of the finite element implementation is verified by some examples.The viscoelastic constitutive model is very important for studying the mechanical behavior of cells and soft tissues,we established the specific adhesion model between the viscoelastic body and the elastic body and studied the effects of loading rate and viscosity coefficient on the specific adhesion behavior.