A Study On The Stress Relaxation Properties Of Cells

Cell is the basic unit of organism and also a complex mechanical system.In the life course of a cell,mechanical force and three-dimensional microenvironments are constantly stimulating and affecting the cell.At the same time,the cell displays a unique mechanical response by changing its behavior.As an essential property of cells,viscoelasticity determines the degree of cell deformation induced by force and environment,and then affects its structure and function.Research on the changes of viscoelastic properties in cell physiological activities will not only help to explore the internal mechanism of cell behavior,but also bring new opportunities to cell identification,drug evaluation,and cancer detection in medical diagnosis and treatment.As the inherent mechanical behavior of viscoelastic materials,creep and stress relaxation are different manifestations of the same physical phenomenon.In this thesis,different types and states of cells are taken as the research object,and their stress relaxation characteristics are studied.The specific content and results are as follows:(1)Based on membrane theory and cell indentation experiments,a mechanical model of spherical cells and a mechanical model of semi-ellipsoidal cells were constructed,and material parameters were obtained by indentation tests on two macroscopic spheres(latex balls and PVC balls)to verify the applicability of the theoretical model.(2)The stress relaxation model based on the steady-state creep theory was used to fit the stress relaxation curves of different cells,and the applicability of the model for characterizing the stress relaxation behavior of cells was verified.(3)By comparing the differences in the parameters of the stress relaxation characteristics,the internal mechanism of the different behaviors of cells was analyzed,and a new way of identifying the type and state of cells was shown.(4)Abaqus was used to construct a two-dimensional finite element model of the cell's indentation and relaxation process,and the mechanical response of the cell was obtained by simulation.Based on the control variable method,the different effects of the stiffness of the substrate,the radius of the indenter,and the parameters of the cells on the stress relaxation characteristics of cells were analyzed.