The Determination Of Hyperelastic Material Parameters And The Application In The Micropipette Aspiration Experiment Model

At present, the half-space model and the sphere model are mainly used in the mechanical model of micropipette aspiration experiment analysis. In order to verify the rationality of approximate solution of sphere model derived by Li Yongsheng etal,110methyl vinyl silicone rubber materials were selected. The material was made into the cylinder specimens. The uniaxial compression test was operated on each specimen by INSTRON5544testing machine. Substituting the experimental data into the Neo-Hookea, Mooney-Rivilin and Yeoh three constitution models, the respective constitution relation based on the small deformation assumption was obtained by Taylor series expansion method. Combining the experimental data and the constitutive relations, then, the corresponding material parameters of the above three models were nonlinearly fitted by the Origin software. The fitted nominal stress-strain curves were well agreed with the experiment results.In order to analysis the rationality of the material parameters, an asymmetric element model, in which the material parameters was represented by the fitting ones and the boundary condition was in accord with the experimental one, was created by the ABAQUS finite element software. Comparing the simulation nominal stress-strain relationships with the experimental data, the rationality of the material parameters obtained by the above three models was demonstrated. Micropipette aspiration experiment process was proceed with the different diameters of small globes specimens. The small globes specimens were absorbed by the steel tube (0=12mm, d=10mm). During the experiment, the pressure was applied by a manual pump; the suction length of a globe was measured by the laser displacement sensor; and the variation of the displacement signal image was recorded and observed by the DHVTC vibration test system. However, the DHVTC vibration test system only outputs the voltage signal; the experimental data should be converted into the corresponding force and displacement with the relative formula. The force-displacement curves obtained by the uniaxial compression experiments were converted into the corresponding nominal stress-strain curves through the formulations.The nominal stress and strain curves were used to solve the elastic modulus before calculating. Then substituting the elastic modulus into the elastic approximate equation of the micropipette aspiration and its approximate solution of the force-displacement relations were obtained by calculation. Then comparing the experiment data with this approximate solution, they were also well agreed with each other. This indicates that the elastic approximate solution of the micropipette aspiration is accurate to some extent, we can use it to analyze the micropipette aspiration of cell more precise.