Three Dimensional Numerical Simulation, Design and Structural Optimization of Pneumatically Actuated Cell Stretching Device
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Utilizing biomimetic mechanical forces for differentiation of stem cells toward osteogenic, cardiomyocytes and other cell types is a technique that has been applied increasingly in recent years. Different types of apparatuses and devices are being designed and fabricated in order to accurately direct these mechanical forces onto stem cells in both 2D and 3D configurations. In this thesis, a novel and easy-to-fabricate structure is designed to provide mechanical stimulation of cells in a cell culture environment. This is facilitated by means of pneumatic actuation. The pneumatic actuation of the hyperelastic PolyDiMethylSiloxane (PDMS) material directs a tensile strain on cell population in the environment. The structure has been previously designed at Micro- and Nanosystems research group to provide equiaxial strain. In this study, steps are taken to modify the structure to provide not only the equiaxial strain, but also uniaxial strain for stimulation of stem cells in vitro. As the primary objective of this study, the modified structure makes two aforementioned types of mechanical strain achievable. In this study, computational model of the device is developed based on Neo-Hookean hyperelastic material model using COMSOL Multiphysics 5.1 software. Finite element based model of the structure is implemented and numerical simulations are performed to analyze stress and strain under applied vacuum. The structure is then optimized based on various geometric parameters to improve the performance of the device according to defined requirements and objective functions. The optimized structure is then further analyzed to completely identify the performance characteristics of the device. Two different geometries are proposed for the device structure. The designed structures are demonstrated to provide relatively good performance based on requirements. The structures provide rather high strain magnitude in case of equiaxial strain. In case of uniaxial strain, they provide a relatively high average value for the first principal strain and a low average value for the second principal strain. The structures also exhibit an almost uniform uniaxial strain field. The results indicate an acceptable performance of the devices in both cases.