Finite element analysis of strain distribution on a PDMS membrane

Mechanotransduction and mechanosensing are two main mechanisms by which the cells respond when exposed to mechanical stimuli. These types of cellular responses can be investigated using dedicated cell stretching devices. However, strain uniformity which greatly affects the collected data's accuracy and reliability is the main challenge when using these devices. In this thesis, a polydimethylsiloxane (PDMS) membrane with uniform strain distribution has been designed and fabricated. Parametric finite element analysis (FEA) has optimized the membrane's size and shape. The FEA study is performed by modeling the problem as a displacement-controlled problem, where strains up to 20% have been examined. Hole diameter, membrane thickness, chamfer length, and sidewall thickness are the parameters that are optimized. A uniformity index of 90 % has been achieved, equivalent to an 80% improvement compared to commercial membranes. Suitable hyperelastic material model parameters are calculated to model the nonlinear behavior of the membrane materials under uniaxial tension. A five-parameter Mooney-Rivlin material model is shown to be the most suitable material model when compared to the experimental data. The issues related to the failure of the membranes have been solved by tailoring material properties by changing the ratio of the cross-linker to the base material and curing time and temperature. A PDMS with a ratio of 0.75:10 cured at 60°C for four hours fulfills the cell stretching requirements.