Swelling of pH-sensitive hydrogel pressure vessel under altered-pH coupled with inflation, extension, and torsion

pH-sensitive hydrogels are a unique class of hydrophilic polymers with fascinating characteristics that can be harnessed for future innovative applications such as drug delivery and tissue engineering. To employ hydrogels in various applications, the swelling behavior of these materials are required to be well studied. In this research, the mechanical swelling response of pressure vessels composed of the pH-sensitive hydrogel is studied in response to pH-variation as well as combined inflation, extension, and torsion loading. In this regard, an analytical solution is proposed to inspect this problem, which is utilized as a common experimental protocol for the characterization and modeling of polymeric materials. Evaluating the analytical solution, a 3D finite element study was conducted for the same problem. The consistency of the results in both FE analysis and the proposed method confirms the accuracy of our method. However, considering the much lower computational cost of analytical solutions compared to FEM (< 1%), proposing such solution for this complex problem is of great interest. Therefore, the developed solution can be employed as a beneficial tool for calibrating the material parameters, and examining the swelling behavior of pH-sensitive hydrogels under various factors such as mechanical properties, geometric dimensions, and loading parameters.