Mechanical and viscoelastic characterization of polyvinyl alcohol (PVA) hydrogel membranes using the shaft-loaded blister test

Abstract

The shaft loaded blister test was used as an alternative method to develop three different tests to study the mechanical properties of polyvinyl alcohol (PVA) hydrogel on thin circular membranes and see how the number of freeze/thaw cycles used in their fabrication would affect the stiffness of the material. The first test consisted of a quasistatic experiment, the membrane was clamped along its periphery and a spherical indenter connected to the load cell of the instrument was then used to apply a deformation. The second test was a creep test under the same geometric configuration, but in this case the load consisted of the weight of a stainless steel ball, and a long focal microscope was used to monitor the deformation. This allowed the study of the material behavior over a long span of time. Finally, the third experiment was a cyclic loading test that allowed the study of the dynamic properties of the material over a brief span of time, as well as the energy storing capabilities of the same. By analyzing the results for samples fabricated with 2, 3 and 4 freeze/thaw cycles in their processes, we demonstrated that the increase of the number of these cycles increased the material stiffness, and also that as the quantity of cycles were increased the material behaved more as an elastic solid and less like a viscous fluid. The results of these tests were then applied to the design of asample fixture capable of holding a membrane for collagen cleavage and cell differentiation studies. In both cases the goal is to study the sample biomechanical behavior while a different set of stresses are applied to various regions of the membrane.