Transversely isotropic freeze-dried PVA hydrogels: Theoretical modelling and experimental characterization

Polyvinyl alcohol (PVA) hydrogels have recently emerged as suitable bio-mimetic materials for various applications such as scaffold engineering, controlled drug delivery and cell culture. In this paper, PVA hydrogels with different concentrations of PVA have been synthesized using uni-directional freeze-drying technique. Unidirectional freeze-dried hydrogels exhibit transverse isotropy. The microstructurally aligned porous architecture of the hydrogels has been confirmed from Scanning Electron Microscope (SEM) images. Experiments have been conducted to characterize their transversely isotropic and viscoplastic behavior. These materials have been observed to behave non-linearly when subjected to compressive mechanical loads. Theoretical models are proposed to predict the mechanical behavior of the transversely isotropic microstructurally aligned hydrogels. The first model is a visco-elasto-plastic model that incorporates the effect of non-Newtonian behavior effectively using a fractal dashpot. The second model is an anisotropic finite viscoplastic model. The predictions of both the models are found to be in close agreement with the experimental results.