In silico investigation on the role of microfiber architecture in the transient swelling of fiber-reinforced hydrogels

Hydrogels are polymeric materials that absorb solvent and swell in a time-dependent manner, known as transient swelling. Despite numerous modeling efforts, the effects of reinforcing microfiber orientation and complex distributions on the transient swelling behavior of hydrogels have not yet been considered. In this study, a finite element approach is employed to analyze the time-dependent deformation and mechanical response of hydrogels by incorporating a diffusion equation and considering the influence of microfiber presence, orientation, and distribution over time. The strong agreement between the modeling results and experimental data from prior studies demonstrates the model’s calibration capability. The time-dependent swelling behavior of hydrogels was modeled under three microfiber configurations: perfectly aligned, uniform plate, and uniform volumetric. The results showed that in fiber-reinforced hydrogels, solvent uptake and deformation were lower along the fiber direction and higher in the perpendicular direction, compared with hydrogels without fibers. Greater variation in microfiber orientation led to more restricted solvent absorption; thus, after 12 h, the volume of the non-reinforced hydrogel was 1.33 times that of the hydrogel with a uniform plate microfiber configuration. Finally, bilayer structures consisting of hydrogel-hydrogel and hydrogel-elastomer composites were designed with different microfiber orientations in the hydrogel layer.