Model development for numerical simulation of the behaviors of pH-stimulus responsive hydrogels

Abstract

The modulation of the swellng ability of the hydrogels in respons to environmental stimuli (e.g. electrical, pH, temperature or ionic strength) enables us to dynamically control the conversion of electrochemical energy into mechanical energy, thereby obtaining effective diffusivity or permeability of the solutes or performing mechanical work. A chemo-electro-mechanical model, termed Multi-Effect-Coupling of pH Stimulus (MECpH), is developed to simulate the deformation characteristics of the pH-stimulus responsive hydrogel. This model accounts for the coupling effects between the ionic diffusion, electrostatic potential, and mechanical deformation of both the hydrogel and bathing medium. The model also incorporates the relationship between the concentrations of the ionizable groups fixed to the hydrogel matrix and the diffusive hydrogen ion. The MECpH model is solved numerically via the meshless Hermite Cloud method with Newton-Raphson method as the iterative procedure to simulate the deformation characteristics (i.e. swelling and bending) of the pH-stimuli responsive hydrogel under the application of chemical or electrical stimuli.