Viscoelastic and poroelastic relaxations of polymer-loaded gels

Gel layers are prevalent in many applications including water purification, fuel cells, tissue engineering and drug delivery. In these materials, their performance is closely linked to controlling transport of solutes such as solvent or polymer. Thus, understanding the critical time- and length-scale that regulate solute transport will enable development of membrane materials with the desired performance. In this contribution, we present the Poroelastic Indentation Relaxation (PRI) approach in quantifying the viscoelastic and poroelastic relaxations of geometrically-confined hydrogel layers. We demonstrate this indentation-based measurement approach in characterizing several materials properties including diffusion coefficient, shear modulus, and average pore dimensions of the hydrogel independent of the extent of geometric confinement. Additionally, we present a relaxation model that accounts for the viscoelastic and poroelastic contributions to the total relaxation process. Finally, we show that the PRI approach can quantify diffusion of solvent and polymer solution in a single test simply by changing the extent of deformation.