Loading velocity dependent permeability in agarose gel under compression

A new approach for characterization of agarose gel permeability under compression at different loading velocities is proposed. Uniaxial compression tests on thin agarose gel specimens in a rigid porous confinement cell immersed in a water bath are undertaken. The equilibrium response of the gel, which is assumed to be achieved under extremely low-loading velocity (of the order of tens nanometers per second) is considered to be the response of the hydrated gel scaffold. The water exudation behavior from the agarose gel was extracted from the load-displacement response under various loading velocities by subtracting the equilibrium response. It was found that the pressure on water in the gel is not a linear function of loading velocity or volume flow rate and therefore, the permeability of agarose gel was observed to vary with deformation and water flow velocity. In addition, it was inferred from the analysis that at low velocities and large strain levels the gel permeability dominates the compression behavior, and at higher velocities and small strain levels the viscosity of the hydrated matrix may contribute to the load. Finally, permeability variation in agarose gel at different loading velocities is attributed to the two states (free water and bound water) of water molecules in the gel.