Hydraulic permeability of agarose gels

A new technique was developed to measure the hydraulic permeability of reinforced gel membranes and allows calculation of the Darcy permeability (κ) of the gel. It was applied to agarose with concentrations ranging from 2.0 to 7.3%. To create membranes that would be thin enough to yield easily measured filtration rates at modest applied pressures and yet withstand handling, gels were cast on woven polyester meshes. The resulting membranes had thicknesses of 70–100 μm and a fractional open area of 0.32. To correct for the presence of the mesh, finite‐element solutions were obtained for the pressure field in the 3‐D region occupied by the gel. For the meshes used here, the hydraulic permeability of the reinforced membrane was calculated to be 0.47–0.55 times that for a layer of pure gel, the exact value depending on the thickness of the composite membrane. The principal determinant of κ was the agarose concentration, but there was a secondary effect of applied pressure. The Darcy permeability extrapolated to zero applied pressure (κ 0 ) varied from 616 nm 2 for 2.0% agarose to 22 nm 2 for 7.3% agarose. At a given gel concentration, the value for κ 0 was as much as twice the value for κ measured at the maximum pressure difference of 20 kPa. This method can be adapted to a variety of other gel materials.