Water transport through reconstituted collagen hollow‐fiber membranes

The hydraulic permeability κ of reconstituted collagen hollow‐fiber membranes has been determined from measurements of the volumetric flow rate of aqueous solutions through the membrane for various pressure differences across the membrane. Increasing the ultraviolet crosslinking time during manufacture of the membrane markedly decreases κ, whereas decreasing the pH of the aqueous solution increases κ. Applying a tensile strain of only 10% along the fiber axis decreases κ approximately fivefold. These results are in good agreement with those expected from a recent model of the membrane structure in which collagen fibrils, oriented preferentially along the hollow‐fiber axis, bend between crosslinks to accept water in a pore structure. If the average fibril volume fraction and diameters are known, estimates can be made of κ. These estimates, based on direct small‐angle x‐ray scattering measurements of fibril diameters, are in good agreement with the measured κ values.