Hydrogels, widely used for contact lenses, are a class of materials that consists of both fluid and solid components. The aqueous fluid phase is supported by a solid polymer matrix. In this study, we characterize the water transport characteristics of an Etafilcon-A (copolymer of 2-hydroxyethyl methacrylate and methacrylic acid) membrane. A flow rate-controlled permeameter consisting of a syringe pump, membrane holder, pressure transducer, and tubing was developed and used to measure the pressure drop across a flat membrane (average thickness similar to 686 pm +/- 40). The relation between velocity and pressure drop was measured. These data were fit to rigid media and biphasic models of I-D flow to determine hydraulic permeability, k = 1.80 X 10(-14) m(4) /N s. The results provide insight into the fluid flow properties of this hydrogel under low flow and low pressure conditions (< 3 kPa). Physiological implications of these measured parameters on flow and deformation across the lens due to blinking are discussed. (c) 2007 Wile), Periodicals, Inc.