permeabilite

Permeability is a property of a material that indicates the ease with which a permeant—such as a fluid, gas, or solute—can pass through the material when driven by a gradient of pressure, concentration, temperature, or electrical potential. It is influenced by the nature of the permeant, the microstructure of the material, and environmental conditions. Permeability is related but not identical to diffusivity.

In geoscience and hydrology, intrinsic permeability, often denoted k, measures the ability of a porous medium to transmit fluids. Measurements are in square meters or darcies. The rate of flow also depends on fluid properties; hydraulic conductivity combines k with fluid density and viscosity. Darcy's law describes laminar flow through porous media and is used to model groundwater movement and oil recovery. Porosity, pore size, and connectivity control permeability.

In biology and membranes, permeability refers to the selective passage of substances across membranes. Biological membranes are selectively permeable, permitting some molecules to diffuse freely while requiring transport proteins for others. Permeability governs processes such as osmosis, nutrient uptake, and signaling.

In materials science, polymer and membrane engineers study permeability to design barriers against gases and liquids. Permeability P is the product of diffusion coefficient D and solubility S. Temperature, pressure, and material free volume affect P. Higher D and S yield higher permeability, which is critical for packaging and protective coatings.

Applications include groundwater protection, catalysis, filtration, packaging, and medical devices. Permeability is a central concept across disciplines, linking structure to transport behavior.