Porous Diffusion Barrier
A specialized material layer permits the passage of gases while obstructing the entry of liquid water. Integrating a hydrophobic membrane into a pressure sensor housing protects internal electronics from moisture ingress without sealing the reference port. The surface energy of the material prevents liquid droplets from wetting the pores.
Surface Tension Principle
Repulsion occurs because the surface energy of the polymer is significantly lower than the surface tension of water. Molecules of the fluid bead into spheres rather than spreading across the hydrophobic membrane. The interaction maintains a dry interface even when the component is submerged at shallow depths.
Permeability Function
Air molecules move freely through the microscopic openings to equalize internal and external pressures. If a hydrophobic membrane becomes clogged by dust or salt crystals, the resulting pressure differential creates a measurement offset. Effective venting depends on maintaining a clear path for molecular flow across the entire surface area.
Exclusion Limit
Protection remains effective until the liquid pressure exceeds the entry pressure of the pores. Highly pressurized jets or the presence of surfactants can force water through the hydrophobic membrane. Selection of the pore size balances the need for rapid venting against the requirement for liquid exclusion.
