Pore Symmetry

Pore Symmetry describes the pore structure of one surface structure of a membrane compared the other. Membranes are typically described as Isotropic, Anisotropic and Asymmetric.

Isotropic structure describes pores of similar size through the cross-section from one side to the other.

Asymmetric structure describes a pore size difference from one side to the other.

Anisotropic structure describes a pore structure, which gradually changes from one surface to the other. Some membranes have been described as "dual anisotropic". The pores are open on one side, finer in the middle and back to open on the opposite side.

Isotropic	Aysymmetric	Dual Anisotropic
Membrane with an even pore structure from top to bottom.	Membrane having a graduated pore size from top to bottom.	Membrane with finest pores in the center.

Membrane symmetry affects retention, flow rate and propensity for damage.

The thinner the thickness of the smallest pore size structure, the higher the flow rate, the lower the redundancy and potential for particle retention, and the greater the chance for it being damaged.

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