Patent ID: 7005301

Claim:
A flow channel, comprising: a plurality of connected channel regions, each of said channel regions comprising a longitudinal axis, a top surface substantially parallel to a bottom surface, and first and second side walls each aligned substantially parallel to said longitudinal axis; adjacent first and second channel regions intersecting at a first intersection plane, wherein said first and second side walls of said respective first and second channel regions meet at said first intersection plane, and wherein a normal to said first intersection plane is oriented at an angle, θ 11 , with respect to said longitudinal axis of said first channel region, and oriented at an angle, θ 12 , with respect to the longitudinal axis of said second channel region; and means for establishing a first channel permeability, σ a1 , in said first channel region, wherein 0.75σ 1 <σ a1 <1.25σ 1 , and means for establishing a second channel permeability, σ a2 , in said second channel region, wherein 0.75σ 2 <σ a2 <1.25σ 2 , where σ 1 and σ 2 are first and second predetermined design permeabilities related by a compatibility condition comprising tan ⁢ ⁢ θ 11 σ 1 = tan ⁢ ⁢ θ 12 σ 2 , wherein a fluid flowing from said first channel region into said second channel region and comprising a flux that is substantially uniform in said first channel region remains substantially uniform in said second channel region.