Microchannel technologies for artificial lungs: (3) Open rectangular channels

Lithographic techniques were used to develop patterned silicone rubber membranes that provide 15 mu m high micro-channels for artificial lungs. Two types of devices were fabricated as a proof-of-concept: one has a series of parallel, straight, open rectangular channels that are each 300 mu m wide, separated by 200-mu m walls, and 3-mm long and the other is a wide rectangular channel with support posts, also 3-mm long. Experiments with 30% hematocrit, venous, bovine blood showed average oxygen fluxes ranging from 11 x 10(-7) moles/(min. cm(2) at a residence time of 0.04 sec to 6.5 X 10(-7) moles/(min cm(2)) at a residence time of 0.20 sec. The average oxygen flux vs. residence time, which is due to transverse molecular diffusion, follows the same relation for all membranes tested. The corresponding increase in hemoglobin saturation ranged from 9% at the residence time of 0.04 sec to 24% at the residence time of 0.20 sec. The support-post channel membranes are attractive for designers because they can be arbitrarily wide and would be less prone to blockage.