A Staged, Tortuous Microcapillary System: Hemodialysis and Ultrafiltration

A microcapillary system has been constructed by etching staged, tortuous microchannels onto stainless steel sheets; a flat membrane over the channel completes the microcapillary. The microcapillaries are sinusoidal and terminate every ¿¿to form a region where the output of all capillaries mix. There are three stages per centimeter. Tortuosity and staging greatly reduce boundary layers and increase mass transfer through the membrane. There are 430 000 capillaries per square meter of membrane. The capillaries are oval (125 ¿m X 250¿m); thus membrane area per unit volume is only 36 percent less than a hollow-fiber capillary. Initial testing indicates satisfactory clearances and hydraulic conductivities for Cuprophane PT-150 membrane. This microcapillary system should find many industrial and biomedical applications where prime volume per unit membrane area and concentration polarization are major concerns of design.