High performance micro-engineered hollow fiber membranes by smart spinneret design

Can hollow fiber membranes be produced in other geometries than circular? If so, are membrane properties maintained and what could be the possible benefits of other geometries? This article gives answers and describes the fabrication of micro-structured hollow fiber membranes using micro-fabricated orifices or needles with characteristic patterns, which are replicated either in the shell surface or in the bore surface of the fiber. By a dry-wet spinning process using short air gaps, hollow fiber gas separation membranes with geometrical structures like rims on the outer perimeter have been produced. The benefit of the produced fibers has been demonstrated with gas permeation measurements. The selectivity of the membrane remained unchanged (αO2/N2 (ideal) = 6.5) and the apparent skin thickness of both fiber types were comparable. Compared to circular fibers, an increase of gas flow (19%) was found due to the introduced surface increase taking variations in the skin thickness into account. This shows that the membrane properties are independent of the type of spinneret used. Finally, it was shown that not only the shell surface, but also the bore surface could be successfully micro-structured.