Rope coiling spinning of curled and meandering hollow-fiber membranes

• A novel method to directly produce curled membrane geometries is presented.
• One step dry wet spinning of helical hollow-fiber membranes.
• Detailed discussion of rope coiling adapted to coextruded jets and phase separation.

Curved and structured membrane geometries are known to have the potential to reduce concentration polarization and fouling rates in membrane filtration and membrane contacting applications. However, their production is cumbersome and often comprises various successive processing steps. We present a new direct fabrication process of two new hollow fiber geometries: Curled and meandering hollow fibers. The phenomenon of liquid rope-coiling is adapted to a membrane spinning process resulting in mostly spiralling curly fiber geometries. Parameters influencing geometric properties are evaluated and experimentally obtained structures are presented. Fibers were prepared from a polyethersulfone-based polymer solution in an air gap spinning process. Prepared structured hollow fibers are investigated regarding geometrical measures and pore structures. A comprehensive analysis of the complex interplay between the influencing parameters is suggested.

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