Rotating microstructured spinnerets produce helical ridge membranes to overcome mass transfer limitations

Abstract

Membrane geometry evolution boosts membrane applications to become even more sustainable, resource- and energy-efficient. This evolution is crucial as increasingly permeable membrane materials introduce the major drawback of promoting fluid resistance due to boundary layer formation. We present how to break these boundary layers with Helical Ridge Membranes produced by rotating microstructured spinnerets. 3D printing enables us to manufacture polymeric, microstructured spinnerets featuring grooved orifices. When integrating these spinnerets into a wet spinning process, microstructured hollow fiber membrane surfaces evolve. Our home-engineered spinning technology sets the spinneret in motion. Rotation twists the nascent microstructure and creates a helical ridge on the lumen side. A robust spinning process especially establishes for our novel spinneret device to rotate the needle inside the spinneret. The interplay of spinning conditions and spinneret rotation uncovers a range of producible helical ridge shapes, sizes and pitches. In addition, spinneret rotation speed affects intrinsic membrane properties, about which we derive general correlations. The helical ridges prove the manipulation of hydrodynamics inside hollow fiber membranes by inducing secondary flow. The latter enhances mass transfer to diminish boundary layers. Ultimately, a cross-flow ultrafiltration showcase reveals TMP gradients reduced by 350% and demonstrates the disruptive impact of Helical Ridge Membranes on membrane filtration.