Rotation-in-a-Spinneret integrates static mixers inside hollow fiber membranes

Abstract

Turbulence promoters boost the efficiency of membrane applications suffering from mass transfer limitations. To counteract these mass transfer limitations, static mixers were established for flat sheet and tubular membrane geometries. However, the combination of static mixers with hollow fiber membranes has not been possible because of tedious assembly into modules consisting of small-sized and fragile hollow fiber membranes. Here, we introduce a scalable hollow fiber membrane fabrication methodology overcoming said tedious assembly challenges. It comprises the simultaneous fabrication and integration of static mixers inside hollow fiber membranes by a single-step spinning process. Conceptually, this process builds upon our Rotation-in-a-Spinneret platform technology featuring a microstructured 3D printed hollow fiber spinneret. In particular, we integrate a rotating microstructured needle into the spinneret for extruding a static mixer into the nascent hollow fiber membrane. Specifically designed spinning parameters enabled us to engineer twisted tape-shaped static mixers with an adjustable pitch and pitch direction. The emerging Static-Mixer-Membranes exhibit a separate arrangement of both components with an inner diameter below 2.5mm. Characteristic membrane properties are independent of the needle rotation and static mixer integration. Static mixers introduce secondary flow evolution proven by pressure drop manipulation and streamline visualization. Ultimately, two application show cases – oxygenation and CO2 capture with gas–liquid membrane contactors – reveal improved transmembrane gas fluxes up to 440%. The static mixer pitch controls these improvements demonstrating process intensification. Additionally, the technique enabled fabricating nanoparticle-equipped static mixers for improved static mixer shaping and potentially catalytic functionality.