Controllable fabrication of polyethersulfone hollow fiber membranes with a facile double co-axial microfluidic device

Abstract

A facile and efficient double co-axial microfluidic device has been developed for fabricating polyethersulfone (PES) hollow fiber membranes via phase separation. The co-axial microchannels with easy center alignment consist of a cylindrical tube for bore fluid, a cylindrical tube for dope fluid and a rectangular tube for coagulation fluid. In such a double co-axial microfluidic device, three phase core-annular flows are formed for continuously fabricating hollow fibers via phase separations at the interfaces. The nascent PES hollow fibers can be extruded from the outlet of microfluidic device continuously without clogging. Typical PES hollow fiber membranes have two dense skin layers on both outer and inner surfaces, due to the phase separation at both interfaces between the dope fluid and the bore fluid as well as the coagulation fluid. The effects of fabrication conditions including microfluidic flowrates, PES concentration in dope fluid and operation temperature on the structures of microfluidic-fabricated PES hollow fiber membranes are investigated systematically. Ternary fluid-flow diagrams are created for fabricating PES hollow fiber membranes with different PES concentrations and operation temperatures. The results in this study provide valuable guidance for fabricating hollow fiber membranes with controllable microstructures and dimensions via microfluidic approach.