Controllable preparation of microscale tubes with multiphase co-laminar flow in a double co-axial microdevice

This article describes a simple method for the fabrication of microscale polymer tubes. A double co-axial microchannel device was designed and fabricated. Liquid/liquid/liquid multiphase co-laminar flows were realized in a microchannel by choosing working systems. Three kinds of polymeric solutions were selected as the middle phase while a polyethyleneglycol aqueous solution was used as the inner and outer phases in the microfluidic process. The outer and inner phases acted as extractants of the polymer solvent. A stable double core-annular flow was formed by optimizing the composition of the outer and inner phases, and highly uniform tubes were successfully fabricated by the solvent extraction method. Both the outer diameter of the tubes and the wall thickness could be adjusted from 300 µm to 900 µm and from 40 µm to 150 µm by varying the flux of the fluids and the rolling velocity of the collection roller. In addition, titanium dioxide (TiO₂) nanoparticles were successfully encapsulated into the polymer tubes with this technique. This technology has the potential to generate hollow fiber membranes for applications in separation and reaction processes.