Helical flow-driven alignment of off-axial silver-functionalized titanium dioxide fibers in polypropylene tube suitable for medical applications

Inspired by Bouligand-type structure in natural materials featured with helically-aligned reinforcing fibers and superior kink-resistance, we demonstrated an analogous architectural configuration in polypropylene (PP) tube by mean of manipulating helical flow and Ag-coated titanium dioxide (TiO2) fibers. Firstly, the dopamine-assisted immobilization and in situ reduction of Ag ions were completed on the surface of TiO2 fiber, endowing the latter with antibacterial property. Then, the functionalized fibers were introduced into PP matrix, and extruded longitudinally, simultaneously with mandrel rotation, constructing a unique helical flow. Preferred orientation driven by the applied flow assembled the bioinspired Bouligand-like structure with helically-aligned functionalized TiO2 fibers, benefiting torque load bearing and thereby the bulk kink-resistance of polymer tube accompanied by high antibacterial activity. This was exemplified by a substantial increase of 40% in hoop strength with large bacterial inhibition zone in comparison with the pure PP counterpart prepared via convention extrusion. This Bouligand-mimetic alignment strategy can open up a promising possibility of engineering and develop a series of reinforced architectures via simple industrial melt process, satisfying special functionalities and applications unavailable with the other processing technologies.