Formation of Core-Sheath Polymer Fibers by Free Surface Spinning of Aqueous Two-Phase Systems

Core-sheathfibers have numerous applicationsranging from composite materials for advanced manufacturing tomaterials for drug delivery and regenerative medicine. Here, asimple and tunable approach for the generation of core-sheathfibers from immiscible solutions of dextran and polyethylene oxideis described. This approach exploits the entanglement of polymermolecules within the dextran and polyethylene oxide phases forfree surface spinning into dryfibers. The mechanism by whichthese core-sheathfibers are produced after contact with a solidsubstrate (such as a microneedle) involves complexflows of thephase-separating polymer solutions, giving rise to a liquid-liquidcore-sheathflow that is drawn into a liquid bridge. This liquidbridge then elongates into a core-sheathfiber through extensionalflow as the contacting substrate is withdrawn. The core-sheathstructure of thefibers produced by this approach is confirmed by attenuated total reflection Fourier-transform infrared spectroscopyand confocal microscopy. Tuning of the core diameter is also demonstrated by varying the weight percentage of dextran added to thereservoir from which thefibers are formed

Automated summary

This study describes a simple and tunable approach for generating core-sheath fibers from immiscible solutions of dextran and polyethylene oxide. The mechanism of core-sheath fiber formation and the ability to tune the core diameter by varying the weight percentage of dextran are revealed.