Solution blow spinning of polymer/nanocomposite micro-/nanofibers with tunable diameters and morphologies using a gas dynamic virtual nozzle.

Uniform endless fibers are ubiquitous and their applications range from functional textiles over biomedical engineering to high-performance filtering and drug delivery systems. Here, we report a new method for the direct, reproducible fabrication of uniform polymer and composite micro-/nanofibers using a microfluidic gas flow focusing nozzle (Gas Dynamic Virtual Nozzle (GDVN)) relinquishing the need for external fiber pulling mechanisms. Compared to other methods, this technique is inexpensive, user-friendly and permits precise fiber diameter control (~250 nm to ~15 µm), high production rate (m/s-range) and direct fiber deposition without clogging due to stable, gas-focused jetting. Control over shape (flat or round) and surface patterning are achieved by simply tuning the air pressure and polymer concentration. The main thinning process happens after the polymer exits the device and is, therefore, mostly independent of the nozzle's internal geometry. Nevertheless, the lithography-based device design is versatile, allowing for precise flow-field control for operation stability as well as particle alignment control. As an example, we demonstrate the successful production of endless hematite nanocomposite fibers which highlights this technology's exciting possibilities that can lead to the fabrication of multifunctional/stimuli-responsive fibers with thermal and electrical conductivity, magnetic properties and enhanced mechanical stability.