Microfluidics-Based On-Demand Generation of Nonwoven and Single Polymer Microfibers.

In this work, we present a microfluidics-based microfiber fabrication method with the ability to control both the fiber size and the extent of coiling of the generated fiber. This latter feature allows on-demand generation of both nonwoven and single fiber within the same device, broadening the scope of application of the fabricated fibers. Using a hybrid poly(dimethylsiloxane) (PDMS)-glass microfluidic device, we implement a coflowing solvent removal technique to generate poly(ethylene oxide) (PEO) fibers. Characterization of fibers by Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) confirms the production of solvent-free, pure PEO fibers. Control over fiber size using both inner and outer liquid flow rates is demonstrated by scanning electron microscopy (SEM) imaging. More crucially, we employ a complementary flow toward the downstream end of the fiber solidification region to control the extent of coiling of the generated fiber. By simple variation of the complementary flow, we induce a transition from a nonwoven fiber to a single fiber. The presented technique is expected to broaden the scope of microfluidics as a tool for the continuous generation of microfibers with a wider range of applications than the existing microfluidics techniques.