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

Abstract

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.

Role of Interfacial Tension on Viscous Multiphase Flows in Coaxial Microfluidic Channels

“…Microfluidic systems enable enhanced flow manipulations with precise control of microgeometries over a wide range of flow rates. Droplets and bubbles can be produced one-by-one for the generation of monodisperse emulsions and foams in the presence of a surfactant. − Typical microflow geometries used for the generation of droplets include T-junctions, − focusing sections, − and coaxial channels. − Coaxial microchannels are composed of small centerline injectors inserted in ducts of various sizes and offer versatility and high throughput for an array of applications, including synthesis of nanoparticles − and microfibers. − Hence, microfluidic injectors are practical flow devices that allow for manipulating a wide range of materials. The role of basic fluid properties in the interaction and combination of fluid streams in coaxial microchannels, however, has remained relatively unexplored despite their potential for methodical examination of novel multiphase flow configurations with immiscible and miscible fluids at the small scale.…”

Advances in Functional Polymer Nanofibers: From Spinning Fabrication Techniques to Recent Biomedical Applications

“…Over the past decade, microfluidic spinning has emerged as a simple and cost-effective strategy to produce fibers at the micro- and nanoscale exhibiting diverse structures and compositions. − In this method, two different fluids are simultaneously injected within microscale channels through separate input ports forming a 3D coaxial flow at the channel intersection, as illustrated in Figure a, where the core fluid consists of a polymer precursor solution, and the sheath fluid acts as a lubricant to facilitate fiber extrusion and in some cases also as a cross-linking solution . Fiber formation occurs via solidification of the core fluid by using strategies such as photopolymerization, chemical or ionic cross-linking reactions, nonsolvent-induced phase separation, and solvent evaporation, , as shown in Figure b. By adjusting the design and dimensions of the microchannel as well as the composition, viscosity, surface tension, and flow rates of fluids, micro-/nanoscale fibers with controllable shapes including cylindrical, flat, core–shell, hollow, Janus, triple, and helical can be prepared. ,, …”

Microfluidics for Drug Development: From Synthesis to Evaluation

“…Pullagura et al fabricated poly(ethylene oxide) (PEO) microfibers through a customized PDMS−glass hybrid microfluidic platform for encapsulating aluminum oxide nanoparticles, which demonstrated versatility in drug delivery. 395 In another example, Yu et al presented fiber-shaped alginate microcarriers for drug delivery and wound healing, as shown in Figure 19A. 396 They used a capillary microfluidic device to fabricate microfibers with alginate shells and metal−organic framework (MOF) cores.…”

“…Microfibers derived from the microfluidic spinning process also serve as drug delivery carriers. ,− These microfibers are made of various materials and possess diversified morphologies. Pullagura et al fabricated poly­(ethylene oxide) (PEO) microfibers through a customized PDMS–glass hybrid microfluidic platform for encapsulating aluminum oxide nanoparticles, which demonstrated versatility in drug delivery . In another example, Yu et al presented fiber-shaped alginate microcarriers for drug delivery and wound healing, as shown in Figure A .…”