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We introduce electro-coflow as a way to generate emulsion drops with an average size that can be larger, comparable, and smaller than the smallest geometric feature of the device. The method relies on using three immiscible liquids, two of them having a finite electrical conductivity. There are three regimes of operation that allow the steady generation of drops: dripping, electro-dripping, and an electrically dominated regime. We transit from one to the other by increasing the applied voltage and describe the changes in drop size by balancing the relevant forces in each regime.

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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.

The rapid increase in multidrug resistant biofilm infections is a major concern for global health. A highly effective therapy is required for the treatment of biofilm related infections. In this study, curcumin loaded alginate microfibers were generated by using the microfluidic technique. In this strategy, alginate microfibers are used as a carrier for the encapsulation of curcumin and then are irradiated with blue light to assess the efficacy of a combined therapy (blue light + curcumin) against drug resistant Staphylococcus aureus (S. aureus). The advantage of utilizing photodynamic therapy (PDT) is the usage of a non-antibiotic mode to inactivate bacterial cells. In the presence of blue light, the curcumin loaded alginate microfibers have shown good eradication activity against biofilms formed by multidrug resistant S. aureus. We achieved different diameters of curcumin loaded alginate microfibers through manipulation of flow rates. The curcumin loaded microfibers were characterized for their size, morphology, and curcumin encapsulation. Further, the efficacy of these microfibers in the presence of blue light has been evaluated against biofilm forming S. aureus (NCIM 5718) through optical and electron microscopy. This study employs microfluidic techniques to obtain an efficacious and cost-effective microfibrous scaffold for controlled release of curcumin to treat biofilms in the presence of blue light.

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