Encapsulation of Monodisperse Microdroplets in Nanofibers through a Microfluidic–Electrospinning Hybrid Method

Fibers with droplets encapsulated in them could build bridges between a 0D dispersed structure and a 1D continuous wire and thus provide optimal solutions requiring high surface-to-volume ratio and strong mechanical properties. However, current methods are mostly focusing on the architectures with the size of droplets smaller than that of fibers; the relatively thick barrier of fibers usually limits the rate of diffusion from inner droplets to the outer environment. Here, we report a hybrid method combining microfluidics and electrospinning to fabricate nanofibers with microdroplets encapsulated in them. Monodisperse microdroplets with controllable sizes from 36 to 95 μm are generated through microfluidic flow-focusing and split into a string of smaller droplets from 1 to 3 μm, respectively, during the electrospinning stretching. The size of encapsulated droplets could be tuned by controlling the flow rate ratio during the microfluidic process, and the shape of that could be varied by changing the viscosity of encapsulated solution. This marriage of microfluidics and electrospinning could be applied to produce a nanofiber-based moisture barrier and drug carrier, also providing efficient tools to study the under-electric-field stretching and splitting of droplets trapped in the polymer network.