Extrusion of a solvated polymer into a moving viscous medium allows generation of continuous polymer nanofibers via hydrodynamic focusing

Continuous, small-diameter polymer fibers may be fabricated by a method that involves injecting a solvated polymer into a highly viscous moving medium through a microaperture. The extruded fiber moves in a predictable spiral path and is collected around a spinning mandrel that also serves to pull the extruded fiber away from the aperture. In this study, fibers as small as 400 nm diameter were observed, but there was no indication that the experiments reported here have achieved the smallest structures possible by this technique. Video microscopy experiments revealed significant fiber diameter reduction in close proximity to the point of precursor injection via hydrodynamic focusing. This occurred due to flow mismatch between the precursor and surrounding media. This effect may be the dominant draw-down mechanism in a process that can produce truly continuous nanofiber. This method is capable of generating fibers from precursors with viscosities that would render them unspinnable by any other known method.