Abstract
Building two-dimensional (2D) and three-dimensional (3D) fibrous structures in the micro- and nanoscale will offer exciting prospects for numerous applications spanning from sensors to energy storage and tissue engineering scaffolds. Electrospinning is a well-suited technique for drawing micro- to nanoscale fibers, but current methods of building electrospun fibers in 3D are restrictive in terms of printed height, design of macroscopic fiber networks, and choice of polymer. Here, we combine low-voltage electrospinning and additive manufacturing as a method to pattern layers of suspended mesofibers. Layers of fibers are suspended between 3D-printed supports in situ in multiple fiber layers and designable orientations. We examine the key working parameters to attain a threshold for fiber suspension, use those behavioral observations to establish a “fiber suspension indicator”, and demonstrate its utility through design of intricate suspended fiber architectures. Individual fibers produced by this method approach the micrometer/submicrometer scale, while the overall suspended 3D fiber architecture can span over a centimeter in height. We demonstrate an application of suspended fiber architectures in 3D cell culture, utilizing patterned fiber topography to guide the assembly of suspended high-cellular-density structures. The solution-based fiber suspension patterning process we report offers a unique competence in patterning soft polymers, including extracellular matrix-like materials, in a high resolution and aspect ratio. The platform could thus offer new design and manufacturing capabilities of devices and functional products by incorporating functional fibrous elements.
Highlights
Building on our existing 2D work, in this manuscript we significantly extend the patterning capabilities of low-voltage electrospinning (LEP)[23] to 3D through integration with fused filament fabrication (FFF) 3D printing
The FFF process prints a support structure, which has the dual function of fiber initiation via LEP, as well as acting as a support structure for fiber suspension in multiple layers
After fiber patterning is completed in one layer, the stage is moved downward by a small distance, and the tool-head carrier exchanges tool-heads to return to the FFF process, building a new layer of support structure and repeating the layering process
Summary
Electrospinning is a well-established and simple method to draw nano- to microscale fibers by applying a high voltage to a polymer solution or melt, typically yielding mats of randomly positioned mesofibers on the top of a substrate.[10−12] Advances in precision electrospinning methodologies, such as near-field electrospinning, electrohydrodynamic writing, and direct writing electrospinning,[13−21] have led to a significant progress in controlling fiber placement on a substrate compared to conventional “far-field” electrospinning configurations. Thicker fibrous structures can be formed by folding or layering electrospun mats with manual intervention.[26,27] Suspended layered membranes can be formed using separated guiding electrodes,[28,29] and orderly stacked fibers have been demonstrated using melt electrospinning[18,30] or directed electrohydrodynamic printing.[13−15,31] Integrating electrospinning with other printing mechanisms, for example, with polymer extrusion[32,33] or hydrogel printing,[34−36] has been.
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