Production of core/shell fibers by electrospinning from a free surface

Abstract

Electrostatic fiber formation ("electrospinning") is the leading technology for production of continuous fibers with submicron diameter. Applications such as drug delivery and sensors benefit from the ability to produce submicron fibers with a core/shell morphology from electrified coaxial jets of two liquids. However, low productivity of the conventional needlebased coaxial process is a barrier for commercialization. We present a novel technology that overcomes this limitation by the development of coaxial jets directly from compound droplets of immiscible liquids entrained on wires, and control of mass transfer processes to produce uniform, core/shell fibers. The enabling feature of controlled evaporation by design of solution properties is verified by a simple mass transfer model. Electron micrographs confirm the formation of fibers with the desired morphology. The proposed technology creates the opportunity to produce nanofibers with core/shell morphology on an industrial scale for a wide variety of applications.

In Pursuit of Functional Electrospun Materials for Clinical Applications in Humans

“…Although most emulsion electrospinning studies are conducted with a simple needle electrospinning set up, translation of emulsion electrospinning to two different scalable free-surface designs has been shown [87,88]. One design uses a rotating wire module where solution entrainment occurs by passing a wire electrode through an emulsion bath [87].…”

“…One design uses a rotating wire module where solution entrainment occurs by passing a wire electrode through an emulsion bath [87]. This study uses a simple mass transport model to design solutions with compatible properties, including evaporation rate, viscosity and conductivity, to optimize the jetting instability wavelength parameter for each phase (core-shell) in order to produce uniform core-shell fibers [87]. Another design attempts to overcome the requirement of precisely compatible solutions by using a dual-wire spinneret that draws droplet bridges into the jetting zone by capillary force [88].…”

Control of the electric field–polymer solution interaction by utilizing ultra-conductive fluids

“…Increased nanofiber production rate has been demonstrated by concurrently utilizing several needles [32e37], spinnerets with multiple nozzles [38], or analogous structures having many apertures [30,31,39], but such methods are often complicated to implement and prone to clogging. To avoid these detriments, alternative scale-up electrospinning methods which utilize polymer fluid in an unconfined manner [40] (i.e., spinning directly from a reservoir or sheet of fluid without a confining orifice) have been developed, including needleless electrospinning [41], cleft electrospinning [42], roller electrospinning [43e45] (and analogous geometries [46,47]) using a fluid bath, free surface electrospinning [48], as well as the recently demonstrated edge electrospinning, which is utilized in this work [49e52]. As reported previously [49e53] under unconfined electrospinning and utilized in this work, stationary fluid is subjected to a strong electric field and deforms, creating fingering perturbations which eventually transition into cone-jets (with fluid being expelled from the cone terminus).…”

Electrospinning of Collagen and Its Derivatives for Biomedical Applications

“…These electrospun nanofibers often possess extremely high surface areas, high porosities, tunable pore structures, and superior mechanical properties, which means they can be processed into materials with a wide variety of structure and function design [1][2][3][4][5][6]. Due to these advantages, electrospun nanofibers have been used for a broad range of biomedical and industrial applications, such as protective clothing, wound dressings, drug delivery applications, and tissue engineering [7][8][9][10].…”