Free Surface Electrospinning Core-Shell Fiber Production
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Solution Overview
Problem
Conventional methods for producing electrospun core-shell fibers, such as coaxial electrospinning, face limitations in productivity and uniformity, particularly when attempting to use free surface electrospinning techniques which struggle to produce core-shell morphologies.
Innovation Solution
A method involving a cylindrical electrode coated with two immiscible fluids, where the electrode is drawn through a bath of liquids with different viscosities and dielectric constants, allowing for the formation of a bilayer-coated electrode that, when subjected to an electric voltage, produces core-shell particles or fibers as it is collected on a grounded surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional coaxial electrospinning is used to produce core-shell fibers, then core-shell morphology can be achieved, but productivity is limited to 0.001-0.1 g/h per spinneret
Solution Approach 1:
The invention divides the single spinneret into multiple independent electrode segments arranged in an array. Each electrode acts as an independent jet source, enabling parallel production of core-shell fibers. This segmentation transforms the single-point production limitation into multi-point simultaneous production, dramatically increasing productivity from 0.001-0.1 g/h to potentially grams per hour while maintaining uniform fiber quality.
Solution Approach 2:
The invention transitions from a single-axis spinneret configuration to a two-dimensional electrode array. By arranging electrodes in a planar configuration rather than stacking them along a single needle axis, the system utilizes spatial distribution across a surface area, enabling multiple jets to operate simultaneously without the mechanical complexity of multi-layer spinnerets.
2Productivity
If free surface electrospinning is used to increase productivity, then fiber production rate increases 2-3 orders of magnitude, but core-shell morphology cannot be produced
Solution Approach 1:
The invention applies preliminary action by pre-coating the electrode surfaces with core and shell solutions before electrospinning begins. The electrodes are dipped into respective polymer solutions, allowing the coatings to form and stabilize before the high-voltage discharge initiates jet formation. This pre-coating step ensures that core-shell structure is established beforehand, enabling the high-productivity free surface electrospinning mode to produce morphologically precise core-shell fibers.
Solution Approach 2:
The electrode surface acts as an intermediary carrier that holds both core and shell materials in controlled layers. Rather than attempting to form core-shell structures directly from bulk liquid surfaces, the electrode intermediary provides a stable platform for sequential or simultaneous coating of core and shell solutions, which then serve as the source for the electrospinning jets.
3Productivity
If multi-spinneret configurations are attempted to increase productivity, then fiber production rate may increase, but uniformity of mats and fibers deteriorates
Solution Approach 1:
The invention applies local quality by allowing each electrode in the array to be independently coated with specific core and shell solutions tailored to desired fiber properties. Different regions of the electrode array can produce fibers with different compositions, diameters, or functional characteristics, while maintaining uniformity within each jet. This localized control enables high productivity through parallel production while preserving manufacturing precision for each fiber type.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances productivity and uniformity in producing core-shell fibers with controlled morphology, overcoming the limitations of conventional methods by enabling the simultaneous coating and deposition of core-shell structures with tunable properties.
Implementation Method 1
drawing the coated cylindrical electrode through a second fluid, wherein the first fluid is more viscous than the second fluid, thereby forming a bilayer-coated cylindrical electrode
Implementation Method 2
wherein the dielectric constant of the first fluid is greater than the dielectric constant of the second fluid
Implementation Method 3
Free surface electrospinning has been shown to be capable of producing electrospun fibers at rates that are two to three orders of magnitude higher than spinneret-based methods
Implementation Method 4
positioning the bilayer-coated cylindrical electrode at a distance from a grounded collection surface; wherein the plurality of core-shell particles or the plurality of core-shell fibers is deposited on the grounded collection surface
Data Source
AI summary
Disclosed are methods that utilize the differences in physical properties between two coating fluids to form core-shell particles or core-shell fibers by coaxial free-surface electrospinning. The methods are able to achieve higher productivity than known methods, and are tunable. Nonwoven fiber mats of electrospun fibers have garnered much scientific and commercial interest in recent years due to their unique properties, such as their high porosity, high surface area and small diameter fibers.