US20220018039A1

US20220018039A1 - Electrospinning apparatus and method for forming aligned fibres

Info

Publication number: US20220018039A1
Application number: US17/413,695
Authority: US
Inventors: Shao Siheng; Fernando Gerard
Original assignee: Gerard Gernando; Shao Siheng; Siheng Shao
Current assignee: Gerard Gernando; Shao Siheng
Priority date: 2018-12-14
Filing date: 2019-12-13
Publication date: 2022-01-20
Also published as: CN113710835A; GB201820411D0; GB2594861B; GB2594861A; CN113710835B; GB202110133D0; WO2020120985A1

Abstract

A spinning apparatus (1) for forming aligned fibres, the apparatus (1) comprises a nozzle (12) for ejecting material (P) for forming fibres from a tip thereof, an electrode (14A, 14B), a substrate (S) for receiving fibres (NF) thereon, and first and second electrically insulating members (15A, 15B), wherein the tip of the nozzle (12) is located between the first and the second electrically insulating members (15A, 15B).

Description

This invention relates generally to spinning, e.g. electrospinning. More specifically, although not exclusively, this invention relates to an apparatus for aligning spun (e.g. electro-spun melts, solutions, gels, suspensions) fibres, a method for aligning spun fibres, and products comprising said fibres.
There are many methods for forming fibres. One such method is electrospinning, which is a versatile method for producing microfibres and nanofibres from various materials including polymer solutions and melts. Fibre mats containing aligned fibres, e.g. microfibres or nanofibres, find use in many applications including gas filters, chemical gas sensors, electrodes, separation membranes, lithium ion batteries, scaffolds for tissue engineering, reinforced composites, catalytic supports and opto-electronic devices.
In a typical electrospinning process, a high potential difference e.g. several kilovolts, is applied between a conductive nozzle and an electrode. The fibres are formed from a liquid, e.g. a polymer solution or melt, which is stored in a reservoir for delivery through the nozzle.
In use, the nozzle ejects a pendant droplet of the liquid stored in the reservoir. Exposure to the electric field causes the shape of the droplet of liquid to deform as a result of changes to its surface tension. As the droplet deforms, the liquid becomes charged, and electrostatic repulsion counteracts the surface tension to stretch the droplet (known as a Taylor cone). At a critical point, a stream of liquid erupts from the surface of the droplet to form a jet of liquid. The solvent is able to evaporate from the jet of liquid, causing its viscosity to change. As this occurs, the Coulomb forces generated inside the electrified jet cause the jet of liquid to bend and spin in a ‘whipping process’, which causes the jet of liquid to elongate. In this way, the diameter of the fibre is reduced to micrometre or nanometre scale. The resultant fibre is then deposited on an electrode, in a random orientation to form a non-woven fibre mat.
It is desirable to be able to control the position, e.g. the alignment, in which the fibres are deposited onto the target electrode. Fibre mats exhibiting a greater degree of alignment are known to have enhanced properties in various applications. For example, it is known that aligned nanofibres can increase the performance, for example, the sensitivity in chemical sensors, and conductivity in fuel cell membranes. In addition, it is known that the mechanical strength of a composite material may be improved when the fibres are aligned, and when the uniformity of the fibre mat in increased, in contrast to random alignment. Several solutions have been proposed to seek to control the alignment of deposited fibres in electrospinning processes. For example, one approach that has been suggested is the use of a rotating mandrel. Nguyen et al, European Polymer. J. 77; 54-64 (2016) and US2011/264235 each describe the production of aligned fibres in an electrospinning process, in which a rotating drum is used as the collector. However, this approach has a relatively complex set-up, and the width and length of the aligned fibre mat is limited by the dimensions of the rotating collector drum. In addition, many proposed prior art methods require an additional transferal step of the fibre mat, once it has been fabricated in an electrospinning process, onto a secondary substrate.
Another approach to control fibre orientation in an electrospinning process is described in Matthias M L Arras et al, Sci. Technol. Adv. Mater. 13; 035008 (2012). The apparatus described in FIG. 1 comprises a nozzle, a target electrode for receipt of the substrate, and a pair of auxiliary parallel plate electrodes positioned above the target electrode in facing relations. The pair of auxiliary parallel is plate electrodes provide a symmetric electric field to the electrospinning jet. The publication describes how the target electrode was either a stationary grounded carbon fibre plate, or a rotatable aluminium cylinder. In all Examples, at least a portion of the fibres are aligned in an orientation perpendicular to the plate electrodes. As will be appreciated, a limitation of this approach is that the length of the fibre mat is restricted to the distance between the electrodes, and/or the width of the target electrode.
Therefore, it remains a challenge to fabricate a fibre mat comprising aligned fibres, e.g. microfibres or nanofibres, of a desired length.
US2018/0015423 A1 discloses an electrospinning pattern forming apparatus that includes double insulating blocks to quasi-align nanofibres in a specific direction. The direction of alignment may be changed by rotating the current collector by 90° to transform the electric field. The double insulating blocks are in parallel relations and have an interval ranged from 1 to 6 cm. The interval between the top surfaces of the double insulating blocks and a tip of the nozzle that ranges from 2 to 5 cm and the nanofibres are deposited directly onto the counter electrode.
It is therefore a first non-exclusive object of the invention to provide a spinning apparatus, e.g. an electrospinning apparatus, for use in a method for the fabrication a fibre mat comprising longitudinally aligned fibres, e.g. microfibres or nanofibres, of desired length.
Accordingly, a first aspect of the invention provides a spinning apparatus for forming aligned fibres, e.g. an electrospinning apparatus, the apparatus comprising a nozzle for ejecting material for forming fibres from a tip thereof, an electrode, a substrate for receiving fibres thereon, and first and second electrically insulating members, wherein the tip of the nozzle is located between the first and the second electrically insulating members.
Advantageously, the first and second electrically insulating members act to cause the fibres to be deposited on the substrate with a high degree of alignment.
Preferably the substrate comprises or is formed from an electrically insulative material.
Advantageously, a substrate comprising or being formed from an electrically insulative material io provides a means to collect deposited nanofibres. This enables the aligned nanofibres to be easily collected or retrieved in-tact from the spinning apparatus.
A further aspect of the invention provides a spinning apparatus for forming aligned fibres, e.g. an electrospinning apparatus, the apparatus comprising a nozzle for ejecting material for forming fibres is from a tip thereof, an electrode, a substrate for receiving fibres thereon, and first and second electrically insulating members, wherein the substrate comprises an electrically insulative material.
Preferably the tip of the nozzle is located between the first and the second electrically insulating members.
In operation, the apparatus deposits fibres, e.g. nanofibres onto the substrate, the deposited fibres, e.g. nanofibres being aligned longitudinally with respect to the substrate.
Although we do not wish or intend to be bound by an particular theory, we believe that the first and second electrically insulating members interfere with the electric field lines, which are generated between the nozzle tip and the electrode of the spinning apparatus, to control the deposition of the ejected material for the formation of fibres.
The nozzle tip is located between the first and the second electrically insulating members, that is, the tip of the nozzle is spaced from the substrate at a distance such that the first and second insulating members are located laterally (either side) of the nozzle tip. It has been surprisingly found that locating the nozzle tip in this way enables the fibres to deposit onto the substrate with a greater degree of alignment.
The nozzle tip is below the plane of the uppermost edge of the first and second electrically insulating members. It has been surprisingly found that locating the nozzle tip in this way enables the fibres to deposit onto the substrate with an even greater degree of alignment.
Without wishing to be bound by any particular theory, the inventors believe that the first and second electrically insulating members modify the electric field lines such that nanofibres generated from the tip of the needle, which is below the plane of the uppermost edge of the first and second electrically insulating members, oscillate between the opposite ends of the substrate (for example, located on a flat, grounded electrode), leading to a greater degree of alignment.
Advantageously, the apparatus according to the invention prevents or mitigates substantial nanofibre deposition in locations or regions that are remote from the substrate. The arrangement of the nozzle tip in combination with the first and second electrically insulating members, and for example a io substrate formed from electrically insulative material, has been found to be effective in modifying the electric field lines to produce highly aligned nanofibres.
In embodiments, the first electrically insulating member and the second electrically insulating members are located in facing relations. Preferably, the substrate extends between the first electrically insulating member and the second electrically insulating members.
In embodiments, the first electrically insulating member, the second electrically insulating member, and/or the substrate may be a unitary body and/or integrally formed. For example, the first and second electrically insulating member and/or the substrate may form a substantially U-shaped or V-shaped electrically insulating member. In alternative embodiments, the first electrically insulating member and/or the second electrically insulating member and/or the substrate may be separate and distinct components. In embodiments, the first electrically insulating member and the second electrically insulating may be a unitary body, and the substrate may be provided as a separate component. In other embodiments, the first electrically insulating member and the second electrically insulating member may be provided as separate components. The substrate for the receipt of fibres may be provided as a separate component, that is, separate from the first and second electrically insulating member. In embodiments, the substrate may be provided as part of, i.e. integral to, one or both of the first and/or second electrically insulating members, that is, a separate substrate need not be provided.
In embodiments, each of the first electrically insulating member and second electrically insulating member comprise a first, e.g. lower, portion and a second, e.g. upper, portion. In embodiments, the first electrically insulating member and second electrically insulating member are located parallel to one another. In embodiments the first electrically insulating member and second electrically insulating member extend in directions which are not parallel to one another, for example the facing portions of the first electrically insulating member and second electrically insulating member may define planes which planes extend in non-parallel relation to one another. For example the planes may together define an included angle which is greater than 0° and less than 180°, preferably greater than 0° and less than 160°, say greater than 0° and less than 140°, 130°, 120°, 110°, 100°. In a preferred embodiment, the first portions of the first and second electrically insulating members are located adjacent or proximate the substrate, the second portions of each of the first and second electrically insulating members extend away from the respective first portions in a direction which is non-parallel and non-perpendicular to the substrate.
It has been surprisingly found that location of an angled first electrically insulating member and an angled second electrically insulating member in an electrospinning apparatus produces longitudinally aligned fibres, e.g. nanofibres, on a substrate. The provision of angled (i.e. non parallel) io first and second electrically insulating members is preferred to achieve aligned fibres.
Preferably, the angle created between each of the first and second electrically insulating members with the plane of the substrate is between 25 to 55°, say 35 to 45°. The angle between the first and second electrically insulating members may be between 70 and 130°, say 90 to 110°.
It has been surprisingly found that an angle of between 25 to 55° mitigates against the deposition of fibres that are aligned perpendicular to the length of the substrate, i.e. not longitudinal alignment with respect to the substrate.
In embodiments, the at least one electrode may comprise a flat, grounded electrode, e.g. parallel to the substrate. In embodiments, the at least one electrode comprises a disc-shaped electrode. In embodiments, each of the first and second electrically insulating members creates an acute angle of greater than 0 and less than 90° with the plane of the flat electrode (and the plane of the su bst rate) .
In alternative embodiments, the apparatus may comprise a first and second grounded plate electrode, for example, in facing relations. In embodiments, each of the first and second electrically insulating members may be located adjacent or proximate a respective one of the first and second plate electrodes.
A further aspect of the invention provides an apparatus, e.g. an electrospinning, the apparatus comprising a nozzle for delivery of material for forming fibres from a tip thereof, a first and second grounded plate electrodes in facing relations and a first and second electrically insulating member, each of the first and second electrically insulating members being located adjacent or proximate a respective one of the first and second plate electrodes, and preferably a substrate for receipt of fibres extending between the first and second electrically insulating members, wherein the tip of the nozzle is located between the first and the second electrically insulating members.
Preferably the substrate is formed from an electrically insulating material.
A yet further aspect of the invention provides an electrospinning apparatus, the apparatus comprising a nozzle for delivery of material for forming fibres from a tip thereof, a rotatable ring electrode and a first and second electrically insulating member, and a substrate for the receipt of fibres.
A further aspect of the invention provides a method of forming aligned nanofibers, the method comprising providing at least one electrode, locating a first and second electrically insulating member in facing relations, locating a substrate that extends between the first and second electrically o insulating members, locating the tip of the nozzle between the first and the second electrically insulating members, applying an electric field between a nozzle and the at least one electrode and depositing aligned nanofibers on a substrate.
The method may further comprise positioning the first and second electrically insulating members to is be non-parallel and non-perpendicular to the plane of the substrate.
In embodiments, the method comprises providing two electrodes, e.g. a first and second facing grounded plate electrode.
In embodiments, the method of forming aligned nanofibers comprises providing first and second facing grounded plate electrodes, locating a first and second electrically insulating member adjacent or proximate a respective one of the first and second facing grounded plate electrodes, applying an electric field between a nozzle and the first and second grounded plate electrodes and depositing aligned nanofibers on a substrate extending between the first and second electrically insulating members.
It has been surprisingly found that the presence of a first and second electrically insulating member, each of the first and second electrically insulating members being located adjacent or proximate a respective one of the first and second plate electrodes, causes the fibres to align longitudinally, at least substantially parallel to the first and second plate electrodes. Advantageously, this enables the fabrication of a fibre mat comprising longitudinally aligned fibres, e.g. microfibres or nanofibres, of variable length, i.e. that is not limited in length by the distance between the first and second electrode.
The first and second electrically insulating members extend away from each other in a direction away from the at least one electrode. We believe that this helps to align fibres and mitigates against the deposition of fibres that are aligned perpendicularly to the length of the substrate.
In embodiments, the substrate may be movable, e.g. movable with respect to the electrode, e.g. the first and second electrodes.
In embodiments, the substrate may be an endless belt.
The spinning apparatus may further comprise a feed reel comprising a length of substrate being located upstream of the at least one, e.g. the first and second plate, electrode. The feed reel may be configured such that, in use, the feed reel supplies a length of substrate for receipt of fibres.
o The spinning apparatus may further comprise an exhaust or take-up reel being located downstream of the at least one, e.g. the first and second plate, electrode. The exhaust reel may be configured such that, in use, the exhaust reel takes-up the substrate in receipt of fibres.
The feed reel and/or the exhaust reel may be driven, e.g. rotationally driven. Preferably, the exhaust is reel is configured to cause the substrate to run, in a running direction, through the electrospinning apparatus, e.g. in between the first and second electrically insulating members. Preferably, the exhaust reel is configured to cause the substrate to run, in a running direction, from the feed reel, through the electrospinning apparatus e.g. in between the first and second electrically insulating members, to be taken up by the exhaust reel.
Advantageously, the provision of a feed reel and/or an exhaust reel enables continuous production of a substrate comprising a longitudinally aligned fibre mat of any given length.
The first and/or second electrically insulating members may be formed from, or comprise a dielectric material, for example a material that has a dielectric constant of between 1.5 and 10, for example between 2 to 5, or 2 to 3, for example, the dielectric constant of the first and second electrically insulating members may be between any one of 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 to any one of 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2 or 2.1. Preferably the dielectric constant of the one or more electrically insulating members is lower than 5.0, for example, lower than 4.0, or lower than 3.0, or lower than 2.5.
The first and/or second electrically insulating members and/or the substrate may be formed from the same material, e.g. as a unitary body. Alternatively, the first and/or second electrically insulating members may be formed from the same material, and the substrate may be formed from a different material.
The first and second electrically insulating members may be formed from, or comprise, glass. For example, glass has a dielectric constant of between 4 to 5. Additionally or alternatively, the electrically insulating members may be formed from, or comprise, a polymer, for example, a synthetic polymer, e.g. polyurethane and/or polytetrafluoroethylene (PTFE). For example, PTFE has a dielectric constant of 2.0 and so its use for the fabrication of the electrically insulating members for use in the invention is particularly preferred.
The first and second electrically insulating members may be formed from, or comprise, a polymeric foam, i.e. an expanded polymer foam comprising a solid phase and a gas phase. The polymeric foam may be porous, for example, the polymeric foam may comprise an open-cell network. Additionally or alternatively, the polymeric foam may comprise a closed-cell network.
Additionally or alternatively, the first and second electrically insulating members may comprise only a solid phase, that is, not be a foam.
The first and second electrically insulating members may be formed from, or comprise, any suitable is non-electrically conductive material. The electrical conductivity of the first and second electrically insulating members may less than 1×10⁻⁵S/m, e.g. less than 1×10⁻¹° S/m, for example, less than 1×10⁻¹⁵, or less than 1×10⁻²⁰.
The first and second electrically insulating members may be any suitable size. Preferably, in embodiments comprising a first and a second electrode, each of the first and second electrically insulating members is sized to be larger than the height and width of each of the first and second electrode.
The first and second electrically insulating members may be, but need not be, integrally formed. The first and second electrically insulating members may be joined by a joining portion. Alternatively, the first and second electrically insulating members may be separate and not adjoined, and/or in intimate contact with one another.
The first and/or second insulating members, and/or the or a joining portion may be located between the substrate and the at least one electrode.
Preferably, the electrode is distanced from 0.25 to 5 cm from the first and/or second insulating members, and/or the or a joining portion, say from 0.5 to 2.5 cm, preferably 0.75 to 1.25 cm.
The at least one electrode, e.g. the first and/or second electrode, may be formed from any suitable material. In embodiments, the first and/or second electrode is/are formed from metal, for example copper, aluminium, gold, silver or an alloy, for example brass.
The electrode, e.g. the first and second electrode may be any suitable size. Preferably, in embodiments comprising a first and second electrode, each of the first and second electrode is sized to be smaller than the height and width of each of the first and second electrically insulating members.
The disc-shaped electrode may describe an annulus.
In embodiments comprising a first and second plate electrode, the separation distance between the first and second plate electrode may be between 10 mm and 40 mm, although it is understood that to this depends on the dimensions and geometry of the other components of the electrospinning apparatus. Preferably, the separation distance between the first and second electrode is between 15 to 35 mm.
The tip of the nozzle may be spaced at a distance of between 4 to 13 cm from the substrate
Each of the first and second electrically insulating members may be any length and may be chosen according to the material for forming fibres for the deposition of aligned fibres.
In a specific embodiment, each of the first and second electrode is 100 mm wide, 14 mm in height, and 3 mm thick; the separation distance between the first and/or second electrode in these embodiments is between 15 to 35 mm, and the nozzle is spaced at a distance of 4 to 13 cm from the substrate; the first and second electrically insulating members are between 0.1 and 10 mm thick (in depth), for example, between 0.25 mm to 5 mm thick.
The selection of the thickness of the first and second electrically insulating members depends on the material for forming fibres from a tip thereof for the deposition of aligned fibres, and/or the electric field strength applied between the nozzle and the electrode(s). For example, electrically insulating members of a greater thickness are able to be used with a higher field strength and vice versa.
The first and/or second electrically insulating members may be located in intimate contact with the first and/or second electrodes.
In embodiments comprising a first and second grounded plate electrode, the first and second electrically insulating members are located adjacent or proximate a respective one of the first and second plate electrodes. In embodiments, the first and/or second electrically insulating member are not located in parallel to the respective one of the first and second plate electrode. In this case, an internal angle A1 is created between the first electrically insulating member and the first electrode, and likewise an angle A2 is created between the second electrically insulating member and the second electrode. The angles A1 and A2 may be equal or may be non-equal. In these embodiments, each of the internal and/or A2 may be between greater than 0 and less than 89°, but is preferably between 45 degrees and 55°, e.g. from any one of 45, 46, 47, 48, 49, 50, 51, 52, 53, 54°, to any one of 55, 54, 53, 52, 51. 50, 49, 48, 47, or 46°. The optimum angle A1 , A2 is dependent on the distance d between the first electrode and the second electrode.
The material for forming fibres for delivery onto the substrate may be any suitable electrospinning material that is known to the skilled person. The material for forming fibres may be formed from, or comprise, a polymer, for example, poly(vinylpyrrolidone) (PVP), polyacrylonitrile (PAN), and/or io polyethylene glycol (PEO). The material for forming fibres may comprise carbon, e.g. graphene. In embodiments, the material for forming fibres may be formed from a solution of dissolved polymer in a solvent. Wherein the material for forming fibres is a polymer in solution, suitable concentrations of the polymer in a solution will depend on the composition used, as is known to the skilled person. The solvent may be water, and/or ethanol, and/or dimethylformamide (DMF).
For example, the polymer solution may be or comprise poly(vinylpyrrolidone) (PVP) in ethanol. In embodiments, the PVP may have a molecular weight of 1.5 megagrams per mol. The PVP in ethanol may be provided in a concentration (wt.%) of between 10 wt. % to 20 wt. % PVP in ethanol, e.g. from any one of 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 wt. % to any one of 20, 19, 18, 17, 16, 15, 14, 13, 12, 11 wt. % PVP in ethanol. Additionally or alternatively, the material for forming fibres may be formed from a solution of polyacrylonitrile (PAN) in dimethylformamide (DMF) and/or in dimethyl sulfoxide (DMSO). In embodiments, the PAN may have a molecular weight of 150 kilograms per mol to 230 kilograms per mol. The PAN in, for example DMF or DMSO, may be provided in a concentration of between 8 wt. % to 16 wt. % PAN in DMF or DMSO, e.g. from any one of 8, 9, 10, 11, 12, 13, 14, or 15 wt. % to any one of 16, 15, 14, 13, 12, 11, 10, or 9 wt. % PAN in DMF or DMSO.
Additionally or alternatively, the material for forming fibres may be formed from a solution of cellulose acetate (CA) in acetone and/or DMSO. For example, the material for forming fibres may be formed from a solution of cellulose acetate (CA) in a binary solvent system of acetone and DMSO, e.g. in a 2:1 solvent weight ratio of acetone to DMSO. In embodiments, the CA may have a molecular weight of say 50 to 100 kilograms per mol. The CA in, for example a binary solvent system of acetone and DMSO in a 2:1 solvent weight ratio of acetone to DMSO may be provided in a concentration of between 12 wt. % to 24 wt. % CA in 2:1 acetone to DMSO weight ratio, e.g. from any one of 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 wt. % to any one of 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13 wt. % CA in 2:1 acetone to DMSO weight ratio. Additionally or alternatively, the material for forming fibres may be formed from a solution of lignin, for example, a solution of lignin dissolved in acetone and/or DMSO. Additionally or alternatively, the material for forming fibres may be formed from a solution of nanocellulose.
In embodiments, the material for forming fibres for delivery onto the substrate may be formed from a melted polymer. The melted polymer may be one or more of polycaprolactone, polylactic acid, poly(lactide-co-glycolide), poly(methyl methacrylate), polypropylene, polyethylene, poly(caprolactone-block-ethylene glycol), and/or polyurethane.. These polymers may be used in a melt electrospinning apparatus.
The material for forming fibres may be or may comprise a nanofibre, for example, fibres with a diameter of between 200×10⁻⁹m (200 nm) to 500×10⁻⁹m (500 nm). In embodiments, the material for forming fibres may be or may comprise a nanofibre with a diameter of less than 200×10⁻⁹m (200 nm), e.g. less than 100×10⁻⁹(100 nm). The diameter of the fibre is dependent on the viscosity and concentration of the material for forming fibres.
In embodiments in which the material for forming fibres is formed from, or comprises, a melted polymer, then fibres with a diameter of less than 250 micrometers may be formed, e.g. less than 200 micrometres, less than 150 micrometres, or less than 100 micrometres, say less than 50 micrometres.
The substrate for receipt of the fibres may be any suitable material. Preferably, the substrate is formed from an electrically insulating material. For example, the substrate may be formed from glass fibre, e.g. aligned glass fibre. In alternative embodiments, the substrate may be formed from paper, i.e. a cellulose-based material. Preferably, the substrate has a dielectric constant that is slightly greater than, or is equal to, the dielectric constant of the electrically insulating members.
Advantageously, if a material comprising aligned fibres is used as the substrate, for example, an aligned glass fibre substrate, then the apparatus and the method of the present invention may be used to fabricate composites, e.g. nanofibre composites.
The electrospinning apparatus may further comprise a dispensing unit for storing and/or dispensing a material before it is dispensed to form fibres. The dispensing unit may comprise a reservoir, and/or a syringe and/or the nozzle. The reservoir may be used to store the electrospinning material before it is delivered to the syringe and/or the nozzle. The syringe may comprise or be a screw driven syringe and/or a syringe pump, i.e. for controlling the volume of electrospinning material dispensed over a specific period of time.
The nozzle may be any suitable size. Preferably, the nozzle is a suitable size for forming microfibres or nanofibres. For example, the inner diameter of the nozzle may be between 0.45 mm and 0.01 mm. The nozzle gauge may be between 25 and 34 gauge, e.g. 25, 26, 26s, 27, 28, 29, 30, 31, 32, 33, 34 gauge. In embodiments, the nozzle is a custom-made glass nozzle having an outer diameter of 397 micrometres and an inner diameter of 166 micrometres. Preferably, the nozzle is a blunt-end nozzle.
The voltage applied between the nozzle and the first and second grounded plate electrodes to generate an electric field may be between 4 kV to 21 kV, for example, between 5 kV to 20 kV, or between 7 to 15 kV. For example, the voltage applied between the nozzle and the first and second grounded plate electrodes to generate an electric field may be between any one of 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 kV to any one of 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, or 5 kV.
The nozzle may be formed from any suitable material. In embodiments, the nozzle is formed from copper. In other embodiments, the nozzle may comprise glass.
In embodiments, the nozzle is positively charged and the electrode(s) is negatively charged. However, in alternative embodiments, the nozzle is negatively charged and the electrode is positively charged. This is dependent on selection of the material for forming fibres for use in the apparatus of the invention.
The apparatus may further comprise a means for translationally and/or rotationally moving the substrate. The apparatus may further comprise a means for moving the substrate along an x-, y- and/or a z-axis relative to the nozzle. The apparatus may further comprise a means for rotationally moving the substrate and/or the electrically insulating members between 0 and 360-degrees.
The method may further comprise translationally and/or rotationally moving the substrate. The method may further comprise translationally moving the substrate along an x- and/or a z- axis. The method may further comprise rotationally moving the substrate between 0 and 360-degrees.
Advantageously, translationally moving the substrate enables the fibres to be deposited, e.g. deposited continuously, at different locations on the substrate, in a ‘printing’ operation.
More advantageously, rotationally moving the substrate enables the aligned fibres to be deposited in layers, each layer exhibiting a different orientation to the previous layer, the difference in orientation depending on the amount or degree of rotational movement.
A further aspect of the invention provides an apparatus comprising two or more electrospinning apparatus of the invention, e.g. three, four, or n^thelectrospinning apparatus of the invention, located in series for use with a single substrate.
Advantageously, the use of two more electrospinning apparatus located in series may be used to fabricate a fibre mat with multiple layers of aligned fibres, i.e. a first layer of aligned nanofibres, a second layer of aligned nanofibres, and an n^thlayer of aligned nanofibres.
More advantageously, the first, second, and n^thelectrospinning apparatus may be positioned at different angles to one another, such that the first and/or second and/or third layers of aligned nanofibres are aligned at different angles, i.e. extend in different directions, to one another.
A further aspect of the invention provides a fibre mat, e.g. a microfibre mat or a nanofibre mat, io fabricated in the method of the invention and/or using the apparatus of the invention. For example, the fibre mat may comprise fibre composed of one or more of poly(vinylpyrrolidone) (PVP), polyacrylonitrile (PAN), and/or polyethylene oxide (PEO), carbon, e.g. graphene, polycaprolactone, polylactic acid, poly(lactide-co-glycolide), poly(methyl methacrylate), polypropylene, polyethylene, poly(caprolactone-block-ethylene glycol), polyurethane, nanocellulose and/or lignin.
The fibre mat may comprise nanofibres, for example, fibres with a diameter of between 200×10⁻⁹m (200 nm) to 500×10⁻⁹m (500 nm).
The fibre mat may comprise plural layers of aligned fibres, e.g. plural layers of aligned fibres, each of which are aligned in the same and/or a different direction.
Advantageously, the fibre mat of the invention may be removed or detached from the substrate and/or may be transferred to a secondary substrate.
The fibre mat of the invention may be further used in applications such as tube wrapping, filament winding, and/or pultrusion techniques.
The fibre mat of the invention may comprise plural layers of aligned fibres, e.g. plural layers of aligned fibres, each of which are aligned in the same and/or a different direction. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. For the avoidance of doubt, the terms “may”, “and/or”, “e.g.”, “for example” and any similar term as used herein should be interpreted as non-limiting such that any feature so-described need not be present. Indeed, any combination of optional features is expressly envisaged without departing from the scope of the invention, whether or not these are expressly claimed. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

FIG. 1A is an electrospinning apparatus, according to a first embodiment of the invention;

FIG. 1B is a side elevation of an insulating member and an electrode, according to the embodiment of the invention shown in FIG. 1A;

FIG. 2 is an electrospinning apparatus, according to a second embodiment of the invention;

FIG. 3A is a side elevation of an electrospinning apparatus, according to a third embodiment of the invention;

FIG. 3B is an image of the electrospinning apparatus of FIG. 3B showing the dimensions of the electrode;

FIG. 4 is an image of a nozzle for use in the electrospinning apparatus of the invention;

FIG. 5 is an electrospinning apparatus, according to a further embodiment of the invention;

FIG. 6 is an electrospinning apparatus, according to a yet further embodiment of the invention;

FIG. 7 is a photograph of a substrate comprising an aligned nanofibre mat, according to an Example of the invention;

FIGS. 8A to 8E are SEM images of substrate comprising aligned fibres, which were fabricated according to Examples of the invention;

FIGS. 9A and 9B are SEM micrographs of substrate comprising aligned fibres at 0 and 90°, according to Examples of the invention; and

FIG. 10 is a micrograph showing highly aligned and multi-layered nanofibres at different angles produced using the apparatus of FIG. 6.

Referring now to FIG. 1A, there is shown an electrospinning apparatus 1, according to a first embodiment of the invention. The electrospinning apparatus 1 comprises a dispensing unit 1A and a platform 1B.
The dispensing unit 1A comprises a reservoir 10, a syringe 11, and a nozzle 12. The reservoir 10 comprises an electrospinning material in the form of a precursor P for the formation of nanofibres NF. In this embodiment, the syringe 11 comprises a screw driven 5 mL syringe for controlling the volume of precursor P dispensed over a specified period of time.
The platform 1B comprises a base 13, a first electrode 14A, a second electrode 14B, and an insulating member 15. In this embodiment, the insulating member 15 comprises a first insulating member 15A, a second insulating member 15B, interconnected by a joining portion 15C, such that the first insulating member 15A, the joining portion 15C, and the second insulating member 15B form a unitary U-shaped member.
In this embodiment, the insulating member 15 is formed from a foamed polyurethane sheet.
The first electrode 14A and the second electrode 14B are grounded plate electrodes, which are io upstanding from the base 13 of the platform 1B in a parallel configuration and in facing relations. In this embodiment, the base 13 is formed from plastic, and the first and second electrodes 14A and 14B are formed from copper, although in alternative embodiments, other suitable materials may be used such as aluminium.
is The first insulating member 15A and the second insulating member 15B are also upstanding from the base 13 of the platform 1B. The first insulating member 15A is located adjacent the first electrode 14A and the second insulating member 15B is located adjacent the second electrode 14B. The joining portion 15C of the insulating member is located adjacent to, and parallel to, the base B. The first and second insulating members 15A, 15B are located in facing relations, and in-between the first and second electrodes 14A, 14B, such that the first and second insulating members 15A, 15B are located between the first and second electrodes 14A, 14B.
A substrate S is located on the electrospinning apparatus 1. The substrate S extends longitudinally between the first and second insulating members 15A, 15B, on the joining portion 15C of the insulating member 15, and in parallel to the base 13 of the platform 1B. In this embodiment, the substrate S is formed from paper. It is to be understood that the substrate S is optional, and the aligned nanofibres ANF may be deposited on the insulating member 15 instead.
Referring also to FIG. 1B, there is shown a side elevation of highlighted section C of the electrospinning apparatus 1 shown in FIG. 1A. The first electrode 14A and the second electrode 14B are parallel, in facing relations, and are substantially perpendicular to the base 13 of the platform 1B.
The first insulating member 15A is located adjacent or proximate the first electrode 14A such that an internal angle Al is created therebetween. The second insulating member 15B is located adjacent or proximate the second electrode 14B such that an internal angle A2 is created therebetween. In this embodiment, the angle A1 and the angle A2 are substantially equal. In this embodiment, A1=A2=35 to 45°, e.g. 40°.
The dimensions and geometry of the electrospinning apparatus 1 are shown in FIGS. 1A and 1B. There is shown the height h and width w of the first insulating member 15A. The first and second insulating members 15A, 15B are equal in size and have the same dimensions.
The distanced between the first electrode 14A and the second electrode 14B is shown in FIG. 1B. There is also shown the width w′ and the height h′ of the first electrode 14A. The first and second electrode 14A, 14B are equal in size and have the same dimensions.
There is further shown in FIG. 1A the height h″ of the tip of the nozzle 12 from the platform 1 B, i.e. the distance between the tip of the nozzle 12 and the platform 1 B.
In this particular embodiment, the dimensions of each of the first and second electrode 14A, 14B are 100 mm in width w′, 14 mm in height h′, and 3 mm thick. The distanced between the first electrode 14A and the second electrode 14B is preferably between 15 to 35 mm.
The first and second insulating members 14A, 14B are formed from polyurethane foam. In this embodiment, the first and second insulating members 14A, 14B are between 0.1 mm to 7 mm thick, for example, between 0.25 mm to 5 mm thick.
The height h″ of the tip of the nozzle 12 from the platform 1B may be between 4 to 13 mm.
Preferably, the height h of the first and/or second insulating member 15A, 15B is greater than or equal to the height h″ of the tip of the nozzle 12 from the platform 1 B. It has been surprisingly found that greater alignment of nanofibres ANF may be obtained using this configuration of the apparatus
It is understood that the dimensions of the electrospinning apparatus of the invention are not absolute, and the function of the invention is dependent on the geometric relationships between the components, such that the components, e.g. the electrode(s), the first and second insulating members, may be scaled up in size or down in size to obtain smaller or larger apparatus that functions in the same way.
In use, the first and second electrode 14A, 14B of the platform 1B are energised by applying a potential difference between a nozzle 12 and the first and second electrodes 14A, 14B.
The dispensing unit 1A of the electrospinning apparatus 1 dispenses the precursor P from the reservoir 10 and through the syringe 11. The precursor P passes through the nozzle 12 to form fibres, e.g. nanofibres NF.
The precursor L may be any suitable electrospinning material, for example, in this embodiment the precursor L is 15% PVP (poly(vinyl pyrrolidone) in ethanol.
The nanofibres NF are formed by ejection of the precursor P from the nozzle 12 into the atmosphere, where, the solvent of the precursor P evaporates to form continuous nanofibres NF.
The nanofibres NF align on the substrate S to form continuous aligned nanofibres ANF. Interaction of the nanofibres NF with the electric field that is formed between the nozzle 12 and the first and second electrodes 14A, 14B causes the nanofibres NF to deposit onto the substrate S to produce aligned nanofibers ANF. The aligned nanofibres ANF are aligned in parallel with the first and second electrodes 14A, 14B, and longitudinally along the substrate S.
It has been shown in the prior art that, in the absence of the insulating member 15, i.e. the first and second insulating members 15A and 15B, the nanofibres NF align to be perpendicular to the first and second electrode 14A, 14B (e.g. see supra).
Without wishing to be bound by theory, it is thought that the insulating members 15A, 15B influences or modifies the electric field so that the electrospun fibres are aligned in parallel with the first and second plate electrodes 14A, 14B to create a highly aligned fibre mat. The insulating members 15A, 15B interfere with the line of sight between the nozzle 12 and the first and second plate electrodes 14A, 14B, and it is thought that this controls the substantially longitudinal alignment of the aligned nanofibres ANF. The angled first and second insulating members 15A, 15B mitigate or reduce the deposition of nanofibres that are aligned perpendicular with respect to the length of the substrate S and/or the first and second electrodes 14A, 14B. It has been found that when the first and second insulating members 15A, 15B are aligned in parallel, a greater quantity of nanofibres are deposited perpendicularly to the length of the substrate S.
Referring now to FIG. 2, there is shown an electrospinning apparatus 2 according to a second embodiment of the invention. The references for like features that have previously been described in FIG. 1 are designated with a prime (′) and will not be described further.
The electrospinning apparatus 2 comprises a first insulating member 16A and second insulating member 16B in place of the insulating member 15 of FIG. 1. In this embodiment, the first and second insulating members 16A, 16B, are separate and are not joined by a joining portion.
The first insulating member 16A and second insulating member 16B of the electrospinning apparatus 2 function in a like-manner to the insulating member 15 shown in FIG. 1, to produce a fibre mat on the substrate S2 comprising the aligned nanofibres ANF′.
The electrospinning apparatus 2 further comprises a first end 2A, located upstream of the platform 1B′, i.e. in use, before receipt of the aligned nanofibres ANF′ onto the substrate S2, and a second end 2B, located downstream of the platform 1B′, i.e. in use, after receipt of the aligned nanofibres ANF′ onto the substrate S2.
The electrospinning apparatus 2 further comprises a feed reel (not shown) located at the first end 2A of the electrospinning apparatus 2, and an exhaust reel (not shown) located at the second end 2B of the electrospinning apparatus 2.
The feed reel (not shown) is a spool, onto which is wound a length of the substrate S2 that is free from the aligned nanofibres ANF′. In use, the feed reel (not shown) is configured to supply a length of the substrate S2 from the first end 2A of the electrospinning apparatus 2, to the platform 1B′ for receipt of aligned nanofibres ANF′.
The exhaust reel (not shown) is a spool, onto which a length of the substrate S2 in receipt of aligned nanofibres ANF′ may be wound. In use, the exhaust reel (not shown) is configured to take-up the substrate S2 from the platform 1B′ at the second end 2B of the electrospinning apparatus 2.
In this embodiment, the feed reel (not shown) and the exhaust reel (not shown) are rotationally driven. In use, the substrate S2 runs, in a running direction RD (shown by the arrows labelled RD in FIG. 2) from the feed reel (not shown) at the first end 2A, through the platform 1B′ of the electrospinning apparatus 2, i.e. in between both of the first and second electrodes 14A′, 14B′, and the first and second insulating members 16A, 16B; to the second end 2B and onto the exhaust reel (not shown).
During the electrospinning process, the nanofibres NF′ are aligned and deposited onto a section of the substrate S2 located on the platform 1B′ to produce aligned nanofibres ANF′. The feed reel (not shown) and the exhaust reel (not shown) work in concert to run the substrate S2 in a running direction RD through the platform 1B′ of the electrospinning apparatus 2 to constantly renew the section of the substrate S2 that receives the aligned nanofibres ANF′. The substrate S2 in receipt of aligned nanofibres ANF′ is then wound onto, and may be stored on, the exhaust reel (not shown).
In this way, a fibre mat containing aligned nanofibres ANF′ of any desired length may be fabricated, the only limitation being the length of substrate S2 that is provided to the electrospinning apparatus 2.
Advantageously, the substrate S2 may be a material for use in the final product comprising the aligned nanofibres ANF′. For example, the substrate S2 may be a glass fibre sheet for use in a composite material, e.g. a reinforced composite panel.
Alternatively, the substrate S2 may be a sacrificial substrate. In this case, the aligned nanofibres ANF′ may be removed after the electrospinning process is complete, and affixed to an appropriate secondary substrate.
Referring now to FIG. 3A, there is shown a side elevation of an electrospinning apparatus 3 according to a third embodiment of the invention.
The electrospinning apparatus 3 is analogous to the electrospinning apparatus 1 of the first embodiment of the invention (shown in FIGS. 1A and 1B), and differs only in that the electrodes 14A, 14B have been replaced with a flat plate electrode 34. It is understood that the electrospinning apparatus 3 comprises all other analogous features such as a dispensing unit, although this is not shown or described further.
The electrospinning apparatus comprises a platform 3B. In this case, the platform 3B comprises a flat plate electrode 34 and an insulating member 35.
In this embodiment, the insulating member 35 comprises a first insulating member 35A, a second insulating member 35B, interconnected by a joining portion 35C to form a unitary U-shaped member. In this embodiment, the insulating member 35 is formed from a foamed polyurethane sheet.
In this embodiment, the electrode 34 is formed from copper.
The first insulating member 35A and the second insulating member 35B each upstand from the flat plate electrode 34 of the platform 1 B. The flat plate electrode 34 is spaced approximately 1 cm from the joining portion 35C of the insulating member 35.
A substrate S3 is located on the electrospinning apparatus 3 in the plane labelled as X. The substrate S3 extends longitudinally between the first and second insulating members 35A, 35B, on the joining portion 15C of the insulating member 15, and in parallel to the flat plate electrode 34 of the platform 3B. In other embodiments, the first insulating member 35A and the second insulating member 35B may be distinct and absent a joining portion 35C. In this case, the substrate S3 may be located directly on, and parallel to, the flat plate electrode 34.
In the geometry shown in FIG. 3A, each of the first and second electrically insulating members 35A, 35B creates an angle A3, A4 of greater than 0 and less than 90° with the plane X of the substrate and/or the flat plate electrode 34. In this embodiment, the angle A3 is equal to A4, each of which are equal to 40°.
The electrospinning apparatus 3 functions in an analogous manner to that described for the electrospinning apparatus of FIGS. 1A and 1B such that nanofibres align on the substrate S3 to form continuous aligned nanofibres, which are aligned in parallel with the first and second insulating members 35A, 35B, and longitudinally along the substrate S3.
It is understood that the electrospinning apparatus 3 may further comprise a feed reel (not shown) is located at a first end (not shown) of the electrospinning apparatus 3, and an exhaust reel (not shown) located at a second end 2B (not shown) the electrospinning apparatus 3 such that a fibre mat containing aligned nanofibres of any desired length may be fabricated, in an analogous manner to that shown in and described for FIG. 2.
Referring also to FIG. 3B, there is shown an image of the electrospinning apparatus 3 of FIG. 3A. There is shown the dimensions of the flat plate electrode 34; the width w3 and the length L.
In this particular embodiment, the dimensions of the flat plate electrode 34 are 100 mm in length L, 65 mm in width w3, and 0.3 mm in thickness.
The first and second insulating members 34A, 34B are formed from polyurethane foam. In this embodiment, the first and second insulating members 34A, 34B are between 0.1 mm to 7 mm thick, for example, between 0.25 mm to 5 mm thick.
The minimum width of the flat plate electrode 34 is the width of the substrate S3. There is no upper limit for the width of the flat plate electrode 34.
Without wishing to be bound by theory, it is thought that the insulating members 35A, 35B influences or modifies the electric field so that the electrospun fibres are aligned in parallel with the flat plate electrode 34 to create a highly aligned fibre mat. The insulating members 35A, 35B interfere with the line of sight between the nozzle (not shown) and the flat plate electrode 34 such that the spun fibre is influenced by the electric field only at the terminal ends of the insulating members 35A, 35B. In this way, the spun fibres oscillate back and forth along the substrate S3 and it is thought that this controls the substantially longitudinal alignment of the aligned nanofibres ANF.
Referring now to FIG. 3C, there is shown the electrospinning apparatus 3 of FIGS. 3A and 3B. There is further shown the nozzle 32 in relation to the first and second insulating members 35A, 35B, and the substrate S3.
In a preferred embodiment, the tip of the nozzle 32 is below the plane Y of uppermost edge of the first and second insulating members 35A, 35B, as is shown in FIG. 3C.
The height h3 of the tip of the nozzle 32 from the platform 3B may be between 5 to 17 cm, for example, 5 to 15 cm.
Preferably, the substrate S3 is located between the first and second insulating members 35A, 35B ata height from the flat plate electrode 34 of no more than h3, i.e. below the upper edge of the first and second insulating members 35A, 35B.
It is understood that the dimensions of the electrospinning apparatus of the invention are not absolute, and the function of the invention is dependent on the geometric relationships between the components, such that the components, e.g. the electrode(s), the first and second insulating members, may be scaled up in size or down in size to obtain smaller or larger apparatus with the same function.
It is preferable that the dielectric constant of the substrate, e.g. substrate S, S2, S3, is higher than the material from which the first and second insulating members, e.g. 15A, 15B, 35A, 35B, are fabricated.
Referring now to FIG. 4, there is shown an image 4 of a custom-made glass nozzle 40 for use in electrospinning apparatus of the invention. The custom-made glass nozzle 40 has an outer diameter of 397 micrometres and an inner diameter of 166 micrometres.
Referring now to FIG. 5, there is shown an electrospinning apparatus 5 according to a further embodiment of the invention.
The electrospinning apparatus 5 comprises a disc-shaped electrode 54, a first insulating member 55A, and a second insulating member 55B. A substrate S5 is located in between the first insulating member 55A, and the second insulating member 55B.
The electrospinning apparatus 5 is analogous to the electrospinning apparatus 1 of FIGS. 1A and 1B, and also the electrospinning apparatus 3 of FIG. 3A to 3C, which differs only in that the electrode comprises a circular, disc-shaped electrode 54. It is understood that the electrospinning apparatus 5 comprises all other analogous features such as a dispensing unit, although this is not shown or described further.
Advantageously, the disc-shaped electrode 54 is rotatable. In this way, the disc-shaped electrode 54 may be cleaned by rotation, e.g. to remove unwanted and/or misaligned and/or randomly aligned nanofibre deposition on the edges of the disc-shaped electrode 54. For example, the apparatus 5 may comprise a cleaning means, e.g. a brush or a wipe, so that the upper surface of the disc-shaped electrode 54 may be cleaned during rotation of the disc-shaped electrode 54 to remove unwanted nanofibre deposition.
Referring now to FIG. 6, there is shown an apparatus 6 according to a yet further embodiment of is the invention. The apparatus 6 comprises three separate electrospinning apparatus 5 a, 5 b, 5 c of FIG. 5, each of which function to deposit aligned nanofibres ANF onto a substrate S6.
The apparatus 6 is analogous to that shown in FIG. 2, in that the apparatus 6 further comprises a feed reel (not shown) located at the first end 6A of the substrate S6, and an exhaust reel (not shown) located at the second end 6B of the substrate S6. The feed reel and exhaust reel function in a like-manner to than described for FIG. 2 in that substrate comprising aligned fibres may be fabricated of infinite length.
Each of the three separate electrospinning apparatus 5 a, 5 b, 5 c is positioned at a different angle with respect to one another such that the deposited aligned nanofibres on the substrate may be aligned at different angles. The angles of alignment are shown as 0° (5 a), 90° (5 b), and 45° (5 c) with respect to the longitudinal direction of the substrate S6.
In this way, it is possible to fabricate substrates comprising multiple layers of fibres, each of which are aligned in a different direction, i.e. a different angle with respect to that of the longitudinal direction of the substrate S6. Therefore, stacked layers of aligned nanofibres on a substrate may be fabricated without the need for lamination and/or a separate, further manufacturing step.
To further exemplify the invention, reference is also made to the following non-limiting Examples.

EXAMPLES

Referring now to FIG. 7, there is shown a photograph of a substrate comprising aligned nanofibres, according to Example 1 of the invention, which was fabricated using the apparatus shown in FIG. 6 according to the invention.
Referring now to FIGS. 8A to 8E, there is shown SEM images of aligned nanofibres on a substrate, according to Example 2 of the invention.
The aligned nanofibre mat of Example 2 was produced using the electrospinning apparatus shown in FIG. 3B.
The aligned fibre mats of Example 1 and Example 2 were both produced using the following parameters:

- Needle to substrate distance: 75 mm
- Working potential: 7.5 kV
- Feeding rate: 0.2 ml/h
- U/V shaped dielectric material: PTFE sheet
- U/V shaped dielectric dimension:
  - Height: 75.5 mm
  - Length: 100 mm
  - Angle: 37°
  - Thickness: 1 mm
- Electrode dimension: 65*0.3*80 mm (flat plate electrode)
- Substrate material: Crafting papers with 0.15 mm thick
- Average fibre diameter: 1 μm

The material used was PAN (Mw=230 k 14 wt. % in DMSO).
It should be noted that DMF (dimethylformamide) and/or DMAc (dimethylacetamide) may be used in place of DMSO.
Referring now to FIGS. 9A and 9B, there is shown SEM images of aligned PAN fibres on a substrate, according to Example 3 of the invention. The aligned nanofibre mat of Example 3 was produced using the electrospinning apparatus shown in FIG. 3B and FIG. 6 using the following parameters:

- Needle to substrate distance: 70 mm
- Working potential: 6.5 kV
- Feeding rate: 0.2 ml/h
- U/V shaped dielectric material: PTFE sheet
- U/V shaped dielectric dimension:
  - Height: 70.5 mm
  - Length: 100 mm
  - Angle: 37°
  - Thickness: 1 mm
- Electrode dimension: 65*0.3*80 mm (flat plate electrode)
- Substrate material: Kitchen baking papers, 0.25 mm thick
- Fibres formed had an average fibre diameter of 0.5 μm

The material used was PAN (Mw=150 k 10 wt. % in DMSO).
There SEM images show layers of aligned fibres; the first (base) layer aligned at 0′ and the second (top) layer aligned at 90°.
Referring now to FIG. 10, there is shown a micrograph showing highly aligned and multi-layered nanofibres at different angles produced using the apparatus of FIG. 6. The micrograph shows a high-density of nanofibres aligned and successively overlaid at different angles of −45°, +45° and 0°. This demonstrates how the substrate may be rotated as desired to change the angle of the aligned and electro-spun fibres.
Advantageously, the electrospinning apparatus according to the invention provides a facile and inexpensive means to allow the width and length of the substrate, and therefore the width and length of the aligned fibre mat, to be varied in a facile manner. For example, the distance between the electrodes may be altered and varied to deposit aligned nanofibres onto any width of substrate, to fabricate fibre mats of any suitable width.
More advantageously, a substrate of any given length may be used and continuously run through the apparatus of the present invention to provide a continuously aligned fibre mat.
Additionally, substrates comprising layers of fibres may be fabricated, for example, substrates comprising layers of aligned fibres and/or substrates comprising layers of aligned fibres in which at least one layer is aligned in a different direction (i.e. at a different angle) to another, different layer, and/or layers of aligned fibres in which at least one layer consists of aligned fibres and another, different layer consists of random fibres.
It will be appreciated by those skilled in the art that several variations to the aforementioned embodiments are envisaged without departing from the scope of the invention. For example, the dimensions of the electrodes, electrically insulating members, nozzle height and dimensions provided herein are examples only and may be altered accordingly.
It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and/or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.

Claims

1. A spinning apparatus for forming aligned fibres, the apparatus comprising a nozzle for ejecting material for forming fibres from a tip thereof, an electrode, a substrate for receiving fibres thereon, and first and second electrically insulating members, wherein the tip of the nozzle is located between the first and the second electrically insulating members.

2. A spinning apparatus according to claim 1, wherein the substrate comprises or is formed from an electrically insulative material.

3. (canceled)

4. (canceled)

5. A spinning apparatus according to claim 1, wherein the substrate extends between the first and second electrically insulative member.

6. A spinning apparatus according to claim 1, wherein the first electrically insulating member and the second electrically insulating member are integrally formed or wherein the first electrically insulating member and the second electrically insulating member are separate, distinct components.

7. A spinning apparatus according to claim 1, wherein each of the first electrically insulating member and second electrically insulating comprise a first, e.g. lower, portion and a second, e.g. upper, portion, the first portions of the first and second electrically insulating members are located adjacent or proximate the substrate, the second portions of each of the first and second electrically insulating members extend away from the respective first portions in a direction which is non-pararllel and non-perpendicular to the substrate.

8. A spinning apparatus according to claim 7, wherein the angle created between each of the first and second electrically insulating members with the plane of the substrate is between 25 to 55.

9. A spinning apparatus according to claim 1, wherein the electrically insulating material is formed from, or comprises, a dielectric material.

10. A spinning apparatus according to preceding claim 1, wherein the first electrically insulating material and/or second electrically insulating material and/or the substrate is formed from or comprises one or more of polyurethane, polytetrafluoroethylene (PTFE), and glass.

11. A spinning apparatus according to claim 1, wherein the at least one electrode is selected from a flat, grounded electrode, and a disc-shaped electrode.

12. A spinning apparatus according to claim 1, comprising a first and second grounded plate electrode.

13. A spinning apparatus according to claim 12, wherein each of the first and second electrically insulating members are located adjacent or proximate a respective one of the first and second grounded plate electrodes.

14. A spinning apparatus according to claim 13, wherein the substrate extends between first and second grounded plate electrodes.

15. A spinning apparatus according to claim 1, further comprising a feed reel comprising a length of substrate located upstream of the at least one electrode.

16. A spinning apparatus according to claim 1, further comprising an exhaust or take-up reel being located downstream of the at least one electrode.

17. (canceled)

18. A spinning apparatus according to claim 1, further comprising at least one more spinning apparatus.

19. A method of forming aligned nanofibers, the method comprising providing at least one electrode, locating a first and second electrically insulating member in facing relations, locating a substrate that extends between the first and second electrically insulating members, locating the tip of the nozzle between the first and the second electrically insulating members, applying an electric field between a nozzle and the at least one electrode and depositing aligned nanofibers on a substrate.

20. A method according to claim 19, further comprising positioning the first and second electrically insulating members to be non-parallel and non-perpendicular to the plane of the substrate.

21. A method according to claim 19, comprising moving the substrate with respect to the at least one electrode.

22. A method according to claim 21, wherein the method comprises translationally and/or rotationally moving the substrate.

23. A method of claims 20, wherein the substrate is an endless belt.

24. (canceled)