U.S. patent application number 17/413695 was filed with the patent office on 2022-01-20 for electrospinning apparatus and method for forming aligned fibres.
The applicant listed for this patent is The University of Birmingham. Invention is credited to Fernando Gerard, Shao Siheng.
Application Number | 20220018039 17/413695 |
Document ID | / |
Family ID | |
Filed Date | 2022-01-20 |
United States Patent
Application |
20220018039 |
Kind Code |
A1 |
Siheng; Shao ; et
al. |
January 20, 2022 |
ELECTROSPINNING APPARATUS AND METHOD FOR FORMING ALIGNED FIBRES
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).
Inventors: |
Siheng; Shao; (Birmingham,
West Midlands, GB) ; Gerard; Fernando; (Birmingham,
West Midlands, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The University of Birmingham |
Birmingham |
|
GB |
|
|
Appl. No.: |
17/413695 |
Filed: |
December 13, 2019 |
PCT Filed: |
December 13, 2019 |
PCT NO: |
PCT/GB2019/053542 |
371 Date: |
June 14, 2021 |
International
Class: |
D01D 5/00 20060101
D01D005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 14, 2018 |
GB |
1820411.5 |
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)
Description
[0001] 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.
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] Therefore, it remains a challenge to fabricate a fibre mat
comprising aligned fibres, e.g. microfibres or nanofibres, of a
desired length.
[0008] 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.degree. 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] Preferably the substrate comprises or is formed from an
electrically insulative material.
[0013] 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.
[0014] 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.
[0015] Preferably the tip of the nozzle is located between the
first and the second electrically insulating members.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] 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.
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.degree.
and less than 180.degree., preferably greater than 0.degree. and
less than 160.degree., say greater than 0.degree. and less than
140.degree., 130.degree., 120.degree., 110.degree., 100.degree.. 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.
[0025] 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.
[0026] 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.degree., say 35 to 45.degree.. The
angle between the first and second electrically insulating members
may be between 70 and 130.degree., say 90 to 110.degree..
[0027] It has been surprisingly found that an angle of between 25
to 55.degree. 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.
[0028] 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.degree. with the plane of the flat
electrode (and the plane of the su bst rate) .
[0029] 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.
[0030] 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.
[0031] Preferably the substrate is formed from an electrically
insulating material.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] In embodiments, the method comprises providing two
electrodes, e.g. a first and second facing grounded plate
electrode.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] In embodiments, the substrate may be movable, e.g. movable
with respect to the electrode, e.g. the first and second
electrodes.
[0040] In embodiments, the substrate may be an endless belt.
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] Additionally or alternatively, the first and second
electrically insulating members may comprise only a solid phase,
that is, not be a foam.
[0050] 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.times.10.sup.-5 S/m, e.g. less than 1.times.10.sup.-1.degree.
S/m, for example, less than 1.times.10.sup.-15, or less than
1.times.10.sup.-20.
[0051] 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.
[0052] 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.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] 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.
[0057] The disc-shaped electrode may describe an annulus.
[0058] 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.
[0059] The tip of the nozzle may be spaced at a distance of between
4 to 13 cm from the substrate
[0060] 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.
[0061] 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.
[0062] 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.
[0063] The first and/or second electrically insulating members may
be located in intimate contact with the first and/or second
electrodes.
[0064] 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.degree., but is preferably between 45 degrees and 55.degree.,
e.g. from any one of 45, 46, 47, 48, 49, 50, 51, 52, 53,
54.degree., to any one of 55, 54, 53, 52, 51. 50, 49, 48, 47, or
46.degree.. The optimum angle A1 , A2 is dependent on the distance
d between the first electrode and the second electrode.
[0065] 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).
[0066] 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.
[0067] 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.
[0068] 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.
[0069] The material for forming fibres may be or may comprise a
nanofibre, for example, fibres with a diameter of between
200.times.10.sup.-9 m (200 nm) to 500.times.10.sup.-9 m (500 nm).
In embodiments, the material for forming fibres may be or may
comprise a nanofibre with a diameter of less than
200.times.10.sup.-9 m (200 nm), e.g. less than 100.times.10.sup.-9
(100 nm). The diameter of the fibre is dependent on the viscosity
and concentration of the material for forming fibres.
[0070] 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.
[0071] 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.
[0072] 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.
[0073] 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.
[0074] 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.
[0075] 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.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] 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.
[0080] 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.
[0081] 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.
[0082] A further aspect of the invention provides an apparatus
comprising two or more electrospinning apparatus of the invention,
e.g. three, four, or n.sup.th electrospinning apparatus of the
invention, located in series for use with a single substrate.
[0083] 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.sup.th layer of aligned nanofibres.
[0084] More advantageously, the first, second, and n.sup.th
electrospinning 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.
[0085] 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.
[0086] The fibre mat may comprise nanofibres, for example, fibres
with a diameter of between 200.times.10.sup.-9 m (200 nm) to
500.times.10.sup.-9 m (500 nm).
[0087] 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.
[0088] Advantageously, the fibre mat of the invention may be
removed or detached from the substrate and/or may be transferred to
a secondary substrate.
[0089] The fibre mat of the invention may be further used in
applications such as tube wrapping, filament winding, and/or
pultrusion techniques.
[0090] 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.
[0091] Embodiments of the invention will now be described by way of
example only with reference to the accompanying drawings in
which:
[0092] FIG. 1A is an electrospinning apparatus, according to a
first embodiment of the invention;
[0093] FIG. 1B is a side elevation of an insulating member and an
electrode, according to the embodiment of the invention shown in
FIG. 1A;
[0094] FIG. 2 is an electrospinning apparatus, according to a
second embodiment of the invention;
[0095] FIG. 3A is a side elevation of an electrospinning apparatus,
according to a third embodiment of the invention;
[0096] FIG. 3B is an image of the electrospinning apparatus of FIG.
3B showing the dimensions of the electrode;
[0097] FIG. 4 is an image of a nozzle for use in the
electrospinning apparatus of the invention;
[0098] FIG. 5 is an electrospinning apparatus, according to a
further embodiment of the invention;
[0099] FIG. 6 is an electrospinning apparatus, according to a yet
further embodiment of the invention;
[0100] FIG. 7 is a photograph of a substrate comprising an aligned
nanofibre mat, according to an Example of the invention;
[0101] FIGS. 8A to 8E are SEM images of substrate comprising
aligned fibres, which were fabricated according to Examples of the
invention;
[0102] FIGS. 9A and 9B are SEM micrographs of substrate comprising
aligned fibres at 0 and 90.degree., according to Examples of the
invention; and
[0103] FIG. 10 is a micrograph showing highly aligned and
multi-layered nanofibres at different angles produced using the
apparatus of FIG. 6.
[0104] 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.
[0105] 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.
[0106] 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.
[0107] In this embodiment, the insulating member 15 is formed from
a foamed polyurethane sheet.
[0108] 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.
[0109] 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.
[0110] 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.
[0111] 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.
[0112] 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.degree., e.g. 40.degree..
[0113] 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.
[0114] 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.
[0115] 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.
[0116] 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.
[0117] 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.
[0118] The height h'' of the tip of the nozzle 12 from the platform
1B may be between 4 to 13 mm.
[0119] 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
[0120] 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.
[0121] 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.
[0122] 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.
[0123] 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.
[0124] 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.
[0125] 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.
[0126] 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).
[0127] 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.
[0128] 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.
[0129] 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.
[0130] 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'.
[0131] 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.
[0132] 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.
[0133] 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'.
[0134] 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.
[0135] 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).
[0136] 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).
[0137] 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.
[0138] 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.
[0139] 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.
[0140] Referring now to FIG. 3A, there is shown a side elevation of
an electrospinning apparatus 3 according to a third embodiment of
the invention.
[0141] 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.
[0142] The electrospinning apparatus comprises a platform 3B. In
this case, the platform 3B comprises a flat plate electrode 34 and
an insulating member 35.
[0143] 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.
[0144] In this embodiment, the electrode 34 is formed from
copper.
[0145] 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.
[0146] 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.
[0147] 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.degree. 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.degree..
[0148] 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.
[0149] 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.
[0150] 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.
[0151] 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.
[0152] 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.
[0153] 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.
[0154] 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.
[0155] 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.
[0156] 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.
[0157] 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.
[0158] 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.
[0159] 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.
[0160] 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.
[0161] 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.
[0162] Referring now to FIG. 5, there is shown an electrospinning
apparatus 5 according to a further embodiment of the invention.
[0163] 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.
[0164] 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.
[0165] 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.
[0166] 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 5a,
5b, 5c of FIG. 5, each of which function to deposit aligned
nanofibres ANF onto a substrate S6.
[0167] 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.
[0168] Each of the three separate electrospinning apparatus 5a, 5b,
5c 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.degree. (5a), 90.degree. (5b), and 45.degree. (5c) with respect
to the longitudinal direction of the substrate S6.
[0169] 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.
[0170] To further exemplify the invention, reference is also made
to the following non-limiting Examples.
EXAMPLES
[0171] 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.
[0172] 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.
[0173] The aligned nanofibre mat of Example 2 was produced using
the electrospinning apparatus shown in FIG. 3B.
[0174] The aligned fibre mats of Example 1 and Example 2 were both
produced using the following parameters: [0175] Needle to substrate
distance: 75 mm [0176] Working potential: 7.5 kV [0177] Feeding
rate: 0.2 ml/h [0178] U/V shaped dielectric material: PTFE sheet
[0179] U/V shaped dielectric dimension: [0180] Height: 75.5 mm
[0181] Length: 100 mm [0182] Angle: 37.degree. [0183] Thickness: 1
mm [0184] Electrode dimension: 65*0.3*80 mm (flat plate electrode)
[0185] Substrate material: Crafting papers with 0.15 mm thick
[0186] Average fibre diameter: 1 .mu.m
[0187] The material used was PAN (Mw=230 k 14 wt. % in DMSO).
[0188] It should be noted that DMF (dimethylformamide) and/or DMAc
(dimethylacetamide) may be used in place of DMSO.
[0189] 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: [0190] Needle to substrate
distance: 70 mm [0191] Working potential: 6.5 kV [0192] Feeding
rate: 0.2 ml/h [0193] U/V shaped dielectric material: PTFE sheet
[0194] U/V shaped dielectric dimension: [0195] Height: 70.5 mm
[0196] Length: 100 mm [0197] Angle: 37.degree. [0198] Thickness: 1
mm [0199] Electrode dimension: 65*0.3*80 mm (flat plate electrode)
[0200] Substrate material: Kitchen baking papers, 0.25 mm thick
[0201] Fibres formed had an average fibre diameter of 0.5 .mu.m
[0202] The material used was PAN (Mw=150 k 10 wt. % in DMSO).
[0203] There SEM images show layers of aligned fibres; the first
(base) layer aligned at 0' and the second (top) layer aligned at
90.degree..
[0204] 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.degree., +45.degree. and 0.degree.. This
demonstrates how the substrate may be rotated as desired to change
the angle of the aligned and electro-spun fibres.
[0205] 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.
[0206] 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.
[0207] 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.
[0208] 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.
[0209] 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.
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