EP1871929A1

EP1871929A1 - A method and a device for forming a fibre from a material and directing said fibre, using an electric field, and an object thus formed

Info

Publication number: EP1871929A1
Application number: EP06733007A
Authority: EP
Inventors: Gerardus Wilhelmus Maria Peters; Marinus Jacobus Gerardus Van De Molengraft
Original assignee: Eindhoven Technical University
Current assignee: Eindhoven Technical University
Priority date: 2005-04-22
Filing date: 2006-04-18
Publication date: 2008-01-02
Also published as: WO2006112697A1; NL1028847C2

Abstract

The invention relates to a method and a device for forming a fibre from a material and directing said fibre, using an electric field, wherein said electric field is applied between at least two electrodes. A first electrode is formed by a capillary for supplying the material, and the first electrode is brought to a first electrical potential. A second electrode is brought to a second electrical potential for locally applying said second electrical potential in at least one point for the purpose of pulling the fibre in a specified direction. The location of the point at which the second electrical potential is applied can be changed in a time-controlled manner. The invention also relates to a fibre and to an object comprising a surface formed in this manner.

Description

Title

A method and a device for forming a fibre from a material and directing said fibre, using an electric field, and an object thus formed

Field of the invention

The present invention relates to a method for forming a fibre from a material, using an electric field, wherein said electric field is applied between at least two electrodes, and wherein a first electrode is formed by a capillary for supplying the material, which first electrode is brought to a first electrical potential. The invention further relates to a device for forming a fibre from a material, using an electric field, which device comprise a capillary for supplying a material, in which the capillary forms a first electrode for bringing the material to a first electrical potential, and which further comprises a second electrode.

The invention further relates to an object formed by using a method or a device as described above.

Background

Such methods and devices are better known by the name of "electrospinning" in the industry. A material is introduced into a space by an electrode formed by a capillary, and is accelerated by means of a further electrode under the influence of an electric field. The electric field exerts a pulling force on the material, thereby stretching the material, so that a fibre is formed. Since the material has already been brought to a first potential upon exiting the capillary, the fibre will fan out after some time. After all, the charged fibre exerts an electrostatic force on itself.

The second electrode is usually formed by an earthed plate, on which the fibre is deposited. In addition to that, the second electrode may for example be made up of a cylindrical body or reel capable of rotary motion, so that the fibre can be wound onto the reel. Although fibres (typically < 10 m) can be formed in an elegant manner by using a method according to the prior art, such a method has this drawback that after the material has exited the capillary and is stretched into a fibre under the influence of the electric field, the fibre will fan out, as described above. One of the consequences of said fanning out of the fibre is that it is difficult to control the positioning of the fibre.

Summary of the invention

Consequently it is an object of the present invention to provide a method and a device for forming a fibre from a material, using an electric field, wherein the fibre can be directed in any desired direction upon being formed.

This object is accomplished by the present invention in that the invention provides a method for forming a fibre from a material and directing said fibre, using an electric field, wherein the electric field is applied between at least two electrodes, and wherein a first electrode is formed by a capillary for supplying the material, which first electrode is brought to a first electrical potential, characterised in that a second electrode is brought to a second electrical potential for locally applying said second electrical potential in at least one point for the purpose of pulling the fibre in a specified direction, wherein the location of the point at which the second electrical potential is applied can be changed in a time-controlled manner.

The invention is based on the perception that by concentrating a second electrical potential in one point, the field lines of the electric field, and thus the pulling force exerted on the fibre by the electric field, will likewise be directed towards this point. The location of this point can subsequently be changed dynamically, so that the electric field between the electrodes is changed dynamically and the fibre can be pulled in another direction. The fibre can thus be pulled in any desired direction by means of the electrode, so that it becomes possible to direct the fibre. Those skilled in the art will appreciate that if the fibre can be pulled in a specified direction upon being formed, a large number of advantages are obtained. By pulling the fibre in a specified direction during manufacturing thereof, the method can be used for realising geometrically complex structures constituted by fibres, for example for forming objects.

Preferably, the second electrode has a pointed end. According to a specific embodiment, the second electrode comprises a needle electrode and said at least one point is formed by an end of the needle electrode. Using the right mechanical supporting systems, a needle electrode can be easily moved within a space for changing the location of the point at which the second potential is applied in a time-controlled manner, so that it becomes possible to pull the fibre in a desired direction during manufacturing thereof. According to another embodiment of the present invention, the second electrode consists of an arrangement or array of local electrodes, each local electrode being arranged for applying an electrical potential at one point. Think in this connection of a matrix structure of electrodes, in which each local electrode forms a point in a system of coordinates, and in which the fibre can be directed to any desired local electrode, for example by (temporarily) bringing such an electrode of the array to the second potential.

According to another embodiment, various local electrodes of the array are brought to the second potential for the purpose of pulling the fibre in various directions. This can take place in a time-controlled manner, for example.

Those skilled in the art will understand that if the second electrode consists of such a group of local electrodes, the method can be carried out very efficiently, since it is comparatively straightforward to bring the various local electrodes of the group to the second potential independently of each other, so that switching between the various electrodes can be performed quickly and efficiently. This makes it possible to effect last modifications in the fibre direction.

According to another embodiment of the invention, a dielectric and optionally curved or suitably shaped substrate is disposed between the second and the first electrode for receiving the fibre. The second electrode may be disposed under the substrate, whilst the capillary that supplies the material is disposed above the substrate. By directing the fibre by means of the second electrode, the fibre can be deposited at any desired location on the substrate. Thus a coating may, for example, be applied to the substrate by means of the fibre. It is also possible, of course, to use the substrate as a mould for a surface to be created by means of the fibre, for example if the substrate is selected such that no adhesive or binding forces between the fibre and the substrate takes place. According to another embodiment, the substrate therefore comprises a surface having a desired shape for forming a surface or fibre pattern corresponding to the shape of the substrate surface from the fibre that is to be received. The present method makes it possible to form complex structures from the fibre in a relatively simple manner, it may for example be used for forming so-called "scaffolds" or artificial objects for use in a human or animal body. Such scaffolds usually require complex surfaces and structures, as is the case with an artificial heart valve, for example. Said surfaces and structures can be produced in a relatively simple manner by using the method as described above.

The forming of complex geometric structures and platforms in a precise manner may also be of importance in the electrotechnical and optical industries. For example, if conductive materials are used for producing the fibres, complex structures having relatively small dimensions can be formed with great precision on printed circuit boards (PCBs) and the like, for example, in a relatively simple manner by using the method according to the invention.

According to another embodiment of the invention, a method is provided wherein material is supplied by two or more capillaries, and wherein each of the first electrodes formed by the capillaries can be brought to a first potential for the purpose of pulling the fibres in a specified direction from each of said at least two capillaries.

It may be appreciated that the force being exerted on the fibre by the electric field can be controlled by varying the strength of the electric field. If both the first and the second electrode are on the same potential, there will be no electric field between the electrodes and no force will be exerted on the fibre. If two or more capillaries are used for supplying material and the force being exerted on the material from the two capillaries can be controlled independently of the force being exerted on the material from the other capillaries, it will be relatively easy to realise complex structures by means of the method according to the invention.

In the above-described embodiment comprising two or more capillaries this can be achieved, for example, by interrupting the drawing of fibres from each of said at least two capillaries in a time-controlled manner, by bringing the first electrode formed by the capillary of the material of the fibre to be interrupted (temporarily) to the second potential. Those skilled in the art will realise that it is important that a force that may be exerted between first electrodes or capillaries being on different potentials must be sufficiently small to ensure that the fibres are not pulled in the direction of one of the other capillaries. The first electrodes or capillaries can be disposed a sufficiently large distance apart, so that the electrical force being exerted between first electrodes will not be large enough to interfere with the operating principle of the invention. Furthermore it is possible to isolate or separate the first electrodes electrically from each other in order to prevent the occurrence of electric fields between the first electrodes or capillaries.

Using such an embodiment it is possible, for example, to intertwine two or more fibres in a specific manner, or to realise other structures consisting of two or more different fibres which have a complex geometric, two-dimensional or three-dimensional shape. Thus it becomes possible to combine properties of fibres made from different materials in a simple manner on a local and very small geometric scale. It is possible, for example, to provide a porous 3D electrode structure from two electrically isolated materials for combining all kinds of optical, electrical, chemical or biological properties, in which various effects are for example obtained as a result of the interaction of the fibres with each other and/or with the environment. According to another embodiment, the material is brought to the first potential by the electrode formed by the inlet, wherein the second electrode is connected to ground. Thus an electric field is created between the two electrodes, which field will exert an electrical force on the material.

According to a second aspect of the invention, a device is provided for forming a fibre from a material, using an electric field, which device comprises a capillary for supplying a material, wherein the capillary forms a first electrode for bringing the material to a first electrical potential, and which furthermore comprises a second electrode, characterised in that the second electrode is arranged for locally applying a second electrical potential in at least one point for the purpose of pulling the fibre in a specified direction.

According to a preferred embodiment of the above device, the second electrode consists of an array of local electrodes, each electrode being arranged for locally applying a second electrical potential at one point.

According to another embodiment, the device may furthermore comprise means for bringing each of the local electrodes of said array individually to the second potential. Said bringing of the local electrodes on the second potential may take place in a time-controlled manner, if desired.

According to a third aspect of the invention, a fibre manufactured by using the device or a method as described above is provided.

Brief description of the drawings

The invention will now be explained in more detail by means of a description of non-limitative embodiments thereof, in which reference is made to the appended drawings, in which: Figure 1A shows an embodiment of a device according to the invention;

Figure 1 B shows a further substrate, which can be used in a device according to the invention; Figure 2 shows an electrode according to the invention, which consists of a group of local electrodes as well as means for addressing the same;

Figure 3 shows a circuit diagram according to the invention for driving local electrodes of a group according to figure 2; and

Figure 4 schematically shows another embodiment of the invention.

Detailed description of the drawings

Figure 1 A is a schematic representation of a device according to the invention, which can be used for carrying out the method according to the invention. The device, which is generally indicated at 1 , comprises a first electrode 3, which also forms a capillary for supplying a material 5 from which a fibre 8 can be formed. The device furthermore comprises a second electrode 7, which is positioned on the other side of a substrate or plate 10 relative to the first electrode 3. De electrode 7 is capable of movement in an X-direction, a Y-direction and/or a Z-direction under the substrate 10, as is indicated by the coordinate system 9. The electrodes 7 and 3 can be brought to a second potential by connecting them, for example, to a voltage source 14. In figure 1A said connection is schematically represented by cables 11 and 12. The capillary/electrode 3 is connected to a reservoir 16, from which the material 5 is supplied to the capillary 3 via a pipe 15. Optionally, said pipe can be opened and closed by means of a valve 18.

An electric field is created between the electrodes 3 and 7 by bringing said electrodes to the second potential. Since the electrode 3 is on a first electrical potential, the material 5 that exits the electrode 3 will be electrically charged as well. The material 5 that exits the capillary 3 will experience a pulling force under the influence of the electric field, which is mainly generated between the pointed ends of the electrodes 3 and 7. The material is stretched in such a manner that a fibre 8 is obtained. The exertion of the force on the material 5 will take place in the direction of the points of the electrode 7.

By moving the electrode 7 present at the underside of the substrate 10 in the X-direction or the Y-direction, the fibre 8 being drawn may be moved in desired directions while being drawn, and thus it is possible to change the location at which the fibre 8 is deposited on the substrate 10. In this way a desired pattern of fibres can be obtained on the surface of the substrate 10. If a curved substrate is used instead of a flat substrate (such as the substrate 10 in figure 1A), or a substrate having a random three-dimensional surface, the electrode 7 can also be moved in the Z-direction for following the substrate surface. Said following can take place at the underside of the substrate, for example, as shown in figure 1a with regard to the substrate 10. After completion of the method, the fibre pattern can be easily removed from the substrate 10 if no bonding between the fibre and the substrate has taken place, and be separately processed to obtain a product. In the case that bonding between the substrate 10 and the fibre has actually taken place, the fibre can be separated from the substrate in a suitable manner, for example by using a suitable solvent. The substrate 10 may be provided with a coating or a surface on which no adhesive or binding force on the fibre takes place, or only to a limited extent, so that it can be easily removed from the substrate.

In figure 1A the substrate 10 is schematically indicated as a flat plate. It should be understood that the substrate 10 may comprise a surface that has been given a desired shape, for example a saddle surface or a surface having a more complex shape, so that the substrate 10 can function as a "mould" for a three- dimensional surface to be formed of the fibre 8. An example of such a surface would be a cylindrical surface or a reel, which can function as a mould for forming a stent or a graft, for example. The electrode 7 can be moved on the inner side of the reel or the cylinder in that case, possibly in combination with a movement of the reel itself. It is also possible to use more complex surfaces, for example for manufacturing an artificial heart valve.

An example of an alternative that can be used instead of the substrate 10 in figure 1A is the substrate the 13 that is shown in figure 1 B. What catches the eye in the substrate 13 is that the surface thereof comprises a deep and "steep" valley 17, whose walls are spaced relatively close together. What can be achieved by using a method and a device according to the invention, such as the device that is shown in figure 1A, is that the fibre can be deposited at any location on the substrate 13, and consequently also in the valley 17 and on the walls thereof. In figure 1A the second electrode 7 consists of a needle electrode, which can be moved in an X-direction or a Y-direction under the surface of the substrate 10, so that it is possible to "write" on the surface of the substrate 10 with the fibre 8, as it were. In figure 2 an alternative electrode 25 is shown, which could take the place of the electrode 7 in figure 1A, extending under the substrate 10. Said alternative electrode 25 consists of an arrangement or array of local electrodes, which may be formed as a flat plate, a flexible mass, a deformable surface or have any other desired shape. In the illustrated case, the array of local electrodes 25 comprises forty-nine local electrodes. It should be understood that the illustrated example is only a schematic representation and that it is possible to use a larger or a smaller number of electrodes, if desired. Since the local electrodes must have a small surface area so as to bring only one point on a surface to a second electrical potential, those skilled in the art will appreciate that 1 million electrodes, each having a surface area of about 0.1 x 0.1 mm² could readily be provided on a 10 x 10 cm plate, if desired.

The array 25 is connected to a pair of addressing systems 27 and 28, which can designate a row or a column, respectively, of the array 25. The electrode 26 is for example activated by having the addressing block 28 designate the second column and having the addressing block 27 designate the fourth row. The local electrode is brought to a second potential upon activation thereof. Since the local electrodes of the group 25 can be activated independently of each other, a fibre to be drawn, such as the fibre 8 from the device 1 of figure 1A, can readily be pulled and moved in different directions. Those skilled in the art will appreciate that switching of such an embodiment can take place in a quick and efficient manner, thereby increasing the range of application of the invention. The addressing blocks 27 and 28 are controlled by a control unit 29, which can be programmed by a user by means of a computer 30, if desired.

The phrase "activating the local electrodes" is to be understood to include, for example, the connecting of a local electrode to be activated to ground (for example the local electrode 26) if the capillary or first electrode, as well as the other local electrodes of the array 25, are for example on a first potential.

Figure 3A schematically shows a possible addressing circuit for the array of electrodes that is shown in figure 2. The addressing blocks 37 and 38 address a plurality of conductors that form part of an array of conductors 36. By having the addressing block 37 address the conductor in the first row and at the same time having the addressing block 38 address the third column, a drivable switch 42 will be driven at the intersection 40 of the conductors if the conductors are interconnected in a manner that will be apparent to a person skilled in the art at the points of intersection 40 thereof, which switch can be switched to a conducting state, for example. The local electrode 48 is brought to a second electrical potential by switching the switch 42 to a conducting state, since the electrode 48 is connected to a controllable switch 42 via the connection 49. In the illustrated embodiment, the positive side of the voltage source is connected to ground 45. It should be understood that a part of the group 47 comprising the local electrodes, such as the local electrode 48, has been broken away for the sake of clarity of the drawing. The broken-away part is schematically indicated at 35.

Figure 3 shows a controllable switch 42, via which the voltage supplied by the voltage source 43 can be transferred to the electrode 48. It should be understood that the controllable switch may be substituted for a transistor, a thyristor, a triac, a diac or other electronic switching means.

The addressing blocks 37 and 38 may be connected to a control unit, such as the control unit 29 that is shown in figure 2.

Figure 4 shows another embodiment of the invention, in which two first electrodes 55 and 56 form the capillaries for supplying material for producing the fibres 63 and 64. The fibres produced by the device as illustrated are deposited on the substrate 59. Disposed under the substrate 59 is the second electrode 60, which is a needle electrode in the illustrated embodiment. Bringing either the electrode 55 or the electrode 56 to the same electrical potential as the electrode 60 achieves that no pulling force is exerted between the electrode 60 and the electrode (55 or 56) that have been brought to the same potential. It is important in that case that the two electrodes 55 and 56 be sufficiently screened from each other, in order to ensure that no pulling force will be exerted between the two electrodes 55 and 56. An electric field between the electrodes 55 and 56 must be sufficiently weak, therefore. Such screening can be implemented in various ways, with a simple screening being realised by spacing the electrodes 55 and 56 sufficiently far apart. The manner in which the two electrodes 55 and 56 can be screened or isolated from each other so as to suppress undesirable effects will be apparent to those skilled in the art . The advantage of the embodiment that is shown in figure 4 is that the fibres 63 and 64 can be arranged on top of each other and through each other on the substrate 59 in a desired manner. The fact is that the fibre 63 can be drawn independently of the fibre 64. The user has a choice between bringing the electrode 55 to the same potential as the electrode 60 and bringing the electrode 56 to the same potential as the second electrode 60. The fibres 63 and 64, respectively, can thus be drawn independently of each other.

The embodiment that is shown in figure 4 is schematically represented, and only those parts are shown that are relevant to the invention. Those skilled in the art will appreciate that the device that is schematically shown in figure 4 will be provided with means for bringing each of the electrodes 55, 56 and 60 to an electrical potential. Instead of using the needle electrode 60, it is moreover possible to use a group of electrodes as shown in figure 2 or 3. The capillaries/electrodes 55 and 56 are connected to containers for supplying material for drawing the fibres 63 and 64.

The embodiments as shown in the figures are only meant to illustrate the system and the method described in the invention. Many alternative embodiments are conceivable in which electrodes arranged for applying an electrical potential at only one point in the space for the purpose of pulling the fibre to that point are used as the second electrode. The scope of the invention as described herein is limited only by the appended claims. It will be understood that the embodiments as shown and described herein must not be construed as being limitative to the invention.

It is furthermore noted that the circuit diagram for switching the electrodes 48 of the group 47 that is shown in figure 3 is only a single circuit diagram used for switching a single electrode. The other electrodes of the group can be driven in a similar manner. All kinds of switching systems may be used for switching the electrodes. A plurality of switching elements, such as the controllable switch 42, may be integrated on an integrated circuit.

Claims

1. A method for forming a fibre from a material and directing said fibre, using an electric field, wherein said electric field is applied between at least two electrodes, and wherein a first electrode is formed by a capillary for supplying the material, which first electrode is brought to a first electrical potential, characterised in that a second electrode is brought to a second electrical potential for locally applying said second electrical potential in at least one point for the purpose of pulling the fibre in a specified direction, wherein the location of the point at which the second electrical potential is applied can be changed in a time-controlled manner.

2. A method according to claim 1 , wherein the second electrode has a pointed end.

3. A method according to claim 2, wherein the second electrode comprises a needle electrode and said at least one point is formed by an end of the needle electrode.

4. A method according to any one of the preceding claims, wherein the second electrode is moved relative to the first electrode space for changing the location of the point at which the second potential is applied in a time-controlled manner so as to make it possible to pull the fibre in different directions.

5. A method according to any one of the preceding claims, wherein the second electrode consists of an array of local electrodes, each local electrode being arranged for applying an electrical potential at one point.

6. A method according to claim 5, wherein various local electrodes of the array are brought to the second potential for the purpose of pulling the fibre in various directions.

7. A method according to claim 6, wherein said bringing of the various local electrodes to the second potential takes place in a time-controlled manner.

8. A method according to any one of the preceding claims, wherein the fibre is received on a dielectric substrate disposed between the first and the second electrode for forming an object.

9. A method according to claim 8, wherein the substrate is given a desired shape and wherein the fibre is directed and received on the substrate in such a manner that a surface or a fibre pattern corresponding to the shape of the substrate is formed therefrom.

10. A method according to any one of the preceding claims, wherein material is supplied by two or more capillaries, and wherein each of the first electrodes formed by the capillaries is brought to a first potential for the purpose of pulling the fibres in a specified direction from each of said at least two capillaries.

11. A method according to claim 10, wherein the drawing of fibres from each of said at least two capillaries is interrupted in a time-controlled manner by bringing the first electrode formed by the capillary of the material of the fibre to be interrupted to the second potential.

12. A method according to any one of the preceding claims, wherein the material is brought to the first potential by the electrode formed by the inlet, wherein the second electrode is connected to ground.

13. A device for forming a fibre from a material, using an electric field, which device comprises a capillary for supplying a material, wherein the capillary forms a first electrode for bringing the material to a first electrical potential, and which furthermore comprises a second electrode, characterised in that the second electrode is arranged for locally applying a second electrical potential in at least one point for the purpose of pulling the fibre in a specified direction.

14. A device according to claim 13, wherein said second electrode has a pointed end.

15. A device according to claim 13 or 14, wherein the second electrode comprises a needle electrode and said at least one point is formed by an end of the needle electrode.

16. A device according to any one of the claims 13-15, further comprising means for moving the second electrode relative to the inlet.

17. A device according to any one of the claims 13-16, wherein the second electrode consists of an array of local electrodes, each electrode being arranged for locally applying a second electrical potential at one point.

18. A device according to claim 17, further comprising means for bringing each of the local electrodes of the array individually to the second potential.

19. A device according to claim 18, wherein the means for bringing each of the local electrodes of the array individually to the second potential are arranged for bringing the local electrodes to the second potential in a time-controlled manner.

20. A device according to any one of the claims 13-19, further comprising a dielectric substrate disposed between the inlet and the second electrode for receiving the fibre.

21. A device according to claim 13-19, wherein the substrate comprises a surface having a desired shape for forming a surface or a fibre pattern corresponding to the shape of the surface of the substrate from the fibre to be deposited thereon.

22. A device according to any one of the claims 1-12, further comprising at least one further capillary for supplying material, wherein said further capillary forms a further first electrode.

23. A device according to claim 22, further comprising means for bringing said first electrode and said further first electrode to a first or a second potential independently of each other in a time-controlled manner.

24. An object formed by using a method according to any one of the claims 8-12.