Electrode arrangement for plasma discharge forming a dielectric barrier

Abstract

An electrode device is used to form a dielectrically blocked plasma discharge between an electrode (1) and a surface (21) to be treated of an electrically conductive object (22), wherein the electrode is fed with an AC high voltage by a control device (20), and the surface to be treated serves as a ground electrode, wherein a dielectric (8) completely covers the electrode (1) toward the surface (21) to be treated and forms a contact side for the surface (21). In the case of a large surface (21) to be treated, the plasma (23) can be formed effectively and uniformly in particular in the following manner: the electrode (1) is composed of at least two partial electrodes (2, 3), which are arranged side by side with equal spacing (6) to the contact sides and separated from each other by the dielectric (8), and the control device feeds adjacent partial electrodes with partial AC high voltages that are equal in waveform and voltage magnitude and cancel each other out.

Description

Technical Field

[0001] The invention relates to an electrode arrangement for forming a dielectrically blocked plasma discharge between an electrode fed with an alternating high voltage by a control device and a surface to be treated of an electrically conductive object, the surface to be treated serving as a ground electrode, wherein a dielectric completely covers the electrode facing the surface to be treated and forms an abutment side to the surface. Background Art

[0002] DE 10 2009 060 627 B4 discloses a planar electrode arrangement of this type that can be flexibly constructed. Here, the planar electrode is embedded between a dielectric bottom and a dielectric top, each of which extends flatly beyond the electrode and thus also covers the narrow edge of the electrode, thereby preventing contact with the electrode carrying the high voltage. Furthermore, proximity to the electrode, which could cause sparks to fly, is also eliminated. More precisely, the dielectric blocks the flow of current from the electrode to the surface to be treated (which serves as a ground electrode). Therefore, the electrode arrangement does not have its own ground electrode. To ensure that plasma forms in the air layer between the surface to be treated and the dielectric, if the surface to be treated is smooth, the bottom side of the electrode arrangement, facing the surface to be treated, can be configured with a protruding projection. This projection, with its top side, rests against the surface to be treated and has a continuous gap in which plasma can form when a high AC voltage is applied to the electrode.

[0003] Such an electrode arrangement can be placed on a surface to be treated, wherein the surface to be treated can be in particular the skin of a human or animal body. In this case, the plasma treatment leads to deep pore disinfection of the skin and improves the skin's ability to absorb care substances applied to the treated skin.

[0004] It is also known that plasma treatment can be beneficial for wound healing. According to DE 10 2009 047 220 A1, a plasma is generated in a pin-shaped device through which a treatment gas flows, which plasma is emitted at the nozzle-shaped end face of the device and can be directed onto the skin or wound to be treated.

[0005] DE 10 2011 01 416 A1 discloses a planar flexible wound treatment device. In this wound treatment device, two planar electrodes are formed from interwoven insulated conductors. A high voltage is applied between the conductors, generating plasma in the air gap. To achieve this, the entire electrode assembly must allow gas to flow through.

[0006] Furthermore, electrode arrangements are known that can generate dielectrically blocked surface plasmons. WO 2009 / 098662 A1 describes an arrangement in which a first planar electrode and a second grid-like electrode are embedded in a dielectric medium at a distance from each other in the height direction of the electrode arrangement, thereby forming an electric field suitable for plasma formation on the dielectric surface, which is located close to the grid-like electrodes. A high AC voltage is applied to the grid-like electrodes, while a planar electrode located below the grid-like electrodes is at ground potential. This arrangement has high energy requirements and low efficiency in generating surface plasmons.

[0007] In this respect, an electrode arrangement is advantageous, the electrodes of which are designed in such a way that a field distribution that is as uniform as possible is generated between the planar electrode and the surface to be treated as a ground electrode, which field distribution leads to a defined and ideally uniform plasma.

[0008] There is also an increasing need to treat larger surfaces by providing (particularly flexible) electrode arrangements of the type described. However, as the treated surface increases, it becomes increasingly difficult to generate the required field strengths for forming a uniform plasma between the contact side of the dielectric and the surface to be treated using conventional technologies. The present invention is therefore based on the problem of designing an electrode arrangement of the type described so that, on the one hand, a plasma that is as uniform as possible is formed in an advantageous manner, and, on the other hand, larger surfaces can be treated with a correspondingly larger electrode arrangement at a lower energy expenditure. Summary of the Invention

[0009] In order to solve the problem, according to the present invention, an electrode device of the type described at the outset is characterized in that the electrode is composed of at least two partial electrodes, which are arranged side by side with equal spacing to the contact side and isolated from each other by a dielectric, and the control device feeds the adjacent partial electrodes with partial AC high voltages that are oppositely equal in waveform and voltage magnitude and offset each other.

[0010] The electrode arrangement according to the present invention is based on the known principle that the surface of an electrically conductive object to be treated serves as a ground electrode. Thus, in principle, only a single electrode is required to form the plasma field, which interacts with the surface to be treated as a ground electrode to form the plasma. A largely ideally uniform electric field is generated above the electrode surface, in which the electric field lines run parallel to one another. Only at the edges of the electrode do the electric field lines, which are curved or angled in a known manner, arise. The electrode arrangement according to the present invention preferably comprises partial electrodes, each of which has an area size such that the extension of the electric field and the ideally parallel electric field lines occupy more than 50%, preferably more than 65%, and more preferably more than 80% of the partial electrode surface. The electrode according to the present invention extends flat and is positioned parallel to the contact side of the dielectric. According to the present invention, at least two partial electrodes are provided, each of which is independently supplied with an AC high voltage by a control device. Preferably, the AC high voltage oscillates about ground potential. Ideally, the AC high voltage can run sinusoidally. Based on the capacitance and inductance present in the control device, an oscillating circuit arrangement can also be provided, by means of which the excitation pulses each trigger a high-frequency oscillation process.

[0011] If side-by-side partial electrodes are operated in phase, ideally, a uniform plasma will form in the region of uniform field between the relevant partial electrodes and the surface to be treated. However, in the connection region between the side-by-side partial electrodes, voltages will add up and result in undesirable voltage peaks that disrupt the uniform plasma field. Furthermore, significant potential differences will form within the conductive object where the surface to be treated is located, which can lead to undesirable current flows within the object. This can cause discomfort to the living subject and potentially lead to dangerous situations.

[0012] According to the invention, therefore, the side-by-side partial electrodes are controlled by means of oppositely directed high AC voltages, so that a substantially field-free isolation zone is generated in the edge regions of the partial electrodes between adjacent partial electrodes. Since this isolation zone can be narrow and linear, disinfecting products formed in the plasma (e.g., OH radicals and ozone formed in the air in the plasma) also act in the isolation zone, since these products reach the surface area within the isolation zone within a very short service life.

[0013] Therefore, the electrode arrangement according to the present invention, comprising at least two partial electrodes, is designed such that the partial electrodes ideally form a substantially uniform field (and therefore an ideally uniform plasma) with the surface to be treated over substantially their entire surface, and a narrow, essentially field-free, isolation region can be generated facing adjacent partial electrodes. Thus, for two adjacent partial electrodes, one partial electrode can be operated with the positive half-wave of an AC high voltage, while the other partial electrode can be operated with the negative half-wave, so that the two voltages cancel each other out in the isolation region. In a preferred embodiment, the respective half-waves are equal in size and shape, resulting in a constant potential in the isolation region that does not change over the period of the AC high voltage and corresponds to the ground potential of the ground electrode. In practice, the intensities of the oppositely aligned half-waves can only be approximately sufficient to achieve a constant total potential in the isolation region, even with minor fluctuations in the total potential (e.g., less than 5 percent of the peak voltage). In practice, even if such filamentary discharges are avoided, an ideally uniform plasma can be superimposed or disrupted by slight filamentary discharges.

[0014] The peak voltage of the AC high voltage used can expediently be between ±10 kV and ±100 kV. The AC frequency of the AC high voltage expediently is between several hundred Hz and approximately 100 MHz.

[0015] In order to adapt to uneven surfaces, it is expedient if parts of the electrodes and the dielectric are flexible, so that the entire electrode arrangement can follow the irregular surface and can therefore ideally be processed with a uniform plasma field.

[0016] In a known manner, the contact side of the dielectric facing the surface to be treated can preferably have a grid-like or protrusion-like structure, between which plasma can form when the dielectric rests with the upper side of the protrusions or other protruding structures against the surface to be treated.

[0017] If the dielectric consists of a wound-compatible material (e.g. a suitable silicone) or if a layer of a wound-compatible material (e.g. gauze) is placed on the contact side of the dielectric, the electrode arrangement according to the invention can also be designed as a wound dressing.

[0018] The electrode arrangement according to the invention is also suitable for draining wound fluid or for providing fluid that heals or promotes wound healing if the dielectric and the partial electrodes have a through-opening that extends through the electrode arrangement in the height direction and is continuously delimited by the dielectric surrounding the partial electrodes.

[0019] The electrode arrangement according to the invention preferably has a high degree of symmetry with respect to the partial electrodes. For this purpose, it is expedient if the partial electrodes have the same size so that the surface active for plasma formation is evenly distributed over a certain number of partial electrodes.

[0020] The partial electrodes can be formed from a flat metallic material, preferably covered on both sides by a dielectric. It is also possible to form the electrodes from a conductive plastic that can be connected in a form-fitting manner to a dielectric also made of plastic (e.g., silicone). For example, the electrodes can be formed from silicone with conductive additives (in the form of metal particles, carbon particles, etc.). BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below with reference to the embodiments described in the accompanying drawings. The accompanying drawings show:

[0022] Figure 1 The electrode structure is shown in exploded view;

[0023] Figure 2 Show the basis Figure 1 A top view of the assembled electrode device;

[0024] Figure 3 Schematic diagram showing the function of the structural principle according to the present invention. DETAILED DESCRIPTION

[0025] according to Figure 1 , the electrode 1 is formed by two partial electrodes 2, 3, which are not connected to each other and have a defined distance from each other. The partial electrodes 2, 3 are each formed by a narrow, planar power supply line 4, which passes through a planar structure 5. The planar structures 5 of the two partial electrodes 2, 3 together form a roughly square electrode surface, wherein in the exemplary embodiment shown, there is a distance 6 between the planar structures 5 in the longitudinal direction defined by the power supply lines 4.

[0026] The planar structure 5 of the partial electrode 3 has a plurality of through-holes 7, the function of which is explained in more detail below. As mentioned, the material of the partial electrode can be a metal foil, a thin metal sheet or a plastic layer (especially a silicone layer) made conductive by adding conductive particles.

[0027] Figure 1 It can be seen that in the direction of the distance 6 , there are approximately semicircular through-holes in the two planar structures 5 of the partial electrodes 2 , 3 , which ensure a secure engagement of the partial electrodes with the dielectric filling the distance 6 .

[0028] The electrode 1 is covered on all sides by a dielectric 8 which is Figure 1, it is shown as consisting of an upper dielectric layer 9 and a lower dielectric layer 10. The upper dielectric layer 9 projects on all sides with its surface beyond the common surface of the two partial electrodes 2, 3 and is also provided with through-holes 11, which are arranged so as to align with the through-holes 7 of the partial electrodes 2, 3. In the region of the spacing 6 between the partial electrodes 2, 3, the upper dielectric layer is solid in design to achieve reliable electrical insulation between the partial electrodes 2, 3. Both the upper dielectric layer 9 and the lower dielectric layer 10 each have an extension 12, which shields the power supply line 4 from environmental influences.

[0029] The through-hole 11 in the upper dielectric layer 9 is formed concentrically with the through-hole 7, but the through-hole in the upper dielectric layer has a smaller diameter, so that even in the region of the through-hole 7, the dielectric layer shields the material of the partial electrodes 2, 3. Therefore, a direct electrical connection to the partial electrodes 2, 3 cannot be established even through the liquid.

[0030] Like upper dielectric layer 9, lower dielectric layer 10 is constructed as a continuous, through-hole layer. Upper dielectric layer 9 may be penetrated by a through-hole 14. Through-hole 14 is also constructed concentrically with through-hole 7 of the partial electrode and through-hole 11 of the upper dielectric layer. In lower dielectric layer 10, the diameter of through-hole 14 is also smaller than the diameter of through-hole 7 of the partial electrodes 2 and 3 and is the same diameter as through-hole 11 of the upper dielectric layer 9.

[0031] On the side facing away from the partial electrodes 2 , 3 , the lower dielectric layer 10 forms a grid structure 15 with intersecting plate-like walls, the free edges 16 of which define the contact side with which the electrode arrangement can rest against the surface to be treated.

[0032] Figure 1 It can also be seen that the continuous lower dielectric layer 10 laterally extends beyond the contour of the upper dielectric layer with lateral strips 17, 18 and thus forms extensions by means of which the electrode arrangement can be fixed to the surface to be treated. For this purpose, the lateral strips can be coated with an adhesive on their underside or consist of an adhesive material.

[0033] Figure 2 Show the basis Figure 1 , a top view of the lower side (i.e., the contact side) of the electrode arrangement. This view shows that the grid structure forms a square chamber, in the center of which lies a through-hole 14 of the lower dielectric layer, which is arranged concentrically with the (larger) through-hole 7 of the partial electrodes 2, 3. In this way, a channel is formed through the mutually aligned through-holes 7, 14, which is bounded on all sides by the material of the dielectric 8 and, in particular, shields the material of the partial electrodes 2, 3 even in the region of the through-hole 7.

[0034] Figure 2It can also be seen that the dielectric material is solid in the region of the spacing 6 between the partial electrodes 2 , 3 . The grid structure 15 is reinforced outside the region of the partial electrodes 2 , 3 by an edge structure 19 consisting of cells arranged in a frame-like manner.

[0035] exist Figure 2 , the feeder 4 is connected in the control device 20 by means of a schematically illustrated connection device. Obviously, care must be taken here to ensure contact protection for the high-voltage feeder 4. For this purpose, the feeder 4 can be connected, for example, by means of a cutting contact that independently cuts through the material of the dielectric 8 to the conductive feeder 4 and encloses the insulating housing. Such cutting contacts are commercially available and require no further explanation. However, the feeder is schematically illustrated by supplying an AC high voltage that is offset relative to one another in terms of periodicity so that the AC high voltages cancel each other out in sum (ideally, zero).

[0036] The encapsulation of the partial electrodes 2, 3 and their power supply lines 4 can be achieved in a conventional manner by means of the material of the dielectric 8. Figure 1 In the device, the upper dielectric layer 9 and the lower dielectric layer 10 are constructed so that they can be welded to each other as thermoplastic materials or simply glued to each other. Obviously, the entire dielectric with inserted partial electrodes 2, 3 can also be manufactured in one piece during the casting process.

[0037] Figure 3 Schematically, the partial electrodes 2 and 3, which are embedded in the dielectric 8 and separated from each other by a distance 6, form a plasma in the area of the grid structure 15 (acting as a distance retainer) and are therefore uniform, and the electric field that triggers the plasma extends uniformly between the partial electrodes 2 and 3 and the surface 21 to be processed of the electrically conductive object 22, which is shown here by the parallel-oriented electric field lines. It is also obvious that no plasma is formed in the area of the distance 6, because this area is practically free of electric fields. This is due to the fact that the two partial electrodes 2 and 3 are controlled by means of an AC high voltage that is equal in waveform and magnitude in opposite directions, as in Figure 3 As schematically shown above the sub-electrodes 2 and 3 in FIG. The overall curve Σ, also shown, shows that the resulting field is zero in the region of the distance 6 because the two AC high voltages ideally cancel each other out to zero. This prevents field distortion phenomena in the region between the sub-electrodes 2 and 3. In particular, voltage peaks are avoided.

[0038] The configuration of an electrode 1 with two partial electrodes 2, 3 is preferred because it is the easiest to implement. However, for larger surfaces to be treated, it is conceivable to provide an apparatus with, for example, four partial electrodes, which together with four square planar structures 5 form a common square electrode surface. The partial electrodes are then actuated diagonally with identical waveforms, and adjacent partial electrodes are actuated with oppositely directed, identical waveforms.

[0039] Of course, other geometric shapes of the partial electrodes are also conceivable, for example partial electrodes in the form of triangles, rhombuses, hexagons or even circular areas.

Claims

1. An electrode device comprising an electrode (1) and a dielectric (8), the electrode device being used to form a dielectrically blocked plasma discharge between the electrode (1) and a surface (21) to be treated of an electrically conductive object (22), the electrode being fed with an AC high voltage by a control device (20), wherein: The dielectric (8) completely covers the electrode (1) toward the surface (21) to be processed and forms a contact side for the surface (21), and the electrode (1) is composed of at least two partial electrodes (2, 3), which are arranged side by side at equal intervals (6) to the contact side and separated from each other by the dielectric (8), and the control device feeds the at least two adjacent partial electrodes with AC high voltages that are equal in waveform and voltage magnitude and cancel each other out, characterized in that the surface (21) to be processed of the conductive object (22) serves as a ground electrode, and the at least two partial electrodes act together with the ground electrode to form plasma, wherein the at least two partial electrodes, except for the edge region between the at least two adjacent partial electrodes, form a uniform field for the plasma together with the surface.

2. The electrode device according to claim 1, characterized in that The sum of the partial AC high voltages supplied to the at least two adjacent partial electrodes (2, 3) forms a temporally constant value that corresponds to the potential of the ground electrode.

3. The electrode device according to claim 1 or 2, characterized in that The at least two partial electrodes (2, 3) and the dielectric (8) covering the at least two partial electrodes have flat surfaces (21).

4. The electrode device according to claim 1 or 2, characterized in that The at least two partial electrodes (2, 3) and the dielectric (8) are flexible.

5. The electrode device according to claim 1 or 2, characterized in that When the electrode arrangement rests on the surface (21) to be treated, the contact side of the dielectric (8) facing the surface (21) to be treated has a structure that forms a recess.

6. The electrode device according to claim 1 or 2, characterized in that The dielectric (8) and the at least two partial electrodes (2, 3) have a through-opening (14), which extends through the electrode arrangement in the height direction and is continuously delimited by the dielectric (8) surrounding the at least two partial electrodes (2, 3).

7. The electrode device according to claim 1 or 2, characterized in that The at least two partial electrodes (2, 3) have the same size.

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