Plasma jet device

Abstract

The invention relates to a cold plasma jet device (1) comprising: - at least one gas supply inlet (2); - at least one tube (4) fluidically connected to the gas supply inlet and comprising at least one plasma outlet (5), the gas supply inlet and the plasma outlet defining a direction of flow of the gas and of the plasma; - at least one high-voltage electrode (6) outside the tube configured to create an electric field in the tube; and - at least one electrically conductive element (7) having a floating electric potential and extending axially inside the tube at least partially between the high-voltage electrode and the plasma outlet.

Description

[0001] Description

[0002] Title: Plasma Jet Device

[0003] technical field

[0004] The present invention relates to the field of plasmas, in particular their use in cosmetic or medical applications such as the treatment of cancer cells, the healing or sterilization of wounds, for example of chronic or acute post-operative wounds, or in the context of transplantation, post-transplant to promote healing and prevent infections or pre-transplant to prepare the skin.

[0005] The invention relates more particularly to a cold plasma jet device, especially at atmospheric pressure.

[0006] The invention also relates to a cold plasma jet generation assembly comprising such a device.

[0007] Previous technique

[0008] The use of cold plasma, particularly plasma produced from a noble gas, typically helium or argon, subjected to an electrical discharge delivered by a high-voltage power supply at room temperature, is well-established in the field of cutaneous medical applications. The plasma propagates in a pulsed, and possibly periodic, manner until it exits a tube, and upon contact with the ambient air, it produces reactive oxygen and nitrogen species, which, along with the electric field, are responsible for the biological effects of cold plasmas.

[0009] Cold plasma therapy at atmospheric pressure has proven effective in treating skin wounds, pruritus, and skin infections. Specifically, plasma is known to accelerate wound healing by promoting re-epithelialization, recruiting and activating immune cells in the wound area, activating fibroblasts which induce actin cytoskeleton rearrangement and promote matrix synthesis, activating healing cytokines and growth factors in fibroblasts and keratinocytes, and inducing neovascularization and the production of pro-angiogenic proteins in endothelial cells. The use of cold plasma has the advantage, in some cases, of being non-contact and painless for patients.Furthermore, treatment times are relatively short, and no allergic reactions, bacterial resistance, or other side effects have been observed so far.

[0010] In addition, several studies have shown that microorganisms such as bacteria, fungi, biofilms, viruses and spores can be killed very effectively using cold plasma (biocidal activity).

[0011] Applications FR2300132 and FR2300133, filed on January 5, 2023, and published under numbers FR3144899A1 and FR3144900A1 respectively, disclose a plasma jet generation device. While fully satisfactory, the disclosed device operates preferentially with helium as the plasma-generating gas. However, the supply of helium can be relatively difficult.

[0012] Therefore, there is a need to offer a plasma generation device that facilitates the use of different plasma-generating gases.

[0013] The aim of the invention is to meet at least part of this need.

[0014] Summary of the invention

[0015] To this end, the invention relates, in one of its aspects, to a cold plasma jet device comprising:

[0016] - at least one gas supply inlet;

[0017] - at least one tube fluidically connected to the gas supply inlet and having at least one plasma outlet, the gas supply inlet and the plasma outlet defining a direction of gas and plasma flow;

[0018] - at least one high-voltage electrode outside the tube configured to generate an electric field within the tube; and

[0019] - at least one electrically conductive element having a floating electrical potential and extending axially inside the tube at least partially between the high-voltage electrode and the plasma outlet.

[0020] The conductive element significantly reduces the plasma ignition and maintenance voltage. The invention also limits the peak current and controls the power of the plasma jets, thereby reducing sensations of tingling or even electric shock when the jets are applied to a patient. The position and shape of the conductive element are advantageously chosen to optimize its effect.

[0021] The invention therefore facilitates the use of different source gases. The source gas can be a noble gas, such as helium, neon, argon, krypton, or xenon. The source gas can also be a mixture of gases, such as a mixture of a noble gas, particularly argon, and oxygen, for example, a mixture of 95% by mass argon and 5% by mass oxygen.

[0022] In particular, the device is especially well-suited for use with argon as the source gas, as argon jets are often more difficult to control than helium jets due to argon's physical properties. For example, generating plasma jets from argon requires higher starting voltages than with helium.

[0023] Argon is particularly advantageous for the production of medical plasma because it produces plasma at relatively low temperatures compared to some other gases. Furthermore, argon has a relatively low ionization energy, making it possible to generate plasma at low power levels. This minimizes thermal stress on the treated tissues.

[0024] Floating electrical potential refers to the absence of direct electrical contact with an element at a fixed potential. Thus, the conducting element is not electrically connected to any element at a fixed potential.

[0025] A tube is defined as a tube in which the cold plasma jet is created and propagates. This can include, for example, a capillary tube.

[0026] Preferably, the gas supplying the device is at atmospheric pressure, and the generated plasma is also at atmospheric pressure.

[0027] According to an optional feature, the high-voltage electrode surrounds the tube, specifically over a proximal portion of the tube. If the device comprises a plurality of tubes, the high-voltage electrode can surround one or more tubes, including all of them.

[0028] According to another optional feature, the conductive element and the high-voltage electrode partially overlap axially. According to an advantageous feature, the device includes a grounding electrode connected to ground and positioned around the outer wall of the tube, at a distance from the outlet less than the distance between the high-voltage electrode and the outlet, downstream of the conductive element, preferably near the plasma outlet, for example, at a distance of less than 50 mm, 20 mm, or 5 mm from the plasma outlet. The grounding electrode may be positioned on a distal portion of the tube. The grounding electrode advantageously improves the stability and reproducibility of the generated plasma jets by allowing control of the plasma jets formed at the tube outlets.

[0029] The conductive element is preferably made of a semiconducting material or a conductive material such as stainless steel.

[0030] H can have any elongated shape allowing it to be placed in the recess of the tube, for example a rod shape, a hook shape, a helical spring shape or even a V shape.

[0031] The conductive element may have a length greater than or equal to 1 mm, 10 mm or 100 mm, and / or less than or equal to 150 mm, 50 mm or 10 mm, in particular between 6 mm and 7 mm. The conductive element may have a diameter greater than or equal to 0.1 mm and / or less than or equal to 5 mm.

[0032] The ratio between the diameter of the section of the conducting element and the diameter of the inner section of the tube, particularly at the level of the conducting element, can be between 0.1 and 0.95. If the section of the conducting element and / or the inner section of the tube are not circular, the diameter is understood to be the diameter of the smallest circle circumscribing these sections.

[0033] One end of the upstream conducting element is preferably located at the center of the tube within its cross-section. It is positioned longitudinally between the upstream and downstream ends of the high-voltage electrode, preferably at a distance of between 40% and 60% of the distance between the upstream and downstream ends of the high-voltage electrode, and more preferably equidistant from the upstream and downstream ends of the electrode. These distances are measured along the tube's axis.

[0034] A second end of the conductive element on the downstream side extends beyond the downstream end of the high-voltage electrode, preferably by a length less than 20% or 10% of the length of the conductive element, or greater than or equal to 1 mm, 2 mm, or 5 mm, and / or less than or equal to 10 mm, 5 mm, or 2 mm. The conductive element may lack an internal channel that would allow gas or plasma to flow through it.

[0035] According to an advantageous feature, the conducting element has one end, which can be the second end, having an acute shape, in particular conical with a conicity angle between 5° and 120°. This strengthens the electric field at the second end and thus facilitates the ionization of the gas.

[0036] Thus, the conductive element extends primarily within the portion of the tube's volume defined by the high-voltage electrode. This enables coupling, particularly capacitive coupling, between the electrode and the conductive element, transferring electrical power to the conductive element, which is concentrated towards the second end of the conductive element.

[0037] The conductive element is advantageously fixed within the tube or secured in such a way that its position can only vary slightly, for example, by less than 5% of the conductive element's length. The conductive element can, in particular, be fixed within the tube by fins attached on one side to the conductive element and on the other to the inner wall of the tube, by hooks, or by ferrules. It can also be overmolded or inserted into the tube using a cold or hot process.

[0038] According to one embodiment, the conductive element has a nail shape, comprising a head forming a first end of the conductive element and a shank whose free end forms a second end of the conductive element.

[0039] The stem of the conductive element can advantageously be positioned within a section of the tube shaped to prevent the insertion of the head of the conductive element. In other words, the dimensions of the head of the conductive element are such that it cannot be inserted into the portion of the tube that receives the stem. For this purpose, for example, the tube has a shoulder, with the head and shoulder configured so that the head can contact the shoulder when the stem is received in that section of the tube. Specifically, the head of the conductive element can have a maximum diameter greater than the diameter of the stem. The diameters are measured in a plane perpendicular to the axis of the tube.

[0040] The head can be flat or convex. A flat head means that the end surface of the head opposite the stem is flat. A convex head means that the end surface of the head opposite the stem is not flat and forms a single projection or several projections; in particular, this end surface may be curved, lacking a flat portion and a sharp edge, so as to form a single projection.

[0041] The head can have a circular, oval, square, or rectangular cross-section. The conductive element can be T-shaped, with the head forming a crossbar.

[0042] Advantageously, the device includes a blocking element comprising at least one protrusion extending into at least one tube upstream of at least one conductive element, so as to limit the upstream movement of the conductive element, with respect to the direction of gas flow. Specifically, the head and the protrusion can be configured so that the head can abut against the protrusion. Thus, the upstream movement of the conductive element is limited. The head of the conductive element can also limit its downstream movement, for example, due to the dimensions of the head or the contact between the head and the aforementioned shoulder. The conductive element is thus held in position, optionally with a clearance due to the maximum distance between the downstream end of the protrusions and the head of the conductive element. This clearance can be, for example, between 1 mm and 12 mm.When the aforementioned shoulder is present, this maximum distance is reached when the head is in contact with the shoulder.

[0043] The locking element can be fixedly assembled with at least one tube.

[0044] According to one embodiment of the invention, the tube has a circular cross-sectional recess. The diameter of the recess's cross-section is preferably greater than the diameter of the conducting element to allow the gas and plasma to flow within the tube.

[0045] Alternatively, the tube has a cross-sectional recess comprising a central portion configured to receive and optionally retain the conducting element, and one or more secondary portions arranged around the central portion and configured to allow the flow of gas and / or plasma. When the aforementioned shoulder is present, the secondary portion(s) are configured to allow the flow of gas and / or plasma even when the head is in contact with the shoulder. In one embodiment, the tube defines, along at least a portion of the conducting element, a recess with a non-circular cross-section, preferably multilobed, in particular a three-leaf clover, a four-leaf clover, or star-shaped, in particular a three-pointed or more-pointed star, the conducting element preferably being centered within this recess.A cloverleaf shape has a central portion that can receive the conductive element and opens onto three or more secondary portions forming the leaves, each of which may be circular or oval. A star shape has a central portion that can receive the conductive element and opens onto secondary portions forming the points of the star.

[0046] The recess within the tube can have a cross-section of varying dimensions along the tube, particularly upstream or downstream of the conducting element.

[0047] The tube is notably made of a non-conductive material, for example a plastic material such as polycarbonate.

[0048] The tube may include a flared distal portion that includes the plasma outlet. The flared distal portion may extend for a length, in the direction of plasma flow, of 20 cm or less, preferably 10 cm or less, and preferably 5 cm or less. The ratio of the maximum diameter of the distal portion to the minimum diameter of the distal portion may be between 1 and 100.

[0049] The tube may have a wall of fixed or variable thickness. In the specific case of a wall of variable thickness, the wall of the distal portion may be wider than the wall upstream of the distal portion. The wall of the distal portion may have a thickness ranging from 0.1 mm to 5 mm. The ratio of the wall thickness of the upstream portion to the thickness of the distal portion may range from 0.1 to 10.

[0050] A device according to the invention may comprise more than two plasma outlets and / or more than two tubes. Preferably, the number of plasma outlets is between 1 and 100, preferably between 1 and 50, and more preferably between 1 and 10. In a preferred embodiment of the invention, the device comprises several tubes, each tube being able to comprise several plasma outlets.

[0051] Each tube may have a gas supply inlet. Alternatively, the device may have a single gas supply inlet fluidly connected to a distribution chamber, which is itself fluidly connected to each of the tubes. According to an advantageous feature, the device has a single gas supply inlet fluidly connected to a distribution chamber, and the device has a plurality of tubes, for example, four tubes, each fluidly connected to the distribution chamber.

[0052] The device according to the invention is optionally configured so that the high-voltage electrode can deliver a first electrical signal and a second electrical signal having two distinct frequencies, the frequency of the first electrical signal being defined so that when the electrode delivers this first electrical signal, the rare gas introduced into the tube and subjected to the voltage of the first electrical signal generates the plasma, the frequency of the second electrical signal being defined so as to generate a initiation pulse of plasma propagation towards the plasma outlet, the frequency of the second electrical signal being lower than the frequency of the first electrical signal, preferably in a ratio first signal frequency / second signal frequency greater than 1 and less than or equal to 1000, preferably between 3 and 100, better between 5 and 50.

[0053] The second signal advantageously allows for initiating and / or accelerating plasma propagation within the tube. In particular, the second signal allows for adjusting the plasma dose ejected from the device.

[0054] Plasma dose refers to the amount of plasma energy delivered to the target.

[0055] In another embodiment, the first and second electrical signals are delivered via a first high-voltage electrode and a second high-voltage electrode respectively, the first high-voltage electrode being positioned upstream of the second electrode, in the direction of plasma propagation. The second high-voltage electrode can be positioned downstream of the first high-voltage electrode, for example around a distal portion of the tube.

[0056] The invention further relates to a cold plasma jet generation assembly comprising a handle receiving a cold plasma jet device as described above.

[0057] Optionally, the assembly includes a spacer arranged on the handle around at least one plasma outlet and configured to prevent direct contact between at least one plasma outlet and a surface to be treated, the spacer preferably being removable.

[0058] The invention further relates to a method of generating one or more plasma jets by means of a device as described above, the gas supply inlet being supplied with argon or a mixture of argon and oxygen.

[0059] Brief description of the drawings

[0060] [Fig 1] Figure 1 represents a plasma jet device according to the invention.

[0061] [Fig 2] Figure 2 is a longitudinal cross-sectional view of the device shown in Figure 1.

[0062] [Fig. 2A] Figure 2A is an enlargement of part of Figure 2.

[0063] [Fig. 2B] Figure 2B is a cross-sectional view of a conductive element of the device of Figure 1, according to an alternative embodiment.

[0064] [Fig 3] Figure 3 is a side view of the device in Figure 1.

[0065] [Fig 4] Figure 4 is a cross-sectional view of the device shown in Figure 3.

[0066] [Fig 5] Figure 5 is a longitudinal cross-sectional view of the device shown in Figure 3.

[0067] [Fig 6] Figure 6 is a cross-sectional view of tubes of a plasma jet device according to the invention.

[0068] [Fig 7] Figure 7 illustrates different variants of tube cross-sections for a plasma jet device according to the invention.

[0069] [Fig 8] Figure 8 is a cross-sectional view of a handle comprising a plasma jet device according to the invention.

[0070] [Fig 9] Figure 9 represents a plasma jet generation assembly comprising a plasma jet device according to the invention.

[0071] Detailed description

[0072] In the following description, identical elements or elements with identical functions bear the same reference sign.

[0073] The terms "upstream," "downstream," "inlet," and "outlet" are defined relative to the direction of gas and plasma propagation. The terms "inside" and "outside" are defined relative to the plasma's positioning within the device, with the plasma being inside the device. The terms "transverse" and "longitudinal" are defined relative to the axis of the tubes, which therefore extend in the longitudinal direction.

[0074] Figures 1 to 5 illustrate an embodiment of a plasma jet device 1 according to the invention. Figures 4 and 5 are respectively cross-sectional views of the device in plane AA and longitudinal section in plane BB, planes A-A and BB appearing in Figure 3.

[0075] Device 1 comprises a lower part 19 and an upper part 18 assembled on the lower part, and extends parallel to an axis X which is oriented from upstream to downstream in the direction of gas and plasma flow.

[0076] Device 1 includes a tubular gas inlet 2 that allows gas to be injected into the device. The injected gas can be, in particular, a noble gas such as helium, argon, neon, or a gas mixture such as a mixture of argon and oxygen. Preferably, the gas is helium or argon. The gas flow rate can be between 0.2 L / min and 5 L / min, preferably approximately 1 L / min.

[0077] The gas inlet 2 is fluidly connected to a distribution chamber 3, which is itself fluidly connected to several tubes 4, for example four as illustrated, belonging to the lower part 19. The free ends of the tubes 4 form plasma outlets 5 through which the plasma generated by the device 1 can be ejected.

[0078] The tubes 4 can in particular be straight and extend parallel to the X axis. The tubes 4 are advantageously rigid and made of a non-conductive material, for example a plastic such as polycarbonate.

[0079] Device 1 includes a high-voltage electrode 6 arranged around the four tubes 4, near the distribution chamber 3. The high-voltage electrode 6 is electrically connected to a voltage source. It is configured to generate an electric field in the tubes 4 and thus enable the generation of plasma from the source gas in a plasma generation zone of the tubes.

[0080] The high-voltage electrode 6 surrounds the tubes 4. The upstream and downstream ends of the electrode each define a plane transverse to the X axis.

[0081] Device 1 also includes a ground electrode 13 arranged around the four tubes 4, near the plasma outlets 5. The ground electrode 13, which is connected to the electrical ground, advantageously improves the stability and reproducibility of the plasma jets.

[0082] An electrically conductive element 7, made of conductive or semi-conductive material, is arranged in each of the tubes 4.

[0083] According to one embodiment, the ground electrode electrically connected to ground forms, with the high-voltage electrode, a capacitor so that the coupling with the conducting element is capacitive.

[0084] According to another embodiment, the high-voltage electrode is in the form of a coil, one end of which is electrically connected to a voltage source and the other end is electrically connected to an electrical ground, so that the coupling with the conducting element is inductive.

[0085] Preferably, as illustrated, there is an axial overlap along the X-axis between each conductive element 7 and the high-voltage electrode 6. The conductive elements 7 have a floating electrical potential: they are not in electrical contact with an element with a fixed potential.

[0086] As particularly visible in Figure 2, a conductive element 7 may have a head 8 arranged in the extension of a rod 9, the head 8 being dimensioned so as not to be able to penetrate the portion of the tube 4 which receives the rod 9. Thus, the head 8 prevents the conductive element 7 from moving in the tube in the downstream direction.

[0087] Figure 2A is an enlargement of Figure 2 and shows in more detail a conductive element 7 in a tube 4. Reference numeral 49 in Figure 2A designates the portion of the tube 4 that receives the rod 9 and into which the head 8 cannot penetrate. The tube 4 has a shoulder 498 at the junction between portion 49 and another portion 48 of the tube 4 located upstream. The head 8 blocks the conductive element 7 in the downstream direction when it is in contact with shoulder 498.

[0088] The conductive elements 7 can have a length between 1 mm and 150 mm and / or a diameter between 0.1 mm and 2 mm.

[0089] The conductive elements 7 can notably be made of stainless steel, a material resistant to corrosion and oxidation, biocompatible, easy to sterilize, inert, strong and durable.

[0090] The free end of the rods 9 is advantageously acute, i.e. tapered, for example conical in shape with a conicity angle between 5° and 120°. Other shapes of conducting elements are also conceivable.

[0091] The device 1 may include a blocking element 10 comprising a main part 11 arranged in the distribution chamber 3 and protrusions 12 which each extend into a tube 4.

[0092] The main part 11 is fixed to the device 1, for example by screws or by clips, and the protrusions 12 extend into the tubes so that the free ends of the protrusions are close to the heads 8 of the conductive elements 7. The protrusions 12 thus limit the movement of the conductive elements in the upstream direction.

[0093] The locking element 10 and the heads 8 of the conductive elements 7 thus allow the conductive elements 7 to be locked in their position within the tubes 4 in both the downstream and upstream directions. The conductive elements 7 may, however, have limited play along the X-axis, for example, between 1 mm and 12 mm, corresponding to the maximum distance between the free end of the protrusions 12 and the heads 8 of the conductive elements 7. This maximum distance is reached when a head 8 is in contact with the corresponding shoulder 498.

[0094] The locking element 10 can be made of a plastic material such as polycarbonate.

[0095] Other means of blocking or holding the conductive element can be considered.

[0096] The high-voltage electrode 6, not shown in figures 2 to 5, is arranged around the tubes 4 over a height H.

[0097] The heads 8 of the conducting elements 7, which form a first end of the conducting elements 7, are preferably as illustrated arranged at mid-height of the height H, that is to say at an equal distance along the X axis from the upstream and downstream ends of the high-voltage electrode 6.

[0098] As particularly visible in Figure 2, the rods 9 of the conducting elements 7 extend beyond the downstream end of the high-voltage electrode 6 along the X-axis. Thus, the free ends of the rods 9, which form a second end of the conducting elements 7, are arranged downstream of the high-voltage electrode 6.

[0099] Preferably, the free ends of the rods 9 extend beyond the high-voltage electrode 6 by a length along the X-axis greater than or equal to 1 mm, 2 mm, or 5 mm and / or less than or equal to 10 mm, 5 mm, or 2 mm. As can be seen in Figures 2, 2A, and 5, the conductive elements 7 lack an internal channel that would allow gas or plasma to flow through them, even over only a portion of their length along the X-axis. Gas and plasma in the tubes 4 can only flow around the conductive elements 7. It will therefore be understood that gas and / or plasma present in portion 48 of the tube 4 can penetrate portion 49 even when the head 8 is in contact with the shoulder 498.

[0100] In some variants, the heads 8 are convex, meaning that the end surface 85 (see Figure 2A) of the head 8 opposite the rod 9 is not flat but forms a single projection or several projections. In the example shown in Figures 2, 2A, and 5, the end surface 85 is curved, without any flat portion or sharp edge, so as to form a single projection. In other variants, as shown in Figure 2B, the heads 8 are flat, meaning that the end surface 85 is flat. Figure 2B also shows that the free end of the rods 9 is advantageously acute, as already mentioned above.

[0101] Figure 6 illustrates an advantageous embodiment of tubes 4. Figure 6 is a cross-sectional view of four tubes 4.

[0102] Each tube 4 has a recess 40 which receives a conductive element 7 and allows the gas and plasma to flow from upstream to downstream. In the illustrated example, the recess 40 has a three-leaf clover-shaped cross-section with a central portion 41, generally circular in cross-section, receiving the stem 9 of a conductive element 7, and three secondary portions, or channels, 42 arranged around the central portion 41 and open to it. The channels 42 are distributed equiangularly around the central portion 41. The recess 40 is also visible in Figure 2A, and the channels 42 are also visible in Figure 4. Thanks to the channels 42, the gas and plasma flow from upstream to downstream is permitted even when the head 8 is in contact with the shoulder 498, because the head 8 in contact with the shoulder 498 does not obstruct the channels 42.

[0103] Figure 7 shows the cross-sections of other embodiments of tubes 4. In these embodiments, a tube 4 has a recess 40 whose cross-section is in the shape of a four-, five-, six-, or seven-pointed star. At the center of the star, the dimensions of the recess are adapted to receive the rod 9 of a conducting element 7. In these embodiments as well, the upstream-downstream flow of gas and plasma is permitted even when the head 8 is in contact with the shoulder 498, because the head 8 in contact with the shoulder 498 does not obstruct the points of the star.

[0104] The recesses within the tubes can have a constant or variable cross-section along the X-axis. Thus, the cross-section of a tube recess can have variable dimensions along the X-axis.

[0105] As an example, a circular cross-section recess may have a larger diameter in an upstream part of the tube that receives the conducting element 7 than in a downstream part, the diameter being for example between 1 mm and 5 mm in the upstream part and between 0.1 mm and 3 mm in the downstream part.

[0106] Similarly, the cross-section of a more complex shaped recess, such as a multi-pointed star or a three- or four-leaf clover, may have different dimensions along the X-axis.

[0107] Figure 8 represents a plasma jet device 1 according to the invention arranged in a handle 20, in longitudinal section view.

[0108] The handle 20 facilitates the gripping and use of the device 1. The handle 20 comprises a housing 21 which receives the device 1, a gas inlet tube 22 fluidly connected to the gas inlet 2, and an electrical power cable 23 having a first wire 24 electrically connected to the high-voltage electrode 6 and a second wire 25 electrically connected to the ground electrode 13. A spacer 25 is advantageously fixed to the handle 20 so as to surround the free ends of the tubes 4. The spacer 25 extends beyond the plasma outlets 5 in the downstream direction, so that physical contact between the tubes 4 and the surface to be treated is prevented by the presence of the spacer 25.

[0109] The spacer 25 is preferably removable so that it can be changed after each use. The spacer 25 is, for example, mounted on the handle 20 by clipping (spring clips, fixing clips), by bayonet locking, by snapping or by screwing.

[0110] Figure 9 shows an example of a cold plasma jet generation assembly 100, comprising a handle 20, which includes a cold plasma jet device 1, connected to a housing 101 by a single cable 102. The cable 102 contains the power supply cable 22 and the gas supply tube 21. The housing 101 advantageously includes a control interface 103.

[0111] Functioning

[0112] The operation of a plasma jet device 1 according to the invention follows directly from the above.

[0113] A source gas, which may include a rare gas such as argon or helium, enters the device 1 through the gas supply inlet 2. The gas, which is typically at room temperature, then enters the distribution chamber 3 from which it is distributed into the various tubes 4.

[0114] The high-voltage electrode 6, which is electrically connected to a voltage source, delivers a first electrical signal which generates an electric field in each of the tubes 4. The electric field tends to concentrate at the downstream end of the conductive elements 7 and allows the plasma to be initiated.

[0115] The conductive elements 7 facilitate the initiation of the plasma, in particular by allowing the concentration of the electric field at the free end of the rods 9.

[0116] The first electrical signal may have a frequency between 50 Hz and 100 kHz, preferably between 5 kHz and 50 kHz, for example approximately 10 kHz or 20 kHz. It may also have a voltage between 1 kV and 30 kV, preferably between 5 kV and 10 kV, for example approximately 5 kV or 7 kV.

[0117] Optionally, the high-voltage electrode 6 can deliver a second electrical signal adapted to promote the propagation of the generated plasma towards the plasma outlets 5.

[0118] When the plasma reaches the plasma outlets 5, it forms one or more jets that can be used to treat a surface.

[0119] As is now clear, a device according to the invention makes it possible to considerably reduce the voltage required to initiate the plasma, which facilitates the use of different gases, particularly argon, which requires a higher initiation voltage than helium. Furthermore, the reduction in the initiation voltage advantageously reduces the electromagnetic noise generated by the device. The use of a plurality of tubes increases the treatment area. Moreover, a low plasma dose can be sufficient, particularly by using a frequency between 7 kHz and 20 kHz for the field generated by the high-voltage electrode. The device according to the invention therefore improves the treatment speed, making it possible, for example, to obtain treatment times on the order of 4 s per cm². 2 versus 30 to 60 seconds per cm 2 for existing devices.

[0120] The ground electrode also ensures good homogeneity of the power and shapes of the plasma jets.

[0121] A device according to the invention is particularly advantageous for the treatment of chronic wounds, such as ulcers, diabetic foot ulcers, and bedsores; for the treatment of burns, for example, for treating severe burns; and for cosmetic applications, such as the treatment of acne. In general, such a device is suitable for treating all types of wounds.

[0122] Of course, the invention is not limited to the examples of implementation that have just been described.

[0123] In particular, a device according to the invention may include a safety system configured to control the plasma dose ejected from the device, and / or control the delivered current, and / or control the plasma temperature at the device outlet, and / or control the plasma power, and / or control the rare gas pressure in a rare gas cylinder supplying the rare gas inlet of the tube, and / or control the rare gas pressure within the tube. For example, the safety system may be a fast circuit breaker, or a microcontroller control of the high-voltage power supply to the electrode that generates the plasma.

[0124] A device according to the invention preferably includes redundancy, in particular to comply with regulations concerning medical devices.

[0125] In particular, a device according to the invention is preferably configured to comply with all or part of the following standards: ISO 13485:2016, ISO 14971:2019, IEC 62304 / AE2018, IEC 62366-1:2015, ISO 15223-1:2016, ISO 10993, IEC 60601-1, AAMI TIR 57, 14155:2020 (if RIPH1), DIN SPEC 91315. This list is not exhaustive.

[0126] The device illustrated in the figures has four tubes, but the invention applies to a different number of tubes, for example 1, 2 or 3. The expression "comprising one" should be understood as a synonym for "comprising at least one".

Claims

Demands 1. Cold plasma jet device (1) comprising: - at least one gas supply inlet (2); - at least one tube (4) fluidically connected to the gas supply inlet and having at least one plasma outlet (5), the gas supply inlet and the plasma outlet defining a direction of gas and plasma flow; - at least one high-voltage electrode (6) outside the tube configured to generate an electric field in the tube; and - at least one electrically conductive element (7) having a floating electrical potential and extending axially inside the tube at least partially between the high-voltage electrode and the plasma outlet.

2. Device according to claim 1, the high-voltage electrode surrounding the tube.

3. Device according to claim 1 or 2, the conducting element and the high-voltage electrode partially overlapping axially.

4. Device according to any one of the preceding claims, comprising a ground electrode (13) connected to electrical ground and disposed around the outer wall of the tube, at a distance from the outlet less than that separating the high-voltage electrode from the outlet, downstream of said conductive element, preferably near the plasma outlet.

5. Device according to any one of the preceding claims, the conducting element having a nail shape, comprising a head (8) forming a first end of the element and a shank (9) whose free end forms a second end of said element.

6. Device according to any one of the preceding claims, the conducting element having an end having an acute shape, in particular conical with a conicity angle between 5° and 120°.

7. Device according to any one of the preceding claims, comprising a blocking element (10) including at least one protrusion (12) extending in the tube upstream of said conducting element, so as to limit the upstream movement of the conducting element, having regard to the direction of gas flow.

8. Device according to any one of the preceding claims, the tube defining along at least a part of the conducting element a recess (40) whose cross-section is non-circular, preferably multilobed, in particular of a three-leaf clover, a four-leaf clover, or star-shaped, in particular of a three-pointed or more star, the conducting element being preferably centered in this recess.

9. Device according to any one of the preceding claims, the tube having a variable internal cross-section along the tube, particularly upstream or downstream of the conducting element.

10. Device according to any one of the preceding claims, comprising a single gas supply inlet fluidly connected to a distribution chamber (3), the device comprising a plurality of tubes each fluidly connected to the distribution chamber.

11. Cold plasma jet generation assembly (100) comprising a handle (20) receiving a cold plasma jet device according to one of the preceding claims.

12. Assembly according to the preceding claim, comprising a spacer (25) disposed on the handle around F at least one plasma outlet and configured to prevent direct contact between F at least one plasma outlet and a surface to be treated, F spacer being preferably removable.

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