Metallic filter with microstructured architecture of controlled porosity, and process for manufacturing the same

Abstract

To provide a filter for sanitary masks with a longer shelf life.SOLUTION: A metallic filter includes a microstructured architecture (2) defined in a three-dimensional space having orthogonal axes (X, Y, Z). The microstructured architecture (2) includes a metallic network (10) formed by a plurality of longitudinal connecting strands (12), i.e., extending along a longitudinal axis direction (X), and a pore network (20) formed of a plurality of longitudinal interstices (22) located along connecting strands (12), each longitudinal interstice corresponding to a subset of pores (24) of the pore network (20) such that the pores are aligned along the longitudinal axis (X), where the longitudinal interstices (22) thereby define an axis of anisotropy of the microstructured architecture.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a metallic filter having a microstructured architecture. [Background technology]

[0002] An architecture is said to be microstructured as long as the main elements forming the architecture have micrometric dimensions, ie dimensions less than 1000 μm, in at least two spatial dimensions.

[0003] Such metal filters are typically used to filter fluids, liquids or gases, but are sufficiently permeable to allow at least a portion of the fluid to circulate.

[0004] The present invention also relates to a method for manufacturing a metal filter having a microstructured architecture.

[0005] The present invention is applicable to systems requiring fluid filtration. For example, the present invention can be used in sanitary filtration systems such as sanitary filters or sanitary masks. For example, the present invention can also be used in gas diffusion plates. The present invention can also be used in air pollution control systems or radioactive waste filtration systems.

[0006] Since the spread of COVID-19, surgical and FFP1 / FFP2 masks have become everyday consumer goods for billions of people worldwide. Because these masks are inherently temporary and non-reusable, they are now a significant source of potentially contaminated waste. Washing surgical masks is not recommended by health authorities because they lose their effectiveness when moisture is absorbed during use. Furthermore, even if mask washing is taken into account, there are other environmental drawbacks, as shown, for example, by an analysis of wastewater from the city of Paris. This analysis revealed the presence of trace amounts of COVID-19 in this wastewater. The challenge therefore shifts to managing the environmental impact of washing millions of surgical masks.

[0007] One possible option to address these issues is to use sanitary masks that have a longer shelf life.

[0008] In this regard, metal filters manufactured by powder sintering are already known. However, apart from the complexity of the sintering process, they are also very expensive. Furthermore, metal filters obtained in this way can only be manufactured in limited shapes and have non-uniform porosity. This non-uniform porosity makes it difficult to achieve low pressure drop, i.e., low fluid flow rate, while simultaneously achieving efficient filtration. Considering maximum filtration of small particles, i.e., grade 0.1 filtration, which filters out more than 99% of particles larger than 100 nm, the pressure drop is high. Therefore, a compromise must be found.

[0009] Uniformly porous filters with microstructured architectures fabricated by 3D printing have also been proposed (Fig. 1). However, such filters do not fully address the problem of pressure loss when filtration efficiency increases. In fact, it is much easier to find a compromise between pressure loss and filtration efficiency, but the pressure loss remains large. Summary of the Invention

[0010] The present invention makes it possible to overcome the aforementioned drawbacks and, to this end, proposes a metallic filter comprising a microstructured architecture formed in a three-dimensional space with orthogonal axes X, Y and Z, the microstructured architecture comprising: a metal network formed by a plurality of longitudinal connecting strands, i.e. extending along a longitudinal axis (axis X); a pore network formed by a plurality of longitudinal gaps located along the connecting strands, each longitudinal gap corresponding to a pore subset of the pore network, i.e. a pore subset whose pores are aligned along the longitudinal axis X; wherein the longitudinal gap thereby forms the anisotropy axis of the microstructured architecture.

[0011] In practice, therefore, the pores are distributed within the pore network in such a way that the anisotropy of the microstructured architecture is realized in the longitudinal axis direction X with respect to the other two directions Y, Z.

[0012] The pores in a given gap are generally parallel to the pores in other gaps, and this is true for all gaps. Thus, the gaps in the pore network are generally parallel to each other. Thus, the porosity is controlled within the microstructured architecture. Therefore, the metal filter according to the present invention allows for low pressure loss while having high filtration efficiency.

[0013] According to different features of the invention, which may be taken together or separately, there are the following: -The pore size is the same, -Porosity is between 10%~70%, The connecting strands have a width of 10 μm to 500 μm and the longitudinal gaps have a width of 1 μm to 100 μm; The metal filter has a thickness of 250 μm to 300 mm formed along the longitudinal axis, the metal network is made of a metal selected from aluminum, nickel, cobalt, iron, copper, palladium, titanium, tungsten, silver or platinum, or an alloy of materials such as stainless steel, a metal alloy or a metal oxide, The metal filter further comprises two opposing main faces that delimit the microstructured architecture, the longitudinal faces being each covered with a thin virucidal or bactericidal layer.

[0014] The present invention also relates to a functional component comprising a metal filter according to the present invention and a zero-porosity periphery surrounding the microstructured architecture of the metal filter.

[0015] The present invention further relates to an additive manufacturing method for a metal filter as described above, the additive manufacturing method comprising: - depositing a metal powder layer of a given material or an alloy of several materials on a support, the metal powder layer having a thickness of between 1 μm and 200 μm; - executing a computer program to perform localized laser melting of the metal grains of the powder at a temperature higher than the melting temperature of the material or alloy of materials forming the metal powder deposited in the step of depositing the metal powder layer, to create a predetermined pattern of a microstructured architecture formed in a three-dimensional space having orthogonal axes X, Y, and Z; and the microstructured architecture comprises: a metal network formed by a plurality of longitudinal connecting strands, i.e. extending along a longitudinal axis (axis X); a pore network formed by a plurality of longitudinal gaps along the connecting strands, each longitudinal gap being a subset of pores of the pore network; That is, a pore network in which the pores correspond to pore subsets aligned along the longitudinal axis X. wherein the longitudinal gap thereby forms the anisotropy axis of the microstructured architecture.

[0016] The method according to the invention may comprise at least one of the following steps taken alone or in combination: The support is heated to a temperature strictly above ambient temperature and not exceeding 250°C. The support is heated to a temperature between 180°C and 220°C, preferably between 190°C and 210°C. The volumetric energy density of the laser beam during the localized laser melting process corresponds to 30% to 90% of the value of the volumetric energy density of the laser beam required to form a non-porous block from a metal powder. [Brief explanation of the drawings]

[0017] Other objects and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings. [Figure 1] 1 is a schematic perspective view of a metal filter according to an exemplary embodiment of the present invention; [Figure 2]1 is a schematic cross-sectional view of a metal filter along the plane of directional vectors X and Y, illustrating the microstructured architecture of the metal filter according to one embodiment of the present invention. [Figure 3] 1 is a schematic cross-sectional view of a metal filter along the plane of directional vectors Y and Z, illustrating the microstructured architecture of the metal filter according to one embodiment of the present invention. [Figure 4] 1 is an image of a microstructured architecture according to the prior art; [Figure 5] 1 is an image of a microstructured architecture according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Referring to FIG. 1, the present invention relates to a metallic filter 1 that includes a microstructured architecture formed in three-dimensional space having orthogonal axes X, Y, and Z.

[0019] The metal filter 1 allows the filtration of a liquid or gaseous fluid F. For example, when the metal filter is used as a sanitary mask, the fluid is the air exhaled and inhaled by the individual. This air can therefore be charged with droplets. The metal filter 1 can have any shape, and can be a parallelepiped as shown in Figure 1, but can also be a prism or a polyhedron. The shape can be adapted as needed.

[0020] Regardless of the selected geometric shape, in the following, we will consider the fluid F moving in the direction of the thickness e of the metal filter 1. The thickness e of the metal filter corresponds to the smallest dimension of the metal filter. In this case, it is therefore the distance between the first main surface 3 and the second main surface 4 of the metal filter 1. Thus, in the example shown in FIG. 1, the thickness e is formed in the longitudinal axis direction, and this axis (axis X) is perpendicular to the main surfaces 3 and 4. Therefore, when the fluid F moves in the direction of the thickness e of the metal filter 1, this means that the fluid F first passes through the first main surface 3 of the metal filter, then enters the metal filter 1, and finally passes through the second main surface 4 of the metal filter in this order. Note that this does not define the actual trajectory or dynamics of the fluid F outside or inside the metal filter 1, but only its overall motion.

[0021] The metal filter 1 comprises a microstructured architecture 2. The architecture 2 is said to be microstructured as long as the main elements forming the architecture have micrometer dimensions, i.e., dimensions less than 1000 μm, in at least two spatial dimensions. The main elements of the microstructured architecture are described below. First, it should be noted that the microstructured architecture 2 extends from the first main surface 3 to the second main surface 4. It can also be pointed out that the metal filter may incorporate a functional part comprising a periphery 32 surrounding the microstructured architecture 2. In other words, the functional part comprises the metal filter 1 surrounded by the periphery. The periphery 32 has a porosity of zero (i.e., equal to 0), i.e., is non-porous. This improves the mechanical strength of the entire metal filter 1 and facilitates its integration into the manufacturing method of functional components.

[0022] 2, the microstructured architecture 2 comprises a metallic network 10 formed by a plurality of connecting strands 12 extending in a longitudinal axial direction (axis X). The cross section of the microstructured architecture 2 shown in FIG. 2 is perpendicular to the main faces 3, 4 of the metallic filter 1. This plane is defined by the direction vector TIFF2023086693000002.tif21156 and 2 is a subspace of the previously introduced space X, Y, and Z of TIFF2023086693000003.tif21156. This corresponds, for example, to the plane E bounded by the dashed line in the perspective view of FIG. 1. The cross section of FIG. 2 is also indicated by dashed line E in FIG. 3 (perpendicular to the plane of the paper). Each connecting strand 12 is an elongated structure with a filament-like appearance and a nonlinear profile. As explained in more detail below, connecting strand 12 is formed by localized laser melting of grains of a metal powder. Connecting strand 12 is micrometer-sized in at least two spatial directions, which means that it is, in fact, substantially disk-shaped with a micrometer diameter in a cross-sectional plane perpendicular to its length.

[0023] Preferably, the metal network 10 may include material bridges 14 that ensure the cohesion of the metal strands 12. The material bridges 14 allow the metal network 10 to form a cohesive assembly.

[0024] The microstructured architecture 2 also comprises a network 20 of pores 24 that form the connecting strands 12. The pores 24 have the usual meaning given in the prior art and correspond to the voids left in a porous material. Figure 2 is a schematic illustration of the microstructured architecture 2. Contrary to what is shown, the pores 24 may therefore have different shapes from one another, even if their distribution and size are controlled, as will be explained below. In fact, the pores 24 also result from the local melting of the grains of the metal powder, but only as an indirect consequence.

[0025] The network 20 of pores 24 includes a plurality of longitudinal (axis X) gaps 22 that correspond to pore 24 subsets. More specifically, these are pore 24 subsets located along the connecting strands 12. Note that each longitudinal gap 22 corresponds to a pore 24 subset located between connecting strands 12 that are side-by-side but not in direct contact with one another. While each individual pore 24 has a micrometer dimension, the longitudinal gaps 22 have a dimension that is significantly larger than the other dimensions, resulting in an elongated shape of the pore.

[0026] According to the invention, the longitudinal gaps 22 are all oriented along the same direction X, but not along the other directions Y and Z, resulting in anisotropy of the microstructured architecture. Note that the longitudinal gaps 22 are parallel to each other along this longitudinal direction. This anisotropy is due to the directional vector TIFF2023086693000004.tif21156 and This is shown schematically in Figure 2, which shows the distribution of pores in the plane of TIFF2023086693000005.tif21144. Hereinafter, the longitudinal axis X may be referred to as the anisotropy axis.

[0027] Of course, the direction of each longitudinal gap 22 considered in isolation corresponds to a line parallel to the longitudinal axis passing through the centers of the pores 24 that form that longitudinal gap 22. Therefore, the direction of a longitudinal gap 22 necessarily depends on the arrangement of the subset of pores 24 that form it. It should be noted, however, that the pores 24 of a longitudinal gap 22 do not necessarily follow a perfect alignment. This is shown, for example, for the longitudinal gap 22 shown by the dotted line on the right side of FIG. 2. The direction of a longitudinal gap 22 thus corresponds to a line oriented as defined by the longitudinal axis X passing through the midpoint (x, y), whose ordinate y is the median of the ordinates of the centers of the pores 24.

[0028] This anisotropy allows for a microstructured architecture 2 with controlled porosity, where the porosity is controlled by controlling the distribution of pores 24 within the longitudinal gaps 22, as defined above. When fluid F passes through the metal filter 1, the fluid F is constrained by the microstructure of the microstructured architecture 2, with flow being facilitated by the presence of the longitudinal gaps 22. Thus, the present invention allows for high filtration efficiency with low pressure loss. Therefore, circulation of the fluid F within the microstructured architecture is improved.

[0029] Preferably, the pores 24 of the pore network 20 have substantially the same size. Therefore, in addition to the distribution of the pores 24, the porosity of the microstructured architecture 2 can also be controlled due to the uniform size of the pores. Insofar as the longitudinal gaps 22 define the anisotropy of the microstructured architecture along the longitudinal axis direction (axis X), and if the pores 24 are all the same size in the microstructured architecture 2, it is easily understood that, depending on the envisioned application, the filtration efficiency and simultaneously the pressure drop can be very precisely controlled by varying only the size of the pores 24. However, it should be noted that the pores 24 are micrometers in size.

[0030] Figure 3 shows the microstructured architecture 2 in a plane parallel to the main faces 3, 4 of the metallic filter 1. This plane is defined by the direction vector TIFF2023086693000006.tif21144 and 3 are subspaces of the space X, Y, Z introduced above of TIFF2023086693000007.tif21144. As can be clearly seen in this figure, each gap 22, of which only one pore 24 is shown in each case in FIG. 3, is generally surrounded by four connecting strands 12, located two next to each other. The same applies to each connecting strand 12, which in some examples is generally surrounded by four longitudinal gaps 22. However, the distribution of pores 24 as shown in FIG. 3 is not mandatory, and other distributions are also conceivable, provided that:

[0031] Within the pore network, the pores 24 are distributed in an anisotropic manner in the longitudinal axis direction X relative to the other two directions Y, Z. The distribution of the pores 24 is configured to favor the movement of fluid F through the longitudinal gaps 22 and thus facilitate the movement of fluid F with respect to the other directions.

[0032] Preferably, the porosity (or porosity) of the microstructured architecture 2 is between 10% and 70%, which results in a pressure drop between the main faces 3, 4 of about 100 Pa and a permeability of 11 to 200 l.m. -2 .s -1 The aforementioned porosity ranges are particularly suitable for hygienic filtering masks such as those described in the preamble of this specification. However, the higher the porosity, the lower the pressure drop, and vice versa. Other applications may be envisaged within the scope of the present invention.

[0033] Preferably, the connecting strands 12 have a width between 10 μm and 500 μm, while the longitudinal gaps 22 have a width between 1 μm and 100 μm. In the accompanying figures, the widths are taken along axis Y, which is perpendicular to the longitudinal axis. This does not imply a maximum dimension for the connecting strands 12 and the longitudinal gaps 22. These parameters allow for a microstructure of the architecture 2 suited to the desired type of filtration.

[0034] Particularly preferably, the thickness e of the metal filter 1, i.e., the smallest dimension of the metal filter 1, extends along the anisotropic axis X. When the metal filter 1 has this configuration, the fluid F moves in a preferred direction that is also the smallest dimension of the metal filter. Thus, there is less friction within the microstructured architecture 2, and as a result, the dynamics of the fluid F within the microstructure are primarily guided by the anisotropic distribution of the longitudinal gaps 22 and the size of the pores 24. The pressure loss and filtration efficiency experienced by the fluid F as it passes through the metal filter 1 are further controlled.

[0035] The thickness e of the metal filter 1 is preferably 250 μm to 300 mm. In practice, it essentially depends on the intended use. For example, in the case of a hygienic filtering mask, a thickness of 400 μm to 2 mm is selected. If the metal filter 1 according to the present invention is used to manufacture a functional part, such as an air filter with high processing efficiency, which is commonly used in air treatment devices or pollution control devices, the thickness can be much greater.

[0036] The metal network 10 is made of metals in pure form or in the form of alloys of metals or metal oxides, and the metals are selected from aluminum, stainless steel, nickel, cobalt, iron, copper, palladium, titanium, tungsten, silver and platinum. These metals are not only solid at ambient temperature, but also good candidates for microstructuring by laser melting. Furthermore, they have good mechanical properties and are suitable for thin film deposition.

[0037] In this regard, the metal filter 1 may further comprise a thin viricidal or bactericidal layer covering the major surfaces 3, 4 of the metal filter 1. Depending on the deposition technique envisaged, this thin layer may extend from the major surfaces 3, 4 to a certain pore depth. This thin viricidal or bactericidal layer is a barrier layer against infectious microorganisms such as bacteria and viruses. For example, such a thin layer may be made of a pure metal, an alloy of a metal or metal oxide, such as titanium, copper, zinc, nickel or silver.

[0038] In this way, or by means of additional thin layers, other useful functions may be added to the metal filter 1 to enhance its properties. For example, this thin layer may enable the microstructured architecture 2 to be hydrophilic on one of the main faces 3, 4 and hydrophobic on the other of the main faces 3, 4. This may in particular make it possible to control the humidity of a functional component comprising such a metal filter.

[0039] The present invention also relates to an additive manufacturing method for the metal filter 1 described above.

[0040] The first step 110 of the additive manufacturing method according to the invention consists of depositing on a support at least one layer of metal powder of a given material or alloy of materials. The thickness of each layer of metal powder can be between 1 μm and 200 μm. Preferably, the thickness of each layer of powder is between 1 μm and 150 μm, between 1 μm and 120 μm, or even more precisely between 10 μm and 120 μm. Typically, layers with thicknesses of about 30 μm, 50 μm or 100 μm can be used.

[0041] The support can be heated to a temperature strictly above ambient temperature up to 250°C. Preferably, the support can be heated to a temperature of 180°C to 220°C, more precisely, and even more effectively, 190°C to 210°C. This enhances adhesion to the substrate and structurally stabilizes the layer thus formed. The finished product is therefore less likely to break.

[0042] The second step of the additive manufacturing method according to the invention consists in carrying out localized laser melting of the metal grains of the powder at a temperature higher than the melting temperature of the given material or alloy of the given material to form the metal powder deposited during step 110. Laser melting carried out under these conditions makes it possible to locally supply energy under the action of a laser beam, which allows the grains of the powder to be locally melted.

[0043] This localized and therefore selective melting is carried out by a computer program that creates a predetermined pattern M of the microstructured architecture 2 from a pre-established computer database.

[0044] Figure 5 is an image of a microstructured architecture 2 according to the invention. It is possible to see the anisotropy of the longitudinal pores 22, which are all parallel to one another in a given direction. In contrast, in the microstructured architecture obtained by a method according to the prior art, as shown in Figure 4, the pores are distributed according to an isotropic distribution.

[0045] It may be necessary to repeat steps 110 and 120 several times to form a connector strand 12 of appropriate dimensions.

[0046] In each laser melting step, the path taken by the laser beam includes displacement vectors that are spatially offset in pairs by an offset value, and the porosity of the pores in the metal filter 1 is adjusted by adapting the offset value for a given laser beam power and layer thickness, with the porosity increasing as the offset value increases. The offset value HD affects the metal filter 1 produced.

[0047] In this respect, the volumetric energy density of the laser beam in each pass during the laser melting process is 30% to 90% of the volumetric energy density value of the laser beam required to obtain a non-porous block from the metal powder at the level of the microstructured architecture 2. To adapt this volumetric energy density, other parameters, e.g., HD, V, and e c The laser power can be set by influencing the parameters. See the following formula (F1) which defines these parameters:

[0048] The computer program, with the aid of a database, controls the displacement of the laser beam relative to the metal powder deposited during step 110 according to at least one of the following parameters: the relative trajectory between the laser beam and the previously deposited powder of metallic material; - a displacement velocity "V" corresponding to the relative velocity between the laser beam and the previously deposited metal material powder, - power "P" of the laser beam, -Volumetric energy density of the laser beam "E"

[0049] The volume energy density E of the laser beam is J / mm 3 and is defined by the following formula (F1): TIFF2023086693000008.tif21144 where P is the laser beam power in watts (W), V is the laser beam displacement speed in mm / s, HD is the offset between two adjacent applied vectors of the laser beam in mm, and e c is the layer thickness in mm, and E is the volumetric energy density of the laser beam.

[0050] The three-dimensional additive manufacturing solution of depositing successive layers according to a pre-established, computer-controlled trajectory and then melting them with a laser is known as "SLM" technology, which stands for "Selective Laser Melting" and can also be expressed as "Localised Laser Melting".

[0051] In SLM additive manufacturing, operations take place in a neutral gas environment (typically argon) in which a thin layer of metal powder is spread on a metal substrate. A laser beam then melts the powder, providing it with the energy necessary to selectively deposit it in layers according to the part's shape. Repeating these operations allows the production of metal parts with complex three-dimensional geometries. To do this, the part must be cut into slices with the desired manufacturing layer thickness, a "computer-aided control" type file of the part must be prepared, and a set of two-dimensional design drawings must be created. Furthermore, a holding support must be created and a set of parameters must be assigned that define the trajectory of the laser beam on the powder. The result of all these operations is a file that is transferred to drive the manufacturing machine.

[0052] Other methods of additive manufacturing of materials can be envisaged, such as a technique known as "SLS," which stands for "Selective Laser Sintering," and can also be expressed as "localized laser sintering." There are other techniques as well.

[0053] Finally, within the scope of the present invention, if functionality is required, it is possible to provide a step of depositing a thin layer interposed between the laser melting step 120 and the step of depositing the metal powder layer 110. Other modifications of the method may be made in order to functionalize the successive layers thus formed. Practical implementation of the method according to the invention

[0054] According to a particular embodiment, the method comprises the following steps: During step 110, a metal powder is deposited on the support with a thickness equal to 50 μm. Step 120 is carried out with a laser beam power of 275 W, an offset value HD fixed at 0.1 mm or 0.12 mm and a lower threshold displacement speed of the laser beam (relative to the powder bed) of 1500-6000 mm / s.

[0055] Within the scope of this example, it was possible to demonstrate that, above a lower threshold displacement rate, the porosity within the microstructured architecture increases with increasing displacement rate.

[0056] It was therefore possible to show that by adapting the volumetric energy density of the laser beam, the porosity of the pores in the microstructured architecture 2 can also be tuned. Indeed, below an upper threshold of volumetric energy density, the porosity increases as the volumetric energy density decreases.

[0057] In this regard, according to a particular embodiment, the method comprises the following steps: In step 110, a metal powder having a thickness equal to 50 μm is deposited on the support. Step 120 is performed with a laser beam power of 275 W and an upper threshold energy density of the laser beam of 7 J / mm 3 ~80J / mm 3 In this example, the range is 7 J / mm (depending on the offset value HD of 0.1 mm or 0.12 mm). 3 ~30J / mm 3 The temperature can vary in the range of

[0058] Tests were carried out using 316L stainless steel powder sold by SLMSolutions®, the results of which are shown in Figures 4 and 5. The metallic material may also be aluminum or an aluminum alloy, which has the advantage of being photo- and thermally stable at disinfection temperatures.

Claims

1. A metallic filter (1) comprising a microstructured architecture (2) formed in a three-dimensional space having orthogonal axes (X, Y, Z), said microstructured architecture (2) comprising: a metal network (10) formed by a plurality of longitudinal connecting strands (12), i.e. extending along a longitudinal axis (X); a pore network (20) formed by a plurality of longitudinal gaps (22) located along the connecting strands (12), each longitudinal gap corresponding to a subset of pores (24) of said pore network (20), i.e., said subset of pores (24) being aligned along said longitudinal axis (X), A metallic filter (1), wherein said longitudinal gap (22) thereby forms the anisotropy axis of said microstructured architecture.

2. 2. The metal filter (1) according to claim 1, wherein the pores (24) are of the same size.

3. The metal filter (1) according to claim 1, wherein said porosity is between 10% and 70%.

4. 2. The metal filter (1) according to claim 1, wherein the connecting strands (12) have a width of 10 μm to 500 μm and the longitudinal gaps (22) have a width of 1 μm to 100 μm.

5. 2. The metal filter (1) according to claim 1, having a thickness (e) formed along said longitudinal axis (X) of between 250 μm and 300 mm.

6. 2. The metal filter (1) according to claim 1, wherein the metal network (10) is made of a metal selected from aluminum, nickel, cobalt, iron, copper, palladium, titanium, tungsten, silver or platinum, or an alloy of a material such as stainless steel, a metal alloy or a metal oxide.

7. 2. The metal filter (1) according to claim 1, further comprising two opposing main surfaces (3, 4) forming said microstructured architecture (2), said longitudinal surfaces (3, 4) each being covered with a thin virucidal or bactericidal layer.

8. A functional component (30) comprising a metal filter (1) according to any one of claims 1 to 7 and a zero-porosity periphery (32) surrounding the microstructured architecture (2) of said metal filter.

9. An additive manufacturing method (100) for a metal filter (1) according to any one of claims 1 to 7, comprising: The additive manufacturing method (100) Depositing (110) at least one layer of metal powder of a predetermined material or a predetermined alloy of materials on a support, said metal powder layer having a thickness of 1 μm to 200 μm; and executing (120) a computer program to carry out localized laser melting of metal grains of said powder at a temperature higher than the melting temperature of said predetermined material or predetermined alloy of said materials forming said metal powder deposited in step (110) to create a predetermined pattern (M) of a microstructured architecture (2) formed in a three-dimensional space with orthogonal axes (X, Y, Z), said microstructured architecture (2) a metal network (10) formed by a plurality of longitudinal connecting strands (12), i.e. extending along a longitudinal axis (axis X); a pore network (20) formed by a plurality of longitudinal gaps (22) along the connecting strands, each longitudinal gap (22) corresponding to a subset of pores (24) of said pore network (20), i.e. a pore subset in which said pores are aligned along said longitudinal axis (X), The additive manufacturing method (100) for a metallic filter (1) according to any one of claims 1 to 7, wherein the longitudinal gap (22) thereby forms an anisotropy axis of the microstructured architecture.

10. 10. The method (100) of claim 9, wherein the support is heated to a temperature strictly above ambient temperature and not exceeding 250°C.

11. The method (100) according to claim 9, wherein the support (S) is heated to a temperature between 180°C and 220°C, preferably between 190°C and 210°C.

12. 10. The method (100) of claim 9, wherein the volumetric energy density of the laser beam during the localized laser melting step (120) corresponds to 30% to 90% of the value of the volumetric energy density of the laser beam required to form a non-porous block from the metal powder.

13. 10. The method (100) of claim 9, wherein the depositing step (110) and the localized laser melting step (120) are repeated several times in succession.

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