Translucent disposable mask

Abstract

The present invention relates to a breathable filtering device comprising a structural frame and filtration units. The filtration units may be made from a non-woven material composed of fibers, while the structural frame may comprise openings and an amorphous material which may be operatively coupled to the fibers to occlude partially the openings.

Description

[0001] P4310CP00 Specs (AOFF)

[0002] Translucent disposable mask

[0003] CORRESPONDING APPLICATION

[0004] The present PCT application claims the priority of the prior European application no. 25159486.7 filed on 21 February 2025 in the name of HM Care SA, the content of this prior application being incorporated by reference in its entirety in the present PCT application.

[0005] FIELD OF INVENTION

[0006] The present invention relates generally to the field of breathable filtering devices. By way of example, and without limitation, the invention may concern devices designed to provide effective filtration while maintaining optimal airflow and transparency. The invention may be applicable in various contexts where filtration efficiency and structural integrity are critical, utilizing materials and configurations that enhance the overall functionality, transparency / translucency, and durability of the filtering device.

[0007] STATE OF THE ART

[0008] Historically, long before the challenges posed by the Covid-19 pandemic, masks, such as surgical masks, have always been a barrier in human interactions, particularly in hospital environments. In general, these masks hinder human relations because they cover a significant portion of the wearer’s face, making communication less natural. This issue has led to the development of numerous transparent mask models designed to facilitate communication while still providing adequate protection.

[0009] The vast majority of these transparent masks, such as those described in patents US11465001 B2 and US7802572B2, include a non-breathable transparent section over the mouth, combined with a filtration system. However, these devices are often complex, costly to manufacture (due to the many components that need to be assembled), highly polluting, and inefficient in terms of filtration as they offer limited airflow. Moreover, these designs expose only a small portion of the face, limiting their effectiveness in improving visual interaction and communication.

[0010] Additionally, masks with remote filtration systems can be uncomfortable to wear due to the added weight and the complexity of the attachment mechanisms.

[0011] Other designs, such as described in KR 2022 0042964 and US 2022 / 118295, propose masks where transparent zones and filtering zones are arranged separately, for example as alternating bands or as a transparent film inserted into a portion of the filtering material. In such designs, the transparent zones are typically made of impermeable plastic films that do not allow air to pass through. As a result, only a portion of the mask surface is available for filtration and respiration, condensation tends to occur on impermeable films, and the assembly of separate transparent and filtering elements may require complex manufacturing processes.P4310CP00 Specs (AOFF)

[0012] Other approaches have proposed masks made from materials that are both transparent and filtering. For example, US 2022 / 184430 describes face masks made of transparent polymeric nanofibers. However, the main challenge lies in their production. Although these masks may incorporate multiple transparent layers to ensure both durability and filtration efficiency, the addition of layers significantly impacts transparency. Furthermore, their manufacturing process is particularly complex, as the layers must be extremely thin, often made of nanofibers with diameters less than 100 nm. These layers, being extremely light, tend to "fly" in production machines, making them difficult to handle and keep in place. This makes large-scale manufacturing difficult, further increasing industrial constraints. Moreover, such designs lack a structural frame with defined openings, relying instead on uniform nanofiber layers, which may result in insufficient mechanical strength for industrial manufacturing and practical use.

[0013] Masks made from these transparent and filtering materials also face performance challenges. The ultrathin nanofibers needed to ensure both transparency and breathability are not only difficult to produce but also fragile, which can affect the overall durability of the mask.

[0014] Attempts to optimize transparency while maintaining adequate filtration efficiency have resulted in compromises that do not fully meet users’ expectations. For instance, adding additional layers to strengthen the mask’s structure increases opacity and the complexity of the manufacturing process, while reducing the number of layers to improve transparency may compromise the structural integrity and filtration capacity.

[0015] Some prior art solutions have proposed multilayer structures comprising three or more layers which are fused together to create fused domains. However, these multilayer structures result in increased thickness, complexity, and manufacturing costs. Furthermore, the fusion process may create opaque domains that reduce transparency. The present invention overcomes these drawbacks by providing a two-layer structure (structural frame with openings + fiber layer) that is integrated into a single coplanar monolayer during the manufacturing process, without creating fused domains and while preserving the fibrous morphology and transparency ofthe fibers.

[0016] The objective of the invention described in this document is to overcome these issues by providing a solution that combines transparency, breathability, durability, and filtration efficiency, while remaining simple to produce on an industrial scale.

[0017] Unlike the prior art approaches described above, the present invention provides a structural frame with micro-openings covered by transparent fibers that are integrated into the frame, thereby achieving simultaneous transparency, filtration, and breathability across the entire surface ofthe device.

[0018] GENERAL DESCRIPTION OF THE DISCLOSURE

[0019] This general description is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This general description is not intended to necessarily identifyP4310CP00 Specs (AOFF)

[0020] key features or essential features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter.

[0021] According to one aspect, the present document discloses a filtering device configured for breathable use (e.g., for use in a surgical mask or similar application). The filtering device may comprise a structural frame and filtration units. The filtration units may comprise a non-woven material made of fibers and the structural frame may comprise openings and an amorphous material operatively coupled to the fibers of the filtration units to cover and partly occlude the openings. The fibers may form a porous network that partially occludes the openings while remaining permeable to air, thereby providing both filtration and breathability. The fibers may be at least partially embedded in the amorphous material at contact areas between the fibers and the structural frame.

[0022] In one embodiment, the structural frame openings may be at least partially occluded by the fibers, forming filtration units that can achieve a filtration efficiency greater than 95% for particles measuring 3 microns, while maintaining a pressure differential of less than 40 Pa / cm2or less than 60 Pa / cm2fortype HR masks.

[0023] In one embodiment, the fibers may be configured to form a layer at least partially or fully integrated into the structural frame during the manufacturing process (for example at least a part of the fibers may be embedded in the amorphous material for example more than 10% of the thickness of the fiber layer may be embedded into the structural frame, preferably more than 50%, more preferably substantially all of the fiber layerthickness.). This embedding process preserves the structural integrity and continuity of the fibers, such that the fibers are not fused or melted but remain intact while being anchored into the amorphous material. This integration may be configured to create a strong adherence between the fibers and the structural frame, resulting in a single layer whose total thickness may be less than the combined thicknesses of the fibers layer and the structural frame before the manufacturing process. Furthermore, the structural frame orthe combination structural frame / filtration units may be configured to provide mechanical strength to prevent any deformation or tearing of the device, both during use and throughout the industrialization process.

[0024] In one embodiment, afterthe manufacturing process, the fibers and the structural frame form a substantially coplanar structure, wherein the fibers extend within the plane defined by the structural frame rather than forming a separate layer above the structural frame. In other words, the fibers are disposed within the openings of the structural frame such that the upper surface of the fibers at the filtration units is substantially aligned with the upper surface of the structural frame, resulting in a monolayer structure. This coplanar configuration is distinct from multilayer structures where fibers are deposited on top of a support layer, as it provides enhanced mechanical integration and reduced overall thickness.

[0025] The amorphous material may comprise a low crystallinity of < 10%. The amorphous material may comprise a biodegradable material and / or biocompatible material. In one embodiment, the amorphous material comprises at least one thermoplastic polymer selected from polyesters, polyamides, or polylactic acid.P4310CP00 Specs (AOFF)

[0026] The fibers of the filtration units may comprise a direct light transmission of at least 70%. The fibers may comprise at least one of a thermoplastic polymer, an elastomeric polymer, a thermoplastic-elastomer polymer, or thermoplastic polyurethane.

[0027] In one possible embodiment, the filtration units may comprise a direct light transmission between 70% and 99%, while the structural frame may comprise a direct light transmission between 50% and 70%. As a result, the filtering device exhibits a substantially uniform direct light transmission across its entire surface, without opaque filtration zones. The filtration units are translucent rather than opaque, which distinguishes the present invention from prior art designs where filtering zones are typically opaque and only the nonfiltering zones are transparent. In one embodiment, the filtering device is optically translucent such that facial features of a wearer are perceptible to a human observer during use. This transparency enables visual communication, including lipreading, between the wearer and other persons.

[0028] The material of the structural frame may have a melting temperature lower than that of the material of the filtration units. The filtration units and the structural frame may be bonded together. For example, the filtration units and the structural frame may be thermally bonded together or glued together.

[0029] In embodiments employing thermal bonding, the filtration units and the structural frame are bonded at a temperature selected relative to the thermal properties of the respective materials. In particular, the thermal bonding may be carried out at a temperature higherthan the softening temperature of the structural frame, for example higherthan the glass transition temperature of the amorphous material forming the structural frame, and optionally higherthan the melting point of the structural frame. The thermal bonding temperature is preferably lower than the melting point of the filtration fibers, so as to avoid damage to the fibers of the filtration units. During the thermal bonding process, the filtration fibers protruding over edges of the openings are pressed against the structural frame such that the amorphous material of the structural frame at least partially flows around and surrounds the fibers, thereby embedding the fibers at the edges of the openings. For example, when the structural frame comprises polylactic acid (PLA) having a softening temperature of about 60-80°C and the fibers comprise thermoplastic polyurethane (TPU) having a melting temperature of about 160-220°C, the thermal bonding may be performed at a temperature between 80°C and 150°C, preferably between 100°C and 120°C, for example at about 100-110°C. The thermal bonding may be performed under a pressure of between 0.5 bar and 5 bar, preferably between 1 bar and 3 bar, for example at about 1.5 bar.

[0030] In one possible embodiment, the fibers of the filtration units may be deposited onto the amorphous material of the structural frame, for instance by electrospinning, centrifugal spinning or electro-centrifugal spinning. In case of thermal bonding, the thermal bonding process may be performed after the fibers of the filtration units have been deposited onto the amorphous material of the structural frame.

[0031] In one embodiment, the combined thickness of the filtration units and the structural frame may be less than 100 pm. The openings may be round, square or rectangular in shape and may be arranged in a regular pattern. The openings may have a diameter or length smaller than 300 pm, and / or greater than 10 pm, preferably between 100 pm and 200 pm, for example between 160 pm and 180 pm. The openings may beP4310CP00 Specs (AOFF)

[0032] distributed with a density of between 5 and 50 openings per mm2, preferably between 10 and 25 openings per mm2, for example about 15 to 20 openings per mm2for example around 17 per mm2. The dimensions of the openings may be selected such that the individual openings are not discernible to the naked eye at typical viewing distances. For example, openings having a diameter or characteristic dimension below about 280 pm may be substantially invisible at a viewing distance of about 1 meter, and openings below about 140 pm may be substantially invisible at a viewing distance of about 50 centimeters. Openings below about 50-80 pm may be optically invisible regardless ofviewing distance. Openings between about 100 pm and 200 pm may provide a balance between optical invisibility (appearing as a uniform translucent texture rather than a visible pattern) and adequate filtration surface area. Openings larger than about 300 pm may result in a visible spotted or patterned appearance.

[0033] The edges of the openings, formed from the amorphous material of the structural frame, may be operatively coupled to cross-sectional fibers of the filtration units. The fibers of the filtration units may have a mean diameter between 100 nm and 300 nm.

[0034] According to a second aspect, the present document discloses a transparent disposable mask (for example a surgical mask) that may comprise a transparent structural frame with openings, and filtration units made of non-woven fibers configured to partially coverthese openings. In one possible embodiment, the filtration units may cover at least 30% (preferably at least 40% but potentially less than 70% or 60% (for example between 40% and 60% or between 45% and 50%)) of the total surface area of the mask (or of the total operating area, i.e., the area comprising the filtration units). The remaining area of the mask may substantially consist of the fibers embedded within the structural frame, and the distribution of filtration units may be homogeneous or non-homogeneous across the surface of the mask.

[0035] The filtration units may comprise a direct light transmission between 70% and 99%, while the structural frame may comprise a direct light transmission between 50% and 70% (or 80%). The remaining part is the diffuse light transmission, consisting of the light passing the filtering device with scattering. This design allows fora visual perception of transparency because the airgap distance between the mask and the face of the wearer is very short.

[0036] According to a third aspect, the present document discloses a transparent filtering device designed for use in a surgical mask or similar application. This filtering device comprises a transparent structural frame and filtration units comprising fibers. The structural frame comprises openings that may be at least partially obstructed or filled by the fibers forming the filtration units, achieving a filtration efficiency greater than 95% for particles measuring 3 microns, while maintaining a pressure differential of less than 40 Pa / cm2. In other terms, the transparent filtering device is configured such that a layer of the structural frame with openings is filled with fibers, forming filtration units arranged at the openings.

[0037] The fibers may be configured to be at least partially or fully integrated into the structural frame during the manufacturing process. This integration may be configured to create a strong adherence between the filtration unit fibers and the structural frame, resulting in a single layer whose total thickness may be less than the combined thicknesses of the filtration unit fibers and the structural frame before the manufacturingP4310CP00 Specs (AOFF)

[0038] process. Furthermore, the structural frame or the combination structural frame / filtration units may be configured to provide mechanical strength to prevent any deformation or tearing of the device, both during use and throughout the industrialization process.

[0039] According to a fourth aspect, the present document discloses a method for manufacturing a filtering device, the method comprising: (a) providing a structural frame made of an amorphous material and comprising a plurality of openings; (b) depositing fibers onto the structural frame by electrospinning, centrifugal spinning, or electro-centrifugal spinning, so as to cover the openings, the fibers forming a porous network that partially occludes the openings while remaining permeable to air; and (c) applying a thermal bonding treatment at a temperature above the softening temperature of the amorphous material and below the melting temperature of the fibers, so as to at least partially embed the fibers into the amorphous material. After step (c), the fibers and the structural frame may form a substantially coplanar monolayer structure.

[0040] According to a fifth aspect, the present document discloses a surgical mask comprising the filtering device according to any of the preceding aspects. The surgical mask may comprise at least one of: horizontal pleats, an adjustable nose clip, and fasteners such as elastic loops or ties.

[0041] In comparison with conventional three-ply surgical masks, the translucent mask disclosed herein may have a mass that is approximately 3 to 4 times lower and a thickness that is approximately 6 to 7 times smaller. Due to this reduced thickness and mass, the mask may provide improved wearing comfort, in particular by reducing airflow resistance during inhalation and exhalation and by limiting heat and moisture accumulation in the breathing zone when worn over extended periods.

[0042] Furthermore, the filtering structure is formed as a single composite layer rather than a stack of multiple nonwoven layers. As a consequence, the mask may exhibit reduced attenuation of airborne sound waves generated by speech, thereby facilitating oral communication between the wearer and other persons. Such an effect may be particularly relevant in environments in which verbal interaction and facial cues are important, including medical, caregiving, or educational settings.

[0043] In addition, the reduced quantity of material required for the mask, together with the simplified layer architecture, may result in a reduced environmental impact, including lower raw material consumption and reduced emissions associated with manufacturing, transportation, and disposal. This effect may be further enhanced when the composite layer comprises bio-based and / or biodegradable polymer materials.

[0044] LIST OF FIGURES

[0045] The present invention will be better understood at the light of the following detailed description which contains non-limiting examples illustrated by the following figures:

[0046] Fig. 1 illustrates the use of a mask (1) by a user (2).

[0047] Fig. 2 illustrates an embodiment of the composition ofthe filter (3).

[0048] Fig. 3 presents a 3D view ofthe filter.P4310CP00 Specs (AOFF)

[0049] Figs.4a, 4b, and 4c are photographs of the filtertaken at different magnifications: 150xfor Figure 4a, 600x for Figure 4b, and 1500x for Figure 4c.

[0050] Fig. 5 illustrates certain characteristics ofthe filter (3).

[0051] Figs. 6a, 6b, and 6c are scanning electron microscopy (SEM) photographs of the filtertaken at different magnifications.

[0052] Fig. 7 illustrates a schematic view ofthe filter

[0053] LIST OF ELEMENTS

[0054] 1 Mask

[0055] 2 User

[0056] 3 Filter

[0057] 4 Pleat

[0058] 5 Adjustable nose clip

[0059] 6 Fastener

[0060] 7 Structural frame

[0061] 8 Fibers

[0062] 9 Opening

[0063] 10 Filtration unit

[0064] 11 Edge of opening

[0065] 12 Protruding fibers, partly embedded in amorphous material

[0066] 13 Particles larger than 3 microns

[0067] 14 Opening at least partially occluded by fibers

[0068] 15 Fibers at least partially embedded by the amorphous material

[0069] 16 Fiber layer (before integration)

[0070] 17 Structural frame layer (before integration)

[0071] 18 Coplanar monolayer structure (after integration)

[0072] DETAILED DESCRIPTION OF THE DISCLOSURE

[0073] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration several embodiments of devices, systems and methods. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit ofthe present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense.

[0074] All scientific and technical terms used herein have meanings commonly used in the art unless otherwise specified. The definitions provided herein are to facilitate understanding of certain terms used frequently herein and are not meant to limit the scope ofthe present disclosure.P4310CP00 Specs (AOFF)

[0075] As used in this specification and the appended claims, the singular forms "a", "an", and "the" encompass embodiments having plural referents, unless the content clearly dictates otherwise.

[0076] As used in this specification and the appended claims, any direction referred to herein, such as "top", "bottom", "left", "right", "upper", "lower", and other directions or orientations are described herein for clarity in reference to the figures and are not intended to be limiting of an actual device or system. Devices and systems described herein may be used in a number of directions and orientations.

[0077] As used herein, "have", "having", "include", "including", "comprise", "comprising" orthe like are used in their open-ended sense, and generally mean "including, but not limited to.

[0078] As used herein, "at least one of A, B, and C", "at least one of A, B or C", "selected from the group consisting of A, B, C, and combinations thereof orthe like are used in their open ended sense including " only A, or only B, or only C, or any combination of A, B and C" unless the content clearly dictates otherwise.

[0079] As used in this specification and the appended claims, the term "or" is generally employed in its sense including "and / or" unless the content clearly dictates otherwise.

[0080] One of the objectives of the disclosure described in this document is to use the filterforthe manufacturing of surgical masks that meet the performance and safety requirements defined by international standards, such as the EN 14683 standard in Europe and its equivalent in the United States, the ASTM F2100 standard. These standards set several key performance criteria for surgical masks, including:

[0081] • Bacterial Filtration Efficiency (BFE): The mask must be capable of filtering a high percentage of particles, particularly those with a size of 3 microns and larger, with a bacterial filtration efficiency greater than 95% (forType I masks) or 98% (forType II and HR masks, as defined by the EN 14683 standard).

[0082] • Pressure Differential (Breathability): The mask must provide good breathability with a pressure differential of less than 40 Pa / cm2for Type I and Type II and less than 60 Pa / cm2for Type HR masks.

[0083] • Splash Resistance: For Type HR masks, it is necessary to provide fluid splash resistance under a minimum pressure of 120 mmHg to protect against liquid splashes.

[0084] • Anti-Contamination Properties: The mask material must not be a source of microbiological contamination, in compliance with the defined microbiological standards.

[0085] The mask may also offer sufficient mechanical strength to prevent deformation or tearing during use.

[0086] In addition to meeting the aforementioned requirements, this filter also offers a certain level of transparency. Transparency is the transmission of visible light through a given material. Transparency has no specific unit and is generally reported as the percentage of light transmitted which is the percentage of incident light transmitted through a specimen. The higherthe transmittance, the higherthe transparency. A material with good transparency will have high transmittance and low haze.P4310CP00 Specs (AOFF)

[0087] Unlike transparent masks from prior art, the filtration unit of the filter is transparent and in one embodiment the mask made with the filter described in this document can have a shape similar to that of traditional surgical masks. Indeed, to encourage adoption by users (practitioners, doctors, nurses, patients, etc.), it is essential that the mask retains a shape and usage very similar to current standard masks. This is particularly important to reduce the risk of contamination, as the process of putting on and removing a mask follows a well-defined procedure. Ifthe mask had a different shape or method of use, this process could be altered, limiting the acceptance and proper usage of the mask by users.

[0088] For example, the mask manufactured using the filter described in this document may comprise at least one of the following features:

[0089] • Rectangular shape

[0090] • Flat storage;

[0091] • Horizontal pleats that allow the mask to be extended to fit various face sizes and to cover the user’s nose, mouth, and chin;

[0092] • Adjustable nose clip, made of metal or plastic, integrated into the upper part of the mask to ensure a secure fit around the nose, thus reducing air leakage and improving adherence;

[0093] • Fasteners, such as elastic loops that fit behind the ears or ties that can be tied around the head.

[0094] Fig. 1 illustrates the use of a mask (1) by a user (2). The mask includes a filter (3) with a certain level of transparency, allowing the user’s facial features and expressions to be visible through the mask. The mask may comprise at least one of a pleat (4), an adjustable nose clip (5), and a fastener (6) (shown here as elastic loops but which may include othertypes or shapes).

[0095] According to one embodiment, the filter (3) may comprise a structural frame (7) and fibers (8). Fig. 2 illustrates an embodiment of the composition of the filter (3), showing the arrangement and structure. The structural frame may comprise a plurality of openings (9) which may be intended to be covered by fibers (8). Each opening covered by fibers is configured to function as a filtration unit.

[0096] In one embodiment, the fibers (8) may be deposited onto the structural frame (7) through techniques such as electrospinning, centrifugal spinning, or electro-centrifugal spinning. These methods allow for precise control over the fiber deposition, ensuring uniform coverage and optimal integration with the structural frame. Each technique provides distinct advantages in terms of fiber alignment, density, and structural stability, contributing to enhanced filtration performance and mechanical strength of the overall filter.

[0097] The structural frame (7) may comprise a low-crystallinity material or an amorphous polymer (such as, without limitation, acrylics, polycarbonate, polystyrene, polylactic acid, etc.). For instance, the structural frame (7) may have a crystallinity of less than 10%. In one embodiment, the amorphous material may comprise a biodegradable material and / or biocompatible material.

[0098] In one embodiment, the structural frame may have a thickness of between 30 pm and 100 pm, preferably between 50 pm and 80 pm, for example about 60 pm. The fiber layer deposited onto the structural frame before the bonding process may have a thickness of between 0.1 pm and 2 pm, preferably between 0.2P4310CP00 Specs (AOFF)

[0099] pm and 1 pm, for example about 0.3-0.5 pm. After the bonding process, the fibers may be at least partially embedded into the structural frame such that the total thickness of the filtering device is less than the sum of the individual thicknesses before bonding.

[0100] Fibers (8) may form a non-woven material which may be permeable to fluids (e.g., gas), but their transparency may be limited due to the complex interface formed by the fiber network, which can scatter or absorb incoming light. As the areal density of the fibers increases, the difference in refractive indices between air and fibers at the interface increases, resulting in decreased direct light transmission.

[0101] The fibers may be designed to limit the occurrence of reflection and / or refraction. To minimize transparency loss, the fibers (8) may have a very small diameter. As an electromagnetic wave, visible light can theoretically pass through fibers with a diameter below 400 nm with minimal reflection and / or refraction. Therefore, in one embodiment, the diameter of the fibers is less than 400 nm. In one embodiment, the fibers of the filtration units may have a mean diameter between 100 nm and 300 nm.

[0102] In one embodiment, the basic weight of the fibers may be in the range of about 0.30 g / m2to about 0.50 g / m2, for example in the range of 0.35 to 0.45 g / m2.

[0103] The fibers (8) may comprise polymers with high transparency properties, for example, with a direct light transmission greater than 70%. The fibers (8) may comprise at least one thermoplastic polymer, such as a polyester or a polyamide, or may alternatively comprise an elastomeric polymer, a thermoplastic-elastomer polymer, or a thermoplastic polyurethane. Thermoplastic polyurethane (TPU), for instance, is a class of polymer with high abrasion resistance, elasticity, stability, and biocompatibility, as well as a high direct light transmission of around 70-99%, which is largely maintained even after being formed into fibers.

[0104] The filtration units may be configured in such a way that they are not visible to the human eye and do not affect perceived transparency. The size of the filtration units and their spacing can be kept below the resolution threshold of the human eye (for example, less than 0.28 mm (280 micrometers) or 0.14 mm (140 micrometers)), so that at viewing distances of 100 cm or 50 cm, the fibers and their arrangement do not significantly compromise the transparency of the mask.

[0105] Figure 3 presents a 3D view of the filter. The structural frame (7) is depicted as a structure comprising openings (9). These openings may be round, square, or rectangular in shape. Their diameter or length may be less than 300 pm, and greater than 10 pm depending on the desired design.

[0106] In one embodiment, the edges ofthe openings, formed from the amorphous material of the structural frame, may be operatively coupled to the cross-sectional fibers ofthe filtration units, ensuring a strong attachment and optimal integration between the frame and the fibers.

[0107] For instance, the fibers (8) may be configured to be bonded to the structural frame (7) by any suitable means, including adhesive bonding, thermal fusion, ultrasonic sealing, mechanical interlocking, or fiber entanglement. The material ofthe structural frame may have a melting temperature lowerthan that of theP4310CP00 Specs (AOFF)

[0108] fibers. In the case of thermal fusion, the bonding process can be applied at a temperature higher than the melting point of the structural frame (or preferably at a temperature above the softening temperature but below the melting point of the structural frame, such that the structural frame softens without fully melting) but lower than the melting point of the fibers. This ensures that only the structural frame melts (or softens) and bonds to the fibers, without damaging them. As a result, the fibers are encased or embedded within the softened material of the structural frame. During this process, the fibers maintain their structural integrity and continuity (they are not fused or melted, but rather anchored into the softened amorphous material). Each fiber extends continuously from an embedded portion within the structural frame (at the edges of the openings) to a free portion that spans across the opening and forms the filtration unit. This continuity between the embedded and free portions of the fibers contributes to the mechanical strength and durability of the filtering device. This creates optimal filtration units and enhances the overall strength and durability of the filter.

[0109] The structural framework provides the mechanical strength that is required for the industrial process of converting the material into a mask.

[0110] Thanks to the structural frame, the fasteners (6) can be securely attached to the filterwithout compromising its integrity. The structural frame provides a robust and stable support that allows the fasteners to be fixed without exerting excessive stress on the filtration material. This prevents any deformation or weakening of the filter, ensuring that its performance and durability are maintained even after repeated use.

[0111] Fig. 5 illustrates several key characteristics of the filter (3). The filtration units are configured to be air-permeable, efficiently capturing dust and particles larger than 3 microns, while maintaining a low-pressure differential of less than 40 Pa / cm2. Additionally, the fibers (8) used in the filtration units can exhibit a high direct light transmission, with values of at least 70%, and potentially reaching up to 90%. Fig. 5 further illustrates an example where reference 14 indicates an opening at least partially obstructed by fibers, and reference 15 shows fibers that are at least partially embedded in amorphous material.

[0112] Figures 6a, 6b, and 6c are scanning electron microscopy (SEM) photographs of the filtering device according to one embodiment of the present invention, taken at increasing magnifications to illustrate the structural integration between the fibers (8) and the structural frame (7).

[0113] Figure 6a, taken at a magnification of 150x, provides an overview of the filtering device showing the structural frame (7) with its regular pattern of openings (9) and the filtration units (10) formed by the fibers covering the openings. At this magnification, the structural frame is clearly visible, with the openings arranged in a regular grid pattern. The fibers deposited onto the structural frame form a continuous web that spans across the openings while being integrated into the structural frame at the edges of the openings. The overall structure appears uniform and translucent, demonstrating that both the structural frame and the filtration units contribute to the transparency of the filtering device. This figure illustrates that the filtering device is free from opaque filtration zones, the entire surface, including the filtration units, exhibits a substantially uniform light transmission.P4310CP00 Specs (AOFF)

[0114] Figure 6b, taken at a magnification of 600x, provides a closer view of the interface between the structural frame (7) and the filtration units (10). At this magnification, the individual openings (9) of the structural frame are clearly visible, with the fibers (8) extending across each opening to form the filtration units. The edges (11) of the openings, formed from the amorphous material of the structural frame, can be seen to be in intimate contact with the fibers. An embedded fibers zone is visible at the periphery of each opening, where the fibers transition from being free (spanning across the opening) to being at least partially embedded within the amorphous material of the structural frame. This embedded fibers zone demonstrates the integration between the fibers and the structural frame, which contributes to the mechanical strength of the filtering device and prevents delamination. The fibers within the openings appear as a fine mesh that provides filtration while maintaining high light transmission.

[0115] Figure 6c, taken at a high magnification of 5000x, provides a detailed view of the embedded fibers zone (19) at the edge of an opening. At this magnification, individual fibers (8) are visible, and it can be observed that the fibers maintain their structural integrity and fibrous morphology even in the regions where they are embedded in the amorphous material of the structural frame. The fibers are not fused or melted — they remain as distinct, continuous filaments that extend from the embedded portion (within the structural frame) to the free portion (spanning across the opening). This structural continuity between the embedded and free portions of the fibers is one of key features of the present invention, as it provides strong mechanical anchoring while preserving the filtration and transparency properties ofthe fibers. The image clearly shows that the fibers are partially embedded in the softened amorphous material, with a portion of each fiber's cross-section being encased within the structural frame while the remaining portion remains exposed. This partial embedding, ratherthan complete fusion, ensures that the fibers retain theiroriginal diameter, surface properties, and light transmission characteristics. The resulting structure is translucent ratherthan opaque, confirming that the embedding process does not create opaque fused domains as may occur in prior art multilayer structures.

[0116] The scanning electron microscopy images of Figures 6a-6c demonstrate several key features that distinguish the present invention from prior art solutions:

[0117] • First, the fibers maintain their structural integrity throughout the filtering device. Even in the embedded fibers zone where the fibers are anchored into the amorphous material, the individual fibers remain intact and continuous. This is achieved by performing the thermal bonding process at a temperature above the softening temperature of the structural frame but below the melting temperature ofthe fibers, so that only the structural frame softens while the fibers remain solid.

[0118] • Second, the filtering device exhibits uniform transparency across its entire surface. Unlike prior art designs where opaque filtering zones alternate with transparent non-filtering zones, the present invention provides filtration units that are themselves translucent. The fibers, having a direct light transmission between 70% and 99%, allow light to pass through the filtration units, resulting in a filtering device that is substantially uniformly transparent.

[0119] • Third, the integration between the fibers and the structural frame creates a robust mechanical bond without the need for separate adhesive layers or welding at discrete points. The fibers are continuously anchored along the entire periphery of each opening, providing uniform stress distribution and eliminating potential weak points that could lead to delamination.P4310CP00 Specs (AOFF)

[0120] Because the structural frame may comprise a woven or knitted fabric, the surface of the structural frame is not perfectly flat but presents an irregular topography with raised portions (where the threads cross) and lower portions (between the threads). As a result, when the fibers are deposited onto the structural frame and subsequently subjected to thermal bonding, only the fibers that are in direct contact with the amorphous material of the structural frame become embedded therein. Fibers that are not in direct contact with the structural frame (for example, fibers located above other fibers, or fibers located in recessed areas of the woven structure) may remain unembedded. This partial and localized embedding is sufficient to provide strong mechanical anchoring between the fiber layer and the structural frame, while preserving the filtration properties of the fibers spanning across the openings.

[0121] Figure 7 illustrates a schematic representation of the filtering device according to one embodiment of the present invention, showing both a top view and an exploded cross-sectional view to illustrate the coplanar integration of the fibers and the structural frame.

[0122] The upper part of Figure 7 shows a top view of the flat filtering device comprising the structural frame with its openings and the fibers covering the openings to form the filtration units. From this top view, the filtering device appears as a substantially uniform, translucent sheet with a regular pattern of filtration units distributed across its surface. The structural frame provides a grid-like support structure, while the fibers span across the openings within this grid.

[0123] The lower part of Figure 7 shows an exploded cross-sectional view that illustrates the manufacturing process and the resulting coplanar structure. This exploded view separates the components to show:

[0124] The fiber layer (16), which represents the layer of fibers as deposited onto the structural frame before the thermal bonding process. This fiber layer has a thickness of between 0.1 pm and 2 pm, preferably between 0.2 pm and 1 pm, for example about 0.3-0.5 pm.

[0125] The structural frame layer (17), which represents the structural frame with its openings before the thermal bonding process. This structural frame layer has a thickness of between 30 pm and 100 pm, preferably between 50 pm and 80 pm, for example about 60 pm.

[0126] The coplanar monolayer structure (18), which represents the integrated filtering device after the thermal bonding process. In this coplanar structure, the fibers are no longer a separate layer sitting on top of the structural frame; instead, the fibers are disposed (at least partially or substantially) within the plane ofthe structural frame, with the fibers extending within the openings at substantially the same level as the upper surface ofthe structural frame.

[0127] Figure 7 illustrates one of key aspects ofthe present invention: the transition from a two-layer configuration (fiber layer + structural frame layer) before the manufacturing process to a single coplanar monolayer structure after the manufacturing process. During the thermal bonding process, the application of heat (above the softening temperature ofthe structural frame) and pressure causes the fibers to become at least partially embedded into the softened amorphous material ofthe structural frame. As a result, the fibers sink into the plane defined by the structural frame, rather than remaining as a separate layer above it.P4310CP00 Specs (AOFF)

[0128] This coplanar integration has several important consequences:

[0129] First, the total thickness of the filtering device afterthe manufacturing process is less than the sum of the thicknesses of the fiber layer (16) and the structural frame layer (17) before the manufacturing process. For example, if the structural frame has a thickness of 60 pm and the fiber layer has a thickness of 0.5 pm before integration, the combined thickness before integration would be 60.5 pm. After integration, the total thickness may be reduced to approximately 60 pm or less, as the fibers are embedded within the structural frame rather than adding to its thickness. This thickness reduction is a measurable indicator of true integration, as opposed to mere superposition of layers. Second, the coplanar configuration provides enhanced mechanical integration compared to multilayer structures. Because the fibers are anchored within the plane of the structural frame, rather than being attached to its surface, the bond between the fibers and the structural frame is more robust and resistant to peeling or delamination forces.

[0130] Third, the coplanar configuration distinguishes the present invention from prior art multilayer structures where multiple layers (such as a nanofiber layer, a support layer, and a patterned layer) are stacked on top of each other and fused together. In such prior art structures, each layer retains its identity as a distinct stratum within the multilayer stack, and the total thickness corresponds to the sum of the individual layer thicknesses. In contrast, the present invention provides a true integration where the two initial components (fibers and structural frame) merge into a single coplanar structure.

[0131] Tablet : Test results for breathability and filtration:

[0132]

[0133] *BFE: Bacterial Filtration Efficiency

[0134] Table 1 presents the test results for the transparent filtering device described in the present document, which is configured for use in surgical masks or similar applications. The device achieves a bacterial filtration efficiency (BFE) of at least 97% and maintains a differential pressure (Ap) below 40 Pa / cm2, complying with the requirements of EN 14683 for Type I and Type II classifications. This filtering device incorporates a transparent structural frame and filtration units composed of fibers, ensuring both high filtration performance and optimal breathability.

[0135] Therefore, the transparent filtering device described in this document meets the performance requirements outlined by the EN 14683 standard for surgical masks, which specifies key criteria for bacterial filtration efficiency (BFE) and breathability (differential pressure, Ap). According to this standard:P4310CP00 Specs (AOFF)

[0136] • Type I masks, designed for general use in non-sterile environments, must achieve a BFE of at least 95% and maintain a Ap below 40 Pa / cm2to ensure both effective filtration and user comfort. • Type II masks, intended formedical applications where a high filtration level is critical but resistance to liquid splashes is not required, must achieve a BFE of at least 98% while also maintaining a Ap below 40 Pa / cm2.

[0137] The amorphous material of the structural frame (7) enables it to have a direct light transmission between 50% and 70% (or 80%). The fibers, on the other hand, are even more transparent, with a direct light transmission between 70% and 99%. As the filtering device comprises areas combining fibers embedded within the structural frame and areas with openings covered by fibers (i.e. , the fiber-covered openings of the structural frame forming the filtration units), this design allows for a visual perception of transparency. Furthermore, the filtration units (and thus the most transparent areas) may be distributed homogeneously (or not) across the entire surface of the mask, and may represent at least 30% or preferably at least 40% (for example between 40 and 60% or between 45 and 50%) of the total mask area (or of the total operating area, i.e., the area comprising the filtration units). This ensures that the filter remains highly transparent while providing effective filtration, making it suitable for applications where visibility and air permeability are both critical. In one embodiment, the combined thickness of the fibers (8) and the structural frame (7) may be less than 100 pm.

[0138] Thanks to this innovative structure, the mask does not require additional layers. Thanks to this structure, which integrates two layers into a single layer, unlike prior art masks that require three or more (and are often opaque), the mask offers sufficient mechanical strength and filtration capacity to meet strict standards, such as EN 14683 or ASTM F2100.

[0139] The transparent structure of the frame, combined with the filtration fibers, ensures an even distribution of mechanical stress, thereby enhancing the overall durability and stability of the mask. This single-layer design (with only a portion of its surface area dedicated to filtration) not only reduces breathing resistance but also maintains a filtration efficiency comparable to, or even betterthan, conventional multi-layer masks.

[0140] Moreover, this new configuration significantly improves light transmission, guaranteeing increased transparency while maintaining essential filtration performance. This makes the mask more aesthetically acceptable, particularly in environments where the visibility of facial expressions is important.

[0141] Furthermore, the new configuration greatly simplifies the industrialization process. With a single layer to process, the mask can be produced more efficiently, making it well-suited to the existing manufacturing processes used by current mask producers.

[0142] The structure wherein the fibers are at least partially embedded in the amorphous material of the structural frame provides several technical advantages:

[0143] • Uniform transparency: Unlike prior art solutions using alternating opaque filtering bands and transparent films, the present invention provides a substantially uniform direct light transmission across the entire surface of the filtering device. The filtration units are translucent, not opaque, withP4310CP00 Specs (AOFF)

[0144] a direct light transmission between 70% and 99%. As a result, the filtering device is free from opaque filtration zones.

[0145] • Monolayer structure without delamination risk: The partial embedding of the fibers into the amorphous material creates an integrated structure without assembly interfaces. Unlike multilayer structures where separate layers are bonded or welded together, the present invention provides a single coplanar layer where the fibers are anchored directly into the structural frame. This eliminates the risk of delamination that may occur at bonding interfaces in prior art designs. • Reduced thickness: The integration of the fibers into the structural frame results in a total thickness that is less than the sum of the individual thicknesses before the manufacturing process. This demonstrates a true integration rather than a mere superposition of layers.

[0146] • Intrinsic anti-fog properties: Since the fibers are breathable across the entire surface of the filtering device, exhaled air passes through all areas of the mask. Unlike prior art designs having impermeable transparent films where condensation tends to accumulate, the present invention prevents localized fogging.

[0147] • The filtering device is thus free from: separate transparent films that do not provide filtration, opaque filtration zones, and assembly joints between transparent elements and filtering elements.

Claims

P4310CP00 Specs (AOFF)CLAIMS1. A filtering device configured for breathable use, the filtering device comprising a structural frame and filtration units; wherein the filtration units comprise a non-woven material made of fibers and wherein the structural frame comprises openings and an amorphous material operatively coupled to the fibers of the filtration units to cover and partly occlude the openings wherein the fibers are at least partially embedded in the amorphous material at contact areas between the fibers and the structural frame.

2. The filtering device according to the claim 1, wherein the filtering device thickness is less than the combined thicknesses ofthe fibers and the structural frame before the manufacturing process.

3. The filtering device according to any one ofthe preceding claims, wherein the amorphous material comprises a direct light transmission between 50% to 80%.

4. The filtering device according to any one of the preceding claims, wherein the fibers comprise a direct light transmission between 70% to 99%.

5. The filtering device according to the any one of the preceding claims, wherein the filtering device is optically translucent such that facial features of a wearer are perceptible to a human observer during use.

6. The filtering device according to any one of the preceding claims, wherein the material of the structural frame has a melting temperature lower than that ofthe material ofthe filtration units.

7. The filtering device according to any one of the preceding claims, wherein the filtration units and the structural frame are bonded together.

8. The filtering device according to any one of the preceding claims, wherein the filtration units and the structural frame are thermally bonded together.

9. The filtering device according to the claim 7, wherein the thermal bonding is applied to the filtration units and the structural frame at a temperature higher than the softening temperature of the structural frame.

10. The filtering device according to the claim 7, wherein the thermal bonding is applied to the filtration units and the structural frame at a temperature below the melting point of the filtration units but above the softening temperature ofthe structural frame, so as to prevent damage to the fibers of the filtration units.

11. The filtering device according to claim 7, wherein during the thermal bonding process, the filtration fibers protruding over the edge ofthe openings and the structural frame are pressed together such that the amorphous material ofthe structural frame at least partially surrounds the fibers.

12. The filtering device according to any one ofthe preceding claims, wherein the fibers ofthe filtration units are deposited onto the amorphous material ofthe structural frame.

13. The filtering device according to any one ofthe preceding claims, wherein the combined thickness ofthe filtration units and the structural frame is less than 100 pm.

14. The filtering device according to any one of the preceding claims, wherein the openings have a diameter below 300 pm.P4310CP00 Specs (AOFF)15. The filtering device according to any one of the preceding claims, wherein the edges of the openings, formed from the amorphous material of the structural frame, are operatively coupled to cross-sectional fibers of the filtration units.

16. The filtering device according to any one of the preceding claims, wherein the filtration units cover at least 30% of a surface area of the filtering device while the remaining area of the surface substantially consists of fibers embedded within the structural frame.

17. The filtering device according to any one of the preceding claims, wherein the fibers and the structural frame form a substantially coplanar structure, the fibers being disposed within the plane of the openings of the structural frame.

18. The filtering device according to any one of the preceding claims, wherein the fibers maintain their structural integrity and extend continuously from an embedded portion within the amorphous material to a free portion spanning across the openings.

19. The filtering device according to any one of the preceding claims, wherein the openings have a diameter or characteristic dimension between 100 pm and 200 pm.

20. The filtering device according to any one of the preceding claims, wherein the openings are distributed with a density of between 10 and 25 openings per mm2.

21. The filtering device according to claim 7, wherein the thermal bonding is performed at a temperature between 80°C and 150°C and at a pressure between 0.5 bar and 5 bar.

22. The filtering device according to any one of the preceding claims, wherein a ratio of the filtering device thickness after the manufacturing process to the sum of the structural frame thickness and the fiber layer thickness before the manufacturing process is less than 0.95, preferably less than 0.90, more preferably less than 0.85.

23. A filtering device obtained by a process comprising:• depositing fibers by electrospinning, centrifugal spinning, or electro-centrifugal spinning onto a structural frame made of an amorphous material and having openings, and• applying a thermal treatment at a temperature above the softening temperature of the amorphous material and below the melting temperature of the fibers,such that the fibers are at least partially embedded in the amorphous material over a depth of at least 10% of the fiber layer thickness.

24. A method for manufacturing a filtering device, the method comprising:a) providing a structural frame made of an amorphous material and comprising a plurality of openings;b) depositing fibers onto the structural frame by electrospinning, centrifugal spinning, or electro-centrifugal spinning, so as to cover the openings, the fibers forming a porous network that partially occludes the openings while remaining permeable to air;c) applying a thermal bonding treatment at a temperature above the softening temperature of the amorphous material and below the melting temperature of the fibers, so as to at least partially embed the fibers into the amorphous material;wherein after step c), the fibers and the structural frame form a substantially coplanar monolayer structure.

25. The method according to claim 23, wherein the thermal bonding treatment is performed at a temperature between 80°C and 150°C, preferably between 100°C and 120°C.P4310CP00 Specs (AOFF)26. The method according to claim 23 or 24, wherein the thermal bonding treatment is performed at a pressure between 0.5 bar and 5 bar, preferably between 1 bar and 3 bar.

27. The method according to any one of claims 23 to 25, wherein after step c), the total thickness of the filtering device is less than the sum of the thickness of the structural frame and the thickness of the fiber layer before step c).

28. A surgical mask comprising a filtering device according to any one of claims 1 to 22.

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