The present invention refers to an antibacterial and antiviral filtering device.

In general, the present invention relates to an apparatus for separation processes using semipermeable membranes; tubular membrane modules, with a porous block having membrane-coated passages; separation processes using semipermeable membranes, eg. dialysis, osmosis, ultrafiltration; Reverse osmosis; hyperfiltration; nanofiltration. In particular, the present invention relates to details relating to the preparation of the membrane, hydrophilization, hydrophobing; manufacturing of three-dimensional 3D objects by additive deposition, additive agglomeration or additive layers, for example by 3D printing, stereolithography or selective laser sintering.

Regarding the filtration strategy, the state of the art is represented by JP 5 052 741 B2 concerning a waterproof and breathable hydrophobic filter element arranged after removing a hermetic and watertight closure of an opening of a bottom portion. For the hydrophobic element, PTFE and material selected from the group of silicone materials is used. Bacterial and/or sterilizing means are arranged between at least the hydrophilic filter elements. The bundle of hydrophilic filter elements is wrapped around a lower portion secured by the first end and the second end of the hydrophilic filter element. A membrane filter in which water passes through the hydrophilic filter element towards the bottom during use is composed of a hydrophilic filter part comprising a bundle of hydrophilic filter elements each fixed to the lower part by at least one first end so that only and at least some of the hydrophilic and hydrophobic filter elements can pass and/or so that air can only pass through the membrane filter via a hydrophobic filter portion. A hydrophobic filter part is provided so that a hydrophobic filter element is arranged on the filter membrane, so that a hollow space is enclosed near the bottom. The beam elements of the filter are wound in the form of a coil, delimiting at least a portion of the hollow space of the hydrophobic filter portion, membrane filter. In the membrane filter, means for retaining and/or sterilizing the bacteria are included between the hydrophilic and/or hydrophobic filter elements.

Furthermore, the state of the art is represented by patent application US 2020/0156014 A1 concerning a rotating nozzle having in particular two mass flow dividers, in a second stage of the cascade, whereby the flow guiding elements of the second stage of the cascade are preferably arranged with a staggered orientation of about +/- 90° with respect to the flow guide element of a first phase of the cascade. Arrangement with an orientation offset by a defined angle therefore means an arrangement that is rotated by a defined angle.

As regards the filter structure, the state of the art is represented by US patent 7,323,143 B2 concerning some embodiments of improved microfluidic systems and methods for manufacturing improved microfluidic systems, which contain one or more levels of microfluidic channels. The inventive methods can provide a cost-effective path for topologically complex and improved microfluidic systems. The microfluidic systems provided according to the invention may include three- dimensional array networks of fluid flow paths therein including channels that traverse above or below other channels of the network without physical intersection at the crossing points. The microfluidic networks of the invention can be fabricated by replication molding processes, also provided by the invention, using master molds that include surfaces having topological features formed by photolithography. The microfluidic networks of the invention are, in some cases, made up of a single replica molded layer and, in other cases, consist of two, three or more replica molded layers that have been assembled to form the overall microfluidic network structure. Furthermore, the state of the art is represented by patent application US 2019/0358367 A1 concerning a channel arranged in a different position and/or orientations, including but not limited to a centered orientation or an offset orientation, a flow of material in the channel internally embedded opposes a flow direction in the other channel.

As far as maintenance is concerned, the state of the art is represented by patent EP 3089 813 B1 concerning the use of an asymmetrical composite membrane to selectively pervaporate alcohol from a feed mixture of alcohol and gasoline, the asymmetrical composite membrane comprising a substrate porous comprising first and second opposing main surfaces and a plurality of pores, and a pore-filling polymer disposed in at least some of the pores to form a layer which covers the entire first main surface of the porous substrate and having an overall thickness of the interior of the porous substrate, with the amount of the pore fill polymer adjacent the first main surface being greater than the amount of the pore fill polymer at or adjacent the second main surface, wherein the starting materials for the fill polymer of the pores include a monomer and/or an oligomer containing (meth)acrylate, and the starting materials for the pore-filling polymer also include one or more polymer additives which enter the pores of the porous substrate with the materials and thereby form an interpenetrating polymer network, the polymer additive being selected from polyacrylic acid, polymethacrylic acid, polyacrylamide or its copolymers, polyethylene oxide, polyvinyl alcohol, poly (ethylene-co-vinyl alcohol) (EVAL), poly (N-vinylpyrrolidone), and their mixtures or copolymers, wherein the amount of the polymeric additive is in the a range of at least 0.20% by weight up to 25% based on the total amount of pore-filling polymer plus polymer additive, wherein the molecular weight (weight average) of the polymer additive is between 1,000 and 500,000, and where the pore-filling polymer is more permeable to alcohol than gasoline but not soluble in alcohol or gasoline. Object of the present invention is combining the solutions known from a wide but not very connected state of the art between the different technological branches, in particular that of filtration for medical use with respect to manufacturing by means of three-dimensional printing.

A further object is adopting the 3D printing technology to produce an antibacterial and antiviral filtering device. A further object is creating a geometrically modular device in order to define and control a compromise between the filtration capacity and the fluid dynamic energy necessary to move the fluid mass charged with contaminant particles.

The aforesaid and other objects and advantages of the invention, as will emerge from the following description, are achieved with an antibacterial and antiviral filtering device such as the one described in claim 1. Preferred embodiments and non-trivial variants of the present invention form the subject of the dependent claims.

It is understood that all attached claims form an integral part of the present description.

It will be immediately obvious that innumerable variations and modifications (for example relating to shape, dimensions, arrangements and parts with equivalent functionality) can be made to what is described without departing from the scope of the invention as appears from the attached claims.

The present invention will be better described by some preferred embodiments, provided by way of non-limiting example, with reference to the attached drawings, in which: FIG. 1 shows a diagram of the essential elements of an embodiment of the antibacterial and antiviral filtering device according to the present invention;

FIG. 2 shows a front view of a fundamental component of an embodiment of the antibacterial and antiviral filtering device according to the present invention;

FIG. 3 shows a perspective view of the component of the previous figure; FIG. 4 shows an exploded perspective view taken from the previous figure;

FIGS. 5, 6, 7 show diagrams of the spatial arrangement of a fundamental element of an embodiment of the antibacterial and antiviral filtering device according to the present invention;

FIG. 8 shows a perspective view of an assembly of fundamental components of a second embodiment of the antibacterial and antiviral filtering device according to the present invention;

FIG. 9 shows the previous figure sectioned in a plane of axial symmetry;

FIG. 10 shows a relevant component of the previous figure; FIG. 11 shows a further component of FIG. 9 in a maintenance context of the second embodiment of the antibacterial and antiviral filtering device according to the present invention;

FIG. 12 shows a perspective view in section of an assembly of fundamental components of a third embodiment of the antibacterial and antiviral filtering device according to the present invention; and

FIG. 13 shows a relevant component of the previous figure.

Referring to FIG. 1, it is possible to note that an antibacterial and antiviral filtering device crossed by contaminated air comprises at least a column structure of a plurality of contiguous filter modules 1 delimited by a lateral inlet surface lin and a lateral outlet surface lout.

Advantageously, at least one biological pre filter 2 is located in a seat 3. The seat 3 is located upstream of the lateral inlet surface lin in a fall and collection area of a quantity of fine particles of biological contaminants and/or residues of aerosol released by contaminated air.

Such at least one biological pre-filter 2 consists of a tablet of absorbent hydrophilic material with activated carbon capable of absorbing and retaining a quantity of fine particles of biological contaminants and/or aerosol residues released from the contaminated air. According to a forced filtration configuration, at least one HEPA filtration device is located in a space downstream of the lateral surface at the outlet lout, not shown.

Optionally, at least one germicidal lamp 4 is fixed in a space upstream of the lateral inlet surface lin.

Supporting means 6 and sealing means 7 are installed to effectively separate a space downstream of the lateral outlet surface lout from the space upstream of the lateral inlet surface lin.

Referring to FIG. 2, 3, 4, the column structure of a plurality of contiguous filter modules 1 is enclosed between a cover 8 of the seat 3 and a flanged base 9.

Preferably, a hermetic seal 10, 11 is provided, in contact with the filter module adjacent to the cover 8 and the filter module adjacent to the flanged base 9, and a hermetic seal 12 between the contiguous filter modules of the column structure of a plurality of contiguous filter modules 1.

Each module of the column structure of a plurality of contiguous filter modules 1 is constituted by a three-dimensional structure obtained by 3D printing conformed with a plurality of micro-holes arranged in a phase displacement, in order to be able to parameterize a filtration path from the lateral inlet surface lin to the exit side surface lout.

The micro-holes of each filter module of the plurality of contiguous filter modules 1 are rectangles, while each filter module of the plurality of contiguous filter modules 6 is oriented orthogonally with respect to the adjacent module.

Referring to FIGS. 5, 6, 7, the ratio between the full space and that of the micro-holes allows the creation of interstices 13 to confine a quantity of fine particles of biological contaminants and/or aerosol residues released from the contaminated air.

Each filter module of said plurality of contiguous filter modules 1 is made by means of a 3D printing process with a mixture of material with a graphene base in an amount between 2% and 5%.

According to a first variant, the material mix comprises polylactic acid, other materials and graphene nano-platelets, the graphene added at 0.5%, 2%, 5% by weight. According to a further variant, graphene is present in the form of an oxide.

Referring to FIG. 8 to 11, the germicidal lamp 4 is constituted by a UVC torch powered by battery and fixed to a cap 14 with quick coupling, bayonet or screw, to allow the connection of the germicidal lamp 4 respectively to the flanged base 9 and to an external battery charger 15.

Referring to FIG. 12, 13, the germicidal lamp 4 can be constituted by a plurality of infrared

LEDs powered through electrical connection and fixed in correspondence with the hermetic gaskets 12.

Examples Antibacterial and antiviral filtering device.

The goal is creating an antibacterial and antiviral filtering device with Covidl9 certification for the medical market, where there is proximity between patient and doctor, dentist, ophthalmologist, orthopedist.

A first application concerning the dental sector sees the device of the invention inserted in suction arms, suction systems near the patient or doctor of the aerosol generated by the action of the drills, ultrasound devices, or water showers during care activities. These systems are generally connected to systems, distinct from generic suction systems, with Hepa filtrations downstream.

An antibacterial and antiviral filtering device has the following distinct characteristics in filtration strategy, filter structure, maintenance.

Filtration strategy. A hydrophobic and antibacterial part allows retaining the aerosol droplets that carry the bacterial and viral contaminant. The antibacterial property of the graphene-based nanomaterial is bacteriostatic therefore it does not allow bacterial growth. The compound is made to achieve a balance between cost and performance. Percentages of graphene between 2% and 5% are expected. For the most demanding applications, the use of graphene oxide is envisaged.

Hydrophilic part: compressed in highly absorbent fabric.

Activated carbon part: compressed in fabric.

PM filter fabric: use of H13-H14 non-woven filter fabric to cut particles 0.03 - 0.01 thousandths of a millimeter. A filter made with this PM filter fabric allows to integrate the action of a biological pre-filter with action on the finest PM that can carry biological contaminants and to integrate the action on residues in% of aerosols that may not be treated by the pre-filter. A membrane is placed outside the filter.

Structure of the filter. Cartridge filter, dimensions in millimeters, 60/90 x 100/120.

3D printing. Filter: multiple 3D printed layers with rectangular design of the holes of 50 thousandths of a millimeter that allow, with orthogonal orientation of the layers, to obtain the optimal hole size for effective filtration, but at the same time allow the passage of air and contain the pressure loss generated by the filter. The limit of 50 thousandths of a millimeter is imposed by 3D printers. The compound is antibacterial, antiviral and water repellent so the aerosol slides on the wall, settling on the hydrophilic tablet (frequent maintenance). The compound does not allow the growth of the airborne biological material (tests in progress: 76% bacteria and viruses eliminated). Conventional filters even with higher filtration efficiency, for example, 99%, do not eliminate biological contaminants, due to a rapid obstruction of the channels caused by droplets, moreover being devoid of antiviral charge they maintain bacterial growth. Viruses are transported by the aerosol which is stopped (tests are underway but we expect more than 90-99% of the aerosol to be blocked). The positioning of the layers creates small rooms/interstices in which the transported droplets are forced to collide with the mixture of antibacterial and antiviral material, neutralizing it. It is possible that we will intervene to increase the size of the holes (currently 50 microns) for applications that allow less filtration performance (civil environments) and ventilation with lower pressure drops. Modular elements of about 5 millimeters in order to define, based on the behavior of the filter itself in the suction arm, the length as an increase in the filtering surface and reduction in pressure drop. The filter design was conceived to allow the use of low-cost printers.

Cartridge filter: periodic defined in monthly periods. Maintenance with sterilization of the filter in 60% ethanol solution, with extraction of the cartridge from the suction arm. Hydrophilic and activated carbon tablet: daily, disposable.

Filter H13 H14 - very long life (thanks to the biological pre-filter in graphene). Also used in the civil field, in an environment subject to crowding of people, with a high risk of transmission of infections, for example, restaurants, taxis.

Use of the device combined with a fan. Application in the dental market.

A bespoke elastic ring has been designed between the molded filter elements to ensure a perfect seal between the parts.

Mechanical characteristics of the graphene- based filter. Several blends of polylactic acid (PLA) and graphene nanoplatetes (graphene composed of more than a single atomic layer) were made. Graphene is added at 0.5%, 2%, 5% by weight. An increase in filter resistance was measured both in traction and in compression. The measured values of elastic modulus are shown in the following tables. It can be seen that both in traction and in compression the resistance of the material increases by about 30-35%.

TABl. Elastic modulus under compression

TAB2. Elastic modulus under traction Morphological characteristics of the graphene- based filter. To verify that the filter slits were about 50um we performed scanning electron microscopy (SEM) experiments. The product cracks were actually about 50um. As can be seen from this electron microscopy detail, the gap la between the upper fabricated structure and the lower fabricated one leaves a gap of about 50 pm. Given the limits of the accuracy of 3D printing in some places the gap can be slightly different, however much less than lOOum. However, to avoid areas with incorrect filtering due to a local defect, the filter structure has been designed and built as a very long repetition of the filtering slots (see diagram in Fig. 3) so that, even if a area should have a defect, there would be other cracks downstream to repeat the same filtering procedure. Furthermore, the repetition of filtering slits creates a series of empty spaces capable of containing, given the hydrophobic nature of the material, a large amount of liquids.

Photothermal characteristics of the graphene- based filter for sterilization with infrared light (NIR). We have verified that by illuminating with low infrared light it enhances graphene was able to transform infrared (808nm wavelength) light into heat. You can easily reach temperatures well above 100 degrees, a temperature at which almost all known bacteria die. Even a protocol of exposure for 5 minutes to an infrared light of about lw/cm ^A 2 allows reaching temperatures higher than 70 degrees, temperatures that cause the immediate death of E. Coli and S. Aureus. It is therefore possible to apply low-power infrared light to be able to sterilize the filter. Development of graphene-based antibacterial 3D printed cylindrical filters. Contact antibacterial tests with E. Coli and S. Aureus. In accordance with the ISO 2019 standard procedures, the contact death of E. Coli and S. Aureus was evaluated. As can be seen, the bacterial load reduction effect seems to be effective for both gram + and gram- bacteria.

In the range of concentrations analyzed, up to a 75% reduction in the bacterial load is reached even after only 2 hours of contact.

Tab.3 S. Aureus percentage of deaths by contact with filter material

Tab.4 E. Coli percentage of deaths by contact with filter material

Development of cylindrical filters with antiviral 3D printing, Sars-Cov-2, based on graphene.

Antiviral tests on Sars-Cov-2 by contact. In accordance with the standard procedures ISO 18184: 2019, the contact death of the Sars-cov-2 virus was evaluated. In the range of concentrations analyzed there is up to a 73% reduction in viral load.

The biological filter acts on the aerosol, i.e. on the means of transport of biological contaminants, thanks to the properties of the antibacterial and hydrophobic compound of graphene- based nanomaterial, blocking and eliminating a high percentage of viruses and bacteria that deposit on the filter surface. The possible use of the UV lamp allows to increase the bacterial and viral reduction of the filtration system.

The possible use of ultra-fine HEPA filtration allows increasing the filtration efficiency by reducing the presence of aerosols in the air flow, allowing to block the residual ultrafine particles of particulate matter.

The antibacterial and antiviral filtering device crossed by contaminated air of the invention is suitable for being made with recyclable material, for example, plastic derived from corn, beet.

According to a further variant of the device in question, the PLA graphene filter is equipped with infrared lamps, VIR, in order to combine the filtering action with the thermal action, not used according to the known technique.

In the version with discs equipped with a plurality of infrared LEDs placed in the cylindrical structure of the filter, the filtration strategy made available by the device object of the invention is given by the contribution of an antibacterial and antiviral action (properties of graphene), water repellent (properties graphene), thermal (properties of infrared and graphene). In the body of the filter 2-3 rings containing infrared LEDs are inserted. In this case the irradiation is continuous during the suction phase. This solution includes: a wiring inside the suction arm for power supply; the use of infrared LEDs of the type resistant to water and humidity.

In the UVC version, a UVC lamp has a sterilizing effect, but it can be harmful and affect both patient and healthcare professionals. For this reason, the UVC lamp acts on the device object of the invention only during an inoperative phase. During the non-use phase of the suction arm, a UVC torch powered by a battery is inserted into the filter. At the end of the irradiation phase, the torch is placed in its charging base.