FLUID DISINFECTION METHOD, FLUID DISINFECTION DEVICE AND METAL FILTER FOR DISINFECTING PATHOGENS OF A FLUID FLOW

Field of the invention

The present invention relates to a fluid disinfection method for disinfecting pathogens of a fluid flow by thermal action using an improved microporous metal sintered filter of stainless-steel, which is capable of being magnetically and/or optically heated for thermal disinfection of pathogens of a fluid flow in communication with the metal filter. In particular, the fluid disinfection method is capable of disinfecting the pathogens in fluid circulation.

The present invention also relates to a fluid disinfection device for disinfecting pathogens in real-time fluid circulation, which is provided with the improved microporous metal sintered filter of stainless-steel and it is configured to cooperate with an alternating magnetic field and/or an electromagnetic radiation to be heated by means of such cooperation, whereby inactivating the pathogens of the fluid flow.

The present invention also relates to an improved microporous metal sintered filter of stainless- steel for performing such fluid disinfection.

Background of the invention

Various methods are used today for reducing the concentration of active viral particles in the air and/or in a liquid.

JP S5597219 discloses a method of removing impurities from a liquid by using a filter with a coating of carbon material. In said document, a filter is coated with a slurry or large carbon pieces in a size range between 0.2 mm and 1 mm, and these carbon pieces are only used for removing impurities in an already heated fluid. JP S5597219 does not describe nor suggest removing impurities by means of heating the fluid through the own filter, but solely filtering an already heated fluid using a filter coated of a carbon material, not nanostructured.

On the other hand, one of the widespread methods for inactivating pathogens in the air is ultraviolet germicidal irradiation (UVGI). UVGI damages pathogens’ DNA/RNA, decreasing their reproduction rate and leading to their extinction. However, the application of UVGI devices has raised concerns of potential injury to people, specifically to eyes and skin. Mercury-based ultraviolet lamps, which are filled with mercury and a starting gas (typically argon), are the most common UVGI devices. However, mechanical damage to the lamp, which uses a gas discharge in mercury vapor, can release hazardous mercury or mercury-containing compounds into the environment. Light-emitting diodes (LEDs) are alternative materials to replace conventional mercury- containing ultraviolet lamps. However, at present, LED based ultraviolet in-duct air disinfection systems is limited by the output power.

Current air filtering systems in sterile spaces, passenger cabins, and many air conditioning systems, are based on the use of HEPA filters, which only mechanically trap the pollutants. These systems do not guarantee the filtering of small viral particles and the filters used for such filtration can become a biohazard due to the accumulation of active bioelements. Thus, the HEPA filters must be regularly replaced and disposed, and do not support high temperatures or air pressures.

It is known in the art that high temperatures can lead to thermal destruction of the constituent parts of the viruses, for instance, thermal denaturation of the surface proteins. In fact, there are currently various methods of thermal treatment for disinfecting pathogens.

Jonges et al. showed that thermal inactivation of influenza viruses (human influenza H3N2 and avian influenza H7N3) is associated with the loss of functionality of the surface hemagglutinin and other glycoproteins. Virus inactivation is considerably enhanced above 50 °C.

Zou et al. studied thermal inactivation of the avian influenza A (H7N9) virus. The results showed that the virus in the solution can be effectively inactivated by treatment at 56 °C for 30 min, at 65 °C for 10 min, and at 70 °C and above for no more than 1 min. The virus remained active when treated for 1 min at 56 °C or 5 min at 65 °C.

Tomasula et al. studied thermal inactivation of the foot and mouth disease virus in milk at temperatures ranging from 72 to 95 °C, for 18.6 or 36 s. The virus concentration in the raw material was 104 PFU. Thermal inactivation reduced it by 4 logs to a value below the detection limit.

Bat'ejat et al. heated a cell culture, samples from the nasopharynx, and serums, containing SARS-CoV-2. They showed that SARSCoV-2 was inactivated in less than 30 min, 15 min and 3 min at 56 °C, 65 °C, and 95 °C, respectively. All samples initially contained 6 logs TCID50/ml of SARS-CoV-2. The virus detection limit was 0.67 log TCID50/ml.

Yu et al. developed filters based on foamed nickel for disinfection by heating air up to 200 °C. The prototype device was tested with an aerosol containing SARS-CoV-2. Air passed through six curved strips of foamed nickel with the size of 24 cm x 4 cm and a depth (hot zone length) of 1.6 cm. The air flow rate was 10 l/min. They showed that one pass of aerosol containing SARS-CoV-2 was sufficient to inactivate 99.8 % of the viruses. The same method achieved an inactivation efficiency of 99.9 % with the airborne bacterium Bacillus anthracis.

All these methods, to one degree or another, reduce the viral load of the air that a person breathes or of the liquids for drinking.

However, all these methods present certain disadvantages and limitations. Moreover, most of these methods and/or devices are performed in closed places and, therefore, are not suitable for disinfecting and/or sterilizing in real-time fluid circulation.

Therefore, there is still the need to provide an alternative to the prior art that resolves the shortcomings thereof, by providing a fluid disinfection method for disinfecting pathogens of a fluid flow with high efficiency; by providing a fluid disinfection device for disinfecting pathogens in real-time fluid circulation of low-cost, compact and easy to use; and by providing a metal filter of homogeneous heating, high thermal performance, which is easy to clean and, therefore, suitable to be reused.

Description of the invention

The present invention was made in view of the prior art described above, and an aspect of the invention is a novel fluid disinfection method for disinfecting pathogens of a fluid flow using an improved metal filter (herein indistinctly named “metal filter” or “improved metal filter”), which is also another aspect of the present invention.

The improved metal filter of the present invention is capable of cooperating with an energy source external to the fluid flow to be heated, the energy source being selected from an alternating magnetic field and/or electromagnetic radiation, for thermally inactivating the pathogens with high thermal performance.

As described below in detail, the improved metal filter superficially comprises:

A: - a nanostructured material layer, including (I) a dielectric material adhered to the surface of the metal filter, and (II) a coating that coats the dielectric material or partially coats the metal filter surface where the dielectric material has not been adhered;

Or alternatively, the surface of the metal filter superficially comprises:

B: - a nanostructured carbon coating that fully or partially directly coats the metal filter surface.

To solve the problem, the present invention provides, in an aspect, a fluid disinfection method for disinfecting pathogens of a fluid flow that uses the improved metal filter capable of being heated by means of an energy source external to the fluid flow to thermally inactivate the pathogens of the fluid flow, which overcomes the drawbacks and presents the advantages described below.

The fluid disinfection method for disinfecting pathogens of a fluid flow uses the improved metal filter, and the method is characterized in that comprises the steps of:

- a) passing the fluid flow through the metal filter (3),

- b) while the fluid flow passes through the metal filter (3), heating the metal filter (3) to a temperature (T) which is within a temperature window to which pathogens thermally inactivate by means of an energy source external to the fluid flow, and measuring the temperature of the metal filter and/or of the fluid flowing there through to assure that the metal filter has been heated at said temperature (T), and

- c) thermally inactivating pathogens of the fluid flow by means of the heat coming from the heated metal filter, wherein in step b), the metal filter cooperates with the energy source external to the fluid flow, the energy source being selected from an alternating magnetic field and/or an electromagnetic radiation to magnetically and/or optically heat the metal filter (3), thereby the heated metal filter thermally inactivating pathogens by thermal transfer to the fluid flow there through.

Such cooperation between the metal filter, superficially nanostructured either including (A) a nanostructured material layer, or alternatively, (B) a nanostructured carbon coating, and the alternating magnetic field and/or the electromagnetic radiation is being performed in a wireless way.

Thus advantageously, the method of this aspect is capable of performing the fluid disinfection in a wireless way, that is, without direct contact between the metal filter and the energy source, regardless of whether the energy source is of electromagnetic radiation or of alternating magnetic field.

Unexpectedly, the improved metal filter works in a similar way to an autoclave, that is, there is a local increase in the temperature and the air pressure within the micropores of the sintered filter. This local increase in the temperature and in the pressure into the micropores allows pathogenic proteins, lipids, and DNA/RNA to be degraded, thereby disinfecting pathogens from the fluid flowing through the heated metal filter.

Advantageously, the fluid disinfection method is capable of performing such disinfection in realtime fluid circulation.

According to the method of this invention, the fluid is a gas or a liquid.

Preferred gas is air. When the fluid is a gas, such as air, which is compressible, the pressure and the temperature are related by the ideal gas law (PV=nRT). Therefore, if the metal filter temperature increases, then automatically increase the pressure, thereby the microporous filter still further works as an autoclave.

As stated above, the metal filter superficially includes a nanostructured material layer (A), or alternatively, a nanostructured carbon coating material (B), and it is capable of cooperating with an alternating magnetic field and/or an electromagnetic radiation and in response to such cooperation it is heated. The metal filter temperature can be increased by means of such cooperation up to attain a temperature value (T) that is within the temperature window at which the pathogens are thermally inactivated.

The temperature window at which pathogens are thermally inactivated is within the general knowledge of one skilled in the art. For example, such temperatures enable thermal destruction of the constituent parts of the viruses, for instance, thermal denaturation of their proteins, lipids or DNA/RNA. A Table 1 including the known temperatures enabling thermal inactivation of the main viruses is included only for reference in the detailed description section of this invention.

The method of this invention is suitable for disinfecting large flows. Generally, the fluids susceptible to be disinfected of pathogens circulating through the pipes do so at a flow rate between 1 and 100 liter/minutes. Preferable flow rate passing through the metal filter is between 1 and 20 liters/minute.

The flow rate passing through the metal filter can be still higher by using a thicker or larger diameter metal filter, so that the fluid flowing there through remains a higher time in contact with the micropores of the heated metal filter to heat the flow. The flow rate passing through the metal filter is the same as the flow rate to be disinfected, usually circulating into a channel or pipeline.

According to one embodiment of the method of the invention, in step b), the heating of the metal filter is done by cooperating with an alternating magnetic field as energy source external to the fluid flow, thereby the metal filter is being heated by magnetic heating.

According to another embodiment of the method of the invention, in step b), the heating of the metal filter is done by cooperating with an electromagnetic radiation as energy source external to the fluid flow, thereby the metal filter is being heated by optical heating.

According to still another embodiment of the method of the invention, in step b), the heating of the metal filter is done by simultaneous cooperating an alternating magnetic field with an electromagnetic radiation as energy sources external to the fluid flow, thereby the metal filter is being heated to higher temperatures by magneto-optical heating.

- Alternating magnetic field -

According to the method of this invention, the metal filter (A, B) can cooperate with an alternating magnetic field to generate an inductive heating in the metal filter, thereby magnetically heating the metal filter. Advantageously, such cooperation is performed in a wireless way.

To that purpose, the surface of the superficially nanostructured metal filter used in the method comprises:

(A, A.1): - a nanostructured material layer including (I) a dielectric material adhered to the surface of the metal filter, and (II) a coating that coats the dielectric material and fully or partially coats the metal filter surface, that is, the surface where the dielectric material is not adhered , wherein the coating material includes i) a ferromagnetic material. Optionally, the ferromagnetic material can have also damped-plasmonic properties (iii).

In this embodiment, in step b), said ferromagnetic material present in the nanostructured material layer cooperates with the energy source comprising an alternating magnetic field at a frequency and intensity to magnetically excite the material of the metal filter to heat the metal filter by means of electromagnetic induction, thereby the metal filter is being heated by magnetic heating.

Advantageously, the metal filter superficially including the coating (II) material being i) a ferromagnetic material in the nanostructured material layer embodiment allows improving the cooperation with the alternating magnetic field and, therefore, the thermal performance is also improved as well as the heat transfer between the metal filter and the fluid flow to be disinfected of pathogens.

Alternatively, although the metal filter superficially nanostructured with a nanostructured carbon coating (B) is capable to be heated by an alternating magnetic field due to its electrical conductivity, the electromagnetic radiation is the most preferable energy source to heat the metal filter with high thermal performance, or a combination of electromagnetic radiation and alternating magnetic field.

- Electromagnetic radiation -

According to the method of this invention, the improved metal filter can cooperate with an electromagnetic radiation to generate optical absorption in the metal filter surface that is transformed into heat, thereby optically heating the metal filter. Advantageously, such cooperation is performed in a wireless way.

In order to the metal filter be suitable for cooperating with electromagnetic radiation, the surface of the superficially nanostructured metal filter includes (A): -a nanostructured material layer including (I) a dielectric material and (II) a coating of ii) a damped-plasmonic material, Or alternatively, (B): -a nanostructured carbon coating.

In this embodiment, the energy source external to the fluid flow is an electromagnetic radiation and the metal filter used in the fluid disinfection method superficially comprises:

(A, A.2): - a nanostructured material including (I) a dielectric material adhered to the surface of the metal filter, and (II) a coating that coats the dielectric material and fully or partially coats the metal filter surface, that is, the surface where the dielectric material is not adhered, wherein the coating material includes ii) a damped-plasmonic material. Optionally, the damped-plasmonic material can have also ferromagnetic properties (iii).

Or alternatively, the metal filter superficially comprises (B): - a nanostructured carbon coating that fully or partially directly coats the metal filter surface.

In these two above embodiments, in step b), said damped-plasmonic material or said nanostructured carbon material cooperates with the energy source comprising an electromagnetic radiation emitted at a wavelength value which is selected within the wavelength range in which the surface material of the metal filter has optical absorption for converting the electromagnetic radiation into heat, thereby the metal filter is being heated by optical heating.

Advantageously, the metal filter superficially comprising the nanostructured material layer (A, A2) or the nanostructured carbon coating (B) allows improving the cooperation with the electromagnetic radiation and, therefore, the thermal performance be also improved as well as the heat transfer between the metal filter and the fluid flow.

- Alternating magnetic field combined with electromagnetic radiation -

According to the method of this invention, the metal filter can cooperate, simultaneously or consecutively, with an alternating magnetic field and an electromagnetic radiation to magnetically and optically heating the metal filter accordingly. Advantageously, such cooperation is performed in a wireless way.

In this embodiment, the energy source external to the fluid flow is a combination of an alternating magnetic field with an electromagnetic radiation and the metal filter superficially comprises:

(A, A.3): - a nanostructured material including (I) a dielectric material adhered to the surface of the metal filter, and (II) a coating that coats the dielectric material and fully or partially coats the metal filter surface, that is, the surface where the dielectric material is not adhered, wherein the coating material includes iii) a ferromagnetic and a damped-plasmonic material.

Or alternatively, the metal filter superficially comprises (B): - a nanostructured carbon coating that fully or partially directly coats the metal filter surface.

The nanostructured carbon coating is particularly suitable for converting the electromagnetic radiation into heat. Moreover, the microporosity and stainless-steel material of metal filter makes it also adequate for converting an alternating magnetic field into heat due to its electrical conductivity. Therefore, the metal filter superficially including a nanostructured carbon layer can be also magneto-optically heated.

In these two above embodiments, in step b), said ferromagnetic and damped-plasmonic material, or alternatively said nanostructured carbon material, cooperates with the energy source comprising alternating magnetic field and electromagnetic radiation, thereby the metal filter is being heated by magneto-optical heating.

As described above, the method of this invention can be performed for fluid disinfection of pathogens of a liquid or a gas.

Particularly preferred fluid disinfection method for liquid disinfection of pathogens is a liquid sterilization, wherein being the liquid not transparent, such as milk, in step b), the metal filter can be heated by an alternating magnetic field, and wherein being the liquid transparent, such as water, in step b), the metal filter can be heated by an alternating magnetic field, or by an alternating magnetic field combined with an electromagnetic radiation.

Uperization is an example of a method of sterilizing milk by injecting steam under pressure to raise the temperature to 150°C, those sterilization can be performed by the method of this invention.

In a most preferable fluid disinfection method, the method further comprises the step of:

- pre-heating the fluid flow before passing it through the metal filter by means of the thermal energy generated in the method itself.

Advantageously, the thermal energy generated in the method itself includes the thermal energy given off by the alternating magnetic field source and/or by the electromagnetic radiation.

Therefore, when the energy source external to the fluid flow is provided by an electromagnetic actuator generating alternating magnetic field on the metal filter, the fluid flow can be preheated passing the fluid around or inside to the electromagnetic actuator provided with an induction coil that releases thermal energy before passing it through the metal filter, thereby taken advantage of the thermal energy generated in the method itself. The circulation of fluid around or inside the induction coil allows pre-heating the fluid before passing it through the metal filter but advantageously also allows refrigerating the induction coil provided by the electromagnetic actuator, thereby it also working as an intercooler.

In addition, when the energy source external to the fluid flow is provided by a laser device generating electromagnetic radiation on the metal filter, the fluid flow can be pre-heated passing the fluid around to the laser device that releases thermal energy before passing it through the metal filter, thereby taken advantage of the thermal energy generated in the method itself. The circulation of fluid around the laser device allows pre-heating the fluid before passing it through the metal filter but advantageously also allows refrigerating the laser device, thereby it also working as an intercooler.

Advantageously, this optional pre-heating step allows the electromagnetic actuator and/or the laser device being cooled by means of the fluid flow circulating around or inside them prior to the fluid passes through the metal filter for disinfecting it, this intercooling step allowing increasing the current intensity of the electromagnetic actuator and/or of the laser device, whereby also allowing increasing the temperature of the metal filter or saving energy when performing the disinfection.

In a further aspect, the present invention provides a fluid disinfection device for disinfecting pathogens of a fluid flow, the device being provided with the improved metal filter of the present invention (A, B) configured to cooperate with an energy source external to the fluid flow, the device being capable of disinfecting pathogens in real-time fluid circulation.

To solve this problem, the present invention provides a fluid disinfection device for disinfecting pathogens of a fluid flow suitable for carrying out the fluid disinfection method defined above using also the improved metal filter, the device being characterized in that it comprises:

- a body provided with a channel for the passage of the fluid flow to be disinfected of pathogens, - the metal filter (A, B) according to the invention arranged in the passage channel and configured to be submitted to an energy source external to the fluid flow, the energy source being selected from an alternating magnetic field and/or electromagnetic radiation, and in response to be heated to heat the fluid flowing there through,

- temperature monitoring means configured to measure the temperature of the metal filter and/or, in use, of the fluid flowing there through, and

- processing and control means operatively connected to said temperature monitoring means and configured to receive a signal therefrom, which is representative of the measured temperature to at least assure that the metal filter has been heated at a temperature (T) that is within a temperature window to which pathogens thermally be inactivated.

Advantageously, the device of this invention is suitable for real-time fluid disinfection.

Also advantageously, the processing and control means are operatively connected to the temperature monitoring means to enable keeping very stable temperature at the metal filter for different fluid flows.

The alternating magnetic field and/or electromagnetic radiation can be configured to magnetically and/or optically heating the metal filter superficially nanostructured (A, B) up to a temperature (T) that is within a temperature window to which pathogens are thermally inactivated.

The authors of the present invention have found that an alternating magnetic field generated at a metal filter (A, B) including a ferromagnetic material (A1 , A3) is capable of causing high magnetic induction heating efficiency, despite the fact that the metal filter of stainless-steel is an austenitic alloy not provided with ferromagnetic properties. As stated above, the metal filter superficially nanostructured with a nanostructured carbon coating (B) is also capable to be heated by an alternating magnetic field, although with minor magnetic induction heating efficiency and, therefore, when using a metal filter superficially nanostructured with a nanostructured carbon coating (B) it is preferable a combination of an alternating magnetic field with electromagnetic radiation.

The authors of the present invention have also found that an electromagnetic radiation submitted to the metal filter (A, B) provided with optical absorption properties (A2, A3, B) can cause a very intense broadband optical absorption on the metal filter surface, which allows maximizing the optical heating efficiency. The optical heating is proportional to the intensity of the light beam. In a preferable embodiment, the device comprises an electromagnetic actuator provided with an induction coil (L) configured to generate the alternating magnetic field (H( _ro )), said induction coil being arranged external to the fluid flow and in cooperation with the metal filter to magnetically cause the heating in the metal filter by means of such cooperation (Figure 6).

The electromagnetic actuator provided with an induction coil is associated to a resonant LC circuit. It is desirable a maximum amplitude of the magnetic field and a high frequency in order to achieve faster and more efficient magnetic heating. The preferable frequency is the resonant frequency which can be tuned by means of modifying the capacitance (C) and/or the inductance of the resonant LC circuit.

Preferably, the electromagnetic actuator is powered by alternating currents at a frequency (a>) within the range from 20 KHz to 1 MHz and an amplitude within the range from 1 to 700 Oe.

The metal filter can be located inside (Figure 6.1) or next to the induction coil (Figure 6.2), so that the metal filter receives the alternating magnetic field, and it is in cooperation with it to heat it. Moreover, the metal filter is separated of the induction coil by means of the material forming the channel where the metal filter is arranged inside, and the induction coil is arranged outside.

In another preferable embodiment, the device comprises a laser, a LED, or at least a light beam ( i, x ₂ , ₃ ,..) as electromagnetic radiation source, which is configured to illuminate the metal filter at a light intensity and wavelengths (X) at which the metal filter material has optical absorption to enable optical heating the metal filter. The laser or LEDs is arranged external to the fluid flow and in cooperation with the metal filter to optically cause the heating in the metal filter by means of such cooperation (Figure 7).

Preferably, the laser or LEDs illuminates the metal filter at a wavelength within the range from 300nm to 3 pm and an intensity within the range from 1 W/cm ² to 1000 W/cm ² .

For electromagnetic radiation purposes, the device is provided with transparent apertures (T.A.) to enable the transmission of the light beam into the channel where the metal filter is arranged, so that the metal filter receive the light beam to being optically heated.

According to a preferred device of this invention, the processing and control means are further electrically connected to the electromagnetic actuator and/or to the light source (sunlight not included) and configured to receive a signal therefrom to control their operation sending the electric signals adequate to heat up more or less the metal filter temperature in accordance with the signal received of the temperature monitoring means (Figure 5). The processing and control means can be a software automatically adapted to the different embodiments of metal filters to maximize the heating efficiency by means of an electronic control unit.

Advantageously, the device of this invention can externally control electronically by means of digital signals the amount of heat applied to the metal filter to regulate the level of filtering of the pathogens to be processed.

In an embodiment of the device of this invention, the metal filter is configured to be submitted to an alternating magnetic field and in response to be magnetically heated to heat the fluid flowing there through by magnetic heating.

In another alternative embodiment of the device of this invention, the metal filter is configured to be submitted to an electromagnetic radiation and in response to be optically heated to heat the fluid flowing there through by optical heating.

In still another preferred embodiment of the device of this invention, the metal filter is configured to be submitted, simultaneously or consecutively, to an alternating magnetic field and to an electromagnetic radiation and in response to be magnetically and optically heated to heat the fluid flowing there through by magnetic and optical heating.

Advantageously, a configuration in which the metal filter is submitted consecutively to an alternating magnetic field and thereafter to an electromagnetic radiation allows that the generated heat at the electromagnetic actuator and/or at the laser device (LC circuit and laser electronics) be lower. Moreover, such configuration allows reducing the energy consumption and allows increasing the lifetime of the electromagnetic actuator and/or of the laser device. Also advantageously, this configuration allows higher current intensities to be submitted to the electromagnetic actuator and/or to the laser device, whereby also allowing further increase of the temperature at the metal filter. A cooling system for refrigerating the electromagnetic actuator and/or the laser device is not particularly necessary, although it can be used whether a higher increase of the metal filter temperature is desired.

Thus, in a preferred embodiment, the device of this invention comprises a body provided with a channel for the passage of the fluid flow to be disinfected of pathogens, wherein the channel is configured to the fluid be passed first through the area where the induction coil and/or laser device are arranged to cool them and to pre-heat the fluid and, then, the pre-heated fluid be passed through the metal filter (Figure 5, Figure 9).

According to several optional features of the device of this invention, which can be combined with each other whenever technically possible:

- The device comprises processing and control means operatively connected to temperature monitoring means and configured to receive a signal therefrom, and further electrically connected to the electromagnetic actuator and/or to the laser device and configured to receive a signal therefrom to control their operation sending the electric signals adequate to heat up the metal filter temperature in accordance with the signal received of the temperature monitoring means (Figure 5).

- The device comprises an electromagnetic actuator provided with an induction coil to generate an alternating magnetic field (H) to heating the metal filter by magnetic heating (Figure 6.1 , Figure 6.2).

- The device comprises a laser device configured to emit at a wavelength and intensity to heating the metal filter by optical heating (Figure 7).

- The device comprises an electromagnetic actuator and a laser device to heating the metal filter by magnetic and optical heating (Figure 8).

- The device is provided with a channel for the passage of the fluid flow to be disinfected of pathogens, wherein the channel is configured to the fluid be passed first through the area where the induction coil is to cool it and to pre-heat the fluid and then, the pre-heated fluid be passed through the metal filter (Figure 5, Figure 9).

- The device includes attachable means for installation in a pipeline.

- The metal filter does not have electrical connections to cooperate with the electromagnetic actuator, such cooperation is by wireless means.

- The metal filter does not have electrical connections to cooperate with the light source, usually a laser device, such cooperation is by wireless means.

- The material forming the channel is suitable to receive the alternating magnetic field there through, such as plastic, glass, or ceramic material.

All the advantages described herein allow the fluid disinfection device of this invention be of low-cost, compact and easy to use.

As described herein, the metal filter is configured to be submitted to the selected energy source to which it is in cooperation to be heated. Such cooperation between the metal filter and the selected energy source is in a wireless way.

Advantageously, the metal filter of this invention is capable of wireless heating.

Different embodiments of the improved metal filter in accordance with the present invention and their cooperation with the selected energy source are described below in more detail.

Thus, it is a further aspect of the present invention to provide an improved metal filter for disinfection of pathogens of a fluid flow which is used in the fluid disinfection method and/or in the fluid disinfection device described herein.

The improved metal filter can work in cooperation with an alternating magnetic field to magnetically heating the metal filter by means of such cooperation and/or in cooperation with an electromagnetic radiation to optically heating the metal filter by means of such cooperation.

The improved metal filter for disinfection of pathogens of a fluid flow of this aspect is characterized in that the metal filter is a microporous metal sintered filter of stainless-steel capable of cooperating with an energy source external to the fluid flow to be heated by means of such cooperation, the energy source being selected from an alternating magnetic field and/or electromagnetic radiation, and in that the metal filter superficially further comprises:

(A) - a nanostructured material layer including:

(I) a dielectric material adhered to the surface of the metal filter, and

(II) a coating that coats the dielectric material and fully or partially coats the metal filter surface where the dielectric material has not been adhered, wherein the coating material includes a metal material selected from i) a ferromagnetic material, ii) a damped-plasmonic material, and iii) a ferromagnetic and damped- plasmonic material;

Or, alternately,

(B) - a nanostructured carbon coating that fully or partially directly coats the metal filter surface.

The nanostructured metal filter of this aspect of the invention is capable of cooperating with an energy source external to the fluid flow to be heated by means of such cooperation.

As stated above the improved metal filter of the present invention is of microporous metal sintered filter of stainless-steel whose surface is nanostructured in accordance with the nanostructure defined in A (Figure 2) or alternatively in B (Figure 3).

The microporous metal sintered filters of stainless-steel known in the art generally comprise pores of an average pore size from 0.02 pm to 270 pm and a porosity from 20 to 80% in volume. Figure 1 shows one commercially available microporous metal sintered filters of stainless-steel, in particular the AmesPore® filter. These microporous metal sintered filters of stainless-steel known in the art can be obtained by sintering of stainless-steel micro-powder. The microporous metal sintered filter of stainless- steel can include different pore sizes and porosity because of sintering. Varying such pore size and porosity within the above stated range forms part of the general knowledge in the state of the art by means of the known sintering technique.

Preferable microporous metal sintered filter of stainless-steel suitable for including a nanostructured surface (A, B) as described in the improved metal filter of the present invention comprises an average pore size from 1 pm to 50 pm with a porosity from 20 to 80% in volume. Advantageously, the microporous metal sintered filter of stainless-steel has high density and small pore size.

The metal filters of stainless-steel offer tunable geometry and micropore size, high mechanical robustness, are adequate for working under very high fluid pressures and temperatures and have good electrical conductivity.

The superficially nanostructured microporous metal sintered filter of stainless-steel is suitable for use under large fluid flows, and its shape and thickness can be easily adapted to industrial, automotive, commercial, or domestic fluid flows.

Advantageously, the superficially nanostructured metal filter (A, B) allows to maximize the cooperation with an alternating magnetic field and/or with an electromagnetic radiation in accordance with the superficial nanostructure, thereby further improving the thermal efficiency of the metal filter as well as the heat transfer between the metal filter and the fluid flowing there through.

- A- : Nanostructured material layer

At the nanostructured metal filter described herein, the dielectric material (I) is discontinuously adhered to the surface of the metal filter. Preferably, the dielectric material is adhered to at least the surface where the metal filter receives the light source.

Preferable dielectric material are nanoparticles (NP). Preferable NP material is of SiC>2 or polystyrene, although it is not limited to these materials. The NPs have an average diameter size within the range of 10 nm to 1000 nm. In a preferred embodiment, the dielectric material are silica nanoparticles of an average particle size within the range of 20 nm to 1000 nm. The use of other particulate materials having dielectric properties and that are suitable to be adhered at the metal filter surface of this invention forms part of the general knowledge in the matter and, thus, they are also included herein.

The dielectric NPs can adhere to the filter surface by electrostatic self-assembly of a colloid containing the NPs.

Once the NPs are assembled, the coating material (II) can be deposited by physical vapour deposition, chemical vapour deposition or by electrochemical deposition.

It is part of the general knowledge of the person skilled in the art to select a particular physical vapour deposition method known in the art such as sputtering, e-beam evaporation, thermal evaporation etc., or chemical vapour deposition, as well as to select a particular electrochemical deposition method known in the art such as electroless plating, applying a potential on the filter, etc. for depositing the coating on the metal filter surface.

The thickness of the nanostructured material layer - A - can be from 1 nm to 5,000 nm.

The nanostructured material layer (A) can partially cover the microporous metal sintered filter surface of stainless-steel, which is irregular, so that the limits of the top and bottom of the nanostructured material layer can be also irregulars.

It forms part of the general knowledge of the person skilled in the art to select a ferromagnetic material available in the art. Preferable ferromagnetic material (i) is selected from Fe, Co, Ni, oxides and alloys thereof. These materials are suitable for generating a magnetic heating at the microporous metallic sintered filter of stainless steel in response to being submitted to an alternating magnetic field of frequency and amplitude within the ranges described herein.

It forms part of the general knowledge of the person skilled in the art to select a damped- plasmonic material available in the art. Preferable damped-plasmonic material (ii) is selected from Cr, Ti, W, Pt, Mo, Cu, Pd and alloys thereof. Still preferable it is selected from Cr, Cu, Mo, Ti and W or alloys thereof. These materials are suitable for generating an optical heating at the microporous metallic sintered filter of stainless steel in response to being submitted to a light beam at intensity and wavelength within the ranges described herein.

It forms part of the general knowledge of the person skilled in the art to select a ferromagnetic material having also damped-plasmonic properties, or vice versa. Preferable ferromagnetic and damped-plasmonic material (iii) is selected from Fe, Co and Ni. Fe, Co and Ni are metals suitable for generating, simultaneously or consecutively, a magnetic heating and an optical heating at the microporous metallic sintered filter of stainless steel in response to being submitted to an alternating magnetic field and/or an electromagnetic radiation, respectively.

The authors of the invention have found that the nanostructured metal filter in accordance with this embodiment including damped-plasmonic material (ii, iii) submitted to an electromagnetic radiation is capable of causing a very intense broadband optical absorption within the wavelength range from UV to IR that makes it advantageous for using in the herein thermal disinfection method and device.

The damped-plasmonic material can have also ferromagnetic properties.

Moreover, the metal filter of this embodiment, in which the coating material (II) is i) a ferromagnetic material or iii) a ferromagnetic and damped-plasmonic material, is also adequate for magnetically heating the metal filter.

Thus, the metal filter whose surface is metal nanostructured in accordance with the embodiment - A - is capable of heating by means of an alternating magnetic field, an electromagnetic radiation or a combination of an alternating magnetic field with an electromagnetic radiation in accordance with the selected coating (II) material (i, ii, iii).

- B Nanostructured carbon coating

The nanostructured carbon material can be fully or partially embedded into the microporous metal sintered filter surface of stainless-steel, which is irregular, so that the limits of the top and bottom of the layer can be also irregulars.

Preferable thickness of the nanostructured carbon coating is from 1 nm to 50 nm, or greater, if the porosity of the metal filter is not adversely affected.

The nanostructured carbon layer can include graphene, carbon nanotubes, mixtures thereof, or others micro-, nanocarbon structures such as fullerenes having broadband optical absorption within the wavelength range from ultraviolet to infrared.

Preferable nanostructured carbon material includes graphene and/or carbon nanotubes.

The nanostructured carbon material can be deposited on the metal filter surface by means of chemical vapor deposition.

Unexpectedly, these carbon nanostructures have broadband optical absorption within the wavelength range from ultraviolet to infrared and, therefore, they are adequate for generating an optical heating at the surface of the microporous metallic sintered filter of stainless steel in response to being submitted to a light beam at intensity and wavelength within the ranges described herein.

Advantageously, the metal filter in accordance with this embodiment allows maximizing the cooperation with an electromagnetic radiation, thereby improving the thermal efficiency of the metal filter as well as the heat transfer between the metal filter and the fluid flow.

Thus, the metal filter whose surface is directly carbon nanostructured in accordance with the embodiment - B - is capable of heating by means of an electromagnetic radiation, and optionally of heating by means of an alternating magnetic field likely due to the electrical conductivity of the metal filter of stainless-steel, or a combination thereof.

In use, the superficially nanostructured metal filter of this aspect of the present invention is easy to clean, have long service time and can be easily recycled and reused.

The metal filter can be subjected to a pyrolytic treatment to clean the filter and leave it for a new use.

The metal filter can be applied to other purposes linked to heating, but different from pathogen disinfection of a fluid stream. Therefore, the metal filter of this invention for heating purposes other than pathogen disinfection by means of cooperation with an alternating magnetic field and/or an electromagnetic radiation can be an invention in itself.

Definitions

According to the scope of the present invention, the term “fluid” is intended to encompass a gas or a liquid. The liquid can be transparent or not. Preferable gas is air. Preferable liquid is water or milk.

In the present invention, the term “pathogen” includes microorganisms such as virus, bacteria, and fungi.

In the present invention, the term “disinfecting” is understood with the purpose of eliminating microorganisms, and includes denaturalization, sterilization, destruction or equivalent.

In the present invention, the term “metal filter” or “microporous metal sintered filter of stainless steel” includes one individual metal filter or several individual metal filter that can be separated from each other or intimately contacted, each facing each other, to form a thicker metal filter. Usually, the thickness of one microporous metallic sintered filter of stainless steel is within the range from 3 mm to 5 mm. A thicker metal filter can be used for improving thermal efficiency, particularly in flows of high rates.

According to the present invention, the expression “ferromagnetic material” is understood as a metal material having ferromagnetic properties. A ferromagnetic material allows to easily concentrate magnetic field lines, accumulating high magnetic flux density. These materials are used to delimit and direct magnetic fields in well-defined paths.

According to the present invention, the expression “damped-plasmonic material” is understood as a metal material that has damped plasmonic properties. The most common damped- plasmonic materials are Cr, Ti, W, Pt, Mb, Cu, Pd, Fe, Co, Ni and alloys thereof. However, many other materials display metal-like optical absorption properties in specific wavelength ranges. According to the present invention, the expression “carbon material” is understood as a nanostructured carbon material composed of carbon. Preferable nanostructured carbon material can be selected from graphene, carbon nanotubes, mixtures thereof, or others micro- , nano-carbon structures such as fullerenes.

The term “electromagnetic actuator” is understood as a solenoid/coil. The solenoid is a physical device capable of creating a highly uniform and intense alternating magnetic field inside, and very weak on the outside. For magnetic heating the frequency of the magnetic field might preferably be between 20 KHz to 1 MHz, preferable between 50 KHz and 500 KHz, and amplitude between 1 to 700 Oe.

The term “electromagnetic radiation” is intended to encompass at least a light source. A light source includes a source capable of emitting a light intensity within the range from 0.05 W/cm ² to 1000 W/cm ² , preferably from 0.1 to 100 W cm ^-2 , more preferably from 0.5 to 50 W cm ^-2 . The light source includes a laser light source or another light source such as a LED.

According to the present invention, the expression “wireless way” means without direct contact between the metal filter (3) and the energy source (4) as can be seen in any one of Figures 5 to 9, regardless of whether the energy source (4) is of electromagnetic radiation or of electromagnetic induction coil (alternating magnetic field).

Brief Description of the Drawings

In order to better understand the description made, a set of drawings has been provided which, schematically and solely by way of non-limiting example, represents practical cases of various embodiments.

Figure 1 depicts: a) a picture of the metal filters of different geometries (40 mm, 12,7 mm), and b) a schematic drawing of the metal filter surface of the picture showing the stainless steel micrograins and the microporous structure of the metal filter perse.

Figure 2 depicts a schematic drawing of an alternative embodiment (A) of the stainless-steel metal filter of this invention in which the metal filter surface is nanostructured including dielectric nanoparticles coated with a coating of a metal material (M coating).

Figure 3 depicts a schematic drawing of an alternative embodiment (B) of the stainless-steel metal filter of this invention in which the metal filter surface comprises a coating of a nanostructured carbon material (C coating).

Figure 4 depicts a heating efficiency graph of the metal filter represented in Figure 3. The graph was obtained when characterizing the metal filter irradiating with a near infrared laser (emission at 915 nm) with a power of 6W. This graph reveals the improved heating efficiency compared with a metal filter.

Figure 5 depicts a schematic drawing of the device of this invention showing a configuration including an electromagnetic actuator provided with an induction coil and a laser device operatively connected to the processing and control means. The parts of the drawing with a grid pattern represent an alternative configuration of the device for working also as intercooler.

Figure 6 depicts two embodiments of the device of this invention. Figure 6.1 shows one configuration in which the metal filter is located inside the induction coil and Figure 6.2 shows another alternative configuration in which the metal filter is located next to the induction coil.

Figure 7 depicts another alternative embodiment of the device of this invention in which an electromagnetic radiation source arranged external to the fluid is in cooperation with the metal filter by means of transparent apertures provided in the device, the metal filter being arranged in the passage channel of the fluid flow.

Figure 8 depicts still another alternative embodiment of the device of this invention in which an induction coil and an electromagnetic radiation arranged external to the fluid are in cooperation with the metal filter, the electromagnetic radiation by means of transparent apertures (T.A.), the metal filter being arranged in the passage channel of the fluid flow and being separated of the induction coil by means of the material forming the channel.

Figure 9 depicts an embodiment of the device of this invention in which the induction coil is further working as an intercooler, thereby taking advantage of the thermal energy generated in the method itself.

Figure 10 shows three graphs of an assay performed with different temperature and flow treatments of an air flow passing through the metal filter. The graphs show the evolution of the temperature (°C) of the metal filter with respect to the voltage (Vpp) applied to the induction coil (not shown), the time (s) of the air passing through the heated metal filter versus the reference selected pathogen disinfection temperature, as well as the temperature of device air inlet and outlet.

Detailed Description of the Invention

Hereinafter, the best mode for carrying out the present invention is described in detail.

According to Figures 6.1 and 6.2, the metal filter 3 was configured to be submitted to an alternating magnetic field in two different configurations, when it be located inside the induction coil (Figure 6.1) or it be located next to the induction coil (Figure 6.2). Figure 6.1 shows the fluid disinfection device for disinfecting pathogens of an air flow comprising a body 1 provided with a channel 2 for the passage of the air flow to be disinfected of pathogens. The microporous metal sintered filter of stainless-steel 3 was arranged in the passage channel 2, separated of the induction coil 41 by a plastic material forming the channel

2 where the metal filter 3 was arranged for the air flow crosses the metal filter 3 at a flow of 14 L/min. Meanwhile, the metal filter 3 was submitted to an alternating magnetic field by means of an induction coil 41. The induction coil 41 was arranged external to the air flow as shown in Figure 6.1 , i.e., external to the plastic material forming the channel 2 and in cooperation with the metal filter 3. The induction coil 41 of 7 turns (Cu wire of 1 mm of diameter) was coiled with 18 mm of diameter around where the metal filter 3 was arranged. The inductance measured was of 1.25 pH. The induction coil 41 was connected to a resonant LC circuit (not represented) showing a resonance at 142 kHz. The induction coil 41 was actuated by an alternating current at 142 kHz to externally, wirelessly, heating the metal filter 3 by electromagnetic induction. The metal filter 3 had a diameter of 12.5 mm and a thickness of 3 mm. While the air flow at 14L/min passed through the metal filter 3, an IR thermometer 5 (not represented) measured 140 °C at the center of the metal filter 3 and 170 °C at the perimeter of the metal filter 3. The average consumed electric power was of 20W.

Figure 6.2 shows another embodiment of the device of this invention. In this embodiment, the device differs from the above embodiment in that the material forming the channel was of ceramic instead of plastic, and in that the induction coil 41 was arranged next to the metal filter

3 instead of around as in Figure 6.1 .

According to Figure 7, the metal filter 3 was configured to be submitted to an electromagnetic radiation. Figure 7 shows the fluid disinfection device for disinfecting pathogens of an air flow comprising a body 1 provided with a channel 2 for the passage of the air flow to be disinfected of pathogens. The microporous metal sintered filter of stainless-steel 3 was configured to be submitted to an electromagnetic radiation by means of a blue laser 42.

In this embodiment, the metal filter 3 superficially comprised first a monolayer of silica nanoparticles (diameter 200 nm), randomly distributed on the surface of the metal filter, as described in Example 1 , then a Ni layer (thickness 150 nm) was totally deposited on the metal filter as described in Example 1.1. The Ni possess ferromagnetic and damped-plasmonic properties.

The nanostructured metal filter 3 was arranged in the passage channel 2, separated of the blue laser 42 by a plastic material forming the channel 2 which has transparent apertures (T.A.) to enable light transmission of the blue laser 42 into the channel 2 where the metal filter 3 was arranged for the air flow crossing the metal filter 3 at a flow of 14 L/min. Meanwhile, the metal filter 3 was submitted to the blue laser 42 (emission at 405 nm) with power of 6W to heating the metal filter 3 and the heated metal filter 3 heating the air flowing therethrough. The metal filter 3 had a diameter of 12.5 mm and a thickness of 3 mm. While the air flow at 14L/min passed through the metal filter 3, an IR thermometer 5 (not represented) measured 170 °C at the center of the metal filter 3 and 150 °C at the perimeter of the metal filter 3. The consumed electric power was of 20W. All the components were controlled from a hardware and a software 6 (not represented) that were operatively connected to receive signals therefrom and to assure that the metal filter 3 was heated at the temperature to which pathogens thermally are inactivated.

According to Figure 8, the metal filter 3 was configured to be submitted, simultaneously or consecutively, to an alternating magnetic field and to an electromagnetic radiation. Figure 8 shows the fluid disinfection device for disinfecting pathogens of an air flow comprising a body 1 provided with a channel 2 for the passage of the air flow to be disinfected of pathogens. The microporous metal sintered filter of stainless-steel 3 was configured to be submitted to an alternating magnetic field by means of an induction coil 41 and to an electromagnetic radiation by means of a blue laser 42.

In this embodiment, the metal filter 3 superficially comprised first a monolayer of silica nanoparticles (diameter 200 nm), randomly distributed on the surface of the metal filter, as described in Example 1 , then a Ni layer (thickness 150 nm) was partially deposited on the metal filter as described in Example 1 .2. The nanostructured metal filter 3 was arranged in the passage channel 2, separated of the induction coil 41 and blue laser 42 by a plastic material forming the channel 2 which has transparent apertures to enable light transmission of the blue laser 42 into the channel 2 where the metal filter 3 was arranged for the air flow crossing the metal filter 3 at a flow of 14 L/min. Meanwhile, the metal filter 3 was simultaneously submitted to the induction coil 41 with the conditions described above in Figure 6.1 , and to the blue laser 42 with the conditions described above in Figure 7. The metal filter 3 had a diameter of 12.5 mm and a thickness of 3 mm. While the air flow at 14L/min passed through the metal filter 3, an IR thermometer 5 (not represented) measured 350 °C at the center of the metal filter 3 and 340 °C at the perimeter of the metal filter 3. The consumed electric power was of 20+20W. All the components were controlled from an electronic control unit 6 (not represented) that were operatively connected to receive signals therefrom and to assure that the metal filter 3 were heated at the temperature to which pathogens thermally are inactivated.

According to Figure 9, the device can be working as an intercooler. Starting from the configuration of Figure 5.1 , configuration of Figure 9 further includes a channel 2 configured to the fluid be passed first through the area where the induction coil 41 is to cool it and to preheat the fluid and then the pre-heated fluid be passed through the metal filter 3. Figure 5 shows a similar configuration of Figure 9 working as an intercooler, in which the channel 2 further has transparent apertures (T.A.) to enable light transmission of the light beam 42 into the channel

2 where the metal filter 3 is arranged and in cooperation to it.

All the components (induction coil 41 , laser 42, thermometer 5 see also Figure 5) were controlled from an electronic control unit 6 (shown in Figure 5) that were operatively connected to receive signals therefrom and to assure that the metal filter 3 was heated at the temperature to which pathogens thermally are inactivated. The induction coil 41 was further configured to work as an intercooler system. Therefore, the pumped air was passed first around the induction coil 41 to refrigerate it and to pre-warm the air before passing through the metal filter 3 (Figure 9).

According to another embodiment (not represented), the fluid flow is pre-heated passing the fluid around to a laser device 42 that releases thermal energy prior to passing the fluid through the metal filter 3, thereby taking advantage of the thermal energy generated in the method itself. The circulation of fluid around the laser device 42 allows pre-heating the fluid before passing it through the metal filter 3 but advantageously also allows refrigerating the laser device 42, thereby the laser device 42 also working as an intercooler.

Figure 10 shows the graphs of the temperature evolution (°C) at a metal filter (3) with respect to the voltage (Vpp) applied to an induction coil. This assay demonstrated that the metal filter

3 was suitable for disinfecting pathogens by thermal action. The assay was performed under a constant air flow, the temperature of the stainless-steel sintered filter 3 by an electromagnetic induction actuation 41 are shown in the graphs. A stainless-steel sintered filter 3 of an average pore size comprised between 5 and 10 pm ² , external diameter of 12.7 mm and a thickness of 3 mm was used. The electromagnetic coil 41 was composed of 7 turns around the filter with an internal diameter of 18 mm. The wire of the coil was a copper wire coated with Kapton and an external diameter of 1 mm. The induction coil 41 was actuated with an alternating current of 142 kHz, input current of 5 A and voltage of 12 V. The temperature of the metal filter was monitored with a non-contact infrared thermometer. The maximum temperature of the filter was specified in a software, and this temperature was controlled by switching on and off the induction coil when the metal filter temperature was the set temperature +/-5°C. The air flow was controlled by a diaphragm pump and a manometer.

In this assay, the air flow was opened at the specified flow rate shown in each graph, and then the induction coil 41 was switched on. A fast temperature increase was observed when the induction coil 41 was on. Once the set temperature was reached, the software kept the set temperature until the coil was switched off. When the induction coil 41 was switched off, a temperature decrease was observed due to the cooling of the stainless-steel sintered filter 3 by the air flow. Graph 1 : The flow rate was set at 18 L/min and the maximum temperature at 124°C. The set temperature was reached after 90 secs. Graph 2: The flow rate was set at 12 L/min and the maximum temperature at 170°C. The set temperature was reached after 60 secs. Graph 3: The flow rate was set at 8 L/min and the maximum temperature at 170°C. The set temperature was reached after 30 secs.

As described above in detail, the device according to this invention further has at least one of the following advantages:

- The device provides a highly innovative and very versatile wireless air sterilization technology that can be easily integrated in an air pipeline of any air circulation system.

- The device is applicable to very diverse sectors such as the health, industrial, automotive, commercial, or domestic fields.

- The device does not require harmful UV or ionizing radiation, neither the application of high voltages. Its low cost and small footprint allow the device be integrated in any air circulation system.

A still further object of the present invention is the use of the metal filter defined herein for disinfection of pathogens of a fluid flow.

Preferable fluid is selected from the group consisting of air, water and milk.

The pathogens to be disinfected by the method described herein can be selected from the group consisting of viruses, bacteria, and fungi. The temperature to which each type of pathogen can be disinfected forms part of the acknowledgment of the skilled person in the art.

Examples

Hereinafter, the present invention is described in more detail and specifically with reference to the Examples and Figures, which however are not intended to limit the present invention.

Example 1: Nanostructured material Filter

To self-assemble the silica nanoparticles, the surface of the stainless-steel micrograins was previously coated with a monolayer of a positive polyelectrolyte (e.g., poly(diallyldimethylammonium chloride)) that enables the electrostatic attachment of negatively charged silica nanoparticles to the surface. The coating was performed by immersing the metal filters in a water solution at a 2% mass concentration of polyelectrolyte for 10 min. The metal filters were thoroughly washed in water and dried. Next the filters were immersed in a bath containing the negatively charges Silica colloids (diameter 200 nm) at a concentration of 0.5% for 10 min. The metal filters were washed in water and dried, thus yielding a monolayer of silica nanoparticles randomly distributed at the stainless-steel metal filter surface. Next, a Ni layer of a thickness of 150 nm was deposited fully (Example 1.1) or partially (Example 1.2).

Example 1.1 : Nanostructured material Filter

The stainless-steel metal filter charged with silica nanoparticles was then fully covered by a Ni film of thickness of 150 nm was by electrical or electroless plating.

Electrical plating was performed in an electrochemical bath composed of nickel sulfate (200 g/L), nickel chloride (100 g/L) and boric acid (40 g/L) and applying an electrical current density of 2-10 A/dm ^A 2 at a temperature of 40-60°C.

The Ni electroless plating requires activation of the stainless-steel metal filter surface using a palladium catalyzation bath. The palladium bath was composed of a water solution of 5 mM PdCh, 0.2 M HCI, 4 g/L of SnCh and 32 g/L of SnCh. The metal filters were then immersed in the palladium catalyzation bath for 25 min at 35°C. The electroless plating was performed in an electroless bath composed of 0.2 M sodium citrate tribasic dehydrate and 0.1 M NiSC tW. This aqueous solution was stirred (400 rpm) for 30 min and, before starting the electroless deposition, borane dimethylamine complex was added, and the pH was adjusted with 0.5 M NaOH. Prior to beginning the electroless deposition, the electroless bath was heated and maintained at 70°C.

Example 1.2: Nanostructured material Filter

This example differs from Example 1 in that the stainless-steel metal filter charged with silica nanoparticles was then partially covered by a Ni film of thickness from 150 nm by physical vapor deposition.

The partial coverage of the metal filter was carried out by physical vapor deposition, by inserting the filters in a vacuum chamber and evaporating the Ni film on the metal filters by electron-beam evaporation or sputtering. The Ni film was deposited only in the first layer of grains of the metal filter.

Example 2: Nanostructured material Filter

This example differs from Example 1 only in that a Nickel plating of a 250 nm thick layer instead of 150 nm thick layer was performed by electroless as described in Example 1.1 or in Example 1.2. Example 3: Nanostructrured carbon Filter

This example differs from Example 1 in that the stainless-steel metal filter was fully or partially covered by a graphene and carbon nanotubes layer thickness around 2 nm by chemical vapor deposition.

In this example, the stainless-steel sintered filter was covered by a layer of graphene and carbon nanotubes with a thickness of 2 nm by chemical vapor deposition. The samples were heated under an Argon (Ar flow 400 ml/min) and Hydrogen (H2 flow 200 ml/min) atmosphere at a rate of 1 °C /s up to reach a temperature of 1020°C. Prior to the growth, the samples were activated in Ar (400 ml/min) and H2 (200 ml/min) at 1020°C for 50 minutes. This step helps to anneal the substrate by increasing the diffusion of the atoms and at the same time reduces it chemically, removing oxide moieties and making it more catalytically active for graphene growth. The growth was performed under a nucleation/growth process from the decomposition of methane as carbon source (CH4 -> C+2H2). The growth was also performed in an Ar/ H2 atmosphere, keeping the same flow of Ar (400 ml/min) but at a reduced flow of H2 (15 ml/min). CH4 was introduced with a flow rate of 35 ml/min. The process was kept under such conditions for 2 minutes at the temperature of 1020°C. Finally, the samples were fast cooled to room temperature in presence of H2 (15 seem) and Ar (400 seem).

Example 4: Fluid disinfection method by means of electromagnetic radiation

The superficially nanostructured metal filter had a nanostructured material layer in the surface of the metal filter that includes first a monolayer of silica nanoparticles (diameter 200 nm), randomly distributed on the surface of the filter, then a deposited Ni layer of thickness 150 nm (fully layer, Example 1 .1 , or partially layer, Example 1 .2) as described in Example 1 . Ni possess ferromagnetic and damped-plasmonic properties.

The plastic or ceramic pipe had a transparent window to enable the transmission of the electromagnetic radiation to the metal filter. A blue laser (emission at 450 nm) with power of 10W was used to heat the filter with electromagnetic radiation.

In this configuration, enhanced heating efficiency was achieved with both electromagnetic radiation (from the ultraviolet to the near infrared spectral range) and electromagnetic induction. In addition, enhanced heat transfer from the metal filter to the air was achieved due to the increased surface area.

Example 5: Fluid disinfection method by means of electromagnetic radiation

The superficially nanostructured metal filter had a layer of graphene and carbon nanotubes with a thickness of 2 nm obtained by chemical vapor deposition as described in Example 3 above.

The plastic or ceramic pipe had a transparent window to enable the transmission of the electromagnetic radiation to the filter. A near infrared laser (emission at 915 nm) with power of 6W was used to heat the filter with electromagnetic radiation. In this configuration, enhanced heating efficiency was achieved with electromagnetic radiation (from the ultraviolet to the near infrared spectral range). In addition, enhanced heat transfer from the filter to the air was achieved due to the increased surface area.

Example 6 - Fluid disinfection method by means of alternating magnetic field

The superficially nanostructured metal filter of Example 1 includes a Ni layer. Ni possess ferromagnetic and damped-plasmonic properties.

The superficially nanostructured metal filter was heated by an induction coil of 7 turns (Cu wire of 1 mm of diameter) coiled around the pipe with 18 mm of diameter, showing an inductance of 1.25 pH. The induction coil was connected to a resonant LC circuit showing a resonance at 142 kHz. A temperature value at the metal filter from 140 °C at the center of the filter up to 170 °C at the perimeter of the filter was measured when the air flow was 14 L/min.

As the superficially nanostructured metal filter includes Ni, it can cooperate, simultaneously or consecutively, with an alternating magnetic field and an electromagnetic radiation to magnetically and optically heating the metal filter accordingly, the fluid disinfection method was carried out by cooperating the alternating magnetic field as described herein with the electromagnetic radiation as described in Example 4, thereby the metal filter be heated to higher temperatures by magneto-optical heating.

Example 7- Fluid disinfection method by means of electromagnetic radiation and alternating magnetic field

The superficially nanostructured metal filter of Example 3 includes a nanostructured carbon layer including graphene and carbon nanotubes.

As described in the description, the metal filter whose surface is directly coated with the nanostructured carbon layer is capable of heating by means of an electromagnetic radiation as demonstrated in Example 5, and optionally simultaneously of heating by means of an alternating magnetic field likely due to the electrical conductivity of the metal filter of stainless- steel. The same alternating magnetic field conditions of Example 6 were applied to the metal filter including the nanostructured carbon layer, thereby the metal filter including the nanostructured carbon layer be heated to higher temperatures by magneto-optical heating.

Example 8 - Preheating the fluid flow in the fluid disinfection method by means of alternating magnetic field

The fluid disinfection method of Example 6 was performed by saving energy passing first the pumped air containing pathogens to be disinfected around the induction coil to refrigerate it and to pre-warm the air before passing through the metal filter. It is a matter of course that the features mentioned above and those explained below can be used in other combinations in addition to those described, on in isolation, without departing from the scope of the invention.

Below is included a Table 1 of temperatures enabling thermal inactivation of viruses that is available in the art only as reference.