Nanostructured coating for controlled biocidal and self-cleaning functions

Abstract

The present disclosure relates to a nanostructured coating for controlled biocidal and self-cleaning functions. It is disclosed a nanostructured coating for controlled biocidal and self-cleaning functions, comprising: an adhesion layer deposited on a substrate; a transition layer deposited on the adhesion layer; and a top layer comprising a passive matrix phase and a biocidal active phase; wherein the transition layer promotes mechanical compatibility between the adhesion layer and the top layer bounding the layers; wherein the coating is configured to electrochemically release biocidal species in response to an applied electrical potential, while maintaining corrosion resistance and mechanical hardness; and wherein the coating is electrochemically reversible, such that the biocidal release is controllable and stoppable by adjusting or reversing an electrical potential.

Description

D E S C R I P T I O N NANOSTRUCTURED COATING FOR CONTROLLED BIOCIDAL AND SELF-CLEANING FUNCTIONSTECHNICAL FIELD

[0001] The present disclosure relates to a nanostructured coating for controlled biocidal and self-cleaning functions.BACKGROUND

[0002] Biofouling and corrosion are critical issues concerning several devices, such as water tanks, pipelines, external walls, offshore structures, etc. In the maritime industry, these issues cause ship drag or coating damage, increasing operational and maintenance costs. These problems create a gap that multifunctional coatings could fill.

[0003] For instance, within the maritime industry, the coatings currently in use are predominantly polymers, which often lack mechanical strength and can pose serious environmental risks. Despite their affordability and ease of use, these paint coatings come with significant drawbacks in maintenance and downtime, ultimately leading to higher operation costs. However, the International Maritime Organisation (IMO) has taken steps to significantly reduce the release of harmful agents into the seas. Products like Tributyltin (TBT), commonly used as a biocidal agent in ships, were banned by the IMO in 2008 due to their severe pollution.

[0004] Industry, governments, and societies are interested in environmentally friendly solutions, as they constantly worry about climate change and mankind's environmental impact. Some solutions have been explored recently, such as surface nano-texturisation, bio-inspired surfaces, or biocide-release coatings. Therefore, coatings with high tailoring capabilities have a huge potential that can be explored for this application. The coating enlarges the functionality of the substrate (base material) and, in many cases, increases its life span, mechanical properties or corrosion resistance. However, antagonistic properties are uncommon to gather in onemultifunctional coating. This is the case of anti-biofouling and anti-corrosion properties. On one side, biofouling is commonly fought with active agents, which are not suitable for resisting corrosion. Conversely, high corrosion resistance is achieved in materials with low chemical activity to the surrounding media.

[0005] These facts are disclosed in order to illustrate the technical problem addressed by the present disclosure.GENERAL DESCRIPTION

[0006] The present disclosure relates to a nanostructured coating for controlled biocidal and self-cleaning functions.

[0007] The disclosed technology relates to the development of a nanostructured coating capable of releasing a biocidal agent without compromising its integrity. This release is meticulously controlled through the application of an electrical potential within the coating. The biocidal agent is encapsulated within a protective matrix, achieved through a specialised nanoarchitecture created using a hybrid magnetron sputtering system in a reactive atmosphere. By applying a specific electrical potential to this nanoarchitecture in contact with an electrolyte, the coating becomes multifunctional, exhibiting antimicrobial activity, high corrosion resistance, and robust mechanical properties, without compromising the environment. These attributes make the coating valuable across various applications, including smart biodevices, ship components, architectural elements, water treatment facilities, and frequently touched surfaces. The implementation of this solution has the potential to significantly reduce maintenance costs and mitigate pollution, particularly in scenarios like ship coatings.

[0008] The present technology raises the design concept fora nanostructured coating using line-of-sight technologies, such as physical vapour deposition and, in particular, magnetron sputtering, which achieves effective multifunctionality of surfaces in terms of corrosion resistance, antibiofouling, and reliable mechanical properties. The nanostructured coating is based on depositing different layers to gather the desired properties with different materials under a controlled atmosphere. Various materialsare possible; hence, the concept could be exported and adapted to other technologies, configurations, or designs.

[0009] This specification discloses an innovative nanostructured coating with a specific nano-architecture in two different possible configurations, namely nanolayers and embedded nanoparticles or stacked nanolayers, capable of controlling the biocidal release rate employing an electrical potential and at the same time, keeping the integrity of the coating, for example, in anticorrosion action, and the mechanical properties. This mechanism allows control the biocide amount to achieve the mentioned multifunctionality, decreasing the potential harmful effects over the surroundings such as seas, human body or any other environment which needs a surface with antibiofouling action, corrosion resistance and mechanical reliability. The coating's capabilities are kept regardless of whether the electrical potential for activation is retired, and it can return to the activated state, applying a new electrical potential.

[0010] Therefore, the now disclosed nanostructured coating, when compared to the state of the art and after submitting to an innovative electrochemical activation, offers a versatile solution that can be tailored to different applications, providing reassurance and confidence in its effectiveness. Furthermore, the now disclosed nanostructured coating allows for achieving a good relation between antagonist features, such as antibiofouling and anti-corrosion, and increases another critical feature to the wellfunctioning and lifespan of the developed coating: reliable mechanical properties.

[0011] This nanostructured coating is aligned with several United Nations sustainable development goals (SDGs), which advocate for the planet's health. SDG 3, SDG 6, SDG 13, and SDG 14 are related to clean water and sanitation, climate action, and marine ecosystems, respectively. The method presented in this invention for multifunctional coatings could be the solution to avoid the mentioned problems and tailor it according to our needs.

[0012] An aspect of the disclosure comprises a nanostructured coating for controlled biocidal and self-cleaning functions, comprising: an adhesion layer deposited on a substrate; a transition layer deposited on the adhesion layer; and a top layer comprising a passive matrix phase and a biocidal active phase; wherein the transitionlayer promotes mechanical compatibility between the adhesion layer and the top layer bounding the layers; wherein the coating is configured to electrochemically release biocidal species in response to an applied electrical potential, while maintaining corrosion resistance and mechanical hardness; and wherein the coating is electrochemically reversible, such that the biocidal release is controllable and stoppable by adjusting or reversing an electrical potential.

[0013] In an embodiment, the adhesion layer of the nanostructured coating is selected from Ti, Zr, Cr, Nb, Ta, and their combinations and wherein the transition layer of the nanostructured coating is selected from graded nitrides, oxynitrides, and their combinations.

[0014] In an embodiment, the top layer of the nanostructured coating is configured as a multilayer stack of nanolayers, each from 5 to 40 nm thick, alternating between active and passive materials.

[0015] In an embodiment, the top layer of the nanostructured coating is configured as a composite matrix in which active nanoparticles, having diameters from 5 nm to 50 nm, are uniformly embedded within a solid passive matrix.

[0016] In an embodiment, the passive matrix phase of the nanostructured coating comprises a metal oxynitride of formula Me(C,O)N, where Me is a transition metal selected from Ti, Zr, Cr, Nb, or Ta, or a carbon-based matrix selected from DLC or a-C:H.

[0017] In an embodiment, the biocidal active phase of the nanostructured coating comprises a biocidal agent selected from Cu, Ag, Zn and their oxides or nitrides (CuO, AgO, ZnO, CuN, AgN, ZnN).

[0018] In an embodiment, the biocidal active phase of the nanostructured coating is encapsulated or embedded within the passive matrix phase to prevent premature release in the absence of electrical activation.

[0019] In an embodiment, the adhesion layer of the nanostructured coating comprises a thickness of 50 to 300 nm, preferably from 100 to 290 nm, more preferably from 150 to 250 nm.

[0020] In an embodiment, the transition layer of the nanostructured coating comprises a thickness of 500 to 2000 nm, preferably from 550 to 1950 nm, more preferably from 800 to 1800 nm.

[0021] In an embodiment, the top layer of the nanostructured coating comprises a thickness of 200 to 2000 nm, preferably from 300 to 1900 nm, more preferably from 400 to 1800 nm.

[0022] In an embodiment, the total coating thickness of the nanostructured coating does not exceed 3 pm, preferably from 1.5 to 2.9 pm, more preferably from 1.9 to 2.8 pm.

[0023] In an embodiment, the top layer of the nanostructured coating is structured as alternating nanolayers of active and passive materials.

[0024] In an embodiment, the total concentration of biocidal agent in the nanostructured coating is lower than or equal to 40 at. % and the released amount of active species does not exceed 40 ppm under electrical activation.

[0025] In an embodiment, the nanostructured coating is deposited by a reactive hybrid magnetron sputtering process combining HiPIMS and DC or RF power sources, in a plasma atmosphere containing an inert gas (Ar, He, Ne) and a reactive gas (N2, O2, CH4, C2H2).

[0026] In an embodiment, the activation of the nanostructured coating occurs by applying an electrical potential between 0.001 V and 1.2 V between the coated surface and an inert counter electrode, the potential being continuous or pulsed.

[0027] In an embodiment, the nanostructured coating reverses the potential between -1.2 V and -0.001 V, deactivating or reversing the biocidal release.

[0028] It is also disclosed a method of manufacturing the nanostructured coating comprising the steps of: depositing the adhesion layer on the substrate; depositing the transition layer by reactive magnetron sputtering; co-depositing the passive matrix phase and the biocidal active phase under controlled plasma conditions; and optionally applying an electrical potential in an electrolyte to activate or stop the biocidal release.

[0029] It is also disclosed an article comprising the described nanostructured coating.

[0030] In an embodiment, the article is selected from a list consisting of marine hulls, offshore structures, architectural panels, biomedical implants, fluidic devices, and their combinations.BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The following figures provide preferred embodiments for illustrating the disclosure and should not be seen as limiting the scope of the invention.

[0032] Figure 1: Schematic representation of an embodiment of the processing of the nanostructured coating.

[0033] Figure 2: Photographic representation exhibiting the top and cross-section micrographs of an embodiment of the nanostructured coating obtained by scanning electron microscopy.

[0034] Figure 3: Photographic representation exhibiting the details of the transition between the graded nitride and top layer of an embodiment of the nanostructured coating obtained in high magnification transmission electron micrographs and its respective chemical composition distribution through an elemental mapping.

[0035] Figure 4: Schematic representation of an embodiment of the setup for the electrochemical activation of the nanostructured coating.

[0036] Figure 5: Photographic representation exhibiting the antibiofouling action of an embodiment of the nanostructured coating.

[0037] Figure 6: Graphic representation of the potentiodynamic polarisation tests made for the comparison of an activated nanostructured coating and a non-activated nanostructured coating.

[0038] Figure 7: Graphic representation of the Cu 2p spectra of ZrN-Cu(A) without etching cleaning.

[0039] Figure 8: Graphic representation of the open circuit potential of Cu, ZrN and ZrON coatings in 3.5 % w / w NaCI solution for 3600 seconds.

[0040] Figure 9: Photographic representation of Biofilm (C. Marina) formed over a ZrN film after 24 hours and applying a +0.5 V potential.DETAILED DESCRIPTION

[0041] The present disclosure relates to a nanostructured coating for controlled biocidal and self-cleaning functions.

[0042] In an embodiment, the disclosed technology establishes the use of two materials, one of which should work as a biocidal agent. Regarding the other material, it brings corrosion resistance and mechanical reliability to the coating. As Figure 1 establishes, in the substrate, which could be any material capable of being coated, three different layers should be deposited: (1) the adhesion layer, with a thickness from 50 to 300 nm, preferably from 100 to 290 nm, more preferably from 150 to 250 nm, which acts as an anchoring point between the substrates and the posterior deposited layers; (2) the transition layer, which in a possible embodiment is labelled as graded nitride layer, which works as an intermediate protection layer with high corrosion resistance and reliable mechanical properties, with a thickness from 500 to 2000 nm, preferably from 550 to 1950 nm, more preferably from 800 to 1800 nm; (3) the top layer, which could be possible in two different configurations: a.) nanolayers in an active / passive stacked structure or b.) active nanoparticles embedded in a passive matrix. The active material or biocidal element and the passive material from the top layer must be deposited carefully to avoid cross-contamination, defects and / or porosity, or bad adhesion. The example shown in Figure 2 clearly shows the division of these layers. An example of b.) the configuration of the top layer is exhibited Figure 3.

[0043] In an embodiment, afterwards, the nanostructured coating must be activated by applying an electrical potential and connected to a counter / reference electrode in a two-electrode electrochemical cell configuration to achieve the desired multifunctionality in terms of antibacterial / antibiofouling and self-cleaning actions, as illustrated in Figure 4. The electrodes, namely the coating and the counter / reference electrode, must be immersed in the same solution or electrolyte, capable of transmitting ions and making electrochemical activation possible. A direct current power source must be employed to activate the coating. The electrical potential is applied to the electrode, connecting the negative pole to the counter / reference electrode and the positive pole to the coating. Figure 5 exhibits the biocidal effect of the coating against the formed biofouling (composed of C. marina) after the activationand how its non-activated counterpart is colonised microbiologically. Regarding the corrosion tests, Figure 6 shows the reduction of the corrosion current density (X axis) and a higher corrosion potential (Y axis) of the activated coating, hence its superior corrosion resistance. According to nano-hardness, the maximum depth allowed in each measurement is 10% of the total coating thickness, and adhesion, the last one obtained through scratch test assessments, applying the ASTM C1624-05 standard -ASTM C1624-05: 2010 - Standard Test Method for Adhesion Strength and Mechanical Failure Modes of Ceramic Coatings by Quantitative Single Point Scratch Testing, employing a progressive load up to 100 N, in a diamond stylus, the activated coating exhibits an approximately 30% decrease in hardness and approximately 10% decrease in critical load for total detachment after activation. However, the measured values are superior to any polymer coatings, such as paintings. For instance, polyester coating in steel substrate shows nano-hardness values around 187 MPa [1], which is quite inferior when compared to the activated coating, which features values of approximately 10 GPa. These results corroborate the effectiveness of the disclosed technology in achieving a multifunctional surface, gathering high corrosion resistance, reliable mechanical properties and antibiofouling action.

[0044] In an embodiment, the nanostructured coating is composed of at least two distinct elements or phases, comprising a passive matrix phase and an active biocidal agent. The passive matrix may comprise metal oxynitrides or carbon-based compounds, such as Me(C,O)N where Me denotes a transition metal, for example, Ti, Zr, Cr, Nb, Ta, or amorphous carbon materials such as diamond-like carbon (DLC) or hydrogenated amorphous carbon (a-C:H). The active biocidal agent is preferably selected from copper, silver, or zinc, and their respective oxides, CuO, AgO, ZnO, or nitrides, CuN, AgN, ZnN. The coating can be produced by physical vapour deposition (PVD) using two or more distinct targets coupled to one or more power supplies, including direct current (DC), pulsed DC, high-power impulse magnetron sputtering (HiPIMS), or radio-frequency (RF) excitation. The passivation of the matrix phase is obtained by introducing inert gases such as argon, helium or neon, together with reactive gaseous species such as nitrogen (N2), oxygen (O2), methane (CH4) oracetylene (C2H2), thereby tailoring the chemical and mechanical behaviour of the deposited film.

[0045] In an embodiment, the coating is structured in a three-layer nanoarchitecture designed to optimise adhesion, corrosion resistance, and biocidal control. The architecture comprises:an adhesion layer, typically from 50 nm to 300 nm in thickness, promoting adhesion to the substrate;a transition layer, typically from 500 nm to 2000 nm in thickness, providing mechanical stability and corrosion resistance, preferably composed of graded nitrides or oxynitrides; anda top layer, typically from 200 nm to 2000 nm thick, which constitutes the active surface. The top layer may adopt one of two configurations: a multilayer stack of nanolayers, each 5 - 40 nm thick, alternating between active and passive materials; or a composite matrix in which active nanoparticles, having diameters between 5 nm and 50 nm, are uniformly embedded within a solid passive matrix. This hierarchical structure enables controlled release of the active agent while maintaining structural integrity.

[0046] The disclosed nanostructured coating exhibits multifunctional performance, combining high corrosion resistance, mechanical durability, and antibiofouling activity. Corrosion rates, calculated applying the ASTM G102-89 standard, ASTM G102-89:2023 - Standard Practice for Calculation of Corrosion Rates and Related Information from Electrochemical Measurements, are below 0.008 mm / year when tested in 3.5 wt.% NaCI aqueous solution. Mechanical performance, determined via nano-indentation and scratch testing, according to the conditions aforementioned, demonstrates hardness between 2 GPa and 10 GPa, adhesion strength between 30 N and 80 N, and a specific wear rate below 0.001 mm3 / Nm in reciprocating ball tests using a 6 mm diameter SiO2ball with 1 N force immersed in the same saline medium. The antibiofouling action is effective against representative microorganisms such as Cobetia marina and Staphylococcus aureus. The biocidal component constitutes a maximum of 40 atomic % of the total coating composition, ensuring environmentalsafety while permitting a controlled release of up to 40 ppm of the active species into the surrounding medium.

[0047] In a preferred embodiment, the coating is electrochemically activated to initiate and control the release of the biocidal agent. The activation is achieved by applying an electrical potential between 0.001 V and 1.2 V, either continuous or pulsed, across the coated surface acting as a working electrode and an inert counterelectrode, such as graphite, titanium or platinum. Reversing the polarity, applying between -1.2 V and -0.001 V, deactivates the release process. Suitable electrolytes for activation include saline solutions, such as 0.1-10% NaCI, artificial seawater, simulated body fluids, such as Hank's solution, SBF, PBS, artificial saliva, Fukuyama or sweat solutions, and other conductive liquids allowing ionic transport. This activation method enables a reversible, fine-tuned control of the biocidal release without damaging the coating or the substrate.

[0048] In an embodiment, the coating, whether activated or non-activated, is applicable to articles exposed to microorganisms, including bacteria, microalgae, viruses, protozoa, fungi, or mammalian cells. Typical examples include marine vessel hulls, offshore structures, water-treatment modules, biomedical implants, hospital touch surfaces, and food-processing equipment. The combination of biocidal and selfcleaning functionalities ensures long-term performance with reduced maintenance and minimised environmental impact.

[0049] In an embodiment, the total thickness of the nanostructured coating is controlled to not exceed 3 pm, which balances the requirements of mechanical stability, flexibility, and deposition time. This limitation allows efficient use in thin-film applications and ensures compatibility with precision components and micro-devices, without significantly altering their dimensions or surface topology.

[0050] In an embodiment, the coating is preferably produced by plasma-assisted deposition techniques, particularly magnetron sputtering, plasma-enhanced chemical vapour deposition (PECVD), or hybrid PVD / CVD processes. The plasma environment promotes dense, adherent films with controlled stoichiometry and nanoscale architecture. Process parameters such as power density, substrate bias, workingpressure, and reactive gas flow are adjusted to achieve the desired phase distribution between the passive matrix and the active biocidal agent.

[0051] In an embodiment, the nanostructured coating can be deposited on a wide variety of substrate materials, including metallic, such as stainless steel, titanium, aluminium alloys, polymeric, such as polyether ether ketone (PEEK), Polytetrafluoroethylene (PTFE), Poly(methyl methacrylate) (PMMA), ceramic, glass, or composite substrates. This broad compatibility results from the presence of the adhesion layer, which accommodates differences in thermal expansion and surface chemistry, ensuring strong adhesion and stable performance under different environmental or operational conditions.

[0052] Figure 1 shows a schematic representation of an embodiment of the processing of the nanostructured coating using a hybrid magnetron co-sputtering system in a reactive atmosphere, such as argon + any reactive gas, which could be oxygen, nitrogen, C2H2, among other suitable gases.

[0053] Figure 2 illustrates a photographic representation exhibiting the top and crosssection micrographs of an embodiment of the nanostructured coating obtained by scanning electron microscopy.

[0054] Figure 3 illustrates a photographic representation exhibiting the details of the transition between the graded nitride and top layer of an embodiment of the nanostructured coating obtained in high magnification transmission electron micrographs and its respective chemical composition distribution through an elemental mapping. From this photographic representation, it is also possible to see that the matrix encapsulates the biocidal nanoparticles entirely, limiting the action of the active material when exposed to air and their impact over other properties in working conditions, such as hardness, Young modulus, adhesion critical load, corrosion resistance, among others.

[0055] Figure 4 illustrates a schematic representation of an embodiment of the setup for the electrochemical activation of the nanostructured coating.

[0056] Figure 5 illustrates a photographic representation exhibiting the antibiofouling action of an embodiment of the nanostructured coating. In the test, it was tested theinteraction with Cobetia marina was tested, with an outstanding reduction of the bacteria on the surface.

[0057] Figure 6 illustrates the results of potentiodynamic polarisation tests, using a GAMRY reference 600 potentiostat, 1 mV / s scan rate, from -1 V to + 2 V, in a three-cell configuration with saturated Ag / AgCI, platinum and the coating as reference, counter and working reference, respectively and 3.5 % w / w NaCI solution as electrolyte, made for the comparison of an activated nanostructured coating and a non-activated nanostructured coating. From said comparison, it is possible to establish the superior corrosion resistance of the activated nanostructured coating when compared to a nonactivated sample.

[0058] Figure 7 illustrates the graphic representation of the Cu 2p spectra of ZrN-Cu(A) without etching cleaning. This graphic comprises a unique peak at approximately 933.4 eV, which corresponds to the CuO binding energy [1],

[0059] Figure 8 illustrates the graphic representation of the open circuit potential (OCP) of Cu, ZrN and ZrON coatings in 3.5 % w / w NaCI solution for 3600 seconds. Here, the Zr(O)N coatings are nobler than Cu, confirming that oxidised zirconium (oxy)nitrides can work as the cathode in the galvanic cell with the inner copper in the coating when it is activated electrochemically.

[0060] Figure 9 illustrates the photographic representation of Biofilm (C. Marina) formed over a ZrN film after 24 hours and applying a +0.5 V potential, demonstrating that the electrical potential does not influence the antibiofouling action of the coating.

[0061] The term "comprising" whenever used in this document is intended to indicate the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0062] Where ranges are given, endpoints are included. Furthermore, it is to be understood that unless otherwise indicated or otherwise evident from the context and / or the understanding of one of ordinary skill in the art, values that are expressed as ranges can assume any specific value within the stated ranges in differentembodiments of the invention, to the tenth of the unit of the lower limit of the range, unless the context clearly dictates otherwise

[0063] The disclosure should not be seen in any way restricted to the embodiments described, and a person with ordinary skill in the art will foresee many possibilities for modifications thereof. The above-described embodiments are combinable.

[0064] The following dependent claims further set out particular embodiments of the disclosure.

[0065] References[1] W. Lin, Y. Zhao, G. Edwards, Q. Guo, T. Chen, S. Song, M. Heitzmann, D. Martin, L.Grpndahl, M. Lu, H. Huang, Mechanical properties and scratch recovery of nanoclay / polyester composite coatings for pre-coated metal (PCM) sheets, Compos. Part B Eng. 273 (2024). https: / / doi.Org / 10.1016 / j.compositesb.2024.111217.

Claims

C L A I M S1. A nanostructured coating for controlled biocidal and self-cleaning functions, comprising:an adhesion layer deposited on a substrate;a transition layer deposited on the adhesion layer; anda top layer comprising a passive matrix phase and a biocidal active phase; wherein the transition layer promotes mechanical compatibility between the adhesion layer and the top layer bounding the layers;wherein the coating is configured to electrochemically release biocidal species in response to an applied electrical potential, while maintaining corrosion resistance and mechanical hardness; andwherein the coating is electrochemically reversible, such that the biocidal release is controllable and stoppable by adjusting or reversing an electrical potential.

2. The nanostructured coating according to the previous claim,wherein the adhesion layer is selected from Ti, Zr, Cr, Nb, Ta, and their combinations;wherein the transition layer is selected from graded nitrides, oxynitrides, and their combinations.

3. The nanostructured coating according to any of the previous claims, wherein the top layer is configured as a multilayer stack of nanolayers, each from 5 to 40 nm thick, alternating between active and passive materials.

4. The nanostructured coating according to any of the previous claims 1 to 2, wherein the top layer is configured as a composite matrix in which active nanoparticles, having diameters from 5 nm to 50 nm, are uniformly embedded within a solid passive matrix.

5. The nanostructured coating according to any of the previous claims, wherein the passive matrix phase comprises a metal oxynitride of formula Me(C,O)N, whereMe is a transition metal selected from Ti, Zr, Cr, Nb, or Ta, or a carbon-based matrix selected from DLC or a-C:H.

6. The nanostructured coating according to any of the previous claims, wherein the biocidal active phase comprises a biocidal agent selected from Cu, Ag, Zn and their oxides or nitrides (CuO, AgO, ZnO, CuN, AgN, ZnN).

7. The nanostructured coating according to any of the previous claims, wherein the biocidal active phase is encapsulated or embedded within the passive matrix phase.

8. The nanostructured coating according to any of the previous claims, wherein the adhesion layer comprises a thickness of 50 to 300 nm, preferably from 100 to 290 nm, more preferably from 150 to 250 nm.

9. The nanostructured coating according to any of the previous claims, wherein the transition layer comprises a thickness of 500 to 2000 nm, preferably from 550 to 1950 nm, more preferably from 800 to 1800 nm.

10. The nanostructured coating according to any of the previous claims, wherein the top layer comprises a thickness of 200 to 2000 nm, preferably from 300 to 1900 nm, more preferably from 400 to 1800 nm.

11. The nanostructured coating according to any of the previous claims, wherein the total coating thickness does not exceed 3 pm, preferably from 1.5 to 2.9 pm, more preferably from 1.9 to 2.8 pm.

12. The nanostructured coating according to any of the previous claims, wherein the top layer is structured as alternating nanolayers of active and passive materials.

13. The nanostructured coating according to any of the previous claims, wherein the total concentration of biocidal agent is lower than or equal to 40 at. % and the released amount of active species does not exceed 40 ppm under electrical activation.

14. The nanostructured coating according to any of the previous claims, wherein the coating is deposited by a reactive hybrid magnetron sputtering process combining HiPIMS and DC or RF power sources, in a plasma atmosphere containing an inert gas (Ar, He, Ne) and a reactive gas (N2, O2, CH4, C2H2).

15. The nanostructured coating according to any of the previous claims, wherein activation occurs by applying an electrical potential between 0.001 V and 1.2 V between the coated surface and an inert counter electrode, the potential being continuous or pulsed.

16. The nanostructured coating according to the previous claim, wherein reversing the potential between -1.2 V and -0.001 V deactivates or reverses the biocidal release.

17. A method of manufacturing the nanostructured coating described in any of the claims 1-16, comprising the steps of:depositing the adhesion layer on the substrate;depositing the transition layer by reactive magnetron sputtering;co-depositing the passive matrix phase and the biocidal active phase under controlled plasma conditions; andoptionally applying an electrical potential in an electrolyte to activate or stop the biocidal release.

18. An article comprising the nanostructured coating according to any of claims 1-16.

19. The article according to the previous claim, wherein the article is selected from a list consisting of marine hulls, offshore structures, architectural panels, biomedical implants, fluidic devices, and their combinations.

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