Coupling agent, coating system comprising the same, related method and uses

Abstract

A coupling agent (10A) is provided, the coupling agent configured to bind to heterogenous substrate surfaces (12-1, 12-2) and comprising at least two non-identical functional groups R1 and R2. By virtue of its functional groups the coupling agent renders heterogenous substrate surfaces with enhanced receptiveness to adhesion of subsequent chemical substances, such as surface coatings. A coating system comprising the coupling agent, a method for adapting heterogenous substrates to surface coatings, and related uses of the coupling agent and / or the coating system are further provided.

Description

[0001]COUPLING AGENT, COATING SYSTEM COMPRISING THE SAME, RELATED METHOD AND USES FIELD OF THE INVENTION The present invention generally relates to compounds and methods for surface- modification of heterogenous substrates aiming at improving adhesion of coatings on said substrates. In particular, the invention concerns multifunctional precursor compounds that adapt the substrates with distinct site-specific surface characteristics to further coatings. BACKGROUND OF THE INVENTION Chemical deposition methods in vapour phase, such as Chemical Vapor Deposition (CVD) and Atomic Layer Deposition (ALD) are well-established techniques to deposit a variety of different thin film materials in highly conformal manner. Amongst those, ALD is based on alternating self-saturating surface reactions, wherein different reactants (precursors) provided as molecular compounds or elements in a nonreactive (inert) gaseous carrier are sequentially pulsed into a reaction space accommodating a substrate. Deposition of a reactant is followed by purging the substrate by inert gas. Conventional ALD cycle (a deposition cycle) proceeds in two half-reactions (pulse first precursor – purge; pulse second precursor – purge), whereby a layer of material referred to as a deposition layer is formed in a self-limiting (self-saturating) manner, typically being 0.05–0.2 nm thick. The cycle is repeated as many times as required for obtaining a film with a predetermined thickness. Typical substrate exposure time for each precursor ranges within 0.01–1 seconds. Common ALD precursors include metal oxides, elemental metals, metal nitrides, metal sulfides, metal halides, metal alkylamides and water, for example. Hence, ALD offers an effective method to provide conformal coatings over entire substrates without modifying core material. However, ALD coatings have experienced problems when deposited on complex heterogenous substrates with multiple and diverse growth surfaces, such as used in biomedical applications, for example. These substrates may include surfaces made of ceramics, polymers, metals and other materials at once. Chemical reactivity of these layers is different as well, which leads to different nucleation behavior of any ALD film deposited on a sample, causing local variation in stress and adhesion force, which ultimately lead to coating failure when the film is stressed (for example, when the sample's functionality is tested by exposing it to operational (target) environment and / or applying electricity thereto). Poor adhesion of the coating results in dissatisfactory reliability of a coated item, which is absolutely unacceptable in case of medical instruments and particularly implants, and low / inconsistent yield of the process. Area-selective deposition methods, as well as the use of self-assembled monolayers (SAMs) as chemically selective mask layers is well-known. However, the SAMs studied so far appear to exhibit selective reactivity toward individual materials, which does not address the challenges outlined above. Additionally, attempts to adapt flexible substrates to coatings with high elastic moduli, such as those deposited with molecular layer deposition techniques, for example, in order to achieve good adhesion while preserving flexibility, have been unsuccessful so far. In this regard, an update in the field of development of coating systems for diverse and / or multicomponent substrates is still desired, in view of addressing challenges associated with achieving reasonable adhesion of coatings on substrates used in manufacturing of biomedical devices and / or (bio)electronic solutions. SUMMARY OF THE INVENTION An objective of the present invention is to solve or to at least alleviate each of the problems arising from the limitations and disadvantages of the related art. The objective is achieved by various embodiments of a coupling agent according to what is defined in independent claim 1. In an embodiment, the coupling agent is configured to bind to a heterogenous substrate comprising non-identical surface areas and / or surface areas made of different materials and to render said surface areas with enhanced receptiveness to adhesion of a subsequent coating. The coupling agent can thus be viewed as a surface-modification agent which adapts substrate surfaces, having in unmodified form different ability to interact with molecules arriving thereat, to anchor said molecules with such binding capacity, binding strength and reactivity, that an essentially uniform coating layer is formed throughout the heterogenous substrate. The term “receptiveness” is used herewith to define ability of a molecule or a compound to interact with another molecule or compound with formation of stable chemical bonds. The coupling agent thus evens out the differences in receptiveness of heterogenous substrate surface areas to the molecules of a subsequent coating. In an embodiment, the coupling agent is configured to bind to the substrate surface areas made of two or more different materials. In embodiments, the coupling agent is configured to bind to materials selected from metals and metal alloys, polymers, ceramics, composite materials, and combinations thereof. In an embodiment, the coupling agent is configured to render the entire substrate surface with essentially equal reactivity towards the coating substance. In an embodiment, the coupling agent is configured to bind to the heterogenous substrate comprising surface areas made of at least two different materials. In such an event the coupling agent comprises at least two non-identical functional groups, each of said functional groups having specific reactivity towards material of a corresponding substrate surface area. The coupling agent is configured to modify a surface of said heterogenous substrate to render the substrate surface areas with enhanced (more uniform) receptiveness to adhesion of a subsequent coating. This is implemented by virtue of having at least one of the functional groups of the coupling agent reacted with the material of the corresponding substrate surface area (i.e. the surface area, towards which said functional group has specific reactivity), as at least one other functional group of said coupling agent remains available for reaction(s) with molecules of the subsequent coating. In an embodiment, the coupling agent comprises at least two non-identical functional groups, wherein each functional group is independently selected to possess site-specific reactivity towards a particular substrate surface area, also referred to as a target surface area. In an embodiment, the coupling agent comprises at least three non-identical functional groups, wherein each functional group is independently selected to possess site-specific reactivity towards a particular substrate surface area. In an embodiment, the coupling agent is represented with a molecule comprising a hydrocarbon skeleton structure X with at least two non-identical functional groups R1and R2connected thereto, wherein X is selected from the group consisting of: (i) linear or branched structures comprising alkanes, alkenes or alkynes with 2-12 carbon atoms, (ii) aromatic structures comprising cycloalkanes or cycloalkenes with 3-12 carbon atoms, or (iii) benzene derivatives, and wherein any one of said at least two non-identical functional groups R1and R2is independently selected from the group consisting of: a thiol group (–SH), an amine group (–NH2), a hydroxyl group (–OH), a carboxyl group (–СООН), an aldehyde group (–CHO), a phosphate group (H2PO3), a C1-C6 alkyl group, a halogen group, and a silane group (–SiR'3), where R' is represented with hydrogen or alkoxy group (–OR"), in which R" is C1-C6 alkyl or hydrogen. Silane coupling can further be used to couple any other appropriate functional group or moiety to the hydrocarbon skeleton structure X. In another aspect, a coating system for a substrate comprising non-identical surfaces areas and / or surface areas made of different materials is provided, according to what is defined in the independent claim 8. In an embodiment, the coating system comprises: a coupling layer comprising or consisting of the coupling agent according to some previously defined embodiments and configured, when deposited on the substrate surface, to render essentially heterogenous target substrate surface areas with enhanced, in terms of (adhesion) uniformity, receptiveness to adhesion of a subsequent deposition layer, and a deposition layer or layers deposited over the coupling layer and formed through a process of chemical deposition in vapour phase, preferably, through Atomic Layer Deposition (ALD). In an embodiment, the coupling layer of said coating system is a self-assembled monolayer (SAM). In embodiments, deposition layers of said coating system are composed of any compound selected from the group consisting of: aluminium(III) oxide (Al2O3), titanium(IV) oxide (TiO2), hafnium(IV) oxide (HfO2), tantalum(V) oxide (Ta2O5), zirconium(IV) oxide (ZrO2), niobium(V) oxide (Nb2O5), yttrium oxide (Y2O3), magnesium oxide (MgO), zinc oxide (ZnO), silicon dioxide (SiO2), aluminium nitride (AlN), titanium nitride (TiN), gallium nitride (GaN), niobium nitride (NbN), silicon nitride (SiNx), and any combination thereof. Other oxide- or nitride compounds can be used where appropriate. In some configurations, the deposition layer(s) can be further composed of carbides, selenides, sulfides, and tellurides, as well as pure metals. In some other configurations, the coating system can comprise hybrid metal-organic films containing inorganic clusters, such as for example aforementioned metal oxide clusters, linked with organic molecules, such as polymers. In an embodiment, at least one deposition layer of the coating system is a Molecular Layer Deposition (MLD) film. In some configurations, said MLD film is a pure organic film or a hybrid organic-inorganic polymer film, such as for example poly(aluminum trioxysilylheptanoate) (Al-TOSH). In an embodiment, in said coating system the MLD film is deposited over the coupling layer. In an embodiment, said deposition layers are arranged into a stack on / over the coupling layer laid, in turn, against the substrate. In some embodiments, said stack is formed with a plurality of inorganic ALD layers, which in some instances alternate with MLD films. Total thickness of the coating system is provided, in embodiments, within a range of about 5 nm to about 500 nm, preferably, within a range of about 10 nm to about 300 nm, still preferably, within a range of about 50 nm to about 150 nm. In another aspect, a method for adapting heterogenous substrates to surface coatings is provided, according to what is defined in the independent claim 17. In an embodiment, the method comprises: on a substrate comprising surface areas made of at least two different materials, depositing a coupling agent comprising at least two non-identical functional groups having specific reactivity towards materials of corresponding substrate surface areas, wherein, by virtue of at least one of the functional groups of the coupling agent reacting with the material of the corresponding substrate surface area, a coupling layer is formed that renders said essentially heterogenous substrate surface areas more uniformly receptive to adhesion of a subsequent coating by virtue of having at least one functional group of the coupling agent available for subsequent reactions with molecules of said subsequent coating. In embodiments, the coupling agent is represented with a compound of Formulae (I), (II), (III), as described in detail herein below. In a further aspect, use of the coupling agent according to previously defined embodiments is provided to modify surfaces of heterogenous substrates in order to make said heterogenous substrate surfaces more uniformly receptive to adhesion of subsequent coatings, according to what is defined in the independent claim 20. The substrate surface(s) to be modified encompass the substrate’s external surfaces and / or internal surfaces. The term “internal surfaces” is used, in present context, to define surfaces inside internal cavities, pores or perforations within the substrate. For example, for porous substrates, the surfaces to be modified may localize inside the pores. Complex 3D-shaped substrates may also comprise external and internal surfaces. In still further aspect, an item is provided according to what is defined in the independent claim 21, said item comprising a heterogenous substrate with non- identical surface areas and / or surface areas made of different materials and further surface-modified with the coupling agent according to previously defined embodiments. In embodiments, the item is configured as a medical device, a printed circuit board (PCB), a PCB assembly (PCBA) and / or an electrical component. The utility of the present invention arises from a variety of reasons depending on each particular embodiment thereof. The invention provides for a novel compound, referred to as a coupling agent or a surface-modification agent, that renders surface areas of essentially heterogenous substrates with enhanced receptiveness to adhesion, by chemisorption, of a subsequent coating, such as an ALD film. The compound is effectively a bi-, tri- or multi-substituted molecule configured, by virtue of its functional groups, to bind to the surface of a variety of (substrate) materials and hence make the diverse substrate surface homogenic in terms of its capability to further interact with ALD precursor chemicals. In this manner, potential failure sites that appear due to delamination can be reduced. Substrate surfaces may include metals, ceramics, and polymers of synthetic or natural origin, as well as their composites and combinations, having different chemical reactivity towards subsequent coatings. Provision of the coupling agent disclosed hereby allows to overcome problems associated with different nucleation behavior of ALD films deposited on diverse substrates, as well as lattice mismatch associated failures. By virtue of the coupling agent, local variations in residual stress and adhesion force commonly causing coating failures in operational environments can be avoided. The coupling agent as described herewith is applicable for use with any kind of substrate and enable deposition of either rigid or flexible coatings. In the present disclosure, materials with a layer thickness below 1 micrometer (µm) are referred to as “thin films”. The terms “film” and “coating” are used in the present disclosure interchangeably to define a layer or layers of a substance that covers a surface of a substrate. Same meaning is preserved when these terms are used in combination, e.g. in an expression “coating film”. The term “stack” is used in the present disclosure to indicate a layered structure, which comprises two or more layers arranged on top of one another. The stack comprises layers deposited with chemical deposition methods, including ALD, it’s analogues and modifications (such as for example plasma enhanced- or photon enhanced ALD), and in some instances, MLD, unless explicitly indicated otherwise. The term “item” is used in the present disclosure to indicate a separate physical object implemented as a discrete (non-separable) entity (e.g. a medical screw) or as a kit-of-parts, which undergoes coating by the methods disclosed herewith. The item may be implemented with or without electronic components. Exemplary items with electronic components include so-called smart implants (implants including measurement devices to measure various physical parameters in the body), sensors, and the like. In some instances, the item may be provided as a part of a system or a larger entity. A non-coated item may be referred to, in the present disclosure, as a “substrate”. The term “medical device” is used, in the present disclosure, to refer to any device (instrument, apparatus, appliance, etc.) intended to be used for medical purposes. Particular applications of the coated item configured as a medical device, such as for example in orthopedics, are presented herewith. The expressions “reactive fluid” and “precursor fluid” are indicative in the present disclosure of a fluidic flow comprising at least one chemical compound (a precursor compound), hereafter, a precursor, in an inert (gas) carrier. In some instances, precursor fluid contains a precursor compound co-dosed with another precursor compound in inert gas carrier. The term “molecule” is referred to in the present disclosure to a group of two or more atoms held together by chemical bonds. Molecules that include combinations of solely one type of atom are referred to as “elements”. Molecules that include combinations of different types of atoms are referred to as “compounds”. Hence, the molecule designates the smallest particle into which an element or a compound can be divided without changing its chemical and physical properties. The term “chemisorption” is used in the present disclosure to refer to chemical adsorption, which is a process of creating ionic or covalent chemical bonds between adsorbate molecules (where “adsorbate” is a substance that undergoes chemical reaction, via a process of adsorption, on the surface) and specific surface locations on a substrate material (adsorbent), whereupon the adsorbate molecules become anchored to the substrate surface. The term “material” is used herewith to indicate a matter or a substance of a physical nature of which something is composed or can be made. In the present disclosure, the term “body” (in the context of the expressions “body implantable” etc.) is used primarily with regard to a human. However, the concept of the present invention is fully applicable to the items, such as medical devices, designed and / or used with a nonhuman mammal or other animal. The expression “a number of” refers herein to any positive integer starting from one (1), e.g. to one, two, or three; whereas the expression “a plurality of” refers herein to any positive integer starting from two (2), e.g. to two, three, or four. The terms “first” and “second” are not intended to denote any order, quantity, or importance, but rather are used to merely distinguish one element from another, unless explicitly stated otherwise. BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1A-1C and Figs. 2A-2C schematically illustrate a process of surface- modifying a heterogenous substrate with a coupling agent, according to the embodiments. Fig. 2D schematically illustrates one of the process stages for surface-modifying heterogenous substrate with a coupling agent, according to some embodiment. Figs. 3A and 3B schematically illustrate coating systems, according to the embodiments, deposited on the substrate. DETAILED DESCRIPTION OF THE EMBODIMENTS The present invention pertains to novel compounds selectively reactive to multiple diverse materials, where material-specific reactions occur at the same time. This is achieved by provision of a coupling agent 10A configured to simultaneously bind to a number of materials non-identical in terms of composition and / or any one of binding capacity, binding strength and reactivity towards other substances. Binding capacity is defined as the ability of a molecule (element or compound) to bind or attach to another molecule; and binding strength or binding affinity – as the strength of binding interaction between two molecules. Reactivity is, in turn, defined with the relative capacity of a molecule to enter and / or to undergo chemical reaction with another molecule. In embodiments, the coupling agent 10A is a chemical compound, which binds to substrate surface areas made of different materials (see areas 12-1, 12-2, 12-3 and 10-4 with different fill patterns shown on Figs. 1A-1C and Figs. 2A-2D) and / or having different characteristics with regard to interaction with substances envisaged as coatings (to be applied on the target surface of substrate), and renders these surface areas with enhanced, in terms of uniformity, receptiveness to adhesion of said further substances. In embodiments, the compound 10A can be configured to bind, through a process of chemical adsorption (chemisorption), to different substances essentially simultaneously and / or with essentially the same binding strength to cover the entire substrate surface with all non-identical surface areas as described above. In this regard, the compound 10A enables improved chemisorption of different substances to the substrate as explained herein above and further – renders essentially heterogenous target surface areas 12-1, 12-2, 12- 3, 12-4 with more uniform receptiveness to chemisorption of a subsequent coating. The compound 10A thus acts as an adapter molecule which enhances the substrate surface ability to bind subsequent coatings. As mentioned hereinabove, depending on material the substrate is made from, the substrate surface may include external and / or internal surfaces (the latter is particularly applicable for profiled, porous and / or perforated substrates, as well as substrates of complex 3D shapes). By binding to surface areas with distinct characteristics, the compound 10A renders said areas with essentially equal or similar reactivity towards further substances envisaged as coatings. Overall, by having the compound 10A bound on the substrate surface(s), provision of uniform, continuous coating throughout the substrate surface can be achieved. In embodiments, the compound 10A prepares the substrate surface for binding a coating formed through a process of chemical deposition in vapour phase, such as Atomic Layer Deposition (ALD) or Molecular Layer Deposition (MLD). A process of surface-modifying a substrate 12 with the coupling agent 10A realized according to an embodiment is schematically illustrated on Figs. 1A-1C and 2A-2D. Substrate materials comprise or consist of metals, metal alloys, ceramics, and polymers of synthetic or natural origin, as well as their composites and combinations, having different chemical reactivity towards subsequent coatings. The substrates may comprise or consist of biomaterials, defined herewith as any one of metal-, ceramic, and / or polymer-based materials to be used in contact with human body in biomedical applications, including, but not limited to medicine, dentistry, medical devices, biosensors, implants, drug delivery systems, scaffolds for tissue engineering, etc. The substrates may further comprise or consist of synthetic fibers. In some configurations, substrate materials include, but are not limited to metals and metal alloys, polymers, ceramics, and composite materials. Metal alloys are provided as mixtures of metal elements with other metals and / or non-metals, where non-metals can be for example silicon or carbon. Common metal alloys include steel, provided as a series of iron alloys with chromium (for form stainless steel), nickel, silicon, carbon, and other elements. The substrates may further include any one of: semiconductors, biomaterials, smart materials, and nanoengineered materials. Metal substrates include, but are not limited to transition metal elements, such as for example titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), and gold (Au); basic metal elements, such as for example aluminium (Al), alkali metal elements, such as for example lithium (Li), alkaline earth metal elements, such as for example magnesium (Mg). In some configurations, the substrate materials are metal elements from a group of so-called noble metals, commonly defined as platinum group metals, namely ruthenium, rhodium, palladium, osmium, iridium, platinum, and, additionally, gold and silver. In some classifications, also copper, rhenium and mercury are assigned to noble metals. Metal elements mentioned above can be provided, in the metal substrate, alone (pure metal substrate) or as a part of an alloy composition. Ceramic materials or “ceramics” are referred to in the present disclosure primarily as metal and non-metal oxide, nitride and carbide compounds. In embodiments, ceramic substrates include aluminum oxide (alumina, Al2O3), silicon dioxide (silica, SiO2), silicon carbide (SiC), and silicon nitride (Si3N4). In some instances, ceramic substrates may comprise or consist of clay materials (e.g. porcelain) or glass. Utilization of other ceramic substrates is not excluded. Polymer substrates preferably include heat-resistant plastics and resins, e.g. thermoplastics. Composite substrates are typically composed of two or more of materials discussed above, viz., metals and their alloys, ceramics and polymers. Exemplary composite materials include glass fiber reinforced polymers (fiberglass), carbon fiber reinforced polymers, ceramic-metal composites (cermets), and the like. In embodiments, the substrate has a surface with surface areas or sites 12-1, 12-2, 12-3, 12-4 made of two or more non-identical materials. A process of surface- modifying heterogenous substrates comprising surface areas made of two- and three different materials is schematically illustrated by Figs.1A-1C and Figs.2A- 2C, respectively. The process may further be modified for substrates made of multiple materials, as shown on Fig.2D. Fig.1A thus shows depositing the compound 10A on the substrate 12 comprising surface areas 12-1 and 12-2 made of at least two different materials. Fig. 2A, in turn, shows depositing the compound 10A on the substrate 12 comprising surface areas 12-1, 12-2 and 12-3 made of at least three different materials. By way of example, but not limitation, the substrate 12 may be made predominantly of composite material (area 12-1) and include metal parts (areas 12-2 and 12-3) made of copper and / or platinum. Any other configuration may be conceived involving substrate materials described herein above. The compound 10A comprises at least two non-identical functional groups R1, R2, wherein each functional group is independently selected to possess specific reactivity towards material of a corresponding surface area 12-1, 12-2, 12-3, 12-4 … 12-x, but not to the rest of the substrate surface (see Figs. 1B, 2B and 2D). In the example shown on Fig. 1B, the compound 10A has two functional groups R1and R2configured to possess specific reactivity towards the substrate surface areas 12-1 and 12-2, respectively. In some configurations, the compound 10A comprises two or more non-identical functional groups R1, R2, R3, R4, (Figs.2B, 2D). The functional groups are selected such, as to possess specific reactivity towards different substrate surface areas such as those illustrated as12-1, 12-2, 12-3 and 12-4, respectively. For example, if the functional group R1reacts with the material of the surface area 12-1 with sufficiently high affinity, it has lower- or no affinity to any one of materials 12-2, 12-3 and / or 12-4. Functional groups R are selected such, as to avoid cross-reactions and / or polymerization. The coupling agent 10A is preferably represented with a molecule comprising a hydrocarbon skeleton structure X with at least two non-identical functional groups R1and R2connected thereto, wherein X is preferably selected from the group consisting of: (i) linear or branched structures comprising alkanes, alkenes or alkynes with 2-12 carbon atoms, (ii) aromatic structures comprising cycloalkanes (also known as naphthenes) or cycloalkenes with 3-12 carbon atoms, or (iii) benzene or its derivatives. Hydrocarbon skeleton structure X may include at least one heteroatom (an atom other than carbon), including, but not limited to nitrogen (N), oxygen (O), phosphorus (P), or sulfur (S). Aromatic structures may be represented with homo- and heterocyclic ring systems. Mono-, bi-, tri- and multicyclic structures may be conceived. Each of said at least two functional groups R1and R2can be connected to the hydrocarbon skeleton structure X at a carbon atom or via heteroatom including, but not limited to nitrogen (N), oxygen (O), phosphorus (P), or sulfur (S). In embodiments, functional groups are connected to the hydrocarbon backbone X via side chains comprising 0-2 carbon atoms. Any one of the at least two functional groups R1and R2is independently selected from the group consisting of: a thiol group (–SH), an amine group (–NH2), a hydroxyl group (–OH), a carboxyl group (–СООН), an aldehyde group (–CHO), a phosphate group (H2PO3), a C1-C6 alkyl group, a halogen group, and a silane group (–SiR'3), where R' is represented with hydrogen or alkoxy group (–OR"), in which R" is C1-C6 alkyl or hydrogen. Silane coupling can further be used to couple any other appropriate functional group or moiety to the hydrocarbon skeleton structure X. Halogen group is preferably represented with fluorine; however, e.g. chlorine or other halogen substituents are not excluded. In an embodiment, the coupling agent 10A is represented with a molecule of general formulae (I), (II) or (III): wherein X is a structure having a hydrocarbon skeleton selected from the group consisting of: (i) linear or branched structures comprising alkanes, alkenes or alkynes with 2-12 carbon atoms, (ii) aromatic structures comprising cycloalkanes or cycloalkenes with 3-12 carbon atoms, or (iii) benzene or its derivatives; wherein n is 0, 1 or 2; and wherein any one of R1, R2, R3and R4is independently selected from the group consisting of: a thiol group (–SH), an amine group (–NH2), a methyl group (–CH3), a hydroxyl group (–OH), a carboxyl group (–СООН), an aldehyde group (–CHO), a phosphate group (H2PO3), a halogen group, and a silane group (–SiR'3), where R' is represented with hydrogen or alkoxy group (–OR"), in which R" is C1-C6 alkyl or hydrogen. Compound 10A thus comprises a hydrocarbon skeleton structure X with a substantially rigid carbon backbone with or without side chains (where n designates a number of carbon atoms in a side chain). Addition of short side chains (n = 1 or 2) adds flexibility and increases volatility of the molecule 10A. By way of example, thiol groups possess reactivity towards noble metals; amine groups possess reactivity towards copper or steel; and hydroxyl groups possess reactivity towards metal oxides. On the other hand, for example silanes react with hydroxyl groups (water molecules) to form strong covalent bonds, while for example methyl group (–CH3) and halogen enable additional adjustment of volatility and / or reactivity. In an embodiment, the coupling agent 10A is represented with the molecule of general formula (II) shown above comprising a backbone structure X as described above, wherein any one of R1, R2and R3is independently represented with a) a thiol group (–SH), b) an amine group (–NH2), or a phosphate group (H2PO3), and c) a hydroxyl group (–OH), a carboxyl group (–СООН), an aldehyde group (– CHO), or a silane group (–SiR'3), where R' is represented with hydrogen or alkoxy group (–OR"), in which R" is C1-C6 alkyl or hydrogen. In an embodiment the coupling agent 10A is represented with the molecule of general formula (III) shown above comprising a backbone structure X as described above, wherein any one of R1, R2, R3and R4 is independently represented with a) a thiol group (–SH), b) an amine group (–NH2), or a phosphate group (H2PO3), c) a hydroxyl group (–OH), a carboxyl group (–СООН), an aldehyde group (–CHO), or a silane group (–SiR'3), where R' is represented with hydrogen or alkoxy group (–OR"), in which R" is C1-C6 alkyl or hydrogen, and d) a C1-C6 alkyl group (e.g. a methyl group (–CH3)) or a halogen group, preferably, fluorine. Some of exemplary implementations of the compound 10A are shown in Table 1 below, where A and B each represents compound 10A comprising a 2C-alkene- or 2C-alkyne backbone (X), respectively, with at least two distinct functional groups R1 and R2; and C and D represent compound 10A comprising aromatic backbone (X) composed of at least three- and at least five carbon atoms, respectively. Implemented at “C”, aromatic backbone may comprise 3-12 carbon atoms (m = 1- 10); and the same implemented at “D” may comprise 5-12 carbon atoms (m = 1- 8), respectively. Compound A(ii) may comprise more than two functional groups, e.g. R1-R4 (not shown). Table 1. Exemplary configurations of the compound 10A (i) (ii) E F In some instances, the compound 10A is a bi-, tri- or multisubstituted benzene derivative (Table 1, E and D). Exemplary embodiment with the coupling agent 10A configured as a tetrasubstituted benzene derivative is shown on Fig.2D. Instead of benzene ring, tetrasubstituted compound of Fig.2D may comprise linear or branched backbone, a naphthene ring system or a cycloalkene ring system. In preferred embodiments, compound 10A is applicable on / over the substrate(s) by vapour-phase deposition methods (vapour exposure in situ). However, appropriate ex situ methods, such as spraying or absorption from solution, are not excluded. Figs.1C and 2C show formation of a coupling layer 10 by virtue of reacting each of the functional groups R1, R2and R3of the compound 10A with the substrate surface areas 12-1, 12-2, 12-3, respectively. The coupling layer 10 adapts the substrates with multiple and diverse surfaces areas (also referred to as “growth surfaces”) to subsequent deposition (growth) of ALD coatings. The coupling layer 10 thus formed on the substrate can be defined as an interfacial region associated with a finite thickness and formed during interaction between the compound 10A, in particular, functional groups thereof, and the underlying substrate. Hence, by virtue of at least one of the functional groups of the coupling agent 10A reacting with the material of the corresponding substrate surface area, the coupling layer 10 is formed that renders essentially heterogeneous target substrate surface areas with enhanced, in terms of uniformity, receptiveness to adhesion of a subsequent coating. By binding to the target substrate, the coupling layer 10 (coupling agent 10A) modifies essentially heterogeneous surfaces of said substrate such, that conditions more favourable for chemisorption of the subsequent coating are established, as at least one functional group of the coupling agent 10A remains available for subsequent reaction(s). The coupling agent 10A / coupling layer 10 thus enhances the substrate’s ability to chemisorb adsorbate molecules in a more uniform manner. Remaining functional group(s) stay unbound to the substrate material. Preferably these remaining groups are selected such as to possess reactivity towards precursor molecules of subsequent coating layers 21, 22, as described herein below. In embodiments, the coupling layer 10 is provided as a self-assembled monolayer (SAM). The coupling layer 10 formed by deposition of the coupling agent 10A on the substrate surface(s) 12-1, 12-2, 12-3, 12-4 … 12-x forms an interfacial layer between the substrate 12 and subsequent coating. Coatings laid on the substrate (pre)coated with the coupling agent are shown on Figs. 3A and 3B. In preferred embodiments, the coating comprises a deposition layer or layers 21, 22 deposited over the coupling layer 10 and formed through a process of chemical deposition in vapour phase, preferably ALD. The basics of an ALD growth mechanism are known to a skilled person. ALD is a special chemical deposition method based on the sequential introduction of at least two reactive precursor species to at least one substrate. It is to be understood, however, that one of these reactive precursors can be substituted by energy when using, for example, photon-enhanced ALD or plasma-enhanced ALD. Thin films grown by ALD are dense, continuous and have uniform thickness. In ALD, the at least one substrate is typically exposed to temporally separated precursor pulses in a reaction vessel to deposit material on the substrate surfaces, also referred to as “growth surfaces”, by sequential self-saturating surface reactions. In the context of present disclosure, the term ALD comprises all applicable ALD based techniques and any equivalent or closely related technologies, such as, for example the following ALD sub-types: plasma-assisted ALD, PEALD (Plasma Enhanced Atomic Layer Deposition), Molecular layer deposition (MLD) and photon-enhanced Atomic Layer Deposition (known also as photo-ALD or flash enhanced ALD). A deposition setup may be the one based on an ALD installation described in the U.S. patent no. 8211235 (Lindfors), for example, or on any installation, such as Picosun R-200, P-300 or P-1000 ALD system, available from Picosun Oy, Finland. Nevertheless, the features underlying a concept of the present invention can be incorporated into any other chemical deposition reactor embodied as an ALD, PEALD, Molecular Layer Deposition (MLD), or a Chemical Vapour Deposition (CVD) device, for example. An exemplary ALD reactor comprises a reaction chamber that establishes the reaction space (deposition space), in which the items / substrates are deposited with the coatings. The reactor further comprises a number of appliances configured to mediate fluidic flow (inert fluids and reactive fluids containing precursor compounds P1, P2, into the reaction chamber. These appliances are provided as a number of intake lines / feedlines and associated switching and / or regulating devices, such as valves, measurement and detection devices, etc. A basic ALD deposition cycle consists of four sequential steps: pulse A, purge A, pulse B, and purge B. Reactive fluid entering the reaction chamber during pulses A and B is preferably a gaseous substance comprising a predetermined precursor chemical (P1, P2) carried by an inert carrier (gas). Delivery of the precursor chemicals into the reaction space and film growth on the substrate is / are regulated by means of the abovesaid regulating appliances, such as e.g. three-way ALD valves, mass-flow controllers or any other device suitable for this purpose. The above-described deposition cycle can be repeated until the deposition sequence has produced a thin film or coating of desired thickness. Deposition cycles can also be either simpler or more complex. For example, the cycles can include three or more reactant vapor pulses separated by purging steps, or certain purge steps can be omitted. On the other hand, photo-enhanced ALD has a variety of options, such as only one active precursor in the corresponding set, with various options for purging. All these deposition cycles form a timed deposition sequence that is controlled by a logic unit or a microprocessor. It is noted that while atomic layer deposition utilizes inorganic materials to generate thin films, the method of molecular layer deposition allows for depositing organic films or organic-inorganic hybrid films. MLD films are softer, and hence less brittle than ALD films. Therefore, MLD films are often used as so-called decoupling layers in order to separate conformal inorganic (ALD) films from the substrate and / or from one another and to minimize defect propagation through the coating film. Defects typically include mechanical damages, such as cracks, scratches, etc., as well as localized delamination and / or other damages induced by a variety of factors, such as exposure to moisture and / or ions, UV light, heat, oxygen, and the like. The coupling layer 10 and one or more deposition layers 21, 22 form a coating system 100, 110 according to another aspect of the present invention. Figs. 3A and 3B show exemplary embodiments of the coating system formed on the substrate 12. Fig. 3A shows the coating system 100 comprising the coupling layer 10 and a coating film formed as an ALD-deposited stack; and Fig.3B shows the coating system 110 comprising the coupling layer 10 and a coating film formed as an ALD-MLD hybrid laminate stack. ALD deposition layers are generally designated with reference numeral 21 (n(21-y); 21-1, 21-2, 21-3, 21-4 and 21-5); and MLD deposition layers are generally designated with reference numeral 22 (n(22-y); 22-1, 22-2, 22-3 and 22-4). Reference is made to Fig. 3A. The coating system 100 of Fig. 3A thus comprises the coupling layer 10 formed with the coupling agent 10A as described herein above and an ALD coating film comprising a number (n) of ALD layers 21-y (ALD deposition layers are not shown). The number of ALD layers may vary with a number of deposition cycles needed to deposit a coating of a predetermined thickness. For example, a 5 nm coating can be deposited in 50-80 deposition cycles, and a 500 nm coating – in 5000-8000 deposition cycles. The ALD-coating film may be provided as a homogenous film (all deposition layers have same composition), or as a (nano)laminate, wherein deposition layers have different composition (not shown). In a latter case, a wide variety of configurations may be conceived, with deposition layers varying in terms of composition and / or arrangement in the stack. Thus, in said ALD-film, one or more deposition layer with a first composition may alternate with one or more layers with a second composition to form a stack. In some configurations, the ALD-film may include deposition layers having third, fourth or further composition not identical to any one of first and / or second compositions. In such an event, deposition layers can be arranged into repetitive patterns, wherein each said pattern comprises one (1) to ten (10), preferably, one (1) to four (4), deposition layers composed of non-identical chemical compounds. Inorganic deposition layers 21 (ALD-deposited layers) can be individually composed of oxide compounds or nitride compounds. Oxide compounds include, but are not limited to: aluminium(III) oxide (Al2O3), titanium(IV) oxide (TiO2), hafnium(IV) oxide (HfO2), tantalum(V) oxide (Ta2O5), zirconium(IV) oxide (ZrO2), niobium(V) oxide (Nb2O5), yttrium oxide (Y2O3), magnesium oxide (MgO), zinc oxide (ZnO), and silicon dioxide (SiO2). Nitride compounds include, but not limited to titanium nitride (TiN), aluminium nitride (AlN), gallium nitride (GaN), niobium nitride (NbN), silicon nitride (Si3N4), and any combination thereof. Utilization of any other appropriate oxide or nitride compound is not excluded. Deposition layer(s) 21 can be further composed of carbides, selenides, sulfides, and tellurides, as well as pure metals, such as for example aluminium, titanium, zirconium, etc. Exemplary ALD coating stacks may be formed with repeating (n times) binary (sub)stacks, such as Al2O3-SiO2, Al2O3-HfO2, Al2O3- ZrO2, Al2O3-Ta2O5, Al2O3- TiO2, Al2O3-MgO, Al2O3-ZnO, HfO2-SiO2, ZrO2-SiO2, MgO-SiO2, ZnO-SiO2, and the like; ternary (sub)stacks or quaternary (sub)stacks, such as for example Al2O3–HfO2–ZrO2, TiO2+[(Al2O3–TiO2)], MgO-Al2O3-SiO2-ZnO, Al2O3–SiO2– Al2O3–TiO2, Al2O3–HfO2–Al2O3–ZrO2, Al2O3–Ta2O5–Al2O3–HfO2, and the like. Coatings utilizing a single inorganic material, such as alumina or silica, can also be formed. Ternary and quaternary sub-stacks may have same or different thickness (e.g. 5nm / 5nm / 5nm / 5nm repeated n times or 5nm / 20nm / 5nm / 20nm repeated n times, etc.). Fig. 3B shows the coating system 110 formed on the substrate 12 and comprising the coupling layer 10 formed with the coupling agent 10A as described herein above and the ALD-MLD film comprising a number of ALD deposition layers 21- 1, 21-2, 21-3, 21-4 and 21-5 alternating with MLD deposition layers 22-1, 22-2, 22-3 and 22-4. Configuration of Fig. 3B is particularly beneficial for coating flexible substrates. In the hybrid coating stack of Fig. 3B, deposition layers 21 (ALD) can be formed with the same compounds as described with regard to Fig. 3A. On the other hand, MLD films 22 (22-1, 22-2, 22-3, 22-4) can be provided as pure organic films or hybrid organic-inorganic films. While in production of pure organic (polymeric) structures, a combination of two or more organic precursors is adopted, hybrid organic–inorganic films are typically synthesized using a combination of inorganic compounds with organic polymers. Common organic precursors are polymer molecules that contain -OH, -COOH, CONH2, -CHO, -NH2, -SH, -CN functional groups, for example. In embodiments, hybrid MLD films include metal alkoxide films formed from metal precursors and various organic alcohols and collectively referred to as “metalcones”. Common metalcone films include alucones, titanicones, and zincones based on reactions of trimethylaluminum (TMA), titanium tetrachloride and diethylzinc, respectively, with various organic alcohols such as ethylene glycol (EG) or glycerol; aromatic organic diols, such as hydroquinone (benzene-1,4-diol), etc. In embodiments, the MLD film is deposited over the coupling layer 10. It is preferred that the MLD film deposited directly on / over the coupling layer 10 has low elastic modulus to efficiently decouple the coating from the substrate. MLD films with elastic moduli 5-10 lower than that of alumina can be advantageously utilized. On Figs. 3A and 3B, MLD film laid directly over the coupling layer is designated with reference numeral 22. In embodiments, the coupling layer 10 formed with the coupling agent 10A forms an interfacial layer between the substrate 12 with a variety of diverse growth surfaces 12-1, 12-2, 12-3 and the MLD (decoupling) film 22. The decoupling MLD layer 22 is typically 15-30 nm film. By way of example, the hybrid coating structure of Fig. 3B may utilize hybrid MLD films 22, 22-1, 22-2, 22-3, 22-4 formed with poly(aluminum trioxysilylheptanoate) (Al-TOSH) based on reaction of TMA with ozone activated 7-octenyltrichlorosilane SAM. MLD film laid (directly) against the coupling layer 10 may have same or different composition than other MLD layers (22-1, 22-2, 22-3, 22-4) in the laminate coating (Fig.3B). It is preferred that a stack formed with a plurality of all deposition layers 21, 22 within the coating has thickness within a range of about 10 nm to about 1000 nm; therefore, the coating structure presented herewith may be referred to as “nanocoating” or “nanolaminate”. Coating stacks comprising deposition layers 21, 22 having thicknesses within a range of 10 nm to 500 nm, preferably, within a range of 20 nm to 300 nm, still preferably, within a range of 50 nm to 150 nm, can be produced. Most typical and, in some instances, preferred ranges for the deposited coatings include 10-300 nm, namely, 25 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, and any value in between. Still, nanolaminate structures having thicknesses exceeding 300 nm (up to about 1000 nm) can be produced in a predetermined number of deposition cycles. Overall, the above values correctly define the thickness of the coating system 100, 110, because thickness of the coupling layer 10 is generally a within a range of a molecular monolayer, i.e. within a range of about 0.5-1 nm. By way of example, the coating deposited as shown on Fig. 3A may comprise a 15-30 nm decoupling MLD layer 22 (laid over the coupling layer 10) and a 75-200 nm inorganic ALD film 21. Deposition process(-es) (ALD, MLD) utilized to produce coating films shown on Figs. 3A and 3B employ deposition temperatures within a range of about 80-200 °C (and up to 250 °C). Deposition within a range of 100-125 °C enables or facilitates coating of heat-sensitive substrates, such as those containing polymers and / or electric circuits. Still, higher deposition temperatures are generally not excluded. The coating system 100, 110 as shown on Figs. 3A and 3B may comprise, as a topmost layer, at least one inorganic deposition layer (see 21-5, Fig. 3B), an organic MLD- or hybrid MLD layer(s) (not shown) or an additional deposition layer formed with any other appropriate method. In some instances, the topmost layer is rendered with an additional functionality, such as mechanical protection and / or protection from corrosive species, or as a dissolving layer to enable time- controlled dissolution. Present invention further pertains to use of the coupling agent 10A described herein above to modify surfaces of heterogenous substrates to make said heterogenous substrates more uniformly receptive to adhesion of subsequent coatings. The coupling agent 10A thus forms a homogenous film (coupling layer 10) over multiple different growth areas 12-1, 12-2, 12-3, 12-4 and adapts the (entire) substrate surface for interacting with ALD / MLD precursors in essentially uniform manner. Still further, the present invention pertains to an item, comprising a heterogenous substrate 12 with surface areas 12-1, 12-2, 12-3, 12-4 … 12-x made of different materials and surface-modified with the coupling agent 10A. In embodiments, the item comprises heterogenous substrate 12 with surface areas (growth surfaces) 12- 1, 12-2, 12-3, 12-4 … 12-x made of at least two different materials and the coating system 100, 110 described herein above. In embodiments, the item comprises heterogenous substrate 12 with surface areas 12-1, 12-2, 12-3, 12-4 … 12-x made of at least three different materials and the coating system 100, 110. In embodiments, the item is configured as a medical device. The medical device can be a diagnostic or a surgical tool, a wearable sensor, or a body implantable medical device, optionally including functional electronic components to develop so-called (bio)electronics solutions. The item can thus be configured without electronic components (e.g. surgical scalpel or an orthopedic screw, for example) or it may contain electrical / electronic systems, optionally self-powered systems. Implantable medical devices may be designed such as to completely reside in the body, or it may be provided external to the body and connect to an internal organ or another body part. Such devices include, but are not limited to implantable cardiac pacemakers, monitors and defibrillators (e.g. implantable cardioverter defibrillators, ICDs), cochlear implants, a variety of neurological implants and stimulators, infusion pumps, haemodynamic systems, micro-electrical mechanical systems (MEMS), Implanted Myoelectric Sensor (IMES) systems, and a variety of (miniaturized) sensors including biosensors for measuring pressure, flow, strain, etc., as well as (bio)chemical sensors, such as the ones for use for example in the treatment of diabetes (e.g. sensors for continuous glucose monitoring, CGM), and other chemically regulated conditions. The item can be further configured as a control unit for implants, e.g. prosthetic implants, in which case the item can be configured at least partly residing inside the body or provided as a kit-of-part comprising components residing in the body (e.g. inside the implant) and external controller(s). In terms of functionality, the medical item may include a variety of monitoring and / or metering devices / sensors, such as devices for measuring the levels of chemical substances, which serve as markers for certain diseases, in biological fluids, and the devices applicable in treatment of certain conditions or syndromes through neuromodulation (stimulators used in the treatment of migraine, for example) or through regulating the levels of said chemical substances in biological fluids. The item can be also provided as a part or a component used in fabrication of optionally miniaturized sensors and / or semiconductor devices. The item can be further provided as a Printed Circuit Board (PCB), a PCB assembly (PCBA) and / or an electrical component for the same. The item can be further provided as a non- invasive (medical) device or a part thereof (e.g. a wearable sensor (sensor system) or a semiconductor component / PCB(A)). It shall be appreciated by those skilled in the art that with the advancement of technology the basic ideas of the present invention may be implemented and combined in various ways. The invention and its embodiments are thus not limited to the examples described hereinabove, instead they may generally vary within the scope of the claims.

Claims

CLAIMS 1. A coupling agent (10A) configured to bind to a heterogenous substrate (12) comprising surface areas (12-1, 12-2, 12-3, 12-4) made of at least two different materials, the coupling agent (10A) comprising at least two non- identical functional groups, each of said functional groups having specific reactivity towards material of a corresponding substrate surface area (12-1, 12-2, 12-3, 12-4), wherein said coupling agent (10A) is configured to modify a surface of said heterogenous substrate (12) to render said substrate surface areas with enhanced receptiveness to adhesion of a subsequent coating by virtue of having at least one of the functional groups of the coupling agent reacted with the material of the corresponding substrate surface area, as at least one other functional group of said coupling agent remains available for reaction(s) with molecules of the subsequent coating.

2. The coupling agent of claim 1 , configured to bind to substrate materials selected from metals and metal alloys, polymers, ceramics, and composite materials.

3. The coupling agent of claim 1, represented with a molecule comprising a hydrocarbon skeleton structure X with at least two non-identical functional groups R1and R2connected thereto, wherein X is selected from the group consisting of: (i) linear or branched structures comprising alkanes, alkenes or alkynes with 2-12 carbon atoms, (ii) aromatic structures comprising cycloalkanes or cycloalkenes with 3-12 carbon atoms, or (iii) benzene or its derivatives, and wherein any one of said at least two functional groups R1and R2is independently selected from the group consisting of: a thiol group (–SH), an amine group (–NH2), a hydroxyl group (–OH), a carboxyl group (–СООН), an aldehyde group (–CHO), a phosphate group (H2PO3), a C1- C6 alkyl group, a halogen group, and a silane group (–SiR'3), where R' is represented with hydrogen or alkoxy group (–OR"), in which R" is C1-C6 alkyl or hydrogen.

4. The coupling agent of claim 3, wherein each of said at least two functional groups R1and R2is connected to the hydrocarbon skeleton structure X at acarbon atom or via a side chain comprising 0-2 carbon atoms.

5. The coupling agent of any one of claims 1-4, represented with a molecule of general formula (I):wherein X is a structure having a hydrocarbon skeleton selected from the group consisting of: (i) linear or branched structures comprising alkanes, alkenes or alkynes with 2-12 carbon atoms, (ii) aromatic structures comprising cycloalkanes or cycloalkenes with 3-12 carbon atoms, or (iii) benzene or its derivatives; wherein n is 0, 1 or 2; and wherein any one of R1and R2is independently selected from the group consisting of: a thiol group (–SH), an amine group (–NH2), a hydroxyl group (–OH), a carboxyl group (–СООН), an aldehyde group (–CHO), a phosphate group (H2PO3), a C1-C6 alkyl group, a halogen group, and a silane group (–SiR'3), where R' is represented with hydrogen or alkoxy group (–OR"), in which R" is C1-C6 alkyl or hydrogen.

6. The coupling agent of any one of claims 1-4, represented with a molecule of general formula (II):wherein X is a structure having a hydrocarbon skeleton selected from the group consisting of: (i) linear or branched structures comprising alkanes, alkenes or alkynes with 2-12 carbon atoms, (ii) aromatic structures comprising cycloalkanes or cycloalkenes with 3-12 carbon atoms, or (iii) benzene or its derivatives; wherein n is 0, 1 or 2; andwherein any one of R1, R2and R3is independently represented with a) a thiol group (–SH), b) an amine group (–NH2), or a phosphate group (H2PO3), and c) a hydroxyl group (–OH), a carboxyl group (–СООН), an aldehyde group (–CHO), or a silane group (–SiR'3), where R' is represented with hydrogen or alkoxy group (–OR"), in which R" is C1-C6 alkyl or hydrogen.

7. The coupling agent of any one of claims 1-4, represented with a molecule of general formula (III):wherein X is a structure having a hydrocarbon skeleton selected from the group consisting of: (i) linear or branched structures comprising alkanes, alkenes or alkynes with 2-12 carbon atoms, (ii) aromatic structures comprising cycloalkanes or cycloalkenes with 3-12 carbon atoms, or (iii) benzene or its derivatives; wherein n is 0, 1 or 2; and wherein any one of R1, R2, R3and R4 is independently represented with a) a thiol group (–SH), b) an amine group (–NH2), or a phosphate group (H2PO3), c) a hydroxyl group (–OH), a carboxyl group (–СООН), an aldehyde group (–CHO), or a silane group (–SiR'3), where R' is represented with hydrogen or alkoxy group (–OR"), in which R" is C1-C6 alkyl or hydrogen, and d) a C1-C6 alkyl group or a halogen group, preferably, fluorine 8. A coating system (100, 110) for a substrate (12) comprising surface areas (12-1, 12-2, 12-3, 12-4) made of different materials, said coating system comprises: - a coupling layer (10) comprising or consisting of a coupling agent (10A) as defined in any one of claims 1-7, said coupling layer configured, when deposited on the substrate surface, to render said substrate surface areas with enhanced receptiveness to adhesion of a subsequentdeposition layer, and - a deposition layer or layers (21, 22) deposited over the coupling layer and formed through a process of chemical deposition in vapour phase, preferably, through Atomic Layer Deposition (ALD).

9. The coating system of claim 8, wherein the coupling layer (10) is provided as a self-assembled monolayer (SAM).

10. The coating system of any one of claims 8 or 9, wherein individual deposition layers (21) are composed of any compound selected from the group consisting of: aluminium(III) oxide (Al2O3), titanium(IV) oxide (TiO2), hafnium(IV) oxide (HfO2), tantalum(V) oxide (Ta2O5), zirconium(IV) oxide (ZrO2), niobium(V) oxide (Nb2O5), yttrium oxide (Y2O3), magnesium oxide (MgO), zinc oxide (ZnO), silicon dioxide (SiO2), aluminium nitride (AlN), titanium nitride (TiN), gallium nitride (GaN), niobium nitride (NbN), and silicon nitride (SiNx).

11. The coating system of any preceding claim 8-10, wherein at least one deposition layer (22) of the coating is a Molecular Layer Deposition (MLD) film.

12. The coating system of claim 11, wherein the MLD film is an organic film or a hybrid organic-inorganic polymer film, such as poly(aluminum trioxysilylheptanoate) (Al-TOSH).

13. The coating system of any one of claims 11 or 12, wherein the MLD film is deposited over the coupling layer (10).

14. The coating system of any one of claims 8-13, comprising a plurality of deposition layers (21, 22) arranged into a stack.

15. The coating system of claim 14, wherein, in said stack, deposition layers (21) formed with ALD alternate with MLD films (22).

16. The coating system of any preceding claim 8-15, having thickness within a range of about 5 nm to about 500 nm, preferably, within a range of about 10 nm to about 300 nm, still preferably, within a range of about 50 nm toabout 150 nm.

17. A method for adapting heterogenous substrates to surface coatings, the method comprises: on a substrate (12) comprising surface areas made of at least two different materials, depositing a coupling agent (10A) comprising at least two non- identical functional groups having specific reactivity towards materials of the corresponding substrate surface areas, wherein, by virtue of having at least one of the functional groups of the coupling agent reacted with the material of the corresponding substrate surface area, a coupling layer (10) is formed that renders said substrate surface areas with enhanced receptiveness to adhesion of a subsequent coating, as at least one functional group of the coupling agent (10A) remains available for reaction(s) with molecules of the subsequent coating.

18. The method of claim 17, wherein the coupling agent (10A) is represented with a molecule comprising a hydrocarbon skeleton structure X with at least two non-identical functional groups R1and R2connected thereto, wherein X is selected from the group consisting of: (i) linear or branched structures comprising alkanes, alkenes or alkynes with 2-12 carbon atoms, (ii) aromatic structures comprising cycloalkanes or cycloalkenes with 3-12 carbon atoms, or (iii) benzene or its derivatives, and wherein any one of said at least two functional groups R1and R2is independently selected from the group consisting of: a thiol group (–SH), an amine group (–NH2), a hydroxyl group (–OH), a carboxyl group (–СООН), an aldehyde group (– CHO), a phosphate group (H2PO3), a C1-C6 alkyl group, a halogen group, and a silane group (–SiR'3), where R' is represented with hydrogen or alkoxy group (–OR"), in which R" is C1-C6 alkyl or hydrogen.

19. The method of claim 17, wherein the coupling agent is represented with a molecule with general formulae (I), (II), (III), as defined in claims 5, 6, and 7, respectively.

20. Use of a coupling agent as defined in any one of claims 1-7 to modify surfaces of heterogenous substrates to render said heterogenous substratesmore uniformly receptive to adhesion of subsequent coatings.

21. An item, comprising a heterogenous substrate (12) with surface areas (12- 1, 12-2, 12-3, 12-4) made of different materials and surface-modified with a coupling agent as defined in any one of claims 1-7.

22. An item, comprising a heterogenous substrate (12) with surface areas (12- 1, 12-2, 12-3, 12-4) made of at least two different materials, and a coating system according to what is defined in claims 8-16.

23. The item of any one of claims 21 or 22, wherein the heterogenous substrate has surface areas made of materials selected metals and metal alloys, polymers, ceramics, and composite materials.

24. The item of any one of claims 21-23, configured as a printed circuit board (PCB), a PCB assembly (PCBA) and / or an electrical component.

25. The item of any one of claims 21-24, configured as a medical device.

26. The item of claim 25, configured as an implantable medical device.

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