ELECTROCHEMICAL SENSOR

Abstract

The invention relates to an electrochemical sensor (10) having at least three elements (18, 20, 22, 24, 28), comprising a transducer element (20) and a membrane element (22) that is selective for at least one target species, wherein the membrane element (22) and another element (18, 20, 24, 28) of the electrochemical sensor (10) are in direct contact and bonded to each other by covalent chemical bonds at an interface between them, and wherein at least two elements (18, 20, 24, 28) different from the membrane element (22) are in direct contact and bonded to each other by covalent chemical bonds at an interface between them. Figure 4

Description

Title of the invention: Electrochemical sensor

[0001] The invention relates to an electrochemical sensor.

[0002] Common electrochemical sensors, for example ion selective electrodes, comprise a membrane element which is selective for at least one target species and a transducer element which converts the presence of the target species (also called analyte) into an electrical signal, in particular the concentration into an electrical potential or current.

[0003] Such electrochemical sensors can be used for many different purposes, for example to detect ions, molecules, proteins, bacteria, enzymes or other species for uses in the clinical, biological, pharmaceutical or similar fields.

[0004] The lifetime of these sensors is however usually limited. The functionality of the sensor may deteriorate over time due to delamination of layers and / or accumulation of water at the interfaces of the sensor elements.

[0005] The object of the invention is to provide an electrochemical sensor having an improved lifetime and durability.

[0006] The object of the invention is achieved by an electrochemical sensor having at least three elements, comprising a transducer element and a membrane element which is selective for at least one target species. The membrane element and another element of the electrochemical sensor are in direct contact and bound to each other by covalent chemical bonds at an interface between them. At least two different elements of the membrane element are further in direct contact and bound to each other by covalent chemical bonds at an interface between them.

[0007] The invention is based on the conclusion that covalent chemical bonds can improve the contact and adhesion between individual elements, in particular layers of electrochemical sensors. In other words, the layers can be grafted to each other to improve the robustness of the electrochemical sensor. It has been found that in addition to the lifetime, the temperature resistance of electrochemical sensors can be significantly improved by bonding not only the ion-selective membrane, but also other elements of the electrochemical sensor to each other by covalent chemical bonds. The bonding of the interface further allows the improvement of the signal and / or charge transport properties through the individual elements.

[0008] In one variant, the electrochemical sensor comprises a conductive element which is in direct contact with and bonded to the transducer element by chemical bonds co valent at an interface between the two elements. The conductive element or the ion-electron transducer element may in particular be a conductive or semiconducting material. It is possible to use materials such as metal or metalloid and their derivatives (e.g., oxidized or halogenated forms) or other materials intrinsically doped with chemical elements to influence their electrical conductivity, for example, an electrode made of platinum (Pt), gold (Au), carbon (C), indium tin oxide (ITO), silver / silver chloride (Ag / AgCl), tantalum oxide (Ta2O5), iridium oxide (IrOx), n-type or p-type silicon. The ion-electron transducer element may also comprise structures such as clusters of individual molecules at the nanoscale, or polymers that are intrinsically electrically conductive or semiconducting.These may be organic conductive polymers and their copolymers, e.g., polyacetylene (PAC), polyphenylene-vinylene (PPV), polypyrrole (PPY), polyaniline (PANI), polyphenylene sulfide (PPS), poly-thiophene (PT), their corresponding derivatives and / or their mixtures, such as poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The transducer element and the conductive element are examples for two different elements of the membrane element, which can be bonded to each other to increase the overall stability and lifetime of the sensor.

[0009] Additionally or alternatively, the conductive element may be in direct contact with and bonded to the membrane element by covalent chemical bonds at an interface between the two elements.

[0010] It is also possible for the transducer element and the conductor element to be made of an identical material, for example, conductive platinum or carbon-based materials. This facilitates the manufacture of the sensor, since the transducer and the conductor can be manufactured in a single processing step.

[0011] It is also conceivable that the electrochemical sensor comprises an insulating substrate, the conductive element, the transducer element and / or the selective membrane element partially covering the substrate. In an area of ​​the substrate which is not covered by the conductive element, the substrate is in direct contact with and bonded to another element, in particular the membrane element or the transducer element or a hydrophilic element, by covalent chemical bonds at an interface between the substrate and the element in direct contact.

[0012] The substrate serves as a carrier for the electrochemical sensor. Covalent chemical bonds between the substrate and other contacting elements further improve the mechanical stability and lifetime of the sensor.

[0013] The substrate may further serve as an electrical insulator. It may be made of an inorganic material, for example a ceramic or glass material (e.g. quartz, mica, porcelain, SiO2, Al2O3, AlN, Si3N4) or a composite material, e.g., a fiberglass and epoxy plastic printed circuit board material (e.g., FR-4). These materials have various interesting combinations of chemical inertness, robustness, and / or excellent electrical insulation properties, thus avoiding unwanted interference with the detection signal.

[0014] In an advantageous variant, the conductive element and / or the transducer element comprises / comprise a structured electrically conductive or semiconducting material, in particular randomly or specifically organized. It is possible to use materials such as aggregated, dendritic or self-assembled crystalline particles, nanotubes, nanosheets, nanoflakes, nanocubes, nanorods, nanowires or any compound in a specific morphology with a high specific surface area (e.g. a porous or nanoflower shape). The aforementioned materials, composites or also mixtures are of course possible.

[0015] The contact interface with other elements can be enlarged by using a structured material. The charge transport and electrical properties can further be improved.

[0016] In another preferred embodiment, the conductive element is made of a solid electrically conductive material having a functionalized, in particular silanized, interface with a neighboring element. The conductor and / or the transducer may for example be a solid and flat contact made of graphite, graphene, doped or glassy carbon (C), gold (AU), platinum (Pt), copper (Cu) or silver (Ag). The functionalization, in particular the silanization, is technically easy to implement and allows and / or improves the formation of covalent chemical bonds between the conductive element and layers in direct contact.

[0017] Each element, in particular each layer of the electrochemical sensor, is optionally in direct contact with and bonded to at least one other element of the electrochemical sensor by covalent chemical bonds at an interface / several interfaces between the elements in direct contact. This configuration ensures the greatest thermal and mechanical stability of the sensor.

[0018] In another embodiment, the membrane element comprises a polymer matrix. The polymer matrix may be insulating, hydrophobic and / or based on a repeating structure of the same monomers or a mixture of different monomers and comonomers. Materials composing the polymer matrix and based on organic hydrophobic polymers, for example epoxies, polyethylenes, polystyrenes, poly(vinyl chloride), polysiloxanes, polyesters, polyurethanes, poly([metah]acrylates), polyethers or fluorocarbon polymers, and derivatives may be used. It may also contain reactive agents. crosslinking, plasticizers, detergents or several of these to adapt the membrane hardness and control the transport of the target species.

[0019] Alternatively, the monomers and comonomers may comprise an alkyl group (e.g., acrylate or methacrylate derivatives) to replace the use of plasticizers.

[0020] It is also conceivable to be able to replace at least some of the alkyl groups with other functionalized groups containing elements or halogen atoms such as chloride or fluoride. This improves the hydrophobicity of the membrane element and prevents permeation and accumulation of water at the interfaces.

[0021] In another embodiment, the membrane element comprises a polymer matrix and at least one chemical selective agent, in particular an ionophore for recognizing the target species and / or at least one neutral carrier for improving the transport properties of the target species through the selective membrane element. The selectivity of the sensor for the target species is thus improved.

[0022] In order to avoid depletion of the membrane constituents, the selective agent(s) and / or the neutral carrier(s) may be covalently bound to the polymer matrix.

[0023] In a technically simple arrangement, the polymer matrix is ​​made of polymerized monomers and comonomers, the polymerized comonomers or a portion of the polymerized comonomers constituting the selective agent.

[0024] It is also conceivable that the electrochemical sensor comprises a hydrophilic element arranged between the transducer element and the membrane element. The hydrophilic element may be in direct contact with and bound to the transducer element by covalent chemical bonds at an interface between the two elements and / or be in direct contact with and bound to the membrane element by covalent chemical bonds at an interface between the two elements.

[0025] The hydrophilic element may comprise at least one hydrophilic polymer matrix with favorable interactions with a polar solvent, resulting in solubility or swelling capacity (e.g., a hydrogel), and an internal electrolyte comprising a polar solvent (e.g., water), soluble salts used to increase electrical conductivity (e.g., KCl, NaCl), interfering salts used as potential-determining ions, a known amount of the target species, a free chemical doping agent (e.g., one or both forms of a redox couple), a chelating agent (e.g., ethylenediaminetetraacetic acid, EDTA), and / or chemical substances for buffering the internal pH, or several of them. It is possible to apply the materials composing the hydrophilic polymer matrix and based on organic hydrophilic polymers, for example, those originating from natural compounds such as polysaccharides (e.g.,dextran, alginate, chitosan, agarose and . pullulan) and / or proteins (e.g. albumin, gelatin, collagen, lectin, legumin and vicilin), and / or synthetic compounds such as polyacrylamides, poly([alkyl]acrylic acids), poly([meth]acrylates), poly(ethylene glycols), poly(ethylene oxides), poly(styrene sulfonic acids), poly(vinyl amides), poly(vinyl amines), poly(vinyl azines), poly(N-vinyl imidazoles), poly(vinyl pyridines), poly(ethylene imines), poly(L-histidines), poly(methyl vinyl ethers), poly(oxymethylenes), poly(L-prolines), polyfurans or poly(vinyl alcohols), their respective derivatives and / or mixtures thereof.

[0026] The hydrophilic layer may generally be applied to obtain a fixed concentration(s) of target species and / or interferent(s) at the interface(s) of the transducer and / or the membrane. It may thus improve the sensitivity, the detection limit and / or the selectivity of the sensor.

[0027] In another embodiment, the transducer element comprises chemical groups and / or contains chemical substances, in particular crosslinking agents, which form covalent chemical bonds at the interface with neighboring elements in direct contact. The chemical bonds can be formed with the membrane element, the conductive element or both. The risk of delamination of layers and accumulation of water at the interfaces is thus reduced.

[0028] It is also conceivable that the chemical groups and / or chemical substances form covalent chemical bonds with the transducer element. This improves the thermal and chemical stability of the transducer element and prevents possible depletion of the constituents.

[0029] In another variant, the transducer element may comprise a conductive polymer, in particular having a chemical doping agent (for example an electroactive and / or redox species). The doping agent may for example improve the conductivity of the transducer element and / or increase the sensitivity of the sensor or the reaction time to changes in the concentration of the target species.

[0030] In another preferred embodiment, the transducer element and / or a hydrophilic element comprises / comprise a chelating agent. By using the chelating agent (e.g. EDTA), it is possible to fix the amount of target species at the layers and / or the interfaces of the layers. This in particular improves the lower detection limit of the sensor.

[0031] It is further conceivable that the electrochemical sensor comprises a substrate which is made of an insulating material having a functionalized, in particular silanized, interface with a neighboring element. The modification of the surface of a material provides physical, chemical and / or biological characteristics different from those of the initial surface of the material. The process of functionalizing the substrate for example, results in the formation of a monolayer that acts as a coupling agent between the substrate and the neighboring element(s), thereby improving their adhesion at the interface. Functionalization includes the addition of small functional groups, moieties, oligomers and / or polymers to the surface or interface, particularly by oxidation or grafting treatment methods using, for example, plasma, flame or corona treatments. The added functionalizing portion may be an integral part of at least one of the components of a neighboring element(s), for example, as a copolymer of a neighboring polymer matrix, or may be used to bond to it, for example, by an additional chemical reaction. Functionalization provides a simple yet very effective method for establishing covalent chemical bonds between the substrate and a neighboring element(s).

[0032] In another variant, the substrate is partially covered by the aforementioned conductive element and / or transducer element. To facilitate the manufacturing procedure of the electrochemical sensor, the substrate, the conductive element and / or the transducer element can be functionalized together in a single processing step.

[0033] Other advantages and characteristics will emerge from the following description of the invention and from the attached figures which show an example of a non-limiting embodiment of the invention and in which:

[0034] - [Fig.l] schematically represents a side view in cross section of a first embodiment of an electrochemical sensor according to the invention;

[0035] - [Fig.2] schematically represents a side view in cross section of a second embodiment of an electrochemical sensor according to the invention;

[0036] - [Fig.3] schematically represents a side view in cross section of a third embodiment of an electrochemical sensor according to the invention;

[0037] - [Fig.4] schematically represents a side view in cross section of a fourth embodiment of an electrochemical sensor according to the invention;

[0038] - [Fig.5] schematically represents a side view in cross section of the layers and two interfaces grafted with an electrochemical sensor according to the invention;

[0039] - [Fig.6] schematically represents a side view in cross section of the layers and three interfaces grafted with an electrochemical sensor according to the invention; and

[0040] - [Fig.7] schematically represents a side view in cross section of the layers and three grafted interfaces as well as grafted selective agents and neutral carriers of an electrochemical sensor according to the invention.

[0041] [Fig.l] schematically represents a first embodiment of an electrochemical sensor 10 according to the invention.

[0042] The sensor 10 is located in a liquid sample 12 and is connected to a reference electrode 14 (for example Ag / AgCl / 3M KC1) by an electrical measuring device 16 (for example a potentiometer).

[0043] The sensor 10 comprises a conductive element 18, a transducer element 20 and a selective membrane element 22.

[0044] In the embodiment described, the conductive element 18 is a solid contact, which is for example made of glassy carbon.

[0045] The transducer element 20 is a thin layer of PEDOT:PSS covering the conductive element 18.

[0046] The selective membrane element 22 is composed of a polymer, for example made from polyvinyl chloride (PVC), and other chemical species, and covers the transducer element 20. It is selective for at least one target species, for example calcium ions.

[0047] In this context, selective means that the affinity of the membrane element 22 with the target species, due to polymeric properties (e.g. hydrophobicity) and / or the binding efficiency of the selective and transport agents, is better than with other species such as interferents and / or water. In simplified terms, the mass transport of species other than the analyte is hindered through the membrane element 22 and during transfer / exchange processes across interfaces, for example between the membrane element 22 and the liquid sample 12.

[0048] In the described embodiment, the conductive element 18 and the transducer element 20 are in direct contact and bonded to each other by covalent chemical bonds at an interface between them. The transducer element 20 and the selective membrane element 22 are further in direct contact and bonded to each other by covalent chemical bonds at an interface between them. The direct chemical bonds make the sensor 10 very durable and robust at high application temperatures.

[0049] The illustrated sensor 10 operates as follows: the membrane element 22 selectively transports target species from the liquid sample 12 to the transducer element 20. The membrane element 22 can optionally be loaded with the target species before measurement in order to reduce the sensor implementation. A concentration gradient of the target species is generated between the respective interfaces of the liquid sample 12 - the membrane element 22 and the membrane element 22 - the transducer element 20. The transducer element 20 converts the information of the presence of the analyte, such as its concentration, into an electrical signal, in particular an electrical potential or current, resulting for example from a discharge of the target species with the transducer element 20. The conductive element 18 conducts the electrical signal to the electrical measuring apparatus 16 where it is detected. Information concerning the gradient of the interfaces and consequently the target species in the liquid sample 12 can be obtained by evaluating the detected signal. In accordance with the semi-empirical Nikolsky-Eisenman model, the potential difference, measured by the electrical device 16 such as a potentiometer, between the sensor 10 and the reference electrode 14 is for example proportional to the concentration of the target species in the liquid sample 12.

[0050] The examples given of the operating principle and the materials do not of course limit the scope of the invention. It is possible to use other types of conductive elements 18, for example made of copper, graphite, graphene or doped carbon, and / or transducer elements 20, for example made of Pt nanoflowers produced by electrodeposition, nanoparticles bound to iridium oxides (IrOx) or a redox conductive polymer based on an electropolymerized or chemically polymerized PANI derivative, and / or other types of membrane elements 22, for example a composition based on urethane acrylate polymerized under UV.

[0051] The conductive elements 18 and / or the transducer elements 20 may for example comprise an electrically conductive or semiconductive material structured and organized in a random or specific manner to obtain an increased contact of the surface area of ​​the interface and / or improved charge transport or charge transfer properties towards the neighboring layers.

[0052] Further details regarding the individual elements, their components and their interfaces are described below with the aid of Figures 5 to 7.

[0053] [Fig.2] schematically represents a second embodiment of an electrochemical sensor 10 according to the invention.

[0054] The second embodiment corresponds in several essential points to the first embodiment, so that only the differences will be explained in the following. Identical and functionally identical parts are indicated by the same reference numbers.

[0055] Unlike the first embodiment, the sensor 10 according to the second embodiment comprises an additional hydrophilic element 24 which is arranged between the membrane element 22 and the transducer element 20.

[0056] The hydrophilic element 24 comprises a hydrophilic layer, in particular a hydrogel swollen by an electrolyte, which improves the detection limit and / or the selectivity of the sensor 10 by fixing the concentration of the analyte at the interface of the transducer.

[0057] The operating principle corresponds, with the exception of the additional hydrophilic element 24, to that described above.

[0058] In [Fig.2], the hydrophilic element 24 is in direct contact with and bonded to the element transducer 20 by covalent chemical bonds at an interface between them.

[0059] The hydrophilic element 24 is further in direct contact with and bonded to the membrane element 22 by covalent chemical bonds at an interface between them.

[0060] In the second embodiment, the conductive element 18, the transducer element 20 and the membrane element 22 are arranged inside a housing 26 having an opening closed by the selective membrane element 22. The housing 26 and the selective membrane element 22 protect the hydrophilic element 24 from the liquid sample 12.

[0061] The housing 26 is optionally in direct contact with and bonded to the selective membrane element 22 and / or the hydrophilic element 24 by covalent chemical bonds at the interface therebetween. The direct chemical bonding prevents delamination of the individual elements of the housing 26, even at high application temperatures and pressure variations of the sensor 10.

[0062] [Fig. 3] schematically represents a third embodiment of an electrochemical sensor 10 according to the invention.

[0063] The third embodiment corresponds in several essential points to the first embodiment, so that only the differences will be explained in the following. Identical and functionally identical parts are indicated by the same reference numbers.

[0064] Unlike the first embodiment, the sensor 10 according to the third embodiment comprises a substrate 28. In the embodiment, the substrate 28 is an electrically and chemically inert flat ceramic plate, for example a thin Si / SiO2 wafer substrate.

[0065] The conductive element 18 is a flat-deposited metal layer partially covering the substrate 28, for example a titanium-platinum (Ti / Pt) electrode deposited locally by nanofabrication methods such as photolithography and vacuum electron beam evaporation procedures.

[0066] The substrate 28 and / or the conductive element 18 may optionally be functionalized, in particular silanized.

[0067] In [Fig. 3], the substrate 28 and the conductive element 18 are both silanized (a silanization step is performed after the deposition of the conductive element 18 during the fabrication of the sensor 10) to add on both surfaces functional groups used for covalent bonding with the selective membrane component 22 and / or the transducer element component 20.

[0068] Thanks to silanization, the sensor 10 shown comprises interfaces connected by direct chemical bonds between the substrate 28 and the membrane element 22, and between the conductive element 18 and the transducer element 20.

[0069] In a first zone 30 of the substrate 28 which is not covered by the element conductor 18, nor by the transducer element 20, the substrate 28 is in direct contact with and bonded to the membrane element 22 by covalent chemical bonds at an interface between them.

[0070] Furthermore, in a second area 32 of the substrate 28 which is not covered by the conductive element 18, the substrate 28 is in direct contact with and bonded to the transducer element 20 by covalent chemical bonds at an interface between them.

[0071] In the embodiment, the direct chemical bonding prevents delamination of the individual elements of the substrate 28 even at high application temperatures and extended application times of the sensor 10.

[0072] [Fig.4] schematically represents a fourth embodiment of a electrochemical sensor 10 according to the invention.

[0073] The fourth embodiment is a combination of the second and third embodiments. Corresponding features and functionally identical parts are again indicated by the same reference numerals.

[0074] Unlike the first embodiment, the sensor 10 comprises a substrate 28 and a hydrophilic element 24.

[0075] In the fourth embodiment, each element of the electrochemical sensor 10 is in direct contact with and linked to at least one other element by covalent chemical bonds at an interface between them.

[0076] The sensor 10 shown in [Fig.4] comprises interfaces with covalent chemical bonds between the substrate 28 and the membrane element 22 in a first zone 30, between the substrate 28 and the transducer element 20 in a second zone 32, and between the substrate 28 and the hydrophilic element 24 in a third zone 34.

[0077] It further comprises interfaces with covalent chemical bonds between the conductive element 18 and the transducer element 20, between the transducer element 20 and the hydrophilic element 24, and between the hydrophilic element 24 and the selective membrane element 22.

[0078] The described embodiment does not, of course, limit the scope of the invention. Similar sensors 10 having fewer or even more chemically bonded interfaces are possible.

[0079] In the following, the individual elements of the electrochemical sensor 10 according to the invention and the interfaces are described in more detail with the aid of FIGS. 5 to 7.

[0080] [Fig. 5] schematically represents a side view of a section of an electrochemical sensor 10. It is conceivable that this is the electrochemical sensor 10 according to the first and / or the third embodiment ([Fig. 1] and / or 3).

[0081] The sensor 10 comprises a conductive element 18, a transducer element 20 and a selective membrane element 22.

[0082] The interfaces in direct contact between the conductive element 18, the transducer element 20 and the selective membrane element 22 are grafted (linked to each other by covalent chemical bonds). This is symbolized in [Fig.5] by vertical stripe patterns 36.

[0083] In the embodiment, the transducer element 20 comprises a conductive polymer 38 having a chemical doping agent, for example PEDOT:PSS.

[0084] The transducer element 20 further comprises chemical coupling groups and / or contains coupling agent chemicals 40, in particular crosslinking agents that form covalent chemical bonds at the interface with neighboring elements in direct contact. The chemical coupling groups and / or the coupling agent chemicals 40 further form covalent chemical bonds with the transducer element 20, resulting in improved stability and reduced delamination and / or reduced water accumulation at the interface.

[0085] The membrane element 22 further comprises at least one polymer matrix 42 and at least one chemical selective agent 44, in particular an ionophore selective for the target species, and / or at least one neutral carrier 46 to improve the transport properties of the target species through the selective membrane element 22.

[0086] [Fig. 6] schematically shows another side view of a section of an electrochemical sensor 10. It corresponds in several essential points to the side view of [Fig. 5], so that only the differences will be explained in the following. Identical and functionally identical parts are indicated by the same reference numbers.

[0087] Compared to the sensor 10 of [Fig.5], the sensor 10 of [Fig.6] has an additional hydrophilic element 24 arranged between the transducer element 20 and a selective membrane element 22.

[0088] It is conceivable that [Fig.6] shows a section of the electrochemical sensor 10 according to the second and / or fourth embodiment ([Fig.2] and / or [Fig.4]).

[0089] As indicated by the vertical stripe patterns 36, the directly contacting interfaces between the conductive element 18, the transducer element 20, the hydrophilic element 24 and the selective membrane element 22 are all grafted. This makes the sensor 10 very durable.

[0090] In the described embodiment, the electrolyte contained in the hydrophilic element 24 comprises, in addition to a small amount of the target species, a chelating agent 48 (for example EDTA) to improve the performance of the sensor 10, in particular the lower detection limit.

[0091] The transducer element 20 can of course optionally also contain an agent chelating 48 and / or crosslinking agents.

[0092] [Fig.7] schematically represents another side view of a section of a electrochemical sensor 10. It corresponds in several essential points to the side view of [Fig.6]. Again, only the differences will be explained in what follows. Identical and functionally identical parts are indicated by the same reference numbers.

[0093] Compared to the sensor 10 of [Fig. 6], the sensor 10 of [Fig. 7] has a selective membrane element 22 with selective agents 44 and / or neutral carriers 46 which are grafted (covalently bonded) to the polymer matrix 42 to prevent depletion. This is indicated in [Fig. 7] by a spring-like rear portion 50 connected to the respective species.

[0094] In the embodiment, the polymer matrix 42 is composed of polymerized monomers and comonomers. The polymerized comonomers or portions of the polymerized comonomers constitute the selective agents 44 and / or the neutral carriers 46.

Claims

Claims

1. An electrochemical sensor having at least three elements (18, 20, 22, 24, 26, 28), comprising a transducer element (20) and a membrane element (22) which is selective for at least one target species, wherein the membrane element (22) and another element (18, 20, 24, 26, 28) of the electrochemical sensor (10) are in direct contact and bonded to each other by covalent chemical bonds at an interface therebetween, and wherein at least two different elements (18, 20, 24, 26, 28) of the membrane element (22) are in direct contact and bonded to each other by covalent chemical bonds at an interface therebetween.

2. An electrochemical sensor according to claim 1, comprising a conductive element (18) which is in direct contact with and bonded to the transducer element (20) by covalent chemical bonds at an interface between the two elements (18, 20), and / or wherein the conductive element (18) is in direct contact with and bonded to the membrane element (22) by covalent chemical bonds at an interface between the two elements (18, 22).

3. An electrochemical sensor according to claim 2, comprising a substrate (28), the conductive element (18) partially covering the substrate (28), and wherein in an area (30, 32, 34) of the substrate (28) which is not covered by the conductive element (18), the substrate (28) is in direct contact with and bonded to another element (20, 22, 24), in particular the membrane element (22) or the transducer element (20) or a hydrophilic element (24), by covalent chemical bonds at an interface between the substrate (28) and the element (18, 20, 22, 24, 28) in direct contact.

4. An electrochemical sensor according to claim 3, wherein the substrate (28) is made of an inorganic material.

5. Electrochemical sensor according to one of claims 2 to 4, wherein the conductive element (18) and / or the transducer element (20) is / are made of a structured electrically conductive material, in particular randomly or specifically organized.

6. Electrochemical sensor according to one of claims 2 to 5, in which the conductive element (18) is made of a solid electrically conductive material having a functionalized, in particular silanized, interface with a neighboring element (20, 22, 24).

7. An electrochemical sensor according to one of the preceding claims, comprising a hydrophilic element (24) arranged between the transducer element (20) and the membrane element (22), wherein the hydrophilic element (24) is in direct contact with and bonded to the transducer element (20) by covalent chemical bonds at an interface between the two elements (20, 24), and / or wherein the hydrophilic element (24) is in direct contact with and bonded to the membrane element (22) by covalent chemical bonds at an interface between the two elements (22, 24).

8. An electrochemical sensor according to any preceding claim, wherein each element (18, 20, 22, 24, 26, 28) of the electrochemical sensor (10) is in direct contact with and bonded to at least one other element (18, 20, 22, 24, 26, 28) of the electrochemical sensor (10) by covalent chemical bonds at one or more interfaces between the elements (18, 20, 22, 24, 26, 28) in direct contact.

9. Electrochemical sensor according to one of the preceding claims, wherein the membrane element (22) comprises a polymer matrix (42) and at least one chemical selective agent (44), in particular an ionophore selective for the target species and / or at least one neutral carrier (46) for improving the transport properties of the target species through the selective membrane element (22).

10. An electrochemical sensor according to claim 9, wherein the selective agent(s) (44) and / or the neutral carrier(s) (46) is / are covalently bound to the polymer matrix (42).

11. An electrochemical sensor according to claim 9 or 10, wherein the polymer matrix (42) is composed of polymerized monomers and comonomers, the polymerized comonomers or a portion of the polymerized comonomers constituting the selective agent(s) (44).

12. Electrochemical sensor according to one of the preceding claims, wherein the transducer element (20) comprises chemical groups and / or contains chemical substances (40), in particular crosslinking agents, which form covalent chemical bonds at the interface with directly neighboring elements (18, 22, 24, 26, 28).

13. An electrochemical sensor according to claim 12, wherein the chemical groups and / or chemical substances (40) form covalent chemical bonds in the transducer element (20).

14. Electrochemical sensor according to one of the preceding claims, wherein the transducer element (20) comprises a conductive polymer (38), in particular comprising a chemical doping agent.

15. An electrochemical sensor according to any preceding claim, wherein the transducer element (20) and / or a hydrophilic element (24) comprises a chelating agent (48).

16. Electrochemical sensor according to one of the preceding claims, comprising a substrate (28) which is made of an insulating material with a functionalized, in particular silanized, interface with a neighboring element (18, 20, 22, 24).

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