Coating or surface treatment method and apparatus

Abstract

The present invention relates to a method of coating or surface treatment, in which a substrate holder (2) and a slot die head (3) are provided. The slot die head has a slit nozzle (4). A substrate (5) is placed on the substrate holder. The substrate is moved relative to the slit nozzle such that liquid is deposited on the substrate by supplying a conductive liquid onto the substrate through the slit nozzle. A potential difference is applied between the slit nozzle and the substrate by a power source (6) while supplying the conductive liquid to the substrate through the slit nozzle. The power source applies a first potential to the slit nozzle and a second, different potential to the substrate.

Description

[Technical field]

[0001] The present invention relates to a coating or surface treatment method, an apparatus for coating or surface treatment, a system for coating or surface treatment, and a substrate coated or surface treated by the coating or surface treatment method. The methods, apparatus and systems provided can be used to coat polymers, biopolymers, conductive polymers or metals, or to electrochemically treat conductive electrode materials. [Background technology]

[0002] Electrodeposition is a widely used technique that can produce metal or polymer coatings by passing an electric current through a conductive material immersed in a solution containing metal ions or polymerized monomers. For example, electrodes of electrochemical sensors are often coated with catalytically active metal nanoparticles, polymers, conductive polymers, and / or biopolymers. This can increase sensitivity, improve signal-to-noise ratio, selectivity, and / or reduce fouling of the electrode, e.g., the sensor. Furthermore, electrodeposition is often applied in the fabrication of electrodes for energy conversion and storage applications (e.g., supercapacitors, batteries, fuel cells, etc.), as well as in the fabrication of flexible electronics. In particular, in the fabrication of electrodes for electroanalysis and electrocatalysis, coating the electrode material can improve the performance of the sensor. Examples of electrode materials include carbon or metal electrodes, conductive polymers, metal nanoparticles, carbon nanoparticles, or combinations thereof.

[0003] As a specific example of electrodeposition, active noble metal nanoparticles such as platinum and gold can be electrodeposited for the detection of hydrogen peroxide in an electrochemical enzyme sensor. In addition, silver and nickel, or palladium and rhodium can be evaporated.

[0004] Some sensing applications require diffusion through a porous layer. In such applications, advantageously the coating thickness is in the range of 10 nm to 1000 nm. In other applications, continuous (e.g., in the range of 100 nm to 10 μm), thicker coatings may be preferred. Electrodeposition is an efficient method to conformally coat porous electrode materials with thin functional films or metal nanoparticles.

[0005] A similar process can be used for molecular imprinting of electrodes with electrodeposited coatings such as polydopamine or conductive polymers. Electrodeposition can provide conformal thin film coatings with imprinted recognition sites for a wide range of analytes. Furthermore, electrodeposition techniques provide rapid deposition of such coatings. Conformal coatings on porous conductive layers as well as precise thickness control can be achieved.

[0006] Similarly, electrodeposition techniques can be applied to dissolve or break bonds using oxidative or reductive potentials as well as to promote chemical reactions between molecules in the electrolyte and the electrode surface, and therefore can be used for surface chemical modifications such as etching and grafting reactions. Examples of etching and surface functionalization are described in Wei, D., Liu, Y., Cao, L., Zhang, H., Huang, L., Yu, G., Kajiura, H. and Li, Y., "Selective Electrochemical Etching of Single-Walled Carbon Nanotubes," Adv. Funct. Mater. 2019:3618-3624, or E. Leppanen, S. Sainio, H. Jiang, B. Mikladal, I. Varjos, T. Laurila, "Effect of Electrochemical Oxidation on Physicochemical Properties of Fe-Containing Single-Walled Carbon Nanotubes," ChemElectroChem 2020,7,4136. A review of electrografting is given in Belanger D, Pinson J., "Electrografting: a powerful method for surface modification," Chem. Soc. Rev. 2011 July, 40(7):3995-4048. Similarly, electrodeposition techniques can be used to modify the morphology of electrode materials, for example to create porous surfaces on graphite electrodes or to significantly increase the surface area of ​​electrodes.

[0007] Traditionally, electrodeposition (also called electroplating) requires a bath containing an electrolyte solution. An anode made of the coating material and a cathode to be coated are immersed in the electrolyte solution. Traditionally, a solid counter electrode can also be used as a source material. In some applications, the anode is also coated. When an electrical potential is applied between the anode and the cathode, the anode material can be deposited as a layer on the cathode. However, after the coating process, the bath containing the electrolyte solution and the solubilized coating agent, e.g., the cathode material, must be disposed of or recycled. This is particularly inconvenient for expensive materials such as gold, silver, platinum, or rare materials such as biomolecules or pharmaceutical actives that may be present as ionic species in the electrolyte solution. Thus, the electrolyte solution may have to be disposed of. Furthermore, in applications such as molecular imprinting, the template molecules may be rare and / or prohibitively expensive.

[0008] EP 1182278 shows a method for producing electrodeposited copper foil. An electrolyte containing copper sulfate is filled at a substantially constant gap between a cylindrical cathode drum and an anode arranged along the cathode drum. A current for copper electrodeposition is supplied so that copper is electrodeposited on the surface of the rotating cathode drum. The copper foil with a constant thickness is continuously released from the cathode drum and wound on a roll winder. However, EP 1182278 still requires the use of an electrolyte bath in which the substrate is fed or in which the sheet is immersed. For large sheets or wide rolls, large baths are required, which leads to the disposal of chemicals and the generation of hazardous waste. Metal ions can be recovered from such solutions, but it is more difficult to recover polymer precursor monomers, template molecules (e.g. of biological or synthetic origin) and particles from colloidal suspensions. In both cases, the recovery process requires resources.

[0009] It is therefore an object of the present invention to provide an apparatus and method that offers improvements over known processes. In particular, it is an object of the present invention to provide an electrodeposition method that results in less waste and more efficient use of the deposited material. Summary of the Invention

[0010] This object is achieved by means of the features of the respective independent claims. Each dependent claim relates to preferred embodiments.

[0011] A first aspect of the invention relates to a method of coating or surface treatment, in which a substrate holder and a slot die head are provided. The slot die head has a slit nozzle. A substrate is placed on the substrate holder. The substrate is moved relative to the slit nozzle such that liquid is deposited on the substrate by supplying a conductive liquid onto the substrate through the slit nozzle. A power source provides a potential difference between the slit nozzle and the substrate while supplying the conductive liquid to the substrate through the slit nozzle. The power source applies a first potential to the slit nozzle and a second, different potential to the substrate.

[0012] In contrast to known processes, no bath is required in the proposed electrodeposition. Precisely, a slot-die coating process is modified and used for electrodeposition. In the proposed method, the substrate is coated with the exact amount required. There is a minimal amount of waste of the deposited material. Once the coating or process is finished, the remaining conductive liquid can be stored and used at another time without recovering the material from the bath. Furthermore, the present invention allows faster throughput times for surface treatment and coating.

[0013] The coating or surface treatment method involves one of the following: electrophoretic deposition of charged particles, electrodeposition, electrochemical treatment, etching, and electrochemically driven grafting reactions. In general, any conductive material can be coated with a functional material or functionalized to adapt the substrate to many applications. Electrodeposition according to the present invention can be carried out using a reduction or oxidation reaction at the substrate. Functionalization can also involve oxidation or reduction of the electrode surface to change the interfacial chemistry (e.g., removal of oxides from metals or addition of oxygen-containing functional groups to carbon electrodes).

[0014] Grafting reactions can occur on substrate surfaces to allow surface functionalization with, for example, amines and carboxylic acids. For example, aliphatic amines can be covalently attached to carbon and metal electrodes by electrochemically initiating radical formation. These groups are preferentially generated at the electrode surface and are attached to the surface by subsequent chemical and / or electrochemical reactions. Functionalization of conductive materials by grafting reactions can improve sensor performance, electrocatalysis, catalysis, and / or immobilization of molecules and biorecognition elements.

[0015] The conductive liquid may contain dissolved ions, molecules, or particles dissolved or suspended. The conductive liquid may be a conductive electrolyte with metal salts / ions or monomer precursors for electropolymerization. The electrolyte used may depend on the material and substrate to be deposited. In one example, the electrolyte may be a salt electrolyte such as KCl or lithium perchlorate. These electrolytes may be useful for polymers. Preferably, a high conductive electrolyte may be used to reduce the resistivity of the conductive liquid. The conductivity of the conductive liquid may vary from 0.5 S / m to 1000 S / m. In some cases, a low conductive electrolyte may be used, such as acetonitrile or a liquid with low ionic strength.

[0016] In a preferred embodiment, the potential difference of the power source can be adjusted, and the method includes adjusting the potential between the slit nozzle and the substrate. In a preferred embodiment, the power source includes an adjustable current source, and the method includes adjusting the current between the slit nozzle and the substrate. Thus, the method can be adapted for a variety of processes. Furthermore, the potential difference can be decreased (and possibly increased again) while the substrate is moved further relative to the slot die head, such that only a portion of the substrate is coated or processed.

[0017] In a preferred embodiment, the conductive liquid is in contact with the substrate electrode and the slit nozzle such that a closed circuit is formed.

[0018] In a preferred embodiment, the electrodes are deposited on the substrate before or after moving the substrate relative to the slit, or by moving the substrate relative to the slit (i.e., while moving). In one embodiment, the methods provided above can be used to deposit the electrodes on the substrate. In further embodiments, the electrodes deposited using the above processes can be further coated or processed, again using the above processes. In some embodiments, the electrodes can be patterned. Alternatively, the electrodes can be deposited prior to the above processes by first depositing a conductive layer and then patterning the conductive layer. The conductive layer can be deposited by screen printing, dip coating, slot die coating, spray coating, physical vapor deposition, chemical vapor deposition, and / or dry transfer of the conductive material. The pattern can be generated, for example, by standard lithography followed by patterning. In other embodiments, the pattern can be applied using laser patterning. Preferably, the conductive pattern can be directly deposited by screen printing conductive inks, physical vapor deposition through a shadow mask, stencil printing, and inkjet printing, or combinations thereof. Alternatively, the coated pattern can be defined by depositing and patterning a patterned dielectric layer on the conductive substrate, or by directly depositing a patterned dielectric layer as described above. Alternatively or in addition, a polymer layer with an adhesive can be patterned by stencil printing, laser patterning, and applied as a dielectric layer onto the conductive substrate. These electrodes can then be further coated and / or treated as described above and below.

[0019] In another embodiment, the electrodes can include an array of electrodes, which can include electrodes ranging in size from 0.1 μm to 200 μm for performing single cell and electrode electrophysiological or electrochemical measurements.

[0020] In some embodiments, the substrate can include a first electrode, which can be patterned as described above, and a second electrode. The first electrode can be treated or coated as described herein. The second electrode can form a reference electrode, which can be used to monitor the potential in the conductive liquid. The first and second electrodes and the slit nozzle can be connected to a potentiostat. This allows for more precise control of the potential and / or current at the first electrode (working electrode).

[0021] In a preferred embodiment, the depositing step includes depositing a conductive pattern that forms an electrode.

[0022] In a preferred embodiment, instead or in addition, the method includes a step of electrochemically pretreating the electrodes. Alternatively, the methods outlined above can be used to treat the substrate and the electrodes disposed thereon. In one example, the treatment can include oxidizing or passivating the electroactive metal particles and / or surface functional groups. Oxidation can cause background currents at the electrodes. This can include oxidizing or reducing plasticizers and other contaminants in the electrodes.

[0023] This oxidation can be induced by applying a potential difference. This can eliminate the need to use aggressive organic solvents or acids and can be applied to disposable electrodes and flexible electronics on polymer substrates. For example, active electrode materials are prone to fouling by organic molecules from the atmosphere or present as contaminants in the polymer substrate (e.g. bisphenol A and phthalic acid). These surface contaminants can affect both the sensor performance and subsequent processing steps, where clean gold (bonding by thiolation) or carbon surfaces are required (π-π stacking). Such contaminants can be removed with the proposed method and device. Similarly, metal contaminants, e.g. Fe catalysts used to grow carbon nanotubes, can be oxidized, so that they become ionic species soluble in aqueous solutions. This can also be used when electrode materials such as carbon nanotubes are deposited on polymers and need to be removed from them. Carbon nanotubes can be effectively removed from the surface by electrochemical oxidation.

[0024] In one embodiment, the proposed method and apparatus can also be used to pattern carbon nanotube films. For example, parts of the substrate can be protected with a non-reactive, e.g., photo-resistant, layer. This layer can be removed later. Furthermore, the proposed process can be used for selective etching of metallic single-walled carbon nanotubes, leaving only semiconducting nanotubes. The general chemistry of this process is described in "Selective Electrochemical Etching of Single-Walled Carbon Nanotubes" by Wei, D., Liu, Y., Cao, L., Zhang, H., Huang, L., Yu, G., Kajiura, H., and Li, Y., Adv. Funct. Mater. 2019:3618-3624.

[0025] Another embodiment of the method of the present invention is to functionalize the surface of the carbon electrode with oxygen-containing functional groups that can change the affinity of various molecules to the surface, thus improving the selectivity and sensitivity of the sensor. By using an aqueous acid or a weak acid as the conductive liquid, the carbon electrode can be oxidized to provide oxygen-containing functional groups on the carbon electrode. By controlling the conductive liquid composition and the applied potential difference, the formation of specific functional groups can be promoted. For example, carboxy groups are highly desirable because they can be activated with EDC / NHS.

[0026] In a preferred embodiment, the slot die head and the substrate are positioned relative to each other to form a meniscus between the slit nozzle and the substrate when the conductive liquid is dispensed from the slit nozzle. This meniscus can complete an electrical circuit between the slit nozzle and the substrate. This meniscus can help to spread the conductive liquid evenly on the substrate. The portion of the slot die head that is directed toward the substrate can be triangular in shape. In certain examples, the slot die head can be flat-ended (e.g., blunt slit nozzle) or the slot die head can be pointed (i.e., sharp slit nozzle). A blunt slit nozzle can reduce the current density at the slit nozzle and therefore reduce the risk of gassing (e.g., hydrogen generation when depositing a conductive polymer).

[0027] In a preferred embodiment, the potential difference is 0.1 V or more and / or 50 V or less. In other embodiments, the potential difference may be at least 0.2 V, 0.3 V, 0.5 V, 0.7 V, 1 V, 2 V, 5 V, 10, or 15 V. In further embodiments, the potential difference may be at most 0.3 V, 0.5 V, 0.7 V, 1 V, 2 V, 5 V, 7 V, 10 V, 15 V, 20 V, 25 V, or 30 V. In some applications, the potential applied to the slit nozzle is higher than the potential applied to the substrate (potentials shown herein as positive voltages). In other applications, the potential applied to the substrate may be higher than the potential to the slit nozzle (potentials shown herein as negative voltages). Any of the above voltages may represent positive or negative voltages. The power source may provide direct or alternating current.

[0028] The substrate can be rigid or flexible. In a preferred embodiment, the method is a sheet-based process or a roll-to-roll process. In a sheet-based process, the substrate can be a sheet, for example a rigid planar sheet, which is transported under the slit nozzle (or vice versa). In a roll-to-roll process, a flexible substrate is rolled from one roll to another. The flexible substrate can be coated or treated between the rolls or on the rolls.

[0029] The present invention can be implemented, for example, using a conventional slot die coater and corresponding slot die head, which can be provided with external connectivity as described below. One example of a slot die head is manufactured by FOMTECHNOLOGIES, Inc. (e.g., "Research series|XX-Large").

[0030] In a preferred embodiment, the method further comprises the step of heating the substrate before, during and / or after the application of the conductive liquid. For example, the holding device may include a heater, e.g. one or more heated rolls, for heating the substrate. The device may comprise a means for generating a negative pressure or vacuum. This allows the thermal and / or vacuum treatment to be combined with the coating or surface treatment.

[0031] In a preferred embodiment, the conductive liquid contains metal particles, preferably nickel (Ni), platinum (Pt), gold (Au), iron (Fe), cadmium (Ca), chromium (Cr), copper (Cu), titanium (Ti), zinc (Zn), brass and / or silver (Ag). These particles are particularly suitable for coating electrodes and sensors. These metal particles may be present in colloidal suspension, for example as microparticles or nanoparticles in the conductive liquid. When these metal particles are present in colloidal suspension, they can be electrophoretically deposited.

[0032] In another embodiment, these particles can be soluble in the conducting liquid as ionic species. In this case, they can be electrodeposited, for example, by electrochemical reduction. These materials can be used in electrocatalytic applications such as energy conversion and storage, as well as sensor applications. The deposition of noble metals can be used for thiol-based immobilization of molecules such as antibodies, aptamers, and enzymes.

[0033] In a preferred embodiment, the conductive liquid includes a conductive polymer, preferably PANI, polypyrrole, PEDOT, and / or PEDOT:PSS. The conductive polymer can be electrophoretically deposited as polymer particles in suspension or from precursor monomers in suspension (e.g., aniline, pyrrole, EDOT, EDOT PSS mixture). In the latter case, the polymerization reaction can be initiated at the substrate surface by oxidizing the monomers to radical species that lead to polymerization. Such materials can be useful for spectroelectrochemical applications, such as electrochemiluminescence. In an embodiment, one or more conductive polymer and / or non-conductive polymer layers can be electrodeposited onto one or more electrodes.

[0034] Preferably, the aforementioned materials or combinations of materials may be optically transparent, including but not limited to polypyrrole, PEDOT, PEDOT:PSS or any other doped conductive polymer, graphene, single-walled carbon nanotubes, multi-walled carbon nanotubes, amorphous carbon, and combinations thereof.

[0035] The thickness of the layer can be controlled by the amount of liquid dispensed through the slit nozzle and the relative movement speed between the slit nozzle and the substrate. Furthermore, the thickness of the layer can be controlled by the potential difference. The conductive polymer can be deposited in a layer with a thickness of about 2 nm to about 1000 nm. Such a thin layer can act as a binder and protective layer for the nanomaterial electrode, providing additional electrochemically active areas and also surface functionalization.

[0036] Conductive polymers can also be deposited in layers with thicknesses of about 100 nm to about 10 μm, which can provide conductors and / or mechanical protection. The deposited conductive polymer layer can also function as a highly porous layer in a composite matrix antifouling membrane for biological samples such as milk, other foods, and blood. Furthermore, the conductive polymer layer can functionalize electrode materials such as metal foils or non-conductive substrates with a conductive seed layer to provide inexpensive electrodes with improved electrochemical properties.

[0037] While the method can be used to coat a substrate as described above, it can also be used to treat an electrode on a substrate. In a preferred embodiment, the conductive liquid includes a chemical etchant. Examples of chemical etchants include hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), and / or any mixture thereof. In etching, the conductive liquid can include sodium chloride (NaCl), potassium chloride (KCl). The electrodes can include carbon, such as carbon nanotubes and / or single-walled carbon nanotubes graphene, or metal. These electrodes can be electrochemically etched. After treatment, or regardless of treatment, the same methods can be used (with various liquids and potential differences) to functionalize carbon electrodes with conductive polymers (e.g., transparent conductive polymers) to reduce biofouling, increase surface area, or improve conductivity. In some embodiments, electrochemical etching can be combined with conventionally known chemical etching. This can include examples where more energy can be added (at room temperature) to electrochemically drive chemical reactions at the surface than by purely chemical means. For example, instead of using concentrated heated acid baths with long reaction times, a simple aqueous electrolyte with hydrochloric acid (or a weak acid) can be used to oxidize carbon.

[0038] In etching, the electrolyte may be only a salt solution (e.g., NaCl or KCl). This is advantageous if the reaction product of the contaminating species (after the electrochemical reaction) is soluble or dispersible in the electrolyte and therefore can be washed away from the surface.

[0039] In a preferred embodiment, the substrate includes an optically transparent electrode.

[0040] In a preferred embodiment, the conductive liquid includes template molecules. The template molecules can be deposited on a layer, for example a polymer layer. The method can further include washing away the template molecules after the conductive liquid is deposited. For example, in sensing applications, molecular imprinting or capture and washing of template molecules can be used to generate a surface that can clearly recognize the template. Such surfaces are also called synthetic receptors.

[0041] The addition of template molecules allows electrodeposition of a molecularly imprinted polymer layer containing sites for recognizing the template molecules. This polymer layer can be conductive. For example, methanol, acetone, ethanol, isopropanol, acid, base, oxidative or reductive electrochemical treatments can be used as solvents to wash away the template molecules. This washing can be done using the methods described above, but also with a different conductive liquid, i.e. one of the solvents mentioned above. This leaves empty sites where the template molecules can be selectively bound. One particular example of this involves the selective measurement of paracetamol in blood samples.

[0042] In some embodiments, the method may further include applying an inert gas blanket during, before, and / or after dispensing the conductive liquid to minimize oxidation of reactive reagents, such as oxygen-sensitive precursor chemicals. In some embodiments, the apparatus may include a glove box or other airtight container for applying an inert atmosphere. The inert atmosphere may include or consist essentially of, for example, nitrogen or argon.

[0043] In one embodiment of the method, the method includes a step of co-depositing micro- or nanoparticles, molecules, biomolecules, proteins with a conductive or non-conductive matrix, or any combination thereof. Conductive or non-conductive particles can be embedded in a conductive or non-conductive matrix. The micro- or nanoparticles can be made of metal, conductive or non-conductive polymers. The micro- or nanoparticles can be functionalized. In one embodiment, platinum or gold nanoparticles can be suspended in an EDOT or pyrrole-containing electrolyte, and in a step, the metal particles and the conductive polymer can be co-deposited. In electroanalysis and electrocatalysis, conductive catalytically active particles can be embedded in a matrix, preferably conductive, but possibly non-conductive. To improve electrocatalytic properties, iron and iron oxide metal nanoparticles can be co-deposited with a conductive polymer, or they can act as redox mediators, for example, reacting chemically with enzyme cofactors in biosensors.

[0044] A further aspect relates to a substrate coated with the above-mentioned coating method, which results in a more uniform distribution of the coated material. Unlike conventional electrodeposition, the present invention allows for patterning of the substrate to be coated. This can be achieved by increasing or decreasing the potential difference as the substrate moves relative to the slot die head. This potential difference can also be switched on and off. In contrast, in conventional electrodeposition, such patterning requires the use of a patterned insulator layer. The method can also be combined with masking with a dielectric layer. The patterning obtained by increasing or decreasing the potential difference as the substrate moves has unique properties compared to conventional patterning.

[0045] In a further aspect of the invention, a coating or surface treatment apparatus is provided. The apparatus includes a substrate holder for holding a substrate. The apparatus includes a slot die head including a slit nozzle. The slit nozzle and substrate are configured to move relative to one another. The slot die head is configured to dispense a conductive liquid through the slit nozzle and onto the substrate. The apparatus also includes a power source configured to provide a potential difference. The power source is electrically connected to the slit nozzle and includes an interface for electrically connecting to the substrate. The power source is configured to provide a potential difference between the slit nozzle and the substrate.

[0046] The slot die head can include an inlet for coating. The slot die head can include a fluid reservoir for holding the conductive liquid within the slot die head. The apparatus can include a pump and / or an injector for the conductive liquid. The pump can be configured to supply the conductive liquid to the slot die head. The substrate holder can include support rollers for holding and / or moving the substrate. In another example, the substrate holder includes a sample holder (e.g., for holding individual substrate samples). In a further example, the substrate holder can include a vacuum holder for holding the sample substrate to be coated in place during the coating process.

[0047] The slit nozzle is electrically conductive and forms an electrode. The slot die head can be made of an electrically conductive material, such as an electrically conductive metal, or the slot die head can include an electrically conductive material. For example, the slot die head can be made of a metal such as aluminum, titanium, brass, or steel. This allows a power source to be connected to any part of the slot die head, not necessarily directly to the slit nozzle.

[0048] In one embodiment, the surfaces of the slot die head (excluding the slit nozzle) are coated with a dielectric material or anodized to reduce electrical interference and risks to the user.

[0049] The slot die head can be separated into two parts. A shim can be inserted between them to adjust the width of the slit nozzle. The length of the slit nozzle can be 150 mm to 300 mm. The slit nozzle can have a linear nozzle opening, preferably a straight nozzle opening. In an embodiment, the apparatus can include a liquid reservoir outside the slot die head. The liquid reservoir can be fluidly connected to the liquid reservoir outside the slot die head. The apparatus can further include a filter and / or a degasser for the conductive liquid.

[0050] In a preferred embodiment, the potential difference of the power supply can be adjusted, allowing the slit nozzle to be tailored to the manufacturing process, particularly for deposition of different materials, different combinations of materials, deposition at different rates, etc. Furthermore, by adjusting the potential or switching the potential on and off, it is possible to selectively deposit or treat certain areas of the substrate.

[0051] In a preferred embodiment, the power supply includes an adjustable current source. In some processes, it may be preferable to adjust the potential difference by setting a fixed current rather than setting a fixed potential difference, i.e. voltage. The power supply may be equipped with an ammeter to monitor the current flowing through the system. This allows the electrochemical reaction to be monitored.

[0052] Coatings can be deposited on substrates, for example by reduction of metal ions or oxidation of monomers to form polymer coatings. Alternatively, the substrate can be energized to effect electrophoretic deposition of charged particles. The kinetics of these reactions, and therefore the resulting morphology, particle size and thickness, can be controlled by the applied potential or by controlling the current flowing through the system. Similarly, the morphology, particle size and thickness of the coating can be controlled by varying the composition of the supporting electrolyte (e.g., ionic strength, pH, choice of ion, choice of precursor, and concentration of precursor).

[0053] A further aspect of the invention relates to a system comprising the above-described apparatus and a substrate, which may include a polymer, a ceramic, a metal, or any combination thereof, and which is electrically connected to a power source.

[0054] In a preferred embodiment, the substrate includes or forms an electrode that is connected to an interface of a power source. In some embodiments, the substrate can include a layer that is electrically connected to a power source. In other embodiments, only certain portions of the substrate can be conductive and form a counter electrode for the slit nozzle. For example, the substrate can include a pattern that forms an electrode. In this case, material can be deposited only on the portions that form the electrode. [Brief description of the drawings]

[0055] A more detailed description of the subject matter of the invention is given in the following text with reference to preferred exemplary and non-limiting embodiments shown in the attached schematic drawings, which disclose embodiments of the invention by way of example only, and in particular, the disclosure presented by the drawings and the description is not meant to limit the scope of protection afforded by the invention. [Figure 1] 1 is a schematic diagram of an apparatus according to the present invention; [Diagram 2] FIG. 2 is a schematic top view of a part of the device according to FIG. 1 and a substrate comprising first and second electrodes. [Diagram 3] 1 is an image of a device according to the present invention. [Figure 4] 1 is an image of the inner part of a slot according to the present invention. [Diagram 5] 5A and 5B show a circular SWCNT film on a polymer substrate that is partially coated with a polypyrrole layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0056] 1 shows a schematic of an apparatus 1 for coating or surface treatment. The apparatus includes a slot die head 3 with a slit 8. The apparatus also includes a fluid reservoir and pump (not shown) for providing a conductive liquid into the slit 8. Within the slot die head 3, the slit 8 may include a slot die head reservoir 9. The pump may be configured to maintain the conductive liquid under pressure for uniformly discharging the conductive liquid through the slit nozzle 4.

[0057] The apparatus 1 also comprises a substrate holder. Here, the substrate holder is constituted by a support roller 2. The substrate 5 can be held on the support roller 2 and conveyed by the support roller under the slot die head 3. Alternatively, the slot die head 3 can be moved over the substrate 5 held in place. Furthermore, the apparatus comprises a power supply 6. The power supply 6 is electrically connected to the slot die head by a wire 10. The slot die head 3 is made of a conductive material such as stainless steel. The power supply 6 is also connected to the substrate 5 by a wire 11. The power supply 6 is adapted to provide a potential difference between the slot die head 3 and the substrate 5. That is, a voltage is applied between the slot die head 3 and the substrate 5. The power supply 6 can also be connected to a reference electrode by a wire using an interface 12. The power supply 6 can include a potentiostat for controlling the potential of the substrate 5 to be coated in a multi-electrode electrochemical cell, or the power supply 6 can be connected to a potentiostat.

[0058] As the conductive liquid is discharged from the slit nozzle 4, a meniscus 7 is formed by the discharged conductive liquid and a layer 13 of conductive liquid is deposited on the substrate 5 in the usual manner by a slot die coating process as the substrate 5 moves under the slot die head. While the conductive liquid is being deposited on the substrate, a potential difference is applied by a power source between the slit nozzle 4 and the substrate 5. This potential in combination with the conductive liquid is used to coat or treat the substrate as described herein.

[0059] In a particular application, a polymer sheet with a Single-Walled Carbon Nanotube (SWCNT) film was used as the substrate 5 to be treated. The conductive liquid is 37% hydrochloric acid diluted 200 times with deionized water. The substrate 5 comprises a frame surrounding the edge of the SWCNT film to make contact with the wire 11 and the power supply 6. Optionally, as described with reference to FIG. 2, an Ag wire can be printed over the area to be treated to sense the potential of the electrode to be treated and compensate for resistive losses in the system. The Ag wire can also be coated with a dielectric material to reduce gassing on the substrate and to allow more accurate potential sensing by exposing only the area close to the coated electrode to the potential.

[0060] A positive (oxidative) potential is applied to the substrate 5 and a negative (reductive) potential is applied to the slot die head 3. The highly hydrophobic SWCNT surface allows the electrolyte to be drawn along the surface without leaving a trace of electrolyte, thus further reducing chemical consumption.

[0061] The potential can be increased to 35V until the current etching of the SWCNTs is visually observed. Alternatively, the current through the system can be controlled and limited. In this way, a high potential can be selected and the system can apply the potential required to achieve the desired current through the system. This provides a positive feedback across the conductive liquid to compensate for some resistance. The removal of the SWCNTs occurs in less than a minute. Thus, the SWCNTs are efficiently removed in the desired areas.

[0062] In another specific application, a polymer sheet with a SWCNT film was used as substrate 5. Here, wires 11 were attached directly to the SWCNT film. The conductive liquid was a 1M KCl solution of pyrrole monomer. A potential difference of 10 V was applied between the slit nozzle 4 and the substrate 5. A positive potential was applied to the SWCNT film. This resulted in a polypyrrole coating. The resulting coating can be seen in Figures 5A and 5B.

[0063] In a further example, uncured Nafion layers are treated. These layers may contain impurities from the treatment that cause an increase in background current and an unstable background. In one embodiment, such impurities can be oxidized by applying a potential difference in the range of -0.2V to 3V and using phosphate buffered saline or other simple aqueous solution containing salt, e.g., KCl, as the electrolyte. A weak acid can also be used as the electrolyte (e.g., 0.1M sulfuric acid). Oxidation removes contaminants and / or passivates active surface functions, stabilizing the background current of the electrochemical sensor.

[0064] Further use cases for the device 1 are described above.

[0065] FIG. 2 shows a top view of a portion of the slot die head 3 and the substrate 5, and illustrates an exemplary electrode configuration. The substrate 5 is moved in the direction of the arrow 55 under the slot die head 3. The substrate 5 includes a first electrode and a second electrode. The first electrode (also the working electrode) is connected to a power supply 6 including a potentiostat and is used to apply a potential difference. The first electrode includes a contact strip 51, a connecting strip 52, and an end 53. The first electrode is a laser patterned CNT electrode. The end 53 is intended to be coated with a conductive polymer to enhance the sensor performance, as described above. In another embodiment, electropolymerized molecular imprinting, as described above, is used to functionalize the end 53. Additionally, the second electrode includes a contact strip 55, a connecting strip 56, and an end 57. The first and second electrodes can be screen printed with Ag, as is known in the art. The second electrode (also a reference electrode) is used to measure the now applied potential difference and to precisely monitor and adjust the potential difference. Carbon nanotubes can then be deposited onto the first electrode using the apparatus 1 and slot die head 3. The contact strips 51 and 55 are electrically connected to a wire and a power supply 6. Alternatively, electrical contact can be achieved by a conductive metal roll pressed against the contact strips 51 and 55. In this way, a continuous roll-to-roll electrodeposition or electrochemical process can be performed. The second electrode is screen printed and consists of Ag.

[0066] Figure 3 shows an image of an apparatus 1 for coating or surface treatment. The apparatus comprises a substrate holder (conveyor belt with red casing) and a slot die head mounted on top of the substrate holder. The substrate is held on the conveyor belt and transported against the slot die head. The slot die head is connected to a power supply (grey box) via wires.

[0067] As explained above, the slot die head can be separated into two parts. The slot ahead head 3 as shown in FIG. 1 can be separated along the slit 8 as shown in FIG. 1 for example. FIG. 4 shows one half of the slot die head. In a particular embodiment, the one half of the slot die head is connected by a screw (or otherwise) and the wire connecting the slot die head to the power supply meshes with the screw connecting the one half of the slot die head. In a particularly simple embodiment, a bare strand of wire can be wrapped around each screw connecting the one half of the slot to the head as shown in FIG. 4. FIG. 4 also shows a shim that can be inserted between the parts to adjust the width of the slit nozzle (perforated sheet metal).

[0068] While the present invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are to be considered as illustrative or exemplary and non-limiting. Thus, the present invention is not limited to the disclosed embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art from a study of the drawings, the disclosure, and the appended claims, and from practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality, but may mean "at least one".

[0069] A preferred embodiment of the present invention is as follows.

[0070] 1. A method of coating or surface treatment comprising the steps of: The method includes the steps of providing a slot die head (3) having a substrate holder (2) and a slit nozzle (4), mounting a substrate (5) on the substrate holder, moving the substrate relative to the slit nozzle while supplying a conductive liquid onto the substrate through the slit nozzle such that the liquid is deposited on the substrate, and applying a potential difference between the slit nozzle and the substrate using a power source (6) while supplying the conductive liquid to the substrate through the slit nozzle, the power source applying a first potential to the slit nozzle and a second, different potential to the substrate.

[0071] 2. The method according to aspect 1, wherein the potential difference of the power source can be adjusted, comprising a step of adjusting the potential between the slit nozzle and the substrate.

[0072] 3. The method according to aspect 1 or 2, wherein the power supply includes an adjustable current source, comprising the step of adjusting the current between the slit nozzle and the substrate by the adjustable current source.

[0073] 4. The method according to one of aspects 1 to 3, wherein a conductive liquid contacts the substrate and the slit nozzle so as to form a closed circuit.

[0074] 5. A method according to one of aspects 1 to 4, comprising depositing an electrode on the substrate prior to or by moving the substrate relative to the slit nozzle.

[0075] 6. The method according to embodiment 5, wherein the depositing step includes depositing a conductive pattern that forms an electrode.

[0076] 7. The method according to one of aspects 3 to 6, further comprising the step of electrochemically pretreating the electrode.

[0077] 8. A method according to one of aspects 1 to 7, comprising positioning the slot die head and the substrate relative to one another such that a meniscus (7) is formed between the slit nozzle and the substrate when the conductive liquid is dispensed from the slit nozzle.

[0078] 9. The method according to one of the preceding aspects, wherein the potential difference is 0.1 V or more and / or 50 V or less.

[0079] 10. The method according to one of aspects 1 to 9, which is a sheet-based or roll-to-roll process.

[0080] 11. The method according to one of aspects 1 to 10, comprising heating the substrate before, during, and / or after dispensing the conductive liquid.

[0081] 12. The method according to one of the preceding aspects, wherein the conductive liquid comprises metal particles, preferably Ni, Pt, Au, Fe and / or Ag.

[0082] 13. The method according to one of aspects 1 to 12, wherein the conductive liquid comprises a conductive polymer, preferably PANI, polypyrrole, PEDOT, and / or PEDOT:PSS.

[0083] 14. The method according to one of aspects 1 to 13, wherein the substrate comprises an optically transparent electrode material, preferably carbon nanotubes, single-walled carbon nanotubes, graphene, and / or indium tin oxide.

[0084] 15. The method according to one of the preceding aspects, wherein the conductive liquid comprises a chemical etchant, preferably hydrochloric acid, sulfuric acid, or nitric acid, or a mixture thereof.

[0085] 16. The method according to one of aspects 1 to 15, wherein the conductive liquid comprises template molecules, and further comprising the step of washing away the template molecules after the conductive liquid is deposited.

[0086] 17. A substrate (4) coated by a coating method according to one of embodiments 1 to 16.

[0087] 18. An apparatus (1) for coating or surface treatment, comprising: A substrate holder (2) for holding a substrate; a slot die head (3) including a slit nozzle (4), the slit nozzle and the substrate being configured to move relative to one another, the slot die head (3) being configured to dispense a conductive liquid onto the substrate through the slit nozzle; and a power source (6) configured to provide a potential difference, the power source (6) being electrically connected to the slit nozzle and including an interface for electrically connecting to a substrate, the power source (6) being configured to provide a potential difference between the slit nozzle and the substrate.

[0088] 19. The apparatus according to embodiment 18, wherein the slit nozzle is made of a conductive material.

[0089] 20. The device according to embodiment 18 or 19, wherein the potential difference of the power supply can be adjusted.

[0090] 21. The apparatus according to one of aspects 18 to 20, wherein the power supply includes an adjustable current source.

[0091] 22. A system comprising an apparatus according to one of aspects 18 to 21 and a substrate.

[0092] 23. The system according to embodiment 22, wherein the substrate includes or forms an electrode (21) connected to an interface of a power source.

[0093] 24. The system according to embodiment 22 or 23, wherein the substrate comprises an electrode (21), and the electrode is patterned.

[0094] 25. The system according to embodiment 22 or 23, wherein the substrate comprises a second electrode, the second electrode being a reference electrode for measuring the potential.

Claims

1. 1. A method of coating or surface treatment comprising the steps of: Providing a slot die head (3) having a substrate holder (2) and a slit nozzle (4); Mounting a substrate (5) on the substrate holder; moving the substrate relative to the slit nozzle while supplying a conductive liquid onto the substrate through the slit nozzle such that liquid is deposited on the substrate; applying a potential difference between the slit nozzle and the substrate using a power source (6) while supplying the conductive liquid to the substrate through the slit nozzle; The method, wherein the power supply applies a first potential to the slit nozzle and a second, different potential to the substrate.

2. The method of claim 1 , wherein the potential difference of the power supply is adjustable, comprising adjusting the potential between the slit nozzle and the substrate.

3. The method of claim 1 or 2, wherein the power supply comprises an adjustable current source, and further comprising the step of adjusting the current between the slit nozzle and the substrate.

4. 4. The method according to claim 1, wherein the conductive liquid contacts the substrate and the slit nozzle so as to form a closed circuit.

5. 5. The method according to claim 1 , further comprising depositing an electrode on the substrate prior to or by moving the substrate relative to the slit nozzle.

6. The method of claim 5 , wherein the depositing step comprises depositing a conductive pattern that forms the electrode.

7. The method according to claim 3 , further comprising the step of electrochemically pretreating the electrodes.

8. 8. The method according to claim 1, comprising positioning the slot die head and the substrate relative to each other such that a meniscus (7) is formed between the slit nozzle and the substrate when the conductive liquid is dispensed from the slit nozzle.

9. 9. The method according to claim 1, wherein the potential difference is 0.1 V or more and / or 50 V or less.

10. The method according to claim 1 , wherein the method is a sheet-based or roll-to-roll process.

11. 11. The method according to claim 1, comprising the step of heating the substrate before, during and / or after the application of the conductive liquid.

12. 12. The method according to claim 1, wherein the conductive liquid comprises metal particles, preferably Ni, Pt, Au, Fe and / or Ag.

13. 13. The method according to claim 1, wherein the conductive liquid comprises a conductive polymer, preferably PANI, polypyrrole, PEDOT, and / or PEDOT:PSS.

14. 14. The method according to claim 1, wherein the substrate comprises an optically transparent electrode material, preferably carbon nanotubes, single-walled carbon nanotubes, graphene, and / or indium tin oxide.

15. 15. The method according to claim 1, wherein the conductive liquid comprises a chemical etchant, preferably hydrochloric acid, sulfuric acid or nitric acid, or a mixture thereof.

16. 16. The method of claim 1, wherein the conductive liquid comprises template molecules, and further comprising the step of washing away the template molecules after the conductive liquid has been deposited.

17. A substrate (4) coated with a coating method according to one of the preceding claims.

18. An apparatus (1) for coating or surface treatment, comprising: A substrate holder (2) for holding a substrate; a slot die head (3) comprising a slit nozzle (4), the slit nozzle and the substrate being configured to move relative to one another, the slot die head (3) being configured to dispense a conductive liquid onto the substrate through the slit nozzle; an electrical power source (6) configured to provide a potential difference, the electrical power source (6) being electrically connected to the slit nozzle and including an interface for electrically connecting to the substrate, and configured to provide the potential difference between the slit nozzle and the substrate.

19. 20. The apparatus of claim 18, wherein the slit nozzle is made of a conductive material.

20. 20. Apparatus according to claim 18 or 19, in which the potential difference of the power supply is adjustable.

21. 21. Apparatus according to one of claims 18 to 20, wherein the power supply comprises an adjustable current source.

22. A system comprising an apparatus according to one of claims 18 to 21 and a substrate.

23. 23. The system of claim 22, wherein the substrate includes or forms an electrode (21) connected to the interface of the power supply.

24. 24. The system of claim 22 or 23, wherein the substrate comprises an electrode (21), the electrode being patterned.

25. 24. The system of claim 22 or 23, wherein the substrate comprises a second electrode that is a reference electrode for measuring electrical potential.

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