EP1843864A1

EP1843864A1 - Component with a coating for reducing the wettability of the surfaces and method for production thereof

Info

Publication number: EP1843864A1
Application number: EP06707915A
Authority: EP
Inventors: Christian Hansen; Ursus KRÜGER; Manuela Schneider
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2005-02-04
Filing date: 2006-01-31
Publication date: 2007-10-17
Anticipated expiration: 2026-01-31
Also published as: MX2007009397A; BRPI0607111A2; CN101119811B; DK1843864T3; EP1843864B1; CN101119811A; US20080118772A1; DE102005006014A1; US7935428B2; WO2006082180A1

Abstract

The invention relates to a component made from a substrate with a coating, whereby the coating forms a surface of the component with reduced wettability. The invention further relates to production of said component. The coating which forms a surface with projections (19) and recesses (20), brings about a reduction in wettability, in particular, by means of an effect based on the properties of lotus blossom. According to the invention, a metal with antimicrobial properties, in particular, silver is provided under the coating, which is not fully covered by the coating, in other words, regions (21) remain free of the coating in which the surface of the component is formed by the metal with antimicrobial properties.

Description

description

Component with a coating to reduce the wettability of the surface and method for its preparation

The invention relates to a component, comprising a substrate with a coating, which has a surface with a low wettability in comparison to the uncoated substrate.

Surfaces with a low wettability, as stated above, come z. B. are used as so-called lotus effect surfaces and are described, for example, in DE 100 15 855 A1. According to this document, such surfaces are characterized by a microstructure, which can be obtained by a layer deposition from solutions, but also by an electrolytic deposition. This mimics an effect observed on the leaves of the lotus flower, accordingly a microstructuring of the surface produced for this purpose

Elevations and depressions with a radius of 5 to 100 μm must have the wettability for water as well as dirt ^¬ particle lowers. As a result, contamination of the corresponding surface can be counteracted.

The object of the invention is to provide a component with egg ^¬ ner coating to reduce the wettability of the surface of the component is available, which also ensures a comparatively good resistance to contamination by micro-organisms in addition to a low wettability of the surface. This object is achieved with the component specified in the introduction ^{according to the} invention in that a metal with antimicrobial properties is located under the coating, which is not completely covered by the coating. As the metal having antimicrobial properties (hereinafter referred to briefly as metal) can in particular silver USAGE be det ^¬, whose antimicrobial effect is known. As alternative metals but also, for example, palladium or platinum in question.

The invention makes use of the fact that the timikrobiellen to ^¬ properties, so the properties or an increase. to prevent the settlement of micro-organisms or viruses on the surface of the component, and then come into play when the metal surface is not a closed upper ^¬ forms of the component, but in part by the loading ^¬ coating to reduce the wettability is covered. A component having such a layer structure can thus be a low wettability of surface che ensure and antimicrobial effect before ^¬ geous simultaneously. In particular ^¬ sondere are thereby guaranteed the properties of the low wettability of the surface over a longer period of time as a surface contamination by micro-organisms ^¬ and the like is prevented. For this, the antimicrobial activity of the surface of the component is pre ^¬ set. Namely, microorganisms can form a film-like layer on components which is very stable and would reduce or even abolish the surface properties of a wetting-reducing coating.

According to a particular embodiment of the invention it is provided that the metal strat an intermediate layer between the sub ^¬ and the coating is formed. The metal can thus be applied as a thin coating, so that it is not necessary for the antimicrobial effect that the entire component consists of the metal. Rather, the choice of material ^{¬ of} the metal is arbitrary, the coating is applied, for example, electrochemically or by vapor deposition on the substrate of the component. Thereby, the material is ^¬ consumption of the metal in the preparation of antimikro- biellen properties of the component advantageously low, resulting in economical solutions.

According to a further embodiment of the invention, the metal with the antimicrobial effect consists of a biaxially textured, epitaxial layer. These layers can be preferably formed by coating on an equally biaxially tex-structured substrate, with this structure ^¬ texture during the coating onto the layer of the Me ^¬ tall transmits (this, for example, J. C. Moore et al., Fabrication of cube -textured Ag-buffered Ni substrates by electroepitaxial deposition, Supercond, Sei., Technol., 14, 124-129, (2001)). As a result, the properties of the metal layer can be advantageously influenced. For example, the biaxially textured epitaxial metal layer offers greater resistance to corrosive attack. Such a layer such as silver thus has increased compared to the literature values of silver standard potential compared to what ^¬ serstoff (hereafter standard potential) in the electrochemical series of metals. DC ^¬ time, the antimicrobial property of the metal ^¬ layer can be affected because this antimicrobial effect is caused on the film due to not yet fully clarified electrochemical processes. A further embodiment of the invention provides that the coating on the metal is metallic and forms a biaxially textured, epitaxial layer on the layer of antimicrobial metal. The coating is preferably made of copper. However, other metals such as iron used who ^¬ the. The biaxially textured, epitaxial production of the coating can also be advantageously used selectively in order to change the electrochemical properties of the coating. In the event that the coating is metallic, the area of application in which the component is to be used must be taken into account in the production of the component. Namely, the antimicrobial, partially exposed metal layer and the metallic coating form local elements, which can promote a corrosive attack of the component. To prevent this, the standard potentials of the coating and the underlying metal layer must not be too far apart. At the same time, the interim ^¬ the coating of the antimicrobial metal layer occurring electrochemical processes to consider a rule factor influencing the antimicrobial activity of the metal layer.

The selection of metals for the coating and the underlying antimicrobial metal layer thus depends on the A ^¬ rate case and must for. B. be appropriate experiments he ^¬ averages. In this case, the choice of suitable metals as the influencing ^parameter, as well as the possibility of providing the coating or the like, are available to the ^person skilled in the art. the underlying layer is biaxially textured, epitaxially formed.

The decrease the wettability of the surface of the component ^¬ de effect can be advantageously improved when the upper surface of the coating has a lotus effect favoring microstructure. In this case, the microstructure with its elevations and depressions, as already mentioned, is designed such that the effect of leaves of the lotus flower is imitated. Production methods for such a microstructure on the surface are described in the initially mentioned DE 100 15 855 A1.

According to a particularly advantageous method, the microstructure can be produced by pulse plating. In this case, according to a particular embodiment of the invention, a component is obtained in which the microstructure is superimposed on a nanostructure produced by pulse plating. This nanostructure advantageously also forms finer elevations and depressions (for example nanotubes), which further reduce the wettability of the surface of the component.

A further improvement for the component results if the structural elements of the nanostructure (for example the needle needles) consist of a metal oxide. This results in another way, the electrochemical properties of the structural elements of the nanostructure to beeinflus ^¬ sen, since the metal oxides (such as copper) in my general ^¬ have a higher standard potential. In this case, for example, a coating of copper can be essentially converted into copper oxide, whereby the standard ^¬ electrode potential approaches that of the antimicrobial, partially exposed layer.

Furthermore, the invention relates to a method for

Producing a coating on a component, which has a surface with a low wettability compared to the uncoated substrate. Such a method is ten in the above-described already erwähn ^¬ DE 100 15 855 Al. For example, the coating (lotus effect surface) can take the form of a layer separation from solutions.

A further object of the invention is therefore to specify a method for producing a coating on a component having a wettability-reducing surface, which ensures a comparatively long-lasting effect with regard to reduced wettability.

This object is according to the invention ren with said procedural ^¬ achieved in that the coating is produced on a metal having antimicrobial properties, in particular silver in such a way that the metal processing by the Beschich ^¬ is not completely covered, wherein the surface by electrochemical pulse plating is treated with a the Benetz ^¬ bility reducing microstructure of the surface is manufactured. It has been found that is supported by the s ^¬ Pul se Plating an irregular layer growth, then a microstructure that can develop, which decreases the wettability by forming elevations and depressions in the micrometer range. The inventive method is therefore advantageous adapted to provide solely by means of electrochemical method, a hard wettable surface on a component and to place the same time, for example, by an incomplete coating of the metal with at ^¬ timikrobiellen properties a surface available on the colonization of microorganisms or viruses is made difficult. According to a particular embodiment of the invention it is provided that the pulse plating is carried out of the ^¬ art as reverse pulse plating, the s a, this overlapping, the wettability further reducing nano structure is produced with the microstructure. The pulse length in the method step for producing the nanostructure is advantageously less than 500 ms. Thus ge deposition parameters can be set on the surface to be generated, so that the nanostructure generated sufficiently different in their dimensions of the microstructure produced in this process step günsti ^¬. The interaction between the microstructure and the nanostructure superimposed on the microstructure leads to a considerable reduction in the wettability of the surface of the electrochemically produced coating.

When reverse pulse plating, the current pulses are generated by jewei ^¬ celled reversing the polarity of Abscheidestroms, so that advantageously a strong temporal gradient in the La ^¬ dung displacements at the surface can be achieved. Advantageously, the individual current pulses are in the range between 10 and 250 ms in terms of their length. It has ge ^¬ shows that with the above parameters, the nanostructure of the surface strongly expresses particularly advantageous. At ^¬ the cathodic pulses may have at least three times the length of the anodic pulses. As a cathodic pulses who construed ^¬ those pulses arrives at the dung it to a Abschei ^¬ on the surface, while the anodic pulses cause dissolution of the surface. For the specified ratio between cathodic and anodic pulses, it has been shown that the needle-like basic elements of the nanostructure Na ^¬ advantageously be produced structure with a high density on the micro ^¬, which favors the Lotus effect to be achieved. There is also the possibility of reverse Pulse plating to perform the cathodic pulses with a higher current density, than the anodic pulses. Also by this measure, the deposition rate of the cathodic pulses is increased compared to the removal rate of the anodic pulses. The pulse length for generating a microstructure in an upstream process step may be at least one second. With pulse lengths in the range of seconds the required microstructure can the surface be made on time low elekt ^¬ rochemischem way. A microstructure forms simultaneously with the nanostructure of the surface when the mentioned process parameters for generating the nanostructure of the surface are set.

According to a particularly advantageous embodiment of the invention, it is provided that, after the generation of the nanostructure, a further reverse pulse plating is carried out, such that the nanostructure elements are oxidized. The reverse pulse plating for the oxidation of the nanostructure elements can be ^¬ vorzugt the following process parameters performed advertising to: The pulse-called follow the growth of the layer with cathodic and anodic pulse is supplemented by a third potential-controlled pulse, whereby the Oxidationspro- process of the nanostructure elements befordert becomes. The oxidation process of the nanostructure elements, it accommodates that the nanostructure elements consist of elevations with preferably nadelarti ^¬ ger structure whose tips are exposed to an electrochemical attack stronger than the areas around the Na ^¬ nostrukturelemente around. Therefore, an oxidation reaction will preferably take place on the nanostructure elements.

In a further process step, unoxidized parts of the coating can then be electrochemically dissolved while exposing the metal. This is for example by applying a DC potential to the coating, since the oxidized nanostructure elements have a higher standard potential than the non-oxidizing parts of the coating. If the coating has been produced from copper, for example, then this copper will dissolve faster than the copper oxide nanostructure elements. For example, as soon as a silver layer is exposed under the coating, so this also has a higher standard potential than copper, so that this is largely retained. As a result, it is advantageous to control the exposure of the silver, with the electrochemical process occurring in the process being stable. A Nachbear ^¬ processing the surface with reduced wetting and antimicrobial properties at the same time is not necessary.

Alternatively, instead of electrochemically dissolving unoxidized portions of the coating, the coating may also be applied using, for example, a mask which covers portions of the layer of antimicrobial metal underlying the coating. This mask, the example ^¬ may be made of photoresist, may be dissolved by means of a geeigne ^¬ th solvent once the coating has been completed. In this way, a part of the layer of the antimicrobial material can be released again to an inventive antimicrobial and simultaneously reducing the wettability of the surface to he ^¬ testify.

Further details of the invention are described below with reference to the drawing. In the individual figures, identical or corresponding drawing elements are each provided with ^¬ weils the same reference numerals, which only To that extent, it will be explained several times how differences arise between the figures. Show it

1 shows the schematic structure of a Ausführungsbei ^¬ game of the surface according to the invention in a schematic section,

2 shows the surface profile of a lotus effect surface with antimicrobial properties as an exemplary embodiment of the surface according to the invention in section and FIGS. 3 and 4 show perspective views of the lotus effect surface with antimicrobial properties according to FIG.

FIG. 1 shows a component 11 with a surface whose wettability is reduced. The surface 12 can be described schematically by a superimposition of a macrostructure 12 (which, for example, may also be predetermined by the component geometry) with a microstructure 13 and a nanostructure 14. The microstructure produces a waviness of the surface. The microstructure is indicated by hemispherical ^¬ shaped elevations on the wavelength macrostructure 12th The nanostructure 14 is illustrated in FIG. 1 by nubs which are located on the hemispherical elevations (microstructure) and partly in the parts located between the elevations of the macrostructure 12 which form the depressions of the microstructure 13.

The adhesion-reducing properties of the surface formed by the superposition of the macrostructure 12, the microstructure 13 and the nanostructure 14 become clear on the basis of a water droplet 15 which forms a water ^pearl on the surface. Due to the low wettability of the surface on the one hand and the surface tension of the water drop the other hand is formed between the water drop 15 and the surface of a relatively large contact angle γ from defined runs through an angle leg 16a, the paral ^¬ lel to the surface, and an angle leg 16b which forms a tangent to the skin of the water drop, by the edge of the contact surface of the water droplet 15 with the surface (or more precisely the angle leg 16a) runs. FIG. 1 shows a contact angle γ of more than 140 °, so that the surface shown schematically is a so-called superhydrophobic surface.

The component 11 according to FIG. 1 is made of silver, with the macrostructure 12 forming part of the overall surface of the component 11. This part of the surface is characterized by the fact that silver can come into direct contact with the environment, with the antimicrobial properties of silver being used. As a result, z. B. causes microorganisms that would cause a reduction in the contact angle γ can not fix on the surface, whereby the low wettability of the surface can be obtained even over a longer period of use of the component 11.

In experiments, Reverse Pulse Plating can be used to produce a lotus effect surface by depositing copper on a surface of silver smoothed by electropolishing. Here, the following process parameters can be selected.

1. Generation of the coating with the microstructure and the nanostructure in one process step by reverse pulse plating: Pulse length (reverse pulse): 240 ms at 10 A / dm ² cathodic, 40 ms at 8 A / dm ² anodic

Electrolyte contained 50 g / l Cu, 20 g / l free cyanide, 5 g / l KOH (alternatively following composition: 72 g / l CuCN, 125 g / l KCN, 5 g / l KOH)

2. Oxitation of the predominantly needle-shaped nanostructured elements in a subsequent process step: Pulse length (extended reverse pulse): 240 ms at 10 A / dm ² cathodic, 40 ms at 8 A / dm ² anodic and 50 to 100 ms potential-controlled with u = + l, 2V anodic. Electrolyte as in step 1

3. dissolution of the coating in the unoxidized areas exposing the silver with the following parameters:

The pulse is a unipolar - potential-controlled pulse in anodic direction: i (cath.) = 0 A / dm ² ; u (anod.) = +0, 5V; t (cath.) = 200-250 ms; t (anod.) = 50 - 100ms.

The electrochemically generated surface can be examined below by means of an SPM (Scanning Probe Microscope - also called AFM or Atomic Force Microscope). With an SPM, surface structures down to the nanometer range can be determined and displayed. A section of the mi- partly producible the experimental parameters above surface is shown in Figure 2 in section schematically where ^¬ is excessive at the profile (diagram on the model of SPM examinations).

With respect to a zero line 17 is a waveform 18 in

2, which illustrates the macrostructure superimposed on the surface structure. The microstructure 13 is due to the elevation as a sequence needle-like Er- increases 19 and depressions 20 shown. Furthermore, in certain areas, the nanostructure 14 has been indicated, which results from a narrow sequence of elevations and depressions, which are no longer to be resolved in the scale shown in Figure 2 and therefore can only be seen as a thickening of the profile line of the surface profile.

Further details can be found in FIG. 3, which shows a perspective view of the copper surface. It is a square area of 100x100 μm as

Section has been selected, wherein the microstructure 13 determining needle-like elevations 19 are clearly visible. The resulting image reminds the viewer of egg ^¬ nen "coniferous forest", wherein the intermediate spaces between the "needle trees" (increases 19), the cavities form 20th The surface according to Figure 3 is shown inflated to the He ^¬ heightening 19 and the recesses 20 of the microstructure to clarify. 13

As can also be seen from FIG. 3, the coating consisting of the elevations 19 and depressions 20 does not cover the entire surface of the substrate, ie. H . In some places, the silver is exposed as the surface of the component 11. These areas 21 are in the Figure 3 by more o less the "smooth" Ariale to recognize the form of the "needle park ^¬" "clearings". In these regions 21, the surface formed by the silver may be the component which for silver develop typical anitmicrobial properties.

As shown in the perspective view of the surface according Fi gur ^¬ 4, which illustrates an enlarged detail of the view according to Figure 3 can be seen, the microstructure 13 wei ^¬ superimposed terhin a nanostructure fourteenth In the less creased representation according to Figure 4, the elevations 19 and depressions 20 appear more like a waviness of the surface (but not ligkeit according to Figure 2 may be confused due to the different scale with the Wel ^¬). Superimposed on this brightness are furthermore smallest elevations 19n and depressions 2On, which characterize the nanostructure of the surface. These, too, are reminiscent in their construction of the expression of a "coniferous forest" already explained with reference to FIG. 3, the geometrical dimensions of which are smaller by approximately two orders of magnitude, that is to say can not be recognized at the scale selected in FIG.

To illustrate the size relationships are shown in Figu ^¬ ren each characterized by a clamp 2 and 3, the macrostructure 12, the microstructure 13 and the nanostructure fourteenth The bracket always comprises only a section of the respective structure, which contains an elevation and a depression, so that the brackets allow one another in each case within a figure a comparison of the orders of magnitude of the structures in relation to one another. With the illustrated embodiment, contact angle of 150 ° and more can be achieved for what. The superhydrophobic properties of the illustrated copper layer, which cause a lotus effect, is achieved by an interaction of at least the microstructure 13 and the nanostructure 14, wherein the superimposition of a macrostructure 12 can still improve the observed effects. By selecting suitable process parameters such lotus effect surfaces can be produced for different layer materials and for liquids with different wetting behavior.

Claims

claims

1. component, comprising a substrate (11) with a coating (19, 20), which in comparison to the uncoated substrate has a surface with a low wettability ^¬ , characterized in that under the coating, a metal with antimicrobial properties, in particular silver, which is not completely covered by the coating.

2. Component according to claim 1, characterized in that the metal forms an intermediate layer between the substrate (11) and the coating.

3. Component according to claim 2, characterized in that the metal consists of a biaxially textured, epitaxial layer.

4. Component according to one of the preceding claims, characterized in that the coating (19, 20) is metallic, in particular consists of copper, and forms a biaxially textured, epi ^¬ tactical layer.

5. Component according to one of the preceding claims, characterized in that the surface of the coating (19, 20) has a Lotus ^¬ effect favoring microstructure (13).

6. Component according to claim 5, characterized in that the microstructure (13) generates a pulse-plating

Nanostructure (14) is superimposed.

7. The component according to claim 6, characterized in that the structural elements of the nanostructure (14) consist of a metal oxide.

8. A method for producing a coating (19, 20) on a component (11), which has a surface with a low wettability in comparison to the uncoated substrate, characterized in that the coating (19, 20) on a metal with anti- microbial properties, in particular silver, such that the metal is not completely covered by the coating (19, 20), the surface being produced by electrochemical pulse plating with a wettability reducing microstructure (13) of the surface.

9. The method according to claim 8, characterized in that the pulse plating is carried out as reverse pulse plating, the s with the microstructure (13) a superimposed this, the wettability further reducing Na ^¬ nostruktur (14) is generated.

10. The method according to claim 9, characterized in that after the generation of the nanostructure (14) a further reverse pulse plating is performed, such that s the nanostructure elements (19n) are oxidized.

11. The method according to claim 10, characterized in that non-oxidized parts of the coating under exposure (21) of the metal are dissolved electrochemically.