Title of Invention

A METHOD FOR ELECTROCHEMICALLY PRODUCING A SURFACE WITH AN ANTI-ADHESION MICROSTRUCTURE

Abstract The invention relates to a surface comprising a microstructure that reduces adhesion and to a method for producing said microstructure. Microstructures of this type that reduce adhesion are known and are used, for example, to configure self-cleaning surfaces that use the Lotus effect. According to the invention, the surface is produced electrochemically by means of reverse pulse plating, the known microstructure being first produced and a nanostructure that is overlaid on the microstructure is produced at the same time or in a subsequent step. To achieve this for example, the pulse length of the current pulse that is used during the reverse pulse plating lies in the millisecond range and has a pulse length ratio greater than 1:3 (anodic;cathodic). The microstructure that has been produced, consisting of peaks (19) and troughs (20) and troughs (20)is then overlaid with peaks (19n) and troughs (20n) of a smaller size order belonging to the nanostructure, thus permitting the Lotus effect that is achieved by the surface to be greatly improved.
Full Text PCT/EP2005/053902 / 2004P12591WOUS
1 Description
Surface with an anti-adhesion microstructure and method for producing same
The invention relates to a surface with an anti-adhesion microstructure and a method for electrochemically producing such a surface.
Anti-adhesion surfaces of the abovementioned type are used e.g. as so-called lotus-effect surfaces and are described, for example, in DE 100 15 855 Al. According to this publication, such surfaces are characterized by a microstructure which can be obtained by film deposition from solutions, but also by electrolytic deposition. This mimics an effect observed on the leaves of the lotus plant, according to which the resulting micropatterning, which for this purpose must have peaks and valleys with a radius of 5 to 100 µm, reduces the adhesion of water and dirt particles. This enables contamination of the corresponding surface to be counteracted. The formation of limescale, for example, can also be prevented.
The object of the invention is to specify a surface with an anti-adhesion microstructure and a production method for said surface, the adhesion-reducing effect being comparatively strongly marked.
This object is achieved according to the invention by a method in which the surface is produced by electrochemical pulse plating, a nanostructure overlying the microstructure being created by reverse pulse plating. According to the invention, the nanostructure is overlaid on the microstructure by producing, on the surface topology having surface profile

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bending radii in the micrometer range (microstructure), a surface topology whose bending radii are preferably in the range of a few nanometers to 100 nanometers (nanostructure). The formation of the nanostructure on the microstructure is achieved by reverse pulse plating using current pulses whose length is in the millisecond range. The microstructure can be produced simultaneously or separately depending on the process parameters such as pulse length and deposition density.
The surface's nanostructure in conjunction with the microstructure advantageously improves the effect of reducing the adhesion of substances to the surface, thereby advantageously improving the surface's lotus effect.
Although US 5,853,897 discloses a method of electrodepositing films with a rough surface by means of pulse plating, the films produced according to this document are designed solely for optical applications, as they have excellent light absorbing properties in a wide optical wavelength range. For this purpose it merely suffices to create a dendritic microstructure without having to overlay same with a nanostructure.
Advantageously the pulse length for the process step of producing the nanostructure is less than 500 ms. This means that, during this step, favorable deposition parameters can be set on the surface to be produced, so that the resulting nanostructure differs sufficiently in its dimensions from the microstructure created.
The current pulses for reverse pulse plating are generated by reversing the polarity of the deposition current so that a significant time differential for the charge transfers at the

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surface can be advantageously achieved. In respect of their length, the individual current pulses are advantageously in the range between 10 and 250 milliseconds. It has been shown that advantageously, for the parameters specified, the surface's nanostructure is particularly pronounced.
It is particularly advantageous if during reverse pulse plating the cathodic pulses are at least three times as long as the anodic pulses. For the purposes of the invention, cathodic pulses are taken to mean those pulses resulting in deposition on the surface, whereas the anodic pulses produce dissolution of the surface. For the specified ratio between cathodic and anodic pulses it has been found that the needle-like basic elements of the nanostructure are advantageously produced with a high density on the microstructure, to the benefit the lotus effect to be achieved.
Another advantageous possibility is that, for reverse pulse plating, the cathodic pulses are implemented with a higher current density than the anodic pulses. This also increases the deposition rate of the cathodic pulses compared to the erosion rate of the anodic pulses so that nanopatterning layer growth is advantageously produced. Self-evidently, the measures of modifying the pulse duration and varying the current density can be combined together, an optimum having to be found for the material to be deposited by adjusting the specified parameters.
According to one embodiment of the method it is provided that the pulse length is at least one second for an upstream microstructure producing step. With pulse lengths in the seconds range, the surface's required microstructure can be advantageously produced time-efficiently by electrochemical

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means if it is not produced, or not with sufficient markedness, in the nanostructure producing step.
According to another embodiment of the method, the surface is additionally produced with a macrostructure superimposed on the microstructure. The macrostructure can be produced electrochemically or by other means, e.g. mechanically. The term macrostructure is to be understood here as a surface topology whose elementary structural components' geometrical dimensions are at least an order of magnitude greater than those of the microstructure. In the case of a wavy macrostructure, this would mean e.g. for the radius of the waves that said radius is greater to a corresponding degree than the radii of the peaks and valleys of the microstructure. The macrostructure advantageously allows ttie anti-adhesion properties of the surface to be increased still further. In addition, the surface's macrostructure can advantageously assume additional functions such as improving the flow characteristics of the surface.
The surface according to the invention achieves its stated object by a nanostructure created by pulse plating being overlaid on the microstructure. This inventive surface composition enables the already mentioned advantages to be achieved, in particular improving the anti-adhesion properties of the surface.
According to a particular embodiment of the surface, same is superhydrophobic. This means that the adhesion of water or other hydrophilic substances is particularly greatly reduced. The superhydrophobic properties in particular cause poor wettability of the surface for water, so that water present on the surface forms individual droplets which, because of the

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surface's contact angle of more than 140°, readily roll off and possibly also entrain dirt particles present on the surface with them. Surfaces with superhydrophobic properties are therefore particularly suitable for making the surface a lotus-effect surface.
Further details of the invention will now be described with reference to the accompanying drawings in which the same or corresponding elements are provided with the same reference numerals and will only be explained more than once where they differ from drawing to drawing. Figure 1 schematically illustrates an embodiment of the
surface according to the invention in schematic cross
section, Figure 2 shows the surface profile of a lotus-effect surface
as an example of the inventive surface in cross
section and Figure 3 shows perspective views of the lotus-effect surface
according to Figure 2.
Figure 1 shows a body 11 having a surface with reduced adhesion properties. The surface 12 can be schematically described by an overlaying of a macrostructure 12 with a microstructure 13 and a nanostructure 14. The microstructure creates surface waviness. The microstructure is indicated by hemispherical peaks on the wavy macrostructure 12. The nanostructure 14 is represented in Figure 1 by bumps on the hemispherical peaks (microstructure) and in the parts of the macrostructure 12 located between the peaks and forming the valleys of the microstructure 13.
The anti-adhesion properties of the surface formed by the superimposition of the macrostructure 12, the microstructure

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13 and the nanostructure 14 are indicated by a water droplet 15 which form a pearl of water on the surface. Due to the low wettability of the surface on the one hand and the surface tension of the water droplet on the other, there is formed between the water droplet 15 and the surface a relatively large contact angle y which is defined by an angle leg 16a running parallel to the surface and an angle leg 16b forming a tangent to the skin of the water droplet, said tangent running through the edge of the contact area of the water droplet 15 with the surface (or more precisely the angle leg 16a). Figure 1 shows a contact angle y of more than 14 0° so that the schematically represented surface is superhydrophobic surface.
As part of an experiment, reverse pulse plating has been used to produce a lotus-effect surface by depositing copper on a surface smoothed by electroplating, the following process parameters having been selected:
Production of the nanostructure in a process step:
Pulse length (reverse pulses): 240 ms at 10 A/dm2 cathodic,
4 0 ms at 8 A/dm2 anodic
Electrolyte contains 50 g/1 Cu, 20 g/1 free cyanide, 5 g/1 KOH
The electrochemically produced surface was then examined using an SPM (Scanning Probe Microscope - also known as AFM or Atomic Force Microscope). An SPM enables surface structures down to the nanometer range to be identified and displayed. A segment of the surface produced is shown in cross section in Figure 2 as an SPM test result, the profile being exaggerated. Relative to a zero line 17, there is drawn in Figure 2 a waveform 18 making clear the macrostructure superimposed on the surface structure. Because of the exaggeration, the microstructure 13 is identifiable as a succession of peaks 19

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and valleys 20. In addition, there can be identified, in particular regions, the nanostructure 14 resulting from a close succession of peaks and valleys which cannot be resolved further at the scale shown in Figure 2 and are therefore only identifiable as a thickening of the profile line of the surface profile.
Further details may be obtained from Figure 3a which provides a perspective view of the SPM recording of the copper surface. A region 100x100 µm square was selected as the extracted segment, the needle-like peaks 19 determining the microstructure 13 being clearly visible. The resulting image has the appearance of a "coniferous forest", with interspaces between the "conifers" (peaks 19) forming the valleys 20. The surface as shown in Figure 3a is also represented in exaggerated form in order to make clear the peaks 19 and valleys 20 of the microstructure 13.
As can be seen from the perspective view of the surface according to 3b which constitutes a segment enlargement of the representation according to Figure 3a, a nanostructure 14 is additionally superimposed on the microstructure 13. In the less exaggerated representation according to Figure 3b, the peaks 19 and valleys 20 look more like a waviness of the surface (which, however, because of the different scale must not be confused with the waviness according to Figure 2). Additionally superimposed on this waviness are very small peaks 19n and valleys 20n characterizing the nanostructure of the surface. These are again reminiscent in terms of their structure of a coniferous forest already explained in connection with Figure 3a, their geometrical dimensions turning out to be about two orders of magnitude smaller, i.e. totally imperceptible at the scale selected in Figure 3a.

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In order to make the size relationships clear, the macrostructure 12, the microstructure 13, and the nanostructure 14 are each marked with a bracket in Figures 2 and 3. The bracket in each case encloses only one segment of the relevant structure, which contains a peak and a valley, so that, among one another, the brackets within a Figure allow the orders of magnitude of the structures in relation to one another to be compared. In the example shown, the contact angle measured for a water droplet was 152°. The superhydrophobic properties of the copper coating shown, which produce a lotus effect, are achieved by an interplay of at least the microstructure 13 and the nanostructure 14, the overlaying of a macrostructure 12 improving the observed effects still further. By selecting suitable process parameters, such lotus-effect surfaces can be produced for different coating materials (silver coatings have been successfully tested, for example) and for liquids with different wetting behaviors.

PCT/EP2005/053902 / 2004P12591WOUS
9 Claims
1. A method for electrochemically producing a surface with an
anti-adhesion microstructure (13)
characterized in that the surface is produced by-electrochemical pulse plating, a nanostructure (14) overlying the microstructure (13) being produced by reverse pulse plating.
2. The method as claimed in claim 1,
characterized in that the pulse length for the process step of producing the nanostructure is less than 500 ms.
3. The method as claimed in one of the preceding claims,
characterized in that, for reverse pulse plating, the cathodic
pulses are at least three times as long as the anodic pulses.
4. The method as claimed in one of the preceding claims,
characterized in that for reverse pulse plating, the cathodic
pulses are implemented with a higher current density than the
anodic pulses.
5. The method as claimed in one of the preceding claims,
characterized in that the pulse length for an upstream process
step for producing the microstructure is at least one second.
6. The method as claimed in one of the preceding claims,
characterized in that the surface is additionally produced
with a macrostructure (12) superimposed on the microstructure
(13) .
7. A surface with an anti-adhesion microstructure (13),

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characterized in that a nanostructure (14) produced by pulse plating is superimposed on the microstructure (13).
8. The surface as claimed in claim 7,
characterized in that the surface is superhydrophobic.
9. The surface as claimed in one of claims 7 or 8,
characterized in that a macrostructure (12) is superimposed on
the microstructure (13) and the nanostructure (14).


The invention relates to a surface comprising a microstructure that reduces adhesion and to a method for producing said microstructure. Microstructures of this type that reduce adhesion are known and are used, for example, to configure self-cleaning surfaces that use the Lotus effect. According to the invention, the surface is produced electrochemically by means of reverse pulse plating, the known microstructure being first produced and a nanostructure that is overlaid on the microstructure is produced at the same time or in a subsequent step. To achieve this for example, the pulse length of the current pulse that is used during the reverse pulse plating lies in the millisecond range and has a pulse length ratio greater than 1:3 (anodic:cathodic). The microstructure that has been produced, consisting of peaks (19) and troughs (20) is then overlaid with peaks (19n) and troughs (20n) of a smaller size order belonging to the nanostructure, thus permitting the Lotus effect that is achieved by the surface to be greatly improved.

Documents:

00694-kolnp-2007 correspondence-1.2.pdf

00694-kolnp-2007 others document-1.1.pdf

00694-kolnp-2007-correspondence-1.1.pdf

00694-kolnp-2007-correspondence-1.3.pdf

00694-kolnp-2007-form-18.pdf

00694-kolnp-2007-priority document.pdf

0694-kolnp-2007 abstract.pdf

0694-kolnp-2007 assignment.pdf

0694-kolnp-2007 claims.pdf

0694-kolnp-2007 correspondence others.pdf

0694-kolnp-2007 description(complete).pdf

0694-kolnp-2007 drawings.pdf

0694-kolnp-2007 form-1.pdf

0694-kolnp-2007 form-2.pdf

0694-kolnp-2007 form-3.pdf

0694-kolnp-2007 form-5.pdf

0694-kolnp-2007 international publication.pdf

0694-kolnp-2007 international search authority report.pdf

0694-kolnp-2007 others.pdf

0694-kolnp-2007 pct form.pdf

694-KOLNP-2007-ABSTRACT.pdf

694-KOLNP-2007-CANCLLED DOCUMENT.pdf

694-KOLNP-2007-CLAIMS.pdf

694-KOLNP-2007-DESCRIPTION COMPLETE.pdf

694-KOLNP-2007-FORM 1.pdf

694-KOLNP-2007-FORM 2.pdf

694-KOLNP-2007-FORM-27.pdf

694-KOLNP-2007-OTHERS.pdf

694-KOLNP-2007-REPLY TO EXAMINATION REPORT.pdf

abstract-00694-kolnp-2007.jpg


Patent Number 235695
Indian Patent Application Number 694/KOLNP/2007
PG Journal Number 33/2009
Publication Date 14-Aug-2009
Grant Date 07-Aug-2009
Date of Filing 26-Feb-2007
Name of Patentee SIEMENS AKTIENGESELLSCHAFT
Applicant Address WITTELSBACHERPLATZ 2, 80333 MUNCHEN
Inventors:
# Inventor's Name Inventor's Address
1 CHRISTIAN DOYE UHLANDSTR.48 13156 BERLIN
2 URSUS KRÜGER KRAMPNITZER WEG 11 14089 BERLIN
3 MANUELA SCHNEIDER PICHELSDORFER STR. 71 13595 BERLIN
PCT International Classification Number C25D 5/18
PCT International Application Number PCT/EP2005/053902
PCT International Filing date 2005-08-08
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10 2004 041 813.6 2004-08-26 Germany