Method for producing an abrasion-resistant nanostructure, carrier bodies with such a nanostructure and associated uses

Abstract

A method for producing an abrasion-resistant nanostructure (40) on a surface (5) of a support body (2) is proposed in order to permanently provide the support body (2) with advantageous surface effects. The method can be used, in particular, to permanently anchor nanostructures (40) to a surface (5) in an abrasion-resistant manner. For this purpose, in a first process step A, the nanostructure (40) is first applied to or produced on the surface (5), in particular by growing it. In a subsequent process step B, the nanostructure (40) produced in step A is then permanently and abrasion-resistantly bonded to the surface (5) by means of a separate embedding layer (20). For this purpose, the embedding layer (20) is produced separately from the already produced nanostructure (40) on, in particular on and / or in, the surface (5).The embedding layer (20) only partially covers the nanostructure (40), so that surface properties of the nanostructure (40) can be at least partially preserved. At the same time, the embedding layer (20) anchors the nanostructure (40) to the surface (5), whereby the embedding layer (20) can grow into the support body (2), in particular through the nanostructure (40).

Description

[0001] The invention relates to a method for producing an abrasion-resistant nanostructure on a surface, in particular on partial areas of this surface, which can be understood as a type of nanobonding of the nanostructure to the surface. This surface can be formed by a carrier body. In a method according to the invention, the nanostructure is first applied to the surface in a first process step A, wherein the nanostructure can, in particular, be grown on the surface. Reference to the term nanostructure in the following always refers to multiple nanoscopic elements or multiple nanostructures.

[0002] The invention further relates to a layer composite comprising such a nanostructure, as well as to a carrier body carrying such a layer composite on its surface.

[0003] Finally, the invention also relates to certain uses of such a layer composite for specific purposes. background

[0004] The use of nanostructures on surfaces offers remarkable opportunities to utilize the inherent properties of materials and patterns at the nanoscale. These nanostructures have a major influence on the surface properties of materials, making them, for example, hydrophobic, oleophobic, or giving them improved adhesion properties. This, in turn, increases their functionality in a wide variety of applications. Furthermore, nanostructures can increase the hardness and wear resistance of materials, which is particularly advantageous when the surface is subjected to strong mechanical stress in the application. At the same time, nanostructures have a pronounced influence on optical, electrical, or chemical interactions and can thus, for example, generate optical phenomena, such as:Anti-reflective properties (i.e., acting as an optical anti-reflection layer), a desired color shift, or a desired light absorption, which is already used in solar cells, for example. Furthermore, nanostructures can also change the electrical or chemical properties of the substrate (at least near the surface) to which they are applied.

[0005] Another property of nanostructures is their ability to exponentially increase their effective surface area. This is of practical importance for catalysts and materials intended for use in highly reactive environments. In particular, these advances have far-reaching implications in the field of biomedicine, where nanostructures play a key role in enabling precise molecular and cellular interactions. Nanostructures can also contribute to advancing drug delivery mechanisms, the engineering of specific tissues, or diagnostic tools, thus revolutionizing medical and pharmaceutical sciences.

[0006] Nanostructures can also be tailored to exhibit specific functionalities. This is of utmost importance for the production of sensors, optical filters, and coatings, for example. In line with modern demands for ecological responsibility, nanostructured materials have also proven to be tools for increasing energy efficiency, particularly in photovoltaics, where they help reduce energy consumption and thus promote sustainability.

[0007] The nanotechnology landscape thus continually offers new and groundbreaking applications in a wide variety of scientific disciplines. Despite these compelling advantages, one notable drawback is emerging: the poor adhesion and stability of nanostructures created by common manufacturing processes such as lithography and etching. This architectural fragility often undermines the potential advantages of nanostructures. Nanostructures that are inherently scratch-resistant to adhere to a surface would be particularly desirable.

[0008] As described, nanostructures are already routinely used to improve the functional and performance characteristics of surfaces. However, without robust scratch / abrasion resistance, i.e., sufficient anchoring / adhesion of the nanostructures to the respective surface, the beneficial properties of these nanostructures can degrade very quickly, thus jeopardizing the longevity of technical surfaces. Scratches can disrupt the precision of nanostructured interactions in critical areas such as electronics and optics, further underscoring the importance of scratch resistance. Maintaining the benefits of nanostructuring is not limited to extending performance characteristics and preserving surface aesthetics.It can also lead to increased safety in the application / use of nanostructures and thus support the sustainable development of a whole spectrum of scientific and technological applications.

[0009] Based on this, the present invention is therefore based on the object of providing an abrasion-resistant nanostructure which is particularly suitable for use on stressed surfaces. Summary of the invention

[0010] To achieve this object, a method according to claim 1 is proposed. In particular, in a method for producing an abrasion-resistant nanostructure as described above, it is proposed that the nanostructure produced in process step A be permanently and abrasion-resistantly bonded to the surface in a second process step B by means of an embedding layer. The embedding layer is produced on the surface and only partially embeds the nanostructure. In particular, the embedding layer can be deposited on the nanostructure.

[0011] The deposition of the embedding layer can be effected in particular by means of a chemical conversion of an uppermost material layer of the carrier body, ie the embedding layer can be produced by means of a chemical conversion of an uppermost material layer of the carrier body, in particular with an increase in volume.

[0012] The invention thus describes a method for producing a nanostructure that is bonded to the surface of a carrier body in an abrasion-resistant manner, which is of particular interest in the field of surface technology. The abrasion-resistant nanostructures according to the invention can be used wherever the surface properties of a carrier body are to be specifically and permanently modified.

[0013] Process step A can be understood as a form of nanostructuring. Process step B, on the other hand, can be understood as a form of mechanical bonding of the nanostructure to the carrier body at the nanoscopic level. The method according to the invention therefore creates a nanostructure on a surface that is / will be mechanically stably bonded to the surface by means of the additional embedding layer. In particular, reproducible and constant, i.e. permanent, surface properties can be ensured in this way. This applies in particular when the abrasion-resistant nanostructure is applied to an implant surface. The invention can therefore be used advantageously in particular when the carrier body is designed in the form of a permanent or temporary implant. However, the invention is not limited to implantology, as will be explained further below.

[0014] The method explained can be further developed in many ways according to the invention: Thus, an inner layer thickness D1 of the embedding layer, measured below the original surface of the carrier body, can be at least 6 nm, preferably at least 12 nm, particularly preferably at least 18 nm. During the second process step B, the embedding layer can grow both into the surface of the carrier material and out of the original surface. This further increases the abrasion resistance of the layer because robust nanomechanical anchoring is achieved by means of the embedding layer.

[0015] Furthermore, it is preferred if the respective nanostructure is designed to be conically tapered. In this case, a tip of the nanostructure points away from the surface, and the gap or spacing between the individual nanostructures increases with increasing distance from the surface. On the one hand, such a shape is advantageous so that the nanostructure exerts a desired repelling effect on microorganisms such as bacteria. On the other hand, it allows for very reliable nanomechanical anchoring by means of the embedding layer, since this can fill the gaps (increasingly, i.e., bit by bit) as it grows, thus anchoring the nanostructure to the surface.

[0016] A maximum layer thickness / embedding height D2 of the embedding layer, measured above the original surface of the carrier body, can preferably be smaller than an average height H of the nanostructure, again measured above the original surface of the carrier body. This is because in this case, the nanostructure protrudes from the embedding layer. It is preferred if the nanostructure protrudes from the embedding layer by at least 20%, preferably by at least 50%, particularly preferably by at least 66% of the average height H. The protrusion of the nanostructure results in surface-active properties, for example anti-adhesive or bactericidal properties, of the nanostructured surface being at least partially retained even after the embedding layer has been created. This is because these properties are caused by the nanostructure, more precisely by the morphology of the nanostructure.

[0017] The embedding layer can therefore be deposited or produced, preferably by means of an electrochemical process and / or by means of an oxidation process, in such a way that the embedding layer both grows into the carrier body and grows out of the original surface. Such a process can in particular be designed such that, after completion of process step B, the embedding layer extends deeper into the carrier body than the nanostructure, preferably so that the embedding layer not only embeds the nanostructure but also mechanically anchors it in the carrier body at a nanoscopic level. An embedding layer that grows into the surface and onto the surface increases the mechanical stability of the layer or of the layer system comprising the nanostructure and embedding layer because this causes the embedding layer to grow together with the carrier body at the nanoscopic level. This significantly increases the abrasion resistance of the nanostructure on the carrier body.

[0018] The first process step A can, for example, be a hydrothermal oxidation carried out in a pressure reactor. In particular, during process step A, the nanostructure can grow only on the surface, in particular on a native oxide layer of the support body, but not into the support body (like the embedding layer). The oxidation can preferably be carried out using ultrapure water or aqueous ammonia or potassium hydroxide (KOH) as the reactive liquid. It is also particularly preferred if the surface of the support body to which the nanostructure is to be applied remains completely immersed in the reactive liquid during process step A.

[0019] The carrier body can be made of metal, for example, particularly titanium. In such a case, hydrothermal oxidation produces a metal oxide, particularly titanium oxide, in the form of nanoparticles, which forms the nanostructure. Nanostructuring by hydrothermal oxidation is advantageous because it leads to a homogeneous surface structuring, especially of complex-shaped carrier structures. This makes the process particularly suitable for structuring surfaces with a complex 3D geometry (which can be particularly true for implant surfaces).

[0020] The second process step B can, for example, be an electrochemical anodization to produce the embedding layer. This anodization can preferably be carried out using a liquid, preferably fluorine-free (i.e., not containing any fluorine-containing compounds), electrolyte such as diluted sulfuric acid or a comparable suitable electrolyte.

[0021] Furthermore, process step B can be carried out using a direct current voltage for anodization. It is preferred if the direct current voltage is below 20 V, preferably below 15 V, and particularly preferably below 10 V, because this allows a suitable thickness of the embedding layer to be set reliably and with good control.

[0022] Electrochemical anodization can, for example, be carried out with an exposure time of less than 30 minutes, preferably less than 5 minutes, and particularly preferably less than 2 minutes, thus enabling very short overall process times. Electrochemical anodization of the nanostructured surface leads to a very homogeneous creation of the embedding layer, even on complex-shaped substrates such as implants. This enables a conformal surface coating. The use of low voltages and short process times makes the process particularly easy to apply and cost-effective, as it can be carried out with simple equipment and allows for high throughput. Furthermore, this process can be applied gently to complex-shaped substrates.

[0023] Alternatively, the second process step B can also be a wet-chemical oxidation to produce the embedding layer, preferably using an oxidizing liquid. It is particularly preferred if the surface of the carrier body on which the embedding layer is to be deposited remains completely immersed in the oxidizing liquid, including the nanostructure, during process step B. Wet-chemical oxidation to produce the embedding layer allows the production of abrasion-resistant nanostructures on carrier bodies made of various materials and with various material and surface properties. In particular, HNO3, H2SO4, HCLO4, H2O2, KOH, or NaOH, or (aqueous) compositions thereof, can be used as the oxidizing liquid during the oxidation.

[0024] The second process step B can also be implemented using a plasma-assisted or plasma-induced process for producing the embedding layer, preferably using an oxygen-containing plasma. This allows surfaces of other materials to be homogeneously modified by chemical and / or physical action using plasmas of different compositions.

[0025] The nanostructure produced using this process can comprise nanoparticles whose tips are, on average, aligned in the same direction, particularly perpendicular to the surface. This allows for highly homogeneous surface properties.

[0026] Preferably, the nanoparticles may have a predominantly tetragonal pyramidal and / or tetragonal bipyramidal and / or a conical or biconical basic shape. Furthermore, the nanoparticles may have an average height H, measured above the original surface, of less than 300 nm, preferably less than 250 nm, particularly preferably less than 175 nm.

[0027] Furthermore, the nanoparticles can have an average tip spacing of less than 300 nm, preferably less than 250 nm, more preferably less than 150 nm, and even more preferably less than 75 nm. If the tip spacing is larger, however, it has been observed that the desired repelling effect on bacteria can only be achieved to an insufficient extent. Such parameters are advantageous for creating homogeneous surface properties. This is because the uniform nature of the nanostructures can ensure a homogeneous surface quality of the treated carrier body. The nanostructures can be shaped in such a way that they create, for example, anti-adhesive and / or bacteria-repellent and / or bactericidal properties of the surface. In particular, bactericidal properties can only be observed (at least partially) at the aforementioned structural sizes of the nanoparticles.

[0028] In one embodiment, the carrier body is made of metal, preferably titanium or a titanium alloy. In this case, the embedding layer produced in process step B can be an amorphous, partially amorphous, or purely crystalline titanium oxide layer, and / or the nanostructure produced in process step A can then be formed by an at least partially crystalline titanium oxide layer. With such a choice of material, the thermal and / or electrochemical processes mentioned above can be carried out with particularly good reproducibility. The metal surfaces can have an oxide layer, in particular a natural oxide layer or a previously deliberately produced oxide layer, even before application of the method according to the invention.

[0029] In one embodiment, the surface of the carrier body accordingly has an oxide layer, preferably a titanium oxide layer (e.g., TiO2 or TiOx), and the nanostructure is applied to this oxide layer or produced from this oxide layer by (morphological) transformation of the oxide layer. In this case, too, the thermal and electrochemical processes can be carried out reproducibly. The oxide layer can preferably be a natural oxide layer of the carrier material.

[0030] In one embodiment of the method, a natural and / or previously additionally produced oxide layer can first be removed by a preceding process (e.g. etching).

[0031] Due to the described process, a portion of the embedding layer grown (on the original surface of the carrier body) can have a structure and / or shape that is complementary to a shape of the nanostructure. The embedding layer, or more precisely its grown portion, can also at least partially fill gaps between individual nanostructures (created on the surface in step A). ​​This can achieve nanomechanical wedging between the embedding layer and the nanostructure, particularly with a conical design of the nanostructures (i.e., tapering outwards).

[0032] For example, the grown portion of the embedding layer can have recesses which are complementary in shape to the base area of ​​the nanostructure and (e.g. following the normal to the surface) to a, in particular conical, shape / form of the nanostructure.

[0033] In other words, the embedding layer can be designed in such a way that its grown portion, i.e. the portion above the original surface, at least partially fills spaces between elements of the nanostructure (for example spaces between the described pyramid-shaped nanostructures).

[0034] This filling or embedding can be adjusted by selecting appropriate parameters, in particular by selecting a suitable electrical voltage and / or duration, for process step B so that the embedding layer fills the gaps between the nanostructures up to a certain embedding height above the original surface. This embedding height (or "maximum layer thickness D2" of the embedding layer measured above the original surface) thus corresponds to the height of the grown portion of the embedding layer (while the total thickness of the embedding layer can be higher if a portion of the embedding layer has grown into the carrier body).Since the nanostructures are intended to protrude from the embedding layer so that they can exert the desired surface effects, in particular a repelling effect on bacteria, it is preferred if the embedding height is less than a maximum height of the nanostructures (again measured above the original surface). Preferably, the embedding height can be selected to be at most half the maximum or average height of the nanostructure to be embedded.

[0035] With an embedding layer designed in this way, individual elements of the nanostructure, especially conically tapered elements such as pyramids, can be wedge-shaped within the embedding layer. This allows for reliable nanomechanical anchoring of the nanostructure to the carrier body.

[0036] A further aspect of the invention describes a layered composite comprising a nanostructure. This nanostructure can, as explained, be applied in an abrasion-resistant manner to a surface of a carrier body and / or produced by means of a method as explained above and / or according to one of the claims directed to a method, in particular applied or grown on the carrier body. The layered composite is characterized in that the nanostructure comprises nanoparticles that produce at least one surface-active effect, for example an optical effect and / or an anti-adhesive effect and / or a bactericidal effect, and further in that the nanostructure is at least partially embedded in an embedding layer. Preferably, the nanostructure protrudes from the embedding layer to such an extent that at least one surface-active effect is at least partially retained.In other words, not all surface-active effects necessarily have to be retained after nanobonding.

[0037] A further aspect of the invention describes a layer composite comprising such an abrasion-resistant nanostructure and an embedding layer. The layer components can be applied to the surface of a carrier body, for example, by thermal, oxidative, or electrochemical processes. Nanoparticles of the nanostructure can lead to special surface properties. In particular, such nanoparticles influence the wettability of the surface in addition to optical properties and / or produce anti-adhesive and / or bactericidal effects. The nanoparticles are preferably embedded in the embedding layer, but protrude sufficiently far from the embedding layer that the surface properties created by them are at least partially retained. This creates a mechanically stable, reproducibly producible surface with specifically adjustable surface properties.

[0038] The embedding layer can extend so far beyond the nanostructure, in particular inwards towards the carrier body, that a nanomechanical anchoring of the nanostructure on a surface of the carrier body and / or in the carrier body is achieved. This means that the embedding layer can extend in particular deeper into the carrier body compared to / than the nanostructure. By the embedding layer growing into the surface of the carrier body, the abrasion resistance of the layer system consisting of nanostructure and embedding layer is further increased. In other words, the embedding layer can extend into the bulk of the carrier body. In this case, the embedding layer exceeds the original interface between the carrier body and the nanostructure, in a direction that points away from the outer tips of the nanostructures.

[0039] The embedding layer can differ from the nanostructure, at least morphologically. Alternatively, the embedding layer and the nanostructure can be made of the same material, particularly a metal oxide. This allows the nanostructure to be enclosed in an abrasion-resistant manner by the embedding layer, without the nanostructure losing its surface-active properties and / or its morphology / crystal structure.

[0040] A further aspect of the invention describes a carrier body with a layered composite as described above. This carrier body can be designed, for example, in the form of an implant. However, it can also be another technical carrier body whose surface properties (optical, electrical, chemical, biological, mechanical, rheological, etc.) are to be specifically adjusted by the nanostructure. Preferably, the embedding layer can also be morphologically different from the nanostructure and / or the embedding layer can be at least partially integrated into the carrier body.Such a carrier body can permanently exhibit advantageous surface properties caused by the nanostructure because the latter is enclosed in an abrasion-resistant manner by the embedding layer and thus mechanically anchored to the carrier body, without the nanostructure changing or losing its surface-active properties and / or its desired morphology and crystal structure.

[0041] A further aspect of the invention describes a specific use of a layer composite as described above on a carrier body for producing tailored surface properties of the carrier body. In this case, the layer composite can have been produced using a method as described above and / or using a method according to one of the method claims and / or can have been anchored in an abrasion-resistant manner to a surface of the carrier body using such a method. With the approach according to the invention, the anchoring can in particular be designed to be so strong that, with sufficient pressure, an associated contact body of the carrier body, for example a bone, is abraded against the nanostructure and not the nanostructure against the contact body when the carrier body slides along the contact body under the pressure together with the layer composite.

[0042] The composite layer, or more precisely the nanostructure of the composite layer, can, for example, produce a (at least partial) bactericidal effect and / or an anti-adhesive effect, thereby slowing down dangerous biofilm formation. This allows the composite layer to be used, for example, on the surfaces of components that must meet hygienic standards and / or that are exposed to particular contamination, for example, through frequent contact.

[0043] Another application example is carrier bodies that have a surface whose properties must be specifically adjusted to make it technically usable. In other words, at least one surface-active effect attributable to the nanostructure can be provided by the layered composite and exploited in a technical application. Such a surface-active effect can be used, in particular, to improve wetting properties, or to increase hydrophobicity, oleophilicity, or lipophilicity, or to reduce sliding friction, or to increase surface hardness, or to achieve an optical effect, or to achieve a chemical effect, or to achieve a biological effect.In other words, physical and / or chemical and / or biological and / or mechanical and / or electrical and / or optical properties of the surface can be specifically adapted and adjusted with the nanostructure depending on the desired application.

[0044] In one application example, the carrier body is an implant and the layer composite produces a (at least partial or temporary) bactericidal effect and / or an anti-adhesive effect, for example with respect to bacteria that should not adhere to the implant surface (in each case with respect to the outermost surface of the implant, which is also formed by the nanostructure).

[0045] The invention is described in more detail below using several preferred embodiments.

[0046] It shows: Fig. 1 a schematic cross-section of an embodiment of a layer composite on a carrier body; Fig. 2 a schematic cross-section of an embodiment of an embedded nanostructure on the surface of a carrier body; Fig. 3 is a flow chart describing an embodiment of a method according to the invention for producing an abrasion-resistant nanostructure on a surface of a carrier body; Fig. 4 a schematic sketch of the anti-adhesive property of the nanostructured surface; Fig. 5 a schematic representation of a pressure reactor for the production of nanostructures; Fig. 6 a schematic representation of the process for nanostructuring by hydrothermal oxidation; Fig. 7 a schematic representation of the nanostructure after different treatment times; Fig. 8 a schematic representation of the process for producing an embedding layer; Fig. 9 a schematic representation of an electrochemical anodization setup; Fig. 10 a schematic representation of the incorporation and growth of an embedding layer onto the surface of the carrier body; Fig. 11 a schematic representation of the dependence of the layer thickness of the embedding layer on the process voltage and Fig. 12 illustrates the complementary shape of an embedding layer produced according to the invention if the nanostructure 40 is omitted.

[0047] In the following description of various embodiments of the invention, elements that correspond in function are given the same reference numbers even if they have a different design or shape.

[0048] Fig. 1 shows a cross section through an outer layer, for example of a component 1, comprising a carrier body or base body 2 and optionally an (in particular native) oxide layer 10. Such a component can in particular be an implant.

[0049] The carrier body 2 preferably consists of a metal as the base material 3, in particular titanium, stainless steel, or aluminum, or metal alloys, preferably Ti6Al4V, alternatively chromium-cobalt-based alloys or aluminum alloys. The base material 3 can have a microstructure 4. Alternatively, the carrier body 2 consists of a ceramic as the base material 3.

[0050] Preferably, the carrier body 2 is formed from titanium or a titanium alloy and forms a native oxide layer 10 which is chemically very inert and (at least partially) mechanically stable.

[0051] The oxide layer 10 consists of a material 11, for example the natural oxide of the base material 3, in the case of titanium or titanium alloys of TiO2 or TiOx. The natural oxide layer is typically 2-5 nm thick. Alternatively, the oxide layer 10 can also be a previously applied or deliberately produced oxide layer. The oxide layer 10 can be produced, for example, by chemical or physical deposition processes, in particular PVD ("physical vapor deposition") or CVD ("chemical vapor deposition") processes, plasma processes, or sputtering processes. The oxide layer has a microstructure 12 and a layer thickness 13. An interface 14 can exist between the oxide layer 10 and the base material 3.

[0052] The surface of the oxide layer 10, i.e., the interface between the oxide layer 10 and the environment, for example, air, has a surface roughness 6. This interface is also referred to below as the starting surface 5. This surface 5 thus forms the starting point for the inventive method described below, with which a nanostructure 40 is to be anchored to the surface 5 in an abrasion-resistant manner: The method 70 according to the invention for producing an abrasion-resistant nanostructure 40 is shown schematically in Fig. 3: In the first step 71, a carrier body 3 is provided, approximately as just described. In step 72, a nanostructure is created on the surface 5 in process step A. In step 73, an embedding layer is created in process step B. Process steps A and B are described in more detail below.

[0053] In the first process step A, a nanostructure 40 is created on the carrier body 2. For example, the nanostructure 40 can be specifically applied to certain parts or the entire surface 5, grown, or, for example, created lithographically on this surface 5. The masking of partial areas of the surface 5 can preferably be carried out with positive photoresist in layer thicknesses of less than 10 µm, preferably less than 2 µm. The nanostructure 40 is preferably completely and conclusively created in this process step A. This means that the external shape of the nanostructure 40 is not changed or is changed only insignificantly by subsequent process steps.

[0054] Preferably, the nanostructure 40 is produced by hydrothermal oxidation. The process is carried out in a pressure reactor at an internal pressure of > 15 bar, for example 20 bar. A suitable pressure reactor 90 is Fig. 5. The pressure reactor 90 is designed using a stainless steel cylinder as the base vessel 93, which is lined on the inside with Teflon (PTFE) 95.

[0055] The process for nanostructuring the surface 5 of the carrier body 2 is shown schematically in Fig. 6: The carrier bodies 2 (for example titanium implants 1) to be coated with the nanostructure or nanoparticles 40 are loaded onto a Teflon frame 94 (step 1) in Fig. 6) and introduced together with the frame into the pressure reactor 90 (step 2) in Fig. 6). The carrier bodies 2 are completely immersed in ultrapure water 96 as the reaction solution used, as shown by the fill level 97. At a temperature of 220 °C and a pressure of approximately 20 bar, the hydrothermal oxidation is then carried out for 24 hours, whereby this process can be carried out in parallel on several components 1 or carrier bodies 2 (step 3) in Fig. 6). After the process is complete, the pressure reactor 90 is discharged (step 4) into Fig. 6).

[0056] Through this process, a nanostructured, crystalline titanium oxide layer is grown on the titanium component 1. The oxide front does not grow into the material, but rather grows outward evenly throughout and in all spatial directions on the surface 5. This allows a highly conformal layer thickness of the nanostructure 40 to be achieved, and no shadowing is observed, allowing, for example, undercuts, sharp edges, or holes to be provided with the nanostructure 40.

[0057] Fig. Figure 2 schematically illustrates the result of the method, namely a pyramid-shaped nanostructure 40 which is only partially embedded by means of an inventive amorphous embedding layer 20 but is thereby anchored in abrasion-resistant manner on the carrier body 2 and which tapers conically (with the tip of the pyramid / cone pointing away from the starting surface 5). This can be seen from the hatching in Fig. 2, that the embedding layer 20 has grown inwards beyond the original starting surface 5 into the carrier body 2 (= grown-in portion 22). Furthermore, the embedding layer 20 also has a grown portion 24 above the starting surface 5 with an embedding height 103 that is less than 50% of a maximum height 102 of the pyramid-shaped nanostructures 40 (see also the double arrows in the right-hand part of the Fig. 10). The grown portion 24 fills the spaces between the nanostructures 40 and (if one imagines the nanostructures 40 away) has corresponding gaps 35 at the locations of the nanostructures 40, which emphasizes the “embedding”, as in Fig. 12. Moreover, the shape of the grown portion 24 in the interstices is precisely complementary to the pyramidal shape of the nanostructures 40, which exhibit a high degree of crystallinity. This complementary shape 35 virtually wedges the nanostructures 40 into the embedding layer 20 and thus firmly anchors them nanomechanically to the carrier body 2. This anchoring is thus based on a geometric effect at the nanoscopic level.

[0058] This selective embedding (which can also be seen from the Fig. 11 - note that the shape of the nanostructure 40 remains unchanged) is achieved in process step B, by which the chemically base embedding layer 20 is selectively deposited on the (chemically more stable) nanostructure 40, without the crystalline nanostructure 40 being significantly altered in its shape or morphology. The reason for this is the high order in the crystal structure of the nanostructure 40 compared to the predominantly amorphous structure of the embedding layer 20, which leads to the nanostructures 40 not being altered or only slightly being altered in process step B (e.g., by electrical anodization) due to their high chemical stability, while the amorphous embedding layer 20 grows selectively. Such a process is particularly successful, for example, when the nanostructures 40 are formed in the form of TiO2 crystals (e.g., anatase), as in Fig. 11 is schematically illustrated.

[0059] Fig. Figure 7 shows schematically the configuration of the nanostructure 40 after a treatment time of the carrier bodies 2 of 1 hour ( Fig. 7, left) and 24 hours ( Fig. 7, right). The grain size of the microstructure of the amorphous titanium oxide layer 42 and / or the microstructure and spatial orientation of the grains of the underlying material layer (bulk) determine the formation of nanoparticles. The nanoparticles initially grow, for example, after 1 hour, in different spatial directions, and after a few hours, for example, after 24 hours, align themselves predominantly normal to the surface 5. The nanoparticles thus exhibit an averagely uniform orientation, as in Fig. 2 with the normal direction 47. If appropriate process parameters are selected, growth can be very uniform, resulting in pyramid-shaped nanoparticles with an opening angle of 48. The nanoparticles 40 have an average height of 43, an average width of 44, an average tip size of 45, and an average distance of 46.

[0060] Fig. Figure 4 shows a schematic diagram illustrating the desired anti-adhesive properties of a nanostructured surface compared to an unstructured surface. The nanostructure 40 causes bacteria 81 (in Fig. 4 kidney-shaped) due to fewer surface contacts 86, they do not adhere to the surface or adhere with reduced adhesion force 82. Compared to an untreated surface, this can lead to a lower or slower cell proliferation (biofilm formation 84). This effect results from a reduced biological contact width 87 (see Fig. 4). In some cases, the nanostructure may also kill the bacteria 81 ( Fig. 4 right), where the former is referred to as the anti-adhesive effect and the latter as the bactericidal effect of the nanostructure 40. To create this desired anti-adhesive effect, the tips 50 of the nanoparticles must be designed with suitable tip spacings 46. If this tip spacing 46 is too large, no anti-adhesive effect can be achieved. If, however, the tip spacing 46 is too small, it has been observed that the bactericidal effect of the nanostructure 40 decreases, which is also undesirable.

[0061] In another example, the nanostructure 40 can change the wettability of the surface 5 of the component 1.

[0062] For example, surface 5 can be modified to exhibit a lotus effect. To achieve this, the tip spacing 46 and the opening angle 48 of the tips 50 are selected to be small, and the average height 43 is selected to be large to create a (super-)hydrophobic surface. This allows for the creation of a dirt-repellent surface.

[0063] The invention now provides, after carrying out the production of the nanostructure 40, an additional process step B, which significantly improves the adhesion of the nanostructure 40 already produced on the surface 5 and adhering thereto.

[0064] An abrasion-resistant connection of the nanostructure 40 to the surface 5 of the carrier body 2 can be understood here in particular as a nanomechanical connection that is sufficiently stable against mechanical abrasion for the intended use. This is relevant, for example, in technical applications in which the carrier body 2 slides or rolls along a counter surface with its surface 5. With a suitable choice of process parameters, the method according to the invention can ensure such a high abrasion resistance of the nanostructure 40 (for example, when used on titanium implants 1) that any abrasion or counter surfaces rub off against the nanostructure 40 and not vice versa, without the nanostructure 40 being largely or even completely destroyed. This means that the nanostructure 40 can repeatedly roll or slide along a counter body without sustaining significant damage.This can significantly expand the application possibilities of the respective nanostructure 40.

[0065] In another example, the abrasion resistance of the nanostructure 40 is so high that under pressure / shear stress, only individual nanoparticles 40 break out of it, but the nanostructure 40 is not detached from the surface 5 in its entirety. This ensures that the surface properties provided by the nanostructure 40 are permanently effective, even if a certain amount of abrasion occurs.

[0066] In the second process step B, the nanostructure 40 is permanently and abrasion-resistant "fixed" on the surface 5 by creating an embedding layer 20 on the surface 5, and thus a layer composite 60. The embedding layer 20 does not completely cover the nanoparticles 40, i.e. the respective lateral surface 51 of the nanoparticles 40 is not completely enveloped by the embedding layer 20, but the embedding layer 20 is mainly created at the interface between the nanostructure 40 and the interface 14 of the carrier body 2 to its oxide layer 10. The embedding layer 20 can be applied, for example, by thermal or oxidative layer growth processes, i.e. in particular by chemical conversion of parts of the surface 14 of the carrier body 2, or by means of a deposition process: In the first case, a conversion of the uppermost material layer from metal to, for example,Metal oxide or metal nitride, which is usually accompanied by a volume change and results in an ingrowing portion 21, measured from the original surface 5, and a growing portion 24. In the second case, the entire embedding layer 20 can consist of a material that was deposited on the surface 14 or 5 of the carrier body 2, for example by means of physical evaporation (PVD), chemical vapor deposition (CVD), or by means of other methods.

[0067] The embedding layer 20 therefore does not completely embed the nanostructures 40, but only partially. This is because a portion 49 of the nanostructure 40 protrudes from the embedding layer 20. This portion is responsible for the resulting new surface properties.

[0068] In particular, the embedding layer 20 can be produced by electrochemical anodization. During anodization, the electrical voltage used is below the breakdown voltage of the material 3 of the carrier body 2. The electrochemical anodization of the nanostructured surface leads to a very homogeneous production of the embedding layer 20, even on complexly shaped carrier bodies 2. This enables a conformal surface coating to be realized. The use of low voltages and short process times makes the process particularly easy to apply and cost-effective, as the process can be carried out with simple equipment and allows for high throughput. Furthermore, this process can be applied gently to complexly shaped carrier bodies 2. In principle, a comparable result can also be achieved with electrochemical oxidation using an alternating electrical voltage using suitable parameters.However, electrochemical oxidation using a direct current is preferred because this allows for easier process control.

[0069] Process step B using electrochemical anodization is shown schematically in the Fig. 8 and Fig. 9. During electrochemical anodization, the carrier body 2 with the nanostructure 40 is loaded onto a holder 94 (step 1) in Fig. 8) and immersed together with the holder 94 in a vessel 111 filled with a liquid electrolyte, for example, one percent sulfuric acid (H2SO4). The liquid electrolyte 112 contains no fluorine-containing compound and is thus fluorine-free. A DC voltage below 20 V is then applied by means of a voltage source 113 (step 2) in Fig. 8), for example, a voltage of 8 V for 90 seconds. The voltage should be below the breakdown voltage of the base material 3 of the carrier body 2. The bath properties 115 can vary, in particular temperature, movement, and concentration of the electrolyte.

[0070] The holder 94 can be designed so that it can be used in both process step A and process step B and it offers a possibility 114 to electrically contact the carrier bodies 2 and to connect them to the voltage source.

[0071] Fig. Figure 11 schematically shows the dependence of the thickness of the embedding layer 20 on the level of the DC voltage in step B. If voltages above this limit are used, it was observed that the entire nanostructure is overgrown by the embedding layer, so that the nanoscopic tips 50 of the nanoparticles 40 then disappear practically completely or even completely in the embedding layer 20 (far right in Fig. 11) and accordingly the desired effects are no longer achieved.

[0072] A particularly favorable process window is a DC voltage of 6-10 V, which is often sufficient, for example, to form a layer thickness 21 of the embedding layer of 10-20 nm (third from the top in Fig. 11). The exact values ​​also depend on the reaction temperature and the electrolyte concentration and the initial roughness of the carrier bodies 2. If very low voltages are used, it was observed that the embedding layer 20 is not formed (at the very top in Fig. 11) or has a layer thickness that is too small to create an anchoring effect (second image from the top in Fig. 11). After the process is complete, the carrier body is discharged from the reaction liquid (step 3) into Fig. 8) and removed from the holder 94 (step 4) in Fig. 8). Of course, further work steps, in particular cleaning steps, drying or tempering steps, can be carried out between the process steps presented here. More precisely, before applying process step B, the nanoparticles 40 can, for example, have an average height 43. It is then preferred that the process control in oxidation process B is selected such that at least 20%, preferably at least 50%, and particularly preferably at least 80% of the height 43 of the nanoparticles 40 still protrudes from the embedding layer 20 at the end of the process. In other words, the thickness 21 of the embedding layer 20, measured from the original surface 5 before carrying out oxidation process B, should reach a value of 80%, preferably 50%, particularly preferably even only 20% of the original height 43 of the nanostructure 40 (again measured above the original surface 5).

[0073] In the process described, a transformation of the uppermost material layer from titanium to titanium oxide takes place. In this process, the oxide layer 10 grows into the base material 3 (measured from the original starting surface 5 before the process) and thus forms an in-grown portion 22 of the embedding layer 20. This is made possible by the increase in volume during the transformation from the base material 3. Accordingly, the embedding layer also forms a grown portion 24 of the embedding layer 20. The in-growth and growth of the titanium layer onto the surface 5 of the carrier body 2 is also in Fig. 10 (left) is shown schematically. In particular, the ingrown layer thickness 23 can be approximately 16-24 nm. The embedding layer 20 thus provides abrasion resistance.

[0074] The maximum grown layer thickness 25 ("embedding height"), designated as D2 in the figure, can be smaller than a total thickness 21 of the embedding layer 20, provided that the embedding layer 20 also grows into the carrier body 2 and thus spreads inward beyond the original surface 4 or 14 (e.g., grows into a titanium body used as the carrier body 2). This depends on the method used to apply the embedding layer 20 to the surface 4 / 5. Furthermore, it is preferred if this embedding height D2 is less than 50% of a maximum height 102 of the nanostructure 40, because then the desired surface effects come into effect.

[0075] When using a titanium body as the carrier body 2, on which the nanostructure 40 was grown in step A, an amorphous titanium oxide layer 24 is grown using oxidation process B, so that no crystalline nanoparticles are formed in the embedding layer 20. This amorphous titanium layer comprises, in particular, titanium dioxide.

[0076] Due to its crystalline structure and the associated chemical inertness, the nanostructure 40 produced in process step A is no longer altered in its morphology, shape, stoichiometry and / or crystallography in process step B. This can be ensured in particular if the nanostructure 40, after production by process step A, consists of TiO2 crystals (e.g., anatase), which are chemically very inert and, in particular, stable with respect to process step B. The embedding layer 20 can therefore, in particular, be chemically less noble (i.e., less chemically stable) than the nanostructure 40, wherein both the nanostructure 40 and the embedding layer 20 can be additionally doped with other materials.

[0077] Furthermore, the nanostructure 40 is not altered, in particular, if no fluorine-containing compound, i.e., in particular, a fluorine-free electrolyte, is used in process step B, as described above. In other words, process step B selectively modifies only the original surface 5 of the carrier body 2, because the embedding layer grows out of this surface 5 or out of the carrier body 2 and, if necessary, into this surface 5 or into the carrier body 2, but process step B does not modify the nanostructure 40.

[0078] Since the color of component 1 can change due to interference effects after performing oxidation process B, a particularly preferred embodiment provides that the voltage is limited to 8-10 V in order to create specific optical properties of the surface 5 of component 1. This allows a structural color of component 1 to be adjusted or undesired discoloration to be avoided. This can be very relevant, for example, for dental implants to create a desired aesthetic appearance.

[0079] In summary, a method for producing an abrasion-resistant nanostructure 40 on a surface 5 of a carrier body 2 is proposed in order to permanently equip the carrier body 2 with advantageous surface effects. The method can be used in particular to permanently anchor nanostructures 40 in an abrasion-resistant manner on a surface 5 of a component; however, it can also be used on other surfaces 5, for example to modify wetting properties. For this purpose, in a first process step A, the nanostructure 40 is first applied to the surface 5, or produced or grown thereon. In a subsequent process step B, the nanostructure 40 produced in step A is then permanently and abrasion-resistantly bonded to the surface 5 by means of a separate embedding layer 20, wherein the embedding layer 20 fills the gaps between the produced nanostructures 40 and thus grows onto the nanostructure 40.Such growth (from the carrier body 2) can, in particular, result in a complementary shape of the embedding layer 20. For this purpose, the embedding layer 20 is produced separately from the already produced nanostructure 40 on, in particular on and / or in, the surface 5, wherein the nanostructure 40 is not modified in process step B. However, the embedding layer 20 only partially covers the nanostructure 40, so that the surface properties of the nanostructure 40 can be at least partially retained. At the same time, the embedding layer 20 anchors the nanostructure 40 on the surface 5, wherein the embedding layer 20 can, for this purpose, grow into the carrier body 2, in particular through the nanostructure 20. List of reference symbols 1 component (especially in the form of a titanium body) 2 carrier bodies, base bodies 3 Base material 4 Structure of the base material 5 Output surface 6 Surface roughness 7 Resulting new surface 10 Any oxide layer present 11 Material of any oxide layer 12 Structure of any oxide layer present 13 Thickness of any oxide layer present 14 Interface between any oxide layer present and the base material of the base body 20 embedding layer 21 Thickness of the embedding layer 22 Ingrown portion of the embedding layer 23 Thickness of the ingrown portion of the embedding layer 24 Grown portion of the embedding layer 25 Thickness of the grown portion of the embedding layer 26 Interface between any existing oxide layer and the embedded embedding layer 27 Interface between any existing oxide layer and grown embedding layer 28 Growth direction of the ingrown embedding layer 29 Growth direction of the growing embedding layer 30 Embedding area of ​​the nanostructures through the embedding layer 31 Area of ​​the embedding layer between the nanostructures 32 Surface of the embedding layer 33 Material of the embedding layer 34 Structure of the embedding layer 35 resulting connection area between embedding layer 20 and nanostructure 40 40 nanostructures (or nanoparticles) 41 Material of the nanostructures 42 Structure of the nanostructures 43 Average height of nanostructures 44 Average width of nanostructures 45 Average tip size or tip diameter 46 Average distance between two nanostructures 47 Center line, normal direction of the nanostructures 48 opening angles of the nanostructures 49 Part of the nanostructures protruding from the embedding layer 50 Top of Nanostructures 51 Surface, lateral surface of the nanostructures 52 Contact area between nanostructure 40 and original surface 5 60 layer composite 70 Process for producing an abrasion-resistant nanostructure 71-73 Steps of the procedure 70 81 Bacteria 82 Adhesion forces 83 Anti-adhesive properties 84 Biofilm formation 85 Bactericidal effects 86 Interaction between bacteria and surface 87 Interaction area, wing 90 pressure reactor 91 lid 92 closure 93 Basic vessel 94 PTFE frame 95 PTFE inlet 96 Aqueous solution 97 Fill level 98 gas mixture 99 print 100 Heating system / jacket heating / stove 101 Repelling effect 102 maximum height (from 40 measured over 5) 103 Embedment height D2 110 Device for process step B 111 Process tank, vessel 112 Electrolyte 113 Voltage source 114 Adapter for electrical contacts 115 bathroom features 116 intermediate work steps 117 Counter electrode 120 Structural properties, structure of the base material 1 121 grains of base material 122 grain boundaries 123 Normals to crystal orientation

Claims

[1] Method for producing an abrasion-resistant nanostructure (40) on a surface (5), in particular on partial areas of the surface (5), of a carrier body (2), - wherein in a first process step A the nanostructure (40) is applied to the surface (5), in particular grown on the surface (5), characterized by , - that the nanostructure (40) produced in process step A is permanently and abrasion-resistantly bonded to the surface (5) in a second process step B by means of an embedding layer (20), - wherein the embedding layer (20) is produced on the surface (5), and - wherein the embedding layer (20) only partially embeds the nanostructure (40). [2] Method according to claim 1, wherein the embedding layer (20) is produced by chemical conversion of an uppermost material layer of the carrier body (2), in particular with an increase in volume. [3] Method according to claim 1 or claim 2, wherein an inner layer thickness D1 of the embedding layer (23), measured below the original surface (5) of the carrier body (2), is at least 6 nm, preferably at least 12 nm, particularly preferably at least 18 nm and / or - wherein the respective nanostructure (40) is designed to taper conically, in particular so that a repelling effect (83) on microorganisms is achieved. [4] Method according to one of the preceding claims, wherein a maximum layer thickness / embedding height D2 (25) of the embedding layer (5), measured above the original surface (5) of the carrier body (2), is smaller than an average height H (43) of the nanostructure (40), again measured above the original surface (5) of the carrier body (2), - in particular so that the nanostructure (40) protrudes from the embedding layer (20), - preferably wherein the nanostructure (40) protrudes from the embedding layer (20) by at least 20%, preferably by at least 50%, particularly preferably by at least 66% of the average height H (43). [5] Method according to one of the preceding claims, wherein the embedding layer (20) is produced, preferably by means of an electrochemical process and / or by means of an oxidation process, in such a way that the embedding layer (20) grows both into the carrier body (2) and out of the original surface (5), - in particular such that after completion of process step B, the embedding layer (20) extends deeper into the carrier body (2) than the nanostructure (40), preferably such that the embedding layer (20) not only embeds the nanostructure (40) but also nanoscopically anchors it mechanically in the carrier body (2). [6] Process according to one of the preceding claims, wherein the first process step A is a hydrothermal oxidation carried out in a pressure reactor, - in particular wherein during process step A the nanostructure (40) grows only on the surface (5), in particular on a native oxide layer of the carrier body (2), but not into the carrier body (2), - preferably using ultrapure water, or aqueous ammonia or KOH as the reactive liquid, - particularly preferably wherein the surface (5) of the carrier body (2) on which the nanostructure (40) is to be applied remains completely immersed in the reactive liquid during process step A, - in particular wherein the carrier body (2) is made of metal, in particular of titanium, so that the hydrothermal oxidation produces a metal oxide, in particular titanium oxide, in the form of nanoparticles, which forms / forms the nanostructure (40). [7] Method according to one of the preceding claims, wherein the second process step B is an electrochemical anodization for producing the embedding layer (20), - preferably using a liquid electrolyte such as diluted sulphuric acid or comparable suitable electrolyte and using an electrical direct voltage, preferably below 20 V, preferably below 15 V, particularly preferably below 10 V and / or - wherein the electrochemical anodization is carried out with an exposure time of less than 30 minutes, preferably less than 5 minutes, particularly preferably less than 2 minutes. [8] Method according to one of claims 1 to 6, wherein the second process step B is a wet-chemical oxidation for producing the embedding layer (20), preferably using an oxidizing liquid, - particularly preferably wherein the surface (5) of the carrier body (2) on which the embedding layer (20) is to be deposited remains completely immersed in the oxidizing liquid together with the nanostructure (40) during process step B. [9] Method according to one of claims 1 to 6, wherein the second process step B is a plasma-assisted or plasma-induced process for producing the embedding layer (20), - preferably using a plasma containing oxygen. [10] Method according to one of the preceding claims, wherein the nanostructure (40) produced by the method comprises nanoparticles, in particular in the form of nanocrystals, the tips of which are on average aligned in the same direction, in particular normal, to the surface (5), - preferably wherein the nanoparticles have a predominantly tetragonal pyramidal, tetragonal bi-pyramidal and / or a conical or biconical basic shape and / or - wherein the nanoparticles have an average height H (43), measured above the original surface (5), of less than 300 nm, preferably of 250 nm, particularly preferably less than 175 nm and / or - wherein the nanoparticles have an average tip spacing of less than 300 nm, preferably less than 250 nm, particularly preferably less than 150 nm or less than 75 nm. [11] Method according to one of the preceding claims, wherein the carrier body (2) is made of metal, preferably of titanium or a titanium alloy, and / or - wherein the embedding layer (20) produced in process step B is an amorphous, partially amorphous or purely crystalline titanium oxide layer and / or - wherein the nanostructure (40) produced in process step A is formed by an at least partially crystalline titanium oxide layer. [12] Method according to one of the preceding claims, wherein the surface (5) of the carrier body (2) has an oxide layer, preferably a titanium oxide layer (TiO2 or TiOx), and the nanostructure (40) is applied to this oxide layer or produced therefrom by conversion. [13] Layered composite (60) comprising a nanostructure (40), - preferably wherein the nanostructure (40) is applied in an abrasion-resistant manner to a surface (5) of a carrier body (2) and / or - preferably wherein the nanostructure (40) was produced by means of a method according to one of the preceding claims, in particular applied or grown on the carrier body (2), characterized by , - that the nanostructure (40) comprises nanoparticles, in particular in the form of nanocrystals, which have at least one surface-active effect, for example - an optical effect and / or - an anti-adhesive effect and / or - a bactericidal effect and / or - an electrical effect and / or - produce a mechanical effect, and - that the nanostructure (40) is at least partially embedded in an embedding layer (20), - preferably wherein the nanostructure (40) protrudes from the embedding layer (20) to such an extent that at least one surface-active effect is at least partially retained. [14] Layer composite (60) according to the preceding claim, wherein the embedding layer (20) extends beyond the nanostructure (40) inwards in the direction of the carrier body (2), - in particular so that the embedding layer (20) extends deeper into the carrier body (2) compared to the nanostructure (40), - preferably so that a nanomechanical anchoring of the nanostructure (40) on a surface (5) of the carrier body (2) and / or in the carrier body (2) is achieved. [15] Layer composite (60) according to one of claims 13 or 14, wherein the embedding layer (20) differs at least morphologically from the nanostructure (40), - in particular wherein the embedding layer (20) and the nanostructure (40) are made of the same material, in particular of a metal oxide. [16] Carrier body (2), in particular in the form of a component (1), with a layer composite (60) according to one of the preceding claims 13 to 15, - preferably wherein the embedding layer (20) differs morphologically from the nanostructure (40) and / or - wherein the embedding layer (20) has been / is at least partially grown into the carrier body (2). [17] Use of a layer composite (60) according to one of claims 13-15 on a carrier body (2) for producing tailor-made surface properties of the carrier body (2), - preferably wherein the layer composite (60) was produced by a method according to one of claims 1-11 and / or was anchored abrasion-resistant to a surface (5) of the carrier body (2) by such a method, - in particular so that, with sufficient pressure, an associated contact body of the carrier body (2) is abraded on the nanostructure (40) and not the nanostructure (40) on the contact body when the carrier body (2) slides along the contact body under the pressure together with the layer composite (60). [18] Use according to the preceding claim, wherein the layer composite (60) produces a bactericidal effect and / or an anti-adhesive effect. [19] Use according to claim 17 or 18, wherein the carrier body (2) has a surface (5) whose properties must be specifically adjusted in order to make it technically usable, and - wherein at least one surface-active effect attributable to the nanostructure (40) is provided by the layer composite (60) and utilized in a technical application, in particular - to improve the wetting properties and / or - to increase hydrophobicity and / or oleophilicity or lipophilicity and / or - to reduce sliding friction and / or - to increase surface hardness and / or - to achieve an optical effect and / or - to achieve a chemical effect and / or - to achieve a biological effect on the surface (5).

Images