METHOD FOR PRODUCING AN ABRASION-RESISTANT NANOSTRUCTURE, CARRIER BODY WITH SUCH A NANOSTRUCTURE AND ASSOCIATED USE

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, whereby the invention can be used particularly advantageously if the carrier body is designed in the form of a permanent or temporary implant. In the method, the nanostructure is first applied to the surface in a first process step A, whereby the nanostructure can in particular be grown on the surface. When reference is made to the term nanostructure below, this always refers to several nanoscopic elements or several 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] Current developments in the field of implantology are driven by the need to address a number of challenges in the field of medical implants.

[0005] For example, extending the lifespan of implants is a key goal that serves patient safety. Implants are exposed to various mechanical stresses and friction in the human body. Over time, this wear can lead to deterioration of the implant's properties, particularly its surface. An increased lifespan would reduce the need for implant replacement and thus spare the patient unnecessary surgical interventions.

[0006] Improved biocompatibility is another important goal in the further development of implants. This is desirable to prevent inflammation, allergies, or rejection reactions in the body. Finally, further developments are also of interest, especially if they can prevent or at least reduce bacterial implant infections.

[0007] Such properties of implants can be achieved, for example, by nanostructuring the surface of the implant. However, wherever nanostructures are to be applied to a carrier surface, such as an implant, the fundamental challenge is to achieve sufficient adhesion of the nanostructure to the surface. It has often been observed in the prior art that, although nanostructures can be produced, they are removed from the respective surface simply by touching it, so that the effects provided by the nanostructure are then lost. Therefore, in order to actually be able to permanently utilize the technical effects provided by the nanostructure in practical applications, it is necessary to apply the respective nanostructure to the surface in an abrasion-resistant manner.

[0008] S. Ecoffey et al., J. Vac. Sci. Technol. B 29 / 6, 2011, describes a two-step process for the fabrication of top-down titanium nanostructures. The first step involves electron beam lithography followed by a titanium plasma etching process. The second step is a damascene process in which the titanium nanostructures are embedded in the oxide.

[0009] L.A. Martinez-Chavez, Applied Physics A, 127:808, 2021, describes a method for fabricating Bi / TiO2 / Bi / TiO2 / Bi / TiO2 multilayer thin films by pulsed laser deposition (PLD) using a crossed-beam configuration. To stack the Bi layers on TiO2, two laser beams are used to alternately ablate two perpendicularly positioned targets (TiO2 and Bi).

[0010] 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 implant surfaces. Summary of the invention

[0011] 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.

[0012] 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.

[0013] 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 implantology. However, the possible applications of the invention are not limited to implants; rather, 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.

[0014] 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 thus creates a nanostructure on a surface that is / will be mechanically and stably bonded to the surface by means of the additional embedding layer. This ensures reproducible and consistent, i.e., permanent, surface properties, particularly when designing the abrasion-resistant nanostructure on an implant surface.

[0015] The described method can be further developed in a variety of ways according to the invention: For example, 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.

[0016] 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 fills the gaps (increasingly over time) during growth and can thus anchor the nanostructure to the surface.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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 implant surfaces with a complex 3D geometry.

[0021] 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.

[0022] 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.

[0023] 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 (implant) carrier bodies. 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 carrier bodies.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] Preferably, the nanoparticles may have a predominantly tetragonal pyramidal and / or tetragonal bipyramidal and / or conical and / or biconical basic shape or a conical basic shape. The nanoparticles may further 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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).

[0032] 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).

[0033] For example, the grown portion of the embedding layer can have recesses whose shape is complementary to the base area of ​​the nanostructure and (e.g., following the normal to the surface) to a shape / contour of the nanostructure, particularly a conical one. In other words, the embedding layer can be designed such that its grown portion, i.e., the portion above the original surface, at least partially fills gaps between elements of the nanostructure (e.g., gaps between the described pyramid-shaped nanostructures).

[0034] This filling or embedding can be adjusted by selecting suitable 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 substrate).Since the nanostructures are intended to protrude from the embedding layer so that they can exert the desired surface effects, in particular a repellency effect on bacteria, it is preferable for the embedding height to be 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, in particular in the form of an implant, with a layer composite as described above. Preferably, the embedding layer can also be morphologically different from the nanostructure and / or the embedding layer can be at least partially embedded in the carrier body. Such a carrier body can permanently exhibit advantageous surface properties caused by the nanostructure because the latter is abrasion-resistantly enclosed 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] In one embodiment, 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 with respect to the outermost surface of the implant, which is co-formed by the nanostructure.

[0044] The invention is described in more detail below using several preferred embodiments.

[0045] It shows: Fig. 1a 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 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 using 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. 9a schematic representation of an electrochemical anodization setup; Fig. 10 a schematic representation of the deposition 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.

[0046] 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.

[0047] Figure 1 shows a cross-section through an outer layer, for example of an implant 1, comprising a carrier body or base body 2 and optionally an (in particular native) oxide layer 10.

[0048] The carrier body 2 can preferably be a permanent or temporary implant 1. 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.

[0049] Preferably, the carrier body 2 is formed from titanium or a titanium alloy and forms a native oxide layer 10 that is chemically very inert and (at least partially) mechanically stable, which is the reason why titanium implants can grow well into the bone. This is particularly advantageous in endoprosthetics but also for dental implants.

[0050] 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.

[0051] 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 method according to the invention described below, with which a nanostructure 40 is to be anchored on 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 Figure 3 described: 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.

[0052] 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 altered or is only slightly altered by subsequent process steps.

[0053] 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 at 20 bar. A suitable pressure reactor 90 is Figure 5shown schematically. The pressure reactor 90 is designed using a stainless steel cylinder as the base vessel 93, which is lined internally with Teflon (PTFE) 95.

[0054] The process for nanostructuring the surface 5 of the carrier body 2 is shown schematically in Figure 6 The carrier bodies 2 to be coated with the nanostructure or nanoparticles 40, for example titanium implants 1, 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 can be subjected to a separate cleaning step beforehand. 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 over 24 hours, whereby this process can be carried out in parallel on several implants 1 or carrier bodies 2 (step 3) in Fig. 6 ). Heating can be done in a furnace or by means of a jacket heater. After the process is complete, the pressure reactor 90 is discharged (step 4) into Fig. 6 ).

[0055] Through this process, a nanostructured crystalline titanium oxide layer is grown on the titanium implant 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.

[0056] Figure 2 schematically illustrates the result of the process, 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 Figure 2that 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 which 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 figure). Figure 10 ). The grown portion 24 fills the spaces between the nanostructures 40 and (if one imagines the nanostructures 40 away) has corresponding gaps at the locations of the nanostructures 40, which emphasizes the "embedding", as in Figure 12shown. 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.

[0057] This selective embedding (which can also be seen from the Figure 11can be understood - 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 Figure 11 illustrated schematically.

[0058] Figure 7 shows schematically the configuration of the nanostructure 40 after a treatment time of the carrier bodies 2 of less than 1 hour ( Fig. 7 , left) at a temperature of 220 °C and for 24 hours ( Fig. 7 , right) at a temperature of 220 °C. 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, but after a few hours, for example, 24 hours, of the process time, they align themselves normal to the surface 5. The nanoparticles thus exhibit an averagely uniform orientation, as in Figure 2marked 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 48. The nanoparticles 40 have an average height 43, an average width 44, an average tip size 45, and an average distance from one another 46.

[0059] Figure 4 shows a schematic sketch illustrating the desired anti-adhesive property of the nanostructured surface compared to an unstructured surface. The nanostructure 40 causes bacteria 81 (in Figure 4kidney-shaped) due to fewer surface contacts 86, or 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. 4right), 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.

[0060] 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.

[0061] 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. Such abrasion is usually generated, for example, in implants 1 when the implant 1 comes into contact with bone with its surface 5 and shear forces arise between the bone and the implant surface. With a suitable choice of the process parameters, the method according to the invention can ensure such high abrasion resistance of the nanostructure 40, for example when used on titanium implants 1, that the bone abrades against the nanostructure 40 and not the other way around, without the nanostructure 40 being largely or even completely destroyed.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, in particular a bacteria-repellent and / or bactericidal effect, are permanently effective even when used, for example, in dentistry or endoprosthetics.

[0062] In the second process step B, the nanostructure 40 is permanently and abrasion-resistantly "fixed" to the surface 5 by creating an embedding layer 20 on the surface 5, thus creating 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. Instead, the embedding layer 20 is created primarily at the interface between the nanostructure 40 and the interface 14 of the carrier body 2 and its oxide layer 10.

[0063] 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 can occur, which is generally accompanied by a change in volume. This 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 processes.

[0064] 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.

[0065] 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.

[0066] Process step B using electrochemical anodization is shown schematically in the Figures 8 and 9 shown. During electrochemical anodization, the carrier body 2 with the nanostructure 20 is loaded onto a holder 94 (step 1) in Fig. 8 ) and immersed together with the holder 94 into a vessel 99 filled with a liquid electrolyte 100, for example, one percent sulfuric acid (H2SO4). The liquid electrolyte 100 contains no fluorine-containing compound and is thus fluorine-free. A direct 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.

[0067] 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.

[0068] Figure 11shows schematically 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, for example 20 V when using a titanium carrier body, 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.

[0069] 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 has been observed that the embedding layer 20 is not formed (above in Fig. 11 ) or, for example at 5 V, has a layer thickness that is too small to produce an anchoring effect (second image from the top in Fig. 11 ). After the process, 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, drying or tempering steps, can be carried out between the process steps described here.

[0070] 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).

[0071] 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 Figure 10 (left) shown schematically. In particular, the ingrown layer thickness 23 can be approximately 16-24 nm. The embedding layer 20 thus provides abrasion resistance.

[0072] The maximum grown layer thickness 25 ("embedding height"), designated as D2 in the figure, can preferably 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, as mentioned, 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.

[0073] 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.

[0074] 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 TiO 2 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.

[0075] 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.

[0076] Since the color of the implant 1 may change after performing the oxidation process B due to interference effects, a particularly preferred embodiment provides that, when the process is used for dental implants, the voltage is limited to 8-10 V. This prevents discoloration of the implant 1, which would be disruptive in the dental area.

[0077] 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 and abrasion-resistantly nanomechanically anchor nanostructures 40 on a surface 5 of a permanent or temporary implant; 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 created or grown on 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, 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 form 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 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 grow into the carrier body 2, in particular through the nanostructure 20. List of reference symbols

[0078] 1Implant, titanium body 2Support body, base body 3Base material 4Structure of the base material 5Initial surface 6Surface roughness 7Resulting new surface 10If necessary. Existing oxide layer 11Material of the oxide layer, if present 12Structure of the oxide layer, if present 13Thickness of the oxide layer, if present 14Interface between the oxide layer, if present, and the base material of the base body 20Embedding layer 21Total thickness of the embedding layer 22Ingrown portion of the embedding layer 23Thickness of the grown portion of the embedding layer 24Grown portion of the embedding layer 25Thickness of the grown portion of the embedding layer 26Interface between the oxide layer, if present, and the grown embedding layer 27Interface between the oxide layer, if present, and the grown embedding layer 28Growth direction of the growing embedding layer 29Growth direction of the growing embedding layer 30Embedding area of ​​the nanostructures through the embedding layer31Area of ​​the embedding layer between the nanostructures 32Surface of the embedding layer 33Material of the embedding layer 34Microstructure of the embedding layer 35Resulting connection area between embedding layer 20 and nanostructure 40 40Nanostructures (or nanoparticles) 41Material of the nanostructures 42Microstructure of the nanostructures 43Average height of the nanostructures 44Average width of the nanostructures 45Average tip size or tip diameter 46Average distance between two nanostructures 47Center line, normal direction of the nanostructures 48Aperture angle of the nanostructures 49Part of the nanostructures protruding from the embedding layer 50Tip of the nanostructures 51Surface, lateral surface of the nanostructures 52Contact area between nanostructure 40 and original surface 5 60Layer composite 70Process for producing an abrasion-resistant nanostructure 71-73Steps of the process 70 81Bacterium 82Adhesion forces 83Antiadhesive properties84Biofilm formation 85Bactericidal effects 86Bacteria / surface interaction 87Interaction area, support surface 90Pressure reactor 91Lid 92Closure 93Main vessel 94PTFE frame 95PTFE inlet 96Aqueous solution 97Filling level 98Gas mixture 99Pressure 100Heating system / jacket heating / furnace 101Repelling effect 102Maximum height (of 40 measured over 5) 103Embedding height D2 110Device for process step B 111Process basin, vessel 112Electrolyte 113Voltage source 114Adapter for electrical contact 115Bath properties 116Intermediate work steps 117Counter electrode 120Microstructure properties, microstructure of the base material 1 121Grains of the Base material 122Grain boundaries 123Normals to crystal orientation

Claims

1. Method for producing an abrasion-resistant nanostructure (40) on a surface (5), in particular on portions of the surface (5), of a carrier body (2), in particular in the form of a permanent or temporary implant (1), - wherein, in a first process step A, the nanostructure (40) is applied to the surface (5), in particular grown on the surface (5), characterized in that - the nanostructure (40) produced in process step A is bonded permanently and in an abrasion-resistant manner 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), in particular deposited on the nanostructure (40) - wherein the embedding layer (20) only partially embeds the nanostructure (40), and - wherein the embedding layer (20) is produced by chemical conversion of an uppermost material layer of the carrier body (2) with an increase in volume.

2. Method according to claim 1, wherein an inner layer thickness D1 of the embedding layer (20), 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 repellent effect (83, 101) on microorganisms is achieved.

3. Method according to one of the preceding claims, wherein a maximum layer thickness / embedding height D2 (25, 103) of the embedding layer (5), measured above the original surface (5) of the carrier body (2), is smaller, preferably half as high as an average height H (43) of the nanostructure (40), measured again 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).

4. Method according to one of the preceding claims, wherein a grown portion (24) of the embedding layer (20) has a shape that is complementary to a shape of the nanostructure (40), - preferably wherein the embedding layer (20) partially fills intermediate spaces between individual nanostructures (40) on the surface (5) and / or - wherein the grown portion (24) of the embedding layer (20) has recesses which correspond in shape to a respective base area of the respective nanostructure (40) and / or which are designed to be complementary to a conical shape of the nanostructure (40) with respect to a direction of a normal to the surface (5).

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 anchors it mechanically in the carrier body (2) at the nanoscale.

6. Method 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) only grows 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) onto 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 titanium, so that the hydrothermal oxidation produces a metal oxide, in particular titanium oxide, in the form of nanoparticles, which forms / form the nanostructure (40).

7. Method according to one of the preceding claims, wherein the second process step B is an electrochemical anodization to produce the embedding layer (20), - preferably using a liquid electrolyte such as diluted sulfuric acid or comparable suitable electrolytes and applying a direct electric voltage, preferably of less than 20 V, preferably of less than 15 V, particularly preferably of less than 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 to produce 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 method 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 has nanoparticles, in particular in the form of nanocrystals, whose tips 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 conical or double conical 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 250 nm, particularly preferably less than 175 nm, and / or - wherein the nanoparticles have an average tip-to-tip distance of less than 300 nm, preferably less than 250 nm, particularly preferably less than 150 nm, and further particularly preferably 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 of 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 and / or - 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 from it by conversion.

12. Layer composite (60) comprising a nanostructure (40), wherein the nanostructure (40) is applied in an abrasion-resistant manner to a surface (5) of a carrier body (2), - preferably wherein the nanostructure (40) has been produced by means of a method according to one of the preceding claims, in particular applied or grown on the carrier body (2), characterized - in that the nanostructure (40) comprises nanoparticles, in particular in the form of nanocrystals, which generate at least one surface-active effect, for example - an optical and / or - an anti-adhesive effect and / or - a bactericidal effect, - in that the nanostructure (40) is at least partially embedded in an embedding layer (20), 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, and - in that the embedding layer (20) has a grown-on portion (24) above the surface (5) and a grown-in portion (22) below the surface (5).

13. Layer composite (60) according to the preceding claim, wherein the embedding layer (20) extends inwardly toward the carrier body (2) beyond the nanostructure (40), - in particular so that the embedding layer (20) extends deeper into the carrier body (2) than the nanostructure (40), - preferably so that nanomechanical anchoring of the nanostructure (40) on a surface (5) of the carrier body (2) and / or in the carrier body (2) is achieved and / or - 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.

14. Carrier body (2), in particular in the form of an implant (1), having a layer composite (60) according to one of the preceding claims 12 or 13, - 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).

15. Use of a layer composite (60) according to one of claims 12 or 13 on a carrier body (2) for producing customized surface properties of the carrier body (2), - preferably wherein the layer composite (60) has been produced by a method according to one of claims 1-11 and / or has been anchored in an abrasion-resistant manner on a surface (5) of the carrier body (2) by such a method, - in particular so that, under sufficient pressure, an associated contact body of the carrier body (2), for example a bone, 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), - preferably wherein the carrier body (2) is an implant (1) and wherein the layer composite (60) produces a bactericidal effect and / or an anti-adhesive effect with respect to the outermost surface of the implant (1), which is also formed by the nanostructure (40).