Transparent component with functionalized surface

Abstract

The invention relates to a transparent component (1) having a functionalized surface, the surface having pits (2) and a laser-induced periodic surface structure (3) and being functionalized by the pits (2) and the laser-induced periodic surface structure (3), the pits (2) and the laser-induced periodic surface structure (3) spatially overlapping, and the depth of the pits (2) being between 100 nm and 2000 nm.

Description

Technical Field

[0001] The invention relates to a transparent component having a functionalized surface. Background Art

[0002] It is known that during laser material processing, material of a component can be removed by evaporating the material in the focal region of the laser beam by means of an intense light-matter interaction. The resulting structural depressions are referred to as dimples.

[0003] It is further known that so-called laser-induced periodic surface structures (hereinafter referred to as LIPSS) can be produced by means of the successive interaction of one and the same material region with at least two laser pulses.

[0004] In this context, dimples and LIPSS are suitable for functionalizing component surfaces, wherein in particular the optical properties, wetting properties and tribological properties can be influenced.

[0005] From DE 10 2017 006 358 A1, a method for producing a structured surface on a substrate is known, in which surface structures having dimensions in the submicrometer range are produced by treatment with an intense pulsed laser beam.

[0006] From EP 2 692 855 B1, a device for cell biology and / or medical applications is known, wherein the device has at least one surface which at least partially has a surface structure produced by electromagnetic radiation, the surface structure having a microstructure superimposed by a nanostructure.

[0007] In addition, according to C. Kunz's paper "Selektive Herstellung multifunktionaler mittels laser-induzierter periodischer ”, Friedrich Schiller University Jena, 2021, Laser-based surface modification of quartz glass by LIPSS is known. Summary of the invention

[0008] Starting from the known prior art, it is an object of the present invention to provide an improved transparent component with a functionalized surface.

[0009] This object is achieved by a transparent component having the features of claim 1. Advantageous developments follow from the dependent claims, the description and the drawing.

[0010] Accordingly, a transparent component with a functionalized surface is proposed, wherein the surface has pits and LIPSS, and the surface is functionalized thereby. According to the invention, the pits and the LIPSS overlap in space.

[0011] Here, the transparent material of the component can be a material such as a polymer or a plastic. The material to be processed can also be a semiconductor, for example an elemental semiconductor such as silicon or germanium, or a III-V semiconductor such as gallium arsenide, or an organic semiconductor or any other type of semiconductor. Exemplarily, the material can be a silicon wafer. In particular, the material can be a layer system, wherein each layer can be selected from the group of metals, polymers, plastics or semiconductors. In particular, the material can also be glass, for example sapphire or quartz glass.

[0012] "Transparent" may mean that the component is optically transparent, i.e., transparent to wavelengths visible to the human eye. For example, the material may transmit more than 80%, or more than 85%, or more than 90%, or more than 95%, or more than 99% of visible light. "Transparent" may also mean that the material is transparent to the wavelength of the processing laser.

[0013] Laser machining methods can be used to generate the pits and LIPSS. Here, a laser provides laser pulses of a laser beam, wherein each laser pulse forms a laser beam along a beam propagation direction. The pulse duration of the laser pulses can be between 300 fs and 10 ps, ​​and / or the wavelength of the laser pulses can be between 300 nm and 3000 nm, preferably between 900 nm and 2200 nm.

[0014] It is thereby possible to select a laser wavelength at which the material is transparent, so that pits and LIPSS can be introduced into the material via nonlinear interactions. In addition, the short pulse duration can prevent unwanted heating of the material, which inhibits the formation of LIPSS.

[0015] Additionally, the laser light may have a linear polarization, for example the polarization degree of the laser beam may be more than 80%, preferably more than 95%.

[0016] Instead of a single laser pulse, the laser can also provide a laser pulse train, wherein each pulse train comprises the emission of a plurality of laser pulses. Here, the laser pulses can be emitted very densely in succession at intervals of a few picoseconds to a few nanoseconds in a specific time period. In particular, the laser pulse train can be a GHz pulse train, wherein the sequence of successive laser pulses of each pulse train occurs in the GHz range. For example, a pulse train can contain 2 to 10 laser pulses, wherein the time interval between the laser pulses is between 10ns and 50ns. However, a pulse train can also contain 30 to 300 laser pulses, whereby the time interval between the laser pulses can be between 100ps and 1000ps.

[0017] For example, the length of the laser pulse can be between 100ps and 100ns, in particular between 1ns and 20ns, wherein the wavelength can be between 300nm and 550nm, in particular 355nm, wherein the repetition frequency of the laser pulse can be between 10kHz and 100kHz, in particular between 10kHz and 50kHz, wherein the energy of the laser pulse can be between 60μJ and 300μJ, and each light spot can output 1 to 4 pulses.

[0018] For example, the length of the laser pulse can be between 200fs and 1000fs, in particular between 300fs and 450fs, wherein the wavelength can be between 900nm and 2300nm, in particular 1030nm, wherein the repetition frequency of the laser pulse can be between 10kHz and 400kHz, wherein the laser pulses are output in a laser pulse train, wherein each laser pulse train can contain 2 to 4 laser pulses, wherein the energy of the laser pulse train can be between 100μJ and 400μJ, and the numerical aperture can be between 0.01 and 0.2, in particular 0.08.

[0019] The laser pulse is introduced into the material, wherein the energy of the laser beam is at least partially absorbed in the material, for example by nonlinear interactions, in particular by multiphoton processes.

[0020] Here, the focal point of the laser beam can be located above the surface of the material to be processed in the beam propagation direction, or below the surface in the volume of the material to be processed. The focal position can also be exactly at the surface of the material to be processed. In particular, the focal position can be within ten Rayleigh lengths from the surface, wherein the Rayleigh length is the distance along the optical axis that the laser beam needs to travel from the beam waist or focus until its cross-sectional area doubles.

[0021] In particular, the term "focus" may be generally understood as a targeted area of ​​increased intensity. Therein, the laser energy is focused into a "focal region". Therefore, in particular, the term "focus" is used below independently of the beam shape actually used and the method for causing the intensity increase. The position of the intensity increase along the beam propagation direction can also be influenced by "focusing". For example, the intensity increase can be approximately point-shaped and the focal region can have a Gaussian-shaped intensity profile, as provided by a Gaussian laser beam. The intensity increase can also be designed linearly, wherein a Bessel-type focal region is obtained around the focal position, as can be provided by a non-diffracting beam. In addition, other more complex beam shapes are also possible, whose focal position extends in three dimensions, such as a multi-point profile consisting of a Gaussian laser beam and / or a non-Gaussian intensity distribution.

[0022] Due to the absorbed laser beam energy, the material heats up, depending on the intensity distribution of the laser, and / or due to the electromagnetic interaction between the laser and the material is converted into a temporary plasma state. In particular, in addition to linear absorption processes, nonlinear absorption processes can also be used, which can be achieved by using high laser energy or laser intensity. Accordingly, the material is modified in particular at the focus of the laser, since this is where the intensity of the laser beam is greatest. In particular, it can be achieved that a part of the material can be removed from the material complex, for example melted or evaporated. For this purpose, known processing processes are possible with regard to the interaction between the laser and the material to be processed, which are known, for example, as laser drilling, percussion drilling or laser ablation.

[0023] Due to the interaction of the laser pulses with the material to be processed, corresponding depressions are produced in the surface of the transparent component.

[0024] The pits are produced by evaporation of material on the surface due to the intensity of the irradiated laser. In particular, material is evaporated where the intensity of the laser beam exceeds a critical material-specific processing threshold. The shape and morphology of the laser beam, in particular the beam profile, are therefore crucial for the shape and form of the pits.

[0025] In the simplest case, the laser beam is a Gaussian laser beam with a Gaussian beam profile. There is a certain spatial region around the focus in which the laser energy exceeds a critical threshold. In other words, there is an isointensity surface in the intensity distribution of the laser beam at the focus within which the material is evaporated. The shape and morphology of the pit is therefore derived from this isointensity surface.

[0026] In particular, the pit can thus have a circular or oval cross section in the plane of the material surface, wherein the pit has a depth that increases from the edge to the center. In particular, the cross section of the pit in a plane perpendicular to the surface can also be circular or rounded.

[0027] By introducing pits into the surface of a material, for example, the optical properties / visual characteristics of the material can be determined, for example, in that light guided through the transparent material is scattered at the pits and thus makes the material appear hazy and / or matte. In particular, the pits on the surface of the material can suppress reflections on the material.

[0028] The dimples may be randomly arranged on the surface.

[0029] A random arrangement occurs if the spatial distances between the dimples are of random size. The spatial distances can be derived from the center point distance or the minimum distance from dimple edge to dimple edge.

[0030] In particular, the spatial frequency distribution of the pits is generated, for example, from the spatial distribution of the pits together with their size via Fourier transformation. The more irregular the distances between the pits, the greater the bandwidth of the spatial frequency distribution and the more divergently the incident light beam is reflected by the transparent component.

[0031] In particular, "randomly arranged" may therefore mean that the pits are randomly distributed in the spatial frequency space. By displaying the positions of the pits in the spatial frequency space, potential spatial directions in which interference of reflected or transmitted light may occur may also be identified in order to optimize the arrangement.

[0032] “Random distribution” may also mean that the spatial distribution of the pits follows a random distribution, such as a uniform distribution, a Gaussian distribution, a triangular distribution or other statistical distributions.

[0033] This has the advantage that the pits are introduced into the material at irregular spacings relative to one another, so that disruptive optical effects such as interference are reduced or avoided. Currently, for example, at least two laser pulses of a pulse train can overlap spatially. For example, each laser pulse can independently generate a pit, while a so-called LIPSS is generated in the overlap. This occurs if an excited plasma state is present in the first pit, with which the second laser pulse can interact, so that the heated material is oriented along the electric field of the laser pulse.

[0034] The combination of dimples and LIPSS leads to complex functionalization of the surface of the transparent component.

[0035] For example, the tactile feel or the roughness can be adjusted by the type and shape of the dimples and their distribution on the surface of the component. However, it is also possible to adjust the scattering of light and thus the optical properties of the material.

[0036] By means of the size of the LIPSS, for example, other functionalizations of the surface can be achieved. For example, since the LIPSS changes the contact angle between the liquid and the material, the wetting properties of the surface can be adjusted by the LIPSS. In addition, the tribological properties of the material can also be changed and, for example, the sliding properties of the material can be adjusted.

[0037] Thus, the combination of dimples and LIPS enables the surface of a transparent component to be functionalized optically and mechanically.

[0038] The pits may have a depth between 100 nm and 2000 nm, preferably between 200 nm and 1000 nm.

[0039] The roughness of the surface can thereby be adjusted particularly advantageously, wherein deep weakening of the material can be avoided.

[0040] The pits may have a diameter between 3 μm and 25 μm, preferably between 3 μm and 10 μm.

[0041] This makes it possible to adapt the diameter particularly advantageously to the microstructure required for the functionalization.

[0042] The dimples may have a size variation relative to the diameter of between 5% and 80%.

[0043] For example, the size variation may be 50% and the diameter of the pits may be 20 μm. The diameter of the pits on the surface may then be between 10 μm and 30 μm.

[0044] LIPSS may have a periodicity between 40 nm and 1000 nm, preferably between 50 nm and 300 nm.

[0045] The periodicity is determined by the average distance between two adjacent valleys or two adjacent peaks in the profile of LIPSS. The functionalization of the surface can be adjusted particularly advantageously by the periodicity. For example, for the medical field, the periodicity of LIPSS can be 100nm, so that the surface acts particularly hydrophobically. Thus, the surface treated in this way can be particularly advantageously used in endoscopes or laryngoscopes, for example, so that the correspondingly treated surface has a liquid-repellent effect, and correspondingly when used in vivo, for example, enables clear observation of the inside of the body. In particular, such a functionalized surface is correspondingly particularly suitable for use in the following medical devices, which enable optical access to the inside of the body.

[0046] The roughness of the transparent part may be between 0.05 μm and 1.5 μm.

[0047] This makes it possible to produce a particularly high-quality tactile impression of the surface.

[0048] Here, surface roughness can be defined as the peak-to-valley value, ie the distance from the highest ridge to the lowest depression. However, surface roughness can also be defined as the standard deviation of the depth of the pits.

[0049] Filling ratio of a surface with pits It can be between 20% and 95%.

[0050] The surface filling factor of the surface is given by the area ratio of the surface processed by the recesses to the total surface of the transparent component. The surface filling factor of the surface can be adapted depending on the desired roughness or functionalization.

[0051] In particular, when machining the surface, the pits can also be introduced stepwise or in several passes, wherein the surface coverage is increased stepwise and wherein distortion or tailing of the pits is reduced.

[0052] In particular, at least two recesses may overlap spatially.

[0053] "Overlapping in space" may mean that the dimples touch at the edges, or that the faces of the dimples are partially located on each other, ie there is an intersection of the faces of the dimples.

[0054] LIPSS can cover less than 90% of the pits.

[0055] For example, LIPSS may be located in the center of a pit. For example, a pit may have a diameter of 10 μm, while LIPSS is present only in the area of ​​the surface with a diameter of 9 μm.

[0056] However, it is also possible that two or more depressions overlap and that a LIPSS is formed only in the spatial overlap.

[0057] In a preferred embodiment, the transparent component has pits, wherein the pits have a depth between 100 nm and 2000 nm, a diameter between 3 μm and 25 μm, and the pits have a size variation relative to the diameter between 5% and 80%, wherein the laser-induced periodic surface structure has a periodicity between 40 nm and 1000 nm and the roughness of the functionalized surface is between 0.05 μm and 1.5 μm, wherein the surface filling rate with the pits is between 20% and 95%, and wherein the laser-induced periodic surface structure covers less than 90% of the pits.

[0058] In a particularly preferred embodiment, the transparent component has pits, wherein the pits have a depth between 200 nm and 1000 nm, a diameter between 3 μm and 10 μm, and a size variation of the pits relative to the diameter of between 5% and 80%, wherein the laser-induced periodic surface structure has a periodicity between 50 nm and 300 nm and the roughness of the functionalized surface is between 0.05 μm and 1.5 μm, wherein the surface filling rate with the pits is between 20% and 95%, and the laser-induced periodic surface structure covers less than 90% of the pits.

[0059] In a further particularly preferred embodiment, the pits have a diameter of between 13 μm and 20 μm, wherein the laser-induced periodic surface structure has a periodicity of between 650 nm and 1000 nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The preferred further embodiments of the present invention are described in more detail by the following description of the accompanying drawings. In the accompanying drawings:

[0061] Figure 1 Scanning electron microscope images of pits with LIPSS are shown;

[0062] Figure 2 A scanning electron microscope image showing two pits with LIPSS overlapped; and

[0063] Figure 3 A schematic representation showing the spatial overlap of two pits with LIPSS is shown; and

[0064] Figure 4 A schematic representation of the spatial overlap of two pits with LIPSS in the overlap is shown. DETAILED DESCRIPTION

[0065] Preferred embodiments are described below with reference to the accompanying drawings. Here, the same, similar or elements having the same effect have the same reference numerals in different figures, and repeated descriptions of these elements are partially omitted to avoid redundancy.

[0066] Figure 1 A scanning electron microscope image of a pit 2 with LIPSS 3 on a transparent component 1 is shown. The pit 2 has a diameter of 25 μm and a depth of 200 nm. In addition, LIPSS 3 is present in the pit 2, which can be recognized as a wave-like pattern. For example, such a pit 2 may be generated when at least two laser pulses, for example two laser pulses of a pulse train, are output successively to the same position of the component 1.

[0067] Figure 2 The scanning electron microscope image of two overlapping dimples 2 is shown, wherein each dimple 2 itself already has LIPSS 3. In the overlap 30 of two dimples 2, the dimples 2 reinforce each other, i.e. there is a variation in depth. In addition, the LIPSS 3 also overlap, so that here a variation of the LIPSS is generated to a certain extent due to the spatial addition of the wave-like pattern. This allows the functionalization of the surface to be adjusted particularly finely.

[0068] Figure 3A schematic representation of two pits 2 is shown. For example, the pits 2 have different sizes, namely 25 μm and 15 μm. For example, two pits 2 are generated with two laser pulses of a laser pulse train, so that LIPSS 3 is generated in the pits 2 (see Figure 2 ). The LIPSS overlaps in the spatial overlap 30 of the depressions 2 and can thereby be reinforced.

[0069] Figure 4 A schematic representation of two pits 2 is shown, each pit being generated by one laser pulse. Thus, the first laser pulse generates the first pit 2 and the second laser pulse generates the second pit 2. In the spatial overlap of the pits 2, the second laser pulse can then interact with the plasma state induced by the first laser pulse. Thus, a corresponding LIPSS will only appear in the overlap.

[0070] For example, the dimples 2 and the LIPSS 3 produce advantageous optical and tribological properties of the surface of the transparent component.

[0071] To the extent applicable, all individual features presented in the embodiments may be combined with one another and / or interchanged without departing from the scope of the invention.

[0072] Reference numerals list

[0073] 1 Transparent parts

[0074] 2. Pits

[0075] 3LIPSS

[0076] 30 Overlap

Claims

1. A transparent component (1) having a functionalized surface, wherein: The surface has pits (2) and a laser-induced periodic surface structure (3), and the surface is functionalized by the pits (2) and the laser-induced periodic surface structure (3), It is characterized in that The pits (2) and the laser-induced periodic surface structure (3) overlap in space, and the pits (2) have a depth between 100 nm and 2000 nm.

2. The transparent component according to claim 1, characterized in that The pit (2) has a depth between 200 nm and 1000 nm.

3. The transparent component according to claim 1 or 2, characterized in that: The pit (2) has a diameter between 3 μm and 30 μm, preferably, has a diameter between 3 μm and 10 μm.

4. The transparent component according to any one of the preceding claims, characterized in that The dimples (2) have a size variation relative to the diameter of between 5% and 80%.

5. The transparent component according to any one of the preceding claims, characterized in that The laser-induced periodic surface structure (3) has a periodicity between 40 nm and 1000 nm, preferably between 50 nm and 300 nm.

6. The transparent component according to any one of the preceding claims, characterized in that The roughness of the functionalized surface is between 0.05 μm and 1.5 μm.

7. Transparent element according to the preceding claim, characterized in that The surface filling rate of the pits (2) is between 20% and 95%.

8. The transparent component according to any one of the preceding claims, characterized in that The pits (2) are randomly arranged on the surface.

9. The transparent component according to any one of the preceding claims, characterized in that At least two pits overlap in space.

10. The transparent component according to any one of the preceding claims, characterized in that The laser-induced periodic surface structure (3) covers less than 90% of the pits (2).

Images