阅读说明：本技术 用于基于光刻进行三维部件的生成性制造的方法 (Method for generative manufacturing of three-dimensional components based on lithography ) 是由 P·格鲁贝尔 于 2020-02-26 设计创作，主要内容包括：在用于基于光刻进行三维部件(3)的生成性制造的方法中,其中由辐照装置发射的电磁辐射相继地聚焦到材料内的焦点(5)上,由此借助多光子吸收分别固化所述材料的位于所述焦点(5)处的体积元件,其中在所述辐照装置的写区域(4)中由体积元件分别构建子结构(6),所述部件(3)的构建包括如下步骤：a)将多个子结构(6)并排地设置,然后b)将子结构(6)相叠地布置,使得上部子结构(6)桥接彼此并排布置的下部子结构(6)之间的界面(7)。(In a method for the generative production of a three-dimensional component (3) on the basis of lithography, in which electromagnetic radiation emitted by an irradiation device is successively focused onto a focal point (5) within a material, thereby solidifying volume elements of the material located at the focal point (5) by means of multiphoton absorption in each case, wherein a substructure (6) is built up from the volume elements in a writing region (4) of the irradiation device in each case, the building of the component (3) comprises the following steps: a) arranging a plurality of substructures (6) side by side, then b) arranging the substructures (6) on top of each other such that the upper substructures (6) bridge the interface (7) between the lower substructures (6) arranged side by side to each other.)

1. A method for the generative production of three-dimensional components (3) on the basis of lithography, wherein electromagnetic radiation emitted by an irradiation device is successively focused onto a focal point (5) within a material, thereby respectively solidifying volume elements of the material located at the focal point (5) by means of multiphoton absorption, wherein substructures (6) are respectively built up from volume elements in a writing region (4) of the irradiation device,

it is characterized in that the preparation method is characterized in that,

the construction of the component comprises the following steps:

a) arranging a plurality of substructures (6) side by side, and then

b) The substructures (6) are arranged one above the other such that the upper substructure (6) bridges an interface (7) between the lower substructures (6) arranged side by side to each other.

2. The method of claim 1, wherein the first and second light sources are selected from the group consisting of,

it is characterized in that the preparation method is characterized in that,

the component comprises a plurality of superposed layers (10) each formed from a plurality of substructures (6) arranged next to one another, wherein the component (6) is built up layer by layer, wherein the substructures of an upper layer (10) bridge the interfaces (7) between adjacent substructures (6) of the layer (10) directly below it.

3. The method of claim 2, wherein the first and second light sources are selected from the group consisting of,

it is characterized in that the preparation method is characterized in that,

the boundary (11) between the superposed layers (10) is designed to be continuously flat.

4. The method according to claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the interfaces (11) between the superposed substructures (6) are formed stepwise.

5. The method of any one of claims 1 to 4,

it is characterized in that the preparation method is characterized in that,

the writing area (4) of the irradiation device is moved transversely to the direction of entry (2) of the irradiation device by changing the relative position of the irradiation device with respect to the material in order to build a next substructure (6) next to it after the substructure (6) is built.

6. The method of any one of claims 1 to 5,

it is characterized in that the preparation method is characterized in that,

the two lower substructures (6) adjoining one another at the interface (7) each overlap the upper substructure (6) bridging the interface (7) by at least 10%, preferably by at least 30%, particularly preferably by at least 40%, in particular by 50%.

7. The method of any one of claims 1 to 6,

it is characterized in that the preparation method is characterized in that,

the thickness of the substructure (6) and/or the layer (10) is less than 100 μm, preferably less than 50 μm, preferably less than 30 μm, in particular less than 10 μm.

8. The method of any one of claims 1 to 7,

it is characterized in that the preparation method is characterized in that,

the material is present on a material support, such as, for example, in a basin, and is irradiated from below by means of the material support which is at least regionally transparent to the radiation.

9. The method of claim 8, wherein the first and second light sources are selected from the group consisting of,

it is characterized in that the preparation method is characterized in that,

a build platform is positioned in spaced relation to a material carrier and the component is built on the build platform by solidifying material located between the build platform and the material carrier.

10. The method of any one of claims 1 to 9,

it is characterized in that the preparation method is characterized in that,

the volume of the focal spot (5) is changed at least once during the building of the component, such that the component (3) is built up of solidified volume elements of different volumes.

11. The method of claim 10, wherein the first and second light sources are selected from the group consisting of,

it is characterized in that the preparation method is characterized in that,

the focal volumes vary in at least one, preferably two, in particular three, spatial directions perpendicular to each other.

12. The method of any one of claims 1 to 11,

it is characterized in that the preparation method is characterized in that,

the electromagnetic radiation is deflected by means of a deflection unit in order to adjust the focal point (5) within the writing area (4) in a plane extending substantially perpendicularly to the entry direction (2).

13. A three-dimensional part (3) manufactured by a method according to any one of claims 1 to 12.

Technical Field

The invention relates to a method for the generative production of three-dimensional components based on lithography, in which electromagnetic radiation emitted by an irradiation device is focused successively onto a focal point within a material, whereby volume elements of the material located at the focal point are respectively solidified by means of multiphoton absorption, wherein substructures are respectively built up from the volume elements in a writing region of the irradiation device and a plurality of substructures are arranged next to one another.

Background

A method for forming shaped bodies is known, for example, from DE 10111422 a1, in which curing of a liquid photosensitive material is carried out by means of multiphoton absorption. For this purpose, a focused laser beam is injected into the photosensitive material cell, wherein the irradiation conditions for the multiphoton absorption process triggering the curing are only fulfilled in the region immediately surrounding the focal point, so that the focal point of the beam is directed to the region to be cured depending on the geometric data of the molded body to be produced in the cell volume. In the method according to DE 10111422 a1, the material bath is irradiated from above, wherein the radiation intensity is selected such that the liquid is substantially transparent to the radiation used above the focal point, so that direct polymerization of the bath material takes place in a position-selective manner within the bath volume, i.e. also well below the bath surface.

The irradiation device for the multiphoton absorption method includes an optical device for focusing a laser beam and a deflection device for deflecting the laser beam. Such an irradiation device has, subject to construction, a limited writing area within which the deflection means move the laser beam. The predefined writing area is usually smaller than the volume required for the component to be produced. Therefore, the component must be divided into a plurality of substructures, each corresponding to a write region and being built up one after the other. After building the sub-structure, the irradiation device used for building the next sub-structure is displaced relative to the material, and the next sub-structure is written next to the previous sub-structure. This so-called "stitching" can cause discontinuities in the butt-joint region between two adjacent substructures, which form mechanically weak points of the component.

When applying multiphoton absorption methods, a further problem is that the already formed cured structures subsequently block the region to be structured. This means that, in certain cases, the radiation introduced into the material must penetrate through the already cured structural region in order to reach the volume element to be cured. Such occlusion may lead to structural errors.

In EP 3093123 a1 a method is described which avoids shadowing by: the envelope interfaces between adjacent substructures run obliquely with respect to the main direction of the structure entrance. The envelope interface of the substructure extends obliquely with respect to the main direction of the structure entry, so that the structure entry is prevented from being covered or obscured in the main direction by an already existing substructure. Thus, a numerically larger depth along the main direction may be selected for the sub-structure. Therefore, a relatively small number of sub-structure blocks need to be divided in order to manufacture the entire structure.

Disclosure of Invention

The invention aims to propose an improved method with which not only the problem of shadowing is taken into account, but also the mechanical fragility of the component due to the sewing method is improved.

In order to solve this object, the invention proposes, in a method of the type mentioned at the outset, that the component is constructed with the following steps:

a) arranging a plurality of substructures side by side, and then

b) The sub-structures are arranged one above the other such that the upper sub-structure bridges the interface(s) between the lower sub-structures arranged side by side to each other. Since the component is divided not only into substructures lying alongside one another, but also into superposed substructures, the thickness of these substructures can be selected to be smaller. In particular, the thickness of the substructure may be chosen so small that there is no occlusion.

Preferably, it can be provided that the component comprises a plurality of superimposed layers, each of which is formed from a plurality of substructures arranged next to one another, wherein the component is built up layer by layer, wherein a substructure of an upper layer bridges the interface(s) between adjacent substructures of a layer directly below it. In this case, to form the lower layer, a plurality of substructures can first be built side by side before the substructure of the next upper layer is built directly on top of it. In this way, blocking is significantly reduced or completely avoided if the layers are made correspondingly thin, since the shadow is produced only by the height of the layer. The invention therefore takes a different approach to EP 3093123 a1, in EP 3093123 a1 the component is built up only from substructures arranged side by side, i.e. from a single layer.

In the method according to the invention, therefore, in contrast to the solution according to EP 3093123 a1, a numerically greater depth along the main direction is not selected for each substructure, but rather the depth of the substructure is limited to the thickness of the layer, which in turn is selected to be greater than the unshaded penetration depth.

It is therefore possible within the scope of the invention to dispense with the formation of an interface between two adjacent substructures, which extends obliquely to the direction of entry, thereby reducing the control effort of the structuring device. Rather, the interface preferably runs parallel to the entry direction.

However, it is also conceivable within the scope of the invention, as in the case of the solution according to EP 3093123 a1, to form an interface between two adjacent substructures which runs obliquely to the direction of entry.

Furthermore, the layer-by-layer construction of the component enables an improvement in the mechanical stability by: the substructure of one layer bridges the interface(s) between adjacent substructures of the layer directly below it. Thereby, an offset is formed between the substructures of the various layers, similar to the offset of bricks in a bricklayed composite. Due to this offset, weak points occurring as a result of a butt joint or interface between two adjacent substructures of a layer are compensated for and in particular propagation of cracks along the interface in the component is prevented.

Within the scope of the present invention, a substructure is understood to be a region of the body to be produced which corresponds to a writing region of the irradiation device and whose thickness measured along the direction of entry corresponds to the thickness of one layer in the case of a layer-by-layer build-up. In order to form a plurality of substructures, it is preferably provided that the writing region of the irradiation device is moved transversely to the direction of entry of the irradiation device by changing the relative position of the irradiation device with respect to the material, in order to build a next substructure after the substructure is built. In this case, the irradiation arrangement may be moved relative to the stationary material, or the material or the container containing the material may be moved relative to the stationary irradiation arrangement.

If, within the scope of the invention, side-by-side substructures are mentioned, this means: the writing area of the irradiation device is moved transversely to the entry direction as described above in order to first produce one of the side-by-side substructures and subsequently the other substructure. The side-by-side substructures are thus immediately adjacent to each other transverse to the direction of entry of the irradiation arrangement.

It is preferably provided that the interface between the superposed layers is designed to be continuously flat. The adjacent substructures constituting a layer therefore have the same thickness, so that a layer of uniform thickness results. In this case, the layer extends transversely to the entry direction.

Alternatively, however, the interface between the superposed substructures may also be formed stepwise. It is particularly advantageous if the upper substructure has a surface on its underside which has a step at the interface between the two lower substructures. Furthermore, it is advantageous if the lower partial structure has a surface on its upper side, which surface has a step at the interface between the two upper partial structures. Due to this stepped configuration, the thickness of adjacent sub-structures appears to be lower by the height of the step, so that the shielding effect can be further reduced or the thickness of the sub-structures can be increased by the height of the step without a deterioration of the shielding conditions.

In this case, an advantageous embodiment provides that the height of the step is selected to be 10 to 50%, in particular 20 to 40%, of the thickness (measured in the height direction) of the substructure.

For satisfactory mechanical stability of the component, the offset of the superposed substructures is preferably designed such that sufficient coverage or overlap of the substructures is formed. A preferred embodiment provides that the two lower substructures adjoining one another at the interface each overlap the upper substructure bridging the interface by at least 10%, preferably by at least 30%, particularly preferably by at least 40%, in particular by 50%.

In order to avoid that the already constructed substructure obscures adjacent regions of adjoining substructures of the same layer, it is preferably proposed that: the thickness of the substructures and/or layers is less than 100. mu.m, preferably less than 50 μm, preferably less than 30 μm, in particular less than 10 μm. In particular, the thickness of the substructure and/or the layer is at most 10 μm in the case of a numerical aperture of the irradiation system of 1.4, at most 30 μm in the case of a numerical aperture of the irradiation system of 0.8, and at most 50 μm in the case of a numerical aperture of the irradiation system of 0.4.

The individual substructures may be built up layer by layer, i.e. manufactured from multiple layers.

A particularly preferred mode is obtained in the following cases: the material is present on a material support, such as, for example, in a basin, and is irradiated from below by means of the material support which is at least regionally transparent to the radiation. In this case, the build platform may be positioned in spaced relation to the material carrier and the component built on the build platform by solidifying material located between the build platform and the material carrier. But it is alternatively also possible to irradiate the material from above.

Structuring suitable materials by means of multiphoton absorption offers the advantage of extremely high structural resolution, wherein volume elements having a minimum structural dimension of up to 50nm x 50nm can be realized. However, due to the small focal volume, the throughput of this method is very low, since for example for 1mm³Must be exposed to a total of more than 10⁹And (4) points. This results in a very long build time, which is a major reason for the low industrial use of multiphoton absorption methods.

In order to increase the throughput of the component without losing the possibility of high structural resolution, a preferred refinement of the invention provides that the volume of the focal point is changed at least once during the component build so that the component is built up from cured volume elements of different volumes.

High resolution is possible (in case the focal volume is small) due to the variable volume of the focal spot. At the same time, it is possible (in the case of a large focal volume) toHigh writing speeds (in mm) are achieved³In/h). By changing the focal volume, high resolution can then be combined with high throughput. The change in focal volume can be used here, for example, such that a large focal volume is used inside the component to be built in order to increase the throughput, and a smaller focal volume is applied at the surface of the component in order to form a component surface with high resolution. The increase in focal volume enables higher structuring throughput because the volume of material cured during exposure increases. In order to maintain high resolution at high throughput, small focal volumes may be used for finer structures and surfaces, and larger focal volumes may be used for coarse structures and/or to fill internal spaces.

In a preferred manner, the focal volume is varied such that the volume ratio between the maximum focal volume and the minimum focal volume during the manufacture of the component is at least 2, preferably at least 5.

The multiphoton absorption principle is used within the scope of the invention in order to initiate photochemical processes in the photosensitive material cell. For example, the multiphoton absorption method also includes a 2-photon absorption method. As a result of the photochemical reaction, the material changes to at least one other state, in which photopolymerization typically takes place. The multiphoton absorption principle is based on the fact that the above-described photochemical processes occur only in regions of the optical path in which a sufficient photon density for multiphoton absorption exists. The highest photon density occurs in the focal spot of the optical imaging system, so that multiphoton absorption occurs only in the focal spot with sufficient probability. Outside the focus, the photon density is low, so that the probability of multiphoton absorption outside the focus is too low to cause irreversible changes in the material by photochemical reactions. The electromagnetic radiation can pass through the material substantially unimpeded in the wavelengths used and the interaction between the photosensitive material and the electromagnetic radiation occurs only in the focal point. The multiphoton absorption principle is described, for example, in Zipfel et al, "Nonlinear mac, multiphoton microscopy in the biosciences (NATURE BIOTECHNOLOGY, Vol. 21, No. 11, 11/2003)".

A collimated laser beam may be preferred as the source for the electromagnetic radiation. The laser may not only emit one or more fixed or variable wavelengths. In particular, the laser is a continuous or pulsed laser having a pulse length in the nanosecond, picosecond or femtosecond range. The pulsed femtosecond laser offers the following advantages here: the average power required for multiphoton absorption is low.

A photoactive material is understood to be any material which is flowable under construction conditions and which is converted into a second state by multiphoton absorption in the focal volume, for example by polymerization. The material change must be limited to the focal volume and its immediate surrounding area. The change in the property of the substance may be permanent and for example change from a liquid state to a solid state, but may also be only temporary. In addition, the permanent change may also be reversible or irreversible. The change in material properties does not necessarily have to be completely transferred from one state to the other, but can also occur as a mixture of two states.

The power and duration of exposure of the electromagnetic radiation affect the quality of the produced parts. By adjusting the radiation power and/or the exposure time, the volume of the focal spot can be varied within a narrow range. At too high a radiation power, additional processes occur which can cause damage to the components. If the radiation power is too low, no permanent material property change can occur. Thus, for any photosensitive material, there are typical fabrication process parameters associated with good feature characteristics.

However, the above-mentioned change of the focal volume is not in this case based on a change of the intensity of the electromagnetic radiation used. Rather, the machining is performed with a (optimal) radiation intensity selected for the build process, which remains constant during the part build. The method is therefore preferably carried out such that the focal volume is changed while the radiation intensity remains constant, the average power of the electromagnetic radiation used being adjusted accordingly.

The volume of the spot exposed after the preparation step in the case of typical build process parameters is therefore understood as the focal volume. The above-described variation of the focal volume is understood to be a variation of the spatial intensity distribution in the focal spot. The spatial intensity distribution of the focal spot may in this case be changed in one or more directions. In this way, the intensity distribution in all three spatial directions can be increased, for example, by reducing the effective numerical aperture of the optical imaging system. In the case of using a diffractive optical element, the focal point may be changed to a line or a plane, or the number of focal points may be increased.

A series of device possibilities for changing the focal volume is described in WO 2018/006108 a 1.

It is preferably provided that the focal volume varies in at least one, preferably two, in particular in three spatial directions perpendicular to one another.

In particular, the electromagnetic radiation can be deflected by means of the deflection unit in order to adjust the focal point within the writing area in a plane extending substantially perpendicularly to the entering direction.

Drawings

The invention will be explained in more detail below with reference to an embodiment which is schematically shown in the drawing. Wherein the content of the first and second substances,

figure 1 shows a schematic view of a conventional method for building a three-dimensional part,

figure 2 shows a method according to the invention,

figure 3 shows a modified embodiment of the method according to figure 2,

figure 4 shows another modified embodiment of the method according to figure 2,

figure 5 shows another modified embodiment of the method according to figure 2,

FIG. 6 shows a further modified embodiment of the method according to FIG. 2, and

fig. 7 and 8 show other modified embodiments.

Detailed Description

In fig. 1, an optical unit 1 of an irradiation arrangement is schematically shown in cross-section by 1, the optical unit 1 having an entry direction 2. The direction of entry 2 indicates the direction in which the electromagnetic radiation is emitted from the irradiation arrangement onto the component 3 to be built in the basic setting. The irradiation device has a writing area with an extension 4 which corresponds to the width within which the emitted radiation can be focused onto a focal point 5 within the material to be cured by the radiation. In order to be able to focus successively on different focal points in the writing area, the irradiation arrangement comprises elements, not shown in detail, such as deflection elements. The term "entry direction" is to be understood as meaning the main entry direction of the irradiation arrangement in the basic position if the unit is designed to change the direction of incidence.

Since the stretch 4 of the writing area is not sufficient to create a whole part, the part is built up of a plurality of substructures 6 arranged side by side. In this case, it is possible to construct the substructure 6 from a plurality of layers 9 in the height direction. First, a first substructure 6 is formed, which is located in the writing area of the irradiation arrangement. Thereafter, the writing area is laterally moved by displacing the irradiation arrangement relative to the component 3 or by displacing the component 3 relative to the irradiation arrangement, so that the second substructure 6 is built up next to the first substructure 6. This is repeated until the finished component 3 has been composed of all substructures. The component constructed in this way has mechanical weak points at the interfaces 7 between the substructures 6 arranged side by side.

Furthermore, occlusion occurs beyond a certain height of the substructure 6 measured in the direction of entry. This means that the sub-structure 6 that has been built up can shield the beam from the optical unit 1 that is directed to the focal point within the sub-structure connected to it on the left, as schematically shown by means of the line 8. In the region delimited by the line 8, structuring errors occur which are to be avoided.

In fig. 2, it can be seen that the component 3 is again built up from a plurality of substructures 6 according to the method according to the invention, the substructures 6 now being arranged not only side by side but also one above the other. In the embodiment according to fig. 2, the partial structure 6 is arranged for this purpose as superposed layers 10, so that the interface 11 between the superposed layers 10 is formed continuously flat. By the component 3 being composed of a plurality of substructures 6 both in the lateral direction and in the height direction, each individual substructure 6 can be constructed with a reduced height in order to avoid shading. Furthermore, the following possibilities are thereby opened up: the substructures 6 of the individual layers 10 are laterally offset with respect to one another such that the upper substructure 6 bridges the interface 7 between the substructures 6 arranged side by side directly below it. In the construction variant according to fig. 2, the lateral offset is half the width of the individual substructures 6, so that two lower substructures 6 adjoining one another at the interface 7 each overlap by up to 50% with the upper substructure 6 bridging this interface 7.

In the modified embodiment according to fig. 3, the offset is only 10%.

Although the interfaces 7 between the substructures 6 arranged side by side extend parallel to the entry direction 2, fig. 4 shows different alternatives, namely curved and stepped interfaces 7 running obliquely to the entry direction. This additionally prevents shadowing.

In fig. 5, a further modified embodiment is shown, in which the superimposed substructures 6 are not arranged in layers, but rather according to a stepped arrangement. The substructure 6 has a surface on its underside and on its upper side, respectively, which has a step at the location of the interface 7 between the substructures below or above it. Due to such a stepped configuration, the projection b of the height a of the substructure 6, which is relevant in terms of shielding, is smaller compared to the construction variant according to fig. 2, so that shielding can be avoided more effectively or the height of the substructure can be increased without increasing the risk of shielding.

Fig. 6 shows an alternative arrangement of the substructures 6, in which the interfaces 11 between the superposed substructures 6 or between the layers 10 are now not at right angles to the entry direction 2, but run at an angle of at most 45 °, preferably at most 30 °, to the entry direction 2.

Fig. 7 shows a further possibility of the arrangement according to the invention of the substructure 6. The substructures 6 here have a hexagonal cross section, so that a honeycomb arrangement of substructures arranged side by side and one above the other results.

In the embodiment according to fig. 8, the substructure 6 is formed in a cruciform shape. It should be noted that: the substructures 6 as shown in fig. 1 to 8 are only indicated by means of a perimeter line, which indicates the spatial region in which the volume element is cured within the respective substructure, without showing a specific structuring. It should be understood that in the framework of the production of the respectively desired geometry of the component, not all volume elements have to be cured within the substructure, but rather a volume region can be left free within the substructure.