Photo-polymerization system and method for producing a three-dimensional object

Abstract

A photo-polymerization system (10) comprises a vat (120) for housing a photocurable liquid (123) and an array of pixels (102). The array comprises a plurality of pixels (102), wherein each of the pixels (102) comprises a first and a second LED (105, 106) emitting different wavelengths, respectively. The array is arranged so as to be facing the vat (120).

Description

[0001] PHOTO-POLYMERIZATION SYSTEM AND METHOD FOR PRODUCING A THREE- DIMENSIONAL OBJECT

[0002] 3D printers may be based on the photo-polymerization of a photocurable liquid, e.g. a photocurable resin or a photocurable polymer due to irradiation with an appropriate light source. For example, layers of a predetermined thickness may be repeatedly stacked by curing the layer portions using e.g. UV radiation.

[0003] Generally, efforts are made to improve the performance of 3D printers .

[0004] It is an object of the present invention to provide an improved photo-polymerization system and an improved method for producing a three-dimensional object.

[0005] According to embodiments, the above objects are achieved by the claimed matter according to the independent claims. Further developments are defined in the dependent claims.

[0006] SUMMARY

[0007] According to embodiments, a photo-polymerization system comprises a vat for housing a photocurable liquid and an array of pixels. The array of pixels comprises a plurality of pixels. Each of the pixels comprises a first and a second LED emitting different wavelengths, respectively. The array is arranged so as to be facing the vat.

[0008] For example, the array of pixels is integrated in a bottom wall of the vat. According to embodiments , the first LED is configured to emit a first wavelength which is configured to cure the photocurable liquid and the second LED is configured to emit a second wavelength which is configured to inhibit curing of the photocurable liquid . For example , the photocurable liquid may be especially designed, e . g . comprise a photoinitiator that may be activated by the first wavelength, and a photoinhibitor that may be activated by the second wavelength or vice versa .

[0009] For example , the photocurable liquid may comprise a first and a second component . The first component may be curable by irradiation with electromagnetic radiation emitted by the first LED and the second component may be curable by irradiation with electromagnetic radiation emitted by the second LED .

[0010] According to embodiments , at least some of the pixels further comprise a micro-duct for supplying the photocurable liquid or a component of the photocurable liquid . For example , when the photocurable liquid comprises a first and a second component as explained above , the first or the second component may be supplied using the micro-duct .

[0011] According to further embodiments , at least some of the pixels comprise a first micro-duct for supplying the first component of the photocurable liquid and a second micro-duct for supplying the second component of the photocurable liquid .

[0012] According to further embodiments , a photo-polymeri zation system comprises a vat for housing a photocurable polymer and an array of LEDs . The array may be arranged so as to be facing the vat . The array of LEDs comprises at least one first LED emitting electromagnetic radiation of a first wavelength and a plurality of second LEDs emitting electromagnetic radiation of a second wavelength .

[0013] For example , the array of LEDs may be integrated in a bottom wall of the vat .

[0014] For example , the first LED may be configured to emit a first wavelength which is configured to cure the photocurable liquid and the second LED may be configured to emit a second wavelength which is configured to inhibit curing of the photocurable liquid .

[0015] According to embodiments , a method for producing a three- dimensional obj ect comprises placing a photocurable liquid in the vat of the photo-polymeri zation system as defined above , placing a stamp in the vat , and activating the array of pixels in accordance with a three-dimensional obj ect to be produced .

[0016] The method may further comprise moving the stamp in a direction opposite to a bottom side of the vat .

[0017] According to embodiments , placing the photocurable polymer in the vat may comprise feeding the photocurable liquid component or a component of the photocurable liquid through a microduct . For example , when the photocurable liquid comprises a first and a second component as explained above , the first or the second component may be supplied using the micro-duct .

[0018] According to further embodiments , a method for producing a three-dimensional obj ect comprises placing a photocurable liquid in the vat of the photo-polymeri zation system as defined above , placing a stamp in the vat , and activating the array of LEDs in accordance with a three-dimensional obj ect to be produced . BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this speci fication . The drawings illustrate the embodiments of the present invention and together with the description serve to explain the principles . Other embodiments of the invention and many of the intended advantages will be readily appreciated, as they become better understood by reference to the following detailed description . The elements of the drawings are not necessarily to scale relative to each other . Like reference numbers designate corresponding similar parts .

[0020] Fig . 1 shows a schematic view of a photo-polymeri zation system .

[0021] Fig . 2A shows an example of pixels and of an illumination pattern generated by a pixel .

[0022] Fig . 2B shows a further example of an array of LEDs and an illumination pattern generated by the LEDs .

[0023] Fig . 3A shows an example of a bottom wall of a vat according to further embodiments .

[0024] Fig . 3B shows an example of a photo-polymeri zation system according to further embodiments .

[0025] Fig . 4 summari zes a method according to embodiments .

[0026] DETAILED DESCRIPTION In the following detailed description reference is made to the accompanying drawings, which form a part hereof and in which are illustrated by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology such as "top", "bottom", "front", "back", "over", "on", "above", "leading", "trailing" etc. is used with reference to the orientation of the Figures being described. Since components of embodiments of the invention can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope defined by the claims.

[0027] The description of the embodiments is not limiting. In particular, elements of the embodiments described hereinafter may be combined with elements of different embodiments.

[0028] The terms "lateral" and "horizontal" as used in this specification intends to describe an orientation parallel to a first surface of a substrate or semiconductor body. This can be for instance the surface of a wafer or a die.

[0029] The term "vertical" as used in this specification intends to describe an orientation which is arranged perpendicular to the first surface of a substrate or semiconductor body.

[0030] The term "LED" as used within the present disclosure is intended to relate to any kind of light emitting diode. Examples comprise, inter alia, semiconductor based LEDs, e.g. emitting incoherent electromagnetic radiation, micro LEDs, laser devices, e.g. laser diodes, surface emitting laser diodes such as VCSELs ("vertical cavity surface emitting lasers") , OLEDs (organic light emitting diodes) and others. Fig. 1 is a schematic drawing of a photo-polymerization system 10 according to embodiments. The photo-polymerization system 10 comprises a vat 120 for housing a photocurable liquid 123, e.g. a photocurable polymer or photocurable resin. The photopolymerization system 10 further comprises an array 103 of pixels comprising a plurality of pixels 102. The array 103 is arranged so as to be facing the vat 120. Specific configurations of the array 103 of pixels will be explained below with reference to Figs. 2A and 2B.

[0031] For example, the array 103 of pixels 102 may be formed integrally with a bottom wall 121 of the vat. For example, the bottom wall 121 of the vat may comprise a transparent material in which the single LEDs constituting the pixels 102 are arranged. According to further embodiments, the array 103 of pixels 102 may be arranged at a distance to the bottom wall 121 of the vat 120. For example, in this case, the photo-polymerization system 10 may further comprise an optical system for focusing electromagnetic radiation emitted by the pixels 102. An optical element for imaging a radiation pattern generated by the array 103 of pixels 102 may comprise lenses.

[0032] A stamp 122 is placed in the photocurable liquid 123. Each of the pixels 102 may be separately addressed in accordance with a three-dimensional object to be produced. Upon irradiation with electromagnetic radiation emitted by the array of pixels 102, a polymerized sample 127 is formed at a bottom portion of the stamp 122. During the manufacturing process, the stamp 122 may be moved in the direction of the arrow to form the 3D object.

[0033] Fig. 2A shows a schematic view of pixels 102 of the array 103 illustrated in Fig. 1. As is shown, each of the pixels 102 comprises a first LED 105 and a second LED 106. The first LED 105 may be configured to emit a wavelength which is different from a wavelength emitted by the second LED 106. For example, the pitch between adjacent pixels 102, i.e. LED groups, may be approximately more than 20 pm, e.g. approximately 30 pm. A lateral size of the single LEDs 105, 106 may be less than 10 pm, e.g. approximately 5 pm. In this manner, the array of LEDs implements a micro LED array. The distance between the first LED 105 and the second LED 106 of one pixel 102 may be less than a size of a single LED, e.g. less than 5 pm, e.g. approximately 2 pm.

[0034] The lower portion of Fig. 2A shows a first beam 111 which has been emitted by the first LED 105 and which partially overlaps with a second beam 112 emitted by the second LED 106. Each single LED, e.g. the first and the second LEDs 105, 106 of one pixel

[0035] 102 may be controlled individually in emission brightness. Within the printing area in the vat 120 above the bottom wall 121, the first beam 111 and the second beam 112 overlap to a large extent. For example, an optical element between the array

[0036] 103 of pixels and the print area may be especially designed to accomplish that the first beam 111 and the second beam 112 overlap to a large extent. In this way, the print area can be illuminated in small pixelated spots with a well-controlled combination of light of two different wavelengths. For example, some of the spots may be illuminated with different intensities of the two different wavelengths. Other spots may be illuminated with only one wavelength, and it is possible that further spots are not illuminated.

[0037] Depending on the photocurable liquid 123 used, the effect of the illumination with two different wavelengths may be different. For example, electromagnetic radiation emitted by the first LED 105 may be used for photo activation of resin curing. Further, electromagnetic radiation emitted by the second LED 106 may be used to act as a deactivation of resin curing . Accordingly, the photocurable liquid may comprise photoinitiators and photoinhibitors with distinct absorption spectra . Examples of photocurable liquids are e . g . described in Nikolaos Liaros and John T . Fourkas "Ten years of two-color photolithography" , Opt . Mater . Express 9 , pp . 3006-3020 ( 2019 ) . As a result , a curing process close to the bottom wa2 1 121 of the vat may be inhibited .

[0038] For example , the photoinhibitors may be present at a high concentration . In this case , emitted electromagnetic radiation having the second wavelength wil l be attenuated in a region slightly above the bottom wall 121 due to absorption by the photoinhibitor . Accordingly, in this region, curing of the photocurable liquid does not take place . Further, thi s region only transmits at most a small amount of electromagnetic radiation having the second wavelength . The first wavelength is transmitted by this region and is then able to cure the portion of the photocurable liquid including the photoinitiator . Due to the small amount of transmitted electromagnetic radiation having the second wavelength, in this region, electromagnetic radiation of the second wavelength is hardly absorbed by the photoinhibitor .

[0039] Hence , a larger gap between the polymeri zed sample 127 and the bottom wall 121 may be achieved . As a consequence , the photocurable liquid 123 may flow much faster between the stamp and the bottom wall 121 . Accordingly, the printing speed may be increased .

[0040] According to further embodiments , the photocurable liquid 123 comprises two di f ferent photocurable liquid materials where a selective hardening of either of the two materials may be triggered by the electromagnetic radiation emitted by the first or the second LED 105 , 106 . As a consequence , 3D obj ects may be printed, where di f ferent parts are printed with di f ferent materials of potentially di f ferent properties . For example , a first material may be mechanically soft whereas another part of the obj ect is mechanically hard . According to further embodiments , the colors of the first and the second materials may be di f ferent .

[0041] According to further embodiments , due to electromagnetic radiation emitted e . g . by the second LED 106 , a thermal treatment of the printed sample 127 may be accomplished . The printed sample 127 may have been manufactured by 3D printing using the first LED 105 . Accordingly, an additional thermal treatment may be dispensed with .

[0042] According to further embodiments , the array of LEDs may comprise at least one first LED 115 emitting electromagnetic radiation of a first wavelength and a plurality of second LEDs 116 emitting electromagnetic radiation of a second wavelength . For example , the first wavelength may cure the photocurable liquid 123 . The second wavelength may inhibit curing of the photocurable liquid 123 .

[0043] The upper portion of Fig . 2B shows an example of an arrangement of a first LED 115 and a plurality of second LEDs 116 . The second LEDs 116 may be arranged to surround the first LED 115 . The lower portion of Fig . 2B shows a first beam 124 of electromagnetic radiation emitted by the first LED 115 and a second beam 125 of electromagnetic radiation emitted by the second LED 116 .

[0044] The middle portion of Fig . 2B shows an illumination pattern 107 comprising a first beam 124 and the second beam 125 . In more detail , the first beam 124 emitted by the first LEDs 115 and having the first wavelength overlaps with the second beams 125 emitted by the second LED 116 in the outer spot region . In this portion, curing may be inhibited . In contrast , only the central portion 126 of the spot being exclusively illuminated with the first beam 124 having the first wavelength is cured . In this way, the resolution may be enhanced in the central portion 126 . For example , the resolution may be improved by a factor ranging from 1 . 1 to 3 . According to further implementations , the enhancement of the resolution may as well be accomplished in a vertical direction .

[0045] As has been described, according to this example , the wavelength of the first LEDs 115 may be chosen such that it triggers photo activation to cure the resin, while the wavelength of electromagnetic radiation emitted by the second LED 116 is chosen to trigger photo inhibition in the resin . In the illuminated area, the spots of the second LEDs 116 will overlap with the outer end of the spot formed by the first LED 115 . In this way, curing may be inhibited in the outer end of the central portion 126 of the first LED 115 , thus ef fectively reducing the spot si ze where curing of the resin takes place . This results in an enhanced resolution of the printing process . This printing process may be switched on on-demand by activating the illumination with the first LEDs 115 . This allows for more fine features to be printed than possible with the usual resolution given by the spot si ze of the single LED only . For example , this functionality may be achieved with the curable liquids 123 disclosed in the publication mentioned above . Further suitable curable liquids 123 are described in M . O . De Beer et al . , "Rapid, continuous additive manufacturing by volumetric polymeri zation inhibition patterning" , Science Advances 5 ( 1 ) , 2019 .

[0046] According to further implementations , at least some of the pixels 102 may further comprise at least one micro-duct 108 , 109 for supplying a photocurable liquid . For example , at least some of the pixels may comprise a micro-duct 108 for supplying a single photocurable liquid. According to further embodiments, the pixels 102 may comprise e.g. two micro-ducts 108, 109, for supplying two photocurable liquids.

[0047] In more detail, according to embodiments, each of the pixels 102 may further comprise a first micro-duct 108 for supplying a first photocurable liquid and a second micro-duct 109 for supplying a second photocurable liquid. The first photocurable liquid may be curable by a first wavelength emitted by the first LED 105, and the second photocurable liquid may be curable by a second wavelength emitted by the second LED 106.

[0048] Fig. 3A shows an example of a plan view of a bottom wall 121 comprising a plurality of pixels 102 which is designed accordingly. In more detail, each of the pixels 102 comprises a first LED 105 and a second LED 106. Each of the pixels 102 further comprises a first and a second micro-ducts 108, 109 which may be arranged in the bottom wall 121 of the vat 120.

[0049] Fig. 3B shows an example of a cross-sectional view. The single micro-ducts 108, 109 extend through the bottom wall 121 of the vat 120. The single micro-ducts 108, 109 may be selectively addressable, e.g. by corresponding valves 117. In a corresponding manner, the single LEDs 105, 106 of each pixel 102 are configured to be individually addressed.

[0050] In this manner, each of e.g. two wavelengths-sensitive photocurable liquids which have been explained above with reference to Fig. 2A, are supplied by a matrix of micro-ducts 108, 109 which are located next to the respective micro-LED 105, 106. As a consequence, the photocurable liquid sensitive to the respective wavelength emitted by the LED 105, 106 is injected into the vat at a position close to a micro-LED 105, 106 emitting the respective wavelength. As a consequence, a pixel-resolved supply for a single photocurable liquid in a pixelated LED array 103 comprising first and second LEDs may be accomplished .

[0051] By way of example , the liquid supply via each of the micro-ducts 108 , 109 may be controlled by a corresponding one-directional two-port micro-valve 117 which may be opened or closed according to the imminent printing action of the associated adj acent LED 105 , 106 . For example , the micro-valves 117 may be electrically connected to a common power and control circuitry .

[0052] In this way, the liquid to be cured by the adj acent LED 105, 106 is directly supplied in a pixel-resolved way to each of the printing LEDs 105 , 106 . The liquid may be supplied on-demand, e . g . in dependence from the emission activity of an adj acent LED . To be more speci fic, when a certain LED is activated for a certain amount of time , a corresponding amount of photocurable liquid 123 is needed . Accordingly, the corresponding micro-valve 117 is activated to supply the needed amount of photocurable liquid 123 . As a consequence , a faster, more accurate and more stable printing process may be enabled in comparison with a mixture of wavelength-sensitive photocurable liquid components which may be distributed homogeneously in the photocurable liquid 123 present in the vat 120 . For example , due to this implementation, there might be no need for a back-and- forth motion of the printing stamp 122 or long waiting times for a uni form local replenishment of consumed printing liquid components . Fig . 3B shows a polymeri zed sample 127 attached to the stamp 122 . As is illustrated, the polymeri zed sample 127 comprises a first material 128 and a second material 129 . The first material 128 may obtained due to polymeri zation of a photocurable liquid that has been irradiated with the first wavelength emitted by the first LED 105 . The second material 128 may obtained due to polymeri zation of a photocurable liquid that has been irradiated with the second wavelength emitted by the second LED 106.

[0053] For example, any of the materials described e.g. in P. Fiedor et al., "Photochemical Study of a new bimolecular photoinitiating system for vat polymerization 3D printing technique under visible light," Catalysts 10 (3) , 284, 2020 may be used as a photocurable liquid in these implementations.

[0054] As has been described above, a pixelated LED, e.g. micro-LED, illumination unit for vat 3D printing with two (or more) different wavelengths per pixel may be implemented, resulting in a controlled pixelated resin illumination with any combination of two or more wavelengths. According to embodiments, the use of photo activation and photo inhibition triggered by different wavelengths emitted by the first and second LEDs 105, 106 may enhance resolution of the printing by a specific arrangement of the LEDs in the array of LEDs. As has been described, selective curing of materials with different curing wavelengths may be accomplished. This may result in 3D-printed objects comprising two or more different materials. Further, due to illumination with the second LED 106 having the second wavelength, a thermal treatment may be applied. According to further embodiments, a pixel-resolved localized supply of wavelength-sensitive photocurable liquid components by an array of micro-ducts 108, 109 and controlled micro-valves 117, may further improve the printing process. As a consequence, the printing process may be faster, more accurate and more stable.

[0055] Fig. 4 summarizes a method according to embodiments. A method for producing a three-dimensional object may comprise placing (S100) a photocurable liquid in the vat of the photopolymerization system as explained above. The method may further comprise placing (Slid) a stamp in the vat. The method may further comprise activating (S120) the array of pixels in accordance with a three-dimensional object to be produced. The method may further comprise moving (S130) the stamp in a direction opposite to a bottom side of the vat. For example, placing a photocurable polymer in the vat may comprise feeding a photocurable liquid component through any of the first and second micro-ducts.

[0056] According to further embodiments, a method for producing a three-dimensional object may comprise placing (S100) a photocurable liquid in the vat of the photo-polymerization system as described above, placing (Slid) a stamp in the vat, and activating (S120) the array of LEDs in accordance with a three-dimensional object to be produced.

[0057] While embodiments of the invention have been described above, it is obvious that further embodiments may be implemented. For example, further embodiments may comprise any subcombination of features recited in the claims or any subcombination of elements described in the examples given above. Accordingly, this spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein .

[0058] LIST OF REFERENCES photo-polymeri zation system pixel array first LED second LED illumination pattern first micro-duct second micro-duct first beam second beam first LED second LED valve vat bottom wall print stamp photocurable liquid first beam second beam central portion polymeri zed sample first material second material

Claims

CLAIMS1. A photo-polymerization system (10) comprising: a vat (120) for housing a photocurable liquid (123) ; and an array (103) of pixels (102) , comprising a plurality of pixels (102) , wherein each of the pixels (102) comprises a first and a second LED (105, 106) emitting different wavelengths, respectively, the array (103) being arranged so as to be facing the vat (120) , wherein at least some of the pixels (102) further comprises a micro-duct (108, 109) for supplying the photocurable liquid (123) or a component of the photocurable liquid.

2. The photo-polymerization system (10) according to claim 1, wherein the array (103) of pixels (102) is integrated in a bottom wall (121) of the vat (120) .

3. The photo-polymerization system (10) according to claim 1 or 2, wherein the first LED (105) is configured to emit a first wavelength which is configured to cure the photocurable liquid (123) and the second LED (106) is configured to emit a second wavelength which is configured to inhibit curing of the photocurable liquid (123) .

4. The photo-polymerization system (10) according to claim 1 or 2, wherein the photocurable liquid (123) comprises a first and a second component, the first component being curable by irradiation with electromagnetic radiation emitted by the first LED (105) , the second component being curable by irradiation with electromagnetic radiation emitted by the second LED (106) .

5. The photo-polymerization system (10) according to claim4, wherein at least some of the pixels (102) comprises a first micro-duct (108) for supplying the first component of the photocurable liquid (123) and a second micro-duct (109) for supplying the second component of the photocurable liquid (123) .

6. A photo-polymerization system (10) comprising: a vat (120) for housing a photocurable liquid (123) ; and an array (103) of LEDs (115, 116) , the array (103) being arranged so as to be facing the vat (120) , wherein the array (103) of LEDs (102) ) comprises at least one first LED (115) emitting electromagnetic radiation of a first wavelength and a plurality of second LEDs (116) emitting electromagnetic radiation of a second wavelength, wherein at least some of the pixels (102) further comprises a micro-duct (108, 109) for supplying the photocurable liquid (123) or a component of the photocurable liquid (123) .

7. The photo-polymerization system (10) according to claim 6, wherein the array (103) of LEDs (115, 116) is integrated in a bottom wall (121) of the vat (120) .

8. The photo-polymerization system (10) according to claim 6 or 7, wherein the first LED (115) is configured to emit a first wavelength which is configured to cure the photocurable liquid (123) and the second LED (116) is configured to emit a second wavelength which is configured to inhibit curing of the photocurable liquid (123) .

9. A method for producing a three-dimensional object comprising :placing (S100) a photocurable liquid (123) in the vat(120) of the photo-polymerization system (10) according to any of claims 1 to 5, comprising feeding the photocurable liquid (123) or a component of the photocurable liquid (123) through a micro-duct (108, 109) ; placing (S110) a stamp (122) in the vat (120) ; activating (S120) the array (103) of pixels (102) in accordance with a three-dimensional object to be produced.

10. The method according to claim 9, further comprising moving (S130) the stamp (122) in a direction opposite to a bottom side of the vat (120) .

11. A method for producing a three-dimensional object comprising : placing (S100) a photocurable liquid (123) in the vat (120) of the photo-polymerization system (10) according to any of claims 6 to 8, comprising feeding the photocurable liquid (123) or a component of the photocurable liquid (123) through a micro-duct (108, 109) ; placing (S110) a stamp (122) in the vat (120) ; and activating (S120) the array (103) of LEDs in accordance with a three-dimensional object to be produced.

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