Additive manufacturing on flexible substrates

Abstract

Provided herein are systems and methods for printing 3D objects on flexible substrates. In some embodiments, the flexible substrate is moved through a bath of polymer precursors while a mechanism (e.g., having opposing belts) maintains contact with the periphery of the substrate. The systems and methods described herein may have certain advantages, such as precise control over the flexible substrate, allowing for precise printing of 3D articles.

Description

[Technical field]

[0001] Related Applications This application is a nonprovisional extension of U.S. Provisional Patent Application No. 63 / 147,960 (35 U.S.C. § 119(e)), entitled “SYSTEMS AND METHODS FOR 3D PRINTING ON PLIABLE SUBSTRATES,” filed on February 10, 2021. The entire contents of these applications are hereby incorporated by reference in their entireties.

[0002] Notice regarding copyrighted material Portions of the material in this patent document are subject to copyright protection under the copyright laws of the United States and other countries. The copyright owner has no objection to the facsimile reproduction by anyone of this patent document and the patent disclosure as it appears in the publicly available files or records of the U.S. Patent and Trademark Office, but otherwise reserves all copyrights. The copyright owner hereby does not waive any right to have this patent document maintained in confidence, including, without limitation, the right pursuant to 37 CFR 1.14. [Background technology]

[0003] Additive manufacturing techniques, also known as 3D printing, allow for the production of finished products with complex geometries that are difficult or impossible to make with other techniques. High-resolution stereolithography 3D printing, and in particular the Digital Light Processing (DLP) printing technique, allows for print resolutions of less than 100 micrometers (um). High-resolution 3D printing makes it possible to manufacture complex structures that can reduce the weight of objects, build metamaterials, realize biomimicry designs, or simply achieve aesthetic surface textures. Summary of the Invention

[0004] Although the resolution of modern 3D printers has improved, economical production of 3D printed articles may be limited by the throughput of the 3D printer, for example, if the printer is not configured for serial production. Serial or batch printing of individual articles may have non-productive downtime associated with resetting the printer, for example.

[0005] The systems and methods described herein can improve 3D printing productivity, for example, by printing articles on flexible substrates that are dispensed from a roll and moved through a volume of polymer precursor. Such systems can print continuously without the need to return to an initial state. Productivity can be further improved by increasing the width of the roll of flexible substrate. However, the wider the substrate, the more prone it is to sagging, bending, warping, wrinkling, or being consistently uneven during 3D printing. In one aspect, systems and methods are provided herein for maintaining a flat and well-controlled flexible substrate for 3D printing.

[0006] According to one aspect, a method of printing a 3D object is provided. The method includes directing radiation to a first location of a volume of polymer precursor adjacent to a flexible substrate, thereby forming a first polymer layer on or adjacent to the substrate, moving the flexible substrate through the volume of polymer precursor while maintaining contact with a periphery of the substrate, and directing radiation to a second location of the volume of polymer precursor adjacent to the first location, thereby forming a second polymer layer on the first polymer layer. According to one embodiment, the periphery is substantially parallel to the direction in which the substrate is moved. According to one embodiment, the flexible substrate is pinched at its periphery. According to one embodiment, the surface of the substrate on which the first polymer layer is formed is not contacted by a roller across the width of the substrate.

[0007] According to one embodiment, the flexible substrate moves into the volume of polymer precursor, bends, and exits the volume of polymer precursor. According to one embodiment, a first linear pinch zone occurs before the bending of the flexible substrate, and a second linear pinch zone occurs after the bending of the flexible substrate. According to one embodiment, a series of rollers guide the flexible substrate through the bend. According to one embodiment, the method further comprises supporting a back surface of the flexible substrate opposite the front surface of the flexible substrate on which the first polymer layer is printed. According to one embodiment, contact with the periphery is maintained along substantially the entire portion of the flexible substrate in contact with the volume of polymer precursor. According to one embodiment, contact with the periphery of the substrate is maintained until the second polymer layer is cured. According to one embodiment, the flexible substrate is under substantially constant tension while the substrate is within the volume of polymer precursor.

[0008] According to one embodiment, the method further comprises guiding or positioning the flexible substrate prior to maintaining contact with the periphery of the substrate. According to one embodiment, the method further comprises smoothing the flexible substrate. According to one embodiment, the flexible substrate is smoothed prior to maintaining contact with the periphery of the substrate. According to one embodiment, the method further comprises repeating (c) to produce the 3D polymer object. According to one embodiment, the method further comprises removing the 3D polymer object from the substrate. According to one embodiment, the method further comprises cutting the substrate. According to one embodiment, the mechanism that maintains contact with the periphery does not contact the portion of the flexible substrate on which the first polymer layer is formed. According to one embodiment, the method further comprises changing a direction in which the substrate is moved through the polymer precursor.

[0009] According to one embodiment, the substrate is moved through the polymer precursor with a mechanical precision of less than about 100 micrometers (um), less than about 50 um, less than about 30 um, less than about 20 um, or less than about 10 um. According to one embodiment, the second polymer layer is formed on the first polymer layer with a pixel-by-pixel precision of less than about 100 micrometers (um), less than about 50 um, less than about 30 um, less than about 20 um, or less than about 10 um. According to one embodiment, the first and second layers of polymer have a thickness precision of less than about 100 micrometers (um), less than about 50 um, less than about 30 um, less than about 20 um, or less than about 10 um. According to one embodiment, (b) and (c) are performed substantially simultaneously such that the first and second layers of polymer are substantially continuous. According to one embodiment, (b) and (c) are performed substantially simultaneously such that the first and second layers of polymer are not separate layers. According to one embodiment, the flexible substrate is elastic. According to one embodiment, the flexible substrate is a nylon mesh. According to one embodiment, the radiation is UV light. According to one embodiment, the radiation is directed using a digital light processor (DLP).

[0010] According to one aspect, a system for printing a 3D object is provided. The system includes a bath configured to maintain a solution of polymer precursors at a substantially constant liquid level, a mechanism configured to move a flexible substrate through the bath while maintaining contact with a periphery of the substrate, and a digital light processor (DLP) configured to direct radiation to a selected portion of the solution of polymer precursors. According to one embodiment, the mechanism and the digital light processor are configured to print the 3D object. According to one embodiment, (i) the DLP creates a first polymer layer on or adjacent to the flexible substrate, (ii) the mechanism moves the flexible substrate through the bath, and (iii) the DLP creates a second polymer layer on the first polymer layer. According to one embodiment, (ii-iii) are performed substantially simultaneously. According to one embodiment, the first and second layers of polymer are not separate layers.

[0011] According to one embodiment, the periphery is substantially parallel to the direction in which the substrate is moved. According to one embodiment, the mechanism is configured to pinch the flexible substrate at its periphery. According to one embodiment, the mechanism does not include a roller that spans the width of the substrate on the surface of the substrate on which the first polymer layer is formed. According to one embodiment, the mechanism is configured to move the flexible substrate into the volume of polymer precursor, bend the flexible substrate, and remove the volume of polymer precursor. According to one embodiment, the first linear pinch zone occurs before bending the flexible substrate, and the second linear pinch zone occurs after bending the flexible substrate. According to one embodiment, the mechanism includes a series of rollers to guide the flexible substrate through the bend.

[0012] According to one embodiment, the mechanism further comprises a roller supporting a back surface of the flexible substrate opposite the front surface of the flexible substrate on which the first polymer layer is printed. According to one embodiment, the mechanism maintains contact with the periphery along substantially the entire portion of the flexible substrate in contact with the volume of polymer precursor. According to one embodiment, the mechanism maintains contact with the periphery of the substrate until the second polymer layer is cured. According to one embodiment, the mechanism places the flexible substrate under substantially constant tension while the substrate is within the volume of polymer precursor. According to one embodiment, the system further comprises a guide configured to position the flexible substrate for contact with the periphery of the substrate. According to one embodiment, the system further comprises a clamp spring for smoothing the flexible substrate. According to one embodiment, the system can repeat (c) to produce the 3D polymer object. According to one embodiment, the system can remove the 3D polymer object from the substrate. According to one embodiment, the system further comprises a module configured to cut the substrate after it exits the bath.

[0013] According to one embodiment, the mechanism does not contact the portion of the flexible substrate on which the first polymer layer is formed. According to one embodiment, the mechanism can change the direction in which the substrate is moved through the polymer precursor. According to one embodiment, the mechanism can move the substrate through the polymer precursor with a mechanical precision of less than about 100 micrometers (um), less than about 50 um, less than about 30 um, less than about 20 um, or less than about 10 um. According to one embodiment, the second polymer layer is formed on the first polymer layer with a pixel-by-pixel precision of less than about 100 micrometers (um), less than about 50 um, less than about 30 um, less than about 20 um, or less than about 10 um. According to one embodiment, the first and second layers of polymer have a thickness precision of less than about 100 micrometers (um), less than about 50 um, less than about 30 um, less than about 20 um, or less than about 10 um. According to one embodiment, the flexible substrate is elastic. According to one embodiment, the flexible substrate is a nylon mesh. According to one embodiment, the radiation is UV light.

[0014] According to one aspect, a method of printing a 3D object is provided. The method includes directing radiation through a transparent window of a vat containing a volume of polymer precursor, where the radiation is directed to a first location adjacent to a flexible substrate, thereby forming a first polymer layer on or adjacent to the substrate, moving the flexible substrate through the volume of polymer precursor, and directing radiation through the transparent window to a second location adjacent to the first location, thereby forming a second polymer layer on the first polymer layer. According to one embodiment, the flexible substrate is a nylon mesh. According to one embodiment, the flexible substrate is supported on its backside along substantially all of the printing path. According to one embodiment, the printing path begins adjacent to the first location and ends when the substrate exits the vat. According to one embodiment, the flexible substrate is supported on a belt. According to one embodiment, the backside of the substrate is distal to the transparent window. According to one embodiment, the flexible substrate is moved through the volume of polymer precursor using a mechanism that maintains contact with the periphery of the substrate. According to one embodiment, the first polymer layer has a higher affinity for the flexible substrate than the transparent window. According to one embodiment, the transparent window is vibrated. According to one embodiment, the transparent window has a channel that allows the non-polymerized polymer precursor to flow between the transparent window and the first polymer layer. According to one embodiment, the temperature of the transparent window is higher or lower than the temperature of the bath of polymer precursor. According to one embodiment, a quantity of polymer precursor is directed toward the transparent window by applying a force.

[0015] According to one aspect, a system for printing a 3D object is provided. The system includes a vat having a transparent window configured to maintain a solution of polymer precursors at a substantially constant level, a mechanism configured to move a flexible substrate through the vat proximate to the transparent window, and a digital light processor (DLP) configured to direct radiation through the transparent window to a selected portion of the solution of polymer precursors. According to one embodiment, the flexible substrate is a nylon mesh. According to one embodiment, the mechanism supports the flexible substrate on its back surface along substantially all of the printing path. According to one embodiment, the printing path begins adjacent to a first location and ends when the substrate exits the vat. According to one embodiment, the flexible substrate is supported by a belt. According to one embodiment, the back surface of the substrate is distal to the transparent window. According to one embodiment, the first polymer layer has a higher affinity for the flexible substrate than the transparent window. According to one embodiment, the transparent window can be vibrated. According to one embodiment, the transparent window has a channel that allows non-polymerized polymer precursors to flow between the transparent window and the first polymer layer. According to one embodiment, the temperature of the transparent window is higher or lower than the temperature of the bath of polymer precursor. According to one embodiment, the system further comprises a nozzle capable of directing an amount of the polymer precursor towards the transparent window.

[0016] It should be understood that all combinations of the foregoing concepts, and additional concepts discussed in more detail below, provided that such concepts are not mutually inconsistent, are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of subject matter within this disclosure are contemplated as being part of the inventive subject matter disclosed herein.

[0017] Further aspects, examples and advantages of these exemplary aspects and examples are discussed in detail below. Moreover, it should be understood that both the foregoing information and the following detailed description are merely illustrative of the various aspects and examples and are intended to provide an overview or framework for understanding the nature and characteristics of the claimed aspects and examples. Any example disclosed herein can be combined with any other example in any manner consistent with at least one of the objectives, goals and needs disclosed herein, and references to "examples," "several examples," "alternative examples," "various examples," "one example," "at least one example," "this example and other examples," or the like are not necessarily mutually exclusive and are intended to indicate that a particular feature, structure or characteristic described in connection with an example may be included in at least one example. Appearances of such terms in this specification do not necessarily all refer to the same example. [Brief description of the drawings]

[0018] The patent or application file contains at least one color drawing. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0019] [Figure 1] An example of printing a 3D object on a flexible substrate is shown. [Diagram 2] 1 shows some example control points for printing 3D objects on flexible substrates. [Diagram 3] An example of clamping the periphery of a flexible substrate is shown. [Figure 4] An example is provided in which the systems and methods described herein are used to move a flexible substrate through a series of processing modules. [Diagram 5] 1 illustrates an example of a side view of one embodiment of the systems and methods described herein. [Figure 6] 1 illustrates an example of a top view of one embodiment of the systems and methods described herein. [Figure 7]1 illustrates an example of a top view of an embodiment of the systems and methods described herein having a support belt. [Figure 8] 1 shows an example of a scale diagram of one embodiment of the systems and methods described herein. [Figure 9] 1 illustrates an example of a system for maintaining a relatively constant tension in a flexible substrate as it is dispensed from a roll. [Figure 10] FIG. 1 illustrates an example of a mechanism for smoothing, guiding, and / or tensioning a flexible substrate in preparation for 3D printing on the flexible substrate. [Figure 11] 1 shows an example of a scaled view of a mechanism for smoothing, guiding, and / or tensioning a flexible substrate. [Figure 12] 1 illustrates an example of an enclosure for a system described herein within a vessel configured to hold a volume of a polymer precursor. [Figure 13] 1 illustrates an example of a system of the present disclosure for printing through a transparent window. [Figure 14] 1 illustrates an example of a system of the present disclosure for printing through a transparent window. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Additive manufacturing, also known as 3D printing, is a manufacturing method that utilizes equipment to produce "layered" finished parts with complex shapes that may be difficult or impossible to make with other traditional manufacturing methods such as molding (such as injection molding and transfer molding) and subtractive manufacturing (such as laser cutting and milling). Additive manufacturing methods can have a wide range of advantages over traditional methods. First, parts with very complex shapes and internal lattice structures can be produced. Second, there is less waste generation and a higher utilization of starting materials, especially compared to subtractive manufacturing such as milling. Third, it allows for rapid production with short lead times and low tooling costs. This is especially true compared to molding methods, where a mold must be made before the desired part can be manufactured using a mold. Fourth, parts can be produced on demand in small quantities without the need for expensive molds to be prepared in advance. It also allows for easy modifications based on evaluation of the parts produced, which is very useful for making prototypes. Overall, additive manufacturing can have a wide range of advantages over traditional manufacturing methods in many aspects.

[0021] Additive manufacturing can be classified according to the materials and techniques used. Material choices for printing include, but are not limited to, thermoplastic polymers, thermosetting polymers, photopolymers (precisely photomonomers / oligomers), metals, ceramics, (hydro)gels, pastes, sand, composites, etc. Common 3D printing techniques include Fused Deposition Modeling (FDM, also known as FFF, Fused Filament Fabrication), Digital Light Processing (DLP), Stereolithography (SLA), Selective Laser Sintering (SLS), Directed Energy Deposition (DED), Direct Ink Writing (DIW), Binder Jetting (BJ), etc. FDM / FFF, SLS and SLA / DLP are by far the three most popular printing techniques and are constantly being researched and developed worldwide.

[0022] Materials for additive manufacturing can utilize multiple polymerization techniques to create 3D articles with material performance properties desired for the end application. These polymerization reactions are typically initiated by UV radiation directed at a portion of a solution of polymer precursors. Here, the radiation can be directed onto the surface of a volume of solution adjacent to a flexible substrate (i.e., as an image) such that a layer of polymer is deposited onto the substrate. The substrate can then be moved further into the solution, and a thin layer of polymer precursor can flow over the first polymer layer, initiating a second polymerization to print a second polymer layer onto the first polymer layer. This process can be repeated to print 3D objects.

[0023] DLP and SLA are suitable 3D printing technologies for implementing the systems and methods described herein. SLA and DLP 3D printers can differ with respect to the way light is projected onto the UV-curable polymer resin. Previous printers generally used SLA, which is based on a laser system that moves around to cure the target area pixel by pixel. However, DLP can cure an entire layer at once. DLP 3D printers can use a digital projector screen to flash the image of a layer across the entire platform, curing all points of the same layer at the same time. This light can be reflected off a digital micromirror device (DMD). A DMD is a dynamic mask that contains microscopic sized mirrors arranged in a matrix on a semiconductor chip. Rapidly switching this small mirror between lenses that direct light onto the resin can determine the coordinates where the liquid resin will cure within a given layer. Because the projector is a digital screen, the image of each layer is a three-dimensional layer made up of square pixels and formed from small rectangular prisms called voxels. This allows DLP to be one of the fastest 3D printing technologies. Other advantages include, but are not limited to, relatively low cost, choice of versatile printing polymers, high printing resolution, and ease of operation.

[0024] DLP allows the printing of a selection of polymers and composites, including acrylate and methacrylate functional polymers. UV-curable formulations used in the DLP additive manufacturing industry may include ethylene and / or vinyl functional (i.e. double bond) oligomers and monomers (e.g., acrylates, methacrylates, vinyl ethers, vinyl carbonates), diluents, chain extenders, photoinitiators, and additives. The oligomers and monomers can impart mechanical properties to the final product upon polymerization. The diluents are used to reduce the overall viscosity of the formulation, making it easier to process and handle. The diluents are reactive and can be incorporated into the polymer matrix of the final product. The photoinitiators can form free radicals when exposed to actinic radiation (e.g., by photolysis of the photoinitiator molecule). The free radicals interact with the vinyl moieties of the oligomers and monomers to form vinyl-based crosslinked polymers. The additives include, but are not limited to, pigments, dyes, UV absorbers, hindered amine light stabilizers, fillers, and the like. Additives can be used to impart useful properties such as color, shelf stability, improved shelf life performance, improved UV stability, and the like.

[0025] Printing on flexible substrates In one aspect, provided herein is a method of printing a 3D object. With reference to FIG. 1, the method can include directing radiation 100 to a first location of a volume of polymer precursor 102. The location can be adjacent to a flexible substrate 104 that is moved through a bath of polymer precursor. The radiation can polymerize the polymer precursor where the radiation contacts (and optionally adjacent thereto) to form a first polymer layer 106 on or adjacent the substrate. It is noted that FIG. 1 is a schematic diagram that is not to scale (e.g., the location where the radiation is directed can be finely controlled, i.e., to create an object with fine features, and can be directed to a relatively small area of ​​the bath of polymer precursor).

[0026] 1 , the method may include moving 108 the flexible substrate through the volume of polymer precursor while maintaining contact with a periphery 110 of the substrate. Radiation may be directed at a second location of the volume of polymer precursor adjacent the first location, thereby forming a second polymer layer on the first polymer layer. In this manner, a 3D object may be additively manufactured (i.e., successive layers of polymer are polymerized on top of one another in a shape determined by the areas of radiation exposure).

[0027] In one aspect, provided herein are systems and methods for precisely controlling the movement of a flexible substrate (e.g., for precisely printing 3D articles). As shown in FIG. 2, the angle 200 at which the substrate enters the solution can be controlled. The substrate can then be rotated and bent to exit the solution. The motion of the substrate can be precisely controlled to print a polymer layer of precise thickness. Additionally, the position and tension of the substrate can be controlled 202, for example, before, during, and throughout the exit of the flexible substrate from a bath of polymer precursor. The mechanisms described herein can, for example, control the return radius 204 and maintain contact (e.g., pinch) with the periphery of the flexible substrate to maintain perfect control and positioning of the substrate.

[0028] 3 is a side view showing how a flexible substrate is clamped at its periphery, which may be substantially parallel to the direction in which the substrate is moved through the bath, where the flexible substrate 300 is clamped between first and second opposing pinch points 302, 304 that move with and can maintain contact with the flexible substrate.

[0029] The flexible substrate can move into, bend, and exit the volume of the polymer precursor. Turning the substrate is particularly difficult because the roller cannot span the width of the substrate on the side of the substrate with the printed article because the printed article is on the surface. As described herein, this challenge can be addressed by pinching the substrate along the edge of the substrate in a mechanism that holds and then releases the substrate as shown here. In some examples, the surface of the substrate on which the first polymer layer is formed does not contact the roller that spans the width of the substrate. The 3D printed part is attached to the top surface of the substrate, so using a roller to guide the substrate could flatten or scratch the 3D printed object. Thus, the flexible substrate can be pinched at its edge without harming the 3D printed object. The mechanism that maintains contact with the periphery does not contact the part of the flexible substrate on which the first polymer layer is formed in some cases.

[0030] Such a system can be used with any length of flexible media, including an endless loop of flexible substrate. The system can limit the degrees of freedom of the media. The clamp and release mechanism can bend the flexible substrate at any angle, for example, between 0 degrees and 180 degrees.

[0031] It may be advantageous to print in areas where the substrate moves linearly (e.g., areas where the 3D object is not deformed) and perform the initial curing of the resin. Optionally, during printing, the substrate is moving at an angle of 45 degrees to the surface of the resin. Among other advantages, the constant angle may be useful for representing the printed object as a series of planar slices (e.g., during digital rendering to control the 3D printer). Optionally, a first linear pinch zone occurs before the bending of the flexible substrate. A second linear pinch zone may occur after the bending of the flexible substrate (as the 3D object exits the resin). A series of rollers may guide the flexible substrate through the bends between the linear pinch zones. The back surface of the flexible substrate may be supported (e.g., it is opposite the surface of the flexible substrate on which the polymer layer is printed). Contact with the periphery may be maintained along substantially the entire portion of the flexible substrate in contact with the volume of the polymer precursor. Optionally, contact with the periphery of the substrate is maintained until the second polymer layer is cured.

[0032] Multiple bends can be chained together to form more complex flow paths, as shown in Figure 4. The flexible substrate 400 can be moved through a series of modules that can perform a variety of functions. Without limitation, those functions can include initial 3D printing 402 to form an article, cleaning 404 the article, secondary curing 406 the article, or surface coating the article.

[0033] The systems and methods described herein can have any number of advantages. For example, sensing or monitoring the position of the substrate may be less important or even unnecessary, since the position of the pinch and drive mechanisms is known and may be strongly coupled to the substrate. The direction of substrate movement can be reversed. The entrance angle of the substrate into and through the print zone can be controlled and potentially adjusted. The tension of the substrate can be controlled, as can the return radius, which can act to reduce distortion of the printed article during printing.

[0034] The figures show various exemplary implementations of the systems and methods described herein in more detail. For example, FIG. 5 shows a side view of one embodiment, which is not to scale. A substrate 500 can be fed between a clamp belt 502 and a timing control belt 504. A series of rollers 506 control the movement of the belt (i.e., do not contact the printed side of the flexible substrate). A print layer 508 is shown where the substrate enters the solution of monomer precursors. A series of backbend rollers 510 can change the direction the substrate exits from the polymer precursors. Note that the backbend rollers do not span the width of the substrate because the printed article is on top of the flexible substrate.

[0035] 6 shows a top view of one embodiment of the systems and methods described herein, where a flexible substrate 600 can be clamped along its periphery between a clamp belt 602 and a timing control belt 604. A backbend roller 606 can be used to change the direction of the flexible substrate without spanning the width of the printing surface.

[0036] 7, the back surface of the flexible substrate can be supported by a support belt 700. The support belt can change angle in cooperation with a clamp belt, a timing control belt, and / or a backbend roller mechanism.

[0037] FIG. 8 is a scaled view of one embodiment of the system described herein. The conveyor system can include a wide conveyor belt 800, a thin clamp belt or roller 802, a tension adjustment system 804, and a supporting guide plate. The conveyor system can provide a high level of precision and accuracy when handling flexible substrates. Some design features that can provide precision and accuracy include a wide conveyor belt supporting a flexible substrate 806. The running geometry of the conveyor plate can be controlled to follow the flexible substrate. In some cases, the belt alignment does not shift side to side during the printing process. The wide conveyor belt can have guide geometries built into the belt and rollers that keep the belt aligned. The conveyor belt can run around two idlers that create a flat plane across the printing area when the proper tension is applied 804. The running plate can further facilitate creating a flat plane. The position of the conveyor belt can be controlled, for example, by a motor 808 with feedback control. The conveyor belt can have the proper tension to prevent slippage against the drive roller. The belt can have teeth and / or sensors to further increase confidence in the precision and accuracy of the system. The conveyor system can capture the flexible substrate 806 at the edge by a thin clamp belt or roller 802. The thin clamp belt or roller can move with the conveyor belt. This action can clamp the belt and prevent slippage. The flexible substrate can be controlled on the conveyor from the beginning and across the print area. The clamp belt or roller can be positioned to maximize the clamping force but not distort the print area.

[0038] In some cases, a flexible substrate is fed into the system from a roll. As shown in Figure 9, the system may include a mechanism 900 for maintaining the substrate at constant tension, for example, as the radius of the roll of substrate 902 decreases. Such a system allows elastic substrates to be used for 3D printing.

[0039] Additional mechanisms for tensioning, guiding, and / or smoothing the substrate for clamping and 3D printing along the periphery of the substrate may also be used. As shown in FIG. 10, a flexible substrate 1000 may be directed through a substrate guide 1002, which may have adjustable tension applied by a clamp spring 1004. The substrate may then be clamped between a clamp belt 1006 and a support belt 1008 and moved through a print zone 1010 for printing of a 3D article 1012. A three-dimensional drawing is shown in FIG. 11, where like numbers indicate like elements compared to FIG. 10. This feature may help prevent wrinkling and / or lateral movement of the flexible substrate.

[0040] The systems described herein can be used in and adjacent to a tank configured to hold a volume of polymer precursor. Figure 12 shows a side of a tank 1200 to which rollers 1202 for clamp belts and support belts can be attached. A bottom (not shown) can hold a volume of polymer precursor.

[0041] The flexible substrate can be any suitable material, such as nylon, polypropylene, or polyethylene. The flexible substrate can be a continuous sheet or mesh and is typically thin. The flexible substrate can be rigid or elastic. The radiation directed at the polymer precursor in proximity to the flexible substrate is typically UV light (e.g., emitted using a digital light processor (DLP)).

[0042] The 3D article can be printed as a series of layers. That is, a subsequent layer of polymer precursor can be polymerized on top of the previous layer. The shape of the 3D object can be created by changing the size, shape, and position of the layers. The substrate can be advanced in a discontinuous manner during printing of a layer (e.g., if it is substantially stationary during printing of a layer). However, in some embodiments, the substrate advances at substantially the same time that radiation is directed at the resin and / or the resin is cured. For example, the 3D object may not be printed as a series of layers.

[0043] The 3D article and / or flexible substrate can undergo any suitable processing step before or after printing. For example, the substrate and / or the 3D article can be washed (e.g., to remove uncured resin). The 3D article can be further cured after printing (e.g., by exposure to heat). The method can further include removing the 3D polymer object from the substrate. Optionally, the substrate is cut.

[0044] The systems and methods described herein can be used to control the movement of a flexible substrate with high precision. Such precision can be advantageous for printing layers of a 3D object with controlled thickness and can improve the overall resolution of the printed object. For example, the substrate can be moved through a polymer precursor with a mechanical precision of less than about 100 micrometers (um) (i.e., finer), less than about 50 um, less than about 30 um, less than about 20 um, or less than about 10 um. A second polymer layer can be formed on the first polymer layer with pixel-by-pixel precision of less than about 100 micrometers (um) (i.e., finer), less than about 50 um, less than about 30 um, less than about 20 um, or less than about 10 um. The first and second layers of polymer can have a thickness precision of less than about 100 micrometers (um) (i.e., finer), less than about 50 um, less than about 30 um, less than about 20 um, or less than about 10 um.

[0045] Printing System In another aspect, provided herein is a system for printing a 3D object, which may include a bath configured to maintain a solution of polymer precursors at a substantially constant level, a mechanism configured to move a flexible substrate through the bath while maintaining contact with a periphery of the substrate, and a digital light processor (DLP) configured to direct radiation to a selected portion of the solution of polymer precursors.

[0046] The mechanism and digital light processor can be configured to print the 3D object. For example, the DLP creates a first polymer layer on or adjacent to a flexible substrate, the mechanism moves the flexible substrate through a bath, and the DLP creates a second polymer layer on the first polymer layer. The creation of the polymer layer and the movement of the flexible substrate can occur substantially simultaneously. In some cases, the first and second layers of polymer are not separate layers.

[0047] The periphery can be substantially parallel to the direction in which the substrate is moved. The mechanism can be configured to pinch the flexible substrate at its periphery. In some examples, the mechanism does not include a roller that spans the width of the substrate on the surface of the substrate on which the first polymer layer is formed. The mechanism can be configured to move the flexible substrate into the volume of polymer precursor, bend the flexible substrate, and remove the volume of polymer precursor.

[0048] The mechanism may include a series of rollers for guiding the flexible substrate through the bend. The mechanism may further include a roller supporting a back surface of the flexible substrate opposite the front surface of the flexible substrate on which the first polymer layer is printed. The mechanism may maintain contact with the periphery along substantially all of the portion of the flexible substrate that is in contact with the volume of polymer precursor. The mechanism may maintain contact with the periphery of the substrate until the second polymer layer is cured.

[0049] In some cases, the mechanism places the flexible substrate under a substantially constant tension while the substrate is within the volume of the polymer precursor. The system may further include a guide configured to position the flexible substrate for contact with a periphery of the substrate. The system may further include a clamping spring for smoothing the flexible substrate. The mechanism, in some instances, does not contact the portion of the flexible substrate on which the first polymer layer is formed. The mechanism may be capable of changing the direction in which the substrate is moved through the polymer precursor.

[0050] The systems and methods described herein can be implemented in a variety of printing architectures. In some cases, the DLP directs light onto the open surface of the polymer precursor volume (e.g., as shown in FIG. 1). Although this approach has some advantages, in some instances, it is limited by the time it may take for the viscous polymer precursor solution to flow over a previously printed layer (i.e., before it can be printed on a second layer). In some instances, directing light through a transparent window so that the DLP contacts the polymer precursor solution speeds up the reflow of the solution.

[0051] 13 and 14 show an embodiment of the present disclosure for printing through a transparent window. Where like numbers indicate like elements, a digital light processor 1300 can direct radiation through a transparent window 1302 onto a polymer precursor 1304 in proximity to a flexible substrate 1306. The flexible substrate can be pinched around its periphery and supported on its underside 1308 by a belt while being moved through the polymer precursor. A printed article 1310 is initially formed at the point where the radiation strikes the polymer precursor and can exit the bath resting on the flexible substrate.

[0052] One potential drawback of 3D printing through a transparent window could be the suction forces between the printed article and the transparent window. These forces could damage or destroy the printed article. In some cases, the printed article has a greater affinity for flexible substrates than the transparent window.

[0053] To facilitate reflow of the polymer precursor between the printed article and the transparent window, various strategies can be employed. For example, the transparent window can be vibrated or a jet of the solution can be directed at the transparent window. The transparent window can have channels through which the solution can flow. Furthermore, the temperature of the transparent window can be higher or lower than the temperature of the solution (e.g., so that the viscosity of the solution is lower at the window and / or the degree of polymerization is lower at the window).

[0054] A transparent window can be at the bottom of the polymer precursor bath. The embodiment with a transparent window can utilize the mechanisms described herein to control the movement of the flexible substrate. The flexible substrate can be clamped at its edges and supported by a belt on the side of the substrate opposite the side on which the article is printed.

[0055] In another aspect, provided herein is a method for printing a 3D object on a flexible substrate through a transparent window.The method may include: directing radiation through a transparent window of a tank containing a volume of polymer precursor, the radiation being directed to a first position adjacent to the flexible substrate, thereby forming a first polymer layer on or adjacent to the substrate; moving the flexible substrate through the volume of polymer precursor; and directing radiation through the transparent window to a second position adjacent to the first position, thereby forming a second polymer layer on the first polymer layer.

[0056] In another aspect, provided herein is a system for printing a 3D object. The system may include a vat having a transparent window configured to maintain a solution of polymer precursors at a substantially constant liquid level, a mechanism configured to move a flexible substrate through the vat in proximity to the transparent window, and a digital light processor (DLP) configured to direct radiation through the transparent window to a selected portion of the solution of polymer precursors.

[0057] The flexible substrate can be supported on its back surface along substantially all of the printing path. The printing path can begin adjacent to the first location and end when the substrate exits the bath. The back surface of the substrate can be distal to the transparent window.

[0058] The first polymer layer can have a higher affinity for the flexible substrate than the transparent window. Optionally, the transparent window is vibrated. The transparent window can have a groove that allows the non-polymerized polymer precursor to flow between the transparent window and the first polymer layer. The temperature of the transparent window can be higher or lower than the temperature of the bath of polymer precursor. The polymer precursor can be directed toward the transparent window by applying a force.

[0059] It should also be understood that one or more 3D printing systems may be used to implement the methods described herein. For example, some embodiments may be used with one or more systems described in U.S. Patent Application Publication No. 16 / 552,382, filed August 27, 2019, which is incorporated herein in its entirety. However, it should be understood that other printing methods and systems may be used with the embodiments as described herein.

[0060] The shape of the article to be printed can be digitally represented in any suitable file structure (e.g., for use in controlling a 3D printer). Such systems may include slicing the shape into multiple layers, such as described in U.S. Patent Application Publication No. 17 / 211,603, filed March 24, 2021, which is incorporated herein in its entirety. Such systems, methods and file formats may be suitable for printing microstructures.

[0061] The above-described embodiments can be implemented in any of a number of ways. For example, the embodiments can be implemented using hardware, software, or a combination thereof. When implemented in software, the software code can be executed on any suitable processor or collection of processors, whether provided in a single computer or distributed across multiple computers. It should be understood that any component or collection of components performing the functions described above can be generally thought of as one or more controllers that control the functions described above. The one or more controllers can be implemented in a number of ways, such as dedicated hardware or one or more processors programmed using microcode or software to perform the functions described above.

[0062] In this regard, it should be understood that one implementation of an embodiment of the present invention includes at least one non-transitory computer-readable storage medium (e.g., computer memory, portable memory, compact disk, etc.) encoded with a computer program (i.e., a plurality of instructions), which when executed on a processor, performs the above-mentioned functions of the embodiments of the present invention. The computer-readable storage medium may be transportable such that the program stored thereon can be loaded onto any computer resource to perform the aspects of the present invention discussed herein. Furthermore, it should be understood that the reference to a computer program that when executed performs the above-mentioned functions is not limited to an application program running on a host computer. Rather, the term computer program is used in a generic sense herein to refer to any type of computer code (e.g., software or microcode) that can be employed to program a processor to perform the above-mentioned aspects of the present invention.

[0063] Various aspects of the invention may be used alone, in combination, or in various arrangements not specifically contemplated in the embodiments described above, and therefore are not limited in their application to the details and arrangements of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.

[0064] The embodiments of the invention may also be implemented as one or more methods, examples of which are provided. The acts performed as part of a method may be ordered in any suitable manner. Thus, although acts are shown as sequential in the exemplary embodiments, embodiments may be constructed in which acts are performed in an order different from that shown, which may include performing some acts simultaneously.

[0065] The use of hierarchical terms such as "first," "second," "third," etc. to modify claim elements in the claims does not, of itself, imply a priority, precedence, order, or temporal order in which the actions of a method are performed of a claim element relative to other claim elements. Such terms are used merely as labels to distinguish a claim element having a certain name from other elements having the same name (except when hierarchical terms are used).

[0066] The phraseology and terminology used herein are for purposes of description and should not be regarded as limiting. The use of "including," "including," "having," "containing," "involving," and variations thereof are meant to encompass the items listed thereafter as well as additional items.

[0067] Although several embodiments of the present invention have been described in detail, various modifications and improvements will be readily apparent to those skilled in the art. Such modifications and improvements are intended to be within the spirit and scope of the present invention. Accordingly, the foregoing description is by way of example only and is not intended to be limiting. The present invention is limited solely as defined by the following claims and their equivalents.

Claims

1. 1. A method of printing a 3D object, comprising: a. directing radiation at a first location of a volume of polymer precursor adjacent to a flexible substrate, thereby forming a first polymer layer on or adjacent to said substrate; b. moving a flexible substrate through the volume of the polymer precursor while maintaining contact with the periphery of the substrate; c. directing radiation at a second location of the volume of polymer precursor adjacent to the first location, thereby forming a second polymer layer on the first polymer layer; The method includes:

2. The method of claim 1 , wherein the periphery is substantially parallel to a direction in which the substrate is moved.

3. The method of claim 1 , wherein the flexible substrate is clamped around its periphery.

4. The method of claim 1 , wherein the surface of the substrate on which the first polymer layer is formed is not contacted by a roller across the width of the substrate.

5. The method of claim 1 , wherein the flexible substrate moves into, bends, and exits from a volume of the polymer precursor.

6. The method of claim 5 , wherein a first linear pinch zone occurs prior to bending of the flexible substrate and a second linear pinch zone occurs after the bending of the flexible substrate.

7. The method of claim 5 , wherein a series of rollers guides the flexible substrate through the bend.

8. The method of claim 1 , further comprising supporting a back surface of the flexible substrate opposite a front surface of the flexible substrate on which the first polymer layer is printed.

9. The method of claim 1 , wherein contact with the periphery is maintained along substantially the entire portion of the flexible substrate that is in contact with the volume of the polymer precursor.

10. The method of claim 1 , wherein contact with the periphery of the substrate is maintained until the second polymer layer is cured.

11. The method of claim 1 , wherein the flexible substrate is under substantially constant tension while the substrate is within the volume of the polymer precursor.

12. The method of claim 1 , further comprising guiding or positioning the flexible substrate prior to maintaining contact with the peripheral edge of the substrate.

13. 1. A system for printing 3D objects, comprising: a. a vessel configured to maintain a solution of polymer precursor at a substantially constant level; b. a mechanism configured to move a flexible substrate through the bath while maintaining contact with a peripheral edge of the substrate; c. a digital light processor (DLP) configured to direct radiation at selected portions of the polymer precursor solution; A system including:

14. 1. A method of printing a 3D object, comprising: a. directing radiation through a transparent window of a vat containing a volume of a polymer precursor, said radiation being directed to a first location adjacent a flexible substrate, thereby forming a first polymer layer on or adjacent to said substrate; b. moving the flexible substrate through a volume of the polymer precursor; c. directing radiation through said transparent window to a second location adjacent said first location, thereby forming a second polymer layer on said first polymer layer; The method includes:

15. 1. A system for printing a 3D object, the method comprising: a. a vessel having a transparent window, the vessel being configured to maintain a solution of polymer precursor at a substantially constant liquid level; b. a mechanism configured to move a flexible substrate through the bath and adjacent to the transparent window; c. a digital light processor (DLP) configured to direct radiation through the transparent window onto a selected portion of the polymer precursor solution; Including, the system.

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