Methods of additive manufacturing with liquid crystalline build surfaces

Abstract

An additive manufacturing apparatus for forming a three-dimensional object includes an optically transparent member (104) having a liquid crystal compound dispersed therein, optionally wherein the optically transparent member includes a polymer dispersed liquid crystal layer (112); a resin supply operatively associated with a build surface of the optically transparent member and configured to supply resin thereto; a radiation source configured to emit light through the optically transparent member and solidify resin on the build surface; and a controller (110) operatively associated with the optically transparent member and configured to modify a voltage across the optically transparent member to adjust the orientation of the liquid crystal compound in the optically transparent member, thereby adjusting a light scattering property of the optically transparent member.

Description

Attorney Docket No. 1151.257.WOMETHODS OF ADDITIVE MANUFACTURING WITH LIQUID CRYSTALLINE BUILD SURFACESRELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application Serial No. 63 / 704,768, filed October 8, 2024, the disclosure of which is hereby incorporated by reference in its entirety.FIELD OF THE INVENTION

[0002] The present invention relates to additively manufactured parts. The present invention also relates to methods of forming additively manufactured parts.BACKGROUND OF THE INVENTION

[0003] A group of additive manufacturing techniques sometimes referred to as “stereolithography” create a three-dimensional object by the sequential polymerization of a light polymerizable resin. Such techniques may be “bottom-up” techniques, where light is projected into the resin onto the bottom of the growing object through a light transmissive window, or “top down” techniques, where light is projected onto the resin on top of the growing object, which is then immersed downward into a pool of resin.

[0004] The introduction of a rapid stereolithography technique sometimes referred to as continuous liquid interface production (CLIP) has expanded the usefulness of stereolithography from prototyping to manufacturing. See e.g., J. Tumbleston, et al., Continuous liquid interface production of 3D objects, Science, 347, 1349-1352; R. Janusziewicz, et al., Layerless fabrication with continuous liquid interface production, PNAS, 113, 11703-11708 (18 October 2016); and U.S. Pat. Nos. 9,211,678, 9,205,601, and 9,216,546.

[0005] The light scattering parameters of an optically transparent surface in additive manufacturing are sometimes altered by the inclusion of scattering particles dispersed therein. However, as the light scattering needs may vary from object to object, multiple types of optically transparent surfaces may be required, thereby increasing expense and decreasing efficiency.Attorney Docket No. 1151.257.WOSUMMARY OF THE INVENTION

[0006] According to some embodiments, an additive manufacturing apparatus for forming a three-dimensional object includes an optically transparent member having a liquid crystal compound dispersed therein, optionally wherein the optically transparent member includes a polymer dispersed liquid crystal layer; a resin supply operatively associated with a build surface of the optically transparent member and configured to supply resin thereto; a radiation source configured to emit light through the optically transparent member and solidify resin on the build surface; and a controller operatively associated with the optically transparent member and configured to modify a voltage across the optically transparent member to adjust the orientation of the liquid crystal compound in the optically transparent member, thereby adjusting a light scattering property of the optically transparent member.

[0007] In some embodiments, the apparatus includes a build platform, and the build platform and the build surface of the optically transparent member define a build region therebetween.

[0008] In some embodiments, the controller is operatively associated with the radiation source and / or the build platform.

[0009] In some embodiments, the liquid crystal compound is present in the optically transparent member as a thermotropic liquid crystal (e.g., a nematic or cholesteric liquid crystal), optionally dispersed in a polymer.

[0010] In some embodiments, the optically transparent member comprises a polymer dispersed liquid crystal (PDLC) layer, optionally wherein the liquid crystal compound is present in the PDLC layer at a concentration in a range of 20 weight percent to 80 weight percent.

[0011] In some embodiments, the optically transparent member further comprises a build layer (e.g., a flexible, optically transparent, gas-permeable polymer layer) on the PLDC film layer, optionally wherein an upper surface of the build layer forms the build surface of the build plate.

[0012] In some embodiments, the optically transparent member further comprises a support layer (e.g., a rigid, optically transparent base) under the PLDC film layer.

[0013] In some embodiments, the optically transparent member further comprises a transparent, electrically conductive layer above and / or below PDLC film layer, the voltage is applied to the layer comprising a liquid crystalline compound dispersed therein through the transparent, electrically conductive layer(s), and the transparent, electrically conductive layer is in electrical communication with the controller.

[0014] In some embodiments, at least one electrode is in electrical communication with the transparent, electrically conductive layer(s) of the optically transparent member, and theAttorney Docket No. 1151.257.WO voltage is applied to the transparent, electrically conductive layer(s) via the at least one electrode, and wherein the electrode is in electrical communication with the controller.

[0015] In some embodiments, the optically transparent member comprises a layer that includes channels that provide a gas flow (e.g., an inhibitor gas) to the build surface.

[0016] In some embodiments, the voltage is modified in a range of 0V to 50V (AC) or 120 V (AC).

[0017] In some embodiments, the controller is operatively connected to a user interface, and the apparatus modifies the voltage across the optically transparent member based on inputs at the user interface.

[0018] According to some embodiments, a method of additive manufacturing includes irradiating polymer resin on a build surface of an additive manufacturing device (e.g., the additive manufacturing apparatus as described above, or an additive manufacturing device including a build plate of the inventive concept) through an optically transparent member comprising a liquid crystal compound dispersed therein to form a solid polymer layer on or above the build surface, and applying a voltage across the optically transparent member to adjust the orientation of the liquid crystal compound in the optically transparent member, thereby adjusting a light scattering property of the optically transparent member.

[0019] In some embodiments, the additive manufacturing device comprises a build platform and the optically transparent member comprises the build surface, and the build platform and the build surface of the optically transparent member define a build region therebetween. The method may include continuously or intermittently advancing the build platform away from the build surface while continuously or intermittently irradiating the resin to form a three- dimensional object.

[0020] In some embodiment, the method includes filling the build region with the polymer resin, continuously or intermittently irradiating the build region with actinic radiation or light through the optically transparent member to form the solid polymer from the polymer resin, and continuously or intermittently advancing (e.g., sequentially or concurrently with the irradiating step) the build platform away from the build surface to form the three-dimensional object from the solid polymer. The voltage may be applied across the optically transparent member during a portion of or all of the irradiation step.

[0021] In some embodiments, the voltage is modified during the irradiation in step (b) so that the light scattering properties of the optically transparent member are modified (e.g., increased and / or decreased) during the formation of the three-dimensional object.Attorney Docket No. 1151.257.WO

[0022] In some embodiments, no voltage is applied during a first portion of the irradiation in step (b), and a voltage is applied during a second portion of the irradiation in step (b), thereby producing the three-dimensional object having a first surface appearance at a first portion of the object and a second surface appearance at a second portion of the object.

[0023] In some embodiments, the method includes applying a different voltage during a third portion of the irradiation in step (b), thereby producing a third surface appearance at a third portion of the three-dimensional object.

[0024] In some embodiments, the liquid crystal compound is present in the optically transparent member as a thermotropic liquid crystal (e.g., a nematic or cholesteric liquid crystal).

[0025] According to some embodiments, a build plate for additive manufacturing includes an optically transparent member comprising a polymer-dispersed liquid crystal (PDLC) film layer in electrical communication with a voltage source; and a frame holding the PDLC film layer, wherein the frame is configured to secure into an additive manufacturing device.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 is a schematic diagram of an additive manufacturing apparatus according to an embodiment of the invention.

[0027] FIG. 2A and FIG. 2B is a diagram of a build plate including an optically transparent member. FIG. 2A is a top-down view of the build plate while FIG. 2B is a cross-sectional view of the build plate.

[0028] FIG. 3A is cross sectional view of an optically transparent member according to an embodiment of the invention without any applied voltage.

[0029] FIG. 3B is cross sectional view of an optically transparent member according to an embodiment of the invention with applied voltage.

[0030] FIG. 3C is cross sectional view of an optically transparent member according to an embodiment of the invention with applied voltage and electrodes connected thereto.

[0031] FIG. 4A is an image of optically transparent member of an embodiment of the invention. FIG. 4B is an image of a build plate including an optically transparent member according to an embodiment of the invention. FIG. 4C is an image of the build plate in use in an additive manufacturing device according to an embodiment of the invention.Attorney Docket No. 1151.257.WO

[0032] FIG. 5 is an image illustrating how the appearance of an additive manufactured part can vary according to the voltage applied across an optically transparent member that includes a liquid crystal compound.DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0033] The present invention is now described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art.

[0034] Like numbers refer to like elements throughout. In the figures, the thickness of certain lines, layers, components, elements or features may be exaggerated for clarity.

[0035] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an” and “the” are intended to include plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements components and / or groups or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups or combinations thereof.

[0036] As used herein, the term “and / or” includes any and all possible combinations or one or more of the associated listed items, as well as the lack of combinations when interpreted in the alternative (“or”).

[0037] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and claims and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Well-known functions or constructions may not be described in detail for brevity and / or clarity.

[0038] It will be understood that when an element is referred to as being “on,” “attached” to, “connected” to, “coupled” with, “contacting,” etc., another element, it can be directly on, attached to, connected to, coupled with and / or contacting the other element or interveningAttorney Docket No. 1151.257.WO elements can also be present. In contrast, when an element is referred to as being, for example, “directly on,” “directly attached” to, “directly connected” to, “directly coupled” with or “directly contacting” another element, there are no intervening elements present. It will also be appreciated by those of skill in the art that references to a structure or feature that is disposed “adjacent” another feature can have portions that overlap or underlie the adjacent feature.

[0039] Spatially relative terms, such as “under,” “below,” “lower,” “over,” “upper” and the like, may be used herein for ease of description to describe an element's or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is inverted, elements described as “under” or “beneath” other elements or features would then be oriented “over” the other elements or features. Thus the exemplary term “under” can encompass both an orientation of over and under. The device may otherwise be oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. Similarly, the terms “upwardly,” “downwardly,” “vertical,” “horizontal” and the like are used herein for the purpose of explanation only, unless specifically indicated otherwise.

[0040] It will be understood that, although the terms first, second, etc., may be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. Rather, these terms are only used to distinguish one element, component, region, layer and / or section, from another element, component, region, layer and / or section. Thus, a first element, component, region, layer or section discussed herein could be termed a second element, component, region, layer or section without departing from the teachings of the present invention. The sequence of operations (or steps) is not limited to the order presented in the claims or figures unless specifically indicated otherwise.

[0041] As used herein, a “plurality” of any element refers to two or more of such elements and may include 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 99% or 100%, or any range defined therein, of the total number of elements.

[0042] All patents or published patent applications referenced are herein incorporated by reference in their entirety. In the case of conflicting terminology, the present application controls.

[0043] Provided according to embodiments of the invention are additive manufacturing apparatus, build plates, and methods that directed to the irradiation of a polymer resin throughAttorney Docket No. 1151.257.WO an optically transparent member that includes a liquid crystal (LC) compound dispersed therein. The LC compound can modify its orientation with the application of an external voltage or electrical field to the optically transparent member, and the change in orientation of the LC compound thus modulates the light scattering properties of the optically transparent member.

[0044] Specifically, provided according to some embodiments of the invention are additive manufacturing apparatus that include an optically transparent member comprising a layer (e.g., polymer layer) comprising a liquid crystalline compound dispersed therein; a resin supply operatively associated with a build surface of the optically transparent member and configured to supply resin thereto; a radiation source configured to emit light through the optically transparent member and solidify resin on the build surface; and a controller operatively associated with the optically transparent member and configured to modify a voltage across the optically transparent member to adjust the orientation of the LC compound in the optically transparent member, thereby modulating a light scattering property of the optically transparent member. In some embodiments, the light scattering property is the % transmission through the optically transparent member. Other properties that may reflect a scattering of the optically transparent member include but are not limited to, a scattering distribution function and surface roughness of the printed object.

[0045] A non-limiting embodiment of an apparatus of the invention is shown in FIG. 1. In the present embodiment, apparatus 100 includes a radiation source 101, such as a digital light processor (DLP), that provides electromagnetic radiation 102, optionally though reflective mirror (not shown), into a build chamber 105 through a build plate 103 including an optically transparent member 104. Liquid resin 106 is present on the optically transparent member 104 and in the build chamber 105. The build plate 103 includes an optically transparent member 104 (e.g., semipermeable optically transparent member) that includes a liquid crystal compound therein, as discussed further below. The electromagnetic radiation 102 solidifies the liquid resin 106 (e.g., via a CLIP process) to form a growing object 107. The top of object 107 being fabricated attaches to build platform 108 (also referred to as a carrier). In FIG. 1, the build platform 108 is driven in the vertical direction by linear stage 109, although alternate configurations can be used.

[0046] A liquid resin reservoir, tubing, pumps, liquid level sensors and / or valves (not shown for clarity) can be included to replenish the pool of liquid resin 106 in build chamber 105, though in some embodiments, a simple gravity feed may be employed. Drives / actuators for the build platform 108 or linear stage 109, along with associated wiring (not shown), can beAttorney Docket No. 1151.257.WO included in accordance with known techniques. The drives / actuators for build platform 108, linear stage 109, and / or radiation source 101 (and in some embodiments, pumps and liquid level sensors, and other optional components) can all be operatively associated with a suitable controller 110, again in accordance with known techniques. A single controller 110 may be used or multiple controllers 110 may be used as desired to control different elements.

[0047] A controller 110, either the same or different controller as used for the other components in the apparatus 100, is further in electrical communication with electrical components (not shown) that contact the build plate 103 in order to modify the properties of the liquid crystals in the optically transparent member 104. As described in further detail below, the controller 110 may modify a voltage across the optically transparent member 104 via the electrical connections to adjust the orientation of the LC compound in the optically transparent member 104, thereby modulating a light scattering property of the optically transparent member 104.

[0048] Other types of additive manufacturing apparatus may include an optically transparent build plate that includes LC compounds dispersed therein. Accordingly, the specific type of apparatus may be varied provided that the light passes through an optically transparent member to solidify liquid resin, and the alignment of LC compounds is modified by modifying the voltage across the build plate, thereby modulating the light scattering properties of the optically transparent member. Also provided are additive manufacturing apparatus that include a build plate and / or optically transparent member of the invention.Build Plates and Optically Transparent Members

[0049] FIG. 2A shows a top-down view of build plate 103. Build plate 103 generally comprises or consists of a (typically rigid or solid, stationary, and / or fixed) optically transparent member 104, alone or in combination with one or more additional supporting substrates 111 (e.g., frames, clamps and / or tensioning members, e.g., to rigidify an otherwise flexible semipermeable material). FIG. 2B provides a cross-sectional view of build plate 103 and shows that optically transparent member 104 typically comprises a top surface portion 104a, a bottom surface portion 104b, and an edge surface portion 104c, with the build surface being on the top surface portion 104a. While the optically transparent member 104 in FIGS. 2A and 2B is shown as having a rounded square shape, other shapes may be used, including round, elliptical, polygonal, and non-uniform shapes. The location and configuration of additional supporting substrate(s) 111, if present, may also be varied in size, shape, and configuration as desirable for the particular additive manufacturing apparatus used.Attorney Docket No. 1151.257.WO

[0050] The optically transparent member 104 (e.g., rigid or semi-rigid member) can be made of any suitable material that is optically transparent at the relevant wavelengths (or otherwise transparent to the radiation source, whether or not it is visually transparent as perceived by the human eye — i.e., an optically transparent window may in some embodiments be visually opaque). The optically transparent member 104 may be a single layer or may be formed from multiple layers but the optically transparent member 104 includes a liquid crystal compound in at least a portion thereof. For example, one or more layers of the optically transparent member 104 may include a liquid crystal compound dispersed therein.

[0051] Any liquid crystal compound that changes orientation upon application of an electrical or magnetic force (e.g., voltage) may be included in the optically transparent member. For example, in some embodiments, the liquid crystal compound is present in the optically transparent member as a thermotropic liquid crystal (e.g., a nematic or cholesteric liquid crystal) but other liquid crystalline components may be used in certain embodiments.

[0052] In some embodiments, the optically transparent member 104 comprises a polymer dispersed liquid crystal (PDLC) film layer, optionally wherein the liquid crystal compound is present in the PDLC film at a concentration in a range of 20 weight percent to 80 weight percent (including 20 weight percent, 30 weight percent, 40 weight percent, 50 weight percent, 60 weight percent, 70 weight percent, 80 weight percent, and any range defined between any two of the foregoing concentrations). In some embodiments, the PDLC film layer includes a pixelated PDLC film and / or patterned conductive layers such that concentration of LC compound may be varied or patterned throughout the X-Y plane and / or Z plane of the film. Such films may allow for spatial control of scattering. For example, in some embodiments, such pixelated or patterned films may allow for multiple scattering levels within a single slice / manufacturing layer of the additive manufacturing process. In some embodiments, the PDLC film includes LC compound pixels in a range of 1 pm to 100 pm (e.g., 25 pm to 50 pm, 60 pm, 75 pm, or 80 pm).

[0053] In some embodiments, the optically transparent member 104 includes a transparent, electrically conductive layer above and / or below a layer having a liquid crystal compound therein (i.e., a PDLC layer). A voltage may be applied to the layer comprising a liquid crystalline compound dispersed therein through the transparent, electrically conductive layer(s) due to their conductivity. The transparent, electrically conductive layer(s) may be in electrical communication with a controller which may modulate the voltage across the layers to thus module the alignment of the liquid crystal compound and therefore modulate the scattering properties of the optically transparent member.Attorney Docket No. 1151.257.WO

[0054] One possible configuration of the transparent, electrically conductive layers is shown in FIGS. 3A and 3B. In FIG. 3A, an optically transparent member 104 includes a PDLC layer 112, an upper transparent, electrically conductive layer 113a above the PDLC layer 112, and a lower transparent, electrically conductive layer 113b below the PDLC layer 112. The electrically conductive layers 113a, 113b are in electrical communication with a voltage source or other device capable of creating a voltage across the conductive layers. In the embodiments illustrated in FIGS. 3A and 3B, a build surface layer 114 is on the upper transparent, electrically conductive layer 113a and a support layer 115 is below the lower transparent, electrically conductive layer 113b. In FIG. 3A, no voltage is applied to the electrically conductive layers 113a, 113b and so the liquid crystalline compounds 116 are randomly oriented / not aligned and so the optically transparent member 104 has a first scattering property (e.g., greater scattering). FIG. 3B shows the optically transparent member 104 after a voltage is applied across the electrically conductive layers 113a, 113b, whereby the liquid crystalline compounds 116 become aligned and so the optically transparent member 104 has a second scattering property (e.g., less scattering). While FIG. 3A shows randomly oriented liquid crystalline compounds 116 and FIG. 3B shows highly aligned liquid crystalline compounds 116, it will be understood that intermediate alignments between random and aligned are possible based on the voltage applied so that a number of different scattering properties may be obtained by modulating the voltage between the electrically conductive layers 113a, 113b. In addition, different alignment orientations may be provided (e.g., off axis alignment).

[0055] In some embodiments, build surface layer 114 includes a flexible polymer film (having any suitable thickness, e.g., from 0.001, 0.01, 0.1 or 1 millimeters to 5, 10, or 100 millimeters, or more) layer having a top surface 114a positioned for contacting said liquid resin 106 (see FIG. 1) and a bottom surface 114b opposite of the top surface, and on another layer, such as the electrically conductive layer 113a. In particular embodiments, the build surface layer 114 may be semipermeable to a polymerization inhibitor (e.g., oxygen). For example, the build surface layer 114 may, for example, be a fluoropolymer film, such as an amorphous thermoplastic fluoropolymer like TEFLON AF 1600™ or TEFLON AF 2400™ fluoropolymer films, or perfluoropoly ether (PFPE), particularly a crosslinked PFPE film, or a silicone (e.g., polydimethylsiloxane) or crosslinked silicone polymer film.

[0056] In some embodiments, support layer 115 is a rigid, gas permeable, optically transparent supporting member (having any suitable thickness, e.g., from 0.01, 0.1 or 1 millimeters to 10, 100, or 200 millimeters, or more) having an upper surface 115a and a lower surface 115b. In some embodiments, the upper surface 115a of the support layer 115 may contact a lowerAttorney Docket No. 1151.257.WO surface of an optically transparent, conducting layer 113b, and the lower surface 115b of the support layer 115 may serve as a feed surface for the polymerization inhibitor. In some embodiments, the support layer 115 comprises a silicone or crosslinked silicone polymer member such as a polydmiethylxiloxane member, a rigid gas permeable polymer member, or a porous or microporous glass member. The layers above the support layer 115 may, in some embodiments, be laminated or clamped directly to support layer 115 without adhesive (e.g., using PFPE and PDMS materials) or adhesive layers (not shown) may be used. Examples of adhesives include silane coupling agents that react with the upper surface of a PDMS layer can be utilized to adhere to the first polymer film layer and UV-curable and silicones (e.g., acrylate- functional silicones). Adhesive may also be used between any of the other layers in the optically transparent member 104.

[0057] The electrically conductive layers 113a, 113b may be formed of any conductive and optically transparent material. Examples of such materials include but are not limited to transparent conducting oxides such as indium tin oxide (ITO), fluorine doped tin oxide (FTO), doped titanium dioxide, and doped zinc oxide. Other examples include conducting organic polymers. In some embodiments, the electrically conductive layer is patterned and / or includes switchable optical lenses and / or gratings. Switchable optical lenses and / or gratings are described in Huang et al., Polarization-Dependent Gratings Based on Polymer-Dispersed Liquid Crystal Cells with In-Plane Switching Electrodes, Polymers 2022, 14(2), 297, which is incorporated herein by reference in its entirety.

[0058] In some embodiments, the optically transparent member 104 is semipermeable to a polymerization inhibitor. The permeability of the semipermeable member 104 to the polymerization inhibitor will depend upon conditions such as the pressure of the atmosphere and / or inhibitor, the choice of inhibitor, the rate or speed of fabrication, and the like. In general, when the inhibitor is oxygen, the permeability of the semipermeable member to oxygen may be from 10 or 20 Barrers, up to 1000 or 2000 Barrers, or more. For example, a semipermeable member with a permeability of 10 Barrers used with a pure oxygen, or highly enriched oxygen, atmosphere under a pressure of 150 psi may perform substantially the same as a semipermeable member with a permeability of 500 Barrers when the oxygen is supplied from the ambient atmosphere under atmospheric conditions. In embodiments wherein the optically transparent member is semipermeable to a polymer inhibitor, it may be fed on or through one, two, or all three of the top surface portion, the bottom surface portion, and / or the edge surface portion. In particular embodiments, the inhibitor feed surface is on the bottom surface of the support layerAttorney Docket No. 1151.257.WO

[0059] In some embodiments, the semipermeable optically transparent member 104 allows inhibitor to pass therethrough, and it can simply be configured to contain a sufficient amount (or “pool”) of inhibitor to continuously maintain the dead zone for a sufficient length of time, to produce the article being fabricated without additional feeding of inhibitor during the process (which “pool” may be replenished or recharged between production runs). The size and internal volume of the optically transparent member can be configured as appropriate for the particular article being fabricated to contain a sufficient pool of inhibitor. In some embodiments, the optically transparent member includes a layer that includes channels which provide a gas flow (e.g., an inhibitor gas) to the build surface.

[0060] The optically transparent member 104 has, in some embodiments, a thickness in a range of from 0.01, 0.1 or 1 millimeters to 10 or 100 millimeters, or more (depending upon the size of the item being fabricated), whether or not it is laminated to or in contact with an additional supporting plate such as glass.

[0061] In some embodiments, additional and / or alternative layers in the optically transparent member may be present. Additional configurations of the optically transparent member may be used, including but not limited to those described in U.S. PatentNos. 9,498,920, 11,518,096, 10,792,856, 11,642,836, and 11,446,871, the contents of each of which is hereby incorporated by reference in its entirety.

[0062] Referring to FIG. 3C, in some embodiments, the apparatus further includes at least one electrode 117a, 117b in electrical communication with the optically transparent member 104 (e.g., in electrical communication with a portion of the optically transparent member that includes a liquid crystal dispersed therein, e.g., via an optically transparent conductive layer 113a, 113b in the optically transparent member 104). In FIG. 3C, a first electrode 117a is in electrical communication with the upper transparent, electrically conductive layer 113a of the optically transparent member 104 and a second electrode 117b is in electrical communication with lower transparent, electrically conductive layer 113b such that a voltage may be created between the upper transparent, electrically conductive layer 113a and the lower transparent, electrically conductive layer 113b, thereby applying a voltage to the PDLC layer 112. The first electrode 117a and second electrode 117b are then in electrical communication with the controller 110 (and / or voltage source or other suitable electrical device) so that the voltage between the upper transparent, electrically conductive layer 113a and the lower transparent, electrically conductive layer 113b can be modulated as desired. In some embodiments, the controller 110 is operatively connected to a user interface (not shown), and wherein theAttorney Docket No. 1151.257.WO controller 110 modifies the voltage across the optically transparent member based on inputs at the user interface.

[0063] Also provided according to embodiments of the invention are build plates (also referred to as windows) for additive manufacturing that include an optically transparent member comprising a liquid crystalline compound (e.g., a polymer-dispersed liquid crystal (PDLC) film layer); and a frame or connector attached to the optically transparent member, wherein the frame and / or connector is configured to secure into an additive manufacturing device. The build plates include optically transparent members as described herein (e.g., with respect to FIGS. 1, 2, and 3A-3B).

[0064] Further provided according to embodiments of the invention are methods of additive manufacturing. Such methods include continuously or intermittently irradiating polymer resin on a build surface of an additive manufacturing device (e.g., an additive manufacturing apparatus of an embodiment of the invention, or an additive manufacturing device including a build plate of the invention) through an optically transparent member comprising a liquid crystalline compound (e.g., an optically transparent member comprising a PDLC layer) to form a solid polymer layer and / or three-dimensional object from the resin, and applying a voltage across the optically transparent member to adjust the orientation of the liquid crystal compound in the optically transparent member, thereby adjusting a light scattering property of the optically transparent member.

[0065] In some embodiments, the methods include filling the build region with the polymer resin; continuously or intermittently irradiating the build region with actinic radiation or light through the optically transparent member to form a solid polymer from polymer resin, and continuously or intermittently advancing (e.g., sequentially or concurrently with the irradiating step) the build platform away from the build surface to form the three-dimensional object from the solid polymer; wherein the voltage is applied across the optically transparent member during a portion of or all of the irradiation step. In some embodiments, the voltage is modified during the irradiation in step so that the light scattering properties of the optically transparent member are modified (e.g., increased and / or decreased) during the formation of the three- dimensional object.

[0066] In some embodiments, no voltage is applied during a first portion of the irradiation and a voltage is applied during a second portion of the irradiation, thereby producing the three- dimensional object having a first surface appearance at a first portion of the object and a second surface appearance at a second portion of the object. In some embodiments, methods furtherAttorney Docket No. 1151.257.WO include applying a different voltage during a third portion of the irradiation in step (b), thereby producing a third surface appearance at a third portion of the three-dimensional object. In some embodiments, the voltage may be modulated such that different slices of a build may have different scattering properties. Further, in some embodiments, a single build plate may be used for a wide variety of applications wherein a number of different scattering properties may be desirable.

[0067] The voltage applied across the PDLC layer may be varied depending on the LC compound, the PDLC layer, etc. However, in some embodiments, the voltage applied to an optically transparent member of a build plate (or a PDLC layer in a build plate) is in a range of 0V to 50V (DC or AC) or 120 V (DC or AC).

[0068] The modulation of voltage may be useful in a number of different applications. For example, in parts with branding or features that need to visually stand out, the voltage may be modulated at certain points in the print to create different scattering properties to achieve this goal. As another example, in certain cases, parts or portions of parts may require or desire certain tactile properties (e.g., smooth mating surface of connectors). Modulation of voltage during the additive manufacturing process to create such tactile properties may be useful. As an additional example, certain surfaces may benefit from a non-uniform surface appearance (e.g., prosthetic teeth) to appear more realistic. Modulation of the voltage during a print using PDLC-containing optically transparent members may allow for such non-uniform surface appearances to be created.Example

[0069] An optically transparent member (also referred to as a window) was prepared as follows. A polymer dispersed liquid crystal (PDLC) film was sandwiched between two optically transparent ITO layers and applied to a rigid support member of borosilicate glass with an adhesive layer. A channeled substrate layer was placed on the upper ITO layer and a fluorinated build surface layer was applied on the channeled substrate layer. As shown in FIG. 4A, bus bars (electrodes) were connected to the ITO conductive layers and connected to external wiring. As shown in FIG. 4B, the optically transparent member was installed into a frame (also referred to as a cassette) for installing into the Carbon M3 printer (shown in FIG. 4C). The external wiring was connected to a voltage generator and a voltmeter to measure the applied voltage.

[0070] As shown in FIG. 5, the voltage across the PDLC layer was varied from 0V AC (top) to 40V AC (bottom) in a print with UMA90 resin from Carbon, Inc. As can be seen in FIG. 5,Attorney Docket No. 1151.257.WO the surface finish of the part varied based on the voltage applied with the lower voltages leading to increased scattering and the higher voltages providing less scattering.

[0071] While embodiments of the present disclosure have been particularly shown and described with reference to embodiments thereof, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope of the following claims.

Claims

Attorney Docket No. 1151.257.WOWe claim '.

1. An additive manufacturing apparatus for forming a three-dimensional object comprising:(a) an optically transparent member having a liquid crystal compound dispersed therein, optionally wherein the optically transparent member includes a polymer dispersed liquid crystal layer;(b) a resin supply operatively associated with a build surface of the optically transparent member and configured to supply resin thereto;(c) a radiation source configured to emit light through the optically transparent member and solidify resin on the build surface; and(d) a controller operatively associated with the optically transparent member and configured to modify a voltage across the optically transparent member to adjust the orientation of the liquid crystal compound in the optically transparent member, thereby adjusting a light scattering property of the optically transparent member.

2. The additive manufacturing apparatus of claim 1, further comprising a build platform, wherein the build platform and the build surface of the optically transparent member define a build region therebetween.

3. The additive manufacturing apparatus of claim 1 or claim 2, wherein the controller is operatively associated with the radiation source and / or the build platform.

4. The additive manufacturing apparatus of one of claims 1-3, wherein the liquid crystal compound is present in the optically transparent member as a thermotropic liquid crystal (e.g., a nematic or cholesteric liquid crystal), optionally dispersed in a polymer.

5. The additive manufacturing apparatus of one of claims 1-4, wherein the optically transparent member comprises a polymer dispersed liquid crystal (PDLC) layer, optionally wherein the liquid crystal compound is present in the PDLC layer at a concentration in a range of 20 weight percent to 80 weight percent.

6. The additive manufacturing apparatus of one of claims 1-5, wherein the optically transparent member further comprises a build layer (e.g., a flexible, opticallyAttorney Docket No. 1151.257.WO transparent, gas-permeable polymer layer) on the PLDC film layer, optionally wherein an upper surface of the build layer forms the build surface of the build plate.

7. The additive manufacturing apparatus of one of claims 1-6, wherein the optically transparent member further comprises a support layer (e.g., a rigid, optically transparent base) under the PLDC film layer.

8. The additive manufacturing apparatus of one of claims 1-7, wherein the optically transparent member further comprises a transparent, electrically conductive layer above and / or below PDLC film layer, wherein the voltage is applied to the layer comprising a liquid crystalline compound dispersed therein through the transparent, electrically conductive layer(s), and wherein the transparent, electrically conductive layer is in electrical communication with the controller.

9. The additive manufacturing apparatus of claim 8, further comprising at least one electrode in electrical communication with the transparent, electrically conductive layer(s) of the optically transparent member, and wherein the voltage is applied to the transparent, electrically conductive layer(s) via the at least one electrode, and wherein the electrode is in electrical communication with the controller.

10. The additive manufacturing apparatus of one of claims 1-9, wherein the optically transparent member comprises a layer that includes channels that provide a gas flow (e.g., an inhibitor gas) to the build surface.

11. The additive manufacturing apparatus of any one of claims 1-10, wherein the voltage is modified in a range of 0V to 50V (AC) or 120 V (AC).

12. The additive manufacturing apparatus of any one of claims 1-11, wherein the controller is operatively connected to a user interface, and wherein the apparatus modifies the voltage across the optically transparent member based on inputs at the user interface.

13. A method of additive manufacturing comprising: irradiating polymer resin on a build surface of an additive manufacturing device (e.g., the additive manufacturing apparatus of any one of claims 1-12, or an additive manufacturingAttorney Docket No. 1151.257.WO device including a build plate of the invention) through an optically transparent member comprising a liquid crystal compound dispersed therein to form a solid polymer layer on or above the build surface, and applying a voltage across the optically transparent member to adjust the orientation of the liquid crystal compound in the optically transparent member, thereby adjusting a light scattering property of the optically transparent member.

14. The method of claim 13, wherein the additive manufacturing device comprises a build platform and wherein the optically transparent member comprises the build surface, and wherein the build platform and the build surface of the optically transparent member define a build region therebetween, and wherein the method further comprises continuously or intermittently advancing the build platform away from the build surface while continuously or intermittently irradiating the resin to form a three-dimensional object.

15. The method of claim 14, wherein the method comprises:(a) filling the build region with the polymer resin;(b) continuously or intermittently irradiating the build region with actinic radiation or light through the optically transparent member to form the solid polymer from the polymer resin, and continuously or intermittently advancing (e.g., sequentially or concurrently with the irradiating step) the build platform away from the build surface to form the three-dimensional object from the solid polymer; wherein the voltage is applied across the optically transparent member during a portion of or all of the irradiation in step (b).

16. The method of claim 15, wherein the voltage is modified during the irradiation in step (b) so that the light scattering properties of the optically transparent member are modified (e.g., increased and / or decreased) during the formation of the three-dimensional object.

17. The method of claim 15 or claim 16, wherein no voltage is applied during a first portion of the irradiation in step (b), and a voltage is applied during a second portion of the irradiation in step (b), thereby producing the three-dimensional object having a first surfaceAttorney Docket No. 1151.257.WO appearance at a first portion of the object and a second surface appearance at a second portion of the object.

18. The method of claim 17, further comprising applying a different voltage during a third portion of the irradiation in step (b), thereby producing a third surface appearance at a third portion of the three-dimensional object.

19. The method of any one of claims 13-18, wherein the liquid crystal compound is present in the optically transparent member as a thermotropic liquid crystal (e.g., a nematic or cholesteric liquid crystal).

20. A build plate for additive manufacturing comprising: an optically transparent member comprising a polymer-dispersed liquid crystal (PDLC) film layer in electrical communication with a voltage source; and a frame holding the PDLC film layer, wherein the frame is configured to secure into an additive manufacturing device.

21. The build plate of claim 20, wherein the optically transparent member further comprises a build layer (e.g., a flexible, optically transparent, gas-permeable polymer layer) on the PLDC film layer, optionally wherein an upper surface of the build layer forms a build surface of the build plate.

22. The build plate of claim 20 or claim 21, wherein the optically transparent member further comprises a support layer (e.g., a rigid, optically transparent base) under the PLDC film layer.

23. The build plate of any one of claims 20-22, further comprising a transparent, electrically conductive layer above and / or below PDLC film layer.

24. The build plate of any one of claims 20-23, further comprising at least one electrode in electrical communication with the transparent, electrically conductive layer(s).

25. The build plate of any one of claims 20-24, wherein the PDLC film layer comprises thermotropic liquid crystals (e.g., in the nematic or cholesteric phase).Attorney Docket No. 1151.257.WO26. The build plate of any one of claims 20-25, wherein the optically transparent member comprises a channel layer including channels therein configured to increase gas flow to the build surface.

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