Laser object printing from gaseous substrates

Abstract

A method and apparatus for 3D printing solid materials from the vapor phase and recovering valuable gaseous by-products. Some reactor designs use novel configurations of efficient, low-cost semiconductor lasers.

Description

[Technical Field]

[0001] The embodiments described herein relate generally to methods and systems for creating solid objects from gaseous feedstocks, and more particularly to printers that use laser radiation to cause the feedstocks to solidify at specific locations to form desired objects.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of and priority to U.S. Provisional Application No. 63 / 378,357, filed October 4, 2022, and U.S. Provisional Application No. 63 / 432,139, filed December 13, 2022, the entire disclosures of each of which are incorporated herein by reference as if set forth in their entirety. [Background technology]

[0003] A small section of the literature beginning in the 1980s has demonstrated laser-based growth of carbon fibers from low-cost gaseous hydrocarbon feedstocks (e.g., methane or olefins). The laser can be focused to maintain a hot spot (e.g., hundreds to thousands of degrees Celsius) a few microns in diameter on a suitable surface. The feedstock gas locally pyrolyzes to deposit solid carbon, and by continuing to adjust the focus to remain near the tip of the deposit, a thin fiber is grown. The diameter of the grown fiber typically matches well with the size of the focused light spot.

[0004] Under appropriate growth conditions, the resulting fibers can have tensile strengths and moduli comparable to those of carbon fibers produced via polyacrylonitrile. The optical energy required per mass of deposited carbon fiber can be significantly less than 100 MJ / kg, suggesting the potential for significant energy improvements over the polyacrylonitrile process. According to the literature, linear fiber growth rates typically range from 10 microns to 1 mm per second. Furthermore, very similar techniques have been used to grow other fibers from gaseous precursors, often with similar growth rates and energy requirements (e.g., boron fibers from BCl3 and H2, silicon carbide fibers from SiCl4 and CH4, silicon fibers from SiCl4 and H2, tungsten fibers from WF6 and H2, and germanium fibers from GeH4 and H2).

[0005] A major problem in commercializing this technique has been the energy efficiency of the laser. As an example, if the optical energy intensity required to grow a particular fiber is 100 MJ / kg (a magnitude typically found in the literature), but the laser system used is only 10% efficient at converting electrons from the power supply output into photons that strike the target (this 10% figure is typical for the types of lasers used in the literature, e.g., Nd:YAG and fiber lasers), the power required to grow the fiber would be 1000 MJ / kg. Using typical industrial electricity, which costs $0.08 / kWh, this translates to over $22 / kg for the power alone, making fiber grown this way quite expensive.

[0006] The capital cost of growth equipment is yet another commercial obstacle. Lasers with high-quality optical modes (e.g., fiber lasers) are used for controlled fiber growth, but often cost more than $20 / W. If such costs are amortized over a 10-year laser lifetime with 100% utilization, the capital cost of the laser effectively amounts to $0.22 / kWh, or 2.5 times the electricity cost, which in the example above is already $22 / kg.

[0007] Therefore, there is a need for a laser manufacturing system and method that overcomes these drawbacks. Summary of the Invention

[0008] This Summary is provided to introduce a selection of concepts in a simplified form that are further described in the Detailed Description section below. This Summary is not intended to identify or exclude key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0009] Embodiments of the present invention relate to methods and apparatus for 3D printing solid materials from the gas phase while recovering valuable gaseous by-products by utilizing physical mechanisms similar to those described above for fibers. Some reactor designs use novel configurations of efficient, low-cost semiconductor lasers to overcome the aforementioned commercialization challenges associated with laser-induced deposition from the gas phase.

[0010] In one aspect, an embodiment relates to a laser reactor for additive manufacturing, comprising a reaction chamber having an inlet for receiving a gaseous feedstock, an optical window, and a substrate, and a laser module configured to emit laser light to heat the substrate through the window and thereby induce a gas-to-solid deposition reaction in the vicinity of the heated substrate to convert the gaseous feedstock into at least one reaction product that forms at least a portion of a desired solid object supported by the substrate.

[0011] In various embodiments, the substrate has at least one degree of freedom.

[0012] In various embodiments, at least one reaction product is a refractory material.

[0013] In various embodiments, the laser module is movable and has at least one degree of freedom.

[0014] In various embodiments, the laser module includes a plurality of laser emitters, and the reactor further comprises an optical arrangement configured to direct the output of each laser emitter onto a different region of the substrate.

[0015] In various embodiments, the reactor further includes a first optical element that splits the output of the laser module into multiple beams and a second optical element configured to direct each beam to a different region of the substrate.

[0016] In various embodiments, the reactor further includes a plurality of optical windows and a plurality of laser modules, each laser module in the plurality of laser modules configured to emit laser light into the chamber through an optical window in the plurality of optical windows, and the laser light of the plurality of laser modules is focused onto a region of the substrate.

[0017] In various embodiments, the reactor further includes a mechanism for adjusting one or more of the reactor pressure, the temperature of the substrate, and the temperature of the reactants.

[0018] In various embodiments, the reactor further includes optics for controlling the target of the emitted laser light within the reaction chamber.

[0019] In various embodiments, the reactor further includes a controller in communication with the at least one sensor, the controller configured to control at least one of a power output, a deflection, or a position of the laser module based on information received from the at least one sensor.

[0020] In various embodiments, the desired object is an array of carbon fibers.

[0021] In various embodiments, the laser module includes an array of semiconductor laser diode bars or a vertical cavity surface emitting laser array.

[0022] In various embodiments, the reactor further includes a controller in communication with the at least one sensor, the controller configured to control the position of the substrate based on information received from the at least one sensor.

[0023] In various embodiments, the desired object is an array of silicon carbide fibers.

[0024] In another aspect, an embodiment relates to a method for additive manufacturing, the method including providing a reaction chamber having an inlet for receiving a gaseous feedstock, an optical window, and a substrate, introducing the gaseous feedstock into the reaction chamber via the inlet, and heating the substrate through the optical window by applying laser light to thereby cause a gas-to-solid deposition reaction in the vicinity of the heated substrate to convert the gaseous feedstock into at least one reaction product that forms at least a portion of a desired object supported on the substrate.

[0025] In various embodiments, the method further includes moving the substrate in at least one degree of freedom to form the desired object.

[0026] In various embodiments, the method further includes moving the laser beam in at least one degree of freedom to form the desired object.

[0027] In various embodiments, the method further comprises adjusting one or more of the pressure of the reaction chamber, the temperature of the reactants, or the temperature of the substrate.

[0028] In various embodiments, the reaction chamber further includes at least one sensor, and the method further includes controlling at least one of the power, deflection, or position of the laser light based on information received from the at least one sensor.

[0029] In various embodiments, at least one reaction product is a refractory material.

[0030] In various embodiments, the desired object is an array of carbon fibers.

[0031] In various embodiments, the reaction chamber further comprises at least one sensor, and the method further comprises controlling the position of the substrate based on information received from the at least one sensor.

[0032] In various embodiments, the desired object is an array of silicon carbide fibers.

[0033] In yet another aspect, an embodiment relates to a reactor for additive manufacturing, the reactor including an inlet for introducing gaseous reactants into a chamber and a laser radiation source configured to convert the gaseous reactants into a solid product having a desired composition. [Brief explanation of the drawings]

[0034] Non-limiting and non-exhaustive embodiments of the present disclosure are described with reference to the following drawings, in which like numerals refer to like parts throughout the various views unless otherwise specified. [Figure 1] FIG. 1 shows an exemplary reactor concept for 3D printing. [Figure 2] FIG. 2 shows an exemplary semiconductor laser diode bar. [Figure 3] FIG. 3 shows an exemplary high-power laser module based on the diode bar of FIG. [Figure 4] FIG. 4 shows the use of a laser diode module and a single lens to project an array of spots onto a target substrate. [Figure 5] FIG. 5 shows an exemplary high-power laser module based on a VCSEL array. [Figure 6] FIG. 6 shows an exemplary laser reactor concept using laser diode bar modules. [Figure 7]FIG. 7 shows an exemplary laser module based on a typical input beam. [Figure 8] FIG. 8 shows a growth chamber with a motorized stage. [Figure 9] FIG. 9 shows an example of the alignment plate concept. DETAILED DESCRIPTION OF THE INVENTION

[0035] Various embodiments are further described below with reference to the accompanying drawings. The accompanying drawings, which form a part of this specification, show certain exemplary embodiments. However, the concepts of the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, which are provided as part of a thorough and complete disclosure to fully convey the scope of the concepts, techniques, and implementations of the present disclosure to those skilled in the art. The embodiments may be implemented as methods, systems, or devices. The embodiments may take the form of hardware implementations, entirely software implementations, or implementations combining software and hardware aspects. Therefore, the following detailed description should not be taken in a limiting sense.

[0036] References herein to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one exemplary implementation or technology according to the present disclosure. The appearances of the phrase "in one embodiment" in various places throughout the specification are not necessarily all referring to the same embodiment.

[0037] Furthermore, the language used herein has been selected primarily for purposes of readability and description, and may not be selected to define or limit the subject matter of the disclosure. Accordingly, the present disclosure is intended to be illustrative, not limiting, of the scope of the concepts described herein.

[0038] Recent technological advances have made it possible to precisely print three-dimensional structures ("3D printing") from a variety of materials, including plastics, composites, and metals. These approaches often involve converting a solid or liquid precursor material into a final product, for example, by applying heat or light. Embodiments herein relate to methods and apparatus for 3D printing various materials directly from the gas phase using a laser.

[0039] Attractive features of this approach include high energy efficiency, low cost, high throughput, the ability to print refractory solids, and the potential co-production of valuable gaseous by-products (e.g., hydrogen, hydrocarbons, etc.). Embodiments can be used, for example, to 3D print solid carbon structures or arrays of carbon fibers from methane or other hydrocarbon precursors, producing gaseous hydrogen as a saleable by-product.

[0040] Figure 1 shows one novel reactor concept for 3D printing. A reaction chamber 100 is pressurized with appropriate precursor gases at appropriate flow rates and temperatures. A motorized platform 112 within the reaction chamber holds the part to be 3D printed. One or more laser modules 104 N (described in more detail below) projects an array of focused light spots onto or near components 108 within reaction chamber 100 through a suitable optical access port (e.g., an optical window, lens, or other transmissive optical element [not shown] embedded in the wall of reaction chamber 100, e.g., an optical access port constructed from sapphire, diamond, fused silica, quartz, etc.). N can adjust the power of each light spot and / or reposition the light spots within the chamber to achieve a desired spatiotemporal heating profile that results in suitable deposition of solid material from the precursor gas phase. The part 108 is supported by a motorized stage 112, which can be repositioned to expose the appropriate surface to the focused laser beam, thereby enabling growth of the desired part 108.

[0041] It may be advantageous to flow a coolant through channels (not shown) in the motorized stage 112 or other elements of the reactor 100 to extract heat. It may also be advantageous to provide additional heat (e.g., resistive, inductive, or radiative) to the part 108, precursor gases, or other elements of the reactor 100. It may also be advantageous to appropriately collect generated particulate matter (e.g., pyrolysis products that do not deposit on the part; in the absence of such a collection method, such particulate matter could obstruct the optical path between the laser module and the part) using one or more methods (e.g., electrostatic deflection of airborne particles by applying appropriate potentials to appropriately positioned electrodes and / or the part being fabricated, blowing away airborne particles using appropriate gas flow patterns, intermittent particle sweeping by mechanical means, etc.). One or more gas inlets (not shown) may be appropriately positioned near the optical surfaces of the reactor, and an appropriate gas mixture (e.g., precursor gas, inert gas, etc.) may be flowed into the chamber through the inlets in a manner that mitigates solid deposition on the optical surfaces.

[0042] To fabricate desired 3D shapes within this reactor, motorized stage movements, laser module adjustments, gas flows, coolant flows, and other reactor parameters (all of which are digitally controllable) can be planned in advance, for example, using appropriate computer algorithms that account for appropriate physical effects (e.g., fluid dynamics, heat transport, etc.). These planned movements and adjustments can be further adjusted in real time using appropriate algorithms operating on data collected from sensors (not shown), such as visible or infrared cameras (e.g., to image cross sections of the part being fabricated, create temperature maps of the surface, etc.), lidar scanners or other depth sensors (e.g., to create 3D maps of the part), auxiliary lasers (e.g., to monitor gas temperature, composition, and / or turbulence), thermometers, pressure sensors, gas flow meters, etc.

[0043] This reactor can be used with a variety of gaseous precursors to 3D print a variety of solid materials. Using gaseous precursors can be advantageous for 3D printing parts made of refractory materials, such as solid carbon. Often, the pyrolysis reaction also produces one or more gaseous byproducts. For example, when printing solid carbon, hydrogen gas is produced from the pyrolysis of hydrocarbon precursors (e.g., methane, ethylene). These byproduct gases can be separated from the precursor gases exiting the reactor by any suitable means (e.g., membranes, pressure swing adsorption, cryogenic separation, etc.) (e.g., under conditions where a continuous flow of precursor gases enters the chamber at a controlled rate and a combination of excess precursor and byproduct gases exits the outlet port). The separated precursor gases are recycled to the reaction chamber, while the byproduct gases are sold or otherwise used. The hydrogen produced in this manner is "clean hydrogen" and can be sold commercially or burned to generate heat or electricity.

[0044] The heat carried by the gases or coolant exiting the reactor can be routed into a heat exchanger to heat the gases (e.g., if preheating of input precursors is desired to reduce the required input laser power or improve growth quality) and / or to generate electricity in combination with a suitable heat engine. The low-temperature heat extracted from the gases or coolant can be used in other processing steps applied to the 3D printed part. Such steps improve the net energy efficiency of growth and reduce manufacturing costs.

[0045] Other reactor variations similar to that shown in Figure 1 will be apparent to those skilled in the art. For example, the parts can be completely fixed within the reaction chamber, with only the focused beam being manipulated by the laser module, thereby controlling the spatiotemporal heating profile and, therefore, the growth. Alternatively, the entire laser module can be mounted on a motorized platform and moved, or the laser beam can be deflected, for example, with a fast steering mirror, or the focused light spot can be moved within the reactor by translating the emitter light source relative to a fixed lens.

[0046] It may also be useful to periodically or continuously remove deposits (e.g., pyrolytic deposits, contaminants, etc.) from optical surfaces. This can be achieved by injecting an appropriate etching gas into the reaction chamber to selectively etch away the deposits. The etching gas can be injected during a designated cleaning period or along with the precursor during fiber growth. The etching process may be facilitated by laser heating (e.g., due to deposits adhering to optical surfaces in the beam path) or plasma discharge (e.g., arc discharge, microwave plasma, etc.). Optical surfaces can also be mechanically cleaned by applying an appropriate etching solution to the surface or by other methods. It may also be useful to control the temperature of the optical surface during operation to mitigate deposit buildup, for example, by utilizing thermophoresis.

[0047] laser light source Laser module 104 N There are several suitable options for this, which can be used in combination with appropriate optical elements (e.g., lenses) to project an array of light spots or other focused shapes onto the stage 112 or onto the part 108 to be printed, thereby achieving a desired heating profile.

[0048] One laser module design is based on a semiconductor laser diode bar, shown in Figure 2. The diode bar 200 has an "emitter" 208N 204 (shaded for contrast), each of which emits a separate beamlet 212, typically in the near infrared. N Each emitter 208 constitutes a separate laser that emits a beam (shown as a cone). The length of the bar 200 (which is also the cavity length) is often on the order of one to several mm, although other lengths are possible. N The laser cavity (typically a Fabry-Perot cavity) is often formed by a cleaved facet of the semiconductor wafer 204 and may be coated to adjust the reflection coefficient. N is often selected to radiate from only one of the two faces of the semiconductor piece 204.

[0049] Each emitter 208 in the periodic direction of the array 200 N The width of each emitter 208 is typically much larger than a wavelength, e.g., 10-500 microns, while the height of each emitter (i.e., the vertical dimension in FIG. 2) is typically small enough to confine a single optical mode to that dimension. N Beam 212 emitted from N often have significant divergence (e.g., 40 degrees) and near-diffraction-limited beam quality along the vertical direction (i.e., "fast" axis), while the divergence along the periodic direction (i.e., "slow" axis) is much smaller (e.g., well below 10 degrees) but with poorer beam quality.

[0050] Adjacent emitter 208 N The spacing between emitters ("emitter spacing" in FIG. 2) is often tens to hundreds of microns, and the possible fill factor (i.e., the number of emitters 208 N The percentage of the total width of the diode bar 200 that is filled with the emitters 208 can vary widely. Each diode bar 200 is often about 1 cm wide in the periodic direction, although other widths are possible, and within this width various individual emitters 208 N There may be between 10 and 200 emitters (e.g., 10-200 emitters).N The width along the slow axis of the diode bars can also vary significantly between different diode bars.

[0051] The electrical-to-optical conversion efficiency of diode bars is often very high (e.g., 50-80% for the latest devices), an important feature for laser printing from gaseous sources, resulting in a low capital cost per watt compared to most other laser technologies. The maximum achievable optical power per emitter can vary, for example, between 0.01 W and 10 W, depending on design details, while the maximum total continuous-wave optical power per cm can be several hundred watts.

[0052] Using simple optical elements (e.g., low cost, few optical surfaces, and minimal light loss), it is possible to "reimage" the emitting surface of the diode bars to project an array of light spots onto or near the part being printed. Figure 3 shows one example of a laser diode module 300 that can be used to implement this concept, showing a view from the "front" (which includes the emitting surface of the individual semiconductor laser diode bars 304) and a view from the "side." In the side view, optional optical elements (e.g., lenses) 308 are shown attached to the module 300. These optical elements 308 can be aligned with individual emitters or rows of emitters.

[0053] The module comprises multiple diode bars 304 stacked together to form a two-dimensional array of emitters. The diode bars 304 are mounted in contact with a heat sink 308 of appropriate size (e.g., copper or other material with suitably high thermal conductivity), which in turn can be connected to a suitable structure for removing heat from the entire assembly (e.g., microchannels carrying coolant, a radiator for air cooling, etc.). The electrical pads of the diode bars 304 can be contacted using conventional means (e.g., wire bonds, conductive paste, solder, direct metal-to-metal contact, etc.). It may be advantageous to independently control the drive current, and therefore the emitted power, of different emitters in the array; to this end, individual electrical connections can be made to each individual laser diode (or group of laser diodes) in the array.

[0054] FIG. 4 illustrates how the laser diode modules described above can be used to project an array of spots on or near a printed part. In this illustration, a single laser diode module 400 having a two-dimensional array of emitters (as shown in FIG. 3) projects light collected by a single lens 404 to project an array of spots 408 onto a target substrate 412. For example, it may be advantageous to attach small optical elements (e.g., microlenses) to one or more of the emitters to adjust the emitter's beam divergence in the fast axis or to correct for off-axis spot distortion. While only one laser module 400 is shown in this side view, any number of laser modules can be arranged side-by-side in this manner along multiple axes.

[0055] The light emitting surface of each laser module 400 is re-imaged by one or more lenses 404 to project an array of light spots 408 into a reactor filled with appropriate precursor gases. Solid material is deposited near the light spots 408 at a rate that depends on the focused light power and other conditions. To grow a desired three-dimensional object, the array of light spots 408 can be moved relative to the part (e.g., by moving the part on a motorized stage, moving the emitter relative to a focusing lens, moving the entire laser module relative to the chamber, deflecting the light using motorized mirrors, etc.) and / or the light power of individual focused spots in the array can be temporally modulated (e.g., by modulating the drive current to individual laser diodes in the array) to create the appropriate spatiotemporal heating profile.

[0056] The specific parameters of each individual diode bar in the array can be selected appropriately to accommodate growth (e.g., geometric parameters such as emitter width and length can be increased to achieve higher power per emitter, and electrical parameters such as drive current can be used to fine-tune the light output) and heat dissipation requirements within the overall laser module assembly 400. As an example, to project a dense array of spots approximately 10 microns in diameter onto the growth surface, the laser module can include diode bars with emitter widths of 10 μm and emitter-to-emitter spacing of 40 μm. A short cavity length (e.g., approximately 1 mm) would be appropriate. The diode bars can be stacked on a thin copper heat sink, with approximately 1 mm spacing between emitter tips. The resulting emitter array can be reimaged using a simple 1× magnification lens into a deposition chamber filled with the appropriate precursor gases.

[0057] For example, it may be advantageous to use small optical elements (e.g., cylindrical or other lenses) to shape individual beamlets or columns of beamlets to correct for fast-axis divergence, adjust the shape of the focused light spot in the growth chamber, or address optical aberrations to improve the uniformity of the array of light spots. The use of microlenses to reduce fast-axis divergence can be particularly useful in reducing the required effective aperture of the lens re-imaging the emitter array, and can also be useful as a means of generating focused spots that are considered desirable as being circular rather than elliptical. It should be noted that spatial overlap of focused spots from adjacent emitters may or may not be advantageous, depending on details such as gas convection and diffusion and gas temperature profiles. With appropriate lens selection, both overlapping and non-overlapping arrangements at the focal plane can be achieved.

[0058] Diode bars suitable for this application may be contrasted with those configured for typical commercial applications (e.g., laser cutting and welding, optical pumping of other lasers, etc.). In typical commercial applications, it is often desirable to maximize the power and brightness per emitter. This can be achieved by increasing the area per emitter (i.e., increasing the emitter width and length). However, increasing the emitter length can increase optical losses and reduce the electrical-to-optical conversion efficiency of the laser, while increasing the emitter width can reduce beam quality along the slow axis.

[0059] In this application, the desired power per emitter can be sufficiently low (e.g., in some cases well below 1 W) to allow for the use of short cavity lengths to correspondingly improve laser efficiency and small emitter widths to correspondingly improve beam quality. Because this application does not necessarily require coupling light from the diode bar into an optical fiber, as is often the case in other situations, and relatively few optical elements can be used, the end-to-end efficiency (from electrons in the wall to photons focused on the target) can be very high (e.g., well above 50%), while the capital cost per watt of the overall laser system can be very low (e.g., due to minimal assembly requirements and the low cost of bare semiconductor chips). Furthermore, spectral requirements are also modest, allowing wavelengths to be selected that optimize desired system parameters (e.g., wall-plug efficiency, cost, etc.). For example, when depositing solid carbon from hydrocarbon precursor gases, most wavelengths in the near-infrared are well absorbed by previously deposited carbon surfaces and the various substrates (e.g., ceramics) used to initiate growth.

[0060] Another laser module design that creates a 2D array of emitters that can be used for 3D printing according to the scheme in Figure 4 is based on vertical-cavity surface-emitting lasers (VCSELs). VCSELs are individual laser emitters formed using a patterned semiconductor wafer, with the emitting aperture on one side of the wafer surface rather than on the cleaved wafer face. High-density arrays of VCSELs can be produced, with individual VCSELs emitting optical powers in the range of, for example, 1 mW to several hundred mW, with the laser wavelength typically in the near-infrared. The total optical power emitted per unit surface area of ​​a VCSEL array can be quite high (e.g., approximately 1 kW / cm). 2 ), and have high electrical-to-optical conversion efficiencies (e.g., greater than 50%). The capital cost per watt of VCSEL arrays can be very low.

[0061] Figure 5 shows an exemplary high-power laser module based on a VCSEL array. Its front view shows the emitting surface of a VCSEL array chip 500, which is part of a semiconductor wafer containing a two-dimensional array of individual VCSEL emitters 504. As shown in side view, the VCSEL array 500 is attached to a suitable heat sink 508 with appropriate electrical connections to form a laser module suitable for use in this application. The emitting surface of the VCSEL array faces away from the heat sink 508. A lens 512 (e.g., a microlens array) can be used to adjust the beam divergence and other beam characteristics.

[0062] As with laser diode bars, it may be advantageous to provide separate electrical contacts to individual VCSEL emitters. Alternatively (e.g., if fabricating contacts to individual VCSEL emitters is difficult due to geometric or other constraints), it may be advantageous to implement a “matrix-addressed” scheme in which individual contacts are fabricated to each row and column of the device. A matrix-addressed scheme may not allow power to be applied to any selected set of desired emitters. However, by applying appropriate voltages to the targeted columns and rows, it is possible to simultaneously power any set of emitters within a particular row, for example. Because VCSEL emitters can be modulated on very short timescales (e.g., sub-nanosecond timescales for some devices), while the thermal time constants associated with 3D printing reactions can be much longer, a matrix-addressed scheme allows for the use of time multiplexing to create appropriate heating profiles (e.g., by rapidly cycling through the rows while powering the appropriate columns).

[0063] It should be noted that other laser module designs are possible. Any suitably powerful light source can be used for 3D printing from the gas phase, so long as the apparatus includes a means for moving the light source around the object to be printed. For example, a light beam of appropriate intensity can be moved over the target by a fast steering mirror, or the part can be moved within and around a fixed light beam using a motorized stage. Furthermore, the methods and apparatus described herein (which enable efficient, spatiotemporally reconfigurable laser heating for deposition) can also be useful for 3D printing from liquid or solid precursors (e.g., the disclosed laser apparatus can be used to deposit solid carbon from liquid hydrocarbons, and the disclosed laser apparatus can be used to sinter solid powders).

[0064] Various other extensions and modifications of the above-described concepts may be advantageous. As one example, this laser-induced vapor 3D printing method may be combined with another 3D printing method (e.g., fused deposition modeling) to produce composite materials (e.g., solid carbon or boron deposited from the vapor phase via a laser as described herein co-deposited with a thermoplastic or other polymer deposited by fused deposition modeling). As another example, materials (e.g., polymers, aluminum, etc.) may be first processed via any suitable means (e.g., 3D printing, CNC milling) and then inserted into a laser-based 3D printer for additional material deposition (e.g., for additional reinforcement, to build a useful composite) and / or removal (e.g., by laser ablation).

[0065] As another extension of the laser-based 3D printing method described herein, precursor gases can be switched or continuously adjusted to tailor the material composition and properties of the deposited solid.

[0066] As another extension of the laser-based 3D printing methods described herein, by process steps that shut off the precursor gases and evacuate the chamber, or modify the input gas composition to specific species (capable of reacting with the solid material being deposited), intense laser radiation focused on the workpiece can result in subtraction rather than addition of solid material by driving removal processes such as ablation or oxidation. In this way, the shape of the workpiece can be intentionally laser trimmed in situ after or during the deposition sequence.

[0067] FIG. 6 shows the laser diode bar module 604 previously described for growing an array of fibers. N 6 shows an example of a laser reactor 600 using two laser modules 604. N Although only one laser module 604 is shown, any number of laser modules can be aligned along multiple axes in this manner. N includes a two-dimensional array of emitters (as shown in Figures 3 and 5), and each module 604 N The light from the light emitting surface of the lens 608 N The two-dimensional array of fibers 612 is collected by and re-imaged to project an array of light spots into a growth chamber filled with the appropriate precursor gases. N The fiber grows as gases pyrolyze within the hot spot formed by the focused laser beam. In this example, the focal plane of the light spot is fixed, and the fiber 612 is rotated as the fiber grows to keep the position of the growing fiber tip nearly constant in space. N It is necessary to steadily pull the array apart (to the right).

[0068] The specific parameters of the diode bars are selected to suit the growth (e.g., geometric parameters such as emitter width and length can be increased to achieve higher power per emitter, and electrical parameters such as drive current can be used to fine-tune the optical output) and to comply with heat dissipation requirements within the laser module assembly. As an example, to grow a dense array of fibers approximately 10 microns in diameter, the laser module can include diode bars with emitter widths of 10 μm and emitter-to-emitter spacings of 40 μm. Short cavity lengths (e.g., approximately 1 mm) may be suitable. The diode bars can be stacked on a thin copper heat sink, resulting in approximately 1 mm spacing between emitter tips. The resulting emitter array can be reimaged using a simple 1× magnification lens into a deposition chamber filled with the appropriate precursor gases.

[0069] For example, it may be advantageous to use small optical elements (such as cylindrical or other lenses) to shape individual beamlets or rows of beamlets to correct for fast axis divergence, adjust the shape of the light spot focused into the growth chamber, or address optical aberrations to improve the uniformity of the array of light spots. The use of microlenses to reduce fast axis divergence is particularly useful in reducing the required effective aperture of the lens that reimages the emitter array, and can also be useful as a means of producing circular rather than elliptical focused spots (although fibers grown with elliptical spots may be of interest in some circumstances, such as when producing fibers with mechanical anisotropy).

[0070] Figure 7 shows two other preferred laser module designs that can be used in combination with any light source (e.g., a fiber laser) that generates a light beam. In one design, an input light beam (e.g., a collimated light beam or a light beam shaped by top-hat optics) enters a microlens array, projecting an array of focused spots. This array is formed at an intermediate plane, as in the scheme in Figure 6, and then re-imaged into the fiber growth chamber using lenses. Alternatively, the microlens array can focus its light directly into the growth chamber.

[0071] The bottom embodiment of Figure 7 shows a collimated input beam 700' traversing a diffractive optical "beam splitter" element 708, which splits the incident input beam into multiple output beams with different propagation vectors. These individual beams can be focused (e.g., using a single lens 712) into a one- or two-dimensional array of spots. The power distributed to each beam is appropriately selected (e.g., so that all beams have approximately equal optical power).

[0072] Fiber Growth Chamber FIG. 8 illustrates one approach for growing fibers of limited length. A laser module 800 (e.g., any of the laser modules described above) projects a two-dimensional array of spots 804 into a growth chamber 808 that is appropriately pressurized (e.g., to optimize growth conditions) and flowing with appropriate precursor gases. The precursors are first pyrolyzed on a suitable substrate attached to a motorized platform 812. This platform 812 retracts at a rate consistent with fiber growth. The length of the fiber thus grown is limited by the movement of the platform. It should be understood that because the array of spots is two-dimensional, the array of fibers 816 extends both in and out of the plane of the drawing.

[0073] Depending on the characteristics of the grown fiber (e.g., stiffness, length), it may be advantageous to orient the chamber so that the motorized platform is pulled upward against gravity, thereby minimizing the possibility of the fiber flexing during growth and misaligning with the associated light spot. Furthermore, it may be advantageous to flow the precursor gas against gravity or at a sufficiently high flow rate to avoid solids deposition on the optical window and to keep as much free solids out of the light beam as possible. Minimizing relative vibrations between the laser module and the fiber end is very useful, and this can be achieved by using a smooth, low-vibration motorized platform, minimizing vibrations from the surrounding environment, minimizing turbulence in the precursor gas flow, etc. Alternatively, vibrations can be minimized by inverting the chamber so that the base of the growing fiber is immersed in a viscous fluid and confined within the chamber by gravity. In either case, it may be advantageous to use flowing precursor gases to carry heat away from the reactor, which may require a suitably high flow rate and / or appropriate cooling devices installed in the chamber (e.g., metal fins connected to a block with circulating coolant).

[0074] To further assist in stabilizing the position of the growing fiber end relative to the optical focus, an alignment plate 820 patterned with an array of through-holes, e.g., in the manner shown in FIG. 8, can be optionally used to hold the fiber end in the proper laser beam and mitigate effects such as fiber deflection due to vibration or gas flow. The alignment plate 820 can be fabricated using a material with suitable heat resistance, thermal expansion coefficient, thermal conductivity, etc., preferred materials include sapphire, aluminum nitride, silica, silicon, or other suitable materials. The alignment plate 820 can be fabricated using, for example, standard lithography techniques, laser cutting, water jet cutting, etc.

[0075] Figure 9 shows one embodiment of an alignment plate. The alignment plate has holes 900N through which the fiber 904 N 900. The holes can be precisely matched to the diameter of the grown fiber, as shown in the top left of the figure. Alternatively, looser through-holes can be used, which has advantages such as accommodating growth non-uniformities and mitigating clogging issues. For looser through-holes, it may be useful to deterministically position the fiber within the through-hole, for example, using electrostatic forces. The alignment plate can optionally include embedded electrodes 908, which can be used to position the fiber within the larger holes 900 using electrostatic forces, as shown in the bottom left of the figure. 2 Fiber 904 2 The electrodes can be used to appropriately deflect the electrodes. Suitable electrical connections (not shown) can be made to the electrodes.

[0076] For example, as also shown in FIG. 9, electrode 908 may be inserted through loose hole 900 2 The fiber 904 can be embedded in the alignment plate (e.g., using lithography techniques) in the vicinity of the fiber 904. 2 is sufficiently conductive, (e.g., using a conductive roller [not shown]) N Electrical contact can be made to the electrode 908 on the alignment plate and the fiber 904. N A voltage difference can be applied between the fiber 904 N Through hole 900 N The suction cup 100 can serve to draw the suction cup 100 into a well-defined position within the suction cup 100.

[0077] Alternatively, electrostatic forces can be used to center the fiber within the through-hole. To accomplish this, suitable electrodes can be patterned around the alignment plate hole or on another suitable structure, and a charge can be accumulated on the electrodes. Alternatively, the alignment plate can be made partially or entirely from an insulating material, with electrostatic charges embedded within it. By simultaneously maintaining a charge of the same sign as the charge accumulated on the alignment plate near the end of the growing fiber (e.g., by applying a voltage between the fiber and a suitable metal structure near the tip), a repulsive force can be created between the fiber and the edge of the through-hole. The electrodes used in any of the above schemes can be embedded in a suitable insulator to mitigate concerns such as electrical shorts and breakdown due to high voltages.

[0078] If tight alignment tolerances are required, the alignment plate can be aligned to the laser spot using, for example, micro- or nanopositioners (e.g., stepper motors, piezoelectric elements) and can utilize an active feedback scheme to maintain alignment (e.g., an optical camera can be used to observe the position of the spot on the alignment plate, and these images can be used to actively correct the position of either the alignment plate or the laser spot). It may also be advantageous to fabricate the alignment plate entirely or partially in situ (i.e., within the reaction chamber). For example, a laser spot can be projected onto a suitable photosensitive or heat-sensitive material (e.g., photoresist, thermoplastic, etc.) attached to the alignment plate. In this way, the exact position of the spot is imprinted in the material, which can then be subjected to appropriate processing (e.g., chemical etching, heat treatment, etc.), in situ or ex situ, to obtain the appropriate alignment plate.

[0079] The laser growth chamber presented here can be easily parallelized to achieve the growth throughput required for a commercial facility within a reasonable footprint. For example, consider building a world-scale carbon fiber growth facility producing 5,000 tonnes of solid carbon per year. A growth rate of 1 mm / s, a fiber diameter of 10 microns, and a density of 2 g / cm3 are all possible. 3 This would require approximately 1 billion fibers to be grown in parallel at any one time. Using the vertical growth concept disclosed herein, a 1000m 2 To achieve this in a modest footprint would require growing roughly one million fibers per square meter of floor space. Such spot densities can be achieved using the laser module concept described above.

[0080] For example, consider a laser diode bar module with an emitter width of 10 microns, a spacing between emitters of 40 microns, and a spacing of 1 mm between rows of emitters in the diode bar stack. This corresponds to a density of 20 million emitters per square meter, or 20 times the desired optical spot density, leaving sufficient margin for spacing between laser modules (e.g., to accommodate the diverging beams from the emitters within the effective aperture of the imaging lens). Furthermore, the power density requirement is reasonable: if the required power per optical spot is on the order of 0.1 W, then the required optical power density averaged over the entire facility is only about 10 W / cm. 2 which is orders of magnitude lower than the power density limits (e.g., set by thermal constraints) of the laser modules described herein.

[0081] The methods, systems, and devices described above are examples. In various configurations, various procedures or components may be omitted, substituted, or added, as appropriate. For example, in alternative configurations, methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to particular configurations may be combined in various other configurations. Different aspects or elements of the configurations may be combined in a similar manner. Also, technology evolves, and thus many of the elements are illustrative and do not limit the scope of the disclosure or the claims.

[0082] Embodiments of the present disclosure have been described above with reference to block diagrams and / or operational illustrations of methods, systems, and computer program products according to embodiments of the present disclosure. The functions / acts noted in the blocks may occur out of the order shown in any flowchart. For example, two blocks shown in succession may in fact be executed substantially concurrently, or the blocks may be executed in the reverse order, depending on the functions / acts involved. Additionally or alternatively, not all of the blocks shown in any flowchart need to be performed and / or executed. For example, if a given flowchart has five blocks containing functions / acts, only three of the five blocks may be performed and / or executed. In this example, any of the three of the five blocks may be performed and / or executed.

[0083] A statement that a value exceeds (or is greater than) a first threshold is equivalent to a statement that the value reaches or exceeds a second threshold that is slightly greater than the first threshold, e.g., the second threshold is one value higher than the first threshold within the resolution of the associated system. A statement that a value is less than (or is within) a first threshold is equivalent to a statement that the value is less than or equal to a second threshold that is slightly lower than the first threshold, e.g., the second threshold is one value lower than the first threshold within the resolution of the associated system.

[0084] Specific details are included in the description to provide a thorough understanding of example configurations (including implementations). However, configurations can be practiced without these specific details. For example, well-known circuits, processes, algorithms, structures, and techniques are shown without unnecessary detail to avoid obscuring the configurations. This description merely provides example configurations and does not limit the scope, applicability, or configuration of the claims. The above configuration description provides those skilled in the art with an enabling description for practicing the described technology. Various changes can be made in the function and arrangement of elements without departing from the spirit or scope of the present disclosure.

[0085] While several example configurations have been described, various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the present disclosure. For example, the elements described above may be components of larger systems, and other rules may take precedence over or otherwise modify the application of various embodiments or techniques of the present disclosure. Also, multiple steps may be performed before, during, or after the above elements are considered.

Claims

1. 1. A laser reactor for additive manufacturing, comprising: a reaction chamber having an inlet for receiving a gaseous source, an optical window, and a substrate; a laser module; the laser module is configured to emit laser light to heat the substrate through the window, thereby inducing a gas-to-solid deposition reaction in the vicinity of the heated substrate to convert gaseous precursors into at least one reaction product, the at least one reaction product forming at least a portion of a desired solid object supported by the substrate.

2. 10. The reactor of claim 1, A reactor wherein the substrate has at least one degree of freedom.

3. 10. The reactor of claim 1, A reactor wherein said at least one reaction product is a refractory material.

4. 10. The reactor of claim 1, A reactor wherein the laser module is movable and has at least one degree of freedom.

5. 10. The reactor of claim 1, The reactor, wherein the laser module includes a plurality of laser emitters, the reactor further comprising an optical mechanism configured to direct the output of each laser emitter onto a different region of the substrate.

6. 10. The reactor of claim 1, 10. The reactor of claim 9, further comprising: a first optical element configured to split the output of the laser module into multiple beams; and a second optical element configured to direct each beam onto a different region of the substrate.

7. 10. The reactor of claim 1, 10. The reactor, further comprising: a plurality of optical windows and a plurality of laser modules, each laser module in the plurality of laser modules configured to emit laser light into the chamber through an optical window in the plurality of optical windows, wherein the laser light of the plurality of laser modules is focused onto a region of the substrate.

8. 10. The reactor of claim 1, The reactor further comprises a mechanism for adjusting one or more of the pressure of the reactor, the temperature of the substrate, or the temperature of the reactants.

9. 10. The reactor of claim 1, The reactor further comprising an optical element for controlling the target of the emitted laser light within the reaction chamber.

10. 10. The reactor of claim 1, 10. The reactor of claim 9, further comprising a controller in communication with at least one sensor, the controller configured to control at least one of a power output, a deflection, or a position of the laser module based on information received from the at least one sensor.

11. 10. The reactor of claim 1, A reactor wherein the desired object is an array of carbon fibers.

12. 10. The reactor of claim 1, The reactor, wherein the laser module comprises an array of semiconductor laser diode bars or a vertical cavity surface emitting laser array.

13. 10. The reactor of claim 1, 10. The reactor, further comprising: a controller in communication with at least one sensor, the controller configured to control a position of the substrate based on information received from the at least one sensor.

14. 10. The reactor of claim 1, A reactor wherein the desired object is an array of silicon carbide fibers.

15. 1. A method of additive manufacturing, comprising: providing a reaction chamber, said reaction chamber having an inlet for receiving a gaseous source, an optical window, and a substrate; introducing a gaseous source into the reaction chamber via the inlet; and heating the substrate through the optical window by applying laser light to thereby induce a gas-to-solid deposition reaction in the vicinity of the heated substrate to convert gaseous precursors into at least one reaction product that forms at least a portion of a desired object supported on the substrate.

16. 16. The method of claim 15, The method further comprising moving the substrate in at least one degree of freedom to form the desired object.

17. 16. The method of claim 15, The method further comprising the step of moving a laser beam in at least one degree of freedom to form the desired object.

18. 16. The method of claim 15, The method further comprising adjusting one or more of the pressure of the reaction chamber, the temperature of the reactants, or the temperature of the substrate.

19. 16. The method of claim 15, The method, wherein the reaction chamber further comprises at least one sensor, the method further comprising controlling at least one of a power, a deflection, or a position of a laser light based on information received from the at least one sensor.

20. 16. The method of claim 15, The method of claim 1, wherein the at least one reaction product is a refractory material.

21. 16. The method of claim 15, The method of claim 1, wherein the desired object is an array of carbon fibers.

22. 16. The method of claim 15, The method, wherein the reaction chamber further comprises at least one sensor, the method further comprising controlling the position of the substrate based on information received from the at least one sensor.

23. 16. The method of claim 15, The method, wherein the desired object is an array of silicon carbide fibers.

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