Method for forming geometrically-complex core assemblies using dissolvable, 3d-printed molds and process for forming fluidic modules using such core assemblies

Abstract

A process for forming a fluidic module for a flow reactor is disclosed. The process comprises positioning a core assembly comprising cores within a mold. The cores comprise a first channel core with a first shape. The process further comprises covering the core assembly with a volume of binder-coated particles and then pressing the mold with the core assembly and the volume of the particles therein to form a pressed body. The process further comprises heating the pressed body to remove the cores of the core assembly. Thereafter, the process comprises sintering the pressed body to form the fluidic module having fluid channels extending therethrough such that each fluid channel corresponds, respectively, to the cores removed during the heating.

Description

METHOD FOR FORMING GEOMETRIC ALLY-COMPLEX CORE ASSEMBLIES USING DISSOLVABLE, 3D-PRINTED MOLDS AND PROCESS FOR FORMING FLUIDIC MODULES USING SUCH CORE ASSEMBLIESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application No. 63 / 603,260 filed November 28, 2023, the content of which is incorporated herein by reference in its entirety.FIELD

[0002] The present disclosure relates to fabrication of parts using lost material approaches. More particularly, the present disclosure relates to methods for forming geometrically-complex core assemblies using dissolvable, three-dimensional (3D) printed molds and processes for forming fluidic modules using such core assemblies.BACKGROUND

[0003] Ceramic material is a desirable material for fluidic modules for flow chemistry production and / or laboratory work and for structures for other technical uses. Silicon carbide ceramic (SiC) is particular well-suited for fluidic module applications. SiC has relatively high thermal conductivity, which is useful in performing and controlling endothermic or exothermic reactions. SiC has good physical durability and thermal shock resistance. SiC also possesses extremely good chemical resistance. But these properties, combined with high hardness and abrasiveness, make the practical production of SiC structures with internal features, such as SiC flow modules with tortuous internal passages or channels, challenging.

[0004] Flow reactors and other structures formed of SiC and other ceramics have been fabricated recently by this Applicant using a variation of the “lost-material” approach. This approach is generally depicted with reference to FIGS. 17-19. A positive channel mold 904 formed from a heat-removable material, as shown in FIG. 17, is incorporated within a volume of binder-coated ceramic powder. The ceramic powder with the positive channel mold inside is then pressed to form a green ceramic body 908 in a desired shape, such as the plate-like shape illustrated in FIG. 18. The green ceramic body 908 is shown partially transparent in FIG. 18 to illustrate the positive channel mold 904 disposed therein. The green ceramic body908 thereafter undergoes further processing, such as demolding (e.g., to remove the positive channel mold 904), debinding, and sintering, to form a sintered ceramic body 1000 with one or more smooth-surfaced fluid channels C extending therethrough, as shown in FIG. 19. The sintered ceramic body 1000 is shown partially transparent in FIG. 19 to illustrate the positive channel mold 904 removed and the volume previously occupied by the positive channel mold forming the fluid channels C.

[0005] While different approaches have been considered for shaping the positive channel molds, most of these approaches are limited to formation of two-dimensional positive channel molds and ceramic bodies with corresponding two-dimensional fluid channels. Consequently, it would be advantageous to develop processes that enable fabrication of more complex channel molds, such as channel molds with complex three-dimensional geometries. It would be further advantageous to develop processes that use such complex channel molds to form ceramic fluidic modules with fluid channels having corresponding complex three-dimensional geometries.SUMMARY

[0006] The following summary is a brief description of certain aspects of the present disclosure. The summary should not be considered as limiting of the breadth, scope, or applicability of the present disclosure.

[0007] According to aspect (1), a method for forming a core assembly for use with a pressforming fabrication process is provided. The method comprises: forming a one-piece mold that defines one or more cavities therein using a dissolvable material, the one or more cavities comprising a first cavity configured to negatively define a first shape of a first channel core of the core assembly to be formed; molding the core assembly inside the mold, the core assembly formed from a heat-removeable material; and dissolving the dissolvable material of the mold after the molding to expose the core assembly.

[0008] According to aspect (2), the method of aspect (1) is provided, wherein the first shape comprises a first profile swept along a first path that defines a three-dimensional curve along a majority of a length of the first path between opposed ends thereof through the mold.

[0009] According to aspect (3), the method of aspect (1) or aspect (2) is provided, wherein forming the one-piece mold comprises three-dimensional printing the mold using the dissolvable material.

[0010] According to aspect (4), the method of aspect (2) or aspect (3) is provided, wherein the one or more cavities comprise a second cavity configured to negatively define a second shape of a second channel core of the core assembly to be formed, the second shape comprising a second profile swept along a second path that defines a three-dimensional curve between opposed ends thereof through the mold, the second path at least partially intertwined and substantially coextensive with the first path.

[0011] According to aspect (5), the method of aspect (4) is provided, wherein the first path is configured as a first helical path that revolves for multiple turns about a longitudinal axis through the mold.

[0012] According to aspect (6), the method of aspect (5) is provided, wherein the second path is configured as a second helical path that revolves for multiple turns about the longitudinal axis through the mold.

[0013] According to aspect (7), the method of aspect (6) is provided, wherein the multiple turns of the second helical path alternate with the multiple turns of the first helical path.

[0014] According to aspect (8), the method of any one of aspects (4) to (7) is provided, wherein the first cavity and the second cavity are fluidically discrete within a first axial segment of the mold.

[0015] According to aspect (9), the method of aspect (8) is provided, wherein the one or more cavities comprise a fourth cavity configured to negatively define a fourth shape of a first connecting core of the core assembly to be formed, the fourth cavity fluidically connecting the first cavity and the second cavity within a second axial segment of the mold, the second axial segment adjacent to a first end of the first axial segment.

[0016] According to aspect (10), the method of aspect (9) is provided, wherein the one or more cavities comprise a fifth cavity configured to negatively define a fifth shape of a second connecting core of the core assembly to be formed, the fifth cavity fluidically connecting the first cavity and the second cavity within a third axial segment of the mold, the third axial segment adjacent to a second end of the first axial segment.

[0017] According to aspect (11), the method of aspect (8) is provided, wherein the one or more cavities comprise a third cavity configured to negatively define a third shape of a third channel core of the core assembly to be formed, the third shape comprising a third profile swept along a third path between opposed ends thereof through the mold.

[0018] According to aspect (12), the method of aspect (11) is provided, wherein the first cavity, the second cavity, and the third cavity are fluidically discrete within the first axial segment of the mold.

[0019] According to aspect (13), the method of aspect (12) is provided, wherein the one or more cavities comprise a fourth cavity configured to negatively define a fourth shape of a first connecting core of the core assembly to be formed, the fourth cavity fluidically connecting the first cavity, the second cavity, and the third cavity within a second axial segment of the mold, the second axial segment adjacent to a first end of the first axial segment.

[0020] According to aspect (14), the method of aspect (13) is provided, wherein the one or more cavities comprise a fifth cavity configured to negatively define a fifth shape of a second connecting core of the core assembly to be formed, the fifth cavity fluidically connecting the first cavity, the second cavity, and the third cavity within a third axial segment of the mold, the third axial segment adjacent to a second end of the first axial segment.

[0021] According to aspect (15), the method of any one of aspects (1) to (14) is provided, wherein molding the core assembly comprises: filling the one or more cavities of the mold with the heat-removeable material in liquid form at a material temperature, maintaining a mold temperature of the mold during the filling, the mold temperature maintained in a range of from about 5 °C less than the material temperature to about 50 °C less than the material temperature, and cooling the mold and the heat-removeable material after the filling to solidify the heat- removeable material before the dissolving.

[0022] According to aspect (16), the method of aspect (15) is provided, wherein: the mold, at an axial end thereof, comprises a reservoir that is fluidically connected to the one or more cavities of the mold, and cooling the mold and the heat-removeable material comprises maintaining a volume of the heat-removeable material in the reservoir at a reservoir temperature that is higher than the material temperature of the heat-removeable material within the one or more cavities during the cooling.

[0023] According to aspect (17), the method of aspect (16) is provided, wherein the mold is configured to define the reservoir using the dissolvable material.

[0024] According to aspect (18), the method of aspect (16) is provided, wherein the reservoir is formed separately from the mold and configured to be releasably attached to the mold.

[0025] According to aspect (19), the method of any one of aspects (1) to (18) is provided, wherein the dissolvable material comprises one or more of polyvinyl alcohol (PVA) and high- impact polystyrene (HIPS).

[0026] According to aspect (20), the method of any one of aspects (1) to (19) is provided, wherein dissolving the dissolvable material comprises submerging the mold in one or more of water, a solvent, and an acid.

[0027] According to aspect (21), a process for forming a fluidic module for a flow reactor is provided. The process comprises: positioning a one-piece core assembly comprising one or more cores within a mold, the one or more cores comprising a first channel core with a first shape; covering the core assembly with a volume of binder-coated particles; pressing the mold with the core assembly and the volume of the particles therein to form a pressed body; heating the pressed body to remove the one or more cores of the core assembly; and sintering the pressed body to form the fluidic module having one or more fluid channels extending therethrough, each fluid channel corresponding, respectively, to the one or more cores removed during the heating.

[0028] According to aspect (22), the process of aspect (21) is provided, wherein the first shape comprises a first profile swept along a first path that defines a three-dimensional curve for a majority of a length of the first path between opposed ends thereof.

[0029] According to aspect (23), the process of aspect (22) is provided, wherein the one or more cores comprise a second channel core with a second shape, the second shape comprising a second profile swept along a second path that defines a three-dimensional curve between opposed ends thereof, the second channel core at least partially intertwined and substantially coextensive with the first channel core.

[0030] According to aspect (24), the process of aspect (23) is provided, wherein the first path is configured as a first helical path that revolves about a longitudinal axis such that the first channel core has a plurality of first turns.

[0031] According to aspect (25), the process of aspect (24) is provided, wherein the second path is configured as a second helical path that revolves about the longitudinal axis such that the second channel core has a plurality of second turns.

[0032] According to aspect (26), the process of aspect (25) is provided, wherein the second turns of the second channel core alternate with the first turns of the first channel core.

[0033] According to aspect (27), the process of any one of aspects (22) to (26) is provided, wherein, prior to the heating, the first channel core and the second channel core are spaced from one another so as to be physically discrete within a first axial segment of the core assembly.

[0034] According to aspect (28), the process of aspect (27) is provided, wherein, prior to the heating, the one or more cores comprise a first connecting core configured to connect the first channel core and the second channel core within a second axial segment of the core assembly so as to maintain positions of the first channel core and the second channel core relative to one another during the positioning, the covering, and the pressing, the second axial segment disposed adjacent to a first end of the first axial segment.

[0035] According to aspect (29), the process of aspect (28) is provided, wherein covering the core assembly with the volume of particles comprises contacting the first connecting core to maintain a position of the core assembly relative to the mold during the covering.

[0036] According to aspect (30), the process of aspect (29) is provided, wherein, prior to the heating, the one or more cores comprise a second connecting core configured to connect the first channel core and the second channel core within a third axial segment of the core assembly and maintain positions of the first channel core and the second channel core relative to one another during the positioning, the covering, and the pressing, the third axial segment disposed adjacent to a second end of the first axial segment.

[0037] According to aspect (31), the process of aspect (30) is provided, wherein covering the core assembly with the volume of particles comprises contacting the second connecting core to maintain the position of the core assembly relative to the mold during the covering.

[0038] According to aspect (32), the process of aspect (31) is provided, further comprising removing one or more of the first connecting core and the second connecting core after the pressing and before the heating.

[0039] According to aspect (33), the process of aspect (27) is provided, wherein the one or more cores comprise a third channel core with a third shape, the third shape comprising a third profile swept along a third path between opposed ends thereof.

[0040] According to aspect (34), the process of aspect (33) is provided, wherein, prior to the heating, the first channel core, the second channel core, and the third channel core are spaced from one another so as to be physically discrete within the first axial segment of the core assembly.

[0041] According to aspect (35), the process of aspect (34) is provided, wherein, prior to the heating, the one or more cores comprise a first connecting core configured to connect the first channel core, the second channel core, and the third channel core within a second axial segment of the core assembly and maintain positions of the first channel core, the second channel core, and the third channel core relative to one another during the positioning, the covering, and the pressing, the second axial segment disposed adjacent to a first end of the first axial segment.

[0042] According to aspect (36), the process of aspect (35) is provided, wherein covering the core assembly with the volume of particles comprises contacting the first connecting core to maintain a position of the core assembly relative to the mold during the covering.

[0043] According to aspect (37), the process of aspect (36) is provided, wherein, prior to the heating, the one or more cores comprise a second connecting core configured to connect the first channel core, the second channel core, and the third channel core within a third axial segment of the core assembly and maintain positions of the first channel core, the second channel core, and the third channel core relative to one another during the positioning, the covering, and the pressing, the third axial segment disposed adjacent to a second end of the first axial segment.

[0044] According to aspect (38), the process of aspect (37) is provided, wherein covering the core assembly with the volume of particles comprises contacting the second connecting core to maintain the position of the core assembly relative to the mold during the covering.

[0045] According to aspect (39), the process of aspect (38) is provided, further comprising removing one or more of the first connecting core and the second connecting core after the pressing and before the heating.

[0046] According to aspect (40), the process of any one of aspects (28) to (39) is provided, wherein the first fluid channel and the second fluid channel have common walls that define a minimum gap therebetween, the minimum gap selected from a range of gaps between 0.1 mm and 10 mm.

[0047] According to aspect (41), the process of aspect (40) is provided, wherein the minimum gap has a maximum deviation of ± 5% over at least 50% of the coextensive portions of the first fluid channel and the second fluid channel.

[0048] According to aspect (42), the process of any one of aspects (21) to (41) is provided, wherein the particles are selected from glass, glass ceramic, ceramic, and metal.

[0049] According to aspect (43), the process of aspect (42) is provided, wherein the particles are binder-coated ceramic powder.

[0050] According to aspect (44), the process of any one of aspects (21) to (43) is provided, wherein the mold is a flexible mold, and the pressing comprises isostatically pressing the flexible mold with the core assembly and the volume of the particles therein to form a pressed body.BRIEF DESCRIPTION OF THE DRAWINGS

[0051] FIGS. 1A and IB are a perspective view and a cross-sectional view, respectively, of a dissolvable, 3D-printed mold configured to form a geometrically-complex core assembly;

[0052] FIGS. 2A and 2B are a perspective view and a cross-sectional view, respectively, of the mold of FIGS. 1A and IB filled with a heat-removable material in liquid form;

[0053] FIG. 2C is a cross-sectional view of an axial end region of the mold 200 of FIG. 2B enlarged to show features of a reservoir;

[0054] FIGS. 3A and 3B are a perspective view and a cross-sectional view, respectively, of the core assembly after the mold has been dissolved;

[0055] FIGS. 4-6 are individual perspective views of the different channel cores of the core assembly of FIGS. 3A and 3B;

[0056] FIG. 7 is perspective view that shows the different channel cores of FIGS. 4-6 nested into a single core assembly equivalent the core assembly of FIGS. 3 A and 3B;

[0057] FIGS. 8 A and 8B are a top view and a cross-sectional view, respectively, of the core assembly of FIGS. 3 A and 3B positioned within a flexible mold and covered with a volume of binder-coated particles in preparation for an isostatic pressing process;

[0058] FIG. 9 is a cross-sectional representation of an embodiment of an apparatus configured to perform an isostatic pressing process using the flexible mold of FIGS. 8A and 8B;

[0059] FIG. 10 is a cross-sectional representation of a pressed body comprising the core assembly after the isostatic pressing process of FIG. 9;

[0060] FIG. 11 is a cross-sectional representation of a step of the process in which axial end regions of the pressed body of FIG. 10 are separated from an axial central region;

[0061] FIG. 12 is a cross-sectional representation of a step of the process in which the pressed body is heated to remove the heat-removable material and expose fluid channels therein;

[0062] FIG. 13 is a cross-sectional representation of a step of the process in which the pressed body is sintered to form a sintered body;

[0063] FIGS. 14A-14D are digital images that illustrate process steps for making a core assembly Example 1;

[0064] FIGS. 15A-15C are digital images of different strategies to control mold temperature during filling of the mold according to Example 2;

[0065] FIG. 16 is a digital image of a cross-section of a silicon carbide (SiC) fluidic module fabricated using the core assembly forming method and the fluidic module forming process described herein; and

[0066] FIGS. 17-19 are schematic representations of a lost material approach for fabricating fluidic modules using binder-coated ceramic powder.DETAILED DESCRIPTION

[0067] For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the disclosure is thereby intended. It is further understood that the present disclosure includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles disclosed herein as would normally occur to one skilled in the art to which this disclosure pertains.

[0068] As used herein, the term “and / or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0069] In this document, relational terms, such as first and second, top and bottom, and the like, are used solely to distinguish one entity or action from another entity or action, withoutnecessarily requiring or implying any actual such relationship or order between such entities or actions.

[0070] As used herein, the term “about” means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and / or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. When the term “about” is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to. Whether or not a numerical value or end-point of a range in the specification recites “about,” the numerical value or end-point of a range is intended to include two embodiments: one modified by “about,” and one not modified by “about.” It will be further understood that the end-points of each of the ranges are significant both in relation to the other end-point, and independently of the other end-point.

[0071] The terms “substantial,” “substantially,” and variations thereof as used herein, unless defined elsewhere in association with specific terms or phrases, are intended to note that a described feature is equal or approximately equal to a value or description. For example, a “substantially planar” surface is intended to denote a surface that is planar or approximately planar. Moreover, “substantially” is intended to denote that two values are equal or approximately equal. In some embodiments, “substantially” may denote values within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0072] Directional terms as used herein — for example up, down, right, left, front, back, top, bottom, above, below, and the like — are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0073] As used herein the terms "the," "a," or "an," mean "at least one," and should not be limited to "only one" unless explicitly indicated to the contrary. Thus, for example, reference to "a component" includes embodiments having two or more such components unless the context clearly indicates otherwise.

[0074] A method for forming a core assembly 300 for use with a press-forming fabrication process is now described with reference to FIGS. 1 A, IB, 2A, 2B, 3A, 3B, and 4-7. As used herein, the term “press-forming fabrication process” refers to any process in which a portion of the process comprises depositing any heat-formable material (e.g., glass, glass ceramic, ceramic, metal, etc.) in a solid, flowable form (e.g., particles, powder, beads, etc.) andoptionally other additives (e.g., lubricants, binders, etc.) into a press and thereafter pressing or compacting the deposited material and optional additives into a pressed body configured to sufficiently retain its (green) shape for further processing (e.g., debinding, sintering, etc.). In an exemplary embodiment, the core assembly 300 is configured for use with a ceramic pressforming fabrication process in which ceramic material, such as ready-to-press silicon carbide (“RTP SiC” or “SiC”), is deposited into the press and thereafter pressed into a pressed body for further processing.

[0075] Referring now to FIGS. 1 A and IB, the method includes forming a one-piece mold 200 that defines one or more cavities 204 therein. FIG. 1A is a perspective view of an embodiment of the mold 200. FIG. IB is a cross-sectional view of the mold 200 taken along a longitudinal axis 208 of the mold 208. The mold 200 is formed using a dissolvable material. For example, the mold 200 may have a plurality of walls 202 that define the one or more cavities 204, and the walls are formed from the dissolvable material. In embodiments, the dissolvable material comprises polyvinyl alcohol (PVA) or PVA filaments, high-impact polystyrene (HIPS), and / or other materials that are similarly formable and dissolvable. In embodiments, forming the one-piece mold 200 comprises three-dimensional (3D) printing the mold 200 using the dissolvable material. Various 3D printing techniques can be used to form the mold 200, such as fused deposition modeling (FDM) or digital light processing (DLP). In an exemplary embodiment, the mold 200 is formed from PVA filaments that are 3D printed at a temperature in a range of from about 200 °C to about 230 °C, from about 205 °C to about 225 °C, from about 210 °C to about 220 °C, or from about 212 °C to about 218 °C.

[0076] The one or more cavities 204 of the mold 200 are configured to negatively define the shape(s) of one or more cores 304 of the core assembly 300 to be formed by the method. The one or more cores 304 of the core assembly 300 are described later in this disclosure with reference to FIGS. 3 A, 3B, and 4-7. In embodiments that employ 3D printing, the 3D printing techniques used to form the mold 200 are easily adaptable to provide different numbers and geometries of the one or more cavities 204 so as to correspondingly form different numbers and geometries of the one or more cores 304. The disclosure of specific numbers and geometries of the cavities 204 of the mold 200 and the corresponding cores 304 of the core assembly 300 is meant to be generally illustrative and not intended to limit the scope of this disclosure to only those specific configurations. Details of the cavities 204 and the cores 304 are described hereinbelow.

[0077] FIGS. 2A and 2B illustrate a molding step of the method. FIGS. 2A and 2B are perspective and cross-sectional views of the mold 200, respectively, similar to the views of FIGS. 1A and IB. The method further comprises molding the core assembly 300 inside the mold 200. The core assembly 300 is formed from a heat-removeable material 308. As used herein, a “heat-removable material” refers to a low melting point material having a melting point that is lower than the dissolvable material of the mold 200. When in solid form, the heatremovable material can be capable of defining an outer surface with a smooth exterior (e.g., low surface roughness). When in solid form, the heat-removable material can have compression and / or release curves similar to the material disclosed in International Application Publication No. W02022204019A1, published on September 29, 2022, the disclosure of which is herein incorporated by reference in its entirety. In embodiments, the heat-removable material is removed by heating the material above its melting point so the material can be removed in liquid form. In embodiments, useful heat-removable materials may include waxes with suspended particles such as carbon and / or inorganic particles, rosin containing waxes, high modulus brittle thermoplastics, and organic solids suspended in organic fats such as cocoa powder in cocoa butter — or combinations of these the heat removable — as described in International Application Publication No. W02022204019A1. In some embodiments, such as when the heat-removable material comprises chocolate (e.g., cocoa powder suspended in cocoa butter), after pressing (as described later in this disclosure), the cocoa butter is pressed out of the chocolate and into surrounding ceramic particle (e.g., SiC powder), leaving an organic material that chars in debinding and is removed via flowing air at 800 °C.

[0078] In embodiments, molding the core assembly 300 comprises filling the one or more cavities 204 of the mold 200 with the heat-removeable material in liquid form 308a. In particular, the heat-removable material is heated to be in liquid form 308a. In embodiments, the heat-removable material 308 is a wax that is heated to be in liquid form 308a. The wax can be heated to a material temperature in a range of from about 80 °C to about 160 °C, or from 100 °C to about 140 °C, or from about 110 °C to about 130 °C for the filling. In embodiments, the heat-removable material 308 is any material that satisfies the definition of heat-removable material as used herein.

[0079] In embodiments, molding the core assembly 300 comprises maintaining a mold temperature of the mold 200 during the filling. In embodiments, the mold temperature is maintained in a range of from about 5 °C less than the material temperature to about 50 °C less than the material temperature. In embodiments, maintaining the mold temperature of the mold200 during the filling comprises preheating the mold 200 to the mold temperature prior to the filling. Managing the mold temperature of the mold 200 before and / or during the filling can help reduce the quantity of small air bubbles that can form in the heat-removable material 308 and can increase homogeneity of the core assembly 300.

[0080] After the filling step, the method further includes cooling the heat-removeable material 308 in the mold 200 to solidify the heat-removeable material before a dissolving step. The dissolving step is described later in this disclosure with reference to FIGS. 3A and 3B. In embodiments, the cooling can be active cooling or passive cooling. In embodiments, the cooling can be controlled to improve the uniformity and / or integrity of the solidified heatremovable material 308b (e.g., small bubbles are minimized or not present in the solidified material after the cooling). In embodiments, one or more insulation layers can be positioned around the mold 200 during the filling. In embodiments, the mold 200 can be preheated before the filling. The insulation layers and / or the preheating can be used to control the temperature during the filling of the mold 200 and during the cooling of the mold 200.

[0081] Referring now to FIG. 2C, an axial end region of the mold 200 of FIG. 2B (e.g., the region denoted by dashed box 222) is enlarged to show additional features of the method. In embodiments, a reservoir 224 is disposed at an axial end of the mold 200. It was discovered during experiments that the heat-removeable material 308 was retracting within the mold 200 during the cooling. Such retraction may be undesirable to the integrity and / or dimensional accuracy of the one or more cores 304 of the core assembly 300 to be formed by the method. To counteract such retraction, the reservoir 224 can be implemented as described herein.

[0082] The reservoir 224 is configured to be fluidically connected to the one or more cavities 204 of the mold 200. In embodiments, the step of cooling the mold 200 comprises maintaining a volume of the heat-removeable material 308 in the reservoir 224 at a reservoir temperature that is higher than a material temperature of the heat-removeable material 308 within the one or more cavities 204 during the cooling. In embodiments, for example, the heat- removeable material in liquid form 308a is maintained at a material temperature of about 120 °C during the filling of the one or more cavities 204 in the mold 200. In such embodiments, the heat-removable material in liquid form 308a contained within the reservoir 224 can be heated to a reservoir temperature that is higher than the material temperature, such as 1 °C, 2 °C, 3 °C, 4 °C, 5 °C, 6 °C, 7 °C, 8 °C, 9 °C, or 10 °C higher than the material temperature. In embodiments, the difference between the reservoir temperature and the material temperature is substantially maintained after the filling and during the cooling of the heat-removeable material308. In embodiments, the reservoir temperature can be controlled separately from the material temperature by using thermocouples and a wrap-around heating element disposed proximate to the reservoir 224.

[0083] In some embodiments, the mold 200 is configured to define the reservoir 224 using the dissolvable material. In other embodiments, the reservoir 224 is formed separately from the mold 200 and configured to be releasably attached to the mold 200. For example, when formed separately from the mold 200, the reservoir 224 can be attached to the mold 200 during the filling with the heat-removeable material in liquid form and then removed during or after the cooling. The reservoir 224 can be reusable when formed separately from the mold 200. The reservoir 224 can be formed from a material different than the dissolvable material when the reservoir 224 is formed separately from the mold 200. In embodiments, the reservoir 224 can be formed separately from the mold 200 using 3D printing techniques. Further details of the reservoir 224 are described hereinbelow.

[0084] FIGS. 3A and 3B, when viewed in connection with FIGS. 2A and 2B, illustrate a dissolving step of the method. The method further includes dissolving the dissolvable material of the mold 200 after the molding to expose the core assembly 300. FIGS. 3A and 3B are perspective and cross-sectional views, respectively, similar to the views of FIGS. 2A and 2B except that the mold 200 (e.g., the walls 202 formed from the dissolvable material) is completely dissolved and only the core assembly 300 (e.g., the solidified heat-removable material 308b) remains. In embodiments, dissolving the dissolvable material comprises submerging the mold 200 in water, such as when the dissolvable material comprises PVA. In embodiments in which the mold 200 comprises HIPS, dissolving the dissolvable material comprises submerging the mold 200 in an acidic liquid, such as d-Limonene.

[0085] In embodiments, depending on the dissolution rate of the dissolvable material of the mold 200 in the water or other solvent (e.g., depending on the dissolvable material of the mold 200), the cooling step and the dissolving step can be at least partially combined. In other words, if the dissolution rate is relatively slow and solidification rate of the heat-removable material in liquid form 308a is relatively fast while the mold 200 is submerged in the water, the steps can be executed concurrently.

[0086] Referring again to FIGS. 1 A and IB, embodiments of the one or more cavities 204 are shown. The one or more cavities 204 are described with additional reference to the one or more cores 304 shown in FIGS. 3 A, 3B, and 4-7. The one or more cavities 204 comprise a firstcavity 204a configured to negatively define a first shape of a first channel core 304a (FIGS. 3A, 3B, 4, and 7) of the core assembly 300 to be formed by the method. The first shape comprises a first profile 312a (FIGS. IB, 3B, and 4) swept along a first path that defines a three-dimensional curve along a majority of a length of the first path between opposed ends thereof through the mold 200. As best described with reference to FIGS. 3A and 4, the first cavity 204a can optionally branch into two sub-cavities at one of the opposed ends so as to negatively define a pair of input stubs 306 at one end of the first channel core 304a.

[0087] The one or more cavities 204 further comprise a second cavity 204b configured to negatively define a second shape of a second channel core 304b (FIGS. 3A, 3B, 5, and 7) of the core assembly 300 to be formed by the method. The second shape comprises a second profile 312b (FIGS. IB, 3B, and 5) swept along a second path that defines a three-dimensional curve between opposed ends thereof through the mold 200. As best shown in FIGS. 3 A and 7 with reference to the first channel core 304a and the second channel core 304b (negatively) defined by the first cavity 204a and the second cavity 204b, respectively, the second path of the second channel core 304b is at least partially intertwined and substantially coextensive with the first path of the first channel core 304a.

[0088] In general, geometrically complex shapes that follow three-dimensional curves, such as the shapes of the first and second channel cores 304a, 304b described herein, are challenging to fabricate in terms of accuracy, repeatability, scalability, and economics (e.g., costs). Moreover, some geometrically complex shapes simply cannot be fabricated by casting / molding or subtractive manufacturing techniques (e.g., machining) due to features that revolve onto themselves and / or intertwined features that substantially obstruct line of site in multiple axes. The method disclosed herein enables fabrication of a core assembly 300 with one or more cores 304 that have geometrically complex shapes. Additionally, since the core assembly 300 is formed from a heat-removable material, the core assembly can be incorporated as a sacrificial mold in a separate press-forming fabrication process.

[0089] In embodiments, such as shown in FIGS. 3 A, 3B, 4, and 7, the first path (e.g., along which the first channel core 304a is (negatively) defined by the first cavity 204a) is configured as a first helical path that revolves for multiple turns 316a about the longitudinal axis 208 through the mold 200. In embodiments, such as shown in FIGS. 3A, 3B, 5, and 7, the second path (e.g., along which the second channel core 304b is (negatively) defined by the second cavity 204b) is configured as a second helical path that revolves for multiple turns 316b about the longitudinal axis 208 through the mold 200. In embodiments, the multiple (second) turnspath.

[0090] Although the first path and the second path are depicted as helical paths in some embodiments, the first path and the second path should not be limited to such path geometries. Instead, the first path can have any complex geometry that defines a three-dimensional curve along a majority of its length through the mold 200. Similarly, the second path can have any complex geometry that defines a three-dimensional curve through the mold 200 and that is at least partially intertwined and substantially coextensive with the first path. According to an aspect, the term “three-dimensional curve” can mean that the path (e.g., the centroid of a geometric shape along its extent) is mostly or predominantly arcuate (e.g., not linear) along most or the entirety of the length of the path. According to an aspect, “three-dimensional curve” can mean that the path (e.g., the centroid of a geometric shape along its extent) includes arcuate and linear sections along the length of the path as long as the path is continuous and at least some portions of the path extend out of a two-dimensional plane. For example, paths that include path portions that lie within two or more planes but are connected via further path portions that extend between the two more planes can constitute a three-dimensional curve. The language of the claims will determine the meaning of the term “three-dimensional curve.”

[0091] In embodiments, the first cavity 204a and the second cavity 204b are fluidically discrete within a first axial segment 212 (FIGS. IB and 3B) of the mold 200 along the longitudinal axis 208. As used herein, the term “fluidically discrete” means that fluid, such as the heat-removeable material in liquid form 308a, does not communicate between the indicated cavities along any portion of the mold 200 that comprises the indicated segment. In other words, fluid does not communicate between the first cavity 204a and the second cavity 204b along any portion of the mold 200 that comprises the first axial segment 212. As shown in FIGS. IB and 3B, the first axial segment 212 comprises a central portion of the mold 200 along the longitudinal axis 208. In embodiments, the first axial segment 212 comprises at least 50%, at least 65%, at least 70%, at least 75%, at least 80%, or at least 85% or more of a length of the mold 200 along the longitudinal axis 208.

[0092] In embodiments, the one or more cavities 204 comprise a third cavity 204c configured to negatively define a third shape of a third channel core 304c of the core assembly 300 to be formed by the method. The third shape comprises a third profile swept along a third path between opposed ends thereof through the mold 200. As best shown in FIG. 6, the third profile is circular, and the third path is coextensive with the longitudinal axis 208 such that thethird core 304 approximates a solid cylinder. In embodiments, the third profile can have any shape and that shape can vary (e.g., continuously, periodically, etc.) or be constant along the third path (e.g., the longitudinal axis 208). In embodiments, the first cavity 204a, the second cavity 204b, and the third cavity 204c are fluidically discrete within the first axial segment 212 of the mold 200 along the longitudinal axis 208.

[0093] As used herein, the term “profile” can refer to the periphery or outline of the shape as viewed along a cross-sectional plane normal to the path along which the profile is swept. The profile can have any shape (circular, square, rectangular, oblong, etc.) for portions or for the entirety of the length of the path, and the profile can vary between shapes along the length of the path. In embodiments, the first profile 312a, the second profile 312b, and the third profile can be the same or different. In embodiments, the first and second profiles 312a, 312b are the same and the third profile is different.

[0094] In embodiments, the one or more cavities comprise a fourth cavity 204d configured to negatively define a fourth shape of a first connecting core 304d of the core assembly 300 to be formed by the method. The fourth cavity 204d is configured to fluidically connect the first cavity 204a, the second cavity 204b, and the third cavity 204c within a second axial segment 216 of the mold 200 along the longitudinal axis 208. As shown in FIGS. IB and 3B, the second axial segment 216 is adjacent to a first end of the first axial segment 212.

[0095] In embodiments, the reservoir 224 (FIG. 2C) can be fluidically connected to the fourth cavity 204d of the mold 200 such that the volume of the heat-removeable material in liquid form 308a in the reservoir 224 can feed directly into the fourth cavity 204d. In such embodiments, after the heat-removeable material cools and solidifies in the mold 200, the reservoir 224 (and the solidified, heat-removeable material therein) can be severed from the mold 200, for example, along a cutting plane indicated by dashed line 228 in FIG. 2C. In embodiments in which the dissolvable material of the mold 200 is dissolved before the reservoir 224 is severed from the mold 200, the heat-removeable material that solidified in the reservoir 224 after the cooling can be severed from the exposed core assembly 300, for example, by using a heated wire. As shown in FIG. 2C, the cutting plane 228 is positioned such that substantially all of the first connecting core 304d remains (fluidically) connected to the core assembly 300 after the reservoir 224 and / or the solidified, heat-removeable material that solidified in the reservoir 224 after the cooling is / are severed from the mold 200.

[0096] In embodiments, the one or more cavities comprise a fifth cavity 204e configured to negatively define a fifth shape of a second connecting core 304e of the core assembly 300 to be formed by the method. The fifth cavity 204e is configured to fluidically connect the first cavity 204a, the second cavity 204b, and the third cavity 204c within a third axial segment 220 of the mold 200 along the longitudinal axis 208. As shown in FIGS. IB and 3B, the third axial segment 220 is adjacent to a second end of the first axial segment 212. Throughout this disclosure, the reference numbers for the first axial segment 212, the second axial segment 216, and the third axial segment 220 are used with respect to both the cavities 204 of the mold 200 and the cores 304 of the core assembly 300 since the cavities 204 (negatively) define the cores 304.

[0097] In embodiments, one or more of the second cavity 204b, the third cavity 204c, and the fifth cavity 204e can be omitted from the mold 200. In such embodiments, one or more of the second channel core 304b, the third channel core 304c, and the fifth channel core 304e of the core assembly 300 will not be formed during the molding. In one embodiment, the third cavity 204c is omitted from the mold 200 such that the third channel core 304c will not be formed during the molding. In this embodiment, the fourth cavity 204d is configured to fluidically connect the first cavity 204a and the second cavity 204b within the second axial segment 216. Similarly, in this embodiment, the fifth cavity 204e is configured to fluidically connect the first cavity 204a and the second cavity 204b within the third axial segment 220.

[0098] Referring still to FIGS. 1 A and IB, the walls 202 of the mold 200 have one or more thicknesses configured to ensure structural integrity of the mold 200 and dimensional accuracy of the core assembly 300 during the molding of the core assembly 300 inside the mold 200. In embodiments, the walls 202 can have a uniform thickness throughout the entire mold 200. In embodiments, the walls 202 have can have different uniform thicknesses for different portions of the mold 200. For example, a first portion of the mold 200 can have a first uniform thickness and a second portion of the mold can have a second uniform thickness that is different than the first uniform thickness. In embodiments, the walls 202 can have a variable thickness for portions of the mold 200.

[0099] As best shown in FIG. IB, some walls of the mold 200 are common or shared walls 202a that define portions of multiple features (e.g., two or more of the first cavity 204a, the second cavity 204b, the third cavity 204c, the fourth cavity 204d, and the fifth cavity 204e). For example, in a direction parallel to the longitudinal axis 208, the mold 200 has common walls 202a that respectively define portions of each of the first cavity 204a and the secondcavity 204b. Referring still to FIG. IB, some walls of the mold 200 are external walls 202b that define a portion of a feature one side and bound the external environment (e.g., the environment outside of the mold 200) on the other side. For example, the mold 200 has external walls 202b that respectively define a portion of the first cavity 204a or the second cavity 204b on one side and bound the external environment on the other side.

[0100] In embodiments, the commons walls 202a have a thickness in a range of from about 2.94 mm to about 3.06 mm, from about 2.82 mm to about 3.18 mm, from about 2.7 mm to about 3.3 mm, from about 2.58 mm to about 3.42 mm, from about 2.9 mm to about 3.0 mm, from about 2.9 mm to about 3.6 mm, from about 2.9 mm to about 4.2 mm, from about 2.9 mm to about 4.8 mm, or from about 2.9 mm to about 5.4 mm, and also comprising all sub-ranges and sub-values between these range endpoints. In an exemplary embodiment, the common walls have a thickness of at least about 3.0 mm to provide a minimum gap between the one or more cores 304 of the core assembly 300 after dissolving the dissolvable material of the mold 200 after the molding.

[0101] In embodiments, the external walls 202b have a thickness in a range of from about 0.39 mm to about 1.5 mm, from about 0.39 mm to about 1.25 mm, from about 0.39 to about 1.0 mm, from about 0.39 mm to about 0.75 mm, from about 0.39 mm to about 0.41 mm, from about 0.37 mm to about 0.43 mm, from about 0.35 mm to about 0.45 mm, from about 0.33 mm to about 0.47 mm, from about 0.31 mm to about 0.49 mm, from about 0.29 mm to about 0.51 mm, from about 0.375 mm to about 0.4 mm, from about 0.375 mm to about 0.45 mm, from about 0.375 mm to about 0.5 mm, from about 0.375 mm to about 0.55 mm, from about 0.375 mm to about 0.6 mm, or from about 0.375 mm to about 0.65 mm, and also comprising all subranges and sub-values between these range endpoints.

[0102] In an exemplary embodiment, the external walls 202b have a thickness selected to correspond to the diameter of the nozzle of a 3D printer configured to print the mold 200, such as a thickness of about 0.4 mm. In embodiments, the common walls 202a have a thickness that is greater than or equal to the thickness of the external walls 202b. In embodiments, the common walls 202a have a thickness that is greater than the thickness of the external walls 202b.

[0103] The different embodiments of the core assemblies formed by the methods described hereinabove with reference to FIGS. 1A-1C, 2A, 2B, 3A, 3B, and 4-7 can be used to form a variety of structures using press-forming fabrication techniques. One such structure is a fluidicmodule for a flow reactor. An embodiment of a process for forming a fluidic module for a flow reactor is described hereinbelow with reference to FIGS. 8A, 8B, and 9-13.

[0104] Referring now to FIGS. 8A and 8B, a positioning step and a covering step of the process are shown. The process includes positioning a one-piece core assembly comprising one or more cores within a flexible mold 400. In the following description, the core assembly used in the process corresponds to the core assembly 300 described hereinabove with reference to FIGS. 1 A-1C, 2A, 2B, 3A, 3B, and 4-7. It should be appreciated that the core assembly can be configured differently in various embodiments of the process. FIG. 8A is a top view of the flexible mold 400, which is configured for use with an isostatic pressing process. FIG. 8B is a cross-sectional view through the flexible mold 400 and the core assembly 300 positioned therein along line A-A.

[0105] The core assembly 300 comprises the one or more cores 304, as described hereinabove. For example, the one or more cores 304 can include one or more of the first channel core 304a with the first shape, the second channel core 304b with the second shape, and the third channel core 304c with the third shape. In embodiments, the one or more cores 304 include at least two of the first channel core 304a, the second channel core 304b, and the third channel core 304c. In embodiments, the one or more cores 304 include each of the first channel core 304a, the second channel core 304b, and the third channel core 304c. The one or more cores 304 can also include one or both of the first connecting core 304d and the second connecting core 304e.

[0106] Referring still to FIGS. 8A and 8B, the process further comprises covering the core assembly 300 with a volume of binder-coated particles 404. The particles 404 are poured into the flexible mold 400 so as to flow and fill any unoccupied spaces within the flexible mold 400. Distribution of the particles 404 to all regions within the flexible mold 400 not occupied by core assembly 300 can be promoted by vibrating the flexible mold 400 during and / or after particle filling.

[0107] In embodiments, the particles 404 can be particles of any material that can be (i) provided in a solid, flowable form (e.g., particles, powder, beads, etc.), (ii) pressed or compacted (with or without additives, such as lubricants, binders, etc.) into a pressed body configured with sufficient (green) strength to retain its shape for further processing (e.g., debinding, sintering, etc.), and (iii) densified upon application of heat (e.g., via sintering or firing) to form a sintered or fired body. In embodiments, the particles 404 are selected fromglass, glass ceramic, ceramic, and metal. In embodiments, the particles 404 are binder-coated ceramic powder.

[0108] In an exemplary embodiment, the binder-coated ceramic powder comprises ready- to-press (RTP) ceramic powder, such as RTP silicon carbide (SiC) powder. Such RTP SiC powder is commercially available from various suppliers, such as SiCS-18 from GNPGraystar of Buffalo, NY, United States; IKH 601 and 604 from Industriekeramik Hochrhein (IKH) GmbH of Wutoschingen, Germany; and StarCeram S alpha-SiC types SQ and RQ from KYOCERA Fineceramics Precision GmbH of Selb, Germany.

[0109] One advantage of using the one-piece core assembly 300 in the process disclosed herein is that the cores 304 of the core assembly 300 are all interconnected such that any gaps or spacing between the (as-formed or as-provided) cores 304 are fixed or otherwise maintained during the positioning step, the covering step, and a pressing step (e.g., the pressing step is described hereinbelow with reference to FIGS. 9 and 10) disclosed herein.

[0110] Referring now to FIG. 3B and 8B, when the core assembly 300 is positioned in the flexible mold 400, the first channel core 304a and the second channel core 304b are spaced from one another so as to be physically discrete within a first axial segment 212 of the core assembly 300. In embodiments that include the third channel core 304c, the first channel core 304a, the second channel core 304b, and the third channel core 304c are spaced from one another so as to be physically discrete within the first axial segment 212.[OHl] In embodiments that include the first connecting core 304d, the first connecting core 304d is configured to connect the first channel core 304a and the second channel core 304b (and optionally the third channel core 304c) within a second axial segment 216 of the core assembly 300. The second axial segment 216 is adjacent to a first end of the first axial segment 212, as shown in FIG. 3B. With this connection within the second axial segment 216, the first connecting core 304d maintains the positions of (and thus the gap or spacing between) the first channel core 304a and the second channel core 304b (and optionally the third channel core 304c) relative to one another during the positioning step, the covering step, and the pressing step.

[0112] In embodiments that include the first connecting core 304d, the covering step can include contacting the first connecting core 304d to maintain a position of the core assembly 300 relative to the flexible mold 400 during the covering. For example, as shown in FIG. 8B, a first positioning device 408 can be used to contact portions of the flexible mold 400 andportions of the first connecting core 304d so as to align and maintain a position of the core assembly 300 relative to the flexible mold 400 during the covering.

[0113] In embodiments that include the second connecting core 304e, the second connecting core 304e is configured to connect the first channel core 304a and the second channel core 304b (and optionally the third channel core 304c) within a third axial segment 220 of the core assembly 300. The third axial segment 220 is adjacent to a second end of the first axial segment 212, as shown in FIG. 3B. With this connection within the third axial segment 220, the second connecting core 304e further maintains the positions of (and thus the gap or spacing between) the first channel core 304a and the second channel core 304b (and optionally the third channel core 304c) relative to one another during the positioning step, the covering step, and the pressing step.

[0114] In embodiments that include the second connecting core 304e, the covering step can include contacting the second connecting core 304e to maintain a position of the core assembly 300 relative to the flexible mold 400 during the covering. For example, a second positioning device (not shown) can be used to contact portions of the flexible mold 400 and portions of the second connecting core 304e so as to align and maintain the position of the core assembly 300 relative to the flexible mold 400 during the covering. In embodiments, multiples of the first positioning device 408 can be provided such that the first positioning device 408 can also be used to contact portions of the flexible mold 400 and portions of the second connecting core 304e so as to align and maintain the position of the core assembly 300 relative to the flexible mold 400 during the covering.

[0115] In embodiments, the core assembly 300 can further include position keepers (not shown) located at different positions along the core assembly 300 between the first connecting core 304d and the second connecting core 304e. Each position keeper is configured to temporarily occupy the gap or space between at least two adjacent channel cores 304, such as between the first channel core 304a and the second channel core 304b, between the first channel core 304a and the third channel core 304c, and / or between the second channel core 304b and the third channel core 304c.

[0116] In embodiments, the position keepers can be formed from the heat-removable material as small, U-shaped projections that attach to two adjacent channel cores (e.g., two of the first channel core 304a, the second channel core 304b, and the third channel core 304c). In such embodiments, the mold 200 can define additional sub-cavities that negatively define theshape of the position keepers at the desired locations. The projections can be configured with narrow cross-sections near the surface of the channel cores to allow the positioned keepers to be easily removed from the channel cores, such as by breaking them off of the channel cores or by severing them from the channel cores with a hot wire prior to or during the covering step.

[0117] In one embodiment of the covering step, the core assembly 300 comprises at least two of the first channel core 304a, the second channel core 304b, and the third channel core 304c, and a plurality of position keepers configured as small, U-shaped projections. The position keepers are located at different positions along the core assembly 300 to maintain the alignment and relative position of the channel cores during the covering. Once lower portions of the core assembly 300 are covered with a layer of particles 404, the channel cores become more stabilized with the flexible mold 400. At this point, at least some of the position keepers can be removed as the covering continues.

[0118] In other embodiments, the position keepers can be formed as pre-pressed spacers comprising discrete volumes of the particles 404 being pre-pressed to hold their shape and positioned accordingly at different position along the core assembly 300 as described hereinabove. Examples of similar pre-pressed ceramic bodies for fabrication of ceramic modules via isostatic pressing are described in International Application No. PCT / US2023 / 080009, filed on November 16, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0119] In yet further embodiments, the position keepers are configured as a separate, temporary spacers, similar to the first position device 408 described with reference to FIG. 8B, except the temporary spacers are applied at locations other than the axial ends of the core assembly 300. For example, the temporary spacer could be configured as a comb structure that fits over the core assembly 300 so that the tines of the comb structure fit between adj acent cores 304 to maintain precise spacing therebetween. As with the heat-removable-based, U-shaped position keepers, the temporary spacers would be progressively removed as the particles 404 are poured into the flexible mold 400.

[0120] The temporary spacer, such as the comb structure, could be 3D printed and, in principle, it could be 3D printed at the same time as the mold 200, using a different material that does not dissolve with exposure to water or solvents. An advantage of this configuration is that the temporary spacer would be substantially aligned to the mold 200, and it could provide mechanical stability to the mold 200 prior to filling the mold 200 with the heat-removablematerial, and to the core assembly 300 after fabrication thereof. The temporary spacer should be removed from the surface of the core assembly 300 after printing with consideration of difficulties that may arise if a rough surface exists at the interface between the core assembly 300 and the 3D printed temporary spacer.

[0121] The first connecting core 304d, the second connecting core 304d, and / or the position keepers are configured to help maintain a minimum gap (e.g., about 3.0 mm) between the cores 304 of the core assembly 300 in order to facilitate adequate particle flow around channel cores 304 during the covering / filling of the flexible mold 400 and to enable crack-free, isostatic pressing of the particles. The minimum gap further described hereinabove with respect to the forming of the core assembly 300 using the mold 200 and, in particular, with respect to the thickness of the common walls 202a of the mold 200.

[0122] Referring now to FIGS. 8B and 9, a thin layer of the particles 404 can be deposited on the bottom of the flexible mold 400 prior to positioning the core assembly 300 therein so as to provide a small gap or space between the bottom of the core assembly 300 (e.g., the second connecting core 304e) and the bottom of the flexible mold 400. Similarly, as best shown in FIG. 9, the particles 404 can be added until the flexible mold 400 is (uniformly) filled and a thin layer of the particles 404 provides a small gap or space between the top of the core assembly 300 (e.g., the first connecting core 304d) and a separate flexible cap 412 inserted into the opening to the flexible mold 400. In embodiments, the flexible cap 412 is formed from the same or a similar flexible material as the flexible mold 400. The thin layers of particles 404 disposed above and below the core assembly 300 can provide advantages during subsequent steps of the process, as described later in this disclosure.

[0123] In embodiments, the process includes pulling a vacuum on the flexible mold 400 via a tube (not shown) that is configured to extend through the flexible cap 412. Pulling the vacuum causes the flexible mold 400 to draw in and press against the particles 404, the core assembly 300, and any optional particle-based positioning devices, so as to stabilize these features with the surrounding particles 404.

[0124] Referring now to FIGS. 9 and 10, a pressing step of the process is shown. The process further comprises isostatically pressing the flexible mold 400 and the flexible cap 412 with the core assembly 300 and the volume of the particles 404 therein to form a pressed body 500 (FIG. 10). Although the process has been described in the context of isostatically pressing the flexible mold 400, it should be appreciated that the process may instead comprise pressing,more generally, so as to include uniaxial pressing using a mold, such as a rigid mold. As such, any or all aspects of the positioning, covering, and pressing steps discussed hereinabove or hereinbelow can be accomplished via (isostatically) pressing the (flexible) mold or (uniaxially) pressing the (rigid) mold.

[0125] In embodiments, as illustrated in FIG. 9, an isostatic press chamber 600 is configured to isostatically press the flexible mold 400, the flexible cap 412, and the contents therein. For example, the flexible mold 400, the flexible cap 412, and the contents therein are placed inside the isostatic press chamber 600, which contains fluid 604 (e.g., water) to which pressure is configured to be applied by the isostatic press chamber 600. In embodiments, the fluid 604 is configured to be pressurized so as to produce essentially isostatic pressure on all surfaces of the flexible mold 400, which causes the particles 404, the core assembly 300, and any optional particle-based positioning devices therein to be compressed and densified.

[0126] In embodiments, the fluid 604 is pressurized to a pressure (e.g., isostatic pressure, main pressure, and / or primary pressure) in a range of from about 20 MPa to about 200 MPa, or from about 25 MPa to about 195 MPa, or from about 30 MPa to about 190 MPa, or from about 35 MPa to about 185 MPa, or from about 40 MPa to about 180 MPa, or from about 45 MPa to about 175 MPa, or from about 50 MPa to about 170 MPa, and also comprising all subranges and sub-values between these range endpoints.

[0127] The thin layers of particles 404 disposed above and below the core assembly 300 can provide advantages during the isostatic pressing. For example, the thin layers of particles 404 can help avoid distortion near the end or edge of fluidic modules formed by the process disclosed herein. Shape distortion during pressing can be high near edges and corners of isostatically pressed parts. For example, if a cylindrical press mold is used, the two ends of the mold can experience “elephant foot” distortion, where the cylinder diameter is larger at the ends of the cylinder. This distortion occurs because the particles (e.g., SiC powder) are not as free to compress at the ends of the cylinder as compared to regions that are located away from the ends of the cylinder. A core assembly that terminates on the end of the cylinder may experience some of this distortion, where a straight core channel could be slightly bent as it approaches the end of the pressed part. This effect can be compensated for by adjusting the shape of the core assembly near the end of the part, but it may still result in some channel distortion.

[0128] In another example, the thin layers of particles 404 help stabilize the core assembly. It can be helpful to press the core assembly into a thin layer of particles (e.g., SiC powder) to help stabilize the core assembly during subsequent loose particle filling. In this case it is likely that a thin layer of particles will remain between the core assembly and the bottom of the mold. An alternative solution is to use jigs to help position and stabilize the core assembly in the proper location within the mold.

[0129] Referring now to FIG. 11, a removing step of the process is shown. The process further comprises removing one or more of the first connecting core 304d and the second connecting core 304e from the pressed body 500 after the isostatically pressing and before the heating. The first connecting core 304d and the second connecting core 304e can be removed from the pressed body 500 by separating axial end regions of the pressed body 500 from an axial central region of the pressed body 500. As shown in FIG. 11, the axial central region containing the first channel core 304a, the second channel core 304b, and the third channel core 304c corresponds substantially to the first axial segment 212 described hereinabove with reference to FIGS. IB and 3B. Similarly, the axial end regions containing the first connecting core 304d and the second connecting core 304e correspond substantially to the second axial segment 216 and the third axial segment 220, respectively, described hereinabove with reference to FIGS. IB and 3B.

[0130] In embodiments, the axial end regions 216, 220 are separated by cutting, sawing, or any removal process that can separate the axial end regions 216, 220 with minimum disruption to the integrity of the (green) pressed body 500. The pressed body 500 has axial end faces 504 after separating the axial end regions 216, 220. The axial end faces 504 are preferably smooth or reasonably smooth after the separating so as to eliminate or minimize the need for subsequent surface finishing before the heating and sintering steps of the process. After the removing, the first channel core 304a, the second channel core 304b, and the third channel core 304c remain spaced from one another so as to be physically discrete within the axial central region 212 of the pressed body 500. The opposed ends of the first channel core 304a, the second channel core 304b, and the third channel core 304c are exposed at the axial end faces 504 to facilitate the subsequent heating step.

[0131] Referring now to FIG. 12, a heating step of the process is shown. The process further includes heating the pressed body 500 to remove the one or more cores 304 of the core assembly 300. After removing / separating the axial end regions 216, 220 of the pressed body 500 (FIG. 11), the pressed body 500 is heated, preferably at a relatively high rate, such that theremaining core assembly 300 is melted and removed from the pressed body 500 by flowing out of the pressed body 500 and / or by being blown and / or sucked out in addition so as to expose the fluid channels C. In embodiments, this heating step can be divided into two parts, where first the pressed body is heated (optionally while applying pressure to the exterior of the body via, for example, heated isostatic pressing in the isostatic press chamber 600), and then next, separately, the material of the core assembly can flow out of the pressed body. It is also possible, in embodiments, to remove the core assembly 300 by heating the pressed body 500 to melt the core assembly material (e.g., the heat-removable material), and only then drill holes or fluidic ports, while the pressed body is still hot, allowing the core assembly material to flow out and complete demolding in this manner. The heating may be under partial vacuum, if desired.

[0132] The thin layers of particles 404 disposed above and below the core assembly 300 can provide advantages during the heating when combined with isostatic pressing (hereinafter “isostatic demolding”). For example, the thin layers of particles 404 can help avoid vacuum bag tearing. In general, care should be taken to not allow large areas of core assembly material to be present on the surface of an isostatically pressed part during isostatic demolding. If large areas of core assembly material are present at the surface of the fluidic module, then during isostatic demolding this can lead to problems where the isostatic pressing bag is pressed into the hole formed by the core assembly when the core assembly material melts. If the hole is too large, the isostatic pressing bag can tear. A solution is to place a small plate over the core assembly surface location to support the bag.

[0133] In another example, the thin layers of particles 404 can help avoid vacuum bag damage to green pressed material. During isostatic demolding, if large areas of core assembly material is present at the surface of the fluidic module, then the material can easily be redistributed laterally away from areas when the core assembly material melts, allowing the isostatic pressing bag to be pressed into the surface opening area. If the bag does not tear, then the force of the bag on the green pressed particles (e.g., SiC powder) can result in distortion and damage of the green pressed particles in regions around the surface material area.

[0134] Referring now to FIG. 13, a sintering step of the process is shown. The process further includes sintering the pressed body 500 to form the fluidic module 700 having one or more fluid channels C extending therethrough. As shown by comparing FIGS. 10 and 11 with FIGS. 12 and 13, each fluid channel C corresponds, respectively, to the one or more cores 304 removed during the heating.

[0135] EXAMPLES

[0136] Various embodiments of the present disclosure can be better understood by reference to the following Examples which are offered by way of illustration. The present disclosure is not limited to the Examples given herein.

[0137] Example 1 — Process Steps for Making a Core Assembly

[0138] FIGS. 14A-14D are digital images that illustrate the process steps for making a core assembly according to the method disclosed herein. FIG. 14A depicts a mold 200 that was three-dimensional (3D) printed using a polyvinyl alcohol (PVA) material (i.e., a water- dissolvable material). The mold 200 comprises each of the cavities 204 (e.g., the first cavity 204a, the second cavity 204b, the third cavity 204c, the fourth cavity 204d, and the fifth cavity 204e) described above with reference to FIGS. 1 A and IB. The mold 200 also comprises the reservoir 224 described above with reference to FIG. 2C. FIG. 14B depicts the mold 200 after the heat-removable material 308 (e.g., wax) has been poured into the mold 200 and allowed to cool and solidify therein. FIG. 14C depicts a dissolving step in which the mold 200, which is filled with the solidified, heat-removable material 308, is submerged in a volume of water. FIG. 14D shows the core assembly 300 formed from the heat-removable material 308 after full dissolution of the PVA material of the mold 200. The core assembly 300 includes each of the cores 300 (e.g., the first channel core 304a, the second channel core 304b, the third channel core 304c, the first connecting core 304d, and the second connecting core 304e) as well as a volume of heat-removable material corresponding to the reservoir 224 shown in FIG. 14A.

[0139] Example 2 — Controlling Mold Temperature to Improve Core Quality

[0140] FIGS. 15A-15C are digital images of different strategies to control mold temperature during filling of the mold 200. FIG. 15A shows a first insulation layer 802 positioned around the mold 200 as one strategy to passively maintain the temperature of the mold 200 and heat-removable material therein during and after the mold filling step. FIG. 15B shows a second insulation layer 804 positioned around the first insulation layer 802 to encourage further heat retention during the mold filling step. FIG. 15C shows a heating device 806 into which the mold 200 is positioned as one strategy to actively control the temperature of the mold 200 and the heat-removable material therein during and after the mold filling step, such as by pre-heating the mold 200 prior to filling and maintaining the mold 200 at a setpoint temperature during the filling. The final solidified core assembly obtained by employing these temperature controlling strategies showed no more small air bubbles within the heat-removablematerial. Accordingly, managing the temperature of the mold during filling has been demonstrated to significantly reduce the number of small air bubbles within the final solidified cores and is likely to increase homogeneity of the core assembly.

[0141] Example 3 — Silicon Carbide Fluidic Module with Intricated Helical Paths

[0142] FIG. 16 is a digital image of a cross-section of a silicon carbide (SiC) fluidic module 700 fabricated using the core assembly forming method and the fluidic module forming process described herein. The SiC fluidic module includes double helix fluid channels C as shown in FIG. 16.

[0143] While the disclosure has been illustrated and described in detail in the drawings and foregoing description, the same should be considered as illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications, and further applications that come within the spirit of the disclosure are desired to be protected.

Claims

CLAIMSWhat is claimed is:

1. A method for forming a core assembly for use with a press-forming fabrication process, comprising: forming a one-piece mold that defines one or more cavities therein using a dissolvable material, the one or more cavities comprising a first cavity configured to negatively define a first shape of a first channel core of the core assembly to be formed; molding the core assembly inside the mold, the core assembly formed from a heat- removeable material; and dissolving the dissolvable material of the mold after the molding to expose the core assembly.

2. The method of claim 1, wherein the first shape comprises a first profile swept along a first path that defines a three-dimensional curve along a majority of a length of the first path between opposed ends thereof through the mold.

3. The method of claim 1 or claim 2, wherein forming the one-piece mold comprises three-dimensional printing the mold using the dissolvable material.

4. The method of claim 2 or claim 3, wherein the one or more cavities comprise a second cavity configured to negatively define a second shape of a second channel core of the core assembly to be formed, the second shape comprising a second profile swept along a second path that defines a three-dimensional curve between opposed ends thereof through the mold, the second path at least partially intertwined and substantially coextensive with the first path.

5. The method of claim 4, wherein the first path is configured as a first helical path that revolves for multiple turns about a longitudinal axis through the mold.

6. The method of claim 5, wherein the second path is configured as a second helical path that revolves for multiple turns about the longitudinal axis through the mold.

7. The method of claim 6, wherein the multiple turns of the second helical path alternate with the multiple turns of the first helical path.

8. The method of any one of claims 4-7, wherein the first cavity and the second cavity are fluidically discrete within a first axial segment of the mold.

9. The method of claim 8, wherein the one or more cavities comprise a fourth cavity configured to negatively define a fourth shape of a first connecting core of the core assembly to be formed, the fourth cavity fluidically connecting the first cavity and the second cavity within a second axial segment of the mold, the second axial segment adjacent to a first end of the first axial segment.

10. The method of claim 9, wherein the one or more cavities comprise a fifth cavity configured to negatively define a fifth shape of a second connecting core of the core assembly to be formed, the fifth cavity fluidically connecting the first cavity and the second cavity within a third axial segment of the mold, the third axial segment adjacent to a second end of the first axial segment.

11. The method of claim 8, wherein the one or more cavities comprise a third cavity configured to negatively define a third shape of a third channel core of the core assembly to be formed, the third shape comprising a third profile swept along a third path between opposed ends thereof through the mold.

12. The method of claim 11, wherein the first cavity, the second cavity, and the third cavity are fluidically discrete within the first axial segment of the mold.

13. The method of claim 12, wherein the one or more cavities comprise a fourth cavity configured to negatively define a fourth shape of a first connecting core of the core assembly to be formed, the fourth cavity fluidically connecting the first cavity, the second cavity, and the third cavity within a second axial segment of the mold, the second axial segment adjacent to a first end of the first axial segment.

14. The method of claim 13, wherein the one or more cavities comprise a fifth cavity configured to negatively define a fifth shape of a second connecting core of the core assembly to be formed, the fifth cavity fluidically connecting the first cavity, the second cavity, and the third cavity within a third axial segment of the mold, the third axial segment adjacent to a second end of the first axial segment.

15. The method of any one of claims 1-14, wherein molding the core assembly comprises: filling the one or more cavities of the mold with the heat-removeable material in liquid form at a material temperature, maintaining a mold temperature of the mold during the filling, the mold temperature maintained in a range of from about 5 °C less than the material temperature to about 50 °C less than the material temperature, and cooling the mold and the heat-removeable material after the filling to solidify the heat-removeable material before the dissolving.

16. The method of claim 15, wherein: the mold, at an axial end thereof, comprises a reservoir that is fluidically connected to the one or more cavities of the mold, and cooling the mold and the heat-removeable material comprises maintaining a volume of the heat-removeable material in the reservoir at a reservoir temperature that is higher than the material temperature of the heat-removeable material within the one or more cavities during the cooling.

17. The method of claim 16, wherein the mold is configured to define the reservoir using the dissolvable material.

18. The method of claim 16, wherein the reservoir is formed separately from the mold and configured to be releasably attached to the mold.

19. The method of any one of claims 1-18, wherein the dissolvable material comprises one or more of polyvinyl alcohol (PVA) and high-impact polystyrene (HIPS).

20. The method of any one of claims 1-19, wherein dissolving the dissolvable material comprises submerging the mold in one or more of water, a solvent, and an acid.

21. A process for forming a fluidic module for a flow reactor, comprising: positioning a one-piece core assembly comprising one or more cores within a mold, the one or more cores comprising a first channel core with a first shape; covering the core assembly with a volume of binder-coated particles; pressing the mold with the core assembly and the volume of the particles therein to form a pressed body; heating the pressed body to remove the one or more cores of the core assembly; and sintering the pressed body to form the fluidic module having one or more fluid channels extending therethrough, each fluid channel corresponding, respectively, to the one or more cores removed during the heating.

22. The process of claim 21, wherein the first shape comprises a first profile swept along a first path that defines a three-dimensional curve for a majority of a length of the first path between opposed ends thereof.

23. The process of claim 22, wherein the one or more cores comprise a second channel core with a second shape, the second shape comprising a second profile swept along a second path that defines a three-dimensional curve between opposed ends thereof, the second channel core at least partially intertwined and substantially coextensive with the first channel core.

24. The process of claim 23, wherein the first path is configured as a first helical path that revolves about a longitudinal axis such that the first channel core has a plurality of first turns.

25. The process of claim 24, wherein the second path is configured as a second helical path that revolves about the longitudinal axis such that the second channel core has a plurality of second turns.

26. The process of claim 25, wherein the second turns of the second channel core alternate with the first turns of the first channel core.

27. The process of any one of claims 22-26, wherein, prior to the heating, the first channel core and the second channel core are spaced from one another so as to be physically discrete within a first axial segment of the core assembly.

28. The process of claim 27, wherein, prior to the heating, the one or more cores comprise a first connecting core configured to connect the first channel core and the second channel core within a second axial segment of the core assembly so as to maintain positions of the first channel core and the second channel core relative to one another during the positioning, the covering, and the pressing, the second axial segment disposed adjacent to a first end of the first axial segment.

29. The process of claim 28, wherein covering the core assembly with the volume of particles comprises contacting the first connecting core to maintain a position of the core assembly relative to the mold during the covering.

30. The process of claim 29, wherein, prior to the heating, the one or more cores comprise a second connecting core configured to connect the first channel core and the second channel core within a third axial segment of the core assembly and maintain positions of the first channel core and the second channel core relative to one another during the positioning, the covering, and the pressing, the third axial segment disposed adjacent to a second end of the first axial segment.

31. The process of claim 30, wherein covering the core assembly with the volume of particles comprises contacting the second connecting core to maintain the position of the core assembly relative to the mold during the covering.

32. The process of claim 31, further comprising removing one or more of the first connecting core and the second connecting core after the pressing and before the heating.

33. The process of claim 27, wherein the one or more cores comprise a third channel core with a third shape, the third shape comprising a third profile swept along a third path between opposed ends thereof.

34. The process of claim 33, wherein, prior to the heating, the first channel core, the second channel core, and the third channel core are spaced from one another so as to be physically discrete within the first axial segment of the core assembly.

35. The process of claim 34, wherein, prior to the heating, the one or more cores comprise a first connecting core configured to connect the first channel core, the second channel core, and the third channel core within a second axial segment of the core assembly and maintain positions of the first channel core, the second channel core, and the third channel core relative to one another during the positioning, the covering, and the pressing, the second axial segment disposed adjacent to a first end of the first axial segment.

36. The process of claim 35, wherein covering the core assembly with the volume of particles comprises contacting the first connecting core to maintain a position of the core assembly relative to the mold during the covering.

37. The process of claim 36, wherein, prior to the heating, the one or more cores comprise a second connecting core configured to connect the first channel core, the second channel core, and the third channel core within a third axial segment of the core assembly and maintain positions of the first channel core, the second channel core, and the third channel core relative to one another during the positioning, the covering, and the pressing, the third axial segment disposed adjacent to a second end of the first axial segment.

38. The process of claim 37, wherein covering the core assembly with the volume of particles comprises contacting the second connecting core to maintain the position of the core assembly relative to the mold during the covering.

39. The process of claim 38, further comprising removing one or more of the first connecting core and the second connecting core after the pressing and before the heating.

40. The process of any one of claims 28-39, wherein the first fluid channel and the second fluid channel have common walls that define a minimum gap therebetween, the minimum gap selected from a range of gaps between 0.1 mm and 10 mm.

41. The process of claim 40, wherein the minimum gap has a maximum deviation of ± 5% over at least 50% of the coextensive portions of the first fluid channel and the second fluid channel.

42. The process of any one of claims 21-41, wherein the particles are selected from glass, glass ceramic, ceramic, and metal.

43. The process of claim 42, wherein the particles are binder-coated ceramic powder.

44. The process of any one of claims 21-43, wherein the mold is a flexible mold, and the pressing comprises isostatically pressing the flexible mold with the core assembly and the volume of the particles therein to form a pressed body.

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