Bragg-peak three-dimensional manufacturing with resins

Abstract

This patent application claims the use of directed energy in the form of electronically scanned ion beams (e.g., proton beams) to form plastic parts by selectively curing commodity or engineering resin in the shape of the part. Polymerization is limited to the vicinity of the controlled Bragg-peak of the ion beam (i.e., where linear energy transfer is maximized), if necessary, by the use of chemical polymerization inhibitors or conditions that inhibit polymerization. This technology is more flexible than conventional or continuous three-dimension printing/production (e.g., CLIP™) because (i) it is not confined to layer-by-layer construction, (ii) it does not require a moving stage upon which the plastic part is formed, (iii) it is independent of orientation of the part (not dependent on gravity), and (iv) it allows the incorporation of fillers and pre-formed elements of almost any material into the final part. The process can be faster than “printing” processes because multiple beams can work from different directions simultaneously and the freedom from the layer-by-layer constraint allows time-saving strategies for building and final curing of the part.

Claims

1. A method for manufacturing useful plastic products by initiating curing of resins at the Bragg-peak of a controlled ion beam comprising the steps of: a. providing a reaction mixture, a controlled particle beam, and a temperature-controlled reaction vessel; b. placing the reaction mixture, which will normally be a viscous liquid or solid, into the reaction vessel; c. selectively sending a controlled beam of ions (e.g., protons or heavier charged particles) into the reaction mixture to create three-dimensional regions (defined by the trace of the Bragg peak of the beam of ions) in which effective curing of the resin occurs; d. removing the partially cured resin from the reaction mixture and completing the cure to a fully formed part by general heating or application of other forms of energy.

2. The method of manufacturing useful plastic products as claimed in claim 1, wherein the reaction mixture is a polymer resin that can be cured by a free radical mechanism that contains appropriate polymerization initiators or inhibitors as necessary to facilitate controlled curing and to set a lower limit for the applied energy density needed to trigger effective polymerization/crosslinking/curing of the resin.

3. The method of manufacturing useful plastic products as claimed in claim 1 or 2, wherein the reaction mixture includes inert materials of various types to enhance the formation or function of the desired product including, but not limited to, materials for reinforcing the product, increasing the durability of the product, increasing the functionality of the product, increasing the aesthetics of the product, increasing the biodegradability or recycling efficiency of the product, or reducing the cost of the product.

4. The method of manufacturing useful plastic products as claimed in claim 3, wherein the reaction mixture includes inert materials such as prefabricated: fibers, meshes; strands; wires; tubes; foams; chips or fully formed parts made from metals, metalloids, carbon, silicon, phosphorus, sulfur, organic polymers, partially cured resins, silicate glass, wood, inorganic compounds, minerals or biological materials individually or in combination.

5. The method of manufacturing useful plastic products as claimed in claim 3, in which the reaction vessel is purged or pressurized to saturate the reaction mixture with a gas (e.g., oxygen, carbon dioxide, nitric oxide, helium, HF, SO.sub.2, Fe(CO).sub.5, etc.) which may act as a polymerization inhibitor or accelerator or provide desired properties in the product.

6. The method of manufacturing useful plastic products as claimed in claim 1 or 3, in which the ion beam and/or the reaction mixture are moved or rotated such that the paths of the particles traverse different zones of the resin in route to the same planned curing zone (as defined by traces of the Bragg peak).

7. The method of manufacturing useful plastic products as claimed in claim 1 or 3, in which two or more ion beams from different directions are simultaneously applied to expedite curing.

8. The method of manufacturing useful plastic products as claimed in claim 1 or 3, in which any other form of energy (directed or undirected) is applied to the reaction mixture concurrent with the ion beams used to facilitate the formation of curing of the product.

9. The method of manufacturing useful plastic products as claimed in claim 1 or 3, in which prefabricated parts positioned in the reaction mixture are joined by curing resin between them.

10. The method of manufacturing useful plastic products as claimed in claim 1 or 3, in which prefabricated parts or materials are introduced to the reaction mixture before application of the ion beam, concurrent with the application of the ion beam, during a pause in the application of the ion beam or after application of the ion beam.

11. The method of manufacture of parts in which particles of solid materials (which may be of the same material as the resin and react with the resin, inert solids, or fusible solids (e.g., metals, plastics or silica glass that can be melted together) are in contact with one another with the resin filling the spaces among them such that after application of the ion beam the cured resin acts as an adhesive among the particles.

12. The method of manufacture of parts in which particles of metals or alloys are in contact with one another with the resin filling the spaces among them; such that, after application of the ion beam or induction heating, the metal and resin (or carbon derived from the resin) form a solid part.

13. The method of manufacture of parts as claimed in claim 1 or 3 in which a liquid or gas is injected into the reaction mixture to form one or more bubbles within the resin before during or after application of the ion beam.

14. The method of manufacture of parts as claimed in claim 1 or 3 in which a movable stage or support for the part being manufactured in introduced into the resin to act as a platform upon which the part is manufactured.

15. The method of manufacture of parts as claimed in claim 1 or 3 in which (high density) shielding is used inside or outside the reaction container to assist in attenuating the ion beam without necessarily becoming an element of the part being manufactured.

16. The method of manufacture of parts as claimed in claim 1 or 3 in which the ion beam is guided by a program intended to guide a ion beam to deliver energy to biological material such as a tumor or localized infection, e.g., to manufacture a model of a tumor to be treated by proton therapy.

17. The method of manufacture of parts as claimed in claim 1 or 3 in which the main function of the ion beam is to cause heating of a target within the reaction mixture.

18. The method of manufacture of parts as claimed in claim 1 or 3 in which a reactive gas (e.g. 1,1-dichloroethene, C.sub.2H.sub.2Cl.sub.2 or Fe(CO).sub.5) is allowed to come into contact with a surface heated by an ion beam.

19. A method of manufacture of parts (e.g., replacement bone or connective tissue) as claimed in claim 1 or 3 in which the resin is cured within living tissue.

20. A method of treating tumors, localized infections or other adverse biological conditions by use of the ion beam to decompose a nontoxic resin into a toxic chemical within a target tissue.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1. This figure demonstrates the principle of Bragg peak activation of resin curing. A particle beam [2] enters a resin mixture [1] and initiates effective curing (polymerization) only at the Bragg peak (i.e., Bragg pixel) [3] where the LET density exceeds the threshold set by suppressing agents and conditions [4]. The concept is illustrated in the graph at the top which shows the typical profile of linear energy transfer (LET) [5] and the threshold for initiation of effective curing (polymerization) [6].

[0011] FIG. 2. This embodiment show use of simultaneously applied ion beams from two sources [7] to fabricate a part [10] in contact with an inert part [8] introduced into the reaction medium [9]. The beams are being scanned independently from different directions to produce Bragg pixels [10] of preselected size of curing resin in a. preselected order. This demonstrates the speed and flexibility of this form of “directed energy Three-Dimensional Manufacturing” relative to e.g., continuous liquid interface production (CLIP), casting, milling or extruding.

[0012] FIG. 3. This embodiment shows ion beams from two independent sources [7] building a part [10] within a mesh [11] of (reinforcing) fibers in the reaction mixture [9]. Once, the resin is removed from the excess resin and completely cured, the unwanted fibers can be trimmed.

[0013] FIG. 4. This embodiment shows ion beams from two independent sources [7] building a part [12] on a stage [14]. The approach used here saves time by producing the “skin” of the part while leaving the core of the part as uncured resin [13]. The part will be removed from excess resin and curing of the core and skin will be completed using general heating or some other method of directed energy.

[0014] FIG. 5. This embodiment shows ion beams from two independent sources [7] building a part [15] within a matrix composed of metallic or other inert material particles (e.g. glass, plastic) [16] and a small amount of resin such that the particles are in contact and the resins is used as an adhesive.

DETAIL DESCRIPTION OF THE INVENTION

[0015] The generation and application of ion beans is not within the scope of this invention; it is regarded as a well-developed tool (invented and developed for a different application) that can be adapted to produce protons or other ions of interest, accelerate the ions to very high velocities and guide them into a reaction mixture. It is also known that the depth of penetration of an ion beam into a target (i.e., a human being) or condensed phase (liquid or solid) can be calculated and adjusted by changing the velocity of the ions, or adding condensed phase shielding to the exterior of the target. The ion beam can be finely adjusted by electromagnetic effects on the beam and gross adjustments can be made by reorienting the target or the beam. Finally, the current electron beam technology includes the ability to quickly scan the beam and adjust the depth of penetration and to program exactly how much energy (actually “energy density” typically measured in Grays, 1 G=1 J/kg) will be delivered into a specifically defined three-dimensional volume (i.e., pixel). This tool is currently being used to selectively kill tumors in human beings while sparing adjacent healthy tissues.

[0016] Here we will only refer to the “ion beam” [2 in FIG. 1] with the understanding that it can be rapidly adjusted and scanned [7 in FIG. 2] according to a pre-determined program to deliver a selected energy density (J/kg) into a pre-determined volume of virtually any shape inside a “reaction medium.” The Bragg peak (i.e., the point of maximum delivered energy density) [3 in FIG. 1] is scanned in three dimensions and each ion (or ion cluster) impact results in what we call a “three-dimensional pixel” [10 in FIG. 2 or 3] where free radical density is created and can initiate a polymerization chain reaction, which radiates outward. The rate and effective distance of spread of the free radical reaction (i.e., curing the resin) is limited by the presence of compounds (inhibitors) that terminate the chain reaction or conditions (e.g., temperature) that suppress the propagation rate. Thus, the size of the three-dimensional pixel of cured resin can be controlled. If the three-dimensional pixels are close enough to overlap, effective macroscopic curing of resins occurs. If these pixels are widely dispersed or very small, effective curing of a resin does not occur.

[0017] The invention of interest here is the application of particle beams to curing resins to manufacture products. The chemistry is not significantly different from the chemistry of resin curing using UV light. What is novel and original is the use of proton beams to selectively polymerize/cure the resins in a three-dimensional pattern deep within the resin reaction mixture [FIG. 1, 2, or 3]. This pattern can be completely independent of a working surface, it can take on any shape, it can be formed in any sequence, it can be formed around inert inclusions [FIGS. 2 and 3], and it can be formed using multiple ions beams currently [FIGS. 2 and 3]. Moreover, ions beams can arrive at the same spot (Bragg peak) from different directions; thus, minimizing the energy density delivered to regions of the reaction mixture that are not intended for ailing.

[0018] Of course, the equipment needed to establish a manufacturing facility (including an ion accelerator and a complex computer-controlled beam director and target stage) is very expensive. Nonetheless, commercial applications have been introduced at a number of sites for treatment of tumors in humans. The unit cost of these treatments is very high and the market is currently relatively small. Moreover, the treatment of tumors in humans requires that the tumor (which is out of the control of the operator) be located, mapped and positioned appropriately for targeting with the ion beam. These requirements are much more stringent than envisioned for manufacturing. In manufacturing, the operator will determine the shape of the object to be manufactured and can make use of well-known geometrical shapes in developing the scanning program(s). Nonetheless, the techniques that have been developed to map tumors, might be useful to scan existing objects and develop a program for manufacturing identical objects using the methodology claimed here.

[0019] Instead of treating one unique tumor, a manufacturing process will typically produce thousands of each object. Thus, the process can be highly automated driving down the unit cost. In addition, production runs can be interrupted to make “one-off” special order (e.g., prototype) parts simply by replacing one program with another (i.e., no retooling necessary). Thus, we believe that the use of the ion beam for manufacturing will be fast, allow unique manufacturing options and produce high quality products cost-competitively with three-dimensional printing technologies or other manufacturing techniques. Moreover, by co-locating manufacturing and medical (e.g., proton therapy) facilities, key elements can be shared (e.g., the ion accelerator) and the cost of proton therapy for cancer will go down significantly, while it is made more available to the patients that need it. In particular, it may prove economical to extend proton therapy to treatment of localized infections, which are not amenable to drug therapy (including antibiotic resistant tuberculosis nodules in the lungs, abscesses and cysts). There are likely other applications that a currently not economically available in medicine and other manufacturing, chemical or metallurgical applications.

EXAMPLES

[0020] Example 1. A viscous polymer resin (commodity or engineering) is placed in a temperature-controlled container and mounted in an ion beam device (similar to that used in proton therapy for cancer). The ion beam controls have been programmed to produce a three-dimensional image of a standard part [FIGS. 2 and 3]. The beam(s) is turned on and the part is produced in the viscous resin. The resin is warmed or diluted with solvent to make it mobile and the part is gently extracted from the resin. Curing is completed by exposure of the partially cured object to heat or other energy sources. The excess resin is recycled into the process. The entire process is automated to robotically operate around and interface with the ion beam equipment.

[0021] Example 2. The system operates as in Example 1, except the resin is prepared with dispersed inert particles that are to be encapsulated in the final product. These particles might be small pieces of metal, glass, ceramics, polymers, fibers [11 in FIG. 2], foams, biodegradable materials or pigments, which are intended to modify the bulk properties of the final material (e.g., color, conductivity, flexibility, hardness, finish, density, biodegradability etc.).

[0022] Example 3. The system operates as in Example 1, but the reaction vessel can be sealed and pressurized. The resin is placed under vacuum to remove any gases (air) and then it is pressured with the pure gases of interest (e.g., oxygen). To enhance the bulk concentration of gas (e.g., oxygen) small porous inert particles (e.g., molecular sieve, wood fiber) may be pressurized and incorporated into the resin. The pressure and gas can be varied to introduce a variety of bulk properties in the final product. In the case of oxygen, the gas may be used to limit the growth of cured pixels of the resin.

[0023] Example 4. The system is operated as in Example 1, but one or more (large) items made of inert materials are placed in predetermined arrays in the reaction vessel [8 in FIG. 2]. These items might be parts (made of metals, plastics, carbon fiber etc.) that are to be partially or totally encapsulated by or chained to the finished plastic product. The items may become integral parts of the final product by bonding with the resin; or they may be used as forms around which the resin is cured. They, may or may not be intended to help support the resin as it cures. These preformed and prepositioned items contribute to the final shape, hardness, rigidity, conductivity, etc. of the part and may be intended to provide specific features in a complex part such as passageways for light, fluids or electrical conductors. They could also provide heavy-duty mounting accessories for the part (e.g., a metal mounting bracket build into a plastic part) or a special metallic covering for part or all of the part (e.g., for thermal insulation or chemical resistance). After curing the resin, any excess projecting fibers etc. can be trimmed mechanically. The compatibility of this process with solid additives in the resin is one of the features that cannot easily be accomplished with step-wise or continuous three-dimensional printing techniques. Incorporation of inert materials in the resin is also desirable because it might allow a commodity plastic to acquire properties (e.g. strength, rigidity) similar to an engineering plastic.

[0024] Example 5. To expedite any of the processes in examples 1-4, multiple independent ion beams can be directed into the reaction mixture from different directions [FIGS. 2, 3 and 4]. In addition, the critical shape elements of the part [12 in FIG. 4] can be formed in the resin without taking the time to fully cure the resin contained inside [13 in FIG. 4] the three-dimensional surface. The “skinned” part can be removed from the resin and completely cured by heat or other source of energy.

[0025] Example 6. To minimize random polymerization in unintended zones in the reaction mixture, the ion beam(s) and reaction mixture can be reoriented in any of the Examples 1-5, so that the unavoidable linear energy transfer from incoming ions is diluted over larger volumes of material. This technique is used in ion beam cancer therapy to minimize damage to healthy tissues.

[0026] Example 7. If desired the ion beam, can operate in a mode very similar to UV-based continuous interface printing. In this case, the Bragg peak is adjusted to facilitate adhesion of the build to a movable stage and is redundantly scanned at that depth as the stage is progressively moved away from the interface. The interface could be the top surface of the resin or near any side or bottom of the container. The container would not need to be permeable to oxygen (as in CLIP). Thus, even though the ion beam is operating more or less like three-dimensional printing, it provides much more flexibility.

[0027] Example 8. This embodiment is similar to Example 2 except that the particles and resin are in a ratio that brings the particles into continuous contact. In this configuration [FIG. 5], the resin merely acts as an adhesive among the particles when it is cured. The liquid resin may be of the same material as the particles or it may be different. This configuration would allow for very fast fabrication because of the relatively small amounts of resin that actually have to be cured. The particles may be inert materials (meta: s, glass, plastic, carbon) and/or they may be fusible such that the cured part may be heated to melt the particles into a solid mass.

[0028] Example 9. As in Example 8, the filler may be metal particles (e.g., alloys of Al, Cu, Fe) and the resin is selectively cured by the ion beam to form a “skin” defining the part to be manufactured. The resin and metallic filler that is not encapsulated by the “skin” is diluted and washed away, The proto-part defined by the skin may be perforated to displace and remove the interior resin, leaving essentially only the metal particles retained inside the skin. Then the proto-part is heated (e.g., by induction heating) to fuse the metal particle together into a metal part. In some cases, it will be possible to remove the skin and encapsulated resin by heating and oxidizing or reducing the resin (e.g., to CO.sub.2 or CH.sub.4, which can be removed as a gas) before fusing the metal particles into a single part.

[0029] Example 10. A liquid resin might be injected into biological tissue and cured by an ion beam, e.g., to heal or replace bones or connective tissue or fill a cavity.

[0030] Example 11. An ion beam might be used as a method of initiating a chemical reaction that releases toxic products from a resin or monomer within a targeted biological system. For example, a small piece of resin might be introduced into a tumor or abscess and targeted with an ion beam causing it to breakdown and release compounds that are toxic at high concentration but biologically innocuous at low concentrations (e.g., HCl).