Patent Application
20170159184
The present inventive subject matter relates to methods and systems for generating conductive circuits for flexible substrates and/or temperature-sensitive substrates.
The following description includes information that may be useful in understanding the present inventive subject matter. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed inventive subject matter, or that any publication specifically or implicitly referenced is prior art.
Metalized plastic, ceramic and composite materials have widespread applications. Metallization of polymer films has previously been achieved under some circumstances using appropriate palladium precursors, followed by thermal treatment, to generate catalytic palladium which initiates electroless metal deposition. However, substrates and polymers that are thermally sensitive, such as paper, polyethylene, clear olefinic polymers (COP), acrylonitrile butadiene styrene(ABS), nylon and cotton based materials, plant leaves, protein and keratin based substrates (human hair) can suffer permanent degradation or deformation, and/or cannot be properly metalized at a high temperature, e.g., 100-200° C. or more. For example, some materials (e.g., ABS material, etc.) can be sufficiently softened at a temperature higher than 100° C. to become difficult to be properly metalized.
Thus, while conventional metallization methods can be used to metalize rigid substrates and/or high-temperature resistant subtrates, such methods cannot be practically or efficiently applied to a many non-rigid substrates and fibers.
Many have made efforts to efficiently metalize fabrics or temperature sensitive materials. For example, Wang et al., in a publication titled “Optimization of process conditions for electroless copper plating on polyester fabric”, published Apr. 16-18, 2011 in 2011 International Conference on Consumer Electronics, Communications and Networks, disclose a method of creating a copper-coated polyester fabric by electroless plating using sodium hypophosphite as a reducing reagent. For another example, U.S. Pat. No. 3,589,962 to Bonjour discloses that metallic layer can be produced over a fabric using a thermoplastic adhesive.
Others have made effort to metalize fabrics using catalysts. For example, U.S. Pat. No. 2,474,502 to Suchy discloses a method of metallization of non-conductive porous material including fabrics. In Suchy, colloidal silver was deposited on textiles via an electro-deposition process using a catalyzer such as stannous chloride. It is also known in the art that various techniques (e.g., vacuum deposition, ion plating, electroplating, electroless plating) can be used to metalize fabrics. Yet, currently available methods are not very effective in creating a thin metal layer (e.g., atomic layer, etc.) on the fabric.
Related arts also include the following, each of which is incorporated herein as references in its entirety.
1. Ceramic Substrates and Packages for Electronic Applications (Advances in Ceramics. W. S. Young (Editor). 1989. ISBN-10: 0916094359.
2. Metalized plastics—fundamentals and applications. Edited by K. L. Mittal, Marcel Dekker, New York, 1998. ISBN 0-8247-9925-9.
3. Sunity Sharma, et. al., U.S. Pat. No. 7,981,508.
4. Sunity Sharma, et. al., US Pat. Application No. 2012/0100286 A1.
5. Sunity Sharma, et. al., US Pat. Application No. 2014/0083748 A1.
6. U.S. Pat. No. 8,110,254: FLEXIBLE CIRCUIT CHEMISTRY: Catalytic ink chemistry for flexible circuit applications (5515-3).
7. U.S. Pat. No. 7,981,508: ADHESIVELESS FLEXIBLE CIRCUIT: All flexible circuits which are copper directly on substrate with only single molecules of active palladium on the surface and with no tie coat or adhesive layer (5516-3).
8. U.S. Pat. No. 8,124,226: ADDITIVE ADHESIVELESS FLEXIBLE CIRCUIT: All flexible circuits which are copper directly deposited on a precursor pattern on a substrate with no tie coat or adhesive layer (5516-5).
9. U.S. Pat. No. 7,989,029: REDUCED POROSITY COPPER DEPOSITION: Flex circuits and coatings with reduced copper porosity (5564-2).
10. U.S. Pat. No. 8,628,818: CONDUCTIVE PATTERN FORMATION: All flexible circuits which are made using a semi-additive process for which the conductive layer is copper directly deposited on a substrate with only single molecules of active palladium on the surface and with no tied coat or adhesive layer (5553-2).
Thus, there is still a need for materials and processes that can be used to generate metal films on the surfaces of temperature-sensitive materials due to application of excessive heat and/or radiation.
The present inventive subject matter provides metalized temperature-sensitive materials, metalized flexible materials, and systems and methods for metalizing a temperature-sensitive material, which includes papers, polymers, clothes and fibers.
One aspect of the inventive subject matter includes a method of metalizing a temperature-sensitive material. The method begins with a step of applying a catalyst solution on the temperature-sensitive material to form an at least partially catalyst-coated substrate. Then the method continues with a step of incubating the catalyst-coated substrate at a temperature less than 100° C. Once the incubation is substantially completed, then a layer of a metal is deposited on the incubated catalyst-coated substrate using an electroless metal deposition technique.
Another aspect of the inventive subject matter includes a method of metalizing a fabric. The method begins with a step of applying a catalyst solution on the fabric to form a catalyst-coated fabric. Then the method continues with a step of incubating the catalyst-coated substrate at a temperature less than 100° C. Once the incubation is substantially completed, then the catalyst-coated substrate is heated at a temperature at least 250° C. Then, an electroless metal layer is placed on the heated catalyst-coated fabric.
Another aspect of the inventive subject matter includes a method of metallizing a substrate. The method begins with a step of applying to the substrate a catalyst precursor that has limited solubility in aqueous or mixed aqueous media to form a catalyst precursor layer. Then, the catalyst precursor layer is substantially dried. Once the catalyst precursor is dried, the substrate is treated with an aqueous or mixed aqueous solution of a reducing agent to converts the catalyst precursor to its active form. Then, an electroless metal layer is placed on the substrate.
Still another aspect of the inventive subject matter includes a method of metallizing a substrate. The method begins with a step of applying to the substrate a catalyst precursor that has limited solubility in aqueous or mixed aqueous media to form a catalyst precursor layer. Then, the catalyst precursor layer is substantially dried. Once the catalyst precursor is dried, the substrate is treated with electromagnetic radiation to generate an active catalyst from the catalyst precursor. Then, an electroless metal layer is placed on the substrate.
Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
The present inventive subject matter relates to methods, systems and devices for metalizing cloth or other temperature-sensitive materials, and, in some embodiments, for constructing circuits for “Smart Clothing”. Further, the present inventive subject matter relates to methods, systems and devices for providing or improving electrostatic safety for large composite structures such as aircraft and wind turbine blades.
The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
As used herein, and unless the context dictates otherwise, the term “coupled to” is intended to include both direct coupling (in which two elements that are coupled to each other contact each other) and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms “coupled to” and “coupled with” are used synonymously.
In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the inventive subject matter are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the inventive subject matter are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the inventive subject matter may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints and open-ended ranges should be interpreted to include only commercially practical values. The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value within a range is incorporated into the specification as if it were individually recited herein. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary.
All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the inventive subject matter and does not pose a limitation on the scope of the inventive subject matter otherwise claimed. No language in the application should be construed as indicating any non-claimed element essential to the practice of the inventive subject matter.
Groupings of alternative elements or embodiments of the inventive subject matter disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.
The present inventive subject matter uses a variation of a precursor catalytic ink to print a precursor metalized pattern on a substrate at a range of temperatures suitable for a wide range of substrates and fibers. At least one of advantages of the present inventive subject matter is that it allows for efficient metallization for Smart Clothing, electrically safe composite structures, and lower cost medical applications.
One aspect of the present inventive subject matter includes a metalized temperature-sensitive material.
Preferably, the substrate layer 105 comprises a flexible material, and the flexibility of metallized substrate 100 maintains at least 50%, preferably at least 70%, more preferably at least 90% of the flexibility (e.g., rigidity, stiffness, etc.) of the substrate layer 105. It is also preferred that the metallized substrate 100 substantially maintains the shape of the substrate layer 105 (i.e., without substantial deformation (e.g., wrinkling, shrinking, tearing, loosening, shearing, pilling, etc.) from the original shape of the substrate layer such as)
Another aspect of the present inventive subject matter includes a method of metalizing a temperature-sensitive material.
As used herein, the term “temperature-sensitive” as applied to a material means that the material suffers a temporary or permanent decomposition or deformation as a result of being subjected to a temperature between 100° C. and 200° C. (e.g., directly heated, indirectly exposed, etc.).
It is contemplated that many precious metals can be used as catalyst for electroless plating, including for example, palladium, gold, silver, tin, ruthenium and platinum. In a preferred embodiment, a palladium precursor solution is used as a catalyst solution. In this embodiment, it is contemplated that the palladium precursor solution is prepared in a form of palladium propionate (e.g., palladium (II) propionate-cyclopentylamine complex, etc.). Additional details on preparing a palladium propionate solution are described in the U.S. Pat. No. 8,628,818, which is incorporated herein by reference in its entirety.
In a preferred embodiment, the catalyst layer is thin enough not to substantially change the flexibility or the thickness of the substrate material. Thus, it is preferred that the catalyst layer has an average thickness of less than 20 atoms, preferably less than 10 atoms, more preferably less than 5 atoms, and most preferably less than 3 atoms. In some embodiments, the thickness of the catalyst layer is achieved by modulating the concentration of catalyst metals in the solution. For example, it is preferred that a palladium propionate solution contains palladium in a concentration less than 10,000 ppm, more preferably 7,000 ppm, most preferably, less than 5,000 ppm.
In some embodiments, the temperature-sensitive material is treated with a solution (e.g., potassium permanganate, sulfuric acid, formic acid, etc.) at a temperature less than 100° C. before applying the catalyst solution. In a preferred embodiment, the temperature-sensitive material is further treated with acidic solution (e.g., oxalic acid, etc.). To remove the acid residue, it is contemplated that the temperature-sensitive material is washed with water (e.g., deionized water, distilled water, etc.) and/or methanol before placing the catalyst layer.
Once the catalyst layer is placed on the substrate, the method continues with a step 210 of incubating the catalyst-coated substrate at a relatively low temperature. For example, it is contemplated that the catalyst-coated substrate is incubated at a temperature less than 100° C., preferably less than 80° C., more preferably less than 60° C.
Optionally, the catalyst-coated substrate can be treated (e.g., washed, etc.) with reducing agent solutions. In a preferred embodiment, the reducing agent is in an aqueous or mixed aqueous solvent (e.g., alcoholic and water solvent, etc.) or solvents (e.g., aqueous and nonaqueous solvent mixtures, etc.). For example, the reducing agent include hydrazineN2H4 in its various forms (e.g., in a form of an aqueous solution, salts, ascorbic acid, aldehydes, alcohols, etc.)
After the incubation of the catalyst-coated substrate, the method continues with a step 215 of placing an electroless metal layer (e.g., copper, nickel, etc.) on the catalyst-coated substrate. The details of the electroless metal deposition technique are described in the inventors' co-pending application, U.S. Pub. No. US 2016/0113121, which is incorporated in its entirety herein.
It is contemplated that this method 200 enables the user to generate the metalized substrate without a substantial deformation or degeneration of the original substrate materials (e.g., the substrate that is prone to be deformed or degenerated at a temperature at or around 100° C., or at a temperature between 100° C. and 200° C., etc.). Because the conventional method of metalizing requires a treatment step at high temperatures (e.g., higher than 200° C., etc.), such conventional method cannot be used to metalize various non heat-resistant or less heat-resistant materials. Thus, this method is contemplated to widen the use and scope of metalizing techniques to more various substrate materials.
Another aspect of the present inventive subject matter includes a method 300 of metalizing a fabric. Similar to the method 200 of metalizing temperature-sensitive materials, The method 300 begins with a step 305 of applying a catalyst solution (e.g., palladium (II) propionate-cyclopentylamine complex, etc.) on the fabric to form a catalyst-coated fabric. Any suitable type of fabric can be used. For example, a substrate can comprise a carbon fiber cloth, a Kevlar cloth, a cloth containing a natural fiber, or a cloth containing a synthetic fiber.
Once the catalyst solution is applied on the fabric, the method continues with a step 310 of incubating the catalyst-coated substrate at a relatively lower temperature. For example, it is contemplated that the catalyst-coated substrate is incubated at a temperature less than 100° C., preferably less than 80° C., more preferably less than 60° C. In a preferred embodiment, once the catalyst-coated substrate is incubated at a low temperature, then the method continues with an additional step 315 that the catalyst-coated substrate is heated at a temperature at a relatively high temperature (e.g., at least 250° C., at least 300° C., at least 350° C., etc.).
After the incubation of the catalyst-coated substrate, the method continues with a step 320 of placing an electroless metal layer (e.g., copper, nickel, etc.) on the catalyst-coated substrate.
It is contemplated that this method enables the user to generate a metalized substrate that substantially maintains original characters of the substrate materials so that the metalized substrates can be used for the same purpose as the original substrate materials are used. For example, it is highly preferred that the metalized substrate substantially maintains the original flexibility, texture, and/or shape of the substrate material. In this example, when the electroless metal is coated on the nylon fabric, the coated nylon fabric maintains at least 60%, preferably at least 70%, more preferably at least 90% of the nylon substrate's flexibility. For another example, the metalized substrate substantially maintains the original shape of the substrate material (i.e., without substantial deformation (e.g., wrinkling, shrinking, tearing, loosening, shearing, pilling, etc.) from the original shape of the substrate layer, etc.). It is also preferred that the metalized substrate substantially maintains the original texture of the original substrate material (e.g., without substantially additional roughness added to the original substrate material, etc.). Further, it is also preferred that the weight of the metalized substrate is no more than 130%, preferably no more than 120%, more preferably no more than 110% of original substrate material. Thus, for example, if the original substrate is suitable for manufacturing clothing (e.g., T-shirts, a jacket, pants, hats, etc.), the metalized substrate can be also used for clothing without substantially providing discomforts (e.g., excessive weight added on the original fabric substrate, uncomfortable texture, etc.) to the wearer.
Still another aspect of the present inventive subject matter includes a method 400 of metalizing a substrate. The method begins with a step 405 of applying to the substrate a catalyst precursor that has limited solubility in aqueous or mixed aqueous media to form a catalyst precursor layer. Then the method continues with a step 410 of drying the catalyst precursor layer (e.g., air-dried, oven-dried, etc.). Once the catalyst coated substrate is substantially dried (e.g., contains less than 50%, preferably less than 30%, more preferably less than 15%, most preferably less than 10% of the water content before the step of drying), the method continues with a step 415 of treating the substrate with an aqueous or mixed aqueous solution of a reducing agent to convert the catalyst precursor to its active form. Once the catalyst precursor is converted to active catalyst, the method continues with a step 415 of placing an electroless layer of metal (e.g., copper, nickel, etc.) on the substrate.
Still another aspect of the present inventive subject matter includes a method 500 of metalizing a substrate. The method begins with a step 505 of applying to the substrate a catalyst precursor that has limited solubility in aqueous or mixed aqueous media to form a catalyst precursor layer. Then the method continues with a step 510 of drying the catalyst precursor layer (e.g., air-dried, oven-dried, etc.). Once the catalyst coated substrate is substantially dried (e.g., contains less than 50%, preferably less than 30%, more preferably less than 15%, most preferably less than 10% of the water content before the step of drying), the method continues with a step 515 of treating the substrate with coherent or non-coherent electromagnetic radiation to generate an active catalyst from the catalyst precursor. Once the catalyst precursor is converted to active catalyst, the method continues with a step 520 of placing an electroless layer of metal (e.g., copper, nickel, etc.) on the substrate. In some embodiments, the step of treating the substrate can be performed with convective heat transfer. In other embodiments, the step of treating the substrate can be performed with conductive heat transfer.
It should be noted that the palladium solution used herein is not an aqueous solution that are used in metathetical reactions. In metathetical reactions, ionic palladium is converted to catalytic palladium in situ using electroless metal chemistries having reducing agents. Alternatively, a reducing agent is used subsequent to the substrate surface treatment followed by electroless metal deposition. The ionic palladium precursors are water-based soluble palladium salts. Generally, metathetical reactions lead to a formation of colloidal, nano, aggregate nano or bulk precipitation of electroless metals. For example, a precipitation of barium sulfate from a soluble barium salt followed by treatment with a solution containing SO42− ions leads to a bulk precipitation of barium sulfate. A substrate soaked with an aqueous or a mixed aqueous solution of a metal salt and then treated with a suitable reducing agent or agents reduces the soluble metal salt to metal. Because metals are generally insoluble in water, the reduced metal will be precipitated. Thus it is redox reaction that converts a soluble metal salt to a precipitated metal and is similar to a precipitation reaction similar to the example of barium sulfate precipitation from a soluble barium salt. The deposition of the catalyst using a soluble metal compound can be depicted as following:
This represents a typical example of generating ionic palladium catalyst.
Instead of aqueous solutions, the inventors use a palladium compound that is water insoluble or has limited water solubility. A non-aqueous precursor is deposited on a porous or non-porous substrate followed by treatment with a reducing agent. By using non-aqueous palladium compound, the inventors could avoid metathetical reaction of precipitation of palladium in the aqueous medium. As the inventors could avoid bulk precipitation of palladium metals, the inventors could achieve the formation of near “atomic” or sub-nano palladium particles.
The above chemical reaction typically represents the generation of the active catalytic palladium according to the present inventive subject matter.
Inventors have successfully developed materials and processes for the metallization of such materials. The following examples illustrate the basic and key features of this inventive subject matter. The process described below is generic enough to be used for those porous materials which can stand high temperatures.
A solution of palladium propionate was prepared in dimethyl sulfoxide (DMSO) solvent as follows: Solution (A): Pd(II)propionate=9.5 gm of palladium was added to 45 gm dimethyl sulfoxide (DMSO) and warmed to dissolve; Solution (B): The following ingredients were mixed together: 54.45 gm DMSO, 0.66 gm Et3N, 0.25 gm HCOOH, 22 gm isopropyl alcohol (IPA) and 22 gm HCONH2.
An ABS substrate was dipped in a solution of 5% potassium permanganate (w/v) prepared in 20% sulfuric acid at 60-70 degree Celsius for 3 minutes. The substrate was then dipped in 5% oxalic acid solution in 10% sulfuric acid (w/v) for 1 minute at room temperature followed by washing with water. The substrate was washed with IPA and dried. It was then coated with a coating solution prepared by mixing 1 gm of solution A with 7.26 gm of solution B. The mixed solution was quickly coated on the ABS substrate using Meyer rod #8. The substrate was placed in a convection oven at 85° C. for 40 minutes. The substrate was then dipped in electroless copper solution using commercially available electroless copper from MacDermid (Electroless Copper 22). A copper film was obtained on the substrate. The substrate was washed with de-ionized (DI) water and then with methanol and kept in oven at 60° C. for couple of hours.
A challenging issue is the metallization of cellulosic porous media (e.g., photocopying paper, filter papers, etc.). These substrates have cellulose as the main component which is composited with suitable binders to fabricate products for different applications. A filter paper, (e.g., Whatman Filter #1, etc.) is used in teaching and research for routine filtration. One of the issues is that the filter paper becomes very fragile in aqueous media which is normally the media for routine chemical, physicochemical and even biological applications. The filter paper cannot be used in acidic and alkaline media as the cellulose fibers and/or the compositing binders are dissolved or attacked by alkalis or acids thus rendering the filter paper unworthy of use under such conditions. However, if the filter paper is metalized in such a way that the fibers of the filtering substrate are completely covered by the metal with the retention of porosity, the resulting metalized filter paper can be used for neutral, alkaline, acidic aqueous and non-aqueous media.
A Whatman Filter #5 was coated with a 3000 ppm palladium ink using palladium propionate in amyl acetate. The substrate was dried in oven at 50° C. It was then dipped in a 10% solution of formic acid in water at 25-35° C. for 1 minute. The filter paper was gently washed with water and methanol and then dipped in electroless copper solution for 15 minutes. An electrically conducting copper coated filter paper was obtained that has porosity. The above method can also be used to metalize fabrics of different varieties. Thus, for example, a clean room swipe was metalized as described in Example 3.
A clean room wipe was soak-coated with a 3000 ppm palladium solution as palladium propionate in amyl acetate. It was dried around 25-40° C. for 45 minutes and dipped in a 10% solution of formic acid in water for 1 minute. It was washed with water and then dipped in electroless copper solution (Electroless Copper 22) for 30 minutes. An electrically conducting swipe was obtained.
A Kevlar cloth was soak coated with a 3000 ppm palladium solution as palladium propionate in amyl acetate as described above. It was dried 40-50° C. for 15 minutes and then heated at 300° C. for 9 min followed by treatment by electroless copper solution. A nice copper deposition was obtained on the entire fabric cloth. An electrically conducting swipe was obtained.
A carbon fiber cloth was soak-coated with a 3000 ppm palladium solution as palladium propionate in amyl acetate as described above. It was dried 40-50° C. for 15 minutes and then heated at 300° C. for 9 min followed by treatment by electroless copper solution. A nice copper deposition was obtained on the entire fabric cloth. An electrically conducting swipe was obtained.
It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C . . . and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.
This application claims the benefit of priority to U.S. Provisional Patent Application No. 62/264,237, filed Dec. 7, 2015. Where a definition or use of a term in a reference that is incorporated by reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein is deemed to be controlling.
| Number | Date | Country | |
|---|---|---|---|
| 62264237 | Dec 2015 | US |
