WO2016126212A1

WO2016126212A1 - A process for plating a metal on a textile fiber

Info

Publication number: WO2016126212A1
Application number: PCT/SG2016/050061
Authority: WO
Inventors: Shuang-yuan ZHANG; Kwok Wei Shah; Hongchen GUO; Michelle Dela Cruz REGULACIO; Jie Zhang; Ming-yong Han
Original assignee: Agency For Science, Technology And Research
Priority date: 2015-02-04
Filing date: 2016-02-04
Publication date: 2016-08-11

Abstract

There is provided a process for plating a metal on a textile fiber comprising the steps of: an optional pretreatment process (2); contacting the textile fiber with a first formulation comprising metal ions to thereby deposit the metal ions onto the textile fiber (4); contacting the metal ion deposited textile fiber with a second formulation comprising a reducing agent to thereby reduce the deposited metal ions to form the metal on the textile fiber (6); a repeat step (8) in which the first contacting step (4) and second contacting step (6); an optional contacting step (10) in which the metal plated textile fibers are contacted with a surface capping ligand to encapsulate the plated metal.

Description

Title of Invention : A Process for Plating a

Metal on a Textile Fiber

Technical Field

The present invention generally relates to a process for plating a metal on a textile fiber. The present invention also relates to a textile having a pattern thereon.

Background Art

The incorporation of metals into textile materials has a long history in mankind's civilization. During the ancient Egyptian era, noble metals including copper had been used mainly for decoration of textiles for the kings and nobilities. In modern times, the incorporation of conductive metals into insulating textile materials can serve a variety of purposes

Copper is an earth- abundant conductive material that has excellent electromigration resistance and relatively low specific resistance. Therefore, when copper is plated onto clothing and interior decoration, it is expected that unique properties including anti-static, electromagnetic interference (EMI) shielding, UV radiation screen, radar reflectivity, antibacterial/fungicide, lightning strike protection, as well as intelligent usage can be realized. When copper is used for ultra-large-scale integration fine wiring, it is desirable that current carrying capacity will remain unchanged in proportion to miniaturization and high integration density of the smaller devices.

Suitable methods of forming copper structures onto surfaces of insulating textile materials include electroless plating, which deposits a copper metal film by the reaction between a reductant and an oxidant in solution. It can provide a copper layer throughout the entire surfaces without using an external power source or thermal heater. This holds great promise as a method to form a copper film on insulating textiles, and as a replacement for the sputtering, vapor deposition and electrolytic copper plating methods currently in use.

Conventional methods of reducing copper from solution to the metallic state are well documented. However, when conventional electroless plating was used to deposit copper onto an insulating substrate such as textile, it did not satisfactorily produce a continuous conducting film having good adhesion to an insulating surface. In addition, the plating reactivity was low and it was difficult to plate uniformly over the entire substrate. Such processes were often accomplished with considerable heating of the solution, which resulted in the processes becoming impractical for substrates made of certain thermoplastic materials. Needless to say, the use of conventional electroless copper plating for insulating textile materials faces several issues such as low adhesive strength, poor plating uniformity, and high plating temperature.

Currently, a number of new electroless plating approaches have been proposed to address the above issues, but such approaches have always required extensive pretreatments such as sealing, sandblasting, etching, as well as using chemical sensitizers, plasma or supercritical carbon oxide. Pretreatments are necessary to enhance the chemical bonding interactions between metallic copper and textile materials, and improve the hydrophilic and absorption properties of textile materials prior to electroless copper plating. These require special machinery and long processing times and have thus increased the cost of such platings.

Apart from this, the existing approaches are based on immersing the insulating textile materials into one-port plating solution, which results in a substrate completely coated with copper but having no patterns. Thus, with the known methods, it is impossible to achieve selective deposition of copper into lithography like designs.

There is a need to provide a process for plating a material that overcomes, or at least ameliorates, one or more of the disadvantages described above.

There is a need to provide process for forming a pattern on a material.

Summary of Invention

According to a first aspect, there is provided a process for plating a metal on a textile fiber comprising the steps of (a) contacting the textile fiber with a first formulation comprising metal ions to thereby deposit the metal ions onto the textile fiber; and (b) contacting the metal ion deposited textile fiber with a second formulation comprising a reducing agent to thereby reduce the deposited metal ions to form the metal on the textile fiber.

The process may be a form of electroless plating. However, compared to conventional electroless plating in which the metal ions and reducing agent are present in the same formulation, the first formulation of the present application is separate from the second formulation. By having the first formulation separate from the second formulation, this may enable a strong reducing agent or a high concentration of the reducing agent to be used in the second formulation. This is not possible with conventional electroless plating since if the concentration of the reducing agent is too high or if the reducing agent is too strong, this causes premature reduction of the metal ion to the corresponding metal in the plating bath, such that the deposition of the metal ions on the article to be plated is reduced or prevented significantly. In addition, by using a high concentration of the reducing agent or a strong reducing agent in the second formulation, this may advantageously enable a fast deposition of the metal ion onto the textile fiber or may result in better adhesion of the metal or metal ion onto the textile fiber.

Due to the use of a strong reducing agent, the process may not require a pre -treatment step or a pre-activation step. Hence, the process of the present application may be different from a conventional electroless plating process which does require a pre-treatment and/or pre- activation step(s). Hence, in the process of the first aspect, the process may optionally exclude a step of pre-treatment or pre-activation.

According to a second aspect, there is provided a process for forming a pattern on a textile comprising the steps of (a) contacting an area of the textile to be patterned with a first formulation comprising metal ions to thereby deposit the metal ions onto the area of the textile; and (b) contacting the textile or the area of the textile with a second formulation comprising a reducing agent to thereby reduce the deposited metal ions to form a metal, wherein the metal forms the pattern on the textile. According to a third aspect, there is provided a textile having a pattern thereon, wherein the pattern is formed on an area of the textile and wherein the pattern is composed of a plurality of metal plated textile fibers.

The pattern on the textile may be defined by a user or may be a random pattern. Hence, the patterned textile is different from other articles coated via conventional electroless plating because in conventional electroless plating, the article tend to be fully immersed into the plating solution. However, the inventors of the present application have been able to form patterns on the textile, which can aid in the production of wearable technology, where the patterns on the textile may form circuit lines that allow the patterned area of the textile to conduct electricity.

According to a fourth aspect, there is provided a system for forming a pattern on a textile, wherein the pattern is formed on an area of the textile, the system comprising (a) a first formulation comprising a metal ion; (b) means for depositing the metal ion onto the area of the textile; (c) a second formulation comprising a reducing agent; and (d) means for contacting the textile having metal ions deposited thereon with the second formulation to reduce the metal ion into a metal.

Definitions

The following words and terms used herein shall have the meaning indicated:

The term 'textile' is to be interpreted broadly to include a flexible material consisting of a network of natural or artificial fibers. The fibers of the textile may be termed herein as "textile fiber" and may be from natural sources or may be synthetic. The fiber may be from cotton, silk, wool, linen or synthetic yarn, polyester, nylon, aramid, polyamide, etc. The fiber may be synthetic cellulosic fibers, regenerated protein fibers, acrylic fibers, polyolefin fibers, polyurethane fibers, vinyl fibers, nylon fibers, polyester fibers, aramid fibers, polyamide fibers, etc and blends thereof. The synthetic cellulosic fibers may be regenerated cellulose fibers such as rayon, and cellulose derivative fibers such as acetate fibers.

The term "electroless plating" is to be interpreted broadly to refer to the metallic deposition (from a suitable formulation or bath) of metals and/or alloys onto a textile fiber. Electroles s plating is a chemical reduction process in which a chemical reducing agent in an aqueous solution is used to drive a catalytic reduction of metal ions to metal, such that metal is resultantly deposited on the textile fiber without the use of electrical energy.

The word "substantially" does not exclude "completely" e.g. a composition which is "substantially free" from Y may be completely free from Y. Where necessary, the word "substantially" may be omitted from the definition of the invention.

Unless specified otherwise, the terms "comprising" and "comprise", and grammatical variants thereof, are intended to represent "open" or "inclusive" language such that they include recited elements but also permit inclusion of additional, unrecited elements.

As used herein, the term "about", in the context of concentrations of components of the formulations, typically means +/- 5% of the stated value, more typically +/- 4% of the stated value, more typically +/- 3% of the stated value, more typically, +/- 2% of the stated value, even more typically +/- 1% of the stated value, and even more typically +/- 0.5% of the stated value.

Throughout this disclosure, certain embodiments may be disclosed in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosed ranges. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

Certain embodiments may also be described broadly and generically herein. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the disclosure. This includes the generic description of the embodiments with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein.

Detailed Disclosure of Embodiments

Exemplary, non-limiting embodiments of a process for plating a metal on a textile fiber will now be disclosed.

The process for plating a metal on a textile fiber comprises the steps of (a) contacting the textile fiber with a first formulation comprising metal ions to thereby deposit the metal ions onto the textile fiber; and (b) contacting the metal ion deposited textile fiber with a second formulation comprising a reducing agent to thereby reduce the deposited metal ions to form the metal on the textile fiber.

The process may not require heating, and may be carried out at an ambient or room temperature, such as from about 10°C to about 40°C, about 10°C to about 20°C, about 10°C to about 30°C, about 20°C to about 40°C, about 30°C to about 40°C, about 20°C to about 30°C, about 20°C to about 25°C, or about 25°C to about 30°C.

The process may be fast in the sense that each contacting step may be carried out for a few seconds to a few minutes, or less than 30 minutes. It is to be noted that these time periods are only guidelines and are dependent on the type of reducing agent used in the second formulation.

The process may further comprise the step of (c) repeating steps (a) and (b) to increase the thickness or density of the plated metal on the textile fiber. The repeating step (c) may be carried out at least once, such as one, two, three, four, five, or more times.

Before the process is carried out, an optional pretreatment process may be carried out. It is to be noted that this is an optional step and that in some embodiments; this step is not required at all. Hence, in such embodiments, the process may optionally exclude a step of pre-treatment or pre-activation. In embodiments where the optional pretreatment process is carried out, this may be a sensitization process in which the textile material may be immersed in a sensitizing solution. The sensitizing solution may comprise tin(II) ions, titanium(II) ions, zirconium(II) ions or thorium(II) ions, at a concentration in the range of about 0.0001 mol L to about 0.1 mol L. The pH of the sensitizing solution can be adjusted as appropriate to dissolve and release the above ions from their corresponding compounds. The ions in the sensitizing solution are absorbed by the textile material to sensitize the insulating surfaces.

The textile material then undergoes a pre-activation process in which nucleation takes place on the sensitized surfaces by placing the textile material in an activation solution under acidic conditions. The activation solution may comprise palladium(II) ions or platinum ions, or ions from other noble metals, at a concentration that is comparable to that of the ions in the sensitizing solution. The pH of the activation solution can be adjusted as appropriate to dissolve and release the above ions from their corresponding compounds. The ions on the sensitized surfaces react with the ions in the activation solution to produce small metal clusters on the textile surfaces, which act as a series of nuclei for the adhesion and deposition of metal atoms in the subsequent plating process. The textile materials after pretreatment and pre-activation have to be rinsed and washed thoroughly to get rid of excess ions.

In the plating process, the metal that is plated onto the textile fiber may be a transition metal. Since the plated metal is derived from the metal ion, the metal of the metal ion may also be a transition metal. The transition metal may be a noble metal. The transition metal may be selected from the group consisting of copper, nickel, silver, cobalt, gold, palladium, iron, and mixtures thereof.

The first formulation may comprise a metal compound as a source for the metal ions. The metal compound may be soluble in water, forming an aqueous solution. The metal compound may be selected from the group consisting of a metal sulphate, metal nitrate, metal chloride, a metal bromide, a metal iodide, a metal perchlorate, a metal acetate and a metal cyanide. The metal compound may be selected from the group consisting of a copper(II) sulphate, a copper(II) nitrate, a copper(II) chloride, a copper(II) bromide, a copper(II) iodide, a copper(II) perchlorate, a copper(II) acetate, a copper(II) cyanide, a nickel sulphate, a nickel nitrate, a nickel chloride, a nickel bromide, a nickel iodide, a nickel perchlorate, a nickel acetate, a silver nitrate, a silver perchlorate, a silver acetate, a cobalt(II) sulphate, a cobalt(II) nitrate, a cobalt(II) chloride, a cobalt(II) bromide, a cobalt(II) iodide, a cobalt(II) perchlorate, a cobalt(II) acetate, a gold chloride, a gold bromide, a gold iodide, a gold acetate, a palladium(II) sulphate, a palladium(II) nitrate, a palladium(II) chloride, a palladium(II) bromide, a palladium(II) iodide, a palladium(II) perchlorate, a palladium(II) acetate, an iron(II) sulphate, an iron(II) nitrate, an iron(II) chloride, an iron(II) bromide, an iron(II) iodide, an iron(II) perchlorate, an iron(II) acetate, an iron(III) sulphate, an iron(III) nitrate, an iron(III) chloride, an iron(III) bromide, an iron(III) iodide, an iron(III) perchlorate and an iron(III) acetate.

The concentration of the metal ions in the first formulation may be in the range of about 0.001 mol L to about 0.2 mol/L, about 0.001 mol/L to about 0.005 mol/L, about 0.001 mol/L to about 0.01 mol/L, about 0.001 mol/L to about 0.05 mol/L, about 0.001 mol/L to about 0.1 mol/L, about 0.001 mol/L to about 0.15 mol/L, about 0.005 mol/L to about 0.2 mol/L, about 0.01 mol/L to about 0.2 mol/L, about 0.05 mol/L to about 0.2 mol/L, about 0.1 mol/L to about 0.2 mol/L, about 0.15 mol/L to about 0.2 mol/L, or about 0.01 mol/L to about 0.05 mol L.

The first formulation may further comprise a complexing agent for the metal ions. The complexing agent may be selected from hydroxy(poly)carboxylic acids or carboxylates, such as salicylic acid, tartrates, glycolic acid, propanoic acid or carnitine. The complexing agent may be selected from amino(poly)carboxylic acids, such as Fura-2, iminodiacetic acid, nitriloacetic acid, EDTA, diethylene triamine pentaacetic acid, ethylene glycol bis(2- aminoethylether)-N,N,N',N'- tetraacetic acid, l,2-bis(o-aminophenoxy)ethane- Ν,Ν,Ν',Ν'- tetraacetic acid, 1,4,7, 10-tetraazacyclododecane- l, 4,7, 10-tetraacetic acid or nicotinamine. The complexing agent may be selected from nitrogen-containing functional groups, carboxylic acids, post-transition metal oxides, or esters of phosphoric acids with nucleosides. In particular, the complexing agent may be selected from the group consisting of potassium sodium tartrate, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, ammonia solution, acetic acid, guanylic acid, and stannate. The complexing agent may form a strongly bonded complex with the metal ions, providing long-term stability of the metal ion formulation and increasing the deposition speed of the metal ions on the textile fiber. The concentration of the complexing agent in the first formulation may be at a value that is about two to ten times (such as about two, about three, about four, about five, about six, about seven, about eight, about nine or about ten times) larger than the concentration of the metal ions.

The pH of the first formulation may be adjusted by a pH adjusting agent. The pH adjusting agent may be selected from inorganic bases, such as alkali hydroxides. The pH adjusting agent may be selected from quaternary alkyl ammonium salts, wherein alkyl may be methyl, ethyl, propyl, butyl, pentyl and hexyl. The pH adjusting agent may be selected from mineral acids. The pH adjusting agent may be selected from acetates. The pH adjusting agent may be selected from sulfates. The pH adjusting agent may be selected from halogenides, such as chlorides. The pH adjusting agent may be selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, sulphuric acid, hydrochloric acid, ammonium chloride, ammonium acetate, ammonium sulphate, etc, such that the pH of the first formulation is adjusted to be a value in the range of about 11 to about 14, or about 11, about 12, about 13 or about 14. The alkaline condition of the first formulation advantageously results in the formation of a metal hydroxide complex which increases the viscosity of the first formulation. When using such viscous formulation to create patterns in a textile, the metal ions will not diffuse away and a well-defined pattern can be achieved.

In the second formulation, the reducing agent may be selected from the group consisting of sodium borohydride, potassium borohydride, sodium hypophosphite, ascorbic acid, hydrazine, formaldehyde, formalin, polysaccharide, paraformaldehyde and glyoxylic acid. The concentration of the reducing agent may be two to ten times (such as about two, about three, about four, about five, about six, about seven, about eight, about nine or about ten times) the concentration of the metal ions. By having a high concentration of the reducing agent or by using a strong reducing agent, this may result in a fast deposition speed and better adhesion of the metal.

The pH of the second formulation may be adjusted by a pH adjusting agent. The pH adjusting agent may be selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, sulphuric acid, hydrochloric acid, ammonium chloride, ammonium acetate, ammonium sulphate, etc, such that the pH of the second formulation is adjusted to be a value in the range of about 2 to about 12, or about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, about 10, about 11 or about 12. The pH of the second formulation is dependent on the stability of the reducing agent used.

The first and second formulation may independently further comprise at least one of an additive or a surfactant.

The additive may be selected from the group consisting of a nitrogen-containing compound (such as 2,2'-dipyridyl, 1,2,4-benzoriazole, 1,10-phenanthroline, 2,9-dimethyl-l,10- phenanthroline, potassium ferrocyanide), a sulphur-containing compound (such as thiourea, thiosulphuric acid, 2-mercaptobenzothiazole), an iodine-containing compound (such as sodium iodide, potassium iodide), a monocarboxylic acid (such as glycolic acid, acetic acid, glycine), a dicarboxylic acid (such as oxalic acid, succinic acid), a tricarboxylic acid (such as citric acid, nitrilotriacetic acid) and a poly alky lene glycol (such as polyethylene glycol). The concentration of the additive in either the first or second formulation (or respective concentration in both formulations) may be in the range of about 0.0001 to about 0.2 mol L, about 0.0001 to about 0.0005 mol/L, about 0.0001 to about 0.001 mol/L, about 0.0001 to about 0.005 mol/L, about 0.0001 to about 0.01 mol/L, about 0.0001 to about 0.05 mol/L, about 0.0001 to about 0.1 mol/L, about 0.0001 to about 0.15 mol/L, about 0.0005 to about 0.2 mol/L, about 0.001 to about 0.2 mol/L, about 0.005 to about 0.2 mol/L, about 0.01 to about 0.2 mol/L, about 0.05 to about 0.2 mol/L, about 0.1 to about 0.2 mol/L or about 0.15 to about 0.2 mol/L. Ultimately, the concentration of the additive used may be less than the concentration of the metal ion in the first formulation.

The surfactant may be selected from the group consisting of a non-ionic surfactant, an anionic surfactant, a cationic surfactant and an amphoteric surfactant. The non-ionic surfactant may be selected from the group consisting of fatty alcohol, cetyl alcohols, stearyl alcohol, cetostearyl alcohol or oleyl alcohol. The cationic surfactant may be selected from the group consisting of primary, secondary or tertiary amines at a pH value selected to protonate them, or quaternary ammonium cations. The anionic surfactant may be selected from the group consisting of carboxylates, sulphates, sulphonates or phosphate esters. The amphiphilic surfactant may be selected from molecules which contain a hydrophobic group, such as a straight or branched chain alkyl, alkylene, cycloalkyl, aromatic, and a hydrophilic group, such as ionic functionalities. The amphiphilic surfactant may be, for example, a phosphorlipid. The surfactant may be added to improve the properties of the plating film. The amount of the added surfactant may be in the range of about 0.005 mol/L to about 0.3 mol/L, about 0.005 mol/L to about 0.01 mol/L, about 0.005 mol/L to about 0.05 mol/L, about 0.005 mol/L to about 0.1 mol/L, about 0.005 mol/L to about 0.2 mol/L, about 0.01 mol/L to about 0.3 mol/L, about 0.05 mol/L to about 0.3 mol/L, about 0.1 mol/L to about 0.3 mol/L, or about 0.2 mol/L to about 0.3 mol/L.

Hence, the first formulation may be made up of the metal ions (from the metal compound) , and optionally with one or all of a metal ion complexing agent, a pH adjusting agent, an additive and/or a surfactant. In one embodiment, the first formulation may be made of up the metal ions (from the metal compound), the metal ion complexing agent, the pH adjusting agent and at least one additive. The second formulation may then be made up of the reducing agent, and optionally with one or all of a pH adjusting agent, an additive and/or a surfactant. In one embodiment, the second formulation may be made of up the reducing agent, the pH adjusting agent and at least one additive.

The process may further comprise the step of: (d) contacting the metal plated textile fiber with a surface capping ligand to encapsulate the metal. The surface capping ligand functions to protect the plated metal from oxidation and corrosion. The surface capping ligand may be in the second formulation or in a separate (third) formulation. Where the two contacting steps are to be repeated, the surface capping agent may additionally or alternatively be present in the first formulation. The plated metal may be encapsulated by the surface capping ligands through one or more of the following methods such as soaking, immersion, painting, dripping, etc for a few seconds to several minutes. The final product after capping needs to be rinsed and washed thoroughly to get rid of excess ions.

The surface capping ligand may include various classes of amphiphilic molecules, which contain metal coordinating functional groups at one end and solvophilic functional groups at the other end. The metal coordinating groups are typically electron-donating to allow the formation of coordinating bonds between them and the electron-poor metal atoms at the nanocrystal surface. The metal coordinating functional groups may be selected from oxygen- containing functionalities such as acid and alcohol functionalities. The metal coordinating functional groups may be selected from nitrogen functionalities, such as primary amines, secondary amines or tertiary amines. The metal coordinating functional groups may be selected from sulfur- containing functionalities such as thiols, thiourea, sulfuric acids, dithionates or thiosulfuric acids. The metal coordinating functional groups may be selected from phosphor-containing functionalities, such as phosphines, phosphine oxides and phosphonic acids. The metal coordinating functional groups may be selected from heteroaromatic moieties, for example nitrogen -containing heterocycles such as pyridine, imidazole, pyrazole, pyrazine, pyrimidine, piperidine or morpholine. The solvophilic functional groups are generally hydrophobic, which makes them compatible with organic solvents. The solvophilic functional groups may be selected from straight or branched chain alkyl, alkylene, cycloalkyl, cycloalkylene or aromatic functionalities. Hence, the surface capping ligand may be selected from amines, carboxylic acids, amino acids, alkylthiols, alkylphosphine oxides, alkylphosphonic acids, alkylphosphines, and some nitrogen- containing aromatics. In particular, the surface capping ligand may be selected from ascorbic acid, thiourea, trioctylphosphine oxide, acetic acid, glycine, glycolic acid, alanine, lactic acid, citric acid, etc. The amount of the surface capping ligand may be in the range of about 0.005 mol L to about 0.3 mol L, about 0.005 mol L to about 0.01 mol L, about 0.005 mol L to about 0.05 mol/L, about 0.005 mol/L to about 0.1 mol/L, about 0.005 mol/L to about 0.2 mol/L, about 0.01 mol/L to about 0.3 mol/L, about 0.05 mol/L to about 0.3 mol/L, about 0.1 mol/L to about 0.3 mol/L, or about 0.2 mol/L to about 0.3 mol/L.

The plated metal on the textile fibers may be in the form of structures. The structures may be layered structures. The structures may comprise nanoparticles (forming nanostructures) or microparticles (forming microparticles).

Exemplary, non-limiting embodiments of a process for forming a pattern on a textile will now be disclosed. The process for forming a pattern on a textile comprises the steps of (a) contacting an area of the textile to be patterned with a first formulation comprising metal ions to thereby deposit the metal ions onto the area of the textile; and (b) contacting the textile or the area of the textile with a second formulation comprising a reducing agent to thereby reduce the deposited metal ions to form a metal, wherein the metal forms the pattern on the textile.

The pattern may be formed on selected areas of the textile, or the pattern may be formed by random areas of the textile. The desired area of the textile may be contacted with the first formulation by painting or dripping. Following which, the (entire) textile or the same areas as before may be contacted with the second formulation by soaking, immersing, painting or dripping. The above can be repeated by cycling between the first and second formulations.

Exemplary, non-limiting embodiments of a textile will now be disclosed. The textile may have a pattern thereon, wherein the pattern is formed on an area of the textile and wherein the pattern is composed of a plurality of metal plated textile fibers.

The metal plated onto the textile fiber may be encapsulated with a surface capping ligand.

The textile, due to the presence of the plated metal, is able to conduct electricity (compared to a non-plated textile which cannot conduct electricity). The conductivity may be measured according to the equation stated in Example 3 below and may be in the range of about 2 x 10⁶ s/m to about 5 x 10⁶ s/m, about 2 x 10⁶ s/m to about 3 x 10⁶ s/m, about 2 x 10⁶ s/m to about 4 x 10⁶ s/m, about 3 x 10⁶ s/m to about 5 x 10⁶ s/m, about 4 x 10⁶ s/m to about 5 x 10⁶ s/m, or about 3 x 10⁶ s/m to about 4 x 10⁶ s/m.

The resistivity of the patterned textile may be determined also according to Example 3 below and may be in the range of about 0.1 Ω to about 0.3 Ω, about 0.1 Ω to about 0.15 Ω, about 0.1 Ω to about 0.2 Ω, about 0.1 Ω to about 0.25 Ω, about 0.15 Ω to about 0.3 Ω, about 0.2 Ω to about 0.3 Ω, about 0.25 Ω to about 0.3 Ω, or about 0.15 Ω to about 0.2 Ω.

The average thickness of the platted metal as measured according to Example 3 below may be in the range of about 1 μηι to about 3 μιη, about 1 μηι to about 1.5 μπι, about 1 μιτι to about 2 μιτι, about 1 μιη ΐο about 2.5 μπι, about 1.5 μπι to about 3 μιτι, about 2 μπι to about 3 μπι, about 2.5 μπι to about 3 μπι, or about 1.25 μπι to about 1.75 μπι.

Exemplary, non-limiting embodiments of a system for forming a pattern on a textile, wherein the pattern is formed on an area of the textile, will now be disclosed. The system comprises (a) a first formulation comprising a metal ion; (b) means for depositing the metal ion onto the area of the textile; (c) a second formulation comprising a reducing agent; and (d) means for contacting the textile having metal ions deposited thereon with the second formulation to reduce the metal ion into a metal.

As mentioned, the means for depositing the metal ion onto the area of the textile may include painting or dripping, while the means for contacting the textile having metal ions deposited thereon with the second formulation may include soaking, immersing, painting or dripping.

Brief Description of Drawings The accompanying drawings illustrate a disclosed embodiment and serves to explain the principles of the disclosed embodiment. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.

Fig.l

[Fig. 1] is a schematic description of the electroless copper plating with patterns.

Fig.2

[Fig. 2] shows the difference of cotton material before and after the electroless copper plating.

[Fig. 2A] shows the XRD patterns of untreated cotton (bottom graph) and electroless copper plated cotton (top graph).

[Fig. 2B] shows a photo of untreated cotton.

[Fig. 2C] shows a SEM image of untreated cotton.

[Fig. 2D] shows a photo of electroless copper plated cotton.

[Fig. 2E] shows a SEM image of electroless copper plated cotton.

Fig.3

[Fig.3] shows the chemical composition of the electroless copper plated cotton. The scale bars are the same for Fig.s 3A to 3D.

[Fig. 3A] shows an electron image.

[Fig. 3B] shows the electron image for copper.

[Fig. 3C] shows the electron image for carbon.

[Fig. 3D] shows the electron image for oxygen.

[Fig. 3E] shows an EDS spectrum of the electroless copper plated cotton fibers.

Fig.4

[Fig. 4] shows XRD patterns and SEM images of the electroless copper plating on different textiles.

[Fig. 4A] shows the XRD patterns of an untreated textile consisting of 65% polyester and 35% cotton (bottom graph) and an electroless copper plated textile consisting of 65% polyester and 35% cotton (top graph).

[Fig. 4B] shows the SEM images of an untreated textile consisting of 65% polyester and 35% cotton and an electroless copper plated textile consisting of 65% polyester and 35% cotton.

[Fig. 4C] shows the XRD patterns of an untreated textile consisting of 87% polyester and 13% nylon (bottom graph) and an electroless copper plated textile consisting of 87% polyester and 13% nylon (top graph).

[Fig. 4D] shows the SEM images of an untreated textile consisting of 87% polyester and 13% nylon and an electroless copper plated textile consisting of 87% polyester and 13% nylon.

Fig.5 [Fig.5] shows the physical properties of the electroless copper plated cotton. [Fig. 3 A] shows an electron image.

[Fig. 5A] shows a schematic diagram of the 4 probe sheet resistance measurement.

[Fig. 5B] shows a cross-section SEM image of a typical electroless copper plated cotton cloth.

Detailed Description of Drawings

Referring to Fig. 1, there is provided a schematic description of the process for plating a metal on a textile fiber. As shown in Fig. 1, the textile was subjected to an optional pretreatment (2) process. The textile was then subjected to a first contacting step (4) such that the fibers of the textile are contacted with a first formulation comprising metal ions to thereby deposit the metal ions onto the textile fibers. Following which, the textile was subjected to a second contacting step (6) such that the metal ion deposited textile fibers are contacted with a second formulation comprising a reducing agent to thereby reduce the deposited metal ions to form the metal on the textile fibers. Where required (hence optional), the textile is subjected to a repeat step (8) in which the first contacting step (4) and second contacting step (6) are repeated a number of times as desired. Lastly, the textile is subjected to a third contacting step (10) (which is also optional) in which the metal plated textile fibers are contacted with a surface capping ligand to encapsulate the plated metal.

Examples

Non-limiting examples of the invention and a comparative example will be further described in greater detail by reference to specific Examples, which should not be construed as in any way limiting the scope of the invention.

Example 1

Chemicals. Copper (II) sulfate pentahydrate (CuS0₄-5H₂0, 99.995%), 2,2'-dipyridyl Ν,Ν'- dioxide (98%), L-ascorbic acid (99%) and polyethylene glycol (average molecule weight 8000) were purchased from Sigma-Aldrich. Sodium borohydride (99.99%) and thiourea (99.0%) were purchased from Acros. Sodium hydroxide (99%) was purchased from Merck. All the chemicals were used without further purification.

A first formulation such as a copper ion bath was prepared by dissolving 224 mg CuS0₄.5H₂0 in 30 mL water. 3 to 4 mg 2,2-diyridyl Ν,Ν-dioxide was added to the solution following by 80 mg polyethylene glycol (average molecule weight 8000). The pH of the above solution was adjusted to about 13 by adding 120 mg NaOH. A second formulation such as a reducing bath was prepared by dissolving 250 mg ascorbic acid and 3 to 4 mg 2,2-diyridyl Ν,Ν-dioxide in 20 mL water. The process of Fig. 1 was used here, but without the pretreatment step (2) and third contacting step (10).

A user-defined pattern can be painted onto the textile materials, e.g. cotton cloth, using a brush with copper ion bath for 5- 10 times. The copper ion pattered textile materials were then immersed in the reducing bath for 1 minute at room temperature. A dense copper deposition was achieved by repeating the copper ion pattern and copper deposition steps for 5 times. The textile materials after above process were washed and rinsed to get rid of extra chemicals. The platted copper patterns were well-defined and appeared bright yellow in color. The platted copper surfaces of the textile materials were subjected to the tape peel test, which revealed a good adhesion, with no peeling at all.

Example 2

A first formulation such as a copper ion bath was prepared by dissolving 224 mg CuS0₄.5H₂0 in 30 mL water. 3 to 4 mg 2,2-diyridyl Ν,Ν-dioxide was added to the solution following by 40 mg polyethylene glycol (average molecule weight 8000). The pH of above solution was adjusted to about 13 by adding 120 mg NaOH. A second formulation such as a reducing bath was prepared by dissolving 300 mg NaBH₄ in 20 mL water. 3 mg NaOH was added to adjust the reducing bath pH so that minimizing the reaction between NaBH₄ and water. The process of Fig. 1 was used here, but without the pretreatment step (2).

Additional surface capping ligand bath was prepared by dissolving 250 mg thiourea in 20 mL water. A user-defined pattern can be painted onto the textile materials, e.g. cotton cloth, using a brush with copper ion bath for 5- 10 times. The copper ion pattered textile materials were then immersed in the reducing bath for 30 second at room temperature. A dense copper deposition was achieved by repeating the copper ion pattern and copper deposition steps for 5 times. The textile materials were then subjected to surfactant protection by soaking in surfactant bath for 3- 10 minute. The textile materials after above process were washed and rinsed to get rid of extra chemicals. The platted copper patterns were well- defined and appeared dark brown/black in color. The platted copper surfaces of the textile materials were subjected to the tape peel test, which revealed a good adhesion, with no peeling at all.

Example 3

A first formulation such as a copper ion bath was prepared by dissolving 224 mg CuS0₄.5H₂0 in 30 mL water. 115 mg rochelle salt was added to the solution. The pH of above solution was adjusted to about 12-13 by adding 80 mg NaOH. A second formulation such as a reducing bath was prepared by adding 10 mL 37% formaldehyde solution. The process of Fig. 1 was used here, but without the pretreatment step (2) and third contacting step (10).

A user-defined pattern can be painted onto the textile materials, e.g. cotton cloth, using a brush with copper ion bath for 5- 10 times. The copper ion pattered textile materials were then immersed in the reducing bath for 3 minute at room temperature. A dense copper deposition was achieved by repeating the copper ion pattern and copper deposition steps for 5 times. The textile materials after above process were washed and rinsed to get rid of extra chemicals. The platted copper patterns were well-defined and appeared yellow-to-brown in color. The platted copper surfaces of the textile materials were subjected to the tape peel test, which revealed a good adhesion, with no peeling at all.

Most of the textile materials can be plated using the above-mentioned method. In particular, textiles such as cotton, silk, polyester, nylon, aramid and polyamide, or the like, can be electroless copper plated using stated methods and plating solutions.

A few examples of textiles that have been copper-plated using the above-mentioned electroless copper plating technique are shown below. Fig. 2 lists the difference of cotton material before and after the electroless copper plating. The XRD pattern of electroless copper plated cotton (shown in Fig. 2A) matches well with the diffraction pattern of metallic copper. All the new peaks that emerged from copper plating can be indexed to orthorhombic copper (ICSD code 53247). Scanning electron microscope (SEM) is used to probe the microstructures of cotton fibers. Before the electroless copper plating, as shown in Fig.s 2B and 2C, the cotton piece, around 1.5 cm x 1.5 cm in size, appears white and has smooth microstructures. After the electroless copper plating, as shown in Fig.s 2D and 2E, a dark brown color with metallic luster is stained onto the cotton and small crystal grains are coated onto the surfaces of the cotton fibers.

These small crystals grains on the cotton fibers are further analyzed to reveal their chemical composition. SEM elemental mapping is conducted on electroless copper plated cotton fibers. As can be seen in Fig.s 3A to 3D, the copper element is incorporated all around the cotton fiber surfaces together with the carbon and oxygen present in cotton. The corresponding energy-dispersive X-ray spectroscopy (EDS) spectrum reveals a dose of copper content on the surfaces of cotton fibers.

Other than cotton, composite textile materials such as (a) 65% polyester and 35% cotton, and (b) 87% polyester and 13% nylon are tested using electroless copper plating. The results are depicted in Fig. 4. Similar to the case of cotton, the XRD diffraction patterns of both materials after plating are indexed well to metallic copper structure. Meanwhile, the SEM images after plating demonstrate that microsized crystal grains are successfully coated along the textile fibers.

A piece of 1.5 cm x 1.5 cm cotton cloth is electroless copper platted using the following method. The copper ion bath was prepared by dissolving 224 mg CuS0₄ . 5H₂0 in 30 mL water. 3 to 4 mg 2,2-dipyridyl Ν,Ν-dioxide was added to the solution following by 40 mg polyethylene glycol (average molecule weight 8000). The pH of above solution was adjusted to about 13 by adding 120 mg NaOH. The reducing bath was prepared by dissolving 300 mg NaBH₄ in 20 mL water. 3 mg NaOH was added to adjust the reducing bath pH so that minimizing the reaction between NaBH₄ and water. Additional surfactant bath was prepared by dissolving 250 mg thiourea in 20 mL water. The whole cotton cloth is brushed with copper ion bath for 10 times. The copper ion pattered cotton cloth is then immersed in the reducing bath for 30 second at room temperature. A dense copper deposition is achieved by repeating the copper ion pattern and copper deposition steps for 5 times. The cotton cloth is then subjected to surfactant protection by soaking in surfactant bath for 3- 10 minute. The cotton cloth after above process is washed and rinsed to get rid of extra chemicals. The platted copper patterns were well-defined and appeared brown in color.

The electroless copper platted cotton cloth is then subjected to 4 probe sheet resistance measurement (Fig. 5A) and cross-section scanning electron microscope (SEM) measurement. The sheet resistance (R_s) of as-prepared cotton cloth is 0.17 Ω. The average thickness of platted copper measured by the cross section SEM measurement (Fig. 5B) is around 1.5 μηι. Therefore, the conductivity (σ) of the cotton cloth after electroless copper plating is calculated according to the formula below.

[Math. 1] where 1 is the thickness and A is the area (or l²).

More specifically, σ is 3.9 ^χ 10⁶ s/m according to the calculation below, which is around three times better than that of bulk metal stainless steel.

[Math. 2]

0.17 fi x 1.5 cm x 1.5 μιη

Comparative Example

One comparative example is depicted in Fig. 2, wherein the XRD pattern and SEM images of untreated textiles are shown. In another comparative example, the cotton cloth without any treatment is also tested against the sheet resistance, in which it is open, i.e. not conducting.

Industrial Applicability

The electroless copper plating process and the corresponding copper plating solutions provide unprecedented features, which makes them industrially applicable such as:

(1) Patterned copper plating on textile materials, which provides the basis for wearable electronics.

(2) Stabilized copper structures (free from oxidation and corrosion) in the ambient environment via surfactant capping so that the plated textile materials have good storage properties and do not deteriorate.

(3) Ultrafast copper plating, which can form a copper layer on textile materials within 30 seconds.

(4) Optional pretreatment for textile materials which can avoid the use of noble metals so that the plating process can be simplified and the cost can be reduced.

(5) A wide range of selection of reductants to be used from high reducing power to low reducing power.

(6) Plating at low temperatures such as room temperature, which makes the process feasible for substrates made of thermoplastic materials.

(7) Providing electrical conductivity to previously insulating textile materials after copper plating.

(8) . No requirement on special equipment, adaptable with conventional treating devices.

It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.

Claims

1. A process for plating a metal on a textile fiber comprising the steps of: a) contacting the textile fiber with a first formulation comprising metal ions to thereby deposit the metal ions onto the textile fiber; and b) contacting the metal ion deposited textile fiber with a second formulation comprising a reducing agent to thereby reduce the deposited metal ions to form the metal on the textile fiber.

2. The process of claim 1, further comprising the step of: c) repeating steps (a) and (b) to increase the thickness or density of the plated metal on the textile fiber.

3. The process of claim 1 or 2, wherein the metal is a transition metal.

4. The process of claim 3, wherein the transition metal is selected from the group consisting of copper, nickel, silver, cobalt, gold, palladium, iron, and mixtures thereof.

5. The process according to any one of the preceding claims, wherein said first formulation comprises a metal compound as a source for the metal ions.

6. The process according to claim 5, wherein said metal compound is soluble in water, forming an aqueous solution.

7. The process according to claim 6, wherein said metal compound is selected from the group consisting of a metal sulphate, metal nitrate, metal chloride, a metal bromide, a metal iodide, a metal perchlorate, a metal acetate and a metal cyanide.

8. The process according to claim 5, wherein said metal compound is selected from the group consisting of a copper(II) sulphate, a copper(II) nitrate, a copper(II) chloride, a copper(II) bromide, a copper(II) iodide, a copper(II) perchlorate, a copper(II) acetate, a copper(II) cyanide, a nickel sulphate, a nickel nitrate, a nickel chloride, a nickel bromide, a nickel iodide, a nickel perchlorate, a nickel acetate, a silver nitrate, a silver perchlorate, a silver acetate, a cobalt(II) sulphate, a cobalt(II) nitrate, a cobalt(II) chloride, a cobalt(II) bromide, a cobalt(II) iodide, a cobalt(II) perchlorate, a cobalt(II) acetate, a gold chloride, a gold bromide, a gold iodide, a gold acetate, a palladium(II) sulphate, a palladium(II) nitrate, a palladium(II) chloride, a palladium(II) bromide, a palladium(II) iodide, a palladium(II) perchlorate, a palladium(II) acetate, an iron(II) sulphate, an iron(II) nitrate, an iron(II) chloride, an iron(II) bromide, an iron(II) iodide, an iron(II) perchlorate, an iron(II) acetate, an iron(III) sulphate, an iron(III) nitrate, an iron(III) chloride, an iron(III) bromide, an iron(III) iodide, an iron(III) perchlorate and an iron(III) acetate.

9. The process according to any one of the preceding claims, wherein the concentration of the metal ions in the first formulation is in the range of 0.001 mol L to 0.2 mol L.

10. The process according to any one of the preceding claims, wherein the first formulation further comprises a complexing agent for the metal ions.

11. The process according to claim 10, wherein the complexing agent is selected from the group consisting of potassium sodium tartrate, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, ammonia solution, acetic acid, guanylic acid, and stannate.

12. The process according to any one of the preceding claims, wherein the pH of the first formulation is in the range of 11 to 14.

13. The process according to any one of the preceding claims, wherein the reducing agent of the second formulation is selected from the group consisting of sodium borohydride, potassium borohydride, sodium hypophosphite, ascorbic acid, hydrazine, formaldehyde, formalin, polysaccharide, paraformaldehyde and glyoxylic acid.

14. The process according to any one of claims 9 to 13, wherein the concentration of the reducing agent is two to ten times the concentration of the metal ions.

15. The process according to any one of the preceding claims, wherein the pH of the second formulation is in the range of 2 to 12.

16. The process according to any one of the preceding claims, wherein the first and second formulation independently further comprises at least one of an additive or a surfactant.

17. The process according to claim 16, wherein the additive is selected from the group consisting of a nitrogen-containing compound, a sulphur- containing compound, an iodine-containing compound, a monocarboxylic acid, a dicarboxylic acid, a tricarboxylic acid and a polyalkylene glycol.

18. The process according to claim 17, wherein the concentration of the additive is in the range of 0.0001 to 0.2 mol L.

19. The process according to any one of the preceding claims, wherein the surfactant is selected from the group consisting of a non-ionic surfactant, an anionic surfactant, a cationic surfactant and an amphoteric surfactant.

20. The process according to any one of the preceding claims, further comprising the step of: d) contacting the metal plated textile fiber with a surface capping ligand to encapsulate the metal.

21. The process according to claim 20, wherein the surface capping ligand is selected from the group consisting of amines, carboxylic acids, alkylthiols, alkylphosphine oxides, alkylphosphonic acids, alkylphosphines and nitrogen-containing aromatics.

22. A process for forming a pattern on a textile comprising the steps of: a) contacting an area of the textile to be patterned with a first formulation comprising metal ions to thereby deposit the metal ions onto the area of the textile; and

b) contacting the textile or the area of the textile with a second formulation comprising a reducing agent to thereby reduce the deposited metal ions to form a metal,

wherein the metal forms the pattern on the textile.

23. A textile having a pattern thereon, wherein said pattern is formed on an area of the textile and wherein the pattern is composed of a plurality of metal plated textile fibers.

24. A system for forming a pattern on a textile, wherein the pattern is formed on an area of the textile, the system comprising: a) a first formulation comprising a metal ion; b) means for depositing the metal ion onto the area of the textile; c) a second formulation comprising a reducing agent; and d) means for contacting the textile having metal ions deposited thereon with the second formulation to reduce the metal ion into a metal.