WO2022081130A1

WO2022081130A1 - Inkjet fluid set

Info

Publication number: WO2022081130A1
Application number: PCT/US2020/055260
Authority: WO
Inventors: Hector Jose Lebron; Simge UZUN; Ronald Albert ASKELAND
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2020-10-12
Filing date: 2020-10-12
Publication date: 2022-04-21

Abstract

An example of an inkjet fluid set includes a pre-treatment fluid and an inkjet ink. The inkjet ink includes water and neat MXene flakes. Another example of the inkjet fluid set includes the pre-treatment fluid, the inkjet ink, which includes water and the neat MXene flakes, and an overcoat composition.

Description

INKJET FLUID SET

[0001] Inkjet printing is a non-impact printing method that utilizes electronic signals to control and direct droplets or a stream of ink to be deposited on media. Some commercial and industrial inkjet printers utilize fixed printheads and a moving substrate web in order to achieve high speed printing. Current inkjet printing technology involves forcing the ink drops through small nozzles by thermal ejection, piezoelectric pressure or oscillation onto the surface of the media.

[0002] Inkjet technology has become a popular way of recording images on various media surfaces, for a number of reasons, including, low printer noise, capability of high-speed recording and multi-color recording. In addition to home and office usage, inkjet technology has been expanded to high-speed, commercial and industrial printing. For example, inkjet printing is gaining rapid acceptance for digital textile printing, in part because it enables flexibility in the printing process, where images of any desirable size can be printed immediately from an electronic image without pattern repeats.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Features of examples of the present disclosure will become apparent by reference to the following detailed description and drawings, in which like reference numerals correspond to similar, though perhaps not identical, components. For the sake of brevity, reference numerals or features having a previously described function may or may not be described in connection with other drawings in which they appear. [0004] Fig. 1 schematically illustrates two example fluid sets and two example textile printing kits disclosed herein; [0005] Fig. 2A is a top perspective view of an example of a printed article formed with an example of the fluid set disclosed herein;

[0006] Fig. 2B is a cross-sectional view of the printed article of Fig. 2A;

[0007] Fig. 2C is an exploded view of the print of Fig. 2A;

[0008] Fig. 3 is a flow diagram illustrating an example printing method;

[0009] Fig. 4 schematically illustrates one example of the printing method;

[0010] Fig. 5 schematically illustrates another example of the printing method;

[0011] Fig. 6 is a schematic illustration of a printed article, formed by the method of Fig. 5, being stretched, and its effect on the electronic component;

[0012] Fig. 7 includes two bar graphs illustrating intensity distribution (%, Y-axis) versus MXene flake diameter (nm, X-axis) of a dispersion formed with large MXene flakes (top graph) and a dispersion formed with small MXene flakes (bottom graph); [0013] Fig. 8 is a bar graph illustrating ink concentration (mg mL'¹, Y-axis) versus ink viscosity (cP, mPa s, X-axis) for six different MXene inks;

[0014] Fig. 9 is a bar graph illustrating resistance (O cm'¹, Y-axis) for different MXene inks printed on different types of substrates;

[0015] Fig. 10 is a bar graph illustrating resistance (O cm'¹, Y-axis) for two MXene inks printed on cotton woven fabric at different numbers of printing passes; and

[0016] Fig. 11 is a black and white reproduction of an originally colored photograph of four different circuits thermally inkjet printed with an example MXene ink and light emitting diodes operatively connected to the circuits, and one the circuits in operation using a 9 V battery.

DETAILED DESCRIPTION

[0017] Disclosed herein is a fluid set that is compatible with inkjet printers, including thermal inkjet printers, and that enables the printing of electronic components on a wide variety of media, including porous media such as uncoated paper and textile fabrics. The fluid set includes a pre-treatment fluid and an inkjet ink. The inkjet ink includes two-dimensional inorganic nanomaterials, known as MXenes. In the examples disclosed herein, the concentration and lateral dimensions of the MXenes are controlled, which results in a reliably printable thermal inkjet ink. In some examples, the pre-treatment fluid may be selected to improve print attributes of the printed electronic component, such as its edge definition. In other examples, the pretreatment fluid may be selected to improve the topography of the porous substrate upon which the printed electronic article is generated. Improved substrate topography aims to improve the efficiency and/or help to maintain the conductivity of the printed electronic component. Some examples of the fluid set also include an overcoat, which may improve the durability of the printed electronic component.

[0018] Throughout this disclosure, a weight percentage that is referred to as “wt% active” refers to the loading of an active component of a dispersion or other formulation that is present in a printing fluid. For example, cationic polymers may be present in a water-based formulation (e.g., a stock solution or dispersion) before being incorporated into an example pre-treatment fluid. In this example, the wt% active of the cationic polymer accounts for the loading (as a weight percent) of the cationic polymer solids that are present in the pre-treatment fluid, and does not account for the weight of the other components (e.g., water, co-solvent(s), etc.) that are present in the stock solution or dispersion with the cationic polymer. The term “wt%,” without the term actives, refers to the loading of a 100% active component.

[0019] Fluid and Printing Kits

[0020] The pre-treatment fluid and the inkjet ink may be part of an inkjet fluid set and/or of an inkjet printing kit, examples of which are shown schematically in Fig. 1 . [0021] One example of the inkjet fluid set 10 includes i) the pre-treatment fluid 12 and ii) the inkjet ink 14 including water and neat MXene flakes. Another example of the inkjet fluid set 10 includes i) the pre-treatment fluid 12, ii) the inkjet ink 14 including water and neat MXene flakes, and iii) an overcoat composition 16. It is to be understood that any example of the pre-treatment fluid 12, the inkjet ink 14, and the overcoat composition 16 disclosed herein may be used in the inkjet fluid set 10.

[0022] The fluids 12 and 14 or 12, 14, and 16 of the inkjet fluid set 10 may be maintained in separate containers (e.g., respective reservoirs/fluid supplies of respective inkjet cartridges) or separate compartments (e.g., respective reservoirs/fluid supplies) in a single container (e.g., inkjet cartridge). [0023] The inkjet fluid set 10 may also be part of an inkjet printing kit 18. In addition to the inkjet fluid set 10, the inkjet printing kit 18 includes a substrate 20. As such, one example of the inkjet printing kit 18 includes i) the pre-treatment fluid 12, ii) the inkjet ink 14 including water and neat MXene flakes, and iii) the substrate 20. Another example of the inkjet printing kit 18 includes i) the pre-treatment fluid 12, ii) the inkjet ink 14 including water and neat MXene flakes, iii) the overcoat composition 16, and iv) the substrate 20. It is to be understood that any example of the pretreatment fluid 12, the inkjet ink 14, the overcoat composition 16, and the substrate 20 disclosed herein may be used in the inkjet printing kit 18.

[0024] One specific example of the inkjet printing kit 18 is a textile printing kit. The textile printing kit includes i) a textile fabric (as the substrate 20), ii) the pre-treatment fluid 12, and iii) the inkjet ink 14 including water and neat MXene flakes. Some examples of the textile printing kit also include the overcoat composition 16.

[0025] Pre-Treatment Fluids

[0026] Two different pre-treatment fluids 12 are disclosed herein. Generally, the pre-treatment fluid 12 is one of: i) a fixer fluid including water and a fixing agent selected from the group consisting of a multi-valent metal salt and a cationic polymer; or ii) a topography normalization fluid including water and latex particles.

[0027] In one example, the pre-treatment fluid 12 is a fixer fluid including a fixing agent, which is cationic. When the fixer fluid and the inkjet ink 12 are printed together on the substrate 20, the fixing agent in the fixer fluid chemically reacts with anionic components (e.g., the neat MXene flakes, dispersants, etc.) in the inkjet ink 14. The chemical reaction drives flocculation of the MXene flakes to lock in place at or near the substrate surface. The fixer fluid may be used to generate printed electronic components with precise print attributes, such as edge definition or very small features.

[0028] In another example, the pre-treatment fluid 12 is a topography normalization fluid including a polymeric component. When the topography normalization fluid is printed and cured on a porous substrate 20, the polymeric component forms a film that helps to planarize, and thus smooth, the surface of the porous substrate 20. This film can block the pores located at or near the surface of the porous substrate 20, thus creating a more planar and less porous surface on the otherwise porous substrate 20. When printed on the film (which is smoother than the bare porous substrate 20), the MXene flakes from the inkjet ink 14 assemble on the substrate surface, as opposed to penetrating into the pores. The film also serves to promote improved contact and/or overlap between the printed MXene flakes. More overlap between the flakes contributes to particle contact, and thus electrical conductivity, being maintained even when the porous substrate 20 (e.g., textile fabric) is stretched.

[0029] Each of the fixer fluid and the topography normalization fluid is described in more detail hereinbelow. It is to be understood, however, that the viscosity of any example of the pre-treatment fluid 12 (e.g., fixer fluid or topography normalization fluid) may vary depending upon the inkjet architecture that is to be used to apply the pretreatment fluid 12. As an example, when the pre-treatment fluid 12 is to be applied with a thermal inkjet applicator/printhead, the viscosity of the pre-treatment fluid 12 may range from about 1 cP to about 9 cP (at 20°C to 25°C and a shear rate of about 3,000 Hz). As another example, when the pre-treatment fluid 12 is to be applied with a piezoelectric inkjet applicator/printhead, the viscosity of the pre-treatment fluid 12 may range from about 1 cP to about 20 cP (at 20°C to 25°C and a shear rate of about 3,000 Hz).

[0030] Fixer Fluid

[0031 ] In some examples, the pre-treatment fluid 12 is a fixer fluid including water and a fixing agent selected from the group consisting of a multi-valent metal salt and a cationic polymer. In some examples, the fixer fluid consists of the water and the fixing agent. In other examples, the fixer fluid may include additional components.

[0032] The multi-valent metal salt that may be used as the fixing agent includes a multi-valent metal cation and an anion. In an example, the multi-valent metal salt includes a multi-valent (e.g., divalent or trivalent) metal cation selected from the group consisting of a calcium cation (e.g., Ca²⁺), a copper cation (e.g., Cu²⁺), a magnesium cation (e.g., Mg²⁺), a nickel cation (e.g., Ni²⁺), a zinc cation (e.g., Zn²⁺), an iron cation (e.g., Fe³⁺), an aluminum cation (e.g., Al³⁺), a chromium cation (e.g., Cr³⁺), and combinations thereof; and an anion selected from the group consisting of a chloride anion (e.g., Cl ), an iodide anion (e.g., I’), a bromide anion (e.g., Br ), a nitrate anion (e.g., NO3 ), a carboxylate anion (-RCOCT), a sulfonate anion (-RSOOO ), a sulfate anion (e.g., SCU²'), and combinations thereof. The carboxylate anions are derived from a saturated aliphatic monocarboxylic acid having 1 to 6 carbon atoms or a carbocyclic monocarboxylic acid having 7 to 11 carbon atoms. Examples of saturated aliphatic monocarboxylic acid having 1 to 6 carbon atoms include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid and hexanoic acid. One example of the carboxylate anion is acetate (CH₃COO'). In some examples, the fixing agent is a polyvalent metal salt selected from the group consisting of calcium chloride, calcium nitrate, calcium propionate, magnesium nitrate, magnesium acetate, or zinc acetate. In some other examples, the polyvalent metal salt is calcium chloride or calcium nitrate.

[0033] When used as the fixing agent, the multi-valent metal salt (containing the multi-valent metal cation) may be present in any suitable amount. In an example, the metal salt is present in an amount ranging from about 2 wt% active to about 20 wt% active based on a total weight of the fixer fluid. In further examples, the metal salt is present in an amount ranging from about 4 wt% active to about 12 wt% active; or from about 5 wt% active to about 15 wt% active; or from about 6 wt% active to about 10 wt% active, based on a total weight of the fixer fluid.

[0034] The cationic polymer that may be used as the fixing agent has a weight average molecular weight ranging from about 3,000 to about 3,000,000. Any weight average molecular weight throughout this disclosure is in Daltons or g/mol. Weight average molecular weight (Mw) can be measured by Gel Permeation Chromatography with polystyrene standard.

[0035] Examples of the cationic polymer may be selected from the group consisting of poly(diallyldimethylammonium chloride); poly(methylene-co-guanidine) anion, wherein the anion is selected from the group consisting of hydrochloride, bromide, nitrate, sulfate, and sulfonates; a polyamine; poly(dimethylamine-co-epichlorohydrin); a polyethylenimine; a polyamide epichlorohydrin resin; a polyamine epichlorohydrin resin; and a combination thereof. Some examples of commercially available polyamine epichlorohydrin resins may include CREPETROL™ 73, KYMENE™ 736, KYMENE™ 736NA, POLYCUP™ 7360, and POLYCUP™ 7360A, each of which is available from Solenis LLC.

[0036] When used as the fixing agent, the cationic polymer may be present in any suitable amount. In an example, the cationic polymer is present in an amount ranging from about 1 wt% active to about 15 wt% active based on a total weight of the fixer fluid. In further examples, the cationic polymer is present in an amount ranging from about 1 wt% active to about 10 wt% active; or from about 4 wt% active to about 8 wt% active; or from about 2 wt% active to about 7 wt% active; or from about 6 wt% active to about 10 wt% active, based on a total weight of the fixer fluid.

[0037] In addition to the fixing agent, the fixer fluid includes water, either alone or in combination with other co-solvent(s) and/or additive(s). As such, the fixer fluid includes an aqueous fixer fluid vehicle. The term “aqueous fixer fluid vehicle” may refer to the liquid(s) in which the multi-valent metal salt or cationic polymer is mixed to form one example of the pre-treatment fluid 12.

[0038] The aqueous fixer fluid vehicle may include a co-solvent. The co-solvent may be a water soluble or water miscible organic co-solvent. Examples of co-solvents include alcohols, amides, esters, ketones, lactones, and ethers. In additional detail, the co-solvents may include aliphatic alcohols, aromatic alcohols, diols, glycol ethers, polyglycol ethers, lactams, formamides, acetamides, glycols, and long chain alcohols. Examples of such compounds include primary aliphatic alcohols, secondary aliphatic alcohols, 1 ,2-alcohols, 1 ,3-alcohols, 1 ,5-alcohols, ethylene glycol alkyl ethers, propylene glycol alkyl ethers (e.g., DOWANOL™ TPM or DOWANOL™ TPnB (from Dow Chemical), higher homologs (C6-C12) of polyethylene glycol alkyl ethers, N-alkyl caprolactams, unsubstituted caprolactams, both substituted and unsubstituted formamides, both substituted and unsubstituted acetamides, and the like. Some specific examples include dimethyl sulfoxide, sulfolane, propylene carbonate, ethylene carbonate, 2-pyrrolidone, 1-(2-hydroxyethyl)-2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, and triethanolamine. Specific examples of alcohols may include ethanol, isopropyl alcohol, butyl alcohol, and benzyl alcohol. Other alcohols, such as polyhydric alcohols or derivatives thereof, may also be used. Examples of polyhydric alcohols may include ethylene glycol, diethylene glycol, propylene glycol, 2,2-dimethyl-1 ,3-propanediol, 2-ethyl-2-(hydroxymethyl)-1 ,3-propanediol, butylene glycol, triethylene glycol, 1 ,5-pentanediol, 1 ,2-hexanediol, 1 ,2-butanediol, 1 ,2,6- hexanetriol, glycerin, trimethylolpropane, and xylitol. Examples of polyhydric alcohol derivatives may include an ethylene oxide adduct of diglycerin. Some examples of the co-solvent also function as a humectant.

[0039] When included in the fixer fluid, the co-solvent(s) may be present in an amount ranging from about 4 wt% to about 30 wt% (based on the total weight of the fixer fluid).

[0040] The fixer fluid may also include an additive selected from the group consisting of a surfactant, an antimicrobial agent, an anti-kogation agent, a pH adjuster, and combinations thereof.

[0041 ] The surfactant in the fixer fluid may be a non-ionic surfactant or a cationic surfactant.

[0042] Examples of the non-ionic surfactant may include polyoxyethylenenonyl phenylether, polyoxyethyleneoctyl phenylether, and polyoxyethylenedodecyl. Further examples of the non-ionic surfactant may include silicon surfactants such as a polysiloxane oxyethylene adduct; fluorine surfactants such as perfluoroalkylcarboxylate, perfluoroalkyl sulfonate, and oxyethyleneperfluoro alkylether; and biosurfactants such as spiculisporic acid, rhamnolipid, and lysolecithin. Still other examples of suitable non-ionic surfactants include a silicone-free alkoxylated alcohol surfactant, such as TEGO® Wet 510 (Evonik Degussa) and/or a self- emulsifiable wetting agent based on acetylenic diol chemistry, such as, for example, SURFYNOL® SE-F (Evonik Degussa). Other suitable commercially available non- ionic surfactants include SURFYNOL® 465 (ethoxylatedacetylenic diol), SURFYNOL® 440 (an ethoxylated low-foam wetting agent) SURFYNOL® CT-211 (now CARBOWET® GA-211 , non-ionic, alkylphenylethoxylate and solvent free), and SURFYNOL® 104 (non-ionic wetting agent based on acetylenic diol chemistry), (all of which are from Evonik Degussa); ZONYL® FSO (a.k.a. CAPSTONE®, which is a water-soluble, ethoxylated non-ionic fluorosurfactant from DuPont); TERGITOL® TMN-3 and TERGITOL® TMN-6 (both of which are branched secondary alcohol ethoxylate, non-ionic surfactants), and TERGITOL® 15-S-3, TERGITOL® 15-S-5, and TERGITOL® 15-S-7 (each of which is a secondary alcohol ethoxylate, non-ionic surfactant) (all of the TERGITOL® surfactants are available from The Dow Chemical Company); and BYK® 345, BYK® 346, BYK® 347, BYK® 348, BYK® 349 (each of which is a silicone surfactant) (all of which are available from BYK Chemie).

[0043] Examples of the cationic surfactant include quaternary ammonium salts, such as benzalkonium chloride, benzethonium chloride, methylbenzethonium chloride, cetalkonium chloride, cetylpyridinium chloride, cetrimonium, cetrimide, dofanium chloride, tetraethylammonium bromide, didecyldimethylammonium chloride, domiphen bromide, alkylbenzyldimethylammonium chlorides, distearyldimethylammonium chloride, diethyl ester dimethyl ammonium chloride, dipalmitoylethyl hydroxyethylmonium methosulfate, and ACCOSOFT® 808 (methyl (1 ) tallow amidoethyl (2) tallow imidazolinium methyl sulfate available from Stepan Company). Other examples of the cationic surfactant include amine oxides, such as lauryldimethylamine oxide, myristamine oxide, cocamine oxide, stearamine oxide, and cetamine oxide.

[0044] In any of the examples disclosed herein, the surfactant may be present in an amount ranging from about 0.01 wt% active to about 5 wt% active (based on the total weight of the fixer fluid). In an example, the surfactant is present in the fixer fluid in an amount ranging from about 0.05 wt% active to about 3 wt% active, based on the total weight of the fixer fluid. In another example, the surfactant is present in the fixer fluid in an amount of about 0.3 wt% active, based on the total weight of the fixer fluid.

[0045] The aqueous fixer fluid vehicle may also include antimicrobial agent(s). Antimicrobial agents are also known as biocides and/or fungicides. Examples of suitable antimicrobial agents include the NUOSEPT® (Ashland Inc.), UCARCIDE™ or KORDEK™ or ROCIMA™ (The Dow Chemical Company), PROXEL® (Arch Chemicals) series, ACTICIDE® B20 and ACTICIDE® M20 and ACTICIDE® MBL (blends of 2-methyl-4-isothiazolin-3-one (MIT), 1 ,2-benzisothiazolin-3-one (BIT) and Bronopol) (Thor Chemicals), AXIDE™ (Planet Chemical), NIPACIDE™ (Clariant), blends of 5-chloro-2-methyl-4-isothiazolin-3-one (CIT or CMIT) and MIT under the tradename KATHON™ (The Dow Chemical Company), and combinations thereof. [0046] In an example, the total amount of antimicrobial agent(s) in the fixer fluid ranges from about 0.01 wt% active to about 0.05 wt% active (based on the total weight of the fixer fluid). In another example, the total amount of antimicrobial agent(s) in the fixer fluid is about 0.04 wt% active (based on the total weight of the fixer fluid).

[0047] The fixer fluid may also include an anti-kogation agent. Examples of suitable anti-kogation agents that may be included in the fixer fluid include oleth-3- phosphate (commercially available as CRODAFOS™ O3A or CRODAFOS™ N-3A) or dextran 500k. Other suitable examples of the anti-kogation agents include CRODAFOS™ HCE (phosphate-ester from Croda Int.), CRODAFOS® N10 (oleth-10- phosphate from Croda Int.), or DISPERSOGEN® LFH (polymeric dispersing agent with aromatic anchoring groups, acid form, anionic, from Clariant), etc. It is to be understood that any combination of the anti-kogation agents listed may also be used. [0048] The anti-kogation agent may also be included in the fixer fluid. Kogation refers to the deposit of dried printing liquid on a heating element of a thermal inkjet printhead. Anti-kogation agent(s) is/are included to assist in preventing the buildup of kogation. In some examples, the anti-kogation agent may improve the jettability of the fixer fluid. The anti-kogation agent(s) may be present in the pre-treatment composition in a total amount ranging from about 0.1 wt% active to about 1 .5 wt% active, based on the total weight of the fixer fluid. In an example, the anti-kogation agent(s) is/are present in an amount of about 0.5 wt% active, based on the total weight of the fixer fluid.

[0049] A pH adjuster may also be included in the fixer fluid. A pH adjuster may be included in the fixer fluid to achieve a desired pH (e.g., 6) and/or to counteract any slight pH increase that may occur over time. Suitable pH ranges for examples of the fixer fluid can be from pH 4 to less than pH 9, from pH 5 to pH 8, or from pH 5.5 to pH 7. In one example, the pH of the pre-treatment composition is pH 6. An example of a suitable pH adjuster that may be used in the fixer fluid includes methane sulfonic acid. [0050] In an example, the total amount of pH adjuster(s) in the fixer fluid ranges from greater than 0 wt% to about 0.1 wt% (based on the total weight of the fixer fluid). In another example, the total amount of pH adjuster(s) in the fixer fluid is about 0.03 wt% (based on the total weight of the fixer fluid). [0051 ] The balance of the fixer fluid is water. As such, the weight percentage of the water present in the fixer fluid will depend, in part, upon the weight percentages of the other components. The water may be purified water or deionized water.

[0052] Topography Normalization Fluid

[0053] In other examples, the pre-treatment fluid 12 is a topography normalization fluid including water and latex particles. In some examples, the topography normalization fluid consists of the water and the latex particles. In other examples, the topography normalization fluid may include additional components.

[0054] As used herein, “latex particles” refer to any polymer (homopolymer, copolymer, or heteropolymer) that is capable of being dispersed in an aqueous medium. [0055] As examples, the latex particles may be acrylic polymers, acrylic copolymers, styrene copolymers, styrene-butadiene copolymers, acrylonitrilebutadiene copolymers, polyester-based copolymers, vinyl chloride-based copolymers, or combinations thereof. Several example monomers that may be used for form these polymers and copolymers are provided below.

[0056] In some examples, the latex particles are heteropolymers or copolymers. In an example, a heteropolymer can include a hydrophobic component and a hydrophilic component. The hydrophilic component renders the particles dispersible in the topography normalization fluid, while the hydrophobic component is capable of coalescing upon reaching the minimum film formation temperature (MFFT) in order to uniformly coalesce into a film.

[0057] An example of the heteropolymer includes a hydrophobic component that makes up from about 65% to about 99.9% (by weight) of the heteropolymer, and a hydrophilic component that makes up from about 0.1 % to about 35% (by weight) of the heteropolymer, where the hydrophobic component may have a lower glass transition temperature than the hydrophilic component.

[0058] Examples of monomers that may be used to form the hydrophobic component include Ci to Cs alkyl acrylates or methacrylates, styrene, substituted methyl styrenes, polyol acrylates or methacrylates, vinyl monomers, vinyl esters, ethylene, maleate esters, fumarate esters, itaconate esters, or the like. Some specific examples include methyl methacrylate, butyl acrylate, butyl methacrylate, hexyl acrylate, hexyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexy methacrylate, hydroxyethyl acrylate, lauryl acrylate, lauryl methacrylate, octadecyl acrylate, octadecyl methacrylate, isobornyl acrylate, isobornyl methacrylate, stearyl methacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetrahydrofurfuryl acrylate, alkoxylated tetrahydrofurfuryl acrylate, 2-phenoxyethyl methacrylate, benzyl acrylate, ethoxylated nonyl phenol methacrylate, cyclohexyl methacrylate, trimethyl cyclohexyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, tridecyl methacrylate, isodecyl acrylate, dimethyl maleate, dioctyl maleate, acetoacetoxyethyl methacrylate, diacetone acrylamide, pentaerythritol triacrylate, pentaerythritol tetra-acrylate, pentaerythritol tri-methacrylate, pentaerythritol tetra-methacrylate, divinylbenzene, styrene, methylstyrenes (e.g., a-methyl styrene, p- methyl styrene), 1 ,3-butadiene, vinyl chloride, vinylidene chloride, vinylbenzyl chloride, acrylonitrile, methacrylonitrile, N-vinyl imidazole, N-vinylcarbazole, N-vinyl- caprolactam, combinations thereof, derivatives thereof, or mixtures thereof.

[0059] The heteropolymer may be formed of at least two of the previously listed monomers, or at least one of the previously listed monomers and a higher T_g hydrophilic monomer, such as an acidic monomer. Examples of acidic monomers that can be polymerized in forming the latex polymer particles include acrylic acid, methacrylic acid, ethacrylic acid, dimethylacrylic acid, maleic anhydride, maleic acid, vinylsulfonate, cyanoacrylic acid, vinylacetic acid, allylacetic acid, ethylidineacetic acid, propylidineacetic acid, crotonoic acid, fumaric acid, itaconic acid, sorbic acid, angelic acid, cinnamic acid, styrylacrylic acid, citraconic acid, glutaconic acid, aconitic acid, phenylacrylic acid, acryloxypropionic acid, aconitic acid, phenylacrylic acid, acryloxypropionic acid, vinylbenzoic acid, N-vinylsuccinamidic acid, mesaconic acid, methacroylalanine, acryloylhydroxyglycine, sulfoethyl methacrylic acid, sulfopropyl acrylic acid, styrene sulfonic acid, sulfoethylacrylic acid, 2-methacryloyloxymethane-1 - sulfonic acid, 3-methacryoyloxypropane-1 -sulfonic acid, 3-(vinyloxy)propane-1 -sulfonic acid, ethylenesulfonic acid, vinyl sulfuric acid, 4-vinylphenyl sulfuric acid, ethylene phosphonic acid, vinyl phosphoric acid, vinyl benzoic acid, 2 acrylamido-2-methyl-1 - propanesulfonic acid, combinations thereof, derivatives thereof, or mixtures thereof. Other examples of high T_g hydrophilic monomers include acrylamide, methacrylamide, monohydroxylated monomers, monoethoxylated monomers, polyhydroxylated monomers, or polyethoxylated monomers.

[0060] Any suitable polymerization process can be used. In some examples, an aqueous dispersion of latex particles can be produced by emulsion polymerization or co-polymerization of any of the above monomers. In one example, the latex particles can be prepared by polymerizing high T_g hydrophilic monomers to form the high T_g hydrophilic component and attaching the high T_g hydrophilic component onto the surface of the low T_g hydrophobic component. In another example, the latex particles can be prepared by polymerizing the low T_g hydrophobic monomers and the high T_g hydrophilic monomers at a ratio of the low T_g hydrophobic monomers to the high T_g hydrophilic monomers that ranges from 5:95 to 30:70. In this example, the low T_g hydrophobic monomers can dissolve in the high T_g hydrophilic monomers. In yet another example, the latex particles can be prepared by polymerizing the low T_g hydrophobic monomers, then adding the high T_g hydrophilic monomers. In this example, the polymerization process can cause a higher concentration of the high T_g hydrophilic monomers to polymerize at or near the surface of the low T_g hydrophobic component. In still another example, the latex particles can be prepared by copolymerizing the low T_g hydrophobic monomers and the high T_g hydrophilic monomers, then adding additional high T_g hydrophilic monomers. In this example, the copolymerization process can cause a higher concentration of the high T_g hydrophilic monomers to copolymerize at or near the surface of the low T_g hydrophobic component.

[0061 ] A co-polymerizable dispersing agent may also be used during the polymerization process. The co-polymerizable dispersing agent can be a polyoxyethylene compound, such as a HITENOL® compound (Montello Inc.) e.g., polyoxyethylene alkylphenyl ether ammonium sulfate, sodium polyoxyethylene alkylether sulfuric ester, polyoxyethylene styrenated phenyl ether ammonium sulfate, or mixtures thereof.

[0062] The latex particles may have several different morphologies. For example, the latex particles may be individual spherical particles containing polymer compositions of hydrophilic (hard) component(s) and/or hydrophobic (soft) component(s) that may be interdispersed according to IPN (interpenetrating networks), although it is contemplated that the hydrophilic and hydrophobic components may be interdispersed in other ways. For another example, the latex particles may be made of a hydrophobic core surrounded by a continuous or discontinuous hydrophilic shell. For still another example, the latex particle morphology may resemble a raspberry, in which a hydrophobic core is surrounded by several smaller hydrophilic particles that are attached to the core. For still another example, the latex particles may include 2, 3, or 4 particles that are at least partially attached to one another.

[0063] The latex particles may have a weight average molecular weight ranging from about 5,000 to about 2,000,000. As examples, the weight average molecular weight of the latex particles may range from about 100,000 to about 1 ,000,000, from about 150,000 to about 750,000, or from about 10,000 to about 300,000.

[0064] In an example, the latex particles are present in the topography normalization fluid in an amount ranging from about 1 wt% active to about 30 wt% active based on a total weight of the topography normalization fluid. In another example, the latex particles are present in the topography normalization fluid in an amount ranging from about 2 wt% active to about 25 wt% active based on the total weight of the topography normalization fluid. In still another example, the latex particles are present in the topography normalization fluid in an amount ranging from about 5 wt% active to about 15 wt% active based on the total weight of the topography normalization fluid.

[0065] In addition to the latex particles, the topography normalization fluid includes water, either alone or in combination with other co-solvent(s) and/or additive(s). As such, the topography normalization fluid includes an aqueous topography normalization fluid vehicle. The term “aqueous topography normalization fluid vehicle” may refer to the liquid(s) in which the latex particles are mixed to form another example of the pre-treatment fluid 12.

[0066] Any of the co-solvent(s), non-ionic surfactant(s), antimicrobial agent(s), anti- kogation agent(s), and/or pH adjusters, and the respective amounts of such components set forth herein for the fixer fluid may be used in the topography normalization fluid, except that the weight percentages are with respect to the total weight of the topography normalization fluid. The pH of the topography fluid may be similar to that of the inkjet ink 14.

[0067] In some instances the topography normalization fluid is colorless, and does not include a pigment. This will result in the formation of an at least substantially colorless film on the substrate 20. In other instances, it may be desirable for the topography normalization fluid to include a pigment. This will result in the formation of a colored film on the substrate 20. The colored film may be desirable either to at least substantially match the color of the underlying substrate or to mask the color of the underlying substrate. If a pigment is included, it should be selected so that it does not interfere with the desired electrical properties of the component that is to be formed with the inkjet ink 14.

[0068] White pigments may be particularly desirable for either matching or masking the color of the substrate 20. Examples of white pigments include white metal oxide pigments, such as titanium dioxide (TiO2), zinc oxide (ZnO), zirconium dioxide (ZrO2), or the like. In one example, the white pigment is titanium dioxide. In an example, the titanium dioxide is in its rutile form. In still another example, the white pigment may be coated with silicon dioxide (SiO2) or with SiO2 and aluminum oxide (AI2O3). One example of the white pigment includes TI-PURE® R960 (TiO2 pigment powder with 5.5 wt% silica and 3.3 wt% alumina (based on pigment content)) available from Chemours. Another example of the white pigment includes TI-PURE® R931 (TiO2 pigment powder with 10.2 wt% silica and 6.4 wt% alumina (based on pigment content)) available from Chemours. Still another example of the white pigment includes TI-PURE® R706 (TiO2 pigment powder with 3.0 wt% silica and 2.5 wt% alumina (based on pigment content)) available from Chemours.

[0069] Colored pigments may also be desirable for either matching or masking the color of the substrate 20. Examples of color pigments include a black pigment (e.g., aniline black, such as C.l. Pigment Black 1 ), a cyan pigment (e.g., C.l. Pigment Blue - 1 , -2, -3, -15, -15:1 , -15:2, -15:3, -15:4, -16, -22, and -60), a yellow pigment (e.g., C.l. Pigment Yellow -1 , -2, -3, -12, -13, -14, -16, -17, -73, -74, -75, -83, -93, -95, -97, -98, - 114, -128, -129, -138, -151 , -154, and -180), or a magenta pigment (e.g., C.l. Pigment Red -5, -7, -12, -48, -48:1 , -57, -112, -122, -123, -146, -168, -177, -184, -202, and C.l. Pigment Violet-19).

[0070] The average particle size of the pigment may range anywhere from about 10 nm to about 750 nm. In some examples, the average particle size ranges from about 120 nm to about 500 nm, from about 150 nm to about 400 nm, from about 150 nm to about 300 nm, or from about 200 nm to about 500 nm. Smaller particles may be desirable depending upon the jetting architecture that is used. The term “average particle size”, as used herein, may refer to a volume-weighted mean diameter of a particle distribution.

[0071] The pigment can be present in the topography normalization fluid in an amount from about 0.5 wt% active to about 15 wt% active based on a total weight of the topography normalization fluid. In one example, the pigment can be present in an amount from about 1 wt% active to about 12 wt% active. In another example, the pigment can be present in an amount from about 5 wt% active to about 10 wt% active. [0072] When the topography normalization fluid includes a pigment, the topography normalization fluid may also include a dispersant that helps to disperse the pigment. The pigment(s) can be dispersed by a dispersant that is adsorbed or ionically attracted to a surface of the pigment, or the dispersant can be covalently attached to a surface of the pigment (e.g., a self-dispersed pigment). In one example, the dispersant can be an acrylic dispersant, such as CARBOSPERSE® K7028 (polyacrylic acid having a weight average molecular weight of about 2,300), CARBOSPERSE® K752 (polyacrylic acid having a weight average molecular weight of about 2,000), CARBOSPERSE® K7058 (polyacrylic acid having a weight average molecular weight of about 7,300), and CARBOSPERSE® K732 (polyacrylic acid having a weight average molecular weight of about 6,000), all available from Lubrizol Corporation. In another example, the dispersant can be a branched co-polymer of the comb-type structure with polyether pendant chains and acidic anchor groups, such as DISPERBYK®-190 (an acid number of about 10 mg KOH/g) and DISPERBYK®-199, both available from BYK Additives and Instruments, as well as DISPERSOGEN® PCE available from Clariant. While some example dispersants have been provided, it is to be understood that other dispersants suitable for keeping the pigment suspended in the aqueous topography normalization fluid vehicle may be used. The amount of dispersant included will depend upon the amount of pigment included. In one example, the dispersant is present in an amount ranging from about 0.01 % active to about 0.5 wt% active, based on a total weight of the fixer fluid.

[0073] Inkjet Ink

[0074] The inkjet ink 14 includes water and neat MXene flakes. In some examples, the inkjet ink 14 consists of these components, and thus no other solvents or additives are present. In these examples, the inkjet ink 14 is additive free. In other examples, the inkjet ink 14 may include other components, such as co-solvents, inkjet performance additives, and/or conductivity additives.

[0075] MXenes are two-dimensional inorganic materials with the composition: M_n+iX_n(T_x), where M is an element from Group 3, 4, 5, 6, or 7 of the periodic table, X is carbon, nitrogen or a combination of both, n = 1 , 2, 3, or 4, and T_x is a surface termination group. In the examples disclosed herein, the MXenes are neat materials. The phrase “neat material” refers to the as generated material which has not been further modified with capping groups.

[0076] MXenes include at least one layer having a substantially two-dimensional array of crystal cells, where each crystal cell has the empirical formula of M_n+iX_n, such that each X is positioned within an octahedral array of M, and each of M, n, and X are as described herein. Each layer has two opposed surfaces, wherein at least one of the surfaces has surface terminations (e.g., T_x from the formula above), which may include an alkoxide, an alkyl, a carboxylate, a halide, a hydroxide, a hydride, an oxide, a sub-oxide, a nitride, a sub-nitride, a sulfide, a sulfonate, a thiol, or a combination thereof. In one example, the surface termination groups, T_x, are selected from the group consisting of a halide (e.g., -F or -Cl), a hydroxide, a hydride, and an oxide.

[0077] Metals of Group 3, 4, 5, 6, or 7 (corresponding to Group 11 IB, IVB, VB, VIB, or VI IB of the periodic table) may be used as M. These metals may be used alone or in combination. Additionally, oxides of any of these metals may also be used. Some specific examples of the transition metal, M, include Cr, Hf, Mn, Mo, Nb, Sc, Ta, Ti, V, W, Zr, or combinations thereof. In other examples, the transition metal, M, may include any one or combination of Cr, Hf, Mn, Mo, Nb, Ta, Ti, V, W, or Zr. In still other examples, the transition metal, M, is one or more of Cr, Mo, Nb, Ta, Ti, V, or Zr. In yet further examples, the transition metal, M, is Cr, Mo, Nb, Ta, Ti, V, or a combination thereof.

[0078] In some specific examples of M_n+1X_n(T_x), M_n+1X_n is M_n+1C_n (i.e. , where X = C, carbon). Specific examples of M_n+iC_n may include Ti₂C, V₂C, V₂N, Cr₂C, Zr₂C, Nb₂C, Hf₂C, Ta₂C, Mo₂C, TisC₂, VsC₂, TasC₂, TisC₂, MosC₂, (Cr₂/3 Tii/₂)sC₂, Ti4Cs, V4C3, Ta₄C3, Nb₄C3, or a combination thereof. Two specific examples of M_n+iX_n(T_x) include Ti₂C(T_x) and Ti₃C₂(T_x), where at least one of the surfaces of each layer of the two dimensional crystal cells is coated with surface terminations, T_x, which may be an alkoxide, a fluoride, a hydroxide, an oxide, a sub-oxide, a sulfonate, or a combination thereof.

[0079] The MXene material may include free standing and/or stacked assemblies of two-dimensional crystalline solids. The stacked assemblies may be capable of, or have atoms, ions, or molecules, that are intercalated between at least some of the layers. In other embodiments, these atoms or ions are lithium.

[0080] The neat MXene material may be generated from chemical exfoliation of layered MAX phase materials. Layered MAX phase materials are layered ternary carbides, nitrides, or carbonitrides (i.e., “X” as defined herein), which also includes layers of “M” (as defined herein) and “A”, which is an A-group element of the period table (e.g., IIIA, such as Al, or IVA). Chemical exfoliation selectively etches the A element from the layered MAX phase materials. One example of a suitable etchant is hydrofluoric acid.

[0081 ] As mentioned herein, the neat MXene flakes are two-dimensional and thus have a flake shape. The lateral flake size distribution of the neat MXene flakes may vary, ranging from about 100 nm to about 20 pm. Small neat MXene flakes have a lateral flake size distribution ranging from about 100 nm to about 1000 nm (1 pm), while large neat MXene flakes have a lateral flake size distribution ranging from about 1 pm to about 10 pm. In some examples, the inkjet ink 14 includes a mixture of the small and large neat MXene flakes. In an example, the lateral flake size distribution of a first portion of the neat MXene flakes in the inkjet ink 14 ranges from about 100 nm to about 1000 nm, and the lateral flake size distribution of a second portion of the neat MXene flakes in the inkjet ink 14 ranges from about 1 pm to about 10 pm. The weight ratio of the first portion (e.g., small neat MXene flakes) to the second portion (large neat MXene flakes) ranges from about 1 :99 to about 99: 1. In other examples, the weight ratio of the small neat MXene flakes to the large neat MXene flakes ranges from about 20:80 (1 :4) to about 80:20 (4: 1 ), or from about 25:75 (1 :3) to about 75:25 (3: 1 ), or from about 40:60 (2:3) to about 60:40 (3:2). In one specific example, the weight ratio of the small neat MXene flakes to the large neat MXene flakes in the inkjet ink 14 is about 50:50 (1 : 1 ).

[0082] The concentration of MXene flakes in the inkjet ink 14 may vary, depending in part upon whether the particles are small, large, or a combination thereof. In an example, the concentration of the small MXene flakes in the inkjet ink 14 ranges from about 0.1 mg/mL to about 60 mg/mL. In another example, the concentration of the large MXene flakes in the inkjet ink 14 ranges from about 0.1 mg/mL to about 18 mg/mL. When a combination of the small and large MXene flakes is used, the concentration of each of the small and large particles may be within the respective ranges, as long as the resulting inkjet ink 14 has a viscosity suitable for the inkjet architecture that is to be used.

[0083] When the inkjet ink 14 is a thermal inkjet ink, the thermal inkjet ink should have a viscosity up to 5.1 cP at 25°C and at a shear rate of 10⁶ s’¹. When the inkjet ink 14 is a piezoelectric inkjet ink, the piezoelectric inkjet ink should have a viscosity up to 20 cP at 25°C and at a shear rate of 10⁶ s’¹. The viscosity may be measured using a Brookfield Viscometer. The viscosity may also depend, in part, upon the geometry and diameter of the nozzle of the thermal inkjet printhead that is to be used for printing. In one example, an ink 14 with a viscosity up to 5.1 cP can be successfully jetted using a circular nozzle with a dimeter of 30 pm. In another example, an ink 14 with a viscosity up to 1.7 cP can be successfully jetted using a non-circular, infinityshaped nozzle that is 30 pm in diameter with a 5 pm-wide pinch at its center.

[0084] The MXenes with the surface terminations are hydrophilic, allowing them to be readily dispersed in the aqueous vehicle of the inkjet ink 14. When the aqueous inkjet vehicle is maintained at a neutral pH (ranging from 6 to 7), the MXene flakes are negatively charged. The zeta potential of these MXene flakes may range from about - 39.5 mV to about -80 mV depending, at least in part, upon the composition of MXene material and the pH of the inkjet ink 14.

[0085] In any of the example inkjet inks 14 disclosed herein, the aqueous vehicle includes water. In some examples, the inkjet ink 14 is an additive free ink that consists of water and the neat MXene flakes. This example of the inkjet ink 14 has been found to be reliably printable via thermal inkjet applicators/printheads and piezoelectric inkjet applicators/printheads, and also able to generate electronic components on a variety of substrates 20. In these examples, the aqueous vehicle consists of the water and nothing else.

[0086] In other examples, the inkjet ink 14 further includes: an electrically conductive active material (in addition to the MXene flakes); an additive selected from the group consisting of co-solvents, surfactants, anti-kogation agents, antimicrobial agents, polymeric dispersants, chelating agents, humectants, and combinations thereof; or a combination of the active material and the additive. These additive(s) may improve the electrical properties of the electronic printed component and/or improve the jettability performance (e.g., decel, decap, etc.), stability, etc.

[0087] The inkjet ink 14 may include an electrically conductive active material, in addition to the MXene flakes, to enhance the conductivity. Examples of the electrically conductive active material include other two-dimensional nanomaterials such as graphene or transition metal dichalcogenide (TMD), one-dimensional nanomaterials such as carbon nanotubes or metal nanowires, and/or zero-dimensional materials, such as activated carbon.

[0088] The other electrically conductive active material may be added to enhance the ink’s conductivity, but not at a concentration that will undesirably increase the viscosity and deleteriously affect the jettability of the inkjet ink 14. As such, the concentration of the other electrically conductive active material may depend, in part, upon the electrically conductive active material, the concentration of the MXene flakes in the inkjet ink 14, and the viscosity of the inkjet ink 14. The concentration of the other electrically conductive active material in the inkjet ink 14 is generally less than the concentration of the MXene flakes in the inkjet ink 14. [0089] Any of the co-solvent(s), non-ionic surfactant(s), anti-kogation agent(s), antimicrobial agent(s), and/or polymeric dispersants, and the respective amounts of such components set forth herein for the fixer fluid and/or topography normalization fluid may be used in the inkjet ink 14, except that the weight percentages are with respect to the total weight of the inkjet ink 14.

[0090] In addition to or instead of the non-ionic surfactant, the inkjet ink 14 may include an anionic surfactant. Examples of the anionic surfactant may include alkylbenzene sulfonate, alkylphenyl sulfonate, alkylnaphthalene sulfonate, higher fatty acid salt, sulfate ester salt of higher fatty acid ester, sulfonate of higher fatty acid ester, sulfate ester salt and sulfonate of higher alcohol ether, higher alkyl sulfosuccinate, polyoxyethylene alkylether carboxylate, polyoxyethylene alkylether sulfate, alkyl phosphate, and polyoxyethylene alkyl ether phosphate. Specific examples of the anionic surfactant may include dodecylbenzenesulfonate, isopropylnaphthalenesulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenyl sulfonate, monobutylbiphenylsul fonate, and dibutylphenylphenol disulfonate. Examples of the non-ionic surfactant may include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester, polyoxyethylene glycerin fatty acid ester, polyglycerin fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene fatty acid amide, alkylalkanolamide, polyethylene glycol polypropylene glycol block copolymer, acetylene glycol, and a polyoxyethylene adduct of acetylene glycol. Whether the non- ionic surfactant, the anionic surfactant, or the combination of non-ionic and anionic surfactants are used, the total amount of surfactant(s) in the inkjet ink should be within the ranges provided herein.

[0091] The inkjet ink 14 may additionally include a chelating agent (also known as a sequestering agent). When included, the chelating agent is present in an amount greater than 0 wt% active and less than or equal to 0.5 wt% active based on the total weight of the inkjet ink 14. In an example, the chelating agent is present in an amount ranging from about 0.05 wt% active to about 0.2 wt% active based on the total weight of the inkjet ink 14. [0092] In an example, the chelating agent is selected from the group consisting of methylglycinediacetic acid, trisodium salt; 4,5-dihydroxy-1 ,3-benzenedisulfonic acid disodium salt monohydrate; ethylenediaminetetraacetic acid (EDTA); hexamethylenediamine tetra(methylene phosphonic acid), potassium salt; and combinations thereof. Methylglycinediacetic acid, trisodium salt (Na3MGDA) is commercially available as TRILON® M from BASF Corp. 4,5-dihydroxy-1 ,3- benzenedisulfonic acid disodium salt monohydrate is commercially available as TIRON™ monohydrate. Hexamethylenediamine tetra(methylene phosphonic acid), potassium salt is commercially available as DEQUEST® 2054 from Italmatch Chemical.

[0093] Some examples of the inkjet ink 14 may also include a humectant. An example of a suitable humectant is ethoxylated glycerin having the following formula:

in which the total of a+b+c ranges from about 5 to about 60, or in other examples, from about 20 to about 30. An example of the ethoxylated glycerin is LIPONIC® EG-1 (LEG-1 , glycereth-26, a+b+c=26, available from Lipo Chemicals).

[0094] The humectant may be present in an amount ranging from about 0.2 wt% active to about 5 wt% active (based on the total weight of the inkjet ink 14). In an example, the humectant is present in the inkjet ink 14 in an amount of about 1 wt% active, based on the total weight of the inkjet ink 14.

[0095] As mentioned herein, when the inkjet ink 14 is a thermal inkjet ink, the thermal inkjet ink should have a viscosity up to 5.1 cP at 25°C and at a shear rate of 10⁶ s’¹, and when the inkjet ink 14 is a piezoelectric inkjet ink, the piezoelectric inkjet ink should have a viscosity up to 20 cP at 25°C and at a shear rate of 10⁶ s’¹. In some instances, a viscosity modifier may be added to increase the viscosity to within the desirable range. Examples of thickening viscosity modifiers include polyvinyl alcohol, polyacrylamide, polyacrylic acids, and alkali soluble emulsions (such as acrylic and styrene maleic emulsion). When included, the viscosity modifier can be present in an amount ranging from about 0.01 wt% active to about 2 wt% active, based on the total weight of the inkjet ink 14.

[0096] The pH of the inkjet ink 14 is neutral. For example, the pH of the inkjet ink may be 7. A suitable pH range for examples of the inkjet ink 14 can be from pH 6 to pH 7.

[0097] Overcoat

[0098] In some examples of the fluid set 10, the printing kit 18, and the methods disclosed herein, an overcoat composition 16 is included and used. The overcoat composition 16 is a composition that can be applied over the printed electronic component and that can form a transparent, protective film.

[0099] Examples of suitable overcoat compositions 16 may include aqueous varnishes, silicone water-based emulsions, waxes, and/or ultraviolet (UV) varnishes. [0100] When the overcoat composition 16 is an aqueous varnish, the composition 16 may include water and a film-forming polymer. In one example, the film-forming polymer is any example of the latex particles disclosed herein for the topography normalization fluid. In the aqueous varnish, the latex particles are dispersed in water. In some examples, the latex particles are acrylic polymers or styrene/acrylic copolymers. The aqueous varnish may contain from about 40 wt% active to about 50 wt% active of latex particles based on the total weight of the aqueous varnish. The aqueous varnish may also contain non-ionic surfactants in an amount representing from about 0.1 wt% active to about 5 wt% active of the aqueous varnish. The aqueous varnish may also contain a coalescent solvent in an amount representing up to about 10 wt%. In some examples, such coalescent solvent is 2,2,4-Trimethyl-1 ,3- pentanediol monoisobutyrate (e.g., TEXANOL™ available from Eastman Chemical Co.). Examples of other water-based varnishes include those available under the tradename SICPAPROTECT® from SICPA, under the tradename NICOAT® from ICP Industrial, and under the tradename DigiGuard® IJ from Michelman.

[0101] The overcoat composition 16 may also be an ultraviolet (UV) varnish. The UV varnishes include UV curable polymers, such as urethanes, epoxies, acrylates, and thiols. Examples of ultraviolet varnishes include those available under the tradename NICOAT® (from ICP Industrial), WESSCO®3032 (available from Schmidt Rhyner), those available under the tradename EXCURE™ (available from Toyo Ink), and those available under the tradename ULTRASHEEN™ (available from Actega). [0102] The overcoat composition 16 may also be a wax varnish. Examples of wax varnishes include the MICHEM® Emulsion series, including MICHEM® Emulsion 43040, MICHEM® Emulsion 91240G and MICHEM® Emulsion 95535 (available from Michelman).

[0103] An example of a silicone water-based emulsion includes Web Protect™ Premium from Shackell Edwards.

[0104] In some instances, it may be desirable for the overcoat composition 16 to be transparent, and in these instances, the overcoat composition 16 does not include a colorant (e.g., a pigment or a dye). In other instances, it may be desirable for the overcoat composition 16 to mask the electronic component 24 or to form a nonfunctional (e.g., non-electronic) image over the electronic component, and in these instances, the overcoat composition 16 may include a pigment. Examples of suitable pigments and pigment amounts include those set forth herein for the topography normalization fluid.

[0105] Substrates

[0106] The pre-treatment fluid 12 and the inkjet ink 14 may be printed on any suitable substrate 20. When used, the overcoat composition 16 may also be printed on any suitable substrate 20.

[0107] As examples, the substrate 20 may be selected from cellulosic or synthetic paper (coated or uncoated), cardboard, polymeric films (e.g., plastic sheets such as polyethylene terephthalate (PET), polycarbonate, polyethylene, polypropylene, vinyl, etc.), fabric, cloth and other textile fabrics. Coated papers may include raw base paper substrates coated with SiO2 and/or AI2O3, anti-curl coatings, whitening coatings, etc.

[0108] The textile fabric may have a woven, knitted, or non-woven fabric structure, and includes natural fibers, synthetic fibers, or blends of natural and synthetic fibers. [0109] In one example, the textile fabric can be a woven fabric where warp yams and weft yarns can be mutually positioned at an angle of about 90°. This woven fabric can include fabric with a plain weave structure, fabric with a twill weave structure where the twill weave produces diagonal lines on a face of the fabric, or fabric with a satin weave structure. In another example, the textile fabric can be a knitted fabric with a loop structure. The loop structure can be a warp-knit fabric, a weft-knit fabric, or a combination thereof. A warp-knit fabric refers to every loop in a fabric structure that can be formed from a separate yam mainly introduced in a longitudinal fabric direction. A weft-knit fabric refers to loops of one row of fabric that can be formed from the same yam. In a further example, the textile fabric can be a non-woven fabric. For example, the non-woven fabric can be a flexible fabric that can include a plurality of fibers or filaments that are bonded together and interlocked together by a chemical treatment process (e.g., a solvent treatment), a mechanical treatment process (e.g., embossing), a thermal treatment process, or a combination of multiple processes.

[0110] Example natural fiber fabrics that can be used include treated or untreated natural fabric textile substrates, e.g., wool, cotton, silk, linen, jute, flax, hemp, rayon fibers, thermoplastic aliphatic polymeric fibers derived from renewable resources (e.g. cornstarch, tapioca products, sugarcanes), etc. Example synthetic fibers that can be used include polymeric fibers such as nylon fibers, polyvinyl chloride (PVC) fibers, PVC-free fibers made of polyester, polyamide, polyimide, polyacrylic, polypropylene, polyethylene, polyurethane, polystyrene, polyaramid (e.g., KEVLAR®) polytetrafluoroethylene (PTFE) (TEFLON®) (both trademarks of Chemours), fiberglass, polytrimethylene, polycarbonate, polyethylene terephthalate, polyester terephthalate, polybutylene terephthalate, or a combination thereof. In an example, natural and synthetic fibers may be combined at ratios of 1 : 1 , 1 :2, 1 :3, 1 :4, 1 :5, 1 :6, 1 :7, 1 :8, 1 :9, 1 :10, 1 :11 , 1 :12, 1 :13, 1 :14, 1 :15, 1 :16, 1 :17, 1 :18, 1 :19, 1 :20, or vice versa. In some examples, the fiber can be a modified fiber from the above-listed polymers. The term “modified fiber” refers to one or both of the polymeric fiber and the fabric as a whole having undergone a chemical or physical process such as copolymerization with monomers of other polymers, a chemical grafting reaction to contact a chemical functional group with one or both the polymeric fiber and a surface of the fabric, a plasma treatment, a solvent treatment, acid etching, or a biological treatment, an enzyme treatment, or antimicrobial treatment to prevent biological degradation.

[0111] In addition, the textile fabric can contain additives, such as a colorant (e.g., pigments, dyes, and tints), an antistatic agent, a brightening agent, a nucleating agent, an antioxidant, a UV stabilizer, a filler, and/or a lubricant, for example.

[0112] The textile fabric may be in the form of fabric material, or in the form of fabric that has been crafted into a finished article, such as, e.g., clothing, blankets, tablecloths, napkins, towels, bedding material, curtains, carpet, handbags, shoes, banners, signs, flags, etc.

[0113] In an example, the textile fabric may be selected from the group consisting of polyester fabrics, polyester blend fabrics, cotton fabrics, cotton blend fabrics, nylon fabrics, nylon blend fabrics, silk fabrics, silk blend fabrics, wool fabrics, wool blend fabrics, and combinations thereof. It is to be understood that the polyester fabrics may include other fibers whose surfaces are coated with polyester. The polyester blend fabrics may be blends of polyester and other materials (e.g., cotton, linen, etc.).

[0114] In one example, the textile fabric can have a basis weight ranging from 10 gsm to 500 gsm. In another example, the textile fabric can have a basis weight ranging from 50 gsm to 400 gsm. In other examples, the textile fabric can have a basis weight ranging from 100 gsm to 300 gsm, from 75 gsm to 250 gsm, from 125 gsm to 300 gsm, or from 150 gsm to 350 gsm.

[0115] Printed Articles

[0116] MXenes have a unique combination of electrical, electrochemical, rheological, and mechanical properties. Some MXenes exhibit electrical conductivity and/or energy storage capabilities. As an example, freestanding films of Ti₃C₂T_x produced by vacuum-assisted filtration may have a conductivity up to 20,000 S cm'¹. As such, examples of the inkjet ink 14 disclosed herein may be particularly suitable for generating printed articles including one or more components that are capable of electrical conductivity and/or electrochemical performance. [0117] An example of the printed article 30 is shown in Fig. 2A and Fig. 2B. The top view of the printed article 30 is shown in Fig. 2A, a cross-sectional view of the printed article 30 is shown in Fig. 2B. An exploded view of the print 28 generated is shown in Fig. 2C.

[0118] In the example shown in Fig. 2A through Fig. 2C, the printed article 30 includes the substrate 20 and the print 28 generated on the substrate 20. The substrate 20 may be any example set forth herein. In one example, the substrate 20 is uncoated paper. In another example, the substrate 20 is a textile fabric.

[0119] As shown in Fig. 2B and Fig. 2C, this example of the print 28 has three layers, including a pre-treatment layer 22, an electronic component 24, and an overcoat layer 26. As such, at least part of the generated print 28 includes an electronic component 24. Other examples prints may have two layers, including the pre-treatment layer 22 and the electronic component 24. Still other prints may have a single layer, including the electronic component 24.

[0120] The pre-treatment layer 22 is formed using an example of the pre-treatment fluid 12, e.g., either the fixer fluid or the topography normalization fluid. When the fixer fluid is used as the pre-treatment fluid 12, the fixing agent reacts or interacts with the MXene flakes of the applied inkjet ink 14, and thus the pre-treatment layer 22 and the electronic component 24 may be intermingled (unlike the physically separate layers 22, 24 schematically shown in Fig. 2B and Fig. 2C). An example method for generating the pre-treatment layer 22 with the fixer fluid will be described in more detail in reference to Fig. 4. When the topography normalization fluid is used as the pre-treatment fluid 12, the applied fluid is cured to form the pre-treatment layer 22. This generates a film at the surface of the substrate 20, and the electronic component 24 may be formed on this film. An example method for generating the pre-treatment layer 22 with the topography normalization fluid will be described in more detail in reference to Fig. 5.

[0121 ] The electronic component layer 24 is formed with the inkjet ink 14. In an example, the electronic component 24 is selected from the group consisting of conductors, resistors, capacitors, supercapacitors, inductors, memristors, diodes, transistors, rectifiers, transducers, relays, chemical or electronic sensors, transformers, antennas, radio frequency identifiers (RFID), batteries, switches, light emitting diodes (LED), thermoelectric devices, piezo-responsive devices, and photovoltaics. Some example conductors include a conductive trace or track or a conductive contact pad.

[0122] In one particular example, the electronic component 24 is an interdigitated capacitor structure. In another example, the electronic component 24 is a capacitor plate. When a capacitor plate is printed on a textile fabric substrate, substrate may be folded or rolled to create a parallel-plate capacitor structure. In this example, the printed areas are configured to allow unprinted textile areas to act as dielectric in a parallel plate capacitor arrangement. Alternatively, other thin dielectric materials can be introduced to the capacitor locations as part of garment assembly process.

[0123] The substrate 20 may be a textile fabric, and thus the electronic component 24 can be printed directly on a textile fabric substrate. The direct application of printed electronic components 24 onto textile fabric substrates is an effective platform for seamlessly integrating wearable technologies. For example, the inkjet ink 14 disclosed herein enables computing devices to be embedded in everyday wearable devices, e.g., clothing, watches, activity trackers, etc. The interconnection of these computing devices (i.e., the Internet of things, loT) enables them to send and receive data.

[0124] The printed article 30 shown in Fig. 2A through Fig. 2C also includes the overcoat layer 26. The overcoat layer 26 is formed with the overcoat composition 16, and may be applied and dried or cured to form a protective coating over the electronic component 24.

[0125] Printing Methods

[0126] Fig. 3 depicts several examples of the printing method 100. This method 100 generally includes generating a print by: inkjet printing a pre-treatment fluid 12 on a substrate (reference numeral 102), thereby generating a pre-treated substrate; and inkjet printing an inkjet ink 14 on the pre-treated substrate, the inkjet ink 14 including water and neat MXene flakes (reference numeral 104). [0127] Referring now to Fig. 4, an example of the printing method 100 utilizing the fixer fluid 12_FF is depicted. The fixer fluid 12_FF may be particularly suitable for pretreating an uncoated paper or textile fabric substrate.

[0128] It is to be understood that any example of the fixer fluid 12_FF may be used in this example of the method 100. The fixer fluid 12_FF may be applied digitally using inkjet technology. Any suitable inkjet applicator, such as a thermal inkjet cartridge/printhead, a piezoelectric cartridge/printhead, or a continuous inkjet cartridge/printhead, may eject the fixer fluid 12_FF in a single pass or in multiple passes. As an example of single pass printing, the cartridge(s) of an inkjet printer deposit the desired amount of the fixer fluid 12_FF during the same pass of the cartridge(s) across the substrate 20. In other examples, the cartridge(s) of an inkjet printer deposit the desired amount of the fixer fluid 12_FF over several passes of the cartridge(s) across the substrate 20.

[0129] It is also to be understood that any example of the inkjet ink 14 may be used in this example of the method 100. The inkjet ink 14 may be ejected onto the substrate 20 using inkjet technology. Any of the inkjet applicators may eject the inkjet ink 14 in a single pass or in multiple passes (as described herein).

[0130] In this example of the method 100, the inkjet ink 14 is printed onto the previously applied layer (pre-treatment layer 22_FF) while it is wet. Wet on wet printing may be desirable because it is desirable for the fixing agent in the fixer fluid 12_FF to react or otherwise interact with the MXene flakes in the inkjet ink 14 on the surface of the substrate 20. In an example of wet on wet printing, the inkjet ink 14 is printed onto the printed fixer fluid 12_FF (e.g., the fixer fluid layer 22_FF) within a period of time ranging from about 0.01 second to about 30 seconds after the fixer fluid 12_FF is printed. In other examples, the inkjet ink 14 is printed onto the previously applied fixer fluid 12_FF within a period of time ranging from about 0.1 second to about 20 seconds; or from about 0.2 second to about 10 seconds; or from about 0.2 second to about 5 seconds. Wet on wet printing may be accomplished in a single pass, or each of the fixer fluid 12_FF and inkjet ink 14 may be deposited in multiple passes.

[0131] The applied fixing agent 12_FF and inkjet ink 14 may be exposed to radiant heat and forced airflow to evaporate at least some of the water from the applied fixing agent 12_FF and inkjet ink 14. As shown schematically in Fig. 4, the fixing agent in the fixer fluid 12_FF react or otherwise interacts with the MXene flakes 34 in the inkjet ink 14 to lock the MXene flakes 34 at or near the surface of the substrate 20 to form the electronic component 24.

[0132] Referring now to Fig. 5, an example of the printing method 100 utilizing the topography normalization fluid 12_TF is depicted. The topography normalization fluid 12_TF may be particularly suitable for pre-treating an uncoated paper or textile fabric substrate.

[0133] It is to be understood that any example of the topography normalization fluid 12_TF may be used in this example of the method 100. The topography normalization fluid 12_TF may be applied digitally using inkjet technology. Any of the inkjet applicators may eject the topography normalization fluid 12_TF in a single pass or in multiple passes (as described herein).

[0134] This example of the method 100 also involves curing the applied topography normalization fluid 12_TF (as shown at reference numeral 106 in Fig. 3). Curing may be performed of a series of heating stages. In the first stage, radiant heat and forced airflow generated by one or more heating components 32 evaporates most of the water from the applied topography normalization fluid 12_TF- The temperature in the first stage is at least 10° lower than the minimum film formation temperature (MFFT) of the latex particles in the topography normalization fluid 12_TF- During this process, the liquid film condenses to a viscous mixture of the latex particles and remaining components of the aqueous topography normalization fluid vehicle. Chemical interactions between the surface of the substrate 20 and the latex particles may also take place to initially bind the latex to the substrate 20. In the second stage, the temperature may be raised to at least a minimum film formation temperature (MFFT) of the latex particles in the topography normalization fluid 12_TF- In this stage, the process of film formation takes place. More particularly, the latex particles coalesce into a continuous polymer film 22_TF smooths out the surface of the substrate 20. This film 22_TF can block the pores located at or near the surface of the porous substrate 20, thus creating a non-porous surface on the otherwise porous substrate 20. This continuous polymer film 22_TF may chemically attach to the substrate 20. The MFFT, and thus the drying and curing temperatures, depend, in part, upon the composition of the latex particles. As examples, drying temperatures may range from about 40°C to about 60°C, and curing temperatures may range from about 70°C to about 110°C. [0135] In this example of the method 100, the inkjet ink 14 is printed onto the continuous polymer film 22_TF- It is also to be understood that any example of the inkjet ink 14 may be used in this example of the method 100. The inkjet ink 14 may be ejected onto the continuous polymer film 22_TF using inkjet technology. Any of the inkjet applicators may eject the inkjet ink 14 in a single pass or in multiple passes (as described herein).

[0136] Radiant heat and forced airflow may be used to evaporate at least some of the water from the applied inkjet ink 14, leaving the MXene flakes 34 oriented on the continuous polymer film 22_TF in the shape of the electronic component 24. Because the MXene flakes 34 cannot penetrate the pores of the substrate 20, the concentration of MXene flakes 34 at the substrate surface may be increased, e.g., when compared to the example electronic component 24 formed by the method shown in Fig. 4.

[0137] The higher concentration of MXene flakes 34 in the example shown in Fig. 5 may also contribute to more overlap among the MXene flakes 34. This overlapping orientation may be particularly desirable when the electronic component 24 is formed on a stretchable fabric substrate 20. When a stretchable fabric substrate 20 is stretched, the MXene flakes 34 may be moved with the underlying fabric substrate 20. As a result of the movement, the contact between the MXene flakes 34 may be reduced, leading to reduced conductivity and electric performance. In contrast, the overlapping orientation of the MXene flakes 34 may help to maintain contact between the MXene flakes 34 even when the fabric substrate 20 is stretched. This is shown in Fig. 6, where the MXene flakes 34 on the continuous polymer film 22_TF are maintained in physical contact, and thus electrical contact, even when the substrate 20 is stretched in opposite directions (as noted by the arrows). The continuous polymer film 22_TF may allow for multiple stretching and contraction cycles without losing or otherwise deleteriously affecting the electrical conductivity of the electrical component 24. [0138] While the examples of the method 100 describe the printing of one inkjet ink 14, it is to be understood that two or more different inkjet inks 14 may be printed to generate the electronic component 24. When two or more different inkjet inks 14 are printed, the pre-treatment fluid 12 may or may not be used.

[0139] In one particular example, two different inkjet inks 14 may be used, one of which includes small neat MXene flakes and the other of which includes large neat MXene flakes. Small neat MXene flakes can readily penetrate into the pores of a porous substrate 20 (e.g., uncoated paper, textile fabrics), which can increase the surface area of the generated print. Large neat MXene flakes tend to orient themselves in an overlapping position on or near the surface of the substrate 20, which can increase the conductivity of the generated print. The use of small or large neat MXene flakes independently may depend upon the electronic component 24 that is to be generated and the substrate 20 that is to be used. In this example of the method 100, a first inkjet ink containing small neat MXene flakes (as defined herein) may be printed on the substrate 20 (pre-treated or not), and then a second inkjet ink containing large neat MXene flakes (as defined herein) may be printed over the printed first inkjet ink. The small neat MXene flakes from the first inkjet ink may penetrate into the pores of the substrate 20, thus increasing the surface area and the z-axis of the print, and the subsequently printed large neat MXene flakes may concentrate at the surface of the substrate 20, this increasing the conductivity of the print. The number of printing passes of each of the first and second inkjet inks may be tuned to adjust the conductivity and/or the electrochemical performance of the resulting electronic component 24.

[0140] Referring back to Fig. 3, any example of the method 100 may further include applying the overcoat composition 16 over the print 28, as shown at reference numeral 108. More particularly, the overcoat composition 16 may be applied over the electronic component 24.

[0141 ] Some examples of the overcoat composition 16 may be applied digitally using inkjet technology. For example, an aqueous varnish with latex particles and some of the UV varnishes may be applied using inkjet technology. This technique allows for the overcoat composition 16 to be applied over the electronic component 24 without being applied over the entire substrate 20.

[0142] Other examples of the overcoat composition 16 may be applied using an analog technique. For example silicone water-based emulsion varnishes and wax varnishes may be applied using an analog technique. When an analog technique is used, the overcoat composition 16 may be applied using an auto analog pretreater, a drawdown coater, a slot die coater, a roller coater, a fountain curtain coater, a blade coater, a rod coater, an air knife coater, a sprayer, or a gravure application. In these examples, the overcoat composition 16 may be coated on all or substantially all of the substrate 20, including areas where the print 28 is generated and areas where print 28 is not generated. As such, in this example, the overcoat layer 26 that is formed may be a continuous layer that covers all or substantially all of the textile fabric 20.

[0143] Depending upon the type of overcoat composition 16 that is used, this example of the method 100 may further include curing or drying the overcoat composition 16. For example, when an aqueous varnish with latex particles or a UV varnish is used, the applied overcoat composition 16 may be exposed to thermal or UV curing. For another example, when a silicone water-based emulsion varnish or a wax varnish is used, the applied overcoat composition 16 may be exposed to radiant heat and forced airflow to evaporate at least some of the water from the overcoat composition 16.

[0144] When thermal inkjet printers are used, the following operating parameters may be desirable for the inkjet inks 14 disclosed herein. The operating energy may range from about 0.8 pJ to about 3.8 pJ, depending on the resistor size and sheet resistance (drop weight) as well as the fire pulse. The warming temperature may range from about 30°C to about 65°C. The fire pulses may include one main fire pulse, or may include split pulses, such as a precursor fire pulse followed by some head time followed by another fire pulse. The total pulse time with one main pulse or with split pulses may range from about 0.7 ps to about 2 ps. The voltage may vary depending upon the specific print head features and energy needed to operation. In an example, the voltage may range from about 24 V to about 32 V. [0145] In another example of the printing method 100, the inkjet ink 14 can be directly printed on the substrate 20 without the pre-treatment fluid 12 or the overcoat fluid 16. The MXene flake size and concentration contribute to the inkjet ink 14 having a suitable viscosity at the shear rates used during jetting, which enable them to be successfully inkjet printed even when the inkjet ink 14 is additive free. This example method does not involve pre- or post- printing treatment steps.

[0146] When the inkjet ink 14 is directly printed onto a hydrophilic textile fabric, the fabric can accelerate the rate evaporation due, in part, to its high surface area. The dehydrated MXene flakes 34 rapidly assemble and adhere along the substrate 20 along the print pattern.

[0147] To further illustrate the present disclosure, an example and prophetic examples are given herein. It is to be understood that the example and the prophetic examples are provided for illustrative purposes and are not to be construed as limiting the scope of the present disclosure.

EXAMPLE

[0148] Single-layer Ti₃C₂T_x MXenes were prepared by etching the Al layer from the MAX phase precursor Ti₃AIC2 using a HF-HCI acid mixture to produce multilayer Ti₃C₂T_x powder, followed by delamination using an aqueous solution of LiCI.

Centrifugation was used to isolate the single-layer Ti₃C₂T_x flakes from the multilayer Ti₃C₂T_xand the unreacted MAX phase particles.

[0149] The single-layer Ti₃C₂T_x flakes were dispersed in water. The resulting aqueous Ti₃C₂T_x dispersions had a large degree of polydispersity, where the size of the Ti₃C₂T_x flakes ranged from a few hundreds of nanometers up to 10 micrometers. The size of the Ti₃C₂T_x flakes was reduced by probe sonication, resulting in Ti₃C₂T_x flakes with smaller lateral dimensions (referred to as small Ti₃C₂T_x flakes) than the as- synthesized Ti₃C₂T_x flakes (referred to as large Ti₃C₂T_x flakes). X-ray diffraction (XRD) results (not reproduced herein) showed that the Ti₃AIC₂ MAX powder was successfully converted to Ti₃C₂T_x MXene and the delamination was successful.

[0150] Three large example MXene inks (Inks L1 , L2, L3) were prepared by mixing the as-synthesized (large) Ti₃C₂T_x flakes in water to obtain different concentrations, and filtering the dispersion through a 10 pm filter. Three small MXene inks (Inks S1 , S2, S3) were prepared by mixing the probe sonicated (small) Ti₃C2T_x flakes in water to obtain different concentrations. The concentrations of the large or small MXene flakes in each of the inks is shown in Table 1 .

TABLE 1

[0151 ] The size of the MXene flakes in Ink L3 and Ink S3 was determined using a MICROTRAC® dynamic light scattering instrument (Nanotrac Wave). The results are shown in Fig. 7. As depicted, these results indicated that the large Ti₃C2T_x flakes primarily included flakes with lateral sizes between 1 pm and 10 pm, with an average lateral flake size of 2 pm; and that the small Ti₃C2T_x flakes were sub-micron sized having an average lateral flake size of 350 nm.

[0152] The viscosity of each of the inks was also measured using a VISCOLITE® 700, HP-d15 viscometer. The viscosity measurements were taken at 25°C and a shear rate of 10⁶ s’¹. The results are shown in Fig. 8. As the concentration of the MX flakes was increased, the viscosity also increased. Additionally the inks including the large MXene flakes had higher viscosities than the inks including the small MXene flakes. All of the inks, including Ink L3, with the highest concentration of large MXene flakes, were successfully thermally inkjet printed using a circular nozzle with a dimeter of 30 pm. With an infinity-shaped nozzle with a dimeter of 30 pm and a 5 pm-wide pinch at its center, the maximum viscosity that was able to be jetted was 1 .7 cP (Ink S3).

[0153] The surface tension of Ink L3 and Ink S3 were also measured using a Force Tensiometer - K100 (Kruess, Germany). At room temperature, the surface tension of Ink L3 was approximately 76.5 mN rrT¹ and the surface tension of Ink S3 was 68.8 mN m'¹. Based on the measured surface tension values, the Z values were calculated to be about 19.9 and about 18.9 for Ink L3 and Ink S3, respectively.

[0154] Inks L1 -L3 and S1 -S3 were printed on the following substrates: cotton knit fabric, cotton woven fabric, and solar paper (HP Inc.). The inks were printed with an HP thermal inkjet printer using from 2 to 24 printing passes.

[0155] Fig. 9 is a graph depicting the resistance of printed lines (width: 1 .00 ± 0.04 mm) using 6-print passes (<N> = 6). As depicted, the resistance (O cm'¹) of the printed lines decreased with an increase in the concentration of the Ti₃C₂T_x flakes, which can be explained by the higher amount of material deposited at higher concentrations. Inks L1 -L3, containing large Ti₃C₂T_x flakes, exhibited relatively lower resistance compared to inks S1-S3, containing small Ti₃C₂T_x flakes, which can be attributed to the minimal inter-sheet contacts per unit length between the large flakes. The lines printed on paper demonstrated the highest conductivity, and the lines printed on cotton woven fabric exhibited lower resistance compared to the cotton knit fabric for all the inks. The difference in the resistance values due to the substrate type was more obvious with S1 and S2, which had lower concentrations of small Ti₃C₂T_x flakes. [0156] The number of printing passes should increase the amount of MXene flakes deposited on the substrate, and decrease the resistance (O cm'¹) of the printed lines. As shown in Fig. 10, the resistance (O cm'¹) of the lines printed on cotton woven fabric decreased as a function of printing pass number, <N>, for both Inks S3 and L3 with the highest concentration of small S-Ti₃C₂T_x flakes (22.4 mg mL'¹) and large Ti₃C₂T_x flakes (18 mg mL'¹), respectively. The improved electrical conductivity shown in Fig.

10 may be attributed to the better percolation of the deposited Ti₃C₂T_x flakes, which improves the number of electrical pathways. Using porous substrates such as fabric and paper enhances fast and uniform solvent absorption, which helps to print successive print cycles without waiting between each cycle as the solvent is adsorbed or wicked into the substrate rapidly, leading to a more even material deposition.

[0157] Ink L1 was used to print four individual circuits on cotton knit fabric. A single printing pass was used to print the circuits. Light emitting diodes (LEDs) were connected to each of the circuits. A 9 V battery was placed on each circuit to supply power to the respective light-emitting diode. Each of the LEDs lit up with the battery in place, demonstrating the electrical conductivity of the inkjet printed MXene circuits.

Fig. 11 is a black and white photograph of each of the circuits, with the battery in place on one of the circuits and the LED powered. These results demonstrate that the MXene inks disclosed herein can be thermally inkjet printed to generate conductive circuits and other electronic components.

PROPHETIC EXAMPLES

[0158] Prophetic Example 1

[0159] A fixer fluid having the composition shown in Table 2 is prepared.

TABLE 2

[0160] A MXene ink having the composition shown in Table 3 is prepared.

TABLE 3

[0161] The fixer fluid and MXene ink are printed using a thermal inkjet printer on plain (uncoated) paper and on a 100% cotton textile fabric. Six printing passes are used to deposit the fixer fluid and then six printing passes are used to deposit the MXene ink on each of the substrates to form straight line traces. No drying is performed in between the passes.

[0162] As a comparison, the MXene ink is printed in the same manner without the fixer fluid.

[0163] While the example and comparative example straight line traces are all conductive, the edge acuity of the example straight line traces is more precise and has less bleed than the comparative example straight line traces.

[0164] Prophetic Example 2

[0165] A topography normalization fluid in accordance with the composition shown in Table 4 is prepared. The MXene ink of prophetic example 1 is used.

TABLE 4

[0166] The topography normalization fluid and MXene ink are printed using a thermal inkjet printer on a 100% cotton textile fabric. Six printing passes are used to deposit the topography fluid and then the fluid is cured. Curing involves first heating the substrate to a temperature at least 10° lower than the minimum film formation temperature (MFFT) of the latex particles, and then raising the temperature to at least a minimum film formation temperature (MFFT) of the latex particles in the topography normalization fluid 12_TF- Six printing passes are then used to deposit the MXene ink on the pre-treated portion of the substrate to form straight line traces.

[0167] As a comparison, the MXene ink is printed in the same manner without the topography normalization fluid.

[0168] The example and comparative example substrates are stretched and the conductivity of the straight line traces is measured. After being stretched, the conductivity of the straight line traces on the comparative example substrates (without the film generated using the topography normalization fluid) is lower than the conductivity of the straight line traces on the example substrates.

[0169] It is to be understood that the ranges provided herein include the stated range and any value or sub-range within the stated range, as if the value(s) or subrange^) within the stated range were explicitly recited. For example, a range from about 1 wt% to about 15 wt%, should be interpreted to include not only the explicitly recited limits of from about 1 wt% to about 15 wt%, but also to include individual values, such as about 1 .15 wt%, about 2.5 wt%, 4.0 wt%, 6.77 wt%, 8.85 wt%, 9 wt%, 12.33 wt%, 14 wt%, etc., and sub-ranges, such as from about 2 wt% to about 5.65 wt%, from about 3 wt% to about 7 wt% from about 4.35 wt% to about 8.95 wt%, etc. Furthermore, when “about” is utilized to describe a value, this is meant to encompass minor variations (up to +/- 10%) from the stated value.

[0170] Reference throughout the specification to “one example”, “another example”, “an example”, and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the example is included in at least one example described herein, and may or may not be present in other examples. In addition, it is to be understood that the described elements for any example may be combined in any suitable manner in the various examples unless the context clearly dictates otherwise.

[0171] In describing and claiming the examples disclosed herein, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0172] While several examples have been described in detail, it is to be understood that the disclosed examples may be modified. Therefore, the foregoing description is to be considered non-limiting.

Claims

What is claimed is:

1. An inkjet fluid set, comprising: a pre-treatment fluid; and an inkjet ink including water and neat MXene flakes.

2. The inkjet fluid set as defined in claim 1 wherein the inkjet ink is a thermal inkjet ink having a viscosity up to 5.1 cP at 25°C and at a shear rate of 10⁶ s’¹.

3. The inkjet fluid set as defined in claim 1 wherein the neat MXene flakes in the inkjet ink have a lateral flake size distribution ranging from about 100 nm to about 20 pm.

4. The inkjet fluid set as defined in claim 3 wherein: the lateral flake size distribution of a first portion of the neat MXene flakes in the inkjet ink ranges from about 100 nm to about 1000 nm; and the lateral flake size distribution of a second portion of the neat MXene flakes in the inkjet ink ranges from about 1 pm to about 10 pm.

5. The inkjet fluid set as defined in claim 4 wherein a weight ratio of an amount of the first portion to an amount of the second portion ranges from about 1 :99 to about 99:1.

6. The inkjet fluid set as defined in claim 1 wherein the pre-treatment fluid is a fixer fluid including water and a fixing agent selected from the group consisting of a multi-valent metal salt and a cationic polymer.

7. The inkjet fluid set as defined in claim 1 wherein the pre-treatment fluid is a topography normalization fluid including water and latex particles.

8. The inkjet fluid set as defined in claim 1 , further comprising an overcoat composition including water and a film-forming polymer.

9. The inkjet fluid set as defined in claim 1 wherein the inkjet ink further includes: an electrically conductive active material; an additive selected from the group consisting of co-solvents, surfactants, anti- kogation agents, antimicrobial agents, polymeric dispersants, chelating agents, humectants, and combinations thereof; or a combination of the active material and the additive.

10. A textile printing kit, comprising: a textile fabric; a pre-treatment fluid; and an inkjet ink including water and neat MXene flakes.

11 . The textile printing kit as defined in claim 10 wherein the textile fabric substrate has a woven, knitted, or non-woven fabric structure, and includes natural fibers, synthetic fibers, or blends of natural and synthetic fibers.

12. The textile printing kit as defined in claim 10 wherein the pre-treatment fluid is one of: i) a fixer fluid including water and a fixing agent selected from the group consisting of a multi-valent metal salt and a cationic polymer; or ii) a topography normalization fluid including water and latex particles.

13. A method, comprising: generating a print by: inkjet printing a pre-treatment fluid on a substrate, thereby generating a pre-treated substrate; and inkjet printing an inkjet ink on the pre-treated substrate, the inkjet ink including water and neat MXene flakes.

14. The method as defined in claim 13, further comprising applying an overcoat composition on the print.

15. The method as defined in claim 13 wherein at least part of the generated print comprises an electronic component selected from the group consisting of conductors, resistors, capacitors, supercapacitors, inductors, memristors, diodes, transistors, rectifiers, transducers, relays, chemical or electronic sensors, transformers, antennas, radio frequency identifiers (RFID), batteries, switches, light emitting diodes (LED), thermoelectric devices, piezo-responsive devices, and photovoltaics.