WO2015083160A2

WO2015083160A2 - Process for controlling wettability features

Info

Publication number: WO2015083160A2
Application number: PCT/IL2014/051048
Authority: WO
Inventors: Michael Grouchko; Shlomo Magdassi
Original assignee: Clearjet Ltd
Priority date: 2013-12-02
Filing date: 2014-12-02
Publication date: 2015-06-11
Also published as: WO2015083160A3

Abstract

The invention provides a process of forming a continuous pattern on a surface composed of two or more surface regions, each of the regions being of a different surface energy, the process utilizing a novel ink formulation for printing on such multi-region surfaces.

Description

Process for Controlling Wettability Features

FIELD OF THE INVENTION

The present invention provides transparent conductive coatings and processes for their manufacture.

BACKGROUND OF THE INVENTION

Electronic devices, specifically, integrated circuits consist of many components, including many electronic components such as transformators, capacitors, inductors, resistors, wiring, etc. and are made of different materials, conductors, insulators and semiconductor.

The processes currently employed for constructing the different electronic components and their wiring typically involve lithography— a complex process which is comprised of many sub-steps, such as photoresist deposition, masking, exposing (developing), etching, and many others. The process of fabrication of the electronic device is even more complex, as there are different components of different materials that require assemblies. Such assembly processes are not only complex but also greatly expensive.

Thus, there is a need for a simple process which will provide cheaper, scaled down, and improved electronic components and devices.

A process for forming "coffee cup ring" structures by ink jet printing has been previously described to afford conductive and transparent films [1].

REFERENCES

[1] WO 2011/051925

SUMMARY OF THE INVENTION

As demonstrated herein, it is typically very hard or impossible to form a continuous line or ring patterns such as the patterns provided in the art [1] on a material surface composed of two or more regions of different wettabilities, namely each of the two or more regions having a different surface energy property. As such materials are of great importance in a variety of technological fields, the inventors of the present invention have embarked on developing a methodology which would enable forming a continuous uninterrupted pattern, typically a conductive line pattern, on a surface having two or more regions of different wettabilities, more importantly a pattern that crosses a physical or chemical boundary between the surface regions.

The inventors of the present invention faced with the challenge have developed a methodology for enabling printing of an ink formulation on surface regions having varying surface energies, the printed pattern crossing a physical or chemical boundary between such surface regions, without affecting the structure, its form, integrity and other properties associated with the printed pattern. Where the printed pattern is a line pattern made of a conductive ink, the line pattern formed maintains integrity, thickness and form, and at the same time maintains conductivity.

The inventors have thus developed a novel ink formulation and a method of printing that enable efficient printing on such surfaces as well as on surfaces characterized by a single continuous surface energy.

In one aspect, the invention provides a process of forming a continuous pattern on a surface composed of two or more surface regions, each of the surface regions being of a different surface energy, the process comprising:

-forming a continuous pattern on said surface such that the pattern crosses at least one boundary between the two or more surface regions of the surface, the two or more regions differing in their wettability (a surface energy parameter); the continuous pattern being formed by an organic ink formulation configured to adhere to each of said two or more surface regions; and

-permitting said pattern to dry to afford the continuous pattern, the pattern at least partially covering two or more of said regions of differing wettabilities.

In an additional aspect, the invention provides a process of forming a continuous pattern on a surface composed of two or more surface regions, each of the surface regions being of a different surface energy, the process comprising:

-forming a continuous pattern on said surface such that the pattern crosses at least one boundary between the two or more surface regions of the surface, the two or more regions differing in their wettability (a surface energy parameter); the continuous pattern being formed by an organic ink formulation configured to adhere to each of said two or more regions, said formulation comprising an organic solvent, at least one binder selected from organic and inorganic binders and nanoparticles; and

-permitting said pattern to dry to afford the continuous pattern, the pattern at least partially covering two or more of said surface regions of differing wettabilities.

In some embodiments, organic formulation is water-free, namely containing 0% water, and the solvent constitutes at least 95% of the formulation by weight.

In another aspect, the invention provides a process of forming a continuous ring pattern on a surface composed of two or more surface regions, each of the surface regions being of a different surface energy, the process comprising:

-forming a continuous pattern of rings on said surface such that the pattern crosses at least one boundary between the two or more surface regions of the surface, the two or more regions differing in their wettability (a surface energy parameter); the continuous pattern of rings being formed by an ink formulation configured to adhere to each of said two or more surface regions; and

-permitting said pattern to dry to afford the continuous pattern of rings, the pattern at least partially covering two or more of said surface regions of differing wettabilities.

In some embodiments, the ink is an organic ink, free of water.

Wettability is a measure of a surface energy of a material, namely variation of the wettability means variation of the surface energy. The ink and processes of the invention permit modulation of the ink formulation or the process parameters to increase adherence of the pattern onto the surface regions with the same or similar properties. The invention thus allows varying a wettability parameter of the ink formulation for achieving efficient patterning on hydrophilic - hydrophobic regions of a material, or on surfaces having varying hydrophobicities or varying hydrophilicities, including on boundaries between the surface regions.

The ability to modify a wettability property of the ink formulation permits modifying the affinity of the ink formulation to the surface at the various regions, thus promoting adhesion or coupling of the ink components to the two or more surface regions. As experimental data provided herein demonstrate, exiting ink formulations are not typically suitable for printing on a multitude of surface regions with varying wettabilities. Exiting ink formulations are suitable for printing on a single surface having a single wettability property, surface energy, and do not typically form continuous patterns on other surfaces.

Thus, in some embodiments, an ink formulation according to the invention is configured to comprise at least one component which endows the formulation as a whole with a wettability parameter, e.g., surface adhesiveness, which is suited to the two or more surface regions, thus removing the need for using different ink formulations or for switching between different ink formulations. The at least one component may be introduced to an existing ink formulation, in any amount as needed, to adjust its wettability parameter to the two or more of the surface regions.

According to the invention, the ink formulation comprises an organic solvent, an organic binder and/or an inorganic binder, (nano)particles, as hereindefined, and optionally additional additives. Thus, in some embodiments, the at least one component which endows the formulation as a whole with a wettability parameter is selected amongst at least one organic solvent and at least one organic or inorganic binder, or any combination or solvents, or any combination of binders or any combination of binders and solvents.

The ink formulation is an organic ink substantially free of water. Namely, the ink may contain up to 10% by weight of water; in other embodiments, up to 5% by weight of water; in yet other embodiments, up to 3% by weight of water; in yet other embodiments, up to 2% by weight of water; in yet other embodiments, up to 1% by weight of water; in yet other embodiments, up to 0.5% by weight water; in yet other embodiments, up to 0.3% by weight water. In some embodiments, the formulation comprises 0% water, namely being free of water.

The organic ink formulation is based on organic solvents which may comprise other inorganic components. In some embodiments, the formulation comprises at least 50% by weight organic solvent. In other embodiments, the organic solvent constitutes more than 60% by weight of the formulation (namely the formulation comprises at least 60% by weight of the organic solvent). In other embodiments, the organic solvent constitutes more than 70% by weight of the formulation. In other embodiments, the organic solvent constitutes more than 80% by weight of the formulation. In some embodiments, the organic solvent constitutes more than 90% by weight of the formulation. In other embodiments, the organic solvent constitutes more than 92% by weight of the formulation. In other embodiments, the organic solvent constitutes more than 93% by weight of the formulation. In other embodiments, the organic solvent constitutes more than 94% by weight of the formulation. In other embodiments, the organic solvent constitutes more than 95% by weight of the formulation. In yet other embodiments, the organic solvent constitutes more than 96% by weight of the formulation. In yet other embodiments, the organic solvent constitutes more than 97% by weight of the formulation. In yet other embodiments, the organic solvent constitutes more than 98% by weight of the formulation. In yet other embodiments, the organic solvent constitutes more than 99% by weight of the formulation. The solvent may be a combination of at least two solvents.

In some embodiments, the solvent may be any one of, but not limited to, a glycol ether, an alcohol, or an acetate, and any combination thereof.

In some embodiments, the at least one organic solvent is an organic liquid having at least one hydroxyl (-OH) group; an alcohol. The organic liquid may be selected amongst mono-ols (having one OH group), diols (having two OH groups), triols (having three OH groups) and organic solvents comprising more than 3 OH groups. In some embodiments, the solvent is at least one glycol ether, namely an alkyl ether having one or more hydroxyl groups. The glycol ethers may be selected from "e-series" or "p-series" glycol ethers, as known in the art.

In some embodiments, the glycol ether is selected amongst ethylene glycol monoalkyl ethers, polyglycol monoalkyl ethers, ethylene glycol phenyl ethers, polyglycol phenyl ethers, ethylene glycol benzyl ethers and polyglycol benzyl ethers. As used herein, the "alkyl" of the "alkyl ether" may be a Cl-C6alkyl, namely an alkyl comprising between 1 and 6 carbon atoms e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl. The alkyl is typically n-alkyl, but in some embodiments may be further substituted or a branched alkyl.

Further as used, the "polyglycol" is an oligomer or a polymer of the monoalkyl ether. The polyglycol is typically a polyethylene glycol.

In some embodiments, the glycol ether is selected from ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, ethylene glycol monohexyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol monohexyl ether, their corresponding acetates, such as diethylene glycol n-butyl ether acetate and others.

The organic solvent may alternatively be an alcohol selected from methanol, ethanol (EtOH), butanol (Bu'OH), nonanol, octanol and any other alcohol.

The ink formulation further comprises a binder. The binder may be in an amount of up to 5% by weight of the ink formulation. In some embodiments, the binder is present in an amount of up to 3% by weight of the ink formulation. In other embodiments, the binder is present in an amount of up to 2% by weight of the ink formulation. In some embodiments, the binder is present in an amount of up to 1.5% by weight of the ink formulation. In other embodiments, the binder is present in an amount of up to 1% by weight of the ink formulation. In some embodiments, the binder is present in an amount of up to 0.7% by weight of the ink formulation. In other embodiments, the binder is present in an amount of up to 0.5% by weight of the ink formulation. In other embodiments, the binder is present in an amount of up to 0.3% by weight of the ink formulation.

The organic binder is typically an organic material which enables or improves adhesion of the ink to the surface and formation of a continuous uninterrupted pattern. The binder may be selected to etch (at any required degree) the surface to permit better adhesion. In some embodiments, the organic binder is an organic material having at least one cellulose.

In some embodiments, the organic binder is selected from polyvinyl pyridine, polyvinyl butyral, ethyl cellulose, methyl cellulose, and others.

The ink formulation may further comprise at least one additive. The additive may be in an amount of less than 5% by weight of the ink formulation. In some embodiments, the additive is less than 3% by weight of the ink formulation. In other embodiments, the additive is less than 2% by weight of the ink formulation. In some embodiments, the additive is less than 1.5% by weight of the ink formulation. In other embodiments, the additive is less than 1% by weight of the ink formulation. In some embodiments, the additive is less than 0.7% by weight of the ink formulation. In other embodiments, the additive is less than 0.5% by weight of the ink formulation. In other embodiments, the additive is less than 0.3% by weight of the ink formulation. In some embodiments, the at least one additive is a wetting agent permitting proper wetting of the ink on the surface. Such wetting agents may be selected, in a non-limiting fashion, from BYK 348, BYK 333, BYK 110, morwet and any other wetting agent.

The ink formulation additionally comprises a material in a particulate form, which makes-up the dry printed pattern. The particulate material may be comprised in the formulation as a colloid. In some embodiments, the particles are microparticles. In other embodiments, the particles are nanoparticles.

In further embodiments, the particles are nanoparticles having an average diameter of less than 500 nm or a diameter of less than 300 nm or a diameter of less than 100 nm or a diameter of less than 10 nm.

In some embodiments, the material is composed of coalesced particles. In other embodiments, the material is composed of sintered particles.

The particles content within the ink formulation may be less than 5% by weight of the ink formulation. In some embodiments, the particles make up less than 3% by weight of the ink formulation. In other embodiments, the particles make up less than 2% by weight of the ink formulation. In some embodiments, the particles make up less than 1.5% by weight of the ink formulation. In other embodiments, the particles make up less than 1% by weight of the ink formulation. In some embodiments, the particles make up less than 0.7% by weight of the ink formulation. In other embodiments, the particles make up less than 0.5% by weight of the ink formulation. In other embodiments, the particles make up less than 0.3% by weight of the ink formulation.

In some embodiments, the particulate material (e.g., nanoparticles) is a conductive material, a semiconductor material or an insulator material. In some embodiments, the particulate material (e.g., nanoparticles) is of a material which may be rendered conductive once the pattern is formed.

In some embodiments, the particulate material is conductive, and may be selected from a metal, a transition metal, a semiconductor, an alloy, an intermetallic material, a conducting polymer, a carbon based material such as carbon black, carbon nanotubes (CNT), graphite, graphene, fullerenes, and carbon allotropes. The conductive material may be a combination of two or more different materials. In some embodiments, the conductive material is or comprises an element of Groups IIIB, IVB, VB, VIB, VIIB, VIIIB, IB, IIB, IIIA, IVA and VA of block d of the Periodic Table of the Elements.

In other embodiments, the conductive material is or comprises a transition metal selected from Groups IIIB, IVB, VB, VIB, VIIB, VIIIB, IB and IIB of block d the Periodic Table. In some embodiments, the transition metal is a metal selected from Sc, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Y, Zr, Nb, Tc, Ru, Mo, Rh, W, Au, Pt, Pd, Ag, Co, Cd, Hf, Ta, Re, Os, Ir and Hg.

In other embodiments, the conductive material is selected, in a non-limiting fashion, from indium(III) acetate, indium(III) chloride, indium(III) nitrate, indium(III) acetylacetonate, for the creation of CuInS₂ and Cu(InGa)S₂; iron(II) chloride, iron(III) chloride, iron(II) acetate, iron(III) acetylacetonate for the formation of CuFeS₂; gallium(III) acetylacetonate, gallium(II) chloride, gallium(III) chloride, gallium(III) nitrate for the formation of CuGaS₂ and Cu(InGa)S₂; aluminum(III) chloride, aluminum(III) stearate for the formation of CuAlS₂; silver nitrate, silver chloride for the formation of AgS; dimethlyzinc, diethylzinc, zinc chloride, tin(II) chloride, tin(IV) chloride, tin(II) acetylacetonate, tin(II) acetate for the formation of Cu₂(ZnSn)S₄; cadmium(II) chloride, cadmium(II) nitrate, cadmium(II) acetate, cadmium(II) acetlyacetonate, cadmium(II) stearate for CdS; lead(II) acetate, lead(II) acetlylacetonate, lead(II) chloride, lead(II) nitrate and PbS.

In other embodiments, the particulate material is selected amongst semiconductor materials. The semiconductor material may be selected from elements of Group II- VI, Group III-V, Group IV- VI, Group III- VI, Group IV semiconductors and combinations thereof.

In some embodiments, the semiconductor material is a Group II- VI material being selected from CdSe, CdS, CdTe, ZnSe, ZnS, ZnTe, HgS, HgSe, HgTe, CdZnSe and any combination thereof.

In other embodiments, Group III-V material are selected from InAs, InP, InN, GaN, InSb, InAsP, InGaAs, GaAs, GaP, GaSb, AlP, AIN, AlAs, AlSb, CdSeTe, ZnCdSe and any combination thereof. In additional embodiments, the particulate material is selected from Group IV- VI, the material being selected from PbSe, PbTe, PbS, PbSnTe, Tl₂SnTe₅ and any combination thereof.

In further embodiments, the conductive material is selected amongst metal alloys and intermetallics of the above metal and/or transition metals. Non-limiting examples of such alloys are WMo, MoRh, MoRh₃, Rho.₃₄Ru₀.66, Rh₀.₄Ru₀.6, PdRh, PdRu, MoPd₂, Pd_{0 3}Moo.8, MoPt, Mo₂Pt, PtPd, Pt₀.₄Ru₀.6, Pt₀.₂Ru₀.8, PtRh, WPt, AuPd, AuPt, AuRh, AuRu, AuMo, and AuW.

In additional embodiments, the conductive material is a carbon based material such as carbon black, carbon nanotubes (CNT), graphite, graphene, fullerenes, or other carbon allotropes. The carbon based material need not be in particulate form.

The conductive material may alternatively be a conductive polymer such as poly(3,4-dioctyloxythiophene) (PDOT), poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PDOT:PSS), polyaniline and polypyrrole. The conductive polymer need not be in particulate form.

In some embodiments, the conductive material is a metal selected from silver, gold, copper, nickel, cobalt, aluminum or any other metal. In some embodiments, the conductive material may be a carbon material such as carbon nanotubes and graphene.

In some embodiments, the conductive material is a metal selected from silver, gold and copper or is a carbon based material, in some embodiments being CNT.

In some embodiments, the conductive material is silver or gold or any combination thereof.

In some embodiments, the ink formulation comprises at least one type of particles (nanoparticles), as defined; at least one solvent, as defined; and at least one binder as defined.

The pattern formed on the at least two or more surface regions as described herein, may be formed by any printing methodology known in the art. Typically, the pattern is formed by treating a surface of a substrate with a plurality of ink droplets which are applied onto the surface to form a continuous pattern. In some embodiments, the ink droplets are applied by inkjet printing. In other embodiments, the ink droplets are applied by spraying. In other embodiments, the ink droplets are applied by brushing the surface (e.g., by an air brush).

The volume of the ink droplets may be in the range of 1 picoliter to 10 microliters. In some embodiments, the volume of the droplets is in the picoliters range.

According to the invention, once the droplets are placed, e.g., by printing, on the surface to form a desired pattern, they are permitted to dry. In some embodiments, drying is achievable under ambient conditions (e.g., room temperature). In other embodiments, the droplets are printed on top of a heated substrate or once the pattern is formed, the pattern is treated by heating and/or irradiation and/or plasma to induce, promote or affect solidification and pattern, thereby increasing the pattern stability.

After a first layer of droplets is printed and let dry and the first layer of patterns, e.g., rings, is formed, a second layer of the same or different patterns may be deposited to form a continuous pattern. The same ink formulation is used for patterning the second and each of the further layers. In some embodiments, where it is desired to layer a pattern of a different property, e.g., conductivity, a further pattern may be formed using an ink formulation of a different set of properties, e.g., an ink formulation comprising different nanoparticles, a different binder or solvent or a different amount of any of its components.

For example, one patterned layer may be in the form of spaced-apart regions of a conductive material; another patterned layer may be formed between some of the spaced apart regions of a conductive material, said pattern being of a resistor material; and a further layer may be formed as a bridge between the different regions of a conductive material, the bridge material may be of a different conductive material.

Any such pattern may be dried at room temperature; however, in some embodiments, in order to endow the pattern with particular properties, e.g., conductivity, post-treatment may be required. Such post-treatment may include, in a non-limiting fashion, sintering, heating, chemical treatment, plasma, UV, laser, or microwave irradiation, flash lamp (Xenon) electroless plating, further coating and other treatments.

The pattern may be formed by placing the ink droplets one next to the other to afford a desired pattern, as is the case with inkjet printing. However, in some embodiments, the pattern may be obtained by self-assembly as described in [1], herein incorporated by reference. The type of technique used may depend inter alia on the structure of the pattern and its complexity. In some embodiments, the pattern is formed by a combination of printing techniques, some of which permitting self-assembly.

The pattern formed may be a line pattern or any substantially one dimensional or two dimensional or three dimensional pattern. The pattern may be a collection of spaced- apart patterns or a continuous pattern extending from one end of the surface to one of the surface's other ends. In some embodiments, where the pattern is a collection of two or more spaced-apart patterns, at least one of said patterns is formed on a boundary between the two or more surface regions having different wettabilities (different surface energies). In some embodiments, where the pattern is a collection of two or more spaced-apart patterns, at least one of said patterns is formed on a surface region having a certain surface energy, and another pattern is formed on a region of a different surface energy. The pattern may be formed by printing the same ink formulation. Where the pattern is a single continuous pattern, it may be formed to extend a boundary between the two or more surface regions having different surface energies, or may be formed on only one of said regions.

In some embodiments, the pattern is a line pattern which may be a closed loop line pattern such as a ring structure. In further embodiments, the line pattern is a closed loop ring pattern having a shape different from a circle (being non-spherical).

In some embodiments, the line pattern is a pattern of dissecting or spaced-apart ring structures, or an array of ring structures. Each or the ring structure may be spherical or non- spherical or a combination thereof.

Each of the ring structures may be intersecting another of the ring structures or may be intersecting a pattern of a different shape, or may be spaced apart. In some embodiments, the ring structures are positioned at a distance from each other (i.e., spaced apart); whereby a line structure being a different ring structure of a different material or a line structure different from a ring structure (of the same or different material) connects any two of the spaced apart ring structures.

The ring structures may be formed by ink jetting an ink formulation to form the structure or by material displacement, namely by self-assembly, as demonstrated in [1]. The self-assembly permits formation of a pattern of rings or an array of rings. The pattern or array of rings may be obtained by ink-jetting droplets of an ink formulation, as defined hereinabove, onto a surface region of a substrate. Each of the droplets form a dot on the surface region and is subsequently self-assembled into a ring by the well known "coffee ring effect" [1].

A ring structure as used herein is a closed loop pattern having a material void within the closed loop pattern walls, i.e., material-free voids, or empty cell, through which the substrate is exposed. A ring may be spherical ring or non-spherical ring.

The void diameter (average diameter) may be less than 1,000 micrometer. In some embodiments, the void diameter is less than 500 micrometer. In some embodiments, the void diameter is less than 300 micrometer. In some embodiments, the void diameter is less than 100 micrometer. In some embodiments, the void diameter is less than 50 micrometer. In some embodiments, the void diameter is less than 30 micrometer. In some embodiments, the void diameter is less than 20 micrometer. In some embodiments, the void diameter is less than 10 micrometer.

In some embodiments, the void diameter (average diameter) is between 1 and 1,000 micrometers. In some embodiments, the void diameter is between 20 and 1,000 micrometers. In some embodiments, the void diameter is between 10 and 300 micrometers. In some embodiments, the void diameter is between 5 and 300 micrometers. In some embodiments, the void diameter is between 10 and 300 micrometers. In some embodiments the void diameter is between 100 and 300 micrometers. In some embodiments, the void diameter is between 200 and 300 micrometers.

The average ring width may be less than 50 micrometers. In some embodiments, the ring width is less than 20 micrometers. In some embodiments, the ring width is less than 10 micrometers. In other embodiments, the ring width is less than 5 micrometers.

The average ring width may be between 0.5 and 50 micrometers. In some embodiments, the ring width is between 1 and 20 micrometers. In some embodiments, the ring width is between 1 and 10 micrometers. In some embodiments, the ring width is between 0.5 and 10 micrometers. In other embodiments, the ring width is between 0.5 and 10 micrometers. In some embodiments, the ring width is between 0.5 and 5 micrometers. In some embodiments, the ring width is between 1 and 5 micrometers.

The average ring height may be less than 10 micrometers. In some embodiments, the ring height is less than 1 micrometer. In some embodiments, the ring height is less than 0.5 micrometer. In other embodiments, the ring height is less than 0.3 micrometer. In some embodiments, the ring height is less than 0.2 micrometer. In other embodiments, the ring height is less than 0.1 micrometer.

The average ring height may be between 0.01 and 10 micrometers. In some embodiments, the ring height is between 0.01 and 1 micrometer. In some embodiments, the ring height is between 0.01 and 2 micrometers. In some embodiments, the ring height is between 0.01 and 0.5 micrometer. In some embodiments, the ring height is between 0.05 and 0.5 micrometer. In some embodiments, the ring height is between 0.05 and 0.2 micrometer. In some embodiments, the ring height is between 0.1 and 0.5 micrometer. In other embodiments, the ring height is between 0.1 and 0.3 micrometer.

It is expected that as the concentration of the dispersed material in the ink formulation increases, the ring width and height will increase as well. However, in order to obtain high transparency there is a need for narrow (in width) rings, which usually lead to thin (in height) rings. The disadvantage of thin (below 50nm) rings is their tendency to form discontinuous networks, exhibiting cracks; therefore usually thicker (above 50nm) rings are advantageous.

As Figs. 1A-D demonstrate, the ring height may be tailored by the number of droplets, as there is a linear dependency of the height on the number of printed droplets. Thus, to increase the height of the ring rim, instead of jetting a single drop of ink at each pixel, several drops are jetted, to enable the formation of rings with a higher rim. Another advantage of this approach is the ability to control the obtained width and diameter without changing the single droplet volume. That way the same amount of metal nanoparticles can be printed at the same position while using various metal loadings. For example, one drop of 3wt% is equal to two drops of 1.5wt% and to three drops of lwt% or six drops of 0.5 wt%. However, as the amount of solvent is not equal, the obtained rings will not be the same.

Figs. 2A-B provide a summary of the effect of the metal load and the number of droplets. It can be noted that various ring diameters and widths can be obtained at the same amount of silver (represented by # of 1% Ag drops), by varying the ink concentration. More specifically, lower metal load leads to narrower rings.

As stated above, a pattern of rings typically refers to a plurality (two or more) of ring-void arrangements. The plurality of ring-voids are typically arranged in a pattern or as an array or as a film. The pattern of rings may be an array of spaced-apart rings. The pattern of rings may be a net of spaced apart voids connected by a material forming a continuous line net. The pattern of rings may be a network of thin lines between the material-free voids. The pattern of rings may be a plurality of intersecting rings structures.

The intersecting patterns may comprise at least one line structure, e.g. ring structure, that intersects another line structure at one point or at more than one point of intersection (2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 points). In some embodiments, the pattern comprises a plurality of intersecting rings, wherein each ring intersects each of its neighboring rings. In some embodiments, the pattern of rings comprises a plurality of intersecting rings, wherein each ring intersects each of its neighboring line patterns at one or more points (2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 points).

The density of the rings in a pattern of rings may be less than 500,000 rings/cm . In some embodiments, the density of rings is less than 250,000 rings/cm . In some embodiments, the density of rings is less than 100,000 rings/cm . In some embodiments, the density of rings is less than 50,000 rings/cm . In some embodiments, the density of rings is less than 10,000 rings/cm .

The density of rings in a pattern of rings may be between 100 and 500,000 rings/cm . In some embodiments, the density of rings is between 100 and 250,000 rings/cm . In some embodiments, the density of rings is between 500 and 250,000 rings/cm . In some embodiments, the density of rings is between 400 and 250,000 rings/cm . In some embodiments, the density of rings is between 200 and 100,000

2 2 rings/cm . In some embodiments, the density of rings is between 100 and 10,000 rings/cm .

The pattern of rings (or film) may be transparent. The pattern may also be conductive.

In some embodiments, the pattern has at least 30%, at least 50%, at least 70%, at least 85%, at least 90%, at least 95% or at least 97% transparency (e.g., in visible light and/or IR).

In some embodiments, the pattern has light transparency of between 80% and 99%, between 85% and 99%, between 90% and 99%.

The pattern of rings (or film) may be conductive. The pattern of rings may have a sheet resistance of less than 10,000 Ohm/square. In other embodiments, the sheet resistance of the pattern of rings is less than 500 Ohm/square. In other embodiments, the sheet resistance is less than 300 Ohm/square. In some embodiments, the sheet resistance is less than 100 Ohm/square. In other embodiments, the sheet resistance is less than 50 Ohm/square. In some embodiments, the sheet resistance is less than 30 Ohm/square. In some embodiments, the sheet resistance is less than 20 Ohm/square. In other embodiments, the sheet resistance is less than 10 Ohm/square. In other embodiments, the sheet resistance is less than 1 Ohm/square.

The pattern of rings may be a conductive pattern of rings having a sheet resistance of between 500 and 10 Ohm/square. In other embodiments, the sheet resistance is between 300 and 10 Ohm/square. In some embodiments, the sheet resistance is between 100 and 10 Ohm/square. In other embodiments, the sheet resistance is between 100 and 5 Ohm/square.

The pattern of rings may be transparent and conductive. The pattern of the rings may have a transparency of less than 97% (e.g., in visible light and/or IR) and a sheet resistance of less than 80 Ohm/square. In other embodiments, transparency is less than 95% and the sheet resistance is less than 70 Ohm square.

The pattern of the rings may have a transparency of between 50% and 97% (e.g., in visible light and/or IR) and a sheet resistance of between 100 and 1 Ohm/square. In some embodiments, the transparency is between 85% and 97% (e.g., in visible light and/or IR) and a sheet resistance of between 70 and 5 Ohm/square.

The surface on which a pattern according to the invention is formed comprises is a surface of a substrate material. As used herein, the "surface" is a surface region of a substrate onto which a pattern is formed. The surface comprises two or more surface regions which are different in their wettabilities, namely each has a different surface energy. The term "region" refers to an area of the substrate surface or to a component, a body, or an element placed on (connected to) said substrate surface such that across a boundary between two such regions the surface energy changes. The regions may be defined by a different surface material, or a phase or any difference in size and shape, having a boundary with at least one other component, body, surface material and/or a phase of the same or different size and/or shape. The boundary between such regions may be further defined by a change in surface energies, i.e., a region of one material having a certain surface energy is in contact with another region of another material having a different surface energy. Putting it differently, the line of contact between the regions defining a boundary whereby the surface energy changes. The differences in surface energies may be due to differing chemical compositions, differing material phases (e.g., crystallographic phases), the presence or absence of doping, regions of concentrated doping, and others. Thus, the boundary may be an interface with another region of a material defined by a different chemical composition, phase, dopants, dopants concentration, and so forth.

The different regions of materials may be different regions on the surface of a commonly shared substrate. In some other embodiments, the different regions may be on different substrates or bodies.

In some embodiments, the different regions may be at different thicknesses or heights on the same substrate, i.e. different planes of the same material or different materials. In other embodiments, the different regions may be different components laid on the surface substrate, the different components having a shared boundary therebetween. In some embodiments, the two or more different components are of different thicknesses and/or heights.

The continuous pattern may be formed on two or more regions of different thicknesses or heights. The obtained continuous pattern may be at different heights and/or thicknesss and/or widths (along the pattern).

The different regions may be formed by doping certain regions of the substrate material while leaving other regions undoped or limitedly doped or doped with a different dopant material.

In some embodiments, the different regions are formed by deposition of a film or a material on a region of the surface, such that the surface energies of the deposited film surface and the surface of the substrate are different. In other embodiments, the different regions are formed by pasting one region of a material to another (e.g., component). In other embodiments, different regions are formed by placing one region of a material on top of another region of a material. In other embodiments, the different regions are formed by printing a pattern of a foreign material on a region of the surface material of the substrate, whereby the printed pattern of a foreign material and the surface material have different surface energies.

The substrate on the surface of which a pattern is formed may comprise at the surface the same materials (or components, or bodies or phases) as the material of the substrate itself. In other words, the substrate material and the surface materials may be the same. In some embodiments, the substrate material and the surface material are different.

In most general terms, the substrate may be of a solid material selected from a conducting material, a semiconductor material and an insulator material. In some embodiments, the substrate materials may be selected from glass, sapphire, ZnS (or any other transparent material), paper, a semiconductor material, an inorganic or organic material, a polymeric material, a ceramic material and a metallic material.

In some embodiments, the substrate is an inorganic material comprising a semiconductor material, including but not limited to, silicon, tin, compounds of boron, tellurium, geranium, gallium, gallium arsenide (GaAs), gallium phosphide (GaP), cadmium telluride (CdTe), gallium aluminum arsenide (GaAlAs), indium phosphide (InP), gallium arsenide phosphide (GaAsP), cadmium sulfide (CdS), copper indium gallium diselenide (CIGS), mercury cadmium telluride (HgCdTe), and copper indium sulfide or selenide.

In some embodiments, the substrate is a polymeric material such as a polyamide, polyester, a polyacrylate, a polyolefin, a polyimide, a polycarbonate and polymethyl methacrylate. In some embodiments, the polymeric material is selected from polyethylene terephthalate film (PET), polyethylene naphthalate (PEN) (poly(ethylene 2,6-naphthalate), and polyethylene (PE).

In some embodiments, the substrate material is an oxide or a metal oxide, such as silicon oxide, titanium oxide, aluminum oxide or zinc oxide.

The substrate may be a flexible or rigid substrate, which may be substantially two- dimensional (a thin flat substrate) or a three-dimensional curved (non-flat) surface. The substrate can be of any smoothness.

In some embodiments, the pattern is formed on a rigid or flexible substrate. In some embodiments, the rigid substrate may be any one of glass, silicon, and any inorganic or ceramic material. A pattern or a film of line structures, as defined herein, may be part of a device or a component of a device such as an electronic device or an optoelectronic device.

Thus, in another aspect, the invention provides a pattern of ring structures comprising at least one conductive region and at least one non-conductive region, the conductive region being formed of conducting ring structures and the non-conductive region being formed of non-conductive ring structures. In some embodiments, the pattern comprises at least two conductive regions, whereby each of said at least two conductive regions is separated from the other by a non-conductive region. In some further embodiments, the two or more of said conductive regions are connected to each other by a conductive bridge. In some embodiments, the conductive bridge is formed of conducting ring structures.

In some embodiments, the pattern is formed by a process of the invention.

The invention further contemplates a device comprising or implementing at least one continuous line structure according to the invention or prepared according to any process of the invention. The device may be an electronic device or an optoelectronic device.

In some embodiments, the device is an optoelectronic device that sources, detects or controls light. In some embodiments, the device is an electrical-to-optical or an optical-to- electrical transducer. In other embodiments, the device is a photoconductor or a photodiode or a solar cell or a dye-sensitized solar cell (DSSC) or a light emitting diode (LED) or an organic light emitting diode or laser or a light sensor or a specialized transistor or an organic transistor, or an inorganic transistor or a hybrid transistor.

The device may be related to electronic displays or printed electronics. In some embodiments, the device is a touch screen or a display backplane or a large or small area display. In some embodiments, the device is a display. In other embodiments, the device is a touch panel display.

The device may be related to electronic sensors. In some embodiments, the device is a touch sensor.

The device may be related to flexible electronics. Non-limiting examples include flexible displays, e-paper, electronic books, electronic journals, and electronic newspapers. The device may be related to monitoring or detection devices for healthcare, security or safety-related uses, including low-cost or disposable sensors or optical devices, as well as in smart packaging such as for incorporation of tags or RFID components into the packaging. In addition, the technology can be employed in building applications such as smart windows, or in specialty coatings and paints which function as part of a semiconductor device. In some embodiments the device is used as electromagnetic shielding (EMS).

The device may be a photovoltaic solar cell. In some embodiments, the solar cell may be a silicon-based solar cell, an organic solar cell, a plastic solar cell, a dye-sensitized solar cell (DSSC), a multi-junction solar cell, and others.

The device may be a luminescent concentrator.

In the field of touch sensors, there is a great need to simplify the process of forming a transparent conductive jumper, as defined hereinbelow. The goal of the conductive jumper is to connect two conductive regions separated by an insulating region. In the field of transparent conductors, the jumper should be not only conductive, but also transparent. To achieve that, very thin lines of a metal (usually silver) are typically deposited by sputtering and lithography to form submicrometer lines. Due to the very narrow dimension (<10um), vacuum deposition is necessary to permit deposition of transparent conductive oxides or PEDOT-PSS as jumpers. In such cases, the dimensions are larger, but the jumper is still transparent due to the transparent materials used (ITO or PEDOT-PSS). The disadvantages of using these methods include high resistivity of the jumper, which limits the sensor dimensions, and the high cost of making the sensor (as the process becomes highly complex and thus highly costly).

The methodology of the present invention permits formation of a ring pattern (spherical or non-spherical rings, as described herein) as a transparent conductive jumper, on two or three different surface regions. While known lithographic methods for deposition of multiple materials (such as ITO/Insulator/silver), in multiple layers, requires multiple separate lithographic steps, in the processes of the invention, the different layers may be formed in a single continuous printing step or in far fewer and simpler printing steps. The processes of the invention provide a much sought for simplification of and alternative to the lithographic processes. Thus, in another aspect, the invention provides a pattern of ring structures comprising at least one conductive region and at least one insulating region, the conductive region being formed of conducting ring structures and the insulating region being formed of non-conductive ring structures. In some embodiments, the pattern comprises at least two conductive regions, whereby each of said at least two conductive regions is separated from the other by an insulating region. In some further embodiments, the two or more of said conductive regions are connected to each other by a conductive jumper. In some embodiments, the conductive jumper is formed of conducting ring structures.

As described above and known in the art, a "bridge electrode" or a "jumper" component is a component or an element connecting two or more other components. In some embodiments, the component forms a direct contact two or more components or material regions, as defined herein. The component or the material region may be selected from electrodes, capacitors, inductors, resistors, transformators, transistors, diodes, gate, conductor and wirings. The bridge electrode may be or may be part of an electronic device or an optoelectronic device.

In another aspect, there is provided a process for forming a multilayer structure, wherein all layers are printed by inkjet, namely the ITO (indium tin oxide) substitutive pattern (the rings), the insulator and the jumper. The differences in the surface energies of the substrate and the insulator materials are overcome as described herein.

As Fig. 3 demonstrates, ring structures printed on a specific region of a glass substrate coated with a polymeric insulator exhibit a different shape and line integrity as compared with ring structures printed on a glass surface. The droplets jetted on the glass surface formed well defined rings, while those deposited on the insulator did not form ring structures. The differences originate from the surface energy differences between the two surfaces.

Figs. 4A-C present an example of a pattern of ring structures on the same interface (glass-polymeric insulator), but after the required adjustment of the ink formulation, as described herein. The jumper was found to be conductive and the resistance along 1mm was measured to be 30 Ohms. The resistance along a single jumper may be in the range of 0.01 ohm to 1000 kiloOhms. Furthermore, as mentioned above, the ability to print such connected rings on two different surfaces enables the formation of a transparent conductive jumper. The schematic structure of such a jumper is presented in Fig. 5A-B. As shown, the printing of such a jumper enables the formation of a diamond like pattern. At the first layer, the diamond like pattern is printed, forming connected rings in one axis and disconnected rings in the other. Then, an insulator is printed at the junction with two unconnected diamonds. Finally, the jumper is printed to connect the two unconnected diamonds, enabling the formation of an all inkjet printed touch sensor. The three-step printing may be achieved in separate steps or continuously by using different inkjet units or inkjet printing heads.

A person versed in the art would realize that the same printed structure may be formed by first printing the jumper on the substrate, and thereafter printing the insulator and the diamond pattern.

Thus, in some embodiments, the device is a bridge electrode or a jumper. In some embodiments, the bridge electrode or the jumper is provided or formed directly on the substrate. In some embodiments, the bridge electrode or the jumper is provided or formed using the process of the invention (or ink jet printing techniques). In some embodiments, the bridge electrode or the jumper is transparent. In some embodiments, the bridge electrode or jumper is conductive.

The bridge electrode or the jumper may be a continuous bridge electrode or jumper.

It is a further embodiment of the invention to provide small transparent electrodes that may be directly printed as bridge electrodes or jumper components, e.g., for use in a touch sensor as a transparent electrode connecting between two other transparent electrodes or other components separated by an insulating area.

The bridge electrode or jumper may connect at least two different components (parts) in a system (or array of components or a device). In some embodiments, the bridge electrode or the jumper connects at least two conductive components in a device. In some embodiments, the bridge electrode or the jumper connects at least two semiconducting components in a device. In some embodiments, the bridge electrode or the jumper connects at least two components, wherein one is a semiconductor and the other is a conductor in a device. In some embodiments, the two or more components are at different thicknesses and/or heights.

The bridge connecting the two or more components may be formed on two or more components of different thicknesses or heights. The obtained bridge may be at different heights and/or thicknesss and/or widths (along the bridge).

In some embodiments, the bridge electrode or the jumper is a line pattern (e.g., a line of rings) or any substantially one dimensional or two dimensional or three dimensional pattern (e.g., pattern of rings).

In some embodiments, the bridge electrode or jumper connects at least two components having different dopants or dopant concentrations. In some embodiments, the bridge electrode or the jumper connects p-doped component (or region of material) with an n-doped component. In some embodiments, the bridge electrode or the jumper connects p- or n- doped component with another p- or n-doped component.

In some embodiments, the bridge electrode or the jumper connects at least two components of (within) a transistor, in particular bipolar transistor, e.g., n-p-n, p-n-p and n- i-p.

The at least two components may have a common boundary or may be separated by at least one other material region. In some embodiments, an insulator separates between the at least two components, whereby the bridge electrode or the jumper connects the at least two components.

The bridge electrode or the jumper may form a single connection. In some embodiments, the bridge electrode or jumper may form more than one connection.

The bridge electrode or the jumper or plurality of bridge electrodes or jumpers may connect the different components in series.

The number of connections or the number of bridge electrodes or jumpers may be as the number of connections needed between the different components of the device. The number of connections or the number of bridge electrodes or jumpers may be 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 or more components in a device. In some embodiments, the number of connections or the number of bridge electrodes or jumpers may be 10 or 20 or 30 or 40 or 50 or 60 or 70 or 80 or 90 or 100 or more components in a system or array of components or a device. In some embodiments, the number of bridge electrodes or jumpers in a device according to the invention ranges from 100 to a few thousands. In some embodiments, the number of jumpers is between 100 and 1,000; between 100 and 2,000; between 100 and 3,000; between 100 and 4,000; between 100 and 5,000; between 100 and 6,000; between 100 and 7,000; between 100 and 8,000; between 100 and 9,000; between 100 and 10,000; between 200 and 1,000; between 300 and 1,000; between 400 and 1,000; between 500 and 1,000; between 600 and 1,000; between 700 and 1,000; between 800 and 1,000; between 900 and 1,000; between 1,00 and 2,000; between 1,00 and 3,000; between 1,000 and 4,000; between 1,000 and 5,000; between 1,000 and 6,000; between 1,000 and 7,000; between 1,000 and 8,000; between 1,000 and 9,000; between 1,000 and 10,000; or between 10,000 and 100,000.

In some embodiments, e.g., in a touch sensor, according to the invention, e.g., having a diamond like shape, the number of jumpers may be in the range of 100 to 50,000 jumpers. In some embodiments, e.g., in a touch sensor, according to the invention, e.g., having a diamond like shape, the number of jumpers may be in the range of 100 to 5,000 jumpers.

The components may be a panel (or array) of components. The panel of components may comprise hundreds or thousands or more components. The number of connections and/or the number of bridge electrodes or jumpers may be in the order of magnitude of the number of components or double or triple that.

In some embodiments, the device comprises a conductive transparent electrode having at least one array of rings, a conductive electrode, and a jumper electrode having at least one continuous ring or pattern of rings, wherein the jumper electrode connects the transparent conductive electrode and the conductive electrode.

As noted herein, the pattern formed on a surface according to the invention may be a line pattern, or a closed loop pattern which may or may not be spherical (circular). To achieve such non-spherical ring structures, the inventors have developed a novel process which involves positioning of multiple ink droplets, simultaneously or one after the other, in close proximity to each other.

In another aspect of the invention provides a method of forming a non-spherical ring structure or a non-spherical ring pattern on a substrate, the method comprising: -applying at least one ink droplet on a surface of a substrate;

-at a distance from said at least one droplet, applying at least one additional ink droplet, wherein the at least one additional droplet is applied at a distance to said at least one droplet while being wet, such that the at least one droplet and the at least one additional droplet are tangent to each other or intersect each other;

-optionally applying at least one subsequent droplet at a distance from said at least one droplet and at least one additional droplet, wherein the at least one subsequent droplet is applied at a distance to said at least one droplet and at least one additional droplet while being wet, such that the at least one droplet, the at least further droplet and the at least one subsequent droplet are tangent to each other or intersect each other;

and

-permitting the droplets to form a non-spherical pattern.

The ink formulation may be any ink formulation known in the art. In some embodiments, the patterns are formed with an ink formulation according to the present invention. In some embodiments, the ink is an organic based ink. In other embodiments, the ink is an aqueous based ink.

In some embodiments, each of said at least one droplet, at least one additional droplet and at least one subsequent droplet define a plurality of droplets.

As noted above, any of the additional and subsequent droplets are applied at a position resulting in the droplets being tangent to each other or intersecting each other. To allow the formation of the non-spherical structures, the additional and subsequent droplets must be applied while the first droplets are still wet, namely at a time point prior to the first droplets solidifying. In other words, the first applied droplets must remain in their dispersion form, e.g., particulate material dispersed in a carrier (solvent); and with the solvent not substantially evaporated. Any subsequent droplet which is applied tangent or intersecting with an already applied droplet, must be applied while the droplets on the surface are wet.

In order to obtain non-spherical ring structures, such as triangles, squares, diamonds and so forth, the process needs to fulfill the following requirements: (i) two or more ink droplets should be applied simultaneously or one after the other, such that a first ink droplet is applied on a surface; subsequently, a second droplet is applied in close proximity to the first droplet; a further droplet is applied in close proximity to either the first or second droplet; and so forth, as define above; (ii) the second or further droplets are applied before the first droplet is permitted to self-assemble into a ring and dry, namely the second or further droplets are applied on a wet surface.

The distance between the applied droplets is said to be such that the droplets are tangent to each other or intersect, while being wet. For defining the degree of intersection of the droplets, the tangent point is considered the shortest distance between the droplets centers, thus defining 100% of the distance. Any distance which is less than 100% is considered interesting. Thus, the droplets may be positioned at a distance which is more than 70% of the shortest distance between the droplets, or less than 100% and more than 80% of the shortest distance between the droplets, or less than 100% and more than 90% of the shortest distance between the droplets, or less than 95% and more than 70% of the shortest distance between the droplets, or less than 95% and more than 80% of the shortest distance between the droplets, or less than 95% and more than 90% of the shortest distance between the droplets, or less than 90% and more than 70% of the shortest distance between the droplets, or less than 90% and more than 80% of the shortest distance between the droplets.

In some embodiments, each of the additional and/or subsequent droplets are positioned at a distance which is less than 30% of the shortest distance between the droplets and more than 0.1% of the shortest distance between the droplets, or less than 30% and more than 1% of the shortest distance between the droplets, or less than 20% and more than 1% of the shortest distance between the droplets, or less than 10% and more than 0.1% of the shortest distance between the droplets, or less than 10% and more than 1% of the shortest distance between the droplets, or less than 5% and more than 0.1% of the shortest distance between the droplets or less than 5% and more than 1% of the shortest distance between the droplets.

The distance between the deposited droplets and the droplets to be deposited may depend inter alia on the non-spherical shape which is desired and on the size or volume of the droplets deposited and to be deposited. In some embodiments, the size or volume of the second and further droplets is different, larger or smaller, than the size or volume of the first deposited droplets. In some further embodiments, the droplets are all the same in size and/or volume.

As noted above, to achieve the non-spherical pattern, the first droplets should not be allowed to dry, and must remain wet or substantially not dried, i.e., the droplets are in their dispersion form. Therefore, the solvent contained in the ink formulation should not be allowed to evaporate before the subsequent droplets are deposited. As shown in Scheme 1, the positioning of the droplets one next to the other permits self assembly of the droplets into a continuous pattern which is defined by the material flow making the outer most rims of the patterns. For example, depositing droplets as shown in the left depiction of Scheme 1 would provide a triangular line pattern; depositing droplets as shown in the middle depiction would provide a square pattern; and depositing droplets as shown in the right depiction would provide a pentagon. Higher patterns may be similarly provided.

Scheme 1

Thus, the non-spherical ring structures may be of any non-spherical shape. In some embodiments, the non-spherical ring is an ellipse. In some embodiments, the non-spherical ring is a polygon. The polygon may have 3, 4, 5, 6, 7, 8, 9, 10 or more sides. In some embodiments, the non-spherical ring is a triangle or a square or a pentagon.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: Figs. 1A-D present the rings parameters as a function of number of drops of 3 wt% silver ink. Fig. 1A presents results of improved pattern rings. Fig. IB presents ring width as a function of number of drops of 3% silver ink. Fig. 1C presents ring diameter as a function of number of drops of 3% silver ink. Fig. ID presents ring height as a function of number of drops of 3% silver ink.

Figs. 2A-B present effect of metal load and number of drops. Fig. 2A presents ring width as a function of number of drops of 0.5%, 1% and 1.5% of silver ink normalized to 1% (i.e. 2 drops of 0.5% are equivalent to 1 drop of 1%). Fig. 2B presents ring height as a function of number of drops of 0.5%, 1% and 1.5% of silver ink normalized to 1% (i.e. 2 drops of 0.5% are equivalent to 1 drop of 1%).

Fig. 3 presents a ring ink formulation printed on glass coated with a polymeric insulator at the interface between the two surfaces (insulator/glass, left/right).

Fig. 4A-C present rings printed at the insulator/glass (left/right) interface.

Figs. 4A-C presents an example of printed rings on the same interface (glass- polymeric insulator), but after the required adjustment of the ink formulation.

Figs. 5A-B present schematic structure of a jumper.

Fig. 6 presents examples of printed non-spherical rings.

DETAILED DESCRIPTION OF EMBODIMENTS

Ink formulations

Example of printing silver rings on a complex interface:

1. An ink formulation comprising: 1 wt% silver nanoparticles, 0.3 wt% of a binder and a glycol ether as a solvent, was inkjet printed on top of a hot glass (110 °C) partially coated by a polymeric insulator (2um thick). The deposited nonconnected drops formed separated rings on both surfaces. Then a second layer of rings were printed in between the first layer of rings to form a line of connected rings. The rings were connected from the glass to the insulator through there interface. Then, the rings were sintered under plasma sintering and the obtained line of rings was found to be conductive. The resistance measure between the two ends of the line, glass and insulator, was found to be 200Ohms. 2. The same printing experiment was repeated while using a different ink formulation comprising: 1 wt% silver nanoparticles, 0.1 wt% of a binder and a glycol ether as a solvent.

3. The same printing experiment was repeated while using a different ink formulation comprising: 0.8 wt% silver nanoparticles, 0.3 wt% of a binder and a glycol ether as a solvent.

4. The same printing experiment was repeated while using a different ink formulation comprising: 0.8 wt% silver nanoparticles, 0.1 wt% of a binder and a glycol ether as a solvent.

5. The same printing experiment was repeated while using a different ink formulation comprising: 0.6 wt% silver nanoparticles, 0.1 wt% of a binder and a glycol ether as a solvent.

6. The same printing experiment was repeated while using a different ink formulation comprising: 0.6 wt% silver nanoparticles, 0.3 wt% of a binder and a glycol ether as a solvent.

7. The same printing experiment was repeated while using a different ink formulation comprising: 1 wt% silver nanoparticles, 0.1 wt% of a binder and an alcohol as a solvent.

8. The same printing experiment was repeated while using a different ink formulation comprising: 0.8 wt% silver nanoparticles, 0.3 wt% of a binder and an alcohol as a solvent.

9. The same printing experiment was repeated while using a different ink formulation comprising: 0.8 wt% silver nanoparticles, 0.1 wt% of a binder and an alcohol as a solvent. 10. The same printing experiment was repeated while using a different ink formulation comprising: 0.6 wt% silver nanoparticles, 0.1 wt% of a binder and an alcohol as a solvent.

11. The same printing experiment was repeated while using a different ink formulation comprising: 0.6 wt% silver nanoparticles, 0.3 wt% of a binder and an alcohol as a solvent.

12. The same printing experiment was repeated after pretreating the non- homogeneous surface by plasma. It was found that the plasma treatment enable to obtain a more homogeneous surface energy.

Interconnected rings on a substrate comprising multiple areas (Jumper)

In the case of printing conductive rings, the formation of connected rings on two different surfaces is even more challenging. Fig. 3 presents an example of the printing of rings on a glass substrate coated with a polymeric insulator at specific areas. It can be clearly seen that the formed rings are totally different on the two surfaces. The drops jetted on the glass formed nice well defined rings, while those deposited on the insulator did not form any ring. That difference originates from the surface energy difference between the two surfaces which prevents the formation of rings on one of the sides and obviously at the interface. Therefore, the formation of connected rings which should connect the two sides is not possible.

In order to overcome this challenge the ink formulation should be tailored to both surfaces and/or a surface pretreatment is required.

Figs. 4A-B presents an example of printed rings on the same interface (glass- polymeric insulator), but after the required adjustment of the ink formulation. That jumper was found to be conductive and the resistance along 1mm was measured to be 30 Ohms.

The resistance along a single jumper may be in the range of 0.01 ohm to 1000 kiloOhms.

Furthermore, as mentioned above, the ability to print such connected rings on two different surfaces, enable the formation of a transparent conductive jumper. The schematic structure of such a jumper is presented in Fig. 5B, the small grey rings should form metallic contact with the first layer of rings (blue rings) deposited on the substrate, and still form well defined and connected rings on the insulator (green area). As presented schematically in Fig. 5B, and as shown in a pattern obtained in accordance with the invention, shown in Fig. 6, the printing of such a jumper enables the formation of diamond like pattern. At the first layer, the diamond like patter is printed, forming connected rings in one axis and disconnected rings in the other axis. Then, the insulator is printed at the junction with two not connected diamonds. Finally, the described jumper is printed to connect these two disconnected diamonds, enabling the formation of an all inkjet printed touch sensor.

It should be mentioned that the same structure may be formed by printing first the small jumper on the substrate, then the insulator and finally the diamond pattern.

The length of the jumper is typically few hundreds microns and its width may be tens to hundreds of microns (with one or more rings as the width).

As mentioned below, another aspect of the invention is the formation of rings with non spherical shape. Therefore, the jumper may be formed with a long warm like ring or any other shape.

Array of rings with controlled parameters

One approach is printing on a non-heated substrate and then heating it to form the rings. In that second approach, the printing is performed at room temperature, forming a "wet pattern" of rings. After printing, the pattern is heated and the ring pattern is formed. The advantage of printing on a non-heated substrate is the higher stability of the jetting relative to the printing on a heated substrate. Since the print head should be as close as possible to the substrate (in order to achieve high accuracy), while printing on a heated substrate, there might be some jetting stability issues due to partial drying of the ink in or near the nozzles. Therefore it is advantageous to print at room temperature (~20°C) and not on a heated substrate. The suggested process, printing on non-heated substrate and only then heating the substrate, enable to print on a non-heated substrate.

Another approach is printing algorithm based on using a multi-drop approach where several drops are printed at the same position without drying in between printing each ink droplet. Controling the ring height. It is expected that as the concentration of dispersed material in the ink increases, the ring width and height increases as well. However, in order to obtain high transparency there is a need for narrow (in width) rings, which usually leads to thin (in height) rings. The disadvantage of thin (below 50nm) rings is their tendency to form discontinuous networks and cracks, therefore usually thicker (above 50nm) rings are advantageous. Here we present a printing algorithm to obtain thick and narrow rings. This printing algorithm is based on using a multi-drop approach, where several drops are printed at the same position without drying in between printing each ink droplet. The effect of such an approach is summarized in the graphs presented in Fig.lB-D.

It can be seen that the ring height can be tailored by the number of drops, while there is a linear dependence of the height on the number of printed droplets.

Another advantage of this approach is the ability to control the obtained width and diameter without changing the single drop volume. That way, the same amount of metal nanoparticles can be printed at the same position while using various metal loadings. For example, one drop of 3wt% will be equal to two drops of 1.5wt% and three drops of lwt% or six drops of 0.5 wt%. However, the amount of solvent is not equal, and therefore, the obtained rings will not be the same. Fig. 2 summarizes the effect of the metal load and the number of drops.

It can be seen that various ring diameters and widths can be obtained at the same amount of silver (represented by # of 1% Ag drops), by varying the ink concentration. More specifically, lower metal load leads to narrower rings.

In summary:

The printing algorithm may include therefore the following or part of the following steps:

• Printing multi-drops to form one layer of non-connected rings.

• Printing multi-drops to form a second layer of rings which connect the first non- connected rings.

• Printing multi-drops to form more layers.

• Sintering the printed rings before or after connecting them, i.e. as non-connected rings or as connected rings or the both. • printing a plurality of drops on a heated substrate. In that process the ring is formed once printed on the hot surface leading to the evaporation of the ink solvents and the formation of the ring.

The sintering may be carried out by heating in an oven, or by hot fan, plasma treatment, photonic irradiation, NIR lamp, Xenon lamp, chemical sintering process or any other sintering approach.

Array of non-spherical rings

Another aspect of the invention is using the above mentioned printing algorithm, a multi-drop approach, where several drops are printed without drying in between, at position near the position of previous droplet, i.e. not at the exact same position. By that approach, drops with various shapes are deposited and once drying, forms structures with various shapes. For example, triangle, square and elliptic rings can be formed. Fig. 6 presents some examples of such non-spherical rings.

Such non-spherical rings can function as small transparent electrodes or after connected to other non-spherical or spherical rings may function as large transparent electrodes.

Claims

CLAIMS:

1. A process of forming a continuous pattern on a surface composed of two or more surface regions, each of the regions being of a different surface energy, the process comprising:

-forming a continuous pattern on said surface such that the pattern crosses at least one boundary between the two or more regions of the surface, the two or more regions differing in their wettability; the continuous pattern being formed by an organic ink formulation configured to adhere to each of said two or more regions; and

2. A process of forming a continuous pattern on a surface composed of two or more regions, each of the regions being of a different surface energy, the process comprising:

-forming a continuous pattern on said surface such that the pattern crosses at least one boundary between the two or more regions of the surface, the two or more regions differing in their wettability; the continuous pattern being formed by an organic ink formulation configured to adhere to each of said two or more regions, said formulation comprising an organic solvent, at least one binder selected from organic and inorganic binders and nanoparticles; and

3. The process according to claim 2, wherein the organic formulation is water free and the solvent constitutes at least 95% of the formulation by weight.

4. A process of forming a continuous ring pattern on a surface composed of two or more regions, each of the regions being of a different surface energy, the process comprising:

-forming a continuous pattern of rings on said surface such that the pattern crosses at least one boundary between the two or more regions of the surface, the two or more regions differing in their wettability; the continuous pattern of rings being formed by an ink formulation configured to adhere to each of said two or more regions; and

-permitting said pattern to dry to afford the continuous pattern of rings, the pattern at least partially covering two or more of said regions of differing wettabilities.

5. The process according to claim 4, wherein the ink is an organic ink.

6. The process according to any one of claims 1 to 5, wherein said ink formulation is configured to comprise at least one component which endows the formulation with surface adhesiveness to said two or more surface regions.

7. The process according to claim 6, wherein the at least one component is selected amongst at least one organic solvent and at least one organic or inorganic binder, or any combination of solvents, or any combination of binders or any combination of binders and solvents.

8. The process according to claim 7, wherein the ink formulation is substantially free of water.

9. The process according to claim 8, wherein the amount of water is up to 0.5% by weight.

10. The process according to any one of claims 1 to 9, wherein the organic solvent is present in the formulation in an amount greater than 94% by weight of the formulation.

11. The process according to claim 10, wherein the solvent is a combination of at least two solvents.

12. The process according to claim 7, wherein the solvent is selected from glycol ether, an alcohol, or acetate, and any combination thereof.

13. The process according to claim 12, wherein the glycol ether is selected amongst ethylene glycol monoalkyl ethers, polyglycol monoalkyl ethers, ethylene glycol phenyl ethers, polyglycol phenyl ethers, ethylene glycol benzyl ethers and polyglycol benzyl ethers.

14. The process according to claim 13, wherein the glycol ether is selected from ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, ethylene glycol monohexyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol monohexyl ether, there corresponding acetate like diethylene glycol n-butyl ether acetate and others.

15. The process according to claim 12, wherein the organic solvent is an alcohol selected from methanol, ethanol (EtOH), butanol (Bu'OH), nonanol, octanol and any other alcohols.

16. The process according to claim 7, comprising a binder in an amount of up to 5% by weight of the ink formulation.

17. The process according to claim 16, wherein the binder is present in an amount up to 3% by weight of the ink formulation.

18. The process according to claim 16, wherein the binder is present in an amount up to 2% by weight of the ink formulation.

19. The process according to claim 16, wherein the binder is present in an amount up to 1.5% by weight of the ink formulation.

20. The process according to claim 16, wherein the binder is present in an amount up to 1 % by weight of the ink formulation.

21. The process according to claim 16, wherein the binder is present in an amount up to 0.7% by weight of the ink formulation.

22. The process according to claim 16, wherein the binder is present in an amount up to 0.5% by weight of the ink formulation.

23. The process according to claim 16, wherein the binder is present in an amount up to 0.3% by weight of the ink formulation.

24. The process according to claim 7, wherein the binder is an organic material having at least one cellulose.

25. The process according to claim 7, wherein the organic binder is selected from polyvinyl pyridine, polyvinyl butyral, ethyl cellulose, methyl cellulose, and others.

26. The process according to any one of claim 1 to 25, further comprising a wetting agent or any one or more other additives.

27. The process according to any one of claims 1 to 26, comprising a material in a particulate form.

28. The process according to claim 27, wherein the particulate material is in the form of nanoparticles.

29. The process according to claim 28, wherein the nanoparticles having a diameter of less than 300 nm or a diameter of less than 10 nm.

30. The process according to any one of claims 27 to 29, wherein the particulate material is a conductive material selected from a metal, a transition metal, a semiconductor, an alloy, an intermetallic material, a conducting polymer, a carbon based material such as carbon black, carbon nanotubes (CNT), graphite, graphene, fullerenes, and carbon allotropes.

31. The process according to claim 30, wherein the conductive material is or comprises an element of Groups IIIB, IVB, VB, VIB, VIIB, VIIIB, IB, IIB, IIIA, IV A and VA of block d of the Periodic Table of the Elements.

32. The process according to claim 30, wherein the conductive material is or comprises a transition metal selected from Groups IIIB, IVB, VB, VIB, VIIB, VIIIB, IB and IIB of block d the Periodic Table.

33. The process according to claim 32, wherein the transition metal is a metal selected from Sc, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Y, Zr, Nb, Tc, Ru, Mo, Rh, W, Au, Pt, Pd, Ag, Co, Cd, Hf, Ta, Re, Os, Ir and Hg.

34. The process according to claim 30, wherein the conductive material is selected from indium(III) acetate, indium(III) chloride, indium(III) nitrate, indium(III) acetylacetonate, for the creation of CuInS₂ and Cu(InGa)S₂; iron(II) chloride, iron(III) chloride, iron(II) acetate, iron(III) acetylacetonate for the formation of CuFeS₂; gallium(III) acetylacetonate, gallium(II) chloride, gallium(III) chloride, gallium(III) nitrate for the formation of CuGaS₂ and Cu(InGa)S₂; aluminum(III) chloride, aluminum(III) stearate for the formation of CuAlS₂; silver nitrate, silver chloride for the formation of AgS; dimethlyzinc, diethylzinc, zinc chloride, tin(II) chloride, tin(IV) chloride, tin(II) acetylacetonate, tin(II) acetate for the formation of Cu₂(ZnSn)S₄; cadmium(II) chloride, cadmium(II) nitrate, cadmium(II) acetate, cadmium(II) acetlyacetonate, cadmium(II) stearate for CdS; lead(II) acetate, lead(II) acetlylacetonate, lead(II) chloride, lead(II) nitrate and PbS.

35. The process according to claim 30, wherein the material is selected amongst semiconductor materials. The semiconductor material may be selected from elements of Group II- VI, Group III-V, Group IV- VI, Group III- VI, Group IV semiconductors and combinations thereof.

36. The process according to claim 35, wherein the semiconductor material is a Group II- VI material being selected from CdSe, CdS, CdTe, ZnSe, ZnS, ZnTe, HgS, HgSe, HgTe, CdZnSe and any combination thereof.

37. The process according to claim 35, wherein Group III-V material are selected from InAs, InP, InN, GaN, InSb, InAsP, InGaAs, GaAs, GaP, GaSb, AlP, AIN, AlAs, AlSb, CdSeTe, ZnCdSe and any combination thereof.

38. The process according to claim 35, wherein the semiconductor material is selected from Group IV- VI, the material being selected from PbSe, PbTe, PbS, PbSnTe, Tl₂SnTe₅ and any combination thereof.

39. The process according to claim 30, wherein the conductive material is selected amongst metal alloys and intermetallics of the above metal and/or transition metals. Non- limiting examples of such alloys are WMo, MoRh, M0RI13, Rho.34Ruo.66, Rho.₄Ruo.6, PdRh, PdRu, MoPd₂, Pdo.₃Mo₀.8, MoPt, Mo₂Pt, PtPd, Pt₀.₄Ruo.6, Pt₀.₂Ru₀.₈, PtRh, WPt, AuPd, AuPt, AuRh, AuRu, AuMo, and AuW.

40. The process according to claim 30, wherein the conductive material is a carbon based material such as carbon black, carbon nanotubes (CNT), graphite, graphene, fullerenes, or other carbon allotropes. The carbon based material need not be in particulate form.

41. The process according to claim 30, wherein the conductive material is a conductive polymer such as poly(3,4-dioctyloxythiophene) (PDOT), poly(3,4- ethylenedioxythiophene):poly (styrenesulfonate) (PDOT:PSS), polyaniline and polypyrrole.

42. The process according to claim 30, wherein the conductive material comprised in the ink formulation is a metal selected from silver, gold, copper, nickel, cobalt, aluminum or any other metal.

43. The process according to claim 30, wherein the conductive material may be a carbon material such as carbon nanotubes and graphene.

44. The process according to claim 30, wherein the conductive material comprised in the ink formulation is a metal selected from silver, gold and copper or is a carbon based material.

45. The process according to any one of the preceding claims, wherein the pattern formed on the at least two or more surface regions is a continuous pattern formed by inkjet printing.

46. The process according to claim 45, wherein the pattern formed is permitted to dry under ambient conditions.

47. The process according to according to claims 1 to 45, wherein the pattern is formed on top of a heated substrate or once the pattern is formed, the pattern is treated by any one of heating, plasma and irradiation.

48. The process according to any one of the preceding claims, wherein the pattern is printed in layers.

49. The process according to claim 48, wherein after a first layer is printed and let dry and the first layer of patterns is formed, a second layer of the same or different patterns is deposited to form together with the first layer a continuous pattern.

50. The process according to any one of the preceding claims, wherein the pattern is substantially a one dimensional or a two dimensional or a three dimensional pattern.

51. The process according to claim 50, wherein the pattern having different heights or thicknesses or widths along the pattern.

52. The process according to claim 50, wherein the pattern is a line pattern.

53. The process according to claim 50, wherein the pattern is a closed loop line pattern.

54. The process according to any one of the preceding claims, wherein the pattern is or comprises a ring structure or ring structures.

55. The process according to claim 54, wherein the ring structure is a closed loop pattern having a spherical shape or a shape different from a circle (being non-spherical).

56. The process according to claims 52 or 53, wherein the line pattern is a pattern of ring structures, or an array of ring structures, each of the ring structures being spherical or non-spherical or a combination thereof.

57. The process according to any one of preceding claims, wherein the pattern is or comprises ring structures, wherein the ring structures are intersecting or spaced apart.

58. The process according to any one of claims 54 to 57, wherein the ring structure is a closed loop pattern having a material void within the closed loop pattern walls, the ring structure is optionally a spherical ring structure.

59. The process according to any one of claims 54 to 58, wherein the ring structure having a void diameter of less than 1 ,000 micrometer.

60. The process according to any one of claims 54 to 58, wherein the ring structure having a void diameter of between 1 and 1,000 micrometers.

61. The process according to any one of claims 54 to 60, wherein the ring width is less than 50 micrometers.

62. The process according to any one of claims 54 to 60, wherein the ring width is between 0.5 and 50 micrometers.

63. The process according to any one of claims 54 to 62, wherein the ring height is less than 10 micrometers.

64. The process according to any one of the preceding claims, wherein the pattern is a pattern of rings comprising a plurality of ring-void arrangements, arranged in a pattern or as an array or a film, the ring patterns being optionally intersecting rings structure.

65. The process according to claim 64, wherein the density of the rings in a pattern is less than 500,000 rings/cm .

66. The process according to claim 65, wherein the density of rings in a pattern is between 100 and 500,000 rings/cm².

67. The process according to any one of the preceding claims, wherein the pattern has at least 30%, at least 50%, at least 70%, at least 85%, at least 90%, at least 95% or at least 97% transparency.

68. The process according to claim 67, wherein the pattern has light transparency of between 80% and 99%, between 85% and 99%, between 90% and 99%.

69. The process according to any one of the preceding claims, wherein the pattern of rings is conductive.

70. The process according to claim 69, wherein the pattern of rings has a sheet resistance of less than 10,000 Ohm/square.

71. The process according to claim 69, wherein the pattern of rings is a conductive pattern of rings having a sheet resistance of between 500 and 10 Ohm/square.

72. A pattern or a film of line structures prepared according to any one of claims 1 to 71.

73. A pattern of ring structures comprising at least one conductive region and at least one non-conductive region, the conductive region being formed of conducting ring structures and the non-conductive region being formed of non-conductive ring structures.

74. The pattern according to claim 73, wherein the pattern comprises at least two conductive regions, whereby each of said at least two conductive regions is separated from the other by a non-conductive region.

75. The pattern according to claim 73, wherein the two or more of said conductive regions are connected to each other by a conductive bridge.

76. The pattern according to claim 75, wherein the conductive bridge is formed of conducting ring structures.

77. The pattern according to any one of claims 72 to 76, being formed on device surface or a component of a device.

78. A device comprising or implementing at least one continuous pattern formed according to the process of any one of claims 1 to 71.

79. The device according to claim 74, wherein the continuous pattern is a line pattern.

80. The device according to any one of claims 74 to 79 being an electronic device or an optoelectronic device.

81. The device according to claim 80, wherein the device is an optoelectronic device that sources, detects or controls light.

82. The device according to claim 80, wherein the device is an electrical-to-optical or an optical-to-electrical transducer.

83. The device according to claim 80, wherein the device is a photoconductor or a photodiode or a solar cell or a dye-sensitized solar cell (DSSC) or a light emitting diode (LED) or an organic light emitting diode or laser or a light sensor or a specialized transistor or an organic transistor, or an inorganic transistor or a hybrid transistor.

84. The device according to claim 80, wherein the device is an electronic display or a printed electronic.

85. The device according to claim 84, wherein the device is a touch screen or a display backplane or a large or small area display.

86. The device according to claim 85, wherein the device is a display.

87. The device according to claim 85, wherein the device is a touch panel display.

88. The device according to claim 80, wherein the device is an electronic sensor.

89. The device according to claim 88, wherein the device is a touch sensor.

90. The device according to claim 80, wherein the device is a photovoltaic solar cell.

91. The device according to claim 90, wherein the solar cell is a silicon-based solar cell, an organic solar cell, a plastic solar cell, a dye-sensitized solar cell (DSSC), or a multi- junction solar cell.

92. The device according to any one of claims 74 to 91, comprising at least one transparent conductive jumper formed according to the process of any one of claims 1 to 71 on two or three or more different surface regions of a device surface.

93. The device according to claim 92, comprising at least one conductive ring pattern, at least one insulator and at least one jumper, each of said conductive pattern, insulator and jumper being formed according to a process according to any one of claims 1 to 71.

94. A bridge electrode or a jumper formed according to a process of any one of claims 1 to 71.

95. The bridge electrode according to claim 94 being or being part of an electronic device or an optoelectronic device.

96. The bridge electrode or jumper according to claim 94, for use in a touch sensor as a transparent electrode connecting between two other transparent electrodes separated by an insulating area.

97. The bridge electrode or jumper according to any one of claims 94 to 96, for connecting at least two components having different dopants or dopant concentrations.

98. The bridge electrode or the jumper according to claim 97, for connecting p-doped component with an n-doped component.

99. The bridge electrode or the jumper according to claim 97 for connecting p- or n- doped component with another p- or n-doped component.

100. The bridge electrode or the jumper according to any one of claims 94 to 99 for connecting at least two components of a device.

101. The bridge electrode or the jumper according to claim 100, wherein the device is a transistor.

102. The bridge electrode or the jumper according to claim 94 or 101, wherein the at least two components have a common boundary or are separated by at least one other material region.

103. The bridge electrode or the jumper according to claim 102, wherein an insulator separates between the at least two components, whereby the bridge electrode or the jumper connects the at least two components.

104. The bridge electrode or the jumper according to any one of claims 94 to 103, forming a single connection.

105. The bridge electrode or the jumper according to any one of claims 94 to 103, forming more than one connection.

106. The bridge electrode or the jumper according to claim 105, wherein the number of connections is 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 or more in a device. The bridge electrode or the jumper according to any one of claims 88 to 100 being transparent.

107. A device comprising a plurality of bridge electrodes or jumpers, each of said bridge electrodes or jumpers being prepared according to a process of any one of claims 1 to 69.

108. The device according to claim 107, wherein the number of bridge electrodes or jumpers ranges from 100 to a few thousands.

109. The device according to claim 108, wherein the number of bridge electrodes or jumpers ranges from 100 to 50,000.

110. A method of forming a non-spherical ring structure on a substrate, the method comprising:

-applying at least one ink droplet on a surface of a substrate;

-optionally applying at least one subsequent droplet at a distance from said at least one droplet and at least one additional droplet, wherein the at least one subsequent droplet is applied at a distance to said at least one droplet and at least one additional droplet while being wet, such that the at least one droplet, the at least further droplet and the at least one subsequent droplet are tangent to each other or intersect each other; and

-permitting the droplets to form a non-spherical pattern.

111. The process of claim 110, wherein the non-spherical ring is a polygon having 3, 4, 5, 6, 7, 8, 9, 10 or more sides.

112. The process of claim 111, wherein the non-spherical ring is a polygon selected from triangle, square and a pentagon.

113. The process of claim 111, wherein the non-spherical ring is an ellipse.