Method for manufacturing three-dimensional nanostructures having a large aspect ratio

Abstract

The invention relates to a method for manufacturing a three-dimensional nanostructure, the method comprising the following steps: - causing an injector (100) to oscillate between a low position in contact with a substrate (20) and a high position not in contact with the substrate (20), the injector (100) comprising an ejection port (108), the diameter of which is greater than 0.1 µm; - depositing an ink on the substrate (20) by means of the injector while the ejection port (108) of the injector (100) is in contact with the substrate (20), the ink comprising, in % by volume with respect to the total volume of the ink: - less than 15% of nanoparticles chosen from metal nanoparticles, nanoparticles of metal oxides, nanoparticles of graphene oxide or combinations thereof; - 0.5% to 5% of a dispersant; - at least 80% of a solvent that is capable of dispersing the metal nanoparticles in order to form the ink to be injected and sufficiently volatile to allow the ink to solidify once it has been deposited; and - moving the injector (100) away from the substrate (20) at a speed less than or equal to 10 µm / s along a direction substantially perpendicular to the substrate while ensuring the ink continues to flow from the injector. The invention also relates to cell lines obtained by the method.

Description

[0001] Method for manufacturing three-dimensional nanostructures with a large aspect ratio

[0002] FIELD OF THE INVENTION

[0003] The invention relates to the production of three-dimensional nanostructures and in particular nanostructures having a high aspect ratio - greater than 1 - such as, for example, nanostructured pillars. These pillars may in particular have the form of columns having a diameter in the height direction that is substantially constant or of rounded conical pins having a diameter that decreases in the height direction.

[0004] Three-dimensional nanostructures can be used in the fields of microelectronics, optoelectronics, energy conversion, the manufacture of nano-devices or nano-sensors, in particular for integration into screens, processors (and in particular quantum processors) or in vitro diagnostic devices.

[0005] STATE OF THE ART

[0006] Different techniques exist for producing three-dimensional nanostructures with an aspect ratio greater than 1.

[0007] The aspect ratio of a structure is understood here as the ratio of two dimensions of this structure. In particular when the structure extends in a direction of extension and forms for example a pillar or a pin, the aspect ratio is the ratio between the length of the structure in the direction of extension and a width of the structure in a direction transverse or perpendicular to this direction of extension. The higher the ratio, the more the structure appears stretched in the direction of extension, and in the case of a pillar, the smaller its diameter is compared to its height.

[0008] A three-dimensional nanostructure with an aspect ratio greater than 10:1 can be fabricated by direct 3D printing of Newtonian silver ink, which has the property of drying quickly. See Lee et al. ACS Appl. Mater. Interfaces 2017, 9, 22, 18918-18924. However, this technique produces structures with very rough surfaces.

[0009] There are also techniques based on the polymerization of photosensitive solutions. These require the use of mixtures of a colloidal metal suspension and photosensitive monomers, which polymerize during manufacturing. The resulting structure is, however, porous and has poor electrical conduction properties. These techniques can also be used to create molds for nanoimprint lithography (NIL). The manufacturing process is more expensive because it requires a mold for each size and arrangement of nanostructures.

[0010] There are also techniques based on the application of an electric field between a conductive substrate and a conductive suspension, such as electrodeposition techniques or redox electrohydrodynamic techniques such as the one described by Reiser et al. (Nature Communications, vol 10, 1, 2019). They require the use of a conductive ink and support, in particular due to galvanization constraints. Manufacturing speeds are slow because they are limited by the kinetics of the chemical reaction that takes place at the capillary tip or the FM tip used. In addition, in the case of electrohydrodynamic techniques, these require drop-by-drop (i.e. discontinuous) deposition, producing satellite droplets that generate undesirable surface irregularities.

[0011] Finally, there are techniques based on direct printing application in which the deposition of metallic ink is monitored by a camera.

[0012] There is therefore a need for a method for manufacturing three-dimensional nanostructures with a better surface finish, allowing a shorter or simpler manufacturing time by eliminating the need for a camera-based deposition monitoring system.

[0013] STATEMENT OF THE INVENTION

[0014] An aim of the invention is to propose a method for manufacturing three-dimensional nanostructures, and in particular nanostructures having an aspect ratio greater than 1, making it possible to produce nanostructures having surfaces which may be smoother or which may be layered, at a higher speed than in the prior art, and this without requiring a conductive substrate as in certain prior arts.

[0015] This aim is achieved within the framework of the present invention by means of a manufacturing method according to the claim, that is to say a method comprising the following steps:

[0016] - oscillating an injector (100) between a low position in contact with a substrate (20) and a high position out of contact with the substrate (20), the injector (100) comprising an ejection orifice (108) whose diameter is greater than 0.1 μm;

[0017] - depositing an ink on the substrate (20) by means of the injector upon contact of the ejection orifice (108) of the injector (100) with the substrate (20), the ink comprising, in % by volume relative to the total volume of the ink: - less than 15% of nanoparticles chosen from metal nanoparticles, metal oxide nanoparticles, graphene oxide nanoparticles, quantum dots or combinations thereof;

[0018] - 0.5% to 5% dispersant,

[0019] - at least 80% of a solvent capable of dispersing the metal nanoparticles to form the ink to be injected and sufficiently volatile to allow the ink to solidify once it is deposited; and

[0020] - moving the injector (100) away from the substrate (20) at a speed less than or equal to 10 pm / s in a direction substantially perpendicular to the substrate while maintaining an ink flow rate exiting the injector.

[0021] The expression "substantially perpendicular" means that the direction forms an angle of 90° ± 10° with the substrate which serves as its base.

[0022] The step of the process consisting of moving the injector away from the substrate in a direction non-parallel to the substrate while maintaining an ink flow rate exiting the injector makes it possible to manufacture nanostructured pillars having an aspect ratio greater than 1, such as for example pillars 1 μm in diameter and 30 μm in length. These pillars also advantageously have low surface roughness. In addition, this process accelerates the manufacture of the pillars - by a few seconds per pillar - and can be implemented with any substrate, without galvanization constraints.

[0023] Such a method is advantageously supplemented by the following different characteristics taken alone or in combination:

[0024] - the ink comprises from 0.05% to 15% by volume, advantageously from 0.2% to 10% by volume, more advantageously 4 to 8%, by volume of nanoparticles, relative to the total volume of the ink;

[0025] - the diameter of the ejection orifice (108) ranges from 0.1 pm to 50 pm, advantageously from 0.5 pm to 30 pm;

[0026] - the volatile solvent comprises a solvent selected from water, an alcohol, a glycol, a glycol ether, and mixtures thereof;

[0027] - the ink comprises from 80% to 99.45% by volume of said solvent, relative to the total volume of the ink;

[0028] - the volatile solvent further comprises a second solvent, said second solvent being glycerol, advantageously in a content such that the ink comprises from 0% to 25% by volume of glycerol, relative to the total volume of the ink;

[0029] - the metal of the metal nanoparticles is chosen from silver, copper, gold, platinum, nickel, aluminum, cobalt, their combinations or their alloys; - the metal oxide of the metal oxide nanoparticles is chosen from ZnO, TiCh or V2O5;

[0030] - the ink further comprises a dispersant, advantageously chosen from polyvinylpyrrolidone (PVP), gum arabic, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyallylamine (PAAm), polysodium styrene sulfonate (PSS), 3-(aminopropyl)trimethylsylane (APS), a fatty acid, cetyltrimethylammonium bromide (CTAB), tetraoctylammonium bromide (TOAB), sodium citrate, lauryl amine, dodecanethiol, mercapto-polyethylene glycol, mercapto-polypropylene glycol, or combinations thereof;

[0031] - the injector moves away at a speed ranging from 1 pm / s to 10 pm / s during the step of moving the injector away from the substrate;

[0032] - the method comprises a step of breaking between the three-dimensional nanostructure formed and the ink to be deposited, advantageously by moving the injector (100) away from the substrate (20) at a speed greater than 10 pm / s;

[0033] - the method comprises carrying out at least once a cycle of the following steps so as to form at least one second three-dimensional nanostructure: relative movement of the injector with respect to the substrate (20) in a direction parallel (x,y) to the substrate, and carrying out the steps of the method described above.

[0034] - the method comprises a step of baking the substrate containing the formed nanostructure.

[0035] The invention also relates to a product comprising a three-dimensional nanostructure obtained by means of a method as just presented.

[0036] Such a product is advantageously supplemented by the characteristic that the nanostructure has a length at least ten times greater than the widths of the nanostructure.

[0037] In another variant, such a product is advantageously supplemented by the characteristic that the nanostructure has a diameter which decreases in the direction of height.

[0038] DESCRIPTION OF FIGURES

[0039] Other characteristics and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and must be read in conjunction with the appended drawings in which: [Fig. 1] is a schematic representation of the formation of the pillars;

[0040] [Fig. 2] is a schematic representation of a system for manufacturing a three-dimensional nanostructure according to one of the embodiments of the invention;

[0041] [Fig. 3] gives pictures of the shapes of pillars that can be obtained by the process according to the invention.

[0042] [Fig. 4] gives pictures of the shapes of pillars obtained in test 3 (4A), in test 4 (4B) or of the flattened dome according to test 8 (4C).

[0043] [Fig. 5] gives a snapshot of the result after implementing comparative example 1.

[0044] [Fig. 6] gives pictures of the pillar shapes obtained in example 6 (6À: D=5 pm, 6B: D=10 pm);

[0045] [Fig. 7] gives the photograph of the pillar obtained in test 33.

[0046] [Fig. 8] gives two pictures of the result after implementing comparative example 2.

[0047] [Fig. 9] gives the photograph of the pillar obtained in test 35.

[0048] [Fig. 10]: Figure 10A is a graphical representation showing the maximum removal speed of the pipette, Ve in pm / s, as a function of the diameter of the pipette used for a volume concentration of metal particles in the ink of 5.8% and Figure 10B is a graphical representation showing the maximum removal speed of the pipette, Ve in pm / s, the pipette having a diameter of 5 ± 1 pm, as a function of the volume concentration of metal particles in the ink.

[0049] [Fig. 11] gives the photograph of the pillar obtained in test 37.

[0050] [Fig. 12] gives the photograph of the pillar obtained in example 9.

[0051] DETAILED DESCRIPTION OF THE INVENTION

[0052] A system for controlled deposition of an ink on any substrate has already been described in application WO2020 / 128310. The system described in this application allows the deposition of an ink having a shape defined by a length greater than or equal to 1 pm. The system comprises a mechanical resonator attached to an injector.

[0053] It has now been discovered that under certain conditions it is possible to deposit an ink and stretch it in an extensional direction to form a nanostructure such as a column or a pion.

[0054] For this, the method as described in application WO 2020 / 128310 comprises a step of moving the injector away from the substrate in a direction not parallel to the substrate, in particular substantially perpendicular, at a speed less than or equal to 10 pm / s and the ink to be deposited comprises metal nanoparticles and / or metal oxide nanoparticles and / or graphene oxide particles and a sufficiently volatile solvent.

[0055] In the present invention, the term "stretching" means that the deposition is continuous, unlike a drop-by-drop deposition for example.

[0056] The three-dimensional nanostructure is formed by localized evaporation at the outlet of the ejection orifice of the solvent present in the ink. As shown in Figure 1:

[0057] - the substrate and the ejection orifice of the injector are brought closer to each other. When contact is made, a meniscus of liquid from the ink contained in the injector appears between the outlet of the ejection orifice and the substrate (1 A);

[0058] - the ejection orifice of the injector and the substrate are moved away from each other at a speed less than or equal to 10 pm / s, the solvent evaporates inducing a concentration and / or a localized accumulation of the nanoparticles the inventors think of the liquid-gas interface of the meniscus, which causes the formation of a solid phase composed of a dense agglomerate of nanoparticles (1 B and 1 C);

[0059] - the ejection orifice of the injector and the substrate are moved away from each other at a speed greater than 10 pm / s to detach the ejection orifice of the injector from the formed three-dimensional nanostructure (1 D).

[0060] The ink used comprises metal nanoparticles or metal oxide nanoparticles or graphene oxide nanoparticles or possibly quantum dots, also referred to as nanoparticles in the following, and a volatile solvent.

[0061] Advantageously, the ink comprises from 0.05% to 15% by volume, advantageously from 0.2% to 10% by volume, more advantageously from 4 to 8%, by volume of nanoparticles, relative to the total volume of the ink.

[0062] The nanoparticles advantageously have an average particle size, D50, ranging from 1 nm to 300 nm, advantageously from 30 nm to 200 nm. The particle size can be determined by high-resolution scanning electron microscopy (HRSEM) or by light transmission analysis (such as with the Lumisizer® device).

[0063] The nanoparticles are advantageously conductive or semiconductive nanoparticles. They are advantageously metallic nanoparticles whose metal is chosen from silver, copper, gold, platinum, nickel, aluminum, cobalt, zinc, indium, palladium, their combinations or their alloys. In particular, the nanoparticles are metallic nanoparticles whose metal is chosen from silver, copper, gold, platinum, nickel, aluminum, cobalt, their combinations or their alloys.

[0064] The metal oxide of the metal oxide nanoparticles is advantageously chosen from ZnO, TiCh, ITO (indium tin oxide), or V2O5.

[0065] The quantum dots may advantageously be as described in documents EP2820108, US2014353579 or W02023274486 for example.

[0066] The ink advantageously further comprises a dispersant, that is to say an additive promoting the dispersion of the metal particles in the ink and in particular enabling the stability of the ink.

[0067] Advantageously, the ink comprises from 0.5% to 5% by volume, advantageously from 1% to 2% by volume, of dispersant, relative to the total volume of the ink.

[0068] The dispersant is advantageously selected from polyvinylpyrrolidone (PVP), gum arabic, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyallylamine (PAAm), polysodium styrene sulfonate (PSS), 3-(aminopropyl)trimethylsylane (APS), a fatty acid, cetyltrimethylammonium bromide (CTAB), tetraoctylammonium bromide (TOAB), sodium citrate, lauryl amine, dodecanethiol, mercapto-polyethylene glycol, mercapto-polypropylene glycol, or combinations thereof. The dispersant may be a polymer having a number-average molecular weight, Mw, ranging from 5,000 g / mol to 2,000,000 g / mol. Preferably, the dispersant is PVP. The molecular weight, Mw, of PVP is preferably at least 8,000 g / mol, more preferably 10,000 g / mol to 1,600,000 g / mol, even more preferably 10,000 g / mol to 200,000 g / mol.

[0069] When the nanoparticles are silver or copper nanoparticles, the dispersant is advantageously chosen from polyvinylpyrrolidone (PVP), gum arabic, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyallylamine (PAAm), polysodium styrene sulfonate (PSS), 3-(aminopropyl)trimethylsylane (APS), a fatty acid, cetyltrimethylammonium bromide (CTAB), tetraoctylammonium bromide (TOAB), sodium citrate, lauryl amine or combinations thereof.

[0070] When the nanoparticles are gold nanoparticles, the dispersant is advantageously chosen from mercapto-polyethylene glycol, mercapto-polypropylene glycol, dodecanethiol, sodium citrate, polyvinylpyrrolidone (PVP) or combinations thereof. Preferably, the dispersant is mercapto-polyethylene glycol. The molecular weight, Mw, of mercapto-polyethylene glycol is advantageously at least 100 g / mol, more advantageously from 400 g / mol to 2,000 g / mol. The solvent is first of all a solvent allowing the dispersion of the nanoparticles, without agglomeration in particular, in the ink. Since the ink is most often a commercial ink, the solvents used are already solvents allowing good dispersion of the nanoparticles. In certain cases, a miscible solvent is added to these commercial inks to modify the volatility.

[0071] When the metal particles are made of silver or copper, examples of solvents allowing their good dispersion, and suitable for the process according to the invention, are in particular alcohols, glycols, glycol ethers, and their mixtures. Of course, the mixtures which can be retained are those between miscible solvents.

[0072] When the metal particles are gold, examples of solvents allowing their good dispersion, and suitable for the process according to the invention, are in particular water, alcohols, toluene and their mixtures. Of course, the mixtures which can be retained are those between miscible solvents.

[0073] In addition to this ability to disperse the nanoparticles, the solvent must be sufficiently volatile to allow the formation of a solid phase. Indeed, we want the solvent to evaporate quickly enough once contact has been made between the injector's ejection orifice and the substrate to allow localized concentration / accumulation of the nanoparticles while limiting, or even preventing, the ink from spreading on the substrate.

[0074] On the other hand, to avoid any blockage at the outlet of the injector ejection port, the solvent must not evaporate too quickly.

[0075] The solvent or solvent mixture is therefore advantageously adapted to allow the formation of a solid phase, while avoiding on the one hand the formation of a plug or the rupture of the deposit, and on the other hand avoiding or limiting the spreading of the ink on the substrate.

[0076] The speed of evaporation of the solvent obviously depends on the volatility of the solvent, which itself depends on the operating conditions (temperature, pressure, ambient humidity, speed of separation of the substrate / ejection orifice and diameter of the ejection orifice) but also on the volume fraction of nanoparticles in the ink.

[0077] Thus, depending on the operating conditions, the ink will include one or more solvents, the solvents in this case being miscible with each other.

[0078] In particular, it is possible to plan to add a second solvent of lower volatility to ensure sufficient handling time between the formation of two structures.

[0079] Without wishing to limit themselves, the inventors believe that the characteristic time of the evaporation of the solvent T corresponds to the following formula [Math. 2] with D the diameter of the ejection orifice (108),

[0080] P vapthe saturated vapor pressure of the solvent or solvent mixture at the printing temperature, usually room temperature, p soi the density of the solvent or solvent mixture at the printing temperature, usually room temperature, x v NPs the volume fraction of nanoparticles.

[0081] Alternatively, and without wishing to be bound by theory, based on the work of Davis and Ray (J. Chem. Phys. 67, 414 (1977)), the inventors postulate that the rate of evaporation of the solvent in a drop of ink follows the following equation: [Math. 3] in which

[0082] XNP represents the volume fraction of nanoparticles in the ink, a represents the radius of a drop (in m),

[0083] D12 represents the diffusion coefficient of the solvent (1) in the gas (2) (in m 2 .s' 1 ), p vaprepresents the saturated vapor pressure of the solvent at temperature T (in Pa), Mi represents the molar mass of the solvent (in kg. mol' 1 ) puq represents the density of the ink solvent at temperature T (in kg.nr 3 ) R represents the universal constant of ideal gases (in J. K' 1 , mol' 1 )

[0084] T represents the temperature (in Kelvin).

[0085] Gas (2) is usually air.

[0086] After integration, we deduce that the characteristic time of solvent evaporation T is proportional to the following formula: [Math. 4] in which

[0087] XNP represents the volume fraction of nanoparticles in the ink, r represents the radius of the ejection orifice (108) (in m), Di2 represents the diffusion coefficient of the solvent (1) in the gas (2) (in m 2 .s' 1 ), p vaprepresents the saturated vapor pressure of the solvent at temperature T (in Pa), Mi represents the molar mass of the solvent (in kg. mol' 1 ) puq represents the density of the ink solvent at temperature T (in kg.m 3 ) R represents the universal constant of ideal gases (in J. K' 1 , mol' 1 ) T represents the temperature (in Kelvin).

[0088] Gas (2) is usually air.

[0089] In the case where the solvent is a mixture, we will of course use the weighted average values ​​according to the volume fraction of each solvent for the values ​​of Pvap, Pliq, Gt Dl2.

[0090] These laws have been verified by experimental measurements, which seem to indicate that the coefficient of proportionality is approximately equal to 1.

[0091] Advantageously, the conditions of diameter of the ejection orifice, saturated vapor pressure of the solvent or mixture of solvents, density of the solvent or mixture of solvents and volume fraction of the nanoparticles are such that the characteristic time of evaporation of the solvent, T, varies from 0.1 s to 1000 s, in particular from 0.1 to 300 s, advantageously from 1 s to 30 s, more advantageously from 2 s to 10 s. Preferably, the conditions of radius of the ejection orifice, saturated vapor pressure of the solvent or mixture of solvents, the density of the solvent or mixture of solvents and the volume fraction of the nanoparticles are such that the characteristic time of evaporation of the solvent, T, advantageously as determined according to the equation Math4, varies from 10s to 300s, in particular from 30s to 300s.

[0092] Following the two equations Math2 and Math4, we see that when the volume fraction of nanoparticles in the ink increases, the volatility of the solvent must be reduced.

[0093] It is also observed that the removal rate must be reduced when the solvent has a lower evaporation rate.

[0094] Advantageously, the volume fraction of the nanoparticles in the ink, the radius of the ejection orifice (108), and the solvent (the temperature and the gas being fixed, generally at 300 Kelvin and air respectively) will be chosen so that the characteristic time of the evaporation of the solvent, T, advantageously as determined according to the equation Math4, varies from 10s to 300s, in particular from 30s to 300s.

[0095] Advantageously, the volatile solvent comprises a solvent chosen from water, an alcohol, a glycol, a glycol ether, and mixtures thereof. In the case of mixtures of solvents, of course the solvents must be miscible and the mixture continues to fulfill its role of dispersing the nanoparticles.

[0096] Examples of alcohol include methanol, ethanol, isopropanol, 1-propanol, benzyl alcohol, and terpineol.

[0097] Examples of glycol include ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, diethylene glycol, and triethylene glycol.

[0098] Examples of glycol ether include:

[0099] - ethylene glycol ether, propylene glycol ether;

[0100] - propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol mono-t-butyl ether, propylene glycol monophenyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, propylene glycol mono-t-butyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether and tripropylene glycol monobutyl ether;

[0101] - ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol monopropyl ether and triethylene glycol monobutyl ether.

[0102] In particular, the solvent is selected from water, ethanol, ethylene glycol (EG), diethylene glycol methyl ether (DGME), diethylene glycol ethyl ether (DGEE), diethylene glycol butyl ether (DGBE), triethylene glycol methyl ether (TGME), propylene glycol methyl ether (PGME), tripropylene glycol methyl ether (TPME), and mixtures thereof.

[0103] Advantageously, the ink comprises from 80% to 99.45% by volume of said solvent, relative to the total volume of the ink. This content corresponds to the content of 1 er solvent and as a second solvent, when present, as defined below.

[0104] This solvent, also called 1 er solvent, can be used alone. Alternatively, it can be mixed with a less volatile solvent, called 2 ème solvent.

[0105] As indicated, the ink may comprise a second solvent of much lower volatility than the first solvent. This second solvent is advantageously hygroscopic. Thus, advantageously, the volatile solvent comprises a second solvent chosen from glycerol, advantageously in a content such that the ink comprises more than 0% to 25% by volume of glycerol, relative to the total volume of the ink.

[0106] The presence of the second solvent is intended to prevent the ejection port from drying out and clogging too quickly. Depending on the air humidity and the volume fraction of the second solvent, the ejection port can be left unused in the air for 1 min to 30 min, before resuming the formation of nanostructures.

[0107] For example, it is possible to create nanostructures one after the other with a time interval ranging from 30 s to 30 min between each, without the ejection orifice becoming blocked between two nanostructures.

[0108] Advantageously, the ink comprises, more advantageously consists of, four families of ingredients:

[0109] - nanoparticles as previously described, in a volume concentration ranging from 0.05% vol to 15% vol, preferably between 4% vol and 8% vol;

[0110] - the dispersant as previously described in a volume concentration ranging from 0.5% vol to 5% vol, preferably from 1% vol to 2% vol;

[0111] - a first solvent selected from water, ethanol, ethylene glycol (EG), diethylene glycol methyl ether (DGME), diethylene glycol ethyl ether (DGEE), diethylene glycol butyl ether (DGBE), triethylene glycol methyl ether (TGME), propylene glycol methyl ether (PGME), tripropylene glycol methyl ether (TPME), and mixtures thereof;

[0112] - 0 to 25% vol of glycerol.

[0113] The percentages are expressed by volume relative to the total volume of the ink. When the ink consists of these four families of ingredients, it comprises from 55% to 99.45% vol of the said first solvent.

[0114] System for manufacturing a three-dimensional nanostructure

[0115] Figure 2 shows an embodiment of a system 10 for fabricating a three-dimensional nanostructure on a substrate 20.

[0116] In this case, the system 10 includes all the features of the system for controlled deposit of an ink on a substrate as presented in application WO2012 / 078590. The latter is incorporated by reference. Reference may be made to this application for further details on the known aspects of the technique implemented. The system 10 for manufacturing a three-dimensional nanostructure on a substrate 20 includes a nanometric-sized injector 100.

[0117] The injector 100 comprises a reservoir 102 for storing the ink and a non-deformable protrusion 104. The injector 100 comprises an ejection orifice 108 for extracting the ink from the reservoir 102.

[0118] The diameter of the ejection orifice 108 ranges from 0.1 to 50 microns, advantageously from 0.5 μm to 30 μm.

[0119] The system 10 also comprises a conveyor or displacement means 160 adapted to relatively move the substrate 20 relative to the injector 100. The displacement can be carried out in a z direction non-parallel to the substrate, as well as in x and y directions parallel to the substrate. The displacement means 160 can be a piezoscanner on which the substrate 20 is deposited. It can in particular be a three-axis piezoscanner with a sub-nanometric displacement resolution.

[0120] The system 10 further comprises a mechanical resonator attached to the injector 100.

[0121] The mechanical resonator can be presented in the form of a tuning fork whose body is screwed at its base onto a block which can move along the three axes of space by a system of micrometric screws.

[0122] The system 10 further comprises a controller or control means 18 of the mechanical resonator. The controller 148 comprises a first PID corrector 1 connected to an exciter or exciter means 142 adapted to excite the mechanical resonator.

[0123] The system 10 comprises the exciter means 142, which may be a piezoelectric exciter. This exciter is bonded to the mechanical resonator.

[0124] The control means 148 is further connected to a detector or detector means 144 adapted to detect the oscillation of the mechanical resonator so as to read the response of the mechanical resonator to the excitation of the exciter means 142. The system 10 comprises the detector 144 which can be an accelerometer stuck on the mechanical resonator.

[0125] The detector 144 is capable of detecting oscillation variations, and in particular variations in the oscillation frequency of the injector of less than 1 Hz, advantageously between 10 mHz and 200 mHz.

[0126] The control means 148 is further connected to a regulator or regulating means 146 adapted to adjust the contact between the protrusion 104 and the substrate 20 by controlling the oscillation of the mechanical resonator. The system 10 comprises the regulator 146 which is a second PI D 2 corrector and allows the adjustment of the contact using the conveyor or displacement means 160 to which it is connected.

[0127] Regarding the excitation of the resonator, it should be noted that the piezoelectric exciter can be powered by an electrical signal whose frequency corresponds to its mechanical excitation frequency. The frequency of this electrical signal is adjusted by the first PID corrector 1 to control the oscillation of the tuning fork so that the response detected by the tuning fork by the accelerometer is in phase with the signal from the piezoelectric exciter so that the tuning fork oscillates according to the oscillation of the piezoelectric exciter. The setpoint of this feedback loop is therefore that the phase shift between the oscillation of the piezoelectric exciter and that of the tuning fork is zero. The tuning fork is then in phase with the piezoelectric exciter. The tuning fork is thus excited at its resonance frequency, which depends on its mechanical properties but also on interactions with its environment.

[0128] The control means 148 is adapted to deposit the ink previously described on the substrate 20 by means of the injector during contact of the injector 100 with the substrate 20.

[0129] The control means 148 is connected to the conveyor 160 and is adapted to move the injector away from the substrate 20 in the z direction non-parallel to the substrate while maintaining an ink flow rate exiting the injector. The z direction may be the direction perpendicular to the plane of the substrate 20.

[0130] Method for manufacturing a three-dimensional nanostructure

[0131] A manufacturing system as just presented makes it possible to implement a method according to the invention for manufacturing a three-dimensional nanostructure.

[0132] We will present a method of implementing this process.

[0133] A first step of the method consists of oscillating the injector 100 between a low position in contact with a substrate 20 and a high position out of contact with the substrate 20.

[0134] Typically, the injector oscillates over an amplitude ranging from 0.5 to 100 nm, advantageously from 1 to 20 nm, during this step. For this purpose, the control means 148 can control the excitation means 142 to excite the mechanical resonator which itself causes the injector 100 to oscillate. The protrusion 104 then oscillates between a low position in which the protrusion 104 is in contact with the substrate 20 and a high position in which the protrusion 104 and the substrate 20 are not in contact.

[0135] The resonance of the system consisting of the tuning fork, the piezoelectric exciter and the accelerometer can be measured in order to determine the resonant frequency of the tuning fork and its quality factor.

[0136] It is also possible to predefine a setpoint oscillation phase shift of the second PID corrector 2, this phase shift corresponding to a phase shift induced by a predefined contact between the protuberance and the substrate 20. For example, this phase shift can be less than 1 Hz, advantageously ranging from 10 mHz to 200 mHz (milliHertz).

[0137] The substrate 20 is brought closer to the protrusion 104 using the conveyor 160 so that the protrusion 104 oscillates between a low position in which it is in contact with the substrate 20 and a high position in which it is not in contact with the substrate 20. In this particular configuration of the protrusion 104 and the substrate 20, the forces applied to the assembly consisting of the tuning fork and the injector 100 are modified. This creates a modification of the resonant frequency, and therefore of the excitation frequency of the piezoelectric exciter which is maintained at the resonant frequency of the tuning fork.

[0138] It is possible to choose to define this configuration by a particular modification of the resonance frequency of the assembly constituted by the tuning fork and the injector 100, for example a modification of less than 1 Hz, advantageously ranging from 10 mHz to 200 mHz. This modification is the induced phase shift mentioned above.

[0139] The system 10, thanks to the detector 144, is adapted to identify this particular configuration between the injector and the substrate which involves a variation of oscillations less than 1 Hz, advantageously ranging from 10 mHz to 200 mHz.

[0140] It is possible to adjust, using the second PID corrector 2 and depending on the oscillation variations, the configuration so as to form an ink meniscus between the protuberance 104 and the substrate 20. The regulator or second PID corrector 2 controls the fine approach between the substrate 20 and the injector 100 using a feedback loop, until the modification of the resonance frequency is less than 1 Hz, advantageously ranging from 10 mHz to 200 mHz.

[0141] A second step of the method consists of depositing the ink previously described on the substrate 20 by means of the injector during contact of the injector 100 with the substrate 20. When contact is made, a meniscus of the liquid contained in the pipette (the ink previously described) appears between the ejection orifice 108 and the substrate 20 (see figure 1).

[0142] The contact is maintained by applying a constraint on the frequency shift of the resonance, a shift resulting from the interaction between the ejection orifice 108 and the substrate 20. The “frequency shift” values ​​used advantageously range from 40 mHz to 500 mHz.

[0143] As previously indicated, the oscillation amplitude of the tuning fork, and therefore of the protuberance 104, is fixed between 0.5 nm and 100 nm.

[0144] The ink thus deposited on the substrate forms the basis of the three-dimensional nanostructure produced.

[0145] The method may comprise, before the third step which follows, a step during which contact is maintained without moving away from the injector 100. This step, corresponding to a primer time, makes it possible to concentrate the meniscus formed into nanoparticles. Thus, the more diluted the ink is, the more it will be advantageous to observe a primer time. This primer time advantageously varies from 1 s to 180 s.

[0146] A third step of the method consists of moving the injector 100 away from the substrate 20 in a non-parallel direction, advantageously substantially perpendicular, to the substrate while maintaining a flow of ink exiting the injector.

[0147] The ink exiting the injector during this step is deposited on the previously deposited ink so as to gradually compose the three-dimensional nanostructure. The nanostructure produced thus comprises a part which extends in the non-parallel direction, advantageously substantially perpendicular, to the substrate.

[0148] As previously stated, the injector's retraction speed is adjusted so that the exiting ink solidifies quickly enough to serve as a deposition base for the subsequent exiting ink.

[0149] For example, the system can be adjusted so that the injector moves away at a predetermined speed less than or equal to 10 pm / s, advantageously ranging from 1 pm / s to 10 pm / s during this step.

[0150] Advantageously, once contact is established, the substrate 20 is moved away from the protuberance 104 according to one of the following two modes:

[0151] 1) the displacement means control loop 160 via the regulator 146 (PID corrector 2) is kept active: The appearance of the solid phase induces a local unevenness on the substrate, which causes a frequency shift, detected by the phase-locked loop. The displacement means 160 responds to this increase in the frequency shift by moving the substrate 20 sufficiently away to return to the setpoint value of the frequency shift set at a value ranging from 40 mHz to 500 mHz. Thus, the creation of the pillar is initiated. This routine continues autonomously as long as the operator leaves the control loop active and the pillar is continuously pulled from the tip of the ejection orifice 108. Deactivation of the displacement means control loop 160 suspends the generation of the pillar.

[0152] The pillars obtained according to this variant advantageously have a smooth appearance (figures 3A, 3C). If the set value is varied, the pillar can be given a wavy shape (figure 3E).

[0153] 2) the control loop of the displacement means 160 via the regulator 146 (PID corrector 2) is deactivated:

[0154] Immediately after the formation of the meniscus, the operator waits 1 s to 60 s at contact to initiate the formation of the pillar before manually moving the substrate 20 away from the protuberance 104 using the control software. The distance increments range from 0.01 pm to 10 pm, giving moving away speeds ranging from 0.01 pm / s to 10 pm / s. A starting time, advantageously from 0.1 s to 60 s, can be provided between each distance increment. The pillars obtained according to this variant advantageously have a stratified appearance (Figures 3B, 3D). If the moving away speed is varied, the pillar can be given a wavy shape.

[0155] In all cases, to detach the protrusion 104 from the pillar, in a fourth step also called the breaking step, the substrate is moved away at a speed of at least 10 pm / s. Knowing that the faster the movement (>500 pm / s), the flatter the roof of the pillar will be (Figures 3C, 3D). Conversely, a slower movement (<20 pm / s) gives the roof of the pillar a conical shape, and the slower the movement, the more elongated the cone will be (Figures 3 A, 3 B).

[0156] The process allows for a pillar manufacturing time of approximately a few seconds.

[0157] This process eliminates the need for a camera to monitor and control the deposition. This process eliminates the need for pressure on the ink to be deposited. It is thus possible to manufacture nanostructured pillars with an aspect ratio greater than 1, advantageously ranging from 10:1 to 50:1, such as pillars 1 μm in diameter and 30 μm in length.

[0158] Such pillars are notably obtained with injectors whose ejection orifice 108 has a diameter ranging from 0.1 pm to 50 pm, advantageously from 0.5 pm to 30 pm, more advantageously from 1 pm to 15 pm.

[0159] The shape of the pillars will depend on the operating conditions. As illustrated in Example 1 and Figure 3, pillars with the following characteristic shapes can be formed:

[0160] - Smooth column of substantially constant diameter ending in a conical roof (figure 3A);

[0161] - Stratified column of substantially constant diameter ending in a conical roof (figure 3B);

[0162] - Smooth column of substantially constant diameter ending in a flat roof (figure 3C);

[0163] - Stratified column of approximately constant diameter ending in a flat roof

[0164] (figure 3D);

[0165] - Smooth column with varying diameter giving a wavy shape (figure 3E);

[0166] - Column showing alternating smooth zones and stratified zones (figure 3F);

[0167] - Pillar in the form of a rounded conical pin with a diameter which decreases in the direction of the height (figure 3G).

[0168] The method advantageously further comprises performing a relative movement of the injector with respect to the substrate (20) in a direction parallel (x,y) to the substrate, to deposit the ink to form at least one line, according to the method described in WO 2020 / 128310.

[0169] The method may be adapted to manufacture several nanostructures successively. For this purpose, the method may further comprise carrying out at least once a cycle of the following steps so as to form at least one second three-dimensional nanostructure:

[0170] - relative displacement of the injector with respect to the substrate 20 in a direction parallel (x,y) to the substrate, and

[0171] - carrying out the steps of the process as presented previously.

[0172] The relative movement is ensured by the movement means 160. During relative movement of the injector relative to the substrate (20) in a direction parallel (x,y) to the substrate, it is possible to deposit the ink to form at least one line, according to the method described in WO 2020 / 128310.

[0173] With each execution of the step cycle, a new nanostructure is fabricated.

[0174] Once the pillar(s) have been formed, the process advantageously includes a firing step. The conditions of this step can be adapted depending on the nature of the metal or oxide of the nanoparticles. For example, gold or silver pillars are heated to a temperature ranging from 130°C to 200°C for a duration that can vary from 10 min to 2 h. For copper pillars, the temperature and duration conditions can be the same, it is just necessary to operate in a non-oxidizing atmosphere, for example under argon, nitrogen, hydrogen. Photonic firing can also be carried out, which can be implemented in an ambient atmosphere even for copper pillars.

[0175] Advantageously, all steps of the process are carried out at room temperature (18-22°C) and at atmospheric pressure.

[0176] Finally, the invention relates to a product comprising a substrate on which is deposited a three-dimensional nanostructure obtained by means of a method such as has just been presented.

[0177] According to a variant, such a nanostructure is a column as described above. Such a column advantageously has an aspect ratio greater than 10:1, more advantageously greater than 15:1, even more advantageously up to 50:1, such that the column extends in an extension direction over an extension length at least ten times greater than widths of the nanostructure in directions perpendicular to the extension direction.

[0178] The extension direction corresponds to the direction z not parallel to the substrate, advantageously substantially perpendicular, in which the injector is moved away from the substrate during the process.

[0179] The base diameter of the column, corresponding to its greatest width, is advantageously less than 10 pm, more advantageously less than 5 pm, even more advantageously less than 2 pm, such as for example 1 pm.

[0180] According to another variant, such a nanostructure is a pion as described previously.

[0181] The controllable parameters are the diameters of the base and the top of the pin, as well as the angle of the slope formed between its vertical wall and the axis perpendicular to the substrate. The diameter of the base advantageously varies from 0.5 pm to 50 pm, more advantageously from 1 to 30 pm. The diameter of the top advantageously varies from 0.2 pm to 30 pm, more advantageously from 0.5 pm to 10 pm. The angle of the slope formed between its vertical wall and the axis perpendicular to the substrate advantageously varies from 0.1° to 70°, more advantageously from 10° to 45°.

[0182] Such a shape is of interest for the production of solder bumps in the packaging stages of electronic chips. The conical pin is mechanically more stable than a column when a shear stress is applied to it. Typically during a wafer bonding stage where the pin deposited on the wafer 1 is compressed vertically by pressure from a wafer 2. The small xy displacements of said wafers during compression can shift the column and compromise the proper bonding of the two wafers. The conical pin is, due to its morphology, less subject to this phenomenon.

[0183] Advantageously, in any one of the variants, the substrate is non-conductive.

[0184] The following examples illustrate the invention.

[0185] Characteristic time of evaporation of several solvents

[0186] Using the Math4 formula with the following parameters:

[0187] XNpest set to 0.06.

[0188] 2a (pipette diameter) = 1.5*10' 5 m

[0189] R = 8.3 J. K' 1 . mol' 1

[0190] T = 300 K

[0191] D12 represents the diffusion coefficient of the solvent (1) in air (gas (2)). It was calculated using the Chapman-Enskog formula: in which

[0192] N represents Avogadro's Number (6.022 1 0 76 x 10 23 soft -1 ) k represents the Boltzmann Constant (1,380 649 x 10 -23 J. K -1 )

[0193] T represents temperature, in Kelvin (300 K) Msoi represents the molar mass of the solvent, in kg. mol' 1

[0194] Mair represents the molar mass of air in kg. mol' 1 (0.029 kg. mol' 1 ) p represents the pressure in Pa (1.01*10 5 Pa) o represents the diameter corresponding to the effective section of a solvent molecule, in m

[0195] O represents the collision integral reduced by its value for the collision of hard spheres, approximated to 1 p vap represents the saturated vapor pressure of the solvent at a temperature of 300K. puq represents the density of the ink solvent at a temperature of 300K. The characteristic evaporation time values ​​of the above solvents were measured on an experimental device as described in Examples 1 to 10. The experimental values ​​are in good agreement with the theoretical values ​​obtained according to the Math4 equation. In particular, with a pipette diameter of 1.5*10' 5m, TEG alone or glycerol alone are solvents that are not volatile enough to allow the ink to solidify once it is deposited.

[0196] Example 1: Silver nanoparticles - commercial ink

[0197] A commercial PVnanocell ink ref (Sycris™ I40DM-106), the composition of which, as indicated by the supplier, includes: - silver nanoparticles (d50=70 nm, d90 = 152 nm, determined by Lumisizer®) coated with a layer of polyvinylpyrrolidone; their mass concentration is between 38% and 42% by weight, or approximately 5.8% vol.

[0198] - the DGME solvent is injected into a drawn glass capillary (= pipette) whose tip diameter is as indicated in table 1, taking care that the liquid reaches the end of the pipette tip.

[0199] The pipette is fixed on one of the two teeth of the tuning fork and its tip is approached according to the method described in Figure 2 of application WO 2020 / 128310. First, the tip of the pipette is mechanically approached using micrometric verniers, at a distance of less than 300 pm from the substrate, here a silicon wafer. Then, the approach to the contact of the substrate is carried out using the loop which maintains the resonance of the tuning fork (in English "phase locked loop" abbreviated to PLL) and the servo loop on the piezoscanner to achieve contact between the tip of the pipette and the substrate. Here the substrate is placed on the piezoscanner, the pipette is therefore fixed and it is the substrate which approaches it.

[0200] Contact is maintained by applying a constraint on the frequency shift (FS) of the resonance, a shift resulting from the interaction between the pipette and the substrate. The value of "frequency shift", FS, used is 150 mHz (milliHertz).

[0201] The oscillation amplitude of the tuning fork (and therefore of the pipette) is fixed at 10 nm.

[0202] When contact is made, a meniscus of the liquid contained in the pipette (the ink) appears between the tip of the pipette and the substrate.

[0203] Once contact is established, the substrate is moved away from the pipette in one of two ways:

[0204] 1) the piezoscanner control loop is kept active:

[0205] The appearance of the solid phase induces a local unevenness on the substrate, which results in a FS, detected by the PLL. The piezoscanner responds to this increase in FS by moving the substrate far enough away to return to the FS setpoint value of 150 mHz. Thus, pillar creation is initiated. This routine continues autonomously as long as the operator leaves the servo loop active and the pillar is continuously pulled from the pipette tip. Deactivating the piezoscanner's servo loop suspends pillar generation.

[0206] To detach the pipette from the pillar, it is moved away at a speed of at least 10 pm / s.

[0207] 2) the piezoscanner servo loop is deactivated:

[0208] Immediately after the meniscus has formed, the operator waits 1 s to 60 s on contact to initiate pillar formation before manually moving the substrate away from the pipette using the control software. The distance increments range from 0.01 to 10 pm, giving removal speeds ranging from 0.01 to 10 pm / s. To detach the pipette from the pillar once the correct size has been obtained, proceed as in the previous point.

[0209] All steps of the process are carried out at room temperature (18-22°C) and atmospheric pressure. The results obtained are summarized in the following table:

[0210] [Table 1]

[0211] D = Pipette diameter (pm)

[0212] Ve = Distance speed (pm / s)

[0213] Vr = Rupture speed (pm / s) We give in the following figures:

[0214] Figure 4A: A pillar obtained according to test 3;

[0215] Figure 4B: A pillar obtained according to test 4;

[0216] Figure 4C: The flattened dome according to test 8 With a pipette with a diameter of 30 pm, the ratio of the deposition surface area to the volume of ink to be deposited is higher. To allow faster solidification of the nanoparticles and thus obtain a pillar with a constant diameter over its entire height, a more volatile solvent than DGME is required.

[0217] In test 8, the removal speed is too fast to form a pillar. In test 9, a pillar is pulled but not a column of approximately constant diameter is formed.

[0218] The pillars are then baked at 150°C for 30 minutes on a hot plate. Example 2: Silver nanoparticles - diluted commercial ink

[0219] The ink of Example 1 is diluted with a similar solvent, DGEE, to obtain a nanoparticle volume concentration of 5%vol (= 35% by weight). The approach and contact are carried out as described in Example 1, with a pipette whose tip diameter is 1.5 pm or 8 pm. The servo loop is not activated.

[0220] The results obtained are summarized in the following table:

[0221] [Table 2] TJ

[0222] D = Pipette diameter (pm)

[0223] Ve = Distance speed (pm / s)

[0224] Vr = Rupture velocity (pm / s)

[0225] Since the ink is more diluted, and the quantity of liquid to be evaporated to obtain the solid phase of the nanoparticles is greater, the speed of removal is lower.

[0226] The pillars are then baked at 150°C for 30 minutes on a hot plate.

[0227] Example 3: Silver nanoparticles - concentrated commercial ink

[0228] The ink from Example 1 is centrifuged for 30 min at 7000 rpm in order to remove the DGME solvent and increase the nanoparticle concentration.

[0229] Glycerol is added as a second solvent to achieve the following formulation:

[0230] - nanoparticles: 10% vol;

[0231] - DGME: 65% vol;

[0232] - glycerol: 25% vol.

[0233] Approach and contact are performed as described in Example 1, with a pipette with a tip diameter of 1.5 pm or 8 pm. The servo loop is deactivated.

[0234] The results obtained are summarized in the following table:

[0235] [Table 3] D = Pipette diameter (pm)

[0236] Ve = Distance speed (pm / s)

[0237] Vr = Rupture velocity (pm / s)

[0238] The ink can be deposited and pulled to form columns without the pipette clogging. The low volatility of glycerol compensates for the increased volume fraction of nanoparticles.

[0239] The pillars are then baked at 150°C for 30 minutes on a hot plate.

[0240] Example 4: Silver nanoparticles - commercial ink

[0241] The ink used is the commercial PVnanocell ink ref (Sycris™ P75DB-1), the composition of which indicated by the supplier includes:

[0242] - silver nanoparticles (d50 = 70 nm, d90 = 130 nm, determined by Lumisizer®) coated with a layer of polyvinylpyrrolidone; their mass concentration is between 72 and 78% by weight, or approximately 10% by volume.

[0243] - the DGBE solvent,

[0244] The approach and contact are carried out as described in Example 1, with a pipette whose tip diameter is given in the following table. The servo loop is deactivated.

[0245] The results obtained are summarized in the following table:

[0246] [Table 4]

[0247] D = Pipette diameter (pm)

[0248] Ve = Distance speed (pm / s)

[0249] Vr = Rupture velocity (pm / s)

[0250] The DGBE solvent is less volatile than DGME, under the same temperature and atmospheric pressure conditions it evaporates less quickly than DGME, hence the lower removal speed.

[0251] The pillars are then baked at 150°C for 30 minutes on a hot plate.

[0252] Comparative test 1:

[0253] The ink from Example 1 is centrifuged for 30 min at 7000 rpm in order to remove the DGME solvent and increase the nanoparticle concentration.

[0254] - nanoparticles: 16% vol;

[0255] - DGME: 84% vol;

[0256] The approach and contact are carried out as described in Example 1, with a pipette with a tip diameter of 8 μm. The pipette clogs too quickly to be able to form pillars. No matter how fast the pipette is moved away, only a few particles are deposited on the substrate (see Figure 5).

[0257] Example 5: Copper nanoparticles - diluted commercial ink

[0258] The commercial PVnanocell ink ref (Sycris™ IC50DM-7), the composition of which is indicated by the supplier, includes:

[0259] - copper nanoparticles (d50 = 50 nm, d90 = 120 nm, determined by Lumisizer®) coated with a layer of polyvinylpyrrolidone; their mass concentration is between 48% and 52% by weight, or 9.8% vol.

[0260] - the DGME solvent, is diluted with DGME or DGEE and glycerol, with volume proportions of 70:15:15 - ink: DGEE / DGME:glycerol. The volume fraction thus achieved is 6.5% vol in copper nanoparticles.

[0261] Approach and contact are performed as described in Example 1, with a pipette with a tip diameter of 5 or 10 pm. The servo loop is deactivated.

[0262] The pillars are then baked at 150°C for 30 min on a hot plate under a nitrogen atmosphere.

[0263] The results obtained are summarized in the following table: [Table 5] D = Pipette diameter (pm)

[0264] Ve = Distance speed (pm / s)

[0265] Vr = Rupture velocity (pm / s)

[0266] Examples of photos are given in Figure 6. Figure 6A: D=5pm, Figure 6B: D=10pm.

[0267] Example 6: Copper nanoparticles - diluted commercial ink

[0268] The commercial PVnanocell ink ref (Sycris™ IC50DM-7), the composition of which is indicated by the supplier, includes:

[0269] - copper nanoparticles (d50 = 50 nm, d90 = 120 nm, determined by Multisizer®) coated with a layer of polyvinylpyrrolidone; their mass concentration is between 48% and 52% by weight, or 9.8% vol.

[0270] - the DGME solvent, is diluted with DGME or DGEE and glycerol, with volume proportions of 50:40:10 - ink: DGEE / DGME:glycerol. The volume fraction thus achieved is 4.9% vol in copper nanoparticles.

[0271] Approach and contact are performed as described in Example 1, with a pipette with a tip diameter of 5 μm. The servo loop is deactivated.

[0272] The pillars are then baked at 150°C for 30 min on a hot plate under a nitrogen atmosphere.

[0273] The results obtained are summarized in the following table:

[0274] [Table 6]

[0275] Ve = Distance speed (pm / s) Vr = Breaking speed (pm / s)

[0276] Figure 7 shows the photo corresponding to test 32.

[0277] Comparative example 2

[0278] The commercial PVnanocell ink ref (Sycris IC50DM-7) whose composition indicated by the supplier includes:

[0279] - copper nanoparticles (d50 = 50 nm, d90 = 120 nm, determined by Multisizer®) coated with a layer of polyvinylpyrrolidone; their mass concentration is between 48% and 52% by weight, or 9.8% vol. the DGME solvent, is diluted with glycerol at 50-50 in volume proportions.

[0280] The volume fraction thus achieved is 4.9% vol in copper nanoparticles.

[0281] Following the same routine as before to form pillars, we manage to deposit ink lines and dots (see Figures 8A, 8B) containing nanoparticles with a 5 pm pipette but fail to create pillars, even at removal speeds as low as 0.01 pm / s.

[0282] Here the solvent is not volatile enough: even after complete evaporation of the DGME there remains enough glycerol to keep the ink liquid and prevent the nanoparticles from solidifying.

[0283] Example 7: Gold nanoparticles - commercial ink

[0284] A gold ink made in the laboratory and composed of:

[0285] - gold nanoparticles (d50 = 6 nm and d90 = 10 nm, determined by dynamic light scattering - DLS) coated with a layer of dispersant; their volume concentration is 0.4% vol.

[0286] - ethanol as component 1 of the first solvent, at a level of 59.6% vol,

[0287] - water as component 2 of the first solvent, at a level of 30% vol,

[0288] - glycerol as a second solvent, at a level of 10% vol, is injected into a pipette with a diameter of 1.5 or 8 pm, following the protocol detailed in example 1. The control loop is deactivated. The rupture speed is 100 pm / s.

[0289] The pillars are then baked at 200°C for 30 minutes on a hot plate.

[0290] The results obtained are summarized in the following table: [Table 7]

[0291] D = Pipette diameter (pm)

[0292] Ve = Distance speed (pm / s)

[0293] Figure 9 shows the photo corresponding to test 35.

[0294] Example 8: variation of the removal speed as a function of the pipette diameter

[0295] The ink from Example 1 is used to form pillars following the protocol detailed in Example 1. The maximum speed of pillar formation without meniscus rupture is shown in the graph in Figure 10A as a function of the diameter of the pipette used, and in the graph in Figure 10B as a function of the nanoparticle volume fraction. The diameter of the pipette varies from 1 to 30 pm. It can be seen that the larger the diameter of the pipette, the slower the removal speed must be to form pillars. The surface / volume ratio increases and the time required to evaporate the solvent increases with the size of the meniscus, and therefore the diameter of the pipette.

[0296] The volume fraction varies between 0 and 6% vol. The higher the volume fraction occupied by nanoparticles, the faster the speed of removal to form a pillar. Since the amount of solvent to evaporate is lower when the volume fraction of nanoparticles increases, solidification of the ink in the meniscus is achieved more quickly.

[0297] Example 9: conductive line connected to a pillar, in silver or copper

[0298] The inks of examples 4 (for silver) and 6 (for copper) are used here to deposit a conductive line and then a pillar; respectively tests 36 and 37.

[0299] The approach and contact are carried out as described in Example 1, with a pipette whose tip diameter is 5 μm. Once the pipette is in contact, the PLL loop is kept active in order to keep the pipette close to the surface and therefore to avoid rupture of the meniscus. The substrate is moved horizontally at a speed ranging from 1 to 1000 μm / s so as to deposit the ink along the path drawn by the pipette on the substrate. Once the line of nanoparticles is formed, the pipette is kept in contact for 1 s to 30 s, stationary, then the substrate is moved away from the pipette as described in Example 1 (the servo loop is deactivated). A pillar is thus obtained.

[0300] The pillars are then baked at 150°C for 30 min (under a nitrogen atmosphere for copper) on a hot plate.

[0301] The results obtained are summarized in the following table:

[0302] [Table 8]

[0303] Ve = Distance speed (pm / s)

[0304] Vr = Rupture velocity (pm / s)

[0305] Figure 11 shows the photo corresponding to test 37.

[0306] Example 10: Silver nanoparticles - commercial ink

[0307] The ink from Example 1 is used in this example.

[0308] It is injected into a 4 pm diameter pipette, following the protocol detailed in example 1. The control loop is activated. The rupture speed is 100 pm / s.

[0309] The pillars are then baked at 200°C for 30 min on a hot plate. A pillar with a diameter of 4 μm and a height of 280 μm (aspect ratio 70) is obtained. An SEM image of this pillar is shown in Figure 12.

Claims

CLAIMS 1. A method of manufacturing a three-dimensional nanostructure, the method comprising the following steps: - oscillating an injector (100) between a low position in contact with a substrate (20) and a high position out of contact with the substrate (20), the injector (100) comprising an ejection orifice (108) whose diameter is greater than 0.1 μm; - depositing an ink on the substrate (20) by means of the injector upon contact of the ejection orifice (108) of the injector (100) with the substrate (20), the ink comprising, in % by volume relative to the total volume of the ink: - less than 15% of nanoparticles chosen from metal nanoparticles, metal oxide nanoparticles, graphene oxide nanoparticles, quantum dots, or combinations thereof; - 0.5% to 5% dispersant, - at least 80% of a solvent capable of dispersing the metal nanoparticles to form the ink to be injected and sufficiently volatile to allow the ink to solidify once it is deposited; and - moving the injector (100) away from the substrate (20) at a speed less than or equal to 10 pm / s in a direction substantially perpendicular to the substrate while maintaining a flow of ink exiting the injector.

2. Method according to the preceding claim, in which the ink comprises from 0.05% to 15% by volume, advantageously from 0.2% to 10% by volume, more advantageously 4 to 8%, by volume of nanoparticles, relative to the total volume of the ink.

3. Method according to any one of the preceding claims, in which the diameter of the ejection orifice (108) ranges from 0.1 pm to 50 pm, advantageously from 0.5 pm to 30 pm.

4. A method according to any preceding claim, wherein the volatile solvent comprises a solvent selected from water, an alcohol, a glycol, a glycol ether, and mixtures thereof.

5. Method according to the preceding claim, in which the ink comprises from 80% to 99.45% by volume of said solvent, relative to the total volume of the ink.

6. Method according to any one of claims 4 or 5, in which the volatile solvent further comprises a second solvent, said second solvent being glycerol, advantageously in a content such that the ink comprises from 0% to 25% by volume of glycerol, relative to the total volume of the ink.

7. Method according to any one of the preceding claims, in which the metal of the metallic nanoparticles is chosen from silver, copper, gold, platinum, nickel, aluminum, cobalt, zinc, indium, palladium, their combinations or their alloys.

8. A method according to any one of claims 1 to 7, wherein the metal oxide of the metal oxide nanoparticles is selected from ZnO, TiCh, ITO (indium tin oxide) or V2O5.

9. Method according to any one of the preceding claims, in which the ink further comprises a dispersant, advantageously chosen from polyvinylpyrrolidone (PVP), gum arabic, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyallylamine (PAAm), polysodium styrene sulfonate (PSS), 3- (aminopropyl)trimethylsylane (APS), a fatty acid, cetyltrimethylammonium bromide (CTAB), tetraoctylammonium bromide (TOAB), sodium citrate, lauryl amine, dodecanethiol, mercapto-polyethylene glycol, mercapto-polypropylene glycol, or combinations thereof.

10. A method according to any preceding claim, wherein the injector moves away at a speed ranging from 1 pm / s to 10 pm / s during the step of moving the injector away from the substrate.

11. Method according to any one of the preceding claims, comprising a step of rupture between the three-dimensional nanostructure formed and the ink to be deposited, advantageously by moving the injector (100) away from the substrate (20) at a speed greater than 10 pm / s.

12. Method according to any one of the preceding claims, further comprising carrying out at least once a cycle of the following steps so as to form at least one second three-dimensional nanostructure: - relative displacement of the injector with respect to the substrate (20) in a direction parallel (x,y) to the substrate, and - carrying out the steps of any one of claims 1 to 11.

13. Method according to any one of the preceding claims, comprising a step of baking the substrate containing the formed nanostructure.

14. Product comprising a substrate on which is deposited at least one three-dimensional nanostructure obtained by means of a method according to one of the preceding claims, in which the nanostructure is in the form of a conical pin having a diameter which decreases in the direction of the height and meeting at least one of the following characteristics: - the base diameter varies from 0.5 pm to 50 pm; - the diameter of the top varies from 0.2 pm to 30 pm; - the angle of the slope with the vertical varies from 0.1° to 70°.

15. Product comprising a substrate on which is deposited at least one three-dimensional nanostructure obtained by means of a method according to one of claims 1 to 13, in which the nanostructure is in the form of a column having a height at least fifteen times greater than the diameter of the base, the diameter of the base being advantageously less than 1 μm.

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