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

Abstract

The invention relates to a method for 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 or combinations thereof;- 0.5% to 5% of 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 µm / s in a direction substantially perpendicular to the substrate while maintaining a flow rate of ink exiting the injector. The invention also relates to the nanostructures obtained by this method. Figure for the abstract: Fig. 1;

Description

Title of the invention: Method for manufacturing three-dimensional nanostructures having a high aspect ratio FIELD OF THE INVENTION

[0001] The invention relates to the manufacture 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 which is substantially constant or of rounded conical pins having a diameter which decreases in the height direction.

[0002] 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. STATE OF THE ART

[0003] Different techniques exist for producing three-dimensional nanostructures with an aspect ratio greater than 1.

[0004] 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 greater 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.

[0005] A three-dimensional nanostructure with an aspect ratio greater than 10:1 can be fabricated by direct 3D printing of a Newtonian silver ink that 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.

[0006] There are also techniques based on the polymerization of photosensitive solutions. They require the use of mixtures of a colloidal metal suspension and photosensitive monomers, monomers which polymerize during manufacture. The structure produced is, however, porous and has poor electrical conduction properties. These techniques can also be used for make molds for nanoimprint lithography (also known as “nanoimprint lithography” or NIL). The manufacturing process is then more expensive because it requires a mold for each size and arrangement of nanostructures.

[0007] There are also techniques based on the application of an electric field between a conductive substrate and a conductive suspension, such as electrodeposition techniques. They require the use of a conductive ink and support, in particular because of 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 AFM tip used.

[0008] Finally, there are techniques based on direct printing application in which the deposition of the metallic ink is monitored by a camera.

[0009] There is therefore a need for a method for manufacturing three-dimensional nanostructures having a better surface condition, allowing a shorter or simpler manufacturing time by eliminating the need for a camera-based deposition monitoring system. Statement of the invention

[0010] 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 that can be smoother or that can be layered, at a higher speed than in the prior art, and this without requiring a conductive substrate as in certain prior arts.

[0011] 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: - 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 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.

[0012] The expression “substantially perpendicular” means that the direction forms an angle of 90° ± 10° with the substrate which serves as its base.

[0013] The step of the method 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 method accelerates the manufacture of the pillars - by a few seconds per pillar - and can be implemented with any substrate, without galvanization constraints.

[0014] Such a method is advantageously supplemented by the following different characteristics taken alone or in combination:

[0015] - 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;

[0016] - the diameter of the ejection orifice (108) ranges from 0.1 pm to 50 pm, advantageously from 0.5 pm to 30 pm;

[0017] - the characteristic time of the evaporation of the solvent r corresponds to the following formula:

[0018] [Math.l] 2 D2 TP vap 'x / ™

[0019] with D the diameter of the ejection orifice (108), P vap the saturated vapor pressure of the solvent or solvent mixture, P sol the density of the solvent or solvent mixture, the volume fraction of nanoparticles;

[0020] - the volatile solvent comprises a solvent chosen from water, an alcohol, a glycol, a glycol ether, and mixtures thereof;

[0021] - the ink comprises from 80% to 99.45% by volume of said solvent, relative to the volume total ink;

[0022] - the volatile solvent further comprises a second solvent chosen from 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;

[0023] - the metal of the metallic nanoparticles is chosen from silver, copper, gold, platinum, nickel, aluminum, cobalt, their combinations or their alloys;

[0024] - the metal oxide of the metal oxide nanoparticles is chosen from ZnO, TiO2 or V2O5;

[0025] - 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;

[0026] - the injector moves away at a speed ranging from 1 pm / s to 10 pm / s during the step to move the injector away from the substrate;

[0027] - 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;

[0028] - the method comprises executing at least once a cycle of following steps of 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 the method previously described.

[0029] - the method comprises a step of baking the substrate containing the nanostructure formed.

[0030] The invention also relates to a product comprising a three-dimensional nanostructure obtained by means of a method such as has just been presented.

[0031] Such a product is advantageously completed by the characteristic according to which the nanostructure has a length at least ten times greater than the widths of the nanostructure.

[0032] In another variant, such a product is advantageously supplemented by the characteristic according to which the nanostructure has a diameter which decreases in the direction of the height. DESCRIPTION OF FIGURES

[0033] 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:

[0034] [Fig.l] is a schematic representation of the formation of the pillars;

[0035] [Fig.2] is a schematic representation of a system for manufacturing a three-dimensional nanostructure according to one of the embodiments of the invention;

[0036] [Fig.3] gives pictures of the shapes of pillars that can be obtained by the process according to the invention.

[0037] [Fig.4] gives pictures of the shapes of pillars obtained in test 3 (4A), in test 4 (4B) or the flattened dome according to test 8 (4C).

[0038] [Fig.5] gives a snapshot of the result after implementation of comparative example 1.

[0039] [Fig.6] gives pictures of the shapes of pillars obtained in example 6 (6A: D=5pm, 6B: D=10 pm);

[0040] [Fig.7] gives the photograph of the pillar obtained in test 33.

[0041] [Fig.8] gives two pictures of the result after implementation of the comparative example 2.

[0042] [Fig.9] gives the photograph of the pillar obtained in test 35.

[0043] [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.

[0044] [Fig. 11] gives the photograph of the pillar obtained in test 37. DETAILED DESCRIPTION OF THE INVENTION

[0045] A system for controlled deposit of an ink on any substrate has already been described in application WO2020 / 128310. The system described in this application allows the deposit of an ink having a shape defined by a length greater than or equal to 1 μm. The system comprises a mechanical resonator attached to an injector.

[0046] 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.

[0047] 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.

[0048] The three-dimensional nanostructure is formed by the localized evaporation at the outlet of the ejection orifice of the solvent present in the ink. As shown in [Fig.l]:

[0049] - 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 (IA);

[0050] - the ejection port of the injector and the substrate are spaced apart 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 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 (IB and IC);

[0051] - the ejection port of the injector and the substrate are spaced apart from each other at a speed greater than 10 pm / s to unhook the ejection orifice of the injector from the formed three-dimensional nanostructure (1D).

[0052] The ink used comprises metal nanoparticles or metal oxide nanoparticles or graphene oxide nanoparticles, also referred to as nanoparticles in the following, and a volatile solvent.

[0053] 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.

[0054] 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).

[0055] The nanoparticles are advantageously metallic nanoparticles whose metal is chosen from silver, copper, gold, platinum, nickel, aluminum, cobalt, their combinations or their alloys.

[0056] The metal oxide of the metal oxide nanoparticles is advantageously chosen from ZnO, TiO2, or V2O5.

[0057] 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 allowing the stability of the ink.

[0058] 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.

[0059] 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, dodecanethiol, mercapto-polyethylene glycol, mercapto-polypropylene glycol, or combinations thereof.

[0060] 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 the PVP is advantageously at least 8,000 g / mol, more preferably from 10,000 g / mol to 1,600,000 g / mol, even more preferably from 10,000 g / mol to 200,000 g / mol.

[0061] 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.

[0062] When the nanoparticles are gold nanoparticles, the dispersant is advantageously selected 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 the mercapto-polyethylene glycol is advantageously at least 100 g / mol, more advantageously from 400 g / mol to 2,000 g / mol.

[0063] The solvent is first of all a solvent allowing the dispersion of the nanoparticles, without agglomeration in particular, in the ink. The ink being most often a commercial ink, the solvents used are already solvents allowing the good dispersion of the nanoparticles. To these commercial inks, we will, in certain cases, add a miscible solvent allowing the volatility to be modified.

[0064] 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.

[0065] 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.

[0066] In addition to this ability to disperse the nanoparticles, the solvent must be sufficiently volatile to allow the formation of a solid phase. Indeed, it is desired that once contact has been made between the ejection orifice of the injector and the substrate, the solvent evaporates quickly enough to allow localized concentration / accumulation of nanoparticles while limiting, or even preventing, ink spreading on the substrate.

[0067] On the other hand, to avoid any blockage phenomenon at the outlet of the injector ejection orifice, the solvent must also not evaporate too quickly.

[0068] 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.

[0069] Thus, depending on the operating conditions, the ink will comprise one or more solvents, the solvents in this case being miscible with each other.

[0070] In particular, it is possible to provide for the addition of a second solvent of lower volatility to ensure sufficient handling time between the formation of two structures.

[0071] Without wishing to be limited, the inventors believe that the characteristic time of the evaporation of the solvent r corresponds to the following formula

[0072] [Math.2] 2 D2 TP vap 'x / ™

[0073] with D the diameter of the ejection orifice (108), P vap the saturated vapor pressure of the solvent or the mixture of solvents, P sol the density of the solvent or the mixture of solvents, the volume fraction of the nanoparticles.

[0074] Advantageously, the conditions of diameter of the ejection orifice, of saturated vapor pressure of the solvent or of the mixture of solvents, of density of the solvent or of the mixture of solvents and of volume fraction of the nanoparticles are such that the characteristic time of the evaporation of the solvent, r, varies from 0.1 s to 300 s, advantageously from 1 s to 30 s, more advantageously from 2 s to 10 s.

[0075] It is thus observed that when the volume fraction of nanoparticles in the ink increases, the volatility of the solvent must be reduced.

[0076] It is also noted that the removal rate must be reduced when the solvent has a lower evaporation rate.

[0077] 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 perform its role of dispersing the nanoparticles.

[0078] Examples of alcohol that may be mentioned include methanol, ethanol, isopropanol, 1-propanol, benzyl alcohol and terpineol.

[0079] Examples of glycol that may be mentioned include ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, diethylene glycol and triethylene glycol.

[0080] As an example of glycol ether, we can notably cite: - ethylene glycol ether, propylene glycol ether; - 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; - 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.

[0081] In particular, the solvent is chosen 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.

[0082] 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 1st solvent and second solvent, when present, as defined below.

[0083] This solvent, also called 1st solvent, can be used alone. Alternatively, it can be mixed with a less volatile solvent, called 2nd solvent.

[0084] As indicated, the ink may comprise a second solvent of much lower volatility compared to 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.

[0085] The presence of the second solvent is intended to prevent the ejection orifice from drying out and clogging too quickly. Depending on the humidity level of the air and the fraction volume 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.

[0086] Thus, it is for example 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.

[0087] Advantageously, the ink comprises, more advantageously consists of, four families of ingredients: - nanoparticles as previously described, in a volume concentration ranging from 0.05% vol to 15% vol, preferably between 4% vol and 8% vol; - the dispersant as previously described in a volume concentration ranging from 0.5% vol to 5% vol, preferably from 1% vol to 2% vol; - a first solvent chosen 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; - 0 to 25% vol of glycerol.

[0088] 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 said first solvent.

[0089] System for manufacturing a three-dimensional nanostructure

[0090] [Fig.2] represents an embodiment of a system 10 for manufacturing a three-dimensional nanostructure on a substrate 20.

[0091] 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. Reference may be made to this application for further details on the known aspects of the technique implemented.

[0092] The system 10 for manufacturing a three-dimensional nanostructure on a substrate 20 comprises a nanometric-sized injector 100.

[0093] 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.

[0094] The diameter of the ejection orifice 108 ranges from 0.1 to 50 microns, advantageously from 0.5 μm to 30 μm.

[0095] The system 10 also comprises a conveyor or movement means 160 adapted to move the substrate 20 relatively to the injector 100. The movement 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 movement means 160 can be a piezoscanner on which the substrate 20 is deposited. It may in particular be a three-axis piezoscanner with sub-nanometric displacement resolution.

[0096] The system 10 further comprises a mechanical resonator attached to the injector 100.

[0097] The mechanical resonator can be 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.

[0098] The system 10 further comprises a controller or control means 148 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.

[0099] The system 10 comprises the exciter means 142, which may be a piezoelectric exciter. This exciter is bonded to the mechanical resonator.

[0100] 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.

[0101] 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.

[0102] The control means 148 is further connected to a regulator or regulating means 146 adapted to adjust the contact between the protuberance 104 and the substrate 20 by controlling the oscillation of the mechanical resonator.

[0103] The system 10 comprises the regulator 146 which is a second PID corrector 2 and allows the adjustment of the contact using the conveyor or displacement means 160 to which it is connected.

[0104] Concerning 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 in such a way that the detected response of 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 instruction 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 the interactions with its environment.

[0105] 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.

[0106] 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.

[0107] Method for manufacturing a three-dimensional nanostructure

[0108] A manufacturing system as just presented makes it possible to implement a method according to the invention for manufacturing a three-dimensional nanostructure.

[0109] We will present a mode of implementation of this process.

[0110] 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.

[0111] Typically, the injector oscillates over an amplitude ranging from 0.5 to 100 nm, advantageously from 1 to 20 nm, during this step.

[0112] 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 protuberance 104 then oscillates between a low position in which the protuberance 104 is in contact with the substrate 20 and a high position in which the protuberance 104 and the substrate 20 are not in contact.

[0113] The resonance of the system consisting of the tuning fork, the piezoelectric exciter and the accelerometer can be measured so as to determine the resonant frequency of the tuning fork and its quality factor.

[0114] 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).

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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 [Fig.l]).

[0121] 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.

[0122] As indicated previously, the oscillation amplitude of the tuning fork, and therefore of the protuberance 104, is fixed between 0.5 nm and 100 nm.

[0123] The ink thus deposited on the substrate forms the basis of the three-dimensional nanostructure manufactured.

[0124] 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 beneficial to observe a primer time. This primer time advantageously varies from 1 s to 180 s.

[0125] 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.

[0126] The ink leaving 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.

[0127] As previously indicated, the speed of removal of the injector is adjusted so that the exiting ink solidifies quickly enough to serve as a deposition base for the ink exiting later.

[0128] 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.

[0129] Advantageously, once contact is established, the substrate 20 is moved away from the protuberance 104 according to one of the following two modes:

[0130] 1) the means of movement control loop 160 via the regulator 146 (PID corrector 2) is kept active:

[0131] 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 set 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 servo loop active and the pillar is continuously pulled from the tip of the ejection orifice 108. Deactivation of the servo loop of the displacement means 160 suspends the generation of the pillar.

[0132] 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).

[0133] 2) the control loop of the displacement means 160 via the regulator 146 (PID corrector 2) is disabled:

[0134] 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.

[0135] The pillars obtained according to this variant advantageously have a stratified appearance (figures 3B, 3D). If the speed of removal is varied, the pillar can be given a wavy shape.

[0136] In all cases, to detach the protuberance 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 moving away (>500 pm / s), the flatter the roof of the pillar will be (Figures 3C, 3D). Conversely, a slower moving away (<20 pm / s) gives the roof of the pillar a conical shape, and the slower the distance, the more elongated the cone will be (figures 3A, 3B).

[0137] The process allows a pillar manufacturing time of approximately a few seconds.

[0138] This method eliminates the need for a camera to monitor and control the deposit. This method eliminates the need for pressure on the ink to be deposited.

[0139] It is thus possible to manufacture nano-structured pillars having an aspect ratio greater than 1, advantageously ranging from 10:1 to 50:1, such as for example pillars 1 μm in diameter and 30 μm in length.

[0140] 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.

[0141] The shape of the pillars will depend on the operating conditions. As illustrated in Example 1 and in [Fig.3], pillars having the following characteristic shapes can be formed: - Smooth column of substantially constant diameter ending in a conical roof (figure 3A); - Stratified column of substantially constant diameter ending in a conical roof (figure 3B); - Smooth column of substantially constant diameter ending in a flat roof (figure 3C); - Stratified column of substantially constant diameter ending in a flat roof (figure 3D); - Smooth column with varying diameter giving a wavy shape (figure 3E); - Column showing alternating smooth zones and stratified zones (figure 3F); - Pillar in the form of a rounded conical pin with a diameter which decreases in the direction of the height (figure 3G).

[0142] 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.

[0143] 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: - 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 the process as presented previously.

[0144] 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.

[0145] At each execution of the cycle of steps, a new nanostructure is fabricated.

[0146] Once the pillar(s) have been formed, the method advantageously comprises a firing step. The conditions of this step may 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 may vary from 10 min to 2 h. For copper pillars, the temperature and duration conditions may be the same, it is just appropriate to operate in a non-oxidizing atmosphere, for example under argon, nitrogen, hydrogen. Photonic firing may also be carried out, which may be implemented in an ambient atmosphere even for copper pillars.

[0147] Advantageously, all the steps of the process are carried out at room temperature (18-22°C) and at atmospheric pressure.

[0148] 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.

[0149] 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.

[0150] The extension direction corresponds to the direction z not parallel to the substrate, advantageously substantially perpendicular, along which the injector is moved away from the substrate during the process.

[0151] The base diameter of the column, corresponding to its greatest width, is advantageously less than 10 μm, more advantageously less than 5 μm, even more advantageously less than 2 μm, such as for example 1 μm.

[0152] According to another variant, such a nanostructure is a pion as described previously.

[0153] 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 μm to 50 μm, more advantageously from 1 to 30 μm. The diameter of the top advantageously varies from 0.2 pm to 30 pm, more preferably 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 preferably from 10° to 45°.

[0154] Such a shape is of interest for the production of solder bumps in the packaging steps 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 step 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.

[0155] Advantageously, in any one of the variants, the substrate is non-conductive.

[0156] The following examples illustrate the invention.

[0157] Example 1: Silver nanoparticles - commercial ink

[0158] A commercial PVnanocell ink ref (Sycris™ I40DM-106), the composition of which 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. - 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.

[0159] 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 [Fig.2] of application WO 2020 / 128310. Firstly, the tip of the pipette is mechanically approached using micrometer probes, 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.

[0160] 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 (milliHerz).

[0161] The oscillation amplitude of the tuning fork (and therefore of the pipette) is fixed at 10 nm.

[0162] 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.

[0163] Once contact is established, the substrate is moved away from the pipette in one of the following two ways:

[0164] 1) the piezoscanner control loop is kept active:

[0165] 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 the FS by moving the substrate far enough away to return to the FS setpoint value set at 150 mHz. Thus, the creation of the pillar is initiated. This routine continues autonomously as long as the operator leaves the servo loop active and the pillar is continuously pulled from the tip of the pipette. Deactivation of the piezoscanner servo loop suspends the generation of the pillar.

[0166] To detach the pipette from the pillar, it is moved away at a speed of at least 10 pm / s.

[0167] 2) the piezoscanner servo loop is deactivated:

[0168] Immediately after the formation of the meniscus, the operator waits 1s to 60s on contact to initiate the formation of the pillar before manually moving the substrate away from the pipette using the control software. The distance increments range from 0.01 to 10 pm, giving moving away speeds ranging from 0.01 to 10 pm / s.

[0169] To detach the pipette from the pillar once the correct size has been obtained, proceed as in the previous point.

[0170] All process steps are carried out at room temperature (18-22°C) and at

[0171]

[0172] atmospheric pressure. The results [Tables 1 s obtained are summarized in the following table: Test D Ve Control Vr shape Height ( pm) Base diameter 1 1 0.1 Yes 10 Smooth column of substantially constant diameter ending in a flat roof 10 1 2 1 0.1 No, increments of 100 nm 10 Stratified column of substantially constant diameter 8 1 t constant terminating in a conical roof 3 7 2 Yes 100 Smooth column of approximately constant diameter of about 7 pm, terminating in a flat roof 55 10 4 7 1 No with 1 pm increments 100 Stratified column of approximately constant diameter of about 8 pm terminating in a flat roof 40 10 5 7 1 No with 1 pm increments 10 Stratified column of approximately constant diameter of about 8 pm terminating in a conical roof 50 10 6 7 3.2 No with 100 nm increments 100 Smooth column with a diameter varying from 6 to 10 pm giving a corrugated shape 105 10 7 7 5 No with 100 nm increments 10 Rounded conical peg with a diameter that decreases in the height direction. Vertical slope of 30 O 22 10 8 7 20 No 20 No column or peg. Flattened dome 3 10 9 10 10 No with 100 nm increments 10 Rounded conical peg with a diameter that decreases in the height direction. Vertical slope of 20 O 22 14 10 10 1 No with 1 pm increments 10 Layered column of substantially constant diameter of about 1 1 pm terminating in a rounded conical roof 55 15 11 10 1 No with 1 pm increments 100 Layered column of substantially constant diameter of about 1 1 pm terminating in a flat roof 50 15 12 30 0.01 Yes 10 Rounded conical peg with a diameter that decreases in the direction of height. Vertical slope of 15 O 50 150 13 30 10 No 10 No column or peg. Flattened dome 3 100

[0173] D = Pipette diameter (pm)

[0174] Ve = Distance speed (pm / s)

[0175] Vr = Rupture velocity (pm / s)

[0176] The following figures are given: - Figure 4A: A pillar obtained according to test 3; - Figure 4B: A pillar obtained according to test 4; - Figure 4C: the flattened dome according to test 8

[0177] With a pipette with a diameter of 30 μm, the ratio of deposition surface area to volume of ink to be deposited is higher. To allow faster solidification of the nanoparticles and thus to obtain a pillar having a constant diameter over its entire height, a more volatile solvent than DGME is required.

[0178] In test 8, the speed of removal is too fast to form a pillar.

[0179] During test 9, we manage to pull a pillar but not to form a column of substantially constant diameter.

[0180] The pillars are then cooked at 150°C for 30 min on a hot plate.

[0181] Example 2: Silver nanoparticles - diluted commercial ink

[0182] The ink of Example 1 is diluted with a similar solvent, DGEE, to obtain a volume concentration of nanoparticles of 5% vol (= 35% by weight).

[0183] 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.

[0184] The results obtained are summarized in the following table:

[0185] [Tables2] Test D Ve Increments Vr shape Height ( pm) Base diameter ( pm) 14 1.5 3 100 nm 10 Laminated column of substantially constant diameter ending in a rounded conical roof 5.5 1.5 15 8 1 1 pm 100 Laminated column of substantially constant diameter ending in a flat roof 30 10 16 8 1 10 nm 100 Smooth column of substantially constant diameter ending in a flat roof 22 9 17 8 10 100 nm 10 No column Rounded conical peg having a diameter that decreases in the direction of height. Vertical slope of 18°. 10 10 18 8 20 100 nm 20 No column or even peg Flattened lens 1 9

[0186] D = Pipette diameter (pm)

[0187] Ve = Distance speed (pm / s)

[0188] Vr = Rupture velocity (pm / s)

[0189] The ink being more diluted, and the quantity of liquid to be evaporated to obtain the solid phase of the nanoparticles being greater, the speed of removal is lower.

[0190] The pillars are then cooked at 150°C for 30 min on a hot plate.

[0191] Example 3: Silver nanoparticles - concentrated commercial ink

[0192] The ink of example 1 is centrifuged for 30 min at 7000 rpm so as to be able to remove the DGME solvent and increase the concentration of nanoparticles.

[0193] Glycerol is added as a second solvent to achieve the following formulation: - nanoparticles: 10% vol; - DGME: 65% vol; - glycerol: 25% vol.

[0194] 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 deactivated.

[0195] The results obtained are summarized in the following table:

[0196] [Tables3] Test D Ve Vr shape Height ( pm) Base diameter ( pm) 19 1.5 0.4 10 Laminated column of substantially constant diameter ending in a rounded conical roof 12 1.5 20 8 0.1 100 Smooth column of substantially constant diameter ending in a flat roof 35 11 21 8 0.1 10 Smooth column of substantially constant diameter ending in a rounded conical roof 11 12

[0197] D = Pipette diameter (pm)

[0198] Ve = Distance speed (pm / s)

[0199] Vr = Rupture velocity (pm / s)

[0200] 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.

[0201] The pillars are then cooked at 150°C for 30 min on a hot plate.

[0202] Example 4: silver nanoparticles - commercial ink

[0203] The ink used is the commercial PVnanocell ink ref (Sycris™ P75DB-1), the composition of which indicated by the supplier includes: - 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. - the DGBE solvent,

[0204] 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 control loop is deactivated.

[0205] The results obtained are summarized in the following table:

[0206] [Tables4] Test D Ve Vr shape Height ( pm) Base diameter ( pm) 22 1.5 1 10 Laminated column of substantially constant diameter ending in a rounded conical roof 4.5 2 23 5 0.3 10 Smooth column of substantially constant diameter ending in a rounded conical roof 36 7 24 5 0.2 100 Smooth column of substantially constant diameter ending in a flat roof 42 8 25 8 0.01 10 Rounded conical stud with a diameter that decreases in the direction of height. Vertical slope of 22°. 10 11

[0207] D = Pipette diameter (pm)

[0208] Ve = Distance speed (pm / s)

[0209] Vr = Rupture velocity (pm / s)

[0210] 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.

[0211] The pillars are then cooked at 150°C for 30 min on a hot plate. Comparative test 1#:

[0212] The ink of example 1 is centrifuged for 30 min at 7000 rpm so as to be able to remove the DGME solvent and increase the concentration of nanoparticles.

[0213] - nanoparticles: 16% vol;

[0214] - DGME: 84% vol;

[0215] The approach and contact are carried out as described in Example 1, with a pipette whose tip diameter is 8 μm. The pipette clogs too quickly for manage to form pillars. No matter how fast the pipette moves away, only a few particles are deposited on the substrate (see [Fig.5]).

[0216] Example 5: Copper nanoparticles - diluted commercial ink

[0217] The commercial PVnanocell ink ref (Sycris™ IC50DM-7), the composition of which is indicated by the supplier, includes: - 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. - the DGME solvent, is diluted with DGME or DGEE and glycerol, with the volume proportions 70:15:15 - ink:DGEE / DGME:glycerol. The volume fraction thus achieved is 6.5% vol in copper nanoparticles.

[0218] The approach and contact are carried out as described in Example 1, with a pipette whose tip diameter is 5 or 10 μm. The servo loop is deactivated.

[0219] The pillars are then baked at 150°C for 30 min on a hot plate under a nitrogen atmosphere.

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

[0221] [Tables5] Test D Ve Vr shape Height ( pm) Base diameter ( pm) 26 5 10 10 Rounded conical stud with a diameter that decreases in the direction of height Vertical slope of 16°. 7 5 27 5 1 10 Smooth column of substantially constant diameter ending in a rounded conical roof 48 7 28 5 1 100 Smooth column of substantially constant diameter ending in a flat roof 42 7 29 10 10 10 Rounded conical stud with a diameter that decreases in the direction of height. 10 12 Vertical slope of 26°. 30 10 100 100 No column or even a pedestal Flattened dome 3 11 31 10 1 100 Smooth column of approximately constant diameter ending in a flat roof 40 13

[0222] D = Pipette diameter (pm)

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

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

[0225] Examples of photos are given in [Fig.6]. Figure 6A: D=5pm, Figure 6B: D=10 pm.

[0226] Example 6: Copper nanoparticles - diluted commercial ink

[0227] The commercial PVnanocell ink ref (Sycris™ IC50DM-7), the composition of which is indicated by the supplier, includes: - 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 DGME or DGEE and glycerol, with the volume proportions 50:40:10 - ink:DGEE / DGME:glycerol. The volume fraction thus achieved is 4.9% vol in copper nanoparticles.

[0228] The approach and contact are carried out as described in Example 1, with a pipette whose tip diameter is 5 μm. The servo loop is deactivated.

[0229] The pillars are then baked at 150°C for 30 min on a hot plate under a nitrogen atmosphere.

[0230] The results obtained are summarized in the following table:

[0231] [Tableauxô] Test Ve Increments Vr shape Height ( pm) Base diameter ( pm) 32 0.15 10 nm 20 Smooth column of substantially constant diameter ending in a rounded roof 22 pm 7 33 1 1 pm 100 Stratified column of substantially constant diameter 20 pm 6 both ending in a flat roof

[0232] Ve = Distance speed (pm / s)

[0233] Vr = Rupture velocity (pm / s)

[0234] [Fig.7] gives the photo corresponding to test 32. Comparative example 2

[0235] The commercial PVnanocell ink ref (Sycris IC50DM-7) whose composition indicated by the supplier includes: - 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 50-50 in volume proportions.

[0236] The volume fraction thus achieved is 4.9% vol in copper nanoparticles.

[0237] Following the same routine as before for forming 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 small as 0.01 pm / s.

[0238] 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 solidification of the nanoparticles.

[0239] Example 7: gold nanoparticles - commercial ink

[0240] A gold ink made in the laboratory and composed of: - 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. - ethanol as component 1 of the first solvent, at a level of 59.6% vol, - water as component 2 of the first solvent, at a level of 30% vol, - glycerol as the 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 breakout speed is 100 pm / s.

[0241] The pillars are then baked at 200°C for 30 min on a hot plate.

[0242] The results obtained are summarized in the following table:

[0243] [Tables7] Test D Ve shape Height (pm) Base diameter (pm) 34 1.5 0.15 Laminated column of substantially constant diameter ending in a conical roof 8 5 35 8 0.05 Laminated column of substantially constant diameter ending in a flat roof 17 9

[0244] D = Pipette diameter (pm)

[0245] Ve = Distance speed (pm / s)

[0246] [Fig.9] gives the photo corresponding to test 35.

[0247] Example 7: variation of the removal speed as a function of the pipette diameter

[0248] The ink of Example 1 is used to form pillars by following the protocol detailed in Example 1. The maximum speed of formation of a pillar without rupture of the meniscus 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 volume fraction of nanoparticles.

[0249] 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.

[0250] The volume fraction varies between 0 and 6% vol. The higher the volume fraction occupied by the nanoparticles, the faster the speed of removal to form a pillar. The quantity of solvent to be evaporated being less when the volume fraction in nanoparticles increases, the solidification of the ink in the meniscus is reached more quickly.

[0251] Example 8: conductive line connected to a pillar, in silver or copper

[0252] The inks of examples 4 (for silver) and 6 (for copper) are used here to deposit a conductive line then a pillar; respectively tests 36 and 37.

[0253] The approach and the 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.

[0254] The pillars are then baked at 150°C for 30 min (under a nitrogen atmosphere for the copper) on a hot plate.

[0255] The results obtained are summarized in the following table:

[0256] [Tables8] Test Ve Increments Vr shape Height ( pm) Base diameter ( pm) 36 0.2 10 nm 100 Silver conductive line connected to a smooth column of substantially constant diameter ending in a flat roof 26 9 37 1 100 nm 100 Copper conductive line connected to a smooth column of substantially constant diameter ending in a flat roof 20 7

[0257] Ve = Distance speed (pm / s)

[0258] Vr = Rupture velocity (pm / s)

[0259] [Fig. 11] gives the photo corresponding to test 37.

Claims

Claims

1. A method of manufacturing a three-dimensional nanostructure having an aspect ratio greater than 1, 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) having a diameter 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 or combinations thereof;- 0.5% to 5% of 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 solidification of the ink 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. A method according to the preceding claim, wherein 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. A method according to any preceding claim, wherein 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. A method according to the preceding claim, wherein the ink comprises from 80% to 99.45% by volume of said solvent, relative to the total volume of the ink.

6. A method according to claim 4 or 5, wherein the volatile solvent further comprises a second solvent, the second solvent being glycerol, advantageously in a content such that the ink comprises from more than 0% to 25% by volume of glycerol, relative to the total volume of the ink.

7. A method according to any preceding claim, wherein the metal of the metal nanoparticles is selected from silver, copper, gold, platinum, nickel, aluminum, cobalt, combinations thereof or alloys thereof.

8. A method according to any one of claims 1 to 6, wherein the metal oxide of the metal oxide nanoparticles is selected from ZnO, TiO2 or V2O5.

9. A method according to any preceding claim, wherein the ink further comprises a dispersant, 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.

10. A method according to any preceding claim, wherein the injector moves away at a rate of 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 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.

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. A method according to any preceding claim, comprising a step of baking the substrate containing the formed nanostructure.

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