EP3245010A1

EP3245010A1 - Method for forming a compact film of particles on the surface of a carrier liquid

Info

Publication number: EP3245010A1
Application number: EP16700955.4A
Authority: EP
Inventors: Olivier Dellea
Original assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2015-01-16
Filing date: 2016-01-14
Publication date: 2017-11-22
Also published as: CN107107098A; KR20170105070A; FR3031683A1; US20180001340A1; FR3031683B1; WO2016113324A1

Abstract

The invention concerns an improved method for forming a compact film of particles (4) on the surface of a carrier liquid (16), comprising the following steps: - positioning at least one particle support (40) in the carrier liquid (16), the support comprising at least one solidified portion in which the particles (4) are trapped and that is made from at least one cooled liquid, the melting of the support (40) in said carrier liquid resulting in the release of the particles (4) on the surface of said carrier liquid; and - organising the released particles (4) in such a way as to obtain the compact film of particles on the surface (16') of the carrier liquid (16).

Description

PROCESS FOR FORMING COMPACT PARTICLE FILM

AT THE SURFACE OF A CARRIER LIQUID

DESCRIPTION

TECHNICAL AREA

The invention relates to the field of processes for forming a compact film of particles on the surface of a carrier liquid, the compact film obtained is generally intended to be deposited on a substrate, preferably in scrolling.

More specifically, the invention relates to the formation of a compact film of particles, also called ordered particles film, preferably of the monolayer type and whose particle size may be between a few nanometers and several hundred micrometers. The particles, preferably non-spherical in shape, may for example be silica particles, glass fibers, carbon nanotubes, or gallium nitride fibers. In this respect, it is noted that recent studies have shown that the use of non-spherical particles / colloids is a very promising avenue in the design of materials with novel properties. Colloids can be in slender forms such as fibers, threads, tubes or rods, or in more complex forms such as polygons, tetrapods, cubes, prisms, etc.

The invention relates to the formation of simple compact films, or to the formation of structured compact films, this structuring aimed at putting the film into shape in order, for example, to integrate other particles, and / or objects. Another possibility is to provide hollow areas of particles, surrounded by the film which remains ordered. In the case of the integration of objects in the film, it is in particular to manufacture devices of a hybrid nature, such as for example, ca ptors. As an indication, a hybrid device associates by definition on the same substrate objects having various functions, for example electronic, optical, electro-optical, piezoelectric, thermoelectric, mechanical, etc.

The objects to be integrated into the particle film are for example:

active electronic components, such as transistors, microprocessors, integrated circuits, etc. ;

passive components of the electronics, such as resistors, capacitors, diodes, photodiodes, coils, conductive tracks, welding preforms, etc. ;

optical components, such as lenses, microlenses, diffraction gratings, filters, etc. ;

- batteries, micro-batteries, micro-batteries, photo-detectors, solar cells, RFID system, etc. ;

nano or micrometric particles or aggregates, active or passive, for example of the oxides, polymers, metals, semiconductors, Janus type (particles having two faces of different types or properties), nanotubes, etc.

Nevertheless, the invention relates more to the formation of simple compact films rather than to the formation of structured compact films.

More generally, the invention has applications in many fields such as mechanics, fuel cells, optics, photonics, polymer coating, chips, MEMs, organic and photovoltaic electronics, heat exchangers, heat, sensors such as chemical sensors, tribology, etc.

STATE OF THE PRIOR ART

Many techniques are known for the formation and deposition of compact films of particles on a substrate, the latter being or not running, and flexible or rigid nature.

In general, there is provided an accumulation and transfer zone fed with particles, which float on a carrier liquid contained in this same zone. The ordered particles in the transfer zone, forming a monolayer of particles called thin film, are pushed by the arrival other particles as well as by the circulation of the carrier liquid to an outlet of this zone through which they reach the substrate. They are then deposited on the moving substrate. To do this, a capillary bridge usually ensures the connection between the substrate and the carrier liquid contained in the accumulation and transfer zone.

Under normal operating conditions of the installation, in the accumulation and transfer zone, the particles are kept ordered thanks in particular to the pressure exerted upstream by the moving particles intended to later reach this transfer zone. The cohesion of the particle scheduling is further ensured by weak forces of capillary or electrostatic type. When the particle transfer zone is connected upstream to an inclined ramp on which the particles coming from a dispensing device run, the same particles present on the inclined ramp exert pressure on the particles contained in the transfer zone, and which thus allow, in cooperation with the capillary forces of proximity, to keep the ordering of the particles in this zone, until the deposit on the substrate, by capillarity or direct contact.

In this regard, it is noted that the technique of particle compression scheduling is particularly known from the document Lucio Isa et al., "Particle Lithography from Colloidal Self-Assembly at Liquid_Liquid Interfaces", acsnano, VOL. 4 ^■ NO. 10 ^■ 5665-5670 ^■ 2010 document Markus Retsch, "Manufacture of Large-Area, Transferable Colloidal Monolayers Utilizing Self-Assembly at the Air / Water Interface", Macromol. Chem. Phys. 2009, 210, 230-241, or Still from the document Maria Bardosova, "The Langmuir-Blodgett Approach to Making Colloidal Photonic Crystals from Silica Spheres", Adv. Mater. 2010, 22, 3104-3124. The compression technique using an inclined ramp is more specifically described in document CA 2 695 449. With this particular technique, it is the kinetic energy associated with the moving particles on the ramp which allows these are automatically arranged on the same ramp, when they impact the front of particles, also located on the inclined ramp. The scheduling is thus established on the ramp, then preserved when the ordered particles enter the transfer zone, thanks to the continuous supply of the particles coming to impact the front. The kinetic energy required for the self-sequencing of the particles is here brought by the inclined ramp carrying the carrier liquid and the particles. In this regard, it is noted that the particles are generally suspended in a solvent placed in the dispensing device, which takes for example the shape of a nozzle. This dispensing device is arranged to deliver the particles to the surface of the carrier liquid, at a reservoir zone placed upstream of the inclined ramp and communicating with the inlet thereof.

Alternatively, the particles suspended in a solvent can be dispensed directly to the surface of the carrier liquid, using a pipette or a peristaltic pump. The particles dispersed on the surface of the carrier liquid are then ordered using barriers or similar elements to bring them closer to each other, in order to obtain the compact film of particles to be subsequently deposited on the substrate.

Nevertheless, these particle dispensing techniques suffer from several disadvantages mentioned below, which are moreover accentuated when the particles are of non-spherical shape.

First, if the particles contained in the dispensing device sediment quickly, it may be difficult or impossible to obtain a uniform and uniform dispensing on the carrier liquid. This sedimentation may even accidentally lead to the obstruction of the end of the dispensing device, such as the disposable tip of a pipette. In addition, particles are likely to be deposited inside the dispensing device, thereby distorting the actual amount of particles introduced to the surface of the carrier liquid.

On the other hand, in the particular case of a pipette, multiple factors can influence the amount of solvent / particles actually aspirated and dispensed. These include, for example, the temperature and pressure of the outside air, the density of the solvent, the value of the dead volume, and so on. All of these factors can influence the amount of aspiration / dispensing, which affects the accuracy and repeatability of operations. STATEMENT OF THE INVENTION

The invention therefore aims to at least partially meet the disadvantages identified above. To do this, the invention firstly relates to a process for forming a compact film of particles on the surface of a carrier liquid, comprising the following steps:

placing at least one support of particles in said carrier liquid, said support comprising at least one solidified part in which the particles are trapped and which is made from at least one cooled liquid, said support being melted in said carrier liquid leading to the release of particles on the surface of this carrier liquid; and

arranging the released particles to obtain said compact film of particles on the surface of the carrier liquid.

The invention is thus remarkable in that it breaks drastically with conventional techniques for dispensing particles on the surface of a carrier liquid. The technique specific to the invention has the advantage of not being exposed to the sedimentation risks mentioned above, nor to the risk of obstruction of a dispensing device of the pipette type, which is no longer necessary.

The accuracy and repeatability of the operations are advantageously improved, since the amount of particles released during melting of the support is accurate, without risk of losses. In addition, the technique proposed by the invention is likely to be applied in a similar manner whatever the shape and size of the particles, and regardless of the nature of the solvent in which the particles are optionally placed at the time of initiation. of the method according to the invention. It is thus compatible with all colloid / particle solutions, even those with non-spherical shapes.

Overall, the invention greatly improves the reliability of the operation of introducing the particles to the surface of the carrier liquid.

In addition, it is preferably made so that the support floats in the carrier liquid. This makes it possible to approach as closely as possible the particles released from the surface of the carrier liquid, on which they must be ordered before being deposited on a substrate. Thanks to the progressive melting / melting of the support, it advantageously creates a progressive exemption of the particles.

Furthermore, it is noted that the solidified support initially has a negative temperature. Due to the temperature gradient and the phase change during melting, the fluid does not remain at rest, in particular because of the descent of the cold fluid. The liquid movements thus promote a surface agitation favorable to the dispersion of the particles.

Finally, it is noted that the local lowering of the temperature causes an increase in the surface tension of the carrier liquid located near the ice cube. This phenomenon is profitable because it participates in maintaining the particles on the surface of the carrier liquid, that is to say at the gas / liquid interface.

The invention also has at least one of the following optional features, taken alone or in combination.

Said particles are preferably of non-spherical shape, and preferably of any of the forms mentioned above. Nevertheless, the invention remains applicable to particles of any shape and type.

Preferably, said particles are of micrometric or nanometric size, preferably having a large dimension of between 1 nm and 500 μιη. By way of illustrative examples, the particles / colloids used may be of the oxide particle type (SiO 2, ZnO, Al 2 O 3, etc.), polymers (latex, PMMA, polystyrene, etc.) or metal (Au, Cu, alloys). , etc.). It can also be particles composed of several materials: polymer / metal, oxide / metal, oxide / polymer, metal / oxide / polymer, or even particles Janus.

Even if the size range of the particles is preferably between 1 nm and 500 μιη, it is also possible to use glass fibers or other fibers mentioned above, for example with a diameter of between 0.01 and 10 μιη, and lengths ranging from 10 to 4000 μιη. Other particles of the silicon type or graphene sheets or hBN sheets are also conceivable, without departing from the scope of the invention.

Preferably, the carrier liquid is deionized water. Preferably, said solidified part of the support, in which the particles are trapped, is made at least from water. More generally, the solidified part is preferably made from a water-based liquid, for example water containing additives. This promotes the flotation of the support, the benefits of which have been mentioned above.

Preferably, said solidified part of the support, in which particles are trapped, is also produced from a solvent in which said particles were initially present, in suspension.

The presence of the solvent, in solidified form or simply in the form of liquid film on the solidified part made from water, is advantageous. Indeed, due to the difference in surface tension between the water and the solvent, the interfacial tension gradient induces hydrodynamic instabilities whose consequences are a local agitation of the two liquids. This agitation phenomenon, known as the Marangoni effect, promotes the dispersion of particles on the surface of the carrier liquid.

As mentioned above, the step of placing said at least one particle support is preferably carried out so that this support floats on the surface of said carrier liquid. Even more preferentially, the particles are grouped together at a loaded surface of the support, and the step of placing said at least one support of particles is carried out so that said loaded face of the support is substantially at the level of the surface of the carrier liquid. This further facilitates the dispersion of the particles on the surface of the carrier liquid.

Preferably, the method comprises a preliminary step of manufacturing said at least one support in which said particles are trapped. This manufacture can be implemented according to several techniques.

According to a first manufacturing technique, said manufacture of said support in which said particles are trapped comprises the following operations:

a) introducing a quantity of water into a container containing a solvent immiscible in water and of a density lower than that of water, with said particles arranged in suspension in said solvent, so that the particles migrate to the interface between the water and the solvent, possibly with stirring; b) cooling so as to obtain said support comprising at least one solidified part in which said particles are trapped.

Preferably, between operations a) and b), an operation for extracting all or part of the solvent is carried out. Alternatively, the cooling operation also aims to totally or partially solidify said solvent introduced into the container.

According to a second technique, said manufacture of said support in which said particles are trapped comprises an operation for forming a block of solidified water. The manufacture then comprises an operation of pouring on the solidified water block, a solvent in which said particles are arranged in suspension. Instead of pouring it, the solvent can be dispensed, sprayed or sprayed.

The assembly can then be used as is, or this assembly formed by the solidified water block and the solvent incorporating particles, is cooled so that said solidified part of the support comprises at least a part of said solvent, and preferably all of it.

According to yet another alternative for this second technique, said manufacture of said support in which said particles are trapped then comprises an operation of pouring directly, on the solidified water block, said particles in the form of powder.

According to a third manufacturing technique, said manufacture of said support in which said particles are trapped comprises the following operations:

a) introducing the particles into the bottom of a container;

b) introducing water into the container so as to keep the particles in the bottom of the container;

c) cooling so as to obtain said support comprising at least one solidified part in which said particles are trapped.

The invention also relates to a method of depositing a compact film of particles on a substrate, comprising the implementation of the method of forming a compact film of particles on the surface of a carrier liquid, followed by a step of depositing the compact film of particles on a substrate.

Preferably, said step of depositing the compact film of particles is implemented on a moving substrate, that is to say with the film gradually deposited on a moving substrate. Alternatively, the deposition of all the particles of the film on the substrate can be carried out simultaneously, for example by approaching the substrate of the film, from above or below, in the manner of the Langmuir-Schaefer technique.

Other advantages and features of the invention will become apparent in the detailed non-limiting description below.

BRIEF DESCRIPTION OF THE DRAWINGS

This description will be made with reference to the appended drawings among which:

- Figure 1 shows an installation for implementing the method according to the invention, in longitudinal section;

- Figure 2 shows a schematic top view of the installation shown in Figure 1;

FIGS. 2a to 5b show diagrammatically different steps of a method for forming and depositing a compact film of particles according to a preferred embodiment of the invention, implemented using the installation shown on FIGS. the preceding figures; and

- Figures 6 to 8 show different possibilities of manufacturing the particle carrier implemented in the process shown schematically in Figures 2a to 5b.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring firstly to FIGS. 1 and 2, there is shown an installation 1 for the formation of a compact film of particles and its transfer onto a substrate, preferably in a scrolling fashion. The particles concerned, not shown in FIGS. 1 and 2, are intended to be initially placed in suspension in a solvent. These particles have a size that can be between a few nanometers and several hundred micrometers. The particles or colloids are preferably of non-spherical shape. They can be in slender forms such as fibers, threads, tubes or rods, or in more complex forms such as polygons, tetrapods, cubes, prisms, polygons, etc. For reasons of simplification of the following figures, the particles will be represented in the form of simple tubes, with dimensions greater than the actual dimensions.

The materials that can be envisaged for these particles depend on the desired applications. It may for example be silica particles, glass fibers, carbon nanotubes, or gallium nitride fibers. Other particles of interest can be made of metal or metal oxide such as platinum, TiO 2, polymer such as polystyrene or PMMA, carbon, etc., or even particles composed of several materials.

More specifically, in the preferred embodiment, the particles are glass fibers with a diameter of about 10 μιη, and whose length is of the order of 4 mm. It is noted that the invention is particularly applicable to wire elements whose large dimension is more than ten times greater than the small dimension. As will be detailed below, the particles are intended to be placed in suspension in a solvent, here of the butanol or chloroform type, the proportion of the medium being about 7 g of particles per 200 ml of solvent.

The installation also comprises a liquid conveyor 10, receiving a carrier liquid 16 on which the particles are intended to float. The carrier liquid 16 is preferably deionized water. The conveyor 10 includes a zone 14 for accumulation and transfer of particles, the bottom is substantially horizontal, or slightly inclined so as to promote the emptying of the installation, if necessary.

Zone 14 has a particle outlet 26, defined by means of two lateral flanges 28 holding the carrier liquid 16 in zone 14. These flanges 28, opposite and at a distance from one another, extend parallel to a main direction shown schematically by the arrow 30 in Figures 1 and 2. This direction 30 corresponds to that of the moving the compact particle film during its transfer to the substrate, as will be detailed below.

The bottom of the downstream portion of the zone 14 has a plate slightly inclined upstream relative to the horizontal direction, for example a value of the order of 5 to 10 °. It is the downstream end of this same plate, also called "blade", which partly defines the output of the particles 26.

The installation 1 is also provided with a substrate conveyor 36, for putting the substrate 38 in motion. This substrate can be rigid or flexible. In the latter case not shown, it can be set in motion on a roller whose axis is parallel to the outlet 26 of the zone 14, near which it is located.

Whatever the configuration envisaged, the substrate 38 is intended to run very close to the outlet 26, so that the particles reaching this outlet can be easily transferred to this substrate, via a capillary bridge 42, also called meniscus, which the connected to the carrier liquid 16. The capillary bridge 42 is provided between the carrier liquid 16 which is located at the outlet 26, and a portion of the substrate 38 conforming to the guide / driving roll 40. Alternatively, the substrate may be in contact directly with the transfer zone, without departing from the scope of the invention. The capillary bridge mentioned above is then no longer required.

For information, in the case where the substrate is rigid and the objects to be transferred are also rigid and can not adapt to an angle break during transfer, it may be advantageous to immerse the substrate in the liquid of the accumulation zone and transfer 14, and draw in this configuration. This makes it possible to maximize the angle formed between the horizontal plane of the liquid of the zone 14, and the plane of the substrate.

In the example shown in the figures, the width of the substrate 38 is slightly greater than the width of the zone 14 and its output 26. The width of the zone 14 also corresponds to the maximum width of the particle film that it is possible to deposit on the substrate 38. This width can be of the order of 25 to 30 cm. The width of the substrate on which the particles must be deposited may however be less than the width of the zone 14, without departing from the scope of the invention. A method of forming and depositing a compact particle film according to a preferred embodiment of the invention will now be described with reference to Figures 2a to 5b.

Firstly, with reference to FIGS. 2a and 2b, a support 40 of particles is placed in said carrier liquid 16. Initially, this support 40 comprises at least one solidified part in which the particles are trapped. 4, this solidified part being made from at least one cooled liquid. Preferably, the support is, before its introduction into the carrier liquid 16, fully solidified, and comprises a lower portion 42 corresponding to frozen pure water, and an upper portion 44 corresponding to the solidified solvent. Alternatively, the solvent may be in the form of a liquid film resting on frozen pure water. Be that as it may, the particles 4 are trapped at the interface between the two upper 44 and lower 42 parts. The manufacture of the support 40 will be detailed later.

The support 40, in its initial state, has for example a cylindrical shape of circular section, about 5 mm thick and about 40 mm in diameter. Higher dimensions can be retained, without departing from the scope of the invention. The particles 4 are grouped together at a loaded surface of the support, corresponding to the upper surface 40 ', which is substantially flat and oriented horizontally.

Due to its composition essentially based on frozen water, the support 40 floats when it is introduced into the carrier liquid 16. This introduction is carried out so that the loaded face 40 'of the support 40 is substantially at the level of the surface 16 'of the carrier liquid 16, or close thereto. This goal is easily achieved when the solidified solvent thickness 44 is low. Nevertheless, the solvent may not be completely solidified, but for example brought to the viscous state.

Once introduced into the carrier liquid 16, the support 40 is melted and melts gradually, releasing the particles 4, which can then also be dispersed progressively on the surface of the carrier liquid 16, as shown schematically in FIGS. 3a and 3b. . Due to the temperature gradient and the phase change during the melting of the support 40, the fluid does not remain at rest, in particular because of the descent of the cold fluid. The movements of liquid within the zone 14 thus promote a surface agitation favorable to the dispersion of the particles 4. In addition, the local lowering of the temperature causes an increase in the surface tension of the carrier liquid 16 located near the This phenomenon is profitable because it participates in the maintenance of the particles 4 on the surface 16 'of the carrier liquid 16. In addition, because of the difference in surface tension between the water and the molten solvent, the gradient of interfacial tension induces hydrodynamic instabilities which also participate in the local agitation of the two liquids, favoring the dispersion of the particles on the surface 16 'of the carrier liquid.

It is noted that several supports 40 can be introduced successively or simultaneously into the carrier liquid, in order to benefit from the quantity of desired particles. A pump system (not shown) can also regulate the total volume of liquid in the zone 14, taking into account the water supply by the supports 40 introduced into this zone.

When all the particles 4 are present on the surface 16 'in the accumulation and transfer zone 14, they are pushed towards the outlet 26 by a barrier 50 or a similar element. This barrier 50 is indeed moved in the direction 30 so that the particles 4 are ordered by being held downstream by the substrate 38 forming a stop.

This scheduling via the barrier 50 and the substrate 38 generates a compact film 4 'of particles 4, as has been schematized in FIGS. 4a and 4b.

Alternatively, it is possible to implement a ramp conveyor as described above, with which the particles are ordered automatically, without assistance, thanks in particular to their kinetic energy and capillary forces used at the time of impact on the particle front on the ramp. In this case, the supports 40 are then preferentially placed in the conveyor tank, upstream of the ramp. Other scheduling means known to those skilled in the art are also conceivable, without departing from the scope of the invention.

The desired ordering is such that the compact film obtained has a structure similar to a "hexagonal compact" structure in the case of spheres, in which each particle 4 is surrounded and contacted by six other particles 4 in contact with each other. It is then indifferently spoken of compact film of particles, or film of ordered particles.

Once the film 4 'is obtained on the surface of the carrier liquid 16 in the zone 14, it can be proceeded with a structuring step of this film, which will not be detailed here, but which is known to the man of the job. It consists for example in the placing of objects on the compact film.

Subsequently, the substrate 38 is put in motion, carried out at the same time as the further movement of the barrier 50 downstream, so as to progressively deposit the film 4 'on the same substrate 38, via the bridge capillary 42. This step of depositing the film 4 ', also called the transfer step, has been shown schematically in FIGS. 5a and 5b. Indeed, when the substrate 38 begins to scroll, the film 4 'is deposited there through the outlet 26 and through the capillary bridge 42, in the manner of that described in CA 2 695 449. A solution contact rather than capillary bridge is also possible, without departing from the scope of the invention.

To facilitate the deposition and adhesion of the particles 4 on the substrate 38, for example made of polymer, there may be provided thermal annealing subsequent to the transfer. This thermal annealing is for example carried out at 80 ° C, using a low-temperature matt rolling film based on polyester, for example sold under the reference PERFEX-MATT ™, of thickness 125μιη. The advantage of such a film as a substrate is that one of its faces becomes sticky at a temperature of the order of 80 ° C, which facilitates the adhesion of the particles 4 thereon. More precisely, at this temperature, the particles 4 sink into the softened film 38, and thus allow direct contact with the film, which leads to their bonding. Alternatively, the substrate 38 may be of the silicon, glass or piezoelectric film type.

During the transfer, the linear velocity of the substrate 38, also called pulling speed, can be of the order of 0.1 cm / min to 100 cm / min.

Referring now to FIG. 6, there is shown a first technique for manufacturing the support 40.

First, it is provided in a container 60 in which is arranged the solvent 3 incorporating the particles 4 in suspension. A given quantity of pure water is then introduced into the container 60. The solvent 3, butanol, is immiscible in water and of a density lower than that of water. Also, after introduction of pure water, the particles 4 migrate to come together in a horizontal plane at the interface between the water 5 above, and the solvent below. Migration can be promoted by agitation in the container.

According to a first possibility, the assembly 60 'is then directly cooled so as to obtain the support 40 mentioned above. The cooling temperature is then preferably lower than the melting point of the solvent, so that the solidified part of the support integrates both the pure water and the solvent, with the particles trapped at the interface.

According to another possibility, it is carried out a solvent extraction operation, so as to keep only a very thin layer above the water, or even to remove all of this solvent. The assembly 60 "is then frozen, so as to obtain the support 40, the solidified portion of pure water incorporates the particles 4. The remaining film 3 'of solvent that remains can be kept in the liquid state at low temperature before the introduction of the support 40 into the carrier liquid, or can also be solidified if the cooling temperature is sufficiently low.

According to a second technique of manufacturing the support 40 shown diagrammatically in FIG. 7, an operation is first carried out for forming a block of solidified solid water 70 in a container 60. Next, an operation consisting in pour into the container 60 and the block of water solidified 70, a solvent 3 in which the particles 4 are in suspension. This leads the particles 4 to migrate to the interface between the solvent 3 and the solidified water block 70, to be trapped on the upper surface thereof. The delivery of the particles to the interface can also be obtained by decantation. Then, the excess solvent is here also preferably removed, so that only a very thin layer of solvent remains with the particles arranged at the interface between this layer and the ice. Removal of the solvent may be by pipetting, or by gravity flow.

The assembly then forms the support 40 which can then be introduced as is in the carrier liquid.

According to another possibility, the resulting assembly 60 'can be cooled below the melting temperature of the solvent 3, so that the whole of the support 40 is solidified before it is introduced into the carrier liquid.

According to another possibility, after obtaining the solidified water block 70, it can be implemented an operation of pouring directly, on the upper surface of the block 70, the particles 4 in the form of powder. These particles 4, when they come into contact with the upper surface of the block 70, are trapped by the latter.

Finally, with reference to FIG. 8, a third manufacturing technique of the support 40 is schematized, which consists first of introducing particles 4 into the bottom of a container 60. Next, water 5 is poured into the container 60 so as to keep the particles 4 in the bottom of the container, and pouring the water with a low flow rate. Finally, the assembly is cooled and solidified in order to obtain the support 40. The solidified part of the latter then consists of a block of water in which the particles 4 are trapped on the lower surface. When this support is introduced into the carrier liquid, it is preferably returned so that the surface charged with particles constitutes the upper support surface 40.

Of course, various modifications may be made by those skilled in the art to the invention which has just been described, solely by way of non-limiting examples.

Claims

A process for forming a compact film of particles (4) on the surface of a carrier liquid (16), characterized in that it comprises the following steps:

placing at least one carrier (40) of particles in said carrier liquid (16), said support comprising at least one solidified part in which the particles (4) are trapped and which is made from at least a cooled liquid, said support (40) melting in said carrier liquid leading to the release of the particles (4) on the surface of this carrier liquid; and

- Scheduling the released particles (4) so as to obtain said compact film of particles on the surface (16 ') of the carrier liquid (16).

2. Method according to claim 1, characterized in that said particles (4) are of non-spherical shape.

3. Method according to claim 1 or claim 2, characterized in that said particles (4) are of micrometric or nanometric size, preferably having a large dimension of between 1 nm and 500 μιη.

4. Method according to any one of the preceding claims, characterized in that the carrier liquid (16) is deionized water.

5. Method according to any one of the preceding claims, characterized in that said solidified part of the support (40), in which the particles (4) are trapped, is made at least from water (5).

6. Method according to claim 5, characterized in that said solidified portion of the support (40), in which the particles (4) are trapped, is also produced from a solvent (3) in which said particles were initially present. (4), in suspension.

7. Method according to any one of the preceding claims, characterized in that the step of placing said at least one particle carrier (40) is performed such that this support floats on the surface (16 ') of said carrier liquid (16).

8. Method according to claim 7, characterized in that the particles (4) are grouped together at a loaded face (40 ') of the support (40), and in that the step of placing said at least one a particle carrier (40) is formed such that said loaded face (40 ') of the carrier is substantially at the surface (16') of the carrier liquid.

9. Method according to any one of the preceding claims, characterized in that it comprises a prior step of manufacturing said at least one support (40) in which are trapped said particles (4).

10. Process according to claim 9, characterized in that said manufacture of said support (40) in which said particles (4) are trapped comprises the following operations:

a) introducing a quantity of water (5) in a container (60) containing a solvent (3) immiscible in water and of a density lower than that of water, with said particles (4) arranged in suspending in said solvent (3), so that the particles (4) migrate at the interface between the water and the solvent;

b) cooling so as to obtain said support (40) comprising at least one solidified part in which said particles (4) are trapped.

11. The method of claim 10, characterized in that it is implemented, between operations a) and b), an extraction operation of all or part of the solvent (3).

12. The method of claim 10, characterized in that the cooling operation also aims to completely or partially solidify said solvent (3) introduced into the container (60).

13. The method of claim 9, characterized in that said manufacture of said support (40) wherein are trapped said particles (4) comprises an operation for forming a solidified water block (70).

14. The method of claim 13, characterized in that said manufacture of said support in which said particles are trapped then comprises an operation of pouring, on the solidified water block (70), a solvent (3) in which said particles (4) are arranged in suspension.

15. Method according to claim 14, characterized in that the assembly (60 ') formed by the solidified water block (70) and the solvent (3) integrating particles (4), is cooled so that said solidified portion of the support comprises at least a portion of said solvent (3).

16. The method of claim 13, characterized in that said manufacture of said support in which said particles are trapped then comprises an operation of pouring directly, on the block of water solidified (70), said particles (4) to the powder state.

17. The method of claim 9, characterized in that said manufacture of said support (40) in which are trapped said particles (4) comprises the following operations:

a) introducing the particles (4) into the bottom of a container (60);

b) introducing water (5) into the container (60) so as to keep the particles (4) in the bottom of the container; c) cooling so as to obtain said support (40) comprising at least one solidified part in which said particles (4) are trapped.

18. A method of depositing a compact film (4 ') of particles (4) on a substrate, comprising the implementation of the process for forming a compact film of particles (4) on the surface of a carrier liquid (16) according to any one of the preceding claims, followed by a step of depositing the compact film (4 ') of particles (4) on a substrate (38).

19. deposition process according to claim 18, characterized in that said deposition step of the compact film (4 ') of particles is implemented on a substrate (38) in scrolling.