Acoustic levitation device

Abstract

The invention relates to an acoustic levitation device comprising a set of ultrasonic emitters, referred to as emitters, which are arranged so that each emits an acoustic wave focused at a centre of the acoustic device, wherein the set of emitters is arranged so as to obtain stationary acoustic waves, the intensity of which is maximum at the centre of the levitation device, and wherein the levitation device comprises two domes facing one another. Each dome comprises a first group of ultrasonic emitters, referred to as emitters, forming a cap that extends between a pole and a stabiliser, and a second group of ultrasonic emitters, referred to as emitters, forming the stabiliser and extending from the cap in the direction of a plane of the device, referred to as the median plane, which is perpendicular to the axis connecting the pole of each of the domes, referred to as the axis of revolution, and which is located equidistantly between the two poles. The stabilisers are arranged so as to form at least two pairs of emitters each comprising two subgroups of emitters located on either side of the median plane, wherein one subgroup of emitters of a pair belonging to the stabiliser of one dome is facing the other subgroup of emitters of the pair belonging to the stabiliser of the other dome. The emitters of the cap of each of the domes are arranged so as to emit an acoustic wave that has a first frequency f1 and the emitters of the stabiliser of each of the domes are arranged so as to emit an acoustic wave that has a frequency f2 different from f1. The two subgroups of emitters of one of the pairs of emitters are arranged so as to emit acoustic waves, a phase of which differs from a phase of the acoustic waves emitted by the two subgroups of emitters of another of the pairs.

Description

[0001] DESCRIPTION

[0002] Acoustic levitation device

[0003] Technical field

[0004] The present invention relates to the field of levitation devices.

[0005] The present invention relates, in particular, to a levitation device for the characterization of materials at high temperatures, typically temperatures above 800°C. For example, the study of metals in the liquid state is a key step in metallurgy. In practice, this step corresponds to the adjustment of the chemical composition of the alloy as well as to the operations necessary for the elimination of inclusion defects, immiscible elements in the alloy which degrade its usage properties.

[0006] Mastering industrial tools for the development of new generations of alloys requires a perfect knowledge of thermophysical properties at very high temperatures, as well as an understanding of the mechanisms of inclusion defect genesis. Furthermore, knowledge of thermophysical properties in the liquid state is particularly critical in additive metallurgy, whether for developing powders or at the heart of the 3D printing process.

[0007] It is necessary to study liquid metal in detail at very high temperatures to precisely characterize certain thermophysical properties, for example viscosity or surface tension, or even the reactive phenomena at the origin of inclusions. Such an approach poses great difficulties on the experimental level.

[0008] State of the prior art

[0009] The use of a crucible in which the metal to be analyzed is brought to a liquid state is known in the state of the art. Beyond the difficult-to-access operating conditions, which can be from 1500 to 2000 °C, the alloys are very reactive and there is no crucible that can guarantee the absence of pollution of the sample in the liquid state by the crucible.

[0010] Also known in the state of the art is the use of levitating the alloy in order to eliminate any potential chemical pollution from a crucible.

[0011] Among these techniques, we know induction levitation-melting: it is generated by a vertical coil. The strong coupling between levitation and heating imposes a reduced heating temperature range. In addition, the induced forces generate internal flows that are detrimental to the study of molten metals. This technique is only applicable to metals. Finally, this technique requires adapting the coil to each type of material studied.

[0012] Aerodynamic levitation is also known. This technique involves lifting the material by a jet of gas under the sample. Heating is provided independently by a laser. The technique is well suited to the intended objectives, but it does have drawbacks. The sample is partially hidden by the nozzle expelling the gas, and the flow of gas around the sample generates a flow on the surface of the sample.

[0013] Electrostatic levitation is also particularly suitable for studying liquid metal. However, this technique is difficult to implement. Furthermore, it is limited to metals and difficult to adapt to poorly conductive materials.

[0014] Currently, no acoustic levitation device can maintain the levitation of high-density metals in the liquid state at temperatures above 700°C. The main obstacle is related to the use of a single high-power source coupled with a reflector. However, the speed of waves in gas varies greatly with temperature. With such a system, heating systematically causes strong disturbances in the acoustic pressure field.

[0015] An aim of the invention is, in addition, to propose an acoustic levitation device:

[0016] - allowing the handling of any type of metal alloy, and / or

[0017] - allowing the levitating object to be stabilized, and / or

[0018] - allowing an object to be manipulated with micrometric precision, and / or

[0019] - allowing the manipulation of a solid or liquid object, and / or

[0020] - allowing a sample to be studied over a wide temperature range and up to temperatures of 2500°C, and / or

[0021] - allowing the study of any type of sample, whatever its density, and / or

[0022] - not requiring complex electronic control means or feedback loop, and / or

[0023] - easy to use, and / or

[0024] - inexpensive and easy to implement.

[0025] Presentation of the invention To this end, an acoustic levitation device is proposed comprising a set of ultrasonic emitters, called transmitters, each arranged to emit an acoustic wave focused at a center of the acoustic device, the set of emitters is arranged to obtain standing acoustic waves whose intensity is maximum at the center of the levitation device. The levitation device comprises two facing domes. Each dome comprises:

[0026] - a first group of ultrasonic emitters, called transmitters, forming a cap extending between a pole and a stabilizer,

[0027] - a second group of ultrasonic emitters, called emitters, forming the stabilizer and extending from the cap towards a plane of the device, called the median plane, which is perpendicular to the axis connecting the pole of each of the domes, called the axis of revolution, and which is located equidistant from the two poles.

[0028] The stabilizers are arranged to form or comprise, preferably the emitters of each stabilizer are arranged to form, at least two pairs of emitters each comprising two sub-groups of emitters located on either side of the median plane, a sub-group of emitters of a pair belonging to the stabilizer of a dome is opposite the other sub-group of emitters of the pair belonging to the stabilizer of the other dome, each sub-group of emitters comprises at least one emitter.

[0029] Preferably, the emitters of the cap of each of the domes are arranged to emit an acoustic wave having a first frequency fi and the emitters of the stabilizer of each of the domes are arranged to emit an acoustic wave having a frequency f2 different from fi. More preferably, the acoustic levitation device further comprises a control unit arranged so that the emitters of the cap of each of the domes are arranged to emit an acoustic wave having a first frequency fi and the emitters of the stabilizer of each of the domes are arranged to emit an acoustic wave having a frequency f2 different from fi.

[0030] Preferably, the two subgroups of transmitters of one of the pairs of transmitters are arranged to emit acoustic waves, one phase of which differs from a phase of the acoustic waves emitted by the two subgroups of transmitters of at least one other of the pairs. More preferably, the control unit is further arranged so that a phase of the acoustic waves emitted by the two subgroups of transmitters of one of the pairs of transmitters differs from a phase of the acoustic waves emitted by the two subgroups of transmitters of at least one other of the pairs.

[0031] Preferably, the ultrasonic emitters are piezoelectric emitters. Preferably, the center of the acoustic device is a geometric center of the levitation device.

[0032] Preferably, the center of the levitation device is intersected by the axis of maximum intensity of the acoustic wave emitted by each of the transmitters.

[0033] The domes can be ovoid in shape, preferably spherical in shape.

[0034] Preferably, the concave part of one dome is located opposite the concave part of the other dome.

[0035] Preferably, the first and second groups of emitters of a dome constitute the set of emitters of the dome.

[0036] Preferably, each emitter of the first group of emitters of one dome is radially opposite another emitter of the first group of emitters of the other dome. Preferably, each emitter of the second group of emitters of one dome is radially opposite another emitter of the second group of emitters of the other dome.

[0037] Preferably, the pole of a dome is, or constitutes, also a pole of the levitation device.

[0038] Preferably, the cap of a dome considered extends between the pole and the stabilizer of the dome considered in a direction extending from the pole of the dome considered towards the median plane.

[0039] Preferably, the axis connecting the pole of each of the domes is an axis of symmetry of the levitation device. The axis connecting the pole of each of the domes can be defined as the axis connecting the two poles of the levitation device.

[0040] Preferably, an object or sample to be analyzed is intended to levitate in the center of the levitation device.

[0041] Preferably, each dome comprises at least two subgroups of transmitters.

[0042] Preferably, the phase of the wave emitted by one of the pairs of transmitters differs from the phases of the standing waves emitted by each of the other pairs of transmitters.

[0043] Preferably, a pair of transmitters emits a standing wave having a phase different from a phase of a standing wave emitted by another of the pairs of transmitters. Preferably, each pair of transmitters emits a standing wave having a different phase.

[0044] Preferably, the emitters of the stabilizer, and preferably the emitters of the cap, of each dome are distributed or extend over 360°. Preferably, the emitters of the stabilizer, and preferably the emitters of the cap, of each dome are distributed or extend over the entire part of the dome formed by the stabilizer. Preferably, the emitters of the stabilizer of each dome form a slice or a portion of a sphere whose axis of revolution coincides with the axis of revolution of the levitation device.

[0045] Preferably, the first group of emitters comprises at least two rows of emitters. Preferably, the second group of emitters comprises at least one row of emitters.

[0046] Preferably, a row is defined as a curved line or a ring. Preferably, one row is parallel to another row. Preferably, the rows are parallel to each other and / or parallel to the median plane.

[0047] Preferably, a row forms a ring. Preferably, a center of a ring of emitters, more preferably the center of each of the rings, coincides with or belongs to the axis of revolution. Preferably, the rings form a stack of rings distributed along the axis of revolution.

[0048] Preferably, the levitation device comprises, more preferably the stabilizers comprise or are arranged to form, at least one pair of transmitter pairs. Each pair of transmitter pairs is arranged such that each subgroup of a pair of a pair of pairs considered is radially opposite a subgroup of the other pair of the pair of pairs considered.

[0049] The control unit can be arranged so that a phase of the acoustic waves emitted by the two couples of a pair of couples is identical.

[0050] The levitation device may comprise at least three pairs. Preferably, the levitation device comprises at least three pairs and the control unit may be arranged so that a phase of the acoustic waves emitted by one of the pairs is identical to a phase emitted by another of the pairs.

[0051] The levitation device may comprise at least two pairs of couples. Preferably, the levitation device comprises at least two pairs of couples and the control unit may be arranged so that a phase of the acoustic waves emitted by two couples, preferably by both couples of a pair of couples, is identical.

[0052] Preferably, the control unit is arranged so that a phase of the acoustic waves emitted by the two couples of a pair of couples, preferably by each pair of couples, is different. Preferably, the control unit is arranged so that the acoustic waves emitted by the two couples of a pair of couples, preferably by each pair of couples, are in phase opposition.

[0053] Preferably, a portion of sphere comprising the median plane and extending between the stabilizer of each of the domes is devoid of an emitter, the portion of sphere forms an annular opening providing access to the center of the levitation device.

[0054] Preferably, the sphere portion forms a row or, more preferably, a ring.

[0055] Preferably, access to the center of the device is understood to mean access to the object intended to levitate.

[0056] Preferably, the annular opening extends over 360°, i.e. over the entire circumference of the levitation device. Preferably, access to the center of the levitation device, from outside the levitation device, is permitted from the entire circumference of the levitation device. Preferably, access to the center of the levitation device, from outside the levitation device, is achieved at or near the median plane.

[0057] Preferably, the first group of transmitters of each dome is arranged so that the generated standing acoustic waves levitate an object intended to levitate at the center of the levitation device.

[0058] Preferably, the second group of emitters of each dome is arranged so that the generated standing acoustic waves laterally stabilize the object intended to levitate.

[0059] Preferably, according to the invention, laterally is understood to mean a direction extending along an axis perpendicular to the axis of revolution.

[0060] Preferably, the control unit is arranged so that the phase of the acoustic wave emitted by a given pair of transmitters is greater or less than the phase of the acoustic wave emitted by a pair of transmitters adjacent and / or consecutive, by rotation around or relative to the axis of revolution, to the given pair of transmitters.

[0061] Preferably, the control unit is arranged so that the phase of the acoustic wave emitted by a given pair of emitters, or respectively a given pair of pairs of emitters, is greater or less than the phase of the acoustic wave emitted by a pair of emitters, or respectively a pair of pairs of emitters, adjacent and / or consecutive, by rotation around or relative to the axis of revolution, to the given pair of emitters, or respectively to the given pair of pairs of emitters.

[0062] Preferably, the term "pair of transmitters, or respectively pair of pairs of transmitters, adjacent and / or consecutive" is understood to mean a pair of transmitters, or respectively a pair of pairs of transmitters, which is adjacent and / or consecutive, by rotation around the axis of revolution in the clockwise or counterclockwise direction, to a given pair of transmitters, or respectively to a given pair of pairs of transmitters.

[0063] Preferably, the control unit is arranged so that the phase of the acoustic wave emitted by the at least two pairs of transmitters increases or decreases, preferably by successive increments, from a given pair of transmitters to an adjacent pair of transmitters.

[0064] Preferably, the phase of the acoustic wave emitted by the at least two pairs of transmitters increases or decreases by the same successive increment or by the same successive increment value from a given pair of transmitters to an adjacent pair of transmitters.

[0065] Preferably, the control unit is arranged so that the phase of the acoustic wave emitted by each pair of emitters, or respectively by each pair of pairs of emitters, increases or decreases, preferably by successive incrementation, from a given pair of emitters, or respectively from a given pair of pairs of emitters, to an adjacent pair of emitters, or respectively to a pair of pairs of emitters.

[0066] Preferably, the frequency fi is higher or lower than the frequency f2 by at least 10%, preferably by at least 20%, more preferably by at least 30%, more preferably by at least 40% and advantageously by at least 50%.

[0067] Preferably, the frequency fi is higher or lower than the frequency f2 by at least 5 kHz, more preferably by at least 10 kHz, more preferably by at least 15 kHz.

[0068] According to the invention, there is also provided an acoustic levitation method comprising the steps of:

[0069] - emit acoustic waves having a first frequency fi, the acoustic waves of frequency fi are emitted by a first group of ultrasonic transmitters forming a cap extending between a pole and a stabilizer of each of two domes, arranged opposite one another, of an acoustic levitation device, the acoustic levitation device comprises a set of ultrasonic transmitters, called transmitters, arranged to emit an acoustic wave focused at a center of the acoustic device, the set of transmitters is arranged to obtain standing acoustic waves whose intensity is maximum at the center of the levitation device,

[0070] - emit acoustic waves having a second frequency f2 different from fi, the acoustic waves of frequency f2 are emitted by a second group of ultrasonic transmitters forming the stabilizer of each of the two domes and extending from the cap towards a plane of the device, called the median plane, which is perpendicular to the axis connecting the pole of each of the domes and which is located equidistant from the two poles.

[0071] Preferably, the stabilizers form at least two pairs of emitters located on either side of the median plane, a subgroup of emitters of a pair belonging to the stabilizer of a dome is opposite the other subgroup of emitters of the pair belonging to the stabilizer of the other dome. Preferably, each subgroup of emitters comprises at least one emitter.

[0072] Preferably, a phase of the acoustic waves of frequency f2 emitted by a pair of transmitters differs from a phase of the acoustic waves emitted by at least one other pair of transmitters.

[0073] Preferably, the method comprises the step of, more preferably for each pair of transmitter pairs, emitting by a pair of transmitters of a pair of transmitter pairs, acoustic waves whose phase is higher or lower than the phase of the acoustic waves emitted by the other pair of the pair of transmitter pairs.

[0074] Preferably, the method comprises the step of emitting, by a given pair of transmitters, acoustic waves whose phase is greater or less than the phase of the acoustic waves emitted by a pair of transmitters adjacent to and / or following the given pair of transmitters.

[0075] Preferably, the method comprises the step of emitting, by a given pair of transmitters, or respectively by a given pair of pairs of transmitters, acoustic waves whose phase is higher or lower than the phase of the acoustic waves emitted by a pair of transmitters, or respectively by a pair of pairs of transmitters, adjacent to and / or consecutive to the given pair of transmitters, or respectively to the given pair of pairs.

[0076] Preferably, the method comprises the step of emitting, by the at least two pairs of transmitters, acoustic waves whose phase increases or decreases, preferably by successive increments, from a given pair of transmitters to an adjacent pair of transmitters.

[0077] Preferably, the phase of the acoustic wave emitted by the at least two pairs of transmitters increases or decreases by the same successive increment or by the same successive increment value from a given pair of transmitters to an adjacent pair of transmitters.

[0078] Preferably, the method comprises the step of, more preferably for each pair of transmitters, or respectively for each pair of transmitter pairs, emitting, by a pair of transmitters, or respectively by a pair of transmitter pairs, acoustic waves whose phase increases or decreases, preferably by successive incrementation, from a given pair of transmitters, or respectively from a given pair of transmitter pairs, to an adjacent pair of transmitters, or respectively from a pair of transmitter pairs.

[0079] Preferably, the phase of the acoustic wave emitted by a pair of emitters, or respectively by at least one pair of pairs of emitters, increases or decreases by the same successive increment or by the same successive increment value from a given pair of emitters, or respectively from a given pair of pairs of emitters, to an adjacent pair of emitters, or respectively to a pair of pairs of emitters.

[0080] Preferably, the method comprises the step of varying over time, by an identical or proportional gradient, the phase of the acoustic wave emitted by each of the pairs of transmitters so as to prevent rotation or to cause controlled rotation or to prevent translation, along an axis perpendicular to the axis of revolution, or to cause controlled translation, along an axis perpendicular to the axis of revolution, of an object intended to levitate.

[0081] Preferably, the method comprises the step of varying over time, by an identical or proportional gradient, the phase of the acoustic wave emitted by each pair of transmitters or by each of the pairs of pairs of transmitters so as to prevent rotation or to cause controlled rotation or to prevent translation, along an axis perpendicular to the axis of revolution, or to cause controlled translation, along an axis perpendicular to the axis of revolution, of an object intended to levitate.

[0082] Preferably, the method comprises the step of applying an active rotation of the phase of the acoustic wave emitted by each of the pairs of transmitters and / or by each of the pairs of pairs of transmitters, in the clockwise or counterclockwise direction, so as to prevent rotation or to cause controlled rotation of an object intended to levitate.

[0083] The active rotation of the phase of the acoustic wave emitted by each of the pairs of emitters and / or, respectively, by each of the pairs of pairs of emitters can be defined as a coordinated and / or synchronous and / or proportional variation of the phase of the acoustic wave emitted by the pairs of emitters relative to each other and / or, respectively, by the pairs of pairs of emitters relative to each other.

[0084] Preferably, the method comprises the step of introducing an offset between a value of the phase of the acoustic wave emitted by one of the pairs of emitters of a pair of pairs relative to a value of the phase of the acoustic wave emitted by the other pair of the pair of pairs.

[0085] Preferably, the levitation device according to the invention is suitable, more preferably is particularly suitable, more preferably is designed and particularly advantageously is specially designed, for implementing the levitation method according to the invention.

[0086] Any characteristic of the levitation device according to the invention can be directly transposed to the levitation method according to the invention and vice versa.

[0087] Description of figures

[0088] Other advantages and particularities of the invention will appear on reading the detailed description of implementations and embodiments which are in no way limiting, and the following appended drawings:

[0089] [Fig. 1] FIGURE 1 is a schematic representation of a side view section of an embodiment of the acoustic levitation device according to the invention, [Fig. 2a] FIGURE 2a is a schematic representation in side view of the caps of the acoustic levitation device according to the embodiment,

[0090] [Fig. 2b] FIGURE 2b is a schematic representation in side view of the couples of the stabilizers of the acoustic levitation device according to the embodiment,

[0091] [Fig. 2c] FIGURE 2c is a schematic side view showing the caps and stabilizer torques of the acoustic levitation device according to the embodiment,

[0092] [Fig. 2d] FIGURE 2d is a schematic representation in top view illustrating a cap and the subgroups of a stabilizer of a dome of the acoustic levitation device according to the embodiment,

[0093] [Fig. 3a] FIGURE 3a is a sectional side view of an embodiment of the acoustic waves generated by the caps of the acoustic levitation device according to the embodiment,

[0094] [Fig. 3b] FIGURE 3b is a sectional side view of an embodiment of the acoustic waves generated by the stabilizers of the acoustic levitation device according to the embodiment,

[0095] [Fig. 3c] FIGURE 3c is a sectional side view of the embodiment of the acoustic waves generated by the acoustic levitation device according to the embodiment,

[0096] [Fig. 4] in FIGURE 4 are presented three sectional images in top view, in the median plane, of the acoustic waves emitted, according to three distinct embodiments, by the stabilizers of the acoustic levitation device according to the embodiment,

[0097] [Fig. 5] FIGURE 5 shows, on the left, an image of a steel ball being melted and levitated in the acoustic levitation device with contribution from the stabilizers and, on the right, an image of the steel ball being melted and levitated in the acoustic levitation device without contribution from the stabilizers. Description of the embodiments

[0098] The embodiments described below being in no way limiting, it will be possible in particular to consider variants of the invention comprising only a selection of the described characteristics, isolated from the other described characteristics (even if this selection is isolated within a sentence comprising these other characteristics), if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art. This selection comprises at least one characteristic, preferably functional without structural details, or with only a part of the structural details if this part only is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art.

[0099] With reference to FIGURES 1 and FIGURES 2a, 2b, 2c and 2d, an embodiment of the acoustic levitation device 1 according to the invention is presented. The levitation device 1 comprises a set of ultrasonic transmitters 2, called emitters 2. The transmitters 2 are arranged to each emit an acoustic wave focused at a center 3 of the acoustic device 1. The ultrasonic transmitters 2 used are manufactured by Manorshi® under the references MSO-P1640H12T and MSO-P1625H12T. The set of transmitters 2 is arranged to obtain standing acoustic waves whose intensity is maximum at the center 3 of the levitation device 1. The embodiment presented is a non-limiting example of a possible arrangement of the transmitters 2.A person skilled in the art will understand the concept of a standing acoustic wave as being a superposition of two acoustic waves, propagating along the same axis and in an opposite direction, the zero-pressure nodes of which are fixed in space. According to the non-limiting embodiment, the acoustic levitation device 1 comprises fifty-eight emitters 2. Each emitter 2 of a dome 41, 42 is radially opposite a different emitter 2 of the other dome 41, 42.

[0100] The levitation device 1 comprises two domes 41, 42 facing each other. An axis of revolution 5 connects the poles 61, 62 of each of the domes 41, 42. A median plane 7 perpendicular to the axis of revolution 5 is located equidistant between the poles 61, 62. According to the embodiment, the domes 41, 42 are spherical.

[0101] Each dome 41, 42 comprises a first group 411, 421 of emitters 2 forming a cap 81, 82 extending between a pole 61, 62 and a stabilizer 91, 92. The first group 411, 421 of each cap 81, 82 of each dome 41, 42 comprises 54 emitters. Each emitter 2 of a cap 81, 82 of a dome 41, 42 is radially opposite a different emitter 2 of the other cap 81, 82 of the other dome 41, 42.

[0102] Each dome 41, 42 comprises a second group 412, 422 of emitters 2 forming the stabilizer 91, 92. The second group 412, 422 of emitters 2 extends between the cap 81, 82 of each dome 41, 42 and in the direction of the median plane 7. The second group 412, 422 of emitters of each cap 81, 82 of each dome 41, 42 comprises 54 emitters. Each emitter 2 of a stabilizer 2 of a dome 41, 42 is radially opposite a different emitter 2 of the other stabilizer 91, 92 of the other dome 41, 42.

[0103] According to the embodiment and advantageously, the emitters 2 of the first group 411, 421 cover or form a paving of or are distributed over, preferably evenly or homogeneously, the whole of each cap 81, 82. According to the embodiment and advantageously, the emitters 2 of the second group 412, 422 cover or form a paving of or are distributed over, preferably evenly or homogeneously, the whole of each stabilizer 91, 92.

[0104] According to the non-limiting embodiment, the first group 411, 421 of emitters 2 of each dome 41, 42 comprises six rings of emitters 2, one center of which coincides with the axis of revolution 5. The second group 412, 422 of emitters 2 comprises two rings of emitters 2, one center of which coincides with the axis of revolution 5. The center 3 of the acoustic levitation device 1 is located at a distance of approximately eight centimeters (cm) from the emitters 2. The acoustic levitation device 1 according to the embodiment is arranged for samples whose size is between one and three millimeters (mm). Any type of sample, and in particular high-density samples, for example Platinum with a density of 21.5, could be levitated in a controlled manner with the acoustic levitation device 1 according to the invention.

[0105] The levitation device 1 comprises a volume or a space zone 10, extending between the two domes 41, 42, devoid of emitters 2. The space zone 10 constitutes a portion of a sphere 10 or a ring 10. The portion of a sphere 10 comprises the median plane 7. The portion of a sphere 10 extends between the two stabilizers 91, 92. Preferably, the portion of a sphere 10 is devoid of any solid element or solid part. Thus, the portion of a sphere 10 constitutes or forms an annular opening 10 offering 360° access to the center 3 of the levitation device 1. In this way, access to the center 3 of the levitation device 1 is possible over the entire periphery of the levitation device 1.

[0106] Those skilled in the art will understand that the acoustic device 1 is intended to be powered by one or more power supplies without the latter necessarily being an integral part of the invention. In practice, and in a non-limiting manner, the caps 81, 82 are intended to be powered by a power supply separate from the power supply intended to power the stabilizers 91, 92. The acoustic levitation device 1 may comprise a control unit and / or a processing unit without the latter necessarily being an integral part of the invention. The control unit may be arranged, among other things, to control and / or modulate the output parameters, for example a voltage and / or a frequency and / or a phase and / or a power of a signal intended to power one or more transmitters 2, of the power supply(s). By way of non-limiting example, the control unit may be or may comprise a microcontroller.

[0107] The levitation of an object under the effect of acoustic waves causes instabilities and disturbances inherent in the process of levitation by acoustic waves to appear, in particular due to the geometric irregularities of the sample. In addition, under certain experimental conditions of study of the sample, in particular when it is heated or a fortiori melted, additional instabilities, such as for example flows of hot gases and the geometric deformation of the sample, appear. To overcome these instabilities and disturbances, the emitters 2 of the cap 81, 82 of each of the domes 41, 42 emit an acoustic wave having a first frequency fi and the emitters 2 of the stabilizer 91, 92 of each of the domes 41, 42 emit an acoustic wave having a frequency f2 different from fi.According to the non-limiting embodiment, the acoustic waves emitted by the caps 81, 82 have the same frequency f1 which is 40 kHz and the acoustic waves emitted by the stabilizers 91, 92 have the same frequency f2 which is 25 kHz. This characteristic makes it possible to avoid coupling between the acoustic waves emitted by the caps 81, 82 and the acoustic waves emitted by the stabilizers 91, 92. Thus, this characteristic makes it possible to decorrelate the effect of the caps 81, 82 from the effect of the stabilizers 91, 92. This absence of coupling allows the arrangement of the caps 81, 82 to have the effect of levitating the object by countering gravity. This absence of coupling allows the arrangement of the stabilizers 91, 92 to have the effect of laterally stabilizing the object by countering instabilities or disturbances in the horizontal plane.This provides increased control of the levitation and allows the sample to be confined to the center 3 of the levitation device 1, limiting or even eliminating lateral movements of the sample. It should be noted that the frequency f1 could just as easily be lower than the frequency f2. Those skilled in the art will be able to adapt the frequencies according to the size of the sample intended to levitate.

[0108] The levitation of a liquid object under the effect of acoustic waves also causes the sample to be crushed or flattened vertically under the effect of its own weight and under the effect of the acoustic waves, countering the effect of gravity, ensuring the levitation of the sample. This effect is inherent in the acoustic levitation devices of the state of the art. The characteristic of the levitation device 1 according to which the emitters 2 of the cap 81, 82 of each of the domes 41, 42 emit an acoustic wave which has a frequency f1 different from a frequency f2 of a wave emitted by the emitters 2 of the stabilizer 91, 92 also makes it possible to overcome this effect of crushing the poles of the levitating sample.

[0109] The emitters 2 of the second group 412, 422 of emitters of each dome 41, 42 are arranged so that the stabilizers 91, 92 form at least two pairs of emitters 2. For example, the use of two pairs of emitters will make it possible to act on two lateral directions, preferably perpendicular. The use of three pairs of emitters will make it possible to act on three lateral directions, preferably forming an angle of 120° between them.

[0110] According to the embodiment, the stabilizers 91, 92 form six pairs 93, 94, 95, 96, 97, 98 of emitters 2 according to the non-limiting embodiment. Two pairs of emitters 2 are sufficient to obtain the expected minimum effect of controlled lateral stabilization. Six pairs 93, 94, 95, 96, 97, 98 of emitters 2 allow better lateral control of the sample and offer a good compromise between control of the lateral stabilization and complexity of the electronics required for the control of the emitters 2 of the pairs 93, 94, 95, 96, 97, 98. However, there is nothing to prevent using a larger number of pairs of emitters 2 to provide increased control of the lateral stabilization. Each pair 93, 94, 95, 96, 97, 98 of transmitters 2 is formed by two subgroups 931, 932, 941, 942, 951, 952, 961, 962, 971, 972, 981, 982 of transmitters 2 opposite the second groups 412, 422 of transmitters.Each pair 93, 94, 95, 96, 97, 98 of emitters comprises a subgroup 931, 941, 951, 961, 971, 981 of emitters 2 of the stabilizer 91 of the dome 41 and a subgroup 932, 942, 952, 962, 972, 982 of emitters 2 of the stabilizer 92 of the dome 42. The two subgroups 931, 932, 941, 942, 951, 952, 961, 962, 971, 972, 981 and 982 of emitters 2 of a pair 93, 94, 95, 96, 97, 98 of emitters 2 are located on either side of the median plane. A subgroup 931, 932, 941, 942, 951 of emitters 2 of a pair 93, 94, 95, 96, 97, 98 belongs to the stabilizer 91 of a dome 41 and is opposite the other subgroup 932, 942, 952, 962, 972, 982 of emitters 2 of the pair 93, 94, 95, 96, 97, 98 which belongs to the stabilizer 92 of the other dome 92. Each subgroup 931, 932, 941, 942, 951, 952, 961, 962, 971, 972, 981, 982 of emitters 2 comprises at least one transmitter 2.Each subgroup 931, 932, 941, 942, 951, 952, 961, 962, 971, 972, 981, 982 of transmitters 2 comprises 9 transmitters 2 according to the non-limiting embodiment.

[0111] Advantageously, the stabilizers 91, 92 are arranged to form at least one pair of pairs of transmitters 2. According to the embodiment in which the stabilizers 91, 92 form six pairs 93 to 98 of transmitters 2, the stabilizers 91, 92 are further arranged to form three pairs 93-96, 94-97 and 95-98 of pairs of transmitters 2. Each pair 93-96, 94-97, 95-98 of pairs is arranged so that each subgroup 931 to 981 of a pair 93 to 98 of a pair 93-96, 94-97, 95-98 of pairs considered is located opposite a subgroup 932 to 982 of the other pair 93 to 98 of the pair of couples considered.

[0112] In other words, according to the embodiment, for the pair of couples 93-96, the subgroup 931, which is included in the stabilizer 91, of the couple 93 is radially opposite to the subgroup 962, which is included in the stabilizer 92, of the couple 96 and the subgroup 961, which is included in the stabilizer 91, of the couple 96 is radially opposite to the subgroup 932, which is included in the stabilizer 92, of the couple 93. For the pair of couples 94-97, the subgroup 941, which is included in the stabilizer 91, of the couple 94 is radially opposite to the subgroup 972, which is included in the stabilizer 92, of the couple 97 and the subgroup 971, which is included in the stabilizer 91, of the couple 97 is radially opposite to subgroup 942, which is included in stabilizer 92, of couple 94.For the pair of couples 95-98, the subgroup 951, which is included in the stabilizer 91, of the couple 95 is radially opposite to the subgroup 982, which is included in the stabilizer 92, of the couple 98 and the subgroup 981, which is included in the stabilizer 91, of the couple 98 is radially opposite to the subgroup 952, which is included in the stabilizer 92, of the couple 95.

[0113] The arrangement of the pairs 93 to 98 makes it possible to stabilize laterally, that is to say perpendicular to the axis of revolution, and in a controlled manner, the levitating object by acting on the levitating object in several lateral directions independently. It should be noted that this effect is made possible due to the absence of coupling between the acoustic waves emitted by the emitters 2 of the caps 81, 82 and the acoustic waves emitted by the emitters 2 of the stabilizers 91, 92.

[0114] In other words, considering as an example the pair 93-96 of couples 93, 96 of emitters 2 whose subgroups 931 and 932 of the pair 93 are each radially opposite, respectively, to the subgroup 962 and 961. The pair 93-96 of couples 93, 96, considered independently of the other pairs 94-97, 95-98 of couples 94, 95, 96, 97, 98, makes it possible to stabilize the levitating object laterally by acting on the levitating object in the first lateral direction included in the plane of FIGURE 1, 2a, 2b and 2c, including the center 3 of the device 1, perpendicular to the axis of revolution 8 and included in the median plane 7. Also, the use of the pair 93-96 of couples 93 and 96, makes it possible to stabilize the levitating object laterally by acting on the levitating object in the first lateral direction.The description given in this paragraph can be transposed to the other pairs 94-97 and 95-98 of couples 94, 95, 96, 97, 98 of transmitters 2 and to the respective lateral stabilization directions.

[0115] Advantageously, the use of the pair 93-96 of pairs of emitters 2, considered independently of the other pairs 94-97, 95-98 of pairs, makes it possible to further improve the lateral stabilization of the levitating object by acting on the levitating object in the first lateral direction. In this case, preferably, a phase of the acoustic waves emitted by the emitters 2 of the subgroups 931 and 932 of the pair 93 is identical and a phase of the acoustic waves emitted by the emitters 2 of the subgroups 961 and 962 of the pair 96 is identical. The description given in this paragraph is transposable to the other pairs 94-97, 95-98 of pairs of emitters 2 and to the respective lateral stabilization directions. Also, in a preferred embodiment, a phase of the acoustic waves emitted by the transmitters 2 of the two subgroups 931-932, 941-942, 951-952, 961-962, 971-972 and 981-982 of each of the pairs 93 is identical.

[0116] The inventors observed, counter-intuitively, that individualized control of the emitters does not allow optimal lateral stabilization of the levitating sample to be obtained. It was observed, surprisingly, that lateral stabilization is improved by regionalizing the control of the acoustic waves emitted by subgroups of emitters 931-932, 941-942, 951-952, 961-962, 971-972 and 981-982 within each of the pairs 93-98. The arrangement of the pairs 93, 94, 95, 96, 97, 98 also allows the object intended to levitate to be laterally translated.To do this, and for a pair of couples considered, and therefore for a translation in the lateral stabilization direction associated with the pair of couples considered, it is appropriate to introduce a shift between the phase of the acoustic wave emitted by a subgroup 931, 941, 951, 961, 971 and 981 of the two subgroups 931-962, 941-972, 951-982, 961-932, 971-942 and 981-952 radially opposite of each of the pairs 93-96, 94-97, 95-98 of couples of emitters 2 and the other 962, 972, 982, 932, 942 and 952 of the two subgroups 931-962, 941-972, 951-982, 961-932, 971-942 and 981-952 radially opposite each of the pairs 93-96, 94-97, 95-98 of transmitter pairs 2.In other words, by way of example, to translate the object, in a controlled manner in the first lateral direction, a shift is introduced, within the pair 93-96 of couples, between the phase of the acoustic wave emitted by the subgroup 931 of emitters 2 and the subgroup 962 of emitters 2 and / or to introduce a shift, between the phase of the acoustic wave emitted by the subgroup 961 of emitters 2 and the subgroup 932 of emitters 2. To translate the object intended to levitate laterally, it is advantageous to introduce a phase shift, preferably identical, between the acoustic waves emitted by each of the four subgroups 931-962 / 932-961, 941-972 / 942-971 and 951-982 / 952-981 of emitters 2 of the two couples 93 and 96, 94 and 97, 95 and 98, of each pair 93-96, 94-97, 95-98 of couples.In this case, advantageously, a phase of the acoustic waves emitted by the transmitters 2 of the same pair 93, 96, 94, 97, 95 and 98 of transmitters are identical and in phase opposition with the phase of the acoustic waves emitted by the other pair 96, 93, 97, 94, 98 of the pair 93-96, 94-97 and 95-98 of pairs. Thus, the acoustic levitation device 1 according to the embodiment makes it possible to manipulate an object without direct contact with the object.

[0117] Levitation of an object under the effect of acoustic waves causes the rotation of the object to be levitated due to the change in angular momentum of the waves when they are reflected and scattered by the sample. To compensate for this rotation, and considering the pair 93 of emitters 2, the phase of the acoustic waves emitted by the subgroups 931, 932 of emitters 2 differs from the phase of the acoustic waves emitted by at least one other subgroup 941, 942, 951, 952, 961, 962, 971, 972, 981, 982 of emitters 2 of at least one other of the pairs 94, 95, 96, 97, 98. Preferably, to counter the rotation of the object, the phase of the acoustic waves emitted by the pairs 93 and 96 of couples is identical and differs from the phase of the acoustic waves emitted by at least one of the other two of the pairs 94-97 and 95-98.According to the non-limiting embodiment, in a particularly advantageous manner, each pair 93, 94 and 95 of a pair of pairs 93-96, 94,-97 and 95-98 emits an acoustic wave in phase opposition with the other of the pairs 96, 97 and 98 of the pair of pairs considered. This characteristic also makes it possible to stabilize the object laterally, that is to say perpendicular to the axis of revolution, even more by countering the instabilities and disturbances inherent in the process of levitating an object intended to levitate by acoustic waves. Indeed, in the presence of hot gases in the levitation device, and when the latter are not evacuated from the levitation device, gas recirculations occur which disturb the ultrasounds on the scale of the entire levitation device. Such a levitation device 1 therefore makes it possible to completely manipulate an object without direct contact with the object.It is thus possible to position the object, that is to say to orient it, to rotate it and / or to translate it, to allow its observation and / or its analysis and / or to subject it to local processing without resorting to direct interaction with the latter.

[0118] Even more advantageously, to compensate for the rotation of the object to be levitated, it is appropriate that the phase of the acoustic wave emitted by at least one pair 93, 94, 95, 96, 97, 98 of transmitters 2 considered is greater or less than the phase of the acoustic wave emitted by a pair 93, 94, 95, 96, 97, 98 of transmitters 2 which is adjacent, by rotation relative to the axis of revolution 5, to the pair of transmitters considered. More preferably, but not necessarily, the two pairs 93-96, 94,-97 and 95-98 of a pair of pairs emit acoustic waves in phase opposition and each of the pairs 93-96, 94,-97 and 95-98 of pairs of emitters 2 emits an acoustic wave whose phase is higher or lower than the phase of the acoustic wave emitted by the pair of pairs of emitters 2 which is adjacent to it, by rotation in the clockwise or counterclockwise direction relative to the axis of revolution 5.

[0119] Furthermore, in a complementary manner, introducing a phase difference between the acoustic wave emitted by at least one pair 93, 94, 95, 96, 97, 98 of emitters 2 and the other pairs of emitters makes it possible to rotate an object intended to levitate by dynamically varying, by controlled rotation, the phase difference of the acoustic waves emitted from one pair to an adjacent pair, by rotation relative to the axis of revolution 5. In other words, and by way of non-limiting example, the value of the phase of the acoustic wave emitted by the pairs 931 and 932 at time t becomes the value of the phase of the acoustic wave emitted by the pairs 941 and 942 at time t+At, the value of the phase of the acoustic wave emitted by the pairs 941 and 942 at time t becomes the value of the phase of the acoustic wave emitted by the pairs 951 and 952 at time t+At, ... 952 at time t+At,the value of the phase of the acoustic wave emitted by pairs 951 and 952 at time t becomes the value of the phase of the acoustic wave emitted by pairs 961 and 962 at time t+At, the value of the phase of the acoustic wave emitted by pairs 961 and 962 at time t becomes the value of the phase of the acoustic wave emitted by pairs 971 and 972 at time t+At, the value of the phase of the acoustic wave emitted by pairs 971 and 972 at time t becomes the value of the phase of the acoustic wave emitted by pairs 981 and 982 at time t+At and the value of the phase of the acoustic wave emitted by pairs 981 and 982 at time t becomes the value of the phase of the acoustic wave emitted by pairs 931 and 932 at the instant t+At. Preferably, but not necessarily, the two pairs 93-96, 94,-97 and 95-98 of a pair of couples emit acoustic waves in phase opposition and the value of the phase of the acoustic wave emitted by the pair of couples 93-96 at time t becomes the value of the phase of the acoustic wave emitted by the pair of couples 94-97 at time t+At, the value of the phase of the acoustic wave emitted by the pair of couples 94-97 at time t becomes the value of the phase of the acoustic wave emitted by the pair of couples 95-98 at time t+At and the value of the phase of the acoustic wave emitted by the pair of couples 95-98 at time t becomes the value of the phase of the acoustic wave emitted by the pair of couples 93-96 at time t+At. Furthermore, the value of the phases of the acoustic waves emitted by each of the pairs 93, 94, 95, 96,97 and 98 can also vary and / or be modulated during the controlled rotation of the phase of the acoustic waves. The angular rotation speed of the phase of the acoustic waves can also vary and / or be modulated during this controlled rotation.

[0120] Furthermore, to improve the effect of compensating for the rotation of the object to be levitated and / or of rotating an object intended to levitate, it is advantageous, preferably by combining the arrangement of the pairs 93, 94, 95, 96, 97, 98 of emitters 2 and / or the arrangement of the pairs of pairs 93-96, 94,-97 and 95-98 of emitters 2 as described above, that the phase of the acoustic wave emitted by at least one pair 93, 94, 95, 96, 97, 98 of emitters 2 considered increases or decreases by successive incrementation of a pair 93, 94, 95, 96, 97, 98 of emitters 2 considered to a pair of emitters 2 which is adjacent to it by rotation relative to the axis of revolution 5.More preferably, but not necessarily, the pairs 93-96, 94,-97 and 95-98 of a pair of pairs emit acoustic waves in phase opposition and the phase of the acoustic wave emitted by each of the pairs 93-96, 94,-97 and 95-98 of pairs of emitters 2 increases or decreases by successive incrementation from a pair 93-96, 94,-97 and 95-98 of pairs of emitters 2 to an adjacent pair of pairs 93-96, 94,-97 and 95-98 of emitters 2 by rotation relative to the axis of revolution 5.

[0121] FIGURES 3a, 3b and 3c illustrate images of the acoustic waves generated by the stabilizer 91, 92 taken in the plane perpendicular to the median plane 7 and which includes the axis of revolution 5. On the abscissa axis and on the ordinate axis is reported the distance in meters. The acoustic waves emitted by the emitters 2 of the caps 81, 82 and the acoustic waves emitted by the emitters 2 of the stabilizers 91, 92 are obtained with a reference emission intensity. In FIGURE 3a is presented an image of the acoustic waves generated by the caps 81, 82 of the acoustic levitation device 1 according to the embodiment. In FIGURE 3b is presented an image of the acoustic waves generated by the stabilizers 91, 92 of the acoustic levitation device 1 according to the embodiment.FIGURE 3c shows an image of the acoustic waves generated simultaneously by the caps 81, 82 and the stabilizers 91, 92 of the acoustic levitation device according to the embodiment.

[0122] With reference to FIGURE 4, the effect of using pairs of emitters 2 for each stabilizer 91, 92 is illustrated. According to the non-limiting embodiment of the levitation device 1, the effect of using six pairs 93, 94, 95, 96, 97, 98 of emitters 2, i.e., six subgroups 931, 941, 951, 961, 971, 981 of emitters 2 for the stabilizer 91 and six subgroups of emitters 932, 942, 952, 962, 972, 982 for the stabilizer 92 is shown. Each pair 93-96, 94-97 and 95-98 of pairs emits acoustic waves in phase opposition. The images in FIGURE 4 are taken in the median plane 7. The acoustic waves emitted by the emitters 2 of the caps 81, 82 and the acoustic waves emitted by the emitters 2 of the stabilizers 91, 92 are obtained with a reference emission intensity. The distance in meters is plotted on the abscissa axis and on the ordinate axis.

[0123] FIGURE 4 illustrates the case where a phase shift of the acoustic wave is introduced between the adjacent pairs 93, 94 and 95 of neighboring emitters 2 with a value of n (image 4a), a value of n / 3 (image 4b) and a value of 0 (image 4c). For these three cases, pairs 96, 97 and 98 are in phase opposition respectively with pairs 93, 94 and 95.

[0124] In other words, for the center image of FIGURE 4 (image 4b), the phase of the acoustic wave emitted by the subgroups 931, 932, 961 and 962 is higher, or respectively lower, by a value of n / 6 than the phase of the acoustic wave emitted by the subgroups 941, 942, 971 and 972, the phase of the acoustic wave emitted by the subgroups 941, 942, 971 and 972 is higher, or respectively lower, by a value of n / 3 than the phase of the acoustic wave emitted by the subgroups 951, 952, 981 and 982 and the phase of the acoustic wave emitted by the subgroups 951, 952, 981 and 982 is higher, or respectively lower, by a value of n / 3 than the phase of the acoustic wave emitted by the subgroups 931, 932, 961 and 962. This embodiment creates a potential barrier 11 completely confining the sample to the center 3 of the levitation device 1.This embodiment is particularly suitable for the case where the sample must be completely confined in the center 3 of the levitation device 1.

[0125] The left image of FIGURE 4 (image 4a) illustrates the case where a phase shift of the acoustic wave of n is introduced between pairs 93-96, 94,-97 and 95-98 of pairs of neighboring emitters 2. This embodiment results in the creation of flow channels 12 of small dimensions, with a width of the order of 1 to 2 mm. The size of the flow channels 12 is sufficient for gases to flow out of the center 3 but sufficiently small so as not to impact the stabilization of the levitating object. This embodiment is particularly suitable, among other things, for the case where hot gases are present or generated, for example by heating, at the center 3 of the levitation device 1 and therefore at the levitating sample.

[0126] In particular, the annular opening 10 has the effect of ensuring the evacuation of gases, in particular gases flowing through the flow channels 12, out of the levitation device 1. Furthermore, even in the presence of these flow channels 12, it has been observed that the configuration of the acoustic field obtained as illustrated in image 4c of FIGURE 4, makes it possible to maintain a restoring force of the sample in the levitation zone in a quasi-isotropic manner in the horizontal plane and therefore to obtain good horizontal stabilization of the sample.

[0127] The right image of FIGURE 4 (image 4c) illustrates the case where no phase shift is introduced between pairs 93-96, 94,-97 and 95-98 of neighboring pairs of emitters 2. This embodiment results in the creation of two walls 13 of potentials facing each other. The configuration of the pairs 93, 94, 95, 96, 97 and 98 and of the pairs 93-96, 94,-97 and 95-98 of pairs of emitters 2 according to the invention makes it possible to control and modulate the orientation and arrangement of these walls 13.

[0128] The results of FIGURE 4 are only three non-limiting examples and a wide choice of phase shift values ​​of the acoustic wave pairs 93, 94, 95, 96, 97, 98 of neighboring 2 emitters or between pairs 93-96, 94,-97 and 95-98 of neighboring 2 emitter pairs is possible. Thus, many configurations of the acoustic field are available depending on the intended application.

[0129] By comparing images 4a and 4b with FIGURE 4, a person skilled in the art will unequivocally deduce that the emission by at least two pairs 93, 94, 95, 96, 97, 98, preferably by each pair 93, 94, 95, 96, 97, 98, of an acoustic wave having a phase which increases or decreases, in particular by continuous successive incrementation, from a given pair of emitters to a neighboring or adjacent pair of emitters, by rotation relative to the axis of revolution 5, makes it possible to obtain modulatable acoustic pressure field(s) making it possible to confine the levitating object. Indeed, in image 4c of FIGURE 4, the person skilled in the art observes the presence of two walls 13 of potentials facing each other and a zone of lesser stability along the axis which is parallel and extends between these two walls 13.On the contrary, in image 4a of FIGURE 4, the person skilled in the art observes the presence of six discrete or punctual standing acoustic waves of intense pressure having the effect of providing flow channels 12 of sufficient size for gases to flow out of the center 3 but sufficiently weak not to impact the stabilization of the levitating object. Similarly in image 4b ​​of FIGURE 4, the person skilled in the art observes the creation of a potential barrier 11 forming a continuous envelope of high intensity completely confining the sample.

[0130] With reference to FIGURE 4, a person skilled in the art will unequivocally deduce that the emission by at least a portion of the pairs 93, 94, 95, 96, 97, 98, preferably by each pair 93, 94, 95, 96, 97, 98, of an acoustic wave having a phase which increases or decreases, in particular by continuous successive incrementation, from a given pair of emitters to a neighboring or adjacent pair of emitters 93, 94, 95, 96, 97, 98, by rotation relative to the axis of revolution 5, makes it possible to obtain a restoring force exerted on the sample which is omnidirectional (as illustrated in images 4a and 4b of FIGURE 4) and not a unidirectional restoring force of adjustable orientation (as illustrated in image 4c of FIGURE 4).

[0131] With reference to FIGURE 4, the person skilled in the art will unequivocally deduce that the emission by at least part of the pairs 93, 94, 95, 96, 97, 98, preferably by each pair 93, 94, 95, 96, 97, 98, of an acoustic wave having a phase which increases or decreases, in particular by continuous successive incrementation, from a given pair of emitters to a neighboring or adjacent pair of emitters 93, 94, 95, 96, 97, 98, by rotation relative to the axis of revolution 5, makes it possible to adapt to the experimental needs. For example, in the case of an ambient or low working temperature, the person skilled in the art may opt to obtain an acoustic field as illustrated in image 4b ​​of FIGURE 4 or any equivalent acoustic field that the levitation device 1 according to the invention makes it possible to obtain. On the contrary, in the case

[0132] Also, with reference to FIGURE 4, the person skilled in the art will unequivocally deduce that the emission by at least a portion of the pairs 93, 94, 95, 96, 97, 98, preferably by each pair 93, 94, 95, 96, 97, 98, of an acoustic wave having a phase which increases or decreases, in particular by continuous successive incrementation, from a given pair of emitters to a neighboring or adjacent pair of emitters 93, 94, 95, 96, 97, 98, by rotation relative to the axis of revolution 5, makes it possible to generate acoustic fields with a modulable geometry having the effect of improving the horizontal stabilization of the sample.

[0133] Equivalently, with reference to FIGURE 4, a person skilled in the art will unequivocally deduce that the emission by at least part of the pairs 93, 94, 95, 96, 97, 98, preferably by each pair 93, 94, 95, 96, 97, 98, of an acoustic wave having a phase greater or less than the phase of the acoustic wave emitted by a neighboring or adjacent pair of emitters 93, 94, 95, 96, 97, 98, by rotation relative to the axis of revolution 5, also makes it possible to generate acoustic fields with a modulable geometry having the effect of improving the horizontal stabilization of the sample.

[0134] With reference to FIGURE 5, images acquired during the melting of a 100Cr6 steel ball with a diameter of 2.38 mm are illustrated, which is levitated by the acoustic levitation device 1 according to the invention. The melting is carried out using a DLR-200-AC model laser sold by the company IPG. The emitted wavelength is 970 nm and the maximum power of the laser is 200 W. The steel ball 14 is levitated and then irradiated by the laser beam so as to cause the melting. The steel ball is kept levitated throughout the experiment.

[0135] The right images of FIGURE 5 show photos of the steel ball 14 being melted and levitated in the acoustic levitation device 1 without contribution from the stabilizers 91, 92, i.e. without the stabilizers 91, 92 emitting acoustic waves. The left images of FIGURE 5 show photos of the steel ball 14 being melted and levitated in the acoustic levitation device 1 with contribution from the stabilizers 91, 92, i.e. when the stabilizers 91, 92 are emitting acoustic waves. In this case, a phase shift of the acoustic wave of n / 2 between pairs 93-96, 94,-97 and 95-98 of neighboring pairs of emitters 2 is applied. The top images of FIGURE 5 correspond to the maximum lateral shift of steel ball 14 observed along the x direction and the bottom images of FIGURE 5 correspond to the maximum lateral shift of steel ball 14 observed along the y direction.The left images of FIGURE 5 were obtained with a voltage of 12 Volts applied to the emitters 2 of the stabilizers 91, 92.

[0136] The distance B separating the maximum lateral displacements of the steel ball 14 observed without contribution from the stabilizers 91, 92 is 128 pixels, which corresponds approximately to a lateral movement of 2.6 mm. The distance C separating the maximum lateral displacements of the steel ball 14 observed with contribution from the stabilizers 91, 92 and for a voltage applied to the emitters 2 of 12 Volts is 56 pixels, which corresponds approximately to a lateral movement of 1.2 mm. It is therefore possible to obtain a minimum lateral stabilization gain of 2.3 with the levitation device 1 according to the embodiment.

[0137] According to one embodiment of the invention, it is proposed to modulate the intensity of the acoustic waves emitted by at least one of the subgroups 941, 942, 951, 952, 961, 962, 971, 972, 981, 982 of emitters 2 relative to another subgroup of emitters to increase the lateral control of the stabilization of the sample and / or to move the sample laterally.

[0138] The power required for lateral stabilization by the subgroups 931, 932, 941, 942, 951, 952, 961, 962, 971, 972, 981, 982 being less than the intensity required by the emitters 2 of the caps 81, 82 to counter gravity, the excess power available, which is notably increased by the arrangement of the stabilizers 91, 92 providing omnidirectional lateral stabilization, can be distributed between the subgroups 941, 942, 951, 952, 961, 962, 971, 972, 981, 982 of emitters 2 of the stabilizers 91, 92 to improve the control of the lateral stabilization.

[0139] Preferably, the acoustic levitation method according to the invention comprises the step of delivering a sinusoidal power supply signal, centered on, or delivering at, the resonance frequency of the transmitters 2. Indeed, the power supply of the transmitters of the state-of-the-art devices is provided by square waves. These square waves do not correspond precisely to the resonance frequency of the transmitters and involve heat dissipation due to the partial conversion of the injected power. The heat dissipation induces a reduction in the conversion efficiency of the supplied power. This heat dissipation also leads to heating of the transmitters and, consequently, to a shift in the resonance frequency of the acoustic transmitters. This shift in the resonance frequency induces an additional reduction in efficiency which is added to the previous one.

[0140] Thus, the power supply of the transmitters 2 by a sinusoidal signal makes it possible to avoid thermal dissipation and, consequently, the shift in the resonance frequency of the transmitters 2, and contributes to the improvement of the stabilization of the sample provided by the levitation device 1 according to the invention.

[0141] Furthermore, powering the emitters 2 with a sinusoidal signal also makes it possible to increase the levitation time of dense samples, for example metals, at high temperatures. Indeed, these experimental conditions require that the emitters 2 operate at a higher power (typically 30% higher than the nominal power) to compensate for additional instabilities. In addition, powering the emitters 2 with a sinusoidal signal also makes it possible to limit the wear (or increase the lifetime) of the emitters 2.

[0142] According to one embodiment of the invention, the transmitters 2 of the device 1 according to the invention are intended to be powered by an operational amplifier, denoted AOP, of power. Preferably, the device 1 comprises an AOP arranged to power the transmitters 2. The AOP is arranged to deliver a sinusoidal wave. Advantageously, the AOP is arranged to operate in linear mode. The AOP is intended to be powered, and it is advantageously powered, by a symmetrical power supply. The symmetrical power supply operates in continuous mode. The symmetrical power supply provides two outputs of opposite voltage as well as a common ground output at zero potential. In practice, as a non-limiting example of an embodiment, the output of the AOP is controlled by a low-power signal from a low-frequency generator (LFG). This signal has a sinusoidal shape, controlled in frequency and amplitude.The power inputs of the AOP are connected to the outputs of the symmetrical power supply.

[0143] According to one embodiment of the invention, the emitters 2 of the device 1 according to the invention are intended to be powered by a power supply device, called modular, comprising an electronic circuit with H-bridge transistors coupled to one or more RLC circuits, acting as electronic filters. The RLC circuit(s) are arranged to convert the square signal delivered by the H-bridge electronic circuit into a sinusoidal power signal. Preferably, the device 1 comprises the modular power supply device.

[0144] This embodiment further provides better control of the waveforms delivered at the output of the power supply device, for example by controlling the control of the H-bridges, for example by means of a microcontroller.

[0145] Preferably, the AOP supplies the emitters 2 of the device 1 with, or delivers, a sinusoidal supply signal, centered on, or delivering at, the resonant frequency of the emitters 2. This embodiment makes it possible to avoid losses and heating induced by the electronic H-bridge structures with transistors delivering a square signal.

[0146] The use of the AOP according to the embodiment also makes it possible to limit the wear of the emitters 2 of the device 1 according to the invention by limiting the wear of the emitters 2 (or increasing the lifespan) induced by heating and mechanical stresses outside the operating range of the emitters 2.

[0147] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention, in particular by means of variants which can be combined with each other of the embodiments previously described.

[0148] In addition, the various features, forms, variations and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive.

Claims

CLAIMS 1. Acoustic levitation device (1) comprising a set of ultrasonic transmitters (2), called transmitters, arranged to each emit an acoustic wave focused at a center (3) of the acoustic device, the set of transmitters is arranged to obtain standing acoustic waves whose intensity is maximum at the center of the levitation device, the levitation device comprises two domes (41, 42) facing each other; each dome comprises: - a first group of ultrasonic emitters (411, 421), called emitters, forming a cap (81, 82) extending between a pole (61, 62) and a stabilizer (91, 92), - a second group of ultrasonic emitters (412, 422), called emitters, forming the stabilizer and extending from the cap towards a plane (7) of the device, called the median plane, which is perpendicular to an axis (5) connecting the pole of each of the domes, called the axis of revolution, and which is located equidistant from the two poles; the stabilizers are arranged to form at least two pairs (93, 94, 95, 96, 97, 98) of transmitters each comprising two subgroups (931, 932, 941, 942, 951, 952, 961, 962, 971, 972, 981, 982) of transmitters located on either side of the median plane, a subgroup of transmitters of a pair belonging to the stabilizer of a dome is opposite the other subgroup of transmitters of the pair belonging to the stabilizer of the other dome;each subgroup of emitters comprises at least one emitter, the emitters of the cap of each of the domes are arranged to emit an acoustic wave having a first frequency fi and the emitters of the stabilizer of each of the domes are arranged to emit an acoustic wave having a frequency f2 different from fi, the two subgroups of emitters of a pair of emitters are arranged to emit acoustic waves of which a phase differs from a phase of the acoustic waves emitted by the two subgroups of emitters of at least one other of the pairs.; 2. Levitation device (1) according to claim 1, comprising at least one pair (93-96, 94-97, 95-98) of couples (93, 94, 95, 96, 97, 98) of transmitters (2), each pair of couples is arranged so that each subgroup (931, 932, 941, 942, 951, 952, 961, 962, 971, 972, 981, 982) of a couple of a pair of couples considered is radially opposite to a subgroup of the other couple of the pair of couples considered.

3. Levitation device (1) according to the preceding claim, wherein the control unit is arranged so that a phase of the acoustic waves emitted by the two couples (93, 94, 95, 96, 97, 98) of a pair (93-96, 94-97, 95-98) of couples is identical or different, preferably in phase opposition.

4. Levitation device (1) according to claim 2 or 3, and wherein the control unit is arranged so that the phase of the acoustic waves emitted by a pair (93-96, 94-97, 95-98) of couples (93, 94, 95, 96, 97, 98) is identical, and differs from the phase of the acoustic waves emitted by at least one other of the couples.

5. Levitation device (1) according to any one of the preceding claims, in which a portion of sphere (10) comprising the median plane (7) and extending between the stabilizer (91, 92) of each of the domes (41, 42) is devoid of transmitter (2), said portion of sphere forms an annular opening providing access to the center (3) of the levitation device.

6. Levitation device (1) according to any one of the preceding claims, wherein: - the first group (411, 421) of transmitters (2) of each dome (41, 42) is arranged so that the generated standing acoustic waves levitate an object intended to levitate in the center (3) of the levitation device, - the second group (412, 422) of transmitters of each dome is arranged so that the generated standing acoustic waves laterally stabilize the object intended to levitate.

7. Levitation device (1) according to any one of the preceding claims, wherein the control unit is arranged so that the phase of the acoustic wave emitted by a given pair (93, 94, 95, 96, 97, 98) of transmitters (2) is greater or less than the phase of the acoustic wave emitted by a pair of transmitters adjacent, by rotation relative to the axis of revolution (5), to the given pair of transmitters.

8. Levitation device (1) according to any one of the preceding claims, wherein the control unit is arranged so that the phase of the acoustic wave emitted by each pair (93, 94, 95, 96, 97, 98) of transmitters (2) is greater or less than the phase of the acoustic wave emitted by a pair of transmitters adjacent, by rotation relative to the axis of revolution (5), to the given pair of transmitters.

9. Levitation device (1) according to any one of the preceding claims, in which the control unit is arranged so that the phase of the acoustic wave emitted by the at least two pairs (93, 94, 95, 96, 97, 98) of transmitters (2) increases or decreases, by successive increments, from a given pair of transmitters to a pair of transmitters adjacent, by rotation relative to the axis of revolution (5), to the given pair of transmitters.

10. Levitation device (1) according to any one of the preceding claims, wherein the control unit is arranged so that the phase of the acoustic wave emitted by each pair (93, 94, 95, 96, 97, 98) of transmitters (2) increases or decreases, by successive incrementation, from a given pair of transmitters to an adjacent pair of transmitters, by rotation relative to the axis of revolution (5), to the given pair of transmitters.

11. Levitation device (1) according to any one of the preceding claims, wherein the frequency fi is higher or lower than the frequency f2 by at least 20%.

12. Acoustic levitation method comprising the steps of: - emit acoustic waves having a first frequency fi, the acoustic waves of frequency fi are emitted by a first group (411, 421) of ultrasonic transmitters (2) forming a cap (81, 82) extending between a pole (61, 62) and a stabilizer (91, 92) of each of two domes, arranged opposite one another, of an acoustic levitation device (1), the acoustic levitation device comprises a set of ultrasonic transmitters, called transmitters, arranged to emit an acoustic wave focused at a center (3) of the acoustic device, the set of transmitters is arranged to obtain standing acoustic waves whose intensity is maximum at the center of the levitation device, - emit acoustic waves having a second frequency f2 different from fi, the acoustic waves of frequency f2 are emitted by a second group (412, 422) of ultrasonic transmitters forming the stabilizer of each of the two domes and extending from the cap towards a plane (7) of the device, called the median plane, which is perpendicular to an axis (5) connecting the pole of each of the domes and which is located equidistant from the two poles;the stabilizers form at least two pairs (93, 94, 95, 96, 97, 98) of transmitters each comprising two subgroups (931, 932, 941, 942, 951, 952, 961, 962, 971, 972, 981, 982) of transmitters located on either side of the median plane, a subgroup of transmitters of a pair belonging to the stabilizer of a dome is opposite the other subgroup of transmitters of the pair belonging to the stabilizer of the other dome, each transmitter subgroup comprises at least one transmitter, a phase of the acoustic waves of frequency f2 emitted by a pair of transmitters differs from a phase of the acoustic waves emitted by at least one other pair of transmitters.; 13. Levitation method according to claim 9, comprising the step of varying over time, by an identical or proportional gradient, the phase of the acoustic wave emitted by each of the pairs (93, 94, 95, 96, 97, 98) of transmitters (2) so as to prevent rotation or to cause controlled rotation or to prevent translation, along an axis perpendicular to the axis of revolution (5), or to cause controlled translation, along an axis perpendicular to the axis of revolution, of an object intended to levitate.

14. A levitation method according to claim 9 or 10, comprising the step of introducing an offset between a value of the phase of the acoustic wave emitted by one of the pairs (93, 94, 95, 96, 97, 98) of emitters (2) of a pair (93-96, 94-97, 95-98) of pairs with respect to a value of the phase of the acoustic wave emitted by the other pair of the pair of pairs; each pair of pairs is arranged so that each subgroup (931, 932, 941, 942, 951, 952, 961, 962, 971, 972, 981, 982) of a pair of a pair of pairs considered is radially opposite to a subgroup of the other pair of the pair of pairs considered.

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