Printing nozzle for a printer

Abstract

The present description relates to a printing nozzle (20) for a 3D printer comprising a duct (21) that has an opening (23), wherein the duct (21) contains a fluid material to be printed (30) which forms an interface (31) with the air at the opening (23), wherein the printing nozzle further comprises an electro-acoustic transducer (40) configured to generate and send first ultrasonic waves (50) through the fluid material to be printed (30) to the interface (31), resulting in the formation of a droplet (32) of the fluid material to be printed at the interface (31) as a result of acoustic radiation forces.

Description

DESCRIPTION TITLE: Printer Nozzle This patent application claims priority from French patent application FR24 / 01598 which will be considered as an integral part of this description. Technical field

[0001] The present application relates to a printhead nozzle for a printer, a printhead comprising such a nozzle, and a printer comprising a printhead. Prior art

[0002] A printing nozzle is used to eject droplets of a fluid material onto a substrate. A single layer of the fluid material can be deposited on the substrate by the printing nozzle. The fluid material then generally corresponds to an ink, and the printing nozzle is intended for a print head integrating an inkjet printer. Several successive layers of the fluid material can be deposited on the substrate by the printing nozzle. This is called 3D printing or additive manufacturing, which brings together manufacturing processes for creating parts in volume by adding a fluid material in successive layers. The fluid material can then correspond to a more or less viscous liquid phase, which may include polymer particles mixed with solvents and chemical agents to modify the rheological properties of the polymer during deposition or after deposition.

[0003] A disadvantage of the print nozzles of known printers is the clogging of certain elements of the print nozzle. Another disadvantage of the print nozzles of known printers is that the time between the successive ejection of two droplets cannot usually be reduced below a threshold. Another disadvantage of known printer nozzles is the difficulty in achieving precise control of droplet shape. Another disadvantage of known printer nozzles is that they may become inoperative with viscous resins or inks, particularly those with a dynamic viscosity greater than >50mPa.s. Summary of the invention

[0004] An embodiment overcomes all or part of the disadvantages of printing nozzles for known printers.

[0005] One embodiment provides a printing nozzle for a 3D printer comprising a conduit having an orifice, the conduit containing a fluid material to be printed forming an interface with air at said orifice, the printing nozzle further comprising an electro-acoustic transducer configured to generate first ultrasonic waves in the fluid material to be printed up to the interface, resulting in the formation of a droplet of the fluid material to be printed at the interface under the action of acoustic radiation forces.

[0006] According to one embodiment, the electroacoustic transducer comprises at least two separate elements for supplying the first ultrasonic waves.

[0007] According to one embodiment, the electroacoustic transducer comprises at least one piezoelectric material.

[0008] According to one embodiment, the conduit extends at least partly along an axis, the orifice being located on said axis and the electro-acoustic transducer being located on said axis.

[0009] According to one embodiment, the printing nozzle further comprises an electronic circuit for controlling the electro-acoustic transducer.

[0010] According to one embodiment, the electronic control circuit is configured to control the electro-acoustic transducer to provide the first ultrasonic waves in a first phase and to control the electro-acoustic transducer to pick up second ultrasonic waves in a second phase.

[0011] According to one embodiment, the electroacoustic transducer is configured to generate the first ultrasonic waves in the fluid material to be printed up to the interface at two distinct areas of the interface, resulting in the simultaneous formation of two droplets of the fluid material to be printed at the interface under the action of acoustic radiation forces.

[0012] An embodiment also provides a 3D printer comprising a print head, the print head comprising at least one print nozzle as defined previously, and a reservoir of fluid material to be printed feeding the print nozzle, the 3D printing not comprising a non-return valve between the orifice and the reservoir. Brief description of the drawings

[0013] These and other features and advantages will be set forth in detail in the following description of particular embodiments given without limitation in relation to the attached figures, among which:

[0014] Figure 1 is a partial, schematic, sectional view of an example of a 3D printer printing nozzle;

[0015] Figure 2 is a partial, schematic, sectional view of the printing nozzle of Figure 1 at a droplet formation stage;

[0016] Figure 3 is a partial, schematic, sectional view of another example of a 3D printer printing nozzle;

[0017] Figure 4, Figure 5, and Figure 6 are each a partial, schematic, sectional view of embodiments of a printing nozzle;

[0018] Figure 7 is a figure similar to Figure 4 illustrating the operation of the printing nozzle;

[0019] Figure 8 is a partial, schematic perspective view of one embodiment of an electro-acoustic transducer of the printing nozzle of Figure 4;

[0020] Figure 9 and Figure 10 are partial and schematic sectional views of other embodiments of electro-acoustic transducers of the printing nozzle of Figure 4;

[0021] Figure 11, Figure 12, Figure 13, Figure 14, Figure 15, Figure 16, Figure 17, and Figure 18 are top views, for Figures 11 to 16, or in perspective, for Figures 17 and 18, of embodiments of an electro-acoustic transducer of the printing nozzle of Figure 4;

[0022] Figure 19 represents a curve of evolution as a function of time of a control signal of an electro-acoustic transducer of the printing nozzle of Figure 4;

[0023] Figure 20, Figure 21, Figure 22, and Figure 23 each represent, in the left part, a curve of evolution as a function of time of a control signal of an electro-acoustic transducer of the printing nozzle of Figure 4 and, in the right part, the frequency spectrum of the control signal represented in the left part for different embodiments of control of the electroacoustic transducer;

[0024] Figure 24 represents a curve of the evolution of the pressure of an ultrasonic wave supplied by an electro-acoustic transducer of the printing nozzle of Figure 4;

[0025] Figure 25 is a partial and schematic sectional view of an alternative embodiment of the printing nozzle shown in Figure 4; and

[0026] Figure 26 is a partial and schematic sectional view of another alternative embodiment of the printing nozzle shown in Figure 4. Description of the embodiments

[0027] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0028] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, the acoustic transducer control circuits are well known to those skilled in the art and are not described in detail.

[0029] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") together, this means that these two elements can be connected or be connected by means of one or more other elements.

[0030] In the following description, when referring to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made unless otherwise specified to the orientation of the figures.

[0031] Unless otherwise specified, the expressions "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%. Furthermore, the terms "insulator" and "conductor" are considered here to mean "electrically insulating" and "electrically conducting", respectively. Furthermore, the "average diameter" of a surface is the diameter of a disc having the same area as the surface.

[0032] Embodiments of a printing nozzle will now be described in the case of 3D printing. However, these embodiments of printing nozzle can also be implemented in the case of printing other than 3D printing, for example for an inkjet printer.

[0033] Figure 1 is a partial, schematic, sectional view of an example of a print nozzle 10 of a print head of a 3D printer. A print head may comprise several print nozzles 10.

[0034] The printing nozzle 10 comprises a conduit 11 comprising an inlet opening 12 at one end and an outlet orifice 13 at the opposite end. The inlet opening 12 is intended to receive a fluid material to be printed from a reservoir, not shown, for storing the fluid material to be printed. The outlet orifice 13 serves to expel droplets of the fluid material to be printed.

[0035] Between the openings 12 and 13, the pipe 11 comprises a zone 14 forming a temporary reservoir. The nozzle printing 10 comprises a non-return valve 15 between the temporary reservoir 14 and the inlet opening 12. The non-return valve 15 allows the passage of the fluid material to be printed from the inlet opening 12 to the temporary reservoir 14 but totally or partially prevents the passage of the fluid material to be printed from the temporary reservoir 14 to the inlet opening 12.

[0036] The walls of the pipe 11 are at least partly deformable at the level of the temporary reservoir 14. The printing nozzle 10 further comprises an actuator 16 adapted to deform the pipe 11 to reduce the volume of the temporary reservoir 14.

[0037] Figure 2 is a partial and schematic sectional view of the printing nozzle of Figure 1 at a step of forming a droplet 17, while the actuator 16 deforms the temporary reservoir 14 to reduce its volume. The reduction in the volume of the temporary reservoir 14 causes a portion of the fluid material to be expelled through the outlet orifice 13 since the non-return valve 15 blocks the passage of the fluid material to the inlet opening 12. A droplet 17, shown in the process of being formed in Figure 2, is then expelled from the printing nozzle 10 through the outlet orifice 13.

[0038] A disadvantage of the printing nozzle 10 illustrated in Figures 1 and 2 is that after the ejection of a droplet, the temporary reservoir 14 must be refilled with the fluid material in order to allow the ejection of a new droplet. The time between the successive ejection of two droplets cannot be less than the time for filling the temporary reservoir 14.

[0039] The non-return valve 15 may comprise a membrane crossed by holes whose diameter is generally less than or equal to 10 μm and which therefore impose a limit on the maximum flow rate of the fluid material through the membrane. In particular, the holes allow the fluid material to pass through at low speed during a temporary reservoir filling phase 14. On the contrary, during the deformation of the pipe 11 by the actuator 16, the check valve 15 behaves substantially like a sealed membrane due to the high speed flow rate of the fluid material. Another disadvantage of the printing nozzle 10 is the clogging of the holes in the membrane of the check valve 15 as well as the clogging of the outlet orifice 13.

[0040] Figure 3 is a partial and schematic sectional view of an example of a printing nozzle 18 of a 3D printer. The printing nozzle 18 shown in Figure 3 comprises all of the elements of the printing nozzle 10 shown in Figure 1 except that the actuator 16 is replaced by a heat source 19, located near the outlet orifice 13, and that the non-return valve 15 may not be present. In operation, the heat source 19 locally heats a portion of the fluid material. The expansion of the portion of the fluid material causes a droplet to be expelled through the outlet orifice 13.

[0041] Advantageously, the printing nozzle 18 does not include a non-return valve. Indeed, the ejection of the droplet does not involve circulation of the fluid material in the pipe 21 which could cause the fluid material to rise through the inlet opening 21. However, a disadvantage of the printing nozzle 18 illustrated in FIG. 3 is that after the ejection of a droplet, it is necessary to wait for the fluid material to cool in order to allow the ejection of a new droplet. The time between the successive ejection of two droplets cannot be less than the cooling time. Another disadvantage is that the material fluid is heated very locally. This limits the number of polymer materials that can be used, since local heating must not initiate a polymerization reaction too early, and must not modify the rheological behavior of the fluid material during printing and on the destination substrate.

[0042] Figure 4, Figure 5, and Figure 6 are each a partial, schematic, sectional view of one embodiment of a printing nozzle 20.

[0043] The printing nozzle 20 comprises a conduit 21 comprising an inlet opening 22 at one end and an outlet orifice 23 at the opposite end. According to another embodiment, the conduit 21 comprises, on the side opposite the inlet opening 22, two or more separate and adjacent outlet orifices 23.

[0044] The pipe 21 delimits an internal volume 24 open to the inlet opening 22 and to the outlet orifice 23. The pipe 21 comprises an internal wall 25 on the side of the internal volume 24 and an external wall 26 on the side opposite the internal wall 25.

[0045] In operation, the printing nozzle 20 is filled with a fluid material to be printed 30. The inlet opening 22 is intended to receive the fluid material 30 from a reservoir, not shown, for storing the fluid material 30. The outlet orifice 23 is used for expelling droplets of the fluid material 30. The fluid material 30 contained in the internal volume 24 of the conduit 21 has a fluid material / air interface 31 with the ambient air at the outlet orifice 23.

[0046] The printing nozzle 20 includes an electro-acoustic transducer 40 configured for the generation of ultrasonic waves in the fluid material 30 contained in the duct 21. The printing nozzle 20 further comprises a control circuit 41 for the electro-acoustic transducer 40. The control circuit 41 may correspond to an application-specific integrated circuit (ASIC). The control circuit 41 is configured to transmit a control signal S to the electro-acoustic transducer 40. The electro-acoustic transducer 40 comprises at least one face 42 closest to the outlet orifice 23. The control circuit 41 may be close to the electro-acoustic transducer 40 or may be remote from the electro-acoustic transducer 40.

[0047] In the embodiment illustrated in Figure 4, the electro-acoustic transducer 40 rests on the external wall 26 of the conduit 21, on the side opposite the internal volume 24 of the conduit 21. In the embodiment illustrated in Figure 5, the electro-acoustic transducer 40 rests on the internal wall 25 of the conduit 21 in the internal volume 24 of the conduit 21 and in direct physical contact with the fluid material 30. In the embodiment illustrated in Figure 6, the electro-acoustic transducer 40 is integrated in the conduit 21, in direct physical contact with the fluid material 30 as illustrated in Figure 6, or without direct physical contact with the fluid material 30.

[0048] H is the distance between the face 42 of the electro-acoustic transducer 40 and the outlet orifice 23. According to one embodiment, the outlet orifice 23 has a circular, oval, or polygonal shape, for example square, rectangular, or hexagonal, with axis A. The outlet orifice 23 has an average diameter DI. According to one embodiment, the internal volume 24 of the conduit 21 has a cross section of circular, oval, or polygonal shape, for example square, rectangular, or hexagonal, with axis A near the orifice outlet 23, that is to say at a distance equal to one tenth of the distance H. The internal volume 24 of the conduit 21 has a maximum average diameter D2 near the outlet orifice 23. According to one embodiment, the electroacoustic transducer 40 is located on the axis A of the outlet orifice 23.

[0049] The dimensions of the printing nozzle 20 depend on the intended application. According to one embodiment, the distance H is between 0.1 pm and 100 pm. According to one embodiment, the average diameter DI of the outlet orifice 23 is between 10 nm and 60 pm. According to one embodiment, the average diameter D2 of the internal volume 24 of the conduit 21 near the outlet orifice 23 is between 0.1 pm and 500 pm.

[0050] Figure 7 is a figure similar to Figure 4 illustrating the operation of the printing nozzle 20.

[0051] In operation, the control circuit 41 controls the electro-acoustic transducer 40 for the generation of ultrasonic waves 50 in the fluid material contained in the internal volume 24 of the pipe 21. The ultrasonic waves 40 propagate to the interface 31. This results in acoustic radiation forces which act on the fluid material 30 causing a deformation of the interface 31 which projects outside the outlet orifice 23, until the formation of a droplet 32 ​​which escapes from the rest of the fluid material 30 contained in the printing nozzle 20. In FIG. 7, the shape of the interface 31 is shown at successive times during the formation of a droplet 32. The acoustic radiation forces are mechanical forces whose amplitude depends in particular on the acoustic absorption capacity of the fluid material 30 during the propagation of the ultrasonic waves 50 and on the difference acoustic impedance between the fluid material 30 and the air at the interface 31.

[0052] The dimensions of the droplet 32 ​​can advantageously be precisely controlled. According to one embodiment, the dimensions of the droplet 32 ​​depend on the acoustic radiation forces exerted on the interface 31 and on the shape of the conduit 21 near the outlet orifice 23. According to one embodiment, the dimensions of the droplet 32 ​​depend only on the acoustic radiation forces exerted on the interface 31. According to one embodiment, the volume of each droplet 32 ​​is between 0.1 μm 3 and 10 mm 3 . According to another embodiment, the flow of the fluid material through the outlet orifice 23 may be continuous, for example constant, which allows the deposition of a film rather than droplets.

[0053] Advantageously, the duration between the successive ejection of two droplets 32 can be short insofar as it only depends on the duration between the supply of two successive sequences of ultrasonic waves 50 by the electro-acoustic transducer 40.

[0054] Advantageously, the printing nozzle 20 does not include a non-return valve. Indeed, the ejection of the droplet does not involve circulation of the fluid material in the internal volume 24 of the pipe 21 which could cause the fluid material to rise through the inlet opening 21.

[0055] The ultrasonic electro-acoustic transducer 40 converts an electrical signal (current, voltage, electrical charges) into ultrasound. The electro-acoustic transducer 40 is for example made of a plate of monocrystalline or polycrystalline piezoelectric material, for example PZT (Lead-Zirconia Titanate) whose thickness varies when a voltage is applied to it. The transducer electro-acoustic 40 is for example a microelectromechanical system (or MEMS from the English Micro-electro-mechanical System), which uses microelectronics production technologies. This microelectromechanical system is for example made up of a deformable membrane suspended above a cavity. The deformable membrane is for example moved by capacitive effect using an electrode fixed to the membrane and an electrode separated by the cavity. This type of transducer is known by the acronym CMUT from the English Capacitive Micro-machined Ultrasonic Transducer. The deformable membrane is for example moved by piezoelectric effect using a layer of piezoelectric material provided with two electrodes attached to the membrane. This type of transducer is known by the acronym PMUT, from the English Piezoelectric Micro-machined Ultrasonic Transducer.The electro-acoustic transducer 40 is for example a magnetostrictive transducer made of a material that slightly changes size when exposed to a magnetic field. Depending on the type of the acoustic transducer 40, the control signal S transmitted by the control circuit 41 to the electro-acoustic transducer 40 may correspond to a voltage, a current, or an electrical charge.

[0056] Figure 8 is a partial and schematic perspective view of an embodiment of the electro-acoustic transducer 40 of the piezoelectric type. The electro-acoustic transducer 40 comprises a pellet 43 of a piezoelectric material between two electrodes 44 and 45. The pellet 43 and each electrode 44, 45 has, for example, a circular, oval, or polygonal shape in top view, for example a square, rectangular, or hexagonal shape. The average diameter of the pellet 43 in top view is, for example, between 1 μm and 10 mm. The thickness of the pellet 43 is, for example, between 1 μm and 1 mm. The signal S can correspond to a variable voltage applied between the two electrodes 44 and 45, which causes the deformation of the pellet 43, in particular a variation in its thickness, and the generation of ultrasonic waves.

[0057] Figure 9 is a partial and schematic sectional view of an embodiment of the electro-acoustic transducer 40 of the CMUT type. The electroacoustic transducer 40 comprises an electrode 46 fixed relative to the tube 21 and an electrode 47 positioned on one of the main surfaces of a membrane 49 movable relative to the fixed electrode 46, and forming a cavity 48 with the electrode 46, a cavity for example filled with air or for example under vacuum. Each electrode 46, 47 has for example in top view a circular, oval, or polygonal shape, for example square, rectangular, or hexagonal. The average diameter of each electrode 46, 47 in top view is for example between 1 μm and 10 mm. The signal S can correspond to a variable voltage applied between the two electrodes 46 and 47, which causes the displacement of the movable membrane 49 relative to the fixed electrode 46 and the generation of ultrasonic waves.

[0058] Figure 10 is a partial and schematic sectional view of an embodiment of the electro-acoustic transducer 40 of the PMUT type. The electroacoustic transducer 40 comprises a deformable membrane 49 mounted on the tube 21 and forming, with the tube 21, a cavity 48 for example filled with air or under vacuum. A pellet 43 of a piezoelectric material between two electrodes 44 and 45 is fixed to the membrane 49. The signal S can correspond to a variable voltage applied between the two electrodes 44 and 45, which causes the deformation of the pellet 43, which in turn causes the displacement of the membrane 49 and the generation of ultrasonic waves. The electrode 44 can be structured into several zones, for example into a central zone and an external zone surrounding the central region. These two zones can be controlled independently or in opposition. There are a multitude of configurations and structuring of the electrode well known to those skilled in the art, the aim being to operate the piezoelectric material according to a mode 31 and that the central zone does not annihilate the curvature of the external zone and vice versa. The control signals can correspond to variable voltages applied to the electrodes and thus create a flexional type deformation driving the membrane 49 and the generation of ultrasonic waves.

[0059] The electroacoustic transducer 40 may include a single ultrasonic wave generating element, two ultrasonic acoustic wave generating elements, or more than two ultrasonic acoustic wave generating elements.

[0060] Figure 11, Figure 12, Figure 13, Figure 14, Figure 15, Figure 16, Figure 17, and Figure 18 are top views, for Figures 11 to 16, or in perspective, for Figures 17 and 18, of embodiments of the electro-acoustic transducer 40 in which the electro-acoustic transducer 40 comprises several ultrasonic wave generating elements 60. According to one embodiment, each ultrasonic wave generating element 60 can be controlled independently by the control circuit 41.

[0061] In Figures 11 and 12, each ultrasonic wave generating element 60 has a rectangular shape in top view. In Figure 11, the ultrasonic wave generating elements 60 are arranged in a single column. In Figure 12, the ultrasonic wave generating elements 60 are arranged in three columns of elements 60 of ultrasonic wave generation, the ultrasonic wave generation elements 60 of the central column have a length greater than the length of the ultrasonic wave generation elements 60 of the other two columns.

[0062] In Figure 13, each ultrasonic wave generating element 60 has a top view of a square shape and the ultrasonic wave generating elements 60 are arranged in rows and columns to form a matrix of ultrasonic wave generating elements 60.

[0063] In Figure 14, one of the ultrasonic wave generating elements 60 has a disc shape and the other ultrasonic wave generating elements 60 each have an annular shape and are concentrically arranged around the central ultrasonic wave generating element 60.

[0064] In Figure 15, each ultrasonic wave generating element 60 has the shape of an annular sector in top view and the ultrasonic wave generating elements 60 are distributed in a ring.

[0065] In Figure 16, one of the ultrasonic wave generating elements 60 has the shape of a disc and the other ultrasonic wave generating elements 60 each have the shape of an annular sector and are distributed in several concentric rings surrounding the central ultrasonic wave generating element 60.

[0066] Figures 17 and 18 illustrate embodiments in which the ultrasonic wave generating elements 60 are arranged on a surface corresponding, at least at the electroacoustic transducer 40, to a cylindrical sector. In Figure 17, each ultrasonic wave generating element 60 extends substantially parallel to the axis of the cylindrical sector. In Figure 18, each wave generating element 60 ultrasound extends substantially along an arc of a circle whose axis corresponds to the axis of the cylindrical sector.

[0067] The embodiments described previously in relation to figures 11 to 18 make it possible in particular to electronically focus the ultrasonic waves 50 emitted by the electro-acoustic transducer 40 towards a given focusing point in the internal volume 24.

[0068] According to one embodiment, the frequency of the ultrasonic waves 50 is between 25 kHz and 1 GHz.

[0069] According to one embodiment, the electroacoustic transducer 40 is controlled by the control circuit 41 to emit one or more bursts of ultrasonic waves 50. The duration of each burst of ultrasonic waves 50 may be between 1 ns and 100 ms. In each burst of ultrasonic waves 50, the wavelength of the ultrasonic waves 50 may be substantially constant or may be variable.

[0070] According to one embodiment, the electroacoustic transducer 40 is adapted to provide ultrasonic waves 50 in different frequency bands. According to one embodiment, the frequencies of the ultrasonic waves 50 in a first burst of ultrasonic waves may be in a first frequency band and the frequencies of the ultrasonic waves 50 in a second burst of ultrasonic waves may be in a second frequency band different from the first frequency band. According to one embodiment, the electroacoustic transducer 40 is adapted to simultaneously provide in the same burst ultrasonic waves 50 in a first frequency band and in a second frequency band different from the first frequency band.

[0071] According to one embodiment, a burst of ultrasonic waves may be composed of multiple frequencies that evolve continuously or discontinuously, regularly or irregularly during the time of a burst of excitation.

[0072] Figure 19 represents a curve of evolution as a function of time t of the control signal S of the electro-acoustic transducer 40 making it possible to obtain a burst of ultrasonic waves corresponding to a pseudoperiodic signal modulated in frequency around a carrier frequency and also modulated in amplitude by an envelope whose variations are slow compared to the oscillations of the phase, such a signal also being called Chirp.

[0073] According to one embodiment, the wavelength of the ultrasonic waves 50 is at least 5 times less than half the distance H between the outlet orifice 23 and the surface 42 of the electro-acoustic transducer 40.

[0074] According to another embodiment, the wavelength of the ultrasonic waves is equal to twice or an odd multiple of twice the distance H between the outlet orifice 23 and the surface 42 of the electro-acoustic transducer 40. This makes it possible in particular to use a mode of propagation of the ultrasonic waves in which the pipe 21 plays the role of a resonator.

[0075] According to another embodiment, the electro-acoustic transducer 40 is controlled so that the ultrasonic waves 50 form shock waves by moving the focusing point of the ultrasonic waves 50 in the internal volume 24 at a supersonic speed in the fluid material 30.

[0076] According to one embodiment, in the case where the electro-acoustic transducer 40 comprises several ultrasonic wave generating elements 60, the ultrasonic wave generating elements 60 can be controlled by the control circuit 41 to control the direction ejection direction of the droplet 32 ​​relative to the axis A of the outlet orifice, so that the direction of ejection of the droplet 32 ​​is inclined relative to the axis A of the outlet orifice.

[0077] According to one embodiment, the control signal S corresponds to a periodic waveform, for example a sinusoidal signal, an oscillating signal of increasing or decreasing frequency, a signal with multiple frequencies, etc.

[0078] Figure 20, Figure 21, Figure 22, and Figure 23 each represent, in the left part, a curve of evolution as a function of time t of the control signal S of the electro-acoustic transducer 40 and, in the right part, the amplitude M of the spectrum as a function of the frequency F of the control signal S represented in the left part for different embodiments of control of the electro-acoustic transducer 40.

[0079] Figure 24 represents a curve of evolution as a function of time of the pressure P of an ultrasonic wave supplied by the electroacoustic transducer 40 according to an embodiment in which the electroacoustic transducer 40 is controlled to supply successive bursts of ultrasonic waves 50 of different amplitudes.

[0080] According to one embodiment, the operation of the printing nozzle 20 may comprise a phase of cleaning the printing nozzle 20 after or before the emission of the droplet 32. The cleaning phase may comprise the control of the electro-acoustic transducer 40 by the control circuit 41 for the emission of ultrasonic waves suitable for cleaning the printing nozzle 20.

[0081] Figure 25 is a partial and schematic sectional view of an alternative embodiment of the nozzle. printing 20 shown in Figure 4. According to this variant, the electro-acoustic transducer 40 is further adapted to operate as an ultrasonic wave sensor 52, and to provide the control circuit 41 with a signal S' representative of the ultrasonic waves 52 captured. The control circuit 41 is then further adapted to carry out processing of the signal S'. The ultrasonic waves 52 captured by the electro-acoustic transducer 40 may come from reflections of the ultrasonic waves 50 emitted by the electro-acoustic transducer 40 on the interface 31. According to one embodiment, the electro-acoustic transducer 40 is used alternately as an ultrasonic wave generator and as an ultrasonic wave sensor.During a control phase in which the electro-acoustic transducer 40 is used as an ultrasonic wave generator, the control circuit 41 transmits the control signal S to the electro-acoustic transducer 40 for the emission of the ultrasonic waves 50 and, during a measurement phase during which the electro-acoustic transducer 40 is used as an ultrasonic wave sensor, the control circuit 41 receives the signal S' transmitted by the electro-acoustic transducer 40 following the reception of the ultrasonic waves 52 by the electro-acoustic transducer 40.

[0082] According to one embodiment, the control circuit 41 is adapted to analyze the signal S' provided by the electro-acoustic transducer 40 during a measurement phase to modify the signal S provided during a subsequent control phase. According to one embodiment, the control circuit 41 is adapted to determine the evolution of the interface 31 during the formation of the droplet 32 ​​by implementing a time-of-flight method by determining the propagation time of the ultrasonic waves 50 from the electro-acoustic transducer 40 to the interface 31 and the propagation time of the reflected ultrasonic waves 51 from the interface 31 to the electro-acoustic transducer 40 According to one embodiment, the control circuit 41 is adapted to determine the evolution of the interface 31 during the formation of the droplet 32 ​​by an analysis of the resonance of the interior volume 24 by determining the spectrum of the reflected ultrasonic waves 52 or of the acoustic response of the cavity 21 to the excitation S. The modification of the signal S comprises for example the increase in the intensity of the emitted ultrasonic waves 50, the decrease in the intensity of the emitted ultrasonic waves 50, or the stopping of the emission of the ultrasonic waves 50, the change in frequency of the emitted ultrasonic waves 50, the change in phase of the emitted ultrasonic waves 50, the linear modification of the spectral content of the emitted ultrasonic waves 50 and possibly the non-linear modification of the spectral content of the emitted ultrasonic waves 50 issued.

[0083] Figure 26 is a partial and schematic sectional view of an alternative embodiment of the printing nozzle 20 shown in Figure 4. According to this alternative, the electro-acoustic transducer 40 is controlled by the control circuit 41 to simultaneously form two droplets 32 through the same outlet orifice 23. According to one embodiment, the electro-acoustic transducer 40 is controlled by the control circuit 41 to simultaneously eject at least three droplets 32 through the same outlet orifice 23.

[0084] The embodiments described above relate to the formation of at least one droplet 32 ​​by the printing nozzle 20. According to another embodiment, the electro-acoustic transducer 40 is controlled by the control circuit 41 to cause the ejection of a continuous stream of the fluid material 30 through the outlet orifice 23.

[0085] According to one embodiment, the fluid material is suitable for producing a semiconductor, conductive, or insulating region by 3D printing. According to one embodiment, the fluid material is used for manufacturing an electronic device.

[0086] According to one embodiment, the fluid material comprises one or more p-type semiconductor compounds, in particular one or more p-type organic semiconductor compounds, one or more n-type semiconductor compounds, in particular n-type organic semiconductor compounds, one or more conductive materials, and / or one or more insulating materials.

[0087] Examples of p-type organic semiconductor compounds suitable for the flowable material include compounds, oligomers, and derivatives of compounds selected from the group consisting of conjugated hydrocarbon polymers such as polyacene, polyphenylene, poly(phenylene vinylene), polyfluorene, including oligomers of these conjugated hydrocarbon polymers; condensed aromatic hydrocarbons, such as tetracene, chrysene, pentacene, pyrene, perylene, coronene, or soluble substituted derivatives thereof; para-substituted phenylenes with oligomers such as p-quaterphenyl (p-4P), p-quinquephenyl (p-5P), p-sexiphenyl (p-6P), or soluble substituted derivatives thereof;conjugated heterocyclic polymers such as poly(3-substituted thiophenes), poly(3,4-bisubstituted thiophenes), optionally substituted polythieno[2,3-b]thiophene, optionally substituted polythieno[3,2-b]thiophene, poly(3-substituted selenophenes), polybenzothiophene, polyisothianaphthene, poly(N-substituted pyrrole), poly(3-substituted pyrrole 3), poly(3,4-bisubstituted pyrrole), polyfuran, polypyridine, poly-1,3,4-oxadiazoles, polyisothianaphthene,; poly(N-substituted aniline), poly(2-substituted aniline), poly(3-substituted aniline), poly(2,3-disubstituted aniline), polyazulene, polypyrene; pyrazoline compounds; polyselenophene; polybenzofuran; polyindole; polypyridazine; benzidine compounds; stilbene compounds; triazines; porphines, phthalocyanines, fluorophthalocyanines, naphthalocyanines or fluoronaphthalocyanines substituted without metals or with metals; N,N'-dialkyl, dialkyl-substituted, diaryl or diaryl-substituted)-1,4,5,8-naphthalenetetracarboxylic diimide and fluorinated derivatives; N,N'-dialkyl, substituted dialkyl, diaryl or substituted diaryl 3,4,9,10-perylenetetracarboxylicdiimide; bathophenanthroline; diphenoquinones; 1,3,4-oxadiazoles; 11,11,12,12-tetracyanonaptho-2,6-quinodimethane; a,a'-bis(dithieno[3,2-b-2',3T-d]thiophene); 2,8-dialkyl, substituted dialkyl, diaryl or substituted diaryl anthradithiophene;2,2'-bisbenzo[1,2-b:4,5-b']dithiophene. Another example of organic semiconductor compound of suitable type for flowable material is a mixture of 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene (dif-TES-ADT) and polystyrene (PS).;

[0088] Examples of suitable n-type organic semiconductor compounds for the flowable material include graphene, fullerene, and substituted fullerene, such as PCBM-C 60 , PCBM-C70, PCBM-C6I, PCBM-C71, bis-PCBM-C 6i , bis-PCBM-C 7i , ICMA-Cgo (1%4 '-dihydronaphtho [2%3': 1, 2] [5, 6] fullerene-Cgo) r ICBA-Cgo, oQDM-Cgo (1%4 '-dihydronaphtho [2', 3': 1, 9] [5, 6] fullerene-C6o _lh) , bis- oQDM-Cgo- Another example of an n-type organic semiconductor compound suitable for the fluid material is 4,4'- (2 4o2- Benzo[l,2-c:4,5-c' ]bis[l,2,5] thiadiazole-4 , 8 -di y ldi -5, 2- thiophenediyl ) bis [ 2-dodecylbenzonitrile ] , marketed for example under the name TU-3.

[0089] According to one embodiment, the fluid material may further comprise a solvent or solvents, for example, chlorinated solvents such as chloroform, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, chlorobenzene and o-dichlorobenzene, ether-based solvents such as tetrahydrofuran, methyltetrahydrofuran, dimethyltetrahydrofuran, dioxane and anisole, aromatic hydrocarbon solvents such as toluene, o-xylene, m-xylene, p-xylene, benzaldehyde, tetralin (1,2,3,4-tetrahydronaphthalene) and 1,3-dimethoxybenzene, aliphatic hydrocarbon solvents such as cyclohexane, methylcyclohexane, trimethylcyclohexane, n-pentane, n-hexane, n-heptane, n-octane, n-nonane and n-decane, ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, methylhexanone, benzophenone and acetophenone,ester solvents such as ethyl acetate, butyl acetate, ethyl acetate cellosolve, methyl benzoate, benzyl phenyl acetate and phenyl acetate, polyhydric alcohols and their derivatives such as ethylene glycol, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, dimethoxyethane, propylene glycol, diethoxymethane, triethylene glycol monoethyl ether, glycerol and 1,2-hexanediol, alcoholic solvents such as methanol, ethanol, propanol, isopropanol and cyclohexanol, sulfoxide solvents such as dimethyl sulfoxide and amide solvents such as N-methyl-2-pyrrolidone and N,N-dimethylformamide.,

[0090] According to one embodiment, the fluid material may further comprise polymer particles. Preferably, said polymer particles comprise a polymer that exhibits crosslinking, i.e., a polymer with a certain degree of crosslinking. Examples of polymers crosslinkable compounds that can be used in the flowable material may be, for example, selected from the group consisting of polystyrene, polyacrylic acid, polytetracrylic acid, poly(methyl methacrylate), epoxy resins, polyesters, vinyl polymers, or any mixture of at least two of these compounds, of which polystyrene and polyacrylic acid are preferred, and polystyrene is most preferred.

[0091] According to one embodiment, the polymer particles can increase the sound absorption capacity of the fluid material 30.

[0092] The formulation used preferably has a dynamic viscosity at 20°C of at least 1 mPa.s, for example between 1 mPa.s and 6000 mPa.s.

[0093] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art.

[0094] Finally, the practical implementation of the embodiments and variants described is within the reach of those skilled in the art from the functional indications given above.

Claims

CLAIMS 1. A printing nozzle (20) for a 3D printer comprising a conduit (21) having an orifice (23), the conduit (21) containing a fluid material to be printed (30) forming an interface (31) with the air at said orifice (23), the printing nozzle further comprising an electro-acoustic transducer (40) configured to generate first ultrasonic waves (50) in the fluid material to be printed (30) up to the interface (31), the electro-acoustic transducer (40) comprising at least two separate elements (60) for supplying the first ultrasonic waves (50), resulting in the formation of a droplet (32) of the fluid material to be printed at the interface (31) under the action of acoustic radiation forces.

2. Printing nozzle according to claim 1, wherein the electro-acoustic transducer (40) comprises a matrix of elements (60) for providing the first ultrasonic waves (50) arranged in rows and columns.

3. Printing nozzle according to claim 1 or 2, wherein each element (60) for supplying the first ultrasonic waves (50) has, in top view, the shape of a rectangle, a square, a disc, a ring, or an annular sector.

4. Printing nozzle according to any one of claims 1 to 3, wherein the electro-acoustic transducer (40) comprises at least one piezoelectric material (43).

5. Printing nozzle according to any one of claims 1 to 4, in which the conduit (21) extends at least partly along an axis (A), the orifice (23) being located on said axis and the electro-acoustic transducer (40) being located on said axis.

6. Printing nozzle according to any one of claims 1 to 5, further comprising an electronic circuit (41) for controlling the electro-acoustic transducer (40).

7. A printing nozzle according to claim 6, wherein the electronic circuit (41) is configured to control Tl independently each element (60) for supplying the first ultrasonic waves (50).

8. A printing nozzle according to claim 6, wherein the electronic control circuit (41) is configured to control the electro-acoustic transducer (40) to provide the first ultrasonic waves (50) in a first phase and to control the electro-acoustic transducer (40) to pick up second ultrasonic waves (50) in a second phase.

9. A printing nozzle according to any one of claims 1 to 8, wherein the electro-acoustic transducer (40) is configured to generate the first ultrasonic waves (50) in the fluid material to be printed (30) up to the interface (31) at two distinct areas of the interface (31), resulting in the simultaneous formation of two droplets (32) of the fluid material to be printed at the interface (51) under the action of acoustic radiation forces.

10. 3D printer comprising a print head, the print head comprising at least one print nozzle according to any one of claims 1 to 9, and a reservoir of the fluid material to be printed (30) supplying the print nozzle, the 3D printing not comprising a non-return valve between the orifice (23) and the reservoir.

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