Printer nozzle

Abstract

Printing Nozzle for Printer This description relates to a printing nozzle (20) for a 3D printer comprising a conduit (21) having an orifice (23), the conduit (21) containing a printing fluid material (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 printing fluid material (30) up to the interface (31), resulting in the formation of a droplet (32) of the printing fluid material at the interface (31) under the action of acoustic radiation forces. Figure for the abbreviation: Fig. 7

Description

Title of the invention: Printing nozzle for printer technical field

[0001] The present application relates to a print head nozzle for a printer, a print head comprising such a nozzle, and a printer comprising a print head. Previous technique

[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 onto the substrate by the printing nozzle. The fluid material is generally an ink, and the printing nozzle is designed for a print head integrated into an inkjet printer. Several successive layers of the fluid material can be deposited onto the substrate by the printing nozzle. This is referred to as 3D printing or additive manufacturing, which encompasses manufacturing processes that create three-dimensional parts 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 that modify the rheological properties of the polymer during or after deposition.

[0003] One drawback of known printer nozzles is the clogging of certain nozzle components. Another drawback is that the time between successive droplet ejections cannot generally be reduced below a certain threshold. A further drawback is the difficulty in achieving precise control of droplet shape. Finally, known printer nozzles can become ineffective with viscous resins or inks, particularly those with a dynamic viscosity exceeding 50 mPa·s. Summary of the invention

[0004] One embodiment overcomes all or part of the disadvantages of known printer nozzles.

[0005] One embodiment provides a 3D printer printing nozzle comprising a conduit having an orifice, the conduit containing a fluid material to be printed forming an interface with the 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 electro-acoustic transducer comprises at least two separate elements for supplying the first ultrasonic waves.

[0007] According to one embodiment, the electro-acoustic 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 includes an electronic control circuit for 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 capture second ultrasonic waves in a second phase.

[0011] According to one embodiment, the electro-acoustic transducer is configured to generate the first ultrasonic waves in the fluid material to be printed up to the interface at two distinct zones 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] One embodiment also provides for a 3D printer comprising a print head, the print head comprising at least one print nozzle as defined above, and a fluid material reservoir to be printed supplying the print nozzle, the 3D printing not comprising a check valve between the orifice and the reservoir. Brief description of the drawings

[0013] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0014] [Fig.1] is a partial and schematic cross-sectional view of an example of a 3D printer nozzle;

[0015] [Fig.2] is a partial and schematic cross-sectional view of the printing nozzle of [Fig.1] at a droplet formation stage;

[0016] [Fig.3] is a partial and schematic cross-sectional view of another example of a 3D printer printing nozzle;

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

[0018] [Fig.7] is a figure analogous to [Fig.4] illustrating the operation of the printing nozzle;

[0019] [Fig.8] is a partial and schematic perspective view of an embodiment of an electro-acoustic transducer of the printing nozzle of [Fig.4];

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

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

[0022] [Fig. 19] represents a time-dependent evolution curve of a control signal from an electro-acoustic transducer of the printing nozzle of [Fig. 4];

[0023] [Fig.20], [Fig.21], [Fig.22], and [Fig.23] each represent, on the left, a time-dependent evolution curve of a control signal of an electro-acoustic transducer of the printing nozzle of [Fig.4] and, on the right, the frequency spectrum of the control signal represented on the left for different control embodiments of the electro-acoustic transducer;

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

[0025] [Fig. 25] is a partial, schematic cross-sectional view of an alternative embodiment of the printing nozzle shown in [Fig. 4]; and

[0026] [Fig.26] is a partial and schematic cross-sectional view of another embodiment of the printing nozzle shown in [Fig.4]. Description of the implementation methods

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

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

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

[0030] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "superior", "inferior", 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 "approximately", "roughly", "about", and "on the order of" mean to the nearest 10%, preferably to the nearest 5%. Furthermore, the terms "insulating" and "conducting" are taken to mean "electrically insulating" and "electrically conductive", respectively. In addition, the "average diameter" of a surface is defined as the diameter of a disk 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 printing nozzle embodiments can also be implemented in the case of printing other than 3D printing, for example for an inkjet printer.

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

[0034] The printing nozzle 10 includes a conduit 11 having 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 conduit 11 includes a zone 14 forming a temporary reservoir. The printing nozzle 10 includes a check valve 15 between the temporary reservoir 14 and the inlet opening 12. The check valve 15 allows the flow of the fluid material to be printed from the inlet opening 12 to the temporary reservoir 14 but completely or partially prevents the flow of the fluid material to be printed from the temporary reservoir 14 to the inlet opening 12.

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

[0037] Figure 2 is a partial, schematic cross-sectional view of the printing nozzle of Figure 1 at a droplet formation stage 17, while the actuator 16 deforms the temporary reservoir 14 to reduce its volume. The reduction in the volume of the temporary reservoir 14 results in the expulsion of a portion of the material. fluid through outlet orifice 13 since the check valve 15 blocks the passage of fluid material towards the inlet opening 12. A droplet 17, shown during formation in [Fig.2], is then expelled out of the printing nozzle 10 through outlet orifice 13.

[0038] One drawback of the printing nozzle 10 illustrated in Figures 1 and 2 is that after a droplet is ejected, the temporary reservoir 14 must be refilled with the fluid material in order to allow the ejection of another droplet. The time between the successive ejections of two droplets cannot be less than the time required to refill the temporary reservoir 14.

[0039] The check valve 15 may include a membrane with holes whose diameter is generally less than or equal to 10 µm, thus limiting 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. Conversely, during the deformation of the conduit 11 by the actuator 16, the check valve 15 behaves essentially like a watertight membrane due to the high-speed flow rate of the fluid material. Another drawback 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, schematic cross-sectional view of an example of a printing nozzle 18 of a 3D printer. The printing nozzle 18 shown in Figure 3 comprises all 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 the non-return valve 15 may not be present. During operation, the heat source 19 locally heats a portion of the fluid material. The expansion of this 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 cause the fluid material to circulate in the conduit 21, which could lead to the fluid material flowing back up through the inlet opening 21. However, a drawback of the printing nozzle 18 illustrated in [Fig. 3] is that after the ejection of a droplet, the fluid material must cool down before another droplet can be ejected. The time between the successive ejections of two droplets cannot be less than the cooling time. Another drawback is that the fluid material 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 alter the rheological behavior of the fluid material during printing and on the target substrate.

[0042] Fig. 4, Fig. 5, and Fig. 6 are each a partial cross-sectional view and schematic, of an embodiment of a printing nozzle 20.

[0043] The printing nozzle 20 comprises a conduit 21 having an inlet opening 22 at one end and an outlet orifice 23 at the opposite end. In 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 conduit 21 delimits an internal volume 24 open on the inlet opening 22 and on the outlet orifice 23. The conduit 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] During 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 serves to expel droplets of the fluid material 30. The fluid material 30 contained in the internal volume 24 of the conduit 21 presents a fluid material / air interface 31 with the ambient air at the outlet orifice 23.

[0046] The printing nozzle 20 includes an electroacoustic transducer 40 configured for generating ultrasonic waves in the fluid material 30 contained in the conduit 21. The printing nozzle 20 further includes a control circuit 41 for the electroacoustic transducer 40. The control circuit 41 may be an application-specific integrated circuit (ASIC). The control circuit 41 is configured to transmit a control signal S to the electroacoustic transducer 40. The electroacoustic transducer 40 includes at least one face 42 closest to the outlet orifice 23. The control circuit 41 may be located near the electroacoustic transducer 40 or may be located away from the electroacoustic transducer 40.

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

[0048] H denotes 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 straight section of circular shape, . oval, or polygonal, for example square, rectangular, or hexagonal, with axis A near the outlet orifice 23, i.e. 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 electro-acoustic 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. In one embodiment, the distance H is between 0.1 µm and 100 µm. In one embodiment, the average diameter DI of the outlet orifice 23 is between 10 µm and 60 µm. In one embodiment, the average diameter D2 of the internal volume 24 of the conduit 21 near the outlet orifice 23 is between 0.1 µm and 500 µm.

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

[0051] In operation, the control circuit 41 controls the electroacoustic transducer 40 to generate ultrasonic waves 50 in the fluid material contained in the internal volume 24 of the conduit 21. The ultrasonic waves 40 propagate to the interface 31. This results in acoustic radiation forces acting on the fluid material 30, causing a deformation of the interface 31 which is projected out of 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.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 ultrasonic waves 50 and on the difference in 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. In 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. In another embodiment, the dimensions of the droplet 32 ​​depend only on the acoustic radiation forces exerted on the interface 31. In one embodiment, the volume of each droplet 32 ​​is between 0.1 pm³ and 10 mm³. In yet another embodiment, the flow of the fluid material through the outlet orifice 23 can be continuous, for example, constant, which allows the deposition of a film rather than droplets.

[0053] Advantageously, the time between the successive ejection of two droplets 32 can be small insofar as it depends only on the time between the supply of two successive sequences of ultrasonic waves 50 by the electroacoustic transducer 40.

[0054] Advantageously, the printing nozzle 20 does not include a non-return valve. Indeed, the ejection of the droplet does not cause the fluid material to circulate within the internal volume 24 of the conduit 21, which could lead to the fluid material flowing back up through the inlet opening 21.

[0055] The ultrasonic electro-acoustic transducer 40 converts an electrical signal (current, voltage, electric charge) into ultrasound. The electro-acoustic transducer 40 is, for example, made of a plate of single-crystal or polycrystalline piezoelectric material, for example PZT (Zirconium-Lead Titanate), the thickness of which varies when a voltage is applied to it. The electro-acoustic transducer 40 is, for example, a microelectro-mechanical system (MEMS), which uses microelectronic production technologies. This microelectro-mechanical system is, for example, made of a deformable membrane suspended above a cavity. The deformable membrane is, for example, driven by capacitive motion using an electrode attached 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, driven by the piezoelectric effect using a layer of piezoelectric material equipped 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 changes slightly in size when exposed to a magnetic field. Depending on the type of acoustic transducer 40, the control signal S transmitted by the control circuit 41 to the electro-acoustic transducer 40 can correspond to a voltage, a current, or an electrical charge.

[0056] Figure 8 is a partial, schematic perspective view of an embodiment of the piezoelectric electroacoustic transducer 40. The electroacoustic transducer 40 comprises a pellet 43 of a piezoelectric material between two electrodes 44 and 45. The pellet 43 and each electrode 44, 45 have, for example, a circular, oval, or polygonal shape when viewed from above, such as a square, rectangular, or hexagonal shape. The average diameter of the pellet 43 when viewed from above 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 may correspond to a variable voltage applied between the two electrodes 44 and 45, which causes the pellet 43 to deform, in particular a change in its thickness, and generates ultrasonic waves.

[0057] Figure 9 is a partial, schematic cross-sectional view of an embodiment of the CMUT-type electro-acoustic transducer 40. The electro-acoustic transducer The acoustic device 40 comprises an electrode 46 fixed relative to the tube 21 and an electrode 47 positioned on one of the principal 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 under vacuum. Each electrode 46, 47 has, for example, a circular, oval, or polygonal shape when viewed from above, for example, a square, rectangular, or hexagonal shape. The average diameter of each electrode 46, 47 when viewed from above is, for example, between 1 µm and 10 mm. The signal S may correspond to a variable voltage applied between the two electrodes 46 and 47, which causes the movable membrane 49 to move relative to the fixed electrode 46 and generates ultrasonic waves.

[0058] Figure 10 is a partial, schematic cross-sectional view of an embodiment of the PMUT-type electroacoustic transducer 40. 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 membrane 49 to move and generate ultrasonic waves. The electrode 44 can be structured into several zones, for example, a central zone and an outer zone surrounding the central region. These two zones can be driven independently or in opposition.There are a multitude of electrode configurations and structures well known to those skilled in the art, the aim being to operate the piezoelectric material in a mode 31 and to ensure that the central zone does not negate the curvature of the outer zone and vice versa. The control signals can correspond to variable voltages applied to the electrodes and thus create a flexural deformation driving the membrane 49 and the generation of ultrasonic waves.

[0059] The electro-acoustic transducer 40 may comprise a single ultrasonic wave generation element, two ultrasonic acoustic wave generation elements, or more than two ultrasonic acoustic wave generation elements.

[0060] Figures 11, 12, 13, 14, 15, 16, 17, and 18 are top views (Figures 11-16) or perspective views (Figures 17-18) 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 independently controlled by the control circuit 4L.

[0061] In Figures 11 and 12, each ultrasonic wave-generating element 60 has a rectangular shape when viewed from above. In [Fig. 11], the ultrasonic wave-generating elements 60 are arranged in a single column. In [Fig. 12], the ultrasonic wave-generating elements 60 are arranged in three columns, with the ultrasonic wave-generating elements 60 in the central column being longer than the ultrasonic wave-generating elements 60 in the other two columns.

[0062] In [Fig. 13], each ultrasonic wave generation element 60 has the shape of a square when viewed from above, and the ultrasonic wave generation elements 60 are arranged in rows and columns to form a matrix of ultrasonic wave generation elements 60.

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

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

[0065] In [Fig. 16], one of the ultrasonic wave generation elements 60 has the shape of a disc and the other ultrasonic wave generation elements 60 each have the shape of an annular sector and are distributed according to several concentric rings surrounding the central ultrasonic wave generation 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 level of the electro-acoustic transducer 40, to a cylindrical sector. In [Fig. 17], each ultrasonic wave-generating element 60 extends substantially parallel to the axis of the cylindrical sector. In [Fig. 18], each ultrasonic wave-generating element 60 extends substantially along an arc of a circle whose axis corresponds to the axis of the cylindrical sector.

[0067] The embodiments described above 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 focal 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 electro-acoustic 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 can be between 1 ns and 100 ms. In each burst of 50 ultrasonic waves, the wavelength of the 50 ultrasonic waves 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 can be composed of multiple frequencies which evolve continuously or discontinuously, regularly or irregularly during the time of an excitation burst.

[0072] Fig. 19 represents a curve of evolution as a function of time t of the control signal S of the electro-acoustic transducer 40 allowing to obtain a burst of ultrasonic waves corresponding to a pseudo-periodic 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 being also 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 conduit 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 focal 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 ejection direction of the droplet 32 ​​with respect to the axis A of the outlet orifice, so that the ejection direction of droplet 32 ​​is inclined with respect 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 multi-frequency signal, etc.

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

[0079] Figure 24 shows a curve of the evolution of pressure P over time. of an ultrasonic wave supplied by the electro-acoustic transducer 40 according to an embodiment in which the electro-acoustic 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 include a cleaning phase of the printing nozzle 20 after or before the emission of the droplet 32. The cleaning phase may include the control of the electro-acoustic transducer 40 by the control circuit 41 for the emission of ultrasonic waves adapted to the cleaning of the printing nozzle 20.

[0081] Figure 25 is a partial, schematic cross-sectional view of a variant of The printing nozzle 20 is shown in [Fig. 4]. According to this variant, the electro-acoustic transducer 40 is further adapted to function as an ultrasonic wave sensor 52, and to provide the control circuit 41 with a signal S' representative of the captured ultrasonic waves 52. The control circuit 41 is then further adapted to process the signal S'. The ultrasonic waves 52 captured by the electro-acoustic transducer 40 can originate from reflections of the ultrasonic waves 50 emitted by the electro-acoustic transducer 40 on the interface 31. In 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 ultrasonic waves 50 and, during a measurement phase in 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 in order to modify the signal S provided during a subsequent control phase. According to another 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 analyzing the resonance of the internal volume 24 by determining the spectrum of the reflected ultrasonic waves 52 or the acoustic response of the cavity 21 to the excitation S. The modification of the signal S includes, for example, increasing the intensity of the emitted ultrasonic waves 50, decreasing the intensity of the emitted ultrasonic waves 50, or stopping the emission of the ultrasonic waves 50, changing the frequency of the emitted ultrasonic waves 50, changing the phase of the emitted ultrasonic waves 50, linearly modifying the spectral content of the emitted ultrasonic waves 50 and possibly non-linearly modifying the spectral content of the emitted ultrasonic waves 50.

[0083] Figure 26 is a partial, schematic cross-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 from 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 from 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] In one embodiment, the fluid material is adapted for the 3D printing of a semiconductor, conductive, or insulating region. In another embodiment, the fluid material is used for the fabrication of 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, and 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 suitable p-type organic semiconductor compounds for the fluid 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 their soluble substituted derivatives; para-phenylenes substituted by oligomers such as p-quaterphenyl (p-4P), p-quinquephenyl (p-5P), p-sexiphenyl (p-6P), or their soluble substituted derivatives;Conjugated heterocyclic polymers such as poly(3-substituted thiophenes), poly(3,4-disubstituted thiophenes), polythieno[2,3-b]thiophene (optionally substituted), polythieno[3,2-b]thiophene (optionally substituted), poly(3-substituted selenophenes), polybenzothiophene, polyisothianaphthene, poly(N-substituted pyrrole), poly(3-substituted pyrrole), poly(3,4-disubstituted 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 substituted fluoronaphthalocyanines without metals or with metals;N,N'-dialkyl, substituted dialkyl, diaryl or substituted diaryl)-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; α,α'-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 an organic semiconductor compound suitable for fluid materials is a mixture of 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene (dif-TES-ADT) and polystyrene (PS).

[0088] Examples of n-type organic semiconductor compounds suitable for fluid materials include graphene, fullerene, and substituted fullerene, such as PCBM-C60, PCBM-C70, PCBM-C61, PCBM-C71, bis-PCBM-C61, bis-PCBM-C71, ICMA-C60 (1-4'-dihydronaphtho[2-3':1,2][5,6]fullerene-C60), ICBA-C60, oQDM-C60 (1-4'-dihydronaphtho[2',3':1,9][5,6]fullerene-C60), bis-oQDM-C 60. Another example of an n-type organic semiconductor compound suitable for fluid material is 4,4'-(2X4o2-Benzo[l,2-c:4,5-c']bis[l,2,5]thiadiazole-4,8-diyldi-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, tetraline (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, methyl hexanone, 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-pyrolidone 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, that is, a polymer with a certain degree of crosslinking. Examples of crosslinkable polymers that can be used in the fluid material may, for example, be chosen from the group consisting of polystyrene, polyacrylic acid, polytethacrylic acid, poly(methyl methacrylate), epoxy resins, polyesters, vinyl polymers, or any mixture of at least two of these compounds, among which polystyrene and polyacrylic acid are preferred, and polystyrene is preferred above all.

[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. A person skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will become apparent to a person skilled in the art.

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

Claims

Demands

1. A 3D printer nozzle (20) 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 an array of elements (60) for supplying the first ultrasonic waves (50) arranged in rows and columns.

3. Printing nozzle according to claim 1 or 2, wherein each element (60) of supplying the first ultrasonic waves (50) has, in top view, the shape of a rectangle, a square, a disk, 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, wherein the conduit (21) extends at least in part along an axis (A), the orifice (23) being located on said axis and the electroacoustic 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. Printing nozzle according to claim 6, wherein the electronic circuit (41) is configured to independently control 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 capture second ultrasonic waves (50) in a second phase.

9. 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), whereby the simultaneous formation of two droplets (32) of the fluid material to be printed at the interface (51) results 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 check valve between the orifice (23) and the reservoir.

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