WO2020083833A1 - Manufacture of piezoelectric components and devices with a three-dimensional printing method - Google Patents

Abstract

Method for manufacturing a piezoelectric component, comprising a step of manufacturing a three-dimensional structure by means of three-dimensional printing by multilayer deposition of molten wire of a polymer, copolymer or polymer-based or copolymer-based composite material, on a print medium, and a step of electrical polarisation of at least one portion of the three-dimensional structure, so as to ensure that at least one portion of the structure is piezoelectric, characterised in that the polarisation step is a polarisation carried out using the Corona effect or by contact, the polarisation step being carried out during or following the step of manufacturing the mechanical structure, and characterised in that at least one portion of the print medium is heated and has a surface tension greater than 70 mN/m.

Description

 MANUFACTURE OF PIEZOELECTRIC COMPONENTS AND DEVICES WITH A THREE-DIMENSIONAL PRINTING PROCESS

The invention relates to a method for manufacturing piezoelectric components and devices, a manufacturing apparatus suitable for implementing such a method and a piezoelectric system obtainable using such a method. The invention is based on three-dimensional printing techniques, also called additive manufacturing.

Plastronics, which allows electronics to be integrated into plastic objects, particularly uses the three-dimensional printing of components for various applications: health, for example a connected soleplate or physiological sensors; rehabilitation devices, for example a rehabilitation system adapted to patients and exercises;

 vehicle parts and components, such as a dashboard with sensors, or a bumper with sensors;

 connected objects, such as bracelets, shoes, sensors, etc.

Researchers from the University of Warwick in Great Britain (SJ. Leigh, RJ. Bradley, CP Purssell, DR Billson, DA Hutchins, "A simple, low-cost conductive composite material for 3D printing of electronic sensors", PLos ONE 7 (11), 2012) have proposed using conductive polymers for three-dimensional printing (or 3D printing), by depositing molten filament (FDM), of pressure sensors on three-dimensional objects (3D objects). It is also possible to use functional thermoplastics for the printing of elementary components, such as antennas (J. O'Brien et al., "Miniaturization of microwave components and antennas using 3D manufacturing", EuCAP 2015).

The University of Minnesota has modified a Stratasys Connex 3D printer to print multi-material touch sensors. However, piezoelectricity is not used. Inkjet and screen printing printers can be used to produce flexible electronics, but essentially on a flat substrate, or on an already manufactured support. At the industrial level, there is the OPTOMEC system which allows to print conductive tracks on 3D object surfaces for electronics.

There is also Voxel8, a spin-off from Harvard University, which offers a platform that combines the printing of the structure of the object by FDM deposition, the printing of a metallic ink by "Direct Ink Writing". (DIW, or "Direct continuous ink printing" in French) for the conductive tracks of the circuit, and a positioning system for discrete components. This platform allows the routing of electronic components placed more or less automatically in a mechanical structure, giving rise to on-board electronics on the 3D object. However, it does not make it possible to produce piezoelectric 3D objects, such as sensors or actuators, and the printed structures are necessarily rigid. Inkjet printers can be used to produce flexible electronics, but mainly on a flat substrate, or on an already manufactured support.

An American team proposed to print piezoelectric polymers (US 2016/016369; Lee et al., “Electronic polling-assisted additive manufacturing processe for PVDF polymer-based piezoelectric device applications”, Smart Mater. Struct. 23, 095044, 2014 ; Kirkpatrick et al., “Characterization of 3D printed piezoelectric sensors”, Proceedings of the IEEE Sensors 2016, 1409-1411, 2016) by 3D printing of the polyvinylidene fluoride polymer (PVDF). In the case of these studies, the molten PVDF polymer is both subjected to mechanical stretching stresses and an electric field. Indeed, it has been demonstrated the possibility of extruding a PVDF wire by applying a high voltage electric field, at 6 kV, associated with mechanical stresses during deposition, which makes it possible to produce a deposited wire, whose constant of d ₃₃ piezoelectricity is extremely low (0.36 pC / N). This low value does not allow commercial applications to be envisaged. The low values of the constant d ₃₃ result from the low rate of formation of the polar crystalline phase of the PVDF during printing. The polar phases allow the material to exhibit good piezoelectric properties. In addition, the extruded wire obtained is a one-dimensional object and not a multi-layer 3D object obtained by additive manufacturing of material. These different platforms or printers allow the manufacture of mechatronic objects and sensors requiring to manufacture the structures separately, then to assemble them in industrial chains to carry out the complete manufacture of the objects and components. However, not all shapes are possible, and the design process requires taking into account how the electronics will be integrated into the object. This process is achievable but it is not trivial. Indeed, it is complex, time-consuming and requires expensive equipment. Furthermore, the production of mechatronic components by assembly limits the form and design of the objects. Indeed, to be profitable, this assembly process requires large volumes of production, and therefore does not allow customization.

The invention aims to overcome the aforementioned drawbacks and limitations of the prior art. More particularly, it aims to enable the production of piezoelectric components or devices by three-dimensional printing by depositing molten filament of polymers with a single technology, and to provide a platform for manufacturing the structural parts and the functional parts of the piezoelectric component or device. It also allows optimal integration of components, great freedom of form, short design and manufacturing cycles, reduced cost of raw materials and of the printing device and partial or even total recyclability of the parts produced.

In accordance with the invention, this object is achieved by using, during 3D printing of the piezoelectric component, electrical polarization by the Corona effect, advantageously carried out at a temperature of at least 25 ° C, to make piezoelectric at least part of the deposited polymer, the latter forming the mechanical structure of the component.

An object of the invention is therefore a method of manufacturing a piezoelectric component comprising a step of manufacturing a three-dimensional structure by three-dimensional printing by multilayer deposition of molten wire of a polymer, copolymer or composite material based on polymer or copolymer, on a printing medium comprising at least one conductive part, and a step of electrically polarizing at least a part of the three-dimensional structure, so as to make piezoelectric at at least part of this structure, characterized in that the electrical polarization step is a polarization effected by the Corona effect or a contact polarization, the polarization step being carried out during or following the step of manufacturing the mechanical structure, and characterized in that at least part of the printing medium is heating and has a surface tension greater than 70 mN / m.

According to embodiments of the invention: the polarization step is carried out at a temperature of at least 25 ° C, preferably at a temperature above 80 ° C;

 the deposited material is chosen from PVDF, P (VDF-TrFE), PVF, PVC, P (VDCN / VAc), PTUFB, Nylon-11, Nylon-11 / PVDF, PVDF / PZT, and Rubber / PZT; the method also comprises a step of manufacturing a first electrode by three-dimensional printing by depositing a conductive ink, preceding the step of manufacturing the three-dimensional structure, and a step of manufacturing a second electrode by three-dimensional printing by deposit of a conductive ink, according to the polarization step, at least part of the material being deposited on the first electrode, the first electrode forming the conductive part of the printing medium and at least part of the second electrode being deposited on the material ;

 in the case where the method comprises the manufacture of two electrodes, it may comprise the use of at least two separate deposition heads for the deposition of the material and of the conductive ink, and the two stages of manufacture of the electrode may be followed by a step of drying the conductive ink by ultraviolet which can be carried out by the use of an ultraviolet light source fixed on the head for depositing the conductive ink;

the step of manufacturing the three-dimensional structure comprises depositing a layer of a conductive material on a polarized layer of the material; the polarization step is polarization effected by the Corona effect, and in this case, a positive voltage can be applied between the conductive part of the printing medium and a printing nozzle placed above the surface of the deposited material or between the layer of conductive material and a printing nozzle placed above the surface of the deposited material; and the method also includes a step of generating a print file for producing at least one piezoelectric component, this step being implemented by computer and comprising:

 o A substep consisting in providing the computer with data indicative of a position of one or more points of contact between the electrodes and the material, of a spatial region where the component is to be manufactured, of at least an electrical property of the materials making up the piezoelectric component, and a voltage to be applied for the polarization step;

 o A substep for calculating the geometry and connections of the component by applying to the data of a predefined mathematical model; and

 o A sub-step for generating the print file allowing the geometry to be produced by three-dimensional printing of the piezoelectric component.

Another object of the invention is an apparatus for implementing a method according to one of the embodiments of the invention comprising a three-dimensional printer of the molten wire deposition type having at least one deposition head carried by a printing carriage and a printing medium, characterized in that the deposition head is configured to deposit a polymer, copolymer or composite material based on polymer or copolymer, and to polarize by Corona effect or by contact at least part of the material deposited and in that the print medium is heated.

According to a particular embodiment of the invention, the apparatus comprises a computer system for generating a print file for controlling the three-dimensional printer so as to manufacture a piezoelectric component, the computer system being configured to: receive input data indicative of a position of one or more contact points, of a spatial region where the component is to be manufactured, of at least one electrical property of the materials composing the piezoelectric component and of a voltage to be applied for the polarization step; calculating a geometry of the component by applying to the data of a predefined mathematical model; and generating a print file making it possible to produce the geometry by three-dimensional printing of the piezoelectric component.

Yet another object of the invention is a piezoelectric system comprising two conductive electrodes surrounding a three-dimensional piezoelectric multilayer structure, characterized in that the three-dimensional structure and the electrodes are made in one piece by three-dimensional printing of at least one first material polymer, copolymer or composite based on polymer or copolymer forming said three-dimensional structure and at least one second conductive material forming the two electrodes and in that at least part of the three-dimensional structure is electrically polarized by Corona effect or by contact .

Other characteristics, details and advantages of the invention will emerge on reading the description made with reference to the appended figures given by way of example, and which represent, respectively: FIG. 1, a three-dimensional printing device according to a embodiment of the invention;

 FIG. 2, a diffractogram of two polymeric materials printed according to another embodiment of the invention;

 FIGS. 3A - 3C, a vibration sensor produced according to another embodiment of the invention, as well as its responses in output voltage; and FIGS. 4A and 4B, the measured displacements of an actuator produced according to the same embodiment as the vibration sensor as a function of the applied voltage and as a function of the applied frequency.

FIG. 1 shows a three-dimensional printing device 120 according to an embodiment of the invention. The printer 120 comprises at least one extrusion head or deposition head 110, suitable for depositing a polymer material, carried by a printing carriage 121, movable in three orthogonal directions x, y and z (the z direction corresponding to the direction of extrusion of the deposition head 110), by means of a movement 122, the structure of which is not shown in detail, since it is conventional, controlled by a computer system 123 (computer or microcontroller card). For the production of complex devices, the printer 120 may comprise several separate deposition heads to facilitate the deposition of several different materials, for example a polymeric material 102 and a conductive material 107. The same head can however be used to deposit several materials different, but this slows down the process, because it is necessary to change the feed material of the head and introduces a risk of contamination. These deposit heads can be arranged side by side and be carried by the same printing carriage or by separate printing carriages.

An actuating mechanism 124 makes it possible to adjust the relative vertical position (in z) of each deposition head with respect to the other heads or with respect to the printing surface. This makes it possible in particular to raise the inactive heads during the production of complex structures, where the risk of collision between the deposition heads and the elements already printed becomes significant. Even in the case of single-layer printing, residues present on the inactive heads are found involuntarily and uncontrolled, which can alter the aesthetic and functional properties of the final device. For example, this can lead to short circuits between conductive tracks.

In a conventional manner, each deposition head 110 comprises a nozzle 106, a heating block 105, a heat cut screw 103 and a radiator 101. The heating block 105 also comprises a heating cartridge 104. During the deposition of the polymer 102 , the polymer filament 102 is driven by an extrusion motor towards the nozzle 106. The filament is pushed through the screw 103 to the heating block 105. The heating block 105 transmits heat to the edges of the nozzle 106 by thermal conduction. The end of the filament 102 in contact with the heating edges of the nozzle 106 melts, and the molten material is ejected from the nozzle 106 under the effect of the pressure exerted by the not yet melted part of the filament, which acts as a piston . Generally, the filament is brought to the deposition head 110 in the form of a coil 125. The temperature of the heating block depends on the material deposited. Indeed, the different materials are not always available on the market in the form of filaments for 3D printing. For example, the filaments of P (VDF-TrFE) do not exist on the market, the inventors therefore had to adapt this material and the printing parameters to produce an object printed in 3D. For example, new filaments based on PVDF or on copolymer P (VDF-TrFE) can be manufactured and used as raw materials for printing objects at a temperature between 150 ° C and 280 ° C. The molten polymer flows through the outlet of the nozzle 106. The deposition of the polymers, and more generally of the other materials, takes place above a printing medium 100. The support 100 and the deposition head 110 can move so as to stack the deposited layers or to draw a geometric shape with the deposited polymer to form a three-dimensional object. The deposited polymer then constitutes the mechanical structure of the piezoelectric component.

The control of the quantity of material by the printer can be carried out by a simple weight control, by knowing the density of the filament, the weight of the spool 125 (standard, but can be deduced from its dimensions and the density of the material constitutive), and the diameter of the filament. Weight can be measured by a simple pressure sensor, or a more complex force sensor. For the sake of accuracy, the real-time measurement of the weight by the sensor can be supplemented by a more conventional approach which consists in using a contact sensor to measure the number of rotations performed by the coil. At each revolution, a counter increments by 1. The length consumed for a complete revolution is equal to the perimeter of the coil; by multiplying this length by the section of the filament and by its density, we obtain the quantity of material deposited.

The reliability of the printing of the mechanical and functional structure of the piezoelectric component depends in particular on the precision of the positioning of the different deposition heads 110. It is first of all based on an automated calibration procedure for the spacing between the heads of deposit 110 and the support 100 (in the direction z), and for the position of the heads in the plane (x, y) of the support 100.

The calibration of the spacing between the deposition heads 110 and the print medium 100 in height (z), and of the flatness of the medium 100 is generally done by means of a sensor. limit switch and an adjustment of the corners of the support 100. But when using large surface supports (for example of the order of 20 cm x 20 cm or more), it becomes difficult to ensure its flatness and therefore the use of a limit switch is not satisfactory. This is why a capacitive sensor 126 secured to the printing carriage 121 may be present on the printing apparatus 120. This sensor 126 makes it possible to calibrate the support 100 at several points without touching it and to avoid inaccuracies. mechanical inherent to mechanical limit switches commonly used on servomotors. The capacitive sensor 126 acts as a contactless switch. Unlike an inductive sensor, it detects non-ferrous materials such as glass, wood, skin, etc. This sensor 126 will simply replace the limit switch by being installed directly on the printing carriage 121.

The calibration of the position of the deposition heads 110 in the plane (x, y) of the support 100 is important in order to properly align or stack the layers of material deposited with the different heads. For a first layer (making, for example, a surface of the three-dimensional structure of the piezoelectric component), an initial calibration is carried out using the capacitive sensor 126 with integrated ground electrode, and metallic mass electrodes placed in the corners of the support 100 Indeed, at constant distance between the sensor and the support, the measured capacity will be greater with a metal piece between the two electrodes of the sensor rather than with a coating or insulating material of the support. However, the capacitive sensor also works with insulating materials, so the presence of this metal part is not compulsory. It is also possible to take other measurement points on the support to increase accuracy.

For the following layers, in particular when several printheads are used, and therefore several materials are printed, the alignment with the previous layer and with the part printed with another material must be checked using a servo visual using a camera 127 connected to an image processing system, which coincides with the computer control system 123 in the embodiment of FIG. 1. The visual control is carried out as follows: an image of the printing surface, on which at least one layer of material has been deposited, is acquired by the camera 127; possibly several images can be acquired and averaged to improve the signal to noise ratio;

 a reference point is chosen on the image, automatically or manually;

 the position of this reference point on the image taken by the camera 127 is compared with its position on the model of the last layer deposited, already in memory in the printer 120;

 the position of the printing carriage 121 along the x and y axes is calculated, and stored in memory;

 the printing of the upper layer takes these possible offsets into account.

Preferably, the calibration camera 127 can be integral with the printing carriage 121, with a relative position relative to the known deposit heads 110. However, as in the case of FIG. 1, the camera 127 can be fixed and use a visual cue fixed to the printing carriage 121 to determine the relative position of the latter relative to the reference point on the image.

In order to obtain a piezoelectric component, that is to say to make piezoelectric at least part of the three-dimensional structure, formed by the various deposited layers, the polar domains which constitute the deposited polymer material must be oriented under an electric field, either by the Corona effect (contactless polarization), or by application of a high electric field between two electrodes placed below and above the object (contact polarization).

A Corona system can be used in the printer 120. For example and advantageously, the Corona system can be fixed to the deposition head 110 of the polymer, and more advantageously the printing nozzle 106 of the polymer is used as in a Corona system . Typically, the print nozzle 106 is moved above the polymer layer at a minimum distance of 1 mm from the deposited layer, and a voltage of at least 10 kV is applied for at least 5 s between the nozzle d printing 106 and a conductive part of the printing medium 100 connected to an electrical ground. More generally, a voltage of at least 10 kV will be applied between the print nozzle 106 and a conductor, which may be the conductive part of the print medium 100 or a intermediate conductive layer deposited on already polarized polymer layers and on which are deposited the layers to be polarized. For example, the distance between the printing nozzle 106 and the deposited polymer layer is 2 cm, the applied voltage is 14 kV for 3 min. If the polarization takes place at room temperature, the measured values of d ₃₃ remain low and are also unstable over time. The inventors have realized that by carrying out the polarization at a higher temperature (for example between 100 ° C. and 140 ° C.), large d ₃₃ values can be obtained (up to 15 pC / N). Table 1 shows the values of d ₃₃ obtained with and without polarization. These observations remain valid even when the number of layers deposited increases (cf. Table 2).

Table 1: Values of d ₃₃ for a printed object with a polarization temperature between 100 ° C and 140 ° C

Table 2: Values of d ₃₃ for different deposited layers

To effect the polarization at high temperature, at least part of the printing medium 100 can therefore be heated.

The polarization of the layers can be done as the deposition takes place or can be done at the end of the deposition. We can therefore polarize each layer as soon as it is deposited or polarize all of the layers when all the layers have been deposited.

In addition, so that the different layers deposited adhere to the support 100, the heating part of the support has a surface tension greater than 70 mN / m (70 dynes / cm); this is typically obtained by means of a suitable coating, for example by means of a film based on PET functionalized so as to obtain a surface tension greater than 70 dynes / cm. The printing medium 100 therefore comprises at least one conductive part and at least one heating part whose surface tension is greater than 70 mN / m.

According to another embodiment of the invention, electrodes can also be deposited. In this case, a first electrode 107 is printed. It then constitutes the conductive part of the printing medium 100 on which the polymer is at least partly deposited. A second electrode is at least partially printed on the layer of polarized polymer. These electrodes can be made on the basis of conductive ink based on solvent or conductive ink curable by ultraviolet or on any conductive ink which can be dried. Advantageously, conductive ink curable by ultraviolet will be used, because the drying of the solvent-based ink is too slow or else if it is carried out by heat treatment, it may cause deformations of the samples. The ink depositing head 111 is based on the “Eco-pen 300” dosing system 128. It is a volumetric dosing system based on the principle of the infinite piston (use of a “worm "). The ink deposition head can be fixed to the support of the polymer deposition head or be independent. The shape of the electrode layer is produced by the movement of the actuators 124 on the x, y and z axes. The deposition rate and the movements of the head are also controlled by the computerized control system 123. The printing of an electrode consists, for example, in depositing a layer of conductive silver ink with a thickness of 50 μm . Then the ink is subjected to ultraviolet radiation for drying. This allows for local drying which is faster and more efficient than drying with an oven or a lamp, drying with an oven can also damage the polarized polymer (for example, loss of polarization when the temperature increases). The ultraviolet source 129 can be fixed to the ink deposition head, advantageously, the UV source is a UV optical fiber. As with the deposition of the polymer, it is also possible to stack the ink layers so as to create 3D electrodes or to create conductive tracks at the ends of the electrodes. In order to facilitate the implementation of the printing, the heads for depositing the polymer and the conductive ink are separate.

According to another embodiment of the invention, the polymer can also be polarized during its deposition. A printing nozzle placed above the surface of the deposited polymer material is connected to a high voltage generator by a special cable. The cable can withstand voltages of a few kilovolts, for example between 15 kV and 30 kV and it is flexible so that it can follow the print nozzle. The generator then makes it possible to apply, during printing, a positive voltage between the printing nozzle placed above the surface of the polymer material deposited and the conductive part of the printing medium 100. Advantageously, this nozzle is the polymer material print nozzle. The polarization and voltage parameters are sent to the generator by the control computer system 123. During this printing and polarization step, one or more layers of polymeric material can be deposited. A voltage of 2.5 xz kV / mm is applied during deposition, with z the distance between the deposition head and the conductive part of the support. This polarization is called contact polarization.

According to embodiments of the invention, the nozzle 106 can be made of metal or ceramic. The heat cut screw 103 can be made of aluminum or ceramic, for example aluminum nitride. The heating block 105 can be made of ceramic, and the radiator 101 can be made of aluminum. Nevertheless, if the printing nozzle 106 of the polymer is made of metal (for example brass or stainless steel) and it is used for the polarization therefore connected to a high voltage source, the amplitude of the voltage applied for the polarization is limited by the breakdown voltage. This breakdown voltage represents the voltage value from which an electrical discharge occurs between the nozzle and another conductive element having a lower potential (if necessary earthed, ie 0 V). To prevent such discharges from occurring between the nozzle 106 and the heating cartridge 104, the heating block 105 must be made with a dielectric ceramic material. The ceramic must have good thermal conductivity. The main ceramics combining good thermal conductivity and good dielectric constant are alumina (38), aluminum nitride (285), beryllum oxide (370), boron nitride (300) and cubic boron nitride (1300). Furthermore, to increase the breakdown voltage and therefore the voltage applied for polarization, it suffices to increase the distance between the heating cartridge 104 and the nozzle 106. However, by increasing this distance, the volume of the heating block is increased 105 and therefore the power required to reach the extrusion temperatures. This distance depends on the electrical constant of the ceramic constituting the heating block 105. For example, to obtain a breakdown voltage of 10 kV, the inventors calculated a distance of 2.5 mm between the nozzle 106 and the heating cartridge 104 for a ceramic having an electrical constant of 65 kV / mm.

The deposited material 102 can be a polymer, a copolymer or a composite based on a polymer or copolymer. For example, the material deposited is of PVDF type, this includes PVDF, polymers and copolymers based on PVDF or composites having a polymer or copolymer based on PVDF as a matrix. The deposited material may contain, for example, piezoelectric ceramic particles. More generally, the deposited material, called polymer material, contains polar domains which can be oriented, polymers of the PVDF type are moreover an example of this. Advantageously, the deposited polymer is a copolymer, and more particularly P (VDF-TrFE). Unlike PVDF, when it is printed, P (VDF-TrFE) has a high phase b rate (diffractogram in Figure 2, showing the phase b rate for PVDF and P (VDF-TrFE) after printing according to the same embodiment of the invention). This makes it possible to obtain a piezoelectric coefficient d ₃₃ up to 15 pC / N for P (VDF-TrFE) whereas for printed PVDF, d ₃₃ remains less than 0.8 pC / N.

The polymer material deposited is for example chosen from: PVDF, P (VDF-TrFE), PVF, PVC, P (VDCN / VAc), PTUFB, Nylon-ll / PVDF, PVDF / PZT, and Rubber / PZT.

In order to facilitate the design of the printed piezoelectric components, a design interface 130 is advantageously provided. This interface 130 is a computer system (computer, computer network, microprocessor card, etc.) programmed to receive as input parameters of a piezoelectric component to be manufactured, such as the desired electrical properties, the position of its points of making contact, its location within or on the surface of a mechanical structure, etc. and providing as output, thanks to the application of appropriate algorithms, a print file (generally in G-Code format) which allows piloting the three-dimensional printer

120.

The interface 130 is notably composed of computer-aided design software 131, called CAD software, a plugin 132 executed by CAD software 131, software 135, called P-Tronics software, and d 'a “slicer” 136. The plugin 132 makes it possible to transmit the 3D model designed by the user in the CAD software 131 to the P-Tronics 135 software as well than the materials and parameters chosen. This plugin 132 advantageously allows the P-Tronics 135 software to receive the 3D model designed by any CAD software. P-Tronics 135 software allows the user to add components and / or modify the 3D model received, to communicate with the slicer 136 which allows to analyze and visualize a 3D image layer by layer and to convert the model 3D in G-Code usable by the printer 120 and to provide the printer 120 with a print file 133 in G-Code. Advantageously, the CAD software 131.1 plugin 132 and the software 135 can use a database 134 grouping together a library of components, materials, etc.

The software 135 and the slicer 136 make it possible to: generate a single component;

 generate components and conductive tracks within a CAD document (document created by CAD software);

 modify the settings of each sub-part of the CAD document (such as the material, the print patterns, the voltage applied during polarization, etc.); modify global printing settings (layer thickness, filament type, etc.); and

 conversion of the CAD document into G-Code.

For the generation of a single component, the user chooses, in the CAD software 131, the type of component to be generated, then the parameters of the component, such as its dimensions or the parameters specific to each type of component. A CAD document is then created, containing only the desired component (and if necessary an insulating support layer of the same dimensions). In this CAD document, the user can then generate new components and / or conductive tracks. To do this, it delimits areas in the document, defining the location and size of the new components to be generated. For each of the zones, the user specifies the type of component to be generated as well as its parameters (for example, electrical parameters). Then the user executes the plugin 132 which will itself execute the P-Tronics 135 software, in order to generate the new components. The software 135 examines the CAD document in order to identify the areas representing these new components to be generated. For each zone, it generates a single component and inserts it into the CAD document on the zone delimited by the user. The user can also modify certain properties of a generated component or a part of the component or of any other object which he has modeled himself in the CAD software 131, such as for example the electrical properties of the material (insulator , conductive, piezoelectric), print pattern, wire spacing, voltage applied for polarization, etc. In the case of a component automatically generated by software 135, these settings are pre-assigned, but still modifiable by the user.

The user can also modify the global print settings, such as the print quality, or the materials present in each deposition head. The software 135 makes it possible to take into account all the components and the settings given by the user for the generation of the print file 133 in G-Code. If no particular setting is given by the user on a sub-part, this sub-part will be printed with a default material (insulation).

For the creation of conductive tracks, the user has the choice between a manual process and an automatic process.

For the manual process, the user builds, in the CAD document, segments representing the conductive tracks to be generated. The ends of these tracks can: be connected together; or

 connected to components; or

 not be linked to any element.

When the user requests software 135, via the plugin 132, to generate these tracks, the software 135 examines the CAD document to identify the tracks to be generated, that is to say the segments constructed by the user. For each segment of the "same layer" type, that is to say a segment remaining in the same layer, therefore in the same plane (x, y), it generates a right block following the path of the segment, of the same length as the size of the segment, the width of a track and the height thickness _C0Uche x num_couches_pistes.

For each segment of type “via”, that is to say a segment crossing several layers, therefore along the z axis, the software 135 generates a right block following the vertical layout of the segment, the height of which is equal to the size of the segment and the other two dimensions of which are equal to the thickness of the via. The straight blocks thus generated are unified into conductive tracks for each connected set of segments, and the resulting 3D volumes are integrated into the CAD document in the same place as the corresponding segments.

For the automatic process, the user selects: a pair of components in the CAD document; or

 a component and a connection point; or

 a pair of connection points, the connection points being constructed beforehand by the user.

The user indicates to the software 135 that these two objects must be linked and the plugin saves this relation in the CAD document. If necessary, the user can also specify to which input or output a component is linked, if it has several terminations. Then, the software 135 will generate the conductive tracks connecting the two objects. It will first generate segments connecting the different objects. Several cases are then possible:

For the ends of the tracks:

 o In the case of a component without specific connection locations, the end of the track is on the edge of the component closest to the object to be connected,

 o In the case of a component having several connection locations, the location chosen by the user defines the end of the track,

 o In the case of a link point, the point constitutes the end of the track;

For segment plots:

o The parts of the document made of insulating material are cut into voxels of dimensions ma x [ _track width, - thickness _via \ + _track separation, the voxels formed are not necessarily made only of insulating material;

For each pair of objects to be linked: o Voxels that do not contain 100% insulating material are marked as invalid, because they may indeed contain previously generated tracks, the other voxels being considered as valid,

 o The software starts from one end of the pair of objects to be linked, and connects it to the other end by generating segments (of the “same layer” or “same via” type), the segments can possibly cross voxels valid, and in this case, they pass through the center of these voxels,

 o The set of segments thus generated constitutes a conductive track connecting the two objects,

 Then the product segments are automatically transformed into 3D volumes in the same way as the manual process.

According to another embodiment of the invention, an electronic chip or an electronic card can be inserted on the three-dimensional structure of the piezoelectric component. Indeed, the 3D printer described is not capable of printing the equivalent of a microprocessor. It must therefore be able to add it to the object and program it to take into account all of the components present in the piezoelectric component. The addition of the chip is facilitated by the generation of specific connectors by the software 135, said connector for chips. This type of component can accommodate an electronic card or a chip fitted with metal tabs, thanks to holes arranged in the same configuration and of appropriate depth. It provides a number of terminations to which conductive tracks can be connected. Knowledge by the software 135 of the tracks connected to each tab also makes it possible to generate a tailor-made code for the card or the chip intended to control the components connected to it, which will make the printed piezoelectric component immediately functional.

FIG. 3A shows a vibration sensor manufactured according to one of the embodiments of the invention. This sensor was printed with conductive silver inks and a P polymer material (VDF-TrFE). Its dimensions are 30x30x1 mm3. The values of d ₃₃ for this sensor are close to 13 pC / N. Figure 3B shows the response of the sensor, i.e. its output voltage, as a function of time for different frequencies vibration. Figure 3C shows the response of the sensor as a function of the vibration amplitude for different vibration frequencies.

An actuator was manufactured according to one of the embodiments of the invention. This actuator was printed with conductive silver inks and a P polymer material (VDF-TrFE). Its dimensions are identical to those of the sensor shown in Figure 3: 30 x 30 x 1 mm ³ . The values of d ₃₃ for this actuator are close to 13 pC / N. FIG. 4A shows the displacement of the actuator as a function of the voltage applied to 1 kHz and FIG. 4B presents the displacement of the actuator as a function of the frequency applied to

10 V.

Claims

Claims 1. Method for manufacturing a piezoelectric component comprising:  a step of manufacturing a three-dimensional structure by three-dimensional printing by multilayer deposition of molten wire of a polymer, copolymer or composite material based on polymer or copolymer, on a printing medium comprising at least one conductive part; and  a step of electrically polarizing at least part of the three-dimensional structure, so as to make piezoelectric at least part of this structure,  characterized in that the electrical polarization step is a polarization effected by the Corona effect or a contact polarization, the polarization step being carried out during or following the step of manufacturing the mechanical structure, and characterized in that that at least part of the printing medium is heating and has a surface tension greater than 70 mN / m and characterized in that the method also comprises a step of manufacturing a first electrode by three-dimensional printing by depositing a conductive ink, preceding said step of manufacturing the three-dimensional structure, and a step of manufacturing a second electrode by three-dimensional printing by depositing a conductive ink, following said polarization step, at least part of said material being deposited on the first electrode, the first electrode forming said conductive part of said print medium and at least part of the second electrode being deposited on said material. 2. A method of manufacturing a piezoelectric component according to claim 1 wherein the polarization step is carried out at a temperature of at least 25 ° C, preferably at a temperature above 80 ° C. 3. Method of manufacturing a piezoelectric component according to one of the preceding claims wherein said material is chosen from PVDF, P (VDF-TrFE), P VF, PVC, P (VDCN / VAc), PTUFB, Nylon-11 , Nylon-ll / PVDF, PVDF / PZT, and Rubber / PZT. 4. A method of manufacturing a piezoelectric component according to one of the preceding claims comprising the use of at least two separate deposition heads for the deposition of said material and said conductive ink. 5. A method of manufacturing a piezoelectric component according to one of the preceding claims wherein the two said electrode manufacturing steps are followed by a step of drying said conductive ink by ultraviolet. 6. A method of manufacturing a piezoelectric component according to claim 5 comprising the use of an ultraviolet light source fixed on the deposition head of said conductive ink for said ultraviolet drying. 7. A method of manufacturing a piezoelectric component according to one of the preceding claims wherein the step of manufacturing the three-dimensional structure comprises depositing a layer of a conductive material on a polarized layer of said material. 8. A method of manufacturing a piezoelectric component according to one of the preceding claims wherein said polarization step is a polarization performed by Corona effect. 9. A method of manufacturing a piezoelectric component according to claim 8, wherein during said polarization step performed by Corona effect, a positive voltage is applied between the conductive part of the print medium and a print nozzle placed au- above the surface of the deposited material or between the layer of conductive material and a print nozzle placed above the surface of the deposited material. 10. A method of manufacturing a piezoelectric component according to one of the preceding claims also comprising a step of generating a print file for producing at least one said piezoelectric component, said step being implemented by computer and comprising:  a sub-step consisting in providing said computer with data indicative of a position of one or more points of contact between the electrodes and said material, of a spatial region where said component is to be manufactured, of at least one electrical property materials composing said piezoelectric component, and a voltage to be applied for the polarization step;  a substep for calculating a geometry and connections of said component by applying to said data a predefined mathematical model; and  a sub-step for generating said print file making it possible to produce said geometry by three-dimensional printing of said piezoelectric component. 11. Apparatus for implementing a method according to one of claims 1 to 10 comprising a three-dimensional printer of the type by deposit of molten wire having at least two deposition heads carried by a printing carriage and a support d printing, characterized in that one of the deposition heads is configured to deposit a polymer, copolymer or composite material based on polymer or copolymer, and to polarize by Corona effect or by contact at least a part of said deposited material and in that the print medium is heated and in that one of the deposition heads is configured to deposit a conductive ink. 12. Apparatus according to claim 11, in which the apparatus comprises a computer system for generating a print file for controlling said three-dimensional printer so as to manufacture a piezoelectric component, said computer system being configured to:  receive as input data indicative of a position of one or more contact points, of a spatial region where said component is to be manufactured, of at least one electrical property of the materials composing said piezoelectric component and of a voltage at apply for said polarization step; calculating a geometry of said component by applying to said data a predefined mathematical model; and generate a print file making it possible to produce said geometry by three-dimensional printing of said piezoelectric component. 13. Piezoelectric system, manufactured by a method according to one of claims 1 to 10, comprising two conductive electrodes surrounding a three-dimensional piezoelectric multilayer structure, characterized in that the three-dimensional structure and the electrodes are produced in one piece by three-dimensional printing at least one first polymer, copolymer or composite material based on polymer or copolymer forming said three-dimensional structure and at least one second conductive material forming the two electrodes and in that at least part of the three-dimensional structure is polarized electrically by Corona effect or by contact.