WO2021130280A1

WO2021130280A1 - Autonomous membrane sensor

Info

Publication number: WO2021130280A1
Application number: PCT/EP2020/087714
Authority: WO
Inventors: Jean-Philippe Polizzi; Philippe Robert; Sara LOI; Alberto Pagani
Original assignee: Commissariat A L'energie Atomique Et Aux Energies Alternatives
Priority date: 2019-12-23
Filing date: 2020-12-22
Publication date: 2021-07-01
Also published as: FR3105415B1; FR3105415A1

Abstract

The invention relates to an autonomous sensor with a deformable membrane, comprising a housing (10) in two parts (11, 12) assembled together and configured to form a sealed cavity (100), a detector (20) configured to detect a deformation of the deformable membrane (13, 13a, 13b), a wireless communication system (21) configured to communicate an item of data of deformation of the membrane (13, 13a, 13b) outside of the housing (10), and an electrical supply system (22) configured to supply the detector (20) and/or the communication system (21), the sensor being characterised in that at least one of the first and second parts (11, 12) comprises a first zone (z1) having a thickness (e1) and a second zone (z2) having a thickness (e2) such that e2 < e1, the second zone forming the at least one membrane (13, 13a, 13b) of the sensor.

Description

Autonomous membrane sensor

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the field of microelectronic sensors, for example those manufactured by silicon micromachining technologies widely known by the English acronym MEMS (Microelectromechanical Systems, or microelectromechanical systems in French). The invention finds a particularly advantageous application in the production of autonomous membrane sensors.

STATE OF THE ART

With the rise of the concept of “Internet of Things” or loT (acronym for “Internet of Things”), based on the interconnection between the Internet and objects, places and physical environments, wireless sensor networks distributed in our environment have developed considerably.

Such wireless sensors, also called stand-alone sensors, typically include a box without a wired connection. Therefore, the energy supply of these autonomous sensors can be done directly from their environment, by energy recovery for example, or by a radio link. Communication with these autonomous sensors can be done via an antenna integrated into the box. These autonomous sensors are developed for various uses. They can in particular make it possible to measure one or more physical parameters (temperature, pressure, vibration, C02, etc.) and transmit them by radio waves for analysis.

FIG. 1 illustrates an example of a stand-alone sensor configured to measure the pressure outside the housing. This sensor typically comprises a housing 10 closed vis-à-vis the outside, comprising a support 11, a cover 12 and a deformable membrane 13 assembled hermetically. The housing 10 typically houses a detector 20 and an antenna 30. The detector 20 is configured to detect a deformation of the membrane 13, and the antenna 30 is configured to transmit data relating to this measurement of deformation. It is also preferably configured to receive energy in the form of radio waves. The support 11 is pierced so as to leave a passage towards the membrane 13. The membrane 13 is attached directly or indirectly to the support 11, typically by gluing. This membrane 13 may in particular be formed on a chip 130 which is itself bonded to the support 11.

Such an autonomous pressure sensor is nevertheless relatively expensive and complex to manufacture. This type of sensor is also not suitable for certain pressure measurement applications.

Autonomous pressure sensors can in fact be used in the automotive field, for example to measure the pressure of the tires or of the brake fluid in a braking phase. They can also be used in the building industry, for example to measure the deformation of an infrastructure. Such uses generally involve the integration of the stand-alone pressure sensor in a hostile environment. Such a sensor can thus be subjected to high temperatures and / or pressure, for example of the order of 200 ° C and / or 200 atmospheres (atm) respectively. It can also be embedded in a matrix, for example a building material, which can form a corrosive medium. There is therefore also a need to provide a robust independent pressure sensor, exhibiting improved reliability.

An object of the present invention is to at least partially overcome some of the drawbacks mentioned above.

In particular, an object of the present invention is to provide an autonomous sensor with a deformable membrane limiting the cost and / or the complexity of manufacture.

The other objects, features and advantages of the present invention will become apparent on examination of the following description and the accompanying drawings. It is understood that other advantages can be incorporated. SUMMARY OF THE INVENTION

To achieve this objective, a first aspect of the invention relates to a self-contained sensor with a deformable membrane comprising at least one deformable membrane, a housing comprising at least a first part and a second part assembled together and configured to form a closed cavity, a detector configured to detect a deformation of the deformable membrane, at least one antenna and a wireless communication system associated with said at least one antenna, said wireless communication system being configured to communicate at least one data of deformation of the membrane in outside the housing, and a power supply system configured to power at least one of the detector and the communication system.

Advantageously, at least one of the first and second parts comprises a first zone having a thickness e1 and a second zone, also called thinned zone, having a thickness e2 such that e2 <e1, said second zone forming the at least one sensor membrane.

Thus, the waterproof case comprises a limited number of parts, in this case the first and second parts. The membrane is formed directly by thinning an area of at least one of said first and second parts. This avoids having to resort to the supply of a separately formed membrane, then to the mounting of this membrane on one or the other of said parts. This limits the number of parts to be assembled. The cost associated with the assembly of the housing is thus reduced. Assembly is also simplified. Such a simplified architecture also makes it possible to improve the reliability of the sensor, since the number of parts and / or assembly areas susceptible to failure decreases. Furthermore, when the sensor is subjected to severe conditions, for example high pressures, the risk of the membrane becoming detached from the housing is considerably limited compared to existing solutions, or even eliminated.

Such a sensor, in which the membrane is made directly in and in continuity with one of the parts of the housing, is particularly suitable for detecting pressure or deformation in a hostile environment.

The membrane according to the invention is a thinned zone of one and the same part. The thinned area means that it is thinner than the remaining portions of said part. The thinned zone has the thickness e2 while the remaining portions have the thickness e1. Thus, as is clear from the description and the figures, the first zone z1 and the second zone z2 have continuity of material. Thus, they do not belong to two separate parts fixed or attached to one another.

Thus, the part taken from the first and second parts is free of physical interface or material discontinuity between the first zone z1 and the second zone z2.

A second aspect of the invention relates to a system comprising a matrix and at least one sensor according to the first aspect of the invention. Advantageously, at least one sensor is embedded in the matrix.

According to one example, the system is a vehicle tire comprising at least one sensor as described above. According to another example, the system forms one of: a vehicle tire, a deformable polymer structure, for example rubber, a brake pad.

According to another aspect, the invention relates to a method of manufacturing an autonomous sensor with a deformable membrane, comprising:

A supply of a first part and a second part,

A thinning of only a portion of one of the first and the second part, so that said first part or said second part has a first zone z1 of thickness e1 and a second thinned zone z2 of thickness e2, with e2 <e1, said second zone z2 forming at least one membrane of the sensor,

A supply of a detector configured to detect a deformation of the deformable membrane,

A provision of at least one antenna and a wireless communication system associated with said at least one antenna, said wireless communication system being configured to communicate at least one piece of membrane deformation data, and a system of power supply configured to power at least one of the detector and the communication system,

An assembly of the first and second parts so as to form a housing having a closed cavity accommodating said detector, said at least one antenna and the wireless communication system, and the power supply system.

Thus, the difference in the thicknesses e1 and e2 of the first zone z1 and second zone z2 is obtained by thinning of one of the first and the second part. This difference is not obtained by assembling two parts with thicknesses different. The thinning can be carried out mechanically, by trimming for example, from a cover of constant thickness. Thinning can also be carried out directly during molding of the cover, for example. The thinned area of the cover has in all cases a continuity of material with the other areas of the cover, not thinned.

BRIEF DESCRIPTION OF THE FIGURES

The aims, objects, as well as the characteristics and advantages of the invention will become more apparent from the detailed description of an embodiment thereof which is illustrated by the following accompanying drawings in which:

FIG. 1 illustrates in section a known architecture of an autonomous membrane sensor.

FIG. 2 illustrates in section a self-contained membrane sensor according to an embodiment of the present invention.

FIG. 3 illustrates in section a self-contained membrane sensor according to another embodiment of the present invention.

FIG. 4A illustrates in section a self-contained membrane sensor according to another embodiment of the present invention.

FIG. 4B illustrates in perspective the autonomous membrane sensor illustrated in FIG. 4A.

FIG. 5A illustrates in section a self-contained membrane sensor according to another embodiment of the present invention.

FIG. 5B illustrates in perspective an autonomous membrane sensor of the type illustrated in FIG. 5A, according to an embodiment of the present invention.

FIG. 5C illustrates in wire view an autonomous membrane sensor of the type illustrated in FIG. 5B, according to an embodiment of the present invention.

The drawings are given by way of example and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate understanding of the invention and are not necessarily on the scale of practical applications. In particular, the relative dimensions of the various elements of the sensor (for example cover, support, membrane, antenna, detector, etc.) are not representative of reality.

DETAILED DESCRIPTION OF THE INVENTION

Before starting a detailed review of embodiments of the invention, it is recalled that the invention according to its first aspect comprises in particular the optional features below which can be used in combination or alternatively:

According to one example, the thickness e2 of the second zone is at least five times less than the thickness e1 of the first zone.

According to one example, the first zone is adjacent to the second zone. According to one example, the first zone surrounds, preferably entirely, the second zone. According to one example, the first zone extends around the entire periphery of the second zone.

Said second zone alone forms at least one membrane.

According to one example, the case is entirely formed by the first part and the second part.

According to one example, the power system and the detector are located in the cavity, outside the second zone. Thus, these elements are not in contact with the membrane. More precisely, they are not in contact with the internal face of the membrane.

According to one example, the sensor includes the antenna. The antenna is located inside or outside the cavity.

According to one example, the detector is located opposite the second zone. For example, the detector is located on a straight line passing through the membrane and perpendicular to the plane in which mainly extends the internal face of the membrane.

According to one example, at least one antenna is located outside the second zone.

According to one example, the first and second zones respectively have first and second surfaces S1, S2 such as S2 £ 0.5 S1.

According to one example, the second zone comprises an element projecting from a side opposite the cavity, directed towards a zone external to the housing.

According to one example, the second zone supports at least one of a capacitive, piezo-resistive, or piezoelectric element. According to one embodiment, the capacitive, piezo-resistive or piezoelectric element is attached to the second zone.

According to one example, the detector is configured to cooperate with said at least one capacitive, piezo-resistive or piezoelectric element.

According to one example, the sensor comprises a plurality of membranes arranged on one of the first and the second parts. Preferably, the sensor comprises a detector configured to detect a deformation of each of the membranes. The detector can be common to all or more of the membranes. Alternatively, the sensor can comprise a single detector per membrane. According to a first mode of realization, this makes it possible to capture several parameters. According to another embodiment, this plurality of membranes makes it possible to introduce redundancy in the detection, which improves the general reliability of the sensor.

According to one example, the first and second parts each comprise at least one second zone forming a deformable membrane.

According to one example, the membrane of the first part is located opposite the membrane of the second part. According to one example, the cavity is located between the membrane of the first part and the membrane of the second part.

In one example, the cavity is empty except for the components. Thus, a vacuum is created inside the cavity before it is sealed. This allows for example a better resistance of the sensor in an environment where the temperature is high. Alternatively, the cavity is filled with gas before being sealed. This gas is preferably a neutral gas.

In one example, at least one of the first and second parts is silicon.

The invention according to its second aspect comprises in particular the optional characteristics below which can be used in combination or alternatively:

According to one example, the matrix is made of a material taken from a polymer, a geopolymer, a composite material, a metal alloy, a ceramic.

Unless there is a technical incompatibility, it is understood that the device, the manufacturing process, and the system may include, mutatis mutandis, all of the above optional characteristics.

In the context of the present invention, the term “sealed” cavity is understood to mean a closed cavity preventing or limiting the exchange of fluid with the environment outside said cavity. The term "hermetic" can be used synonymously. These qualifiers applied to a sensor housing including a cavity are understood under normal conditions of use and / or within manufacturing tolerances. A closed cavity is not necessarily waterproof. A closed cavity at least prevents the introduction of small objects or particles.

By deformable membrane is meant a membrane capable of being elastically deformed. In contrast, the part of the housing forming a support or a frame supporting the membrane is rigid. This support or this frame has an ability to deform much lower than that of the membrane. The flexibility of the membrane is obtained mainly by its low thickness. We thus have a ratio greater than 20 or even 50 and even 100 between the thickness of the membrane (typically of the order of a micron) and the thickness of the frame (typically of the order of the thickness of a silicon wafer or of the order of 500 or 750 microns).

More generally, a "deformable" element is understood to mean an ability of this element to deform elastically under the action of pressure. This property is in particular characterized by its Young modulus. Thus, a silicon-based membrane has, for example, a Young's modulus of between 130 and 185 GPa (Gigapascals). Such a membrane can deform when subjected to pressures in the range of a few atmospheres to a few hundred atmospheres. A deformable membrane can optionally have other properties or functionalities, in addition to its deformation capacities. The membrane is not limited to a silicon-based membrane. It may for example be based on ceramic or stainless steel.

In the present application, pressure values are mentioned. The pressure unit (s) associated with these values are not necessarily the pascal (symbol Pa) of the international system of units. The pressure values can be expressed, in a manner known and customary to those skilled in the art, in bars or in atmospheres. One bar is equivalent to 1 bar = 10 ⁵ Pa. One atmosphere (symbol atm) is equivalent to 1 atm = 101 325 Pa.

By a substrate, a film, a membrane or a cover "based" on a material M is meant a substrate, a film, a membrane or a cover comprising this material M only or this material M and possibly other materials. , for example alloying elements, impurities or doping elements. Thus, a membrane made of a silicon-based material can for example be a thin part of a silicon substrate or a more complex structure incorporating a silicon part associated with one or more other thin layers. Where appropriate, the material M can exhibit different stoichiometries and / or crystallographic structures.

In the present patent application, the first, second and third directions correspond respectively to the directions carried by the x, y, z axes of a preferably orthonormal coordinate system. This mark is shown in the appended figures.

In the following, the length is taken in the first direction x, the width is taken in the second direction y, and the thickness is taken in the third direction z.

By a “thinned” part of an element is meant a part of this element having a thickness less than the thicknesses of the parts of this element surrounding said thinned part. A part can be thinned a posteriori, by a thinning or machining step for example, or a priori, that is to say directly during the formation, by molding for example. A silicon-based membrane can typically be formed by localized thinning of a silicon substrate. This localized thinning can be carried out by plasma, which typically forms vertical walls around the membrane, as illustrated in FIG. 2. Alternatively, this localized thinning can be carried out by wet etching, for example based on a solution. of KOH (potassium hydroxide) or TMAH (tetramethylammonium hydroxide), which typically forms sloping walls around the membrane, as shown in Figure 3.

The membrane has an internal face turned towards the inside of the case and an external face, opposite to the internal face and turned towards the outside of the case. According to one example, the internal face extends mainly along a first plane parallel to the xy plane. According to one example, the outer face extends mainly along a second plane, also parallel to the xy plane. The thickness of the membrane is measured in a z direction perpendicular to the first and second planes. The thickness e1 of the first zone Zi and the thickness e2 of the second zone z ₂ are measured in the direction z.

According to a preferred example, the thickness e2 of the membrane is preferably substantially constant over the entire zone z2. According to one possibility, this thickness can vary over the membrane zone z2. The membrane may for example be thinner at its center and thicker at its periphery. In this case, the thickness e2 is an average thickness, if the variation in thickness does not exceed a factor 2. Alternatively, for greater variations in thickness, the thickness e2 is the minimum thickness of the membrane .

According to a preferred example, the thickness e1 is an average thickness, if the variation in thickness of the zone z1 does not exceed a factor 2. Alternatively, for greater variations in thickness, the thickness e1 is the minimum thickness of zone 1

The terms “substantially”, “approximately”, “of the order of” mean “within 10%” or, in the case of an angular orientation, “within 10 °”. Thus, a direction substantially normal to a plane means a direction having an angle of 90 ± 10 ° with respect to the plane.

According to the invention, the housing typically comprises two parts assembled together. These two parts are more precisely designated “support” and “cover” in the following. The membrane of the sensor according to the invention is formed in at least one of these parts and is delimited by a zone of thickness e2 thinner than the rest of the part considered, that is to say the support or the hood, as appropriate. This thinned area is marked "z ₂ " in the accompanying figures. In the following, for the sake of brevity, reference will be made more simply to the “membrane”.

The invention will now be described in detail through a few non-limiting embodiments.

Referring to Figure 2, a first embodiment of a membrane sensor comprises a housing 10 formed by at least two parts. In the example shown, the box

10 is formed by a support 11 and a cover 12 assembled together. This housing 10 forms a cavity 100 comprising detection and / or communication and / or power supply means. The detection means, typically a detector 20, are configured to cooperate with a membrane 13 formed directly in the cover 12. The communication means, for example a communication module or system 21 comprising a transceiver associated with an antenna 30, are configured to emit and / or receive signals to or from an element external to the sensor, i.e. outside the housing 10.

The means for supplying energy to the sensor, for example an electrical supply module or system, are configured to supply the sensor directly from its environment, by energy recovery for example, or by a radio link. Thus the sensor is preferably an energy independent sensor. Alternatively, provision can be made for the sensor to be supplied with energy by a battery integrated in the housing 10.

Housing 10 is closed. It is preferably waterproof. According to one example, a vacuum is created in the cavity 10. This allows for example better resistance of the sensor in an environment where the temperature is high. This also makes it possible, for a pressure sensor, to measure the pressure in an absolute or quasi-absolute manner, with respect to the vacuum created in the cavity. Alternatively, the cavity 100 is filled with a gas before being sealed. This gas is preferably a neutral gas.

The assembly of the housing 10 can be done by gluing, sintering, thermocompression or sealing by thermocompression or soldering of the cover 12 on the support 11 at the level of the interfaces 121. The interfaces 121 can therefore be in the form of a weld, of a solder, an adhesive or a sintered part, intermediate between the support

11 and the cover 12. This assembly can be done by respecting standards or directives associated with the level of sensitivity to humidity MSL (acronym for Moisture Sensitive Level) of the components (for example detector 20, transceiver 21) located in the cavity 100. The dimensions of the housing are preferably less than 10 cm, and more preferably less than 5 cm, in length, width and height, respectively according to x, y and z. The case may for example have a length along x of the order of 2 cm, a width along y of the order of 1.5 cm and a height along z of the order of 1 mm to 2 mm, for example approximately 1.5 mm - which corresponds to the sealing of two wafers or silicon substrates, cover and support, 750 μm thick. The housing 10 can have different shapes, for example in the form of a polyhedron or a cylinder. The housing 10 makes it possible to protect the components 20, 21, 30 located inside the cavity 100. It essentially comprises two parts 11, 12 assembled together at the level of the interfaces 121. The number of interfaces is thus limited. This makes it possible to minimize the areas of weakness linked to the assembly. The housing 10 therefore has improved mechanical strength and / or corrosion resistance. The cost of assembly is thus further reduced.

The support 11 can typically be a silicon-based substrate. This makes it possible to easily integrate on this support 11 detection and / or communication means in the form of a chip by microelectronic technologies. Alternatively, the support 11 can be based on a material taken from: a metal, a ceramic, or glass. The housing, preferably the support 11 has a face 110 facing the cavity 100. The different detection (detector 20) and / or communication (transceiver 21, antenna 30) and / or supply (antenna) means 30) are preferably in the form of components 20, 21, 22, 30 transferred to this face 110. The face 110 preferably comprises electrically conductive regions so as to electrically connect several components together. As illustrated in Figure 2, the antenna 30 can be electrically connected to the connection wire B2 through the face 110 of the support 11. The electrical connection of the various components 20, 21, 30 between them can be made by the 'intermediate connection son B1, B2, or conductive tracks directly deposited on the face 110, or a combination of son and tracks.

In this embodiment, the components 20, 21, 22, 30 are arranged on the support 11 which improves the robustness of the sensor and facilitates the manufacturing and assembly steps. In particular, all the electronic connections can be made on the same part of the housing 10. Alternatively, all or some of the components 20, 21, 22, 30 can be arranged on the cover 12 rather than on the support 11.

The cover 12 can typically be based on a material taken from: a metal or a metal alloy, a plastic, a ceramic, a glass. In this example of FIG. 2, the cover 12 comprises the deformable membrane 13. Thus, the cover 12 directly integrates a sensor detection element. The cover 12 therefore makes it possible to protect the sensor while contributing to the detection function of the sensor. The cover 12 is thus functionalized. The material of the cover 12 is preferably chosen as a function of its mechanical properties. The cover 12 may have a thickness e1 of a few hundred microns to a few tens of millimeters.

For standard detection applications, for example, the cover 12 can be made of a plastic material loaded with silica or carbon fibers. This makes it possible to obtain both a good deformation capacity of the membrane 13 along z and a sufficient mechanical strength to protect the components 20, 21, 30 in the cavity 100. Such a cover 12 and its membrane 13 made of composite plastic can be obtained. be easily shaped by molding or extrusion. Its manufacturing cost is relatively low.

For detection applications in a hostile environment, other hermetic housings made from metal / glass or ceramics can be used. Such housings advantageously withstand high temperature and pressure conditions, and / or corrosive environments. The techniques for assembling these housings, for example using Kovar type alloys or vitreous pastes, are known to those skilled in the art. Such housings are generally machined. Machining of the cover 12 can in particular be carried out to thin the part of the cover 12 forming the membrane 13.

In general, the cover 12 is preferably configured to have sufficient deformability at the level of the membrane 13, and low deformability outside the membrane, for example less by a factor of 10 than that of the membrane 13.

In this embodiment, the membrane 13 is directly formed in the cover 12. The material of the membrane 13 is therefore identical to that of the cover 12. It is in the form of a zone z2 defined by a thinned part of the cover 12. , of thickness e2. Thus, the housing part 10 integrating the membrane 13, the cover 12 in this embodiment, has at least a first zone z1 having a thickness e1 and a second zone z2 having a thickness e2 less than z1.

The thickness ratio e1 / e2 can be greater than 3, preferably greater than or equal to 5. This increases the deformability of the membrane 13 with respect to that of the cover 12.

The membrane 13 can have a uniform thickness e2. The variation in thickness between the membrane 13 and the rest of the cover 12 therefore takes place abruptly. This makes it possible to clearly delimit the deformation zone. This makes it possible, for example, to optimize the piezoelectric detection of the stresses applied to the membrane. According to an alternative possibility, this variation in thickness takes place more or less keep on going. The external face 132 of the membrane 13 typically has, in projection in the xy plane, a surface S2 less than the surface S1 (in projection in the xy plane) of the unthinned parts of the cover 12.

Preferably the cover 12 has a substantially uniform thickness throughout the first zone z1 with the exception of the second zone z2 forming the membrane 13. The thickness e1 or e2 at a point on the surface of the housing 10 is measured in one direction. perpendicular to the tangent at the point considered.

The membrane 13 can be partly covered by a functional layer. In the example illustrated in Figure 2, the membrane 13 is coated on its inner face 130 with a metal layer 131 (not visible). By placing the detector 20 facing the membrane 13, the latter can in particular detect a variation in capacitance induced by the deformation of the membrane 13.

In this example, the detector 20 is configured to detect a variation in capacitance between the face 130 of the membrane and an upper face 201 of the detector 20. The capacitance varies in particular when the distance between said faces 130, 201 varies. This ultimately makes it possible to measure a pressure exerted on the membrane 13. The detector 20 can be associated with a signal processing module (not illustrated), a power supply module (not illustrated), a transceiver 21.

As briefly mentioned above, the autonomous sensor preferably comprises, in addition to the detector 20, at least one power system 22 and a wireless communication system 21 (transceiver and antenna 30). The antenna 30 can be produced by lithography or screen printing or by metallic inkjet printing, for example. It can have different known shapes taken from a circle, a spiral, a cross, an H shape, etc.

Other embodiments of the sensor according to the invention can be envisaged. Only the distinct characteristics of the first embodiment are described below, the other characteristics not described being deemed to be identical to those of the first embodiment.

According to a second embodiment illustrated in FIG. 3, the membrane 13 is formed directly in the support 11. The components 20, 21, 30 are in this case arranged in the zone z1 of greater thickness, that is to say. ie outside the zone z2 forming the membrane 13. This makes it possible, for example, to avoid a disturbance in the behavior of the membrane during deformation, or fatigue of the component during repeated deformations of the membrane. In this example, the membrane 13 is made of silicon, and the deformation of the membrane 13 is detected by means of piezoelectric or piezo-resistive gauges 131. These gauges 131 are preferably arranged on a perimeter of the face 130 of the membrane 13. The piezoelectric or piezo-resistive effect induced by the deformation of the membrane 13 is in fact maximized at this perimeter. The detection by the gauges 131 is thus optimized. The external face 132 of the membrane 13 typically has, in projection in the xy plane, a surface S2 less than the surface S1 (in projection in the xy plane) of the non-thinned parts of the support 11.

More generally, the second zone z2 of the sensor 20 supports at least one of a capacitive, piezo-resistive, or piezoelectric element.

Preferably in this embodiment, the internal face 130 of the membrane 13 is located in the same plane as an internal face 111 of the support 11 on which the components rest. On the other hand, the external face 132 of the membrane 13 is not located in the same plane as an external face 112 of the support 11. Typically, the thinning of the zone z2 forming the membrane 13 is obtained by removing material from it. the outer face 112 of the support 11.

According to a third embodiment illustrated in FIGS. 4A, 4B, the sensor comprises at least two deformable membranes 13a, 13b. In this example, the sensor is more particularly configured to detect a deformation resulting from at least one traction exerted in at least one direction parallel to the plane in which extends at least one of the two membranes 13a, 13b, more precisely their internal faces 130. In this example, the two membranes 13a, 13b, more precisely their internal faces 130, extend in parallel planes. These planes are parallel to the xy plane of the xyz coordinate system.

In this example, the membranes have, in this xy plane, a main dimension along the x axis.

As illustrated in FIG. 4A, the tensile force is exerted along the x axis and is represented by the tensile forces F _T , -F _T. The membranes 13a, 13b are respectively formed directly in the support 11 and the cover 12 of the housing 10. They respectively have thicknesses e2 ′, e2 ″ which may be substantially equal to each other. These thicknesses e2 ', e2 ”can be determined as a function of the mechanical properties of the corresponding membranes. Thus, if the support 11 and the cover 12 are formed from different materials, the thicknesses e2 ', e2 ”of the membranes can be chosen so that one and the other of the membranes 13a, 13b exhibit resistance to the equivalent traction. This makes it possible to calibrate the tensile behavior of the sensor. The membranes 13a, 13b are arranged in this example opposite one from the other. They may have identical width and / or length dimensions.

In this example, the deformation during traction is measured on the inner face 130 of the silicon membrane 13a, through the piezoelectric or piezo-resistive gauges 131. These gauges 131 can be placed around and in the center of the membrane 13a, as illustrated in FIG. 4A. Of course, these gauges 131 can be distributed differently on the membrane. The components in chip form, for example the detector 20, are preferably located in the zone z1 and therefore outside the zone z2 delimiting the membrane 13a. The antenna 30 can be formed or deposited directly on the internal face 130 of the membrane 13a. The antenna can alternatively be formed on an unthinned part of the case, for example to prevent it from being subjected to too great deformation.

FIG. 4B illustrates in perspective such a sensor. The general shape of the housing 10 may resemble that of a tensile test specimen, well known to those skilled in the art in the field of the resistance of materials. The shape of the housing 10 thus reflects the function of the sensor. The outer faces 132a, 132b of the membranes 13a, 13b can in particular extend in xy planes parallel to each other. The external faces 132a, 132b have respectively, in projection in the xy plane, surfaces S2 ', S2 ”typically greater than the surfaces S1', S1” (in projection in the xy plane) of the respective non-thinned parts of the support and of the cover of the box 10. However, it is not necessary for the thinned surfaces to have surfaces S2 ', S2 ”greater than the surfaces S1', S1” in projection in the xy plane.

According to a fourth embodiment illustrated in FIGS. 5A to 5C, the sensor comprises a deformable membrane 13 comprising on its external face 132 a projecting element 133. This element 133 forms a projection with respect to the external face 112 of the support 11. In this example, the sensor is more particularly configured to detect a deformation resulting from a flow directed for example along the x axis, as illustrated on FIG. 5A by force F. Alternatively, the projecting element 133 can constitute a multi-axis sensor, associated with strain gauges distributed so as to each detect a movement of the projecting element 133 in a direction or around it. a specific axis of rotation.

The projecting element 133 preferably has a height h greater than the thickness e1 of the non-thinned parts of the support 11. The element 133 is thus more sensitive to the flow outside the housing 10. This makes it possible to increase the sensitivity of the sensor. . FIG. 5B illustrates in perspective such a sensor. The general shape of the element 133 projecting from the membrane 13 may be similar to that of a joystick. In particular, the element 133 may be centered on the membrane 13 and have freedom of movement in a cone of revolution, the apex of which is located substantially at the base of the element 133, and the axis of which is substantially perpendicular to the membrane 13. The membrane 13 may have a circular shape. This makes it possible to have a deformation behavior of the membrane which is reproducible whatever the direction of the flow F in the xy plane, for a membrane whose mechanical properties are isotropic in such an xy plane. Other forms of membranes are also conceivable. The element 133 may have a cylindrical shape and a symmetry of revolution. This makes it possible to offer the same bearing surface whatever the direction of the flow F in the xy plane. Alternatively, the element 133 may have a flattened shape in a plane substantially perpendicular to that of the membrane. This makes it possible to favor a particular direction of detection of the flux F in the xy plane.

In this example, the deformation of the silicon membrane 13 induced by the flow F outside the housing 10 is measured on the face 130, by means of the piezoelectric or piezo-resistive gauges 131. These gauges 131 can be placed around the periphery of the membrane 13, as illustrated in FIG. 5C. The gauges 131 are preferably distributed uniformly around the periphery of the membrane 13, at regular intervals. They can be four in number, as illustrated in Figure 5C, or eight for example. They can be sized as main gauges and secondary gauges, with different degrees of sensitivity for example.

The components in chip form, for example the detector 20, the transceiver 21, the power supply system 22 are preferably located outside the zone z2 delimited by the membrane 13. The antenna 30 can be formed around of the face 130 of the membrane 13, for example in the form of a ring.

Thus, as clearly emerges from the preceding paragraphs as well as from FIGS. 2, 3, 4A, 5A, the autonomous sensor with a deformable membrane is typically manufactured by a process comprising the following steps:

Provide a first part 11 (typically the support) and a second part 12 (typically the cover),

- Thinning only a portion of the support 11 or of the cover 12, so that said support 11 or cover 12 has a first zone z1 of thickness e1 and a second thinned zone z2 of thickness e2, with e2 <e1, said second zone z2 forming at least one membrane 13 of the sensor, Provide a detector 20 configured to detect a deformation of the deformable membrane 13,

Provide at least one antenna 30 and a wireless communication system 21 associated with said at least one antenna 30, said wireless communication system 21 being configured to communicate at least one deformation data of the membrane 13, and a system of power supply 22 configured to power at least one of the detector 20 and the communication system 21,

- Assemble the support 11 and the cover 12 so as to form a housing 10 having a closed cavity 100 accommodating said detector 20, said at least one antenna 30 and the wireless communication system 21, and the power supply system 22.

A principle common to the embodiments of the sensor according to the invention is that part of the housing forms the membrane, so that the housing is "functionalized". Such an autonomous membrane sensor can advantageously be embedded in different materials, for example construction materials such as concrete according to a non-limiting example. For example, this sensor can be abandoned in a concrete matrix, within a building infrastructure. It can thus make it possible to follow the variations of constraints applied to said infrastructure. This sensor can also be embedded in rubber used for tire manufacturing, in order to measure tire pressure during use. This sensor can also be embedded in a brake pad matrix, so as to measure the force applied to said pad by a braking system. Other uses of the sensor according to the invention are of course possible. The invention is not limited to the embodiments described above and extends to all the embodiments covered by the claims. In particular, the number of membranes of the sensor can be greater than two. The shape of the membrane (s) can be adapted depending on the use of the sensor.

Claims

1. Autonomous sensor with a deformable membrane comprising at least one deformable membrane (13, 13a, 13b), a housing (10) comprising at least a first part and a second part (11, 12) assembled together and configured to form a cavity (100) closed, a detector (20) configured to detect a deformation of the membrane (13, 13a, 13b), at least one antenna (30) and a wireless communication system (21) associated with said at least one antenna (30), said wireless communication system being configured to communicate at least one piece of membrane deformation data (13, 13a, 13b) outside the housing (10), and a power supply system (22) configured to powering at least one of the detector (20) and the communication system (21), the sensor being characterized in that at least one of the first and second parts (11, 12) comprises a first zone (zi ) having a thickness ei and a second zone (z ₂ ) having a thickness e ₂ te lle that e ₂ <ei, said second zone forming the at least one membrane (13, 13a, 13b) of the sensor, so that said at least one membrane (13, 13a, 13b) is produced directly in and in continuity with said at least one of the first and second parts (11, 12) of the housing.

2. Sensor according to the preceding claim wherein the thickness e2 of the second zone (z ₂ ) is at least five times less than the thickness e1 of the first zone.

(zi)

3. Sensor according to any one of the preceding claims, in which the first zone (zi) surrounds, preferably entirely surrounds, the second zone (z ₂ ).

4. Sensor according to any one of the preceding claims, in which the supply system and the detector (22, 20) are located in the cavity (100), outside the second zone (z ₂ ).

5. Sensor according to any one of the preceding claims, in which the detector (20) is located opposite the second zone (z ₂ ).

6. Sensor according to any one of the preceding claims, in which the at least one antenna (30) is located outside the second zone (z ₂ ).

7. Sensor according to any one of the preceding claims, in which the first and second zones (zi, z ₂ ) respectively have first and second surfaces S1, S2 such that S2 £ 0.5 S1.

8. Sensor according to any one of the preceding claims wherein the second zone (z ₂ ) comprises an element (133) projecting from a side opposite the cavity (100), directed towards a zone external to the housing (10). .

9. Sensor according to any one of the preceding claims, in which the second zone (z ₂ ) supports at least one of a capacitive, piezo-resistive or piezoelectric element (131), and in which the detector (20 ) is configured to cooperate with said at least one element (131).

10. Sensor according to any one of the preceding claims, in which the housing (10) is waterproof.

11. A sensor according to any preceding claim comprising a plurality of membranes (10, 13a, 13b) disposed on one of the first and second parts (11, 12).

12. Sensor according to any one of the preceding claims, in which the first and second parts (11, 12) each comprise at least one second zone (z ₂ ) forming a deformable membrane (13a, 13b).

13. Sensor according to the preceding claim wherein the membrane (13a) of the first part (11) is located opposite the membrane (13b) of the second part (12), the cavity (100) being located between the membrane ( 13a) of the first part (11) and the membrane (13b) of the second part (12).

14. A sensor according to any preceding claim wherein at least one of the first and second parts (11, 12) is made of silicon.

15. A method of manufacturing an autonomous sensor with a deformable membrane (13, 13a, 13b), comprising:

A supply of a first part (11) and a second part (12),

A thinning of only a portion of the first part (11) or of the second part (12), so that said first part (11) or second part (12) has a first zone (z1) of thickness e1 and a second thinned zone (z2) of thickness e2, with e2 <e1, said second zone (z2) forming at least one membrane (13, 13a, 13b) of the sensor,

A supply of a detector (20) configured to detect a deformation of the deformable membrane (13, 13a, 13b),

A provision of at least one antenna (30) and a wireless communication system (21) associated with said at least one antenna (30), said wireless communication system (21) being configured for communicating at least one membrane deformation datum (13, 13a, 13b), and a power supply system (22) configured to power at least one of the detector (20) and the communication system (21) , - An assembly of the first and second parts (11, 12) so as to form a housing (10) having a closed cavity (100) accommodating said detector (20), said at least one antenna (30) and the communication system (21) wireless, and the power supply system (22).

16. System comprising a matrix and at least one sensor according to any one of claims 1 to 14, wherein at least one sensor is embedded in the matrix.

17. System according to the preceding claim wherein the matrix is made of a material selected from a polymer, a geopolymer, a composite material, a metal alloy, a ceramic.

18. The system of claim 16, forming one of: a vehicle tire, a deformable polymer structure, a brake pad.