Vibration sensor and device for measuring periodic biosignals emitted by the human or animal body

Abstract

The present invention relates to a vibration sensor (100) for measuring periodic biosignals from an individual, comprising a laminate (10) including an active layer (11) made of a piezoelectric material and two contact electrodes (12, 13) arranged on the active layer (11), the active layer having a thickness of less than or equal to 20 microns and a Young's modulus of more than or equal to 60 GPa; a flexible support layer (30) including a printed circuit (31) with two electrical terminals (32, 33); and an electrical connection layer (20) arranged between the laminate (10) and the flexible support layer (30) for connecting each of the electrodes (12, 13) to the terminals (32, 33).

Description

[Technical field]

[0001] The present invention relates to the field of collecting periodic biosignals emitted by the human / animal body, in particular signals including heart rate and respiration rate. The invention particularly relates to a vibration sensor and a device comprising said sensor, which is applied to the body in contact with the skin or an intermediate layer (clothing, fur, leather, etc.), allowing the measurement of said periodic biosignals in a quiet or noisy environment. [Background technology]

[0002] Phonocardiography is a non-invasive acoustic method for measuring the heart rate. From the phonocardiograms (PCG) obtained by this method, it is possible, after analysis, to deduce different indices that indicate the general operation of the heart and / or the state of the subject (health, stress, emotions, fatigue, etc.). For example, Heart Rate Variability (HRV) is a particularly relevant index that is frequently used to determine physiological responses related to emotions, stress, fatigue or sleep.

[0003] Although proven and recognized by the scientific community, phonocardiography nevertheless has certain constraints today that limit its widespread adoption. Indeed, current devices in most cases require close contact with the subject (directly on the skin), knowledge of the proper positioning of the measuring device and of the pressure to be applied to the skin, as well as a quiet sound environment. This is especially the case for the portable device described in Korean Patent No. 101957110, which comprises a piezoelectric ceramic sensor intended to be in direct contact with the user's skin and an adhesive ring that allows maintaining contact with the skin.

[0004] Object of the invention The present invention aims to remedy all or some of the above mentioned drawbacks, and in particular relates to a miniature device that is applied to the body of an individual in contact with the skin or an intermediate layer (clothing, fur, leather, etc.) and is capable of capturing and analyzing periodic biosignals, and does so in quiet or noisy environments, whether the subject is stationary or moving. Summary of the Invention

[0005] The present invention relates to a vibration sensor for measuring at least one periodic biosignal of an individual, comprising: a stack including an active layer made of piezoelectric material extending parallel to its main faces and two contact electrodes arranged on at least one face of the active layer, the active layer having a thickness less than or equal to 20 microns and a Young's modulus greater than or equal to 60 GPa; a flexible support layer configured to transmit deformations to the active layer of the stack at each pulse of the biosignal, said support layer (30) extending parallel to its main plane and including a printed circuit with two electrical terminals; an electrical connection layer arranged between the laminate and the support layer, connecting each contact electrode to an electrical terminal, It concerns a vibration sensor, which is intended to be in contact with an individual on the side of the support layer.

[0006] According to other advantageous, non-limiting characteristics of the present invention, taken alone or according to any technically feasible combination, the following: - Vibration sensor: 5 x 10 5 Pa * s / m~3×10 6 Pa * an impedance matching layer having an acoustic impedance comprised within s / m and disposed on a surface of the support layer opposite the surface in contact with the electrical connection layer; the piezoelectric material of the active layer is chosen from ceramics in monocrystalline, polycrystalline or composite form; the contact electrodes have a cumulative thickness less than twice the thickness of the active layer; the support layer is self-supporting and has a thickness of 500 microns or less; the impedance matching layer has a thickness of 10 microns or greater; the electrical connection layer is formed by an interposer or an anisotropic conductive film, the support layer comprises a film disposed on a side of the printed circuit opposite to the side in contact with the electrical connection layer; the laminate and the support layer each have a first surface area and a second surface area on a major plane, the first surface area being no more than 30% of the second surface area; the support layer comprises a reinforcing structure rigidly connected to a peripheral zone of said support layer, the printed circuit comprises wire connection elements for connecting the vibration sensor to electronic terminals, the reinforcing structure supports two electrical contact outlets each connected to an electrical terminal for connecting the vibration sensor to an electronic terminal; The vibration sensor includes a peripheral seal; The vibration sensor comprises a protective layer arranged above the stack and spaced apart from the stack, the protective layer being firmly connected to the support layer.

[0007] The present invention further provides a non-invasive device for measuring at least one periodic biosignal of an individual, comprising: at least one vibration sensor as described above for measuring a raw signal representative of a periodic biosignal, and an electronic terminal connected to the vibration sensor, for analysing and interpreting the raw signal, and for outputting a periodic biosignal or an output parameter representative of the periodic biosignal.

[0008] The electronic terminal advantageously comprises: an analog stage for conditioning the raw signal measured by the vibration sensor; - an analog-to-digital conversion stage for the signal coming from the conditioning stage; a digital signal processing stage for forming a digital signal and for calculating output parameters representative of the biosignal; Potentially, a communication stage with external systems. [Brief description of the drawings]

[0009] Other features and advantages of the present invention will become apparent from the following detailed description of the invention which refers to the accompanying drawings. [Figure 1a] A vibration sensor according to the invention is shown in a schematic cross-sectional view and a perspective cross-sectional view, respectively. [Figure 1b] A vibration sensor according to the invention is shown in a schematic cross-sectional view and a perspective cross-sectional view, respectively. [Figure 2a] A vibration sensor according to the invention is shown in a schematic cross-sectional view and a perspective cross-sectional view, respectively. [Figure 2b] A vibration sensor according to the invention is shown in a schematic cross-sectional view and a perspective cross-sectional view, respectively. [Figure 2c] A vibration sensor according to the invention is shown in a schematic cross-sectional view and a perspective cross-sectional view, respectively. [Figure 3a] A vibration sensor according to the invention is shown in a schematic cross-sectional view and a perspective cross-sectional view, respectively. [Figure 3b] A vibration sensor according to the invention is shown in a schematic cross-sectional view and a perspective cross-sectional view, respectively. [Figure 4] 1 shows different shapes of a vibration sensor according to the invention in plan view; [Diagram 5] 1 shows various configurations of a device for measuring periodic biosignals according to the present invention; [Figure 6a] 1 shows a spectrogram A captured by a vibration sensor according to the invention and a reference spectrogram (reference) captured by a conventional microphone. [Figure 6b] 1 shows a spectrogram B from spectrogram A after applying a frequency filter, and biological signals C, D as waveforms captured and processed by a device according to the invention.

[0010] The same reference numbers in the figures may be used for the same type of elements. Some figures include schematic diagrams that are not to scale for ease of reading. In particular, layer thicknesses along the z-axis are not to scale with respect to lateral dimensions along the x- and y-axes, and the relative thicknesses of layers therebetween are not necessarily taken into account.

[0011] The different possibilities (variants and embodiments depicted and / or detailed in the following description) must be understood as not being mutually exclusive and may be combined together. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention relates to a vibration sensor 100 for measuring at least one periodic, regular or irregular biosignal of an individual. An "individual" is considered here in a broad sense and may correspond to a human or an animal. The periodic biosignal may in particular be the heart rate or the respiratory rate.

[0013] Various configurations of a vibration sensor 100 according to the present invention are shown in Figures 1a, 1b, 2a, 2b, 3a and 3b.

[0014] The vibration sensor 100 comprises a stack 10 extending parallel to a main plane (x, y), i.e. the main faces of this stack 10 are substantially parallel to said main plane (x, y) and the thickness of the stack 10 is measured along an axis z perpendicular to said main plane. In the present invention, the term "layer" means that the thickness of a layer (or stack) is generally significantly smaller than the lateral dimensions (in the main plane) of the layer.

[0015] The stack 10 includes an active layer 11 made of a piezoelectric material having a thickness of 20 microns or less and a Young's modulus of 60 GPa or greater. These physical properties provide the active layer 11 with a high level of sensitivity and provide the sensor 100 with a high signal-to-noise ratio to detect sound waves at frequencies associated with the target periodic biosignal. The small thickness of the active layer 11 also facilitates miniaturization of the sensor 100.

[0016] In a manner known per se, the active layer 11 made of piezoelectric material will become polarized (thus generating a flow of charges resulting in a measurable electrical signal) when subjected to a deformation, in particular a deformation caused here by the angular frequency of a periodic biological signal.

[0017] Advantageously, to further improve the sensitivity of detection of acoustic waves, the thickness of the active layer 11 is less than 10 microns, or even less than 5 microns, and it will be ensured that the thickness of the active layer 11 is sufficient to generate a bias voltage during deformation, typically greater than 500 microvolts.

[0018] The lateral dimensions of the active layer 11 (in the main plane (x,y)) may for example be chosen to be between 500 microns and 50 mm, with small dimensions being naturally preferred for reasons of miniaturization of the vibration sensor 100.

[0019] The material of the active layer 11 is preferably selected from piezoelectric ceramics in monocrystalline, polycrystalline or composite form (corresponding to a dispersion of piezoelectric ceramic powder in a matrix, generally a polymer). By way of example, the following ceramics may be mentioned: lithium niobate (LiNbO3), lithium tantalate (LiTaO3), potassium niobate (KNbO3), (BaTiO3), quartz (SiO2), lead magnesium niobate-lead titanate (PMN-PT), lead zirconate titanate (PZT), materials based on potassium sodium niobium lithium antimony (KNN-LS) or modified with calcium titanate (KNN-LS-CT), materials based on potassium sodium lithium niobium tantalum antimony (KNNLNTS), bismuth sodium titanate (BNKLBT), etc.

[0020] The stack 10 also includes two contact electrodes 12, 13 arranged on one or both faces of the active layer 11 (i.e., on either side of the active layer 11), allowing the free circulation of charges driven by the polarization of the layer 11 (representing a periodic biosignal).

[0021] Preferably, the contact electrodes 12, 13 have a cumulative thickness that is less than twice the thickness of the active layer 11, or less than the thickness of the active layer 11, and therefore each electrode 12, 13 advantageously has a thickness of less than 10 microns, or less than 5 microns.

[0022] The contact electrodes 12, 13 may be made of a pure metallic material (e.g., Ag, Au, Pd, Pt, Cu, Ni, W, or Ti), a conductive alloy, or a two-dimensional (2D) conductive material (e.g., graphene). Between the conductive material of each electrode 12, 13 and the active layer 11, a diffusion barrier (e.g., made of TiN, WN, or TaN) and an adhesion layer (e.g., made of Cr or Ti) may be provided.

[0023] Advantageously, the stack 10 consists only of an active layer 11 and two contact electrodes 12,13.

[0024] The vibration sensor 100 also comprises a flexible support layer 30 extending parallel to the main plane (x, y) and including a printed circuit 31 with two electrical terminals 32, 33. An electrical connection layer 20 (which also forms part of the vibration sensor 100) is disposed between the laminate 10 and the support layer 30 and connects each contact electrode 12, 13 to the electrical terminals 32, 33.

[0025] The electrical connection layer 20 is formed by an interposer or an anisotropic conductive film (ACF). In all cases, the aim is that the two contact electrodes 12, 13 of the stack 10 can be reached on one and the same face of the stack 10. This face (called the lower face) is then associated with the connection layer 20. When the contact electrodes 12, 13 are respectively arranged on the lower face and on the other face (called the upper face) of the active layer 11, it is advantageous to provide a conductive via 14 that penetrates the active layer 11 and electrically connects the electrode 12 arranged on the upper face to a stud part 12a arranged on the lower face and electrically insulated from the other electrode 13 also arranged on the lower face.

[0026] The interposer may be constructed from a thermoplastic (insulating) resin and a conductive material (eg nickel) that allows connection between each contact electrode 12,13 and the electrical terminals 32,33.

[0027] Anisotropic conductive films are traditionally composed of conductive beads dispersed in an insulating polymer matrix, and when pressure or thermocompression is applied to the laminate 10 / ACF 20 / support layer 30, vertical electrical conduction is established between the electrodes 12a, 13 and the terminals 32, 33 through the conductive beads (usually with excess thickness), while the interlayer zones remain insulating.

[0028] There are also Anisotropic Conductive Adhesives (ACA) that can be used to form the electrical connection layer 20. These adhesives are based on the same principle as the Anisotropic Conductive Films (ACF) described above, except that the polymer matrix is ​​replaced by a liquid precursor that can be thermally activated (by polymerization) to form the final polymer, and the end result remains similar to the ACF (conductive beads dispersed in an insulating matrix), but considering the fact that the application is done in the liquid phase, it is possible to significantly reduce the thickness of the electrical connection layer 20.

[0029] It may also be envisaged to implement a more basic solution, i.e. a conductive paste to connect each electrode and stud portion on the underside to the associated terminal 32, 33, and an insulating filler material to electrically insulate the electrodes 12a, 13 from each other and the terminals 32, 33 from each other.

[0030] The electrical connection layer 20 is in contact with only one of the main faces of the laminate 10 ; the edges and the other main face of the laminate 10 are completely free without mechanical contact with the connection layer 20 .

[0031] Thus, the electrical connection layer 20 is at least partially constructed from a conductive material and provides a direct vertical connection between the electrodes and the terminals, as opposed to a connection by a cable or wire, for example, optionally coated with insulation. The absence of a cable improves the sensitivity of the vibration sensor 100 and avoids the introduction of additional stiffness into the structure coupled with the associated cables and welds.

[0032] Thus, preferably, the electrical connection layer 20 is in direct and uniform contact with the entire main surface of the laminate 10. On the other side, the layer 20 is advantageously in direct and uniform contact with the surface of the support layer 30.

[0033] The electrical connection layer 20 typically has a thickness of less than 50 microns, and more particularly, a thickness of between 1 micron and 10 microns.

[0034] The support layer 30 is advantageously a self-supporting layer having a thickness of less than 500 microns, which gives it the necessary flexibility.

[0035] According to one variant, the support layer 30 consists essentially of the material forming the printed circuit 31 (FIG. 2a): for example a composite of epoxy resin reinforced with glass fibre. According to another variant, the support layer 30 also comprises a membrane 35, the printed circuit 31 then being located between the membrane 35 and the electrical connection layer 20 (FIGS. 1a and 3a). The material of the membrane 35 and its thickness can therefore be selected and adjusted to give the support layer 30 a targeted flexibility. The membrane 35 may for example be made of metal, polyvinyl chloride (PVC) or epoxy and glass fibre. By way of example, the membrane 35 (if present) may have a thickness of 50 to 300 microns and the printed circuit 31 may have a thickness of 30 to 200 microns.

[0036] Typically, the support layer 30 has a stiffness of 1,150,000 N / m to 6,900,000 N / m. The flexibility of the support layer 30, in conjunction with its thickness and its stiffness, allows it to effectively transmit deformations to the active layer 11 at each pulse of the biosignal.

[0037] Advantageously, the laminate 10 and the support layer 30 have a first surface area and a second surface area, respectively, in the main plane (x, y), the first surface area being not more than 30% of the second surface area. The laminate 10 can be arranged in the central part of the support layer 30, particularly for ease of assembly, or on the periphery so as to interfere as little as possible with the deformations of the support layer 30 generated by the periodic pulsation of the biosignal to be measured, but the overall objective is to optimize the deformations undergone by the laminate 10 depending on the geometry of the vibration sensor 100.

[0038] According to a first embodiment of the sensor according to the invention, the support layer 30 is intended to be in contact with the individual (against their skin or against their clothing or fur).

[0039] The support layer 30 then deforms due to the periodic pulsing of the biosignal and transmits this deformation to the active layer 11 of the stack 10 .

[0040] According to the second embodiment, the vibration sensor 100 is ideally 5×10 5 Pa * s / m~3×10 6 Pa * The support layer 30 further includes an impedance matching layer 40 having an acoustic impedance comprised within a range of 1.3×10 s / m. This acoustic impedance is adjusted to match the acoustic impedance of muscle and fat (1.3×10 s / m) to facilitate the transmission of the biosignal pulse to the support layer 30. 6 Pa * s / m~1.5×10 6 Pa * For example, the impedance matching layer 40 is silicone (acoustic impedance 1.6×10 6 Pa *s / m), or bioplastic, such as brand Ecoflex® (acoustic impedance 1.053×10 6 Pa * s / m).

[0041] The impedance matching layer 40 is disposed on the surface of the support layer 30 opposite to the surface in contact with the electrical connection layer 20. The impedance matching layer 40 typically has a thickness of 10 microns or more, for example, 50 microns to 5 mm. When the support layer 30 includes the film 35, the film is in contact with the impedance matching layer 40.

[0042] The impedance matching layer 40 is intended to be in contact with the individual (against the skin or against clothing or fur). In addition to effectively transmitting the pulse due to its impedance matching with the body tissue, this layer 40 also facilitates the holding of the sensor 100 on the individual, since its flexible and deformable material tends to "stick" to the contact surface by adhesive friction. Therefore, the presence of the impedance matching layer 40 in the second embodiment of the sensor 100 is particularly preferred when the measurement environment around the individual whose biosignal is to be captured is noisy and / or when the individual is moving.

[0043] In any of the described embodiments, it may be advantageous for the vibration sensor 100 to comprise a peripheral seal 60 surrounding at least the impedance matching layer 40 (if present) or surrounding all or part of the support layer 30 (if the impedance matching layer 40 is not present), as shown in Figures 3a and 3b, which allows the sensor 100 to accommodate the local topology when placed in contact with an individual.

[0044] The support layer 30 of the vibration sensor 100 may also comprise a reinforcing structure 50, firmly connected to a peripheral zone of the support layer 30. The function of the reinforcing structure 50 is to immobilize the peripheral edges of the support layer 30 and the impedance matching layer 40 (if present), thus accentuating their deformations generated by the periodic pulsation of the biosignal to be measured. The reinforcing structure 50 can take various shapes, for example: a continuous frame (FIG. 4(a)), advantageously a ring (as shown in FIGS. 1b and 2b), but optionally a rectangle (FIG. 2c), a triangle or another polygon, or - A discontinuous frame consisting of two rigid regions (Figure 4(b)), three rigid regions (Figure 4(c)) or more.

[0045] The reinforcing structure is advantageously made from a material having a hardness greater than 30 Shore D, such as PET (polyethylene terephthalate), PMMA (polymethyl methacrylate), PU (polyurethane), PVC (polyvinyl chloride), PP (polypropylene), etc.

[0046] Furthermore, considering the reduced total thickness of the assembly comprising the laminate 10, the connecting layer 20, the support layer 30 and potentially the impedance matching layer 40, it may be advisable to provide a system that facilitates handling of the sensor 100 and promotes its robustness: a reinforcing structure 50 participates in such a system.

[0047] In order to further improve the robustness of the vibration sensor 100 and in particular to protect the active layer 11, the sensor 100 is preferably provided with a protective layer 70 arranged above the stack 10 at a distance therefrom. The protective layer 70 may advantageously be rigidly connected to the reinforcing structure 50. As shown in figures 1b, 2b, 2c and 3b, this protective layer 70 may in particular consist of a plastic shell, for example 500 microns thick. It is arranged at a distance (along the z-axis in the figures) from the stack 10 (and therefore without contact with it) so that it does not hinder its deformations in relation to the support layer 30.

[0048] It should be noted that Figures 1b, 2b and 3b show a vibration sensor 100 that is generally circular in the main plane (x, y), with a square laminate 10. Any other configurations for both the laminate 10 and the support layer 30 (and other layers of the assembly that form the sensor 100) are of course conceivable.

[0049] The vibration sensor 100 according to the invention is defined to form part of a non-invasive device 200 for measuring at least one periodic biosignal of an individual. Such a device 200, which is also the subject of the present invention, comprises at least one vibration sensor 100 as described above for measuring a raw signal (associated with a characteristic periodic biosignal of the individual) and electronic terminals 150 connected to said vibration sensor 100 for analyzing and interpreting the raw signal and then extracting the periodic biosignal or information about said biosignal. The device 200 may comprise a vibration sensor 100 (FIG. 5(a), (b)) or a plurality (two or more) sensors 100 (FIG. 5(c)) connected to the electronic terminals 150. In the case of a plurality of sensors 100, it is possible to measure the same signal or different biosignals (heart rate and respiration) from the same individual or from a number of individuals (such as, for example, a pregnant woman and her fetus).

[0050] As mentioned above, the support layer 30 of the vibration sensor 100, or the impedance matching layer 40, if present, is intended to be placed against an individual, either directly against the skin, or against clothing (humans), fur (animals), etc. The sensitivity of the vibration sensor 100 allows it to capture a raw signal regardless of the configuration (skin contact or an intermediate layer such as clothing).

[0051] The vibration sensor 100 according to the invention further has the advantage of significantly attenuating frequencies located outside the frequency range of interest (for heart rate and respiration rate, typically a frequency range between 0.2 Hz and 500 Hz, or frequencies below 70 Hz): in particular, it has been observed that speech and other environmental sounds do not contaminate the measurement signal, most especially in the case of the second embodiment with the impedance matching layer 40. Thus, the sound environment of the individual when the measurement is taken does not have to be quiet and silent, and the individual does not have to remain immobile. This significantly expands the possibilities of tracking vital signals, and does so under less restrictive conditions than with prior art devices.

[0052] Preferably, the vibration sensor 100 (i.e., the support layer 30 or, optionally, the impedance matching layer 40) is selected to be placed relative to a zone of the body where the biopulse (respiration rate, heart rate) that it is desired to measure is palpable to the touch.

[0053] To connect the vibration sensor 100 to the electronic terminals 150, the printed circuit 31 of the sensor 100 may include wire connection elements 31b, for example strips in the form of a sheet, 1a, 1b and 3a, 3b. The end piece of the wire connection element 31b comprises an electrical contact connector connected to the electrical terminals 32, 33 of the printed circuit 31, which may be connected to an electronic terminal 150. The electronic terminal 150 may in this case be arranged remote from the sensor 100, in particular on a module for fastening to an individual (for example a pocket, a belt, a bracelet, etc.). Further away from the sensor 100, the electronic terminal may be connected to or integrated into a more complex external system, such as a fixed or, if desired, mobile monitor.

[0054] Alternatively, the reinforcing structure 50 of the vibration sensor 100 may be the support of two electrical contact outlets 82, 83, each connected to an electrical terminal 32, 33 of the printed circuit 31, as can be seen in FIG. 2a. In such a case, the electronic terminal 150 may be superimposed directly on the reinforcing structure 50 and electrically connected to the sensor 100 via the two electrical contact outlets 82, 83. According to a variant, the protective layer 70 may provide intermediate contact plugs 82', 83' intended to relay the electrical contact outlets 82, 83 and to be connected to the electronic terminal 150 (FIG. 2b, FIG. 2c). In this case, the latter may be located directly on the protective layer 70. In these configurations, in which the terminals 150 are superimposed on the sensor 100, the device 200 may take on a particularly compact form, but may form a portable and potentially autonomous device.

[0055] The terminal 150 includes various electronic stages that make it possible to analyze and interpret the raw signal measured by the vibration sensor 100. The analog stage for conditioning the raw signal measured by the vibration sensor 100 first amplifies and filters the electrical signal received from the sensor 100. This stage typically consists of a first block of charge amplification type, whose resistance ratio sets the amplification gain of the electrical signal received from the sensor 100, and a second block of Sallen & Key filter type that makes it possible to filter the frequencies beyond the acoustic spectrum of the target biosignal. The electronic terminal 150 then includes a stage of analog-to-digital conversion of the signal coming from the conditioning stage. A digital signal processing stage, then consisting of a microcontroller, carries out the shaping of the signal by calculating the Shannon energy envelope function. Finally, from the shaped signal, the desired output parameters representative of said biosignal can be calculated.

[0056] The collected data relating to the biosignal or output parameter of interest may be stored for subsequent analysis or may be interpreted in real time to trigger a response of a secondary system, whether contained in device 200 or an external device. The response may be information feedback (visual, audible, mechanical, etc.) and / or the triggering of one or more of the following actions: -Mechanical(s): opening / closing the system, -Electrical(s): On / Off / Change systems, hydraulic, pneumatic, heat etc.

[0057] To allow the transmission of the desired output parameters to a possible external system, the electronic terminal 150 may include a communication stage: for example, well-known connection protocols (CAN (Controller Area Network), UART (Universal Asynchronous Receiver / Transmitter), USB (Universal Serial Bus)) or wireless data transmission (Wi-Fi, Bluetooth, etc.) may be used.

[0058] In the case of the portable device 200, a battery, preferably rechargeable, may be provided to power the various aforementioned stages of the electronic terminal 150.

[0059] The vibration sensor 100 and the non-invasive device 200 for measuring periodic bio-signals according to the present invention may address many fields of application in the fields of medicine, health, transportation, industry, sports or leisure.

[0060] As mentioned above, the device 200 can be decomposed into various configurations: a portable autonomous device in compact form (sensor 100 and terminals 150 stacked) or in separated form (sensor 100 connected to terminals 150 by wire connection elements 31b); a portable device in a compact or separate form, the terminal 150 being adapted for wired connection to a more complex external system (in particular a monitor) in, for example, a backup transport means or a medical examination room; A fixed device in a small portable or separate form, in which the terminals 150 are connected by wires or are integrated into a fixed, more complex external system.

[0061] Representative embodiments: We now turn to a description of an example of the manufacture of the vibration sensor 100 and the device 200. Since there are other methods for stacking and assembling different types of layers that can be implemented to manufacture the sensor 100 and the device 200 that are the subject of the present invention, Of course, this example is not limiting.

[0062] To manufacture the laminate 10 of the vibration sensor 100, it is possible to use a transfer method, in particular similar to that described by T Dufay et al. in the publication "Flexible PZT thin film transferred on polymer substrate" (Surface and Coatings Technology, Elsevier, 2018, 343, pp. 148-152).

[0063] A solution of PZT (lead zirconate titanate) precursor is deposited by spin coating onto a sacrificial substrate (e.g. aluminum) to form a viscous layer. Openings are formed through said layer to allow the passage of electrical paths. A heat treatment of 650°C is then applied to crystallize the PZT and form an active layer 11 made of piezoelectric material with a thickness of 5 microns.

[0064] A platinum contact electrode 12 with a thickness of 400 nm is deposited by a chemical vapor deposition technique (e.g. PECVD (Plasma Enhanced Chemical Vapor Deposition)) on the upper (free) surface of the active layer 11 made of PZT and then covered with a polyurethane adhesive layer. Openings are also made through the electrode / adhesive layer stack to allow electrical paths to pass. To facilitate handling of the active layer 11, a temporary layer made of a polymer (e.g. PET) with a thickness of 200 microns is attached to the thermocompressed polyurethane adhesive layer. The temporary layer is opened to allow the passage of electrical paths and filled with a conductive adhesive, which forms a conductive via 14 that is in electrical contact with the contact electrode 12. The sacrificial substrate is then chemically etched until the underside of the active layer 11 made of PZT is exposed. The other contact electrodes 13 and the studs 12a, which are in electrical contact with the vias 14, are formed by aluminum deposition (about 400 nm) on the underside of the PZT.

[0065] The manufacturing method may allow the creation of a PZT film with large lateral dimensions, which is then cut to define an active layer 11 with lateral dimensions desired for its integration in a vibration sensor 100 according to the invention. In the example described, the active layer 11 has lateral dimensions (along the main faces (x,y)) of 5 mm by 15 mm.

[0066] A printed circuit board (PCB) 31 is then selected, having a thickness of 100 microns, lateral dimensions substantially identical to those of the active layer 11, and comprising two electrical terminals 32, 33. An anisotropic conductive film (ACF) 20 is laminated onto the printed circuit board 31. Using a handling machine (of the "pick and place" type), the active layer 11 is placed against the connection layer 20, such that each electrode 12a, 13 (on the lower surface of the active layer 11) is aligned with the electrical terminals 32, 33 of the printed circuit 31. Assembly by thermocompression is then performed.

[0067] The temporary polymer layer may then be removed.

[0068] The printed circuit 31 is then bonded to a PVC film 35 having a thickness of 300 microns and a lateral dimension of 50 mm to complete the formation of the support layer 30.

[0069] An impedance matching layer 40 made of 3 mm thick silicone may be assembled to the membrane 35 by lamination, screen printing or molding.

[0070] A polypropylene reinforcing structure 50 and a silicone peripheral seal 60 are attached by interfitting to the periphery of the membrane 35. Above and spaced from the active layer 11, a polypropylene coating forming a protective layer 70 is poured, injected or laminated onto the reinforcing structure 50.

[0071] In this embodiment, the printed circuit 31 comprises wire elements 31b (webs) making it possible to connect, via electrical contact plugs, the electrical terminals 32, 33 of the printed circuit 31 to electronic terminals 150. The terminals 150 comprise the electronic stages described in the general description.

[0072] An example application of the device 200 thus formed for measuring the heart rate in a human is shown in Figures 6a and 6b.

[0073] The cardiac cycle includes two phases, the first being the contraction phase (systole) and the second being the relaxation phase (diastole). During systole, blood is expelled from the ventricles of the heart and during diastole, the ventricles fill with blood. Ventricular contraction results in the closure of the mitral and tricuspid valves. Heart sounds are named based on their location in the cardiac cycle and occur at specific times. This initial heart sound is called the first heart sound S1. It occurs at the beginning of ventricular systole when the ventricular volume is at its maximum. The first sound S1 corresponds to the time that appears early in the rise of the ventricular pressure curve when it becomes greater than the atrial pressure and the mitral and tricuspid valves close. It corresponds to the QRS complex of the ECG (electrocardiogram). In a graphical recording of heart sounds called a phonocardiogram, it is the first of the recorded components. The second heart sound, S2, occurs when the pulmonary and aortic valves close at the end of ventricular systole, at the time of the dicrotic pulse on the ventricular pressure curve. It is the second of the components recorded on the phonocardiogram. The period between S1 and S2 represents ventricular contraction.

[0074] The acoustic spectrum of the heart typically extends between 0 Hz and 1300 Hz, however the majority of the acoustic power emitted by the heart is below 70 Hz.

[0075] Recall that the level of "speaking" voice varies with gender and age, but is typically between 75 Hz and 450 Hz. This allows separation of cardiac and audio information.

[0076] For measuring heart rate, the device 200 is placed substantially on the left side of the individual's chest and the impedance matching layer 40 is placed in contact with their clothing (in this embodiment two thicknesses of cotton and wool clothing).

[0077] Fig. 6a shows a raw spectrogram A acquired by a vibration sensor 100 according to the invention on a frequency scale ranging from 0 to 1300 Hz (acquisition frequency 128 kHz). The reference spectrogram (Ref) corresponds to a conventional microphone acquisition (in parallel with the measurement of the heart rate performed by the vibration sensor 100) of signals relating to the sound environment. The individual on whom the measurement of the vital signals is performed is talking with other people and therefore the sound environment is noisy, as can be seen from the reference spectrogram (Ref).

[0078] In Fig. 6b, a 15 second extract B of spectrogram A is reported on the frequency scale 0-300 Hz after applying a low-pass filter at 300 Hz. It should be noted that regular peaks in the frequency range 0-70 Hz (pointed out by white arrows on spectrogram B) are very clearly identifiable and correspond to the heart rate measured by the vibration sensor 100 according to the invention. By cutting at 300 Hz, most of the information related to the heart pulse is preserved, but many parasitic frequencies are removed, in particular related to speech and in particular to any other ambient noise between 300 Hz and 1300 Hz that may be experienced in aviation, marine or automotive (individual, mass, emergency or other) or in noisy places in general.

[0079] The peaks shown on the spectrogram B can be visualized in the form of waves. This is the signal C shown in Fig. 6b. A close-up D on this signal C reveals peaks representing a first noise S1 and a second noise S2 corresponding to the individual's heart rate.

[0080] From signals C and D it is possible to extract a periodic signal and / or output parameters representative of the individual's heart rate.

[0081] As described above, the vibration sensor 100 and the non-invasive device 200 for measuring periodic bio-signals according to the present invention provide reliable information regarding the bio-signals regardless of the sound environment and the activity of the individual at the time of measurement, but they do not require direct contact with the individual's skin, thus further relaxing measurement constraints.

[0082] Naturally, the invention is not limited to the embodiments and examples described, but variants can be provided thereto without departing from the scope of the invention as defined by the claims.

Claims

1. A vibration sensor (100) for measuring at least one periodic biosignal of an individual, comprising: a stack (10) including an active layer (11) made of piezoelectric material, extending parallel to its main planes (x, y), and two contact electrodes (12, 13) arranged on at least one face of said active layer (11), said active layer (11) having a thickness of less than or equal to 20 microns and a Young's modulus of more than or equal to 60 GPa; - a flexible support layer (30) configured to transmit a deformation to the active layer (11) of the laminate (10) at each pulse of the biosignal, the flexible support layer (30) comprising a printed circuit (31) extending parallel to the main plane (x, y) and provided with two electrical terminals (32, 33); an electrical connection layer (20) arranged between said laminate (10) and said flexible support layer (30) and connecting each contact electrode (12, 13) to an electrical terminal (32, 33); A vibration sensor (100) intended to be placed in contact with the individual on the side of said flexible support layer (30).

2. 5×10 5 P * s / m ~ 3 x 10 6 P * 2. The vibration sensor (100) of claim 1, further comprising an impedance matching layer (40) having an acoustic impedance comprised in s / m and disposed on a surface of the flexible support layer (30) opposite to the surface in contact with the electrical connection layer (20).

3. Vibration sensor (100) according to one of the preceding claims, wherein the piezoelectric material of the active layer (11) is selected from ceramics in monocrystalline, polycrystalline or composite form.

4. - said contact electrodes (12, 12a, 13) have a cumulative thickness less than twice the thickness of said active layer (11); - said flexible support layer (30) is self-supporting and has a thickness of less than or equal to 500 microns; A vibration sensor (100) according to claim 2, wherein said impedance matching layer (40) has a thickness of 10 microns or more.

5. Vibration sensor (100) according to one of claims 1 to 2, wherein the electrical connection layer (20) is formed by an interposer or by an anisotropic conductive film.

6. The vibration sensor (100) according to any one of claims 1 to 2, wherein the flexible support layer (30) comprises a membrane (35) arranged on a side of the printed circuit (31) opposite to the side in contact with the electrical connection layer (20).

7. The vibration sensor (100) of any one of claims 1 to 2, wherein the laminate (10) and the flexible support layer (30) have a first surface area and a second surface area in the main plane (x, y), respectively, and the first surface area is less than or equal to 30% of the second surface area.

8. Vibration sensor (100) according to one of the preceding claims, wherein the flexible support layer (30) comprises a reinforcing structure (50) rigidly connected to a peripheral zone of the flexible support layer (30).

9. Vibration sensor (100) according to one of the preceding claims, wherein the printed circuit (31) comprises wire connection elements (31b) for connecting the vibration sensor (100) to electronic terminals (150).

10. 9. The vibration sensor (100) of claim 8, wherein the reinforcing structure (50) supports two electrical contact outlets (82, 83) each connected to an electrical terminal (32, 33) for connecting the vibration sensor (100) to an electronic terminal (150).

11. The vibration sensor (100) according to any one of claims 1 to 2, comprising a peripheral seal (60).

12. The vibration sensor (100) according to any one of claims 1 to 2, further comprising a protective layer (70) disposed above the stack (10) and spaced apart from the stack (10), the protective layer (70) being firmly connected to the flexible support layer (30).

13. A non-invasive device (200) for measuring at least one periodic biosignal of an individual, comprising: - the vibration sensor (100) according to claim 1 for measuring a raw signal representative of said periodic biosignal; - an electronic terminal (150) connected to said vibration sensor (100) for analysing and interpreting said raw signal and for extracting said periodic biosignal or an output parameter representative of said periodic biosignal.

14. The electronic terminal (150) - an analog stage for conditioning the raw signal measured by the vibration sensor (100); a conversion stage which converts the signal coming from said analog stage into a digital signal; A digital signal processing stage for forming said digital signal and for calculating output parameters representative of said bio-signal.

15. The non-intrusive device (200) according to one of claims 13 and 14, wherein the electronic terminal (150) includes a stage for communicating with an external system.

Images