An asymmetric gap cantilever beam arrayed MEMS heart sound sensor

Abstract

The application discloses an asymmetric gap cantilever beam array MEMS heart sound sensor, and relates to the field of biomedical devices.The microstructure of the heart sound sensor comprises a plurality of gap cantilever beam structures which are radially arranged around a ring-shaped support body.Each gap cantilever beam structure comprises a mechanical layer cantilever beam, a piezoelectric layer cantilever beam and a mass block.The piezoelectric layer cantilever beam is connected to a conditioning circuit board of the heart sound sensor through a wire, and the signals output by the plurality of piezoelectric layer cantilever beams are connected in parallel.The width of the piezoelectric layer cantilever beam is smaller than that of the mechanical layer cantilever beam, and the piezoelectric layer cantilever beam is arranged above the mechanical layer cantilever beam with a distance between the two.The two ends of the piezoelectric layer cantilever beam are connected to the ring-shaped support body and the mass block respectively.The plurality of mass blocks are different in size and are arranged in order of size.The heart sound sensor disclosed by the application can improve sensitivity, widen the working frequency band, further improve the signal-to-noise ratio and has higher test precision.

Description

Technical Field

[0001] This application relates to the field of biomedical devices, specifically to an asymmetric gap cantilever beam array MEMS (Microelectro Mechanical Systems) heart sound sensor. Background Technology

[0002] In medicine, heart sounds are the sounds produced by the contraction of the myocardium, the closure of the heart valves, and the vibrations caused by blood flow impacting the ventricular walls. Heart sound signals contain a wealth of physiological and pathological information about the heart and are considered important physiological signals for diagnosing heart disease. Obtaining and identifying heart sound signals is of great significance in the diagnosis of organic heart disease in medicine.

[0003] The primary method for early diagnosis of heart disease in clinical practice is auscultation of heart sounds. This method is simple to perform and inexpensive, allowing healthcare professionals to understand a patient's cardiac health by listening to their heart sounds and potentially predicting pathological heart defects from heart murmurs. However, the interpretation of heart sounds using this traditional auscultation method depends on subjective factors such as the experience, skills, and hearing ability of the healthcare professional, resulting in significant individual variability and uncertainty. Furthermore, auscultation of heart sounds cannot be used for continuous health monitoring, making it difficult to capture rare heart sounds to understand the evolution of heart disease and to obtain long-term information on changes in physiological indicators.

[0004] To address these issues, electronic stethoscopes have rapidly developed. Modern electronic stethoscopes possess functions such as signal amplification, filtering, signal acquisition, signal analysis, and Bluetooth module transmission, enabling the digitization and visualization of heart sounds. However, heart sound signals are typically weak signals, characterized by low frequency, low amplitude, and high noise. Therefore, accurate detection of heart sound signals requires highly sensitive sensors. However, high sensitivity also means higher sensitivity to ambient noise, making heart sound signals susceptible to interference from the external environment during acquisition, and sensors suffer from low signal-to-noise ratios. Furthermore, sensor sensitivity is usually mutually constrained by operating bandwidth; achieving higher sensitivity often results in a reduction in the operating frequency band, making it difficult to detect some high-frequency heart murmurs. In addition, heart murmur signals containing pathological information are easily distorted by algorithmic noise reduction alone, leading to inaccurate detection results. Summary of the Invention

[0005] This application provides an asymmetric gap cantilever beam array MEMS heart sound sensor to solve the problem of low signal-to-noise ratio and reduced operating bandwidth when the sensor has high sensitivity in related technologies.

[0006] In a first aspect, an asymmetric gap cantilever beam array MEMS heart sound sensor is provided. The microstructure of the heart sound sensor includes multiple gap cantilever beam structures, which are arranged radially from an annular support. Each gap cantilever beam structure includes a mechanical layer cantilever beam, a piezoelectric layer cantilever beam, and a mass block. The piezoelectric layer cantilever beam is connected to the conditioning circuit board of the heart sound sensor via wires, and the signals output by the multiple piezoelectric layer cantilever beams are connected in parallel. The width of the piezoelectric layer cantilever beam is smaller than that of the mechanical layer cantilever beam, and it is located above the mechanical layer cantilever beam with a distance between them. The two ends of the piezoelectric layer cantilever beam are connected to the annular support and the mass block, respectively. The multiple mass blocks have different sizes and are arranged in order of size.

[0007] In some embodiments, the piezoelectric layer cantilever beam uses a Cr-Au alloy sputtered onto lead zirconate titanate (PZT) as its upper and lower electrode layers, and the leads of the two electrode layers are respectively connected to the conditioning circuit board of the heart sound sensor via a wire.

[0008] In some embodiments, the leads of the lower electrode layer include:

[0009] Multiple lower electrode stainless steel sheets are respectively attached to the lower electrode layer of each piezoelectric layer cantilever beam;

[0010] Multiple serpentine connecting wires for the lower electrode connect to two adjacent stainless steel plates for the lower electrode, respectively.

[0011] The serpentine extension extends from any of the lower electrode stainless steel sheets or a lower electrode serpentine connecting wire.

[0012] In some embodiments, the leads of the upper electrode layer include:

[0013] Multiple upper electrode stainless steel sheets are respectively attached to the upper electrode layer of each piezoelectric layer cantilever beam;

[0014] A central stainless steel sheet is located in the middle of all the upper electrode stainless steel sheets and is connected to the wire;

[0015] Multiple upper electrode serpentine connecting wires connect each upper electrode stainless steel sheet to the central stainless steel sheet.

[0016] In some embodiments, the device further includes a housing with an opening and a thin film covering the opening, the housing being filled with silicone oil, and the inner wall of the housing having a mounting groove for fixing an annular support for the microstructure, the mounting groove housing a conditioning circuit board for mounting a heart sound sensor.

[0017] In some embodiments, a film fixing groove is provided at the opening of the housing, and the edge of the film is fixed in the film fixing groove.

[0018] In some embodiments, the film is a high-temperature resistant polyester film with a thickness of 0.2 mm, the lead zirconate titanate has a thickness of 100 μm, and there are 10 gap cantilever beam structures.

[0019] In some embodiments, the side wall of the housing is further provided with an oil injection hole, which is sealed after oil is injected.

[0020] In some embodiments, the housing sidewall is further provided with lead holes for the wires to pass through.

[0021] In some embodiments, the plurality of piezoelectric layer cantilever beams are long strips of different sizes, and the two ends of the piezoelectric layer cantilever beams are respectively bonded to the top surface of the annular support and the top surface of the mass block by epoxy resin.

[0022] The beneficial effects of the technical solution provided in this application include:

[0023] In this application, the piezoelectric layer cantilever beam and the mechanical layer cantilever beam are independent of each other and spaced apart, with different widths, forming an asymmetric gap structure. Compared to traditional cantilever beam structures under the same vibration environment, this structure significantly increases the stress on the piezoelectric layer, thereby increasing the sensitivity of the heart sound sensor. This improves the heart sound sensor's ability to detect weak signals, making heart sound signal detection more accurate.

[0024] Multiple cantilever beam structures with gaps are arranged radially outward from a ring support to form a ring array. Each mass block has a different size, and the output signals are connected in parallel, improving sensitivity while widening the operating frequency band. Furthermore, the noise received during sensor testing includes external noise and inherent noise. When the number of units is small, the array units respond uniformly to external noise, meaning the external noise is completely correlated. Therefore, the ring array-type heart sound sensor can further improve the signal-to-noise ratio and test accuracy, enhancing the accuracy and efficiency of doctors' diagnoses.

[0025] Because the array structure improves sensitivity while also broadening the operating bandwidth to some extent, this heart sound sensor can also be used to detect lung sound signals. It can be used for the diagnosis and prediction of cardiopulmonary diseases, and has great potential for clinical application. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1This is a schematic diagram of the asymmetric gap cantilever beam array MEMS heart sound sensor structure of this application;

[0028] Figure 2 for Figure 1 A schematic diagram of the microstructure of the center tone sensor;

[0029] Figure 3 for Figure 1 A partial schematic diagram of a cantilever beam structure with medium clearance;

[0030] Figure 4 This is a schematic diagram of a piezoelectric layer cantilever beam structure;

[0031] Figure 5 This is a schematic diagram of the lead wires of the lower electrode layer of the piezoelectric layer cantilever beam in an embodiment of this application;

[0032] Figure 6 This is a schematic diagram of the lead wires of the electrode layer on the piezoelectric layer cantilever beam in an embodiment of this application;

[0033] Figure 7 This is a schematic diagram of the shell structure in an embodiment of this application.

[0034] Figure label:

[0035] Housing 1, mounting groove 11, diaphragm fixing groove 12, oil injection hole 13, lead wire hole 14;

[0036] Microstructure 2, ring support 21, mechanical layer cantilever beam 22, piezoelectric layer cantilever beam 23, mass block 24, epoxy resin 25;

[0037] Lead zirconate titanate 230;

[0038] Upper electrode layer 231, upper electrode stainless steel sheet 2311, central stainless steel sheet 2312, upper electrode serpentine connecting line 2313;

[0039] Lower electrode layer 232, lower electrode stainless steel sheet 2321, lower electrode serpentine connecting line 2322, serpentine extension end 2323. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0041] This application provides an asymmetric gap cantilever beam array MEMS heart sound sensor, which solves the problem of low signal-to-noise ratio and reduced operating bandwidth when the sensitivity is high in related technologies. It increases the sensitivity of the heart sound sensor while widening the operating bandwidth.

[0042] like Figure 1 As shown, an embodiment of an asymmetric gap cantilever beam array MEMS heart sound sensor is provided. The heart sound sensor includes a housing 1 with an opening and a thin film covering the housing 1, as well as microstructures 2 and a conditioning circuit board (not shown) located within the housing.

[0043] like Figure 2 As shown, the microstructure 2 of the heart sound sensor includes multiple gap cantilever beam structures, which are arranged radially outward from the annular support 21. Multiple mass blocks 24 of different sizes are arranged sequentially around the annular support 21 according to their size order, so that the multiple gap cantilever beam structures form a ring array.

[0044] like Figure 3 As shown, each gap cantilever beam structure includes a mechanical layer cantilever beam 22, a piezoelectric layer cantilever beam 23, and a mass block 24. The piezoelectric layer cantilever beam 23 is connected to the conditioning circuit board of the heart sound sensor via wires, and the signals output by multiple piezoelectric layer cantilever beams 23 are connected in parallel. The two ends of the mechanical layer cantilever beam 22 and the piezoelectric layer cantilever beam 23 are connected to the annular support 21 and the mass block 24, respectively. The piezoelectric layer cantilever beam 23 is located above the mechanical layer cantilever beam 22, and there is a gap between them, forming a cavity; the width of the piezoelectric layer cantilever beam 23 is smaller than the width of the mechanical layer cantilever beam 22, and the two are in an asymmetrical state. The mechanical layer cantilever beam 22 and the mass block 24 can be fabricated from aluminum metal material through 3D printing.

[0045] In some embodiments, the multiple piezoelectric layer cantilever beams 23 are elongated structures of varying sizes. The two ends of each piezoelectric layer cantilever beam 23 are respectively bonded to the top surface of the annular support 21 and the top surface of the mass block 24 using epoxy resin 25. In this embodiment, there are 10 gap cantilever beam structures. By adjusting the size of the 10 piezoelectric layer cantilever beams 23 and the mass block 24, the sensitivity of the sensor can be improved. Simultaneously, the outputs of the 10 gap cantilever beam structures (equivalent to piezoelectric sensors) are connected in parallel to broaden the operating frequency band and effectively improve the signal-to-noise ratio.

[0046] like Figure 4As shown, each piezoelectric layer cantilever beam 23 uses lead zirconate titanate (PZT) 230 as the piezoelectric sensitive layer, and sputters a Cr-Au alloy onto the PZT 230 as its upper electrode layer 231 and lower electrode layer 232. The leads of the two electrode layers are connected to the conditioning circuit board of the heart sound sensor through a wire. Specifically, in the fabrication process of the piezoelectric layer cantilever beam 23, the lead zirconate titanate 230 is first polished and ground using mechanical polishing technology to reduce its thickness to 100μm; then, Cr-Au alloy is sputtered onto the polished lead zirconate titanate (PZT) using magnetron sputtering technology as the upper electrode layer 231 and lower electrode layer 232. When sputtering the upper electrode layer 231 and then the lower electrode layer 232 of the lead zirconate titanate 230, in order to avoid conduction with the upper electrode layer 231, PI tape can be used to completely wrap the areas that do not need to be sputtered to prevent short circuits. Finally, using laser cutting technology, the lead zirconate titanate 230 after sputtering the lower electrode layer 232 was cut into 10 rectangles of different sizes to serve as piezoelectric layer cantilever beams 23.

[0047] like Figure 5 The diagram shows a schematic of the leads for the lower electrode layer 232. The leads for the lower electrode layer 232 include multiple lower electrode stainless steel sheets 2321 and multiple lower electrode serpentine connecting wires 2322. The multiple lower electrode stainless steel sheets 2321 are respectively attached to the lower electrode layer 232 of each piezoelectric layer cantilever beam 23; the multiple lower electrode serpentine connecting wires 2322 connect adjacent lower electrode stainless steel sheets 2321. In this embodiment, there are 10 piezoelectric layer cantilever beams 23, therefore there are also 10 lower electrode stainless steel sheets 2321 and 9 lower electrode serpentine connecting wires 2322. The lower electrode stainless steel sheets 2321 are connected to form a loop. Any lower electrode stainless steel sheet 2321 or a lower electrode serpentine connecting wire 2322 extends outward with a serpentine extension end 2323. Then, a 5μm copper wire (not shown) is used as the conductor for the lower electrode, with one end connected to the serpentine extension end 2323 and the other end connected to the conditioning circuit board of the heart sound sensor. Preferably, the lower electrode stainless steel sheet 2321, the lower electrode serpentine connecting wire 2322, and the serpentine protruding end 2323 are manufactured in one step.

[0048] like Figure 6The diagram shows a schematic of the leads for the upper electrode layer 231. The leads for the upper electrode layer 231 include multiple upper electrode stainless steel sheets 2311, a central stainless steel sheet 2312, and multiple upper electrode serpentine connecting lines 2313. The multiple upper electrode stainless steel sheets 2311 are respectively attached to the upper electrode layer 231 of each piezoelectric layer cantilever beam 23; the central stainless steel sheet 2312 is located in the middle of all the upper electrode stainless steel sheets 2311, and the multiple upper electrode serpentine connecting lines 2313 connect each upper electrode stainless steel sheet 2311 to the central stainless steel sheet 2312. Similarly, a 5μm copper wire (not shown) is used as the upper electrode conductor, with one end connected to the central stainless steel sheet 2312 and the other end connected to the conditioning circuit board of the heart sound sensor. Preferably, the upper electrode stainless steel sheets 2311, the central stainless steel sheet 2312, and the upper electrode serpentine connecting lines 2313 are fabricated in one step.

[0049] In some embodiments, the leads of the upper electrode layer 231 and the lower electrode layer 232 are made of 20μm thick stainless steel foil, which is patterned using laser cutting to form square upper electrode stainless steel sheets 2311 and lower electrode stainless steel sheets 2321, as well as serpentine connecting lines. The serpentine line structure increases the strength of the leads and makes them less prone to detachment during vibration experiments. Furthermore, the leads of the upper electrode layer 231 and the lower electrode layer 232 are fixed with polyimide tape 26, which also serves as an insulating protective layer to prevent interference from external circuits or conductive structures. Conductive silver paste is uniformly applied to the upper electrode stainless steel sheets 2311 and 2321 using screen printing technology, and then bonded to the upper electrode layer 231 and lower electrode layer 232 of each piezoelectric layer cantilever beam 23. The leads of the lower electrode layer 232 are in a ring structure, with a hollowed-out section in the middle to accommodate the conditioning circuit board. The leads of the upper electrode layer 231 are formed by converging multiple upper electrode stainless steel sheets 2311 at the central stainless steel sheet 2312, completing the parallel connection of multiple piezoelectric layer cantilever beams 23. In this embodiment, two copper wires with a diameter of 5μm are used as the conductors of the upper electrode layer 231 and the lower electrode layer 232, respectively. The other ends of the two copper wires are used to solder to the conditioning circuit board to complete the signal output. The connection between the leads is simple and easy to distinguish, and the experimental operation is convenient and reliable.

[0050] like Figure 1 and Figure 7As shown, the housing 1 of the heart sound sensor can be fabricated using 3D printing, and its material is aluminum. The inner bottom wall of the housing 1 has a mounting groove 11, which is used to mount the conditioning circuit board of the heart sound sensor. The mounting groove 11 also serves to fix the annular support 1 of the microstructure 2. Preferably, the mounting groove 11 is also annular, and the microstructure 2 of the heart sound sensor and the conditioning circuit board are bonded together using UV-curable adhesive. A thin film fixing groove 12 is provided at the opening of the housing 1, located at the top of the side wall of the housing 1, to fix the edge of the thin film. Preferably, the housing 1 is a circular housing, and the thin film fixing groove 12 is an annular groove.

[0051] Two holes are formed on the side wall of the housing 1. One is a lead wire hole 14, which allows the wires of the piezoelectric layer cantilever beam 23 to pass through and connect to the external acquisition circuit. The other is an oil injection hole 13, which is used to inject oil into the housing. In this embodiment, the film is a high-temperature resistant polyester film (PET), which has advantages such as skin-friendliness, insulation and sound transmission properties, as well as low permeability and water resistance. The edges of the film are fixed in the film fixing groove 12 using UV-curable adhesive. Preferably, the film thickness is 0.2 mm. After the film is applied, silicone oil is injected into the housing 1 through the oil injection hole 13, and then epoxy resin AB glue is used to seal the holes.

[0052] In some embodiments, the preamplifier circuit of the array-type gap cantilever beam structure of this application includes a filtering and noise reduction module, which can further process the output signal of the piezoelectric layer to improve the electromagnetic compatibility and anti-interference capability of the sensor, making the acquired signal more accurate. Simultaneously, it is paired with a multi-channel data acquisition device to enable visualization of the heart sound signal via a host computer.

[0053] The asymmetric gap cantilever beam array MEMS heart sound sensor of this application, when a heart sound vibration signal occurs, the mass block 24 drives the piezoelectric layer cantilever beam 23 to deform, causing stress changes in the piezoelectric layer cantilever beam 23, resulting in charge output, completing the force-to-electric conversion, and realizing the measurement of the vibration signal. Furthermore, the cavity formed by the piezoelectric layer cantilever beam 23 and the mechanical layer cantilever beam 22 increases the normal strain on the piezoelectric layer, thus increasing its sensitivity. Simultaneously, the parallel output of multiple piezoelectric cantilever beams 23 reduces internal resistance and charge leakage during operation, and also allows double the charge to enter the test circuit, enhancing the output signal.

[0054] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0055] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An asymmetric gap cantilever beam array MEMS heart sound sensor, characterized in that: The microstructure of the heart sound sensor includes multiple gap cantilever beam structures, which are arranged radially from a ring support. Each gap cantilever beam structure includes a mechanical layer cantilever beam, a piezoelectric layer cantilever beam, and a mass block. The piezoelectric layer cantilever beams are connected to the conditioning circuit board of the heart sound sensor through wires, and the signals output by the multiple piezoelectric layer cantilever beams are connected in parallel. The width of the piezoelectric layer cantilever beam is smaller than that of the mechanical layer cantilever beam, and it is located above the mechanical layer cantilever beam with a distance between them. The two ends of the piezoelectric layer cantilever beam are connected to a ring support and a mass block, respectively. Multiple mass blocks of different sizes are arranged in order of size. The piezoelectric layer cantilever beam uses a Cr-Au alloy sputtered onto lead zirconate titanate (PZT) as its upper and lower electrode layers. The leads of the two electrode layers are respectively connected to the conditioning circuit board of the heart sound sensor through a wire. The leads of the upper electrode layer include: Multiple upper electrode stainless steel sheets are respectively attached to the upper electrode layer of each piezoelectric layer cantilever beam; A central stainless steel sheet is located in the middle of all the upper electrode stainless steel sheets and is connected to the wire; Multiple upper electrode serpentine connecting wires connect each upper electrode stainless steel sheet to the central stainless steel sheet.

2. The asymmetric gap cantilever beam array MEMS heart sound sensor as described in claim 1, characterized in that, The leads of the lower electrode layer include: Multiple lower electrode stainless steel sheets are respectively attached to the lower electrode layer of each piezoelectric layer cantilever beam; Multiple serpentine connecting wires for the lower electrode connect to two adjacent stainless steel plates for the lower electrode, respectively. The serpentine extension extends from any of the lower electrode stainless steel sheets or a lower electrode serpentine connecting wire.

3. The asymmetric gap cantilever beam array MEMS heart sound sensor as described in claim 1, characterized in that: It also includes a housing with an opening and a thin film covering the opening. The housing is filled with silicone oil, and the inner wall of the housing has a mounting groove for fixing an annular support for the microstructure. The conditioning circuit board of the heart sound sensor is installed in the mounting groove.

4. The asymmetric gap cantilever beam array MEMS heart sound sensor as described in claim 3, characterized in that: The shell opening is provided with a film fixing groove, and the edge of the film is fixed in the film fixing groove.

5. The asymmetric gap cantilever beam array MEMS heart sound sensor as described in claim 3, characterized in that: The film is a high-temperature resistant polyester film with a thickness of 0.2 mm, the lead zirconate titanate has a thickness of 100 μm, and there are 10 gap cantilever beam structures.

6. The asymmetric gap cantilever beam array MEMS heart sound sensor as described in claim 3, characterized in that: The side wall of the housing is also provided with an oil injection hole, which is sealed after oil is injected.

7. The asymmetric gap cantilever beam array MEMS heart sound sensor as described in claim 3, characterized in that: The side wall of the housing is also provided with lead holes for the wires to pass through.

8. The asymmetric gap cantilever beam array MEMS heart sound sensor as described in any one of claims 1-7, characterized in that: The multiple piezoelectric layer cantilever beams are long strips of different sizes, and the two ends of the piezoelectric layer cantilever beams are respectively bonded to the top surface of the annular support and the top surface of the mass block with epoxy resin.

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