A piezoelectric sensor for measuring normal pressure and shear force and a method for preparing the same

Abstract

The present invention provides a piezoelectric sensor for measuring normal pressure and shear force and a preparation method thereof, comprising: a support part, which is a frame, a connecting beam and a connecting platform are arranged in the frame, the connecting beam is composed of four beams forming a cross-shaped distribution, the connecting platform is located in the middle of the cross, the connecting beam is respectively connected to the side of the connecting platform, and the length of the frame is greater than the width; a piezoelectric ceramic film sensor unit arranged above the support part, the piezoelectric ceramic film sensor unit has four, correspondingly distributed on the four beams of the connecting beam; a cilia arranged above the support part, the cilia are arranged in the middle of the connecting platform, and are located in the middle of the four piezoelectric ceramic film sensor units. The present invention is based on a piezoelectric mechanism, and through the structural arrangement of the cilia and the sensor unit, the shear stress of the XY axis, the shear stress of the Y axis, and the normal pressure from the Z direction can be tested.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a piezoelectric sensor for measuring normal pressure and shear force and a preparation method thereof. Background Art

[0002] Flexible sensors can monitor various mechanical signals (such as tension, compression, shearing, bending, torsion, and vibration).

[0003] Flexible pressure sensors are generally divided into three types according to their working mechanism, including capacitive, piezoresistive and piezoelectric. Compared with the other two sensors, piezoelectric sensors can achieve self-generation, do not require external energy supply, and have the advantages of wide bandwidth, high sensitivity, high signal-to-noise ratio and simple structure. Piezoelectric pressure sensors use the piezoelectric effect of piezoelectric elements to convert the measured pressure into an electrical signal. The piezoelectric effect refers to the phenomenon that when a piezoelectric material is subjected to an external force, an electric polarization is generated inside, so that the same number of positive and negative charges exist on the upper and lower surfaces of the piezoelectric material. There is a certain proportional relationship between the amount of charge and the force, which can be amplified by a charge amplifier or a voltage amplifier and converted into a voltage or current output. According to the output voltage or current signal finally collected, the corresponding measured pressure value can be obtained.

[0004] In the prior art, there are many technologies that can measure normal pressure and shear force. For example, in the Chinese invention patent application CN110987031A, the tactile sensor can simultaneously measure the magnitude and direction of shear force and normal pressure. It achieves the measurement purpose through the principle of capacitance change between multiple electrodes. However, its detection sensitivity needs to be further improved, and the structure is relatively complex. Summary of the invention

[0005] In view of the defects in the prior art, an object of the present invention is to provide a piezoelectric sensor for measuring normal pressure and shear force and a preparation method thereof.

[0006] According to one aspect of the present invention, there is provided a piezoelectric sensor for measuring normal pressure and shear force, comprising:

[0007] The support part is a frame, in which a connecting beam and a connecting platform are arranged, wherein the connecting beam is composed of four beams arranged in a cross shape, the connecting platform is located in the middle of the cross, and the four beams are connected to the side surfaces of the connecting platform and are symmetrical with each other with the connecting platform as the center;

[0008] A piezoelectric ceramic thin film sensor unit is arranged above the support portion, wherein there are four piezoelectric ceramic thin film sensor units, which are correspondingly distributed on the four beams of the connecting beam to form a two-by-two symmetrical structure;

[0009] A cilia is arranged above the supporting part, wherein the cilia is arranged in the middle of the connecting platform and is located in the middle of the four piezoelectric ceramic film sensing units;

[0010] The piezoelectric ceramic film sensor unit, the cilia support and the support portion are hollow below.

[0011] Optionally, the frame is a rectangle, a beam is provided at the center of each of the four sides of the rectangle, and the beams extend toward the center of the rectangle and are connected to the connecting platform to form a symmetrical cross-shaped distribution.

[0012] Optionally, the connecting platform is a square, and the four beams are respectively connected to the midpoints of four sides of the connecting platform.

[0013] Optionally, each of the piezoelectric ceramic film sensing units is composed of a piezoelectric layer lower electrode, a piezoelectric ceramic film layer, and a piezoelectric layer upper electrode, wherein the piezoelectric layer lower electrode is located on the connecting beam, the piezoelectric ceramic film layer is arranged on the piezoelectric layer lower electrode, and the piezoelectric layer upper electrode is arranged on the piezoelectric ceramic film layer.

[0014] Optionally, the cilia are vertically fixed to the connecting platform, and one or more of the shear stress of the X-axis, the shear stress of the Y-axis and the positive pressure from the Z direction are tested through the stress condition of the cilia.

[0015] A second aspect of the present invention provides a method for preparing the above-mentioned piezoelectric sensor, comprising:

[0016] S1, preparing a substrate layer for support;

[0017] S2, depositing a piezoelectric layer lower electrode on the lower surface of a piezoelectric ceramic press piece, forming a piezoelectric ceramic thin film layer by a bonding thinning process, and depositing a piezoelectric layer upper electrode on the upper surface of the piezoelectric ceramic thin film layer;

[0018] S3, depositing a cilia structure on the upper surface of the piezoelectric ceramic film layer and patterning it;

[0019] S4, etching the front surface of the piezoelectric ceramic film layer and the substrate layer to form a connecting beam, a connecting platform and a piezoelectric ceramic film sensing unit;

[0020] S5, etching the back of the substrate layer to form a frame structure.

[0021] Optionally, the S2 includes:

[0022] S11, depositing a first layer of metal film on the lower surface of the piezoelectric ceramic pressing piece by a magnetron sputtering process to form a piezoelectric layer lower electrode;

[0023] S12, bonding the piezoelectric ceramic pressing piece on which the first metal film is deposited to the substrate layer, wherein the first metal film is in close contact with the substrate layer;

[0024] S12, thinning the upper surface of the piezoelectric ceramic pressing piece by a chemical mechanical polishing process to form a piezoelectric ceramic thin film layer;

[0025] S13, depositing a second metal film on the upper surface of the thinned piezoelectric ceramic film layer to form an upper electrode of the piezoelectric layer.

[0026] Compared with the prior art, the embodiments of the present invention have at least one of the following beneficial effects:

[0027] The piezoelectric sensor for measuring normal pressure and shear force provided by the present invention has a ciliary structure as an external force sensing device, which can generate normal force and shear force in response to external force. The four piezoelectric sensing units connected thereto are then used to test the shear stress of the X and Y axes, and can also test the normal pressure from the Z direction. While the piezoelectric mechanism can be used to simultaneously measure the normal pressure and shear force, the detection sensitivity can be further improved through the ciliary structure setting.

[0028] The piezoelectric sensor for measuring normal pressure and shear force provided by the present invention completes the measurement through a support portion, a sensing unit and a ciliary structure, does not require external energy supply, has a high signal-to-noise ratio and a simple structure.

[0029] The present invention provides a method for preparing a piezoelectric sensor for measuring normal pressure and shear force. The piezoelectric ceramic layer adopts a bonding thinning process to achieve processing of a higher performance functional layer, providing conditions for further improving the detection sensitivity of the piezoelectric sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0031] Figure 1 It is a structural schematic diagram of a sensor in a preferred embodiment of the present invention;

[0032] Figure 2 A cross-sectional view of a sensor in a preferred embodiment of the present invention;

[0033] Figure 3 This is a flow chart of the preparation process of a sensor in a preferred embodiment of the present invention;

[0034] In the figure: cilia 1, piezoelectric ceramic thin film sensing units 2, 3, 4, 5, support part 6, piezoelectric layer upper electrode 7, piezoelectric layer lower electrode 8, beam 9, connecting platform 10, piezoelectric ceramic thin film layer 11. DETAILED DESCRIPTION

[0035] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0036] Reference Figure 1 , 2 As shown, the piezoelectric sensor for measuring normal pressure and shear force in this embodiment includes: a support part 6, piezoelectric ceramic film sensor units 2, 3, 4, 5 and cilia 1, wherein: the support part 6 plays a role in supporting other components, such as Figure 1 As shown, a frame is provided in which a connecting beam and a connecting platform 10 are arranged. The connecting beam is composed of four beams 9 forming a cross-shaped distribution. The connecting platform 10 is located in the middle of the cross, and the four beams 9 are connected to the side of the connecting platform 10 and are centered on the connecting platform to form a two-by-two symmetrical structure. The piezoelectric ceramic thin film sensor unit is arranged above the support portion 6, and the four piezoelectric ceramic thin film sensor units 2, 3, 4, and 5 are correspondingly distributed on the four beams 9 to form a two-by-two symmetrical structure, that is, a cross-shaped distribution is also formed, and the lower surfaces of the four piezoelectric ceramic thin film sensor units 2, 3, 4, and 5 are tightly fitted with the four beams in the support portion 6. The cilia 1 is arranged on the cilia above the support portion 6. As shown in the figure, the cilia 1 is arranged in the middle of the connecting platform 10 and is located in the middle of the four piezoelectric ceramic thin film sensor units 2, 3, 4, and 5.

[0037] Among the four piezoelectric ceramic thin film sensor units 2, 3, 4, and 5, the piezoelectric ceramic thin film sensor units 2 and 4 are the first pair, and the piezoelectric ceramic thin film sensor units 3 and 5 are the second pair. The first pair of piezoelectric ceramic thin film sensor units 2 and 4 cooperate with the cilia 1 to measure the shear stress of the X-axis, and the second pair of piezoelectric ceramic thin film sensor units 2 and 4 cooperate with the cilia 1 to measure the shear stress of the Y-axis. The four piezoelectric ceramic thin film sensor units 2, 3, 4, and 5 cooperate to measure the positive pressure at the same time.

[0038] In some embodiments, Figure 1 , 2 As shown, the bottom of the frame of the four piezoelectric ceramic film sensing units 2, 3, 4, 5, the cilia 1 and the supporting part 1 is hollow. The hollow structure is designed to reduce the overall rigidity, thereby improving the sensitivity of the piezoelectric sensor.

[0039] In some embodiments, Figure 1 , 2As shown, for the support portion 6, its frame can be a rectangle, and a beam 9 is set at the center of each of the four sides of the rectangle. The beams 9 extend to the center of the rectangle and are connected to the connecting platform 10 located at the center of the rectangle. The four beams 9 form a symmetrical cross distribution. Specifically, the four beams 9 are perpendicular to the side of the connecting platform 10 and the connection point is located at the center of the side of the connecting platform 10. This symmetrical structure can be used to test the shear force well. Of course, in other embodiments, the support portion 6 can also be a frame of other shapes, which can only achieve the above functions.

[0040] In some embodiments, Figure 1 , 2 As shown, the connecting platform 10 is a square, and the four beams 9 are respectively connected to the midpoints of the four sides of the connecting platform. The connecting platform 10 and the four beams 9 can be an integrated structure with the same height and thickness, wherein the four piezoelectric ceramic film sensor units 2, 3, 4, and 5 are located higher than the connecting platform 10 and the four beams 9. The shape of the four beams 9 can be a square column. Except for the frame and the connecting platform 10 and the four beams 9 in the frame, the other parts of the support part 6 are hollow. Of course, in other embodiments, the four beams 9 and the connecting platform 10 can also be other shapes, which can be selected according to the frame shape of the support part 6.

[0041] In some embodiments, Figure 1 , 2 As shown, the cilia 1 is located in the middle of the entire device and is higher than the connecting platform 10 and the four beams 9. The cilia 1 is preferably a cylinder, and its bottom surface is located at the center of the connecting platform 10. At the same time, the bottom surface diameter is smaller than the length and width of the connecting platform 10. Of course, in other embodiments, the cilia 1 can also be other shapes. Furthermore, in order to better achieve measurement, the cilia can be prepared using silicon or polymers, wherein the polymer can be selected from polyethylene terephthalate (PET), polyimide (PI) or polyparaxylene (Parylene), etc. In this embodiment, the number of cilia 1 is one, and the test can be achieved without an array structure, and the structure is simple.

[0042] like Figure 2 As shown, the connecting platform 10 and the cilia 1 are an integrated structure. The cilia 1 acts as an external force sensor, which can be subjected to force directly above or from the side, thereby causing the connecting platform 10 below to deform. The deformation of the connecting platform 10 causes the four piezoelectric ceramic film sensor units 2, 3, 4, and 5 on the four beams 9 connected thereto to produce different deformations, thereby being able to test the positive pressure and shear force. If the cilia 1 is not provided, the positive pressure test can also be achieved, but the shear force test cannot be achieved.

[0043] The four piezoelectric ceramic thin film sensing units 2, 3, 4, and 5 are used as sensitive units to realize the test of the shear stress of the X and Y axes and the positive pressure from the Z direction together with the cilia 1. In some embodiments, each piezoelectric ceramic thin film sensing unit is composed of a piezoelectric layer lower electrode 8, a piezoelectric ceramic thin film layer 11, and a piezoelectric layer upper electrode 7, wherein the piezoelectric layer lower electrode 8 is located on the beam 9, the piezoelectric layer lower electrode 8 is provided with a piezoelectric ceramic thin film layer 11, and the piezoelectric layer upper electrode 7 is provided on the piezoelectric ceramic thin film layer 11. The contact surfaces between the piezoelectric layer lower electrode 8, the piezoelectric ceramic thin film layer 11, and the piezoelectric layer upper electrode 7 are tightly fitted. The piezoelectric layer lower electrode 8 extends to the upper surface end of the frame, and the piezoelectric layer upper electrode 7 is located on the beam 9 in the frame.

[0044] In the above embodiment of the present invention, the cilia 1 is vertically fixed to the connecting platform, and one or more of the shear stress of the X-axis, the shear stress of the Y-axis and the positive pressure from the Z-direction are tested through the cooperation of the cilia 1 and the four piezoelectric ceramic film sensor units 2, 3, 4, and 5. Specifically:

[0045] When the piezoelectric sensor is subjected to positive pressure, that is, when the top of the cilia 1 is subjected to pressure, the four piezoelectric ceramic film sensing units 2, 3, 4, and 5 all deform up and down, generating output voltage, thereby testing the positive pressure;

[0046] When the piezoelectric sensor is subjected to shear force in the X direction, that is, when the side of the cilia 1 is subjected to pressure in the X direction, the first pair of piezoelectric ceramic thin film sensing units 2 and 4 in the symmetrical structure are deformed and an output voltage is generated, while the second pair of piezoelectric ceramic thin film sensing units 3 and 5 in the symmetrical structure are not deformed and have no output, thereby testing the shear force in the X direction;

[0047] When the piezoelectric sensor is subjected to shear force in the Y direction, that is, when the side of the cilia 1 is subjected to pressure in the Y direction, the second pair of piezoelectric ceramic film sensor units 3 and 5 in the symmetrical structure are deformed and an output voltage is generated, while the first pair of piezoelectric ceramic film sensor units 2 and 4 in the symmetrical structure do not deform and have no output, thereby testing the shear force in the Y direction.

[0048] The sensor in the above embodiment of the present invention can simultaneously measure normal pressure and shear force by using a piezoelectric mechanism, and can further improve the detection sensitivity by setting a ciliary structure. Moreover, the measurement is completed by the support part, the sensing unit and the ciliary structure, and no external energy is required, and the signal-to-noise ratio is high and the structure is simple.

[0049] Reference Figure 3 As shown, in another embodiment of the present invention, a method for preparing the above-mentioned piezoelectric sensor is also provided, comprising:

[0050] S1, prepare the substrate layer; Figure 3 As shown in (a), the substrate layer is a silicon or metal substrate;

[0051] S2, using a piezoelectric ceramic press sheet, depositing a piezoelectric layer lower electrode on the lower surface of the piezoelectric ceramic press sheet, and forming a piezoelectric ceramic thin film layer by a bonding thinning process; Figure 3 As shown in (b);

[0052] S3, depositing an upper electrode of the piezoelectric layer on the upper surface of the piezoelectric ceramic film layer; Figure 3 As shown in (c);

[0053] S4, depositing a cilia structure on the upper surface of the piezoelectric ceramic film layer and patterning it; Figure 3 As shown in (d);

[0054] S5, etching the front side of the piezoelectric ceramic film layer and the substrate layer to form a connecting beam, a connecting platform and a piezoelectric ceramic film sensing unit; Figure 3 As shown in (e);

[0055] S6, etching the back of the substrate layer to form a frame structure, refer to Figure 3 As shown in (f).

[0056] In the above-mentioned method for preparing the piezoelectric sensor, the materials of the upper electrode of the piezoelectric layer and the lower electrode of the piezoelectric layer are the same, both of which are metal electrodes, such as gold, silver, etc.

[0057] In a specific embodiment, S2 and S3 of the above-mentioned method for preparing the piezoelectric sensor may refer to the following specific operation steps:

[0058] S11, depositing a first layer of gold (Au) thin film on the lower surface of the piezoelectric ceramic pressing piece by a magnetron sputtering process to form a piezoelectric layer lower electrode;

[0059] S12, bonding the piezoelectric ceramic pressing piece on which the first layer of gold (Au) film is deposited to the substrate layer, wherein the first layer of gold (Au) film is in close contact with the substrate layer;

[0060] S12, thinning the upper surface of the piezoelectric ceramic pressing piece by a chemical mechanical polishing process to form a piezoelectric ceramic thin film layer;

[0061] S13, depositing a second layer of gold (Au) film on the upper surface of the thinned piezoelectric ceramic film layer to form an upper electrode of the piezoelectric layer.

[0062] The piezoelectric ceramic pressed sheet mentioned above can be made of lead zirconate titanate piezoelectric ceramic pressed sheet.

[0063] In the above-mentioned method for preparing the piezoelectric sensor, the material of the cilia structure includes one or more of silicon and polymer, and the polymer can be polyethylene terephthalate (PET), polyimide (PI) or polyparaxylene (Parylene), etc. The connecting platform 10 can be made of the same material as the cilia 1 to form an integrated structure.

[0064] The preparation method of the piezoelectric sensor for measuring normal pressure and shear force provided in this embodiment uses a bonding thinning process to achieve the processing of a higher performance functional layer, providing conditions for further improving the detection sensitivity of the piezoelectric sensor. The piezoelectric sensor for measuring normal pressure and shear force provided in this embodiment can be used in environments with external forces in different directions, such as underwater sound pressure, weak wind force monitoring, etc.

[0065] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various modifications or variations within the scope of the claims, which does not affect the essence of the present invention. The above preferred features can be used in any combination without conflicting with each other.

Claims

1. A piezoelectric sensor for measuring normal pressure and shear force, characterized in that: include: The support part is a frame, in which a connecting beam and a connecting platform are arranged, wherein the connecting beam is composed of four beams arranged in a cross shape, the connecting platform is located in the middle of the cross, and the four beams are connected to the side surfaces of the connecting platform and are symmetrical with each other with the connecting platform as the center; A piezoelectric ceramic thin film sensor unit is arranged above the support portion, wherein there are four piezoelectric ceramic thin film sensor units, which are correspondingly distributed on the four beams of the connecting beam to form a two-by-two symmetrical structure; A cilia is arranged above the supporting part, wherein the cilia is arranged in the middle of the connecting platform and is located in the middle of the four piezoelectric ceramic film sensing units; The piezoelectric ceramic film sensing unit, the ciliary support and the support portion are hollow below; The cilia are columnar and fixed vertically to the connecting platform. The shear stress of the X-axis, the shear stress of the Y-axis and the positive pressure from the Z-direction are tested by the stress condition of the cilia. When the piezoelectric sensor is subjected to positive pressure, the four piezoelectric ceramic film sensing units are deformed to generate output voltage, thereby testing the positive pressure; When the piezoelectric sensor is subjected to a shear force in the X direction, the first pair of piezoelectric ceramic thin film sensing units in the symmetrical structure deforms and generates an output voltage, while the second pair of piezoelectric ceramic thin film sensing units in the symmetrical structure does not deform and has no output, thereby testing the shear force in the X direction; When the piezoelectric sensor is subjected to a shear force in the Y direction, the second pair of piezoelectric ceramic thin film sensing units in the symmetrical structure deforms and generates an output voltage, while the first pair of piezoelectric ceramic thin film sensing units in the symmetrical structure does not deform and has no output, thereby testing the shear force in the Y direction; The piezoelectric ceramic thin film sensing unit is prepared by the following method: a first layer of metal film is deposited on the lower surface of the piezoelectric ceramic pressing piece by a magnetron sputtering process to form a piezoelectric layer lower electrode; the piezoelectric ceramic pressing piece on which the first layer of metal film is deposited is bonded to a substrate layer, wherein the first layer of metal film is in close contact with the substrate layer; the upper surface of the piezoelectric ceramic pressing piece is thinned by a chemical mechanical polishing process to form a piezoelectric ceramic thin film layer; and a second layer of metal film is deposited on the upper surface of the thinned piezoelectric ceramic thin film layer to form a piezoelectric layer upper electrode.

2. The piezoelectric sensor for measuring normal pressure and shear force according to claim 1, characterized in that: The frame is a rectangle, and a beam is arranged at the center of each of the four sides of the rectangle. The beams extend toward the center of the rectangle and are connected to the connecting platform to form a symmetrical cross-shaped distribution.

3. The piezoelectric sensor for measuring normal pressure and shear force according to claim 2, characterized in that: The connecting platform is a square, and the four beams are respectively connected to the midpoints of the four sides of the connecting platform.

4. The piezoelectric sensor for measuring normal pressure and shear force according to claim 1, characterized in that: Each of the piezoelectric ceramic thin film sensing units is composed of a piezoelectric layer lower electrode, a piezoelectric ceramic thin film layer, and a piezoelectric layer upper electrode, wherein the piezoelectric layer lower electrode is located on the connecting beam, the piezoelectric ceramic thin film layer is arranged on the piezoelectric layer lower electrode, and the piezoelectric layer upper electrode is arranged on the piezoelectric ceramic thin film layer.

5. The piezoelectric sensor for measuring normal pressure and shear force according to claim 4, characterized in that: The piezoelectric layer lower electrode extends to the upper surface end of the frame, and the piezoelectric layer upper electrode is located on the beam in the frame.

6. A method for preparing a piezoelectric sensor according to any one of claims 1 to 5, characterized in that: include: S1, preparing a substrate layer for support; S2, depositing a piezoelectric layer lower electrode on the lower surface of a piezoelectric ceramic press piece, forming a piezoelectric ceramic thin film layer by a bonding thinning process, and depositing a piezoelectric layer upper electrode on the upper surface of the piezoelectric ceramic thin film layer; S3, depositing a cilia structure on the upper surface of the piezoelectric ceramic film layer and patterning it; S4, etching the front surface of the piezoelectric ceramic film layer and the substrate layer to form a connecting beam, a connecting platform and a piezoelectric ceramic film sensing unit; S5, etching the back of the substrate layer to form a frame structure.

7. The method for preparing a piezoelectric sensor according to claim 6, characterized in that: The S2 comprises: S11, depositing a first layer of metal film on the lower surface of the piezoelectric ceramic pressing piece by a magnetron sputtering process to form a piezoelectric layer lower electrode; S12, bonding the piezoelectric ceramic pressing piece on which the first metal film is deposited to the substrate layer, wherein the first metal film is in close contact with the substrate layer; S13, thinning the upper surface of the piezoelectric ceramic pressing piece by a chemical mechanical polishing process to form a piezoelectric ceramic thin film layer; S14, depositing a second metal film layer on the upper surface of the thinned piezoelectric ceramic film layer to form an upper electrode of the piezoelectric layer.

8. The method for preparing a piezoelectric sensor according to claim 6, characterized in that: Also includes one or more of the following options: - The ciliary structure is made of one or more materials selected from silicon and polymers; - The substrate layer is a silicon or metal substrate; - The upper electrode of the piezoelectric layer and the lower electrode of the piezoelectric layer are both metal electrodes.

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