A vibration coupling double micro-cantilever plate MEMS viscosity sensor chip and a working method thereof

Abstract

The application belongs to the field of MEMS sensors, and particularly relates to a vibrating coupling double-micro-cantilever plate MEMS viscosity sensor chip and a working method thereof. The chip comprises a silicon-based fixed support body, a fixed support body cavity is arranged on the silicon-based fixed support body, a first micro-cantilever plate and a second micro-cantilever plate which are rectangular and oppositely arranged at free ends are arranged in the fixed support body cavity, a vibrating coupling gap is arranged between the free ends of the first micro-cantilever plate and the second micro-cantilever plate, the length of the second micro-cantilever plate is less than the length of the first micro-cantilever plate, the first micro-cantilever plate is symmetrically provided with a first piezoelectric driving electrode and a first piezoelectric pickup electrode in the width direction of the first micro-cantilever plate, the second micro-cantilever plate is symmetrically provided with a second piezoelectric driving electrode and a second piezoelectric pickup electrode in the width direction of the second micro-cantilever plate, and the first piezoelectric driving electrode, the first piezoelectric pickup electrode, the second piezoelectric driving electrode and the second piezoelectric pickup electrode are all connected with metal leads. The vibrating coupling double-micro-cantilever plate MEMS viscosity sensor chip can significantly improve the measurement performance such as fluid measurement precision and stability.

Description

Technical Field

[0001] This invention belongs to the field of MEMS (Micro Electromechanical Systems) sensors, specifically relating to a vibration-coupled dual microcantilever plate MEMS viscosity sensor chip and its working method. Background Technology

[0002] In the chemical industry, fluid viscosity is used as a crucial indicator for quality control. However, traditional viscometers, such as those using rotating cylinders, suffer from drawbacks such as bulky equipment, high measurement costs, and slow efficiency, making them unsuitable for the demands of efficient fluid detection. To address these viscosity measurement challenges, viscosity sensors based on MEMS technology offer advantages such as low manufacturing costs, miniaturized integration, and online measurement, demonstrating significant research potential and application prospects in recent years. However, most current MEMS viscosity sensors rely on resonant measurement methods that use the quality factor as a key vibration parameter. For measuring high-viscosity fluids in industries such as energy and chemicals, issues like poor measurement accuracy, low quality factors, and cumbersome sensor measurement processes hinder performance improvements. Therefore, it is necessary to focus on MEMS viscosity sensors, optimizing their design from the perspectives of structural design and working mechanism to improve their overall measurement performance, including measurement accuracy and viscosity applicability range. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention aims to provide a vibration-coupled dual microcantilever plate MEMS viscosity sensor chip and its working method, in order to improve the overall performance of MEMS viscosity sensors, such as measurement accuracy, measurement range, and stability.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A vibration-coupled dual microcantilever MEMS viscosity sensor chip includes a silicon-based solid support with a cavity. A dual piezoelectric microcantilever suspension structure is provided on the silicon-based solid support within the cavity. The dual piezoelectric microcantilever suspension structure includes a rectangular first microcantilever plate and a second microcantilever plate with their free ends facing each other. A vibration coupling gap exists between the free ends of the first and second microcantilever plates. The length of the second microcantilever plate is less than the length of the first microcantilever plate.

[0006] The first microcantilever plate is symmetrically provided with a first piezoelectric driving electrode and a first piezoelectric vibration pickup electrode in its width direction. The second microcantilever plate is symmetrically provided with a second piezoelectric driving electrode and a second piezoelectric vibration pickup electrode in its width direction. The first piezoelectric driving electrode and the second piezoelectric driving electrode are located on the same side. The first piezoelectric vibration pickup electrode and the second piezoelectric vibration pickup electrode are located on the same side. The first piezoelectric driving electrode, the first piezoelectric vibration pickup electrode, the second piezoelectric driving electrode and the second piezoelectric vibration pickup electrode are all connected with metal leads.

[0007] Preferably, the first microcantilever plate and the second microcantilever plate have the same width and the same thickness. The width of the first microcantilever plate is greater than or equal to its length, and both the width and length of the first microcantilever plate are more than 5 times its thickness. The width of the second microcantilever plate is greater than or equal to its length, and both the width and length of the second microcantilever plate are more than 5 times its thickness.

[0008] Preferably, the free end of the first microcantilever plate is provided with a first rectangular protrusion, and the first piezoelectric driving electrode and the first piezoelectric vibration pickup electrode are symmetrically located on both sides of the first rectangular protrusion. The free end of the second microcantilever plate is provided with a second rectangular protrusion, and the second piezoelectric driving electrode and the second piezoelectric vibration pickup electrode are symmetrically located on both sides of the second rectangular protrusion. The first rectangular protrusion and the second rectangular protrusion face each other, and a gap is left between the first rectangular protrusion and the second rectangular protrusion.

[0009] Preferably, the first microcantilever plate and the first rectangular protrusion have the same thickness, the second microcantilever plate and the second rectangular protrusion have the same thickness, and the first rectangular protrusion and the second rectangular protrusion have the same length, width and thickness.

[0010] Preferably, the net distance between the first rectangular protrusion and the second rectangular protrusion is 33% to 48% of the width of the vibration coupling gap, the width of the first rectangular protrusion is 33% to 36% of the width of the first microcantilever plate, the width of the second rectangular protrusion is 33% to 36% of the width of the second microcantilever plate, and the length of the second microcantilever plate is 80% to 84% of the length of the first microcantilever plate.

[0011] Preferably, the first piezoelectric driving electrode and the first piezoelectric pickup electrode have the same length, width, and thickness; the second piezoelectric driving electrode and the second piezoelectric pickup electrode have the same length, width, and thickness.

[0012] Preferably, the first piezoelectric driving electrode, the first piezoelectric vibration pickup electrode and the first microcantilever plate have the same length, and the second piezoelectric driving electrode, the second piezoelectric vibration pickup electrode and the second microcantilever plate have the same length.

[0013] Preferably, the solid support cavity is rectangular in shape, and the axis of symmetry of the first and second microcantilever plates along their length is coaxial with the axis of symmetry of the wide side of the solid support cavity.

[0014] Preferably, the silicon-based solid support includes a monocrystalline silicon substrate. Both the bottom and top surfaces of the monocrystalline silicon substrate are provided with a thermo-oxidized silicon thin film. A piezoelectric layer bottom electrode molybdenum thin film is provided on the surface of the thermo-oxidized silicon thin film on the top surface of the monocrystalline silicon substrate. A low-stress aluminum nitride piezoelectric thin film is provided on the surface of the piezoelectric layer bottom electrode molybdenum thin film. An electrode metal layer serving as a first piezoelectric driving electrode, a first piezoelectric pickup electrode, a second piezoelectric driving electrode, and a second piezoelectric pickup electrode is provided on the surface of the low-stress aluminum nitride piezoelectric thin film and the electrode metal layer. A silicon nitride thin film is provided on the surfaces of the low-stress aluminum nitride piezoelectric thin film and the electrode metal layer. The first microcantilever plate, the second microcantilever plate, and the silicon-based solid support share the thermo-oxidized silicon thin film, the piezoelectric layer bottom electrode molybdenum thin film, the low-stress aluminum nitride piezoelectric thin film, the silicon nitride thin film, and a portion of the monocrystalline silicon substrate on the top surface of the monocrystalline silicon substrate. The thickness of the monocrystalline silicon substrate on the first and second microcantilever plates is less than that of the monocrystalline silicon substrate of the silicon-based solid support.

[0015] The present invention also provides a method for operating the vibration-coupled dual microcantilever plate MEMS viscosity sensor chip as described above, including:

[0016] When the vibration-coupled dual microcantilever plate MEMS viscosity sensor chip is immersed in fluid, the fluid fills the vibration coupling gap and acts as the vibration coupling medium.

[0017] The first microcantilever plate is used as an active cantilever plate. When an alternating electric field is applied to the first piezoelectric driving electrode of the first microcantilever plate, the top electrode of the piezoelectric layer of the first microcantilever plate is energized and the bottom electrode is grounded, causing the first microcantilever plate to generate non-resonant bending vibration at the frequency of the driving voltage, and simultaneously causing the fluid around the first microcantilever plate to vibrate accordingly. The second microcantilever plate is used as a passive cantilever plate. It generates vibration coupling with the first cantilever plate through the fluid medium, and the fluid medium in the vibration coupling gap is subjected to shear force between the first and second microcantilever plates, so that the vibration amplitude of the second microcantilever plate is directly related to the fluid viscosity and the vibration amplitude of the first microcantilever plate. In the non-resonant bending vibration state, the first and second piezoelectric vibration pickup electrodes are configured with the top electrode connected to an external electrical output port and the bottom electrode grounded. Through the piezoelectric effect, an alternating voltage detection signal is generated and output, and then the output voltage ratio of the dual piezoelectric microcantilever plate cantilever structure is extracted to realize the measurement of fluid viscosity.

[0018] The present invention has the following beneficial effects:

[0019] The vibration-coupled dual-microcantilever MEMS viscosity sensor chip of this invention employs a dual-piezoelectric microcantilever structure. Compared to traditional slender microcantilever beam structures, this structure can achieve a high Reynolds number by increasing the width dimension, which helps improve the fluid damping resistance of the sensor chip immersed in fluid, thereby enhancing the vibration stability of the sensor. This invention utilizes the fluid medium to achieve vibration coupling between the dual piezoelectric microcantilever structures. Through the non-resonant vibration of the active piezoelectric microcantilever (i.e., the first microcantilever) coupled with the vibration of the fluid medium, the passive piezoelectric microcantilever (i.e., the second microcantilever) is driven to generate non-resonant bending vibration at a specific frequency. Compared to existing resonant fluid viscosity measurement methods based on quality factor vibration parameters, the viscosity sensor chip method proposed in this invention does not require resonance curve fitting. It also avoids the problem of poor fluid viscosity measurement accuracy, or even difficulty in obtaining experimental fluid viscosity values, caused by the complexity of the quality factor in high-viscosity fluids. By directly measuring the fluid viscosity through the sensor's output vibration amplitude, it significantly improves measurement efficiency and accuracy. The vibration-coupled dual piezoelectric microcantilever MEMS viscosity sensor chip of the present invention realizes piezoelectric driven vibration and output voltage detection of the suspended structure of the dual piezoelectric microcantilever through the arrangement of piezoelectric driving electrodes and vibration pickup electrodes. Compared with electromagnetic, electrothermal and electrostatic excitation methods, it has excellent packaging characteristics and anti-interference ability. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the overall structure of the vibration-coupled dual microcantilever plate MEMS viscosity sensor chip in an embodiment of the present invention.

[0022] Figure 2 for Figure 1 A schematic diagram of the cross section along line A-A'.

[0023] Figure 3 The image shows the bending vibration mode simulation of the microcantilever plate suspended array structure according to an embodiment of the present invention.

[0024] Figure 4 The simulation curves of the vibration amplitude ratio of the microcantilever plate suspended array structure in different fluids are shown in the embodiment of the present invention.

[0025] In the figure, 1-silicon-based solid support, 2-first microcantilever plate, 3-1-first piezoelectric driving electrode, 3-2-first piezoelectric vibration pickup electrode, 4-second microcantilever plate, 5-1-second driving electrode, 5-2-second vibration pickup electrode, 6-metal lead, 7-solid support cavity, 8-single crystal silicon substrate, 9-thermal oxidation silicon thin film, 10-piezoelectric layer bottom electrode molybdenum thin film, 11-low-stress aluminum nitride piezoelectric thin film, 12-electrode metal layer, 13-silicon nitride thin film, 14-rectangular protrusion, 15-vibration coupling gap. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0027] Reference Figure 1This embodiment of the vibration-coupled dual-cantilever MEMS viscosity sensor chip includes a silicon-based solid support 1, a rectangular solid support cavity 7 on the silicon-based solid support 1, and a dual-piezoelectric microcantilever suspension structure within the solid support cavity 7. The dual-piezoelectric microcantilever suspension structure includes a rectangular first microcantilever 2 and a second microcantilever 4 with their free ends facing each other. The axis of symmetry of the length direction of the first microcantilever 2 and the second microcantilever 4 is coaxial with the axis of symmetry of the width side of the solid support cavity 7. A vibration coupling gap 15 is provided between the free ends of the first microcantilever 2 and the second microcantilever 4. The length of the second microcantilever 4 is less than the length of the first microcantilever 2. The first microcantilever 2 and the second microcantilever 4 have the same width and the same thickness. The width and length of the first microcantilever plate 2 are both more than 5 times its thickness; the width of the second microcantilever plate 4 is greater than or equal to its length, and both its width and length are more than 5 times its thickness; the free ends of the first microcantilever plate 2 and the second microcantilever plate 4 are provided with rectangular protrusions 14, the rectangular protrusions 14 in the first microcantilever plate 2 and the second microcantilever plate 3 are the same size, the rectangular protrusions 14 on the first microcantilever plate 2 and the rectangular protrusions 14 on the second microcantilever plate 4 are directly opposite each other, and there is a gap between the two rectangular protrusions; the thickness of the first microcantilever plate 2 and its rectangular protrusions is the same, the thickness of the second microcantilever plate 4 and its rectangular protrusions is the same, and the length, width and thickness of the two rectangular protrusions 14 are the same; the silicon-based fixed support plate 1 and The lower bases of the first microcantilever plate 2 and the second microcantilever plate 4 are coaxially connected; the first microcantilever plate 2 and the second microcantilever plate 4 are coaxially arranged along the length direction, and there is a free end gap between them; the double piezoelectric microcantilever plate suspended structure is arranged with piezoelectric electrode pairs, wherein the first microcantilever plate 2 is arranged with a first piezoelectric driving electrode 3-1 and a first piezoelectric vibration pickup electrode 3-2, and the second microcantilever plate 4 is arranged with a pair of piezoelectric vibration pickup electrodes (i.e., a second piezoelectric driving electrode 5-1 and a second piezoelectric vibration pickup electrode 5-2), and the piezoelectric electrode pairs are used as the top electrodes of the double piezoelectric microcantilever plate suspended structure; the piezoelectric electrode pairs on the double piezoelectric microcantilever plate suspended structure are symmetrical about the axis of symmetry of the width direction of the rectangular protrusion 14, and are arranged on both sides of the microcantilever plate along the width direction, that is, the first microcantilever plate 2 and the second piezoelectric microcantilever plate 4 are arranged with a free end gap width of 5-1 and 5-2. The first piezoelectric driving electrode 3-1 and the first piezoelectric vibration pickup electrode 3-2 on the cantilever plate 2 are symmetrical about the axis of symmetry in the width direction of the rectangular protrusion 14. The second piezoelectric driving electrode 5-1 and the second piezoelectric vibration pickup electrode 5-2 on the second microcantilever plate 4 are symmetrical about the axis of symmetry in the width direction of the rectangular protrusion 14. The first piezoelectric driving electrode 3-1 and the second piezoelectric driving electrode 5-1 are located on the same side, and the first piezoelectric vibration pickup electrode 3-2 and the second piezoelectric vibration pickup electrode 5-2 are located on the same side. The piezoelectric driving electrode and the vibration pickup electrode on the same microcantilever plate (i.e., the first microcantilever plate 2 or the second microcantilever plate 4) have the same length, the same width, and the same thickness. The length of the piezoelectric driving electrode and the vibration pickup electrode is the same as the length of the microcantilever plate (i.e., the first microcantilever plate 2 or the second microcantilever plate 4).The width dimension of the dual piezoelectric microcantilever plate cantilever structure is greater than or equal to its length dimension; each piezoelectric driving electrode and piezoelectric pickup electrode is connected to a metal lead 6. The length direction is along; Figure 1 In the X direction, the X direction is parallel to the axis of the microcantilever plate along its length, while the Y direction is the width direction, along the width direction of the microcantilever plate.

[0028] Reference Figure 1 and combined Figure 3 The operating method of the vibration-coupled dual microcantilever plate MEMS viscosity sensor chip in this embodiment includes the following steps:

[0029] When the vibration-coupled dual microcantilever MEMS viscosity sensor chip is immersed in a fluid, the fluid fills the gap between the free ends of the dual piezoelectric microcantilever structures (i.e., the gap between the free ends of the first microcantilever 2 and the second microcantilever 4) and acts as a vibration coupling medium. The first microcantilever 2, as an active cantilever, generates non-resonant bending vibrations at the frequency of the driving voltage when an alternating electric field is applied to its first piezoelectric driving electrode 3-1, forming a piezoelectric layer with the top electrode energized and the bottom electrode grounded. This causes the first microcantilever 2 to vibrate non-resonantly at the frequency of the driving voltage, simultaneously causing the surrounding fluid to vibrate accordingly. Furthermore, the vibration of the surrounding fluid generates a vibration driving force on the second microcantilever 4, causing it to generate passive bending vibrations at a specific frequency. The second microcantilever plate 4, acting as a passive cantilever plate, vibrates and couples with the first cantilever plate 2 through a fluid medium. The fluid medium in the gap between the free ends of the dual piezoelectric microcantilever plate cantilever structure is subjected to shear force between the first and second microcantilever plates (2, 4), causing the vibration amplitude of the second microcantilever plate 4 to be directly related to the fluid viscosity and the vibration amplitude of the first microcantilever plate 2. Under non-resonant bending vibration conditions, the piezoelectric pickup electrodes are configured with an external electrical output port at the top electrode and grounded at the bottom electrode. An alternating voltage detection signal is generated and output through the piezoelectric effect, thereby extracting the output voltage ratio of the dual piezoelectric microcantilever plate cantilever structure to measure the fluid viscosity.

[0030] This invention employs a dual-microcantilever MEMS viscosity sensor chip with a free-end gap (i.e., vibration coupling gap 15) to excite the vibration coupling effect of the dual microcantilever plates through a fluid medium. The rectangular protrusions 14 on the microcantilever plates create a non-uniform vibration distribution in the fluid medium within the free-end gap (i.e., vibration coupling gap 15, which can be experimentally determined and designed according to the type of fluid being detected and the overall size of the sensor; this invention does not impose specific limitations, as long as vibration coupling occurs between the first microcantilever plate 2 and the second microcantilever plate 4). This enhances the bending vibration transmission effect of the fluid on the dual microcantilever plates. The dual cantilever plate structure operates under non-resonant bending vibration conditions, and fluid viscosity is measured using the sensor's vibration amplitude. This avoids problems such as poor fluid viscosity measurement accuracy caused by the difficulty in accurately fitting complex resonance parameters like the quality factor in high-viscosity fluids, thereby improving the fluid viscosity measurement accuracy and efficiency of this type of sensor.

[0031] In this embodiment, the dimensions of the first microcantilever plate 2 in the dual piezoelectric microcantilever plate suspension structure are: length × width = (1100±10) × (1400±10) μm 2 The thickness is 20±5μm; the dimensions of the second microcantilever plate 4 are: length × width = (900±10) × (1400±10)μm 2 The thickness is 20±5μm; the dimensions of the rectangular protrusion 14 are: length × width = (30±5) × (480±10)μm 2 The thickness is 20±5μm; the length of the vibration coupling gap 15 at the free end between the first microcantilever plate 2 and the second microcantilever plate 4 is 100±5μm, that is, the distance between the two rectangular protrusions 14 of the first microcantilever plate 2 and the second microcantilever plate 4 is 40±5μm.

[0032] like Figure 2As shown in the cross-sectional view of the vibration-coupled microcantilever plate MEMS viscosity sensor chip of the present invention, the sensor chip is fabricated on a single-crystal silicon substrate 8. Both the upper and lower surfaces of the single-crystal silicon substrate 8 are covered with a thermo-oxidized silicon thin film 9, which serves as an electrical insulating layer for the single-crystal silicon substrate. A piezoelectric bottom electrode molybdenum thin film 10 is disposed on the surface of the thermo-oxidized silicon thin film 9 on the upper side of the single-crystal silicon substrate 8. The piezoelectric bottom electrode molybdenum thin film 10 can be used as the chip's bottom electrode grounding layer, or as a substrate layer for the deposition of a low-stress aluminum nitride piezoelectric thin film 11. The upper surface of the piezoelectric bottom electrode molybdenum thin film 10... A low-stress aluminum nitride piezoelectric film 11 is provided. The low-stress aluminum nitride piezoelectric film 11 is used to generate inverse piezoelectric effect and piezoelectric effect, realizing the excitation of vibration modes and electrical signal detection. An electrode metal layer 12 is provided on the upper surface of the low-stress aluminum nitride piezoelectric film 11, which serves to form a piezoelectric electrode pair and metal leads 6. A silicon nitride insulating layer film 13 is provided on the upper side of the low-stress aluminum nitride piezoelectric film 11 and the electrode metal layer 12. The silicon nitride insulating layer film 13 covers the surface of the sensor chip and serves as insulation in the fluid medium. Figure 2 In the cross-sectional view shown, the area with a larger thickness of the single-crystal silicon substrate 8 on the left represents the silicon-based fixed support 1 of the sensor chip, while the area with a smaller thickness of the single-crystal silicon substrate 8 represents the suspended structure of the dual piezoelectric microcantilever plate. Specifically, the first microcantilever plate 2, the second microcantilever plate 4, and the silicon-based fixed support 1 share the thermo-oxidative silicon thin film 9, the piezoelectric layer bottom electrode molybdenum thin film 10, the low-stress aluminum nitride piezoelectric thin film 11, the silicon nitride thin film 14, and part of the single-crystal silicon substrate 8 on the top surface of the single-crystal silicon substrate 8. Among them, the thickness of the single-crystal silicon substrate 8 on the first microcantilever plate 2 and the second microcantilever plate 4 is smaller than that on the single-crystal silicon substrate 8 of the silicon-based fixed support 1.

[0033] like Figure 3 and Figure 4 As shown, the fluid-structure interaction simulation analysis of the dual piezoelectric microcantilever plate cantilever structure of the above embodiment size was performed using Comsol Multiphysics simulation software. Figure 3 The simulation results are for non-resonant bending vibration under the vibration coupling effect of the first microcantilever plate 2 and the second microcantilever plate 4. The simulation liquid is cyclohexane (density 779 kg / m³). 3 (The viscosity is 1.0 cP). It can be seen that the first microcantilever plate 2 and the second microcantilever plate 4 undergo bending vibrations of specific amplitudes. The vibration is transmitted between the two piezoelectric microcantilever plate suspension structures through the fluid medium in the vibration coupling gap. The active bending vibration of the first microcantilever plate 2 is coupled to the second microcantilever plate 4, causing the second microcantilever plate 4 to undergo passive bending vibration. This verifies the vibration mode of the dual piezoelectric microcantilever plate suspension structure proposed in this invention.

[0034] Figure 4In this study, four different liquids were selected for fluid-structure interaction simulation analysis, including n-heptane, cyclohexane, MD2M, and D4 liquids. The variation curves between the vibration amplitude ratio of the dual piezoelectric microcantilever plate suspended structure (vibration amplitude of the second microcantilever plate 4 / vibration amplitude of the first microcantilever plate 2) and the fluid viscosity were obtained. It can be seen that a univariate correspondence between the vibration amplitude ratio of the microcantilever plate suspended structure and the fluid viscosity can be established, thereby realizing the measurement of fluid viscosity. This verifies the working mode of the viscosity sensor chip proposed in this invention.

[0035] In summary, the dual piezoelectric microcantilever plate suspension structure of this invention adopts a free-end gap design, and achieves vibration coupling between the dual piezoelectric microcantilever plate suspension structures through the fluid medium, so that the dual piezoelectric microcantilever plate suspension structures can undergo active and passive non-resonant bending vibrations. The rectangular protrusion design of the dual piezoelectric microcantilever plate suspension structure is used to enhance the vibration transmission effect of the fluid medium, and at the same time, it is used to space the piezoelectric electrode pairs, reducing the suppression effect of the parasitic effect of the piezoelectric layer on the output amplitude of the sensor chip. The sensor chip uses locally arranged piezoelectric driving electrodes to excite non-resonant bending vibrations, and piezoelectric pickup electrodes are used to convert the vibration signal into an electrical signal output through the piezoelectric effect, realizing the self-excitation and self-detection performance of the viscosity sensor chip, which helps to improve the comprehensive measurement performance of the viscosity sensor chip, such as fluid measurement accuracy and stability.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A vibrational coupling dual micro-cantilever plate (MEMS) viscosity sensor chip, characterized in that, The application relates to a silicon-based fixed support body (1) provided with a fixed support body cavity (7), and a double-piezoelectric micro-cantilever plate suspension structure arranged on the fixed support body cavity (7) of the silicon-based fixed support body (1), wherein the double-piezoelectric micro-cantilever plate suspension structure comprises a first micro-cantilever plate (2) and a second micro-cantilever plate (4) which are rectangular and oppositely arranged at free ends, and the first micro-cantilever plate (2) and the second micro-cantilever plate (4) are provided with a vibration coupling gap (15) between the free ends; the length of the second micro-cantilever plate (4) is smaller than that of the first micro-cantilever plate (2). The first micro-cantilever plate (2) is symmetrically provided with a first piezoelectric driving electrode (3-1) and a first piezoelectric pickup electrode (3-2) in the width direction, the second micro-cantilever plate (4) is symmetrically provided with a second piezoelectric driving electrode (5-1) and a second piezoelectric pickup electrode (5-2) in the width direction, the first piezoelectric driving electrode (3-1) and the second piezoelectric driving electrode (5-1) are located on the same side, the first piezoelectric pickup electrode (3-2) and the second piezoelectric pickup electrode (5-2) are located on the same side, and the first piezoelectric driving electrode (3-1), the first piezoelectric pickup electrode (3-2), the second piezoelectric driving electrode (5-1) and the second piezoelectric pickup electrode (5-2) are all connected with metal leads (6).

2. The vibrational coupling dual micro-cantilever plate MEMS viscosity sensor chip according to claim 1, wherein, The first micro-cantilever plate (2) and the second micro-cantilever plate (4) have the same width and the same thickness.

3. The vibrational coupling double micro-cantilever plate MEMS viscosity sensor chip according to claim 1 or 2, characterized in that, The free end of the first micro-cantilever plate (2) is provided with a first rectangular protrusion, the first piezoelectric driving electrode (3-1) and the first piezoelectric pickup electrode (3-2) are symmetrically arranged on the two sides of the first rectangular protrusion, the free end of the second micro-cantilever plate (4) is provided with a second rectangular protrusion, the second piezoelectric driving electrode (5-1) and the second piezoelectric pickup electrode (5-2) are symmetrically arranged on the two sides of the second rectangular protrusion, the first rectangular protrusion and the second rectangular protrusion are opposite to each other, and a gap is left between the first rectangular protrusion and the second rectangular protrusion.

4. The vibrational coupling dual micro-cantilever plate MEMS viscosity sensor chip according to claim 3, wherein, The first micro-cantilever plate (2) has the same thickness as the first rectangular protrusion, the second micro-cantilever plate (4) has the same thickness as the second rectangular protrusion, and the first rectangular protrusion and the second rectangular protrusion have the same length, the same width and the same thickness.

5. The vibrational coupling dual micro-cantilever plate MEMS viscosity sensor chip according to claim 3, wherein, The net distance between the first rectangular protrusion and the second rectangular protrusion is 33% to 48% of the width of the vibration coupling gap (15), the width of the first rectangular protrusion is 33% to 36% of the width of the first micro-cantilever plate (2), the width of the second rectangular protrusion is 33% to 36% of the width of the second micro-cantilever plate (4), and the length of the second micro-cantilever plate (4) is 80% to 84% of the length of the first micro-cantilever plate (2).

6. The vibrational coupling dual micro-cantilever plate MEMS viscosity sensor chip according to claim 1, wherein, The first piezoelectric driving electrode (3-1) and the first piezoelectric pickup electrode (3-2) have the same length, the same width and the same thickness, and the second piezoelectric driving electrode (5-1) and the second piezoelectric pickup electrode (5-2) have the same length, the same width and the same thickness.

7. The vibrational coupling dual micro-cantilever plate MEMS viscosity sensor chip according to claim 1, wherein, The first piezoelectric driving electrode (3-1), the first piezoelectric pickup electrode (3-2), the second piezoelectric driving electrode (5-1) and the second piezoelectric pickup electrode (5-2) have the same length as the first micro-cantilever plate (2) and the second micro-cantilever plate (4).

8. The vibrational coupling dual micro-cantilever plate MEMS viscosity sensor chip according to claim 1, wherein, The shape of the fixed support body cavity (7) is rectangular, and the symmetry axes of the length directions of the first micro-cantilever plate (2) and the second micro-cantilever plate (4) are coaxial with the symmetry axes of the wide edges of the fixed support body cavity (7).

9. The vibrational coupling dual micro-cantilever plate MEMS viscosity sensor chip according to claim 1, wherein, The silicon-based fixed support body (1) comprises a monocrystalline silicon substrate (8), the bottom surface and the top surface of the monocrystalline silicon substrate (8) are provided with thermal-oxidized silicon films (9), the surface of the thermal-oxidized silicon film (9) on the top surface of the monocrystalline silicon substrate (8) is provided with a molybdenum film (10) of a bottom electrode of a piezoelectric layer, the surface of the molybdenum film (10) of the bottom electrode of the piezoelectric layer is provided with a low-stress aluminum nitride piezoelectric film (11), the surface of the low-stress aluminum nitride piezoelectric film (11) is provided with an electrode metal layer (12) serving as a first piezoelectric driving electrode (3-1), a first piezoelectric pickup electrode (3-2), a second piezoelectric driving electrode (5-1) and a second piezoelectric pickup electrode (5-2), and the surfaces of the low-stress aluminum nitride piezoelectric film (11) and the electrode metal layer (12) are provided with a silicon nitride film (13); the first micro-cantilever plate (2), the second micro-cantilever plate (4) and the silicon-based fixed support body (1) share the thermal-oxidized silicon film (9), the molybdenum film (10) of the bottom electrode of the piezoelectric layer, the low-stress aluminum nitride piezoelectric film (11), the silicon nitride film (13) and part of the monocrystalline silicon substrate (8) on the top surface of the monocrystalline silicon substrate (8), wherein the thicknesses of the monocrystalline silicon substrates (8) on the first micro-cantilever plate (2) and the second micro-cantilever plate (4) are less than that of the silicon-based fixed support body (1).

10. The method of operating a vibrational coupling dual micro-cantilever MEMS viscosity sensor chip according to any one of claims 1-9, wherein, Comprise: When the vibration-coupled double-micro-cantilever plate MEMS viscosity sensor chip is immersed in a fluid, the fluid fills the vibration-coupled gap (15) and acts as a vibration-coupled medium; The first micro-cantilever plate (2) is used as an active cantilever plate, when an alternating electric field is applied on the first piezoelectric driving electrode (3-1) of the first micro-cantilever plate (2), the piezoelectric layer top electrode of the first micro-cantilever plate (2) is powered and the bottom electrode is grounded, so that the first micro-cantilever plate (2) produces non-resonant bending vibration at the frequency of the driving voltage, and the fluid around the first micro-cantilever plate (2) also produces corresponding vibration; the second micro-cantilever plate (4) is used as a passive cantilever plate, and the vibration-coupling effect between the first micro-cantilever plate (2) and the second micro-cantilever plate (4) is realized through the fluid medium, and the fluid medium in the vibration-coupled gap (15) is subjected to shear force between the first micro-cantilever plate (2) and the second micro-cantilever plate (4), so that the vibration amplitude of the second micro-cantilever plate (4) is directly related to the viscosity of the fluid and the vibration amplitude of the first micro-cantilever plate (2); in the non-resonant bending vibration state, the first piezoelectric pickup electrode (3-2) and the second piezoelectric pickup electrode (5-2) form a top electrode external electrical output port and a bottom electrode grounding mode, and an alternating voltage detection signal is generated and output through the piezoelectric effect, and then the output voltage ratio of the double-piezoelectric micro-cantilever plate suspended structure is extracted, so as to realize the measurement of the viscosity of the fluid.

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