1. A microelectromechanical resonant viscosity sensor, characterized in that the viscosity sensor comprises a first liquid contact membrane (100), an SOI assembly (600), and a second liquid contact membrane (500) bonded in that order, the first liquid contact membrane (100) and the second liquid contact membrane (500) being mirror symmetric with respect to the SOI assembly (600), wherein:

the SOI assembly (600) comprises a resonator (400), the first liquid contact membrane (100) is provided with a first thin membrane (120) at the side far away from the SOI assembly (600), the second liquid contact membrane (500) is provided with a second thin membrane (520) at the side far away from the SOI assembly (600), and the centers of the first thin membrane (120) and the second thin membrane (520) are connected with the center of the resonator (400) through a rigid body (700);

a vacuum cavity (800) is formed between the first film (120) and the second film (520), the resonator (400) is located in the vacuum cavity (800), and the resonator (400) drives the first film (120) and the second film (520) to work in a resonant mode along a direction perpendicular to a film plane under the action of a driving force L.

2. The microelectromechanical resonant viscosity sensor of claim 1, characterized in that the resonator (400) comprises:

a resonant structure (420); and

a peripheral frame (410) formed around the resonant structure (420) for securing the resonant structure (420).

3. A microelectromechanical resonant viscosity sensor of claim 2, characterized in that the resonant structure (420) comprises two first movable electrodes (421), two second movable electrodes (422), one fourth rigid connection block (423), four biased connection beams (425), and four movable electrode connection beams (426), wherein:

the fourth rigid connecting block (423) is positioned at the center of the resonance structure (420), and the two first movable electrodes (421) and the two second movable electrodes (422) are uniformly arranged at intervals along a circumference with the fourth rigid connecting block (423) as the center, so that the two first movable electrodes (421) are symmetrical to each other and the two second movable electrodes (422) are symmetrical to each other;

two first movable electrodes (421), two second movable electrodes (422) and four bias connection beams (425) are connected to the fourth rigid connection block (423), the bias connection beams (425) are arranged in a gap between the first movable electrodes (421) and the second movable electrodes (422), and the movable electrode connection beams (426) fixedly connect the adjacent first movable electrodes (421) and second movable electrodes (422) to the bias connection beams (425) so that the first movable electrodes (421), the second movable electrodes (422) and the bias connection beams (425) are connected into a whole.

4. A microelectromechanical resonant viscosity sensor of claim 3, characterized in that the first movable electrode (421) and the second movable electrode (422) are provided with a plurality of damping weakening holes (424) arranged in an array for reducing squeeze film damping effect of out-of-plane vibration of the movable electrodes.

5. A microelectromechanical resonant viscosity sensor of claim 3, characterized in that the SOI assembly (600) further comprises:

the driving and detecting structure (200) is arranged above the resonator (400) and positioned in the vacuum cavity (800) and is used for driving the resonator (400) to vibrate and detecting an output signal of the resonator (400); and

an insulating layer (300) disposed between the driving and detecting structure (200) and the resonator (400) for electrically insulating isolation between the driving and detecting structure (200) and the resonator (400).

6. A microelectromechanical resonant viscosity sensor of claim 5, characterized in that the driving and detecting structure (200) comprises two first fixed electrodes (210), two second fixed electrodes (220), a second rigid connection block (230), and a sealing ring (240), wherein:

the second rigid connection block (230) is positioned at the center of the driving and detecting structure (200), and the two first fixed electrodes (210) and the two second fixed electrodes (220) are uniformly arranged at intervals along a circumference centered on the second rigid connection block (230), so that the two first fixed electrodes (210) are symmetrical to each other and the two second fixed electrodes (220) are symmetrical to each other;

the sealing rings (240) are formed around the two first fixed electrodes (210) and the two second fixed electrodes (220) and are not connected to the two first fixed electrodes (210) and the two second fixed electrodes (220), and the sealing rings (240) participate in forming the vacuum chamber (800).

7. A micro-electromechanical resonance type viscosity sensor according to claim 6, wherein the resonator (400) adopts an electrostatic driving-capacitance detection working principle, the movable electrodes in the resonator (400) are parallel to the fixed electrodes in the driving and detecting structure (200) and are arranged in a one-to-one corresponding position relationship, the first movable electrode (421) and the first fixed electrode (210) form a driving electrode pair, and the second movable electrode (422) and the second fixed electrode (220) form a detecting electrode pair.

8. The microelectromechanical resonant viscosity sensor of claim 7,

the first fixed electrode (210) is connected with a rear end driving circuit and is used for providing driving force of out-of-plane vibration for the first movable electrode (421);

the second fixed electrode (220) is connected with a rear end detection circuit and is used for picking up capacitance variation caused by vibration of the second movable electrode (422);

the second rigid connecting block (230) and the fourth rigid connecting block (423) correspond in parallel and are concentric.

9. A microelectromechanical resonant viscosity sensor of claim 6, characterized in that the insulating layer (300) comprises:

a third rigid connection block (310); and

a peripheral insulating layer (320) formed around the third rigid connection block (310) to isolate the drive and sense structure (200) from the resonator (400);

wherein the peripheral insulating layer (320) participates in forming the vacuum cavity (800); the third rigid connecting block (310) corresponds to the second rigid connecting block (230) and the fourth rigid connecting block (423) in parallel, has coaxial centroids, and rigidly connects the second rigid connecting block (230) and the fourth rigid connecting block (423) together.

10. A microelectromechanical resonant viscosity sensor of claim 5, characterized in that the drive and sense structure (200), the insulating layer (300), and the resonator (400) are fabricated on a single SOI wafer to form an SOI composite (600).

11. The microelectromechanical resonant viscosity sensor of claim 5,

the first liquid contact membrane (100) comprises a first thin film (120), a first rigid connecting block (130) and a plurality of driving and detecting electrode through holes (110), wherein the driving and detecting electrode through holes (110) are used for passing through electric leads to realize the connection of two first fixed electrodes (210) and a rear end driving circuit and the connection of two second fixed electrodes (220) and the rear end detecting circuit;

the second liquid contact membrane (500) comprises a second membrane (520), a fifth rigid connection block (530) and a bias electrode via (510), wherein the bias electrode via (510) is used for passing through an electrical wire to realize the connection of the resonator (400) with a back-end bias circuit;

the first rigid connection block (130) rigidly connects the first membrane (120) to the second rigid connection block (230), and the fifth rigid connection block (530) rigidly connects the second membrane (520) to the fourth rigid connection block (423), so as to enable the connection of the first membrane (120), the second membrane (520) and the resonant structure (420).

12. A microelectromechanical resonant viscosity sensor of claim 11, characterized in that the first membrane (120) and the second membrane (520) are identical in structure and parallel to each other, the outer surfaces of the membranes contact the liquid to be measured, and the centers of the membranes are coaxially and sequentially rigidly connected with the centroids of the first rigid connecting block (130), the second rigid connecting block (230), the third rigid connecting block (310), the fourth rigid connecting block (423), and the fifth rigid connecting block (530) to form the rigid body (700).

13. A microelectromechanical resonant viscosity sensor of claim 12, characterized in that the vacuum chamber (800) is constructed by bonding and connecting the first liquid contact membrane (100), the SOI assembly (600), and the second liquid contact membrane (500) in sequence;

the resonance structure (420) works in the vacuum cavity (800) formed by the first liquid contact membrane (100), the second liquid contact membrane (500), the sealing ring (240), the insulating layer (300) and the peripheral frame (410), and the first thin film (120) and the second thin film (520) are driven to vibrate in the measured liquid when the resonance structure (420) vibrates out of plane.

14. A microelectromechanical resonant viscosity sensor of claim 13, characterized in that the viscosity sensor components are fabricated using MEMS wafer level fabrication processes, wherein:

the first liquid contact membrane (100) and the second liquid contact membrane (500) are made using a glass etching process,

the driving and detecting structure (200) and the resonator (400) are made by a silicon wafer dry etching process,

the insulating layer (300) is made by adopting an SOI (silicon on insulator) sheet oxide layer corrosion process;

the joining of the first liquid contact membrane (100), the SOI assembly (600), and the second liquid contact membrane (500) is accomplished using an anodic bonding process.

Background

The micro-electromechanical resonance type viscosity sensor mainly realizes viscosity measurement by measuring the resonance frequency or the resonance quality factor (Q value) of a resonance structure in fluid damping. The sensor outputs periodic string signals containing resonance characteristics, and after the periodic string signals are analyzed and processed through impedance or gain, the resolution of resonance Q values and the like can be achieved. With the development of sensors in the direction of miniaturization, digitization, intellectualization and networking, the micro-electromechanical resonant viscosity sensor is concerned in the viscosity measurement industry because of the advantages of easy digital integration, compact structure, small volume, light weight, low power consumption, batch production and the like.

The micromechanical resonant viscosity sensor can be mainly divided into a plurality of realization forms such as a quartz crystal microbalance, a resonant tuning fork, a micro-cantilever/flat plate and the like according to the structure. The quartz crystal microbalance has large resonant frequency and strong anti-interference capability, but the correlation between the resonant frequency shift and the fluid viscosity is poor, the resonant Q value is sharply reduced along with the increase of the fluid viscosity, and the measurement range is limited. The resonant tuning fork has large resonant energy and simple structure, but has relatively large size, low resolution, easy environmental influence and limited measurement precision. Due to the advantages of high sensitivity, high miniaturization degree, easy in-situ integration and the like, the micro cantilever/flat plate is a hotspot direction for research in the field of micro resonant fluid viscosity measurement in recent years.

However, the three types of micromechanical resonant viscosity sensor structures have a common structure problem, that is, in the existing reports, a flat plate/beam structure is mostly adopted to directly contact liquid, the intrinsic Q value (i.e., the zero-point Q value of the sensor) of a resonator is very low, the maximum value is only hundreds to thousands, the Q value of the resonant structure is sharply reduced along with the increase of the viscosity of the liquid, and the viscosity measurement range of the sensor is greatly limited.

On the other hand, the Q value of the resonant structure packaged in the vacuum environment is at least 2-3 orders of magnitude higher than that of the resonant structure packaged in the air environment at present, and can reach tens of thousands or even hundreds of thousands, and if the vacuum packaging resonant structure can be used for viscosity measurement, a better solution is provided for overcoming the application defect of the micro-cantilever/flat plate.

Disclosure of Invention

Technical problem to be solved

In view of the above, it is a primary object of the present disclosure to provide a micro-electromechanical resonant viscosity sensor to at least partially solve the above-mentioned technical problems.

(II) technical scheme

According to an aspect of the present disclosure, there is provided a micro-electromechanical resonance type viscosity sensor, comprising a first liquid contact film 100, an SOI assembly 600, and a second liquid contact film 500 bonded in this order, the first liquid contact film 100 and the second liquid contact film 500 being mirror-symmetrical with respect to the SOI assembly 600, wherein: the SOI assembly 600 includes a resonator 400, the first liquid contact film 100 has a first thin film 120 on a side away from the SOI assembly 600, the second liquid contact film 500 has a second thin film 520 on a side away from the SOI assembly 600, and centers of the first thin film 120 and the second thin film 520 are connected to a center of the resonator 400 through a rigid body 700; a vacuum cavity 800 is formed between the first thin film 120 and the second thin film 520, the resonator 400 is located in the vacuum cavity 800, and the resonator 400 drives the first thin film 120 and the second thin film 520 to perform resonant operation along a direction perpendicular to the film plane under the action of a driving force.

In some embodiments, the resonator 400 includes: a resonant structure 420; and a peripheral frame 410 formed around the resonant structure 420 for fixing the resonant structure 420.

In some embodiments, the resonant structure 420 comprises two first movable electrodes 421, two second movable electrodes 422, one fourth rigid connecting block 423, four biased connecting beams 425, and four movable electrode connecting beams 426, wherein: the fourth rigid connection block 423 is located at the center of the resonant structure 420, and the two first movable electrodes 421 and the two second movable electrodes 422 are uniformly arranged at intervals along a circumference centered on the fourth rigid connection block 423, so that the two first movable electrodes 421 are symmetrical to each other and the two second movable electrodes 422 are symmetrical to each other; two first movable electrodes 421, two second movable electrodes 422, and four bias connection beams 425 are all connected to the fourth rigid connection block 423, the bias connection beams 425 are disposed in a gap between the first movable electrodes 421 and the second movable electrodes 422, and the movable electrode connection beams 426 fixedly connect the adjacent first movable electrodes 421 and second movable electrodes 422 to the bias connection beams 425, so that the first movable electrodes 421, the second movable electrodes 422, and the bias connection beams 425 are integrally connected.

In some embodiments, the first movable electrode 421 and the second movable electrode 422 are each provided with a plurality of damping weakening holes 424 arranged in an array for reducing squeeze film damping effect of vibration outside the movable electrode surface.

In some embodiments, the SOI assembly 600 further comprises: a driving and detecting structure 200 disposed above the resonator 400 and in the vacuum chamber 800, for driving the resonator 400 to vibrate and detecting an output signal of the resonator 400; and an insulating layer 300 disposed between the driving and detecting structure 200 and the resonator 400 for electrical insulation and isolation between the driving and detecting structure 200 and the resonator 400.

In some embodiments, the driving and detection structure 200 comprises two first fixed electrodes 210, two second fixed electrodes 220, one second rigid connection block 230 and one sealing ring 240, wherein: the second rigid connection block 230 is located at the center of the driving and detecting structure 200, and the two first fixed electrodes 210 and the two second fixed electrodes 220 are uniformly spaced along a circumference centered on the second rigid connection block 230, such that the two first fixed electrodes 210 are symmetrical to each other and the two second fixed electrodes 220 are symmetrical to each other; the sealing ring 240 is formed around the two first fixed electrodes 210 and the two second fixed electrodes 220, and is not connected to the two first fixed electrodes 210 and the two second fixed electrodes 220, and the sealing ring 240 participates in forming the vacuum chamber 800.

In some embodiments, the resonator 400 adopts the working principle of electrostatic driving-capacitance detection, the movable electrodes in the resonator 400 are parallel to the fixed electrodes in the driving and detecting structure 200 and are arranged in a one-to-one corresponding position relationship, the first movable electrode 421 and the first fixed electrode 210 form a driving electrode pair, and the second movable electrode 422 and the second fixed electrode 220 form a detecting electrode pair.

In some embodiments, the first fixed electrode 210 is connected to a back-end driving circuit for providing a driving force for out-of-plane vibration to the first movable electrode 421; the second fixed electrode 220 is connected with a rear end detection circuit and is used for picking up capacitance variation caused by vibration of the second movable electrode 422; the second rigid connecting block 230 and the fourth rigid connecting block 423 correspond to each other in parallel and have coaxial centroids.

In some embodiments, the insulating layer 300 includes: a third rigid connection block 310; and a peripheral insulating layer 320 formed around the third rigid connection block 310 to isolate the driving and detecting structure 200 from the resonator 400; wherein the peripheral insulating layer 320 participates in forming the vacuum chamber 800; the third rigid connecting block 310 corresponds to the second rigid connecting block 230 and the fourth rigid connecting block 423 in parallel, is concentric, and rigidly connects the second rigid connecting block 230 and the fourth rigid connecting block 423 together.

In some embodiments, the driving and sensing structure 200, the insulating layer 300, and the resonator 400 are fabricated on a single SOI wafer to form an SOI assembly 600.

In some embodiments, the first liquid contact membrane 100 comprises a first membrane 120, a first rigid connection block 130, and a plurality of driving and detection electrode through holes 110, wherein the driving and detection electrode through holes 110 are used for passing electrical leads to enable connection of two first fixed electrodes 210 to a back end driving circuit and two second fixed electrodes 220 to a back end detection circuit; the second liquid contact film 500 comprises a second thin film 520, a fifth rigid connection block 530 and a bias electrode via 510, wherein the bias electrode via 510 is used for passing through an electrical wire to connect the resonator 400 with a back-end bias circuit; the first rigid connecting block 130 rigidly connects the first membrane 120 to the second rigid connecting block 230, and the fifth rigid connecting block 530 rigidly connects the second membrane 520 to the fourth rigid connecting block 423, so as to connect the first membrane 120, the second membrane 520 and the resonant structure 420.

In some embodiments, the first membrane 120 and the second membrane 520 are identical in structure and parallel to each other, the outer surfaces of the membranes contact with the liquid to be measured, and the centers of the membranes are coaxially and sequentially rigidly connected with the centroids of the first rigid connecting block 130, the second rigid connecting block 230, the third rigid connecting block 310, the fourth rigid connecting block 423 and the fifth rigid connecting block 530 to form the rigid body 700.

In some embodiments, the vacuum chamber 800 is constructed by sequentially bonding and connecting the first liquid contact membrane 100, the SOI assembly 600, and the second liquid contact membrane 500; the resonant structure 420 works in the vacuum cavity 800 formed by the first liquid contact film 100, the second liquid contact film 500, the sealing ring 240, the insulating layer 300, and the peripheral frame 410, and the first thin film 120 and the second thin film 520 are driven to vibrate in the measured liquid when the resonant structure 420 vibrates out of plane.

In some embodiments, the viscosity sensor components are fabricated using a MEMS wafer level fabrication process, wherein: the first liquid contact membrane 100 and the second liquid contact membrane 500 are made by a glass etching process; the driving and detecting structure 200 and the resonator 400 are manufactured by a silicon wafer dry etching process; the insulating layer 300 is made by adopting an SOI (silicon on insulator) sheet oxide layer corrosion process; the joining of the first liquid contact membrane 100, the SOI assembly 600, and the second liquid contact membrane 500 is accomplished using an anodic bonding process.

(III) advantageous effects

According to the technical scheme, the micro-electromechanical resonant viscosity sensor provided by the disclosure has at least the following beneficial effects:

1. according to the micro-electromechanical resonant viscosity sensor provided by the disclosure, the first film 120 and the second film 520 form a symmetrical film, the resonator 400 works in a resonant mode perpendicular to the symmetrical film, the resonator 400 is connected with the symmetrical film through the simple rigid body 700 with the volume as small as possible, the symmetrical film is in contact with external liquid to be detected in a form of planar extrusion liquid, and the viscous force of the external liquid to be detected and the symmetrical film is consistent with the vibration direction of the resonator, so that the conversion process of viscosity change and resonant energy loss is simple, the improvement of viscosity detection sensitivity is facilitated, the processing difficulty of a rear-end algorithm is reduced, and the output precision of the sensor is improved.

2. According to the micro-electromechanical resonant viscosity sensor provided by the disclosure, the symmetrical thin films formed by the first thin film 120 and the second thin film 520 are a pair of structurally symmetrical liquid contact thin films which are arranged for constructing a vacuum environment for the resonator 400, the resonator 400 is arranged between the first thin film 120 and the second thin film 520 in parallel and is connected with the first thin film 120 and the second thin film 520 through the rigid body 700, the pressure effect of the external pressure on the resonator 400 is counteracted, the resonator 400 does not change the position along with the change of the external pressure, on one hand, the sensitivity of the resonator 400 to the external pressure can be weakened, and on the other hand, the realization difficulty of driving and detecting the resonator 400 is also reduced.

3. According to the micro-electromechanical resonant viscosity sensor provided by the disclosure, the resonator 400 works in a high-vacuum environment, and the zero Q value of the sensor is higher than 10⁴Magnitude order, compare in the resonant mode viscosity sensor of direct contact liquid work that awaits measuring, the range of the resonant mode viscosity sensor of micro-electromechanical system that this disclosure provided can have by a wide margin promotion.

Drawings

The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure with reference to the accompanying drawings, in which:

fig. 1 is a schematic structural diagram of a micro-electromechanical resonant viscosity sensor according to an embodiment of the disclosure;

FIG. 2 is a cross-sectional view of the micro-electromechanical resonant viscosity sensor shown in FIG. 1;

FIG. 3a is an isometric view of a resonator 400 in the microelectromechanical resonant viscosity sensor of FIG. 1;

FIG. 3b is an enlarged view of a portion of the resonant structure 420 of the MEMS resonant viscosity sensor shown in FIG. 1;

FIG. 4 is a schematic diagram of a driving and detecting structure 200 in the micro-electromechanical resonant viscosity sensor shown in FIG. 1;

FIG. 5 is a schematic diagram of an insulating layer 300 in the micro-electromechanical resonant viscosity sensor shown in FIG. 1;

fig. 6 is an isometric view of a first liquid contact membrane 100 in the microelectromechanical resonant viscosity sensor shown in fig. 1;

fig. 7 is an isometric view of a second liquid contact membrane 500 in the microelectromechanical resonant viscosity sensor of fig. 1;

FIG. 8 is a perspective view of the components of a microelectromechanical resonant viscosity sensor, in accordance with an embodiment of the present disclosure;

fig. 9 is a schematic diagram of an operation mode of a resonator 400 in a micro-electromechanical resonant viscosity sensor according to an embodiment of the disclosure.

[ description of reference ]

100-a first liquid contact membrane;

110-drive and sense electrode vias;

120-a first film;

130-first rigid connection block

200-a drive and sense structure;

210-a first stationary electrode;

220-a second stationary electrode;

230-a second rigid connection block;

240-a seal ring;

300-an insulating layer;

310-third rigid connection block

320-peripheral insulating layer

400-a resonator;

410-a peripheral frame;

420-a resonant structure;

421-a first movable electrode; 422-a second movable electrode; 423-a fourth rigid connection block;

424-damping weakening holes; 425-offset connecting beam; 426-Movable electrode connecting Beam

500-a second liquid contact membrane;

510-bias electrode vias;

520-a second film;

530-a fifth rigid connection block;

wherein, the driving and detecting structure 200, the insulating layer 300, and the resonator 400 form an SOI composite 600; the first rigid connecting block 130, the second rigid connecting block 230, the third rigid connecting block 310, the fourth rigid connecting block 423 and the fifth rigid connecting block 530 form a rigid body 700;

800-vacuum chamber.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is illustrative only and is not intended to limit the scope of the present disclosure. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.

All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It is noted that the terms used herein should be interpreted as having a meaning that is consistent with the context of this specification and should not be interpreted in an idealized or overly formal sense.

And the shapes and sizes of the respective components in the drawings do not reflect actual sizes and proportions, but merely illustrate the contents of the embodiments of the present disclosure. Furthermore, in the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Furthermore, the word "comprising" or "comprises" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

In one exemplary embodiment of the present disclosure, a microelectromechanical resonant viscosity sensor is provided based on a vacuum-packed out-of-plane vibrating resonator and parallel facing liquid contact membranes. Fig. 1 is a schematic structural diagram of a micro-electromechanical resonant viscosity sensor according to an embodiment of the disclosure, and fig. 2 is a cross-sectional view of the micro-electromechanical resonant viscosity sensor shown in fig. 1.

As shown in fig. 1 and fig. 2, the mems resonant viscosity sensor provided by the embodiment of the disclosure includes a first liquid contact film 100, an SOI assembly 600, and a second liquid contact film 500 bonded in sequence, where the first liquid contact film 100 and the second liquid contact film 500 are mirror-symmetrical with respect to the SOI assembly 600. The SOI assembly 600 includes a resonator 400, the first liquid contact film 100 has a first thin film 120 on a side away from the SOI assembly 600, the second liquid contact film 500 has a second thin film 520 on a side away from the SOI assembly 600, and centers of the first thin film 120 and the second thin film 520 are connected to a center of the resonator 400 through a rigid body 700. The first thin film 120 and the second thin film 520 are respectively embedded in the first liquid contact film 100 and the second liquid contact film 500, a vacuum cavity 800 is formed between the first thin film 120 and the second thin film 520, the resonator 400 is located in the vacuum cavity 800, and the resonator 400 drives the first thin film 120 and the second thin film 520 to perform resonant operation along a direction perpendicular to the plane of the thin films under the action of a driving force.

Fig. 3a is an isometric view of a resonator 400 in the micro-electromechanical resonant viscosity sensor shown in fig. 1, and as shown in fig. 3a, the resonator 400 includes a peripheral frame 410 and a resonant structure 420, and the peripheral frame 410 is formed around the resonant structure 420 to fix the resonant structure 420. Resonant structure 420 operates in an out-of-plane vibration mode under the driving force. In addition, the peripheral frame 410 participates in forming the vacuum chamber 800.

Fig. 3b is a partial enlarged view of a resonant structure 420 in the microelectromechanical resonant viscosity sensor of fig. 1, according to an embodiment of the present disclosure. As shown in fig. 3b, the resonant structure 420 comprises two first movable electrodes 421, two second movable electrodes 422, one fourth rigid connection block 423, four biased connection beams 425 and four movable electrode connection beams 426.

According to the embodiment of the present disclosure, the fourth rigid connection block 423 is located at the center of the resonance structure 420, and the two first movable electrodes 421 and the two second movable electrodes 422 are uniformly spaced along a circumference centered on the fourth rigid connection block 423, so that the two first movable electrodes 421 are symmetrical to each other and the two second movable electrodes 422 are symmetrical to each other.

According to the embodiment of the present disclosure, two first movable electrodes 421, two second movable electrodes 422, and four bias connection beams 425 are all connected to the fourth rigid connection block 423, the bias connection beams 425 are disposed in the gap between the first movable electrodes 421 and the second movable electrodes 422, and the movable electrode connection beams 426 fixedly connect the adjacent first movable electrodes 421 and second movable electrodes 422 to the bias connection beams 425, so that the first movable electrodes 421, the second movable electrodes 422, and the bias connection beams 425 are integrally connected.

According to the embodiment of the present disclosure, the first movable electrode 421 and the second movable electrode 422 are both provided with a plurality of damping weakening holes 424 arranged in an array, and the damping weakening holes 424 are used for reducing a squeeze film damping effect of out-of-plane vibration of the movable electrodes.

In this embodiment, the components of the resonant structure 420 are connected together, and the working mode of the out-of-plane vibration of the resonant structure 420 is easily adjusted to the first-order resonant mode of the resonator 400, so that the asymmetry problem of the mode shape caused by the uneven processing can be better reduced, and the output signal of the sensor is stronger and more stable.

According to an embodiment of the present disclosure, in the micro-electromechanical resonant viscosity sensor provided by the present disclosure, the SOI assembly 600 further includes, in addition to the resonator 400, as shown in fig. 2, a driving and detecting structure 200 and an insulating layer 300, wherein the driving and detecting structure 200 is disposed above the resonator 400 and located in the vacuum cavity 800, and is configured to drive the resonator 400 to vibrate and detect an output signal of the resonator 400. The insulating layer 300 is disposed between the driving and detecting structure 200 and the resonator 400 for electrical insulation and isolation between the driving and detecting structure 200 and the resonator 400.

Fig. 4 is a schematic diagram of a driving and detecting structure 200 in the micro-electromechanical resonant viscosity sensor shown in fig. 1, according to an embodiment of the present disclosure. The driving and detecting structure 200 comprises two first fixed electrodes 210, two second fixed electrodes 220, a second rigid connecting block 230 and a sealing ring 240, wherein: the second rigid connection block 230 is located at the center of the driving and detecting structure 200, and the two first fixed electrodes 210 and the two second fixed electrodes 220 are uniformly spaced along a circumference centered on the second rigid connection block 230, such that the two first fixed electrodes 210 are symmetrical to each other and the two second fixed electrodes 220 are symmetrical to each other. The sealing ring 240 is formed around the two first fixed electrodes 210 and the two second fixed electrodes 220, and is not connected to the two first fixed electrodes 210 and the two second fixed electrodes 220, and the sealing ring 240 participates in forming the vacuum chamber 800.

According to the embodiment of the present disclosure, the resonator 400 adopts the working principle of electrostatic driving-capacitance detection, the movable electrodes in the resonator 400 are parallel to the fixed electrodes in the driving and detecting structure 200 and are arranged in a one-to-one corresponding position relationship, the first movable electrode 421 and the first fixed electrode 210 form a driving electrode pair, and the second movable electrode 422 and the second fixed electrode 220 form a detecting electrode pair. The first fixed electrode 210 is connected to a back end driving circuit, and is configured to provide a driving force for out-of-plane vibration to the first movable electrode 421; the second fixed electrode 220 is connected with a rear end detection circuit and is used for picking up capacitance variation caused by vibration of the second movable electrode 422; the second rigid connecting block 230 and the fourth rigid connecting block 423 correspond to each other in parallel and have coaxial centroids.

Fig. 5 is a schematic diagram of an insulating layer 300 in the microelectromechanical resonant viscosity sensor of fig. 1, according to an embodiment of the present disclosure. The insulating layer 300 comprises a third rigid connection block 310 and a peripheral insulating layer 320 formed around the third rigid connection block 310 to isolate the driving and detecting structure 200 from the resonator 400, wherein the peripheral insulating layer 320 participates in forming the vacuum chamber 800; the third rigid connecting block 310 corresponds to the second rigid connecting block 230 and the fourth rigid connecting block 423 in parallel, is concentric, and rigidly connects the second rigid connecting block 230 and the fourth rigid connecting block 423 together.

According to the embodiment of the disclosure, the insulating layer 300 can be prepared by adopting an oxidized insulating layer of an SOI (silicon on insulator) sheet and matching with a micro-nano processing technology.

According to an embodiment of the present disclosure, the driving and detecting structure 200, the insulating layer 300 and the resonator 400 may be fabricated on a single SOI wafer to form an SOI assembly 600.

Fig. 6 is an isometric view of a first liquid contact membrane 100 in the microelectromechanical resonant viscosity sensor shown in fig. 1, according to an embodiment of the present disclosure. As shown in fig. 6, the first liquid contact membrane 100 includes a first thin film 120, a first rigid connection block 130, and a plurality of driving and detecting electrode through holes 110, wherein the driving and detecting electrode through holes 110 are used to pass through electrical wires to enable connection of two first fixed electrodes 210 to a rear end driving circuit and connection of two second fixed electrodes 220 to a rear end detecting circuit.

Fig. 7 is an isometric view of a second liquid contact membrane 500 in the microelectromechanical resonant viscosity sensor shown in fig. 1, according to an embodiment of the present disclosure. As shown in fig. 7, the second liquid contact membrane 500 comprises a second membrane 520, a fifth rigid connection block 530 and a bias electrode via 510, wherein the bias electrode via 510 is used to pass through an electrical wire to connect the resonator 400 to a back-end bias circuit.

According to an embodiment of the present disclosure, the first rigid connection block 130 rigidly connects the first membrane 120 with the second rigid connection block 230, and the fifth rigid connection block 530 rigidly connects the second membrane 520 with the fourth rigid connection block 423, thereby enabling connection of the first membrane 120, the second membrane 520 and the resonant structure 420. The first film 120 and the second film 520 have the same structure and are parallel to each other, the outer surfaces of the films are all in contact with liquid to be measured, and the centers of the films are coaxially and sequentially rigidly connected with the centroids of the first rigid connecting block 130, the second rigid connecting block 230, the third rigid connecting block 310, the fourth rigid connecting block 423 and the fifth rigid connecting block 530 to form the rigid body 700.

According to an embodiment of the present disclosure, the vacuum chamber 800 is constructed by sequentially bonding and connecting the first liquid contact film 100, the SOI assembly 600, and the second liquid contact film 500. The resonant structure 420 works in the vacuum cavity 800 formed by the first liquid contact film 100, the second liquid contact film 500, the sealing ring 240, the insulating layer 300, and the peripheral frame 410, and the first thin film 120 and the second thin film 520 are driven to vibrate in the measured liquid when the resonant structure 420 vibrates out of plane.

Fig. 8 is a perspective view of the components of a microelectromechanical resonant viscosity sensor, in accordance with an embodiment of the present disclosure. Referring to fig. 1 to 8, the first membrane 120 and the second membrane 520 have the same structure and are parallel to each other, and the centers of the membranes are coaxially and sequentially rigidly connected to the centroids of the first rigid connection block 130, the second rigid connection block 230, the third rigid connection block 310, the fourth rigid connection block 423, and the fifth rigid connection block 530 to form a rigid body 700.

The resonant structure 420 works in the vacuum cavity 800 formed by the first liquid contact film 100, the second liquid contact film 500, the sealing ring 240, the insulating layer 300 and the peripheral frame 410, and the first thin film 120 and the second thin film 520 are driven to vibrate in the measured liquid when the resonant structure 420 vibrates out of the plane.

The micro-electromechanical resonance type viscosity sensor disclosed by the embodiment of the disclosure is formed by processing all the components by adopting an MEMS wafer-level manufacturing process. The first liquid contact film 100 and the second liquid contact film 500 are manufactured by a glass etching process, the driving and detecting structure 200 and the resonator 400 are manufactured by a silicon wafer dry etching process, the insulating layer 300 is manufactured by an SOI wafer oxidation layer etching process, and the connection of the first liquid contact film 100, the SOI assembly 600 and the second liquid contact film 500 is completed by an anodic bonding process.

Fig. 9 is a schematic diagram of an operation mode of a resonator 400 in a micro-electromechanical resonant viscosity sensor according to an embodiment of the disclosure. Referring to fig. 2 and 9, in an embodiment of the disclosure, a micro-electromechanical resonant viscosity sensor based on a vacuum-packaged out-of-plane vibration resonator and a symmetric liquid contact film has the following operating principle: through electrostatic excitation and capacitance detection of the driving and detecting structure, a resonant Q value of the sensor is obtained by matching with a rear-end Q value measuring circuit; when the sensor is placed in liquid to test the viscosity of the liquid, the liquid generates viscous damping on the surfaces of the vibrating first thin film 120 and the vibrating second thin film 520, the damping is transmitted to the resonant structure 420 through the first rigid connecting block 130, the second rigid connecting block 230, the third rigid connecting block 310, the fourth rigid connecting block 423 and the fifth rigid connecting block 530 in sequence, the vibration damping of the resonant structure 420 is changed, the Q value measured by the rear end circuit is further changed, and the change of the Q value reflects the change of the viscosity of the measured liquid.

In addition, when the sensor is oriented to high-precision integrated application, a temperature sensor needs to be configured, and before the sensor is actually used, calibration with a dependent variable of standard liquid viscosity and external temperature and an independent variable of a Q value needs to be carried out. When the sensor is used specifically, the output of the circuit is the liquid viscosity after temperature compensation through the polynomial fitting and the calculation function embedded in the back end circuit.

So far, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. It is to be noted that, in the attached drawings or in the description, the implementation modes not shown or described are all the modes known by the ordinary skilled person in the field of technology, and are not described in detail. Further, the above definitions of the various elements and methods are not limited to the various specific structures, shapes or arrangements of parts mentioned in the examples, which may be easily modified or substituted by those of ordinary skill in the art.

From the above description, those skilled in the art should clearly recognize that the micro-electromechanical resonant viscosity sensor of the present disclosure is applicable.

In summary, based on the out-of-plane vibration resonator and the symmetric liquid contact film packaged in vacuum, the disclosure provides a micro-electromechanical resonant viscosity sensor, in which the resonator operates in a high vacuum environment, and a pair of structurally symmetric liquid contact films is provided for the structure of the resonator constructing the vacuum environmentThe film, the resonator is arranged between the two films in parallel and connected with the films through a rigid body structure, and the zero Q value of the sensor can be higher than 10⁴The magnitude order, the expected sensor range and sensitivity are greatly improved, meanwhile, the sensitivity of the resonator to the external pressure is greatly weakened, and the method has wide application requirements and market prospects.

It should also be noted that directional terms, such as "upper", "lower", "front", "rear", "left", "right", and the like, used in the embodiments are only directions referring to the drawings, and are not intended to limit the scope of the present disclosure. Throughout the drawings, like elements are represented by like or similar reference numerals. Conventional structures or constructions will be omitted when they may obscure the understanding of the present disclosure.

Unless otherwise indicated, the numerical parameters set forth in the specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the present disclosure. In particular, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about". Generally, the expression is meant to encompass variations of ± 10% in some embodiments, 5% in some embodiments, 1% in some embodiments, 0.5% in some embodiments by the specified amount.

The use of ordinal numbers such as "first," "second," "third," etc., in the specification and claims to modify a corresponding element does not by itself connote any ordinal number of the element or any ordering of one element from another or the order of manufacture, and the use of the ordinal numbers is only used to distinguish one element having a certain name from another element having a same name.

Similarly, it should be appreciated that in the foregoing description of exemplary embodiments of the disclosure, various features of the disclosure are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various disclosed aspects. However, the disclosed method should not be interpreted as reflecting an intention that: that is, the claimed disclosure requires more features than are expressly recited in each claim. Rather, as the following claims reflect, disclosed aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this disclosure.

The above-mentioned embodiments are intended to illustrate the objects, aspects and advantages of the present disclosure in further detail, and it should be understood that the above-mentioned embodiments are only illustrative of the present disclosure and are not intended to limit the present disclosure, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present disclosure should be included in the scope of the present disclosure.