Low-temperature-drift flexible pressure sensor and preparation method thereof

Abstract

The invention relates to the technical field of flexible pressure sensors, and provides a low-temperature-drift flexible pressure sensor and a preparation method thereof.The low-temperature-drift flexible pressure sensor comprises an upper insulating layer, an upper sensor layer, a pressure isolation microstructure layer, a lower sensor layer and a lower insulating layer which are arranged from top to bottom; the electrodes of the first piezoresistive sensor group in the upper sensor layer are exposed to the external environment through the electrode holes of the upper insulating layer, and the electrodes of the second piezoresistive sensor group in the lower sensor layer are exposed to the external environment through the electrode holes and the communicating holes in the pressure isolation microstructure layer; the pressure isolation microstructure layer is provided with a concave part which covers the second piezoresistive sensor group; the two piezoresistive sensor groups are identical and are electrically connected to form a Huygens bridge circuit. The low-temperature-drift flexible pressure sensor realizes the compensation of the temperature drift of the sensor, reduces the influence of the temperature on the measurement precision of the sensor, has a high integration level, and facilitates the measurement of the surface of integrated equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flexible pressure sensors, in particular to a low-temperature-drift flexible pressure sensor and a preparation method thereof. BACKGROUND

[0002] Pressure distribution measurement technology is of great significance for understanding the aerodynamic performance of aircraft, the hydrodynamic characteristics of ships, etc. When measuring gas pressure by using traditional hard sensors, the measured structure needs to be pre-bored to embed the sensors, which is a cumbersome operation process and the number of measuring points is small, and the measurement results obtained are inaccurate.

[0003] In the prior art, a flexible thin film pressure sensor is usually used, which can be conformally attached to the equipment to realize rapid, large-area and multi-channel pressure measurement. The existing flexible pressure sensor is usually based on the working principle of piezoresistance effect. However, the flexible pressure sensor based on the piezoresistance effect is usually seriously affected by temperature, and the piezoresistance coefficient changes significantly with temperature, which seriously interferes with the measurement accuracy. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application provides a low-temperature-drift flexible pressure sensor and a preparation method thereof, which solves the technical problem that the flexible pressure sensor based on the piezoresistance effect in the prior art is usually seriously affected by temperature and the temperature drift seriously interferes with the measurement accuracy.

[0005] The present application provides a low-temperature-drift flexible pressure sensor, which comprises, from top to bottom, an upper insulating layer, an upper sensor layer, a pressure isolation microstructure layer, a lower sensor layer and a lower insulating layer.

[0006] The upper insulating layer is provided with a plurality of electrode holes;

[0007] The upper sensor layer comprises a first piezoresistance sensor group, and the lower sensor layer comprises a second piezoresistance sensor group. The electrodes of the first piezoresistance sensor group are exposed to the external environment through the electrode holes.

[0008] The pressure isolation microstructure layer is provided with a recess on the side close to the lower sensor layer. The recess is the same in shape as the second piezoresistance sensor group and covers the upper surface of the second piezoresistance sensor group. The pressure isolation microstructure layer is provided with a communication hole. The communication hole is correspondingly arranged with part of the electrode holes. The electrodes of the second piezoresistance sensor group are exposed to the external environment through the communication hole and the electrode hole in sequence.

[0009] The first piezoresistance sensor group and the second piezoresistance sensor group are the same in size, shape and material. The electrodes of the first piezoresistance sensor group exposed to the external environment are electrically connected with the electrodes of the second piezoresistance sensor group to form a Huygens bridge circuit.

[0010] Optionally, the upper sensor layer and the lower sensor layer each comprise a first copper-clad layer, an intermediate layer and a second copper-clad layer arranged in a top-down manner;

[0011] The first piezoresistive sensor group is arranged in the intermediate layer of the upper sensor layer, and the first copper-clad layer and the second copper-clad layer of the upper sensor layer respectively constitute two electrodes of the first piezoresistive sensor group;

[0012] The second piezoresistive sensor group is arranged in the intermediate layer of the lower sensor layer, and the first copper-clad layer and the second copper-clad layer of the lower sensor layer respectively constitute two electrodes of the second piezoresistive sensor group.

[0013] Optionally, the first piezoresistive sensor group comprises a first spiral piezoresistive sensor and a second spiral piezoresistive sensor, and the first spiral piezoresistive sensor and the second spiral piezoresistive sensor are nested in the same plane;

[0014] The first end of the first piezoresistive sensor and the first end of the second piezoresistive sensor are arranged opposite to each other at the center of the upper sensor layer, the second end of the first piezoresistive sensor is connected with a first insulating piece on one side of the upper sensor layer, the second end of the second piezoresistive sensor is connected with another first insulating piece on the other side of the upper sensor layer, a first through hole is formed on the first insulating piece, and the second copper-clad layer covering the lower surface of the first insulating piece is exposed to the external environment through the first through hole;

[0015] The second piezoresistive sensor group comprises a third spiral piezoresistive sensor and a fourth spiral piezoresistive sensor, and the third spiral piezoresistive sensor and the fourth spiral piezoresistive sensor are nested in the same plane;

[0016] The first end of the third piezoresistive sensor and the first end of the fourth piezoresistive sensor are arranged opposite to each other at the center of the lower sensor layer, the second end of the third piezoresistive sensor is connected with a second insulating piece on one side of the lower sensor layer, the second end of the fourth piezoresistive sensor is connected with another second insulating piece on the other side of the lower sensor layer, a second through hole is formed on the second insulating piece, and the second copper-clad layer covering the lower surface of the second insulating piece is exposed to the external environment through the second through hole.

[0017] Optionally, the first end of the first piezoresistive sensor is connected with the first end of the fourth piezoresistive sensor, the second end of the fourth piezoresistive sensor is connected with the first end of the second piezoresistive sensor, the second end of the second piezoresistive sensor is connected with the second end of the third piezoresistive sensor, and the first end of the third piezoresistive sensor is connected with the second end of the first piezoresistive sensor;

[0018] An external power source is connected between the first end of the first piezoresistive sensor and the second end of the third piezoresistive sensor to apply an external voltage; and a voltage measuring device is connected between the second end of the first piezoresistive sensor and the second end of the fourth piezoresistive sensor to obtain an output voltage of the Wheatstone bridge circuit.

[0019] Optionally, a material of at least one of the first piezoresistive sensor, the second piezoresistive sensor, the third piezoresistive sensor and the fourth piezoresistive sensor is carbon nanotube conductive paste; and / or a material of at least one of the first insulating member and the second insulating member is polydimethylsiloxane or polyimide.

[0020] Optionally, at least one of the upper insulating layer and the lower insulating layer is a rectangular thin film structure; and / or the pressure isolation microstructure layer is a rectangular thin film structure containing microstructures; and / or a material of at least one of the upper insulating layer, the lower insulating layer and the pressure isolation microstructure layer is polydimethylsiloxane or polyimide.

[0021] Optionally, a thickness of at least one of the upper insulating layer and the lower insulating layer is 0.05-0.1 mm; and / or a thickness of the upper sensor layer and the lower sensor layer is 0.15-0.2 mm; and / or a thickness of the pressure isolation microstructure layer is not less than a thickness of the lower sensor layer; and / or the thickness of the pressure isolation microstructure layer is 0.3-0.35 mm.

[0022] Optionally, the recess is in interference fit with an upper surface of the second piezoresistive sensor group.

[0023] In another aspect, the application provides a preparation method of the low-temperature drift flexible pressure sensor according to any one of the above aspects, comprising:

[0024] The upper insulating layer, the lower insulating layer and the isolation microstructure layer are prepared;

[0025] The intermediate layer of the upper sensor layer and the intermediate layer of the lower sensor layer are prepared, and copper pole plates are covered on upper and lower surfaces of the intermediate layer of the upper sensor layer and upper and lower surfaces of the intermediate layer of the lower sensor layer, to complete preparation of the upper sensor layer and the lower sensor layer;

[0026] The upper insulating layer, the upper sensor layer, the pressure isolation microstructure layer, the lower sensor layer and the lower insulating layer are stacked and pasted, to complete preparation of the low-temperature drift flexible pressure sensor.

[0027] Optionally, the stacking and pasting of the upper insulating layer, the upper sensor layer, the pressure isolation microstructure layer, the lower sensor layer and the lower insulating layer comprises:

[0028] An adhesive is arranged around the side of the upper insulating layer close to the upper sensor layer, around the sides of the pressure isolation microstructure layer, and around the side of the lower insulating layer close to the lower sensor layer;

[0029] After the upper insulating layer, the upper sensor layer, the pressure isolation microstructure layer, the lower sensor layer, and the lower insulating layer are precisely positioned from top to bottom, they are stacked and pasted;

[0030] The electrodes of the first piezoresistive sensor group in the upper sensor layer and the electrodes of the second piezoresistive sensor group in the lower sensor layer are stripped higher than the structure material of the upper insulating layer.

[0031] The low-temperature-drift flexible pressure sensor provided by the application forms a Huygens bridge circuit by electrically connecting the first piezoresistive sensor group and the second piezoresistive sensor group through the openings in the upper insulating layer and the pressure isolation microstructure layer, wherein the second piezoresistive sensor group is protected by the recess of the pressure isolation microstructure layer, and the bed layer does not deform and the resistance does not change during pressure, so that the second piezoresistive sensor group always serves as a known reference resistance, the temperature drift of the pressure sensor is compensated, the influence of temperature on the measurement accuracy of the pressure sensor is effectively reduced, and the change of the sensor output voltage depends on the change of the resistance of the first piezoresistive sensor group. At the same time, the pressure sensor adopts a multi-layer film superposition structure, has high integration, small volume, and is convenient for integrated equipment surface measurement. The low-temperature-drift flexible pressure sensor can compensate for the temperature drift of the sensor, effectively reduce the influence of temperature on the measurement accuracy of the sensor, has high integration, is convenient for measurement, and has a wide range of application scenarios.

[0032] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. The objects and other advantages of the present application can be realized and achieved by the structure particularly pointed out in the written description, claims, and drawings.

[0033] The technical solutions of the present application will be further described in detail below with the help of the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0034] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, together with the embodiments of the present application, to explain the present application, and do not constitute a limitation on the present application. In the drawings:

[0035] Figure 1 The structure schematic diagram of the low-temperature-drift flexible pressure sensor provided in one embodiment of the present application;

[0036] Figure 2A schematic diagram of the upper insulating layer in a low-temperature drift flexible pressure sensor provided in this application;

[0037] Figure 3 A schematic diagram of the upper sensor layer in a cryogenic drift flexible pressure sensor provided in one embodiment of this application;

[0038] Figure 4 A schematic diagram of the lower sensor layer in a cryogenic drift flexible pressure sensor provided in this application;

[0039] Figure 5 This application provides a schematic diagram of the structure of the intermediate layer of the lower sensor layer in one embodiment of the cryogenic drift flexible pressure sensor.

[0040] Figure 6 A circuit diagram showing the electrical connection of four piezoresistive sensors to form a Huygens bridge in a low-temperature drift flexible pressure sensor provided in one embodiment of this application;

[0041] Figure 7 This is a schematic diagram of the pressure isolation microstructure layer in a low-temperature drift flexible pressure sensor provided in one embodiment of this application;

[0042] Figure 8 This is a schematic flowchart of a method for fabricating a low-temperature drift flexible pressure sensor in one embodiment of this application.

[0043] In the picture:

[0044] 1. Third piezoresistive sensor; 2. Fourth piezoresistive sensor; 3. Second insulating component. Detailed Implementation

[0045] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0046] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0047] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0048] This invention provides a low-temperature drift flexible pressure sensor, such as... Figure 1 As shown, the structure includes, from top to bottom, an upper insulating layer, an upper sensor layer, a pressure isolation microstructure layer, a lower sensor layer, and a lower insulating layer. The upper insulating layer has multiple electrode holes. The upper sensor layer includes a first piezoresistive sensor group, and the lower sensor layer includes a second piezoresistive sensor group. The electrodes of the first piezoresistive sensor group are exposed to the external environment through the electrode holes. The pressure isolation microstructure layer has a recess on the side near the lower sensor layer. The recess has the same shape as the second piezoresistive sensor group and covers the upper surface of the second piezoresistive sensor group. The pressure isolation microstructure layer has connecting holes, which are corresponding to some of the electrode holes. The electrodes of the second piezoresistive sensor group are exposed to the external environment through the connecting holes and the electrode holes in sequence. The first piezoresistive sensor group and the second piezoresistive sensor group have the same size, shape, and material. The electrodes of the first piezoresistive sensor group exposed to the external environment are electrically connected to the electrodes of the second piezoresistive sensor group to form a Huygens bridge circuit.

[0049] The low-temperature drift flexible pressure sensor provided by this invention, through openings in the upper insulating layer and the pressure isolation microstructure layer, allows the first and second piezoresistive sensor groups to be electrically connected to form a Huygens bridge circuit. The second piezoresistive sensor group is protected by the recesses in the pressure isolation microstructure layer, preventing bed deformation and resistance change during pressure application. This ensures the second piezoresistive sensor group always serves as a known reference resistor, compensating for the temperature drift of the pressure sensor and effectively reducing the impact of temperature on the measurement accuracy. The change in the sensor's output voltage depends on the change in the resistance of the first piezoresistive sensor group. Furthermore, the pressure sensor employs a multi-layer film stacked structure, resulting in high integration, small size, and easy integration into equipment surfaces for measurement. This low-temperature drift flexible pressure sensor effectively compensates for sensor temperature drift, reduces the impact of temperature on sensor measurement accuracy, has high integration, is easy to measure, and has a wide range of applications.

[0050] Specifically, in the above embodiments, both the upper sensor layer and the lower sensor layer include a first copper layer, an intermediate layer, and a second copper layer that are bonded together from top to bottom; the first piezoresistive sensor group is disposed in the intermediate layer of the upper sensor layer, and the first copper layer and the second copper layer of the upper sensor layer respectively constitute two electrodes of the first piezoresistive sensor group; the second piezoresistive sensor group is disposed in the intermediate layer of the lower sensor layer, and the first copper layer and the second copper layer of the lower sensor layer respectively constitute two electrodes of the second piezoresistive sensor group.

[0051] In this embodiment, the structure of the upper sensor layer is as follows: Figure 3 As shown, the structure of the lower sensor layer is as follows: Figure 4 As shown, both the upper and lower sensor layers adopt a three-layer structure. The first copper-clad layer covers the upper surface of the middle layer, and the second copper-clad layer covers the lower surface of the middle layer. The first and second copper-clad layers have different coverage areas and, after being isolated by the middle layer, can be used as electrodes for the first and second piezoresistive sensor groups respectively for electrical connection, realizing sensitive detection and measurement of pressure signals. The upper and lower sensor layers are clearly separated, which improves the stability and sensitivity of the sensor layer and can better adapt to the working requirements under different environmental conditions.

[0052] Furthermore, the first piezoresistive sensor group includes a spiral-shaped first piezoresistive sensor and a spiral-shaped second piezoresistive sensor, which are nested within each other in the same plane. The first ends of the first and second piezoresistive sensors are positioned opposite each other at the center of the upper sensor layer. The second end of the first piezoresistive sensor is connected to a first insulating member on one side of the upper sensor layer, and the second end of the second piezoresistive sensor is connected to another first insulating member on the other side of the upper sensor layer. A first through-hole is formed on the first insulating member, and the second copper-clad layer covering the lower surface of the first insulating member is exposed to the outer ring through the first through-hole. In the environment; the second piezoresistive sensor group includes a spiral-shaped third piezoresistive sensor and a spiral-shaped fourth piezoresistive sensor, which are nested in the same plane; the first end of the third piezoresistive sensor and the first end of the fourth piezoresistive sensor are positioned opposite each other at the center of the lower sensor layer; the second end of the third piezoresistive sensor is connected to a second insulating member on one side of the lower sensor layer; the second end of the fourth piezoresistive sensor is connected to another second insulating member on the other side of the lower sensor layer; a second through hole is provided on the second insulating member, and the second copper cladding layer covering the lower surface of the second insulating member is exposed to the external environment through the second through hole.

[0053] In this embodiment, with Figure 5Taking the middle layer structure of the lower sensor layer as an example, both the third piezoresistive sensor 1 and the fourth piezoresistive sensor 2 adopt a spiral structure design, which increases the force-bearing area of ​​the piezoresistive sensor. Furthermore, the two spiral piezoresistive sensors in the same plane are nested together, which can improve the integration of the sensor, reduce the overall size of the second piezoresistive sensor group, and make the structure more compact and more efficient in space utilization. Regarding the overall structure of the lower sensor layer, at the center of the lower sensor layer, the first end of the third piezoresistive sensor and the first end of the fourth piezoresistive sensor are positioned opposite each other. The first ends of the two piezoresistive sensors can also be connected by a connecting insulating component. On both sides of the lower sensor layer, the second ends of the two piezoresistive sensors are respectively connected to a second insulating component 3. The area of ​​the first copper-clad layer covering the upper surface of the second insulating component 3 is smaller than the area of ​​the second insulating component 3, while the area of ​​the second copper-clad layer covering the lower surface of the second insulating component 3 is larger than the area of ​​the second insulating component 3. When the copper-clad layer is exposed to the external environment as an electrode, the second insulating component 3 distinguishes the two copper-clad layers so that they can be used as two different electrodes of the second piezoresistive sensor group. The middle layer structure of the upper sensor layer is similar to that of the middle layer structure of the lower sensor layer.

[0054] Furthermore, the first end of the first piezoresistive sensor is connected to the first end of the fourth piezoresistive sensor, the second end of the fourth piezoresistive sensor is connected to the first end of the second piezoresistive sensor, the second end of the second piezoresistive sensor is connected to the second end of the third piezoresistive sensor, and the first end of the third piezoresistive sensor is connected to the second end of the first piezoresistive sensor; an external power supply is connected between the first end of the first piezoresistive sensor and the second end of the third piezoresistive sensor to apply an external voltage; a voltage measuring device is connected between the second end of the first piezoresistive sensor and the second end of the fourth piezoresistive sensor to obtain the output voltage of the Huygens bridge circuit.

[0055] In this embodiment, the electrodes of the four piezoresistive sensors are exposed to the external environment. The four piezoresistive sensors are connected using these electrodes to form a Huygens bridge circuit, specifically as follows: Figure 6 As shown, the Huygens bridge circuit is a common bridge circuit that can effectively process the signal output from the sensor. By acquiring the output voltage through a voltage measurement device, signal processing becomes more efficient, improving the sensor's response speed and sensitivity. Specifically, in this application, the resistance values ​​of the third and fourth piezoresistive sensors remain unchanged. However, when an external voltage is applied, the changes in the resistance values ​​of the first and second piezoresistive sensors affect the final output voltage.

[0056] Furthermore, the relationship between the output voltage of the Huygens bridge circuit and the resistance changes of each piezoresistive sensor is as follows:

[0057]

[0058] Where ΔU is the output voltage of the Huygens bridge, E is the external voltage, and R... u1 Let ΔR be the resistance value of the first piezoresistive sensor. u1 R represents the change in resistance of the first piezoresistive sensor. u2 The resistance value of the second piezoresistive sensor is ΔR. u2 R represents the change in resistance of the second piezoresistive sensor. d1 The resistance value of the third piezoresistive sensor is ΔR. d1 R represents the change in resistance of the third piezoresistive sensor. d2 The resistance value of the fourth piezoresistive sensor is ΔR. d2 This represents the change in resistance of the fourth piezoresistive sensor;

[0059] When the resistance changes of the first, second, third, and fourth piezoresistive sensors are the same, the output voltage of the Huygens bridge is 0; when the resistance changes of the first and second piezoresistive sensors are the same, and both are ΔR... p At that time, the output voltage of the Huygens bridge circuit was

[0060]

[0061] In this embodiment, the formula for calculating the output voltage of the Huygens bridge circuit in balanced state is as follows:

[0062]

[0063] When subjected to strain, if the resistance of the strain gauge changes by ΔR, while the other bridge arms remain fixed, and the output voltage U≠0, then the bridge is unbalanced, and the output voltage is:

[0064]

[0065] Let the bridge arm ratio n = R d1 / R u1 Due to ΔR u1 < <R u1 ΔR u1 / R u1 It can be ignored, and the equilibrium condition R is taken into account. d1 / R u1 =R u2 / R d2 Therefore, the output voltage is:

[0066]

[0067] Specifically in this application, the resistance values ​​of the four piezoresistive sensors are exactly the same, therefore n=1. Considering the voltage of each bridge arm, the final formula for the total output voltage change is:

[0068]

[0069] Therefore, when the temperature changes, Ru1, Ru2, Rd1, and Rd2 all undergo the same change ΔR. T When the temperature is constant, ΔU = 0, meaning that temperature changes do not affect the sensor's output voltage; however, when the sensor is subjected to pressure, Ru1 and Ru2 change in the same way, ΔR. p At that time, the output voltage is approximately That is, the output voltage and the resistance of each bridge arm have an approximately linear relationship.

[0070] Specifically, in the above embodiments, at least one of the first piezoresistive sensor, the second piezoresistive sensor, the third piezoresistive sensor, and the fourth piezoresistive sensor is made of carbon nanotube conductive paste; and / or, at least one of the first insulating member and the second insulating member is made of polydimethylsiloxane or polyimide.

[0071] In this embodiment, carbon nanotube conductive paste is used as the material for the piezoresistive sensor, which has excellent conductivity and sensitivity, enabling it to accurately sense pressure changes and improve the measurement accuracy of the sensor. Polydimethylsiloxane or polyimide is used as the material for the first and second insulating components 3, which gives the insulating components good insulation and durability, ensuring the stable operation of the sensor in different environments.

[0072] Specifically, in the above embodiments, at least one of the upper insulating layer and the lower insulating layer is a rectangular thin film structure; and / or, the pressure isolation microstructure layer is a rectangular thin film structure containing microstructures; and / or, at least one of the upper insulating layer, the lower insulating layer and the pressure isolation microstructure layer is made of polydimethylsiloxane or polyimide.

[0073] In this embodiment, polydimethylsiloxane or polyimide is used as the insulating layer of the cryogenic drift flexible pressure sensor. It has good insulation performance, which can effectively isolate the internal circuits and components of the sensor, improve the stability and safety of the sensor, and also has good high and low temperature resistance and chemical corrosion resistance, making it suitable for operation under various environmental conditions. This ensures the stability of the sensor at different temperatures and improves the service life and stability of the sensor. Both the upper and lower insulating layers can adopt a thin film structure design with small thickness, which can better adapt to the design requirements of the flexible sensor, maintain the flexibility of the sensor, reduce the weight of the entire cryogenic drift flexible pressure sensor, and improve the portability and comfort of the sensor.

[0074] Specifically, in the above embodiments, the thickness of at least one of the upper insulating layer and the lower insulating layer is 0.05-0.1 mm; and / or, the thickness of at least one of the upper sensor layer and the lower sensor layer is 0.15-0.2 mm; and / or, the thickness of the pressure isolation microstructure layer is not less than the thickness of the lower sensor layer; and / or, the thickness of the pressure isolation microstructure layer is 0.3-0.35 mm.

[0075] In this embodiment, the thickness of each structural layer is limited, wherein the structure of the upper insulating layer is as follows: Figure 2 As shown, eight electrode holes are symmetrically formed at the center of both sides of the upper insulating layer to expose the electrodes of the two piezoresistive sensor groups to the external environment for electrical connection. Four electrode holes on the sides of the upper insulating layer expose the electrodes of the first piezoresistive sensor group in the upper sensor layer, while four electrode holes completely inside the upper insulating layer, in conjunction with connecting holes in the pressure isolation microstructure layer, expose the electrodes of the second piezoresistive sensor group in the lower sensor layer. The structure of the pressure isolation microstructure layer is as follows: Figure 7 As shown, considering that the recess is opened on the side of the pressure isolation microstructure layer near the lower sensor layer and is a groove corresponding to the shape of the second piezoresistive sensor group, and that the connecting hole opened on the pressure isolation microstructure layer corresponds to the four electrode holes completely opened inside the upper insulating layer to expose the electrodes of the second piezoresistive sensor, the thickness of the pressure isolation microstructure layer needs to be no less than the thickness of the lower sensor layer in order to play a protective role.

[0076] Furthermore, the recess is interference-fitted with the upper surface of the second piezoresistive sensor group.

[0077] In this embodiment, the groove corresponding to the shape of the second piezoresistive sensor group in the concave part is slightly larger than the size of the second piezoresistive sensor group to form protection for the second piezoresistive sensor group, ensuring that the lower bed does not deform during the pressure process of the second piezoresistive sensor group, and the resistance values ​​of the third and fourth piezoresistive sensors in the second piezoresistive sensor group do not change when pressure is applied, and always serve as a stable reference voltage for the Huygens bridge circuit.

[0078] Another aspect of the present invention provides a method for fabricating a low-temperature drift flexible pressure sensor, such as... Figure 8 As shown, the process includes first fabricating an upper insulating layer, a lower insulating layer, and an isolation microstructure layer; then fabricating an intermediate layer of the upper sensor layer and an intermediate layer of the lower sensor layer, and covering the upper and lower surfaces of the intermediate layer of the upper sensor layer, as well as the upper and lower surfaces of the intermediate layer of the lower sensor layer, to complete the fabrication of the upper and lower sensor layers; finally, stacking and bonding the upper insulating layer, the upper sensor layer, the pressure isolation microstructure layer, the lower sensor layer, and the lower insulating layer to complete the fabrication of the low-temperature drift flexible pressure sensor.

[0079] The method for fabricating a low-temperature drift flexible pressure sensor provided by this invention involves layering an insulating layer, a sensor layer, and an isolation microstructure layer. Specifically, injection molding can be used to effectively separate the functional layers, facilitating the realization and collaborative operation of each layer, and improving the sensor's performance and stability. Then, an intermediate layer for the upper sensor layer and an intermediate layer for the lower sensor layer are fabricated using inkjet printing or screen printing. A copper electrode plate is then quickly and efficiently placed over the intermediate layer between the two sensor layers, completing the electrode coverage of the sensor quickly and efficiently, thus completing the fabrication of both sensor layers and improving production efficiency and speed. The use of multiple processes such as injection molding, inkjet printing, and screen printing allows for the realization of complex structures and functions at different levels, enriching the diversity of fabrication processes and meeting the fabrication requirements of sensors under various conditions. In the final stacking and bonding process, the structural layers are stacked and bonded together, helping to ensure the tightness and strength of the adhesion between different layers, improving the overall stability and reliability of the sensor.

[0080] Specifically, in the above embodiments, stacking and pasting the upper insulating layer, upper sensor layer, pressure isolation microstructure layer, lower sensor layer, and lower insulating layer includes firstly setting adhesives around the sides of the upper insulating layer near the upper sensor layer, around both sides of the pressure isolation microstructure layer, and around the sides of the lower insulating layer near the lower sensor layer; then using an optical microscope, accurately positioning the upper insulating layer, upper sensor layer, pressure isolation microstructure layer, lower sensor layer, and lower insulating layer sequentially from top to bottom before stacking and pasting; finally, peeling off the structural material above the upper insulating layer at the electrodes of the first piezoresistive sensor group in the upper sensor layer and the electrodes of the second piezoresistive sensor group in the lower sensor layer.

[0081] In this embodiment, adhesive can be used as the bonding agent. By dripping a certain amount of adhesive onto the key bonding areas between adjacent layers and using an optical microscope for precise positioning, it helps to ensure the accurate alignment and stacking of each layer of material, thereby improving the overall accuracy and stability of the structure, effectively increasing the adhesion between each layer of material, enhancing the structural strength and stability after stacking, and preventing loosening or detachment of materials, thus enhancing the reliability of the sensor. Peeling off the structural material above the insulating layer at the electrodes simplifies the separation process, improves operational efficiency, and reduces the risk of damage to the electrodes, ensuring the normal operation of the sensor.

[0082] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A low-temperature drift flexible pressure sensor, characterized in that, It includes, from top to bottom, an upper insulating layer, an upper sensor layer, a pressure-isolated microstructure layer, a lower sensor layer, and a lower insulating layer; The upper insulating layer has multiple electrode holes; The upper sensor layer includes a first piezoresistive sensor group, and the lower sensor layer includes a second piezoresistive sensor group. The electrodes of the first piezoresistive sensor group are exposed to the external environment through the electrode holes. The pressure isolation microstructure layer has a recess on the side near the lower sensor layer. The recess has the same shape as the second piezoresistive sensor group and covers the upper surface of the second piezoresistive sensor group. The pressure isolation microstructure layer has a connecting hole, which is corresponding to a portion of the electrode holes. The electrodes of the second piezoresistive sensor group are exposed to the external environment through the connecting hole and the electrode holes in sequence. The first piezoresistive sensor group and the second piezoresistive sensor group are the same in size, shape and material. The electrodes of the first piezoresistive sensor group exposed to the external environment are electrically connected to the electrodes of the second piezoresistive sensor group to form a Huygens bridge.

2. The low-temperature drift flexible pressure sensor according to claim 1, characterized in that, Both the upper sensor layer and the lower sensor layer include a first copper layer, an intermediate layer and a second copper layer that are bonded together from top to bottom; The first piezoresistive sensor group is disposed in the middle layer of the upper sensor layer, and the first copper layer and the second copper layer of the upper sensor layer respectively constitute the two electrodes of the first piezoresistive sensor group; The second piezoresistive sensor group is disposed in the middle layer of the lower sensor layer, and the first copper layer and the second copper layer of the lower sensor layer respectively constitute the two electrodes of the second piezoresistive sensor group.

3. The low-temperature drift flexible pressure sensor according to claim 1 or 2, characterized in that, The first piezoresistive sensor group includes a spiral-shaped first piezoresistive sensor and a spiral-shaped second piezoresistive sensor, which are nested in the same plane. The first end of the first piezoresistive sensor and the first end of the second piezoresistive sensor are disposed opposite to each other at the center of the upper sensor layer. The second end of the first piezoresistive sensor is connected to a first insulating member on one side of the upper sensor layer. The second end of the second piezoresistive sensor is connected to another first insulating member on the other side of the upper sensor layer. A first through hole is provided on the first insulating member. The second copper cladding layer covering the lower surface of the first insulating member is exposed to the external environment through the first through hole. The second piezoresistive sensor group includes a helical third piezoresistive sensor and a helical fourth piezoresistive sensor, wherein the third piezoresistive sensor and the fourth piezoresistive sensor are nested in the same plane; The first end of the third piezoresistive sensor and the first end of the fourth piezoresistive sensor are positioned opposite each other at the center of the lower sensor layer. The second end of the third piezoresistive sensor is connected to a second insulating member on one side of the lower sensor layer, and the second end of the fourth piezoresistive sensor is connected to another second insulating member on the other side of the lower sensor layer. A second through hole is provided on the second insulating member, and the second copper cladding layer covering the lower surface of the second insulating member is exposed to the external environment through the second through hole.

4. The low-temperature drift flexible pressure sensor according to claim 3, characterized in that, The first end of the first piezoresistive sensor is connected to the first end of the fourth piezoresistive sensor, the second end of the fourth piezoresistive sensor is connected to the first end of the second piezoresistive sensor, the second end of the second piezoresistive sensor is connected to the second end of the third piezoresistive sensor, and the first end of the third piezoresistive sensor is connected to the second end of the first piezoresistive sensor. An external power supply is connected between the first end of the first piezoresistive sensor and the second end of the third piezoresistive sensor to apply an external voltage; a voltage measuring device is connected between the second end of the first piezoresistive sensor and the second end of the fourth piezoresistive sensor to obtain the output voltage of the Huygens bridge circuit.

5. The low-temperature drift flexible pressure sensor according to claim 3, characterized in that, At least one of the first piezoresistive sensor, the second piezoresistive sensor, the third piezoresistive sensor, and the fourth piezoresistive sensor is made of carbon nanotube conductive paste; And / or, at least one of the first insulating element and the second insulating element is made of polydimethylsiloxane or polyimide.

6. The low-temperature drift flexible pressure sensor according to claim 1, characterized in that, At least one of the upper insulating layer and the lower insulating layer is a rectangular thin film structure; And / or, the pressure-isolation microstructure layer is a rectangular thin film structure containing microstructures; And / or, at least one of the upper insulating layer, the lower insulating layer and the pressure isolation microstructure layer is made of polydimethylsiloxane or polyimide.

7. The low-temperature drift flexible pressure sensor according to claim 1, characterized in that, The thickness of at least one of the upper insulating layer and the lower insulating layer is 0.05-0.1 mm; And / or, the thickness of at least one of the upper sensor layer and the lower sensor layer is 0.15-0.2 mm; And / or, the thickness of the pressure isolation microstructure layer is not less than the thickness of the lower sensor layer; And / or, the thickness of the pressure-isolating microstructure layer is 0.3-0.35 mm.

8. The low-temperature drift flexible pressure sensor according to claim 1, characterized in that, The recessed portion is interference-fitted with the upper surface of the second piezoresistive sensor group.

9. A method for preparing a low-temperature drift flexible pressure sensor as described in any one of claims 1-8, characterized in that, include: The upper insulating layer, the lower insulating layer, and the isolation microstructure layer are prepared. The intermediate layer of the upper sensor layer and the intermediate layer of the lower sensor layer are prepared, and copper electrode plates are covered on the upper and lower surfaces of the intermediate layer of the upper sensor layer and the upper and lower surfaces of the intermediate layer of the lower sensor layer, thus completing the preparation of the upper sensor layer and the lower sensor layer. The upper insulating layer, the upper sensor layer, the pressure isolation microstructure layer, the lower sensor layer, and the lower insulating layer are stacked and bonded together to complete the fabrication of the low-temperature drift flexible pressure sensor.

10. The method according to claim 9, characterized in that, The step of stacking and pasting the upper insulating layer, the upper sensor layer, the pressure isolation microstructure layer, the lower sensor layer, and the lower insulating layer includes: Adhesives are provided around the upper insulating layer on the side near the upper sensor layer, around both sides of the pressure isolation microstructure layer, and around the lower insulating layer on the side near the lower sensor layer. The upper insulating layer, the upper sensor layer, the pressure isolation microstructure layer, the lower sensor layer, and the lower insulating layer are precisely positioned from top to bottom and then stacked and bonded together. The structural material above the upper insulating layer is removed from the electrodes of the first piezoresistive sensor group in the upper sensor layer and the electrodes of the second piezoresistive sensor group in the lower sensor layer.

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