Manufacturing method of underwater flexible pressure sensor based on structured cavity

Abstract

The invention discloses a manufacturing method of an underwater flexible pressure sensor based on a structured cavity. The manufacturing method of the underwater flexible pressure sensor based on the structured cavity comprises the following steps: designing and preparing a cavity mold; fluorinating the surface of the cavity mold; preparing a PDMS (Polydimethylsiloxane) cavity base; preparing a pressure sensitive film; packaging the pressure sensitive part; and assembling the packaged pressure sensitive part and the PDMS cavity base. According to the manufacturing method of the underwater flexible pressure sensor based on the structured cavity, an advanced achievement of a flexible electronic manufacturing technology is applied, and effective balance and offset of hydrostatic pressure influence are realized by designing and constructing a flexible micro-cavity structure, so that the sensor can be used in a complex underwater environment, and the underwater flexible pressure sensor based on the structured cavity can be manufactured. And the dynamic pressure change generated by water flow disturbance can be accurately detected, so that a brand new solution is provided for the field of underwater pressure measurement.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater flexible pressure sensors, and in particular to a method for manufacturing an underwater flexible pressure sensor based on a structured cavity. Background Art

[0002] As one of the key technologies in many fields such as marine science, underwater engineering and environmental monitoring, underwater pressure detection has far-reaching and extensive significance. This technology is not only related to the exploration and development of marine resources, the health monitoring and safety assessment of underwater structures, but also directly related to the protection and sustainable utilization of the marine ecological environment. At present, many scholars have conducted extensive exploration in the field of underwater dynamic pressure research. Existing research mainly covers two categories: one is the traditional pressure sensor built on rigid materials, and the other is the flexible pressure sensor technology that has emerged in recent years.

[0003] The design principles and manufacturing processes of underwater pressure sensors based on rigid materials are relatively mature, and they have accumulated rich experience in long-term application practice. Such sensors usually use high-strength and high-stability rigid materials such as metals or ceramics as substrates, and ensure their stable operation and high-precision measurement in extreme underwater environments through precise processing and packaging technology. However, although rigid pressure sensors have excellent performance in measurement range, accuracy and reliability, their inherent limitations cannot be ignored. Specifically, the use of rigid materials leads to relatively large volume and heavy weight of the sensors, which can easily cause irreversible damage to the real flow field distribution information underwater. In addition, in the actual deployment process, additional waterproof packaging measures are often required to ensure its sealing and durability. In addition, for complex underwater environments, especially in scenes with three-dimensional curved structures, the adaptability and flexibility of rigid sensors are particularly insufficient, and it is difficult to achieve close fit and comprehensive coverage with curved structures.

[0004] In contrast, flexible pressure sensor technology has attracted much attention for its unique softness, lightweight design and good adaptability to curved surfaces. Such sensors usually use organic polymer materials or composite materials as the substrate, and through advanced thin film preparation and patterning technology, the sensor structure is flexible and miniaturized. Flexible pressure sensors can not only be easily attached to various complex curved surfaces, but also significantly improve the portability and ease of use of the sensor while maintaining high-precision measurement. However, due to the immaturity of the technology, flexible pressure sensors also face many challenges in practical applications. On the one hand, due to the relatively weak mechanical properties and stability of flexible materials, the measurement accuracy and service life of the sensor may be seriously affected when it is subjected to high pressure or long-term high-pressure environment. On the other hand, how to achieve a large range and high-precision pressure measurement while ensuring the softness of the sensor is still a key issue that needs to be urgently solved in the current flexible pressure sensor technology.

[0005] In the field of traditional pressure detection, Literature 1 reported that a MEMS wake detection pressure sensor with two-dimensional vector characteristics was designed, inspired by the lateral line of fish. The core sensitive element is a ciliary cross beam structure. The wake signal is converted into a voltage signal by arranging piezoresistors to form a Wheatstone bridge. This simulates the pressure gradient sensing mechanism of the neuromasts of the lateral line duct of fish. However, due to packaging reasons, the actual sensitivity of the sensor is only one-third of the simulation result. This shows that in the current design and preparation process of such sensors, due to the limitations of packaging technology and insufficient test conditions, the sensor performance has not reached the optimal state.

[0006] Reference 2 reports a fluid dynamic pressure sensor inspired by the lateral line system of fish. The steps of the method are as follows:

[0007] The first step is the preparation of the substrate and microheater. First, a 10-micron thick polyimide (PI) layer is covered on the silicon wafer by spin coating. Then, a gold / chromium (Au / Cr) film is deposited by photolithography and electron beam evaporation to form the microheater and the upper electrode, and then the structure is completed by a lift-off process.

[0008] The second step is the preparation of the piezoelectric layer. A poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) piezoelectric layer is spin-coated and annealed on the above structure with a thickness of about 4 μm and annealed at 135° C. for 2 hours.

[0009] The third step is the fabrication of micro-cantilever beams. The PI / P (VDF-TrFE) micro-cantilever beams are fabricated by reactive ion etching (RIE) process.

[0010] The fourth step is the preparation of the cup-shaped structure of the hydrogel. A double network hydrogel is formed in a sodium chloride (CaCl2) solution by polymerizing N-isopropylacrylamide (NIPAM), a crosslinker N,N-methylenebisacrylamide (BIS) and a photoinitiator 2,2-diethoxyacetophenone (DEOP). The obtained hydrogel is precisely mounted on the top of the microcantilever and fixed with epoxy resin.

[0011] The fifth step is encapsulation of the microfluidic channel. The above structure is encapsulated into a microfluidic channel made of polydimethylsiloxane (PDMS) to form a complete fluid dynamic pressure sensor.

[0012] The flexible pressure sensor based on this method requires complex micro-nano processing technology in the production of micro-cantilever beams and micro-heaters, which requires extremely high process accuracy and repeatability, and the process is relatively cumbersome. In addition, there are micro-nano holes and metal interconnect structures inside the multi-layer substrate, which easily lead to stress concentration and cracks during the processing. These defects may cause leakage of cooling medium and reduce the reliability of the electronic system.

[0013] Although existing research in the field of underwater pressure detection has made significant progress in some aspects, there are still many shortcomings, especially the contradiction between the volume and weight of the sensor, the contradiction between surface adaptability and long-term reliability and stability, and the contradiction between measurement accuracy and range. These significant problems need to be solved urgently. Summary of the invention

[0014] In order to solve the above problems, the purpose of the present invention is to provide a method for manufacturing an underwater flexible pressure sensor based on a structured cavity, so as to solve the many shortcomings of the flexible pressure sensor in the field of underwater pressure detection in the prior art, namely, the inherent contradiction between the large-range measurement requirements and the high-precision sensing capabilities. In a low-pressure environment, it is often difficult for a flexible pressure sensor to effectively capture and sense small pressure changes; while in a high-pressure environment, it is difficult to accurately distinguish and detect subtle changes in the low-pressure range. The advanced achievements of flexible electronic manufacturing technology are cleverly used. By designing and constructing a flexible micro-cavity structure, an effective balance and offset of the influence of hydrostatic pressure is achieved, so that the sensor can more accurately detect the dynamic pressure changes caused by water flow disturbances in a complex underwater environment, thereby providing a new solution path and technical support for the field of underwater pressure measurement.

[0015] In order to achieve the above object, the technical solution of the present invention is as follows:

[0016] A method for manufacturing an underwater flexible pressure sensor based on a structured cavity, characterized in that it comprises the following steps:

[0017] S1. Design and prepare cavity mold;

[0018] S2. Fluorinizing the surface of the cavity mold;

[0019] S3. Preparation of PDMS cavity base;

[0020] S4. Preparation of pressure sensitive film;

[0021] S5. Packaging of pressure sensitive parts;

[0022] S6. Assemble the encapsulated pressure sensitive part with the PDMS cavity base.

[0023] Furthermore, the cavity mold in S1 is made of acrylic or traditional metal.

[0024] Further, the S2 comprises the following steps:

[0025] S21. The cavity mold is cleaned in a plasma machine for 5 minutes to allow the surface to contain oxygen free radicals;

[0026] S22. The cleaned cavity mold is placed in a dryer and a few drops of a fluorinating agent are added to the dryer. The fluorinating agent is 1H, 1H, 2H, 2H perfluorodecyltrimethoxysilane;

[0027] S23. Evacuate the dryer and place it in an oven at 80°C for 4 hours to obtain a fluorinated cavity mold.

[0028] Further, the S3 comprises the following steps:

[0029] S31. Prepare PDMS prepolymer solution according to the standard ratio of main agent: curing agent = 10:1;

[0030] S32. If the flexibility of the cavity needs to be changed, the ratio of the main agent to the curing agent is adjusted from 20:1 to 5:1;

[0031] S33. The prepared PDMS prepolymer solution is introduced into the fluorinated cavity mold, and the bubbles are removed by vacuuming;

[0032] S34. Place the cavity mold from which bubbles have been removed in step S33 into an oven at 80°C for curing for 4 hours, thereby preparing a PDMS cavity base.

[0033] Further, the S4 comprises the following steps:

[0034] S41. The pressure sensitive film is selected as PEDOT:PSS-based film or graphene paper sensitive film;

[0035] S42. According to the selected PEDOT:PSS-based film or graphene paper sensitive film, prepare a pressure sensitive film according to the respective step processes.

[0036] Further, the S42 comprises the following steps:

[0037] S421. If it is a PEDOT:PSS-based film, the PEDOT:PSS conductive film can be directly prepared by spin coating, or a polymer network can be further introduced to compound the PEDOT:PSS conductive film.

[0038] S422. If you are using graphene paper sensitive film, just buy 50 micron conductive graphene paper and then cut it into the required shape.

[0039] Further, the S421 includes the following steps:

[0040] S4211. The purchased PEDOT:PSS solution was spin-coated onto a glass plate and then placed in an oven at 80°C for 12 h to obtain a pure PEDOT:PSS conductive film;

[0041] S4212. In order to improve the flexibility of PEDOT:PSS film, polymer network PVA was introduced to compound it to form PVA / PEDOT:PSS composite film.

[0042] Further, the S4212 includes the following steps:

[0043] S42121. Prepare a PVA / PEDOT:PSS aqueous solution, and then spin-coat it onto a glass plate, wherein the PVA has a molecular weight of 100,000-150,000, a hydrolysis degree of 98%, a mass fraction of PVA of 5%-13% of water, and a mass ratio of PEDOT:PSS to PVA of 1:10-1:1;

[0044] S42122. Freeze in a -20°C refrigerator for 12 hours to obtain a PVA / PEDOT:PSS gel film.

[0045] Further, the S5 comprises the following steps:

[0046] S51. Preparation of electrode layer PI-Au: sputtering Au on the PI film to serve as an electrode layer;

[0047] S52. The pressure sensitive film and the electrode layer PI-Au prepared in step S4 are waterproofly encapsulated with PDMS.

[0048] By adopting the above technical solution, the present invention has the following advantages:

[0049] 1. The present invention provides a method for manufacturing an underwater flexible pressure sensor based on a structured cavity, which innovatively adopts flexible electronic technology with high flexibility and adaptability, and realizes effective cost control by simplifying the manufacturing process. Compared with traditional rigid electronic components, flexible electronic technology not only reduces material cost and processing complexity, but also improves production efficiency, making the entire pressure detection system more economical and efficient. This process simplification and cost control strategy makes large-scale application possible.

[0050] 2. The present invention provides a method for manufacturing an underwater flexible pressure sensor based on a structured cavity, and the resulting pressure detection element can fit tightly on surfaces of various complex curvatures. This attachment capability not only enhances the adaptability and flexibility of the system, but also significantly reduces the interference of the detection element itself to the flow field environment. At the same time, thanks to the characteristics of small size and light weight, the method of the present invention can maintain the natural state of the flow field to the maximum extent in practical applications, thereby more accurately capturing and recording the pressure change information in the flow field. This protection of flow field environmental information is of great significance for improving detection accuracy and reliability, especially in situations where high-precision measurements are required.

[0051] 3. The present invention provides a method for manufacturing an underwater flexible pressure sensor based on a structured cavity. Through an innovative balancing strategy, the influence of hydrostatic pressure on the sensor performance is cleverly offset, thereby achieving long-term stable use of the sensor under high-pressure environments. This strategy not only significantly improves the sensor's ability to work under extreme conditions, but also effectively solves the long-standing contradiction between large range and high precision in traditional pressure sensors.

[0052] 4. The present invention provides a method for manufacturing an underwater flexible pressure sensor based on a structured cavity, using a high-performance flexible material as a sensing element. This material not only has excellent flexibility and durability, but also can closely cooperate with the structured cavity to achieve accurate measurement of underwater pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is the principle diagram of underwater dynamic pressure detection based on microstructure;

[0054] Figure 2 The present invention is a process for preparing the PDMS cavity base;

[0055] Figure 3 The present invention is a process for preparing the pressure sensitive film;

[0056] Figure 4 It is a schematic structural diagram of the pressure sensitive part of the present invention;

[0057] Figure 5Schematic diagram of the underwater flexible pressure sensor with a structured cavity according to the present invention. DETAILED DESCRIPTION

[0058] The technical solution of the present invention is described in detail below in conjunction with the drawings in the specification. It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0059] For an ideal fluid in steady flow, the relationship between the pressure, velocity and height at any two points along a streamline is:

[0060]

[0061] Right now

[0062] This equation shows that for a flowing fluid element, its mechanical energy (including pressure energy, kinetic energy and potential energy) is conserved in the absence of external forces. For the fluid at the same height, ignoring the effect of its gravitational potential energy, that is

[0063]

[0064] P0 is the total pressure of the fluid, and p1 is the static pressure of the fluid, which is mainly related to the position of the fluid and the effect of gravity. It refers to the pressure exerted by the fluid in a static state. It is a measure of the pressure at each point inside the fluid and does not change with time. Then, the dynamic pressure of the fluid can be expressed as the difference between the total pressure and the static pressure, that is:

[0065]

[0066] in, ρ represents the fluid density, v Represents the speed of fluid movement, that is, flow velocity.

[0067] The dynamic pressure detection principle is as follows Figure 1As shown in the figure, when the fluid is in a static state, due to the effect of the hydrostatic pressure, part of the fluid will penetrate into the inner area of ​​the cavity structure. At this time, according to Newton's second law in physics, the pressure sensitive element located on the upper surface of the cavity structure will be in a state of force balance. The realization of this equilibrium state is due to the effective offset of the influence of the hydrostatic pressure by the cavity structure, which ensures that the pressure sensitive element will not be deformed, thereby maintaining the initial state of the sensor.

[0068] However, when the fluid has a certain flow velocity in the direction perpendicular to the cavity structure, the situation will change significantly. The introduction of flow velocity leads to the generation of fluid dynamic pressure, which is an additional pressure caused by fluid movement. Under the action of this dynamic fluid pressure, the pressure sensitive element on the upper surface of the cavity will no longer maintain the original force balance state, but will be subjected to an additional pressure. This additional pressure will cause the pressure sensitive element to deform to a certain extent (the specific degree of deformation depends on the size of the fluid dynamic pressure and the geometric characteristics of the cavity structure), thereby causing the change of the resistance of the pressure sensitive element itself, realizing the perception and measurement of the dynamic pressure of the fluid.

[0069] A method for manufacturing an underwater flexible pressure sensor based on a structured cavity comprises the following specific steps:

[0070] S1. Design and prepare a cavity mold; wherein the cavity mold can be made of acrylic material or traditional metal material.

[0071] S2. Fluorinizing the surface of the cavity mold;

[0072] Among them, S2 includes the following specific steps:

[0073] S21. First, the cavity mold is cleaned in a plasma machine for 5 minutes to make its surface contain oxygen free radicals;

[0074] S22. The cleaned cavity mold is then placed in a dryer and a few drops of a fluorinating agent are added to the dryer. The fluorinating agent is 1H, 1H, 2H, 2H perfluorodecyltrimethoxysilane;

[0075] S23. Evacuate the dryer and place it in an oven at 80°C for 4 hours to obtain a fluorinated cavity mold.

[0076] S3. Preparation of PDMS cavity base;

[0077] Among them, S3 includes the following steps: Figure 2 As shown, in Figure 2 In the figure, A represents the fluorinated cavity mold, B represents the PDMS prepolymer solution introduced into the fluorinated cavity mold, and C represents the prepared PDMS cavity base.

[0078] S31. Prepare PDMS prepolymer solution according to the standard ratio of main agent: curing agent = 10:1;

[0079] S32. If the flexibility of the cavity needs to be changed, the ratio of the main agent to the curing agent is adjusted from 20:1 to 5:1;

[0080] S33. The prepared PDMS prepolymer solution is introduced into the fluorinated cavity mold, and the bubbles are removed by vacuuming;

[0081] S34. Place the cavity mold from which bubbles have been removed in step S33 into an oven at 80°C for curing for 4 hours, thereby preparing a PDMS cavity base. The thickness of the cavity mold is 50 microns to 1 mm.

[0082] S4. Preparation of pressure sensitive film;

[0083] Among them, S4 includes the following specific steps:

[0084] S41. The pressure sensitive film is selected as PEDOT:PSS-based sensitive film or graphene paper sensitive film;

[0085] S42. According to the selected PEDOT:PSS-based sensitive film or graphene paper sensitive film, prepare a pressure sensitive film according to the respective step processes.

[0086] Wherein, S42 includes the following specific steps:

[0087] S421. If it is a PEDOT:PSS-based film, the PEDOT:PSS conductive film can be directly prepared, or a polymer network can be further introduced to compound the PEDOT:PSS conductive film.

[0088] S421 includes the following steps:

[0089] S4211. The purchased PEDOT:PSS solution was spin-coated onto a glass plate and then placed in an oven at 80°C for 12 h to obtain a pure PEDOT:PSS conductive film;

[0090] S4212. In order to improve the flexibility of the PEDOT:PSS film, a polymer network PVA can be introduced to compound it. For example, a PVA / PEDOT:PSS composite film can be used. The specific operation is as follows: Figure 3 shown.

[0091] Among them, S4212 includes the following steps:

[0092] S42121. Prepare a PVA / PEDOT:PSS aqueous solution, and then spin-coat it onto a glass plate, wherein the PVA has a molecular weight of 100,000-150,000, a hydrolysis degree of 98%, a mass fraction of PVA of 5%-13% of water, and a mass ratio of PEDOT:PSS to PVA of 1:10-1:1;

[0093] S42122. Freeze in a -20°C refrigerator for 12 hours to obtain a PVA / PEDOT:PSS gel film.

[0094] S422. If you are using graphene paper sensitive film, just buy 50 micron conductive graphene paper and then cut it into the required shape.

[0095] S5. Packaging of pressure sensitive parts;

[0096] S5 includes the following steps:

[0097] S51. Preparation of electrode layer PI-Au: sputtering Au on the PI film to serve as an electrode layer;

[0098] S52. The pressure-sensitive film and electrode layer PI-Au prepared in step S4 are waterproofly encapsulated with PDMS to obtain a packaged pressure-sensitive part, the specific structure of which is shown in Figure 4, including an upper elastic layer (PMDS) a, a pressure-sensitive film layer b, an electrode layer c, and a lower elastic layer (PMDS) d from top to bottom.

[0099] S6. Assemble the packaged pressure sensitive part D with the PDMS cavity base C prepared in step S3. Figure 5 As shown, the pressure sensitive part and the PDMS cavity base are bonded together using PDMS, thereby obtaining the final structured cavity underwater flexible pressure sensor E.

[0100] The present invention proposes a flexible underwater dynamic pressure sensing method based on a structured cavity. The method innovatively designs a unique structured cavity structure, which can effectively capture and respond to underwater dynamic pressure changes by balancing the influence of hydrostatic pressure, thereby achieving high-precision pressure sensing.

[0101] Finally, it should be pointed out that although the present invention has been described with reference to the current specific embodiments, ordinary technicians in this technical field should realize that the above embodiments are only used to illustrate the present invention and are not used as a limitation of the present invention. Various equivalent changes or substitutions can be made without departing from the concept of the present invention. Therefore, as long as the changes and modifications to the above embodiments are within the essential spirit of the present invention, they will fall within the scope of the claims of the present invention.

Claims

1. A method for manufacturing an underwater flexible pressure sensor based on a structured cavity, characterized in that: The following steps are involved: S1. Design and prepare cavity mold; S2. Fluorinizing the surface of the cavity mold; S3. Preparation of PDMS cavity base; S4. Preparation of pressure sensitive film; S5. Packaging of pressure sensitive parts; S6. Assemble the encapsulated pressure sensitive part with the PDMS cavity base.

2. The method for manufacturing an underwater flexible pressure sensor based on a structured cavity according to claim 1, characterized in that: The cavity mold in S1 is made of acrylic or traditional metal.

3. The method for manufacturing an underwater flexible pressure sensor based on a structured cavity according to claim 1, characterized in that: The S2 comprises the following steps: S21. The cavity mold is cleaned in a plasma machine for 5 minutes to make its surface contain oxygen free radicals; S22. The cleaned cavity mold is placed in a dryer and a few drops of a fluorinating agent are added to the dryer. The fluorinating agent is 1H, 1H, 2H, 2H perfluorodecyltrimethoxysilane; S23. Evacuate the dryer and place it in an oven at 80°C for 4 hours to obtain a fluorinated cavity mold.

4. The method for manufacturing an underwater flexible pressure sensor based on a structured cavity according to claim 1, characterized in that: The S3 comprises the following steps: S31. Prepare PDMS prepolymer solution according to the standard ratio of main agent: curing agent = 10:1; S32. If the flexibility of the cavity needs to be changed, the ratio of the main agent to the curing agent is adjusted from 20:1 to 5:1; S33. The prepared PDMS prepolymer solution is introduced into the fluorinated cavity mold, and the bubbles are removed by vacuuming; S34. Place the cavity mold from which bubbles have been removed in step S33 into an oven at 80°C for curing for 4 hours, thereby preparing a PDMS cavity base.

5. The method for manufacturing an underwater flexible pressure sensor based on a structured cavity according to claim 1, characterized in that: The S4 comprises the following steps: S41. The pressure sensitive film is selected as PEDOT:PSS-based sensitive film or graphene paper sensitive film; S42. According to the selected PEDOT:PSS-based sensitive film or graphene paper sensitive film, prepare a pressure sensitive film according to the respective step processes.

6. The method for manufacturing an underwater flexible pressure sensor based on a structured cavity according to claim 5, characterized in that: The S42 comprises the following steps: S421. If it is a PEDOT:PSS-based film, the PEDOT:PSS conductive film is directly prepared by spin coating, or a polymer network is further introduced to composite the PEDOT:PSS conductive film. S422. If you are using graphene paper sensitive film, just buy 50 micron conductive graphene paper and then cut it into the required shape.

7. The method for manufacturing an underwater flexible pressure sensor based on a structured cavity according to claim 6, characterized in that: The S421 includes the following steps: S4211. The purchased PEDOT:PSS solution was spin-coated onto a glass plate and then placed in an oven at 80°C for 12 h to obtain a pure PEDOT:PSS conductive film; S4212. In order to improve the flexibility of PEDOT:PSS film, polymer network PVA was introduced to compound it to form PVA / PEDOT:PSS composite film.

8. The method for manufacturing an underwater flexible pressure sensor based on a structured cavity according to claim 7, characterized in that: The S4212 includes the following steps: S42121. Prepare a PVA / PEDOT:PSS aqueous solution, and then spin-coat it onto a glass plate, wherein the PVA has a molecular weight of 100,000-150,000, a hydrolysis degree of 98%, a mass fraction of PVA of 5%-13% of water, and a mass ratio of PEDOT:PSS to PVA of 1:10-1:1; S42122. Freeze in a -20°C refrigerator for 12 hours to obtain a PVA / PEDOT:PSS gel film.

9. The method for manufacturing an underwater flexible pressure sensor based on a structured cavity according to claim 1, characterized in that: The S5 comprises the following steps: S51. Preparation of electrode layer PI-Au: sputtering Au on the PI film to serve as an electrode layer; S52. The pressure sensitive film and the electrode layer PI-Au prepared in step S4 are waterproofly encapsulated with PDMS.

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