Pressure sensor with adjustable microstructure and preparation method thereof

Abstract

The invention relates to a pressure sensor with an adjustable microstructure and a preparation method thereof. The pressure sensor with the adjustable microstructure comprises two groups of external electrodes, a sensing unit layer is arranged between the two groups of external electrodes, and an adjustable structural member is arranged in the sensing unit layer; the adjustable structural member comprises at least one layer of microsphere structure, and one layer of microsphere structure comprises a plurality of tiled microspheres; the pressure sensor with the adjustable microstructure is simple in structure, high in controllability, convenient to manufacture, sensitive in response, low in cost and suitable for application scenes with complex pressure response, such as wearable electronics, electronic skin, robot surface pressure signal capture and many other fields.

Description

Technical Field

[0001] The present invention belongs to the technical field of pressure sensors, and in particular relates to a pressure sensor with an adjustable microstructure and a preparation method thereof. Background Art

[0002] In modern technology applications, pressure, as a common physical quantity, involves many fields, such as smart devices, medical health monitoring, industrial automation, etc. Therefore, the research and development of pressure sensors has received widespread attention in recent years. The core function of pressure sensors is to sense and convert pressure signals, and signal conversion is performed through different sensing mechanisms. At present, many different types of sensors have been developed. Common sensing mechanisms include resistive, capacitive, piezoelectric and triboelectric, each of which has its own characteristics and advantages. Resistive sensors sense pressure changes by measuring changes in resistance, capacitive sensors rely on changes in capacitance, piezoelectric sensors use the piezoelectric effect caused by pressure, and triboelectric sensors sense through voltage changes generated by the triboelectric effect.

[0003] Among these sensing mechanisms, capacitive sensors have become a research hotspot due to their high sensitivity and strong stability, and have shown great potential in commercial applications. Capacitive sensors sense pressure changes by measuring the capacitance change between two electrodes. This type of sensor has high accuracy, sensitivity and low noise impact, so it has broad application prospects in fields with high demand for high-performance sensors. For example, the development of electronic skin and wearable devices requires sensors to not only have high sensitivity and stability, but also meet special requirements such as flexibility and stretchability. Therefore, capacitive sensors have become the first choice due to their excellent performance.

[0004] However, with the rapid development of emerging fields such as electronic skin and wearable devices, the performance requirements for sensors are becoming increasingly higher, and the large-scale production and low-cost manufacturing of high-performance sensors have become urgent issues to be addressed. An effective way to improve sensor performance is to optimize the microstructure design. The microstructure has a direct impact on the performance of the sensor, especially in terms of improving sensitivity, reducing power consumption, and increasing response speed. The fine design and preparation method of the microstructure are particularly important. Therefore, how to quickly and accurately prepare high-quality microstructures has become a key direction of current research.

[0005] Traditional microstructure preparation methods mainly rely on the template method, which is a method of replicating microstructure patterns by using pre-made templates. Although the template method has achieved remarkable success in many applications, it also has some significant disadvantages. For example, the preparation of templates often requires high costs and a long time, especially for micro molds with complex structures, which often require customized design and fine processing, which prolongs the production cycle and increases costs. In addition, the molds used in the template method are usually disposable, which means that a lot of waste will be generated during mass production.

[0006] The present invention aims to provide a rapid preparation method which does not require a printing mold and can adjust the microstructure distribution and shape at any time, thereby greatly improving the sensor preparation efficiency and reducing the manufacturing cost. Summary of the invention

[0007] The purpose of the present invention is to provide a pressure sensor with a simple structure, reasonable design and adjustable microstructure and a preparation method thereof in order to solve the above problems.

[0008] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0009] A first aspect of the present invention provides a pressure sensor with an adjustable microstructure, comprising two groups of external electrodes, a sensitive unit layer being arranged between the two groups of external electrodes, and an adjustable structural member being arranged in the sensitive unit layer.

[0010] As a further optimization solution of the present invention, the adjustable structural member includes at least one layer of microsphere structure, and one layer of the microsphere structure includes a plurality of flat microspheres.

[0011] As a further optimization solution of the present invention, the adjustable structural member includes two layers of microsphere structures, wherein the microspheres in one layer of the microsphere structure are arranged at intervals, and the microspheres in the other layer of the microsphere structure are arranged in the intervals.

[0012] As a further optimization solution of the present invention, the material of the sensitive unit layer is polydimethylsiloxane;

[0013] Or it may be a mixed material of polydimethylsiloxane, barium titanate and multi-walled carbon nanotubes.

[0014] As a further optimization scheme of the present invention, the microsphere material in the microsphere structure is one or more of polyethylene, polyoxymethylene, polypropylene or polystyrene.

[0015] As a further optimization solution of the present invention, a packaging layer is provided on the outer side of the external electrode.

[0016] A second aspect of the present invention provides a method for preparing a pressure sensor with an adjustable microstructure, the method comprising:

[0017] The polyoxymethylene microspheres were obtained, ultrasonically cleaned in deionized water for 1-10 min, and then dried at 40-60° C. for 0.5-1 h;

[0018] obtaining a sensitive layer solution; obtaining microspheres;

[0019] After fixing the microspheres, the sensitive layer solution is poured on the surface of the microspheres;

[0020] After solidification, electrodes are pasted on the upper and lower surfaces and sealed.

[0021] As a further optimization scheme of the present invention, the microspheres are stored in 75% medical alcohol;

[0022] As a further optimization scheme of the present invention, the microspheres are fixed on the surface of the sensitive unit layer composed of the sensitive layer solution;

[0023] As a further optimization solution of the present invention, the thickness of the sensitive unit layer is 0.1mm-0.5mm;

[0024] As a further optimization scheme of the present invention, the sensitive layer solution is PDMS or PDMSBaTiO 3 / MwCNTs / PDMS mixed solution.

[0025] The beneficial effects of the present invention are as follows: the present invention uses self-assembly technology to coat alcohol with polyformaldehyde microspheres, so that polyformaldehyde microspheres of different sizes naturally form a specific distribution under the action of gravity, and the microstructure shape of the pressure sensor medium layer is controlled by demolding the mold with a custom pattern, thereby achieving the purpose of freely adjusting the microstructure of the sensor medium layer. The microstructure shape and Young's modulus of the sensor can be designed according to actual application requirements, and then the preparation of sensors with different performances can be completed without printing molds. The pressure sensor prepared by the present invention has a simple structure, strong controllability, easy production, sensitive response, and low cost. It is suitable for application scenarios with complex pressure responses, such as wearable electronics, electronic skin, robot surface pressure signal capture and many other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the overall structure of a pressure sensor with an adjustable microstructure according to the present invention;

[0027] Figure 2 It is a method flow chart of a method for preparing a pressure sensor with an adjustable microstructure of the present invention;

[0028] Figure 3 This is a stress simulation diagram of the microstructure of Example 1 of the present invention when it is compressed and deformed by 1.5 mm;

[0029] Figure 4This is a stress simulation diagram of the microstructure of Example 2 of the present invention when it is compressed and deformed by 1.5 mm;

[0030] Figure 5 is a diagram showing the relationship between the contact area and the pressure outputted by the simulation during the compression process of the microstructure and the electrode in Example 1 of the present invention;

[0031] Figure 6 It is a diagram showing the relationship between the contact area and the pressure output of the microstructure and the electrode during the compression process according to Example 2 of the present invention.

[0032] In the figure: 1. Packaging layer; 2. External electrode; 3. Sensitive unit layer; 4. Adjustable structural part. DETAILED DESCRIPTION

[0033] The present application is further described in detail below in conjunction with the accompanying drawings. It is necessary to point out here that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technical personnel in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0034] refer to Figure 1 The structure shown is a pressure sensor with an adjustable microstructure, comprising two groups of external electrodes 2, a sensitive unit layer 3 is arranged between the two groups of external electrodes 2, and an adjustable structural member 4 is arranged inside the sensitive unit layer 3.

[0035] In fact, the adjustable structural member 4 may include only one layer of microsphere structure, and the layer of microsphere structure includes a plurality of flat microspheres.

[0036] Optimally, the adjustable structural member 4 comprises two layers of microsphere structures, wherein the microspheres in one layer of the microsphere structure are arranged at intervals, and the microspheres in the other layer of the microsphere structure are arranged in the intervals.

[0037] Specifically, the size of the microspheres is 1 μm to 1 cm, and the microsphere material in the microsphere structure is one or more of polyethylene (PE), polyoxymethylene (POM), polypropylene (PP) or polystyrene (PS); the liquid carrying the microspheres is one of volatile liquids such as alcohol, water, and ethyl acetate solution. In this embodiment, alcohol is selected as the liquid carrying the microspheres.

[0038] Specifically, the sensitive unit layer 3 is actually formed by demolding a template with microspheres of the same size and density (single layer). The density and distribution of the microspheres can be adjusted according to demand, and microspheres can be added to the upper and lower layers to form a structure with higher sensitivity; wherein, the size is the radius of the microspheres carried by alcohol; and the density is the average number of microspheres contained in each liter of alcohol when carried by alcohol.

[0039] Furthermore, the material of the sensitive unit layer 3 is polydimethylsiloxane;

[0040] Or it may be a mixed material of polydimethylsiloxane, barium titanate and multi-walled carbon nanotubes.

[0041] Specifically, the sensitive unit layer 3 can be molded into microstructures of different shapes by changing the distribution of microspheres to form different templates. The sensitive unit layer 3 can be made of polydimethylsiloxane or polydimethylsiloxane / barium titanate / multi-walled carbon nanotube mixed materials according to structural characteristics to achieve the best effect.

[0042] Furthermore, a packaging layer 1 is disposed on the outer side of the external electrode 2 .

[0043] The external electrode 2 is one of electrode materials such as copper wire, conductive copper cloth, conductive silver cloth, etc.

[0044] The encapsulation layer 1 is a flexible encapsulation layer, which is composed of one of polydimethylsiloxane, thermoplastic polyurethane elastomer, PI film or polyimide; the thickness of the encapsulation layer should be 50 to 200 μm.

[0045] Example 1

[0046] In this embodiment, polyoxymethylene microspheres are selected as an implementation demonstration. Figure 2 The process shown is a method for preparing a pressure sensor with an adjustable microstructure, and the specific process of the method is as follows:

[0047] Place polyoxymethylene microspheres (radius 0.1-2 mm) in deionized water for ultrasonic cleaning for 1-10 minutes to remove dust, oil stains and other impurities on the surface; take them out and dry them at 40-60° C. for 0.5-1 hour to release surface stress.

[0048] Then put the polyoxymethylene microspheres into 75% medical alcohol. Use 75% alcohol to wipe the polyvinyl alcohol workbench to clean the surface.

[0049] Alcohol with polyoxymethylene microspheres of different sizes and contents was applied to a polyvinyl alcohol (PVA) workbench (pre-coated with a layer of polydimethylsiloxane less than 0.5 mm thick) to form a uniformly distributed microsphere network, and dried at 40-60°C for 1 h until the alcohol was completely evaporated.

[0050] Liquid polydimethylsiloxane was poured on the workbench with the microsphere structure. After the polydimethylsiloxane solidified, the dielectric layer with the adjustable microsphere structure was removed and conductive cloth was pasted on the upper and lower plates as flexible electrodes, which were packaged and fixed by PI film to obtain the flexible capacitive sensor. The stress simulation diagram of the sensor prepared in Example 1 with a displacement of 1.5 mm is shown in Figure 1. Figure 3As shown, the force is relatively uniform, and the pressure range is 0~5×10 2 Pa; the curve of its displacement and pressure is as follows Figure 5 As shown, the pressure range is 0~7×10 5 kPa, sensor output characteristics (△C / C 0) Increases linearly with pressure.

[0051] Among them, the cleaning of polyoxymethylene microspheres is to remove surface dust, oil and other substances that may affect the performance of the dielectric layer. It can be replaced with other cleaning liquids such as alcohol according to actual conditions. The number of microspheres in alcohol will affect the distribution density of the microstructure. The process of adding microspheres to alcohol can adjust the ratio of the number of microspheres to the volume of alcohol according to the sensitivity requirements.

[0052] It should be noted that the workbench on which the microspheres are placed should be easy to form hydrogen bonds with the liquid carrying the microspheres and have an adsorption effect. One of glass, polyvinyl alcohol (PVA), polyacrylamide, silicon dioxide, and aluminum oxide can be used as the workbench to stabilize the position of the microspheres. The method of cleaning the workbench can be, but is not limited to, chemical reagent cleaning and plasma cleaning.

[0053] Example 2

[0054] Based on Example 1, the sensitive layer solution is adjusted as follows:

[0055] Polystyrene microspheres (with a radius of 0.5 mm and 1 mm) were placed in deionized water for ultrasonic cleaning for 1-10 minutes, and then taken out and dried at 40-60° C. for 0.5-1 hour to release surface stress. The polystyrene microspheres were then placed in 75% medical alcohol.

[0056] Disperse polydimethylsiloxane and barium titanate / multi-walled carbon nanotubes (BaTiO3 / MwCNTs) in isopropanol solution (isopropanol solution is selected in this embodiment, but ethanol, acetone, chloroform and other volatile organic solvents can also be selected). Mix the two solutions to obtain BaTiO3 / MwCNTs / PDMS solution. Stir continuously until the isopropanol is completely evaporated. The mixing method is one of magnetic stirrer, mechanical stirring, gas penetration stirring.

[0057] The glass workbench was cleaned with 75% wipe, and alcohol with polystyrene microspheres of different sizes and contents was applied on the glass workbench and dried at 40-60°C for 1h until the alcohol was completely evaporated. The barium titanate / multi-walled carbon nanotubes / polydimethylsilane (BaTiO3 / MwCNTs / PDMS) composite solution was cast on the workbench with the microsphere structure.

[0058] When the BaTiO3 / MwCNTs / PDMS composite solution is not completely solidified, a layer of alcohol solution carrying polystyrene microspheres is coated on the composite solution. Due to gravity, the microspheres will naturally form a single layer arrangement, and a layer of microstructure with microsphere structure will also be formed above the solution.

[0059] After the composite material solidifies, the dielectric layer with the adjustable microsphere structure is removed and conductive cloth is pasted on the upper and lower plates as flexible electrodes, which are packaged and fixed by a polydimethylsiloxane film to obtain the flexible capacitive sensor.

[0060] It should be further explained that the preparation process of the composite solution is: 15% by mass of barium titanate and 3% by mass of multi-walled carbon nanotubes are dispersed in an isopropanol solution, and polydimethylsiloxane is also dispersed in the isopropanol solution. The solution is magnetically stirred at 45-60°C for 1-2 hours to fully dissolve, and the two solutions are mixed and stirred continuously until the isopropanol is completely volatilized to obtain a barium titanate / multi-walled carbon nanotube / polydimethylsilane (BaTiO3 / MwCNTs / PDMS) composite solution. The addition of barium titanate / multi-walled carbon nanotubes is to increase the dielectric constant, increase the sensitivity, and improve the performance of the sensor; if the microstructure is adjusted to a smaller Young's modulus, polydimethylsiloxane can also be used directly without doping.

[0061] In actual preparation, polyoxymethylene microspheres of different sizes can be selected according to the sensitivity requirements of different positions of the sensor, and coated on the workbench in a certain way to form a custom microstructure shape distribution dielectric layer mold. After pouring the barium titanate / multi-walled carbon nanotubes / polydimethylsilane (BaTiO3 / MwCNTs / PDMS) composite solution, alcohol with microspheres can also be coated on the uncured colloid according to actual needs to form a hollow microsphere structure on both the top and the bottom.

[0062] The force simulation of the sensor prepared in Example 2 when the force displacement is 1.5 mm is as follows: Figure 4 As shown in the simulation diagram, it can be seen that this structure has a higher sensitivity than Example 1, and a larger displacement can occur under a smaller pressure, which can prove that the preparation method of the adjustable microstructure can prepare sensors with diverse performances. The curve of its displacement and pressure is as follows Figure 6 As shown, the pressure range is 0~5×10 5 kPa, sensor output characteristics (△C / C 0 ) increases linearly with pressure.

[0063] It should be noted that the adjustable microstructure pressure sensor and its preparation method, when in use, uses self-assembly technology, after coating alcohol with polyformaldehyde microspheres, so that polyformaldehyde microspheres of different sizes naturally form a specific distribution under the action of gravity, and by demolding the mold with a custom pattern, the microstructure shape of the pressure sensor medium layer is controlled, thereby achieving the purpose of freely adjusting the microstructure of the sensor medium layer. The microstructure shape and Young's modulus of the sensor can be designed according to actual application requirements, and thus sensors with different performances can be prepared without printing molds.

[0064] The microstructure of the flexible dielectric layer of the present invention does not require the design of a printing mold, and the mold shape can be changed in real time according to the needs of different regions. After demolding, the microspheres with adjustable mold shapes can be recycled and reused. This method can be used to prepare a variety of sensors with different performance characteristics, and the method of changing the mold shape is simple and convenient, highly controllable, and easy to make. It is suitable for a variety of emerging fields such as wearable electronics and human-computer interaction.

[0065] The pressure sensor prepared by the present invention has a simple structure, strong controllability, easy production, sensitive response and low cost, and is suitable for application scenarios with complex pressure responses, such as wearable electronics, electronic skin, robot surface pressure signal capture and many other fields.

[0066] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0067] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0068] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

[0069] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A pressure sensor with an adjustable microstructure and a method for preparing the same, characterized in that: It comprises two groups of external electrodes, a sensitive unit layer is arranged between the two groups of external electrodes, and an adjustable structural component is arranged in the sensitive unit layer.

2. The adjustable microstructure pressure sensor according to claim 1, characterized in that: The adjustable structural member comprises at least one layer of microsphere structure, wherein the layer of microsphere structure comprises a plurality of flat microspheres.

3. The adjustable microstructure pressure sensor according to claim 1, characterized in that: The adjustable structural member comprises two layers of microsphere structures, wherein the microspheres in one layer of the microsphere structure are arranged at intervals, and the microspheres in the other layer of the microsphere structure are arranged in the intervals.

4. The adjustable microstructure pressure sensor according to claim 1, characterized in that: The material of the sensitive unit layer is polydimethylsiloxane; Or it may be a mixed material of polydimethylsiloxane, barium titanate and multi-walled carbon nanotubes.

5. The adjustable microstructure pressure sensor according to claim 1, characterized in that: The microspheres in the microsphere structure are made of one or more of polyethylene, polyoxymethylene, polypropylene or polystyrene.

6. The adjustable microstructure pressure sensor according to claim 1, characterized in that: A packaging layer is arranged on the outer side of the external electrode.

7. A method for preparing a pressure sensor with an adjustable microstructure, characterized in that: The method includes, The obtained microspheres were ultrasonically cleaned in deionized water for 1-10 min, and then dried at 40-60°C for 0.5-1 h; obtaining a sensitive layer solution; After fixing the microspheres, the sensitive layer solution is poured on the surface of the microspheres; After solidification, electrodes are pasted on the upper and lower surfaces and sealed.

8. The method for preparing a pressure sensor with an adjustable microstructure according to claim 7, characterized in that: The microspheres are stored in 75% medical alcohol; the microspheres are fixed on the surface of the sensitive unit layer composed of the sensitive layer solution.

9. The method for preparing a pressure sensor with an adjustable microstructure according to claim 8, characterized in that: The thickness of the sensitive unit layer is 0.1 mm-0.5 mm.

10. The method for preparing a pressure sensor with an adjustable microstructure according to claim 9, characterized in that: The sensitive layer solution is PDMS or a mixed solution of PDMSBaTiO3 / MwCNTs / PDMS.

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