Flexible film sensor

Abstract

The invention relates to the technical field of space dust measurement, in particular to a flexible film sensor, which comprises a packaging layer, a fixed substrate, an electrode layer and a sensing unit, and is characterized in that the sensing unit is a PVDF (Polyvinylidene Fluoride) film; the electrode layer comprises an upper electrode layer and a lower electrode layer, and each of the upper electrode layer and the lower electrode layer is of a multi-layer stacked structure prepared through a magnetron sputtering process by taking a PVDF film as a substrate; the fixed substrate comprises an upper fixed substrate and a lower fixed substrate, the upper fixed substrate is fixedly assembled with the upper electrode layer, and the lower fixed substrate is fixedly assembled with the lower electrode layer; the packaging layer comprises an upper packaging layer and a lower packaging layer, the upper packaging layer is fixedly connected with the upper fixing substrate through bolts, and the lower packaging layer is fixedly connected with the lower fixing substrate through bolts. The sensor is used for dust momentum characteristic measurement, the sensitivity of the sensor is improved by performing Au / Cr metal magnetron sputtering on the PVDF film, and meanwhile, the response layer is the polarized PVDF film and has a high piezoelectric coefficient.

Description

Technical Field

[0001] The present application relates to the technical field of space dust measurement, and in particular to a flexible thin film sensor. Background Art

[0002] In the current lunar exploration and deep space exploration missions, the measurement of high-speed dust in space is of vital importance to gaining a deeper understanding of the origin and evolution of the universe, the safe operation of spacecraft, and the health protection of astronauts. However, traditional space dust measurement instruments have a series of challenges, one of which is their large size and weight, which leads to low operational reliability in long-term space environments.

[0003] Currently, the commonly used space dust measurement instruments are often large in size and weight, which limits the carrying of other scientific instruments and experimental equipment. In addition, large-volume measurement equipment also increases the technical difficulty and risk during the launch, deployment and operation of spacecraft. Its size not only increases the mass of the spacecraft, but may also cause instability or have a negative impact on the navigation system, restricting the execution efficiency of space missions.

[0004] In the long-term space environment, these measuring instruments are also faced with factors such as extreme temperature, radiation and microgravity, which may cause the instrument performance to gradually decline or even cause equipment failure. Therefore, in order to improve the accuracy and reliability of space dust measurement, it is urgent to develop more compact, lightweight and advanced measuring instruments that are suitable for long-term space missions. Summary of the invention

[0005] The present application provides a flexible thin film sensor for measuring the momentum characteristics of high-speed dust in space, which has a short response time, a wide detection range, and can also obtain the velocity value of the dust.

[0006] In order to achieve the above-mentioned purpose, the present application provides a flexible thin film sensor, including a packaging layer, a fixed substrate, an electrode layer and a sensitive unit, wherein: the sensitive unit is a PVDF film with a thickness of 8-12μm; the electrode layer includes an upper electrode layer and a lower electrode layer, the upper electrode layer is arranged above the PVDF film, and the lower electrode layer is arranged below the PVDF film, and the upper electrode layer and the lower electrode layer are both multi-layer superimposed structures prepared by a magnetron sputtering process with the PVDF film as a substrate; the fixed substrate includes an upper fixed substrate and a lower fixed substrate, the upper fixed substrate is fixedly assembled with the upper electrode layer, and the lower fixed substrate is fixedly assembled with the lower electrode layer; the packaging layer includes an upper packaging layer and a lower packaging layer, the upper packaging layer is fixedly connected to the upper fixed substrate by bolts, and the lower packaging layer is fixedly connected to the lower fixed substrate by bolts.

[0007] Furthermore, the material of the packaging layer is aluminum alloy.

[0008] Furthermore, the material of the fixed substrate is glass.

[0009] Furthermore, the upper electrode layer and the lower electrode layer are both composed of a superimposed Au layer and a Cr layer, wherein: the Cr layer is sputtered on a PVDF film substrate, and the thickness of the Cr layer is 5-6nm; the Au layer is sputtered on the Cr layer, and the thickness of the Au layer is 50-60nm.

[0010] Furthermore, the PVDF film is prepared by the following steps: Step 1: dissolving PVDF in N-methylpyrrolidone solution; Step 2: applying the mixed solution to the surface of the silicon wafer by magnetic stirring and spin coating; Step 3: removing residual bubbles by a vacuum debubbling process; Step 4: volatilizing the N-methylpyrrolidone solution by evaporating at a high temperature to obtain a PVDF film; Step 5: using dimethyl silicone oil as an insulating medium, performing a high-voltage thermal polarization treatment on the PVDF film by a thermal polarization method.

[0011] Furthermore, the electrode layer is provided with a lead wire, and the lead wire is fixed and led out by means of a clamp and a hollow rivet.

[0012] Furthermore, before the PVDF film is assembled, it is cleaned with alcohol and deionized water, and then plasma treated.

[0013] Furthermore, the speed range of high-speed space dust that can be measured is ≥1km / s, and the maximum flux of space dust that can be measured is 1000 particles / m 2 ·s, sampling rate is 300-350kHz.

[0014] Furthermore, the temperature tolerance range is -30°C-+60°C, the stability is 10%, and the response time is <1s.

[0015] The flexible film sensor provided by the present application has the following beneficial effects:

[0016] This application is used to measure the momentum characteristics of dust. The sensitivity of the sensor is improved by magnetron sputtering of Au / Cr metal on the PVDF film. At the same time, the response layer is a polarized PVDF film with a high piezoelectric coefficient. The sensor is packaged by upper and lower packaging shells made of aluminum alloy. It can not only be installed on the curved surface structure of the spacecraft, but also greatly saves the carrying space and weight. It has the characteristics of short response time, wide measurement range and high measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings constituting a part of this application are used to provide a further understanding of this application, so that other features, purposes and advantages of this application become more obvious. The schematic embodiment drawings and their descriptions of this application are used to explain this application and do not constitute an improper limitation on this application. In the drawings:

[0018] Figure 1 is a schematic diagram of the structure of a flexible film sensor provided according to an embodiment of the present application;

[0019] Figure 2 is a schematic diagram of measuring dust momentum characteristics using a flexible film sensor provided in an embodiment of the present application;

[0020] Figure 3 It is a flow chart of preparing the PVDF film of the flexible film sensor provided in the embodiment of the present application;

[0021] Figure 4 It is a schematic diagram of high-voltage thermal polarization of a PVDF film of a flexible film sensor provided in an embodiment of the present application;

[0022] Figure 5 It is a display diagram of the signal response of the flexible film sensor under the impact state of thermoplastic polyurethane (TPU) particles;

[0023] Figure 6 It is an actual reference diagram for fixing the lead wires of the flexible film sensor provided in the embodiment of the present application;

[0024] In the figure: 1-sensitive unit, 2-upper electrode layer, 3-lower electrode layer, 4-upper fixed substrate, 5-lower fixed substrate, 6-upper packaging layer, 7-lower packaging layer, 8-chuck, 9-hollow rivet. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0026] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0027] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0028] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0029] In addition, the term "plurality" shall mean two or more.

[0030] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0031] like Figure 1 As shown, the present application provides a flexible thin film sensor, including a packaging layer, a fixed substrate, an electrode layer and a sensitive unit 1, wherein: the sensitive unit 1 is a PVDF film with a thickness of 8-12 μm; the electrode layer includes an upper electrode layer 2 and a lower electrode layer 3, the upper electrode layer 2 is arranged above the PVDF film, and the lower electrode layer 3 is arranged below the PVDF film, and the upper electrode layer 2 and the lower electrode layer 3 are both multi-layer stacked structures prepared by a magnetron sputtering process with the PVDF film as a substrate; the fixed substrate includes an upper fixed substrate 4 and a lower fixed substrate 5, the upper fixed substrate 4 is fixedly assembled with the upper electrode layer 2, and the lower fixed substrate 5 is fixedly assembled with the lower electrode layer 3; the packaging layer includes an upper packaging layer 6 and a lower packaging layer 7, the upper packaging layer 6 is fixedly connected to the upper fixed substrate 4 by bolts, and the lower packaging layer 7 is fixedly connected to the lower fixed substrate 5 by bolts.

[0032] Specifically, the flexible film sensor provided in the embodiment of the present application is mainly used for measuring the momentum characteristics of dust, such as Figure 2As shown, the measurement principle is that when space dust hits the sensor, the pressure applied to the surface of the sensitive unit 1 will cause a slight deformation of the PVDF film, resulting in changes in its internal charge distribution; PVDF, as a piezoelectric polymer, will produce changes in charge distribution when under pressure. These changes can be collected and processed by an external signal acquisition system through electrode leads, and then monitored and displayed by an oscilloscope. The signal acquisition system can convert it into an easily detectable voltage signal by setting a specific charge amplification circuit; the intensity of the voltage signal is proportional to the impact force and momentum of the space dust, so the momentum of the space dust can be indirectly detected by measuring the voltage signal.

[0033] More specifically, in the embodiment of the present application, the sensitive unit 1 is a PVDF film, which serves as the core response layer. The PVDF film is subjected to a specific polarization treatment so that the sensor has strong anti-interference ability and higher sensitivity; the electrode layer includes an upper electrode layer 2 and a lower electrode layer 3, which are formed by a magnetron sputtering process with a PVDF film as a substrate in order to enhance the detection capability of space dust and to extract charge signals; the fixed substrate includes an upper fixed substrate 4 and a lower fixed substrate 5, which are used to fix the electrode layer and protect the sensitive unit 1; the packaging layer includes an upper packaging layer 6 and a lower packaging layer 7, in order to reduce the interference of external noise and improve the wear resistance requirements.

[0034] Furthermore, the material of the packaging layer is aluminum alloy. Aluminum alloy material is light in texture and has high mechanical strength, which can improve the overall anti-interference performance of the sensor; the thickness of the upper packaging layer 6 and the lower packaging layer 7 is preferably 15 mm.

[0035] Furthermore, the material of the fixed substrate is glass. The glass substrate has high chemical stability and can resist the influence of radiation, gas and other chemicals in the space environment; this can protect the sensor components from chemical corrosion or damage, and the surface of the glass substrate is flat and has high-quality surface treatment, which helps to maintain the flatness and cleanliness of the sensor surface, thereby improving the accuracy and sensitivity of detecting space dust.

[0036] Furthermore, the upper electrode layer 2 and the lower electrode layer 3 are both composed of a superimposed combination of an Au layer and a Cr layer, wherein: the Cr layer is sputtered using a PVDF film as a substrate, and the thickness of the Cr layer is 5-6nm; the Au layer is sputtered on the Cr layer, and the thickness of the Au layer is 50-60nm.

[0037] Specifically, in the embodiment of the present application, the electrode layer is mainly a superposition combination of Au / Cr layers, wherein the Au layer and the Cr layer are of the same size, and the internal size is preferably 5cm×5cm. The overall receiving area of ​​the electrode layer is large, and it can detect a larger range of space dust, and can firmly fix the polarized PVDF film. The sputtering thickness of the Cr layer is preferably 5nm, and the sputtering thickness of the Au layer is preferably 50nm; Cr, as the bottom layer of Au, enhances the adhesion between the Au layer and the PVDF intermediate layer, and prevents the metal layer from peeling or falling off. The Au layer can protect the Cr layer from oxidation or corrosion, maintain the integrity and stability of the coating, and has good corrosion resistance, protecting the sensor from damage by the external environment. The metal electrode layer composed of Au / Cr, as a sensing transition layer, can not only protect the PVDF film, but also better transmit the electrical signal to the PVDF film, so that the sensor has a higher sensitivity.

[0038] More specifically, the PVDF film with the upper and lower electrode layers 3 sputtered is etched into a suitable shape by nanosecond laser, and the length direction of the sensor should be consistent with the stretching direction of the PVDF film. During the etching process, it is easy to leave a lot of metal burrs on the edge of the metal electrode, which can easily cause the PVDF piezoelectric film to short-circuit in the thickness direction, thereby affecting the normal operation of the sensor made later. Therefore, when etching the PVDF film, it is necessary to process the edge flatness, use acetone and alcohol as corrosive agents, and perform non-metallization treatment on the edge of the PVDF film, that is, corrode the edge electrode burrs that may be connected to the edge, and finally use a multimeter to detect whether there is a short circuit; the film after treatment can avoid short circuit in the thickness direction, ensuring the separation of the electrodes on the two surfaces.

[0039] Further, such as Figure 3 As shown, the PVDF film is prepared by the following steps: Step 1: dissolving PVDF in a quantitative N-methylpyrrolidone solution, wherein the solubility of PVDF in the N-methylpyrrolidone solution is preferably 10%; Step 2: applying the solution to the surface of the silicon wafer by magnetic stirring and spin coating, wherein the rotation speed is set to 300-500rpm, so that the spin coating thickness is thinner, i.e., 26-28μm; Step 3: removing residual bubbles by a vacuum degassing process to ensure the stability and reliability of the film quality; Step 4: volatilizing the N-methylpyrrolidone solution by heating and evaporating, wherein the heating temperature is set to 60°C, and the baking duration is 30 minutes, to obtain a PVDF film; Step 5: using dimethyl silicone oil as an insulating medium, the PVDF film is subjected to high-voltage thermal polarization treatment by a thermal polarization method.

[0040] Specifically, for PVDF film, the stretching process is generally used to obtain a piezoelectric β phase with a high content, but at this time the dipoles in the film are arranged disorderly and do not show electrical properties on a macro scale, so artificial polarization treatment is required. By applying a high voltage, the dipoles in the film can be arranged in an orderly manner along the direction of the external electric field. When the electric field is removed, part of the dipole orientation disappears instantly, and the other part of the dipole orientation remains, which is called the residual polarization intensity, which directly reflects the piezoelectricity of the PVDF film.

[0041] More specifically, in the embodiment of the present application, the PVDP film is treated by high-voltage thermal polarization, such as Figure 4 As shown, the thermal polarization process is accompanied by the movement of molecular chains, ions, and space charges, which causes the film surface to bend and deform, affecting the stable polarization of the sensitive area. Therefore, the polarization process requires a certain pressure to be applied to the sample; preferably, H201# type dimethyl silicone oil is used as the insulating medium. Dimethyl silicone oil has excellent insulation properties, can avoid arcing at the edge of the electrode, and can also apply a higher voltage.

[0042] Furthermore, a lead wire is provided on the electrode layer, and the lead wire is fixed and led out by means of a clamp 8 and a hollow rivet 9 .

[0043] Specifically, Figure 6 As shown, the PVDF film itself has a small thickness and high flexibility, and the electrodes on its surface are relatively thin, so the electrodes cannot be led out by conventional welding methods. In order to ensure a good connection between the led-out wires and the film, the embodiment of the present application preferably uses hollow rivets 9 and crimping terminals for penetrating connection, and leads out the upper and lower electrode layers of the PVDF film in the same direction and on the same surface, thereby maximizing the protection of the charge signal from being transmitted to the front circuit without interference, and is fixed in the form of a clamp 8, which has a small thickness, is convenient for packaging and shielding at the junction of the wires and the electrode layers, and can prevent interference from external signals.

[0044] More specifically, the lead wire is connected to the subsequent signal acquisition system, which mainly includes signal conditioning circuit, signal processing circuit and signal transmission circuit. The signal conditioning circuit is composed of charge amplification and low-pass filtering circuit, which can realize signal conditioning; the signal processing circuit is a power supply circuit, a microprocessor control circuit and a circuit control program design; the signal transmission circuit uses wired transmission to transmit data to the display end; finally, the signal display software is used to realize the visual display of the signal.

[0045] Furthermore, before assembling the PVDF film, it is cleaned with alcohol and deionized water, and then plasma treated. Before assembling the PVDF film, it needs to be pre-treated, first cleaned with alcohol, then cleaned with deionized water, and finally plasma treated; wherein, the vacuum degree of the plasma treatment is set to 30-50Pa, and this pressure level can provide enough gas molecules to form plasma, while maintaining the mean free path of the particles, ensuring that the plasma can effectively interact with the surface of the material for cleaning; after 3 minutes of this vacuum degree, the activity of the PVDF film surface is enhanced, which can improve the dust detection capability of the sensor.

[0046] Furthermore, the speed range of high-speed space dust that can be measured is ≥1km / s, and the maximum flux of space dust that can be measured is 1000 particles / m 2 ·s, sampling rate is 300-350kHz.

[0047] Furthermore, the temperature tolerance range is -30℃-+60℃, the stability is 10%, and the response time is <1so

[0048] Specifically, when space dust hits the PVDF film, the momentum characteristics of the dust can be analyzed based on the conversion relationship between the momentum of the particle and the voltage response of the PVDF film. Figure 5 As shown, under the simulated impact of TPU particles weighing 1g, the electrical signal of the flexible film sensor provided in the embodiment of the present application will respond quickly (response time <1s), and the maximum change reaches 30V, reflecting the characteristics of the sensor's short response time and high sensitivity.

[0049] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A flexible thin film sensor, characterized in that: It includes a packaging layer, a fixed substrate, an electrode layer and a sensitive unit, wherein: The sensitive unit is a PVDF film with a thickness of 8-12 μm; The electrode layer includes an upper electrode layer and a lower electrode layer, wherein the upper electrode layer is arranged above the PVDF film, and the lower electrode layer is arranged below the PVDF film, and the upper electrode layer and the lower electrode layer are both multi-layer stacked structures prepared by a magnetron sputtering process with the PVDF film as a substrate; The fixed substrate comprises an upper fixed substrate and a lower fixed substrate, the upper fixed substrate is fixedly assembled with the upper electrode layer, and the lower fixed substrate is fixedly assembled with the lower electrode layer; The packaging layer includes an upper packaging layer and a lower packaging layer. The upper packaging layer is fixedly connected to the upper fixed substrate by bolts, and the lower packaging layer is fixedly connected to the lower fixed substrate by bolts.

2. The flexible film sensor according to claim 1, characterized in that: The material of the packaging layer is aluminum alloy.

3. The flexible film sensor according to claim 2, characterized in that: The material of the fixed substrate is glass.

4. The flexible film sensor according to claim 3, characterized in that: The upper electrode layer and the lower electrode layer are both composed of a stacked Au layer and a Cr layer, wherein: The Cr layer is formed by sputtering with the PVDF film as a substrate, and the thickness of the Cr layer is 5-6 nm; The Au layer is formed by sputtering on the Cr layer, and the thickness of the Au layer is 50-60 nm.

5. The flexible film sensor according to claim 4, characterized in that: The PVDF film is prepared by the following steps: Step 1: dissolve PVDF in N-methylpyrrolidone solution; Step 2: The mixed solution is applied to the surface of the silicon wafer by magnetic stirring and spin coating; Step 3: Remove the remaining bubbles using a vacuum debubbling process; Step 4: volatilize the N-methylpyrrolidone solution by heating and evaporating to obtain a PVDF film; Step 5: Using dimethyl silicone oil as the insulating medium, the PVDF film is subjected to high-voltage thermal polarization treatment by a thermal polarization method.

6. The flexible film sensor according to claim 5, characterized in that: The electrode layer is provided with a lead wire, and the lead wire is fixed and led out by means of a clamp and a hollow rivet.

7. The flexible film sensor according to claim 6, characterized in that: Before assembling the PVDF film, it is cleaned with alcohol and deionized water, and then plasma treated.

8. The flexible film sensor according to claim 7, characterized in that: The measurable space high-speed dust velocity range is ≥1km / s, and the maximum flux of space dust that can be measured is 1000 particles / m 2 ·s, sampling rate is 300-350kHz.

9. The flexible film sensor according to claim 8, characterized in that: The temperature tolerance range is -30℃-+60℃, the stability is 10%, and the response time is <1s.

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