Preparation method of flexible film pressure sensor
The flexible film pressure sensor with a meandering conductive layer and hollow structure was prepared through hot pressing and laser cutting technology, which solved the problem of large thickness and poor ductility of the sensor, and achieved high-precision pressure tests that adapt to large curvature and small space surfaces.
Patent Information
- Application Number
- CN202411896825.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-20
- Publication Date
- 2025-05-27
AI Technical Summary
The existing flexible film pressure sensors have a large thickness and poor ductility, which cannot adapt to surfaces with large curvature and small spaces, affecting the test accuracy and being easily damaged.
A flexible film pressure sensor is prepared by hot pressing and laser cutting. A meandering conductive layer is prepared by laser cutting, and the electrode layer is combined with the thermoplastic polyurethane elastomer rubber substrate layer by hot pressing to form a hollow area to adapt to different curved surfaces.
The ductility and fatigue resistance of the sensor are improved, making it suitable for stress testing in areas with large curvature and small spaces, such as wrists and elbows, enhancing the test accuracy and reducing the risk of device damage.
Smart Images
Figure CN120043666A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to piezoresistive sensing technology, and in particular to a preparation method of a flexible thin-film pressure sensor. Background Art
[0002] A resistive strain sensor is a sensor that uses resistance change to measure the strain of an object (i.e., the deformation of an object under an external force). Its working principle is based on the strain resistance effect, that is, when a material is stretched or compressed, its resistance value will change. It usually consists of a sensitive element, a substrate material, and electrodes. It is usually made of flexible materials (such as polymers, thin films, etc.) and contains sensitive elements inside. Commonly used materials include conductive polymers, carbon nanotubes, and metal nanowires, etc., which can ensure the stability and accuracy of signal acquisition of the sensor under changing pressures, and have high sensitivity and fast response, and can be used in different scenarios.
[0003] However, at present, some sensors have a relatively large thickness and poor ductility, and cannot adapt to surfaces with large curvatures and small spaces, which affects their test accuracy and the devices are prone to damage. At the same time, larger sensors will affect the original condition of the surface, making the measurement results affected by the sensors. In view of the above disadvantages, sensor devices with a thin thickness and good ductility are needed, and an arrayed structure design is adopted to obtain richer sensing signals of the surface to be measured.
[0004] In view of this, it is necessary to provide a new technical solution to solve the above problems existing in the existing flexible thin-film pressure sensors. Summary of the Invention
[0005] The present invention provides a preparation method of a flexible thin-film pressure sensor, and the method includes the following steps.
[0006] Hot-press one side of the flexible high-temperature resistant material on the release paper, and hot-press a copper foil layer on the other side of the flexible high-temperature resistant material to form a first conductive layer, and the first conductive layer is patterned and exposes the wiring area.
[0007] Connect a wire in the wiring area, connect a water-soluble tape on the other side of the wire, peel the release paper from the flexible high-temperature resistant material, and peel the water-soluble tape in water to form a first conductive layer with a packaging layer, and form a second conductive layer with a packaging layer in the same steps as above.
[0008] Arrange the first packaging layer, the first conductive layer, the pressure-sensitive film, the second conductive layer, and the second packaging layer from bottom to top, and package the device by hot-pressing.
[0009] Further, the first conductive layer is a positive electrode structure, and the second conductive layer is a negative electrode structure.
[0010] Further, the first conductive layer is a negative electrode structure, and the second conductive layer is a positive electrode structure.
[0011] Further, the conductive embryo layer with the release paper attached is cut in a meandering shape by means of laser cutting.
[0012] Further, the conductive layer includes an electrode layer and a substrate layer.
[0013] Further, the substrate layer is thermoplastic polyurethane elastomer rubber.
[0014] Further, the wire is welded using zebra paper.
[0015] Further, the flexible high-temperature resistant material can withstand temperatures above 100 °C.
[0016] Further, the electrode layer in the conductive layer is composed of meandering connecting lines and circular connection points.
[0017] Further, the flexible high-temperature resistant material is selected from thermoplastic polyurethane elastomer rubber, ethylene / vinyl acetate copolymer film, etc.
[0018] Further, the thickness of the flexible high-temperature resistant material is between 0.05 mm and 0.1 mm.
[0019] Further, the pressure-sensitive film is prepared using polyurethane, dioxane reagent, and carbon fiber powder.
[0020] Further, the heating temperature of the pressure-sensitive film is 70 °C - 100 °C, and it is stirred for 3 h.
[0021] Further, the temperature of the hot pressing method is 70 °C - 100 °C, the vacuum time is 20 s - 40 s, and the hot pressing time is 60 s - 90 s.
[0022] In summary, the present invention provides a preparation method of a flexible thin-film pressure sensor by means of hot pressing and laser cutting. By means of laser cutting, a meandering conductive layer is prepared, which enhances the extensibility of the device. Further, by means of hot pressing, the electrode layer is combined with the thermoplastic polyurethane elastomer rubber substrate layer, further enhancing its extensibility and fatigue resistance. The flexible high-temperature resistant material outside the wire and the pressure-sensitive area is removed to form a hollow area to adapt to fitting different curved surfaces, and it can be applied to areas with large curvature and small space, such as pressure testing of parts like wrists and elbows. Description of the Drawings
[0023] Figures 1 to 7 The structural schematic diagrams of the steps of the preparation method of the flexible thin-film pressure sensor provided by the present invention are shown.
[0024] Figure 8 Schematic front view structure of the conductive layer in the flexible thin-film pressure sensor prepared by the preparation method provided by the present invention. Figure 9 Main flow chart of the preparation method of the flexible thin-film pressure sensor provided by the present invention, and also the attached drawing of the abstract of the specification of the present invention. Detailed implementation manners
[0025] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description in conjunction with the attached drawings and preferred embodiments.
[0026] The present invention provides a preparation method of a flexible thin-film pressure sensor. The flexible thin-film pressure sensor obtained by this preparation method has good ductility, a thin thickness, and is applicable to the tests of various scenarios on different curved surfaces.
[0027] Figures 1 to 7 The following shows the schematic structural diagrams of the steps of the preparation method of the flexible thin-film pressure sensor provided by the present invention. Figure 8 Schematic front view structure of the conductive layer of the flexible pressure thin-film sensor prepared by the preparation method provided by the present invention. As Figures 1 to 7 shown, the preparation method of the flexible thin-film pressure sensor provided by the present invention includes the following steps.
[0028] In some implementations of step S1. As Figure 1 shown, a flexible high-temperature resistant material (such as a TPU film embryo layer 3 with a backing paper 2, and the heat-resistant temperature is greater than 100 °C) is hot-pressed on the release paper 1, a copper foil embryo layer 4 is hot-pressed on the other side of the flexible high-temperature resistant material, and a release paper 5 is covered on the upper layer of the copper foil embryo layer 4 to protect the copper foil embryo layer 4.
[0029] The above-mentioned release paper 1, backing paper 2, and release paper 5 are removed to form a first conductive layer embryo layer 14 (composed of a TPU film embryo layer 3 and a copper foil embryo layer 4). As Figure 2 shown, the first conductive layer embryo layer 14 is patterned and exposes the wiring area.
[0030] In some of the above implementations, the release paper 1 (the release paper can be used multiple times) is used as a support layer, and the release paper 5 is covered on the copper foil embryo layer 4 to play a protective role. By hot-pressing, the TPU film embryo layer 3 is fully combined with the release paper 1. While removing the air bubbles between the films, the first conductive layer embryo layer 14 is fixed to prevent the device from bending and deforming during the subsequent laser cutting process, resulting in processing failure.
[0031] In some of the above embodiments, the entire copper foil and the TPU film embryo layer 3 supported by the release paper 1 are hot-pressed using a dry film machine, and vacuum treatment is performed. After discharging the air gap between the TPU film embryo layer 3 and the copper foil, the release paper 5 is removed to complete the preparation of the materials.
[0032] In some of the above embodiments, the first conductive layer embryo 14 is cut using a laser cutting machine to complete the preparation of the meandering electrode pattern, and the first conductive layer 15 (composed of the TPU film 6 and the copper foil 7) is formed as Figure 3 shown.
[0033] More specifically, the first conductive layer 15 has a layer of TPU film 6 that functions to fix the copper foil 7. During hot pressing, a layer of polytetrafluoroethylene film is pasted on the upper hot pressing template and the lower hot pressing template respectively to prevent the first conductive layer 15 from being damaged by direct contact with the upper and lower hot pressing templates. Therefore, it is necessary to control the temperature of the upper and lower templates of the dry film machine, the vacuum time, and the film pressing time: the upper film temperature is 100 °C, the lower film temperature is 70 °C, the vacuum time is 20 s - 40 s, and the film pressing time is 60 s - 90 s. During laser cutting, the laser cutting parameters are: the power is 72 W - 80 W, the cutting frequency is 50 kHz - 60 kHz, the number of cutting times per time is 10 times until the pattern falls off, and the focusing distance is adjusted according to the thickness of the actual processed device.
[0034] As Figure 4 shown, a zebra paper (i.e., the lower wire 8) is used as the connecting wire for welding. Since it has good adhesion and folding performance, it can adapt to a variety of different curved surfaces, and itself has an ultra-thin performance. When pasting on the surface, there is no protrusion, which greatly reduces the measurement error.
[0035] More specifically, during welding, the welding temperature of the soldering iron rises to between 300 °C and 350 °C, and the welding time is 3 s - 5 s. During welding, since the melting temperature of the TPU film material is between 90 °C and 150 °C, in order to prevent it from melting due to direct contact with the soldering iron, a layer of polytetrafluoroethylene film is covered above the zebra paper for heat insulation.
[0036] The TPU film 6 and the copper foil 7 are the products corresponding to the TPU film embryo layer 3 and the copper foil embryo layer 4 after laser cutting.
[0037] In some of the embodiments of step S2. As Figure 5 shown, a water-soluble tape 9 is connected to the other side of the wire to separate the first conductive layer 15 from the release paper 1. As Figure 6 shown, after hot-pressing another large-area TPU film containing a backing paper under the TPU film 6 and removing the peripheral backing paper, it is used as the first encapsulation layer 17. The water-soluble tape 9 is peeled off in water.
[0038] More specifically, since the width of the copper foil 7 is 0.5 mm, and after the release paper 1 as the support layer is hot-pressed, it is tightly bonded to the underlying TPU film. Without other assistance, the copper foil 7 is extremely prone to breakage during peeling; while the water-soluble tape 9 has strong adhesiveness and dissolves in water, it can effectively serve as a peeling auxiliary material; after peeling, it is placed in water for 1 h - 2 h, or in warm water for about 1 h, and it can be dissolved, thus completing the preparation of the first encapsulation layer 17 and the first conductive layer 15.
[0039] The pressure-sensitive film 10 can be prepared by using PU (polyurethane) particles, dioxane reagent, carbon fiber powder, pure water, and PPG (polyether) dispersant.
[0040] The preparation steps of the pressure-sensitive film 10 are as follows: Weigh 0.5 g of PU particles, add 4.5 ml of dioxane solvent and 0.5 ml of pure water, heat and stir at 90 °C on a magnetic heating stirrer for 3 hours to obtain a PU solution; add 0.2 g of carbon fiber powder and 0.01 g of polyether dispersant to the PU solution, and stir evenly to obtain a carbon fiber / PU mixed solution; pour the carbon fiber / PU mixed solution into a film-making machine, press it into a film, and the thickness of the dried film is 0.1 mm. Use a laser cutting machine to cut the pressure-sensitive layer. Since its temperature resistance, hardness, and thickness are different, the cutting parameters are different from those for cutting the copper foil. The parameters are: power 40 W - 56 W, cutting frequency 50 kHz - 60 kHz, number of cuts per time 5 times, until the pattern falls off, and the focusing distance is adjusted according to the thickness of the actual processed device.
[0041] In some implementations of step S3, the first encapsulation layer 17, the first conductive layer 15, the pressure-sensitive film 10, the second conductive layer 16 (composed of the second TPU film 13 and the second copper foil 12), and the second encapsulation layer 18 are arranged from bottom to top, and the device is encapsulated by a hot-pressing method. Figure 7 It is an overall encapsulation structure.
[0042] Further, the second conductive layer 16 and the second encapsulation layer 18 are prepared in the same steps as the first conductive layer 15 and the first encapsulation layer 17.
[0043] Further, in this embodiment, as Figure 7 shown, the first conductive layer 15 and the second conductive layer 16 are arranged above and below the pressure-sensitive film 10. The first conductive layer 15 and the second conductive layer 16 are respectively connected to the lower wire 8 and the upper wire 11 to form a sensing unit. A plurality of sensing units are arranged in an array, and the array collects sensing information.
[0044] In this embodiment, the first conductive layer 15 and the second conductive layer 16 are composed of a collection area with circular connection points and a meandering connection line, as Figure 8As shown. The width of the meandering connecting line at the tail of the conductive layer pattern can be 0.3 mm - 0.5 mm, the radius of the circular acquisition area is 2 mm, and the line widths of the lower wire 8 and the upper wire 11 can be 0.5 mm - 1 mm.
[0045] Furthermore, during hot pressing, a layer of polytetrafluoroethylene film is pasted on the upper hot pressing template and the lower hot pressing template respectively to prevent the first encapsulation layer 17 and the second encapsulation layer 18 from being damaged by direct contact with the lower hot pressing template and the upper hot pressing template. Therefore, it is necessary to control the temperature of the upper and lower templates of the dry film machine, the vacuum time, and the film pressing time: the upper film temperature is 100 °C, the lower film temperature is 70 °C, the vacuum time is 20 s - 40 s, and the film pressing time is 60 s - 90 s.
[0046] Furthermore, more specifically for the above steps, the hot-pressed flexible sensor device is subjected to a hollowing-out process.
[0047] In this embodiment, the overall thickness of the device is between 0.2 mm and 0.3 mm.
[0048] More specifically, a laser cutting method is used for the hollowing-out process. The purpose is to prevent mutual interference between the electrodes and increase the ductility. The laser cutting parameters are: the power is 72 W - 80 W, the cutting frequency is 50 kHz - 60 kHz, the number of cuts per time is 10 times until the pattern falls off, and the focusing distance is adjusted according to the actual thickness of the processed device.
[0049] To better illustrate the technical solution of the present invention, it is further illustrated by the following examples.
[0050] The TPU film and the pressure-sensitive film are respectively cleaned with an anhydrous ethanol solution to remove impurities and oil stains on the surfaces of the TPU film and the pressure-sensitive film, so as to reduce the influence of other factors on the overall device. In the above preparation method, a laser cutting process is used to prepare the conductive layer, and a hot pressing process is used to encapsulate the flexible device, which can make the conductive layer closely arranged on the flexible substrate, and the layout of each acquisition area and the wire arrangement will not interfere with each other.
[0051] Furthermore, since the acquisition areas on the device are arranged by multiple pressure-sensitive unit arrays, the pressure signals distributed in space at any part of the surface can be collected at one time, and the collected signals are richer. Through the one-piece forming method, the conductive layer has a circular connection point and a meandering connection line structure, which can greatly improve the ductility of the device, fit the surface better, and better realize the acquisition of pressure signals at small areas, large curvatures, and large deformation positions.
[0052] Furthermore, the pressure signal is transmitted through the transmission unit, which facilitates the pressure sensor device to realize the wearable function.
[0053] That is, in this embodiment, the first conductive layer 15 and the second conductive layer 16 are respectively connected to the acquisition module through the lower wire 8 and the upper wire 11, and the connecting wires can be folded arbitrarily without damage, which facilitates the pressure sensor device to realize the wearable function.
[0054] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.
Claims
1. A method for preparing a flexible thin film pressure sensor, characterized in that: The method comprises the following steps. One side of the flexible high temperature resistant material is hot pressed on the release paper, and the copper foil layer is hot pressed on the other side of the flexible high temperature resistant material to form a first conductive layer germ layer, which is patterned and exposes the wiring area. Connect the wires in the wiring area, transfer them as a whole onto the flexible high temperature resistant material using a water-soluble tape, peel off the water-soluble tape in water to form a first conductive layer with an encapsulation layer, and form a second conductive layer with an encapsulation layer using the same steps as above. The first packaging layer, the first conductive layer, the pressure-sensitive film, the second conductive layer, and the second packaging layer are arranged from bottom to top, and the device is packaged by hot pressing.
2. The method for preparing the flexible thin film pressure sensor according to claim 1, characterized in that: The conductive layer includes a positive electrode structure and a negative electrode structure, and a small gap is provided between the positive electrode structure and the negative electrode structure to form a hollow area. The first conductive layer is a positive electrode structure, and the second conductive layer is a negative electrode structure: or The first conductive layer is a cathode structure, and the second conductive layer is a cathode structure.
3. The method for preparing the flexible thin film pressure sensor according to claim 1, characterized in that: The flexible high temperature resistant material can withstand temperatures above 100°C.
4. The method for preparing the flexible thin film pressure sensor according to claim 1, characterized in that: The flexible high temperature resistant material is selected from one of thermoplastic polyurethane elastomer rubber and ethylene / vinyl acetate copolymer film. The thickness of the flexible high temperature resistant material is between 0.05 mm and 0.1 mm.
5. The method for preparing the flexible thin film pressure sensor according to claim 1, characterized in that: When forming the conductive layer, the method comprises the following steps: The conductive embryonic layer with the release paper attached thereto is cut by laser, and the formed conductive layer includes an electrode layer and a substrate layer.
6. The method for preparing the flexible thin film pressure sensor according to claim 1, characterized in that: The pressure-sensitive film shown is prepared by using polyurethane, dioxane reagent, and carbon fiber powder.
7. The method for preparing the flexible thin film pressure sensor according to claim 6, characterized in that: The heating temperature of the pressure-sensitive film is 70° C.-100° C. and the film is stirred for 3 hours, and the pressure-sensitive film is arranged in an array.
8. The method for preparing the flexible thin film pressure sensor according to claim 1, characterized in that: The conductive layer is composed of meandering connection lines and circular connection points.
9. As claimed in claim 1, the conductive layer is transferred from the release paper to the flexible high temperature resistant material using a water soluble tape.
10. The method for preparing a flexible thin film pressure sensor as claimed in claim 1, wherein the hot pressing method is characterized by: temperature of 70°C-100°C, vacuum time of 20s-40s, and hot pressing time of 60s-90s.