Flexible piezoresistive sensor for human motion detection and manufacturing method thereof
By designing a flexible piezoresistive sensor, the PDMS film, TPU spacer layer, polyimide film, conductive film and flexible interdigital electrode are used to solve the problems of low ductility and large volume of the sensor, and high sensitivity detection and rapid response to human movement are achieved.
Patent Information
- Application Number
- CN202510361402.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-26
- Publication Date
- 2025-06-20
AI Technical Summary
The existing sensors have low ductility, large size, inconvenient portability, and difficult to effectively monitor human movement.
A flexible piezoresistive sensor is designed, including a PDMS film, a TPU spacer layer, a polyimide film, a conductive film and a flexible interdigital electrode, and the flexibility and high sensitivity of the sensor are achieved through the combination of these materials and structures.
It realizes the detection of large and small movements of the human body, has good minimum detection ability, high sensitivity, large linear intervals and fast response, and is suitable for wearable electronic devices.
Smart Images
Figure CN120167947A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of sensors, and particularly to a flexible piezoresistive sensor for human motion detection and a manufacturing method thereof. Background Art
[0002] In the field of health care, real-time personalized motion monitoring and analysis are very important for human health. It can timely detect potential health risks of the human body or monitor the movements and recovery of patients in real time. The real-time piezoelectric signals of human motion are monitored by sensors and sent to wireless devices for display, so that professional medical staff can conduct remote analysis and guidance, which is beneficial to human health and recovery. In order to adapt to human motion, sensors need to have good ductility, small size and be easy to carry. Summary of the Invention
[0003] The purpose of the present invention is to provide a flexible piezoresistive sensor for human motion detection, aiming to solve the problems of low ductility, large size and inconvenient carrying of sensors.
[0004] To achieve the above purpose, the present invention adopts the following technical solutions:
[0005] In the first aspect, a flexible piezoresistive sensor for human motion detection is provided, including: a PDMS film, a TPU spacer layer, a polyimide film, a conductive film and interdigital electrodes.
[0006] A spiky structure is provided on one side of the PDMS film, and the spiky structures are randomly distributed on one side of the PDMS film.
[0007] The conductive film is disposed between the PDMS film and the TPU spacer layer, and the interdigital electrodes are disposed between the TPU spacer layer and the polyimide film.
[0008] In the flexible piezoresistive sensor for human motion detection provided by at least one embodiment of the present disclosure, positioning frames are provided on both the PDMS film and the polyimide film, and the positioning frames are used to position the conductive film and the interdigital electrodes.
[0009] In the flexible piezoresistive sensor for human motion detection provided by at least one embodiment of the present disclosure, a packaging structure is further included.
[0010] The packaging structure is used to package the edges of the PDMS film and the polyimide film.
[0011] In the flexible piezoresistive sensor for human motion detection provided by at least one embodiment of the present disclosure, the packaging structure is a high-temperature tape.
[0012] In at least one embodiment of the present disclosure, in the flexible piezoresistive sensor for human motion detection, the positioning frame is rectangularly arranged.
[0013] In at least one embodiment of the present disclosure, in the flexible piezoresistive sensor for human motion detection, the interdigital electrodes are flexible interdigital electrodes.
[0014] In a second aspect, a method for manufacturing a flexible piezoresistive sensor for human motion detection is provided, including the following steps:
[0015] 1) Fabricate a PDMS film: Mix a PDMS solution and a PDMS curing agent in a weight ratio of 10:1 to prepare a PDMS prepolymer; Place the PDMS prepolymer in a beaker and stir it with a stirrer for 15 minutes; Coat the PDMS mixture on a template to form a film with a spiky structure; Degas the PDMS film with a spiky structure in a vacuum dryer for 30 minutes to remove air bubbles; After curing at 70°C for two hours, peel off the PDMS film with a spiky structure and rinse it twice with absolute ethanol and ultrapure water to remove surface impurities, obtaining a PDMS film with a spiky structure;
[0016] 2) Fabricate a TPU spacer layer: First, add 3.2 g of thermoplastic polyurethane elastomer to 10 mL of tetrahydrofuran solution and stir at room temperature for 4 hours to prepare a precursor solution; Then inject the solution into a 10 mL syringe for electrospinning; Control the feeding speed at 1 mL / h, select a spinning needle gauge of 22G, and apply a voltage of 13 kv between the needle tip and the collector; By changing the electrospinning time to 30 s, 60 s, and 90 s respectively, form TPU spacer layers at three different densities; Finally, peel off the obtained TPU film and cure it at 70°C for 4 hours;
[0017] 3) Fabricate a polyimide film: At room temperature, dissolve 2.11 g of 4,4'-diaminodiphenyl ether solute in 30 g of N-methylpyrrolidone solvent and stir it with a stirrer for 30 minutes; Weigh 2.3 g of pyromellitic dianhydride and slowly add it to the solution, and under the condition of a 30°C water bath, stir it constantly for 2 hours; Use a dropper to drop the solution on a silicon wafer, and adopt a two-step spin-coating method to evenly spread the solution on the silicon wafer. The first step is set at 500 revolutions per minute for 5 seconds, and the second step is set at 3000 revolutions per minute for 1 minute; Place the silicon wafer on a heating table, bake it at 150°C for 5 minutes first, and then bake it at 250°C for 1 hour to form a layer of polyimide film;
[0018] 4) Fabricate the conductive thin film: Prepare a conductive liquid by adding 0.8 g of multi-walled carbon nanotubes to 10 ml of N,N-dimethylformamide solution; place the conductive liquid in a beaker and ultrasonically disperse it at room temperature for 60 minutes; add 10 ml of tetrahydrofuran solution and 3.2 g of thermoplastic polyurethane elastomer to the above solution and stir for 4 hours to prepare an electrospinning solution; place the solution in a vacuum desiccator to degas for 15 minutes to remove air bubbles; draw 17 ml of the electrospinning solution with a 20 ml syringe, and select an 18G needle for the spinning needle, with an inner diameter of 0.86 mm and an outer diameter of 1.26 mm; place the syringe in an electrospinning machine, set the parameters of the electrospinning machine, the solution feeding speed is 5 ml / hour, the electrospinning voltage is set to 20 kV, and the distance between the collector and the needle is set to 15 cm; the collector uses a drum collection method, with a layer of tin foil coated on the drum, and the drum rotation speed is set to 400 revolutions per minute; after spinning, remove the tin foil from the drum, place it in a constant temperature drying oven at 70 °C for 4 hours to cure, peel off the spun conductive film, and rinse it twice with absolute ethanol and ultrapure water to remove surface impurities to obtain the conductive thin film;
[0019] 5) Fabricate the flexible interdigital electrode: Use a dropper to drop photoresist at the center of the polyimide film, and adopt a two-step spin coating method to evenly spread the photoresist on the film. The first step is set to 1500 revolutions per minute for 20 seconds, and the second step is set to 8000 revolutions per minute for 40 seconds; place the silicon wafer with photoresist under a beam of light passing through a mask plate with an interdigital electrode pattern. After partial photoresist is dissolved, spray the surface of the wafer with a low-speed mist flow of potassium hydroxide in a trough, and spray and wash it with distilled water after development; treat the developed silicon wafer with soft oxygen plasma; use a magnetron sputtering system to deposit a 50 nm gold film on the polyimide film; dry it in a vacuum drying oven at 120 °C for 20 minutes to remove the remaining photoresist; peel the polyimide film from the silicon wafer to form a flexible electrode;
[0020] 6) Place the conductive thin film, TPU spacer layer and interdigital electrode between the PDMS film and the polyimide film, and encapsulate the PDMS film, TPU spacer layer, polyimide film, conductive thin film and interdigital electrode.
[0021] The beneficial effects of the present invention are as follows: Through the selection of conductive materials and the design of the sensing structure, the sensor system can detect large and small human movements. In addition, the sensor has good minimum detection, high sensitivity, a large linear range and fast response. The wearable electronic device composed of this sensor can make a substantial contribution in the fields of wearable sensing devices such as electronic skin and artificial intelligence, and has great application value. Description of the Drawings
[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.
[0023] Figure 1 It is a three-dimensional exploded view of a flexible piezoresistive sensor for human motion detection according to the present invention.
[0024] In the figure:
[0025] 10. PDMS film;
[0026] 20. TPU spacer layer;
[0027] 30. Polyimide film;
[0028] 40. Conductive film;
[0029] 50. Interdigitated electrodes. Detailed implementation manners
[0030] The following will clearly and completely describe the technical solutions in the embodiments in conjunction with the accompanying drawings in the embodiments. Obviously, the described embodiments are only some of the embodiments, rather than all of the embodiments.
[0031] Embodiment
[0032] As Figure 1 shown, this embodiment provides a flexible piezoresistive sensor for human motion detection, including a PDMS film 10, a TPU spacer layer 20, a polyimide film 30, a conductive film 40, interdigitated electrodes 50, and a packaging structure (not shown); the conductive film 40 is disposed between the PDMS film 10 and the TPU spacer layer 20, and the interdigitated electrodes 50 are disposed between the TPU spacer layer 20 and the polyimide film 30.
[0033] Rectangular positioning frames (not shown) are bonded to both the PDMS film 10 and the polyimide film 30. The positioning frames are used to position the conductive film 40 and the interdigitated electrodes 50, so that the conductive film 40 and the interdigitated electrodes 50 are located in the middle of the PDMS film.
[0034] The packaging structure is used to package the edges of the PDMS film and the polyimide film. The packaging structure is a high-temperature tape.
[0035] The following will provide an overall introduction to the PDMS film in the embodiments of the present disclosure.
[0036] Specifically, one side of the PDMS film 10 has randomly distributed spiky structures. Its production process involves placing the PDMS mixed solution on sandpaper, and after drying, peeling it off to obtain a surface with micro-protrusions. The sandpaper selected is No. 120 sandpaper. The PDMS film with spiky structures prepared using such sandpaper as a template has excellent sensitivity and conductivity.
[0037] Next, a general introduction to the conductive film 40 of the present disclosure embodiment will be given.
[0038] The conductive film 40 is a film formed by electrospinning multi-walled carbon nanotubes and thermoplastic polyurethane elastomer. The conductive film is installed between the PDMS film and the polyimide film. In the conductive film, the multi-walled carbon nanotubes are contained in the spun fibers formed by the thermoplastic polyurethane elastomer, forming a stable conductive network. The thermoplastic polyurethane elastomer provides good protection, which makes the conductive film have high repeatability, stability, and conductivity.
[0039] Next, a general introduction to the TPU spacer layer 20 of the present disclosure embodiment will be given.
[0040] The TPU spacer layer 20 is a conductive film formed by electrospinning thermoplastic polyurethane elastomer. The introduction of this film allows for the control of electrode contact, thereby avoiding the side effects of preload on sensitivity, and effectively reducing the initial current and tunneling current, improving the performance of the sensor.
[0041] Next, a general introduction to the polyimide film 30 of the present disclosure embodiment will be given.
[0042] The polyimide film 30 serves as a protective layer for the sensor, encapsulating the flexible piezoresistive sensor and functioning to prevent water and dust ingress and protect the core conductive film. Moreover, the polyimide film is soft enough to be attached to the human skin surface, and at the same time, its thickness is sufficient to provide strong support for the sensor.
[0043] Next, a general introduction to the interdigital electrode 50 of the present disclosure embodiment will be given.
[0044] The interdigital electrode 50 uses a flexible interdigital electrode. The fabrication of the flexible interdigital electrode can control the surface roughness and width / space ratio of the electrode, thereby improving the performance of the sensor. Creating a relatively rough electrode surface can generate a greater change in contact between the active material and the electrode under pressure load, thus improving the sensitivity of the sensor. And increasing the width / space ratio of the electrode can reduce the initial contact between the electrode and the material, thereby reducing the initial current of the sensor. The width / space ratio of the fabricated flexible interdigital electrode is 2 / 1.
[0045] During use, the pressure value (kPa) on the flexible piezoresistive sensor can be expressed as:
[0046] P(kPa) = F(N) / S(m 2 );
[0047] Where F(N) represents the external load (compressive force, N) of the sensor, and S(m 2 ) represents the effective sensing area. When the external load of the sensor reaches a certain value, the spiky structure can effectively reduce the effective sensing area, thereby causing an increase in the pressure value on the sensor.
[0048] Next, the preparation method of the flexible piezoresistive sensor for human motion detection will be further disclosed.
[0049] Specifically, the preparation method of the flexible piezoresistive sensor for human motion detection includes the following steps:
[0050] 1) Fabricate the PDMS film: Mix the PDMS solution and the PDMS curing agent at a weight ratio of 10:1 to prepare the PDMS prepolymer; Place the PDMS prepolymer in a beaker and stir it with a stirrer for 15 minutes; Coat the PDMS mixture on the template to form a film with a spiky structure; Degas the PDMS film with a spiky structure in a vacuum dryer for 30 minutes to remove air bubbles; After curing at 70°C for two hours, peel off the PDMS film with a spiky structure and rinse it twice in absolute ethanol and ultrapure water to remove surface impurities, obtaining a PDMS film with a spiky structure;
[0051] 2) Fabricate the TPU spacer layer: First, add 3.2 g of thermoplastic polyurethane elastomer to 10 mL of tetrahydrofuran solution and stir at room temperature for 4 hours to prepare the precursor solution; Then inject the solution into a 10 mL syringe for the electrospinning process; Control the feeding speed at 1 mL / h, select the spinning needle gauge of 22G, and apply a voltage of 13 kv between the tip of the needle and the collector; By changing the electrospinning time to 30 s, 60 s, and 90 s respectively, form the TPU spacer layer at three different densities; Finally, peel off the obtained TPU film and cure it at 70°C for 4 hours;
[0052] 3) Fabricate the polyimide film: At room temperature, dissolve 2.11 g of 4,4'-diaminodiphenyl ether solute in 30 g of N-methylpyrrolidone solvent and stir it with a stirrer for 30 minutes; Weigh 2.3 g of pyromellitic dianhydride and slowly add it to the solution, and under the water bath condition of 30°C, stir it at a constant temperature for 2 hours; Use a dropper to drop the solution on the silicon wafer, and adopt the two-step spin-coating method to spread the solution evenly on the silicon wafer. The first step is set at 500 revolutions per minute for 5 seconds, and the second step is set at 3000 revolutions per minute for 1 minute; Place the silicon wafer on the heating table, bake it at 150°C for 5 minutes first, and then bake it at 250°C for 1 hour to form a layer of polyimide film;
[0053] 4) Fabricate the conductive thin film: Add 0.8 g of multi-walled carbon nanotubes to 10 ml of N,N-dimethylformamide solution to prepare a conductive liquid; place the conductive liquid in a beaker and ultrasonically disperse it at room temperature for 60 minutes; add 10 ml of tetrahydrofuran solution and 3.2 g of thermoplastic polyurethane elastomer to the above solution and stir for 4 hours to prepare an electrospinning solution; place the solution in a vacuum desiccator to degas for 15 minutes to remove air bubbles; draw 17 ml of the electrospinning solution with a 20-ml syringe, and select an 18G needle for the spinning needle, with an inner diameter of 0.86 mm and an outer diameter of 1.26 mm; place the syringe in the electrospinning machine, set the parameters of the electrospinning machine, the solution feeding speed is 5 ml / hour, the electrospinning voltage is set to 20 kV, and the distance between the collector and the needle is set to 15 cm; the collector uses a drum collection method, with a layer of tin foil coated on the drum, and the drum rotation speed is set to 400 revolutions per minute; after spinning, remove the tin foil from the drum, place it in a 70°C constant temperature drying oven to cure for 4 hours, peel off the spun conductive film, and rinse it twice with absolute ethanol and ultrapure water to remove surface impurities to obtain the conductive thin film;
[0054] 5) Fabricate the flexible interdigital electrode: Use a dropper to drop photoresist at the center of the polyimide film, and adopt a two-step spin-coating method to evenly spread the photoresist on the film. The first step is set to 1500 revolutions per minute for 20 seconds, and the second step is set to 8000 revolutions per minute for 40 seconds; place the silicon wafer with photoresist under a beam of light passing through a mask plate with an interdigital electrode pattern. After partial photoresist is dissolved, spray the surface of the wafer with a low-speed mist flow of potassium hydroxide in a trough, and spray and wash it with distilled water after development; treat the developed silicon wafer with soft oxygen plasma; deposit a 50-nm gold film on the polyimide film using a magnetron sputtering system; dry it in a vacuum drying oven at 120°C for 20 minutes to remove the remaining photoresist; peel the polyimide film from the silicon wafer to form a flexible electrode;
[0055] 6) Place the conductive thin film, the TPU spacer layer, and the interdigital electrode between the PDMS film and the polyimide film, and encapsulate the PDMS film, the TPU spacer layer, the polyimide film, the conductive thin film, and the interdigital electrode.
[0056] Although the embodiments of the present application have been shown and described above, the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be thought of without creative efforts should be covered within the protection scope of the present invention; unless otherwise clearly stated, any element, action, or instruction used herein should not be construed as critical or essential.
Claims
1. A flexible piezoresistive sensor for human motion detection, characterized in that: include: PDMS film, TPU spacer layer, polyimide film, conductive film and interdigital electrodes; A thorn-like structure is provided on one side of the PDMS film; The conductive film is arranged between the PDMS film and the TPU spacer layer, and the interdigital electrodes are arranged between the TPU spacer layer and the polyimide film.
2. A flexible piezoresistive sensor for human motion detection according to claim 1, characterized in that: The PDMS film and the polyimide film are both provided with positioning frames, and the positioning frames are used to position the conductive film and the interdigital electrodes.
3. The flexible piezoresistive sensor for human motion detection according to claim 2, characterized in that: Also includes a packaging structure; The packaging structure is used to package the edges of the PDMS film and the polyimide film.
4. The flexible piezoresistive sensor for human motion detection according to claim 3, characterized in that: The packaging structure is a high temperature tape.
5. The flexible piezoresistive sensor for human motion detection according to claim 4, characterized in that: The positioning frame is arranged in a rectangular shape.
6. The flexible piezoresistive sensor for human motion detection according to claim 5, characterized in that: The interdigital electrodes are flexible interdigital electrodes.
7. A method for manufacturing a flexible piezoresistive sensor for human motion detection as claimed in any one of claim 6, characterized in that: The following steps are involved: 1) preparing a PDMS film: mixing a PDMS solution and a PDMS curing agent at a weight ratio of 10:1 to prepare a PDMS prepolymer; placing the PDMS prepolymer in a beaker and stirring with a stirrer for 15 minutes; coating the PDMS mixture on a template to form a film with a spine-like structure; degassing the PDMS film with the spine-like structure in a vacuum dryer for 30 minutes to remove bubbles; after curing at 70° C. for two hours, peeling off the PDMS film with the spine-like structure, and rinsing it twice in anhydrous ethanol and ultrapure water to remove surface impurities, thereby obtaining a PDMS film with a spine-like structure; 2) Preparation of TPU spacer layer: First, 3.2 g of thermoplastic polyurethane elastomer was added to 10 mL of tetrahydrofuran solution and stirred at room temperature for 4 hours to prepare a precursor solution; then the solution was injected into a syringe with a capacity of 10 mL for electrospinning process; the feed rate was controlled to be 1 mL / h, the spinning needle specification was selected to be 22G, and a voltage of 13 kV was applied between the needle tip and the collector; by changing the electrospinning time, a TPU spacer layer was formed at three different densities; finally, the obtained TPU film was peeled off and cured at 70°C for 4 hours; 3) Preparation of polyimide film: at room temperature, dissolve 2.11 g of 4'4-diaminodiphenyl ether solute into 30 g of N-methylpyrrolidone solvent, and stir with a stirrer for 30 minutes; weigh 2.3 g of pyromellitic anhydride and slowly add it to the solution, and stir at a constant temperature for 2 hours in a water bath at 30°C; use a rubber-tipped dropper to drop the solution on a silicon wafer, and use a two-step spin coating method to evenly spread the solution on the silicon wafer, the first step is set to 500 revolutions per minute, the duration is 5 seconds, and the second step is set to 3000 revolutions per minute, the duration is 1 minute; place the silicon wafer on a heating table, first bake at 150°C for 5 minutes, and then bake at 250°C for 1 hour to form a layer of polyimide film; 4) Preparation of conductive film: Add 0.8g of multi-walled carbon nanotubes to 10ml of N,N-dimethylformamide solution to prepare a conductive liquid; place the conductive liquid in a beaker and ultrasonically disperse it at room temperature for 60 minutes; add 10ml of tetrahydrofuran solution and 3.2g of thermoplastic polyurethane elastomer to the above solution and stir for 4 hours to prepare an electrospinning solution; place the solution in a vacuum dryer and degas for 15 minutes to remove bubbles; use a 20ml syringe to extract 17ml of the electrospinning solution, and use an 18G needle with an inner diameter of 0.86mm for the spinning needle. The outer diameter is 1.26mm; the needle tube is placed in the electrospinning machine, and the parameters of the electrospinning machine are set, the solution advancement speed is 5ml / hour, the electrospinning voltage is set to 20kV, and the distance between the collector and the needle is set to 15cm; the collector adopts a drum collection method, a layer of tin foil is coated on the drum, and the drum speed is set to 400 rpm; after the spinning is completed, the tin foil is removed from the drum, and placed in a 70℃ constant temperature drying oven for curing for 4 hours, the spun conductive film is peeled off, and it is rinsed twice with anhydrous ethanol and ultrapure water to remove surface impurities to obtain a conductive film; 5) Making flexible interdigital electrodes: using a rubber-tipped dropper, drip photoresist into the center of the polyimide film, and use a two-step spin coating method to evenly spread the photoresist on the film, the first step is set to 1500 revolutions per minute, the duration is 20 seconds, and the second step is set to 8000 revolutions per minute, the duration is 40 seconds; placing a silicon wafer with photoresist under a beam passing through a mask with an interdigital electrode pattern, after part of the photoresist is dissolved, using potassium hydroxide in a tank to form a mist flow to spray the wafer surface at a low speed, and after development, spray and clean it with distilled water; treating the developed silicon wafer with soft oxygen plasma; using a magnetron sputtering system to deposit a 50nm gold film on the polyimide film; drying at 120°C in a vacuum drying oven for 20 minutes to remove the remaining photoresist; peeling the polyimide film from the silicon wafer to form a flexible electrode; 6) placing the conductive film, TPU spacer layer and interdigital electrodes between the PDMS film and the polyimide film, and encapsulating the PDMS film, TPU spacer layer, polyimide film, conductive film and interdigital electrodes.