Flexible strain sensor for sensing automobile seat and preparation method thereof

Abstract

The invention relates to the technical field of automobile seats, micro-nano sensing technologies and flexible electronics, in particular to a flexible strain sensor for sensing an automobile seat and a preparation method thereof, and the method comprises the following steps: firstly, attaching an MWCNTs dispersion solution to the surface of a fiber CF to prepare an MCF conductive composite material; then, dropwise adding the MWCNTs dispersion solution into the PDMS colloid, heating and stirring, and then adding a curing agent to prepare an MWCNTs / PDMS composite colloid; and finally, pouring the MWCNTs / PDMS colloid into a mold, inserting the dried MCF conductive composite material into the mold for positioning, pouring, and carrying out vacuum curing to obtain the flexible strain sensor. The invention provides a flexible strain sensor for sensing an automobile seat and a preparation method of the flexible strain sensor, and aims to solve the problem that an existing flexible sensor is poor in impact resistance, piezoresistive material structure, sensing performance and the like.

Description

Technical Field

[0001] The present application relates to automobile seats, micro-nano sensing technology and flexible electronic technology, and in particular to a flexible strain sensor for automobile seat sensing and a preparation method thereof. Background Art

[0002] With the advancement of science and technology in recent years, sensors have been widely used in various fields, such as aerospace, military industry, healthcare, and new energy. In the automotive sensing field, sensors in different locations and applications can provide important vehicle information to drivers and passengers, providing real-time feedback on vehicle status. They play an increasingly important role in driving safety and achieving automation. They generate electrical signals when pressure is applied to sensing elements. Signal processing circuits convert the received electrical signals into precise digital signals and transmit them to control modules for subsequent processing, enabling precise monitoring and automatic control. Consequently, various types of automotive sensors have been extensively studied.

[0003] Automotive seat sensors are used in occupant sensing systems to detect whether a seat occupant is present, providing seatbelt warnings and airbag activation, thereby improving driving safety. Piezoresistive strain sensors have attracted widespread attention due to their simple manufacturing process, fast response, and high sensitivity. However, they also suffer from issues such as the inability to combine high sensitivity with a wide stress response range and poor repeatability.

[0004] To date, researchers and designers have been working towards novel piezoresistive materials and structures, aiming to improve sensor sensitivity and pressure-sensitive range, and using these metrics to evaluate the performance of piezoresistive strain sensors. In practical applications of flexible sensors, especially those involving violent vehicle collisions, conventional sensor structures lack the impact resistance, ultimately leading to sensor failure. Therefore, research on sensors with both sensing and impact resistance is of great significance. Summary of the Invention

[0005] The embodiments of the present application provide a flexible strain sensor for automobile seat sensing and a preparation method thereof, aiming to solve the problems of existing flexible sensors in terms of poor impact resistance, piezoresistive material structure, and sensing performance.

[0006] To solve the above technical problems, an embodiment of the present application provides a method for preparing a flexible strain sensor for automobile seat sensing, comprising the following steps: first, attaching a MWCNTs dispersed solution to the surface of a fiber CF to obtain an MCF conductive composite material; then, dripping the MWCNTs dispersed solution into a PDMS colloid, heating and stirring, and then adding a curing agent to obtain a MWCNTs / PDMS composite colloid; finally, pouring the MWCNTs / PDMS colloid into a mold, and inserting the dry MCF conductive composite material into the mold for positioning, and vacuum curing after casting to obtain a flexible strain sensor.

[0007] In some exemplary embodiments, the fiber CF is an acetate filter rod based on cigarette filter material; and the MWCNTs dispersion solution is prepared by mixing multi-walled carbon nanotubes and anhydrous ethanol.

[0008] In some exemplary embodiments, a MWCNTs dispersion solution is attached to the surface of a fiber CF to prepare an MCF conductive composite material, comprising: first, placing MWCNTs and a dispersant in anhydrous ethanol and mixing them to obtain a mixed solution; then, the mixed solution is sequentially dispersed and ultrasonically dispersed to obtain a MWCNTs dispersion solution; finally, a syringe is used to inject the dispersion solution at a predetermined point on the end of a fiber CF filter rod and the mixture is dried to obtain the MCF conductive composite material.

[0009] In some exemplary embodiments, the ratio of MWCNTs to dispersant is 10:1, and the ratio of the mixture of MWCNTs and dispersant to anhydrous ethanol is 50:1; MWCNTs and dispersant are placed in anhydrous ethanol in proportion, and then stirred in a magnetic stirrer for 12 hours to obtain a mixed solution.

[0010] In some exemplary embodiments, the mixed solution is placed in an ultrasonic vibrator for ultrasonic dispersion; the dispersion treatment is carried out at 25° C. and 1500 rpm, the dispersion treatment time is 10 to 12 hours, and the ultrasonic dispersion time is 10 to 15 minutes.

[0011] In some exemplary embodiments, a syringe is used to inject the dispersion at a predetermined point on the end of the fiber CF filter rod. After the injection is completed, the fiber CF is dried in a vacuum oven at 60-70°C for 2 hours; the process of injecting the dispersion and drying is repeated 2-3 times to form a complete conductive network to obtain an MCF conductive composite material.

[0012] In some exemplary embodiments, five injection points are set at the end of the fiber CF filter rod, wherein four edge points are evenly distributed around a central point; 3 mL of dispersion is injected into the central point using a syringe, and 1 mL of dispersion is injected into each of the four edge points.

[0013] In some exemplary embodiments, a MWCNTs dispersed solution is dripped into a PDMS colloid, and a curing agent is added after heating and stirring to prepare a MWCNTs / PDMS composite colloid, including: subjecting the PDMS colloid to magnetic stirring, and during the stirring process, using a dropper to drip the MWCNTs dispersed solution into the high-speed rotating PDMS colloid, and continuing to stir for 2 to 3 hours to obtain a mixed colloid; placing the mixed colloid in a water bath, and magnetically stirring for 3 to 4 hours while completely evaporating anhydrous ethanol; then adding a curing agent to the mixed colloid, with a mass ratio of PDMS colloid to curing agent of 15:1, and magnetically stirring for 20 to 30 minutes to obtain a composite colloid; and vacuuming the composite colloid in a vacuum oven at room temperature.

[0014] In some exemplary embodiments, MWCNTs / PDMS colloid is poured into a mold, and a dry MCF conductive composite material is inserted into the mold for positioning, and vacuum cured after pouring to prepare a flexible strain sensor, including: pouring MWCNTs / PDMS colloid into 1 / 2 of the mold, and slowly inserting the dry MCF conductive composite material into the mold for positioning, letting it stand for 10 to 15 minutes, and then pouring the colloid until it is flush with the mold mouth, and finally placing the sample in a vacuum curing furnace at an environment of 60 to 70°C. After 4 hours, the flexible strain sensor is prepared; after the flexible strain sensor is prepared, it also includes: connecting the flexible strain sensor, the electrochemical workstation, and the fatigue testing machine online to test the specific electrical signal response of the sensor under the action of cyclic load; the flexible strain sensors that have been tested are connected with wires and arranged in a uniform and symmetrical array to obtain a car seat sensor with force-electricity response.

[0015] In a second aspect, an embodiment of the present application also provides a flexible strain sensor for automobile seat sensing, which is manufactured using the preparation method of the flexible strain sensor for automobile seat sensing as described in the above embodiment, and the outer layer of the sensor is provided with a link structure with a bellows shape.

[0016] The technical solution provided by the embodiments of the present application has at least the following advantages:

[0017] This embodiment of the present application provides a flexible strain sensor for automotive seat sensing and its preparation method. The method includes the following steps: first, attaching a MWCNTs dispersion solution to the surface of a fiber (CF) to produce an MCF conductive composite material; then, dripping the MWCNTs dispersion solution into a PDMS colloid, heating and stirring, and adding a curing agent to produce an MWCNTs / PDMS composite colloid; finally, pouring the MWCNTs / PDMS colloid into a mold, inserting the dried MCF conductive composite material into the mold for positioning, and vacuum curing after casting to produce the flexible strain sensor.

[0018] The flexible strain sensor for automotive seat sensing provided in this application is, first, a flexible impact strain sensor based on porous energy-absorbing material, made from an MCF conductive composite material developed based on acetate fiber filter rods (CF). The raw materials are inexpensive and readily available, significantly reducing costs. Secondly, the flexible impact strain sensor based on porous energy-absorbing material proposed in this application utilizes the discovery of a porous material CF with energy-absorbing properties, combining two-dimensional conductive materials (MWCNTs) with three-dimensional porous materials. While maintaining the excellent energy-absorbing properties of CF, two-dimensional MWCNTs are attached to its skeleton to form a three-dimensional, highly efficient conductive network, enhancing its electrical conductivity. This results in the fabrication of an MCF conductive composite material that is both conductive and energy-absorbing, providing a new, cost-effective strategy.

[0019] The flexible impact strain sensor based on porous energy-absorbing materials proposed in this application combines MWCNTs / PDMS composite colloid with MCF conductive composite material. The MWCNTs / PDMS composite colloid fills the pores of the MCF instead of air, which not only solves the problem of poor axial compression recovery performance of the MCF, but also greatly improves the Young's modulus of the sensor. In addition, the flexible impact strain sensor based on porous energy-absorbing materials proposed in this application has extremely high sensitivity, and the sensitivity adjustment method is flexible and changeable. The content of MWCNTs on the MCF skeleton can be changed by adjusting the injection dipping process. In addition, the flexible impact strain sensor based on porous energy-absorbing materials proposed in this application has a bellows-shaped link structure designed on the outer layer of the sensor. This structure enhances the structural stability of the sensor when it is subjected to axial cyclic loads while also improving fatigue resistance. The mechanical properties can be adjusted by changing the corrugation angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] One or more embodiments are exemplarily described by pictures in the corresponding drawings. These exemplifications do not constitute limitations on the embodiments. Unless otherwise stated, the pictures in the drawings do not constitute proportional limitations.

[0021] Figure 1 A schematic flow chart of a method for preparing a flexible strain sensor for automobile seat sensing provided in one embodiment of the present application.

[0022] Figure 2 This is a schematic diagram of the appearance structure of a flexible impact strain sensor based on porous energy-absorbing material provided in one embodiment of the present application.

[0023] Figure 3 A bionic segment structure outside the conductive core of a flexible impact strain sensor based on porous energy-absorbing material provided in one embodiment of the present application.

[0024] Figure 4 This is a schematic diagram of the cross-sectional structure of the conductive core provided in one embodiment of the present application.

[0025] Figure 5 A diagram illustrating the specific dimensions of a 3D printing mold used to manufacture a sensor provided in one embodiment of the present application.

[0026] Figure 6 A flow chart for producing an MCF conductive composite material according to an embodiment of the present application.

[0027] Figure 7 This is a flow chart for preparing MWCNTs / PDMS composite colloid according to one embodiment of the present application.

[0028] Figure 8 A flow chart for manufacturing a sensor according to an embodiment of the present application.

[0029] Figure 9 This is a diagram of the sensing element array of a car seat sensor provided in one embodiment of the present application.

[0030] Figure 10 A comparison curve of the mechanical properties of the sensor and its components provided in one embodiment of the present application.

[0031] Figure 11 This is a gesture recognition test diagram provided in an embodiment of the present application.

[0032] Figure 12 A sensitivity curve diagram provided in an embodiment of the present application.

[0033] Figure 13 Compression cycle test curves under different strains provided in one embodiment of the present application.

[0034] Figure 14 The volt-ampere characteristic curves under different strains provided by an embodiment of the present application. DETAILED DESCRIPTION

[0035] As can be seen from the background technology, existing flexible sensors have problems in terms of impact resistance, piezoresistive material structure, sensing performance, etc.

[0036] To address the above technical issues, the present invention provides a flexible strain sensor for automotive seat sensing and a method for preparing the same. The method comprises the following steps: first, attaching a MWCNTs dispersion solution to the surface of a fiber (CF) to produce an MCF conductive composite material; then, dripping the MWCNTs dispersion solution into a PDMS colloid, heating and stirring, and adding a curing agent to produce an MWCNTs / PDMS composite colloid; finally, pouring the MWCNTs / PDMS colloid into a mold, inserting the dried MCF conductive composite material into the mold for positioning, and vacuum curing after casting to produce a flexible strain sensor. Finally, the flexible strain sensor is measured online with an electrochemical workstation and a fatigue testing machine, revealing its excellent physical and mechanical properties and stable electrical signal response. The sensors are connected by wires in an array to form a car seat sensor. The sensor can transmit the measured electrical signals to relevant vehicle actuators, thereby improving driving and parking safety. This application provides a certain approach and research foundation for the development of vehicle active and passive safety and sensor development.

[0037] The following detailed description of the various embodiments of the present application is provided in conjunction with the accompanying drawings. However, those skilled in the art will appreciate that many technical details are provided in the various embodiments of the present application to facilitate a better understanding of the present application. However, even without these technical details and the various variations and modifications based on the following embodiments, the technical solutions claimed in the present application can still be implemented.

[0038] See Figure 1 The present invention provides a method for preparing a flexible strain sensor for automobile seat sensing, comprising the following steps:

[0039] Step S1: attaching a MWCNTs dispersion solution to the surface of the fiber CF to prepare an MCF conductive composite material.

[0040] Step S2: dripping the MWCNTs dispersed solution into the PDMS colloid, heating and stirring, and then adding a curing agent to prepare a MWCNTs / PDMS composite colloid.

[0041] Step S3: pouring the MWCNTs / PDMS colloid into a mold, inserting the dried MCF conductive composite material into the mold for positioning, and vacuum curing after pouring to obtain a flexible strain sensor.

[0042] Under the premise of taking into account dynamic sensing and impact resistance, the present application develops a more economically conductive composite material using an acetate filter rod (Cellulose Acetate Fiber, CF for short) based on cigarette filter material. The acetate filter rod prepared from acetate fiber has a porosity of more than 70%, has the characteristics of large water permeability and ultra-light weight, and is an anisotropic material, a typical three-dimensional porous material. Due to its high porosity, during the axial compression process, there will be an energy absorption section in the stress-strain curve. In this stage, as the strain increases, the stress does not change significantly, so it has a higher resistance threshold in the axial direction, and can absorb external impact energy through the compression of the pores between the fibers, reducing or eliminating the destructive effects of instantaneous impact on the object. CF has excellent energy absorption characteristics, but is not conductive. In order to meet this condition, it is necessary to combine conductive fillers with CF.

[0043] The conductive filler used in this application is a two-dimensional material multi-walled carbon nanotube (MWCNTs). The MWCNTs need to be configured into a dispersion. Specifically, MWCNTs and a dispersant are placed in an appropriate amount of anhydrous ethanol in proportion, and magnetic stirring and ultrasonic dispersion processes are performed in sequence to complete the dispersion preparation.

[0044] In this application, the three-dimensional porous material CF and the two-dimensional material MWCNTs dispersion are combined together through a dip-coating process. After drying and evaporation, MWCNTs are attached along the CF three-dimensional skeleton with high porosity and energy absorption characteristics, so that CF has conductive properties and is prepared into an MCF conductive composite material, which serves as the highly conductive core of the sensor. The overall shape is cylindrical, with a diameter not exceeding 8 mm and a height not exceeding 13 mm.

[0045] In this application, to overcome the low axial compressive resistance and poor cyclability of conductive composite materials (MCFs), a MWCNTs / PDMS composite colloid was used to fill the fiber pores. This MWCNTs / PDMS composite colloid and MCF were combined to form the main structure of a flexible strain sensor. This effectively compensates for the poor compression cycling of the MCFs, providing support for the three-dimensional skeleton. Furthermore, it significantly increases the Young's modulus of the flexible strain sensor structure, enhancing its axial load-bearing capacity.

[0046] The embodiment of the present application also provides a flexible strain sensor for automobile seat sensing, which is manufactured using the method for manufacturing a flexible strain sensor for automobile seat sensing as described in the above embodiment. The outer layer of the sensor is provided with a link structure in the shape of a bellows, such as Figure 2 and Figure 3In this application, the flexible strain sensor main structure is designed to have a bellows shape by combining MWCNTs / PDMS composite colloid and MCF. The flexible strain sensor is molded using a bellows mold.

[0047] In this application, in order to protect the conductive composite material and improve the impact resistance and cycle performance, such as Figure 4 As shown, a soft PDMS shell is encapsulated on the outside. The shell adopts a bellows-shaped design, which not only adapts to deformation at various angles but also improves the sensor's sealing performance and cycle life. First, a bellows-shaped sensor shell mold was created using 3D printing technology. The mold consists of two symmetrical parts and is printed using a fully transparent resin material. This gives the mold a high degree of transparency, making it easy to observe and adjust the MCF position during sensor preparation.

[0048] In this application, the bellows mold is made of transparent resin material and formed by a 3D printer. The number of mold corrugations changes with the corrugation angle. The corrugation angle is between 45° and 90°, and the number of corrugations is 4 to 10. The mechanical properties of the sensor can be adjusted by changing the corrugation angle or number.

[0049] In this application, the MWCNTs / PDMS composite colloid is filled in a bellows-shaped mold, such as Figure 5 As shown, a casting-curing process was used to fabricate a shock sensor with excellent electrical conductivity, impact resistance, and packaging properties. The bellows shape prevents damage to the internal conductive network when subjected to large external loads (compression or bending). Compared to pure PDMS filling, the MWCNTs / PDMS composite colloid further enhances electrical signal stability and sensitive sensing performance.

[0050] In this application, the flexible strain sensors after curing and molding are arrayed and connected with wires to form the sensing element part of the car seat sensor.

[0051] In this application, the flexible strain sensor after curing and molding has a bellows-shaped MWCNTs / PDMS composite colloid and the synergistic effect of the internal MCF, which leads to stable compression cycle performance, more indentation resistance and more energy dissipation under impact load, showing a stable electrical signal and recovery effect.

[0052] In some embodiments, the fiber CF is an acetate filter rod based on cigarette filter material; and the MWCNTs dispersion solution is prepared by mixing multi-walled carbon nanotubes and anhydrous ethanol.

[0053] In some embodiments, in step S1, the MWCNTs dispersion solution is attached to the surface of the fiber CF to prepare the MCF conductive composite material, including the following steps: Figure 6 As shown, first, MWCNTs and a dispersant are placed in anhydrous ethanol and mixed to obtain a mixed solution; then, the mixed solution is sequentially dispersed and ultrasonically dispersed to obtain a MWCNTs dispersed solution; finally, a syringe is used to inject the dispersion at a predetermined point on the end of a fiber CF filter rod and the mixture is dried to obtain an MCF conductive composite material.

[0054] In some embodiments, the ratio of MWCNTs to dispersant is 10:1, and the ratio of the mixture of MWCNTs and dispersant to anhydrous ethanol is 50:1; MWCNTs and dispersant are placed in anhydrous ethanol in proportion, and then stirred in a magnetic stirrer for 12 hours to obtain a mixed solution.

[0055] In some embodiments, the mixed solution is placed in an ultrasonic vibrator for ultrasonic dispersion; the dispersion treatment is carried out at 25° C. and 1500 rpm, the dispersion treatment time is 10 to 12 hours, and the ultrasonic dispersion time is 10 to 15 minutes.

[0056] In some embodiments, a syringe is used to inject the dispersion at a predetermined point on the end of the fiber CF filter rod. After the injection is completed, the fiber CF is dried in a vacuum oven at 60-70°C for 2 hours; the process of injecting the dispersion and drying is repeated 2-3 times to form a complete conductive network to obtain an MCF conductive composite material.

[0057] In some embodiments, five injection points are set at the end of the fiber CF filter rod, among which four edge points are evenly distributed around a central point; 3 mL of dispersion liquid is injected into the central point with a syringe, and 1 mL of dispersion liquid is injected into the four edge points.

[0058] In some embodiments, in step S2, the MWCNTs dispersed solution is dripped into the PDMS colloid, and a curing agent is added after heating and stirring to prepare a MWCNTs / PDMS composite colloid, which includes the following steps: Figure 7 As shown, the PDMS colloid is magnetically stirred. During the stirring process, the MWCNTs dispersion solution is dropped into the high-speed rotating PDMS colloid with a dropper, and the stirring is continued for 2 to 3 hours to obtain a mixed colloid; the mixed colloid is placed in a water bath and magnetically stirred for 3 to 4 hours while the anhydrous ethanol is completely evaporated; then a curing agent is added to the mixed colloid, the mass ratio of PDMS colloid to curing agent being 15:1, and after magnetic stirring for 20 to 30 minutes, a composite colloid is obtained; the composite colloid is vacuumed in a vacuum oven at room temperature.

[0059] In some embodiments, in step S3, the MWCNTs / PDMS colloid is poured into a mold, and the dried MCF conductive composite material is inserted into the mold for positioning, and vacuum cured after pouring to prepare a flexible strain sensor, including the following steps: Figure 8 As shown, MWCNTs / PDMS colloid is poured into 1 / 2 of the mold, and the dry MCF conductive composite material is slowly inserted into the mold for positioning. After standing for 10 to 15 minutes, the colloid is poured until it is flush with the mold mouth. Finally, the sample is placed in a vacuum curing furnace at 60 to 70°C. After 4 hours, the flexible strain sensor is prepared.

[0060] Then, connect the wires to the prepared sensor substrate. First, wipe the upper and lower ends of the sensor with anhydrous ethanol, air-dry them, and inject a certain amount of conductive silver paste on the upper and lower ends. Then, place the wires on the ends respectively, and finally use tweezers to clamp the copper foil and press it to fix it. Figure 8 As shown. The sensor array of the prepared car seat sensor is assembled as shown. Figure 9 shown. Figure 10 、 Figure 11 and Figure 12 The following graphs show the mechanical performance comparison curves, gesture recognition test graphs, and sensitivity curves of the sensor and its components prepared in this application. The sensor was tested for electrical signal response using "regular rapid pressing for 1 second each" and "random slow pressing." Figure 13 and Figure 14 This indicates that changes in resistance under external load induce changes in current, and the electrical signal response is sensitive. Next, we will conduct further testing on sensors that demonstrate electrical signal response. We will connect the electrochemical workstation to a fatigue testing machine to test the sensor's electrical signal response under cyclic loads. We will also fabricate a seat sensor by connecting the fabricated flexible impact sensors to an array of wires.

[0061] After the flexible strain sensor is made, the method also includes: connecting the flexible strain sensor, electrochemical workstation, and fatigue testing machine to test the specific electrical signal response of the sensor under the action of cyclic load; connecting the tested flexible strain sensors with wires and forming a uniform and symmetrical array to obtain a car seat sensor with force-electricity response.

[0062] The following is a detailed introduction to the preparation method of the flexible strain sensor for automobile seat sensing provided by the present application through specific embodiments.

[0063] It should be noted that the acetate filter rods (CF) used in the following examples were purchased from Huanghelou Cigarettes (China). The anhydrous ethanol used in the following examples was purchased from Wuhan Aopu Chemical Glass Experimental Equipment Co., Ltd. The MWCNTs and corresponding dispersants used in the following examples were purchased from Shenzhen Suiheng Graphene Technology (China). The PDMS and corresponding curing agents used in the following examples were purchased from Dow Corning Inc. (USA).

[0064] This application provides a method for preparing a flexible impact sensor based on a porous energy-absorbing material, the steps of which are as follows:

[0065] Step 1: Preparation of MCF to conductive composite material.

[0066] First, a MWCNTs dispersion solution is prepared, and then the dispersion solution is attached to the surface of the fiber CF through a dip-coating process. After drying, the preparation of the MCF conductive composite material is completed, so that the acetate fiber filter rod has increased conductivity on the basis of its energy absorption characteristics.

[0067] The MWCNTs dispersion solution is prepared by the following method:

[0068] (1) First, MWCNTs and the corresponding dispersant were placed in a certain amount of anhydrous ethanol, and the mixed solution was dispersed at 25 ° C and 1500 rpm for 10-12 hours, and finally ultrasonically dispersed for 10-15 minutes to complete the preparation of the MWCNTs dispersion solution.

[0069] In the example, the ratio of MWCNTs to the corresponding dispersant is 10:1, and the ratio of the two to anhydrous ethanol is 50:1. The mixture is then stirred in a magnetic stirrer for 12 hours, and finally the dispersion is placed in an ultrasonic vibrator for ultrasonic dispersion.

[0070] (2) The dip coating process uses a syringe to inject the dispersion at a predetermined point on the end of the filter rod. After the injection is completed, it is dried in a vacuum oven at 60-70°C for 2 hours. In order to make the MWCNTs completely adhere to the acetate fiber, the injection drying process needs to be repeated 2 to 3 times to form a complete conductive network and obtain the MCF conductive composite material.

[0071] In the example, five injection points are set at the end of the filter rod, one central point and four edge points evenly distributed around it. 3 mL of dispersion liquid is injected into the central point with a syringe, and 1 mL of dispersion liquid is injected into each of the four edge points.

[0072] Step 2: Preparation of MWCNTs / PDMS composite colloid.

[0073] First, magnetically stir an appropriate amount of PDMS colloid. During this stirring process, use a dropper to drop the prepared MWCNT dispersion into the rapidly rotating PDMS colloid. Continue stirring for 2-3 hours to ensure a better mixing of the two. The mixed colloid is then placed in a water bath and magnetically stirred for 3-4 hours while the anhydrous ethanol is completely evaporated. A curing agent is then added to the mixed colloid, with a mass ratio of 15:1 PDMS colloid to curing agent. After magnetic stirring for 20-30 minutes, the composite colloid is evacuated in a vacuum oven at room temperature.

[0074] Step 3: Flexible impact sensor manufacturing process.

[0075] Pour the prepared MWCNTs / PDMS colloid into the 1 / 2 of the mold, slowly insert the dry MCF into the mold and position it. After standing for 10 to 15 minutes, pour the colloid until it is flush with the mold mouth. Finally, place the sample in a vacuum curing furnace at 60 to 70°C. The sensor preparation can be completed after 4 hours.

[0076] Finally, the wires are connected to the prepared sensor substrate. First, clean the upper and lower ends of the sensor with anhydrous ethanol. After air drying, a predetermined amount of conductive silver paste is injected onto the upper and lower ends. The wires are then placed on the ends, and finally, the copper foil is grasped with tweezers and pressed to secure. After the sensor is assembled, its electrical signal response is tested using both a "regular, rapid press of 1 second each" and a "random, slow press" test. Figure 13 and Figure 14 This indicates that changes in resistance under external load stimulation cause changes in current, and the electrical signal response is sensitive. Next, we will conduct further testing on sensors that respond to electrical signals. We will connect the electrochemical workstation to a fatigue testing machine to test the sensor's electrical signal response under cyclic loads.

[0077] Based on the above technical solution, the present invention provides a flexible strain sensor for automotive seat sensing and a method for its preparation. The method includes the following steps: first, attaching a MWCNTs dispersion solution to the surface of a fiber (CF) to produce an MCF conductive composite material; then, dripping the MWCNTs dispersion solution into a PDMS colloid, heating and stirring, and adding a curing agent to produce an MWCNTs / PDMS composite colloid; finally, pouring the MWCNTs / PDMS colloid into a mold, inserting the dried MCF conductive composite material into the mold for positioning, and vacuum curing after casting to produce the flexible strain sensor.

[0078] The flexible strain sensor for automotive seat sensing provided in this application is, first, a flexible impact strain sensor based on porous energy-absorbing material, made from an MCF conductive composite material developed based on acetate fiber filter rods (CF). The raw materials are inexpensive and readily available, significantly reducing costs. Secondly, the flexible impact strain sensor based on porous energy-absorbing material proposed in this application utilizes the discovery of a porous material CF with energy-absorbing properties, combining two-dimensional conductive materials (MWCNTs) with three-dimensional porous materials. While maintaining the excellent energy-absorbing properties of CF, two-dimensional MWCNTs are attached to its skeleton to form a three-dimensional, highly efficient conductive network, enhancing its electrical conductivity. This results in the fabrication of an MCF conductive composite material that is both conductive and energy-absorbing, providing a new, cost-effective strategy.

[0079] The flexible impact strain sensor based on porous energy-absorbing materials proposed in this application combines MWCNTs / PDMS composite colloid with MCF conductive composite material. The MWCNTs / PDMS composite colloid fills the pores of the MCF instead of air, which not only solves the problem of poor axial compression recovery performance of the MCF, but also greatly improves the Young's modulus of the sensor. In addition, the flexible impact strain sensor based on porous energy-absorbing materials proposed in this application has extremely high sensitivity, and the sensitivity adjustment method is flexible and changeable. The content of MWCNTs on the MCF skeleton can be changed by adjusting the injection dipping process. In addition, the flexible impact strain sensor based on porous energy-absorbing materials proposed in this application has a bellows-shaped link structure designed on the outer layer of the sensor. This structure enhances the structural stability of the sensor when it is subjected to axial cyclic loads while also improving fatigue resistance. The mechanical properties can be adjusted by changing the corrugation angle.

[0080] Those skilled in the art will appreciate that the above-described embodiments are specific examples for implementing the present application, and that in actual applications, various changes in form and detail may be made thereto without departing from the spirit and scope of the present application. Any person skilled in the art may make changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be subject to the scope defined in the claims.

Claims

1. A method for preparing a flexible strain sensor for automobile seat sensing, characterized in that: The following steps are involved: The MWCNTs dispersion solution was attached to the surface of fiber CF to prepare the MCF conductive composite material; The MWCNTs dispersed solution was dropped into the PDMS colloid, heated and stirred, and then a curing agent was added to prepare the MWCNTs / PDMS composite colloid; The MWCNTs / PDMS colloid was poured into the mold, and the dried MCF conductive composite material was inserted into the mold for positioning. After pouring, vacuum curing was carried out to produce a flexible strain sensor.

2. The method for preparing a flexible strain sensor for automobile seat sensing according to claim 1, characterized in that: The fiber CF is an acetate filter rod based on cigarette filter material; The MWCNTs dispersion solution is prepared by mixing multi-walled carbon nanotubes and anhydrous ethanol.

3. The method for preparing a flexible strain sensor for automobile seat sensing according to claim 1, characterized in that: The MWCNTs dispersion solution is attached to the surface of the fiber CF to prepare the MCF conductive composite material, including: Putting MWCNTs and dispersant into anhydrous ethanol and mixing them to obtain a mixed solution; The mixed solution is sequentially subjected to dispersion treatment and ultrasonic dispersion to prepare a MWCNTs dispersion solution; The dispersion is injected into a predetermined point on the end of the fiber CF filter rod by using a syringe and then dried to obtain the MCF conductive composite material.

4. The method for preparing a flexible strain sensor for automobile seat sensing according to claim 3, characterized in that: The ratio of MWCNTs to dispersant was 10:1, and the ratio of the mixture of MWCNTs and dispersant to anhydrous ethanol was 50:1; MWCNTs and a dispersant were added to anhydrous ethanol in proportion, and then stirred in a magnetic stirrer for 12 hours to obtain a mixed solution.

5. The method for preparing a flexible strain sensor for automobile seat sensing according to claim 3, characterized in that: The mixed solution is placed in an ultrasonic vibrator for ultrasonic dispersion; The dispersion treatment is carried out at 25° C. and 1500 rpm. The dispersion treatment time is 10 to 12 hours, and the ultrasonic dispersion time is 10 to 15 minutes.

6. The method for preparing a flexible strain sensor for automobile seat sensing according to claim 3, characterized in that: The dispersion was injected into a predetermined point on the end of the fiber CF filter rod using a syringe. After the injection, the fiber CF was dried in a vacuum oven at 60-70°C for 2 hours. The process of injecting the dispersion and drying is repeated 2 to 3 times to form a complete conductive network and obtain an MCF conductive composite material.

7. The method for preparing a flexible strain sensor for automobile seat sensing according to claim 3, characterized in that: Five injection points are set at the end of the fiber CF filter rod, among which four edge points are evenly distributed around a central point; 3 mL of dispersion liquid is injected into the central point with a syringe, and 1 mL of dispersion liquid is injected into the four edge points.

8. The method for preparing a flexible strain sensor for automobile seat sensing according to claim 1, characterized in that: The MWCNTs dispersed solution is dropped into the PDMS colloid, heated and stirred, and then a curing agent is added to prepare a MWCNTs / PDMS composite colloid, including: The PDMS colloid was magnetically stirred. During the stirring process, the MWCNTs dispersion solution was dropped into the high-speed rotating PDMS colloid using a dropper and the stirring was continued for 2 to 3 hours to obtain a mixed colloid. The mixed colloid was placed in a water bath and magnetically stirred for 3 to 4 hours to completely evaporate the anhydrous ethanol; a curing agent was then added to the mixed colloid, with the mass ratio of PDMS colloid to curing agent being 15:1, and magnetically stirred for 20 to 30 minutes to obtain a composite colloid; The composite colloid was vacuum-treated in a vacuum oven at room temperature.

9. The method for preparing a flexible strain sensor for automobile seat sensing according to claim 1, characterized in that: The MWCNTs / PDMS colloid is poured into a mold, and the dried MCF conductive composite material is inserted into the mold for positioning. After pouring, vacuum curing is performed to produce a flexible strain sensor, including: Pour MWCNTs / PDMS colloid into the 1 / 2 of the mold, and slowly insert the dry MCF conductive composite material into the mold for positioning. After standing for 10 to 15 minutes, pour the colloid again until it is flush with the mold opening. Finally, place the sample in a vacuum curing furnace at 60 to 70 ° C. After 4 hours, the flexible strain sensor is completed. After the flexible strain sensor is prepared, the method further includes: The flexible strain sensor, electrochemical workstation, and fatigue testing machine are connected online to test the specific electrical signal response of the sensor under cyclic load; The flexible strain sensors that have been tested are connected using wires and arranged in a uniform and symmetrical array to obtain a car seat sensor with force-electric response.

10. A flexible strain sensor for car seat sensing, characterized in that: The sensor is manufactured by the method for preparing a flexible strain sensor for automobile seat sensing according to any one of claims 1 to 9, and the outer layer of the sensor is provided with a segment structure in the shape of a bellows.

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