A RB / CB composite flexible strain sensor and its preparation method and application

Abstract

The present invention discloses an RB / CB composite flexible strain sensor and a preparation method and application thereof. A latex rubber ring is completely immersed in xylene to swell the latex rubber ring to obtain a swollen latex rubber ring. Conductive carbon black is added to a mixed solvent of tetrahydrofuran and water to obtain conductive ink. The swollen latex rubber ring is immersed in the conductive ink and subjected to an immersion treatment to obtain the RB / CB composite flexible strain sensor. The method provided by the present invention has the advantages that the preparation process and materials have little environmental pollution, the materials are low-priced, abundant and easily available, and the provided sensor can accurately recognize human body movements, has high sensitivity and fast response speed.

Description

Technical Field

[0001] The present invention belongs to the field of flexible electronic devices, and in particular relates to a RB / CB composite flexible strain sensor and a preparation method and application thereof. Background Art

[0002] The demand for flexible strain sensors has grown rapidly in recent years, primarily due to their potential applications in a wide range of fields, including sports, personal health monitoring, soft robotics, and prosthetic devices. These sensors are highly bendable and stretchable, allowing them to tightly adhere to objects and monitor their deformation and strain in real time. Integrating flexible strain sensors into sports equipment can enable more accurate posture detection and motion tracking, thereby improving athletic performance and safety. Furthermore, flexible strain sensors need to maintain excellent electrical conductivity and compatibility with the human body even under prolonged stretching. Therefore, with the continuous advancement of technology and the expansion of application areas, it is of great significance to prepare flexible composite sensors that are harmless to the human body, have high stretchability, and are simple and inexpensive to prepare.

[0003] Traditional flexible conductive composites are composed of an elastic substrate and a conductive material, designed to maintain electrical conductivity under extreme deformations such as bending and stretching. However, the conductive portion of such materials often suffers from poor stability, making the fabrication process for strain sensors relatively complex and costly, which limits their widespread adoption in practical applications. RB, with its high tensile properties and low cost, is an ideal material for ultra-stretchable strain sensors. Common conductive materials include carbon nanotubes, metal nanowires and nanosheets, graphite, graphene, metal particles, and two-dimensional materials such as MXene. Conductive carbon black, primarily composed of carbon, is widely used in many fields due to its excellent electrical and thermal conductivity. Its high electrical conductivity enables rapid transmission of electrical energy while maintaining the continuity and stability of the current flow. This makes it widely used in sensors, smart electronics, batteries, and other fields. Conductive carbon black also has good thermal conductivity. It not only has good electrical conductivity but also high thermal conductivity. It releases heat through conduction, effectively reducing the material's temperature and improving the heat resistance and lifespan of electronic components. At the same time, its particles are small and uniform, which makes it easy to prepare them into thin films and coatings, or to mix them with other materials. Good oxidation resistance. Conductive carbon black has excellent oxidation resistance and is not prone to oxidation reactions, so it can maintain the long-term stability and reliability of the material. This makes it play an important role in the preparation of electronic components with high oxidation stability. Low cost. Compared with other conductive materials (such as metals, carbon nanotubes, etc.), the production cost of conductive carbon black is relatively low. It can be prepared from resources such as petroleum products or natural gas, so it is widely used in many large-scale production occasions. In recent years, the preparation cost of many flexible sensors has been high, the stability of the sensors has been relatively poor, and the conductivity has decreased after repeated cycles of use. Therefore, it is necessary to prepare flexible materials and conductive materials with a wide detection range, good conductivity, low preparation cost, and good stability. Summary of the Invention

[0004] In order to solve the above technical problems, improve the pulling performance of traditional flexible strain sensors, and increase the stability and conductivity of the sensors, the first object of the present invention is to provide a preparation method of a RB / CB composite flexible strain sensor.

[0005] The second object of the present invention is to provide a RB / CB composite flexible strain sensor prepared by the above preparation method.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a preparation method of an RB / CB composite flexible strain sensor, comprising the following steps: completely immersing a latex rubber ring in xylene to swell the latex rubber ring to obtain a swollen latex rubber ring; adding conductive carbon black to a mixed solvent of an organic solvent and water to obtain a conductive ink; immersing the swollen latex rubber ring in the conductive ink, and performing an immersion treatment to obtain the RB / CB composite flexible strain sensor; the organic solvent is selected from tetrahydrofuran and / or N,N-dimethylformamide.

[0008] In the present invention, latex rubber rings are directly used as raw materials. Compared with other modified rubbers, latex rubber rings are cheaper and have the advantages of high elasticity, wear resistance, oxidation resistance, and chemical corrosion resistance. However, it is difficult to compound with conductive carbon black. The present invention obtains conductive ink by adding conductive carbon black to a mixed solvent of tetrahydrofuran and / or N,N-dimethylformamide and water. Since tetrahydrofuran and / or N,N-dimethylformamide can form hydrogen bonds with the latex rubber ring, the molecules of the latex rubber ring are dispersed therein, thereby increasing the roughness of its surface and achieving the purpose of carbon black adhering to its surface, thereby obtaining an RB / CB composite flexible strain sensor.

[0009] In a preferred embodiment, the latex rubber ring is first cleaned and pretreated. The cleaning and pretreatment process is as follows: the latex rubber ring is added to ethanol and ultrasonically cleaned for 1 to 4 minutes, and then the cleaned latex rubber ring is vacuum-dried at 50 to 60° C. for 10 to 30 minutes.

[0010] In the treatment process of the present invention, the cleaned latex rubber ring needs to be vacuum dried at 50-60° C. If the temperature is too high, it will affect the adsorption of carbon black on the surface.

[0011] In a preferred embodiment, the latex rubber ring is completely immersed in xylene for 12 to 24 hours.

[0012] By completely immersing the latex rubber ring in xylene for 12 to 24 hours, the latex rubber ring will swell, its volume will expand 1 to 2 times its original size, and it will become more transparent and elastic. However, the immersion time needs to be effectively controlled. If the immersion time is too long, it will affect the original tensile properties of the latex rubber ring. If the time is too short, the swelling is insufficient and the adsorption uniformity of the conductive carbon black on its surface will be affected.

[0013] In a preferred embodiment, in the mixed solvent of the organic solvent and water, the volume ratio of tetrahydrofuran to water is 1:3-4.

[0014] The inventors found that the ratio of organic solvent and water needs to be effectively controlled. The mixed solvent needs to ensure that the solubility of carbon black in tetrahydrofuran is lower than the solubility of carbon black in xylene, so that the carbon black is stripped from the liquid phase of the mixed solvent and adsorbed on the expanded RB surface. An unreasonable volume ratio will affect the solubility of carbon black in the mixed solvent, and will also have a great impact on the degree and uniformity of carbon black adsorption on the RB surface.

[0015] In actual operation, after the organic solvent and water are mixed in proportion, a glass rod is used to stir for 1 to 3 minutes to allow the water and tetrahydrofuran to be fully mixed.

[0016] In a preferred embodiment, conductive carbon black is added to a mixed solvent of an organic solvent and water, and after sealing, ultrasonic treatment is performed for ≥3 minutes to obtain conductive ink.

[0017] In actual operation, after adding conductive carbon black to a mixed solvent of tetrahydrofuran and water, the mixture is sealed with a polyethylene film and placed in an ultrasonic cleaning machine for ultrasonic treatment, so that the conductive carbon black is evenly dispersed in the solvent to obtain a more uniform conductive ink. In the present invention, the sealing process can prevent the volatilization of tetrahydrofuran, thereby ensuring the ratio of tetrahydrofuran to water.

[0018] In a preferred embodiment, the conductive carbon black concentration in the conductive ink is 0.01-0.02 g / ml. The inventors have found that controlling the conductive carbon black concentration within this range results in the most complete and uniform adsorption of the conductive carbon black on the surface of the latex rubber ring, resulting in optimal performance. Excessively high or low concentrations of the conductive carbon black can affect adsorption of the carbon black on the RB surface.

[0019] In a preferred embodiment, the immersion treatment time is ≥ 20 min, preferably 20 to 50 min.

[0020] In a preferred embodiment, after the impregnation treatment, the resulting conductive latex rubber ring is vacuum dried at 50-60°C for 2-5 hours, then immersed in ethanol for cleaning, and then vacuum dried at 50-60°C for 10-30 minutes to obtain the RB / CB composite flexible strain sensor. In the present invention, the drying process after the impregnation is also required to be controlled at a temperature of 50-60°C.

[0021] The present invention also provides a RB / CB composite flexible strain sensor prepared by the above preparation method.

[0022] The present invention also provides an application of a RB / CB composite flexible strain sensor prepared by the above-mentioned preparation method, and the RB / CB composite flexible strain sensor is applied to flexible wearable electronic products.

[0023] The RB / CB composite flexible strain sensor of the present invention has high tensile properties and a wide detection range. The sensor is made of a latex rubber ring as a stretching material. The latex rubber ring has good scalability and elasticity and can adapt to strains of various shapes and sizes. This enables the rubber band to achieve a wide range of strain measurements and can be installed and used on a variety of curved surfaces and structures. The latex rubber ring is very sensitive to strain, and even tiny strains can be accurately detected. This allows the latex rubber ring to be used for high-precision strain measurement and posture monitoring. The rubber band can be cut, stretched and customized as needed to meet the requirements of different strain measurements. Its shape and size can be adjusted according to the needs of specific applications and has good plasticity.

[0024] The RB / CB composite flexible strain sensor of the present invention changes its resistance when the latex rubber ring is subjected to tensile strain. Specifically, when the latex rubber ring is stretched, its internal conductivity path changes, causing the resistance to increase or decrease. This is because tensile strain causes changes in the electronic structure within the latex rubber ring, thereby affecting the flow of electrons in the material. Therefore, by measuring the change in the resistance of the latex rubber ring, we can indirectly understand the degree of tensile strain it has been subjected to.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention features a simple preparation method. Latex rubber rings and conductive carbon black are both relatively low-cost materials, so combining them into a composite material enables cost-effective flexible strain sensor designs. The conductive carbon black in the composite material typically exhibits excellent corrosion and wear resistance, maintaining stable conductivity over extended use. This makes the composite material excellent for strain measurement applications requiring long-term use and exposure to harsh environmental conditions.

[0027] 2. The conductive carbon black of the present invention is a material with excellent electrical conductivity. Combining it with a latex rubber ring can significantly improve the material's electrical conductivity. This means that the composite material can conduct current more efficiently, thereby achieving more accurate resistance measurement.

[0028] 3. The latex rubber ring and conductive carbon black composite material of the present invention exhibits excellent plasticity and can be cut, stretched, and customized as needed. This makes the composite material suitable for strain sensor designs of various shapes and sizes, adapting to different strain measurement requirements. The latex rubber ring offers excellent flexibility and scalability, while the conductive carbon black exhibits high strength and durability. Combining the two enhances the mechanical stability of the composite material, enabling it to withstand significant strain without losing functionality.

[0029] In summary, the composite material of latex rubber rings and conductive carbon black in this invention exhibits beneficial effects in flexible strain sensors, including improved conductivity, enhanced mechanical stability, plasticity and customizability, durability and stability, and cost-effectiveness. These characteristics make this composite material an ideal choice for various strain measurement and posture monitoring applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Flow chart of the preparation of a RB / CB composite flexible strain sensor according to an embodiment of the present invention;

[0031] Figure 2 This is a SEM photo of the RB / CB composite flexible strain sensor prepared in Example 1 of the present invention, wherein Figure 2 (a) with Figure 2 (b) SEM photos at different magnifications.

[0032] Figure 3 The RB / CB composite flexible strain sensor prepared in Example 1 of the present invention and the graph of the electrical signal changes when detecting finger joint motion;

[0033] Figure 4 This is a graph showing the resistance change rate versus time during the stretching-releasing process of the RB / CB composite flexible strain sensor prepared in Example 1 1000 times;

[0034] Figure 5 This is a comparison chart of the RB / CB composite flexible strain sensor prepared in Example 1 under different strain cycle loading tests.

[0035] Figure 6 RB / CB composite flexible strain sensor prepared in Comparative Example 1 Figure 6 (b) RB / CB composite flexible strain sensor prepared in Example 1 Figure 6 (a) Comparative Example.

[0036] Figure 7 This is the response time diagram of the RB / CB composite flexible strain sensor prepared in Example 2, where Figure 7 (a) is the response time diagram of stretching and releasing in Example 2, Figure 7 (b) is the response time diagram of stretching and releasing of Example 2.

[0037] Figure 8 is the resistance value of the RB / CB composite flexible strain sensor prepared in Example 1 and Comparative Example 2, where Figure 8 (a) is the resistance value of the RB / CB composite flexible strain sensor prepared in Example 1, and Figure (b) is the resistance of the RB / CB composite flexible strain sensor prepared in Comparative Example 2. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0039] Example 1

[0040] Step 1: Place the latex rubber ring in ethanol and ultrasonically clean it for 2 minutes, then place the cleaned latex rubber ring in a vacuum drying oven at 55° C. and dry it for 15 minutes.

[0041] Step 2: Immerse the latex rubber ring completely in xylene for 12 hours. The latex rubber ring will swell and its volume will expand to 1 times its original size, and it will become more transparent and elastic.

[0042] Step 3: Mix tetrahydrofuran and water in a ratio of 1:4 and stir with a glass rod for 2 minutes to allow the water and tetrahydrofuran to be fully mixed.

[0043] Step 4: Add conductive carbon black to the solvent prepared in step 3 and mix to prepare a conductive ink having a conductive carbon black concentration of 0.01 g / ml.

[0044] Step 5: Seal the conductive ink from step 4 with a polyethylene film and place it in an ultrasonic cleaning machine for ultrasonic treatment to allow the conductive carbon black to be evenly dispersed in the solvent to obtain a more uniform conductive ink.

[0045] Step 6: Completely immerse the latex rubber ring prepared in step 2 in the conductive ink obtained in step 5 for 30 minutes.

[0046] Step 7: Place the conductive latex rubber ring prepared in step 6 in a vacuum drying oven and dry for 4 hours. Then, immerse it in ethanol for a simple cleaning and place it in a vacuum drying oven to dry for 15 minutes to obtain a flexible strain sensor of RB / CB composite material. The preparation process of this embodiment is as follows: Figure 1 shown.

[0047] The composite material samples prepared in this embodiment were analyzed and characterized: the SEM images of the conductive latex rubber ring were as follows: Figure 2 As shown in (a) and 2(b), after modification, the conductive particles are tightly adhered to the surface of the latex rubber ring and have a large roughness.

[0048] Step 8: Use conductive silver glue to bond the composite material of this embodiment to copper wire to form a stretch sensor. Figure 3 The flexible sensor prepared in this embodiment and its electrical signal change diagram for detecting finger joint movement show that when the finger joint is repeatedly bent at the same angle, the electrical signal of the flexible sensor will respond quickly, and the response signal has a good recognition effect on the same action.

[0049] Figure 4 The flexible sensor prepared in this embodiment was stretched and released more than 1,000 times, and ΔR / R0 changed stably with strain, showing excellent stability and reliability, indicating that the sensor has good durability and repeatability.

[0050] Figure 5 The flexible sensor prepared in this embodiment was subjected to a cyclic loading test under 10%-150% strain conditions. It can be seen from the figure that the flexible strain sensor of Example 1 has good repeatability, stability and reliability.

[0051] Example 2

[0052] Step 1: Place the latex rubber ring in ethanol and ultrasonically clean it for 2 minutes, then place the cleaned latex rubber ring in a vacuum drying oven at 55° C. and dry it for 15 minutes.

[0053] Step 2: Immerse the latex rubber ring completely in xylene for 12 hours. The latex rubber ring will swell and its volume will expand to 1 times its original size, and it will become more transparent and elastic.

[0054] Step 3: Mix N,N-dimethylformamide and water in a ratio of 1:4 and stir with a glass rod for 2 minutes to allow the water and N,N-dimethylformamide to be fully mixed.

[0055] Step 4: Add conductive carbon black to the solvent prepared in step 3 and mix to prepare a conductive ink having a conductive carbon black concentration of 0.01 g / ml.

[0056] Step 5: Seal the conductive ink from step 4 with a polyethylene film and place it in an ultrasonic cleaning machine for ultrasonic treatment to allow the conductive carbon black to be evenly dispersed in the solvent to obtain a more uniform conductive ink.

[0057] Step 6: Completely immerse the latex rubber ring prepared in step 2 in the conductive ink obtained in step 5 for 30 minutes.

[0058] Step 7: Place the conductive latex rubber ring prepared in step 6 in a vacuum drying oven and dry for 4 hours. Then, immerse it in ethanol for a simple cleaning and place it in a vacuum drying oven to dry for 15 minutes to obtain a flexible strain sensor of RB / CB composite material. The preparation process of this embodiment is as follows: Figure 1 shown.

[0059] The performance analysis of the composite material samples prepared in this embodiment: the response time of the conductive latex rubber ring is as follows: Figure 7 (a) and 7(b), Figure 7 (a) is the response time diagram of stretching and releasing in Example 2, Figure 7(b) is a response time diagram of stretching and releasing of Example 2. It can be seen from the figure that the sensor prepared in this example also has good performance.

[0060] Comparative Example 1

[0061] Step 1: Place the latex rubber ring in ethanol and ultrasonically clean it for 2 minutes, then place the cleaned latex rubber ring in a vacuum drying oven at 55° C. and dry it for 15 minutes.

[0062] Step 2: Immerse the latex rubber ring completely in xylene for 12 hours. The latex rubber ring will swell and its volume will expand to 1 times its original size, and it will become more transparent and elastic.

[0063] Step 3: Mix tetrahydrofuran and water in a ratio of 1:2, and stir with a glass rod for 2 minutes to allow the water and tetrahydrofuran to be fully mixed.

[0064] Step 4: Add conductive carbon black to the solvent prepared in step 3 and mix to prepare a conductive ink having a conductive carbon black concentration of 0.01 g / ml.

[0065] Step 5: Seal the conductive ink from step 4 with a polyethylene film and place it in an ultrasonic cleaning machine for ultrasonic treatment to allow the conductive carbon black to be evenly dispersed in the solvent to obtain a more uniform conductive ink.

[0066] Step 6: Completely immerse the latex rubber ring prepared in step 2 in the conductive ink obtained in step 5 for 30 minutes.

[0067] Step 7: Place the conductive latex rubber ring prepared in step 6 in a vacuum drying oven and dry for 4 hours. Then, immerse it in ethanol for a simple cleaning and place it in a vacuum drying oven to dry for 15 minutes to obtain a flexible strain sensor of RB / CB composite material. The preparation process of this embodiment is as follows: Figure 1 shown.

[0068] Figure 6 This is a digital photo of the flexible sensor prepared in comparative example 1 and example 1. Comparing the two pictures, it can be seen from the figure that the sample prepared according to example 2 has defects and the carbon black is unevenly adhered to its surface.

[0069] Comparative Example 2

[0070] Step 1: Place the latex rubber ring in ethanol and ultrasonically clean it for 2 minutes, then place the cleaned latex rubber ring in a vacuum drying oven at 55° C. and dry it for 15 minutes.

[0071] Step 2: Immerse the latex rubber ring completely in xylene for 12 hours. The latex rubber ring will swell and its volume will expand to 1 times its original size, and it will become more transparent and elastic.

[0072] Step 3: Mix ethanol and water in a ratio of 1:4 and stir with a glass rod for 2 minutes to allow the water and ethanol to mix thoroughly.

[0073] Step 4: Add conductive carbon black to the solvent prepared in step 3 and mix to prepare a conductive ink having a conductive carbon black concentration of 0.01 g / ml.

[0074] Step 5: Seal the conductive ink from step 4 with a polyethylene film and place it in an ultrasonic cleaning machine for ultrasonic treatment to allow the conductive carbon black to be evenly dispersed in the solvent to obtain a more uniform conductive ink.

[0075] Step 6: Completely immerse the latex rubber ring prepared in step 2 in the conductive ink obtained in step 5 for 30 minutes.

[0076] Step 7: Place the conductive latex rubber ring prepared in step 6 in a vacuum drying oven and dry for 4 hours. Then, immerse it in ethanol for a simple cleaning and place it in a vacuum drying oven to dry for 15 minutes to obtain a flexible strain sensor of RB / CB composite material. The preparation process of this embodiment is as follows: Figure 1 shown.

[0077] The resistance values ​​of the composite material samples prepared in this example were measured. The resistance values ​​of the samples with tetrahydrofuran and hexanol mixed solvents are shown in Figures 8(a) and 8(b), respectively. It can be seen from the figure that the resistance value of the sample with ethanol mixed solvent is very large, indicating that its electrical performance is lower than that of the sample with tetrahydrofuran mixed solvent.

[0078] Comparative Example 3

[0079] Other conditions were the same as those in Example 1, except that in step 4, conductive carbon black was added to the solvent mixture in step 3 to prepare a conductive ink with a conductive carbon black concentration of 0.05 g / ml. The carbon black on the surface of the resulting composite material sample was uneven, affecting the performance. This was because the high concentration of carbon black affected the uniformity of carbon black in the solvent.

[0080] Specific examples are provided in this specification to illustrate the principles and implementation methods of the present invention. These examples are intended only to help the reader understand the method and core concept of the present invention. For those with general technical knowledge in this field, the specific implementation methods and scope of application may vary. Any modifications, supplements, or equivalent substitutions made by those skilled in the art based on these examples are within the scope of protection claimed in the claims of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A method for preparing a RB / CB composite flexible strain sensor, characterized by: The latex rubber ring is completely immersed in xylene to swell the latex rubber ring to obtain a swollen latex rubber ring, conductive carbon black is added to a mixed solvent of an organic solvent and water to obtain a conductive ink, and the swollen latex rubber ring is immersed in the conductive ink for immersion treatment to obtain an RB / CB composite flexible strain sensor, wherein the organic solvent is selected from tetrahydrofuran and / or N,N-dimethylformamide.

2. The method for preparing a RB / CB composite flexible strain sensor according to claim 1, characterized in that: The latex rubber ring is firstly subjected to cleaning pretreatment, wherein the cleaning pretreatment process is as follows: the latex rubber ring is added into ethanol and ultrasonically cleaned for 1 to 4 minutes, and then the cleaned latex rubber ring is vacuum dried at 50 to 60° C. for 10 to 30 minutes.

3. The method for preparing a RB / CB composite flexible strain sensor according to claim 1, characterized in that: The latex rubber ring is completely immersed in xylene for 12 to 24 hours.

4. The method for preparing a RB / CB composite flexible strain sensor according to claim 1, characterized in that: In the mixed solvent of the organic solvent and water, the volume ratio of the organic solvent to water is 1:3-4.

5. The method for preparing a RB / CB composite flexible strain sensor according to claim 1, characterized in that: Conductive carbon black is added to a mixed solvent of an organic solvent and water, sealed, and then subjected to ultrasonic treatment for ≥3 minutes to obtain a conductive ink.

6. The method for preparing a RB / CB composite flexible strain sensor according to claim 1 or 5, characterized in that: In the conductive ink, the concentration of conductive carbon black is 0.01-0.02 g / ml.

7. The method for preparing a RB / CB composite flexible strain sensor according to claim 1, characterized in that: The time of the immersion treatment is ≥20 min.

8. The method for preparing a RB / CB composite flexible strain sensor according to claim 1 or 7, characterized in that: After the impregnation treatment is completed, the obtained conductive latex rubber ring is vacuum dried at 50-60°C for 2-5 hours, then immersed in ethanol for cleaning, and then placed at 50-60°C for vacuum drying for 10-30 minutes to obtain the RB / CB composite flexible strain sensor.

9. A RB / CB composite flexible strain sensor prepared by the preparation method according to any one of claims 1 to 8.

10. Application of a RB / CB composite flexible strain sensor prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The RB / CB composite flexible strain sensor is applied to flexible wearable electronic products.

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