Paper-based pressure sensor composite material, preparation method and application

Abstract

The invention discloses a paper-based pressure sensor composite material and a preparation method and application thereof, and the composite material comprises the following raw materials in parts by mass: 30 parts of paper pulp, 2-8 parts of carboxylated multi-walled carbon nanotubes, 3-6 parts of a sizing agent and 3 parts of a wet strength agent. The paper-based pressure sensor material disclosed by the invention shows good mechanical properties (relatively high tension resistance, tear resistance and folding resistance) and high sensitivity, the properties can be kept under various environmental conditions, the sensing performance is particularly outstanding, and the pressure change can be rapidly and accurately detected. In addition, the material also has good hydrophobicity, can effectively prevent the influence of moisture on the performance of the material, also has biodegradability, is helpful for reducing environmental pollution, becomes an ideal flexible electronic material, and has important application value in the fields of wearable equipment, health monitoring, electronic skin and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of pressure sensor composite materials, and in particular relates to a paper-based pressure sensor composite material, a preparation method and an application thereof. Background Art

[0002] Flexible, environmentally friendly, and wearable pressure sensors are crucial for the development of smart homes, intelligent human monitoring, and electronic skin. Piezoresistive flexible sensors, which directly convert pressure into a resistance signal, have advantages such as excellent mechanical properties, simple device structure, and easily accessible output signals, and are becoming a hot topic in new material research.

[0003] Paper and pulp, as a sustainable, biodegradable, low-cost material, show great potential in wearable sensors. Traditional pressure sensors are mostly made of petroleum-based elastomeric polymers, which are complex in structure, expensive, difficult to degrade, and cause varying degrees of pollution to the environment. The use of natural pulp to prepare sensor materials can not only effectively give paper a high value-added utilization, but also reduce the impact on the environment. Therefore, it has important significance in the diversified development of sensors, resource recycling and environmental protection. The method of preparing pulp into piezoresistive sensor materials according to the present invention is particularly suitable for sensor materials with low cost, high strength and high sensing performance (high sensitivity, fast response / recovery time) required by industrial applications.

[0004] Therefore, developing a piezoresistive sensor material with excellent performance using pulp as raw material has important practical value and social significance. Summary of the Invention

[0005] On the one hand, the purpose of the present invention is to provide a paper-based pressure sensor composite material and a preparation method. Through specific chemical and physical treatment processes, paper pulp can be converted into a high-performance flexible piezoresistive sensor composite material.

[0006] Another aspect provides the use of the aforementioned paper-based pressure sensor composite material in the preparation of a paper-based pressure sensor. The prepared paper-based pressure sensor is lightweight, low-cost, high-strength, and offers excellent sensing performance (high sensitivity and fast response / recovery time), and can be applied in sensing fields such as smart homes, intelligent human body monitoring, and electronic skin.

[0007] In order to achieve the above object, the technical solution of the present invention is as follows:

[0008] A paper-based pressure sensor composite material. The pulp-based sensor material is prepared by comprising the following raw materials in parts by mass: 30 parts of pulp, 2-8 parts of impregnating conductive slurry (carboxylated multi-walled carbon nanotubes), 0-6 parts of sizing agent, and 3 parts of wet strength agent.

[0009] Preferably, the pulp-based sensor material is prepared by including the following raw materials in parts by weight: 30 parts of pulp, 3.3-8 parts of impregnation conductive paste (carboxylated multi-walled carbon nanotubes), 3-6 parts of sizing agent, and 3 parts of wet strength agent.

[0010] More preferably, the pulp-based sensor material is prepared by including the following raw materials in parts by mass: 30 parts of pulp, 5 parts of impregnation conductive paste (carboxylated multi-walled carbon nanotubes), 4 parts of sizing agent, and 3 parts of wet strength agent.

[0011] The pulp is one or a combination of two or more of softwood pulp, hardwood pulp, reed pulp, and corn straw pulp; the paper can be finished paper, such as toilet paper, printing paper, hard napkin paper, porous ultra-thin paper, filter paper, etc.; preferably, the pulp is softwood pulp.

[0012] The carboxylated multi-walled carbon nanotubes can be selected from low-cost carboxylated multi-walled carbon nanotubes, effectively reducing costs without affecting their effectiveness. Alternatively, one or a combination of two or more of carbon ink, carboxylated multi-walled carbon nanotubes, multi-walled carbon nanotubes, redox graphene, or graphene powder can be selected as the alternative; however, the most preferred option is low-cost carboxylated multi-walled carbon nanotubes.

[0013] Preferably, the sizing agent is one or a combination of two or more of rosin, AKD (alkyl ketene dimer), ASA (alkyl succinic anhydride), and AKS (alkyl ketone); preferably, the sizing agent is AKD (alkyl ketene dimer).

[0014] Preferably, the wet strength agent is one or a combination of two or more of PAE (polyamide-epichlorohydrin), urea-formaldehyde resin, melamine-formaldehyde resin, polyacrylamide, and modified starch; preferably, the wet strength agent is PAE (polyamide-epichlorohydrin).

[0015] The method for preparing the above-mentioned paper-based pressure sensor composite material comprises the following steps:

[0016] (1) Add the paper pulp to the slurry dispersion barrel, then add the diluted sizing agent, stir evenly, then add the diluted wet strength agent to the slurry dispersion barrel, continue stirring evenly, fully disperse the paper pulp, make paper, dry, and obtain paper;

[0017] (2) adding carboxylated multi-walled carbon nanotubes to water and uniformly dispersing the carbon nanotubes by ultrasonication to prepare a conductive slurry of carboxylated multi-walled carbon nanotubes with a concentration of 1 to 8 wt %;

[0018] (3) Cutting the paper into appropriate sizes, and dipping it into the carboxylated multi-walled carbon nanotube conductive slurry for 4 to 72 hours; placing the impregnated paper in an oven at 80° C. and drying it for 12 hours to obtain a paper-based pressure sensor composite material.

[0019] In the above preparation method, preferably, the basis weight of the paper is 30g / m 2 .

[0020] The pulp can be selected from existing pulp or prepared by itself. Preferably, the pulp preparation method is as follows: cut the pulp board into small pieces, soak it in deionized water, stir and disperse it evenly, fully swell it, and remove dust and impurities at the same time; take it out after soaking and place it in a pulp bag to balance the moisture; add an appropriate amount of water to make the pulp concentration reach 10wt% and balance the moisture; add the pulp to a beater for beating. Preferably, the soaking temperature is 16-25°C, the soaking time is 10-12h, and the moisture balance time is 12-18h. For moisture determination, take at least 3 groups and bake them in an oven at 105°C for more than 4 hours, and take the average value to obtain the moisture content.

[0021] The present invention also discloses the use of the paper-based pressure sensor composite material or the paper-based pressure sensor composite material obtained by the preparation method in the preparation of a paper-based pressure sensor. The structure of the paper-based pressure sensor includes a middle sensor, an innermost ultra-thin insulating interlayer, an outer electrode, and an outermost encapsulation protective layer. The specific preparation method is as follows:

[0022] (1) Cut the paper-based pressure sensor composite material into a square shape with a size of 11×11 mm, and take 2 pieces for assembly; select conductive tape as the electrode layer material, cut it into a size of 10×30 mm, and take 2 pieces for assembly; select polyimide tape as the packaging protective layer material, cut it into a size of 20×40 mm, and take 2 pieces for assembly; select a quantitative of only 5g / m 2 The ultra-thin porous paper is used as the insulating layer in the middle of the sensor. It is cut into 12×12mm size and two pieces are taken for assembly.

[0023] (2) After aligning the two insulating layers in parallel, two layers of sensor material are laminated on top of the insulating layers to form four centrally symmetrical layers, with the insulating layers inside and the sensors outside.

[0024] (3) The electrode layers are attached to the outside of the two-layer sensor, and the long strips of conductive tape are exposed as electrodes to form symmetrical 6 layers. After ensuring good contact between the electrodes and the conductive parts of the sensor material, the packaging protective layer is covered on the outermost layer for overall coating, exposing only the electrodes at both ends to form symmetrical 8 layers. The flexible paper-based pressure sensor is completed.

[0025] Among them, the paper-based pressure sensor can be applied to various fields such as high-performance pressure sensing, smart home, intelligent human body monitoring and electronic skin materials.

[0026] Advantages of the present invention:

[0027] 1. The raw materials of the paper-based sensor material of the present invention are cheap and easy to obtain, and the preparation process is simple, efficient and clean, without the need for complicated experimental operations. In the preparation process of the present invention, paper pulp is first used as raw material, and the pulp plate is treated by soaking at a specific temperature to determine the pulp concentration and prepare the initial paper pulp. The subsequent beating plays a role in fiber separation and brooming. The higher the beating degree, the greater the degree of fiber separation and brooming, and the tighter the fiber bonding, laying the foundation for the high strength of the sensor paper. Then, conductive materials such as conductive carboxylated multi-walled carbon nanotubes are added to the system, which are composited with pulp fibers to form a preliminary sensor substrate. By optimizing the material ratio and treatment process, the paper-based sensing sensor material finally prepared has the characteristics of low quantity and high strength, while ensuring the hydrophobicity and structural stability of the material. Its green and environmentally friendly characteristics, as well as high tensile, tearing and folding resistance, give it significant advantages in the field of flexible electronics.

[0028] 2. The carboxylated multi-walled carbon nanotubes used in the present invention play a vital role in the process of preparing paper-based sensor materials. On the one hand, it significantly improves the electrical conductivity of the material, effectively reduces the sheet resistance, and maintains structural stability, ensuring the rapid response and high sensitivity of the sensor material. On the other hand, the carboxylated multi-walled carbon nanotubes used in the present invention are non-toxic, safe and environmentally friendly, and will not cause harm to the human body and the environment. In addition, its flexible, non-toxic and skin-friendly properties allow it to be used as electronic skin, reducing the dangers that may arise during large-scale industrial production, and has broad application prospects. The water dispersibility of carboxylated multi-walled carbon nanotubes is very good, the slurry is uniform and easy to preserve, and it can greatly improve production efficiency in actual industrial production and effectively reduce production costs.

[0029] 3. The specific types and proportions of reagents used in the present invention are designed specifically for the pulp raw material system. A low-energy, high-efficiency solution is selected, and a small amount of sizing agent, low beating degree, low impregnation concentration, and short impregnation time are used as much as possible on the basis of ensuring the high performance of the material. This preparation method using composite materials can achieve the expected high conductivity and high sensitivity with a smaller amount of conductive materials and additives, improve production efficiency and make it easier to form. By precisely controlling the amount of reagents used in the sensor formation process, it is possible to avoid poor effects due to insufficient dosage and unnecessary production costs due to excessive use, thereby achieving dual optimization of cost-effectiveness and production efficiency.

[0030] 4. The raw material composition of the paper-based sensor material of the present invention is specific, ensuring the unique performance and effect of the material. Only through the specific raw material types and precise ratios of the present invention can the high sensitivity, rapid response, good hydrophobicity and other characteristics of the sensor material be achieved. For example, pulp as the main raw material, its unique chemical structure and physical properties are the key to achieving the flexibility and high strength of the sensor material. In addition, the addition of carboxylated multi-walled carbon nanotubes not only provides the necessary conductivity for the material, but also improves the mechanical properties of the material. Suitable deionized water is crucial to achieving the excellent performance of the material; insufficient dosage may lead to uneven dispersion of the material, while excessive dosage may affect the conductivity and stability of the material. Only when the raw materials interact with each other in precise ratios can a sensor material with the desired performance be effectively formed. The raw material composition of the present invention, as a whole, achieves the expected effect of the sensor material through the synergistic effect of each raw material.

[0031] 5. In the paper-based sensor material preparation method of the present invention, the order in which the conductive material is added and the processing steps are crucial. If this sequence is altered, the high-performance sensor material described herein cannot be obtained, nor can the expected physical properties and application characteristics be achieved. In each reaction step, the order in which the reagents and raw materials are added, as well as the type and ratio of the conductive material and additives, are key factors influencing the quality of the final sensor material. Only by adding the sizing agent and wet strength agent during the papermaking process and then impregnating the conductive material after the paper is formed, can the conductive material be uniformly combined with the pulp fibers during subsequent processing, forming a uniform and stable sensor structure.

[0032] For example, during preliminary experiments, the order of impregnation was reversed—carboxylated multi-walled carbon nanotubes were impregnated first, followed by the sizing agent and wet strength agent. This resulted in impregnation failure, with the paper stretching and rotting during impregnation, making subsequent operations impossible and the experiment aborted. This effectively prevented uniform dispersion of the materials, thus affecting the ultimate performance of the sensor material. Therefore, the precise coordination of each step and condition in the preparation method of the present invention as a whole is fundamental to achieving the excellent performance of the sensor material.

[0033] 6. The paper-based sensing material of the present invention exhibits good mechanical properties (having high tensile, tearing and folding resistance) and high sensitivity, and can maintain its performance under various environmental conditions. This has important application value in many fields such as wearable devices and health monitoring, and also makes it widely used as an excellent flexible pressure sensor in fields such as electronic skin. The sensing performance of this sensor material is particularly outstanding, and it can detect pressure changes quickly and accurately. In addition, the sensor material of the present invention also has good hydrophobicity, which can effectively prevent the influence of moisture on the material properties, further improving its stability and reliability in practical applications. Moreover, due to the natural properties of pulp, this sensor material is biodegradable, which helps to reduce environmental pollution and promote sustainable development, making it an ideal flexible electronic material.

[0034] At the same time, the present invention can effectively utilize recycled pulp from the papermaking industry, reduce environmental pollution, and provide new environmentally friendly materials for the industrial field; it increases the added value of paper, and provides innovative solutions for the environmentally friendly treatment of sensor substrates and the high-value utilization of traditional papermaking, which has important social and economic significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The figure shows a model (a) and a physical picture (b) of the sensor, and a physical picture (c) of the sensor material prepared in Example 1;

[0036] Figure 2 is the response / recovery time of the sensor made of the sensor material prepared in Example 1;

[0037] Figure 3 is the water contact angle of the sensor material prepared in Example 1. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to specific examples, and the advantages and features of the present invention will become more apparent as the description proceeds. However, the specific experimental methods involved in the following examples, unless otherwise specified, are all conventional methods or are performed under the conditions recommended by the manufacturer's instructions.

[0039] Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. The experimental methods in the following examples are all conventional methods unless otherwise specified. Unless otherwise specified, the reagents and materials used can be purchased from the market.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods and materials similar or equivalent to those described herein can be applied to the present invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0041] In order to obtain the best effect, the present invention conducted the following experiments for discussion.

[0042] 1. Effects of different beating degrees on the physical properties and sensing performance of the sensing layer

[0043] Table 1 shows that when other conditions are the same (9.42g of 10% wt pulp, 0.1884g of AKD, 0.1413g of PAE, 5% wt of carboxylated multi-walled carbon nanotube aqueous slurry, and immersion time of 48h), and only the beating degree is different (①15°SR, ②33°SR, ③57°SR, ④82°SR, and ⑤89°SR), the physical properties (tensile strength, tear strength, and folding endurance) of the sensing layer increase with increasing beating degree, and the strongest physical properties can be achieved when the beating degree reaches 89°SR; while the sensing performance of the sensing layer (mainly reflected in the recovery / response time and sensitivity) will first increase and then decrease with increasing beating degree, and the strongest sensing performance can be achieved when the beating degree reaches 82°SR. However, too high a beating degree will result in higher energy consumption. Considering the cost factor and the comprehensive performance of the sensing layer, the preferred beating degree for preparing the sensing layer in the present invention is 82°SR.

[0044] Table 1

[0045]

[0046] 2. Effect of different sizing agent (AKD) dosage on the physical properties and sensing performance of the sensing layer

[0047] Table 2 shows that under the same other conditions (10% wt pulp 9.42g, PAE 0.1413g, beating degree 82°SR, carboxylated multi-walled carbon nanotube aqueous slurry 5% wt, immersion time 48h), only the amount of sizing agent (AKD) was different (compared to pulp fiber ①0, ②10%, ③20%, ④30%). The physical properties of the sensing layer (mainly reflected in the water contact angle) increased with increasing AKD dosage. The strongest physical properties were achieved when the AKD dosage reached 30% of the fiber weight, but the sensing performance was poor at this time. The sensing performance of the sensing layer (mainly reflected in the recovery / response time and sensitivity) first increased and then decreased with increasing AKD dosage. The strongest sensing performance was achieved when the beating degree reached 20% of the fiber weight. However, excessive AKD dosage will result in resource waste and increased costs. Considering cost factors and the comprehensive performance of the sensing layer, the preferred AKD dosage for preparing the sensing layer in the present invention is 30% of the fiber weight.

[0048] Table 2

[0049]

[0050] 3. Effects of different impregnation concentrations of conductive paste (carboxylated multi-walled carbon nanotubes) on the physical properties and sensing performance of the sensing layer

[0051] Table 3 shows that under the same other conditions (9.42g of 10% wt pulp, 0.1884g of AKD, 0.1413g of PAE, beating degree 82oSR, immersion time 48h), with only different concentrations of the conductive paste (carboxylated multi-walled carbon nanotubes) (①1% wt, ②2% wt, ③3.3% wt, ④5% wt, ⑤8% wt), the physical properties of the sensing layer (tensile strength, tear strength, number of folding endurance, water contact angle) showed no significant difference with increasing carboxylated multi-walled carbon nanotube concentration; however, the sensing performance of the sensing layer (recovery / response time, sensitivity) first increased and then decreased with increasing concentration, with the strongest sensing performance achieved at a carboxylated multi-walled carbon nanotube concentration of 5% wt. Therefore, the preferred concentration of carboxylated multi-walled carbon nanotubes for preparing the sensing layer in the present invention is 5% wt.

[0052] Table 3

[0053]

[0054] 4. Effects of different immersion times on the physical properties and sensing performance of the sensing layer

[0055] Table 4 shows that under the same other conditions (10% wt pulp 9.42g, AKD 0.1884g, PAE 0.1413g, carboxylated multi-walled carbon nanotube aqueous slurry 5% wt, beating degree 82° SR), only the immersion time is different (①4h, ②10h, ③24h, ④48h, ⑤72h), the physical properties of the sensing layer (tensile strength, tear strength, folding endurance, water contact angle) will first increase and then decrease with immersion time, and the strongest physical properties can be achieved at an immersion time of 48h; while the sensing performance of the sensing layer (sheet resistance, recovery / response time, sensitivity) increases with increasing immersion time and tends to stabilize after the immersion time exceeds 48h. Therefore, the preferred immersion time for preparing the sensing layer in the present invention is 48h.

[0056] Table 4

[0057]

[0058]

[0059] 5. Effects of different paper materials on the physical properties and sensing performance of the sensing layer

[0060] Table 5 shows the other conditions are the same (carboxylated multi-walled carbon nanotubes water slurry 5% wt, immersion time 48h), but the paper materials used (① laboratory papermaking 30g / m 2The physical properties and sensing performance of the sensing layer vary when using different paper materials (1) toilet paper, 2) A4 paper, 3) napkin paper, 4) porous ultra-thin paper, and 5) filter paper. The physical properties of toilet paper and napkin paper are relatively weak, while the weight of A4 paper and filter paper is large, making it difficult to impregnate, resulting in weak sensing performance. In addition, the contact angles of the other selected papers are very small and cannot be used as a hydrophobic sensitive layer. Considering the cost factor and the comprehensive performance of the sensing layer, the preferred paper material for preparing the sensing layer in the present invention is 30g / m2 paper made in the laboratory. 2 Paper.

[0061] Table 5

[0062]

[0063] Example 1

[0064] A pulp-based sensor material is prepared by including the following raw materials in parts by weight: 9.42 g of pulp, 0.1884 g of AKD (sizing agent), 0.1413 g of PAE (wet strength agent), and 5% wt of carboxylated multi-walled carbon nanotube aqueous slurry (conductive slurry).

[0065] The specific steps of the preparation method of the pulp-based sensor material are as follows.

[0066] Step 1: Raw material preparation

[0067] Cut all prepared softwood pulp sheets into short sections. Prepare 500g sections at a time and immerse them in water at 20°C for 12 hours. This soaking removes some dust and impurities and fully swells the material. After soaking, remove the pulp blocks from the water and place them in a slurry bag to allow them to drain and equilibrate naturally. Measure the moisture content of the slurry and add water as needed to achieve a slurry concentration of 10% by weight. Re-equilibrate the slurry to ensure uniformity.

[0068] Step 2: Papermaking

[0069] 300 g of the pulp obtained in step (1) was taken out and placed in a PFI refiner (LW, the Netherlands) for beating treatment; the beating degree reached 82°SR; during the beating process, the beating degree was regularly sampled and tested using a beating degree tester to ensure that the predetermined target value was reached. 9.42 g of the beaten pulp was taken out and placed in a pulp dispersion barrel, and then (sizing agent) AKD 0.1884 g (corresponding to 20% wt of absolute dry pulp) and (wet strength agent) PAE 0.1413 g (corresponding to 15% wt of absolute dry pulp) were added. The mixed pulp was then dispersed using a disperser at 600 revolutions to fully break up the pulp; a standard paper sheet making machine was used for papermaking to obtain formed paper sheets.

[0070] Step (3) Sensing layer molding

[0071] The paper obtained in step (2) was cut into a size suitable for subsequent processing; the conductive slurry was placed in a sealed tube and subjected to ultrasonic dispersion in the laboratory for 40 minutes; the cut strips of paper were then immersed in a fully dispersed conductive slurry (5% wt. aqueous slurry of carboxylated multi-walled carbon nanotubes) at room temperature for 48 hours to allow the conductive material to evenly penetrate the paper. The impregnated paper was carefully removed and allowed to sag naturally to remove excess conductive slurry adhered to the surface. The paper was then placed in an oven and dried at 80°C for 12 hours to solidify the conductive layer and remove excess moisture, ultimately producing the pulp-based sensing layer material.

[0072] Step 4: Sensor molding

[0073] The paper-based sensing layer material obtained in step (3) was cut into a square shape with a size of 11×11 mm, and two pieces were taken for assembly; a low-cost commercial conductive tape was selected as the electrode layer material, cut into a size of 10×30 mm, and two pieces were taken for assembly; a polyimide tape was selected as the packaging protective layer material, cut into a size of 20×40 mm, and two pieces were taken for assembly; a quantitative of only 5g / m was selected. 2 The ultra-thin porous paper is used as the insulating layer in the middle of the sensor, cut into a size of 12×12mm, and two pieces are taken for assembly; after the two insulating layers are aligned parallel to each other, two layers of sensor material are attached to the insulating layer up and down to form four centrally symmetrical layers (the insulating layer is inside and the sensor is outside), and the electrode layers are attached to the outside of the two layers of sensors (the conductive tape with the long strips exposed is used as the electrode) to form six symmetrical layers. After ensuring good contact between the electrodes and the conductive parts of the sensor material, the encapsulation protective layer is covered on the outermost layer for overall coating, exposing only the electrodes at both ends to form eight symmetrical layers. The flexible paper-based pressure sensor is now ready.

[0074] The actual picture (c) of the sensor material prepared in this embodiment and the model picture (a) and actual picture (b) of the sensor made of the sensor are as follows: Figure 1 As shown in the figure, the resulting sensor exhibits a simple structure, compact size, thin thickness, good flexibility, bendability, and stable performance. These properties make the sensor suitable for a variety of applications, including but not limited to health monitoring, human-computer interaction, and smart textiles. Furthermore, the sensor material's simple and low-cost preparation process further enhances its potential for commercial applications.

[0075] The response / recovery time of the sensor prepared in this embodiment is as follows Figure 2As shown in the figure, it can be seen that the paper-based flexible pressure sensor prepared in this embodiment exhibits excellent response and recovery performance. The figure shows the current change of the sensor under two consecutive pressure stimuli, where the red curve represents the response time (Response) and the green curve represents the recovery time (Recovery). The response time of the sensor (T res ) is 44ms, which means that the time from the application of pressure to the sensor output current reaching its peak is only 44ms, showing that the sensor can quickly detect pressure changes. Similarly, the sensor's recovery time (T rec ) is 21ms, meaning the time from pressure removal until the sensor output current returns to baseline levels is only 21ms, demonstrating that the sensor can quickly return to its initial state after pressure release. This rapid response and recovery capability is crucial for real-time monitoring and rapid response applications, such as wearable devices, health monitoring, and robotic tactile feedback.

[0076] The water contact angle of the sensor material prepared in this example is as follows Figure 3 As shown, three samples were tested in parallel. It can be seen from the figure that the sensor material prepared in this embodiment exhibits good hydrophobic properties. The figure shows the contact angle between a water droplet and the surface of the material. The size of the contact angle is an important indicator for measuring the hydrophobicity of the material. The larger the contact angle, the stronger the hydrophobicity of the material surface. As can be seen from the figure, the contact angle of the water droplet on the surface of the sensor material is about 135.9°, which is a very large contact angle, far exceeding 90°, indicating that the material has strong hydrophobicity. This hydrophobic property is especially important for paper-based flexible pressure sensors because it can prevent moisture from penetrating into the interior of the sensor, thereby avoiding performance degradation or damage caused by moisture.

[0077] Example 2

[0078] A pulp-based sensitive layer material is prepared by including the following raw materials in parts by weight: 9.42 g of pulp, 0.1884 g of AKD (sizing agent), 0.1413 g of PAE (wet strength agent), and 5% wt of carboxylated multi-walled carbon nanotube aqueous slurry (conductive slurry).

[0079] The method for preparing the pulp-based sensitive layer material comprises the following steps:

[0080] Step (1) is the same as in Example 1;

[0081] Step 2: Papermaking

[0082] 300 g of the pulp obtained in step (1) was taken out and placed in a PFI pulper (LW, the Netherlands) for beating treatment; by controlling the beating time and beating pressure, the pulping was performed 5 times at 8000 revolutions to make the beating degree reach 89°SR (Schopper-Riegler); during the beating process, a beating degree tester was used to regularly sample and test the beating degree to ensure that the predetermined target value was reached. 9.42 g of the pulp after beating was taken out and placed in a pulp dispersion barrel, and then 0.1884 g of AKD (sizing agent) and 0.1413 g of PAE (wet strength agent) were added, and then the mixed pulp was dispersed with a disperser at 600 revolutions to fully break up the pulp; a standard paper sheet making machine was used for papermaking to obtain a formed paper sheet.

[0083] Steps (3) and (4) are the same as in Example 1.

[0084] Example 3

[0085] A pulp-based sensor material is prepared by including the following raw materials in parts by weight: 9.42 g of pulp, 0.0942 g of AKD (sizing agent), 0.1413 g of PAE (wet strength agent), and 5% wt of carboxylated multi-walled carbon nanotube aqueous slurry (conductive slurry).

[0086] The method for preparing the pulp-based sensor material comprises the following steps:

[0087] Step (1) is the same as in Example 1;

[0088] Step 2: Papermaking

[0089] 300 g of the pulp obtained in step (1) was removed and placed in a PFI refiner (LW, the Netherlands) for beating; the beating degree was 82° SR. 9.42 g of the beaten pulp was removed and placed in a pulp dispersion drum. 0.0942 g of AKD (sizing agent) (corresponding to 10% wt of bone dry pulp) and 0.1413 g of PAE (wet strength agent) were then added. The mixed pulp was then dispersed using a disperser at 600 rpm to thoroughly break up the pulp. A standard sheet making machine was then used to make paper sheets.

[0090] Steps (3) and (4) are the same as in Example 1.

[0091] Example 4

[0092] A pulp-based sensor material is prepared by including the following raw materials in parts by weight: 9.42 g of pulp, 0.2826 g of AKD (sizing agent), 0.1413 g of PAE (wet strength agent), and 5% wt of carboxylated multi-walled carbon nanotube aqueous slurry (conductive slurry).

[0093] The method for preparing the pulp-based sensor material comprises the following steps:

[0094] Step (1) is the same as in Example 1;

[0095] Step 2: Papermaking

[0096] 300 g of the pulp obtained in step (1) was removed and placed in a PFI refiner (LW, the Netherlands) for beating; the beating degree was 82° SR. 9.42 g of the beaten pulp was removed and placed in a pulp dispersion drum. 0.2826 g of AKD (corresponding to 30% wt of bone dry pulp) and 0.1413 g of PAE (wet strength agent) were then added. The mixed pulp was then dispersed using a disperser at 600 rpm to thoroughly break up the pulp. A standard sheet making machine was then used to make paper sheets.

[0097] Steps (3) and (4) are the same as in Example 1.

[0098] Example 5

[0099] A pulp-based sensor material is prepared by including the following raw materials in parts by weight: 9.42 g of pulp, 0.1884 g of AKD (sizing agent), 0.1413 g of PAE (wet strength agent), and 8% wt of carboxylated multi-walled carbon nanotube aqueous slurry (conductive slurry).

[0100] The method for preparing the pulp-based sensor material comprises the following steps:

[0101] Steps (1) and (2) are the same as in Example 1;

[0102] Step (3) Sensing layer molding

[0103] The paper obtained in step (2) was cut into a size suitable for subsequent processing; the conductive slurry was placed in a sealed tube and ultrasonically dispersed in the laboratory for 40 minutes; the cut strips of paper were then immersed in a fully dispersed conductive slurry (8% wt. aqueous slurry of carboxylated multi-walled carbon nanotubes) at room temperature for 48 hours to allow the conductive material to evenly penetrate the paper. The impregnated paper was carefully removed and allowed to sag naturally to remove excess conductive slurry adhered to the surface. The paper was then placed in an oven and dried at 80°C for 12 hours to solidify the conductive layer and remove excess moisture, ultimately producing the pulp-based sensing layer material.

[0104] Step (4) is the same as in Example 1.

[0105] Example 6

[0106] A pulp-based sensor material is prepared by including the following raw materials in parts by weight: 9.42 g of pulp, 0.1884 g of AKD (sizing agent), 0.1413 g of PAE (wet strength agent), and 5% wt of carboxylated multi-walled carbon nanotube aqueous slurry (conductive slurry).

[0107] The method for preparing the pulp-based sensor material comprises the following steps:

[0108] Steps (1) and (2) are the same as in Example 1;

[0109] Step (3) Sensing layer molding

[0110] The paper obtained in step (2) was cut into a size suitable for subsequent processing; the conductive slurry was placed in a sealed tube and subjected to ultrasonic dispersion in the laboratory for 40 minutes; the cut strips of paper were then immersed in a fully dispersed conductive slurry (5% wt. aqueous slurry of carboxylated multi-walled carbon nanotubes) at room temperature for 72 hours to ensure uniform penetration of the conductive material. The impregnated paper was carefully removed and allowed to sag naturally to remove excess conductive slurry from the surface. The paper was then placed in an oven and dried at 80°C for 12 hours to solidify the conductive layer and remove excess moisture, ultimately producing the pulp-based sensing layer material.

[0111] Step (4) is the same as in Example 1.

[0112] Comparative Example 1

[0113] A sensor material, as described in Example 1, except that the conductive paste used for impregnation is commercial carbon ink (Shanghai Chenguang Stationery Co., Ltd.); the other raw material compositions are the same as in Example 1.

[0114] The method for preparing the pulp-based sensor material comprises the following steps:

[0115] Steps (1) and (2) are the same as in Example 1;

[0116] Step (3) Sensing layer molding

[0117] Cut the paper obtained in step (2) into a size suitable for subsequent processing; place the conductive slurry in a sealed tube and perform ultrasonic dispersion in the laboratory for 40 minutes; then immerse the cut strips of paper in the conductive slurry (commercial carbon ink at its original concentration) at room temperature for 48 hours to ensure uniform penetration of the conductive material. Carefully remove the impregnated paper and allow it to sag naturally to remove excess conductive slurry from the surface. Then, place the paper in an oven and dry it at 80°C for 12 hours to solidify the conductive layer and remove excess moisture, ultimately producing the pulp-based sensing layer material.

[0118] Step (4) is the same as in Example 1.

[0119] Comparative Example 2

[0120] A sensor material, as described in Example 1, except that: the conductive slurry for impregnation is graphene water-dispersed slurry; the other raw material compositions are the same as in Example 1.

[0121] The method for preparing the pulp-based sensor material comprises the following steps:

[0122] Steps (1) and (2) are the same as in Example 1;

[0123] Step (3) Sensing layer molding

[0124] The paper obtained in step (2) was cut into a size suitable for subsequent processing. The conductive slurry was placed in a sealed tube and ultrasonically dispersed in the laboratory for 40 minutes. The cut strips of paper were then immersed in the fully dispersed conductive slurry (5% wt graphene powder slurry in water) at room temperature for 48 hours to ensure uniform penetration of the conductive material. The impregnated paper was carefully removed and allowed to sag naturally to remove excess conductive slurry from the surface. The paper was then placed in an oven and dried at 80°C for 12 hours to solidify the conductive layer and remove excess moisture, resulting in the pulp-based sensing layer material.

[0125] Step (IV) is the same as in Example 1. The pulping and papermaking steps are not required, and the commercial product is directly used to impregnate the modified ultra-thin paper for subsequent operations; the other steps and conditions are the same as in Example 1.

[0126] Comparative Example 3

[0127] A sensor material, as described in Example 1, except that: the conductive slurry for impregnation uses carbon powder (c600) water-dispersible slurry; the other raw material compositions are the same as in Example 1.

[0128] The method for preparing the pulp-based sensor material comprises the following steps:

[0129] Steps (1) and (2) are the same as in Example 1;

[0130] Step (3) Sensing layer molding

[0131] The paper obtained in step (2) was cut into a size suitable for subsequent processing. The conductive slurry was placed in a sealed tube and ultrasonically dispersed in the laboratory for 40 minutes. The cut strips of paper were then immersed in the fully dispersed conductive slurry (5% wt. C600 carbon powder slurry in water) at room temperature for 48 hours to ensure uniform penetration of the conductive material. The impregnated paper was carefully removed and allowed to sag naturally to remove excess conductive slurry from the surface. The paper was then placed in an oven and dried at 80°C for 12 hours to solidify the conductive layer and remove excess moisture, resulting in the pulp-based sensing layer material.

[0132] Step (IV) is the same as in Example 1. The pulping and papermaking steps are not required, and the commercial product is directly used to impregnate the modified ultra-thin paper for subsequent operations; the other steps and conditions are the same as in Example 1.

[0133] The sensor materials prepared in the examples and comparative examples were tested for tensile strength, tearing resistance, folding resistance, contact angle, sheet resistance, sensitivity, and response / recovery time. The test results are shown in Table 6.

[0134] Table 6 Test results

[0135]

[0136]

[0137] The test results in Tables 1-6 provide a comparative analysis of the performance of the paper-based flexible pressure sensors in the examples and comparative examples. Key performance indicators include tensile strength, tear resistance, folding endurance, contact angle, sheet resistance, sensitivity, response time, and recovery time. These parameters are crucial for evaluating sensor performance.

[0138] 1. In all successful examples, the tensile strength ranged from 2.27 kN / m to 2.75 kN / m, indicating that the sensor materials of these examples have good mechanical strength.

[0139] The tear strength ranges from 183 mN to 218 mN, indicating that the sensor materials of these examples have good tear resistance.

[0140] The folding times range from 947 to 1465 times, indicating that the sensor materials of these examples have excellent folding resistance.

[0141] The contact angles ranged from 93.1° to 139.2°, indicating that the sensor materials of these examples had good hydrophobic properties.

[0142] The sheet resistance ranges from 69.4 Ω / sq to 971.1 Ω / sq. These values indicate that the sensor materials of these embodiments have lower sheet resistance and thus higher sensing performance.

[0143] Sensitivity ranges from 10.23kPa -1 to 1818.18kPa -1 , indicating that the sensor materials of these embodiments have extremely high sensitivity.

[0144] The response time and recovery time ranged from 21 ms to 174 ms and from 21 ms to 402 ms, respectively, indicating that the sensor materials of these examples have fast response and recovery times.

[0145] 2. In the comparative examples, the tensile strength ranged from 2.27 kN / m to 2.63 kN / m. In contrast, the tensile strength of Example 1 was 2.69 kN / m, higher than the highest value of 2.63 kN / m in the comparative examples, indicating that the sensor material of Example 1 has better mechanical strength.

[0146] The tear strength ranged from 183 mN to 218 mN. Comparative Example 1 had a tear strength of 183 mN, Comparative Example 2 had a tear strength of 200 mN, and Comparative Example 3 had a tear strength of 205 mN. While Example 1 had a tear strength of 205 mN, the same as Comparative Example 3, Example 1 performed better in other performance indicators, demonstrating that the sensor material of Example 1 has a superior overall performance.

[0147] The folding endurance ranged from 947 to 1393 times, with Comparative Example 1 having a folding endurance of 1393 times, Comparative Example 2 having a folding endurance of 947 times, and Comparative Example 3 having a folding endurance of 1021 times. The folding endurance of Example 1 was 1410 times, higher than the highest value of 1393 times among the comparative examples, indicating that the sensor material of Example 1 has a more excellent folding endurance.

[0148] The contact angle ranged from 11.2° to 139.2°, with the contact angle of Comparative Example 1 being 130.2°, that of Comparative Example 2 being 135.7°, and that of Comparative Example 3 being 133.9°. The contact angle of Example 1 was 135.9°, similar to that of Comparative Example 2, but superior in other performance indicators, indicating that the sensor material of Example 1 has a greater advantage in overall performance.

[0149] Sheet resistance ranges from 56.41×10 3 Ω / sq to 971.1Ω / sq, and the sheet resistance of comparative example 1 is 56.41×10 3 Ω / sq, Comparative Example 2 is 94.2Ω / sq, and Comparative Example 3 is 971.1Ω / sq. The sheet resistance of Example 1 is 72.4Ω / sq, which is much lower than the values of Comparative Example 1 and Comparative Example 3, indicating that the sensor material of Example 1 has lower sheet resistance and thus higher sensing performance.

[0150] Sensitivity ranges from 10.23kPa -1 to 1818.18kPa -1 , the sensitivity of comparative example 1 is 0.57 kPa -1 , Comparative Example 2 is 64.71kPa -1 , Comparative Example 3 is 10.23 kPa -1 The sensitivity of Example 1 is 1818.18 kPa -1 , much higher than the highest value of 64.71kPa in the comparative example -1 , which shows that the sensor material of Example 1 has extremely high sensitivity.

[0151] The response time and recovery time ranged from 21ms to 174ms and 21ms to 402ms, respectively. Comparative Example 1 had a response time of 144ms and a recovery time of 131ms, Comparative Example 2 had a response time of 315ms and 174ms, and Comparative Example 3 had a response time of 44ms and a recovery time of 21ms, significantly lower than those in the comparative examples. This indicates that the sensor material of Example 1 has faster response and recovery times.

[0152] The performance of the comparative example is significantly inferior to that of Example 1. The sensor made of the conductive paste selected in Example 1 (i.e., carboxylated multi-walled carbon nanotubes) performs well in key performance indicators such as tensile strength, tear resistance, folding endurance, contact angle, sheet resistance, sensitivity, response time, and recovery time, and is superior to sensors made of other conductive pastes.

[0153] Therefore, the paper-based flexible pressure sensor obtained by the present invention has the advantages of being environmentally friendly, low-cost, flexible, non-toxic, skin-friendly, high strength, high sensing performance, and good hydrophobicity. A comprehensive comparison of the various performance parameters of the materials shows that Examples 1, 4, and 6 perform relatively well. Preferably, Example 1 achieves the best overall performance.

[0154] The sensors of Example 1, Example 4 and Example 6 performed well in terms of mechanical strength, tear resistance, folding resistance, hydrophobicity, sensing performance, and response and recovery time.

[0155] The tensile strength, tear strength, folding endurance, contact angle, sheet resistance, sensitivity, response time and recovery time of Example 1 are all at a high level, indicating that while maintaining good mechanical properties and sensing performance, it also has good hydrophobicity and rapid response capabilities.

[0156] Therefore, according to the above analysis, Example 1 has the best overall effect, which is due to its good balance between various performance parameters. This balance is very important for the practical application of sensors because it is most likely to affect the durability and performance stability of the sensor.

[0157] The embodiments described above are only preferred embodiments of the present invention and are only used to explain the present invention, not to limit the scope of implementation of the present invention. For those skilled in the art, it is of course possible to easily make other implementation methods by replacing or changing the technical content disclosed in this specification. Therefore, all changes and improvements made on the principles of the present invention should be included in the scope of the patent application of the present invention.

Claims

1. A paper-based pressure sensor composite material, characterized in that: The composite material comprises the following raw materials in parts by weight: 30 parts of pulp, 2 to 8 parts of carboxylated multi-walled carbon nanotubes, 0 to 6 parts of sizing agent, and 3 parts of wet strength agent; the concentration of the pulp is 10 wt%.

2. The paper-based pressure sensor composite material according to claim 1, characterized in that: The composite material comprises the following raw materials in parts by mass: 30 parts of pulp, 5 parts of carboxylated multi-walled carbon nanotubes, 4 parts of sizing agent, and 3 parts of wet strength agent.

3. The paper-based pressure sensor composite material according to claim 1, characterized in that: The pulp is one or a combination of two or more of softwood pulp, hardwood pulp, reed pulp, and corn straw pulp; the sizing agent is one or a combination of two or more of rosin, alkyl ketene dimer, alkyl succinic anhydride, and alkyl ketone; and the wet strength agent is one or a combination of two or more of polyamide-epichlorohydrin, urea-formaldehyde resin, melamine formaldehyde resin, polyacrylamide, and modified starch.

4. The paper-based pressure sensor composite material according to claim 3, characterized in that: The paper pulp is softwood pulp, the sizing agent is alkyl ketene dimer, and the wet strength agent is polyamide-epichlorohydrin.

5. The method for preparing the paper-based pressure sensor composite material according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (1) Adding the paper pulp and the diluted sizing agent to the slurry dispersion barrel in sequence, stirring evenly, then adding the diluted wet strength agent to the slurry dispersion barrel, continuing to stir evenly, fully dispersing the paper pulp, making paper, and drying to obtain paper; (2) adding carboxylated multi-walled carbon nanotubes to water and uniformly dispersing the carbon nanotubes by ultrasonication to prepare a conductive slurry of carboxylated multi-walled carbon nanotubes with a concentration of 1 to 8 wt %; (3) Cutting the paper into appropriate sizes, and dipping it into the carboxylated multi-walled carbon nanotube conductive slurry for 4 to 72 hours; placing the impregnated paper in an oven at 80° C. and drying it for 12 hours to obtain a paper-based pressure sensor composite material.

6. The method for preparing the paper-based pressure sensor composite material according to claim 5, characterized in that: The pulp preparation method comprises the following steps: cutting a pulp sheet into small pieces, soaking the pieces in deionized water, stirring and dispersing the pieces uniformly, fully swelling the pieces, and removing dust and impurities; taking the pieces out after soaking and placing them in a pulp bag to balance the moisture content; adding an appropriate amount of water to make the pulp concentration reach 10wt% to balance the moisture content; and adding the pulp into a pulping machine for pulping.

7. The method for preparing the paper-based pressure sensor composite material according to claim 5, characterized in that: The basis weight of the paper is 30 g / m 2 .

8. The method for preparing the paper-based pressure sensor composite material according to claim 6, characterized in that: The soaking temperature is 16-25°C, the soaking time is 10-12 hours, and the moisture equilibrium time is 12-18 hours.

9. Use of the paper-based pressure sensor composite material according to any one of claims 1 to 4 or the paper-based pressure sensor composite material obtained by the preparation method according to claim 5 in the preparation of a paper-based pressure sensor, characterized in that: The preparation method of the paper-based pressure sensor is as follows: (1) Cut the paper-based pressure sensor composite material into a square shape with a size of 11×11 mm, and take 2 pieces for assembly; select conductive tape as the electrode layer material, cut it into a size of 10×30 mm, and take 2 pieces for assembly; select polyimide tape as the packaging protective layer material, cut it into a size of 20×40 mm, and take 2 pieces for assembly; select a quantitative of only 5g / m 2 The ultra-thin porous paper is used as the insulating layer in the middle of the sensor. It is cut into 12×12mm size and two pieces are taken for assembly. (2) After aligning the two insulating layers in parallel, two layers of sensor material are laminated on the insulating layers to form four centrally symmetrical layers, with the insulating layers inside and the sensors outside. (3) The electrode layers are attached to the outside of the two-layer sensor, and the long strips of conductive tape are exposed as electrodes to form symmetrical 6 layers. After ensuring good contact between the electrodes and the conductive parts of the sensor material, the packaging protective layer is covered on the outermost layer for overall coating, exposing only the electrodes at both ends to form symmetrical 8 layers. The flexible paper-based pressure sensor is completed.

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