A paste for a flexible pressure sensor, a method of preparing the same, and a sensor and a method of preparing the same
By improving the dispersion technology and screen printing process of carbon nanotubes, the problems of insufficient dispersion and adhesion in flexible pressure sensors have been solved, thereby improving the sensitivity and stability of the sensors and reducing production costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- INST OF FLEXIBLE ELECTRONICS TECH OF THU ZHEJIANG
- Filing Date
- 2024-12-26
- Publication Date
- 2026-06-26
AI Technical Summary
In the prior art, carbon nanotubes have poor dispersion in the slurry of flexible pressure sensors, resulting in uneven mixing, which affects the sensitivity and stability of the sensor. Furthermore, the adhesion between the slurry and the flexible substrate is insufficient, affecting the long-term stability of the sensor.
A mixture of graphene oxide and multi-walled carbon nanotubes was ultrasonically dispersed to achieve uniform dispersion through the attraction of positive and negative charges. The mixture was then dried and annealed under vacuum conditions. Combined with screen printing technology and optimized electrode materials, the uniformity and adhesion of the slurry were improved.
It improves the sensitivity and stability of the sensor, reduces production costs, meets the requirements of high-precision monitoring, and enhances the conductivity and mechanical properties of the sensor.
Smart Images
Figure CN122276731A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of sensor technology, and in particular to a slurry for a flexible pressure sensor, its preparation method, and the sensor and its preparation method. Background Technology
[0002] In recent years, with the increasing demand for health monitoring, wearable devices, and IoT technologies, flexible pressure sensors have shown great application potential in fields such as medical monitoring, motion tracking, and human-computer interaction due to their unique flexibility, lightweight, biocompatibility, and high sensitivity. Carbon nanotubes, as a nanomaterial with excellent electron transport performance and mechanical strength, have been widely studied and applied in the fabrication of flexible piezoresistive sensors.
[0003] Despite some progress in the fabrication of flexible pressure sensors based on carbon nanotubes, the following drawbacks remain: Uneven slurry preparation: During the preparation of the conductive slurry, the poor dispersibility of carbon nanotubes in the solvent easily leads to agglomeration, resulting in uneven slurry preparation and consequently affecting the sensitivity and stability of the pressure sensor. Insufficient sensitivity: Although carbon nanotubes possess excellent electrical properties, in practical applications, limitations in slurry preparation and integration processes often prevent the sensor's sensitivity from reaching the expected level, failing to meet the demands of high-precision monitoring. Summary of the Invention
[0004] Based on this, this application provides a slurry for a flexible pressure sensor, its preparation method, and the sensor itself, aiming to improve the uniform dispersion of carbon nanotubes in a flexible polymer matrix to ensure significantly enhanced conductivity and mechanical properties of the sensor. Simultaneously, this application also focuses on how to effectively enhance the adhesion between the slurry and the flexible substrate to ensure the long-term stability and reliability of the sensor.
[0005] To achieve the above objectives, this application provides the following technical solution:
[0006] A method for preparing a flexible pressure sensor slurry includes the following steps:
[0007] In the first solvent, the conductive filler is ultrasonically dispersed, the conductive filler comprising: (1) graphene oxide, or (2) the graphene oxide and multi-walled carbon nanotubes, wherein the mass ratio of the multi-walled carbon nanotubes to the graphene oxide is (0-3):(1-2). After the reaction is completed, the remaining amine substances are removed by anhydrous ethanol under ultrasonic oscillation, centrifuged, and pressure-sensitive powder is prepared.
[0008] The binder, curing agent and pressure-sensitive powder are mixed and ultrasonically dispersed in a second solvent to obtain a uniform slurry;
[0009] The first solvent is ethylenediamine, hexamethylenediamine, or decanediamine.
[0010] Furthermore, the ratio of the amount of the first solvent to the mass of the conductive filler is not less than 50 mL: 1 g, preferably 100 mL: 1 g.
[0011] Further, after centrifugation, the powder is dried under vacuum and annealed in a nitrogen atmosphere at 300–400°C for 1–2 hours to prepare the pressure-sensitive powder.
[0012] Furthermore, the adhesive is polydimethylsiloxane, the curing agent is octamethylcyclotetrasiloxane, and the second solvent is dichloromethane.
[0013] Furthermore, the mass ratio of the adhesive, the curing agent, and the pressure-sensitive powder is 1:1:(10-30).
[0014] The slurry is obtained by any of the above-described methods for preparing flexible pressure sensor slurry.
[0015] A flexible pressure sensor comprising the slurry obtained according to any of the above-described methods for preparing flexible pressure sensor slurry, or the slurry described above.
[0016] Furthermore, its encapsulation structure is provided from bottom to top with a base layer, a lower electrode layer, a pressure-sensitive layer, an upper electrode layer and an encapsulation layer, wherein the pressure-sensitive layer is formed by uniformly coating the electrode with the slurry.
[0017] The above-mentioned method for preparing a flexible pressure sensor includes preparing the electrode on the substrate layer by screen printing technology, first heating and curing the substrate layer coated with the electrode to form the electrode layer, uniformly coating the slurry on the electrode, and then heating and curing it a second time to form the pressure-sensitive layer.
[0018] Furthermore, the temperature for the second heating and curing is higher than the temperature for the first heating and curing.
[0019] In the existing technology, there are still many shortcomings in the slurry preparation and integration scheme of carbon nanotube flexible piezoresistive sensors. For example, the uneven dispersion of carbon nanotubes in flexible polymers leads to a decrease in conductivity and mechanical properties; the adhesion between the slurry and the flexible substrate is difficult to guarantee; and there are also problems such as the selection of encapsulation materials and the optimization of encapsulation processes.
[0020] This application presents technological improvements to the slurry preparation and integration scheme of carbon nanotube-based flexible pressure sensors, aiming to overcome the shortcomings of existing technologies and enhance sensor performance and market competitiveness. Specific improvements include optimizing the slurry preparation process, simplifying the integration process, reducing costs, and improving sensitivity. By improving dispersion techniques and stabilizers, the dispersibility of carbon nanotubes in the solvent is enhanced, reducing agglomeration and ensuring uniform slurry preparation. Simultaneously, a novel integrated technology is developed, combining slurry coating, electrode preparation, and encapsulation into a simplified process, reducing operational steps and impurity introduction, optimizing the process, and improving sensor stability and reliability. In terms of the integration process, advanced printing technologies, such as screen printing, are employed to achieve precise slurry coating. Furthermore, by optimizing electrode materials and layout design, interference between electrodes is reduced, improving signal accuracy. In addition, by optimizing material selection and process design, manufacturing costs are reduced, and production efficiency is improved, making the carbon nanotube-based flexible pressure sensor more competitive in the market. Finally, by optimizing the slurry ratio and sensor structure design, the sensor's sensitivity is improved to meet the demands of high-precision monitoring. Attached Figure Description
[0021] Figure 1 This is a schematic diagram of the overall packaging structure. 1 is the base layer, 2 is the lower electrode layer, 3 is the pressure-sensitive layer, 4 is the upper electrode layer, and 5 is the packaging layer.
[0022] Figure 2 The graph shows the change in resistivity of slurry with different mass ratios as a function of pressure. Detailed Implementation
[0023] The technical solution of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.
[0024] A method for preparing a flexible pressure sensor slurry includes the following steps:
[0025] 1. In a first solvent, multi-walled carbon nanotubes (MWCNTs) and graphene oxide (BOO) are ultrasonically dispersed at room temperature. The mass ratio of MBCNTs to BOO is (0–3):(1–2), preferably 1:1, which helps improve the dispersibility and stability of the slurry. The surface-modified NH2CNTs are positively charged, and the BOO is negatively charged. Through the mutual attraction of positive and negative charges, NH2CNTs are successfully assembled on the surface of BOO, resulting in a GO-NH2CNTs mixture. After the reaction, the remaining amines are removed using anhydrous ethanol under ultrasonic oscillation. After centrifugation at 10,000 rpm, the mixture is dried under vacuum at 100°C and annealed in a nitrogen atmosphere at 300–400°C for 1–2 hours to prepare rGO-NH2CNTs pressure-sensitive powder.
[0026] The first solvent is ethylenediamine, hexamethylenediamine, or decanediamine, with hexamethylenediamine being preferred.
[0027] The advantages of this modification method are mainly reflected in the following aspects: (1) Through the mutual attraction of positive and negative charges, the surface-modified aminated carbon nanotubes (NH2-SWCNTs) can be assembled more stably and uniformly on the surface of graphene oxide. This assembly method not only improves the overall stability of the material, but also ensures the uniform distribution of each component in the pressure-sensitive solution, thereby improving the pressure-sensitive performance of the material. (2) This modification method simplifies the preparation process, reduces cumbersome steps and additional processing, and reduces production costs and time costs. At the same time, since the interaction of positive and negative charges is spontaneous, no additional adhesives or additives are needed, thereby avoiding possible impurities and adverse effects. (3) This modification method endows the material with new properties while maintaining the original properties of the material. For example, the introduction of aminated carbon nanotubes not only enhances the conductivity and mechanical strength of the material, but also provides it with more active sites, which is beneficial to further chemical reactions and performance optimization. These advantages make this modification method have a wider range of application prospects in the fields of pressure-sensitive materials and sensors.
[0028] 2. Mix the binder, curing agent, and pressure-sensitive powder in a mass ratio of 1:1:(10-30). Disperse the mixture ultrasonically in dichloromethane at room temperature to obtain a homogeneous slurry.
[0029] A flexible pressure sensor has an encapsulation structure comprising, from bottom to top, a base layer 1, a lower electrode layer 2, a pressure-sensitive layer 3, an upper electrode layer 4, and an encapsulation layer 5. The encapsulation layer 5 is bonded layer by layer to the upper electrode layer 4, the pressure-sensitive layer 3, the lower electrode layer 2, and the base layer 1 using adhesives such as 3M double-sided tape or epoxy resin. Figure 1 As shown.
[0030] The substrate layer is made of a transparent and flexible material, such as PET film.
[0031] The electrode layer comprises electrodes fabricated on the substrate layer using screen printing technology. Electrode materials can be metals such as copper and silver, or conductive polymers. Microstructures or patterns, such as porous structures or array patterns, can be introduced into the electrode layer to further improve the sensor's sensitivity and spatial resolution.
[0032] The pressure-sensitive layer is formed by uniformly coating the electrode with a slurry, which can be achieved by methods such as spin coating, spray coating or blade coating.
[0033] The encapsulation layer can be polydimethylsiloxane, thermoplastic polyurethane elastomer, or polyimide to protect the sensor from the influence of the external environment.
[0034] A method for fabricating a flexible pressure sensor includes preparing electrodes on a substrate layer using screen printing technology; firstly, heating and curing the substrate layer coated with electrodes at 120°C for 30 minutes to form an electrode layer; then uniformly coating the electrodes with a paste and secondly heating and curing at 130–150°C for 20 minutes to form a pressure-sensitive layer. The second curing temperature is higher than the first curing temperature.
[0035] The slurry components of Examples 1 to 5 are shown in Table 1.
[0036] Table 1
[0037]
[0038] The method for preparing the slurry for a flexible pressure sensor includes the following steps:
[0039] Using the above-mentioned dosage, multi-walled carbon nanotubes and graphene oxide were dispersed in ethylenediamine at room temperature using a CNC ultrasonic cleaner at 100W and 40kHz for 1 hour. After the reaction, the remaining amine substances were removed using anhydrous ethanol under ultrasonic oscillation. Subsequently, the mixture was centrifuged at 10,000 rpm to obtain a solid mixture, dried in a vacuum drying oven at 100℃ for 24 hours, and finally annealed in a tube furnace under a N2 atmosphere at 350℃ for 2 hours, with heating and cooling rates of 10℃ / min, to obtain rGO-NH2CNTs pressure-sensitive powder.
[0040] Mix the binder, curing agent and pressure-sensitive powder according to the above dosage, and ultrasonically disperse them in dichloromethane at 100W and 40kHz for 1 hour at room temperature to obtain uniform slurries, which are pressure-sensitive slurries 1 to 5.
[0041] Three control groups were set up, consisting of commercial pressure-sensitive carbon paste-1 (YGTJ), namely commercial pastes 1 to 3, and two control groups were set up, consisting of commercial pressure-sensitive carbon paste-2 (CAPITON-901B-YG), namely commercial pastes 4 and 5.
[0042] 500mg of each slurry was used to fabricate a flexible pressure sensor. Copper electrodes were prepared on a PET film using screen printing. The substrate layer coated with the copper electrodes was first cured by heating at 120℃ for 30 minutes to form the electrode layer. Each slurry was then uniformly coated onto the copper electrodes and cured a second time at 130℃ for 20 minutes to form the pressure-sensitive layer. A PDMS film was then placed over the pressure-sensitive layer. A PDMS encapsulation layer was then used to bond the upper electrode layer, pressure-sensitive layer, lower electrode layer, and substrate layer together layer by layer using adhesives such as 3M double-sided tape or epoxy resin, thus producing various flexible pressure sensors.
[0043] The fabricated flexible pressure sensor samples were placed on a pressure testing platform, and different pressure values were applied using an electronic pressure gauge. The corresponding resistance changes were recorded. By changing the pressure value, a pressure-resistance change curve can be obtained, and the detection results are as follows: Figure 2 As shown, when the mass ratio of multi-walled carbon nanotubes to graphene oxide is 1:1, the material resistance changes more significantly. The resistance variation range of the control group is 15–50 Ω (0.5–45 N), while the resistance variation range of the slurry in the example is 2–60 kΩ (0.5–45 N), and the maximum pressure range is also higher. The maximum repeatability measurement error of the pressure sensitivity of the slurry in the example is <5%, mainly because the addition of NH2CNTs can act as a "bridge" for rGO, and a more complete conductive network structure is constructed through the synergistic effect of the two.
[0044] The above description of the disclosed embodiments enables those skilled in the art to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. The embodiments are merely examples for clearly illustrating the technical solutions of this application and are not intended to limit the scope of this application.
Claims
1. A method for preparing a flexible pressure sensor slurry, characterized in that, Includes the following steps: In the first solvent, the conductive filler is ultrasonically dispersed, the conductive filler comprising: (1) graphene oxide, or (2) the graphene oxide and multi-walled carbon nanotubes, wherein the mass ratio of the multi-walled carbon nanotubes to the graphene oxide is (0-3):(1-2). After the reaction is completed, the remaining amine substances are removed by anhydrous ethanol under ultrasonic oscillation, centrifuged, and pressure-sensitive powder is prepared. The binder, curing agent and pressure-sensitive powder are mixed and ultrasonically dispersed in a second solvent to obtain a uniform slurry; The first solvent is ethylenediamine, hexamethylenediamine, or decanediamine.
2. The method for preparing the flexible pressure sensor slurry according to claim 1, characterized in that, The ratio of the amount of the first solvent to the mass of the conductive filler is not less than 50 mL: 1 g.
3. The method for preparing the flexible pressure sensor slurry according to claim 1, characterized in that, After centrifugation, the powder is dried under vacuum and annealed in a nitrogen atmosphere at 300–400°C for 1–2 hours to prepare the pressure-sensitive powder.
4. The method for preparing the flexible pressure sensor slurry according to claim 1, characterized in that, The adhesive is polydimethylsiloxane, the curing agent is octamethylcyclotetrasiloxane, and the second solvent is dichloromethane.
5. The method for preparing the flexible pressure sensor slurry according to claim 1, characterized in that, The mass ratio of the adhesive, the curing agent, and the pressure-sensitive powder is 1:1:(10-30).
6. The slurry obtained by the preparation method of the flexible pressure sensor slurry according to any one of claims 1 to 5.
7. A flexible pressure sensor, characterized in that, It includes the slurry obtained by the method for preparing flexible pressure sensor slurry according to any one of claims 1 to 5, or the slurry according to claim 6.
8. The flexible pressure sensor according to claim 7, characterized in that, Its encapsulation structure consists of a base layer, a lower electrode layer, a pressure-sensitive layer, an upper electrode layer, and an encapsulation layer, arranged sequentially from bottom to top. The pressure-sensitive layer is formed by uniformly coating the electrode with the slurry.
9. The method for fabricating a flexible pressure sensor according to claim 8, characterized in that, The process includes preparing the electrode on the substrate layer using screen printing technology, first heating and curing the substrate layer coated with the electrode to form the electrode layer, then uniformly coating the slurry onto the electrode and heating and curing it a second time to form the pressure-sensitive layer.
10. The preparation method according to claim 9, characterized in that, The temperature for the second heating and curing is higher than the temperature for the first heating and curing.