Preparation method of reduced graphene oxide-CNC film / interdigital electrode pressure sensor

Abstract

The invention relates to the technical field of pressure sensors, in particular to a preparation method of a reduced graphene oxide-CNC film / interdigital electrode pressure sensor, and the pressure sensor is prepared by using polydimethylsiloxane (PDMS) as a packaging layer and a reduced graphene oxide-CNC film / interdigital electrode as a composite pressure sensing layer. According to the sensor, a reduced graphene oxide-cellulose nanocrystal (CNC) composite film packaged by polydimethylsiloxane (PDMS) and an interdigital electrode (RCI) structure are adopted, the PDMS material used in the method is green and environment-friendly, and physical damage and environmental influence of the interdigital electrode and an rGO / CNC film in the using process are reduced; the constructed sensor has the remarkable advantages of quick response, high stability, high environmental adaptability, multifunctional integration and the like, and has guiding significance for research and development of high-performance pressure sensors and development of intelligent materials in the future.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure sensors, and in particular to a method for preparing a reduced graphene oxide-CNC film / interdigital electrode pressure sensor. Background Art

[0002] There are four main types of wearable pressure sensors: piezoresistive, piezoelectric, capacitive, and triboelectric. Piezoresistive sensors, in particular, have been widely developed due to their simple structure, high cost-effectiveness, and ease of fabrication. Research on sensing materials has focused on metal nanoparticles, conductive polymers, and carbon materials, especially one-dimensional (1D) carbon nanotubes and two-dimensional graphene. However, relying solely on their own structure and properties, it is difficult to construct reliable and stable piezoresistive sensors from nanocarbon-based materials. To address this issue, a method has been proposed that combines a flexible insulating matrix, interdigitated electrodes, and carbon nanomaterials. Biomimetic laminated microstructures can improve the sensing performance of flexible piezoresistive pressure sensors due to their hierarchical and gradient structures. Interdigitated electrode microstructures can construct very highly sensitive piezoresistive sensors.

[0003] This proposal relates to a method for preparing a pressure sensor comprising a polydimethylsiloxane (PDMS)-encapsulated reduced graphene oxide (RGO)-CNC membrane / interdigitated electrodes and its application. The RCI sensor can be fabricated using a simple method. Due to the combination of interdigitated electrodes, rGO / CNC membrane, and PDMS encapsulation, the pressure sensor exhibits excellent sensing performance. The use of PDMS to encapsulate the RGO / CNC composite membrane improves the durability and solvent resistance of the functional composite membrane. This multifunctional, compact, and flexible pressure sensor has applications in wearable medical monitoring, robotics, human-machine interfaces, and other fields. Summary of the Invention

[0004] (1) Technical issues

[0005] In response to the shortcomings of the existing technology, the present invention provides a method for preparing a reduced graphene oxide-CNC film / interdigital electrode pressure sensor, aiming to solve the problem of how to prepare a pressure sensor with fast response speed, high stability and repeatability.

[0006] (2) Technical content

[0007] This solution provides a method for preparing a reduced graphene oxide-CNC film / interdigital electrode pressure sensor, comprising the following steps:

[0008] Step 1: Preparation of graphene oxide dispersion and CNC dispersion:

[0009] Dissolve 1 g of sodium nitrate in 60 mL of concentrated sulfuric acid, stir magnetically in an ice-water bath for 15 minutes, then add 2 g of graphite powder and continue stirring for 30 minutes. Then, slowly add 10 g of potassium permanganate below 10 ° C and stir for 1.5 hours. Adjust the stirrer temperature to 35 ° C and stir for not less than 8 hours. After stirring, add 1000 mL of deionized water to obtain an acidic GO aqueous solution, wash with 8%-10% hydrochloric acid 2-3 times, let it stand for stratification and then pour out the supernatant. Add water and let it stand for 5 minutes until the pH is about 6. Centrifuge and pour out the supernatant. Keep the lower layer solution and set the speed to 6500-9000 rpm to obtain a dark brown GO solution. Dialyze several times until the GO solution is neutral. After ultrasonication, obtain a graphene oxide dispersion for standby use.

[0010] The preparation steps of CNC (cellulose nanocrystals) are as follows:

[0011] Prepare 50 ml of 65% sulfuric acid solution, place it in a three-necked flask, cool to room temperature, and stir magnetically at 500 r / min. Then slowly add 5 g of microcrystalline cellulose, place the flask in a 50°C water bath, and stir magnetically for 1.5 h. After magnetic stirring, ultrasonicate for 15 min. Add 500 mL of deionized water to terminate the reaction, pour the solution into a centrifuge tube, centrifuge for 3-5 min (8000 r / min), then remove and pour out the supernatant, add distilled water to wash, shake well, and centrifuge again until a white suspension appears in the supernatant and the solution no longer separates;

[0012] The colloid after centrifugation is dialyzed (2-3 days) to obtain white gel-like CNC, which is dissolved in aqueous solution to prepare CNC dispersion for future use;

[0013] Step 2: Preparation of reduced graphene oxide / CNC film:

[0014] The graphene oxide dispersion and the CNC dispersion were mixed in proportion and ultrasonicated at room temperature for 1 h to obtain a graphene oxide / CNC mixed dispersion;

[0015] The graphene oxide / CNC mixed dispersion was poured into a Teflon mold, pre-dried at room temperature to obtain a colloidal-semisolid film, and then dried in an oven to obtain a GO / CNC composite film;

[0016] The prepared film was inserted into a sealed beaker containing hydroiodic acid (HI), and then placed in a constant temperature water bath to chemically reduce graphene oxide (GO) to reduced graphene oxide (rGO). The film was taken out and the residual hydroiodic acid was washed with a large amount of anhydrous ethanol. The film was then placed in a vacuum drying oven (60°C) and dried for 6 hours to obtain a smooth rGO / CNC composite film.

[0017] Step 3: Preparation of rGO / CNC interdigitated electrodes:

[0018] Interdigitated electrodes were assembled on a PET base film with an electrode size of 5*10 mm and an interdigitated distance of 50 μm. The interdigitated electrodes were then covered with the rGO / CNC composite film prepared above.

[0019] The positive and negative poles of the interdigital electrodes were connected to the external circuit using copper foil. Then, a PDMS solution with a masterbatch and curing agent mass ratio of 10:1 was applied and annealed at 80°C for 2 hours to solidify the PDMS. Finally, a PDMS / rGO / CNC / interdigital electrode (RCI) sensor was obtained.

[0020] Preferred technical solution 1: When the graphene oxide dispersion and the CNC dispersion in step 2 are mixed, the solid mass ratio of the two is one of GO and CNC, which is 75:25, 66:33 and 50:50, respectively.

[0021] Preferred technical solution 2: The drying conditions of the rGO / CNC composite membrane are 48 hours at room temperature and 4 hours in a 50°C oven, which have a significant impact on the final properties of the film. These conditions need to be strictly controlled to ensure the uniformity and stability of the rGO / CNC composite membrane.

[0022] Preferred technical solution three: The GO / CNC composite film is inserted into a sealed beaker containing hydroiodic acid (HI) and the composite film is taken out after being placed in a constant temperature water bath at 100°C for 1 hour. In this step, GO is chemically reduced to reduced graphene oxide (rGO) by hydroiodic acid (HI). The temperature and time of the reduction process need to be precisely controlled to obtain ideal conductivity and mechanical properties.

[0023] This method is simple and low-cost. It performs PDMS encapsulation on the rGO / CNC film / interdigital electrode sensor and endows it with electromagnetic shielding performance, temperature sensing capability, gesture recognition and tactile feedback capabilities. It has scientific and practical value. Therefore, this scheme also discloses the application of reduced graphene oxide-CNC film / interdigital electrode pressure sensor in wearable medical monitoring, robotics, human-machine interface and other fields.

[0024] (3) Technical effects

[0025] The above structure enables this solution to have the following beneficial effects:

[0026] 1. This sensor, which utilizes a polydimethylsiloxane (PDMS)-encapsulated reduced graphene oxide-cellulose nanocrystal (CNC) composite membrane and an interdigitated electrode (RCI) structure, exhibits significant advantages, including rapid response and high stability, strong environmental adaptability, multifunctional integration, promotion of sustainable development, intelligent health monitoring, and human-computer interaction. It has guiding significance for the development of high-performance pressure sensors and future smart materials.

[0027] 2. The process of this method is simple and easy to operate, the equipment requirements are not high, and the preparation method is environmentally friendly, economical, highly feasible, and widely used. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 This is a physical picture of the sensor of Example 1 of this solution;

[0030] Figure 2 This is a FSEM cross-sectional view of the sensor according to Example 1 of this solution;

[0031] Figure 3 This is the FTIR graph of the sensing material of Example 2 of this solution;

[0032] Figure 4 This is a graph showing the pressure resistance change data of the sensor in Example 1 of this solution;

[0033] Figure 5 This is a graph showing the corrosion resistance test results of the sensor in Example 1 of this solution. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0035] Example 1:

[0036] This embodiment provides a method for preparing a reduced graphene oxide-CNC film / interdigital electrode pressure sensor, which specifically includes the following steps:

[0037] Step 1: Dissolve 1g of sodium nitrate in 60mL of concentrated sulfuric acid and stir magnetically in an ice-water bath for 15 minutes; add 2g of graphite powder and continue stirring for 30 minutes. Slowly add 10g of potassium permanganate at a temperature below 10°C and stir for 1.5 hours; then adjust the stirrer temperature to 35°C and stir for at least 8 hours; after stirring, add 1000mL of deionized water to obtain an acidic GO aqueous solution; wash with 8%-10% hydrochloric acid 2-3 times, let it stand and then discard the supernatant; add water and let it stand and discard the supernatant until the pH is about 6; centrifuge and pour off the supernatant, retaining the lower layer solution, set the speed to 6500-9000rpm to obtain a dark brown GO solution; dialyze multiple times until the GO solution is neutral, and obtain a GO dispersion after ultrasonication for use;

[0038] The preparation steps of CNC (cellulose nanocrystal) are as follows: prepare 50 ml of 65% sulfuric acid solution, place it in a three-necked flask, cool it to room temperature, and then stir it magnetically at a speed of 500 r / min; slowly add 5 g of microcrystalline cellulose, place the flask in a 50°C water bath, and stir it magnetically for 1.5 hours; after magnetic stirring, ultrasonicate it for 15 minutes, and add 500 mL of deionized water to terminate the reaction; pour the solution into a centrifuge tube, centrifuge it for 3-5 minutes (8000 r / min), then take out and pour out the supernatant, add distilled water to wash, shake well, and centrifuge it again until a white suspension appears in the supernatant and the solution no longer separates; dialyze the colloid after centrifugation (2-3 days) to obtain white gel-like CNC, which is dissolved in aqueous solution to obtain a CNC dispersion for standby use;

[0039] Step 2: GO dispersion and CNC dispersion were mixed in a ratio of 75:25 and ultrasonically treated at room temperature for 1 hour; the graphene oxide / CNC mixed dispersion was poured into a Teflon mold and pre-dried at room temperature for 48 hours to obtain a colloidal-semisolid film, which was then dried in an oven at 50°C for 4 hours to obtain a GO / CNC film; the prepared film was inserted into a sealed beaker containing hydroiodic acid (HI) and placed in a constant temperature water bath to chemically reduce GO to reduced graphene oxide (rGO). After heating in a water bath at 100°C for 1 hour, the film was taken out; the residual hydroiodic acid was washed off with a large amount of anhydrous ethanol, and the film was placed in a vacuum drying oven (60°C) and dried for 6 hours to finally obtain a flat rGO / CNC composite film;

[0040] Step 3: The interdigital electrodes were assembled on a PET base film with an electrode size of 5*10MM and an interdigital distance of 50 microns; covered with the rGO / CNC composite film prepared above; copper foil was used to connect the positive and negative poles of the interdigital electrodes to the external circuit; then, a PDMS solution with a masterbatch and curing agent mass ratio of 10:1 was applied, and annealed at 80°C for 2h to solidify the PDMS; finally, a PDMS / rGO / CNC / interdigital electrode (RCI) sensor was obtained, as shown in FIG. Figure 1 As shown;

[0041] Step 4: The morphology and chemical structure of the PDMS / rGO / CNC / interdigitated electrode (RCI) sensor were characterized using field emission scanning electron microscopy (FSEM), as shown in Figure 4. Figure 2 As shown in Figure 2, the electromechanical behavior of the sensor is evaluated by applying different pressures and measuring the resistance changes. Figure 4 As shown in the figure, the stable resistance change characteristics of the sensor under different pressures are demonstrated; the resistance change rate is measured after the sensor is immersed in water, ultrasound, hydrochloric acid and sodium hydroxide solution for 6 hours to detect the corrosion resistance of the sensor, as shown in the figure. Figure 5As shown in the figure, the resistance change of the packaged RCI sensor is less than one thousandth after being immersed in different solutions such as water, ethanol, acid and alkali for 6 hours, which shows the stability of the sensor.

[0042] Example 2:

[0043] This embodiment provides a method for preparing a reduced graphene oxide-CNC film / interdigital electrode pressure sensor, which specifically includes the following steps:

[0044] Step 1: Dissolve 0.5g sodium nitrate in 23mL concentrated sulfuric acid and stir magnetically in an ice-water bath for 30 minutes; add 1g graphite powder and continue stirring for 30 minutes. Slowly add 6g potassium permanganate below 10°C and stir for 1.5 hours; then adjust the stirrer temperature to 35°C and stir for 24 hours; after stirring, add 1000mL deionized water to obtain an acidic GO aqueous solution; wash with 8%-10% hydrochloric acid 2-3 times, let it stand and separate the layers, then pour out the supernatant; add water again and let it stand and pour out the supernatant until the pH is about 6; centrifuge and pour out the supernatant, retain the lower layer solution, set the speed to 6500-9000rpm, and obtain a dark brown GO solution; dialyze multiple times until the GO solution is neutral, and obtain a GO dispersion after ultrasonication for use;

[0045] The preparation steps of CNC (cellulose nanocrystal) are as follows: prepare 50 ml of 65% sulfuric acid solution, place it in a three-necked flask, cool it to room temperature, and then stir it magnetically at a speed of 500 r / min; slowly add 5 g of microcrystalline cellulose, place the flask in a 50°C water bath, and stir it magnetically for 1.5 hours; after magnetic stirring, ultrasonicate it for 15 minutes, and add 500 mL of deionized water to terminate the reaction; pour the solution into a centrifuge tube, centrifuge it for 3-5 minutes (8000 r / min), then take out and pour out the supernatant, add distilled water to wash, shake well, and centrifuge it again until a white suspension appears in the supernatant and the solution no longer separates; dialyze the colloid after centrifugation (2-3 days) to obtain white gel-like CNC, which is dissolved in aqueous solution to obtain a CNC dispersion for standby use;

[0046] Step 2: GO dispersion and CNC dispersion were mixed in a 50:50 ratio and ultrasonically treated at room temperature for 1 hour; the graphene oxide / CNC mixed dispersion was poured into a Teflon mold and pre-dried at room temperature for 48 hours to obtain a colloidal-semisolid film, which was then dried in an oven at 50°C for 4 hours to obtain a GO / CNC film; the prepared film was inserted into a sealed beaker containing hydroiodic acid (HI) and placed in a constant temperature water bath to chemically reduce GO to reduced graphene oxide (rGO). After heating in a water bath at 100°C for 1 hour, the film was taken out; the residual hydroiodic acid was washed off with a large amount of anhydrous ethanol, and the film was placed in a vacuum drying oven (60°C) and dried for 6 hours to finally obtain a flat rGO / CNC composite film;

[0047] Step 3: The interdigitated electrodes were assembled on a PET substrate and covered with the rGO / CNC composite film prepared above. Copper foil was used to connect the positive and negative electrodes of the interdigitated electrodes to an external circuit. A PDMS solution containing a masterbatch and curing agent at a mass ratio of 10:1 was then applied and annealed at 80°C for 2 hours to solidify the PDMS. This resulted in a PDMS / rGO / CNC / interdigitated electrode (RCI) sensor.

[0048] Step 4: The morphology and chemical structure of the PDMS / rGO / CNC / interdigitated electrode (RCI) sensor were characterized using Fourier transform infrared spectroscopy (FTIR), as shown in Figure 4. Figure 3 shown.

[0049] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a reduced graphene oxide-CNC film / interdigital electrode pressure sensor, characterized in that: The steps include: Step 1: Preparation of graphene oxide dispersion and CNC dispersion: Dissolve 1 g of sodium nitrate in 60 mL of concentrated sulfuric acid, stir magnetically in an ice-water bath for 15 minutes, then add 2 g of graphite powder and continue stirring for 30 minutes. Then, slowly add 10 g of potassium permanganate below 10 ° C and stir for 1.5 hours. Adjust the stirrer temperature to 35 ° C and stir for not less than 8 hours. After stirring, add 1000 mL of deionized water to obtain an acidic GO aqueous solution, wash with 8%-10% hydrochloric acid 2-3 times, let it stand for stratification and then pour out the supernatant. Add water and let it stand for 5 minutes until the pH is about 6. Centrifuge and pour out the supernatant. Keep the lower layer solution and set the speed to 6500-9000 rpm to obtain a dark brown GO solution. Dialyze several times until the GO solution is neutral. After ultrasonication, obtain a graphene oxide dispersion for standby use. The preparation steps of CNC are as follows: Prepare 50 ml of 65% sulfuric acid solution, place it in a three-necked flask, cool to room temperature, and stir magnetically at 500 r / min. Then slowly add 5 g of microcrystalline cellulose, place the flask in a 50°C water bath, and stir magnetically for 1.5 h. After magnetic stirring, ultrasonicate for 15 min. Add 500 mL of deionized water to terminate the reaction, pour the solution into a centrifuge tube, centrifuge for 3-5 min (8000 r / min), then remove and pour out the supernatant, add distilled water to wash, shake well, and centrifuge again until a white suspension appears in the supernatant and the solution no longer separates; The colloid after centrifugation was dialyzed to obtain white gel-like CNC, which was dissolved in aqueous solution to obtain CNC dispersion for future use; Step 2: Preparation of reduced graphene oxide / CNC film: The graphene oxide dispersion and the CNC dispersion were mixed in proportion and ultrasonicated at room temperature for 1 h to obtain a graphene oxide / CNC mixed dispersion; The graphene oxide / CNC mixed dispersion was poured into a Teflon mold and pre-dried at room temperature to obtain a colloidal-semisolid film, which was then dried in an oven to obtain a GO / CNC composite film. The prepared film was inserted into a sealed beaker containing hydroiodic acid and placed in a constant temperature water bath to chemically reduce graphene oxide to reduced graphene oxide, i.e., rGO. After heating in a water bath at 100°C for 1 hour, the film was taken out. The residual hydroiodic acid was washed away with a large amount of anhydrous ethanol, and the film was placed in a vacuum drying oven (60°C) and dried for 6 hours to obtain a smooth rGO / CNC composite film. Step 3: Preparation of rGO / CNC interdigitated electrodes: Interdigitated electrodes were assembled on a PET base film. The interdigitated electrodes had a size of 5*10 mm and a distance between the interdigitated electrodes of 50 μm. The interdigitated electrodes were then covered with the rGO / CNC composite film prepared above. The positive and negative poles of the interdigital electrodes were connected to the external circuit using copper foil. Then, a PDMS solution with a masterbatch and curing agent mass ratio of 10:1 was applied and annealed at 80°C for 2 hours to solidify the PDMS. Finally, a PDMS / rGO / CNC / interdigital electrode (RCI) sensor was obtained.

2. The method for preparing a reduced graphene oxide-CNC film / interdigital electrode pressure sensor according to claim 1, characterized in that: In step 1, the colloid dialysis time after centrifugation is 2-3 days.

3. The method for preparing a reduced graphene oxide-CNC film / interdigital electrode pressure sensor according to claim 1, wherein: When the graphene oxide dispersion and the CNC dispersion in step 2 are mixed, the solid mass ratio of the two is one of 75:25, 66:33 and 50:50 for GO and CNC, respectively.

4. The method for preparing a reduced graphene oxide-CNC film / interdigital electrode pressure sensor according to claim 1, characterized in that: In step 2, after the graphene oxide / CNC mixed dispersion was poured into a Teflon mold, the drying conditions were 48 h at room temperature and 4 h in a 50 °C oven.

5. Application of the PDMS / rGO / CNC / interdigital electrode (RCI) sensor obtained according to the preparation method of the reduced graphene oxide-CNC film / interdigital electrode pressure sensor according to claims 1-4 in the fields of wearable medical monitoring, robotics, human-machine interface, etc.

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