A method for rapidly preparing a high-sensitivity three-dimensional circular hole aerogel stress sensor

Abstract

The application discloses a method for rapidly preparing a high-sensitivity three-dimensional circular hole aerogel stress sensor and belongs to the technical field of porous carbon materials. The method comprises the following steps: (1) graphite powder is subjected to an oxidation-reduction method to obtain graphene oxide (GO) with a large specific surface area and good dispersibility; and MAX is etched by hydrochloric acid to obtain a carbon titanium carbide (MXene) suspension with excellent conductive performance; (2) GO, MXene, ascorbic acid and a foaming agent are mixed and then subjected to a hydrothermal reaction to obtain a composite hydrogel; (3) the composite hydrogel is subjected to freezing, freezing and thawing in ethanol and then air drying, and is subjected to carbonization by a Joule heating device to obtain a composite carbon aerogel with good mechanical properties; and (4) the composite aerogel is attached to a graphite foil electrode to assemble a stress sensor. The method is simple and has the potential of rapidly preparing a high-sensitivity aerogel stress sensor; the prepared aerogel has high compressibility and super-high sensitivity, and is expected to be used as a matching device for modern intelligent equipment.

Description

Technical Field

[0001] This invention belongs to the field of electrical sensor technology, and in particular relates to a method for rapidly preparing a high-sensitivity three-dimensional circular hole aerogel stress sensor. Background Technology

[0002] In recent years, with the rapid development of medical technology, health issues have received widespread attention. People are increasingly focused on bionic limbs, health movement detection, and medical devices. Therefore, flexible sensors, which can serve as electronic skin and wearable devices, have attracted extensive attention and research. With the deepening of scientific research, various types of flexible sensors have emerged, including strain, temperature, humidity, and pressure sensors. These sensors can mimic the sensing properties of skin, enabling comprehensive detection of human health. Among the many flexible sensors, the flexible pressure sensor is a representative device. It can convert external mechanical stimuli into electrical signal outputs, enabling applications in fields such as artificial intelligence and medical devices. Compressible carbon aerogels, due to their porous internal structure and based on the piezoresistive effect, exhibit changes in their internal conductive paths during compression, leading to changes in their resistance. Therefore, they can be assembled into piezoresistive sensors for human-computer interaction, biomedical detection, and other fields. Traditional compressible carbon aerogels are mainly composed of carbon nanotubes, graphene and its derivatives, and other materials. However, these traditional carbon materials often suffer from low electrical conductivity, limiting the ability of sensors to detect minute stresses. Furthermore, the preparation of traditional aerogels is restricted by freeze-drying equipment, and is characterized by long preparation cycles, high costs, environmental pollution, and resource waste. Therefore, a rapid method for preparing elastic aerogels is of great significance for applications in modern smart devices. Summary of the Invention

[0003] The purpose of this invention is to address numerous problems existing in current sensors, such as low sensor sensitivity, high detection limits, and inadequate detection of minute stresses; and the high cost and long preparation cycle of traditional freeze-drying techniques used in the preparation of aerogels. This invention provides a method for rapidly preparing compressible composite aerogels and their application in high-sensitivity sensors. This composite aerogel has advantages such as simple preparation process, short process, good mechanical properties, excellent flexibility, and good conductivity. When used in sensors, it features low detection limits and high sensitivity, and has broad application prospects.

[0004] The technical solution adopted in this invention is as follows:

[0005] A method for rapidly fabricating a highly sensitive three-dimensional circular porous aerogel stress sensor includes the following steps:

[0006] 1) Preparation of graphene oxide (GO) solution;

[0007] Preferably, 1 part by weight of graphite powder is uniformly mixed with 5-50 parts by weight of concentrated sulfuric acid (98 wt%), and then 2-4 parts by weight of potassium permanganate is added to the reaction system. The reaction system is then transferred to an oil bath container at a constant temperature of 35-40°C and stirred for 30-60 minutes. Subsequently, 200-400 parts by weight of deionized water is added to the reaction system, and the oil bath temperature is raised to 85-95°C and the reaction continues at this temperature for 20-60 minutes. After the reaction is completed, the reaction solution is poured into 500-1000 parts by weight of ice water, and 10-50 mL of hydrogen peroxide aqueous solution (30 wt%) is added dropwise until the solution changes from brown to orange-yellow. The solution is then filtered, washed with hydrochloric acid to remove metal ions, and then the filtered solution is placed in a dialysis bag for dialysis for 2-4 weeks. Finally, the GO concentrate is obtained by centrifugation to remove impurities.

[0008] 2) Preparation of MXene suspension;

[0009] Preferably, 1-3 parts by weight of lithium fluoride (LiF) are added to 20-50 parts by weight of 9 mol / L hydrochloric acid (HCl) and stirred until completely dissolved. Then, 1 part by weight of MAX (Ti3AlC2) is added to the etching solution and mixed evenly at a stirring speed of 300-500 rpm. The mixture is then reacted at a temperature of 30-40°C for 24-48 hours. The resulting suspension is sonicated to separate MXene into layers, and finally, the MXene suspension is obtained by centrifugation to remove impurities and concentration.

[0010] 3) Mix the GO solution obtained in step 1) and the MXene suspension obtained in step 2) to obtain a homogeneous mixture, and then add the nonionic surfactant alkyl glycoside and the reducing agent ascorbic acid (VC) to obtain a GO / MXene / VC / alkyl glycoside mixed solution.

[0011] Preferably, in the homogeneous mixture, the GO concentration is 1–12 mg / mL (e.g., the GO concentration is 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL, 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL, 10 mg / mL, 11 mg / mL, or 12 mg / mL), and the MXene concentration is 1–13 mg / mL (e.g., the MXene concentration is 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL, 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL, 10 mg / mL, 11 mg / mL, 12 mg / mL, or 13 mg / mL); preferably, in the GO / MX / VC / alkyl glycoside mixed solution, the alkyl glycoside concentration is 5–22 mg / mL (e.g., alkyl glycoside concentration...). The concentrations are 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL, 10 mg / mL, 11 mg / mL, 12 mg / mL, 13 mg / mL, 14 mg / mL, 15 mg / mL, 16 mg / mL, 17 mg / mL, 18 mg / mL, 19 mg / mL, 20 mg / mL, 21 mg / mL or 22 mg / mL), and the ascorbic acid concentration is 5–22 mg / mL (e.g., ascorbic acid concentrations of 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL, 10 mg / mL, 11 mg / mL, 12 mg / mL, 13 mg / mL, 14 mg / mL, 15 mg / mL, 16 mg / mL, 17 mg / mL, 18 mg / mL, 19 mg / mL, 20 mg / mL, 21 mg / mL or 22 mg / mL).

[0012] 4) Use a high-shear homogenizer to emulsify the GO / MX / VC / alkyl glycoside mixed solution prepared in step 3) at a stirring speed of 500-4000 rpm for 10-120 seconds. After the mixture is homogenized and foamed, place it in a freezer and freeze for 6-18 hours.

[0013] 5) Thaw the frozen GO / MXene sample obtained in step 4) at room temperature, perform hydrothermal reaction on the thawed solution, and then freeze it in a freezer for 6-18 hours.

[0014] 6) Thaw the frozen composite hydrogel obtained in step 5), immerse the thawed hydrogel in ethanol, and shake it on a horizontal rotary shaker for 6 to 24 hours.

[0015] 7) The ethanol-filled composite gel obtained in step 6) is dried at room temperature for 6-12 hours to obtain a three-dimensional porous composite aerogel; then carbonization is carried out using a Joule heating device to obtain a composite carbon aerogel.

[0016] 8) Attach graphite foil electrodes to both ends of the aerogel obtained in step 7) and assemble it into a stress sensor.

[0017] Specifically, a method for rapidly fabricating a highly sensitive three-dimensional porous aerogel stress sensor includes the following fabrication steps:

[0018] 1) Preparation of graphene oxide: 150-350 mesh graphite powder was uniformly mixed with concentrated sulfuric acid. Potassium permanganate was added to the reaction system and the temperature of the reaction system was kept below 20℃. Then the reaction system was transferred to an oil bath that had been kept at 40℃ and stirred for 30-60 min. After the reaction was completed, 200-400 mL of deionized water was added to the reaction system and the oil bath temperature was increased to 90℃. The reaction was carried out at this temperature for 20-50 min. After the reaction was completed at 90℃, the reaction solution was poured into 300-500 mL of ice water and hydrogen peroxide aqueous solution (30 wt%) was added dropwise until the solution changed from brown to orange-yellow. Then the solution was filtered and washed with hydrochloric acid to remove metal ions. The filtered solution was then placed in a dialysis bag and dialyzed to remove the acid in the solution. Finally, the solution was concentrated by centrifugation to remove impurities and obtain GO concentrate.

[0019] 2) Preparation of MXene suspension: LiF was added to 9 mol / L hydrochloric acid (HCl) and stirred until completely dissolved to obtain an etching solution. Then, MAX was added to the etching solution and mixed evenly with stirring at 300-500 rpm. The mixture was reacted at 35°C for 24-48 h. The resulting suspension was sonicated to separate the MXene into layers, and finally, the MXene suspension was obtained by centrifugation to remove impurities and concentrate.

[0020] 3) Mix the graphene oxide and MXene suspensions obtained in steps 1) and 2) in a certain proportion, and then add an appropriate amount of foaming agent alkyl glycoside and reducing agent ascorbic acid.

[0021] 4) Use a high-shear homogenizer to stir the mixture from step 3), and after stirring until foamy, place it in a freezer and freeze for 6 hours.

[0022] 5) Place the GO / MXene solution from step 4) into an oven for hydrothermal reaction to obtain a composite hydrogel, and then freeze it in a freezer for 6 hours.

[0023] 6) Immerse the hydrogel obtained in step 5) in ethanol and shake it on a horizontal rotary shaker for 24 hours.

[0024] 7) The composite hydrogel filled with ethanol was dried at room temperature for 48 hours to obtain a three-dimensional porous composite aerogel. Then, it was carbonized using a Joule heating device to obtain a composite carbon aerogel with good mechanical properties.

[0025] Preferably, in step 1), the natural graphite powder used has a size of 325 mesh, and the mass ratio of graphite powder to potassium permanganate is 1–10:5–50. The ratio of concentrated sulfuric acid to graphite powder is 24–400 mL:1–15 g.

[0026] Preferably, in step 2), the sonication time is 10–60 min for multiple times to ensure sufficient MXene stratification. The centrifugation process for acid removal is performed at 6000–12000 rpm for 1–10 min. After centrifugation, the supernatant is discarded to remove excess hydrochloric acid and hydrofluoric acid produced during the reaction. This step is repeated until pH≈6. The centrifugation process for impurity removal is performed at 1000–3000 rpm for 5–20 min. After centrifugation, the supernatant is collected and water is added. This step is repeated 3–4 times. The centrifugation concentration step is performed at 8000–12000 rpm for 10–60 min. More preferably, the sonication time is 30 min, the centrifugation for acid removal is 8000 rpm for 3 min, the centrifugation process for impurity removal is 2000 rpm for 20 min, and the centrifugation concentration step is 10000 rpm for 40 min.

[0027] Preferably, in step 3), the MXene content in the GO / MXene / VC / alkyl glycoside mixed solution is 0-85 wt% (e.g., MXene content at mass concentrations of 0 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%). t%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, 40wt%, 41wt% , 42wt%, 43wt%, 44wt%, 45wt%, 46wt%, 47wt%, 48wt%, 49wt%, 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, 55wt%, 56wt%, 57wt%, 58wt%, 5 9wt%, 60wt%, 61wt%, 62wt%, 63wt%, 64wt%, 65wt%, 66wt%, 67wt%, 68wt%, 69wt%, 70wt%, 71wt%, 72wt%, 73wt%, 74wt%, 75wt%, 76wt%, 77wt%, 78wt%, 79wt%, 80wt%, 81wt%, 82wt%, 83wt%, 84wt%, or 85wt%), wherein the alkyl glycoside has a mass concentration of 10-20 mg / mL (e.g., the alkyl glycoside has a mass concentration of 10 mg / mL). The concentrations of MXene and GO are 11 mg / mL, 12 mg / mL, 13 mg / mL, 14 mg / mL, 15 mg / mL, 16 mg / mL, 17 mg / mL, 18 mg / mL, 19 mg / mL, or 20 mg / mL, respectively. The mass concentration of ascorbic acid is 20–30 mg / mL (e.g., 20 mg / mL, 21 mg / mL, 22 mg / mL, 23 mg / mL, 24 mg / mL, 25 mg / mL, 26 mg / mL, 27 mg / mL, 28 mg / mL, 29 mg / mL, or 30 mg / mL). Alkyl glycosides are good emulsifiers; their addition can make MXene and GO more evenly dispersed, and at the same time generate uniform bubbles during emulsification. Ascorbic acid is a reducing agent for GO, which can accelerate the reduction of GO during hydrothermal reaction to form a structurally stable hydrogel framework. More preferably, the MXene:GO ratio is 1:3, and the mass concentration of alkyl glycoside is 12 mg / mL.

[0028] Preferably, in step 4), the stirring speed of the homogenizing emulsifier is 500–5000 rpm, the stirring time is 0.5–3 min, and the freezing temperature of the freezer is -20°C. More preferably, the stirring speed is 3000 rpm and the stirring time is 30 s.

[0029] Preferably, in step 5), the hydrothermal reaction conditions are 80°C for 3 hours and the freezer temperature is -20°C.

[0030] Preferably, in step 6), the ethanol concentration is 95% (volume fraction), and the rotation speed of the horizontal rotary oscillator is 80 rpm.

[0031] Preferably, in step 7), the Joule heating temperature is controlled at 480°C and the heating time is 30 seconds.

[0032] The compressible composite carbon aerogel that can be rapidly prepared in the above steps is suitable for applications in sensor devices, especially in pressure sensing electronics.

[0033] A rapid fabrication method for a highly sensitive three-dimensional circular hole aerogel stress sensor is described above.

[0034] Compared with the prior art, the present invention has the following technical effects:

[0035] (1) The raw materials selected in this invention are all commercial products, including natural graphite powder, potassium permanganate, concentrated sulfuric acid, concentrated hydrochloric acid, hydrogen peroxide, MAX, lithium fluoride, alkyl glycosides, and ascorbic acid. These raw materials are widely available on the market and are inexpensive, which can effectively save on usage costs.

[0036] (2) The GO preparation process adopts the room temperature oxidation method, and the obtained GO precursor has good dispersibility, excellent structural integrity, and excellent mechanical properties after reduction.

[0037] (3) MXene, which has excellent conductivity, is composited with traditional carbon material graphene oxide. According to the theory of like dissolves like, the hydroxyl terminus of GO can react with Ti3C2T. x The composite solution is well mixed, fully utilizing the large surface area, excellent water solubility, and excellent mechanical properties of GO, as well as the properties of Ti3C2T. x The good conductivity of the alkyl glycosides has a synergistic effect, thereby improving the resistivity of the sensor. After stirring, the added alkyl glycosides form a rich porous structure in the composite solution. The composite aerogel with a rich porous structure can achieve a geometric enhancement effect, giving the piezoresistive sensor better mechanical properties and higher sensitivity.

[0038] (4) The hydrogel of the present invention is dried naturally during the drying process. Compared with the traditional freeze-drying technology, it does not require freeze-drying equipment, reduces production costs, and is not limited by freeze-drying equipment. It can realize the preparation of large-scale aerogels, which greatly improves production efficiency.

[0039] (5) In this invention, the carbonization method is Joule heating, which is different from traditional furnace heating. Joule heating can generate ultra-high temperature at the connection point with high resistance, thereby improving the electrical conductivity of the material and completing carbonization in a short time, shortening industrial production time and saving costs. Attached Figure Description

[0040] Figure 1 The image shows the microscopic circular pore structure characterization of the elastic aerogel described in Example 3 of the present invention at a magnification of 24x.

[0041] Figure 2 The figures shown are comparative images of the elastic aerogels described in Experimental Example 1(a), Example 2(b), Example 3(c) and Example 4(d) of the present invention before and after natural drying. It can be seen that the volume of the gel does not change significantly before and after drying. Therefore, the aerogels of Examples 1 to 4 have the potential to be air-dried.

[0042] Figure 3 The figure shows the stress-strain relationship of the elastic aerogel described in Experimental Example 1(a), Example 2(b), Example 3(c) and Example 4(d) of the present invention under 20%, 40%, and 60% compression strain for 10 cycles.

[0043] Figure 4 The figure shown is a graph showing the stress versus strain relationship of the aerogel compressed to 10-90% strain according to Experimental Example 3 of the present invention.

[0044] Figure 5 The figure shows the mechanical stability of the aerogel (circular hole structure) described in Experimental Example 3 of the present invention after 1000 cycles of compression at 40% strain.

[0045] Figure 6 The figure shows the mechanical stability of the aerogel (without circular pores) described in Experimental Example 5 of the present invention under 40% strain compression for 500 cycles.

[0046] Figure 7 The figure shown is a graph showing the relationship between the current and voltage when the aerogel sensor of the present invention is compressed to 104 Pa to 1543 Pa.

[0047] Figure 8 The figure shown is a graph showing the relationship between the strain current and time of the aerogel sensor compressed from 0% to 80% according to Experimental Example 3 of the present invention.

[0048] Figure 9The figure shows the sensitivity of the aerogel compressed to 40% strain for Experimental Example 1(a), Example 2(b), Example 3(c), Example 4(d) and Example 5(e) of the present invention. Detailed Implementation

[0049] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0050] In the following embodiments of the present invention, the alkyl glycosides were purchased from Wanhua Sample Co., Ltd.

[0051] Example 1

[0052] 1) Preparation of graphene oxide: 10g of 325 mesh graphite powder and 240ml of concentrated sulfuric acid (98wt%) were mixed evenly in an ice-water bath. 35g of potassium permanganate was slowly added to the above solution. The reaction temperature of the system was kept at 20℃ and the addition time was 1h. After stirring at 300rpm for 30min, the mixture was transferred to an oil bath at about 35℃. 400mL of distilled water was slowly added dropwise to the solution using a peristaltic pump. After reacting for 1h, the temperature was raised to 95℃ and stirring was continued for 1h. The reaction solution was then poured into ice water, and 30 mL of hydrogen peroxide (30 wt%) aqueous solution was added until the solution changed from brown to orange-yellow. The reaction solution was then poured into 800 mL of ice water and filtered. After filtration, the filter cake was washed with dilute hydrochloric acid to remove metal ions, and then soaked in 1600 mL of distilled water to obtain filtrate. The obtained filtrate was dialyzed to remove acid for 21 days and centrifuged to remove unpeeled impurities, resulting in a monolayer graphene oxide (GO) dispersion with a concentration of 10 mg / mL.

[0053] 2) Preparation of reduced graphene oxide (rGO) aerogel: Take 2 mL of the GO dispersion prepared in step 1) above, add alkyl glycoside (purchased from Wanhua Sample Co., Ltd.) and ascorbic acid to obtain a mixture. In the mixture, the alkyl glycoside concentration is 12 mg / mL and the ascorbic acid concentration is 20 mg / mL. The mixture is then vortexed for 2 min to ensure homogeneity, followed by stirring at 3000 rpm for 0.5 min using a homogenizer. The mixture is then placed in a freezer (-20°C) and frozen for 6 h. After thawing in air, the frozen mixture undergoes a hydrothermal reaction at 80°C for 3 h to obtain rGO hydrogel. The hydrogel is then placed in a freezer (-20°C) and frozen for 6 h. After thawing at room temperature, the rGO hydrogel is immersed in 95 wt% ethanol and rotated at 80 rpm for 10 h on a horizontal rotary shaker. The ethanol-filled gel is then dried in air for 10 h to obtain rGO composite aerogel. Finally, the obtained rGO aerogel is placed in a Joule heating device and heated to 480°C for 30 s for carbonization to obtain highly elastic rGO aerogel.

[0054] The mechanical and compressive properties of rGO aerogel were measured at room temperature using a C44104 electronic universal testing machine. The aerogel exhibited good compressive elasticity, returning to its original shape after deformation under stress. This is attributed to the abundant porous structure within the aerogel, which deforms during compression, resulting in a favorable mechanical structure and thus excellent compressive elasticity in the composite aerogel. Figure 3 (a) shows the stress-strain curve of the rGO aerogel prepared in this embodiment. It can be seen that the stress of the aerogel will decrease to a certain extent as the number of compression cycles increases. This is because some of the more fragile structures inside the aerogel are destroyed during the compression process. As shown in the figure, the aerogel has a high compressive strength of 5.9 kPa (60% strain).

[0055] The rGO aerogel prepared in this embodiment was used as the main sensing element, and a 5×5cm aerogel was attached to each of the upper and lower clamps of an electronic universal testing machine. 2 A graphite foil electrode was connected to a CHI660E electrochemical workstation. The current (I)-time (t) curve of the sensor was measured in real time at a DC voltage of 0.2V. Figure 9 As shown in (a), the sensitivity of the sensor based on rGO aerogel exhibits three stages. First, under low stress (0–450 Pa stress range), due to external extrusion, dense conductive pathways are formed between the abundant pores inside the aerogel, resulting in a dramatic increase in sensitivity, reaching 309.11 kPa. -1The sensitivity of the aerogel is measured in the first stage (stress range of 0–450 Pa). In the second stage (stress range of 450–800 Pa), when the aerogel is subjected to external force, its sensitivity begins to decrease, reaching 142.86 kPa. -1 In the third stage (stress range of 800–2750 Pa), the aerogel is subjected to external compression. While the pore structure maintains sufficient contact, the increase in conductive paths is minimal. However, as the compression increases, the stress rises sharply, causing the sensitivity to further decrease to 65.82 kPa. -1 (Stress range of 800~2750Pa).

[0056] Figure 2 (a) shows a comparison of the elastic aerogel described in Experimental Example 1 of the present invention before and after natural drying. It can be seen that the volume of the gel did not change significantly before and after drying. Therefore, the aerogel of Example 1 has the potential to be air-dried.

[0057] Example 2

[0058] The preparation steps of rGO / MXene composite aerogel are as follows:

[0059] 1) Preparation of graphene oxide dispersion: A GO dispersion at 25°C with a concentration of 10 mg / ml was prepared using the method in Example 1;

[0060] 2) Preparation of MXene dispersion: 2g of lithium fluoride (LiF) was added to 25mL of 9mol / L hydrochloric acid (HCl) and stirred until completely dissolved. Then, 1g of MAX (Ti3AlC2) was added to the etching solution and mixed evenly at a stirring speed of 350rpm. The mixture was reacted at 35℃ for 24h. The resulting suspension was sonicated for 30min to separate the MXene into layers. Then, it was centrifuged at 8000rpm for 3min to remove the hydrofluoric acid and unreacted hydrochloric acid generated during the reaction. This step was repeated 3-4 times until the solution pH≈6. The solution was then centrifuged at 2000rpm for 20min and repeated 3-4 times. The supernatant was collected to remove the unreacted MAX. Finally, the solution was concentrated by centrifuging at 10000rpm for 30min to obtain an MXene suspension with a mass concentration of 10mg / mL.

[0061] 3) Preparation of rGO / MXene composite aerogel: Take 1.8 mL of the GO dispersion prepared in step 1) above, and 0.2 mL of the MXene solution prepared in step 2) above, with a mass ratio of GO:MXene = 9, mix them, add alkyl glycoside and ascorbic acid to obtain a GO / MXene / VC / alkyl glycoside mixture. In the mixture, the concentration of the alkyl glycoside is 12 mg / mL, and the concentration of ascorbic acid is 20 mg / mL. Vortex the GO / MXene / VC / alkyl glycoside mixture for 2 min to ensure uniform mixing, then stir it using a homogenizer at 3000 rpm for 30 s. Place the mixture in a freezer (-20℃) and freeze for 10 h. After thawing the frozen mixture in air, perform a hydrothermal reaction at 80℃ for 3 h to obtain rGO / MXene hydrogel. The obtained hydrogel was placed in a freezer (-20℃) and frozen for 10 hours. After the frozen rGO / MX hydrogel melted at room temperature, it was immersed in 95wt% ethanol and rotated at 80 rpm for 10 hours on a horizontal rotary shaker. The ethanol-filled gel was then dried in air for 10 hours to obtain rGO / MX composite aerogel. Finally, the obtained rGO / MX aerogel was placed in a Joule heating device and heated to 480℃ for 30 seconds to carbonize, resulting in a highly elastic rGO / MXene aerogel.

[0062] The mechanical and compressive properties of rGO / MX aerogel were measured at room temperature using a C44104 electronic universal testing machine. Figure 3 (b) shows the stress-strain curve of the rGO / MX aerogel prepared in this embodiment. It can be seen that the aerogel stress decreases to a certain extent with the increase of the number of compression cycles. This is because some of the more fragile structures inside the aerogel are destroyed during the compression process. As shown in the figure, the aerogel has a high compressive strength of 9.5 kPa (60% strain).

[0063] The rGO / MX aerogel prepared in this embodiment was used to form the main sensing element, and a 5×5cm aerogel was attached to each of the upper and lower clamps of a universal testing machine. 2 A graphite foil electrode was connected to a CHI660E electrochemical workstation. The current (I)-time (t) curve of the sensor was measured in real time at a DC voltage of 0.2V. Figure 9 As shown in (b), the sensing performance of rGO / MXene aerogel exhibits three stages. First, under low stress (0–450 Pa stress range), due to external extrusion, dense conductive pathways are formed between the abundant pores inside the aerogel, thus dramatically increasing the sensitivity of the aerogel to 660.25 kPa. -1The sensitivity of the aerogel is measured in the first stage (stress range of 0–1000 Pa); in the second stage (stress range of 1000–1600 Pa), when the aerogel is subjected to external force, the sensitivity of the aerogel begins to decrease, reaching 280.31 kPa. -1 In the third stage (stress range of 1600–3500 Pa), the aerogel is subjected to external compression. While the pore structure maintains sufficient contact, the increase in conductive paths is minimal. However, as the compression increases, the stress rises sharply, causing the sensitivity to further decrease to 120.34 kPa. -1 (Stress range of 1600 to 3500 Pa), and compared with Example 1, the sensitivity of all three stages is improved accordingly, which is due to the incorporation of MXene, which enhances the overall conductivity of the aerogel.

[0064] Figure 2 (b) shows a comparison diagram of the elastic aerogel described in Example 2 of the present invention before and after natural drying. It can be seen that the volume of the gel does not change significantly before and after drying. Therefore, the aerogel of Example 2 has the potential to be air-dried.

[0065] Example 3

[0066] The preparation steps of rGO / MXene composite aerogel are as follows:

[0067] 1) Preparation of graphene oxide dispersion: A 10 mg / mL GO dispersion was prepared using the method described in Example 1;

[0068] 2) Preparation of MXene dispersion: An MXene dispersion with a concentration of 10 mg / mL was prepared using the method described in Example 2;

[0069] 3) Preparation of rGO / MXene composite aerogel: Take 1.5 ml of the GO dispersion prepared in step 1) above, and 0.5 ml of the MXene solution prepared in step 2) above, with a mass ratio of GO:MXene = 3, and mix them to obtain a GO / MXene mixed solution. Add ascorbic acid and alkyl glycoside to the GO / MXene mixed solution to obtain a GO / MXene / VC / alkyl glycoside mixed solution. In the GO / MXene / VC / alkyl glycoside mixed solution, the concentration of ascorbic acid is 12 mg / mL and the concentration of alkyl glycoside is 20 mg / mL. Shake the GO / MXene / VC / alkyl glycoside mixed solution on a vortex shaker. Stir the solution for 2 minutes to ensure uniformity, then stir it for 0.5 minutes at 3000 rpm using a homogenizer. Place the mixture in an oven for hydrothermal reaction at 80°C for 3 hours to obtain rGO / MXene hydrogel. Immerse the obtained hydrogel in 95wt% ethanol and rotate it at 80 rpm for 10 hours on a horizontal rotary shaker. Dry the ethanol-filled gel in air for 10 hours to obtain rGO / MXene composite aerogel. Finally, place the obtained rGO / MXene aerogel in a Joule heating device and heat it to 480°C for 30 seconds to carbonize it, obtaining highly elastic rGO aerogel. Figure 1 The image shows the microscopic circular pore structure characterization of the elastic aerogel described in Example 3 of the present invention at a magnification of 24x.

[0070] The mechanical and compressive properties of rGO / MXene aerogel were measured at room temperature using a C44104 electronic universal testing machine. Figure 3 (c) shows the stress-strain curves of the rGO / MXene aerogel prepared in this embodiment after 10 compression cycles at 20%, 40%, and 60% strain. It can be seen that the aerogel stress decreases to a certain extent with the increase in the number of compression cycles. This is because some relatively fragile structures inside the aerogel are destroyed during the compression process. Furthermore, the figure shows that the aerogel has a high compressive strength of 10.2 kPa (60% strain). Figure 4 It can be seen that rGO / MXene aerogel can rebound after being compressed to 90% strain, and the compressive strength at 90% strain can reach 105.6 kPa. Figure 5 The figure shows the mechanical stability of the aerogel (circular hole structure) described in Experimental Example 3 of the present invention after 1000 cycles of compression at 40% strain.

[0071] The rGO / MXene aerogel prepared in this embodiment was used as the main sensing element, and a 5×5cm aerogel was attached to each of the upper and lower clamps of a universal testing machine. 2 A graphite foil electrode was connected to a CHI660E electrochemical workstation. The current (I)-time (t) curve of the sensor was measured in real time at a DC voltage of 0.2V. Figure 7 The image shows the relationship between voltage and current when rGO / MXene aerogel is subjected to stresses ranging from 0 to 1543 Pa. It can be seen that the slope of the image increases with increasing stress on the aerogel. This is because the composite aerogel sensor is piezoresistive; under external stress, its resistance decreases and its conductivity increases. Figure 8 The figure shows the current signal response of rGO / MXene aerogel when compressed to 10-90% deformation. Based on the piezoresistive effect of the aerogel, as the deformation increases, the resistance decreases, thus increasing the current signal. Figure 9 As shown in (c), the sensing performance of rGO / MXene aerogel exhibits three stages. First, under low stress (0–750 Pa stress range), due to external extrusion, dense conductive pathways are formed between the abundant pores inside the aerogel, thus dramatically increasing the sensitivity of the aerogel to 1116.98 kPa. -1 The sensitivity of the aerogel is measured in the first stage (stress range of 0–750 Pa); in the second stage (stress range of 750–1200 Pa), when the aerogel is subjected to external force, the sensitivity of the aerogel begins to decrease, reaching 377.93 kPa. -1 In the third stage (stress range of 1200–3000 Pa), the aerogel is subjected to external compression. While the pore structure maintains sufficient contact, the increase in conductive paths is minimal. However, as the compression increases, the stress rises sharply, causing the sensitivity to further decrease to 123.38 kPa. -1 (Stress range of 1200~3000Pa), and compared with Example 2, the sensitivity of the three stages is correspondingly improved. This is because the increased amount of MXene doping makes the overall conductivity of the aerogel stronger.

[0072] Figure 2 (c) shows a comparison diagram of the elastic aerogel described in Example 3 of the present invention before and after natural drying. It can be seen that the volume of the gel does not change significantly before and after drying. Therefore, the aerogel of Example 3 has the potential to be air-dried.

[0073] Example 4

[0074] The preparation steps of rGO / MXene composite aerogel are as follows:

[0075] 1) Preparation of graphene oxide dispersion: A 10 mg / mL GO dispersion was prepared using the method described in Example 1;

[0076] 2) Preparation of MXene dispersion: An MXene dispersion with a concentration of 10 mg / mL was prepared using the method described in Example 2;

[0077] 3) Preparation of rGO / MXene composite aerogel: Take 1.2 mL of the GO dispersion prepared in step 1) above, and 0.8 mL of the MXene solution prepared in step 2) above, with a mass ratio of GO:MXene = 3:2, mix them, add alkyl glycoside and ascorbic acid, and obtain a GO / MXene / VC / alkyl glycoside mixture. In the GO / MXene / VC / alkyl glycoside mixture, the concentration of alkyl glycoside is 12 mg / mL and the concentration of ascorbic acid is 20 mg / mL. The GO / MXene / VC / alkyl glycoside mixture was vortexed for 2 minutes to ensure homogeneity, then stirred at 3000 rpm for 0.5 minutes using a homogenizer. The mixture was then placed in a freezer (-20℃) and frozen for 10 hours. After thawing in air, the frozen mixture underwent a hydrothermal reaction at 80℃ for 3 hours to obtain rGO / MXene hydrogel. The hydrogel was then placed in a freezer (-20℃) and frozen for 6 hours. After melting at room temperature, the rGO / MXene hydrogel was immersed in 95wt% ethanol and rotated at 80 rpm for 10 hours using a horizontal rotary shaker. The ethanol-filled gel was then dried in air for 10 hours to obtain rGO / MXene composite aerogel. Finally, the obtained rGO / MXene aerogel was placed in a Joule heating device and heated to 480℃ for 30 seconds for carbonization to obtain highly elastic rGO / MXene aerogel.

[0078] The mechanical and compressive properties of rGO / MXene aerogel were measured at room temperature using a C44104 electronic universal testing machine. Figure 3 (d) shows the stress-strain curve of the rGO / MXene aerogel prepared in this embodiment. As can be seen from the figure, the stress-strain curves of the aerogel after 10 compressions at 20%, 40%, and 60% strain are as follows: the stress of the aerogel will decrease to a certain extent as the number of compression cycles increases. This is because some of the more fragile structures inside the aerogel are destroyed during the compression process. It can also be seen that the aerogel has a compressive strength of 16.7 kPa (60% strain).

[0079] The rGO / MXene aerogel prepared in this embodiment was used as the main sensing element, and a 5×5cm piece was glued to each of the upper and lower clamps of a universal testing machine. 2 A graphite foil electrode was used, connected to a CHI660E electrochemical workstation. The current (I)-time (t) curve of the sensor was measured in real time under a DC voltage of 0.2V. For example... Figure 9As shown in (d), the sensing performance of rGO / MXene aerogel exhibits three stages. First, under low stress (0–800 Pa stress range), due to external extrusion, dense conductive pathways are formed between the abundant pores inside the aerogel, thus dramatically increasing the sensitivity of the aerogel to 309.11 kPa. -1 The sensitivity of the aerogel is measured in the first stage (stress range of 0–800 Pa); in the second stage (800–1500 Pa), when the aerogel is subjected to external force, its sensitivity begins to decrease, reaching 142.86 kPa. -1 In the third stage (stress range of 800–1500 Pa), the aerogel is subjected to external compression. While the pore structure maintains sufficient contact, the increase in conductive paths is minimal. However, as the compression increases, the stress rises sharply, causing the sensitivity to further decrease to 65.82 kPa. -1 (1500~3100Pa), and compared to Figure 9 (e) The sensitivity of the aerogel without pores and the aerogel with pores increased significantly in all three stages. This may be because the pore structure allows the aerogel to form more contact area and more conductive pathways during compression, resulting in a significant increase in sensitivity.

[0080] Figure 2 (d) shows a comparison diagram of the elastic aerogel described in Example 4 of the present invention before and after natural drying. It can be seen that the volume of the gel does not change significantly before and after drying. Therefore, the aerogel of Example 4 has the potential to be air-dried.

[0081] Example 5

[0082] The preparation steps of rGO / MXene composite aerogel are as follows:

[0083] (1) Preparation of graphene oxide dispersion: A 10 mg / mL GO dispersion was prepared using the method in Example 1;

[0084] (2) Preparation of MXene dispersion: An MXene dispersion with a concentration of 10 mg / mL was prepared using the method in Example 2;

[0085] (3) Preparation of rGO / MXene composite aerogel: Take 1.5 mL of the GO dispersion prepared in step 1) above, and 0.5 mL of the MXene solution prepared in step (2) above, with a mass ratio of GO:MXene = 3:2, mix them, add 40 mg of ascorbic acid to obtain a GO / MXene / VC mixture, shake the GO / MXene / VC mixture on a vortex shaker for 2 min to make the solution uniform, put the mixture in a freezer (-20℃) and freeze for 10 h, then thaw the frozen mixture in the air and carry out a hydrothermal reaction at a temperature of 80℃. The reaction was carried out at a certain temperature for 3 hours to obtain rGO / MXene hydrogel. The hydrogel was then placed in a freezer (-20℃) and frozen for 6 hours. After the frozen rGO / MX hydrogel was melted at room temperature, it was immersed in 95wt% ethanol and rotated at 80 rpm for 10 hours on a horizontal rotary shaker. The ethanol-filled gel was then dried in air for 10 hours to obtain rGO / MX composite aerogel. Finally, the obtained rGO / MX aerogel was placed in a Joule heating device and heated to 480℃ for 30 seconds to carbonize, resulting in highly elastic rGO / MXene aerogel.

[0086] The mechanical and compressive properties of rGO / MXene aerogel were measured at room temperature using a C44104 electronic universal testing machine. Figure 6 The figure shows the mechanical stability of the rGO / MXene aerogel prepared in this embodiment after 500 cycles of compression at 40% strain. It can be seen that due to the lack of a porous structure inside the aerogel as support, the stress attenuation of the aerogel is large, and there is also more permanent deformation. Its elasticity is worse than that of aerogels with a porous structure.

[0087] The rGO / MXene aerogel prepared in this embodiment was used as the main sensing element, and a 5×5cm piece was glued to each of the upper and lower clamps of a universal testing machine. 2 A graphite foil electrode was used, connected to a CHI660E electrochemical workstation. The current (I)-time (t) curve of the sensor was measured in real time under a DC voltage of 0.2V. For example... Figure 9 As shown in (e), the sensing performance of rGO / MXene (poreless) aerogel exhibits three stages. First, under low stress (0–800 Pa stress range), due to external extrusion, dense conductive pathways are formed between the abundant pores inside the aerogel, thus dramatically increasing the sensitivity of the aerogel to 227.44 kPa. -1 The sensitivity of the aerogel is measured in the first stage (0–800 Pa stress range); in the second stage (800–1700 Pa), when the aerogel is subjected to external force, its sensitivity begins to decrease, reaching 72.15 kPa. -1In the third stage (stress range of 800–1700 Pa), the aerogel is subjected to external compression. While the pore structure maintains sufficient contact, the increase in conductive paths is minimal. However, as the compression increases, the stress rises sharply, causing the sensitivity to further decrease to 39.75 kPa. -1 (1500~4500Pa).

[0088] Matters not covered in this invention are common knowledge.

[0089] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable the present invention to be implemented. They are not intended to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for rapidly fabricating a highly sensitive three-dimensional circular porous aerogel stress sensor, characterized in that, Includes the following steps: 1) Preparation of graphene oxide solution: Mix 1-10 parts by weight of graphite powder with 5-50 parts by weight of concentrated sulfuric acid evenly, add 2-4 parts by weight of potassium permanganate to the reaction system, and then transfer the reaction system to an oil bath container at a constant temperature of 35-40 °C for stirring and reaction for 30-60 min. Then, add 200-400 parts by weight of deionized water to the reaction system, raise the oil bath temperature to 85-95 °C and continue the reaction at this temperature for 20-60 min. After the reaction is completed, pour the reaction solution into 500-1000 parts by weight of ice water, and add 10-50 mL of hydrogen peroxide aqueous solution until the solution changes from brown to orange-yellow. Filter, then wash with hydrochloric acid to remove metal ions, and then put the filtered solution into a dialysis bag for dialyzing for 2-4 weeks. Finally, centrifuge to remove impurities and concentrate to obtain GO concentrate. 2) Preparation of MXene suspension: 1-3 parts by weight of lithium fluoride were added to 20-50 parts by weight of 9 mol / L hydrochloric acid and stirred until completely dissolved. Then, 1 part by weight of MAX was added to the etching solution and mixed evenly at a stirring speed of 300-500 rpm. The mixture was reacted at 30-40 °C for 24-48 h. The resulting suspension was sonicated to separate the MXene into layers. Finally, the MXene suspension was obtained by centrifugation to remove impurities and concentration. 3) Mix the GO solution obtained in step 1) and the MXene suspension obtained in step 2) to obtain a homogeneous mixture. Then add the nonionic surfactant alkyl glycoside and the reducing agent ascorbic acid to obtain a GO / MXene / VC / alkyl glycoside mixed solution. In the homogeneous mixture, the concentration of GO is 1~11 mg / mL and the concentration of MXene is 1~12 mg / mL. In the GO / MXene / VC / alkyl glycoside mixed solution, the concentration of alkyl glycoside is 5~21 mg / mL and the concentration of ascorbic acid is 5~21 mg / mL. 4) Use a high-shear homogenizer to emulsify the GO / MXene / VC / alkyl glycoside mixed solution prepared in step 3) at a stirring speed of 500~4000 rpm for 10~120 s. After the mixture is homogenized and foamed, place it in a freezer and freeze for 6~18 h. 5) Thaw the frozen GO / MXene sample obtained in step 4) at room temperature, perform hydrothermal reaction on the thawed solution, and then freeze it in a freezer for 6-18 h. 6) Thaw the frozen composite hydrogel obtained in step 5), immerse the thawed hydrogel in ethanol, and shake it on a horizontal rotary shaker for 6 to 24 hours. 7) The ethanol-filled composite gel obtained in step 6) is dried at room temperature for 6-12 h to obtain a three-dimensional porous composite aerogel; then carbonized using a Joule heating device to obtain a composite carbon aerogel. 8) Attach graphite foil electrodes to both ends of the aerogel obtained in step 7) and assemble it into a stress sensor.

2. The method according to claim 1, characterized in that, Step 1) uses natural graphite powder with a size of 100-400 mesh.

3. The method according to claim 1, characterized in that, Step 2) uses MAX material with a size of 200-500 mesh. Ultrasonication is used to fully separate MXene into layers. During centrifugation to remove acid, the supernatant is discarded to remove excess hydrochloric acid and hydrofluoric acid produced in the reaction. This step is repeated until pH≈6. During centrifugation to remove impurities, water is added to the supernatant. This step is repeated 3-4 times.

4. The method according to claim 1, characterized in that, In step 3), the proportion of MXene in the GO / MXene / VC / alkyl glycoside mixed solution is 1~85 wt%.

5. The method according to claim 1, characterized in that, Step 4) The stirring speed of the high shear homogenizer is 1000~4000 rpm, and the freezing temperature of the freezer is -20~10℃.

6. The method according to claim 1, characterized in that, In step 5), the hydrothermal reaction conditions are 60~90℃ for 2~5 h; the freezer temperature is -20~10℃.

7. The method according to claim 1, characterized in that, In step 6), the ethanol concentration is 95% by volume, and the rotation speed of the horizontal rotating oscillator is 80 rpm.

8. The method according to claim 1, characterized in that, In step 7), the Joule heating temperature is controlled at 300~500℃ and the heating time is 10~120s.

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