A black phosphorus-gold composite nanomaterial-based sponge strain sensor and a preparation method and application thereof

Abstract

The application discloses a sponge strain sensor based on black phosphorus-gold composite nanomaterials and a preparation method and application thereof, and belongs to the technical field of flexible electronic materials. The sponge strain sensor comprises a sponge strain electrode and a paper printing electrode which are packaged into one body. The sponge strain electrode comprises melamine sponge, and the melamine sponge is filled with black phosphorus-gold composite nanomaterials. The melamine sponge and the paper substrate are good in flexibility, strong in deformation capacity under the action of pressure, sensitive to deformation sensing, and capable of accommodating more black phosphorus-gold composite nanomaterials due to the large number of voids of the melamine sponge. Therefore, the sponge strain sensor has better stability and specification coefficient while improving the comfort, response speed and sensitivity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of flexible electronic materials, and particularly relates to a sponge strain sensor based on black phosphorus-gold composite nanomaterials and a preparation method and application thereof. BACKGROUND

[0002] Traditional metal or inorganic semiconductor sensors are usually rigid and small-range strain detection, and thus are not suitable for wearable electronic human skin. In recent years, with the demand for wearability, simplicity and high sensitivity in the field of wearable devices, flexible wearable sensors have attracted more and more attention in human motion detection, personal health monitoring, speech recognition, human-computer interaction, etc. Flexible pressure sensors are the core components of such devices, and pressure sensors based on sensing mechanisms mainly have four types, namely piezoresistive, piezoelectric, capacitive and triboelectric thermal sensors. Piezoresistive sensors that convert external stimuli into resistance are extremely attractive due to their relatively simple structure, easy measurement, low cost and low power consumption in operation. However, it is still challenging to improve response speed, sensitivity and stability.

[0003] The British market analysis company IDTechEx predicts that the global flexible electronics market is expected to reach 301 billion US dollars by 2028. In addition, IDTechEx has been researching wearable technology for the past decade, and the research results show that during the entire period, wearable technology has experienced a turbulent growth, with a sharp increase in topics, accompanied by billions of dollars in funding, thousands of new patent applications and new companies, and hundreds of thousands of new products and hundreds of millions of dollars in new revenue. So far, wearable technology products have achieved great success, with a total market value of nearly 70 billion US dollars in 2019, doubling since 2014. In the emergency environment, wearable devices can remotely monitor patients, and medical staff can monitor the vital signs of patients at a safe distance. Flexible wearable medical products bring users a comfortable wearing experience due to their soft and thin characteristics. It is obvious that flexible wearable devices have great application value in health management. With the continuous development of technologies such as 5G, AI, and wearable devices, wearable medical devices will overcome various difficulties and become wearable and intelligent medical devices in a true sense, providing solid and powerful protection for people's healthy life in a wider range and deeper level.

[0004] From the comfort of wearing, response speed and sensitivity of flexible wearable devices, the materials of existing flexible wearable devices still need to be further improved in the above three aspects, especially the response speed and sensitivity. SUMMARY

[0005] The first object of the present application is to provide a sponge strain sensor based on black phosphorus-gold composite nanomaterials to solve the problem that the prior art flexible wearable device still needs to be further improved in the above three aspects, especially in response speed.

[0006] The present application discloses a sponge strain sensor based on black phosphorus-gold composite nanomaterials, comprising a sponge strain electrode and a paper printed electrode packaged into one body; wherein the sponge strain electrode comprises melamine sponge, and the melamine sponge is filled with black phosphorus-gold composite nanomaterials.

[0007] In the above technical solution, the melamine sponge and the paper substrate are good in flexibility and strong in deformation capacity under pressure, that is, sensitive to deformation sensing, and since the melamine sponge has a large number of voids, it can accommodate more black phosphorus-gold composite nanomaterials, thus improving comfort, response speed and sensitivity while showing better stability and specification coefficient. In addition, only simple cleaning of the melamine sponge is required in preparation, which has the advantages of low cost, simple production and use, etc. The sponge strain sensor prepared by the present application can be applied to the preparation of flexible wearable devices, wearable medical devices and pressure change sensing devices.

[0008] As a possible design, the black phosphorus-gold composite nanomaterials are obtained by modifying black phosphorus two-dimensional sheet-shaped nanomaterials with gold ions.

[0009] As a possible design, the gold ions are derived from a chloroauric acid solution.

[0010] The two-dimensional sheet-shaped nanomaterials are modified with gold nanoparticles, which fill the edge defects of the two-dimensional sheet-shaped nanomaterials and protect the two-dimensional sheet-shaped nanomaterials. The obtained composite nanomaterials have good conductivity and air acceptability, thereby improving the sensitivity of the flexible wearable device. The two-dimensional sheet-shaped nanomaterials used in the present application include but are not limited to graphene, black phosphorus and titanium carbide nanosheets. Then, by evaporating the water in the composite nanomaterial dispersion liquid, the composite nanomaterials are transferred to the melamine sponge to form an electrode wrapped with the composite nanomaterials.

[0011] The second object of the present application provides a preparation method of a sponge strain sensor, comprising:

[0012] The melamine sponge is added to the black phosphorus-gold composite nanomaterial solution, heated until the liquid evaporates, and then placed in a vacuum drying oven for drying at 30-40℃ for 4-6h to prepare a sponge strain electrode;

[0013] The conductive carbon paste is printed on the paper to form an electrode, and then dried at 40-50℃ for 3-5h to prepare a paper printed electrode;

[0014] The contact area of the sponge strain electrode and the paper printed electrode is bonded by a conductive bonding material and then encapsulated.

[0015] In the above technical solution, the preparation method is simple and easy to operate, and the black phosphorus-gold composite nanomaterial can be easily fixed in the gap of the melamine sponge.

[0016] As a possible design, the preparation method of the black phosphorus-gold composite nanomaterial solution is as follows:

[0017] The chloroauric acid solution and the black phosphorus two-dimensional sheet nanomaterial solution are mixed and oscillated at room temperature to obtain a reaction product; the mass ratio of the chloroauric acid to the black phosphorus two-dimensional sheet nanomaterial is 1:5-10:5.

[0018] As a possible design, the concentration of the chloroauric acid solution is 1 mg / mL; and the concentration of the black phosphorus two-dimensional sheet nanomaterial solution is 1 mg / mL.

[0019] As a possible design, the preparation method of the black phosphorus two-dimensional sheet nanomaterial is as follows:

[0020] The bulk black phosphorus is ground to prepare a black phosphorus dispersion liquid with a concentration of 1 mg / mL, the black phosphorus dispersion liquid is placed in a 500 W ultrasonic ice water bath for 30-35 h, finally, the mixed liquid after peeling is subjected to centrifugal treatment to remove the unpeeled black phosphorus particles, and the upper black phosphorus nanosheet suspension liquid is collected.

[0021] As a possible design, the specific preparation process of the paper printed electrode is as follows:

[0022] The conductive carbon paste is poured onto a screen printing template, and the conductive carbon paste is used to form an electrode on a flexible paper through the screen printing template using a squeegee; the screen printing template is a double-finger circuit shape.

[0023] The screen printing template of the present application is a customized shape, adopts a double-finger circuit shape, has the advantages of reducing impedance, quickly establishing a steady-state signal, high signal-to-noise ratio, and the like, and is convenient for developing a sensitive, fast and specific sensing device.

[0024] As a possible design, the conductive carbon paste is a mixed ink composed of carbon and graphite.

[0025] In the present application, the pressure signal is converted into a point signal by the fact that the mutual contact area of the internal circuits of the black phosphorus-gold composite nanomaterial electrode is different under different pressures, thereby causing different resistances; under no pressure, the contact area of the conductive path on the sponge skeleton is small, and the number of contacts is small; when pressure is applied, the contact area is large, and the number of contacts is large. Therefore, the sponge strain sensor prepared in the present application can be applied to all scenes of sensing pressure changes.

[0026] The beneficial effects of the present application are:

[0027] The sponge strain sensor prepared by the present application has simple manufacturing principle and process, and is made of soft melamine sponge and paper, and is comfortable to wear. Due to the unique structure and composite nanomaterial, the response speed, sensitivity, stability and specification coefficient of the sponge strain sensor prepared by the present application are improved, so that the sponge strain sensor has high practicality and reliability, has high practical value and commercial value, and effectively promotes the development of wearable devices. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 FIG. 1 is a structural schematic diagram of a sponge strain sensor prepared by the present application;

[0029] Figure 2 FIG. 3 is a detection principle diagram of a flexible wearable device of the sponge strain sensor prepared by the present application;

[0030] Figure 3 FIG. 6 is a construction process of a black phosphorus-gold composite nanomaterial electrode of the present application;

[0031] Figure 4 FIG. 9 is the conductive performance of electrodes prepared by different mass ratios of the present application;

[0032] Figure 5 FIG. 12 is a scanning electron microscope photo of a black phosphorus-gold composite nanomaterial electrode prepared by example 4 of the present application;

[0033] Figure 6 FIG. 15 is a sensitivity test result diagram of a sponge strain sensor prepared by example 4 of the present application;

[0034] Figure 7 FIG. 18 is a response speed test result diagram of a sponge strain sensor prepared by example 4 of the present application;

[0035] Figure 8 FIG. 21 is a fatigue test result diagram of a sponge strain sensor prepared by example 4 of the present application. DETAILED DESCRIPTION

[0036] In order to make the technical problems, technical solutions and beneficial effects of the present application more clear and explicit, the present application will be further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0037] Example 1

[0038] A preparation method of a sponge strain sensor, comprising the following steps:

[0039] (1) Under the condition of room temperature, 2mL of chloroauric acid solution (1mg / mL) is added to 5mL of black phosphorus two-dimensional sheet-shaped nanomaterial suspension (1mg / mL), and the reaction is fully carried out under stirring, wherein the mass ratio of chloroauric acid and black phosphorus two-dimensional sheet-shaped nanomaterial is 1:5, and the stirring condition is that the stirring is stopped when the color changes from black to wine red, and the preparation of black phosphorus gold composite nanomaterial is completed;

[0040] The preparation method of the black phosphorus two-dimensional sheet-shaped nanomaterial is as follows:

[0041] The bulk black phosphorus is ground to secretion and mixed with deionized water to prepare a black phosphorus dispersion liquid with a concentration of 1mg / mL. The black phosphorus dispersion liquid is placed in an ultrasonic ice water bath (500W) for 20 hours for peeling. Finally, the mixed liquid after peeling is subjected to centrifugal treatment to remove the unpeeled black phosphorus particles, and the upper layer black phosphorus nanosheet is collected for use.

[0042] (2) The melamine sponge is soaked in the prepared composite nanomaterial suspension liquid, and an alcohol lamp is used for heating to accelerate the evaporation of the liquid. The heating stop condition is that the heating is stopped after the liquid is completely evaporated. The sponge is taken out and dried at 40℃ for 5 hours to obtain a composite nanomaterial electrode;

[0043] (3) The conductive carbon paste is poured into a silk screen printing template, and the conductive carbon paste is made to pass through the template on a flexible cotton cloth to form an electrode using a scraper. After the printing of the conductive carbon paste is completed, the drying condition is that the temperature is 40℃ and the drying time is 3h;

[0044] (4) The composite nanomaterial electrode and the silk screen printed electrode are attached using conductive double-sided adhesive tape, and then packaged using transparent adhesive to obtain a sponge strain sensor.

[0045] Example 2

[0046] A preparation method of a sponge strain sensor comprises the following steps:

[0047] (1) Under the condition of room temperature, 2mL of chloroauric acid solution (1mg / mL) is added to 5mL of black phosphorus two-dimensional sheet-shaped nanomaterial suspension (1mg / mL), and the reaction is fully carried out under stirring, wherein the mass ratio of chloroauric acid and black phosphorus two-dimensional sheet-shaped nanomaterial is 1:5, and the stirring condition is that the stirring is stopped when the color changes from black to wine red, and the preparation of black phosphorus gold composite nanomaterial is completed;

[0048] The preparation method of the black phosphorus two-dimensional sheet-shaped nanomaterial is as follows:

[0049] The bulk black phosphorus is ground to excretion, mixed with deionized water to prepare a 1 mg / mL black phosphorus dispersion, the black phosphorus dispersion is placed in an ultrasonic ice water bath (500 W) for 20 hours, and finally, the mixed solution after exfoliation is centrifuged to remove the unexfoliated black phosphorus particles, and the upper layer black phosphorus nanosheet is collected for standby.

[0050] (2) The melamine sponge is soaked in the prepared composite nanomaterial suspension, an alcohol lamp is used for heating to accelerate the evaporation of the liquid, and the heating is stopped when the liquid is completely evaporated, and the sponge is taken out and dried at 40°C for 5 hours to obtain a composite nanomaterial electrode;

[0051] (3) The conductive carbon paste is poured into the screen printing template, the conductive carbon paste is passed through the template on the flexible cotton cloth using a scraper to form an electrode, and after the printing of the conductive carbon paste is completed, the drying condition is: temperature 40°C, drying time 3h;

[0052] (4) The composite nanomaterial electrode and the screen-printed electrode are attached using conductive double-sided tape, and then packaged with transparent tape to obtain a sponge strain sensor.

[0053] Example 3

[0054] A method for preparing a sponge strain sensor, comprising the following steps:

[0055] (1) Under room temperature conditions, 6 mL of chloroauric acid solution (1 mg / mL) is added to 5 mL of two-dimensional sheet-shaped nanomaterial suspension (1 mg / mL), and stirring is performed to fully react, wherein: the mass ratio of chloroauric acid and black phosphorus two-dimensional sheet-shaped nanomaterial is 6:5, and the stirring condition is: stop stirring when the color changes from black to wine red, and the black phosphorus composite nanomaterial preparation is completed;

[0056] The preparation method of the two-dimensional sheet-shaped nanomaterial is as follows:

[0057] The bulk black phosphorus is ground to excretion, mixed with deionized water to prepare a 1 mg / mL black phosphorus dispersion, the black phosphorus dispersion is placed in an ultrasonic ice water bath (500 W) for 20 hours, and finally, the mixed solution after exfoliation is centrifuged to remove the unexfoliated black phosphorus particles, and the upper layer black phosphorus nanosheet is collected for standby.

[0058] (2) The melamine sponge is soaked in the prepared composite nanomaterial suspension, an alcohol lamp is used for heating to accelerate the evaporation of the liquid, and the heating is stopped when the liquid is completely evaporated, and the sponge is taken out and dried at 40°C for 5 hours to obtain a composite nanomaterial electrode;

[0059] (3) Pour the conductive carbon paste onto the screen printing template, use the scraper to form the electrode on the flexible cotton cloth through the template, after the printing of the conductive carbon paste is completed, the drying condition is: temperature 40℃, drying time 3h;

[0060] (4) Use the conductive double-sided adhesive to paste the composite nanomaterial electrode and the screen-printed electrode, and then use the transparent adhesive to package them to obtain a sponge strain sensor.

[0061] Example 4

[0062] A preparation method of a sponge strain sensor comprises the following steps:

[0063] (1) Under the condition of room temperature, 8mL of chloroauric acid solution (1mg / mL) is added into 5mL of two-dimensional sheet-shaped nanomaterial suspension (1mg / mL) to stir to make the reaction fully proceed, wherein: the mass ratio of chloroauric acid and black phosphorus two-dimensional sheet-shaped nanomaterial is 8:5, the stirring condition is: stop stirring when the color changes from black to wine red, and the preparation of black phosphorus composite nanomaterial is completed;

[0064] The preparation method of the two-dimensional sheet-shaped nanomaterial is as follows:

[0065] The bulk black phosphorus is ground to secretion and mixed with deionized water to prepare a black phosphorus dispersion liquid with a concentration of 1mg / mL. The black phosphorus dispersion liquid is placed in an ultrasonic ice water bath (500W) for 20 hours for peeling. Finally, the mixed liquid after peeling is subjected to centrifugal treatment to remove the unpeeled black phosphorus particles, and the upper layer of black phosphorus nanosheets is collected for use.

[0066] (2) The melamine sponge is soaked in the prepared composite nanomaterial suspension liquid, and an alcohol lamp is used for heating to accelerate the evaporation of the liquid. The heating stop condition is: stop heating after the liquid is completely evaporated, and the composite nanomaterial electrode is obtained by drying the sponge at 40℃ for 5 hours;

[0067] (3) Pour the conductive carbon paste onto the screen printing template, use the scraper to form the electrode on the flexible cotton cloth through the template, after the printing of the conductive carbon paste is completed, the drying condition is: temperature 40℃, drying time 3h;

[0068] (4) Use the conductive double-sided adhesive to paste the composite nanomaterial electrode and the screen-printed electrode, and then use the transparent adhesive to package them to obtain a sponge strain sensor.

[0069] Example 5

[0070] A preparation method of a sponge strain sensor comprises the following steps:

[0071] (1) Under room temperature, 10 mL of chloroauric acid solution (1 mg / mL) was added to 5 mL of two-dimensional sheet-shaped nanomaterial suspension (1 mg / mL), and stirring was performed to fully proceed the reaction, wherein the mass ratio of chloroauric acid and two-dimensional sheet-shaped black phosphorus nanomaterial was 10:5, and the stirring condition was that the stirring was stopped when the color changed from black to wine red, and the preparation of the black phosphorus composite nanomaterial was completed;

[0072] The preparation method of the two-dimensional sheet-shaped nanomaterial is as follows:

[0073] The bulk black phosphorus was ground to secretion and mixed with deionized water to prepare a black phosphorus dispersion liquid with a concentration of 1 mg / mL. The black phosphorus dispersion liquid was placed in an ultrasonic ice water bath (500 W) for peeling for 20 hours. Finally, the mixed liquid after peeling was subjected to centrifugal treatment to remove the unpeeled black phosphorus particles, and the upper layer black phosphorus nanosheet was collected for use.

[0074] (2) The melamine sponge was soaked in the prepared composite nanomaterial suspension liquid, and an alcohol lamp was used for heating to accelerate the evaporation of the liquid. The heating stop condition was that the heating was stopped after the liquid was completely evaporated. The sponge was taken out and dried at 40°C for 5 hours to obtain a composite nanomaterial electrode;

[0075] (3) The conductive carbon paste was poured into a screen printing template, and a squeegee was used to make the conductive carbon paste pass through the template to form an electrode on a flexible cotton cloth. After the printing of the conductive carbon paste was completed, the drying condition was that the temperature was 40°C and the drying time was 3 h;

[0076] (4) The composite nanomaterial electrode and the screen-printed electrode were attached by using a conductive double-sided tape, and then encapsulated by using transparent tape to obtain a sponge strain sensor.

[0077] Comparative Example 1

[0078] Compared with Example 4, PU sponge was used as the carrier in this comparative example, and the same composite nanomaterial suspension liquid was soaked.

[0079] The structure schematic diagram of the sponge strain sensor prepared in Examples 1-4 is shown in Figure 1 The construction process of the composite nanomaterial electrode in Examples 1-4 and Comparative Example 1 is shown in Figure 3 The detection principle diagram of the sensor prepared in Examples 1-4 and Comparative Example 1 is shown in Figure 2

[0080] Experimental Example

[0081] 1. Synthesis of composite nanomaterial and verification of electrode modification results

[0082] The microstructure of the synthesized composite nanomaterial electrode was observed by a scanning electron microscope, and the result is shown in Figure 5 ​As shown, it can be seen that there are gold nanoparticles on the black phosphorus nanosheet, and both the black phosphorus and the gold are nanoscale and densely stacked on the sponge skeleton to form an electrode, proving that the black phosphorus gold nanomaterial with a special structure is synthesized and successfully modified on the melamine sponge.

[0083] 2. GF value (specification coefficient) measurement

[0084] The GF value is one of the core parameters of the strain sensor. A tensile and compressive testing machine with a 5N force sensor and a digital multimeter are used to measure the linear relationship between the deformation S and the resistance change (R0-R) / R0, that is, the specification factor of the flexible wearable device, wherein GF = [(R0-R) / R0] / S, S is the deformation rate of the sponge composite electrode, R is the resistance during the force process, R0 is the original resistance when not under stress, and R is the resistance of the sponge composite electrode when it deforms. The obtained curve is segmented and fitted to obtain the corresponding GF value of each segment, and the detection result is as shown in Figure 6 As shown, in the interval of 0-50% deformation, GF = 0.838; in the interval of 50-90% deformation, GF = 1.50.

[0085] 3. Response speed measurement

[0086] The response speed is one of the core parameters of the sensor. The response speed is measured by using a finger and a digital multimeter in combination with a computer. The finger is pressed quickly and then paused for a certain period of time, and then released. The force is applied to the surface of the flexible wearable device, and the resistance change through the flexible wearable device is monitored at the same time. According to the time difference of the collected signals, the response time is obtained, and the detection result is as shown in Figure 7 As shown, the response time is 10ms at the moment of pressure, and the response time is 20ms at the moment of pressure release.

[0087] 4. Fatigue test

[0088] The fatigue test of the product is one of the core parameters of the sensor. A tensile and compressive testing machine with a force sensor and a digital multimeter are used to measure the repeatability (>1000 times). The flexible wearable device is repeatedly compressed and then released by the tensile and compressive testing machine, and the digital multimeter reads the electric signal to judge the error degree of the electric signal, and the durability of the flexible wearable device is measured. The detection result is as shown in Figure 8 As shown, the sensor can work stably after 1000 times of applying and releasing pressure.

[0089] 5. Conductive performance of composite nanomaterial electrode and screen printed electrode

[0090] The experiment verifies the correctness of the method and the optimal proportion by detecting the resistance signals of the nano flexible electrodes and the screen-printed electrodes made of gold and black phosphorus with different mass ratios. The resistance value of the screen-printed electrode is 30Ω (much smaller than the resistance of the composite nanomaterial electrode, and the resistance of the screen-printed electrode can be ignored).

[0091] As shown in Figure 4 The mass ratio of chloroauric acid and black phosphorus two-dimensional sheet-shaped nanomaterial is 8:5, which is the optimal choice, and good conductivity and resource saving are achieved.

[0092] Through the GF value, response speed and fatigue resistance tests of the sponge strain sensors made of different carriers, it is found that the strain sensor using melamine sponge as the carrier is obviously superior to the PU sponge in the above three aspects, which indicates that the melamine sponge strain sensor has faster response speed, higher sensitivity and better stability, and has good service life.

[0093] The above specific embodiments further illustrate the purposes, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A sponge strain sensor based on black phosphorus gold composite nanomaterials, characterized in that, It includes a sponge strain electrode and a paper-printed electrode encapsulated as one unit; wherein the sponge strain electrode includes a melamine sponge, the melamine sponge being filled with black phosphorus gold composite nanomaterials.

2. The sponge strain sensor according to claim 1, characterized in that, The black phosphorus-gold composite nanomaterial is obtained by modifying black phosphorus two-dimensional sheet-like nanomaterials with gold ions.

3. The sponge strain sensor according to claim 2, characterized in that, The gold ions are derived from a chloroauric acid solution.

4. A method for preparing a sponge strain sensor according to any one of claims 1-3, characterized in that, The preparation method includes: Melamine sponge was added to a black phosphorus gold composite nanomaterial solution, heated until the liquid evaporated, and then placed in a vacuum drying oven at 30~40℃ for 4~6 hours to obtain a sponge strain electrode. Conductive carbon paste is printed on paper to form electrodes, and then dried at 40~50℃ for 3~5h to prepare paper-printed electrodes. The contact areas of the sponge strain electrode and the paper printing electrode are bonded together with a conductive adhesive material and then encapsulated.

5. The preparation method according to claim 4, characterized in that, The preparation method of the black phosphorus gold composite nanomaterial solution is as follows: The mixture of chloroauric acid solution and black phosphorus two-dimensional sheet nanomaterial solution was reacted by shaking at room temperature; the mass ratio of chloroauric acid to black phosphorus two-dimensional sheet nanomaterial was 1:5 to 10:

5.

6. The preparation method according to claim 5, characterized in that, The concentration of the chloroauric acid solution is 1 mg / mL; the concentration of the black phosphorus two-dimensional sheet nanomaterial solution is 1 mg / mL.

7. The preparation method according to claim 5, characterized in that, The preparation method of the black phosphorus two-dimensional sheet-like nanomaterial is as follows: After grinding the blocky black phosphorus, a black phosphorus dispersion with a concentration of 1 mg / mL was prepared. The black phosphorus dispersion was then placed in a 500W ultrasonic ice-water bath for 30-35 hours for exfoliation. Finally, the exfoliated mixture was centrifuged to remove unexfoliated black phosphorus particles, and the upper black phosphorus nanosheet suspension was collected.

8. The preparation method according to claim 5, characterized in that, The specific preparation process of the paper printing electrode is as follows: The conductive carbon paste is poured onto the screen printing template, and a squeegee is used to spread the conductive carbon paste through the screen printing template to form electrodes on the soft paper; the screen printing template is in the shape of a two-finger circuit.

9. The preparation method according to claim 8, characterized in that, The conductive carbon paste is a mixed ink composed of carbon and graphite.

10. The application of the sponge strain sensor according to any one of claims 1-3 in the preparation of a device for sensing pressure changes.

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