Multi-level closed narrow-orifice conductive material and preparation method therefor

Abstract

The present application relates to the technical field of conductive materials, and specifically relates to a multi-level closed narrow-orifice conductive material and a preparation method therefor. Circular through holes communicating with each other are formed in a foam carrier, rectangular foam carriers are inserted into the circular through holes so as to form a foam carrier having a special narrow-orifice structure, and a polydopamine coating and a polypyrrole nano-fiber layer are loaded onto the surface of the foam carrier by means of a certain process, such that the multi-level closed narrow-orifice conductive material in the present application can be obtained. In the present application, a narrow-orifice structure is designed by means of simulating a unique scorpion slit susceptor structure, so as to realize rapid changing of a conductive path under pressure; and polypyrrole nanofibers formed by means of self-polymerization are attached to a polyurethane foam framework by means of a simple coating process, so as to form a continuous conductive network, such that conductive composite foam of a multi-level closed narrow-orifice structure is finally prepared, thereby realizing regulation and control over piezoresistive performance response of a high-performance conductive composite foam material.

Description

A multi-level closed narrow conductive material and its preparation method

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on August 8, 2023, with application number CN202310989624.X and invention name “A multi-level closed narrow conductive material and its preparation method”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of conductive materials, and in particular to a multi-level closed narrow conductive material and a preparation method thereof. Background Art

[0003] In recent years, flexible pressure sensors have attracted extensive research attention in the fields of motion monitoring, speech recognition, robotic prostheses, and intelligent robots. Piezoresistive pressure sensors have attracted great research interest due to their simple device assembly, excellent sensing sensitivity, and ability to monitor mechanical changes by converting mechanical loads applied to conductive materials into changes in resistance signals.

[0004] Commercially available polyurethane foam, with its typical three-dimensional structure, is considered an ideal substrate for piezoresistive pressure sensors due to its low density, high porosity, and good elasticity. The sensing mechanism of polyurethane foam-based piezoresistive pressure sensors is that when the foam sensor is repeatedly pressed and released, the conductive coating on the foam skeleton repeatedly creates and eliminates a conductive path, thereby converting a mechanical signal into an electrical signal.

[0005] Although great progress has been made in the research of piezoresistive pressure sensors, how to prepare high-performance conductive composite foam materials through the selection of active layer materials and the design of sensing structures, realize the rapid change of conductive paths under pressure and the response regulation of piezoresistive performance, and how to achieve low cost, high sensitivity and large-scale preparation, remains a huge challenge.

[0006] Summary of the Invention

[0007] The purpose of this application is to provide a multi-level closed narrow conductive material and a preparation method thereof, so as to achieve the purpose of low-cost and large-scale preparation of high-performance conductive composite foam materials.

[0008] To achieve the above-mentioned purpose, the present application adopts the following technical solution: a multi-level closed narrow conductive material, including a foam carrier, wherein the foam carrier is provided with circular through holes, the number of the circular through holes is at least two and they are interconnected, a rectangular foam carrier is inserted into the connected circular through holes, and a narrow structure is formed between the connected part of the circular through holes and the rectangular foam carrier, and a bonding material coating and a conductive layer are loaded on the surface of the foam carrier.

[0009] Furthermore, the foam carrier is one or more of polyurethane foam, polyimide foam, melamine foam, polylactic acid foam, silicone rubber, thermoplastic polystyrene elastomer, thermoplastic polyolefin elastomer, thermoplastic copolyester elastomer, thermoplastic polyamide elastomer and thermoplastic polyurethane elastomer, the bonding material coating is a polydopamine coating, and the conductive layer is a polypyrrole nanofiber layer.

[0010] Furthermore, the narrow opening structure can be adjusted according to the required sensing performance by adjusting the center distance, number of holes, hole diameter of the circular through holes and the thickness of the rectangular foam carrier.

[0011] A method for preparing a multi-level closed-narrow conductive material comprises the following steps:

[0012] S1. preparing a foam carrier having a narrow structure;

[0013] S2, loading a binding material coating on the surface of the foam carrier prepared in S1 to form a composite foam;

[0014] S3. Attaching a conductive layer to the surface of the composite foam prepared in S2 to obtain the multi-level closed narrow conductive material of the present application.

[0015] Furthermore, in the above-mentioned S1, a punching die is used to form the circular through holes of the foam carrier, and a rectangular foam carrier is inserted into the connected circular through holes to obtain a foam carrier with a narrow mouth structure.

[0016] Furthermore, in the above S1, the obtained foam carrier with a narrow-mouth structure is placed in anhydrous ethanol for ultrasonic cleaning for 10 minutes, and then placed in an oven for drying at a drying temperature of 45° C. for 3 hours.

[0017] Furthermore, in the above S2, the foam carrier is immersed in an ethanol solution of tris(hydroxymethyl)aminomethane and dopamine hydrochloride, the pH is adjusted to a suitable level, the solution is stirred at room temperature, washed with deionized water, and dried at room temperature to form a polydopamine coating on the surface of the foam carrier.

[0018] Furthermore, in the S2, V in the ethanol solution 乙醇 :V 去离子水 =3:7, the mass fraction of tris(hydroxymethyl)aminomethane is 0.08-0.1%, the mass fraction of dopamine hydrochloride is 0.18-0.2%, the pH is adjusted to 8.5, and the stirring time at room temperature is 12 h.

[0019] Furthermore, in the S3, pyrrole and methyl orange are dissolved in deionized water to obtain a first solution, ferric chloride hexahydrate is dissolved in deionized water to obtain a second solution, the two solutions are pre-cooled to 0-4°C and mixed in an equal volume ratio, the composite foam is fully immersed in the mixed solution, polymerized at room temperature and then rinsed with hydrochloric acid until no colored by-products are released, then washed with ethanol and dried in an oven to obtain the multi-level closed narrow conductive material of the present application.

[0020] Furthermore, in the S3, in the first solution, the mass fraction of pyrrole is 0.2-0.3%, the mass fraction of methyl orange is 0.04-0.05%, and in the second solution, the mass fraction of ferric chloride hexahydrate is 2-3%, the room temperature polymerization time is 1 hour, the washing hydrochloric acid concentration is 0.1 mol / L, the drying temperature is 50°C, and the drying time is 8 hours.

[0021] Beneficial effects of this application:

[0022] This application designs a narrow structure by imitating the unique scorpion slit sensor structure to achieve rapid changes in the conductive path under pressure, and through a simple coating process, the self-polymerized polypyrrole nanofibers are attached to the polyurethane foam skeleton to form a continuous conductive network. Finally, a conductive composite foam with a multi-level closed narrow structure is prepared, realizing the piezoresistive performance response regulation of high-performance conductive composite foam materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is a schematic diagram of the conductive material structure of Example 1 of the present application;

[0024] FIG2 is a schematic diagram of the process for preparing the conductive material according to Example 1 of the present application;

[0025] FIG3 is a scanning electron microscope image of the polyurethane foam surface (a), the polydopamine surface (b), and the polypyrrole fiber (c) of Example 1 of the present application;

[0026] FIG4 is a schematic diagram showing the change in relative resistance between the conductive material and ordinary foam as a function of pressure in Example 1 of the present application;

[0027] FIG5 is a schematic diagram of the conductive material sensing mechanism of Example 1 of the present application;

[0028] FIG6 is a cyclic piezoresistive response curve (a) of the conductive material of Example 1 of the present application under a strain of 10% to 40%, a cyclic piezoresistive response curve (b) under a strain of 50% to 70%, and a cyclic piezoresistive response curve (c) when the compression rate is 10 mm / min to 50 mm / min;

[0029] FIG7 is a schematic diagram of current-voltage curves of the conductive material of Example 1 of the present application under different strains;

[0030] FIG8 is a schematic diagram of the response time of the conductive material of Example 1 of the present application at a compression rate of 100 mm / min under 1% strain;

[0031] FIG9 is a schematic diagram of 1000 stability tests of the conductive material in Example 1 of the present application at a compression rate of 20 mm / min;

[0032] FIG10 is a schematic diagram of a narrow mouth structure;

[0033] The names corresponding to the marks in the figure are:

[0034] 1. Foam carrier; 2. Circular through-hole; 3. Rectangular foam carrier; 4. Slit structure; 5. Bonding material coating; 6. Conductive layer. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application.

[0036] In this application, the compression rate refers to the rate at which a conductive material is compressed at a certain rate of millimeters per minute. When the conductive material is compressed, the resistance value decreases as the conductive path is constructed. After the compression is complete, as the applied pressure is slowly reduced, the conductive path is gradually disconnected, and the resistance value returns to its original state. This cycle continues, and a waveform appears. The strain refers to the percentage of the compressed height of the material to the original height of the material. For example, if a 10 cm material is compressed by a force of 1 cm, the height at this time is 9 cm, then the material is said to have undergone a 10% strain.

[0037] As shown in Figure 1, a foam carrier 1 is provided in the conductive material of the present application, and circular through holes 2 that are interconnected are opened in the foam carrier 1. The number of the circular through holes 2 is at least two, and a rectangular foam carrier 3 is inserted into the connected circular through holes 2, and a narrow structure 4 is formed between the connected part of the circular through holes 2 and the rectangular foam carrier 3.

[0038] As shown in Figure 2, the foam carrier 1 is immersed in an ethanol solution of tris(hydroxymethyl)aminomethane and dopamine hydrochloride, the appropriate pH is adjusted and stirred at room temperature, washed with deionized water, and dried at room temperature to form a polydopamine coating on the surface of the foam carrier 1, and then pyrrole and methyl orange are dissolved in deionized water to obtain a first solution, and ferric chloride hexahydrate is dissolved in deionized water to obtain a second solution. The two solutions are pre-cooled to 0-4°C and mixed in an equal volume ratio. The composite foam is fully immersed in the mixed solution, polymerized at room temperature and then rinsed with hydrochloric acid until no colored by-products are released, then washed with ethanol and dried in an oven to obtain the multi-level closed narrow conductive material of the present application.

[0039] As shown in FIG3 , it can be seen that the present application loads a polydopamine coating and polypyrrole nanofibers on the surface of the polyurethane foam.

[0040] As shown in FIG. 4 , it can be seen that under low pressure, the relative resistance value of the conductive material (narrow structure foam) of the present application changes more sensitively than that of ordinary foam materials.

[0041] As shown in FIG5 , as the pressure increases, the conductive path first increases rapidly and then tends to be stable, making the change more sensitive at low pressure and more stable at high pressure.

[0042] As shown in Figure 6 (a) and (b), the conductive material produces a series of stable, noise-free signal outputs during repeated compression cycles at different strains. Furthermore, the peak intensities of these signals vary at different strain values, and the maximum relative resistance change increases with increasing strain amplitude. As shown in Figure 6 (c), at compression rates ranging from 10 to 50 mm / min, the conductive material produces stable and repeatable cyclic sensing signals with a constant peak response, demonstrating typical strain-rate-independent sensing capabilities.

[0043] As shown in Figure 7, the current-voltage curve stabilizes with increasing strain, indicating that the conductive material has good ohmic characteristics and a stable response to constant pressure.

[0044] As shown in FIG8 , when a 1% strain is applied and a 1% strain is removed, the response time and recovery time of the conductive material are measured to be 120 ms and 100 ms, respectively, which are sufficient for detecting human motion.

[0045] As shown in FIG9 , it can be seen that after thousands of tests, the stability of the conductive material of the present application is still good.

[0046] The principles of this application are:

[0047] By designing a unique macroscopic narrow structure inspired by the bionic scorpion slit sensor, and then using methyl orange as a self-polymerizing template to prepare wrinkled polypyrrole nanofibers, a narrow-structured conductive composite foam with a multi-level closure mechanism was obtained. The closure of the narrow structure formed by the outer foam layer and the inner sandwich foam enables rapid changes in the conductive path under minimal pressure. At the same time, the micron-scale foam skeleton and the nanoscale wrinkled polypyrrole nanofibers work together with the macroscopic narrow structure to achieve multi-level closure of the polyurethane conductive composite foam. In addition, due to the excellent adhesion of the polydopamine layer, a polydopamine layer was introduced as a bonding material to further enhance the adhesion of the polypyrrole nanofibers to the polyurethane skeleton. The result is a highly durable and sensitive sensor device.

[0048] Among them, the foam carrier 1 is one or more of polyurethane foam, polyimide foam, melamine foam, polylactic acid foam, silicone rubber, thermoplastic polystyrene elastomer, thermoplastic polyolefin elastomer, thermoplastic copolyester elastomer, thermoplastic polyamide elastomer and thermoplastic polyurethane elastomer, the bonding material coating 5 is a polydopamine coating, and the conductive layer 6 is a polypyrrole nanofiber layer.

[0049] Multi-level closure mechanism: By designing a biomimetic slit structure of a scorpion slit sensor and using methyl orange as a self-polymerization template to self-polymerize pleated polypyrrole nanofibers onto polyurethane foam, the researchers achieved a macroscopic slit structure. This multi-level structure is a synergistic effect of the micron-scale foam skeleton and nanoscale polypyrrole nanofibers. The strong attachment of the polypyrrole nanofibers facilitates nanoscale contact and separation of the foam, resulting in highly stable and durable sensing performance.

[0050] Scorpion-inspired slit structure mechanism: Inspired by the mechanism of slit receptors in the scorpion's legs, the slit structure was designed. When pressure is applied to the foam or the pressure is relieved, the narrow structure formed by the outer and inner foam layers of the slit structure significantly increases or decreases the conductive path of the polyurethane foam when squeezed, causing the structure to switch back and forth between disconnected and reconnected states.

[0051] Example 1

[0052] The steps for preparing a multi-level closed narrow conductive material according to the method of the present application are as follows:

[0053] S1. Cut the polyurethane foam into a 25 mm × 12 mm × 15 mm rectangular parallelepiped, i.e., the foam carrier 1. Use a punching die to open three interconnected circular through holes 2 on the foam carrier 1. Insert a rectangular foam carrier 3 (also polyurethane foam) with a size of 22 mm × 12 mm × 3 mm into the interconnected circular through holes 2. Form a narrow structure 4 between the connecting portion of the circular through holes 2 and the rectangular foam carrier 3. Place the cut polyurethane foam in anhydrous ethanol and ultrasonically clean it for 1 minute, and then dry it in a 45°C oven for 3 hours.

[0054] S2. Dissolve 0.4325 g of tris(hydroxymethyl)aminomethane and 1 g of dopamine hydrochloride in 500 mL of ethanol solution (V 乙醇 :V 去离子水 =3:7), and adjusting the pH to 8.5, soaking the polyurethane foam in the prepared solution, stirring at room temperature for 12 hours, forming a polydopamine coating on the foam surface, and then washing the treated composite foam with deionized water and drying at room temperature to obtain a polydopamine / polyurethane composite foam;

[0055] S3. Dissolve 0.24 g of pyrrole and 0.047 g of methyl orange in 100 mL of deionized water to prepare a first solution, and dissolve 2.414 g of ferric chloride hexahydrate in 100 mL of deionized water to prepare a second solution. Then precool the two solutions to 4°C and mix them in a volume ratio of 1:1. Fully immerse the polydopamine / polyurethane composite foam in the mixed solution, polymerize it at room temperature for 1 h, rinse it with 0.1 mol / L hydrochloric acid until no colored by-products are released, wash it with ethanol, and dry it in a 50°C oven for 8 h to obtain a polypyrrole / polydopamine / polyurethane narrow structure composite foam.

[0056] The characterization analysis of the polypyrrole / polydopamine / polyurethane narrow-structure composite foam prepared above is shown in Figures 3 to 9.

[0057] This application is not limited to the above-mentioned optimal implementation method. Anyone can derive various other forms of products based on the inspiration of this application. However, no matter what changes are made in their shape or structure, any technical solution that is the same or similar to that of this application falls within the scope of protection of this application.

Claims

1. A multi-level closed narrow conductive material, characterized in that: The invention comprises a foam carrier (1), wherein the foam carrier (1) is provided with circular through holes (2), wherein the number of the circular through holes (2) is at least two and the circular through holes (2) are interconnected, a rectangular foam carrier (3) is inserted into the interconnected circular through holes (2), a narrow opening structure (4) is formed between the connecting part of the circular through holes (2) and the rectangular foam carrier (3), and a bonding material coating (5) and a conductive layer (6) are loaded on the surface of the foam carrier (1).

2. The multi-level closed-narrow conductive material according to claim 1, characterized in that: The surface of the rectangular foam carrier (3) is loaded with a bonding material coating (5) and a conductive layer (6).

3. The multi-level closed-narrow conductive material according to claim 1, characterized in that: The foam carrier (1) is one or more of polyurethane foam, polyimide foam, melamine foam, polylactic acid foam, silicone rubber, thermoplastic polystyrene elastomer, thermoplastic polyolefin elastomer, thermoplastic copolyester elastomer, thermoplastic polyamide elastomer and thermoplastic polyurethane elastomer.

4. The multi-level closed-narrow conductive material according to claim 1 or 2, characterized in that: The bonding material coating (5) is a polydopamine coating.

5. The multi-level closed-narrow conductive material according to claim 1 or 2, characterized in that: The conductive layer (6) is a polypyrrole nanofiber layer.

6. The multi-level closed-narrow conductive material according to claim 1, characterized in that: The number of the circular through holes (2) is three.

7. The multi-level closed-narrow conductive material according to claim 1, characterized in that: The narrow opening structure (4) is used to adjust the center distance, number of holes, hole diameter of the circular through holes (2) and the thickness of the rectangular foam carrier (3) according to the required sensing performance.

8. The method for preparing a multi-level closed-narrow conductive material according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. preparing a foam carrier (1) having a narrow structure (4); S2, loading a binding material coating (5) on the surface of the foam carrier (1) prepared in S1 to form a composite foam; S3. A conductive layer (6) is attached to the surface of the composite foam prepared in S2 to obtain the multi-level closed-narrow conductive material.

9. The method for preparing a multi-level closed-narrow conductive material according to claim 8, characterized in that: In the above-mentioned S1, a punching die is used to form the circular through holes (2) of the foam carrier (1), and a rectangular foam carrier (3) is inserted into the connected circular through holes (2) to obtain a foam carrier (1) having a narrow mouth structure (4).

10. The method for preparing a multi-level closed-narrow conductive material according to claim 9, characterized in that: In the above-mentioned S1, the obtained foam carrier (1) with a narrow structure (4) is placed in anhydrous ethanol for ultrasonic cleaning for 10 minutes, and then placed in an oven for drying at a drying temperature of 45° C. for 3 hours.

11. The method for preparing a multi-level closed-narrow conductive material according to claim 8, characterized in that: In the above-mentioned S2, the foam carrier (1) is immersed in an ethanol solution of tris(hydroxymethyl)aminomethane and dopamine hydrochloride, the pH is adjusted to a suitable level, the solution is stirred at room temperature, washed with deionized water, and dried at room temperature, so that a polydopamine coating is loaded on the surface of the foam carrier (1).

12. The method for preparing a multi-level closed-narrow conductive material according to claim 11, characterized in that: In the S2, V in the ethanol solution 乙醇 :V 去离子水 =3:7, the mass fraction of tris(hydroxymethyl)aminomethane is 0.08-0.1%, the mass fraction of dopamine hydrochloride is 0.18-0.2%, the pH is adjusted to 8.5, and the stirring time at room temperature is 12h.

13. The method for preparing a multi-level closed-narrow conductive material according to claim 8, characterized in that: In the S3, pyrrole and methyl orange are dissolved in deionized water to obtain a first solution, ferric chloride hexahydrate is dissolved in deionized water to obtain a second solution, the first solution and the second solution are precooled to 0-4°C and mixed in an equal volume ratio to obtain a mixed solution; the composite foam is fully immersed in the mixed solution, polymerized at room temperature and then rinsed with hydrochloric acid until no colored by-products are released, then washed with ethanol, and dried in an oven to obtain the multi-level closed narrow conductive material.

14. The method for preparing a multi-level closed-narrow conductive material according to claim 13, characterized in that: In the S3, in the first solution, the mass fraction of pyrrole is 0.2-0.3%, the mass fraction of methyl orange is 0.04-0.05%, in the second solution, the mass fraction of ferric chloride hexahydrate is 2-3%, the room temperature polymerization time is 1 hour, the concentration of hydrochloric acid for washing is 0.1 mol / L, the drying temperature is 50°C, and the drying time is 8 hours.

Images