A multilevel closed slot conductive material and method of making the same

Abstract

The present application relates to the technical field of conductive material, in particular to a multi-layer closed narrow mouth conductive material and a preparation method thereof. A circular through hole is opened in a foam carrier, and a rectangular foam carrier is inserted into the circular through hole, so that a foam carrier with a special narrow mouth structure is formed, and a polydopamine coating and a polypyrrole nanofiber layer are loaded on the surface of the foam carrier through a certain process, so that the multi-layer closed narrow mouth conductive material is obtained. The narrow mouth structure is designed by imitating the unique scorpion slit receptor structure, the rapid change of the conductive path under pressure is realized, and the polypyrrole nanofiber formed by self-polymerization is attached to the polyurethane foam skeleton through a simple coating process, so that a continuous conductive network is formed, and finally the multi-layer closed narrow mouth conductive composite foam is prepared, and the piezoresistive performance response regulation of the high-performance conductive composite foam material is realized.

Description

Technical Field

[0001] This invention relates to the field of conductive materials technology, specifically to a multi-level closed-aperture conductive material and its preparation method. Background Technology

[0002] In recent years, flexible pressure sensors have attracted widespread research attention in fields such as motion monitoring, speech recognition, robotic prostheses, and intelligent robots. Piezoresistive pressure sensors have garnered significant 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.

[0003] Due to its low density, high porosity, and good elasticity, commercially available polyurethane foam with a typical three-dimensional structure is considered an ideal substrate for piezoresistive pressure sensors. The sensing mechanism of polyurethane foam-based piezoresistive pressure sensors is that when the foam sensor is repeatedly pressed and released, conductive paths are repeatedly generated and eliminated through the contact and separation of the conductive coating decorated on the foam skeleton, thereby realizing the conversion from mechanical signals to electrical signals.

[0004] Despite significant progress in the research of piezoresistive pressure sensors, a major challenge remains how to prepare high-performance conductive composite foam materials through the selection of active layer materials and the design of sensing structures, to achieve rapid changes in the conductive path under pressure and to regulate the response of piezoresistive performance, and how to achieve low-cost, high-sensitivity and large-scale fabrication. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-level closed-aperture conductive material and its preparation method, so as to achieve the goal of low-cost, large-scale preparation of high-performance conductive composite foam materials.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a multi-layer closed-aperture conductive material, comprising a foam carrier, wherein the foam carrier is provided with circular through holes, the number of circular through holes being at least two and interconnected, a rectangular foam carrier is inserted into the interconnected circular through holes, and a narrow structure is formed between 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.

[0007] 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.

[0008] Furthermore, the narrow-mouth structure can be adjusted according to the required sensing performance by adjusting the center distance, number of holes, hole diameter, and thickness of the rectangular foam carrier.

[0009] A method for preparing multi-level closed-aperture conductive materials includes the following steps:

[0010] S1. Prepare a foam carrier with a narrow opening structure;

[0011] S2. Load a bonding material coating onto the surface of the foam carrier prepared in S1 to form a composite foam;

[0012] S3. Attach a conductive layer to the surface of the composite foam prepared in S2 to obtain the multi-level closed-aperture conductive material of the present invention.

[0013] Furthermore, in S1, a punching die is used to form a circular through hole in the foam carrier, and a rectangular foam carrier is inserted into the connected circular through hole to obtain a foam carrier with a narrow opening structure.

[0014] Further, in step S1, the obtained foam carrier with a narrow opening structure is placed in anhydrous ethanol for ultrasonic cleaning for 10 minutes, and then placed in an oven for drying at 45°C for 3 hours.

[0015] Furthermore, in step 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, and the mixture 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.

[0016] Furthermore, in 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.

[0017] Further, in step S3, 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 equal volume ratio. The composite foam is fully impregnated in the mixed solution, polymerized at room temperature, and then washed with hydrochloric acid until no colored byproducts are released. It is then washed with ethanol and dried in an oven to obtain the multi-level closed narrow-mouth conductive material of the present invention.

[0018] Further, in S3, the mass fraction of pyrrole in the first solution is 0.2-0.3%, the mass fraction of methyl orange is 0.04-0.05%, the mass fraction of ferric chloride hexahydrate in the second solution is 2-3%, the polymerization time at room temperature is 1 h, the concentration of rinsing hydrochloric acid is 0.1 mol / L, the drying temperature is 50 °C, and the drying time is 8 h.

[0019] The beneficial effects of this invention are:

[0020] This invention designs a narrow-mouth structure by incorporating a unique biomimetic scorpion slit receptor structure to achieve rapid changes in the conductive path under pressure. Through a simple coating process, self-polymerized polypyrrole nanofibers are attached to a polyurethane foam skeleton to form a continuous conductive network. Finally, a multi-level closed-mouth conductive composite foam is prepared, realizing the piezoresistive performance response regulation of high-performance conductive composite foam materials. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the conductive material structure in Embodiment 1 of the present invention;

[0022] Figure 2 This is a schematic diagram of the electrical material preparation process in Embodiment 1 of the present invention;

[0023] Figure 3 These are scanning electron microscope images of the polyurethane foam surface (a), polydopamine surface (b), and polypyrrole fiber (c) of Embodiment 1 of the present invention.

[0024] Figure 4 This is a schematic diagram illustrating the change in relative resistance between the conductive material and ordinary foam in Embodiment 1 of the present invention as a function of pressure;

[0025] Figure 5 This is a schematic diagram of the conductive material sensing mechanism in Embodiment 1 of the present invention;

[0026] Figure 6 The figures are the cyclic piezoresistive response curves (a) of the conductive material under 10% to 40% strain, (b) of 50% to 70% strain, and (c) of cyclic piezoresistive response curves (c) at compression rates of 10 mm / min to 50 mm / min in Embodiment 1 of the present invention.

[0027] Figure 7 This is a schematic diagram of the current-voltage curves of the conductive material under different strains in Embodiment 1 of the present invention;

[0028] Figure 8 This is a schematic diagram of the response time of the conductive material in Embodiment 1 of the present invention at a compression rate of 100 mm / min under 1% strain;

[0029] Figure 9This is a schematic diagram of a stability test of the conductive material in Embodiment 1 of the present invention after 1000 cycles at a compression rate of 20 mm / min.

[0030] The names corresponding to each mark in the diagram:

[0031] 1. Foam carrier; 2. Circular through-hole; 3. Rectangular foam carrier; 4. Narrow structure; 5. Bonding material coating; 6. Conductive layer. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0033] In this invention, compression rate refers to the rate at which the conductive material is compressed at a certain millimeter 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 gradually breaks, and the resistance value returns to its original state. This cycle continues, resulting in a waveform. Strain refers to the percentage of the original height of the material that has been compressed. For example, if a 10cm material is compressed by 1cm, and its height is now 9cm, then it is said that the material has undergone 10% strain.

[0034] like Figure 1 As shown, a foam carrier 1 is provided in the conductive material of the present invention. Interconnected circular through holes 2 are provided in the foam carrier 1. The number of circular through holes 2 is at least two. A rectangular foam carrier 3 is inserted into the interconnected circular through holes 2. A narrow structure 4 is formed between the interconnected circular through holes 2 and the rectangular foam carrier 3.

[0035] like Figure 2 As shown, foam carrier 1 is immersed in an ethanol solution of tris(hydroxymethyl)aminomethane and dopamine hydrochloride, the pH is adjusted to a suitable level, and the mixture is stirred at room temperature, washed with deionized water, and dried at room temperature to form a polydopamine coating on the surface of foam carrier 1. Then, pyrrole and methyl orange are dissolved in deionized water to obtain the first solution, and ferric chloride hexahydrate is dissolved in deionized water to obtain the 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 byproducts are released. After washing with ethanol, the mixture is dried in an oven to obtain the multi-layer closed narrow-mouth conductive material of the present invention.

[0036] like Figure 3 As shown, the present invention loads a polydopamine coating and polypyrrole nanofibers onto the surface of a polyurethane foam.

[0037] like Figure 4As shown, it can be seen that the relative resistance of the conductive material of the present invention changes more sensitively than that of ordinary foam material under low pressure.

[0038] like Figure 5 As shown, with increasing pressure, the conductive path first increases rapidly and then tends to stabilize, making it more sensitive to changes at low pressure and more stable at high pressure.

[0039] like Figure 6 As shown in Figures a and b, the conductive material exhibits a series of stable and noise-free signal outputs during repeated compression cycles at different strains. Furthermore, the intensity of these signal peaks varies with different strain values, and the maximum value of the relative resistance change increases with increasing strain amplitude. As shown in Figure c, at different compression rates from 10 to 50 mm / min, the conductive material can output stable and repeatable periodic sensing signals with constant response peaks, demonstrating typical strain rate-independent sensing capabilities.

[0040] like Figure 7 As shown, the current-voltage curve stabilizes with increasing strain, indicating that the conductive material has good ohmic properties and a stable response to constant pressure.

[0041] like Figure 8 As shown, when a 1% strain is applied and a 1% strain is removed, the measured response time and recovery time of the conductive material are 120ms and 100ms, respectively, which are sufficient for detecting human motion.

[0042] like Figure 9 As shown in the figure, the stability of the conductive material of the present invention remains good even after thousands of tests.

[0043] The principle of this invention is as follows:

[0044] A unique macroscopic narrow-mouth structure was designed using a biomimetic scorpion slit receptor, and then wrinkled polypyrrole nanofibers were prepared using methyl orange as a self-polymerizing template to obtain a conductive composite foam with a multi-level closure mechanism. The contact between the narrow-mouth structure and the built-in sandwich foam allows for rapid changes in the conductive path under minute pressures. Simultaneously, the micron-scale foam skeleton and the nanoscale wrinkled polypyrrole nanofibers work together with the macroscopic narrow-mouth structure to achieve multi-level closure of the polyurethane conductive composite foam. Furthermore, due to the excellent adhesion of the polydopamine layer, it was introduced as a bonding material to further enhance the adhesion of the polypyridine nanofibers to the polyurethane skeleton. Ultimately, a highly durable and highly sensitive sensor device was obtained.

[0045] 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.

[0046] Multi-level closure mechanism: By designing a biomimetic narrow-mouth structure inspired by a scorpion slit receptor and using methyl orange as a self-polymerization template to achieve the self-polymerization of wrinkled polypyrrole nanofibers on polyurethane foam, a multi-level structure is ultimately achieved, featuring a macroscopic narrow-mouth structure, a micron-scale foam skeleton, and nanoscale polypyrrole nanofibers working synergistically. The strong adhesion of the polypyrrole nanofibers facilitates nanoscale contact and separation of the foam, and provides sensing performance with high stability and durability.

[0047] Scorpion-inspired slit structure mechanism: Inspired by the mechanism of the slit receptors in the scorpion's legs, a slit structure was designed. When the foam is subjected to pressure or the pressure is removed, the gap formed between the slit structure and the built-in foam causes the conductive path of the polyurethane foam to increase or decrease significantly during extrusion, allowing the structure to switch back and forth between disconnected and reconnected states.

[0048] Example 1

[0049] The multi-level closed-aperture conductive material is prepared according to the method of the present invention, and the steps are as follows:

[0050] S1. Cut polyurethane foam into cuboids of 25mm×12mm×15mm size, which are foam carriers 1. Use a punching die to make three interconnected circular holes 2 on the foam carrier 1. Insert rectangular foam carriers 3 (also polyurethane foam) with dimensions of 22mm×12mm×3mm into the interconnected circular holes 2. A narrow structure 4 is formed between the interconnected circular holes 2 and the rectangular foam carriers 3. Place the cut polyurethane foam in anhydrous ethanol for ultrasonic cleaning for 1 minute, and then dry it in an oven at 45℃ for 3 hours.

[0051] 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 adjust the pH to 8.5. Soak polyurethane foam in the prepared solution and stir at room temperature for 12 hours to form a polydopamine coating on the foam surface. Then wash the treated composite foam with deionized water and dry at room temperature to obtain polydopamine / polyurethane composite foam.

[0052] S3. Dissolve 0.24g of pyrrole and 0.047g of methyl orange in 100mL of deionized water to prepare the first solution. Dissolve 2.414g of ferric chloride hexahydrate in 100mL of deionized water to prepare the second solution. Then, pre-cool the two solutions to 4℃ and mix them in a 1:1 volume ratio. Fully impregnate the polydopamine / polyurethane composite foam in the mixed solution and polymerize at room temperature for 1h. Wash with 0.1mol / L hydrochloric acid until no colored byproducts are released, then wash with ethanol and dry in an oven at 50℃ for 8h to obtain polypyrrole / polydopamine / polyurethane narrow-mouth structure composite foam.

[0053] Characterization analysis of the polypyrrole / polydopamine / polyurethane narrow-slot composite foam prepared above is shown in [reference needed]. Figures 3-9 .

[0054] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes in shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A multi-level closed-aperture conductive material, characterized in that: The foam carrier (1) includes a foam carrier (1) with a circular through hole (2) provided therein. The number of circular through holes (2) is at least two and they are interconnected. A rectangular foam carrier (3) is inserted into the interconnected circular through hole (2). A narrow structure (4) is formed between the circular through hole (2) and the rectangular foam carrier (3). 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-aperture 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. The bonding material coating (5) is a polydopamine coating, and the conductive layer (6) is a polypyrrole nanofiber layer.

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

4. The method for preparing a multi-level closed-aperture conductive material according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Prepare a foam carrier (1) with a narrow opening structure (4). S2, A bonding material coating (5) is loaded onto the surface of the foam carrier (1) prepared in S1 to form a composite foam; S3. Attach a conductive layer (6) to the surface of the composite foam prepared in S2 to obtain a multi-level closed-slit conductive material.

5. The method for preparing the multi-level closed-aperture conductive material according to claim 4, characterized in that: In S1, a circular through hole (2) of the foam carrier (1) is formed using a punching die, and a rectangular foam carrier (3) is inserted into the connected circular through hole (2) to obtain a foam carrier (1) with a narrow opening structure (4).

6. The method for preparing the multi-level closed-aperture conductive material according to claim 5, characterized in that: In S1, the foam carrier (1) with the narrow structure (4) is placed in anhydrous ethanol for ultrasonic cleaning for 10 min, and then placed in an oven for drying at 45°C for 3 h.

7. The method for preparing the multi-level closed-aperture conductive material according to claim 4, characterized in that: In 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, and the mixture is stirred at room temperature, washed with deionized water, and dried at room temperature to load a polydopamine coating onto the surface of the foam carrier (1).

8. The method for preparing the multi-level closed-aperture conductive material according to claim 7, characterized in that: In 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.

9. The method for preparing the multi-level closed-aperture conductive material according to claim 4, characterized in that: In step S3, 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 equal volume ratio. The composite foam is fully impregnated in the mixed solution, polymerized at room temperature, and then washed with hydrochloric acid until no colored byproducts are released. After washing with ethanol, it is dried in an oven to obtain a multi-layered closed-aperture conductive material.

10. The method for preparing a multi-level closed-aperture conductive material according to claim 9, characterized in that: In S3, the first solution contains 0.2-0.3% pyrrole and 0.04-0.05% methyl orange. The second solution contains 2-3% ferric chloride hexahydrate. The polymerization time is 1 hour at room temperature. The rinsing hydrochloric acid concentration is 0.1 mol / L. The drying temperature is 50°C and the drying time is 8 hours.

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