Friction nano-generator with controllable negative Poisson's ratio structure and preparation method of friction nano-generator

Abstract

The invention discloses a friction nano generator with a controllable negative Poisson's ratio structure, which comprises a three-layer structure, the upper layer is a polydimethylsiloxane skeleton with a negative Poisson's ratio structure, the middle layer is a positive friction layer, and the positive friction layer is a polyethyleneimine modified collagen aggregate; the upper layer is a polydimethylsiloxane skeleton, the lower layer is a negative friction layer, the negative friction layer is a fluorinated ethylene propylene copolymer containing a negative Poisson's ratio structure, the polydimethylsiloxane skeleton and the positive friction layer are subjected to curing connection, and the positive friction layer and the negative friction layer are connected through elastic foam. The invention also discloses a preparation method of the friction nanometer generator. According to the friction nano-generator with the controllable negative Poisson's ratio structure, the effective contact area of the friction layer in the contact-separation process is increased by utilizing the deformable characteristic of the negative Poisson's ratio structure, so that charge transfer is enhanced, the output power and stability are improved, and the friction nano-generator can adapt to the mechanical energy collection requirement in a complex environment; the method is suitable for the fields of wearable equipment, intelligent medical treatment, sports protection equipment and the like.

Description

Technical Field

[0001] This invention belongs to the field of nanogenerator fabrication technology, specifically relating to a triboelectric nanogenerator with a controllable negative Poisson's ratio structure, and also to a method for fabricating the triboelectric nanogenerator with the controllable negative Poisson's ratio structure. Background Technology

[0002] Triboelectric nanogenerators (TGNs) effectively convert mechanical energy into electrical energy through the synergistic coupling effect of contact electrification and electrostatic induction. Their exceptional ability to harvest low-frequency mechanical energy lays a crucial physical foundation for self-powered flexible sensors. As an emerging technology, self-powered sensors based on TGNs exhibit significant advantages, including high sensitivity, ease of fabrication, low cost, strong environmental adaptability, and sustainability. However, current TGN sensors still suffer from issues such as low energy conversion efficiency, insufficient quantitative characterization, and poor signal stability.

[0003] Currently, most self-powered sensors are deployed on the human body, integrating sensing and energy harvesting by capturing biomechanical energy (such as joint movement and cardiac activity). Among them, joint motion sensors offer optimal signal amplitude and sensitivity due to their high mechanical energy output. However, the Poisson's ratio characteristic of traditional flexible materials fundamentally limits their performance; as the curvature of the joint increases, the contact area between the sensor and the skin gradually decreases. This leads to a decrease in energy harvesting efficiency and distortion of the sensing signal, ultimately limiting their performance in various application scenarios. Therefore, designing strain-adaptive self-powered sensing materials that can adapt to complex strain environments constitutes a key approach to overcoming these obstacles.

[0004] Negative Poisson's ratio materials exhibit a deformation pattern contrary to intuition, undergoing lateral contraction under axial compression and lateral expansion under axial tension. This scale invariance stems from a rationally designed substructure geometry, rather than inherent chemical properties of the material, and is evident at both the macroscopic system and microscopic unit cell scales. Two-dimensional concave hexagonal honeycomb structures are typical examples of negative Poisson's ratio configurations. Under uniaxial tensile loads (e.g., along the horizontal direction), the inclined struts undergo cooperative in-plane rotation, driving the concave angle to unfold. This motion mechanism forces the vertical struts to displace outward, resulting in lateral expansion and a significant negative Poisson's ratio effect. Crucially, this rotation-dominated deformation mechanism forms the basis of the inherent tensile-expansion response of the concave system.

[0005] Under complex, non-uniform strain fields (such as those generated by buckling or conformal bending), these structures exhibit synergistic mechanical behavior. Emergent negative stiffness facilitates their conformation to highly curvature surfaces, while extremely low effective out-of-plane flexural modulus enables robust interfacial adhesion. These properties make negative Poisson's ratio structures ideal substrates for strain-sensitive devices. Combining concave honeycomb structures with functional sensing materials effectively addresses the key challenge of dynamic tissue-device mechanical mismatch in self-powered sensors, particularly suitable for dynamic biological interfaces requiring both high stretchability and precise signal conversion capabilities. Summary of the Invention

[0006] The purpose of this invention is to provide a triboelectric nanogenerator with a controllable negative Poisson's ratio structure, which improves the output power and stability of the triboelectric nanogenerator.

[0007] Another objective of this invention is to provide a method for preparing a triboelectric nanogenerator with a controllable negative Poisson's ratio structure.

[0008] The technical solution adopted in this invention is a triboelectric nanogenerator with a controllable negative Poisson's ratio structure, comprising a three-layer structure: an upper layer is a polydimethylsiloxane backbone with a negative Poisson's ratio structure; a middle layer is a positive friction layer, which is a collagen aggregate modified with polyethyleneimine; and a lower layer is a negative friction layer, which is a fluorinated ethylene propylene copolymer containing a negative Poisson's ratio structure. The surfaces of both the positive and negative friction layers are uniformly coated with nano-silver paste.

[0009] Another technical solution adopted in this invention is a method for preparing a triboelectric nanogenerator with a controllable negative Poisson's ratio structure, which is specifically implemented according to the following steps: Step 1: Preparation of a polydimethylsiloxane framework with a negative Poisson's ratio structure; Step 2, Preparation of fluorinated ethylene propylene copolymer with negative Poisson's ratio structure; Step 3, Preparation of polyethyleneimine-modified collagen aggregates; Step 4: Using a polydimethylsiloxane framework as the upper layer, a positive friction layer as the middle layer (constituted as a polyethyleneimine-modified collagen aggregate), and a negative friction layer as the lower layer (constituted as a fluorinated ethylene propylene copolymer with a negative Poisson's ratio structure), nano-silver paste is sprayed onto the surfaces of the positive and negative friction layers. The polydimethylsiloxane framework is then cured and connected to the positive friction layer. Finally, the positive and negative friction layers are connected using elastic foam to obtain a triboelectric nanogenerator with a controllable negative Poisson's ratio structure.

[0010] Step 1 specifically involves: Step 1.1: Mix liquid silicone rubber and platinum catalyst, stir until homogeneous, add nano-silica, mix and then degas under vacuum to obtain a mixed precursor; Step 1.2: Place the mixed precursor on the printing platform of the 3D printer. The printing platform is pre-coated with a hydrophobic layer. Upload the printing model for printing. The pattern of the model is a concave hexagonal honeycomb structure. After printing, place the structure in a constant temperature oven for annealing and let it stand to obtain a polydimethylsiloxane skeleton with a negative Poisson's ratio structure. In step 1.1, the mass ratio of liquid silicone rubber, platinum catalyst, and nano silica is 2-10:0.2-1:3-6; the liquid silicone rubber is any one of Dow Corning Sylgard 184, ShinEtsu, and Momentive RTV615; the platinum catalyst is a divinyltetramethyldisiloxane platinum complex or bis(divinyltetramethyldisiloxane) platinum complex.

[0011] In step 1.2, the unit side length of the concave hexagonal honeycomb structure is 1-2 mm, the wall thickness is 0.2-1.0 mm, and the concave angle is 30-60°; the printing layer height is set to nozzle diameter × 0.8, the printing speed is 5-10 mm / s, the extrusion air pressure is 0.3-0.6 MPa, and the printing chamber temperature is maintained at 25±2°C.

[0012] Step 2 specifically involves: The fluorinated ethylene propylene copolymer film was laser-engraved using an ultraviolet nanosecond laser in a spiral engraving sequence from the inside out. The engraved pattern was a concave hexagonal honeycomb structure with a unit side length of 2 mm, a wall thickness of 0.8 mm, and a concave angle of 60°. After engraving, the film was cleaned sequentially with deionized water, fluorocarbon surfactant, and O2 plasma. After cleaning, a fluorinated ethylene propylene copolymer with a negative Poisson's ratio structure was obtained.

[0013] Step 3 specifically involves: Step 3.1: Dissolve the collagen aggregates in acetic acid solution and stir at 40-60℃ for 1-2 hours to obtain a collagen aggregate solution with a mass fraction of 2-5 wt%; the collagen aggregates can be any one of sheepskin, pigskin, fish skin, cowskin, bovine tendon, or ostrich skin. Step 3.2: Dissolve polyethyleneimine and triglyceride isocyanurate in anhydrous ethanol and stir for 1-2 hours to obtain polyethyleneimine solution and triglyceride isocyanurate solution, respectively. Step 3.3: Under mechanical stirring at 40-50℃, add triglyceride isocyanurate solution dropwise to collagen aggregate solution and react for 2-3 hours. Then add polyethyleneimine solution and continue reacting for 6 hours. The resulting homogeneous solution is then cast into a presilicified glass mold and cured at 30-45℃ for 2-3 hours to obtain polyethyleneimine modified collagen aggregate with a thickness of 0.1-0.4 mm.

[0014] In step 3.3, the volume ratio of the isocyanuric triglyceride solution, the collagen aggregate solution, and the polyethyleneimine solution is 1-5:10-30:1-5.

[0015] The beneficial effects of this invention are: (1) The method of the present invention introduces 3D printing technology into the preparation of negative Poisson's ratio structure of triboelectric nanogenerator. By adjusting the printing parameters, the precise matching between the pore gradient distribution and the negative Poisson's ratio structure is achieved, which solves the problem that traditional molding / etching processes cannot continuously produce complex topological structures.

[0016] (2) The triboelectric nanogenerator with controllable negative Poisson's ratio structure of the present invention enables the material to achieve efficient mechanical energy absorption during bending deformation through the negative Poisson's ratio expansion effect, ensuring that the electrical signal output can still be maintained under large deformation conditions, thus optimizing the energy conversion efficiency.

[0017] (3) The triboelectric nanogenerator with controllable negative Poisson's ratio structure of the present invention utilizes the deformable characteristics of the negative Poisson's ratio structure to increase the effective contact area of ​​the friction layer during the contact-separation process, thereby enhancing charge transfer, improving output power and stability, and enabling it to adapt to the mechanical energy harvesting requirements in complex environments. It is applicable to wearable devices, smart medical and sports protective equipment and other fields. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the triboelectric nanogenerator with controllable negative Poisson's ratio structure of the present invention. Figure 2 This is a comparison diagram of the output open-circuit voltage of the triboelectric nanogenerator with controllable negative Poisson's ratio structure and the triboelectric nanogenerator without negative Poisson's ratio structure when bent at different displacements. Figure 3 Power density diagram of the controllable negative Poisson's ratio triboelectric nanogenerator prepared in this invention; Figure 4 A comparison of the output voltage and output power of a triboelectric nanogenerator with and without negative Poisson's ratio when bent; Figure 5 This is a comparison diagram of mechanical energy conversion between triboelectric nanogenerators with and without negative Poisson's ratio. Detailed Implementation

[0019] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0020] This invention relates to a triboelectric nanogenerator with a controllable negative Poisson's ratio structure, such as... Figure 1As shown, it comprises a three-layer structure: the upper layer is a polydimethylsiloxane backbone with a negative Poisson's ratio structure; the middle layer is a positive friction layer, which is a collagen aggregate modified with polyethyleneimine; and the lower layer is a negative friction layer, which is a fluorinated ethylene propylene copolymer with a negative Poisson's ratio structure. The surfaces of the positive and negative friction layers are uniformly coated with nano-silver paste. The three layers are assembled, with the positive and negative friction layers connected by elastic foam, and the polydimethylsiloxane backbone tightly bonded to the positive friction layer through curing.

[0021] Collagen aggregates can be derived from any of the following: sheepskin, pigskin, fish skin, cowhide, bovine tendon, or ostrich skin.

[0022] The polydimethylsiloxane framework with a negative Poisson's ratio structure was prepared by 3D printing technology. Its internal pore structure is a gradient swell configuration composed of concave hexagonal honeycomb units.

[0023] The method for preparing the triboelectric nanogenerator with a controllable negative Poisson's ratio structure of the present invention is specifically implemented according to the following steps: Step 1, Preparation of the polydimethylsiloxane framework with a negative Poisson's ratio structure; specifically: Step 1.1: Mix liquid silicone rubber and platinum catalyst, stir evenly, add nano silica to increase viscosity to 3000-5000 mPa·s, vacuum degas the mixture to eliminate the effect of bubbles on structural integrity, and obtain the mixed precursor. The mass ratio of liquid silicone rubber, platinum catalyst, and nano silica is 2-10:0.2-1:3-6; The liquid silicone rubber can be any one of Dow Corning Sylgard 184, ShinEtsu, or Momentive RTV615; The platinum catalyst is a divinyltetramethyldisiloxane platinum complex or a bis(divinyltetramethyldisiloxane) platinum complex; Step 1.2: Use a high-precision pneumatic extrusion 3D printer (Nordson EFD ValveMate, nozzle diameter 0.2-0.4 mm). Place the mixed precursor on the printing platform, which is pre-coated with a hydrophobic layer (Teflon film) to prevent adhesion. Upload the printing model for printing. The model pattern is a concave hexagonal honeycomb structure, with each concave hexagonal honeycomb unit having a side length of 1-2 mm, a wall thickness of 0.2-1.0 mm, and a concave angle of 30-60° (optimized for negative Poisson's ratio). Set the printing layer height to nozzle diameter × 0.8, the printing speed to 5-10 mm / s, the extrusion pressure to 0.3-0.6 MPa, and maintain the printing chamber temperature at 25±2°C (to avoid premature curing of PDMS). After printing, anneal the structure in a 50°C constant temperature oven for 2 hours to eliminate residual stress; remove and let stand for 15-20 minutes to obtain a polydimethylsiloxane skeleton with a negative Poisson's ratio structure. Step 2, the preparation of fluorinated ethylene propylene copolymer with a negative Poisson's ratio structure, specifically involves: A 0.1 mm (Saint-Gobain) thick fluorinated ethylene propylene copolymer film with a scratch-free and wrinkle-free surface was laser-etched using a UV nanosecond laser (wavelength 355 nm) in a spiral engraving sequence from the inside out. The engraved pattern is a concave hexagonal honeycomb structure with a unit side length of 2 mm, a wall thickness of 0.8 mm, and a concave angle of 60°. After engraving, the film was sequentially cleaned with deionized water, fluorocarbon surfactant, and O2 plasma to remove the carbonized layer. After cleaning, a fluorinated ethylene propylene copolymer with a negative Poisson's ratio structure was obtained. Step 3, preparation of polyethyleneimine-modified collagen aggregates, specifically: Step 3.1: Dissolve the collagen aggregates in acetic acid solution and stir at 1000 r / min at 40-60℃ for 1-2 h until completely dissolved to obtain a collagen aggregate solution with a mass fraction of 2-5 wt%. Step 3.2: Dissolve polyethyleneimine and triglyceride isocyanurate in anhydrous ethanol and stir for 1-2 hours to obtain polyethyleneimine solution and triglyceride isocyanurate solution, respectively. Step 3.3: Under mechanical stirring at 40-50℃, add triglyceride isocyanate solution dropwise to collagen aggregate solution and react for 2-3 hours. Then add polyethyleneimine solution and continue reacting for 6 hours. Then cast the resulting homogeneous solution into a presilicified glass mold and cure at 30-45℃ for 2-3 hours to obtain a uniform polyethyleneimine modified collagen aggregate with a thickness of 0.1-0.4 mm. The volume ratio of isocyanuric triglyceride solution, collagen aggregate solution, and polyethyleneimine solution is 1-5:10-30:1-5; Step 4: Using a polydimethylsiloxane backbone as the upper layer, a positive friction layer as the middle layer (constituted as a polyethyleneimine-modified collagen aggregate), and a negative friction layer as the lower layer (constituted as a fluorinated ethylene propylene copolymer with a negative Poisson's ratio structure), nano-silver paste is sprayed onto the surfaces of the positive and negative friction layers. The polydimethylsiloxane backbone is then cured and connected to the positive friction layer. Finally, the positive and negative friction layers are connected using elastic foam to form a triboelectric nanogenerator with a controllable negative Poisson's ratio structure.

[0024] The present invention discloses a method for fabricating a controllable negative Poisson's ratio triboelectric nanogenerator. A polydimethylsiloxane (PDS) framework with a negative Poisson's ratio structure is prepared using 3D printing technology. A layer-by-layer assembly strategy is used to solidify polyethyleneimine-modified collagen aggregates on the surface of the PDS framework as a positive friction layer. Simultaneously, an identical negative Poisson's ratio structure is laser-engraved on the surface of a fluorinated ethylene propylene copolymer as an auxiliary framework, which also serves as a negative friction layer. Utilizing the tensile effect of the PDS framework with a negative Poisson's ratio structure, the negative Poisson's ratio layer undergoes lateral expansion under axial bending stress, driving the modified collagen aggregate positive friction layer to exhibit a unidirectional tensile expansion effect. This significantly increases the contact area of ​​the friction interface during bending and improves the mechanical energy absorption efficiency, thereby optimizing the interfacial charge separation effect. This triboelectric nanogenerator exhibits high energy conversion efficiency, good flexibility and adaptability, and is suitable for mechanical energy harvesting and self-powering in smart medical devices, sports protective equipment, and flexible wearable devices.

[0025] Example 1 The method for preparing the triboelectric nanogenerator with a controllable negative Poisson's ratio structure of the present invention is specifically implemented according to the following steps: (1) Preparation of polydimethylsiloxane backbone with negative Poisson's ratio structure; Dow Corning Sylgard 184 and divinyltetramethyldisiloxane platinum complex were mixed and stirred evenly. Nano-silica was then added to increase the viscosity to 4500 mPa·s. After mixing, vacuum degassing (0.1 MPa, 30 minutes) was performed to eliminate the influence of bubbles on structural integrity and obtain the mixed precursor. The mass ratio of liquid silicone rubber, platinum catalyst, and nano silica is 10:1:3; A high-precision pneumatic extrusion 3D printer was used. The hybrid precursor was placed on the printing platform, which was pre-coated with a hydrophobic layer to prevent adhesion. The printing model was then uploaded for printing. The model's pattern was a concave hexagonal honeycomb structure, with each concave hexagonal honeycomb unit having a side length of 2 mm, a wall thickness of 0.8 mm, and a concave angle of 60°. The printing layer height was set to 0.16, the printing speed to 5 mm / s, the extrusion pressure to 0.3 MPa, and the printing chamber temperature to 25°C. After printing, the structure was annealed in a 50°C constant temperature oven for 2 hours to eliminate residual stress. After being removed and allowed to stand for 15 minutes, a polydimethylsiloxane skeleton with a negative Poisson's ratio structure was obtained. (2) Preparation of negative friction layer: A fluorinated ethylene propylene copolymer film with a thickness of 0.1 mm (Saint-Gobain) was used. The surface was free of scratches and wrinkles. The film was laser-etched in a spiral pattern from the inside out using a UV nanosecond laser (wavelength 355 nm). The etched pattern was a concave hexagonal honeycomb structure with a unit side length of 2 mm, a wall thickness of 0.8 mm, and a concave angle of 60°. After the etching was completed, the film was cleaned with deionized water, fluorocarbon surfactant, and O2 plasma (50 W, 1 min) to remove the carbonized layer. After cleaning, a fluorinated ethylene propylene copolymer film with a negative Poisson's ratio structure was obtained. (3) Preparation of positive friction layer: Collagen aggregates were dissolved in acetic acid solution and stirred at 1000 r / min at 60℃ for 2 h until completely dissolved to obtain a collagen aggregate solution with a mass fraction of 5 wt%; Polyethyleneimine and triglyceride isocyanurate were dissolved in anhydrous ethanol and stirred for 1 h to obtain polyethyleneimine solution and triglyceride isocyanurate solution, respectively. Under mechanical stirring at 40°C, isocyanuric acid triglyceride solution was added dropwise to collagen aggregate solution and reacted for 2 hours. Polyethylene imine solution was then added and the reaction continued for 6 hours. The resulting homogeneous solution was then cast into a presilicified glass mold and cured at 30°C for 2 hours to obtain a uniform polyethyleneimine modified collagen aggregate composite film with a thickness of 0.3 mm. The volume ratio of isocyanuric acid triglyceride solution, collagen aggregate solution, and polyethyleneimine solution is 3:20:3; Step 4: Using a polydimethylsiloxane backbone as the upper layer, a positive friction layer as the middle layer (constituted by a polyethyleneimine-modified collagen aggregate), and a negative friction layer as the lower layer (constituted by a fluorinated ethylene propylene copolymer with a negative Poisson's ratio structure), nano-silver paste is sprayed onto the surfaces of the positive and negative friction layers. The three layers are then assembled, and the positive and negative friction layers are connected by elastic foam to form a triboelectric nanogenerator with a controllable negative Poisson's ratio structure.

[0026] Example 2 The method for preparing the triboelectric nanogenerator with a controllable negative Poisson's ratio structure of the present invention is specifically implemented according to the following steps: (1) Preparation of polydimethylsiloxane backbone with negative Poisson's ratio structure; Momentive RTV615 and platinum catalyst were mixed and stirred evenly. Nano-silica was added to increase the viscosity to 4750 mPa·s. After mixing, vacuum degassing was performed to eliminate the influence of bubbles on structural integrity and obtain the mixed precursor. The mass ratio of liquid silicone rubber, bis(divinyltetramethyldisiloxane)platinum alloy, and nano silica is 5:1:4; Step 1.2: Using a high-precision pneumatic extrusion 3D printer, the hybrid precursor is placed on the printing platform. The printing platform is pre-coated with a hydrophobic layer (Teflon film) to prevent adhesion. The printing model is uploaded for printing. The model pattern is a concave hexagonal honeycomb structure. The concave hexagonal honeycomb structure unit has a side length of 2 mm, a wall thickness of 1.0 mm, and a concave angle of 60°. The printing layer height is set to 0.32, the printing speed is 10 mm / s, the extrusion pressure is 0.4 MPa, and the printing chamber temperature is maintained at 25°C (to avoid premature curing of PDMS). After printing, the structure is placed in a 50°C constant temperature oven for annealing for 2 hours to eliminate residual stress. After removal, it is allowed to stand for 20 minutes to obtain a polydimethylsiloxane skeleton with a negative Poisson's ratio structure. (2) Preparation of fluorinated ethylene propylene copolymers with negative Poisson's ratio structure, specifically: A 0.1 mm thick (Saint-Gobain) fluorinated ethylene propylene copolymer film with a scratch-free and wrinkle-free surface was laser-etched using a 355 nm ultraviolet nanosecond laser in a spiral engraving sequence from the inside out. The engraved pattern is a concave hexagonal honeycomb structure with a unit side length of 2 mm, a wall thickness of 0.8 mm, and a concave angle of 60°. After engraving, the film was sequentially cleaned with deionized water, fluorocarbon surfactant, and O2 plasma to remove the carbonized layer. After cleaning, a fluorinated ethylene propylene copolymer film with a negative Poisson's ratio structure was obtained. (3) Preparation of polyethyleneimine-modified collagen aggregates, specifically as follows: Collagen aggregates were dissolved in acetic acid solution and stirred at 1000 r / min at 50°C for 2 h until completely dissolved, to obtain a collagen aggregate solution with a mass fraction of 4 wt%. Polyethyleneimine and triglyceride isocyanurate were dissolved in anhydrous ethanol and stirred for 1.5 h to obtain polyethyleneimine solution and triglyceride isocyanurate solution, respectively. Under mechanical stirring at 50°C, isocyanuric acid triglyceride solution was added dropwise to collagen aggregate solution and reacted for 3 hours. Polyethylene imine solution was then added and the reaction continued for 6 hours. The resulting homogeneous solution was then cast into a presilicified glass mold and cured at 35°C for 2 hours to obtain a 0.3 mm thick uniform polyethyleneimine modified collagen aggregate composite film. The volume ratio of isocyanuric acid triglyceride solution, collagen aggregate solution, and polyethyleneimine solution is 1:10:5; Step 4: Using a polydimethylsiloxane backbone as the upper layer, a positive friction layer as the middle layer (constituted by a polyethyleneimine-modified collagen aggregate), and a negative friction layer as the lower layer (constituted by a fluorinated ethylene propylene copolymer with a negative Poisson's ratio structure), nano-silver paste is sprayed onto the surfaces of the positive and negative friction layers. The three layers are then assembled, and the positive and negative friction layers are connected by elastic foam to form a triboelectric nanogenerator with a controllable negative Poisson's ratio structure.

[0027] Example 3 The method for preparing the triboelectric nanogenerator with a controllable negative Poisson's ratio structure of the present invention is specifically implemented according to the following steps: (1) Preparation of a polydimethylsiloxane backbone with a negative Poisson's ratio structure; specifically: Dow Corning Sylgard 184 and divinyltetramethyldisiloxane platinum complex were mixed and stirred evenly. Nano-silica was added to increase the viscosity to 5000 mPa·s. After mixing, vacuum degassing was performed to eliminate the influence of bubbles on structural integrity and obtain the mixed precursor. The mass ratio of liquid silicone rubber, platinum catalyst, and nano silica is 8:0.5:3; Step 1.2: A high-precision pneumatic extrusion 3D printer (Nordson EFD ValveMate, nozzle diameter 0.2mm) was used. The mixed precursor was placed on the printing platform, which was pre-coated with a hydrophobic layer (Teflon film) to prevent adhesion. The printing model was uploaded and printed. The model pattern was a concave hexagonal honeycomb structure, with each concave hexagonal honeycomb unit having a side length of 2 mm, a wall thickness of 0.8 mm, and a concave angle of 60°. The printing layer height was set to 0.16, the printing speed to 5 mm / s, the extrusion pressure to 0.6 MPa, and the printing chamber temperature to 26°C (to prevent premature curing of PDMS). After printing, the structure was annealed in a 50°C constant temperature oven for 2 hours to eliminate residual stress. After removal, it was allowed to stand for 20 minutes to obtain a polydimethylsiloxane skeleton with a negative Poisson's ratio structure. (2) Preparation of fluorinated ethylene propylene copolymers with negative Poisson's ratio structure, specifically: A 0.1 mm thick (Saint-Gobain) fluorinated ethylene propylene copolymer film with a scratch-free and wrinkle-free surface was laser-etched using a 355 nm ultraviolet nanosecond laser in a spiral engraving sequence from the inside out. The engraved pattern is a concave hexagonal honeycomb structure with a unit side length of 2 mm, a wall thickness of 0.8 mm, and a concave angle of 60°. After engraving, the film was sequentially cleaned with deionized water, fluorocarbon surfactant, and O2 plasma to remove the carbonized layer. After cleaning, a fluorinated ethylene propylene copolymer film with a negative Poisson's ratio structure was obtained. (3) Preparation of polyethyleneimine-modified collagen aggregates, specifically as follows: Collagen aggregates were dissolved in acetic acid solution and stirred at 1000 r / min at 60℃ for 1 h until completely dissolved, to obtain a collagen aggregate solution with a mass fraction of 2 wt%. Polyethyleneimine and triglyceride isocyanurate were dissolved in anhydrous ethanol and stirred for 2 hours to obtain polyethyleneimine solution and triglyceride isocyanurate solution, respectively. Under mechanical stirring at 50°C, isocyanuric acid triglyceride solution was added dropwise to collagen aggregate solution and reacted for 3 hours. Polyethylene imine solution was then added and the reaction continued for 6 hours. The resulting homogeneous solution was then cast into a presilicified glass mold and cured at 45°C for 2 hours to obtain a 0.3 mm thick uniform polyethyleneimine modified collagen aggregate composite film. The volume ratio of isocyanuric acid triglyceride solution, collagen aggregate solution, and polyethyleneimine solution is 5:10:1; Step 4: Using a polydimethylsiloxane backbone as the upper layer, a positive friction layer as the middle layer (constituted by a polyethyleneimine-modified collagen aggregate), and a negative friction layer as the lower layer (constituted by a fluorinated ethylene propylene copolymer with a negative Poisson's ratio structure), nano-silver paste is sprayed onto the surfaces of the positive and negative friction layers. The three layers are then assembled, and the positive and negative friction layers are connected by elastic foam to form a triboelectric nanogenerator with a controllable negative Poisson's ratio structure.

[0028] Comparative Example 1 The preparation method of the triboelectric nanogenerator without negative Poisson's ratio structure is as follows: Step 1, Preparation of polyethyleneimine-modified collagen aggregates: Collagen aggregates were dissolved in acetic acid solution and stirred at 1000 r / min at 60℃ for 2 h until completely dissolved, to obtain a collagen aggregate solution with a mass fraction of 5 wt%. Polyethyleneimine and triglyceride isocyanurate were dissolved in anhydrous ethanol and stirred for 1 h to obtain polyethyleneimine solution and triglyceride isocyanurate solution, respectively. Under mechanical stirring at 40°C, isocyanuric acid triglyceride solution was added dropwise to collagen aggregate solution and reacted for 2 hours. Polyethylene imine solution was then added and the reaction continued for 6 hours. The resulting homogeneous solution was then cast into a presilicified glass mold and cured at 30°C for 2 hours to obtain a uniform polyethyleneimine modified collagen aggregate composite film with a thickness of 0.3 mm. The volume ratio of isocyanuric acid triglyceride solution, collagen aggregate solution, and polyethyleneimine solution is 3:20:3; Step 2, the preparation of fluorinated ethylene propylene copolymer, specifically involves: The film is made of fluorinated ethylene propylene copolymer with a thickness of 0.1 mm (Saint-Gobain), with no scratches or wrinkles on the surface, and is cut to a size of 5×4 cm. 2 ; Step 3: Using the polyethyleneimine-modified collagen aggregate composite film obtained in Step 1 as the positive friction layer and the fluorinated ethylene propylene copolymer film obtained in Step 2 as the negative friction layer, nano silver paste is sprayed onto the surfaces of the negative and positive friction layers, and the positive and negative friction layers are connected by elastic foam to form a triboelectric nanogenerator with a negative Poisson's ratio-free structure.

[0029] Example 4 like Figure 2 The diagram shows a comparison of the open-circuit voltage output of the triboelectric nanogenerator with a controllable negative Poisson's ratio structure in Embodiment 1 and the triboelectric nanogenerator without a negative Poisson's ratio structure in Comparative Example 1 at different bending displacements (2 mm, 4 mm, 6 mm, 8 mm, 10 mm). The open-circuit voltages of the triboelectric nanogenerator without the negative Poisson's ratio structure are 8 V, 15 V, 23 V, 33 V, and 44 V, respectively. The open-circuit voltages of the triboelectric nanogenerator with a controllable negative Poisson's ratio structure are 18 V, 22 V, 34 V, 43 V, and 58 V, respectively. It can be seen that the negative Poisson's ratio structure layer effectively improves the open-circuit voltage of the triboelectric nanogenerator under bending conditions.

[0030] Example 5 like Figure 3 As shown, the area of ​​the triboelectric nanogenerator with controllable negative Poisson's ratio structure of this invention is 5 × 4 cm. 2 The voltage output and charge density under different external resistances during contact separation under an external force of 200 kPa are measured. The maximum output voltage is 485V, and the maximum charge density is 14 W / m² when the external resistance is 2 MΩ. 2 .

[0031] Example 6 like Figure 4 As shown, the output voltage and output energy of the triboelectric nanogenerator with a controllable negative Poisson's ratio structure (58 V, 0.045 J) in Embodiment 1 of the present invention are compared with those of the triboelectric nanogenerator without a negative Poisson's ratio structure (37 V, 0.021 J) in Comparative Example 1 under the same force conditions. The results show that the negative Poisson's ratio stretching effect increases the output power of the triboelectric nanogenerator. like Figure 5 As shown, the mechanical energy conversion efficiency of the triboelectric nanogenerator with a controllable negative Poisson's ratio structure (7.58%) in Example 1 of the present invention is compared with that of the triboelectric nanogenerator without a negative Poisson's ratio structure (2.37%) in Comparative Example 1. The results show that under biaxial bending, the negative Poisson's ratio structure effectively increases the energy conversion efficiency.

[0032] This invention utilizes the tensile effect of a polydimethylsiloxane backbone with a negative Poisson's ratio structure. Under axial bending stress, the negative Poisson's ratio layer undergoes lateral expansion, which in turn drives the modified collagen aggregate positive friction layer to produce a unidirectional tensile expansion effect. This significantly increases the contact area of ​​the friction interface during bending and improves the mechanical energy absorption efficiency, thereby optimizing the interfacial charge separation effect. This triboelectric nanogenerator exhibits high energy conversion efficiency, good flexibility and adaptability, and is suitable for mechanical energy harvesting and self-powering in smart medical devices, sports protective equipment, and flexible wearable devices.

Claims

1. A triboelectric nanogenerator with a controllable negative Poisson's ratio structure, characterized in that, It comprises a three-layer structure: the upper layer is a polydimethylsiloxane backbone with a negative Poisson's ratio structure; the middle layer is a positive friction layer, which is a collagen aggregate modified with polyethyleneimine; and the lower layer is a negative friction layer, which is a fluorinated ethylene propylene copolymer with a negative Poisson's ratio structure.

2. The triboelectric nanogenerator with a controllable negative Poisson's ratio structure as described in claim 1, characterized in that, The surfaces of the positive and negative friction layers are uniformly coated with nano-silver paste.

3. A method for preparing a triboelectric nanogenerator with a controllable negative Poisson's ratio structure, characterized in that, The specific steps are as follows: Step 1: Preparation of a polydimethylsiloxane framework with a negative Poisson's ratio structure; Step 2, Preparation of fluorinated ethylene propylene copolymer with negative Poisson's ratio structure; Step 3, Preparation of polyethyleneimine-modified collagen aggregates; Step 4: Using a polydimethylsiloxane framework as the upper layer, a positive friction layer as the middle layer (constituted as a polyethyleneimine-modified collagen aggregate), and a negative friction layer as the lower layer (constituted as a fluorinated ethylene propylene copolymer with a negative Poisson's ratio structure), nano-silver paste is sprayed onto the surfaces of the positive and negative friction layers. The polydimethylsiloxane framework is then cured and connected to the positive friction layer. Finally, the positive and negative friction layers are connected using elastic foam to obtain a triboelectric nanogenerator with a controllable negative Poisson's ratio structure.

4. The method for preparing the triboelectric nanogenerator with a controllable negative Poisson's ratio structure as described in claim 3, characterized in that, In step 1, specifically: Step 1.1: Mix liquid silicone rubber and platinum catalyst, stir until homogeneous, add nano-silica, mix and then degas under vacuum to obtain a mixed precursor; Step 1.2: Place the hybrid precursor on the printing platform of the 3D printer. The printing platform is pre-coated with a hydrophobic layer. Upload the printing model for printing. The pattern of the model is a concave hexagonal honeycomb structure. After printing, place the structure in a constant temperature oven for annealing and let it stand to obtain a polydimethylsiloxane skeleton with a negative Poisson's ratio structure.

5. The method for preparing the triboelectric nanogenerator with a controllable negative Poisson's ratio structure as described in claim 4, characterized in that, In step 1.1, the mass ratio of liquid silicone rubber, platinum catalyst, and nano silica is 2-10:0.2-1:3-6; the liquid silicone rubber is any one of Dow Corning Sylgard 184, ShinEtsu, and Momentive RTV615; the platinum catalyst is a divinyltetramethyldisiloxane platinum complex or a bis(divinyltetramethyldisiloxane) platinum complex.

6. The method for preparing the triboelectric nanogenerator with a controllable negative Poisson's ratio structure as described in claim 4, characterized in that, In step 1.2, the unit side length of the concave hexagonal honeycomb structure is 1-2 mm, the wall thickness is 0.2-1.0 mm, and the concave angle is 30-60°; the printing layer height is set to nozzle diameter × 0.8, the printing speed is 5-10 mm / s, the extrusion air pressure is 0.3-0.6 MPa, and the printing chamber temperature is maintained at 25±2°C.

7. The method for preparing a triboelectric nanogenerator with a controllable negative Poisson's ratio structure as described in claim 3, characterized in that, Step 2 specifically involves: The fluorinated ethylene propylene copolymer film was laser-engraved using an ultraviolet nanosecond laser in a spiral engraving sequence from the inside out. The engraved pattern was a concave hexagonal honeycomb structure with a unit side length of 2 mm, a wall thickness of 0.8 mm, and a concave angle of 60°. After engraving, the film was cleaned sequentially with deionized water, fluorocarbon surfactant, and O2 plasma. After cleaning, a fluorinated ethylene propylene copolymer with a negative Poisson's ratio structure was obtained.

8. The method for preparing a triboelectric nanogenerator with a controllable negative Poisson's ratio structure as described in claim 3, characterized in that, Step 3 specifically involves: Step 3.1: Dissolve the collagen aggregates in acetic acid solution and stir at 40-60℃ for 1-2 hours to obtain a collagen aggregate solution with a mass fraction of 2-5 wt%; the collagen aggregates can be any one of sheepskin, pigskin, fish skin, cowskin, bovine tendon, or ostrich skin. Step 3.2: Dissolve polyethyleneimine and triglyceride isocyanurate in anhydrous ethanol and stir for 1-2 hours to obtain polyethyleneimine solution and triglyceride isocyanurate solution, respectively. Step 3.3: Under mechanical stirring at 40-50℃, add triglyceride isocyanurate solution dropwise to collagen aggregate solution and react for 2-3 hours. Then add polyethyleneimine solution and continue reacting for 6 hours. The resulting homogeneous solution is then cast into a presilicified glass mold and cured at 30-45℃ for 2-3 hours to obtain polyethyleneimine modified collagen aggregate with a thickness of 0.1-0.4 mm.

9. The method for preparing a triboelectric nanogenerator with a controllable negative Poisson's ratio structure as described in claim 8, characterized in that, In step 3.3, the volume ratio of the isocyanuric triglyceride solution, the collagen aggregate solution, and the polyethyleneimine solution is 1-5:10-30:1-5.

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