Friction Nanogenerator and Preparation Method Thereof, Self-Powered Sensing System and Joint Angle Detection Method

Abstract

The present invention provides a triboelectric nanogenerator based on 4D printing technology, which includes a first base layer and a first triboelectric power generation component of a friction unit. A plurality of friction units are arranged at intervals with the geometric center of the first base layer as the center of a circle; a second triboelectric power generation component including a second base layer, a first electrode, and a second electrode. A plurality of first electrodes and a plurality of second electrodes are arranged at intervals with the geometric center of the second base layer as the center of a circle, and there is a gap between the first electrode and the second electrode; the first base layer and the second base layer are inserted together through the provided flanges and grooves, so that the friction units are in contact and friction with the first electrode and the second electrode. The present invention also provides a self-powered sensing system, a method for detecting the rotation angle of a joint, and a preparation method for a 4D printing triboelectric nanogenerator. The present invention solves the technical problems of complex preparation process of the sensing device, low preparation efficiency and accuracy, and short service life of the produced sensing device.

Description

Technical Field

[0001] The present invention relates to an interdisciplinary technical field combining 4D printing technology, sensing technology and self-powered system. More specifically, it relates to a triboelectric nanogenerator based on 4D printing technology, a self-powered sensing system, a method for detecting the joint rotation angle based on the self-powered sensing system, and a preparation method for the triboelectric nanogenerator based on 4D printing technology. Background Art

[0002] With the advent of the Internet of Things era, a large number of portable electronic devices have been applied, and the power supply methods of these electronic devices generally choose to use batteries for power supply. However, using batteries for power supply requires frequent charging or battery replacement, and at the same time, the discarded batteries will also cause serious environmental pollution. Therefore, there is an urgent need for a self-powered sensing technology that can achieve detection without external power supply. To solve this problem, self-powered sensing systems based on triboelectric nanogenerators have received extensive attention.

[0003] However, on the way to widespread application, self-powered sensing systems based on triboelectric nanogenerators still have some problems. First, when the device works for a long time, the device performance will decay, resulting in incorrect detection results. Second, the preparation process of self-powered sensors based on triboelectric nanogenerators is relatively backward. Finally, the traditional preparation process involves processing, assembling each component, and finally assembling them into a complete device; however, such a process is difficult to ensure the performance of the same batch of devices, and ultimately affects the detection effect.

[0004] Patent document CN111564985A (publication date: August 21, 2020) discloses a sensing triboelectric nanogenerator, a sensing device for a tire, and a force monitoring system, in which by designing the structure of the triboelectric nanogenerator, each base layer, electrode layer, and friction layer are sequentially pasted on the inner wall of the flexible base layer to obtain a relatively closed triboelectric nanogenerator; the friction layers are in contact with each other under the action of a pre-tightening force; when opposite forces are applied to both sides of the base layer, the friction layers move away from each other, generating an electrical signal related to the deformation amount; according to the characteristics of the electrical signal, the deformation characteristics of the triboelectric nanogenerator can be judged, so that the sensing triboelectric nanogenerator of this invention has an induction function. However, its preparation process is complex, the preparation efficiency and preparation accuracy are not high, and the service life of the produced sensing device is not satisfactory.

[0005] To promote the application and development of sensing devices based on triboelectric nanogenerators, there is an urgent need for a brand-new process to improve the preparation efficiency and preparation accuracy of sensing devices, and at the same time improve the service life of sensing devices. Summary of the Invention

[0006] The present invention aims to solve, at least to some extent, the technical problems of the complex preparation process of the sensing device, the low preparation efficiency and precision, and the unsatisfactory service life of the fabricated sensing device.

[0007] The primary object of the present invention is to provide a triboelectric nanogenerator based on 4D printing technology. To solve the above technical problems, the technical solution of the present invention is as follows:

[0008] A triboelectric nanogenerator based on 4D printing technology includes a first triboelectric component and a second triboelectric component that can rotate relative to each other; the first triboelectric component includes a first base layer and friction units provided on the surface of the first base layer, and the plurality of friction units are arranged at intervals with the center of the first base layer as the center of the circle; the second triboelectric component includes a second base layer, a first electrode and a second electrode provided on the inner surface of the second base layer, and a plurality of first electrodes and a plurality of second electrodes are arranged at intervals with the geometric center of the second base layer as the center of the circle, and there is a gap between the first electrode and the second electrode; the first base layer and the second base layer are inserted together through the flanges and grooves provided on each other, so that the friction units can rotate and contact and rub against the first electrode and the second electrode; wherein the first triboelectric component and the second base layer are prepared by 4D printing technology.

[0009] Preferably, the 4D printing uses a shape memory polymer or a self-healing material, and adopts fused deposition modeling printing, ink direct writing printing or digital light processing printing.

[0010] Preferably, the surface of the friction unit has protrusions or grooves.

[0011] Preferably, a solution with a conductive substance is sprayed on the surface of the second base layer, and after the solvent is volatilized, the first electrode and the second electrode are obtained, and the conductive substance includes silver nanowires, carbon nanotubes or graphene.

[0012] Preferably, the longitudinal cross-sectional shape of the first triboelectric component and the second triboelectric component is polygonal or curvilinear.

[0013] Preferably, the central angle corresponding to each friction unit is a, and the same central angle b is separated between adjacent two friction units; the central angle corresponding to each first electrode is c, and the central angle corresponding to each second electrode is e, where a = c = d, and b = c + 2*e.

[0014] A further object of the present invention is to provide a self-powered sensing system, in which the triboelectric nanogenerator based on 4D printing technology is assembled at a joint, wherein a first triboelectric generating component and a second triboelectric generating component are installed on one side of the joint. When the joint moves, it drives relative rotation between one triboelectric generating component and the other triboelectric generating component to generate an alternating current signal, and the angle of joint movement can be inferred according to the characteristics of the alternating current signal.

[0015] A third object of the present invention is to provide a method for detecting the rotation angle of a joint based on the self-powered sensing system, comprising the following steps:

[0016] S1. Measure the phases of the output electrical signals of the triboelectric nanogenerator at different rotation angles respectively, and establish a corresponding relationship table of "rotation angle - output electrical signal phase";

[0017] S2. Obtain the output electrical signal of the self-powered sensing system installed at the joint in real time, and perform smoothing and noise reduction processing on the output electrical signal;

[0018] S3. Detect the phase information corresponding to the output electrical signal after smoothing and noise reduction processing in step S2;

[0019] S4. According to the corresponding relationship table of "rotation angle - output signal phase" calibrated in step S1, match the phase information of the output electrical signal;

[0020] S5. Obtain the joint rotation angle according to the matching result of the phase information of the output electrical signal and the rotation angle in S4.

[0021] Preferably, in step S2, a plurality of self-powered sensing systems are installed at the joint simultaneously. Correspondingly, in step S3, the average value of the phase information corresponding to a plurality of output electrical signals after smoothing and noise reduction processing is taken as the final phase information.

[0022] A fourth object of the present invention is to provide a preparation method for a triboelectric nanogenerator of 4D printing technology, comprising the following steps:

[0023] S1. Design an independent layer type triboelectric nanogenerator model;

[0024] S2. After modeling, perform a force analysis on the working process of the model and conduct a simulation test on the potential field distribution;

[0025] S3. Import the tested model into slicing software for slicing and layering, select the processing sequence according to the actual structure of the model and generate processing instructions;

[0026] S4. Import the processing instructions into the 3D printer to complete the printing and processing of the first triboelectric component and the second base layer respectively. If there are problems with the printed product not meeting the usage requirements during the processing, return to S1 to re-complete the design and simulation test of the model and generate new processing instructions.

[0027] S5. Spray the surface of the printed second base layer with a volatile solution doped with a conductive substance using a sprayer. After the solvent volatilizes, the first electrode and the second electrode can be obtained.

[0028] S6. Assemble the second triboelectric component and the first triboelectric component with the first electrode and the second electrode prepared into a triboelectric nanogenerator.

[0029] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0030] 1. The present invention introduces 4D printing technology into the preparation of triboelectric nanogenerators and designs and prepares an independent layer-type triboelectric nanogenerator. First, the introduction of 4D printing technology enables the triboelectric nanogenerator to achieve personalized, high-precision, and high-efficiency preparation, and surface protrusions or grooves can be made on the surface of the friction unit to increase the contact area, thereby improving the output performance of the triboelectric nanogenerator. Second, the triboelectric nanogenerator made of shape memory material also has a shape memory function. When there is performance attenuation caused by device deformation during use, as long as the deformed device is placed under certain conditions, the shape of the device can be restored and the performance will also be restored accordingly, thereby indirectly increasing the service life of the triboelectric nanogenerator.

[0031] 2. The present invention assembles the independent layer-type triboelectric nanogenerator at the joint as a self-powered sensing system and combines a new method for detecting the rotation angle of the joint, and uses the triboelectric nanogenerator as a self-powered sensor for detecting joint movement. Different from the previous method of detecting by sensing the strength of the output signal of the triboelectric nanogenerator, the present invention starts from the principle of the output signal of the triboelectric nanogenerator and judges the angle of joint movement according to the relationship between the relative rotation angle between the triboelectric components and the characteristics of the output electrical signal. This method can effectively avoid the detection error caused by device performance attenuation, thereby improving the reliability of detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a top view of the surface of the first triboelectric component of the triboelectric nanogenerator based on 4D printing technology provided by Embodiment 1 of the present invention.

[0033] Figure 2 It is a top view of the surface of the second triboelectric component of the triboelectric nanogenerator based on 4D printing technology provided by Embodiment 1 of the present invention.

[0034] Figure 3 Cross-sectional schematic diagram of the triboelectric nanogenerator based on 4D printing technology provided in Embodiment 1 of the present invention.

[0035] Figure 4 Schematic diagram of the first step of the working process of the triboelectric nanogenerator based on 4D printing technology provided in Embodiment 1 of the present invention.

[0036] Figure 5 Schematic diagram of the second step of the working process of the triboelectric nanogenerator based on 4D printing technology provided in Embodiment 1 of the present invention.

[0037] Figure 6 Schematic diagram of the third step of the working process of the triboelectric nanogenerator based on 4D printing technology provided in Embodiment 1 of the present invention.

[0038] Figure 7 Schematic diagram of the fourth step of the working process of the triboelectric nanogenerator based on 4D printing technology provided in Embodiment 1 of the present invention.

[0039] Figure 8 Assembly schematic diagram of the self-powered sensing system for detecting human joint movement provided in Embodiment 2 of the present invention.

[0040] Figure 9 Voltage change diagram of the self-powered sensing system provided in Embodiment 2 of the present invention.

[0041] Figure 10 Flowchart of the steps of the method for detecting the rotation angle of a human joint based on the self-powered sensing system provided in Embodiment 3 of the present invention.

[0042] Figure 11 Flowchart of the steps of a preparation method of a triboelectric nanogenerator based on 4D printing technology provided in Embodiment 4 of the present invention. Detailed implementation manners

[0043] The drawings are only for illustrative purposes and should not be construed as limitations on this patent;

[0044] To better illustrate this embodiment, some components in the drawings are omitted, enlarged or reduced, and do not represent the dimensions of the actual product;

[0045] For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0046] The technical solutions of the present invention will be further described below with reference to the drawings and embodiments.

[0047] Embodiment 1

[0048] See Figures 1-3, A triboelectric nanogenerator based on 4D printing technology, comprising a first triboelectric component 1 and a second triboelectric component 2 that can rotate relative to each other; the first triboelectric component 1 includes a first base layer 11 and a friction unit 12 provided on the surface of the first base layer 11, and the plurality of friction units 12 are arranged at intervals with the geometric center of the first base layer 11 as the center of the circle; the second triboelectric component 2 includes a second base layer 21, a first electrode 22 and a second electrode 23 provided on the surface of the second base layer 21, and a plurality of first electrodes 22 and a plurality of second electrodes 23 are arranged at intervals with the geometric center of the second base layer 21 as the center of the circle, and there is a gap between the first electrode 22 and the second electrode 23; the first base layer 11 and the second base layer 21 are inserted together through the flanges 24 and grooves 13 provided on each other, so that the friction unit 12 can rotate and contact and rub with the first electrode 22 and the second electrode 23; wherein the first triboelectric component 1 and the second base layer 21 are prepared by 4D printing technology.

[0049] Specifically, the first triboelectric component 1 and the second base layer 21 use shape memory polymers or self-healing materials. Further, the printing wire can be polyurethane. It is prepared by 3D printing methods such as fused deposition modeling printing, direct ink writing printing or digital light processing printing; the first electrode 22 and the second electrode 23 are sprayed with a solution containing a conductive substance using a spraying machine, and under the action of a mask plate, the corresponding electrode pattern is obtained, and finally the solvent is volatilized to obtain the corresponding electrode layer. The conductive substance includes silver nanowires, carbon nanotubes or graphene. More specifically, the solution used to prepare the conductive layer can be a silver nanowire methanol solution.

[0050] Specifically, the longitudinal cross-sectional shapes of the first base layer 11 and the second base layer 21 are polygons or curved surfaces, and can be further set as regular polygons or circles. The friction unit 12 is in the shape of a rectangle, a triangle or a sector. The central angle corresponding to each friction unit 12 is a, and the same central angle b is separated between adjacent two friction units 12; the central angle corresponding to each first electrode 22 is c, and the central angle corresponding to each second electrode 23 is e, where a = c = d and b = c + 2*e.

[0051] In the specific implementation process, the first triboelectric power generation component 1 and the second triboelectric power generation component 2 are assembled together through a flange 24 and a groove 13 provided at their geometric centers, so that the friction unit 12 is in contact with the first electrode 22 and the second electrode 23 to form an independent layer-type triboelectric nanogenerator. The cross-sectional shapes of the flange 24 and the groove 13 are circular. In order to increase the effective contact area, the surfaces of a number of friction units 12 can be obtained with surface protrusions or groove patterns through 4D printing technology, thereby increasing the output performance of the triboelectric nanogenerator. When the first triboelectric power generation component 1 and the second triboelectric power generation component 2 rotate relative to each other, under the action of triboelectrification and electrostatic induction, the triboelectric nanogenerator generates alternating current.

[0052] Next, the working principle of the 4D-printed triboelectric nanogenerator of this embodiment will be described:

[0053] The working mode of the triboelectric nanogenerator in this embodiment is an independent layer type. As Figures 4-7 shown, under the action of an external force, the first electrode 22 and the second electrode 23 rotate relative to the friction unit with the flange and the groove as the center; during the rotation process, a number of friction units 12 alternately overlap with the first electrode 22 and the second electrode 23, affecting the charge distribution on the electrode surface, thereby causing a potential difference to be generated between the first electrode 22 and the second electrode 23; when there is an electrical connection between the first electrode 22 and the second electrode 23, the triboelectric nanogenerator generates an alternating current signal in the external circuit, and when the first electrode 22 and the second electrode 23 are open-circuited, the triboelectric nanogenerator outputs an alternating voltage signal; specifically, when friction occurs, the friction unit has a large electronegativity, so the surface is charged negatively; when a number of friction units 12 completely overlap with a number of first electrodes 22, under the action of electrostatic induction, an equal amount of positive charge appears on the surfaces of a number of first electrodes 22, and there is no charge on the surfaces of a number of second electrodes 23 at this time, so there is a potential difference between the first electrode 22 and the second electrode 23; as the friction unit continues to rotate until it completely covers the second electrode 23, at this time, an equal amount of positive charge appears on the surface of the first electrode 22, and there is no charge on the surface of the first electrode 22, so there is a potential difference between the second electrode 23 and the first electrode 22; when the external force continues to act, the above power generation cycle will occur repeatedly.

[0054] The performance of triboelectric nanogenerators often degrades due to the deformation of some components, which greatly affects the working stability and service life of triboelectric nanogenerators. In this embodiment, the above-mentioned triboelectric nanogenerator prepared by 4D printing technology using polyurethane as the printing wire has a shape memory function. When the device deforms and causes the device performance to decay, the deformed device is heated at 60 °C for 1 min, and then the shape of the device can be restored to its original state. After testing, it is found that the performance of the device can also be effectively restored.

[0055] Example 2

[0056] This embodiment provides a self-powered sensing system based on Example 1. The triboelectric nanogenerator based on 4D printing technology is assembled at a human joint. The first triboelectric power generation component 1 and the second triboelectric power generation component 2 are installed on one side of the human joint. When the human joint moves, it drives one triboelectric power generation component to rotate relative to the other triboelectric power generation component to generate an alternating current signal. The angle of joint movement can be inferred according to the characteristics of the alternating current signal. Specifically, a = c = d = 29°, b = 31°, and e = 1°. In practical applications, the detection accuracy of the self-powered sensing system will change according to the changes of the above parameters.

[0057] When the friction unit 12 is located at the middle position between the first electrode 22 and the second electrode 23, at this time, equal amounts of positive charges are distributed on the surfaces of the first electrode 22 and the second electrode 23, and there is no potential difference between the two electrodes. At this time, it corresponds to Figure 8 point i in it.

[0058] When the friction unit 12 rotates by 15°, at this time, the friction unit completely overlaps with the first electrode 22. Under the action of electrostatic induction, positive charges equal to the negative charges on the surface of the friction unit appear on the surface of the first electrode 22. At this time, the potential difference between the first electrode 22 and the second electrode 23 reaches the maximum value. When the friction unit 12 rotates by 15° along the same direction, the friction unit 12 reaches the middle position between the first electrode 22 and the second electrode 23 again. At this time, there are equal amounts of positive charges on the surfaces of the first electrode 22 and the second electrode 23, and the potential difference between the electrodes disappears, corresponding to Figure 8 the potential difference change curve between point i and point ii in it.

[0059] When the friction unit rotates by 30° along the same direction, the potential difference between the electrodes first appears and then returns to zero, corresponding to Figure 8 the potential difference change curves between point ii - point iii and between point iii - point iv in it.

[0060] Therefore, by observing the rotation angle of the friction unit and the output waveform, we can find that when the relative rotation angles are 30°, 60°, and 90° respectively, the waveform phases generated by the sensor are π, 2π, and 3π; therefore, according to the phase characteristics of the output waveform generated by the sensor, we can know the relative rotation angle between the first triboelectric power generation component and the second triboelectric power generation component, that is, the rotation angle of the joint;

[0061] It should be noted that the relationship between the relative rotation angle and the waveform phase is not fixed as (30°, π), (60°, 2π), (90°, 3π). The specific correspondence is affected by the specific structure of the device. That is to say, the central angle corresponding to each friction unit 12 is a, the central angle between adjacent two friction units 12 is the same, the central angle corresponding to each first electrode 22 is c, and the central angle corresponding to each second electrode 23 is e, and these values will affect the final judgment result.

[0062] In addition, the application scenario of the self-powered sensing system is not limited to human joints, but various positions where rotation occurs, such as the arms of industrial robots. When the triboelectric nanogenerator based on 4D printing technology is assembled at different joints, it has different sizes. For example, the sizes of the triboelectric nanogenerators installed at the elbow joint, wrist joint, and finger joint of a person change from large to small.

[0063] Figure 9 The detection results of the self-powered sensing system at the finger joint are shown. It can be seen that when the joint rotates 30°, 60°, and 90° respectively, the phases of the output electrical signal waveforms of the sensor are π, 2π, and 3π respectively, and the peak voltage is maintained at about 0.7V; when the device is deformed, it can be seen that the phase of the output electrical signal of the sensor does not change, only the peak voltage drops, dropping to about 0.3V, a decrease of about 55%; however, after heating the deformed sensor at 60°C for 1 minute, the shape of the sensor is restored, and from Figure 8 the data in it can be seen that the performance of the sensor output is also restored, the phase characteristics are the same, and the peak voltage also returns to about 0.7V.

[0064] Embodiment 3

[0065] See Figure 10 , this embodiment provides a method for detecting the rotation angle of a human joint based on the self-powered sensing system, including the following steps:

[0066] S1. Measure the phases of the output electrical signals of the triboelectric nanogenerator at different rotation angles respectively, and establish a correspondence table of "rotation angle - output electrical signal phase";

[0067] S2. Acquire the output electrical signal of the self-powered sensor system installed at the human joint in real time, and perform smoothing and noise reduction processing on the output electrical signal;

[0068] S3, detecting phase information corresponding to the output electrical signal after smoothing and noise reduction processing in step S2;

[0069] S4, matching the phase information of the output electrical signal according to the corresponding relationship table of "rotation angle-output signal phase" calibrated in step S1;

[0070] S5. Obtain the rotation angle of the human body joint according to the matching result of the phase information of the output electrical signal in S4 and the rotation angle.

[0071] In step S2, multiple self-powered sensing systems can be installed simultaneously at the joints of the human body, and accordingly, in step S3, the average value of the phase information corresponding to the multiple smoothed and noise-reduced output electrical signals is obtained as the final phase information.

[0072] The self-powered sensor proposed in this embodiment adopts a new detection method based on the working principle of an independent layer friction nanogenerator. The movement of the joint is judged according to the phase relationship of the waveform output by the friction nanogenerator under different conditions. During operation, even if performance degradation occurs due to device deformation, it will not affect the effective detection of the sensor, thereby greatly improving the reliability of sensor detection.

[0073] Example 4

[0074] A method for preparing a friction nanogenerator using 4D printing technology, see Figure 11 , including the following steps:

[0075] S1. Design an independent layer triboelectric nanogenerator model;

[0076] S2. After modeling, the working process of the model is subjected to stress analysis and the electric potential field distribution is simulated and tested;

[0077] S3. Import the tested model into the slicing software for slicing and layering, select the processing sequence according to the actual structure of the model and generate processing instructions (such as Gcode code);

[0078] S4. Import the processing instructions into the 3D printer to complete the printing of the first triboelectric component 1 and the second base layer 21 respectively; if the printed product collapses, deforms, or has problems affecting assembly during the processing and does not meet the use requirements, return to S1, complete the model design and simulation test again, and generate new processing instructions (such as GCODE code);

[0079] S5. Spray the surface of the second base layer after printing and processing with a volatile solution doped with a conductive substance using a spraying machine. After the solvent volatilizes, the first electrode 22 and the second electrode 23 can be obtained.

[0080] S6. Assemble the second triboelectric power generation component 2 and the first triboelectric power generation component 1 with the first electrode 22 and the second electrode 23 prepared into a triboelectric nanogenerator.

[0081] Among them, in step S2, 3ds MAX software is used for modeling, and software such as COMSOL is used to analyze the force during the working process of the model and simulate and test the potential field distribution.

[0082] The above preparation method of the triboelectric nanogenerator based on 4D printing technology can also be used to prepare triboelectric nanogenerators in various modes, including but not limited to the lateral sliding mode, the single electrode mode, and the contact-separation mode.

[0083] The same or similar reference numerals correspond to the same or similar components.

[0084] The terms used to describe the positional relationship in the drawings are only for illustrative purposes and should not be construed as a limitation of this patent.

[0085] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A triboelectric nanogenerator based on 4D printing technology, characterized in that, It includes a first triboelectric power generation component (1) and a second triboelectric power generation component (2) that can rotate relative to each other; the first triboelectric power generation component (1) includes a first base layer (11) and a friction unit (12) provided on the surface of the first base layer (11), and the plurality of friction units (12) are arranged at intervals with the geometric center of the first base layer as the center of the circle; the second triboelectric power generation component (2) includes a second base layer (21), a first electrode (22) and a second electrode (23) provided on the surface of the second base layer (21), and a plurality of first electrodes (22) and a plurality of second electrodes (23) are arranged at intervals with the geometric center of the second base layer (21) as the center of the circle, and there is a gap between the first electrode (22) and the second electrode (23); the first base layer (11) and the second base layer (21) are inserted together through the flanges (24) and grooves (13) provided on each other, so that the friction unit (12) can rotate and contact and rub with the first electrode (22) and the second electrode (23); Among them, the first triboelectric power generation component (1) and the second base layer (21) are prepared by 4D printing; the surface of the friction unit (12) has protrusions or grooves; the central angle corresponding to each friction unit (12) is a, and the same central angle b is separated between adjacent two friction units (12); the central angle corresponding to each first electrode (22) is c, and the central angle corresponding to each second electrode (23) is e, where a = c = d, b = c + 2 * e; Among them, the first electrode (22) and the second electrode (23) rotate relative to the friction unit (12) with the flange (24) and the groove (13) as the center; during the rotation process, a plurality of friction units (12) alternately overlap with the first electrode (22) and the second electrode (23), affecting the charge distribution on the surface of the electrode, thereby causing a potential difference to be generated between the first electrode (22) and the second electrode (23); when there is an electrical connection between the first electrode (22) and the second electrode (23), the triboelectric nanogenerator generates an alternating current signal in the external circuit, and when the first electrode (22) and the second electrode (23) are open, the triboelectric nanogenerator outputs an alternating voltage signal, specifically including: When friction occurs, the friction unit (12) has a negative electro-negativity, so the surface is charged negatively; when a plurality of friction units (12) completely overlap with a plurality of first electrodes (22), under the action of electrostatic induction, an equal amount of positive charges to the plurality of friction units (12) appear on the surface of the plurality of first electrodes (22), and there is no charge on the surface of the plurality of second electrodes (23) at this time, so there is a potential difference between the first electrode (22) and the second electrode (23); as the friction unit (12) continues to rotate until it completely covers the second electrode (23), at this time, an equal amount of positive charges to the friction unit (12) appear on the surface of the first electrode (22), and there is no charge on the surface of the first electrode (22), so there is a potential difference between the second electrode (23) and the first electrode (22); when the external force continues to act, the above power generation cycle will occur cyclically; The triboelectric nanogenerator based on 4D printing technology is assembled at the joint as a self-powered sensing system. The first triboelectric component (1) and the second triboelectric component (2) are installed on one side of the joint. When the joint moves, it drives relative rotation between one triboelectric component and the other triboelectric component to generate an alternating current signal, and the angle of joint movement can be inferred according to the characteristics of the alternating current signal. Among them, the method for detecting the joint rotation angle of the self-powered sensing system includes the following steps: S1. Measure the phases of the output electrical signals of the triboelectric nanogenerator at different rotation angles respectively, and establish a corresponding relationship table of "rotation angle - output electrical signal phase". S2. Obtain the output electrical signal of the self-powered sensing system installed at the joint in real time, and perform smoothing and noise reduction processing on the output electrical signal. S3. Detect the phase information corresponding to the output electrical signal after smoothing and noise reduction processing in step S2. In step S2, multiple self-powered sensing systems are installed at the joint. Correspondingly, in step S3, the average value of the phase information corresponding to multiple output electrical signals after smoothing and noise reduction processing is obtained as the final phase information. S4. According to the corresponding relationship table of "rotation angle - output signal phase" calibrated in step S1, match the phase information of the output electrical signal. S5. According to the matching result of the phase information of the output electrical signal and the rotation angle in S4, obtain the joint rotation angle.

2. The triboelectric nanogenerator based on 4D printing technology according to claim 1, characterized in that The 4D printing uses shape memory polymers or self-healing materials, and uses fused deposition modeling printing, inkjet direct writing printing or digital light processing printing.

3. The triboelectric nanogenerator based on 4D printing technology according to claim 1, characterized in that A solution with a conductive substance is sprayed on the surface of the second base layer (21), and after the solvent is volatilized, the first electrode (22) and the second electrode (23) are obtained. The conductive substance includes silver nanowires, carbon nanotubes or graphene.

4. The triboelectric nanogenerator based on 4D printing technology according to claim 1, characterized in that The longitudinal cross-sectional shapes of the first base layer (11) and the second base layer (21) are polygons or curved polygons.

5. A method for preparing a triboelectric nanogenerator of the 4D printing technology according to any one of claims 1-4, characterized in that It includes the following steps: Step1. Design an independent layer type triboelectric nanogenerator model. Step2. After modeling, perform a force analysis on the working process of the model and conduct a simulation test on the potential field distribution. Step3. Import the tested model into slicing software for slicing and layering, select the processing sequence according to the actual structure of the model and generate processing instructions. Step4. Import the processing instructions into a 3D printer to complete the printing and processing of the first triboelectric component (1) and the second base layer (21) respectively. If there are problems with the printed product that do not meet the usage requirements during the processing, return to Step1 to re-complete the design and simulation test of the model and generate new processing instructions. Step5. Spray a volatile solution doped with a conductive substance on the surface of the second base layer (21) that has been printed and processed, and after the solvent is volatilized, the first electrode (22) and the second electrode (23) can be obtained. Step6. Assemble the first base layer (11) and the second base layer (21) with the first electrode (22) and the second electrode (23) prepared into a triboelectric nanogenerator.

Images