Flexible thermoelectric generator based on Seebeck effect and preparation method

Abstract

The invention provides a Seebeck effect-based flexible thermoelectric generator and a preparation method and application system thereof, the flexible thermoelectric generator comprises a flexible substrate, a plurality of bismuth telluride thermoelectric materials, an electrode layer and a packaging layer, and the flexible substrate is an FPCB (flexible printed circuit board) which is a bendable circuit board and is of a snakelike line structure. Wherein the insulating material is PI (polyimide) and has good flexibility and mechanical strength. The bismuth telluride thermoelectric material is arranged on the flexible substrate in a cuboid form and is connected through the electrode layer to form a thermocouple array. According to the cold end, the flexible substrate on the side of the cold end is wrapped with hydrogel, and the heat dissipation performance of the device is improved under the condition that the flexibility of the flexible thermoelectric generator is not affected. The flexible thermoelectric generator in the embodiment of the invention can directly convert the temperature difference in the environment into electric energy, and is suitable for power supply of low-power-consumption electronic equipment such as wearable equipment and Internet of Things sensors.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermoelectric materials and thermoelectric applications, and particularly relates to a flexible thermoelectric generator and a preparation method thereof. Background Art

[0002] With the rapid development of electronic devices and sensing technologies, people's demand for portable power sources is increasing continuously. Against the background of the continuous improvement of environmental awareness, green energy has attracted much attention, so energy harvesting technologies are highly favored. On the one hand, a large amount of mechanical energy is generated in human daily activities, but it is challenging to effectively accumulate this energy. On the other hand, due to the temperature gradient between the human body and the environment and the relatively stable body temperature, heat energy can be used as another available energy source. By utilizing the temperature difference (thermoelectricity) between the human body and the surrounding environment, this energy can be continuously converted into electrical energy. Subsequently, through an energy harvesting system such as a supercapacitor and an amplification circuit, sufficient current and voltage are provided to drive various sensors, and finally, various functions of the capture device are realized. In some special applications, such as thermal sensing and personal health monitoring, the heat energy capture technology has shown great potential and provided a new solution for powering devices.

[0003] Flexible thermoelectric generators are gradually breaking through the efficiency limit of human heat energy collection through material innovation and structural design. Despite challenges such as small temperature difference and low power, their natural compatibility with wearable electronics makes them one of the core technologies in the "invisible power supply" era. Currently, rigid thermoelectric generators are difficult to be used for human wear due to their inflexibility. Therefore, a flexible thermoelectric generator based on the Seebeck effect and its preparation method are proposed to collect human heat energy and solve the existing technical problems. Summary of the Invention

[0004] Object of the present invention: In order to overcome the above problems, a flexible thermoelectric generator based on the Seebeck effect and a preparation method thereof are proposed.

[0005] In a first aspect, the present invention provides a flexible thermoelectric generator based on the Seebeck effect, comprising: a flexible substrate, a plurality of bismuth telluride thermoelectric materials, an electrode layer, and a packaging layer; A plurality of the hot - end electrodes (4) are arranged in a 6×14 array on the upper surface of the flexible substrate. One bismuth telluride particle is arranged on the upper surface of each hot - end electrode (4). Each bismuth telluride particle includes a P - type bismuth telluride particle (1) and an N - type bismuth telluride particle (2). Meanwhile, the lower surface of the cold - end electrode (3) also corresponds to the corresponding bismuth telluride particle. Each cold - end electrode (3) connects the bismuth telluride particles of one type with the bismuth telluride particles of the other type adjacent to the hot - end electrode end - to - end, forming a series - connected flexible thermoelectric generator. The hydrogel film wraps the flexible substrate on the side composed of the cold - end electrodes, without affecting the flexibility of the flexible thermoelectric generator.

[0006] Preferably, it further includes: a spring structure (8); The spring structure (8) is arranged on the lower surface of a plurality of cold - end electrodes and the upper surface of a plurality of hot - end electrodes (4); It is embodied by an FPCB folded - line circuit board. Each two adjacent electrodes are connected to each other through a serpentine line, making the whole device have better flexibility.

[0007] Preferably, the material of the flexible substrate is PI (polyimide). The material of each hot - end electrode (4) and each cold - end electrode (3) is a Cu / polyimide (PI) composite electrode made of FPCB; Each bismuth telluride material is a semiconductor material.

[0008] Preferably, it further includes: a heat - dissipation structure; The heat - dissipation structure is arranged on the surface of the flexible substrate composed of the cold - end electrodes (3); Specifically, it is realized by a hydrogel film (12). The cold - end electrodes (3) are wrapped by the hydrogel film (12), enhancing the heat - dissipation performance of the flexible thermoelectric generator.

[0009] In the second aspect, the embodiments of this article also provide a flexible thermoelectric generator set, including a plurality of the flexible thermoelectric generators described in the first aspect connected in series and parallel.

[0010] In the third aspect, this article provides a preparation method of the flexible thermoelectric generator described in the first aspect, including: Preparing a plurality of hot - end electrodes (4) on the upper surface of the flexible substrate. The plurality of hot - end electrodes (4) are arranged in a 6×14 array. Preparing a bismuth telluride with a corresponding polarity on the upper surface of each hot - end electrode (4); A cold - end electrode (3) is jointly prepared on the upper surface of each hot - end electrode (4) by connecting one bismuth telluride particle of one type with the bismuth telluride particle of the other type adjacent to the hot - end electrode (4).

[0011] Preferably, preparing a plurality of hot - end electrodes (4) and a plurality of cold - end electrodes (3) on the upper surface of the flexible substrate specifically includes: Deposit an electrode material layer on the upper surface of the flexible substrate, and etch the electrode material layer to form a plurality of the hot-end electrodes (4). The electrode material layer deposited on the flexible substrate is made of copper. When drawing the electrode material layer, a teardrop structure (9) is adopted to make the whole device more robust.

[0012] Among them, the preparation method of the cold-end electrode (3) is the same as that of the hot-end electrode (4).

[0013] Preferably, the thermoelectric material is bismuth telluride, and bismuth telluride is connected to the lower surface of the cold-end electrode (3) and the upper surface of the hot-end electrode (4) with tin, and the size of the bismuth telluride is 1mm×1mm×1.2mm.

[0014] Preferably, it further includes:[[]] Prepare a hydrogel film (12) with insulation function, and adhere the film sealing cavity to the upper surfaces of a plurality of the cold-end electrodes (3).

[0015] The present invention has the following advantages and beneficial effects: One of the advantages of the present invention is that a spring structure is adopted. The spring structure realized by the FPCB folded circuit board endows the device with excellent flexibility to adapt to human joint movement or curved heat sources (such as pipelines, wearable devices). Another advantage of the present invention is that a teardrop-shaped structure design is adopted during electrode etching, which reduces stress concentration points, increases the tensile strength of the electrodes by more than 30%, avoids electrode fracture during dynamic use, and the teardrop structure increases the contact area between the electrodes and the thermoelectric material, reduces the interface resistance, and ensures efficient charge transfer under a small temperature difference. The third advantage of the present invention is that a high-density array design is adopted. 84 pairs of P-N junctions are connected in series and integrated (6×14 array), which significantly increases the output voltage and meets the power supply requirements of micro-watt-level wearable devices. The fourth advantage of the present invention is that the device adopts a bismuth telluride semiconductor material. The ZT value of the bismuth telluride semiconductor material at room temperature reaches 1.0 to 1.2, which is much higher than that of organic thermoelectric materials, ensuring the practical output of the device under the human body temperature difference. When soldering and fixing the bismuth telluride particles to the electrodes, the interface thermal stability is excellent, avoiding performance degradation caused by the aging of traditional conductive adhesives.

[0016] The fifth advantage of the present invention is that a heat dissipation structure is adopted. A hydrogel film is used as a packaging layer and adhered to the surface of the cold-end electrode, which improves the thermoelectric power generation effect without affecting the flexibility of the device. Description of the Drawings

[0017] Figure 1 It is a three-dimensional structural schematic diagram of the flexible thermoelectric generator of the present invention; Figure 2Schematic three-dimensional structure diagram of the flexible thermoelectric generator without encapsulation layer of the present invention; Figure 3 Schematic diagram of the top electrode of the flexible thermoelectric generator of the present invention; Figure 4 Schematic diagram of the bottom electrode of the flexible thermoelectric generator of the present invention; Figure 5 Schematic flow diagram of the preparation method of the flexible thermoelectric generator of the present invention; Wherein: 1: P-type bismuth telluride particles, 2: N-type bismuth telluride particles, 3: cold-end electrode layer, 4: hot-end electrode layer, 5: flexible substrate 1, 6: flexible substrate 2, 7: wire, 8: spring structure, 9: teardrop structure, 10: power supply end, 11: grounding end, 12: hydrogel film Specific embodiments

[0018] The present invention provides a flexible thermoelectric generator including: a flexible substrate, a plurality of bismuth telluride thermoelectric materials, and an electrode layer; A plurality of the hot-end electrodes are arranged in a 6×14 array on the upper surface of the flexible substrate. One bismuth telluride particle is arranged on the upper surface of each hot-end electrode. Each of the bismuth telluride particles includes P-type bismuth telluride particles (1) and N-type bismuth telluride particles (2). At the same time, corresponding bismuth telluride particles also exist on the lower surface of the cold-end electrode; Each cold-end electrode (3) connects the bismuth telluride particles of one type end to end with the bismuth telluride particles of the other type adjacent to the hot-end electrode (4), forming a series-connected flexible thermoelectric power generation device; The hydrogel film (12) wraps the side of the flexible substrate composed of the cold-end electrodes, and does not affect the flexibility of the flexible thermoelectric generator at the same time.

[0019] Specifically, Figure 1 Schematic three-dimensional structure diagram of the flexible thermoelectric generator provided by the present invention, which shows the overall shape of the flexible thermoelectric generator. Figure 3 Schematic diagram of the top electrode of the flexible thermoelectric generator provided by the present invention, Figure 3 In which, the cold-end electrode layer (3) is arranged in a 6×14 array on the lower surface of the flexible substrate 1 (5), and the material used is copper. One bismuth telluride particle is arranged on the lower surface of each cold-end electrode (3). Each bismuth telluride particle is a semiconductor particle, and the types of bismuth telluride particles are P-type bismuth telluride particles (1) and N-type bismuth telluride particles (2), and the polarities of each adjacent bismuth telluride particle are opposite. Figure 4 Schematic diagram of the bottom electrode of the flexible thermoelectric generator of the present invention, Figure 4 In which, the hot-end electrode layer (4) is arranged in a 6×14 array on the upper surface of the flexible substrate 2 (6), and the material used is copper.

[0020] Each cold-end electrode (3) connects the bismuth telluride particles of one type end to end with the bismuth telluride particles of the other type adjacent to the hot-end electrode (4). That is, two adjacent cold-end electrodes are connected together by a wire (7). After leaving a wire width interval, two adjacent hot-end electrodes are connected together by a wire (7). At this time, the P-type bismuth telluride particles (1) and the N-type bismuth telluride particles (2) are connected together to form a flexible thermoelectric power generation device in series connection.

[0021] The spring structure (8) is arranged on the lower surfaces of a plurality of the cold-end electrodes and the upper surfaces of a plurality of the hot-end electrodes; it is embodied by an FPCB folded line circuit board. In this way, a complementary relationship can be formed with the wire, making the whole device more flexible. Among them, when the wire (7) is connected to the cold-end electrode (3), a teardrop structure (9) is added during the design process.

[0022] The heat dissipation structure is arranged on the surface of the flexible substrate composed of cold-end electrodes; specifically, it is realized by a hydrogel film (12). The cold-end electrode (3) is wrapped with the hydrogel film (12), enhancing the heat dissipation of the flexible thermoelectric generator.

[0023] Based on the above embodiments, an embodiment of the present invention provides a preparation method of a flexible thermoelectric generator based on the Seebeck effect, where Figure 5 is a schematic flow chart of the preparation method of the flexible thermoelectric generator of the present invention. Specifically, it includes: S1. Prepare a plurality of cold-end electrodes on the upper surface of the flexible substrate 1, and the plurality of electrodes are arranged in an array.

[0024] S2. Prepare a plurality of hot-end electrodes on the upper surface of the flexible substrate 2, and the plurality of electrodes are arranged in an array.

[0025] S3. Connect the two ends of the bismuth telluride particles to the corresponding hot-end electrodes and cold-end electrodes respectively.

[0026] S4. Prepare a hydrogel film and adhere the hydrogel film to the upper surface of the cold-end electrode.

[0027] Specifically, first execute S1. Prepare a plurality of cold-end electrodes (3) on the lower surface of the flexible substrate. The plurality of cold-end electrodes (3) are arranged in a 6×14 array; among them, the electrode material layer is specifically copper. Deposit an electrode material layer on the upper surface of the flexible substrate 1 (5), and etch the electrode material layer to form the cold-end electrode (3).

[0028] Among them, the preparation of the wire (7) includes: In the serpentine line part of the PCB board, when drawing, draw the wire (7) in a curved shape, as Figure 2As shown, a curvature is added between the wire (7) and the electrode to form a teardrop structure (9). The size of the teardrop can be adjusted by itself, and the material used for drawing is copper.

[0029] Then, step S2 is performed. Similar to step S1, a layer of electrode material layer is deposited on the upper surface of the flexible substrate 2 (6), and the electrode material layer is etched to form a hot-end electrode (4). The electrode material layer is copper. The wire preparation method is the same as that in S1, but the connection between the wire (7) and the hot-end electrode (4) just forms a gap with the connection between the wire (7) and the cold-end electrode (3). Then, step S3 is performed, that is, two different types of bismuth telluride particles and the cold-end electrode (3) are calibrated through a stencil mold, and then thermally cured and connected with tin, so that the P-type bismuth telluride particles (1) and the N-type bismuth telluride particles (2) are connected to the cold-end electrode (3). After the connection is completed, the other ends of the P-type bismuth telluride particles (1) and the N-type bismuth telluride particles (2) are calibrated with the hot-end electrode (5), and then thermally cured and connected with tin. Finally, step S4 is performed, that is, the prepared hydrogel solution is poured into a container mold. At this time, Figure 2 the side of the flexible substrate 1 (5) of the flexible thermoelectric generator without the encapsulation layer is placed horizontally in the container mold, that is, the cold-end electrode (3) is fully fused with the hydrogel solution, and then frozen in an environment of -20°C and then melted at room temperature. This cycle is repeated 3 times to form a hydrogel film (12).

[0030] The preparation process of the hydrogel solution includes: The hydrogel solution ratio is 10% (w / v) PVA, 5% (w / w to PVA) SiO2 nanoparticles, 3% glycerol, 81% deionized water, and 1% glutaraldehyde. First, the prepared PVA powder is added to deionized water at 85°C and stirred with a magnetic stirrer for 2 hours until completely dissolved; then SiO2 nanoparticles are added, and ultrasonic treatment is performed for 30 minutes under the conditions of a frequency of 40 kHz and a power of 300 W to prevent agglomeration; then glycerol is added, and stirring is continued for 30 minutes to make it solidify; the mixture is degassed in a vacuum drying oven at a gauge pressure of -0.1 MPa and a constant temperature of 25°C for 1 hour to remove bubbles; pre-cooled glutaraldehyde solution is added, and the pre-cooled glutaraldehyde solution is required to maintain the system temperature <10°C to delay the reaction. Finally, it is poured into a container mold and crosslinked in an oven at 50°C for 6 hours.

[0031] Working principle: The base 2 (6) serves as the hot end for attaching to the skin. The hot end is at the human body temperature, while the cold end is at the ambient temperature. Based on the Seebeck effect, there is a temperature difference between the human body temperature and the ambient temperature. The kinetic energy of the carriers (electrons or holes) at the high-temperature end increases and diffuses towards the low-temperature end. This diffusion causes the accumulation of charges at the cold end, forming an internal electric field. At this time, an electromotive force is generated, and then two wires can be led out through the power supply terminal (10) and the ground terminal (11) to supply power to the backend, achieving the effect of a flexible thermoelectric generator.

[0032] Preferably, to ensure the flexibility of the overall device, in addition to the wire (7) part adopting a serpentine structure, the spring structure (8) part also adopts a serpentine structure.

[0033] Preferably, the final internal resistance can be changed by changing the width of the wire (7) and the radian size of the teardrop structure (9).

[0034] It should be noted that the above technical features continue to be combined with each other to form various embodiments not listed above, which are all regarded as within the scope described in the specification of the present invention; and for those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A flexible thermoelectric generator based on the Seebeck effect, characterized in that Comprising: A flexible substrate, a plurality of bismuth telluride thermoelectric materials, an electrode layer, and a packaging layer. A plurality of the hot-end electrodes (4) are arranged in a 6×14 array on the upper surface of the flexible substrate. On the upper surface of each hot-end electrode (4), there is provided one bismuth telluride particle. Each of the bismuth telluride particles includes a P-type bismuth telluride particle (1) and an N-type bismuth telluride particle (2). At the same time, on the lower surface of the cold-end electrode (3), there are also corresponding bismuth telluride particles. Each cold-end electrode (3) connects the bismuth telluride particles of one type to the bismuth telluride particles of the other type adjacent to the hot-end electrode end to end, forming a series-connected flexible thermoelectric generator. The hydrogel film wraps the flexible substrate on the side composed of the cold-end electrodes, and at the same time does not affect the flexibility of the flexible thermoelectric generator.

2. The flexible thermoelectric generator according to claim 1, characterized in that, Further comprising: A spring structure (8). The spring structure (8) is arranged on the lower surface of a plurality of the cold-end electrodes and the upper surface of a plurality of the hot-end electrodes (4), and is embodied by an FPCB folded-line circuit board. Each two adjacent electrodes are connected to each other by a serpentine line, making the whole device have better flexibility.

3. The flexible thermoelectric generator according to claim 1, characterized in that, The material of the flexible substrate is PI (polyimide). The material of each hot-end electrode (4) and each cold-end electrode (3) is a Cu / polyimide (PI) composite electrode made of FPCB. Each bismuth telluride material is a semiconductor material.

4. The flexible thermoelectric generator according to claim 1, wherein Further comprising: A heat dissipation structure. The heat dissipation structure is arranged on the surface of the flexible substrate composed of the cold-end electrodes (3), and is specifically realized by a hydrogel film (12). The cold-end electrodes (3) are wrapped by the hydrogel film (12), enhancing the heat dissipation of the flexible thermoelectric generator.

5. According to the flexible thermoelectric generator described in claim 1, a plurality of the flexible thermoelectric generators can be connected in series or in parallel to form a flexible thermoelectric generator set, increasing the open-circuit voltage of the device.

6. The preparation method of the flexible thermoelectric generator according to claim 1, wherein Comprising: On the upper surface of the flexible substrate, a plurality of hot-end electrodes (4) are prepared. The plurality of hot-end electrodes (4) are arranged in a 6×14 array. On the upper surface of each hot-end electrode (4), a bismuth telluride with a corresponding polarity is prepared. On the upper surface of each hot-end electrode, a cold-end electrode (3) is jointly prepared with the bismuth telluride particles of the other type adjacent to the hot-end electrode (4).

7. The preparation method of the flexible thermoelectric generator according to claim 1, characterized in that, The preparation of a plurality of hot-end electrodes (4) and a plurality of cold-end electrodes (3) on the upper surface of the flexible substrate specifically includes: Depositing an electrode material layer on the upper surface of the flexible substrate and etching the electrode material layer to form a plurality of the hot-end electrodes (4). The deposited electrode material layer is realized by copper. When drawing the electrode material layer, a teardrop structure (9) is adopted to make the whole device more robust. At the same time, the preparation method of the cold-end electrode (3) is the same as that of the hot-end electrode (4).

8. The preparation method of the flexible thermoelectric generator according to claim 1, wherein The thermoelectric material is bismuth telluride. Bismuth telluride is connected to the lower surface of the cold-end electrode (3) and the upper surface of the hot-end electrode (4) with tin. The size of the bismuth telluride is 1mm×1mm×1.2mm.

9. The preparation method of the flexible thermoelectric generator according to claim 1, wherein Further comprising: Prepare a hydrogel film (12) with insulating function, and adhere the film-sealed cavity to the upper surfaces of a plurality of the cold-end electrodes (3).

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