A lattice-type flexible thermoelectric energy harvesting structure and its preparation method

Abstract

This invention discloses a lattice-type flexible thermoelectric energy harvesting structure and its preparation method. The harvesting structure includes a flexible glass fiber substrate with two layers; multiple thermoelectric units are disposed between the two layers of flexible glass fiber substrate and arranged along the entire length of the flexible glass fiber substrate, forming a zigzag thermoelectric stack; silver electrode films are provided at the top and bottom of each thermoelectric unit for electrical connection; the bottom layer of flexible glass fiber substrate is used to adhere to the surface of the heat source, and the top layer of flexible glass fiber substrate is in contact with the cold end region of the heat source. This invention is based on high-performance thermoelectric materials and is prepared using screen printing technology to ultimately form a flexible thermoelectric thick film structure with high output power density, strong mechanical properties, adaptability to thermal energy harvesting on complex curved surfaces, and ease of installation, showing broad application prospects.

Description

Technical Field

[0001] This invention belongs to the technical field of flexible thermoelectric energy harvesting devices, specifically relating to a lattice-type flexible thermoelectric energy harvesting structure and its preparation method. Background Technology

[0002] With the rapid development of science and technology, the amount of energy required for scientific research and social development is becoming increasingly enormous. Traditional energy sources, such as coal, oil, and natural gas, are being used extensively, and the rapid depletion of these non-renewable resources has led to many worrying problems. Therefore, finding practical solutions to the energy shortage problem is extremely important. Energy harvesting technology is a solution that collects widely available energy from the environment for storage and power supply to devices, primarily relying on the harvesting of usable energy sources such as solar, thermal, and mechanical energy. Thermal energy is widely present in buildings, machinery, and even the human body, therefore thermoelectric energy harvesting has high application value in industry, manufacturing, and medical electronics.

[0003] Currently, widely used traditional rigid thermoelectric devices are large and heavy, making them unsuitable for energy harvesting from irregular surfaces. While flexible thermoelectric devices are lightweight, they suffer from high cost, weak output capacity, and poor mechanical reliability. Therefore, this paper aims to develop a high-power-density, highly reliable flexible thermoelectric energy harvester based on high-performance thermoelectric materials and through thin-film fabrication processes. This will overcome the shortcomings of existing flexible thermoelectric energy devices and provide a solution for waste heat recovery from irregular surfaces such as medical devices and human bodies, thereby improving environmental energy utilization efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide a lattice-type flexible thermoelectric energy harvesting structure and its preparation method, so as to solve the technical defects of existing flexible thermoelectric devices, which, although lightweight, suffer from high cost, weak output capability, and poor mechanical reliability.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] Firstly, a lattice-type flexible thermoelectric energy harvesting structure is provided, comprising:

[0007] The flexible glass fiber substrate has two layers.

[0008] Thermoelectric units are disposed between the two layers of the flexible glass fiber substrate, and multiple units are arranged along the entire length of the flexible glass fiber substrate, forming a zigzag thermoelectric stack.

[0009] The thermoelectric unit is provided with silver electrode films at both the top and bottom, and the silver electrode films are used for the electrical connection of the thermoelectric unit.

[0010] The bottom layer of flexible glass fiber substrate is used to adhere to the surface of the heat source, while the top layer of flexible glass fiber substrate is in contact with the cold end region of the heat source.

[0011] Furthermore, the plurality of thermoelectric units are connected in series;

[0012] Each thermoelectric unit includes an N-type thermoelectric arm and a P-type thermoelectric arm, and the tops of the N-type thermoelectric arm and the P-type thermoelectric arm are connected by a silver electrode film.

[0013] The bottoms of the N-type thermoelectric arm and the P-type thermoelectric arm are connected to the N-type thermoelectric arm and the P-type thermoelectric arm in another adjacent thermoelectric unit through a silver electrode film.

[0014] Furthermore, both the N-type thermoelectric arm and the P-type thermoelectric arm are circular thick films, and are electrically connected to the silver electrode film through high-temperature conductive silver paste.

[0015] Furthermore, the angle between the silver electrode film at the top of the N-type thermoelectric arm and the silver electrode film at the bottom of the N-type thermoelectric arm is an acute angle.

[0016] Furthermore, conductive silver paste is used to bond metal leads at both ends of the thermopile to enable the thermopile to collect thermoelectric output.

[0017] Secondly, a method for preparing a lattice-type flexible thermoelectric energy harvesting structure is provided, wherein the structure is prepared using this method, including:

[0018] The flexible glass fiber substrate is cleaned, dried, and cut.

[0019] Two types of patterned silver electrode films are prepared on the cut flexible glass fiber substrate, and the two types of patterned silver electrode films are dried and annealed at high temperature.

[0020] The flexible glass fiber substrate is cut along the silver electrode film after high-temperature annealing to obtain two patterns of flexible glass fiber substrates.

[0021] Clean and dry the rigid alumina substrate;

[0022] Two thermoelectric material pastes were prepared, and bismuth telluride thick films and antimony telluride thick films were printed on the dried rigid alumina substrate, respectively. The bismuth telluride thick films and antimony telluride thick films were then dried and annealed.

[0023] The annealed bismuth telluride thick film and antimony telluride thick film were polished on both sides and then bonded to flexible glass fiber substrates with two different patterns using high-temperature conductive silver paste.

[0024] Furthermore, two types of patterned silver electrode films are prepared, specifically including:

[0025] The screen printing method is used, with 3-5g of 2-3μm silver powder, 0.6-1g of epoxy resin, 0.2-0.5g of polyetheramine and 0.4-0.6g of terpineol.

[0026] In this process, epoxy resin is used as a binder, and terpineol is used as a solvent to adjust the viscosity of the slurry. After the slurry is stirred evenly, a silver electrode film array with two patterns is printed using a 200 mesh screen printing process.

[0027] Furthermore, the thickness of the silver electrode thin film arrays with both upper and lower patterns is 20~40μm.

[0028] Furthermore, the preparation of the two thermoelectric material slurries specifically includes:

[0029] When preparing screen printing paste with bismuth telluride powder, use 3-5g of 500-mesh tellurium powder, 2.2-4g of 500-mesh bismuth powder, 0.1-0.3g of ethyl cellulose, and 0.55-0.8g of diethylene glycol butyl ether acetate.

[0030] When preparing screen printing paste with antimony telluride powder, use 3-5g of 500-mesh tellurium powder, 0.8-1.5g of 500-mesh bismuth powder, 1.5-2g of 500-mesh antimony powder, 0.1-0.2g of ethyl cellulose, and 0.5-1.1g of diethylene glycol butyl ether acetate.

[0031] In this process, the ethyl cellulose acts as a binder, and the diethylene glycol butyl ether acetate acts as a solvent, which is used to adjust the viscosity of the slurry.

[0032] After the slurry is thoroughly mixed, a circular thick film array of thermoelectric units is printed on a stainless steel plate with a custom pattern.

[0033] Furthermore, the thickness of the circular thick film array is 350~400μm.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 3. High-temperature conductive silver paste has excellent conductivity, which can ensure efficient and stable electrical connection between N-type and P-type thermoelectric arms and silver electrode film, helping to reduce resistance loss and improve energy harvesting efficiency.

[0036] 4. The sharp angle design helps to make the heat transfer path inside the thermoelectric arm smoother, reducing heat loss and accumulation. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is an overall structural diagram of the lattice-type flexible thermoelectric energy harvesting structure provided by the present invention;

[0039] Figure 2 This is a schematic diagram of a single pair of thermoelectric arms in the lattice-type flexible thermoelectric energy harvesting structure provided by the present invention;

[0040] Figure 3 Figure 4 These are schematic diagrams of two silver electrode patterns in the lattice-type flexible thermoelectric energy harvesting structure provided by the present invention.

[0041] Figure 5 This is a schematic diagram of the thermopile in the lattice-type flexible thermoelectric energy harvesting structure provided by the present invention;

[0042] Figure 6 This is a schematic diagram illustrating the application of the lattice-type flexible thermoelectric energy harvesting structure provided by the present invention;

[0043] Figure 7 This is a test diagram of the output performance of the lattice-type flexible thermoelectric energy harvesting structure provided by the present invention;

[0044] Figure 8 This is a flowchart of the fabrication method of the lattice-type flexible thermoelectric energy harvesting structure provided by the present invention;

[0045] Among them: 1. N-type thermoelectric arm; 2. P-type thermoelectric arm; 3. Silver electrode film; 4. Flexible glass fiber substrate; 5. Heat source. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0047] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0048] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0049] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0050] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0051] With the rapid development of science and technology, the amount of energy required for scientific research and social development is becoming increasingly enormous. Traditional energy sources, such as coal, oil, and natural gas, are being used extensively, and the rapid depletion of these non-renewable resources has led to many worrying problems. Therefore, finding practical solutions to the energy shortage problem is extremely important. Energy harvesting technology is a solution that collects widely available energy from the environment for storage and power supply to devices, primarily relying on the harvesting of usable energy sources such as solar, thermal, and mechanical energy. Thermal energy is widely present in buildings, machinery, and even the human body, therefore thermoelectric energy harvesting has high application value in industry, manufacturing, and medical electronics.

[0052] Currently, widely used traditional rigid thermoelectric devices are large and heavy, making them unsuitable for energy harvesting from irregular surfaces. While flexible thermoelectric devices are lightweight, they suffer from high cost, weak output capacity, and poor mechanical reliability. Therefore, this paper aims to develop a high-power-density, highly reliable flexible thermoelectric energy harvester based on high-performance thermoelectric materials and through thin-film fabrication processes. This will overcome the shortcomings of existing flexible thermoelectric energy devices and provide a solution for waste heat recovery from irregular surfaces such as medical devices and human bodies, thereby improving environmental energy utilization efficiency.

[0053] To address the aforementioned technical deficiencies, the inventors have provided a lattice-type flexible thermoelectric energy harvesting structure and its preparation method.

[0054] The present invention will now be described in further detail with reference to the accompanying drawings:

[0055] like Figures 1-7As shown, in an embodiment of the present invention, a first aspect provides a lattice-type flexible thermoelectric energy harvesting structure, including a flexible glass fiber substrate 4 with two layers; thermoelectric units disposed between the two layers of flexible glass fiber substrate 4, and multiple units arranged along the length of the flexible glass fiber substrate 4, forming a zigzag thermoelectric pile. According to the thermoelectric effect, when there is a temperature difference between the top and bottom of each pair of thermoelectric arms, a thermoelectric potential is generated at both ends of the thermoelectric arms; when there is the same temperature difference in each pair of thermoelectric arms in the thermoelectric pile, the thermoelectric potential generated by each pair is the same, and the total output of the thermoelectric pile is equal to the output of a single pair of thermoelectric arms multiplied by the total number of thermoelectric arms; silver electrode films 3 are provided at the top and bottom of the thermoelectric units, and the silver electrode films 3 are used for electrical connection of the thermoelectric units; wherein, the flexible glass fiber substrate 4 located at the bottom layer is used to adhere to the surface of the heat source 5, and the flexible glass fiber substrate 4 located at the top layer is in contact with the cold end region of the heat source 5. By employing a zigzag thermopile design, the temperature gradient on the surface of the heat source 5 can be utilized more effectively. The zigzag layout not only increases the contact area between the thermoelectric unit and the heat source 5 but also optimizes the heat transfer path in the thermoelectric material, thereby improving the thermoelectric conversion efficiency. This allows the structure to collect and convert the heat energy generated by the heat source 5 more efficiently, providing continuous power support for the device. Using a flexible glass fiber substrate 4 as the support structure for the thermoelectric unit gives the entire energy harvesting structure excellent flexibility and bendability, enabling it to adapt to various complex shapes of the heat source 5 surface, such as human skin and irregular surfaces of machinery, thus broadening its application range. Furthermore, the flexible glass fiber substrate 4 has good high-temperature resistance, wear resistance, and corrosion resistance, protecting the thermoelectric unit from damage caused by the external environment. At the same time, the use of the silver electrode film 3 not only ensures the stability and reliability of the electrical connection but also improves the conductivity of the entire structure, further enhancing its durability. In summary, due to its lightweight and flexible structure, this lattice-type flexible thermoelectric energy harvesting structure is easier and quicker to install, requiring no complex fixing devices or tools. Maintenance or replacement of some thermoelectric units can be performed more easily, reducing maintenance costs and time. Furthermore, the series connection between multiple thermoelectric units achieves the technical effect of electrical series connection and thermal parallel connection, significantly improving the overall voltage output of the entire energy harvesting structure. Each thermoelectric unit includes an N-type thermoelectric arm 1 and a P-type thermoelectric arm 2. The tops of the N-type thermoelectric arm 1 and the P-type thermoelectric arm 2 are connected by a silver electrode film 3. The bottoms of the N-type thermoelectric arm 1 and the P-type thermoelectric arm 2 are connected to the N-type thermoelectric arm 1 and the P-type thermoelectric arm 2 in an adjacent thermoelectric unit via the silver electrode film 3.The combination of N-type thermoelectric arm 1 and P-type thermoelectric arm 2 constitutes the basic unit of a thermocouple. Sensitive to temperature gradients, it converts thermal energy into electrical energy. By precisely connecting these thermoelectric arms in series, the temperature difference generated by the heat source 5 can be utilized more effectively, optimizing the thermoelectric conversion process and improving energy conversion efficiency. Simultaneously, the series-connected thermoelectric units are tightly linked by a silver electrode film 3, ensuring not only the stability and reliability of the electrical connection but also enhancing the mechanical strength of the entire structure. The silver electrode film 3, acting as a good conductor and adhesive, effectively fixes the thermoelectric arms together, preventing structural loosening or damage due to vibration or external forces. Notably, the flexible glass fiber substrate 4 is primarily composed of silicon dioxide, possessing excellent high-temperature resistance and flexibility. The flexible glass fiber substrate 4 is bonded to the heat source 5 and the cold end surface, forming a certain temperature gradient, enabling energy harvesting through thermoelectric conversion. The electrical connection unit, primarily composed of silver, exhibits good stability and conductivity. Attached to the flexible glass fiber substrate 4 and bonded to both ends of the thermocouple, it achieves electrical connection while reducing contact resistance.

[0056] like Figure 2As shown, both the N-type thermoelectric arm 1 and the P-type thermoelectric arm 2 are circular thick films, electrically connected to the silver electrode film 3 via high-temperature conductive silver paste. The silver electrode film 3 at the top of the N-type thermoelectric arm 1, along with the high-temperature conductive silver paste, exhibits excellent conductivity, ensuring efficient and stable electrical connections between the N-type thermoelectric arm 1 and the P-type thermoelectric arm 2 and the silver electrode film 3. This helps reduce resistance loss and improve energy harvesting efficiency. Furthermore, the high-temperature conductive silver paste maintains stable conductivity even at high temperatures and has good adhesion, ensuring reliable connections between the thermoelectric arm and the silver electrode film 3, thus extending the lifespan of the entire energy harvesting structure. The circular thick film design of the N-type thermoelectric arm 1 and the P-type thermoelectric arm 2 increases the contact area between the thermoelectric arm and the heat source 5, improving heat absorption efficiency. Simultaneously, the combination of the circular thick film thermoelectric arm and the flexible glass fiber substrate 4 gives the entire energy harvesting structure good flexibility and adaptability, helping to adapt to various complex shapes of heat source 5 surfaces, improving the flexibility and efficiency of energy harvesting. The silver electrode film 3 at the top of the N-type thermoelectric arm 1 forms an acute angle with the silver electrode film 3 at the bottom of the N-type thermoelectric arm 1. Both ends of the thermopile are bonded with conductive silver paste to metal leads to enable the thermoelectric pile to collect thermoelectric output. In this process, the acute angle between the silver electrode film 3 and the N-type thermoelectric arm 1 helps optimize the current flow path within the thermoelectric arm, reducing current transmission losses and thus improving thermoelectric conversion efficiency. Heat loss is a crucial factor in thermoelectric conversion, and reducing heat loss contributes to improving the overall performance of the thermoelectric pile. Using conductive silver paste to bond the metal leads enhances the connection strength between the thermoelectric arm and the metal leads, providing not only good conductivity but also the ability to withstand significant mechanical stress, ensuring the stability of the thermoelectric pile during long-term use.

[0057] In this embodiment, the thick film of the N-type thermoelectric arm is composed of bismuth telluride, which has a high negative Seebeck coefficient and good conductivity. The thick film of the N-type thermoelectric arm is a circle with a size of 3mm×3mm and a thickness of about 400μm.

[0058] In this embodiment, the P-type thermoelectric arm thick film is composed of antimony telluride, which has a high positive Seebeck coefficient and good conductivity. The P-type thermoelectric arm thick film is also a circle with a size of 3mm×3mm and a thickness of about 400μm.

[0059] In this embodiment, the main component of the silver electrode film 3 is silver, which has good conductivity and oxidation resistance. The size of the silver electrode film 3 is 3mm × 9mm.

[0060] like Figure 6As shown, one side of the lattice-type flexible thermoelectric energy harvesting structure is closely fitted with the curved surface of the heat source 5, while the other side is in contact with the cold end shell of the heat source 5 or exposed to the air atmosphere to form a temperature difference. The entire lattice-type flexible thermoelectric energy harvesting structure has the characteristics of being lightweight and highly flexible, which allows it to adapt to various complex surfaces, including constantly changing surfaces. It can effectively collect the surface waste heat of the instrument during movement and realize the recovery and utilization of energy.

[0061] When the above structure is applied, PDMS can be used for flexible packaging. The purpose of flexible packaging is to ensure the overall mechanical strength of the structure and avoid performance degradation due to structural damage.

[0062] Secondly, a method for fabricating a lattice-type flexible thermoelectric energy harvesting structure is provided, wherein the structure is fabricated using this method, such as... Figure 8 As shown, it includes:

[0063] Example 1:

[0064] S101. The flexible glass fiber substrate is cleaned, dried and cut. For example, the flexible glass fiber substrate 4 is a thin glass fiber cloth with a relatively flat surface. Then, acetone and ethanol are used to ultrasonically clean the flexible glass fiber substrate 4 in sequence, and each cleaning time is not less than 20 minutes. Then, deionized water is used to rinse away the residual organic matter on the surface of the flexible glass fiber substrate 4. After being placed on a heating table for rapid drying, it is cut into appropriate sizes.

[0065] S102. Two patterned silver electrode films are prepared on the cut flexible glass fiber substrate, and the two patterned silver electrode films are dried and annealed at high temperature; for example, they are prepared on the cut flexible glass fiber substrate 4 by screen printing, such as... Figure 3 and Figure 4 The two patterns of silver electrode films 3 shown are then dried, and the thickness of the dried silver electrode films 3 is approximately 30 μm. The dried silver electrode films 3 are then subjected to high-temperature annealing. The annealed silver electrode films 3 exhibit good conductivity, oxidation resistance, and flexibility, making them highly suitable for connecting two high-performance thermoelectric materials, thereby improving the overall thermoelectric performance and mechanical strength of the device. In preparing the two patterns of silver electrode films 3, a screen printing method is used, employing 3-5 g of 2-3 μm silver powder, 0.6-1 g of epoxy resin, 0.2-0.5 g of polyetheramine, and 0.4-0.6 g of terpineol. The epoxy resin is used as a binder, and the viscosity of the slurry is adjusted using terpineol as a solvent. After the slurry is stirred evenly, a 200-mesh screen is used to screen print the upper and lower patterned silver electrode film arrays, as shown. Figure 3 and Figure 4As shown, the thickness of the silver electrode film 3 array with the two patterns is 20~40μm. Next, the printed silver electrode film 3 array is left to stand for 20 minutes to reduce surface streaks, and then placed on a heating stage and slowly heated to 150℃ for 20 minutes to dry. Finally, the dried silver electrode film 3 array is placed on a heating stage for annealing. The heating stage is slowly heated to 350℃ and annealed for 60 minutes. The color of the silver film changes from light yellow to white, and the silver electrode film 3 is finally obtained.

[0066] S103. The flexible glass fiber substrate is cut along the silver electrode film after high-temperature annealing to obtain flexible glass fiber substrates with two patterns. For example, each silver electrode film 3 has a size of 3mm × 9mm. The number of silver electrode film 3 arrays varies depending on the number of thermocouple arms. In Embodiment 1, the number of electrode units in the silver electrode film 3 array is 20, and the overall pattern size is 18mm × 55mm. Therefore, the glass fiber substrate 4 is cut to 20mm × 60mm along the edge of the silver electrode film 3 pattern. The specific size can be adjusted according to the printed silver electrode pattern and the number of thermocouple pairs.

[0067] S104. Clean and dry the rigid alumina substrate; for example, select a rigid alumina substrate with a smooth and rough surface, ultrasonically clean it in acetone for 30 minutes, rinse it in ethanol, and dry it with a high-pressure air gun to prepare bismuth telluride thick film and antimony telluride circular thick film.

[0068] S105. Prepare two thermoelectric material pastes, and print bismuth telluride thick films and antimony telluride thick films respectively on the dried rigid alumina substrate. Then, dry and anneal the bismuth telluride thick films and antimony telluride thick films. For example, prepare two thermoelectric material pastes respectively, and print bismuth telluride thick films and antimony telluride thick films respectively on the cleaned alumina substrate using a customized stainless steel plate. Slowly dry the printed thermoelectric material thick films. The thickness of the dried thermoelectric thick films is about 400 μm. Place the two dried thermoelectric thick films into a tube furnace under nitrogen protection for annealing treatment to improve thermoelectric performance. When preparing the screen printing paste using bismuth telluride powder, 3-5g of 500-mesh tellurium powder, 2.2-4g of 500-mesh bismuth powder, 0.1-0.3g of ethyl cellulose, and 0.55-0.8g of diethylene glycol butyl ether acetate are selected. When preparing the screen printing paste using antimony telluride powder, 3-5g of 500-mesh tellurium powder, 0.8-1.5g of 500-mesh bismuth powder, 1.5-2g of 500-mesh antimony powder, 0.1-0.2g of ethyl cellulose, and 0.5-1.1g of diethylene glycol butyl ether acetate, together with the diethylene glycol butyl ether acetate as a solvent, determine the viscosity of the paste. After the paste is stirred evenly, a circular thick-film array of thermoelectric units is printed using a stainless steel plate with a customized pattern. The thickness of the circular thick-film array is 350-400μm.

[0069] Subsequently, the printed thermoelectric thick film arrays were placed in a vacuum drying oven, a vacuum environment was set, and the temperature was slowly increased from room temperature to 130°C for 90 minutes. After cooling to room temperature, the arrays were removed. The dried thermoelectric thick film arrays were then placed in an alumina crucible and annealed in a tube furnace. The annealing process included sample placement, furnace tube sealing, vacuuming, nitrogen atmosphere introduction, heating, holding, and cooling. Nitrogen was used as a protective gas to prevent oxidation of the thermoelectric materials at high temperatures. During high-temperature annealing of bismuth telluride and antimony telluride in the furnace tube, tellurium is prone to volatilization, affecting sintering quality. Placing tellurium powder (0.2g) in the crucible provided a tellurium-rich annealing environment, which helped suppress tellurium volatilization in the thermoelectric thick film. Different annealing temperatures and times were used for the two thermoelectric thick films to ensure optimal thermoelectric performance. The annealing time for bismuth telluride thick film was 60 minutes, the holding time was 30 minutes, and the holding temperature was 450℃. The annealing time for antimony telluride thick film was 50 minutes, the holding time was 20 minutes, and the holding temperature was 400℃. Both thermoelectric thick films were allowed to cool naturally after annealing and then removed from the tube furnace.

[0070] S106. The sides of the annealed bismuth telluride thick film and antimony telluride thick film are polished, and then bonded to flexible glass fiber substrates with two different patterns using high-temperature conductive silver paste. For example, the annealed bismuth telluride thick film and antimony telluride circular thick film are removed from the alumina substrate to obtain an N-type thermoelectric circular thick film and a P-type thermoelectric circular thick film. The sides of the thermoelectric thick films are polished to make their surfaces smoother. The obtained N-type thermoelectric circular thick film and P-type thermoelectric circular thick film are then bonded to flexible glass fiber substrates with two different patterns using high-temperature conductive silver paste to obtain the final product.

[0071] This invention employs a dense lattice thermoelectric thick-film structure with high output power density, lightweight and compact design, and excellent mechanical strength. It can deform in multiple directions and maintain good stability under repeated deformation actions such as bending, twisting, and stretching, exhibiting low thermoelectric output and internal resistance change rates. The entire structure is fabricated on a flexible substrate using a screen printing process, offering advantages such as simplicity, efficiency, and low cost. The fabrication process improves the quality and thermoelectric performance of the thick film by controlling the paste ratio, printing thickness, and drying time. Furthermore, a suitable nitrogen annealing process further enhances the final performance of the thermoelectric thick film. The flexible thermoelectric energy harvester designed in this invention has a high space utilization rate, can be tightly attached to complex curved surfaces within a certain curvature, and is easy to disassemble and can be applied non-destructively. The substrate is made of high-temperature resistant glass fiber, bonded with high-temperature conductive silver paste, and can be used for thermoelectric energy harvesting over a wide temperature range.

[0072] Example 2:

[0073] The difference from Example 1 is that this example uses a separate N / P type thermoelectric material, Bi2Te. 2.7 Se 0.3 and Bi 0.5 Sb 1.5 Te3, used as a thermoelectric powder raw material in screen printing paste, is added in excess tellurium powder to optimize the sintering quality during annealing, resulting in a higher Seebeck coefficient overall. During the printing process, two thermoelectric thin films are obtained through screen printing, and the printing and drying cycles are repeated to achieve the target thickness. The thermoelectric circular thick film and silver electrode are connected using high-temperature conductive silver paste to ultimately form a flexible thermoelectric device. The flexible thermoelectric energy harvesting structure ultimately formed in Example 2 is structurally and functionally identical to that in Example 1.

[0074] S101. The flexible glass fiber substrate is cleaned, dried and cut. For example, the flexible glass fiber substrate 4 is a thin glass fiber cloth with a relatively flat surface. Then, acetone and ethanol are used to ultrasonically clean the flexible glass fiber substrate 4 in sequence, and each cleaning time is not less than 20 minutes. Then, deionized water is used to rinse away the residual organic matter on the surface of the flexible glass fiber substrate 4. After being placed on a heating table for rapid drying, it is cut into appropriate sizes.

[0075] S102. Two patterned silver electrode films are prepared on the cut flexible glass fiber substrate, and the two patterned silver electrode films are dried and annealed at high temperature; for example, they are prepared on the cut flexible glass fiber substrate 4 by screen printing, such as... Figure 3 and Figure 4 The two patterns of silver electrode films 3 shown are then dried, and the thickness of the dried silver electrode films 3 is approximately 30 μm. The dried silver electrode films 3 are then subjected to high-temperature annealing. The annealed silver electrode films 3 exhibit good conductivity, oxidation resistance, and flexibility, making them highly suitable for connecting two high-performance thermoelectric materials, thereby improving the overall thermoelectric performance and mechanical strength of the device. In preparing the two patterns of silver electrode films 3, a screen printing method is used, employing 3-5 g of 2-3 μm silver powder, 0.6-1 g of epoxy resin, 0.2-0.5 g of polyetheramine, and 0.4-0.6 g of terpineol. The epoxy resin is used as a binder, and the viscosity of the slurry is adjusted using terpineol as a solvent. After the slurry is stirred evenly, a 200-mesh screen is used to screen print the upper and lower patterned silver electrode film arrays, as shown. Figure 3 and Figure 4 As shown, the thickness of the silver electrode film 3 array with the two patterns is 20~40μm. Next, the printed silver electrode film 3 array is left to stand for 20 minutes to reduce surface streaks, and then placed on a heating stage and slowly heated to 150℃ for 20 minutes to dry. Finally, the dried silver electrode film 3 array is placed on a heating stage for annealing. The heating stage is slowly heated to 350℃ and annealed for 60 minutes. The color of the silver film changes from light yellow to white, and the silver electrode film 3 is finally obtained.

[0076] S103. The flexible glass fiber substrate is cut along the silver electrode film after high-temperature annealing to obtain flexible glass fiber substrates with two patterns. For example, each silver electrode film 3 has a size of 3mm × 9mm. The number of silver electrode film 3 arrays varies depending on the number of thermocouple arms. In Embodiment 1, the number of electrode units in the silver electrode film 3 array is 20, and the overall pattern size is 18mm × 55mm. Therefore, the glass fiber substrate 4 is cut to 20mm × 60mm along the edge of the silver electrode film 3 pattern. The specific size can be adjusted according to the printed silver electrode pattern and the number of thermocouple pairs.

[0077] S104. Ball milling of N-type / P-type thermoelectric powders aims to reduce the particle size of both powders, resulting in a thermoelectric film with lower porosity after printing, and more complete sintering during annealing; N-type thermoelectric powder (Bi2Te) is selected. 2.7 Se 0.3 ) and P-type thermoelectric powder (Bi 0.5 Sb1.5 20g of each of Te3 and 5g of alcohol were used for ball milling. Zirconia grinding balls with diameters of 8mm, 5mm, and 3mm were used with a grinding jar of the same material. The ratio of the three sizes of grinding balls was 1:1:2, and the total volume ratio of grinding balls to powder was 5:1. Grinding was carried out at 350 rpm for more than 12 hours. After ball milling, the powder and grinding balls in the grinding jar were removed, cleaned with alcohol, and collected in a container. The container containing the thermoelectric powder and alcohol was placed in a vacuum drying oven and dried at 60 degrees Celsius for 120 minutes. Finally, two types of refined thermoelectric powders that can be used were obtained. The particle size of the ball-milled thermoelectric powder was less than 2μm.

[0078] S105. Two thermoelectric printing pastes were prepared separately. Using a customized screen printing stencil, bismuth telluride and antimony telluride films were printed on a flexible glass fiber substrate with silver electrodes. The printed thermoelectric material films were slowly dried, and the printing and drying steps were repeated multiple times to increase the thickness of the thermoelectric films, ultimately forming a thermoelectric thick film of approximately 200 μm. The two dried thermoelectric thick films were then annealed in a nitrogen-protected tube furnace to improve their thermoelectric performance. The mixed solution used to prepare the screen printing paste consisted of: 7-10 g of diethylene glycol butyl ether acetate, 1-2 g of ethyl cellulose, 1-2 g of dibutyl phthalate, and 0.1 g of Tween 80. Diethylene glycol butyl ether acetate was used as a solvent, ethyl cellulose as a binder, dibutyl phthalate as a plasticizer, and Tween 80 as a dispersant. The prepared solution was stirred at 80°C for 4 hours at 300 rpm on a magnetic stirrer until completely dissolved. The N-type screen printing paste consisted of 3.5-5 g of Bi₂Te₂.₇Se₀.₃ powder and 0.3-0.8 g of diethylene glycol butyl ether acetate solution. The P-type screen printing paste consisted of 3.5-5 g of Bi₀.₅Sb₁.₅Te₃ powder and 0.3-0.8 g of diethylene glycol butyl ether acetate solution. After the pastes were stirred evenly, a custom-patterned screen printing plate was used to repeatedly print a thermoelectric circular thick film array on the obtained silver electrode, with a thickness of approximately 200 μm-250 μm. The printed thermoelectric thick film arrays were placed in a vacuum drying oven, a vacuum environment was set, and the temperature was slowly increased from room temperature to 130°C for 90 minutes. After cooling to room temperature, the arrays were removed. The dried thermoelectric thick film arrays were placed in an alumina crucible and annealed in a tube furnace. The annealing process includes placing the sample, sealing the furnace tube, vacuuming, introducing a nitrogen atmosphere, heating, holding, and cooling. Nitrogen is used as a protective gas to prevent oxidation of the thermoelectric material at high temperatures. During high-temperature annealing of bismuth telluride and antimony telluride in the furnace tube, tellurium is prone to volatilization, affecting sintering quality. Placing 0.2g of tellurium powder in the crucible provides a tellurium-rich annealing environment, helping to suppress tellurium volatilization in the thermoelectric thick film. Different annealing temperatures and times are used for the two thermoelectric thick films to ensure optimal thermoelectric performance. Specifically, the bismuth telluride thick film is annealed with a heating time of 60 minutes, a holding time of 30 minutes, and a holding temperature of 450℃; the antimony telluride thick film is annealed with a heating time of 50 minutes, a holding time of 20 minutes, and a holding temperature of 400℃. Both thermoelectric thick films are allowed to cool naturally after annealing and then removed from the tube furnace. Finally, the obtained product was bonded to a silver electrode pattern using high-temperature resistant conductive silver paste to obtain the final product. The performance of the resulting lattice-type flexible thermoelectric energy harvesting structure was then tested. Figure 7 As shown, the output performance of the prepared lattice-type flexible thermoelectric energy harvesting structure was tested. Figure 7The output voltage curve of the lattice flexible thermoelectric energy harvesting structure under continuous heating and heat preservation, as well as the internal resistance change curve after 0-800 bending in different directions, are shown. The results show that the prepared lattice flexible thermoelectric energy harvesting structure has stable thermoelectric output and mechanical properties, and can efficiently and continuously harvest thermoelectric energy from complex curved surfaces and the residual heat of moving parts.

[0079] In summary, the lattice-type flexible thermoelectric energy harvesting structure proposed in this invention relates to the field of flexible thermoelectric energy storage. It can be applied to surface waste heat energy harvesting in various locations such as human bodies, vehicles, aircraft, and large equipment. Combined with energy management circuits, it can drive low-power devices. Structurally, the lattice-type flexible thermoelectric energy harvesting structure proposed in this invention includes a bipolar thermoelectric conversion unit, a flexible glass fiber substrate, and an electrical connection unit. The main component of the flexible glass fiber substrate is silicon dioxide, which has good high-temperature resistance and flexibility. The main component of the electrical connection unit is silver, which has good stability and conductivity. It is attached to the surface of the flexible substrate and bonded to both ends of the thermocouple to achieve electrical connection while reducing contact resistance. The dense lattice-type thermoelectric thick-film structure used in this invention has high output power density, is lightweight and compact, and has good mechanical strength. This thermoelectric device has a high space utilization rate, can be tightly attached to complex curved surfaces within a certain curvature, is easy to disassemble, and can be applied non-destructively, exhibiting high thermoelectric performance and practical application value.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. A lattice-type flexible thermoelectric energy harvesting structure, characterized in that, include: The flexible glass fiber substrate (4) has two layers; Thermoelectric units are disposed between the two layers of the flexible glass fiber substrate (4) and multiple units are arranged along the entire length of the flexible glass fiber substrate (4), forming a zigzag thermoelectric stack between the multiple thermoelectric units; The top and bottom of the thermoelectric unit are provided with silver electrode films (3), which are used for the electrical connection of the thermoelectric unit; Among them, the flexible glass fiber substrate (4) at the bottom layer is used to adhere to the surface of the heat source (5), and the flexible glass fiber substrate (4) at the top layer is in contact with the cold end region of the heat source (5). The multiple thermoelectric units are connected in series; Each thermoelectric unit includes an N-type thermoelectric arm (1) and a P-type thermoelectric arm (2), and the tops of the N-type thermoelectric arm (1) and the P-type thermoelectric arm (2) are connected by a silver electrode film (3). The bottom of the N-type thermoelectric arm (1) and the P-type thermoelectric arm (2) are connected to the N-type thermoelectric arm (1) and the P-type thermoelectric arm (2) in another adjacent thermoelectric unit through a silver electrode film (3). The N-type thermoelectric arm (1) and the P-type thermoelectric arm (2) are both circular thick films, and are electrically connected to the silver electrode film (3) through high-temperature conductive silver paste. The angle between the silver electrode film (3) at the top of the N-type thermoelectric arm (1) and the silver electrode film (3) at the bottom of the N-type thermoelectric arm (1) is an acute angle. Both ends of the thermopile are bonded with conductive silver paste to metal leads so that the thermopile can collect thermoelectric output.

2. A method for preparing the lattice-type flexible thermoelectric energy harvesting structure according to claim 1, characterized in that, include: The flexible glass fiber substrate is cleaned, dried, and cut. Two types of patterned silver electrode films are prepared on the cut flexible glass fiber substrate, and the two types of patterned silver electrode films are dried and annealed at high temperature. The flexible glass fiber substrate is cut along the silver electrode film after high-temperature annealing to obtain two patterns of flexible glass fiber substrates. Clean and dry the rigid alumina substrate; Two thermoelectric material pastes were prepared, and bismuth telluride thick films and antimony telluride thick films were printed on the dried rigid alumina substrate, respectively. The bismuth telluride thick films and antimony telluride thick films were then dried and annealed. The annealed bismuth telluride thick film and antimony telluride thick film were polished on both sides and then bonded to flexible glass fiber substrates with two different patterns using high-temperature conductive silver paste.

3. The method for preparing the lattice-type flexible thermoelectric energy harvesting structure according to claim 2, characterized in that, The preparation of two patterned silver electrode films specifically includes: The screen printing method is used, with 3-5g of 2-3μm silver powder, 0.6-1g of epoxy resin, 0.2-0.5g of polyetheramine and 0.4-0.6g of terpineol. In this process, epoxy resin is used as a binder, and terpineol is used as a solvent to adjust the viscosity of the slurry. After the slurry is stirred evenly, a silver electrode film array with two patterns is printed using a 200 mesh screen printing process.

4. The method for preparing the lattice-type flexible thermoelectric energy harvesting structure according to claim 3, characterized in that, The thickness of the silver electrode thin film arrays with the two patterns is 20~40μm.

5. The method for preparing the lattice-type flexible thermoelectric energy harvesting structure according to claim 2, characterized in that, The preparation of the two thermoelectric material slurries specifically includes: When preparing screen printing paste with bismuth telluride powder, use 3-5g of 500-mesh tellurium powder, 2.2-4g of 500-mesh bismuth powder, 0.1-0.3g of ethyl cellulose, and 0.55-0.8g of diethylene glycol butyl ether acetate. When preparing screen printing paste with antimony telluride powder, use 3-5g of 500-mesh tellurium powder, 0.8-1.5g of 500-mesh bismuth powder, 1.5-2g of 500-mesh antimony powder, 0.1-0.2g of ethyl cellulose, and 0.5-1.1g of diethylene glycol butyl ether acetate. In this process, the ethyl cellulose acts as a binder, and the diethylene glycol butyl ether acetate acts as a solvent, which is used to adjust the viscosity of the slurry. After the slurry is thoroughly mixed, a circular thick film array of thermoelectric units is printed on a stainless steel plate with a custom pattern.

6. The method for preparing the lattice-type flexible thermoelectric energy harvesting structure according to claim 5, characterized in that, The thickness of the circular thick film array is 350~400μm.

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