Preparation method of wearable thermoelectric refrigeration device based on radiation refrigeration

Abstract

The application discloses a wearable thermoelectric refrigeration device based on radiation refrigeration and a preparation method thereof, adopts radiation refrigeration and convection heat dissipation as the heat dissipation mode of the wearable thermoelectric refrigeration, adopts an integrated heat dissipation layer, and has better heat dissipation effect than a discrete heat dissipation layer, adopts a network structure high-strength low-thermal-conductivity packaging material to package the flexible electrode plate and the thermoelectric arm, improves the flexibility of the device, greatly enhances the reliability of the device, and has higher reliability and higher efficiency compared with traditional PDMS or foam aerogel as the packaging material.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of wearable thermoelectric refrigeration, and particularly relates to a preparation method of a wearable thermoelectric refrigeration device based on radiation refrigeration. BACKGROUND

[0002] The comfortable temperature of human skin is between 32 DEG C and 34 DEG C, when the environmental temperature rises to make the human skin temperature higher than the comfortable temperature, the human body will take away heat through sweating, but a large amount of sweating will also increase the cardiovascular burden of the human body. Although air conditioners and other refrigeration equipment can meet the daily life needs, on the one hand, a large amount of power is consumed, and on the other hand, the refrigeration equipment is not suitable for providing cooling services for outdoor workers, construction workers, sanitation workers and the like in a hot environment, and is also the main reason for the urban heat island effect. The individualized refrigeration clothes for individual body temperature regulation are more and more widely concerned by people. On the one hand, the personal refrigeration device directly acts on the human body, greatly reducing the resource consumption, and on the other hand, the refrigeration device can meet the different needs of individuals in different environments and different states, and widens the actual application field.

[0003] At present, the main cooling means of the wearable refrigeration device is to match the refrigeration liquid with the refrigeration machine or to accelerate the evaporation of sweat through the fan to cool down. However, the former is bulky and heavy, is not convenient for the movement of individuals and has high energy consumption and strict energy demand, and the latter has limited refrigeration capacity and is difficult to control the temperature and is not friendly to the weak, which to some extent limits the application. The thermoelectric refrigeration device is widely concerned due to its small size and high efficiency, but the refrigeration capacity is greatly affected by the heat dissipation of the hot end. The radiation refrigeration material can reflect sunlight and emit specific band infrared radiation to outer space through high infrared emissivity, and is matched with the thermoelectric refrigeration to dissipate heat and cool down the thermoelectric device, but it is urgent to solve the problem of ensuring the flexibility and high refrigeration performance. The previous research results of the research group CN113644189A disclose a wearable thermoelectric refrigeration device based on double-network hydrogel heat dissipation and a preparation method thereof, the double-network hydrogel soaked in a hygroscopic salt solution is used as a heat dissipator of the flexible thermoelectric refrigeration device, the performance of the device is effectively improved, the foamed nickel-heat-conducting silica gel connection mode is adopted, the contact thermal resistance between the hot end of the thermoelectric refrigeration device and the heat dissipation end of the hydrogel is effectively reduced, and the refrigeration performance of the device is further improved, but the lower conductive electrode is only encapsulated, the thermoelectric arm is not encapsulated, the reliability is low, and the thermoelectric arm is prone to falling off in the use process, and in addition, the heat dissipation layer is discrete, and the heat dissipation effect needs to be further improved. SUMMARY

[0004] The application aims to provide a wearable thermoelectric refrigeration device based on radiation refrigeration and a preparation method thereof, and solves the problems of poor heat dissipation effect of the prior art and easy falling off of the thermoelectric arm in the use process.

[0005] The application is implemented through the following technical solutions:

[0006] A wearable thermoelectric refrigeration device based on radiation refrigeration, which is composed of a radiation refrigeration heat dissipation layer and a thermoelectric refrigeration layer from top to bottom, the radiation refrigeration heat dissipation layer covers the non-close-fitting surface of the thermoelectric refrigeration layer, the radiation refrigeration heat dissipation layer is integrated, the thermoelectric refrigeration layer is composed of a plurality of discrete thermoelectric refrigeration units, the thermoelectric refrigeration unit includes a π-type thermoelectric arm, an upper and lower group of flexible electrode plates matched in size with the π-type thermoelectric arm, the back surface of the upper and lower group of flexible electrode plates is provided with an insulating protective layer, and the π-type thermoelectric arm is packaged by a non-porous low-thermal-conductivity high-strength flexible material with a thermal conductivity lower than 0.12 W / mK; the upper flexible electrode plate of the thermoelectric refrigeration unit is connected with the radiation refrigeration heat dissipation layer through viscous heat-conducting silica gel; the upper flexible electrode plate is connected in series between each thermoelectric refrigeration unit, and a low-thermal-conductivity high-strength flexible material is filled between the thermoelectric refrigeration units, and the filling material is provided with a network structure of holes to improve flexibility.

[0007] The radiation heat dissipation layer is coated with a radiation refrigeration coating on a flexible heat-conducting silica gel, a thin metal sheet or a graphene heat dissipation sheet with high thermal conductivity; the radiation refrigeration coating can exchange heat with the outer space to discharge heat through high emission in the atmospheric window, and can be composed of multiple layers of micrometer or millimeter thick film materials, such as depositing aluminum on the back of a polydimethylsiloxane (PDMS) film or a composite material added with silica microspheres, or by adding specific particles to the base film material or manufacturing optical structures, such as adding silica particles to P(VDF-HFP) and then reshaping or manufacturing micropores in the P(VDF-HFP) film during the shaping stage by a phase separation method.

[0008] The thickness of the radiation refrigeration heat dissipation layer is not more than 0.3 mm.

[0009] The non-porous low-thermal-conductivity high-strength flexible material with a thermal conductivity lower than 0.12 W / mK includes polyurethane, PDMS or epoxy resin added with silica microspheres, etc.

[0010] The holes in the filling material between the thermoelectric refrigeration units can be rhombic, square, quadrilateral, hexagonal or circular according to different bending conditions.

[0011] A preparation method of a wearable thermoelectric refrigeration device based on radiation refrigeration, which comprises the following steps:

[0012] 1) Preparation of a radiation refrigeration heat dissipation layer:

[0013] 2) Preparation of electrode plates and π-type thermoelectric pair array: two pieces of copper sheet are prepared as conductive electrodes, the thickness of the copper sheet is 0.04mm-1mm, the back of the copper sheet is coated with an oxidation-resistant paint or sintered with alumina or boron nitride ceramic as an insulating protective layer to fix and protect the copper sheet from oxidation, and a transfer re-etching method is used to obtain two sets of electrode plates matching the size of the thermoelectric arm, and then a connected π-type thermoelectric pair array is obtained by hot pressure welding technology, see CN113644189A; the aspect ratio (AR value) of the thermoelectric arm should be > 2, and the fill factor (FF) of the device is between 5% and 20% (the ratio of the total area of the thermoelectric arm to the total cross-sectional area of the thermoelectric device);

[0014] 3) Preparation of high-strength low-thermal-conductivity packaging material: add PDMS or polyurethane or epoxy resin and SiO2 microspheres with a particle size of 100-200μm in a mass ratio of 10:2 and stir uniformly in a blender to obtain a mixture, then add 1 / 10 of the mass of the curing agent to the mixture and stir for 10 minutes to obtain a high-strength low-thermal-conductivity packaging material;

[0015] 4) Heat the liquid metal with a melting point of 50℃ to 70℃ to completely melt and pour into a custom-made silicone mold, and after solidification at room temperature, remove the metal from the mold to obtain a metal mold for pore formation, and the silicone mold can be customized into rhombus, square, quadrilateral, hexagonal, circular, etc. according to the bending requirements;

[0016] 5) Apply adhesive thermal conductive silicone with a thermal conductivity greater than 0.5W / mK to the electrodes of the π-type thermoelectric pair array obtained in step 2), and apply the radiation refrigeration heat dissipation layer obtained in step 1) to the other side of the silicone, place it in an 8cm*8cm square glass mold with an opening at the top, pour the high-strength low-thermal-conductivity packaging material obtained in step 3) into the glass mold until the thermoelectric pair array is completely submerged, then insert the metal mold obtained in step 4) into the gap between the thermoelectric pairs, and then heat the device to 40℃ for 12 hours until the packaging material is completely cured;

[0017] 6) Heat the device obtained in step 5) to 70℃ until the liquid metal is completely melted to obtain a device with a network structure; finally, the remaining liquid metal residue on the device can be placed in a hydrochloric acid solution to be etched away.

[0018] Specifically, step 1) includes the following steps: Prepare a flexible, highly thermally conductive thin metal sheet or graphene sheet according to the size of the device, and then add vinylidene fluoride-hexafluoropropylene copolymer P(VdF-HFP) particles to acetone solvent; the mass ratio of vinylidene fluoride-hexafluoropropylene copolymer P(VdF-HFP) particles to the volume ratio of acetone is (1-2) g / 15 ml, stir at 60-70°C for 1 hour, then add deionized water of the same mass as P(VdF-HFP) particles as a non-solvent, stir continuously for 1 hour until transparent, and then pour the prepared solution onto the thin metal sheet placed in a glass petri dish and evaporate at room temperature to form a radiation cooling heat dissipation coating for later use.

[0019] The beneficial effects of this invention are as follows:

[0020] 1) This invention uses radiation cooling and convection cooling as the heat dissipation methods for wearable thermoelectric cooling. Compared with traditional refrigerant or air cooling, it is lighter and more flexible, consumes less energy, is cheaper, and has a simple preparation method.

[0021] 2) The present invention uses an integrated heat dissipation layer, which has a better heat dissipation effect than discrete heat dissipation layers.

[0022] 3) This invention employs a high-strength, low-thermal-conductivity encapsulation material with a network structure to encapsulate both the flexible electrode plate and the thermoelectric arm, significantly enhancing the device's flexibility and reliability. Compared to traditional encapsulation materials such as PDMS or foam aerogel, it offers higher reliability and efficiency. Results show that in indoor environments with temperatures below 34°C, it can reduce human skin temperature to a comfortable level of 32°C. Outdoors, even in sunny conditions with temperatures below 32°C or on a clear night with temperatures below 36°C, it can also reduce human skin temperature to a comfortable level of 32°C.

[0023] In summary, this patent discloses a wearable thermoelectric cooling device based on radiation cooling and its preparation method, which solves the problems of poor heat dissipation effect and easy detachment of the thermoelectric arm in the prior art during use. Attached image description:

[0024] Figure 1 This is a cross-sectional schematic diagram of the wearable thermoelectric device of the present invention;

[0025] Figure 2 This is a plan view of the cooling layer of a wearable thermoelectric device based on radiation cooling;

[0026] Among them, 1. Radiation cooling heat dissipation layer, 2. Thermoelectric cooling layer, 3. Insulation protection layer, 4. Upper flexible electrode plate, 5. Low thermal conductivity high strength flexible material, 6. π-type thermoelectric arm, 7. Lower flexible electrode plate, 8. Insulation protection layer, 9. Adhesive thermally conductive silicone, 10. Opening, 11. Thermoelectric cooling unit.

[0027] Figure 3 This is a process flow diagram for fabricating a wearable thermoelectric device based on radiation cooling;

[0028] Figure 4 Examples 2 show the bending diagram and testing of the wearable thermoelectric device based on radiation cooling.

[0029] Figure 5 The image shows the cooling test and stress resistance diagram of the wearable thermoelectric device based on radiation cooling prepared in Example 2. Detailed implementation method:

[0030] The following is a further description of the invention, but not a limitation thereof.

[0031] like Figure 1 The device shown is a wearable thermoelectric cooling device based on radiative cooling. From top to bottom, the device consists of a radiative cooling heat dissipation layer 1 and a thermoelectric cooling layer 2. The radiative cooling heat dissipation layer 1 covers the non-body surface of the thermoelectric cooling layer 2 and is a single unit. The thermoelectric cooling layer consists of multiple discrete thermoelectric cooling units 11. Each thermoelectric cooling unit includes a π-shaped thermoelectric arm 6 and two sets of flexible electrode plates 4 and 7, matching the size of the π-shaped thermoelectric arm. Insulating protective layers 3 and 8 are provided on the back of the two sets of flexible electrode plates. The π-shaped thermoelectric arm 6 is encapsulated by a non-porous, low-thermal-conductivity, high-strength flexible material 5 with a thermal conductivity lower than 0.12 W / mK. The flexible electrode plate 4 on the thermoelectric cooling unit is connected to the radiative cooling heat dissipation layer 1 via adhesive thermally conductive silicone 9. Each thermoelectric cooling unit 11 is connected in series by the upper flexible electrode plate 4. The spaces between each thermoelectric cooling unit are filled with a low-thermal-conductivity, high-strength flexible material 5, with openings 10 in the filling material forming a network structure to improve flexibility.

[0032] Example 1:

[0033] 1) Prepare a 5cm x 5cm flexible, highly thermally conductive thin metal or graphene sheet. Add 0.5g of P(VdF-HFP) to 7.5ml of acetone solvent, stir at 70℃ for 1 hour at a stirring speed of 600rpm, then add 0.5ml of deionized water as a non-solvent and stir continuously for 1 hour until it becomes transparent. Then, pour the prepared solution onto the thin metal or graphene sheet placed in a glass petri dish and allow it to evaporate at room temperature. Initially, the acetone begins to evaporate, forming a translucent gel solution at room temperature. Later, the water evaporates to form a white radiation-cooling thin film coating, and the resulting radiation-cooling heat dissipation layer is ready for use.

[0034] 2) Prepare two copper sheets, each 5cm x 5cm, as conductive electrodes. The copper sheets are 0.04mm thick. The back of the copper sheets is coated with anti-oxidation paint or sintered with alumina or boron nitride ceramic as an insulating protective layer to fix and protect the copper sheets from oxidation. Using CAD software, design the upper and lower electrode circuit patterns of the thermoelectric device according to requirements. Print the drawn upper and lower electrode circuit patterns onto transfer paper using a laser printer. Transfer the circuit patterns on the transfer paper to the copper sheets using hot pressing technology. The upper electrode circuit pattern is transferred to the upper copper sheet, and the lower electrode circuit pattern is transferred to the lower copper sheet. The copper sheet parts covered with ink are the designed upper and lower electrode circuits. Immerse the transferred copper sheets in an etching agent; the parts not covered by ink are etched. After etching, wash off the ink on the circuit surface with acetone to obtain two sets of flexible electrode plates matching the size of the thermoelectric arm. Print the upper and lower flexible electrode plates with Sn composition using stencil printing technology. 42 Bi 52 Solder paste with a thickness of 0.09mm; bismuth telluride (Bi) P-type thermoelectric material with dimensions of 1mm x 1mm and a height of 3mm. 0.5 Sb 1.5 Te3 and N-type thermoelectric materials bismuth telluride Bi2Se 0.3 Te 2.7 The thermocouples are alternately placed on the lower electrode plate printed with solder paste. Then the electrode plate with the thermocouples arranged is placed on a hot press for hot pressing and welding. The lower electrode plate is processed in the same way to obtain a connected π-type thermocouple array. The fill factor FF of the device is 5%.

[0035] 3) Prepare a beaker, add PDMS and SiO2 microspheres with a particle size of 200μm in a mass ratio of 10:2, and stir in a mixer for 30 minutes until a homogeneous mixture is obtained. Then add curing agent in a mass ratio of 10:1 for the mixture and stir in a mixer for 10 minutes to obtain the encapsulation material for later use.

[0036] 4) Heat the GaIn alloy with a melting point of 50°C to 70°C until it is completely melted and pour it into a custom silicone mold (as a concave mold, arranged in a hexagonal concave mold array). After it is completely cured at room temperature, remove the metal from the mold to obtain a metal mold for creating holes in the encapsulation material.

[0037] 5) Coat the electrodes of the π-type thermocouple array obtained in step 2) with a sticky thermally conductive silicone with a thermal conductivity of 0.8 W / mK. Attach the radiative cooling heat dissipation layer obtained in step 1) to the other side of the silicone. Place the array into an 8cm*8cm square glass mold with an open top. Pour the encapsulation material obtained in step 3) into the glass mold until it completely submerges the thermocouple array. Then, insert a metal mold with holes made in the encapsulation material obtained in step 4) into the gaps between the thermocouples. Heat the device to 40°C and maintain this temperature for 12 hours until the encapsulation material is completely cured.

[0038] Since the metal mold and the packaging material have a certain degree of adhesion and are not easily detached, the device obtained in step 5) can be heated to 70°C until the liquid metal is completely melted to obtain a device with a mesh structure. Finally, any remaining liquid metal residue on the device can be corroded away in a hydrochloric acid solution.

[0039] Example 2:

[0040] Referring to Example 1, the difference is that the thermoelectric arm in step 2) is replaced with a P-type thermoelectric material, bismuth telluride (Bi), with dimensions of 1mm x 1mm and a height of 5mm. 0.5 Sb 1.5 Te3 and N-type thermoelectric materials bismuth telluride Bi2Se 0.3 Te 2.7 The device's fill factor FF is 8%. Everything else is the same as in Example 1.

[0041] Example 3:

[0042] Referring to Example 2, the difference is that the thickness of the lower electrode copper sheet in step 2) is 1mm, and the back is coated with anti-oxidation paint, otherwise it is the same as Example 2.

[0043] Example 4:

[0044] Referring to Example 1, the difference is that in step 4), instead of using a liquid metal mold, a custom-made metal mold is used online, and a release agent is applied to the metal mold. In step 6), the mold is directly peeled off from the device by hand. The rest is the same as in Example 1.

Claims

1. A method for fabricating a wearable thermoelectric cooling device based on radiation cooling, characterized in that, The method includes the following steps: 1) Fabrication of a radiation-cooled heat dissipation layer: 2) Fabrication of electrode plates and π-type thermocouple array: Prepare two copper sheets as conductive electrodes, with a thickness of 0.04mm to 1mm. The back of the copper sheets is coated with anti-oxidation paint or sintered with alumina or boron nitride ceramic as an insulating protective layer. Use a transfer and etching method to obtain two sets of electrode plates that match the size of the thermocouple arm. Then, use hot-press welding technology to obtain a connected π-type thermocouple array. The thermocouple arm should meet the following requirements: aspect ratio > 2, and the fill factor of the device should be between 5% and 20%. 3) Preparation of high-strength, low-thermal-conductivity encapsulation material: Add PDMS or polyurethane or epoxy resin and SiO2 microspheres with a particle size of 100-200μm in a mass ratio of 10:2 and stir evenly in a mixer to obtain a mixture. Then add 1 / 10 of the mass of curing agent to the mixture and stir for 10 minutes to obtain the high-strength, low-thermal-conductivity encapsulation material. 4) Heat the liquid metal with a melting point of 50°C to 70°C until it is completely melted and pour it into a customized silicone mold. After curing at room temperature, remove the metal from the mold to obtain a metal mold for creating holes in the encapsulation material. The silicone mold can be customized into a quadrilateral, hexagonal or circular shape according to the bending requirements. 5) Coat the electrodes of the π-type thermocouple array obtained in step 2) with a sticky thermally conductive silicone with a thermal conductivity greater than 0.5 W / mK. Attach the radiative cooling heat dissipation layer obtained in step 1) to the other side of the silicone. Place the array into an 8cm*8cm square glass mold with an opening at the top. Pour the high-strength, low-thermal-conductivity encapsulation material obtained in step 3) into the glass mold until it completely submerges the thermocouple array. Then insert the metal mold obtained in step 4) into the gaps between the thermocouples. Heat the device to 40°C and maintain it for 12 hours until the encapsulation material is completely cured. 6) Heat the device obtained in step 5) to 70°C until the liquid metal is completely melted to obtain a device with a mesh structure; the liquid metal residue remaining on the device can be corroded away in hydrochloric acid solution.

2. The method for fabricating a wearable thermoelectric cooling device based on radiation cooling according to claim 1, characterized in that, Step 1) includes the following steps: Prepare a flexible, highly thermally conductive thin metal sheet or graphene sheet according to the size of the device. Then, add vinylidene fluoride-hexafluoropropylene copolymer P(VdF-HFP) particles to acetone solvent. The mass ratio of the vinylidene fluoride-hexafluoropropylene copolymer P(VdF-HFP) particles to the volume ratio of acetone is (1-2) g / 15 ml. Stir at 60-70℃ for 1 hour. Then, add deionized water of the same mass as the P(VdF-HFP) particles as a non-solvent and stir continuously for 1 hour until transparent. Then, pour the prepared solution onto the thin metal sheet placed in a glass petri dish and evaporate at room temperature to form a radiation cooling heat dissipation coating for later use.

3. A wearable thermoelectric cooling device based on radiation cooling obtained by the preparation method of claim 1, characterized in that, The device consists of a radiative cooling heat dissipation layer and a thermoelectric cooling layer from top to bottom. The radiative cooling heat dissipation layer covers the non-contact surface of the thermoelectric cooling layer and is a single unit. The thermoelectric cooling layer is composed of multiple discrete thermoelectric cooling units. Each thermoelectric cooling unit includes a π-shaped thermoelectric arm and two sets of flexible electrode plates that match the size of the π-shaped thermoelectric arm. The back of the two sets of flexible electrode plates is provided with an insulating protective layer. The π-shaped thermoelectric arm is encapsulated by a non-porous, low thermal conductivity, high-strength flexible material with a thermal conductivity of less than 0.12 W / mK. The flexible electrode plates on the thermoelectric cooling unit are connected to the radiative cooling heat dissipation layer via adhesive thermally conductive silicone. Each thermoelectric cooling unit is connected in series by the upper flexible electrode plate. The spaces between each thermoelectric cooling unit are filled with a low thermal conductivity, high-strength flexible material with openings in the filling material to form a network structure.

4. The wearable thermoelectric cooling device based on radiation cooling according to claim 3, characterized in that, The radiative heat dissipation layer is a flexible thermally conductive silicone, thin metal sheet or graphene heat sink with high thermal conductivity coated with a radiative cooling coating. The radiation cooling coating dissipates heat by exchanging heat with the outer space through high emission at atmospheric windows.

5. The wearable thermoelectric cooling device based on radiation cooling according to claim 4, characterized in that, Radiation-cooled coatings are composed of multiple micron- or millimeter-thick thin film materials or are obtained by adding specific particles to a substrate thin film material or by fabricating optical structures.

6. The wearable thermoelectric cooling device based on radiation cooling according to claim 5, characterized in that, The radiation cooling coating is achieved by depositing aluminum on the back of a polydimethylsiloxane film or a composite material containing silica microspheres, or by adding silica microparticles to P(VDF-HFP) before molding, or by creating micropores during the molding stage of the P(VDF-HFP) film through phase separation.

7. The wearable thermoelectric cooling device based on radiation cooling according to claim 3 or 4, characterized in that, The thickness of the radiative cooling heat dissipation layer shall not exceed 0.3 mm.

8. The wearable thermoelectric cooling device based on radiation cooling according to claim 3 or 5, characterized in that, Non-porous, low thermal conductivity, high strength, flexible materials with a thermal conductivity below 0.12 W / mK include silica microspheres doped with polyurethane, PDMS, or epoxy resin.

9. The wearable thermoelectric cooling device based on radiation cooling according to claim 3 or 5, characterized in that, The openings in the filling material between each thermoelectric refrigeration unit are quadrilateral, hexagonal, or circular.

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