A flexible thermoelectric device based on negative Poisson's ratio structure and its application

Abstract

The present invention relates to the technical field of electronic devices, and in particular to a flexible thermoelectric device based on a negative Poisson's ratio structure and its application. A flexible thermoelectric device based on a negative Poisson's ratio structure includes a heat-conducting layer for fitting with human skin; a hot end installed at one end of the top of the heat-conducting layer; a heat-insulating layer installed on the top of the heat-conducting layer and abutting the hot end at one end; a cold end installed on the top of the heat-insulating layer and located away from the hot end; a thermoelectric conversion layer installed on the top of the heat-insulating layer, one end connected to the hot end and the other end connected to the cold end; and a heat-insulating packaging layer covering the top of the thermoelectric conversion layer; the thermoelectric conversion layer includes a plurality of thermoelectric units arranged in an array and interconnected; the thermoelectric unit is a negative Poisson's ratio structure. The flexible thermoelectric device based on a negative Poisson's ratio structure provided by the present invention has good energy conversion performance, good flexibility, good bending strength, and long service life, and is suitable for use in wearable devices, especially wearable medical devices.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic devices, and in particular to a flexible thermoelectric device based on a negative Poisson's ratio structure and its application. Background Art

[0002] With the continuous development and progress of science and technology, wearable devices are gradually developing in the direction of lightweight and miniaturization. Therefore, the size of batteries in wearable devices also needs to be reduced. However, the reduction in battery size weakens its ability to store electricity, which cannot meet the endurance of wearable devices and limits the further development of wearable devices. The human body is a constant temperature heat source. Using energy harvesting technology to convert the heat energy released by the human body into electrical energy is an ideal choice for achieving continuous self-powering of wearable devices. Thermoelectric devices can convert human heat energy into electrical energy, thereby achieving continuous self-powering of wearable devices.

[0003] At present, thermoelectric devices in wearable devices usually use organic thermoelectric materials, such as the conductive polymer PEDOT:PSS. Organic thermoelectric materials have good deformation ability, but poor energy conversion performance, so it is difficult to carry out large-scale commercial application. Traditional inorganic thermoelectric materials have excellent energy conversion performance, but poor mechanical properties, and cannot fit tightly to the surface of the human body, resulting in a large amount of heat loss and poor comfort when worn. In addition, thermoelectric devices will be subjected to large bending loads during wearing, resulting in large bending deformation. However, the bending strength of thermoelectric devices in existing wearable devices is low. After repeated wearing, thermoelectric devices will experience problems such as interface cracking and fatigue fracture, which will reduce the energy conversion performance of thermoelectric devices.

[0004] The above-mentioned defects are expected to be overcome by those skilled in the art. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects in the prior art. In a first aspect, the present invention provides a flexible thermoelectric device based on a negative Poisson's ratio structure.

[0006] Based on the first aspect of the present invention, the second aspect of the present invention further provides an application of a flexible thermoelectric device based on a negative Poisson's ratio structure.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A flexible thermoelectric device based on a negative Poisson's ratio structure comprises a heat-conducting layer for fitting with human skin; a hot end installed at one end of the top of the heat-conducting layer; a heat-insulating layer installed at the top of the heat-conducting layer and abutting the hot end at one end; a cold end installed at the top of the heat-insulating layer and located away from the hot end; a thermoelectric conversion layer installed at the top of the heat-insulating layer and connected to the hot end at one end and the cold end at the other end; and a heat-insulating packaging layer covering the top of the thermoelectric conversion layer; the thermoelectric conversion layer comprises a plurality of thermoelectric units arranged in an array and connected to each other; the thermoelectric units are of a negative Poisson's ratio structure.

[0009] The heat absorbed by the heat-conducting layer of the present invention will not be conducted upward from the heat-insulating layer to the thermoelectric conversion layer, but can only be conducted from the hot end connected to the heat-conducting layer to the cold end through the thermoelectric conversion layer. The cold end performs convection heat exchange with the external environment, and a temperature difference is formed between the hot and cold ends of the flexible thermoelectric device, thereby forming an electric potential difference, thereby realizing the output voltage to the load. The heat flow inside the flexible thermoelectric device provided by the present invention can only be conducted from the hot end to the cold end through the thermoelectric conversion layer, and no heat exchange occurs with the external environment, which is beneficial to improving the energy conversion performance.

[0010] Furthermore, the thermoelectric unit is a hollow concave hexagonal honeycomb structure; the thermoelectric unit has a P-type thermoelectric leg, an N-type thermoelectric leg, a first electrode for connecting adjacent P-type thermoelectric legs, a second electrode for connecting adjacent N-type thermoelectric legs, and an insulating layer arranged between the P-type thermoelectric leg and the N-type thermoelectric leg; the number of the P-type thermoelectric legs, the N-type thermoelectric legs, and the insulating layer is equal. When the flexible thermoelectric device is subjected to bending deformation during wearing, the thermoelectric legs in the thermoelectric unit move outward, driving the electrodes to rotate and bend, thereby causing the thermoelectric unit to expand and produce a negative Poisson's ratio effect; during the deformation process, the displacement is mainly caused by the rotation and bending deformation of the electrodes, and the elastic deformation of the thermoelectric legs can be ignored. The flexible thermoelectric device has good flexibility, good bending strength, and a long service life.

[0011] Preferably, the length, width and thickness of the P-type thermoelectric leg, the N-type thermoelectric leg and the insulating layer are equal; and the length of the first electrode is equal to the length of the second electrode.

[0012] Preferably, the length of the P-type thermoelectric leg and the N-type thermoelectric leg is twice the length of the first electrode and the second electrode.

[0013] Preferably, the angle formed by the P-type thermoelectric leg and the first electrode is equal to the angle formed by the N-type thermoelectric leg and the second electrode, and the range of the angle is 0° to 90°.

[0014] Preferably, the angle ranges from 45° to 60°.

[0015] Preferably, the formula for the optimal angle of the included angle is:

[0016]

[0017] Among them, β opt is the optimal angle, in degrees; H p is the thickness of the P-type thermoelectric leg and the N-type thermoelectric leg, in m; N is the number of P-type thermoelectric legs or N-type thermoelectric legs.

[0018] Preferably, the P-type thermoelectric legs and the N-type thermoelectric legs are made of inorganic thermoelectric materials; the first electrode and the second electrode are made of copper; and the insulating layer is made of polyimide. By setting the P-type thermoelectric legs and the N-type thermoelectric legs to be made of inorganic thermoelectric materials, the flexible thermoelectric device has good flexibility and bending strength as well as good energy conversion performance, and is suitable for large-scale commercial applications.

[0019] The present invention also provides an application of the flexible thermoelectric device as described above in a wearable device.

[0020] The present invention also provides an application of the flexible thermoelectric device as described above in a wearable medical device.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. A flexible thermoelectric device based on a negative Poisson's ratio structure of the present invention comprises a heat-conducting layer, a heat-insulating layer, a thermoelectric conversion layer, a hot end, a cold end and a heat-insulating packaging layer, wherein the heat-conducting layer is used to fit with human skin; the hot end is arranged at one end on the top of the heat-conducting layer; the heat-insulating layer is arranged on the top of the heat-conducting layer and one end of the heat-insulating layer abuts against the hot end; the cold end is arranged on the top of the heat-insulating layer and is located at an end away from the hot end; the thermoelectric conversion layer is installed on the top of the heat-insulating layer and one end is connected to the hot end and the other end is connected to the cold end; so that the heat absorbed by the heat-conducting layer It will not be conducted upward from the heat insulation layer to the thermoelectric conversion layer, but can only be conducted from the hot end connected to the heat conduction layer to the cold end through the thermoelectric conversion layer; the cold end performs convection heat exchange with the external environment, and a temperature difference is formed between the hot and cold ends of the flexible thermoelectric device, thereby forming an electric potential difference, and realizing output voltage to the load; by arranging a heat insulation packaging layer cover on the top of the thermoelectric conversion layer, the heat flow inside the flexible thermoelectric device can only be conducted from the hot end through the thermoelectric conversion layer to the cold end, and no heat exchange occurs with the external environment, which is conducive to improving energy conversion performance;

[0023] 2. The thermoelectric conversion layer is composed of a number of thermoelectric units arranged in an array and interconnected, and the thermoelectric unit is a negative Poisson's ratio structure. When the flexible thermoelectric device is subjected to bending deformation during wearing, the thermoelectric legs in the thermoelectric unit move outward, driving the electrode to rotate and bend and deform, thereby causing the thermoelectric unit to expand and produce a negative Poisson's ratio effect; during the deformation process, the displacement is mainly caused by the rotation and bending deformation of the electrode, and the elastic deformation of the thermoelectric legs can be ignored. The flexible thermoelectric device has good flexibility, good bending strength and long service life; by arranging the thermoelectric legs to be made of inorganic thermoelectric materials, the flexible thermoelectric device has good flexibility and bending strength, as well as good energy conversion performance, and is suitable for large-scale commercial applications; it is suitable for use in wearable devices, especially wearable medical devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of a flexible thermoelectric device based on a negative Poisson's ratio structure provided by the present invention;

[0025] Figure 2 It is a schematic structural diagram of a thermoelectric conversion layer in a flexible thermoelectric device based on a negative Poisson's ratio structure provided by the present invention;

[0026] Figure 3 yes Figure 2 The enlarged schematic diagram of point A in the middle;

[0027] Figure 4 It is a partial structural schematic diagram of a thermoelectric unit in a flexible thermoelectric device based on a negative Poisson's ratio structure provided by the present invention;

[0028] Figure 5 These are fatigue life test results of a flexible thermoelectric device based on a negative Poisson's ratio structure provided by the present invention and existing homogeneous thermoelectric materials.

[0029] [Explanation of Figure Marks] 1. Thermal conductive layer; 2. Thermal insulation layer; 3. Thermoelectric conversion layer; 31. Thermoelectric unit; 311. P-type thermoelectric leg; 312. N-type thermoelectric leg; 313. First electrode; 314. Second electrode; 315. Insulation layer; 4. Thermal insulation packaging layer; 5. Hot end; 6. Cold end. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] See also Figure 1 The present invention provides a flexible thermoelectric device based on a negative Poisson's ratio structure, which includes a heat-conducting layer 1, a heat-insulating layer 2, a thermoelectric conversion layer 3, a heat-insulating packaging layer 4, a hot end 5 and a cold end 6; the heat-conducting layer 1 is used to fit with human skin to absorb the heat continuously radiated from the human body to the outside world; the hot end 5 is installed at one end of the top of the heat-conducting layer 1; the heat-insulating layer 2 is installed on the top of the heat-conducting layer 1, and one end of the heat-insulating layer 2 is abutted against the hot end 5; the cold end 6 is installed on the top of the heat-insulating layer 2, and the cold end 6 is located at an end away from the hot end 5; the thermoelectric conversion layer 3 is installed on the top of the heat-insulating layer 2, and one end of the thermoelectric conversion layer 3 is connected to the hot end 5, and the other end is connected to the cold end 6; the heat-insulating packaging layer 4 is covered on the top of the thermoelectric conversion layer 3.

[0032] In this embodiment, the heat-conducting layer 1 is made of thin copper sheet. Copper has a large thermal conductivity and good thermal conductivity, and can quickly absorb the heat that the human body continuously radiates to the outside world. The heat-insulating layer 2 is made of polyimide. Polyimide has a good thermal insulation effect. The heat absorbed by the heat-conducting layer 1 from the human skin is not conducted upward from the heat-insulating layer 2 to the thermoelectric conversion layer 3, but can only be conducted from the hot end 5 connected to the heat-conducting layer 1 through the thermoelectric conversion layer 3 to the cold end 6; the cold end 6 conducts convection heat exchange with the external environment, and the hot end 5 and the cold end 6 of the flexible thermoelectric device form a temperature difference, thereby forming an electric potential difference, and realizing the output voltage to the load. The heat-insulating packaging layer 4 is made of polyimide. Polyimide has a good thermal insulation effect. The heat flow inside the flexible thermoelectric device can only be conducted from the hot end 5 through the thermoelectric conversion layer 3 to the cold end 6, and no heat exchange occurs with the external environment, which effectively reduces the heat loss inside the flexible thermoelectric device and is conducive to improving the energy conversion performance of the flexible thermoelectric device.

[0033] Please also read Figures 2 to 4, the thermoelectric conversion layer 3 includes a plurality of thermoelectric units 31 arranged in an array and connected to each other; the thermoelectric unit is a negative Poisson's ratio structure. Specifically, the thermoelectric unit 31 is a hollow concave hexagonal honeycomb structure; the thermoelectric unit 31 includes a P-type thermoelectric leg 311, an N-type thermoelectric leg 312, a first electrode 313, a second electrode 314 and an insulating layer 315; the first electrode 313 is used to connect adjacent P-type thermoelectric legs 311; the second electrode 314 is used to connect adjacent N-type thermoelectric legs 312; the insulating layer 315 is arranged between the P-type thermoelectric leg 311 and the N-type thermoelectric leg 312. The number of the P-type thermoelectric leg 311, the N-type thermoelectric leg 312 and the insulating layer 315 is equal. The length, width and thickness of the P-type thermoelectric leg 311, the N-type thermoelectric leg 312 and the insulating layer 315 are all equal; in this embodiment, the width of the P-type thermoelectric leg 311, the N-type thermoelectric leg 312 and the insulating layer 315 is 1 mm, and the thickness is 2 mm. The length of the first electrode 313 is equal to the length of the second electrode 314; the length of the P-type thermoelectric leg 311 and the N-type thermoelectric leg 312 is twice the length of the first electrode 313 and the second electrode 314, so as to ensure that the first electrode 313 and the second electrode 314 can be rotated, bent and deformed.

[0034] When the flexible thermoelectric device is bent and deformed during wearing, the P-type thermoelectric legs 311 and the N-type thermoelectric legs 312 in the thermoelectric unit 31 move outward, driving the first electrode 313 and the second electrode 314 to rotate and bend, thereby causing the thermoelectric unit 31 to expand and produce a negative Poisson's ratio effect. During the deformation process, the displacement is mainly caused by the rotation and bending deformation of the first electrode 313 and the second electrode 314, and the elastic deformation of the P-type thermoelectric legs 311 and the N-type thermoelectric legs 312 can be ignored. The flexible thermoelectric device has good flexibility, good bending strength, and a long service life.

[0035] The P-type thermoelectric leg 311 and the N-type thermoelectric leg 312 are made of inorganic thermoelectric materials, which have good energy conversion performance. Therefore, the flexible thermoelectric device also has good energy conversion performance and is suitable for large-scale commercial applications. In this embodiment, the P-type thermoelectric leg 311 and the N-type thermoelectric leg 312 are made of bismuth telluride. In other embodiments, the P-type thermoelectric leg 311 and the N-type thermoelectric leg 312 can also be made of antimony telluride, tin telluride, silver selenide, etc., so it is not limited to this. The first electrode 313 and the second electrode 314 are made of copper; the insulating layer 315 is made of polyimide.

[0036] The angle formed by the P-type thermoelectric leg 311 and the first electrode 313 is equal to the angle formed by the N-type thermoelectric leg 312 and the second electrode 314, and the range of the angle is 0° to 90°; preferably, the range of the angle is 45° to 60°. The angle can be, but is not limited to, 45°, 50°, 55°, and 60°.

[0037] In the present invention, the formula for the optimal angle of the included angle is:

[0038]

[0039] Among them, β opt is the optimal angle, in degrees; H p is the thickness of the P-type thermoelectric leg 311 and the N-type thermoelectric leg 312 , in m; N is the number of the P-type thermoelectric legs 311 or the N-type thermoelectric legs 312 .

[0040] When the angle is the optimal angle, the internal stress of the flexible thermoelectric device is minimal, which is beneficial to improving the fatigue life of the flexible thermoelectric device, thereby improving the service life.

[0041] In order to further verify the advantages of the present invention, fatigue life test analysis was performed on a flexible thermoelectric device based on a negative Poisson's ratio structure provided by the present invention and an existing homogeneous thermoelectric material. The flexible thermoelectric device based on a negative Poisson's ratio structure to be tested has the same total length, width, and initial crack length as the existing homogeneous thermoelectric material.

[0042] The results are as follows Figure 5 As shown, under a tensile strain of 20%, the existing homogeneous thermoelectric material will suffer fatigue failure after 6 stretching cycles; while for a flexible thermoelectric device based on a negative Poisson's ratio structure provided by the present invention, when the angle formed by the P-type thermoelectric leg 311 and the first electrode 313, and the angle formed by the N-type thermoelectric leg 312 and the second electrode 314 are 30°, fatigue failure will occur after 1200 stretching cycles; when the angle formed by the P-type thermoelectric leg 311 and the first electrode 313, and the angle formed by the N-type thermoelectric leg 312 and the second electrode 314 are 45°, fatigue failure will occur after 3100 stretching cycles; when the angle formed by the P-type thermoelectric leg 311 and the first electrode 313, and the angle formed by the N-type thermoelectric leg 312 and the second electrode 314 are 60°, fatigue failure will occur after 5600 stretching cycles. It can be seen that the fatigue life of the flexible thermoelectric device based on the negative Poisson's ratio structure provided by the present invention is significantly improved compared with the existing homogeneous thermoelectric materials.

[0043] The flexible thermoelectric device provided by the present invention has the advantages of good energy conversion performance, good flexibility, ability to withstand deformation such as pulling and bending, and long service life, and can be used in wearable devices, especially wearable medical devices.

[0044] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A flexible thermoelectric device based on a negative Poisson's ratio structure, characterized in that: The invention comprises a heat-conducting layer (1) for contacting with human skin; a hot end (5) installed at one end of the top of the heat-conducting layer (1); a heat-insulating layer (2) installed at the top of the heat-conducting layer (1) and having one end abutting against the hot end (5); a cold end (6) installed at the top of the heat-insulating layer (2) and located at an end away from the hot end (5); a thermoelectric conversion layer (3) installed at the top of the heat-insulating layer (2) and having one end connected to the hot end (5) and the other end connected to the cold end (6); and a heat-insulating packaging layer (4) covering the top of the thermoelectric conversion layer (3); the thermoelectric conversion layer (3) comprises a plurality of thermoelectric units (31) arranged in an array and connected to each other; the thermoelectric units (31) are negative Poisson's ratio structures; The thermoelectric unit (31) is in a hollow concave hexagonal honeycomb structure; the thermoelectric unit (31) comprises a P-type thermoelectric leg (311), an N-type thermoelectric leg (312), a first electrode (313) for connecting adjacent P-type thermoelectric legs (311), a second electrode (314) for connecting adjacent N-type thermoelectric legs (312), and an insulating layer (315) arranged between the P-type thermoelectric leg (311) and the N-type thermoelectric leg (312); the number of the P-type thermoelectric legs (311), the N-type thermoelectric legs (312), and the insulating layer (315) is equal; When the flexible thermoelectric device is subjected to bending deformation, the P-type thermoelectric legs 311 and the N-type thermoelectric legs 312 in the thermoelectric unit 31 move outward, driving the first electrode 313 and the second electrode 314 to rotate and bend, thereby causing the thermoelectric unit 31 to expand and produce a negative Poisson's ratio effect.

2. A flexible thermoelectric device based on a negative Poisson's ratio structure according to claim 1, characterized in that: The length, width and thickness of the P-type thermoelectric leg (311), the N-type thermoelectric leg (312) and the insulating layer (315) are all equal; and the length of the first electrode (313) is equal to the length of the second electrode (314).

3. A flexible thermoelectric device based on a negative Poisson's ratio structure according to claim 2, characterized in that: The lengths of the P-type thermoelectric leg (311) and the N-type thermoelectric leg (312) are twice the lengths of the first electrode (313) and the second electrode (314).

4. The flexible thermoelectric device based on a negative Poisson's ratio structure according to claim 1, characterized in that: The angle formed by the P-type thermoelectric leg (311) and the first electrode (313) is equal to the angle formed by the N-type thermoelectric leg (312) and the second electrode (314), and the range of the angle is 0° to 90°.

5. A flexible thermoelectric device based on a negative Poisson's ratio structure according to claim 4, characterized in that: The angle ranges from 45° to 60°.

6. The flexible thermoelectric device based on a negative Poisson's ratio structure according to claim 4, characterized in that: The formula for the optimal angle of the angle is:

7. The flexible thermoelectric device based on a negative Poisson's ratio structure according to claim 1, characterized in that: The P-type thermoelectric leg (311) and the N-type thermoelectric leg (312) are made of inorganic thermoelectric material; the first electrode (313) and the second electrode (314) are made of copper; and the insulating layer (315) is made of polyimide.

8. Application of a flexible thermoelectric device based on a negative Poisson's ratio structure as described in any one of claims 1 to 7 in a wearable device.

9. Application of a flexible thermoelectric device based on a negative Poisson's ratio structure as described in any one of claims 1 to 7 in a wearable medical device.

Images