Flexible thermoelectric device based on negative poisson ratio structure and applicationTechnical Field
The invention relates to the technical field of electronic devices, in particular to a flexible thermoelectric device based on a negative poisson ratio structure and application thereof.
Background
With the continuous development and progress of technology, wearable devices gradually develop to light weight and miniaturization, and therefore, the battery volume in the wearable devices needs to be reduced. However, the capacity of the battery for storing electric quantity is weakened due to the reduction of the volume of the battery, the cruising capacity of the wearable device cannot be met, and further development of the wearable device is limited. The human body is a constant temperature heat source, and the energy collection technology is adopted to convert the heat energy released by the human body into electric energy, so that the energy collection device is an ideal choice for realizing continuous self-power supply of the wearable equipment. The thermoelectric device can convert human body heat energy into electric energy, so that continuous self-power supply of the wearable equipment is realized.
Currently, thermoelectric devices of wearable devices typically employ organic thermoelectric materials, such as the conductive polymer PEDOT: PSS. Organic thermoelectric materials have good deformability, but poor energy conversion properties, and thus are difficult to be applied commercially on a large scale. The conventional inorganic thermoelectric material has excellent energy conversion performance, but has poor mechanical properties, cannot be closely attached to the surface of a human body, causes a large amount of heat loss, and is poor in comfort when worn. In addition, the thermoelectric device can bear larger bending load during the wearing process, and larger bending deformation is generated. However, the thermoelectric device of the existing wearable equipment has low bending strength, and after repeated wearing, the thermoelectric device can have problems of interface cracking, fatigue fracture and the like, so that the energy conversion performance of the thermoelectric device is reduced.
The above drawbacks are to be overcome by those skilled in the art.
Disclosure of Invention
The present invention aims to overcome the above-mentioned drawbacks of the prior art and a first aspect of the present invention provides a flexible thermoelectric device based on a negative poisson's ratio structure.
Based on the first aspect of the invention, the second aspect of the invention also provides an application of the flexible thermoelectric device based on the negative poisson ratio structure.
In order to solve the technical problems, the invention adopts the following technical scheme:
A flexible thermoelectric device based on a negative Poisson ratio structure comprises a heat conducting layer, a hot end, a heat insulation layer, a cold end, a thermoelectric conversion layer and a heat insulation packaging layer, wherein the heat conducting layer is used for being attached to human skin, the hot end is arranged at one end of the top of the heat conducting layer, the heat insulation layer is arranged at the top of the heat conducting layer, one end of the heat insulation layer is in butt joint with the hot end, the cold end is arranged at one end far away from the hot end, the thermoelectric conversion layer is arranged at the top of the heat insulation layer, one end of the thermoelectric conversion layer is connected with the hot end, the other end of the thermoelectric conversion layer is connected with the cold end, the heat insulation packaging layer is arranged at the top of the thermoelectric conversion layer in a covering mode, the thermoelectric units are arranged in an array mode and are connected with each other, and the thermoelectric units are of the negative Poisson ratio structure.
The heat absorbed by the heat conducting layer can not be conducted upwards from the heat insulating layer to the thermoelectric conversion layer, and can only be conducted from the hot end connected with the heat conducting layer to the cold end through the thermoelectric conversion layer, the cold end performs convection heat exchange with the external environment, the cold end and the hot end of the flexible thermoelectric device form a temperature difference, so that a potential difference is formed, load output voltage is realized, and the heat flow in the flexible thermoelectric device can only be conducted from the hot end to the cold end through the thermoelectric conversion layer, so that the heat exchange with the external environment is avoided, and the energy conversion performance is improved.
The thermoelectric unit is of a hollow concave hexagonal honeycomb structure, wherein the P-type thermoelectric legs, the N-type thermoelectric legs, first electrodes used for connecting adjacent P-type thermoelectric legs, second electrodes used for connecting adjacent N-type thermoelectric legs and insulating layers arranged between the P-type thermoelectric legs and the N-type thermoelectric legs are equal in number. When the flexible thermoelectric device is subjected to bending deformation in the wearing process, the thermoelectric legs in the thermoelectric unit move outwards to drive the electrodes to rotate and bend and deform, so that the thermoelectric unit is expanded to generate a negative poisson ratio effect, in the deformation process, displacement is mainly generated by the rotation and bending deformation of the electrodes, and the elastic deformation of the thermoelectric legs is negligible.
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.
Preferably, the lengths of the P-type thermoelectric leg and the N-type thermoelectric leg are twice that of the first electrode and the second electrode.
Preferably, an included angle formed by the P-type thermoelectric leg and the first electrode is equal to an included angle formed by the N-type thermoelectric leg and the second electrode, and the included angle ranges from 0 degrees to 90 degrees.
Preferably, the included angle ranges from 45 degrees to 60 degrees.
Preferably, the formula of the optimal angle of the included angle is:
Wherein, betaopt is the optimal included angle with the unit of degree, Hp is the thickness of the P type thermoelectric legs and the N type thermoelectric legs with the unit of m, and N is the number of the P type thermoelectric legs or the N type thermoelectric legs.
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. The P-type thermoelectric legs and the N-type thermoelectric legs are made of inorganic thermoelectric materials, so that the flexible thermoelectric device has good flexibility and bending strength, and meanwhile has good energy conversion performance, and is suitable for large-scale commercial application.
The invention also provides an application of the flexible thermoelectric device in wearable equipment.
The invention also provides an application of the flexible thermoelectric device in wearable medical equipment.
Compared with the prior art, the invention has the following beneficial effects:
1. The invention relates to a flexible thermoelectric device based on a negative poisson ratio structure, which comprises a heat conduction layer, a heat insulation layer, a thermoelectric conversion layer, a hot end, a cold end and a heat insulation packaging layer, wherein the heat conduction layer is used for being attached to human skin; the heat-insulating layer is arranged on the top of the heat-insulating layer, one end of the heat-insulating layer is abutted against the hot end, the cold end is arranged on the top of the heat-insulating layer and is positioned at one end far away from the hot end, the thermoelectric conversion layer is arranged on the top of the heat-insulating layer, one end of the thermoelectric conversion layer is connected with the hot end, the other end of the thermoelectric conversion layer is connected with the cold end, so that heat absorbed by the heat-insulating layer cannot be conducted upwards into the thermoelectric conversion layer, and can only be conducted from the hot end connected with the heat-insulating layer to the cold end through the thermoelectric conversion layer;
2. The thermoelectric conversion layer is formed by arranging a plurality of thermoelectric units which are arranged in an array and are connected with each other, and the thermoelectric units are of a negative poisson ratio structure, when the flexible thermoelectric device is bent and deformed in the wearing process, thermoelectric legs in the thermoelectric units move outwards to drive electrodes to rotate and bend and deform, so that the thermoelectric units expand to generate a negative poisson ratio effect; in the deformation process, displacement is mainly generated by rotation and bending deformation of the electrode, the elastic deformation of the thermoelectric legs is negligible, the flexible thermoelectric device is good in flexibility, good in bending strength and long in service life, and the thermoelectric legs are made of inorganic thermoelectric materials, so that the flexible thermoelectric device has good flexibility and bending strength, meanwhile, good energy conversion performance, and is suitable for large-scale commercial application, and is suitable for being applied to wearable equipment, particularly wearable medical equipment.
Drawings
Fig. 1 is a schematic structural diagram of a flexible thermoelectric device based on a negative poisson's ratio structure according to the present invention;
Fig. 2 is a schematic structural diagram of a thermoelectric conversion layer in a flexible thermoelectric device based on a negative poisson ratio structure according to the present invention;
FIG. 3 is an enlarged schematic view at A in FIG. 2;
FIG. 4 is a schematic diagram of a part of the structure of a thermoelectric unit in a flexible thermoelectric device based on a negative Poisson ratio structure according to the present invention;
Fig. 5 is a fatigue life test result of a flexible thermoelectric device based on a negative poisson's ratio structure and an existing homogeneous thermoelectric material provided by the present invention.
1, A heat conduction layer, 2, a heat insulation layer, 3, a thermoelectric conversion layer, 31, a thermoelectric unit, 311, a P-type thermoelectric leg, 312, an N-type thermoelectric leg, 313, a first electrode, 314, a second electrode, 315, an insulation layer, 4, a heat insulation packaging layer, 5, a hot end, 6 and a cold end.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, the invention provides a flexible thermoelectric device based on a negative poisson ratio structure, which comprises 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, wherein the heat conducting layer 1 is used for being attached to human skin to absorb heat continuously emitted by the human body to the outside, the hot end 5 is arranged at one end of the top of the heat conducting layer 1, the heat insulating layer 2 is arranged at the top of the heat conducting layer 1, one end of the heat insulating layer 2 is abutted against the hot end 5, the cold end 6 is arranged at the top of the heat insulating layer 2, the cold end 6 is positioned at one end far away from the hot end 5, the thermoelectric conversion layer 3 is arranged at the top of the heat insulating layer 2, one end of the thermoelectric conversion layer 3 is connected with the hot end 5, the other end is connected with the cold end 6, and the heat insulating packaging layer 4 is arranged at the top of the thermoelectric conversion layer 3 in a covering manner.
In this embodiment, the heat conducting layer 1 is made of a thin copper sheet, and copper has a large heat conductivity coefficient and good heat conducting property, so that heat emitted by a human body to the outside can be rapidly absorbed. The heat insulation layer 2 is made of polyimide, the heat insulation effect of the polyimide is good, heat absorbed by the heat conduction layer 1 from the skin of a human body is not conducted upwards from the heat insulation layer 2 to the thermoelectric conversion layer 3, only heat is conducted from a hot end 5 connected with the heat conduction layer 1 to a cold end 6 through the thermoelectric conversion layer 3, the cold end 6 performs 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, so that a potential difference is formed, and load output voltage is realized. The heat insulation packaging layer 4 is made of polyimide, the heat insulation effect of the polyimide is good, and heat flow in the flexible thermoelectric device can only be conducted from the hot end 5 to the cold end 6 through the thermoelectric conversion layer 3, so that heat exchange with the external environment is avoided, heat dissipation in the flexible thermoelectric device is effectively reduced, and the energy conversion performance of the flexible thermoelectric device is improved.
Referring to fig. 2 to 4, the thermoelectric conversion layer 3 includes a plurality of thermoelectric units 31 arranged in an array and connected to each other, and the thermoelectric units have a negative poisson's ratio structure. Specifically, 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, a second electrode 314 and an insulating layer 315, the first electrode 313 is used for connecting adjacent P-type thermoelectric legs 311, the second electrode 314 is used for connecting adjacent N-type thermoelectric legs 312, and the insulating layer 315 is arranged between the P-type thermoelectric legs 311 and the N-type thermoelectric legs 312. The number of the P-type thermoelectric legs 311, the N-type thermoelectric legs 312, and the insulating layer 315 are equal. The P-type thermoelectric leg 311, the N-type thermoelectric leg 312 and the insulating layer 315 have equal length, width and thickness, and in this embodiment, the P-type thermoelectric leg 311, the N-type thermoelectric leg 312 and the insulating layer 315 have a width of 1mm and a thickness of 2mm. The lengths of the first electrode 313 and the second electrode 314 are equal, and the lengths of the P-type thermoelectric legs 311 and the N-type thermoelectric legs 312 are twice as long as the lengths of the first electrode 313 and the second electrode 314, so that the first electrode 313 and the second electrode 314 can be rotationally bent and deformed.
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 outwards to drive the first electrode 313 and the second electrode 314 to rotate and bend and deform, so that the thermoelectric unit 31 expands to generate a negative poisson ratio effect. In the deformation process, the displacement is mainly generated by the rotation and bending deformation of the first electrode 313 and the second electrode 314, the elastic deformation of the P-type thermoelectric leg 311 and the N-type thermoelectric leg 312 is negligible, and the flexible thermoelectric device has good flexibility, good bending strength and long service life.
The P-type thermoelectric legs 311 and the N-type thermoelectric legs 312 are made of inorganic thermoelectric materials, and the inorganic thermoelectric materials have good energy conversion performance, so that the flexible thermoelectric device has good energy conversion performance and is suitable for large-scale commercialization, in this embodiment, the P-type thermoelectric legs 311 and the N-type thermoelectric legs 312 are made of bismuth telluride, and in other embodiments, the P-type thermoelectric legs 311 and the N-type thermoelectric legs 312 can also be made of antimony telluride, tin telluride, silver selenide, etc., so that the flexible thermoelectric device is not limited. The first electrode 313 and the second electrode 314 are made of copper, and the insulating layer 315 is made of polyimide.
The included angle formed by the P-type thermoelectric leg 311 and the first electrode 313 is equal to the included angle formed by the N-type thermoelectric leg 312 and the second electrode 314, and the included angle is in the range of 0-90 degrees, preferably, the included angle is in the range of 45-60 degrees. The included angle may be, but is not limited to, 45 °,50 °, 55 °, 60 °.
In the invention, the formula of the optimal angle of the included angle is as follows:
Wherein, betaopt is the optimal included angle in degrees, Hp is the thickness of the P-type thermoelectric legs 311 and the N-type thermoelectric legs 312 in m, and N is the number of the P-type thermoelectric legs 311 or the N-type thermoelectric legs 312.
When the included angle is the optimal angle, the internal stress of the flexible thermoelectric device is minimum, which is beneficial to improving the fatigue life of the flexible thermoelectric device, thereby improving the service life.
In order to further verify the advantages of the invention, fatigue life test analysis is carried out on the flexible thermoelectric device based on the negative poisson ratio structure and the conventional homogeneous thermoelectric material. The flexible thermoelectric device based on the negative poisson ratio structure is the same as the existing homogeneous thermoelectric material in total length, width and initial crack length.
As shown in FIG. 5, when the tensile strain is 20%, the conventional homogeneous thermoelectric material undergoes fatigue fracture after 6 stretching cycles, but when the angle between the P-type thermoelectric leg 311 and the first electrode 313 and the angle between the N-type thermoelectric leg 312 and the second electrode 314 are 30 degrees, the flexible thermoelectric device based on the negative Poisson ratio structure provided by the invention undergoes fatigue fracture after 1200 stretching cycles, when the angle between the P-type thermoelectric leg 311 and the first electrode 313 and the angle between the N-type thermoelectric leg 312 and the second electrode 314 are 45 degrees, the flexible thermoelectric device undergoes fatigue fracture after 3100 stretching cycles, and when the angle between the P-type thermoelectric leg 311 and the first electrode 313 and the angle between the N-type thermoelectric leg 312 and the second electrode 314 are 60 degrees, the flexible thermoelectric device based on the negative Poisson ratio structure undergoes fatigue fracture after 5600 stretching cycles. Compared with the existing homogeneous thermoelectric material, the flexible thermoelectric device based on the negative poisson ratio structure has the advantage that the fatigue life is remarkably prolonged.
The flexible thermoelectric device provided by the invention has the advantages of good energy conversion performance, good flexibility, capability of bearing deformation such as tension, bending and the like and long service life, and can be used in wearable equipment, in particular wearable medical equipment.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.