Flexible thermal diode with asymmetric streaming air passage structure and processing method of flexible thermal diode

Abstract

The invention provides a flexible thermal diode with an asymmetric streaming air passage structure, the flexible thermal diode comprises a flexible tube shell, the asymmetric streaming air passage structure and a hydrophilic liquid absorption core, the asymmetric streaming air passage structure and the hydrophilic liquid absorption core are arranged in the flexible tube shell, the asymmetric streaming air passage structure is made by 3D printing, and the hydrophilic liquid absorption core is provided with an upper layer and a lower layer. According to the 3D printing device, directional flow of gas can be controlled through the flow-around air channels so that directional heat transfer can be achieved, the asymmetric flow-around air channels and the hydrophilic liquid absorption core for 3D printing can be greatly bent, and the heat transfer performance cannot be reduced due to bending. The flexible thermal diode with the asymmetric streaming air passage structure not only inherits the directional efficient heat transfer advantage of a traditional thermal diode, but also breaks through the physical limitation of a rigid device through the innovation of materials and structures, and opens up a new direction for the next generation of thermal diode technology.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of microelectronic components, in particular to a flexible heat diode with an asymmetric flow channel structure and a processing method thereof. BACKGROUND

[0002] A heat diode is a high-efficiency one-way heat transfer component, widely used in the field of heat dissipation of electronic products. Moreover, due to its advantages such as one-way controllable heat conduction, high heat transfer rate, no need for external force input, compact structure, etc., it has been applied in various fields. At present, heat diodes are mostly gravity type diodes, which rely on gravity to drive the return flow of working medium in the heat pipe, and the working conditions are relatively harsh, with limited application scenarios.

[0003] As a device with one-way heat conduction characteristics, the heat diode functions similarly to a diode in electricity, allowing heat to efficiently transfer in a specific direction while significantly suppressing reverse heat flow. Its working principle is based on the phase change heat transfer mechanism: at the evaporation end, the working medium absorbs heat and undergoes phase change from liquid to gas. This process absorbs latent heat, significantly increasing the specific enthalpy of the working medium. The generated vapor flows to the condensing end under the combined action of pressure gradient (generated by acceleration pressure difference) and gravity field. At the condensing end, the vapor releases latent heat and recondenses into liquid, simultaneously transferring heat to the medium surrounding the condensing end, achieving efficient heat transfer.

[0004] The condensed liquid returns to the evaporation end under the driving of capillary force (generated by hydrophilic wicking structure) and gravity field. This process constitutes a closed heat circulation system. With the continuous repetition of evaporation and condensation processes, heat continuously transfers from the evaporation section to the condensing end in one direction, and the working medium circulates within the system without the need for external replenishment. This heat conduction mechanism based on phase change and fluid mechanics principles gives the heat diode extremely high heat conduction efficiency and direction selectivity, making it unique in the field of thermal management and having wide application prospects Due to the fact that traditional heat diodes mainly use rigid packaging structures (such as metal shells), they are difficult to meet the needs of flexible electronic devices, foldable devices and human thermal control systems. In this context, the flexible heat diode with an asymmetric flow channel structure not only retains the one-way heat control advantages of traditional heat diodes, but also overcomes the physical limitations of rigid components through material and structural innovation.

[0005] Based on the above problems, there is an urgent need to develop a heat diode that is flexible, has high heat rectification ratio, and adapts to complex working conditions to meet the needs of modern microelectronic devices. Therefore, a flexible heat diode with an asymmetric flow channel structure is proposed. SUMMARY

[0006] In order to meet the needs of flexible electronic devices, foldable devices and human body heat control systems, the purpose of the present application is to provide a flexible heat diode with an asymmetric flow channel structure and a processing method thereof. The flexible heat diode with an asymmetric flow channel structure has good flexibility, can adapt to various space limited environments, does not rely on gravity and can work stably under a certain inclination angle and bending working condition, and realizes effective directional heat transfer.

[0007] In one aspect, the present application provides a flexible heat diode with an asymmetric flow channel structure, comprising a flexible pipe shell, an asymmetric flow channel structure arranged inside the flexible pipe shell and a hydrophilic wicking core, the asymmetric flow channel structure is made of 3D printing, and the hydrophilic wicking core is provided with upper and lower layers.

[0008] Further, the flexible pipe shell is made of an aluminum plastic composite film, and the aluminum plastic composite film comprises a nylon outer layer, an aluminum foil and a polypropylene inner layer.

[0009] Further, the asymmetric flow channel structure is provided with a plurality of parallel flow channels, and the flow channel comprises a plurality of unit structures connected in sequence.

[0010] Further, the unit structure comprises a main channel and an arc-shaped channel, the main channel is a straight channel, the arc-shaped channel comprises a first arc, a second arc and a third arc, a first included angle is obtained by intersecting the tangent lines corresponding to the first arc and the second arc, the first included angle is less than 45°, a second included angle is obtained by intersecting the tangent lines corresponding to the second arc and the third arc, the second included angle is less than 180°; the arc-shaped channel comprises a first connecting end and a second connecting end, the first connecting end is the connection between the first arc and the main channel, the second connecting end is the connection between the third arc and the main channel, and the included angles between the first connecting end, the second connecting end and the main channel are all less than 45°.

[0011] Further, the unit structure comprises a first side small unit structure and a second side small unit structure, the second side small unit structure is obtained by mirroring the first side small unit structure and counterclockwise rotating 45° around the mirror axis, and the first side small unit structure and the second side small unit structure both contain the main channel and the arc-shaped channel.

[0012] Further, the length of the main channel of the first side small unit structure is 5mm, the gas channel width of the main channel of the first side small unit structure ranges from 1-1.4mm, and the gas channel width of the arc-shaped channel of the first side small unit structure ranges from 1-2.5mm.

[0013] Further, the first arc is a 7.4-7.5mm long arc corresponding to a R=6.8-7mm circle; the second arc is a 2.5mm long arc corresponding to a R=1.4-1.5mm circle; and the third arc is a 2mm long arc corresponding to a R=2.8-3mm circle.

[0014] Further, the hydrophilic wicking core is a chemically modified copper mesh with the same size as the asymmetric flow channel structure; and the hydrophilic wicking core is filled with liquid working medium, which is deionized water.

[0015] Further, the asymmetric flow channel structure is made of polycarbonate.

[0016] In another aspect, the present application also provides a processing method of the flexible thermal diode with the asymmetric flow channel structure, comprising the following steps: S1: preparing the hydrophilic wicking core: cutting the copper mesh, chemically modifying the copper mesh to obtain the hydrophilic copper mesh, then drying the hydrophilic copper mesh in a drying machine at 100℃ for 15 minutes, and then sealing the hydrophilic copper mesh in a sealed bag; S2: preparing the asymmetric flow channel structure: using a 3D printer to print the asymmetric flow channel structure; S3: preparing the internal structure of the flexible thermal diode: placing the prepared hydrophilic wicking core and asymmetric flow channel structure in the order from bottom to top, and the order is 2 layers of hydrophilic wicking core and asymmetric flow channel structure; S4: assembling the flexible thermal diode: placing the internal structure into the flexible tube shell, and then inserting the needle tip of the vacuum pump and the needle tip of the liquid injection tube into the two ends of the flexible tube shell, respectively; S5: sealing treatment: hot pressing the vacuum pump and the liquid injection tube between the flexible tube shell, and sealing the connection position of the vacuum pump, the liquid injection tube and the flexible tube shell by using epoxy resin; S6: vacuum treatment: vacuumizing through the vacuum pump and then clamping the vacuum pump; S7: liquid injection treatment: injecting a small amount of liquid working medium into the flexible tube shell through the liquid injection tube, discharging the air existing in the connection position of the liquid injection tube and the flexible tube shell into the thermal diode, and then clamping the liquid injection tube; S8: secondary degassing: opening the vacuum pump for secondary degassing, and then clamping the vacuum pump again.

[0017] Compared with existing technologies, the advantages of this invention are as follows: the flexible thermal diode with an asymmetric flow channel structure can not only achieve directional heat transfer by controlling the directional flow of gas through the flow channel, but also the 3D-printed flexible channel and hydrophilic liquid-absorbing core can be bent significantly without performance degradation due to bending. This flexible thermal diode with an asymmetric flow channel structure not only inherits the directional and efficient heat transfer advantages of traditional thermal diodes, but also breaks through the physical limitations of rigid devices through material and structural innovation, opening up new directions for next-generation thermal diode technology. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is an exploded view of the internal structure of the flexible thermal diode with an asymmetric flow channel structure according to an embodiment of the present invention. Figure 2 This is a three-dimensional structural diagram of the airway structure according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the airway structure unit according to an embodiment of the present invention; Figure 4 This is a plan view of the airway structure according to an embodiment of the present invention; Figure 5 This is an exploded view of the overall structure of the flexible thermal diode with an asymmetric flow channel structure according to an embodiment of the present invention. Figure 6 This is a schematic diagram of the injection tube and vacuum tube used in the embodiments of the present invention.

[0020] Explanation of reference numerals in the attached figures: 1: Vacuum tube; 2: Asymmetric flow channel structure; 3: Liquid injection tube; 4: Hydrophilic liquid absorption core; 5: Flexible tube shell; 6: Flat-head needle tube; 7: Nylon cable tie; 8: Heat shrink tubing; 9: Metal tube. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this 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. Therefore, they should not be construed as limiting this invention.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] Example 1 like Figures 1 to 6 As shown, this invention provides a flexible thermal diode with an asymmetric flow channel structure, comprising a flexible shell 5, an asymmetric flow channel structure 2 disposed inside the flexible shell 5, and a hydrophilic liquid-absorbing core 4. The asymmetric flow channel structure 2 is 3D printed, and the hydrophilic liquid-absorbing core 4 has upper and lower layers. A vacuum tube 1 and a liquid injection tube 3 are respectively disposed at both ends of the asymmetric flow channel structure 2. The arrangement from top to bottom is: 3D printed asymmetric flow channel structure 2 - hydrophilic liquid-absorbing core 4 - hydrophilic liquid-absorbing core 4.

[0025] The flexible housing 5 is made of an aluminum-plastic composite film, which includes a nylon outer layer, an aluminum foil, and a polypropylene inner layer. The internal structure of the flexible thermal diode is hot-pressed between the two polypropylene inner layers. During hot pressing, the two polypropylene inner layers melt and bond together to achieve a sealing effect.

[0026] The asymmetric flow channel structure 2 has several parallel flow channels, each comprising several sequentially connected unit structures. Each unit structure includes a main channel and an arc-shaped channel. The main channel is a straight channel. The arc-shaped channel includes a first arc segment, a second arc segment, and a third arc segment. A first angle, less than 45°, is formed by the intersection of the tangents of the first and second arc segments. A second angle, less than 180°, is formed by the intersection of the tangents of the second and third arc segments. The arc-shaped channel includes a first connecting end and a second connecting end. The first connecting end is where the first arc segment connects to the main channel, and the second connecting end is where the third arc segment connects to the main channel. The angles formed between the first and second connecting ends and the main channel are both less than 45°.

[0027] The unit structure includes a first side small unit structure and a second side small unit structure. The second side small unit structure is obtained by mirroring the first side small unit structure and rotating it counterclockwise by 45° around its mirror axis. Both the first side small unit structure and the second side small unit structure include a main channel and an arc-shaped channel.

[0028] The length of the main channel of the first side small unit structure is 5mm, the width of the gas channel of the main channel of the first side small unit structure is in the range of 1-1.4mm, and the width of the gas channel of the arc-shaped channel of the first side small unit structure is in the range of 1-2.5mm.

[0029] The first arc segment is an arc segment with a length of 7.4-7.5mm corresponding to a circle with R=6.8-7mm; the second arc segment is an arc segment with a length of 2.5mm corresponding to a circle with R=1.4-1.5mm; and the third arc segment is an arc segment with a length of 2mm corresponding to a circle with R=2.8-3mm.

[0030] The hydrophilic liquid-absorbing core 4 is a chemically modified copper mesh, and its size is the same as that of the asymmetric flow channel structure 2; the hydrophilic liquid-absorbing core 4 is filled with a liquid working medium, which is deionized water.

[0031] The 3D-printed asymmetric flow channel structure is made of polycarbonate, which not only enables efficient unidirectional heat transfer, but also allows for significant bending while maintaining stable operation.

[0032] This invention also provides a method for fabricating a flexible thermal diode with an asymmetric flow channel structure, specifically including the following steps: S1. Making a hydrophilic absorbent core: Cut copper mesh, chemically modify the copper mesh to obtain a hydrophilic copper mesh; then put it into a dryer and dry it at 100℃ for 15 minutes, and then seal it in a sealed bag; S2 Fabrication of asymmetric flow-around airway structure 2: Using a 3D printer to print asymmetric flow-around airway structure 2; S3 fabricates the internal structure of a flexible thermal diode: The completed hydrophilic liquid-absorbing core and asymmetric flow channel structure 2 are arranged in order from bottom to top, with the order being 2 layers of hydrophilic liquid-absorbing core and asymmetric flow channel structure 2. S4 Assembly of Flexible Thermal Diode: The internal structure is installed inside the flexible tube shell 5, and then the tips of the vacuum tube needle and the liquid injection tube needle are inserted into the two ends of the flexible tube shell 5 respectively. S5 Sealing treatment: Both the vacuum tube and the liquid injection tube are hot-pressed between the flexible tube shell 5, and epoxy resin is applied to the connection between the vacuum tube, the liquid injection tube and the flexible tube shell 5 for sealing. S6 Vacuuming process: After vacuuming through the vacuum tube, the vacuum tube is clamped. S7 Liquid Injection Processing: A small amount of liquid working fluid is injected into the flexible tube shell 5 through the injection tube, and the air present at the connection between the injection tube and the flexible tube shell 5 is discharged into the interior of the thermal diode. Then the injection tube is clamped. S8 Secondary Degassing: After opening the vacuum tube for secondary degassing, clamp the vacuum tube again.

[0033] The preparation method of vacuum tube 1 and liquid injection tube 3 is as follows: First, cut two heat shrink tubes 8 of a certain length. One end of the heat shrink tube 8 is connected to a custom metal tube 9, and the other end is connected to a flat-head needle tube. Then, heat the two connection points with a hot air gun to heat shrink the heat shrink tubes into shape, and further tighten the two connection points with nylon cable ties to finally obtain vacuum tube 1 and liquid injection tube 3.

[0034] The working principle of this invention is as follows: Under normal circumstances, the end containing the injection tube 3 is the evaporation end, and the other end is the condensation end, at which point the flexible thermal diode is in a forward heat transfer state. When the electronic device chip starts working, the temperature of the evaporation end rises along with the chip temperature. Heat is rapidly transferred to the inside of the tube, causing the liquid working medium adsorbed on the hydrophilic wick 4 at the evaporation end to be heated and evaporate. The evaporated vapor enters the vapor channel, and most of the vapor flows to the condensation end through the main channel. Due to the lower temperature at the condensation end, the vapor condenses into liquid at the condensation end, releasing heat during the phase change process. The condensed liquid drips onto the hydrophilic wick 4 at the condensation end and flows into the interior of the hydrophilic wick 4. The liquid working medium on the outer surface of the hydrophilic wick 4 evaporates due to heat, while the liquid working medium inside the hydrophilic wick 4 moves towards the surface under the action of capillary force, thus continuously transferring liquid from the condensation end to the evaporation end. This process is continuous, transferring heat from the evaporation end to the condensation end, thereby reducing the heat flux density of the heat source and achieving the purpose of heat dissipation. When the ambient temperature is higher than the temperature of the electronic device chip, one end containing the vacuum tube 1 is the evaporation end and the other end is the condensation end. At this time, the flexible thermal diode is in the reverse heat transfer state. When the liquid working fluid at the evaporation end is heated and evaporates, the steam enters the steam channel. Due to the small angle between the first connection end and the main channel, the steam splits into two at the first connection end. One part of the steam enters the arc channel, and the other part enters the main channel. Due to the existence of the first angle formed by the intersection of the tangents of the first and second arc segments, the steam changes its flow direction (to the opposite of the initial direction). Under the transition of the second angle formed by the intersection of the tangents of the second and third arc segments, the steam that initially entered the arc channel collides in the opposite direction with the steam that initially entered the main channel after flowing out of the arc channel. This blocks the steam coming from the main channel, increasing the reverse flow resistance in the entire steam channel. As a result, the liquid working fluid cannot flow to the condensation end in time after vaporization at the evaporation end. Since the evaporation end is constantly heated, the liquid working fluid at the evaporation end will slowly evaporate, disrupting the internal circulation of the thermal diode. Therefore, this achieves the purpose of protecting electronic devices.

[0035] Example 2 A flexible thermal diode with an asymmetric flow channel structure can not only maintain stable and efficient operation under normal working conditions, with the same effect as in Example 1, but also maintain stable operation under large bending conditions (i.e., bending the flexible thermal diode by 30-90°).

[0036] 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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A flexible thermal diode with an asymmetric flow channel structure, characterized in that, It includes a flexible tube shell (5), an asymmetric flow channel structure (2) disposed inside the flexible tube shell (5), and a hydrophilic liquid-absorbing core (4). The asymmetric flow channel structure (2) is made by 3D printing, and the hydrophilic liquid-absorbing core (4) is provided with upper and lower layers.

2. The flexible thermal diode with an asymmetric flow channel structure according to claim 1, characterized in that, The flexible tube shell (5) is made of aluminum-plastic composite film, which includes a nylon outer layer, aluminum foil and a polypropylene inner layer.

3. The flexible thermal diode with an asymmetric flow channel structure according to claim 1, characterized in that, The asymmetric flow channel structure (2) has several parallel flow channels, and the flow channels include several unit structures connected in sequence.

4. The flexible thermal diode with an asymmetric flow channel structure according to claim 3, characterized in that, The unit structure includes a main channel and an arc-shaped channel. The main channel is a straight channel. The arc-shaped channel includes a first arc segment, a second arc segment, and a third arc segment. The first included angle formed by the intersection of the tangents of the first arc segment and the second arc segment is less than 45°. The second included angle formed by the intersection of the tangents of the second arc segment and the third arc segment is less than 180°. The arc-shaped channel includes a first connecting end and a second connecting end. The first connecting end is the connection point between the first arc segment and the main channel, and the second connecting end is the connection point between the third arc segment and the main channel. The included angles formed between the first connecting end and the second connecting end and the main channel are both less than 45°.

5. The flexible thermal diode with an asymmetric flow channel structure according to claim 4, characterized in that, The unit structure includes a first side small unit structure and a second side small unit structure. The second side small unit structure is obtained by mirroring the first side small unit structure and rotating it counterclockwise by 45° around its mirror axis. Both the first side small unit structure and the second side small unit structure include a main channel and an arc-shaped channel.

6. The flexible thermal diode with an asymmetric flow channel structure according to claim 5, characterized in that, The length of the main channel of the first side small unit structure is 5mm, the width of the gas channel of the main channel of the first side small unit structure is in the range of 1-1.4mm, and the width of the gas channel of the arc-shaped channel of the first side small unit structure is in the range of 1-2.5mm.

7. The flexible thermal diode with an asymmetric flow channel structure according to claim 6, characterized in that, The first arc segment is an arc segment with a length of 7.4-7.5mm corresponding to a circle with R=6.8-7mm; the second arc segment is an arc segment with a length of 2.5mm corresponding to a circle with R=1.4-1.5mm; and the third arc segment is an arc segment with a length of 2mm corresponding to a circle with R=2.8-3mm.

8. The flexible thermal diode with an asymmetric flow channel structure according to claim 1, characterized in that, The hydrophilic liquid-absorbing core (4) is a chemically modified copper mesh, and its size is the same as that of the asymmetric flow channel structure (2); the hydrophilic liquid-absorbing core (4) is filled with a liquid working medium, which is deionized water.

9. The flexible thermal diode with an asymmetric flow channel structure according to claim 1, characterized in that, The asymmetric flow channel structure (2) is made of polycarbonate.

10. A method for fabricating a flexible thermal diode with an asymmetric flow channel structure as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. Making a hydrophilic absorbent core: Cut copper mesh, chemically modify the copper mesh to obtain a hydrophilic copper mesh; then put it into a dryer and dry it at 100℃ for 15 minutes, and then seal it in a sealed bag; S2 Fabrication of asymmetric flow channel structure (2): Printing asymmetric flow channel structure (2) using a 3D printer. S3 Fabrication of the internal structure of the flexible thermal diode: The completed hydrophilic liquid-absorbing core and asymmetric flow channel structure (2) are arranged in order from bottom to top, with the order being 2 layers of hydrophilic liquid-absorbing core and asymmetric flow channel structure (2). S4 Assembly of Flexible Thermal Diode: The internal structure is installed into the flexible tube shell (5), and then the tip of the vacuum tube needle and the tip of the liquid injection tube needle are inserted into the two ends of the flexible tube shell (5) respectively. S5 Sealing treatment: The vacuum tube and the liquid injection tube are both hot-pressed between the flexible tube shell (5), and epoxy resin is applied to the connection between the vacuum tube, the liquid injection tube and the flexible tube shell (5) for sealing. S6 Vacuuming process: After vacuuming through the vacuum tube, the vacuum tube is clamped. S7 Liquid injection process: A small amount of liquid working medium is injected into the flexible tube shell (5) through the liquid injection tube, and the air at the connection between the liquid injection tube and the flexible tube shell (5) is discharged into the thermal diode. Then the liquid injection tube is clamped. S8 Secondary Degassing: After opening the vacuum tube for secondary degassing, clamp the vacuum tube again.

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