A moisture-absorbing expansion heat dissipation method and system

Abstract

The application discloses a moisture-absorbing expansion heat dissipation method and system, and relates to the technical field of heat management. The moisture-absorbing expansion heat dissipation structure comprises a gradient moisture-absorbing expansion layer with orthogonal anisotropic grids, the average pore diameter and the hemicellulose content of the gradient moisture-absorbing expansion layer increase from a first side to a second side along the thickness direction. After the gradient moisture-absorbing expansion layer absorbs ambient moisture, anisotropic moisture-absorbing deformation is generated, the difference in the hemicellulose content is utilized to promote the migration of the moisture to the second side, and the moisture transport is pushed by the moisture-absorbing deformation compression pores. The heat generated by a heat dissipation object causes the moisture transported to the second side to desorb and vaporize, heat dissipation is realized, and thus the problem that the moisture is difficult to be effectively transported to the vaporization heat dissipation position in the moisture-absorbing heat dissipation process is solved.

Description

Technical Field

[0001] This invention relates to the field of thermal management technology, and specifically to a method and system for heat dissipation through moisture absorption and expansion. Background Technology

[0002] As electronic devices, energy units, and other equipment generate increasing amounts of heat during operation, heat dissipation performance significantly impacts their operational stability. Existing heat dissipation methods include active and passive cooling. Passive cooling, requiring no additional power source, offers advantages such as simple structure and low energy consumption. In passive cooling, hygroscopic materials absorb moisture from the external environment. During heat exchange between the hygroscopic material and the object being cooled, the desorption and vaporization of the moisture carries away heat, thus achieving heat dissipation.

[0003] However, in existing moisture-absorbing evaporative cooling structures, the transfer of moisture within the structure after absorbing moisture from the external environment is easily limited by the material's own mass transfer capacity, making it difficult for some moisture to be transported to suitable locations for vaporization in a timely manner. Consequently, the moisture absorption process and the subsequent vaporization and heat dissipation process cannot be well coordinated, thus affecting the heat dissipation effect of the moisture-absorbing evaporative cooling structure. Summary of the Invention

[0004] The main objective of this invention is to provide a method and system for moisture absorption and expansion heat dissipation. This addresses the problem of effectively transporting absorbed moisture to the vaporization heat dissipation location during the moisture absorption and heat dissipation process, achieving directional transport of moisture within the moisture absorption and expansion heat dissipation structure, and utilizing the vaporization of the transported water to dissipate heat from the object being cooled.

[0005] To achieve the above objectives, the embodiments of this application provide the following technical solutions: According to a first aspect of the embodiments of this application, a moisture absorption, expansion, and heat dissipation method is provided, comprising: The moisture-absorbing and expansion heat dissipation structure is connected to the object to be cooled by heat exchange. The moisture-absorbing and expansion heat dissipation structure includes a gradient moisture-absorbing and expansion layer. The gradient moisture-absorbing and expansion layer includes multiple gradient regions arranged from a first side to a second side along the thickness direction and has an orthogonal anisotropic grid. In two adjacent gradient regions, the average pore size of the gradient region closer to the second side is greater than the average pore size of the gradient region closer to the first side, and the hemicellulose content of the gradient region closer to the second side is greater than the hemicellulose content of the gradient region closer to the first side. The gradient moisture-absorbing expansion layer absorbs moisture from the external environment, causing the orthogonal anisotropic mesh to undergo moisture-absorbing deformation. The degree of expansion in the thickness direction is greater than the degree of expansion in the in-plane direction perpendicular to the thickness direction. By utilizing the difference in hemicellulose content between two adjacent gradient regions, moisture in the gradient moisture-absorbing expansion layer migrates to the second side, and the moisture-absorbing deformation compresses the pores in the gradient moisture-absorbing expansion layer to promote the transport of moisture to the second side. The heat generated by the object to be cooled is transferred to the moisture transported to the second side, causing the moisture to desorb from the gradient hygroscopic expansion layer and vaporize, thereby cooling the object to be cooled.

[0006] Optionally, the gradient hygroscopic expansion layer further includes a moisture-regulating component; the step of allowing moisture in the external environment to be absorbed by the gradient hygroscopic expansion layer includes: This allows water vapor from the external environment to enter the gradient moisture-absorbing expansion layer; The water vapor is captured by the pores in the gradient region near the first side, thus obtaining captured moisture; The captured water is stored using the moisture conditioning component or the retention and release of the captured water are regulated to obtain water to be transported. The hemicellulose absorbs the water to be transported.

[0007] Optionally, the gradient hygroscopic expansion layer further includes a skeleton component; the process of causing the orthogonal anisotropic mesh to undergo hygroscopic deformation includes: The hemicellulose absorbs water and swells; By using the skeleton components to restrict the expansion of the orthogonal anisotropic mesh along the in-plane direction, the orthogonal anisotropic mesh expands along the thickness direction, resulting in the moisture-absorbing deformation. The moisture-absorbing deformation is used to compress the pores within the gradient moisture-absorbing expansion layer, thereby driving the moisture within the pores to move along the thickness direction.

[0008] Optionally, the step of utilizing the difference in hemicellulose content between two adjacent gradient regions to cause moisture in the gradient hygroscopic expansion layer to migrate to the second side, and utilizing the hygroscopic deformation to compress the pores in the gradient hygroscopic expansion layer to promote the transport of moisture to the second side, includes: According to the arrangement order of the multiple gradient regions from the first side to the second side, the moisture in the current gradient region migrates to the next gradient region based on the difference in hemicellulose content between the current gradient region and the next adjacent gradient region that is close to the second side. During the migration of moisture to the next gradient region, the hygroscopic deformation compresses the pores in the current gradient region to push the moisture into the next gradient region. According to the arrangement order of the multiple gradient regions, the gradient region closest to the second side is used as the next gradient region for water migration and pore compression until the water is transported to the gradient region closest to the second side.

[0009] Optionally, before connecting the moisture-absorbing expansion heat dissipation structure to the object to be cooled in a heat exchange manner, the method further includes: The first surface of the unidirectional moisture-wicking layer is attached to the second side of the gradient moisture-absorbing expansion layer. The unidirectional moisture-wicking layer also includes a second surface that is away from the gradient moisture-absorbing expansion layer. The first surface has a greater wettability to water than the second surface. A breathable and shape-conserving support layer is placed on the side of the unidirectional moisture-wicking layer that is away from the gradient moisture-absorbing and expansion layer.

[0010] Optionally, before connecting the moisture-absorbing expansion heat dissipation structure to the object to be cooled through heat exchange, the method further includes preparing the gradient moisture-absorbing expansion layer; the preparation of the gradient moisture-absorbing expansion layer includes: Prepare a first printing material, a second printing material, and a third printing material, wherein the second printing material includes hemicellulose; The first printing material, the second printing material, and the third printing material are respectively fed into the corresponding channels of the multi-channel coaxial printhead; Coaxial composite fibers are obtained by extruding the first printing material, the second printing material, and the third printing material through the multi-channel coaxial printing nozzle. The coaxial composite fibers are printed layer by layer to obtain a printed blank; The printed blank is post-processed to obtain the gradient moisture-absorbing expansion layer.

[0011] Optionally, the step-by-step printing of the coaxial composite fibers to obtain a printed preform includes: The coaxial composite fibers are printed parallel to the in-plane direction to obtain the first fiber layer; The coaxial composite fibers are printed parallel to the second in-plane direction on the first fiber layer to obtain the second fiber layer, wherein the second in-plane direction is perpendicular to the first in-plane direction. The coaxial composite fibers are printed layer by layer alternately in the first in-plane direction and the second in-plane direction to obtain a printed blank with the orthogonal anisotropic mesh.

[0012] Optionally, the step of printing the coaxial composite fiber layer by layer to obtain a printed blank further includes: Multiple fiber layers to be printed are divided into multiple printing layer groups arranged along the printing height direction, each of the printing layer groups is used to form a gradient region, and the printing height direction corresponds to the thickness direction; Based on the arrangement of each printing layer group along the printing height direction, the extrusion amount of the first printing material, the extrusion amount of the second printing material, and the extrusion amount of the third printing material corresponding to each printing layer group are determined respectively, so that the proportion of the second printing material corresponding to the printing layer group closer to the second side in two adjacent printing layer groups is greater than the proportion of the second printing material corresponding to the printing layer group closer to the first side. According to the first printing material extrusion amount, the second printing material extrusion amount, and the third printing material extrusion amount corresponding to each printing layer group, each printing layer group is printed sequentially, so that the hemicellulose content of the gradient region closer to the second side in two adjacent gradient regions is greater than the hemicellulose content of the gradient region closer to the first side.

[0013] Optionally, the post-processing of the printed preform to obtain the gradient moisture-absorbing expansion layer includes: The printed preform is subjected to a wet heat treatment, which causes the hemicellulose to absorb moisture and causes the expansion of the printed preform along the thickness direction to be greater than the expansion along the in-plane direction, thus obtaining a wet heat-treated preform. The wet-heat treated green body is dried to obtain a dried green body; The first side of the dried blank is subjected to hydrophilic treatment to obtain the gradient moisture-absorbing expansion layer.

[0014] According to a second aspect of the embodiments of this application, a moisture absorption and expansion heat dissipation system is provided, comprising: A heat exchange connection module is used to connect a moisture-absorbing expansion heat dissipation structure to an object to be cooled via heat exchange. The moisture-absorbing expansion heat dissipation structure includes a gradient moisture-absorbing expansion layer. The gradient moisture-absorbing expansion layer includes multiple gradient regions arranged along the thickness direction from a first side to a second side and has an orthogonal anisotropic grid. In two adjacent gradient regions, the average pore size of the gradient region closer to the second side is greater than the average pore size of the gradient region closer to the first side, and the hemicellulose content of the gradient region closer to the second side is greater than the hemicellulose content of the gradient region closer to the first side. A moisture-absorbing deformation module is used to allow moisture in the external environment to be absorbed by the gradient moisture-absorbing expansion layer, so that the orthogonal anisotropic mesh undergoes moisture-absorbing deformation. The degree of expansion in the thickness direction is greater than the degree of expansion in the in-plane direction perpendicular to the thickness direction. A moisture transport module is used to utilize the difference in hemicellulose content between two adjacent gradient regions to cause moisture in the gradient moisture-absorbing expansion layer to migrate to the second side, and to use the moisture-absorbing deformation to compress the pores in the gradient moisture-absorbing expansion layer to promote the transport of moisture to the second side. The heat dissipation module is used to transfer the heat generated by the object to be cooled to the moisture transported to the second side, so that the moisture is desorbed and vaporized from the gradient hygroscopic expansion layer, thereby dissipating heat from the object to be cooled.

[0015] According to a third aspect of the present application, an electronic device is provided, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method described in the first aspect above.

[0016] According to a fourth aspect of the embodiments of this application, a computer-readable storage medium is provided having computer-readable instructions stored thereon, the computer-readable instructions being executable by a processor to implement the method described in the first aspect above.

[0017] In summary, this application provides a moisture-absorbing expansion heat dissipation method and system. By connecting a moisture-absorbing expansion heat dissipation structure to an object to be cooled through heat exchange, the moisture-absorbing expansion heat dissipation structure includes a gradient moisture-absorbing expansion layer. This gradient moisture-absorbing expansion layer includes multiple gradient regions arranged along the thickness direction from a first side to a second side, and has orthogonal anisotropic grids. In two adjacent gradient regions, the average pore size of the gradient region closer to the second side is larger than the average pore size of the gradient region closer to the first side, and the hemicellulose content of the gradient region closer to the second side is greater than the hemicellulose content of the gradient region closer to the first side. This allows moisture from the external environment to be absorbed by the gradient moisture-absorbing expansion layer, thereby making the orthogonal anisotropic grids... Anisotropic mesh undergoes hygroscopic deformation, with the expansion in the thickness direction being greater than the expansion in the in-plane direction perpendicular to the thickness direction. Utilizing the difference in hemicellulose content between adjacent gradient regions, moisture within the gradient hygroscopic expansion layer migrates to the second side. The hygroscopic deformation compresses the pores within the gradient hygroscopic expansion layer, further promoting moisture transport to the second side. Heat generated by the object to be cooled is transferred to the moisture transported to the second side, causing the moisture to desorb from the gradient hygroscopic expansion layer and vaporize, thus dissipating heat from the object. This addresses the problem of effectively transporting absorbed moisture to the vaporization cooling location during hygroscopic heat dissipation, achieving directional transport of moisture within the hygroscopic expansion heat dissipation structure, and utilizing the vaporization of transported water to dissipate heat from the object. Attached Figure Description

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

[0019] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0020] Figure 1 A flowchart of a moisture absorption, expansion, and heat dissipation method provided in an embodiment of this application; Figure 2 A schematic diagram of the overall structure of the biomimetic moisture-absorbing, expansion, and heat-dissipating structure provided in the embodiments of this application; Figure 3 The dual gradient variation curve provided in the embodiments of this application; Figure 4 This is a schematic diagram showing the deformation comparison of the embodiments of this application; Figure 5 The structural diagram of the three-channel coaxial printing device and the schematic diagram of the cross-sectional structure of the shell-shell-core fiber are provided in the embodiments of this application. Figure 6 A comparative curve showing the change of interface temperature over time at a given heat flux density, provided for embodiments of this application; Figure 7 Infrared thermal image comparison diagram provided for embodiments of this application; Figure 8 The equivalent heat dissipation flux attenuation curve provided in the embodiments of this application; Figure 9 This is a schematic diagram of a moisture absorption and expansion heat dissipation system provided in an embodiment of this application; Figure 10 A structural diagram of an electronic device provided in an embodiment of this application; Figure 11 A diagram of a computer-readable storage medium provided in an embodiment of this application.

[0021] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0024] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0025] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0026] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0027] Figure 1 This application illustrates a moisture absorption, expansion, and heat dissipation method according to an embodiment, comprising: Step 101: Connect the moisture-absorbing expansion heat dissipation structure to the object to be cooled via heat exchange. The moisture-absorbing expansion heat dissipation structure includes a gradient moisture-absorbing expansion layer. The gradient moisture-absorbing expansion layer includes multiple gradient regions arranged along the thickness direction from the first side to the second side and has an orthogonal anisotropic grid. In two adjacent gradient regions, the average pore size of the gradient region closer to the second side is greater than the average pore size of the gradient region closer to the first side, and the hemicellulose content of the gradient region closer to the second side is greater than the hemicellulose content of the gradient region closer to the first side. Step 102: The gradient moisture-absorbing expansion layer absorbs moisture from the external environment, causing the orthogonal anisotropic mesh to undergo moisture-absorbing deformation. The degree of expansion in the thickness direction is greater than the degree of expansion in the in-plane direction perpendicular to the thickness direction. Step 103: Utilizing the difference in hemicellulose content between two adjacent gradient regions, the moisture in the gradient moisture-absorbing expansion layer migrates to the second side, and the moisture-absorbing deformation compresses the pores in the gradient moisture-absorbing expansion layer to promote the transport of the moisture to the second side; Step 104: Transfer the heat generated by the object to be cooled to the moisture transported to the second side, so that the moisture is desorbed from the gradient hygroscopic expansion layer and vaporized, thereby cooling the object to be cooled.

[0028] In this embodiment, a hygroscopic expansion heat dissipation method is provided. The aim is to improve the transport capacity of moisture within the heat dissipation structure during the hygroscopic heat dissipation process, enabling the continuous transport of moisture absorbed from the external environment to suitable locations for desorption and vaporization. The heat generated by the object being cooled further promotes water decomposition and vaporization, thus forming a passive heat dissipation process that integrates environmental moisture absorption, moisture transport, and vaporization heat dissipation. Compared to methods that rely solely on the natural diffusion of moisture within the material, this embodiment utilizes the component gradient of the gradient hygroscopic expansion layer and the hygroscopic deformation to jointly promote moisture transport along the thickness direction, thereby improving the utilization rate of absorbed moisture and the continuity of the heat dissipation process.

[0029] In step 101, a heat exchange connection is established between the hygroscopic expansion heat dissipation structure and the object to be cooled, allowing the heat generated by the object to be transferred to the hygroscopic expansion heat dissipation structure. The gradient hygroscopic expansion layer forms multiple gradient regions along its thickness from the first side to the second side. These different gradient regions exhibit continuous variations in average pore size and hemicellulose content, with the average pore size and hemicellulose content increasing closer to the second side. This creates differences in pore structure and hygroscopic components distributed along the thickness direction within the same gradient hygroscopic expansion layer, providing a structural basis for the absorption, retention, and subsequent transport of moisture from the external environment along the thickness direction. Simultaneously, the gradient hygroscopic expansion layer possesses an orthogonal anisotropic grid, enabling it to undergo directional deformation after absorbing moisture.

[0030] In steps 102 and 103, after moisture from the external environment enters and is absorbed by the gradient hygroscopic expansion layer, the hemicellulose absorbs water and expands, causing the orthotropic mesh to undergo hygroscopic deformation. Since the expansion along the thickness direction of the orthotropic mesh is greater than that along the in-plane direction, the volume change during hygroscopic absorption is primarily manifested as deformation along the thickness direction. Simultaneously, differences in hemicellulose content exist between adjacent gradient regions, allowing moisture to migrate from areas with lower hemicellulose content to areas with higher hemicellulose content, thus creating a moisture migration trend towards the second side. Furthermore, the hygroscopic deformation along the thickness direction further compresses some pores within the gradient hygroscopic expansion layer, pushing the moisture within the pores and continuing to transport it towards the second side. Therefore, this embodiment does not rely solely on a single moisture diffusion process, but combines moisture migration formed by the hemicellulose content gradient with the hygroscopic deformation generated by the orthotropic mesh to promote moisture transport along a predetermined direction.

[0031] In step 104, after the moisture is transported to a position near the second side, the heat generated by the object to be cooled is transferred to the moisture through the hygroscopic expansion heat dissipation structure, causing the moisture to desorb from the gradient hygroscopic expansion layer and further vaporize. During the desorption and vaporization process, the moisture absorbs the heat transferred from the object to be cooled and leaves the gradient hygroscopic expansion layer in the form of water vapor, thereby carrying away some of the heat generated by the object to be cooled. Through the above process, the moisture obtained by the gradient hygroscopic expansion layer from the external environment can participate in heat dissipation through absorption, directional transport, and desorption and vaporization, so that the moisture acquisition process and the heat release process are continuously coordinated, thereby improving the ability to passively dissipate heat using environmental moisture.

[0032] In one possible implementation, before the hygroscopic expansion heat dissipation structure is connected to the object to be cooled for heat exchange, the method further includes: attaching a first surface of the unidirectional moisture-wicking layer to a second side of the gradient moisture-wicking expansion layer, wherein the unidirectional moisture-wicking layer also includes a second surface facing away from the gradient moisture-wicking expansion layer, and the first surface has a greater wettability to water than the second surface; and disposing a breathable shape-conserving support layer on the side of the unidirectional moisture-wicking layer facing away from the gradient moisture-wicking expansion layer.

[0033] In one possible implementation, after the moisture is desorbed and vaporized from the gradient hygroscopic expansion layer, the method further includes: allowing the water vapor formed by the vaporization of the moisture to enter the one-way moisture-wicking layer from the second side of the gradient hygroscopic expansion layer; and allowing the water vapor passing through the one-way moisture-wicking layer to be discharged to the external environment through the breathable shape-conserving support layer.

[0034] In one possible implementation, the one-way moisture-wicking layer comprises a fiber membrane with different wettability, the water contact angle of the first surface of the one-way moisture-wicking layer is not greater than 15°, and the water contact angle of the second surface of the one-way moisture-wicking layer is not less than 120°; the breathable and conformal support layer comprises a mesh structure with interconnected pores to allow water vapor to be discharged through the breathable and conformal support layer.

[0035] In one possible implementation, the gradient hygroscopic expansion layer further includes a moisture-regulating component; in step 102, the step of absorbing moisture from the external environment by the gradient hygroscopic expansion layer includes: allowing water vapor from the external environment to enter the gradient hygroscopic expansion layer; capturing the water vapor using pores in the gradient region near the first side to obtain captured moisture; storing the captured moisture using the moisture-regulating component or regulating the retention and release of the captured moisture to obtain moisture to be transported; and allowing the hemicellulose to absorb the moisture to be transported.

[0036] In one possible implementation, the gradient hygroscopic expansion layer further includes a moisture conditioning component. When moisture from the external environment is absorbed by the gradient hygroscopic expansion layer, water vapor from the external environment enters the layer and comes into contact with pores in the gradient region near the first side. Because the gradient region near the first side has a relatively small average pore size, the pores can be used to capture the water vapor entering the gradient hygroscopic expansion layer, converting at least a portion of the water vapor into captured moisture that can be retained within the layer. The moisture conditioning component further stores the captured moisture or regulates the retention and release process of the captured moisture in the gradient hygroscopic expansion layer, enabling the captured moisture to form transportable moisture that can continue to participate in subsequent transport processes. The hemicellulose absorbs the transportable moisture and generates a hygroscopic response, providing conditions for the subsequent hygroscopic deformation of the orthotropic mesh.

[0037] In one possible implementation, the gradient moisture-absorbing expansion layer further includes a skeleton component; in step 102, causing the orthotropic mesh to undergo moisture-absorbing deformation includes: causing the hemicellulose to absorb water and swell; using the skeleton component to restrict the expansion of the orthotropic mesh along the in-plane direction, causing the orthotropic mesh to expand along the thickness direction, thereby obtaining the moisture-absorbing deformation; using the moisture-absorbing deformation to compress the pores in the gradient moisture-absorbing expansion layer, thereby promoting the movement of water in the pores along the thickness direction.

[0038] In one possible implementation, the gradient hygroscopic expansion layer further includes a framework component. Hemicellulose absorbs moisture and expands, causing deformation of the composite structure forming the orthotropic mesh. The framework component restricts the expansion of the orthotropic mesh along the in-plane direction, allowing more of the structural deformation generated during moisture absorption to be released along the thickness direction. This results in the gradient hygroscopic expansion layer expanding more along the thickness direction than along the in-plane direction. Through this directional deformation during moisture absorption, the overall structure of the gradient hygroscopic expansion layer can be maintained while compressing some of the internal pores, thereby promoting the movement of moisture within the pores along the thickness direction. Cellulose can serve as a material forming a continuous framework and bear part of the expansion stress generated during moisture absorption and expansion.

[0039] In one possible implementation, the method of utilizing the difference in hemicellulose content between two adjacent gradient regions to cause moisture in the gradient hygroscopic expansion layer to migrate towards the second side, and utilizing the hygroscopic deformation to compress the pores in the gradient hygroscopic expansion layer to promote the transport of moisture to the second side, includes: according to the arrangement order of the plurality of gradient regions from the first side to the second side, causing moisture in the current gradient region to migrate towards the next gradient region based on the difference in hemicellulose content between the current gradient region and the adjacent next gradient region closer to the second side; during the migration of moisture towards the next gradient region, utilizing the hygroscopic deformation to compress the pores in the current gradient region to promote the moisture into the next gradient region; and according to the arrangement order of the plurality of gradient regions, sequentially using the gradient region closer to the second side as the next gradient region for moisture migration and pore compression promotion, until the moisture is transported to the gradient region closer to the second side.

[0040] During the transport of moisture to the second side, the hemicellulose content gradient and the pore compression effect generated by hygroscopic deformation can be utilized simultaneously. Because the hemicellulose content differs between adjacent gradient regions, the moisture to be transported can migrate from the gradient region with lower hemicellulose content to the gradient region with higher hemicellulose content. As multiple gradient regions are sequentially arranged from the first side to the second side, moisture can continuously migrate along the direction of gradually increasing hemicellulose content. Simultaneously, the thickness-direction hygroscopic deformation generated by the orthogonal anisotropic mesh compresses the pores that accommodate the migrating moisture, causing the moisture in the pores to be pushed along the thickness direction and continue to be transported to the second side along the interconnected pores within the gradient hygroscopic expansion layer. Thus, the moisture migration caused by the difference in hemicellulose content and the mechanical pushing generated by hygroscopic deformation work together to allow moisture to be gradually transported from the vicinity of the first side to the vicinity of the second side.

[0041] In one possible implementation, when the orthogonal anisotropic mesh undergoes the moisture-absorbing deformation, the expansion rate of the gradient moisture-absorbing expansion layer along the thickness direction is controlled to be 30% to 50%, the expansion rate along the in-plane direction is not greater than 5%, and the ratio of the expansion rate along the thickness direction to the expansion rate along the in-plane direction is not less than 6.

[0042] Through the above implementation method, the gradient region near the first side can capture and initially retain ambient moisture. The moisture regulating component provides usable moisture for subsequent transport. After absorbing water, hemicellulose undergoes hygroscopic expansion, and the skeletal component further guides structural deformation in the thickness direction, and promotes moisture movement through pore compression. On this basis, the hemicellulose content gradient set along the thickness direction is used to continuously guide moisture migration to the second side, so that moisture capture, storage, hygroscopic response, and directional transport form a continuous process, thereby providing a moisture basis for the further thermal desorption and vaporization of the moisture transported to the second side.

[0043] In one possible implementation, before the hygroscopic expansion heat dissipation structure is heat-exchange connected to the object to be cooled, the gradient hygroscopic expansion layer is prepared. The preparation of the gradient hygroscopic expansion layer includes: preparing a first printing material, a second printing material, and a third printing material, wherein the second printing material includes hemicellulose; conveying the first printing material, the second printing material, and the third printing material to corresponding channels of a multi-channel coaxial printhead; extruding the first printing material, the second printing material, and the third printing material through the multi-channel coaxial printhead to obtain coaxial composite fibers; printing the coaxial composite fibers layer by layer to obtain a printed preform; and performing post-processing on the printed preform to obtain the gradient hygroscopic expansion layer.

[0044] In one possible implementation, a gradient hygroscopic expansion layer can be prepared before heat exchange connection between the hygroscopic expansion heat dissipation structure and the object to be cooled. The purpose of preparing the gradient hygroscopic expansion layer is to achieve a relatively stable distribution of different materials within the composite fiber through the synergistic forming of multiple printing materials and a layer-by-layer printing process, providing a foundation for the subsequent construction of a material composition and pore structure that varies along the thickness direction. Specifically, a first printing material, a second printing material, and a third printing material can be prepared separately, wherein the second printing material includes hemicellulose, and the three printing materials are respectively delivered to different channels of a multi-channel coaxial printhead. During the printing process, the multi-channel coaxial printhead simultaneously extrudes the three printing materials, forming coaxial composite fibers during extrusion, and then using the coaxial composite fibers to build the printed preform layer by layer. After printing, the printed preform undergoes post-processing to further stabilize the printed structure and obtain a gradient hygroscopic expansion layer capable of hygroscopic absorption, deformation, and moisture transport.

[0045] By employing a multi-channel coaxial printing method, different printing materials can be configured within the same composite fiber, allowing a second printing material containing hemicellulose to form a composite structure with other printing materials at the fiber scale. Compared to simply mixing multiple materials and forming a single bulk material, delivering them separately through different channels and extruding them together at the nozzle allows for individual adjustment of the supply state of different printing materials. This provides the conditions for changing the proportion of each printing material in the coaxial composite fiber along the printing height direction. Therefore, during the layer-by-layer printing process, the material composition can be adjusted according to different height positions, resulting in a gradient hygroscopic expansion layer with an internal structure adapted to moisture absorption, moisture deformation, and moisture transport.

[0046] In one possible implementation, the step of printing the coaxial composite fibers layer by layer to obtain a printed blank includes: printing the coaxial composite fibers parallel to a first in-plane direction to obtain a first fiber layer; printing the coaxial composite fibers parallel to a second in-plane direction on the first fiber layer to obtain a second fiber layer, wherein the second in-plane direction is perpendicular to the first in-plane direction; and printing the coaxial composite fibers layer by layer alternately according to the first in-plane direction and the second in-plane direction to obtain a printed blank having the orthogonal anisotropic mesh.

[0047] In one possible implementation, when printing coaxial composite fibers layer by layer, the coaxial composite fibers are first printed parallel to a first in-plane direction to form a first fiber layer; then, coaxial composite fibers are printed parallel to a second in-plane direction perpendicular to the first in-plane direction on the first fiber layer to form a second fiber layer. In subsequent printing processes, the printing directions of each fiber layer are alternately set according to the first in-plane direction and the second in-plane direction, so that the coaxial composite fibers in adjacent fiber layers extend in mutually perpendicular directions, thereby gradually forming an orthogonal anisotropic mesh.

[0048] By employing the alternating printing method described above, the printed preform can form an interlaced fiber support relationship within its surface, while simultaneously allowing fiber layers in different directions to be stacked sequentially along the thickness direction. This structure helps maintain the overall shape of the printed preform and enables the gradient hygroscopic expansion layer to exhibit different degrees of deformation in different directions after absorbing moisture, making the expansion along the thickness direction more pronounced. This provides a structural basis for subsequently utilizing hygroscopic deformation to compress internal pores and drive moisture movement along the thickness direction.

[0049] In one possible implementation, the step of printing the coaxial composite fibers layer by layer to obtain a printed preform further includes: dividing the multiple fiber layers to be printed into multiple printing layer groups arranged along the printing height direction, each printing layer group being used to form a gradient region, the printing height direction corresponding to the thickness direction; determining the first printing material extrusion amount, the second printing material extrusion amount, and the third printing material extrusion amount corresponding to each printing layer group according to the arrangement position of each printing layer group along the printing height direction, such that the proportion of the second printing material corresponding to the printing layer group closer to the second side in the first printing material, the second printing material, and the third printing material in two adjacent printing layer groups is greater than the proportion of the second printing material corresponding to the printing layer group closer to the first side; and printing each printing layer group sequentially according to the first printing material extrusion amount, the second printing material extrusion amount, and the third printing material extrusion amount corresponding to each printing layer group, so that the hemicellulose content of the gradient region closer to the second side in two adjacent gradient regions is greater than the hemicellulose content of the gradient region closer to the first side.

[0050] In one possible implementation, multiple fiber layers to be printed can be divided into multiple printing layer groups according to the printing height direction, with each printing layer group corresponding to a gradient region in the gradient moisture-absorbing expansion layer. Since the different printing layer groups are located at different positions along the printing height direction, the extrusion amounts of the first, second, and third printing materials can be set according to the position of each printing layer group. By controlling the extrusion amount of each printing material in layers, the proportion of the second printing material is higher in the printing layer groups closer to the second side. Because the second printing material includes hemicellulose, after printing each printing layer group sequentially according to the corresponding extrusion amount, the resulting multiple gradient regions can have a gradually changing hemicellulose content along the thickness direction, providing a material composition basis for subsequently utilizing the difference in hemicellulose content to promote moisture migration to the second side.

[0051] In the actual printing process, the extrusion amount of printing material corresponding to each printing layer group can be used as the forming parameter for that printing layer group. After completing one printing layer group, the supply amount of each printing material is adjusted according to the extrusion amount corresponding to the next printing layer group, and then printing continues layer by layer. Through this layer-by-layer adjustment method, it is not necessary to perform separate component treatment for different thickness positions after printing, and the difference in hemicellulose content distributed along the thickness direction can be formed during the printing process. After multiple printing layer groups are formed in sequence, the structure between each gradient region remains continuous, allowing moisture to continue to migrate from one gradient region to adjacent gradient regions within the gradient hygroscopic expansion layer.

[0052] In one possible implementation, the post-processing of the printed preform to obtain the gradient moisture-absorbing expansion layer includes: subjecting the printed preform to a wet heat treatment, causing the hemicellulose to absorb moisture and making the expansion of the printed preform along the thickness direction greater than the expansion along the in-plane direction, to obtain a wet heat-treated preform; subjecting the wet heat-treated preform to a drying treatment, to obtain a dried preform; and subjecting a first side of the dried preform to a hydrophilic treatment, to obtain the gradient moisture-absorbing expansion layer.

[0053] In one possible implementation, after the printed preform is formed, the printed structure can be further adjusted through hydrothermal treatment. During hydrothermal treatment, the hemicellulose in the printed preform absorbs moisture from the environment and expands. Since the printed preform has formed an orthogonal anisotropic mesh, its structural deformation after absorbing moisture varies in different directions, with the expansion along the thickness direction being greater than the expansion along the in-plane direction. Through hydrothermal treatment, the printed mesh structure can be further transformed from its initial formed state into a state with significant anisotropic moisture absorption deformation capability, providing conditions for compressing internal pores and promoting moisture movement through deformation along the thickness direction during subsequent use.

[0054] After the hydrothermal treatment, the treated green body is dried to bring it to a state suitable for subsequent use and assembly. Then, the first side of the dried green body undergoes a hydrophilic treatment to improve its wetting ability, allowing moisture from the external environment to more easily enter near the first side and be captured by the gradient hygroscopic expansion layer. After the hydrothermal treatment, drying treatment, and first-side hydrophilic treatment, a hemicellulose content gradient, anisotropic hygroscopic deformation capacity, and hydrophilic properties of the first side are formed within the same gradient hygroscopic expansion layer, thus creating a better balance between moisture entry, hygroscopic deformation, and transport along the thickness direction.

[0055] In one possible implementation, the wet heat treatment of the printed blank includes: placing the printed blank in a treatment environment with a temperature of 38°C to 45°C and a relative humidity of 90% to 98%; and subjecting the printed blank to wet heat treatment for 12 to 24 hours in the treatment environment, causing the printed blank to expand along the thickness direction.

[0056] In one possible implementation, the hydrophilization treatment of the first side of the dried blank includes: treating the first side of the dried blank with oxygen plasma to reduce the contact angle of the first side with water.

[0057] In one possible implementation, the first printing material comprises cellulose, and the third printing material comprises pectin or lignin; the step of extruding the first printing material, the second printing material, and the third printing material through the multi-channel coaxial printhead to obtain coaxial composite fibers includes: forming an outer layer of the coaxial composite fiber using the first printing material; forming a middle layer located inside the outer layer using the second printing material; and forming an inner layer located inside the middle layer using the third printing material, thereby obtaining the coaxial composite fiber having an outer layer, a middle layer, and an inner layer.

[0058] In one possible implementation, printing each of the printed layer groups sequentially according to the extrusion amounts of the first, second, and third printed materials corresponding to each printed layer group includes: decreasing the proportion of the first printed material in the coaxial composite fiber and increasing the proportion of the second printed material in the coaxial composite fiber according to the arrangement order from the printed layer group corresponding to the first side to the printed layer group corresponding to the second side; maintaining the proportion of the third printed material in the coaxial composite fiber corresponding to each printed layer group within a set range; and printing each printed layer group according to the adjusted proportions of the first, second, and third printed materials.

[0059] In one possible implementation, when the third printing material includes lignin, the post-processing of the printed preform further includes: applying a cross-linking enzyme to the surface of the printed preform after performing a wet heat treatment; using the cross-linking enzyme to cross-link the lignin in the printed preform to obtain a lignin-crosslinked preform; and performing the drying treatment on the lignin-crosslinked preform.

[0060] In one possible implementation, the first printing material comprises cellulose, the second printing material comprises hemicellulose, and the third printing material comprises pectin or lignin. When the three printing materials are extruded together through a multi-channel coaxial printhead, the first printing material forms the outer layer of the coaxial composite fiber, the second printing material forms the middle layer inside the outer layer, and the third printing material forms the inner layer inside the middle layer, thereby forming a composite fiber structure with an outer, middle, and inner layer. The outer layer formed by cellulose mainly serves to form a continuous fiber skeleton and maintain the overall shape of the composite fiber. The middle layer formed by hemicellulose can absorb moisture and expand. When pectin is used for the inner layer, it can store moisture that enters the interior of the composite fiber. When lignin is used, it can form a relatively hydrophobic internal region and improve the stability of the structure under heat conditions. By placing materials with different functions at different locations within the composite fiber, moisture absorption response, structural support, and moisture regulation can be coordinated within the same fiber.

[0061] In one possible implementation, when printing multiple printing layers sequentially, the proportions of the first, second, and third printing materials in the coaxial composite fiber can be adjusted according to the arrangement of each printing layer from the first side to the second side. Specifically, as the printing layer gradually moves closer to the second side, the proportion of the first printing material is reduced while the proportion of the second printing material is increased, while the proportion of the third printing material is kept within a set range. Then, the corresponding printing layer is printed according to the adjusted material proportions. Since the first printing material includes cellulose and the second printing material includes hemicellulose, through the above-mentioned layer adjustment, while maintaining the continuous composition of each printing layer from the first side to the second side along the thickness direction, the hemicellulose content can be gradually increased, and the compositional relationship between cellulose and hemicellulose can be adjusted accordingly with the thickness position, all while ensuring that each printing layer is continuously composed of coaxial composite fibers.

[0062] This layered adjustment of material proportions ensures that the material composition of the gradient hygroscopic expansion layer is not formed through additional processing after printing, but rather directly constructed during the layer-by-layer forming process. The region closer to the first side has a relatively low hemicellulose content, while the region closer to the second side has a relatively high hemicellulose content, thus providing a compositional gradient for moisture migration from the first side to the second side. Simultaneously, the cellulose outer layer maintains the structural connections between the composite fibers in different gradient regions, allowing the changes in material composition to be combined with the overall structure of the orthogonal anisotropic mesh, which is beneficial for the stable progress of subsequent hygroscopic expansion and moisture transport processes.

[0063] In one possible implementation, when the third printing material includes lignin, the lignin can be further cross-linked after the printing preform has undergone hydrothermal treatment. Specifically, a cross-linking enzyme can be applied to the surface of the hydrothermally treated printing preform, allowing the enzyme to contact the lignin in the preform and promote the formation of a more stable cross-linked structure between the lignin particles, resulting in a lignin-cross-linked preform. This lignin-cross-linked preform is then dried. By adding a lignin cross-linking process after hydrothermal treatment, the inner layer structure containing lignin can be further stabilized, reducing the possibility of significant changes in the material structure during subsequent moisture absorption, desorption, and heating processes. This ensures that the gradient hygroscopic expansion layer using a lignin system maintains a relatively stable composite structure.

[0064] In one possible implementation, the layer-by-layer printing of the coaxial composite fiber includes: placing the multi-channel coaxial printhead and the printing substrate in a printing environment with a temperature of 4°C to 10°C and a relative humidity of 70% to 85%; and extruding and printing the coaxial composite fiber layer by layer through the multi-channel coaxial printhead in the printing environment.

[0065] In one possible implementation, the average pore size of the gradient region near the first side is 3 μm to 8 μm, and the average pore size of the gradient region near the second side is 50 μm to 90 μm; the hemicellulose mass fraction of the gradient region near the first side is 10% to 15%, and the hemicellulose mass fraction of the gradient region near the second side is 35% to 45%.

[0066] In one possible implementation, from the first side to the second side, the average pore size of the plurality of gradient regions is controlled to increase in a non-linear increasing relationship, and the hemicellulose content of the plurality of gradient regions is controlled to increase in a linear increasing relationship.

[0067] In one possible implementation, after dissipating heat from the object to be cooled by the water decomposition and vaporization, the method further includes: after the temperature of the gradient hygroscopic expansion layer decreases, allowing the gradient hygroscopic expansion layer to reabsorb moisture from the external environment; and using the reabsorbed moisture for the next moisture migration, transport, and desorption vaporization to cyclically dissipate heat from the object to be cooled.

[0068] The moisture absorption and expansion heat dissipation method and structure provided in the embodiments of this application will be further described below with reference to the accompanying drawings.

[0069] This embodiment utilizes moisture from the external environment as a heat dissipation medium. A gradient hygroscopic expansion layer absorbs moisture from the external environment, and the difference in hemicellulose content along the thickness direction and the hygroscopic deformation of the orthogonal anisotropic grid promote moisture transport along the thickness direction. After the moisture is transported to the second side of the gradient hygroscopic expansion layer, the heat generated by the object to be cooled is transferred to the moisture, causing the moisture to desorb from the gradient hygroscopic expansion layer and vaporize, thereby carrying away some of the heat generated by the object. In this process, there is no need for an external pumping device to drive the transport of moisture within the gradient hygroscopic expansion layer; the environmental moisture absorption, moisture transport, and desorption / vaporization processes can be interconnected to form a passive heat dissipation process.

[0070] The moisture absorption and expansion heat dissipation method provided in this application can be applied to equipment or structures with passive thermal management requirements, such as electronic devices, power batteries, communication equipment, and other objects that need to dissipate heat with continuous or periodic heat dissipation requirements. It can also be applied to environments with low-grade heat release or where it is inconvenient to set up an independent liquid water source.

[0071] The gradient hygroscopic expansion layer in this embodiment can be prepared using additive manufacturing and can undergo predetermined structural changes when environmental conditions such as humidity and temperature change. 4D printing refers to obtaining an initial structure through 3D printing, and enabling the printed structure to undergo predetermined morphological or performance changes under subsequent environmental stimuli. The 4D deformation in this embodiment can include two stages. During the post-printing hydrothermal treatment, the printed blank expands significantly more along its thickness direction than in the in-plane direction, transforming the printed blank from its initial printed state into a functional state with anisotropic deformation characteristics. In subsequent use, the gradient hygroscopic expansion layer can also expand and contract accordingly with moisture absorption and loss, allowing structural deformation to participate in the transport and release of moisture.

[0072] Figure 2 This diagram illustrates the overall composition of the moisture-absorbing expansion heat dissipation structure provided in this embodiment. The moisture-absorbing expansion heat dissipation structure may include a gradient moisture-absorbing expansion layer 100, a one-way moisture-guiding layer 110, and a breathable shape-conserving support layer 120 arranged sequentially along the thickness direction. The gradient moisture-absorbing expansion layer 100 serves as the main body of the moisture-absorbing expansion heat dissipation structure, used to absorb moisture from the external environment, retain moisture, transport moisture, and transfer heat generated by the object to be cooled. The one-way moisture-guiding layer 110 is disposed on the second side of the gradient moisture-absorbing expansion layer 100, providing a channel for water vapor generated in the gradient moisture-absorbing expansion layer 100 to dissipate to the external environment, and reducing the possibility of external liquid water and pollutants entering the gradient moisture-absorbing expansion layer 100 from the second side. The breathable shape-conserving support layer 120 is disposed on the side of the one-way moisture-guiding layer 110 opposite to the gradient moisture-absorbing expansion layer 100, providing support for the moisture-absorbing expansion heat dissipation structure and maintaining the breathability required for water vapor transfer.

[0073] In this embodiment, the gradient moisture-absorbing and swelling layer 100 can be formed from cellulose, hemicellulose, and pectin or lignin. As a specific implementation, the dry weight composition of the gradient moisture-absorbing and swelling layer 100 may include 20% to 30% cellulose, 20% to 30% hemicellulose, and 30% to 40% pectin or lignin, and may also include auxiliary components such as bound proteins or minerals in total not exceeding 5%. These auxiliary components are not essential for the formation of the gradient moisture-absorbing and swelling layer 100 and can be selected and added according to the material source and actual preparation conditions.

[0074] In one specific implementation, the unidirectional moisture-wicking layer 110 can be a composite membrane of nanocellulose and beeswax with different wetting properties on both sides, and its thickness can be from 80 μm to 120 μm. The water contact angle of the first surface of the unidirectional moisture-wicking layer 110 facing the gradient moisture-wicking expansion layer 100 can be no greater than 15°, and the water contact angle of the second surface facing away from the gradient moisture-wicking expansion layer 100 can be no less than 120°. By making the two surfaces have different wetting capabilities, water vapor formed in the gradient moisture-wicking expansion layer 100 can continue to be discharged to the external environment through the unidirectional moisture-wicking layer 110, and the reverse entry of external liquid water and pollutants into the gradient moisture-wicking expansion layer 100 from the outside can be reduced.

[0075] The breathable and conformal support layer 120 can be a microporous mesh structure formed of polylactic acid or natural rubber. As an example, the pore size of the breathable and conformal support layer 120 can be 5 μm to 10 μm, and the porosity can be no less than 60%, thereby providing structural support while allowing water vapor to pass through the required pores. In some embodiments, the compressive strength of the breathable and conformal support layer 120 can reach 1 MPa or higher to reduce the impact of moisture absorption and expansion, as well as external loads during cyclic use, on the morphology of the moisture absorption and expansion heat dissipation structure.

[0076] It should be noted that, Figure 2 The direction of moisture migration in the text represents the overall process of moisture entering the gradient hygroscopic expansion layer 100 from the external environment, the transport of moisture within the gradient hygroscopic expansion layer 100 to the second side, and the eventual discharge of moisture as water vapor. It does not limit the entry of moisture from the external environment into the gradient hygroscopic expansion layer 100 to a single, defined surface. In practical use, water vapor from the external environment can enter the gradient hygroscopic expansion layer 100 through pores connected to the external environment, based on the contact area between the gradient hygroscopic expansion layer 100 and the object to be cooled, as well as the area exposed to the external environment.

[0077] The gradient moisture-absorbing expansion layer 100 includes multiple gradient regions along the thickness direction from the first side to the second side. In two adjacent gradient regions, the average pore size of the gradient region closer to the second side is greater than that of the gradient region closer to the first side. At the same time, the hemicellulose content of the gradient region closer to the second side is greater than that of the gradient region closer to the first side, thereby forming a dual-gradient structure in which the average pore size and hemicellulose content change together along the thickness direction.

[0078] Figure 3 The relationship between the average pore size and hemicellulose content along the thickness direction is shown in the gradient hygroscopic expansion layer 100. Curve A represents the change in average pore size along the thickness direction, and curve B represents the change in hemicellulose content along the thickness direction.

[0079] As a specific implementation, the average pore size can gradually increase from 3 μm to 8 μm near the first side to 50 μm to 90 μm near the second side, increasing non-linearly along the thickness direction. The gradient region near the first side has relatively small pores, which can improve the capture capacity of ambient water vapor entering the gradient hygroscopic expansion layer 100. Under specific material and porosity conditions, a pore size range of 3 μm to 8 μm can correspond to a capillary pressure of not less than 15 kPa. The gradient region near the second side has relatively large pores, which helps to reduce the resistance encountered by water vapor after water decomposition and vaporization when it diffuses from the interior of the gradient hygroscopic expansion layer 100 to the external environment. Under specific porosity conditions, a pore size range of 50 μm to 90 μm can reduce the water vapor escape resistance to below 0.5 kPa.

[0080] The hemicellulose content can gradually increase from 10% to 15% near the first side to 35% to 45% near the second side. In one specific implementation, the hemicellulose content can increase along the thickness direction in an approximately linear relationship. Hemicellulose and water have a strong interaction, and differences in hemicellulose content between different gradient regions can cause different regions to exhibit different water affinity. According to the thermodynamic relationship of the hemicellulose-water mixture, changes in the hemicellulose volume fraction can promote water migration along the thickness direction of the gradient hygroscopic expansion layer 100. Under one example condition, when the hemicellulose content near the first side is approximately 12% and the hemicellulose content near the second side is approximately 40%, water can migrate from areas with lower hemicellulose content to areas with higher hemicellulose content.

[0081] Figure 3 The dual gradients shown act on the moisture absorption, transport, and discharge processes, respectively. The smaller pores near the first side primarily trap ambient moisture entering the gradient hygroscopic expansion layer 100. The gradually increasing hemicellulose content along the thickness direction promotes moisture migration to the second side, while the larger pores near the second side facilitate the discharge of water vapor formed after moisture vaporization due to heating. By continuously setting different gradient regions, moisture trapping, internal migration, and water vapor discharge can be coordinated with the structural characteristics of the gradient hygroscopic expansion layer 100 at different locations along its thickness direction.

[0082] In one possible implementation, in addition to the hemicellulose content gradient, the pectin or lignin content can also vary along the thickness direction. For example, the pectin or lignin content can gradually decrease from 40% to 45% near the first side to 20% to 25% near the second side. When using pectin, the higher pectin content near the first side can improve the storage capacity for capturing moisture. Under specific material conditions, the water absorption capacity of pectin can reach several times its own dry weight. When using lignin, it can be used to form relatively hydrophobic regions, and the thermal stability of lignin can be used to improve the structural stability of the gradient hygroscopic expansion layer 100 during heating and cyclic moisture absorption processes.

[0083] In another possible implementation, the content of the third printing material in different gradient regions can also be maintained within a set range, and the hemicellulose content gradient is mainly formed by changing the relative proportion between the first and second printing materials. Therefore, the gradual change of the third printing material along the thickness direction and the basic stability of the third printing material in different gradient regions can correspond to different material configurations, and it is not necessary to use them simultaneously in the same gradient moisture-absorbing expansion layer 100.

[0084] In addition to the component gradient and pore size gradient formed along the thickness direction, the gradient hygroscopic expansion layer 100 also has an orthotropic grid. The orthotropic grid can be formed by changing the printing direction of the coaxial composite fibers layer by layer. Specifically, coaxial composite fibers can be printed parallel to a first in-plane direction in the first fiber layer, and then parallel to a second in-plane direction perpendicular to the first in-plane direction in the adjacent second fiber layer. Subsequent fiber layers are printed alternately in the first and second in-plane directions, causing the coaxial composite fibers in adjacent fiber layers to extend in mutually perpendicular directions, thereby forming the orthotropic grid.

[0085] Figure 4 The deformation relationship of orthogonal anisotropic meshes under dry and hygroscopic conditions is shown. Figure 4 Taking the illustrated grid cell as an example, in a dry state, the cell dimensions along the two in-plane directions can be 1.0 mm, and the dimension along the thickness direction can be 0.3 mm. When the orthotropic grid absorbs moisture, the dimensions along the two in-plane directions can change to approximately 1.02 mm, corresponding to an in-plane expansion of approximately 2%, and the dimension along the thickness direction can change to approximately 0.426 mm, corresponding to a thickness expansion of approximately 42%. Therefore, the structural deformation of the orthotropic grid after moisture absorption is mainly concentrated in the thickness direction.

[0086] In some embodiments, the thickness-direction expansion rate of the gradient moisture-absorbing expansion layer 100 after moisture absorption can be 30% to 50%, the in-plane expansion rate can be no more than 5%, and the ratio of the thickness-direction expansion rate to the in-plane expansion rate can be no less than 6. One reason for the above-mentioned directional differences is that during the formation of coaxial composite fibers, cellulose microfibers can form a certain degree of preferential orientation along the material extrusion direction, which restricts the expansion of the fiber skeleton in the in-plane direction. However, after hemicellulose absorbs moisture, the chain segment mobility increases and the volume expands, allowing the overall structural deformation to be released more along the thickness direction.

[0087] In one specific measurement method, the thickness and in-plane dimensions of the gradient hygroscopic expansion layer 100 in both the dry and hygroscopic equilibrium states can be obtained. The thickness expansion rate and in-plane expansion rate are then determined based on the dimensional changes before and after moisture absorption. For example, a 10mm × 10mm × 13.5mm test sample can be prepared, equilibrated at 25℃ and 80% relative humidity for 24 hours, and then its thickness and side length can be measured. The thickness and side length measured after drying the sample at 105℃ for 2 hours are taken as the dimensions in the dry state. The thickness expansion rate is determined based on the dimensional changes in thickness between the hygroscopic and dry states, and the in-plane expansion rate is determined based on the changes in side length between the hygroscopic and dry states.

[0088] When the orthogonal anisotropic mesh expands along its thickness, the effective volume of some pores within the gradient hygroscopic expansion layer 100 is compressed. Moisture stored in the corresponding pores is mechanically propelled along the thickness direction by the structural deformation. Therefore, the moisture transport in this embodiment includes not only moisture migration caused by differences in hemicellulose content but also pore compression caused by anisotropic hygroscopic deformation. The combined effect of these two factors allows the moisture to be transported to be gradually transported from the vicinity of the first side through multiple gradient regions to the second side.

[0089] Under certain specific test conditions, when the migration effect generated by the hemicellulose content gradient and the mechanical driving effect generated by the orthogonal anisotropic mesh coexist, the moisture transport rate can be improved compared to structures that rely solely on diffusion. The hemicellulose content gradient mainly provides the moisture migration trend along the thickness direction, while hygroscopic deformation further promotes moisture movement by compressing internal pores, so that changes in material composition and structural deformation jointly participate in the moisture transport process.

[0090] As moisture continues to desorb from the gradient hygroscopic expansion layer 100, the moisture content of the hemicellulose gradually decreases, and the orthotropic mesh shrinks accordingly along its thickness. With this structural shrinkage, the compressed pores from the hygroscopic expansion process re-enlarge, which helps reduce the resistance to further water vapor transfer to the second side. Under certain test conditions, the thickness of the dehydrated structure can recover to approximately 85% to 90% of the corresponding dimensional changes before and after hygroscopic expansion. Thus, the orthotropic mesh can participate in moisture propulsion through structural deformation during hygroscopic process, and after water loss, it can reopen its internal pores through structural retraction, thereby adapting to both hygroscopic and desorption phases.

[0091] Figure 5 The three-channel coaxial printing method used to prepare the gradient moisture-absorbing expansion layer 100 and the cross-sectional structure of the coaxial composite fiber are further illustrated. Figure 5 The left figure illustrates the basic structure of a three-channel coaxial printing apparatus. The three-channel coaxial printing apparatus may include a first material storage unit 210, a second material storage unit 220, a third material storage unit 230, and a coaxial nozzle 240. The first material storage unit 210 is used to hold a first printing material including cellulose, the second material storage unit 220 is used to hold a second printing material including hemicellulose, and the third material storage unit 230 is used to hold a third printing material including pectin or lignin. The three printing materials are each fed to the coaxial nozzle 240 through independent channels and are jointly extruded by the coaxial nozzle 240 to form coaxial composite fibers 250, which are then deposited on the printing platform.

[0092] like Figure 5 As shown in the right figure, the coaxial composite fiber 250 formed by three printing materials can have an outer layer, a middle layer, and an inner layer. The first printing material forms the outermost cellulose outer layer, the second printing material forms the hemicellulose middle layer inside the cellulose outer layer, and the third printing material forms the pectin or lignin inner layer inside the hemicellulose middle layer. Through this layered arrangement, different printing materials can maintain their corresponding spatial positions within the same coaxial composite fiber 250, allowing different materials to participate in structural support, moisture absorption response, and moisture regulation processes respectively.

[0093] In one specific implementation, the position, corresponding material, volume percentage, and main function of each component in the coaxial composite fiber 250 can be shown in Table 1 below.

[0094] Table 1 outer layer Cellulose The percentage decreased from approximately 60% to approximately 30% from the first side to the second side. A continuous framework is formed, and a heat transfer pathway is created. Middle layer hemicellulose The percentage increases from approximately 15% to approximately 45% from the first side to the second side. As a hygroscopic response component, it generates volume changes through water absorption and loss, and participates in the absorption and desorption of moisture. Inner layer Pectin or lignin Approximately 25% and remaining relatively stable. Pectin is used to absorb and store moisture, while lignin is used to form relatively hydrophobic regions and improve thermal stability and resistance to structural creep. The outer cellulose layer primarily serves to form a continuous skeleton and provides a pathway for heat generated by the object to be dissipated to transfer into the gradient hygroscopic expansion layer 100. Under specific material conditions, the tensile strength of the cellulose skeleton can reach over 200 MPa, and the overall equivalent thermal conductivity of the gradient hygroscopic expansion layer 100 can reach 1.2 W / m Kelvin to 1.8 W / m Kelvin.

[0095] The middle layer of hemicellulose, as the main moisture-responsive component, undergoes a significant volume change upon absorbing moisture. The glass transition temperature of hemicellulose varies with its moisture content. In one material system, the glass transition temperature of hemicellulose in a dry state can be 50°C to 70°C, while in a humid state it can decrease to 30°C to 50°C, thus allowing its chain segment mobility to change with moisture content and temperature.

[0096] When pectin is used as the inner layer, its high water absorption and retention capacity can be utilized to create a moisture storage area. Under specific material conditions, pectin can absorb 5 to 8 times its own dry weight in water. When lignin is used as the inner layer, a relatively hydrophobic internal region can be formed, and lignin can be used to improve the structural stability under heat conditions and resistance to structural creep. Therefore, either a pectin system or a lignin system can be selected based on the different requirements for water storage capacity and desorption performance in the actual application environment.

[0097] It should be noted that the table above corresponds to a specific implementation where the content of the third printing material remains basically stable in different gradient regions. In other implementations where the third printing material varies along the thickness direction, the volume percentage of each component can be adjusted according to the corresponding material configuration and is not limited to the values ​​listed in the table above.

[0098] During the moisture absorption stage, water vapor from the external environment enters the gradient moisture-absorbing expansion layer 100 and is captured in the pore area near the first side. Some of the water vapor can undergo capillary condensation in the pores. When using a pectin system, the captured moisture can be further absorbed and stored by the inner pectin layer. Subsequently, the hemicellulose middle layer absorbs moisture, the hemicellulose chain segments become more mobile and expand in volume, and the skeleton formed by the outer cellulose layer bears part of the stress generated during the moisture absorption expansion process, so that the coaxial composite fiber 250 maintains a continuous structural connection during the moisture absorption process.

[0099] During the directional transport stage, the high hemicellulose region near the second side has a stronger water affinity than the low hemicellulose region near the first side, causing the water to be transported to migrate along the direction of gradually increasing hemicellulose content. Simultaneously, the thickness-direction expansion caused by the moisture absorption of the orthotropic mesh compresses the internal pores, further propelling the water within the pores along the thickness direction. Through the combined effect of water migration and mechanical propulsion, water can be gradually transported from the vicinity of the first side to the vicinity of the second side.

[0100] During the thermo-induced desorption stage, the heat generated by the object to be cooled is transferred to the gradient hygroscopic expansion layer 100, and further transferred to the moisture transported to the vicinity of the second side. As the temperature rises, the interaction between hemicellulose and moisture weakens, causing the moisture to desorb from the gradient hygroscopic expansion layer 100 and vaporize. Moisture vaporization requires the absorption of heat; near atmospheric pressure, the latent heat of vaporization of water is approximately 2260 kJ per kilogram. Therefore, when moisture changes from a liquid or adsorbed state to water vapor, it can carry away some of the heat generated by the object to be cooled. The formed water vapor continues to be discharged to the external environment through the one-way moisture-wicking layer 110 and the breathable shape-conforming support layer 120.

[0101] When the temperature decreases or the external humidity increases, the gradient hygroscopic expansion layer 100 can reabsorb moisture from the external environment, allowing the hygroscopic expansion heat dissipation structure to enter a regeneration state. After the hemicellulose reabsorbs moisture, it resumes its hygroscopic response, and the pectin system can again store environmental moisture, thereby providing moisture for the next moisture transport and vaporization heat dissipation. Therefore, this embodiment can form a cyclical process of moisture absorption, moisture transport, desorption vaporization, and re-hygroscopic absorption under periodic changes in environmental temperature and humidity conditions.

[0102] The following describes a specific preparation method of the gradient moisture-absorbing expansion layer 100, using pectin as the third printing material.

[0103] In some embodiments, the coaxial composite fiber 250 can be printed layer by layer in an environment with a temperature of 4°C to 10°C and a relative humidity of 70% to 85%. After printing, the formed printed preform can be placed in an environment with a temperature of 38°C to 45°C and a relative humidity of 90% to 98% for 12 to 24 hours of humid heat treatment. After the humid heat treatment is completed and dried, the first side of the dried preform can be hydrophilized using oxygen plasma. The oxygen plasma treatment power can be 40W to 60W, and the treatment time can be 30 to 60 seconds. The following description uses specific process parameters.

[0104] First, three printing materials were prepared. For the first printing material, 25g of microcrystalline cellulose was added to a 175g aqueous solution of sodium hydroxide and urea pre-cooled to -12°C, wherein the mass fraction of sodium hydroxide was 7% and the mass fraction of urea was 12%. After mechanical stirring for 2 hours, the mixture was allowed to stand at 0°C to remove bubbles, resulting in a cellulose printing material with a solid content of approximately 12.5% ​​and a viscosity of approximately 55 Pa·s.

[0105] For the second printing material, alkali-soluble hemicellulose extracted from corn cobs can be used. As a specific example, the hemicellulose has a molecular weight of approximately 35,000 and a purity of approximately 88%. 20g of hemicellulose is dissolved in 80g of deionized water, and 5g of glycerol is added. The mixture is stirred in a 60°C water bath for 1 hour, and after cooling to room temperature, a hemicellulose printing material with a viscosity of approximately 42 Pa·s is obtained.

[0106] For the third printing material, high-ester apple pectin can be used. As a specific example, the degree of pectin esterification can be 72%. Dissolving 10g of pectin in 90g of deionized water and adding 2g of calcium chloride dihydrate, and stirring at room temperature for 2 hours, yields a pectin printing material with a solid content of approximately 10% and a viscosity of approximately 18 Pa·s.

[0107] After preparing the three printing materials, the first, second, and third printing materials are fed into the corresponding channels of the coaxial printhead 240. In one specific embodiment, the outer diameter of the coaxial printhead 240 can be 1.3 mm, the inner diameter of the middle channel can be 0.8 mm, and the inner diameter of the inner channel can be 0.4 mm. The coaxial printhead 240 can be mounted on a three-axis motion platform, with the printing chamber temperature controlled at approximately 6°C and the relative humidity controlled at approximately 80%. The printing substrate can be made of porous alumina ceramic with a porosity of approximately 30% and an average pore size of approximately 20 μm. A chitosan solution with a mass fraction of approximately 1% can be applied to the surface of the printing substrate to improve the adhesion between the first layer of printing material and the printing substrate.

[0108] During printing, the slice layer height can be set to 0.3 mm, the printing speed can be set to 8 mm per second, and the line spacing between the coaxial composite fibers 250 can be set to 0.6 mm. The first fiber layer is printed parallel to the first in-plane direction, the next fiber layer is printed in the second in-plane direction perpendicular to the first in-plane direction, and subsequent fiber layers are printed alternately in the first in-plane direction and the second in-plane direction. In this embodiment, 45 layers can be printed, with a total thickness of approximately 13.5 mm, thereby forming a printed blank with an orthogonal anisotropic mesh.

[0109] To achieve a hemicellulose content that varies along the thickness direction, multiple fiber layers to be printed can be divided into multiple printing layer groups. The extrusion amounts of the first, second, and third printing materials are controlled according to the position of each printing layer group along the printing height direction. The extrusion amount of printing material in each channel can be controlled by an independent drive mechanism. In one specific embodiment, the printing parameters corresponding to each printing layer group are shown in Table 2 below.

[0110] Table 2 Floors 1-10 0.90 0.15 0.30 60：10：20 12 5 Floors 11-20 0.75 0.30 0.30 50：20：20 22 25 Floors 21-35 0.60 0.45 0.30 40：30：20 32 55 Floors 36-45 0.45 0.60 0.30 30：40：20 40 80 As shown in the table above, with increasing printing height, the extrusion amount of the first printing material gradually decreases, the extrusion amount of the second printing material gradually increases, and the extrusion amount of the third printing material remains relatively stable. Since the second printing material includes hemicellulose, the above-mentioned layering adjustments allow different printing layer groups to form different hemicellulose contents, and the hemicellulose content in the gradient region closer to the second side is higher than that in the gradient region closer to the first side. Under the specific printing parameters described above, the average pore size corresponding to each printing layer group also gradually increases from approximately 5 μm to approximately 80 μm, thereby resulting in corresponding differences in the pore structure of the multiple gradient regions formed by printing.

[0111] After printing, the printed preform, along with the printing substrate, can be transferred to a constant temperature and humidity environment for hydrothermal treatment. In one specific embodiment, the treatment temperature is 40°C, the relative humidity is 95%, and the treatment time is 15 hours. During the hydrothermal treatment, the hemicellulose in the printed preform absorbs moisture, causing the printed preform to undergo anisotropic expansion. In this embodiment, the thickness direction expansion rate is approximately 42%, the in-plane expansion rate is approximately 3.5%, and the ratio of the thickness direction expansion rate to the in-plane expansion rate is approximately 12, thereby transforming the printed preform from its initial printed state into a functional state with significant anisotropic moisture absorption and deformation characteristics.

[0112] In some embodiments, hydrothermal treatment can also alter the hemicellulose microstructure in the printed preform. Characterization of samples before and after hydrothermal treatment can increase the crystallinity of hemicellulose by 5% to 15%. The crystallinity of hemicellulose can be characterized using X-ray diffraction or infrared spectroscopy.

[0113] After the hydrothermal treatment, the printed preform can be naturally dried at room temperature for 4 hours. Subsequently, the first side of the dried preform undergoes oxygen plasma hydrophilization treatment. In one specific embodiment, the oxygen plasma treatment power is 50W, the oxygen flow rate is 30 sccm, and the treatment time is 40 seconds. After treatment, the water contact angle on the first side can be reduced from approximately 60° to approximately 8°, thereby improving the wetting ability of the area near the first side.

[0114] To verify the distribution of hemicellulose along the thickness direction after printing, the 45-layer gradient hygroscopic expansion layer 100 prepared in this embodiment was divided into four regions along the thickness direction: layers 1 to 10, layers 11 to 20, layers 21 to 35, and layers 36 to 45. Samples were taken from each region, and the xylose content in the hydrolysis products of each region was determined by high performance liquid chromatography. The hemicellulose mass fraction of the corresponding region was calculated based on the measurement results. The preset hemicellulose content and the measured results for each region are shown in Table 3 below.

[0115] Table 3 Floors 1 to 10 12 11.8 -0.2％ Floors 11 to 20 22 22.2 +0.2％ Floors 21 to 35 32 31.7 -0.3％ Floors 36 to 45 40 39.2 -0.8％ As can be seen from the table above, the measured hemicellulose content in each region is close to the corresponding preset hemicellulose content, with the deviation all within 1 percentage point. This indicates that by adjusting the extrusion amount of the second printing material according to the printing layer group, a hemicellulose content distribution that varies along the printing height direction can be formed in the printed blank.

[0116] After the gradient moisture-absorbing expansion layer 100 is prepared, the unidirectional moisture-wicking layer 110 and the breathable shape-conserving support layer 120 can be further assembled. In one specific embodiment, the second side of the gradient moisture-absorbing expansion layer 100 is hot-pressed onto an electrospun nanofiber cellulose membrane. The nanofiber cellulose membrane is approximately 100 μm thick, with a water contact angle of approximately 12° on the side in contact with the gradient moisture-absorbing expansion layer 100 and approximately 128° on the side away from the gradient moisture-absorbing expansion layer 100. The hot-pressing pressure can be 0.2 MPa, and the hot-pressing temperature can be 60°C. Subsequently, a 3D-printed polylactic acid mesh is set on the outside of the unidirectional moisture-wicking layer 110 as the breathable shape-conserving support layer 120. The mesh size can be 2 mm × 2 mm, the wire diameter can be 0.3 mm, and the thickness can be 1 mm. A circumferential sealing structure can be used to fix each layer.

[0117] In another embodiment, lignin can be used instead of pectin as the third printing material. As a specific example, 20g of alkali lignin can be dissolved in 80g of a 0.5mol / L sodium hydroxide aqueous solution, and 0.2g of laccase can be added. The molecular weight of the alkali lignin used can be approximately 5000. The lignin printing material can be placed in an ice-water bath for 2 hours before use to delay the cross-linking reaction. The remaining printing process and damp heat treatment process can be performed in accordance with the pectin system described above.

[0118] When using a lignin system, a cross-linking treatment can be added after the hydrothermal treatment. Specifically, a laccase solution with a concentration of 0.2 U per milliliter can be uniformly applied to the surface and sides of the hydrothermally treated green body, and it can be left to stand at 25°C for 4 hours to allow the laccase to promote further cross-linking of the lignin in the green body. The resulting lignin-cross-linked green body is then dried and subjected to further processing. By adding the lignin cross-linking step, the ability of the lignin inner layer to maintain its structural morphology during subsequent moisture absorption, desorption, and temperature changes can be improved.

[0119] In another parameter embodiment, the ratio of cellulose, hemicellulose, and pectin can be adjusted to 20:30:40, while allowing the average pore size to vary from approximately 3 μm to 90 μm and the hemicellulose content to vary from approximately 10% to 45%. The gradient hygroscopic expansion layer prepared using the above parameters can also complete the processes of environmental moisture absorption, water transport, and desorption vaporization.

[0120] To verify the impact of different structural features on water transport and heat dissipation performance, corresponding comparative structures can also be set up.

[0121] For homogeneous, non-gradient structures, the material ratios of the outer, middle, and inner layers can be kept constant across different printed layers. For example, the volumetric flow rate ratio of the three can be fixed at 45:30:25, ensuring that the average pore size at different thickness locations is maintained at approximately 35 μm and the hemicellulose content is maintained at approximately 25%.

[0122] For isotropic contrast structures, a regular hexagonal honeycomb printing path can be used to prevent the formation of mutually perpendicular fiber layer relationships between different printed layers, while maintaining the same material composition and gradient settings as in the corresponding embodiments. This contrast structure allows for the analysis of the effects of orthotropic meshes and the hygroscopic deformation generated by the orthotropic meshes on moisture transport and heat dissipation processes.

[0123] Furthermore, comparative structures with only a hemicellulose content gradient and those with only an average pore size gradient can be set up separately. In the comparative structure with only a hemicellulose content gradient, the average pore size remains essentially constant along the thickness direction, while the hemicellulose content increases from the first side to the second side. In the comparative structure with only an average pore size gradient, the hemicellulose content remains essentially constant along the thickness direction, while the average pore size increases from the first side to the second side. Therefore, the effects of differences in hemicellulose content and average pore size on the moisture absorption, expansion, and heat dissipation process can be analyzed separately.

[0124] To evaluate the heat dissipation performance of the moisture-absorbing expansion heat dissipation structure, a test sample measuring 40mm × 40mm × 13.5mm can be placed on a 20mm × 20mm ceramic heating element, with a maximum power density of 20W per square centimeter. Thermal grease can be applied between the test sample and the ceramic heating element to reduce the impact of differences in contact conditions during testing. The entire testing setup can be housed in a programmable temperature and humidity chamber.

[0125] During the test, a type K thermocouple can be used to measure the interface temperature between the object to be cooled and the test sample, as well as the temperature on the second side of the test sample. A precision balance with an accuracy of 0.1 mg is used to record the mass change of the test sample in real time. An increase in the mass of the test sample can be used to characterize the moisture absorption process, while a decrease in the mass of the test sample can be used to characterize the desorption process.

[0126] During the daytime heat dissipation phase, the ambient temperature can be set to 45℃, the relative humidity to 30%, and the ceramic heating element can be made to work continuously for 4 hours at a set power density of 10W per square centimeter. The interface temperature change between the object to be cooled and the test sample, as well as the mass change of the test sample, can be recorded.

[0127] The response time can be determined based on the change in interface temperature over time. Specifically, timing can begin from the initial application of a set power density of 10 W per square centimeter. The time elapsed until the interface temperature reaches a state where the change in temperature does not exceed 0.5°C per minute is defined as the heat dissipation response time. Under the above test conditions, when using the structure described in the embodiments of this application, the heat dissipation response time can be 8 to 15 minutes, with the heat dissipation response time of Embodiment 1 being approximately 12 minutes, and the time required for the homogeneous moisture-absorbing structure to reach the corresponding stable state being approximately 40 to 60 minutes.

[0128] It should be noted that the heat dissipation response time here is used to reflect the time it takes for the hygroscopic expansion heat dissipation structure to start receiving heat and for the interface temperature to reach a steady state. This is a different evaluation parameter from the time it takes for moisture to migrate from the first side to the second side, which is measured using a tracer method.

[0129] During the nighttime re-moisture absorption phase, the ceramic heating element can be turned off, the ambient temperature set to 25°C, and the relative humidity set to 80%, and the test sample maintained in this environment for 8 hours. By measuring the mass increase of the sample during this phase, the ability of the test sample to reabsorb moisture from the external environment can be determined. Repeating the above daytime heat dissipation phase and nighttime re-moisture absorption phase can form multiple moisture absorption and desorption cycles. In this embodiment, 30 consecutive day-night cycles can be performed.

[0130] The equivalent heat flux can be determined based on the heat source's operating state, measured interface temperature, and contact thermal resistance calibrated through blank tests, combined with a pre-set thermal resistance model. The equivalent heat flux is used to characterize the equivalent heat dissipation capacity of different hygroscopic expansion heat dissipation structures under the same test conditions; its value is a performance evaluation index calculated based on test parameters.

[0131] Figure 6 The diagram illustrates the temperature variation over time at a set power density of 10 W per square centimeter for Example 1 and the different comparative structures shown in the figure. Figure 6 It can be seen that the initial temperatures of the various test samples were basically similar at the start of the test. As the ceramic heating element continued to operate, the interface temperatures of each test sample gradually increased and tended to stabilize. The interface temperature corresponding to Example 1 was generally lower than that of the comparative structures shown in the figure, and stabilized at approximately 53°C in the later stages of the test. The interface temperature of the homogeneous non-gradient structure was approximately 71°C in the later stages of the test, while the stable temperatures of the other comparative structures were between the two. The above results indicate that, under the same test conditions, simultaneously setting a material gradient and an orthogonal anisotropic grid can enable the absorbed and transported moisture to participate more fully in the desorption and vaporization process.

[0132] Figure 7The surface temperature distribution of Example 1 and the isotropic contrast structure under the same test conditions is shown. The surface temperature distribution of Example 1 is relatively uniform, with a central region temperature of approximately 53°C and an edge region temperature of approximately 51°C. The isotropic contrast structure exhibits a more pronounced high-temperature region in its central area, with a central region temperature of approximately 65°C and an edge region temperature of approximately 55°C. This demonstrates that using an orthogonal anisotropic mesh allows for more uniform moisture transport to the evaporation area, thereby reducing the likelihood of significant hotspots due to insufficient local moisture supply.

[0133] To further evaluate the migration rate of moisture within the gradient hygroscopic expansion layer 100, tracers such as Rhodamine B can be added to the third printing material, and the time it takes for moisture to migrate from near the first side to near the second side can be determined by observing the positional change of the moisture front along the thickness direction. Under one test condition, in Example 1, it took an average of approximately 12 minutes for moisture to migrate from near the first side to near the second side, while it took approximately 35 minutes when using an isotropic mesh structure. These results are consistent with... Figure 4 The anisotropic hygroscopic deformation shown indicates that the hygroscopic expansion and pore compression generated along the thickness direction can participate in the water transport process.

[0134] The daytime heat dissipation and nighttime re-moisture absorption tests were performed on each embodiment and comparative structure, and 30 consecutive day-night cycles were conducted. The test results are shown in Table 4 below.

[0135] Table 4 Example 1 52.7 86 0.89 +1.2 Pectin system Example 2 49.3 102 0.71 +0.9 Lignin system Example 3 57.4 73 0.82 +1.8 Parameter Boundaries Comparative Example 1 71.2 31 0.38 +5.8 Homogeneous non-gradient structure Comparative Example 2 63.5 57 0.65 +3.1 isotropic structure First single-gradient comparison structure 67.4 41 0.52 +4.2 Single gradient structure Second single-gradient comparison structure 64.8 48 0.59 +3.8 Single gradient structure Figure 8 The diagram illustrates the changes in equivalent heat flux during multiple day-night cycles for Example 1, Example 2 using a lignin system, and the different comparative structures shown in the figure. Example 1 had an equivalent heat flux of approximately 86 W / cm² at the initial cycle and approximately 81 W / cm² after 30 cycles. Example 2 using a lignin system had an equivalent heat flux of approximately 102 W / cm² at the initial cycle and approximately 96 W / cm² after 30 cycles. In comparison, Figure 7 The equivalent heat dissipation flux of the comparative structures shown is generally low, and some of the comparative structures show a more obvious downward trend as the number of cycles increases.

[0136] The test results for the dual-gradient and single-gradient structures show that when only one gradient is set, the equivalent heat dissipation flux of the corresponding test samples is approximately 41 W / cm² and 48 W / cm², respectively. In contrast, the equivalent heat dissipation flux of Example 1, which simultaneously sets both the average pore size gradient and the hemicellulose content gradient, is approximately 86 W / cm². This indicates that, under the above test conditions, the structure with both average pore size and hemicellulose content gradients exhibits better heat dissipation performance than the structure with only one gradient.

[0137] The test results from orthogonal anisotropic and isotropic meshes show that, under similar material conditions, the equivalent heat dissipation flux corresponding to the isotropic structure is approximately 57 W / cm², lower than the 86 W / cm² corresponding to Example 1. Combined with... Figure 7 The temperature distribution and moisture migration tracing results shown indicate that the hygroscopic deformation in the thickness direction generated by the orthogonal anisotropic mesh can participate in internal moisture transport and help improve the uniformity of moisture supply in the evaporation region.

[0138] The test results for the pectin and lignin systems show that, under the same or similar test conditions, Example 2, using the lignin system, has a higher equivalent heat flux than Example 1, using the pectin system, while Example 1 has a higher nighttime re-hygroscopicity rate than Example 2. These results indicate that the pectin system has a relatively high capacity for moisture storage and re-hygroscopicity, while the lignin system exhibits different material properties in terms of thermal stability and water decomposition and absorption. Therefore, a suitable third printing material can be selected based on the specific requirements for water storage capacity, re-hygroscopicity capacity, and heating conditions in the working environment.

[0139] The cyclic test results show that after 30 day-night cycles, the interface temperatures of Examples 1 and 2 increased by approximately 1.2°C and 0.9°C respectively compared to their initial states, while the interface temperature of the homogeneous non-gradient structure increased by approximately 5.8°C after the same number of cycles. This indicates that the hygroscopic expansion heat dissipation structure using gradient material composition and orthogonal anisotropic grids can maintain a relatively stable heat dissipation state during repeated moisture absorption and desorption processes.

[0140] In further long-term stability tests, Example 1 was continuously operated for 500 hours in an environment of 60°C and 90% relative humidity. After the test, the heat dissipation flux retention rate of Example 1 still reached over 93%, indicating that the gradient moisture absorption expansion layer 100 can maintain relatively stable working performance under continuous temperature and humidity conditions.

[0141] The cellulose, hemicellulose, and pectin materials used in this embodiment can be derived from agricultural byproducts such as corn cobs, bagasse, and fruit peels, or from commercially available bio-based raw materials. In an accelerated degradation test, waste samples were placed in an industrial composting environment with a temperature of approximately 58°C and a relative humidity of no less than 90%. After three months, the degradation rate of the samples reached over 95%. Under normal operating conditions of -20°C to 60°C and a relative humidity of 10% to 80%, the materials did not undergo significant degradation during short-term use. Therefore, the appropriate bio-based material system can be selected based on the actual service life and waste disposal requirements.

[0142] Through the above-described embodiments, this application first utilizes a gradient moisture-absorbing expansion layer 100 to acquire moisture from the external environment, and utilizes the varying hemicellulose content along the thickness direction to promote the migration of moisture from the first side to the second side. During the moisture absorption process, the orthogonal anisotropic mesh generates a more pronounced structural deformation along the thickness direction, further propelling the moisture along the thickness direction by compressing the internal pores. When the moisture is transported to the vicinity of the second side, the heat generated by the object to be cooled causes the water to decompose and vaporize, and the resulting water vapor is further discharged to the external environment through the unidirectional moisture-wicking layer 110 and the breathable shape-conserving support layer 120. When the temperature decreases or the humidity of the external environment increases, the gradient moisture-absorbing expansion layer 100 can reabsorb moisture, providing moisture for the next heat dissipation process. Thus, a cyclical heat dissipation process can be formed, in which moisture absorption, moisture transport, desorption and vaporization, and re-moisture absorption are interconnected.

[0143] In summary, this application provides a moisture-absorbing expansion heat dissipation method. This method involves connecting a moisture-absorbing expansion heat dissipation structure to an object requiring heat exchange. The moisture-absorbing expansion heat dissipation structure includes a gradient moisture-absorbing expansion layer. This layer comprises multiple gradient regions arranged along the thickness direction from a first side to a second side, and has an orthogonal anisotropic mesh. In two adjacent gradient regions, the average pore size of the gradient region closer to the second side is larger than that of the gradient region closer to the first side, and the hemicellulose content of the gradient region closer to the second side is greater than that of the gradient region closer to the first side. This allows moisture from the external environment to be absorbed by the gradient. The moisture-expanding layer absorbs moisture, causing the orthogonal anisotropic mesh to undergo moisture-absorbing deformation. The expansion in the thickness direction is greater than the expansion in the in-plane direction perpendicular to the thickness direction. Utilizing the difference in hemicellulose content between adjacent gradient regions, moisture within the gradient moisture-absorbing expansion layer migrates to the second side. The moisture-absorbing deformation compresses the pores within the gradient moisture-absorbing expansion layer, further promoting moisture transport to the second side. The heat generated by the object to be cooled is transferred to the moisture transported to the second side, causing the moisture to desorb from the gradient moisture-absorbing expansion layer and vaporize, thus dissipating heat from the object. This addresses the problem of effectively transporting absorbed moisture to the vaporization cooling location during moisture-absorbing heat dissipation, achieving directional transport of moisture in the moisture-absorbing expansion heat dissipation structure, and utilizing the vaporization of transported water to dissipate heat from the object.

[0144] Based on the same technical concept, embodiments of this application also provide a moisture absorption and expansion heat dissipation system, such as... Figure 9 As shown, it includes: A heat exchange connection module 901 is used to heat exchange the moisture-absorbing expansion heat dissipation structure with the object to be cooled. The moisture-absorbing expansion heat dissipation structure includes a gradient moisture-absorbing expansion layer. The gradient moisture-absorbing expansion layer includes a plurality of gradient regions arranged along the thickness direction from a first side to a second side and has an orthogonal anisotropic grid. In two adjacent gradient regions, the average pore size of the gradient region closer to the second side is greater than the average pore size of the gradient region closer to the first side, and the hemicellulose content of the gradient region closer to the second side is greater than the hemicellulose content of the gradient region closer to the first side. The moisture-absorbing deformation module 902 is used to allow moisture in the external environment to be absorbed by the gradient moisture-absorbing expansion layer, so that the orthogonal anisotropic mesh undergoes moisture-absorbing deformation. The degree of expansion in the thickness direction is greater than the degree of expansion in the in-plane direction perpendicular to the thickness direction. The moisture transport module 903 is used to utilize the difference in hemicellulose content between two adjacent gradient regions to cause moisture in the gradient moisture-absorbing expansion layer to migrate to the second side, and to use the moisture-absorbing deformation to compress the pores in the gradient moisture-absorbing expansion layer to promote the transport of moisture to the second side. The heat dissipation module 904 is used to transfer the heat generated by the object to be cooled to the moisture transported to the second side, so that the moisture is desorbed from the gradient hygroscopic expansion layer and vaporized, thereby dissipating heat from the object to be cooled.

[0145] This application also provides an electronic device corresponding to the method provided in the foregoing embodiments. Please refer to... Figure 10 The diagram illustrates an electronic device provided by some embodiments of this application. The electronic device 20 may include: a processor 200, a memory 201, a bus 202, and a communication interface 203, wherein the processor 200, the communication interface 203, and the memory 201 are connected via the bus 202; the memory 201 stores a computer program that can run on the processor 200, and when the processor 200 runs the computer program, it executes the method provided by any of the foregoing embodiments of this application.

[0146] The memory 201 may include high-speed random access memory (RAM) or non-volatile memory, such as at least one disk storage device. Communication between this system network element and at least one other network element is achieved through at least one physical port (which can be wired or wireless), such as the Internet, wide area network, local area network, or metropolitan area network.

[0147] Bus 202 can be an ISA bus, PCI bus, or EISA bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. The memory 201 is used to store programs. After receiving an execution instruction, the processor 200 executes the program. The method disclosed in any of the foregoing embodiments of this application can be applied to the processor 200, or implemented by the processor 200.

[0148] The processor 200 may be an integrated circuit chip with signal processing capabilities. In implementation, each step of the above method can be completed by the integrated logic circuitry in the hardware of the processor 200 or by instructions in software form. The processor 200 may be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it may also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), an off-the-shelf programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor may be a microprocessor or any conventional processor. The methods disclosed in the embodiments of this application can be directly embodied as being executed by a hardware decoding processor, or executed by a combination of hardware and software modules in the decoding processor. The software modules may reside in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. The storage medium is located in memory 201. Processor 200 reads the information in memory 201 and performs the above method in conjunction with its hardware.

[0149] The electronic devices and methods provided in the embodiments of this application are based on the same inventive concept and have the same beneficial effects as the methods they employ, operate, or implement.

[0150] This application also provides a computer-readable storage medium corresponding to the method provided in the foregoing embodiments. Please refer to... Figure 11 The computer-readable storage medium shown is an optical disc 30, on which a computer program (i.e., a program product) is stored, which, when run by a processor, executes the methods provided in any of the foregoing embodiments.

[0151] It should be noted that examples of the computer-readable storage medium may also include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other optical and magnetic storage media, which will not be elaborated here.

[0152] The computer-readable storage medium provided in the above embodiments of this application and the method provided in the embodiments of this application are based on the same inventive concept and have the same beneficial effects as the methods adopted, run or implemented by the applications stored therein.

[0153] It should be noted that the above embodiments are illustrative of this application and not restrictive, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. This application can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0154] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0155] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made under the concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for absorbing moisture, expanding, and dissipating heat, characterized in that, include: The moisture-absorbing and expansion heat dissipation structure is heat-exchange connected to the object to be cooled. The moisture-absorbing and expansion heat dissipation structure includes a gradient moisture-absorbing and expansion layer. The gradient moisture-absorbing and expansion layer includes multiple gradient regions arranged along the thickness direction from a first side to a second side and has an orthogonal anisotropic grid. In two adjacent gradient regions, the average pore size of the gradient region closer to the second side is greater than the average pore size of the gradient region closer to the first side, and the hemicellulose content of the gradient region closer to the second side is greater than the hemicellulose content of the gradient region closer to the first side. The gradient moisture-absorbing expansion layer absorbs moisture from the external environment, causing the orthogonal anisotropic mesh to undergo moisture-absorbing deformation. The degree of expansion in the thickness direction is greater than the degree of expansion in the in-plane direction perpendicular to the thickness direction. By utilizing the difference in hemicellulose content between two adjacent gradient regions, moisture in the gradient moisture-absorbing expansion layer migrates to the second side, and the moisture-absorbing deformation compresses the pores in the gradient moisture-absorbing expansion layer to promote the transport of moisture to the second side. The heat generated by the object to be cooled is transferred to the moisture transported to the second side, causing the moisture to desorb from the gradient hygroscopic expansion layer and vaporize, thereby cooling the object to be cooled.

2. The method as described in claim 1, characterized in that, The gradient hygroscopic expansion layer further includes a moisture-regulating component; the process of allowing moisture from the external environment to be absorbed by the gradient hygroscopic expansion layer includes: This allows water vapor from the external environment to enter the gradient moisture-absorbing expansion layer; The water vapor is captured by the pores in the gradient region near the first side, thus obtaining captured moisture; The captured water is stored using the moisture conditioning component or the retention and release of the captured water are regulated to obtain water to be transported. The hemicellulose absorbs the water to be transported.

3. The method as described in claim 2, characterized in that, The gradient moisture-absorbing expansion layer further includes a skeleton component; the process of causing the orthogonal anisotropic mesh to undergo moisture-absorbing deformation includes: The hemicellulose absorbs water and swells; By using the skeleton components to restrict the expansion of the orthogonal anisotropic mesh along the in-plane direction, the orthogonal anisotropic mesh expands along the thickness direction, resulting in the moisture-absorbing deformation. The moisture-absorbing deformation is used to compress the pores within the gradient moisture-absorbing expansion layer, thereby driving the moisture within the pores to move along the thickness direction.

4. The method as described in claim 3, characterized in that, The method of utilizing the difference in hemicellulose content between two adjacent gradient regions to cause moisture in the gradient hygroscopic expansion layer to migrate to the second side, and utilizing the hygroscopic deformation to compress the pores in the gradient hygroscopic expansion layer to promote the transport of moisture to the second side, includes: According to the arrangement order of the multiple gradient regions from the first side to the second side, the moisture in the current gradient region migrates to the next gradient region based on the difference in hemicellulose content between the current gradient region and the next adjacent gradient region that is close to the second side. During the migration of moisture to the next gradient region, the hygroscopic deformation compresses the pores in the current gradient region to push the moisture into the next gradient region. According to the arrangement order of the multiple gradient regions, the gradient region closest to the second side is used as the next gradient region for water migration and pore compression until the water is transported to the gradient region closest to the second side.

5. The method as described in claim 1, characterized in that, Before connecting the moisture-absorbing expansion heat dissipation structure to the object to be cooled in heat exchange, the following is also included: The first surface of the unidirectional moisture-wicking layer is attached to the second side of the gradient moisture-absorbing expansion layer. The unidirectional moisture-wicking layer also includes a second surface that is away from the gradient moisture-absorbing expansion layer. The first surface has a greater wettability to water than the second surface. A breathable and shape-conserving support layer is placed on the side of the unidirectional moisture-wicking layer that is away from the gradient moisture-absorbing and expansion layer.

6. The method as described in claim 1, characterized in that, Before connecting the moisture-absorbing expansion heat dissipation structure to the object to be cooled through heat exchange, the method further includes preparing the gradient moisture-absorbing expansion layer; the preparation of the gradient moisture-absorbing expansion layer includes: Prepare a first printing material, a second printing material, and a third printing material, wherein the second printing material includes hemicellulose; The first printing material, the second printing material, and the third printing material are respectively fed into the corresponding channels of the multi-channel coaxial printhead; Coaxial composite fibers are obtained by extruding the first printing material, the second printing material, and the third printing material through the multi-channel coaxial printing nozzle. The coaxial composite fibers are printed layer by layer to obtain a printed blank; The printed blank is post-processed to obtain the gradient moisture-absorbing expansion layer.

7. The method as described in claim 6, characterized in that, The process of printing the coaxial composite fiber layer by layer to obtain a printed preform includes: The coaxial composite fibers are printed parallel to the in-plane direction to obtain the first fiber layer; The coaxial composite fibers are printed parallel to the second in-plane direction on the first fiber layer to obtain the second fiber layer, wherein the second in-plane direction is perpendicular to the first in-plane direction. The coaxial composite fibers are printed layer by layer alternately in the first in-plane direction and the second in-plane direction to obtain a printed blank with the orthogonal anisotropic mesh.

8. The method as described in claim 7, characterized in that, The step-by-step printing of the coaxial composite fiber to obtain a printed blank further includes: Multiple fiber layers to be printed are divided into multiple printing layer groups arranged along the printing height direction, each of the printing layer groups is used to form a gradient region, and the printing height direction corresponds to the thickness direction; Based on the arrangement of each printing layer group along the printing height direction, the extrusion amount of the first printing material, the extrusion amount of the second printing material, and the extrusion amount of the third printing material corresponding to each printing layer group are determined respectively, so that the proportion of the second printing material corresponding to the printing layer group closer to the second side in two adjacent printing layer groups is greater than the proportion of the second printing material corresponding to the printing layer group closer to the first side. According to the first printing material extrusion amount, the second printing material extrusion amount, and the third printing material extrusion amount corresponding to each printing layer group, each printing layer group is printed sequentially, so that the hemicellulose content of the gradient region closer to the second side in two adjacent gradient regions is greater than the hemicellulose content of the gradient region closer to the first side.

9. The method as described in claim 8, characterized in that, The post-processing of the printed preform to obtain the gradient moisture-absorbing expansion layer includes: The printed preform is subjected to a wet heat treatment, which causes the hemicellulose to absorb moisture and causes the expansion of the printed preform along the thickness direction to be greater than the expansion along the in-plane direction, thus obtaining a wet heat-treated preform. The wet-heat treated green body is dried to obtain a dried green body; The first side of the dried blank is subjected to hydrophilic treatment to obtain the gradient moisture-absorbing expansion layer.

10. A moisture-absorbing expansion heat dissipation system, characterized in that, include: A heat exchange connection module is used to connect a moisture-absorbing expansion heat dissipation structure to an object to be cooled via heat exchange. The moisture-absorbing expansion heat dissipation structure includes a gradient moisture-absorbing expansion layer. The gradient moisture-absorbing expansion layer includes multiple gradient regions arranged along the thickness direction from a first side to a second side and has an orthogonal anisotropic grid. In two adjacent gradient regions, the average pore size of the gradient region closer to the second side is greater than the average pore size of the gradient region closer to the first side, and the hemicellulose content of the gradient region closer to the second side is greater than the hemicellulose content of the gradient region closer to the first side. A moisture-absorbing deformation module is used to allow moisture in the external environment to be absorbed by the gradient moisture-absorbing expansion layer, so that the orthogonal anisotropic mesh undergoes moisture-absorbing deformation. The degree of expansion in the thickness direction is greater than the degree of expansion in the in-plane direction perpendicular to the thickness direction. A moisture transport module is used to utilize the difference in hemicellulose content between two adjacent gradient regions to cause moisture in the gradient moisture-absorbing expansion layer to migrate to the second side, and to use the moisture-absorbing deformation to compress the pores in the gradient moisture-absorbing expansion layer to promote the transport of moisture to the second side. The heat dissipation module is used to transfer the heat generated by the object to be cooled to the moisture transported to the second side, so that the moisture is desorbed and vaporized from the gradient hygroscopic expansion layer, thereby dissipating heat from the object to be cooled.

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