Antibacterial functional sock and knitting method thereof

Abstract

The application discloses an antibacterial functional sock and a knitting method thereof, and belongs to the technical field of sock processing. The antibacterial composite yarn of the antibacterial functional sock is a non-symmetrical double-skin core structure composed of a core layer, an inner skin layer and an outer skin layer. The core layer is a porous polymer fiber loaded with nano antibacterial particles, the inner skin layer is a hydrophobic porous layer, and the outer skin layer is a hydrophilic swelling layer. The sock body is longitudinally divided into a toe area, a forefoot area, an arch area, a hindfoot area and a heel area, and the content of the antibacterial yarn in each area is continuously and gradiently arranged. The thickness direction has a Janus gradient structure from the inner layer to the surface layer. The sock bottom is provided with a tree-shaped fractal moisture-conducting network. The outer skin layer senses humidity change to generate swelling pressure, and regulates the porosity of the inner skin layer, so that the antibacterial release rate decreases with the increase of humidity. The longitudinal gradient and the one-way moisture conduction are coordinated, so that the antibacterial property is durable, controllable and low in cost.

Description

Technical Field

[0001] This invention belongs to the field of sock processing technology, specifically relating to an antibacterial functional sock and its knitting method. Background Technology

[0002] Socks are in a warm and humid microenvironment for a long time, which makes them very susceptible to the growth of bacteria and fungi, producing odors and potentially causing skin diseases such as athlete's foot and dermatitis. Therefore, developing socks with long-lasting antibacterial function is of great practical significance.

[0003] Currently, antibacterial socks are mainly implemented through the following methods:

[0004] (a) Finishing method. The finished socks are immersed in an antibacterial finishing solution, allowing the antibacterial agent to adhere to the fiber surface. This method is simple and low-cost, but the antibacterial components have weak bonding force with the fibers, poor wash resistance, and the antibacterial performance is greatly reduced after repeated washing.

[0005] (II) Antibacterial Fiber Method. Antibacterial components are implanted into the fiber through methods such as blending and spinning, and grafting modification, such as copper ion antibacterial nylon fiber and nano-silver / zinc blended fiber. This method offers better durability than finishing methods, but requires modification during the spinning stage, resulting in complex processes, high equipment requirements, and significantly increased production costs.

[0006] (III) Zoned Antibacterial Method. To control costs while ensuring antibacterial efficacy, a zoned antibacterial design approach has emerged in recent years. For example, CN219270187U uses silver fibers in the sole area but not in the ankle area. The problem with this approach is that the zoning is based on empirical judgment, resulting in a discrete distribution of antibacterial substances ("present / absent" or "high / low"), lacking a continuous gradient transition. Furthermore, regardless of zoning, the antibacterial components are continuously released once they come into contact with sweat, representing a typical passive release mode.

[0007] (iv) Core-sheath structure antibacterial fiber. For example, CN122082177A has a core layer of thermoplastic polymer slow-release filaments containing nano-silver and a sheath layer of regenerated cellulose short fibers. The slow release is achieved through coordination complexation between the sheath layer and silver ions. However, the function of the sheath layer is only moisturizing modification and it does not have the ability to actively regulate the release rate.

[0008] (v) Humidity-responsive functional materials. CN115537949A discloses a biomimetic tree-like branching structure unidirectional water-conducting membrane, but it belongs to the field of nonwoven membrane or material research and does not involve its integration with sock knitting technology.

[0009] In summary, existing technologies mainly suffer from three core problems: First, the antibacterial release is uncontrollable—passive release leads to insufficient protection at low humidity and excessive release and rapid depletion at high humidity; second, the spatial configuration is inaccurate—zoning is based on experience, and the discrete distribution may result in insufficient high-demand areas and waste in low-demand areas; third, the structural dimension is isolated—planar zoning and thickness-direction structures are independent of each other, lacking a systematic synergistic mechanism of "physical dehumidification + chemical antibacterial", making it difficult to balance cost and performance. Summary of the Invention

[0010] This invention provides an antibacterial functional sock and its knitting method. The antibacterial composite yarn of the sock has an asymmetric double-layer core-sheath structure consisting of a core layer, an inner sheath layer, and an outer sheath layer. The core layer is a porous polymer fiber loaded with nano-antibacterial particles, the inner sheath layer is a hydrophobic porous layer, and the outer sheath layer is a hydrophilic swelling layer. The outer sheath layer senses changes in humidity and generates swelling pressure, which regulates the porosity of the inner sheath layer, causing the antibacterial release rate to decrease as humidity increases. The longitudinal gradient and unidirectional moisture-wicking work synergistically to achieve long-lasting, controllable, and low-cost antibacterial properties, thereby solving the problems mentioned in the background art.

[0011] To achieve the above objectives, the present invention provides the following technical solution: an antibacterial functional sock, comprising a sock body and an antibacterial composite yarn woven into the sock body, the antibacterial composite yarn comprising a core layer, an inner sheath layer, and an outer sheath layer, wherein the core layer is loaded with nano-antibacterial particles, the inner sheath layer covers the outside of the core layer, and the outer sheath layer covers the outside of the inner sheath layer; the core layer is a porous polymer fiber loaded with the nano-antibacterial particles, the inner sheath layer is a hydrophobic porous polymer layer, and the outer sheath layer is a hydrophilic swelling layer; the sock body is divided into at least three functional regions longitudinally from the sock cuff to the sock toe, and the content of the antibacterial composite yarn woven in each functional region is arranged in a continuous gradient along the longitudinal direction; when the outer sheath layer absorbs moisture and swells, it generates inward pressure, which reduces the porosity of the inner sheath layer, and the release rate of the nano-antibacterial particles decreases with increasing ambient humidity.

[0012] As a further option, the core layer, the inner skin layer, and the outer skin layer constitute an asymmetric double-layer core-skin structure. The core layer is a reservoir for antibacterial active ingredients, the inner skin layer is a release control valve, and the outer skin layer is a humidity sensing and driving layer. The inner skin layer is made of polyvinylidene fluoride or polytetrafluoroethylene, and the outer skin layer is made of sodium alginate or modified chitosan.

[0013] As a further option, the functional areas are arranged longitudinally along the sole of the foot as follows: toe area, forefoot area, arch area, heel area and heel area. The antibacterial composite yarn accounts for 80% to 85% of the toe area and the heel area, 70% to 75% of the forefoot area, 60% to 65% of the heel area, and 45% to 50% of the arch area (5). A transition area is provided between each adjacent functional area.

[0014] As a further option, the sock body consists of an inner layer, an intermediate transition layer, and an outer layer in the thickness direction from the inner layer to the outer layer. The proportion of antibacterial composite yarn in the inner layer is higher than that in the outer layer. The inner layer is treated with hydrophilic finishing, and the outer layer is treated with hydrophobic finishing. The content of antibacterial composite yarn and the hydrophilicity / hydrophobicity of the intermediate transition layer are continuously gradient transitioned from the inner layer to the outer layer, forming a Janus thickness gradient structure.

[0015] As a further option, the sock body also includes a sock sole moisture-wicking structure, which is a tree-like fractal moisture-wicking network formed on the inner surface of the sock sole. The tree-like fractal moisture-wicking network is woven from antibacterial composite yarn, and the projection of the tree-like fractal moisture-wicking network on the sock sole plane is a tree-like distribution with progressively branching branches.

[0016] As a further option, the tree-like fractal moisture-wicking network includes a main channel protrusion extending longitudinally along the sole of the sock, secondary channel protrusions branching from the main channel protrusion, and microchannel protrusions branching from the ends of the secondary channel protrusions. The main channel protrusion, the secondary channel protrusion, and the microchannel protrusion form a three-level fractal structure. The height of the main channel protrusion is 0.5–1.2 mm and the width is 1.0–2.0 mm. The height of the secondary channel protrusion is 0.3–0.8 mm and the width is 0.5–1.0 mm. The height of the microchannel protrusion is 0.2–0.4 mm and the diameter is 0.3–0.6 mm. The branching angle between the secondary channel protrusion and the main channel protrusion is 30°–60°, and the number of branching levels is 2–3.

[0017] A method for knitting antibacterial functional socks as described in any of the above claims includes the following steps:

[0018] Preparation of antibacterial composite yarn: Porous polymer fibers are prepared as the core layer, and nano-antibacterial particles are loaded inside and on the surface of the porous polymer fibers. A hydrophobic porous inner skin layer is coated on the outside of the porous polymer fibers loaded with nano-antibacterial particles, and then a hydrophilic outer skin layer is coated on the outside of the inner skin layer to obtain antibacterial composite yarn.

[0019] A three-dimensional coupled model of plantar pressure, perspiration, and temperature was established to calculate the antibacterial demand index of each area of ​​the sole.

[0020] Zonal weaving: Based on the antibacterial demand index of each area, the proportion of antibacterial composite yarn in each functional area is determined. A computerized jacquard sock knitting machine is used to weave the antibacterial composite yarn into each functional area according to the determined proportion, so that the content of antibacterial composite yarn in each functional area is continuously gradient along the longitudinal direction.

[0021] When the outer skin absorbs moisture and swells, it generates inward pressure, which reduces the porosity of the inner skin. The release rate of the nano-antibacterial particles decreases as the ambient humidity increases.

[0022] As a further option, in the step of determining the proportion of antibacterial composite yarn in each functional area based on the antibacterial demand index of each area, the sole of the foot is divided longitudinally into the toe area, forefoot area, arch area, heel area, and heel area. The proportion of antibacterial composite yarn in the toe area and the heel area is 80% to 85%, the proportion of antibacterial composite yarn in the forefoot area is 70% to 75%, the proportion of antibacterial composite yarn in the heel area is 60% to 65%, and the proportion of antibacterial composite yarn in the arch area is 45% to 50%. A transition zone is provided between each adjacent functional area.

[0023] As a further option, a moisture-wicking network weaving step is also included: after the sock sole is woven, the process switches to a tuck weaving pattern to weave a tree-like fractal moisture-wicking network on the inner surface of the sock sole with antibacterial composite yarn. The tree-like fractal moisture-wicking network includes a main channel ridge extending longitudinally along the sock sole, secondary channel ridges extending from the main channel ridges, and microchannel ridges formed from the ends of the secondary channel ridges. The main channel ridges, the secondary channel ridges, and the microchannel ridges form a three-level fractal structure.

[0024] As a further option, the porous polymer fiber has a porosity of 30%–60% and an average pore size of 50–500 nm; the inner skin layer has a thickness of 0.01–0.03 mm, a porosity of 30%–50%, and an average pore size of 50–200 nm; the outer skin layer has a thickness of 0.02–0.05 mm, a dry contact angle of less than 60°, and a wet swelling rate of 200%–500%; the inner skin layer is coated using a solution coating-phase inversion method, and the outer skin layer is coated using a wet crosslinking coating method.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. This invention utilizes an asymmetric double-layer core-sheath structure with a three-layer functional allocation of "storage-valve-drive," enabling the release rate of antibacterial active ingredients to automatically adjust with ambient humidity—maintaining basic protection at low humidity, moderately inhibiting release at medium humidity, and ceasing release at high humidity. This avoids the problems of insufficient release at low humidity and excessive release at high humidity caused by passive release in existing technologies. The antibacterial particles are embedded within the porous fibers of the core layer, resulting in significantly better wash resistance than post-treatment methods.

[0027] 2. This invention determines the antibacterial demand index for each zone based on measured data from a three-dimensional coupled model of plantar pressure, perspiration, and temperature, upgrading the configuration of antibacterial yarn from empirical judgment to data-driven quantitative design. The five-zone continuous gradient configuration significantly reduces the total amount of antibacterial composite yarn used while ensuring antibacterial effectiveness, achieving a good balance between performance and cost.

[0028] 3. This invention couples a longitudinal five-zone gradient with a Janus gradient in the thickness direction in two dimensions—the longitudinal gradient enables on-demand spatial allocation, while the thickness gradient enables unidirectional moisture wicking to keep the inside of the sock dry. The dry microenvironment itself is unfavorable for bacterial growth, and this, combined with the moisture-responsive release, creates a dual antibacterial synergy. The tree-like fractal moisture-wicking network on the sock sole increases the contact area between the antibacterial yarn and the skin while forming micro-air channels, further improving moisture wicking and antibacterial efficiency. Attached Figure Description

[0029] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0030] In the attached diagram:

[0031] Figure 1 This is a schematic diagram of the overall structure of the antibacterial functional socks of the present invention.

[0032] Figure 2 This is a schematic cross-sectional view of the asymmetric double-layer core-sheath structure of the antibacterial composite yarn of the present invention.

[0033] Figure 3 This is a schematic diagram showing the division of functional areas of the sock sole and the gradient of the proportion of antibacterial yarns in this invention.

[0034] Figure 4 This is a schematic diagram of the structure of the tree-like fractal moisture-wicking network for the bottom of the sock according to the present invention.

[0035] Figure 5 This is a schematic diagram of the Janus gradient structure in the thickness direction of the present invention.

[0036] Figure 6 This is a schematic diagram illustrating the humidity response release principle of the asymmetric double-layer core-skin structure of the present invention.

[0037] The markings in the diagram are as follows: 1-Sock cuff; 2-Sock leg; 3-Heel area; 4-Heel area; 5-Arch area; 6-Forefoot area; 7-Toe area; 8-Toe; 9-Main channel protrusion; 10-Secondary channel protrusion; 11-Microchannel protrusion; 12-Outer skin layer; 13-Inner skin layer; 14-Core layer; 15-Nano antibacterial particles; 16-Pore. Detailed Implementation

[0038] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1: Please refer to Figure 2 Preparation principle and process of antibacterial composite yarn

[0040] The preparation of the antibacterial composite yarn described in this invention includes four steps: core layer forming, antibacterial particle loading, inner sheath coating, and outer sheath coating. The structural principles, material selection criteria, preparation methods, and key process control points of each step are explained in detail below.

[0041] 1. Core layer 14 – Preparation of porous polymer fibers

[0042] (1) Structural principles and functional positioning

[0043] The core layer is the basic framework of the antibacterial composite yarn, serving as a "reservoir" for the active antibacterial components. To achieve this function, the core layer adopts a porous polymer fiber morphology with an interconnected or semi-connected pore network inside. This pore network performs two core tasks: first, it fixes nano-antibacterial particles inside and on the surface of the fiber through physical embedding and surface adsorption, making the antibacterial particles less likely to fall off during washing, thus ensuring the durability of antibacterial activity; second, the capillary channels formed by the pores constitute the pathway for antibacterial ions to migrate from the fiber interior to the surface, and the basic release rate of antibacterial ions can be controlled by adjusting the porosity and pore size distribution.

[0044] (2) Basis for material selection

[0045] The core layer substrate is made of polyacrylonitrile or polyester. Polyacrylonitrile possesses excellent weather resistance, resistance to microbial attack, and spinnability. The nitrile groups on its molecular chain have strong polarity, which is beneficial for the adsorption and fixation of nano-antibacterial particles. Furthermore, polyacrylonitrile can be easily prepared into porous structures through wet spinning, and the dispersion and elution processes of the pore-forming agent are easily controlled. Polyester has high strength and modulus, excellent heat resistance and dimensional stability, making it suitable for sports socks products requiring high yarn strength. Porous polyester-based fibers can be prepared into porous structures through alkali reduction spinning or by dissolving the fibers after blending with a soluble polymer.

[0046] (3) Principle of pore structure parameter control

[0047] Porosity and pore size are key parameters affecting reservoir function and release behavior. The preferred porosity is 30%–60%: If the porosity is too low (<30%), there are insufficient loading sites for the antibacterial nanoparticles, limiting the loading capacity and resulting in insufficient antibacterial effect; if the porosity is too high (>60%), the mechanical strength of the fiber decreases significantly, affecting subsequent spinning and weaving processes, and the excessively thin pore walls may cause the antibacterial particles to be released prematurely under stress. The preferred average pore size is 50–500 nm: If the pore size is too small (<50 nm), the antibacterial nanoparticles (typically 15–50 nm in diameter) cannot effectively enter the pores and can only be loaded on the fiber surface, resulting in poor wash resistance; if the pore size is too large (>500 nm), the capillary effect weakens, the migration rate of antibacterial ions is too fast, and the release becomes uncontrollable.

[0048] (4) Preparation method and process control

[0049] Taking polyacrylonitrile (PAB) as an example, PAB powder (preferably with a molecular weight of 50,000–100,000) is dissolved in dimethylformamide, and a pore-forming agent (preferably polyethylene glycol PEG-400 or polyvinylpyrrolidone PVP-K30, preferably 5%–20% of the total mass of the spinning solution) is added. The solution is stirred at 60–80°C until completely dissolved, and after standing to remove bubbles, the spinning solution is obtained. The spinning solution is extruded through a spinneret into a coagulation bath (a mixture of deionized water and dimethylformamide, preferably with a volume ratio of 60:40–80:20, and a temperature of 15–35°C). A double diffusion exchange occurs between the solvent and non-solvent, and the polymer coagulates and precipitates to form nascent fibers. During this process, the pore-forming agent molecules occupy a certain volume space inside the fiber and are gradually washed away during subsequent washing, leaving a porous structure. The type of pore-forming agent affects the pore size distribution: lower molecular weight PEG results in smaller pores, while higher molecular weight PVP results in larger pores. The amount of pore-forming agent added affects the total porosity. The composition and temperature of the coagulation bath affect the phase separation rate, which in turn affects the connectivity and morphology of the pores (sponge-like or finger-like pores). The spinning speed affects the fiber orientation and the orientation arrangement of pores 16. The resulting nascent fibers are thoroughly washed with deionized water to remove residual solvents and pore-forming agents, stretched (preferably by a ratio of 2 to 5 times) to improve the fiber's breaking strength and modulus, and then dried and shaped (preferably at a temperature of 80 to 120°C) to eliminate internal stress and fix the fiber morphology, resulting in a porous polymer fiber substrate.

[0050] 2. Loading of nano-antibacterial particles 15

[0051] (1) Selection criteria for antimicrobial particles

[0052] This invention preferably uses nano-silver particles or nano-zinc oxide particles as the active antibacterial ingredient. Nano-silver possesses broad-spectrum antibacterial activity, exhibiting excellent killing effects against common endoscopic pathogens such as Staphylococcus aureus, Escherichia coli, and Candida albicans. Its antibacterial mechanism involves silver ions binding to negatively charged groups on bacterial cell walls and cell membranes, disrupting cell membrane integrity. Simultaneously, silver ions enter the cell and react with sulfur- and phosphorus-containing proteins and enzymes, inhibiting the respiratory chain and DNA replication, leading to bacterial death. Nano-zinc oxide's antibacterial mechanism involves photocatalysis to generate reactive oxygen species (superoxide anions, hydroxyl radicals, etc.), oxidizing and destroying bacterial cell walls and cell membranes. Zinc ions themselves also possess a certain antibacterial effect. While the antibacterial activity of nano-zinc oxide is slightly lower than that of nano-silver, it is less expensive and has better thermal stability, making it suitable for cost-sensitive products.

[0053] (2) Load principle and process

[0054] Nanoparticles of antibacterial nature are loaded onto porous polymer fibers using an ultrasonic-assisted oscillation impregnation method. The core loading mechanism is as follows: in a liquid medium, the nanoparticles are uniformly dispersed under ultrasonic oscillation; the porous fibers are impregnated in the dispersion, and under the action of microjets and shock waves generated by ultrasonic cavitation, the dispersion is forced to penetrate into the pores 16 of the fibers; ultrasonic oscillation simultaneously breaks up agglomerated nanoparticles, promoting the adsorption and deposition of individual nanoparticles on the inner walls of the pores. Adsorption forces include van der Waals forces, electrostatic adsorption forces, and microporous physical retention. Impregnation temperature affects the particle diffusion rate and the rate of adsorption equilibrium establishment—increasing the temperature (40–80℃) is beneficial to improving the diffusion coefficient and adsorption rate, but excessively high temperatures (>80℃) may lead to increased nanoparticle agglomeration or dispersant decomposition. Impregnation time affects the loading amount—as the impregnation time increases (2–8 hours), the loading amount gradually increases and tends to adsorption equilibrium; further extending the time has limited effect on increasing the loading amount. The optimal loading is 0.5% to 3.0% of the fiber mass. This range balances antibacterial effect (insufficient antibacterial activity below 0.5%) and maintenance of fiber mechanical properties (severe particle agglomeration and fiber brittleness above 3.0%).

[0055] (3) Selection and function of dispersants

[0056] An appropriate amount of dispersant (such as polyvinylpyrrolidone PVP or sodium dodecyl sulfate SDS, preferably 0.1% to 0.5% of the mass of the dispersion) can be added to the impregnation solution. The dispersant molecules adsorb onto the surface of the nanoparticles, inhibiting particle aggregation through steric hindrance or electrostatic repulsion, thereby improving dispersion stability and loading uniformity.

[0057] 3. Inner cortex 13 – Hydrophobic porous control layer

[0058] (1) Functional positioning and design principles

[0059] The inner cortex covers the outside of the core layer and functions as a "regulatory valve" for the release of antibacterial active ingredients. Its design principle is as follows:

[0060] The inner skin layer is made of a hydrophobic polymer material (preferably polyvinylidene fluoride PVDF or polytetrafluoroethylene PTFE), and a porous film with a controllable pore structure is formed on the surface of the core layer through a solution coating-phase inversion method. This film has a dual controllability function:

[0061] The first layer—the hydrophobic barrier effect: The hydrophobic properties of the outer layer create a high energy barrier for antibacterial ions in the aqueous phase as they pass through its pores. According to the Young-Laplace equation, the pressure required for a liquid to enter a hydrophobic capillary is inversely proportional to the pore size and directly proportional to the surface tension—the higher the hydrophobic surface tension and the smaller the pore size, the higher the required breakthrough pressure. Therefore, the hydrophobic porous layer acts as a "valve" to restrict the outward diffusion of antibacterial ions from the core layer, controlling the basic release rate at an appropriate level and preventing the uncontrolled consumption of antibacterial components at low humidity.

[0062] The second layer—pressure response deformation: The inner porous layer possesses compressible elasticity. When the outer hydrophilic layer swells in a wet state, generating inward swelling pressure, this pressure is transmitted to the inner porous layer through the interlayer interface. The pore structure of the inner porous layer undergoes elastic compression—porosity decreases, pore size shrinks, and some channels may completely close. According to the Hagen-Poiseuille equation in fluid mechanics, the flow rate through a circular capillary is proportional to the fourth power of the tube diameter—if the pore size shrinks to 50% of its original size, the flow rate decreases to 6.25%. Therefore, the compression of the inner pores can exponentially increase the resistance to antibacterial ion transport, causing a sharp drop in the release rate. When the outer hydrophilic layer contracts and the swelling pressure is relieved, the elastic restoring force of the inner porous layer reopens the pores, and the release rate recovers.

[0063] (2) Basis for material selection

[0064] Both PVDF and PTFE are high-performance hydrophobic fluoropolymers. PVDF has a crystallinity of approximately 50%–60%, allowing for the convenient fabrication of porous membranes with sponge-like or finger-like pore structures via phase inversion. Its chain segments also possess a certain degree of mobility, endowing the porous layer with excellent elastic recovery properties. PTFE exhibits stronger hydrophobicity (contact angle > 120°), lower elastic modulus, and better flexibility, but its melt processing is difficult, typically requiring sintering or stretching methods to create pores. Considering both processing convenience and elastic recovery properties, PVDF is the preferred material.

[0065] (3) Principle of structural parameter control

[0066] The thickness of the inner skin layer is preferably 0.01–0.03 mm: if the thickness is too thin (<0.01 mm), the valve effect is insufficient, antibacterial ions can easily penetrate, and it may rupture under swelling pressure; if the thickness is too thick (>0.03 mm), the basic release rate is too low, antibacterial protection is insufficient in low humidity, and the yarn stiffens, affecting wearing comfort. The porosity is preferably 30%–50%: if the porosity is too low (<30%), the basic release rate is too low, and antibacterial protection is insufficient in low humidity; if the porosity is too high (>50%), the valve effect is weakened, and the mechanical strength and elastic recovery performance of the porous layer decrease. The average pore size is preferably 50–200 nm: if the pore size is too small (<50 nm), the transport resistance of antibacterial ions is too high, making release difficult even in dry conditions; if the pore size is too large (>200 nm), the hydrophobic barrier effect is insufficient, and it is difficult to achieve an effective pore closure state during compression.

[0067] (4) Preparation method and process control

[0068] PVDF (preferably with a weight-average molecular weight Mw of 200,000 to 500,000) is dissolved in dimethylformamide or dimethylacetamide to prepare a coating solution with a mass concentration of 10% to 20%. The concentration of the coating solution affects the film thickness and pore structure—lower concentrations result in thinner films with higher porosity, while higher concentrations result in thicker films with lower porosity. The core yarn is passed through the coating solution bath under appropriate tension (excessive tension may cause fiber stretching and deformation, while insufficient tension may lead to uneven coating), resulting in a coating solution layer of a certain thickness adhering to the surface of the core yarn. The coated yarn is then immersed in a deionized water coagulation bath (preferably at a temperature of 20–40°C). In the coagulation bath, the solvent (DMF) and the non-solvent (water) undergo a double diffusion exchange—the solvent diffuses into the coagulation bath, and the non-solvent diffuses into the coating solution layer. When the non-solvent content in the coating solution layer reaches a critical value, the polymer undergoes phase separation and precipitation, forming a polymer film with a porous structure. Phase transformation temperature affects the phase separation rate—higher temperatures result in faster double diffusion, easily forming finger-like macroporous structures; lower temperatures lead to slower phase separation, easily forming sponge-like microporous structures. The optimal phase transformation time is 30–120 seconds—too short a time results in incomplete phase separation, insufficient film densification, and excessively high porosity; too long a time results in overly dense films with excessively low porosity. After phase transformation, residual solvent is removed by washing with water, followed by drying and setting.

[0069] (5) Process optimization methods

[0070] An appropriate amount of non-solvent (such as water or ethanol, preferably 1% to 5% of the total mass of the coating solution) can be added to the coating solution. The presence of the non-solvent makes the coating solution metastable before entering the coagulation bath. After entering the coagulation bath, instantaneous phase separation occurs, forming a finger-like pore structure, which is beneficial to improving the connectivity of the pores and the transport efficiency of antibacterial ions.

[0071] 4. Outer skin layer 12 – hydrophilic moisture-absorbing layer

[0072] (1) Functional positioning and design principles

[0073] The outer cortex covers the outer cortex, and its design principle is as follows:

[0074] The outer skin layer is made of a hydrophilic polymer material (preferably sodium alginate or modified chitosan), whose molecular chains contain a large number of hydrophilic groups (hydroxyl, carboxyl, amino, etc.), giving the material strong hygroscopic and swelling capabilities. The function of the outer skin layer is to convert environmental humidity signals into mechanical pressure signals—when the environmental humidity increases, the outer skin layer absorbs water and swells, generating inward swelling pressure; when the environmental humidity decreases, the outer skin layer loses water and contracts, relieving the swelling pressure. This "humidity sensing-pressure conversion" function is the starting point of the entire three-stage asymmetric regulation.

[0075] (2) Basis for material selection

[0076] Sodium alginate is a natural polysaccharide extracted from brown algae. Its molecular chain contains numerous carboxyl and hydroxyl groups, giving it excellent hydrophilicity and swelling properties. Furthermore, it can cross-link in the presence of calcium ions to form water-insoluble calcium alginate gel. The swelling rate of sodium alginate can be controlled by the degree of cross-linking—the higher the degree of cross-linking, the lower the swelling rate. Modified chitosan (such as carboxymethyl chitosan and quaternary ammonium chitosan) has better water solubility and a higher swelling rate. Simultaneously, chitosan itself possesses certain antibacterial activity and can produce a synergistic antibacterial effect with silver / zinc ions.

[0077] (3) Principles of swelling behavior regulation

[0078] The thickness of the outer skin layer is preferably 0.02–0.05 mm: if the thickness is too thin (<0.02 mm), the absolute volume change generated by swelling is insufficient, and the pressure transmitted inward is inadequate, which is insufficient to effectively compress the inner porous layer; if the thickness is too thick (>0.05 mm), the yarn diameter increases significantly, affecting weavability, and excessive swelling in the wet state may cause the skin layer to peel off from the yarn surface. The dry contact angle is preferably <60° to ensure good hydrophilicity (water molecules can be quickly adsorbed and penetrate into the skin layer). The wet swelling rate is preferably 200%–500%—if the swelling rate is too low (<200%), the swelling pressure generated is insufficient to compress the inner pores; if the swelling rate is too high (>500%), repeated swelling-shrinkage cycles may lead to material fatigue and structural damage.

[0079] (4) Preparation method and process control

[0080] Sodium alginate (preferably with a viscosity of 200–800 mPa·s, which balances the coating performance of the coating solution and the mechanical properties of the crosslinking product) is dissolved in deionized water to prepare a coating solution with a mass concentration of 2%–5%. The concentration of the coating solution affects the thickness of the outer skin layer and the density of the gel layer—a higher concentration results in a thicker coating layer and a denser gel network. The yarn coated with the first layer is immersed in the coating solution, allowing the sodium alginate solution to adhere evenly to the surface of the inner skin layer. The immersed yarn is then placed in a calcium chloride coagulation bath (preferably with a mass concentration of 1%–5% and a temperature of 25–50°C). The carboxyl groups on the sodium alginate molecular chains coordinate and crosslink with calcium ions, forming an "egg-box" structure of calcium alginate gel network, making the coating layer insoluble in water and possessing a stable three-dimensional network structure. The calcium ion concentration in the coagulation bath affects the crosslinking density—a higher calcium ion concentration results in a greater crosslinking density, stronger gel network rigidity, and lower swelling rate. The coagulation bath temperature affects the cross-linking reaction rate and the uniformity of the gel network—at a suitable temperature, the cross-linking is uniform and the structure is dense; at too low a temperature, the cross-linking is incomplete, and the gel easily dissolves after swelling; at too high a temperature, the cross-linking reaction is too fast, resulting in a dense outer surface but insufficient internal cross-linking. The optimal molding time is 60–180 seconds—time affects the thickness and degree of cross-linking of the gel layer. After molding, uncross-linked sodium alginate and residual calcium chloride are removed by washing with water, followed by drying and setting.

[0081] (5) Plasticization and fatigue resistance optimization

[0082] An appropriate amount of plasticizer (such as glycerol, preferably 5% to 15% of the mass of sodium alginate) can be added to the coating solution. Glycerol molecules enter the calcium alginate gel network, reducing the hydrogen bonding between molecular chains, increasing the mobility of chain segments, improving the flexibility and swelling reversibility of the gel layer, and reducing the risk of structural fatigue and crack formation caused by repeated swelling-shrinkage cycles.

[0083] 5. Interlayer interfaces and collaboration mechanisms in a three-layer structure

[0084] (1) Interlayer interface structure and force transmission mechanism

[0085] The core layer (porous polymer fiber), the inner skin layer (hydrophobic porous control layer), and the outer skin layer (hydrophilic moisture-absorbing layer) constitute a complete "storage-valve-drive" functional system. The interface bonding methods between the three layers are different:

[0086] During the phase transition between the core layer and the inner skin layer, PVDF solution precipitates on the surface of the core yarn, and some polymer segments may penetrate into the pores of the core layer surface, forming a mechanically interlocked structure and enhancing the interlayer bonding force. Simultaneously, weak dipole-dipole interactions may exist between the fluorine atoms of PVDF and the cyano groups of polyacrylonitrile. The bonding force between the core layer and the inner skin layer should be moderate—too strong, and the inner skin layer will be difficult to deform under compression; too weak, and the swelling pressure cannot be effectively transmitted to the inner layer.

[0087] Between the inner and outer cortex layers—when sodium alginate coating solution is impregnated on the surface of the PVDF porous layer, some sodium alginate molecular chains may penetrate into the surface pores of the PVDF porous layer, forming an anchoring effect after cross-linking. Furthermore, the fluorine atoms on the PVDF surface are negatively charged, while the sodium alginate molecular chains carry a negative charge (carboxyl groups), resulting in electrostatic repulsion between the two. This is precisely what facilitates the outer cortex's tangential expansion along the interface with the inner cortex during swelling, directing the main direction of the swelling force inward compression rather than interfacial delamination.

[0088] (2) Complete work cycle of three-layer collaboration

[0089] The complete working cycle of the three-layer synergy is as follows: Dry state → Outer hydrophilic layer is in a contracted state → Low pressure on the inner layer → Open pores in the inner layer → Silver ions in the core layer diffuse along the concentration gradient through the inner layer pores and the outer skin layer → High release rate (maintaining basic protection) → Foot sweating, increased humidity → Outer layer absorbs water, swells, and expands in volume → Inward swelling pressure is generated → Pressure is transmitted to the inner layer → Inner layer pores are compressed, pore size decreases, and porosity decreases → Ion transport resistance increases exponentially → Release rate decreases → Foot sweating is profuse, humidity reaches a high level → Outer layer fully swells → Inner layer pores are nearly closed → Release rate tends to stop → External humidity decreases → Outer layer loses water and shrinks → Swelling pressure is relieved → Inner layer elasticity is restored → Pores reopen → Release rate rebounds. This working cycle is completely reversible and entirely driven by environmental humidity, without relying on any external energy or human intervention.

[0090] 6. Complete fabrication process of asymmetric double-layer core-skin structure

[0091] Combining the above four steps, the complete preparation process of antibacterial composite yarn is as follows:

[0092] Preparation of porous polymer fibers (polymer dissolution → addition of pore-forming agent → spinning → coagulation and molding → washing → stretching → drying) → loading of nano antibacterial particles (ultrasonic dispersion → impregnation → vibration adsorption → washing → drying) → inner sheath coating (preparation of PVDF coating solution → coating → phase inversion → washing → drying) → outer sheath coating (preparation of sodium alginate coating solution → impregnation → calcium ion crosslinking → washing → drying) → obtaining asymmetric double-layer sheath-core structure antibacterial composite yarn.

[0093] Example 2: Please refer to Figure 5 The weaving principle of Janus thickness gradient structure

[0094] (1) Structural design and functional division of labor

[0095] The sock's body consists of an inner layer (in contact with the skin) and an outer layer (in contact with the inside of the shoe), arranged sequentially as an inner layer, a middle transition layer, and an outer layer. These three layers form a continuous gradient in terms of both antibacterial component concentration and hydrophilicity / hydrophobicity.

[0096] The inner layer—which comes into direct contact with the skin of the foot—is primarily composed of antibacterial composite yarn (preferably 70%–100%), and undergoes a hydrophilic finishing process (preferably a contact angle of 50°–70°). Its functions are: (a) to rapidly absorb sweat excreted from the feet, converting liquid water into transportable water molecules; and (b) to directly apply high concentrations of antibacterial active ingredients to the skin surface, exerting a chemical antibacterial function.

[0097] The outer layer—in contact with the inner surface of the shoe—is mainly composed of conventional textile yarns (with antibacterial composite yarns preferably comprising 0%–20%), and is treated with a hydrophobic finish (contact angle preferably >110°). Its functions are: (a) to prevent external moisture (such as condensation inside the shoe) from back-permeating into the sock; (b) to quickly evaporate and dissipate sweat from the inner layer into the air layer inside the sock; and (c) to act as a mechanical protective layer to reduce friction and wear on the inner layer.

[0098] The intermediate transition layer—the content of antibacterial composite yarn decreases linearly from the inner layer to the outer layer (preferably decreasing by 20%–40% per millimeter of thickness), with a synchronous gradient transition in hydrophilicity and hydrophobicity (contact angle gradually changes from 50°–70° in the inner layer to 100°–130° in the outer layer). Its function is to eliminate the abrupt change in properties between the inner and outer layers, allowing water molecules to be driven by a smooth change in the thickness direction.

[0099] (2) Physicochemical mechanism of unidirectional hygroscopicity

[0100] Unidirectional hygroscopic transport is based on the chemical potential gradient generated by the hydrophilic-hydrophobic gradient. In thermodynamics, the chemical potential of water molecules in a material is related to the material's surface energy (hydrophilicity)—hydrophilic materials have high surface energy, resulting in a lower chemical potential for water molecules on their surface; conversely, hydrophobic materials have low surface energy, resulting in a higher chemical potential for water molecules on their surface. Therefore, in the hydrophilic-hydrophobic gradient, water molecules are driven by a force from the hydrophobic side (surface layer) towards the hydrophilic side (inner layer). In reality, capillary transport of liquid water between fibers depends on the wettability of the capillary—water molecules migrate more easily in hydrophilic capillaries (small contact angle, negative capillary pressure, and liquid absorption). Because the inner layer is hydrophilic and the outer layer is hydrophobic, the driving force for the absorption of liquid water in the capillaries of the inner layer is much greater than that in the capillaries of the outer layer. Therefore, once sweat is absorbed by the inner layer, it is "pulled" into the inner layer and migrates directionally from the inner layer to the outer layer under the drive of the hydrophilic-hydrophobic gradient (because the capillaries of the inner layer continuously pull water molecules towards the inner layer, and under the action of the gradient, the water molecules gradually move towards the outer layer and evaporate on the outer layer). The essence of this process is that the capillary pressure gradient generated by the hydrophilic-hydrophobic gradient drives the directional transport of liquid water from the hydrophobic side to the hydrophilic side.

[0101] (3) Weaving implementation method

[0102] The knitting process employs a double-sided circular knitting machine. This machine has two needle beds, one upper and one lower, each independently controlling the knitting of the inner and outer layers. During knitting, the lower needle bed (inner layer) primarily feeds antibacterial composite yarn and applies a hydrophilic finishing agent online; the upper needle bed (outer layer) primarily feeds regular yarn and applies a hydrophobic finishing agent online. The intermediate transition layer is achieved by gradually switching the yarn feeding ratio between the lower and upper needle beds—after knitting several rows, the lower needle bed reduces the feeding amount of antibacterial composite yarn and increases the feeding amount of regular yarn, while the upper needle bed correspondingly increases the feeding amount of regular yarn and decreases the feeding amount of antibacterial composite yarn. This gradual switching creates a smooth gradient curve in the thickness direction rather than a sudden abrupt change.

[0103] Example 3: Please refer to Figure 3 The principle and implementation of quantitative zoning in ergonomics

[0104] (1) Partitioning basis - the construction principle of the three-dimensional coupled model

[0105] Significant systemic differences exist in the pressure, sweat secretion, and skin temperature experienced by different parts of the human foot during standing and walking. These three factors are coupled: mechanical pressure stimulates the secretory activity of sweat glands on the soles of the feet (the greater the pressure, the higher the sweat secretion rate); sweat evaporation removes heat, affecting local temperature; and temperature, in turn, influences the sweat gland secretion rate and the growth rate of microorganisms. Therefore, a three-dimensional coupled model is needed, rather than analyzing a single factor in isolation.

[0106] The distribution of plantar pressure is determined by the foot's anatomy and gait mechanics—the calcaneal region bears the greatest peak pressure (at the moment of heel strike), the phalangeal region bears significant pressure during push-off, and the arch region bears the lowest pressure. The distribution of sweat secretion is determined by sweat gland density—the density is highest in the forefoot and heel areas, and lower in the arch region. Temperature distribution is determined by local metabolic rate and blood flow—high-pressure areas have higher metabolic product accumulation, increased blood flow, and higher temperatures.

[0107] (2) Data acquisition methods

[0108] The pressure distribution of volunteers' feet at various points on the soles was measured using a plantar pressure testing system while they were standing and walking. Localized sweating at each site was measured using sweat-absorbing patches (sweat-absorbing patches of known area were applied to various points on the soles of the feet, and the weight gain was measured after a specified time). Skin temperature at each site was measured using infrared thermography. Data collection should cover everyday activities (sitting, standing, walking, jogging, etc.), and the sampling time should be long enough to obtain steady-state data. A statistically sufficient number of volunteers was sampled, and the average values ​​were used to establish a statistical model.

[0109] (3) Calculation of the antibacterial demand index

[0110] After normalization of each parameter, an antibacterial demand index is calculated according to preset weights. The weight allocation reflects the relative contribution of each factor to the antibacterial demand—pressure and perspiration are direct factors affecting bacterial growth conditions (higher weights), while temperature is an indirect factor (lower weight). Weights can be adjusted for different target populations to optimize the design—for example, products for athletes have a higher weight for perspiration (because athletes sweat much more than the general population), while products for diabetic patients have a higher weight for pressure (because diabetic patients have abnormally high plantar pressure and weak skin resistance).

[0111] (4) Quantitative configuration principle of antibacterial yarn proportion

[0112] The percentages for each zone increase progressively based on the antibacterial demand index—the base percentage ensures basic antibacterial protection even in the lowest-demand zone (arch area); the progressive increase ensures that the percentages in the highest-demand zones (toe area and heel area) are sufficient to meet high antibacterial needs. The aforementioned five-zone gradient (toe area 80%–85%, forefoot area 70%–75%, arch area 45%–50%, heel area 60%–65%, heel area 75%–80%) is an optimized range derived from extensive experimental data. In practice, these parameters can be adaptively adjusted based on experimental data from specific target populations.

[0113] Example 4: Please refer to Figure 4 Structure and principle of dendritic fractal moisture-wicking network

[0114] (1) Design principles of fractal structures

[0115] The purpose of the moisture-wicking ridges on the sole of the sock is to increase the contact area between the antibacterial yarn and the skin of the foot, and to create micro-air channels to promote sweat evaporation. This invention draws inspiration from the fractal distribution of plant leaf veins, designing the moisture-wicking ridges as a three-level tree-like fractal network.

[0116] The core geometric features of fractals are self-similarity and fractal dimension. On the sock-bottom plane (two-dimensional space), conventional parallel stripes (one-dimensional lines) have low coverage efficiency—as line length increases, the blank areas between lines still lack coverage. Tree-like fractal networks, through hierarchical branching, make the distribution of lines on the two-dimensional plane more uniform, achieving higher area coverage and contact point density with the same total material usage.

[0117] (2) Structure and function of a three-level network

[0118] Primary main channel ridges 9 (3-5 ridges, extending longitudinally, height 0.5-1.2mm, width 1.0-2.0mm): extending longitudinally along the sole of the sock, located between the main stress areas of the sole (avoiding directly below the calcaneus and metatarsal bones to prevent flattening during walking). The main channel is the main path for sweat to collect and be expelled, with the largest cross-sectional area and the lowest capillary pressure.

[0119] Secondary channel ridges 10 (branching angle 30°–60°, 2–3 levels, height 0.3–0.8 mm, width 0.5–1.0 mm): branch out from the main channel at a certain angle, forming a tree-like distribution. The branching angle affects the coverage area—if the angle is too large, the branches are too lateral, hindering longitudinal drainage; if the angle is too small, the branches are almost parallel to the main channel, limiting the increase in coverage area. The number of levels affects the network density—more levels result in denser coverage but increase material usage.

[0120] Tertiary microchannel bumps 11 (height 0.2–0.4 mm, diameter 0.3–0.6 mm): micro-bumps formed by further branching at the ends of secondary channels, distributed in an array. These microchannel bumps are the "entry points" for sweat to enter the fractal network, directly contacting the skin of the sole of the foot, where capillary pressure is highest.

[0121] (3) Physical mechanism of self-driven moisture conduction

[0122] According to the Young-Laplace equation, the capillary pressure of a liquid is inversely proportional to the capillary radius. The microchannel protrusions have the smallest radius of curvature and the highest capillary pressure (largest absolute negative pressure), while the main channel has the lowest capillary pressure (smallest absolute negative pressure). Therefore, when the soles of the feet sweat, droplets are first drawn in by the strong capillary force of the microchannel protrusions. Then, driven by the capillary pressure difference (from high to low capillary pressure), the sweat automatically flows along the secondary channel → main channel, eventually evaporating and being expelled from the edge of the sock. This self-driven process follows Murray's law (the optimal design principle of fractal networks in nature), minimizing the energy consumption of sweat transport.

[0123] (4) Optimization and balance between contact area and material usage

[0124] The branching structure of the fractal network significantly increases the actual total length of the antibacterial yarn within the same projected area. The contact points between the antibacterial yarn and the skin are upgraded from simple "line contact" (parallel stripes) to a composite contact mode of "line + point", resulting in a substantial increase in the contact area. At the same time, due to the spatial filling characteristics of the fractal structure (the finer the lines, the denser the distribution), the increase in material usage is far less than the increase in contact area.

[0125] (5) Weaving implementation method

[0126] After the sole is knitted, the machine switches to the tuck stitch pattern on the same computerized jacquard knitting machine for additional knitting. Tuck stitch (also known as plating or plush stitch) involves adding one or more overhanging loops on top of existing plain stitch loops, increasing the loop length, piling up the yarn, and creating a three-dimensional raised structure. The height of the raised area is controlled by the number of tuck stitches and the loop length—the more tuck stitches and the longer the loop length, the higher the raised area. The yarn fed into the raised stitch pattern is an antibacterial composite yarn, ensuring that the raised stitches themselves have antibacterial properties (the yarn in contact with the skin is antibacterial). The fractal pattern is controlled by the jacquard program of the knitting machine, which controls needle selection and yarn feeding. Due to the self-similarity of the fractal structure, only the geometric parameters (position, angle, number of levels, and inter-level ratio) of the first-level bifurcation need to be defined; subsequent levels can be automatically generated by the program.

[0127] Example 5: Please refer to Figure 1 Complete weaving process

[0128] Step 1: Dissolve polymer matrix material and pore-forming agent → wet spinning to prepare porous fibers → ultrasonic impregnation to load antibacterial nanoparticles → solution coating-phase inversion method to prepare hydrophobic porous inner layer → wet coating method to prepare hydrophilic outer layer → obtain antibacterial composite yarn.

[0129] Step 2: Input the target sock type parameters based on the three-dimensional coupling model of the foot → The system automatically generates the proportion of antibacterial yarn and the knitting density of each area.

[0130] Step 3: Integrated knitting on a computerized jacquard sock knitting machine – Cuff 1 (rib knit) → Sock Cuff 2 (plain knit) → Heel (reinforced) → Functional areas of the sole (Heel area 3; Heel area 4; Arch area 5; Forefoot area 6; Toe area 7; Gradient knitting, automatic switching of yarn feeding ratio and density, with transition zones between areas) → Toe 8. Simultaneously, a double-sided circular knitting machine forms a Janus gradient structure.

[0131] Step 4: After the sock sole is knitted, switch to the tuck weave pattern and use antibacterial composite yarn to weave a tree-like fractal moisture-wicking network.

[0132] Step 5: Sewing the head (mesh sewing) → Steam setting → Inspection → Packaging.

[0133] Please see Figure 6 Functional verification instructions

[0134] (i) Antibacterial durability: Refer to GB / T 20944.3 oscillation method. After multiple water washings, the antibacterial rate of this invention remains above 96%, which is significantly better than the post-finished type (which drops below 70% after water washing) and the copper ion fiber type (approximately 93%). This indicates that the porous reservoir + double-layer skin effectively slows down the loss of antibacterial particles.

[0135] (II) Controllable Release: Release rate was measured in low / medium / high humidity environments. This invention exhibits a three-stage asymmetric response: release at low humidity → inhibition at medium humidity → cessation at high humidity; the control sample showed a continuous increase in release rate with increasing humidity (passive release). The release concentration ratio in the toe area / arch area was >2.2, while the control was close to 1.0—proving that spatially on-demand distribution was achieved.

[0136] (III) Moisture wicking and comfort: According to AATCC 195, the unilateral moisture wicking index of this invention is >0.85, which is significantly better than that of conventional double-layer structures (0.3-0.4). Subjective evaluation of wearing the product shows that it is superior to the control in terms of dampness, irritation, and overall comfort.

[0137] (iv) Cost-effectiveness: The total amount of antibacterial yarn used is reduced by 40% to 55% compared with the uniform configuration scheme, which has obvious cost advantages.

[0138] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An antibacterial functional sock, comprising a sock body and an antibacterial composite yarn woven into the sock body, characterized in that, The antibacterial composite yarn includes a core layer (14), an inner sheath layer (13), and an outer sheath layer (12). The core layer (14) is loaded with nano antibacterial particles (15). The inner sheath layer (13) covers the outside of the core layer (14), and the outer sheath layer (12) covers the outside of the inner sheath layer (13). The core layer (14) is a porous polymer fiber loaded with the nano antibacterial particles (15). The inner sheath layer (13) is a hydrophobic porous polymer layer, and the outer sheath layer (12) is a hydrophilic swelling layer. The sock body is divided into at least three functional areas in the longitudinal direction from the sock opening to the sock toe. The content of the antibacterial composite yarn woven in each functional area is arranged in a continuous gradient along the longitudinal direction. When the outer sheath layer (12) absorbs moisture and swells, it generates inward pressure, which reduces the porosity of the inner sheath layer (13). The release rate of the nano antibacterial particles (15) decreases as the ambient humidity increases.

2. The antibacterial functional sock according to claim 1, characterized in that, The core layer (14), the inner skin layer (13), and the outer skin layer (12) constitute an asymmetric double-layer core-skin structure. The core layer (14) is a reservoir for antibacterial active ingredients. The inner skin layer (13) is a release control valve. The outer skin layer (12) is a humidity sensing and driving layer. The inner skin layer (13) is made of polyvinylidene fluoride or polytetrafluoroethylene. The outer skin layer (12) is made of sodium alginate or modified chitosan.

3. The antibacterial functional sock according to claim 1, characterized in that, The functional areas along the longitudinal direction of the sole of the foot are, in order, the toe area (7), the forefoot area (6), the arch area (5), the heel area (4), and the heel area (3). The antibacterial composite yarn accounts for 80% to 85% of the toe area (7) and the heel area (3), 70% to 75% of the forefoot area (6), 60% to 65% of the heel area (4), and 45% to 50% of the arch area (5). There is a transition zone between each adjacent functional area.

4. The antibacterial functional sock according to claim 1, characterized in that, The sock body consists of an inner layer, an intermediate transition layer, and an outer layer in the thickness direction from the inner layer to the outer layer. The proportion of antibacterial composite yarn in the inner layer is higher than that in the outer layer. The inner layer is treated with hydrophilic finishing, and the outer layer is treated with hydrophobic finishing. The content of antibacterial composite yarn and the hydrophilicity / hydrophobicity of the intermediate transition layer are continuously gradient transitioned from the inner layer to the outer layer, forming a Janus thickness gradient structure.

5. The antibacterial functional sock according to claim 1, characterized in that, The sock body also includes a moisture-wicking structure on the sole, which is a tree-like fractal moisture-wicking network formed on the inner surface of the sole. The tree-like fractal moisture-wicking network is woven from antibacterial composite yarn, and the projection of the tree-like fractal moisture-wicking network on the sole plane is a tree-like distribution with progressively branching branches.

6. The antibacterial functional sock according to claim 5, characterized in that, The tree-like fractal moisture-wicking network includes a main channel protrusion (9) extending longitudinally along the bottom of the sock, a secondary channel protrusion (10) extending from the main channel protrusion (9), and a microchannel protrusion (11) formed by branching from the end of the secondary channel protrusion (10). The main channel protrusion (9), the secondary channel protrusion (10), and the microchannel protrusion (11) form a three-level fractal structure. The height of the main channel protrusion (9) is 0.5-1.2 mm and the width is 1.0-2.0 mm. The height of the secondary channel protrusion (10) is 0.3-0.8 mm and the width is 0.5-1.0 mm. The height of the microchannel protrusion (11) is 0.2-0.4 mm and the diameter is 0.3-0.6 mm. The branching angle between the secondary channel protrusion (10) and the main channel protrusion (9) is 30°-60°, and the number of branching levels is 2-3.

7. A method for knitting antibacterial functional socks as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Preparation of antibacterial composite yarn: Porous polymer fiber is prepared as core layer (14), nano antibacterial particles (15) are loaded inside and on the surface of the porous polymer fiber, hydrophobic porous inner skin layer (13) is wrapped around the porous polymer fiber loaded with nano antibacterial particles (15), and then hydrophilic outer skin layer (12) is wrapped around the inner skin layer (13) to obtain antibacterial composite yarn; A three-dimensional coupled model of plantar pressure, perspiration, and temperature was established to calculate the antibacterial demand index of each area of ​​the sole. Zonal weaving: Based on the antibacterial demand index of each area, the proportion of antibacterial composite yarn in each functional area is determined. A computerized jacquard sock knitting machine is used to weave the antibacterial composite yarn into each functional area according to the determined proportion, so that the content of antibacterial composite yarn in each functional area is continuously gradient along the longitudinal direction. When the outer skin layer (12) absorbs moisture and swells, it generates inward pressure, which reduces the porosity of the inner skin layer (13). The release rate of the nano antibacterial particles (15) decreases as the ambient humidity increases.

8. The knitting method of an antibacterial functional sock according to claim 7, characterized in that, In the step of determining the proportion of antibacterial composite yarn in each functional area based on the antibacterial demand index of each area, the sole of the foot is divided longitudinally into the toe area (7), the forefoot area (6), the arch area (5), the heel area (4), and the heel area (3). The proportion of antibacterial composite yarn in the toe area (7) and the heel area (3) is 80% to 85%, the proportion of antibacterial composite yarn in the forefoot area (6) is 70% to 75%, the proportion of antibacterial composite yarn in the heel area (4) is 60% to 65%, and the proportion of antibacterial composite yarn in the arch area (5) is 45% to 50%. A transition zone is provided between each adjacent functional area.

9. The knitting method of an antibacterial functional sock according to claim 7, characterized in that, It also includes a sock bottom moisture-wicking network weaving step: after the sock bottom weaving is completed, switch to the tuck weaving mode, and use antibacterial composite yarn to weave a tree-like fractal moisture-wicking network on the inner surface of the sock bottom. The tree-like fractal moisture-wicking network includes a main channel protrusion (9) extending longitudinally along the sock bottom, a secondary channel protrusion (10) extending from the main channel protrusion (9) and a microchannel protrusion (11) formed from the end of the secondary channel protrusion (10). The main channel protrusion (9), the secondary channel protrusion (10) and the microchannel protrusion (11) form a three-level fractal structure.

10. The knitting method of an antibacterial functional sock according to claim 7, characterized in that, The porous polymer fiber has a porosity of 30% to 60% and an average pore size of 50 to 500 nm. The inner skin layer (13) has a thickness of 0.01 to 0.03 mm, a porosity of 30% to 50%, and an average pore size of 50 to 200 nm. The outer skin layer (12) has a thickness of 0.02 to 0.05 mm, a dry contact angle of less than 60°, and a wet swelling rate of 200% to 500%. The method of coating the inner skin layer (13) is solution coating-phase inversion method, and the method of coating the outer skin layer (12) is wet crosslinking coating method.

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