Multilayer composite antibacterial and breathable hemostatic skin dressing and preparation method thereof

Abstract

This invention discloses a multi-layer composite antibacterial, breathable, and hemostatic skin dressing and its preparation method, belonging to the fields of medical dressing technology and knitting technology. The dressing of this invention has a multi-layer composite structure, formed by combining a tucked-loop perforated weft-knitted fabric and a non-woven fabric. The tucked-loop perforated weft-knitted fabric, through a combination of actions such as 1-3 perforation, needle turning, shaking, and staggered needle positions, forms a regularly distributed pore structure, enabling the dressing to have zero Poisson's ratio performance within the allowable strain range. The tucked-loop perforated weft-knitted fabric is modified with carboxymethylation and grafted with copper ions, while the non-woven fabric is made from hydrophilic yarn modified with carboxymethylation and chitosan quaternary ammonium salt. The multi-layer composite structure forms a gradient pore size, utilizing the Laplace pressure difference to achieve unidirectional active drainage of exudate. The dressing of this invention combines zero Poisson's ratio fit, gradient pore size drainage, dual-layer synergistic antibacterial properties, and rapid gel hemostasis, simultaneously meeting multiple needs of wound care and showing good application prospects.

Description

Technical Field

[0001] This invention relates to the fields of medical dressing technology and knitting technology, and in particular to a multi-layer composite antibacterial, breathable, and hemostatic skin dressing and its preparation method. Background Technology

[0002] As the largest organ in the human body, the skin plays a vital physiological role. In clinical practice, the skin's emergency repair mechanisms are crucial when facing local infection risks or exhibiting symptoms of infection in chronic exudative wounds (such as lower extremity ulcers, pressure ulcers, and diabetic foot ulcers) and acute exudative wounds (such as non-full-thickness burns, postoperative wounds, and traumatic wounds). When skin tissue is damaged, the microbial community and necrotic tissue proliferate rapidly, restricting the formation of healthy granulation tissue and angiogenesis, increasing the risk factors for local infection, and in severe cases, leading to systemic infection. Therefore, continuous removal of necrotic tissue and slough, infection control, and management of exudate are key factors in maintaining human skin regeneration.

[0003] Ideal wound dressings should have the following characteristics: (1) good absorbency, which can effectively absorb wound exudate; (2) provide and maintain a moist healing environment to promote granulation tissue growth; (3) have antibacterial function to prevent and control infection; (4) good breathability to allow gas exchange; (5) hemostatic function to control wound bleeding; (6) good fit to adapt to limb movement without displacement; (7) non-cytotoxic and have good biocompatibility; (8) easy to use and well tolerated by patients.

[0004] However, the wound treatment methods commonly used in the prior art have obvious limitations: Existing dressings are mostly designed for a single function, making it difficult to simultaneously meet the multiple needs of wound care. Ordinary gauze dressings only provide coverage and protection, with limited absorption capacity and a tendency to adhere to the wound; alginate dressings, while possessing good absorbency and hemostatic properties, can form a gel upon contact with exudate to provide a moist healing environment, but lack antibacterial function; silver ion dressings have broad-spectrum antibacterial properties, but their absorbency is limited and their antibacterial durability is poor; hydrocolloid dressings provide a good moist healing environment, but their poor breathability can easily lead to maceration of the surrounding skin; foam dressings have good absorbency, but poor adherence, and are prone to shifting when used on joints. None of the above dressings can simultaneously provide multiple functions such as antibacterial properties, breathability, hemostasis, adherence, and drainage.

[0005] While existing composite dressings attempt to achieve multifunctional combinations through multi-layered structures, they mostly employ simple physical stacking of functional materials, lacking synergistic design between layers. For example, simply combining an absorbent layer with an antibacterial layer can easily lead to delamination if the interlayer interface is not properly treated, and each layer functions independently. Regarding knitted dressings, while existing technologies offer some elasticity and fit, they are mostly single-structure designs lacking functional layering. While knitted dressings with porous structures can improve breathability, they cannot achieve zero Poisson's ratio performance and still exhibit significant lateral shrinkage when stretched, resulting in reduced contact area between the dressing and skin, causing wrinkles and displacement.

[0006] In summary, current technologies lack a skin dressing that can simultaneously meet multiple requirements such as antibacterial properties, breathability, hemostasis, adhesion, and drainage, while also exhibiting synergistic function across all layers and intelligent responsiveness. Therefore, there is an urgent need to develop a skin dressing with a rational structural design, high functional integration, and synergistic performance enhancement, integrating antibacterial, breathable, and hemostatic functions, along with its preparation method. Summary of the Invention

[0007] This invention proposes a multi-layer composite antibacterial, breathable, and hemostatic skin dressing and its preparation method to solve the problems of existing dressings having single functions and failing to meet multiple needs; lacking a double-layer synergistic antibacterial design; lacking a zero Poisson's ratio structural design, resulting in poor dressing-wound adhesion; and difficulty in balancing moisture and breathability.

[0008] The core technical solution of this invention lies in the following: after modifying hydrophilic yarn with carboxymethylation and chitosan quaternary ammonium salt, the yarn is crushed to form short fibers to make nonwoven fabric. The loop-knitted weft-knitted fabric is first modified with carboxymethylation, then impregnated with antibacterial substances, and finally bonded with medical adhesive to obtain the finished dressing, forming a double-layer synergistic antibacterial effect. The one-piece molded double-layer weft-knitted fabric design, combined with the 1-3 regular loop-knitting process, enables the dressing to have zero Poisson's ratio performance within the allowable strain range, while forming a gradient structure with gradually decreasing pore size from the inside to the outside, and using the Laplace pressure difference to achieve unidirectional active diversion of exudate.

[0009] The specific solution of the present invention is as follows: A method for preparing a multi-layer composite antibacterial, breathable, and hemostatic skin dressing includes the following steps: S1: Nonwoven fabric for preparing dressings, wherein the nonwoven fabric is made by crushing hydrophilic yarns into short fibers after carboxymethylation modification and chitosan quaternary ammonium salt composite modification. S2: A knitted fabric for preparing the dressing, wherein the knitted fabric is a loop-knitted weft-knitted fabric formed by a computerized flat knitting machine, the knitted fabric comprising a skin-friendly layer knitted from elastic yarn and an adhesive layer knitted from hydrophilic yarn; the knitting of the fabric uses a six-way repeat. The first and fourth rows are knitted with elastic yarn on the front and back needle beds using a skipped needle method, with the needle positions of the fourth row and the first row being arranged alternately. The second and fifth rows weave hydrophilic yarn on all the needles of the front needle bed, and form holes by first turning the needles backward, then moving the needle bed horizontally, and then turning the needles forward again. The 3rd and 6th rows knit hydrophilic yarns on all needles of the front needle bed, and the loops of the 1st and 4th rows that were knitted on the back needle bed are turned over to the front needle bed.

[0010] S3: The knitted fabric described in S2 is first modified by carboxymethylation, and then impregnated with antibacterial substances; S4: The nonwoven fabric prepared in S1 and the knitted fabric prepared in S3 are combined with a medical adhesive and then cured by hot pressing to obtain the finished dressing.

[0011] Furthermore, the carboxymethylation modification of the hydrophilic yarn in S1 includes: alkalization treatment, etherification treatment, and post-treatment; The alkalization treatment involves sodium hydroxide with a mass fraction of 5%-20%, a temperature of 35℃-45℃, and a time of 25min-45min. Preferably, the sodium hydroxide mass fraction is 12%-15%, the temperature is 40℃-45℃, and the time is 30min-45min.

[0012] Furthermore, the chitosan quaternary ammonium salt composite modification in S1 includes: immersing the carboxymethylated modified hydrophilic yarn in a chitosan quaternary ammonium salt solution with a mass fraction of 1.5%-2.5%, wherein the degree of substitution of the chitosan quaternary ammonium salt is >90%, and the solvent is an ethanol / water mixture with a volume ratio of 60%-80%, and reacting at 45℃-55℃ for 45-90 min, so that the chitosan quaternary ammonium salt and carboxymethyl groups form a polyelectrolyte complex.

[0013] Furthermore, the process of crushing short fibers in S1 includes: controlling the average diameter of the short fibers to be 10-20 μm, the average length to be 2-5 mm, and the aspect ratio to be 100-500; and then laying and compacting the crushed short fibers through a web-forming process to form a nonwoven fabric.

[0014] Furthermore, the knitting process in S2, which employs a six-way, one-cycle knitting method, includes: Row 1: The front and back needle beds adopt a 1-separate needle structure and are knitted with elastic yarn; Row 2: Knit all needles on the front needle bed using hydrophilic yarn, and knit with stitch turning and rocking the bed, picking up needles every 3 stitches. First, turn the needle back at the 0 stitch position, then rock the back needle bed to the right for 1 stitch, and then turn the needle back to the front. Row 3: All needles on the front needle bed are knitted with hydrophilic yarn, and the loops that were knitted in Row 1 and located on the back needle bed are transferred to the front needle bed; Row 4: The front and rear needle beds adopt a 1-separate needle structure, using elastic yarn for knitting, and the needle positions are arranged alternately with Row 1; Row 5: All needles on the front needle bed are knitted with hydrophilic yarn. In conjunction with needle turning and rocking the bed, perform a 1-3 stitch picking operation. First, turn the needle back from the 0 stitch position, then rock the back needle bed to the right 1 stitch, and then turn the needle back to the front. Row 6: Knit all needles on the front needle bed using hydrophilic yarn, and transfer the loops from Row 4 that were knitted on the back needle bed to the front needle bed.

[0015] Furthermore, the antibacterial substance impregnated in step S3 includes copper ion grafting: The carboxymethylated modified knitted fabric was immersed in a 0.05-0.2 g / L copper sulfate solution for 55-65 minutes, and then dried at 55℃-65℃ to allow the Cu... 2+ It forms a coordination chelate with the carboxymethyl anion on the knitted fabric.

[0016] Furthermore, the antibacterial substance impregnated in S3 includes copper ion grafting: Cu 2+ With carboxymethyl anion (-COO) - They form coordination chelates at a stoichiometric ratio of 2:1.

[0017] A dressing prepared according to the preparation method described above, the dressing comprising a nonwoven fabric layer and a tucked-in weft-knitted fabric layer; The nonwoven fabric layer is made by crushing hydrophilic yarns into short fibers after carboxymethylation modification and chitosan quaternary ammonium salt composite modification. The tucked loop weft-knitted fabric layer includes a skin-friendly layer that comes into contact with the skin, which is woven from elastic yarn; and an adhesive layer that adheres to the nonwoven fabric, which is woven from hydrophilic yarn; the tucked loop weft-knitted fabric layer is first modified with carboxymethylation and then impregnated with an antibacterial substance.

[0018] Furthermore, the dressing When stretched in the longitudinal direction, it exhibits zero Poisson's ratio properties within the strain range of 0-10%. When stretched in the weft direction, it exhibits zero Poisson's ratio properties within the strain range of 0-17%.

[0019] Furthermore, when the dressing is grafted with copper ion antibacterial substances, the release rate can be adjusted based on the wound microenvironment: In the weakly acidic environment caused by infection, H + With Cu 2+ Competitive binding sites trigger coordination bond breakage, Cu 2+ Released; In an environment with high hydrogen peroxide levels caused by infection, Cu 2+In the presence of H2O2, a Fenton-like reaction can occur, resulting in a change in oxidation state (Cu). 2+ →Cu + ), thereby changing its coordination state with the carboxymethyl group and releasing it.

[0020] The present invention has the following beneficial effects: Utilizing the structural characteristics of combining loop-knitted weft-knitted fabric with non-woven fabric, a three-layer composite structure is adopted. Each layer uses raw materials with specific functions to form a complementary composite system, enabling the dressing to simultaneously possess functions such as antibacterial, breathable, hemostatic, soft, and providing a protective moist environment.

[0021] A pore size gradient structure was constructed to form a Laplace pressure differential driving mechanism in which the capillary pressure gradually increases from the inside to the outside, effectively preventing liquid backflow and avoiding skin maceration around the wound, thus realizing the transformation of liquid from passive absorption to active diversion.

[0022] This invention utilizes a looped perforation structure design to give the dressing zero Poisson's ratio performance. The Poisson's ratio is approximately 0 in the warp direction under 0-10% strain and approximately 0 in the weft direction under 0-17% strain. This characteristic ensures that the dressing's lateral dimensions remain constant during joint movement, maintaining close and uniform contact with the skin and preventing wrinkles and displacement.

[0023] The carboxymethylation process is optimized to achieve a balance between hemostatic performance and gel strength. The coordination bonding method grafts nano-copper ions onto carboxymethyl modified fibers, ensuring the long-lasting antibacterial function, while the release rate can be adjusted based on the wound microenvironment. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the knitting process of a knitted fabric in one embodiment of the present invention; Figure 2 This is a schematic diagram of the fabric structure in one embodiment of the present invention; Figure 3 This is a curve showing the variation of Poisson's ratio in the warp and weft directions in one embodiment of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] In this specification, identical components are represented by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "upper," and "lower" used in the following description refer to directions in the accompanying drawings, while the terms "bottom surface," "top surface," "inner," and "outer" refer to directions towards or away from a specific component, respectively. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this specification, "multiple" means two or more.

[0027] Example 1 This invention provides a method for preparing a multi-layer composite antibacterial, breathable, and hemostatic skin dressing, the specific preparation steps of which include: I. Preparation of Nonwoven Fabric for Dressings 1. Raw material preparation The raw materials used are hydrophilic yarns, including alginate fibers, carboxymethyl cellulose fibers, and modified viscose fibers. In this embodiment, 75D-150D viscose filaments are selected as the base raw material.

[0028] 2. Carboxymethylation modification (1) Alkalization treatment Prepare a 5%-20% sodium hydroxide solution using a mixture of water and anhydrous ethanol as the solvent. Immerse the viscose filaments in the alkalization reagent at a reaction temperature of 35℃-45℃ for 25-45 minutes. Under this process window, the cellulose swells sufficiently without excessive degradation, and the hydroxyl groups are fully activated.

[0029] Gradient effect of alkalization treatment Alkaliization treatment, as a key step in carboxymethylation modification, has a significant impact on the final hemostatic properties and gel strength of viscose filaments due to the NaOH mass fraction gradient (5%-20%) and the combination of temperature and time. ① Low mass fraction zone (5%-10% NaOH) The reaction is mild, with low cellulose swelling, minimal fiber damage, good preservation of original mechanical strength, and relatively good gel strength. However, the cellulose molecular chains were not fully opened, resulting in insufficient exposure of hydroxyl groups. Overall, the gel strength is good, but the water absorption and hemostatic properties are insufficient, failing to meet the needs of exudate absorption.

[0030] ② Medium mass fraction zone (12%-15% NaOH) Cellulose swells fully, partially opening the crystalline regions and expanding the amorphous regions, fully exposing the hydroxyl groups, maintaining good fiber integrity, exhibiting no significant alkaline degradation, and rapidly forming a uniform gel. In this region, NaOH acts as both a swelling agent and a catalyst, moderately extending the cellulose molecular chains without depolymerizing, achieving an optimal balance between reaction kinetics and fiber protection.

[0031] ③ High-quality score zone (>18% NaOH) Excessive swelling of cellulose, alkaline degradation in some areas, decreased degree of polymerization, significantly reduced fiber strength, decreased gel strength, and limited hemostatic properties (structural damage leads to gel fragility).

[0032] Multi-objective optimization requires balancing three core metrics: Water absorption capacity and gel formation rate; fiber strength retention rate determine the stability of the dressing structure; gel strength determines the compressive strength and liquid retention capacity of the gel layer. Therefore, the optimal balance of process parameters is selected as follows: NaOH mass fraction 12%-15%, reaction temperature 40℃-45℃, and time 30min-45min.

[0033] (2) Etherification treatment Prepare a 30% (w / w) monochloroacetic acid solution using anhydrous ethanol as the solvent. Immerse the alkalized sample in the etherification reagent at a reaction temperature of 70°C for 120 min.

[0034] (3) Post-processing The post-processing steps include neutralization, washing, and drying. First, the sample is immersed in an acetic acid solution to neutralize it. Then, the neutralized sample is immersed in an ethanol solution to wash it. Finally, the washed sample is placed in an oven for drying at 50°C for 60 minutes.

[0035] 3. Chitosan quaternary ammonium salt composite modification Prepare a chitosan quaternary ammonium salt solution (substitution degree >90%) with a mass fraction of 1.5%-2.5% using an ethanol / water mixture (ethanol volume ratio 60%-80%). Immerse the carboxymethylated hydrophilic yarn in the solution, reacting at 45℃-55℃ for 45-90 minutes. By controlling the solvent polarity to weaken transient electrostatic adsorption, the long-chain molecules of chitosan quaternary ammonium salt are uniformly penetrated and form a stable polyelectrolyte complex with the carboxymethyl groups.

[0036] Post-treatment: The modified composite sample was immersed in an 80% ethanol aqueous solution for 5-10 minutes to remove unreacted substances and fix the composite layer structure using the dehydrating effect of high-concentration ethanol. Then it was dried at 50℃-60℃ for 60 minutes.

[0037] Chitosan quaternary ammonium salt is a multifunctional material with biocompatibility, antibacterial properties, and healing-promoting effects. If the mass fraction of the chitosan quaternary ammonium salt solution is too low, the number of chitosan quaternary ammonium salt molecules is insufficient, the carboxymethyl groups are not fully utilized, and the antibacterial effect is not long-lasting. If the mass fraction is too high, the molecules accumulate on the surface, forming multilayer physical adsorption, resulting in a loose outer layer that is easily washed away. When the mass fraction is between 1.5% and 2.5%, the chitosan quaternary ammonium salt molecules form a monolayer to sub-monolayer coverage on the fiber surface and inside, achieving saturated coordination with the carboxymethyl groups, with no excess free molecules, thus achieving the optimal balance between antibacterial effect and material cost.

[0038] Sufficient carboxymethyl groups provide binding sites for chitosan quaternary ammonium salts, the retained fiber strength ensures structural stability after composite formation, and the appropriate degree of swelling allows chitosan molecules to permeate uniformly. This process achieves a good balance between hemostatic performance and gel strength, and integrates the high water absorption of carboxymethyl groups, the biocompatibility of the chitosan backbone, and the positive charge antibacterial properties of quaternary ammonium salts at the molecular level. Finally, a composite material with good hemostatic effect, broad-spectrum antibacterial and healing-promoting properties is obtained. Its function is not a simple physical mixing, but a synergistic effect of hemostasis and antibacterial properties.

[0039] 4. Making non-woven fabric Carboxymethyl modified and chitosan quaternary ammonium salt composite viscose filaments are crushed in a crusher to obtain short fibers, which are then laid flat and compacted through wet web forming or air-laid web forming processes to form a nonwoven fabric for use as the upper layer of dressings. Therefore, the control of the crushing process directly determines the distribution of the fiber's geometric parameters.

[0040] The modified material is crushed using a crusher, with the average fiber length controlled to be 2-5 mm, the average diameter to be 10-20 μm, and the aspect ratio to be approximately 100-500.

[0041] Specific surface area (surface area per unit mass of fiber) is inversely proportional to diameter. The carboxymethyl groups and chitosan quaternary ammonium salt on the fiber surface interact with each other on and near the fiber surface. The smaller the diameter, the larger the specific surface area. Finer fiber diameters (10-15 μm) can provide a larger specific surface area, increasing the gelation reaction sites between carboxymethyl groups and chitosan quaternary ammonium salt. The more carboxymethyl groups exposed per unit mass of fiber, the more binding sites for chitosan quaternary ammonium salt, and the faster the gel formation rate. However, excessively fine fibers can lead to dense packing, which reduces the exudate absorption rate.

[0042] The mechanical strength of nonwoven fabrics mainly comes from the physical entanglement and friction between fibers. The longer the fiber, the more intersections each fiber has with other fibers, the denser the entanglement network, and the higher the mechanical strength. When the fiber absorbs water and swells to form a gel, the fiber itself becomes the reinforcing phase in the gel network. With enough entanglement points, a skeletal network is formed that runs through the entire gel layer, resulting in high compressive and tensile strength of the gel layer.

[0043] The aspect ratio reflects the "length" of the fiber, and aspect ratio = length / diameter. If the aspect ratio is too high, the nonwoven fabric is prone to curling and tangling during air-laid web formation and flocculation during wet-laid web formation, resulting in uneven nonwoven fabric thickness and wide pore size distribution; if the aspect ratio is too low, the processability is good, but the performance is insufficient.

[0044] Longer fibers (3-4 mm) and higher aspect ratios (200-400) enhance the physical entanglement between fibers, providing a stable supporting framework for the gel layer after water absorption and swelling, thus improving the overall mechanical strength of the dressing. By optimizing fiber parameters to a diameter of 10-15 μm and a length of 3-4 mm (aspect ratio 200-400), a better balance can be achieved between exudate absorption rate, gel formation rate, and mechanical properties, ultimately obtaining a composite dressing upper layer material that combines good hemostatic effect, broad-spectrum antibacterial properties, and healing-promoting properties.

[0045] II. Preparation of Weft-Knitted Fabrics with Pocket-Piercing Designs for Dressings 1. Equipment and Raw Materials Equipment: In this embodiment, a Longxing KSC-132 computerized flat knitting machine, serial number E14, is used. raw material: Skin-friendly layer: Elastic yarns are used, including spandex, nylon-covered spandex, and spandex-coated yarns. In this embodiment, 3075D / 36f polyester-covered spandex yarn is used. Figure 2 (Middle A yarn).

[0046] Adhesive layer: Uses hydrophilic yarns, including alginate fibers, carboxymethyl cellulose fibers, modified viscose fibers, etc. In this embodiment, 250D-600D viscose yarn is used. Figure 2 (Medium B yarn).

[0047] 2. Weaving Technique according to Figure 1 and Figure 2 The fabric is woven according to the shown structure. This fabric uses a weaving technique with six rows forming a complete cycle. The specific weaving method is as follows: Row 1: Skin-friendly layer knitting, using a 1-separate needle structure in the front and back needle beds, and equipped with A yarn for knitting.

[0048] The front and rear needle beds work simultaneously, and the knitting needles are selected with a 1-every-1-every needle structure (that is, every other needle on the front and rear needle beds participates in knitting), forming a skin-friendly elastic skeleton to provide basic elasticity for the fabric.

[0049] Route 2: Adhesive layer picking up holes (first time), with B yarn on all needles of the front needle bed, picking up holes every 1-3 (i.e., first turn the needle back from the 0 needle position, then turn the needle bed to the right by 1 stitch, and then turn the needle back to the front).

[0050] Needle selection: Select one needle every three needles in the front needle bed to perform the pick-up operation; Flip the needle backward: Flip the selected front needle bed loop to the corresponding needle position on the back needle bed; Move the needle bed to the right by 1 stitch: The entire needle bed will then move to the right by 1 stitch length; Flip the needle forward: Flip the loop on the back needle bed back onto the front needle bed; The holes are arranged in a regular pattern, with one picking point for every four stitches.

[0051] Row 3: Loop transfer (first time), knit with B yarn on all needles of the front needle bed, then flip the loops left on the back needle bed during row 1 to the front.

[0052] The fourth row features an interlaced skin-friendly layer with simultaneous operation of the front and rear needle beds. The needles on the front and rear needle beds are arranged in a 1-separate needle structure and are equipped with A yarn. However, the needle positions of the first row are staggered to avoid the elastic yarn from repeating in the same longitudinal position, thus enhancing the isotropic properties of the fabric.

[0053] 5th row: Adhesive layer picking up holes (second time), with B yarn on all needles of the front needle bed, picking up holes every 3 stitches (i.e., first turn the needle back from the 0 needle position, then turn the needle bed to the right by 1 stitch, and then turn the needle back to the front).

[0054] Needle selection: Select one needle every three needles in the front needle bed to perform the pick-up operation; Flip the needle backward: Flip the selected front needle bed loop to the corresponding needle position on the back needle bed; Move the needle bed to the right by 1 stitch: The entire needle bed will then move to the right by 1 stitch length; Flip the needle forward: Flip the loop on the back needle bed back onto the front needle bed; The holes are arranged in a regular pattern, with one picking point for every four stitches.

[0055] Row 6: Loop transfer (second time), knit with B yarn on all needles of the front needle bed, then flip the loops left on the back needle bed during row 4 to the front.

[0056] The first and fourth rows knit elastic yarns on the front and back needle beds with alternating needles. The needle positions of the fourth row are staggered relative to the first row, which makes the elastic yarns more evenly distributed in the fabric, and the stress is more balanced when the fabric is stretched, thereby enhancing the isotropic nature of the fabric and preventing excessive elasticity in one direction.

[0057] The 2nd and 5th rows weave hydrophilic yarn on all the needles of the front needle bed, and form holes by first turning the needles backward, then moving the needle bed horizontally, and then turning the needles forward again. In rows 3 and 6, hydrophilic yarn is knitted on all needles of the front needle bed, and the loops from rows 1 and 4 that were knitted on the back needle bed are turned over to the front needle bed. Some loops of the skin-friendly layer are introduced into the adhesive layer to form the connection point of the double-layer fabric, preventing delamination and increasing the fabric thickness and structural stability.

[0058] The weft-knitted fabric with a loop-and-hole structure prepared by the above-mentioned computer flat knitting machine has zero Poisson's ratio performance, that is, the transverse dimension remains unchanged when stretched, the width of the dressing does not shrink when stretched in the longitudinal direction, the contact area between the dressing and the skin remains unchanged, and the dressing does not wrinkle or shift when the joint moves.

[0059] Bidirectional tensile tests were conducted on weft-knitted fabrics made of viscose yarn and polyester-overlayed spandex yarn. Within a 40% tensile elongation range, the fabrics exhibited significantly different Poisson's ratio effects in the warp and weft directions. The results indicate that their Poisson's ratio behavior exhibits significant anisotropy and strain dependence. Figure 3 As shown: During warp (Wale) stretching, the Poisson's ratio is zero within the strain range of 0-10%, but gradually increases after exceeding this threshold; During zonal (Course) stretching, the zero Poisson's ratio range extends to 0-17%, and the Poisson's ratio also shows an increasing trend after exceeding the threshold, but its increase is significantly smaller than the Poisson's ratio increment after warp stretching exceeds 10%.

[0060] After weaving, iron the fabric to eliminate internal stress, stabilize the structure, and make it tighter. Final fabric parameters: 26 warp rows / 5cm, 23 weft rows / 5cm.

[0061] 3. Carboxymethylation modification of knitted fabrics Carboxymethylation modification of knitted fabrics was performed. First, an alkalization treatment was conducted: a 5%-20% sodium hydroxide solution was prepared, using a mixture of water and anhydrous ethanol (volume ratio 1:1). The knitted fabric was immersed in the alkalization reagent at a reaction temperature of 35℃-45℃ for 25-45 minutes. Next, an etherification treatment was performed: a 30% monochloroacetic acid solution was prepared, using anhydrous ethanol. The alkalized sample was immersed in the etherification reagent at a reaction temperature of 70℃ for 120 minutes. This post-treatment completed the carboxymethylation modification of the knitted fabric.

[0062] 4. Knitted fabrics impregnated with antibacterial substances Antibacterial substances include, but are not limited to, silver ions, nano-silver, chitosan, polyhexamethylene biguanide, chlorhexidine, povidone-iodine, copper ions, and nano-copper. This example uses nano-copper ion grafting.

[0063] The carboxymethylated modified knitted fabric was immersed in a 0.05-0.2 g / L copper sulfate solution for 55-65 min, and then dried at 55℃-65℃. Preferably, a 0.1 g / L CuSO4 solution was prepared and the immersion time was 60 min. The sample was then removed and placed in an oven to dry at 60℃ for 1 h.

[0064] The previous step involved carboxymethylation modification to introduce -COO into the fiber. -Coordination site, Cu 2+ With the carboxymethyl anion (-COO) on the fiber - They form coordination chelates in a stoichiometric ratio of 2:1, with a stability constant greater than 1.88 × 10⁻⁶. 10 This chemical bonding firmly anchors copper ions to the fiber molecular chains, unlike simple physical adsorption, thus improving the material's elution resistance and long-lasting antibacterial effect. More importantly, this design enables intelligent responsive release based on the wound microenvironment: under weakly acidic conditions caused by infection, H... + With Cu 2+ Competitive binding sites trigger coordination bond breakage, Cu 2+ Released; in infection-associated high hydrogen peroxide environments, Cu 2+ In the presence of H2O2, a Fenton-like reaction can occur, resulting in a change in oxidation state (Cu). 2+ →Cu + This alters the coordination state of the chitosan with the carboxymethyl group, thereby accelerating release. Thus, the lower layer of the dressing is upgraded from a passive antibacterial agent carrier to an intelligent responsive material that actively senses infection signals, forming a dual synergistic mechanism with the positively charged antibacterial properties of the chitosan quaternary ammonium salt in the nonwoven fabric.

[0065] III. Dressing Composite Molding The aforementioned steps produced a tucked-loop weft-knitted fabric. One side is a skin-friendly layer made of polyester-polyester-coated yarn with large pores, which can quickly absorb exudate and uses elastic yarn to comfortably conform to the skin. The other side is an adhesive layer, which is also an absorbent layer, made of modified hydrophilic yarn with medium pores, which absorbs exudate and also has an antibacterial effect. A nonwoven fabric with small pores was also produced using modified hydrophilic yarn, which, upon contact with external air, allows moisture to evaporate and provides a protective barrier.

[0066] A nonwoven fabric is placed on one side of the adhesive layer of the tucked-loop weft-knitted fabric. The adhesive layer is coated with medical adhesive. Then, the nonwoven fabric and the tucked-loop weft-knitted fabric are pressed tightly together to obtain a complete dressing. Specifically, the above materials are laminated using a hot-press bonding method. The hot-pressing process parameters are controlled as follows: hot-pressing temperature: 120-140℃, hot-pressing pressure: 0.03-0.52Mpa, hot-pressing time / speed: 120s-180s.

[0067] While ensuring the interlayer bonding strength, the gradient pore size structure from the inner macropores to the outer micropores is fully preserved. This bonding method utilizes the synergistic effect of pore size differences and material hydrophilicity to construct a progressively enhanced Laplace pressure differential driving mechanism, enabling wound exudate to be actively "pumped" unidirectionally from the lower layer through the middle layer to the outer layer. During forward adsorption, the pore size gradient decreases, the capillary force increases, and the liquid is "pulled" from the small pores to even smaller pores. During reverse flow, an even greater capillary force needs to be overcome, effectively preventing liquid backflow. This achieves functional synergy of the three layers rather than simple superposition, ultimately resulting in a composite dressing that combines high-efficiency drainage, breathability and comfort, and structural stability.

[0068] Example 2 This invention provides a multi-layer composite antibacterial, breathable, and hemostatic skin dressing. The dressing has a multi-layer composite structure, including non-woven fabric and tucked-loop weft-knitted fabric, which are bonded together by a medical adhesive.

[0069] Nonwoven fabric is made from hydrophilic yarns, including alginate fibers, carboxymethyl cellulose fibers, and modified viscose fibers. The raw materials are first modified with carboxymethyl cellulose, then modified with chitosan quaternary ammonium salt, and then the modified materials are crushed using a shredder to control the average fiber length of 2-5 mm, the average diameter of 10-20 μm, and the aspect ratio of about 100-500, thus producing nonwoven fabric.

[0070] Tucked-loop, perforated weft-knitted fabric, made with elastic and hydrophilic yarns, is integrally formed by a computerized flat knitting machine, wherein: The elastic yarn is woven to form the skin-friendly layer of the tucked-loop weft-knitted fabric, which is used to contact the skin wound; the elastic yarn used includes spandex, nylon-covered spandex, and spandex-coated yarn.

[0071] The adhesive layer of the tucked weft-knitted fabric is formed by weaving hydrophilic yarns between the skin-friendly layer and the nonwoven fabric; the hydrophilic yarns used include alginate fibers, carboxymethyl cellulose fibers, and modified viscose fibers.

[0072] Tucked-knit weft fabric consists of six rows per complete weave cycle: Row 1: The front and back needle beds adopt a 1-separate needle structure and are knitted with elastic yarn to form the elastic base of the skin-friendly layer; Row 2: Knit all needles on the front needle bed using hydrophilic yarn. By combining needle turning and rocking the bed, use a 1-3 stitch pick-up method for the first stitch pick-up. First, turn the needle back from the 0 stitch position, rock the back needle bed to the right 1 stitch, and then turn the needle back to the front. Row 3: Knit all needles on the front needle bed using hydrophilic yarn, then turn the loops from Row 1 that were located on the back needle bed to the front needle bed. Row 4: The front and back needle beds adopt a 1-separate needle structure, using elastic yarn for knitting, and the needle positions are staggered with Row 1; 5th row: Knit all needles on the front needle bed using hydrophilic yarn. By combining needle turning and rocking the bed, use 1 stitch every 3 stitches to perform the second needle picking. First turn the needle back from the 0 stitch position, then rock the back needle bed to the right 1 stitch, and then turn the needle back to the front. Row 6: Knit all needles on the front needle bed using hydrophilic yarn, then turn the loops from Row 4 that were on the back needle bed to the front needle bed.

[0073] Tuck-knitted weft fabrics have holes formed by the tuck-knitted structure. Tuck-knitted weft fabrics have zero Poisson's ratio properties. When stretched in the warp direction, the Poisson's ratio is about 0 in the range of 0-10% strain; when stretched in the weft direction, the Poisson's ratio is about 0 in the range of 0-17% strain.

[0074] The dressing of this invention, with its tucked-in weft-knitted fabric layer, can withstand weakly acidic conditions caused by infection, H... + With Cu 2+ Competitive binding sites trigger coordination bond breakage, Cu 2+ Released; in infection-associated high hydrogen peroxide environments, Cu 2+ In the presence of H2O2, a Fenton-like reaction can occur, resulting in a change in oxidation state (Cu). 2+ →Cu + This alters the coordination state of the quaternary ammonium salt with the carboxymethyl group, thereby accelerating its release. Combined with the positively charged antibacterial properties of the quaternary ammonium salt in the nonwoven fabric layer, a dual bactericidal synergistic mechanism is formed.

[0075] Comparative Example Comparison of the structure of knitted fabrics 1. Comparison group settings Control group C1: Ordinary weft-knitted plain knit fabric (without the perforation structure of this invention); Test group T1: Weft-knitted fabric with loop-and-hole weft holes using the present invention; All other parameters are the same.

[0076] 2. Test metric: Poisson's ratio Test method: Universal testing machine was used to perform longitudinal and latitudinal tensile tests, and the Poisson's ratio of transverse strain and longitudinal strain was recorded.

[0077] Test results: Under 10% stretch, the Poisson's ratio of the control group (C1) was >0.3, while the Poisson's ratio of the experimental group (T1) was approximately 0. This experiment verifies that the tucked-loop weft-knitted fabric of this invention effectively improves the Poisson's ratio of the dressing.

[0078] 3. Test index: Change in bonding area Test method: The dressing was attached to an elastic model simulating joint movement. In this experiment, a bent silicone plate was used. Under 10% tension, the rate of change of the contact area between the dressing and the substrate was calculated by image analysis.

[0079] Test results: Under 10% stretch, the bonding area of ​​the control group C1 decreased by 15-25%, while the bonding area of ​​the experimental group T1 changed by <5%. This experiment verifies that the dressing fit of the weft-knitted fabric with loops and perforations of the present invention is better.

[0080] 4. Test index: Dressing edge displacement Test method: The dressing is applied to the elbow / knee, and flexion and extension movements are performed, bending from 0° to 90°. The displacement distance of the dressing edge relative to the skin marker is measured.

[0081] Test results: In the control group (C1), the displacement of the dressing edge relative to the skin marker point was >5 mm, while in the experimental group (T1), the displacement of the dressing edge relative to the skin marker point was <2 mm. This experiment verifies that the dressing with the weft-knitted fabric featuring the tufted loop weft stitch of this invention has better coverage stability.

[0082] In the embodiments disclosed in this application, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; "linking" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments disclosed in this invention according to the specific circumstances.

[0083] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for preparing a multi-layer composite antibacterial, breathable, and hemostatic skin dressing, characterized in that, Includes the following steps: S1: Nonwoven fabric for preparing dressings, wherein the nonwoven fabric is made by crushing hydrophilic yarns into short fibers after carboxymethylation modification and chitosan quaternary ammonium salt composite modification. S2: A knitted fabric for preparing the dressing, wherein the knitted fabric is a loop-knitted weft-knitted fabric formed by a computerized flat knitting machine, the knitted fabric comprising a skin-friendly layer knitted from elastic yarn and an adhesive layer knitted from hydrophilic yarn; the knitting of the fabric uses a six-way repeat. The first and fourth rows are knitted with elastic yarn on the front and back needle beds using a skipped needle method, with the needle positions of the fourth row and the first row being arranged alternately. The second and fifth rows weave hydrophilic yarn on all the needles of the front needle bed, and form holes by first turning the needles backward, then moving the needle bed horizontally, and then turning the needles forward again. The 3rd and 6th rows knit hydrophilic yarn on all needles of the front needle bed, and respectively turn the loops of the 1st and 4th rows that were located on the back needle bed to the front needle bed; S3: The knitted fabric described in S2 is first modified by carboxymethylation, and then impregnated with antibacterial substances; S4: The nonwoven fabric prepared in S1 and the knitted fabric prepared in S3 are combined with a medical adhesive and then cured by hot pressing to obtain the finished dressing.

2. The preparation method according to claim 1, characterized in that, The hydrophilic yarn in S1 is modified by carboxymethylation, which includes alkalization treatment, etherification treatment and post-treatment. The alkalization treatment involves sodium hydroxide with a mass fraction of 5%-20%, a temperature of 35℃-45℃, and a time of 25min-45min. Preferably, the sodium hydroxide mass fraction is 12%-15%, the temperature is 40℃-45℃, and the time is 30min-45min.

3. The preparation method according to claim 1, characterized in that, The chitosan quaternary ammonium salt composite modification in S1 includes: immersing the carboxymethylated modified hydrophilic yarn in a chitosan quaternary ammonium salt solution with a mass fraction of 1.5%-2.5%, wherein the degree of substitution of the chitosan quaternary ammonium salt is >90%, and the solvent is an ethanol / water mixture with a volume ratio of 60%-80%, and reacting at 45℃-55℃ for 45-90 min, so that the chitosan quaternary ammonium salt and carboxymethyl groups form a polyelectrolyte complex.

4. The preparation method according to claim 1, characterized in that, The process of crushing short fibers in S1 includes: controlling the average diameter of the short fibers to be 10-20μm, the average length to be 2-5mm, and the aspect ratio to be 100-500; and then laying and compacting the crushed short fibers through a web-forming process to form a nonwoven fabric.

5. The preparation method according to claim 1, characterized in that, The knitting process in S2, which employs a six-way, one-cycle method, includes: Row 1: The front and back needle beds adopt a 1-separate needle structure and are knitted with elastic yarn; Row 2: Knit all needles on the front needle bed using hydrophilic yarn, and knit with stitch turning and rocking the bed, picking up needles every 3 stitches. First, turn the needle back at the 0 stitch position, then rock the back needle bed to the right for 1 stitch, and then turn the needle back to the front. Row 3: All needles on the front needle bed are knitted with hydrophilic yarn, and the loops that were knitted in Row 1 and located on the back needle bed are transferred to the front needle bed; Row 4: The front and rear needle beds adopt a 1-separate needle structure, using elastic yarn for knitting, and the needle positions are arranged alternately with Row 1; Row 5: All needles on the front needle bed are knitted with hydrophilic yarn. In conjunction with needle turning and rocking the bed, perform a 1-3 stitch pick-up operation. First, turn the needle back from the 0 stitch position, then rock the back needle bed to the right 1 stitch, and then turn the needle back to the front. Row 6: Knit all needles on the front needle bed using hydrophilic yarn, and transfer the loops from Row 4 that were knitted on the back needle bed to the front needle bed.

6. The preparation method according to claim 1, characterized in that, The antibacterial substance impregnated and loaded in S3 includes copper ion grafting: The carboxymethylated modified knitted fabric was immersed in a 0.05-0.2 g / L copper sulfate solution for 55-65 minutes, and then dried at 55℃-65℃ to allow the Cu... 2+ It forms a coordination chelate with the carboxymethyl anion on the knitted fabric.

7. The preparation method according to claim 6, characterized in that, The antibacterial substance impregnated and loaded in S3 includes copper ion grafting: Cu 2+ With carboxymethyl anion (-COO) - They form coordination chelates at a stoichiometric ratio of 2:

1.

8. The dressing prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The dressing comprises a non-woven fabric layer and a tucked-loop weft-knitted fabric layer; The nonwoven fabric layer is made by crushing hydrophilic yarns into short fibers after carboxymethylation modification and chitosan quaternary ammonium salt composite modification. The tucked loop weft-knitted fabric layer is woven in a six-way loop, including a skin-friendly layer that comes into contact with the skin, which is woven from elastic yarn; and an adhesive layer that adheres to the non-woven fabric, which is woven from hydrophilic yarn; the tucked loop weft-knitted fabric layer is first modified with carboxymethylation and then impregnated with antibacterial substances.

9. The dressing according to claim 8, characterized in that, The dressing When stretched in the longitudinal direction, it exhibits zero Poisson's ratio properties within the strain range of 0-10%. When stretched in the weft direction, it exhibits zero Poisson's ratio properties within the strain range of 0-17%.

10. The dressing according to claim 8, characterized in that, When the dressing is grafted with copper ion antibacterial substances, the release rate can be adjusted based on the wound microenvironment: In the weakly acidic environment caused by infection, H + With Cu 2+ Competitive binding sites trigger coordination bond breakage, Cu 2+ Released; In an environment with high hydrogen peroxide levels caused by infection, Cu 2+ In the presence of H2O2, a Fenton-like reaction can occur, resulting in a change in oxidation state (Cu). 2+ →Cu + ), thereby changing its coordination state with the carboxymethyl group and releasing it.

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