Foam dressing and preparation method thereof

Abstract

The invention discloses a foam dressing and a preparation method thereof, relates to the field of medical supplies, and provides a foam dressing with anti-adhesion, high liquid absorption and active antibacterial functions and a preparation method thereof. According to the dressing, polyurethane and bamboo fibers are used as matrixes, a gradient structure with the surface aperture of 50-80 microns and the internal aperture of 150-200 microns is formed through a gradient foaming process, and the synergistic effect of adhesion prevention and high liquid absorption is achieved by combining the aperture difference and the aperture density gradient distribution of a liquid absorption opening and a liquid discharge opening. The antibacterial function is achieved through synergy of natural components of usnic acid and grapefruit essential oil and a polydopamine photo-thermal response layer formed by ultraviolet curing of dopamine hydrochloride. The color developing agent bromophenol blue is uniformly dispersed by virtue of the capillary action of the bamboo fibers, and a traditional laminated structure is replaced. The preparation method comprises the steps of polyurethane / bamboo fiber pre-crosslinking mixing, staged gradient foaming, color developing agent dispersion and post-treatment combining plasma treatment and ultraviolet curing.

Description

Technical Field

[0001] The present invention relates to the field of medical supplies, and in particular to a foam dressing and a preparation method thereof. Background Art

[0002] Traditional foam dressings mostly use a single pore size structure or a homogenized foaming process, and their surface pore size is similar to the internal porosity, which causes the dressing to easily adhere to the tissue due to the large pore size when in contact with the wound, or quickly saturate due to insufficient internal liquid storage space after absorbing liquid. For example, some existing technologies achieve functional composites by laminating color-developing materials or chemical antibacterial agents (such as silver nitrate and silver chloride), but the interface bonding force between the color-developing layer and the substrate is insufficient, which can easily lead to delamination, and the chemical antibacterial ingredients have the risk of drug resistance and poor biocompatibility. In addition, although conventional surface treatment processes (such as single plasma modification) can improve hydrophilicity, it is difficult to maintain long-term antibacterial activity and cannot respond to external stimuli to achieve on-demand functional regulation.

[0003] The above-mentioned existing technologies demonstrate that developing a foam dressing that combines anti-adhesion, high fluid absorption efficiency, rapid color response, and active antimicrobial properties still faces the following challenges: ① A single pore size structure cannot balance the requirements of anti-adhesion and high fluid absorption; ② The laminated color-developing layer is easily peeled and has a delayed response; ③ Chemical antimicrobial agents are easily inactivated and induce drug resistance; and ④ The surface treatment process and functional materials fail to work synergistically. Therefore, it is urgent to overcome the limitations of the existing technologies, which are characterized by single functionality, poor structural stability, and insufficient antimicrobial efficacy, through material compounding and process innovation. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a foam dressing and a preparation method thereof to solve one or more problems in the prior art.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A foam dressing comprising

[0007] The matrix material is a composite of polyurethane and bamboo fiber, wherein the content of the bamboo fiber is 10-20wt%.

[0008] The antibacterial component comprises 5-15 wt % of usnic acid and 2-5 wt % of dopamine hydrochloride.

[0009] Gradient pore size structure, surface pore size 50-80μm, internal pore size 150-200μm.

[0010] The color developer is 0.1-0.5 wt% of bromophenol blue, which is blended and dispersed with the bamboo fiber in a mass ratio of 1:3-1:5.

[0011] The photothermal response layer has a surface treated with plasma and covered with a UV-cured polydopamine photothermal response layer.

[0012] Specifically, in the gradient pore structure:

[0013] The diameter of the liquid suction port through hole is 0.5-3.0mm, and the diameter of the liquid discharge port through hole is 0.2-1.5mm.

[0014] The density of through holes decreases from the center to the edge, with the density of holes in the center area being 20-30 per cm 2 , 5-10 / cm in the edge area 2 .

[0015] Specifically, the antibacterial component further includes grapefruit essential oil, which is compounded with usnic acid in a mass ratio of 1:1.5-1:2.

[0016] Specifically, the polydopamine coating has a thickness of 50-200 nm and is formed by depositing dopamine hydrochloride in a Tris-HCl buffer solution with a pH of 8.5-9.0.

[0017] Specifically, it also includes a release layer, which is glassine release paper with a gram weight of 30-50g / m 2 , silicone oil coating amount 1-3g / m 2 .

[0018] In order to make the technical effect complete, the present invention also provides a second set of technical solutions: a method for preparing a foam dressing, comprising the following steps:

[0019] Pretreatment: polyurethane matrix and bamboo fiber are mixed in a ratio of 10-20 wt%, usnic acid 5-15 wt% and dopamine hydrochloride 2-5 wt% are added, and the mixture is stirred at 60-80° C. for 30-60 minutes to form a pre-crosslinked mixture.

[0020] Gradient foaming: inject the pre-crosslinked mixture into the mold, adjust the stirring speed in stages from 100 rpm to 4500 rpm, the temperature from 60°C to 120°C, and the foaming time for 30-50 seconds.

[0021] Color developer dispersion: 0.1-0.5 wt% of bromophenol blue is mixed with bamboo fiber at a mass ratio of 1:3-1:5, and the mixture is dispersed into the foam by the capillary action of the bamboo fiber.

[0022] Post-treatment: Plasma treatment is performed on the foam surface. The foam is immersed in a dopamine hydrochloride solution with a pH of 8.5-9.0 for 10-30 minutes and cured with ultraviolet light to form a photothermal response layer.

[0023] Specifically, in the gradient foaming step:

[0024] The first stage is stirred at a speed of 100-800 rpm, a temperature of 60-80°C, and lasts for 10-15 seconds.

[0025] The second stage is stirred at a speed of 2000-4500 rpm, a temperature of 100-120°C, and lasts for 20-35 seconds.

[0026] Specifically, in the developer dispersion step:

[0027] The bamboo fiber has a length of 0.5-2 mm and a diameter of 10-30 μm.

[0028] The amount of bromophenol blue added is 0.2-0.3 wt%.

[0029] Specifically, the parameters of the plasma treatment are:

[0030] Power 50-100W, processing time 50-100 seconds.

[0031] The gas is a mixture of argon and oxygen with a volume ratio of 4:1.

[0032] Specifically, in the UV curing step:

[0033] UV wavelength 365-405nm, irradiation intensity 10-30mW / cm 2 , time 5-10 minutes.

[0034] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0035] (1) Combination of a gradient pore size structure and a staged foaming process: By adjusting the stirring speed (100-4500 rpm) and temperature (60-120°C) in stages, combined with pre-crosslinking of polyurethane and bamboo fiber (10-20wt% bamboo fiber), a gradient structure with a surface pore size of 50-80μm (anti-adhesion) and an internal pore size of 150-200μm (high fluid absorption) is formed. This combination solves the contradiction between traditional dressings in being unable to simultaneously meet the requirements of anti-adhesion and high fluid absorption, and optimizes the exudate conduction efficiency through the through-pore diameter gradient (0.5-3.0mm for fluid absorption → 0.2-1.5mm for fluid discharge).

[0036] (2) Synergistic Effect of Co-dispersion of Bamboo Fiber and Color Developer: The capillary action of bamboo fiber (length 0.5-2 mm, diameter 10-30 μm) guides the uniform dispersion of bromophenol blue (0.1-0.5 wt%), replacing the traditional laminated color development layer. This combination avoids the risk of delamination in the lamination process and enhances the antibacterial effect through the natural antibacterial properties of bamboo fiber (compounded with 5-15 wt% usnic acid), while also increasing the color development response speed by 30%.

[0037] (III) Dual antibacterial mechanism of natural antibacterial agent and photothermal response layer: Usnic acid (5-15wt%) and grapefruit essential oil (1:1.5-1:2) provide broad-spectrum antibacterial activity, combined with dopamine hydrochloride (2-5wt%) and UV curing (365-405nm, 10-30mW / cm 2 ) formed by a polydopamine coating (50-200nm) to achieve on-demand sterilization triggered by near-infrared light. This combination breaks through the resistance limitations of chemical antimicrobial agents and increases the inhibition rate from 85% to 99%.

[0038] (IV) Surface enhancement through plasma treatment and UV curing: Plasma treatment (argon / oxygen mixture, 50-100W, 50-100 seconds) increases surface hydrophilicity, followed by UV curing to form a stable photothermal responsive layer. This combination enhances the dressing's adherence to the wound surface, while the photoresponsive properties of the photothermal layer extend the duration of the antibacterial function and reduce the frequency of dressing changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic flow diagram of the preparation method of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and exemplary explanations. It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not intended to limit the conditions for the implementation of the present invention. Therefore, they have no technical significance. Any modification of the structure, change in the proportion relationship or adjustment of the size should still fall within the scope of the technical content disclosed in the present invention without affecting the efficacy and purpose of the present invention.

[0041] Application Overview

[0042] In the existing technology, in order to meet the requirements of anti-adhesion, liquid absorption efficiency and antibacterial function of foam dressings, conventional solutions mostly adopt a single pore structure or homogeneous foaming process, and achieve functional composite by laminating color-developing materials and adding chemical antibacterial agents (such as silver nitrate and silver chloride). For example, the risk of adhesion is reduced by combining static pore design with surface silicone oil coating, or an alginate composite layer is used to improve the liquid absorption capacity. However, such solutions have significant defects: a single pore structure is difficult to take into account the contradiction between anti-adhesion and high liquid absorption, resulting in easy adhesion or rapid saturation failure of the dressing when it contacts the wound; the physical lamination of the color-developing layer and the substrate is easy to peel off due to insufficient interfacial bonding force, and the color response is delayed; chemical antibacterial agents have the risk of drug resistance and biological toxicity, and long-term use may inhibit wound healing. In addition, traditional surface treatment processes (such as single plasma modification) are insufficient in the coordinated regulation of functional materials, and cannot achieve dynamic adaptation of long-term antibacterial and photothermal responses, which restricts the comprehensive performance and clinical applicability of the dressing.

[0043] Comprehensive description

[0044] The present invention provides a foam dressing with gradient liquid absorption, rapid color development, and active antibacterial functions, and a preparation method thereof. The following describes the implementation process in detail in conjunction with the technical solution:

[0045] 1. Preparation of Matrix Materials and Antibacterial Components

[0046] The matrix of the foam dressing is composed of a composite of polyurethane and bamboo fiber. After the bamboo fiber is pretreated (such as alkali boiling, ultrasonic cleaning) to remove impurities, it is mixed with polyurethane particles at a mass ratio of 10-20%. Subsequently, usnic acid powder (particle size ≤ 50 μm) is added as a natural antibacterial agent, and its addition amount is 5-15% of the total mass of polyurethane and bamboo fiber. Dopamine hydrochloride powder (purity ≥ 98%) is added simultaneously during the mixing process, and the addition amount is 2-5% of the total mass for the subsequent formation of a photothermal response layer. The above mixture is stirred at a rate of 500-800 rpm at 60-80°C for 30-60 minutes to allow the bamboo fiber and polyurethane to be preliminarily cross-linked to form a homogeneous premix.

[0047] 2. Gradient foam molding

[0048] Inject the premix into a mold with a through-hole design (such as a silicone mold with suction and discharge ports distributed on the surface) to start the gradient foaming process:

[0049] The first stage: maintain the stirring speed at 100-800 rpm and the temperature at 60-80°C for 10-15 seconds to allow the mixture to initially expand and form surface micropores;

[0050] The second stage: The stirring speed is increased to 2000-4500 rpm and the temperature is raised to 100-120°C for 20-35 seconds. The high shear force and high temperature promote the decomposition of the foaming agent, rapidly expanding the internal pores to form a macroporous structure of 150-200 μm. At the same time, the surface retains dense pores of 50-80 μm due to cooling and solidification. After foaming is completed, the mold is removed to obtain a foam matrix with a gradient pore size.

[0051] 3. Developer dispersion and capillary guidance

[0052] Bromophenol blue powder (purity ≥95%) is mixed with bamboo fiber in a mass ratio of 1:3-1:5. The bamboo fiber is pre-cut into short pieces with a length of 0.5-2mm and a diameter of 10-30μm. The capillary action of the bamboo fiber is used to evenly infiltrate the bromophenol blue solution (solvent: deionized water) into the pores of the foam matrix. The specific operation includes: immersing the foam matrix in the bromophenol blue-bamboo fiber mixed suspension, accelerating the solution penetration through vacuum negative pressure (-0.08 to -0.1MPa), and then drying and curing at 40-50°C to ensure that the color developer is firmly attached to the inner wall of the pores.

[0053] 4. Surface modification and photothermal layer construction

[0054] Plasma treatment: Use a mixture of argon and oxygen (volume ratio 4:1) to bombard the foam surface for 50-100 seconds at a power of 50-100W to remove surface impurities and introduce active groups such as hydroxyl groups to enhance the bonding strength of subsequent coatings;

[0055] Polydopamine coating deposition: The foam is immersed in a dopamine hydrochloride solution (concentration 2-5 mg / mL) at pH 8.5-9.0 for 10-30 minutes. Dopamine molecules self-polymerize on the foam surface to form a coating with a thickness of 50-200 nm.

[0056] UV curing: using a UV light source with a wavelength of 365-405nm and a power of 10-30mW / cm 2 The coating is cured for 5-10 minutes at an irradiation intensity of , forming a polydopamine photothermal layer with near-infrared light response.

[0057] 5. Release layer composite

[0058] Glassine release paper (weight 30-50g / m 2 , silicone oil coating amount 1-3g / m 2 ) is compounded to the back of the foam substrate through a hot pressing process (temperature 80-100°C, pressure 0.2-0.5MPa) to form an anti-adhesion protective layer.

[0059] 6. Functional verification and parameter optimization

[0060] By adjusting the stirring speed and temperature threshold during the gradient foaming stage, the ratio of surface to internal pore size can be controlled (for example, reducing the surface pore size to below 50 μm can further reduce the risk of adhesion); by adjusting the mass ratio of bromophenol blue to bamboo fiber (such as 1:4) and the osmotic pressure, the color response sensitivity can be optimized; by controlling the pH (8.8-9.0) and immersion time (15-20 minutes) of the dopamine hydrochloride solution, the stability and antibacterial efficiency of the photothermal coating can be enhanced.

[0061] Experimental design and transition instructions

[0062] To verify the optimization effect of key process parameters in this protocol on the performance of foam dressings, we selected the stirring speed in the second stage of gradient foaming, the dopamine hydrochloride immersion time, and the amount of bromophenol blue added as core variables, and designed ten comparative experiments. The experiments were conducted according to the national standard (GB) and the International Organization for Standardization (ISO) methods to test the antibacterial rate, liquid absorption rate, and color response time, as follows:

[0063] Antibacterial rate test (GB / T 20944.3-2008 Textiles antibacterial performance test part 3: oscillation method)

[0064] Methods: The foam dressing was cut into 5-cm-diameter discs and incubated with a Staphylococcus aureus (ATCC 6538) suspension (concentration 1×105 CFU / mL) at 37°C with shaking for 24 hours. The inhibition rate was calculated by the plate count method.

[0065] Formula: Inhibition rate (%) = (number of colonies in the blank group - number of colonies in the experimental group) / number of colonies in the blank group × 100%.

[0066] Liquid absorption test (ISO 9073-6 Textiles - Test method for liquid absorption - Vertical absorption method)

[0067] Methods: The dressing was hung vertically in 0.9% NaCl solution, and the amount of liquid absorbed by the dressing per unit mass within 30 minutes was recorded and the liquid absorption rate was calculated.

[0068] Formula: Liquid absorption rate (%) = (mass after liquid absorption - initial mass) / initial mass × 100%.

[0069] Color response time test (GB / T 3920-2008 Textiles - Tests for color fastness - Liquid penetrant testing method)

[0070] Methods: 0.1 mL of simulated exudate (containing 0.1% trypan blue) was added to the dressing surface, and the time required for the color-developed area to completely diffuse was recorded to the nearest 0.01 second.

[0071] Experimental groups and variable settings

[0072] Variable Definition

[0073] The stirring speed in the second stage of gradient foaming was set within a preset range of 2000-4500 rpm, and the control group was set at 500 rpm (too low) and 5000 rpm (too high).

[0074] Dopamine hydrochloride immersion time: The preset limit range is 10-30 minutes, and the control group is set to 5 minutes (too short) and 35 minutes (too long).

[0075] The amount of bromophenol blue added: the preset limit range is 0.1-0.5 wt%, and the control group is set to 0.05 wt% (insufficient) and 0.6 wt% (excess).

[0076] Experimental data table

[0077]

[0078]

[0079] Comprehensive scoring formula: antibacterial rate × 40% + liquid absorption rate × 35% + (1 / color development time) × 25% × 100 (the reciprocal of the color development time is taken for positive conversion).

[0080] Key conclusions

[0081] Parameter synergistic effect: Group 3 (A = 3000 rpm, B = 20 min, C = 0.30%) had the highest comprehensive score (95.83), proving that the preset parameters need to match the balance point of gradient foaming dynamics (stirring speed), coating polymerization rate (immersion time) and colorant diffusion efficiency (addition amount).

[0082] Necessity of preset scope:

[0083] The antibacterial rate (85.67%) and liquid absorption rate (165.43%) of the control group 6 (A=500rpm) were significantly lower than the lowest values of the conventional group (Group 1: 92.34%, 182.45%), indicating that the lower limit of the stirring speed (2000rpm) is crucial to the formation of the pore structure.

[0084] The color development time (12.34 s) of the control group 8 (B = 5 min) was far inferior to the optimal value of the conventional group (5.12 s), confirming that insufficient immersion time resulted in insufficient thickness of the polydopamine coating (<50 nm), affecting the photothermal response efficiency.

[0085] Nonlinear relationship verification: The liquid absorption rate of group 5 (A=4500 rpm) (193.21%) was lower than that of group 3 (208.32%), because the excessively high stirring speed caused the internal pores to collapse and the liquid absorption capacity to decrease.

[0086] Based on the above experimental results, this scheme significantly improves the comprehensive performance of foam dressings through the synergistic effect of gradient foaming, colorant dispersion and photothermal layer construction. The preset parameter range (stirring speed 2000-4500rpm, immersion time 10-30min, bromophenol blue 0.1-0.5wt%) has been experimentally verified to be an effective threshold for performance optimization. For example, when the stirring speed is lower than 2000rpm, the internal pore size of the foam cannot form a gradient structure (the liquid absorption rate of control group 6 is only 165.43%); and the immersion time exceeds 30 minutes (control group 9) will cause the polydopamine coating to be too thick (>200nm), which will reduce the photothermal response activity (antibacterial rate 91.23% vs. 98.12% of group 3). This data shows that the limitation of the parameter range is not an empirical speculation, but is obtained through experimental optimization under multivariate interaction.

[0087] Molecular-level performance trend analysis

[0088] 1. Molecular dynamics relationship between gradient foaming stirring speed and pore structure

[0089] When the gradient foaming stirring speed increases from 2000 rpm to 3000 rpm, the polyurethane molecular chains are oriented under high-speed shear force. The bamboo fiber (mainly composed of cellulose, containing a large number of hydroxyl groups) and the amino groups of the polyurethane are bonded to each other through hydrogen bonds to enhance the interfacial bonding, forming a stable three-dimensional network. At this time, the CO2 gas produced by the decomposition of the foaming agent (such as sodium bicarbonate) diffuses evenly in the shear flow field. The surface forms dense small pores (50-80μm) due to rapid cooling, while the internal continuous high temperature (100-120°C) causes the gas to expand and form large pores (150-200μm). Molecular mechanism: The ratio of hard segments (urea bonds) to soft segments (ether bonds) in polyurethane is regulated by the stirring speed. High speeds (>4500 rpm) lead to excessive aggregation of hard segments and pore collapse. Low speeds (<2000 rpm) cause bubble merging due to insufficient shear force, resulting in uneven pore size distribution.

[0090] 2. Dopamine hydrochloride immersion time and polymerization mechanism of photothermal coating

[0091] Dopamine molecules (containing catechol and amino groups) form a polydopamine coating through oxidative self-polymerization under alkaline conditions (pH 8.5-9.0). When the immersion time increases from 10 to 20 minutes, dopamine molecules gradually deposit on the foam surface, forming a continuous film of 50-200 nm. Its quinone structure (C=O bond) absorbs near-infrared light (700-900 nm) and converts it into heat energy. Molecular mechanism: Short immersion times (<10 minutes) result in a discontinuous coating and low photothermal conversion efficiency; extended immersion times (>30 minutes) result in excessive cross-linking of the molecules, forming a dense, rigid layer that inhibits heat transfer.

[0092] 3. Capillary action and color response of bromophenol blue with bamboo fiber

[0093] Bromophenol blue (containing sulfonic acid groups) hydrogen bonds to the hydroxyl groups of bamboo fiber, penetrating directionally along the fiber surface into the foam pores under capillary action. The micron-scale rough surface of bamboo fiber (10-30 μm in diameter) provides anchoring points, preventing the color developer from aggregating. Molecular mechanism: When the bromophenol blue addition level increases from 0.1% to 0.3%, the sulfonic acid groups form a dynamic equilibrium with the hydroxyl groups of cellulose, allowing the color developer to be evenly dispersed. Excessive addition (>0.5%) leads to supersaturation of the sulfonic acid groups, causing π-π stacking between molecules to induce agglomeration, blocking pores and delaying color development.

[0094] 4. Molecular synergy of comprehensive performance

[0095] Improved antibacterial rate (98.12% vs 83.45% in the traditional group): The catechol group of polydopamine can chelate metal ions (such as Mg) in bacterial cell membranes. 2+ ), destroying the membrane integrity; at the same time, its photothermal effect (heating to 50-60°C under near-infrared irradiation) directly inactivates pathogens.

[0096] Optimized liquid absorption rate (208.32% vs. 120.78% for the traditional group): The gradient pore structure intercepts large molecular pollutants through small surface pores, while the internal large pores accelerate liquid conduction through capillary force (Laplace pressure difference), and the hydrophilic hydroxyl groups of bamboo fiber further enhance interfacial wetting.

[0097] The color response is accelerated (5.12s vs. 15.67s for the traditional group): the sulfonic acid group of bromophenol blue forms a hydrogen bond network with the hydroxyl group of bamboo fiber, making the color developer dispersed in the form of a monomolecular layer and rapidly ionized after contact with the liquid (H + Loss → blue color).

[0098] Summary of deep-seated causes

[0099] Molecular interface interactions dominate structural stability: hydrogen bond crosslinking of polyurethane and bamboo fiber, covalent anchoring of dopamine and foam matrix, and dynamic adsorption of bromophenol blue and cellulose together construct a stable system with functional stratification.

[0100] Kinetic and thermodynamic balance controls performance thresholds: The interaction between stirring speed (shear stress), immersion time (molecular diffusion rate), and color developer concentration (adsorption equilibrium) determines the optimal match between pore size gradient, coating thickness, and color development sensitivity.

[0101] Photo-thermal-chemical synergistic bactericidal mechanism: Polydopamine has both chemical chelation and physical thermal effects, breaking through the single mode of action of traditional antibacterial agents and without the risk of drug resistance.

[0102] Example

[0103] Example 1

[0104] Preparation method

[0105] Matrix mixing: Polyurethane particles (80 wt%) and bamboo fibers (20 wt%) were mixed, and usnic acid powder (5 wt%) and dopamine hydrochloride (2 wt%) were added. The mixture was stirred at 800 rpm at 60° C. for 60 minutes to form a pre-crosslinked mixture.

[0106] Gradient foaming: The mixture was injected into the mold and stirred at 100 rpm and 60°C for 10 seconds in the first stage. In the second stage, it was stirred at 2000 rpm and 100°C for 35 seconds. After foaming was completed, the mold was demoulded to obtain a foam matrix with a surface pore size of 50 μm and an internal pore size of 150 μm.

[0107] Color developer dispersion: Bromophenol blue (0.10 wt%) was mixed with bamboo fiber (0.30 wt%), the bamboo fiber was 0.5 mm in length and 10 μm in diameter, the mixture was infiltrated into the foam pores by vacuum negative pressure (-0.08 MPa), and dried and solidified at 50°C.

[0108] Surface treatment:

[0109] Plasma treatment: using argon and oxygen (volume ratio 4:1), power 50W for 50 seconds;

[0110] Polydopamine coating: The foam was immersed in dopamine hydrochloride solution (2 mg / mL) at pH 8.5 for 10 min and cured with UV light (wavelength 365 nm, intensity 10 mW / cm 2 )5 minutes.

[0111] Release layer composite: Glassine release paper (weight 30g / m 2 , silicone oil coating amount 1g / m 2 ) was hot pressed to the back of the foam at 80°C and 0.2 MPa.

[0112] Example 2

[0113] Preparation method

[0114] Matrix mixing: polyurethane particles (85 wt%) and bamboo fibers (15 wt%) were mixed, usnic acid powder (8 wt%) and dopamine hydrochloride (3 wt%) were added, and the mixture was stirred at 70° C. and 700 rpm for 50 minutes.

[0115] Gradient foaming: The first stage was stirred at 500 rpm and 70°C for 12 seconds, and the second stage was stirred at 2500 rpm and 110°C for 30 seconds. After foaming, the surface pore diameter was 60 μm and the internal pore diameter was 180 μm.

[0116] Color developer dispersion: bromophenol blue (0.20 wt%) and bamboo fiber (0.60 wt%), bamboo fiber length 1.0 mm, diameter 15 μm, vacuum negative pressure -0.09 MPa, 55° C. drying.

[0117] Surface treatment:

[0118] The plasma power was 60 W for 60 seconds, and the gas ratio remained unchanged;

[0119] Dopamine solution pH 8.7, concentration 3 mg / mL, immersed for 15 minutes, UV curing (375 nm, 15 mW / cm 2 )7 minutes.

[0120] Release layer: weight 35g / m 2 , silicone oil coating amount 1.5g / m 2 , hot pressing conditions are 85℃ and 0.3MPa.

[0121] Example 3

[0122] Preparation method

[0123] Matrix mixture: polyurethane (75 wt%) + bamboo fiber (25 wt%), usnic acid (12 wt%) + dopamine hydrochloride (5 wt%), stirred at 600 rpm at 80° C. for 40 minutes.

[0124] Gradient foaming: the first stage was stirred at 800 rpm and 80°C for 15 seconds, the second stage was stirred at 3000 rpm and 120°C for 20 seconds, the surface pore size was 70 μm, and the internal pore size was 200 μm.

[0125] Color developer dispersion: bromophenol blue (0.30 wt%) + bamboo fiber (0.90 wt%), fiber length 2.0 mm, diameter 30 μm, vacuum -0.10 MPa, dried at 60°C.

[0126] Surface treatment:

[0127] Plasma power 100W for 100 seconds;

[0128] Dopamine solution pH 9.0, concentration 5 mg / mL, immersed for 20 minutes, UV (405 nm, 30 mW / cm 2 )10 minutes.

[0129] Release layer: weight 50g / m 2 , silicone oil 3g / m 2 , hot pressing 100℃, 0.5MPa.

[0130] Examples 4 to 9 are substantially the same as those of Example 1, except that the values of the variables controlled in the experiments are different. To keep the description concise, the present invention will not elaborate on the details of the subsequent examples.

[0131] Example 4: Gradient foaming second stage 3500 rpm, usnic acid 10 wt%, bromophenol blue 0.40 wt%;

[0132] Example 5: gradient foaming 4500 rpm, usnic acid 15 wt%, bromophenol blue 0.50 wt%;

[0133] Example 6 (control): gradient foaming at 500 rpm, the rest is the same as Example 3;

[0134] Example 7 (control): gradient foaming at 5000 rpm, the rest is the same as Example 3;

[0135] Example 8 (control): dopamine immersion for 5 minutes, the rest is the same as Example 3;

[0136] Example 9 (control): Dopamine was immersed for 35 minutes, and the rest was the same as Example 3.

[0137] Example 10 (blank control group)

[0138] Preparation method

[0139] Matrix mixing: Polyurethane particles (100 wt%) were stirred at 60°C for 60 minutes and silver nitrate (5 wt%) was added as an antimicrobial agent.

[0140] Uniform foaming: Single-stage foaming was performed at 2000 rpm and 100°C for 30 seconds to form a foam matrix with uniform pore size (120 μm).

[0141] Surface treatment: single plasma treatment (argon, power 50W, 50 seconds), no photothermal coating.

[0142] Composite layer: no color developer, directly composite ordinary release paper (weight 30g / m 2 , without silicone oil coating).

[0143] Specific working process

[0144] After the polyurethane matrix is mixed with bamboo fiber, usnic acid and dopamine hydrochloride are added for pre-crosslinking and stirring to form a homogeneous mixture. After the mixture is injected into the mold, the stirring speed and temperature are adjusted in stages to allow the internal gas to diffuse and form a gradient pore structure with a dense surface and loose interior. The bromophenol blue color developer then penetrates evenly into the foam pores with the help of the capillary action of the bamboo fiber to complete the dispersion. After the foam is activated by plasma bombardment, it is immersed in a dopamine hydrochloride solution, and a polydopamine photothermal response layer is formed on the surface through ultraviolet light-induced polymerization. Finally, the treated foam is composited with glassine release paper to form a complete dressing. In each step, the gradient foaming provides a directional channel for the dispersion of the color developer, the plasma treatment enhances the bonding strength of the photothermal coating, and the release layer composite ensures functional integrity while maintaining the flexibility of the dressing.

[0145] The various technical features described in the above exemplary embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above exemplary embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A foam dressing, characterized in that: include The matrix material is a composite of polyurethane and bamboo fiber, wherein the bamboo fiber content is 10-20wt%; An antibacterial component comprising 5-15 wt% usnic acid and 2-5 wt% dopamine hydrochloride; Gradient pore size structure, surface pore size 50-80μm, internal pore size 150-200μm; The color developer is 0.1-0.5 wt% of bromophenol blue, which is mixed and dispersed with the bamboo fiber in a mass ratio of 1:3-1:5; The photothermal response layer has a surface treated with plasma and covered with a UV-cured polydopamine photothermal response layer.

2. A foam dressing according to claim 1, characterized in that: In the gradient pore structure: The diameter of the liquid suction port hole is 0.5-3.0mm, and the diameter of the liquid discharge port hole is 0.2-1.5mm; The density of through holes decreases from the center to the edge, with the density of holes in the center area being 20-30 per cm 2 , 5-10 / cm in the edge area 2 .

3. The foam dressing according to claim 1, wherein: The antibacterial component also includes grapefruit essential oil, which is compounded with usnic acid in a mass ratio of 1:1.5-1:

2.

4. The foam dressing according to claim 1, wherein: The polydopamine coating has a thickness of 50-200 nm and is formed by depositing dopamine hydrochloride in a Tris-HCl buffer solution with a pH of 8.5-9.

0.

5. The foam dressing according to claim 1, wherein: It also includes a release layer, which is glassine release paper with a gram weight of 30-50g / m 2 , silicone oil coating amount 1-3g / m 2 .

6. A method for preparing a foam dressing, based on any one of claims 1 to 5, characterized in that: The following steps are involved: Pretreatment: Mixing the polyurethane matrix and bamboo fiber at a ratio of 10-20 wt%, adding 5-15 wt% usnic acid and 2-5 wt% dopamine hydrochloride, and stirring at 60-80° C. for 30-60 minutes to form a pre-crosslinked mixture; Gradient foaming: inject the pre-crosslinked mixture into the mold, adjust the stirring speed from 100 rpm to 4500 rpm in stages, increase the temperature from 60°C to 120°C, and the foaming time is 30-50 seconds; Color developer dispersion: 0.1-0.5wt% bromophenol blue is mixed with bamboo fiber at a mass ratio of 1:3-1:5, and dispersed into the foam by the capillary action of the bamboo fiber; Post-treatment: Plasma treatment is performed on the foam surface; the foam is immersed in a dopamine hydrochloride solution with a pH of 8.5-9.0 for 10-30 minutes, and ultraviolet light is cured to form a photothermal response layer.

7. The method for preparing a foam dressing according to claim 6, wherein: In the gradient foaming step: The first stage is stirring at a speed of 100-800 rpm, a temperature of 60-80°C, and lasts for 10-15 seconds; The second stage is stirred at a speed of 2000-4500 rpm, a temperature of 100-120°C, and lasts for 20-35 seconds.

8. The method for preparing a foam dressing according to claim 6, wherein: In the developer dispersion step: The bamboo fiber has a length of 0.5-2 mm and a diameter of 10-30 μm; The amount of bromophenol blue added is 0.2-0.3 wt%.

9. The method for preparing a foam dressing according to claim 6, wherein: The parameters of the plasma treatment are: Power 50-100W, processing time 50-100 seconds; The gas is a mixture of argon and oxygen with a volume ratio of 4:

1.

10. The method for preparing a foam dressing according to claim 6, wherein: In the UV curing step: UV wavelength 365-405nm, irradiation intensity 10-30mW / cm 2 , time 5-10 minutes.

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