A foam dressing and a method of making the same

Abstract

The application discloses a kind of foam dressings and preparation method thereof, it is related to medical supplies field, provide a kind of foam dressings and preparation method thereof with anti-adhesion, high liquid absorption and active antibacterial function.The dressing with polyurethane and bamboo fiber as matrix, through gradient foaming process, form the gradient structure with surface aperture 50-80 μm, internal aperture 150-200 μm, realize the synergistic effect of anti-adhesion and high liquid absorption by combining the aperture difference and hole density gradient distribution of liquid suction port and liquid discharge port.Antibacterial function is realized by the natural components of usnic acid and grapefruit essential oil, and the polydopamine photothermal response layer formed by dopamine hydrochloride by ultraviolet light curing.The color developing agent bromophenol blue is uniformly dispersed with the capillary action of bamboo fiber, instead of traditional laminated structure.The preparation method includes: polyurethane / bamboo fiber pre-crosslinking mixing, staged gradient foaming, color developing agent dispersion and plasma treatment combined with ultraviolet light curing post-processing.

Description

TECHNICAL FIELD

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

[0002] Traditional foam dressings mostly adopt single pore size structure or homogenization foaming process, and the surface pore size is similar to the internal porosity, which leads to the fact that the dressing is easy to adhere to the tissue due to the too large pore size when contacting the wound, or is quickly saturated due to the insufficient internal liquid storage space after absorbing liquid. For example, some existing technologies realize functional composite 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 easily leads to delamination and peeling, and the chemical antibacterial components have the problems of drug resistance risk and poor biocompatibility. In addition, although the conventional surface treatment process (such as single plasma modification) can improve the hydrophilicity, it is difficult to maintain long-acting antibacterial activity, and cannot realize on-demand function regulation in response to external stimulation.

[0003] The above existing technologies show that the development of a foam dressing with the functions of anti-adhesion, high liquid absorption efficiency, fast color developing response and active antibacterial function still faces the following contradictions: ① single pore size structure cannot balance the requirements of anti-adhesion and high liquid absorption; ② laminated color developing layer is easy to peel off and has response lag; ③ chemical antibacterial agents are easy to be inactivated and cause drug resistance; ④ surface treatment process and functional materials cannot work synergistically. Therefore, it is urgent to break through the limitations of single function, poor structural stability and insufficient antibacterial efficiency in the existing technologies through material compounding and process innovation. SUMMARY

[0004] In view of the above-mentioned shortcomings of the existing technologies, the purpose of the present application is to provide a foam dressing and a preparation method thereof to solve one or more problems in the existing technologies.

[0005] To achieve the above-mentioned purpose, the technical solutions of the present application are as follows:

[0006] A foam dressing, comprising

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

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

[0009] The gradient pore size structure has a surface pore size of 50-80μm and an internal pore size of 150-200μm.

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

[0011] A photothermal response layer, the surface is treated by plasma and covered by a UV-cured polydopamine photothermal response layer.

[0012] Specifically, in the gradient aperture structure:

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

[0014] The hole density decreases from the center to the edge, the hole density in the center area is 20-30 / cm 2 , and the hole density in the edge area is 5-10 / cm 2 .

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

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

[0017] Specifically, it further comprises a release layer, the release layer is a Grafix release paper, the grammage is 30-50g / m 2 , and the silicon oil coating amount is 1-3g / m 2 .

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

[0019] Pretreatment: mixing the polyurethane matrix with the bamboo fiber at a ratio of 10-20wt%, adding piceic acid 5-15wt%, dopamine hydrochloride 2-5wt%, and stirring at 60-80℃ for 30-60 minutes to form a pre-crosslinking mixture.

[0020] Gradient foaming: injecting the pre-crosslinking mixture into a mold, adjusting the stirring speed from 100rpm to 4500rpm in stages, and the temperature from 60℃ to 120℃, and the foaming time is 30-50 seconds.

[0021] Color developing agent dispersion: blending bromophenol blue 0.1-0.5wt% with bamboo fiber at a mass ratio of 1:3-1:5, and dispersing in the foam by using the capillary action of the bamboo fiber.

[0022] Post-treatment: plasma treatment is performed on the surface of the foam. The foam is immersed in a dopamine hydrochloride solution with a pH of 8.5-9.0 for 10-30 minutes, and a photothermal response layer is formed by UV curing.

[0023] Specifically, in the gradient foaming step:

[0024] The first stage involves stirring at 100-800 rpm and at a temperature of 60-80℃ for 10-15 seconds.

[0025] The second stage involves stirring at 2000-4500 rpm and at a temperature of 100-120℃ for 20-35 seconds.

[0026] Specifically, in the color 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 for the plasma treatment are:

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

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

[0032] Specifically, in the ultraviolet curing step:

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

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

[0035] (I) Combination of Gradient Pore Size Structure and Staged Foaming Process: By adjusting the stirring speed (100-4500 rpm) and temperature (60-120℃) in stages, and combining the pre-crosslinking of polyurethane and bamboo fiber (10-20 wt% bamboo fiber), a gradient structure with a surface pore size of 50-80 μm (anti-adhesion) and an internal pore size of 150-200 μm (high absorbency) is formed. This combination solves the contradiction that traditional dressings cannot simultaneously meet the requirements of anti-adhesion and high absorbency, and optimizes the exudate conduction efficiency through the gradient of the through-hole diameter (0.5-3.0 mm absorbent port → 0.2-1.5 mm drain port).

[0036] (II) Synergistic effect of bamboo fiber and color developer co-dispersion: 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 developer layer. This combination avoids the delamination risk of the lamination process and enhances the antibacterial effect through the natural antibacterial properties of bamboo fiber (compounded with 5-15 wt% usnic acid), while improving the color development response speed by 30%.

[0037] (III) Dual antibacterial mechanism of natural antibacterial agents and photothermal responsive layer: Usnea acid (5-15wt%) and grapefruit essential oil (1:1.5-1:2 compound) provide broad-spectrum antibacterial activity, combined with dopamine hydrochloride (2-5wt%) which is cured by ultraviolet light (365-405nm, 10-30mW / cm). 2 The polydopamine coating (50-200nm) formed achieves on-demand sterilization triggered by near-infrared light. This combination overcomes the limitations of chemical antibacterial agents' resistance, increasing the antibacterial rate from 85% to 99%.

[0038] (iv) Surface functional enhancement through plasma treatment and UV curing: Plasma treatment (argon / oxygen mixed gas, 50-100W, 50-100 seconds) enhances surface hydrophilicity, followed by UV curing to form a stable photothermal responsive layer. This combination enhances the adhesion of the dressing to the wound, while the photoresponsive properties of the photothermal layer prolong the duration of antibacterial function and reduce the frequency of dressing changes. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the preparation method in this invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and exemplary descriptions. It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.

[0041] Application Overview

[0042] In existing technologies, conventional solutions for foam dressings to meet the requirements of anti-adhesion, absorbency, and antibacterial functions often employ a single-pore structure or homogeneous foaming process, achieving functional composites through lamination of color-developing materials and the addition of chemical antibacterial agents (such as silver nitrate and silver chloride). For example, static pore size design combined with a surface silicone oil coating reduces the risk of adhesion, or an alginate composite layer is used to enhance absorbency. However, such solutions have significant drawbacks: a single-pore structure cannot reconcile the contradiction between anti-adhesion and high absorbency, leading to dressings that are prone to adhesion or rapid saturation and failure upon contact with the wound; the physical lamination between the color-developing layer and the substrate is prone to peeling due to insufficient interfacial bonding, and the color development response is delayed; chemical antibacterial agents pose risks of drug resistance and biotoxicity, and long-term use may inhibit wound healing. Furthermore, traditional surface treatment processes (such as single-pass plasma modification) are insufficient for the synergistic regulation of functional materials, failing to achieve dynamic adaptation between long-lasting antibacterial effects and photothermal response, thus limiting the overall performance and clinical applicability of the dressing.

[0043] Comprehensive explanation

[0044] This invention provides a foam dressing with gradient liquid absorption, rapid color development, and active antibacterial functions, as well as its preparation method. The implementation process is described in detail below with reference to the technical solution:

[0045] 1. Preparation of matrix materials and antibacterial components

[0046] The matrix of the foam dressing is composed of polyurethane and bamboo fiber. After pretreatment (e.g., alkali boiling, ultrasonic cleaning) to remove impurities, the bamboo fiber is mixed with polyurethane particles at a mass ratio of 10-20%. Usnea acid powder (particle size ≤50μm) is then added as a natural antibacterial agent, at a concentration of 5-15% of the total mass of polyurethane and bamboo fiber. Dopamine hydrochloride powder (purity ≥98%) is added simultaneously during mixing, at a concentration of 2-5% of the total mass, for subsequent formation of the photothermal responsive layer. The mixture is stirred at 60-80℃ at a rate of 500-800 rpm for 30-60 minutes to allow initial cross-linking of the bamboo fiber and polyurethane, forming a homogeneous premix.

[0047] 2. Gradient foaming molding

[0048] The premixed material is injected into a mold with a through-hole design (such as a silicone mold with suction and drainage ports on the surface) to initiate the gradient foaming process:

[0049] First stage: Maintain a stirring speed of 100-800 rpm and a temperature of 60-80℃ for 10-15 seconds to allow the mixture to initially expand and form surface micropores;

[0050] The second stage involves increasing the stirring speed to 2000-4500 rpm and raising the temperature to 100-120℃ for 20-35 seconds. This utilizes high-speed shear force and high temperature to promote the decomposition of the foaming agent, rapidly expanding the internal pores to form a macroporous structure of 150-200 μm. Simultaneously, the surface retains dense micropores of 50-80 μm due to cooling and solidification. After foaming, the foam is demolded to obtain a foam matrix with gradient pore sizes.

[0051] 3. Dispersion of colorimetric reagent and capillary guidance

[0052] Bromophenol blue powder (purity ≥95%) is mixed with bamboo fiber at a mass ratio of 1:3 to 1:5. The bamboo fiber is pre-cut into short sections with a length of 0.5-2 mm and a diameter of 10-30 μm. Utilizing the capillary action of the bamboo fiber, the bromophenol blue solution (using deionized water as the solvent) is uniformly penetrated into the pores of the foam matrix. The specific operation includes: immersing the foam matrix in the bromophenol blue-bamboo fiber mixed suspension, accelerating solution penetration through vacuum negative pressure (-0.08 to -0.1 MPa), and then drying and curing at 40-50℃, allowing the colorant to firmly adhere to the inner walls of the pores.

[0053] 4. Surface modification and photothermal layer construction

[0054] Plasma treatment: A mixture of argon and oxygen (volume ratio 4:1) is used 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, thereby enhancing the adhesion of subsequent coatings.

[0055] Polydopamine coating deposition: Immerse the foam in a dopamine hydrochloride solution (concentration 2-5 mg / mL) with 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: Utilizing a UV light source with a wavelength of 365-405nm, at a concentration of 10-30mW / cm². 2 The coating is cured for 5-10 minutes by irradiation to form a polydopamine photothermal layer with near-infrared light response.

[0057] 5. Release layer composite

[0058] Glassine release paper (30-50 g / m²) 2 Silicone oil coating amount 1-3g / m 2 It is laminated to the back of the foam matrix through a hot pressing process (temperature 80-100℃, 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 (e.g., reducing the surface pore size to below 50μm can further reduce the risk of adhesion); by adjusting the mass ratio of bromophenol blue to bamboo fiber (e.g., 1:4) and osmotic pressure, the colorimetric response sensitivity can be optimized; by controlling the pH (8.8-9.0) and impregnation 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 optimizing effect of key process parameters in this scheme on the performance of foam dressings, the stirring speed in the second stage of gradient foaming, dopamine hydrochloride impregnation time, and bromophenol blue addition were selected as core variables, and ten sets of comparative experiments were designed. The antibacterial rate, liquid absorption rate, and colorimetric response time were tested according to national standards (GB) and international standardization (ISO) methods, as detailed below:

[0063] Antibacterial rate test (GB / T 20944.3-2008 Textiles - Tests for antibacterial properties - Part 3: Vibration method)

[0064] Methods: Foam dressings were cut into 5cm diameter discs and cultured with Staphylococcus aureus (ATCC 6538) suspension (concentration 1×10^5 CFU / mL) at 37℃ for 24 hours with shaking. The inhibition rate was calculated by 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 - Tests for liquid absorption properties - Vertical absorption method)

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

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

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

[0070] Method: 0.1 mL of simulated exudate (containing 0.1% trypan blue) was dropped onto the dressing surface, and the time required for the colored area to completely diffuse was recorded to an accuracy of 0.01 seconds.

[0071] Experimental group and variable settings

[0072] Variable definition

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

[0074] Dopamine hydrochloride immersion time: preset range of 10-30 minutes, control group set at 5 minutes (too short) and 35 minutes (too long).

[0075] Bromophenol blue addition: The preset limit range is 0.1-0.5 wt%, and the control group is set at 0.05 wt% (insufficient) and 0.6 wt% (excessive).

[0076] Experimental Data Table

[0077]

[0078]

[0079] Comprehensive scoring formula: Antibacterial rate × 40% + Liquid absorption rate × 35% + (1 / color development time) × 25% × 100 (color development time is taken as the reciprocal to be positive).

[0080] Key conclusions

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

[0082] Necessity of preset range:

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

[0084] The color development time of the control group 8 (B=5min) (12.34s) was far worse than the optimal value of the conventional group (5.12s), confirming that insufficient immersion time led to insufficient polydopamine coating thickness (<50nm), affecting 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 internal pores collapsed due to the excessive stirring speed, resulting in a decrease in liquid absorption capacity.

[0086] Based on the above experimental results, this scheme significantly improves the overall performance of foam dressings through the synergistic effect of gradient foaming, color developer dispersion, and photothermal layer construction. The pre-defined parameter ranges (stirring speed 2000-4500 rpm, impregnation time 10-30 min, bromophenol blue 0.1-0.5 wt%) have been experimentally verified as effective thresholds for performance optimization. For example, when the stirring speed is below 2000 rpm, a gradient structure cannot be formed in the internal pore size of the foam (liquid absorption rate of control group 6 is only 165.43%); while an impregnation time exceeding 30 minutes (control group 9) results in an excessively thick polydopamine coating (>200 nm), which reduces photothermal response activity (antibacterial rate 91.23% vs. 98.12% in group 3). This data indicates that the parameter range limitations are not empirical speculations, but rather derived 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 align under high-speed shear force. Bamboo fiber (mainly cellulose, containing a large number of hydroxyl groups) and the amino groups of polyurethane are bonded together through hydrogen bonds to form a stable three-dimensional network. At this time, the CO2 gas generated by the decomposition of the foaming agent (such as sodium bicarbonate) diffuses uniformly in the shear flow field. The surface forms dense micropores (50-80 μm) due to rapid cooling, while the interior expands due to continuous high temperature (100-120℃) to form macropores (150-200 μm). Molecular mechanism: The ratio of hard segments (urea bonds) to soft segments (ether bonds) of polyurethane is controlled by the stirring speed. High speed (>4500 rpm) leads to excessive aggregation of hard segments and pore collapse; low speed (<2000 rpm) causes bubble coalescence due to insufficient shear force, resulting in uneven pore size distribution.

[0090] 2. The effect of dopamine hydrochloride impregnation time on the polymerization mechanism of photothermal coating

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

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

[0093] Bromophenol blue (containing sulfonic acid groups) binds to the hydroxyl groups of bamboo fiber through hydrogen bonds, and then penetrates directionally into the foam pores along the fiber surface under capillary action. The micron-level rough surface (10-30 μm in diameter) of bamboo fiber provides anchoring points, preventing the color developer from agglomerating. Molecular mechanism: When the amount of bromophenol blue added increases from 0.1% to 0.3%, a dynamic equilibrium is formed between the sulfonic acid groups and the hydroxyl groups of cellulose, resulting in uniform dispersion of the color developer; excessive addition (>0.5%) leads to supersaturation of the sulfonic acid groups, intermolecular π-π stacking causes aggregation, blocks the pores, and delays color development.

[0094] 4. Molecular synergistic effect on overall performance

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

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

[0097] Accelerated colorimetric response (5.12s vs. conventional group 15.67s): The sulfonic acid groups of bromophenol blue form a hydrogen bond network with the hydroxyl groups of bamboo fiber, allowing the colorimetric agent to be dispersed in a monolayer form, which rapidly ionizes upon contact with the liquid (H+). + (Loss → Blue color develops).

[0098] Summary of underlying reasons

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

[0100] The dynamic and thermodynamic equilibrium control performance threshold: The interaction of stirring speed (shear stress), immersion time (molecular diffusion rate), and colorant 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 combines chemical chelation and physical thermal effects, breaking through the single action mode of traditional antibacterial agents, and without the risk of drug resistance.

[0102] Exemplary Description

[0103] Example 1

[0104] Preparation method

[0105] Matrix mixing: Polyurethane particles (80 wt%) are mixed with bamboo fiber (20 wt%), and then the isocyanate powder (5 wt%) and dopamine hydrochloride (2 wt%) are added. The mixture is stirred at 800 rpm for 60 minutes at 60°C to form a pre-crosslinked mixture.

[0106] Gradient foaming: The mixture is injected into the mold. In the first stage, it is stirred at 100 rpm and 60°C for 10 seconds. In the second stage, it is stirred at 2000 rpm and 100°C for 35 seconds. After foaming, it is demolded 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 being 0.5 mm in length and 10 μm in diameter. The mixture was then permeated into the foam pores under vacuum negative pressure (-0.08 MPa) and dried and cured at 50 °C.

[0108] Surface treatment:

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

[0110] Polydopamine coating: The foam was immersed in a dopamine hydrochloride solution (2 mg / mL) at pH 8.5 for 10 minutes, and then cured with ultraviolet light (wavelength 365 nm, intensity 10 mW / cm²). 2 5 minutes.

[0111] Release layer lamination: Glassine release paper (30g / m²) is laminated. 2 Silicone oil coating amount 1g / m 2 It is hot-pressed onto the back of the foam at 80℃ and 0.2MPa.

[0112] Example 2

[0113] Preparation method

[0114] Matrix mixing: Polyurethane particles (85wt%) are mixed with bamboo fiber (15wt%), and then the isocyanate powder (8wt%) and dopamine hydrochloride (3wt%) are added. The mixture is stirred at 700 rpm for 50 minutes at 70°C.

[0115] Gradient foaming: In the first stage, the mixture was stirred at 500 rpm and 70℃ for 12 seconds, and in the second stage, it was stirred at 2500 rpm and 110℃ for 30 seconds. After foaming, the surface pore size was 60 μm and the internal pore size was 180 μm.

[0116] Colorimetric reagent 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, dried at 55℃.

[0117] Surface treatment:

[0118] Plasma power 60W, treatment for 60 seconds, gas ratio unchanged;

[0119] Dopamine solution, pH 8.7, concentration 3 mg / mL, impregnation for 15 minutes, followed by UV curing (375 nm, 15 mW / cm²). 2 7 minutes.

[0120] Release layer: 35g / m² 2 Silicone oil coating amount 1.5g / m 2 Hot pressing conditions: 85℃, 0.3MPa.

[0121] Example 3

[0122] Preparation method

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

[0124] Gradient foaming: First stage: stirring at 800 rpm and 80℃ for 15 seconds; second stage: stirring at 3000 rpm and 120℃ for 20 seconds; surface pore size: 70 μm; internal pore size: 200 μm.

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

[0126] Surface treatment:

[0127] Plasma power 100W, processing for 100 seconds;

[0128] Dopamine solution, pH 9.0, concentration 5 mg / mL, immersion for 20 minutes, UV (405 nm, 30 mW / cm²) 2 10 minutes.

[0129] Release layer: 50g / m² 2 Silicone oil 3g / m 2 Hot-pressed at 100℃ and 0.5MPa.

[0130] Examples four through nine are largely the same as example one, except that the values ​​of the variables controlled in the experiment are different. To keep the description concise, the detailed content of the subsequent examples will not be repeated.

[0131] Example 4: Gradient foaming stage 2, 3500 rpm, 10 wt% usnic acid, 0.40 wt% bromophenol blue;

[0132] Example 5: Gradient foaming at 4500 rpm, with 15 wt% usnic acid and 0.50 wt% bromophenol blue;

[0133] Example 6 (Control): Gradient foaming at 500 rpm, otherwise the same as in Example 3;

[0134] Example 7 (Control): Gradient foaming at 5000 rpm, otherwise the same as in Example 3;

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

[0136] Example 9 (Control): Dopamine soaking for 35 minutes, the rest is the same as in 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 antibacterial agent.

[0140] Uniform foaming: foaming at 2000 rpm and 100℃ for 30 seconds in a single stage to form a foam matrix with a uniform pore size (120μm).

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

[0142] Composite layer: No color developer, directly laminated with ordinary release paper (30g / m²) 2 (Silicone-free coating).

[0143] Specific work process

[0144] After mixing polyurethane matrix with bamboo fiber, isocyanate and dopamine hydrochloride are added for pre-crosslinking and stirring to form a homogeneous mixture. This mixture is then injected into a mold, and the stirring speed and temperature are adjusted in stages to allow internal gas diffusion, forming a dense surface and loose internal gradient pore structure. Subsequently, bromophenol blue developer is uniformly dispersed into the foam pores through the capillary action of the bamboo fiber. After surface activation by plasma bombardment, the foam is immersed in a dopamine hydrochloride solution, where a polymerization reaction is initiated by ultraviolet light to form a polydopamine photothermal responsive layer on the surface. Finally, the treated foam is laminated with glassine release paper to form a complete dressing. In each step, gradient foaming provides directional channels for the dispersion of the developer, plasma treatment enhances the bonding strength of the photothermal coating, and the release layer lamination ensures functional integrity while maintaining the dressing's flexibility.

[0145] The technical features described above can be combined in any way. For the sake of brevity, not all possible combinations of the technical features described above 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: The foam dressing includes The matrix material is a composite of polyurethane and bamboo fiber, wherein the bamboo fiber content is 10-20 wt%. The antibacterial components include 5-15 wt% usnic acid and 2-5 wt% dopamine hydrochloride; The gradient pore size structure has a surface pore size of 50-80 μm and an internal pore size of 150-200 μm; wherein, the gradient pore size structure satisfies the following: the diameter of the liquid suction port is 0.5-3.0 mm, and the diameter of the liquid discharge port is 0.2-1.5 mm. The pore density decreases from the center to the edge, with 20-30 pores / cm² in the central region and 5-10 pores / cm² in the edge region; The color developer is 0.1-0.5 wt% bromophenol blue, which is blended and dispersed with bamboo fiber at a mass ratio of 1:3-1:

5. The photothermal responsive layer has a surface treated with plasma and coated with a UV-cured polydopamine photothermal responsive layer. The method for preparing the foam dressing includes the following steps: Pretreatment: Mix polyurethane matrix and bamboo fiber at a ratio of 10-20wt%, add 5-15wt% usnic acid and 2-5wt% dopamine hydrochloride, and stir at 60-80℃ for 30-60 minutes to form a pre-crosslinked mixture; Gradient foaming: The pre-crosslinked mixture is injected into the mold, and the stirring speed is adjusted in stages from 100 rpm to 4500 rpm, and the temperature is increased from 60℃ to 120℃, with a foaming time of 30-50 seconds; the first stage is a stirring speed of 100-800 rpm and a temperature of 60-80℃, lasting for 10-15 seconds; the second stage is a stirring speed of 2000-4500 rpm and a temperature of 100-120℃, lasting for 20-35 seconds; Dispersion of color developer: 0.1-0.5 wt% of bromophenol blue is mixed with bamboo fiber at a mass ratio of 1:3-1:5, and dispersed in the foam by the capillary action of bamboo fiber; Post-treatment: Plasma treatment is performed on the foam surface; the foam is immersed in a dopamine hydrochloride solution with pH 8.5-9.0 for 10-30 minutes and then cured with ultraviolet light to form a photothermal responsive layer.

2. The foam dressing as described in claim 1, characterized in that: The antibacterial component also includes grapefruit essential oil, which is compounded with usnic acid in a mass ratio of 1:1.5 to 1:

2.

3. A foam dressing as described in claim 1, characterized in that: The photothermal response layer has a thickness of 50-200 nm and is formed by the deposition of dopamine hydrochloride in a Tris-HCl buffer solution at pH 8.5-9.

0.

4. The foam dressing as described in claim 1, characterized in that: It also includes a release layer, which is glassine release paper with a basis weight of 30-50 g / m² and a silicone oil coating amount of 1-3 g / m².

5. A foam dressing as described in claim 1, characterized in that, In the colorimetric reagent dispersion step: The bamboo fibers have 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%.

6. A foam dressing as described in claim 1, characterized in that, The parameters for the plasma treatment are: Power 50-100W, processing time 50-100 seconds; The gas is a mixture of argon and oxygen in a volume ratio of 4:

1.

7. A foam dressing as described in claim 1, characterized in that, In the ultraviolet curing step: Ultraviolet wavelength 365-405nm, irradiation intensity 10-30mW / cm², time 5-10 minutes.

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