Wound dressing for unidirectional pumping of biological fluid and preparation method thereof

Abstract

The present invention provides a wound dressing for unidirectionally pumping biological fluids and a method for preparing the same, relating to a dressing that pumps biological fluids through asymmetrically wetted sides and through-holes and a method for preparing the same. The purpose is to overcome the problem of existing dressings being unable to remove biological fluids. The dressing comprises a self-pumping film layer and a microfluidic channel layer; one side of the self-pumping film layer is a hydrophilic surface, and the other side is a hydrophobic surface; the self-pumping film layer is provided with multiple through-holes that connect the hydrophobic and hydrophilic surfaces, and the inner sides of the multiple through-holes are all hydrophilic surfaces; a biological fluid collection channel is provided on one side of the microfluidic channel layer, and this side is in contact with the hydrophilic surface of the self-pumping film layer; the surface of the biological fluid collection channel is a hydrophilic surface; and the inlet of the biological fluid collection channel is directly opposite the locations of all the through-holes.

Description

Technical Field

[0001] The present invention relates to a dressing for pumping biological fluids through asymmetrically wetted sides and through-holes and a method for preparing the same. Background Art

[0002] Biological fluid management (such as wound exudate, sweat, and urine) is an important process in wound bed preparation and is the basis of wound healing. Excessive biological fluids can damage the surrounding skin, increase the possibility of bacterial infection and colonization, and hinder the wound healing process. Therefore, biological fluids need to be removed.

[0003] Existing dressings have a hydrophilic inner layer and a waterproof outer layer. While the hydrophilic inner layer is easily wetted by biological fluids, it only partially absorbs them. Furthermore, after absorbing wound exudate, this inevitably leaves biological fluid at the interface between the wound and the dressing, leaving the wound in an infiltrated state. This over-moisturizes the wound and hinders wound healing. The waterproof outer layer of the dressing, on the other hand, is made of a hydrophobic material. While this material prevents accidental contact between external fluids and the wound, it does not facilitate the removal of biological fluids. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problem that existing dressings cannot remove biological fluids, and to provide a wound dressing for unidirectionally pumping biological fluids and a preparation method thereof.

[0005] The present invention provides a wound dressing for unidirectionally pumping biological fluids, comprising a self-pumping film layer and a microfluidic channel layer;

[0006] One side of the self-pumping film layer is a hydrophilic side, and the other side is a hydrophobic side; a plurality of through holes are provided in the self-pumping film layer to connect the hydrophobic side and the hydrophilic side, and the inner side surfaces of the plurality of through holes are all hydrophilic sides;

[0007] A biological fluid collection channel is provided on one side of the microfluidic channel layer, and the side is in contact with the hydrophilic surface of the self-pumping film layer; the surface of the biological fluid collection channel is a hydrophilic surface;

[0008] The inlet of the biological fluid collection channel is directly opposite to the locations of all the through holes.

[0009] The present invention also provides a method for preparing a wound dressing for unidirectionally pumping biological fluids. Based on the above-mentioned wound dressing for unidirectionally pumping biological fluids, the specific steps are as follows:

[0010] Step 1: Prepare a first PDMS film with a thickness of 0.1 to 0.5 mm, and punch a plurality of through holes in the first PDMS film;

[0011] Step 2: Cover one side of the punched first PDMS film with a mask and then perform plasma cleaning;

[0012] Step 3: Cover the plasma-cleaned first PDMS film with 5% polyvinyl alcohol solution and let it stand at room temperature for 10 minutes. Blow it dry with nitrogen and then heat it on a hot plate at 110°C for 15 minutes.

[0013] After cooling, the residual polyvinyl alcohol was removed with deionized water and dried;

[0014] Step 4: removing the mask to obtain a self-pumping thin film layer;

[0015] Step 5: The microfluidic channel layer is made by soft lithography and molding the second PDMS film;

[0016] Step 6: Bonding the microfluidic channel layer to the self-pumping film layer.

[0017] The beneficial effects of the present invention are:

[0018] The present invention provides a wound dressing for unidirectionally pumping biological fluids and a preparation method thereof, which can obtain a dressing having a hydrophilic surface, a hydrophobic surface, and a through hole. When biological fluid flows out of the wound, the first opening where the biological fluid contacts the hydrophobic surface contacts the inner wall of the through hole, and the biological fluid can enter the storage area of ​​the microfluidic channel layer through the through hole, thereby ensuring that most of the exudate flows into the microfluidic channel layer for storage. Similar to a unidirectional microfluidic diode, it can unidirectionally pump biological fluid from the hydrophobic surface to the hydrophilic surface, thereby effectively removing excess biological fluid. The hydrophobic surface limits the diffusion and flow of wound exudate to the surroundings, while the biological fluid on the hydrophilic side cannot flow out in the opposite direction, thereby isolating the wound surface from the biological fluid, and can remove excess biological tissue fluid from the wound to prevent excessive infiltration of wound fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic structural diagram of a wound dressing for unidirectionally pumping biological fluids according to the present invention;

[0020] Figure 2 This is a schematic diagram of the main structure of a microfluidic channel layer in a wound dressing for unidirectional pumping of biological fluids according to the present invention;

[0021] Figure 3 This is a schematic diagram of a test cross-sectional structure of a self-pumping film layer in a wound dressing for unidirectionally pumping biological fluids according to the present invention;

[0022] Figure 4 This is a schematic flow chart of a method for preparing a wound dressing capable of unidirectionally pumping biological fluids according to the present invention;

[0023] Figure 5 Schematic diagram of the process of using a microinjection pump to push fluid out to simulate wound bed tissue fluid exudation. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention. Specific implementation method 1

[0028] A wound dressing for unidirectional pumping of biological fluids in this embodiment includes a self-pumping film layer 1 and a microfluidic channel layer 2;

[0029] One side of the self-pumping film layer 1 is a hydrophilic surface, and the other side is a hydrophobic surface; a plurality of through holes 3 are provided in the self-pumping film layer 1 to connect the hydrophobic surface and the hydrophilic surface, and the inner side surfaces of the plurality of through holes 3 are all hydrophilic surfaces;

[0030] A biological fluid collection channel 4 is provided on one side of the microfluidic channel layer 2, and this side is in contact with the hydrophilic surface of the self-pumping membrane layer 1; the surface of the biological fluid collection channel 4 is a hydrophilic surface;

[0031] The inlet of the biological fluid collection channel 4 is directly opposite to the locations of all the through holes 3 . Specific implementation method 2

[0033] This embodiment is a further explanation of the first embodiment. In this embodiment, the through hole 3 is a tapered through hole. The area of ​​the first opening 3-1 of the through hole 3 located on the hydrophobic surface is larger than the area of ​​the second opening 3-2 located on the hydrophilic surface.

[0034] The other technical features of this embodiment are exactly the same as those of embodiment 1. Specific implementation method three

[0036] This embodiment is a further explanation of the second embodiment. In this embodiment, the first opening 3-1 and the second opening 3-2 are both circular openings, and the diameter of the first opening 3-1 is 0.36-1.38 mm, and the diameter of the second opening 3-2 is 0.2-1.2 mm.

[0037] The other technical features of this embodiment are exactly the same as those of the second embodiment. Specific implementation method four

[0039] This embodiment is a further explanation of the first embodiment. In this embodiment, a biological fluid collection cavity 4 - 1 is provided at the inlet of the biological fluid collection channel 4 , and the outlet of the biological fluid collection channel 4 is connected to the outside of the microfluidic channel layer 2 .

[0040] The other technical features of this embodiment are exactly the same as those of embodiment 1. Specific implementation method five

[0042] This embodiment is a further explanation of the first or fourth embodiment. In this embodiment, the inner wall of the biological fluid collection channel 4 is provided with a microstructure array 4-2 for enabling the biological fluid to flow in one direction.

[0043] The microstructure array 4-2 is composed of multiple teardrop-shaped protrusions, and is arranged along the inlet to outlet direction of the biological fluid collection channel 4; the thin ends of the teardrop-shaped protrusions are all facing the inlet direction of the biological fluid collection channel 4, and the thick ends are all facing the outlet direction of the biological fluid collection channel 4.

[0044] The other technical features of this embodiment are exactly the same as those of embodiment one or four. Specific implementation method six

[0046] This embodiment is a further explanation of the fifth embodiment. In this embodiment, the biological fluid collection channel 4 has a width of 1 mm and a depth of 0.3 mm.

[0047] The other technical features of this embodiment are exactly the same as those of embodiment five. Specific embodiment seven

[0049] This embodiment is a further explanation of one of the first, second, third, fourth or sixth embodiments. In this embodiment, the self-pumping film layer 1 and the microfluidic channel layer 2 are both polydimethylsiloxane (PDMS) films.

[0050] The other technical features of this embodiment are exactly the same as those of embodiments one, three, four or six. Specific embodiment eight

[0052] The preparation method of a wound dressing for unidirectionally pumping biological fluids in this embodiment is based on the preparation method of a wound dressing for unidirectionally pumping biological fluids in embodiment 7, and the specific steps are as follows:

[0053] Step 1: Prepare a first PDMS film with a thickness of 0.1 to 0.5 mm, and punch a plurality of through holes 3 in the first PDMS film;

[0054] Step 2: Cover one side of the punched first PDMS film with a mask and then perform plasma cleaning;

[0055] Step 3: Cover the plasma-cleaned first PDMS film with 5% polyvinyl alcohol solution and let it stand at room temperature for 10 minutes. Blow it dry with nitrogen and then heat it on a hot plate at 110°C for 15 minutes.

[0056] After cooling, the residual polyvinyl alcohol was removed with deionized water and dried;

[0057] Step 4: removing the mask to obtain a self-pumping thin film layer 1;

[0058] Step 5: The microfluidic channel layer 2 is formed by performing soft lithography and reverse molding on the second PDMS film;

[0059] Step 6: Bond the microfluidic channel layer 2 to the self-pumping film layer 1. Specific embodiment nine

[0061] This embodiment is a further explanation of one of the eighth embodiments. In step 2, the plasma treatment is performed using oxygen gas with a flow rate of 20 sccm and a pressure of 0.67 mbar.

[0062] The other technical features of this embodiment are exactly the same as those of embodiment nine. Specific embodiment 10

[0064] This embodiment is a further explanation of one of the eighth or ninth embodiments. In step three, the polyvinyl alcohol solution is obtained by dissolving polyvinyl alcohol in deionized water at a mass ratio of 5%, stirring at 75° C. for 12 hours, and then filtering with a 0.45 μm aqueous phase filter.

[0065] The other technical features of this embodiment are exactly the same as those of embodiment eight or nine. Specific embodiments

[0067] To improve treatment efficacy, ideal wound dressings should absorb wound biofluids, provide a moist environment for the wound surface, and facilitate tissue repair and wound healing. Therefore, wound dressings should have a wound biofluid management system, including exudate removal and storage functions, to provide a basic environment for subsequent wound treatment and healing.

[0068] A wound dressing for unidirectional pumping of biological fluids, used for unidirectional pumping and storage of biological fluids, such as Figure 1 As shown, it includes a self-pumping film layer 1, a microfluidic channel layer 2, and a medical tape 5. The self-pumping film layer 1 has an asymmetric wetting conical through-hole 3 array, and the microfluidic channel layer 2 includes a teardrop-shaped microstructure array 4-2, which can meet the biological fluid pumping and removal and liquid storage needs at the wound.

[0069] Medical tape 5 adheres to the pumping film layer 1 and the skin, while the microfluidic channel layer 2 and the self-pumping film layer 1 are plasma-bonded. The surface of the medical tape 5 is coated with an acrylic medical pressure-sensitive adhesive, which is used to adhere and secure the self-pumping film layer 1 and the microfluidic channel layer 2 to the skin, ensuring a tight fit between the self-pumping film layer 1 and the skin.

[0070] The self-pumping membrane layer 1 has asymmetric wettability, with one side being hydrophobic and the other side being hydrophilic. The self-pumping membrane layer 1 contains an array of conical through-holes 3, wherein the bottom circle (first opening 3-1) of the conical through-holes 3 is located on the hydrophobic side of the self-pumping membrane layer 1, and the top circle (second opening 3-2) is located on the hydrophilic side of the self-pumping membrane layer 1. The inner wall of the conical through-holes 3 is hydrophilic.

[0071] When biological fluid flows out of the wound, it contacts the inner wall of the hydrophobic bottom circle. The wound dressing, with its asymmetric wettability, acts like a unidirectional microfluidic diode, unidirectionally pumping the biological fluid from the hydrophobic side to the hydrophilic side, effectively removing excess biological fluid. However, the biological fluid on the hydrophilic side cannot flow back out, effectively isolating the wound surface from the biological fluid.

[0072] Biological fluid pumped unidirectionally through the tapered through-holes 3 of the self-pumping membrane layer 1 flows into the biological fluid collection chamber 4-1 in the microfluidic channel layer 2. The biological fluid collection channel 4 is a hydrophilic channel comprising the biological fluid collection chamber 4-1, a teardrop-shaped microstructure array 4-2 for unidirectional transport of the biological fluid, and an outlet 4-3 for draining the biological fluid.

[0073] Specifically, the droplet-shaped microstructure array 4-2 within the biofluid collection channel 4 and the hydrophilic treatment of the biofluid collection channel 4 enable unidirectional flow of the biofluid within the biofluid collection channel 4, ultimately draining or removing the biofluid through the outlet 4-3 of the biofluid collection channel 4. The asymmetric, self-wetting, self-pumping membrane layer 1, which provides unidirectional pumping of the biofluid, and the microfluidic channel layer 2, which provides unidirectional liquid transport, combine to form a complete system, ultimately achieving both pumping and liquid storage requirements for the wound, maintaining a clean and dry environment.

[0074] The self-pumping film layer 1 has a thickness of 0.1 to 0.5 mm, a first opening 3-1 (the bottom circle of the tapered hole) having a diameter of 0.36 to 1.38 mm, a second opening 3-2 (the top circle) having a diameter of 0.2 to 1.2 mm, and a depth of 0.1 to 0.5 mm. The tapered through-holes 3 in the self-pumping film layer 1 are arranged in a regular array, with a trapezoidal cross-section, and are formed by a punch.

[0075] After mask-assisted plasma and polyvinyl alcohol solution treatment of the self-pumping film layer 1, an asymmetric wettable surface is formed. The static contact angle of a droplet on the hydrophilic side is less than 45°, while the static contact angle on the hydrophobic side is greater than 105°. The film hydrophilizing agent can be a hydroxyl- or carboxyl-rich polymer such as polyvinyl alcohol, polyethylene glycol, polyacrylic acid, or hydroxyethyl methacrylate, or a combination of these. A 5% by mass aqueous solution of polyvinyl alcohol is used for optimal hydrophilicity and cost-effectiveness.

[0076] The biofluid collection chamber 4-1 is 9 mm long and 4 mm wide, and can be scaled up or down proportionally to the overall size of the tapered through-hole array 3. The microfluidic channel layer 2 has an overall thickness of 0.5 mm, with the biofluid collection channel 4 measuring 1 mm wide and 0.3 mm deep. The surface of the biofluid collection channel 4 is treated with a hydrophilic treatment. The biofluid collection channel 4 contains a teardrop-shaped microstructure array 4-2, whose size can be adjusted based on the type of biofluid, enabling unidirectional transport of the biofluid. The biofluid collection channel 4 can also be resized as needed to store varying volumes of liquid.

[0077] When the storage is excessive, the excess biological fluid flows out from the outlet 4 - 3 of the biological fluid collecting channel 4 , prompting the replacement of the wound dressing or the realization of biological fluid drainage.

[0078] The medical tape 5 is mainly made of non-woven fabric or polyurethane.

[0079] In summary, the aforementioned wound dressing with asymmetric wettability, similar to a unidirectional microfluidic diode, can unidirectionally pump liquid from the hydrophobic side to the hydrophilic side, effectively removing excess biofluids. Therefore, designing and controlling the surface wettability of biomaterials can achieve effective biofluid management.

[0080] A hydrophilic PDMS surface is manufactured by coating the channels with polyvinyl alcohol immediately after plasma treatment, thereby realizing the production of asymmetric wetting wound dressing. The dressing effectively pumps and absorbs and stores biological fluids from the wound in one direction. The biological fluid can enter the microfluidic channel storage area through these treated through-holes 3. The surrounding hydrophobic PDMS layer restricts the diffusion and flow of wound exudate to the surrounding areas, thereby ensuring that most of the exudate flows into the microfluidic collection layer for storage. The above-mentioned wound dressing has excellent one-way pumping performance, which can remove excess biological tissue fluid from the wound and prevent excessive infiltration of wound fluid. During the movement of the human body, the skin surface of the body will produce various mechanical deformations such as stretching and bending. The designed wound dressing is composed of PDMS, has good flexibility and stretchability, and can adapt well to skin deformation. Therefore, when the skin at the wound is stretched and bent, the wound dressing can still maintain the one-way fluid pumping function.

[0081] The asymmetric moist wound dressing for unidirectional pumping and storage of biological fluids is prepared by the following steps:

[0082] Step 1: A first PDMS film with a thickness of 0.1 to 0.5 mm is formed by a spin coater, and a conical hole array is formed using a punch as needed.

[0083] Step 2: Cover one side of the first PDMS film containing the tapered holes with a mask and perform plasma treatment in a plasma cleaning machine.

[0084] Step 3: Cover the treated first PDMS film with a 5% polyvinyl alcohol solution and let it sit at room temperature for 10 minutes. Blow it dry with nitrogen and heat it on a 110°C hot plate for 15 minutes. After cooling, remove any remaining polyvinyl alcohol with deionized water and dry it.

[0085] Step 4: removing the mask to form an asymmetric wetting self-pumping thin film layer 1 containing tapered pores.

[0086] Step 5: The second PDMS film is formed into a microfluidic channel layer 2 through soft lithography and PDMS molding.

[0087] Step 6: The microfluidic channel layer 2 and the self-pumping thin film layer 1 are bonded to each other by plasma bonding.

[0088] Step 7: Cover the top of the bonded device with medical tape 5 to form an asymmetric moist wound dressing.

[0089] Furthermore, in the above steps 2 and 7, the plasma treatment uses an oxygen flow rate of 20 sccm and a pressure of 0.67 mbar.

[0090] Furthermore, in the above step 3, the polyvinyl alcohol solution was dissolved in deionized water at a mass ratio of 5%, stirred at 75° C. for 12 h, and then filtered through a 0.45 μm aqueous phase filter.

[0091] The prepared asymmetric wetting wound dressing for unidirectional pumping and storage of biological fluids adheres directly to the wound site via medical tape 5, maintaining a tight fit with the skin. Biological fluids, such as exudate and sweat, flow out of the wound site and collect there, contacting the surface of the tapered through-holes 3. Under the capillary action of the asymmetric wetting between the hydrophilic and hydrophobic sides of the membrane, the biological fluid spontaneously flows unidirectionally from the hydrophobic side to the hydrophilic side, that is, from the wound site to the biological fluid collection chamber 4-1 within the self-pumping membrane layer 1. When the liquid in the biological fluid collection chamber 4-1 reaches a certain volume, the microstructure array 4-2 allows the biological fluid to flow from the biological fluid collection chamber 4-1 into the biological fluid collection channel 4, ultimately draining and discharging the biological fluid through the outlet 4-3 of the biological fluid collection channel 4. The wound dressing of the present invention achieves both biological fluid removal and storage functions, providing a foundational environment for subsequent wound treatment and healing.

[0092] Effects of plasma and polyvinyl alcohol treatment on the hydrophilicity of PDMS surface.

[0093] A series of contact angle measurements were performed to investigate the effects of plasma treatment and polyvinyl alcohol (PVA) deposition on the surface properties of PDMS. The hydrophilicity of the dressing surface was determined by contact angle measurements using a custom-built side-mounted microscope stage. The PDMS film was placed on a stage between a light source and a CCD (CCD-E260K) equipped with a camera. The static contact angle of a 3 μL deionized water droplet on the differently treated PDMS substrates was measured using a camera to capture side-view images of the droplet. The hydrophilicity of the PDMS surface after PVA treatment was assessed by measuring the static contact angle of the droplet. Static contact angles were calculated using Dropsnake in ImageJ. Three different samples were measured for each condition, with two different locations on each sample. Multiple measurements were performed on each sample within 15 days of treatment. All tests and sample storage were performed in a standard cleanroom environment (25°C and 30%-35% humidity).

[0094] Conclusion: Compared with oxygen plasma treatment alone, the combination of plasma treatment and polyvinyl alcohol treatment resulted in long-term, stable, and sustained hydrophilicity of the PDMS surface. Oxygen plasma treatment alone tended to restore its surface hydrophobicity one day after treatment, with an average contact angle of 7.2±0.5° immediately after plasma treatment, which increased to 92.6±0.3° one day later. Oxygen plasma treatment plays an important role in the hydrophilic surface modification of PDMS: high-power plasma treatment combined with polyvinyl alcohol treatment provided a more hydrophilic PDMS surface. Surface hydrophilicity was achieved at a plasma power of 100W, with an average contact angle of 43.5±4.3° after 21 days. Fetal bovine serum (FBS) solution, as a simulated biological fluid, exhibited similar wettability on the PDMS surface.

[0095] Conclusion verification:

[0096] like Figure 5 As shown, a microsyringe pump was used to propel fluid out of the wound bed to simulate tissue fluid exudation. Simultaneously, a CCD camera was used to record the dynamic flow of fluid across the dressing. A syringe with a flat needle was placed above or below the film. The syringe was connected to a microsyringe pump via a flexible tube, which injected deionized water at a rate of 3 μL / min. The dynamic flow of fluid across the film was observed and recorded using a side-view microscope.

[0097] Conclusion: Once a droplet contacts the hydrophobic side, it rapidly flows through the pores of the PDMS membrane to the hydrophilic side. The droplet then spreads on the hydrophilic side, causing the hydrophobic side to dry. Conversely, when liquid is added from the hydrophilic side, the droplet rapidly spreads on the hydrophilic side and does not penetrate the hydrophobic side. These results demonstrate that the membrane exhibits excellent unidirectional pumping properties, enabling it to remove excess biological tissue fluid from wounds.

[0098] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other embodiments.

Claims

1. A wound dressing for unidirectional pumping of biological fluids, characterized in that: It comprises a self-pumping film layer (1) and a microfluidic channel layer (2); One side of the self-pumping film layer (1) is a hydrophilic surface, and the other side is a hydrophobic surface; a plurality of through holes (3) capable of connecting the hydrophobic surface and the hydrophilic surface are provided in the self-pumping film layer (1), and the inner side surfaces of the plurality of through holes (3) are all hydrophilic surfaces; A biological fluid collection channel (4) is provided on one side of the microfluidic channel layer (2), and the side is in contact with the hydrophilic surface of the self-pumping film layer (1); the surface of the biological fluid collection channel (4) is a hydrophilic surface; The inlet of the biological fluid collection channel (4) is directly opposite to the locations of all the through holes (3); A biological fluid collection chamber (4-1) is provided at the inlet of the biological fluid collection channel (4), and an outlet of the biological fluid collection channel (4) is communicated with the outside of the microfluidic channel layer (2); The inner wall of the biological fluid collection channel (4) is provided with a microstructure array (4-2) for enabling the biological fluid to flow in one direction; The microstructure array (4-2) is a plurality of teardrop-shaped protrusions arranged along the direction from the inlet to the outlet of the biological fluid collection channel (4); the thin ends of the teardrop-shaped protrusions are all oriented toward the inlet of the biological fluid collection channel (4), and the thick ends are all oriented toward the outlet of the biological fluid collection channel (4).

2. The wound dressing for unidirectional pumping of biological fluid according to claim 1, characterized in that: The through hole (3) is a tapered through hole, and the area of ​​the first opening (3-1) of the through hole (3) located on the hydrophobic surface is larger than the area of ​​the second opening (3-2) located on the hydrophilic surface.

3. The wound dressing for unidirectional pumping of biological fluid according to claim 2, characterized in that: The first opening (3-1) and the second opening (3-2) are both circular openings, and the diameter of the first opening (3-1) is 0.36-1.38 mm, and the diameter of the second opening (3-2) is 0.2-1.2 mm.

4. The wound dressing for unidirectional pumping of biological fluid according to claim 1, characterized in that: The biological fluid collection channel (4) has a width of 1 mm and a depth of 0.3 mm.

5. A wound dressing for unidirectionally pumping biological fluid according to any one of claims 1, 2, 3 or 4, characterized in that: The self-pumping film layer (1) and the microfluidic channel layer (2) are both polydimethylsiloxane (PDMS) films.

6. A method for preparing a wound dressing for unidirectional pumping of biological fluids, characterized in that: The wound dressing for unidirectionally pumping biological fluid according to claim 5 comprises the following steps: Step 1: preparing a first PDMS film with a thickness of 0.1 to 0.5 mm, and punching a plurality of through holes (3) in the first PDMS film; Step 2: Cover one side of the punched first PDMS film with a mask and then perform plasma cleaning; Step 3: Cover the plasma-cleaned first PDMS film with 5% polyvinyl alcohol solution and let it stand at room temperature for 10 minutes. Blow it dry with nitrogen and then heat it on a hot plate at 110°C for 15 minutes. After cooling, the residual polyvinyl alcohol was removed with deionized water and dried; Step 4: removing the mask to obtain a self-pumping thin film layer (1); Step 5: forming a microfluidic channel layer (2) by performing soft lithography and reverse molding on the second PDMS film; Step 6: Bonding the microfluidic channel layer (2) to the self-pumping film layer (1).

7. The method for preparing a wound dressing for unidirectionally pumping biological fluid according to claim 6, characterized in that: In step 2, the plasma treatment is performed using oxygen gas at a flow rate of 20 sccm and a pressure of 0.67 mbar.

8. The method for preparing a wound dressing for unidirectionally pumping biological fluid according to claim 6 or 7, characterized in that: In step 3, the polyvinyl alcohol solution is prepared by dissolving polyvinyl alcohol in deionized water at a mass ratio of 5%, stirring at 75° C. for 12 h, and then filtering with a 0.45 μm aqueous phase filter.

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