A method for preparing a porous membrane and applications thereof

Abstract

The application discloses a porous membrane preparation method and application. The porous membrane preparation method comprises the following steps: providing degradable hydrogel droplets; converting the hydrogel droplets into hydrogel solid powder; providing a substrate prepolymer, mixing the hydrogel solid powder with the substrate prepolymer as a sacrificial template to obtain a substrate mixture; outputting the substrate mixture into a film to obtain a substrate composite membrane body; and degrading and removing the sacrificial template in the substrate composite membrane body to obtain a porous membrane. The degradable hydrogel droplets are used as a basis for forming the sacrificial template, the hydrogel droplets are converted into powder to be fully mixed with the substrate prepolymer, so that when the sacrificial template is removed by degradation, not only zero-damage or low-damage demolding can be achieved, but also the pore making precision of the porous membrane can be ensured based on the pore diameter of the hydrogel droplets when demolding.

Description

Technical Field

[0001] This application relates to the field of microfluidic cell culture technology, and in particular to a method for preparing porous membranes and their applications. Background Technology

[0002] Currently, the mainstream methods for preparing PDMS (Polydimethylsiloxane) semipermeable membranes can be categorized as follows:

[0003] Method 1: Micromolding based on silicon molds

[0004] This is a method used for organ-on-a-chip applications such as lung-on-a-chip. First, a high-precision array of micropillars is fabricated on a silicon wafer using deep reactive ion etching (DRIE) technology. Then, liquid PDMS is cast onto a silicon mold, solidified, and demolded to form a thin film with an array of through-holes. The silicon mold has extremely high precision and is reusable.

[0005] Method 2: Micromolding based on SU-8 photoresist mold

[0006] To address the issue of excessively high costs associated with silicon molds, researchers proposed using SU-8 epoxy photoresist as a substitute for silicon as the mold material. SU-8 micropillar arrays are directly fabricated on silicon or glass substrates using standard photolithography processes, followed by PDMS casting and mold making. This method can be completed in a standard cleanroom, and the molds can be reused multiple times.

[0007] Method 3: Micromolding based on metal molds

[0008] To further improve the durability of molds, recent research proposes using MEMS electroforming technology to fabricate integrated nickel metal micropillar molds. The nickel mold and metal substrate form a single structure with a bonding strength far exceeding that of photoresist molds. Furthermore, after hydrophobic treatment, PDMS can be directly spin-coated to prepare porous films, making it suitable for large-scale production.

[0009] Method 4: Drilling method based on laser processing

[0010] High-density micropore arrays can be directly fabricated on PDMS thin films using cold processing techniques such as femtosecond lasers. This method eliminates the need for masks and molds, offering high flexibility and enabling one-stop processing of micropores and microchannels.

[0011] Method 5: Sacrificial Layer Demolding Method

[0012] Micropillars are fabricated using sacrificial materials such as positive photoresist. After PDMS curing, the mold is removed by dissolution, achieving stress-free demolding. This method avoids damage to the film structure caused by pulling during demolding, but the mold is for single use only.

[0013] The methods described above generally have drawbacks and limitations in terms of industrial application and performance optimization:

[0014] (1) The contradiction between cost and efficiency is prominent:

[0015] While the classic silicon mold method produces durable molds, the DRIE equipment is extremely expensive and the processing time is long, making it the most costly step.

[0016] Although the SU-8 mold method lowers the process threshold, the micropillars are prone to peeling off from the substrate or breaking during repeated demolding, resulting in insufficient durability and affecting the film formation yield and mold life.

[0017] The sacrificial layer method requires re-molding each time, resulting in low production efficiency and a large amount of labor costs.

[0018] (2) It is difficult to balance the precision of micropore forming and demolding, which is a common dilemma faced by all mold-making methods:

[0019] To achieve high-density, small-aperture (<10μm) micropores, the mold micropillars must be extremely fine and have a high aspect ratio, which is a disaster area for traditional mold casting. They are very easy to break and clog the micropores during demolding.

[0020] Reducing the height of the microcolumn or increasing the pore size to ensure smooth demolding would result in an excessively thick membrane (>30μm) or an excessively large pore size, failing to meet the dual requirements of precise separation and efficient material exchange for organoid co-culture.

[0021] (3) It is difficult to control the uniformity of film thickness and pore size:

[0022] Traditional laser drilling methods are limited by the characteristics of Gaussian beams, which can easily result in a tapered hole wall that is larger at the top and smaller at the bottom. Furthermore, thermal effects can lead to uneven hole diameters and deformation of the hole edges.

[0023] Dry etching without a mold often results in problems such as irregular hole shape and edge erosion, leading to poor consistency of penetration rate between batches.

[0024] (4) Limitations of material compatibility and integration process:

[0025] PDMS itself has a strong adsorption capacity for small molecule drugs, which remains a challenge in the field of organ-on-a-chip. When encapsulating and integrating PDMS porous membranes with other materials such as thermoplastic PMMA, complex surface treatments are often required, resulting in poor process compatibility.

[0026] In summary, existing technologies have significant trade-offs and shortcomings in terms of mass production feasibility (involving cost, efficiency, mold life), core performance indicators (involving ultrathin film thickness, high porosity, pore size uniformity), and process compatibility. Summary of the Invention

[0027] This application proposes a method for preparing porous membranes, which effectively solves the technical problem of difficulty in balancing mass production feasibility, core performance indicators, and process compatibility in related technologies.

[0028] This application also proposes a porous membrane prepared by the above-described porous membrane preparation method.

[0029] This application also proposes an application of the above-mentioned porous membrane preparation method in organoid culture or in organ-on-a-chip.

[0030] The first aspect of this application provides a method for preparing a porous membrane, comprising the following steps:

[0031] Provides biodegradable hydrogel droplets;

[0032] The hydrogel droplets are converted into hydrogel solid powder;

[0033] A substrate prepolymer is provided, and the hydrogel solid powder is used as a sacrificial template to be mixed with the substrate prepolymer to obtain a substrate mixture;

[0034] The substrate mixture is output as a membrane to obtain a substrate composite membrane;

[0035] The sacrificial template in the substrate composite membrane is degraded and removed to obtain a porous membrane.

[0036] Furthermore, the hydrogel droplets are chemically cross-linked biodegradable hydrogels;

[0037] The sacrificial template in the substrate composite membrane is removed by chemical degradation.

[0038] Furthermore, using microfluidic technology, the hydrogel droplets with controllable shape and size were prepared;

[0039] After the hydrogel droplets are solidified, separated, purified, and dried, the hydrogel solid powder is obtained.

[0040] The substrate prepolymer is a PDMS prepolymer. The hydrogel solid powder is used as a sacrificial template and mixed with the PDMS prepolymer to obtain a PDMS mixture.

[0041] The PDMS mixture is spin-coated and cured to obtain a PDMS composite film with controllable film thickness.

[0042] The hydrogel droplets are polyacrylamide hydrogel droplets with disulfide bond crosslinking. An aqueous solution of dithiothreitol (DTT), tris(2-carboxyethyl)phosphine (TCEP) or a combination thereof is used as a reducing agent to reduce the disulfide bonds in the hydrogel solid powder and disintegrate the crosslinking network. This causes the hydrogel solid powder to swell, disintegrate, and dissolve and diffuse out the PDMS matrix, resulting in a PDMS porous membrane.

[0043] Further, the provision of degradable hydrogel droplets includes:

[0044] Preparation of the dispersed aqueous phase: Dissolve the acrylamide monomer and the crosslinking agent N,N'-bis(acryloyl)cysteine ​​in deionized water or PBS buffer;

[0045] Preparation of continuous oil phase: Select fluorinated oil or mineral oil as continuous phase, and add surfactant to stabilize droplets;

[0046] The dispersed phase and the continuous phase are injected into the microfluidic chip, and monodisperse hydrogel droplets of a preset size and shape are generated by adjusting the flow rate ratio of the dispersed phase to the continuous phase.

[0047] Further, the step of converting the hydrogel droplets into hydrogel solid powder includes:

[0048] The hydrogel droplets are thermally or ultraviolet-cured to obtain an oil-hydrogel sphere emulsion.

[0049] A demulsifier is added to the oil-hydrogel ball emulsion, and after centrifugation or natural separation, the upper oil phase is removed and the mixture is washed to obtain a hydrogel ball suspension.

[0050] The hydrogel ball suspension was subjected to stepwise dehydration treatment with ethanol of different concentration gradients to obtain a hydrogel ball slurry containing 100% ethanol, which was then dried to constant weight below the hydrogel degradation temperature, or freeze-dried to obtain a dry hydrogel solid powder.

[0051] Further, the provision of the substrate prepolymer, using the hydrogel solid powder as a sacrificial template, is mixed with the substrate prepolymer to obtain a substrate mixture, comprising:

[0052] The base agent and curing agent are mixed in a preset ratio, stirred evenly, and then degassed under vacuum to obtain the base prepolymer.

[0053] The hydrogel solid powder is added to the substrate prepolymer at a preset mass ratio, and the hydrogel solid powder is uniformly suspended and dispersed by mixing to obtain a substrate mixture.

[0054] Further, the step of outputting the substrate mixture into a film to obtain a substrate composite film includes:

[0055] The substrate mixture is dropped onto a flat substrate and spin-coated based on a preset spin-coating speed and preset spin-coating time to obtain a film with a preset film thickness. Then, it is heated and cured to obtain a substrate composite film.

[0056] Further, the degradation process to remove the sacrificial template from the substrate composite membrane to obtain a porous membrane includes:

[0057] The substrate composite film is surface treated to increase surface wettability;

[0058] The substrate composite membrane is immersed in a degradation solution containing a reducing agent. The degradation solution penetrates the substrate composite membrane and undergoes a reduction reaction, causing the crosslinked network of the substrate composite membrane to disintegrate and a thin film to be obtained.

[0059] The membrane was removed from the degradation solution, washed, and dried to obtain a porous membrane.

[0060] As can be seen from the above technical solutions, the embodiments of this application have at least the following beneficial effects: by using degradable hydrogel droplets as the basis for forming a sacrificial template, the hydrogel droplets are converted into powder so as to be fully mixed with the substrate prepolymer, so that when the sacrificial template is removed by degradation, not only can zero-damage or low-damage demolding be achieved, but also the pore-forming accuracy of the porous membrane can be guaranteed based on the pore size of the hydrogel droplets during demolding.

[0061] Furthermore, compared with existing technologies, the preparation of hydrogel droplets has a greater advantage in terms of mass production feasibility, and the precision of hydrogel droplets is easier to control during preparation. After degradation, the dried hydrogel droplets will form a precise and controllable pore structure in the porous membrane, ensuring that the core performance indicators of the prepared porous membrane can meet the high precision requirements. In addition, since this application adopts the preparation method of mixing dried hydrogel solid powder with substrate prepolymer and then outputting it to form a film, it can also have a significant performance improvement in terms of process compatibility.

[0062] A second aspect of this application provides a porous membrane, comprising: being prepared by a porous membrane preparation method as described in the first aspect of this application.

[0063] The third aspect of this application provides an application of the porous membrane preparation method of the first aspect of this application in organoid culture or in organ-on-a-chip.

[0064] It is easy to understand that the porous membranes in the second aspect of this application and the applications in the third aspect of this application both have the same technical effects as the porous membrane preparation method in the first aspect of this application, and therefore will not be described again.

[0065] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0066] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0067] Figure 1 This is a flowchart of the steps of a porous membrane preparation method provided in one embodiment of this application;

[0068] Figure 2 This is a schematic diagram illustrating the preparation principle of soluble hydrogel microspheres according to one embodiment of this application. Detailed Implementation

[0069] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0070] See Figures 1 to 2 As shown, an embodiment of the first aspect of this application discloses a method for preparing a porous membrane, comprising the following steps:

[0071] S101: Provides biodegradable hydrogel droplets;

[0072] S102: Convert hydrogel droplets into hydrogel solid powder;

[0073] S103: Provide a substrate prepolymer, using hydrogel solid powder as a sacrificial template, and mix it with the substrate prepolymer to obtain a substrate mixture;

[0074] S104: Output the substrate mixture to form a membrane, and obtain a substrate composite membrane;

[0075] S105: Degrade and remove the sacrificial template in the substrate composite membrane to obtain a porous membrane.

[0076] In the embodiments of this application, degradable hydrogel droplets are used as the basis for forming a sacrificial template. The hydrogel droplets are converted into powder so as to be fully mixed with the substrate prepolymer. This allows for zero-damage or low-damage demolding when the sacrificial template is removed by degradation. Furthermore, the pore-forming accuracy of the porous membrane can be guaranteed based on the pore size of the hydrogel droplets during demolding.

[0077] Furthermore, compared with existing technologies, the preparation of hydrogel droplets has a greater advantage in terms of mass production feasibility, and the precision of hydrogel droplets is easier to control during preparation. After degradation, the dried hydrogel droplets will form a precise and controllable pore structure in the porous membrane, ensuring that the core performance indicators of the prepared porous membrane can meet the high precision requirements. In addition, since this application adopts the preparation method of mixing dried hydrogel solid powder with prepolymer before outputting the film, it can also have a significant performance improvement in terms of process compatibility.

[0078] Understandably, hydrogel droplets are processed into solid powder, which is then used as a sacrificial template and thoroughly mixed with the substrate prepolymer to form a stable substrate mixture, while retaining its biodegradability after rehydration. The mixture is then molded into a substrate composite membrane, and finally, the hydrogel powder sacrificial template inside the membrane is removed through a degradation process. The space originally occupied by the powder is hollowed out, ultimately forming a porous membrane with a regular pore structure. Using hydrogel powder as a sacrificial template can maximize the protection of the membrane structure integrity. By controlling the size and shape accuracy of the hydrogel droplets, porous membrane products that meet high-precision performance indicators can be stably prepared.

[0079] In some embodiments, the degradable hydrogel droplets can be prepared by means of, but not limited to, microfluidic technology, piezoelectric on-demand dropping, electrostatic atomization, coaxial jet fragmentation, or membrane emulsification. Further, the degradable hydrogel droplets can be polyacrylamide hydrogels with disulfide crosslinking structures, specifically formed by copolymerization and crosslinking of acrylamide monomers with a disulfide crosslinking agent. The prepared hydrogel droplets can be spherical, ellipsoidal, disc-shaped, or irregularly shaped, and their size can be adaptively adjusted according to the pore size within the actual porous membrane.

[0080] In some embodiments, the conversion of hydrogel droplets into hydrogel solid powder can be achieved through methods including, but not limited to, solidifying, separating, purifying, and drying the hydrogel droplets; directly atomizing and drying the hydrogel droplets; mechanically pulverizing and sieving the solidified hydrogel droplets; freeze-curing the hydrogel droplets and then vacuum-freezing them; or in-situ crosslinking and curing the hydrogel droplets. Furthermore, to further improve the pore formation accuracy of the porous membrane, the hydrogel solid powder can be sieved after preparation to select powders within the target particle size range, which can then be used for subsequent mixing to obtain the substrate mixture.

[0081] In some embodiments, the substrate mixture can be output as a film by means including, but not limited to, spin coating, blade coating, casting, calendering, or spray coating. Furthermore, the film quality can be ensured by curing after film formation, specifically by any one of thermal curing, ultraviolet curing, or room temperature natural curing.

[0082] In some embodiments, the degradation and removal of the sacrificial template in the substrate composite membrane can be achieved through methods including, but not limited to, chemical degradation, enzymatic hydrolysis, and physical swelling degradation. Furthermore, when chemical degradation is used, it can be any one of reducing, acidic, alkaline, or oxidizing reagent degradation. Specifically, the choice of degradation method must be compatible with the actual material of the degradable hydrogel droplets to ensure zero-damage or low-damage demolding.

[0083] In some embodiments, the methods of providing degradable hydrogel droplets and substrate prepolymers are not unique; they can be achieved through preparation or direct sourcing, and are not further limited herein. In other embodiments, the porous membrane preparation method disclosed in the embodiments of this application is performed after directly providing the hydrogel solid powder and substrate prepolymer, and this should also be understood as falling within the protection scope of this application.

[0084] In some embodiments, the substrate prepolymer can be prepared from PDMS prepolymer, phenelzine prepolymer, PI (polyimide) prepolymer, PVA (polyvinyl alcohol) prepolymer, etc. If the substrate prepolymer is made of a material other than PDMS prepolymer, the diameter of the hydrogel solid powder must be greater than the film thickness to form through-pores.

[0085] When using PDMS prepolymer, since PDMS itself has the characteristics of a porous membrane, the reducing agent can dissolve into the membrane when the membrane thickness is less than 5 mm. Therefore, when using PDMS prepolymer as the substrate prepolymer, it is not required that the diameter of the hydrogel solid powder be greater than the membrane thickness.

[0086] Therefore, in this embodiment, PDMS prepolymer is selected as the substrate prepolymer. The following will combine... Figures 1 to 2 The method for preparing PDMS porous membranes disclosed in the embodiments of this application will be explained and described in detail. However, it should be understood that when the substrate preparation material is simply replaced with and selected from Pyrelin, PI (polyimide), or PVA (polyvinyl alcohol) without creative effort, it should also be understood as falling within the scope of the scheme described in this application.

[0087] It should be understood that in the PDMS porous membrane preparation method disclosed in this application, a PDMS porous membrane with precisely controllable pore structure is obtained by introducing a sacrificial template, mixing it with the PDMS prepolymer, outputting the film, and curing it, and then dissolving the sacrificial template. Therefore, it is understandable that the selection and preparation of the sacrificial template material, as well as the method of dissolving the sacrificial template, are key to achieving the above effects in order to remove the sacrificial template quickly and completely. Furthermore, the material of the sacrificial template and the corresponding dissolution method also determine the ease or difficulty of obtaining the PDMS porous membrane.

[0088] In some embodiments of this application, the hydrogel droplets are chemically cross-linked biodegradable hydrogels. It is understood that by using chemically cross-linked biodegradable hydrogels to prepare droplets, a stable gel structure is formed by chemical cross-linking. After subsequent drying and curing, the droplets are mixed with PDMS prepolymer and output as a film. The cross-linked structure can be destroyed by the corresponding degradation method, and the droplets can be completely removed from the PDMS composite film, achieving low-damage demolding and ensuring the integrity of the overall structure of the film.

[0089] Furthermore, in some embodiments, chemical reagents are used to degrade and remove the sacrificial template in the PDMS composite membrane. It is understood that chemical degradation not only removes the template thoroughly, but also, depending on the specific choice of reducing agent, can further avoid damage during demolding, thereby effectively protecting the PDMS membrane and its pore structure.

[0090] It should be noted that the method of using dried soluble hydrogel spheres as sacrificial templates to generate PDMS semipermeable membranes can eliminate the risk of micropillar breakage and pore blockage as thoroughly as possible, achieving almost 100% pore structure transfer fidelity, and providing a feasible technical approach for the preparation of ultrathin films and ultra-high aspect ratio micropores.

[0091] In one embodiment, microfluidic technology is used to prepare hydrogel droplets with controllable shape and size. It is understood that by using microfluidic technology to regulate the fluid state and precisely prepare hydrogel droplets, the droplet parameters are precisely controllable. These droplets can then be used as templates to replicate regularly sized pores, improving the pore-forming accuracy of PDMS porous membranes. Furthermore, the preparation process is stable, easily achievable for mass production, and ensures batch-to-batch droplet consistency.

[0092] Furthermore, based on microfluidic generation of hydrogel droplets with controllable shape and size, the three-dimensional morphology of micropores can be flexibly customized, providing a new solution for constructing anisotropic or gradient porous biomimetic functional interfaces, and enabling the in-situ construction of biochemically active PDMS porous membranes, thus providing a basis for realizing active functional membranes.

[0093] In one embodiment, hydrogel droplets are solidified, separated, purified, and dried to obtain hydrogel solid powder. It can be understood that the droplets are first solidified and shaped, then impurities are removed through separation and purification, and finally internal moisture is removed through drying, thereby transforming the liquid gel droplets into dry hydrogel solid powder for subsequent use as a sacrificial template. This multi-step process minimizes impurity interference within the powder and ensures that the powder morphology and size are as uniform as possible. The dried solid powder exhibits greater stability, avoiding deformation and adhesion issues, and mixes more uniformly with the PDMS prepolymer, significantly improving the precision of porous membrane formation and the performance of the finished product. It should be understood that this process path of drying to powder, mixing, and re-dissolving solves the difficulties in mixing and forming in related technologies.

[0094] In one embodiment, a PDMS mixture is spin-coated and cured to obtain a PDMS composite film with controllable thickness. It can be understood that the uniformly mixed PDMS mixture is laid flat using a spin-coating process, the film thickness is controlled by adjusting the spin-coating parameters, and then the mixture is cured to set and solidify, finally obtaining a PDMS composite film with uniform thickness and controllable specifications, providing a regular film substrate for subsequent degradation and pore formation.

[0095] Furthermore, based on microfluidic droplet generation, independent and precise control of membrane pore size can be achieved, and spin-coating and curing of PDMS mixtures can achieve independent and precise control of membrane thickness. This preparation method enables the fabrication of ultrathin PDMS functional membranes with thicknesses as low as a few micrometers and pore sizes that can be arbitrarily designed within the micrometer to millimeter range, overcoming the design bottleneck of traditional methods where membrane thickness is limited by the height of the mold micropillars.

[0096] In one embodiment, the hydrogel droplets are polyacrylamide hydrogel droplets cross-linked with disulfide bonds. An aqueous solution of dithiothreitol (DTT), tris(2-carboxyethyl)phosphine (TCEP), or a combination thereof is used as a reducing agent to reduce the disulfide bonds in the hydrogel solid powder and disintegrate the cross-linked network. This causes the hydrogel solid powder to swell, disintegrate, and dissolve, diffusing out the PDMS matrix to obtain a porous PDMS membrane. It is understood that this method, based on disulfide-linked, chemically degradable polyacrylamide hydrogel as a sacrificial template, utilizes the high reduction and degradation efficiency of DTT to achieve rapid and complete removal of the template material without harmful residues.

[0097] In summary, the PDMS porous membrane preparation method disclosed in this application uses microfluidic technology to generate polyacrylamide hydrogel droplets with controllable size and disulfide bond crosslinking. After curing and drying, the droplets are used as sacrificial templates, mixed with PDMS prepolymer, spin-coated into a film, and thermally cured. Finally, the template is dissolved by a reducing agent to obtain a PDMS porous membrane with precise and controllable pore structure.

[0098] In some specific embodiments of this application, degradable hydrogel droplets are provided, including:

[0099] Preparation of the dispersed aqueous phase: Dissolve the acrylamide monomer and the crosslinking agent N,N'-bis(acryloyl)cysteine ​​in deionized water or PBS buffer;

[0100] Preparation of continuous oil phase: Select fluorinated oil or mineral oil as continuous phase, and add surfactant to stabilize droplets;

[0101] The dispersed phase and the continuous phase are injected into the microfluidic chip, and monodisperse hydrogel droplets of a preset size and shape are generated by adjusting the flow rate ratio of the dispersed phase to the continuous phase.

[0102] Understandably, this step is used for the preparation of biodegradable polyacrylamide hydrogels containing disulfide bonds.

[0103] In some embodiments, N,N'-bis(acryloyl)cysteine, containing a disulfide bond (-SS-) in its molecular structure, is crucial for subsequent degradation in the preparation of the dispersed aqueous phase. Specifically, the total monomer mass fraction can be set within a range, such as 5%-20% w / v, and the crosslinking agent molar ratio is 0.1%-5% of the total monomers. The crosslinking density directly affects the mechanical strength of the hydrogel spheres.

[0104] In some embodiments, the addition of surfactants can be achieved by adding 2%-5% w / w of fluorinated surfactants (such as Pico-Surf) or Span surfactants to stabilize droplets and prevent them from merging downstream.

[0105] In some embodiments, a flow-focusing microfluidic chip is used in the microfluidic droplet generation step. The dispersed phase and the continuous phase are injected into the chip separately. By precisely controlling the flow rate ratio of the dispersed phase to the continuous phase, monodisperse hydrogel droplets with diameters ranging from 5 μm to 200 μm can be flexibly generated. The final pore size of the PDMS membrane is directly determined by the size of the hydrogel droplets generated in this step.

[0106] In some specific embodiments of this application, converting hydrogel droplets into hydrogel solid powder includes:

[0107] Hydrogel droplets are thermally or UV-cured to obtain oil-hydrogel sphere emulsions.

[0108] A demulsifier is added to the oil-hydrogel ball emulsion. After centrifugation or natural separation, the upper oil phase is removed and the mixture is washed to obtain a hydrogel ball suspension.

[0109] The hydrogel ball suspension was dehydrated stepwise by ethanol of different concentration gradients to obtain a hydrogel ball slurry containing 100% ethanol, which was then dried to constant weight below the hydrogel degradation temperature, or freeze-dried to obtain a dry hydrogel solid powder.

[0110] Understandably, this step is used to transform liquid hydrogel droplets into solid hydrogel spheres and transfer them to an aqueous environment. It is also used to transform the hydrogel spheres into solid dry powders that can be uniformly mixed with hydrophobic PDMS, while retaining their degradability after rehydration.

[0111] In some embodiments, in-situ curing of the hydrogel droplets can be achieved using thermal curing. The method includes adding 1-1.5% (v / v) of N,N,N′,N′-tetramethylethylenediamine (TEMED) as a catalyst to the continuous phase (i.e., the droplet-generating oil) during the microfluidic droplet generation step for subsequent thermal curing at 65°C. The generated hydrogel droplets are collected in a container with a hydrophobic material surface, such as a plastic centrifuge tube. If HFE-7500 is selected as the continuous phase, a layer of mineral oil needs to be applied to the collected hydrogel droplets to prevent the oil phase from evaporating during thermal curing. The collected microdroplets are then placed in a 65°C forced-air drying oven for thermal curing. The curing time needs to be determined based on the concentration of the added catalyst; for example, adding 0.4% TEMED requires at least 16 hours of curing at 65°C, while adding 1.5% TEMED requires at least 2 hours of curing at 37°C.

[0112] In some embodiments, in-situ curing of the hydrogel droplets can be achieved using ultraviolet (UV) light curing. The method includes adding a photoinitiator, 0.1%-1% w / v of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone (I2959), for subsequent UV curing. At the outlet of the downstream channel of the microfluidic chip, the flowing droplets are irradiated with 365nm UV light, causing the photoinitiator to decompose and initiating the polymerization and cross-linking of acrylamide monomers to form interpenetrating network structured hydrogel solid microspheres. The irradiation duration needs to be determined based on the flow rate and light intensity, for example, 5-30 seconds.

[0113] In some embodiments, when demulsifying the collected oil-hydrogel ball emulsion, an excess of demulsifier, such as a 20% HFE-7500 solution of perfluorooctanoic acid, is added, and the mixture is shaken and mixed to disrupt the surfactant-stabilized interfacial film.

[0114] In some embodiments, after centrifugation or natural separation to remove the upper oil phase, the cleaning process involves repeated washing and centrifugation with excess isopropanol or ethanol to thoroughly remove residual oil phase and unreacted monomers from the surface and interior of the hydrogel spheres. Finally, the spheres are replaced with deionized water to obtain a clean suspension of hydrogel spheres dispersed in water.

[0115] In some embodiments, during gradient dehydration, the hydrogel ball suspension can be dehydrated stepwise with ethanol of different concentration gradients (e.g., 30%, 50%, 70%, 90%, 100%), with centrifugation and replacement each time.

[0116] In some embodiments, the temperature below the hydrogel degradation temperature can be 60-80°C. The purpose of this step is to completely remove moisture, causing it to shrink in volume and making it easier to mix with the PDMS prepolymer in the future.

[0117] In some specific embodiments of this application, a PDMS prepolymer is provided, which is mixed with a hydrogel solid powder as a sacrificial template to obtain a PDMS mixture, comprising:

[0118] The PDMS main agent and curing agent are mixed in a preset ratio, stirred evenly and degassed under vacuum to obtain PDMS prepolymer;

[0119] Hydrogel solid powder is added to PDMS prepolymer at a preset mass ratio, and the hydrogel solid powder is uniformly suspended and dispersed by mixing to obtain PDMS mixture.

[0120] Understandably, this step is the core process for achieving a uniform and monodisperse distribution of the template within the PDMS membrane.

[0121] In some embodiments, the preset ratio can be 10:1, and the preset mass ratio can be 1%-30%. Mixing can be performed vigorously using a planetary centrifugal mixer or mechanical stirring to ensure that the dry powder particles are uniformly suspended and dispersed in the viscous PDMS. Because the hydrogel spheres are in a dry powder state, agglomeration and phase separation will not occur.

[0122] In some specific embodiments of this application, a PDMS mixture is output to form a membrane, resulting in a PDMS composite membrane, including:

[0123] The PDMS mixture is dropped onto a flat substrate and spin-coated according to a preset spin-coating speed and time to obtain a film with a preset film thickness. Then, it is heated and cured to obtain a PDMS composite film.

[0124] Understandably, the process parameters for membrane fabrication in this step directly determine the membrane thickness.

[0125] In some embodiments, the spin-coating method includes: dropping a PDMS mixture containing hydrogel sphere powder onto a clean silicon wafer, glass slide, or other flat substrate; and then spin-coating using a spin coater. The film thickness is determined by the spin-coating speed and time, for example, spin-coating at 500-4000 rpm for 30-60 seconds. The final film thickness is completely independent of the size of the hydrogel spheres, and ultrathin films with a thickness much smaller than the diameter of the powder particles can be obtained.

[0126] In some embodiments, the spin-coated film, together with the substrate, can be cured in an oven, for example, at 60°C for 2-4 hours, during heat curing.

[0127] In some specific embodiments of this application, the sacrificial template in the PDMS composite membrane is degraded and removed to obtain a porous PDMS membrane, including:

[0128] The PDMS composite film is surface treated to increase surface wettability;

[0129] The PDMS composite membrane is immersed in a degradation solution containing a reducing agent. The degradation solution penetrates the PDMS composite membrane and undergoes a reduction reaction, causing the cross-linked network of the PDMS composite membrane to disintegrate and a thin film to be obtained.

[0130] The membrane was removed from the degradation solution, washed, and dried to obtain a PDMS porous membrane.

[0131] Understandably, this step is the final step in forming the pore structure, utilizing the chemical degradation of disulfide bonds to remove the template without damage.

[0132] In some embodiments, the cured PDMS film can be cut to the required size along with or after peeling off the substrate, and then surface treated.

[0133] In some embodiments, the surface treatment can be performed using oxygen plasma to increase the wettability of the reducing agent to the PDMS material surface.

[0134] In some embodiments, the reducing agent is an aqueous solution of dithiothreitol (DTT), tris(2-carboxyethyl)phosphine (TCEP), or a combination thereof, with a concentration of 10-100 mM. The degradation solution permeates into PDMS and undergoes a reduction reaction with the disulfide bonds in the dry powder hydrogel spheres, causing the cross-linked network to disintegrate. At this point, the dry hydrogel rapidly absorbs water, swells, disintegrates, and dissolves, diffusing out the PDMS matrix.

[0135] In some embodiments, the temperature of this degradation process can be set at 37°C or room temperature, and the duration depends on the film thickness and pore density, generally ranging from several hours to overnight. It should be understood that this degradation process is essentially a chemical phase transition reaction rather than a physical removal, therefore the inner walls of the pores are smooth, causing no physical damage to the high-density, small-pore film, and the pore structure fidelity is extremely high.

[0136] In some embodiments, after the film is removed from the degradation solution, it is repeatedly soaked and rinsed with a large amount of deionized water to thoroughly remove water-soluble polyacrylamide segments and residual DTT generated during degradation. After natural air drying or critical point drying, a PDMS porous film with a micron-level precision pore structure is obtained.

[0137] The method for preparing a PDMS porous membrane according to a specific embodiment of this application is described in detail below. It should be noted that the following embodiment is merely an exemplary description and should not be construed as limiting the embodiments of this application.

[0138] See Figures 1 to 2 As shown, the PDMS porous membrane preparation method of this embodiment includes the following steps:

[0139] Step 1: Preparation of biodegradable polyacrylamide hydrogels containing disulfide bonds

[0140] The core of this step is the synthesis of a polyacrylamide hydrogel prepolymer containing a disulfide bond crosslinking agent; details can be found in [reference needed]. Figure 2 The preparation principle diagram of the provided soluble hydrogel microspheres is implemented, including:

[0141] Preparation of dispersed phase aqueous solution:

[0142] Acrylamide monomer and cross-linking agent N,N'-bis(acryloyl)cysteine ​​were dissolved in deionized water or PBS buffer. N,N'-bis(acryloyl)cysteine ​​is key to subsequent degradation and its molecular structure contains a disulfide bond (-SS-).

[0143] The total mass fraction of monomers can be set within a range, such as 5%-20% w / v, and the molar ratio of crosslinking agent is 0.1%-5% of the total monomers. The crosslinking density will directly affect the mechanical strength of the hydrogel spheres.

[0144] Preparation of continuous oil phase:

[0145] Choose fluorinated oil (such as HFE-7500) or mineral oil as the continuous phase.

[0146] Add 2%-5% w / w of fluorinated surfactants (such as Pico-Surf) or Span surfactants to stabilize droplets and prevent them from coalescing downstream.

[0147] Microfluidic droplet generation:

[0148] A flow-focusing microfluidic chip is used. The dispersed phase and the continuous phase are injected into the chip separately.

[0149] By precisely controlling the flow rate ratio of the dispersed phase to the continuous phase, monodisperse hydrogel droplets with diameters ranging from 5 μm to 200 μm can be flexibly generated.

[0150] This is a critical process control point: the final pore size of the PDMS membrane is directly determined by the size of the hydrogel droplets generated in this step.

[0151] Step 2: In-situ solidification and "demulsification" of hydrogel droplets;

[0152] This step transforms the liquid droplets into solid hydrogel spheres and transfers them to an aqueous environment, specifically including:

[0153] There are two methods for curing hydrogel balls:

[0154] Thermosetting: In the microfluidic droplet generation step, N,N,N′,N′-tetramethylethylenediamine (TEMED) is added as a catalyst at a volume ratio of 1-1.5% and mixed into the continuous phase (i.e., droplet generation oil) for subsequent thermosetting at 65°C.

[0155] Photocuring: Add a photoinitiator, 0.1%-1% w / v of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone (I2959), for subsequent UV curing.

[0156] If thermosetting is used:

[0157] The generated microdroplets are collected in containers on the surface of a hydrophobic material, such as plastic centrifuge tubes. If HFE-7500 is selected as the continuous phase, a layer of mineral oil needs to be coated on the collected hydrogel liquid to prevent the oil phase from evaporating during thermal curing.

[0158] The collected microdroplets were placed in a 65°C forced-air drying oven for thermal curing. The curing time needs to be determined according to the concentration of the catalyst added. For example, if 0.4% TEMED is added, it needs to be cured in the 65°C oven for at least 16 hours, and if 1.5% TEMED is added, it needs to be cured in the 37°C oven for at least 2 hours.

[0159] If UV curing is used:

[0160] At the outlet of the downstream channel of the microfluidic chip, the flowing droplets are irradiated with 365nm ultraviolet light, causing the photoinitiator to decompose and triggering the polymerization and cross-linking of acrylamide monomers to form hydrogel solid microspheres with an interpenetrating network structure. The irradiation time needs to be determined according to the flow rate and light intensity, for example, 5-30 seconds.

[0161] Hydrogel droplets are thermally or UV-cured to obtain oil-hydrogel sphere emulsions.

[0162] De-milking and washing:

[0163] The collected oil-hydrogel sphere emulsion was subjected to demulsification treatment. An excess of demulsifier, such as a 20% HFE-7500 solution of perfluorooctanoic acid, was added, and the mixture was shaken and mixed to disrupt the surfactant-stabilized interfacial film.

[0164] After centrifugation or natural separation, the upper oil phase is removed to obtain preliminarily separated hydrogel spheres.

[0165] Repeated washing and centrifugation with excess isopropanol or ethanol are used to thoroughly remove residual oil phase and unreacted monomers from the surface and interior of the hydrogel spheres. Finally, the spheres are replaced with deionized water to obtain a clean suspension of hydrogel spheres dispersed in water.

[0166] Step 3: Drying the hydrogel balls

[0167] The aim is to transform hydrogel spheres into a solid dry powder that can be uniformly mixed with hydrophobic PDMS, while retaining its biodegradability after rehydration, including:

[0168] Gradient dehydration:

[0169] To prevent the hydrogel spheres from collapsing during rapid drying, the hydrogel sphere suspension can be dehydrated stepwise with ethanol of different concentration gradients (e.g., 30%, 50%, 70%, 90%, 100%), with centrifugation and replacement each time.

[0170] Completely dry:

[0171] The final hydrogel slurry containing 100% ethanol is placed in an oven and dried to constant weight at a temperature below the hydrogel degradation temperature (e.g., 60-80℃), or dried spherical powder is obtained by freeze drying.

[0172] The purpose of this step is to completely remove moisture, causing it to shrink in volume and making it easier to mix with the PDMS prepolymer later.

[0173] Step 4: Drying the hydrogel spheres and mixing them with PDMS

[0174] This is the core process for achieving a uniform and monodisperse distribution of the template within the PDMS membrane, specifically including:

[0175] PDMS prepolymer preparation:

[0176] Mix the PDMS main agent and curing agent in a standard ratio (e.g., 10:1), stir evenly, and then degas under vacuum.

[0177] Mixed dispersion:

[0178] The dried hydrogel ball powder obtained in step three is added to the PDMS prepolymer at the required mass ratio (e.g., 1%-30%).

[0179] Vigorous mixing is performed using a planetary centrifuge or mechanical agitation to ensure that the dry powder particles are uniformly suspended and dispersed in the viscous PDMS. Because the hydrogel spheres are in a dry powder state, aggregation and phase separation will not occur.

[0180] Step 5: Spin coating and thermosetting of PDMS composite film

[0181] The process parameters for this membrane fabrication step directly determine the membrane thickness, specifically including:

[0182] Spin coating:

[0183] The PDMS mixture containing hydrogel ball powder is dropped onto a clean silicon wafer, glass slide, or other flat substrate.

[0184] Spin coating is performed using a spin coater. The film thickness is determined by the spin coating speed and time, for example, spin coating at 500-4000 rpm for 30-60 seconds.

[0185] The final film thickness is completely independent of the size of the hydrogel spheres, and ultrathin films with a thickness much smaller than the diameter of dry powder particles can be produced.

[0186] Thermosetting:

[0187] The spin-coated film, together with the substrate, is heated and cured in an oven, for example, at 60°C for 2-4 hours.

[0188] Step Six: Dissolution of the Sacrificial Template and Formation of the Porous Membrane

[0189] This is the final step in shaping the pore structure, utilizing the chemical degradation of disulfide bonds to remove the template without damage, specifically including:

[0190] Cutting and soaking:

[0191] The cured PDMS film can be cut to the required size either together with the substrate or after being peeled off.

[0192] First, the PDMS surface is treated with oxygen plasma to increase the wettability of the reducing agent to the PDMS material surface.

[0193] The plasma-treated PDMS film is immersed in a degradation solution containing a reducing agent. The reducing agent is an aqueous solution of dithiothreitol (DTT), tris(2-carboxyethyl)phosphine (TCEP), or a combination thereof, with a concentration of 10-100 mM.

[0194] Degradation reaction and leaching:

[0195] The degradation solution penetrates PDMS and undergoes a reduction reaction with the disulfide bonds in the dry powder hydrogel spheres, causing the cross-linked network to disintegrate. At this point, the dry polyacrylamide hydrogel rapidly absorbs water, swells, disintegrates, and dissolves, diffusing out the PDMS matrix.

[0196] The temperature for this process can be set at 37°C or room temperature, and the duration depends on the film thickness and pore density, generally ranging from several hours to overnight.

[0197] Cleaning and finished product:

[0198] The film was removed from the degradation solution and repeatedly soaked and rinsed with plenty of deionized water to thoroughly remove the water-soluble polyacrylamide segments and residual DTT generated during degradation.

[0199] After natural air drying or critical point drying, a PDMS porous film with a micron-level precision pore structure is obtained.

[0200] It is understandable that the PDMS porous membrane preparation method in this embodiment combines microfluidic droplet technology with stimulus-responsive sacrificial materials, which breaks away from the traditional micropillar mold casting framework in principle, and is expected to systematically solve several industry pain points summarized.

[0201] First, it overcomes the physical limitations of solid micro-column molds.

[0202] The core drawback of traditional methods lies in the presence of physically rigid micropillars, which the solution in this application fundamentally eliminates. The fundamental advantages include:

[0203] Zero-damage or low-damage demolding: The PDMS film does not need to be peeled off from the solid mold. Traditional techniques suffer from yield problems due to micropillar breakage and micropore blockage; this method eliminates these physical demolding resistances.

[0204] The hole shape is not limited by the demolding direction: the demolding direction must be perpendicular, which limits traditional methods to creating only through holes. However, the hydrogel powder used in this application occupies space in situ inside PDMS, theoretically forming isotropic spherical cavities, which provides the possibility of constructing more complex 3D interconnected channel structures.

[0205] II. Achieved "decoupling" of pore size and film thickness and preparation of ultrathin films.

[0206] In traditional methods, the height of the mold micropillars directly determines the minimum thickness of the PDMS film. To achieve small pore sizes, the micropillars must be thinner, limiting their height; if they are too short, the resulting film is too thin and easily torn, creating a vicious cycle of film thickness-pore size-strength. The method described in this application breaks this cycle. Its fundamental advantages include:

[0207] The pore size is determined by the size of the hydrogel droplets generated, while the film thickness is determined by the spin coating process: the size of the hydrogel droplets is precisely controlled by a microfluidic chip to determine the pore size, while the film thickness is completely controlled independently by parameters such as spin coating speed, time, and viscosity of the PDMS mixture.

[0208] Support for ultrathin films and wide pore size range: In theory, it is possible to prepare ultrathin films with a thickness much smaller than the pore size, which is crucial for achieving efficient transmembrane mass exchange.

[0209] Third, a highly efficient and thorough sacrificial template material system was introduced.

[0210] The selection of disulfide-crosslinked polyacrylamide hydrogels, coupled with DTT degradation, is another key technological advantage of this application. The fundamental advantages include:

[0211] Degradation is clearly triggered and responds quickly: disulfide bonds (-SS-) can be efficiently cleaved by the reducing agent DTT, degrading the cross-linked network into linear polymers. The dissolution process is a chemical disintegration, which is faster and more thorough.

[0212] Drying / Rehydration Cycle Enhances Processability: The hydrogel spheres are first completely dried into a powder before being mixed with PDMS. This step is crucial and solves the following problems:

[0213] The challenge of mixing and dispersing hydrophilic gels and hydrophobic PDMS: solid dry powder particles are more easily dispersed uniformly in viscous PDMS, avoiding droplet aggregation and fusion.

[0214] Dimensional stability: The PDMS is embedded in dry powder particles, which avoids the liquid hydrogel being sheared and deformed during spin coating, ensuring the roundness of the final pore shape.

[0215] Fourth, it expands the diversity of the morphology and function of holes.

[0216] Non-cylindrical pores: Through microfluidic technology, not only spherical droplets can be generated, but also flat disc-shaped, elliptical, and even Janus droplets. This means that irregularly shaped pores can be prepared in PDMS membranes, enabling customized control of cell growth and fluid shear force, which is unattainable by traditional cylindrical pore molds.

[0217] Multifunctional Capsules with Potential Microforce: Hydrogel droplets can themselves load growth factors, small molecule drugs, and even nanoparticles. These functional components can be encapsulated during membrane fabrication and released into the porous structure through sustained-release mechanisms after membrane formation, endowing PDMS membranes with biological functions that induce or regulate cell behavior.

[0218] In summary, the PDMS porous membrane preparation method of this embodiment changes the paradigm of solid micropillar molding in the existing technology to that of biodegradable droplet templates. This results in innovation in both process and performance. Specifically, the process innovation involves integrating cross-disciplinary technologies such as microfluidic droplet generation, sacrificial hydrogel templates, and chemical degradation to form a unique droplet template-dry embedding-chemical degradation pore-forming process. The performance innovation involves overcoming the limitations of film thickness-pore size linkage, achieving zero-damage demolding, and opening up new dimensions for irregularly shaped and functionalized pores.

[0219] The second aspect of this application discloses a PDMS porous membrane, which is prepared by the PDMS porous membrane preparation method of the first aspect of this application.

[0220] The third aspect of this application discloses the application of the PDMS porous membrane preparation method of the first aspect of this application in organoid culture or in organ-on-a-chip.

[0221] It is easy to understand that the PDMS porous membrane in the second aspect embodiment and the application in the third aspect embodiment of this application have the same technical effects as the PDMS porous membrane preparation method in the first aspect embodiment, and therefore will not be described again.

[0222] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0223] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "multiple" means two or more. It should be noted that the term "and / or" used herein is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Similarly, at least one of A or B can also represent: A alone, A and B simultaneously, or B alone.

[0224] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0225] In the foregoing description of this specification, references to terms such as "one embodiment," "another embodiment," or "some embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0226] It should be understood that although the steps in the flowcharts of the accompanying figures are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the accompanying figures may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.

Claims

1. A method for preparing a porous membrane, characterized in that, Includes the following steps: Provides biodegradable hydrogel droplets; The hydrogel droplets are converted into hydrogel solid powder; A substrate prepolymer is provided, and the hydrogel solid powder is used as a sacrificial template to be mixed with the substrate prepolymer to obtain a substrate mixture; The substrate mixture is output as a membrane to obtain a substrate composite membrane; The sacrificial template in the substrate composite membrane is degraded and removed to obtain a porous membrane.

2. The method for preparing a porous membrane according to claim 1, characterized in that: The hydrogel droplets are chemically cross-linked biodegradable hydrogels. The sacrificial template in the substrate composite membrane is removed by chemical degradation.

3. The method for preparing a porous membrane according to claim 2, characterized in that: The hydrogel droplets with controllable shape and size were prepared using microfluidic technology. After the hydrogel droplets are solidified, separated, purified, and dried, the hydrogel solid powder is obtained. The substrate prepolymer is a PDMS prepolymer. The hydrogel solid powder is used as a sacrificial template and mixed with the PDMS prepolymer to obtain a PDMS mixture. The PDMS mixture is spin-coated and cured to obtain a PDMS composite film with controllable film thickness. The hydrogel droplets are polyacrylamide hydrogel droplets with disulfide bond crosslinking. An aqueous solution of dithiothreitol (DTT), tris(2-carboxyethyl)phosphine (TCEP) or a combination thereof is used as a reducing agent to reduce the disulfide bonds in the hydrogel solid powder and disintegrate the crosslinking network. This causes the hydrogel solid powder to swell, disintegrate, and dissolve and diffuse out the PDMS matrix, resulting in a PDMS porous membrane.

4. The method for preparing a porous membrane according to claim 1, characterized in that: The provision of biodegradable hydrogel droplets includes: Preparation of the dispersed aqueous phase: Dissolve the acrylamide monomer and the crosslinking agent N,N'-bis(acryloyl)cysteine ​​in deionized water or PBS buffer; Preparation of continuous oil phase: Select fluorinated oil or mineral oil as continuous phase, and add surfactant to stabilize droplets; The dispersed phase and the continuous phase are injected into the microfluidic chip, and monodisperse hydrogel droplets of a preset size and shape are generated by adjusting the flow rate ratio of the dispersed phase to the continuous phase.

5. The method for preparing a porous membrane according to claim 1, characterized in that: The process of converting the hydrogel droplets into hydrogel solid powder includes: The hydrogel droplets are thermally or ultraviolet-cured to obtain an oil-hydrogel sphere emulsion. A demulsifier is added to the oil-hydrogel ball emulsion, and after centrifugation or natural separation, the upper oil phase is removed and the mixture is washed to obtain a hydrogel ball suspension. The hydrogel ball suspension was subjected to stepwise dehydration treatment with ethanol of different concentration gradients to obtain a hydrogel ball slurry containing 100% ethanol, which was then dried to constant weight below the hydrogel degradation temperature, or freeze-dried to obtain a dry hydrogel solid powder.

6. The method for preparing a porous membrane according to claim 1, characterized in that: The provision of the substrate prepolymer, using the hydrogel solid powder as a sacrificial template, is mixed with the substrate prepolymer to obtain a substrate mixture, comprising: The base agent and curing agent are mixed in a preset ratio, stirred evenly, and then degassed under vacuum to obtain the base prepolymer. The hydrogel solid powder is added to the substrate prepolymer at a preset mass ratio, and the hydrogel solid powder is uniformly suspended and dispersed by mixing to obtain a substrate mixture.

7. The method for preparing a porous membrane according to claim 1, characterized in that: The step of outputting the substrate mixture into a membrane to obtain a substrate composite membrane includes: The substrate mixture is dropped onto a flat substrate and spin-coated based on a preset spin-coating speed and preset spin-coating time to obtain a film with a preset film thickness. Then, it is heated and cured to obtain a substrate composite film.

8. The method for preparing a porous membrane according to claim 1, characterized in that: The degradation process removes the sacrificial template from the substrate composite membrane to obtain a porous membrane, comprising: The substrate composite film is surface treated to increase surface wettability; The substrate composite membrane is immersed in a degradation solution containing a reducing agent. The degradation solution penetrates the substrate composite membrane and undergoes a reduction reaction, causing the cross-linked network of the substrate composite membrane to disintegrate and a thin film to be obtained. The membrane was removed from the degradation solution, washed, and dried to obtain a porous membrane.

9. A porous membrane, characterized in that, include: It is prepared by the porous membrane preparation method according to any one of claims 1 to 8.

10. The application of the porous membrane preparation method according to any one of claims 1 to 8 in organoid culture or in organ-on-a-chip.

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