Polydimethylsiloxane (PDMS) porous membrane as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of microfluidic processing, and particularly relates to a PDMS porous membrane as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) uniformly mixing a PDMS prepolymer, a PDMS cross-linking agent and an organic solvent A to obtain a mixed solution; pS microsphere powder is added into the mixed solution, and an N-H-PDMS / PS solution is obtained after ultrasonic treatment and stirring; (2) putting a metal sheet into a container, adding water to submerge the metal sheet, dropwise adding the N-H-PDMS / PS solution into the container, and diffusing the N-H-PDMS / PS solution on the water surface to form an N-H-PDMS / PS film; (3) heating the container containing the metal sheet, water and the N-H-PDMS / PS film in the step (2), and removing the organic solvent A; then water in the container is removed, so that the N-H-PDMS / PS thin film covers the metal sheet, and a film-coated metal sheet is obtained; and (4) after air-drying the coated metal sheet, adding the coated metal sheet into an organic solvent B for soaking, and after soaking is finished, washing with water to obtain the PDMS porous membrane. The preparation method provided by the invention can regulate and control the porosity, aperture and thickness of the PDMS porous membrane, and has good adaptability.

Description

Technical Field

[0001] The present invention belongs to the technical field of microfluidic processing, and particularly relates to a PDMS porous membrane, a preparation method thereof, and an application thereof. Background Art

[0002] A microfluidic chip (Lab-on-a-Chip) is a device that precisely controls and operates fluids using micron-scale channels and structures. Due to its high efficiency and high integration, this technology has gradually become an important production tool in the fields of medicine, biology, environmental detection, etc. Among them, the Organ-on-a-Chip, listed as one of the top ten emerging technologies by the World Economic Forum in Davos, has high requirements for issues such as the biocompatibility, material processing, and process accuracy of microfluidic chips. An organ chip is a device that simulates cells and tissues on a tiny chip through microfluidic technology, thereby simulating the functions and pathological states of human organs. These chips are essential for physiological and pathophysiological research, drug development, testing new drug delivery methods, and detecting drug targets. Polydimethylsiloxane (PDMS) has become the most common material for organ chips due to its simple molding, good gas permeability, high transparency, and good biocompatibility.

[0003] The porous thin film is an important component of a multi-chamber organ chip, serving as a substrate or barrier at the cell or tissue interface, and is particularly crucial for the research of barrier tissues such as the intestinal epithelium, vascular system, and blood-brain barrier. In addition to the biological barriers in organ chips, PDMS porous membranes with different pore sizes can also be used for diagnosis, cell separation, capture, and sorting. However, the commercially available porous thin films on the market currently are polyethylene terephthalate (PET) membranes and polycarbonate (PC) membranes, with pore sizes ranging from 10 nm to 20 μm. The thin films prepared from the above materials have mature processes, but there are great defects in the use in organ chips. The poor light transmittance of the materials reduces the observability of the organ chip; the weak mechanical properties of the thin film cannot be stretched repeatedly, and the elastic barrier in the human tissue cannot be reconstructed. Unmodified PC and PET cannot be hermetically bonded to the chip body made of PDMS or glass, and leakage will occur during the culture and perfusion processes. Therefore, in recent years, the research on using PDMS as a material to manufacture porous thin films to construct biological membranes has gradually increased.

[0004] The most common method is to fabricate the mold through photolithography technology and laser cutting technology. Polydimethylsiloxane (PDMS) is added to the microcolumn array mold, and external pressure is applied above the template. After curing, demolding is carried out. However, this method is prone to the generation of blind holes, and since the thickness of the film is generally very small, it is easy to cause tearing during removal. The transfer of the above-mentioned pressed porous PDMS film is also challenging, and uneven stress application during the peeling process from the substrate will cause the film to rupture. By adding a sacrificial layer or silanizing the mold, the transfer of the ultra-thin PDMS porous film (<5μm) can be improved. Polyacrylic acid (PAA) is used as the sacrificial layer between the silicon wafer and PDMS. Ultrasonic water bath hydrolysis of the sacrificial layer results in low-stress release of the porous film and greatly reduces the damage to the PDMS structure.

[0005] In summary, aiming at the problems of fabricating PDMS porous membranes through imprinting and reverse casting using a microcolumn array mold and the difficulty in transferring brittle porous films in the use of organ chips, there is an urgent need for a method for preparing PDMS porous membranes by a water-based forming process to solve the above problems. Summary of the Invention

[0006] Aiming at the problems and deficiencies in the prior art, the present invention aims to provide a PDMS porous membrane, a preparation method thereof, and an application thereof.

[0007] In order to achieve the object of the present invention, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of the present invention provides a method for preparing a PDMS porous membrane, comprising the following steps:

[0009] (1) Mix PDMS prepolymer, PDMS crosslinker, and organic solvent A evenly to obtain a mixed solution; add polystyrene (PS) microsphere powder to the mixed solution, and obtain an N-H-PDMS / PS solution after ultrasonic treatment and stirring;

[0010] (2) Place a metal sheet in a container, add water to the container to submerge the metal sheet, and drop the N-H-PDMS / PS solution prepared in step (1) into the container. The N-H-PDMS / PS solution diffuses on the water surface to form an N-H-PDMS / PS film;

[0011] (3) Heat the container containing the metal sheet, water, and N-H-PDMS / PS film in step (2) to remove the organic solvent A; then remove the water in the container so that the N-H-PDMS / PS film covers the metal sheet to obtain a metal sheet with a film;

[0012] (4) After air-drying the metal sheet with a film, soak it in organic solvent B, and after the soaking is completed, wash it with water to obtain the PDMS porous membrane.

[0013] Preferably, in step (1), the mass ratio of the PDMS prepolymer to the PDMS crosslinking agent is 5:1 to 20:1, and the mass ratio of the PDMS prepolymer to the organic solvent A is 1:1 to 8:1.

[0014] Preferably, in step (1), the PDMS prepolymer and the PDMS crosslinking agent are Dow Corning SYLGARD 184 silicone rubber. This product is a two-component kit product, divided into Component A and Component B. Component A is the PDMS prepolymer, and Component B is the PDMS crosslinking agent.

[0015] Preferably, in step (1), the organic solvent A is an alkane with 5 to 10 carbon atoms.

[0016] More preferably, in step (1), the organic solvent A is n-hexane.

[0017] Preferably, in step (1), the dosage of the PS microsphere powder is 3 wt% to 25 wt% of the mass of the PDMS prepolymer.

[0018] Preferably, in step (1), the diameter of the PS microspheres is 5 μm to 50 μm.

[0019] Preferably, in step (2), the addition amount of the N-H-PDMS / PS solution is related to the container size and the film thickness, and the calculation formula is: X = SH; where X is the addition amount of the N-H-PDMS / PS solution, in mL; S is the bottom area of the container, in mm 2 ; H is the thickness of the porous membrane to be prepared, in mm.

[0020] Preferably, in step (5), the organic solvent B is one of acetone, benzene, chloroform, and tetrahydrofuran, and the soaking time is 3 to 5 min.

[0021] Preferably, in step (3), the heating temperature is 60 to 80 °C, and the time is 120 min.

[0022] The second aspect of the present invention protects a PDMS porous membrane prepared by the method of the first aspect of the present invention.

[0023] The third aspect of the present invention protects the application of the PDMS porous membrane described in the second aspect in an organ chip.

[0024] The fourth aspect of the present invention protects an organ chip, wherein the organ chip contains the PDMS porous membrane described in the second aspect of the present invention.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) The preparation method of the PDMS porous membrane by the water-based forming process of the present invention has good adaptability to different porosity, pore size, and film thickness, and can fabricate PDMS porous membranes with a porosity of 1.5% - 12.5%, a pore diameter of 5μm - 50μm, and a thickness of 3μm - 40μm. The present invention subverts the conventional method of obtaining PDMS films by spin coating, shortens the preparation time of the porous membrane, eliminates the need for making a mask or a mold, and reduces the prerequisite conditions for the formation of the porous membrane.

[0027] (2) The forming process of the preparation process of the present invention is rapid and has great advantages for the transfer of the film. Since there is no need for steps such as pouring and imprinting through a mold in the PDMS film forming process, the film does not need to be peeled off from the array mold. At the same time, there is no need to use highly toxic chemical reagents such as acetone and photoresist developer. It has the characteristics of high light transmittance, softness, easy stretching, good biocompatibility, and easy transfer and bonding. The stress required during the process of peeling the film from the substrate is small, resulting in high film integrity and easy bonding with the organ chip. Description of the Drawings

[0028] Figure 1 Flow chart for manufacturing the PDMS porous membrane by the water-based forming process;

[0029] Figure 2 Manufacturing diagram by the water-based forming process;

[0030] Figure 3 Electron micrograph of the porous film prepared with 10μm spheres;

[0031] Figure 4 Electron micrograph of a single pore prepared with 10μm spheres;

[0032] Figure 5 Porous films with different porosities prepared from PS microsphere powders with different ratios;

[0033] Figure 6 Cross-sectional view of the bonding between the PDMS porous membrane and the organ chip;

[0034] Figure 7 Perfusion experiment of the three layers bonded by the PDMS porous membrane;

[0035] Figure 8 Staining and bright field images of cell culture on the PDMS porous membrane. Detailed Embodiments

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer and more definite, the present invention will be further described in detail below through embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] Example 1

[0038] A preparation method of a PDMS porous membrane, and the production process is as follows Figure 1 , and the specific steps are as follows:

[0039] (1) Preparation of PDMS porous membrane solution: The PDMS prepolymer, PDMS crosslinker and n - hexane are uniformly mixed according to a mass ratio of 10:1:5. The PDMS prepolymer and PDMS crosslinker are Dow Corning SYLGARD 184 silicone rubber. This product is a two - component kit product, divided into Component A and Component B. Component A is the PDMS prepolymer, and Component B is the PDMS crosslinker. The silicon - hydrogen bond (Si - H) in the crosslinker can undergo a hydrosilylation reaction with the vinyl group in the PDMS prepolymer to form a stable silicon - carbon bond (Si - C), thereby achieving crosslinking. Stir the above - mentioned solution evenly and remove the bubbles, then add 40 mg of dry PS microsphere powder. The mass ratio of the PDMS prepolymer to the PS microsphere powder is 25:1, and the diameter of the PS microspheres is 10 μm. Ultrasonic the above - mentioned N - H - PDMS / PS solution at a power of 80 w and a frequency of 40 KHZ for 15 min, and then magnetically stir it at 600 r / rpm for 30 min to obtain an N - H - PDMS / PS solution with uniform dispersion of PS.

[0040] (2) Surface diffusion of PDMS porous membrane solution: Place a clean metal sheet in a petri dish and pour a certain amount of deionized water to submerge the metal collection sheet. Use a pipette and a syringe to take an appropriate amount of N - H - PDMS / PS solution and drop it on the liquid surface of the solution. The N - H - PDMS / PS will spontaneously diffuse into a uniform and continuous thin film. This process is shown in Figure 2 .

[0041] (3) Curing and forming of PDMS porous membrane: Place the petri dish containing the metal collection sheet, deionized water and N - H - PDMS / PS thin film on a hot plate for baking. The baking temperature is 60 °C, and the baking time is 120 min. After the N - H - PDMS / PS thin film is heated, the n - hexane in the solution volatilizes, and the PDMS prepolymer and crosslinker solidify into a film. The PS microspheres float on the water surface and are embedded in the PDMS thin film, thereby obtaining a PDMS / PS microsphere thin film.

[0042] (4) Collection of PDMS porous membrane: Determine whether the thin film is formed and cured by spraying pure aqueous solution above the thin film. After the petri dish cools to room temperature, insert the syringe along the wall of the petri dish below the water surface, draw out the deionized aqueous solution until the thin film contacts the metal collection sheet at the bottom of the petri dish, and take out the metal collection sheet and air - dry it.

[0043] (5) Cleaning of sacrificial microsphere material: Immerse the metal sheet in acetone solution for 5 minutes to remove the PS microspheres that can be dissolved by the organic solution, and soak and wash it with deionized water multiple times. Finally, a PDMS porous membrane with a porosity of 2.03% is obtained.

[0044] Example 2

[0045] It is basically the same as Example 1, except that: in step (1), the mass ratio of the PDMS prepolymer to the PS microsphere powder is 20:1, and a PDMS porous membrane with a porosity of 2.5% is prepared.

[0046] Example 3

[0047] It is basically the same as Example 1, except that: in step (1), the mass ratio of the PDMS prepolymer to the PS microsphere powder is 20:3, and a PDMS porous membrane with a porosity of 7.5% is prepared.

[0048] Example 4

[0049] It is basically the same as Example 1, except that: the mass ratio of the PDMS prepolymer to the PS microsphere powder is 4:1, and a PDMS porous membrane with a porosity of 12.5% is prepared.

[0050] Characterization test

[0051] The porous thin film prepared in Example 1 was tested by scanning electron microscopy. The results are shown in Figures 3 to 4 . By using an electron microscope with a magnification of 1000 times for shooting, a porous membrane with a porosity of 2.03% can be obtained ( Figure 3 ), and a single-hole image taken by using an electron microscope with a magnification of 1000 times, the pore diameter is 5 μm, and the pores are basically circular ( Figure 4 ). For the porous thin films with different porosities prepared in Examples 2 to 4, the bright-field micrographs are shown in Figure 5 . It is a picture under a 4-fold microscope, and their pore diameters are 5.02 μm, 4.89 μm, and 5.12 μm respectively, which proves that the preparation method of the present invention can adjust the porosity by changing the addition amount of the PS powder microspheres.

[0052] Performance test

[0053] (1) Bonding of the PDMS porous membrane and the organ chip

[0054] Use the PDMS porous membrane prepared in Example 1 to bond with the organ chip. First, treat the surface of the porous membrane with plasma for 100 s to remove the surface that needs to be in contact with the organ chip, so that the porous membrane and the flow channel with a thickness of 50 μm and a width of 800 μm on the lower surface of the organ chip are bonded. The cross-sectional view after bonding is as shown in Figure 5 . Figure 5It can be seen that the porous film will suspend above the flow channel, and this result indicates that the film prepared by the present invention can be in a suspended state in the flow channel of the organ chip, enabling co-culture of cells.

[0055] (2) Perfusion experiment of the three-layer bonded with PDMS porous membrane

[0056] First bond the PDMS porous film prepared in Example 1 with the upper flow channel layer of the organ chip, and then bond it with the lower flow channel of the organ chip. Inject blue ink into the upper horizontal flow channel; inject colorless pure water into the lower sheet-shaped flow channel, and observe the changes in the flow channel within 10 minutes. The results are shown in Figure 6 . From Figure 6 It can be seen that within 10 minutes, the blue ink in the upper layer gradually diffuses and fills the lower chamber, proving that the PDMS porous film has the function of solution exchange.

[0057] (3) Cell culture on PDMS porous membrane

[0058] Use the PDMS porous membrane prepared in Example 1 to culture C2C12 cells (mouse myoblasts). The specific steps of cell culture are as follows:

[0059] (a) Place the prepared PDMS film at the bottom of a 48-well plate;

[0060] (b) After infiltrating the PDMS film with PBS for 30 minutes, remove the PBS and sterilize it with ultraviolet light for 30 minutes;

[0061] (c) Use Laminin (laminin) diluted 1:10 to modify the surface of the porous PDMS film, or gelatin with a concentration of 0.1% - 0.5% can also be used for modification;

[0062] (d) Culture C2C12 cells on the modified PDMS porous film.

[0063] After culturing C2C12 cells for 2 hours, stain the cells with Calcein-AM dye. The results are as shown in Figure 8 shown in the left figure. It is found that the cells show fluorescent green, proving that the cells have adhered and survived. Figure 8 The right figure shows the bright-field microscope image of cell culture on the porous membrane. It can be seen that the PDMS porous membrane prepared by the present invention can be used for cell culture. The experimental results show that the PDMS porous membrane prepared by the present invention has good biocompatibility.

Claims

1. A preparation method of a PDMS porous membrane, characterized in that, It includes the following steps: (1) Mix the PDMS prepolymer, PDMS crosslinker and organic solvent A evenly to obtain a mixed solution; add PS microsphere powder to the mixed solution, and obtain the N-H-PDMS / PS solution after ultrasonic treatment and stirring; (2) Place the metal sheet in a container, add water to the container to submerge the metal sheet, and drop the N-H-PDMS / PS solution prepared in step (1) into the container. The N-H-PDMS / PS solution diffuses on the water surface to form an N-H-PDMS / PS film; (3) Heat the container containing the metal sheet, water and N-H-PDMS / PS film in step (2) to remove the organic solvent A; then remove the water in the container so that the N-H-PDMS / PS film covers the metal sheet to obtain a metal sheet with a film; (4) After air-drying the metal sheet with a film, soak it in organic solvent B, and after the soaking is completed, wash it with water to obtain a PDMS porous membrane.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of the PDMS prepolymer to the PDMS crosslinker is 5:1 to 20:1, and the mass ratio of the PDMS prepolymer to the organic solvent A is 1:1 to 8:

1.

3. The preparation method according to claim 2, characterized in that, In step (1), the organic solvent A is an alkane with 5 to 10 carbon atoms.

4. The preparation method according to claim 3, characterized in that, In step (1), the organic solvent A is n-hexane.

5. The preparation method according to claim 4, wherein In step (1), the dosage of the PS microsphere powder is 3wt% to 25wt% of the mass of the PDMS prepolymer.

6. The preparation method according to claim 5, wherein, In step (1), the diameter of the PS microspheres is 5μm to 50μm.

7. The preparation method according to claim 6, characterized in that, In step (4), the organic solvent B is one of acetone, benzene, chloroform, and tetrahydrofuran, and the soaking time is 3 to 5 minutes.

8. A PDMS porous membrane prepared by the method according to claims 1 to 7.

9. An application of the PDMS porous membrane according to claim 8 in an organ chip.

10. An organ-on-a-chip, characterized in that, The organ chip contains a PDMS porous membrane.

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