A method for preparing a self-supporting ultrathin polymer film

Abstract

The application provides a preparation method of a self-supporting ultrathin polymer film, which comprises the following steps: S1, preparing a microfluidic chip with dendritic structure and an acute angle between two microchannel outlets; S2, continuously supplying a polymer solution into the microfluidic chip, so that a continuous laminar flow is generated after the polymer solution passes through the outlet of the microfluidic chip; and solidifying the formed continuous laminar flow in a coagulation bath to obtain an ultrathin polymer film. In conclusion, the application can realize the continuous laminar flow of the polymer film simply and conveniently, and a self-supporting polymer film can be prepared, the film has good uniformity, and the thickness can be several microns or even nanometers.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer film preparation, and in particular to a method for preparing a self-supporting ultra-thin polymer film. Background Art

[0002] High-performance polymer films hold broad application prospects as key components (e.g., sensors, separators, or solid-state electrolytes) in many emerging fields, particularly flexible electronic products such as wearable devices, electronic skin, and flexible batteries. The thickness of polymer films significantly influences the performance of devices in these emerging fields.

[0003] Traditional methods for preparing polymer films include spin coating, doctor blade coating, vacuum filtration, electrospinning, casting, etc. Although these traditional methods can prepare ultra-thin polymer films, these methods all prepare polymer films on solid substrates, resulting in the need to peel the obtained films off the substrate. These traditional methods generally have a technical defect, that is, the polymer film needs to be mechanically peeled off from the solid substrate to obtain an independent polymer film. In the preparation process of ultra-thin polymer films, this mechanical peeling is likely to cause irreversible damage to the film structure. In the prior art, using mercury as a polymer film-forming substrate is a mature technology that can obtain self-supporting polymer ultra-thin films. However, the disadvantages of this technology are also very obvious. The high toxicity and volatility of mercury make this method of preparing self-supporting ultra-thin polymer films extremely hazardous to health.

[0004] Microfluidics is a method of manipulating fluids in a microscale space and has been widely used in the fields of biological detection, cell culture, clinical diagnosis, organic synthesis, and thin film preparation. Generally, the preparation of polymer films using microfluidics involves curing polymer solutions into films through UV cross-linking. In general, most polymer films prepared using microfluidics are hydrogel films, and the film thickness is in the range of tens to hundreds of microns, or even reaches the centimeter scale. For example, the patent with publication number CN112679221B discloses a method for preparing hollow zirconium dioxide films using microfluidics. In this technology, microfluidics can be used to form a hollow membrane with evenly distributed small pores, which can be adapted to the field of filtration or purification.

[0005] The study found that self-supporting hydrogel polymer films can be prepared on a solution substrate by using ionic cross-linking to solidify the film in a salt solution, which makes it possible to prepare self-supporting ultra-thin polymer films using microfluidic technology. However, the microfluidic preparation technology of general polymer membranes involves three aspects: the size and structural design of the microfluidic chip, the formulation control of the polymer solution, and the film-forming mechanism of the polymer solution. In order to prepare a self-supporting ultra-thin polymer membrane using microfluidic technology, it is necessary to comprehensively consider these three factors, so as to promote the polymer solution to produce a laminar state through the outlet of the microfluidic chip channel, so as to produce a high-quality self-supporting ultra-thin polymer membrane with uniform thickness in the coagulation bath. However, at present, there is little research on the preparation of self-supporting ultra-thin polymer membranes using microfluidic technology. Summary of the Invention

[0006] In view of this, the present invention proposes a method for preparing a self-supporting ultra-thin polymer film, which can make the polymer solution form a continuous laminar state and then evenly enter the coagulation bath to prepare a self-supporting ultra-thin polymer film.

[0007] The technical solution of the present invention is achieved as follows:

[0008] The present invention provides a method for preparing a self-supporting ultrathin polymer film, comprising the following steps:

[0009] Preparation of S1 microfluidic chip

[0010] Using soft lithography and one-step replication technology, polydimethylsiloxane was solidified on the template to prepare the dendritic structure. The angle q between the two microchannel outlets (such as Figure 1 ) is a microfluidic chip with an acute angle, so that an irreversible bond is formed between the chip and the bonding substrate, thereby obtaining a leak-free microfluidic chip with specific size parameters; Preparation of S2 ultrathin polymer film

[0011] The polymer solution is continuously supplied to the microfluidic chip through an injection pump. After passing through the outlet of the microfluidic chip, the polymer solution generates a continuous laminar flow. The formed continuous laminar flow is solidified in a coagulation bath by a suitable film-forming method to obtain a self-supporting ultra-thin polymer film that does not need to be peeled off from the solid substrate.

[0012] The preparation of polymer films using microfluidic laminar flow is carried out by solidifying the laminar flow into a film in a coagulation bath. The obtained film is a self-supporting film in the coagulation bath. Compared with traditional methods, it does not require the peeling process from the substrate, which largely ensures the integrity and uniformity of the film. It also solves the application limitations of difficult peeling of ultra-thin polymer films from the substrate, high energy consumption, and great health hazards.

[0013] In addition, the existing technology for preparing polymer films cannot prepare polymer films continuously. Using microfluidic laminar flow technology to prepare films can simply achieve continuous preparation of polymer films.

[0014] The polydimethylsiloxane of the present invention can be purchased directly from the market as a finished product.

[0015] The template design process of the present invention is as follows: after designing a microchannel with a dendritic shape and an acute angle between two microchannel outlets using AutoCAD, a mask is formed by processing, a photoresist with a desired thickness is obtained by spin coating, and then a silicon wafer with the photoresist with the desired thickness is exposed under the mask to obtain a template with a pattern opposite to the desired microstructure.

[0016] The thickness of the ultra-thin polymer film prepared by the present invention is 0.08 μm-6 μm.

[0017] Since the microfluidic chip is arranged in a dendritic shape, a multi-level shunt structure is formed. Preferably, the shunt structure is arranged with 4 levels, such as Figure 1 , the part between a and b is the first stage, the part between b and c is the second stage, the part between c and d is the third stage, and the part between d and e is the fourth stage. A split flow pattern of 5 or more stages will cause the flow rate of the polymer solution to be too slow, affecting the membrane production efficiency.

[0018] On the basis of the above technical solution, preferably, the bonding substrate is a substrate with a smooth surface, and can be selected from one of a silicon wafer, a glass sheet, and an acrylic plate.

[0019] On the basis of the above technical solution, preferably, during the preparation of the microfluidic chip, the curing condition of PDMS is 60-90° C. for 30-120 min.

[0020] The dimensional parameters of the microfluidic chip are: the width of each microchannel is 300-1500 μm, the length of each microchannel is 3000-8500 μm, and the height of each microchannel is 25-100 μm (the height of the microchannel is the height of the microfluidic chip).

[0021] The height of the microfluidic chip is controlled during the chip fabrication process by adjusting the type of photoresist and the spin coating speed. Different photoresist types and spin coating speeds result in different chip microchannel heights.

[0022] On the basis of the above technical solution, preferably, the injection flow rate of the injection pump is in the range of 150-500 μL / min; and the mass concentration of the polymer solution is in the range of 0.1-25 wt %.

[0023] Further preferably, during the process of continuously supplying the polymer solution to the microfluidic chip, the syringe pump adopts an injection method of a single solution inlet; the continuous laminar flow of the polymer solution and the hydrogel solution can be controlled.

[0024] On the basis of the above technical solutions, preferably, the polymer solution is a polymer organic solution (using an organic solvent to dissolve the polymer) or a hydrogel prepolymer solution (using water to dissolve the polymer). The polymer in the polymer organic solution is one of aramid fiber (ANF), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer, polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) copolymer or polyimide (PI); the polymer in the hydrogel prepolymer solution is one of alginate, hyaluronate or polyethylene glycol dimethacrylate; the present invention includes but is not limited to the range of these polymer solutions. Therefore, the present invention utilizes microfluidic laminar flow to prepare thin films, which can prepare both self-supporting polymer films and self-supporting hydrogel films. The applicability of the preparation method is not limited by the type of film, has a wide range of applications, and has high technical value.

[0025] On the basis of the above technical solution, preferably, the coagulation bath is an organic coagulation bath or an inorganic coagulation bath:

[0026] The volume ratio of the organic coagulation bath is V 水 :V 有机溶剂 =100:0~10:90 mixed solution, used for solidification film formation of polymer organic solution, wherein the organic solvent is one of dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP) or dimethylacetamide (DMAc), but not limited to the above range;

[0027] The inorganic coagulation bath is one of a CaCl2 aqueous solution, a BaCl2 aqueous solution or water, but is not limited to the above range; the inorganic coagulation bath is used for solidification and film formation of the hydrogel prepolymer solution, wherein the concentration of the salt solution is 0.1-2 mol / L.

[0028] On the basis of the above technical solutions, preferably, the film-forming method of the polymer solution is one of non-solvent-induced phase inversion, ionic crosslinking or ultraviolet (UV) photopolymerization.

[0029] The basic principle of the polymer solution forming a laminar flow and then solidifying into a film in the present invention is: under the action of the syringe pump, the above polymer solution flows out from the outlet of the microfluidic chip. Since the angle between the two microchannel outlets is an acute angle, the polymer solution merges at the outlet to form a continuous laminar flow that flows forward uniformly. After the laminar flow contacts the coagulation bath, the polymer solution quickly undergoes phase inversion induced by non-solvent or ionic crosslinking (Ca 2+Or Ba 2+ or cured by UV cross-linking at the outlet of the microfluidic chip, and then contacted with a coagulation bath (water) to form a self-supporting hydrogel film.

[0030] The preparation method of the present invention has the following beneficial effects compared with the prior art:

[0031] (1) The present invention relates to a method for preparing a self-supporting ultrathin polymer film. The thickness of the film can be controlled by regulating the height of the microfluidic chip, the concentration of the polymer solution, the composition of the coagulation bath, and the injection speed of the solution. The thickness of the prepared polymer film can be several micrometers or even nanometers. In particular, in the preparation of nanometer-scale self-supporting polymer films, it has great advantages over the existing technology.

[0032] (2) The present invention adopts a single solution inlet injection method to supply solution into the chip, which can control the continuous laminar flow of polymer solution or hydrogel prepolymer solution, but the solution supply width limits the width of the membrane; in order to obtain a wider ultra-thin film, the present invention designs the microfluidic chip into a tree-like multi-level shunt structure to widen the width of the membrane, so that the width can reach 8 cm.

[0033] (3) Since a microfluidic chip is used to continuously supply polymer solution or hydrogel prepolymer solution to the coagulation bath, and the microfluidic chip is designed as a dendritic multi-stage shunt structure, according to the principle of Bernoulli's formula, the flow rate at the outlet of the microfluidic chip will be lost compared to the flow rate at the inlet; the longer the path through which the solution flows, the more inflection points there are, and the greater the hydraulic head loss; at low flow rates, the greater the difference in inlet and outlet flow rates caused by this hydraulic head loss, the more likely it is to cause changes in the flow rate at the outlets of each branch of the dendritic microfluidic chip, thereby leading to membrane uniformity problems; therefore, the present invention optimizes the dendritic structure and designs the angle between the two microchannel outlets to be an acute angle. Compared with the horizontal and vertical microchannel outlets, the acute-angle outlet can prompt the laminar flow to quickly merge into a uniform liquid flow after flowing out of the outlet and flow forward, thereby ensuring the uniformity of the film.

[0034] (4) In order to further improve the uniformity of the film, the present invention sets the dendritic multi-stage diversion structure into a 4-stage diversion mode. Within the above-mentioned technical limitations of the present invention, continuous laminar extrusion of the polymer solution or hydrogel prepolymer solution in the microfluidic chip is achieved, ensuring the high uniformity of the film. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 is a schematic diagram of the microstructure and microchannel designed by AutoCAD in the present invention;

[0037] Figure 2 This is a physical picture of the microfluidic chip of the present invention;

[0038] Figure 3 is a schematic diagram of the microfluidic laminar flow of the present invention;

[0039] Figure 4 is the height of the microchannel of the microfluidic chip of the present invention;

[0040] Figure 5 is a SEM image of the cross section of the membrane in Example 1 of the present invention;

[0041] Figure 6 is a SEM image of a cross section of the membrane in Example 2 of the present invention;

[0042] Figure 7 is a SEM image of a cross section of the membrane in Example 3 of the present invention;

[0043] Figure 8 is a schematic diagram of a thin film prepared in Example 4 of the present invention;

[0044] Figure 9 is a schematic diagram of a thin film prepared in Example 5 of the present invention;

[0045] Figure 10 is a schematic diagram of a thin film prepared in Example 6 of the present invention;

[0046] Figure 11 is a schematic diagram of a thin film prepared in Example 7 of the present invention;

[0047] Figure 12 is a schematic diagram of a thin film prepared in Example 8 of the present invention;

[0048] Figure 13 Schematic diagram of the film prepared in Example 9 of the present invention. DETAILED DESCRIPTION

[0049] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described 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 creative efforts are within the scope of protection of the present invention.

[0050] Example 1 Preparation of ultra-thin (polyvinylidene fluoride) PVDF membrane

[0051] (1) Using AutoCAD, a four-level dendritic microchannel with an acute angle between the two microchannel outlets is designed, as shown in Figure 1 As shown, it is processed into a mask, and a 100μm photoresist is obtained by spin coating. Then, the silicon wafer with the expected thickness of the photoresist is UV exposed under the mask to obtain a pattern with the opposite microstructure to the expected microstructure; finally, a PDMS chip with the expected microstructure is obtained by a single replication of the PDMS prepolymer, as shown in FIG. Figure 2 As shown, an irreversible bond is formed between the PDMS chip and the glass sheet to obtain a leak-free microfluidic chip.

[0052] (2) PVDF was dissolved in DMF to obtain a 25 wt% PVDF solution. At a flow rate of 500 μL / min, the 25 wt% PVDF solution was injected into the microchannel at the inlet of the microfluidic chip through a syringe pump, and the solution was merged at the acute triangle outlet of the microfluidic chip to form a continuous laminar flow, as shown in FIG. Figure 3 and Figure 4 The microfluidic laminar flow was solidified in a coagulation bath (coagulation bath was V 水 :V DMF = 10:90 mixed solution), a self-supporting PVDF film with a thickness of 80 nm and a width of 3.2 cm was obtained (such as Figure 5 ).

[0053] Example 2 Preparation of ultrathin aramid fiber (ANF) membrane

[0054] (1) Using AutoCAD, design a 4-level dendritic microchannel with an acute angle between the two microchannel outlets, such as Figure 1 As shown, it is processed into a mask, and a 25μm photoresist is obtained by simple spin coating. Then, the silicon wafer with the expected thickness of photoresist is UV exposed under the mask to obtain a pattern with the opposite microstructure to the expected microstructure; finally, a PDMS chip with the expected microstructure is obtained by a single replication of the PDMS prepolymer, as shown Figure 2 As shown, an irreversible bond is formed between the PDMS chip and the silicon wafer to obtain a leak-free microfluidic chip.

[0055] (2) ANF was dissolved in DMSO to obtain a 0.1 wt% ANF solution. At a flow rate of 150 μL / min, the 0.1 wt% ANF solution was injected into the microchannel at the inlet of the microfluidic chip through a syringe pump and merged at the acute triangle outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified in a coagulation bath (the coagulation bath was V 水 :V DMSO = 100:0 mixed solution), a self-supporting ANF film with a thickness of 445 nm and a width of 5.5 cm was obtained (such as Figure 6 ).

[0056] Example 3 Preparation of ultrathin calcium alginate hydrogel film

[0057] (1) Using AutoCAD, design a 4-level dendritic microchannel with an acute angle between the two microchannel outlets, such as Figure 1 As shown, it is processed into a mask, and a 50μm photoresist is obtained by simple spin coating. Then, the silicon wafer with the expected thickness of photoresist is UV exposed under the mask to obtain a pattern with the opposite microstructure to the expected microstructure; finally, a PDMS chip with the expected microstructure is obtained by a single replication of the PDMS prepolymer, as shown Figure 2 As shown, an irreversible bond is formed between the PDMS chip and the acrylic plate to obtain a leak-free microfluidic chip.

[0058] (2) At a flow rate of 300 μL / min, 1.2 wt% calcium alginate solution was injected into the microchannel at the inlet of the microfluidic chip through a syringe pump, and the solution was merged at the acute triangle outlet of the microfluidic chip to form a continuous laminar flow, as shown in FIG. Figure 3 and Figure 4 In a coagulation bath, the microfluidic laminar flow was solidified by calcium ion crosslinking (the coagulation bath was a 0.5 mol / L CaCl2 solution), and a self-supporting calcium alginate hydrogel film with a thickness of 300 nm and a width of 4.6 cm was obtained (as shown in FIG. Figure 7 ).

[0059] Example 4 Microchannel is a straight single channel

[0060] (1) A straight single-channel microchannel with an acute angle between its two microchannel outlets was designed using AutoCAD. A mask was then fabricated and a 100 μm photoresist was obtained by spin coating. A silicon wafer with the desired photoresist thickness was then UV-exposed under the mask to obtain a pattern with the opposite microstructure to the desired one. Finally, a PDMS chip with the desired microstructure was obtained by a single replication of PDMS prepolymer. The PDMS chip was then irreversibly bonded to a glass wafer to obtain a leak-free microfluidic chip.

[0061] (2) PVDF was dissolved in DMF to obtain a 25 wt% PVDF solution. At a flow rate of 500 μL / min, the 25 wt% PVDF solution was injected into the microchannel at the inlet of the microfluidic chip through a syringe pump and merged at the acute triangle outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified in a coagulation bath (the coagulation bath was V 水 :V DMF =10:90 mixed solution).

[0062] Since the fluid in the flat single channel of the chip cannot form an ideal laminar flow state, the flow at the outlet is discontinuous and pulsating, which makes the membrane obviously discontinuous in the length direction and the effective thickness cannot be measured. The width of the prepared membrane is obviously very small, about 5mm (such as Figure 8 ).

[0063] The outlet of the microchannel in Example 5 is a flat port

[0064] (1) A four-level dendritic microchannel with a flat outlet was designed using AutoCAD. A mask was then fabricated and a 100 μm photoresist was obtained by spin coating. A silicon wafer with the desired photoresist thickness was then UV-exposed under the mask to obtain a pattern with the opposite microstructure to the desired one. Finally, a PDMS chip with the desired microstructure was obtained by a single replication of the PDMS prepolymer. The PDMS chip was then irreversibly bonded to a glass wafer to obtain a leak-free microfluidic chip.

[0065] (2) PVDF was dissolved in DMF to obtain a 25 wt% PVDF solution. At a flow rate of 500 μL / min, the 25 wt% PVDF solution was injected into the microchannel at the inlet of the microfluidic chip through a syringe pump and merged at the acute triangle outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified in a coagulation bath (the coagulation bath was V 水 :V DMF =10:90 mixed solution).

[0066] When the solution flows out of the flat outlet, the two adjacent liquid flows collide with each other in the horizontal direction to form a turbulent flow state, which makes it impossible to form a continuous uniform structure. The surface is discontinuous on a macro scale and the effective thickness of the membrane cannot be measured (such as Figure 9 ).

[0067] Example 6 Microchannel is a 2-level dendritic

[0068] (1) A two-stage dendritic microchannel with an acute angle between the two microchannel outlets was designed using AutoCAD. A mask was then fabricated and a 100 μm photoresist was obtained by spin coating. A silicon wafer with the desired photoresist thickness was then UV-exposed under the mask to obtain a pattern with the opposite microstructure to the desired one. Finally, a PDMS chip with the desired microstructure was obtained by a single replication of the PDMS prepolymer. The PDMS chip was then irreversibly bonded to a glass wafer to obtain a leak-free microfluidic chip.

[0069] (2) PVDF was dissolved in DMF to obtain a 25 wt% PVDF solution. At a flow rate of 500 μL / min, the 25 wt% PVDF solution was injected into the microchannel at the inlet of the microfluidic chip through a syringe pump and merged at the acute triangle outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified in a coagulation bath (the coagulation bath was V 水 :V DMF =10:90 mixed solution).

[0070] When the flow rate is very fast, the fluid cannot flow forward smoothly, the film is obviously discontinuous, and the effective thickness cannot be measured. The width of the prepared film is obviously small, about 1.2 cm (e.g. Figure 10 ).

[0071] Example 7 Microchannel is a three-level dendritic

[0072] (1) A three-level dendritic microchannel with an acute angle between the two microchannel outlets was designed using AutoCAD. A mask was then fabricated and a 25 μm photoresist was obtained by simple spin coating. A silicon wafer with the desired photoresist thickness was then UV-exposed under the mask to obtain a pattern with the opposite microstructure to the desired one. Finally, a PDMS chip with the desired microstructure was obtained by a single replication of the PDMS prepolymer. The PDMS chip was then irreversibly bonded to the silicon wafer to obtain a leak-free microfluidic chip.

[0073] (2) ANF was dissolved in DMSO to obtain a 0.1 wt% ANF solution. At a flow rate of 150 μL / min, the 0.1 wt% ANF solution was injected into the microchannel at the inlet of the microfluidic chip through a syringe pump and merged at the acute triangle outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified in a coagulation bath (the coagulation bath was V 水 :V DMSO =100:0 mixed solution).

[0074] When the flow rate is very fast, the fluid cannot flow forward smoothly, the film is obviously discontinuous, and the effective thickness cannot be measured. The width of the prepared film is obviously small, about 1.8 cm (e.g. Figure 11 ).

[0075] Example 8 Microchannel is a straight single channel with a flat mouth

[0076] (1) A straight single-channel microchannel with a flat outlet for each microchannel was designed using AutoCAD. A mask was then fabricated and a 25 μm photoresist was obtained by simple spin coating. A silicon wafer with the desired photoresist thickness was then UV-exposed under the mask to obtain a pattern with the opposite microstructure to the desired one. Finally, a PDMS chip with the desired microstructure was obtained by a single replication of the PDMS prepolymer. The PDMS chip was then irreversibly bonded to the silicon wafer to obtain a leak-free microfluidic chip.

[0077] (2) ANF was dissolved in DMSO to obtain a 0.1 wt% ANF solution. At a flow rate of 150 μL / min, the 0.1 wt% ANF solution was injected into the microchannel at the inlet of the microfluidic chip through a syringe pump and merged at the acute triangle outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified in a coagulation bath (the coagulation bath was V 水 :V DMSO =100:0 mixed solution).

[0078] The film is obviously discontinuous and the effective thickness cannot be measured. The width of the prepared film is obviously small, about 3 mm (e.g. Figure 12 ).

[0079] Example 9 Microchannel is a three-level dendritic, flat-mouthed

[0080] (1) A three-level dendritic microchannel with a flat outlet was designed using AutoCAD. A mask was then fabricated and a 25 μm photoresist was obtained by simple spin coating. A silicon wafer with the desired photoresist thickness was then UV-exposed under the mask to obtain a pattern with the opposite microstructure to the desired one. Finally, a PDMS chip with the desired microstructure was obtained by a single replication of the PDMS prepolymer. The PDMS chip was then irreversibly bonded to the silicon wafer to obtain a leak-free microfluidic chip.

[0081] (2) ANF was dissolved in DMSO to obtain a 0.1 wt% ANF solution. At a flow rate of 150 μL / min, the 0.1 wt% ANF solution was injected into the microchannel at the inlet of the microfluidic chip through a syringe pump and merged at the acute triangle outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified in a coagulation bath (the coagulation bath was V水 :V DMSO =100:0 mixed solution)

[0082] The film is obviously discontinuous and the effective thickness cannot be measured. The width of the prepared film is obviously small, about 2 mm (e.g. Figure 13 ).

[0083] Example 10 The height of the microfluidic chip is less than 25 μm

[0084] (1) A four-level dendritic microchannel with an acute angle between the two microchannel outlets was designed using AutoCAD. A mask was then fabricated and a 15 μm photoresist was obtained by simple spin coating. A silicon wafer with the desired photoresist thickness was then UV-exposed under the mask to obtain a pattern with the opposite microstructure to the desired one. Finally, a PDMS chip with the desired microstructure was obtained by a single replication of the PDMS prepolymer. The PDMS chip was then irreversibly bonded to the silicon wafer to obtain a leak-free microfluidic chip.

[0085] (2) ANF was dissolved in DMSO to obtain a 0.1 wt% ANF solution. At a flow rate of 150 μL / min, the 0.1 wt% ANF solution was injected into the microchannel at the inlet of the microfluidic chip through a syringe pump and merged at the acute triangle outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified in a coagulation bath (the coagulation bath was V 水 :V DMSO =100:0 mixed solution).

[0086] The film is obviously discontinuous and the effective thickness cannot be measured.

[0087] Example 11 The concentration of the polymer solution is greater than 25 wt%

[0088] (1) A four-level dendritic microchannel with an acute angle between the two microchannel outlets was designed using AutoCAD. A mask was then processed and a 100 μm photoresist was obtained by spin coating. A silicon wafer with the desired photoresist thickness was then UV-exposed under the mask to obtain a pattern with the opposite microstructure to the desired one. Finally, a PDMS chip with the desired microstructure was obtained by a single replication of PDMS prepolymer. The PDMS chip was irreversibly bonded to a glass wafer to obtain a leak-free microfluidic chip.

[0089] (2) PVDF was dissolved in DMF to obtain a 36 wt% PVDF solution. At a flow rate of 500 μL / min, the 36 wt% PVDF solution was injected into the microchannel at the inlet of the microfluidic chip through a syringe pump and merged at the acute triangle outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified in a coagulation bath (the coagulation bath was V 水 :V DMF =10:90 mixed solution).

[0090] The flow rate of the polymer solution was too slow, the membrane preparation time was 1.5 times that of the preparation method of the present invention, and the membrane was obviously discontinuous.

[0091] Example 12 Coagulation bath is aluminum chloride solution

[0092] (1) A four-level dendritic microchannel with an acute angle between the two microchannel outlets was designed using AutoCAD. A mask was then fabricated and a 50 μm photoresist was obtained by simple spin coating. A silicon wafer with the desired photoresist thickness was then UV-exposed under the mask to obtain a pattern with the opposite microstructure to the desired one. Finally, a PDMS chip with the desired microstructure was obtained by a single replication of the PDMS prepolymer. The PDMS chip was then irreversibly bonded to an acrylic plate to obtain a leak-free microfluidic chip.

[0093] (2) At a flow rate of 300 μL / min, a 1.2 wt% calcium alginate solution was injected into the microchannel at the inlet of the microfluidic chip via a syringe pump. The solution converged at the acute-angled triangular outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified by ionic crosslinking in a coagulation bath (the coagulation bath was a 0.5 mol / L aluminum chloride solution). A membrane could not be produced in this example.

[0094] Example 13 The injection speed of the polymer solution is less than 150 μL / min

[0095] (1) A four-level dendritic microchannel with an acute angle between the two microchannel outlets was designed using AutoCAD. A mask was then fabricated and a 25 μm photoresist was obtained by simple spin coating. A silicon wafer with the desired photoresist thickness was then UV-exposed under the mask to obtain a pattern with the opposite microstructure to the desired one. Finally, a PDMS chip with the desired microstructure was obtained by a single replication of the PDMS prepolymer. The PDMS chip was then irreversibly bonded to the silicon wafer to obtain a leak-free microfluidic chip.

[0096] (2) ANF was dissolved in DMSO to obtain a 0.1 wt% ANF solution. At a flow rate of 150 μL / min, the 0.1 wt% ANF solution was injected into the microchannel at the inlet of the microfluidic chip through a syringe pump and merged at the acute triangle outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified in a coagulation bath (the coagulation bath was V 水 :V DMSO =100:0 mixed solution).

[0097] The flow rate of the polymer solution was too slow, the membrane preparation time was twice that of the preparation method of the present invention, and the membrane was obviously discontinuous.

[0098] Example 14 The height of the microfluidic chip is greater than 100 μm, and the concentration of the polymer solution is greater than 25 wt%

[0099] (1) A four-level dendritic microchannel with an acute angle between the two microchannel outlets was designed using AutoCAD. A mask was then fabricated and a 150 μm photoresist was obtained by spin coating. A silicon wafer with the desired photoresist thickness was then UV-exposed under the mask to obtain a pattern with the opposite microstructure to the desired one. Finally, a PDMS chip with the desired microstructure was obtained by a single replication of the PDMS prepolymer. The PDMS chip was then irreversibly bonded to a glass wafer to obtain a leak-free microfluidic chip.

[0100] (2) PVDF was dissolved in DMF to obtain a 35 wt% PVDF solution. At a flow rate of 500 μL / min, the 35 wt% PVDF solution was injected into the microchannel at the inlet of the microfluidic chip through a syringe pump and merged at the acute triangle outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified in a coagulation bath (the coagulation bath was V 水 :V DMF =10:90 mixed solution).

[0101] The film preparation time is 2.3 times that of the preparation method of the present invention, and the film is obviously discontinuous.

[0102] Example 15 The height of the microfluidic chip is greater than 100 μm, and the coagulation bath is aluminum chloride solution

[0103] (1) A four-level dendritic microchannel with an acute angle between the two microchannel outlets was designed using AutoCAD. A mask was then fabricated and a 150 μm photoresist was obtained by simple spin coating. A silicon wafer with the desired photoresist thickness was then UV-exposed under the mask to obtain a pattern with the opposite microstructure to the desired one. Finally, a PDMS chip with the desired microstructure was obtained by a single replication of the PDMS prepolymer. The PDMS chip was then irreversibly bonded to an acrylic plate to obtain a leak-free microfluidic chip.

[0104] (2) At a flow rate of 300 μL / min, a 1.2 wt% calcium alginate solution was injected into the microchannel at the inlet of the microfluidic chip via a syringe pump. The solution converged at the acute-angled triangular outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified by ionic crosslinking in a coagulation bath (the coagulation bath was a 0.5 mol / L aluminum chloride solution). A membrane could not be produced in this example.

[0105] Example 16 The height of the microfluidic chip is greater than 100 μm, and the injection speed of the polymer solution is greater than 500 μL / min

[0106] (1) A four-level dendritic microchannel with an acute angle between the two microchannel outlets was designed using AutoCAD. A mask was then fabricated and a 150 μm photoresist was obtained by simple spin coating. A silicon wafer with the desired photoresist thickness was then UV-exposed under the mask to obtain a pattern with the opposite microstructure to the desired one. Finally, a PDMS chip with the desired microstructure was obtained by a single replication of the PDMS prepolymer. The PDMS chip was then irreversibly bonded to an acrylic plate to obtain a leak-free microfluidic chip.

[0107] (2) At a flow rate of 610 μL / min, a 1.2 wt% calcium alginate solution was injected into the microchannel at the inlet of the microfluidic chip via a syringe pump. The solution converged at the acute-angled triangle outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified by calcium ion crosslinking in a coagulation bath (the coagulation bath was a 0.5 mol / L CaCl2 solution).

[0108] A continuous and uniform structure cannot be formed and the effective thickness of the film cannot be measured.

[0109] Example 17 The concentration of the polymer solution is greater than 25 wt%, and the coagulation bath is aluminum chloride solution

[0110] (1) A four-level dendritic microchannel with an acute angle between the two microchannel outlets was designed using AutoCAD. A mask was then processed and a 100 μm photoresist was obtained by spin coating. A silicon wafer with the desired photoresist thickness was then UV-exposed under the mask to obtain a pattern with the opposite microstructure to the desired one. Finally, a PDMS chip with the desired microstructure was obtained by a single replication of PDMS prepolymer. The PDMS chip was irreversibly bonded to a glass wafer to obtain a leak-free microfluidic chip.

[0111] (2) PVDF was dissolved in DMF to obtain a 40 wt% PVDF solution. At a flow rate of 500 μL / min, the 40 wt% PVDF solution was injected into the microchannel at the inlet of the microfluidic chip via a syringe pump and converged at the acute triangle outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified by ionic crosslinking in a coagulation bath (the coagulation bath was a 0.5 mol / L aluminum chloride solution). A membrane could not be produced in this embodiment.

[0112] Example 18 The concentration of the polymer solution is greater than 25 wt %, and the injection speed of the polymer solution is greater than 500 μL / min

[0113] (1) A four-level dendritic microchannel with an acute angle between the two microchannel outlets was designed using AutoCAD. A mask was then fabricated and a 150 μm photoresist was obtained by spin coating. A silicon wafer with the desired photoresist thickness was then UV-exposed under the mask to obtain a pattern with the opposite microstructure to the desired one. Finally, a PDMS chip with the desired microstructure was obtained by a single replication of the PDMS prepolymer. The PDMS chip was then irreversibly bonded to a glass wafer to obtain a leak-free microfluidic chip.

[0114] (2) PVDF was dissolved in DMF to obtain a 42 wt% PVDF solution. At a flow rate of 610 μL / min, the 42 wt% PVDF solution was injected into the microchannel at the inlet of the microfluidic chip through a syringe pump and merged at the acute triangle outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified in a coagulation bath (the coagulation bath was V 水 :V DMF =10:90 mixed solution).

[0115] The film preparation time is 2.4 times that of the preparation method of the present invention, and the film is obviously discontinuous.

[0116] Example 19 The injection speed of the polymer solution is greater than 500 μL / min, and the coagulation bath is aluminum chloride solution

[0117] (1) A four-level dendritic microchannel with an acute angle between the two microchannel outlets was designed using AutoCAD. A mask was then fabricated and a 50 μm photoresist was obtained by simple spin coating. A silicon wafer with the desired photoresist thickness was then UV-exposed under the mask to obtain a pattern with the opposite microstructure to the desired one. Finally, a PDMS chip with the desired microstructure was obtained by a single replication of the PDMS prepolymer. The PDMS chip was then irreversibly bonded to an acrylic plate to obtain a leak-free microfluidic chip.

[0118] (2) At a flow rate of 605 μL / min, a 1.2 wt% calcium alginate solution was injected into the microchannel at the inlet of the microfluidic chip via a syringe pump. The solution converged at the acute-angled triangular outlet of the microfluidic chip to form a continuous laminar flow. The microfluidic laminar flow was solidified by ionic crosslinking in a coagulation bath (the coagulation bath was a 0.5 mol / L aluminum chloride solution). A membrane could not be produced in this example.

[0119] It can be seen from the above embodiments that the method for preparing a self-supporting ultra-thin polymer film of the present invention adopts a microchannel with a four-level dendritic shape and an acute angle between the two microchannel outlets. At the same time, by regulating the height of the microfluidic chip, the concentration of the polymer solution, the composition of the coagulation bath and the injection speed of the solution, the continuous laminar flow of the polymer film can be simply achieved, and the film has good uniformity, so that the thickness of the polymer film prepared by the present invention can be several microns or even nanometers, and the width can reach 8 cm.

[0120] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a self-supporting ultrathin polymer film, characterized in that: The steps include: S1, preparing a microfluidic chip with a dendritic shape and an acute angle between two microchannel outlets; S2, continuously supplying a polymer solution to the microfluidic chip, wherein the polymer solution generates a continuous laminar flow after passing through an outlet of the microfluidic chip; the continuous laminar flow is solidified in a coagulation bath, and an ultrathin polymer film is obtained after solidification; In the dendritic microfluidic chip, a multi-stage shunt structure is formed, and the shunt structure is set at 4 levels; The height of each microchannel of the microfluidic chip is 25-100 μm; The supply flow rate of the polymer solution is 150-500 μL / min; The mass concentration of the polymer solution is in the range of 0.1-25 wt %.

2. The method for preparing a self-supporting ultrathin polymer film according to claim 1, wherein: The polymer solution is a polymer organic solution or a hydrogel prepolymer solution.

3. The method for preparing a self-supporting ultrathin polymer film according to claim 2, wherein: The polymer in the polymer organic solution is one of aramid fiber, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-trifluoroethylene copolymer or polyimide.

4. The method for preparing a self-supporting ultrathin polymer film according to claim 2, wherein: The polymer in the hydrogel prepolymerization solution is one of alginate, hyaluronate or polyethylene glycol dimethacrylate.

5. The method for preparing a self-supporting ultrathin polymer film according to claim 1, wherein: The coagulation bath is an organic coagulation bath or an inorganic coagulation bath, wherein: The organic solvent in the organic coagulation bath is one of dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone or dimethylacetamide; The inorganic coagulation bath is one of a CaCl2 aqueous solution, a BaCl2 aqueous solution, and water.

6. The method for preparing a self-supporting ultrathin polymer film according to claim 5, wherein: In the organic coagulation bath, the volume ratio of water to organic solvent is V 水 :V 有机溶剂 =100:0~10:90; The concentration of the salt solution in the inorganic coagulation bath is 0.1-2 mol / L.

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