A method for preparing a tension-induced nanofilm and the film

Abstract

The application discloses a preparation method of a tension-induced nanometer film, which comprises the following steps: immersing a polymer solution into a mold surface, forming a continuous liquid film in the mold by using the surface tension and directional collapse of the solution, rapidly solidifying the liquid film in a low-temperature environment with a temperature less than the freezing point of the polymer solution, and completing preliminary shaping; then, under solidification conditions, the preliminarily shaped film is solidified; and finally, the tension-induced nanometer film is obtained by drying. The preparation method does not need a vacuum environment, high-temperature treatment or high-energy field assistance, and has the advantages of simple equipment, simple operation, low energy consumption, easy repetition and suitability for batch preparation. The nanometer film prepared by the method has good continuity and thickness uniformity in structure, the film thickness can be about 15 nm, and the overall structure is stable. The nanometer film can be applied to the fields of functional coating, interface regulation, flexible electronics and biological medical surface modification.

Description

Technical Field

[0001] The invention belongs to the field of tissue engineering and biomaterial manufacturing technology under biomedical engineering, and specifically relates to a method for preparing a surface tension driven nanofilm and the film itself. Background Technology

[0002] Nanofilms are a class of functional thin film materials with thicknesses in the nanoscale range. Due to their high specific surface area, tunable mechanical properties, and excellent interfacial characteristics, they have broad application prospects in flexible electronics, biomedicine, separation membranes, sensors, and surface engineering. By processing polymer solutions, continuous and uniform thin film structures can be prepared using solution-based film formation, thereby achieving precise control over the thickness, composition, and properties of the films.

[0003] Currently, the main methods for preparing nanofilms include spin coating, blade coating, spray coating, layer-by-layer self-assembly, and solvent evaporation film formation. These methods typically rely on high-speed rotation, applied shear force, or a long solvent evaporation process to achieve film formation. Although relatively uniform films can be obtained on a laboratory scale, they still have many shortcomings in practical applications. For example, spin coating is highly dependent on equipment, has low material utilization, and is difficult to achieve large-area or batch preparation; layer-by-layer self-assembly is cumbersome and has a long preparation cycle, which is not conducive to large-scale production; while traditional solvent evaporation film formation is easily affected by ambient temperature and humidity, resulting in poor film stability and repeatability.

[0004] Furthermore, as film thickness decreases further towards the nanoscale, interfacial stability issues during film formation become increasingly prominent. During film formation, liquid films are prone to rupture, shrinkage, or uneven thickness, especially in the absence of effective shaping methods. Ultrathin liquid films are highly susceptible to instability during drying or solvent evaporation, thus limiting the controllable fabrication of nanoscale ultrathin films. Existing methods for achieving films with thicknesses below 100 nanometers often require strict process windows or complex auxiliary conditions, making fabrication quite challenging.

[0005] Therefore, there is an urgent need for a preparation method that is simple, reproducible, batch-operable, and capable of rapid prototyping and stable shaping of ultrathin films under mild conditions, in order to meet the requirements of nanofilms for thickness controllability, structural integrity, and large-scale preparation capability in multiple applications. Summary of the Invention

[0006] To address the problems of complex processes, poor film stability, difficulty in achieving controllable ultrathin thickness, and limitations on mass production in existing nanofilm preparation technologies, this invention provides a surface tension-induced condensation film formation method for preparing nanofilms. This method offers advantages such as low equipment requirements, simple operation, stable film formation process, rapid and mass production capability, and low cost. It can prepare nanofilms with thicknesses in the nanoscale range and continuous and uniform structures, with a minimum film thickness as low as 15 nm.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing tension-induced nanofilms, comprising: wetting and attaching a polymer solution to the surface of a mold, utilizing the surface tension and directional collapse of the solution itself to form a continuous liquid film within the mold, rapidly solidifying the liquid film in a low-temperature environment below the freezing point of the polymer solution to complete preliminary shaping; then, under curing conditions, the preliminarily shaped film is cured; and finally, the tension-induced nanofilm is obtained by drying.

[0008] A method for preparing tension-induced nanofilms includes: successfully achieving stable batch production of nanofilms with a thickness of 15 nm by utilizing the surface tension and directional collapse of the solution itself.

[0009] A method for preparing nanofilms involves immersing a polymer solution on the surface of a mold to form a continuous liquid film under surface tension. The liquid film is then rapidly condensed using liquid nitrogen vapor and continuously solidified at low temperatures. Finally, it is allowed to dry under natural conditions to obtain a nanofilm with a stable structure and controllable thickness. This method fully utilizes the combination of surface tension-driven film formation and low-temperature condensation to achieve controllable molding and large-scale preparation of ultrathin nanofilms.

[0010] Specifically, a method for preparing a surface tension-driven nanofilm includes the following steps:

[0011] (1) Prepare a polymer solution of a predetermined concentration;

[0012] (2) After immersing the mold in the polymer solution, remove it so that the polymer solution adheres to the mold under the action of surface tension and forms a liquid film;

[0013] (3) Place the mold carrying the liquid film in a liquid nitrogen vapor environment for rapid condensation;

[0014] (4) The film condensed by liquid nitrogen vapor is transferred to a low-temperature environment for continuous condensation, solidification and shaping;

[0015] (5) After the film is completely cooled and solidified, it is placed under natural environmental conditions to dry, and the tension-induced nanofilm is obtained.

[0016] In step (1) above:

[0017] Preferably, the polymer solution is obtained by the following method:

[0018] The water-soluble polymer was dissolved in deionized water by magnetic stirring and heating, and then filtered and centrifuged to remove bubbles to obtain a polymer solution.

[0019] As an alternative implementation method, centrifugation is performed at a speed of 2000 r / min for 5 min. The purpose of centrifugation is to prevent air bubbles from affecting the continuity and stability of subsequent film formation.

[0020] The viscosity of the polymer solution at room temperature (25°C) should be greater than or equal to 10 mPa·s; further, the viscosity of the polymer solution at room temperature (25°C) should be greater than or equal to 100 mPa·s; even further, the viscosity of the polymer solution at room temperature (25°C) should be greater than or equal to 500 mPa·s; as a specific option, the viscosity of the polymer solution at room temperature (25°C) is 800 mPa·s to 20000 mPa·s; even further, the viscosity of the polymer solution at room temperature (25°C) is 1000 mPa·s to 15000 mPa·s.

[0021] In the actual preparation process, by adjusting the type and concentration of the polymer, the viscosity and surface tension of the resulting polymer solution can be adjusted, thereby enabling the adjustment and control of the film thickness.

[0022] The polymer is one or more of a soluble polymeric material. Further sources of the water-soluble polymer include, but are not limited to, gelatin-based polymers and water-soluble polymers similar to gelatin in terms of water solubility, molecular chain flexibility, and interfacial film-forming behavior, including gelatin, collagen, chitosan, alginate, hyaluronic acid, poly(3,4-ethylenedioxythiophene), polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, and their derivatives. Gelatin is preferred as the water-soluble polymer.

[0023] Preferably, the polymer is an aqueous gelatin solution; the concentration of the aqueous gelatin solution is 1-20 wt%. More preferably, it is 4-10 wt%. Even more preferably, it is 5 wt%.

[0024] Preferably, the specific process for preparing a polymer solution of a predetermined concentration is as follows:

[0025] Melt the prepared 5% gelatin aqueous solution at 50℃ to facilitate subsequent operations.

[0026] In step (2) above:

[0027] Preferably, the mold is made of a hydrophilic material or has a surface modified for hydrophilicity. Furthermore, the mold is made of a hydrophilic polymer material, such as polylactic acid (PLA), hydrophilic polyurethane (PU), or polyvinylpyrrolidone (PVP).

[0028] Preferably, the mold is a frame mold with an open structure, and the polymer solution spontaneously spreads under the action of surface tension of the mold to form a continuous liquid film; more specifically, during preparation, the polymer solution is made to spontaneously spread at the boundary of the mold under the action of surface tension to form a continuous and stable liquid film.

[0029] Furthermore, the mold is a closed ring-shaped frame mold structure. After the mold comes into full contact with the polymer solution, it slowly detaches from the surface of the polymer solution under the action of external force. At the same time, the polymer solution attached to it spreads synchronously into the ring under the action of surface force until the mold is completely detached, forming a complete and continuous liquid film.

[0030] The geometry of the mold is not limited, and it can be a circular / elliptical frame structure, a polygonal (triangle, rectangle, pentagon, hexagon, etc.) frame structure, or other closed-loop frame structure that can support the formation of liquid films.

[0031] Furthermore, the cross-sectional diameter of the mold is generally between 0.5 mm and 5 mm. The size of the annular space enclosed by the mold can be selected according to actual needs, while also taking into account the requirements for continuous film formation.

[0032] In step (2), the lifting speed needs to ensure that the polymer solution adhering to the mold can continuously form a film during and after the mold is removed from the polymer solution.

[0033] Step (2) The operating temperature is generally the temperature at which the polymer solution is in a liquid state, and at which the solution viscosity or surface tension meets the film formation requirements. Generally, 20~40℃ is used. Alternatively, it can be carried out directly at room temperature.

[0034] In step (3) above:

[0035] Preferably, the mold carrying the liquid film is placed in a liquid nitrogen vapor environment for condensation, wherein the liquid film does not come into direct contact with the liquid nitrogen.

[0036] In step (3), the liquid nitrogen vapor is generated through natural or controlled evaporation of liquid nitrogen. In practical use, liquid nitrogen can be added to a container to generate low-temperature cold vapor, and then the liquid film can be placed in the cold vapor.

[0037] The purpose of liquid nitrogen vapor condensation is to achieve rapid condensation and solidification of the liquid film without damaging its integrity, thereby suppressing unstable behaviors such as film retraction and rupture, and completing the initial shaping.

[0038] Step (3) Condensation time is generally determined based on the solidification of the polymer material, ensuring complete solidification (or freezing).

[0039] In step (4) above:

[0040] Preferably, the film condensed by liquid nitrogen vapor is transferred to a low-temperature environment for continuous condensation and shaping.

[0041] This step primarily involves curing and shaping the pre-formed film, requiring the selection of curing conditions corresponding to the polymer solution. For example, the curing conditions can be one or a combination of temperature-induced curing, ionic crosslinking curing, and photocuring. It can be either chemical crosslinking curing (irreversible) or purely physical crosslinking curing (reversible), depending on the specific polymer material.

[0042] For example, gelatin and agar can undergo physical cross-linking and curing at low temperatures.

[0043] The temperature of the low-temperature environment is 0~8 ℃. More preferably, it is 2~6 ℃.

[0044] Preferably, the continuous condensation and setting time is 10-60 min. More preferably, it is 20-40 min. Even more preferably, it is 30 min.

[0045] For other polymers, their corresponding curing conditions can be selected. For example, sodium alginate can be cured by ionic crosslinking, and rapid curing can be achieved by adding cations. For PVA hydrogels, curing can be achieved by freeze-thaw cycles (low-temperature freezing - room-temperature thawing).

[0046] In step (5) above:

[0047] Preferably, the natural environmental conditions are normal temperature and pressure.

[0048] By allowing the film to dry naturally, the moisture in the film is gradually removed, resulting in a structurally stable tension-induced nanofilm.

[0049] In this invention, by adjusting the polymer solution concentration, mold structure, and condensation conditions, the thickness of the obtained tension-induced nanofilm can be as low as 10 nm to 200 μm. In practical applications, the film thickness is mainly adjusted and controlled by selecting the type of polymer and the concentration of the polymer solution.

[0050] The preparation method described herein is suitable for the batch preparation of nanofilms.

[0051] The present invention discloses a method for preparing tension-induced nanofilms. This method involves forming a liquid film on a mold through a spontaneous film-forming process driven by surface tension, combined with rapid condensation induced by liquid nitrogen vapor and continuous condensation and shaping under low-temperature conditions. This process transforms the liquid film into a stable nanofilm structure, resulting in a tension-induced nanofilm with a thickness in the nanoscale range and a continuous and uniform structure. This preparation method offers advantages such as simple equipment, easy operation, rapid and mass production capability, and low cost. The tension-induced nanofilms prepared by this method can be widely applied in fields such as biomedicine, functional interface regulation, separation membranes, and flexible functional materials.

[0052] The present invention also provides a nanofilm prepared by any of the above-described methods for preparing tension-induced nanofilms.

[0053] The nanofilms prepared by this method exhibit good structural continuity and thickness uniformity, with a thickness ranging from approximately 10 to 100 nm (e.g., 15 nm), and demonstrate overall structural stability. These nanofilms can be applied in fields such as functional coatings, interface modulation, flexible electronics, and biomedical surface modification.

[0054] It is worth noting that, unless otherwise specified, all materials involved in this invention can be obtained from commercial channels.

[0055] Compared with the prior art, the present invention has the following significant advantages:

[0056] This invention achieves the gentle preparation of continuous nanofilms by dipping a polymer solution into the solution and utilizing surface tension for spontaneous film formation. This is combined with rapid condensation of liquid nitrogen vapor, low-temperature stabilization (solidification) condensation, and natural drying at room temperature. The entire process requires no vacuum, high-temperature treatment, or high-energy field assistance and can be completed under ambient pressure and low temperature conditions, significantly reducing energy consumption and process complexity. This method relies on a surface tension-driven liquid film self-assembly and condensation control mechanism, enabling the preparation of dense, continuous films with thicknesses of approximately 15 nm to 200 μm without spin coating, template etching, or film transfer, effectively avoiding the film inhomogeneity and structural damage problems common in traditional methods. Since the film formation process does not involve high-temperature or high-energy treatment, the integrity of the polymer molecular structure and function is well maintained, improving the stability and reliability of the film. The method described in this invention has the advantages of simple equipment requirements, easy operation, low energy consumption, easy reproducibility, and suitability for batch preparation. It possesses good repeatability and scalability, making it suitable for applications requiring ultrathin, continuous, and low-damage nanofilm molds, such as flexible electronics, sensor interfaces, biomedical coatings, and functional protective layers. Attached Figure Description

[0057] Figure 1The diagram shows the preparation principle of tension-induced nanofilms; a is a photograph of the film being lifted using a mold; b is a schematic diagram of the tension-induced nanofilm formation process during the mold lifting process; c is the film structure after rapid condensation by liquid nitrogen vapor following film formation using a square mold in Example 1; d is the film structure obtained after step S4 in Example 1; e and f are schematic diagrams of cross-sections corresponding to c and d, respectively.

[0058] Figure 2 High-resolution transmission electron microscopy (TEM) images of tension-induced nanofilms (scale bars are all 50 nm).

[0059] Figure 3 This is an atomic force microscope image of a tension-induced nanofilm (the area between the two vertical dashed lines corresponds to the film formation region). Detailed Implementation

[0060] The present invention will be fully described below with reference to embodiments, which will provide a thorough understanding of the purpose, features, and effects of the invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0061] Example 1:

[0062] A method for preparing tension-induced nanofilms, such as Figure 1 As shown, it includes the following steps:

[0063] This embodiment provides a method for preparing nanofilms based on surface tension-induced film formation and low-temperature hierarchical condensation. The method utilizes the surface tension of a polymer solution to spontaneously spread and form a continuous liquid film at an open mold. The liquid film is rapidly shaped and structurally stabilized by a combination of rapid condensation with liquid nitrogen vapor and low-temperature stable condensation. A continuous and dense nanofilm with a thickness of approximately 15 nm is prepared without the need for vacuum, high temperature, or high energy field assistance.

[0064] Step S1: Prepare polymer solution

[0065] 1 g of water-soluble polymer (pigskin gelatin) was dissolved in 20 mL of deionized water, heated to 50 °C and stirred evenly with a magnetic stir bar, and then centrifuged to remove bubbles, to obtain a polymer solution with a concentration of 5 wt% (denoted as C) (the solution viscosity η at 25 °C is approximately 10000 mPa·s); wherein the centrifugation speed was 2000 r / min and the centrifugation time was 5 min.

[0066] Step S2: Tension-induced nanofilm formation process

[0067] The polymer solution is placed in a container, and the open mold (in this embodiment, a square ring-shaped mold is used, where R is the side length of the square) is immersed in the polymer solution. After the solution temperature stabilizes at approximately 25°C, the mold is slowly lifted (the lifting speed is denoted as U), ensuring that the film remains continuous. The film slowly detaches from the surface of the polymer solution, and under the action of the solution surface tension (denoted as γ), a uniform and continuous thin film liquid surface spontaneously forms at the opening of the mold (i.e., from the ring-shaped structure of the mold towards the center) (see...). Figure 1 (As shown in a and b).

[0068] Step S3: Liquid nitrogen vapor rapidly condenses

[0069] Liquid nitrogen is added to the container to generate cryogenic cold vapor. The continuous thin film surface obtained in step S2 is exposed to the liquid nitrogen vapor environment, achieving rapid condensation and shaping of the film under cryogenic conditions (the thickness at this point is denoted as r, see [reference]). Figure 1 (e).

[0070] Step S4: Further condensation to stabilize the thin film structure

[0071] The pre-shaped film obtained in step S3 is placed in a low-temperature environment of about 4 °C and kept for a predetermined time to achieve further condensation and stabilization of the film structure.

[0072] Step S5: Drying at room temperature and property formation

[0073] The thin film structure obtained in step S4 is placed in an environment of normal temperature and pressure for natural drying to further solidify it, ultimately yielding a thickness (denoted as r', see [reference]). Figure 1 f) A thin film at the nanoscale, wherein the thickness of the thin film may be approximately 15 nm.

[0074] Structural and performance characterization description:

[0075] like Figure 1 As shown ( Figure 1In this diagram, N represents the liquid volume / solid volume ratio, where the liquid is the polymer solution and the solid is the dried film (typically 1000 times). During the process of immersing the open mold in the polymer solution and slowly lifting it, the solution spontaneously spreads towards the center of the mold due to surface tension at the mold boundary, forming a stable and continuous liquid film structure, providing the initial morphological basis for subsequent film forming. The liquid film is then rapidly condensed in liquid nitrogen vapor, quickly transforming from a liquid to a solid state, forming an "ice" film, achieving initial shaping. During further condensation, water molecules gradually escape, and polymer chains rearrange under spatial constraints, causing the solution to collapse from a three-dimensional network structure to a two-dimensional planar structure, significantly reducing the film thickness and stabilizing. As the condensation and drying process continues, hydrophilic and hydrophobic groups in the polymer molecules are oriented at the interface, forming a continuous two-dimensional film structure supported by a hydrophobic interface and dominated by a hydrophilic network, thus achieving the formation of ultrathin, dense, and structurally stable nanofilms.

[0076] like Figure 2 As shown, the tension-induced nanofilm prepared by the method of this invention was characterized by high-resolution transmission electron microscopy. A continuous film structure was clearly observed, exhibiting a uniform and dense two-dimensional layered morphology. The film thickness was approximately 15 nm, and the thickness distribution was uniform within the observation area, without obvious breakage or delamination. This indicates that the surface tension-induced film formation and low-temperature condensation process can stably obtain an ultrathin, continuous nanofilm structure.

[0077] like Figure 3 As shown, the surface morphology and height distribution of the tension-induced nanofilm prepared by the method of this invention were further characterized using atomic force microscopy. The results show that the film continuously covers a large area, with a relatively smooth overall surface and no obvious pores or penetrating defects observed; local areas exhibit only uniformly distributed microscopic undulations, with smooth transitions between regions. The corresponding height distribution and profile curves indicate that the film thickness is stable at the nanoscale, with an overall height difference (i.e., thickness) of approximately 15 nm and a small variation range (the area between the two vertical dashed lines represents the film formation region), further demonstrating that the method can prepare continuous gelatin-based tension-induced nanofilms with uniform thickness and stable structure.

[0078] Application Examples:

[0079] The tension-induced nanofilms prepared by this invention can be applied to the following scenarios:

[0080] Gelatin-based tension-induced nanofilms: These films exhibit good biocompatibility and flexibility, and can be used in biomedical dressings and wound coverings. The tensile strength of the films is 10-150 MPa, and the Young's modulus is 100-2000 MPa.

[0081] Collagen nanofilms: These films can mimic the composition and structural characteristics of the extracellular matrix (ECM) and can be used as ECM-like ultrathin interface membranes in tissue engineering. The films are prepared using the same method described above, except that "collagen" replaces "gelatin," and the preferred thickness is 100–500 nm. Their surface roughness (Ra) is 5–100 nm to provide an ECM-like nanoscale topology. The collagen concentration in the films is 0.1–10 wt%.

[0082] Chitosan nanofilms: possessing natural antibacterial activity, they can be used in food packaging and biomedical antibacterial packaging films. These films are prepared using the same method described above, except that chitosan is used instead of gelatin. They exhibit a tensile strength of 10–100 MPa and an elongation at break of 5–50%, meeting the mechanical requirements of packaging materials.

[0083] Alginate nanofilms and polyvinylpyrrolidone nanofilms: possessing good hydrophilicity and film-forming stability, they can be used in controlled-release systems for drugs and biological agents. These films are prepared using the same method described above, except that "alginate or polyvinylpyrrolidone" replaces "gelatin." The drug loading of the system is 1–30 wt%, the encapsulation efficiency is 50–95%, and it can achieve sustained release behavior with a release cycle of 6 h–14 d.

[0084] Hyaluronic acid nanofilms: These films possess excellent lubrication and moisturizing properties, making them suitable for ophthalmic and dermatological lubrication and moisturizing applications. The films are prepared using the same method described above, except that "hyaluronic acid" replaces "gelatin." The molecular weight of the hyaluronic acid is 10–3000 kDa, and the solution concentration is 0.1–5 wt%. The films have a water content of 70–99% to ensure good moisturizing performance.

[0085] Poly(3,4-ethylenedioxythiophene) nanofilms: Due to their excellent conductivity and flexibility, they can be used in flexible electronic devices and related functional interfaces. These films are prepared using the same method described above, except that "poly(3,4-ethylenedioxythiophene)" replaces "gelatin," and have an electrical conductivity of 1–1000 S·cm. -1 Its sheet resistance is 10–1000 Ω·sq -1 The carrier mobility of the thin film is 0.1–10 cm⁻¹. 2 ·V -1 ·s -1 To meet the conductivity requirements of electronic devices;

[0086] Polyvinyl alcohol nanofilms: These films possess excellent film-forming and barrier properties, making them suitable for packaging materials and barrier films. They are prepared using the same method described above, except that "polyvinyl alcohol" is used instead of "gelatin." The tensile strength is 30–150 MPa, and the elongation at break is 10–50%.

[0087] Polyethylene glycol and its derivative nanofilms: possessing anti-protein adsorption and anti-biofouling properties, they can be used as surface modification layers for medical devices. The films are prepared using the same method as described above, except that "polyethylene glycol" replaces "gelatin." The preferred thickness is 5–200 nm, the molecular weight of PEG is 200–20000 Da, and the contact angle is 10–50°.

[0088] Functional coatings: As ultra-thin continuous covering layers, they are used for device surface protection, interface control or surface functionalization, and are suitable for applications with high requirements for coating thickness, uniformity and film integrity.

[0089] Flexible electronics and microdevice interfaces: as functional thin films on the surface of flexible electronic devices, sensing elements or micro / nano structures, used to achieve interface isolation, structural stability or functional integration, suitable for thermosensitive or finely structured device systems;

[0090] Biomedical surface modification: As a nanoscale modification layer on the surface of biomaterials or implantable devices, it is used to improve surface structure properties and is suitable for biomedical applications that require mild preparation conditions and film continuity.

[0091] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Any equivalent substitutions or modifications made to the preparation methods, process conditions or application scenarios based on the concept of the present invention shall fall within the scope of protection of the present invention.

[0092] In the method described in this embodiment, after the polymer solution is treated by the tension-induced film formation and low-temperature graded condensation process as described in the claims, the resulting nanofilm structure can stably obtain a continuous film morphology with a thickness at the nanoscale, which can be approximately 10nm-200μm. Moreover, the film has good overall uniformity and structural stability, and is suitable for interface control, functional coating and micro / nano device related application scenarios that require ultrathin continuous capping layers.

Claims

1. A method for preparing tension-induced nanofilms, characterized in that, include: The polymer solution is impregnated onto the surface of the mold. Utilizing the surface tension and directional collapse of the solution itself, a continuous liquid film is formed within the mold. The liquid film rapidly solidifies in a low-temperature environment below the freezing point of the polymer solution, completing the initial shaping. Then, under curing conditions, the initially shaped film is cured. Finally, it is dried to obtain the tension-induced nanofilm.

2. The method for preparing tension-induced nanofilms according to claim 1, characterized in that, The mold is a closed ring-shaped frame mold structure; after the mold is immersed in the polymer solution, it is taken out, so that the polymer solution adheres to the mold under the action of surface tension and forms the liquid film.

3. The method for preparing tension-induced nanofilms according to claim 1, characterized in that, The mold is made of a hydrophilic material or its surface has been modified to be hydrophilic; the polymer is a hydrophilic polymer.

4. The method for preparing tension-induced nanofilms according to claim 1, characterized in that, The low-temperature environment is a liquid nitrogen vapor environment.

5. The method for preparing tension-induced nanofilms according to claim 1, characterized in that, The curing conditions are the curing conditions corresponding to the polymer solution, including one or more combinations of temperature-induced curing conditions, ion crosslinking curing conditions, and photocuring conditions.

6. The method for preparing tension-induced nanofilms according to claim 1, characterized in that, The polymer is selected from one or more of gelatin, collagen, chitosan, alginate, hyaluronic acid, poly(3,4-ethylenedioxythiophene), polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol and its derivatives.

7. The method for preparing tension-induced nanofilms according to claim 1, characterized in that, The viscosity of the polymer solution at room temperature (25°C) is greater than or equal to 10 mPa·s.

8. The method for preparing tension-induced nanofilms according to any one of claims 1 to 7, characterized in that, Includes the following steps: (1) Prepare a polymer solution of a predetermined concentration; (2) After immersing the mold in the polymer solution, remove it so that the polymer solution adheres to the mold under the action of surface tension and forms a continuous liquid film; (3) Place the mold carrying the liquid film in a liquid nitrogen vapor environment for rapid condensation to complete the initial shaping; (4) The film condensed by liquid nitrogen vapor is transferred to a curing environment for continuous condensation, curing and shaping; (5) After the film is completely cured and shaped, it is dried to obtain the tension-induced nanofilm.

9. The method for preparing tension-induced nanofilms according to claim 1, characterized in that, The polymer solution is an aqueous gelatin solution; the concentration of the aqueous gelatin solution is 1~20wt%; the curing condition is low-temperature curing, the temperature of the low-temperature environment is 0~8℃; the drying condition is drying at room temperature and pressure.

10. A nanofilm obtained by the method for preparing tension-induced nanofilms according to any one of claims 1 to 9.

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