A method for preparing a wave-modulated flexible film based on femtosecond laser processing

Abstract

The present invention belongs to the field of material preparation, and specifically relates to a method for preparing a wave-modulated flexible film based on femtosecond laser processing. Prepare a polymethyl methacrylate mixed liquid; spin-coat the mixed solution on a metal substrate to obtain a flexible film of uniform thickness; plate a layer of a metal film having an absorption characteristic near the electromagnetic wave band to be regulated on the surface of the flexible film; use a femtosecond laser to process the metal film to obtain a wave-modulated flexible film with a micro-nano structure on the surface. The present invention uses polymethyl methacrylate as a matrix, and the prepared film has a controllable thickness, is transparent, and is easy to bend. Using a femtosecond laser to process micro-nano structures on a film can quickly and accurately process the corresponding wave-modulated micro-nano structures to realize the wave-modulation function of the film, simplify the processing steps, reduce production costs, and broaden the application of flexible films.

Description

Technical Field

[0001] The invention belongs to the field of material preparation, and in particular relates to a method for preparing a modulated flexible film based on femtosecond laser processing. Background Art

[0002] The light absorption of materials is a basic property. When the distance between two metal materials is smaller than the wavelength of the incident wave, a specific electromagnetic wave incident on the structure will produce a local field effect in the structure, which will enhance the absorption of photons. When the size of a metal material of a certain shape is small to a certain extent, a local field effect can also be generated around it, changing the material's absorption of photons. Studies have shown that micro-nano structures and micro-nano particles prepared by micro-nano manufacturing technology can change the optical parameters of the material, thereby achieving the regulation of electromagnetic waves. Research on the regulation of electromagnetic waves by materials is of great significance in the fields of stealth, photovoltaics, and sensing.

[0003] In the past decade, researchers have achieved remarkable results in the field of micro-nano manufacturing technology. A Chinese patent with publication number CN108369302A discloses a method of using nanoimprint technology to form a diffraction pattern on a thin film using a mold with a nano pattern to achieve the preparation of micro-nano structures. However, the nanostructure prepared by this method is dependent on the mold, and the prepared micro-nano structure is single. Various types of molds need to be used in combination for processing complex micro-nano structures. A Chinese patent with publication number CN110634876A discloses a method of using photolithography technology to prepare flash memory devices on the surface of a multilayer film structure. However, the process of preparing devices using the photolithography technology described therein is complicated, with high preparation cost and low efficiency. Nanoimprint technology and photolithography technology can achieve the preparation of micro-nano structures, but for complex micro-nano structures, there is still a lack of fast and efficient methods. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a wave-modulated flexible film based on femtosecond laser processing. The present invention designs a wave-modulated composite material structure of a corresponding structure according to the light absorption characteristics of different materials; based on a femtosecond laser processing system, a micro-nano metal array is processed on a flexible PMMA film, thereby realizing the regulation of the absorption spectrum of electromagnetic waves in the visible light band.

[0005] The technical solution to achieve the purpose of the present invention is: a method for preparing a modulated flexible film based on femtosecond laser processing, preparing a polymethyl methacrylate mixed liquid; spin-coating the mixed liquid on a metal substrate to obtain a flexible film of uniform thickness; coating a layer of metal film with a thickness less than the wavelength of the incident electromagnetic wave on the surface of the flexible film; and processing the metal film using a femtosecond laser to obtain a modulated flexible film with a micro-nanostructured metal array on the surface.

[0006] Further, the specific steps include:

[0007] Step (1): weighing PMMA (polymethyl methacrylate) particles as needed, measuring an organic solvent, and preparing a polymethyl methacrylate mixed liquid;

[0008] Step (2): placing the polymethyl methacrylate mixed liquid prepared in step (1) in a magnetic stirrer and stirring;

[0009] Step (3): Select a metal sheet and pre-treat it as a metal substrate;

[0010] Step (4): adsorbing the metal substrate on the chuck of the coating machine with the pre-treated surface facing upward, dripping the mixed liquid obtained by stirring in step (2) onto the metal substrate for spin coating to form a flexible film of uniform thickness;

[0011] Step (5): coating a metal film on the flexible film prepared in step (4);

[0012] Step (6): The film obtained in step (5) is processed using a femtosecond laser to obtain a modulated flexible film having a micro-nano structure on the surface.

[0013] Furthermore, the molecular weight of the polymethyl methacrylate (PMMA) particles in step (1) is 25,000 to 200,000 g / mol, and the particle size of the particles is 100 to 2000 μm.

[0014] Furthermore, in the step (1), the amount of polymethyl methacrylate (PMMA) particles weighed is 1 to 10 g, and the volume of the organic solvent measured is 5 to 15 ml; the organic solvent is toluene, acetone or ethanol.

[0015] Furthermore, the stirring speed in step (2) is 100 to 500 rpm, and the stirring time is 6 to 12 hours.

[0016] Furthermore, the resistivity of the metal substrate in step (3) is 1-5Ω·M, and the thickness of the metal substrate is less than 2 cm; the pretreatment is specifically: washing with 95% ethanol for 1-3 hours and drying in a natural environment.

[0017] Furthermore, the spin coating speed in step (4) is 1000-3000 rpm; the material of the metal film in step (5) satisfies that the electromagnetic wave absorption peak position is within ±50nm of the electromagnetic wave in the regulated band, and the thickness of the metal film is 1-500nm.

[0018] Furthermore, in step (6), the wavelength of the femtosecond laser is 500nm to 50000nm, the processing power is 10 to 40W, and the galvanometer scanning speed is 10 to 1000mm / s.

[0019] Furthermore, after the femtosecond laser processing in step (6), the shape of the metal film of the modulated flexible film is a cuboid, a cylinder or a prism.

[0020] A wave-modulation flexible film is prepared by the above method.

[0021] Compared with the prior art, the present invention has the following significant advantages:

[0022] (1) The present invention is based on a method for preparing a wave-tuned flexible thin film composite material processed by femtosecond laser. A PMMA film with uniform thickness is prepared by spin coating on a metal thin plate, and a metal film with a thickness less than the wavelength of the regulated electromagnetic wave is arranged on the PMMA film. Due to the low thermal effect, high instantaneous power, and extremely short pulse width of femtosecond laser processing, high-resolution and high-precision surface micro-nano structure processing is achieved. Compared with the processing of micro-nano structures such as nano-etching and photo-etching, the process is simple, the resources consumed are small, and the mechanized production of products can be realized; the processing efficiency is high, the paths are flexible and diverse, and the preparation of complex micro-nano structures can be realized.

[0023] (2) Compared with the preparation process of micro-nano structures such as nano-etching and photolithography, the procedure of processing micro-nano structures using femtosecond laser is simple, consumes less resources, and has high processing efficiency; the paths are flexible and diverse, and the preparation of complex micro-nano structures can be achieved.

[0024] (3) The thin film composite material prepared by the present invention uses PMMA with high electromagnetic wave transmittance and is soft and easy to bend; the substrate metal and the plated metal are combined to form a field enhancement region with a structure similar to a "microcavity" that absorbs electromagnetic waves of a certain wavelength and has the ability to regulate electromagnetic waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the processing path of the femtosecond laser in the processing process of the present invention

[0026] Figure 2 Schematic diagram of the flexible wave-tuning thin film material prepared by femtosecond laser processing in the present invention

[0027] Figure 3 Flow chart of the method for preparing the wave-modulating flexible film composite material of the present invention

[0028] Description of reference numerals:

[0029] 1- vertical direction of the processing path, 2- horizontal direction of the processing path, 3- pulsed laser, 4- modulated flexible film surface DETAILED DESCRIPTION

[0030] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0031] like Figure 1-3As shown in the figure, a method for preparing a modulated flexible film based on femtosecond laser processing is to mix PMMA (polymethyl methacrylate) particles with an organic solvent, use a magnetic stirrer to accelerate the dissolution of PMMA, and wait until the PMMA particles are completely dissolved. A flexible film with uniform thickness is obtained by spin coating on a metal substrate using a coating machine. A layer of metal film is then plated on the surface of the obtained film; finally, a femtosecond laser is used to process along a certain path to obtain a flexible film capable of modulating electromagnetic waves.

[0032] Further, the specific steps include:

[0033] Step (1): weighing a certain amount of PMMA particles and measuring a certain volume of an organic solvent to obtain a mixed liquid;

[0034] Step (2): mixing the PMMA particles weighed in step (1) with an organic solvent, and stirring the mixture in a magnetic stirrer;

[0035] Step (3): select a certain metal sheet and perform cleaning and drying pretreatment on the sheet;

[0036] Step (4): adsorbing the pretreated metal sheet on the chuck of the coating machine with the pretreated surface facing upward, and dripping the mixed liquid obtained in step (2) onto the metal sheet for spin coating;

[0037] Step (5): A metal film is plated on the polymer layer on the composite sheet obtained in step (4); the metal film is selected and determined according to the wavelength range of the regulated electromagnetic wave; the absorption characteristics of the selected plated metal are within ±50nm of the regulated electromagnetic wave band. The thickness of the plated metal is about 500nm. When the thickness of the plated metal changes, the shape and size of the corresponding plated metal array unit changes, and its absorption coefficient and peak position of the electromagnetic wave will change, thereby achieving the regulation of the electromagnetic wave;

[0038] Step (6): The film obtained in step (5) is processed using a femtosecond laser. The femtosecond laser has low thermal effect, high instantaneous power, and extremely short pulse width, and can achieve high-resolution and high-precision surface micro-nanostructure processing, thereby obtaining a modulated flexible film.

[0039] When a metal film of a certain thickness is plated on the surface of the prepared film in step (5), the plated metal and the substrate metal form a field enhancement region with a structure similar to a "microcavity" that absorbs electromagnetic waves of a certain wavelength. The size of the "microcavity" is controlled by the thickness of the spin-coated PMMA layer in step (4). The spin-coated layer is PMMA, which has no effect on the field effect formed by the substrate metal and the plated metal. The field effect formed by the substrate metal and the plated metal has a certain regulating effect on the incident electromagnetic waves of a certain wavelength.

[0040] The molecular weight of the PMMA particles in step (1) is 25000-200000 g / mol, and the particle size of the particles is 100-2000 μm. During the mixing process in step (1), the amount of PMMA is 1-10 g, and the volume of the organic solvent is 5-15 ml. The organic solvent includes toluene, acetone, ethanol, etc.

[0041] In step (2), the rotation speed of the magnet is 100 to 500 rpm; and the stirring time is 6 to 12 hours.

[0042] The metal sheet in step (3) has a resistivity of 1 to 5 Ω·M, such as copper, silver, gold, etc. The metal in step (3) is coupled with the plated metal, the thickness of the metal sheet is less than 2 cm, and is cleaned in 95% ethanol for 1 to 3 hours and dried in a natural environment.

[0043] Step (4) spin coating speed is 1000-3000 rpm.

[0044] Step (5) The coating metal is selected from metals with good conductivity, and the coating metal thickness is 1 to 500 nm.

[0045] In step (6), the wavelength of the femtosecond laser is 500nm to 50000nm, the processing power is 10 to 40W, and the galvanometer scanning speed is 10 to 1000mm / s.

[0046] In step (6), the shape of the metal coating of the modulated flexible film after being processed by the femtosecond laser is a rectangular parallelepiped, a cylinder, a prism, etc.

[0047] The modulated wave flexible film is composed of three layers in total, which are substrate metal, PMMA and coated metal from the bottom layer to the surface layer.

[0048] Step (6) During the femtosecond laser processing, a certain processing path is first designed, which is determined by the designed plated metal shape. After the path is determined, the appropriate femtosecond laser parameters are selected. When selecting the femtosecond laser power density parameter, the damage threshold of the material should be considered. Each material has a certain damage threshold. Only when the energy density provided by the femtosecond laser is greater than or equal to the damage threshold of the material can the material be ablated by the femtosecond laser, thereby processing a certain structure of micro-nanostructure.

[0049] Example 1

[0050] The specific steps include:

[0051] Step (1): weigh 5.9 g of PMMA particles and measure 15 ml of toluene solution;

[0052] Step (2): the PMMA particles weighed in step (1) and the toluene solution were mixed, and a 2 cm magnetic rod was placed in the mixture. The mixture was sealed with a glass bottle, and the glass bottle was placed on a magnetic stirrer and stirred for 8 h.

[0053] Step (3): Select a 3*3cm copper plate with a thickness of 1mm, and pre-treat the plate by washing it with 95% alcohol and drying it naturally.

[0054] Step (4): adsorb the pretreated copper metal sheet on the chuck of the coating machine with the pretreated surface facing upward, and drip the mixed liquid obtained in step (2) onto the sheet for spin coating, wherein the spin coating process is divided into two stages, the time and speed of the first stage are 60s and 1500rpn respectively, and the time and speed of the second stage are 43s and 800rpn respectively;

[0055] Step (5): coating the film obtained in step (4) with a 150 nm thick metal Ag film;

[0056] Step (6): The thin film obtained in step (5) is processed using a femtosecond laser, wherein the processing path is as follows: Figure 1 As shown in the figure, the laser power is 16w, the scanning speed is 240mm / s, and the laser wavelength is 1035nm. Figure 2 As shown in the figure, the parameters of each layer are a, 2000mm, b, 2000mm, c, 0.01mm, p, 460nm, h, 150nm, and m, 300nm. The side length pm of the coated metal film unit is 160nm.

[0057] The flow chart of the method for preparing the wave-modulating flexible thin film composite material of this embodiment is as follows Figure 3 The prepared wave-modulating flexible film can adjust the absorption spectrum of electromagnetic waves, and the absorption rate of electromagnetic waves is increased from the original 10.2% to 65.1%.

Claims

1. A method for preparing a modulated flexible film based on femtosecond laser processing, characterized in that: Prepare a polymethyl methacrylate mixed liquid; spin-coat the mixed liquid on a metal substrate to obtain a flexible film of uniform thickness; plate a metal film with a thickness less than the wavelength of the incident electromagnetic wave on the surface of the flexible film; process the metal film using a femtosecond laser to obtain a wave-modulated flexible film with a micro-nanostructured metal array on the surface; specifically include the following steps: Step (1): weighing PMMA polymethyl methacrylate particles as needed, measuring an organic solvent, and preparing a polymethyl methacrylate mixed liquid; Step (2): placing the polymethyl methacrylate mixed liquid prepared in step (1) in a magnetic stirrer and stirring; Step (3): selecting a metal sheet and pre-treating it to be used as a metal substrate, wherein the resistivity of the metal substrate is 1 to 5 Ω·m and the thickness of the metal substrate is less than 2 cm; the pre-treating in step (3) is specifically as follows: washing with 95% ethanol for 1 to 3 hours and drying in a natural environment; Step (4): adsorb the metal substrate on the chuck of the coating machine with the pre-treated surface facing upward, drip the mixed liquid obtained by stirring in step (2) onto the metal substrate for spin coating to form a flexible film of uniform thickness; the spin coating speed is 1000 to 3000 rpm; Step (5): coating a metal film on the flexible film prepared in step (4), wherein the thickness of the metal film is less than the wavelength of the incident electromagnetic wave to be regulated, and the thickness of the metal film is 1 to 500 nm; Step (6): The film obtained in step (5) is processed using a femtosecond laser to obtain a modulated flexible film having a micro-nanostructured metal array on the surface; the wavelength of the femtosecond laser in step (6) is 500nm to 50000nm, the processing power is 10 to 40W, and the galvanometer scanning speed is 10 to 1000mm / s.

2. The method for preparing a modulated flexible film based on femtosecond laser processing according to claim 1, characterized in that: The molecular weight of the polymethyl methacrylate (PMMA) particles in step (1) is 25000-200000 g / mol, and the particle size of the particles is 100-2000 μm.

3. The method for preparing a modulated flexible film based on femtosecond laser processing according to claim 2, characterized in that: In the step (1), the amount of polymethyl methacrylate (PMMA) particles weighed is 1 to 10 g, and the volume of the organic solvent measured is 5 to 15 ml; the organic solvent is toluene, acetone or ethanol.

4. The method for preparing a modulated flexible film based on femtosecond laser processing according to claim 3, characterized in that: The stirring speed in step (2) is 100 to 500 rpm, and the stirring time is 6 to 12 hours.

5. The method for preparing a modulated flexible film based on femtosecond laser processing according to claim 4, characterized in that: Step (6) After femtosecond laser processing, the shape of the metal film of the modulated flexible film is a cuboid, a cylinder or a prism.

6. A wave-modulating flexible film, characterized in that: The film is prepared by the method for preparing a modulated flexible film based on femtosecond laser processing as described in any one of claims 1 to 5.

Images