Micro-porous carbon spring based on femtosecond laser micro-nano machining and preparation method thereof

Abstract

The application discloses a kind of micro porous carbon spring based on femtosecond laser micro-nano machining and preparation method thereof, it is related to femtosecond laser micro-nano machining technical field.The application provides a kind of preparation method of micro porous carbon spring, take polyimide film and fix on slide, the slide is fixed on object table;Laser parameter is adjusted, laser beam is focused on the surface of the polyimide film and is scanned, and the micro porous carbon spring is obtained;The laser parameter is 500 mW-4000 mW of laser power, and scanning speed is 1-10 mm / s.The application also provides corresponding micro-nano machining system and micro-nano machining parameter database.Micro porous carbon spring prepared by the method has good conductivity, mechanical strength and environmental stability.

Description

Technical Field

[0001] This invention relates to the field of femtosecond laser micro / nano fabrication technology, and particularly to a micro porous carbon spring based on femtosecond laser micro / nano fabrication and its preparation method. Background Technology

[0002] In nature, the helical structure is one of the most common three-dimensional structures. From macroscopic to microscopic, from the whole to the part, almost all substances can be found with helical structures, such as DNA, spirochetal microorganisms, sea snails, and vines. In human society, helical structures are also ubiquitous in devices and parts, such as springs, electromagnetic coils, and screws. This special structure can endow devices with unique properties, making them suitable for various special occasions. With the development of human society, devices are increasingly trending towards miniaturization and integration, and the simple and efficient fabrication of various complex three-dimensional micro-devices is attracting more and more attention.

[0003] Porous carbon materials possess advantages such as high specific surface area, high electrical conductivity, high chemical stability against acid and alkali corrosion, gas-liquid permeability, tunable pore structure, and good electromagnetic wave absorption, showing great promise for applications in energy storage and conversion, catalysis, and adsorption separation. However, fabricating complex three-dimensional micro-carbon devices, such as helical carbon springs, a fundamental component of carbon-based devices, remains a challenge. Currently, micro-carbon springs are mainly fabricated using 3D printing. This method requires expensive additive manufacturing equipment and special graphite inks, and due to the bottom-up, layer-by-layer printing approach, the processing efficiency is extremely low, making it unsuitable for mass production. Summary of the Invention

[0004] This invention provides a microporous carbon spring based on femtosecond laser micro / nano fabrication and its preparation method. The invention utilizes femtosecond laser micro / nano fabrication technology to induce the growth of a microporous carbon spring with a helical structure of opposite polarities on the surface of a polyimide film by controlling laser parameters. This preparation method is simple and convenient, suitable for mass production. The produced microporous carbon spring exhibits good conductivity, mechanical properties, and environmental stability. Specifically, it is achieved through the following techniques.

[0005] In a first aspect, the present invention provides a method for fabricating a microporous carbon spring based on femtosecond laser micro-nano processing, comprising the following steps: taking a polyimide film and fixing it on a glass slide, and fixing the glass slide on a stage; adjusting the laser parameters, focusing the laser beam on the surface of the polyimide film for scanning, thereby obtaining the microporous carbon spring; wherein the laser parameters are a laser power of 500 mW-4000 mW and a scanning speed of 1-10 mm / s.

[0006] The method for preparing the microporous carbon spring provided by the present invention involves focusing a laser onto the surface of a polyimide film and using femtosecond laser direct writing technology. By adjusting the processing parameters to control the heat accumulation effect during the femtosecond laser direct writing process, a microporous carbon spring with a helical structure of opposite polarity is ultimately induced to grow on the surface of the polyimide film.

[0007] The reaction process and working principle of the above preparation method are as follows:

[0008] (1) Under the action of a femtosecond laser pulse with high repetition frequency and high pulse energy, polyimide absorbs laser energy through multiphoton absorption, thereby undergoing multiphoton ionization and ablation.

[0009] (2) The ablation process generates intense heat accumulation, and the accumulated heat diffuses to both ends of the ablation area to form a heat-affected zone. However, polyimide has low thermal conductivity, and coupled with the energy distribution characteristics of Gaussian laser, this leads to a high degree of local heat accumulation.

[0010] (3) The heat-affected zone has an extremely high temperature gradient, which causes graphitization to begin in the area near the ablation tank and form highly crystalline graphitic carbon, while the area far from the ablation tank produces amorphous carbon with low crystallinity. At the same time, the different temperatures lead to different degrees of pyrolysis, and the amount and rate of gas release are also different; the closer the area is to the ablation center, the more gas is released and the more pores are generated.

[0011] When the stress generated by the localized high pressure due to gas accumulation exceeds the induced bonding force between the carbon structure and the substrate, the carbon lines (graphite carbon and amorphous carbon) are rapidly peeled off from the polyimide substrate. Furthermore, because the carbon lines on the left and right sides of the ablation groove are subjected to opposite centripetal forces, when combined with the original peeling trajectory during laser scanning, a pair of pair of symmetrical microporous carbon springs are generated.

[0012] Laser parameters significantly affect the three-dimensional dimensional properties (diameter, thickness, width, and pitch) of microporous carbon springs. This invention reveals that as laser power increases, the width, thickness, diameter, and pitch of the microporous carbon spring gradually increase; conversely, as scanning speed increases, these properties gradually decrease. Based on this reaction process and mechanism, to effectively control the thermal accumulation effect and ensure the growth of a pair of microporous carbon springs with opposite helical structures on the polyimide film surface, it is necessary to pre-calibrate the femtosecond laser processing system to select appropriate laser parameters.

[0013] Furthermore, the objective lens has a numerical aperture (NA) of 0.14 and a magnification of 5x; the laser parameters are adjusted as follows: the fixed parameters after the laser beam passes through the objective lens and is focused are designed as a laser wavelength of 1028 nm, a pulse width of 190 fs, and a repetition frequency of 200 kHz.

[0014] Furthermore, the thickness of the polyimide film is 50-200 μm.

[0015] Furthermore, the polyimide film has a thickness of 100 μm.

[0016] In a second aspect, the present invention provides a microporous carbon spring prepared using any of the above-described preparation methods.

[0017] A third aspect of the present invention provides an application of the above-mentioned micro porous carbon spring for manufacturing micro-mechanical devices and micro-electronic components.

[0018] Because the micro porous carbon spring prepared by this invention has good electrical conductivity, mechanical strength (mainly tensile properties) and environmental stability, it can be used as a component of micromechanical and microelectronic devices and is widely used in fields such as micromechanical devices (e.g., micro robots) and microelectronic components (e.g., micro resistance wires).

[0019] A fourth aspect of the present invention provides a micro / nano fabrication system for fabricating micro porous carbon springs, the micro / nano fabrication system comprising a pulsed laser, an energy attenuator, a first reflector, a polarization rotating mirror, a second reflector, a third reflector, a first semi-transparent and semi-reflective mirror, a fourth reflector, a focusing objective, a stage, and a control assembly; a three-dimensional moving mechanism is provided below the stage, the three-dimensional moving mechanism being electrically connected to the control assembly;

[0020] The laser beam emitted by the pulsed laser passes sequentially through the energy attenuator, the first reflector, the polarization rotating mirror, the second reflector, the third reflector, the first semi-transparent and semi-reflective mirror, the second semi-transparent and semi-reflective mirror, the fourth reflector, and the focusing objective lens, and then illuminates the stage.

[0021] Furthermore, the micro-nano fabrication system also includes an imaging component, a second semi-transparent and semi-reflective mirror, and a light source; the second semi-transparent and semi-reflective mirror is located between the first semi-transparent and semi-reflective mirror and the lens of the imaging component, and the light source is directed toward the second semi-transparent and semi-reflective mirror.

[0022] The fabrication method of the aforementioned microporous carbon spring provided by this invention is generally carried out on a micro / nano fabrication system. This invention provides a specific structure of such a micro / nano fabrication system. In this system, a polyimide film is fixed to the surface of a glass slide, which is then fixed to a stage. An energy attenuator is used to regulate the laser power, introducing a femtosecond laser with adjusted parameters into the system. The laser beam is focused on the surface of the polyimide film, and the movement of the stage is controlled by a control component to achieve femtosecond laser scanning.

[0023] Alternatively, the slide can be fixed by means of negative pressure suction, such as by setting a vacuum pump on the stage.

[0024] If necessary, the aforementioned micro-nano fabrication system can also be equipped with imaging components to monitor the entire fabrication process of the micro porous carbon spring in real time.

[0025] In a fifth aspect, the present invention provides a micro / nano fabrication parameter database for preparing micro-porous carbon springs. This database is constructed by obtaining corresponding micro-porous carbon springs by setting different laser parameters, and then testing and obtaining the diameter, thickness, width, and pitch of the micro-porous carbon springs. In practical applications, appropriate fabrication parameters can be selected based on the actual size requirements of the performance parameters.

[0026] Compared with the prior art, the advantages of the present invention are:

[0027] 1. This invention provides a method for preparing microporous carbon springs. Using this method, a single laser scan can simultaneously induce the production of a pair of microporous carbon springs with opposite helical chirality. This method is fast, convenient, and repeatable, making it suitable for simple and efficient mass production. The thickness, width, pitch, and diameter of the microporous carbon springs, as well as related properties (conductivity, mechanical strength, and environmental stability, etc.), can be precisely controlled by adjusting localized heat.

[0028] 2. The micro porous carbon spring prepared by this invention has an all-carbon structure, can reach the centimeter level in length, and has a good loose porous microstructure.

[0029] When the laser power is 2000 mW and the scanning speed is 5 mm / s, the fabricated microporous carbon spring exhibits good electrical conductivity, with a line resistance of less than 1.68 kΩ / mm; good mechanical strength, under stable external force, the microporous carbon spring can be stretched from its natural state of 26.1 mm to a maximum of 43.5 mm, with a strain of 66.7%, indicating that the microporous carbon spring has a certain degree of stretchability and can store a certain amount of elastic potential energy, with an elastic constant of approximately 1.2 N / m; and good environmental stability, with relative conductivity changes of less than 1% in various gas environments.

[0030] 3. This invention also provides a miniature porous carbon spring that can be widely used in multiple industries such as micromechanics and microelectronics, specifically for assembling and manufacturing miniature springs, miniature robots, and miniature resistance wires.

[0031] 4. This invention also provides a micro / nano fabrication system based on the above-described method for preparing microporous carbon springs, as well as a micro / nano fabrication parameter database. This system allows for the study of the effects of parameters such as laser parameters, polyimide film thickness, and scanning speed on the structural data of microporous carbon springs, including width, thickness, diameter, and pitch, as well as their influence on the conductivity, mechanical properties, and stability of the microporous carbon springs. These data can be correlated to form a micro / nano fabrication parameter database for preparing microporous carbon springs. Attached Figure Description

[0032] Figure 1 The present invention provides a schematic diagram of the structure and optical path of the micro / nano fabrication system.

[0033] Figure 2 This is a product photo of a single miniature porous carbon spring.

[0034] Figure 3 The relationship between the growth range of micro porous carbon springs and the femtosecond laser scanning speed and laser power.

[0035] Figure 4 These are scanning electron microscope (SEM) images of microporous carbon springs. Among them, Figure 4 Image a is a SEM image of a micro porous carbon spring. Figure 4 b is an SEM image of the inner surface of the micro porous carbon spring. Figure 4 c is a SEM image of the outer surface of a micro porous carbon spring.

[0036] Figure 5 This is an elemental distribution map (EDS mapping) of a micro porous carbon spring.

[0037] Figure 6 This is the Raman spectrum of a microporous carbon spring.

[0038] Figure 7-10 The figures show the relationship between the width, thickness, diameter, and pitch of a micro porous carbon spring and the laser power.

[0039] Figure 11-14 The figures show the relationship between the width, thickness, diameter, and pitch of a micro porous carbon spring and the scanning speed.

[0040] Figure 15 This is a side view of a miniature porous carbon spring under tension.

[0041] Figure 16This is a photograph of a microporous carbon spring induced by polyimide films of different thicknesses.

[0042] Figure 17 This is a diagram showing the electrical conductivity test results of a miniature porous carbon spring.

[0043] Figure 1 The reference numerals in the figures are as follows: 1. Pulsed laser; 2. Energy attenuator; 3. First reflector; 4. Polarizing rotating mirror; 5. Second reflector; 6. Third reflector; 7. First semi-transparent and semi-reflective mirror; 8. Second semi-transparent and semi-reflective mirror; 9. Imaging assembly; 10. Light source; 11. Fourth reflector; 12. Focusing objective lens; 13. Polyimide film; 14. Stage. Detailed Implementation

[0044] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] This invention provides a method for controlling local carbonization and stress caused by thermal accumulation during femtosecond laser direct writing to induce micro porous carbon springs. This method can produce micro porous carbon springs with lengths up to the centimeter level within seconds and can be repeatedly produced, making it suitable for simple and efficient mass production.

[0046] like Figure 1 As shown, in some embodiments of the present invention, a micro / nano fabrication system for fabricating micro porous carbon springs is provided. The micro / nano fabrication system includes a pulsed laser 1, an energy attenuator 2, a first reflector 3, a polarization rotating mirror 4, a second reflector 5, a third reflector 6, a first semi-transparent and semi-reflective mirror 7, a fourth reflector 11, a focusing objective lens 12, a stage 14, and a control assembly. A three-dimensional moving mechanism is provided below the stage 14, and the three-dimensional moving mechanism is electrically connected to the control assembly.

[0047] The laser beam emitted by the pulsed laser 1 passes sequentially through the energy attenuator 2, the first reflector 3, the polarization rotating mirror 4, the second reflector 5, the third reflector 6, the first semi-transparent and semi-reflective mirror 7, the fourth reflector 11, and the focusing objective lens 12, and then illuminates the stage 14.

[0048] In some embodiments of the present invention, such as Figure 1As shown, the micro-nano fabrication system also includes an imaging component 9 (i.e., a CCD camera), a second semi-transparent and semi-reflective mirror 8, and a light source 10 (i.e., an LED light source); the second semi-transparent and semi-reflective mirror 8 is located between the first semi-transparent and semi-reflective mirror 7 and the lens of the imaging component 9, and the light source 10 faces the second semi-transparent and semi-reflective mirror 8.

[0049] In some embodiments of the present invention, a three-dimensional moving mechanism is provided below the stage, which can adjust the stage according to the position of the laser, and move the stage through the three-dimensional moving mechanism at a preset scanning speed during laser scanning.

[0050] In some embodiments of the present invention, the control component may use SCA control software to operate the three-dimensional moving mechanism.

[0051] Example

[0052] The method for preparing the micro porous carbon spring provided in this embodiment includes the following steps:

[0053] 1. Debugging the micro / nano fabrication system

[0054] according to Figure 1 The micro-nano fabrication system is assembled in this manner. A femtosecond laser beam is emitted from a pulsed laser, passes through an energy attenuator (energy attenuator), and then sequentially passes through the first reflector, the polarization rotating mirror, the second reflector, the third reflector, the first semi-transparent and semi-reflective mirror, and the fourth reflector before being focused by the objective lens and finally illuminating the stage.

[0055] The objective lens used in this embodiment has a numerical aperture (NA) of 0.14 and a magnification of 5x.

[0056] The laser parameters selected in this embodiment are adjusted as follows: the fixed parameters after the laser beam is focused by the objective lens are designed as follows: laser wavelength 1028 nm, pulse width 190 fs, repetition frequency 200 kHz; laser power 2000 mW.

[0057] 2. Install the polyimide film and glass slide.

[0058] The polyimide film is ultrasonically cleaned and then fixedly placed on a glass slide (glass substrate). The slide is placed on an electric stage, the position is adjusted horizontally, and the stage adsorption device (e.g., air pump) is turned on to make the slide fit tightly against the stage.

[0059] In this embodiment, the polyimide film used has a thickness of 100 μm, and the glass slide has a thickness of 1 mm.

[0060] 3. Focus the laser onto the surface of the polyimide film.

[0061] A femtosecond laser beam with adjusted parameters is focused onto the surface of a polyimide film. A three-dimensional moving mechanism controls the stage to move and scan the film at a scanning speed of 5 mm / s to obtain a micro porous carbon spring with a spiral structure.

[0062] The entire process of sample focusing can be monitored in real time by a CCD camera.

[0063] Experimental Example 1: Morphology and structural characterization of micro porous carbon springs fabricated using different laser powers and scanning speeds

[0064] Using the preparation method described in the above embodiments, and by adjusting different laser powers and scanning speeds, microporous carbon springs of different sizes were prepared, such as... Figure 2 As shown, the growth range of the micro porous carbon spring is as follows: Figure 3 As shown, too low a temperature will prevent the microporous carbon spring from growing from the polyimide substrate, while too high a temperature will prevent the formation of a helical structure and carbon fiber.

[0065] The minimum dimensions of the microporous carbon springs fabricated using the methods described in the above embodiments are: diameter 755 μm, pitch 1210 μm, width 52 μm, and thickness 26 μm; the corresponding laser parameters are: laser power 700 mW and scanning speed 5 mm / s. The maximum dimensions of the microporous carbon springs fabricated using the methods described in the above embodiments are: diameter 1410 μm, pitch 1620 μm, width 130 μm, and thickness 57 μm; the corresponding laser parameters are: laser power 4000 mW and scanning speed 5 mm / s.

[0066] Within the growth region of the microporous carbon spring, the width, thickness, diameter, and pitch of the microporous carbon spring are directly proportional to the laser power and inversely proportional to the scanning speed. This is attributed to the significant thermal accumulation effect during laser scanning, which is directly proportional to the laser power and inversely proportional to the scanning speed.

[0067] The surface and cross-section of the microporous carbon spring prepared in Example 1 were characterized using scanning electron microscopy, such as... Figure 4 As shown. Figure 4 This image shows the microstructure of a single microporous carbon spring, revealing its ribbon-like helical structure. Further observation at higher magnification of the inner and outer surfaces of the microporous carbon spring reveals... Figure 4 As shown in b and 4c, the inner and outer surfaces of the micro porous carbon spring exhibit porous structures. The difference is that, compared to the outer surface, the inner surface exhibits a thinner sheet-like structure with fewer and larger pores, while the outer surface has thicker carbon walls, denser pores, and smaller pores.

[0068] EDS analysis was performed on the microporous carbon spring prepared in Example 1, as follows: Figure 5 The image shows the elemental distribution of some micro porous carbon springs. Figure 5 The images show local SEM images of a microporous carbon spring (top left), elemental distribution map of a microporous carbon spring (top right), C elemental distribution map (bottom left), and O elemental distribution map (bottom right). Figure 5 It can be seen that the main elements are C and O; among them, C occupies the entire structure, while O is only distributed on the surface of the structure, originating from the adsorption of oxygen in the air, proving that the laser-induced micro spring is an all-carbon structure.

[0069] Raman spectroscopy analysis was performed on the microporous carbon spring prepared in Example 1, as follows: Figure 6 As shown, it can be seen that at 1350 cm -1 and 1580 cm -1 The presence of D and G peaks in the vicinity indicates that the main structure is amorphous carbon.

[0070] Experimental Example 2: The Influence of Processing Parameters such as Laser Power and Scanning Speed ​​on the Dimensional Parameters of Microporous Carbon Springs

[0071] Using the preparation method of Example 1, the power of the femtosecond laser was adjusted to 700 mW, 1000 mW, 1500 mW, 2000 mW, 2500 mW, 3000 mW, 3500 mW, and 4000 mW, respectively, and the width, thickness, diameter, and pitch of each prepared microporous carbon spring were measured. The results are as follows... Figure 7-10 As shown, with the increase of laser power, the width, thickness, diameter and pitch of the micro porous carbon spring gradually increase until the polyimide film is ablated and penetrated.

[0072] Using the preparation method of Example 1, the scanning rate of the femtosecond laser was adjusted to 1 mm / s, 2 mm / s, 3 mm / s, 4 mm / s, 5 mm / s, 6 mm / s, 7 mm / s, 8 mm / s, 9 mm / s, and 10 mm / s, and the width, thickness, diameter, and pitch of each prepared microporous carbon spring were measured. The results are as follows: Figure 11-14 As shown, as the scanning speed increases, the width, thickness, diameter and pitch of the microporous carbon spring gradually decrease until the accumulated heat is insufficient to induce the formation of microporous carbon springs on the surface of the polyimide film.

[0073] Based on the above experimental results, microporous carbon springs were repeatedly induced using different laser power and scanning speed parameters, and each spring was characterized individually. The dimensional parameters and performance of the microporous carbon springs were statistically analyzed and summarized. The relationship between different processing parameters and the parameters of the fabricated microporous carbon springs was studied, and a micro / nano processing parameter database for femtosecond laser fabrication of microporous carbon springs was established.

[0074] Experimental Example 3: Mechanical Property Testing of Miniature Porous Carbon Springs

[0075] Tensile tests were performed on the micro porous carbon spring prepared in Example 1, and the results are as follows: Figure 15 As shown, under a steady external force, the micro porous carbon spring stretches from its natural length of 26.1 mm to a maximum of 43.5 mm, with a strain of 66.7%. This indicates that the porous structure endows the micro porous carbon spring with stretchability and the ability to store a certain amount of elastic potential energy. The elastic constant of the micro porous carbon spring is approximately 1.2 N / m.

[0076] Experimental Example 4: The Influence of Polyimide Film Thickness on the Dimensional Parameters of Microporous Carbon Springs

[0077] The microporous carbon springs selected in this experiment were prepared using the method described in the previous example, with the polyimide film thickness adjusted to 50-200 μm. The results are as follows... Figure 16 As shown, when the thickness of the polyimide film is less than 50 μm, the laser will ablate through the film, and the gas generated during pyrolysis and carbonization is insufficient to induce the formation of microporous carbon springs on the surface of the polyimide film.

[0078] Experimental Example 5: Electrical Conductivity Test of Miniature Porous Carbon Springs

[0079] The resistance of the micro porous carbon spring prepared in the example was tested, and the results are as follows: Figure 17 As shown, the carbon spring is approximately 1 cm in length. Using a UT890D digital multimeter, the resistance of the carbon spring prepared under these laser parameters was measured to be 16.8 kΩ. This indicates that the microporous carbon spring prepared using the method of this invention possesses good electrical conductivity.

[0080] Further experiments revealed that a simple circuit was constructed using a carbon spring as a conductor, which could light up an LED when connected to a 3V DC power supply.

[0081] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A method for fabricating a microporous carbon spring based on femtosecond laser micro / nano fabrication, characterized in that, The procedure includes the following steps: A polyimide film is fixed onto a glass slide, and the glass slide is then fixed onto a stage; laser parameters are adjusted, and a laser beam is focused onto the surface of the polyimide film for scanning to obtain the microporous carbon spring; the laser parameters are: laser power 500 mW-4000 mW, scanning speed 1-10 mm / s; the numerical aperture (NA) of the objective lens is 0.14, and the magnification is 5x; the laser parameters are adjusted as follows: the fixed parameters after the laser beam is focused by the objective lens are designed as follows: laser wavelength 1028 nm, pulse width 190 fs, repetition frequency 200 kHz; the thickness of the polyimide film is 50-200 μm. The aforementioned preparation method can induce the simultaneous generation of a pair of microporous carbon springs with opposite helical chirality in a single laser scan; the microporous carbon springs are conductive, stretchable, and capable of storing a certain amount of elastic potential energy.

2. The method for fabricating a microporous carbon spring based on femtosecond laser micro / nano fabrication according to claim 1, characterized in that, The polyimide film has a thickness of 100 μm.

3. The method for fabricating a microporous carbon spring based on femtosecond laser micro / nano fabrication according to claim 1, characterized in that, The scanning speed is 5 mm / s.

4. A micro porous carbon spring prepared by the preparation method according to any one of claims 1-3.

5. An application of the micro porous carbon spring according to claim 4, characterized in that, Used to manufacture micro-mechanical equipment and micro-electronic components.

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