CN113523596B - Device and method for processing patterned photo-deformation crosslinked liquid crystal polymer component by femtosecond laser - Google Patents
Device and method for processing patterned photo-deformation crosslinked liquid crystal polymer component by femtosecond laser Download PDFInfo
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- CN113523596B CN113523596B CN202110772813.2A CN202110772813A CN113523596B CN 113523596 B CN113523596 B CN 113523596B CN 202110772813 A CN202110772813 A CN 202110772813A CN 113523596 B CN113523596 B CN 113523596B
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- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/36—Removing material
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- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
- B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
- B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
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- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
- B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
- B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
- B23K26/0643—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms comprising mirrors
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- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
- B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
- B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
- B23K26/0648—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms comprising lenses
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- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/08—Devices involving relative movement between laser beam and workpiece
- B23K26/083—Devices involving movement of the workpiece in at least one axial direction
- B23K26/0853—Devices involving movement of the workpiece in at least in two axial directions, e.g. in a plane
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/36—Removing material
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Abstract
The invention discloses a device and a method for processing a patterned photo-deformation cross-linked liquid crystal polymer component by femtosecond laser, wherein the device comprises the following steps: the device comprises a femtosecond laser, a clamping device for realizing horizontal fixation of a cross-linked liquid crystal polymer film to be processed and a three-dimensional positioning mechanism for realizing laser patterning path scanning; the device also comprises a shutter element, a beam adjusting element, a power adjusting element, a beam splitting element, a beam expanding element, a light path guiding adjusting system, a diffraction optical element and a focusing element which are sequentially arranged between the femtosecond laser and the to-be-processed cross-linked liquid crystal polymer film along the light path direction. The method has the characteristics of non-invasiveness, high processing flexibility and the like, and the prepared photo-induced deformation cross-linked liquid crystal polymer component has good uniformity, high precision, small heat affected zone and wide application prospect in the fields of micro-nano robot driving, micro-actuator, micro-channel valve control and the like.
Description
Technical Field
The invention relates to a device and a method for processing a patterned photo-induced deformation cross-linked liquid crystal polymer component by femtosecond laser, belonging to the technical field of femtosecond laser application.
Background
In a brand new smart material era, development of a manually actuated material that can mechanically deform upon an external stimulus is a recent research hotspot. Based on the mechanical deformation of the material under the external stimulus, the material can be applied to the fields of bionic devices, micro-nano robots, artificial muscles, micro-fluid control and the like. As an intelligent stimulus response material, the liquid crystal polymer has the characteristics of light weight, high specific strength, fatigue resistance and the like, and the ordered structure of the liquid crystal also endows the material with intermolecular synergism and anisotropy, so that the response speed and strain of the material are greatly improved. The liquid crystalline polymers may be crosslinked with each other to form a network of liquid crystalline polymers, referred to as crosslinked liquid crystalline polymers (Cross-linked Liquid crystalline polyers, CLCP). The cross-linked liquid crystal polymer combines the anisotropy of liquid crystal and the rubber elasticity of a polymer network, and has excellent molecular synergistic effect. Under external stimulus (light, heat, electricity, magnetism, etc.), the crosslinked liquid crystal polymer can generate quick reversible shape change by changing the ordered arrangement of the liquid crystal elements. Compared with external stimulus such as heat, electricity, magnetism, etc., the light stimulus can realize remote accurate control, pollution-free, the source is wide, and response speed and direction of cross-linked liquid crystal polymer can also be regulated and controlled through wavelength, illumination intensity, polarization direction etc., so photo-induced deformation response has become the research focus of cross-linked liquid crystal polymer.
At present, the response mechanisms of the photo-induced deformation crosslinking liquid crystal polymers can be generally divided into two types: photochemical effects or photothermal effects. The deformation of the crosslinked liquid crystal polymer induced by the photochemical effect is generally realized by doping a photosensitive group into the liquid crystal polymer, and azobenzene is the most commonly used photosensitive group, and cis-trans isomerization generated under the irradiation of ultraviolet light and blue light can cause the change of the arrangement of liquid crystal elements, so that the crosslinked liquid crystal polymer is triggered to generate macroscopic deformation. The photo-thermal effect induced cross-linked liquid crystal polymer deformation is mainly based on the thermal phase change of photo-thermally generated materials. For both response mechanisms, the crosslinked liquid crystal polymer generally needs to be molded in a liquid crystal box, and the size of the traditional liquid crystal box is generally more than cm, which brings difficulty to the batch and controllable preparation of the micro-size crosslinked liquid crystal polymer components.
Most of the existing photoinduced deformation liquid crystal polymer materials are crosslinked liquid crystal polymers, and the existing chemical crosslinking network causes the materials to be insoluble and infusible, so that the existing photoinduced deformation liquid crystal polymer materials cannot be compatible with the traditional polymer processing method, and the practical application of the existing photoinduced deformation liquid crystal polymer materials is severely restricted. In addition, the cross-linked liquid crystal polymer film has small thickness and large brittleness, and the traditional mechanical cutting technology is difficult to meet the requirement, and the methods such as FIB cutting, electron beam mask processing and the like have the problems of low efficiency, high cost, long period and the like. The femtosecond laser processing has the advantages of non-invasiveness, high processing flexibility, ultra-high peak power, small heat affected zone and the like, and provides a good solution for the mass preparation of the patterned photo-induced deformation crosslinked liquid crystal polymer component.
Disclosure of Invention
The invention provides a device and a method for processing a patterned photo-deformation crosslinked liquid crystal polymer component by using femtosecond laser, which solve the problems of low efficiency, high cost, single processing shape and the like in the aspect of preparing a micro-size crosslinked liquid crystal polymer component in the prior processing technology by using the femtosecond laser to rapidly and directly write out the patterned photo-deformation crosslinked liquid crystal polymer component through programmed control of a moving path of a two-dimensional electric displacement table.
An apparatus for femtosecond laser processing of patterned photo-deformable cross-linked liquid crystal polymer components, comprising: the device comprises a femtosecond laser, a clamping device for realizing horizontal fixation of a cross-linked liquid crystal polymer film to be processed and a three-dimensional positioning mechanism for realizing laser patterning path scanning; the device also comprises a shutter element, a beam adjusting element, a power adjusting element, a beam splitting element, a beam expanding element, a light path guiding adjusting system, a diffraction optical element and a focusing element which are sequentially arranged between the femtosecond laser and the to-be-processed cross-linked liquid crystal polymer film along the light path direction; and the laser beam after beam expansion climbs up and falls down through the light path guiding and adjusting system, and finally, the laser beam is vertically irradiated to the top surface of the to-be-processed cross-linked liquid crystal polymer film after being shaped and focused through the diffraction optical element and the focusing element.
In the invention, the emergent laser energy of the femtosecond laser realizes primary adjustment by adjusting the pulse repetition frequency of the laser, so that the emergent laser energy is higher than the ablation threshold of a sample to be processed.
Preferably, the shutter element is selected from a mechanical shutter or an electric shutter. As a further preferable aspect, the on/off of the femtosecond laser beam is controlled by a shutter element (mechanical shutter).
Preferably, the beam adjusting element is a diaphragm, and the beam waist diameter of the adjusted laser is 2-3 mm. As a further preference, the diaphragm is used to adjust the laser beam waist diameter to 2.5mm.
Preferably, the power adjusting element is selected from a neutral density attenuator or a combination of an optical half-wave plate and a polarizer. As a further preferred option, the femtosecond laser power is continuously adjusted with a power adjustment element (neutral density attenuator) to be slightly above the ablation threshold of the sample film to be processed.
Preferably, the beam splitting element is transparent glass, a part of laser (reflection part) enters the power measuring element after beam splitting, the rest of laser (transmission part) enters the beam expanding element to expand the beam, and finally, the laser is shaped and focused to form a cutting light spot. As a further preferred option, the power measuring element is selected from the group consisting of a photodetector and an oscilloscope.
Preferably, the beam expanding element consists of two convex lenses which are placed in a confocal mode, and the focal lengths of the two convex lenses are 40-60 mm and 80-120 mm respectively. As a further preference, the focal lengths of the two convex lenses are 50mm and 100mm, respectively.
Preferably, the optical path guiding and adjusting system is composed of three 45-degree placed total reflection mirrors, longitudinal climbing and horizontal transmission of the optical path height are achieved through two 45-degree placed total reflection mirrors, the optical path direction is changed by 90 degrees through the other 45-degree placed total reflection mirrors, and the optical path is vertically incident to the surface of a sample to be processed.
Preferably, the diffractive optical element is a flat-top light spot shaper, and the shaped light beam is a flat-top light spot; the focusing element is a focusing lens, and the focal length of the focusing lens is 20-40 mm. Further preferably, the focal length of the focusing lens is 20mm and the focal spot size after focusing the laser is about 10 μm.
Alternatively, one or more of the following elements may be included:
one or more optical path guiding elements;
an illumination source for illuminating the sample;
industrial cameras and liquid crystal displays for assisting in adjusting the position of the sample, optical focusing and monitoring the processing process in real time;
and the computer is used for controlling the laser emitting parameters of the femtosecond laser.
The light path guiding element can adjust the direction of the light path on one hand and meet the light path requirement; meanwhile, the incident angle (pitch or left and right) of the laser can be adjusted, so that the requirements of subsequent elements are met.
As a specific option, the light path guiding element may select a combination of one or more total reflection mirrors. For example, a total reflection mirror is adopted to change the direction of the emergent laser by 90 degrees, and two total reflection mirrors which are arranged in parallel are adopted to further adjust the pitch and the left and right of the light path, so that the emergent laser vertically enters the central positions of the two beam expanding lenses.
As a specific option, the illumination light source is a gooseneck lamp and is used for polishing the crosslinked liquid crystal polymer film, so that the CCD camera can clearly observe the processing process.
Preferably, the three-dimensional positioning mechanism comprises a one-dimensional manual displacement table for adjusting the distance from the sample to be processed to the focusing element in the longitudinal direction (Z axis) and a two-dimensional (XY) electric displacement table for realizing the patterning moving path of the sample to be processed, wherein the one-dimensional manual displacement table is arranged on the two-dimensional electric displacement table, and the two stages are combined to realize the light beam focusing adjustment and the patterning moving path scanning processing.
Preferably, the displacement table controller is used for controlling the two-dimensional electric displacement table.
Preferably, the one-dimensional manual displacement table is provided with a clamping device, the clamping device is composed of two aluminum sheets with holes in the centers, a cross-linked liquid crystal polymer film is clamped between the two aluminum sheets by double faced adhesive tape or screws, and a sample to be processed is partially exposed to the hole area.
Preferably, the photo-response mechanism of the crosslinked liquid crystal polymer film is based on photochemical or photothermal effects. The cross-linked liquid crystal polymer based on photochemical effect uses azobenzene as a photosensitive group, can generate bending deformation under ultraviolet light irradiation, and can recover to a flat state under blue light irradiation; the cross-linked liquid crystal polymer film based on the photo-thermal effect generates bending deformation under the irradiation of blue light, and the light source is removed to restore to a flat state.
As a preferred embodiment, the present invention includes: the device comprises a femtosecond laser, a first total reflection mirror, a mechanical shutter, a diaphragm, a neutral density attenuation sheet, two parallel total reflection mirrors (a second total reflection mirror and a third total reflection mirror) and transparent glass are sequentially arranged along an output light path of the femtosecond laser, a photoelectric detector is arranged along a reflection light path of the transparent glass and is connected with an oscilloscope through a signal wire, a beam expanding lens system (namely the beam expanding element), a light path guiding and adjusting system, a flat-top spot shaper, a focusing lens and a three-dimensional positioning mechanism fixed with a clamping device, and the clamping device is clamped and fixed with a processing object. The processing object, namely the crosslinked liquid crystal polymer film, is fixed on the three-dimensional positioning mechanism through the clamping device, the electric displacement table controller controls the two-dimensional electric displacement table to move along a specified path, laser ablation cutting is completed, and the focusing and processing process of laser on a sample are monitored in real time by the CCD camera. The CCD camera is connected with the liquid crystal display through a signal wire; the two-dimensional electric displacement platform is connected with the displacement platform controller through a signal wire and is controlled by the controller; the femtosecond laser is connected with a computer through a signal wire and is controlled by the computer.
A method of performing femtosecond laser processing of patterned photodeformation cross-linked liquid crystal polymer components, comprising: femtosecond laser vertically irradiates a sample to be processed through a shutter element, beam size adjustment, power adjustment, beam expansion, climbing, falling, shaping and focusing, the sample moves along a designated path relative to a laser focus, a cutting gap is formed in a corresponding path area under laser irradiation, and a closed-loop track is formed by the cutting path to obtain the patterned photo-induced deformation crosslinked liquid crystal polymer component.
Further, the processing process of the patterned photo-deformation cross-linked liquid crystal polymer component comprises the following steps:
s1: programming the moving path of the two-dimensional electric displacement table is completed on the computer, and the program is written into the displacement table controller through the SD memory card;
s2: the cross-linked liquid crystal polymer film is fixed on a three-dimensional positioning mechanism through a clamping device;
s3: the computer controls the femtosecond laser to emit pulse laser, builds a femtosecond processing light path, and makes the emitted laser vertically incident to the surface of a sample to be processed after passing through a mechanical shutter, a beam waist (beam size adjustment), attenuation (power adjustment), beam expansion, climbing, falling, shaping and focusing;
s4: turning on a gooseneck lamp to illuminate the cross-linked liquid crystal polymer film to be processed, and manually adjusting a one-dimensional manual displacement table under a CCD camera to enable a laser focus to be positioned on the surface of the sample to be processed;
s5: and the displacement table controller is used for programming and controlling the two-dimensional electric displacement table to move along a specified path so as to finish the scanning cutting processing of the patterned cross-linked liquid crystal polymer component.
In the invention, before processing, the moving path of the two-dimensional electric displacement table can be determined according to the target processing shape of the cross-linked liquid crystal polymer film to be processed, the path drawing can be performed by utilizing three-dimensional drawing software, then the three-dimensional graph is converted into codes which can be identified by a computer by utilizing conversion software, and the computer readable program is obtained by programming.
Preferably, the center wavelength of the femtosecond laser is 800-1100 nm, the optical field is Gaussian distribution, the pulse width is 120-140 fs, the pulse repetition frequency is 0.8-2 kHz, the power is 15-30mW, and the sample feeding speed is 0.10-0.25 mm/s. As a further preferable mode, the center wavelength of the femtosecond laser is 1030nm, the pulse repetition frequency is 1kHz, the pulse width is 130fs, the laser processing power is 20mW, and the sample feeding speed is 0.15mm/s.
In the invention, the thickness of the crosslinked liquid crystal polymer film is about 5-30 mu m. The minimum effective size of the photo-induced deformation cross-linked liquid crystal polymer component is about 25 mu m, and the heat affected zone of the cutting edge of the material is about 5 mu m.
In the invention, the crosslinked liquid crystal polymer component based on photochemical effect can generate bending deformation under ultraviolet irradiation and recover to a flat state under blue light irradiation; the cross-linked liquid crystal polymer component based on the photo-thermal effect can deform under the irradiation of blue light, and the light source is removed to restore to a flat state.
The device and the method for processing the patterned photo-induced deformation cross-linked liquid crystal polymer component by the femtosecond laser have the advantages that:
(1) The invention utilizes femtosecond laser to directly write and process on the surface of the crosslinked liquid crystal polymer film, realizes the programmed control of the movement track of the sample by a two-dimensional electric displacement table, and can rapidly prepare the photo-induced deformation crosslinked liquid crystal polymer components with various shapes in large batch.
(2) The Gaussian light spot of the femtosecond laser is shaped into the flat-top light spot by using the flat-top light spot shaper, so that the heat affected zone of the cutting edge of the sample is effectively reduced, the processing precision of the material is improved, the minimum effective size of the prepared photo-induced deformation cross-linked liquid crystal polymer component reaches 25 mu m, and the heat affected zone is as low as 5 mu m;
(3) Compared with the prior art, the invention has the advantages of high operation flexibility, low cost, high efficiency, good processing uniformity, small heat affected zone and the like, and is suitable for the precise processing of most film materials.
Drawings
Fig. 1 is a schematic structural diagram of a device for processing patterned photo-deformable cross-linked liquid crystal polymer components based on femtosecond laser.
Wherein: 1 is a femtosecond laser, 2 is a total reflection mirror, 3 is a mechanical shutter, 4 is a diaphragm, 5 is a neutral density attenuation sheet, 6 is a total reflection mirror, 7 is a total reflection mirror, 8 is transparent glass, 9 is a photodetector, 10 is an oscilloscope, 11 is a convex lens, 12 is a convex lens, 13 is a total reflection mirror, 14 is a total reflection mirror, 15 is a total reflection mirror, 16 is a flat-top spot shaper, 17 is a focusing lens, 18 is a CCD camera, 19 is a crosslinked liquid crystal polymer film, 20 is a clamping device, 21 is a one-dimensional manual displacement table, 22 is a two-dimensional electric displacement table, 23 is a two-dimensional electric displacement table controller, 24 is a gooseneck lamp, 25 is a liquid crystal display, and 26 is a computer.
Fig. 2 is a schematic structural view of a clamping device for clamping a sample according to the present invention, wherein: 19 is a crosslinked liquid crystal polymer film, 20a is an upper part of the holding device, and 20b is a lower part of the holding device.
FIG. 3 is a diagram of a cross-linked liquid crystal polymer member based on photo-thermal effect and a cross-linked liquid crystal polymer member based on photochemical effect.
FIG. 4 is a diagram of a cross-linked liquid crystal polymer member based on photochemical effects of different shapes processed according to the invention, comprising: triangle, quadrangle, pentagon, hexagon, circle, wave, five-pointed star, comb tooth, etc.
FIG. 5 is a partial view of a cross-linked liquid crystal polymer component based on photochemical effect processed under (a) no flat-top spot shaper and (b) a flat-top spot shaper according to the present invention.
FIG. 6 is a graph showing the bending and recovery of a crosslinked liquid crystal polymer member based on photochemical effect produced by the present invention under irradiation of ultraviolet light and blue light.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail by the following detailed description with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The invention provides a device and a method for processing a patterned photo-induced deformation cross-linked liquid crystal polymer component by femtosecond laser, wherein in the processing mode, the two-dimensional electric displacement table is used for programmed control of a moving path of a cross-linked liquid crystal polymer film, and the femtosecond laser is used for directly writing a patterned component with any shape on the cross-linked liquid crystal polymer film; in the device performance, the Gaussian beam is shaped by adopting a flat-top spot shaper, so that the photoinduced deformation cross-linked liquid crystal polymer component which has high precision, good uniformity, small heat affected zone, micron level and patterning is obtained, and the prepared cross-linked liquid crystal polymer component has good photoinduced deformation characteristics.
The invention provides a device and a method for processing a patterned photo-deformation cross-linked liquid crystal polymer component by femtosecond laser, wherein the processing light path structure is shown in figure 1, and comprises the following steps: the laser comprises a femtosecond laser 1, a total reflecting mirror 2, a mechanical shutter 3, a diaphragm 4, a neutral density attenuation sheet 5, a total reflecting mirror 6, a total reflecting mirror 7, transparent glass 8, a photoelectric detector 9, an oscilloscope 10, a convex lens 11, a convex lens 12, a total reflecting mirror 13, a total reflecting mirror 14, a total reflecting mirror 15, a flat-top light spot shaper 16, a focusing lens 17, a CCD camera 18, a crosslinked liquid crystal polymer 19, a clamping device 20, a one-dimensional manual displacement table 21, a two-dimensional electric displacement table 22, an electric displacement table controller 23, a gooseneck lamp 24, a liquid crystal display 25 and a computer 26.
The total reflection mirror 2, the total reflection mirror 6 and the total reflection mirror 7 mainly play a role in guiding an optical path, the total reflection mirror 2 horizontally changes the propagation direction of emergent laser by 90 degrees, the total reflection mirror 6 and the total reflection mirror 7 are placed in parallel, the pitching and the left and right of the optical path of the laser are mainly regulated, the laser vertically enters the central position of a beam expanding convex lens (a convex lens 11 and a convex lens 12), the total reflection mirror 2, the total reflection mirror 6 and the total reflection mirror 7 can be increased or decreased according to actual needs, and the set position can be regulated according to the actual needs.
The mechanical shutter 3 is mainly used for controlling the on-off of the laser beam, and the set position can be adjusted according to actual needs.
The diaphragm 4 is mainly used for adjusting the beam waist diameter of laser, and the set position can be adjusted according to actual needs before laser beam expansion.
The neutral density attenuator 5 is mainly used for adjusting laser power, and can also be replaced by other power adjusting elements, such as elements formed by combining a half-wave plate and a polaroid.
The transparent glass 8 mainly plays a role of beam splitting, laser is incident on the transparent glass 8, about 4% of the laser is reflected and is incident on the photoelectric detector 9, the photoelectric detector 9 is connected with the oscilloscope 10 through a signal wire, the oscilloscope 10 measures the reflected laser power, and the laser transmitted through the transparent glass 8 is vertically incident on the center of the beam expansion convex lens for femtosecond laser processing. The laser power can be detected in real time by arranging the photoelectric detector 9 and the oscilloscope 10, and the laser power adjustment in the early stage can be fed back and guided.
The convex lens 11 and the convex lens 12 are placed in a confocal way, and mainly play a role in beam expansion.
The total reflecting mirror 13, the total reflecting mirror 14 and the total reflecting mirror 15 mainly play the guiding roles of lifting and falling the light path and the like, the total reflecting mirror 13 changes the direction of the light path of laser light by 90 degrees, the horizontal transmission is changed into vertical climbing, the total reflecting mirror 14 changes the direction of the light path of the vertically climbing laser light by 90 degrees into horizontal transmission, the total reflecting mirror 13 and the total reflecting mirror 14 play the role of lifting the height of the light path of the laser light longitudinally together, and the total reflecting mirror 15 changes the direction of the light path of the laser light reflected by the total reflecting mirror 14 by 90 degrees and vertically enters the surface of a sample to be processed;
the flat-top light spot shaper 16 mainly plays a role in beam shaping, shapes the Gaussian light spot of the femtosecond laser into a flat-top light spot, and vertically irradiates the surface of the cross-linked liquid crystal polymer film 19 to be processed after focusing through the focusing lens 17.
The crosslinked liquid crystal polymer film 19 is clamped and fixed by a clamping device 20, the clamping device 20 is of a structure with an open hole in the middle, and a part to be processed is exposed to the open hole area of the clamping device 20.
The clamping device 20 is fixed on the one-dimensional manual displacement table 21 through screws or double-sided adhesive tapes, the one-dimensional manual displacement table 21 is fixed on the two-dimensional electric displacement table 22, and the two-dimensional electric displacement table 22 is connected with the displacement table controller 23 through a signal wire and controlled by the controller 23. The one-dimensional manual displacement table 21 is mainly used for adjusting the initial position of the crosslinked liquid crystal polymer film 19 to be processed (even if the laser focus is positioned at the surface of the crosslinked liquid crystal polymer film 19). The two-dimensional electric displacement table 22 is mainly used for realizing the two-dimensional movement of the cross-linked liquid crystal polymer film 19 to be processed in the processing process.
Fig. 2 is a schematic view of a structure of a clamping device for clamping a sample according to the present invention, wherein the clamping device 20 includes a clamping device upper portion 20a and a clamping device lower portion 20b. The upper part 20a and the lower part 20b of the clamping device are plate-shaped structures with holes in the middle, the size of each hole corresponds to the size of the to-be-processed area of the to-be-processed cross-linked liquid crystal polymer film 19 and is slightly smaller than the outer edge size of the to-be-processed cross-linked liquid crystal polymer film 19, so that the to-be-processed cross-linked liquid crystal polymer film 19 can be clamped and fixed. In the clamping process, the crosslinked liquid crystal polymer film 19 is firstly laid flat on the open hole area of the lower part 20b of the clamping device, and then the upper part 20a of the clamping device is bonded with the lower part 20b of the clamping device through double faced adhesive tape or screws, so that the sample (the crosslinked liquid crystal polymer film 19) is in a flat state between the upper part and the lower part, the periphery of the sample is fixed, and meanwhile, the part of the sample to be processed is kept exposed to the open hole area.
In the processing process, the femtosecond laser 1 generates femtosecond laser, the propagation direction of the beam is changed by 90 degrees after the femtosecond laser passes through the total reflection mirror 2, the reflected laser firstly passes through the mechanical shutter 3, then passes through the diaphragm 4 to adjust the beam waist diameter, and then is incident on the neutral density attenuation sheet 5, after the neutral density attenuation sheet 5 is adjusted to proper power, the emergent laser passes through the total reflection mirror 6 and the total reflection mirror 7 to adjust the pitch and the left and right of the optical path, and is incident on the transparent glass 8, after the beam is split (part of the emergent laser is reflected and the other part of the emergent laser is transmitted) through the transparent glass 8, the reflected laser passes through the transparent glass 8 and is incident on the photoelectric detector 9, the photoelectric detector 9 is connected with the oscilloscope 10, the reflected laser power is measured by the oscilloscope 10, the transmitted laser passes through the transparent glass 8 and vertically enters the center of the beam expanding system formed by the convex lens 11 and the convex lens 12 along the center axis, after beam expansion, the femtosecond laser vertically climbs through the total reflection mirror 13, horizontally propagates through the total reflection mirror 14, vertically and downwards enters the flat-top light spot shaper 16 through the total reflection mirror 15, is shaped through the flat-top light spot shaper 16, vertically enters the surface of the crosslinked liquid crystal polymer film 19 after being focused through the focusing lens 17, adjusts the distance from the crosslinked liquid crystal polymer film 19 to the focusing lens 17 on the one-dimensional manual displacement table 21, enables the laser focus to be positioned on the surface of the crosslinked liquid crystal polymer film 19, and controls the two-dimensional electric displacement table controller 23 to drive the crosslinked liquid crystal polymer film 19 on the two-dimensional electric displacement table 22 to move along a designated path to complete cutting, so that the patterned photo-induced deformation crosslinked liquid crystal polymer member is obtained.
The gooseneck lamp 24 is used for illuminating the crosslinked liquid crystal polymer film 19 so as to observe the focusing of the crosslinked liquid crystal polymer film 19 by the focusing lens 17 under the CCD camera 18 and monitor the whole processing process in real time.
The CCD camera 18 is connected with the liquid crystal display 25 through a signal wire, and the liquid crystal display 25 images the processing process in real time.
The femtosecond laser 1 is connected with a computer 26 through a signal wire and is controlled by the computer 26.
Examples: femtosecond laser processing of cross-shaped photo-induced deformation cross-linked liquid crystal polymer components.
In the embodiment of the invention, the femtosecond laser is ytterbium-doped femtosecond fiber laser (Tangerine HP) of the Amplitude company, the center wavelength of the femtosecond laser is 1030nm, the pulse width is 130fs, the highest repetition frequency is 35MHz, the single pulse energy is more than 200 mu J, and the light field distribution is Gaussian distribution; the cross-linked liquid crystal polymer film uses azobenzene as a photosensitive group, can be bent under ultraviolet light irradiation, can recover a flat state under blue light irradiation, has a film thickness of about 30 mu m and a size of 2cm multiplied by 2cm, and can be replaced by a cross-linked liquid crystal polymer film based on photo-thermal effect as an alternative scheme.
The specific processing steps of this embodiment are as follows:
s1: the computer 26 completes the programming of the cross-shaped moving path, and writes the program into the two-dimensional electric displacement table controller 23 through the SD memory card;
s2: the crosslinked liquid crystal polymer film 19 is fixed on a three-dimensional positioning mechanism formed by a one-dimensional manual displacement table 21 and a two-dimensional electric displacement table 22 through a clamping device 20;
s3: the computer 26 controls the femtosecond laser 1 to emit pulse laser, all optical path elements are sequentially arranged on an optical platform according to the sequence of the figure 1, the optical path is adjusted to enable the femtosecond laser to vertically enter the surface of the crosslinked liquid crystal polymer film 19 after passing through the total reflection mirror 2, the mechanical shutter 3, the diaphragm 4, the neutral density attenuation sheet 5, the total reflection mirror 6, the total reflection mirror 7, the transparent glass 8, the convex lens 11, the convex lens 12, the total reflection mirror 13, the total reflection mirror 14, the total reflection mirror 15, the flat-top spot shaper 16 and the focusing lens 17, the pulse repetition frequency of the femtosecond laser is set to be 1kHz, the diaphragm 4 is adjusted to enable the laser beam waist diameter to be 2.5mm, and the neutral density attenuation sheet 5 is rotated to enable the average laser power to be 20mW.
S4: the gooseneck lamp 24 is turned on to illuminate the crosslinked liquid crystal polymer film 19, the longitudinal feeding of the one-dimensional manual displacement table 21 is regulated under the CCD camera 18, so that the focus of the femtosecond laser focused by the focusing lens 17 is positioned on the surface of the crosslinked liquid crystal polymer film 19, and the whole processing process is monitored in real time by means of the CCD camera 18 and the liquid crystal display screen 25.
S5: setting the feeding speed of the two-dimensional electric displacement table to be 0.15mm/S, loading the program in the step S1 by using the two-dimensional electric displacement table controller 23, and moving the two-dimensional electric displacement table along a specified path to complete the laser ablation cutting of the cross-shaped cross-linked liquid crystal polymer component.
FIG. 3 is a diagram of a cross-linked liquid crystal polymer member based on photo-thermal effect and a cross-linked liquid crystal polymer member based on photochemical effect. Wherein the cross-shaped cross-linked liquid crystal polymer component has a width of 120 μm and a height of 1200 μm, and the diameter of the circular cross-linked liquid crystal polymer component is about 1000 μm.
FIG. 4 is a schematic representation of a cross-linked liquid crystal polymer member based on photochemical effects of different shapes processed according to the invention, comprising: triangle, quadrangle, pentagon, hexagon, circle, wave, five-pointed star, comb tooth, etc. In the processing process, the center wavelength of the femtosecond laser is 1030nm, the pulse width is 130fs, the pulse repetition frequency is 1kHz, the average power of the laser is 20mW, and the feeding speed of the electric displacement table is 0.15mm/s.
FIG. 5 is a partial view of a cross-linked liquid crystal polymer component based on photochemical effect processed under (a) no flat-top spot shaper and (b) a flat-top spot shaper according to the present invention. When the flat-top spot shaper is not used, the light field distribution of the femtosecond laser is Gaussian distribution, the edge heat affected zone of the processed cross-linked liquid crystal polymer component is 10-15 mu m, and after the flat-top spot shaper shapes the laser beam, the femtosecond laser is changed from Gaussian spots to flat-top spots, and the edge heat affected zone of the processed cross-linked liquid crystal polymer component is about 5 mu m.
FIG. 6 shows the bending and recovering behavior of the cross-linked liquid crystal polymer member based on photochemical effect under the action of ultraviolet light and blue light, wherein the white arrow direction represents the alignment direction of the liquid crystal element.
The foregoing is a further detailed description of the invention in connection with specific embodiments, and it is not intended that the invention be limited to such description. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the invention, and these should be considered to be within the scope of the invention.
Claims (5)
1. A method for processing a patterned photo-induced deformation cross-linked liquid crystal polymer component by femtosecond laser is characterized in that the femtosecond laser passes through a shutter element, and a formed focusing light spot is vertically incident on the surface of a cross-linked liquid crystal polymer film to be processed through beam size adjustment, power adjustment, beam expansion, climbing, falling, shaping and focusing, a sample moves along a set path relative to the laser, and a cutting gap is formed in a corresponding path area under the irradiation of the laser, so that the patterned cross-linked liquid crystal polymer component is obtained; the deformation mechanism of the crosslinked liquid crystal polymer film is based on photochemical effect or photo-thermal effect; the center wavelength of the femtosecond laser is 800-1100 nm, the light field is Gaussian, the pulse width is 120-140 fs, the pulse repetition frequency is 0.8-2 kHz, the processing power is 15-30mW, and the moving speed of the electric displacement table is 0.10-0.25 mm/s; the thickness of the crosslinked liquid crystal polymer film is 5-30 mu m;
the device for processing the patterned photo-deformation cross-linked liquid crystal polymer component by the femtosecond laser comprises: the device comprises a femtosecond laser, a clamping device for realizing horizontal fixation of a cross-linked liquid crystal polymer film to be processed and a three-dimensional positioning mechanism for realizing laser patterning path scanning; the device also comprises a shutter element, a beam adjusting element, a power adjusting element, a beam expanding element, a light path guiding adjusting system, a diffraction optical element and a focusing element which are sequentially arranged between the femtosecond laser and the to-be-processed cross-linked liquid crystal polymer film along the light path direction; the laser beam after beam expansion climbs up and falls down through the light path guiding and adjusting system, and finally, the laser beam is vertically irradiated to the top surface of the to-be-processed cross-linked liquid crystal polymer film after being shaped and focused through the diffraction optical element and the focusing element;
the device also comprises a beam splitting element and a power measuring element, wherein the beam splitting element and the power measuring element are arranged behind the power adjusting element; a part of laser split by the beam splitting element is collected by the power measuring element, and the other part of laser enters the beam expanding element to expand;
the shutter element is selected from a mechanical shutter or an electric shutter and is used for controlling the on-off of a laser beam; the beam adjusting element is a diaphragm, and the beam waist diameter of the adjusted laser is 2-3 mm; the power adjusting element is selected from a neutral density attenuation sheet or a combination of an optical half-wave plate and a polaroid, and the power adjusting element is adjusted to enable the femtosecond laser power to reach above a sample ablation threshold; the beam expanding element consists of two convex lenses which are placed in a confocal mode, and the focal lengths of the two convex lenses are 40-60 mm and 80-120 mm respectively; the diffraction optical element is a flat-top light spot shaper, and the flat-top light spot shaper is used for shaping Gaussian light spots of the outgoing laser into flat-top light spots;
the clamping device consists of two aluminum sheets with holes in the centers, the to-be-processed cross-linked liquid crystal polymer film is clamped between the two aluminum sheets, the to-be-processed part is exposed to the hole opening area, and the clamping device is fixed on the three-dimensional positioning mechanism through double faced adhesive tape or screws.
2. The method for processing patterned photo-deformable cross-linked liquid crystal polymer components by femtosecond laser according to claim 1, wherein the optical path guiding and adjusting system comprises three 45-degree placed total reflection mirror combinations, longitudinal climbing and horizontal transmission of the optical path height are realized by using two 45-degree placed total reflection mirrors, the optical path direction is changed by 90 degrees by using another 45-degree placed total reflection mirror, and the optical path guiding and adjusting system vertically enters a horizontally arranged cross-linked liquid crystal polymer film to be processed.
3. The method of claim 1, wherein the beam splitting element is transparent glass; the power measurement element is selected from a combination of a photodetector and an oscilloscope or a power meter.
4. The method of femtosecond laser processing of patterned photovariable crosslinked liquid crystal polymer member according to claim 1, wherein the three-dimensional positioning mechanism includes:
a two-dimensional electric displacement table for realizing horizontal two-dimensional movement of the cross-linked liquid crystal polymer film to be processed in the processing process;
and a one-dimensional manual displacement table fixed on the two-dimensional electric displacement table for focusing the laser.
5. The method of femtosecond laser processing of patterned photovariable crosslinked liquid crystal polymer member according to claim 1, further comprising the following elements:
one or more optical path guiding elements;
an illumination source for illuminating the sample;
industrial cameras and liquid crystal displays for assisting in adjusting sample position, optical focusing and real-time monitoring of the process;
and the computer is used for controlling the laser emitting parameters of the femtosecond laser.
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