Method for manufacturing multi-scale ordered structure through femtosecond laser space-time shaping regulation and control

Abstract

The invention discloses a method for manufacturing a multi-scale ordered structure through femtosecond laser space-time shaping regulation and control, and belongs to the technical field of femtosecond laser application. The implementation method comprises the following steps: preparing precursor processing hydrogel containing high-response micro elements; building a femtosecond laser shaping light path processing platform; a hydrogel precursor is processed by adopting a method of coordinately regulating and controlling exposure time by modulating a light field through airspace shaping, and the shape, the characteristics and the distribution of an additive manufacturing structure are controlled; the femtosecond laser Gaussian pulse is modulated into any light field intensity distribution based on a spatial light field shaping technology; controlling the cavitation radius of the local area based on regulation and control of the exposure time; and the machined additive manufacturing structure is subjected to post-treatment so that the additive manufacturing structure can be cured. Polymer forming control is carried out by regulating and controlling the liquid phase separation process based on the responsiveness of a high-responsiveness micro-element to laser, and the processing morphology is regulated and controlled based on the polymer forming control. By means of the method, the ordered structure with the cross-scale features controllable in position, shape and direction can be manufactured.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a multi-scale ordered structure by spatiotemporal shaping control of femtosecond laser, and in particular to a femtosecond laser additive manufacturing method for a cross-scale functional structure, belonging to the technical field of femtosecond laser application. Background Art

[0002] Additive manufacturing, also known as 3D printing, is a manufacturing technology that builds objects layer by layer by stacking or solidifying materials based on digital models. The processing process is made more controllable by spatially shaping light, and the highly responsive micro-elements of the processed material can be coupled and solidified in the direction of a specific light field. This improves manufacturing efficiency and freedom. Therefore, collaborative shaping femtosecond laser processing has application prospects in the field of additive manufacturing; it can produce a variety of devices and has application value in the fields of metamaterials, bionic structural materials, and biomedicine.

[0003] TPP two-photon polymerization manufacturing technology is a micro-nanoscale additive manufacturing technology based on the principle of two-photon absorption. Compared with methods such as fused deposition and direct ink writing, its selective polymerization method has the advantage of high manufacturing resolution and can break through the diffraction limit when processing some features. Therefore, TPP two-photon polymerization is often used to manufacture complex 3D micro / nano structures with high spatial resolution.

[0004] Taking advantage of the high responsiveness of micro-elements, the direction of multi-layer micro-elements can be controlled by changing the intensity and direction of the light field. By combining this method with the processing process, complex features with certain directional regularity can be prepared. Compared with traditional additive manufacturing, it is more flexible.

[0005] Most additive manufacturing processes that form complex features require digital light processing. Although these methods can optimize the feature manufacturing process by controlling the shape of the light field, the integrity of the processing process makes it impossible to operate locally on the material. Therefore, the properties of the processed features and the size of the local features are uncontrollable. Based on laser additive manufacturing, plastic femtosecond laser additive manufacturing adopts a layer-by-layer solidification manufacturing method and uses micro-element materials with high responsiveness to physical fields to achieve controllable local feature directions and minimize local feature sizes. Summary of the invention

[0006] The purpose of the present invention is to provide a method for manufacturing a multi-scale ordered structure by spatiotemporal shaping of a femtosecond laser, which can manufacture an ordered structure with cross-scale features that are position-controllable, shape-controllable, and direction-controllable. The present invention prepares a PEGDA (polyethylene glycol (diol) diacrylate) hydrogel precursor doped with a highly responsive micro-element, and the hydrogel precursor has good biocompatibility and low polymerization. It is placed in a glass slide container (Φ15mm, depth 0.05mm) by a drop coating method. A 1000Hz femtosecond laser is polymerized on the surface of the hydrogel precursor using a 20x objective lens. Due to two-photon polymerization, the hydrogel precursor doped with a highly responsive micro-element can undergo a polymerization reaction at a power of 5wm with a continuous laser. By changing the shape of the light field, the position and orientation of the micro-element are controlled, and the micro-element is locally self-assembled by the polymerization reaction of the femtosecond laser and the hydrogel precursor to form a single-layer feature. Then, the position of the laser focus in the z direction is adjusted to print the second layer of features and self-assemble the micro-element. By printing layer by layer, an ordered structure with cross-scale features of different morphologies is formed.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] The present invention discloses a method for manufacturing a multi-scale ordered structure by spatiotemporal shaping control of a femtosecond laser, comprising the following steps:

[0009] Step 1: preparing a precursor-processed hydrogel containing highly responsive micro-elements;

[0010] Step 2: Build a femtosecond laser shaping optical path processing platform;

[0011] Step 3: Based on the femtosecond laser shaping optical path processing platform built in step 2, the hydrogel precursor is processed by using a method of spatial shaping modulated light field to coordinately control exposure time, so as to control the shape, characteristics and distribution of the additive manufacturing structure;

[0012] Step 4: Post-process the additive manufacturing structure processed in step 3 to solidify it.

[0013] Step 5: Based on the responsiveness of the highly responsive micro-element to the laser, the polymer molding is controlled by regulating the process of liquid phase separation, and the processing morphology is controlled based on this.

[0014] As a preferred embodiment, the specific implementation method of step three is:

[0015] By modulating the exposure time, the size of the cavitation bubble and thus the size of the aggregated voids can be controlled to obtain bionic structures with different pore sizes.

[0016]

[0017] Among them, the formula fitting function is the Psdvoigt model, the value range of the initial cavitation radius y0 is 4.17132±0.339, the value range of the time offset coefficient tc is 1.94262±0.017, the value range of the radius amplitude coefficient a is 50.44879±36.33316, the value range of the time width parameter w is 2.63169±0.48158, and the value range of the mixing parameter r1 is 0.09023±0.091.

[0018] Preferably, the laser beam power density range is 13.6 J / cm 2 Up to 30J / cm 2 By adjusting the light field shape and exposure time, the cavitation mutation range is reduced to less than 20μm, and the mutation range time is 0μs-2μs.

[0019] Preferably, the method for preparing a precursor-processed hydrogel containing highly responsive micro-elements in step 1 is:

[0020] 1 g of NIPAM (97%) was added to 4 ml of PEGDA (Mn700) solution, and NIPAM was completely dissolved after stirring to obtain a NIPAM-PEGDA composite monomer solution. 1 ml of the composite monomer solution, 2.5 mg of methylene blue and 50 μl of methanol were fully mixed and magnetically stirred for 12 hours to ensure that the components in the solution were completely mixed to obtain a hydrogel precursor. Subsequently, the precursor solution was divided into small doses of solution and stored in a light-free environment to prevent it from crystallizing and solidifying.

[0021] Preferably, step 2 builds a femtosecond laser shaping optical path processing platform, including a femtosecond laser, a transmission mirror, an aperture, a pulse time shaper, a beam splitter, a spatial light modulator, a first plano-convex mirror, a second plano-convex mirror, a reflector, an attenuation plate, a 1 / 2 wave plate, a vortex wave plate, an electrically controlled switch, a dichroic mirror, a 20x oil immersion lens, a processing sample, a six-axis translation stage, an illumination light source, a CCD camera and a computer control system.

[0022] The laser is generated by a femtosecond laser, and enters the pulse light shaper through a transmission mirror and a grating. After pulse shaping, a beam splitter and a spatial light modulator, the light after spatial domain correction passes through two convex lenses for frequency domain correction, and then passes through an attenuation plate, a 1 / 2 wave plate, and a vortex wave plate to shape the light spot into a vortex light with angular momentum. The processing switch is controlled by a shutter, and then the shaped light passes through a dichroic mirror and passes through the processing element and the observation element respectively. The light is focused into the sample through a 20x oil-immersion objective lens for polymerization processing. The CCD receives the optical signal to monitor the processing site, and the processing process is realized through a computer control system.

[0023] Preferably, in step three,

[0024] Spatial shaping: based on spatial light field shaping technology, the original femtosecond laser Gaussian pulse is modulated into an arbitrary light field intensity distribution, thereby achieving controlled processing of complex structures;

[0025] Exposure time control: the size of the bubble radius in the local area is controlled based on the exposure time.

[0026] Beneficial effects:

[0027] 1. The present invention provides a method for manufacturing multi-scale ordered structures by spatiotemporal shaping control of femtosecond lasers, and proposes a method for shaping femtosecond laser processing, which utilizes the high physical field responsiveness of micro-elements and TPP two-photon polymerization technology to achieve fine and controllable manufacturing of local features.

[0028] 2. A method of manufacturing multi-scale ordered structures by spatiotemporal shaping of femtosecond lasers of the present invention adopts a spatiotemporal frequency deviation coordinated shaping femtosecond laser processing system based on electronic dynamic control, which is used to control the position, size, and spatial distribution of aggregate features in additive manufacturing. Pulse time shapers and spatial shapers are used to adjust the spatiotemporal distribution of femtosecond lasers. The light field shaping effects under different adjustment methods are different (see the attached figure), so the characteristic morphology and position in the additive manufacturing process can be adjusted.

[0029] 3. The present invention provides a method for manufacturing multi-scale ordered structures by spatiotemporal shaping control of femtosecond lasers. The method is based on modulating the light field to control the liquid phase separation process during the polymerization of the precursor, which can modulate the polymerization process and help form a porous bionic structure.

[0030] 4. The present invention provides a method for manufacturing multi-scale ordered structures by spatiotemporal shaping control of femtosecond lasers, and obtains a Psdvoigt model for constructing bionic structures with different pore sizes. By quantitatively modulating the exposure time, the size of the cavitation bubbles is controlled, and then the size of the polymerized voids is controlled, thereby achieving quantitative, precise, and controllable manufacturing of bionic structures with different pore sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A flow chart of the invention for shaping femtosecond laser to produce multi-scale ordered structures;

[0032] Figure 2 A schematic diagram of the optical path for implementing time / space / frequency multi-domain shaping femtosecond laser processing in the present invention;

[0033] Among them: 1- femtosecond laser, 2- transmission mirror, 3- aperture, 4- pulse time shaper, 5- beam splitter, 6- spatial light modulator, 7- first plano-convex mirror, 8- second plano-convex mirror, 9- reflecting mirror, 10- attenuation plate, 11- 1 / 2 wave plate, 12- vortex wave plate, 13- electric control switch, 14- dichroic mirror, 15- 20 times oil immersion lens, 16- processed sample, 17- six-axis translation stage, 18- illumination light source, 19- CCD camera, 20- computer control system.

[0034] Figure 3 This is a sample of a processed precursor solution containing highly responsive micro-elements prepared in the present invention.

[0035] Figure 4 These are optical microscopy images of the processing results of the multilayer rectangular array PEGDA polymer of the present invention, wherein Figure a) is a scan of a single-layer 3x3 matrix, Figure b) is a pyramid array, and Figures c) and d) are scans of a multilayer matrix.

[0036] Figure 5 Figure 2 shows the bionic structure diagrams under and without modulation. Figure a) shows the processing result of the unmodulated light field. The liquid phase separation process is violent, and most of the gap radii are above 40 microns. Figure b) shows the processing result of the modulated light field. Most of the gap radii are around 20 microns. The control effect is significant, which is consistent with the time-radius image.

[0037] Figure 6 The figures are comparative diagrams of the light field modulated liquid phase separation process of the present invention, wherein a) and b) are schematic diagrams of liquid phase separation occurring during the processing, c) is an image of the change of the cavitation radius at a certain position of the structure over time under the unmodulated light field processing with different powers, and d) is an image of the change of the cavitation radius at a certain position of the structure over time under the two different light field processings with the same power. The modulated light field has a significant effect on reducing the cavitation radius.

[0038] Figure 7 It is a fitting process diagram of the liquid phase separation process of the unmodulated light field and modulated light field processed polymer of the present invention. Figure a) is a relationship diagram between the structure cavitation radius and time under the action of the unmodulated light field, and Figure b) is a relationship diagram between the structure cavitation radius and time under the action of the modulated light field.

[0039] Figure 8 Schematic diagram of the modulated light field of the present invention. DETAILED DESCRIPTION

[0040] The present invention is described in detail below with reference to the accompanying drawings and implementation examples.

[0041] Example 1

[0042] The average power density of the laser beam is 13.6 J / cm 2, the laser moving speed is 500 μm / s. Under this working condition, the hydrogel precursor is processed so that during the process of forming the structure, its overall pore radius is described by formula 1)

[0043]

[0044] Among them, the formula fitting function is the Psdvoigt model, the value range of the initial cavitation radius y0 is 4.17132±0.339, the value range of the time offset coefficient tc is 1.94262±0.017, the value range of the radius amplitude coefficient a is 50.44879±36.33316, the value range of the time width parameter w is 2.63169±0.48158, and the value range of the mixing parameter r1 is 0.09023±0.091.

[0045] A method for manufacturing multi-scale ordered structures by spatiotemporal shaping control of femtosecond laser, the specific implementation steps are as follows: Step 1, prepare a hydrogel precursor (PEGDA) containing highly responsive micro-elements; add 1g NIPAM (97%) to 4ml PEGDA (Mn700) solution, stir to completely dissolve NIPAM, and prepare a NIPAM-PEGDA composite monomer solution, and fully mix 1ml of the composite monomer solution, 2.5mg methylene blue and 50μl methanol, and stir magnetically for 12 hours to ensure that the components in the solution are completely mixed to prepare a hydrogel precursor. Subsequently, the precursor solution is divided into small doses of solution and stored in a light-free environment to prevent it from crystallization and solidification. The prepared precursor solution is placed in a prepared glass slide container (Φ15mm, depth 0.05mm) by a drop coating method;

[0046] Step 2, build a femtosecond laser shaping optical path processing platform; the platform includes: a femtosecond laser 1, a transmission mirror 2, an aperture 3, a pulse time shaper 4, a beam splitter 5, a spatial light modulator 6, a first plano-convex mirror 7, a second plano-convex mirror 8, a reflector 9, an attenuation plate 10, a 1 / 2 wave plate 11, a vortex wave plate 12, an electric switch 13, a dichroic mirror 14, a 20x oil immersion lens 15, a processing sample 16, a six-axis translation stage 17, an illumination light source 18, a CCD camera 19 and a computer control system 20.

[0047] Step three, use the method of spatiotemporal shaping femtosecond laser collaborative manufacturing to perform additive manufacturing of features, and control the position, morphology, and size of the formed features. Specifically, it includes: (1) Time domain shaping, modulating a single femtosecond laser pulse into a femtosecond laser pulse train, setting the pulse interval and pulse energy ratio, and controlling the electronic temperature / lattice temperature of the hydrogel precursor based on the absorption of the incident laser pulse train photon energy by the electronic system in the material, thereby achieving control of the diameter of a single polymerization point; (2) Spatial shaping, based on the spatial light field shaping technology, modulating the original femtosecond laser Gaussian pulse into a vortex light field intensity distribution, thereby achieving control of the feature spatial distribution; (3) Based on highly responsive micro-elements, by regulating the magnitude of the light field intensity, the direction and position of the local micro-elements in the precursor can be controlled. (4) Based on the modulated light field to regulate the liquid phase separation process during the polymerization of the precursor, the polymerization process can be modulated, which helps to form a porous bionic structure. The modulation of the light field can adjust the liquid phase separation process such as Figure 6 shown.

[0048] Step 4: Let the processed sample stand for 12 hours to solidify, then rinse the remaining precursor with ethanol solution, and then dry it in a dryer to finally obtain the processing characteristics.

[0049] Example 2

[0050] A method for manufacturing multi-scale ordered structures by spatiotemporal shaping control of femtosecond laser, specifically using a drop coating method to process samples such as Figure 3 Then build Figure 2The femtosecond laser processing optical path based on time / space / frequency shaping is shown to perform femtosecond laser processing on the sample. A time / space / frequency shaping femtosecond laser processing optical path is constructed, in which the femtosecond laser 1 is set to the Continuous trigger mode, and emits a continuous pulse with a Gaussian distribution frequency of 1000 Hz. It passes through the transmission mirror 2, the aperture 3, and the pulse light shaper 4 in sequence, and a beam splitter 5 separates a beam of sub-pulses to the spatial light modulator 6. After the shaped light beam reflects the beam splitter 5, it enters the 4f system composed of a pair of plano-convex mirrors 7 and 8 with the same focal length, and then reflects through the reflector 9 and the dichroic mirror 14, and is focused on the surface of the sample 16 by the 20x objective lens 15, wherein the layered high-response micro-element inside the sample is regularized and oriented under the regulation of the local specific light field. The computer system controls the opening and closing of the electric shutter 13, the pulse train design of the pulse time shaper 4, the input of the spatial light modulator 6, the movement of the six-axis translation stage 17, and the imaging of the CCD camera 19. The light field is shaped into a perfect vortex shape by using a vortex phase plate and a 1 / 2 wave plate. In order to eliminate the diffraction effect caused by the propagation of the light beam in the air, a 4f system is used to propagate the spatially shaped light beam to the incident surface of the objective lens 15. In addition, due to the imaging system composed of the illumination light source 19, the dichroic mirror 14, and the CCD camera. The processed sample is cleaned with an ethanol solution, then placed in a dryer for drying, and left to stand at room temperature for 12 hours to solidify.

[0051] The parameters of the femtosecond laser (Spitfire Ace-35F, Spectra Physics) used in the experiment are as follows: central wavelength of 800nm, pulse width of 60fs, trigger mode of continuous triggering (Continuous), spatial light modulator resolution of 1920×1080 pixels, and pixel pitch of 8um.

[0052] A method for manufacturing multi-scale ordered structures by spatiotemporal shaping control of femtosecond laser, the specific implementation steps are as follows:

[0053] (1) Weigh 0.001 g of highly responsive micro-elements and mix them with PEGDA using a high-precision electronic scale, and use a centrifuge to fully mix the highly responsive micro-elements with the additive manufacturing hydrogel precursor PEGDA.

[0054] (2) Use a pipette to take 2uL of the pre-processed precursor solution into a glass slide container (Φ15mm, depth 0.05mm) and shake it evenly.

[0055] (3) Turn on the computer control system 20, the femtosecond laser 1, and the illumination light source 18. Adjust the processing light path so that the incident direction of the laser is perpendicular to the processed sample, and the laser is focused on the surface of the sample after passing through the optical element.

[0056] (4) The spatial light modulator 6 is turned on, and the computer control system inputs the phase map into the DMD. After passing through the DMD, the conventional and linearly polarized Gaussian beams are shaped into Gaussian beams without light field errors. The light field pattern is as follows: Figure 8 shown.

[0057] (5) Adjust the fast axes of the half wave plate and the vortex wave plate so that the vortex shaping light reaches the optimal state.

[0058] (6) The incident laser power is adjusted by rotating the attenuation plate 10, and the laser is focused on the surface of the sample to be processed through the 20x objective lens 15, so as to regulate the chemical bond connection between the micro-elements in the bulk solution and to cause polymerization reaction with PEDGA; the computer control system 20 controls the movement of the six-axis translation stage 17 in the xy direction to perform processing at a specified position on the surface of the sample. After a layer of structure is processed, the z-axis position of the sample is adjusted by the six-axis translation stage 18 and the spatial light shaping pattern input by the computer control system 20 is switched at the same time, so as to realize layer-by-layer additive manufacturing processing.

[0059] (7) The residual waste liquid on the surface of the processed sample was rinsed with anhydrous ethanol and placed in a 50°C dryer for 10 min. Finally, it was placed at room temperature for 12 h for curing reaction to form the final structure.

[0060] (8) Statistical cavitation data obtained during processing to verify the effect of light field on liquid phase separation and the attenuation effect of liquid phase separation caused by modulated light field. The data in the following table are all at 13.6 J / cm 2 The results are shown in Table 1.

[0061] Table 1 Statistical table of the relationship between cavitation radius and time under different light fields

[0062]

[0063] The specific description above further illustrates in detail the purpose, technical solutions and beneficial effects of the invention. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for manufacturing multi-scale ordered structures by spatiotemporal shaping control of femtosecond lasers, characterized in that: The steps include: Step 1: preparing a precursor-processed hydrogel containing highly responsive micro-elements; Step 2: Build a femtosecond laser shaping optical path processing platform; Step 3: Based on the femtosecond laser shaping optical path processing platform built in step 2, the hydrogel precursor is processed by using a method of spatial shaping modulated light field to coordinately control exposure time, so as to control the shape, characteristics and distribution of the additive manufacturing structure; Step 4: Post-processing the additive manufacturing structure processed in step 3 to solidify it; Step 5: Based on the responsiveness of the highly responsive micro-element to the laser, the polymer molding is controlled by regulating the process of liquid phase separation, and the processing morphology is controlled based on this.

2. A method for manufacturing multi-scale ordered structures by spatiotemporal shaping control of femtosecond laser as claimed in claim 1, characterized in that: In step three, By modulating the exposure time, the size of the cavitation bubble and thus the size of the aggregated voids can be controlled to obtain bionic structures with different pore sizes. Among them, the formula fitting function is the Psdvoigt model, the value range of the initial cavitation radius y0 is 4.17132±0.339, and the time offset coefficient t c The value range of is 1.94262±0.017, the value range of the radius amplitude coefficient a is 50.44879±36.33316, the value range of the time width parameter w is 2.63169±0.48158, and the value range of the mixing parameter r1 is 0.09023±0.

091.

3. A method for manufacturing multi-scale ordered structures by spatiotemporal shaping control of femtosecond laser as claimed in claim 2, characterized in that: Laser beam power density range is 13.6J / cm 2 Up to 30J / cm 2 ; By adjusting the light field shape and exposure time, the cavitation mutation range is reduced to within 20μm, and the mutation range time is 0μs-2μs.

4. The method for manufacturing multi-scale ordered structures by spatiotemporal shaping of femtosecond laser as claimed in claim 1, characterized in that: Step 1: The method for preparing a precursor-processed hydrogel containing highly responsive micro-elements is: 1 g of NIPAM was added to 4 ml of PEGDA solution, and NIPAM was completely dissolved after stirring to obtain a NIPAM-PEGDA composite monomer solution. 1 ml of the composite monomer solution, 2.5 mg of methylene blue and 50 μl of methanol were fully mixed and magnetically stirred for 12 hours to ensure that the various components in the solution were completely mixed to obtain a hydrogel precursor; then, the precursor solution was divided into small doses of solution and stored in a light-free environment to prevent it from crystallization and solidification.

5. The method for manufacturing multi-scale ordered structures by spatiotemporal shaping control of femtosecond laser as claimed in claim 1, characterized in that: Step 2: Build a femtosecond laser shaping optical path processing platform, including a femtosecond laser, a transmission mirror, an aperture, a pulse time shaper, a beam splitter, a spatial light modulator, a first plano-convex mirror, a second plano-convex mirror, a reflector, an attenuation plate, a 1 / 2 wave plate, a vortex wave plate, an electric switch, a dichroic mirror, a 20x oil immersion lens, a processing sample, a six-axis translation stage, an illumination light source, a CCD camera, and a computer control system; The laser is generated by a femtosecond laser, passes through a transmission mirror and a grating into a pulse light shaper, and then passes through pulse shaping, a beam splitter and a spatial light modulator. The light after spatial domain correction passes through two convex lenses for frequency domain correction, and then passes through an attenuation plate, a 1 / 2 wave plate and a vortex wave plate to shape the light spot into a vortex light with angular momentum. The processing switch is controlled by a shutter, and then the shaped light passes through a dichroic mirror and passes through the processing element and the observation element respectively. The light is focused into the sample through a 20x oil-immersion objective lens for polymerization processing. The CCD receives the optical signal to monitor the processing site, and the processing process is realized through a computer control system.

6. The method for manufacturing multi-scale ordered structures by spatiotemporal shaping of femtosecond laser according to claim 1, characterized in that: In step three, Spatial shaping: based on spatial light field shaping technology, the original femtosecond laser Gaussian pulse is modulated into an arbitrary light field intensity distribution, thereby achieving controlled processing of complex structures; Exposure time control: the size of the bubble radius in the local area is controlled based on the exposure time.

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