Method for voxelization printing of liquid crystal elastomer

Abstract

The invention provides a method for voxelization printing of a liquid crystal elastomer, and belongs to the technical field of additive manufacturing and liquid crystal high polymer materials. According to the method, the material physical property and the core-shell structure of printing fibers in the printing process are dynamically changed through the multi-nozzle design and selective opening and closing of an electromagnetic valve, and therefore voxelization printing of the liquid crystal elastomer is achieved. Then layer-by-layer printing and ultraviolet light curing treatment are carried out, and a voxelized printed three-dimensional sample is obtained; according to the liquid crystal elastomer voxelization printing method, through differential design of different material physical properties and core-shell structures in liquid crystal elastomer voxelization printing, on-demand regulation and control of material physical properties and driving behaviors of a liquid crystal elastomer printing sample in a three-dimensional space can be achieved; the printing strategy of the liquid crystal elastomer is further enriched, the design freedom degree of the liquid crystal elastomer structure is improved, and an efficient design means is provided for application of the liquid crystal elastomer in the fields of soft robots, artificial muscles, flexible sensors and the like.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing and liquid crystal polymer materials technology, specifically relating to a method for voxelizing liquid crystal elastomers. Background Technology

[0002] Liquid crystal elastomers (LCEs) can produce large, reversible, and anisotropic shape changes under the influence of external stimuli (such as light, heat, electric fields, and magnetic fields), showing great potential in the construction of artificial muscles, soft robots, wearable electronic devices, and other fields.

[0003] Voxel printing is an advanced form of 3D printing technology. Its core is to manufacture complex functional parts by precisely controlling the material, structure or properties of the smallest unit voxel in three-dimensional space. It breaks through the limitations of traditional 3D printing, which involves layering and uniformity within layers, and can customize the characteristics of each tiny volume unit at the microscale. Therefore, it is regarded as three-dimensional pixel-level manufacturing.

[0004] Many strategies have emerged to achieve 3D printing of liquid crystal elastomers, but most of them involve programming complex driving behaviors by changing printing parameters such as printing speed, height, path or ultraviolet intensity, and they all involve single-material printing; while multi-material coaxial printing mostly has a fixed fiber structure and limited performance control during the printing process.

[0005] Therefore, how to achieve on-demand and dynamic control of the material properties and driving behavior of liquid crystal elastomers in three-dimensional space remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for voxelizing and printing liquid crystal elastomers.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for voxelizing and printing liquid crystal elastomers includes the following steps: Multiple printing inks, including at least liquid crystal elastomer ink and photocurable elastomer ink, are fed into a multi-channel coaxial printhead for 3D printing. By independently controlling the on / off state and flow rate of ink in each channel, the material composition and core-shell structure of the extruded fibers distributed along the axial and radial directions are dynamically adjusted during the printing process to achieve voxel printing. The three-dimensional sample is obtained by printing layer by layer and then curing it.

[0008] As a preferred embodiment of the present invention, the multi-channel coaxial nozzle has a three-layer coaxial structure, consisting of a core layer, an intermediate layer, and an outer layer from the inside out. The dimensions of each channel are set according to the fiber size to be printed.

[0009] As a preferred embodiment of the present invention, the process parameters during printing are as follows: the printing temperature is room temperature, the printing air pressure is adjusted according to the ink viscosity, the printing layer height is set according to the nozzle diameter, and the curing treatment is performed by irradiation with ultraviolet light that matches the ink photoinitiator.

[0010] As a preferred embodiment of the present invention, dynamic programming with different core-shell structures in different sections along the axial direction of a single fiber is achieved by independently controlling the selection of ink materials in each layer of the multi-channel coaxial printhead and the opening and closing of corresponding channels; the core-shell structure includes, but is not limited to, a multi-layer structure composed entirely of liquid crystal elastomers, composed entirely of photocurable elastomers, and composed of liquid crystal elastomers and photocurable elastomers in different combinations.

[0011] As a preferred embodiment of the present invention, the preparation method of the liquid crystal elastomer ink includes: mixing liquid crystal monomers, chain extenders, crosslinking agents, photoinitiators and catalysts, heating and melting them and then carrying out a prepolymerization reaction to form an oligomer ink with a liquid crystal phase.

[0012] As a preferred embodiment of the present invention, the method for preparing the photocurable elastomer ink includes: mixing a silicone elastomer substrate, a photoinitiator, and a rheology modifier uniformly to form a composite ink with suitable printing performance.

[0013] In a preferred embodiment of the present invention, the liquid crystal monomer is an acrylate liquid crystal monomer; the chain extender is a compound containing a thiol group; the crosslinking agent is a multifunctional crosslinking monomer; the catalyst is an organic amine catalyst; and the photoinitiator is a free radical photoinitiator.

[0014] In a preferred embodiment of the present invention, the liquid crystal monomer, chain extender, and crosslinking agent are mixed in a preset molar ratio to control the network structure and phase transition temperature of the resulting liquid crystal elastomer; the catalyst and photoinitiator are added in a preset ratio to ensure reaction efficiency and curing speed.

[0015] In a preferred embodiment of the present invention, the silicone elastomer substrate is photocurable polydimethylsiloxane or its derivative; the photoinitiator is a free radical photoinitiator compatible with the silicone system; and the rheology modifier is fumed silica particles used to adjust the shear thinning properties of the ink.

[0016] In a preferred embodiment of the present invention, the silicone elastomer substrate and the photoinitiator are mixed at a preset mass ratio to ensure sufficient photocrosslinking reaction; the amount of the rheology modifier is adjusted according to the required ink viscosity to ensure the continuity of the printing process and the forming accuracy.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes the differentiated design of material properties and core-shell structures in the voxelization printing of liquid crystal elastomers to achieve on-demand control of material properties and actuation behavior in three-dimensional space for printed liquid crystal elastomer samples. Compared to traditional single-material printing or coaxial printing with fixed structures, this invention further enriches the printing strategies for liquid crystal elastomers, greatly improves the design freedom of liquid crystal elastomer structures, and provides an efficient design method for the application of liquid crystal elastomers in soft robots, artificial muscles, flexible sensors, and other fields. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the printing method described in this invention.

[0019] Figure 2 The image shows the liquid crystal phase transition temperature characterization of the liquid crystal elastomer ink prepared in Example 1.

[0020] Figure 3 This is a comparison diagram of the driving behavior of different core-shell structure fibers printed in Embodiment 2 of the present invention before and after heating.

[0021] Figure 4 This is a diagram showing the driving behavior of the elongated structure printed in Embodiment 3 of the present invention before and after heating.

[0022] Figure 5 This is a diagram showing the heating-driven deformation of the cubic structure printed in Embodiment 4 of the present invention in different directions. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0024] Furthermore, in this invention, an element referred to as fixed to or disposed on another element may be directly disposed on the other element, or there may be an intermediate element. When an element is considered to be connected to another element, it may be directly connected to the other element, or there may be an intermediate element present simultaneously. The terms vertical, horizontal, left, right, and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0025] This invention provides a method for voxelizing and printing liquid crystal elastomers, such as... Figure 1As shown, by using a multi-channel coaxial nozzle design and selective switching of solenoid valves in each channel, the material properties and core-shell structure of the printed fibers along the axial and radial distribution are dynamically changed during the printing process, thereby achieving voxel printing of liquid crystal elastomers.

[0026] To achieve the above method, this invention employs a customized multi-axis direct-write 3D printer. This printer is equipped with a multi-channel coaxial nozzle, an independent air pressure control system, an ultraviolet curing device, and a heated printing platform. The multi-channel coaxial nozzle has a three-layer coaxial structure, consisting of a core layer, an intermediate layer, and an outer layer from the inside out. Each layer channel is connected to a different ink source through independent pipelines. Each pipeline is equipped with a solenoid valve and a precision pressure regulating valve to independently control the on / off state and flow rate of each layer's ink. The dimensions of each layer channel can be set according to the required fiber size. For example, the inner diameter of the core layer can be 300-700 μm, the inner diameter of the intermediate layer can be 500-900 μm, and the inner diameter of the outer layer can be 700-1100 μm. The gap between each layer is controlled at 100-200 μm to ensure stable coaxial ink flow.

[0027] Before printing can begin, the required printing ink needs to be prepared; this invention relates to at least two types of printing ink: liquid crystal elastomer oligomer ink and photocurable elastomer ink.

[0028] The preparation principle of liquid crystal elastomer ink is to prepolymerize liquid crystal monomers with chain extenders and crosslinking agents to form oligomer inks with appropriate viscosity and liquid crystal phase. Specifically, liquid crystal monomers, chain extenders, and crosslinking agents are first weighed according to a preset molar ratio. The molar ratio of liquid crystal monomers to chain extenders and crosslinking agents can be adjusted within a wide range. The preferred molar ratio is liquid crystal monomer: chain extender: crosslinking agent = 1:(0.6-1.0):(0.1-0.4), and more preferably 1:0.8:0.2. This ratio can control the obtained liquid crystal... The crosslinking density and network structure of the elastomer affect its phase transition temperature and driving performance. Then, a photoinitiator and catalyst are added in a predetermined ratio. The amount of photoinitiator is 0.5-5% of the total amount of liquid crystal monomers and chain extenders, preferably 1-3%. The amount of catalyst is 1-3% of the total amount of liquid crystal monomers and chain extenders, preferably 2%. Simultaneously, a small amount of polymerization inhibitor, such as 2,6-di-tert-butyl-p-cresol, can be added, approximately 0.5-2% of the total monomer amount, to prevent premature polymerization during storage. The mixture is then heated at 70°C. Melt at -90℃, preferably 80℃, stir evenly, and then transfer to an oven at 60-70℃, preferably 65℃, for 2-5 hours, preferably 3 hours, to form an oligomeric ink with a certain viscosity. Finally, while still hot, the prepared oligomeric ink is loaded into a printing syringe, centrifuged to remove bubbles, and then sealed for later use. The liquid crystal monomer is preferably an acrylate liquid crystal monomer, more preferably RM257 or RM82; the chain extender is a compound containing a mercapto group, preferably ethylene glycol bis(3-mercaptopropionate) or bis(mercaptopropionate). The photoinitiator is one or more of the following: ethylene glycol ester, mercaptoglycerol diphenylboronic acid, and dithiobenzeneboronic acid; the crosslinking agent is a multifunctional crosslinking monomer, preferably triallyl isocyanurate or pentaerythritol tetrakis(3-mercaptopropionic acid); the catalyst is an organic amine catalyst, preferably triethylamine or dipropylamine; the photoinitiator is a free radical photoinitiator, preferably one or more of benzoin dimethyl ether, benzophenone, isopropylthioxanthone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 1-hydroxycyclohexylphenyl ketone.

[0029] For the preparation of photocurable elastomer inks, which are used as non-driven phases or sacrificial materials in conjunction with liquid crystal elastomer inks to achieve complex core-shell structures, the following steps are taken: First, a silicone elastomer substrate and a photoinitiator are weighed according to a preset mass ratio, preferably 1:(0.01-0.05), more preferably 1:0.02. Then, a rheology modifier is added according to a preset ratio to adjust the rheological properties of the ink, giving it appropriate shear-thinning characteristics and shape retention. The amount of rheology modifier is 3-10% of the total amount of silicone elastomer substrate, preferably 5%. The mixture is then placed in a high-speed mixer and stirred at 1000-1500 rpm for 10-20 minutes, preferably at 1300 rpm. Mix thoroughly for 5 minutes; finally, load the prepared composite ink into a printing syringe, centrifuge to remove bubbles, and seal for later use; wherein, the silicone elastomer substrate is a photocurable polydimethylsiloxane or its derivative, preferably one or more of Dow Corning Sylgard 184, Sylgard 186, Ecoflex 0030 or [4-6% (mercaptopropyl)methylsiloxane]-dimethylsiloxane copolymer; the photoinitiator is a free radical photoinitiator compatible with the silicone system, preferably one or more of benzoin dimethyl ether, benzophenone, isopropylthioxanthone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone; the rheology modifier is preferably hydrophobic fumed silica particles.

[0030] Once the inks are prepared, voxel printing can begin. The prepared inks are loaded into printing syringes and mounted onto a multi-channel coaxial printhead. Before printing, a series of printing parameters need to be set. The printing temperature is generally room temperature (20-30℃). For liquid crystal elastomer inks, the printing temperature can be adjusted appropriately according to their liquid crystal phase transition temperature to ensure suitable ink flow and liquid crystal orientation during printing. The printing air pressure is adjusted according to the ink viscosity, printhead size, and required printing speed, generally controlled within the range of 200-1000 kPa, preferably 300-800 kPa. The air pressure of each channel can be adjusted independently to achieve different core-shell structures and fiber diameters. The printing speed is generally controlled between 5-15 mm / s, preferably 8- The printing speed is 10 mm / s, and the air pressure and ink viscosity are adjusted in tandem to ensure fiber continuity and dimensional accuracy. The printing layer height is set according to the nozzle outer diameter and the required printing accuracy, generally 0.5-1 times the nozzle outer diameter, preferably 0.4-0.8 mm. UV curing uses UV light that matches the ink photoinitiator. The UV lamp wavelength can be selected according to the absorption peak of the photoinitiator, generally using an LED UV lamp of 365-405 nm. The UV light intensity is controlled at 5-50 mW / cm². Continuous or layer-by-layer irradiation can be used during printing to achieve in-situ orientation and preliminary curing. After printing, the sample is placed in a UV curing chamber for post-curing. The curing time is generally 10-30 minutes, preferably 20 minutes, to ensure full cross-linking.

[0031] During printing, the computer controls the on / off state and air pressure of the solenoid valves corresponding to each layer channel, allowing for dynamic switching of material composition and core-shell structure in different sections along the axis of a single fiber. For example, if the outer layer, middle layer, and core layer of the printhead are labeled A, B, and C, respectively, and the corresponding ink material is liquid crystal elastomer L or silicone material P, then by controlling the timing of the solenoid valve switching, dynamic programming of various core-shell structures such as "LLL", "LLP", "PLL", "LPL", "PPL", and "PLP" can be achieved. This structural change along the axis of a single fiber, combined with the structural changes between layers, truly realizes voxel-based manufacturing in three-dimensional space.

[0032] The present invention will be further illustrated by specific embodiments below.

[0033] Example 1 Synthesis of liquid crystal oligomer ink: Weigh 22.691g of liquid crystal monomer RM8, 0.072g of polymerization inhibitor BHT, 0.911g of chain extender EDDT, 0.166g of crosslinking agent TATATO, 0.054g of photoinitiator Irgacure819, and 0.036g of catalyst triethylamine; melt-mix the above components at 80℃, stir evenly, and then transfer to a 65℃ oven to react for 3 hours to form oligomer ink; wherein, the molar ratio of liquid crystal monomer, chain extender, and crosslinking agent is 1:0.8:0.2, the amount of catalyst is 2% of the total amount of liquid crystal monomer and chain extender, and the amount of photoinitiator is 1.5% of the total amount of liquid crystal monomer and chain extender; while the prepared ink is still hot, put it into a 3mL printing syringe, centrifuge at 3000rpm for 5 minutes to remove bubbles, and seal and store for later use.

[0034] Synthesis of photocurable silicone ink: Weigh 65g of Dow Corning Sylgard 18, 1g of [4-6% (mercaptopropyl)methylsiloxane]-dimethylsiloxane copolymer, 0.12g of photoinitiator Irgacure 819, and 0.3g of hydrophobic fumed silica particles; place the above components in a high-speed mixer and mix at 1300rpm for 15 minutes to form a uniform composite ink; wherein, the total mass of the silicone substrate is 6g, the amount of photoinitiator is 2% of the silicone substrate, and the amount of hydrophobic fumed silica is 5% of the silicone substrate; put the prepared ink into a 3mL printing syringe, centrifuge at 3000rpm for 5 minutes to remove bubbles, and seal for later use.

[0035] The liquid crystal oligomer ink prepared in this embodiment was characterized by differential scanning calorimetry (DSC) at a heating rate of 10 °C / min and a test temperature range of 0-100 °C; the results are as follows. Figure 2 As shown, the ink exhibits a distinct endothermic peak at approximately 30°C during the heating process, corresponding to the transition from the liquid crystal phase to the isotropic phase; and an exothermic peak at approximately 25°C during the cooling process, corresponding to the transition from the isotropic phase to the liquid crystal phase. This indicates that the prepared ink has a stable liquid crystal phase near room temperature, making it suitable for orientation and driving studies.

[0036] Example 2 The two types of printing inks prepared in Example 1 were respectively loaded into 3mL printing syringes and installed on a direct-write printer equipped with a three-layer coaxial printhead. The printhead size was set to a core layer inner diameter of 500μm, an intermediate layer inner diameter of 700μm, and an outer layer inner diameter of 900μm. The printing parameters were set as follows: printing temperature 25℃, printing layer height 0.8mm, printing speed 8mm / s, UV lamp wavelength 365nm, light intensity 20mW / cm², and continuous irradiation during printing to achieve in-situ curing and orientation. The air pressure of each layer was independently adjusted according to the required core-shell structure, generally controlled within the range of 300-600kPa.

[0037] By independently controlling the switching of the solenoid valves in each layer, various core-shell fiber samples were prepared, including sample A (LLL), where all three layers were liquid crystal elastomer inks, with air pressures P_core=400kPa, P_mid=350kPa, and P_out=300kPa; sample B (PLL), where the outer layer was silicone ink, and the middle and core layers were liquid crystal elastomer inks, with air pressures P_core=400kPa, P_mid=350kPa, and P_out=450kPa; and sample C (PLP), where the outer layer and core were silicone inks. The middle layer is made of liquid crystal elastomer ink, with air pressure P_core=500kPa, P_mid=350kPa, and P_out=450kPa; the outer and middle layers of sample D (LLP) are made of liquid crystal elastomer ink, and the core is made of silicone ink, with air pressure P_core=500kPa, P_mid=350kPa, and P_out=300kPa; the printed fiber diameter is about 800-900μm and the length is about 30mm; the printed fiber is placed in a UV curing chamber and cured for 20 minutes to obtain the final sample.

[0038] Each fiber sample was placed on a heating stage and heated from room temperature to 80°C at a rate of 10°C / min, and its driving behavior was observed; Figure 3 As shown, fibers with different core-shell structures exhibit significantly different driving behaviors: sample A (LLL) shrinks uniformly with a small curvature; sample B (PLL) bends towards the outside of the silicone layer with a moderate curvature; sample C (PLP) exhibits a complex S-shaped bend; and sample D (LLP) bends towards the side with the silicone core with a large curvature. By measuring the curvature changes at different temperatures, the driving performance of each structure can be quantitatively evaluated. The results show that by controlling the core-shell structure, the driving behavior can be adjusted from 0.1 to 2.5 cm. - ¹Adjust the bending curvature of the fiber at 80°C within the range.

[0039] Example 3 Using the same printing equipment and ink as in Example 2, a strip sample with dimensions of 1.5mm × 1mm × 0.8mm was printed; the printing path was a straight line reciprocating along the length direction with a filling interval of 0.8mm.

[0040] During the printing process, the timing of the switching of the solenoid valves in each layer is controlled by computer programming to achieve dynamic switching of the core-shell structure in different sections of the same fiber. Specifically, the programming is as follows: the 0-5mm section uses an LLL structure, the 5-10mm section uses a PLL structure, the 10-15mm section uses a PLP structure, and the 15-20mm section uses an LLP structure. The transition area between each section is controlled within 1mm, which is achieved by rapidly switching the solenoid valve state. Other printing parameters are the same as in Example 2. After printing, the sample is placed in a UV curing chamber and cured for 20 minutes.

[0041] like Figure 4 As shown, after the printed strip sample is heated to 80°C, different sections exhibit different bending directions and curvatures due to their different core-shell structures, thus causing the entire strip to exhibit a complex wave-like driving behavior. This structural change achieved along the axis of a single fiber is something that traditional coaxial printing cannot achieve, fully demonstrating the advantages of voxel printing in this invention. By adjusting the length of each section and the type of core-shell structure, various complex two-dimensional and three-dimensional driving deformations can be designed as needed.

[0042] Example 4 Using the same printing equipment and ink as in Example 2, a cubic sample with a size of 15mm × 15mm × 6mm was printed; the infill density was set to 40%, the infill pattern was arranged in a straight line; the printing layer height was 0.8mm, and a total of 7 layers were printed.

[0043] To achieve anisotropic driving behavior, different core-shell structures are programmed for different printing directions during the printing process: the fibers filled in the X direction adopt an LLL structure, and the fibers filled in the Y direction adopt a PLL structure; during each layer printing, the state of the solenoid valve is switched in real time according to the direction of the filling path, so that the fibers in the X and Y directions have different core-shell structures; other printing parameters are the same as in Example 2; after printing, the sample is placed in a UV curing chamber and cured for 20 minutes.

[0044] After heating the printed cube to 80℃, observe its dimensional changes in different directions; for example... Figure 5 As shown, the cube exhibits a shrinkage rate of approximately 25% in the X direction (LLL structure) and only 10% in the Y direction (PLL structure), demonstrating significant anisotropic driving behavior. This anisotropy is achieved by designing different microstructures in different spatial directions of the same component, providing a new approach for programming complex motions in soft robots.

[0045] Example 5 To further optimize the printing process, this embodiment systematically studies the effects of printing temperature, air pressure, speed, and ultraviolet light intensity on print quality and drive performance.

[0046] Regarding the effect of printing temperature, the fiber forming quality and liquid crystal orientation were observed by varying the printing temperature within the range of 20-40℃. The results showed that when the temperature was below 25℃, the viscosity of the liquid crystal elastomer ink was high, making extrusion difficult and the fiber surface rough. When the temperature was above 35℃, the ink entered the isotropic phase, making effective orientation impossible and reducing the driving performance. Therefore, the preferred printing temperature is 25-30℃, at which point the ink retains the liquid crystal phase and has good fluidity.

[0047] Regarding the impact of printing air pressure, other parameters were kept constant, and the air pressure was adjusted within the range of 200-1000 kPa. The results showed that if the air pressure was too low (below 300 kPa), it would result in insufficient extrusion, with the fiber diameter being smaller than the nozzle orifice diameter, or even fiber breakage. If the air pressure was too high (above 800 kPa), it would result in excessive extrusion, with the fiber diameter being too large and the accuracy decreasing. Preferably, the air pressure was controlled within the range of 300-800 kPa, based on the target fiber diameter being 0.8-1.2 times the nozzle outer diameter, and closed-loop feedback control was used to ensure extrusion stability.

[0048] Regarding the impact of printing speed, the printing speed was adjusted within the range of 5-20 mm / s. The results showed that if the speed was too fast, exceeding 12 mm / s, the fibers would stretch and become thinner, or even break. If the speed was too slow, below 6 mm / s, the material would accumulate and the fiber diameter would be uneven. The preferred printing speed was 8-10 mm / s, at which point fibers with uniform diameter and smooth surface could be obtained.

[0049] Regarding the effect of ultraviolet light intensity, the intensity was adjusted within the range of 5-50 mW / cm². The results showed that if the light intensity was too low (below 10 mW / cm²), incomplete curing would occur, leading to fiber collapse and deformation; if the light intensity was too high (above 30 mW / cm²), curing would be too fast, resulting in decreased interlayer bonding. The optimal light intensity was 15-25 mW / cm², which allowed for good orientation fixation while ensuring printing accuracy.

[0050] Example 6 To verify the universality of the technical solution of this invention, a comparative study was conducted using liquid crystal elastomer inks and photocurable elastomer inks with different formulations.

[0051] To regulate the formulation of liquid crystal elastomer inks, three inks with molar ratios of 1:0.6:0.4, 1:0.8:0.2, and 1:1.0:0.1 were prepared by changing the ratio of liquid crystal monomer RM82 to chain extender EDDT and crosslinker TATATO. Fiber samples were printed using an LLL structure, and their phase transition temperature and driving strain were tested. The results showed that with increasing crosslinker ratio, the crosslinking density increased, and the phase transition temperature slightly increased from 28℃ to 35℃, but the driving strain decreased from 45% to 20%. By adjusting the formulation, the driving performance of liquid crystal elastomers can be controlled within a wide range.

[0052] To regulate the formulation of photocurable elastomer inks, photocurable inks were prepared using different silicone substrates, such as Dow Corning Sylgard 184, Sylgard 186, and Ecoflex 0030, and then composited with liquid crystal elastomer inks to prepare fiber samples with PLL structures. The results showed that the modulus difference of different silicone substrates, ranging from 0.5 MPa to 3 MPa, significantly affected the bending behavior of the composite fibers. Silicones with lower modulus, such as Ecoflex 0030, made it easier for the fibers to bend into the silicone layer, resulting in a larger bending curvature. Silicones with higher modulus, such as Sylgard 184, limited the bending deformation. By selecting silicone substrates with different moduli, the driving behavior of the composite structure can be further regulated.

[0053] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0054] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for voxelizing and printing liquid crystal elastomers, characterized in that, Includes the following steps: Multiple printing inks, including at least liquid crystal elastomer ink and photocurable elastomer ink, are fed into a multi-channel coaxial printhead for 3D printing. By independently controlling the on / off state and flow rate of ink in each channel, the material composition and core-shell structure of the extruded fibers distributed along the axial and radial directions are dynamically adjusted during the printing process to achieve voxel printing. The three-dimensional sample is obtained by printing layer by layer and then curing it.

2. The method according to claim 1, characterized in that, The multi-channel coaxial nozzle has a three-layer coaxial structure, consisting of a core layer, an intermediate layer, and an outer layer from the inside out. The dimensions of each channel are set according to the fiber size to be printed.

3. The method according to claim 1, characterized in that, The process parameters during printing are as follows: the printing temperature is room temperature, the printing air pressure is adjusted according to the ink viscosity, the printing layer height is set according to the nozzle diameter, and the curing treatment is performed by irradiation with ultraviolet light that matches the ink photoinitiator.

4. The method according to claim 1, characterized in that, By independently controlling the selection of ink materials for each layer of the multi-channel coaxial printhead and the on / off state of the corresponding channels, dynamic programming with different core-shell structures in different sections along a single fiber axis can be achieved; the core-shell structure includes, but is not limited to, a multi-layer structure composed entirely of liquid crystal elastomers, a multi-layer structure composed entirely of photocurable elastomers, and a multi-layer structure composed of liquid crystal elastomers and photocurable elastomers in different combinations.

5. The method according to claim 1, characterized in that, The preparation method of the liquid crystal elastomer ink includes: mixing liquid crystal monomers, chain extenders, crosslinking agents, photoinitiators and catalysts, heating and melting them and then carrying out a prepolymerization reaction to form an oligomer ink with a liquid crystal phase.

6. The method according to claim 1, characterized in that, The method for preparing the photocurable elastomer ink includes: mixing a silicone elastomer substrate, a photoinitiator, and a rheology modifier uniformly to form a composite ink with suitable printing performance.

7. The method according to claim 5, characterized in that, The liquid crystal monomer is an acrylate-based liquid crystal monomer; the chain extender is a compound containing a thiol group; the crosslinking agent is a multifunctional crosslinking monomer; the catalyst is an organic amine catalyst; and the photoinitiator is a free radical photoinitiator.

8. The method according to claim 5, characterized in that, The liquid crystal monomer, chain extender, and crosslinking agent are mixed in a preset molar ratio to control the network structure and phase transition temperature of the resulting liquid crystal elastomer; the catalyst and photoinitiator are added in a preset ratio to ensure reaction efficiency and curing speed.

9. The method according to claim 6, characterized in that, The silicone elastomer substrate is photocurable polydimethylsiloxane or its derivatives; the photoinitiator is a free radical photoinitiator compatible with the silicone system; the rheology modifier is fumed silica particles used to adjust the shear thinning properties of the ink.

10. The method according to claim 6, characterized in that, The silicone elastomer substrate and photoinitiator are mixed at a preset mass ratio to ensure a full photocrosslinking reaction; the amount of rheology modifier is adjusted according to the required ink viscosity to ensure the continuity of the printing process and the forming accuracy.

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