Highly oriented 4d printing apparatus and applications of liquid crystal polymers

Abstract

The application discloses a kind of high orientation 4D printing device and application of liquid crystal polymer, it is related to the additive manufacturing technical field of liquid crystal polymer.The printing device includes: ink extrusion system, ultraviolet irradiation system, printing platform and printing path control system;Ink extrusion system includes needle cylinder and printing needle;Needle cylinder inside includes the extrusion channel of length-diameter ratio 50-500, and the inner diameter of printing needle is same with the inner diameter of extrusion channel;Ultraviolet irradiation system includes follow-up ultraviolet lamp installed on needle cylinder, and high-strength ultraviolet lamp installed on the printing platform;Printing path control system is used to make printing ink according to the printing path set, extrusion on the printing platform.In the process of ink direct writing printing, thinner needle and longer extrusion channel are used, so that the liquid crystal element in printing ink tends to be consistent in the extrusion process, the orientation degree of liquid crystal element is improved, and the orientation degree of obtained liquid crystal polymer can reach 0.7.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology for liquid crystal polymers, and more particularly to a highly oriented 4D printing apparatus and application for liquid crystal polymers. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] 4D printing refers to adding a fourth dimension of time to a three-dimensional object obtained through 3D printing. This allows the structure created by 3D printing technology to undergo structural or shape changes in response to external stimuli at different times. It can directly embed material and structural deformation designs into the material, enabling objects to automatically assemble and achieve a one-step integration from product design to manufacturing and assembly. 4D printing is also one of the best methods for creating soft robots, capable of rapidly producing various specialized three-dimensional structures and achieving rich actuation functions in response to external stimuli.

[0004] Liquid crystals (LCs) are ordered fluid intermediate states that exist during the transition from solid to fluid. Liquid crystal polymers are polymers with a moderate degree of cross-linking, possessing both the orientation properties of liquid crystal materials and the elastic properties of ordinary polymer materials. Methods for achieving orientation include surface friction, electric and magnetic fields, and optical alignment. Methods using electric and magnetic fields to orient liquid crystal polymers are less commonly used due to the need for high field strength. Patent application CN114670439A (A Friction-Oriented DLP Liquid Crystal Elastomer 4D Printing Device, Method, and Deformation Control Strategy) discloses a method for adjusting the orientation of liquid crystal elastomers using friction. This method uses the friction between the material forming head and the material forming pool to generate shear force, thereby orienting the liquid crystals. However, because the friction direction includes multiple directions, the degree of mesocrystalline orientation is not high. Patent application CN116288796A (Ultra-fine Oriented Liquid Crystal Elastomer Fibers, Continuous High-Speed ​​Processing Preparation Method, and Application) discloses a method for adjusting the orientation of liquid crystal elastomers using traction stretching, but it can only produce one-dimensional fiber materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a highly oriented 4D printing device and application for liquid crystal polymers. This device utilizes a high aspect ratio pipe to adjust the orientation degree of liquid crystal units within the pipe, thereby achieving the preparation of highly oriented liquid crystal polymers.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] This invention provides a highly oriented 4D printing apparatus for liquid crystal polymers, comprising: an ink extrusion system, an ultraviolet irradiation system, a printing platform, and a printing path control system;

[0008] The ink extrusion system includes a syringe and a printing needle mounted below the syringe. The syringe contains an ink cavity and an extrusion channel with an aspect ratio of 50-500. The extrusion channel is either straight or spiral. Here, the length of the extrusion channel refers to the total length of the straight or spiral channel. The spiral design can further extend the extrusion channel. The lower end of the extrusion channel is connected to the printing needle. The inner diameter of the printing needle is the same as the inner diameter of the extrusion channel. The inner diameter of the extrusion channel is 0.1-0.45 mm.

[0009] The ultraviolet irradiation system includes a follow-up ultraviolet lamp mounted on the syringe and a high-intensity ultraviolet lamp mounted on the printing platform;

[0010] The print path control system is used to cause the print ink to be extruded onto the print platform according to the set print path.

[0011] Optionally, a heating device is installed on the outside of the syringe to heat the printing ink inside the ink cavity and extrusion channel.

[0012] Optionally, the extrusion channels are arranged in a straight line in the syringe, connecting the ink cavity and the printing needle; or, the extrusion channels are distributed in a spiral pattern in the syringe, connecting the ink cavity and the printing needle.

[0013] Optionally, the internal channels of the extrusion orifice and the printing needle are smooth and without bends, allowing the printing ink to be extruded along the smooth channels;

[0014] Optionally, the extrusion channel and printing needle have rifling inside. The rifling is a continuous straight line or curve set along the extrusion direction. The rifling is more conducive to the uniform orientation of liquid crystal cells during the movement of liquid crystal monomers, and there are no bends.

[0015] Optionally, the follow-up ultraviolet lamp is installed on the side of the print head to initially cure the photocurable printing ink; preferably, the irradiation intensity of the follow-up ultraviolet lamp is 6-12 mW·cm. -2 .

[0016] Optionally, the printing platform includes a light-transmitting printing stage, and the high-intensity ultraviolet lamp is installed above and below the light-transmitting printing stage to irradiate the photocurable printing ink on the light-transmitting printing stage in both vertical and horizontal directions; preferably, the irradiation intensity of the high-intensity ultraviolet lamp is 25-35 mw·cm. -2 .

[0017] Optionally, the ink extrusion system includes a pneumatic extrusion device, which includes an air pump connected to the ink chamber via a pipe. The air pump is used to apply air pressure to the upper interface of the printing ink in the ink chamber, so that the printing ink is extruded along the extrusion channel and the printing needle onto the printing platform. Preferably, the range of the applied air pressure is 0.1 MPa to 2.3 MPa.

[0018] Optionally, the printing path control system includes a robotic arm equipped with a syringe that can move along a set path, causing printing ink squeezed from the printing needle to be squeezed onto the printing platform along the set path.

[0019] Secondly, regarding the application of the aforementioned highly oriented 4D printing apparatus for liquid crystal polymers, the apparatus is suitable for applications where the viscosity is 2×10⁻⁶. 2 ~5×10 6 Printing ink with an aspect ratio of 3.2-5.1 for the liquid crystal monomers contained in it, with a per unit area of ​​mPa·s.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. This invention provides a highly oriented 4D printing apparatus and application for liquid crystal polymers. In the ink direct-write printing process, a finer needle and a longer extrusion channel are used. The extrusion channel and the printing needle have rifling inside. The rifling is a continuous straight line or a curve, which can increase the friction force on the sidewalls of the ink during the extrusion process, which is more conducive to the orientation of liquid crystal units. This makes the liquid crystal units in the printing ink tend to be uniformly oriented during the extrusion process, improving the orientation degree of the liquid crystal units. The orientation degree of the obtained liquid crystal polymer can reach 0.7 or higher.

[0022] 2. This invention includes a heating device on the outside of the syringe, a follow-up ultraviolet lamp, and a high-intensity ultraviolet lamp. The reaction process is consistent with that of the liquid crystal polymer. The heating device causes the printing ink containing liquid crystal monomers to undergo an oligomerization reaction, which improves the orientation degree in the extrusion channels. The follow-up ultraviolet lamp causes the printing ink to undergo preliminary curing, forming a whole with a certain strength, which can bond with the ink printed later. The high-intensity ultraviolet lamp causes the printing ink to undergo overall curing, improving its overall strength and obtaining a high-strength liquid crystal elastomer product. By controlling the degree of reaction of the printing ink at different printing stages, it can be made to have physicochemical properties adapted to the printing device and printing process, resulting in high forming accuracy. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0024] The diagram exaggerates the spacing or dimensions between parts to show their positions; the diagram is for illustrative purposes only.

[0025] Figure 1 This is a schematic diagram of the structure of a highly oriented 4D printing device for liquid crystal polymers in a specific embodiment.

[0026] Figure 2 This is a schematic diagram of the extrusion channel inside the syringe in a specific implementation.

[0027] Figure 3 This is a schematic diagram of the crosslinking and curing process in a specific implementation method.

[0028] The components include: 1. Syringe; 2. Heating device; 3. Printing needle; 4. Air pump; 5. Ink chamber; 6. Extrusion channel; 7. Liquid crystal monomer; 8. Flexible polymer carbon chain; and 9. Follow-up ultraviolet lamp. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] Example 1

[0031] A highly oriented 4D printing apparatus for liquid crystal polymers includes: an ink extrusion system, an ultraviolet irradiation system, a printing platform, and a printing path control system;

[0032] The ink extrusion system is used to extrude printing ink onto the printing platform, the ultraviolet irradiation system is used to crosslink the extruded printing ink, and the printing path control system is used to control the printing path of the printing ink on the printing platform to form a highly oriented liquid crystal elastomer of a set shape.

[0033] like Figure 1 As shown, the ink extrusion system includes a syringe 1 and a printing needle 3 mounted below the syringe 1; Figure 2 As shown, the syringe 1 includes an ink cavity 5 and an extrusion channel 6 with an aspect ratio of 50-500. The lower end of the extrusion channel 6 is connected to a printing needle 3. The inner diameter of the printing needle 3 is the same as the inner diameter of the extrusion channel 6. The inner diameter of the extrusion channel 6 is 0.1-0.45mm.

[0034] The total length of the extrusion channel 6 is 0.5cm-22.5cm, which is achievable in the prior art.

[0035] like Figure 1 As shown, the ultraviolet irradiation system includes a follow-up ultraviolet lamp 9 mounted on the syringe 1 and a high-intensity ultraviolet lamp mounted on the printing platform.

[0036] The print path control system is used to ensure that the print ink is extruded onto the print platform according to the set print path.

[0037] A heating device 2 is installed on the syringe 1 to heat the printing ink inside the ink cavity 5 and the extrusion channel 6; preferably, the heating device 2 achieves heating by means of an electric heating wire wrapped around the outer periphery of the ink cavity 5 and the extrusion channel 6.

[0038] like Figure 2 As shown in (a), the extrusion channel 6 is arranged in a straight line in the syringe 1, connecting the ink cavity 5 and the printing needle 3; or, as shown in (a), Figure 2 As shown in (b), the extrusion channels 6 are spirally distributed in the syringe 1, connecting the ink cavity 5 and the printing needle 3 to obtain longer extrusion channels.

[0039] The internal channels of the extrusion channel 6 and the printing needle 3 are smooth and without bends, allowing the printing ink to be extruded along the smooth channels and ensuring a stable printing speed.

[0040] The extrusion channel 6 and the printing needle 3 have rifling inside. The rifling is a continuous straight line or curve set along the extrusion direction, which can increase the friction force on the side wall of the ink during the extrusion process, which is more conducive to the alignment of liquid crystal cells and has no bends.

[0041] Because the ink contains liquid crystal monomers with a high aspect ratio, when these liquid crystal monomers pass through the high aspect ratio pipe, in order to reduce the movement resistance, their orientation will gradually align with the same direction as the extrusion direction, that is, many liquid crystal units are parallel to each other, and become a state of high orientation. The heating effect of the heating device 2 can cause the printing ink to undergo an aggregation reaction, keep the high orientation state of the liquid crystal units in the printing ink stable, and fix it in the subsequent photocuring process.

[0042] The follow-up ultraviolet lamp 9 is installed on the side of the print head 3 to initially solidify the printing ink, forming a whole with a certain strength, and to be able to bond with the ink printed later.

[0043] The printing platform includes a light-transmitting printing stage, on which printing ink is extruded. High-intensity ultraviolet lamps are installed above and below the light-transmitting printing stage to irradiate the printing ink on the stage from both directions, causing the ink to cure as a whole and obtaining a high-strength liquid crystal elastomer product.

[0044] like Figure 1 As shown, the ink extrusion system includes a pneumatic extrusion device, which includes an air pump 4. The air pump 4 is connected to the ink chamber 5 through a pipe and is used to apply air pressure to the upper interface of the printing ink in the ink chamber 5, so that the printing ink is extruded along the extrusion channel 6 and the printing needle 3 onto the printing platform; preferably, air pressure is applied.

[0045] The printing path control system includes a robotic arm with a syringe 1 mounted on it, which can move along a set path to expel printing ink from the printing needle 3 onto the printing platform along the set path.

[0046] Example 2

[0047] The printing process of the highly oriented 4D printing apparatus for liquid crystal polymers according to Example 1 includes the following steps:

[0048] S1, such as Figure 1 As shown, the prepared printing ink is placed into the ink chamber 5 of the syringe;

[0049] S2, such as Figure 2 As shown, the printing ink in the ink cavity 5 is squeezed out along the printing needle 3 of the extrusion channel 6 until the extrusion speed is stable. The orientation of the liquid crystal cells in the printing ink is improved during the process of passing through the extrusion channel 6 and the printing needle 3.

[0050] S3. By designing a print path control system, the syringe is made to extrude printing ink onto the print platform along a set print path, such as... Figure 3 As shown, after the printing ink is extruded, it undergoes preliminary photocuring under the irradiation of the follow-up ultraviolet lamp 9. The flexible polymer carbon chain 8 formed between the chain extender, crosslinker and / or initiator and the liquid crystal monomer 7 fixes the high orientation state of the liquid crystal unit 7 after extrusion.

[0051] S4. After printing is completed, turn on the high-intensity ultraviolet lamp to perform overall photocuring on the printed object, so as to become a highly oriented liquid crystal elastomer.

[0052] S5. Heating the highly oriented liquid crystal elastomer causes it to undergo thermal deformation, thus completing 4D printing.

[0053] In S2, the extrusion speed is set to 1.2 mm / s-50 mm / s.

[0054] In S1, the raw material of the printing ink includes liquid crystal monomers. Since liquid crystal monomers contain both rigid groups and flexible segments, they can undergo thermal deformation along the length direction. Therefore, the highly oriented liquid crystal elastomer formed by highly oriented liquid crystal units has the ability to undergo thermal deformation along the orientation direction.

[0055] Printing ink was obtained by mixing 45 parts of liquid crystal monomer RM82, 40 parts of chain extender n-butylamine, 15 parts of crosslinking agent triallyl isocyanurate, and 1.8 parts of initiator I rgacure 651 and reacting at 95°C for 8 hours. The inner diameter of the extrusion channel was 0.1 mm, the length was 5 cm, and the extrusion speed was 5 mm / s. The intensity of the follow-up UV lamp 9 was 7 mW·cm. -2 The intensity of the high-intensity ultraviolet lamp is 27 mW·cm.-2 Irradiation for 2 hours; the orientation degree of the liquid crystal units in the obtained 4D printed high-orientation liquid crystal elastomer is 0.68.

[0056] Printing ink was obtained by mixing 48 parts of liquid crystal monomer RM82, 38 parts of chain extender n-butylamine, 19 parts of crosslinking agent triallyl isocyanurate, and 2.1 parts of initiator I rgacure 651 and reacting at 95°C for 9 hours. The extrusion channel inner diameter was 0.2 mm, the length was 8 cm, and the extrusion speed was 8 mm / s. The intensity of the follow-up UV lamp 9 was 12 mW·cm⁻¹. -2 The intensity of the high-intensity ultraviolet lamp is 30 mW·cm. -2 Irradiation for 1.2 hours; the resulting 4D-printed high-orientation liquid crystal elastomer had an orientation degree of 0.56.

[0057] When using 49 parts of liquid crystal monomer RM82, 42 parts of chain extender n-butylamine, 17 parts of crosslinking agent triallyl isocyanurate, and 2.2 parts of initiator I rgacure 651, the extrusion channel inner diameter is 0.4 mm and the length is 20 cm; the intensity of the follow-up UV lamp 9 is 10 mW·cm. -2 The intensity of the high-intensity ultraviolet lamp is 28 mW·cm. -2 Irradiation for 3 hours; the resulting 4D-printed high-orientation liquid crystal elastomer had an orientation degree of 0.52.

[0058] The orientation degree of the above high-orientation liquid crystal elastomer is determined by using two-dimensional wide-angle X-ray scattering test to obtain the orientation degree result.

[0059] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A highly oriented 4D printing apparatus for liquid crystal polymers, characterized in that, include: Ink extrusion system, ultraviolet irradiation system, printing platform and printing path control system; The ink extrusion system includes a syringe and a printing needle mounted below the syringe; the syringe contains an ink cavity and an extrusion channel with an aspect ratio of 50-500, and the lower end of the extrusion channel is connected to the printing needle, the inner diameter of the printing needle being the same as the inner diameter of the extrusion channel. The extrusion channel and the printing needle have rifling inside, and the rifling is a continuous straight line or curve set along the extrusion direction. The inner diameter of the extrusion channel is 0.1-0.45 mm; The ultraviolet irradiation system includes a follow-up ultraviolet lamp mounted on the syringe and a high-intensity ultraviolet lamp mounted on the printing platform; the follow-up ultraviolet lamp is installed on the side of the printing needle; the irradiation intensity of the follow-up ultraviolet lamp is 6-12 mw·cm. -2 The printing platform includes a light-transmitting printing stage, on which printing ink is extruded. High-intensity ultraviolet lamps are installed above and below the light-transmitting printing stage; the irradiation intensity of the high-intensity ultraviolet lamps is 25-35 mw·cm. -2 ; The print path control system is used to cause the print ink to be extruded onto the print platform according to the set print path.

2. The highly oriented 4D printing apparatus for liquid crystal polymers according to claim 1, characterized in that, The syringe is equipped with a heating device for heating the printing ink inside the ink cavity and extrusion channel.

3. The highly oriented 4D printing apparatus for liquid crystal polymers according to claim 2, characterized in that, The heating device achieves heating by an electric heating wire wound around the outer periphery of the ink cavity and extrusion channel.

4. The highly oriented 4D printing apparatus for liquid crystal polymers according to claim 1, characterized in that, The extrusion channels are arranged in a straight line in the syringe, connecting the ink chamber and the printing needle.

5. The highly oriented 4D printing apparatus for liquid crystal polymers according to claim 1, characterized in that, The extrusion channels are spirally distributed in the syringe, connecting the ink cavity and the printing needle.

6. The highly oriented 4D printing apparatus for liquid crystal polymers according to claim 1, wherein the total length of the extrusion channels is 0.5 cm to 22.5 cm.

7. The highly oriented 4D printing apparatus for liquid crystal polymers according to claim 1, characterized in that, The ink extrusion system includes a pneumatic extrusion device, which includes an air pump. The air pump is connected to the ink chamber through a pipe and is used to apply air pressure to the upper interface of the printing ink in the ink chamber.

8. The highly oriented 4D printing apparatus for liquid crystal polymers according to claim 7, characterized in that, The range of the applied air pressure is 0.1 MPa to 2.3 MPa.

9. The highly oriented 4D printing apparatus for liquid crystal polymers according to claim 1, characterized in that, The printing path control system includes a robotic arm equipped with a syringe that can move along a set path, causing printing ink squeezed from the printing needle to be extruded onto the printing platform along the set path.

10. An application of a highly oriented 4D printing apparatus for liquid crystal polymers as described in any one of claims 1-9 in highly oriented 4D printing of liquid crystal polymers, characterized in that, Suitable for: Viscosities of 2×10 2 -5×10 6 Printing ink with an aspect ratio of 3.2-5.1 for the liquid crystal monomers contained in it, with a per unit area of ​​mPa·s.

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