Liquid crystal elastomer patterning orientation method and liquid crystal elastomer orientation structure
By layering vertical and in-plane alignment layers on a substrate and controlling the alignment of liquid crystal molecules using light irradiation, the problem of controlling various configurations in the construction of three-dimensional alignment structures of liquid crystal elastomers was solved, and the precise construction of complex three-dimensional configurations was achieved.
Patent Information
- Application Number
- CN202511232549.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-01
- Publication Date
- 2025-11-11
AI Technical Summary
Existing technologies limit the ability of liquid crystal elastomers to construct three-dimensional orientation structures, especially in the construction of complex structures such as radial gradient orientation and torsional orientation, where it is difficult to achieve precise control of various configurations.
A layered coating method is used to form a vertical alignment layer and an in-plane alignment layer on a substrate. Spatial decoupling and precise control of liquid crystal molecules are achieved by irradiation with ultraviolet or blue light. The specific steps include coating a vertical alignment material, forming a patterned in-plane alignment layer, irradiating and curing with light, preparing a liquid crystal cell, and injecting a liquid crystal elastomer precursor mixture.
It enables arbitrary combinations of various configurations of liquid crystal elastomers in three-dimensional orientation structures, including unfolded, inverse unfolded, radial gradient, twisted, and vertical types, thereby improving the ability to construct three-dimensional orientation structures and meeting the requirements of driving accuracy and configuration stability for rigid foldable origami structures.
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Figure CN120928612A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of liquid crystal materials, and more specifically, to a method for patterning and aligning liquid crystal elastomers and a liquid crystal elastomer alignment structure. Background Technology
[0002] Liquid crystal elastomers, as a class of polymeric materials that combine the anisotropy of liquid crystals with the deformability of elastomers, can generate reversible and programmable deformation responses under various external stimuli such as heat, light, electricity, and magnetism. They possess advantages such as a large strain range, fast response speed, and strong controllability, making them suitable for constructing actively deformable structures with distributed actuation, wireless actuation, and multifunctional integration. Among these, photo-alignment technology has attracted widespread attention due to its non-contact, patternable, and high spatial resolution characteristics.
[0003] The orientation of liquid crystal molecules has a crucial impact on the deformation behavior of liquid crystal elastomer devices. Taking origami structures as an example, the orientation difference between the crease region and the panel region determines its mechanical response and folding shape. However, in related technologies, liquid crystal elastomers are mainly limited to orientation control in a single direction, such as a single in-plane (horizontal) direction or a vertical direction. This greatly limits their ability to construct three-dimensional orientation structures (such as radial gradient orientation and torsional orientation). Summary of the Invention
[0004] The technical problem solved by this invention is to improve the ability of liquid crystal elastomers to construct three-dimensional orientation structures.
[0005] In a first aspect, the present invention provides a method for patterning and aligning a liquid crystal elastomer, comprising: A vertically oriented material is coated onto the surface of a substrate and cured to form a vertically oriented layer; An in-plane alignment material is coated on the surface of the vertical alignment layer to form a patterned in-plane alignment layer. The in-plane alignment layer is vertically irradiated with ultraviolet or blue light; Two substrates that have been vertically irradiated are assembled into a liquid crystal cell. After injecting a liquid crystal elastomer precursor mixture into the liquid crystal cell, the liquid crystal cell is uniformly irradiated and cured to obtain a liquid crystal elastomer orientation structure.
[0006] Optionally, the vertically oriented material is polyimide.
[0007] Optionally, the in-plane orientation material is an azo dye or azo compound containing sulfonic acid groups.
[0008] Optionally, the components of the liquid crystal elastomer precursor mixture include liquid crystal monomers and photoinitiators.
[0009] Optionally, the liquid crystal monomer includes at least one of RM257, RM006, and polymerizable acrylate-based liquid crystals.
[0010] Optionally, the coating method includes any one of spin coating, doctor blade coating, knife coating, spraying, and screen printing.
[0011] Optionally, the step of vertically irradiating the in-plane alignment layer with ultraviolet light or blue light includes: both the ultraviolet light and the blue light are linearly polarized light.
[0012] As a second aspect, the present invention also provides a liquid crystal elastomer alignment structure, which is prepared by the liquid crystal elastomer patterning alignment method as described in the first aspect.
[0013] Optionally, the liquid crystal elastomer alignment structure is in the form of a thin film, and the thickness of the thin film liquid crystal elastomer alignment structure is on the order of micrometers.
[0014] The advantages of this invention compared to related technologies include: This invention first covers the entire substrate with a vertically oriented material to form a vertically oriented layer. Then, an in-plane oriented material is covered in specific areas of the vertically oriented layer to form a patterned in-plane oriented layer. By controlling the orientation of the in-plane oriented layers in different areas of the substrate, spatial decoupling and precise control of molecular orientation in the in-plane and thickness directions can be achieved simultaneously in the liquid crystal elastomer orientation structure. Specifically, it can support any combination of various configurations such as unfolded, inverse unfolded, radial gradient, twisted, and vertical, thereby improving the ability of liquid crystal elastomers to construct three-dimensional orientation structures. Attached Figure Description
[0015] Figure 1 This is a schematic diagram of the structure when the substrate is photoinduced in an exemplary embodiment of the present invention; Figure 2 This is a schematic diagram of the light-controlled orientation within the liquid crystal cell and the four three-dimensional configurations prepared in an exemplary embodiment of the present invention; Figure 3 This is a schematic diagram of the light control orientation inside the liquid crystal cell in Comparative Example 1.
[0016] Explanation of reference numerals in the attached figures: 1. Substrate; 2. Vertical alignment layer; 3. In-plane alignment layer; 4. Mixed alignment layer. Detailed Implementation
[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.
[0018] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit this application. The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the description below. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used to distinguish different objects, not to describe a specific order or hierarchy. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.
[0019] Origami structures are configurations that create three-dimensional structures by folding two-dimensional sheets. In recent years, they have been widely used in civil engineering, biomimetic architecture, sensors, metamaterials, soft robotics, and aerospace deployment structures. In origami structures, the orientation difference between the crease area and the panel area determines its mechanical response and folding shape. Among related technologies, rigid foldable origami uses rigid panels and hinge-like creases as basic units, achieving shape transformation without relying on the extension and deformation of the material itself, exhibiting excellent geometric programmability, structural stability, and reconfigurability. However, traditional rigid origami structures typically rely on bulky external electric drives, pneumatic systems, or manual operation, making it difficult to meet the demands for miniaturization, lightweighting, and complex deformation, thus limiting their development in the fields of integration and autonomy.
[0020] Liquid crystal elastomers (LCEs) are a class of polymeric materials that combine the anisotropy of liquid crystals with the flexibility of elastomers. Currently, various liquid crystal molecular alignment methods have been used to construct LCE devices, such as extrusion printing, stress etching, surface etching, and photoalignment. Among these, the photoalignment principle of LCEs refers to the photoalignment of nematic liquid crystal units under light irradiation, meaning that the long axes of the molecules align in a specific direction. This alignment adjustment originates from changes in molecular orientation caused by photochemical reactions, and this change directly affects the macroscopic deformation properties of the material.
[0021] In active rigid origami structures, typical unfolding origami structures require molecules to have a certain gradient arrangement in the thickness direction to achieve unidirectional deformation and suppress reverse warping and undesirable multistable behavior. Although related technologies achieve functional differentiation between crease regions and panel regions through stress induction or photolithographic patterns, they generally suffer from problems such as continuous orientation field distribution, insufficient spatial resolution, and uncontrollable three-dimensional deformation, which limit the driving force and maintenance of stable configuration of rigid foldable structures.
[0022] This invention provides a method for patterning and aligning a liquid crystal elastomer, comprising: Step 1: Coat the vertical alignment material onto the surface of substrate 1 and cure it to form vertical alignment layer 2; Step 2: Coat the surface of the vertically oriented layer 2 with an in-plane oriented material to form a patterned in-plane oriented layer 3; Step 3: Irradiate the inward alignment layer 3 vertically with ultraviolet or blue light; Step 4: Assemble two vertically irradiated substrates 1 into a liquid crystal cell. After injecting the liquid crystal elastomer precursor mixture into the liquid crystal cell, irradiate the liquid crystal cell uniformly and cure it to obtain a liquid crystal elastomer orientation structure.
[0023] Reference Figure 1 As shown, in this embodiment of the invention, a vertically oriented material is first applied to the entire substrate 1 to form a vertically oriented layer 2. Then, an in-plane oriented material is applied to a specific area of the vertically oriented layer 2 to form a patterned in-plane oriented layer 3. By controlling the orientation of the in-plane oriented layer 3 in different areas of the substrate 1, spatial decoupling and precise control of molecular orientation in the in-plane and thickness directions can be achieved simultaneously in the liquid crystal elastomer orientation structure. Specifically, it can support any combination of various configurations such as unfolded, inverse unfolded, radial gradient, twisted, and vertical, thereby improving the ability of liquid crystal elastomers to construct three-dimensional orientation structures.
[0024] It should be noted that the in-plane direction refers to the plane direction of substrate 1, while the perpendicular (thickness) direction is the direction perpendicular to the plane of substrate 1. Taking an origami structure as an example, this invention can achieve functional partitioning of crease and panel areas in the structure through patterned in-plane orientation layers 3. The areas where the in-plane orientation layers 3 are distributed correspond to the crease areas, and the other areas correspond to the panel areas. Furthermore, different three-dimensional origami configurations can be obtained through light orientation, satisfying the key technical requirements of rigid foldable origami structures in terms of driving accuracy, configuration stability, and deformation complexity. Specifically, refer to... Figure 2 As shown, Figure 2 This illustrates a schematic diagram of the light-controlled alignment within a liquid crystal cell in an exemplary embodiment, as well as the structure of four fabricated three-dimensional configurations. Figure 2 It can be seen that vertical alignment, in-plane alignment, and a combination of both exist simultaneously within the liquid crystal cell. Figure 2 The four three-dimensional configurations in the figure are, from top to bottom, curved, vertical, twisted and reverse curved, where the azimuth angle φ represents the rotation angle of the liquid crystal molecules in the plane of substrate 1, and the polar angle β represents the tilt angle of the liquid crystal molecules relative to substrate 1.
[0025] In this embodiment of the invention, a vertically oriented layer 2 and an in-plane oriented layer 3 are sequentially formed using a layered coating method. This allows each layer to undergo its own independent orientation process immediately after coating, physically isolating the two types of orientation materials. This ensures that each layer achieves a highly ordered and uniform molecular arrangement under optimal conditions. Furthermore, since the molecular interaction mechanisms of vertically oriented materials and in-plane oriented materials are typically different, layered coating also avoids the phenomenon of the two orientation materials competing with, interfering with, inhibiting, or even completely destroying each other's ability to form a stable orientation structure. Layered coating also allows for precise control of the interface position and properties between the two layers. For example, controlling the curing degree of the first layer is crucial for subsequent photo-controlled orientation steps (performing region-selective photo-orientation), enabling clearer and steeper orientation pattern boundaries.
[0026] In some optional embodiments, in step one, the substrate 1 can be glass, and the vertical alignment material can be polyimide. Specifically, a vertical alignment material such as polyimide can be coated onto a cleaned glass substrate 1, and then the temperature is raised to 200°C to cure the vertical alignment material, resulting in a vertical alignment layer 2. Polyimide molecules with long side chains or rigid structures can form a stable vertical alignment arrangement through the interaction between the side chains and liquid crystal molecules.
[0027] In some optional embodiments, in step two, the in-plane orientation material is an azo dye containing sulfonic acid groups. More specifically, the azo dye containing sulfonic acid groups can be SD1. The azo dye can also be replaced with an azo compound, which is a compound with the functional group RN=N-R', where R and R' are aryl or alkyl. Furthermore, the distribution area of the in-plane orientation material can be patterned as needed, i.e., the distribution area of the in-plane orientation material can be controlled according to the desired three-dimensional configuration. For example, for origami structures, the in-plane orientation material can be coated onto each fold area.
[0028] In some alternative embodiments, in steps one and two, the coating method includes any one of spin coating, doctor blade coating, doctor blade coating, spraying, and screen printing.
[0029] In some optional embodiments, in step three above, both ultraviolet and blue light are linearly polarized light. Linearly polarized light is light whose light vector vibrates in the same fixed direction throughout its propagation, and whose vibration plane is perpendicular to the propagation direction. When linearly polarized light irradiates the in-plane alignment material perpendicularly, taking SD1 as an example, a cis-trans isomerization reaction occurs. The direction of its light vector induces the in-plane alignment material to align along the in-plane direction. Combined with liquid crystal cell technology, this induces adjacent liquid crystal molecules to align uniformly along the light polarization direction, achieving light orientation control in any in-plane direction. This further induces the liquid crystal elastomer to form a patterned alignment distribution and triggers complex deformation. In addition, to induce the liquid crystal elastomer to form a patterned alignment distribution, the light path of the exposure light source in this step can be modulated by a digital micromirror array to form a linearly polarized image with a spatial pattern, which is then projected onto the in-plane alignment layer 3. It should be understood that the spatial patterned area of the illumination should be selected according to the actual desired orientation. That is, in some alignment configurations, it is not necessary to irradiate all areas of the in-plane alignment layer 3 with linearly polarized light.
[0030] In some optional embodiments, in step four above, the components of the liquid crystal elastomer precursor mixture include liquid crystal monomers and photoinitiators. The liquid crystal monomers include at least one of RM257, RM006, and polymerizable acrylate-based liquid crystals (such as RM 82, C6BAPE). In one exemplary embodiment, the liquid crystal monomers may be a mixture of RM257 and RM006. The photoinitiator may specifically be at least one of Irgacure 651, 2,2-dimethoxy-2-phenylacetophenone, TPO-L, etc. The photoinitiator rapidly initiates a chemical reaction by absorbing light energy of a specific wavelength, thus driving the synthesis process of the liquid crystal elastomer. It should be understood that the wavelengths of ultraviolet and blue light in step three should be selected according to the specific wavelengths of light energy absorbed by the photoinitiator.
[0031] It should be noted that the process of assembling the substrate into a liquid crystal cell can be specifically as follows: two substrates 1 are fixed at a pre-spaced interval, and the vertical alignment layer 2 and the in-plane alignment layer 3 on the two substrates 1 are distributed opposite to each other. Then, the edges of the two substrates 1 are sealed with frame glue and conductive glue, while leaving one or two gaps for filling the liquid crystal precursor mixture. Finally, the filling port is sealed with UV glue.
[0032] It should be understood that, in the embodiments of the present invention, the illumination in step three is used to align the glass substrate 1. After the liquid crystal precursor mixture is poured in, the liquid crystal monomers are further induced by the substrate 1 to form a specific orientation. The illumination in step four is unpolarized light, specifically ultraviolet light or visible light, and its function is to promote the polymerization of liquid crystal monomers into a film under the action of a photoinitiator.
[0033] Another embodiment of the present invention provides a liquid crystal elastomer alignment structure, which is prepared using the liquid crystal elastomer patterning alignment method described above. Specifically, the liquid crystal elastomer alignment structure prepared by liquid crystal cell technology is in the form of a thin film with a thickness on the micrometer scale. It should be noted that, in an exemplary embodiment, the liquid crystal elastomer alignment structure can be deformed into an origami structure under the action of light or heat stimulation. This origami structure may include three-dimensional configurations such as unfolded, vertical, twisted, and inverse unfolded types.
[0034] The present invention will be described in detail below through specific embodiments and comparative examples: Example 1 The method for patterning and aligning liquid crystal elastomers in this embodiment specifically includes the following steps: Step (1): First, spin-coat a layer of polyimide onto the cleaned glass substrate 1, and cure it at 200°C to form a vertical alignment layer 2. Then, spin-coat a layer of SD1 material onto the surface of the vertical alignment layer 2, and control the distribution area of the SD1 material through a mask to form an in-plane alignment layer 3.
[0035] Step (2): After drying the substrate 1 with the vertical alignment layer 2 and the in-plane alignment layer 3, the substrate 1 is patterned using a light alignment platform based on a digital micromirror array projection system. Specifically, the exposure light source is linearly polarized 365 nm ultraviolet light, which is modulated by a digital micromirror array to form a linearly polarized image with a spatial pattern. After focusing, the image is irradiated onto the in-plane alignment layer 3 on the surface of the substrate 1 with a resolution of 22.2 μm, thereby achieving two-dimensional light alignment control in the in-plane direction of the substrate 1 and obtaining a patterned glass substrate 1.
[0036] Step (3): Two patterned glass substrates 1 are assembled to form a liquid crystal cell, and a liquid crystal elastomer precursor mixture is injected into the liquid crystal cell at room temperature. The liquid crystal elastomer precursor solution comprises the following components by mass percentage: 49.5 wt% RM257, 49.5 wt% RM006, and 1 wt% photoinitiator Irgacure 651. The components are stirred and mixed under light-protected conditions to obtain the liquid crystal elastomer precursor mixture. Subsequently, the entire liquid crystal cell is uniformly irradiated with 365 nm ultraviolet light to solidify the liquid crystal elastomer precursor solution into a cross-linked liquid crystal elastomer film with a thickness of 45 μm.
[0037] The obtained liquid crystal elastomer film deforms into a paper-fold structure under light stimulation, and different regions achieve the following: Figure 1 The vertical orientation shown (dominated by polyimide), the in-plane arbitrary orientation (dominated by SD1), and the complex three-dimensional orientations such as unfolded, inverse unfolded and twisted types achieved by superimposing the two are shown.
[0038] Example 2 The difference between this embodiment and Embodiment 1 is that the liquid crystal elastomer precursor solution comprises the following components by mass percentage: 49.5 wt% RM82, 49.5 wt% C6BAPE, and 1 wt% photoinitiator Irgacure 651. The other steps are the same as in Embodiment 1.
[0039] Comparative Example 1 The difference between this comparative example and Example 1 is that in step (1), polyimide and SD1 are mixed in a 1:1 mass ratio to form a mixed orientation material, and then the mixed orientation material is spin-coated onto the surface of glass substrate 1 to form a mixed orientation layer 4. Subsequently, in step (2), the light source is vertically irradiated onto the mixed orientation layer 4 on the surface of substrate 1. The other steps are the same as in Example 1.
[0040] Experimental comparisons revealed that, for example Figure 3 As shown, the orientation of the liquid crystal elastomer film in Comparative Example 1 is uniaxial (i.e., single direction), which cannot achieve the vertical orientation, in-plane arbitrary orientation, and complex three-dimensional orientation such as unfolded, inverse unfolded and twisted types achieved by superimposing the liquid crystal elastomer film in Embodiments 1 and 2 of the present invention in different regions.
[0041] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention, and all such changes and modifications will fall within the scope of protection of the present invention.
Claims
1. A method for patterning and aligning a liquid crystal elastomer, characterized in that, include: A vertically oriented material is coated onto the surface of a substrate and cured to form a vertically oriented layer; An in-plane alignment material is coated on the surface of the vertical alignment layer to form a patterned in-plane alignment layer. The in-plane alignment layer is vertically irradiated with ultraviolet or blue light; Two substrates that have been vertically irradiated are assembled into a liquid crystal cell. After injecting a liquid crystal elastomer precursor mixture into the liquid crystal cell, the liquid crystal cell is uniformly irradiated and cured to obtain a liquid crystal elastomer orientation structure.
2. The method for patterning and aligning liquid crystal elastomers according to claim 1, characterized in that, The vertically oriented material is polyimide.
3. The method for patterning and aligning liquid crystal elastomers according to claim 1, characterized in that, The in-plane orientation material is an azo dye or azo compound containing sulfonic acid groups.
4. The method for patterning and aligning a liquid crystal elastomer according to claim 1, characterized in that, The components of the liquid crystal elastomer precursor mixture include liquid crystal monomers and photoinitiators.
5. The method for patterning and aligning a liquid crystal elastomer according to claim 4, characterized in that, The liquid crystal monomer includes at least one of RM257, RM006, and polymerizable acrylate-based liquid crystals.
6. The method for patterning and aligning a liquid crystal elastomer according to claim 1, characterized in that, The coating method includes any one of spin coating, doctor blade coating, doctor blade coating, spraying, and screen printing.
7. The method for patterning and aligning a liquid crystal elastomer according to claim 1, characterized in that, The step of vertically irradiating the in-plane alignment layer with ultraviolet light or blue light includes: both the ultraviolet light and the blue light are linearly polarized light.
8. A liquid crystal elastomer alignment structure, characterized in that, It is prepared by the liquid crystal elastomer patterning and alignment method as described in any one of claims 1 to 7.
9. The liquid crystal elastomer alignment structure according to claim 8, characterized in that, The liquid crystal elastomer alignment structure is in the form of a thin film, and the thickness of the thin film liquid crystal elastomer alignment structure is on the order of micrometers.