A one-way contractile liquid crystal elastomer fiber and an intelligent fabric thereof combined with a knitted structure

Abstract

The application discloses a one-way contraction type liquid crystal elastomer fiber and an intelligent fabric combined with a knitted structure, and belongs to the field of intelligent polymer materials. The fiber with the one-way contraction-maintenance characteristic is prepared by introducing a specific amount of photo-thermal response material into a liquid crystal elastomer system and combining internal and external double-stretching spinning processes. The fiber prepared by the method is pre-elongated by mechanical stretching, rapidly contracts under infrared light stimulation, maintains the contraction state after the light source is removed, and is restored by mechanical stretching again, so that the "on-off" type precise control is realized. The fiber is combined with the knitted structure to prepare the intelligent fabric with the local fixed-point driving capability; further, the controllable deformation of the material under the cooperation of multiple physical fields is utilized to construct a logic operation unit with "force" instead of "electricity", so that logical functions such as and, or and not are realized. The application can be applied to the fields of artificial muscles, intelligent wear, light-controlled switches and coreless logic devices.

Description

Technical Field

[0001] This invention belongs to the field of intelligent polymer materials technology, specifically relating to a unidirectional shrinkage liquid crystal elastomer fiber and its intelligent fabric composite with knitted structure. Background Technology

[0002] Liquid crystal elastomers (LCEs), as a typical class of smart stimulus-responsive polymer materials, can achieve reversible macroscopic shape changes through the order-disorder transition of liquid crystal units in response to external stimuli such as light and heat. With their sensitive response, large deformation range, and good biocompatibility, they show broad application prospects in fields such as artificial muscles, flexible actuators, and smart textiles. Among them, liquid crystal elastomer fibers, due to their combination of the weavability of fiber materials and the stimulus-responsiveness of liquid crystal elastomers, have become a core basic material for constructing flexible smart devices and smart fabrics, and related preparation and modification technologies have become a research hotspot.

[0003] To improve the mechanical and photothermal response properties of liquid crystal elastomer fibers, existing technologies often introduce one-dimensional nano-photothermal fillers such as carbon nanotubes to modify the liquid crystal elastomer matrix. By functionalizing carbon nanotubes, the problems of their aggregation and orientation in the matrix are solved, achieving covalent grafting and good compatibility between carbon nanotubes and the liquid crystal elastomer matrix. This significantly improves the tensile strength, photothermal actuation stress, and other properties of the composite material, while also endowing the material with multiple stimulus response characteristics such as infrared, ultraviolet, and thermal. This modification technology can also be further used to prepare actuators with multi-layered, serpentine, and other structures through molding processes, optimizing the response flexibility of the actuators. Furthermore, in terms of the preparation process of liquid crystal elastomer fibers, existing technologies have developed continuous high-speed processing methods. By synthesizing high molecular weight linear liquid crystal prepolymers to modulate liquid crystal slurries in a non-Newtonian fluid state, and combining conical nozzle extrusion shearing and roller traction stretching, the orientation of liquid crystal units can be controlled. Combined with photocuring technology to complete fiber forming, ultra-fine oriented liquid crystal elastomer fibers can be efficiently prepared. The diameter of these fibers can be controlled within the range of 5μm-400μm, and they possess high driving strain rate, high driving stress, and excellent cycle stability, significantly improving the preparation efficiency and driving performance of liquid crystal elastomer fibers.

[0004] Although the above technologies have significantly improved the mechanical properties, photothermal responsiveness, and preparation efficiency of liquid crystal elastomer fibers, becoming important research achievements in the field of liquid crystal elastomer fibers, the deformation modes of existing liquid crystal elastomer fibers, including those modified with carbon nanotubes, under light and heat stimulation are all traditional reversible bidirectional deformations. That is, the material undergoes deformations such as shrinkage or bending under external stimulation, and once the stimulation is removed, the material will automatically return to its original form. It is impossible to achieve stable maintenance after stimulation-induced deformation. This inherent characteristic has become a key bottleneck restricting its high-end applications.

[0005] In the field of smart textiles, liquid crystal elastomer fibers with this bidirectional deformation mode have significant technical drawbacks: On the one hand, the fibers cannot achieve point-to-point locking of the deformation state. After the fabric shrinks in the area stimulated by light or heat, it reverts as a whole when the stimulus is removed, making it difficult to independently control the shape of specific areas of the fabric and failing to meet the core requirement of precise point-to-point driving of local shape in smart fabrics. On the other hand, this deformation mode relies on continuous external stimulation to maintain the deformation state, requiring continuous power supply, which presents insurmountable obstacles when constructing low-power, self-powered smart fabric systems. In emerging fields such as flexible actuators and mechanical computing, this characteristic of not maintaining deformation prevents it from achieving true "on / off" precise control, making it difficult to construct stable chipless logic operation units, thus limiting the application expansion of liquid crystal elastomer fibers in high-end smart devices such as radiation-resistant and low-power computing devices.

[0006] Composites of functional responsive fibers with textile structures are a key approach to realizing the functionalization of smart fabrics. The smoothness of plain weave, the high elasticity of rib weave, the double-sided effect of yarn-padded weave, the dotted structure of loop weave, the structural stability of double rib weave, and the three-dimensional forming capability of multi-layer composite weave provide a foundation for the diversified morphological design of smart fabrics. However, existing bidirectional deformation-mode liquid crystal elastomer fibers lack deformation retention capabilities and cannot be combined with various knitted structures to achieve complex and stable morphological control, making it difficult to prepare high-performance smart fabrics with precise morphological control. Meanwhile, utilizing the controllable deformation of materials under external stimuli to achieve "mechanical computation" for information processing and logical operations has become an important direction for exploring new computing paradigms. It provides new ideas for developing radiation-resistant and low-energy-consumption computing devices. Although liquid crystal elastomer materials possess controllable deformation characteristics under the synergistic effect of multiple physical fields such as light and heat, their existing bidirectional deformation mode without deformation retention makes them unsuitable as core building blocks for stable mechanical logic operations, failing to meet the development needs of "chip-free logic" devices.

[0007] In summary, although existing liquid crystal elastomer fiber technologies have been continuously optimized in terms of modification and preparation processes, significantly improving the mechanical and responsive properties of the materials, none of them have broken through the traditional bidirectional reversible deformation mode. They cannot achieve stable retention after stimulus-induced deformation, making it difficult to meet the precise, stable, and low-power morphological control requirements of fields such as smart textiles, flexible actuators, and mechanical computing. Developing novel liquid crystal elastomer fibers with deformation-locking characteristics has become an urgent technical problem to be solved in this field. Summary of the Invention

[0008] To address the aforementioned problems, the present invention aims to provide a unidirectional shrinkage liquid crystal elastomer fiber and a smart fabric composed of it and knitted structure, in order to overcome the shortcomings of existing LCE fibers, such as a single deformation mode and inability to maintain state, meet the demand for "switch" type precise fixed-point drive in the field of smart fabrics, and further expand its application in the field of mechanical logic operation.

[0009] To achieve the above objectives, the present invention first provides a method for preparing unidirectional shrinkable liquid crystal elastomer fibers, comprising the following steps: (1) Preparation of liquid crystal oligomers: Liquid crystal units and spacer groups are added to a solvent, and a catalyst is added and stirred to allow the reaction to proceed. The reaction solution is then washed with dilute hydrochloric acid, salted with saturated sodium chloride solution, dried with anhydrous sodium sulfate, filtered, and desolventized under reduced pressure to obtain white viscoelastic liquid crystal oligomers. (2) Preparation of spinning solution: Add the liquid crystal oligomer, liquid crystal moiety, crosslinking agent, photoinitiator and photothermal response material obtained in step (1) to the solvent, stir until completely dissolved, pour the solution into a polytetrafluoroethylene mold, and let it stand in the dark for 12 hours to allow the solvent to evaporate naturally until the system forms a viscous non-Newtonian fluid. (3) Bionic bi-stretch spinning: The spinning solution is added to a CNC syringe equipped with a conical spinneret, and the spinning solution is extruded by the syringe pump. The solution is internally stretched by the conical wall shear of the conical spinneret. The initial filament is mechanically externally stretched by a winding drum driven by a CNC motor to achieve further refinement and improved orientation of liquid crystal units, thus preparing a liquid crystal elastomer filament bundle. The degree of external stretching is controlled to be less than the maximum stretch ratio of the fiber by 80, and the diameter of the prepared liquid crystal elastomer filament bundle is 20μm-600μm. (4) Curing and winding: The stretched filaments obtained in step (3) are placed in an oven for pre-curing, and then photocured. The cured liquid crystal elastomer fibers are wound in an orderly manner at equal intervals by a guide rail slider to obtain the finished product.

[0010] In one embodiment of the present invention, the liquid crystal unit is at least one of RM82, RM257, a photosensitive monomer containing azobenzene, and a cholesterol derivative liquid crystal unit, and the spacer group is at least one of 3,6-dioxa-1,8-octanedithiol, 1,10-decanedithiol, 1,2-ethanedithiol, 1,3-propanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 1,8-octanedithiol, 1,9-nonanedithiol, and 3,6-dioxa-1,8-octanedithiol.

[0011] In one embodiment of the present invention, in step (1), the molar ratio of the liquid crystal unit to the spacer group is 1:1, the solvent includes at least one of dichloromethane, trichloromethane, tetrahydrofuran, and ethyl acetate, and the amount of solvent added is 2.7 to 3 times the total mass of the liquid crystal unit and the spacer group.

[0012] In one embodiment of the present invention, in step (1), the catalyst includes dipropylamine or triethylamine, and the amount of catalyst added is 1.5 to 2.0% of the total mass of the liquid crystal unit and the spacer group. After adding the catalyst, the mixture is stirred at room temperature for 24 hours.

[0013] In one embodiment of the present invention, in step (2), the crosslinking agent is at least one of pentaerythritol tetra(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionic acid) ester, pentaerythritol tetra(mercaptoacetic acid) ester, trimethylolpropane tri(mercaptoacetic acid) ester, trimethylolpropane tri(3-mercaptopropionic acid) ester, and hexa(3-mercaptopropionic acid) dipentaerythritol ester, and the photoinitiator includes at least one of 2,2-dimethoxy-phenylacetophenone and free radical photoinitiator.

[0014] In one embodiment of the present invention, in step (2), the photothermal responsive material is carbon nanotubes and / or graphene, wherein the carbon nanotubes are single-walled or multi-walled carbon nanotubes with a particle size of 10–80 nm and a purity ≥95%. The mass of the photothermal responsive material in the raw material system accounts for 3–10% of the sum of the masses of the liquid crystal building blocks, crosslinking agent, and spacer groups, more preferably 3–5%. This specific amount of addition is one of the key factors for enabling the fiber to obtain unidirectional shrinkage characteristics.

[0015] In one embodiment of the present invention, in step (2), the carbon nanotubes may also be functionalized carbon nanotubes. If functionalized, the carbon nanotubes are hydroxylated carbon nanotubes, aminolated carbon nanotubes, or carboxylated carbon nanotubes, and their surfaces are grafted with modifying groups containing carbon-carbon double bonds.

[0016] In one embodiment of the present invention, the method for preparing functionalized carbon nanotubes with carbon-carbon double bond modification groups grafted on the surface is as follows: 0.1-1 g of functionalized carbon nanotubes are dispersed in 10-100 mL of dichloromethane, 0.05-0.5 g of glycidyl methacrylate (GMA) and 0.01-0.1 g of 4-dimethylaminopyridine (DMAP) are added, and the mixture is stirred and reacted at 30-50 °C for 6-24 h. After centrifugation, washing, and drying, functionalized carbon nanotubes with carbon-carbon double bonds grafted on the surface are obtained.

[0017] In one embodiment of the present invention, the mass ratios of the liquid crystal oligomer to the liquid crystal moiety, the crosslinking agent and the photothermal response material in step (2) are (1-2):(0.5-1), (1-2):(0.1-0.3), and (1-2):(0.06-0.1), respectively, and the amount of photoinitiator added is 0.1-5%, more preferably 0.5-2%.

[0018] In one embodiment of the present invention, in step (3), the stretching ratio after external stretching is controlled to be between 1 and 40. This stretching process is "incomplete stretching". The present invention controls the degree of external stretching to below the theoretical maximum stretching ratio of the fiber, preferably between 1 and 8, and even more preferably between 1 and 6, so that the fiber retains a certain internal stress and molecular chain entanglement. Combined with the dense physical cross-linking network formed in the stretching flow field by the specific amount of photothermal responsive material in step (2), the two work synergistically to endow the fiber with the final unidirectional shrinkage characteristics.

[0019] In one embodiment of the present invention, in step (3), the viscosity range of the viscous non-Newtonian fluid is 2000 to 8000 cst.

[0020] In one embodiment of the present invention, in step (3), the extrusion flow rate of the syringe pump can be adjusted to 0.01 to 1 mL / h, the rotation speed of the winding drum can be adjusted to 50 to 500 rpm, and the diameter of the liquid crystal elastomer fiber after external stretching can be controlled to 20 to 800 μm.

[0021] In one embodiment of the present invention, in step (4), the pre-curing temperature is 40-80°C, the pre-curing time is 1-4 hours, and the light curing is performed under UV-LED point light source for more than 3 seconds.

[0022] The present invention also provides a unidirectional shrinkable liquid crystal elastomer fiber prepared according to the above preparation method, which is prepared from a raw material system comprising liquid crystal moieties, crosslinking agents, spacers, photoinitiators, and photothermal responsive material solvents; the fiber is pre-stretched by mechanical stretching once, shrinks under photothermal stimulation, and the shrinkage state is maintained after the stimulation is removed, and its length can be restored by mechanical stretching again.

[0023] This unique "one-time stretch deformation" characteristic, or "unidirectional contraction-hold" mode, gives the fiber a true "on / off" precise control function. Compared with bidirectional deformable fibers in the prior art, the fiber of this invention remains in a locked state after the stimulus is removed, achieving precise control over the deformation position and degree.

[0024] The present invention also provides a smart fabric, which is composed of the above-mentioned unidirectional shrinkable liquid crystal elastomer fiber and knitted structure.

[0025] In one embodiment of the present invention, the knitted structure includes one or more of plain weave, rib weave, padded weave, tuck weave, double rib weave, and multi-layer composite weave. Different weave types endow smart fabrics with different deformation characteristics and application scenarios: Plain weave composite: The structure is flat, which can achieve uniform surface shrinkage or local convexity; Ribbed composite structure: Excellent elasticity, allowing for variations in thickness; Added yarn structure composite: double-sided effect, which can achieve front-side drive and back-side maintain a comfortable touch; Loop-based composite structure: It can form raised "pixels" at specific coil positions to achieve dot-matrix pattern writing, which is suitable for information display and Braille expression; Double rib structure composite: stable structure, enabling bidirectional bending control; Multi-layered composite structure: a three-dimensional structure that can achieve complex deformations such as self-standing and self-folding.

[0026] This invention also provides an application of the aforementioned unidirectional shrinkable liquid crystal elastomer fiber in constructing chipless logic devices based on "mechanical calculations". Utilizing the controllable deformation behavior of the unidirectional shrinkable liquid crystal elastomer fiber under the synergistic effects of multiple physical fields (such as light and heat), a logic operation unit that uses "force" instead of "electricity" can be constructed. By designing the initial state of the fiber and applying different combinations of stimulation signals, basic logic functions including AND, OR, NOT, and triggers can be realized.

[0027] The present invention also provides applications of the above-mentioned unidirectional shrinkable liquid crystal elastomer fiber, smart fabric and logic device based thereon in artificial muscles, smart wearables, light-controlled switch circuits, radiation-resistant space equipment, disposable microfluidic chips, physical encryption tags or biomimetic devices.

[0028] Beneficial effects: (1) This invention, through precise control of the content of photothermal responsive materials (such as carbon nanotubes, graphene, functionalized carbon nanotubes, etc.) and an understretching double stretching process, has for the first time produced LCE fibers with the characteristic of "one-time stretching deformation". The unidirectional shrinking liquid crystal elastomer fibers prepared by this method can maintain their state for more than 24 hours after shrinking under photothermal stimulation, until they are mechanically stretched again and can recover their original length. This achieves a precise control mode similar to a "switch", fundamentally solving the technical problem that traditional LCE fibers need continuous energy supply to maintain their state and cannot achieve fixed-point drive.

[0029] (2) This invention is the first to combine unidirectional shrinkage LCE fibers with various knitting structures such as plain weave, rib weave, yarn-padded weave, tuck weave, double rib weave, and multi-layer composite weave, giving full play to the structural advantages of different structures and realizing the functional integration from one-dimensional functional fibers to two-dimensional / three-dimensional smart fabrics. By selecting the weave type and fiber arrangement, it is possible to achieve morphological locking, independent addressing, and complex deformation control of specific areas of the fabric, providing a new approach for the diversified development of smart textiles.

[0030] (3) This invention is the first to propose and verify the use of the multi-physics field cooperative deformation characteristics of unidirectional shrinkable LCE fibers to construct a logic operation unit that uses "force" instead of "electricity". This innovation provides a material basis for realizing new types of computing devices that are radiation resistant and have low energy consumption. It can be widely used in fields such as radiation resistant space equipment with extremely high reliability requirements, disposable microfluidic chips that do not require power supply, and high-security physical encryption tags.

[0031] (4) The preparation method of the present invention is carried out at room temperature and normal pressure, using biomimetic bi-stretch spinning technology, with a spinning speed of up to 8400 m / h, and has good compatibility with existing textile processing technologies. Through the synergistic effect of understretching process and photothermal responsive materials, unidirectional shrinkage fibers with an adjustable diameter of 20~800μm, an absolute shrinkage stroke of 1.5 cm, the ability to achieve 2.5 times reversible stretching and complete recovery, and a driving stress of 4~5MPa can be stably prepared, which has broad prospects for industrial application. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the biomimetic bi-stretch spinning device in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram illustrating the application of the light-controlled switch circuit of the present invention; Figure 3 This is a photograph of the smart fabric made by combining the fibers of the present invention with various knitting structures in Embodiment 5 of the present invention; Figure 4 This is a partial conceptual diagram of the smart fabric combining LCE fibers and knitted structure of the present invention (the darker color represents LCE fibers). Figure 5 This is a schematic diagram of the fiber mechanics calculation logic unit in Embodiment 6 of the present invention. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The scope of protection of the present invention is not limited to the following embodiments.

[0034] Example 1: Preparation of unidirectional shrinkage type LCE fiber (1) Preparation of liquid crystal oligomers: 9.0 g of liquid crystal unit RM82 and 2.46 g of spacer DODT were weighed and dissolved in dichloromethane (11.0 g). Dipropylamine (0.206 g, accounting for 1.8% of the total mass of RM82 and DODT) was added as a catalyst and the mixture was stirred at room temperature for 24 h. After the reaction was completed, the mixture was washed twice with 0.1 mol / L dilute hydrochloric acid and twice with saturated sodium chloride solution. Anhydrous sodium sulfate was added and the mixture was dried at room temperature overnight. After filtration, the solvent was removed under reduced pressure to obtain white viscoelastic liquid crystal oligomers.

[0035] (2) Preparation of spinning solution: Weigh 1g of the liquid crystal oligomer obtained in step (1), 0.5g of RM82, 187.3mg of pentaerythritol tetra(3-mercaptopropionic acid) ester (PETMP), 10mg of photoinitiator I-651 and 0.05g of multi-walled carbon nanotubes (particle size 30nm, purity 98%), and add them to 3g of dichloromethane. Stir magnetically at room temperature for 30min until dissolved, then pour the solution into a polytetrafluoroethylene mold and let it stand at room temperature in the dark for 12h to allow the solvent to evaporate naturally until the system forms a viscous non-Newtonian fluid.

[0036] (3) Bionic bi-stretch spinning: The spinning solution is added to a CNC syringe equipped with a 30G conical spinneret. The syringe pump extrusion flow rate is set to 0.1mL / h, and the winding speed is set to 200rpm. The spinning solution is extruded after being stretched inside the conical spinneret. The initial filament is mechanically stretched 1.6 times to a diameter of 500μm by the winding drum.

[0037] (4) Curing and winding: The stretched fiber bundle is placed in a 60℃ oven for 10 min to pre-cur it and form a weak cross-linked network to fix the orientation; then the pre-cured fiber is placed under a UV-LED point light source (wavelength 395nm, light intensity 500mW / cm²) for 180s, and the cured liquid crystal elastomer fiber is wound up in an orderly manner at equal intervals through the guide rail slider to obtain the finished product.

[0038] Example 2 The difference between this embodiment and embodiment 1 is that the photothermal response material in step (2) is replaced by graphene (0.05g, purity ≥98%, sheet diameter 0.5~5μm) instead of multi-walled carbon nanotubes. The other raw material types, ratios and operation steps are the same as in embodiment 1.

[0039] The specific steps are as follows: (1) Preparation of liquid crystal oligomers: Same as in Example 1.

[0040] (2) Preparation of spinning solution: Weigh 1g of the liquid crystal oligomer obtained in step (1), 0.5g of RM82, 187.3mg of PETMP, 10mg of photoinitiator I-651 and 0.05g of graphene, and add them to 3g of dichloromethane. Stir magnetically at room temperature for 30min until dissolved, then pour the solution into a polytetrafluoroethylene mold and let it stand at room temperature in the dark for 12h to allow the solvent to evaporate naturally until the system forms a viscous non-Newtonian fluid.

[0041] (3) Bionic bi-stretch spinning: The spinning solution is added to a CNC syringe equipped with a 30G conical spinneret. The syringe pump extrusion flow rate is set to 0.1mL / h, and the winding speed is set to 200rpm. The spinning solution is extruded after being stretched inside the conical spinneret. The initial filament is mechanically stretched 1.4 times to a diameter of 580μm by the winding drum.

[0042] (4) Curing, winding and finishing: Same as in Example 1.

[0043] Example 3 The difference between Example 3 and Example 1 is that the multi-walled carbon nanotubes in step (2) are replaced with functionalized carbon nanotubes. The functionalized carbon nanotubes are carboxylated multi-walled carbon nanotubes, and their surfaces are further grafted with glycidyl methacrylate (GMA) containing carbon-carbon double bonds. The specific preparation method is as follows: 1g of multi-walled carbon nanotubes (particle size 30nm, purity 98%) are added to 100mL of a mixed acid mixture of concentrated nitric acid (18.4mol / L) and concentrated sulfuric acid (16mol / L) (volume ratio 1:3), ultrasonically treated at 60℃ for 4h, centrifuged and washed until neutral, and vacuum dried to obtain carboxylated multi-walled carbon nanotubes. 0.5g of carboxylated carbon nanotubes are dispersed in 50mL of dichloromethane, 0.2g of GMA and 0.05g of 4-dimethylaminopyridine (DMAP) are added, and the mixture is stirred at 40℃ for 12h, centrifuged, washed and dried to obtain functionalized carbon nanotubes with carbon-carbon double bonds grafted on their surface.

[0044] Except for replacing carbon nanotubes with the aforementioned functionalized carbon nanotubes, the other raw material types, ratios, and operating procedures are the same as in Example 1: (1) Preparation of liquid crystal oligomers: Same as in Example 1.

[0045] (2) Preparation of spinning solution: Weigh 1g of the liquid crystal oligomer obtained in step (1), 0.5g of RM82, 187.3mg of PETMP, 10mg of photoinitiator I-651 and 0.05g of functionalized carbon nanotubes, and add them to 3g of dichloromethane. Stir magnetically at room temperature for 30min until dissolved, then pour the solution into a polytetrafluoroethylene mold and let it stand at room temperature in the dark for 12h to allow the solvent to evaporate naturally into a viscous non-Newtonian fluid.

[0046] (3) Bionic bi-stretch spinning: Same as Example 1.

[0047] (4) Curing and winding: Same as in Example 1.

[0048] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the amount of multi-walled carbon nanotubes added is 0.01g.

[0049] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the amount of multi-walled carbon nanotubes added is 0.18g.

[0050] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that no carbon nanotubes were added, and only the pure liquid crystal elastomer fiber raw material system of Comparative Document 2 was used.

[0051] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the stretching ratio of the outer stretching in the biomimetic bistretching spinning step is controlled to be 8.

[0052] The performance of the unidirectional shrinking LCE fiber with a diameter of 500 μm prepared in Example 1 was tested. The fiber strip was subjected to a single mechanical stretching to elongate its axial length by 150%. Subsequently, it was tested using an 808 nm infrared laser (intensity 800 mW / cm²). 2 The pre-stretched fiber was irradiated. Results showed that the fiber rapidly contracted under illumination, shrinking completely from 2.5 cm to 1 cm, with an absolute shrinkage stroke of 1.5 cm and a driving strain of 60%. The fiber achieved a reversible stretch of 2.5 times (150% elongation), with a maximum driving stress of 4.3 MPa, and fully recovered, exhibiting excellent stretchability and driving capacity. After the light source was removed, the fiber's shrinkage state remained stable at room temperature, with no significant change in length over 24 hours. When the fiber was mechanically stretched again, it recovered to its pre-shrinkage length, indicating that the unidirectional shrinkage-holding process is repeatable.

[0053] The fiber prepared in Example 2 was subjected to performance testing. The fiber strip was mechanically stretched once, elongating its axial length by 80%. The pre-stretched fiber was then irradiated with an infrared laser. The results showed that the fiber rapidly contracted under illumination, completely recovering from 1.8 cm to its original length of 1 cm, with a maximum driving stress of 4 MPa. After the light source was removed, the fiber's contraction state remained stable at room temperature, with no significant change in length over 24 hours. When the fiber was mechanically stretched again, it recovered to its pre-contraction length. Compared to Example 1, the fiber using graphene exhibited slightly lower driving performance, with the maximum external mechanical stretch ratio decreasing from 2.5 times to 1.8 times after fiber preparation. However, it still maintained good unidirectional shrinkage-holding characteristics, meeting the design requirements of this invention.

[0054] The fiber (approximately 500 μm in diameter) prepared in Example 3 was tested. The fiber strip was mechanically stretched to a pre-elongation of 80% and irradiated with an infrared laser. Under illumination, the fiber rapidly shrank to its original length of 1 cm, with a maximum driving stress of 5.2 MPa. After the laser was removed, the shrunken state remained stable at room temperature for more than 24 hours, and it could recover its original length upon further mechanical stretching. Compared to Example 1, due to the functionalized carbon nanotubes participating in the cross-linking network through double bonds, the interfacial bonding was enhanced, resulting in a slight increase in driving strain rate and driving stress, superior cycle stability, and complete retention of the unidirectional shrinkage-holding characteristics.

[0055] The fiber prepared in Comparative Example 1 rebounded rapidly after mechanical stretching and pre-extension. After the laser was removed, the fiber could not maintain its contracted state and recovered to its pre-stretched length within 10 seconds at room temperature. It completely lost the unidirectional shrinkage-holding characteristics of the present invention and only exhibited the bidirectional reversible deformation behavior of traditional liquid crystal elastomer fibers.

[0056] In Comparative Example 2, when preparing the spinning solution, the carbon nanotubes exhibited severe agglomeration due to excessive addition, making it impossible to disperse evenly in the system. This easily caused blockage of the conical spinneret during spinning, making it difficult to continuously produce complete fibers. The fibers obtained in small quantities had rough surfaces and numerous internal pores, making them prone to breakage after mechanical stretching. They also lacked a significant photothermal shrinkage response, completely failing to achieve the unidirectional shrinkage function of this invention.

[0057] The fibers prepared in Comparative Examples 3 and 4 are similar to those in Comparative Example 1. After mechanical stretching and pre-extension, they show a shrinkage response under 808nm infrared laser irradiation, but immediately return to their original length after the laser is removed. They have no ability to maintain the shrinkage state, which is consistent with the performance of traditional bidirectional reversible deformation liquid crystal elastomer fibers. They cannot achieve the "on / off" unidirectional shrinkage-holding core function of this invention.

[0058] Application of light-controlled switch circuits The unidirectional shrinking LCE fiber prepared in Example 1 was integrated into a simple microcircuit with series-connected and non-closed electrodes, such as Figure 2 As shown, one end of the fiber is fixed, and the other end is connected to a movable conductive contact. After the fiber is mechanically stretched to a pre-elongation of 50%, the conductive contact is disconnected from the circuit electrode, and the circuit is open. When the fiber is irradiated with an 808nm infrared laser, the fiber contracts within 0.3 seconds, pulling the conductive contact to make contact with the electrode, and the circuit is turned on. After the laser is removed, because the fiber remains in a contracted state, the circuit continues to conduct for more than 24 hours, realizing the "trigger-hold" switching function. When the fiber is manually stretched again, the circuit is disconnected. After 5000 light-controlled on / off cycles, the contact resistance change is less than 5%, and the fiber shows no obvious fatigue.

[0059] Composite application of unidirectional shrinkage LCE fibers with various knitted structures To verify the feasibility of combining the unidirectional shrinkage liquid crystal elastomer fiber of the present invention with different knitted structures and its potential for wide application in the field of smart textiles, this embodiment combines the fiber prepared in Example 1 with six typical knitted structures and tests their photoresponse behavior.

[0060] (1) Plain weave composite A plain weave structure is used, in which LCE fibers are interwoven as weft yarns with ordinary cotton warp yarns, such as... Figure 3 As shown. The composite fabric has a smooth structure, with uniformly distributed LCE fibers, a cotton yarn diameter of 327 μm, and a fabric density of 3 × 4 loops / cm². 2 After the fibers are mechanically pre-stretched by 50% during the weaving process, irradiation with an 808nm infrared laser can achieve overall uniform shrinkage or localized point protrusion, with a response time of 3 seconds. This is suitable for smart clothing, curtains, and other applications requiring large-area driving or patterned control.

[0061] (2) Rib-knit composite This composite fabric employs a 1+1 rib knit structure, weaving LCE fibers and cotton yarn together on a flat knitting machine. The excellent elasticity of the rib knit structure combined with the unidirectional shrinkage characteristics of LCE fibers allows the fabric to not only shrink in length under infrared light stimulation but also exhibit significant changes in thickness. This composite fabric is suitable for wearable medical devices requiring an elastic fit, such as smart knee braces and elbow braces.

[0062] (3) Adding yarn to composite structure This fabric employs a weave structure where LCE fibers act as the face yarn, exposed on the front of the fabric, while ordinary polyester yarn serves as the ground yarn to maintain the tactile feel of the back. After pre-stretching, infrared light exposure on the front causes the LCE fibers to shrink, wrinkling the fabric surface to create an embossed pattern, while the back remains flat and comfortable. This structure is suitable for applications such as smart home décor and brand anti-counterfeiting labels.

[0063] (4) Cluster organization composite The fabric employs a loop weave, forming loops at specific coil locations to distribute LCE fibers in a dotted pattern within the fabric. After pre-stretching, infrared light irradiates the looped areas, causing them to shrink and form raised "pixels" approximately 1-2 mm high, while the plain-knit areas remain flat. By designing the distribution of the loop positions, dot-matrix patterns can be written onto the fabric surface, suitable for applications such as information display and Braille representation.

[0064] (5) Double rib structure composite A double-rib knit structure is created by weaving LCE fibers and polyester low-elasticity yarn on a double-sided knitting machine to produce a stable double-layer structure. LCE fibers can be embedded in both the inner and outer layers of the double-rib knit structure. After pre-stretching, irradiation of one side with infrared light causes the fibers on that side to shrink, resulting in the fabric bending towards that side at an angle of 40-70°. Alternating irradiation of both sides allows for bidirectional bending control of the fabric. This structure is suitable for bionic fingers, soft robot grippers, and other applications requiring directional bending actuation.

[0065] (6) Multilayer composite tissue Employing multi-layer weaving technology, this composite fabric uses LCE fiber as the intermediate driving layer, with the upper and lower layers being ordinary knitted fabrics, bonded together by stitching or bonding. After pre-stretching, infrared light irradiates the intermediate layer, causing it to shrink and leading to out-of-plane deformation of the upper and lower layers, forming a three-dimensional structure with a standing height of up to 9mm. This composite fabric can stand upright and fold itself under infrared light irradiation, maintaining its shape for over 24 hours after the light is removed. It is suitable for applications such as deployable structures, emergency tents, and self-deforming packaging materials.

[0066] Performance testing The photoresponse performance of the six smart fabrics was tested. The results showed that all composite fabrics fully retained the unidirectional shrinkage-holding characteristics of the fibers, with response times ranging from 1.5 to 3.0 seconds and state holding times exceeding 24 hours. After 1000 light-controlled stretching cycles, the shrinkage performance showed no significant attenuation. Different weaves endow smart fabrics with differentiated deformation characteristics, allowing for selection and design based on specific application requirements.

[0067] Construction and Application of Chipless Logic Units Based on Unidirectional Shrinkable LCE Fibers This embodiment aims to demonstrate another core application of the fiber of the present invention, in addition to its driving function—constructing a "mechanical calculation" logic unit.

[0068] After pre-stretching, the fibers prepared in Example 1 are fixed onto a specially designed miniature support consisting of detection points, an infrared light source, a mechanical stretching device, a sliding rail, and circuitry, forming the "computing core" of the logic unit. Multiple light sources (such as infrared light A and infrared light B) are designed as irradiation combinations for the logic unit, while the final shrinkage state of the fiber (whether it shrinks to a preset threshold position) serves as the "output signal" (e.g., shrinkage is defined as "1", and no shrinkage as "0").

[0069] (1) AND gate logic: Two pre-stretched fibers are arranged in series. Only when light source A illuminates fiber 1 and light source B illuminates fiber 2, both fibers contract and pull the output terminal to the threshold position, outputting "1"; otherwise, outputting "0".

[0070] (2) OR gate logic: Connect two pre-stretched fibers in parallel to the output terminal. When light source A illuminates fiber 1 or light source B illuminates fiber 2, the contraction of either fiber will pull the output terminal to the threshold position and output "1"; only when neither light source illuminates will the output be "0".

[0071] (3) NOT gate logic: Utilizing the unidirectional contraction-hold characteristic of fibers, more complex logic can be constructed. For example, a pre-stretched fiber can be used as a base. The input signal is a reset light source. In the initial state (without reset light), the fiber remains in a contracted state, and the output is defined as "1". When a reset light (input) is applied, the fiber does not respond (because its contracted state is independent of light), and it needs to be mechanically stretched to recover. Thus, through clever design, the NOT logic relationship is realized, that is, when the input is "1", the output becomes "0" through mechanical linkage. More complex D flip-flops can achieve state latching through the combination of multiple fibers.

[0072] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing a unidirectional shrinkable liquid crystal elastomer fiber, characterized in that, Includes the following steps: (1) Preparation of liquid crystal oligomers: Liquid crystal units and spacer groups are added to a solvent, and a catalyst is added and stirred to allow the reaction to proceed. The reaction solution is then washed with dilute hydrochloric acid, salted with saturated sodium chloride solution, dried with anhydrous sodium sulfate, filtered, and desolventized under reduced pressure to obtain white viscoelastic liquid crystal oligomers. (2) Preparation of spinning solution: Add the liquid crystal oligomer, liquid crystal moiety, crosslinking agent, photoinitiator and photothermal response material obtained in step (1) to the solvent, stir until completely dissolved, pour the solution into a polytetrafluoroethylene mold, and let it stand in the dark for 12 hours to allow the solvent to evaporate naturally until the system forms a viscous non-Newtonian fluid. (3) Bionic bi-stretch spinning: The spinning solution is added to a CNC syringe equipped with a conical spinneret, and the spinning solution is extruded by the syringe pump. The solution is internally stretched by the conical wall shear of the conical spinneret. The initial filament is mechanically externally stretched by a winding drum driven by a CNC motor to achieve further refinement and improved orientation of liquid crystal units, thus preparing liquid crystal elastomer filament bundles. The stretching ratio of the fibers after external stretching is 1~8, and the diameter of the prepared liquid crystal elastomer filament bundles is 20μm-600μm. (4) Curing and winding: The stretched filaments obtained in step (3) are placed in an oven for pre-curing, and then photocured. The cured liquid crystal elastomer fibers are wound in an orderly manner at equal intervals by a guide rail slider to obtain the finished product.

2. The preparation method according to claim 1, characterized in that, In step (1), the liquid crystal unit is at least one of RM82, RM257, a photosensitive monomer containing azobenzene, and a cholesterol derivative liquid crystal unit. The spacer group is at least one of 3,6-dioxa-1,8-octanedithiol, 1,10-decanedithiol, 1,2-ethanedithiol, 1,3-propanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 1,8-octanedithiol, 1,9-nonanedithiol, and 3,6-dioxa-1,8-octanedithiol. The molar ratio of the liquid crystal unit to the spacer group is 1:

1. The solvent includes at least one of dichloromethane, trichloromethane, tetrahydrofuran, and ethyl acetate. The amount of solvent added is 2.7 to 3 times the total mass of the liquid crystal unit and the spacer group.

3. The preparation method according to claim 1, characterized in that, In step (1), the catalyst includes dipropylamine or triethylamine, and the amount of catalyst added is 1.5 to 2.0% of the total mass of the liquid crystal unit and the spacer. After adding the catalyst, the mixture is stirred at room temperature for 24 hours.

4. The preparation method according to claim 1, characterized in that, In step (2), the crosslinking agent is at least one of pentaerythritol tetra(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionic acid) ester, pentaerythritol tetra(mercaptoacetic acid) ester, trimethylolpropane tri(mercaptoacetic acid) ester, trimethylolpropane tri(3-mercaptopropionate) ester, and hexa(3-mercaptopropionate) dipentaerythritol ester. The photoinitiator includes at least one of 2,2-dimethoxy-phenylacetophenone and free radical photoinitiators. The photothermal response material is carbon nanotubes and / or graphene. The carbon nanotubes are single-walled carbon nanotubes or multi-walled carbon nanotubes. The mass of the photothermal response material in the raw material system accounts for 3 to 10% of the sum of the masses of the liquid crystal moiety, the crosslinking agent, and the spacer group.

5. The preparation method according to claim 1, characterized in that, In step (2), the carbon nanotubes can also be functionalized carbon nanotubes, which are hydroxylated carbon nanotubes, aminolated carbon nanotubes or carboxylated carbon nanotubes, and their surfaces are grafted with modifying groups containing carbon-carbon double bonds.

6. The preparation method according to claim 1, characterized in that, In step (2), the mass ratios of the liquid crystal oligomer to the liquid crystal moiety, the crosslinking agent and the photothermal response material are (1-2): (0.5-1), (1-2): (0.1-0.3), and (1-2): (0.06-0.1), respectively, and the amount of photoinitiator added is 0.1-5% of the mass of the liquid crystal oligomer.

7. The unidirectional shrinkable liquid crystal elastomer fiber prepared by the preparation method according to any one of claims 1 to 6, characterized in that, After being mechanically stretched and pre-extended once, the fiber shrinks under photothermal stimulation. After the stimulation is removed, the shrinkage state is maintained, and it can only be restored to its length by mechanical stretching again.

8. A smart fabric, characterized in that, The smart fabric is composed of the unidirectional shrinkage liquid crystal elastomer fiber as described in claim 7 and a knitted structure, wherein the knitted structure includes one or more of plain weave, rib weave, yarn-padded weave, tuck weave, double rib weave, and multi-layer composite weave.

9. The application of the unidirectional shrinkable liquid crystal elastomer fiber of claim 7 and the smart fabric of claim 8 in artificial muscles, smart wearables, light-controlled switch circuits, radiation-resistant space equipment, disposable microfluidic chips, physical encryption tags or biomimetic devices.

10. The application of the unidirectional shrinkable liquid crystal elastomer fiber of claim 7 in constructing a chipless logic device based on "mechanical calculation", the application including using the controllable deformation behavior of the unidirectional shrinkable liquid crystal elastomer fiber under the synergistic action of multiple physical fields (such as light and heat) to construct a logic operation unit that replaces "electricity" with "force", and by designing the initial state of the fiber and applying different combinations of stimulation signals, basic logic functions including AND, OR, NOT, and triggers can be realized.

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