Hybrid crystal material with sandwich structure and preparation method and application thereof

Abstract

The application belongs to the technical field of intelligent materials, and provides a hybrid crystal material with a sandwich structure, a preparation method and application thereof. The application realizes a multi-dimensional breakthrough by constructing a hybrid crystal material with a rGO / PDDA / Crystal / PDDA / TPU sandwich structure, and achieves a humidity sensitivity of 1.65%RH ‑1 0.46%°C ‑1 temperature sensitivity in a wide temperature range of 25-180°C, and a dual-mode sensing is realized, and an optical signal calibration is simultaneously provided, and a complex action can be completed through a near-infrared laser remote control at a deep low temperature of-150°C; the organic crystal base (crystal 1 to crystal 6) still has good elasticity and can be repeatedly bent without breaking at a liquid nitrogen temperature of-196°C; meanwhile, the material integrates sensing, optical and driving functions in a single structure, simplifies a traditional process, reduces system cost, is suitable for extreme environments such as deep low temperature, and has great application potential.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of intelligent materials, and particularly relates to a hybrid crystal material with a sandwich structure and a preparation method and application thereof. BACKGROUND

[0002] As a frontier field, flexible electronics aims to integrate information sensing, processing and execution functions on flexible substrates to build intelligent systems that can seamlessly interact with the human body and the environment. With the expansion of application scenarios such as wearable health monitoring, bionic soft robots, and environmental intelligent sensing, there are high requirements for the functional complexity and environmental adaptability of flexible materials. An ideal flexible material should have good mechanical flexibility, stability and multi-functional integration capability (for example, while sensing environmental changes such as humidity and temperature, it can actively perform specific actions such as movement and deformation), and may provide optical signal feedback, thereby completing the closed-loop task of sensing-decision-execution in a limited space. Such systems play a key role in extreme or special environments such as precision instrument warehouse environment maintenance, spacecraft internal autonomous detection, and biological sample cryogenic processing.

[0003] To achieve the above goal, the scientific research community has explored multiple technical paths, but all have obvious limitations:

[0004] Flexible sensing technology based on composite materials adopts a typical structure of "functional filler + elastic matrix", by dispersing conductive fillers (such as carbon nanotubes, graphene nanosheets, metal nanowires) or sensitive materials (such as hygroscopic polymers) in uncrosslinked polymer precursors (such as polydimethylsiloxane PDMS, thermoplastic polyurethane TPU), and then forming a flexible sensing film or device through thermal or ultraviolet curing. However, its function is limited to single physical quantity sensing, and multiple layers of stacking or patterned design are required to achieve multi-parameter detection, resulting in high system integration complexity and easy interface fatigue; when the environmental temperature drops sharply to deep low temperature (such as below-50°C, up to liquid nitrogen temperature-196°C), the polymer (such as PDMS, TPU) will undergo glass transition, and the material will change from soft and elastic to rigid and brittle, which is prone to cracking and pulverization. At the same time, the large difference in thermal expansion coefficient between the functional filler and the polymer matrix will generate a large internal stress, which will destroy the conductive network and cause the sensing function to fail.

[0005] In the aspect of driving technology, flexible driving materials based on smart polymers have been widely studied. Shape memory polymers (SMPs) can be deformed into temporary shapes when heated above the glass transition temperature, and fixed after cooling. When heated again, they can recover to the original permanent shape. Liquid crystal elastomers (LCEs) can be reversibly stretched or contracted along the orientation direction when stimulated by light, heat, etc., resulting in driving strain. Light-thermal driving LCEs usually need to be doped with light-thermal fillers (such as gold nanorods, carbon materials). The structure of dielectric elastomer (DEA) driver is similar to a soft capacitor, with flexible electrodes attached to both sides of the dielectric elastomer film. When a high voltage is applied, the static electric force causes the film to be compressed in the thickness direction and expanded in the plane direction, resulting in large strain. The molecular chain segment movement of this kind of material is "frozen" at deep low temperature, and the driving ability is completely lost. Moreover, there are problems such as high energy consumption, slow response, high voltage driving, and dependence on complex external control system, which are difficult to meet the needs of integration of high efficiency, precision and local control. Although a few soft robots based on magnetic driving can work at low temperature, they rely on a large and complex external magnetic field control system, which is difficult to miniaturize and integrate, and does not have in-situ sensing capability.

[0006] In order to construct an intelligent system with sensing and driving capabilities, the traditional "heterogeneous integration" strategy integrates commercial or self-made micro rigid sensors (such as MEMS temperature and humidity sensor chips) and actuators (such as micro motors, piezoelectric ceramics) on a flexible printed circuit board (FPCB) through wire bonding, conductive adhesive bonding, etc., and then encapsulates them with flexible polymers (such as silicone). However, this scheme involves multiple independent process steps such as sensor device preparation, actuator preparation, FPCB processing, micro assembly, and encapsulation testing, which is complex. Moreover, the number of interfaces increases, the volume and cost increase significantly, and these interfaces are prone to wire breakage and interface peeling under repeated deformation or temperature cycling, resulting in poor system reliability, which seriously restricts its long-term operation in extreme environments.

[0007] In recent years, flexible organic crystal materials have emerged, which are formed by self-assembly of specific small molecules through weak interactions (such as π-π stacking, hydrogen bonding). With its highly ordered molecules, reversible bending and excellent optical properties, it provides new possibilities for flexible optoelectronic devices. Its typical form is a needle-like or sheet-like single crystal with a size of millimeters to centimeters, which is mainly grown by slow solvent diffusion method or evaporation method. However, current researches mainly focus on single-function applications such as optical waveguide or stress sensing, and the intrinsic insulating property limits the development of electrical sensing. Moreover, there is a lack of effective energy conversion mechanism, which cannot realize driving function, and has not yet realized its potential in multifunctional integrated systems.

[0008] In summary, the existing technology cannot realize the high integration of sensing, driving and optical functions under harsh conditions such as deep low temperature. Therefore, the present application proposes a hybrid crystal material with a sandwich structure and its preparation method and application. SUMMARY

[0009] The present application aims to provide a hybrid crystal material with sandwich structure and its preparation method and application, and aims to solve the problems raised in the background art.

[0010] The purpose of the present application is achieved by the following technical solutions:

[0011] A hybrid crystal material with sandwich structure, the hybrid crystal material has a sandwich configuration of rGO / PDDA / Crystal / PDDA / TPU, including a flexible organic crystal, an interface modification layer, a conductive and photothermal layer, and a driving layer.

[0012] The flexible organic crystal is selected from at least one of compound 1 to compound 6, wherein: compound 1 is (Z)-4-(2-cyano-2-(4-(trifluoromethoxy) phenyl) vinyl) benzonitrile, compound 2 is 2,2'-((1E,1'E)-1,4-benzene di(vinyl-2,1-diyl)) dicyanide, compound 3 is (E)-N'-((E)-3,5-dichloro-2-hydroxyphenyl methylene)-N,N-dimethyl form hydrazide amide, compound 4 is (Z)-4-(3-(5-methoxy-1-methyl-1H-indol-3-yl) acryloyl) benzonitrile, compound 5 is (Z)-3-(furan-2-yl)-2-(4-(((E)-2-hydroxy-5-methyl phenyl methylene) amino) phenyl) acrylonitrile, and compound 6 is (Z)-2-(4-(((E)-5-fluoro-2-hydroxy phenyl methylene) amino) phenyl)-3-(thiophene-2-yl) acrylonitrile.

[0013] The interface modification layer contains polydiallyldimethylammonium chloride, which is adsorbed on the surface of the flexible organic crystal through electrostatic interaction.

[0014] The conductive and photothermal layer contains reduced graphene oxide, which covers one side of the flexible organic crystal modified with the interface modification layer.

[0015] The driving layer contains thermoplastic polyurethane, which covers the other side of the flexible organic crystal modified with the interface modification layer.

[0016] A preparation method of the hybrid crystal material described above, comprising the following steps:

[0017] Step 1: Dissolve at least one of compound 1 to compound 6 in dichloromethane solution, slowly add ethanol solution along the container wall, stand at room temperature for 3-7 days, obtain centimeter level needle-like single crystal, i.e. flexible organic crystal;

[0018] Step 2: Self-assemble polyelectrolyte interface modification layer on the surface of the flexible organic crystal.

[0019] Step 3: depositing reduced graphene oxide on one side of the polyelectrolyte interfacial modification layer to form a conductive and photothermal layer;

[0020] Step 4: coating a thermoplastic polyurethane solution on the other side of the polyelectrolyte interfacial modification layer to form a driving layer;

[0021] Step 5: post-processing to promote the interface bonding of each layer to form a stable rGO / PDDA / Crystal / PDDA / TPU sandwich structure.

[0022] Further, in step 2, the specific operation of self-assembling the polyelectrolyte interfacial modification layer is: after the flexible organic crystal is washed with ethanol or petroleum ether and naturally dried, it is immersed in an aqueous solution containing polydiallyldimethylammonium chloride and sodium chloride, and then dried with nitrogen.

[0023] Further, in step 3, the specific operation of depositing the reduced graphene oxide layer is: the reduced graphene oxide powder is dispersed in deionized water, and ultrasonic treatment is performed until a uniform and stable dispersion liquid is formed, and the dispersion liquid is drop-coated on the target position of the interfacial modification layer with a syringe, and then naturally dried at room temperature.

[0024] Further, in step 4, the thermoplastic polyurethane solution is obtained by dissolving thermoplastic polyurethane particles in tetrahydrofuran or N,N-dimethylformamide.

[0025] Further, in step 5, the post-processing includes: after all the solvents are completely volatilized, the obtained material is heat annealed at 60°C for 30 minutes.

[0026] A multifunctional integrated system comprising the hybrid crystal material as described above, which simultaneously realizes:

[0027] Realizing humidity and temperature sensing based on reduced graphene oxide;

[0028] Realizing optical temperature sensing and fluorescence feedback based on flexible organic crystals;

[0029] Realizing infrared driving deformation and motion control in a low-temperature environment based on the difference in thermal shrinkage rate between thermoplastic polyurethane and flexible organic crystals, and the photothermal effect of reduced graphene oxide.

[0030] Further, the low-temperature environment is -150°C.

[0031] Compared with the prior art, the beneficial effects of the present application are:

[0032] 1. Efficient multi-modal sensing and intelligent actuation: The hybrid crystal material of the present invention can realize high-sensitivity humidity (1.65% RH -1 ) and temperature (0.46% °C -1 ) sensing in a wide temperature range (25-180°C), and simultaneously provide optical signal verification. At the same time, the material can be remotely controlled by near-infrared laser at deep low temperature (-150°C) to complete complex movements such as crawling and jumping, greatly improving the intelligent response and execution capability of flexible systems.

[0033] 2. Excellent adaptability to extreme environments: The organic crystal substrate (Crystal 1 to Crystal 6) of the present invention can maintain good elasticity at liquid nitrogen temperature (-196°C) and will not break upon repeated bending, breaking through the temperature use limit of traditional flexible electronic devices and providing a reliable hardware solution for space exploration, polar research, low-temperature biology, and other frontier fields.

[0034] 3. Highly simplified and integrated system: The hybrid crystal material of the present invention integrates sensing, optical, and actuation functions into a single material structure, eliminating the complex heterogeneous integration and packaging steps in traditional solutions, significantly reducing system complexity, volume, and weight, and laying the foundation for the development of miniaturized, high-reliability intelligent systems.

[0035] 4. Low preparation cost and broad application prospects: The present invention uses solution processing techniques such as solvent diffusion and readily available raw materials, making the preparation cost controllable and easy to promote. It has great application potential in the fields of deep low-temperature soft robot, built-in intelligent monitoring of spacecraft, and adaptive control of precision instrument environment. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a schematic diagram of the preparation process of the hybrid crystal with a sandwich structure.

[0037] Figure 2 is a molecular structure and low-temperature mechanical flexibility characterization diagram of the organic crystal; wherein: a is the molecular formula of Compound 1 to Compound 6; b is the reversible bending fluorescence photo of Crystal 1 to Crystal 6 at -196°C.

[0038] Figure 3 is an XPS spectrum; wherein: a is the C1s spectrum of Crystal 2, 2 / PDDA (PDDA / Crystal 2 / PDDA), and 2 / PDDA treated by high and low temperature and bending fatigue cycle; b is the O1s spectrum of rGO, rGO / PDDA, and rGO / PDDA treated by high and low temperature and bending fatigue cycle; c is the C1s spectrum of TPU, TPU / PDDA, and TPU / PDDA treated by high and low temperature and bending fatigue cycle.

[0039] Figure 4 The electrical and optical responses of the hybrid crystal GT2; wherein: a is the current-voltage curve at 25-90% RH (25°C); b is the linear relationship between humidity and resistance change rate; c is the current-voltage curve at 25-180°C (30% RH); d is the linear relationship between temperature and resistance change rate; e is the emission spectrum of the tip output at 25-180°C (30% RH); f is the linear relationship between temperature and optical signal.

[0040] Figure 5 The low-temperature curling behavior and infrared-driven deformation and motion mode diagram of the hybrid crystal; wherein: a is the fluorescence photo of the hybrid crystal under low-temperature conditions, showing its sensitive curling behavior; b is the low-temperature deformation fluorescence photo of the curled crystal under infrared irradiation; c is the schematic diagram of different motion modes of the hybrid crystal in a low-temperature environment under infrared driving.

[0041] Figure 6 The structural composition, cross-sectional morphology and mechanical flexibility diagram of the hybrid crystal GT2; wherein: a is the composition schematic diagram of the hybrid crystal GT2; b is the cross-sectional SEM image of the rGO and TPU layers of the hybrid crystal; c is the reversible bending process of the hybrid crystal GT2.

[0042] Figure 7 The light transmission performance characterization diagram of the hybrid crystal GT2; wherein: a is the fluorescence image of GT2 at different distances from the excitation point and the detection tip; b is the emission spectrum collected at the tip of the original crystal 2 and the hybrid crystal GT2, respectively; c is the exponential fitting of the decay curves of the original crystal 2 and the hybrid crystal GT2.

[0043] Figure 8 The humidity sensing performance and stability test diagram of the hybrid crystal GT2; wherein: a is the monitoring of water evaporation when the fingertip repeatedly approaches the crystal at different distances; b is the fingertip humidity signal and breathing signal recorded under dry air conditions and after wearing a nitrile glove; c is the monitoring curve of GT2 for breathing and fingertip humidity after being placed at 90% relative humidity for 25 days; d is the characteristic humidity signal of different parts of the human body recorded by GT2.

[0044] Figure 9 The low-temperature infrared-driven motion and signal output system performance diagram of the hybrid crystal GT2; wherein: a is the fluorescence photo of the spiral motion (i.e. peristalsis) of the curled GT2 at low temperature; b is the fluorescence photo of the jumping process of GT2 at low temperature; c is the output signal schematic diagram of the hybrid crystal under infrared driving in a low-temperature environment; d is the current-voltage curve of GT2 at 25°C, -150°C and -150°C (206.8 mW infrared irradiation); e is the reversible response signal of GT2 under periodic infrared irradiation. DETAILED DESCRIPTION

[0045] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present application, the technical solutions of the present application are described in detail as follows, but should not be understood as limiting the scope of the present application. In the present application, the materials, reagents or instruments used are not specified by the manufacturer, and are conventional products that can be purchased on the market.

[0046] The specific implementation of the present application is described in detail below in combination with specific examples.

[0047] The present application provides a multifunctional hybrid crystal material with a sandwich structure, which is assembled and integrated by the conductive / photothermal properties of reduced graphene oxide (rGO), the optical / mechanical properties of flexible organic crystals (Crystal) and the stress-induced properties of thermoplastic polyurethane (TPU) Figure 1 , achieving high-sensitivity humidity / temperature dual-mode sensing in a wide temperature range (-150~180°C) and having infrared light remote precise driving capability. The technical solutions of the present application are described in detail from four aspects of material preparation, interface composite mechanism, dual sensing function and low-temperature photothermal controllable driving.

[0048] (I) Preparation of hybrid crystal material

[0049] 1. Growth and selection of flexible organic crystal substrate

[0050] Small organic molecule compounds 1 to 6 with π-conjugated system and rich intermolecular interaction are selected Figure 2(Z)-4-(2-cyano-2-(4-(trifluoromethoxy)phenyl)vinyl)benzonitrile, 2,2'-((1E,1'E)-1,4-phenylene(vinylene-2,1-diyl))dibenzonitrile, (E)-N'-((E)-3,5-dichloro-2-hydroxyphenylmethylene)-N,N-dimethylformohydrazide amide, (Z)-4-(3-(5-methoxy-1-methyl-1H-indol-3-yl)acryloyl)benzonitrile, (Z)-3-(furan-2-yl)-2-(4-(((E)-2-hydroxy-5-methylphenylmethylene)amino)phenyl)acrylonitrile, (Z)-2-(4-(((E)-5-fluoro-2-hydroxyphenylmethylene)amino)phenyl)-3-(thiophen-2-yl)acrylonitrile. Except for compound 2, which is commercially available, compounds 1 and 3-6 were synthesized according to the literature method (Angew. Chem. Int. Ed. 2021, 60, 11283-11287; Adv. Mater. 2022, 34, 2200471). Using solvent diffusion method, the compounds were dissolved in dichloromethane solution (~10 mmol / L) and placed in a flask or test tube, and ethanol solution was slowly added along the wall of the bottle / tube. After standing at room temperature for 3-7 days, cm-level high-quality needle-like single crystals were obtained. This method can ensure the integrity of the crystal structure and few defects, providing an ideal substrate for subsequent functionalization. The obtained crystals still maintain good elasticity at a low temperature of -196 °C and do not break when repeatedly bent Figure 2 Middle b).

[0051] 2. Self-assembly of interface modification layer:

[0052] The grown crystals were gently rinsed with ethanol or petroleum ether to remove surface impurities and naturally dried. The crystals were immersed in an aqueous solution containing 5.0 mg / mL polydiallyldimethylammonium chloride (PDDA) and 1.0 M sodium chloride, and stood for 20 minutes. The positively charged PDDA molecules were adsorbed on the negatively charged or neutral crystal surface through electrostatic interaction, forming a dense and firm polyelectrolyte layer. This step aims to provide a uniform positively charged surface for the subsequent adsorption of rGO and enhance the interfacial bonding force. Then it was blown dry with nitrogen, and the structure was named PDDA / Crystal / PDDA.

[0053] 3. Construction of conductive and photothermal layer:

[0054] Preparation of rGO dispersion: rGO powder was dispersed in deionized water and ultrasonically treated until a uniform and stable dispersion was formed (concentration about 1 mg / mL).

[0055] rGO deposition: The PDDA-modified crystals were fixed on the substrate, and a syringe was used to precisely drop-cast the rGO dispersion on the wide side of the crystals. By the electrostatic adsorption between PDDA and rGO nanosheets, the rGO nanosheets uniformly and densely covered the surface of the crystals. Subsequently, the water was evaporated at room temperature, and the rGO layer was firmly attached to the surface of the crystals, and the structure was named as rGO / PDDA / Crystal / PDDA.

[0056] 4. Integration of the driving layer:

[0057] TPU solution preparation: Thermoplastic polyurethane (TPU, such as Elastollan 1195A) particles were dissolved in tetrahydrofuran (THF) or N,N-dimethylformamide (DMF) to prepare a transparent solution with a concentration of 1 mg / mL.

[0058] TPU coating: On the other wide side of the crystals (opposite to the rGO layer), the above-mentioned TPU solution was drop-cast or spin-coated. By the rapid evaporation of the solvent, a smooth, continuous, and thickness-controllable TPU film was formed. This layer not only plays a mechanical protection role, but also is the key to low-temperature driving due to the significant difference in the coefficient of thermal expansion between the organic crystal core and the TPU layer.

[0059] 5. Post-processing and forming:

[0060] After all the solvents were completely evaporated, the obtained hybrid crystals were heat-annealed at 60°C for 30 minutes. This process helps to remove residual solvents and promotes further tight bonding between the interfaces, improving the structural stability. Finally, the hybrid crystals with sandwich structures, named as rGO / PDDA / Crystal / PDDA / TPU, are obtained, which are referred to as GT1 to GT6.

[0061] (II) Interfacial composite structure and stability;

[0062] The sandwich structure of the present application is not a simple physical stacking, but a firm composite between the functional layers through careful design of the interface engineering, which is the key to its excellent performance. Its interfacial interaction is shown in Figure 3 .

[0063] Bridge effect of PDDA: The polyelectrolyte PDDA acts as a "molecular glue" in this structure. The positively charged quaternary ammonium salt groups on its long-chain molecules can strongly adsorb on the negatively charged organic crystal surface and the edges and defects of rGO nanosheets; at the same time, its carbon chain part can be entangled with the TPU molecular chain. This dual mechanism of "electrostatic adsorption + physical entanglement" forms a strong bridge between the crystal and rGO, the crystal and TPU. Taking hybrid crystals GT1 and GT2 as examples, the interface chemical state between the layers was analyzed by X-ray photoelectron spectroscopy (XPS), providing strong evidence for the existence of chemical interaction at the interface: compared with the original crystal 2, the binding energy of the C-N component in the C 1s spectrum of 2 / PDDA (i.e. PDDA / Crystal 2 / PDDA) has a negative shift of about 0.2 eV, indicating that PDDA has an electronic interaction with the crystal surface Figure 3 b) in rGO / PDDA, the components of the O 1s spectrum will have a shift of 0.3 and 0.7 eV and the relative intensity will change, confirming the electrostatic complexation between PDDA and the oxygen-containing functional groups of rGO Figure 3 c) for TPU / PDDA, the binding energy of the C-O / C-N component has a negative shift of about 0.3 eV, indicating that there is an interface dipole interaction or charge transfer between PDDA and TPU Figure 3

[0064] Structural stability brought by the interface: As shown in the results of XPS Figure 3 a~c), this strong interface complexation ensures that the hybrid crystal remains intact after repeated bending and high and low temperature (-150~150°C) cycle treatment, and there is no obvious delamination, cracking or peeling off between the functional layers, proving the excellent durability of the interface.

[0065] (Three) Dual sensing function;

[0066] This hybrid crystal can simultaneously serve as a high-sensitivity humidity sensor and a temperature sensor, as follows:

[0067] 1. Humidity sensing mechanism:

[0068] Process: Water molecules in the environment are adsorbed by the hydrophilic groups (such as -OH, -COOH) on the surface of the rGO layer through hydrogen bonds and van der Waals forces. Water molecules act as proton conduction carriers on the one hand and as dielectric media on the other, increasing the tunnel junction resistance between rGO layers, thus overall showing a linear increase in resistance with increasing humidity Figure 4 a).

[0069] ​Signal output: The resistance change rate (ΔR / R0) of the hybrid crystal GT2 shows a high linearity (R 2 > 0.99) with the relative humidity (25~90% RH) at a constant temperature of 25℃, and the sensitivity can reach 1.65% RH -1 . Figure 4 The electrical signal can be monitored in real time by an external circuit, realizing rapid humidity sensing.

[0070] 2. Temperature sensing mechanism:

[0071] Electrical signal: The resistance of the hybrid crystal GT2 decreases with the temperature increasing from 25℃ to 180℃ at a constant humidity of 30% RH (Fig. Figure 4 c). This behavior is attributed to thermal excitation, which increases the carrier density in the rGO layer, allowing more electrons to overcome the energy barrier, thus reducing the resistance. The temperature sensing ability of GT2 shows a high linearity (R 2 > 0.99), and the sensitivity is 0.46% °C -1 . Figure 4

[0072] Optical signal: In addition to electrical sensing, the fluorescence intensity emitted by the hybrid crystal itself shows a temperature-dependent decrease (Fig. Figure 4 e), and the optical signal shows a negative linear correlation with the temperature (Fig. Figure 4 f).

[0073] The synchronous response of electrical and optical signals to temperature changes constitutes a dual temperature sensing mechanism, and the two signals can be cross-checked, improving the reliability and accuracy of measurement.

[0074] (Four) Low-temperature photo-thermal controllable driving;

[0075] In addition to the flexible sensing function, one of the most prominent features of the present application is the ability to remotely control the driving of infrared light in a deep low-temperature environment.

[0076] 1. Driving mechanism:

[0077] Low-temperature bending: When the hybrid crystal is in an extremely low-temperature environment of -150℃, the shrinkage rate of the TPU layer is much greater than that of the organic crystal layer, resulting in a huge internal stress, which causes the crystal to spontaneously bend or curl towards the TPU side (Fig. Figure 5 a), and this process is reversible.

[0078] ​Photo-thermal actuation: Due to the excellent photo-thermal effect of rGO, the local temperature increases when the local position of the hybrid crystal is irradiated by 808 nm near-infrared laser (power ~ 200 mW) at low temperature, which makes the deformation degree of the region decrease or even restore to straight state; once the irradiation is stopped, the region quickly cools down in the ultra-low temperature environment and restores to the curled state. This "local straightening-recovery" cycle constitutes the basic unit of driving the crystal movement Figure 5 b).

[0079] 2. Controllable motion realization:

[0080] The above results show that the low-temperature bending is mainly caused by the thermal shrinkage mismatch between TPU and the crystal, and the photo-thermal heating mediated by rGO provides local energy to drive it. Therefore, by precisely controlling the irradiation position, power (controlling the deformation amplitude) and timing (controlling the motion frequency) of the infrared light spot on the already curled crystal, an asymmetric deformation gradient can be created in the length direction of the crystal. With the cooperation of the surface friction, this periodic deformation can be converted into various complex and controllable macroscopic motion modes, including slow moving, spiral motion, jumping motion and walking, etc. Figure 5 c).

[0081] Example 1: Preparation of hybrid crystal GT2 and its application in sensing-driving integrated system;

[0082] (1) Composition and preparation;

[0083] The single crystal of compound 2 (2,2'-((1E,1'E)-1,4-phenylene(bis(ethene-2,1-diyl)))dibenzoate) is used as the core substrate. The specific preparation process includes:

[0084] Crystal growth: 100 mg of compound 2 is dissolved in 100 mL of dichloromethane, and uniform centimeter-level needle-shaped single crystals are obtained by slow solvent diffusion method at 5°C for 3 days.

[0085] Interface modification: petroleum ether is used as a poor solvent to flush the grown crystal and dry naturally. The crystal is immersed in an aqueous solution containing 5.0 mg / mL PDDA and 1.0 M NaCl for 20 minutes to ensure that the PDDA molecules are fully adsorbed on the surface of the crystal, and then dried with N2 gas flow.

[0086] Functional layer construction: 10 μL of rGO aqueous dispersion with a concentration of 1 mg / mL is accurately dropped on one end of the PDDA modified crystal, and dried at room temperature for 12 hours to form a uniform rGO layer; 8 μL of TPU / THF solution with a concentration of 1 mg / mL is coated on the opposite side, and a uniform TPU film is obtained by controlling the solvent evaporation rate.

[0087] Post-treatment: heat treatment in a vacuum oven at 60 °C for 30 min to promote the firm bonding between interfaces, and finally obtain the structurally integrated hybrid crystal rGO / PDDA / Crystal 2 / PDDA / TPU, named GT2 Figure 6 In a).

[0088] Cross-section analysis shows that both rGO and TPU layers adhere closely to the PDDA layer, and are evenly distributed with thicknesses of 13.47 μm and 11.07 μm, respectively Figure 6 In b). GT2 hybrid crystal maintains excellent mechanical properties and can still be repeatedly bent without breaking Figure 6 In c).

[0089] (2) Performance and application;

[0090] When the hybrid crystal GT2 with the TPU layer facing up is excited by 355 nm laser, green light emission is transmitted from one end to the other end Figure 7 In a). The strong absorption of rGO reduces the output signal intensity of the crystal to 47~57% of the original value Figure 7 In b), and the optical loss coefficient increases from 0.085 dB mm -1 to 0.238 dB mm -1 In c). Although the optical loss coefficient is slightly higher than that of the original crystal, the hybrid crystal GT2 still maintains a low signal attenuation level, and the output signal intensity meets the demand for light transmission performance in practical applications. Figure 7

[0091] The hybrid crystal GT2 exhibits excellent humidity and temperature sensing performance, as shown in Figure 8 . It has a fast response to water vapor evaporation, and when the fingertip is kept at different distances, the GT2 surface can effectively absorb the released vapor, showing consistent response and recovery time of about 10 seconds. Moreover, the response amplitude and rate of the sensor have obvious correlation with the distance, which can effectively capture the humidity changes related to the proximity Figure 8 In a). In addition, the hybrid crystal GT2 can accurately detect the humidity changes of fingertips in different states, and reliably track the stable breathing pattern Figure 8 In b). Even after long-term exposure to a high-humidity environment, i.e., storage for 25 days at 90% relative humidity, the sensor can still maintain consistent response to finger humidity or breathing Figure 8 In c). Benefiting from its flexibility, high sensitivity, and portability, the hybrid crystal GT2 becomes a strong candidate for real-time respiratory humidity monitoring and even distinguishing the characteristic signals of different regions of the human body (fingers, palms, backs of hands, elbows, necks, foreheads, backs, ankles, etc.) Figure 8 In d). These functions make it possible for innovative applications such as user authentication and low-cost physiological sensing. ​

[0092] When exposed to a focused infrared beam in a -150 °C environment, the crystal exhibits controllable bending and motion driven by the local photothermal heating-induced temperature gradient. Under intermittent infrared radiation (808 nm, 206.8 mW) in a -150 °C environment, GT2 rolled 720° achieved a sinuous crawling of about 1 cm in 11 s (Fig. 2a). In addition, the concentrated photothermal energy (408.4 mW) caused rapid expansion and contraction, enabling GT2 to perform jumping motion on a silicon-based surface in 0.22 s (height: 0.55 mm; Fig. 2b). These motions originated from the photothermal effect, inducing a temperature gradient in the crystal structure, leading to asymmetric deformation, with greater rolling corresponding to more intense photothermal motion at lower temperatures. The inherent flexibility of the crystal at low temperatures allowed significant deformation without breaking the structure, thus ensuring continuous motion. These results demonstrate the great potential of hybrid crystals in remote infrared control driving, especially under low-temperature conditions where traditional materials often fail. Figure 9 Figure 9 On the basis of photothermal response and transduction ability, we further integrated low-temperature driving and thermal sensing into a hybrid crystal-based photothermal driving signal output system (Fig. 2c). Electrical evaluation at 25 °C, -150 °C, and -150 °C with infrared radiation (IR on) confirmed stable electrical performance under different thermal and infrared exposure conditions (Fig. 2d). GT2 exhibited stable and reversible resistance responses under repeated infrared irradiation in a low-temperature environment, with resistance decreasing after infrared irradiation (IR on) and recovering after removal (IR off) (Fig. 2e). In addition, the response intensity was obviously dependent on the infrared irradiation intensity, with resistance change rates of -60% and -35% for hybrid crystals irradiated by 808 nm laser at 206.8 mW and 94.8 mW, respectively (Fig. 2e), highlighting the tunable nature of its signal modulation under different infrared conditions. The seamless integration of mechanical durability, environmental responsiveness, and stable electrical performance emphasizes the advanced application potential of hybrid crystals in soft actuators, environmental sensors, and multifunctional adaptive devices.

[0093] On the basis of photothermal response and transduction ability, we further integrated low-temperature driving and thermal sensing into a hybrid crystal-based photothermal driving signal output system (Fig. 2c). Electrical evaluation at 25 °C, -150 °C, and -150 °C with infrared radiation (IR on) confirmed stable electrical performance under different thermal and infrared exposure conditions (Fig. 2d). GT2 exhibited stable and reversible resistance responses under repeated infrared irradiation in a low-temperature environment, with resistance decreasing after infrared irradiation (IR on) and recovering after removal (IR off) (Fig. 2e). In addition, the response intensity was obviously dependent on the infrared irradiation intensity, with resistance change rates of -60% and -35% for hybrid crystals irradiated by 808 nm laser at 206.8 mW and 94.8 mW, respectively (Fig. 2e), highlighting the tunable nature of its signal modulation under different infrared conditions. The seamless integration of mechanical durability, environmental responsiveness, and stable electrical performance emphasizes the advanced application potential of hybrid crystals in soft actuators, environmental sensors, and multifunctional adaptive devices. Figure 9 Figure 9 On the basis of photothermal response and transduction ability, we further integrated low-temperature driving and thermal sensing into a hybrid crystal-based photothermal driving signal output system (Fig. 2c). Electrical evaluation at 25 °C, -150 °C, and -150 °C with infrared radiation (IR on) confirmed stable electrical performance under different thermal and infrared exposure conditions (Fig. 2d). GT2 exhibited stable and reversible resistance responses under repeated infrared irradiation in a low-temperature environment, with resistance decreasing after infrared irradiation (IR on) and recovering after removal (IR off) (Fig. 2e). In addition, the response intensity was obviously dependent on the infrared irradiation intensity, with resistance change rates of -60% and -35% for hybrid crystals irradiated by 808 nm laser at 206.8 mW and 94.8 mW, respectively (Fig. 2e), highlighting the tunable nature of its signal modulation under different infrared conditions. The seamless integration of mechanical durability, environmental responsiveness, and stable electrical performance emphasizes the advanced application potential of hybrid crystals in soft actuators, environmental sensors, and multifunctional adaptive devices. Figure 9 Figure 9 On the basis of photothermal response and transduction ability, we further integrated low-temperature driving and thermal sensing into a hybrid crystal-based photothermal driving signal output system (Fig. 2c). Electrical evaluation at 25 °C, -150 °C, and -150 °C with infrared radiation (IR on) confirmed stable electrical performance under different thermal and infrared exposure conditions (Fig. 2d). GT2 exhibited stable and reversible resistance responses under repeated infrared irradiation in a low-temperature environment, with resistance decreasing after infrared irradiation (IR on) and recovering after removal (IR off) (Fig. 2e). In addition, the response intensity was obviously dependent on the infrared irradiation intensity, with resistance change rates of -60% and -35% for hybrid crystals irradiated by 808 nm laser at 206.8 mW and 94.8 mW, respectively (Fig. 2e), highlighting the tunable nature of its signal modulation under different infrared conditions. The seamless integration of mechanical durability, environmental responsiveness, and stable electrical performance emphasizes the advanced application potential of hybrid crystals in soft actuators, environmental sensors, and multifunctional adaptive devices.

[0094] The above is only the preferred embodiment of the present application, it should be noted that for those skilled in the art, without departing from the concept of the present application, can make several modifications and improvements, these should be considered as the protection scope of the present application, these will not affect the effect and practicality of the patent implementation.​​​

Claims

1. A hybrid crystalline material having a sandwich structure, characterized by, The hybrid crystal material has a sandwich configuration of rGO / PDDA / Crystal / PDDA / TPU, including a flexible organic crystal, an interface modification layer, a conductive and photothermal layer, and a driving layer. The flexible organic crystal is selected from at least one of Compound 1 to Compound 6, wherein Compound 1 is (Z)-4-(2-cyano-2-(4-(trifluoromethoxy)phenyl)vinyl)benzonitrile, Compound 2 is 2,2'-((1E,1'E)-1,4-phenylenebis(ethene-2,1-diyl))dibenzonitrile, Compound 3 is (E)-N'-((E)-3,5-dichloro-2-hydroxyphenylmethylene)-N,N-dimethylformohydrazidamide, Compound 4 is (Z)-4-(3-(5-methoxy-1-methyl-1H-indol-3-yl)acryloyl)benzonitrile, Compound 5 is (Z)-3-(furan-2-yl)-2-(4-(((E)-2-hydroxy-5-methylphenylmethylene)amino)phenyl)acrylonitrile, and Compound 6 is (Z)-2-(4-(((E)-5-fluoro-2-hydroxyphenylmethylene)amino)phenyl)-3-(thiophen-2-yl)acrylonitrile. The interface modification layer contains polydiallyldimethylammonium chloride and is adsorbed on the surface of the flexible organic crystal through electrostatic interaction. The conductive and photothermal layer contains reduced graphene oxide and covers one side of the flexible organic crystal modified with the interface modification layer. The driving layer contains thermoplastic polyurethane and covers the other side of the flexible organic crystal modified with the interface modification layer.

2. A method of producing the hybrid crystalline material according to claim 1, characterized in that, The method comprises the following steps: Step 1: Dissolve at least one of Compound 1 to Compound 6 in a dichloromethane solution, slowly drop an ethanol solution along the wall of a container, and stand at room temperature for 3-7 days to obtain a centimeter-level needle-shaped single crystal, i.e., a flexible organic crystal; Step 2: Self-assemble a polyelectrolyte interface modification layer on the surface of the flexible organic crystal; Step 3: Deposit reduced graphene oxide on one side of the polyelectrolyte interface modification layer to form a conductive and photothermal layer; Step 4: Apply a thermoplastic polyurethane solution to the other side of the polyelectrolyte interface modification layer to form a driving layer; Step 5: Perform post-processing to promote the interface combination of the layers and form a stable rGO / PDDA / Crystal / PDDA / TPU sandwich structure.

3. The preparation method according to claim 2, characterized in that, In Step 2, the specific operation of self-assembling the polyelectrolyte interface modification layer is as follows: after the flexible organic crystal is washed with ethanol or petroleum ether and naturally dried, it is immersed in an aqueous solution containing polydiallyldimethylammonium chloride and sodium chloride, and then dried with nitrogen.

4. The preparation method according to claim 2, characterized in that, In Step 3, the specific operation of depositing the reduced graphene oxide layer is as follows: reduce graphene oxide powder is dispersed in deionized water, ultrasonic treatment is performed until a uniform and stable dispersion liquid is formed, the dispersion liquid is dropped on the target position of the interface modification layer with a syringe, and natural drying is performed at room temperature.

5. The preparation method according to claim 2, characterized in that, In Step 4, the thermoplastic polyurethane solution is obtained by dissolving thermoplastic polyurethane particles in tetrahydrofuran or N,N-dimethylformamide.

6. The preparation method according to claim 2, characterized in that, In step 5, the post-treatment includes: after all the solvents are completely volatilized, the obtained material is heat-annealed at 60°C for 30 minutes.

7. A multi-functional integrated system characterized by, The system simultaneously realizes: Humidity and temperature sensing based on reduced graphene oxide; Optical temperature sensing and fluorescent feedback based on flexible organic crystals; Infrared-driven deformation and motion control in low-temperature environments based on the difference in thermal shrinkage between thermoplastic polyurethane and flexible organic crystals, and the photothermal effect of reduced graphene oxide.

8. The multi-functional integrated system of claim 7, wherein, The low-temperature environment is -150°C.

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