Thermally responsive organic single crystal with fast bending-straightening mechanical response and preparation and application thereof

Abstract

The present application relates to a kind of body temperature sensing quick bending-straightening mechanical response organic single crystal and its preparation, application, belong to flexible crystal material technical field.The organic single crystal is formed by 3,5-dinitrobenzoic acid and 4,4'-dipyridyl co-crystal, is prepared by solvent evaporation method, first natural evaporation crystallization when solvent evaporation, then heat crystal, or heat evaporation crystallization again cooling. The single crystal thermal response shows excellent, breaks the deformation not significant and can only maintain very short time, the limitation of high response temperature in the related material existing report. The method has the advantages such as preparation simple, not by crystal size limit, environment-friendly, room temperature stable, fatigue resistant, can be applied to sensing, driving, flexible robot and other fields as intelligent material.

Description

Technical Field

[0001] This invention relates to a rapidly bending-straightening mechanically responsive organic single crystal with body temperature sensing, its preparation and application, belonging to the field of flexible crystal material technology. Background Technology

[0002] Unlike traditional crystals, which are hard and brittle, molecular-based flexible single-crystal materials can undergo reversible changes in the spatial configuration or orientation of molecules within their crystal lattice under external stimuli (light, temperature, external force, chemical solvents, etc.), resulting in macroscopic crystals exhibiting a series of mechanical response behaviors such as stretching, bending, shearing, and twisting. The rapid mechanical deformation and high energy conversion efficiency make single-crystal materials have enormous application potential in fields such as sensing, actuation, and flexible robotics.

[0003] Among various motion modes, bending-straightening is the most basic and common deformation mode. Existing research has shown that structural gradient is the main reason for achieving the bending-straightening mechanical response of crystals. For example, the Irie research group at Rikkyo University in Japan prepared single crystals using photoresponsive molecules such as diarylethene and azobenzene, achieving a structural gradient induced by localized photochemical reactions. When light irradiates the crystal, the photochemical reaction mainly occurs on the crystal surface, while the internal molecules maintain their original state, thus introducing a structural gradient, leading to internal stress and achieving photoinduced bending deformation of the single crystal. However, limitations imposed by specific molecular functional groups and ultraviolet light dependence hinder the further development of photo-controlled bending mechanical response single crystals.

[0004] To address this issue, researchers have developed dynamically bending thermally responsive crystals induced by instantaneous temperature gradients. In these crystals, rapid heating creates a temperature difference across the two sides of the single crystal. Due to the thermal expansion and contraction properties of the material, the internal lattice structure exhibits different phase states, generating a structural gradient that leads to bending deformation in thermal response. However, since the temperature difference is difficult to maintain for extended periods, the crystal immediately returns to its straight shape after an instantaneous bend. Therefore, the fabrication of readily available, room-temperature-controlled, and stable bending-straightening mechanically responsive single crystals through effective design strategies remains a significant challenge. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a rapidly bending-straightening mechanically responsive organic single crystal for body temperature sensing, as well as its preparation and application. The single crystal exhibits excellent thermal response, overcoming the limitations of existing reports on related materials, such as complex molecular structures and difficulty in effective control under mild conditions. The method described has advantages such as simple preparation, no limitation by crystal size, environmental friendliness, room temperature stability, and fatigue resistance, and can be used as a smart material in sensing, actuation, and flexible robotics.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows.

[0007] A body temperature-sensing, rapidly bending-straightening mechanically responsive organic single crystal, said organic single crystal being formed from a eutectic of 3,5-dinitrobenzoic acid and 4,4'-bipyridine, with the following structural formula:

[0008] ,in, Indicates hydrogen bond; The single crystal is a transparent needle-shaped single crystal, crystallized in a centrosymmetric space group, and its cell parameters at different temperatures are as follows: .

[0009] The single crystal is prepared by solvent evaporation. During solvent evaporation, the crystal is first naturally evaporated and then heated and then cooled, or it is heated to evaporate and then cooled.

[0010] Furthermore, the solvent is methanol or a methanol-ethanol mixture, and the heating temperature is above 323 K.

[0011] A method for preparing a rapid bending-straightening mechanically responsive organic single crystal with body temperature sensing, as described in this invention, includes the following steps: 3,5-dinitrobenzoic acid and 4,4'-bipyridine were dissolved in methanol or a methanol-ethanol mixture to obtain 3,5-dinitrobenzoic acid solution and 4,4'-bipyridine solution, respectively. After mixing and stirring the two solutions evenly, the mixture is allowed to stand naturally until straight needle-shaped single crystals are grown. Then, it is heated to above 323K and cooled to obtain an organic single crystal with a rapid bending-straightening response controlled by body temperature touch.

[0012] A method for preparing a rapid bending-straightening mechanically responsive organic single crystal with body temperature sensing, as described in this invention, includes the following steps: 3,5-dinitrobenzoic acid and 4,4'-bipyridine were dissolved in methanol or a methanol-ethanol mixture to obtain 3,5-dinitrobenzoic acid solution and 4,4'-bipyridine solution, respectively. After mixing and stirring the two solutions evenly, the mixture is heated to above 323 K to volatilize and grow into straight needle-like crystals. Then, the temperature is lowered to below 293 K to obtain organic single crystals with rapid bending-straightening mechanical response that are sensitive to body temperature.

[0013] Furthermore, the concentration of the 3,5-dinitrobenzic acid solution is 0.03~0.06 mmol / mL.

[0014] Furthermore, the concentration of the 4,4'-bipyridine solution is 0.015~0.03 mmol / mL.

[0015] Furthermore, the molar ratio of 3,5-dinitrobenzoic acid to 4,4'-bipyridine is 2:1.

[0016] Furthermore, after stirring and mixing evenly, filter.

[0017] Furthermore, the heating temperature is 323~348 K.

[0018] The present invention relates to the application of a rapid bending-straightening mechanically responsive organic single crystal with body temperature sensing as a smart material.

[0019] Beneficial effects This invention provides a rapidly bending-straightening mechanically responsive organic single crystal that senses body temperature. The crystal is a self-bending crystal at room temperature and exhibits temperature-responsive properties, displaying a significant bending-straightening motion in response to body temperature. When a finger approaches, the single crystal rapidly straightens from a bent shape; when the finger remains stationary, the crystal's shape remains essentially unchanged; and when the finger moves away, the crystal quickly returns to its bent shape.

[0020] The bending-straightening motion of the single crystal can be characterized by a microscope and an infrared imaging camera, with a response temperature of 303.3 K and a response time of only 141 ms.

[0021] The single crystal has excellent fatigue resistance and can withstand more than 10,000 bending-straightening response cycles without damaging the integrity of the crystal using a heat source or laser pointer.

[0022] This invention provides a method for preparing a rapidly bending-straightening mechanically responsive organic single crystal that senses body temperature. An elastic lattice is formed by eutectic synthesis of 3,5-dinitrobenzoic acid and 4,4'-bipyridine in a 2:1 ratio. Furthermore, based on its significant thermal expansion, a temperature gradient is constructed along the thickness direction during rapid cooling, forming a gradient structure. Since the elastic lattice can accommodate significant changes in crystal length caused by symmetry-breaking phase transitions, the single crystal undergoes bending deformation and exhibits a rapid and significant bending-straightening response near body temperature. The preparation process does not require expensive reaction equipment; the target product can be prepared in a standard laboratory using a small amount of raw materials, offering advantages such as simple operation and low cost.

[0023] The single crystal described in this invention has great application potential. Based on its temperature sensitivity and rapid and significant deformation characteristics, the single crystal can be applied to temperature sensor devices, units for detecting weak temperature fluctuations, thermal response directional self-driving units, and flexible robots. Attached Figure Description

[0024] Figure 1 To illustrate the elastic properties of the straight crystal described in Comparative Example 1, it can bend under stress and return to a straight state when no stress is applied.

[0025] Figure 2The thermal response of the crystal described in Comparative Example 1 is measured at body temperature.

[0026] Figure 3 The DSC curve of the crystal described in Comparative Example 1 shows a reversible phase transition near 300 K.

[0027] Figure 4 The variable-temperature X-ray single-crystal diffraction test of the crystal described in Comparative Example 1 showed that symmetry breaking occurred during the phase transition, and the high-temperature phase... P twenty one / n Monoclinic space groups can transform into low-temperature phases. P -1 Triclinal Space Group.

[0028] Figure 5 The crystal described in Comparative Example 1 has anisotropic thermal expansion due to its cell parameters.

[0029] Figure 6 This is for the thermostriction of the crystal described in Comparative Example 1.

[0030] Figure 7 The PXRD pattern and anisotropic expansion of the crystal described in Comparative Example 1 are shown.

[0031] Figure 8 This is a photograph of a self-bending crystal at room temperature prepared by high-temperature growth and rapid cooling in Example 1.

[0032] Figure 9 These are optical microscope images and scanning electron microscope images obtained in Example 1.

[0033] Figure 10 The thermal response behavior of the crystal in Example 1 is as follows: at room temperature, the crystal is in a bent state. When a finger approaches, the bent crystal straightens. The thermal response has no directional requirement. When the finger leaves, the crystal returns to a bent state.

[0034] Figure 11 The crystal in Example 1 has a fast thermal response speed to body temperature, and the response can be completed in 141 ms after a finger approaches.

[0035] Figure 12 The temperature response of the crystal in Example 1 is shown under an infrared imaging device, with a response temperature sensitivity of less than 1K.

[0036] Figure 13 The crystal in Example 1 exhibits excellent fatigue resistance due to its body temperature response. It can withstand more than 10,000 bending-straightening response cycles without damaging the integrity of the crystal using a heat source.

[0037] Figure 14 In Example 1, the crystal can achieve a bending-straightening response behavior by being irradiated with heat by a laser pointer.

[0038] Figure 15-16 The image shows a microscope image of a self-bending crystal prepared by rapidly cooling and bending the high-temperature grown crystal in Example 2, which was then prepared at room temperature.

[0039] Figure 17-18 The crystal in Example 2 is in a bent state at room temperature, and straightens when a finger is brought close, reflecting the body temperature response behavior.

[0040] Figure 19 The crystal in Example 1 can be used as a sensor in a circuit, and the bending-straightening deformation of the crystal controls the on / off state of the circuit.

[0041] Figure 20 The crystal in Example 1 can be used as a device to detect the on / off state of a circuit. Due to the thermal effect of the current, the bending-straightening deformation of the crystal can indicate the on / off state of the circuit.

[0042] Figure 21 The crystal in Example 1 can be applied to the field of self-driven systems. Under the conditions of a corrugated track and intermittent laser irradiation, the crystal can undergo directional movement along the track.

[0043] Figure 22 The crystal in Example 1 can be applied to the field of flexible robots. By making it into the shape of a fan, the robot can spontaneously and controllably rotate by utilizing the heat generated by light and the small temperature fluctuations caused by room temperature. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to specific embodiments.

[0045] Comparative Example 1 Step 1: Preparation of conventional single crystals 0.424 g of 3,5-dinitrobenzic acid and 0.156 g of 4,4'-bipyridine were weighed separately and dissolved in 50 mL of methanol. The two solutions were mixed and stirred, filtered, and then placed in a glass petri dish. The dish was covered with plastic wrap and punctured. It was then placed in a well-ventilated area at room temperature to allow the solvent to evaporate naturally. After 15 days, the solvent had completely evaporated, yielding straight needle-like single crystals.

[0046] Step 2: Optical Testing The crystal photographs obtained in step one were taken using a domestically produced Otek SZ680 stereo microscope and a JOEL JSM-7500F field emission scanning electron microscope. The photographs show that the crystals are all in a straight position.

[0047] Step 2: Mechanical Testing The needle-like crystals are flexible and can undergo significant bending deformation under external force, returning to a straight state after the force is removed. The crystals can be knotted without breaking. Figure 1).

[0048] Step 3: Thermal Response Test The body temperature tactile response behavior of the crystal described in this invention was recorded using a domestically produced NEX stereo microscope equipped with a high frame rate CCD. When a finger approaches, the single crystal rapidly undergoes a nearly invisible micro-bend from its straight state, then instantly returns to its straight state. When the finger moves away, the crystal remains in its straight state. Figure 2 ) Step 4: Thermal-related tests Thermodynamic tests were performed using an aluminum crucible and matching cover plate on a PerkinElmer DSC 8000 differential scanning calorimeter. The DSC curve of the needle-like crystals showed a pair of peaks, indicating a reversible phase transition near 300 K. Figure 3 ).

[0049] The material was subjected to variable-temperature X-ray single-crystal diffraction tests using a Rigaku XtaLab Pro diffractometer equipped with a MoKα radiation source and a continuous liquid nitrogen cooling temperature control system (Oxford Crysystems Cryostream 800). The results are listed in Table 1. The needle-like crystals underwent symmetry breaking during the phase transition, and the high-temperature phase... P twenty one / n Monoclinic space groups can transform into low-temperature phases. P -1 Triclinic Space Group ( Figure 4 ).

[0050] Table 1

[0051] The cell parameters of the needle-like crystal exhibit anisotropic thermal expansion ( Figure 5 During the temperature change process, significant expansion occurs along the length direction; within the temperature range of 250 K to 370 K, the length change rate of the crystal is 6.5%. Figure 6 ).

[0052] The PXRD pattern of the crystal material during heating 2 θ The diffraction peak at an angle of 15° shifts significantly to higher angles, while 2 θ The diffraction peak at an angle of 29° shifts to a lower angle, indicating the anisotropic thermal expansion characteristic of the unit cell parameters. Figure 7 ).

[0053] Example 1 Raw materials: 3,5-dinitrobenzic acid (99% purity, commercially available), 4,4'-bipyridine (99% purity, commercially available), methanol (99.5% purity, commercially available) Equipment: DHG-9035A type forced-air drying oven Step 1: Preparation of bent single crystals Weigh out 2 mmol of 3,5-dinitrobenzoic acid and 1 mmol of 4,4'-bipyridine, and dissolve each in 50 mL of methanol. Mix the two solutions thoroughly, filter, and place in a glass petri dish. Cover with plastic wrap and poke holes in the wrap. Place the petri dish in a 333 K oven for 2 days to evaporate the solvent. Once the solvent has completely evaporated and straight needle-like single crystals are obtained, quickly remove the dish, peel off the plastic wrap, and place it at room temperature (293 K). The adherent crystals quickly bend, thus preparing a body temperature tactile responsive single crystal. Figure 8 ).

[0054] Step 2: Optical Testing Crystal bending photographs were taken using a domestically produced Aote SZ680 stereo microscope and a JOEL JSM-7500F field emission scanning electron microscope. Figure 9 ).

[0055] Step 3: Thermal Response Test The body temperature tactile response behavior of the crystal described in this invention was recorded using a domestically produced NEX stereo microscope equipped with a high frame rate CCD. When a finger approaches, the single crystal quickly straightens from a curved shape; there is a response when the finger approaches from all directions, and the shape of the crystal remains basically unchanged even after the finger is stationary; when the finger moves away, the crystal quickly returns to its curved shape, with significant and rapid deformation. Figure 10 The response time is only 141 ms. Figure 11 ).

[0056] The bending-straightening motion of the thermo-tactile responsive single crystal can be characterized by an infrared imaging camera. The response temperature is 303.3 K, exhibiting a temperature sensitivity of less than 1 K. Figure 12 ).

[0057] The aforementioned body temperature tactile response single crystal has excellent fatigue resistance, and can achieve more than 10,000 bending-straightening response cycles using a heat source without damaging the integrity of the crystal. Figure 13 ).

[0058] The body temperature tactile response single crystal, due to its temperature-sensitive properties, can be responsively deformed using a laser pointer. Figure 14 ).

[0059] Step 4: X-ray single crystal diffraction High-quality single crystals grown under the above conditions were subjected to X-ray single-crystal diffraction. The single crystal cell parameters were: a = 6.224 (5) Å, b = 22.04 (1) Å, c = 9.404 (8) Å. °, °, °, V=1273(1) Å 3 The cell parameters are similar to those shown in the comparative example, but the temperature dependence of the cell parameters can cause subtle differences.

[0060] Example 2: Different growth temperatures in the high-temperature zone Step 1: Preparation of bent single crystals Weigh out 2 mmol of 3,5-dinitrobenzoic acid and 1 mmol of 4,4'-bipyridine, and dissolve each in 50 mL of methanol. Mix the two solutions thoroughly, filter, and place them in glass petri dishes. Cover with plastic wrap and poke holes in the wrap. Place the petri dishes in drying ovens at 323 K and 348 K for 2 days to allow the solvent to evaporate completely. Once the solvent has completely evaporated and straight needle-like single crystals are obtained, quickly remove them, peel off the plastic wrap, and place them at room temperature (293 K). The adherent crystals quickly bend, thus preparing body temperature tactile responsive single crystals.

[0061] Step 2: Optical Testing Photographs of the two crystals obtained in step one were taken using a domestically produced Otek SZ680 stereo microscope. The photographs show that the single crystals grown at 323 K and 348 K both exhibit significant bending at room temperature. Figure 15 and Figure 16 ).

[0062] Step 3: Thermal Response Test The body temperature tactile response behavior of the crystals grown at 323 K and 348 K as described in this embodiment was recorded using a domestically produced NEX stereo microscope equipped with a high frame rate CCD. When a finger approaches, the single crystal quickly straightens from a curved shape, and when the finger remains stationary, the shape of the crystal remains essentially unchanged. When the finger moves away, the crystal rapidly returns to its curved shape, exhibiting significant and rapid deformation. Figure 17 and Figure 18 ).

[0063] Step 4: X-ray single crystal diffraction The unit cell parameters of the single crystal obtained in step one are: a = 6.166(8) Å, b = 22.08(2) Å, c = 9.407(1) Å. °, °, °, V=1231(3) Å 3 Similar to the cell parameters shown in Comparative Example 1, the temperature dependence of the cell parameters can cause subtle differences.

[0064] Example 3: Fabrication of Application Devices Application 1: A small amount of silver paste was applied to the convex surface of the body temperature tactile response single crystal prepared in Example 1 for conductivity. One end of the crystal was fixed and connected to the negative terminal of a power supply with a gold wire. A diode, serving as an indicator light, was connected at one end to the positive terminal and bent at the other end close to the crystal. When a finger approaches, the crystal can form a circuit by straightening due to thermal response and contacting the bent part of the diode, thus lighting the diode. When the finger moves away, the crystal temperature drops and returns to its bent shape, simultaneously breaking the circuit and turning off the indicator light. As a sensor device, the bending-straightening deformation of this crystal exhibits excellent fatigue resistance; after more than 1000 cycles, the crystal remains unchanged. Figure 19 ).

[0065] Application 2: In a circuit consisting of a power source, switch, ammeter, metal wire, voltmeter, and light bulb connected by wires, when the switch is turned on, the temperature of the wires rises due to the thermal effect of the current. The single crystal placed next to the metal wire can sense this temperature rise after the circuit is turned on and undergoes significant deformation. When the switch is turned off, the temperature of the wires immediately drops, and the crystal instantly returns to its original shape. Figure 20 ).

[0066] Application 3: With the aid of a corrugated track, this crystal can achieve unidirectional movement. When illuminated by a laser pointer, the crystal stretches its shape, lying perpendicular to the track. When the laser disappears, the crystal returns to its curved state, lifting itself off the track. Then, due to instability, it tilts in one direction and eventually leans against the track. This movement is repeated under multiple laser pulses, enabling self-driven movement along the track. Figure 21 ).

[0067] Application 4: The single crystal is attached to a triangular piece of paper at a certain angle to the vertical direction, oriented clockwise or counterclockwise. This is then placed in an air-conditioned room at 293 K. Due to the heat generated by the LED lights, a locally fluctuating temperature field is created, allowing the flexible robot to spontaneously rotate clockwise or counterclockwise. Figure 22 ).

[0068] In summary, the invention includes, but is not limited to, the above embodiments. Any equivalent substitutions or partial improvements made under the spirit and principles of this invention shall be considered to be within the protection scope of this invention.

Claims

1. A body temperature-sensing, rapidly bending-straightening mechanically responsive organic single crystal, characterized in that: The organic single crystal is formed from a eutectic of 3,5-dinitrobenzoic acid and 4,4'-bipyridine, with the following structural formula: ,in, Indicates hydrogen bond; The single crystal is a transparent needle-shaped single crystal, crystallized in a centrosymmetric space group, and its cell parameters at different temperatures are as follows: 。 The single crystal is prepared by solvent evaporation. During solvent evaporation, the crystal is first naturally evaporated and then heated and then cooled, or it is heated, evaporated and crystallized, and then cooled.

2. The organic single crystal with rapid bending-straightening mechanical response that senses body temperature as described in claim 1, characterized in that: The solvent is methanol or a methanol-ethanol mixture, and the heating temperature is above 323 K.

3. A method for preparing a rapidly bending-straightening mechanically responsive organic single crystal with body temperature sensing as described in claim 1 or 2, characterized in that: The method steps include: 3,5-dinitrobenzoic acid and 4,4'-bipyridine were dissolved in methanol or a methanol-ethanol mixture to obtain 3,5-dinitrobenzoic acid solution and 4,4'-bipyridine solution, respectively. After mixing and stirring the two solutions evenly, the mixture is allowed to stand naturally for more than 2 days to grow straight needle-shaped crystals. Then, the crystals are heated to above 323 K and cooled to obtain organic single crystals with rapid bending-straightening mechanical response that are sensitive to body temperature.

4. A method for preparing a body temperature-sensing, rapidly bending-straightening mechanically responsive organic single crystal as described in claim 1 or 2, characterized in that: The method steps include: 3,5-dinitrobenzoic acid and 4,4'-bipyridine were dissolved in solvents to obtain 3,5-dinitrobenzoic acid solution and 4,4'-bipyridine solution, respectively. After mixing and stirring the two solutions evenly, the mixture is heated to above 323 K and left to stand for more than 2 days to grow straight needle-like crystals. Then, the temperature is lowered to below 293 K to obtain organic single crystals with rapid bending-straightening mechanical response that are sensitive to body temperature.

5. A method for preparing a body temperature-sensing, rapidly bending-straightening mechanically responsive organic single crystal as described in claim 3 or 4, characterized in that: The concentration of the 3,5-dinitrobenzic acid solution is 0.03~0.06 mmol / mL.

6. The method for preparing a body temperature-sensing, rapidly bending-straightening mechanically responsive organic single crystal as described in claim 3 or 4, wherein the concentration of the 4,4'-bipyridine solution is 0.015~0.03 mmol / mL.

7. The method for preparing a body temperature-sensing, rapidly bending-straightening mechanically responsive organic single crystal as described in claim 3 or 4, wherein the molar ratio of 3,5-dinitrobenzoic acid and 4,4'-bipyridine is 2:

1.

8. The method for preparing a body temperature-sensing, rapidly bending-straightening mechanically responsive organic single crystal as described in claim 3 or 4, wherein the mixture is stirred and then filtered.

9. The method for preparing a body temperature-sensing, rapidly bending-straightening mechanically responsive organic single crystal as described in claim 3 or 4, wherein the heating temperature is 323~348 K.

10. The application of the body temperature sensing rapid bending-straightening mechanical response organic single crystal as described in claim 1 or 2 as a smart material.

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