Flexible sensor material, flexible sensor preparation method and application

Abstract

The invention discloses a flexible sensor material and a preparation method and application of a flexible sensor, the flexible sensor material is a PAN / AgNO3 / IL composite material, and the preparation method comprises the following steps: adding PAN and AgNO3 into DMF, stirring and dissolving to form a PAN / AgNO3 composite solution; and adding an ionic liquid IL into the PAN / AgNO3 composite solution, carrying out ultrasonic mixing, and standing to form the uniform PAN / AgNO3 / IL composite material. According to the material, one-dimensional fibers can be prepared through air spinning, a two-dimensional film is prepared through combination of fused deposition modeling (FDM) and an ink direct writing technology (DIW), a three-dimensional sensing network is prepared through negative pressure injection, seamless integration of complex structures is achieved, and the material has the capacity of synchronously detecting stimulation signals such as mechanical stress, temperature, near-infrared light and solvents. Meanwhile, good mechanical strain performance is achieved, and the rapid self-healing capacity is achieved. The material overcomes the defects that a traditional sensor is difficult to fit on a complex curved surface and single in recognition capacity, has wide application prospects and can be applied to the fields of soft robots, intelligent buildings, bionic engineering and wearable equipment.

Description

Technical Field

[0001] The present invention relates to the technical fields of intelligent materials and sensors, and particularly to a flexible sensor material, a preparation method and an application of the flexible sensor. Background Art

[0002] A flexible sensor is a sensing device prepared based on flexible materials (including but not limited to polymers, nanomaterials, elastomers), which can convert complex external signals (including but not limited to pressure, temperature, humidity, mechanical stress, chemical reactions, etc.) into easily recognizable electrical signals to achieve human-computer interaction, and has become a current research hotspot. Different from traditional rigid sensors, flexible sensors have excellent flexibility and stretchability and can be attached to the object to be measured for detection.

[0003] However, there are still many technical challenges in the actual application fields of existing flexible sensors:

[0004] Poor complex curved surface forming ability: Traditional flexible sensors can often only be attached to simple planes and are difficult to adapt to complex curved surfaces, which limits their applications in space environments.

[0005] Single signal recognition: It is difficult to achieve synchronous detection of multiple excitation signals.

[0006] Poor durability in use: Long-term use will cause a sharp decline in mechanical properties and does not have self-healing ability.

[0007] Therefore, there is an urgent need for a sensor material with excellent mechanical properties, self-healing ability, multi-signal sensing ability, and multi-dimensional forming ability to overcome the above technical problems and promote the application of flexible sensors in various fields. Summary of the Invention

[0008] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a flexible sensor material, a preparation method and an application of the flexible sensor. The flexible sensor material is a polyacrylonitrile / silver nitrate / ionic liquid (PAN / AgNO3 / IL) composite material, which has excellent mechanical properties, multi-signal sensing, multi-dimensional forming and self-healing abilities, and can be widely applied in the fields of soft robots, health detection systems and bionic engineering. The present invention meets various application requirements by introducing innovative functional materials and preparation technologies and utilizing the continuously viscous characteristics of the material itself.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] A flexible sensor material, the flexible sensor material is a polyacrylonitrile / silver nitrate / ionic liquid PAN / AgNO3 / IL composite material, and its preparation method includes the following steps:

[0011] (1) Add polyacrylonitrile (PAN) and silver nitrate (AgNO3) to dimethylformamide (DMF), and stir to dissolve to form a PAN / AgNO3 composite solution;

[0012] (2) Add an ionic liquid (IL), which is 1-butyl-3-methylimidazolium tetrafluoroborate, to the PAN / AgNO3 composite solution. After ultrasonic mixing, let it stand to form a uniform polyacrylonitrile / silver nitrate / ionic liquid PAN / AgNO3 / IL composite material.

[0013] Furthermore, in step (1), the mass ratio of polyacrylonitrile (PAN) to silver nitrate (AgNO3) is 1:2, the mass fraction of polyacrylonitrile (PAN) in dimethylformamide (DMF) is 10%, and the mass ratio of the ionic liquid (IL) to the PAN / AgNO3 composite solution is 1:8.

[0014] Furthermore, in step (1), the stirring conditions are at 24 °C and 800 rpm for 4 h; in step (2), the ultrasonic mixing time is 30 min, and the standing time is 1 to 5 days.

[0015] Furthermore, the polyacrylonitrile / silver nitrate / ionic liquid PAN / AgNO3 / IL composite material can synchronously detect mechanical stress, temperature, near-infrared light, solvent, and fluid flow rate signals, and has self-healing ability;

[0016] Preferably, the present invention also provides a method for preparing a flexible sensor. Based on the above flexible sensor material, it includes:

[0017] Prepare a one-dimensional fiber sensor by electrospinning;

[0018] Combine the fused deposition modeling (FDM) technology and the direct ink writing (DIW) technology to prepare a two-dimensional thin film sensor;

[0019] Prepare a three-dimensional sensing network or a hollow tubular sensor by negative pressure injection method.

[0020] Furthermore, in the process of preparing the one-dimensional fiber sensor, first let the polyacrylonitrile / silver nitrate / ionic liquid PAN / AgNO3 / IL composite material stand until it reaches a spinnable viscosity, then stretch it into a gel fiber, and then the gel fiber undergoes vapor-induced phase separation to form a solid one-dimensional fiber sensor.

[0021] Furthermore, in the process of preparing the one-dimensional fiber sensor, the electrospinning environmental temperature is 24 °C, the humidity is 65% RH, and the one-dimensional fiber sensor can self-heal within 10 minutes after being cut, restoring its initial mechanical and sensing properties.

[0022] Furthermore, the steps for preparing the two-dimensional thin film sensor are:

[0023] First, a thermoplastic polyurethane (TPU) substrate is prepared using the fused deposition modeling (FDM) technique, and the heating temperature of the print head is 210 °C;

[0024] Subsequently, a polyacrylonitrile / silver nitrate / ionic liquid (PAN / AgNO3 / IL) composite material is printed onto the thermoplastic polyurethane (TPU) substrate using the direct ink writing (DIW) technique;

[0025] Finally, encapsulation is performed using the FDM technique to form a two-dimensional thin film sensor.

[0026] Furthermore, the steps for preparing a hollow tubular sensor are as follows:

[0027] First, the polyacrylonitrile / silver nitrate / ionic liquid (PAN / AgNO3 / IL) composite material is injected into a silicone hollow tube and sealed;

[0028] Subsequently, the silicone hollow tube is heat-treated until a sensing layer adhering to the tube wall is formed, thereby forming a hollow tubular sensor;

[0029] Its working principle is that the pressure exerted by the fluid on the sensing layer changes the arrangement of silver nanoparticles inside the sensing layer, thereby changing the resistance and achieving the signal detection of flow rate and pressure.

[0030] The steps for preparing a three-dimensional sensing network are as follows:

[0031] The polyacrylonitrile / silver nitrate / ionic liquid (PAN / AgNO3 / IL) composite material is injected into a three-dimensional model with several channels, and after curing, a three-dimensional sensing structure is formed to achieve the synchronous detection of pressure and temperature in three-dimensional space.

[0032] Preferably, the present invention also provides an application based on the flexible sensor material, and the flexible sensor material is used for complex surface fitting and multi-signal perception in soft robots, smart buildings, bionic engineering, or wearable devices.

[0033] Compared with the prior art, the beneficial effects brought by the technical solution of the present invention are as follows:

[0034] 1. Excellent mechanical properties and durability: By utilizing the low volatility of ionic liquid (IL) at room temperature and its ability to continuously exert a lubricating effect, the flexible sensor material still maintains good elasticity and stability during long-term use; the flexible sensor material exhibits non-volatile characteristics in air, significantly improving the durability, stability, and mechanical properties of the sensor, and avoiding performance degradation due to long-term exposure.

[0035] 2. Multi-signal synchronous detection ability: The flexible sensor material is a polyacrylonitrile / silver nitrate / ionic liquid PAN / AgNO3 / IL composite material. The silver (Ag) and silver nanoparticles AgNPS formed by internal reduction constitute a continuous conductive path, enabling the sensor to simultaneously detect multiple signals such as mechanical stress, temperature, near-infrared light, solvent, and fluid flow rate. This multi-signal sensing ability greatly expands the application range and practicality of the sensor in complex environments.

[0036] 3. Excellent self-healing performance: The presence of a large number of ion pairs inside the flexible sensor material allows the sensor to self-heal within a short period (e.g., within 10 minutes) after being cut or locally damaged. The self-healing process not only restores the mechanical structure but also fully recovers the sensing performance. Its excellent self-healing ability ensures that the sensor can still work stably under harsh conditions and extends its service life.

[0037] 4. Excellent forming ability and wide application: This material can seamlessly adhere to complex curved surfaces and efficiently fill three-dimensional spaces in three ways: air spinning, two-dimensional printing, and three-dimensional injection. This forming advantage enables the sensor to have broad application potential in fields such as soft robots, intelligent buildings, bionic engineering, and wearable devices. Description of the Drawings

[0038] Figure 1 Scanning electron microscope photograph of the one-dimensional fiber sensor prepared by the present invention;

[0039] Figure 2 Resistance signals identified by the one-dimensional fiber sensor prepared by the present invention under different strains;

[0040] Figure 3 Time durability comparison chart of the one-dimensional fiber sensor prepared by the present invention;

[0041] Figure 4a and Figure 4b are respectively the schematic diagram of the manufacturing process of the two-dimensional thin film sensor prepared by the present invention and the signal diagram measured for multiple excitation sources;

[0042] Figure 5a Flow chart for the preparation of the hollow tubular sensor prepared by the present invention, Figure 5b and Figure 5c are respectively the resistance change diagrams of the hollow tubular sensor for identifying pressure and fluid flow rate;

[0043] Figure 6 Sensing effect diagram of the material of the present invention applied to complex curved surfaces. Detailed Description of the Invention

[0044] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0045] Example 1

[0046] In this example, a fiber sensor based on PAN / AgNO3 / IL is prepared. The steps are as follows:

[0047] 1.024 g polyacrylonitrile PAN was added to 10 mL dimethylformamide DMF solution, and mechanically stirred at 24 ° C and 800 rpm for 3 h to obtain a PAN solution; then 2.048 g silver nitrate AgNO3 was added, and mechanically stirred at 24 ° C and 800 rpm for 1 h until completely dissolved to obtain a polyacrylonitrile / silver nitrate PAN / AgNO3 composite solution, and then an ionic liquid (IL) - 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] was added, and then IL was added in a mass ratio of IL:PAN / AgNO3 of 1:8, ultrasonicated for 30 min, and allowed to stand for 3 days to obtain a uniform viscous polyacrylonitrile / silver nitrate / ionic liquid PAN / AgNO3 / IL composite material solution. The PAN / AgNO3 / IL solution that had been standing for 3 days was added to the syringe, and the 21G needle was tightened. The syringe was fixed on the propulsion pump, and the extrusion speed was set to 0.5 mL / min. The PAN / AgNO3 / IL extruded from the needle was pulled with tweezers. The temperature and humidity were controlled at 24°C and 65% RH. After each 10 cm length of fiber was pulled, the air-induced phase separation process was completed before continuing to pull to obtain a fiber sensor. Figure 1 This is an image of the fiber sensor observed under a scanning electron microscope, from which it can be seen that the fiber is intact and uniform. The air-induced phase separation process refers to the water vapor in the air entering the gel fiber, inducing the DMF and water molecules inside the gel to mix and then exit the gel, causing the PAN chain that loses DMF to shrink and cause the fiber to aggregate, forming a solid fiber. In addition, the ion pairs introduced by IL give the fiber self-healing ability, allowing the fiber to heal within 10 minutes of being cut, and the healed fiber can fully restore its mechanical and sensing capabilities.

[0048] Figure 2 This is the response performance of the PAN / AgNO3 / IL fiber sensor prepared in this embodiment to strain. It can be seen from the figure that the fiber sensor can quickly and accurately identify different stretching ratios and has excellent strain recognition performance.

[0049] Figure 3This is the enhancement effect of the PAN / AgNO3 / IL fiber sensor prepared in this example compared to the PAN / AgNO3 fiber sensor without IL in terms of time durability. It can be seen that the addition of IL enables the fiber to maintain a tensile strain of more than 350% after 72 hours in an air environment, while the PAN / AgNO3 fiber without IL liquid has lost its elasticity after 72 hours.

[0050] Example 2

[0051] In this example, a two-dimensional thin film sensor based on PAN / AgNO3 / IL is prepared as follows:

[0052] Add 1.024 g of PAN to 10 mL of DMF solution, and mechanically stir at 24 °C and 800 rpm for 3 h to obtain a PAN solution; then add 2.048 g of AgNO3, and mechanically stir at 24 °C and 800 rpm for 1 h until completely dissolved to obtain a PAN / AgNO3 composite solution. Then add IL in a mass ratio of IL:PAN / AgNO3 of 1:8, ultrasonicate for 30 min, and let stand for 5 days to obtain a uniform viscous PAN / AgNO3 / IL composite material solution. Use SOLIDWORKS software to draw a 30×30 mm thin film substrate, export it in STL format and transfer it into the printer, and 3D print the substrate using a 75A model TPU wire in a fused deposition modeling (FDM) manner; then place the substrate on an ink direct writing workbench, use SOLIDWORKS software to draw the sensing layer pattern, export it in STL format and transfer it into the printer, put the PAN / AgNO3 / IL solution into the printing syringe, and ink direct write print the solution evenly on the substrate thin film. Let stand for 10 min, and after the solvent evaporates, use FDM to encapsulate the thin film again to obtain a two-dimensional thin film sensor.

[0053] Figure 4a and Figure 4b respectively show the manufacturing process and performance of the two-dimensional thin film sensor of PAN / AgNO3 / IL prepared in the present invention. It can be seen from the figure that the thin film can accurately reflect the stimulation mode, magnitude, and position received.

[0054] Example 3

[0055] In this example, a hollow tubular sensor based on PAN / AgNO3 / IL is prepared as follows:

[0056] 1.024 g of PAN was added to 10 mL of DMF solution, and mechanically stirred at 24 °C and 800 rpm for 3 h to obtain a PAN solution; then 2.048 g of AgNO3 was added, and mechanically stirred at 24 °C and 800 rpm for 1 h until completely dissolved to obtain a PAN / AgNO3 composite solution. Subsequently, IL was added at a mass ratio of IL:PAN / AgNO3 of 1:8, sonicated for 30 min, and left standing for 3 days to obtain a uniform viscous PAN / AgNO3 / IL solution. The PAN / AgNO3 / IL composite material solution standing for 3 days was added to a syringe, the 21G needle was tightened, and slowly injected into a silica gel tube with an inner diameter of 1 mm and an outer diameter of 2 mm. Subsequently, both ends of the silica gel tube were sealed using a glue gun, the sealed silica gel tube was placed on a hot stage, the temperature was adjusted to 60 °C, and the heat treatment time was 8 h. The silica gel tube was cooled at room temperature for 30 min to obtain a hollow tubular sensor with a conductive gel material inside. Figures 5a - 5c It is the preparation process of the hollow tubular sensor and the measurement signals of the internal pressure and fluid flow rate. As can be seen from the figure, the hollow tube-shaped sensor can accurately measure the pressure of 0 - 100 Pa inside the tube, and at the same time can accurately measure the fluid flow rate (0 - 0.24 mL / min) flowing inside.

[0057] Figures 5a - 5c It is a schematic diagram of the production process and performance of the PAN / AgNO3 / IL hollow tubular sensor prepared in the present invention. As can be seen from the figure, the hollow tube sensor is very sensitive to the internal pressure of the tube and can also accurately measure the flow rate of the fluid flowing through.

[0058] Example 4

[0059] In this example, the PAN / AgNO3 / IL material was injected into the 3D model pore for complex surface forming sensing, and the steps are as follows:

[0060] 1.024g PAN was added to 10mL DMF solution, and mechanically stirred at 24℃, 800rpm for 3h to obtain PAN solution; then 2.048g AgNO3 was added, and mechanically stirred at 24℃, 800rpm for 1h until completely dissolved to obtain PAN / AgNO3 composite solution, and then IL was added at a mass ratio of IL:PAN / AgNO3 of 1:8, ultrasonicated for 30min, and allowed to stand for 1h to obtain a uniform PAN / AgNO3 / IL composite material solution. The human hand model was drawn using SOLIDWORKS software, and the software scanning and cutting function was used to establish the simulated arterial vascular pores. The file was converted into STL format and transferred to the printing software. The printing material was selected as 75ATPU, and the printing temperature was 210℃ to print the human hand model; the prepared solution was placed in a syringe, a 21G needle was gelled, and then injected into the pores in the human hand model until all pores were filled, and sensing could be performed after solidification.

[0061] Figure 6 The PAN / AgNO3 / IL material prepared in the present invention is used for sensing applications of complex curved surface molding. The PAN / AgNO3 / IL solution is injected into the channels throughout the simulated human hand model and molded in situ for external stimulus signal response, which shows that the material of the present invention can achieve the purpose of sensing on the required complex curved surface.

[0062] The present invention is not limited to the embodiments described above. The above description of the specific embodiments is intended to describe and illustrate the technical solution of the present invention. The above specific embodiments are merely illustrative and not restrictive. Without departing from the scope of the present invention and the scope of protection of the claims, a person of ordinary skill in the art can also make many forms of specific changes under the guidance of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. A flexible sensor material, characterized in that: The flexible sensor material is a composite material of polyacrylonitrile / silver nitrate / ionic liquid PAN / AgNO3 / IL, and its preparation method comprises the following steps: (1) adding polyacrylonitrile (PAN) and silver nitrate (AgNO3) into dimethylformamide (DMF), stirring and dissolving to form a PAN / AgNO3 composite solution; (2) adding an ionic liquid IL to the PAN / AgNO3 composite solution, wherein the ionic liquid IL is 1-butyl-3-methylimidazolium tetrafluoroborate, and then allowing to stand after ultrasonic mixing to form a uniform polyacrylonitrile / silver nitrate / ionic liquid PAN / AgNO3 / IL composite material.

2. The flexible sensor material according to claim 1, characterized in that: In step (1), the mass ratio of polyacrylonitrile PAN to silver nitrate AgNO3 is 1:2, the mass fraction of polyacrylonitrile PAN in dimethylformamide DMF is 10%, and the mass ratio of ionic liquid IL to PAN / AgNO3 composite solution is 1:

8.

3. The flexible sensor material according to claim 1, characterized in that: The stirring conditions in step (1) are 24° C. and 800 rpm; the ultrasonic mixing time in step (2) is 30 minutes, and the standing time is 1 to 5 days.

4. The flexible sensor material according to claim 1, characterized in that: The polyacrylonitrile / silver nitrate / ionic liquid PAN / AgNO3 / IL composite material can simultaneously detect mechanical stress, temperature, near-infrared light, solvent and fluid flow rate signals, and has self-healing ability.

5. A method for preparing a flexible sensor, based on the flexible sensor material according to any one of claims 1 to 4, characterized in that: include: One-dimensional fiber sensors were prepared by air spinning; Combine fused deposition modeling (FDM) technology with ink direct writing (DIW) technology to prepare two-dimensional thin film sensors; Three-dimensional sensing networks or hollow tubular sensors were prepared by negative pressure injection method.

6. A method for preparing a flexible sensor according to claim 5, characterized in that: The process of preparing the one-dimensional fiber sensor is to first let the polyacrylonitrile / silver nitrate / ionic liquid PAN / AgNO3 / IL composite material stand to reach a spinnable viscosity and then stretch it into a gel-state fiber. The gel-state fiber is then induced to phase separate by water vapor to form a solid-state one-dimensional fiber sensor.

7. A method for preparing a flexible sensor according to claim 6, characterized in that: During the preparation of the one-dimensional fiber sensor, the air spinning environment temperature was 24°C and the humidity was 65% RH. The one-dimensional fiber sensor was able to self-heal within 10 minutes after being cut and restore its initial mechanical and sensing properties.

8. A method for preparing a flexible sensor according to claim 5, characterized in that: The steps to prepare a two-dimensional thin film sensor are: First, the thermoplastic polyurethane (TPU) substrate was prepared using the fused deposition modeling (FDM) technology, and the heating temperature of the print head was 210°C. Then, the polyacrylonitrile / silver nitrate / ionic liquid PAN / AgNO3 / IL composite material was printed on the thermoplastic polyurethane TPU substrate using ink direct writing DIW technology; Finally, FDM technology is used to package and form a two-dimensional thin film sensor.

9. A method for preparing a flexible sensor according to claim 5, characterized in that: The steps for preparing the hollow tubular sensor are: Firstly, the polyacrylonitrile / silver nitrate / ionic liquid PAN / AgNO3 / IL composite material was injected into a hollow silica tube and sealed; The hollow silicone tube is then heat treated until a sensing layer attached to the tube wall is formed, thereby forming a hollow tubular sensor; Its working principle is to use the fluid to exert pressure on the sensing layer to change the arrangement of silver nanoparticles inside the sensing layer, thereby changing the resistance and realizing signal detection of flow rate and pressure. The steps to prepare a three-dimensional sensor network are: The polyacrylonitrile / silver nitrate / ionic liquid PAN / AgNO3 / IL composite material is injected into a three-dimensional model with several channels, and after curing, a three-dimensional sensing structure is formed to realize the simultaneous detection of pressure and temperature in three-dimensional space.

10. An application of the flexible sensor material according to any one of claims 1 to 4, characterized in that: The flexible sensor material is used for complex curved surface fitting and multiple signal perception in soft robots, intelligent buildings, bionic engineering or wearable devices.

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