Flexible bionic strain sensor for underground structure monitoring and preparation method thereof

Abstract

The invention discloses a flexible bionic strain sensor for underground structure monitoring and a preparation method thereof, and belongs to the technical field of flexible bionic strain sensors, the flexible bionic strain sensor comprises an LIG layer, the surface of the LIG layer is provided with an Ecoflex layer, and the Ecoflex layer is combined with the LIG layer; a spider web structure is constructed on the Ecoflex layer through an optical fiber laser, the two sides of the Ecoflex layer are connected with the conductive copper foil through elargol, and a PDMS packaging layer is arranged outside the Ecoflex layer. The flexible bionic strain sensor can detect tiny strain changes such as fine deformation and crack propagation of a structure, which is of great significance to early discovery of structural problems and prevention of safety accidents, and the high sensitivity of the sensor enables monitoring data to have high resolution and can more accurately reflect the health condition of the structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible bionic strain sensors, and in particular relates to a flexible bionic strain sensor for underground structure monitoring and a preparation method thereof. Background Art

[0002] It is well known that health monitoring of underground structures is essential to ensure the safety and reliability of infrastructure. Underground structures such as bridges, tunnels, and subways will be affected by various environmental factors during long-term use, such as soil pressure, groundwater erosion, temperature changes, vibrations, etc. These factors may cause deformation, crack propagation, and stress concentration of the structure, thus affecting the safety and service life of the structure.

[0003] Traditional rigid sensors (such as metal strain gauges, fiber optic sensors, etc.) are difficult to adapt to different structural shapes and curvatures in complex environments, and are prone to measurement errors. Rigid sensors are easily affected by environmental factors such as temperature changes, humidity, vibration, etc. during long-term use, resulting in sensor performance degradation or even failure. Rigid sensors require precise alignment and fixation during installation, which is difficult, time-consuming and labor-intensive for complex underground structures. High-quality rigid sensors are expensive, and the maintenance and replacement costs are high. The manufacturing and installation costs of fiber optic sensors are high and are not suitable for large-scale applications. Fiber optic sensors are susceptible to electromagnetic interference in complex environments, affecting the accuracy of monitoring data. The installation of fiber optic sensors requires professional technology and equipment, and the installation process is complex and time-consuming. Nodes in wireless sensor networks usually require battery power, consume a lot of power, and need to be replaced frequently. In underground environments, the transmission of wireless signals is limited, and communication interruptions and data loss are prone to occur. There are a large number of nodes in wireless sensor networks, and maintenance and management are difficult. Therefore, it is of great practical significance to develop efficient, reliable and adaptable monitoring technologies. Summary of the invention

[0004] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to provide a flexible bionic strain sensor for underground structure monitoring and a method for preparing the same, so as to solve the problems that traditional rigid sensors are difficult to adapt to different structural shapes and curvatures in complex environments, are prone to measurement errors, have high manufacturing and installation costs, and are not suitable for large-scale applications.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] In a first aspect, a flexible bionic strain sensor for underground structure monitoring includes a LIG layer; an Ecoflex layer is provided on the surface of the LIG layer, and the Ecoflex layer is combined with the LIG layer; a spider web structure is constructed on the Ecoflex layer by a fiber laser; both sides of the Ecoflex layer are connected to a conductive copper foil by silver glue; and a PDMS encapsulation layer is provided on the outside of the Ecoflex layer.

[0007] Furthermore, there are gaps between the strings in the spider web structure.

[0008] In a second aspect, a method for preparing a flexible bionic strain sensor for underground structure monitoring comprises the following steps:

[0009] S1, fix the PI film on a glass slide;

[0010] S2, fixing the glass slide carrying the PI film on a laser processing platform, using a CO2 laser to locally carbonize the PI film to form a LIG layer;

[0011] S3, dropping the Ecoflex solution evenly on the surface of the LIG layer, and drying at room temperature to obtain the Ecoflex layer;

[0012] S4, peeling the combined LIG layer and Ecoflex layer from the PI film and fixing them on a laser processing platform, and constructing a spider web structure on the Ecoflex layer using a fiber laser;

[0013] S5. Use silver glue to connect the electrodes on both sides of the Ecoflex layer to the copper foil;

[0014] S6. Coating a mixture of PDMS prepolymer and cross-linking agent on the outside of the Ecoflex layer, and forming a PDMS encapsulation layer after drying.

[0015] Furthermore, S1 specifically includes:

[0016] A PI film with a thickness of 100 μm was selected and the PI film was pasted on a 10 cm×10 cm glass slide using a water-soluble double-sided tape.

[0017] Furthermore, in S2, the laser parameters of the CO2 laser are:

[0018] The laser power is 18.12%, the scanning speed is 180 mm / s, the scanning pitch is 3.3 mm, and the focal length is 3.7 mm.

[0019] Furthermore, S3 specifically includes:

[0020] The Ecoflex solution was evenly dropped on the surface of the LIG layer and dried at room temperature for 24 hours until the Ecoflex solution fully penetrated into the porous structure of the LIG layer to obtain the Ecoflex layer.

[0021] Furthermore, in S4, the laser parameters of the fiber laser are:

[0022] Laser power 50%, scanning speed 100mm / s, processing frequency 20kHz.

[0023] Furthermore, S5 specifically includes:

[0024] Silver glue was used to connect the electrodes on both sides of the Ecoflex layer to the copper foil, and the layers were dried in a vacuum drying oven at 150° C. for 20 minutes until the silver glue solidified, completing the electrode connection.

[0025] Furthermore, S6 specifically includes:

[0026] The PDMS prepolymer and the cross-linking agent were mixed in a ratio of 10:1, and the air pressure was adjusted to -0.08 MPa at room temperature. After removing the bubbles, the PDMS prepolymer and cross-linking agent mixture was coated on the sensor and dried in a vacuum drying oven at 80°C for 2 hours to form a PDMS encapsulation layer.

[0027] In a third aspect, a method for using a flexible bionic strain sensor for underground structure monitoring is characterized by comprising the following steps:

[0028] T1: Fix the flexible bionic strain sensor on the surface of the underground structure to be monitored;

[0029] T2: The copper foil electrode of the sensor is connected to the electrochemical workstation to monitor the strain changes of the underground structure in real time;

[0030] T3: Record and analyze the electrical signals output by flexible bionic strain sensors to assess the health of underground structures.

[0031] The flexible bionic strain sensor for underground structure monitoring and the preparation method thereof provided by the present invention have the following beneficial effects:

[0032] 1. In practical applications, the sensor of the present invention can detect tiny strain changes, such as slight deformation of the structure, crack extension, etc., which is of great significance for early detection of structural problems and prevention of safety accidents. The high sensitivity of the sensor makes the monitoring data have high resolution and can more accurately reflect the health status of the structure.

[0033] 2. In dynamic environments such as bridges and tunnels, the sensors of the present invention can monitor the dynamic changes of structures such as vibration and impact in real time, and promptly discover potential safety hazards. When natural disasters such as earthquakes and floods occur, the sensors can respond quickly and provide accurate data support for emergency response. In practical applications, the sensors can maintain stable performance over a monitoring period of up to several years, providing reliable data support for long-term health monitoring of structures. The sensors have good flexibility and plasticity and can adapt to different structural shapes and curvatures, which makes the sensors suitable for various complex underground structures, such as curved tunnel walls, irregular bridge beams and columns, etc.

[0034] 3. The LIG used in the present invention has good thermal stability and chemical stability, and can work stably for a long time in harsh environments such as high temperature and humidity; the Ecoflex material has high elasticity and good weather resistance, and can maintain stable mechanical properties during long-term use; the PDMS encapsulation layer has good waterproof, dustproof and moisture-proof properties, ensuring that the sensor can work stably for a long time in a complex environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a flow chart for preparing the flexible bionic strain sensor for underground structure monitoring.

[0036] Figure 2 A flow chart for using the sensor of the present invention;

[0037] Figure 3 A characteristic schematic diagram of a logarithmic spiral of a spider web structure drawing in the sensor of the present invention;

[0038] Figure 4 Schematic diagram of the spider web structure of the laser scanning Ecoflex layer combined with the LIG layer of the present invention. DETAILED DESCRIPTION

[0039] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0040] Example 1

[0041] This embodiment provides a flexible bionic strain sensor for underground structure monitoring. Figure 1 , which specifically include:

[0042] LIG layer, Ecoflex layer, spider web structure, and PDMS encapsulation layer;

[0043] Among them, an Ecoflex layer is provided on the surface of the LIG layer, the Ecoflex layer is combined with the LIG layer, and a spider web structure is provided on the Ecoflex layer. The spider web structure is constructed on the Ecoflex layer by a fiber laser, and there are gaps between the web strings in the spider web structure.

[0044] Conductive copper foils are provided on both sides of the Ecoflex layer, the conductive copper foils are connected to the Ecoflex layer through silver glue, and a PDMS packaging layer is provided outside the Ecoflex layer.

[0045] refer to Figure 2 and Figure 3 In this embodiment, a spider web structure is constructed on the Ecoflex layer through a fiber laser. There are certain gaps between the strings in the spider web structure, which can effectively amplify the strain signal and improve the sensitivity of the sensor. This design draws on the high sensitivity characteristics of the spider web, so that the sensor can detect tiny strain changes. By optimizing the arrangement and spacing of the strings, the sensitivity of the sensor can be further improved to ensure that the strain changes can still be accurately monitored in complex environments. The spider web structure has good mechanical properties and can maintain stability and durability in complex environments. By simulating the structure of the spider web, the sensor can maintain stable performance during long-term use and is suitable for long-term monitoring. By simulating the structure of the spider web, the sensor can better adapt to different environmental conditions and ensure stable operation under various conditions. The strings in the spider web structure have high strength and elasticity and can quickly return to their original state when subjected to external forces. This characteristic enables the sensor to respond and recover quickly in dynamic monitoring and provide accurate monitoring data.

[0046] Example 2

[0047] This embodiment is based on embodiment 1 and provides a method for preparing a flexible bionic strain sensor for underground structure monitoring. Figure 1 , which specifically includes the following steps:

[0048] Step S1, fixing the PI film on a glass slide;

[0049] Specifically, this embodiment uses a polyimide (PI) film with a thickness of 100 μm. The PI film has good high temperature resistance, corrosion resistance and mechanical properties, and is an ideal substrate for preparing LIG;

[0050] In the specific operation, the PI film was pasted on a 10 cm × 10 cm glass slide with a water-soluble double-sided tape, and the glass slide served as a supporting platform to facilitate subsequent laser processing and treatment.

[0051] Step S2, fixing the glass slide carrying the PI film on a laser processing platform, and using a CO2 laser to partially carbonize the PI film to form a LIG layer;

[0052] Specifically, this embodiment uses a CO2 laser (maximum power 60W, wavelength 10.6μm) to prepare the LIG layer. The CO2 laser has high energy density and good focusing performance, and is suitable for preparing the LIG layer on the PI film. According to the parameters predicted by machine learning, the laser power is set to 18.12%, the scanning speed is 180mm / s, the scanning interval is 3.3mm, and the focal length is 3.7mm. These parameters are optimized to ensure the high conductivity and uniformity of the LIG layer.

[0053] During the specific preparation, the PI film is placed on a laser processing platform and laser scanning is performed according to the set parameters. During the laser scanning process, the high energy density of the CO2 laser causes the PI film to be locally carbonized to form a porous graphene structure (LIG layer).

[0054] Step S3, dropping the Ecoflex solution evenly on the surface of the LIG layer, and drying at room temperature to obtain the Ecoflex layer;

[0055] In this embodiment, the Ecoflex solution is evenly dropped on the surface of the LIG layer to ensure that the solution is evenly distributed. Ecoflex is a highly elastic silicone material with good mechanical properties and biocompatibility. It is dried at room temperature for 24 hours to allow the Ecoflex solution to fully penetrate into the porous structure of LIG. The combination of the Ecoflex layer and the LIG layer not only enhances the mechanical properties of LIG, but also improves the flexibility and durability of the sensor.

[0056] Step S4, peeling the combined LIG layer and Ecoflex layer from the PI film and fixing them on a laser processing platform, and constructing a spider web structure on the Ecoflex layer using a fiber laser;

[0057] Specifically, the combined LIG / Ecoflex film is peeled off from the PI film. The peeled LIG / Ecoflex film has good flexibility and mechanical properties, which is suitable for subsequent processing and use. A fiber laser (maximum power 20W, wavelength 1064nm) is used to construct a spider web structure on the LIG / Ecoflex film. The fiber laser has high precision and good controllability and is suitable for the processing of fine structures. The laser power is set to 50%, the scanning speed is 100mm / s, and the processing frequency is 20kHz. These parameters are optimized to ensure the high sensitivity and stability of the spider web structure.

[0058] During the specific preparation, the LIG / Ecoflex film is placed on a laser processing platform and laser scanning is performed according to the set parameters. During the laser scanning process, the high precision and controllability of the fiber laser enable a uniform spider web structure to be formed on the Ecoflex layer. There is a certain gap between the strings in the spider web structure, which can effectively amplify the strain signal and improve the sensitivity of the sensor. At the same time, the spider web structure has good mechanical properties and can maintain stability and durability in complex environments.

[0059] Step S5, using silver glue to connect the electrodes on both sides of the Ecoflex layer to the copper foil;

[0060] In this embodiment, copper foil with good conductive properties is selected as the electrode material. Copper foil has high conductivity and good mechanical properties and is suitable for electrode connection of the sensor. Silver glue is used to connect the copper foil to the LIG / Ecoflex film. Silver glue has good conductivity and adhesion, and can ensure the stability and reliability of the electrode connection.

[0061] During the specific preparation, the copper foil is connected with silver glue at the electrodes on both sides of the LIG / Ecoflex film and dried in a vacuum drying oven at 150°C for 20 minutes to ensure the solidification of the silver glue. After the electrode connection is completed, the sensor can be connected to the electrochemical workstation to realize the transmission and monitoring of electrical signals.

[0062] Step S6, coating the mixture of PDMS prepolymer and cross-linking agent on the outside of the Ecoflex layer, and forming a PDMS encapsulation layer after drying;

[0063] In this embodiment, PDMS is selected as the packaging material. PDMS has good waterproof, dustproof and moisture-proof properties, can protect the sensor from interference from the external environment, and extend the service life of the sensor.

[0064] During the specific preparation, the PDMS prepolymer and the cross-linking agent were mixed in a ratio of 10:1, the air pressure was adjusted to -0.08MPa at room temperature, and the sensor was coated after removing the bubbles. The bubble removal process ensured the uniformity and density of the PDMS layer. The PDMS encapsulation layer was formed in a vacuum drying oven at 80°C for 2 hours. The drying process ensured the complete curing of the PDMS layer, forming a good protective layer.

[0065] Example 3

[0066] This embodiment is based on Embodiment 1 and provides a method for using a flexible bionic strain sensor for underground structure monitoring. Figure 4 , which specifically includes the following steps:

[0067] Step T1: fixing the flexible bionic strain sensor on the surface of the underground structure to be monitored;

[0068] When installing sensors, select key parts of the underground structure to be monitored, such as the beam-column joints of bridges, the vaults and side walls of tunnels, and the supporting structures of subway platforms. These parts are usually where the structure is most stressed and most susceptible to damage. Ensure that the installation location can represent the stress and strain state of the entire structure in order to fully reflect the health of the structure.

[0069] Step T2: Connect the copper foil electrode of the sensor through an electrochemical workstation to monitor the strain changes of the underground structure in real time;

[0070] Specifically, connect the copper foil electrode of the sensor to the lead of the electrochemical workstation to ensure a firm connection and avoid poor contact. Use a multimeter to check whether the sensor connection is normal to ensure there is no short circuit or open circuit. Turn on the electrochemical workstation, initialize and calibrate the system to ensure the accuracy and stability of the system. Start the electrochemical workstation and begin real-time monitoring of the strain changes of the underground structure.

[0071] Step T3: Record and analyze the electrical signals output by the flexible bionic strain sensor to evaluate the health status of the underground structure;

[0072] Specifically, this embodiment records the electrical signals output by the sensor, including parameters such as voltage and current, and adjusts the monitoring frequency according to actual needs. It is generally recommended to record data once a minute. For key parts or high-risk areas, the monitoring frequency can be appropriately increased. The monitored data is saved in the storage device of the workstation or sent to a remote server through a data transmission module. The data format can be CSV, Excel or other commonly used data file formats to facilitate subsequent analysis. The recorded data is processed and analyzed using data analysis software (such as MATLAB, Python, etc.), the strain value is calculated, the deformation, crack propagation and stress distribution of the structure are analyzed, and a short-term evaluation is performed on the real-time monitoring data to check whether there are abnormal strain changes. If an abnormality is found, immediate measures are taken to inspect and repair it to prevent the potential risk from expanding.

[0073] Although the specific implementation of the invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A flexible bionic strain sensor for underground structure monitoring, characterized in that: The invention comprises a LIG layer; an Ecoflex layer is provided on the surface of the LIG layer, and the Ecoflex layer is combined with the LIG layer; and a spider web structure is constructed on the Ecoflex layer by using a fiber laser; Both sides of the Ecoflex layer are connected to the conductive copper foil through silver glue; and a PDMS packaging layer is arranged outside the Ecoflex layer.

2. The flexible bionic strain sensor for underground structure monitoring according to claim 1, characterized in that: There are gaps between the web strings in the spider web structure.

3. A method for preparing a flexible bionic strain sensor for underground structure monitoring according to claim 1 or 2, characterized in that: The following steps are involved: S1, fix the PI film on a glass slide; S2, fixing the glass slide carrying the PI film on a laser processing platform, using a CO2 laser to locally carbonize the PI film to form a LIG layer; S3, dropping the Ecoflex solution evenly on the surface of the LIG layer, and drying at room temperature to obtain the Ecoflex layer; S4, peeling the combined LIG layer and Ecoflex layer from the PI film and fixing them on a laser processing platform, and constructing a spider web structure on the Ecoflex layer using a fiber laser; S5. Use silver glue to connect the electrodes on both sides of the Ecoflex layer to the copper foil; S6. Coating a mixture of PDMS prepolymer and cross-linking agent on the outside of the Ecoflex layer, and forming a PDMS encapsulation layer after drying.

4. The method for preparing the flexible bionic strain sensor for underground structure monitoring according to claim 3, characterized in that: The S1 specifically includes: A PI film with a thickness of 100 μm was selected and the PI film was pasted on a 10 cm×10 cm glass slide using a water-soluble double-sided tape.

5. The method for preparing the flexible bionic strain sensor for underground structure monitoring according to claim 3, characterized in that: In S2, the laser parameters of the CO2 laser are: The laser power is 18.12%, the scanning speed is 180 mm / s, the scanning pitch is 3.3 mm, and the focal length is 3.7 mm.

6. The method for preparing the flexible bionic strain sensor for underground structure monitoring according to claim 3, characterized in that: The S3 specifically includes: The Ecoflex solution was evenly dropped on the surface of the LIG layer and dried at room temperature for 24 hours until the Ecoflex solution fully penetrated into the porous structure of the LIG layer to obtain the Ecoflex layer.

7. The method for preparing the flexible bionic strain sensor for underground structure monitoring according to claim 3, characterized in that: In S4, the laser parameters of the fiber laser are: Laser power 50%, scanning speed 100mm / s, processing frequency 20kHz.

8. The method for preparing the flexible bionic strain sensor for underground structure monitoring according to claim 3, characterized in that: The S5 specifically includes: Silver glue was used to connect the electrodes on both sides of the Ecoflex layer to the copper foil, and the layers were dried in a vacuum drying oven at 150° C. for 20 minutes until the silver glue solidified, completing the electrode connection.

9. The method for preparing the flexible bionic strain sensor for underground structure monitoring according to claim 3, characterized in that: The S6 specifically includes: The PDMS prepolymer and the cross-linking agent were mixed in a ratio of 10:1, and the air pressure was adjusted to -0.08 MPa at room temperature. After removing the bubbles, the PDMS prepolymer and cross-linking agent mixture was coated on the sensor and dried in a vacuum drying oven at 80°C for 2 hours to form a PDMS encapsulation layer.

10. A method for using the flexible bionic strain sensor for underground structure monitoring according to claim 1 or 2, characterized in that: The following steps are involved: T1: Fix the flexible bionic strain sensor on the surface of the underground structure to be monitored; T2: The copper foil electrode of the sensor is connected to the electrochemical workstation to monitor the strain changes of the underground structure in real time; T3: Record and analyze the electrical signals output by flexible bionic strain sensors to assess the health of underground structures.

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