Flexible sensor and preparation method thereof

Abstract

The invention relates to a flexible sensor and a preparation method thereof, and the preparation method mainly comprises the steps: embedding a first magnetic part into a dielectric layer, putting the dielectric layer embedded with a magnetic material into a second mold, putting a second magnetic part below the second mold, filling the gap of the second mold with conductive colloid ink, and obtaining a first sensing layer of the sensor; the first sensing layer is prepared in the same mode, the second sensing layer is prepared in the same mode, then the first sensing layer, the spacing layer and the second sensing layer are combined in sequence, repulsive force exists between the adjacent first magnetic parts between the assembled flexible sensors, and interface defects and gaps between materials are reduced through the mode of preparing the first sensing layer and the second sensing layer. Therefore, the risks of performance reduction and structure failure caused by factors such as material aging, oxidation or corrosion in the long-term use process of the sensor are reduced, and the long-term stability of the sensor is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible sensors, and particularly to a flexible sensor and a preparation method thereof. Background Art

[0002] With the wide application of flexible wearable electronic devices in fields such as human-computer interaction, the demand for sensors capable of accurately detecting mechanical surface strain is increasing day by day. Such sensors need to be able to adapt to the fitting requirements of various complex curved surfaces. Therefore, flexible sensors have become a key component in the field of sensor research.

[0003] Although certain progress has been made in the research of existing flexible triboelectric sensors, there are still many technical bottlenecks: flexible triboelectric sensors have deficiencies in terms of stability, and problems such as unstable performance or degradation may occur after long-term use, resulting in a decrease in the measurement accuracy of the sensors. Summary of the Invention

[0004] Aiming at the deficiencies in the background art, the purpose of the present invention is to provide a flexible sensor and a preparation method thereof.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A preparation method of a flexible sensor, comprising the following steps:

[0007] S1. Prepare a dielectric layer:

[0008] Add ionic liquid, gaseous SiO2 particles, curing agent liquid and ionic liquid to PDMS liquid, stir for T1 time and perform vacuum filtration for T2 time to obtain a conductive colloidal ink. Fill the conductive colloidal ink into a first mold, and then heat and cure the first mold filled with the conductive colloidal ink. After demolding, a dielectric layer is obtained;

[0009] S2. Prepare a first sensing layer:

[0010] The sensor monolayer includes a first sensing layer and a second sensing layer. Embed a first magnetic part into the dielectric layer, and place the dielectric layer embedded with the first magnetic part into a second mold. Then place a second magnetic part below the outer surface of the second mold, pour the conductive colloidal ink above the dielectric layer, and heat and cure and demold to obtain the first sensing layer;

[0011] S3. Prepare a second sensing layer:

[0012] Repeat the steps in S2 to obtain the second sensing layer;

[0013] S4. Prepare a spacer layer:

[0014] Design the spacer layer mesh plate, fix the spacer layer mesh plate on the printing table, evenly coat the spacer layer ink on the spacer layer mesh plate, and obtain the spacer layer through several overprintings;

[0015] S5. Assemble the flexible sensor:

[0016] After matching the position of one side of the spacer layer with the electrode of the first sensing layer and then adhering them, and then matching the position of the other side of the spacer layer with the electrode of the second sensing layer and adhering them after matching, the flexible sensor is obtained, and the preparation is completed.

[0017] Furthermore, when preparing the single layer of the sensor in step S2 and step S3, the magnetic force between the first magnetic part and the second magnetic part is an attractive force; when assembling the flexible sensor in step S5, the magnetic force between the adjacent first magnetic parts inside the flexible sensor is a repulsive force.

[0018] Furthermore, mix the PDMS liquid, curing agent liquid, ionic liquid, and gaseous SiO2 particles according to a mass ratio of 10:1:10:2 to obtain the conductive colloidal ink; and the time T1 is 2h, and the time T2 is 2min.

[0019] Furthermore, mix TPU and DFM according to a mass ratio of 1:2 to obtain the spacer layer ink, and put the spacer layer ink into a stirrer and stir it at 1100r / min and 80 degrees for 3h.

[0020] Furthermore, perform a surface modification treatment on the spacer layer obtained in step S4.

[0021] Furthermore, the surface modification treatment method is a plasma treatment method. When performing the surface modification treatment on the spacer layer by adopting the plasma treatment method, the plasma treatment power is 100W, and the treatment time is 3min.

[0022] Furthermore, the surface modification treatment method is an ultraviolet light irradiation method. When performing the treatment on the spacer layer surface by adopting the ultraviolet light irradiation method, the ultraviolet light irradiation intensity is 10mW / cm², and the treatment time is 10min.

[0023] Furthermore, when assembling the flexible sensor, the spacer layer is attached to the first sensing layer and the second sensing layer by a hot pressing treatment method or a vacuum heating and curing method.

[0024] Furthermore, when adopting the hot pressing treatment method, the hot pressing temperature is 55 degrees, the pressure is 1.0MPa, and the hot pressing time is 90s.

[0025] Furthermore, when adopting the vacuum heating and curing method, the curing temperature is 55 degrees, and the curing time is 1h.

[0026] A flexible sensor, using the above preparation method, sequentially includes the first sensing layer, the spacer layer, and the second sensing layer from top to bottom.

[0027] The beneficial effects of the present invention are as follows:

[0028] 1. For the preparation method of a flexible sensor proposed by the present invention, after embedding the first magnetic member into the dielectric layer, the second magnetic member is placed below the outer surface of the second mold, and conductive colloidal ink is filled above the dielectric layer to obtain the first sensing layer and the second sensing layer. This preparation method reduces the interfacial defects and voids between materials, thereby reducing the risk of performance degradation and structural failure of the sensor caused by factors such as material aging, oxidation, or corrosion during long-term use, and enhancing the long-term stability of the sensor.

[0029] 2. For the preparation method of a flexible sensor proposed by the present invention, the magnetic force between adjacent first magnetic members is a repulsive force, and the repulsive force can provide an inherent restoring force for the sensor. When the sensor is deformed by an external force, the relative positions of the magnetic members will change, resulting in a change in the distribution of the repulsive force; once the external force is removed, the repulsive force between the magnetic members will cause them to return to their initial positions, thereby driving the entire sensor to return to its original shape. This shape memory effect can extend the service life of the sensor and improve its reliability and stability.

[0030] 3. For the preparation method of a flexible sensor proposed by the present invention, the spacer layer ink is prepared by mixing TPU and DFM according to a mass ratio of 1:2. The obtained spacer layer ink is placed in a stirrer and stirred thoroughly for 3 h under the conditions of 1100 r / min and 80 °C. The addition of DFM can significantly improve the electrical conductivity of TPU. By mixing with TPU, a conductive network can be formed, thereby improving the conductivity of the composite material and enabling the sensor to have good electrical properties.

[0031] 4. For the preparation method of a flexible sensor proposed by the present invention, the surface of the spacer layer is modified by plasma treatment or ultraviolet light irradiation. Plasma treatment can perform physical and chemical modifications on the surface of the spacer layer. After treatment, the surface energy and adhesion of the spacer layer are significantly improved, further enhancing the overall structural stability and dielectric properties of the sensor. At the same time, by modifying the surface of the spacer layer through plasma treatment or ultraviolet light irradiation, the contact between it and the sensing layer or other functional layers can be made closer and more stable, thereby improving the signal transmission efficiency and sensitivity of the sensor.

[0032] 5. The preparation method of a flexible sensor proposed by the present invention can significantly enhance the bonding force between the spacer layer, the first sensor layer and the second sensor layer during the assembly of the flexible sensor through a hot pressing treatment method or a vacuum heating and curing method, improving the stability and reliability of the sensor; at the same time, these treatment methods can also improve the flexibility and electrical properties of the material, thereby enhancing the overall performance and service life of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following-described drawings are only some embodiments of the invention, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0034] Figure 1 It is a flowchart of the preparation method of a flexible sensor of the present invention;

[0035] Figure 2 It is an exploded view of a flexible sensor unit of the present invention;

[0036] Figure 3 It is a schematic diagram of the second magnetic part of a flexible sensor of the present invention;

[0037] Figure 4 It is a schematic diagram of the first mold of a flexible sensor of the present invention;

[0038] Figure 5 It is one of the schematic diagrams of the second mold of a flexible sensor of the present invention;

[0039] Figure 6 It is another schematic diagram of the second mold of a flexible sensor of the present invention;

[0040] Figure 7 It is an exploded view of a flexible sensor array of the present invention;

[0041] Figure 8 It is a graph showing the relationship between the repulsive force between the first magnetic parts of a flexible sensor of the present invention and the change in the magnet spacing;

[0042] Figure 9 It is a graph showing the relationship between the electrical signal output and pressure of a flexible sensor of the present invention and the change in strain during the loading and unloading processes;

[0043] Figure 10 It is a graph showing the change in the electrical signal output of a flexible sensor of the present invention within different strain ranges;

[0044] Figure 11The figure shows the change of the electrical signal output of a flexible sensor of the present invention within different pressure ranges;

[0045] Figure 12 The figure shows the relationship between the capacitance and the number of cycles of a flexible sensor of the present invention under a strain of 15%;

[0046] Figure 13 The figure shows the relationship between the capacitance and time of a flexible sensor of the present invention under a high-frequency oscillation of 3.85 Hz.

[0047] In the figure, 10, dielectric layer; 201, first mold; 202, second mold; 301, first magnetic part; 302, second magnetic part; 401, first sensing layer; 402, second sensing layer; 50, spacer layer; 601, first placement groove; 6011, first protrusion; 6012, second protrusion; 602, second placement groove; 603, third placement groove; 604, fourth placement groove; 701, first covering layer; 702, second covering layer. Detailed implementation mode

[0048] The following combines Figures 1 to 13 to describe the present invention in detail.

[0049] Embodiment 1

[0050] A preparation method of a flexible sensor includes the following steps:

[0051] S1. Prepare the dielectric layer 10:

[0052] Add ionic liquid, gaseous SiO2 particles, and curing agent liquid to PDMS liquid, stir for T1 time and vacuum filter for T2 time to obtain conductive colloidal ink. Fill the conductive colloidal ink into the first mold 201, and then heat and cure the first mold 201 filled with the conductive colloidal ink. After demolding, the dielectric layer 10 is obtained;

[0053] S2. Prepare the first sensing layer 401:

[0054] The sensor monolayer includes a first sensing layer 401 and a second sensing layer 402. Embed the first magnetic part 301 into the dielectric layer 10, and place the dielectric layer 10 embedded with the first magnetic part 301 into the second mold 202. Then place the second magnetic part 302 below the outer surface of the second mold 202. Use the suction force between the first magnetic part 301 and the second magnetic part 302 to reinforce the dielectric layer 10. Introduce the conductive colloidal ink above the dielectric layer 10, and after heating, curing, and demolding, the first sensing layer 401 is obtained. This preparation method reduces the interfacial defects and voids between materials, thereby reducing the risk of performance degradation and structural failure of the sensor caused by factors such as material aging, oxidation, or corrosion during long-term use, and enhancing the long-term stability of the sensor;

[0055] S3. Prepare the second sensing layer 402:

[0056] Repeat the steps in S2 to obtain the second sensing layer 402;

[0057] S4. Prepare the spacer layer 50:

[0058] Design the spacer layer stencil, fix the spacer layer stencil on the printing table, evenly coat the spacer layer ink on the spacer layer stencil, and obtain the spacer layer 50 through several overprinting operations;

[0059] S5. Assemble the flexible sensor:

[0060] Match the positions of the electrodes of the first sensing layer 401 with one side of the spacer layer 50 and then perform adhesion. Then, match the positions of the electrodes of the second sensing layer 402 with the other side of the spacer layer 50 and perform adhesion after matching to obtain the flexible sensor, and the preparation is completed.

[0061] In this embodiment, when preparing the first sensing layer 401 and the second sensing layer 402 in steps S2 and S3, the magnetic force between the first magnetic member 301 and the second magnetic member 302 is an attractive force, and the attractive force can help reinforce the dielectric layer 10; when assembling the flexible sensor in step S5, the magnetic force between adjacent first magnetic members 301 inside the flexible sensor is a repulsive force, and the repulsive force can provide an inherent restoring force for the sensor. When the sensor is deformed by an external force, the relative positions of the magnetic members will change, resulting in a change in the distribution of the repulsive force; once the external force is removed, the repulsive force between the magnetic members will cause them to return to their initial positions, thereby driving the entire sensor to return to its original shape. This shape memory effect can extend the service life of the sensor and improve its reliability and stability.

[0062] In this embodiment, a first placement groove 601 in the shape of a square is provided at the center of the first mold 201, and a cylindrical first convex portion 6011 is provided at the center of the first placement groove 601. A second convex portion 6012 communicating with the edge of the first placement groove 601 is provided at the bottom of the upper surface of the first convex portion 6011.

[0063] Preferably, the side length of the first placement groove 601 is 20 mm, and the groove depth is 1.8 mm; the diameter of the first convex portion 6011 is 10 mm, and the height is 1 mm; the height of the second convex portion 6012 is 1 mm.

[0064] In this embodiment, a second placement groove 602 in the shape of a square is provided at the center of the second mold 202, and a third placement groove 603 communicating with the edge of the second mold 202 is provided at the bottom of the second placement groove 602. A fourth placement groove 604 is provided at the bottom of the outer surface of the second mold 202.

[0065] Preferably, the side length of the second placement groove 602 is 20 mm, and the groove depth is 3.5 mm.

[0066] In this embodiment, when preparing the dielectric layer 10, the first mold 201 needs to be cured and heated, where the heating temperature is 100 degrees and the heating time is 2 h; then when preparing the conductive gum ink, PDMS liquid, curing agent liquid, ionic liquid, and gas-phase SiO2 particles are mixed in a mass ratio of 10:1:10:2, and the mixed solution is stirred in a stirrer for T1 time and then vacuum filtered for T2 time. Sufficient stirring and vacuum filtration can improve the dispersion of gas-phase SiO2 particles, such as, and make them evenly distributed in the conductive gum ink, which helps to reduce the agglomeration phenomenon between conductive fillers and improve the uniformity and conductivity of the conductive network.

[0067] Specifically, take a 20-ml beaker, add 5 g of PDMS liquid, then add 0.5 g of curing agent liquid, then add 5 g of ionic liquid, and then add 1 g of gas-phase SiO2 particles. Stir with a magnetic stirrer for T1 time and vacuum filter for T2 time to obtain the conductive gum ink; then clean a glass plate with alcohol and deionized water, and use the glass plate to print at a 45-degree angle. Fill the first placement groove 601 with the obtained conductive gum ink, and then place the first mold 201 filled with the conductive gum ink on a 100 °C baking table and heat for 2 h to demold and obtain the cured dielectric layer 10.

[0068] Preferably, T1 time is 2 h, and T2 time is 2 min.

[0069] In this embodiment, during the process of preparing the first sensing layer 401 in step S2, first use a conductive cloth to lead out a wire from the first magnetic part 301. By using the conductive cloth to lead out the wire and filling the conductive gum ink above the dielectric layer 10, a stable conduction path can be formed, reducing the loss and interference during signal transmission, which helps to improve the stability and reliability of sensor signal transmission and ensure that the sensor can accurately sense and transmit the magnet repulsive force signal. Embed the first magnetic part 301 into the dielectric layer 10, place the dielectric layer 10 embedded with the first magnetic part 301 into the second placement groove 602 of the second mold 202, place the second magnetic part 302 in the fourth placement groove 604 of the second mold 202, and use the magnet attraction to reinforce the dielectric layer 10. Fill the remaining space above the dielectric layer 10 with the conductive gum ink, heat, cure, and demold to obtain the first sensing layer 401, and repeat step S2 to prepare the second sensing layer 402.

[0070] Specifically, a conductive nickel cloth of the same size as the first magnetic member 301 is made by laser cutting. The conductive nickel cloth is aligned with the first magnetic member 301, and a wire is led out in the middle. The magnet and the wire are embedded in the center of the dielectric layer 10. The dielectric layer 10 embedded with the first magnetic member 301 is placed in the second placement groove 602 of the second mold 202. The second magnetic member 302 is placed in the fourth placement groove 604 of the second mold 202. The dielectric layer 10 is reinforced by the suction force of the magnet. The remaining space above the dielectric layer is filled with conductive colloidal ink by 45-degree inclined printing of the glass plate. Then, the second mold 202 filled with the conductive colloidal ink and the placed dielectric layer 10 is placed on a baking table at 55 °C and heated for 5 h. After demolding, the cured first sensing layer 401 is obtained, and then the second magnetic member 302 is removed. And the above steps are repeated to prepare the second sensing layer 402.

[0071] In this embodiment, the spacer ink in step S4 is configured. TPU and DFM are mixed at a mass ratio of 1:2 and placed in a stirrer and stirred at 1100 r / min and 80 °C for 3 h. The addition of DFM can significantly improve the conductivity of TPU. By mixing with TPU, a conductive network can be formed, thereby improving the conductivity of the composite material and enabling the sensor to have good electrical properties.

[0072] Preferably, the spacer ink is coated on the spacer stencil, and the spacer layer 50 is obtained through 4 overprints.

[0073] In this embodiment, the surface of the spacer layer 50 obtained in step S3 is modified to improve its surface energy and adhesion. The treated spacer layer 50 should have better dielectric stability and bonding strength with the sensor monolayer.

[0074] Specifically, the modification method in this embodiment is the plasma treatment method. When the surface of the spacer layer 50 is modified by the plasma treatment method, the plasma treatment power is 100 W and the treatment time is 3 min. Plasma treatment can physically and chemically modify the surface of the spacer layer 50; in terms of physical modification, high-energy particles such as ions, electrons, and free radicals in the plasma can etch the surface, making the surface rough and increasing the specific surface area of the surface, thereby improving the surface energy; in terms of chemical modification, the plasma can introduce polar groups such as hydroxyl groups and carboxyl groups, and these polar groups can form hydrogen bonds or other chemical bonds with materials such as adhesives, further enhancing the adhesion.

[0075] In this embodiment, the adhesive used in step S5 for assembling the flexible sensor is flexible epoxy resin.

[0076] In this embodiment, when assembling the flexible sensor, the spacer layer 50 is attached to the first sensing layer 401 and the second sensing layer 402 by means of hot pressing or vacuum heating and curing. When using the hot pressing method: the hot pressing temperature is 55 °C, the pressure is 1.0 MPa, and the hot pressing time is 90 s to ensure that each layer is attached to each other; when using the vacuum heating and curing method, the assembled flexible sensor is placed in a vacuum drying oven, the drying temperature is 55 °C, and the time is 1 h.

[0077] In this embodiment, a flexible sensor is also provided. The flexible sensor uses the above preparation method. The flexible sensor sequentially includes a first sensing layer 401, a spacer layer 50, and a second sensing layer 402 from top to bottom.

[0078] Further, the first sensing layer 401 includes a first covering layer 701, a first electrode layer, and a dielectric layer 10; the second sensing layer 402 includes a second covering layer 702, a second electrode layer, and a dielectric layer 10.

[0079] Specifically, both the first electrode layer and the second electrode layer are first magnetic members 301.

[0080] In this embodiment, the flexible sensor can be extended into a two-dimensional array to cover a larger detection area and is suitable for more complex application scenarios. The extension principle is as follows:

[0081] First, set the positions where the sensors need to be arranged on the two-dimensional plane, and then arrange several unit flexible sensors at the set positions to complete the extension.

[0082] In this embodiment, the working principle of the flexible sensor is as follows:

[0083] When the first sensing layer 401 or the second sensing layer 402 is pressed, the distance between the first electrode layer and the second electrode layer in the sensor decreases, resulting in an increase in capacitance or a decrease in resistance, thereby realizing the sensing of pressure.

[0084] As Figure 8 shown, the abscissa represents the interval between the magnetic members, and the ordinate represents the repulsive force magnitude of the flexible sensor, indicating that as the interval between the magnetic members increases, the repulsive force decreases significantly, showing that the repulsive force of the sensor is inversely proportional to its interval.

[0085] As Figure 9As shown, the abscissa represents the strain condition of the sensor, the main ordinate on the left side of the attached figure represents the ratio of the change in the capacitance of the flexible sensor to the initial capacitance, which can reflect the change in the electrical signal output of the flexible sensor. The secondary ordinate on the right side of the attached figure represents the pressure applied to the flexible sensor. The Loading reference mark on the figure indicates that the flexible sensor is in the loading process, and the Unloading reference mark indicates that the flexible sensor is in the unloading process. It shows that during the loading process, both the electrical signal output and the pressure of the flexible sensor increase with the increase of the strain condition, while during the unloading process, the electrical signal output and the pressure of the sensor decrease with the decrease of the strain condition. Overall, the flexible sensor shows stable performance during the loading and unloading processes, indicating that the sensor has the ability of long-term stable monitoring.

[0086] As Figures 10 - 11 shown, Figure 10 the abscissa in Figure 11 represents the strain condition of the flexible sensor, and the ordinate represents the ratio of the change in the capacitance of the flexible sensor to the initial capacitance.

[0087] As Figure 12 shown, the abscissa represents the number of cyclic tests, and the ordinate represents the output capacitance of the flexible sensor. The locally enlarged part in the figure is an arbitrarily intercepted set of experimental values, which shows that under the 15% strain condition, the capacitance of the flexible sensor remains stable for more than 12,000 cycles, demonstrating the long-term stability of the sensor in strain detection.

[0088] As Figure 13 shown, the abscissa represents the number of cyclic tests, and the ordinate represents the output capacitance of the flexible sensor. The locally enlarged part in the figure is an arbitrarily intercepted set of experimental values, which shows that under the high-frequency oscillation condition of more than 3.85 Hz, in the test of 60,000 cycles, the capacitance of the flexible sensor remains stable, demonstrating the long-term stability of the sensor in high-frequency signal detection.

[0089] Example 2

[0090] Different from Example 1, in this example, the modification method of the spacer ink is the ultraviolet light irradiation treatment method, the ultraviolet light irradiation intensity is 10 mW / cm², and the irradiation time is 10 min. Ultraviolet light irradiation can initiate the photochemical reaction on the surface of the spacer 50, causing surface oxidation or cross-linking reactions, etc., thereby changing the surface chemical composition and structure. This modification can increase the surface polarity and roughness, improve the surface energy, and further enhance the surface adhesion.

[0091] The above embodiments are only used to illustrate the technical concept and features of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it, and it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A preparation method of a flexible sensor, characterized in that, It includes the following steps: S1. Prepare a dielectric layer: Add an ionic liquid, gas-phase SiO2 particles, and a curing agent liquid into a PDMS liquid, stir for a time T1 and perform vacuum filtration for a time T2 to obtain a conductive colloidal ink. Fill the conductive colloidal ink into a first mold, and then heat and cure the first mold filled with the conductive colloidal ink. After demolding, a dielectric layer is obtained. S2. Prepare a first sensing layer: A single sensor layer includes a first sensing layer and a second sensing layer. Embed a first magnetic part into the dielectric layer, and place the dielectric layer embedded with the first magnetic part into a second mold. Then place a second magnetic part below the second mold, and introduce the conductive colloidal ink above the dielectric layer. After heating, curing, and demolding, the first sensing layer is obtained. S3. Prepare a second sensing layer: Repeat the steps in S2 to obtain the second sensing layer. S4. Prepare a spacer layer: Design a spacer layer stencil, fix the spacer layer stencil on a printing table, evenly coat the spacer layer ink on the spacer layer stencil, and obtain a spacer layer through several overprintings. S5. Assemble a flexible sensor: Adhere one side of the spacer layer to match the electrode position of the first sensing layer, and then adhere the other side of the spacer layer to match and adhere to the electrode position of the second sensing layer to obtain a flexible sensor, and the preparation is completed.

2. The preparation method of a flexible sensor according to claim 1, characterized in that, When preparing the single sensor layer in step S2 and step S3, the magnetic force between the first magnetic part and the second magnetic part is an attractive force; when assembling the flexible sensor in step S5, the magnetic force between adjacent first magnetic parts inside the flexible sensor is a repulsive force.

3. The manufacturing method of a flexible sensor as described in claim 1, characterized in that, Mix the PDMS liquid, curing agent liquid, ionic liquid, and gas-phase SiO2 particles in a mass ratio of 10:1:10:2 to obtain the conductive colloidal ink; and the time T1 is 2 h, and the time T2 is 2 min.

4. The preparation method of a flexible sensor according to claim 1, characterized in that, Mix TPU and DFM in a mass ratio of 1:2 to obtain the spacer layer ink, and place the spacer layer ink into a stirrer and stir at 1100 r / min and 80 °C for 3 h.

5. The preparation method of a flexible sensor according to claim 1, characterized in that, Perform a modification treatment on the surface of the spacer layer obtained in step S4.

6. The preparation method of a flexible sensor according to claim 5, characterized in that, The modification treatment method is a plasma treatment method. When performing the modification treatment on the surface of the spacer layer by adopting the plasma treatment method, the plasma treatment power is 100 W, and the treatment time is 3 min.

7. The preparation method of a flexible sensor according to claim 5, wherein, The modification method is ultraviolet light irradiation. When the surface of the spacer layer is modified by the ultraviolet light irradiation method, the ultraviolet light irradiation intensity is 10 mW / cm 2 , and the treatment time is 10 min.

8. The preparation method of a flexible sensor according to claim 1, characterized in that, When assembling the flexible sensor, the spacer layer is attached to the first sensing layer and the second sensing layer by a hot pressing treatment method or a vacuum heating and curing method.

9. The preparation method of a flexible sensor according to claim 8, characterized in that, When adopting the hot pressing treatment method, the hot pressing temperature is 55 °C, the pressure is 1.0 MPa, and the hot pressing time is 90 s.

10. The preparation method of a flexible sensor according to claim 8, wherein When adopting the vacuum heating and curing method, the curing temperature is 55 °C, and the curing time is 1 h.

11. A flexible sensor, characterized in that, Using the preparation method according to any one of claims 1-10, the flexible sensor sequentially includes the first sensing layer, the spacer layer, and the second sensing layer from top to bottom.

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