Flexible two-dimensional strain and pressure composite sensor and preparation method and application thereof

Abstract

The invention relates to a flexible two-dimensional strain and pressure composite sensor and a preparation method and application of the flexible two-dimensional strain and pressure composite sensor. The two-dimensional sensing unit comprises a first flexible substrate, and a first sensing layer, an isolation layer, a second sensing layer and a first packaging layer which are sequentially stacked on the first flexible substrate, the first sensing layer and the second sensing layer are arranged in a staggered manner, and the two-dimensional sensing unit comprises a first part and a second part; the elastic modulus of the first part is greater than that of the second part, and the elastic modulus difference is greater than or equal to 160MPa; the pressure sensing unit is arranged on the two-dimensional sensing unit, the third part corresponds to the first part, and the fourth part is of a paper-cut structure. The flexible two-dimensional strain and pressure composite sensor can monitor the strain in the two-dimensional direction in the plane and the pressure in the vertical direction of the plane at the same time, the sub-sensors work independently and do not interfere with one another, the sensitivity is high, and the monitoring accuracy is high.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a flexible two-dimensional strain and pressure composite sensor and a preparation method and application thereof. Background Art

[0002] With the rapid development of flexible electronic technology, its application demand in the fields of electronic skin, soft robots, wearable devices and smart medical care is increasing. Among them, flexible strain sensors and pressure sensors are the two most common types of sensors in the field of flexible electronic technology. However, most traditional flexible strain sensors or pressure sensors can only detect single-dimensional strain / stress, and it is difficult to achieve the selective response capability of the device to tensile strain or stress in different dimensional directions. Although some multidimensional sensor devices have been reported, the multidimensional sensor devices are basically formed by simple splicing of multiple single-dimensional sensors. In actual applications, there is a certain amount of mutual interference between multiple sensor devices, which seriously affects the accuracy of monitoring. Summary of the invention

[0003] Based on this, it is necessary to provide a flexible two-dimensional strain and pressure composite sensor and its preparation method and application to address the above problems. The flexible two-dimensional strain and pressure composite sensor can not only simultaneously monitor the strain in the two-dimensional direction within the plane and the pressure in the vertical direction of the plane, but also each sub-sensor works independently without interfering with each other, with high sensitivity and high monitoring accuracy.

[0004] A flexible two-dimensional strain and pressure composite sensor, the flexible two-dimensional strain and pressure composite sensor comprising:

[0005] A two-dimensional sensing unit, the two-dimensional sensing unit comprising a first flexible substrate and a first sensing layer, an isolation layer, a second sensing layer and a first packaging layer stacked in sequence on the first flexible substrate, the first sensing layer and the second sensing layer are arranged in an alternating manner, a plane parallel to the surface where the first flexible substrate is located is defined as a first surface, a direction in which the first sensing layer, the isolation layer, the second sensing layer and the first packaging layer are stacked in sequence is defined as a first direction, the projections of the first sensing layer and the second sensing layer on the first surface along the first direction partially overlap to form a cross-overlapping area, the two-dimensional sensing unit comprising a first part and a second part, the projection of the first part on the first surface along the first direction coincides with the cross-overlapping area, the second part is the part of the two-dimensional sensing unit other than the first part, wherein the elastic modulus of the first part is greater than the elastic modulus of the second part, and the elastic modulus difference is greater than or equal to 160 MPa;

[0006] A pressure sensing unit, wherein the pressure sensing unit is stacked on the two-dimensional sensing unit, and the pressure sensing unit comprises a third part and a fourth part connected to the third part, wherein the third part corresponds to the first part, and the fourth part is a paper-cut structure.

[0007] In one embodiment, a first adhesive layer is embedded in the first part, and a second adhesive layer is embedded in the second part, wherein the elastic modulus of the first adhesive layer is 170MPa-200MPa, and the elastic modulus of the second adhesive layer is 0.3MPa-1MPa.

[0008] In one embodiment, the first sensing layer and the second sensing layer are arranged in an orthogonal stacking manner;

[0009] And / or, the first sensing layer and the second sensing layer are both in strip shape.

[0010] In one of the embodiments, the orthographic projection of the pressure sensing unit on the first surface completely overlaps with the orthographic projection of the first sensing layer or the second sensing layer on the first surface.

[0011] In one embodiment, the pressure sensing unit includes a second flexible substrate and a first electrode layer, a dielectric layer, a second electrode layer and a second packaging layer stacked in sequence on the second flexible substrate, and the second flexible substrate is arranged on the first flexible substrate or on the first packaging layer.

[0012] In one of the embodiments, the elastic modulus of the second flexible substrate portion corresponding to the first portion is 170 MPa-200 MPa.

[0013] In one embodiment, the first sensing layer and the second sensing layer both include a liquid metal layer, a conductive ink layer and a first metal pin, the liquid metal layer corresponds to the cross-overlapping region, the conductive ink layer is disposed on both sides of the liquid metal layer, and the first metal pin is disposed at one end of the conductive ink layer away from the liquid metal layer;

[0014] And / or, the pressure sensing unit further includes a second metal pin, and the paper-cut structure is disposed between the second metal pin and the third part.

[0015] A method for preparing the flexible two-dimensional strain and pressure composite sensor as described above comprises the following steps:

[0016] Sequentially preparing a first sensing layer, an isolation layer, a second sensing layer and a first packaging layer on a first flexible substrate, and controlling the first sensing layer and the second sensing layer to be arranged in an alternating manner to obtain a prefabricated two-dimensional sensing unit;

[0017] Placing a first glue solution and a second glue solution on the surface of the prefabricated two-dimensional sensing unit, and forming a two-dimensional sensing unit having a first part and a second part through infiltration and curing;

[0018] A pressure sensing unit with a kirigami structure is prepared, and then the pressure sensing unit and the two-dimensional sensing unit are assembled together so that the third part of the pressure sensing unit corresponds to the first part, thereby obtaining a flexible two-dimensional strain and pressure composite sensor.

[0019] In one embodiment, the mass fraction of glue in the first glue solution is 25%-38%, and the first glue solution is selected from a hard glue solution;

[0020] And / or, the mass fraction of glue in the second glue solution is 13%-55%, and the second glue solution is selected from soft glue solution;

[0021] And / or, the steps for preparing a pressure sensing unit with a paper-cut structure are as follows: a first electrode layer, a dielectric layer, a second electrode layer and a second packaging layer are prepared in sequence on a second flexible substrate to obtain a prefabricated pressure sensing unit; a preset part of the prefabricated pressure sensing unit is processed into a paper-cut structure, and a second metal pin connected to one end of the paper-cut structure is formed at the same time, and then a third glue is placed on a partial surface of the second flexible substrate, and a third glue layer embedded in the second flexible substrate is formed through infiltration and curing to obtain a pressure sensing unit with a paper-cut structure, wherein the third glue is selected from a hard glue.

[0022] An application of the flexible two-dimensional strain and pressure composite sensor as described above in electronic skin, soft robots or wearable electronic products.

[0023] In the flexible two-dimensional strain and pressure composite sensor of the present invention, by setting a two-dimensional sensing unit and a pressure sensing unit, the flexible two-dimensional strain and pressure composite sensor can simultaneously monitor the strain in the two-dimensional direction within the plane and the pressure in the vertical direction of the plane; at the same time, by setting the two-dimensional sensing unit to include a first part and a second part, and controlling the relationship between the elastic moduli of the first part and the second part, the first part can be made a rigid unchanged part, and when the two-dimensional sensing unit undergoes tensile deformation along the direction where the first sensing layer or the second sensing layer is located, the first part will not be deformed, so that the first sensing layer and the second sensing layer do not interfere with each other when they work independently. Interference is improved, thereby improving the monitoring accuracy of the sensor in the two-dimensional direction within the plane; and, by arranging the pressure sensing unit to include a third part and a fourth part, the third part corresponds to the first part, and the fourth part is a paper-cut structure; utilizing the characteristics of the paper-cut structure, it can be effectively ensured that the two-dimensional sensing unit and the pressure sensing unit do not interfere with each other when detecting strain, and because the first part is a rigid and unchanged part, when the pressure sensing unit is subjected to pressure in the vertical direction, the pressure deformation in the vertical direction will not be transmitted to the two-dimensional sensing unit, thereby further improving the working independence between the two-dimensional sensing unit and the pressure sensing unit, and improving the sensitivity and monitoring accuracy of the entire sensor.

[0024] Therefore, the flexible two-dimensional strain and pressure composite sensor of the present invention can not only simultaneously monitor the strain in the two-dimensional direction within the plane and the pressure in the vertical direction of the plane, but also each sub-sensor works independently without interfering with each other, with high sensitivity and high monitoring accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 This is a schematic structural diagram of a flexible two-dimensional strain and pressure composite sensor according to Example 1 of the present invention;

[0027] Figure 2 for Figure 1 Exploded diagram of the structure of the two-dimensional sensing unit;

[0028] Figure 3 for Figure 1 Exploded view of the pressure sensing unit;

[0029] Figure 4This is the test result of the flexible two-dimensional strain and pressure composite sensor of Example 1 of the present invention when stretched 100% in the x-axis direction, wherein in the figure, A1 represents the relative resistance change rate of the sub-sensor in the x-axis direction, B1 represents the relative resistance change rate of the sub-sensor in the y-axis direction, and C1 represents the relative capacitance change rate of the sub-sensor in the z-axis direction;

[0030] Figure 5 This is the test result of the flexible two-dimensional strain and pressure composite sensor of Example 1 of the present invention when stretched 100% in the y-axis direction, wherein in the figure, A2 represents the relative resistance change rate of the sub-sensor in the x-axis direction, B2 represents the relative resistance change rate of the sub-sensor in the y-axis direction, and C2 represents the relative capacitance change rate of the sub-sensor in the z-axis direction;

[0031] Figure 6 The test results of the flexible two-dimensional strain and pressure composite sensor of Example 1 of the present invention when stretched in the Z-axis direction and subjected to a pressure of 35 kPa, wherein in the figure, A3 represents the relative resistance change rate of the sub-sensor in the x-axis direction, B3 represents the relative resistance change rate of the sub-sensor in the y-axis direction, and C3 represents the relative capacitance change rate of the sub-sensor in the z-axis direction;

[0032] Figure 7 The test results of the flexible two-dimensional strain and pressure composite sensor of Example 1 of the present invention when it undergoes cyclic stretching of 10%, 20%, and 40% in the x-axis direction, wherein, in the figure, A4 represents the relative resistance change rate of the sub-sensor in the x-axis direction, B4 represents the relative resistance change rate of the sub-sensor in the y-axis direction, and C4 represents the relative capacitance change rate of the sub-sensor in the z-axis direction;

[0033] Figure 8 The test results of the flexible two-dimensional strain and pressure composite sensor of Example 1 of the present invention when stretched by 10%, 20%, and 40% in the y-axis direction, wherein in the figure, A5 represents the relative resistance change rate of the sub-sensor in the x-axis direction, B5 represents the relative resistance change rate of the sub-sensor in the y-axis direction, and C5 represents the relative capacitance change rate of the sub-sensor in the z-axis direction;

[0034] Fig. 9 The test results of the flexible two-dimensional strain and pressure composite sensor of Example 1 of the present invention when it experiences 5 kPa, 10 kPa, and 20 kPa pressures in the z-axis direction, wherein in the figure, A6 represents the relative resistance change rate of the sub-sensor in the x-axis direction, B6 represents the relative resistance change rate of the sub-sensor in the y-axis direction, and C6 represents the relative capacitance change rate of the sub-sensor in the z-axis direction;

[0035] Fig.10The test results of the y-axis and z-axis of the flexible two-dimensional strain and pressure composite sensor of Comparative Example 1 of the present invention when stretched 100% in the x-axis direction, wherein in the figure, B7 represents the relative resistance change rate of the sub-sensor in the y-axis direction, and C7 represents the relative capacitance change rate of the sub-sensor in the z-axis direction;

[0036] Fig.11 The test results of the y-axis and z-axis of the flexible two-dimensional strain and pressure composite sensor of Comparative Example 2 of the present invention when stretched 100% in the x-axis direction, wherein in the figure, B8 represents the relative resistance change rate of the sub-sensor in the y-axis direction, and C8 represents the relative capacitance change rate of the sub-sensor in the z-axis direction;

[0037] Fig.12 The test results of the y-axis and z-axis of the flexible two-dimensional strain and pressure composite sensor of comparative example 3 of the present invention when it is stretched 100% in the x-axis direction, wherein, in the figure, B9 represents the relative resistance change rate of the sub-sensor in the y-axis direction, and C9 represents the relative capacitance change rate of the sub-sensor in the z-axis direction.

[0038] Figure numerals: 1. two-dimensional sensing unit; 2. pressure sensing unit; 3. first flexible substrate; 4. first sensing layer; 5. isolation layer; 6. second sensing layer; 7. first packaging layer; 8. liquid metal layer; 9. conductive ink layer; 10. first metal pin; 11. second flexible substrate; 12. first electrode layer; 13. dielectric layer; 14. second electrode layer; 15. second packaging layer; 16. paper-cut structure; 17. second metal pin; A. first part; B. third part. DETAILED DESCRIPTION

[0039] For ease of understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific implementation methods or embodiments, and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, and the combinations include any two related listed items, any more related listed items, or all related listed items.

[0041] like Figures 1 to 3As shown, a flexible two-dimensional strain and pressure composite sensor according to an embodiment of the present invention is provided, and the flexible two-dimensional strain and pressure composite sensor comprises a two-dimensional sensing unit 1 and a pressure sensing unit 2, and the pressure sensing unit 2 is arranged on the two-dimensional sensing unit 1. It can be understood that by combining the two-dimensional sensing unit 1 and the pressure sensing unit 2 together, the flexible two-dimensional strain and pressure composite sensor can simultaneously monitor the strain in the two-dimensional direction within the plane and the pressure in the vertical direction of the plane.

[0042] Among them, combined Figure 2 As shown, the two-dimensional sensing unit 1 includes a first flexible substrate 3 and a first sensing layer 4, an isolation layer 5, a second sensing layer 6 and a first packaging layer 7 stacked in sequence on the first flexible substrate 3. The direction in which the first flexible substrate 3, the first sensing layer 4, the isolation layer 5, the second sensing layer 6 and the first packaging layer 7 are stacked in sequence is defined as a first direction Z. The first sensing layer 4 and the second sensing layer 6 are arranged in an alternating manner, and the projections of the first sensing layer 4 and the second sensing layer 6 on the first surface along the first direction Z partially overlap to form a cross-overlapping area, and the first surface is a plane parallel to the surface where the first flexible substrate 3 is located. The two-dimensional sensing unit includes a first part A and a second part, wherein the projection of the first part A on the first surface along the first direction coincides with the cross-overlapping area, and the second part is the part of the two-dimensional sensing unit other than the first part A.

[0043] The elastic modulus of the first portion A is greater than the elastic modulus of the second portion, and the elastic modulus difference is greater than or equal to 160 MPa.

[0044] In the present invention, by controlling the elastic modulus of the first part A and the second part of the two-dimensional sensing unit 1, and controlling the hardness of the first part A and the second part, the first part A of the two-dimensional sensing unit 1 is made into a constant rigid part, and the second part is made into a flexible elastic deformable part. Therefore, when the first sensing layer 4 in the two-dimensional sensing unit 1 undergoes tensile deformation, the structure of the sensing layer inside it will change, thereby causing its resistance value to change and realize sensing. At this time, since the first part A will not be deformed, that is, the first sensing layer 4 and the second sensing layer 6 are on the first flexible substrate along the first direction Z in the first The cross-overlapping area formed by the overlapping of the projections on the surface will not be deformed, so that the deformation of the first sensing layer 4 will not be transmitted to the second sensing layer 6. Similarly, when the second sensing layer 6 is working, it will not interfere with the first sensing layer 4, thereby realizing independent sensing between the first sensing layer 4 and the second sensing layer 6, and the work of the two does not interfere with each other; and it can also avoid that the pressure sensing unit 2 is subjected to vertical pressure to interfere with the sensing performance of the first sensing layer 4 and the second sensing layer 6 in the two-dimensional sensing unit 1, thereby improving the sensitivity of the two-dimensional sensing unit 1 in the two-dimensional direction within the plane and the monitoring accuracy.

[0045] It should be noted that in the present invention, the elastic modulus is used as an indicator to measure the ease with which a material undergoes elastic deformation. The larger the elastic modulus value, the greater the stress required to cause a certain elastic deformation of the material. That is, the greater the stiffness of the material, the smaller the elastic deformation under a certain stress; and vice versa.

[0046] Optionally, a first adhesive layer (not shown) is embedded in the first part A, and a second adhesive layer (not shown) is embedded in the second part, wherein the elastic modulus of the first adhesive layer is 170MPa-200MPa, and the elastic modulus of the second adhesive layer is 0.3MPa-1MPa. With such a configuration, the elastic modulus of the first part A can be better controlled to be greater than the elastic modulus of the second part, and the difference in elastic modulus is greater than or equal to 160MPa.

[0047] Furthermore, the material of the first adhesive layer is selected from Zhuoid UV glue D-606, Zhuoid UV glue D-3100, Fuxing Danny UV hard glue or Kasuto UV crystal glue, preferably Zhuoid UV glue D-606, and the material of the second adhesive layer is selected from Zhuoid UV glue D-0082, Zhuoid UV glue D-0084, Kasuto UV soft glue or Energo UV soft glue, preferably Zhuoid UV glue D-0082.

[0048] In one embodiment, the thickness of the first flexible substrate 3 is 60 μm-100 μm; the thickness of the first sensing layer 4 is 3 μm-4 μm; the thickness of the second sensing layer 6 is 3 μm-4 μm; the thickness of the isolation layer 5 is 60 μm-100 μm; and the thickness of the first encapsulation layer 7 is 60 μm-100 μm. In this way, the thickness of the two-dimensional sensing unit 1 and the sensor as a whole can be controlled by controlling the thickness of each layer, which is conducive to further ensuring the structural strength of the two-dimensional sensing unit 1 and the sensor as a whole, while improving the softness and conformability of the two-dimensional sensing unit 1 and the sensor as a whole.

[0049] In one embodiment, the first flexible substrate 3, the isolation layer 5 and the first encapsulation layer 7 are all selected from flexible nanofiber layers, preferably any one of a thermoplastic polyurethane nanofiber layer and a styrene-butadiene-styrene block copolymer nanofiber layer, and more preferably a thermoplastic polyurethane nanofiber layer.

[0050] It is understandable that, combined with Figure 1 As shown, in the present invention, the angle C between the center line of the orthographic projection of the first sensing layer 4 on the first surface and the center line of the orthographic projection of the second sensing layer 6 on the first surface is set to C>0°, preferably 60°≤C≤90°, and more preferably C=90°. Such a setting can further improve the independent sensing between the first sensing layer 4 and the second sensing layer 6, and improve the monitoring accuracy of the two.

[0051] To this end, in the present invention, the first sensing layer 4 and the second sensing layer 6 are arranged in an orthogonal stacking manner.

[0052] Furthermore, the first sensing layer and the second sensing layer are both in strip shape.

[0053] Optionally, the first sensing layer 4 and the second sensing layer 6 both include a liquid metal layer 8, a conductive ink layer 9 and a first metal pin 10, the liquid metal layer 8 corresponds to the cross-overlapping region, the conductive ink layer 9 is provided on both sides of the liquid metal layer 8, and the first metal pin 10 is provided at one end of the conductive ink layer 9 away from the liquid metal layer 8. In this arrangement, the liquid metal layer 8 is used as the conductive electrode of the first sensing layer 4 and the second sensing layer 6 by taking advantage of the low resistance of the liquid metal and the insignificant resistance change when undergoing stretching and compression, while the conductive ink has a high resistance and a large resistance change during stretching, and is used as the sensitive element of the first sensing layer 4 and the second sensing layer 6, which can further improve the working independence between the first sensing layer 4 and the second sensing layer 6, and is conducive to improving the sensitivity of the first sensing layer 4 and the second sensing layer 6, thereby improving the sensitivity of both and the monitoring accuracy.

[0054] In one embodiment, a copper sheet (not shown) is provided at one end of the first metal pin 10 away from the conductive ink layer 9, and an enameled wire is welded on the outer surface of the copper sheet for connecting the two-dimensional sensing unit 1 with an external circuit, wherein the copper sheet is selected from a red copper sheet.

[0055] In one embodiment, the liquid metal layer 8 is selected from a gallium-based liquid metal layer, and the gallium-based liquid metal layer is selected from a liquid gallium-indium alloy layer or a liquid gallium-indium-tin alloy layer, and is more preferably a liquid gallium-indium alloy layer.

[0056] In one embodiment, the material of the first metal pin 10 is liquid metal, wherein the liquid metal is gallium-based liquid metal, and the gallium-based liquid metal is selected from liquid gallium-indium alloy or liquid gallium-indium-tin alloy, preferably liquid gallium-indium alloy.

[0057] The pressure sensing unit 2 is stacked on the two-dimensional sensing unit 1. The pressure sensing unit 2 includes a third part B and a fourth part connected to the third part B. The third part B corresponds to the first part A, and the fourth part is a paper-cut structure 16. It can be understood that in the pressure sensing unit 2, by setting the fourth part as the paper-cut structure 16, the paper-cut structure 16 has a high degree of compliance and deformability, which effectively ensures that the first sensing layer 4 or the second sensing layer 6 does not interfere with the pressure sensing unit 2 when detecting strain, so that the work between the two-dimensional sensing unit 1 and the pressure sensing unit 2 is completely independent and does not interfere with each other. Moreover, under the synergistic effect of the first part A being a rigid unchanged part, when the pressure sensing unit 2 is subjected to pressure in the vertical direction, the pressure deformation in the vertical direction will not be transmitted to the two-dimensional sensing unit 1, which further improves the working independence between the two-dimensional sensing unit 1 and the pressure sensing unit 2, thereby improving the sensitivity and monitoring accuracy of the entire sensor.

[0058] It should be noted that, in the present invention, the paper-cut structure is a kirigami paper-cut structure.

[0059] Optionally, the pressure sensing unit 2 further includes a second metal pin 17 , and the paper-cut structure 16 is disposed between the second metal pin 17 and the third part B.

[0060] In one embodiment, the second metal pin 17 is stacked on the first metal pin 10 to assemble the pressure sensing unit 2 and the two-dimensional sensing unit 1 together.

[0061] In one embodiment, a copper sheet is provided at one end of the second metal pin 17 away from the paper-cut structure 16 , and an enameled wire is welded on the outer surface of the copper sheet to connect the pressure sensing unit 2 with an external circuit, wherein the copper sheet is selected from red copper sheet.

[0062] Combination Figure 3 As shown, the pressure sensing unit 2 includes a second flexible substrate 11 and a first electrode layer 12, a dielectric layer 13, a second electrode layer 14 and a second packaging layer 15 stacked in sequence on the second flexible substrate 11, and the second flexible substrate 11 is arranged on the first packaging layer 7 or the first flexible substrate 3. It can be understood that when the pressure sensing unit 2 is subjected to external pressure, the dielectric layer 13 of the pressure sensing unit 2 will be compressed, so that the distance between the upper and lower electrode layers of the capacitor will change, thereby causing a change in the capacitance value, and realizing capacitive sensing of the pressure sensing unit 2.

[0063] Optionally, the elastic modulus of the second flexible substrate 11 portion corresponding to the first portion A is 170MPa-200MPa. With such a configuration, the elastic modulus of the second flexible substrate 11 and the portion corresponding to the first portion A of the two-dimensional sensing unit 1 can be substantially the same, and both are rigid non-deformable portions, which can further prevent the pressure deformation of the pressure sensing unit 2 from being transmitted to the two-dimensional sensing unit 1, thereby better ensuring independent monitoring between the two-dimensional sensing unit 1 and the pressure sensing unit 2 and improving monitoring accuracy.

[0064] In one embodiment, a third adhesive layer (not shown) is embedded in the second flexible substrate 11, and the elastic modulus of the third adhesive layer is 170MPa-200MPa. This arrangement can effectively ensure that the elastic modulus of the second flexible substrate 11 portion corresponding to the first portion A is 170MPa-200MPa.

[0065] Furthermore, the material of the third adhesive layer is selected from Zhuoid UV glue D-606, Zhuoid UV glue D-3100, Fuxing Danny UV hard glue or Kasuto UV crystal glue, preferably Zhuoid UV glue D-606.

[0066] In one embodiment, the thickness of the second flexible substrate 11 is 60 μm-100 μm; the thickness of the first electrode layer 12 is 3 μm-4 μm; the thickness of the second electrode layer 14 is 3 μm-4 μm; and the thickness of the second packaging layer 15 is 60 μm-100 μm.

[0067] In one embodiment, the second flexible substrate 11, the dielectric layer 13 and the second encapsulation layer 15 are all selected from flexible nanofiber layers, preferably any one of thermoplastic polyurethane nanofiber layers and styrene-butadiene-styrene block copolymer nanofiber layers, and more preferably thermoplastic polyurethane nanofiber layers.

[0068] In one embodiment, the first electrode layer 12 and the second electrode layer 14 are both selected from the liquid metal layer 8, the liquid metal layer 8 is selected from the gallium-based liquid metal layer, the gallium-based liquid metal layer is selected from the liquid gallium-indium alloy layer or the liquid gallium-indium-tin alloy layer, and is further preferably the liquid gallium-indium alloy layer.

[0069] Combination Figure 1As shown, in the present invention, the angle D between the center line of the orthographic projection of the pressure sensing unit 2 on the first surface and the center line of the orthographic projection of the first sensing layer 4 or the second sensing layer 6 on the first surface is 0°≤D≤90°, preferably 0° or 90°. It can be understood that when D is 0° or 90°, the orthographic projection of the pressure sensing unit 2 on the first surface and the orthographic projection of the first sensing layer 4 or the second sensing layer 6 on the first surface can partially overlap or completely overlap, preferably completely overlap. Such an arrangement can help improve the structural compactness of the flexible two-dimensional strain and pressure composite sensor.

[0070] It can be understood that the two-dimensional sensing unit 1 in the present invention contains two sub-sensors, and the pressure sensing unit 2 serves as a sub-sensor, that is, the flexible two-dimensional strain and pressure composite sensor in the present invention actually contains three sub-sensors.

[0071] Therefore, the flexible two-dimensional strain and pressure composite sensor of the present invention can not only simultaneously monitor the strain in the two-dimensional direction within the plane and the pressure in the vertical direction of the plane, but also each sub-sensor works independently without interfering with each other, with high sensitivity and high monitoring accuracy.

[0072] At the same time, the present invention also provides a method for preparing the above-mentioned flexible two-dimensional strain and pressure composite sensor, comprising the following steps:

[0073] S1, sequentially preparing a first sensing layer 4, an isolation layer 5, a second sensing layer 6 and a first packaging layer 7 on a first flexible substrate 3, and controlling the first sensing layer 4 and the second sensing layer 6 to be arranged in an alternating manner to obtain a prefabricated two-dimensional sensing unit.

[0074] In step S1, the method for preparing the prefabricated two-dimensional sensing unit comprises the following steps:

[0075] S11, spinning the first spinning solution onto the surface of the release paper by using an electrospinning technique to form a first flexible substrate 3;

[0076] S12, printing a conductive liquid on the first flexible substrate 3 to form a first sensing layer 4;

[0077] S13, spinning the second spinning solution on the surface of the first sensing layer 4 by using electrospinning technology to form an isolation layer 5;

[0078] S14, printing the conductive liquid on the isolation layer 5 to form the second sensing layer 6, so that the projections of the first sensing layer 4 and the second sensing layer 6 on the first surface along the first direction z partially overlap to form a cross-overlapping area;

[0079] S15, spinning the third spinning solution on the surface of the second sensing layer 6 by using electrostatic spinning technology to form a first encapsulation layer 7, thereby obtaining a prefabricated two-dimensional sensing unit.

[0080] Specifically, in step S11, the specific steps of spinning the first spinning solution on the surface of the release paper using the electrospinning technology to form the first flexible substrate 3 are as follows: the first spinning solution is sucked into two 10mL syringes, a stainless steel dispensing needle with a specification of 19G is used as the syringe needle, and the two syringes are loaded onto the injection pump of the electrospinning machine, and the syringe is loaded onto the injection pump in the electrospinning machine; the release paper is attached to the surface of the drum in the electrospinning machine, and the distance between the syringe needle and the drum is set, and the positive voltage and negative voltage terminal wiring ports of the electrospinning machine are connected to the bottom of the dispensing needle and the drum respectively; various parameters of electrospinning are set to obtain the first flexible substrate 3.

[0081] In step S11, the electrospinning parameters include: an applied positive voltage of 10 kV-20 kV, an applied negative voltage of -1 kV to -5 kV, a drum speed of 200 rpm-800 rpm, a liquid supply rate of 0.05 mL / min-0.07 mL / min, a distance between the needle and the collecting device of 12 cm-18 cm, a temperature of 25°C-35°C, and an ambient relative humidity of 35%-50%. Such a setting is conducive to spinning to form a first flexible nanofiber layer with good air permeability and water permeability, and good stretchability and flexibility.

[0082] Optionally, the electrospinning time is 20 min-30 min, preferably 25 min. Such an arrangement is conducive to controlling the thickness of the first flexible substrate 3 .

[0083] In one embodiment, the first spinning solution is mixed with the first flexible substrate 3 precursor material and the organic solvent, and then stirred evenly at room temperature to obtain the first spinning solution, wherein the stirring rate is 300rpm-500rpm and the stirring time is 3h-7h. The mass volume ratio of the first flexible substrate 3 precursor material and the organic solvent is 22%-26%. Such a setting is conducive to improving the spinning effect.

[0084] It can be understood that, in the present invention, the mass volume ratio of the first spinning solution is the ratio of the mass of the solute to the volume of the solvent.

[0085] Furthermore, the first spinning solution is selected from at least one of a thermoplastic polyurethane solution and a styrene-butadiene-styrene block copolymer solution, preferably a thermoplastic polyurethane solution. This arrangement is conducive to improving the stretchability of the first flexible substrate 3 .

[0086] In one embodiment, the organic solvent is selected from at least one of N,N-dimethylformamide, tetrahydrofuran, and dichloromethane.

[0087] Specifically, when the first spinning solution is selected from a thermoplastic polyurethane solution, the organic solvent is preferably a mixed solvent of tetrahydrofuran and N,N-dimethylformamide, wherein the volume ratio of tetrahydrofuran to N,N-dimethylformamide is 1:1.

[0088] In step S12, the conductive liquid includes liquid metal and conductive ink.

[0089] Specifically, the specific steps of printing the conductive liquid on the first flexible substrate 3 to form the first sensing layer 4 are as follows:

[0090] S121, draw the target pattern in CAD software and save it in DXF format;

[0091] S122, importing the DXF file into the laser cutting machine software and setting cutting parameters, and cutting the liquid metal printing template and the conductive ink printing template on the 0.05 mm thick PET film;

[0092] S123, peel off the release paper with the first flexible substrate 3 from the roller and lay it flat on the table, place the liquid metal printing template obtained above on the first flexible substrate 3, use a fine brush to brush liquid metal in the liquid metal template, then replace the liquid metal printing template with a conductive ink printing template, use a fine brush to brush conductive ink in the conductive ink template, and after curing, form a liquid metal layer 8, a conductive ink layer 9 and a first metal pin 10 respectively, to obtain a first sensing layer 4.

[0093] In step S13, the specific steps and corresponding process parameters of using the electrospinning technology to spin the second spinning solution on the surface of the first sensing layer 4 to form the isolation layer 5 can refer to the specific steps and corresponding process parameters of using the electrospinning technology to spin the first spinning solution on the surface of the release paper to form the first flexible substrate 3 in step S11.

[0094] Similarly, in S14 , the specific step of printing and forming the second sensing layer 6 on the isolation layer 5 may refer to the specific step of printing and forming the first sensing layer 4 on the first flexible substrate 3 in step S12 .

[0095] Also, in step S15, the specific steps and corresponding process parameters of using the electrospinning technology to spin the third spinning solution on the surface of the second sensing layer 6 to form the first encapsulation layer 7 can refer to the specific steps and corresponding process parameters of using the electrospinning technology to spin the first spinning solution on the surface of the release paper to form the first flexible substrate 3 in step S11.

[0096] It can be understood that, in the present invention, the preparation method and components of the second spinning solution and the third spinning solution can refer to the preparation method and components of the first spinning solution.

[0097] S2, placing the first glue and the second glue on the surface of the prefabricated two-dimensional sensing unit, and forming the two-dimensional sensing unit 1 having the first part A and the second part through infiltration and curing.

[0098] In step S2, a mask is set on the prefabricated two-dimensional sensing unit, and the first glue and the second glue are placed in a preset non-mask area of ​​the prefabricated two-dimensional sensing unit. After infiltration and curing, a first glue layer and a second glue layer are formed to obtain a two-dimensional sensing unit 1 having a first part A and a second part, and the first part A is embedded with the first glue layer, and the second part is embedded with the second glue layer.

[0099] In one embodiment, after the first adhesive layer and the second adhesive layer are formed by infiltration and curing, the prefabricated two-dimensional sensing unit with the first adhesive layer and the second adhesive layer is cut into shape using a laser cutting machine according to the drawn pattern, and then the release paper is removed to obtain a two-dimensional sensing unit 1 having a first part A and a second part.

[0100] It should be noted that in the present invention, after the first glue is placed in the first part A of the prefabricated two-dimensional sensing unit, it will penetrate from the surface to the inside of the first part A. Similarly, when the second glue is placed in the second part of the prefabricated two-dimensional sensing unit, it will penetrate from the surface to the inside of the second part, so that the first part A contains the first glue and the second part contains the second glue, which are then cured to form corresponding first glue layers and second glue layers, that is, the first part A and the second part are evenly distributed with corresponding first glue layers and second glue layers.

[0101] Optionally, the mass fraction of glue in the first glue solution is 25%-38%, and the first glue solution is selected from hard glue glue solution, preferably Zhuolide UV glue D-606, Zhuolide UV glue D-3100, Fuxing Danny UV hard glue or Kasuto UV crystal glue, and further preferably Zhuolide UV glue D-606. In this way, the elastic modulus of the first glue layer embedded in the first part A can be 170MPa-200MPa.

[0102] Optionally, the mass fraction of glue in the second glue solution is 13%-55%, and the second glue solution is selected from soft glue solution, preferably Zhuolide UV glue D-0082, Zhuolide UV glue D-0084, Kasute UV soft glue or Anergu UV soft glue, and more preferably Zhuolide UV glue D-0082. In this way, the elastic modulus of the second glue layer embedded in the second part can be better controlled to be 0.3MPa-1MPa.

[0103] In one embodiment, the first glue is placed on the prefabricated two-dimensional sensing surface by coating, and the second glue is coated on the prefabricated two-dimensional sensing unit surface by spin coating, wherein the spin coating speed is 800rpm-1200rpm, and the spin coating time is 40s-80s, preferably the spin coating speed is 1000rpm, and the spin coating time is 60s.

[0104] It should be noted that when the second glue is applied to the surface of the prefabricated two-dimensional sensing unit by spin coating, the first glue is placed on the surface of the prefabricated two-dimensional sensing unit, and after penetration and curing to form a first glue layer, the second glue is then applied to the surface of the prefabricated two-dimensional sensing unit by spin coating, and after penetration and curing to form a second glue layer.

[0105] In one embodiment, in the step of forming the first adhesive layer embedded in the first part A and the second adhesive layer embedded in the second part by curing, ultraviolet light curing is adopted, and the light curing time is 1 min-3 min, preferably 2 min.

[0106] S3, prepare a pressure sensing unit 2 with a paper-cut structure 16, and then assemble the pressure sensing unit 2 and the two-dimensional sensing unit 1 together so that the third part B of the pressure sensing unit 2 corresponds to the first part A, thereby obtaining a flexible two-dimensional strain and pressure composite sensor.

[0107] In step S3, the steps of preparing the pressure sensing unit 2 with a paper-cut structure 16 are specifically as follows: a first electrode layer 12, a dielectric layer 13, a second electrode layer 14 and a second packaging layer 15 are sequentially prepared on the second flexible substrate 11 to obtain a prefabricated pressure sensing unit; a preset part of the prefabricated pressure sensing unit is processed into a paper-cut structure 16, and a second metal pin 17 connected to one end of the paper-cut structure 16 is formed at the same time, and then a third glue is placed on the surface of the second flexible substrate 11, and a third glue layer embedded in the second flexible substrate 11 is formed after infiltration and curing, so as to obtain a pressure sensing unit 2 with a paper-cut structure 16, wherein the mass fraction of the glue in the third glue is 25%-38%, and the third glue is selected from a hard glue, preferably Zhuolide UV glue D-606, Zhuolide UV glue D-3100, Fuxing Danny UV hard glue or Kasuto UV crystal glue, and further preferably Zhuolide UV glue D-606.

[0108] In one embodiment, the specific steps of prefabricating the pressure sensing unit are as follows: using the electrospinning technology to spin the fourth spinning solution on the surface of the release paper to form the second flexible substrate 11; setting a mask plate on the second flexible substrate 11, and printing the liquid metal on the first flexible substrate 3 to form the first electrode layer 12; using the electrospinning technology to spin the fifth spinning solution on the surface of the first electrode layer 12 to form the dielectric layer 13; printing the liquid metal on the dielectric layer 13 to form the second electrode layer 14; finally, using the electrospinning technology to spin the sixth spinning solution on the surface of the second electrode layer 14 to form the second packaging layer 15, thereby obtaining the prefabricated pressure sensing unit.

[0109] In the present invention, the specific steps and process parameters of spinning the fourth spinning solution on the surface of release paper using electrospinning technology to form the second flexible substrate 11, and the specific steps and process parameters of spinning the sixth spinning solution on the surface of the second electrode layer 14 using electrospinning technology to form the second encapsulation layer 15 can all refer to the specific steps and corresponding process parameters of spinning the first spinning solution on the surface of release paper using electrospinning technology to form the first flexible substrate 3 in step S11.

[0110] Similarly, the specific steps and process parameters of setting a mask on the second flexible substrate 11, printing liquid metal on the first flexible substrate 3 to form the first electrode layer 12, and the specific steps and process parameters of printing liquid metal on the dielectric layer 13 to form the second electrode layer 14 can all refer to the specific steps and process parameters of printing on the first flexible substrate 3 to form the first sensing layer 4 in step S12. The only difference is that the pattern structure of the mask set in the above steps is different from that of the mask set in step S12.

[0111] Furthermore, the specific steps and process parameters of using the electrospinning technology to spin the fifth spinning solution on the surface of the first electrode layer 12 to form the dielectric layer 13 can also refer to the specific steps and corresponding process parameters of using the electrospinning technology to spin the first spinning solution on the surface of the release paper to form the first flexible substrate 3 in step S11. The only difference is that the electrospinning time is 30min-50min.

[0112] It can be understood that, in the present invention, the preparation method and components of the fourth spinning solution, the fifth spinning solution and the sixth spinning solution can all refer to the preparation method and components of the first spinning solution.

[0113] In one embodiment, in the step of processing the preset portion of the prefabricated pressure sensing unit into the paper-cut structure 16 , the preset portion of the prefabricated pressure sensing unit is cut into the paper-cut structure 16 according to the set paper-cut structure 16 using laser cutting technology.

[0114] In one embodiment, in the step of placing the third glue on a part of the surface of the second flexible substrate 14, and forming the third glue layer embedded in the second flexible substrate 11 through penetration and curing, a mask with a preset structure is placed on a side of the second flexible substrate 11 away from the first electrode layer 12, and then the third glue is brushed on the non-mask area of ​​the second flexible substrate 11, and the third glue is penetrated and cured to form the third glue layer embedded in the second flexible substrate 11. It can be understood that due to the presence of the first electrode layer 12, the third glue does not penetrate into the dielectric layer 13 and the second packaging layer 15 during the brushing process.

[0115] In one embodiment, when the orthographic projection of the pressure sensing unit 2 on the first surface coincides with the orthographic projection of the first sensing layer 4 on the first surface or the orthographic projection of the second sensing layer 6 on the first surface in the two-dimensional sensing unit 1, in the step of assembling the pressure sensing unit 2 and the two-dimensional sensing unit 1 together, a fourth glue is placed on the surface of the first part A of the two-dimensional sensing unit 1, the first sensing layer 4 and / or the first metal pin 10 of the second sensing layer 6, and then the pressure sensing unit 2 is placed on the two-dimensional sensing unit 1. After curing, the first part A of the two-dimensional sensing unit 1 and the third part B of the pressure sensing unit 2 are bonded together, and the first metal pin 10 and the second metal pin 17 of the pressure sensing unit 2 are bonded together, thereby obtaining a flexible two-dimensional strain and pressure composite sensor.

[0116] It should be noted that, in the present invention, the first part A of the two-dimensional sensing unit 1 and the third part B of the pressure sensing unit 2 are bonded together by bonding the first part A of the two-dimensional sensing unit 1 and a part of the second flexible substrate in the pressure sensing unit 2 together.

[0117] The mass fraction of glue in the fourth glue solution is 25%-38%, and the fourth glue solution is selected from hard glue solution.

[0118] In one embodiment, in the curing step, ultraviolet light curing is adopted, wherein the light curing time is 2 minutes to 6 minutes, preferably 4 minutes.

[0119] It can be understood that the first flexible substrate 3, isolation layer 5 and first packaging layer 7 in the structure of the two-dimensional sensing unit 1 in the present invention and the second flexible substrate 11, dielectric layer 13 and second packaging layer 15 in the structure of the pressure sensing unit 2 all adopt electrospinning technology, and the hardness of different parts is controlled by selective infiltration and curing of photocurable glue, so that the prepared two-dimensional sensing unit 1 and pressure sensing unit 2 work independently without interfering with each other. Moreover, the sensing layer in the two-dimensional sensing unit 1 and the electrode layer in the pressure sensing unit 2 are both made by template printing, with simple processing technology, low production cost and good development prospects.

[0120] In addition, the present invention also provides an application of the flexible two-dimensional strain and pressure composite sensor as described above in electronic skin, soft robots or wearable electronic products.

[0121] The flexible two-dimensional strain and pressure composite sensor and its preparation method and application will be further described by the following specific examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are followed. The reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially.

[0122] Example 1

[0123] 7.5 g of thermoplastic polyurethane, 15 mL of N,N-dimethylformamide and 15 mL of tetrahydrofuran were added into a beaker and stirred evenly at room temperature with a magnetic stirrer, wherein the speed of the magnetic stirrer was 400 rpm and the stirring time was 5 h to obtain a thermoplastic polyurethane spinning solution.

[0124] Two 10mL screw-mouth syringes were used to absorb the thermoplastic polyurethane spinning solution obtained above respectively, and a stainless steel dispensing needle (19G) was installed on the screw-mouth syringe; then the two screw-mouth syringes were fixed on the injection pump in the electrospinning machine (TEADFS-100, Beijing Xinrui Baina Technology Co., Ltd.), and the positive voltage interface of the electrospinning machine was fixed to the bottom of the stainless steel dispensing needle; a layer of release paper was pasted on the drum in the electrospinning machine as an electrospinning collector, and the position of the injection pump was adjusted so that the distance from the stainless steel dispensing needle to the drum was 15cm; finally, the working parameters of the electrospinning machine were set, wherein the external positive voltage was 11kV, the external negative voltage was -3kV, the liquid supply rate was 0.06mL / min, the drum speed was 500rpm, the temperature was 30°C, the relative humidity of the environment was 40%, and the electrospinning machine was started and operated for 25min, and then the electrospinning machine was turned off to obtain a first flexible substrate with a thickness of 50μm.

[0125] A PET film with a thickness of 0.05 mm was cut into a preset liquid metal printing template and a conductive ink printing template using a laser cutting process; the release paper with the first flexible substrate was peeled off from the roller and laid flat on the table, and then the liquid metal printing template obtained was placed on the first flexible substrate, and a fine brush was used to apply liquid gallium-indium alloy to the non-mask area of ​​the liquid metal template, and then the conductive ink printing template was replaced, and a fine brush was used to apply conductive ink to the conductive ink template, and after curing at room temperature for 10 minutes, corresponding liquid gallium-indium alloy layers, conductive ink layers and first liquid gallium-indium alloy pins were formed respectively, and a first sensing layer with a thickness of 4 μm was obtained.

[0126] Then, the electrospinning machine was started again, and the above electrospinning process was repeated for 25 minutes to form an isolation layer with a thickness of 50 μm; then, the above method for preparing the first sensing layer was used to prepare a second sensing layer with a thickness of 4 μm on the isolation layer, and the projections of the first sensing layer and the second sensing layer on the first surface along the first direction partially overlapped to form a positive cross-overlapping area; then, the electrospinning machine was started again, and the above electrospinning process was repeated for 25 minutes to form a first packaging layer with a thickness of 50 μm, thereby obtaining a prefabricated two-dimensional sensing unit.

[0127] A patterned PET film was obtained by laser cutting process as a mask. The prefabricated two-dimensional sensor unit with release paper was peeled off from the roller and laid flat on the table. The mask was placed on the prefabricated two-dimensional sensor unit. 0.05 mL of the first glue (Zhuolid UV glue D-606) was brushed on the surface of the prefabricated two-dimensional sensor unit. After curing for 2 minutes under ultraviolet light, a first glue layer embedded in the prefabricated two-dimensional sensor unit was formed. 2 mL of the second glue (Zhuolid UV glue D-0082) was spin-coated on the prefabricated two-dimensional sensor unit that was not brushed with the first glue. The surface of the unit is cured for 2 minutes under ultraviolet light to form a second adhesive layer embedded in the prefabricated two-dimensional sensing unit, wherein the spin coating speed is 1000 rpm and the spin coating time is 60 s. Then, it is placed on a laser cutting machine, and the prefabricated sensing unit with the first adhesive layer and the second adhesive layer is cut into shape according to a preset size and structure using the laser cutting machine. The release paper is removed to obtain a two-dimensional sensing unit having a first part and a second part, wherein the elastic modulus of the first part is 176 MPa, and the elastic modulus of the second part is 0.8 MPa.

[0128] A new layer of release paper is pasted on the roller in the electrospinning machine as an electrospinning collector, and the electrospinning machine is started. After repeating the above electrospinning process for 25 minutes, a second flexible substrate with a thickness of 50 μm is spun on the surface of the release paper; a PET film with a thickness of 0.05 mm is cut into a preset liquid metal printing template using a laser cutting process; the release paper with the second flexible substrate is peeled off from the roller and laid flat on the table, and then the liquid metal printing template obtained above is placed on the second flexible substrate, and a fine brush is used to brush liquid gallium-indium alloy on the non-mask area of ​​the liquid metal template to form a first electrode layer with a thickness of 4 μm. Then the electrospinning machine is started again, and after repeating the above electrospinning process for 45 minutes, a dielectric layer with a thickness of 90 μm is spun on the first electrode layer.

[0129] A second electrode layer with a thickness of 4 μm was prepared by the method of preparing the first electrode layer; then the electrospinning machine was started again, and the above electrospinning process was repeated for 25 minutes to spin on the second electrode layer to form a second packaging layer with a thickness of 50 μm, thereby obtaining a prefabricated pressure sensing unit.

[0130] According to the set paper-cut structure, the laser cutting technology is used to cut the preset part of the prefabricated pressure sensing unit into a paper-cut structure, and at the same time, a second liquid gallium-indium alloy pin connected to one end of the paper-cut structure is formed. Then, 0.05mL of the third glue (Zhuolid UV glue D-606) is brushed on the partial surface of the second flexible substrate corresponding to the first part. After curing for 2 minutes under ultraviolet light, a third glue layer embedded in the second flexible substrate is formed, and a pressure sensing unit with a paper-cut structure is obtained, wherein the elastic modulus of the part of the second flexible substrate corresponding to the first part is 0.03MPa.

[0131] 0.01 mL of the fourth glue (Zhuolid UV glue D-606) was brushed on the first part of the two-dimensional sensing unit and the surface of the first liquid gallium-indium alloy pin of the first sensing layer, and then the pressure sensing unit was placed on the second flexible substrate of the two-dimensional sensing unit, and cured under ultraviolet light for 4 minutes, so that the first part of the two-dimensional sensing unit and part of the second flexible substrate were bonded together, that is, the first part of the two-dimensional sensing unit and the third part of the pressure sensing unit were bonded together, and the first liquid gallium-indium alloy pin and the second liquid gallium-indium alloy pin of the pressure sensing unit were bonded together, and the following was obtained: Figure 1 The flexible two-dimensional strain and pressure composite sensor shown.

[0132] Example 2

[0133] Compared with Example 1, Example 2 only differs in that the step of brushing the third glue on the partial surface of the second flexible substrate in the pressure sensing unit structure is not included. That is, according to the set paper-cut structure, the preset part of the prefabricated pressure sensing unit is cut into a paper-cut structure by laser cutting technology, and a second liquid gallium-indium alloy pin connected to one end of the paper-cut structure is formed at the same time, so as to obtain a pressure sensing unit with a paper-cut structure. The other conditions are the same, and a flexible two-dimensional strain and pressure composite sensor is obtained.

[0134] Example 3

[0135] Compared with Example 1, Example 3 differs only in that Zhuolide UV glue D-3100 is used as the first glue to replace the first glue (Zhuolide UV glue D-606) in Example 1, and other conditions are the same. The elastic modulus of the first part of the two-dimensional sensing unit is 190MPa, and the elastic modulus of the second part is 0.79MPa, so as to obtain a flexible two-dimensional strain and pressure composite sensor.

[0136] Example 4

[0137] The only difference between Example 4 and Example 1 is that, in the step of preparing the prefabricated two-dimensional sensing unit, the projections of the prepared first sensing layer and the second sensing layer on the first surface along the first direction are partially overlapped to form a cross-overlapping area, and the angle between the center line of the orthographic projection of the second sensing layer on the plane where the first flexible substrate is located and the center line of the orthographic projection of the first sensing layer on the plane where the first flexible substrate is located is 60°, and the other conditions are the same, thereby obtaining a flexible two-dimensional strain and pressure composite sensor.

[0138] Comparative Example 1

[0139] Compared with Example 1, Comparative Example 1 differs only in that the components of the first glue and the second glue are the same, that is, 0.05 mL of Zolide UV glue D-0082 is used as the first glue to replace the first glue (Zholide UV glue D-606) in Example 1, and the other conditions are the same. The elastic modulus of the first part of the two-dimensional sensing unit is 0.79 MPa, and the elastic modulus of the second part is 0.79 MPa, thereby obtaining a flexible two-dimensional strain and pressure composite sensor.

[0140] Comparative Example 2

[0141] Compared with Example 1, Comparative Example 2 only differs in that the step of brushing the third glue on the partial surface of the second flexible substrate is omitted, and the step of cutting the preset part of the prefabricated pressure sensing unit into the paper-cut structure according to the set paper-cut structure by using laser cutting technology is omitted. Other conditions are the same, and a flexible two-dimensional strain and pressure composite sensor is obtained.

[0142] Comparative Example 3

[0143] Compared with Example 1, Comparative Example 3 differs only in that it does not contain the step of cutting the preset part of the prefabricated pressure sensing unit into the paper-cut structure according to the set paper-cut structure using laser cutting technology. Other conditions are the same, and a flexible two-dimensional strain and pressure composite sensor is obtained.

[0144] The performance of the flexible two-dimensional strain and pressure composite sensors prepared in Example 1 and Comparative Examples 1 to 3 were tested respectively. The test results are as follows: Figures 4 to 12 As shown. Figure 4 It can be seen that when the x-axis direction of the flexible two-dimensional strain and pressure composite sensor is stretched uniaxially, that is, the first sensing direction, the relative resistance change value of the first sensing layer will change linearly with the increase of strain, and its sensitivity within the 100% stretching strain range is about 173; and during the stretching process, the values ​​of the sub-sensor (i.e., the second sensing layer) in the y-axis direction (i.e., the second sensing direction) and the sub-sensor (i.e., the pressure sensing unit) in the z-axis direction (vertical direction) have almost no change. Figure 5It can be found that when the uniaxial stretching of the flexible two-dimensional strain and pressure composite sensor is in the y-axis direction, the sub-sensor in the y-axis direction can also produce a linear response, and the sensitivity is basically the same as that in the x-axis direction, and the values ​​of the sub-sensors in the x-axis and z-axis directions have not changed. Figure 6 It can be found that when the capacitive pressure sensor (i.e., the pressure sensing unit) is subjected to vertical pressure, the relative capacitance change value of the sub-sensor in the z-axis direction will produce a nearly linear change with the increase of strain, and its sensitivity within the pressure range of 35kPa is about 0.0237kPa. -1 , and the values ​​of the sub-sensors in the x-axis and y-axis directions did not change during the pressure process. It can be seen that the composite sensor prepared in Example 1 can realize independent sensing in the x-axis, y-axis and z-axis directions, and the sub-sensors do not interfere with each other.

[0145] from Figures 7 to 9 It can be seen that the flexible two-dimensional strain and pressure composite sensor in Example 1 can show stable and reliable sensing performance in the cyclic strain of 10%, 20% and 40%, and the flexible two-dimensional strain and pressure composite sensor shows stable and reliable sensing performance under the cyclic pressure of 5kPa, 10kPa and 20kPa. Moreover, when each sub-sensor is working, it does not interfere with the work of other sensors.

[0146] from Figures 10 to 12 It can be seen that when the flexible two-dimensional strain and pressure composite sensor in comparative example 1 is stretched 100% in the x-axis direction, its sub-sensors in the y-axis and z-axis directions will be significantly disturbed. This is because there is no hard glue structure in the central area. During the stretching of the x-axis, the central area, that is, the first part of the two-dimensional sensing unit, undergoes a large deformation with the stretching, thereby interfering with the sub-sensors in the x-axis and z-axis directions. When the flexible two-dimensional strain and pressure composite sensor in comparative example 2 is stretched 100% in the x-axis direction, its sub-sensor in the y-axis direction does not undergo obvious changes, but the sub-sensor in the z-axis direction is significantly disturbed. This is because after losing the paper-cut structure and the third glue applied on the second flexible substrate, the sub-sensor in the z-axis direction will deform with the stretching in the y-axis direction. Similarly, when the flexible two-dimensional strain and pressure composite sensor in Comparative Example 3 was stretched 100% in the x-axis direction, the sub-sensor in the y-axis direction did not undergo obvious changes, but the sub-sensor in the z-axis direction was also disturbed to a certain extent. Although the degree of interference was less than that in Comparative Example 2 under the action of the third glue applied on the second flexible substrate, it was still unqualified.

[0147] Therefore, the flexible two-dimensional strain and pressure composite sensor of the present invention has good strain and pressure sensing performance, and can stably and reliably monitor the strain in the two-dimensional direction within the plane and the pressure in the vertical direction of the plane. Moreover, each sub-sensor works independently without interfering with each other, and has high sensitivity and high monitoring accuracy.

[0148] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0149] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A flexible two-dimensional strain and pressure composite sensor, characterized in that: The flexible two-dimensional strain and pressure composite sensor comprises: A two-dimensional sensing unit, the two-dimensional sensing unit comprising a first flexible substrate and a first sensing layer, an isolation layer, a second sensing layer and a first packaging layer stacked in sequence on the first flexible substrate, the first sensing layer and the second sensing layer are arranged in an alternating manner, a plane parallel to the surface where the first flexible substrate is located is defined as a first surface, a direction in which the first sensing layer, the isolation layer, the second sensing layer and the first packaging layer are stacked in sequence is defined as a first direction, the projections of the first sensing layer and the second sensing layer on the first surface along the first direction partially overlap to form a cross-overlapping area, the two-dimensional sensing unit comprising a first part and a second part, the projection of the first part on the first surface along the first direction coincides with the cross-overlapping area, the second part is the part of the two-dimensional sensing unit other than the first part, wherein the elastic modulus of the first part is greater than the elastic modulus of the second part, and the elastic modulus difference is greater than or equal to 160 MPa; A pressure sensing unit, wherein the pressure sensing unit is stacked on the two-dimensional sensing unit, and the pressure sensing unit comprises a third part and a fourth part connected to the third part, wherein the third part corresponds to the first part, and the fourth part is a paper-cut structure.

2. The flexible two-dimensional strain and pressure composite sensor according to claim 1, characterized in that: A first adhesive layer is embedded in the first part, and a second adhesive layer is embedded in the second part, wherein the elastic modulus of the first adhesive layer is 170MPa-200MPa, and the elastic modulus of the second adhesive layer is 0.3MPa-1MPa.

3. The flexible two-dimensional strain and pressure composite sensor according to claim 1, characterized in that: The first sensing layer and the second sensing layer are arranged in an orthogonal stacking manner; And / or, the first sensing layer and the second sensing layer are both in strip shape.

4. The flexible two-dimensional strain and pressure composite sensor according to claim 1, characterized in that: The orthographic projection of the pressure sensing unit on the first surface completely overlaps with the orthographic projection of the first sensing layer or the second sensing layer on the first surface.

5. The flexible two-dimensional strain and pressure composite sensor according to claim 1, characterized in that: The pressure sensing unit includes a second flexible substrate and a first electrode layer, a dielectric layer, a second electrode layer and a second packaging layer sequentially stacked on the second flexible substrate, and the second flexible substrate is arranged on the first flexible substrate or on the first packaging layer.

6. The flexible two-dimensional strain and pressure composite sensor according to claim 5, characterized in that: The elastic modulus of the second flexible substrate portion corresponding to the first portion is 170 MPa-200 MPa.

7. The flexible two-dimensional strain and pressure composite sensor according to claim 1, characterized in that: The first sensing layer and the second sensing layer each include a liquid metal layer, a conductive ink layer and a first metal pin, the liquid metal layer corresponds to the cross-overlapping region, the conductive ink layer is disposed on both sides of the liquid metal layer, and the first metal pin is disposed at one end of the conductive ink layer away from the liquid metal layer; And / or, the pressure sensing unit further includes a second metal pin, and the paper-cut structure is disposed between the second metal pin and the third part.

8. A method for preparing a flexible two-dimensional strain and pressure composite sensor according to any one of claims 1 to 7, characterized in that: The steps include: Sequentially preparing a first sensing layer, an isolation layer, a second sensing layer and a first packaging layer on a first flexible substrate, and controlling the first sensing layer and the second sensing layer to be arranged in an alternating manner to obtain a prefabricated two-dimensional sensing unit; Placing a first glue solution and a second glue solution on the surface of the prefabricated two-dimensional sensing unit, and forming a two-dimensional sensing unit having a first part and a second part through infiltration and curing; A pressure sensing unit with a kirigami structure is prepared, and then the pressure sensing unit and the two-dimensional sensing unit are assembled together so that the third part of the pressure sensing unit corresponds to the first part, thereby obtaining a flexible two-dimensional strain and pressure composite sensor.

9. The method for preparing the flexible two-dimensional strain and pressure composite sensor according to claim 8, characterized in that: The mass fraction of glue in the first glue solution is 25%-38%, and the first glue solution is selected from a hard glue solution; And / or, the mass fraction of glue in the second glue solution is 13%-55%, and the second glue solution is selected from soft glue solution; And / or, the steps for preparing a pressure sensing unit with a paper-cut structure are as follows: a first electrode layer, a dielectric layer, a second electrode layer and a second packaging layer are prepared in sequence on a second flexible substrate to obtain a prefabricated pressure sensing unit; a preset part of the prefabricated pressure sensing unit is processed into a paper-cut structure, and a second metal pin connected to one end of the paper-cut structure is formed at the same time, and then a third glue is placed on a partial surface of the second flexible substrate, and a third glue layer embedded in the second flexible substrate is formed through infiltration and curing to obtain a pressure sensing unit with a paper-cut structure, wherein the third glue is selected from a hard glue.

10. Use of the flexible two-dimensional strain and pressure composite sensor according to any one of claims 1 to 7 in electronic skin, soft robots or wearable electronic products.

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