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

Abstract

This invention relates to a flexible two-dimensional strain and pressure composite sensor, its fabrication method, and its application. The flexible two-dimensional strain and pressure composite sensor includes: a two-dimensional sensing unit, comprising a first flexible substrate and a first sensing layer, an isolation layer, a second sensing layer, and a first encapsulation layer sequentially stacked on the first flexible substrate, with the first and second sensing layers arranged alternately; the two-dimensional sensing unit includes a first part and a second part, the elastic modulus of the first part being greater than that of the second part, and the difference in elastic modulus being greater than or equal to 160 MPa; a pressure sensing unit disposed on the two-dimensional sensing unit; a third part corresponding to the first part; and a fourth part having a paper-cut structure. This flexible two-dimensional strain and pressure composite sensor can simultaneously monitor strain in a two-dimensional plane and pressure in a vertical plane. Each sub-sensor operates independently without interference, exhibiting high sensitivity and high monitoring accuracy.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to a flexible two-dimensional strain and pressure composite sensor, its fabrication method, and its applications. Background Technology

[0002] With the rapid development of flexible electronics technology, its application in fields such as electronic skin, soft robots, wearable devices, and smart healthcare is increasingly demanding. Among these, flexible strain sensors and pressure sensors are currently the two most common types of sensors in the field of flexible electronics. However, most traditional flexible strain or pressure sensors can only detect strain / stress in a single dimension, making it difficult to achieve selective response capabilities to tensile strain or stress in different dimensions. Although some multidimensional sensor devices have been reported, these are essentially formed by simply splicing together multiple single-dimensional sensors. In practical applications, there is a certain degree of mutual interference between these multiple sensor devices, which seriously affects the accuracy of monitoring. Summary of the Invention

[0003] Therefore, it is necessary to address the aforementioned problems by providing a flexible two-dimensional strain and pressure composite sensor, its fabrication method, and its applications. This flexible two-dimensional strain and pressure composite sensor can simultaneously monitor strain in the two-dimensional plane and pressure in the vertical direction of the plane. Moreover, each sub-sensor operates independently without interference, exhibiting 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 includes a first flexible substrate and a first sensing layer, an isolation layer, a second sensing layer, and a first encapsulation layer sequentially stacked on the first flexible substrate. The first sensing layer and the second sensing layer are arranged alternately. A plane parallel to the surface of the first flexible substrate is defined as a first surface. The direction in which the first sensing layer, the isolation layer, the second sensing layer, and the first encapsulation layer are sequentially stacked is defined as a first direction. The projections of the first sensing layer and the second sensing layer along the first direction on the first surface overlap to form an intersecting overlapping region. The two-dimensional sensing unit includes a first part and a second part. The projection of the first part along the first direction on the first surface coincides with the intersecting overlapping region. The second part is the part of the two-dimensional sensing unit other than the first part. The elastic modulus of the first part is greater than that of the second part, and the difference in elastic modulus is greater than or equal to 160 MPa.

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

[0007] In one embodiment, the first portion is embedded with a first adhesive layer, and the second portion is embedded with a second adhesive layer, 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 stacked layer;

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

[0010] In one embodiment, the orthographic projection of the pressure sensing unit onto the first surface completely coincides with the orthographic projection of the first sensing layer or the second sensing layer onto 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 encapsulation layer sequentially stacked on the second flexible substrate, wherein the second flexible substrate is disposed on the first flexible substrate or the first encapsulation layer.

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

[0013] In one embodiment, both the first sensing layer and the second sensing layer include a liquid metal layer, a conductive ink layer, and a first metal pin. The liquid metal layer corresponds to the overlapping region. The conductive ink layer is provided on both sides of the liquid metal layer. The first metal pin is located at the 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-cutting structure is disposed between the second metal pin and the third part.

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

[0016] A first sensing layer, an isolation layer, a second sensing layer, and a first encapsulation layer are sequentially fabricated on a first flexible substrate, and the first sensing layer and the second sensing layer are arranged in an alternating manner to obtain a prefabricated two-dimensional sensing unit.

[0017] The first adhesive and the second adhesive are placed on the surface of the prefabricated two-dimensional sensing unit, and then penetrated and cured to form a two-dimensional sensing unit having a first part and a second part.

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

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

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

[0021] And / or, the specific 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 encapsulation layer are sequentially prepared on a second flexible substrate to obtain a pre-fabricated pressure sensing unit; a preset portion of the pre-fabricated 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; then, a third adhesive is placed on a portion of the surface of the second flexible substrate, and after penetration and curing, a third adhesive layer is formed embedded in the second flexible substrate to obtain a pressure sensing unit with a paper-cut structure, wherein the third adhesive is selected from hard adhesives.

[0022] Application of a 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 in the plane and the pressure on the plane in the vertical direction. Simultaneously, 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, constant part. When the two-dimensional sensing unit undergoes tensile deformation along the direction of the first sensing layer or the second sensing layer, the first part will not deform, thereby ensuring that the first sensing layer and the second sensing layer do not interfere with each other when they work independently. This design improves the sensor's monitoring accuracy in the two-dimensional plane by eliminating interference. Furthermore, by configuring the pressure sensing unit into a third and fourth part, with the third part corresponding to the first part and the fourth part being a paper-cut structure, the characteristics of the paper-cut structure effectively ensure that the two-dimensional sensing unit and the pressure sensing unit do not interfere with each other when detecting strain. Moreover, since the first part is a rigid, unchanging component, when the pressure sensing unit is subjected to vertical pressure, it will not transmit the vertical pressure deformation to the two-dimensional sensing unit, further improving the operational independence between the two-dimensional and pressure sensing units, and enhancing the overall sensor sensitivity and monitoring accuracy.

[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 in the plane and the pressure in the vertical direction of the plane, but also the sub-sensors work independently without interfering with each other, with high sensitivity and high monitoring accuracy. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

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

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

[0029] Figure 4The figure shows the detection results of the flexible two-dimensional strain and pressure composite sensor of Embodiment 1 of the present invention when stretched by 100% in the x-axis direction. 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 The figure shows the detection results of the flexible two-dimensional strain and pressure composite sensor of Embodiment 1 of the present invention when stretched by 100% in the y-axis direction. 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 figure shows the detection results of the flexible two-dimensional strain and pressure composite sensor of Embodiment 1 of the present invention when subjected to a 35 kPa pressure in the Z-axis direction. 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 figure shows the detection results of the flexible two-dimensional strain and pressure composite sensor of Embodiment 1 of the present invention when it is subjected to cyclic stretching of 10%, 20%, and 40% in the x-axis direction. 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 figures show the detection results of the flexible two-dimensional strain and pressure composite sensor of Embodiment 1 of the present invention when stretched by 10%, 20%, and 40% in the y-axis direction. 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] Figure 9 The figure shows the detection results of the flexible two-dimensional strain and pressure composite sensor of Embodiment 1 of the present invention when subjected to pressures of 5 kPa, 10 kPa and 20 kPa in the z-axis direction. 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] Figure 10The figure shows the detection results of the flexible two-dimensional strain and pressure composite sensor of Comparative Example 1 of the present invention when stretched by 100% in the x-axis direction, in the y-axis and z-axis directions. 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] Figure 11 The figure shows the detection results of the flexible two-dimensional strain and pressure composite sensor of Comparative Example 2 of the present invention when stretched by 100% in the x-axis direction, in the y-axis and z-axis directions. 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] Figure 12 The figure shows the detection results of the flexible two-dimensional strain and pressure composite sensor of Comparative Example 3 of the present invention when stretched by 100% in the x-axis direction, in the y-axis and z-axis directions. 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] Reference 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 encapsulation 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 encapsulation layer; 16. Paper-cut structure; 17. Second metal pin; A. First part; B. Third part. Detailed Implementation

[0039] To facilitate understanding of the present invention, it 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. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of 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. The flexible two-dimensional strain and pressure composite sensor includes a two-dimensional sensing unit 1 and a pressure sensing unit 2, with the pressure sensing unit 2 disposed 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 strain in the two-dimensional direction within a plane and pressure exerted on the plane in the vertical direction.

[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 encapsulation layer 7 sequentially stacked 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 encapsulation layer 7 are sequentially stacked is defined as the first direction Z. The first sensing layer 4 and the second sensing layer 6 are arranged in an alternating manner, and their projections along the first direction Z on a first surface overlap to form an intersecting overlapping region. 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 along the first direction on the first surface coincides with the intersecting overlapping region, and the second part is the portion of the two-dimensional sensing unit excluding the first part A.

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

[0044] In this invention, by controlling the elastic modulus of the first part A and the second part of the two-dimensional sensing unit 1, the hardness of the first part A and the second part is controlled, so that the first part A of the two-dimensional sensing unit 1 is a constant rigid part, while the second part is a flexible and elastically deformable part. Therefore, when the first sensing layer 4 in the two-dimensional sensing unit 1 undergoes tensile deformation, its internal sensing layer structure will change, resulting in a change in its resistance to achieve sensing. At this time, since the first part A does not deform, that is, the first sensing layer 4 and the second sensing layer 6 are on the first flexible substrate along the first direction Z. The overlapping projections on the surface do not cause deformation in the intersecting areas, preventing deformation of the first sensing layer 4 from being 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, thus achieving independent sensing between the first sensing layer 4 and the second sensing layer 6, with their operation not interfering with each other. Moreover, it can also prevent the pressure sensing unit 2 from interfering with the sensing performance of the first sensing layer 4 and the second sensing layer 6 in the two-dimensional sensing unit 1 when subjected to vertical pressure, thereby improving the sensitivity and monitoring accuracy of the two-dimensional sensing unit 1 in the two-dimensional direction within the plane.

[0045] It should be noted that in this 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 in 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, the first part A is embedded with a first adhesive layer (not shown in the figure), and the second part is embedded with a second adhesive layer (not shown in the figure). The elastic modulus of the first adhesive layer is 170MPa-200MPa, and the elastic modulus of the second adhesive layer is 0.3MPa-1MPa. This configuration allows for better control of the elastic modulus of the first part A being greater than that of the second part, with the difference in elastic modulus being greater than or equal to 160MPa.

[0047] Furthermore, the material of the first adhesive layer is selected from Zhuolide UV Epoxy D-606, Zhuolide UV Epoxy D-3100, Fuxing Dani UV Hard Glue, or Kasute UV Crystal Epoxy, preferably Zhuolide UV Epoxy D-606, and the material of the second adhesive layer is selected from Zhuolide UV Epoxy D-0082, Zhuolide UV Epoxy D-0084, Kasute UV Soft Glue, or Anergu UV Soft Glue, preferably Zhuolide UV Epoxy D-0082.

[0048] In one embodiment, the thickness of the first flexible substrate 3 is 60μm-100μm; the thickness of the first sensing layer 4 is 3μm-4μm; the thickness of the second sensing layer 6 is 3μm-4μm; the thickness of the isolation layer 5 is 60μm-100μm; and the thickness of the first encapsulation layer 7 is 60μm-100μm. This configuration allows for control of the thickness of each layer, thereby adjusting the thickness of the two-dimensional sensing unit 1 and the overall sensor structure. This helps to further ensure the structural strength of the two-dimensional sensing unit 1 and the overall sensor structure while improving their flexibility and fit.

[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 thermoplastic polyurethane nanofiber layers and styrene-butadiene-styrene block copolymer nanofiber layers, and more preferably thermoplastic polyurethane nanofiber layers.

[0050] Understandably, in combination Figure 1 As shown, in this 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 C > 0°, preferably 60° ≤ C ≤ 90°, and more preferably C = 90°. This configuration further enhances the independent sensing between the first sensing layer 4 and the second sensing layer 6, improving their monitoring accuracy.

[0051] Therefore, in this invention, the first sensing layer 4 and the second sensing layer 6 are arranged in an orthogonal stacked configuration.

[0052] Furthermore, both the first and second sensing layers are strip-shaped.

[0053] Optionally, both the first sensing layer 4 and the second sensing layer 6 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 overlapping area, and conductive ink layers 9 are provided on both sides of the liquid metal layer 8. The first metal pin 10 is located at the end of the conductive ink layer 9 away from the liquid metal layer 8. This configuration utilizes the low resistance of the liquid metal and its minimal resistance change during stretching and compression, using the liquid metal layer 8 as the conductive electrode of the first sensing layer 4 and the second sensing layer 6. The conductive ink, with its high resistance and large resistance change during stretching, serves as the sensing element of the first sensing layer 4 and the second sensing layer 6. This further improves the operational independence between the first sensing layer 4 and the second sensing layer 6, while also enhancing their sensitivity, thereby improving both their sensitivity and monitoring accuracy.

[0054] In one embodiment, a copper sheet (not shown in the figure) is provided at the end of the first metal pin 10 away from the conductive ink layer 9. The outer surface of the copper sheet is welded with enameled wire to realize the connection between the two-dimensional sensing unit 1 and the external circuit. The copper sheet is selected from copper sheets.

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

[0056] In one embodiment, the first metal pin 10 is made of 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] Pressure sensing unit 2 is stacked on top of two-dimensional sensing unit 1. 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 by setting the fourth part to a paper-cut structure 16, the high compliance and deformability of the paper-cut structure 16 effectively ensures that there is no interference between the first sensing layer 4 or the second sensing layer 6 and the pressure sensing unit 2 when detecting strain. This makes the operation of two-dimensional sensing unit 1 and pressure sensing unit 2 completely independent and without interference. Furthermore, with the synergistic effect of the rigid first part A, when pressure sensing unit 2 is subjected to vertical pressure, the vertical pressure deformation will not be transmitted to two-dimensional sensing unit 1, further improving the operational independence between two-dimensional sensing unit 1 and pressure sensing unit 2, thereby improving the sensitivity and monitoring accuracy of the entire sensor.

[0058] It should be noted that in this invention, the paper-cutting structure is the kirigami paper-cutting structure.

[0059] Optionally, the pressure sensing unit 2 also includes a second metal pin 17, and the paper-cutting 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 for assembling the pressure sensing unit 2 and the two-dimensional sensing unit 1 together.

[0061] In one embodiment, a copper sheet is provided at the end of the second metal pin 17 away from the paper-cutting structure 16. Enamelled wire is welded to the outer surface of the copper sheet to realize the connection between the pressure sensing unit 2 and the external circuit. The copper sheet is selected from copper sheets.

[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 encapsulation layer 15 sequentially stacked on the second flexible substrate 11. The second flexible substrate 11 is disposed on the first encapsulation 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, causing a change in the spacing between the upper and lower electrode layers of the capacitor, thereby changing 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 part A is 170MPa-200MPa. This configuration ensures that the elastic modulus of the second flexible substrate 11 and the portion corresponding to the first part A of the two-dimensional sensing unit 1 are essentially the same, both being rigid and non-deformable portions. This further prevents the pressure deformation experienced by 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 in the figure) 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 portion of the second flexible substrate 11 corresponding to the first portion A is 170MPa-200MPa.

[0065] Furthermore, the material of the third adhesive layer is selected from Zhuolide UV Epoxy D-606, Zhuolide UV Epoxy D-3100, Fuxing Danny UV Hard Glue or Kasute UV Crystal Epoxy, preferably Zhuolide UV Epoxy D-606.

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

[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, both the first electrode layer 12 and the second electrode layer 14 are selected from the liquid metal layer 8, which 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 more preferably the liquid gallium-indium alloy layer.

[0069] Combination Figure 1As shown, in this 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 coincide, or they can completely coincide, preferably completely coincide. This arrangement helps to improve the structural compactness of the flexible two-dimensional strain and pressure composite sensor.

[0070] It is understood that the two-dimensional sensing unit 1 in this invention contains two sub-sensors, while the pressure sensing unit 2 is a sub-sensor. That is, the flexible two-dimensional strain and pressure composite sensor in this 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 in the plane and the pressure in the vertical direction of the plane, but also the sub-sensors work independently without interfering with each other, with high sensitivity and high monitoring accuracy.

[0072] Meanwhile, the present invention also provides a method for fabricating the flexible two-dimensional strain and pressure composite sensor as described above, comprising the following steps:

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

[0074] In step S1, the fabrication method of the prefabricated two-dimensional sensing unit includes the following steps:

[0075] S11, the first spinning solution is spun on the surface of release paper to form a first flexible substrate 3 using electrospinning technology;

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

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

[0078] S14, the conductive liquid is printed on the isolation layer 5 to form the second sensing layer 6, so that the projection portions of the first sensing layer 4 and the second sensing layer 6 on the first surface overlap along the first direction z to form an intersecting overlapping area.

[0079] S15, the third spinning solution is spun on the surface of the second sensing layer 6 using electrospinning technology to form the first encapsulation layer 7, thus obtaining the prefabricated two-dimensional sensing unit.

[0080] Specifically, in step S11, the steps for forming the first flexible substrate 3 by electrospinning the first spinning solution on the surface of the release paper using electrospinning technology are as follows: The first spinning solution is drawn into two 10mL syringes, and a 19G stainless steel dispensing needle is used as the syringe needle. The two syringes are then loaded onto the injection pump of the electrospinning machine. The release paper is then attached to the surface of the inner roller of the electrospinning machine, and the distance between the syringe needle and the roller is set. The positive and negative voltage terminals of the electrospinning machine are connected to the bottom of the dispensing needle and the roller, respectively. The various parameters of electrospinning are set to obtain the first flexible substrate 3.

[0081] In step S11, the parameters for electrospinning include: an applied positive voltage of 10kV-20kV, an applied negative voltage of -1kV to -5kV, a roller rotation speed of 200rpm-800rpm, a liquid supply rate of 0.05mL / min-0.07mL / min, a needle-to-collecting device distance of 12cm-18cm, a temperature of 25℃-35℃, and an ambient relative humidity of 35%-50%. This configuration facilitates the formation of a first flexible nanofiber layer with good air and water permeability, as well as excellent stretchability and flexibility.

[0082] Optionally, the electrospinning time is 20-30 minutes, preferably 25 minutes. This setting helps to control the thickness of the first flexible substrate 3.

[0083] In one embodiment, the first spinning solution is obtained by mixing a first flexible substrate 3 precursor material and an organic solvent, and then stirring evenly at room temperature. The stirring rate is 300 rpm-500 rpm, and the stirring time is 3 h-7 h. The mass-to-volume ratio of the first flexible substrate 3 precursor material to the organic solvent is 22%-26%. This configuration is beneficial for improving the spinning effect.

[0084] It is understood that in this invention, the mass-to-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 thermoplastic polyurethane solution and styrene-butadiene-styrene block copolymer solution, preferably a thermoplastic polyurethane solution. This configuration is beneficial for 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 steps for printing the conductive liquid onto 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 as a DXF file;

[0091] S122: Import the DXF file into the laser cutting machine software and set the cutting parameters, and cut out liquid metal printing template and conductive ink printing template on a 0.05mm thick PET film;

[0092] S123, peel 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 into 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 into the conductive ink template. After curing, liquid metal layer 8, conductive ink layer 9 and first metal pin 10 are formed respectively, and the first sensing layer 4 is obtained.

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

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

[0095] Furthermore, in step S15, the specific steps and corresponding process parameters for spinning the third spinning solution onto the surface of the second sensing layer 6 using electrospinning technology to form the first encapsulation layer 7 can be referred to in step S11, which describes the specific steps and corresponding process parameters for spinning the first spinning solution onto the surface of the release paper using electrospinning technology to form the first flexible substrate 3.

[0096] It is understood that, in this invention, the preparation methods and components of the second and third spinning solutions can refer to the preparation methods and components of the first spinning solution.

[0097] S2, the first adhesive and the second adhesive are placed on the surface of the prefabricated two-dimensional sensing unit, and after penetration and curing, a two-dimensional sensing unit 1 with a first part A and a second part is formed.

[0098] In step S2, a mask is set on the prefabricated two-dimensional sensing unit, and the first adhesive and the second adhesive are placed in the pre-set non-mask area of ​​the prefabricated two-dimensional sensing unit. After penetration and curing, the first adhesive layer and the second adhesive layer are formed, and a two-dimensional sensing unit 1 with a first part A and a second part is obtained. The first part A is embedded with the first adhesive layer, and the second part is embedded with the second adhesive layer.

[0099] In one embodiment, after the first adhesive layer and the second adhesive layer are formed by penetration 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 this invention, after the first adhesive is placed in the first part A of the prefabricated two-dimensional sensing unit, it will penetrate from the surface into the interior of the first part A. Similarly, when the second adhesive is placed in the second part of the prefabricated two-dimensional sensing unit, it will penetrate from the surface into the interior of the second part, so that the first part A contains the first adhesive and the second part contains the second adhesive. Then, after curing, corresponding first adhesive layer and second adhesive layer are formed. That is, the first part A and the second part are uniformly distributed with corresponding first adhesive layer and second adhesive layer.

[0101] Optionally, the mass fraction of adhesive in the first adhesive solution is 25%-38%, and the first adhesive solution is selected from hard adhesive solutions, preferably Zhuolide UV epoxy resin D-606, Zhuolide UV epoxy resin D-3100, Fuxing Dani UV hard adhesive, or Kasute UV crystal epoxy resin, and more preferably Zhuolide UV epoxy resin D-606. This configuration allows the elastic modulus of the first adhesive layer embedded in the first part A to be 170MPa-200MPa.

[0102] Optionally, the mass fraction of adhesive in the second adhesive solution is 13%-55%, and the second adhesive solution is selected from soft adhesive solutions, preferably Zhuolide UV epoxy resin D-0082, Zhuolide UV epoxy resin D-0084, Kasute UV soft adhesive, or Anergu UV soft adhesive, and more preferably Zhuolide UV epoxy resin D-0082. This configuration allows for better control of the elastic modulus of the second adhesive layer embedded in the second part to be 0.3MPa-1MPa.

[0103] In one embodiment, a first adhesive is applied to a prefabricated two-dimensional sensing surface by coating, and a second adhesive is applied to the surface of the prefabricated two-dimensional sensing unit by spin coating. The spin coating speed is 800 rpm-1200 rpm and the spin coating time is 40 s-80 s, preferably the spin coating speed is 1000 rpm and the spin coating time is 60 s.

[0104] It should be noted that when the second adhesive is applied to the surface of the prefabricated two-dimensional sensing unit by spin coating, the first adhesive needs to be placed on the surface of the prefabricated two-dimensional sensing unit, and after it penetrates and cures to form the first adhesive layer, the second adhesive is then applied to the surface of the prefabricated two-dimensional sensing unit by spin coating, and after it penetrates and cures to form the second adhesive layer.

[0105] In one embodiment, in the step of curing to form a first adhesive layer embedded in the first part A and a second adhesive layer embedded in the second part, ultraviolet light curing is used, and the curing time is 1 min to 3 min, preferably 2 min.

[0106] S3, prepare a pressure sensing unit 2 with a paper-cutting 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, to obtain a flexible two-dimensional strain and pressure composite sensor.

[0107] In step S3, the specific steps for preparing the pressure sensing unit 2 with the paper-cut structure 16 are as follows: a first electrode layer 12, a dielectric layer 13, a second electrode layer 14, and a second encapsulation layer 15 are sequentially prepared on the second flexible substrate 11 to obtain a pre-fabricated pressure sensing unit; the preset part of the pre-fabricated 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; then, a third adhesive is placed on the surface of the second flexible substrate 11, and after penetration and curing, a third adhesive layer is formed embedded in the second flexible substrate 11 to obtain the pressure sensing unit 2 with the paper-cut structure 16. The mass fraction of the adhesive in the third adhesive is 25%-38%, and the third adhesive is selected from hard adhesives, preferably Zhuolide UV epoxy resin D-606, Zhuolide UV epoxy resin D-3100, Fuxing Dani UV hard adhesive, or Kasute UV crystal epoxy resin, and more preferably Zhuolide UV epoxy resin D-606.

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

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

[0110] Similarly, the specific steps and process parameters for printing liquid metal onto the first flexible substrate 3 to form the first electrode layer 12, and the specific steps and process parameters for printing liquid metal onto the dielectric layer 13 to form the second electrode layer 14, can all refer to the specific steps and process parameters for printing the first sensing layer 4 onto the first flexible substrate 3 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 for spinning the fifth spinning solution onto the surface of the first electrode layer 12 using electrospinning technology to form a dielectric layer 13 can also refer to the specific steps and corresponding process parameters for spinning the first spinning solution onto the surface of the release paper using electrospinning technology in step S11 to form a first flexible substrate 3. The only difference is that the electrospinning time is 30 min to 50 min.

[0112] It is understood that, in this invention, the preparation methods and components of the fourth, fifth, and sixth spinning solutions can all refer to the preparation methods 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 a paper-cut structure 16, the preset portion of the prefabricated pressure sensing unit is cut into a paper-cut structure 16 using laser cutting technology according to the set paper-cut structure 16.

[0114] In one embodiment, in the step of placing a third adhesive on a portion of the surface 14 of the second flexible substrate, allowing it to penetrate and cure to form a third adhesive layer embedded within the second flexible substrate 11, a mask with a predetermined structure is placed on the side of the second flexible substrate 11 away from the first electrode layer 12. Then, the third adhesive is brushed onto the non-mask area of ​​the second flexible substrate 11, allowing it to penetrate and cure to form a third adhesive layer embedded within the second flexible substrate 11. It is understood that due to the presence of the first electrode layer 12, the third adhesive will not penetrate into the dielectric layer 13 and the second encapsulation 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 or the second sensing layer 6 on the first surface of 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 adhesive is applied to 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 is bonded together with the third part B of the pressure sensing unit 2, and the first metal pin 10 is bonded together with the second metal pin 17 of the pressure sensing unit 2, thereby obtaining a flexible two-dimensional strain and pressure composite sensor.

[0116] It should be noted that in this 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 to a portion of the second flexible substrate of the pressure sensing unit 2.

[0117] The fourth adhesive solution contains 25%-38% adhesive by mass, and the fourth adhesive solution is selected from hard adhesive solutions.

[0118] In one embodiment, the curing step is performed by ultraviolet light curing, wherein the curing time is 2 min to 6 min, preferably 4 min.

[0119] It is understood that the first flexible substrate 3, the isolation layer 5, and the first encapsulation layer 7 in the two-dimensional sensing unit 1 structure and the second flexible substrate 11, the dielectric layer 13, and the second encapsulation layer 15 in the pressure sensing unit 2 structure of the present invention are all made using electrospinning technology, and the softness and hardness of different parts are controlled by selective impregnation and curing with photocurable adhesive. This allows the two-dimensional sensing unit 1 and the pressure sensing unit 2 to 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 using a template printing method, which is simple to process, low in manufacturing cost, and has good development prospects.

[0120] Furthermore, 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 following specific embodiments will further illustrate the flexible two-dimensional strain and pressure composite sensor, its preparation method, and its applications. However, those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0122] Example 1

[0123] 7.5 g of thermoplastic polyurethane, 15 mL of N,N-dimethylformamide and 15 mL of tetrahydrofuran were added to a beaker and stirred evenly at room temperature using a magnetic stirrer. The stirring 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-in syringes were used to draw the obtained thermoplastic polyurethane spinning solution, and stainless steel dispensing needles (19G) were attached to the screw-in syringes. The two screw-in syringes were then fixed to the injection pump in an 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 attached to the roller in the electrospinning machine as an electrospinning collector. The position of the injection pump was adjusted so that the distance between the stainless steel dispensing needle and the roller was 15cm. Finally, the operating parameters of the electrospinning machine were set as follows: applied positive voltage of 11kV, applied negative voltage of -3kV, liquid supply rate of 0.06mL / min, roller speed of 500rpm, temperature of 30℃, and relative humidity of 40%. The electrospinning machine was started and run for 25 minutes, then turned off to obtain a first flexible substrate with a thickness of 50μm.

[0125] A 0.05mm thick PET film is cut into preset liquid metal printing templates and conductive ink printing templates using laser cutting technology. The release paper with the first flexible substrate is peeled off from the roller and laid flat on the table. The liquid metal printing template is then placed on the first flexible substrate. Liquid gallium indium alloy is brushed onto the non-mask area of ​​the liquid metal template using a fine brush. The conductive ink printing template is then replaced, and conductive ink is brushed onto the conductive ink template using a fine brush. After curing at room temperature for 10 minutes, the corresponding liquid gallium indium alloy layer, conductive ink layer, and first liquid gallium indium alloy pin are formed, resulting in a first sensing layer with a thickness of 4μm.

[0126] Next, the electrospinning machine is restarted, and the above electrospinning process is 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 is 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 overlap along the first direction to form a cross-over overlapping area. Subsequently, the electrospinning machine is restarted, and the above electrospinning process is repeated for 25 minutes to form a first encapsulation layer with a thickness of 50 μm, thus obtaining the prefabricated two-dimensional sensing unit.

[0127] A patterned PET film obtained using laser cutting was used as a mask. A prefabricated two-dimensional sensing unit with release paper was peeled from a roller and laid flat on a table. The mask was placed on the prefabricated two-dimensional sensing unit, and 0.05 mL of the first adhesive solution (Zhuolide UV Epoxy Resin D-606) was brushed onto the surface of the prefabricated two-dimensional sensing unit. After curing under UV light for 2 minutes, a first adhesive layer embedded within the prefabricated two-dimensional sensing unit was formed. Then, 2 mL of the second adhesive solution (Zhuolide UV Epoxy Resin D-0082) was spin-coated onto the prefabricated two-dimensional sensing unit without the first adhesive solution applied. After curing the surface of the unit under ultraviolet light for 2 minutes, a second adhesive layer is formed embedded in the prefabricated two-dimensional sensing unit. The spin coating speed is 1000 rpm and the spin coating time is 60 seconds. Then, the unit is placed on a laser cutting machine and cut into shape according to the preset size and structure. The release paper is removed to obtain a two-dimensional sensing unit with a first part and a second part. 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 release paper is attached to the roller in the electrospinning machine as an electrospinning collector. The electrospinning machine is started, and the above electrospinning process is repeated for 25 minutes to form a second flexible substrate with a thickness of 50 μm on the release paper surface. A 0.05 mm thick PET film is cut into a preset liquid metal printing template using laser cutting technology. The release paper with the second flexible substrate is peeled off from the roller and laid flat on a table. The obtained liquid metal printing template is then placed on the second flexible substrate, and liquid gallium indium alloy is brushed onto the non-mask area of ​​the liquid metal template using a fine brush to form a first electrode layer with a thickness of 4 μm. The electrospinning machine is then started again, and the above electrospinning process is repeated for 45 minutes to form a dielectric layer with a thickness of 90 μm on the first electrode layer.

[0129] A second electrode layer with a thickness of 4 μm was prepared using the same method as the first electrode layer. Then, the electrospinning machine was restarted, and the electrospinning process was repeated for 25 minutes. After that, a second encapsulation layer with a thickness of 50 μm was spun on the second electrode layer to obtain the prefabricated pressure sensing unit.

[0130] According to the set paper-cut structure, the preset part of the prefabricated pressure sensing unit is cut into a paper-cut structure using laser cutting technology. At the same time, a second liquid gallium indium alloy pin connected to one end of the paper-cut structure is formed. Then, 0.05 mL of third adhesive liquid (Zhuolide UV Epoxy Resin D-606) is brushed onto the surface of the second flexible substrate corresponding to the first part. After curing under ultraviolet light for 2 minutes, a third adhesive layer is formed embedded in the second flexible substrate, resulting in a pressure sensing unit with a paper-cut structure. The elastic modulus of the second flexible substrate corresponding to the first part is 0.03 MPa.

[0131] 0.01 mL of the fourth adhesive solution (Zhuolide UV Epoxy Resin D-606) was brushed onto 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, respectively. Then, the pressure sensing unit was placed on the second flexible substrate of the two-dimensional sensing unit and cured under UV light for 4 minutes. This resulted in the first part of the two-dimensional sensing unit bonding to a portion of the second flexible substrate, that is, the first part of the two-dimensional sensing unit bonding to the third part of the pressure sensing unit, and the first liquid gallium indium alloy pin bonding to the second liquid gallium indium alloy pin of the pressure sensing unit, resulting in the following: Figure 1 The flexible two-dimensional strain and pressure composite sensor shown.

[0132] Example 2

[0133] Example 2 differs from Example 1 only in that it does not include the step of brushing a third adhesive onto the surface of a portion of the second flexible substrate in the pressure sensing unit structure. Instead, according to the set paper-cutting structure, a preset portion of the prefabricated pressure sensing unit is cut into a paper-cutting structure using laser cutting technology, while simultaneously forming a second liquid gallium indium alloy pin connected to one end of the paper-cutting structure, thus obtaining a pressure sensing unit with a paper-cutting structure. All other conditions are the same, resulting in a flexible two-dimensional strain and pressure composite sensor.

[0134] Example 3

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

[0136] Example 4

[0137] Compared with Example 1, Example 4 differs only in that, in the step of preparing the prefabricated two-dimensional sensing unit, the projection portions of the first sensing layer and the second sensing layer along the first direction on the first surface overlap to form an intersecting 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°. All other conditions are the same, resulting in 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 and second adhesive solutions are the same. That is, 0.05 mL of Zhuolide UV Epoxy Resin D-0082 is used as the first adhesive solution to replace the first adhesive solution (Zhuolide UV Epoxy Resin D-606) in Example 1. All 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, thus obtaining a flexible two-dimensional strain and pressure composite sensor.

[0140] Comparative Example 2

[0141] Comparative Example 2 differs from Example 1 only in that it does not include the step of brushing a third adhesive onto a portion of the surface of the second flexible substrate, and it does not include the step of cutting a pre-set portion of the prefabricated pressure sensing unit into a paper-cut structure using laser cutting technology according to a set paper-cut structure. All other conditions are the same, resulting in a flexible two-dimensional strain and pressure composite sensor.

[0142] Comparative Example 3

[0143] Comparative Example 3 differs from Example 1 only in that it does not include the step of cutting a pre-set part of the pre-fabricated pressure sensing unit into a paper-cut structure using laser cutting technology according to the set paper-cut structure. All other conditions are the same, resulting in a flexible two-dimensional strain and pressure composite sensor.

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

[0145] from Figures 7 to 9 As can be seen, the flexible two-dimensional strain and pressure composite sensor in Example 1 exhibits stable and reliable sensing performance at 10%, 20%, and 40% cyclic strain, and also shows stable and reliable sensing performance at 5 kPa, 10 kPa, and 20 kPa cyclic pressures. Furthermore, the operation of each sub-sensor does not interfere with the operation of other sensors.

[0146] from Figures 10 to 12 As can be seen, in Comparative Example 1, when the flexible two-dimensional strain and pressure composite sensor undergoes 100% stretching along the x-axis, its sub-sensors in the y-axis and z-axis directions are significantly interfered with. This is because, without the rigid adhesive structure in the central region, the central region, i.e., the first part of the two-dimensional sensing unit, undergoes significant deformation during the stretching along the x-axis, thus interfering with the sub-sensors in the x-axis and z-axis directions. In Comparative Example 2, when the flexible two-dimensional strain and pressure composite sensor undergoes 100% stretching along the x-axis, its sub-sensors in the y-axis direction do not change significantly, but the sub-sensors in the z-axis direction are significantly interfered with. This is because, after losing the paper-cut structure and the third adhesive applied to the second flexible substrate, the sub-sensors in the z-axis direction deform with the stretching along the y-axis. Similarly, in Comparative Example 3, when the flexible two-dimensional strain and pressure composite sensor was stretched by 100% in the x-axis direction, the sub-sensor in the y-axis direction did not change significantly, but the sub-sensor in the z-axis direction was also affected by some interference. Although the degree of interference was less than that in Comparative Example 2 due to the third adhesive applied to 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. It can stably and reliably monitor the strain in the two-dimensional direction in 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 embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above 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 embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A flexible two-dimensional strain and pressure composite sensor, characterized in that, The flexible two-dimensional strain and pressure composite sensor includes: A two-dimensional sensing unit includes a first flexible substrate and a first sensing layer, an isolation layer, a second sensing layer, and a first encapsulation layer sequentially stacked on the first flexible substrate. The first sensing layer and the second sensing layer are arranged alternately. A plane parallel to the surface of the first flexible substrate is defined as a first surface. The direction in which the first sensing layer, the isolation layer, the second sensing layer, and the first encapsulation layer are sequentially stacked is defined as a first direction. The projections of the first sensing layer and the second sensing layer along the first direction on the first surface overlap to form an intersecting overlapping region. The two-dimensional sensing unit includes a first part and a second part. The projection of the first part along the first direction on the first surface coincides with the intersecting overlapping region. The second part is the part of the two-dimensional sensing unit other than the first part. The elastic modulus of the first part is greater than that of the second part, and the difference in elastic modulus is greater than or equal to 160 MPa. A pressure sensing unit is stacked on the two-dimensional sensing unit. The pressure sensing unit includes a third part and a fourth part connected to the third part. The third part corresponds to the first part, and the fourth part has a paper-cut structure. The first sensing layer and the second sensing layer are arranged in an orthogonal stack; the orthographic projection of the pressure sensing unit on the first surface completely coincides with the orthographic projection of the first sensing layer or the second sensing layer on the first surface.

2. The flexible two-dimensional strain and pressure composite sensor according to claim 1, characterized in that, The first part is embedded with a first adhesive layer, and the second part is embedded with a second adhesive layer, 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, Both the first sensing layer and the second sensing layer are strip-shaped.

4. 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 encapsulation layer sequentially stacked on the second flexible substrate. The second flexible substrate is disposed on the first flexible substrate or on the first encapsulation layer.

5. The flexible two-dimensional strain and pressure composite sensor according to claim 4, characterized in that, The elastic modulus of the second flexible substrate portion corresponding to the first portion is 170MPa-200MPa.

6. The flexible two-dimensional strain and pressure composite sensor according to claim 1, characterized in that, Both the first sensing layer and the second sensing layer include a liquid metal layer, a conductive ink layer, and a first metal pin. The liquid metal layer corresponds to the overlapping area. The conductive ink layer is provided on both sides of the liquid metal layer. The first metal pin is located at the 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-cutting structure is disposed between the second metal pin and the third part.

7. A method for fabricating a flexible two-dimensional strain and pressure composite sensor as described in any one of claims 1 to 6, characterized in that, Includes the following steps: A first sensing layer, an isolation layer, a second sensing layer, and a first encapsulation layer are sequentially fabricated on a first flexible substrate, and the first sensing layer and the second sensing layer are arranged in an alternating manner to obtain a prefabricated two-dimensional sensing unit. The first adhesive and the second adhesive are placed on the surface of the prefabricated two-dimensional sensing unit, and then penetrated and cured to form a two-dimensional sensing unit having a first part and a second part. A pressure sensing unit with a paper-cut structure is prepared, and then the pressure sensing unit and the two-dimensional sensing unit are assembled together, such that the third part of the pressure sensing unit corresponds to the first part, to obtain a flexible two-dimensional strain and pressure composite sensor.

8. The method for fabricating the flexible two-dimensional strain and pressure composite sensor according to claim 7, characterized in that, The adhesive in the first adhesive solution has a mass fraction of 25%-38%, and the first adhesive solution is selected from hard adhesive solutions; And / or, the mass fraction of adhesive in the second adhesive solution is 13%-55%, and the second adhesive solution is selected from soft adhesive solutions; And / or, the specific 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 encapsulation layer are sequentially prepared on a second flexible substrate to obtain a pre-fabricated pressure sensing unit; a preset portion of the pre-fabricated 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; then, a third adhesive is placed on a portion of the surface of the second flexible substrate, and after penetration and curing, a third adhesive layer is formed embedded in the second flexible substrate to obtain a pressure sensing unit with a paper-cut structure, wherein the third adhesive is selected from hard adhesives.

9. The application of a flexible two-dimensional strain and pressure composite sensor as described in any one of claims 1 to 6 in electronic skin, soft robots, or wearable electronic products.

Images