Gradient guiding microcrack flexible sensor and manufacturing method thereof

Abstract

The invention discloses a gradient guiding microcrack flexible sensor and a manufacturing method thereof. The sensor comprises an island-bridge micro-nano structure array, the method comprises the following steps: 1) obtaining a micro-nano structure template with an island-bridge micro-nano structure array; 2) depositing on the upper surface of the micro-nano structure template to obtain a micro-nano conformal conductive layer; 3) performing flexible transfer printing on the micro-nano conformal conductive layer through the flexible substrate to obtain a sensitive material with an island-bridge micro-nano structure array; 4) stretching the sensitive material with the island-bridge micro-nano structure array to obtain a sensitive material containing a prefabricated island-bridge micro-crack structure array; and 5) welding electrodes on two ends of the sensitive material containing the prefabricated island-bridge microcrack structure array, and connecting the flexible electrodes to obtain the gradient guiding microcrack flexible sensor. According to the invention, the sensitivity and reliability of the flexible strain sensor in a large tensile full range can be significantly improved.

Description

Technical Field

[0001] The present invention relates to the field of flexible sensors, and in particular to a gradient-guided microcrack flexible sensor and a manufacturing method thereof. Background Art

[0002] Flexible strain sensing breaks through the limitations of traditional strain sensor devices integrated on hard substrate materials such as silicon and metal, and integrates organic / inorganic electronic materials on flexible / stretchable polymer substrates to achieve the flexibility and ductility of sensor devices. As an emerging technology that has developed rapidly in the past decade, it is widely used in industry, medicine, information, energy, national defense and other fields. For flexible strain sensitive units, it is hoped that their resistance is sensitive to strain and needs to have a large resistance-strain change rate, that is, the device sensitivity. Studies have found that when the stretching rate exceeds the strain range of the material, microcracks will be generated and evolved at the strain sensitive unit. This mechanical structural damage will cause the current channel to change, and it will be reflected in the macroscopic resistance change of the sensor device. The evolution of the conductive channel introduced by this microcrack mechanism can significantly improve the sensitivity of the device. However, although disordered microcracks can effectively improve the range or sensitivity of microcrack devices, their stability and reliability are usually difficult to take into account at the same time, because the generation and evolution of microcracks are disordered and uncontrollable. If orderly and controllable microcracks can be obtained through micro-nano manufacturing methods, comprehensive performance can be taken into account at the same time. Summary of the invention

[0003] The object of the present invention is to provide a gradient-guided microcrack flexible sensor and a manufacturing method thereof.

[0004] The technical solution adopted to achieve the purpose of the present invention is as follows: a gradient-guided microcrack flexible sensor, including an island-bridge micro-nano structure array.

[0005] The island-bridge micro-nano structure array includes a plurality of island structures and a plurality of bridge structures.

[0006] The island structure is a protruding or recessed structure in the island-bridge micro-nano structure array.

[0007] The bridge structure is a non-convex or non-concave plain portion in the island-bridge micro-nano structure array.

[0008] The island structures in the island-bridge micro-nano structure array are isolated from adjacent island structures by bridge structures, and the island structures in the island-bridge micro-nano structure array are paired with adjacent island structures according to the main-auxiliary island pairing principle.

[0009] Furthermore, the pairing principle of the main and auxiliary islands is as follows:

[0010] The island structures with the same polygonal structure are defined as main islands, and the island structures with different polygonal structures located between adjacent main islands are defined as auxiliary islands.

[0011] If there is only a main island in the island-bridge micro-nanostructure array, all the vertex corners of the main island are matched one-to-one with the vertex corners of adjacent main islands.

[0012] If there are auxiliary islands between adjacent main islands in the island-bridge micro-nanostructure array, some of the vertex corners of the main islands are paired one-to-one with the vertex corners of the adjacent main islands, and the remaining unpaired vertex corners are paired one-to-one with the vertex corners of the adjacent auxiliary islands.

[0013] Furthermore, the one-to-one pairing of the top corners of the main island and the adjacent main island or the adjacent auxiliary island is as follows:

[0014] The line connecting the polygonal centroids or centroids of the main island and the adjacent main island or the adjacent auxiliary island is collinear with the line connecting the paired vertex angles.

[0015] Furthermore, the polygon of the main island or the auxiliary island has a variant structure.

[0016] The variant structure includes a polygonal structure in which the top angles of the polygon are sharpened into a sharp angle.

[0017] Furthermore, the main island is set to be an n-gon and the auxiliary island is set to be an m-gon, wherein m and n are both integers and n≥m.

[0018] The relationship between m and n is as follows:

[0019] n=r·m,m=i·a (1)

[0020] In the formula, r is an even number, i is an integer, and parameter a=3,4.

[0021] A method for manufacturing the above-mentioned gradient-guided microcrack flexible sensor comprises the following steps:

[0022] 1) Obtain a micro-nanostructure template having an island-bridge micro-nanostructure array.

[0023] 2) A micro-nano conformal conductive layer is obtained by deposition on the upper surface of the micro-nano structure template.

[0024] 3) The micro-nano conformal conductive layer is flexibly transferred through a flexible substrate to obtain a sensitive material with an island-bridge micro-nano structure array.

[0025] 4) Pre-stretching the sensitive material with the island-bridge micro-nano structure array, at this time, the stress gradient guidance tends to generate microcracks in the direction of the top angle connection line of the adjacent island structure pairs, thereby obtaining a sensitive material containing a prefabricated island-bridge microcrack structure array.

[0026] 5) Electrodes are welded to both ends of the sensitive material containing the prefabricated island-bridge microcrack structure array, and the flexible electrodes are connected to obtain a gradient-guided microcrack flexible sensor.

[0027] Furthermore, the material of the conductive layer includes a material that causes a change in resistance due to deformation or cracking in the conductive path.

[0028] Furthermore, the step of flexibly transferring the micro-nano conformal conductive layer through a flexible substrate to obtain a sensitive material with an island-bridge micro-nano structure array includes:

[0029] A flexible matrix in a liquid state is injected into a micro-nano structure template having a conductive layer with a micro-nano conformal surface.

[0030] After the flexible substrate is converted into a solid state, a sensitive material with an island-bridge micro-nano structure array is obtained.

[0031] Furthermore, the method for pre-stretching the sensitive material with the island-bridge micro-nanostructure array includes but is not limited to: 1. applying uniform force to each edge of the flexible substrate for stretching; 2. attaching the flexible material to the micro-balloon and stretching it by a pressure difference method in which air pressure is applied to the micro-balloon to cause expansion.

[0032] Furthermore, the method of connecting the flexible electrodes includes connecting the flexible electrodes at both ends of the plane where the sensitive material containing the prefabricated island-bridge microcrack structure array is located, or placing the sensitive material containing the prefabricated island-bridge microcrack structure array on a single-sided flexible interdigitated electrode, or placing electrodes on the upper and lower surfaces of the plane where the sensitive material is located to form a "sandwich" structure.

[0033] The technical effect of the present invention is unquestionable. The present invention proposes a new performance regulation principle and manufacturing method for constructing a gradient "island-bridge" channel for stress transfer / dissipation using micro-nano conformal graphene, which can significantly improve the sensitivity and reliability of the flexible strain sensor over the entire large tensile range.

[0034] The sensitive material of the sensor manufactured by the present invention has two layers, namely a conductive layer and a flexible substrate layer. Under the action of tensile strain or stress, due to the mismatch of the Young's modulus of the conductive layer and the flexible substrate layer, cracks will open between the bridges of the surface conductive layer, changing the conductive path of the sensitive material. The expansion of the crack area will cause the resistance of the sensor to rise sharply, thereby realizing strain sensing. After the tension is removed, due to the rebound of the substrate, the expanded crack returns to the initial position, forming a closed state again, and the resistance returns to its original position. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a flexible and sensitive material before prefabricating microcracks;

[0036] Figure 2 Schematic diagram of the gradient-induced island-bridge structure;

[0037] Figure 3 A schematic diagram for the derivation of pairing relationships;

[0038] Figure 4 This is a simplified diagram of the pairing relationship between 3-6;

[0039] Figure 5 A schematic diagram comparing the pairing relationship between 3-9 and 3-12; Figure 5 (a) is a schematic diagram of the pairing relationship between 3-9; Figure 5 (b) is a schematic diagram of the pairing relationship between 3-12;

[0040] Figure 6 This is a schematic diagram of sharpening the vertex angles of a regular polygon;

[0041] Figure 7 This is a schematic diagram of the working principle of the sensor; Figure 7 (a) Schematic diagram of the conductive network formed by the initial resistance; Figure 7 (b) Schematic diagram of the sharp increase in the resistance of the conductive network due to cracks;

[0042] In the figure, there are a conductive layer 1 and a flexible base layer 2. DETAILED DESCRIPTION

[0043] The present invention is further described below in conjunction with the embodiments, but it should not be understood that the above subject matter of the present invention is limited to the following embodiments. Without departing from the above technical ideas of the present invention, various substitutions and changes are made according to the common technical knowledge and customary means in the art, which should all be included in the protection scope of the present invention.

[0044] Embodiment 1:

[0045] See also Figures 1 to 7 , a gradient-guided microcrack flexible sensor comprising an island-bridge micro-nanostructure array.

[0046] The island-bridge micro-nano structure array includes a plurality of island structures and a plurality of bridge structures.

[0047] The island structure is a protruding or recessed structure in the island-bridge micro-nano structure array.

[0048] The bridge structure is a non-convex or non-concave plain portion in the island-bridge micro-nano structure array.

[0049] The island structures in the island-bridge micro-nano structure array are isolated from adjacent island structures by bridge structures, and the island structures in the island-bridge micro-nano structure array are paired with adjacent island structures according to the main-auxiliary island pairing principle.

[0050] Embodiment 2:

[0051] A gradient-guided microcrack flexible sensor, the main technical content of which is shown in Example 1. Further, the pairing principle of the main and auxiliary islands is as follows:

[0052] The island structures with the same polygonal structure are defined as main islands, and the island structures with different polygonal structures located between adjacent main islands are defined as auxiliary islands.

[0053] If there is only a main island in the island-bridge micro-nanostructure array, all the vertex corners of the main island are matched one-to-one with the vertex corners of adjacent main islands.

[0054] If there are auxiliary islands between adjacent main islands in the island-bridge micro-nanostructure array, some of the vertex corners of the main islands are paired one-to-one with the vertex corners of the adjacent main islands, and the remaining unpaired vertex corners are paired one-to-one with the vertex corners of the adjacent auxiliary islands.

[0055] Embodiment 3:

[0056] A gradient-guided microcrack flexible sensor, the main technical content of which is shown in any one of Embodiments 1 to 2, and further, the one-to-one pairing of the vertex corners of the main island and the adjacent main island or the adjacent auxiliary island is as follows:

[0057] The line connecting the polygonal centroids or centroids of the main island and the adjacent main island or the adjacent auxiliary island is collinear with the line connecting the paired vertex angles.

[0058] Embodiment 4:

[0059] A gradient-guided microcrack flexible sensor, the main technical content of which is shown in any one of Embodiments 1 to 3, and further, the polygon of the main island or the auxiliary island has a variant structure.

[0060] The variant structure includes a polygonal structure in which the top angles of the polygon are sharpened into a sharp angle.

[0061] Embodiment 5:

[0062] A gradient-guided microcrack flexible sensor, the main technical content of which is shown in any one of embodiments 1 to 4. Further, the main island is set to be an n-gon and the auxiliary island is set to be an m-gon, wherein m and n are both integers and n≥m.

[0063] The relationship between m and n is as follows:

[0064] n=r·m,m=i·a (1)

[0065] In the formula, r is an even number, i is an integer, and parameter a=3,4.

[0066] Embodiment 6:

[0067] A method for manufacturing the gradient-guided microcrack flexible sensor according to any one of embodiments 1 to 5 comprises the following steps:

[0068] 1) Obtain a micro-nanostructure template having an island-bridge micro-nanostructure array.

[0069] 2) A micro-nano conformal conductive layer is obtained by deposition on the upper surface of the micro-nano structure template.

[0070] 3) The micro-nano conformal conductive layer is flexibly transferred through a flexible substrate to obtain a sensitive material with an island-bridge micro-nano structure array.

[0071] 4) Pre-stretching the sensitive material with the island-bridge micro-nano structure array, at this time, the stress gradient guidance tends to generate microcracks in the direction of the top angle connection line of the adjacent island structure pairs, thereby obtaining a sensitive material containing a prefabricated island-bridge microcrack structure array.

[0072] 5) Electrodes are welded to both ends of the sensitive material containing the prefabricated island-bridge microcrack structure array, and the flexible electrodes are connected to obtain a gradient-guided microcrack flexible sensor.

[0073] Embodiment 7:

[0074] A method for manufacturing a gradient-guided microcrack flexible sensor, the main technical content of which is shown in Example 6. Furthermore, the material of the conductive layer includes a material that causes resistance changes in the conductive path due to deformation or cracking.

[0075] Embodiment 8:

[0076] A method for manufacturing a gradient-guided microcrack flexible sensor, the main technical content of which is shown in any one of Embodiments 6 to 7, and further, the step of flexibly transferring the micro-nano conformal conductive layer through a flexible substrate to obtain a sensitive material with an island-bridge micro-nano structure array comprises:

[0077] A flexible matrix in a liquid state is injected into a micro-nano structure template having a conductive layer with a micro-nano conformal surface.

[0078] After the flexible substrate is converted into a solid state, a sensitive material with an island-bridge micro-nano structure array is obtained.

[0079] Embodiment 9:

[0080] A method for manufacturing a gradient-guided microcrack flexible sensor, the main technical content of which is shown in any one of Examples 6 to 8. Furthermore, the method for pre-stretching the sensitive material with an island-bridge micro-nanostructure array includes but is not limited to: 1. Applying uniform force to each edge of the flexible substrate for stretching; 2. Attaching the flexible material to a micro-balloon and stretching it by a pressure difference method in which air pressure is applied to the micro-balloon to cause expansion.

[0081] Embodiment 10:

[0082] A method for manufacturing a gradient-guided microcrack flexible sensor, the main technical content of which is shown in any one of Examples 6 to 9. Furthermore, the method of connecting the flexible electrodes includes connecting the flexible electrodes at both ends of the plane where the sensitive material containing the prefabricated island-bridge microcrack structure array is located, or placing the sensitive material containing the prefabricated island-bridge microcrack structure array on a single-sided flexible interdigitated electrode, or placing electrodes on the upper and lower surfaces of the plane where the sensitive material is located to form a "sandwich" structure.

[0083] Embodiment 11:

[0084] See also Figures 1 to 7 , a gradient-guided microcrack flexible sensor comprising an island-bridge micro-nanostructure array.

[0085] The island-bridge micro-nano structure array includes a plurality of island structures and a plurality of bridge structures.

[0086] The island structure is a protruding or recessed structure in the island-bridge micro-nano structure array.

[0087] The bridge structure is a non-convex or non-concave plain portion in the island-bridge micro-nano structure array.

[0088] The island structures in the island-bridge micro-nano structure array are isolated from adjacent island structures by bridge structures, and the island structures in the island-bridge micro-nano structure array are paired with adjacent island structures according to the main-auxiliary island pairing principle.

[0089] Embodiment 12:

[0090] A gradient-guided microcrack flexible sensor, the main technical content of which is shown in Example 11. Further, the pairing principle of the main and auxiliary islands is as follows:

[0091] The island structures with the same polygonal structure are defined as main islands, and the island structures with different polygonal structures located between adjacent main islands are defined as auxiliary islands.

[0092] If there is only a main island in the island-bridge micro-nanostructure array, all the vertex corners of the main island are matched one-to-one with the vertex corners of adjacent main islands.

[0093] If there are auxiliary islands between adjacent main islands in the island-bridge micro-nanostructure array, some of the vertex corners of the main islands are paired one-to-one with the vertex corners of the adjacent main islands, and the remaining unpaired vertex corners are paired one-to-one with the vertex corners of the adjacent auxiliary islands.

[0094] The micro-nanostructure design principles of the island-bridge gradient-guided microcrack flexible strain sensor must meet the following three points: 1. First, the vertices of the main island are partially self-paired; (if there is only the main island, all of them need to be self-paired) 2. The vertices of the main island that are not self-paired are paired by the vertices of the auxiliary island; 3. The line connecting the polygonal centroid (or centroid) of the main island is collinear with the line connecting the vertices.

[0095] If expressed as a mathematical expression, then: First, if each angle is paired, the angle between each n-gon in the array and the center is like Figure 3 As shown. At this time, in ΔOO1O2, Then the relationship between a and b must satisfy: a=k·b, where k is an integer.

[0096] We can get:

[0097] After sorting, you can get

[0098] Since k is an integer and n is the number of sides of the polygon, which must also be an integer, there are only three solutions for n, n=3, 4, and 6, that is, only regular triangles, regular quadrilaterals, and regular hexagons can satisfy the one-to-one correspondence condition between the main and auxiliary islands.

[0099] It should be noted that any structure in which the main and auxiliary islands are paired with each other with unequal numbers of edges can be considered as a variant of the main and auxiliary island structure with equal numbers of edges. Figure 4 In the pairing situation, if the hexagon is the main island, the triangular auxiliary islands around the hexagon pair the three vertices of the hexagon one by one. After the pairing is completed, the remaining three vertices are evenly distributed, and their positional relationship forms the following Figure 4 The equilateral triangle configuration of the middle wireframe in the figure. Then this hexagon-triangle combination can be regarded as a self-pairing problem of a triangular shape, such as Figure 4 As shown, the 3-3 pairing is solvable, so 3-6 can also be paired successfully.

[0100] According to this rule, if Figure 5 As shown, it is obvious that the units of 3-9 do not form an equivalent regular hexagon, so 3-9 cannot be completely paired, while the equivalent units of 3-12 are regular hexagons, so they can be completely paired.

[0101] Embodiment 13:

[0102] A gradient-guided microcrack flexible sensor, the main technical content of which is shown in any one of Embodiments 11 to 12, further, the one-to-one pairing of the top corners of the main island and the adjacent main island or the adjacent auxiliary island is as follows:

[0103] The line connecting the polygonal centroids or centroids of the main island and the adjacent main island or the adjacent auxiliary island is collinear with the line connecting the paired vertex angles.

[0104] Embodiment 14:

[0105] A gradient-guided microcrack flexible sensor, the main technical content of which is shown in any one of Examples 11 to 13, and further, the polygon of the main island or the auxiliary island has a variant structure.

[0106] The variant structure includes a polygonal structure in which the top angles of the polygon are sharpened into a sharp angle.

[0107] Any m-edge shape can be formed into an m-angle shape by sharpening the vertex angle, such as Figure 6 As shown, or by changing the spacing between the shapes, a better gradient-guided microcrack generation effect can be achieved.

[0108] Embodiment 15:

[0109] A gradient-guided microcrack flexible sensor, the main technical content of which is shown in any one of Examples 11 to 14. Further, the main island is set to be an n-gon and the auxiliary island is set to be an m-gon, wherein m and n are both integers and n≥m.

[0110] The relationship between m and n is as follows:

[0111] n=r·m,m=i·a (1)

[0112] In the formula, r is an even number, i is an integer, and parameter a=3,4.

[0113] Embodiment 16:

[0114] A method for manufacturing the gradient-guided microcrack flexible sensor according to any one of embodiments 11 to 15, comprising the following steps:

[0115] 1) Obtain a micro-nanostructure template having an island-bridge micro-nanostructure array.

[0116] The method for obtaining the micro-nano structure template having a plurality of island structures includes photolithography, laser direct writing, 3D printing or other manufacturing methods.

[0117] 2) A micro-nano conformal conductive layer is obtained by deposition on the upper surface of the micro-nano structure template.

[0118] The deposition method includes physical deposition, chemical deposition, and physicochemical deposition.

[0119] It should be noted that the deposition is to obtain a micro-nano conformal conductive layer material. Therefore, this process includes any manufacturing process that can obtain a micro-nano conformal conductive layer.

[0120] 3) The micro-nano conformal conductive layer is flexibly transferred through a flexible substrate to obtain a sensitive material with an island-bridge micro-nano structure array.

[0121] It should be noted that the purpose of this step is to flexibly transfer the micro-nano conformal sensitive material using a flexible substrate, and after the transfer, a sensitive material with a surface micro-nano conformal conductive layer will be obtained.

[0122] 4) Pre-stretching the sensitive material with the island-bridge micro-nano structure array, at this time, the stress gradient guidance tends to generate microcracks in the direction of the top angle connection line of the adjacent island structure pairs, thereby obtaining a sensitive material containing a prefabricated island-bridge microcrack structure array.

[0123] 5) Electrodes are welded to both ends of the sensitive material containing the prefabricated island-bridge microcrack structure array, and the flexible electrodes are connected to obtain a gradient-guided microcrack flexible sensor.

[0124] Embodiment 17:

[0125] A method for manufacturing a gradient-guided microcrack flexible sensor, the main technical content of which is shown in Example 16. Furthermore, the material of the conductive layer includes a material that causes resistance changes in the conductive path due to deformation or cracking.

[0126] The material of the conductive layer includes but is not limited to graphene, metal, and conductive polymer.

[0127] Any material that changes resistance as the distance in a conductive path changes can be used as a sensing material.

[0128] Embodiment 18:

[0129] A method for manufacturing a gradient-guided microcrack flexible sensor, the main technical content of which is shown in any one of Embodiments 16 to 17, further comprising the step of flexibly transferring the micro-nano conformal conductive layer through a flexible substrate to obtain a sensitive material with an island-bridge micro-nano structure array:

[0130] A flexible matrix in a liquid state is injected into a micro-nano structure template having a conductive layer with a micro-nano conformal surface.

[0131] After the flexible substrate is converted into a solid state, the flexible substrate can be stretched to preform microcracks to obtain a sensitive material with an island-bridge micro-nanostructure array.

[0132] Embodiment 19:

[0133] A method for manufacturing a gradient-guided microcrack flexible sensor, the main technical content of which is shown in any one of Examples 16 to 18. Furthermore, the method for pre-stretching the sensitive material with an island-bridge micro-nanostructure array includes but is not limited to: 1. Applying uniform force to each edge of the flexible substrate for stretching; 2. Attaching the flexible material to a micro-balloon and stretching it by a pressure difference method in which air pressure is applied to the micro-balloon to cause expansion.

[0134] Embodiment 20:

[0135] A method for manufacturing a gradient-guided microcrack flexible sensor, the main technical content of which is shown in any one of Examples 16 to 19. Furthermore, the method of connecting the flexible electrodes includes connecting the flexible electrodes at both ends of the plane where the sensitive material containing the prefabricated island-bridge microcrack structure array is located, or placing the sensitive material containing the prefabricated island-bridge microcrack structure array on a single-sided flexible interdigitated electrode, or placing electrodes on the upper and lower surfaces of the plane where the sensitive material is located to form a "sandwich" structure.

[0136] Embodiment 21:

[0137] See also Figures 1 to 7 , a gradient-guided microcrack flexible sensor and its manufacturing method, the main technical contents include:

[0138] In such Figure 1-2 In the enlarged view of the micro-nano structure shown, the raised part is the "island" and the plain part is the "bridge". The sensor's sensitive material has two layers, namely the conductive layer 1 and the flexible substrate layer 2. Under the action of tensile strain or stress, due to the mismatch of the Young's modulus of the conductive layer 1 and the flexible substrate layer 2, cracks will open between the bridges of the surface conductive layer, changing the conductive path of the sensitive material, thereby causing the resistance of the sensor to change.

[0139] Next, the micro-nanostructure design principles of the island-bridge gradient-guided microcrack flexible strain sensor are explained, which must meet the following three points: 1. First, some of the vertices of the main island are self-paired; (if there is only the main island, all of them need to be self-paired) 2. The vertices of the main island that are not self-paired are paired with the vertices of the auxiliary island; 3. The line connecting the polygonal centroid (or centroid) of the main island is collinear with the line connecting the vertices.

[0140] If expressed as a mathematical expression, then: First, if each angle is paired, the angle between each n-gon in the array and the center is like Figure 3 As shown. At this time, in ΔOO1O2, Then the relationship between a and b must satisfy: a=k·b, where k is an integer.

[0141] We can get:

[0142] After sorting, you can get

[0143] Since k is an integer and n is the number of sides of the polygon, which must also be an integer, there are only three solutions for n, n=3, 4, and 6, that is, only regular triangles, regular quadrilaterals, and regular hexagons can satisfy the one-to-one correspondence condition between the main and auxiliary islands.

[0144] It should be noted that any structure in which the main and auxiliary islands are paired with each other with unequal numbers of edges can be considered as a variant of the main and auxiliary island structure with equal numbers of edges. Figure 4In the pairing situation, if the hexagon is the main island, the triangular auxiliary islands around the hexagon pair the three vertices of the hexagon one by one. After the pairing is completed, the remaining three vertices are evenly distributed, and their positional relationship forms the following Figure 3 The equilateral triangle configuration of the middle wireframe. Then this hexagon-triangle combination can be regarded as a self-pairing problem of a triangular shape, such as Figure 4 As shown, the 3-3 pairing is solvable, so 3-6 can also be paired successfully.

[0145] According to this rule, if Figure 5 As shown, it is obvious that the units of 3-9 do not form an equivalent regular hexagon, so 3-9 cannot be completely paired, while the equivalent units of 3-12 are regular hexagons, so they can be completely paired. Therefore, if the main island is an n-gon or variant, and the auxiliary island is an m-gon or variant, n ≥ m, summarizing cases 1 and 2, it can be concluded that the pairing principle of the main and auxiliary islands is:

[0146] m=i·a,a=3,4

[0147] n=k·m, k is an even number

[0148] In addition, any m-edge shape can be formed into an m-angle shape by sharpening the vertex angle, such as Figure 6 As shown, or by changing the spacing between the shapes, a better gradient-guided microcrack generation effect can be achieved.

[0149] Embodiment 22:

[0150] See also Figures 1 to 7 , a gradient-guided microcrack flexible sensor and its manufacturing method, the main technical contents include:

[0151] The production process of the gradient-guided microcrack sensor is as follows:

[0152] 1. First, the micro-nano structure template of the island is obtained through photolithography, laser direct writing, 3D printing or other manufacturing methods.

[0153] 2. Then, a micro-nano conformal conductive layer is obtained by physical deposition, chemical deposition or physical and chemical deposition. It should be noted that deposition is to obtain a micro-nano conformal conductive layer material. Therefore, this process includes any manufacturing process that can obtain a micro-nano conformal conductive layer. The conductive layer material is not limited to graphene, metal, and conductive polymer. Any material that causes a change in resistance due to a change in distance in the conductive path can be used as a sensitive material.

[0154] 3. Then, the conductive layer is flexibly transferred through the polymer to obtain a sensitive material with a micro-nano structure. It should be noted that the purpose of this step is to flexibly transfer the micro-nano conformal sensitive material with a flexible substrate, and after the transfer, a sensitive material with a surface micro-nano conformal conductive layer will be obtained. In order to meet the requirements of prefabricating microcracks in the fourth step, the flexible substrate needs to: 1. be injected from a liquid state into the mold containing the surface micro-nano conformal conductive layer obtained in the second step; 2. after being converted to a solid state, the flexible substrate can be stretched to prefabricate microcracks.

[0155] 4. By stretching the sensitive material, a sensitive material with a microstructure containing a prefabricated island-bridge structure can be obtained. It should be noted that the stretching method includes but is not limited to: 1. Applying uniform force to the four sides of the flexible substrate and stretching directly; 2. Attaching the flexible material to the micro-airbag and preparing it by the pressure difference method.

[0156] 5. By welding electrodes on both ends of the sensitive material, connecting flexible electrodes on both sides, or placing it on a single-sided flexible fork paper electrode, different flexible sensors can be obtained to measure strain or stress.

[0157] Embodiment 23:

[0158] See also Figures 1 to 7 , a gradient-guided microcrack flexible sensor and a manufacturing method thereof, the main technical contents include:

[0159] Taking the sensor constructed with carbon nanowall and polydimethylsiloxane PDMS matrix as an example, the production process is as follows:

[0160] 1. Through micro-nano processing methods such as exposure-development-dry etching-wet etching, multiple regular polygonal "island" structures are obtained;

[0161] 2. Micro-nano conformal carbon nanowalls are obtained through in-situ growth using high-performance solid film preparation technology PECVD;

[0162] 3. Use flexible substrate PDMS to flexibly transfer micro-nano conformal carbon nanowalls;

[0163] 4. Pre-stretching to obtain a strain sensor device containing prefabricated gradient-guided microcracks.

[0164] Embodiment 24:

[0165] See also Figures 1 to 7 , a gradient-guided microcrack flexible sensor and its manufacturing method, the main technical contents include:

[0166] The working principle of the gradient-guided microcrack flexible sensor is as follows:

[0167] like Figure 7As shown, in the initial state, the prefabricated microcracks of the sensor are closed, and an "island-bridge" unit of the sensor is taken. At this time, the resistance of the sensor is equivalent to Figure 7 (a) shows the equivalent circuit resistance, R0. When the sensor is stretched, the substrate deforms and the prefabricated microcracks between the main and auxiliary islands expand. The expansion of the microcrack area will cause the resistance of the sensor to rise sharply, thereby realizing strain sensing. After the tension is removed, the expanded microcracks return to their initial position due to the rebound of the substrate, forming a closed state again, and the resistance returns to R0.

Claims

1. A gradient-guided microcrack flexible sensor, characterized in that: including island-bridge micro-nanostructure arrays; The island-bridge micro-nano structure array includes a plurality of island structures and a plurality of bridge structures; The island structure is a protruding or recessed structure in the island-bridge micro-nano structure array. The bridge structure is a non-convex or non-concave plain portion in the island-bridge micro-nano structure array. The island structures in the island-bridge micro-nano structure array are isolated from adjacent island structures by bridge structures, and the island structures in the island-bridge micro-nano structure array are paired with adjacent island structures according to the main-auxiliary island pairing principle.

2. A gradient-guided microcrack flexible sensor according to claim 1, characterized in that: The main and auxiliary island pairing principles are as follows: Define the island structures with the same polygonal structure as main islands, and the island structures with different polygonal structures located between adjacent main islands as auxiliary islands; If there is only a main island in the island-bridge micro-nanostructure array, all the vertex corners of the main island are matched one-to-one with the vertex corners of the adjacent main islands; If there are auxiliary islands between adjacent main islands in the island-bridge micro-nanostructure array, some of the vertex corners of the main islands are paired one-to-one with the vertex corners of the adjacent main islands, and the remaining unpaired vertex corners are paired one-to-one with the vertex corners of the adjacent auxiliary islands.

3. A gradient-guided microcrack flexible sensor according to claim 2, characterized in that: The one-to-one pairing of the top corners of the main island and the adjacent main island or the adjacent auxiliary island is as follows: The line connecting the polygonal centroids or centroids of the main island and the adjacent main island or the adjacent auxiliary island is collinear with the line connecting the paired vertex angles.

4. A gradient-guided microcrack flexible sensor according to claim 2, characterized in that: The polygon of the main island or the auxiliary island has a variant structure; The variant structure includes a polygonal structure in which the top angles of the polygon are sharpened into a sharp angle.

5. The gradient-guided microcrack flexible sensor according to claim 2, characterized in that: The main island is set to be an n-gon and the auxiliary island is set to be an m-gon, where m and n are both integers and n≥m; The relationship between m and n is as follows: n=r·m,m=i·a (1) In the formula, r is an even number, i is an integer, and parameter a=3,4.

6. A method for manufacturing the gradient-guided microcrack flexible sensor according to any one of claims 1 to 5, characterized in that: The following steps are involved: 1) obtaining a micro-nanostructure template having an island-bridge micro-nanostructure array; 2) On the upper surface of the micro-nano structure template, a micro-nano conformal conductive layer is obtained by deposition; 3) Flexibly transfer the micro-nano conformal conductive layer through a flexible substrate to obtain a sensitive material with an island-bridge micro-nano structure array; 4) Pre-stretching the sensitive material with the island-bridge micro-nano structure array, at which time the stress gradient guidance tends to generate microcracks in the direction of the vertex connection line of the adjacent island structure pairs, thereby obtaining a sensitive material containing a prefabricated island-bridge microcrack structure array; 5) Electrodes are welded to both ends of the sensitive material containing the prefabricated island-bridge microcrack structure array, and the flexible electrodes are connected to obtain a gradient-guided microcrack flexible sensor.

7. The method according to claim 6, characterized in that The material of the conductive layer includes a material that causes a change in resistance due to deformation or cracking in the conductive path.

8. The method according to claim 6, characterized in that The step of flexibly transferring the micro-nano conformal conductive layer through a flexible substrate to obtain a sensitive material with an island-bridge micro-nano structure array comprises: Injecting a flexible substrate in a liquid state into a micro-nano structure template having a conductive layer with a micro-nano conformal surface; After the flexible substrate is converted into a solid state, a sensitive material with an island-bridge micro-nano structure array is obtained.

9. The method according to claim 6, characterized in that The method for pre-stretching the sensitive material with the island-bridge micro-nanostructure array includes but is not limited to:

1. applying uniform force to each side of the flexible substrate for stretching; 2. attaching the flexible material to the micro-balloon and stretching it by a pressure difference method in which air pressure is applied to the micro-balloon to cause expansion.

10. The method according to claim 6, characterized in that The method for connecting the flexible electrodes includes connecting the flexible electrodes at both ends of the plane where the sensitive material containing the prefabricated island-bridge microcrack structure array is located, or placing the sensitive material containing the prefabricated island-bridge microcrack structure array on a single-sided flexible interdigitated electrode, or placing electrodes on the upper and lower surfaces of the plane where the sensitive material is located to form a "sandwich" structure.

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