A flexible strain sensor and a method of manufacturing the same

Abstract

The application discloses a flexible strain sensor and a preparation method thereof. The strain sensor comprises a substrate for being connected to a surface, and a functional layer connected to the substrate, wherein one side of the functional layer away from the substrate is provided with a slit structure, and at least one side of the slit structure is provided with a plurality of dispersion structures; when the functional layer is stressed, the dispersion structures disperse the stress concentrated on the slit structure. By arranging the slit structure on the functional layer and arranging the plurality of dispersion structures on the circumferential side of the slit structure, after the substrate is connected to the surface, the stress of the functional layer is concentrated on the circumferential side of the slit structure, the slit structure can concentrate and amplify the stress generated by the slight deformation, so as to ensure the sensitivity of the strain sensor, and the plurality of dispersion structures disperse the stress concentrated on the circumferential side of the slit structure, so as to improve the durability and ductility of the strain sensor, and increase the range of the flexible strain sensor.

Description

Technical Field

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

[0002] With the rapid development of the Internet of Things and 5G mobile communication technology, sensors are widely used in various industries. Flexible strain sensors, as an important branch, are widely used in fields such as human movement and health monitoring due to their unique extensibility and deformability.

[0003] Traditional flexible strain sensors inherently contradict the requirements of high precision, wide measurement range, and high durability due to the unique properties of their flexible substrates. Researchers have attempted to use modified polymers as substrate materials for flexible strain sensors to improve their ductility and measurement range. However, the introduction of polymers inevitably sacrifices the precision and sensitivity of the flexible strain sensors to some extent, making them unsuitable for detecting minute deformations and movements.

[0004] However, in existing designs, while adding a single biomimetic microstructure can greatly improve its sensitivity and accuracy, it inevitably leads to varying degrees of decline in its durability and ductility, resulting in a need to improve the range of strain sensors and thus limiting the expansion of their application areas.

[0005] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0006] In view of the above problems, this application provides a flexible strain sensor and its fabrication method, which can increase the range of the strain sensor while ensuring high sensitivity sensing.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] The first aspect of this application provides a flexible strain sensor, comprising:

[0009] A substrate, used for bonding to a surface;

[0010] A functional layer is connected to the substrate, and the functional layer has a slit structure on the side opposite to the substrate, and a plurality of dispersed structures are provided on at least one side of the slit structure;

[0011] When the functional layer is subjected to force, the stress is dispersed and concentrated in the slot structure by the dispersion structure.

[0012] In one possible implementation, a plurality of the dispersed structures are respectively provided on both sides of the slit structure; and / or

[0013] The dispersed structure is a curved hole, and a plurality of the curved holes are distributed along the extension direction of one side of the slit structure.

[0014] In one possible implementation, the curved hole includes a circular hole and / or an elliptical hole;

[0015] Multiple circular holes or multiple elliptical holes are evenly distributed on one side of the slot structure; or

[0016] The circular holes and the elliptical holes are interspersed on one side of the slit structure.

[0017] In one possible implementation, the slot structure is a linear groove, the functional layer has a first longitudinal side and a second longitudinal side, one end of the linear groove is located on the first longitudinal side, and the other end of the linear groove is located on the second longitudinal side.

[0018] In one possible implementation, the distance between the two sides of the linear groove at each transverse position of the functional layer along the longitudinal direction of the functional layer is equal, and both sides of the linear groove are straight and / or curved.

[0019] In one possible implementation, the depth of the linear groove is in the range of 1 / 3 to 2 / 3 of the thickness of the functional layer.

[0020] One possible implementation also includes:

[0021] A surface layer is connected to the side of the functional layer opposite to the base layer, and the surface layer has a clearance structure that avoids the dispersion structure. The conductivity of the surface layer is greater than that of the functional layer.

[0022] In one possible implementation, the seam structure is located at the longitudinal center of the functional layer, and the plurality of circular holes on both sides of the functional layer are symmetrically arranged about the seam structure.

[0023] A second aspect of this application provides a method for fabricating a flexible strain sensor, the method being used to fabricate the flexible strain sensor described in any of the above claims, the method comprising:

[0024] Preparation of flexible thin films and substrates;

[0025] A slit structure is formed on the flexible film, and a plurality of dispersed structures are formed on at least one side of the slit structure to obtain a functional layer;

[0026] After the functional layer is placed on the substrate and cured, a flexible strain sensor is obtained.

[0027] In one possible implementation, the dispersed structure is a curved hole, and the functional layer is a functional layer with distributed curved holes;

[0028] The formation of multiple dispersed structures on at least one side of the seam structure results in a functional layer, including:

[0029] Multiple evenly distributed curved holes are opened on both sides of the seam structure to obtain a functional layer with distributed curved holes; wherein, the multiple curved holes on one side of the seam structure correspond one-to-one with the multiple curved holes on the other side.

[0030] Beneficial Effects: This invention provides a flexible strain sensor and its fabrication method. The strain sensor includes: a substrate for connection to a surface; and a functional layer connected to the substrate. The functional layer has a slit structure on its side facing away from the substrate, and multiple dispersion structures on at least one side of the slit structure. When the functional layer is subjected to force, the dispersion structures disperse the stress concentrated on the slit structure. By providing a slit structure on the functional layer and multiple dispersion structures around the slit structure, after the substrate is connected to the surface, the stress on the functional layer is concentrated around the slit structure. The slit structure can concentrate and amplify the stress generated by minute deformations to ensure the sensitivity of the strain sensor. Furthermore, by dispersing the stress concentrated around the slit structure through multiple dispersion structures, the durability and ductility of the strain sensor are improved, and the measurement range of the flexible strain sensor is increased. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application 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 some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A three-dimensional schematic diagram of a flexible strain sensor provided in an embodiment of this application;

[0033] Figure 2 This is a planar schematic diagram of the slit structure in the open state provided in an embodiment of this application;

[0034] Figure 3 This is a schematic diagram of the stress distribution structure and the seam structure under surface stress concentration provided in the embodiments of this application;

[0035] Figure 4 This is a schematic diagram of the stress on the seam structure when surface stress concentration occurs in the prior art.

[0036] Figure 5 Provided for the embodiments of this application Figure 1 A schematic diagram from a mid-top view;

[0037] Figure 6 Provided for the embodiments of this application Figure 1A schematic diagram from a mid-side view;

[0038] Figure 7 Provided for the embodiments of this application Figure 1 A schematic diagram under a mid-section view.

[0039] Explanation of reference numerals in the attached figures:

[0040] 10. Base;

[0041] 20. Functional layer; 21. Slot structure; 22. Dispersed structure;

[0042] 30. Surface layer. Detailed Implementation

[0043] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0044] The inventors of this invention discovered that the unique properties of the flexible substrate in traditional flexible strain sensors inherently contradict the requirements for high precision, wide measurement range, and high durability. Researchers have attempted to use modified polymers as the substrate material for flexible strain sensors to improve their ductility and measurement range. However, the introduction of polymers inevitably sacrifices the precision and sensitivity of the flexible strain sensor to some extent, making it difficult to apply to the detection of minute deformations. Simultaneously, while adding a single biomimetic microstructure can significantly improve sensitivity and precision, it inevitably leads to varying degrees of decrease in durability and ductility, resulting in a need to expand the measurement range of the strain sensor and thus limiting its application scope.

[0045] Based on this, in one embodiment of the present invention provided by the inventors, a slot structure is provided on the functional layer, and multiple dispersed structures are provided around the slot structure. After the substrate is connected to the surface, the stress on the functional layer is concentrated around the slot structure. The slot structure can concentrate and amplify the stress generated by small deformations to ensure the sensitivity of the strain sensor. The stress concentrated around the slot structure is dispersed by multiple dispersed structures, thereby improving the durability and ductility of the strain sensor and increasing the range of the flexible strain sensor.

[0046] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0047] See Figure 1 and Figure 2 This application provides a flexible strain sensor, comprising:

[0048] Base 10, for bonding to a surface;

[0049] A functional layer 20 is connected to the substrate 10. The functional layer 20 has a slit structure 21 on the side opposite to the substrate 10, and a plurality of dispersed structures 22 are provided on at least one side of the slit structure 21.

[0050] When the functional layer 20 is subjected to force, the dispersion structure 22 disperses the stress concentrated on the slit structure 21.

[0051] It is worth noting that the surface can be planar or curved, including arc or irregular surfaces. The substrate 10 and the functional layer 20 are elastic. After the substrate 10 (i.e., the base adhesive layer, which is non-conductive) and the functional layer 20 (i.e., the composite conductive functional layer 20) are stacked, and the substrate 10 is connected to the planar or curved surface, when the functional layer 20 is subjected to tension or compression, the slot structure 21 (i.e., crack) on the functional layer 20 bears concentrated stress. The stress is relieved by the dispersion structure 22 (i.e., the unloading hole structure) around the slot structure 21. Figure 3 The stress is distributed and borne by the joint structure 21 (as shown), reducing the stress on the joint structure 21. This makes it less likely for the joint structure 21 to exceed its stress limit during use, improving durability and ductility. This allows the invention to withstand forces that existing joint structures 21 (without pores on the periphery) cannot bear, such as... Figure 3 , Figure 4 and Figure 5 As shown, the combined effect of the slit structure 21 and the dispersion structure 22 improves the accuracy of the strain sensor for a larger range, ensuring not only good sensitivity and accuracy but also increasing the range. Under the same size, the strain sensor of the present invention can have a wide range.

[0052] The inventive concept of this invention is a multi-level flexible strain sensor with a multi-level biomimetic microstructure designed based on the unique sensory structure of a typical biological scorpion. It can achieve accurate identification and perception of minute deformations while also enhancing the range of the strain sensor. This allows the strain sensor to have a wider range while having the same size as existing sensors. It achieves an effective combination of multi-level biomimetic microstructures, namely the combination of the dispersed structure 22 and the slit structure 21, as well as the mapping of biological multi-level structures on the device.

[0053] By mimicking the crack-sensing structure of a scorpion's leg, the dense porous structure around the crack, and the gradient multi-level structure of its exoskeleton, a multi-layered flexible strain sensor with multiple biomimetic microstructures was designed. Utilizing biomimetic principles, this sensor achieves a wide range of sensing capabilities for both large and small deformation motion monitoring, while also ensuring overall durability and strength. Through the unloading hole structure (i.e., the dispersion structure 22), the stress concentration and ultra-sensitive sensing capabilities of the seam structure 21 are retained while effectively controlling the stress concentration range and intensity, maximizing overall strength and ensuring high durability. Furthermore, the multi-level structural composite increases the overall tensile strength of the sensor, expanding its measurement range.

[0054] Understandably, the scorpion's surface suture receptors can collect and sense weak mechanical signals through stress amplification. Generally, such a crack structure 21 would lead to safety hazards for the entire structure, making it more prone to breakage than a complete structure. However, the scorpion's surface suture receptors can continue to function normally throughout its lifespan, thanks to the densely distributed circular holes around them. These holes prevent safety hazards caused by excessive stress concentration (along with the gradient structure). This multi-layer flexible strain sensor, composed of multiple biomimetic microstructures, maps the aforementioned biological sensing principle of the scorpion's suture receptors to a mechanical sensing mechanism. The fundamental principle of this hole protection mechanism is that before the stress reaches the crack structure 21, a small-scale stress concentration occurs at the unloading holes on both sides, dispersing the stress before it reaches the crack. This controls the range and intensity of stress concentration, thus enabling this multi-layer flexible strain sensor to retain high sensitivity while also possessing the ability to monitor large and small deformations and movements, increasing its measurement range.

[0055] In the above embodiments, such as Figure 1 The strain sensor shown is presented in a rectangular (top view) form. In actual manufacturing, the strain sensor can be set into various shapes, such as ellipse or polygon, and the size of the strain sensor can be modified according to actual needs.

[0056] In some embodiments, such as Figure 1 , Figure 2 and Figure 3 As shown, multiple dispersed structures 22 are respectively provided on both sides of the slit structure 21; and / or

[0057] The dispersion structure 22 is a curved hole, and the plurality of the curved holes are evenly distributed along the extension direction of one side of the slit structure 21.

[0058] Specifically, curved holes are holes without sharp edges to prevent them from bearing excessive stress around their corners; for example... Figure 1As shown, the functional layer 20 is rectangular, with its short side running horizontally and its long side running vertically. Multiple curved holes are evenly distributed along the extension direction of one side of the seam structure 21. It should be noted that the extension direction of one side (i.e., one edge) of the seam structure 21 can be horizontal or curved. In short, the centers of the multiple curved holes located on one side of the seam structure 21 are equidistant from the side (edge) of the seam structure 21. Figure 5 As shown, the distance from the center of the curved hole to the center of the slit structure 21 is 1. Multiple curved holes on the other side of the slit structure 21 are similarly configured, and will not be described further here.

[0059] Furthermore, by setting curved holes on both sides of the slit structure 21, the stress concentration points on both sides of the slit structure 21 are distributed. Under the premise that the size of the functional layer 20 is fixed, the more curved holes there are, the smaller the interval between them, the more uniform their shape, and the smaller their size, the better the stress is distributed by the slit structure 21 located in the center of the two sets of curved holes, thereby increasing the range of the strain sensor.

[0060] It should be noted that in existing technologies, the stress dispersion structure 22 is not provided around the crack. Although the sensitivity is high, this excessive sensitivity results in a very small measurement range, meaning that even unintentional wind ripples can cause the strain sensor to fail due to insufficient stress. This invention, however, ensures the strain sensor's sensitivity, enabling precise detection of minute deformations. Furthermore, the multiple curved holes around the crack structure 21 ensure better durability and ductility, thus enhancing the strain sensor's measurement range. This results in a wide-range strain sensor applicable to various fields, expanding its application scope.

[0061] It should be noted that, since the size of the strain sensor is set according to actual needs, the size and number of multiple curved holes, the spacing between the curved holes, and the distance from the center of the curved hole to the center of the slit structure 21 can be set according to actual needs, so as to increase the range of the strain sensor at this size while ensuring the sensitivity of the strain sensor.

[0062] In some embodiments, the curved hole includes a circular hole and / or an elliptical hole;

[0063] Multiple circular holes or multiple elliptical holes are evenly distributed on one side of the slot structure 21; or

[0064] The circular holes and the elliptical holes are interspersed on one side of the slit structure 21.

[0065] Specifically, in this embodiment, such as Figure 1 and Figure 3As shown, multiple circular holes are evenly distributed on each side (both sides) of the slit structure 21. That is, the multiple circular holes are arranged in an array along a path parallel to the side (edge) of the slit structure 21. When the curved holes are circular holes, the stress dispersion effect is more uniform. In addition, both sides of the slit structure 21 are straight lines (or curves or lines including curves and straight lines), which allows the strain sensor to retain its detection durability and ductility to the greatest extent, increases the range, and the resulting wide-range strain sensor has a wider range of application scenarios.

[0066] In this embodiment, the seam structure is located in the longitudinal center of the functional layer, and the plurality of circular holes on both sides of the functional layer are symmetrically arranged with respect to the seam structure.

[0067] In some embodiments, such as Figure 1 and Figure 3 As shown, the seam structure 21 is a linear groove, and the functional layer 20 has a first longitudinal side and a second longitudinal side. One end of the linear groove is located on the first longitudinal side, and the other end of the linear groove is located on the second longitudinal side.

[0068] Specifically, such as Figure 5 As shown, the upper and lower sides of the functional layer 20 are longitudinal sides, with one end of the linear groove on the first longitudinal side and the other end on the second longitudinal side. The linear groove runs through the functional layer 20 along its transverse direction. It should be noted that the width of the linear groove (i.e., the crack) (i.e., the distance between the two sides at a certain location) is relatively small. When the strain sensor is placed on a plane and viewed from above, the crack structure 21 appears as a line. This linear groove can be a straight line or a curve, depending on the characteristics of the surface to which the substrate 10 is connected or the specific directional force experienced by the functional layer 20.

[0069] Furthermore, such as Figure 1 and Figure 2 As shown, the cross-section of the linear groove is "V" shaped, meaning the linear groove faces away from the base 10. Figure 1 The top extends outwards, while the bottom of the linear groove in the functional layer 20 is straight or rounded, further ensuring its ductility and durability.

[0070] In some embodiments, the distance between the two sides of the linear groove at each transverse position of the functional layer 20 along the longitudinal direction of the functional layer 20 is equal, and both sides of the linear groove are straight and / or curved.

[0071] Specifically, such as Figure 1 and Figure 5As shown, in this embodiment, both sides of the linear groove are straight lines when viewed from above. The distance from the center of the linear groove to the circular holes on both sides of the linear groove is the same. That is, in this embodiment, the arrangement of the upper seam structure 21 and multiple circular holes on the functional layer 20 is more uniform, making the structure more stable. The circular holes have a better stress dispersion effect on the periphery of the linear groove, ensuring the durability and ductility of the strain sensor and improving its measurement range.

[0072] In another embodiment, the curved hole includes an elliptical hole, and at least a portion of the linear groove is curved, with the minor axis of the elliptical hole oriented towards the curved portion of the linear groove. When the linear groove also has a straight portion, the curved hole further includes circular holes distributed around the periphery of the straight portion to increase the range. The curved hole may also include holes with irregular arcs, corresponding to the irregularly shaped slit structure 21.

[0073] In some embodiments, such as Figure 1 and Figure 2 As shown, it also includes:

[0074] The surface layer 30 is connected to the side of the functional layer 20 that is away from the substrate 10, and the surface layer 30 has a clearance structure that avoids the dispersion structure 22. The conductivity of the surface layer 30 is greater than that of the functional layer 20.

[0075] Specifically, by setting the conductivity of the surface layer 30 to be greater than that of the functional layer 20, the strain sensor achieves higher sensitivity. The surface layer 30 comprises two layers located on both sides of the slit structure 21, which can be disposed separately or deposited together.

[0076] like Figures 1 to 3 As shown, this strain sensor is rectangular in shape and consists of three layers: a surface layer 30, a functional layer 20, and a base layer (substrate 10). The interlayer (functional layer 20) is the main body and is composed of a composite conductive functional layer 20 doped with conductive particles and SiO2 nanoparticles. The surface of the functional layer 20 has a surface layer 30 of conductive nanoparticles (such as gold and silver conductive nanoparticles) formed by conformal deposition. The bottom is a silicone rubber adhesive layer. The three layers together form a multilayer flexible strain sensor, forming a gradient structure with different material properties, which localizes the stress and strain, and gives the sensor better stretchability and ductility, thus enabling it to detect a wider range of deformation movements.

[0077] Among them, the composite conductive functional layer 20 has a slit structure 21 (i.e., crack structure) and an unloading hole structure (i.e., curved hole, the formation of which precedes the deposition of conductive nanoparticles). The crack structure is a single slit structure 21 parallel to the short side of the functional layer 20, and the unloading hole structure is a hole structure (circular hole) uniformly and symmetrically distributed on both sides of the slit structure 21, forming a multilayer flexible strain sensor with multiple biomimetic microstructures.

[0078] It is worth noting that pre-fabricating the slit structure 21 in the composite conductive functional layer 20 allows the conductive nanoparticle surface layer 30, which is conformally deposited on its surface, to naturally generate micron-level cracks after processing, without the need for secondary processing. Based on its unique stress concentration effect, this structure concentrates and amplifies the extremely small stress generated by minute deformations, thereby significantly improving the sensitivity of the multilayer flexible strain sensor composed of multiple biomimetic microstructures, supporting the sensor's ultra-sensitive detection of minute deformations. The presence of the slit structure 21 significantly improves the overall sensitivity of the sensor, but also leads to a decrease in the sensor's durability and range. At this point, the pre-fabricated unloading hole structure comes into play. The presence of the hole structure effectively limits the area and degree of stress concentration effect generated by the slit structure 21. Compared with traditional flexible sensors, this biomimetic flexible strain sensor coupled with a complex multilevel microstructure and heterogeneous multilayer materials achieves a wide detection range and high durability to the greatest extent while improving its sensitivity.

[0079] In some embodiments, the depth of the linear groove is in the range of 1 / 3 to 2 / 3 of the thickness of the functional layer 20.

[0080] Specifically, such as Figure 7 As shown, the linear groove is V-shaped and its depth is 1 / 2 of the thickness of the functional layer 20.

[0081] Furthermore, in this embodiment, as Figure 5 , Figure 6 and Figure 7 As shown, the functional layer 20 and the substrate 10 have a width of 5 mm and a length of 20 mm. The substrate 10 has a thickness of 0.5 mm, the functional layer 20 has a thickness of 1 mm, the linear groove has a depth of 0.5 mm, the surface layer 30 has a thickness of 0.12 mm, the circular hole diameter is 0.5 mm, and four circular holes are distributed on each side of the linear groove. The distance between the centers of every two circular holes is 1 mm, and the distance between the center of the circular hole and the center of the linear groove is 1 mm.

[0082] Based on the above embodiments, this application also provides a method for fabricating a flexible strain sensor, the method being used to fabricate the aforementioned flexible strain sensor. The method includes the following steps:

[0083] Step S100: Prepare flexible thin film and substrate.

[0084] In one implementation, step S100 specifically includes:

[0085] Step S110: Prepare a flexible thin film. Specifically, this includes:

[0086] Step S111: Dissolve flexible polymers such as silicone rubber in an organic solvent, and then dop them with conductive particles such as carbon black, graphene, carbon nanotubes, and other modifying materials such as SiO2 nanoparticles to further improve the mechanical properties of the molded polymer film. Use an ultrasonic vibrator, magnetic stirrer, and other equipment to make a suspension.

[0087] Step S112: Using equipment such as a vacuum drying oven, the suspension is formed into a uniform flexible film, which is then cut into equal-sized rectangles using a laser marking machine. The prepared flexible film prepares for the subsequent fabrication of the functional layer of a multilayer flexible strain sensor with multiple biomimetic microstructures.

[0088] Step S120: Prepare the substrate. Specifically, this includes:

[0089] Step S121: Use materials such as PDMS with high shear strength and low elastic modulus to form a smooth film of uniform thickness. This smooth film, before curing, serves as the substrate for the functional layers to be connected.

[0090] Step S200: A slit structure is formed on the flexible film, and a plurality of dispersed structures are formed on at least one side of the slit structure to obtain a functional layer.

[0091] In one implementation, the dispersed structure is a curved hole, and the functional layer is a functional layer with distributed curved holes; step S200 specifically includes:

[0092] Step S210: Multiple evenly distributed curved holes are opened on both sides of the seam structure to obtain a functional layer with distributed curved holes; wherein, the multiple curved holes on one side of the seam structure correspond one-to-one with the multiple curved holes on the other side.

[0093] Specifically, using equipment such as paper cutters and laser marking machines, the functional layer is pre-processed, and a linear groove with a depth of about 1 / 2 of the thickness of the functional layer is cut out in its center. Uniform and symmetrical through holes are opened on both sides to form a circular hole similar to a biological hole (i.e., unloading hole structure).

[0094] Following step S200, the following step is also included:

[0095] Step S220: Sputter conductive nanoparticles such as gold or silver onto the side of the pretreated functional layer with linear grooves, and conformally deposit a surface layer with multiple biomimetic microstructures on its surface.

[0096] Step S300: After the functional layer is placed on the substrate and cured, a flexible strain sensor is obtained.

[0097] Specifically, the unstructured side of the functional layer is placed on an uncured substrate, and after the substrate is cured, it is cut into a rectangle to complete the fabrication of a multilayer flexible strain sensor with multiple biomimetic microstructures.

[0098] Below, in conjunction with Figure 1 , Figure 5 , Figure 6 and Figure 7 The fabrication process of the flexible strain sensor is explained below:

[0099] S1. Prioritize the preparation of the composite conductive functional layer. Pour 0.7g of CB nanoparticles (BLACK PEEARLS2000) and 0.5g of SiO2 nanoparticles (particle size 20nm) into 37ml of n-hexane (AR analytical grade) and stir evenly for 5min using a magnetic stirrer.

[0100] Alternatively, other organic solvents besides n-hexane can be selected in S1, such as acetone, ethyl acetate, etc. Relatively speaking, n-hexane has lower toxicity and price.

[0101] S2. Place the well-stirred CB nanoparticles, SiO2 nanoparticles and n-hexane mixture into an ultrasonic vibrator and perform ultrasonic vibration for up to 30 minutes to ensure that the nanoparticles are uniformly mixed and distributed in the n-hexane solution to form a stable CB-SiO2-n-hexane suspension.

[0102] S3. After ultrasonic vibration, add 10g of silicone rubber (Zhonglan Chenguang GD-401 single-component room temperature vulcanized silicone rubber with a tensile strength of 1MPa) to the CB-SiO2 blend solution, and stir at high speed for 8 hours using a magnetic stirrer to ensure that the silicone rubber is fully dissolved and uniformly mixed to form a CB-SiO2-n-hexane-silicone rubber solution.

[0103] Alternatively, in addition to the single-component room temperature vulcanizing silicone rubber selected above, other types may be selected, such as two-component silicone rubber or silicone rubber cured under specific conditions, but the above-mentioned types of materials are selected to simplify the preparation process.

[0104] S4. Wipe two 10cm diameter round glass petri dishes thoroughly with alcohol, let them dry, and ensure that there is no alcohol residue on the surface. Then, pour 22g of the thoroughly stirred CB-SiO2-n-hexane-silicone rubber mixed solution into each dish.

[0105] S5. To prevent the formation of cavities inside the CB-SiO2-n-hexane-silicone rubber solution during solidification, a vacuum device is used to fully remove air bubbles from the CB-SiO2-n-hexane-silicone rubber solution in the glass petri dish and distribute them evenly inside the petri dish.

[0106] S6. After ensuring that all air bubbles are expelled and the surface of the CB-SiO2-n-hexane-silicone rubber solution is smooth and free of bumps, place the glass petri dish in a vacuum drying oven. To accelerate the drying process, set the temperature to 50°C above room temperature and heat and dry in a vacuum environment for more than 8 hours.

[0107] S7. After confirming that the solution has completely solidified into a film, the prepared CB-SiO2-n-hexane-silicone rubber film is taken out and cut using a laser marking machine to divide it into rectangles of equal size of 5mm×20mm, thus completing the preparation of the flexible film.

[0108] S8. Subsequently, the flexible film is pre-processed by cutting a slit structure with a depth of 1 / 2 the thickness of the flexible film in the center of the flexible film using a cutting machine.

[0109] S9. Using a laser marking machine, 5 pairs of symmetrical and equal-sized holes are punched on both sides of the central seam structure to form a load-bearing hole structure (i.e., round holes). The diameter of a single hole is 0.5 mm, the distance between the hole and the central seam structure is 1 mm, and the distance between two holes is 1 mm. This completes the pre-processing of the flexible film and obtains the composite conductive functional layer.

[0110] S10. A 120 nm thick silver nanoparticle film is deposited on the side of the composite conductive functional layer with microstructure using a magnetron sputtering coating instrument (108 auto Cressington sputter cover) to form the surface layer of a multilayer flexible strain sensor with multiple biomimetic microstructures.

[0111] Alternatively, other nanoparticles with good conductivity, such as gold, can be sputtered, but silver has good conductivity and is relatively inexpensive.

[0112] S11. Pour PDMS (Dow Corning DC184 / SYLGARD184 with tensile strength 7.1MPa) and its corresponding curing agent into any container after thorough mixing at a ratio of 10:1, and allow it to form a uniform adhesive layer of a certain thickness at the bottom of the container.

[0113] Alternatively, Dow Corning DC184 is chosen as the adhesive base material due to its quick-drying properties, low modulus of elasticity, and high tensile strength.

[0114] S12. Place the container with PDMS at the bottom in a vacuum instrument, remove air bubbles to ensure uniform texture, and when the PDMS is about to solidify, place the unstructured side of the composite conductive functional layer with silver nanoparticle deposition on the PDMS (i.e., the substrate) to bond the two together. After the PDMS is completely cured, remove it and trim it according to the shape to complete the fabrication of a multilayer flexible strain sensor with multiple biomimetic microstructures.

[0115] The method for preparing the flexible strain sensor provided by this invention is used to prepare the above-mentioned flexible strain sensor, thereby having all the beneficial effects of the above-mentioned flexible strain sensor, which will not be repeated here.

[0116] In the description of this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0117] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0118] Generally speaking, terms should be understood at least in part by their use in context. For example, at least in part by context, the term "one or more" as used in the text can be used to describe any feature, structure, or characteristic of the singular meaning, or a combination of features, structures, or characteristics of the plural meaning. Similarly, at least in part by context, terms such as "a" or "the" can also be understood to convey either singular or plural usage.

[0119] It should be readily understood that the terms “on,” “above,” and “on top of” in this disclosure should be interpreted in the broadest possible sense, such that “on” means not only “directly on something” but also “on something” with an intermediate feature or layer therebetween, and that “above” or “on top of” means not only “on top of something” but also “on top of something” without an intermediate feature or layer therebetween (i.e., directly on something).

[0120] For ease of explanation, spatial relative terms such as "below," "below," "under," "above," and "above" may be used to describe the relationship of an element or feature relative to other elements or features as shown in the figures. Spatial relative terms are intended to encompass different orientations of the device in use or operation other than those shown in the figures. The device may have other orientations (rotated 90 degrees or in other orientations), and the spatial relative descriptive terms used herein may be interpreted accordingly.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A flexible strain sensor, characterized in that, include: A substrate, used for bonding to a surface; A functional layer is connected to the substrate, and the functional layer has a slit structure on the side opposite to the substrate, and a plurality of dispersed structures are provided on at least one side of the slit structure; When the functional layer is subjected to force, the dispersion structure disperses and concentrates the stress in the slot structure; Multiple dispersed structures are provided on both sides of the slit structure; The dispersed structure is a curved hole, and a plurality of the curved holes are distributed along the extension direction of one side of the slit structure; The curved hole includes a circular hole and / or an elliptical hole; The plurality of circular holes or the plurality of elliptical holes are evenly distributed on one side of the slit structure; or the circular holes and the elliptical holes are interspersed on one side of the slit structure; The seam structure is located in the longitudinal center of the functional layer, and the plurality of circular holes on both sides of the functional layer are symmetrically arranged about the seam structure; Also includes: A surface layer is connected to the side of the functional layer opposite to the base layer, and the surface layer has a clearance structure to avoid the dispersion structure, and the conductivity of the surface layer is greater than that of the functional layer; The material of the functional layer is a silicone rubber composite material doped with conductive particles and SiO2 nanoparticles. The surface layer is a silver nanoparticle film formed by magnetron sputtering deposition.

2. The flexible strain sensor according to claim 1, characterized in that, The seam structure is a linear groove, and the functional layer has a first longitudinal side and a second longitudinal side. One end of the linear groove is located on the first longitudinal side, and the other end of the linear groove is located on the second longitudinal side.

3. The flexible strain sensor according to claim 2, characterized in that, The distance between the two sides of the linear groove at each transverse position of the functional layer along the longitudinal direction of the functional layer is equal, and both sides of the linear groove are straight and / or curved.

4. The flexible strain sensor according to claim 2, characterized in that, The depth of the linear groove is in the range of 1 / 3 to 2 / 3 of the thickness of the functional layer.

5. A method for fabricating a flexible strain sensor, characterized in that, The method is used to prepare the flexible strain sensor according to any one of claims 1 to 4, and the method includes: Preparation of flexible thin films and substrates; A slit structure is formed on the flexible film, and a plurality of dispersed structures are formed on at least one side of the slit structure to obtain a functional layer; After the functional layer is placed on the substrate and cured, a flexible strain sensor is obtained.

6. The method for fabricating a flexible strain sensor according to claim 5, characterized in that, The dispersed structure is a curved hole, and the functional layer is a functional layer with distributed curved holes; The formation of multiple dispersed structures on at least one side of the seam structure results in a functional layer, including: Multiple evenly distributed curved holes are opened on both sides of the seam structure to obtain a functional layer with distributed curved holes; wherein, the multiple curved holes on one side of the seam structure correspond one-to-one with the multiple curved holes on the other side.

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