Ultra-wide linear flexible force sensor based on bionic frog and preparation method thereof

Abstract

The invention belongs to the technical field of flexible force sensing, and provides an ultra-wide linear flexible force sensor based on a bionic frog and a preparation method thereof, and the ultra-wide linear flexible force sensor comprises a sensing assembly, a first packaging layer and a second packaging layer. The sensing assembly comprises an elastic adjusting mechanism, a first insulating layer, a first electrode layer, a second electrode layer, a second insulating layer and a composite shell, the elastic adjusting mechanism is of an axial symmetry structure and is embedded in the composite shell, and the center of the elastic adjusting mechanism and the center of the composite shell are located on the same straight line. The bionic frog elastic adjusting mechanism is guided by stress deformation, the elastic adjusting mechanism generates negative Poisson's ratio transverse deformation so as to accurately detect force, and the negative Poisson's ratio based on the bionic frog elastic adjusting mechanism is combined with the composite shell. The flexible sensor has the advantages of wider range, higher linearity, good response time, periodic stability and sensitivity in two modes of stretching and compression.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible force sensors, and in particular relates to an ultra-wide linear flexible force sensor based on a bionic frog and a preparation method thereof. Background Art

[0002] Flexible sensors have the characteristics of fast response, environmental adaptability and cyclic stability, and have become a research hotspot in the field of modern intelligent sensing. Specifically, in the fields of motion perception of continuum robots, enhanced perception of soft robots and intention recognition of electronic gloves, flexible sensing shows a wide range of application needs. At the same time, flexible sensors have attracted much attention due to their wide applicability in human-machine interfaces and health detection. Flexible sensors are widely used in the field of human physiological signal monitoring in the field of smart wearables, such as pulse, muscle, joint movement and gait recognition, due to their excellent sensitivity, flexibility and wearability. However, it is still challenging to maintain good linear sensitivity over a wide pressure range.

[0003] At present, most foam-based force sensors can only achieve compression sensing, and cannot guarantee good linearity and a large range during compression. Patent No. CN118027499A discloses a rubber foam sensor and its preparation method. Its sensitivity and linear range are restricted by lateral expansion and lack of skeleton support during compression, resulting in poor sensing performance. Therefore, it is necessary to design an ultra-wide linear flexible force sensor based on a bionic frog and its preparation method. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides an ultra-wide linear flexible force sensor based on a bionic frog and a preparation method thereof. The force deformation is guided by a bionic elastic adjustment mechanism, and the elastic adjustment mechanism produces a negative Poisson's ratio lateral deformation to accurately detect the force. The negative Poisson's ratio based on the bionic frog elastic adjustment mechanism is combined with a composite shell to achieve accurate measurement of an ultra-wide linear range of force in both tension and compression modes, and has the advantages of high sensitivity, wide perception range, good linearity, etc.

[0005] The present invention provides an ultra-wide linear flexible force sensor based on a bionic frog, which includes a sensing component, a first packaging layer and a second packaging layer, the sensing component includes an elastic adjustment mechanism, a first insulating layer, a first electrode layer, a second electrode layer, a second insulating layer and a composite shell, the elastic adjustment mechanism is an axisymmetric structure, the elastic adjustment mechanism is embedded in the composite shell, and the center of the elastic adjustment mechanism is on the same straight line as the center of the composite shell, a first wire passes through the first packaging layer and is connected to the first electrode layer, a second wire passes through the first packaging layer and is connected to the second electrode layer, first end surfaces of the first electrode layer and the second electrode layer are respectively connected to two ends of the composite shell, the first insulating layer is connected to the second end surface of the first electrode layer, the second insulating layer is connected to the second end surface of the second electrode layer, and the first packaging layer is arranged on the second packaging layer; the elastic adjustment mechanism includes a first branch chain, a second branch chain, a third branch chain, a fourth branch chain, a fifth branch chain, a sixth branch chain, a seventh branch chain, an eighth branch chain, a ninth branch chain, a tenth branch chain, an eleventh branch chain, a twelfth branch chain, a thirteenth branch chain and a second branch chain Fourteen branches, the first end of the first branch is connected to the first end of the second branch and the first end of the third branch respectively, the second end of the second branch is connected to the first end of the fourth branch, the second end of the third branch is connected to the first end of the fifth branch, the second end of the fifth branch is connected to the first end of the seventh branch, the first end of the ninth branch and the first end of the eleventh branch respectively, the second end of the fourth branch is connected to the first end of the sixth branch, the first end of the eighth branch and the first end of the tenth branch respectively, the second end of the tenth branch is connected to the first end of the twelfth branch, the second end of the eleventh branch is connected to the first end of the thirteenth branch, and the first end of the fourteenth branch is connected to the second end of the twelfth branch and the second end of the thirteenth branch respectively; in the contraction and extension modes, the elastic adjustment mechanism is subjected to force deformation to generate negative Poisson's ratio lateral deformation, and the contraction and extension process of the elastic adjustment mechanism is as follows: Extension and contraction: when the first branch and the fourteenth branch in the elastic adjustment mechanism are subjected to compression along the Y-axis direction, the first angle θ between the first branch and the third branch 1 , the second angle θ between the third branch chain and the fifth branch chain 2 and the angles on the axisymmetric branches of the first branch chain, the third branch chain and the fifth branch chain are all reduced, so that the elastic adjustment mechanism shrinks inwardly along the X-axis direction, and the composite shell shrinks inwardly under pressure and stretches: when the first branch chain and the fourteenth branch chain in the elastic adjustment mechanism are subjected to a tensile force along the Y-axis direction, the first angle θ between the first branch chain and the third branch chain is 1 , the second angle θ between the third branch chain and the fifth branch chain 2And the angles on the axially symmetrical branches of the first branch chain, the third branch chain and the fifth branch chain are all increased, so that the elastic adjustment mechanism extends outward along the X-axis direction, and the composite shell extends outward under tension.

[0006] Preferably, in the initial state of the elastic adjustment mechanism, a first angle θ between the first branch chain and the third branch chain is 1 is 45°, and the second angle θ between the third branch chain and the fifth branch chain is 2 is 25°, and the third angle θ between the fifth branch chain and the seventh branch chain is 3 is 25°.

[0007] Preferably, the length ratio of the first branch, the third branch, the fifth branch and the seventh branch is 1:1:1:0.8.

[0008] Preferably, the first electrode layer and the second electrode layer are both copper films.

[0009] Preferably, the first encapsulation layer and the second encapsulation layer are both made of 10-30 Shore hardness silicone casting.

[0010] Preferably, both the first insulating layer and the second insulating layer are polyimide films.

[0011] In a second aspect, the present invention further provides a method for preparing an ultra-wide linear flexible force sensor based on a bionic frog, the steps of which include:

[0012] S1. Preparation of sugar-based silica gel:

[0013] Mixing silica gel liquid A and silica gel liquid B of the same mass and stirring them thoroughly to obtain mixed silica gel, and mixing sugar crystals and the mixed silica gel in a ratio of 9:1 and stirring them uniformly to obtain sugar-based silica gel;

[0014] S2. Preparation of sugar-based silica gel layer and sugar-based silicone rubber:

[0015] The first part of the sugar-based silicone is poured into a 3D-printed rectangular mold and compacted to form a compacted sugar-based silicone layer in the rectangular mold, the elastic adjustment mechanism is placed on the compacted sugar-based silicone layer, and the second part of the sugar-based silicone is poured into the rectangular mold and compacted, and after drying at 100 to 120° C. for 2 to 4 hours, the silicone is cured to obtain sugar-based silicone rubber;

[0016] S3: Preparation of skeleton foam:

[0017] Soak the sugar-based silicone rubber obtained in step S2 in water at 50-70° C. for 24-36 hours, take it out after the sugar crystals are dissolved, and obtain a silicone foam with an elastic adjustment mechanism embedded inside, and dry the silicone foam at 120-150° C. for 4-6 hours to obtain a skeleton foam;

[0018] S4: Preparation of conductive skeleton foam:

[0019] Immersing the skeleton foam in a graphene aqueous dispersion, and drying at a pressure of 0 to 0.01 kPa and a temperature of 120 to 150° C. for 8 to 10 hours to obtain a conductive skeleton foam;

[0020] S5: Packaged force sensor:

[0021] The conductive skeleton foam, the electrode layer and the insulating layer are encapsulated in the encapsulation layer. The conductive skeleton foam, the electrode layer and the insulating layer use conductive silver paste as a binder. The first encapsulation layer and the second encapsulation layer use silicone glue as a binder. After the conductive silver paste and the silicone glue are completely dry, an ultra-wide linear flexible force sensor is made.

[0022] Preferably, the preparation method of the elastic adjustment mechanism in step S3 is: mixing silicone liquid A and silicone liquid B of the same mass, stirring and vacuuming to obtain mixed silicone, pouring the mixed silicone into a 3D printed white resin mold, and standing at room temperature and pressure for 6 to 8 hours to obtain the elastic adjustment mechanism.

[0023] Preferably, the preparation method of the graphene aqueous dispersion in step S4 is: mixing graphene powder and pure water in a mass ratio of 1:20, stirring and shaking the mixture with a magnetic stirrer for 45 to 60 minutes, and obtaining the graphene aqueous dispersion.

[0024] Preferably, the mass of water in step S3 is 15-20 times the mass of the silica gel curing mixture.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. The ultra-wide linear flexible force sensor based on the bionic frog of the present invention effectively improves the sensing range and linearity within the sensing range of the sensor by embedding a bionic frog-type elastic adjustment mechanism inside a composite shell. The bionic frog-type elastic adjustment mechanism is guided by force deformation. In both the stretching and compression modes, the elastic adjustment mechanism produces a negative Poisson's ratio lateral deformation, which effectively solves the problem of low sensor sensitivity caused by lateral contraction during stretching and lateral expansion during compression of traditional flexible sensors, and effectively improves the sensing range and sensing sensitivity.

[0027] 2. The ultra-wide linear flexible force sensor based on the bionic frog of the present invention uses silicone foam as the base material, so that the sensor has good fit and comfortable wearability, and uses graphene aqueous dispersion as the conductive material aqueous dispersion, so that the sensor has excellent conductivity and reliability of the output signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1aand Figure 1b It is a schematic diagram of the overall structure of the ultra-wide linear flexible force sensor based on the bionic frog of the present invention.

[0029] Figure 2 It is a schematic diagram of the elastic adjustment mechanism and structural force deformation of the ultra-wide linear flexible force sensor based on the bionic frog of the present invention.

[0030] Figure 3 The present invention is a flow chart for preparing the ultra-wide linear flexible force sensor based on the bionic frog.

[0031] Figure 4 The element mass fraction and carbon element distribution diagram of the composite shell in the ultra-wide linear flexible force sensor based on the bionic frog of the present invention.

[0032] Figure 5 This is a schematic diagram of the microstructure of the composite shell in the ultra-wide linear flexible force sensor based on the bionic frog of the present invention.

[0033] Figure 6a and Figure 6b This is a resistance characteristic analysis diagram of the ultra-wide linear flexible force sensor based on the bionic frog in the dual modes of compression and tension.

[0034] Figure 7a to Figure 7c Measurement graphs of the resistance change of the ultra-wide linear flexible force sensor based on the bionic frog at compressive strains of 7%, 15% and 30%, the resistance change after 300 cycles under 15% compressive strain, and the response time and recovery time of the sensor under 15% compressive strain.

[0035] Figure 8a to Figure 8c Measurement graphs of the resistance change of the ultra-wide linear flexible force sensor based on the bionic frog at tensile strains of 15%, 30% and 50%, the resistance change after 300 cycles under 15% tensile strain, and the response time and recovery time of the sensor under 15% tensile strain.

[0036] Main reference numerals:

[0037] 1-elastic adjustment mechanism, 2-first wire, 3-first insulating layer, 4-first electrode layer, 5-second packaging layer, 6-second electrode layer, 7-second wire, 8-second insulating layer, 9-first packaging layer, 10-composite shell, 111-first branch chain, 124-second branch chain, 121-third branch chain, 144-fourth branch chain, 141-fifth branch chain, 154-sixth branch chain, 151-seventh branch chain, 153-eighth branch chain, 152-ninth branch chain, 143-tenth branch chain, 142-eleventh branch chain, 123-twelfth branch chain, 122-thirteenth branch chain, 112-fourteenth branch chain. DETAILED DESCRIPTION

[0038] In order to fully describe the technical content, structural features, objectives and effects of the present invention, the following will be described in detail with reference to the accompanying drawings.

[0039] like Figure 1a and Figure 1b As shown, the ultra-wide linear flexible force sensor based on the bionic frog of the present invention includes a sensing component, a first packaging layer 9 and a second packaging layer 5. The sensing component includes an elastic adjustment mechanism 1, a first insulating layer 3, a first electrode layer 4, a second electrode layer 6, a second insulating layer 8 and a composite shell 10. The elastic adjustment mechanism 1 is an axisymmetric structure. The elastic adjustment mechanism 1 is embedded in the composite shell 10, and the center of the elastic adjustment mechanism 1 and the center of the composite shell 10 are on the same straight line. The first wire 2 passes through the first packaging layer 9 to connect with the first electrode layer 4, the second wire 7 passes through the first packaging layer 9 to connect with the second electrode layer 6, the first end faces of the first electrode layer 4 and the second electrode layer 6 are respectively connected to the two ends of the composite shell 10, the first insulating layer 3 is connected to the second end face of the first electrode layer 4, the second insulating layer 8 is connected to the second end face of the second electrode layer 6, the first packaging layer 9 is arranged on the second packaging layer 5, the first electrode layer 4 and the second electrode layer 6 are both copper films, the first insulating layer 3 and the second insulating layer 8 are both polyimide films, and the first packaging layer 9 and the second packaging layer 5 are both made of 10-30 Shore hardness silicone casting.

[0040] like Figure 2As shown, the elastic adjustment mechanism 1 includes a first branch chain 111, a second branch chain 124, a third branch chain 121, a fourth branch chain 144, a fifth branch chain 141, a sixth branch chain 154, a seventh branch chain 151, an eighth branch chain 153, a ninth branch chain 152, a tenth branch chain 143, an eleventh branch chain 142, a twelfth branch chain 123, a thirteenth branch chain 122 and a fourteenth branch chain 112. The first end of the first branch chain 111 is respectively connected to the first end of the second branch chain 124 and the first end of the third branch chain 121, the second end of the second branch chain 124 is connected to the first end of the fourth branch chain 144, the second end of the third branch chain 121 is connected to the first end of the fifth branch chain 141, the second end of the fifth branch chain 141 is respectively connected to the first end of the seventh branch chain 151, the first end of the ninth branch chain 152 and the first end of the eleventh branch chain 142, and the fourth branch chain 111 is connected to the first end of the fifth branch chain 141. The second end of 144 is respectively connected to the first end of the sixth branch chain 154, the first end of the eighth branch chain 153 and the first end of the tenth branch chain 143, the second end of the tenth branch chain 143 is connected to the first end of the twelfth branch chain 123, the second end of the eleventh branch chain 142 is connected to the first end of the thirteenth branch chain 122, and the first end of the fourteenth branch chain 112 is respectively connected to the second end of the twelfth branch chain 123 and the second end of the thirteenth branch chain 122; through the force deformation guidance of the elastic adjustment mechanism 1, in the two modes of tension and compression, the elastic adjustment mechanism produces a negative Poisson's ratio lateral deformation, so as to accurately detect the force, and the contraction and extension process of the elastic adjustment mechanism 1 is as follows: Extension and contraction: When the first branch chain 111 and the fourteenth branch chain 112 in the elastic adjustment mechanism 1 are subjected to a compressive force along the Y-axis direction, the first angle θ between the first branch chain 111 and the third branch chain 121 1 , a second angle θ between the third branch chain 121 and the fifth branch chain 141 2 The angles of the first branch chain 111, the third branch chain 121 and the fifth branch chain 141 on the axisymmetric branches are all reduced, so that the elastic adjustment mechanism 1 shrinks inward along the X-axis direction, and the composite shell 10 shrinks inward under pressure and stretches: when the first branch chain 111 and the fourteenth branch chain 112 in the elastic adjustment mechanism 1 are subjected to a tensile force along the Y-axis direction, the first angle θ between the first branch chain 111 and the third branch chain 121 is 1 , a second angle θ between the third branch chain 121 and the fifth branch chain 141 2 The angles of the first branch chain 111, the third branch chain 121 and the fifth branch chain 141 on the axisymmetric branches are all increased, so that the elastic adjustment mechanism 1 extends outward along the X-axis direction, and the composite shell 10 is stretched outward. In the initial state of the elastic adjustment mechanism 1, the first angle θ between the first branch chain 111 and the third branch chain 121 is 1 is 45°, and the second angle θ between the third branch chain 121 and the fifth branch chain 141 is 2 is 25°, and the third angle θ between the fifth branch chain 141 and the seventh branch chain 151 is 3The length ratio of the first branch chain 111, the third branch chain 121, the fifth branch chain 141 and the seventh branch chain 151 is 1:1:1:0.8.

[0041] like Figure 3 As shown, the preparation method of the ultra-wide linear flexible force sensor based on the bionic frog comprises the following steps:

[0042] S1. Preparation of sugar-based silica gel:

[0043] The same mass of silica gel liquid A and silica gel liquid B are mixed and fully stirred to obtain mixed silica gel, and the sugar crystals and the mixed silica gel are fully mixed in a ratio of 9:1 and stirred evenly to obtain sugar-based silica gel.

[0044] S2. Preparation of sugar-based silica gel layer and sugar-based silicone rubber:

[0045] The first part of the sugar-based silicone is poured into a 3D printed rectangular mold and compacted to form a compacted sugar-based silicone layer in the rectangular mold, the elastic adjustment mechanism 1 is placed on the compacted sugar-based silicone layer, and the second part of the sugar-based silicone is poured into the rectangular mold and compacted. After drying at 100-120°C for 2-4 hours, the silicone is solidified to obtain sugar-based silicone rubber.

[0046] S3: Preparation of skeleton foam:

[0047] The sugar-based silicone rubber obtained in step S2 is soaked in 50-70°C water for 24-36 hours, and taken out after the sugar crystals are dissolved to obtain a silicone foam with an elastic adjustment mechanism 1 embedded inside. The silicone foam is dried at 120-150°C for 4-6 hours to obtain a skeleton foam.

[0048] The preparation method of the elastic adjustment mechanism 1 in step S3 is: mixing silicone liquid A and silicone liquid B of the same mass, stirring and vacuuming to obtain mixed silicone, pouring the mixed silicone into a 3D printed white resin mold, and standing at room temperature and pressure for 6 to 8 hours to obtain the elastic adjustment mechanism 1. The mass of water in step S3 is 15 to 20 times the mass of the silicone solidified mixture.

[0049] S4: Preparation of conductive skeleton foam:

[0050] The skeleton foam is immersed in a graphene aqueous dispersion, and dried at a pressure of 0 to 0.01 kPa and a temperature of 120 to 150° C. for 8 to 10 hours to obtain a conductive skeleton foam.

[0051] The preparation method of the graphene aqueous dispersion in step S4 is: mixing graphene powder and pure water in a mass ratio of 1:20, stirring and shaking the mixture with a magnetic stirrer for 45 to 60 minutes, and obtaining the graphene aqueous dispersion.

[0052] S5: Packaged force sensor:

[0053] The conductive skeleton foam, the electrode layer and the insulating layer are encapsulated in the encapsulation layer. The conductive skeleton foam, the electrode layer and the insulating layer use conductive silver paste as a binder. The first encapsulation layer 9 and the second encapsulation layer 5 use silicone glue as a binder. After the conductive silver paste and the silicone glue are completely dry, an ultra-wide linear flexible force sensor is made.

[0054] The ultra-wide linear flexible force sensor based on the bionic frog of the present invention is further described below in conjunction with the embodiments:

[0055] The sensing mechanism of the bionic frog sensor is explained by characterizing the microstructure of the composite shell 10. During the preparation process, graphene adheres to the foam to form a conductive contact. Due to the contact and separation of the conductive points, the resistance changes during compression and stretching.

[0056] like Figure 4 As shown, EDS (energy dispersive x-ray spectroscopy) analysis shows that the mass fraction of carbon element on the composite shell 10 increases to 52.8% after infiltration, confirming the effective adhesion of graphene.

[0057] like Figure 5 As shown in FIG. 1 , the microstructure of the composite shell 10 is observed by using an ultra-depth microscope to count the wire diameter and hole area of ​​the composite shell 10 at a scale of 20 μm and 200 μm, respectively. 1 , S 2 , S 3 ,…S n , ... S 400 The sample statistics of the 10-hole area of ​​the composite shell are shown in the figure. 1 , d 2 , d 3 , …d n , ...d 400 is the sample statistical data of the wire diameter of the composite shell 10. The average wire diameter d is obtained by statistically analyzing the wire diameter and hole area of ​​the composite shell 10. f The average pore area is 25.9 μm and 0.07 mm 2 Under normal circumstances, the average fiber diameter and average pore area of ​​the foam that has not been soaked in graphene aqueous dispersion are 35.6μm and 0.032mm respectively. 2 Compared with the average filament diameter and average pore area of ​​the foam that has not been soaked in the graphene aqueous dispersion under normal circumstances, the average filament diameter and average pore area of ​​the composite shell 10 are reduced and the average pore area is increased, which reflects the good adhesion of graphene on the composite shell 10. At the same time, the data also confirms that despite the adhesion of graphene, the porous characteristics of the foam material remain unchanged.

[0058] As shown in FIG6 , the resistance characteristics of the ultra-wide linear flexible force sensor based on the bionic frog under 15% compressive strain and 100% tensile strain are analyzed. In order to show the repeatability of the data, the range error band of the sensor resistance characteristics is analyzed in FIG6 , and the average relative error calculation formula is as follows:

[0059]

[0060] Among them, M is the average relative error, N is the number of selected measurement points, and Y i is the average resistance change rate at the i-th point, Y max is the maximum rate of change of resistance, Y (i,max) is the maximum resistance change rate at the i-th point, Y (i,min) is the minimum resistance change rate at the i-th point.

[0061] The number of points selected for N is 150, and 50 groups are measured and analyzed. Finally, the average relative error of the sensor under 15% compression strain is 0.027, and the average relative error under 100% tensile strain is 0.032. Considering the range of resistance change rate, the average relative error is within 0.05. This confirms the accuracy and rationality of the sensor measurement signal data.

[0062] In order to characterize the linear range and sensitivity of the sensor, such as Figure 6a and Figure 6b As shown, 50 sets of compression and tension data were linearly fitted. The sensitivity S of the sensor is calculated as follows:

[0063]

[0064] Where R is the current resistance, R 0 is the initial resistance without external force, and ΔP represents the pressure change corresponding to the resistance change.

[0065] Through calculation and analysis, it is found that the ultra-wide linear flexible force sensor based on the bionic frog has a sensitivity of 0.0016 kPa in the sensing range of 0 to 640 kPa under 15% compressive strain. -1 , at 100% tensile strain, the sensitivity is 0.0803 kPa in the range of 0 to 310 kPa -1 , the sensitivity is 0.2388kPa- in the range of 310~800kPa 1 The linear sensitivity of the traditional pure foam sensor in the range of 42-46 kPa under 15% compressive strain is 0.0675 kPa. -1 , the sensitivity in the range of 0 to 12.8 kPa at 100% tensile strain is 0.546 kPa -1 , the sensitivity in the range of 16~55kPa is 0.019kPa-1 . It shows that the ultra-wide linear flexible force sensor based on the bionic frog has good sensing performance within an ultra-wide sensing range.

[0066] The performance parameters of the sensor were tested under compression and tension respectively.

[0067] like Figure 7a to Figure 7c As shown in Figure 7, the resistance change of the sensor under 7%, 15% and 30% compressive strain within 80 seconds. The test results show that the standard deviations of the peak resistance change rates under 7%, 15% and 30% compressive strain are 0.308, 0.229 and 0.327 respectively, and the resistance change amplitude increases with the increase of compressive strain. Figure 7 also shows the results of 300 cycle tests of the sensor under 15% compressive strain within 2400 seconds. The results show that the resistance change rate of the sensor is stable at about 0.4 in the cycle test, which reflects that the sensor has good stability and repeatability under compression. Figure 7 also shows the response time and recovery time of the sensor under 15% compressive strain, which are 150ms and 137ms respectively, confirming the fast response and fast recovery capabilities of the sensor material under compressive strain.

[0068] like Figure 8a to Figure 8c As shown in Figure 8, the resistance change of the sensor under 15%, 30% and 50% tensile strain within 80 seconds. The test results show that the standard deviations of the peak resistance change rate under 15%, 30% and 50% tensile strain are 0.134, 0.133 and 0.158 respectively, and the resistance change amplitude increases with the increase of tensile strain. Figure 8 also shows the results of 300 cycle tests of the sensor under 15% tensile strain within 2400 seconds. The results show that the resistance change rate of the sensor is stable at about 0.7 in the cycle test, which reflects that the sensor has good stability and repeatability under tension. Figure 8 also shows the response time and recovery time of the sensor under 15% tensile strain, which are 168ms and 251ms respectively, confirming the fast response and fast recovery capabilities of the sensor material under tensile strain.

[0069] The ultra-wide linear flexible force sensor based on the bionic frog of the present invention is guided by the force deformation of the bionic elastic adjustment mechanism 1, and the elastic adjustment mechanism 1 produces a negative Poisson's ratio lateral deformation to accurately detect the force. The negative Poisson's ratio based on the bionic frog elastic adjustment mechanism 1 is combined with the composite shell 10 to achieve accurate measurement of the ultra-wide linear range of force in both tension and compression modes, and has the advantages of high sensitivity, wide perception range, good linearity, etc.

[0070] The embodiments described above are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. An ultra-wide linear flexible force sensor based on a bionic frog, characterized in that: It includes a sensing component, a first packaging layer and a second packaging layer, wherein the sensing component includes an elastic adjustment mechanism, a first insulating layer, a first electrode layer, a second electrode layer, a second insulating layer and a composite shell; The elastic adjustment mechanism is an axisymmetric structure, the elastic adjustment mechanism is embedded in the composite shell, and the center of the elastic adjustment mechanism is on the same straight line as the center of the composite shell, the first wire passes through the first packaging layer and is connected to the first electrode layer, the second wire passes through the first packaging layer and is connected to the second electrode layer, the first end surfaces of the first electrode layer and the second electrode layer are respectively connected to the two ends of the composite shell, the first insulating layer is connected to the second end surface of the first electrode layer, the second insulating layer is connected to the second end surface of the second electrode layer, and the first packaging layer is arranged on the second packaging layer; The elastic adjustment mechanism includes a first branch chain, a second branch chain, a third branch chain, a fourth branch chain, a fifth branch chain, a sixth branch chain, a seventh branch chain, an eighth branch chain, a ninth branch chain, a tenth branch chain, an eleventh branch chain, a twelfth branch chain, a thirteenth branch chain and a fourteenth branch chain, wherein a first end of the first branch chain is connected to a first end of the second branch chain and a first end of the third branch chain, a second end of the second branch chain is connected to a first end of the fourth branch chain, a second end of the third branch chain is connected to a first end of the fifth branch chain, a second end of the fifth branch chain is connected to a first end of the seventh branch chain, a first end of the ninth branch chain and a first end of the eleventh branch chain, a second end of the fourth branch chain is connected to a first end of the sixth branch chain, a first end of the eighth branch chain and a first end of the tenth branch chain, a second end of the tenth branch chain is connected to a first end of the twelfth branch chain, a second end of the eleventh branch chain is connected to a first end of the thirteenth branch chain, and a first end of the fourteenth branch chain is connected to a second end of the twelfth branch chain and a second end of the thirteenth branch chain; In both contraction and stretching modes, the elastic adjustment mechanism is subjected to force deformation to guide the generation of negative Poisson's ratio lateral deformation, and the contraction and extension process of the elastic adjustment mechanism is as follows: Contraction: When the first branch chain and the fourteenth branch chain in the elastic adjustment mechanism are subjected to a compressive force along the Y-axis direction, the first angle θ1 between the first branch chain and the third branch chain, the second angle θ2 between the third branch chain and the fifth branch chain, and the angles on the axially symmetrical branches of the first branch chain, the third branch chain, and the fifth branch chain are all reduced, so that the elastic adjustment mechanism contracts inwardly along the X-axis direction, and the composite shell contracts inwardly under pressure; Extension: When the first branch chain and the fourteenth branch chain of the elastic adjustment mechanism are subjected to a tensile force along the Y-axis direction, the first angle θ1 between the first branch chain and the third branch chain, the second angle θ2 between the third branch chain and the fifth branch chain, and the angles on the axially symmetrical branches of the first branch chain, the third branch chain, and the fifth branch chain are all increased, so that the elastic adjustment mechanism extends outwardly along the X-axis direction, and the composite shell extends outward under tension.

2. The ultra-wide linear flexible force sensor based on the bionic frog according to claim 1 is characterized in that: In the initial state of the elastic adjustment mechanism, the first angle θ1 between the first branch chain and the third branch chain is 45°, the second angle θ2 between the third branch chain and the fifth branch chain is 25°, and the third angle θ3 between the fifth branch chain and the seventh branch chain is 25°.

3. The ultra-wide linear flexible force sensor based on bionic frog according to claim 1 is characterized in that: The length ratio of the first branch chain, the third branch chain, the fifth branch chain and the seventh branch chain is 1:1:1:0.

8.

4. The ultra-wide linear flexible force sensor based on bionic frog according to claim 1 is characterized in that: The first electrode layer and the second electrode layer are both copper films.

5. The ultra-wide linear flexible force sensor based on bionic frog according to claim 1 is characterized in that: The first encapsulation layer and the second encapsulation layer are both made of 10-30 Shore hardness silicone casting.

6. The ultra-wide linear flexible force sensor based on the bionic frog according to claim 1 is characterized in that: The first insulating layer and the second insulating layer are both polyimide films.

7. A method for preparing an ultra-wide linear flexible force sensor based on a bionic frog according to any one of claims 1 to 6, characterized in that: The steps include: S1. Preparation of sugar-based silica gel: Mixing silica gel liquid A and silica gel liquid B of the same mass and stirring them thoroughly to obtain mixed silica gel, and mixing sugar crystals and the mixed silica gel in a ratio of 9:1 and stirring them uniformly to obtain sugar-based silica gel; S2. Preparation of sugar-based silica gel layer and sugar-based silicone rubber: The first part of the sugar-based silicone is poured into a 3D-printed rectangular mold and compacted to form a compacted sugar-based silicone layer in the rectangular mold, the elastic adjustment mechanism is placed on the compacted sugar-based silicone layer, and the second part of the sugar-based silicone is poured into the rectangular mold and compacted, and after drying at 100 to 120° C. for 2 to 4 hours, the silicone is cured to obtain sugar-based silicone rubber; S3: Preparation of skeleton foam: Soak the sugar-based silicone rubber obtained in step S2 in water at 50-70° C. for 24-36 hours, take it out after the sugar crystals are dissolved, and obtain a silicone foam with an elastic adjustment mechanism embedded inside, and dry the silicone foam at 120-150° C. for 4-6 hours to obtain a skeleton foam; S4: Preparation of conductive skeleton foam: Immersing the skeleton foam in a graphene aqueous dispersion, and drying at a pressure of 0 to 0.01 kPa and a temperature of 120 to 150° C. for 8 to 10 hours to obtain a conductive skeleton foam; S5: Packaged force sensor: The conductive skeleton foam, the electrode layer and the insulating layer are encapsulated in the encapsulation layer. The conductive skeleton foam, the electrode layer and the insulating layer use conductive silver paste as a binder. The first encapsulation layer and the second encapsulation layer use silicone glue as a binder. After the conductive silver paste and the silicone glue are completely dry, an ultra-wide linear flexible force sensor is made.

8. The method for preparing the ultra-wide linear flexible force sensor based on the bionic frog according to claim 7, characterized in that: The preparation method of the elastic adjustment mechanism in step S3 is: mixing silicone liquid A and silicone liquid B of the same mass, stirring and vacuuming to obtain mixed silicone, pouring the mixed silicone into a 3D printed white resin mold, and standing at room temperature and pressure for 6 to 8 hours to obtain the elastic adjustment mechanism.

9. The method for preparing the ultra-wide linear flexible force sensor based on the bionic frog according to claim 7, characterized in that: The preparation method of the graphene aqueous dispersion in step S4 is: mixing graphene powder and pure water in a mass ratio of 1:20, stirring and shaking the mixture with a magnetic stirrer for 45 to 60 minutes, and obtaining the graphene aqueous dispersion.

10. The method for preparing the ultra-wide linear flexible force sensor based on the bionic frog according to claim 7, characterized in that: The mass of water in step S3 is 15-20 times the mass of the silica gel curing mixture.

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