Tension and compression detection dual-mode flexible sensor and preparation method thereof

Abstract

The invention discloses a tension and compression detection dual-mode flexible sensor and a preparation method thereof. The sensor is composed of a lower strain resistance response layer, a dielectric layer and an upper strain resistance response layer which are sequentially connected from bottom to top. The dielectric layer is located between the lower strain resistance response layer and the upper strain resistance response layer; the lower strain resistance response layer and the upper strain resistance response layer have the same structure, and the respective carbon fiber bands are vertical to each other; the lower strain resistance response layer and the upper strain resistance response layer are used for sensing the magnitude and direction of strain, and the dielectric layer is used for sensing the magnitude and distribution of pressure. The sensor can simultaneously and independently detect tensile strain and normal pressure in a plane, can identify the size and direction of the strain in the plane, can sense the normal pressure and distribution thereof, and realizes multi-dimensional sensing detection. The preparation method is simple, the cost can be effectively reduced by utilizing technologies such as a reverse mold method and ultrasonic anchoring, and the preparation method is suitable for batch production.

Description

Technical Field

[0001] The invention relates to the field of flexible sensors, in particular to a tension and compression detection dual-mode flexible sensor and a preparation method thereof. Background Art

[0002] With the rapid development of science and technology and the increasing demand for health monitoring and smart devices, flexible wearable sensors have shown broad application prospects in the fields of personal health monitoring, electronic skin, smart robots, and human motion detection. Among them, dual-mode sensors that can simultaneously detect tensile strain and compression have received increasing attention due to their versatility and high efficiency.

[0003] At present, most flexible strain sensors focus on single-mode strain detection, that is, they can only detect one of tension and compression. These sensors are usually made of a high-elastic polymer matrix (such as polydimethylsiloxane PDMS, thermoplastic polyurethane TPU, rubber, etc.) and a conductive material (such as carbon nanotubes, graphene, silver nanowires, etc.) to achieve strain detection through the resistance change caused by material deformation. However, single-mode sensors have some limitations in practical applications. For example, in sports monitoring and health testing, the human body has various forms of movement, including both tensile deformation and compressive deformation. Therefore, sensors that can detect tensile strain and compression at the same time are particularly important. Dual-mode strain sensors can not only simplify the design of the sensor system, but also provide more comprehensive and accurate deformation data.

[0004] Current dual-mode sensors still face some challenges in design and performance. First, to achieve simultaneous detection of tensile strain and compression, the sensor needs to have a good structural design to ensure high sensitivity and stability under strain in different directions. Secondly, the selection of materials and the composite process are also crucial. It is necessary to ensure that the conductive network structure of the sensor can effectively cope with the resistance changes caused by different deformations under dual-mode strain. In addition, the sensor should maintain excellent stability during cyclic use to avoid performance degradation after repeated use. Summary of the invention

[0005] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a tension and compression detection dual-mode flexible sensor and a preparation method thereof.

[0006] The technical solution of the present invention to solve the technical problem of the method is to provide a method for preparing a tensile and compressive detection dual-mode flexible sensor, characterized in that the method comprises the following steps:

[0007] Step 1, uniformly dispersing the high dielectric constant material in the flexible polymer A and the flexible polymer B respectively, and then degassing; then uniformly mixing the dispersed flexible polymer A and the flexible polymer B to obtain a high dielectric constant material / flexible polymer composite slurry; after the flexible polymer A and the flexible polymer B are mixed, a curing reaction can occur at an appropriate temperature and an appropriate time;

[0008] Step 2, casting the composite slurry of step 1 in a reverse mold with a convex pattern by using a reverse mold method; then spreading a water-soluble granular material on the surface of the composite slurry, and curing the composite slurry; after curing, immersing it in water to dissolve the water-soluble granular material, forming a layer of microporous structure on the surface, and after demolding, obtaining a strain layer substrate with a microporous structure on one side and a groove structure on the other side;

[0009] Step 3, a plurality of through holes are opened at both ends of the groove structure of the strain layer substrate, the carbon fiber tape is inserted into the groove structure through the through holes, and then the whole is placed in a uniformly dispersed conductive particle suspension for ultrasonication, and the conductive particles are anchored on the surface of the carbon fiber filaments of the carbon fiber tape by ultrasound; then the carbon fiber tape in the groove structure is partially cut off, the area where the carbon fiber tape is cut off is the low modulus difference area of ​​the strain zone, and the area where the carbon fiber tape is retained is the high modulus difference area of ​​the strain zone;

[0010] Step 4, mixing the evenly dispersed conductive particles / low-viscosity volatile solvent suspension into the flexible polymer A, and then adding the flexible polymer B, and mixing evenly to obtain a conductive composite slurry; then injecting the conductive composite slurry into the groove structure of the strain layer substrate on which the carbon fiber tape is placed, and making the carbon fiber tape fully contact with the conductive composite slurry; then curing the conductive composite slurry to form a strain zone consisting of a high modulus difference area and a low modulus difference area, and obtaining a lower strain resistor response layer with a dielectric lower layer or an upper strain resistor response layer with a dielectric upper layer;

[0011] Step 5. Align the dielectric lower layer in the lower strain resistor response layer with the dielectric upper layer in the upper strain resistor response layer, and make the carbon fiber tape in the lower strain resistor response layer and the carbon fiber tape in the upper strain resistor response layer perpendicular to each other. Then glue the edges of the dielectric lower layer and the dielectric upper layer to each other without gluing the middle to form a dielectric layer, and obtain a dual-mode flexible sensor for tension and compression detection.

[0012] The technical solution of the present invention to solve the technical problem of the sensor is to provide a dual-mode flexible sensor for tension and compression detection prepared by the preparation method, characterized in that the sensor consists of a lower strain resistor response layer, a dielectric layer and an upper strain resistor response layer connected in sequence from bottom to top; the dielectric layer is located between the lower strain resistor response layer and the upper strain resistor response layer; the lower strain resistor response layer and the upper strain resistor response layer have the same structure, and their respective carbon fiber tapes are perpendicular to each other; the lower strain resistor response layer and the upper strain resistor response layer are used to sense the size and direction of the strain, and the dielectric layer is used to sense the size and distribution of the pressure.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) The sensor can independently detect the tensile strain and normal pressure in the plane at the same time, identify the magnitude and direction of the strain in the plane, and sense the normal pressure and its distribution, thereby improving the performance in tensile strain and compression detection, realizing multi-dimensional sensing detection, and meeting various needs in practical applications.

[0015] (2) The present invention avoids the problem of data decoupling by combining the carbon fiber tape with the sandwich structure and adopting a vertical stacking configuration in which the capacitive response and the resistive response are separated. One sensor can independently detect the tensile strain and the normal pressure at the same time. When deformation caused by in-plane stretching occurs, the lower strain resistor response layer and the upper strain resistor response layer work, and when deformation caused by normal pressure occurs, the dielectric layer works. The detection result is more accurate and reliable.

[0016] (3) When the conductive particles are evenly distributed in the flexible polymer matrix, a composite material is formed in which the conductive particles constitute a conductive path. When there is no external force, the conductive particles are relatively densely distributed, forming more conductive paths, so that the material as a whole has a lower resistance. When the strain area is deformed by stretching, due to the high elasticity of the flexible polymer, this deformation will cause its volume and shape to change. As the flexible polymer undergoes elastic deformation, the distance between the conductive particles in the flexible polymer matrix increases, causing the conductive path to become sparse or even disconnected. Due to the reduction of the conductive path, the resistance of the overall material increases.

[0017] (4) The present invention utilizes the anisotropy imparted by the carbon fiber tape embedded in the interior of the sensor. The high modulus difference region exhibits anisotropy of Young's modulus, while the low modulus difference region exhibits isotropy of Young's modulus, providing the detection capability of distinguishing strains in different directions, and maintaining high sensitivity and stability under strains in different directions.

[0018] (5) The present invention utilizes the good conductivity and stability of long carbon fibers. The long carbon fibers participate in strain sensing and can also serve as the plates and conductors of the capacitive sensor, thereby providing pressure detection capabilities.

[0019] (6) The preparation method of the present invention is simple, and the reverse mold method and ultrasonic anchoring techniques can effectively reduce costs and achieve large-area preparation, which is suitable for mass production. The sensor should maintain excellent stability during the cyclic use process to avoid performance degradation after repeated use.

[0020] (7) The present invention can be applied to wearable medical care systems to achieve real-time monitoring of human motion, breathing status and pulse conditions, and promote the development of wearable medical devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a three-dimensional diagram of the overall structure of the present invention;

[0022] Figure 2 It is a side view of the overall structure of the present invention;

[0023] Figure 3 It is an exploded view of the overall structure of the present invention;

[0024] Figure 4 A three-dimensional diagram of the lower strain resistor response layer of the present invention;

[0025] Figure 5 is a cross-sectional view of the lower strain resistor response layer of the present invention;

[0026] Figure 6 It is a physical diagram of the overall structure of the present invention;

[0027] Figure 7 is a SEM image of the carbon fiber tape of Example 1 of the present invention;

[0028] Figure 8 This is a SEM image of the carbon fiber tape of Example 1 of the present invention after being ultrasonicated in a CB / IPA suspension;

[0029] Fig. 9 The strain-resistance curve diagram of the lower strain resistance response layer in the low sensitivity direction and the high sensitivity direction of Example 1 of the present invention;

[0030] Fig.10 The three-dimensional structure surface profile diagram of the microporous structure of Example 1 of the present invention;

[0031] Fig.11 This is a pressure-capacitance curve diagram of the tension-compression detection dual-mode flexible sensor according to Example 1 of the present invention;

[0032] Fig.12It is a deformation strain distribution diagram of the lower strain resistor response layer of the present invention in the high sensitivity direction;

[0033] Fig.13 This is a deformation strain distribution diagram of the lower strain resistor response layer of the present invention in the low sensitivity direction.

[0034] In the figure, there are a lower strain resistor response layer 1, an upper strain resistor response layer 2, a dielectric layer 3, a strain layer substrate 4, a strain zone 5, a high modulus difference region 5-1, a low modulus difference region 5-2, a carbon fiber tape 6, a dielectric lower layer 3-1, and a dielectric upper layer 3-2. DETAILED DESCRIPTION

[0035] The specific embodiments of the present invention are given below. The specific embodiments are only used to further illustrate the present invention in detail and do not limit the protection scope of the present invention.

[0036] The present invention provides a method for preparing a dual-mode flexible sensor for tension and compression detection (hereinafter referred to as the method), characterized in that the method comprises the following steps:

[0037] Step 1, uniformly dispersing the high dielectric constant material in the flexible polymer A and the flexible polymer B respectively, and then standing to degas; then uniformly mixing the dispersed flexible polymer A and the flexible polymer B to obtain a high dielectric constant material / flexible polymer composite slurry (referred to as composite slurry) for making the strain layer substrate 4; after the flexible polymer A and the flexible polymer B are mixed, a curing reaction can occur at an appropriate temperature and an appropriate time;

[0038] Preferably, the operating environment of step 1 is a low temperature environment, specifically a temperature of 0 to 10°C.

[0039] Preferably, in step 1, the high dielectric constant material is a material having a dielectric constant greater than 1300 at 23°C, specifically BaTiO 3 (barium titanate, BTO), SrTiO 3 (strontium titanate, STO) and Pb(Zr,Ti)O 3 (lead zirconate titanate, PZT).

[0040] Preferably, in step 1, the dispersion process is: the stirring speed is 1500-1800 r / min, the stirring time is 7-9 min, and it is preferably carried out in a planetary mixer.

[0041] Preferably, in step 1, flexible polymer A is Ecoflex-A or PDMS prepolymer, and flexible polymer B is Ecoflex-B or PDMS curing agent; when flexible polymer A is Ecoflex-A, flexible polymer B is Ecoflex-B; when flexible polymer A is PDMS prepolymer, flexible polymer B is PDMS curing agent.

[0042] Preferably, in step 1, the ratio of the mass of the high dielectric constant material to the sum of the masses of the flexible polymer A and the flexible polymer B is 1:4-10.

[0043] Step 2, casting the composite slurry of step 1 in a reverse mold with a convex pattern by using a reverse mold method; then spreading a water-soluble granular material on the surface of the composite slurry, and curing the composite slurry; after curing, immersing it in water to dissolve the water-soluble granular material, forming a layer of microporous structure on the surface, and after demolding, obtaining a strain layer substrate 4 with a microporous structure on one side (i.e., the dielectric lower layer 3-1 or the dielectric upper layer 3-2) and a groove structure on the other side;

[0044] Preferably, in step 2, the water-soluble granular material is NaCl granules, KCl granules, Na 2 SO 4 Particles and C 6 H 12 O 6 At least one of the particles has a particle size of 0.25 mm to 0.3 mm.

[0045] Preferably, in step 2, the curing temperature of the composite slurry is 50-60° C., and the curing time is 30-60 min.

[0046] Preferably, in step 2, the immersion temperature is room temperature and the immersion time is 24 to 30 hours.

[0047] Step 3, a plurality of through holes are opened at both ends of the groove structure of the strain layer substrate 4, the carbon fiber tape 6 is inserted into the groove structure through the through holes, and then the whole is placed in a uniformly dispersed conductive particle suspension for ultrasonication, and the conductive particles are anchored on the surface of the carbon fiber filaments of the carbon fiber tape 6 by ultrasonication; then the carbon fiber tape 6 in the groove structure is partially cut off, and the area where the carbon fiber tape 6 is cut off is the low modulus difference area 5-2 of the strain zone 5, and the area where the carbon fiber tape 6 is retained is the high modulus difference area 5-1 of the strain zone 5;

[0048] Preferably, in step 3, the process for uniform dispersion is: ultrasonic time is 1 to 4 hours, power is 800 to 1000 W, power ratio is 10% to 15%, and temperature is 10 to 15°C.

[0049] Preferably, in step 3, the mass fraction of the conductive particle suspension is 2.5-5wt%; the conductive particles are carbon-based conductive materials that can maintain good conductivity with carbon fiber filaments, specifically at least one of CB (carbon black), CNT (carbon nanotube) and graphene, the solvent is preferably IPA (isopropyl alcohol), and the particle size of the conductive particles is 20-500nm.

[0050] Preferably, in step 3, the ultrasonic process is: ultrasonic time is 5 to 10 minutes, power is 400 to 500 W, power ratio is 10% to 15%, and temperature is 10 to 15°C.

[0051] Step 4, mixing a uniformly dispersed conductive particle / low-viscosity volatile solvent suspension into a flexible polymer A, and then adding a flexible polymer B, and mixing them uniformly to obtain a conductive composite slurry; then injecting the conductive composite slurry into the groove structure of the strain layer substrate 4 on which the carbon fiber tape 6 is placed, and making the carbon fiber tape 6 fully contact with the conductive composite slurry; then curing the conductive composite slurry to form a strain zone 5 consisting of a high modulus difference region 5-1 and a low modulus difference region 5-2, and obtaining a lower strain resistor response layer 1 having a dielectric lower layer 3-1 or an upper strain resistor response layer 2 having a dielectric upper layer 3-2;

[0052] Preferably, in step 4, the conductive particles are carbon-based conductive materials that can maintain good conductivity with carbon fiber filaments, specifically at least one of CB, CNT and graphene, and the particle size of the conductive particles is 20 to 500 nm.

[0053] Preferably, in step 4, the low-viscosity volatile solvent is at least one of OS-20, tetrahydrofuran and n-hexanol.

[0054] Preferably, in step 4, the mixing process is: the stirring speed is 700-950 r / min, and the stirring time is 4-6 h.

[0055] Preferably, in step 4, the ratio of the mass of the conductive particles to the sum of the mass of the flexible polymer A and the flexible polymer B is 1:12.5-25.

[0056] Preferably, in step 4, the injection process uses a constant flow feed pump with a feed speed of 300-400 μL / min. The function of the constant flow feed pump is to ensure that the volume of the conductive composite slurry injected into the groove structure of the lower strain resistor response layer 1 and the upper strain resistor response layer 2 is consistent.

[0057] Preferably, in step 4, the full contact process is: using an oscillator with a frequency of 10 to 12 Hz for 6 to 8 minutes.

[0058] Preferably, in step 4, the curing process is: the curing temperature is room temperature, and the curing time is 12 to 15 hours.

[0059] Preferably, in step 4, after the strain region 5 is formed, a wire is connected to the strain region 5 and a package is provided.

[0060] Step 5, the dielectric lower layer 3-1 in the lower strain resistor response layer 1 is aligned with the dielectric upper layer 3-2 in the upper strain resistor response layer 2, and the carbon fiber tape 6 in the lower strain resistor response layer 1 and the carbon fiber tape 6 in the upper strain resistor response layer 2 are perpendicular to each other, and then the edges of the dielectric lower layer 3-1 and the dielectric upper layer 3-2 are glued to each other without gluing the middle to form a dielectric layer 3, and obtain a dual-mode flexible sensor for tension and compression detection.

[0061] The present invention also provides a dual-mode flexible sensor for tension and compression detection (referred to as sensor), characterized in that the sensor is a sandwich structure, consisting of a lower strain resistor response layer 1, a dielectric layer 3 and an upper strain resistor response layer 2 connected in sequence from bottom to top; the dielectric layer 3 is located between the lower strain resistor response layer 1 and the upper strain resistor response layer 2; the lower strain resistor response layer 1 and the upper strain resistor response layer 2 have the same structure, and their respective carbon fiber tapes 6 are perpendicular to each other; the lower strain resistor response layer 1 and the upper strain resistor response layer 2 are used to sense the size and direction of the strain, and the dielectric layer 3 is used to sense the size and distribution of the pressure.

[0062] Preferably, the lower strain resistor response layer 1 and the upper strain resistor response layer 2 both include a strain layer substrate 4 and a carbon fiber tape 6; a strain zone 5 is provided in the strain layer substrate 4; the strain zone 5 is divided into a high modulus difference region 5-1 and a low modulus difference region 5-2; the carbon fiber tape 6 is embedded in the high modulus difference region 5-1; and there is no carbon fiber tape 6 in the low modulus difference region 5-2.

[0063] Preferably, the carbon fiber tape 6 is composed of a plurality of directional carbon fiber filaments, and the extension direction of the carbon fiber filaments is consistent with the extension direction of the carbon fiber tape 6. In this embodiment, the specification of the carbon fiber tape 6 is 1k, and it is composed of 1000 directional carbon fiber filaments with a diameter of 6.9 μm.

[0064] Preferably, the high modulus difference region 5-1 exhibits anisotropy of Young's modulus: the Young's modulus of the high modulus difference region 5-1 along the carbon fiber filament direction is 125~275MPa, and the Young's modulus in the direction perpendicular to the carbon fiber filament direction is 0.15~0.25MPa; the low modulus difference region 5-2 exhibits isotropy of Young's modulus, and the Young's modulus is 0.15~0.25MPa.

[0065] The present invention also provides an application of the tension and compression detection dual-mode flexible sensor in a wearable medical care system.

[0066] Embodiment 1:

[0067] Step 1, BTO is dispersed into Ecoflex-A and Ecoflex-B respectively by stirring at a low temperature with a planetary mixer at a speed of 1600r / min for 8 minutes, and then allowed to stand for degassing, and the ratio of the mass of BTO to the mass sum of Ecoflex-A and Ecoflex-B is 1:4; then the dispersed Ecoflex-A and Ecoflex-B are mixed uniformly at 5°C to obtain a BTO / Ecoflex composite slurry for making a strain layer substrate 4;

[0068] Step 2, casting the BTO / Ecoflex composite slurry in a reverse mold with a convex pattern by using a reverse mold method; then spreading screened NaCl particles (particle size of 0.25 mm to 0.3 mm) on the surface of the BTO / Ecoflex composite slurry, and then curing the composite slurry at 50° C. for 50 minutes; then immersing it in water for 24 hours to dissolve the granular material, forming a layer of microporous structure on the surface, and after demolding, obtaining a strain layer substrate 4 having a microporous structure on one side and a groove structure on the other side;

[0069] Step 3, a plurality of through holes are opened at both ends of the groove structure on the strain layer substrate 4, and the carbon fiber tape 6 is embedded in the groove structure through the through holes; a 2.5wt% CB / IPA suspension is subjected to ultrasonic treatment at a power of 1500W, a power ratio of 20%, and a temperature of 20°C for 3 hours to obtain a uniformly dispersed CB / IPA suspension; then the whole is placed in the uniformly dispersed CB / IPA suspension for ultrasonic treatment for 5 minutes, with an ultrasonic power of 500W, a power ratio of 10%, and a temperature of 20°C, so that the conductive particles are anchored on the surface of the carbon fiber tape 6 by ultrasound; then the carbon fiber tape 6 in the groove structure is partially cut off, and the area where the carbon fiber tape 6 is cut off is the low modulus difference area 5-2 of the strain zone 5, and the area where the carbon fiber tape 6 is retained is the high modulus difference area 5-1 of the strain zone 5;

[0070] Step 4, add the uniformly dispersed CB / OS-20 suspension treated with ultrasound for 2 hours to Ecoflex-A, add Ecoflex-B after being uniformly dispersed by mechanical stirring, and stir at 950r / min for 5 hours to obtain a conductive composite slurry; the ratio of the mass of CB to the mass sum of Ecoflex-A and Ecoflex-B is 1:20; then use a constant flow feed pump at a feed speed of 300μL / min to inject the conductive composite slurry into the groove structure of the strain layer substrate 4 where the carbon fiber tape 6 is placed, and oscillate on an oscillator for 8 minutes to make the carbon fiber tape 6 fully contact with the conductive composite slurry; then cure at room temperature for 24 hours to form a strain zone 5; then connect the wire on the strain zone 5 and encapsulate to obtain a lower strain resistor response layer 1 with a dielectric lower layer 3-1 or an upper strain resistor response layer 2 with a dielectric upper layer 3-2;

[0071] Step 5, the dielectric lower layer 3-1 in the lower strain resistor response layer 1 is aligned with the dielectric upper layer 3-2 in the upper strain resistor response layer 2, and the carbon fiber tape 6 in the lower strain resistor response layer 1 is perpendicular to the carbon fiber tape 6 in the middle, and then the edges of the dielectric lower layer 3-1 and the dielectric upper layer 3-2 are glued to each other without gluing the middle to form a dielectric layer 3, and a sandwich structured tensile and compressive detection dual-mode flexible sensor is obtained.

[0072] like Figure 7 and Figure 8 It can be seen that the CB particles are anchored on the surface of the carbon fiber filaments of the carbon fiber tape 6 by ultrasonic action.

[0073] like Fig. 9 It can be seen that the lower strain resistance response layer 1 shows a high-sensitivity resistance response when stretched along the direction of the carbon fiber tape 6 , and shows a low-sensitivity resistance response when stretched in a direction perpendicular to the carbon fiber tape 6 .

[0074] like Fig.10 It can be seen that a layer of microporous structure is formed on the surface of the strain layer substrate 4 .

[0075] like Fig.11 It can be seen that when the sensor is subjected to external pressure, the sensor capacitance increases significantly.

[0076] Embodiment 2:

[0077] Step 1, BTO is dispersed into Ecoflex-A and Ecoflex-B respectively by stirring at low temperature with a planetary mixer at a speed of 1500r / min for 8min, and then allowed to stand for degassing, and the ratio of the mass of BTO to the mass sum of Ecoflex-A and Ecoflex-B is 1:10; then the dispersed Ecoflex-A and Ecoflex-B are mixed evenly at 5°C to obtain a BTO / Ecoflex composite slurry for making a strain layer substrate 4;

[0078] The remaining steps are the same as those in Example 1.

[0079] Embodiment 3:

[0080] Step 3, a plurality of through holes are opened at both ends of the groove structure on the strain layer substrate 4, and the carbon fiber tape 6 is embedded in the groove structure through the through holes; a 2.5wt% CB / IPA suspension is subjected to ultrasonic treatment at a power of 1500W, a power ratio of 20%, and a temperature of 20°C for 4 hours to obtain a uniformly dispersed CB / IPA suspension; then the whole is placed in the uniformly dispersed CB / IPA suspension for ultrasonic treatment for 10 minutes, with an ultrasonic power of 400W, a power ratio of 10%, and a temperature of 20°C, so that the conductive particles are anchored on the surface of the carbon fiber tape 6 by ultrasound; then the carbon fiber tape 6 in the groove structure is partially cut off, and the area where the carbon fiber tape 6 is cut off is the low modulus difference area 5-2 of the strain zone 5, and the area where the carbon fiber tape 6 is retained is the high modulus difference area 5-1 of the strain zone 5;

[0081] Step 4, add a uniformly dispersed CB / tetrahydrofuran suspension solution that has been ultrasonically treated for 2 hours to Ecoflex-A, add Ecoflex-B after being uniformly dispersed by mechanical stirring, and stir at 950r / min for 5 hours to obtain a conductive composite slurry; the ratio of the mass of CB to the mass sum of Ecoflex-A and Ecoflex-B is 1:16; then use a constant flow feed pump at a feed speed of 300μL / min to inject the conductive composite slurry into the groove structure of the strain layer substrate 4 where the carbon fiber tape 6 is placed, and oscillate on an oscillator for 8 minutes to make the carbon fiber tape 6 fully contact with the conductive composite slurry; then cure at room temperature for 24 hours to form a strain zone 5; then connect the wire on the strain zone 5 and encapsulate to obtain a lower strain resistor response layer 1 with a dielectric lower layer 3-1 or an upper strain resistor response layer 2 with a dielectric upper layer 3-2;

[0082] The remaining steps are the same as those in Example 1.

[0083] Embodiment 4:

[0084] Step 1, STO is dispersed into Ecoflex-A and Ecoflex-B respectively by stirring at a low temperature with a planetary mixer at a speed of 1500r / min for 7 minutes, and then allowed to stand for degassing, and the ratio of the mass of BTO to the mass sum of Ecoflex-A and Ecoflex-B is 1:8; then the dispersed Ecoflex-A and Ecoflex-B are mixed evenly at 5°C to obtain a BTO / Ecoflex composite slurry for making a strain layer substrate 4;

[0085] Step 3, a plurality of through holes are opened at both ends of the groove structure on the strain layer substrate 4, and the carbon fiber tape 6 is embedded in the groove structure through the through holes; a 2.5wt% CNT / IPA suspension is subjected to ultrasonic treatment at a power of 1500W, a power ratio of 20%, and a temperature of 20°C for 3 hours to obtain a uniformly dispersed CNT / IPA suspension; then the whole is placed in the uniformly dispersed CNT / IPA suspension for ultrasonic treatment for 5 minutes, with an ultrasonic power of 500W, a power ratio of 10%, and a temperature of 20°C, so that the conductive particles are anchored on the surface of the carbon fiber tape 6 by ultrasound; then the carbon fiber tape 6 in the groove structure is partially cut off, and the area where the carbon fiber tape 6 is cut off is the low modulus difference area 5-2 of the strain zone 5, and the area where the carbon fiber tape 6 is retained is the high modulus difference area 5-1 of the strain zone 5;

[0086] Step 4, add the uniformly dispersed CNT / OS-20 suspension solution that has been ultrasonically treated for 2 hours to Ecoflex-A, add Ecoflex-B after being uniformly dispersed by mechanical stirring, and stir at 950r / min for 5 hours to obtain a conductive composite slurry; the ratio of the mass of CNT to the mass sum of Ecoflex-A and Ecoflex-B is 1:25; then use a constant flow feed pump at a feed speed of 300μL / min to inject the conductive composite slurry into the groove structure of the strain layer substrate 4 where the carbon fiber tape 6 is placed, and oscillate on an oscillator for 8 minutes to make the carbon fiber tape 6 fully contact with the conductive composite slurry; then cure at room temperature for 24 hours to form a strain zone 5; then connect the wire on the strain zone 5 and encapsulate it to obtain a lower strain resistor response layer 1 with a dielectric lower layer 3-1 or an upper strain resistor response layer 2 with a dielectric upper layer 3-2.

[0087] The remaining steps are the same as those in Example 1.

[0088] The test results of various embodiments are shown in Table 1:

[0089] Table 1

[0090]

[0091]

[0092] It can be seen from Table 1 that Examples 1-4 have lower resistance-tensile response sensitivity when stretched in the direction perpendicular to the carbon fiber tape 6, and higher resistance-tensile response sensitivity when stretched along the carbon fiber tape 6, and have obvious capacitive response under a pressure of 0-35kPa.

[0093] The working principle of the tension and compression detection dual-mode flexible sensor prepared by the present invention is as follows:

[0094] The strain generated by the lower strain resistance response layer 1 being stretched along the direction of the carbon fiber tape 6 is called tensile deformation in the direction of high resistance response sensitivity (referred to as high sensitivity direction deformation); the strain generated by the lower strain resistance response layer 1 being stretched in the direction perpendicular to the carbon fiber tape 6 is called tensile deformation in the direction of low resistance response sensitivity (referred to as low sensitivity direction deformation).

[0095] The working process of the lower strain resistor response layer 1 when subjected to high-sensitivity direction deformation is as follows: the high modulus difference region 5-1 has a higher Young's modulus in this direction, showing high resistance to deformation, and the deformation generated here is extremely small; the low modulus difference region 5-2 has a lower Young's modulus in any direction, showing low resistance to deformation, and a large deformation is generated here, that is, the strain is concentrated in the low modulus difference region 5-2. The strain distribution of the lower strain resistor response layer 1 when subjected to high-sensitivity direction deformation is as follows: Fig.12 As shown, the strain is concentrated in the low Young's modulus difference area. When the low modulus difference area 5-2 is strained, the conductive connection between the conductive particles in the low modulus difference area 5-2 becomes weak or disconnected, causing a large change in the resistance of the strain area 5. Therefore, the lower strain resistance response layer 1 has a large resistance response when it is subjected to the strain generated when it is stretched along the direction of the carbon fiber tape 6. The strain and relative resistance change trends of the lower strain resistance response layer 1 when it is deformed in the high-sensitivity direction are shown in Figure 1. Fig. 9 shown.

[0096] The working process of the lower strain resistor response layer 1 when it is deformed in the low sensitivity direction is as follows: in the low sensitivity direction, the Young's modulus of the high modulus difference region 5-1 is substantially the same as the Young's modulus of the low modulus difference region 5-2, so the strain is no longer concentrated in the low modulus difference region 5-2, resulting in a relatively uniform strain distribution of the lower strain resistor response layer 1. The strain distribution of the lower strain resistor response layer 1 when it is deformed in the low sensitivity direction is as follows: Fig.13 As shown. Since the strain is relatively small, the conductive connection effect between the conductive particles changes only slightly or remains relatively stable, so that the resistance change of the strain area 5 is not obvious. Therefore, the resistance response caused by the strain generated by the lower strain resistance response layer 1 when stretched along the low sensitivity direction is small. The trend of the strain and relative resistance change of the lower strain resistance response layer 1 when it is deformed in the low sensitivity direction is shown in Fig. 9 As shown, the relationship curve between strain and relative resistance change is more gentle in the low sensitivity direction.

[0097] Since the upper strain resistor response layer 2 and the lower strain resistor response layer 1 are perpendicular to each other, the high sensitivity direction of the upper strain resistor response layer 2 and the low sensitivity direction of the lower strain resistor response layer 1 are the same direction, and similarly, the low sensitivity direction of the upper strain resistor response layer 2 and the high sensitivity direction of the lower strain resistor response layer 1 are the same direction.

[0098] The specific working process of the dielectric layer 3 when subjected to normal pressure is as follows: the carbon fiber tape 6 on the lower strain resistor response layer 1 and the carbon fiber tape 6 on the upper strain resistor response layer 2 are arranged in a staggered manner in space to form a number of intersections. At each intersection, a structure similar to a parallel plate capacitor is regarded. Among them, the carbon fiber tape 6 of the lower strain resistor response layer 1 serves as the lower plate of the capacitor, and the carbon fiber tape 6 of the upper strain resistor response layer 2 serves as the upper plate of the capacitor. The dielectric layer 3 is located between the two layers of carbon fiber tape 6 and is divided into a dielectric upper layer 3-2 and a dielectric lower layer 3-1. The surfaces of the dielectric upper layer 3-2 and the dielectric lower layer 3-1 both have microporous structures. When the sensor is not subjected to pressure, these microporous structures keep a certain distance between the dielectric upper layer 3-2 and the dielectric lower layer 3-1 or have a small amount of contact in certain areas, thereby forming an initial capacitance; when the sensor is subjected to external pressure, the contact area between the dielectric upper layer 3-2 and the dielectric lower layer 3-1 begins to gradually increase; as the pressure increases, the microporous structure is compressed, and the overall contact surface between the dielectric layers 3 increases. This increase in contact surface directly leads to a significant increase in the capacitance between the two layers of carbon fiber tapes 6. The trend of capacitance changing with pressure can be shown by the pressure-capacitance relationship curve (e.g. Fig.11 ) is used to indicate.

[0099] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A method for preparing a dual-mode flexible sensor for tension and compression detection, characterized in that: The method comprises the following steps: Step 1, uniformly dispersing the high dielectric constant material in the flexible polymer A and the flexible polymer B respectively, and then degassing; then uniformly mixing the dispersed flexible polymer A and the flexible polymer B to obtain a high dielectric constant material / flexible polymer composite slurry; after the flexible polymer A and the flexible polymer B are mixed, a curing reaction can occur at an appropriate temperature and an appropriate time; Step 2, casting the composite slurry of step 1 in a reverse mold with a convex pattern by using a reverse mold method; then spreading a water-soluble granular material on the surface of the composite slurry, and curing the composite slurry; after curing, immersing it in water to dissolve the water-soluble granular material, forming a layer of microporous structure on the surface, and after demolding, obtaining a strain layer substrate (4) with a microporous structure on one side and a groove structure on the other side; Step 3, a plurality of through holes are opened at both ends of the groove structure of the strain layer substrate (4), the carbon fiber tape (6) is inserted into the groove structure through the through holes, and then the whole is placed in a uniformly dispersed conductive particle suspension for ultrasonication, and the conductive particles are anchored on the surface of the carbon fiber filaments of the carbon fiber tape (6) by ultrasonication; then the carbon fiber tape (6) in the groove structure is partially cut off, and the area where the carbon fiber tape (6) is cut off is the low modulus difference area (5-2) of the strain zone (5), and the area where the carbon fiber tape (6) is retained is the high modulus difference area (5-1) of the strain zone (5); Step 4: mixing a uniformly dispersed conductive particle / low-viscosity volatile solvent suspension into a flexible polymer A, and then adding a flexible polymer B, and mixing them uniformly to obtain a conductive composite slurry; then injecting the conductive composite slurry into the groove structure of the strain layer substrate (4) on which the carbon fiber tape (6) is placed, and making the carbon fiber tape (6) fully contact with the conductive composite slurry; then curing the conductive composite slurry to form a strain region (5) consisting of a high modulus difference region (5-1) and a low modulus difference region (5-2), and obtaining a lower strain resistor response layer (1) having a dielectric lower layer (3-1) or an upper strain resistor response layer (2) having a dielectric upper layer (3-2); Step 5: Align the dielectric lower layer (3-1) in the lower strain resistor response layer (1) with the dielectric upper layer (3-2) in the upper strain resistor response layer (2), and the carbon fiber tape (6) in the lower strain resistor response layer (1) and the carbon fiber tape (6) in the upper strain resistor response layer (2) are perpendicular to each other, and then glue the edges of the dielectric lower layer (3-1) and the dielectric upper layer (3-2) to each other without gluing the middle to form a dielectric layer (3), thereby obtaining a tensile and compressive detection dual-mode flexible sensor.

2. The method for preparing the tension and compression detection dual-mode flexible sensor according to claim 1, characterized in that: The operating environment of step 1 is a low temperature environment, specifically a temperature of 0 to 10°C; In step 1, the dispersion process is: the stirring speed is 1500-1800 r / min, and the stirring time is 7-9 min.

3. The method for preparing the tension and compression detection dual-mode flexible sensor according to claim 1, characterized in that: In step 1, the high dielectric constant material is a material having a dielectric constant greater than 1300 at 23° C., specifically at least one of BaTiO 3 , SrTiO 3 and Pb(Zr,Ti)O 3 ; In step 1, the flexible polymer A is Ecoflex-A or a PDMS prepolymer, and the flexible polymer B is Ecoflex-B or a PDMS curing agent; when the flexible polymer A is Ecoflex-A, the flexible polymer B is Ecoflex-B; when the flexible polymer A is a PDMS prepolymer, the flexible polymer B is a PDMS curing agent; In step 1, the ratio of the mass of the high dielectric constant material to the sum of the masses of the flexible polymer A and the flexible polymer B is 1:4-10.

4. The method for preparing the tension and compression detection dual-mode flexible sensor according to claim 1, characterized in that: In step 2, the water-soluble granular materials are NaCl granules, KCl granules, Na2SO4 granules and C6H 12 At least one of the O6 particles, with a particle size of 0.25 mm to 0.3 mm; In step 2, the curing temperature of the composite slurry is 50-60° C., and the curing time is 30-60 min; In step 2, the immersion temperature is room temperature and the immersion time is 24 to 30 hours.

5. The method for preparing the tension and compression detection dual-mode flexible sensor according to claim 1, characterized in that: In step 3, the process of uniform dispersion is: ultrasonic time is 1 to 4 hours, power is 800 to 1000 W, power ratio is 10% to 15%, and temperature is 10 to 15° C.; In step 3, the mass fraction of the conductive particle suspension is 2.5-5wt%; the conductive particles are carbon-based conductive materials, specifically at least one of CB, CNT and graphene, and the particle size of the conductive particles is 20-500nm; In step 3, the ultrasonic process is: ultrasonic time is 5 to 10 minutes, power is 400 to 500 W, power ratio is 10% to 15%, and temperature is 10 to 15°C.

6. The method for preparing the tension and compression detection dual-mode flexible sensor according to claim 1, characterized in that: In step 4, the conductive particles are carbon-based conductive materials, specifically at least one of CB, CNT and graphene, and the particle size of the conductive particles is 20 to 500 nm; In step 4, the low viscosity volatile solvent is at least one of OS-20, tetrahydrofuran and n-hexanol; In step 4, the mixing process is: the stirring speed is 700-950 r / min, and the stirring time is 4-6 h; In step 4, the injection process uses a constant flow feed pump with a feed rate of 300-400 μL / min; In step 4, the full contact process is: using an oscillator with a frequency of 10 to 12 Hz for 6 to 8 minutes; In step 4, the curing process is: the curing temperature is room temperature, and the curing time is 12 to 15 hours; In step 4, after the strain region (5) is formed, a wire is connected to the strain region (5) and packaged.

7. The method for preparing the tension and compression detection dual-mode flexible sensor according to claim 1, characterized in that: In step 4, the ratio of the mass of the conductive particles to the sum of the mass of the flexible polymer A and the flexible polymer B is 1:12.5-25.

8. A tension and compression detection dual-mode flexible sensor prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The sensor comprises a lower strain resistor response layer (1), a dielectric layer (3) and an upper strain resistor response layer (2) which are sequentially connected from bottom to top; the dielectric layer (3) is located between the lower strain resistor response layer (1) and the upper strain resistor response layer (2); the lower strain resistor response layer (1) and the upper strain resistor response layer (2) have the same structure, and their respective carbon fiber strips (6) are perpendicular to each other; the lower strain resistor response layer (1) and the upper strain resistor response layer (2) are used to sense the magnitude and direction of strain, and the dielectric layer (3) is used to sense the magnitude and distribution of pressure.

9. The tension and compression detection dual-mode flexible sensor according to claim 8, characterized in that: The lower strain resistor response layer (1) and the upper strain resistor response layer (2) both comprise a strain layer substrate (4) and a carbon fiber tape (6); a strain zone (5) is provided in the strain layer substrate (4); the strain zone (5) is divided into a high modulus difference region (5-1) and a low modulus difference region (5-2); and the carbon fiber tape (6) is embedded in the high modulus difference region (5-1).

10. The tension and compression detection dual-mode flexible sensor according to claim 8 or 9, characterized in that: The carbon fiber tape (6) is composed of a plurality of directionally arranged carbon fiber filaments, and the extending direction of the carbon fiber filaments is consistent with the extending direction of the carbon fiber tape (6).

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