A dual-mode flexible sensor for tension and compression detection and its preparation method

Abstract

The present invention discloses a dual-mode flexible sensor for tensile and compressive detection and a preparation method thereof. The sensor is composed of a lower strain resistor response layer, a dielectric layer, and an upper strain resistor response layer, which are sequentially connected 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 magnitude and direction of strain, and the dielectric layer is used to sense the magnitude and distribution of pressure. This sensor can simultaneously and independently detect tensile strain and normal pressure in a plane, can identify the magnitude and direction of strain in a plane, and can sense normal pressure and its distribution, thereby realizing multi-dimensional sensing detection. The preparation method of the present invention is simple, and the use of technologies such as the reverse mold method and ultrasonic anchoring can effectively reduce costs, making it suitable for mass production.

Description

Technical Field

[0001] The present invention relates to the field of flexible sensors, in particular to a tension-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 areas such as personal health monitoring, electronic skin, intelligent robotics, and human motion detection. Dual-mode sensors that can simultaneously detect tensile strain and compression have attracted increasing attention due to their versatility and high efficiency.

[0003] Currently, 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 composed of a highly elastic polymer matrix (such as polydimethylsiloxane (PDMS), thermoplastic polyurethane (TPU), rubber, etc.) and a conductive material (such as carbon nanotubes, graphene, silver nanowires, etc.), and achieve strain detection through the change in resistance 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's movements are diverse, including both tensile and compressive deformations. Therefore, sensors that can simultaneously detect tensile strain and compression 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 several design and performance challenges. First, to simultaneously detect tensile strain and compression, the sensor must possess a well-designed structure to ensure high sensitivity and stability under strain in different directions. Second, material selection and composite processing are crucial, ensuring that the sensor's conductive network structure can effectively cope with the resistance changes caused by different deformations under dual-mode strain. Furthermore, the sensor must 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 tensile and compressive 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 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: The composite slurry of step 1 is poured into a reverse mold with a raised pattern using a reverse mold method; a water-soluble granular material is then spread on the surface of the composite slurry, and the composite slurry is solidified; after solidification, the composite slurry is immersed in water to dissolve the water-soluble granular material, forming a layer of microporous structure on the surface; after demolding, a strained layer substrate having a microporous structure on one side and a groove structure on the other side is obtained;

[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 placed in a uniformly dispersed conductive particle suspension for ultrasonication. The conductive particles are anchored to the surface of the carbon fiber filaments of the carbon fiber tape by ultrasonication. The carbon fiber tape in the groove structure is then partially removed. The area where the carbon fiber tape is removed 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 a uniformly dispersed conductive particle / low-viscosity volatile solvent suspension into a flexible polymer A, then adding a flexible polymer B, and mixing uniformly 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 ensuring that the carbon fiber tape and the conductive composite slurry are in full contact; then curing the conductive composite slurry to form a strain region consisting of a high modulus difference region and a low modulus difference region, thereby obtaining a lower strain resistor response layer having a dielectric lower layer or an upper strain resistor response layer having 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 tensile and compressive detection.

[0012] The technical solution of the present invention to solve the above-mentioned sensor technology problem is to provide a dual-mode flexible sensor for tensile and compressive detection prepared by the above-mentioned preparation method, characterized in that the sensor is composed 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 magnitude and direction of strain, and the dielectric layer is used to sense the magnitude and distribution of pressure.

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

[0014] (1) This sensor can independently detect tensile strain and normal pressure in a 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 carbon fiber tape with a sandwich structure and adopting a vertical stacking configuration based on separation of capacitance response and resistance response. One sensor can simultaneously and independently detect tensile strain and normal pressure. When deformation caused by in-plane tension occurs, the lower strain resistance response layer and the upper strain resistance response layer work, and when deformation caused by normal pressure occurs, the dielectric layer works, and the detection results are 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 not subjected to external force, the conductive particles are relatively densely distributed, forming a large number of conductive paths, making the material as a whole have a lower resistance. When the strain area is deformed by tension, due to the high elasticity of the flexible polymer, this deformation causes changes in its volume and shape. As the flexible polymer undergoes elastic deformation, the distance between the conductive particles in the flexible polymer matrix increases, causing the conductive paths to become sparse or even disconnected. Due to the reduction in conductive paths, 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 serve as the plates and conductors of the capacitive sensor, providing pressure detection capabilities.

[0019] (6) The present invention has a simple preparation method. Utilizing techniques such as the reverse mold method and ultrasonic anchoring, it can effectively reduce costs and achieve large-scale preparation, making it suitable for mass production. The sensor should maintain excellent stability during cyclic use to avoid performance degradation after repeated use.

[0020] (7) The present invention can be applied to wearable healthcare systems to achieve real-time monitoring of human movement, respiratory status, and pulse conditions, thereby promoting 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 This is a physical diagram of the overall structure of the present invention;

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

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

[0029] Figure 9 Graphs showing strain-resistance curves 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] Figure 10 This is a three-dimensional structural surface profile diagram of the microporous structure of Example 1 of the present invention;

[0031] Figure 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] Figure 12This is a deformation strain distribution diagram of the lower strain resistor response layer of the present invention in the high sensitivity direction;

[0033] Figure 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, the lower strain resistor response layer 1, the upper strain resistor response layer 2, the dielectric layer 3, the strain layer base 4, the strain zone 5, the high modulus difference region 5-1, the low modulus difference region 5-2, the carbon fiber tape 6, the dielectric lower layer 3-1, and the 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 and do not limit the scope of protection 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: Evenly disperse the high dielectric constant material in the flexible polymer A and the flexible polymer B, respectively, and then allow to stand for degassing; then evenly mix the dispersed flexible polymer A and the flexible polymer B to obtain a high dielectric constant material / flexible polymer composite slurry (hereinafter referred to as the 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 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 at least one of BaTiO3 (barium titanate, BTO), SrTiO3 (strontium titanate, STO) and Pb(Zr, Ti)O3 (lead zirconium titanate, PZT).

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

[0041] Preferably, 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.

[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: The composite slurry of step 1 is cast into a reverse mold with a raised pattern using a reverse mold method; then, a water-soluble granular material is spread on the surface of the composite slurry, and the composite slurry is solidified; after solidification, the composite slurry is immersed in water to dissolve the water-soluble granular material, forming a layer of microporous structure on the surface. After demolding, a strained layer substrate 4 having 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 is obtained;

[0044] Preferably, in step 2, the water-soluble granular material is NaCl granules, KCl granules, Na2SO4 granules and C6H 12 At least one of the O6 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 formed at both ends of the groove structure of the strain layer substrate 4. The carbon fiber tape 6 is inserted through the through holes and embedded into the groove structure. The carbon fiber tape 6 is then placed in a uniformly dispersed conductive particle suspension and ultrasonicated to anchor the conductive particles to the surface of the carbon fiber filaments of the carbon fiber tape 6 by ultrasound. The carbon fiber tape 6 in the groove structure is then partially removed. The area where the carbon fiber tape 6 is removed 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 to 5 wt%; 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 nanotubes) and graphene, the solvent is preferably IPA (isopropyl alcohol), and the particle size of the conductive particles is 20 to 500 nm.

[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, then adding a flexible polymer B, and mixing 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 ensuring that the carbon fiber tape 6 is in full 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, thereby 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 strained region 5 is formed, a wire is connected to the strained region 5 and a package is provided.

[0060] 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 make 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 perpendicular to each other. 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, and obtain a dual-mode flexible sensor for tensile and compressive detection.

[0061] The present invention also provides a dual-mode flexible sensor for tension and compression detection (referred to as the sensor), characterized in that the sensor has a sandwich structure and is composed 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 magnitude and direction of strain, and the dielectric layer 3 is used to sense the magnitude and distribution of 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 extending direction of the carbon fiber filaments is consistent with the extending 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 direction of the carbon fiber filament is 125~275MPa, and the Young's modulus in the direction perpendicular to the carbon fiber filament 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] Example 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 1600 r / min for 8 minutes, and then allowed to stand for degassing. The ratio of the mass of BTO to the sum of the mass 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 preparing the strain layer substrate 4;

[0068] Step 2: The BTO / Ecoflex composite slurry is cast in a reverse mold with a raised pattern using a reverse mold method; then, screened NaCl particles (particle size of 0.25 mm to 0.3 mm) are spread on the surface of the BTO / Ecoflex composite slurry, and then cured at 50° C. for 50 minutes to solidify the composite slurry; then, after immersing in water for 24 hours to dissolve the granular material, a layer of microporous structure is formed on the surface, and after demolding, a strain layer substrate 4 having a microporous structure on one side and a groove structure on the other side is obtained;

[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 entire structure is placed in the uniformly dispersed CB / IPA suspension and ultrasonicated 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 removed, and the area where the carbon fiber tape 6 is removed 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 a uniformly dispersed CB / OS-20 suspension that has been ultrasonically treated for 2 hours to Ecoflex-A, add Ecoflex-B after mechanical stirring and uniform dispersion, 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 rate 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 ensure that the carbon fiber tape 6 is in full contact with the conductive composite slurry; then cure at room temperature for 24 hours to form a strain zone 5; then connect a wire to the strain zone 5 and encapsulate to obtain 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;

[0071] 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 make the carbon fiber tape 6 in the lower strain resistor response layer 1 perpendicular to the carbon fiber tape 6 in the middle. 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, and obtain a sandwich-structured tensile and compressive detection dual-mode flexible sensor.

[0072] like Figure 7 and Figure 8It 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 Figure 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 Figure 10 It can be seen that a microporous structure is formed on the surface of the strain layer substrate 4 .

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

[0076] Example 2:

[0077] 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 1500 r / min for 8 minutes, and then allowed to stand for degassing. 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 uniformly at 5°C to obtain a BTO / Ecoflex composite slurry for preparing the strain layer substrate 4;

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

[0079] Example 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 entire structure is placed in the uniformly dispersed CB / IPA suspension and ultrasonicated 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 removed, and the area where the carbon fiber tape 6 is removed 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 mechanical stirring to disperse it uniformly, 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 rate 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 ensure that the carbon fiber tape 6 is in full contact with the conductive composite slurry; then cure at room temperature for 24 hours to form a strain area 5; then connect a wire to the strain area 5 and encapsulate it to obtain 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;

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

[0083] Example 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 1500 r / min for 7 minutes, and then allowed to stand for degassing. 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 uniformly at 5°C to obtain a BTO / Ecoflex composite slurry for preparing the strain layer substrate 4;

[0085] Step 3, several 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 entire thing is placed in the uniformly dispersed CNT / IPA suspension and ultrasonicated 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 removed, and the area where the carbon fiber tape 6 is removed 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 a uniformly dispersed CNT / OS-20 suspension solution that has been ultrasonically treated for 2 hours to Ecoflex-A, add Ecoflex-B after mechanical stirring to disperse it uniformly, and stir at 950r / min for 5 hours to obtain a conductive composite slurry; the ratio of the mass of CNT to the sum of the masses of Ecoflex-A and Ecoflex-B is 1:25; then use a constant flow feed pump to inject the conductive composite slurry into the groove structure of the strain layer substrate 4 where the carbon fiber tape 6 is placed at a feed speed of 300μL / min, and oscillate on an oscillator for 8 minutes to ensure that the carbon fiber tape 6 is in full contact with the conductive composite slurry; then cure at room temperature for 24 hours to form a strain zone 5; then connect a wire to 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 each embodiment 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 capacitance response under pressure of 0-35kPa.

[0093] The working principle of the tensile and compressive 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 high resistance response sensitivity direction (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 low resistance response sensitivity direction (referred to as low sensitivity direction deformation).

[0095] The working process of the lower strain resistance response layer 1 when it is deformed in the high-sensitivity direction is as follows: the high modulus difference region 5-1 has a high Young's modulus in this direction, showing a high resistance to deformation, and the deformation generated here is extremely small; the low modulus difference region 5-2 has a low Young's modulus in any direction, showing a low resistance to deformation, and a large deformation occurs here, that is, the strain is concentrated in the low modulus difference region 5-2. The strain distribution of the lower strain resistance response layer 1 when it is deformed in the high-sensitivity direction is as follows: Figure 12As 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 trend of the strain and relative resistance change of the lower strain resistance response layer 1 when it is deformed in the high-sensitivity direction is shown in Figure 2. Figure 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: Figure 13 As shown. Due to the relatively small strain, the conductive connection effect between the conductive particles changes only slightly or remains relatively stable, making the resistance change in the strained area 5 insignificant. 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 deformed in the low sensitivity direction is shown in Figure 9 As shown in FIG, 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 in the same direction. 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 in the same direction.

[0098] When subjected to normal pressure, the dielectric layer 3 operates as follows: the carbon fiber tapes 6 on the lower strain-resistance response layer 1 and the carbon fiber tapes 6 on the upper strain-resistance response layer 2 are spatially staggered to form several intersections. Each intersection is considered a structure similar to a parallel-plate capacitor. The carbon fiber tapes 6 on the lower strain-resistance response layer 1 serve as the capacitor's lower plate, while the carbon fiber tapes 6 on the upper strain-resistance response layer 2 serve as the capacitor's upper plate. The dielectric layer 3, located between the two layers of carbon fiber tapes 6, consists of an upper dielectric layer 3-2 and a lower dielectric 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 under 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 area between the dielectric layers 3 increases. This increase in contact area 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. Figure 11 ) 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: The composite slurry of step 1 is cast in a reverse mold with a raised pattern using a reverse mold method; then, a water-soluble granular material is spread on the surface of the composite slurry, and the composite slurry is solidified; after solidification, the composite slurry is immersed in water to dissolve the water-soluble granular material, forming a layer of microporous structure on the surface, and after demolding, a strain layer substrate (4) having a microporous structure on one side and a groove structure on the other side is obtained; 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 embedded in 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 removed, and the area where the carbon fiber tape (6) is removed 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), thereby 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 make 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) 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 while not 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 0-10°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, having 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 minutes; 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 for uniform dispersion is as follows: 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 2.5-5 wt %; 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 20-500 nm; 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: stirring speed is 700-950 r / min, and 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 as follows: 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 a package is provided.

7. The method for preparing a dual-mode flexible sensor for tension and compression detection 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 tensile and compressive 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) 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 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 resistance response layer (1) and the upper strain resistance response layer (2) both include a strain layer substrate (4) and a carbon fiber tape (6); a strain region (5) is provided in the strain layer substrate (4); the strain region (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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