Flexible strain sensor preparation method and flexible strain sensor

Abstract

The invention provides a preparation method of a flexible strain sensor and the flexible strain sensor. The preparation method comprises the following steps: step M1, carbonizing an MOFs material to obtain a porous C-MOF metal framework material; step M2, adding a conductive polymer into the C-MOF material to obtain an interconnection composite material which takes the conductive polymer as a conductive bridge and is connected with isolated C-MOF conductive crystals; step M3, modifying a support material with the interconnected composite material to form a sensitive layer of the strain sensor; step M4, coating a flexible electrode support layer on the substrate, and patterning the flexible electrode support layer; m5, coating the flexible electrode support layer with a flexible conductive material to prepare an electrode conductive layer; step M6, removing the substrate to obtain a flexible electrode; and step M7, placing the sensitive layer of the strain sensor on the flexible electrode. The sensor provided by the invention adopts a structure of modifying and interconnecting the nano composite material on the support material to measure the strain, so that the sensitivity and the stretching range of the sensor are improved, and the service life of the sensor is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible wearable sensors, and in particular to a method for preparing a flexible strain sensor and a flexible strain sensor. Background Art

[0002] As an important branch of flexible pressure sensors, flexible piezoresistive pressure sensors feature simple structure, high sensitivity, wide operating range, fast response speed, and high stability. They have potential for development in areas such as human motion detection, health monitoring, bionic electronic skin development, and human-computer interaction. However, achieving low cost, high performance, low energy consumption, and self-propulsion remains a challenge for flexible piezoresistive pressure sensors. Future development will focus on the development of novel sensing mechanisms, the integration of novel functional nanomaterials, and novel fabrication processes for flexible devices.

[0003] Flexible piezoresistive pressure sensors are usually made by coating a conductive material layer (metal nanoparticles, inorganic nanowires, carbon nanotubes, carbonized nanofibers, graphene, etc.) on a flexible elastomer substrate, and usually exhibit a narrow sensing range, low sensing sensitivity and limited mechanical stability. Metal organic frameworks (MOFs) are a crystalline material with organic ligands as pillars and metal ions as nodes. They are widely used as precursors and templates for the preparation of functional porous nanomaterials, such as carbonized materials, metal oxides and carbon-coated nanoparticles, and have potential applications in chemical sensors, catalysis, energy storage devices and gas separation. Due to their high specific surface area and permanent porous structure, MOFs are porous carbon nanomaterials with high specific surface area (>1000m for zeolitic imidazolate framework (ZIF) derived porous carbon nanomaterials). 2 / g), good electrical conductivity, and excellent thermal and mechanical stability, carbonized porous nanomaterials are promising candidates for flexible piezoresistive sensors to provide excellent sensing performance while improving sensing response time and sensitivity.

[0004] Patent application CN117516358A discloses a flexible strain sensor and its fabrication method. The strain sensor comprises a substrate for attachment to a surface; a functional layer attached to the substrate, a slit structure disposed on a side of the functional layer facing away from the substrate, and multiple dispersion structures disposed on at least one side of the slit structure. When the functional layer is subjected to a force, the dispersion structures disperse the stress concentrated in the slit structure. However, this patent does not fully resolve existing technical issues and does not meet the requirements of the present invention. Summary of the Invention

[0005] In view of the defects in the prior art, the purpose of the present invention is to provide a method for preparing a flexible strain sensor and a flexible strain sensor.

[0006] The method for preparing a flexible strain sensor provided by the present invention comprises:

[0007] Step M1: carbonizing MOFs material to obtain porous C-MOF metal skeleton material;

[0008] Step M2: adding a conductive polymer to the C-MOF material to obtain an interconnected composite material in which the conductive polymer serves as a conductive bridge to connect isolated C-MOF conductive crystals;

[0009] Step M3: modifying the interconnected composite material onto a support material to form a sensitive layer of the strain sensor;

[0010] Step M4: coating a flexible electrode support layer on the substrate and patterning it;

[0011] Step M5: coating a flexible conductive material on the flexible electrode support layer to prepare an electrode conductive layer;

[0012] Step M6: removing the substrate to obtain a flexible electrode;

[0013] Step M7: Place the sensitive layer of the strain sensor on the flexible electrode.

[0014] Preferably, the method further comprises: coating and curing a conductive silver paste between the electrode and the sensitive layer, and connecting a wire to complete the packaging of the flexible strain sensor.

[0015] Preferably, the preparation process of the porous C-MOF metal skeleton material is as follows: MOFs are carbonized at 500° C. to 900° C. for 2 h to 6 h under an inert gas atmosphere, and the carbonized sample is washed multiple times with dilute hydrochloric acid to obtain C-MOF.

[0016] Preferably, the conductive material includes: nano-conductive particles, one-dimensional nano-conductive materials and two-dimensional nano-conductive materials.

[0017] Preferably, the nano-conductive particles include: copper, silver, gold, aluminum, nickel, zinc, platinum, titanium, vanadium, carbon black nano-particles and / or organic nano-conductive particles;

[0018] The one-dimensional nano conductive material includes: copper, silver, gold, aluminum, nickel, zinc, platinum, titanium, vanadium nanowires and / or carbon nanotubes;

[0019] The two-dimensional nano-conductive materials include: graphene, metal nanosheets, topological insulators, transition metal sulfides, transition metal oxides, metal-organic framework materials and / or black phosphorus.

[0020] Preferably, the supporting material includes a porous material substrate including sponge and porous silica gel.

[0021] Preferably, the material of the flexible electrode support layer includes: polyimide or polyethylene terephthalate, polydimethylsiloxane.

[0022] Preferably, the material of the electrode conductive layer includes: metal, conductive metal compound, alloy, carbon black, graphite and / or conductive polymer and a mixture thereof.

[0023] The flexible strain sensor provided by the present invention comprises: a flexible electrode support layer, a flexible electrode conductive layer and a sensitive layer of the strain sensor;

[0024] The flexible electrode supporting layer, the flexible electrode conductive layer, the sensitive layer of the strain sensor, the flexible electrode conductive layer and the flexible electrode supporting layer are sequentially arranged on the flexible polymer from bottom to top.

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

[0026] 1. The process of the present invention is mature, the yield rate is high, and it has the potential for large-scale production;

[0027] 2. The C-MOF composite material used in the present invention has good electrical and mechanical properties. The method of modifying it on the support material and then transferring it to the flexible electrode has better tensile properties and stability than directly modifying it on the flexible electrode;

[0028] 3. The present invention uses flexible electrodes to transmit electrical signals, which has better electrical signal capture and transmission capabilities than the method of extending wires at both ends of the sensitive material, thereby improving the sensitivity and service life of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0030] Figure 1 This is a flow chart of a method for preparing a flexible strain sensor according to the present invention;

[0031] Figure 2 This is a preferred flow chart of a method for preparing a flexible strain sensor according to the present invention;

[0032] Figure 3 This is an example diagram of the process flow of a method for preparing a flexible strain sensor according to the present invention;

[0033] Figure 4 is a cross-sectional view of the flexible strain sensor of the present invention;

[0034] Figure 5 This is an electron microscope photograph of the interconnected composite material of the present invention;

[0035] Figure 6This is a physical picture of the flexible electrode of the flexible strain sensor of the present invention;

[0036] Figure 7 This is a physical picture of the flexible strain sensor of the present invention;

[0037] Among them, 1 is MOFs material, 2 is C-MOF metal skeleton material, 3 is conductive material, 4 is C-MOF composite material, 5 is support material, 6 is the sensitive layer of strain sensor, 7 is substrate, 8 is heat release tape, 9 is copper foil substrate, 10 is flexible electrode support layer, 11 is flexible electrode conductive layer, 12 is flexible electrode, and 13 is conductive silver paste. DETAILED DESCRIPTION

[0038] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0039] Example 1

[0040] A method for preparing a flexible strain sensor according to the present invention includes:

[0041] Step M1: carbonizing MOFs material to obtain C-MOF metal skeleton material;

[0042] Step M2: adding a conductive material to the C-MOF material to obtain a C-MOF interconnected nanocomposite material;

[0043] Step M3: Modifying the C-MOF composite material onto the support material to form the sensitive layer of the strain sensor;

[0044] Step M4: coating a flexible electrode support layer on the substrate and patterning it;

[0045] Step M5: coating a flexible conductive material on the flexible electrode support layer to prepare an electrode conductive layer;

[0046] Step M6: removing the substrate to obtain a flexible electrode;

[0047] Step M7: Place the sensitive layer of the strain sensor on the flexible electrode.

[0048] Metal-organic frameworks (MOFs) are crystalline materials with organic ligands as pillars and metal ions as nodes. MOFs are composed of M and O elements in an F framework structure. M represents an early transition metal (such as Ti, V, and Zn), O represents a polydentate organic ligand containing O and N (such as aromatic polyacids and polybases), and F represents a periodic, porous network structure formed by self-assembly of the metal center and the organic ligand through coordination bonds.

[0049] Specifically, the method further includes: coating a conductive silver paste between the electrode and the sensitive layer and curing the paste, and connecting the wires to complete the packaging of the flexible strain sensor.

[0050] Specifically, the method includes the following steps: carbonizing MOFs at 700-900° C. in an inert gas atmosphere in a tubular furnace, and washing the carbonized sample with dilute hydrochloric acid multiple times to obtain C-MOF.

[0051] Specifically, the conductive material includes nano-conductive particles, one-dimensional nano-conductive materials and two-dimensional nano-conductive materials.

[0052] Specifically, the nano-conductive particles include, but are not limited to: copper, silver, gold, aluminum, nickel, zinc, platinum, titanium, vanadium, carbon black nano-particles and / or organic nano-conductive particles;

[0053] The one-dimensional nano-conductive materials include but are not limited to: copper, silver, gold, aluminum, nickel, zinc, platinum, titanium, vanadium nanowires and / or carbon nanotubes;

[0054] The two-dimensional nanoconductive materials include, but are not limited to, graphene, metal nanosheets, topological insulators, transition metal sulfides, transition metal oxides, metal-organic framework materials and / or black phosphorus.

[0055] Specifically, the supporting material includes but is not limited to a porous material substrate such as sponge.

[0056] Specifically, the material of the flexible electrode support layer includes polyimide, polyethylene terephthalate, or polydimethylsiloxane.

[0057] Specifically, the material of the electrode conductive layer includes copper, silver, gold, aluminum, nickel, zinc, platinum, titanium, vanadium, alloy, carbon black, graphite and / or conductive polymer.

[0058] According to a flexible strain sensor provided by the present invention, the flexible strain sensor is prepared by the flexible strain sensor preparation method described above, comprising: a flexible electrode support layer, a flexible electrode conductive layer, and a strain sensor sensitive layer;

[0059] The flexible electrode supporting layer, the flexible electrode conductive layer, the sensitive layer of the strain sensor, the flexible electrode conductive layer, and the flexible electrode supporting layer are sequentially arranged on the flexible polymer from bottom to top.

[0060] Example 2

[0061] Example 2 is a variation of Example 1

[0062] According to one embodiment of the present invention, a method for preparing a flexible strain sensor is provided. Figure 1 , comprising the following preparation steps:

[0063] Step M1: carbonizing MOFs material 1 to obtain C-MOF metal skeleton material 2;

[0064] Step M2: adding a PEDOT:PSS conductive material 3 to the C-MOF material 2 to obtain a PEDOT:PSS / C-MOF interconnected composite material 4;

[0065] Step M3: modifying the PEDOT:PSS / C-MOF composite material 4 onto the support material 5 to form a sensitive layer 6 of the strain sensor;

[0066] Step M4: coating a flexible electrode support layer 10 on the substrate 9 and patterning it;

[0067] Step M5: coating a conductive silver paste on the flexible electrode support layer 10 to prepare an electrode conductive layer 11;

[0068] Step M6: removing the substrate 9 to obtain the flexible electrode 12;

[0069] Step M7: placing the sensitive layer 6 of the strain sensor on the flexible electrode 12 .

[0070] The flexible strain sensor fabricated using this method exhibits excellent tensile properties and stability, high sensitivity, fast response speed, and a mature fabrication process with high yield. The strain sensor can accurately and rapidly measure large strains, meeting the requirements of medical diagnosis, sports rehabilitation, virtual reality, robotic manipulation, sports training, and entertainment.

[0071] As a preference, see Figure 2 The method further includes step M8: coating a conductive silver paste between the electrode and the sensitive layer and curing the paste, and connecting the wires to complete the packaging of the flexible strain sensor. Figure 6 and Figure 7 shown.

[0072] This embodiment involves a method for preparing a flexible strain sensor. The process flow of preparing the flexible strain sensor is as follows: Figure 3 The cross-sectional diagram of the flexible strain sensor processed by the present invention is shown in FIG. Figure 4 As shown, the material 1 of this embodiment is a MOFs material ZIF-8, the material 2 is a C-MOF metal skeleton material, the material 3 is a PEDOT:PSS conductive material, and the PEDOT:PSS / C-MOF interconnected nanocomposite material 4 is as shown. Figure 5 The figure shows a C-MOF and PEDOT:PSS composite material. Support material 5 is melamine sponge, 6 is the sensitive layer, 7 is a glass sheet, 8 is thermal release tape, and 9 is a copper foil substrate. In this embodiment, the flexible electrode support layer 10 is made of copper foil with a thickness of 5 to 100 microns. The flexible electrode conductive layer 11 is made of conductive silver paste with a thickness of 50 to 50,000 nm. 12 is the flexible electrode, and 13 is the conductive silver paste.

[0073] The specific processing steps of a flexible strain sensor preparation method of this embodiment are as follows:

[0074] (1) Preparation of MOFs material: Take 0.516g of zinc nitrate and dissolve it in 40mL of methanol in a beaker. Take another beaker, dissolve 0.526g of 2-methylimidazole in 40mL of methanol and stir for a while to obtain a colorless and transparent solution. Mix the two solutions and stir for another 5 minutes. The color of the solution turns milky white. The obtained solution is sealed for 24 hours, and a white precipitate is observed at the bottom of the beaker. The precipitate is collected by centrifugation and washed three times with methanol to remove unreacted monomers to obtain a relatively pure white precipitate. After drying for 12 hours, the MOFs material ZIF-8 is obtained and ground into powder in a mortar. The white powder obtained is the MOFs material 1 powder.

[0075] (2) Preparation of C-MOF Metal Framework Material: MOFs material 1 powder was evenly spread in a porcelain boat, placed in front of a tube furnace, filled with argon atmosphere, and carbonized at 800°C at a heating rate of 5°C / min. The carbonized sample was washed three times with dilute hydrochloric acid to remove the uncarbonized powder, thereby obtaining carbonized C-MOF Metal Framework Material 2.

[0076] (3) Preparation of PEDOT:PSS / C-MOF composite material: A PEDOT:PSS material 3 solution containing 5 volume percent DMSO was added to a suspension of C-MOF material 2, and the resulting mixture was ultrasonically treated for 30 minutes to form a uniform suspension, thereby obtaining a PEDOT:PSS / C-MOF composite material 4 solution.

[0077] (4) Preparation of the sensor sensitive layer: Cut a melamine sponge 5, wash the sponge with ethanol, dry it, and immerse it in the prepared PEDOT:PSS / C-MOF composite material 4 solution under mild ultrasonic treatment for 40 minutes. After squeezing out the excess suspension from the sponge, the sponge was placed in a drying oven at 70°C for 2 hours to obtain the sensor sensitive layer 6.

[0078] (5) Preparation of a flexible electrode support layer: Use double-sided thermal release tape 7 to stick a copper foil substrate 8 to the surface of a glass sheet 6, and coat the copper foil substrate 8 with a photosensitive polyimide thickness of 20 μm. Bake on a hot plate at 100°C for 1 minute, expose for 30 to 60 seconds, develop for 4 minutes, and rinse for 1 minute to obtain a patterned flexible electrode support layer 9.

[0079] (6) Preparation of flexible electrodes: 20 μm of photoresist was coated on the electrode conductive layer 11 to protect the electrode conductive layer 11 in the subsequent wet etching process, and the thermal release tape 8 was released by baking on a hot plate at 135° C. for 5 minutes. The copper foil substrate 9 was wet-etched and the photoresist was removed to obtain the flexible electrode 12.

[0080] (7) Encapsulating the sensitive layer: Place the sensitive layer 6 between the two flexible electrodes 12, apply conductive silver paste, and apply pressure to ensure full contact between the sensitive layer 6 and the flexible electrodes 12.

[0081] As a preference, see Figure 2 , the method further comprises the steps of:

[0082] Conductive silver paste is coated and cured between the electrode and the sensitive layer, and the wires are connected to complete the packaging of the flexible strain sensor.

[0083] In the description of this application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0084] Those skilled in the art will appreciate that, in addition to implementing the system, device, and various modules provided by the present invention in purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, embedded microcontrollers, and the like by logically programming the method steps. Therefore, the system, device, and various modules provided by the present invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; the modules for implementing various functions can also be considered both software programs for implementing the method and structures within the hardware component.

[0085] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A method for preparing a flexible strain sensor, characterized in that: include: Step M1: carbonizing MOFs material to obtain porous C-MOF metal skeleton material; Step M2: adding a conductive polymer to the C-MOF material to obtain an interconnected composite material in which the conductive polymer serves as a conductive bridge to connect isolated C-MOF conductive crystals; Step M3: modifying the interconnected composite material onto a support material to form a sensitive layer of the strain sensor; Step M4: coating a flexible electrode support layer on the substrate and patterning it; Step M5: coating a flexible conductive material on the flexible electrode support layer to prepare an electrode conductive layer; Step M6: removing the substrate to obtain a flexible electrode; Step M7: Place the sensitive layer of the strain sensor on the flexible electrode.

2. The method for preparing a flexible strain sensor according to claim 1, wherein: Also includes: Conductive silver paste is coated and cured between the electrode and the sensitive layer, and the wires are connected to complete the packaging of the flexible strain sensor.

3. The method for preparing a flexible strain sensor according to claim 1, wherein: The preparation process of the porous C-MOF metal skeleton material is as follows: MOFs are carbonized at 500°C to 900°C for 2h to 6h under an inert gas atmosphere, and the carbonized sample is washed multiple times with dilute hydrochloric acid to obtain C-MOF.

4. The method for preparing a flexible strain sensor according to claim 1, wherein: The conductive materials include: nano conductive particles, one-dimensional nano conductive materials and two-dimensional nano conductive materials.

5. The method for preparing a flexible strain sensor according to claim 3, wherein: The nano-conductive particles include: copper, silver, gold, aluminum, nickel, zinc, platinum, titanium, vanadium, carbon black nano-particles and / or organic nano-conductive particles; The one-dimensional nano conductive material includes: copper, silver, gold, aluminum, nickel, zinc, platinum, titanium, vanadium nanowires and / or carbon nanotubes; The two-dimensional nano-conductive materials include: graphene, metal nanosheets, topological insulators, transition metal sulfides, transition metal oxides, metal-organic framework materials and / or black phosphorus.

6. The method for preparing a flexible strain sensor according to claim 1, wherein: The supporting material includes: a porous material substrate including sponge and porous silica gel.

7. The method for preparing a flexible strain sensor according to claim 1, wherein: The material of the flexible electrode support layer includes: polyimide or polyethylene terephthalate, polydimethylsiloxane.

8. The method for preparing a flexible strain sensor according to claim 1, wherein: The material of the electrode conductive layer includes: metal, conductive metal compound, alloy, carbon black, graphite and / or conductive polymer and a mixture thereof.

9. A flexible strain sensor, characterized in that: The flexible strain sensor is prepared by the method for preparing the flexible strain sensor according to any one of claims 1 to 8, comprising: a flexible electrode support layer, a flexible electrode conductive layer, and a sensitive layer of the strain sensor; The flexible electrode supporting layer, the flexible electrode conductive layer, the sensitive layer of the strain sensor, the flexible electrode conductive layer and the flexible electrode supporting layer are sequentially arranged on the flexible polymer from bottom to top.

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