A high-sensitivity flexible sensor with fast response and a preparation method thereof

Abstract

The application discloses a kind of high sensitivity flexible sensor of quick response and preparation method thereof, belong to sensor preparation technical field, the flexible sensor includes substrate layer and the carbon structure layer and zinc oxide nanowire network structure layer sequentially arranged on pedestal, the both ends of the carbon structure layer are respectively provided with wire, copper band is negative on wire, the flexible sensor utilizes the high length-diameter ratio of zinc oxide nanowire network structure layer, cooperate carbon structure layer, increase the mobility of carrier, to improve the sensitivity and linear characteristic of entire flexible sensor reduce hysteresis, pressure sensitivity is as high as 2.4×10 ‑2 kPa ‑1 , response time is as low as 5ms, solve the problem that the sensitivity of pressure-sensitive sensor in the prior art is low, nonlinear and hysteresis cannot meet the requirement of current production to flexible sensor, show great potential in the application of electronic skin and wearable device.

Description

Technical Field

[0001] This invention belongs to the field of sensor fabrication technology, and relates to a fast-response, highly sensitive flexible sensor and its fabrication method. Background Technology

[0002] Flexible sensors are essential electronic components in electronic skin and wearable devices, requiring rapid response and high sensitivity even under minute loads. To meet these requirements, experts have developed technologies and products based on micro- and nano-fabrication processes. However, improving sensor performance necessitates incorporating microstructures and metal electrode sputtering into the sensor fabrication process, making the manufacturing process extremely complex and costly.

[0003] Piezoelectric sensors, based on the piezoelectric effect, convert mechanical energy into electrical signals, making them the mainstream type of flexible sensor. Piezoelectric sensors convert external stimuli into voltage or current pulse signals, capable of sensing instantaneous dynamic information. However, the charge in a piezoelectric sensor decreases over time because the output voltage generated by the piezoelectric material is a pulse signal, detectable only at the moment of motion. Therefore, piezoelectric sensors are only suitable for detecting dynamic signals and not for detecting static information. Thus, the main challenge for piezoelectric sensors is achieving stable static signal measurement in a low-cost and easy-to-manufacture manner. Flexible sensors with embedded conductive fillers are widely used due to their ease of fabrication and lower cost.

[0004] Traditional pressure-sensitive polymers in sensors use carbon black as a conductive filler. With the emergence of new nanostructure materials, such as carbon nanotubes and graphene, the sensing materials in flexible sensors are becoming increasingly diverse.

[0005] However, sensors made from these sensing materials typically exhibit defects such as low sensitivity, nonlinearity, and hysteresis, which fail to meet current requirements for flexible sensors and are the main problems hindering the development of flexible sensors. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of low sensitivity, nonlinearity, and hysteresis in existing pressure sensors, which cannot meet the current production requirements for flexible sensors. This invention provides a fast-response, high-sensitivity flexible sensor and its fabrication method. This sensor not only has excellent sensitivity and linearity, but also excellent mechanical properties, and represents the cutting edge of flexible sensor fabrication technology.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] This invention provides a fast-response, highly sensitive flexible sensor, comprising a substrate layer, on which a carbon structure layer and a zinc oxide nanowire network structure layer are sequentially disposed. Wires are respectively disposed at both ends of the carbon structure layer, and copper strips are attached to the wires for collecting electrical signals.

[0009] A method for fabricating a flexible sensor as described above, characterized by comprising the following steps:

[0010] Preparation of the substrate layer;

[0011] A carbon structure layer is prepared on the substrate layer;

[0012] A zinc oxide nanowire network structure layer was prepared on the carbon structure layer;

[0013] Wires and copper strips are connected to both ends of the carbon structure layer and then encapsulated to complete the fabrication of the flexible sensor.

[0014] Preferably, the method for preparing the substrate layer is as follows:

[0015] The polydimethylsiloxane prepolymer and curing agent are mixed and stirred evenly, vacuumed, and allowed to stand to form a film liquid.

[0016] Pour the film liquid into the mold and dry it until it becomes a sticky, solidified state to form the base layer.

[0017] Preferably, the mass ratio of the polydimethylsiloxane prepolymer to the curing agent is 10:1.

[0018] Preferably, the standing time is 15 min to 30 min; the drying temperature is 65℃ to 85℃; and the drying time is 15 min to 30 min.

[0019] Preferably, the method for preparing the carbon structure layer on the substrate is as follows:

[0020] The surfactant and carbon material are placed in deionized water and ultrasonically dispersed to form a uniform mixture.

[0021] The mixture was filtered to deposit a carbon structure layer on the filter membrane, and then allowed to stand at room temperature until the solvent was completely evaporated.

[0022] The carbon structure layer on the filter membrane is transferred and bonded to the substrate layer, then dried at a constant temperature until fully cured, thus completing the preparation of the carbon structure layer.

[0023] Preferably, the mass ratio of the carbon material to the surfactant is (1:200) to (1:50), and the concentration of the surfactant in the mixture is 10 g / L.

[0024] Preferably, the surfactant is an alkylbenzene sulfonate, alkyl sulfonate salt, alkyl sulfonate, alkyl sulfate, fluorinated fatty acid salt, polysiloxane, fatty alcohol sulfate, fatty alcohol polyoxyethylene ether sulfate, α-alkenyl sulfonate, fatty alcohol polyoxyethylene ether phosphate, alkylolamide, alkyl sulfonate acetamide, alkyl succinate sulfonate, alkanolamine alkylbenzene sulfonate, naphthenate, alkylphenol sulfonate, or polyoxyethylene monolaurate; the carbon material is carbon nanotubes, carbon powder, or graphene powder.

[0025] Preferably, the method for preparing the zinc oxide nanowire network structure layer on the carbon structure layer is as follows:

[0026] Zinc nitrate hexahydrate is dissolved in anhydrous ethanol to form the first solution;

[0027] Sodium hydroxide powder is added to the first solution and dissolved by ultrasonication to form the second solution;

[0028] Add polyethylene glycol 600 to the second solution and sonicate until evenly dispersed to form the third solution;

[0029] The third solution was subjected to a hydrothermal reaction. After the reaction was completed, the solution was separated and dried to obtain white powdered zinc oxide nanowires.

[0030] Zinc oxide nanowires were dispersed in anhydrous ethanol and spin-coated onto a carbon structure layer, then dried at a constant temperature to obtain a zinc oxide nanowire network structure layer.

[0031] Preferably, the concentration of zinc nitrate hexahydrate in the first solution is 10 g / L; the concentration of sodium hydroxide in the second solution is 25 g / L to 200 g / L; the volume concentration of polyethylene glycol 600 in the third solution is 50 mL / L to 100 mL / L; the concentration of zinc oxide nanowires dispersed in anhydrous ethanol is 0.1 g / L to 1 g / L; the hydrothermal reaction temperature is 90℃ to 120℃; and the isothermal drying temperature is 65℃ to 85℃.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention provides a fast-response, highly sensitive flexible sensor, comprising a substrate layer on which a multi-walled carbon nanotube structure layer and a zinc oxide nanowire network structure layer are sequentially disposed. Wires are respectively disposed at both ends of the carbon structure layer, and copper strips are attached to the wires. The raw materials for this flexible sensor are inexpensive and readily available, suitable for mass production. Furthermore, the combination of the zinc oxide nanowire network structure layer and the carbon structure layer induces the generation of charged small molecules when the zinc oxide nanowires are subjected to strain, thereby increasing the carrier mobility of the carbon structure layer and thus giving the sensor a very good linear response, thereby improving the sensor's sensitivity and accuracy. In addition, the large aspect ratio of the zinc oxide nanowires helps maintain the stability of the sensor under complex deformation movements such as stretching, rotation, and bending. The sensor uses carbon material as the flexible electrode layer, which not only has excellent conductivity but also improves the tensile strength of the flexible electrode. Verification shows that the pressure sensitivity of this flexible sensor reaches 2.4 × 10⁻⁶. -2 kPa -1 With a response time as low as 5ms, which is higher than the sensitivity of traditional carbon nanotube sensors, it meets the current production requirements for sensor sensitivity; the device is simple, low in cost, and easy to mass-produce.

[0034] This invention provides a method for preparing a fast-response, highly sensitive flexible sensor. The method uses a mild hot solvent method to prepare a zinc oxide nanowire network structure layer. The raw materials are inexpensive and readily available, the process is simple, and the yield is high. The zinc oxide nanowire network structure layer with complete crystal shape, uniform particle size distribution, and good dispersibility can be obtained without high temperature and high pressure treatment. The production has low energy consumption and no pollution, which can effectively reduce production costs. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a structural diagram of the fast-response, high-sensitivity flexible sensor of the present invention.

[0037] Figure 2 This is a flowchart of the fast-response, high-sensitivity flexible sensor fabrication method of the present invention.

[0038] Figure 3 This is a scanning electron microscope image of the zinc oxide nanowire network structure layer prepared according to the present invention.

[0039] Figure 4 This is a transmission electron microscope (TEM) image of the zinc oxide nanowire network structure layer prepared according to the present invention.

[0040] Figure 5 This is a response curve of the fast-response, high-sensitivity flexible sensor of the present invention when strain is generated under bending test.

[0041] Figure 6 The graph shows the response curve of the fast-response, high-sensitivity flexible sensor of the present invention under bending test.

[0042] Figure 7 The graph shows the response curve of the fast-response, high-sensitivity flexible sensor of the present invention under a single load-unload cycle.

[0043] Among them, 1-base layer, 2-carbon structure layer, 3-zinc oxide nanowire network structure layer, 4-wire, 5-copper strip. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0045] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0046] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0047] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0048] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0049] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0050] The present invention will now be described in further detail with reference to the accompanying drawings:

[0051] See Figure 1 The present invention provides a fast-response, highly sensitive flexible sensor, comprising a substrate layer 1, wherein a carbon structure layer 2 and a zinc oxide nanowire network structure layer 3 are sequentially disposed on the substrate layer 1, and wires 4 and copper strips 5 are respectively disposed at the ends of the zinc oxide nanowire network structure layer 3 for collecting electrical signals.

[0052] See Figure 2 The present invention provides a method for fabricating a flexible sensor as described above, comprising the following steps:

[0053] S1: Preparation of basal layer 1:

[0054] The polydimethylsiloxane prepolymer and curing agent are mixed and stirred evenly at a mass ratio of 10:1, vacuumed, and allowed to stand for 15 min to 30 min to form a film liquid.

[0055] Pour the film liquid into the mold and dry it at 65℃~85℃ for 15min~30min until it becomes a sticky solidified state, forming the base layer 1.

[0056] S2: On substrate 1, prepare carbon structural layer 2:

[0057] Carbon material and surfactant in a mass ratio of ~ are placed in deionized water and ultrasonically dispersed to form a mixture; wherein the concentration of surfactant in the mixture is 10 g / L; the surfactant is alkylbenzene sulfonate, alkyl sulfonate salt, alkyl sulfonate, alkyl sulfate, fluorinated fatty acid salt, polysiloxane, fatty alcohol sulfate, fatty alcohol polyoxyethylene ether sulfate, α-alkenyl sulfonate, fatty alcohol polyoxyethylene ether phosphate, alkylolamide, alkyl sulfonate acetamide, alkyl succinate sulfonate, alkanolamine alkylbenzene sulfonate, naphthenate, alkylphenol sulfonate, or polyoxyethylene monolaurate; the carbon material is carbon nanotube, carbon powder, or graphene powder.

[0058] The mixture was filtered to deposit a carbon structure layer on the filter membrane, and then allowed to stand at room temperature until the solvent was completely evaporated.

[0059] The carbon structure layer on the filter membrane is transferred and bonded to the substrate layer 1, and then dried at a constant temperature of 65℃~85℃ until completely cured, thus completing the preparation of the carbon structure layer 2.

[0060] S3: Prepare zinc oxide nanowire network structure layer 3 on carbon structure layer 2:

[0061] Zinc nitrate hexahydrate was dissolved in anhydrous ethanol to form a first solution, wherein the concentration of zinc nitrate hexahydrate in the first solution was 10 g / L.

[0062] Sodium hydroxide powder is added to the first solution and dissolved by ultrasonication to form a second solution. The concentration of sodium hydroxide in the second solution is 25 g / L to 200 g / L.

[0063] Polyethylene glycol 600 is added to the second solution and ultrasonically treated until it is evenly dispersed to form a third solution. The volume concentration of polyethylene glycol 600 in the third solution is 50 mL / L to 100 mL / L.

[0064] The third solution was subjected to a hydrothermal reaction at 90℃~120℃ for 12h~24h. After the reaction was completed, the solution was separated and dried to obtain white powdered zinc oxide nanowires.

[0065] Zinc oxide nanowires were dispersed in anhydrous ethanol at a concentration of 0.1 g / L to 1 g / L and spin-coated onto carbon structure layer 2. The mixture was then dried at a constant temperature of 65°C to 85°C to obtain zinc oxide nanowire network structure layer 3.

[0066] S4: Connect wires 4 and copper strips 5 to both ends of the carbon structure layer and encapsulate to complete the fabrication of the flexible sensor: cover both sides of the carbon structure layer 2 with silver paste as the two ends of the electrodes, and then use wires 4 and copper strips 5 to lead out the two electrodes. Spin coat the film liquid formed in S1 evenly over the top of the entire zinc oxide nanowire network structure layer 3 to encapsulate the entire device and complete the fabrication of a fast-response, high-sensitivity flexible sensor.

[0067] Example 1

[0068] Weigh 10g of polydimethylsiloxane prepolymer, abbreviated as PMDS, trade name: SYLGARD TM 184. Silicon Elastomer: Add 1g of curing agent to the polydimethylsiloxane prepolymer using a dropper. This curing agent is a complementary product to PDMS and is marketed under the name SYLGARD. TM 184Silicone Elastomer Base; Stir at a constant speed in the same direction with a glass rod for 5 minutes to fully mix the PDMS prepolymer and curing agent. After mixing, place the mixture in a vacuum drying oven and let it stand for 15 minutes. Evacuate the PDMS until all air bubbles are expelled to form a film liquid.

[0069] The film liquid was uniformly coated into the mold, and the mold was placed flat in a constant temperature heating box. It was left to stand at a constant temperature of 85℃ for 15 minutes until the surface was viscous and cured. The film was then cleaned in an ultrasonic cleaner for 10 minutes with deionized water, acetone and anhydrous ethanol to remove organic impurities from the film surface. The film was then dried and prepared as the substrate layer 1.

[0070] 1g of sodium dodecyl sulfate powder and 5mg of multi-walled carbon nanotube powder were weighed and placed in 100mL of deionized water. The mixture was ultrasonically dispersed in an ultrasonic cleaner for 20min to form a carbon nanotube dispersion, which was then set aside. A PTFE filter membrane was placed on the sand core of a vacuum filtration funnel. The carbon nanotube dispersion was poured into the vacuum filtration funnel for vacuum filtration, depositing a carbon nanotube layer on the filter membrane. The mixture was allowed to stand at room temperature for 10min until the solvent was completely evaporated. The carbon nanotube layer on the filter membrane was then transferred and bonded to the substrate 1 by pressing. The mixture was then completely cured in a constant temperature heating oven at 65℃ for 15min, thereby forming a uniform carbon nanotube structure layer on the substrate 1.

[0071] Add 2g of zinc nitrate hexahydrate to 200mL of ethanol and sonicate until completely dissolved to form the first solution. Add 5g of sodium hydroxide powder to the first solution and sonicate for 30min until completely dissolved to form the second solution. Add 10mL of polyethylene glycol with an average molecular weight of 600 (PEG600 or polyethylene glycol 600) to the second solution and sonicate for 1h until the solution is completely and evenly dispersed to form the third solution. Place the third solution in a muffle furnace at 90℃ for hydrothermal reaction for 24h. After cooling to room temperature, a white precipitate can be observed at the bottom of the reagent bottle. The upper yellow liquid was separated, and the white precipitate was transferred to a centrifuge tube. The precipitate was washed several times with anhydrous ethanol and deionized water. The resulting solid was then dried in a vacuum drying oven for 4 hours to obtain white powdered zinc oxide nanowires. 5 mg of zinc oxide nanowire powder was weighed and placed in 20 mL of anhydrous ethanol. The mixture was sonicated until the zinc oxide nanowire powder was evenly distributed in the anhydrous ethanol. The solution was then spin-coated onto a carbon nanotube structure layer at a spin speed of 1000 r / min for 1 min. The solution was then placed in a constant temperature heating oven at 65 °C until completely dried to form a zinc oxide nanowire network structure layer 3.

[0072] The carbon nanotube structure is covered with silver paste as the two ends of the electrode. The two electrodes are then led out with wire 4 and copper strip 5 to collect the electrical signal of the flexible sensor. PDMS film solution is uniformly spin-coated to cover the top of the entire zinc oxide nanowire network structure layer 3 at a spin coating speed of 1000 r / min for 1 min to encapsulate the entire device and complete the fabrication of a fast-response, high-sensitivity flexible sensor.

[0073] Example 2

[0074] Weigh 10g of polydimethylsiloxane prepolymer, abbreviated as PMDS, trade name: SYLGARD TM 184. Silicon Elastomer: Add 1g of curing agent to the polydimethylsiloxane prepolymer using a dropper. This curing agent is a complementary product to PDMS and is marketed under the name SYLGARD. TM 184Silicone Elastomer Base; Stir at a constant speed in the same direction with a glass rod for 5 minutes to fully mix the PDMS prepolymer and curing agent. After mixing, place the mixture in a vacuum drying oven and let it stand for 20 minutes. Evacuate the PDMS until all air bubbles are expelled to form a film liquid.

[0075] The film liquid was uniformly coated into the mold, and the mold was placed flat in a constant temperature heating box. It was left to stand at a constant temperature of 65℃ for 20 minutes until the surface was viscous and cured. The film was then cleaned in an ultrasonic cleaner for 10 minutes with deionized water, acetone and anhydrous ethanol to remove organic impurities from the film surface. The film was then dried and prepared as the substrate layer 1.

[0076] Weigh 1g of alkylbenzene sulfonate powder and 10mg of graphene powder into 100mL of deionized water, and ultrasonically disperse them for 20min in an ultrasonic cleaner to form a graphene dispersion. Remove the dispersion for later use. Place a PTFE filter membrane on the sand core of a vacuum filtration funnel, pour the graphene dispersion into the vacuum filtration funnel for vacuum filtration, and deposit a graphene layer on the filter membrane. Let it stand at room temperature for 20min until the solvent is completely evaporated. Then, transfer the graphene layer on the filter membrane to the substrate 1 by pressing, and completely cure it in a constant temperature heating oven at 70℃ for 18min, thereby forming a uniform graphene structure layer on the substrate 1.

[0077] Add 2g of zinc nitrate hexahydrate to 200mL of ethanol and sonicate until completely dissolved to form the first solution. Add 10g of sodium hydroxide powder to the first solution and sonicate for 60min until completely dissolved to form the second solution. Add 15mL of polyethylene glycol with an average molecular weight of 600 (PEG600 or polyethylene glycol 600) to the second solution and sonicate for 1h until the solution is completely and evenly dispersed to form the third solution. Place the third solution in a muffle furnace at 100℃ for hydrothermal reaction for 18h. After cooling to room temperature, the bottom of the reagent bottle can be observed. A white precipitate was collected, and the upper yellow liquid was poured off. The white precipitate was then separated and washed several times with anhydrous ethanol and deionized water. The resulting solid was then placed in a vacuum drying oven and dried for 4 hours to obtain white powdered zinc oxide nanowires. 10 mg of zinc oxide nanowire powder was weighed and placed in 20 mL of anhydrous ethanol. The mixture was ultrasonically treated until the zinc oxide nanowire powder was evenly distributed in the anhydrous ethanol. The solution was then spin-coated onto a graphene layer at a spin speed of 1000 r / min for 1 min. The solution was then placed in a constant temperature heating oven at 70 °C until completely dried to form a zinc oxide nanowire network structure layer 3.

[0078] The sides of the carbon graphene structure layer covered with silver paste are used as the two ends of the electrodes. Then, the two electrodes are led out with wire 4 and copper strip 5 to collect the electrical signal of the flexible sensor. The PDMS film liquid is uniformly spin-coated to cover the top of the entire zinc oxide nanowire network structure layer 3 at a spin coating speed of 1000 r / min for 1 min to encapsulate the entire device and complete the fabrication of the fast-response high-sensitivity flexible sensor.

[0079] Example 3

[0080] Weigh 10g of polydimethylsiloxane prepolymer, abbreviated as PMDS, trade name: SYLGARD TM 184. Silicon Elastomer: Add 1g of curing agent to the polydimethylsiloxane prepolymer using a dropper. This curing agent is a complementary product to PDMS and is marketed under the name SYLGARD. TM184Silicone Elastomer Base; Stir at a constant speed in the same direction with a glass rod for 5 minutes to fully mix the PDMS prepolymer and curing agent. After mixing, place the mixture in a vacuum drying oven and let it stand for 30 minutes. Evacuate the PDMS until all air bubbles are expelled to form a film liquid.

[0081] The film liquid was uniformly coated into the mold, and the mold was placed flat in a constant temperature heating box. It was left to stand at a constant temperature of 70℃ for 30 minutes until the surface was viscous and solidified. The film was then cleaned in an ultrasonic cleaner for 10 minutes with deionized water, acetone and anhydrous ethanol to remove organic impurities from the film surface. The film was then dried and prepared as the substrate layer 1.

[0082] Weigh 1g of fatty alcohol polyoxyethylene ether sulfate and 20mg of multi-walled carbon nanotube powder and place them in 100mL of deionized water. Disperse the dispersion in an ultrasonic cleaner for 20min to form a carbon nanotube dispersion. Remove the dispersion for later use. Place a PTFE filter membrane on the sand core of a vacuum filtration funnel and pour the carbon nanotube dispersion into the funnel for vacuum filtration. Deposit a carbon nanotube layer on the filter membrane and let it stand at room temperature for 30min until the solvent is completely evaporated. Then, transfer and bond the carbon nanotube layer on the filter membrane to the substrate 1 by pressing. Completely cure the layer in a constant temperature heating oven at 85℃ for 20min to form a uniform carbon nanotube structure layer on the substrate 1.

[0083] Add 2g of zinc nitrate hexahydrate to 200mL of ethanol and sonicate until completely dissolved to form the first solution. Add 20g of sodium hydroxide powder to the first solution and sonicate for 90min until completely dissolved to form the second solution. Add 20mL of polyethylene glycol with an average molecular weight of 600 (PEG600 or polyethylene glycol 600) to the second solution and sonicate for 1h until the solution is completely and uniformly dispersed to form the third solution. Place the third solution in a muffle furnace at 120℃ for hydrothermal reaction for 12h. After cooling to room temperature, a white precipitate can be observed at the bottom of the reagent bottle. The upper yellow liquid was separated, and the white precipitate was transferred to a centrifuge tube and washed several times with anhydrous ethanol and deionized water. The final solid was placed in a vacuum drying oven and dried for 12 hours to obtain white powdered zinc oxide nanowires. 15 mg of zinc oxide nanowire powder was weighed and placed in 20 mL of anhydrous ethanol. The mixture was sonicated until the zinc oxide nanowire powder was evenly distributed in the anhydrous ethanol. The solution was then spin-coated onto the carbon nanotube structure layer at a spin speed of 1000 r / min for 1 min. The mixture was then placed in a constant temperature heating oven at 85 °C until completely dried to form a zinc oxide nanowire network structure layer 3.

[0084] The carbon nanotube structure is covered with silver paste as the two ends of the electrode. The two electrodes are then led out with wire 4 and copper strip 5 to collect the electrical signal of the flexible sensor. PDMS film solution is uniformly spin-coated to cover the top of the entire zinc oxide nanowire network structure layer 3 at a spin coating speed of 1000 r / min for 1 min to encapsulate the entire device and complete the fabrication of a fast-response, high-sensitivity flexible sensor.

[0085] Example 4

[0086] Weigh 10g of polydimethylsiloxane prepolymer, abbreviated as PMDS, trade name: SYLGARD TM 184. Silicon Elastomer: Add 1g of curing agent to the polydimethylsiloxane prepolymer using a dropper. This curing agent is a complementary product to PDMS and is marketed under the name SYLGARD. TM 184Silicone Elastomer Base; Stir at a constant speed in the same direction with a glass rod for 5 minutes to fully mix the PDMS prepolymer and curing agent. After mixing, place the mixture in a vacuum drying oven and let it stand for 30 minutes. Evacuate the PDMS until all air bubbles are expelled to form a film liquid.

[0087] The film liquid was uniformly coated into the mold, and the mold was placed flat in a constant temperature heating box. It was left to stand at a constant temperature of 75℃ for 20 minutes until the surface was viscous and cured. The film was then cleaned in an ultrasonic cleaner for 10 minutes with deionized water, acetone and anhydrous ethanol to remove organic impurities from the film surface. The film was then dried and prepared as the substrate layer 1.

[0088] Weigh 1g of fatty alcohol polyoxyethylene ether phosphate and 15mg of toner into 100mL of deionized water, and ultrasonically disperse them in an ultrasonic cleaner for 30min to form a toner dispersion. Remove the dispersion for later use. Place a PTFE filter membrane on the sand core of a vacuum filtration funnel, pour the toner dispersion into the vacuum filtration funnel for vacuum filtration, and deposit a layer of toner on the filter membrane. Let it stand at room temperature for 30min until the solvent is completely evaporated. Then, transfer and bond the carbon nanotube layer on the filter membrane to the substrate 1 by pressing. Completely cure it in a constant temperature heating oven at 85℃ for 20min, thereby forming a uniform carbon nanotube structure layer on the substrate 1.

[0089] Add 2g of zinc nitrate hexahydrate to 200mL of ethanol and sonicate until completely dissolved to form the first solution. Add 15g of sodium hydroxide powder to the first solution and sonicate for 30min until completely dissolved to form the second solution. Add 12mL of polyethylene glycol with an average molecular weight of 600 (PEG600 or polyethylene glycol 600) to the second solution and sonicate for 1h until the solution is completely and uniformly dispersed to form the third solution. Place the third solution in a muffle furnace at 110℃ for hydrothermal reaction for 18h. After cooling to room temperature, a white precipitate can be observed at the bottom of the reagent bottle. The upper yellow liquid was separated, and the white precipitate was transferred to a centrifuge tube and washed several times with anhydrous ethanol and deionized water. The final solid was placed in a vacuum drying oven and dried for 12 hours to obtain white powdered zinc oxide nanowires. 18 mg of zinc oxide nanowire powder was weighed and placed in 20 mL of anhydrous ethanol. The mixture was sonicated until the zinc oxide nanowire powder was evenly distributed in the anhydrous ethanol. The solution was then spin-coated onto the carbon nanotube structure layer at a spin speed of 1000 r / min for 1 min. The mixture was then placed in a constant temperature heating oven at 65 °C until completely dried to form a zinc oxide nanowire network structure layer 3.

[0090] The carbon powder structure is covered with silver paste on both sides as the two ends of the electrode. Then, the two electrode ends are led out with wire 4 and copper strip 5 to collect the electrical signal of the flexible sensor. The PDMS film liquid is uniformly spin-coated to cover the top of the entire zinc oxide nanowire network structure layer 3 at a spin coating speed of 1000 r / min for 1 min to encapsulate the entire device and complete the fabrication of the fast-response high-sensitivity flexible sensor.

[0091] Example 5

[0092] Weigh 10g of polydimethylsiloxane prepolymer, abbreviated as PMDS, trade name: SYLGARD TM 184. Silicon Elastomer: Add 1g of curing agent to the polydimethylsiloxane prepolymer using a dropper. This curing agent is a complementary product to PDMS and is marketed under the name SYLGARD. TM 184Silicone Elastomer Base; Stir at a constant speed in the same direction with a glass rod for 5 minutes to fully mix the PDMS prepolymer and curing agent. After mixing, place the mixture in a vacuum drying oven and let it stand for 25 minutes. Evacuate the PDMS until all air bubbles are expelled to form a film liquid.

[0093] The film liquid was uniformly coated into the mold, and the mold was placed flat in a constant temperature heating box. It was left to stand at a constant temperature of 80℃ for 20 minutes until the surface was viscous and cured. The film was then cleaned in an ultrasonic cleaner for 15 minutes with deionized water, acetone and anhydrous ethanol to remove organic impurities from the film surface. The film was then dried and prepared as the substrate layer 1.

[0094] Weigh 1g of alkylphenol sulfonate and 18mg of multi-walled carbon nanotube powder into 100mL of deionized water, and ultrasonically disperse them in an ultrasonic cleaner for 30min to form a carbon nanotube dispersion. Remove the dispersion for later use. Place a PTFE filter membrane on the sand core of a vacuum filtration funnel, pour the carbon nanotube dispersion into the vacuum filtration funnel for vacuum filtration, and deposit a carbon nanotube layer on the filter membrane. Let it stand at room temperature for 10min until the solvent is completely evaporated. Then, transfer and bond the carbon nanotube layer on the filter membrane to the substrate 1 by pressing. Completely cure it in a constant temperature heating oven at 80℃ for 18min, thereby forming a uniform carbon nanotube structure layer on the substrate 1.

[0095] Add 2g of zinc nitrate hexahydrate to 200mL of ethanol and sonicate until completely dissolved to form the first solution. Add 15g of sodium hydroxide powder to the first solution and sonicate for 80min until completely dissolved to form the second solution. Add 16mL of polyethylene glycol with an average molecular weight of 600 (PEG600 or polyethylene glycol 600) to the second solution and sonicate for 1h until the solution is completely and uniformly dispersed to form the third solution. Place the third solution in a muffle furnace at 100℃ for hydrothermal reaction for 16h. After cooling to room temperature, a white precipitate can be observed at the bottom of the reagent bottle. The upper yellow liquid was poured off, the white precipitate was separated and transferred to a centrifuge tube, and washed several times with anhydrous ethanol and deionized water. The final solid was placed in a vacuum drying oven and dried for 8 hours to obtain white powdered zinc oxide nanowires. 5 mg of zinc oxide nanowire powder was weighed and placed in 20 mL of anhydrous ethanol, and ultrasonically treated until the zinc oxide nanowire powder was evenly distributed in the anhydrous ethanol. The solution was then spin-coated onto the carbon nanotube structure layer at a spin speed of 1000 r / min for 1 min. The solution was then placed in a constant temperature heating oven at 75 °C until completely dried to form a zinc oxide nanowire network structure layer 3.

[0096] The carbon nanotube structure is covered with silver paste as the two ends of the electrode. The two electrodes are then led out with wire 4 and copper strip 5 to collect the electrical signal of the flexible sensor. PDMS film solution is uniformly spin-coated to cover the top of the entire zinc oxide nanowire network structure layer 3 at a spin coating speed of 1000 r / min for 1 min to encapsulate the entire device and complete the fabrication of a fast-response, high-sensitivity flexible sensor.

[0097] Example 6

[0098] Weigh 10g of polydimethylsiloxane prepolymer, abbreviated as PMDS, trade name: SYLGARD TM 184. Silicon Elastomer: Add 1g of curing agent to the polydimethylsiloxane prepolymer using a dropper. This curing agent is a complementary product to PDMS and is marketed under the name SYLGARD.TM 184Silicone Elastomer Base; Stir at a constant speed in the same direction with a glass rod for 5 minutes to fully mix the PDMS prepolymer and curing agent. After mixing, place the mixture in a vacuum drying oven and let it stand for 30 minutes. Evacuate the PDMS until all air bubbles are expelled to form a film liquid.

[0099] The film solution was uniformly coated into the mold, and the mold was placed flat in a constant temperature heating box. It was left to stand at a constant temperature of 85℃ for 15 minutes until the surface was viscous and cured. The film was then cleaned in an ultrasonic cleaner for 15 minutes with deionized water, acetone and anhydrous ethanol to remove organic impurities from the film surface. The film was then dried and prepared as the substrate layer 1.

[0100] Weigh 1g of polyoxyethylene monolaurate and 9mg of multi-walled carbon nanotube powder and place them in 100mL of deionized water. Disperse the dispersion in an ultrasonic cleaner for 18min to form a carbon nanotube dispersion. Set aside. Place a PTFE filter membrane on the core of a vacuum filtration funnel and pour the carbon nanotube dispersion into the funnel for vacuum filtration. Deposit a carbon nanotube layer on the filter membrane and let it stand at room temperature for 20min until the solvent is completely evaporated. Then, transfer and bond the carbon nanotube layer on the filter membrane to the substrate 1 by pressing. Completely cure in a constant temperature heating oven at 85℃ for 15min to form a uniform carbon nanotube structure layer on the substrate 1.

[0101] Add 2g of zinc nitrate hexahydrate to 200mL of ethanol and sonicate until completely dissolved to form the first solution. Add 15g of sodium hydroxide powder to the first solution and sonicate for 30min until completely dissolved to form the second solution. Add 20mL of polyethylene glycol with an average molecular weight of 600 (PEG600 or polyethylene glycol 600) to the second solution and sonicate for 1h until the solution is completely and uniformly dispersed to form the third solution. Place the third solution in a muffle furnace at 100℃ for hydrothermal reaction for 20h. After cooling to room temperature, a white precipitate can be observed at the bottom of the reagent bottle. The upper yellow liquid was separated, and the white precipitate was transferred to a centrifuge tube and washed several times with anhydrous ethanol and deionized water. The final solid was placed in a vacuum drying oven and dried for 12 hours to obtain white powdered zinc oxide nanowires. 20 mg of zinc oxide nanowire powder was weighed and placed in 20 mL of anhydrous ethanol. The mixture was sonicated until the zinc oxide nanowire powder was evenly distributed in the anhydrous ethanol. The solution was then spin-coated onto the carbon nanotube structure layer at a spin speed of 1000 r / min for 1 min. The mixture was then placed in a constant temperature heating oven at 65 °C until completely dried to form a zinc oxide nanowire network structure layer 3.

[0102] The carbon nanotube structure is covered with silver paste as the two ends of the electrode. The two electrodes are then led out with wire 4 and copper strip 5 to collect the electrical signal of the flexible sensor. PDMS film solution is uniformly spin-coated to cover the top of the entire zinc oxide nanowire network structure layer 3 at a spin coating speed of 1000 r / min for 1 min to encapsulate the entire device and complete the fabrication of a fast-response, high-sensitivity flexible sensor.

[0103] See Figure 3 and Figure 4 The zinc oxide nanowire network structure layer 3 in the flexible sensor prepared in Example 1 was characterized by scanning electron microscopy and transmission electron microscopy. It can be seen that the zinc oxide nanowire network structure is densely arranged and the zinc oxide nanowires have a high aspect ratio, thus exhibiting good electrical and tensile properties.

[0104] See Figures 5 to 6 The fast-response high-sensitivity flexible sensor prepared in Example 1 was subjected to a bending test. The measurement results showed that when the sample was subjected to different degrees of bending strain, the current value increased rapidly. The response time of the sensor when strain was generated was about 5ms. When the sample was kept in a bent state, the current value of the piezoresistive sensor remained stable. When the sample recovered its deformation, the current value returned to the initial state, which verified the sensitivity of the fast-response high-sensitivity flexible sensor in detecting static signals.

[0105] See Figure 7 Load-unload cycle tests were conducted on the fabricated flexible sensor, revealing that due to the high carrier mobility of the multi-walled carbon nanotube and zinc oxide nanowire composite structure, the device exhibits a pressure sensitivity as high as 2.4 × 10⁻⁶. -2 kPa -1 It exhibits excellent linear response and higher sensitivity than traditional carbon nanotube-based sensors.

[0106] In summary, this invention provides a fast-response, highly sensitive flexible sensor and its fabrication method. This sensor not only has excellent sensitivity and linearity, but also excellent mechanical properties, solving the problems of low sensitivity, nonlinearity, and hysteresis in existing pressure sensors that cannot meet the current production requirements for flexible sensors.

[0107] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating a fast-response, high-sensitivity flexible sensor, the fast-response, high-sensitivity flexible sensor comprising a substrate layer (1), wherein a carbon structure layer (2) and a zinc oxide nanowire network structure layer (3) are sequentially disposed on the substrate layer (1), and wires (4) are respectively disposed at both ends of the carbon structure layer (2), with copper strips (5) attached to the wires for collecting electrical signals, characterized in that, Includes the following steps: Preparation of the base layer (1) is as follows: The polydimethylsiloxane prepolymer and curing agent are mixed and stirred evenly, vacuumed, and allowed to stand to form a film liquid; the standing time is 15 min to 30 min. The film liquid is poured into a mold and dried to a viscous solid state to form a base layer (1); wherein the drying temperature is 65℃~85℃ and the drying time is 15min~30min; On the substrate layer (1), a carbon structure layer (2) is prepared, specifically as follows: The surfactant and carbon material are placed in deionized water and ultrasonically dispersed to form a mixture; wherein the mass ratio of the carbon material to the surfactant is (1:200) to (1:50), and the concentration of the surfactant in the mixture is 10 g / L. The mixture was filtered to deposit a carbon structure layer on the filter membrane, and then allowed to stand at room temperature until the solvent was completely evaporated. The carbon structure layer on the filter membrane is transferred and bonded to the substrate layer (1), and dried at a constant temperature until it is completely cured, thus completing the preparation of the carbon structure layer (2). A zinc oxide nanowire network structure layer (3) is prepared on the carbon structure layer (2), specifically as follows: Zinc nitrate hexahydrate is dissolved in anhydrous ethanol to form a first solution; wherein the concentration of zinc nitrate hexahydrate in the first solution is 10 g / L; Sodium hydroxide powder is added to the first solution and dissolved by ultrasonication to form a second solution; wherein the concentration of sodium hydroxide in the second solution is 25 g / L to 200 g / L. Polyethylene glycol 600 is added to the second solution and ultrasonically treated until it is evenly dispersed to form a third solution; wherein, the volume concentration of polyethylene glycol 600 in the third solution is 50 mL / L to 100 mL / L; The third solution was subjected to a hydrothermal reaction. After the reaction was completed, the solution was separated and dried to obtain white powdered zinc oxide nanowires. The hydrothermal reaction temperature was 90℃~120℃. Zinc oxide nanowires were dispersed in anhydrous ethanol and spin-coated onto a carbon structure layer (2), and dried at a constant temperature to obtain a zinc oxide nanowire network structure layer (3); wherein the concentration of zinc oxide nanowires dispersed in anhydrous ethanol was 0.1 g / L to 1 g / L; and the temperature for drying at a constant temperature was 65℃ to 85℃. Connect wires (4) and copper strips (5) to both ends of the carbon structure layer (2) and encapsulate them to complete the fabrication of the flexible sensor.

2. The method for fabricating a flexible sensor according to claim 1, characterized in that, The mass ratio of the polydimethylsiloxane prepolymer to the curing agent is 10:

1.

3. The method for fabricating a flexible sensor according to claim 1, characterized in that, The surfactant is an alkylbenzene sulfonate, alkyl sulfonate salt, alkyl sulfonate, alkyl sulfate, fluorinated fatty acid salt, polysiloxane, fatty alcohol sulfate, fatty alcohol polyoxyethylene ether sulfate, α-alkenyl sulfonate, fatty alcohol polyoxyethylene ether phosphate, alkylolamide, alkyl sulfonate acetamide, alkyl succinate sulfonate, alkanolamine alkylbenzene sulfonate, naphthenate, alkylphenol sulfonate, or polyoxyethylene monolaurate; the carbon material is carbon nanotube, carbon powder, or graphene powder.

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