A flexible strain sensor based on patterned carbon nanotubes and a preparation method and application thereof

Abstract

The application discloses a flexible strain sensor based on a patterned carbon nanotube, which comprises a flexible substrate and a patterned circuit embedded on the surface of the substrate, and the patterned circuit is formed by carbon nanotubes coated with magnetic particles. In the application, the patterned circuit can increase the length of the conductive circuit while reducing the cross-sectional area, so that a greater resistance change value can be obtained in the stretching deformation process, the stretching cycle stability is high, the resistance peak value does not decrease obviously with the stretching cycle, and the sensing sensitivity and stability of the strain sensor are improved. In addition, the preparation method of the strain sensor is simple, the equipment is simple, the time consumption is short, there is no chemical pollution, and the pattern and the substrate material can be adjusted according to the requirement. The flexible strain sensor has a good application prospect in the production of flexible wearable devices.

Description

Technical Field

[0001] This invention relates to the field of strain sensor technology. More specifically, it relates to a flexible strain sensor based on patterned carbon nanotubes, its fabrication method, and its applications. Background Technology

[0002] With social development and progress, miniaturized and intelligent strain sensors are ubiquitous in our lives. Compared with traditional strain sensors based on metal and semiconductor materials, flexible strain sensors overcome their brittleness and possess flexibility and stretchability, showing great potential in fields such as human health monitoring, structural health monitoring, and gravity testing.

[0003] Amplifying the geometric deformation and electrical property changes within the packing material itself during strain sensing can improve sensor sensitivity. Therefore, miniaturizing and patterning the sensor circuitry is one approach to enhancing sensor sensitivity.

[0004] Currently, methods for patterning micro and nanostructures can be broadly categorized into top-down and bottom-up approaches. For one-dimensional fillers, processing methods mainly include top-down methods such as laser etching, spraying, transfer printing, and photolithography, and bottom-up methods such as growth-based self-assembly and template methods. While these methods can fabricate many patterned nanostructures with excellent properties, the processes are complex and generally require expensive equipment and tools.

[0005] Therefore, there is a need for a flexible strain sensor with a circuit pattern that can be fabricated using a simple method. Summary of the Invention

[0006] One object of the present invention is to provide a flexible strain sensor based on patterned carbon nanotubes, which has a patterned circuit, high sensing sensitivity, high stability during tensile cycles, and the peak resistance does not decrease significantly with tensile cycles.

[0007] Another objective of this invention is to provide a method for fabricating a flexible strain sensor based on patterned carbon nanotubes. This method is quick, simple, and easy to implement, requires no complex equipment, and is easy to control.

[0008] Another object of the present invention is to provide an application of a flexible strain sensor based on patterned carbon nanotubes.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A flexible strain sensor based on patterned carbon nanotubes includes a flexible substrate and a patterned circuit embedded on the surface of the substrate, the patterned circuit being formed by carbon nanotubes coated with magnetic particles.

[0011] According to the resistance formula When the flexible strain sensor deforms and the circuit is stretched, the circuit length L increases to L + ΔL, the cross-sectional area S decreases to S - ΔS, and R increases accordingly. In this invention, the flexible strain sensor has a patterned circuit diagram. Compared to a non-patterned circuit diagram, its changes in circuit length ΔL and cross-sectional area ΔS are both larger, therefore, the change in R is also larger, resulting in higher sensing sensitivity. Furthermore, the tensile cycle stability of the strain sensor based on this patterned circuit is greatly improved, and the peak resistance of the strain sensor does not decrease with tensile cycles.

[0012] Preferably, the patterned circuit is formed by straight and / or curved circuit lines, wherein the width of the circuit lines is 0.2-5mm and the spacing between adjacent circuit lines is 0.2-5mm.

[0013] Preferably, the mass ratio of the carbon nanotubes to the magnetic particles is 1:(0.08-0.5).

[0014] To fabricate high-performance, structurally sound microcircuits, it is essential to optimize and explore the ratio and content of magnetic particles and carbon nanotubes in the coating material. This ensures that the magnetic particles impart sufficient magnetic properties to the carbon nanotubes while minimizing their impact on their conductivity. Suitable circuit line widths and spacing are crucial for maximizing the peak resistance of the strain sensor while also ensuring the feasibility of the fabrication process.

[0015] Preferably, the carbon nanotubes are selected from one or more of carboxylated multi-walled carbon nanotubes, aminated multi-walled carbon nanotubes, carboxylated single-walled carbon nanotubes, and aminated single-walled carbon nanotubes.

[0016] Preferably, the magnetic particles are selected from iron(II,III) oxide and / or γ-iron(II,III) oxide.

[0017] Preferably, the flexible substrate material includes one or more of Ecoflex resin, PDMS resin, polyurethane, silicone rubber, and Dragonskin.

[0018] Preferably, the average areal density of the patterned circuit is 0.2-2 mg / cm². 2 .

[0019] In practical applications, if the patterned circuit density is less than 0.2 mg / cm³, 2If the content of carbon nanotubes coated with magnetic particles in the patterned circuit is too low, a complete circuit cannot be formed; if the areal density is higher than 2 mg / cm³, the circuit will be incomplete. 2 If the circuit lines in the patterned circuit are too densely distributed, they will stick together, affecting the pattern quality.

[0020] A method for fabricating a flexible strain sensor based on patterned carbon nanotubes as described above, comprising:

[0021] 1) The carbon nanotubes coated with magnetic particles were uniformly dispersed in an ethanol aqueous solution to obtain a dispersion.

[0022] 2) Pour the dispersion into a mold, use a mask and a magnetic field to make the carbon nanotubes coated with magnetic particles complete the patterned distribution, dry the solvent, and obtain a patterned circuit.

[0023] 3) Pour liquid flexible substrate material into the mold and let it solidify; remove the mold, install the electrodes, and obtain a flexible strain sensor.

[0024] The preparation method provided by this invention is a novel and rapid process for achieving multifunctionality, characterized by its speed, ease of operation, and repeatability. During the preparation process, carbon nanotubes are coated with magnetic particles to impart magnetic properties, and a magnetic field is used to precisely control the carbon nanotubes.

[0025] Specifically, such as Figure 1 As shown, the mask is made of iron plate with the target pattern area cut out. A mold containing a carbon nanotube dispersion is placed on the mask. When the mask is placed on a magnetic field, the non-cutout areas of the mask shield the magnetic field lines, while the cutout pattern areas allow the magnetic field lines to pass through. Therefore, the carbon nanotubes coated with magnetic particles in the dispersion form the same pattern as the cutout areas of the mask under the influence of magnetic force, resulting in a carbon nanotube conductive network with the target circuit shape. After drying the solvent, a patterned circuit is obtained. This process is very rapid, achieving the patterned distribution of carbon nanotubes within seconds.

[0026] Meanwhile, the preparation method provided by this invention can efficiently and repeatedly perform patterning without secondary chemical pollution and waste; it does not require the use of large equipment and can be completed with just an external magnetic field; different circuit patterns can be flexibly designed according to requirements, and different substrates can be selected.

[0027] The strength of the magnetic field is a key factor determining the patterning quality. If the magnetic field strength is too low, sufficient magnetic force cannot be generated to guide the carbon nanotubes coated with magnetic particles to form the target pattern. However, if the magnetic field strength is too high, since the mask is made of iron (used for magnetic field patterning shielding), it will be magnetized in a strong magnetic field, resulting in significant hysteresis. Some of the carbon nanotubes coated with magnetic particles will be affected by the magnetic field after the mask is magnetized, thus affecting the integrity of the pattern and the overall electrical properties. Preferably, the strength of the magnetic field is 0.03-0.25T.

[0028] In the specific operation process, in order to provide an easily peelable substrate for the casting of patterned circuits and flexible substrates, a PDMS film is laid flat on the bottom of the mold; wherein, the thickness of the PDMS film is 50-200μm and has a hard protective film.

[0029] This invention also provides a possible preparation process for the above-mentioned magnetic particle-coated carbon nanotubes:

[0030] Carbon nanotubes were added to the alcohol solution at a mass-to-volume ratio of 1:20, and the solution was stirred to obtain a dispersion of carbon nanotubes.

[0031] Iron salt was added to the carbon nanotube dispersion solution at a mass ratio of 1:1 to 5:1, and the cells were subjected to ultrasonic cell disruption to obtain a mixture containing iron salt and carbon nanotubes.

[0032] The alkali solution was dispersed into the alcohol solution at a volume ratio of 1 to 4:10 of 6 mol / L alkali solution to alcohol solution, and stirred until homogeneous to obtain an alkali-alcohol solution.

[0033] An alkaline alcohol solution was added to a mixture containing iron salts and carbon nanotubes, followed by cell disruption and sonication. The resulting solution was then transferred to a reaction vessel and reacted at 180℃~240℃ for 2~4 hours.

[0034] After the reaction was completed and cooled to room temperature, the mixture was filtered under the action of a neodymium iron boron magnet, washed with ethanol and distilled water under centrifugation until neutral, and then vacuum dried to obtain carbon nanotube powder coated with magnetic particles.

[0035] In the preparation process, the alcohol solution is preferably triethylene glycol, ethylene glycol, or diethylene glycol; the iron salt is preferably any one of ferric acetylacetone, ferrous acetylacetone, or ferrous sulfate; the alkaline solution is preferably sodium hydroxide solution or ammonia water; and the mass ratio of iron salt to carbon nanotubes is preferably 4:1.

[0036] Application of a flexible strain sensor based on patterned carbon nanotubes as described above in the fabrication of flexible wearable devices.

[0037] The flexible strain sensor based on patterned carbon nanotubes provided by this invention is a core component of flexible wearable devices, playing a key role in sensing strain. Compared with unpatterned carbon nanotube-based flexible strain sensors, it can significantly improve the sensitivity of flexible wearable devices and enhance the stability of the devices during multiple stretching cycles.

[0038] The beneficial effects of this invention are as follows:

[0039] The flexible strain sensor provided by this invention features a patterned circuit. The patterned circuit increases the length of the conductive circuit while reducing the cross-sectional area, resulting in a larger resistance change during tensile deformation. Furthermore, it exhibits high stability during tensile cycles, with the peak resistance not significantly decreasing with each cycle, thus improving the sensor's sensitivity and stability. In addition, the fabrication method of this strain sensor is simple, requires minimal equipment, is time-efficient, and produces no chemical pollution. The pattern and substrate material can be adjusted as needed. This flexible strain sensor shows promising application prospects in the fabrication of flexible wearable devices. Attached Figure Description

[0040] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0041] Figure 1 This diagram illustrates the fabrication process of the patterned circuit in the flexible strain sensor provided by the present invention.

[0042] Figure 2 (a) shows the flexible strain sensor based on patterned carbon nanotubes obtained in Example 1, and (b) shows the flexible strain sensor without patterned carbon nanotubes obtained in Comparative Example 1.

[0043] Figure 3 The tensile cyclic electrical response diagram of the flexible strain sensor based on patterned carbon nanotubes obtained in Example 1 is shown (tensile strain 8%, number of cycles 500).

[0044] Figure 4 The tensile cyclic electrical response diagram of the flexible strain sensor based on patterned carbon nanotubes obtained in Example 2 is shown (tensile strain 7%, number of cycles 100).

[0045] Figure 5 The image shows the tensile cyclic electrical response of the flexible strain sensor based on patterned carbon nanotubes obtained in Example 3 (tensile strain 9%, number of cycles 100).

[0046] Figure 6 The tensile cyclic electrical response of the flexible strain sensor without patterned carbon nanotubes obtained in Comparative Example 1 is shown (tensile strain 8%, number of cycles 500).

[0047] Figure 7 The tensile cyclic electrical response of the flexible strain sensor without patterned carbon nanotubes obtained in Comparative Example 1 is shown (tensile strain 7%, number of cycles 100).

[0048] Figure 8 The tensile cyclic electrical response of the flexible strain sensor without patterned carbon nanotubes obtained in Comparative Example 1 is shown (tensile strain 9%, number of cycles 100).

[0049] Figure 9 The sensitivity comparison diagrams of the flexible strain sensors without patterned carbon nanotubes obtained in Examples 1-3 and Comparative Example 1 are shown.

[0050] Figure 10 The tensile cyclic electrical response of the flexible strain sensor without patterned pure carbon nanotubes obtained in Comparative Example 2 is shown (tensile strain 8%, number of cycles 500). Detailed Implementation

[0051] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0052] Example 1

[0053] Fabrication of flexible strain sensors:

[0054] 1) Add 0.5% by mass of magnetically coated carbon nanotubes uniformly to deionized water and stir until homogeneous to obtain a carbon nanotube / ferric oxide aqueous solution; then mix 0.5-1 mL of the carbon nanotube / ferric oxide aqueous solution with an ethanol solution and sonicate using a cell disruption sonicator to obtain a very uniformly dispersed carbon nanotube / ferric oxide dispersion with a volume of 1.5-3 mL.

[0055] 2) The PDMS film with a hard protective film (thickness: 50μm) is laid flat on the bottom of the acrylic mold groove using vacuum silicone grease;

[0056] 3) Pour the carbon nanotube / ferric oxide dispersion into an acrylic mold, and place the mold in a magnetic field containing a pre-made mask for patterning preparation (e.g., Figure 1 (As shown), a patterned circuit is prepared by high-temperature drying;

[0057] 4) Weigh the AB components of the liquid resin Ecoflex separately, mix them evenly in a 1:1 ratio, pour them into the mold onto the patterned circuit, and cure for 3-8 hours;

[0058] 5) Remove the molded flexible resin substrate and the patterned circuit embedded in the substrate, peel off the PDMS film layer with a hard protective film on the bottom, apply conductive silver paste to both ends, install copper wire electrodes, and place in an oven at 70-80℃ for curing for 3 hours to obtain a flexible strain sensor with an areal density of 0.8 mg / cm³. 2 .

[0059] Performance testing:

[0060] To facilitate cyclic tensile performance testing, the cured flexible strain sensor was placed in a polytetrafluoroethylene (PTFE) bath to form a flexible base for tensile clamping. Then, the A and B components of the liquid resin Ecoflex were weighed and mixed in a 1:1 ratio, and poured into the PTFE bath to a thickness of approximately 2-4 mm. The mixture was cured for 3-8 hours. The cured flexible strain sensor with the flexible base was then removed from the PTFE bath, and its tensile performance was tested using a self-assembled electromechanical testing platform. The tensile strain was 8%, and the number of tensile cycles was 500.

[0061] The flexible strain sensor obtained in this implementation case (physical image shown) Figure 2 As shown in (a), a tensile cycle test was performed, and the tensile cycle resistance change rate versus cycle number graph was obtained. The results are as follows. Figure 3 As shown. From Figure 3 As can be seen, the obtained flexible strain sensor based on patterned carbon nanotubes tends to stabilize its resistance peak during the stretching cycle, with almost no decrease.

[0062] Example 2

[0063] Fabrication of flexible strain sensors:

[0064] 1) Add 1.0% by mass of magnetically coated carbon nanotubes uniformly to deionized water and stir until homogeneous to obtain a carbon nanotube / ferric oxide aqueous solution; then mix 0.5-1 mL of the carbon nanotube / ferric oxide aqueous solution with an ethanol solution and sonicate using a cell disruption sonicator to obtain a very uniformly dispersed carbon nanotube / ferric oxide dispersion with a volume of 1.5-3 mL.

[0065] 2) The PDMS film with a hard protective film (thickness: 50μm) is laid flat on the bottom of the acrylic mold groove using vacuum silicone grease;

[0066] 3) Pour the carbon nanotube / ferric oxide mixed dispersion into an acrylic mold, and place the mold in a magnetic field containing a pre-made mask for patterning preparation (e.g., Figure 1 (As shown), a patterned circuit is prepared by high-temperature drying;

[0067] 4) Weigh the AB components of the liquid resin Ecoflex separately, mix them evenly in a 1:1 ratio, pour them into the mold onto the patterned circuit, and cure for 3-8 hours;

[0068] 5) Remove the molded flexible resin substrate and the patterned circuit embedded in the substrate, peel off the PDMS film layer with a hard protective film on the bottom, apply conductive silver paste to both ends, install copper wire electrodes, and place in an oven at 70-80℃ for curing for 3 hours to obtain a flexible strain sensor with an areal density of 0.9 mg / cm³. 2 .

[0069] Performance testing:

[0070] To facilitate cyclic tensile performance testing, the cured flexible strain sensor based on patterned carbon nanotubes was placed in a polytetrafluoroethylene (PTFE) bath to form a flexible base for tensile clamping. Then, the A and B components of the liquid resin Ecoflex were weighed and mixed in a 1:1 ratio, and poured into the PTFE bath to a thickness of approximately 2-4 mm. The mixture was cured for 3-8 hours. The cured flexible strain sensor with the flexible base was then removed from the PTFE bath, and its tensile performance was tested using a self-assembled electromechanical testing platform. The tensile strain was 7%, and the number of tensile cycles was 100.

[0071] The flexible strain sensor obtained in this implementation case was subjected to a tensile cycle test, and the tensile cycle resistance change rate versus cycle number graph was obtained. The results are as follows. Figure 4 As shown. From Figure 4 As can be seen, the peak resistance of the obtained flexible strain sensor based on patterned carbon nanotubes tends to stabilize during the tensile cycle, with almost no decrease. This proves the effectiveness of the patterned circuit.

[0072] Example 3

[0073] Fabrication of flexible strain sensors:

[0074] 1) Add 1.0% by mass of magnetically coated carbon nanotubes uniformly to deionized water and stir until homogeneous to obtain a carbon nanotube / ferric oxide aqueous solution; then mix 0.5-1 mL of the carbon nanotube / ferric oxide aqueous solution with an ethanol solution and sonicate using a cell disruption sonicator to obtain a very uniformly dispersed carbon nanotube / ferric oxide dispersion with a volume of 1.5-3 mL.

[0075] 2) The PDMS film with a hard protective film (thickness: 100μm) is laid flat on the bottom of the acrylic mold groove using vacuum silicone grease;

[0076] 3) Pour the carbon nanotube / ferric oxide dispersion into an acrylic mold, and place the mold in a magnetic field containing a pre-made mask for patterning preparation (e.g., Figure 1 (As shown), a patterned circuit is prepared by high-temperature drying;

[0077] 4) Weigh the AB components of the liquid resin Ecoflex separately, mix them evenly in a 1:1 ratio, pour them into the mold onto the patterned circuit, and cure for 3-8 hours;

[0078] 5) Remove the molded flexible resin substrate and the patterned circuit embedded in the substrate, peel off the PDMS film layer with a hard protective film on the bottom, apply conductive silver paste to both ends, install copper wire electrodes, and place in an oven at 70-80℃ for curing for 3 hours to obtain a flexible strain sensor with an areal density of 1.0 mg / cm³. 2 .

[0079] Performance testing:

[0080] To facilitate cyclic tensile performance testing, the cured flexible strain sensor based on patterned carbon nanotubes was placed in a polytetrafluoroethylene (PTFE) bath to form a flexible base for tensile clamping. Then, the A and B components of the liquid resin Ecoflex were weighed and mixed in a 1:1 ratio, and poured into the PTFE bath to a thickness of approximately 2-4 mm. The mixture was cured for 3-8 hours. The cured flexible strain sensor with the flexible base was then removed from the PTFE bath, and its tensile performance was tested using a self-assembled electromechanical testing platform. The tensile strain was 9%, and the number of tensile cycles was 100.

[0081] The flexible strain sensor based on patterned carbon nanotubes obtained in this embodiment was subjected to tensile cycle testing, and the tensile cycle resistance change rate versus cycle number graph was obtained. The results are as follows. Figure 5 As shown. From Figure 5 As can be seen, the obtained flexible strain sensor based on patterned carbon nanotubes exhibits a stable peak resistance during tensile cycling, with a decrease rate of less than 10%. This demonstrates the effectiveness of the patterned circuit.

[0082] Comparative Example 1

[0083] 1) Add 0.5% by mass of magnetically coated carbon nanotubes uniformly to deionized water and stir until homogeneous to obtain a carbon nanotube / ferric oxide aqueous solution; then mix 0.5-1 mL of the carbon nanotube / ferric oxide aqueous solution with an ethanol solution and sonicate using a cell disruption sonicator to obtain a very uniformly dispersed carbon nanotube / ferric oxide dispersion with a volume of 1.5-3 mL.

[0084] 2) Apply a PDMS film with a hard protective film (thickness: 50μm) to the bottom of the acrylic mold groove using vacuum silicone grease;

[0085] 3) Pour the carbon nanotube / ferric oxide dispersion into an acrylic mold and dry it at high temperature to prepare a patternless carbon nanotube circuit.

[0086] 4) Weigh the AB components of the liquid resin Ecoflex separately, mix them evenly in a 1:1 ratio, pour them into the mold onto the unpatterned circuit, and cure for 3-8 hours.

[0087] 5) Remove the molded flexible resin substrate and the patternless circuit embedded in the substrate, peel off the PDMS film layer with a hard protective film on the bottom, apply conductive silver paste to both ends, install copper wire electrodes, and place in an oven at 70-80℃ for curing for 3 hours; the resulting flexible strain sensor has an areal density of 0.8 mg / cm³. 2 .

[0088] Performance testing

[0089] To facilitate cyclic tensile performance testing, the cured flexible strain sensor without patterned carbon nanotubes was placed in a polytetrafluoroethylene (PTFE) bath to form a flexible base for tensile clamping. Then, the A and B components of the liquid resin Ecoflex were weighed and mixed in a 1:1 ratio, and poured into the PTFE bath to a thickness of approximately 2-4 mm. The mixture was cured for 3-8 hours. The cured flexible strain sensor with the flexible base was then removed from the PTFE bath, and its tensile performance was tested using a self-assembled electromechanical testing platform. The tensile strain was 8%, and the number of tensile cycles was 500.

[0090] The flexible strain sensor obtained in this comparative case (physical image shown) Figure 2 A tensile cycle test was performed as shown in (b), and the tensile cycle resistance change rate-cycle number graph was obtained. The tensile strain was 8%, and the number of tensile cycles was 500. The results are as follows. Figure 6 As shown. From Figure 6 As can be seen, the obtained flexible strain sensor without patterned carbon nanotubes shows a significant decrease in peak resistance during tensile cycling, with a decrease rate of 52.2%. The decrease rate is defined as the ratio of the difference between the resistance change rate in the first tensile cycle and the resistance change rate at final equilibrium to the resistance change rate in the first tensile cycle. Using the same method, the flexible strain sensor in Comparative Example 1 was subjected to 7% and 9% tensile cycle tests for 100 cycles, with the results shown below. Figure 7 and Figure 8 As shown, the decrease rates were 24.3% and 35.9%, respectively.

[0091] In addition, sensitivity (GF) calculations were performed on Examples 1-3 and Comparative Example 1, such as... Figure 9 As shown in the figure, sensitivity refers to the slope of the curve representing the rate of change of relative resistance versus strain during a tensile cycle. At strain rates of 4%–8%, the sensitivity of the flexible strain sensor based on patterned carbon nanotubes is 6.5, while the sensitivity of the flexible strain sensor without patterned carbon nanotubes is 4.8, which is 0.74 times higher. At strain rates of 8%–9%, ​​the sensitivity of the flexible strain sensor based on patterned carbon nanotubes is 31.0, while the sensitivity of the flexible strain sensor without patterned carbon nanotubes is 20.2, which is 0.65 times higher. At strain rates of 9%–10%, the sensitivity of the flexible strain sensor based on patterned carbon nanotubes is 103.2, while the sensitivity of the flexible strain sensor without patterned carbon nanotubes is 49.1, which is only 0.48 times higher. It is evident that the flexible strain sensor based on patterned carbon nanotubes not only exhibits excellent cyclic stability but also higher sensitivity than the flexible strain sensor without patterned carbon nanotubes. Furthermore, the advantage of the flexible strain sensor based on patterned carbon nanotubes becomes increasingly significant as the tensile strain increases.

[0092] Comparative Example 2

[0093] 1) Carbon nanotubes (CNTs) were uniformly added to deionized water at a mass percentage of 0.5% and stirred until homogeneous to obtain carbon nanotubes; then, 0.5-1 mL of carbon nanotube aqueous solution was mixed with ethanol solution and ultrasonicated using a cell disruption sonicator to obtain a very uniformly dispersed carbon nanotube dispersion with a volume of 1.5-3 mL.

[0094] 2) Apply a PDMS film with a hard protective film (thickness: 50μm) to the bottom of the acrylic mold groove using vacuum silicone grease;

[0095] 3) Pour the carbon nanotube dispersion into an acrylic mold and dry it at high temperature to prepare a patternless carbon nanotube circuit;

[0096] 4) Weigh the AB components of the liquid resin Ecoflex separately, mix them evenly in a 1:1 ratio, pour them into the mold onto the unpatterned circuit, and cure for 3-8 hours.

[0097] 5) Remove the molded flexible resin substrate and the patternless circuit embedded in the substrate, peel off the PDMS film layer with a hard protective film on the bottom, apply conductive silver paste to both ends, install copper wire electrodes, and place in an oven at 70-80℃ for curing for 3 hours; the resulting flexible strain sensor has an areal density of 1.0 mg / cm³. 2 .

[0098] Performance testing:

[0099] To facilitate cyclic tensile performance testing, the cured, unpatterned pure carbon nanotube-based flexible strain sensor was placed in a polytetrafluoroethylene (PTFE) bath to form a flexible base for tensile clamping. Then, the A and B components of the liquid resin Ecoflex were weighed and mixed in a 1:1 ratio, and poured into the PTFE bath to a thickness of approximately 2-4 mm. The mixture was cured for 3-8 hours. The cured flexible strain sensor with the flexible base was then removed from the PTFE bath, and its tensile performance was tested using a self-assembled electromechanical testing platform. The tensile strain was 8%, and the number of tensile cycles was 500.

[0100] from Figure 10 As can be seen, the obtained flexible strain sensor without patterned pure carbon nanotubes shows a significant decrease in both peak and valley resistance values ​​during the stretching cycle.

[0101] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A flexible strain sensor based on patterned carbon nanotubes, characterized in that, The flexible strain sensor is prepared according to the following steps: 1) Add 0.5% by mass of magnetically coated carbon nanotubes to deionized water and stir until homogeneous to obtain a carbon nanotube / ferric oxide aqueous solution; then mix 0.5-1 mL of the carbon nanotube / ferric oxide aqueous solution with an ethanol solution and sonicate using a cell disruption sonicator to obtain a uniformly dispersed carbon nanotube / ferric oxide dispersion with a volume of 1.5-3 mL. 2) A 50 μm thick PDMS film with a hard protective film is laid flat on the bottom of the acrylic mold groove using vacuum silicone grease; 3) Pour the carbon nanotube / ferric oxide dispersion into an acrylic mold, and place the mold in a magnetic field containing a pre-made mask for patterning preparation. After high-temperature drying, a patterned circuit is prepared. 4) Weigh the A and B components of the liquid resin Ecoflex separately, mix them evenly in a 1:1 ratio, pour them into the mold onto the patterned circuit, and cure for 3~8 hours; 5) Remove the molded flexible resin substrate and the patterned circuit embedded in the substrate, peel off the PDMS film layer with a hard protective film on the bottom, apply conductive silver paste to both ends, install copper wire electrodes, and place in an oven at 70~80 ℃ for curing for 3 h to obtain a flexible strain sensor with an areal density of 0.8 mg / cm³. 2 .

2. A flexible strain sensor based on patterned carbon nanotubes, characterized in that, The flexible strain sensor is prepared according to the following steps: 1) Add 1.0% by mass of magnetically coated carbon nanotubes to deionized water and stir until homogeneous to obtain a carbon nanotube / ferric oxide aqueous solution; then mix 0.5-1 mL of the carbon nanotube / ferric oxide aqueous solution with an ethanol solution and sonicate using a cell disruption sonicator to obtain a uniformly dispersed carbon nanotube / ferric oxide dispersion with a volume of 1.5-3 mL. 2) A 50 μm thick PDMS film with a hard protective film is laid flat on the bottom of the acrylic mold groove using vacuum silicone grease; 3) Pour the carbon nanotube / ferric oxide dispersion into an acrylic mold, and place the mold in a magnetic field containing a pre-made mask for patterning preparation. After high-temperature drying, a patterned circuit is prepared. 4) Weigh the A and B components of the liquid resin Ecoflex separately, mix them evenly in a 1:1 ratio, pour them into the mold onto the patterned circuit, and cure for 3~8 hours; 5) Remove the molded flexible resin substrate and the patterned circuit embedded in the substrate, peel off the PDMS film layer with a hard protective film on the bottom, apply conductive silver paste to both ends, install copper wire electrodes, and place in an oven at 70~80 ℃ for curing for 3 h to obtain a flexible strain sensor with an areal density of 0.9 mg / cm³. 2 .

3. A flexible strain sensor based on patterned carbon nanotubes, characterized in that, The flexible strain sensor is prepared according to the following steps: 1) Add 1.0% by mass of magnetically coated carbon nanotubes to deionized water and stir until homogeneous to obtain a carbon nanotube / ferric oxide aqueous solution; then mix 0.5-1 mL of the carbon nanotube / ferric oxide aqueous solution with an ethanol solution and sonicate using a cell disruption sonicator to obtain a uniformly dispersed carbon nanotube / ferric oxide dispersion with a volume of 1.5-3 mL. 2) A 50 μm thick PDMS film with a hard protective film is laid flat on the bottom of the acrylic mold groove using vacuum silicone grease; 3) Pour the carbon nanotube / ferric oxide dispersion into an acrylic mold, and place the mold in a magnetic field containing a pre-made mask for patterning preparation. After high-temperature drying, a patterned circuit is prepared. 4) Weigh the A and B components of the liquid resin Ecoflex separately, mix them evenly in a 1:1 ratio, pour them into the mold onto the patterned circuit, and cure for 3~8 hours; 5) Remove the molded flexible resin substrate and the patterned circuit embedded in the substrate, peel off the PDMS film layer with a hard protective film on the bottom, apply conductive silver paste to both ends, install copper wire electrodes, and place in an oven at 70~80 ℃ for curing for 3 h to obtain a flexible strain sensor with an areal density of 1.0 mg / cm³. 2 .

4. The application of a flexible strain sensor based on patterned carbon nanotubes as described in any one of claims 1-3 in the fabrication of flexible wearable devices.

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