A Wearable Fabric Strain Sensor and Its Preparation Method and Application

Abstract

The present invention provides a wearable fabric strain sensor, a preparation method thereof and an application. The wearable fabric strain sensor has a layered structure, which includes a modified fabric and a carbon-based ink conductive film coated on one surface of the modified fabric; the modified fabric includes a fabric substrate and a transfer paper heat-melted and cured on the surface of the fabric substrate facing the carbon-based ink conductive film, and a conductive electrode is connected to the carbon-based ink conductive film. The preparation method includes the following steps: (a) heat-melt curing the transfer paper onto the surface of the fabric substrate to form a modified layer to obtain a modified fabric; (b) printing the carbon-based ink on the modified fabric by screen printing and performing several printings; (c) rolling the obtained fabric-based conductive film and then connecting the conductive electrode. The wearable fabric strain sensor of the present invention has the characteristics of a wide response range, stable cycling performance, and the ability to work underwater. Attaching the sensor to the surface of the human skin can realize the recognition of different movement amplitudes of the limbs.

Description

Technical Field

[0001] The present invention belongs to the technical field of resistive strain sensors, and particularly relates to a wearable fabric strain sensor, a preparation method thereof, and an application thereof. Background Art

[0002] The working principle of a resistive strain sensor is to reflect the strain received by a material through a change in resistance, which has received wide attention in the fields of motion monitoring, medical health, human-computer interaction, etc. Compared with traditional metal-based or inorganic material strain sensors, a wearable strain sensor based on fabric overcomes the drawback of excessive material rigidity, has the characteristics of flexibility, thinness, bend resistance, foldability, and wearability, and at the same time exhibits good biocompatibility and the effect of realizing long-term monitoring. However, compared with traditional silicon-based substrates, fabric substrates are rough and porous, and it is very difficult to directly prepare a highly conductive thin film on them. How to prepare an environmentally friendly, low-cost, large-scale wearable fabric strain sensor with excellent electrical properties is a key step in promoting the industrialization of electronic fabric sensors. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the above-mentioned deficiencies and defects in the background art, and provide a wearable fabric strain sensor, a preparation method thereof, and an application thereof.

[0004] To solve the above technical problem, the technical solution proposed by the present invention is as follows:

[0005] A wearable fabric strain sensor, the wearable fabric strain sensor is a layered structure, which includes a modified fabric and a carbon-based ink conductive thin film coated on one surface of the modified fabric; the modified fabric includes a fabric substrate and a transfer paper thermally melted and cured on one side of the fabric substrate facing the carbon-based ink conductive thin film, and a conductive electrode is connected to the carbon-based ink conductive thin film.

[0006] In the above wearable fabric strain sensor, a transfer paper is thermally melted and cured on the fabric substrate of the modified fabric. Under the action of high temperature and pressure, the glue in the transfer paper will partially melt and penetrate into the fabric to form a stable connection, and the structure of the surface paper will not be damaged, greatly reducing the surface roughness of the fabric. After printing, the printing ink will not leak into the porous fabric fibers, and the consistency of the ink diffusing on the surface of the modified fabric will form a more uniform thin film.

[0007] The wearable fabric strain sensor of the present invention can be bent from the original length to a spacing of 1 cm.

[0008] Preferably, the wearable fabric strain sensor further includes another transfer paper heat-melted and cured on the outer surface of the carbon-based ink conductive film. By heat-melting and curing the transfer paper on the upper surface of the carbon-based ink conductive film, an encapsulated wearable fabric strain sensor can be obtained, which has a simple structure and good encapsulation effect.

[0009] Preferably, the carbon-based ink conductive film is prepared from carbon-based ink, and the carbon-based ink includes the following components in parts by weight: 0-12 parts of graphene, 0-12 parts of multi-walled carbon nanotubes, 0.5-1.5 parts of ethyl cellulose, and 30-50 parts of solvent; the total number of parts of graphene and multi-walled carbon nanotubes is 4-12 parts; the solvent is composed of absolute ethanol and n-butanol in a volume ratio of 1:2-1:5. The ink prepared in the present invention has a viscosity suitable for screen printing process, and the printed ink will not diffuse randomly to cause distortion of the printed pattern.

[0010] The carbon-based ink is prepared by the following method:

[0011] (1) Take absolute ethanol and n-butanol, mix them to obtain a mixed solution; add ethyl cellulose to the mixed solution and stir to make the ethyl cellulose disperse evenly to obtain a dispersion.

[0012] (2) Add graphene and multi-walled carbon nanotubes to the dispersion, and continuously stir with a defoamer at a speed of 1000-3000 revolutions per minute for 20-60 minutes to obtain a uniformly dispersed carbon-based ink.

[0013] Preferably, the graphene has a sheet diameter of 1-30 μm, a carbon content greater than 99 wt%, and a powder resistivity ρ < 1.0×10 -3 Ω·m; the multi-walled carbon nanotubes have a diameter of 8-15 nm and a length of 2-50 μm; the viscosity of the ethyl cellulose in a toluene / ethanol mixed solvent with a mass fraction of 5% is 4.0-100 cPa·s, and the volume ratio of toluene to ethanol is 80:20.

[0014] Preferably, the mass ratio of graphene to multi-walled carbon nanotubes is 15:1-15:9. By further controlling the mass ratio of graphene to multi-walled carbon nanotubes in the present invention, the conductivity of the printed ink can be further improved while the multi-walled carbon nanotubes have a high dispersibility.

[0015] Preferably, the fabric substrate is a cotton-containing fabric, and the cotton content in the cotton-containing fabric is 50-100%; the gram weight of the cotton-containing fabric is 80-200 g / m 2; The transfer paper is a composite of a thermoplastic adhesive material and paper, and the thermoplastic adhesive material is polyurethane; specifically, the transfer paper can be TransMax Crown A4 dark transfer paper. The highly elastic polyurethane (PU) can withstand a tensile force of 10 - 300%; it is firmly nested with the fabric substrate and will not crack after washing;

[0016] The thickness range of the carbon-based ink conductive film is 1μm - 200μm;

[0017] Both ends of the carbon-based ink conductive film are connected to conductive electrodes; the conductive electrodes are one of conductive copper foil, copper tape, and conductive carbon tape.

[0018] Preferably, the fabric substrate is pure cotton fabric; the lower the cotton content, the worse the effect of the transfer paper modification; the thickness range of the carbon-based ink conductive film is 90 - 130μm.

[0019] Preferably, a cured silver paste is coated at the junction of the conductive electrode and the carbon-based ink conductive film. The specific preparation method is to coat conductive silver paste at the junction of the conductive electrode and the carbon-based ink conductive film, and after coating the silver paste, the obtained sample needs to be placed in an oven and baked at 80°C for 15 minutes until the silver paste is cured. In the present invention, silver paste is coated at the junction to eliminate the interface resistance and avoid the influence caused by contact.

[0020] As a general inventive concept, the present invention provides a preparation method of a wearable fabric strain sensor, including the following steps:

[0021] (a) Using a heat transfer machine to thermally fuse and cure the transfer paper onto the surface of the fabric substrate to form a modified layer, obtaining a modified fabric;

[0022] (b) By screen printing, the carbon-based ink is printed on the modified fabric in step (a), and several printings are carried out (the conductivity of the film can be improved by multiple printings), obtaining a fabric-based conductive film;

[0023] (c) Rolling the fabric-based conductive film obtained in step (b) through a rolling press to reduce the thickness of the fabric-based conductive film (the sheet resistance of the thin sheet can be reduced), obtaining a rolled fabric-based conductive film, which includes a modified fabric and a carbon-based ink conductive film covering one side surface of the modified fabric; then connecting conductive electrodes to the carbon-based ink conductive film.

[0024] The present invention uses a heat transfer machine to thermally print a layer of transfer paper on the surface of the fabric substrate to modify the rough and porous fabric surface. The prepared pure carbon-based ink is printed on the surface of the modified fabric by screen printing. The sheet resistance of the conductive film is reduced by controlling the number of printings and applying rolling pressure, and then the conductive electrodes are connected to both ends of the film.

[0025] Preferably, step (a) specifically includes the following steps: Clean the fabric substrate by wiping it with absolute ethanol, then place it on the sponge pad of a heat transfer machine. Place the transfer paper on the fabric substrate, and place a piece of silicone oil paper on the top. The silicone oil paper protects the transfer paper from being damaged by the pressure table of the heat transfer machine. Heat-melt and cure the transfer paper onto the surface of the fabric substrate through the heat transfer machine to obtain the modified fabric.

[0026] When the fabric substrate is pure cotton fabric, the heat transfer temperature is 170 - 180 °C, the time is 8 - 15 seconds, and the pressure is moderate (the transfer paper can be heat-melt and cured); when the fabric substrate is non-pure cotton fabric, the heat transfer temperature is 120 - 160 °C, the time is 5 - 10 seconds, and the pressure is suitable (the transfer paper can be heat-melt and cured).

[0027] In step (b), the screen printing mesh count range is 100 - 250 mesh, and the printed pattern can be customized into different styles; between several screen printings, the sample needs to be placed in an oven at 80 °C and dried for 10 - 30 minutes after each printing; the thickness of the first screen printing is 46 ± 2.55 μm, and the thickness of each subsequent screen printing is 28 ± 0.35 μm; the number of screen printings is 1 - 6 times, preferably 3 - 4 times, and further preferably 3 times.

[0028] In step (c), the roller spacing of the roller press is 140 μm - 400 μm. Preferably, the roller spacing of the roller press is 140 μm - 300 μm. Further preferably, the preferred roller spacing of the roller press is 160 μm - 180 μm.

[0029] Preferably, the preparation method further includes the following steps: Place a layer of transfer paper on the uppermost layer of the roll-pressed fabric-based conductive film after being treated in step (d), and then place a piece of silicone oil paper on the top. Heat-melt and cure the transfer paper on the upper surface of the carbon-based ink conductive film through the high temperature and pressure of the heat transfer machine to complete the encapsulation, and then it is obtained. By repeating the heat transfer step, the sensor can be simply encapsulated, and thus the encapsulated flexible strain sensor can be obtained. The temperature, time, etc. of the above heat transfer are generally the same as those in step (a).

[0030] As a general inventive concept, the present invention provides an application of the above wearable fabric strain sensor or the wearable fabric strain sensor prepared by the above preparation method in motion monitoring and gesture recognition.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] (1) The present invention uses all-carbon materials, which have good biocompatibility and environmental protection. The carbon-based ink conductive film has strong conductivity, is not easy to fall off after encapsulation, and has certain waterproof properties, which are beneficial to the large-scale integration and multi-scenario use of wearable electronic devices.

[0033] (2) The wearable fabric strain sensor prepared by the present invention has the characteristics of a wide response range, stable cyclic performance, and the ability to work underwater. When the sensor is attached to the surface of the human skin, it can identify different movement amplitudes of the limbs, specifically including the movement recognition of fingers, wrists, and elbow joints, and can be integrated into a fabric glove. Combined with machine learning, it can well distinguish and recognize different gestures.

[0034] (3) The process of the wearable fabric strain sensor of the present invention is simple, low-cost, and can be rapidly prepared on a large scale, showing broad application prospects in personal motion monitoring, the medical field, human-computer interaction, artificial intelligence, etc. Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0036] Figure 1 Partial structural schematic diagram of the wearable fabric strain sensor;

[0037] Figure 2 SEM image of the fabric substrate in the embodiment of the present invention;

[0038] Figure 3 SEM image of the modified fabric obtained in the embodiment of the present invention;

[0039] Figure 4 SEM image of the fabric-based conductive film obtained in Example 4 of the present invention;

[0040] Figure 5 SEM image of the roll-pressed fabric-based conductive film obtained in Example 7 of the present invention;

[0041] Figure 6 Column chart (a) showing the influence of the number of printing times on the sheet resistance of the film and curve chart showing the influence of the roll-pressing spacing on the sheet resistance of the film during the preparation process of the wearable fabric strain sensor of the present invention;

[0042] Figure 7 Relationship between the change rate of the sensor resistance and time of the wearable fabric strain sensor of the present invention under different bending deformations;

[0043] Figure 8 Relationship between the resistance change and the number of cycles of the wearable fabric strain sensor of the present invention under a fixed length of 40 mm of bending for 5000 cycles;

[0044] Figure 9 For Figure 8 An enlarged view of FIG. a in the middle figure;

[0045] Figure 10 For Figure 8 An enlarged view of FIG. b in the middle figure;

[0046] Figure 11 This is a graph (a) showing the relationship between the resistance change and time of the wearable fabric strain sensor of the present invention for detecting joint movements of fingers in an underwater environment and in the air, and a graph (b) showing the relationship between the resistance change and time during wrist joint movement; the internal inset is a physical display diagram;

[0047] Figure 12 This is a physical display diagram when the wearable fabric strain sensor of the present invention is integrated into a fabric glove;

[0048] Figure 13 This is a graph showing the relationship between the resistance change rate and time obtained by measuring different gestures after the wearable fabric strain sensor of the present invention is integrated with a fabric glove, and the internal inset is the corresponding gesture diagram;

[0049] Figure 14 This is the recognition rate of different gestures obtained by combining the gesture signals measured after the wearable fabric strain sensor of the present invention is integrated with a fabric glove and machine learning. Detailed implementation manners

[0050] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively and meticulously in conjunction with the accompanying drawings of the specification and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0051] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0052] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0053] Example 1: Preparation of carbon-based ink

[0054] Measure 10 ml of anhydrous ethanol with a purity of 99.9% and 30 ml of n-butanol with a purity of 99.4%, and mix them to obtain a mixed solution; weigh 1 g of ethyl cellulose and place it in the mixed solution, and use a magnetic stirrer to stir at a rate of 800 revolutions per minute for 4 hours until it is evenly dispersed to obtain a dispersion;

[0055] Weigh 7.5 g of graphene powder and 0.5 g of multi-walled carbon nanotubes (with a diameter of 8 - 15 nm and a length of 30 - 50 μm), place them in the above-prepared dispersion liquid, and continuously stir for 30 minutes at a speed of 3000 revolutions per minute using a defoaming blender to obtain carbon-based ink.

[0056] Among them, the viscosity of ethyl cellulose in a mixed solvent of toluene / ethanol (toluene and ethanol volume ratio of 80:20) with a mass fraction of 5% is 10 cPa·s; the sheet diameter of the graphene powder is 1 - 5 μm, the carbon content is greater than 99 wt%, the resistivity of the powder ρ < 1.0×10 -3 Ω·m, the diameter of the multi-walled carbon nanotubes is 8 - 15 nm, and the length is 30 - 50 μm.

[0057] Examples 2 - 15: Preparation of wearable fabric strain sensors

[0058] A wearable fabric strain sensor has a layered structure, which includes a modified fabric and a carbon-based ink conductive film coated on one surface of the modified fabric; the modified fabric includes a fabric substrate and a transfer paper thermally melted and cured on one side of the fabric substrate facing the carbon-based ink conductive film, and conductive electrodes are connected to both ends of the carbon-based ink conductive film. The wearable fabric strain sensor also includes another transfer paper thermally melted and cured on the outer surface of the carbon-based ink conductive film. A partial structural schematic diagram of the wearable fabric strain sensor can be as Figure 1 shown.

[0059] The above fabric substrate is a pure cotton fabric, and the gram weight of the pure cotton fabric is 130 g / m 2 ; the transfer papers used are all TransMax Crown A4 dark transfer papers; the conductive electrodes are conductive carbon tapes.

[0060] The preparation method includes the following steps:

[0061] Step 1: Wipe and clean the surface of the fabric substrate (a pure cotton fabric of A4 paper size) with anhydrous ethanol, place the treated fabric substrate on the sponge pad of a heat transfer printer, place an A4-sized transfer paper on the fabric substrate, and then place an isolation silicone oil paper on the transfer paper. Through the action of high temperature and pressure of the heat transfer printer, the transfer paper is thermally melted and cured (heat-printed) on the fabric substrate to obtain a modified fabric; among them, the temperature of heat transfer is 180 °C, the time is 10 seconds, and the pressure is greater than 0.2 kg / cm 2 is sufficient.

[0062] Step 2: Printing and drying: Use screen printing to print the carbon-based ink prepared in Example 1 on the modified fabric obtained in Step 1. The mesh number of the screen printing screen is 150 meshes, and the stripe size is: (a) length 7 cm, width 1 cm; or (b) length 4 cm, width 0.7 cm.

[0063] Print 5 stripes each time, with a spacing of 1 cm between the stripes. The gap between the silk screen and the substrate is approximately 1 - 2 mm (the distance between the patterned template in the silk screen and the modified fabric). Scrape the squeegee evenly across the screen to obtain printed stripes. Place the printed sample in an oven and bake it at 80 °C for 30 minutes;

[0064] Repeat the above printing and drying steps 0 - 4 times for the obtained sample to get a fabric-based conductive film. Subsequently, separate multiple fabric-based conductive films with scissors. The thickness of the first screen printing is 46 ± 2.55 μm, and the thickness of each subsequent screen printing is 28 ± 0.35 μm.

[0065] Step 3: Roll the strip-shaped fabric-based conductive film obtained in Step 2 through a rolling press, and adjust the spacing between the rolling rollers (range 140 μm - 400 μm) to obtain a rolled fabric-based conductive film, which includes a modified fabric and a carbon-based ink conductive film coated on one surface of the modified fabric.

[0066] Step 4: Stick conductive copper tapes at both ends of the above carbon-based ink conductive film, apply conductive silver paste at the junction of the conductive copper tape and the carbon-based ink conductive film. After applying the silver paste, place the obtained sample in an oven and bake it at 80 °C for 15 min until the silver paste is cured.

[0067] Step 5: Place the rolled fabric-based conductive film processed in Step 4 in a heat transfer printer. Place a layer of dark transfer paper on the top, and then place a piece of silicone oil paper on it. Set the parameters of the heat transfer printer (temperature 180 °C, time 10 s), and apply a moderate pressure (greater than 0.2 kg / cm 2 ) to thermally melt and cure the transfer paper on the surface of the conductive film to complete the encapsulation, thus obtaining a wearable fabric strain sensor.

[0068] In the above Examples 2 - 15, the specific number of printing times, stripe size in Step 2, and the spacing of the rollers in Step 3 are shown in Table 1.

[0069] Table 1 Printing times and roller spacing of each example

[0070]

[0071]

[0072] Among them, a partial structural schematic diagram of the wearable fabric strain sensor is as Figure 1 shown. The surface microtopography of the fabric substrate used in the example is as Figure 2 shown. The fabric fibers show a rough structure, which will cause the printing ink to leak or spread unevenly; the microtopography of the obtained modified fabric in the example is as Figure 3As shown, a dense granular film is formed on the surface of the modified fabric, making the fabric surface smoother and blocking the leakage of ink; the surface microtopography of the fabric-based conductive film obtained in Example 4 is as Figure 4 shown. After multiple printings, the carbon-based ink deposition on the surface of the modified fabric tends to be flat. In the enlarged view, the graphene sheets are stacked well, and filamentous carbon nanotubes bridge between the sheets; the surface microtopography of the roll-pressed fabric-based conductive film obtained in Example 7 (corresponding to the example with a total of 3 printings and a roller spacing of 160 μm) is as Figure 5 shown. After roll-pressing, the carbon-based ink conductive film on the modified fabric is denser and more uniform. In the enlarged view, the graphene sheets are stacked more closely, and there are more uniform carbon nanotube bridges.

[0073] In the above examples, the sheet resistance of the fabric-based conductive films prepared in Examples 2-5 was measured, and the sheet resistance of the roll-pressed fabric-based conductive films prepared in Examples 6-14 was measured. The above sheet resistance values were all measured by a four-probe sheet resistance meter. The influence of the specific number of printings on the sheet resistance of the film can be seen in Appendix Figure 6 a, corresponding to Examples 2-5; the influence of the specific roller spacing on the sheet resistance of the film can be seen in Appendix Figure 6 b, corresponding to Examples 6-14.

[0074] From Appendix Figure 6 a and 6b, it can be seen that increasing the number of printings will reduce the sheet resistance of the conductive film. The change in the sheet resistance is relatively large after the second and third printings. This is due to the filling of the unsaturated areas in the printed pattern by the ink. When the number of printings is 4, the decrease in the sheet resistance of the film is relatively slow. At this time, the filling area of the ink is saturated, and the decrease in the sheet resistance is due to the increase in the film thickness. At the same time, reducing the roller width will also reduce the sheet resistance of the conductive film. The reason is that the mechanical force reduces the distance between the graphene sheets in the conductive film, making the stacking more compact.

[0075] Example 16: Electrical performance detection of wearable fabric strain sensors

[0076] First, the wearable fabric strain sensor with a length of 7 cm and a width of 1 cm prepared in Example 15 was attached to a PET film, and the length of the PET film was greater than that of the sensor. The electrical performance of the sensor's bending and resistance change was tested using a tensile test system. The PET film was clamped by the fixture, and the sensor was bent by changing the distance between the fixtures. The resistance change values of the wearable fabric strain sensor at different bending distances from 10 to 60 mm were measured, and a 5000-cycle bending test was carried out under the condition of bending 40 mm at a rate of 16 mm / s. The bending distance was achieved by adjusting the forward distance of the fixture during the operation.

[0077] The test results are shown in Appendix Figures 7 - 10As shown, it can be found that the wearable fabric strain sensor will not be damaged under large deformations. When bent by 10 mm, the relative resistance change is approximately 5%; when bent by 20 mm, the relative resistance change is approximately 6.2%; when bent by 30 mm, the relative resistance change is approximately 7.5%; when bent by 40 mm, the relative resistance change is approximately 8.1%; when bent by 50 mm, the relative resistance change is approximately 9.0%; when bent by 60 mm, the relative resistance change is approximately 9.7%. The sensor has good response and discrimination for different bending deformations, and after 5000 cycles of bending tests, the initial resistance change decreased by about 1%, showing good stability. The above wearable fabric strain sensor can be bent from an original length of 7 cm to a range with a spacing of 1 cm.

[0078] Example 17: The wearable fabric strain sensor is used for motion monitoring

[0079] The wearable fabric strain sensor with a length of 4 cm and a width of 0.7 cm prepared in Example 7 was directly attached to the human finger and wrist. The monitoring ability of the sensor for joint motion was studied, and the results are as follows Figure 11 shown. From Figure 11 it can be seen that the wearable fabric strain sensor has a good recognition effect on wrist bending, and for finger motion recognition, the signal contrast in water and air is almost undistorted.

[0080] Example 18: The wearable fabric strain sensor is used for gesture recognition

[0081] Five wearable fabric strain sensors were integrated into five different finger positions of a fabric glove to obtain an intelligent fabric glove, and its physical diagram is as follows Figure 12 shown. The glove was worn on the hand, and the recognition of 11 different gestures was achieved by collecting the resistance changes corresponding to the deformations of each sensor. The signal waveform diagram is as follows Figure 13 shown. From the figure, it can be seen that the fabric strain sensor can capture the different deformations brought by different gestures, and there are obvious differences in the waveforms of the signals, which can effectively distinguish different gestures. Finally, combining the collected data with machine learning can obtain a good recognition effect, as Figure 14 shown, and its average recognition effect is 99.36%.

Claims

1. A wearable fabric strain sensor, characterized in that, The wearable fabric strain sensor has a layered structure, which includes a modified fabric and a carbon-based ink conductive film coated on one surface of the modified fabric; the modified fabric includes a fabric substrate and a transfer paper thermally melted and cured on one side of the fabric substrate facing the carbon-based ink conductive film, and a conductive electrode is connected to the carbon-based ink conductive film; The carbon-based ink conductive film is prepared from a carbon-based ink, and the carbon-based ink includes the following components in parts by weight: 0-12 parts of graphene, 0-12 parts of multi-walled carbon nanotubes, 0.5-1.5 parts of ethyl cellulose, and 30-50 parts of a solvent; the total number of parts of the graphene and the multi-walled carbon nanotubes is 4-12 parts; the solvent is composed of anhydrous ethanol and n-butanol in a volume ratio of 1:2-1:5; The transfer paper is a composite of a thermoplastic adhesive material and paper, and the thermoplastic adhesive material is polyurethane.

2. The wearable fabric strain sensor according to claim 1, wherein The wearable fabric strain sensor further includes another transfer paper thermally melted and cured on the outer surface of the carbon-based ink conductive film.

3. The wearable fabric strain sensor according to claim 1, wherein The carbon-based ink is prepared by the following method: (1) Take anhydrous ethanol and n-butanol, mix them to obtain a mixed solution; add ethyl cellulose to the mixed solution and stir to make the ethyl cellulose disperse evenly to obtain a dispersion; (2) Add graphene and multi-walled carbon nanotubes to the dispersion, and continuously stir with a defoamer at a speed of 1000-3000 revolutions per minute for 20-60 minutes to obtain a uniformly dispersed carbon-based ink.

4. The wearable fabric strain sensor according to claim 3, wherein The sheet diameter of the graphene is 1-30 μm, the carbon content is greater than 99 wt%, and the powder resistivity ρ < 1.0×10 -3 Ω·m; the diameter of the multi-walled carbon nanotubes is 8-15 nm and the length is 2-50 μm; the viscosity of the ethyl cellulose in a toluene / ethanol mixed solvent with a mass fraction of 5% is 4.0-100 cPa·s, and the volume ratio of toluene to ethanol is 80:20; The mass ratio of the graphene to the multi-walled carbon nanotubes is 15:1-15:

9.

5. The wearable fabric strain sensor according to any one of claims 1-4, characterized in that, The fabric substrate is a cotton-containing fabric, and the cotton content in the cotton-containing fabric is 50-100%; the grammage of the cotton-containing fabric is 80-200 g / m 2 ; the thickness range of the carbon-based ink conductive film is 1 μm-200 μm; Both ends of the carbon-based ink conductive film are connected with conductive electrodes; The conductive electrode is one of a conductive copper foil, a copper tape, and a conductive carbon tape.

6. The wearable fabric strain sensor according to claim 5, wherein, The fabric substrate is a pure cotton fabric; the thickness range of the carbon-based ink conductive film is 90-130 μm; The junction of the conductive electrode and the carbon-based ink conductive film is coated with cured silver paste.

7. A method for preparing a wearable fabric strain sensor according to any one of claims 1-6, characterized in that, It includes the following steps: (a) Use a heat transfer machine to thermally melt and cure the transfer paper onto the surface of the fabric substrate to form a modified layer, obtaining a modified fabric; (b) By means of screen printing, print the carbon-based ink on the modified fabric in step (a) and perform several printings to obtain a fabric-based conductive film; (c) Roll the fabric-based conductive film obtained in step (b) through a rolling machine to obtain a rolled fabric-based conductive film, which includes a modified fabric and a carbon-based ink conductive film coated on one surface of the modified fabric; then connect a conductive electrode to the carbon-based ink conductive film.

8. The preparation method according to claim 7, wherein Step (a) specifically includes the following steps: Wipe and clean the fabric substrate with anhydrous ethanol and then place it on the sponge pad of the heat transfer machine, place the transfer paper on the fabric substrate, and place a piece of silicon oil paper on the top. The silicon oil paper protects the transfer paper from being damaged by the pressure table of the heat transfer machine. Thermally melt and cure the transfer paper onto the surface of the fabric substrate through the heat transfer machine to obtain a modified fabric; When the fabric substrate is a pure cotton fabric, the heat transfer temperature is 170-180 °C and the time is 8-15 seconds; when the fabric substrate is a non-pure cotton fabric, the heat transfer temperature is 120-160 °C and the time is 5-10 seconds; In step (b), the mesh count of the screen printing stencil ranges from 100 to 250 meshes; between several screen printing operations, the sample needs to be placed in an oven at 80 °C for 10 - 30 minutes after each printing; the thickness of the first screen printing is 46 ± 2.55 μm, and the thickness of each subsequent screen printing is 28 ± 0.35 μm; the number of screen printing operations is 1 - 6 times; In step (c), the roller spacing of the roller press is 140 μm - 300 μm.

9. The preparation method according to claim 7, characterized in that, The preparation method further includes the following steps: placing a transfer paper on the uppermost layer of the roll-pressed fabric-based conductive film after being processed in step (c), then padding a piece of silicone oil paper above it, and hot-melting and curing the transfer paper on the upper surface of the carbon-based ink conductive film through the high temperature and pressure of a heat transfer printing machine to complete the encapsulation, thus obtaining the product.

10. Application of a wearable fabric strain sensor according to any one of claims 1 - 6 or a wearable fabric strain sensor prepared by the preparation method according to any one of claims 7 - 9 in motion monitoring and gesture recognition.

Images