Preparation method of bimodal flexible sensor and flexible sensor thereof

Abstract

This disclosure relates to the field of flexible sensor technology, and in particular to a method for preparing a dual-modal flexible sensor and the flexible sensor thereof. The method includes: S1, weighing an aqueous dispersion of multi-walled carbon nanotubes and an aqueous dispersion of monolayer graphene oxide, adding deionized water to prepare a mixed dispersion, and stirring to achieve uniform dispersion; S2, cleaning and drying waterborne polyurethane microfiber leather; S3, uniformly spraying the mixed dispersion prepared in step S1 onto the surface of the waterborne polyurethane microfiber leather to obtain a sprayed sample; S4, pressing and drying the sprayed sample; S5, cutting the dried and cured sprayed sample to obtain a standard-sized sample, and attaching electrodes to both ends of the standard-sized sample to obtain a flexible sensor with dual-modal sensing functions of pressure and temperature. This disclosure enables the flexible sensor to simultaneously possess excellent pressure and temperature sensing performance.

Description

Technical Field

[0001] This disclosure relates to the field of flexible sensor technology, and in particular to a method for fabricating a dual-modal flexible sensor and the flexible sensor thereof. Background Technology

[0002] With the rapid development of the Internet of Things (IoT) and artificial intelligence (AI) technologies, flexible sensing technology, as a core enabling technology in health monitoring, tactile perception, and human-computer interaction, has become a hot topic in interdisciplinary research. Among numerous flexible sensors, flexible piezoresistive sensors, by converting external pressure stimuli into quantifiable changes in resistance signals, exhibit excellent biocompatibility, surface fit, and integration, attracting widespread attention. Skin, as the primary sensory organ of the human body, has the dual function of sensing pressure and temperature. Therefore, designing a dual-modal flexible sensor capable of simultaneously monitoring pressure and temperature is of great significance.

[0003] However, existing technologies include single-function flexible pressure sensors based on carbon nanotubes (CNTs) or graphene, temperature sensors based on thermosensitive polymers, and integrated devices that achieve multimodal sensing through device stacking. However, none of these solutions fundamentally solve the challenge of simultaneously achieving high performance, low complexity, and comfortable wear. The main problems with existing technologies are as follows: (1) Traditional dual-mode sensors are usually composed of independent functional units stacked together, which are complex in structure and have mutually restrictive performance, making it difficult to achieve high sensitivity and wide sensing range at the same time. (2) Although existing single-type thermal resistance-piezoresistive sensors can sense temperature and pressure through a single sensing unit, it is difficult to achieve both higher temperature resistivity and pressure sensitivity. (3) Some sensors use organic solvent-based materials, and the preparation process causes environmental pollution. (4) Existing flexible sensors are not comfortable enough when worn, which limits their application and promotion in real-world scenarios. Summary of the Invention

[0004] This disclosure provides a method for fabricating a dual-modal flexible sensor and the flexible sensor thereof, in order to solve the problems existing in the background art. The technical solution is as follows: In a first aspect, embodiments of this disclosure provide a method for fabricating a dual-modal flexible sensor, comprising the following steps: S1. Weigh out the aqueous dispersion of multi-walled carbon nanotubes and the aqueous dispersion of monolayer graphene oxide in a mass ratio of 2:1-10:1, add deionized water to prepare a mixed dispersion with a total carbon nanomaterial concentration of 0.375wt%-1.5wt%, and stir to make the multi-walled carbon nanotubes and graphene oxide uniformly dispersed. S2. Clean the water-based polyurethane microfiber leather and let it air dry. S3. The mixed dispersion prepared in step S1 is uniformly sprayed onto the surface of the waterborne polyurethane microfiber leather to achieve a carbon nanomaterial loading of 0.81wt%-5wt% to obtain a sprayed sample. S4. Press the sprayed sample and dry and cure it; S5. Cut the dried and cured sprayed sample to obtain a standard size sample, and attach electrodes to both ends of the standard size sample to obtain a flexible sensor with pressure and temperature dual-mode sensing function.

[0005] Optionally, the stirring in step S1 to uniformly disperse the multi-walled carbon nanotubes and graphene oxide includes: stirring at 25°C for 20 minutes and then sonicating in an ultrasonic cell disruptor at 300W power for 2 hours.

[0006] Optionally, the water-based polyurethane microfiber leather is cleaned and dried for later use, including: cleaning the water-based polyurethane microfiber leather three times with deionized water to remove surface impurities and then drying it for later use.

[0007] Optionally, step S3, which involves uniformly spraying the mixed dispersion prepared in step S1 onto the surface of the waterborne polyurethane microfiber leather, includes: loading the mixed dispersion prepared in step S1 into a pneumatic spray gun and uniformly spraying the mixed dispersion onto the waterborne polyurethane microfiber leather with compressed air at 0.3 MPa.

[0008] Optionally, the sprayed sample is pressed and dried for curing, including: pressing the sprayed sample with a pressure roller at a pressure of 0.3 MPa and a speed of 6.5 rpm / min using a pressure dyeing resin machine to promote the penetration of carbon nanomaterials into the deep microfiber layer of the waterborne polyurethane microfiber leather, and then placing it in an oven for drying and curing.

[0009] Optionally, the concentration of the multi-walled carbon nanotube aqueous dispersion in step S1 is 10 wt%, and the concentration of the monolayer graphene oxide aqueous dispersion is 1 wt%.

[0010] Optionally, the waterborne polyurethane microfiber leather has a basis weight of 248 g / m², and the microfiber has a diameter of 3 μm.

[0011] Optionally, the pneumatic spray gun is supplied with compressed air by an oil-free, silent air compressor.

[0012] Secondly, a dual-modal flexible sensor is also provided, which is prepared by the aforementioned preparation method.

[0013] Optionally, the dual-modal flexible sensor further includes a flexible substrate on which the sensing array of the flexible sensor is disposed.

[0014] The advantages or beneficial effects of the above technical solutions include at least the following: 1) Achieving both high pressure sensitivity and wide pressure sensing range in a single sensing unit, balancing both: This results in a pressure sensitivity S1 of 217.1270 kPa for the dual-modal flexible sensor (WMG sensor). -1 (0~5 kPa), S2=83.2031 kPa -1 (0~92 kPa), S3=4.9252 kPa -1 (92~160 kPa), the sensing range covers 0~150 kPa (the detection limit for ultra-light loads reaches 46 Pa), effectively breaking through the traditional constraint between high sensitivity and wide range; 2) By adjusting the mass ratio of water-based multi-walled carbon nanotubes to monolayer graphene oxide (MWCNT / GO) and the loading of carbon nanomaterials, the conductive network structure is optimized, enabling the flexible sensor to simultaneously possess excellent pressure and temperature sensing performance. The same sensing unit can simultaneously sense pressure (NTC characteristics) and temperature, with a temperature sensitivity TCR of -1.46% / ℃ (20~60℃) and a temperature sensing range of 0~150℃, realizing integrated dual-function sensing. 3) A high-performance dual-modal sensor is fabricated using a simple, low-cost, and environmentally friendly process. The sensor's pressure response / recovery time is approximately 100 ms / 70 ms, which can meet the requirements for real-time human motion monitoring. After 2000 dynamic loading / unloading cycles at 20 kPa, the sensor performance shows no significant attenuation and has remarkable long-term durability. 4) While ensuring sensing performance, the breathability and wearing comfort of the sensor are improved. The conductive functional layer is prepared by water-based materials (water-based polyurethane, MWCNT water-based dispersion, GO water-based dispersion) and a one-step pneumatic spraying method. No organic solvents are required, the process is green and controllable, and it has the potential for large-scale production. Good wearing comfort: with microfiber leather as the base, it has excellent breathability and mechanical flexibility, fits the skin without restraint, and the wearing comfort is better than traditional sensor materials. 5) It can be expanded into a sensor array. The sensing units can be integrated and assembled into, for example, a 4×4 pixel flexible sensing array to achieve accurate identification and visualization of spatial pressure distribution.

[0015] The above overview is for illustrative purposes only and is not intended to be limiting in any way. Further aspects, embodiments, and features of this disclosure will become readily apparent from the accompanying drawings and the following detailed description, in addition to the illustrative aspects, embodiments, and features described above. Attached Figure Description

[0016] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this disclosure and should not be construed as limiting the scope of this disclosure.

[0017] Figure 1 The fabrication process flow diagram and structural schematic diagram of the dual-modal flexible sensor in the embodiments of this disclosure are shown; Figure 2 The test results of the flexible sensor in this disclosure example are shown in various test projects. Detailed Implementation

[0018] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this disclosure. Therefore, the drawings and description are to be considered exemplary in nature and not restrictive.

[0019] To better illustrate this disclosure, numerous specific details are set forth in the following detailed description. Those skilled in the art will understand that this disclosure can be practiced without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art have not been described in detail in order to highlight the main points of this disclosure.

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0021] This disclosure provides a method for fabricating a dual-modal flexible sensor, such as... Figure 1 As shown, where, Figure 1 Figure (a) in the diagram is a schematic diagram of the preparation of the mixed dispersion. Figure 1 Figure (b) shows a schematic diagram of the fabrication process of the dual-modal flexible sensor, including the following steps: S1. Weigh out the aqueous dispersion of multi-walled carbon nanotubes and the aqueous dispersion of monolayer graphene oxide at a mass ratio of 2:1-10:1, add deionized water to prepare a mixed dispersion with a total carbon nanomaterial concentration of 0.375wt%-1.5wt%, and stir to ensure uniform dispersion of multi-walled carbon nanotubes and graphene oxide; wherein, S2. Clean the water-based polyurethane microfiber leather and let it air dry. S3. The mixed dispersion prepared in step S1 is uniformly sprayed onto the surface of the waterborne polyurethane microfiber leather to achieve a carbon nanomaterial loading of 0.81wt%-5wt% to obtain a sprayed sample. S4. Press the sprayed sample and dry and cure it; S5. Cut the dried and cured sprayed sample to obtain a standard size sample, and attach electrodes to both ends of the standard size sample to obtain a flexible sensor with pressure and temperature dual-mode sensing function.

[0022] Following the steps outlined above, the following two specific embodiments are implemented: S1. Weigh out the aqueous dispersion of multi-walled carbon nanotubes and the aqueous dispersion of monolayer graphene oxide at a mass ratio of 2:1, add deionized water to prepare a mixed dispersion with a total carbon nanomaterial concentration of 0.375wt%, and stir to make the multi-walled carbon nanotubes and graphene oxide uniformly dispersed. S2. Clean the water-based polyurethane microfiber leather and let it air dry. S3. The mixed dispersion prepared in step S1 is uniformly sprayed onto the surface of the waterborne polyurethane microfiber leather to achieve a carbon nanomaterial loading of 0.81 wt% to obtain a sprayed sample. S4. Press the sprayed sample and dry and cure it; S5. Cut the dried and cured sprayed sample to obtain a standard size sample, and attach electrodes to both ends of the standard size sample to obtain a flexible sensor with pressure and temperature dual-mode sensing function.

[0023] Test results show that the WMG has a sensitivity of S1 = 199.104 kPa within the 2.5 kPa range. - ¹ It exhibits good sensing response over a wide range of 100 kPa, with a response time / recovery time of approximately 90 ms / 80 ms. Its performance remains stable after 2000 cycles of testing under a 20 kPa load, and the lowest detectable load is approximately 46 Pa.

[0024] Example 2: S1. Weigh out the aqueous dispersion of multi-walled carbon nanotubes and the aqueous dispersion of monolayer graphene oxide at a mass ratio of 10:1, add deionized water to prepare a mixed dispersion with a total carbon nanomaterial concentration of 1.5wt%, and stir to make the multi-walled carbon nanotubes and graphene oxide uniformly dispersed. S2. Clean the water-based polyurethane microfiber leather and let it air dry. S3. The mixed dispersion prepared in step S1 is uniformly sprayed onto the surface of the waterborne polyurethane microfiber leather to achieve a carbon nanomaterial loading of 5wt% to obtain a sprayed sample. S4. Press the sprayed sample and dry and cure it; S5. Cut the dried and cured sprayed sample to obtain a standard size sample, and attach electrodes to both ends of the standard size sample to obtain a flexible sensor with pressure and temperature dual-mode sensing function.

[0025] Test results show that the WMG sensitivity S1 is 180.454 kPa within the 5 kPa range. - ¹ It exhibits good sensing response over a wide range of 130 kPa, with a response time / recovery time of approximately 100 ms / 60 ms. Its performance remains stable after 2000 cycles of testing under a 20 kPa load, and the minimum detectable load is approximately 50 Pa.

[0026] As can be seen from the above embodiments, this disclosure optimizes the conductive network structure by adjusting the mass ratio of multi-walled carbon nanotubes (MWCNT / GO) to monolayer graphene oxide (MWCNT / GO) and the loading of carbon nanomaterials, enabling the flexible sensor to simultaneously possess excellent pressure and temperature sensing performance. The same sensing unit can simultaneously sense pressure (NTC characteristic) and temperature, with a temperature sensitivity (TCR) of -1.46% / ℃ (20~60℃) and a temperature sensing range of 0~150℃. This achieves integrated dual-function sensing, simultaneously realizing the dual goals of high pressure sensitivity and wide pressure sensing range within a single sensing unit, thus balancing both. The following is an exemplary description of each of the above steps: In one embodiment, the stirring in step S1 to uniformly disperse the multi-walled carbon nanotubes (MWCNTs) and graphene oxide (GO) includes: stirring at 25°C for 20 minutes, followed by ultrasonic treatment at 300W power for 2 hours in an ultrasonic cell disruptor, thereby ensuring thorough and uniform dispersion of the MWCNTs and GO. The stirring is achieved using a heat-collecting magnetic stirrer, and the ultrasonic cell disruptor can be a power-adjustable benchtop ultrasonic cleaner (SK2200HP).

[0027] In one embodiment, cleaning and drying the waterborne polyurethane microfiber leather includes: washing the waterborne polyurethane microfiber leather three times with deionized water to remove surface oil and impurities, and then drying it. Preferably, air drying at room temperature is sufficient.

[0028] In one embodiment, step S3, uniformly spraying the mixed dispersion prepared in step S1 onto the surface of the waterborne polyurethane microfiber leather, includes: loading the mixed dispersion prepared in step S1 into a pneumatic spray gun and uniformly spraying the mixed dispersion onto the waterborne polyurethane microfiber leather with compressed air at 0.3 MPa. Specifically, a completely oil-free silent air compressor (QWJ-60) is used to provide stable compressed air at 0.3 MPa, uniformly spraying the mixed dispersion onto the surface (upward-facing rough surface) of the pretreated waterborne polyurethane microfiber leather microfiber layer once.

[0029] Preferably, the sprayed sample is pressed and dried to cure, including: pressing the sprayed sample with a pressure roller at a pressure of 0.3 MPa and a speed of 6.5 rpm / min using a pressure dyeing resin machine to promote the penetration of carbon nanomaterials into the ultra-fine fiber layer of the waterborne polyurethane microfiber leather to form a three-dimensional conductive network, and then placing it in an oven to dry and cure, controlling the final MWCNT / GO loading to be 0.81 wt%.

[0030] In one embodiment, the concentration of the multi-walled carbon nanotube aqueous dispersion in step S1 is 10 wt%, and the concentration of the monolayer graphene oxide aqueous dispersion is 1 wt%.

[0031] In one embodiment, the waterborne polyurethane microfiber leather has a basis weight of 248 g / m², and the microfiber has a diameter of 3 μm.

[0032] In one embodiment, in step S5, the standard-sized sample can be 25 mm × 25 mm. Of course, those skilled in the art can cut it to other sizes without affecting the sample's performance. Silver-plated conductive filaments (40D / 12F) are bonded along the width direction at both ends of the sample using conductive silver paste, serving as the conductive electrodes of the sensor. The distance between the two electrodes can be set to 10 mm. Preferably, after assembly, the sensor is placed in an 80°C oven for heat curing for 10 minutes to ensure reliable electrical contact between the electrodes and the conductive layer, thus obtaining the finished WMG dual-modal flexible sensor.

[0033] As another aspect of the present disclosure, a dual-modal flexible sensor is also provided, which is prepared by the preparation method in any of the above embodiments.

[0034] Preferably, the dual-modal flexible sensor further includes a flexible substrate on which the sensor array is disposed. Standard-sized samples prepared according to the method in the above embodiments can be arranged in a 4×4 matrix, connected by wires, and integrated onto the flexible substrate to construct a 4×4 pixel flexible sensor array. By collecting the ΔI / I0 values ​​of each pixel and visualizing them in the form of a heatmap, it is verified that the array can accurately identify the spatial pressure distribution and pressure magnitude, demonstrating its application capabilities in the fields of human-computer interaction and intelligent sensing.

[0035] Without causing contradictions, the above-described modules in the system of the present disclosure embodiments can implement any of the above-described methods.

[0036] The pressure sensor performance of the flexible sensor prepared in this embodiment can be tested by building a pressure testing platform. The platform includes a universal testing machine (CMT Model E42), an electrochemical workstation (ET2000, polarization potential 1 V), and a computer. A load is applied to the sensor at a compression rate of 5 mm / min, and the current signal is acquired in real time. Test results show that the WMG has a sensitivity S1 of 217.1270 kPa in the range of 0–5 kPa. - ¹ It exhibits good sensing response over a wide range of 0~150 kPa, with a response time / recovery time of approximately 100 ms / 70 ms. Its performance remains stable after 2000 cycles of testing under a 20 kPa load, and the lowest detectable load is approximately 46 Pa.

[0037] The temperature sensor performance of the flexible sensor prepared in this embodiment can be tested by building a temperature testing platform. The platform consists of a digital display heating plate (HP500-Pro), an electrochemical workstation, and a computer. The sensor is tested within a temperature range of 0–150°C. The results show that the TCR sensitivity of WMG is S1 = -1.46% / °C in the 20–60°C range and S2 = -0.45% / °C in the 60–150°C range. The sensor exhibits a negative temperature coefficient (NTC) characteristic and maintains high repeatability readings at each stable temperature node.

[0038] The flexible sensor prepared in this embodiment can also be verified through wearable applications: the flexible sensor was worn directly on the fingers, wrists, throats and masks of volunteers, and successfully monitored human physiological signals such as finger bending (30° / 60° / 90°), wrist bending, swallowing movements and breathing, verifying the practical potential of the sensor in smart healthcare and human-computer interaction.

[0039] like Figure 2 The image shows the test results of the flexible sensor prepared in the preferred embodiment of this disclosure using the above-mentioned test items, that is, obtaining the ΔI / I0 values ​​of each pixel point of the flexible sensor as a function of time in various application scenarios. Among them, Figure 2 Figure (a) shows the response result in the "OK" Morse code application. Figure 2 Figure (b) shows the response result in the "SOS" Morse code application. Figure 2 In (a) of the figure and Figure 2 In Figure (b), the implementation of the "OK" and "SOS" Morse code applications involves fixing a sensor to a finger and then clicking on a piece of paper according to the corresponding code pattern, which then produces the corresponding electrical signal on the computer screen. Figure 2Figure (c) shows the response results for different finger bending angles. Figure 2 Figure (d) in the figure shows the response results to wrist flexion behavior; Figure 2 Figure (e) in the diagram shows the response results to swallowing; Figure 2 Figure (f) in the figure shows the response results to respiratory monitoring behavior.

[0040] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0041] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0042] The above are merely specific embodiments of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in this disclosure, and these should all be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A method for fabricating a dual-modal flexible sensor, characterized in that, Includes the following steps: S1. Weigh out the aqueous dispersion of multi-walled carbon nanotubes and the aqueous dispersion of monolayer graphene oxide in a mass ratio of 2:1-10:1, add deionized water to prepare a mixed dispersion with a total carbon nanomaterial concentration of 0.375wt%-1.5wt%, and stir to make the multi-walled carbon nanotubes and graphene oxide uniformly dispersed. S2. Clean the water-based polyurethane microfiber leather and let it air dry. S3. The mixed dispersion prepared in step S1 is uniformly sprayed onto the surface of the waterborne polyurethane microfiber leather to achieve a carbon nanomaterial loading of 0.81wt%-5wt% to obtain a sprayed sample. S4. Press the sprayed sample and dry and cure it; S5. Cut the dried and cured sprayed sample to obtain a standard size sample, and attach electrodes to both ends of the standard size sample to obtain a flexible sensor with pressure and temperature dual-mode sensing function.

2. The preparation method according to claim 1, characterized in that, The stirring in step S1 to uniformly disperse the multi-walled carbon nanotubes and graphene oxide includes: stirring at 25°C for 20 minutes and then sonicating in an ultrasonic cell disruptor at 300W power for 2 hours.

3. The preparation method according to claim 1, characterized in that, Clean the water-based polyurethane microfiber leather and let it dry for later use. This includes washing the water-based polyurethane microfiber leather three times with deionized water to remove surface impurities and then letting it dry for later use.

4. The preparation method according to claim 1 or 2, characterized in that, Step S3, which involves uniformly spraying the mixed dispersion prepared in step S1 onto the surface of the waterborne polyurethane microfiber leather, includes: loading the mixed dispersion prepared in step S1 into a pneumatic spray gun and uniformly spraying the mixed dispersion onto the waterborne polyurethane microfiber leather with compressed air at 0.3 MPa.

5. The preparation method according to claim 1 or 2, characterized in that, The sprayed sample is pressed and dried for curing, including: pressing the sprayed sample with a pressure roller at a pressure of 0.3 MPa and a speed of 6.5 rpm / min using a pressure dyeing resin machine to promote the penetration of carbon nanomaterials into the ultra-fine fiber layer of the waterborne polyurethane microfiber leather, and then placing it in an oven for drying and curing.

6. The preparation method according to claim 1, characterized in that, In step S1, the concentration of the multi-walled carbon nanotube aqueous dispersion is 10 wt%, and the concentration of the monolayer graphene oxide aqueous dispersion is 1 wt%.

7. The preparation method according to claim 5, characterized in that, The waterborne polyurethane microfiber leather has a weight of 248 g / m², and the microfiber has a diameter of 3 μm.

8. The preparation method according to claim 4, characterized in that, The pneumatic spray gun is supplied with compressed air by an oil-free, silent air compressor.

9. A dual-modal flexible sensor, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The dual-modal flexible sensor as described in claim 9, characterized in that, The dual-modal flexible sensor also includes a flexible substrate on which the sensor array is disposed.

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