Carbon nano tube assisted liquid metal dispersion method and application of carbon nano tube assisted liquid metal dispersion method in conductive ink and flexible sensor
By using a carbon nanotube-assisted liquid metal dispersion method, the problem of poor dispersion of liquid metal in polymer matrices was solved, and a flexible sensor with high conductivity and high sensitivity was prepared, which is suitable for wearable devices and human motion monitoring.
Patent Information
- Application Number
- CN202511974402.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-25
- Publication Date
- 2026-03-06
AI Technical Summary
In existing technologies, liquid metals exhibit poor dispersion in polymer matrices, which limits their application in flexible electronic devices. Furthermore, existing methods struggle to achieve long-term stable dispersion and large-scale application.
A carbon nanotube-assisted liquid metal dispersion method was used to form an LM@CNT composite dispersion through ultrasonic treatment. The pH value was adjusted and natural rubber latex was added to prepare conductive ink. A flexible sensor was then fabricated using a direct writing 3D printing process.
Stable dispersion of liquid metal was achieved, improving conductivity and tensile properties. The resulting flexible sensor exhibits high sensitivity and accurate electrical signal response within the 1%-300% strain range, making it suitable for wearable devices and human motion monitoring.
Smart Images
Figure CN121617701A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of flexible electronic devices and conductive composite materials, and in particular to a method for dispersing liquid metal with carbon nanotubes and its application in conductive inks and flexible sensors. Background Technology
[0002] Flexible electronic devices are increasingly used in fields such as medical monitoring, wearable devices, and smart sensing, which places stringent requirements on flexible conductive materials, including high conductivity, high strain capacity, and 3D printability. Liquid metal (LM), with its metallic-grade conductivity and excellent flexibility, has become an ideal candidate for flexible electronic fillers.
[0003] Recent studies have shown that although the Ga2O3 thin layer formed on the surface of liquid metal can prevent droplet aggregation in a short time, its colloidal stability still has obvious defects, resulting in poor dispersion of LM in polymer matrix, which in turn affects the performance of its products and seriously restricts its practical application in elastomer matrix.
[0004] Currently, methods for controlling the dispersion stability of liquid metals are scarce, with surface modification being the mainstream approach, primarily involving the modification of functional groups such as hydroxyl, carboxyl, and amino groups. However, existing methods still struggle to achieve long-term stable dispersion of liquid metals. Carbon nanotubes (CNTs), as conductive nanomaterials with high specific surface area, can effectively encapsulate liquid metal droplets, enhance colloidal stability, and inhibit oxide layer growth by forming physical or chemical bonds with liquid metals through their surface functional groups. However, existing technologies lack an effective and convenient process for preparing LM@CNT dispersions, and there is also a lack of mature routes for their large-scale application in flexible electronics manufacturing. Summary of the Invention
[0005] The purpose of this invention is to provide a method for dispersing liquid metal with carbon nanotubes and its application in conductive inks and flexible sensors, so as to solve the technical problems of poor dispersibility of liquid metal, difficulty in controlling ink viscosity, and low printing fidelity in the prior art. Specifically, a method for dispersing liquid metal with carbon nanotubes is provided, and conductive ink suitable for direct writing 3D printing (DIW) is prepared based on this method. Finally, by constructing an LM@CNT@NRL conductive system, a flexible electronic device with high conductivity, excellent tensile properties and sensitive sensing response is obtained.
[0006] To achieve the above objectives, the following technical solution is adopted: One of the technical solutions of this invention provides a method for preparing a flexible sensor using carbon nanotube-assisted liquid metal dispersion, comprising the following steps: (1) Liquid metal and functionalized carbon nanotubes were dispersed in water and subjected to ultrasonic treatment to obtain liquid metal dispersion and carbon nanotube dispersion. (2) The two dispersions obtained in step (1) are mixed and subjected to secondary ultrasonic treatment so that the carbon nanotubes are coated on the surface of the liquid metal droplets to form an LM@CNT composite dispersion. (3) Adjust the pH value of the LM@CNT composite dispersion to the alkaline range, add natural rubber emulsion and stir to mix, then add super absorbent resin to adjust the viscosity of the system to obtain conductive ink; (4) The conductive ink is printed and cured by direct writing three-dimensional printing process to obtain the flexible sensor.
[0007] Furthermore, the liquid metal is a gallium-indium alloy, and the functionalized carbon nanotubes are carboxyl-modified multi-walled carbon nanotubes.
[0008] Furthermore, in step (1) and / or step (2), the ultrasonic treatment includes a combination of probe-type ultrasonic treatment and water bath ultrasonic treatment.
[0009] Furthermore, the processing time for the probe-type ultrasound is 10-30 minutes, and the processing time for the water bath ultrasound is 5-20 minutes.
[0010] Furthermore, the mass ratio of the liquid metal to the functionalized carbon nanotubes is (1.5-3):1.
[0011] Furthermore, in step (4), the process parameters for the direct writing 3D printing are: nozzle pressure 20-70 kPa, and line speed 50-2500 mm / min.
[0012] In one specific embodiment, the method for preparing a flexible sensor using carbon nanotube-assisted liquid metal dispersion includes the following four steps: Step 1, Dispersion preparation: Liquid metal (gallium indium alloy) and hydroxyl-modified CNTs were subjected to probe-type sonication for 15 minutes and water bath sonication for 10 minutes in ultrapure water, respectively, to obtain LM aqueous dispersion and CNT aqueous dispersion.
[0013] Step 2, Preparation of composite droplets: The two dispersions above are mixed and subjected to a combination of two ultrasonic treatments: 15 minutes of probe-type ultrasonication and 10 minutes of water bath ultrasonication. This process coats the surface of the LM droplets with CNTs, forming an entangled network, thus preparing the LM@CNT composite dispersion.
[0014] Step 3, Preparation of conductive ink: Adjust the pH value of the LM@CNT composite dispersion to 10.5-11.0, add natural rubber emulsion and stir well; then add super absorbent resin and stir further to adjust the viscosity of the system to be suitable for direct writing 3D printing.
[0015] Step 4, 3D Printing: The conductive ink is loaded into the syringe, and a preset pattern is printed using a direct-write 3D printing process. The nozzle pressure is controlled at 35-55 kPa, and the line speed is 100-2000 mm / min (preferably 400 mm / min) to achieve high-precision pattern forming. After printing, the pattern is allowed to dry naturally or cured at low temperature to obtain a flexible sensor device.
[0016] The second technical solution of the present invention provides a conductive ink prepared by the above method, comprising LM@CNT composite dispersion, natural rubber latex and superabsorbent resin, and having an electrical conductivity of not less than 10 S·m. -1 The tensile strength is not less than 5 MPa.
[0017] The third technical solution of the present invention provides a flexible strain sensor, which is made by direct writing three-dimensional printing and curing of the conductive ink as described above.
[0018] Furthermore, the maximum regularity factor (GF) of this flexible strain sensor is not less than 20 within the strain range of 1%-300%.
[0019] The fourth technical solution of the present invention provides an application of the flexible strain sensor described above in the fabrication of wearable devices or human motion monitoring devices.
[0020] The beneficial effects of this invention are reflected in: 1. This invention uses environmentally friendly and non-toxic materials such as liquid metal, carbon nanotubes, and natural latex to achieve surface modification and stable dispersion of liquid metal, while inhibiting the growth of liquid metal oxide layer and improving conductivity.
[0021] 2. This invention uses DIW printing technology to precisely control the nozzle pressure and line speed, thereby improving printing fidelity; the resulting flexible sensor has high sensitivity within the strain range of 1%-300%, enabling precise electrical signal response to the movement of multiple parts of the human body.
[0022] 3. The present invention has a simple process, stable product quality, can realize continuous production of flexible sensors, is easy to mass-produce, and has broad industrial application prospects. Attached Figure Description
[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0024] Figure 1This is an experimental flowchart of the present invention for preparing carbon nanotube-assisted liquid metal dispersion.
[0025] Figure 2 Characterization of the LM and LM@CNT composite droplets prepared in Example 1. (a) and (c) are XPS images of In and Ga elements in pure liquid metal; (b) and (d) are XPS images of In and Ga elements in CNT-modified LM.
[0026] Figure 3 Characterization of the LM and LM@CNTs used and prepared in Example 1. Among them, (a) is a SEM image of liquid metal after ultrasonic fragmentation; (b) is a SEM image of liquid metal after carbon nanotube modification and encapsulation; (c) is a TEM image of liquid metal after carbon nanotube modification and encapsulation; and (d) is a TEM image of liquid metal after ultrasonic fragmentation.
[0027] Figure 4 The performance characterization of the liquid metal-based flexible sensor prepared in Example 2 is shown in (a), which is the stress-strain curve of the liquid metal-based flexible sensor with different liquid metal contents; (b) is the conductivity histogram of the liquid metal-based flexible sensor with different liquid metal contents; and (c) is an optical photograph of the liquid metal-based flexible sensor being stretched, knotted, folded, and pulled up with a 1 kg weight.
[0028] Figure 5 The diagram shows the application of the liquid metal-based flexible sensor prepared in Example 3 and its electrical signal response curve. (a) shows the electrical signal changes with different degrees of finger bending; (b) shows the electrical signal changes with the cervical spine during head-down and head-up movements; (c) shows the electrical signal changes with continuous finger bending; (d) shows the electrical signal changes with continuous wrist bending; (e) shows the electrical signal changes with continuous arm bending; (f) shows the electrical signal changes with knee movement after leg lift and at rest; and (g) shows the electrical signal changes with different degrees of knee bending. Detailed Implementation
[0029] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.
[0030] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.
[0031] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.
[0032] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.
[0033] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.
[0034] The first aspect of this invention provides a method for dispersing liquid metal with the assistance of carbon nanotubes, which is applied to the fabrication of a rubber sensor, and includes the following steps: 1) Carbon nanotubes and liquid metal were ultrasonically treated separately to obtain carbon nanotube dispersions and liquid metal dispersions; 2) The two dispersions were mixed and ultrasonically treated to obtain the LM@CNT composite dispersion.
[0035] A second aspect of the present invention provides a conductive ink obtained by mixing an LM@CNT composite dispersion prepared according to the above preparation method with natural rubber, stabilizing it by mechanical stirring, and then concentrating the mixture.
[0036] The conductive ink sample obtained using the method of this invention has a conductivity of up to 16.64 S·m. -1 The tensile strength is 11.08 MPa and the strain is 660%.
[0037] The third aspect of the present invention provides that the ink obtained above is 3D printed and then heated to form an LM-based flexible sensor; the LM-based flexible sensor obtained by the method of the present invention exhibits accurate electrical signal response to stretching and has a wide sensing range (1%-300%).
[0038] In a preferred embodiment of the present invention, the ratio of liquid metal to carbon nanotubes is 2:1.
[0039] A schematic diagram of the process for fabricating an LM-based flexible sensor according to an embodiment of the present invention is shown below. Figure 1As shown in the figure, 1 represents an ultrasonic device, 2 represents a stirring device, and 3 represents a 3D printing device. Liquid metal and carbon nanotubes are ultrasonically dispersed using ultrasonic device 1. After mixing, the mixture is further ultrasonicated using ultrasonic device 1, causing the carbon nanotubes to adhere to the surface of the liquid metal. After ultrasonication, natural latex is added, and the mixture is stirred thoroughly using mechanical stirring device 2 and then concentrated. The concentrated conductive ink is then 3D printed using 3D printing device 3, which controls the line speed, base pressure, and nozzle diameter, to create an LM-based flexible sensor.
[0040] Unless otherwise specified, all raw materials used in the embodiments of this invention can be obtained through commercial channels.
[0041] The present invention will be further illustrated by the following examples.
[0042] Example 1: This embodiment provides a method for preparing an LM@CNT dispersion, comprising the following steps: (1) Add 0.5g of carbon nanotubes to 20mL of deionized water and disperse for 15min with the aid of an ultrasonic probe to form a stable carbon nanotube dispersion. Add 1g of liquid metal to 20mL of deionized water and disperse for 15min with the aid of an ultrasonic probe to form a stable liquid metal dispersion.
[0043] (2) Mix the two dispersions prepared in step (1) and then disperse them for 30 minutes with the aid of an ultrasonic probe to obtain the LM@CNT dispersion.
[0044] The liquid metal dispersion after ultrasonic treatment in step (1) of this embodiment and the LM@CNT dispersion prepared in step (1) were characterized. Figure 2 Image (a) shows the XPS plot of In element after ultrasonic treatment of pure liquid metal. Figure 2 Figure (b) shows the In element XPS plot of the LM@CNT dispersion, compared with... Figure 2 Compared to (a), the In element XPS plot of LM@CNTs after ultrasonic treatment showed a significant decrease in the In2O3 peak value. Figure 2 Image (c) shows the XPS image of Ga elemental composition after ultrasonic treatment of pure liquid metal. Figure 2 The middle (d) image shows the Ga elemental XPS plot of the LM@CNT dispersion, compared with... Figure 2 Compared to (c), the peak value of Ga2O3 in the XPS image of Ga element is also significantly reduced, indicating that CNT can successfully inhibit the formation of oxide layer on the surface of liquid metal and improve the conductivity of liquid metal.
[0045] The structures of the liquid metal dispersion and the LM@CNT dispersion after ultrasonic treatment in step (1) of this embodiment were characterized. The results are as follows: Figure 3 As shown, Figure 3 In the middle (a) and (b), SEM images of pure liquid metal dispersion and LM@CNT dispersion are shown respectively. It can be seen that carbon nanotubes are entangled on the surface of liquid metal and have a good coverage. Figure 3 (c) and (d) are TEM images of the pure liquid metal dispersion and the LM@CNT dispersion, respectively, which show this phenomenon more clearly.
[0046] Example 2: This embodiment provides a method for preparing conductive ink, including the following steps: (1) Based on Example 1, an LM@CNT dispersion was obtained.
[0047] (2) Add the obtained LM@CNT dispersion to the pre-vulcanized latex, mix it with a mechanical stirring device, and then add SAP balls for concentration to obtain conductive ink.
[0048] The mechanical and electrical properties of the conductive ink sample obtained in this embodiment were characterized, and the results are as follows: Figure 4 As shown. Figure 4 (a) shows the stress-strain curves of liquid metal-based flexible sensors with different liquid metal contents. The liquid metal-based flexible sensor with a 30% LM@CNT loading exhibits the best mechanical properties, with a tensile strength of 11.08 MPa and a strain of 660%. Figure 4 (b) is a bar chart showing the conductivity of liquid metal-based flexible sensors with different liquid metal contents. The conductivity of the liquid metal-based flexible sensor with a 30% LM@CNT loading can reach 16.64 S·m. -1 Figure 4(c) shows optical photographs of the liquid metal-based flexible sensor being stretched, knotted, folded, and pulled up with a 1kg weight, demonstrating the excellent mechanical properties of the liquid metal-based flexible sensor.
[0049] Example 3: This embodiment provides a method for fabricating an LM-based flexible sensor, including the following steps: (1) Based on Example 1, an LM@CNT dispersion was obtained.
[0050] (2) Add the obtained LM@CNT dispersion to the pre-vulcanized latex, mix it with a mechanical stirring device, and then add SAP balls for concentration to obtain conductive ink.
[0051] (3) The obtained conductive ink was processed by 3D printing. The 3D printer parameters were set as follows: linear speed fixed at 400 mm / min, pressure controlled between 35 and 55 kPa. In addition, the extrusion pressure was fixed at 45 kPa, and the linear speed range was set to 100 to 2000 mm / min. The printed device was then heat-treated to obtain an LM-based flexible sensor.
[0052] To detect the electrical signals of the flexible sensor obtained in step (3) of this embodiment for human body sensing, firstly, in order to test the sensitivity of the sensor to changes in the human body, Figure 5 In Figure (a), when a rubber sensor attached to a human finger is bent from 0° to 30°, 60°, and 90°, the stretching generates a periodic signal corresponding to the applied strain. After remaining constant, the electrical signal changes significantly, with different degrees of stretching corresponding to different stages of the electrical signal relationship. Even at rest, there is still a decreasing resistance trend, and after stretching, the resistance almost completely recovers with the recovery movements from 90° to 60°, 30°, and 0°. For continuous movements with small strains, such as… Figure 5 The cervical spine response to head nodding is shown in (b). Figure 5 As shown in (c), the continuous flexion and extension of the fingers all exhibit precise corresponding electrical signal changes, and these changes are remarkably stable. Further investigation was conducted into the electrical signal changes during continuous static responses to human body strain. The sensor was placed at different locations, including the wrist, elbow, and knee, to detect these changes. Figure 5 As shown in (d), the continuous static variation of wrist flexion can be observed. Figure 5 Image (e) shows a continuous static variation of elbow flexion and extension. Figure 5 As shown in (f), the continuous static changes of the knee during leg raising and standing postures exhibit precise variations in electrical signal resistance values. The resistance shows a decreasing trend when the movement is still, and this decreasing trend corresponds to the increase in the range of motion and strain. An attempt was made to test whether this trend would continue through significant knee flexion, thus testing the electrical signal changes for different ranges of knee movement. Figure 5 The increased amplitude of the action observed in (g) has a certain influence on the decreasing trend of resistance.
[0053] The above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also fall within the scope of the present invention, and the patent protection scope of the present invention should be defined by the claims.
Claims
1. A method for fabricating a flexible sensor by carbon nanotube assisted liquid metal dispersion, characterized in that, The method comprises the following steps: (1) dispersing liquid metal and functionalized carbon nanotubes in water respectively, and performing ultrasonic treatment to obtain a liquid metal dispersion and a carbon nanotube dispersion; (2) mixing the two dispersions obtained in step (1) and performing secondary ultrasonic treatment to coat the carbon nanotubes on the surface of the liquid metal droplets to form an LM@CNT composite dispersion; (3) adjusting the pH value of the LM@CNT composite dispersion to the alkaline range, adding natural rubber emulsion and stirring, and then adding superabsorbent resin to regulate the viscosity of the system to obtain a conductive ink; (4) printing and solidifying the conductive ink by a direct writing type three-dimensional printing process to obtain the flexible sensor.
2. The method of claim 1, wherein, The liquid metal is a gallium-indium alloy, and the functionalized carbon nanotubes are carboxyl-modified multi-walled carbon nanotubes.
3. The method according to claim 1 or 2, characterized in that, In step (1) and / or step (2), the ultrasonic treatment comprises a combination of probe-type ultrasonic treatment and water bath ultrasonic treatment.
4. The method of claim 3, wherein, The treatment time of the probe-type ultrasonic treatment is 10-30 minutes, and the treatment time of the water bath ultrasonic treatment is 5-20 minutes.
5. The method of claim 1, wherein, The mass ratio of the liquid metal to the functionalized carbon nanotubes is (1.5-3):
1.
6. The method of claim 1, wherein, In step (4), the process parameters of the direct writing type three-dimensional printing are as follows: nozzle pressure 20-70 kPa, and line speed 50-2500 mm / min.
7. The conductive ink prepared by the method of any one of claims 1-6, wherein, A composite dispersion liquid containing LM@CNT, a natural rubber emulsion, and a superabsorbent resin, having a conductivity of not less than 10 S·m -1 and a tensile strength of not less than 5 MPa.
8. A flexible strain sensor, characterized by The conductive ink is prepared by the method of claim 7.
9. The flexible strain sensor of claim 8, wherein, The maximum regularity factor value thereof in the strain range of 1%-300% is not less than 20.
10. Use of the flexible strain sensor of claim 8 or 9 in the preparation of a wearable device or a human motion monitoring device.