Conductive ink based on high-concentration liquid metal, preparation method and application
By constructing a loose limited gel network and good interface interaction, high-concentration liquid metal conductive ink was prepared, which solved the problems of insufficient rigidity, interface compatibility and stability of conductive inks in the prior art, and achieved efficient and multifunctional preparation of flexible electronic devices.
Patent Information
- Application Number
- CN202510160443.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-13
- Publication Date
- 2025-06-10
AI Technical Summary
The existing conductive inks based on solid conductive fillers have problems of poor rigidity and interface compatibility when achieving highly stretchable and durable flexible electronic devices, and the stability and thixotropy of high-concentration liquid metal inks are insufficient, making it difficult to meet the needs of patterning technology.
By building a relaxed limited gel network and good interface interaction, a high-concentration liquid metal and gel agent is used to prepare high-concentration liquid metal conductive inks using technical means such as ultrasonic, eddy current mixing and high-speed shearing.
The stability and excellent thixotropy of high-concentration liquid metal ink are achieved, and can exhibit high precision and high efficiency in a variety of patterning methods, which is suitable for the preparation of flexible electronic products.
Smart Images
Figure CN120118561A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of electronic materials, and particularly relates to a conductive ink based on high-concentration liquid metal, a preparation method and an application thereof. Background Art
[0002] Conductive ink is the key to the next-generation flexible electronic product patterning technology and has great potential in soft robots, wearable medical monitoring devices and human-machine interfaces. In the past decade, various solid conductive fillers (silver nanowires, carbon nanotubes, graphene, MXene) have been combined with surfactants or polymer matrices into suitable solvents to make conductive inks. Despite significant progress, due to the inherent rigidity and poor interfacial compatibility of these solid filler-based inks, it remains a huge challenge to achieve highly stretchable and durable flexible electronic devices. Compared with rigid solid fillers, liquid metal (LM) has a low modulus, good deformability and excellent stretchability, so it is regarded as an effective alternative for manufacturing stretchable electronic devices. Due to the extremely high surface tension and density of liquid metal, the liquid metal droplets formed in the ink tend to be unstable and easily agglomerate rapidly.
[0003] Existing liquid metals usually add surfactants (such as tannic acid, dopamine, polysaccharides and cellulose nanofibers) to solve the problem of poor stability of LM inks. In fact, these LM inks belong to solution systems, and the LM concentration in the solvent is relatively low (less than 20 g / L) to ensure colloidal stability. For example, glucomannan is 5.0 g / L, alginic acid is 7.9 g / L, and cellulose nanofibers are 10.0 g / L. Due to low viscosity and insufficient viscoelasticity, these solution systems always show poor thixotropy, which brings challenges to direct application in patterning technology. One of the strategies to solve this problem is to increase the LM concentration by centrifugation, but the LM ink obtained in this way lacks uniformity and cannot guarantee the uniformity and high precision in patterning technology. Adding more doses of surfactants or introducing additional polymers can also improve thixotropy, but this strategy is always accompanied by a decrease in the conductivity and stretchability of flexible electronic products. Summary of the Invention
[0004] The present invention provides a conductive ink based on high-concentration liquid metal, a preparation method and an application thereof for the problems existing in the prior art.
[0005] The technical solution adopted by the present invention is: a preparation method of a conductive ink based on high-concentration liquid metal, comprising the following steps:
[0006] Step 1: Add liquid metal (LM) to a solvent and ultrasonically obtain an LM dispersion;
[0007] Step 2: Add a gelling agent to the solvent and obtain a gelling agent dispersion after heat preservation treatment;
[0008] Step 3: Mix the LM dispersion obtained in Step 1 and the gelling agent dispersion obtained in Step 2, and react fully to obtain an LM gel.
[0009] Step 4: After homogenizing the LM gel, the required conductive ink can be obtained.
[0010] Further, the liquid metal in Step 1 is gallium-indium-tin liquid metal; the gelling agent in Step 2 is one of agar, curdlan, linseed gum, carrageenan, gelatin, and gellan gum.
[0011] Further, the heat preservation temperature in Step 2 is 120 °C, and the heat preservation time is 10 min.
[0012] Further, the mixing process in Step 3 is as follows:
[0013] First, use a vortex mixer to mix at a rotation speed of 2500 rpm for 20 s;
[0014] Then use an ultrasonic cell disruptor to perform ultrasonic treatment for 2 min under the condition of a power of 400 W.
[0015] Further, in Step 4, a high-speed shearer is used for homogenization, the rotation speed is 11000 rpm, and the treatment time is 5 min.
[0016] Further, the mass ratio of the liquid metal to the gelling agent in the conductive ink is 1.7 - 60:1.
[0017] A conductive ink based on high-concentration liquid metal, which is formed by liquid metal droplets being confined in a limited gel network formed by a gelling agent.
[0018] An application of a conductive ink based on high-concentration liquid metal, and the conductive ink is used in the preparation of conductive circuits.
[0019] Further, the preparation process of the conductive circuit is as follows:
[0020] Print the conductive ink through screen printing to form an LM conductive circuit on a substrate.
[0021] Further, the substrate is a flexible transparent polyurethane film.
[0022] The beneficial effects of the present invention are:
[0023] (1) By constructing a loose limited gel network and good interfacial interaction, the present invention realizes a high-concentration LM ink;
[0024] (2) The present invention achieves a high LM concentration at a relatively low gelling agent content, resulting in a conductive ink with high stability and excellent thixotropy, enabling various patterning methods. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 It is a schematic flow chart of the method of the present invention.
[0026] Figure 2 It is an effect diagram of the conductive inks obtained in Example 1 and the comparative example of the present invention after being placed for different times. a is the conductive ink obtained in Example 1, and b is the conductive ink obtained in the comparative example.
[0027] Figure 3 It is a schematic diagram of the rheological properties of the conductive inks obtained in Example 1 and the comparative example of the present invention. a is the viscosity curve, b is the modulus curve, and c is the thixotropy curve.
[0028] Figure 4 It is a physical diagram of the conductive circuit prepared from the conductive ink obtained in Example 1 of the present invention.
[0029] Figure 5 It is a physical diagram of the pattern prepared from the conductive ink in the comparative example of the present invention.
[0030] Figure 6 It is a stability mechanism diagram of the conductive ink obtained in Example 1 of the present invention.
[0031] Figure 7 It is an interfacial interaction diagram of agar and liquid metal in the conductive ink obtained in Example 1 of the present invention. a is the Fourier transform infrared spectrum diagram, b is the full spectrum of the X-ray photoelectron spectroscopy diagram, and c is the Ga2p spectrum of the X-ray photoelectron spectroscopy diagram. DETAILED DESCRIPTION OF THE INVENTION
[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0033] As Figure 1 shown, a preparation method of a conductive ink based on high-concentration liquid metal includes the following steps:
[0034] Step 1: Add the liquid metal LM block into deionized water, and use an ultrasonic cell disruptor to perform ultrasonic treatment for 2 min under the condition of a power of 400 W to obtain an LM dispersion. The liquid metal is gallium-indium-tin liquid metal.
[0035] Step 2: Add the gelling agent into deionized water at a certain temperature, place the mixture in an oven at 120 °C for heat preservation for 10 min to obtain a gelling agent dispersion, and cover the dispersion with plastic wrap. The gelling agent is one of agar, curdlan, linseed gum, carrageenan, gelatin, and gellan gum.
[0036] Step 3: Mix the LM dispersion obtained in Step 1 and the gelling agent dispersion obtained in Step 2. First, use a vortex mixer to mix for 20 s at a rotation speed of 2500 rpm.
[0037] Then, use an ultrasonic cell disruptor to perform ultrasonic treatment for 2 min at a power of 400 W.
[0038] Then, place it in an ice-water bath for 30 min to obtain LM gel.
[0039] Step 4: After homogenizing the LM gel, the required conductive ink can be obtained; use a high-speed shearer for homogenization at a rotation speed of 11000 rpm and a treatment time of 5 min. The mass ratio of the liquid metal to the gelling agent in the conductive ink is 1.7 - 60:1.
[0040] The conductive ink is formed by liquid metal droplets being confined in a gel network formed by the gelling agent. The finite gel strategy is used to construct a loose finite gel network and excellent interfacial interaction, and the liquid metal droplets are confined in the loose finite gel network.
[0041] An application of a conductive ink based on high-concentration liquid metal, and the conductive ink is used in the preparation of conductive circuits.
[0042] Scrape and coat the aqueous polyurethane emulsion to obtain a flexible and transparent polyurethane film as a screen printing substrate;
[0043] Print the conductive ink through screen printing to form an LM conductive circuit on the substrate. Scratch the LM conductive circuit to change the circuit from insulating to conductive.
[0044] Example 1
[0045] Prepare a conductive ink based on high-concentration liquid metal according to the following steps:
[0046] Step 1: Add 1.5 g of gallium-indium-tin liquid metal block to 5 mL of room-temperature deionized water, and process it with an ultrasonic cell disruptor, where the ultrasonic power is 400 W and the ultrasonic time is 2 min to obtain a liquid metal dispersion.
[0047] Step 2: Add 0.15 g of agar to 5 mL of 100 °C deionized water, and keep it in an oven at 120 °C for 10 min to obtain an agar dispersion.
[0048] Step 3: Mix the agar dispersion and the liquid metal dispersion. First, use a vortex mixer to mix for 20 s at a rotation speed of 2500 rpm.
[0049] Then, use an ultrasonic cell disruptor to perform ultrasonic treatment for 2 min at a power of 400 W. Then, place it in an ice-water bath for 30 min to obtain LM gel.
[0050] Step 4: Process the LM gel at 11,000 rpm in a high-speed shearing machine for 5 min to obtain Agar@LM ink.
[0051] Prepare a conductive circuit using the Agar@LM ink obtained in this example:
[0052] First, scrape and coat an aqueous polyurethane emulsion (solid content 32%) to obtain a flexible transparent polyurethane film as the screen printing substrate. Pass the obtained 100-mesh screen printing stencil of the LM conductive ink through and print it on the polyurethane film to form an LM conductive circuit. Scratch the LM conductive circuit to change the circuit from insulating to conductive to obtain a conductive circuit.
[0053] Example 2
[0054] All other steps in this example are the same as those in Example 1, except that in this example, the mass of the liquid metal is 0.5 g and the mass of the agar is 0.03 g.
[0055] Example 3
[0056] All other steps in this example are the same as those in Example 1, except that in this example, the mass of the liquid metal is 1.5 g and the mass of the agar is 0.05 g.
[0057] Example 4
[0058] All other steps in this example are the same as those in Example 1, except that in this example, the mass of the liquid metal is 9.0 g and the mass of the agar is 0.15 g.
[0059] Example 5
[0060] All other steps in this example are the same as those in Example 1, except that in this example, the mass of the liquid metal is 0.5 g and the gelling agent used is curdlan, with a mass of 0.3 g.
[0061] Example 6
[0062] All other steps in this example are the same as those in Example 1, except that in this example, the mass of the liquid metal is 0.5 g and the gelling agent used is linseed gum, with a mass of 0.3 g.
[0063] Example 7
[0064] All other steps in this example are the same as those in Example 1, except that in this example, the mass of the liquid metal is 0.5 g and the gelling agent used is carrageenan, with a mass of 0.15 g.
[0065] Example 8
[0066] All other steps of this example are the same as those of Example 1, except that in this example, the mass of the liquid metal is 0.5 g, and the gelling agent is gelatin with a mass of 0.03 g.
[0067] Example 9
[0068] All other steps of this example are the same as those of Example 1, except that in this example, the mass of the liquid metal is 0.5 g, and the gelling agent is gellan gum with a mass of 0.04 g.
[0069] To illustrate the effect of the present invention, a comparative example is set:
[0070] All other steps of the comparative example are the same as those of Example 1, except that it does not contain agar, which is replaced by polyvinylpyrrolidone PVP.
[0071] Figure 2 The following are the effect diagrams of the conductive inks obtained in Example 1 and the comparative example after being placed for different times. It can be seen from the figure that the Agar@LM ink obtained in Example 1 did not show sedimentation within 48 hours. While the ink obtained in Comparative Example 1 showed sedimentation within 1 hour. This shows that the conductive ink obtained by the present invention has high stability.
[0072] The inks obtained in Example 1 of the present invention and the comparative example were used for patterning ability testing, and a rheological test was carried out using an MCR302 rotational rheometer. The results are as Figure 3 shown. It can be seen from the figure that the Agar@LM ink has a relatively high initial viscosity, viscoelasticity, and shear thinning behavior when subjected to shear stress.
[0073] The modulus responds quickly to stress, indicating that the Agar@LM ink has high patterning ability and suitable rheological properties. The Agar@LM ink has shown potential in screen printing and can obtain screen-printed conductive lines with relatively high printing accuracy. The results are as Figure 4 shown. In sharp contrast, the PVP@LM ink is very difficult to form, as Figure 5 shown.
[0074] Figure 6 The following is the modulus curve obtained from the conductive ink test. It can be seen from it that as the temperature rises, the Agar@LM ink shows a typical sol-gel transition, and the transition temperature is about 68 °C. When the temperature is lower than the sol-gel temperature, the agar@LM ink is in a gel state, forming a limited gel network, which has good stability ( Figure 6 left inset). Once the temperature exceeds the sol-gel temperature, the limited gel network in the agar@LM ink will gradually be destroyed, causing the LM droplets to start to sediment ( Figure 6The right illustration). These phenomena indicate that a finite gel network is the key to achieving good stability of Agar@LM ink.
[0075] Figure 7 Figure for the interfacial interaction between agar and liquid metal in the conductive ink, which can be demonstrated by Fourier transform infrared spectroscopy ( Figure 7 In a), the interfacial interaction between agar and LM. As can be seen from the figure, the characteristic peak of O-H stretching vibration shifts from 3339 cm of agar -1 to 3310 cm of agar@LM -1 , which indicates that there may be a coordination interaction between the O-H groups of agar and Ga on LM 3+ .
[0076] The interfacial interaction between agar and LM can be seen from its X-ray photoelectron spectroscopy. Compared with pure LM, the peak area of Ga 2 O 3 in the agar@LM ink increases significantly. This result shows that the interfacial interaction is the coordination interaction between Ga of LM 3+ and agar ( Figure 7 In b, c).
[0077] The present invention discloses a general finite gel strategy to realize the design of high-concentration LM ink for patterning technology by constructing a relaxed finite gel network and good interfacial interaction. In this LM ink, LM droplets are restricted to be distributed in the relaxed finite gel network, which can provide a strong repulsive effect even when the LM concentration is extremely high, avoiding the coincidence of LM droplets. At the same time, the good interfacial interaction between the gelling agent and LM droplets ensures the stability and durability of the gelling agent@LM ink. In previous inventions, only a surface modification layer was formed on the surface of LM droplets by a dispersant or a gelling agent. When the LM concentration is low, the surface modification layer can provide electrostatic repulsion to avoid the agglomeration of LM droplets. When the LM concentration is high, the collision probability of adjacent LM droplets increases significantly. Due to the bridging effect of the surfactant, LM droplets are easily combined with each other to form large agglomerates, resulting in the destruction of colloidal stability. Previous inventions cannot solve the fundamental contradiction between the high concentration and good stability of LM ink. The present invention enables the LM ink to have the following competitive advantages through the finite gel strategy: (1) High LM concentration (up to 900 g / L) can be achieved with a very small content of the gelling agent, exceeding the previous research results; (2) It has excellent thixotropy and can realize various patterning methods such as screen printing without post-treatment; (3) It has good versatility and is applicable to various gel systems such as curdlan, gelatin, gellan gum, etc.
Claims
1. A method for preparing a conductive ink based on high-concentration liquid metal, characterized in that: The following steps are involved: Step 1: Add liquid metal LM into the solvent and obtain LM dispersion by ultrasonication; Step 2: adding the gelling agent into the solvent and performing heat preservation treatment to obtain a gelling agent dispersion; Step 3: mixing the LM dispersion obtained in step 1 and the gelling agent dispersion obtained in step 2, and reacting them sufficiently to obtain LM gel; Step 4: After homogenizing the LM gel, the desired conductive ink can be obtained.
2. The method for preparing a conductive ink based on high-concentration liquid metal according to claim 1, characterized in that: The liquid metal in step 1 is gallium indium tin liquid metal; the gelling agent in step 2 is one of agar, curdlan, flaxseed gum, carrageenan, gelatin and gellan gum.
3. The method for preparing a conductive ink based on high-concentration liquid metal according to claim 1, characterized in that: The insulation temperature in step 2 is 120° C. and the insulation time is 10 min.
4. The method for preparing a conductive ink based on high-concentration liquid metal according to claim 1, characterized in that: The mixing process in step 3 is: First, a vortex mixer was used to mix for 20 s at a rotation speed of 2500 rpm; Then, an ultrasonic cell disruptor was used to perform ultrasonic treatment for 2 min at a power of 400 W.
5. The method for preparing a conductive ink based on high-concentration liquid metal according to claim 1, characterized in that: In step 4, a high-speed shearing machine is used for homogenization, the rotation speed is 11000 rpm, and the processing time is 5 minutes.
6. The method for preparing a conductive ink based on high-concentration liquid metal according to claim 1, characterized in that: The mass ratio of liquid metal to gelling agent in the conductive ink is 1.7 to 60:
1.
7. The conductive ink based on high concentration liquid metal obtained by the preparation method according to any one of claims 1 to 6, characterized in that: The conductive ink is formed by liquid metal droplets being restricted in a limited gel network formed by a gelling agent.
8. The use of a conductive ink based on high-concentration liquid metal as claimed in claim 7, characterized in that: The conductive ink is used in preparing conductive circuits.
9. The use of a conductive ink based on high-concentration liquid metal according to claim 8, characterized in that: The preparation process of the conductive circuit is as follows: Conductive ink is screen printed to form LM conductive circuits on the substrate.
10. The use of a conductive ink based on high-concentration liquid metal according to claim 9, characterized in that: The substrate is a flexible transparent polyurethane film.