Magnetic metal particle, preparation method thereof, liquid metal-based magnetic fluid and application of liquid metal-based magnetic fluid

Abstract

The invention discloses a magnetic metal particle, a preparation method of the magnetic metal particle, a liquid metal-based magnetic fluid and application of the liquid metal-based magnetic fluid, and belongs to the field of materials. The magnetic metal particles comprise metal particles and iron gallium oxide, and gallium oxide is attached to the surfaces of the metal particles. And the magnetic metal particles and the liquid metal matrix are mixed, and the liquid metal matrix magnetic fluid is obtained. The liquid metal magnetofluid comprises the following components in parts by mass: 2-35 parts of magnetic metal particles and 98-65 parts of liquid metal matrix. The liquid metal-based magnetic fluid can be used as a soft robot to realize drug targeted transportation. The invention further discloses the electronic skin containing the liquid metal-based magnetic fluid, and the electronic skin is used for detecting the motion state of a human body.

Description

Technical Field

[0001] The invention belongs to the field of materials, and specifically relates to magnetic metal particles and a preparation method thereof, a liquid metal-based magnetic fluid and an application thereof. Background Art

[0002] Liquid metal-based magnetic fluids are widely used in actual production due to their fast magnetic response, excellent conductivity and simple manufacturing process. Liquid metal-based magnetic fluid composites are divided into two-phase fluids and three-phase polymers. Compared with three-phase liquid metal-based magnetic polymers, two-phase liquid metal-based magnetic fluids usually have higher flexibility and operability and are more suitable for unstructured working conditions.

[0003] In the manufacturing process of two-phase liquid metal-based magnetic fluid, even if the magnetic metal particles and the liquid metal matrix are stirred vigorously for a long time, only a few magnetic metal particles can be mixed into the liquid metal matrix along with the liquid metal oxide, and most of the magnetic metal particles can only adhere to the gallium iron oxide on the outer surface of the liquid metal matrix. Therefore, it is urgent to adjust the wettability at the interface between the liquid metal matrix and the magnetic metal particles and enhance the compatibility of the magnetic metal particles and the liquid metal matrix, so as to obtain a liquid metal-based magnetic fluid with better performance.

[0004] The common method for synthesizing liquid metal-based magnetic fluids is to place magnetic metal particles in a strong acid or strong base solution. Although the acid and base solution can eliminate the oxide layer of the liquid metal matrix and promote the mixing of magnetic metal particles into the liquid metal matrix, the magnetic metal particles cannot maintain stable suspension in the liquid metal matrix, and the liquid metal matrix is ​​easily separated from the magnetic metal particles. The acid and base solution will also damage the magnetism of the magnetic metal particles. In response to the above problems, the literature “Nucleation and Growth of Polyaniline Nanofibers onto Liquid MetalNanoparticles”, C, Zhang. et al, Chemistry of Materials. 2020, 32, 4808–4819.DOI: 10.1021 / acs.chemmater.0c01615 (“Nucleation and Growth of Polyaniline Nanofibers onto Liquid Metal Nanoparticles”, C, Zhang et al., Materials Chemistry. 2020, 32, 4808–4819. DOI: 10.1021 / acs.chemmater.0c01615) records: A layer of SiO2 shell is coated on the surface of magnetic metal Ni particles, and then Ni@SiO2 is mixed with the liquid metal matrix. Although the SiO2 shell can enhance the compatibility of magnetic Ni particles with the liquid metal matrix and protect the Ni particles from corrosion under acidic conditions, the insulating properties of SiO2 will cause the conductivity of liquid metal-based magnetic fluids to decrease, limiting their application in flexible electronics. The paper “Reactive wetting enabled anchoring of non-wettable iron oxide in liquid metal for miniature soft robot”, Y, Shen. et al, Nature Communications. 2023, 14, 6276. DOI: 10.1038 / s41467-023-41920-4, states that a layer of polydopamine is attached to the surface of Fe particles, and Ag can be attached to polydopamine to form a Fe@Polydopamine@Ag composite material, which can be uniformly mixed with the liquid metal matrix without affecting the conductivity of the liquid metal. However, the manufacturing method is complicated and requires additional steps to produce polydopamine to cover the iron particles. Furthermore, the compatibility of Ag on the iron surface with the liquid metal matrix is ​​poor. Summary of the invention

[0005] In view of the shortcomings of existing magnetic metal particle materials, the purpose of the present invention is to provide a magnetic metal particle, which has high compatibility with a liquid metal matrix, strong conductivity, high stability, and a simple manufacturing method. The present invention also provides a method for preparing the magnetic metal particle. The present invention also provides a liquid metal-based magnetic fluid and provides the application of the liquid metal-based magnetic fluid.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: In a first aspect, the present invention provides a magnetic metal particle, characterized in that it comprises metal particles and gallium iron oxide, wherein gallium oxide is attached to the surface of the metal particles, and the metal particles are any one of nickel, iron, cobalt or gadolinium, and a mixture of two or more thereof.

[0007] In a second aspect, the present invention provides a method for preparing magnetic metal particles, comprising the following steps: Step 1, cleaning the metal particles: cleaning the metal particles in an acetone solution by ultrasonic wave, and then filtering through a suction filtration device to obtain metal particles with impurities removed;

[0008] Step 2. Gallium iron oxide is attached to the surface of metal particles: Gallium iron oxide is attached to the surface of metal particles: The cleaned metal particles, gallium salt, reducing agent and stabilizer are added to ultrapure water for a chemical reaction, and then filtered through a suction filtration device to obtain magnetic metal particles with gallium iron oxide attached and impurities removed, and then calcined through a tubular furnace to obtain magnetic metal particles with higher crystallinity.

[0009] Preferably, the reducing agent is sodium citrate or sodium hypophosphite; the stabilizing agent is polyvinyl pyrrolidone, polyethyleneimine or ammonium chloride; and the gallium salt is gallium chloride or gallium nitrate.

[0010] The cleaned metal particles, gallium salt, reducing agent and stabilizer are added to ultrapure water and reacted at 180°C for 10 hours; the magnetic metal particles attached with gallium iron oxide to remove impurities are calcined at 600°C for 4 hours in a tubular furnace.

[0011] In a third aspect, the present invention provides a liquid metal-based magnetic fluid, comprising liquid metal and the above-mentioned magnetic metal particles, wherein by mass, 2 to 35 parts of magnetic metal particles are mixed with 98 to 65 parts of liquid metal; the liquid metal is a gallium-indium alloy or a gallium-indium-tin alloy.

[0012] In a fourth aspect, the present invention provides an application of the above-mentioned liquid metal-based magnetic fluid as a soft robot for targeted drug transportation. The liquid metal-based magnetic fluid is controlled by a magnet to reach the location of the drug, and then the liquid metal-based magnetic fluid is controlled by a magnet to push the drug into the acid solution in the beaker, and the acid solution promotes the release of drug particles to achieve targeted drug transportation.

[0013] In the fifth aspect, the invention provides an electronic skin, in which a liquid metal-based magnetic fluid is moved on an elastic substrate to form a fold line, a sensitive element for deformation of the elastic substrate is used, a conductive wire is connected to both ends of the liquid metal sensitive element, and a viscoelastic material is coated on the surface of the liquid metal sensitive element, and the electronic skin is obtained after solidification.

[0014] The elastic substrate and the viscoelastic material are Ecoflex elastic materials.

[0015] The technical effects of the present invention are: The magnetic metal particle material of the present invention overcomes the disadvantage that magnetic particles and liquid metal are difficult to be compatible. The magnetic metal particles have reduced conductivity, high stability in liquid metal and simple manufacturing method.

[0016] The liquid metal-based magnetic fluid of the present invention can be used as a soft robot for targeted drug transportation, and can also be made into electronic skin for sensing human body movements. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings of the present invention are as follows: Figure 1 Transmission electron microscope image of magnetic metal particles Figure 2 It is the element spectrum of magnetic metal particles; Figure 3 is the X-ray diffraction pattern of magnetic metal particles; Figure 4 is a schematic diagram of the electronic skin structure of an embodiment; Figure 5 The conductivity curves of liquid metal-based magnetic fluids prepared with different contents of magnetic metal particles in Examples 1, 2, 3, 4, 5, 6, and 7; The thick curve represents the error of five experiments, and the error and thickness of each point are different.

[0018] Figure 6 Conductivity curves of liquid metal-based magnetic fluids prepared with different contents of magnetic metal particles in Examples 8, 9, 10, 11, 12, 13, and 14; The thick curve represents the error of five experiments, and the error and thickness of each point are different.

[0019] Figure 7A diagram showing the process of using the liquid metal-based magnetic fluid in Example 1 as a soft robot for targeted drug transport; Figure 8 This is the test curve of the resistance change rate caused by the stretching deformation of the electronic skin; Fig. 9 To detect the movement of human joints using electronic skin made of liquid metal-based magnetic fluid; (a) Resistance response curves of finger, (b) wrist, (c) knee joint, and (d) elbow bending, and (e) schematic diagram of electronic skin used to detect different parts of the human body movement. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: The magnetic metal particles described in the present application refer to metal particles that have magnetism when magnetized.

[0021] Embodiment 1: A magnetic metal particle comprises a metal particle and gallium iron oxide, wherein the gallium iron oxide is attached to the surface of the metal particle.

[0022] The following materials are measured by mass, and the method for preparing magnetic metal particles is as follows: Step 1, cleaning the iron particles: 5 parts of the micron-sized iron particles are cleaned by ultrasonic treatment in a 13.5 mol / L acetone solution for 20 min at room temperature, and filtered through a suction filtration device to obtain cleaned micron-sized iron particles; Step 2, gallium iron oxide attached to the surface of the cleaned iron particles: 5 parts of cleaned micron-sized iron particles, 5 parts of gallium chloride, 15 parts of sodium hypophosphite, and 10 parts of ammonium chloride are added to 200 parts of ultrapure water, transferred to a water bath ultrasonic machine, ultrasonicated at 35°C for 30 minutes, filtered through a suction filtration device to obtain micron-sized iron particles with gallium iron oxide attached, and then calcined at 600°C for 4 hours in a tubular furnace under a nitrogen environment to obtain micron-sized iron particles with gallium iron oxide attached with higher crystallinity.

[0023] Transmission electron microscopy image of micron-sized iron particles attached with gallium iron oxide Figure 1 As shown, a layer of material is attached to the surface of the iron particles. Figure 2 The element spectrum characterization proves the presence of O and Ga elements in the substance. Figure 3 The X-ray diffraction pattern of micron-sized iron particles attached with gallium iron oxide is described. Through X-ray diffractometer testing, it can be proved that the outer layer material belongs to gallium iron oxide and the inner layer material belongs to iron.

[0024] It is worth noting that the method for preparing magnetic metal particles from any one of nickel, iron, cobalt or gadolinium or a mixture of two or more particles is similar.

[0025] The liquid metal-based magnetic fluid of this embodiment is obtained by mixing 5 parts of micron-sized iron particles with gallium iron oxide attached thereto and 95 parts of liquid metal by mass. The liquid metal in this embodiment is a gallium-indium alloy. A gallium-indium-tin alloy can also be used.

[0026] The electronic skin of this embodiment is as follows Figure 4 As shown, a liquid metal-based magnetic fluid 2 is guided by a magnet to move on an Ecoflex00-30 elastic substrate 1 to form a broken line, which is used as a sensitive element for the deformation of the elastic substrate. A conductive copper wire 3 with a diameter of 0.05 mm is pasted on both ends of the liquid metal sensitive element, and a viscoelastic material is coated on the surface of the sensitive element. After solidification for 4 hours, the electronic skin is obtained.

[0027] Conductivity test: The resistance conductivity of the electronic skin is measured using an LCR digital bridge tester, and the resistance range of the LCR digital bridge is from 0 to 99.99MW. In order to evaluate the conductivity of the magnetic fluid of the electronic skin, the conductivity is calculated by the following formula: σ = L / SR In the formula, σ represents the conductivity, L It represents the length of the sensitive element, S represents the cross-sectional area of ​​the sensitive element, and R represents the resistance of the sensitive element.

[0028] The resistance and conductivity test of the liquid metal-based magnetic fluid of the electronic skin of this embodiment is as follows: Figure 5 As shown, the conductivity is 3.11×10 6 S / m.

[0029] Embodiment 2 is different from Embodiment 1 in that: The liquid metal-based magnetic fluid is a mixture of 10 parts of magnetic metal particles and 90 parts of liquid metal, based on mass.

[0030] The resistance and conductivity test of the liquid metal-based magnetic fluid of the electronic skin of this embodiment is as follows: Figure 5 As shown, the conductivity is 3.19×10 6 S / m.

[0031] Embodiment 3 is different from Embodiment 1 in that: The liquid metal-based magnetic fluid is a mixture of 15 parts of magnetic metal particles and 85 parts of liquid metal, based on mass.

[0032] The resistance and conductivity test of the liquid metal-based magnetic fluid of the electronic skin of this embodiment is as follows: Figure 5 As shown, the conductivity is 2.94×10 6 S / m.

[0033] Embodiment 4 is different from Embodiment 1 in that: The liquid metal-based magnetic fluid is a mixture of 20 parts of magnetic metal particles and 80 parts of liquid metal, based on mass.

[0034] The resistance and conductivity test of the liquid metal-based magnetic fluid of the electronic skin of this embodiment is as follows: Figure 5 As shown, the conductivity is 2.72×10 6 S / m.

[0035] Embodiment 5 is different from Embodiment 1 in that: The liquid metal-based magnetic fluid is a mixture of 25 parts of magnetic metal particles and 75 parts of liquid metal, based on mass.

[0036] The resistance and conductivity test of the liquid metal-based magnetic fluid of the electronic skin of this embodiment is as follows: Figure 5 As shown, the conductivity is 2.01×10 6 S / m.

[0037] Embodiment 6 is different from Embodiment 1 in that: The liquid metal-based magnetic fluid is a mixture of 30 parts of magnetic metal particles and 70 parts of liquid metal, based on mass.

[0038] The resistance and conductivity test of the liquid metal-based magnetic fluid of the electronic skin of this embodiment is as follows: Figure 5 As shown, the conductivity is 1.57×10 6 S / m.

[0039] Embodiment 7 is different from Embodiment 1 in that: The liquid metal-based magnetic fluid is a mixture of 35 parts of magnetic metal particles and 65 parts of liquid metal, based on mass.

[0040] The resistance and conductivity test of the liquid metal-based magnetic fluid of the electronic skin of this embodiment is as follows: Figure 5 As shown, the conductivity is 1.22×10 6 S / m.

[0041] Embodiment 8 is different from Embodiment 1 in that: The liquid metal-based magnetic fluid is a mixture of 2 parts of magnetic metal particles and 98 parts of liquid metal by mass. The iron particles in the magnetic metal particles are nanometer-sized.

[0042] The resistance and conductivity test of the liquid metal-based magnetic fluid of the electronic skin of this embodiment is as follows: Figure 6 As shown, the conductivity is 2.84×10 6 S / m.

[0043] Embodiment 9 is different from Embodiment 1 in that: The liquid metal-based magnetic fluid is a mixture of 5 parts of magnetic metal particles and 95 parts of liquid metal by mass. The iron particles in the magnetic metal particles are nanometer-sized.

[0044] The resistance and conductivity test of the liquid metal-based magnetic fluid of the electronic skin of this embodiment is as follows: Figure 6 As shown, the conductivity is 3.04×10 6 S / m.

[0045] Embodiment 10 is different from Embodiment 1 in that: The liquid metal-based magnetic fluid is a mixture of 8 parts of magnetic metal particles and 92 parts of liquid metal by mass. The iron particles in the magnetic metal particles are nanometer-sized.

[0046] The resistance and conductivity test of the liquid metal-based magnetic fluid of the electronic skin of this embodiment is as follows: Figure 6 As shown, the conductivity is 2.70×10 6 S / m.

[0047] Embodiment 11 is different from Embodiment 1 in that: The liquid metal-based magnetic fluid is a mixture of 11 parts of magnetic metal particles and 89 parts of liquid metal by mass. The iron particles in the magnetic metal particles are nanometer-sized.

[0048] The resistance and conductivity test of the liquid metal-based magnetic fluid of the electronic skin of this embodiment is as follows: Figure 6 As shown, the conductivity is 2.38×10 6 S / m.

[0049] Embodiment 12 is different from Embodiment 1 in that: The liquid metal-based magnetic fluid is a mixture of 14 parts of magnetic metal particles and 86 parts of liquid metal by mass. The iron particles in the magnetic metal particles are nanometer-sized.

[0050] The resistance and conductivity test of the liquid metal-based magnetic fluid of the electronic skin of this embodiment is as follows: Figure 6 As shown, the conductivity is 1.77×10 6 S / m.

[0051] Embodiment 13 is different from Embodiment 1 in that: The liquid metal-based magnetic fluid is a mixture of 17 parts of magnetic metal particles and 83 parts of liquid metal by mass. The iron particles in the magnetic metal particles are nanometer-sized.

[0052] The resistance and conductivity test of the liquid metal-based magnetic fluid of the electronic skin of this embodiment is as follows: Figure 6 As shown, the conductivity is 1.53×10 6 S / m.

[0053] Embodiment 14 is different from Embodiment 1 in that: The liquid metal-based magnetic fluid is a mixture of 20 parts of magnetic metal particles and 80 parts of liquid metal by mass. The iron particles in the magnetic metal particles are nanometer-sized.

[0054] The resistance and conductivity test of the liquid metal-based magnetic fluid of the electronic skin of this embodiment is as follows: Figure 6 As shown, the conductivity is 1.26×10 6 S / m.

[0055] Application Example 1: In order to explore the application potential of the above-mentioned liquid metal-based magnetic fluid, the liquid metal-based magnetic fluid of Example 2 is used as a soft robot for targeted drug transportation.

[0056] like Figure 7 As shown, the liquid metal-based magnetic fluid is placed together with an acid solution in a beaker with a certain inclination, and the drug is also placed in the beaker, located at the upper end of the incline, and placed at a position that the acid solution cannot reach; the liquid metal magnetic fluid is controlled by a magnet to pass through the acid-air interface (t = 2 s) and quickly reach the drug position (t = 4 s), and then the liquid metal magnetic fluid is guided by the magnet to push the drug back to the acid solution (t = 6 s), thereby promoting the release of drug particles (t = 12 s).

[0057] Application Example 2: In order to explore the application potential of the above-mentioned liquid metal-based magnetic fluid, the liquid metal-based magnetic fluid of Example 9 is used to make an electronic skin for monitoring human body movement. A metal wire and an LCR digital bridge tester are used to form a series circuit, and then the electronic skin is fixed to various joints, and the resistance change of the joint movement is recorded.

[0058] The production process of electronic skin is as follows: the magnet is under the Ecoflex 00-30 substrate, and the moving magnet can control the liquid metal-based magnetic fluid 2 to move on the Ecoflex 00-30 elastic substrate 1. During the movement, the liquid metal-based magnetic fluid will adhere to the surface of the Ecoflex 00-30 elastic substrate 1 as a sensitive element; a copper conductive wire 3 with a diameter of 0.05mm is pasted on the end of the sensitive element, and a silicone coating glue is applied to the surface of the sensitive element to protect the sensitive element from external interference, and it is cured at room temperature for 4 hours. Figure 4 As shown, the electronic skin is 35 mm long, 35 mm wide and 3 mm high. Figure 8 The test curve of the resistance change rate caused by the stretching deformation of the electronic skin is shown in Figure 1. Figure 8 It can be seen that the straight line fitting degree between the tensile deformation and the resistance change rate is high, satisfying the linear relationship.

[0059] Skin strain sensors are verified by fixing the prepared electronic skin on various joints and monitoring the strain signals generated by human body movements. Metal wires are fixed to the two ends of the electronic skin. The electronic skin can monitor the fingers, wrists, elbows and knees. The two ends of the electronic skin are fixed to the human body with tape to detect the strain information of the bending of each joint.

[0060] In order to evaluate the relative resistance change rate of the strain sensor, the relative resistance change rate is calculated by the following formula: RRC=△R / R0 Where △R represents the resistance change, R0 represents the initial resistance, and RRC represents the relative resistance change rate.

[0061] like Fig. 9 As shown, the electronic skin is able to generate corresponding signals when these joints move, and it is repeatable. Fig. 9 (a) and Fig. 9 In (b), as the bending degree of the subject's index finger and wrist increases, the relative resistance change rate RRC of the electronic skin also increases, and the RRC of the electronic skin remains unchanged at a fixed bending degree. Fig. 9 (c) and Fig. 9 In (d), when the subject's elbow and knee joints are bent, the RRC in the electronic skin increases accordingly with the change in the length and cross-sectional area of ​​the sensitive element; after stretching the calf, the electronic skin quickly restores its output to its original state; when the knee joint is fully bent again, the electronic skin can accurately and quickly detect the signal of repetitive motion. The above tests prove that electronic skin can be used to detect motion signals of human joints.

Claims

1. A magnetic metal particle, characterized in that: The invention comprises metal particles and gallium iron oxide. Gallium oxide is attached to the surface of the metal particles. The metal particles are any one of nickel, iron, cobalt or gadolinium, and a mixture of two or more thereof.

2. A method for preparing magnetic metal particles, characterized in that: The following steps are involved: Step 1, cleaning the metal particles: cleaning the metal particles in an acetone solution by ultrasonic wave, and then filtering through a suction filtration device to obtain metal particles with impurities removed; Step 2, gallium iron oxide attached to the surface of metal particles: the cleaned metal particles, gallium salt, reducing agent and stabilizer are added to ultrapure water for chemical reaction, and then filtered through a suction filtration device to obtain magnetic metal particles with gallium iron oxide attached and impurities removed, and then calcined through a tubular furnace to obtain magnetic metal particles with higher crystallinity.

3. The method for preparing magnetic metal particles according to claim 2, characterized in that: The reducing agent is sodium citrate or sodium hypophosphite; the stabilizing agent is polyvinyl pyrrolidone, polyethyleneimine or ammonium chloride; and the gallium salt is gallium chloride or gallium nitrate.

4. The method for preparing magnetic metal particles according to claim 2, characterized in that: The cleaned metal particles, gallium salt, reducing agent and stabilizer are added to ultrapure water and reacted at 180°C for 10 hours; the magnetic metal particles attached with gallium iron oxide to remove impurities are calcined at 600°C for 4 hours in a tubular furnace.

5. A liquid metal-based magnetic fluid, characterized in that: The invention comprises liquid metal and the magnetic metal particles according to claim 1, wherein 2 to 35 parts of the magnetic metal particles are mixed with 98 to 65 parts of the liquid metal matrix by mass; the liquid metal is a gallium-indium alloy or a gallium-indium-tin alloy.

6. Use of the liquid metal-based magnetic fluid according to claim 5 as a soft robot for targeted drug delivery.

7. The liquid metal-based magnetic fluid according to claim 6 is used for targeted drug delivery in soft robots, characterized in that: The liquid metal-based magnetic fluid is controlled by a magnet to reach the location of the drug, and then the liquid metal-based magnetic fluid is controlled by a magnet to push the drug into the acid solution in the beaker. The acid solution promotes the release of drug particles to achieve targeted transportation of the drug.

8. An electronic skin, characterized by: The liquid metal-based magnetic fluid described in claim 5 is moved on an elastic substrate to form a broken line, which is used as a sensitive element for elastic substrate deformation. Conductive wires are connected to both ends of the liquid metal sensitive element, and viscoelastic material is coated on the surface of the liquid metal sensitive element. After solidification, electronic skin is obtained.

9. The electronic skin according to claim 8, characterized in that: The elastic substrate and the viscoelastic material are Ecoflex elastic materials.

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