A strain sensing fiber with liquid metal and nano silver conductive core and preparation method thereof

Abstract

The invention discloses a strain sensing fiber with a liquid metal and nano silver conductive core and a preparation method thereof, belonging to the field of intelligent fiber technology, wherein the strain sensing fiber comprises a conductive core and a skin layer coated outside the conductive core; the conductive core comprises liquid metal and nano silver, and a polyurethane elastomer; the skin layer comprises a polyurethane elastomer. The prepared strain sensing fiber has the advantages of excellent conductivity, high stretchability, and a wide tensile strain response range, the strain response range is 0-400%, and has excellent mechanical properties, the elongation at break can reach 500%, and the stretch-recovery performance is good.

Description

Technical Field

[0001] The invention relates to a strain sensing fiber with liquid metal and nano silver conductive core and a preparation method thereof, belonging to the technical field of intelligent fibers. Background Art

[0002] Smart fibers have received increasing attention in recent years due to their electrical conductivity, high stretchability, color adjustability, self-healing and shape memory. Flexible, stretchable, lightweight conductive fibers play an indispensable and important role in emerging wearable electronics, soft robots, deformable supercapacitors, flexible displays and other fields. Compared with traditional rigid sensors, flexible fiber-shaped sensors have the characteristics of deformability, weavability and integration, and are expected to play an important role in social production and development. However, existing flexible fiber-shaped sensors still have the problems of narrow tensile strain response range and relatively poor mechanical properties. Summary of the invention

[0003] The object of the present invention is to provide a strain sensing fiber with liquid metal and nano silver conductive core and a preparation method thereof. The prepared strain sensing fiber has the advantages of excellent conductivity, high stretchability, wide tensile strain response range, excellent mechanical properties, and good stretch-recovery performance.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A strain sensing fiber with a liquid metal and nano-silver conductive core comprises a conductive core and a skin layer coated outside the conductive core; the conductive core contains liquid metal, nano-silver and polyurethane elastomer; the skin layer contains polyurethane elastomer.

[0006] Preferably, in the conductive core, the mass ratio of liquid metal to nanosilver is 3:1 to 9:1.

[0007] Preferably, the mass ratio of the total mass of the liquid metal and nanosilver in the conductive core to the mass ratio of the polyurethane elastic material in the conductive core is 17:3-19:1.

[0008] Preferably, the liquid metal is a gallium-indium-tin alloy or a gallium-indium alloy; the nanosilver is a combination of one or more of silver nanowires, silver nanosheets and silver nanoparticles.

[0009] Preferably, the diameter of the conductive core is 0.5-1.3 mm; the thickness of the skin is 0.7-1.3 mm.

[0010] The method for preparing any of the above strain sensing fibers having liquid metal and nano-silver conductive cores comprises the following steps:

[0011] S1, dissolving a polyurethane elastomer in a solvent to obtain a skin spinning solution;

[0012] S2, dispersing liquid metal and nanosilver in a solvent to obtain a mixed suspension, and centrifuging to obtain a conductive powder; adding the conductive powder to a polyurethane elastomer solution, and grinding to obtain a core layer spinning solution;

[0013] S3. Skin-core structure strain sensing fiber was obtained by wet spinning.

[0014] Preferably, in step S1, the mass fraction of the polyurethane elastomer in the skin spinning solution is 20-30%.

[0015] Preferably, in step S1, the solvent is DMF.

[0016] Preferably, in step S2, the mass ratio of liquid metal to nanosilver is 3:1 to 9:1.

[0017] Preferably, in step S2, in the polyurethane elastomer solution, the mass fraction of the polyurethane elastomer is 16-25%; and the mass ratio of the conductive powder to the polyurethane elastomer is 17:3-19:1.

[0018] Preferably, in step S3, the wet spinning draft ratio is 1-3, preferably in the range of 1.29-2.

[0019] The beneficial effects of the present invention are:

[0020] The prepared strain sensing fiber has the advantages of excellent conductivity, high stretchability, and a wide tensile strain response range of 0~400%. It also has excellent mechanical properties, with an elongation at break of up to 500% and good stretch-recovery properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a scanning electron microscope image of the strain sensing fiber obtained in Example 1;

[0022] Figure 2 This is a diagram showing the element distribution results of the strain sensing fiber obtained in Example 1;

[0023] Figure 3 The current-voltage curves of the strain sensing fibers obtained with different mass ratios of gallium-indium alloy liquid metal and silver powder;

[0024] Figure 4 The stress-strain curves of strain sensing fibers obtained with different mass ratios of gallium-indium alloy liquid metal and silver powder;

[0025] Figure 5 The resistance change rate-strain curve of the strain sensing fiber obtained with different mass ratios of gallium-indium alloy liquid metal and silver powder;

[0026] Figure 6The resistance change rate-strain curves of strain sensing fibers obtained at different drawing ratios;

[0027] Figure 7 This is the cyclic stretching-recovery resistance change rate-strain curve of the strain sensing fiber obtained in Example 1. DETAILED DESCRIPTION

[0028] The present invention will be specifically described below in conjunction with the accompanying drawings and embodiments.

[0029] Embodiment 1: This embodiment provides a method for preparing a strain sensing fiber having a liquid metal and a nano-silver conductive core, comprising the following steps:

[0030] (1) Preparation of cortical spinning solution: Weigh TPU (polyurethane elastomer) particles and DMF (N,N-dimethylformamide) solvent in a reagent bottle, mix them at a solid content ratio of 1:4, place them on a magnetic stirring table, and stir for 8 h to completely dissolve the TPU particles to prepare a cortical spinning solution with a mass fraction of 25%.

[0031] (2) Preparation of core spinning solution: Weigh a certain amount of gallium-indium alloy liquid metal and add it to the acetone solution, ultrasonicate for 8 hours, and obtain a black-gray suspension liquid after the ultrasonication. Weigh a certain amount of silver powder and add it to the acetone solution, ultrasonicate for 30 minutes, and obtain a silver-gray suspension liquid after the ultrasonication. Mix the two in a ratio of 5:1 (based on the mass ratio of gallium-indium alloy liquid metal to silver powder of 5:1) and continue ultrasonication for 1 hour to obtain a uniformly mixed suspension. Centrifuge the suspension of liquid metal and silver powder and collect its powder to obtain the core layer conductive component. Finally, according to the ratio of conductive component to TPU dry weight of 9:1, add the core layer conductive component to TPU (DMF as solvent) solution with a solid content of 18%, prepare the core layer solution and grind it in a grinder for 20 minutes to obtain the liquid metal / nanosilver strain sensing fiber core layer spinning solution.

[0032] (3) Preparation of conductive fibers with skin-core structure: G21 / G12 coaxial spinning needles were used for spinning through a wet spinning device. A 10 ml syringe was installed on the injection pump, and the spinning tube and the coaxial spinning needle were connected. The inner diameter of the core layer of the coaxial spinning needle was 0.5 mm, and the inner diameter of the skin layer was 2.3 mm. The spinning solution was allowed to stand for 15 min to completely eliminate the bubbles in the spinning solution. The injection pump pushed the spinning solution out of the coaxial spinning needle into the deionized water coagulation bath to form fibers, and the fibers were pulled onto a drawing machine with a drawing ratio of 1.29. After the fibers were drawn, they were placed in a deionized water coagulation bath and continued to coagulate for 24 hours. They were then collected and sent to an oven and dried at 80 °C for 20 min to obtain liquid metal / nanosilver strain sensing fibers with skin-core structure. The scanning electron microscope image and element distribution result diagram are shown as follows. Figure 1 , Figure 2 shown.

[0033] Figure 3 The test method of the current-voltage curve of the strain sensing fiber obtained by different mass ratios of gallium-indium alloy liquid metal and silver powder is as follows: connect the two ends of the strain sensing fiber to copper wires and connect to a digital source meter to measure the IV curve of the fiber. The figure also includes the IV response values ​​under other conditions where the mass ratio of gallium-indium alloy liquid metal to silver powder is 3:1~9:1, Figure 3 It can be seen that the larger the proportion of liquid metal, the better the conductivity.

[0034] Figure 4 The test method of the resistance change rate-strain curve of the strain sensing fiber obtained by different mass ratios of gallium-indium alloy liquid metal and silver powder is as follows: the sample is subjected to mechanical testing using a universal testing machine, the initial length of the fiber is selected as 4 cm, the stretching rate is 100 mm / min, and the stress-strain curve is recorded. Figure 4 It can be seen that the larger the proportion of liquid metal, the better the tensile properties.

[0035] Figure 5 and Figure 6 The test method for the resistance change rate-strain curve of the strain sensing fiber obtained with different mass ratios of gallium-indium alloy liquid metal and silver powder and the resistance change rate-strain curve of the strain sensing fiber obtained with different drawing ratios is as follows: connect copper wires at both ends of the strain sensing fiber and connect it to a digital source meter. The sample is installed on a tensile tester, and the resistance change of the fiber within the tensile strain range is recorded. As the drawing ratio increases, the resistance value of the sensing fiber shows an increasing trend. This change pattern shows that the sensing fiber has good resistance strain sensitivity and can be used to monitor strain changes. Figure 5 It can be seen that the lower the ratio of gallium-indium alloy liquid metal to silver powder, the higher the relative resistance change of the sensing fiber. Figure 6 It can be seen that the larger the wet spinning draw ratio, the higher the relative resistance change of the sensing fiber.

[0036] Figure 7 The cyclic stretching-recovery resistance change rate-strain curve of the strain sensing fiber prepared in Example 1 is shown. During the stretching and recovery process, the relative resistance change of the strain sensing fiber has good coincidence. During the stretching process, the relative resistance decreases, and during the recovery process, the relative resistance increases. This change pattern shows that the strain sensing fiber has good cyclic stability and can be used for long-term monitoring of strain changes.

[0037] The above is only a preferred implementation of the patent of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the patent of the present invention. These improvements and modifications should also be regarded as the scope of protection of the patent of the present invention.

Claims

1. A strain sensing fiber having a liquid metal and a nanosilver conductive core, characterized in that: The strain sensing fiber includes a conductive core and a skin layer coated on the conductive core; the conductive core contains liquid metal, nanosilver, and polyurethane elastomer; the skin layer contains polyurethane elastomer; in the conductive core, the mass ratio of liquid metal to nanosilver is 3:1~9:1, and the liquid metal is a gallium-indium alloy.

2. The strain sensing fiber with liquid metal and nano silver conductive core according to claim 1, characterized in that: The mass ratio of the total mass of the liquid metal and nanosilver in the conductive core to the mass ratio of the polyurethane elastic material in the conductive core is 17:3-19:

1.

3. The strain sensing fiber with liquid metal and nano silver conductive core according to claim 1, characterized in that: Nanosilver is one or more combinations of silver nanowires, silver nanosheets and silver nanoparticles.

4. The strain sensing fiber with liquid metal and nano silver conductive core according to claim 1, characterized in that: The diameter of the conductive core is 0.5~1.3mm; the thickness of the skin is 0.7~1.3mm.

5. The method for preparing the strain sensing fiber having liquid metal and nano silver conductive core according to any one of claims 1 to 4, characterized in that: The preparation method of the strain sensing fiber comprises the following steps: S1, dissolving a polyurethane elastomer in a solvent to obtain a skin spinning solution; S2, dispersing liquid metal and nanosilver in a solvent to obtain a mixed suspension, and centrifuging to obtain a conductive powder; adding the conductive powder to a polyurethane elastomer solution, and grinding to obtain a core layer spinning solution; wherein the mass ratio of the liquid metal to the nanosilver is 3:1-9:1, and the liquid metal is a gallium-indium alloy; S3. Skin-core structure strain sensing fiber was obtained by wet spinning.

6. The method for preparing the strain sensing fiber with liquid metal and nano silver conductive core according to claim 5, characterized in that: In step S1, the mass fraction of the polyurethane elastomer in the skin spinning solution is 20-30%.

7. The method for preparing the strain sensing fiber with liquid metal and nano silver conductive core according to claim 5, characterized in that: In step S2, in the polyurethane elastomer solution, the mass fraction of the polyurethane elastomer is 16-25%; and the mass ratio of the conductive powder to the polyurethane elastomer is 17:3-19:

1.

8. The method for preparing the strain sensing fiber with liquid metal and nano silver conductive core according to claim 5, characterized in that: In step S3, the wet spinning draft ratio is 1-3.

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