Liquid metal pressure sensing fiber array and preparation method thereof

Abstract

The present invention relates to a liquid metal pressure sensing fiber array and a preparation method thereof, wherein the liquid metal pressure sensing fiber array comprises: a) flexible fibers; b) a liquid metal coating layer covering the flexible fibers; and c) a packaging layer on the surface of the liquid metal coating layer. The liquid metal pressure sensing fiber array provided by the present invention can directly feedback the external force exerted on the fiber and the deformation produced by the electric signal according to the resistance change produced by the liquid metal when it is deformed, and can well realize the detection of stress-strain, and can be widely used in the fields of flexibility, sensing, etc.

Description

Technical Field

[0001] The present invention relates to the field of sensing technology, and in particular to a liquid metal pressure sensing fiber array and a preparation method thereof. Background Art

[0002] Pressure sensing technology has important applications in many fields, and has increasingly wide applications in the fields of information and robotics. At present, sensing technology mainly uses sensing materials to change electrical properties through deformation of metals, semiconductors or polymer materials with piezoelectric functions. However, the cost is high and the accuracy is limited. Liquid metal has the characteristics of metals and fluids, and has important application prospects in the field of pressure sensing. However, the surface tension of liquid metal is very large, and it is difficult to form a fixed shape or to have good adhesion with other materials. There are no reports on the effective use of liquid metal for pressure sensing. At present, there is an urgent need to provide a new flexible structure to achieve rapid and accurate detection of stress-strain sensing materials. Summary of the invention

[0003] An embodiment of the present invention provides a liquid metal pressure sensing fiber array. The liquid metal pressure sensing fiber array can directly feedback the external force exerted on the fiber and the deformation generated by the liquid metal when it is deformed through electrical signals, and can well realize stress-strain detection, and can be widely used in the fields of flexibility, sensing, etc.

[0004] An embodiment of the present invention provides a liquid metal pressure sensing fiber array, comprising:

[0005] a) Flexible fibers;

[0006] b) a liquid metal coating covering the flexible fiber;

[0007] c) an encapsulation layer on the surface of the liquid metal coating layer.

[0008] The liquid metal pressure sensing fiber array provided in the embodiment of this aspect can test forces in different ranges by using fibers (liquid metal pressure sensing fibers) of different lengths to form an array and increase the test range.

[0009] In the present invention, liquid metal is coated on the surface of flexible fibers, and the resistance of the fibers is changed by deformation of the fibers. Based on the relationship between fiber stress-strain-resistance, a series of corresponding values ​​are obtained, and the strain (deformation) and stress of the fibers can be inferred from the resistance change.

[0010] In some preferred embodiments, the diameter of the flexible fiber is 75-500 μm.

[0011] In some preferred embodiments, the thickness of the liquid metal coating layer is 2 to 50 μm, preferably 10 to 50 μm.

[0012] In some preferred embodiments, the thickness of the encapsulation layer is 10-50 μm, preferably 10-30 μm.

[0013] In some preferred embodiments, the flexible fiber is a composite of PBT and PET, or the flexible fiber comprises: a fiber core, and a flexible fiber layer covering the fiber core; and the liquid metal coating layer covers the flexible fiber layer of the flexible fiber.

[0014] In some preferred embodiments, the fiber core is a carbon fiber filament or a copper fiber filament. Preferably, the fiber core is a carbon fiber filament, the diameter of the fiber core is 20 to 50 μm, and the surface of the fiber core is rough, preferably with a roughness of 10 to 50 nm. In the present invention, the use of carbon fiber as commercial carbon fiber and the use of the liquid metal layer together can further solve the problem of electrical conductivity and have better electrical conductivity. The use of a fiber core with a rough surface can improve the bonding strength between the carbon fiber and the PET material.

[0015] In some preferred embodiments, the flexible fiber layer is a composite of PBT (polytetramethylene terephthalate) and PET (polyethylene terephthalate); preferably, the thickness of the flexible fiber layer is 20 to 200 μm, preferably 20 to 50 μm.

[0016] The inventors have found that by further adopting the above-mentioned layers and their layer thicknesses, the flexibility can be improved and better mechanical properties can be obtained.

[0017] In some preferred embodiments, the mass ratio of PBT to PET is 99:1 to 1:99, and the mass ratio of PBT to PET is preferably 20:80 to 60:40.

[0018] In some preferred embodiments, the liquid metal is gallium-indium liquid metal, gallium-indium-tin liquid metal or bismuth-indium-tin liquid metal; and / or the encapsulation layer is silicone rubber prepolymer.

[0019] An embodiment of the present invention further provides a method for preparing the liquid metal pressure sensing fiber array, comprising: providing the flexible fiber, covering the flexible fiber with the liquid metal coating layer, and then covering the packaging layer on the liquid metal coating layer.

[0020] In some preferred embodiments, the steps include:

[0021] 1) PBT and PET are mixed, heated, extruded, and cooled to obtain flexible fibers;

[0022] 2) The liquid metal layer is covered on the surface of the flexible fiber by dipping or coating the liquid metal; then the silicone rubber prepolymer is dipped and heated to cover the surface of the liquid metal layer with an encapsulation layer.

[0023] In some preferred embodiments, in step 1), the heating temperature is 90-190°C, and the cooling treatment adopts 10-20°C water treatment; and / or, in step 2), the heating temperature is 60-80°C, preferably 70°C, and the heating time is 1-2h.

[0024] In some preferred embodiments, the method further comprises: when the mixture of PBT and PET is heated to the glass transition temperature, a fiber core is added, preferably carbon fiber filaments, and extrusion molding is performed to prepare a flexible fiber containing a fiber core in the middle. The present invention can better maintain the mechanics and flexibility of the fiber by adopting the extrusion-cooling method.

[0025] In some preferred embodiments, a hole-shaped die is used for the extrusion molding; preferably, the hole of the hole-shaped die has a certain degree of roughness.

[0026] The beneficial effects of the present invention are at least that: the liquid metal pressure sensing fiber array provided by the present invention forms a conductive layer by attaching liquid metal to the surface of flexible fibers, and changes the resistance of the conductive layer by bending the fibers, thereby realizing a one-to-one correspondence between stress, strain and resistance. It can also effectively improve the accurate measurement of the change in liquid metal resistance, quickly respond to the influence of the outside world on the fiber morphology, and the minimum force detected is 10 -6 N, the minimum resistance change is 1μΩ, achieving rapid detection of stress-strain. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. It is obvious that the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 This is a schematic diagram of the liquid metal wrapped flexible fiber structure of Example 2 of the present invention;

[0029] Figure 2 This is a diagram of the process of liquid metal covering fibers in Example 1 of the present invention;

[0030] Figure 3 This is a picture of liquid metal attached to the fiber surface in Example 1 of the present invention;

[0031] Figure 4This is a schematic diagram of the effect of liquid metal fiber on resistance in Example 1 of the present invention;

[0032] Figure 5 This is a diagram of the liquid metal wire mechanical testing process in Example 1 of the present invention;

[0033] Figure 6 This is a partial schematic diagram of a liquid metal-wrapped flexible fiber structure in Example 3 of the present invention;

[0034] Figure 7 This is a schematic diagram of the hole mold used in Example 4 of the present invention;

[0035] In the figure, 1 is the fiber core, 2 is the flexible fiber layer, 3 is the liquid metal coating layer, and 4 is the packaging layer. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in the field or the product manual shall be followed.

[0037] In the present invention, the instruments used, etc., without indicating the manufacturer, are all conventional products that can be purchased through regular channels. The methods described are conventional methods unless otherwise specified, and the raw materials described can be obtained from public commercial channels unless otherwise specified. If no specific technology or conditions are indicated in the examples, the technology or conditions described in the literature in the field or the product instructions are used.

[0038] Some embodiments of the present invention provide a liquid metal pressure sensing fiber array, comprising:

[0039] a) Flexible fibers;

[0040] b) a liquid metal coating covering the flexible fiber; and

[0041] c) an encapsulation layer on the surface of the liquid metal coating layer;

[0042] The flexible fiber is a composite of PBT and PET with a mass ratio of 99:1 to 1:99, the diameter of the flexible fiber is 75 to 500 μm; the thickness of the liquid metal coating layer is 20 to 50 μm; the thickness of the encapsulation layer is 20 to 50 μm; the liquid metal is gallium indium liquid metal, gallium indium tin liquid metal or bismuth indium tin liquid metal; the encapsulation layer is a silicone rubber prepolymer. In this scheme, after the surface of the PET / PBT fiber is coated with liquid metal, a DC power supply is connected at both ends, and bending the fiber has a significant effect on the change in fiber resistance.

[0043] Some embodiments of the present invention provide a liquid metal pressure sensing fiber array, comprising:

[0044] a) flexible fibers; the flexible fibers comprising:

[0045] The fiber core, and

[0046] a flexible fiber layer covering the fiber inner core;

[0047] b) a liquid metal coating covering the flexible fiber;

[0048] c) an encapsulation layer on the surface of the liquid metal coating layer;

[0049] The fiber core is carbon fiber filament, the flexible fiber layer is a composite of PBT and PET with a mass ratio of 99:1 to 1:99, the diameter of the flexible fiber is 75 to 500 μm, the thickness of the liquid metal coating layer is 20 to 50 μm, the thickness of the encapsulation layer is 10 to 30 μm, the diameter of the fiber core is 20 to 50 μm, the thickness of the flexible fiber layer is 20 to 200 μm, the liquid metal is gallium indium liquid metal, gallium indium tin liquid metal or bismuth indium tin liquid metal, and the encapsulation layer is silicone rubber prepolymer. In this scheme, after the fiber surface is covered with liquid metal, the liquid metal and the carbon fiber inside the fiber form a loop, and after the two ends are connected to direct current, the bending deformation will react sensitively to the resistance.

[0050] Some embodiments of the present invention provide a method for preparing a liquid metal pressure sensing fiber array, which specifically includes the following steps:

[0051] 1) PBT and PET are mixed and heated at 90-190° C. for extrusion molding, and then cooled with water at 10-20° C. to obtain flexible fibers;

[0052] 2) The liquid metal layer is covered on the surface of the flexible fiber by dipping or coating the liquid metal; then the silicone rubber prepolymer is dipped and heated at 70° C. for 1 to 2 hours to cover the surface of the liquid metal layer with a packaging layer.

[0053] Some embodiments of the present invention provide a method for preparing a liquid metal pressure sensing fiber array, which specifically includes the following steps:

[0054] 1) PBT and PET are mixed and heated at 90-190° C. When the mixture of PBT and PET is heated to the glass transition temperature, carbon fiber filaments are added, and extrusion molding is performed using a hole-shaped die to prepare a flexible fiber containing carbon fiber filaments in the middle, and then cooling is performed using water at 10-20° C. to obtain a flexible fiber;

[0055] 2) The liquid metal layer is covered on the surface of the flexible fiber by dipping or coating the liquid metal; then the silicone rubber prepolymer is dipped and heated at 70° C. for 1 to 2 hours to cover the surface of the liquid metal layer with a packaging layer.

[0056] Example 1

[0057] This embodiment provides a liquid metal pressure sensing fiber:

[0058] a) Flexible fibers;

[0059] b) a liquid metal coating covering the flexible fiber;

[0060] c) an encapsulation layer on the surface of the liquid metal coating layer;

[0061] The diameter of the flexible fiber is 80 μm; the liquid metal is GaIn 10 ; The encapsulation layer is a silicone rubber prepolymer; the flexible fiber is a composite of PBT and PET with a mass ratio of 50:50; the thickness of the liquid metal coating layer is 30 μm; the thickness of the encapsulation layer is 50 μm;

[0062] This embodiment also provides a method for preparing the above-mentioned liquid metal pressure sensing fiber, and the method is as follows:

[0063] (1) PBT and PET are mixed in proportion and heated at 125°C. When the mixture reaches the glass transition temperature and enters a creep state, it is pressed into a hole die by an extruder, quickly stretched into filaments, and then treated with 15°C low-temperature water to obtain fibers;

[0064] (2) Apply liquid metal to the surface by coating to form a liquid metal layer. Apply silicone rubber prepolymer, heat to 70°C for 2 hours, and then insulate the surface;

[0065] The liquid metal fiber prepared in Example 1 was tested. Figure 2 As shown, it has good conductivity. As the number of coatings increases, the resistance decreases. After coating 7-8 times, the resistance no longer changes significantly. Figure 3 is a picture of liquid metal attached to the fiber surface in Example 1. When the fiber is bent, it will cause the resistance of the fiber to change, such as Figure 4 As shown, the resistance increases during fiber bending. Figure 5 This is a diagram of the mechanical test process of the liquid metal wire in Example 1. According to the stress-strain data of the fiber, the stress and strain generated by the fiber can be obtained through the resistance change, thereby realizing the sensing function. During the test, a DC power supply of 1V, 1A is used.

[0066] Example 2

[0067] This embodiment provides a liquid metal pressure sensing fiber and a preparation method, which is the same as that of embodiment 1, except that:

[0068] The flexible fiber comprises: a fiber inner core 1 (carbon fiber filament), and a flexible fiber layer 2 (same as the flexible fiber in Example 1) covering the fiber inner core 1; the diameter of the fiber inner core is 20 μm; and the thickness of the flexible fiber layer is 100 μm. Figure 1 As shown, the liquid metal coating layer 3 wraps the flexible fiber (fiber core 1 mixed with flexible fiber layer 2), and the encapsulation layer 4 is on the surface of the liquid metal coating layer 3. During its preparation process, when the PBT and PET mixture reaches the glass transition temperature, carbon fiber filaments are added to the hole mold, and flexible fibers containing carbon fiber filaments in the middle are extruded, and then the liquid metal layer and the encapsulation layer are prepared through the outer surface.

[0069] Through the detection of Example 2: Specifically: the positive electrode (or negative electrode) of the external power supply is connected to the central carbon fiber; the other end is connected to the external liquid metal to form a closed circuit. The other steps are the same as in Example 1, and the stress and strain generated by the fiber can be directly determined by the change in resistance.

[0070] Example 3

[0071] The same method as in Example 2 is used, except that the inner core of the fiber is changed to copper wire, such as Figure 6 shown.

[0072] Example 4

[0073] This embodiment provides a liquid metal pressure sensing fiber and a preparation method. The same as embodiment 1, the only difference is that the surface of the flexible fiber is rough. In order to increase the wettability of the liquid metal and the fiber, a hole mold with a certain roughness (the roughness in the hole is 10 to 50 nm) is selected during the preparation of the flexible fiber. Figure 7 As shown, the prepared fibers with various edges and angles and the increase in fiber roughness can effectively improve the wettability between the liquid metal and the fiber, thereby increasing the adhesion between the liquid metal and the fiber and increasing the accuracy of the sensing results.

[0074] Example 5

[0075] The fibers and method are the same as those in Example 2, except that fibers of different lengths are prepared to form an array to increase the test range.

[0076] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A liquid metal pressure sensing fiber array, characterized in that: include: a) Flexible fibers; The flexible fiber comprises: a fiber inner core, and a flexible fiber layer covering the fiber inner core; b) a liquid metal coating layer, wherein the liquid metal coating layer covers the flexible fiber layer of the flexible fiber; c) an encapsulation layer on the surface of the liquid metal coating layer; Among them, the fiber core is carbon fiber filament, the surface of the fiber core is rough, the flexible fiber layer is a composite of PBT and PET, the thickness of the flexible fiber layer is 20~50μm, the diameter of the flexible fiber is 75~500μm, the thickness of the liquid metal coating layer is 2~50μm, the thickness of the encapsulation layer is 10~30μm, and the diameter of the fiber core is 20~50μm.

2. The liquid metal pressure sensing fiber array according to claim 1, characterized in that: The mass ratio of PBT and PET is 99:1~1:

99.

3. The liquid metal pressure sensing fiber array according to claim 1, characterized in that: The liquid metal is gallium-indium liquid metal, gallium-indium-tin liquid metal or bismuth-indium-tin liquid metal; and / or the encapsulation layer is silicone rubber prepolymer.

4. The method for preparing the liquid metal pressure sensing fiber array according to any one of claims 1 to 3, characterized in that: include: The flexible fiber is provided, the liquid metal coating layer is covered on the flexible fiber, and then the encapsulation layer is covered on the liquid metal coating layer.

5. The method for preparing the liquid metal pressure sensing fiber array according to claim 4, characterized in that: The following steps are involved: 1) Mix PBT and PET, heat, extrude and shape, and cool to obtain flexible fibers; 2) The liquid metal layer is covered on the surface of the flexible fiber by dipping or coating the liquid metal; then the silicone rubber prepolymer is dipped and heated to cover the surface of the liquid metal layer with an encapsulation layer.

6. The method for preparing the liquid metal pressure sensing fiber array according to claim 5, characterized in that: In step 1), the heating temperature is 90-190°C, and the cooling treatment is performed with water at 10-20°C; and / or, in step 2), the heating temperature is 60-80°C, and the heating time is 1-2h.

7. The method for preparing the liquid metal pressure sensing fiber array according to claim 6, characterized in that: In step 2), the heating temperature is 70°C.

8. The method for preparing the liquid metal pressure sensing fiber array according to claim 5, characterized in that: Also includes: When the mixture of PBT and PET is heated to the glass transition temperature, the fiber inner core is added and extrusion molding is performed to prepare a flexible fiber containing the fiber inner core in the middle.

9. The method for preparing the liquid metal pressure sensing fiber array according to claim 5, characterized in that: The extrusion molding is performed using a hole-shaped die.

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