Polymer optical fiber junction sensitive structure and silica gel substrate based pressure distribution sensor

Abstract

The application discloses a pressure distribution sensor based on a polymer optical fiber knot sensitive structure and a silica gel base. The pressure distribution sensor comprises a shell, a bottom plate, a plurality of pressure heads, a plurality of polymer optical fibers and a silica gel layer; a knot is punched on each polymer optical fiber to form a polymer optical fiber knot, the polymer optical fiber knot is embedded in the silica gel layer and is wrapped by the silica gel layer, and the silica gel layer and the polymer optical fiber are arranged at the bottom of an inner cavity formed by connecting the shell and the bottom plate; the inner cavity top corresponding to each polymer optical fiber is provided with a pressure head, and the pressure head is partially exposed to the inner cavity; the polymer optical fiber knot takes the optical fiber kink as a pressure sensitive point, and the pressure sensitive point is arranged close to the pressure head. The application has the characteristics of high integration, small size, simple manufacturing, anti-electromagnetic interference and corrosion resistance.

Description

Technical Field

[0001] This invention relates to a pressure sensor, and more particularly to a pressure distribution sensor based on a polymer fiber optic junction sensing structure and a silicone substrate. Background Technology

[0002] Common pressure sensors measure pressure at a single location, while pressure distribution sensors measure pressure at multiple locations within an area, i.e., pressure distribution, resulting in matrix data output or pressure contour maps. Pressure distribution sensors can be used to measure pressure on the soles of the feet, palms, back, and buttocks, and have numerous applications in motion detection, medical devices, and smart homes. Traditional pressure distribution sensors often use metallic materials and operate based on piezoresistive or piezoelectric effects. Newer pressure distribution sensors are typically thin sheets, plates, or strips, using conductive rubber, conductive silicone, conductive gel, liquid metal, and other sensitive materials, operating based on principles of resistance, capacitance, or piezoelectricity.

[0003] Sensors based on electrical principles are difficult to operate stably in environments with strong electromagnetic interference, thus necessitating the development of pressure distribution sensors based on optical principles. Optical fibers are common optical devices, and fiber-optic pressure sensors are mostly Bragg grating type, requiring complex and precise demodulators for signal analysis. Summary of the Invention

[0004] To address the problems existing in the background technology, the purpose of this invention is to provide a pressure distribution sensor based on a polymer optical fiber junction sensitive structure and a silicone substrate, which has the characteristics of high integration, small size, simple fabrication, anti-electromagnetic interference, and corrosion resistance.

[0005] The technical solution of this invention is:

[0006] I. A pressure distribution sensor based on a polymer fiber optic junction sensing structure and a silicone substrate:

[0007] The pressure distribution sensor includes a housing, a base plate, multiple pressure heads, multiple polymer optical fibers, and a silicone layer. Each polymer optical fiber has a knot to form a polymer optical fiber knot, which is embedded in the silicone layer and wrapped by the silicone layer. Both the silicone layer and the polymer optical fibers are placed at the bottom of the inner cavity constructed by connecting the housing and the base plate. Each polymer optical fiber has a pressure head at the top of the inner cavity, and the pressure head is partially exposed in the inner cavity.

[0008] The pressure head includes a pressure head base and a pressure head cap. One end of the pressure head base is placed in the inner cavity, and the other end extends out of the inner cavity through a column and is fixedly connected to the pressure head cap. The pressure head cap is used to contact the surface to be tested.

[0009] The polymer fiber optic junction uses the fiber optic kink as the pressure-sensitive point, and the pressure-sensitive point is arranged close to the pressure head.

[0010] The two ends of the polymer optical fiber are extended from the silica gel layer and extended outward through the holes in the bottom plate to connect the light source and the light detector respectively.

[0011] The one end of the pressure head base is a flat end surface as a tail, and the flat end surface in the cavity and the silica gel layer is in contact.

[0012] The polymer optical fiber knot is made by first making a loose knot of the polymer optical fiber without tightening, then passing a metal rod through the loop in the loose knot and tightening the polymer optical fiber, and then taking out the metal rod.

[0013] The number of the pressure head is the same as that of the polymer optical fiber, and they are arranged in the same array.

[0014] II. A method for manufacturing a polymer optical fiber knot array wrapped by silica gel and applied to the pressure distribution sensor:

[0015] The method arranges the polymer optical fiber knot wound on the metal rod on the bottom plate, uses the metal rod to define the winding diameter of the polymer optical fiber knot, uses one kind of enclosure to complete the pouring of the main body of the silica gel layer, and uses another kind of enclosure to complete the pouring of the hollow core of the silica gel layer.

[0016] A section of polymer optical fiber is made into a loose knot without tightening, the tail fibers at both ends of the polymer optical fiber are passed through the holes in the bottom plate, a metal rod is passed through the loop in the knot, the polymer optical fiber is tightened to make the loose knot tight, the metal rod forms a polymer optical fiber knot, and the knot is embedded into the positioning groove in the bottom plate, and some adhesive is infiltrated into the tail fibers of the polymer optical fiber passing through the holes in the bottom plate to prevent the knot from loosening.

[0017] A first enclosure is arranged on the periphery edge of the bottom plate, liquid silica gel is injected into the pool formed in the middle of the first enclosure to wrap the upper half of the polymer optical fiber knot and the metal rod, and then the main body of the silica gel layer is solidified; the metal rod is taken out from the main body of the silica gel layer in a spiral manner, and the part of the metal rod taken out forms a hollow core of the silica gel layer; then a second enclosure is arranged on the periphery edge of the bottom plate and at both ends of the original metal rod, the second enclosure blocks the two ports of the hollow core, and the same kind of liquid silica gel is injected into the remaining part of the polymer optical fiber knot in the hollow core of the silica gel layer from the gap formed between the second enclosure and the bottom plate, and then the hollow core of the silica gel layer is solidified.

[0018] The core sensing element of the application is made of a polymer optical fiber knot, the polymer optical fiber knot is wrapped by silica gel, and the twisted knot area of the optical fiber is a pressure sensitive point; the tail of the sensor probe is pressed to compress the silica gel and stimulate the pressure sensitive point for detection.

[0019] Polymer optical fiber is a common optical fiber made of polymethyl methacrylate and other materials. When the polymer optical fiber is knotted, the application of external force at the knot position changes the bending radius, and the transmittance of the optical fiber changes significantly, resulting in a significant change in the light intensity at the output end of the optical fiber. The silica gel wrapped around the optical fiber knot can protect the optical fiber knot from damage due to excessive deformation, and can regulate the sensitivity and range of the optical fiber knot to force. The softer the silica gel, the more sensitive the optical fiber knot to force, but the range of force it can withstand is limited. The harder the silica gel, the less sensitive the optical fiber knot to force, but it can withstand greater force. The present application cleverly uses this principle to make a pressure distribution sensor.

[0020] If the polymer optical fiber of the polymer optical fiber knot is set, the common pressure distribution sensor is difficult to fix the knot type at a specific position, form a specific orientation or a specific diameter. Secondly, if only optical fiber is used, due to the hardness and plasticity of the material, the elasticity and force bearing capacity of the knot type are limited, and it is difficult to flexibly regulate the sensitivity and range of force, resulting in limitations in the use scenarios of the sensor.

[0021] The present application has the innovative feature of wrapping the polymer optical fiber knot with a silica gel layer and then contacting the probe to detect pressure. The polymer optical fiber with a polymer optical fiber knot is coated with a silica gel layer, which takes advantage of the superior elastic mechanical properties and coating ability of silica gel to solve the above technical problems in the manufacturing process and measurement, thereby reducing the manufacturing difficulty, improving the yield, and meeting the wide range of sensitivity and range requirements in various use scenarios.

[0022] Compared with the prior art, the present application has the following advantages:

[0023] (1) Polymer optical fiber and silica gel are common and inexpensive items, so the present application does not need to purchase or synthesize special sensitive materials, nor does it need special chemical synthesis or precise micro-nano processing equipment;

[0024] (2) The number and layout of the pressure sensing points can be increased, decreased and changed by arranging the polymer optical fiber knots

[0025] (3) The range and sensitivity of each pressure sensing point can be adjusted by the fiber material, fiber diameter, polymer optical fiber knot diameter, and silica gel hardness;

[0026] (4) The pressure sensing points work independently and do not interfere with each other;

[0027] (5) The pressure sensing points can be arranged on any curved surface, and only the geometry of the bottom plate, enclosure and shell needs to be modified;

[0028] (6) Based on the principle of light, the present application can resist strong electromagnetic interference and is resistant to humid and corrosive environments. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a cross-sectional view of the pressure distribution sensor of the present application;

[0030] Figure 2 is a schematic view of the appearance of the present application;

[0031] Figure 3 is a schematic view of the explosion of the present application;

[0032] Figure 4 is a schematic view of the making of a polymer fiber knot of a specific size by means of a metal rod in the present application;

[0033] Figure 5 is a schematic view of the arrangement of polymer fiber knots in the present application;

[0034] Figure 6 is a schematic view of the making of a silicone layer body in the present application;

[0035] Figure 7 is a schematic view of the front of the filling of the hollow core of the silicone layer in the present application;

[0036] Figure 8 is a schematic view of the back of the filling of the hollow core of the silicone layer in the present application;

[0037] Figure 9 is a schematic view of the array of polymer fiber knots wrapped by silicone in the present application.

[0038] Figure 10 is a schematic view of the change in transmittance of polymer fiber knots wrapped by silicone of different hardness when under stress in the present application.

[0039] In the figure: 1 - polymer fiber with a knot, 101 - polymer fiber knot not yet tightened, 2 - pressure sensitive point on the knot, 3 - silicone layer, 31 - silicone layer body, 4 - base plate, 5 - outer shell, 6 - pressure head base, 7 - pressure head cap, 8 - metal rod, 9 - enclosure used for making the silicone layer body, 10 - enclosure used for filling the hollow core of the silicone layer, 11 - gap for filling silicone, 121 - change in transmittance of polymer fiber knot sample when wrapped by silicone of hardness Shore A 10, 122 - change in transmittance of polymer fiber knot sample when wrapped by silicone of hardness Shore A 16, 122 - change in transmittance of polymer fiber knot sample when wrapped by silicone of hardness Shore A 20. DETAILED DESCRIPTION

[0040] The present application is further illustrated below in conjunction with the accompanying drawings and examples.

[0041] As Figures 1-3As shown, the specific embodiment sensor includes a shell 5, a base plate 4, a plurality of pressure heads, a plurality of polymer optical fibers 1 and a silica gel layer 3; the shell 5 and the base plate 4 are arranged in sequence from top to bottom and connected to form a shell, and the shell and the base plate are fixed by four screws. Each polymer optical fiber 1 is marked with a ring knot to form a polymer optical fiber knot, which is embedded in and wrapped by the silica gel layer 3, and the silica gel layer 3 and the polymer optical fiber 1 are both placed at the bottom of the inner cavity of the shell formed by the connection of the shell 5 and the base plate 4; each polymer optical fiber 1 is provided with a pressure head at the top of the inner cavity, and the pressure head partially exposes in the inner cavity.

[0042] In the specific embodiment, nine pressure heads and nine polymer optical fibers 1 are arranged in a 3*3 array. The nine polymer optical fiber knots wrapped by silica gel are placed on the base plate, and the upper part is covered by the shell.

[0043] The pressure head includes a pressure head base 6 and a pressure head cap 7, one end of the pressure head base 6 is placed in the inner cavity, the other end is fixedly connected with the pressure head cap 7 after extending out of the inner cavity through a column, and the pressure head cap 7 is used to contact the surface to be measured.

[0044] The boss structure of the base plate facilitates the fixation of the sensor in other objects, tools and mechanical structures, and provides a long enough hole for the tail fiber of the polymer optical fiber knot, which is convenient for fixation.

[0045] The base plate 4, the shell 5, the pressure head base 6 and the pressure head cap 7 are all made of metal materials, such as aluminum alloy, or non-metal materials commonly used in 3D printing, such as acrylonitrile-butadiene-styrene copolymer ABS.

[0046] The polymer optical fiber is a kind of optical fiber made of high transparent polymers such as polymethyl methacrylate PMMA, polystyrene PS and polycarbonate PC as core layer material, and fluoropolymer or PMMA with lower refractive index as cladding layer material.

[0047] The polymer optical fiber knot takes the twisted knot or the overlapping part of the optical fiber as the pressure sensitive point 2, which is arranged close to the pressure head, that is, the thickness of the silica gel layer 3 between the polymer optical fiber knot at the pressure sensitive point and the pressure head is the smallest.

[0048] The two ends of the polymer optical fiber 1 extend out of the silica gel layer 3 and pass through the holes in the base plate 4 to extend outward and connect the light source and the light detector respectively, so that the light enters from one end of the polymer optical fiber 1 and exits from the other end. The hole diameter is the same as the fiber diameter. The polymer optical fiber knot is fixed to the base plate through these holes and silica gel.

[0049] In the embodiment, the diameter of the hole is 270 microns, slightly larger than the diameter of the optical fiber 250 microns. The distance between the two holes is equal to the diameter of the polymer optical fiber coil. In the present application, the diameter of the polymer optical fiber coil refers to the diameter of the inner circle of the polymer optical fiber coil. The diameter of the outer circle of the polymer optical fiber coil is twice the diameter of the optical fiber, i.e. 500 microns. The diameter of the polymer optical fiber coil should not be less than 2 mm, otherwise the polymer optical fiber coil will produce serious plastic deformation and lose pressure sensitivity.

[0050] The silica gel layer 3 wraps all the polymer optical fiber coils inside and is tightly combined with the bottom plate 4. The top surface of the silica gel layer 3 is slightly higher than the pressure sensitive point 2, with a height difference of 250 microns. The height difference should be greater than zero to ensure that the pressure sensitive point 2 is not worn out. The greater the height difference, the higher the lower limit and upper limit of the present application, and the lower the sensitivity.

[0051] The end of the indenter base 6 is a flat end surface as a tail, which is in contact with the flat end surface of the silica gel layer 3 in the cavity.

[0052] As shown in Figure 4 The polymer optical fiber coil is made by first making a loose and not tight knot 101 with the polymer optical fiber 1, then pulling tight the knot 101 with the metal rod 8, and then taking out the metal rod 8. The twisted knot of the optical fiber is the pressure sensitive point 2.

[0053] The number of indenter and polymer optical fiber 1 is the same, and they are arranged in the same array.

[0054] The indenter and the polymer optical fiber coil are arranged in one-to-one alignment, and the indenter and the polymer optical fiber coil can be arranged in a rectangular array or any other suitable layout.

[0055] When external force is applied to the indenter, the indenter cap 7 drives the indenter base 6 to move towards the pressure sensitive point 2 of the polymer optical fiber coil in the silica gel, until the polymer optical fiber coil is deformed, causing the light passing through the polymer optical fiber to be affected, and thus causing the change of the light intensity at the end of the tail fiber.

[0056] When the indenter cap 7 is in contact with the shell 5, additional external force cannot cause the indenter base 6 to continue to press the polymer optical fiber coil, thereby protecting the polymer optical fiber coil from being damaged.

[0057] In the present application, the sensitivity and range of the sensor are adjusted and controlled by adjusting the elastic coefficient of the material of the polymer optical fiber coil, the winding diameter of the polymer optical fiber coil, the hardness and thickness of the silica gel layer, the diameter of the indenter base, and the distance between the indenter cap and the shell.

[0058] The cylinder of the pressure head base 6 passes through the hole of the shell 5, is inserted into the circular groove of the pressure head cap 7, and is fastened by adhesive. The moving range of the pressure head is limited, i.e. when the lower edge of the pressure head cap 7 is in contact with the shell 5, the pressure head cannot be pressed further, and the additional pressure is borne by the shell 5 and cannot be transmitted to the polymer fiber joint through the pressure head. The moving range of the pressure head is determined by the height of the cylinder of the pressure head base 6 and the thickness of the shell 5. The greater the moving range of the pressure head, the greater the range of the present application. The hole of the shell 5 is aligned with the polymer fiber joint, so that the center of the pressure head base 6 is aligned with the polymer fiber joint.

[0059] As shown in Figures 5-9 , the manufacturing method is specifically: arranging the polymer fiber joint wound on the metal rod 8 on the bottom plate 4, using the metal rod 8 to limit the winding diameter of the polymer fiber joint, using one kind of enclosure 9 to complete the pouring of the main body of the silica gel layer 3, and using another kind of enclosure 10 to complete the pouring of the hollow core of the silica gel layer 3.

[0060] In specific implementation, the polymer fiber 1 is first tied into a loose knot, and then the metal rod 8 is passed through the loop of the loose knot and tightened to form the polymer fiber joint wound on the metal rod 8.

[0061] As shown in Figure 5 , the polymer fiber joint wound on the metal rod 8 is arranged on the bottom plate 4, specifically: taking a section of polymer fiber 1 to tie a loose knot but not to tighten, passing the tail fibers at both ends of the polymer fiber 1 through the hole of the bottom plate 4, taking a metal rod 8 to pass through the loop in the knot, tightening the polymer fiber 1 to make the loose knot tighten the metal rod 8 to form the polymer fiber joint, and embedding the knot into the positioning groove pre-formed in the bottom plate 4, the width and depth of the positioning groove being the same as or slightly larger than the diameter of the optical fiber. Some adhesive is infiltrated in the hole of the bottom plate 4 through which the tail fibers pass, so that the knot does not loosen. The width and depth of the positioning groove are the same as or slightly larger than the diameter of the optical fiber, which is 250-300 microns. Some adhesive is infiltrated in the hole of the bottom plate 4 through which the tail fibers pass, so that the knot 1 does not loosen after the tension of the tail fibers is removed. All other polymer fiber joints are fixed on the bottom plate using the same method.

[0062] The pouring of the main body of the silica gel layer 3 is completed using one kind of enclosure 9, and the pouring of the hollow core of the silica gel layer 3 is completed using another kind of enclosure 10, specifically:

[0063] As shown in Figures 5-6 , the first enclosure 9 is arranged on the edge of the bottom plate 4, and the upper half of the polymer fiber joint and the metal rod 8 is wrapped with liquid silica gel in the pool formed in the middle of the first enclosure 9, and then the main body of the silica gel layer 3 is completed by solidification;

[0064] Then the metal rod 8 is taken out from the main body of the silica gel layer 3 in a spiral manner, and the metal rod is pushed or pulled while being rotated, and part of the metal rod 8 is taken out to form the hollow core of the silica gel layer 3;

[0065] As Figures 7-9 shown, then the second enclosure 10 is set on the edge of the bottom plate 4 and the two ends of the original metal rod 8, the second enclosure 10 blocks the two ports of the hollow core, the remaining part of the same liquid silicone wrapping polymer optical fiber joint is injected into the hollow core of the silica gel layer 3 from the gap 11 formed by the second enclosure 10 and the bottom plate 4, and then the silica gel is cured to complete the production of the silica gel layer 3 hollow core. The two injected silica gels are tightly combined at the interface to form an integral whole without delamination.

[0066] The hardness of the silica gel layer can be 10-50 of Shore 00 type or 10-60 of Shore A type. The harder the silica gel, the larger the range of the present application and the lower the sensitivity.

[0067] As Figure 10 shown, the transmittance of the polymer optical fiber joint changes with the force curve 121, 122, 123 and the hardness of the silica gel wrapping joint (Shore A type 10, 16, 20) has a significant relationship. The harder the silica gel used, the more gentle the degree of decrease in the transmittance of the polymer optical fiber joint with the increase of the force, indicating that the polymer optical fiber joint is less sensitive to force; but the polymer optical fiber joint can withstand greater force, indicating that the polymer optical fiber joint has a larger range of force.

Claims

1. A pressure distribution sensor based on polymer fiber knot sensitive structure and silica gel substrate, characterized in that: it comprises a shell (5), a bottom plate (4), a plurality of pressure heads, a plurality of polymer optical fibers (1) and a silica gel layer (3); each polymer optical fiber (1) is knotted to form a polymer optical fiber knot, the polymer optical fiber knot is embedded in the silica gel layer (3) and is wrapped by the silica gel layer (3), the silica gel layer (3) and the polymer optical fiber (1) are arranged at the bottom of the inner cavity formed by the connection of the shell (5) and the bottom plate (4); the top of the inner cavity corresponding to each polymer optical fiber (1) is provided with a pressure head, and the pressure head is partially exposed in the inner cavity. The polymer optical fiber knot takes the fiber kink as a pressure sensitive point (2), and the pressure sensitive point (2) is arranged close to the pressure head. The two ends of the polymer optical fiber (1) extend out of the silica gel layer (3) and pass through the holes in the bottom plate (4) to extend outward and connect the light source and the light detector respectively. The number of pressure heads is the same as that of polymer optical fibers (1), and they are arranged in the same array. The pressure head comprises a pressure head base (6) and a pressure head cap (7), one end of the pressure head base (6) is arranged in the inner cavity, the other end extends out of the inner cavity through a column and is fixedly connected with the pressure head cap (7), and the pressure head cap (7) is used for contacting the surface to be measured.

2. The pressure distribution sensor based on polymer optical fiber junction sensitive structure and silica gel substrate according to claim 1, characterized in that: One end of the pressure head base (6) is a flat end surface as a tail, which contacts the flat end surface of the silica gel layer (3) in the cavity.

3. The pressure distribution sensor based on polymer optical fiber junction sensitive structure and silica gel substrate according to claim 2, characterized in that: The polymer optical fiber knot is made by first knotting a loose knot on the polymer optical fiber (1) without tightening, then passing a metal rod (8) through the loop in the loose knot and tightening the polymer optical fiber (1), and then taking out the metal rod (8).

4. The pressure distribution sensor based on polymer optical fiber junction sensitive structure and silica gel substrate according to claim 1, characterized in that: The polymer optical fiber knot wound on the metal rod (8) is arranged on the bottom plate (4), the metal rod (8) is used to limit the winding diameter of the polymer optical fiber knot, a kind of enclosure (9) is used to complete the pouring of the main body of the silica gel layer (3), and another kind of enclosure (10) is used to complete the pouring of the hollow core of the silica gel layer (3).

5. A method of making a polymer optical fiber array wrapped by silica gel for use in the pressure distribution sensor of any one of claims 1-4, characterized by: The method comprises:

6. A method of manufacture according to claim 5, wherein: A section of polymer optical fiber (1) is knotted to form a loose knot without tightening, the two ends of the polymer optical fiber (1) pass through the holes in the bottom plate (4), a metal rod (8) passes through the loop in the knot, the polymer optical fiber (1) is tightened to make the loose knot tight, the metal rod (8) forms a polymer optical fiber knot, and the knot is embedded in the positioning groove in the bottom plate (4), and some adhesive is infiltrated in the holes in the bottom plate (4) through which the two ends of the polymer optical fiber (1) pass, so that the knot does not loosen. The method comprises:

7. The method of claim 5, wherein: A first enclosure (9) is arranged on the periphery of the bottom plate (4), and liquid silica gel is injected into the pool formed in the middle of the first enclosure (9) to wrap the upper half of the polymer optical fiber knot and the metal rod (8), and then the main body of the silica gel layer (3) is solidified to complete the production of the main body of the silica gel layer (3); The metal rod (8) is taken out from the main body of the silica gel layer (3) in a spiral manner, and the part of the metal rod (8) taken out forms a hollow core of the silica gel layer (3). ​ Then, a second enclosure (10) is arranged on the edge of the bottom plate (4) and at both ends of the original metal rod (8), which blocks the two ports of the hollow core. The remaining part of the liquid silicone is injected into the hollow core of the silicone layer (3) from the gap (11) formed between the second enclosure (10) and the bottom plate (4), and then cured to complete the production of the hollow core of the silicone layer (3).

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