A flexible inductive pressure sensor and a method of manufacturing the same

Abstract

The application discloses a flexible inductive pressure sensor, which comprises a PDMS composite sponge body, a first inductive coil, a second inductive coil and a flexible film, the upper surface of the PDMS composite sponge body is provided with the first inductive coil, the lower surface of the PDMS composite sponge body is provided with the second inductive coil, the first inductive coil and the second inductive coil are reversely connected in series and correspondingly connected with a first out connection port and a second out connection port, the flexible film covers the PDMS composite sponge body, the first inductive coil and the second inductive coil, and the flexible film can fix the first inductive coil and the second inductive coil on the surface of the PDMS composite sponge body, the PDMS-carbonyl iron powder composite sponge body is used, the carbonyl iron powder is mixed into the PDMS sponge body to increase the sensitivity of the sensor, and the honeycomb-like cavities help to improve the flexibility and elasticity of the PDMS sponge body, and the structure of the sensor is optimized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inductive pressure sensors, in particular to a flexible inductive pressure sensor and a preparation method thereof. BACKGROUND

[0002] A flexible pressure sensor is a flexible electronic device that can convert mechanical quantities into electrical quantities, and the conversion process is generally achieved through piezoresistive effect, capacitive effect, piezoelectric effect or electromagnetic induction principle. At present, flexible pressure sensors are widely used in the fields of artificial intelligence, mobile medical treatment, flexible touch screens and wearable devices.

[0003] According to different signal conversion principles, pressure sensors are mainly divided into resistive, capacitive, piezoelectric and inductive sensors. Among them, the working principle of inductive pressure sensors is based on electromagnetic induction. Changes in pressure cause changes in the magnetic circuit and magnetic resistance, which further cause changes in the inductance of the coil, thereby realizing the measurement of pressure. Inductive pressure sensors are widely concerned due to their small size, high stability, long service life, good linear characteristics and no temperature hysteresis.

[0004] Among them, the application number "CN201910564634.2" discloses a "flexible inductive pressure sensor array based on ferrite film and its preparation method, which comprises a flexible substrate layer, the substrate layer is covered with a flexible wave-absorbing material, a support is arranged between the flexible substrate layer and the flexible wave-absorbing material, the flexible substrate layer adopts a flexible planar coil, and the support adopts an elastic support column; the planar coil and the flexible wave-absorbing material are connected and separated by a plurality of elastic support columns to form a flexible inductive pressure sensor. The present application provides a flexible inductive pressure sensor array based on ferrite film, which has the performance characteristics of high sensitivity, fast response, high stability, strong anti-interference and high durability, and can be applied to wearable electronic devices", but the blood oxygen meter still has the following technical problems in actual use:

[0005] The inductive pressure sensor is mostly made of traditional rigid materials, and its working principle is to convert the pressure information into the change of the relative position of the core and the coil, and the change of the relative position of the core and the coil causes the change of the inductance of the coil, so as to realize the detection of the pressure. Such inductive pressure sensor has problems of large volume, poor stability, insufficient sensitivity and the like, and its application range is limited to traditional industrial fields, and it is difficult to be applied to new fields such as artificial intelligence and flexible touch screen. In the prior art, the sensor based on mutual inductance of the opposing coils uses a hollow sponge body made of flexible PDMS material, and the two coils are arranged in the sponge body, but the distance between the two opposing coils is far, and the inductance change rate is small, thereby affecting the sensitivity of the sensor response. Although this technology can realize the measurement of pressure, it has problems of poor stability, easy distortion of the two opposing coils to produce horizontal displacement, and the like, resulting in the decrease of the inductance measurement accuracy.

[0006] Therefore, we propose a flexible inductive pressure sensor and a preparation method thereof. SUMMARY

[0007] The present application proposes a flexible inductive pressure sensor based on PDMS-carbonyl iron powder composite sponge body and a preparation method thereof to solve the problems in the background art. The present application places two parallel and opposite inductive coils on the upper and lower surfaces of the PDMS flexible composite sponge body, covers the two parallel and opposite coils and the composite sponge body with a flexible film, changes the distance between the two opposing coils by using the change of external pressure, changes the inductance value of the two coils in reverse series, and finally realizes the measurement of pressure.

[0008] To achieve the above purpose, the present application provides the following technical scheme: a flexible inductive pressure sensor, comprising a PDMS composite sponge body, a first inductive coil, a second inductive coil and a flexible film, the upper surface of the PDMS composite sponge body is provided with the first inductive coil, the lower surface of the PDMS composite sponge body is provided with the second inductive coil, the first inductive coil and the second inductive coil are connected in reverse series and correspondingly connected with a first out connection port and a second out connection port.

[0009] The flexible film covers the PDMS composite sponge body, the first inductive coil and the second inductive coil, and the flexible film can fix the first inductive coil and the second inductive coil on the surface of the PDMS composite sponge body.

[0010] Preferably, the first inductive coil and the second inductive coil are installed in parallel and opposite positions, and the directions of the two coils are opposite.

[0011] Preferably, the PDMS composite sponge body is a honeycomb-like porous sponge sheet.

[0012] Preferably, the first inductor coil and the second inductor coil are installed in parallel opposition, the distance between the two opposite inductor coils is 5 cm, the flexible film covers the PDMS composite sponge body and the first inductor coil and the second inductor coil, and the thickness of the flexible film is 2 mm.

[0013] Preferably, the top and bottom of the PDMS composite sponge body are respectively provided with an upper strong magnetic ring and a lower strong magnetic ring, the inside of each of the upper strong magnetic ring and the lower strong magnetic ring is fixedly connected with a plurality of clamping blocks, the top of each clamping block is clampingly connected with a protective pad layer, and the side of each of the upper strong magnetic ring and the lower strong magnetic ring is connected with a wiring end.

[0014] A preparation method of a flexible inductive pressure sensor, specifically comprising the following steps:

[0015] Step 1: preparing a PDMS composite sponge body;

[0016] Step 2: preparing two first inductor coils and a second inductor coil;

[0017] Step 3: placing the first inductor coil and the second inductor coil on the upper and lower surfaces of the PDMS composite sponge body respectively, connecting the two coils in reverse series, and leading out a wiring port;

[0018] Step 4: preparing a flexible film for covering the PDMS composite sponge body and the two first inductor coils and the second inductor coil, thereby obtaining the required flexible inductive pressure sensor.

[0019] Further, the preparation process of the PDMS composite sponge body (1) in step 1 is specifically as follows:

[0020] (a) First, weigh the PDMS prepolymer and the curing agent with a mass ratio of 10:1, then weigh the caster sugar with a mass 4 times that of the mixture and the carbonyl iron powder with a mass equal to that of the curing agent, and mix them uniformly.

[0021] (b) Put the mixture into a vacuum extractor for vacuum treatment for 1 h to remove bubbles in the mixture.

[0022] (c) Pour the uniformly stirred mixture into a mold, and put the mold into a constant temperature oven at 80°C for heating for 3 h.

[0023] (d) Take out the solidified solid caster sugar from the mold and put it into deionized water for sugar removal treatment.

[0024] (e) After about 6 h, the caster sugar is completely dissolved, and after drying for a period of time, the PDMS composite sponge body containing the carbonyl iron powder can be obtained by cutting, punching and other operations.

[0025] The first inductor coil (2) and the second inductor coil (3) are made by winding a steel core with a diameter of 2 mm by using a full-automatic hot air winding machine.

[0026] Further, the preparation process of the flexible film (4) in step 4 is specifically: a) uniformly mixing PDMS prepolymer and curing agent at a ratio of 10:1;

[0027] b) placing the mixture into a vacuum box;

[0028] c) immersing the PDMS composite sponge body 1 and the two first inductor coils and the second inductor coil into the PDMS mixture for about 10 seconds;

[0029] d) placing the PDMS composite sponge body wrapped with the PDMS mixture and the two first inductor coils and the second inductor coil into a temperature box, and ensuring that the temperature is 80 DEG C for 3 hours, so as to form the flexible film.

[0030] Compared with the prior art, the present application has the following beneficial effects:

[0031] 1. The present application uses a PDMS-carbonyl iron powder composite sponge body, and the carbonyl iron powder is mixed into the PDMS sponge body to increase the sensitivity of the sensor, and the honeycomb-like cavities help to improve the flexibility and elasticity of the PDMS sponge body, thereby optimizing the structure of the sensor.

[0032] 2. The flexible film used in the present application prevents the two inductor coils from falling off the surface of the PDMS composite sponge body, thereby increasing the stability and service life.

[0033] 3. The present application uses two parallel and opposite inductor coils which extend out of the wiring port of the PDMS composite sponge body, measures the change of the inductance value caused by the change of the distance between the two coils, and reflects the change of the pressure through the change of the inductance value, thereby increasing the practicability of the sensor.

[0034] 4. The present application reduces the relative distance between the two inductor coils, and when pressure is applied to the sensor device, the flexible film deforms and squeezes the PDMS composite sponge body, so that the reaction process is more convenient and the sensitivity is improved. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a schematic diagram of the overall structure of the present application;

[0036] Figure 2 It is a schematic diagram of the upper strong magnetic coil structure of the present application;

[0037] Figure 3 It is a schematic diagram of the flexible film structure of the present application;

[0038] Figure 4The second out line port structure schematic diagram of the present application;

[0039] Figure 5 The first out line port structure schematic diagram of the present application;

[0040] Figure 6 The preparation flow chart of the present application.

[0041] In the figure: 1-PDMS composite sponge body; 101-upper strong magnetic ring; 102-lower strong magnetic ring; 103-clamping block; 104-protection pad layer; 2-first inductance coil; 3-second inductance coil; 4-flexible film; 401-soft sponge body frame; 402-rubber spacer plate; 403-first installation cavity; 404-second installation cavity; 405-large inductance coil; 406-small inductance coil; 5-first out line port; 6-second out line port. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.

[0043] The terms "first", "second", and the like in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are usually a class, not limited to the number of objects, for example, the first object can be one or more. In addition, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / ", generally indicates that the front and rear associated objects are in an "or" relationship.

[0044] In the description of the present application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0045] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "arrangement" should be understood broadly, for example, it can be fixedly connected, arranged, or detachably connected, arranged, or integrally connected, arranged. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. Embodiment one

[0046] Please refer to Figures 1-6 The present application provides a technical solution: a flexible inductive pressure sensor, comprising a PDMS composite sponge body 1, a first inductive coil 2, a second inductive coil 3 and a flexible film 4, the first inductive coil 2 is placed on the upper surface of the PDMS composite sponge body 1, the lower surface of the PDMS composite sponge body 1 is provided with the second inductive coil 3, the first inductive coil 2 and the second inductive coil 3 are reversely connected in series and correspondingly connected to the first out port 5 and the second out port 6.

[0047] The flexible film 4 covers the PDMS composite sponge body 1, the first inductive coil 2 and the second inductive coil 3, and the flexible film 4 can fix the first inductive coil 2 and the second inductive coil 3 on the surface of the PDMS composite sponge body 1.

[0048] The first inductive coil 2 and the second inductive coil 3 are installed in parallel and opposite positions, and the two coils are opposite in direction.

[0049] The PDMS composite sponge body 1 is a honeycomb-like porous sponge sheet.

[0050] The first inductive coil 2 and the second inductive coil 3 are installed in parallel and opposite positions, and the distance between the two opposite inductive coils is 5 cm. The flexible film 4 covers the PDMS composite sponge body 1, the first inductive coil 2 and the second inductive coil 3, and the thickness of the flexible film 4 is 2 mm.

[0051] The top and bottom of the PDMS composite sponge body 1 are respectively provided with an upper strong magnetic ring 101 and a lower strong magnetic ring 102, the inside of the upper strong magnetic ring 101 and the lower strong magnetic ring 102 is fixedly connected with a plurality of clamping blocks 103, the top of the clamping block 103 is clamped and connected with a protective pad layer 104, and the side of the upper strong magnetic ring 101 and the lower strong magnetic ring 102 is connected with a wiring port. Embodiment two

[0052] Please refer to Figure 5The PDMS composite sponge 1 is integrally immersed in a PDMS mixture prepared by mixing a PDMS prepolymer material and a curing agent at a ratio of 10:1, and is placed in a temperature oven for a period of time. After curing, a thin film covering the PDMS composite sponge 1 and the first inductive coil 2 and the second inductive coil 3 is obtained. The flexible thin film 4 makes the first inductive coil 2 and the second inductive coil 3 not easy to fall off from the surface of the PDMS composite sponge 1, thereby increasing the stability and service life. Due to the flexibility of the PDMS material, when pressure is applied to the sensor device, the flexible thin film 4 can deform and press the PDMS composite sponge 1, thereby making the use process more convenient and improving the sensitivity.

[0053] The PDMS prepolymer, the curing agent, the soft white sugar, and the carbonyl iron powder are uniformly stirred and mixed, the mixed solution is poured into a honeycomb-like sheet type mold, and the mold is placed in an environment of 80°C for 3h. After curing, the mold is demolded and soaked in warm water to remove sugar. After drying, the PDMS flexible composite sponge is cut and punched. The mixing of the carbonyl iron powder into the PDMS composite sponge 1 increases the sensitivity of the sensor. The relative distance between the two parallel and opposite first inductive coils 2 and the second inductive coils 3 is reduced. The honeycomb-like cavities help to improve the flexibility and elasticity of the PDMS composite sponge 1. The use of the PDMS composite sponge 1 can determine the position of the two coils in the sensor device, optimize the structure of the sensor, and improve the sensitivity of the sensor.

[0054] Secondly, the two parallel and opposite first inductive coils 2 and the second inductive coils 3 are used, and the first out port 5 and the second out port 6 extending from the PDMS composite sponge 1 are led out. The change of the inductance value caused by the change of the distance between the two first inductive coils 2 and the second inductive coils 3 is measured, and the change of the inductance value is used to reflect the change of the pressure, thereby increasing the practicability of the sensor.

[0055] Please refer to Figure 6 A flexible inductive pressure sensor preparation method, specifically comprising the following steps:

[0056] Step 1: preparing a PDMS composite sponge 1;

[0057] Step 2: preparing two first inductive coils 2 and second inductive coils 3;

[0058] Step 3: placing the first inductive coils 2 and the second inductive coils 3 on the upper and lower surfaces of the PDMS composite sponge 1 respectively, and reversely connecting the two coils in series, and then leading out the connection port;

[0059] Step 4: preparing a flexible thin film 4 covering the PDMS composite sponge 1 and the two first inductive coils 2 and the second inductive coils 3, thereby obtaining the required flexible inductive pressure sensor.

[0060] Further, the preparation process of the PDMS composite sponge body (1) in step 1 is specifically:

[0061] (a) First, weigh the PDMS prepolymer and the curing agent in a mass ratio of 10:1, then weigh the granulated sugar in an amount of 4 times the mass of the mixture and the carbonyl iron powder in an amount equal to the mass of the curing agent, and mix them evenly.

[0062] (b) Put the mixture into a vacuum extraction machine for vacuum treatment for 1h to remove bubbles in the mixture.

[0063] (c) Pour the well-mixed mixture into a mold, and place the mold in a constant temperature oven at 80℃ for heating for 3h.

[0064] (d) After curing, take out the solid granulated sugar and put it into deionized water for sugar removal treatment.

[0065] (e) After about 6h, the granulated sugar is completely dissolved. After drying for a period of time, the PDMS composite sponge body containing carbonyl iron powder can be obtained by cutting, punching, etc.

[0066] Further, the first inductor coil (2) and the second inductor coil (3) in step 2 are made by winding a steel core with a diameter of 2mm using a full-automatic hot air winding machine.

[0067] Further, the preparation process of the flexible film 4 in step 4 is specifically: a. Mix the PDMS prepolymer and the curing agent in a ratio of 10:1;

[0068] b. Put the mixture into a vacuum box;

[0069] c. Dip the PDMS composite sponge body 1 and the two first inductor coils 2 and second inductor coils 3 into the PDMS mixture for about 10 seconds;

[0070] d. Put the PDMS composite sponge body 1 and the two first inductor coils 2 and second inductor coils 3 wrapped with the PDMS mixture into a warm box, and place them in an environment at 80℃ for 3h to form the flexible film 4.

[0071] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting; it is not intended to exclude myriad other embodiments of the present application that other inventors can develop based on the same general inventive concepts embodied by the described embodiments. That is, although the present application is described in terms of particular embodiments and illustrative figures, it should be apparent that the scope of the present application is not limited to these specific embodiments.

[0072] While the embodiments of the application have been shown and described herein, it will be understood by those skilled in the art that many changes, modifications, substitutions and alterations to these embodiments can be made without departing from the principles and spirits of the application, and it is intended that the scope of the application be limited solely by the scope of the appended claims and the equivalents thereof.

Claims

1. A flexible inductive pressure sensor comprising a PDMS composite sponge body (1), a first inductive coil (2), a second inductive coil (3) and a flexible film (4), characterized in that, The first inductance coil (2) is arranged on the upper surface of the PDMS composite sponge body (1), and the second inductance coil (3) is arranged on the lower surface of the PDMS composite sponge body (1); the first inductance coil (2) and the second inductance coil (3) are reversely connected in series and correspondingly connected with the first out connection port (5) and the second out connection port (6); The flexible film (4) covers the PDMS composite sponge body (1), the first inductance coil (2) and the second inductance coil (3), and can fix the first inductance coil (2) and the second inductance coil (3) on the surface of the PDMS composite sponge body (1); The top and bottom of the PDMS composite sponge body (1) are respectively provided with an upper strong magnetic ring (101) and a lower strong magnetic ring (102), the inside of the upper strong magnetic ring (101) and the lower strong magnetic ring (102) is fixedly connected with a plurality of clamping blocks (103), the top of the clamping block (103) is clampingly connected with a protective pad layer (104), and the side of the upper strong magnetic ring (101) and the lower strong magnetic ring (102) is connected with a connection port.

2. A flexible inductive pressure sensor according to claim 1, wherein: The first inductance coil (2) and the second inductance coil (3) are installed in parallel and opposite directions.

3. The flexible inductive pressure sensor of claim 1, wherein: The PDMS composite sponge body (1) is a honeycomb-like porous sponge sheet.

4. The flexible inductive pressure sensor of claim 1, wherein: The first inductance coil (2) and the second inductance coil (3) are installed in parallel and opposite directions, the distance between the two opposite inductance coils is 5 cm, the flexible film (4) covers the PDMS composite sponge body (1), the first inductance coil (2) and the second inductance coil (3), and the thickness of the flexible film (4) is 2 mm.

5. The sensor preparation method of the flexible inductive pressure sensor according to any one of claims 1-4, specifically comprising the following steps: Step 1: preparing a PDMS composite sponge body (1); Step 2: preparing two first inductance coils (2) and the second inductance coil (3); Step 3: placing the first inductance coil (2) and the second inductance coil (3) on the upper and lower surfaces of the PDMS composite sponge body (1) respectively, reversely connecting the two coils in series, and then leading out the connection port; Step 4: preparing a flexible film (4) covering the PDMS composite sponge body (1) and the two first inductance coils (2) and the second inductance coil (3), so as to obtain the required flexible inductive pressure sensor; Further, the preparation process of the PDMS composite sponge body (1) in step 1 is specifically as follows: (a) first, weigh the PDMS prepolymer and the curing agent with a mass ratio of 10:1, then weigh the caster sugar with a mass 4 times that of the mixture and the carbonyl iron powder with a mass equal to that of the curing agent, and mix them uniformly; (b) put the mixture into a vacuum extraction machine for vacuum treatment for 1 h to remove the bubbles in the mixture; (c) pour the uniformly stirred mixture into a mold, and put the mold into a constant temperature oven at 80℃ for heating for 3 h; (d) take out the solidified solid caster sugar from the mold, and put it into deionized water for sugar removal treatment; (e) After about 6h, the icing sugar is dissolved, the PDMS composite sponge containing carbonyl iron powder is obtained by cutting, punching and other operations after being taken out and dried for a period of time; The first inductor coil (2) and the second inductor coil (3) are made by winding a steel core with a diameter of 2mm by using a full-automatic hot air winding machine; Further, the preparation process of the flexible film (4) in step 4 is specifically: a) uniformly mixing PDMS prepolymer and curing agent at a ratio of 10:1; b) placing the mixture into a vacuum box; c) immersing the PDMS composite sponge (1) and the two first inductor coils (2) and the second inductor coil (3) into the PDMS mixture for about 10 seconds; d) placing the PDMS composite sponge (1) and the two first inductor coils (2) and the second inductor coil (3) wrapped with the mixture into a warm box, ensuring that they are placed in an environment at 80℃ for 3h, so as to form the flexible film (4).

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