A capacitive coupling sensor, preparation method and application thereof

Abstract

The present invention discloses a capacitive coupling sensor, comprising a first electrode layer and a second electrode layer, and a dielectric layer located between the first electrode layer and the second electrode layer, wherein the first electrode layer is a hollow structure, and the structure penetrates from the upper surface of the first electrode to the lower surface of the first electrode. The sensor changes the electric field distribution of the sensor through the electrode shape design, thereby enhancing the non-contact detection capability of the sensor. The sensor can be used for non-contact detection of physiological parameter signals of a biological body, such as respiration or pulse, and has high sensitivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and in particular relates to a capacitive coupling sensor, a preparation method and application thereof. Background Art

[0002] At present, most of the commercially available sensor devices that can monitor the physiological parameters of organisms, such as breathing and pulse, are tightly attached to the surface of the organism, which has many disadvantages: first, the tight fit with the surface of the organism can easily cause a sense of oppression to the organism and affect its activities; second, long-term contact with the surface of the organism can easily irritate the skin and cause discomfort such as itching; in addition, this type of sensor equipment is not suitable for organisms with skin defects or diseases.

[0003] Therefore, non-contact sensing devices for monitoring physiological parameters have been proposed. Such sensing devices do not need to be closely attached to the surface of the organism, but only need to be set within the range of the organism's activities, such as clothes, bracelets, sofas, tables and chairs, etc., to detect the physiological parameter signals of the organism without interfering with the organism's activities. At present, the main methods of non-contact monitoring in the medical field include infrared thermal imaging, Doppler radar detection, ballistocardiography based on fiber optic sensing, magneto-impedance monitoring and capacitive coupling sensing.

[0004] Capacitive coupling sensor is a conversion device that uses capacitors as sensing elements to convert the measured physical or mechanical quantity into changes in capacitance. It has the advantages of simple structure, light weight, and low energy consumption. It is widely used to measure displacement, angle, vibration, speed, pressure, etc.

[0005] According to the electrode settings, capacitive coupling sensors can be divided into self-capacitance sensors and mutual capacitance sensors. Figure 1 As shown in the figure, it consists of a single electrode and is based on the relative capacitance between the test electrode and the ground. When this type of sensor is used to test the physiological parameters of an organism, the organism is equivalent to the ground terminal, which increases the relative capacitance between the electrode and the ground. Figure 2 As shown, it consists of a pair of electrodes and is based on testing the capacitance between the two electrodes. When a biological body approaches, it interferes with and destroys the fringe electric field and captures part of the charge between the two electrodes, thereby reducing the capacitance value between the two electrodes.

[0006] The existing capacitive coupling sensors have weak detection capabilities, especially when the signal to be measured is weak, such as physiological signals such as breathing and pulse of a living organism, the sensitivity is low, the detection effect is poor or even unable to detect the signal to be measured. Compared with self-capacitance sensors, mutual capacitance sensors are less susceptible to environmental common-mode noise and air circulation changes, but their detection capabilities are still weak. Summary of the invention

[0007] In view of the above technical status, the present invention aims to provide a capacitive coupling sensor having high sensitivity for non-contact detection of a signal to be measured.

[0008] In order to achieve the above technical objectives, the present invention has found after a large number of experimental explorations that when a mutual capacitance sensor is used, that is, a capacitive coupling sensor includes a first electrode layer and a second electrode layer, and a dielectric layer located between the first electrode layer and the second electrode layer, if the first electrode layer is designed to be a hollow structure, that is, a hollow portion is provided inside the first electrode extending from the upper surface of the first electrode layer to the lower surface of the first electrode, then compared with the case where the first electrode layer does not have a hollow structure, the electric field distribution of the sensor changes, and the electric field distributed at the edge of the sensor increases. When an external object approaches the sensor, the interference and destruction of the edge electric field increases, thereby increasing the change in the capacitance value between the two electrodes, that is, improving the detection sensitivity of the sensor.

[0009] That is, the technical solution of the present invention is: a capacitive coupling sensor, comprising a first electrode layer and a second electrode layer, and a dielectric layer located between the first electrode layer and the second electrode layer; wherein the first electrode layer is a hollow structure, and the hollow structure extends from the upper surface of the first electrode to the lower surface of the first electrode.

[0010] The cross-sectional shape of the first electrode layer is not limited, including a hollow regular shape, such as a hollow circle, ellipse, rectangle, etc., and a hollow irregular shape, etc.

[0011] The cross-sectional shape of the second electrode is not limited, including regular shapes, such as circular, elliptical, rectangular, etc., and irregular shapes, etc.

[0012] The dielectric layer is located between the first electrode layer and the second electrode layer, and its shape is not limited. As an implementation method, the dielectric layer material fills the space between the first electrode layer and the second electrode layer, and the diameter of the dielectric layer is greater than or equal to the outer diameter of the first electrode layer, and the diameter of the dielectric layer is greater than or equal to the diameter of the second electrode layer.

[0013] The hollow structure is not limited, including a column, a platform, etc. The cross-sectional shape of the hollow structure is not limited, including a regular shape, such as a circle, an ellipse, a rectangle, etc., and an irregular shape, etc.

[0014] In order to further improve the detection sensitivity of the sensor, the cross-sectional area of ​​the hollow structure is preferably greater than or equal to the cross-sectional area of ​​the second electrode.

[0015] In order to further improve the detection sensitivity of the sensor, the vertical projection of the second electrode on the first electrode falls into the cross section of the hollow structure.

[0016] In addition, the inventors have also found that under the same conditions, when the dielectric constant of the dielectric layer decreases, the change in the capacitance value between the two electrodes further increases when an external object approaches the sensor, that is, the detection sensitivity of the sensor is further improved. The reason is that when the dielectric constant of the dielectric layer decreases, the sensor's ability to bind the fringe electric field decreases, and when an external object approaches the sensor, electrons are more likely to escape, thereby further increasing the change in the capacitance value between the two electrodes, that is, further improving the detection sensitivity of the sensor.

[0017] Preferably, the dielectric layer is composed of an insulating material with a porous structure, which is conducive to reducing the dielectric constant of the insulating material. As an implementation method, the insulating material with a porous structure is prepared by: one or more insulating materials are uniformly mixed in different proportions, water is added, and then high-temperature curing is performed, and the porous structure is formed after the water evaporates.

[0018] Considering the wearability of the sensor, it is preferred that the capacitive coupling sensor is flexible, that is, the first electrode, the second electrode and the dielectric layer are made of flexible materials, so that it can be well attached to an object. The flexible material refers to a material that can be deformed, such as stretched, bent, etc.

[0019] The material of the flexible dielectric layer includes, but is not limited to, one or more of polydimethylsiloxane (PDMS), rubber, resin, hydrogel, polyurethane, styrene block copolymer (SEBS), polyethylene octene co-elastomer, and thermoplastic elastomer.

[0020] The flexible first electrode layer includes a flexible insulating material and a conductive material. The flexible insulating material includes, but is not limited to, one or more of polydimethylsiloxane (PDMS), rubber, resin, hydrogel, polyurethane, styrene block copolymer (SEBS), polyethylene octene co-elastomer, and thermoplastic elastomer. The conductive material includes, but is not limited to, one or more of graphene, carbon powder, carbon black, carbon nanotubes, silver powder, silver nanowires, copper nanotubes, and liquid metal.

[0021] The flexible second electrode layer includes a flexible insulating material and a conductive material. The flexible insulating material includes, but is not limited to, one or more of polydimethylsiloxane (PDMS), rubber, resin, hydrogel, polyurethane, styrene block copolymer (SEBS), polyethylene octene co-elastomer, and thermoplastic elastomer. The conductive material includes, but is not limited to, one or more of graphene, carbon powder, carbon black, carbon nanotubes, silver powder, silver nanowires, copper nanotubes, and liquid metal.

[0022] The liquid metal includes mercury-based alloys, gallium-based alloys, gallium-based alloys such as gallium-indium alloys, gallium-indium-tin alloys, and gallium-based alloys doped with one or more transition metals and solid non-metallic elements.

[0023] The present invention also provides a method for preparing the capacitive coupling sensor, comprising the following steps:

[0024] A first insulating material layer is prepared on the surface of the first electrode; a second insulating material layer is prepared on the surface of the second electrode; the first insulating material layer and the second insulating material layer are bonded together so that the first insulating material layer and the second insulating material layer are located between the first electrode and the second electrode.

[0025] The preparation method of the first electrode is not limited, including printing, etc. As an implementation method, a mask printing method is adopted, that is, a prepared mask plate is attached to a substrate, the filler for preparing the first electrode is evenly applied on the substrate, and then the mask plate is removed, and the first electrode is obtained after heating and curing.

[0026] The preparation method of the second electrode is not limited, including printing, etc.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention designs the electrode shape of the capacitive coupling sensor so that one of the electrodes has a hollow structure, thereby changing the electric field distribution of the sensor and increasing the electric field at the edge of the sensor. When an external object approaches the sensor, the interference and destructive force on the edge electric field are enhanced, thereby enhancing the non-contact detection capability of the capacitive sensor.

[0029] (2) The present invention preferably uses a dielectric layer with a smaller dielectric constant, or preferably reduces the dielectric constant of the dielectric layer through structural design, such as setting a porous structure in the dielectric layer, so that the sensor's ability to bind the edge electric field is reduced. When an external object approaches the sensor and the edge electric field is disturbed and destroyed, electrons are more likely to escape, thereby further enhancing the non-contact detection capability of the capacitive sensor.

[0030] (3) The sensor of the present invention has a simple structure, is easy to manufacture, and is low in cost. It is a non-contact sensor that does not need to be tightly attached to the surface of the object to be measured. It only needs to be set around the object to be measured and can detect the signal to be measured at a long distance in a non-contact manner, thus overcoming the discomfort and inconvenience caused by traditional wearable monitoring technology.

[0031] (4) The sensor of the present invention has high sensitivity and can detect weak signals. For example, it can be used to detect physiological parameter signals of an organism, such as breathing or pulse. The surface of the organism will undergo slight deformation with the rhythm of breathing or pulse beating, causing slight changes in the distance between the body surface and the sensor. The degree of damage to the edge electric field of the sensor varies, causing the capacitance of the sensor to change. The breathing or pulse parameters of the organism can be detected by detecting the change in the capacitance change rate (ΔC / C) over time. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural diagram of a self-capacitance sensor.

[0033] Figure 2 It is a structural schematic diagram of a mutual capacitance sensor.

[0034] Figure 3 Schematic diagram of the structure of the capacitive coupling sensor in Example 1 of the present invention.

[0035] Figure 4 is a schematic cross-sectional view of the first electrode of the capacitive coupling sensor in Example 1 of the present invention.

[0036] Figure 5 4 is a schematic cross-sectional view of the second electrode of the capacitive coupling sensor in Example 1 of the present invention.

[0037] Figure 6 This is a graph showing the change in capacitance over time detected by the capacitive coupling sensor placed on the user's clothes in Example 1 of the present invention.

[0038] Figure 7 It is a projected electric field diagram of the capacitive coupling sensor when a user approaches the capacitive coupling sensor in Examples 1, 2, and 3.

[0039] Figure 8 3 is a graph showing the change rate of capacitance of the capacitive coupling sensor as a function of distance when a user approaches the capacitive coupling sensor in Embodiments 1, 2, and 3.

[0040] Fig. 9 It is a graph of the capacitance change rate of the capacitive coupling sensors of Examples 1, 4, 5, 6, and 7 when the user approaches the sensor from a position 200 mm away to a position 0 mm away from the sensor. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with the embodiments and drawings. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on the present invention.

[0042] Figure 1 The reference numerals in the figures are: 1-first electrode, 2-second electrode, 3-medium layer.

[0043] Embodiment 1:

[0044] The structure of the capacitive coupling sensor is as follows Figure 3 As shown, it includes a first electrode layer 1, a second electrode layer 2, and a dielectric layer 3 located between the first electrode layer and the second electrode layer.

[0045] The first electrode layer 1 is a hollow structure, which is a cylinder and extends from the upper surface of the first electrode to the lower surface of the first electrode. Figure 4 As shown, the cross section of the first electrode layer is annular, with an inner diameter of 2.5 cm and an outer diameter of 3 cm. The second electrode layer 2 is cylindrical, as shown in FIG. Figure 5 As shown, its cross section is circular with a radius of 2 cm.

[0046] The dielectric layer 3 fills the space between the first electrode layer and the second electrode layer, and its outer diameter is greater than or equal to the outer diameter of the first electrode. The dielectric layer 3 is an insulating elastic material PDMS with a porous structure, which is formed by mixing PDMS and water evenly and then curing at high temperature. The dielectric constant εr of the dielectric layer is 2.0.

[0047] The first electrode layer 1 is formed by curing a first elastic conductor. The first elastic conductor is formed by curing an elastic material PDMS and a liquid metal after being uniformly mixed. The liquid metal is a gallium indium tin alloy, and its mass ratio is gallium:indium:tin=62.5:21.5:16. It is liquid at room temperature and has conductivity.

[0048] The second electrode layer 2 is formed by solidifying the second elastic conductor. The second elastic conductor is formed by uniformly mixing the elastic material PDMS and the liquid metal and then solidifying. The liquid metal is a gallium indium tin alloy, and its mass ratio is gallium:indium:tin=62.5:21.5:16. It is liquid at room temperature and has conductivity.

[0049] The preparation of the capacitive coupling sensor includes the following steps:

[0050] (1) Using a laser engraving machine to engrave a circular mask and a circular mask on a 0.14 mm thick PET film;

[0051] (2) Mixing liquid metal and PDMS at a mass ratio of 15:1 and stirring evenly;

[0052] (3) Place a donut-shaped mask on a smooth glass, with the exposed portion of the glass in the shape of a donut with an inner diameter of 2.5 cm and an outer diameter of 3 cm, and a circle with a radius of 2 cm. Evenly brush the mixture of liquid metal and PDMS prepared in step (2) on the glass, then remove the mask, place the glass in a drying oven at 60°C-80°C and dry for 3h-4h to solidify the mixture, take out the sample after cooling, and obtain the first electrode and the second electrode.

[0053] (4) PDMS and water were mixed uniformly at a mass ratio of 6:4 to obtain a mixture A;

[0054] The mixture A was cast on the surface of the first electrode to a thickness of 1.5 mm, and then placed in a drying oven at 70° C. for 0.5 h, and taken out after cooling to obtain a PDMS layer with a porous structure solidified on the surface of the first electrode;

[0055] The mixture A was cast on the surface of the second electrode to a thickness of 1.5 mm, and then placed in a drying oven at 120° C. for 2 h, and taken out after cooling to obtain a PDMS layer with a porous structure solidified on the surface of the second electrode;

[0056] (5) The PDMS layer with a porous structure cured on the surface of the first electrode obtained in step (4) is connected to the PDMS layer with a porous structure cured on the surface of the second electrode, so that the PDMS layer is located between the first electrode and the second electrode. PDMS is applied to the connecting surface, and then placed in a drying oven at 60°C-80°C for 0.5h to ensure firm adhesion.

[0057] The capacitive coupling sensor prepared as above can be used to detect physiological signals of the human body, such as breathing or pulse. When in use, the capacitive coupling sensor is placed in the activity range of the user to be tested, for example, attached to the clothes of the user to be tested, attached to the seat of the user to be tested, etc. The sensor is turned on, and as the user to be tested breathes or beats, the distance between the body surface of the user to be tested and the sensor changes slightly, and the degree of damage to the edge electric field of the sensor varies, causing the capacitance of the sensor to change. Figure 4 The graph showing the change of capacitance change rate over time can be used to detect the breathing or pulse parameters of the user to be tested.

[0058] Embodiment 2:

[0059] In this embodiment, the structure of the capacitive coupling sensor is basically the same as that of the capacitive coupling sensor in Embodiment 1, except that the dielectric layer is made of insulating elastic material PDMS, which is formed by high-temperature curing of PDMS. That is, compared with Embodiment 1, the dielectric layer does not have a porous structure, and the dielectric constant εr of the dielectric layer is 3.0.

[0060] Embodiment 3:

[0061] In this embodiment, the structure of the capacitive coupling sensor is substantially the same as that of the capacitive coupling sensor in Embodiment 2, except that the first electrode is cylindrical, and its cross section is circular with a radius of 3 cm. That is, the first electrode layer is not provided with a hollow structure.

[0062] The capacitive coupling sensors in the above-mentioned embodiments 2 and 3 can be used to detect physiological signals of the human body, such as breathing or pulse. When in use, the capacitive coupling sensor is placed in the activity range of the user to be tested, for example, attached to the clothes of the user to be tested, attached to the seat of the user to be tested, etc. The sensor is turned on, and as the user to be tested breathes or the pulse beats, the distance between the body surface of the user to be tested and the sensor changes slightly, and the degree of damage to the edge electric field of the sensor is different, causing the capacitance of the sensor to change. Similar to embodiment 1, the breathing or pulse parameters of the user to be tested can be detected by detecting the change in the capacitance change rate over time.

[0063] Figure 7 is the projected electric field diagram of the capacitive coupling sensor when the user approaches the capacitive coupling sensor in embodiments 1, 2, and 3. Figure 7 It can be seen that when the user approaches the sensor, the fringe electric field of the sensors in Example 1 and Example 2 changes more significantly than that of the sensor in Example 3. Comparing the fringe electric fields of the sensors in Example 1 and Example 2, the electric field lines in Example 1 are closer.

[0064] Figure 8 1 is a graph showing the change rate of the capacitance of the capacitive coupling sensor as a function of the distance between the user and the sensor when the user approaches the capacitive coupling sensor in Embodiments 1, 2, and 3. Figure 8 It can be seen that the capacitance of the sensors of Examples 1, 2, and 3 are reduced by 33.17%, 15.34%, and 6.55%, respectively.

[0065] Embodiment 4,5,6,7:

[0066] In this embodiment, the structure of the capacitive coupling sensor is substantially the same as that of the capacitive coupling sensor in Embodiment 1, except that the radii of the second electrodes are 3 cm, 2 cm, 1.5 cm and 1 cm respectively.

[0067] The capacitive coupling sensors in the above-mentioned embodiments 4, 5, 6, and 7 can be used to detect physiological signals of the human body, such as breathing or pulse. When in use, the capacitive coupling sensor is placed in the activity range of the user to be tested, for example, attached to the clothes of the user to be tested, attached to the seat of the user to be tested, etc. The sensor is turned on, and as the user to be tested breathes or the pulse beats, the distance between the body surface of the user to be tested and the sensor changes slightly, and the degree of damage to the edge electric field of the sensor is different, causing the capacitance of the sensor to change. Similar to embodiment 1, the breathing or pulse parameters of the user to be tested can be detected by detecting the change in the capacitance change rate over time.

[0068] When the user approaches the sensor in Examples 1, 4, 5, 6, and 7 from 200 mm to 0 mm away from the sensor, the capacitance change rate of each sensor is tested. The test results are as follows: Fig. 9 As shown, it is shown that as the size difference between the first electrode and the second electrode increases, the capacitance change rate increases, and when the size difference is greater than 5 mm, the change rate tends to be smooth.

[0069] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A capacitive coupling sensor, comprising a first electrode layer and a second electrode layer, and a dielectric layer located between the first electrode layer and the second electrode layer; wherein: The first electrode layer is a hollow structure, and the hollow structure extends from the upper surface of the first electrode to the lower surface of the first electrode; The dielectric layer material fills the space between the first electrode layer and the second electrode layer, and the diameter of the dielectric layer is greater than or equal to the outer diameter of the first electrode layer, and the diameter of the dielectric layer is greater than or equal to the diameter of the second electrode layer.

2. The capacitive coupling sensor according to claim 1, characterized in that: The hollow structure includes a columnar shape and a table shape.

3. The capacitive coupling sensor according to claim 1, characterized in that: The cross-sectional shape of the hollow structure includes circular, elliptical and rectangular.

4. The capacitive coupling sensor according to claim 1, wherein: The cross-sectional area of ​​the hollow structure is greater than or equal to the cross-sectional area of ​​the second electrode.

5. The capacitive coupling sensor according to claim 1, wherein: The vertical projection of the second electrode on the first electrode falls into the cross section of the hollow structure.

6. The capacitive coupling sensor according to claim 1, characterized in that: The cross-sectional shape of the first electrode layer includes a hollow circle, an ellipse, or a rectangle.

7. The capacitive coupling sensor according to claim 1, characterized in that: The cross-sectional shape of the second electrode includes circular, elliptical, and rectangular.

8. The capacitive coupling sensor according to claim 1, characterized in that: The dielectric layer is made of an insulating material with a porous structure.

9. The capacitive coupling sensor according to claim 8, characterized in that: The preparation method of the insulating material with a porous structure is: one or more insulating materials are uniformly mixed in different proportions, water is added, and then high-temperature curing is performed, and the porous structure is formed after the water evaporates.

10. The capacitive coupling sensor according to claim 1, characterized in that: The capacitive coupling sensor is flexible.

11. The capacitive coupling sensor according to claim 10, characterized in that: The dielectric layer material includes one or more of polydimethylsiloxane (PDMS), rubber, resin, hydrogel, polyurethane, styrene block copolymer (SEBS), polyethylene octene co-elastomer, and thermoplastic elastomer.

12. The capacitive coupling sensor according to claim 10, characterized in that: The first electrode layer includes a flexible insulating material and a conductive material.

13. The capacitive coupling sensor according to claim 10, characterized in that: The second electrode layer includes a flexible insulating material and a conductive material.

14. The capacitive coupling sensor according to claim 12, characterized in that: The flexible insulating material includes one or more of polydimethylsiloxane (PDMS), rubber, resin, hydrogel, polyurethane, styrene block copolymer (SEBS), polyethylene octene co-elastomer, and thermoplastic elastomer.

15. The capacitive coupling sensor according to claim 13, characterized in that: The flexible insulating material includes one or more of polydimethylsiloxane (PDMS), rubber, resin, hydrogel, polyurethane, styrene block copolymer (SEBS), polyethylene octene co-elastomer, and thermoplastic elastomer.

16. The capacitive coupling sensor according to claim 12, characterized in that: The conductive material includes one or more of graphene, carbon powder, carbon black, carbon nanotubes, silver powder, silver nanowires, copper nanotubes, and liquid metal.

17. The capacitive coupling sensor according to claim 13, characterized in that: The conductive material includes one or more of graphene, carbon powder, carbon black, carbon nanotubes, silver powder, silver nanowires, copper nanotubes, and liquid metal.

18. The method for preparing a capacitive coupling sensor according to any one of claims 1 to 17, characterized in that: The steps include: Preparing a first insulating material layer on the surface of the first electrode; A second insulating material layer is prepared on the surface of the second electrode; the first insulating material layer and the second insulating material layer are bonded together so that the first insulating material layer and the second insulating material layer are located between the first electrode and the second electrode.

19. The capacitive coupling sensor according to any one of claims 1 to 17 is used for non-contact detection of physiological signals of a living body.

20. The capacitive coupling sensor according to claim 19 is used for non-contact detection of physiological signals of a living body, wherein: The physiological signal includes breathing or pulse.

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