Ultra-sensitive capacitive sensor based on deformable electrode

Abstract

The invention discloses an ultra-sensitive capacitive sensor based on a deformable electrode. The ultra-sensitive capacitive sensor comprises a lower electrode layer, a dielectric layer and an upper electrode layer which are sequentially stacked from bottom to top, the lower electrode layer comprises a lower flexible substrate and a lower electrode plate which are stacked from bottom to top; the lower electrode plate comprises a cylindrical deformable electrode and a flexible packaging layer for packaging the deformable electrode; the dielectric layer comprises a cuboid and a circular truncated cone; the upper electrode layer comprises an upper electrode plate and an upper flexible substrate which are stacked from bottom to top; the upper electrode plate is led out through a lead; when the sensor is stressed, the distance between the upper electrode plate and the lower electrode plate and the opposite area can be changed at the same time, the variable quantity of the capacitance value when the sensor is stressed is increased, high-sensitivity pull pressure detection is achieved, and the sensor can be applied to the fields of flexible wearable equipment, industrial automation, robot tactile feedback, health monitoring, medical equipment and the like and has wide application prospects. The method is especially suitable for scenes requiring high-sensitivity detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of microelectromechanical systems and mechanical sensors, and particularly relates to a super-sensitive capacitive sensor based on a deformable electrode. Background Art

[0002] With the rapid development of industrial automation, robotics, medical devices, and intelligent wearable devices, the demand for high-precision mechanical sensors is increasing day by day. Researchers have developed many mechanical sensors based on principles such as resistive, piezoelectric, triboelectric, and capacitive. Resistive mechanical sensors are prone to being affected by temperature and it is difficult to achieve a linear response for bidirectional measurement of tensile and compressive forces. Piezoelectric and triboelectric mechanical sensors can only measure dynamic forces and cannot detect static forces.

[0003] Among them, capacitive mechanical sensors have received extensive attention due to their advantages such as simple structure, high sensitivity, and low power consumption. Conventional capacitive mechanical sensors include upper and lower electrode layers and a dielectric layer. Capacitive mechanical sensors detect forces based on the principle of a parallel plate capacitor. The capacitance value of a parallel plate capacitor is affected by three parameters: the overlapping area of the upper and lower electrodes, the dielectric constant, and the distance between the upper and lower electrodes. Most current research is based on the change of a single parameter among the dielectric constant, the distance between the electrodes, or the overlapping area of the electrodes when a capacitive three-dimensional force sensor is stressed. Many researchers have improved the sensitivity of capacitive mechanical sensors by introducing materials with high dielectric constants or introducing microstructures such as pillars and pyramids. However, for capacitive mechanical sensors, it is limited to improve the sensitivity of the sensor only by changing a single parameter such as the material or structure of the dielectric layer, because high sensitivity means that the capacitance value is more likely to reach saturation and the dynamic range is reduced. There is still little research on improving the sensitivity of capacitors by causing changes in multiple parameters when stressed. Summary of the Invention

[0004] To solve the above problems, the present invention proposes a super-sensitive capacitive sensor based on a deformable electrode. The super-sensitive capacitive sensor based on a deformable electrode can change the distance between the upper and lower electrodes of the capacitor and the overlapping area of the upper and lower electrodes simultaneously when the sensor is stressed, and has high sensitivity and a wide dynamic range.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A super-sensitive capacitive sensor based on a deformable electrode, comprising a lower electrode layer, a dielectric layer, and an upper electrode layer stacked in sequence from bottom to top;

[0007] The lower electrode layer includes a lower flexible substrate and a lower electrode plate stacked from bottom to top; the lower electrode plate includes a deformable cylindrical electrode and a flexible encapsulation layer for encapsulating the deformable electrode; the deformable electrode is led out through a wire;

[0008] The dielectric layer includes a cuboid and a frustum of a cone; the upper surface of the frustum of the cone is in contact with the lower surface of the cuboid, and the centers of the frustum of the cone and the cuboid coincide in the normal projection; the lower surface of the frustum of the cone is bonded to the upper surface of the lower electrode plate; the lower surface of the frustum of the cone and the deformable electrode of the lower electrode plate coincide in the normal projection;

[0009] The upper electrode layer includes an upper electrode plate and an upper flexible substrate stacked from bottom to top; the upper electrode plate is led out through a wire; the upper electrode plate and the cuboid of the dielectric layer coincide in the normal projection; the center of the upper electrode plate and the center of the deformable electrode of the lower electrode plate coincide in the normal projection.

[0010] Preferably, the materials of the upper flexible substrate and the lower flexible substrate are both polyimide.

[0011] Preferably, the deformable electrode of the lower electrode plate is made of liquid metal.

[0012] Preferably, the material of the liquid metal is gallium indium tin alloy.

[0013] Preferably, the material of the flexible encapsulation layer is polydimethylsiloxane. When preparing the flexible encapsulation layer, the mass ratio of the polydimethylsiloxane stock solution to the curing agent is 10:1 to 28:1, and the height of the deformable electrode is 1 mm to 10 mm; wherein, the polydimethylsiloxane stock solution is polydimethylsiloxane Sylgard 184A, and the curing agent is polydimethylsiloxane Sylgard 184B.

[0014] Preferably, the cuboid and frustum of the cone structure of the dielectric layer are integrally formed by inverting a mold with a photocurable 3D printing mold; the material of the dielectric layer is polydimethylsiloxane. When preparing the dielectric layer, the mass ratio of the polydimethylsiloxane stock solution to the curing agent is 10:1 to 28:1, and the height of the frustum of the cone is 1 mm to 10 mm; wherein, the polydimethylsiloxane stock solution is polydimethylsiloxane Sylgard 184A, and the curing agent is polydimethylsiloxane Sylgard 184B.

[0015] Preferably, the material of the upper electrode plate is magnetron sputtered copper, and the thickness of the upper electrode plate is 20 nm to 60 nm.

[0016] After adopting the above technical solutions, the present invention has the following beneficial effects:

[0017] 1. The present invention relates to an ultra-sensitive capacitive sensor based on a deformable electrode. The deformable electrode of the lower electrode layer adopts liquid metal (gallium indium tin alloy) and is encapsulated into a rectangular shape by polydimethylsiloxane material. When the cylindrical deformable electrode is subjected to force, it can squeeze the surrounding encapsulation material, change the shape of the electrode, increase the facing area between the upper electrode plate and the deformable electrode, and thus increase the change in capacitance value.

[0018] 2. The present invention is an ultra-sensitive capacitive sensor based on a deformable electrode. The deformable electrode of the lower electrode layer is designed to be cylindrical, which can make the deformable electrode deform evenly when subjected to force, thereby increasing the change in area.

[0019] 3. The present invention relates to an ultra-sensitive capacitive sensor based on a deformable electrode. The dielectric layer is designed as a combination of a cuboid and a frustum. The frustum's lower surface coincides with the deformable electrode of the lower electrode layer in its normal projection. This concentrates stress on the deformable electrode of the lower electrode layer, minimizing force loss during transmission, increasing the deformation of the deformable electrode, and boosting the change in capacitance, thereby enhancing sensor sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the explosion structure of the present invention;

[0021] Figure 2 Schematic diagram of the assembly structure of the upper electrode layer and the dielectric layer of the present invention;

[0022] Figure 3 Schematic diagram of the assembly structure of the flexible packaging layer and the deformable electrode in the lower electrode layer of the present invention;

[0023] Figure 4 Schematic diagram of the assembly structure of the flexible packaging layer and the lower flexible substrate of the present invention;

[0024] Figure 5 It is a schematic diagram of the three-dimensional structure of the present invention;

[0025] Figure 6 It is a top perspective view of the overall package of the present invention.

[0026] The reference numerals in the figures are as follows:

[0027] 1. Upper flexible substrate; 2. Upper electrode plate; 3. Dielectric layer; 4. Flexible packaging layer; 5. Deformable electrode; 6. Lower flexible substrate. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] As shown Figures 1 to 6 in the figure, a super-sensitive capacitive sensor based on a deformable electrode includes a lower electrode layer, a dielectric layer 3, and an upper electrode layer stacked in sequence from bottom to top;

[0030] The lower electrode layer includes a lower flexible substrate 6 and a lower electrode plate stacked from bottom to top; the lower electrode plate includes a cylindrical deformable electrode 5 and a flexible encapsulation layer 4 for encapsulating the deformable electrode 5; the deformable electrode 5 is led out through a wire;

[0031] The dielectric layer 3 includes a cuboid and a frustum of a cone; the upper surface of the frustum of the cone is in contact with the lower surface of the cuboid, and the centers of the frustum of the cone and the cuboid coincide in the normal projection; the lower surface of the frustum of the cone is bonded to the upper surface of the lower electrode plate; the lower surface of the frustum of the cone and the deformable electrode 5 of the lower electrode plate coincide in the normal projection;

[0032] The upper electrode layer includes an upper electrode plate 2 and an upper flexible substrate 1 stacked from bottom to top; the upper electrode plate 2 is led out through a wire; the upper electrode plate 2 and the cuboid of the dielectric layer 3 coincide in the normal projection; the center of the upper electrode plate 2 and the center of the deformable electrode 5 of the lower electrode plate coincide in the normal projection.

[0033] Specifically, the materials of the upper flexible substrate 1 and the lower flexible substrate 6 are both polyimide.

[0034] The deformable electrode 5 of the lower electrode plate is made of liquid metal; the material of the liquid metal is gallium indium tin alloy.

[0035] The material of the flexible encapsulation layer 4 is polydimethylsiloxane. When preparing the flexible encapsulation layer 4, the mass ratio of the polydimethylsiloxane stock solution to the curing agent is 10:1 to 28:1, and the height of the deformable electrode 5 is 1 mm to 10 mm; among them, the polydimethylsiloxane stock solution is polydimethylsiloxane Sylgard 184A, and the curing agent is polydimethylsiloxane Sylgard 184B.

[0036] The cuboid and frustum of the cone structure of the dielectric layer 3 are integrally formed by inverting a mold of a photocuring 3D printing mold; the material of the dielectric layer 3 is polydimethylsiloxane. When preparing the dielectric layer 3, the mass ratio of the polydimethylsiloxane stock solution to the curing agent is 10:1 to 28:1, and the height of the frustum of the cone is 1 mm to 10 mm; among them, the polydimethylsiloxane stock solution is polydimethylsiloxane Sylgard 184A, and the curing agent is polydimethylsiloxane Sylgard 184B.

[0037] The material of the upper electrode plate 2 is magnetron sputtered copper, and the thickness of the upper electrode plate 2 is 20 nm to 60 nm.

[0038] As shown Figure 5 As shown in Figure 5 , the lower surface of the frustum of the dielectric layer 3 and the deformable electrode 5 of the lower electrode plate coincide in the normal projection, which can make the stress concentrate on the deformable electrode 5 when transmitting in the dielectric layer 3, reduce the loss of stress during transmission, increase the deformation of the deformable electrode 5, and improve the sensitivity of the sensor.

[0039] For a capacitive sensor, it usually uses the changes of three parameters, namely the distance between the plates, the dielectric constant and the facing area, to cause the change of the capacitance value, and then measures the force through the change of the capacitance value.

[0040] Among them, the formula for the capacitive sensor to measure pressure is:

[0041]

[0042] Among them, C is the capacitance value, with the unit (F); ε0 is the dielectric constant of vacuum; ε r is the relative dielectric constant of the dielectric layer; S is the facing area of the electrode plates; d is the distance between the electrode plates.

[0043] A super-sensitive capacitive sensor based on a deformable electrode provides a method for measuring tensile and compressive forces, which is as follows:

[0044] Pressure measurement: When the upper flexible substrate 1 is subjected to an external normal pressure, the pressure is transmitted to the flexible encapsulation layer 4 and the deformable electrode 5 through the upper flexible substrate 1, the upper electrode plate 2 and the dielectric layer 3; among them, the dielectric layer 3 is squeezed and deformed, the distance d between the upper electrode plate 2 and the lower electrode plate decreases, the deformable electrode 5 of the lower electrode layer is squeezed and deformed, and the facing area S between the upper electrode plate 2 and the deformable electrode 5 increases, and the capacitance value C of the capacitor increases; compared with the existing capacitive mechanical sensor, when the super-sensitive capacitive sensor based on the deformable electrode of the present invention is stressed, not only the distance d between the upper electrode plate 2 and the lower electrode plate changes, but also the facing area S changes. Under the same magnitude of force, the change amount of the capacitance value C increases under the change of the two parameters, and the sensitivity of the sensor is improved. On the contrary, when the upper flexible substrate 1 is subjected to an external normal tensile force, the distance d between the upper electrode plate 2 and the lower electrode plate increases, the facing area S between the upper electrode plate 2 and the deformable electrode 5 decreases, and the capacitance value C of the capacitor decreases.

[0045] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any change or replacement that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. An ultrasensitive capacitive sensor based on a deformable electrode, characterized in that: It includes a lower electrode layer, a dielectric layer, and an upper electrode layer stacked in sequence from bottom to top; The lower electrode layer includes a lower flexible substrate and a lower electrode plate stacked from bottom to top; the lower electrode plate includes a deformable cylindrical electrode and a flexible encapsulation layer for encapsulating the deformable electrode; the deformable electrode is led out through a wire; The dielectric layer includes a cuboid and a frustum of a cone; the upper surface of the frustum of the cone contacts the lower surface of the cuboid, and the centers of the frustum of the cone and the cuboid coincide in the normal projection; the lower surface of the frustum of the cone is adhered to the upper surface of the lower electrode plate; the lower surface of the frustum of the cone and the deformable electrode of the lower electrode plate coincide in the normal projection; The upper electrode layer includes an upper electrode plate and an upper flexible substrate stacked from bottom to top; the upper electrode plate is led out through a wire; the upper electrode plate and the cuboid of the dielectric layer coincide in the normal projection; the center of the upper electrode plate and the center of the deformable electrode of the lower electrode plate coincide in the normal projection.

2. The ultrasensitive capacitive sensor based on a deformable electrode according to claim 1, wherein: The materials of the upper flexible substrate and the lower flexible substrate are both polyimide.

3. The ultrasensitive capacitive sensor based on a deformable electrode according to claim 1, characterized in that: The deformable electrode of the lower electrode plate is made of liquid metal.

4. The ultrasensitive capacitive sensor based on a deformable electrode according to claim 3, characterized in that: The material of the liquid metal is a gallium-indium-tin alloy.

5. The ultrasensitive capacitive sensor based on a deformable electrode according to claim 1, wherein: The material of the flexible encapsulation layer is polydimethylsiloxane. When preparing the flexible encapsulation layer, the mass ratio of polydimethylsiloxane stock solution to curing agent is 10:1 to 28:1, and the height of the deformable electrode is 1 mm to 10 mm; among them, the polydimethylsiloxane stock solution is polydimethylsiloxane Sylgard 184A, and the curing agent is polydimethylsiloxane Sylgard 184B.

6. The ultrasensitive capacitive sensor based on a deformable electrode according to claim 1, characterized in that: The cuboid and frustum of the cone structure of the dielectric layer are integrally formed by inverting a mold with a photocurable 3D printing mold; the material of the dielectric layer is polydimethylsiloxane. When preparing the dielectric layer, the mass ratio of polydimethylsiloxane stock solution to curing agent is 10:1 to 28:1, and the height of the frustum of the cone is 1 mm to 10 mm; among them, the polydimethylsiloxane stock solution is polydimethylsiloxane Sylgard 184A, and the curing agent is polydimethylsiloxane Sylgard 184B.

7. The ultrasensitive capacitive sensor based on a deformable electrode according to claim 1, wherein: The material of the upper electrode plate is magnetron sputtered copper, and the thickness of the upper electrode plate is 20 nm to 60 nm.

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