A kind of interdigital capacitor, bending sensor and manufacturing method thereof

Abstract

The present invention belongs to the field of sensor technology, and provides a finger capacitor, a bending sensor and a manufacturing method thereof, which mainly includes an electrode layer, wherein the electrode layer includes a first electrode and a second electrode; the first electrode includes a plurality of first finger portions spaced apart from each other, and a first installation cavity is reserved between two adjacent first finger portions; the second electrode includes a plurality of second finger portions spaced apart from each other, and a second installation cavity is reserved between two adjacent second finger portions; the first finger portion is inserted into the second installation cavity, and the second finger portion is inserted into the first installation cavity to form a complementary arrangement and form the electrode layer, and an installation gap is reserved between the first electrode and the second electrode, and the cross section of the electrode layer is wavy. The present invention mainly provides a wearable sensor that is flexible, stretchable and has good stability under long-term use.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and in particular relates to an interdigital capacitor, a bending sensor and a manufacturing method thereof. Background Art

[0002] Existing bending sensors mainly include two categories. One is the bending sensor based on optical fiber. This type of sensor measures bending by measuring the light density, phase, wavelength or polarization inside the bent optical fiber. The structure of the bending sensor based on optical fiber includes an LED that emits a light source, a flexible shell, an internal optical fiber, and a receiver that detects the properties of light. The other type is a flexible bending sensor based on resistance or capacitance changes. When bent, this type of sensor deforms, causing resistance or capacitance changes, thereby obtaining bending information.

[0003] For capacitive sensors, superelastic materials with added nanofillers are usually used as electrodes. By adjusting the dielectric structure between the two electrodes, a structure in which the distance between the electrodes is easily changed is obtained, so that bending information can be obtained when external deformation is received. For resistive sensors, the combination of nanofillers and superelastic materials acts as a variable resistor. When deformed, the contact area between the nanofillers changes, and the resistance changes, thereby obtaining bending information. For optical fiber-based bending sensors, due to their complex structure, the light source part and the light receiving part are non-stretchable devices, so they are not suitable for wearable sensor applications, and their application scope is greatly limited.

[0004] For flexible bending sensors that combine nanofillers with hyperelastic materials, there are interface problems between the nanofillers and the hyperelastic materials. During the deformation process, the movement of the nanofillers in the hyperelastic material will cause microcracks, which will affect the stability of the sensor after long-term deformation and recovery. Therefore, the long-term stability of bending sensors based on nanofillers and hyperelastic materials is a serious problem. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the object of the present invention is to provide an interdigital capacitor, a bending sensor and a method for manufacturing the same, so as to provide a wearable sensor that is flexible, stretchable and has good stability under long-term use.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] An interdigital capacitor comprises an electrode layer, wherein the electrode layer comprises a first electrode and a second electrode;

[0008] The first electrode comprises a plurality of first interdigital portions spaced apart from each other, and a first installation cavity is reserved between two adjacent first interdigital portions; the second electrode comprises a plurality of second interdigital portions spaced apart from each other, and a second installation cavity is reserved between two adjacent second interdigital portions;

[0009] The first interdigitated finger is inserted into the second mounting cavity, and the second interdigitated finger is inserted into the first mounting cavity to form a complementary arrangement and form the electrode layer. An installation gap is reserved between the first electrode and the second electrode, and the cross-section of the electrode layer is wavy.

[0010] Preferably, the cross-sections of the first electrode and the second electrode are wavy, and the wavy cross-sections of the first electrode and the second electrode overlap after being complementarily arranged.

[0011] Preferably, plastic film layers are provided on both side surfaces of the electrode layer.

[0012] Preferably, the plastic film layer is made of Parylene C.

[0013] Preferably, a superelastic material layer is further provided on the outer sides of both side surfaces of the electrode layer.

[0014] Preferably, the superelastic material layer is made of PDMS.

[0015] A bending sensor comprises a neutral connection layer, wherein the neutral connection layer comprises a group of first mounting surfaces arranged relatively in parallel, and the above-mentioned interdigital capacitors are respectively arranged on the first mounting surfaces.

[0016] Preferably, the neutral connection layer further comprises a group of second mounting surfaces arranged relatively parallel to each other, and a vertical line between the second mounting surfaces intersects a vertical line between the first mounting surfaces at an angle;

[0017] The interdigital capacitors are respectively arranged on the second mounting surfaces.

[0018] A method for preparing an interdigital capacitor, applicable to the interdigital capacitor described above, comprises the following steps:

[0019] S10. wet-oxidizing a single silicon wafer to form a silicon dioxide layer, after first spin-coating a photoresist on the silicon dioxide layer, etching the silicon dioxide layer with an anisotropic oxide to form a wave structure model, and then spraying a photoresist a second time to form a sacrificial layer on the surface of the wave structure model;

[0020] S20. vapor-depositing a plastic film layer on the surface of the wave structure model for the first time to form a flexible substrate, spraying a photoresist on the formed flexible substrate for the third time, patterning the photoresist layer formed after the third spraying, and sputtering an electrode layer after the patterning to obtain the first electrode and the second electrode on the surface of the wave structure model, and then vapor-depositing the plastic film layer on the surface of the formed electrode layer for the second time;

[0021] S30. Activating the surface of the plastic film layer deposited for the second time to be a hydrophilic surface, and then filling the activated surface with a superelastic material for the first time to form a superelastic material layer;

[0022] S40. Separating the structural layer from the wave structure model at the sacrificial layer, activating the surface of the plastic film layer deposited for the first time to be a hydrophilic surface, and then filling the activated surface with a superelastic material for a second time to form a superelastic material layer;

[0023] S50. Cut the device processed in step S40 to obtain interdigital capacitors, and spin-coat a protective layer on the cut interdigital capacitors.

[0024] A method for manufacturing a bending sensor comprises the following steps:

[0025] A neutral connection layer is provided, and the interdigital capacitors prepared above are bonded and arranged in pairs on opposite surfaces of the central connection layer.

[0026] Compared with the prior art, the beneficial effects of the present invention include:

[0027] 1. In this scheme, a bending sensor based on a wave structure electrode is designed, in which the wave structure electrode is used as the electrode of the interdigital capacitor. When stretched, the angle between the interdigital electrodes will change, resulting in changes in the facing area and distance between the positive and negative electrodes, thereby causing a change in capacitance. When the two interdigital capacitors on both sides of the neutral connection layer change, it indicates that bending has occurred, and the difference in the capacitance change can be used to quantitatively describe the size of the bending.

[0028] 2. In this scheme, a plastic film layer and a superelastic material layer are provided at the corresponding electrode layer. The electrode layer is provided between the two plastic film layers, which can effectively protect the first electrode and the second electrode from being damaged during the stretching process; and the electrode layer provided with the plastic film layer is provided between the two superelastic material layers, so that the superelastic material layer is used as the outer packaging layer, and the mixture of the nanofiller and the superelastic material is replaced by a stretchable wave structure electrode, thereby avoiding the problems of the inability to stretch and bend and the reduced stability in use in traditional technologies, and at the same time realizing the production of flexible and stretchable wearable sensors.

[0029] 3. In terms of preparation plan, the wave structure model is obtained by using silicon wafer-based micromachining technology, and three-dimensional interdigital capacitors are graphically formed, realizing the mass production process of bending sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0031] Figure 1 It is a schematic diagram of the structure of the interdigital capacitor of the present invention.

[0032] Figure 2 It is a schematic structural diagram of one example of the bending sensor of the present invention.

[0033] Figure 3 FIG. 4 is a schematic structural diagram of another example of a bending sensor according to the present invention.

[0034] Figure 4 The figure is a schematic diagram of the preparation process of the interdigital capacitor of the present invention.

[0035] in:

[0036] 1- interdigital capacitor, 11- electrode layer, 111- first electrode, 1111- first interdigital portion, 112- second electrode, 1121- second interdigital portion, 113- mounting gap, 12- plastic film layer, 13- superelastic material layer;

[0037] 2-bending sensor, 21-neutral connection layer;

[0038] 3-silicon wafer, 31-silicon dioxide layer, 32-photoresist. DETAILED DESCRIPTION

[0039] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other. In the following description, many specific details are set forth in order to fully understand the present invention, and the embodiments described are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the art without making creative work are within the scope of protection of the present invention.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0041] Example 1

[0042] like Figure 1-4 As shown, in this embodiment, an interdigital capacitor 1 is provided, which mainly includes an electrode layer 11 , a plastic film layer 12 and a superelastic material layer 13 .

[0043] Specifically, the electrode layer 11 includes a first electrode 111 and a second electrode 112. The first electrode 111 includes a plurality of first interdigital fingers 1111 spaced apart from each other, and a first installation cavity is reserved between two adjacent first interdigital fingers 1111; the second electrode 112 includes a plurality of second interdigital fingers 1121 spaced apart from each other, and a second installation cavity is reserved between two adjacent second interdigital fingers 1121; the first interdigital fingers 1111 are inserted into the second installation cavity, and the second interdigital fingers 1121 are inserted into the first installation cavity to form a complementary arrangement and the electrode layer 11 is formed. In this embodiment, an installation gap 113 is reserved between the first electrode 111 and the second electrode 112 so that the first electrode 111 and the second electrode 112 are not in contact with each other, and the cross section of the electrode layer 11 is arranged to be wavy.

[0044] As a preferred solution, the cross-sections of the first electrode 111 and the second electrode 112 in this embodiment are also arranged in a wavy shape, and after the first electrode 111 and the second electrode 112 are arranged in a complementary manner to form the electrode layer 11, the wavy shapes of their cross-sections are arranged to overlap each other.

[0045] The plastic film layer 12 is disposed on both sides of the electrode layer 11 formed by the first electrode 111 and the second electrode 112. As a preferred solution, the plastic film layer 12 in this embodiment is made of Parylene C. When the interdigital capacitor 1 is deformed, the first electrode 111 and the second electrode 112 can be protected to only undergo the straightening process of the wave structure without experiencing the breaking of the electrode itself, thereby ensuring the stability of the electrical performance of the bending sensor 2 during deformation.

[0046] In addition, a superelastic material layer 13 is also provided on both sides of the electrode layer 11 provided with the plastic film layer 12. As a preferred solution, the superelastic material layer 13 in this embodiment is made of PDMS. The superelastic material layer 13 also serves as a packaging layer to encapsulate the interdigital capacitor 1 with a wave structure, giving the device the ability to stretch and recover, while eliminating the exposure of the electrode layer 11 and the plastic film layer 12 to the air, ensuring the stability of the device in long-term operation.

[0047] On this basis, the present embodiment also provides a bending sensor 2, including a neutral connection layer 21. In the present embodiment, the neutral connection layer 21 is made of PDMS material and is semi-cured. In one application example, a group of relatively parallel first mounting surfaces are arranged on the neutral connection layer 21, and the above-mentioned interdigital capacitors 1 are respectively arranged on the first mounting surfaces, thereby forming a bending sensor 2 in one dimension.

[0048] In another application example, the neutral connection layer 21 is set to a rectangular body, so that the neutral connection layer 21 also includes a group of second mounting surfaces arranged relatively parallel, and the vertical lines between the second mounting surfaces intersect the vertical lines between the first mounting surfaces at right angles; and the interdigital capacitors 1 are respectively arranged on the second mounting surfaces to form a bending sensor 2 in another dimension.

[0049] By using the interdigital capacitor 1 of this solution in conjunction with the neutral connection layer 21, a wearable and stretchable bending sensor 2 is formed, which has an objective application prospect in the field of dynamic motion detection, including human-computer interaction, robot electronic skin and other fields. For example, when a glove with this bending sensor 2 is worn on the hand and a gesture is made, the bending sensor 2 can accurately obtain the gesture and send this information to the robot, thereby controlling the robot's behavior. For example, by placing this bending sensor 2 on the joint surface of the robot, feedback of the bending of the robot joint can be obtained, and the robot electronic skin can be realized.

[0050] In order to facilitate further understanding of the present solution, the present embodiment also provides a method for preparing an interdigital capacitor, which is applicable to the interdigital capacitor 1 described above and mainly includes the following steps:

[0051] S10. The first stage: preparing a wave structure model. A single polished silicon wafer 3 is subjected to wet oxidation treatment to form a silicon dioxide layer 31. After the silicon dioxide layer 31 is first spin-coated with a photoresist, the photoresist is FH6400L photoresist; the silicon dioxide layer 31 is etched by anisotropic oxide and TMAH wet method to form an isosceles triangle-shaped wave structure, and then wetted with a tetramethylammonium hydroxide solution to remove the corner structure of the isosceles triangle; then, a photoresist 32 is sprayed on the surface of the wave structure for the second time, and the photoresist 32 can be AZ 9260 photoresist; then, the wave structure model with smooth corners is formed by reflowing on a hot plate at 100-150°C for 3-5 minutes. At the same time, the second sprayed photoresist 32 is also used as a sacrificial layer to help peel the manufactured device from the wave structure model in the subsequent process.

[0052] S20. The second stage: preparation of a three-dimensional interdigital electrode device. A plastic film layer 12 is first evaporated on the surface of the wave structure model to form a flexible substrate, and the plastic film layer 12 is made of Parylene C; a third spraying of photoresist is performed on the formed flexible substrate, and the photoresist here can be AZ 9260 photoresist; then the photoresist layer formed after the third spraying is patterned, and after the patterning, a layer of TiW / Pt electrode layer 11 is sputtered using ARC-12M Sputterer, and then soaked in acetone and ultrasonic waves for 3-5 minutes to obtain a three-dimensional interdigital electrode device, including the first electrode 111 and the second electrode 112, wherein the interdigital electrodes are distributed on the upper end surface of the wave structure model. At this time, the crest of each wave structure needs to be strictly symmetrically designed to avoid reflection problems during the photolithography process. Then another Parylene C is evaporated onto the interdigital electrode device to protect the electrode device from tensile damage together with the first layer of Parylene C.

[0053] S30. The third stage: single-sided encapsulation of the interdigitated electrode device. The second evaporated Parylene C layer is thinned to the designed thickness using oxygen plasma, and the surface of the Parylene C layer is activated to a hydrophilic surface, preparing for the subsequent PDMS coating process. Then, the PDMS solution is poured on the surface, and vacuum is drawn to ensure complete filling of the PDMS, so as to form a single-sided superelastic material layer 13.

[0054] S40. The fourth stage: double-sided packaging of the interdigital electrode device. After curing in a 70-100°C oven for 1-2 hours, the entire device is immersed in acetone, and the sacrificial layer on the device is scratched with a scalpel to dissolve it in acetone, so as to separate the structural layer with the interdigital electrode device from the wave structure model, thereby separating the stretchable interdigital electrode device on the rigid silicon wafer 3. Then, the PDMS coating is spin-coated on the back of the separated interdigital electrode device using the same process as above to form a double-sided superelastic material layer 13.

[0055] S50. The fifth stage: sealing of the interdigital capacitor. The device processed in step S40 is laser cut to obtain the interdigital capacitor 1, and a protective layer is spin-coated on the cut interdigital capacitor 1; the protective layer is also made of PDMS material to achieve the encapsulation of the cut interdigital capacitor 1 and prevent the interdigital capacitor 1 from being delaminated.

[0056] At the same time, the present invention also provides a method for manufacturing a bending sensor, which mainly includes the following steps:

[0057] A neutral connection layer 21 made of semi-cured PDMS is provided, and the interdigital capacitors 1 prepared above are bonded in pairs on opposite surfaces of the central connection layer 21 , thereby completing the preparation of the bending sensor 2 .

[0058] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Therefore, any modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. An interdigital capacitor, characterized in that: comprising an electrode layer, wherein the electrode layer comprises a first electrode and a second electrode; The first electrode comprises a plurality of first interdigital portions spaced apart from each other, and a first installation cavity is reserved between two adjacent first interdigital portions; the second electrode comprises a plurality of second interdigital portions spaced apart from each other, and a second installation cavity is reserved between two adjacent second interdigital portions; The first interdigital finger portion is inserted into the second mounting cavity, and the second interdigital finger portion is inserted into the first mounting cavity to form a complementary arrangement and to form the electrode layer, and an installation gap is reserved between the first electrode and the second electrode, and the cross-section of the electrode layer is wavy; the cross-sections of the first electrode and the second electrode are wavy, and the wavy cross-sections of the first electrode and the second electrode after the complementary arrangement overlap; A plastic film layer is arranged on both sides of the electrode layer; and a superelastic material layer is also arranged on the outer sides of both sides of the electrode layer; A protective layer is spin-coated on the interdigital capacitor, and the protective layer is made of PDMS.

2. An interdigital capacitor according to claim 1, characterized in that: The plastic film layer is made of Parylene C.

3. The interdigital capacitor according to claim 1, characterized in that: The superelastic material layer is made of PDMS.

4. A bending sensor, characterized in that: It comprises a neutral connection layer, wherein the neutral connection layer comprises a group of first mounting surfaces arranged in parallel with each other, and each of the first mounting surfaces is provided with an interdigital capacitor as described in any one of claims 1 to 3.

5. A bending sensor according to claim 4, characterized in that: The neutral connection layer further comprises a set of second mounting surfaces arranged relatively parallel to each other, wherein a perpendicular line between the second mounting surfaces intersects a perpendicular line between the first mounting surfaces at an angle; The interdigital capacitors are respectively arranged on the second mounting surfaces.

6. A method for preparing an interdigital capacitor, applicable to an interdigital capacitor as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: S10. wet-oxidizing a single silicon wafer to form a silicon dioxide layer, after first spin-coating a photoresist on the silicon dioxide layer, etching the silicon dioxide layer to form a wave structure model, and then spraying a photoresist a second time to form a sacrificial layer on the surface of the wave structure model; S20. vapor-depositing a plastic film layer on the surface of the wave structure model for the first time to form a flexible substrate, spraying a photoresist on the formed flexible substrate for the third time, patterning the photoresist layer formed after the third spraying, and sputtering an electrode layer after the patterning to obtain the first electrode and the second electrode on the surface of the wave structure model, and then vapor-depositing the plastic film layer on the surface of the formed electrode layer for the second time; S30. Activating the surface of the plastic film layer deposited for the second time to be a hydrophilic surface, and then filling the activated surface with a superelastic material for the first time to form a superelastic material layer; S40. Separating the structural layer from the wave structure model at the sacrificial layer, activating the surface of the plastic film layer deposited for the first time to be a hydrophilic surface, and then filling the activated surface with a superelastic material for a second time to form a superelastic material layer; S50. Cut the device processed in step S40 to obtain interdigital capacitors, and spin-coat a protective layer on the cut interdigital capacitors.

7. A method for manufacturing a bending sensor, characterized in that: The following steps are involved: A neutral connection layer is provided, and the interdigital capacitors prepared in claim 6 are bonded and arranged in pairs on opposite surfaces of the neutral connection layer.

Images