CN114018447B

CN114018447B - Flexible capacitive pressure sensor based on paper folding structure

Info

Publication number: CN114018447B
Application number: CN202111289698.XA
Authority: CN
Inventors: 冯雪; 王海瑞; 周伟欣; 马寅佶
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2021-11-02
Filing date: 2021-11-02
Publication date: 2022-07-19
Anticipated expiration: 2041-11-02
Also published as: CN114018447A

Abstract

The application provides a flexible capacitive pressure sensor based on paper folding structure, it includes: the paper folding device comprises a paper folding part body, wherein the surface of the paper folding part body is provided with a plurality of paper folding surfaces which are mutually bent and connected, and when the paper folding part body is pressed along the height direction of the paper folding part body, the sizes of the paper folding part body along the length direction and the width direction of the paper folding part body are increased; the first electrode is arranged on the paper folding surface on one side of the paper folding part body; a second electrode provided on the other side surface of the paper folding portion body. The flexible capacitive pressure sensor based on the paper folding structure can deform when being loaded, so that the relative position relation of the first electrode and the second electrode is adjusted, the capacitance has obvious variation, and the sensitivity of the capacitive pressure sensor is improved.

Description

Flexible capacitive pressure sensor based on paper folding structure

Technical Field

The application relates to the technical field of capacitive pressure sensors, in particular to a flexible capacitive pressure sensor based on a paper folding structure.

Background

The capacitance type pressure sensor can convert an external pressure signal into the change of capacitance, the change of the capacitance is converted into an electric signal through the measuring circuit to be output, and the size of the electric signal is measured, so that the size of the external pressure can be known. Compared with a resistance-type pressure sensor, the capacitance-type pressure sensor has the advantages of high sensitivity, low power consumption, compact layout, higher resistance to temperature fluctuation and thermal noise and the like.

Disclosure of Invention

In order to further improve the sensitivity of the capacitive pressure sensor, the application provides a flexible capacitive pressure sensor based on a paper folding structure.

This flexible capacitive pressure sensor based on paper folding structure includes:

the paper folding device comprises a paper folding part body, wherein the surface of the paper folding part body is provided with a plurality of paper folding surfaces which are mutually bent and connected, and when the paper folding part body is pressed along the height direction of the paper folding part body, the sizes of the paper folding part body along the length direction and the width direction of the paper folding part body are increased;

the first electrode is arranged on the paper folding surface on one side of the paper folding part body;

a second electrode provided on the other side surface of the paper folding portion body.

In at least one embodiment, a cutting plane is provided at a connection of adjacent paper folding surfaces on one side surface and the other side surface of the paper folding portion body.

In at least one embodiment, a carrier film is further disposed between the paper folding portion body and the second electrode.

In at least one embodiment, the bearing film and the paper folding part body are made of the same material and are made of elastic materials.

In at least one embodiment, the elastomeric material comprises polydimethylsiloxane and/or copolyester.

In at least one embodiment, the first electrode and the second electrode are made of the same material and are one of liquid metal, silver nanowires, carbon black, graphite, and conductive rubber.

In at least one embodiment, the flexible capacitive pressure sensor based on a paper folding structure further comprises a lead-out portion for outputting information of the first electrode and the second electrode.

In at least one embodiment, in an unstressed state, the paper folding surface and the other side surface of the paper folding portion body form an included angle, and in a state where the paper folding portion body is pressed in the height direction, the included angle between the paper folding surface and the other side surface becomes smaller, so that the sizes of the paper folding portion body in the length direction and the width direction are increased.

In at least one embodiment, the first electrode includes a plurality of sub-electrodes spaced apart along the width direction and extending along the length direction.

In at least one embodiment, the leading-out part comprises a leading-out block and a plurality of leading-out strips, each leading-out strip is connected with one sub-electrode, and the leading-out block converges and leads out signals of the first electrode and the second electrode.

The flexible capacitive pressure sensor based on the paper folding structure can deform when being loaded, so that the relative position relation of the first electrode and the second electrode is adjusted, the capacitance has obvious variation, and the sensitivity of the capacitive pressure sensor is improved.

Drawings

Fig. 1 shows a schematic structural diagram of a flexible capacitive sensor based on a origami structure according to an embodiment of the present application.

Fig. 2 shows a schematic structural view of the paper folding section body in fig. 1.

Fig. 3 shows a schematic structural view of the first electrode in fig. 1.

Fig. 4 shows a schematic structural view of the second electrode in fig. 2.

Fig. 5 shows a schematic structural view of the monolithic first electrode of fig. 3.

Fig. 6 is a diagram illustrating a positional relationship between a first electrode and a second electrode of a flexible capacitive sensor based on a paper folding structure according to an embodiment of the present application.

Description of the reference numerals

1 a paper folding part; 11 a paper folding part body; 111 folding paper; 112 cutting a plane; 12 a first electrode; 121. 122, 123, 124, 125 sub-electrodes; 13 a second electrode; 14 a carrier film; 2 a lead-out part; 21 leading out a strip; the block is drawn 22.

Detailed Description

Exemplary embodiments of the present application are described below with reference to the accompanying drawings. It should be understood that the detailed description is only intended to teach one skilled in the art how to practice the present application, and is not intended to be exhaustive or to limit the scope of the application.

As shown in fig. 1, the present application provides a paper folding structure-based capacitive pressure sensor (hereinafter, sometimes simply referred to as "pressure sensor") including a paper folding portion 1 and a lead-out portion 2. The paper folding part 1 is used as a probe of a pressure sensor and is used for converting a pressure signal into a change of capacitance. The lead-out section 2 is used for outputting the change in capacitance detected by the paper folding section 1 to an external device.

The paper folding portion 1 includes a paper folding portion body 11, a first electrode 12, and a second electrode 13.

As shown in fig. 2, the paper folding portion body 11 is a structure designed based on a derivative three-pump (Miura) paper folding structure and having in-plane negative poisson's ratio and out-of-plane positive poisson's ratio characteristics (described later). The paper folding section main body 11 includes a plurality of paper folding surfaces 111 having a parallelogram shape. The paper folding faces 111 are connected to each other like paper folding.

On one side surface (the surface on which one side fold of the paper folding part body 11 is located) and the other side surface (the surface on which the other side fold of the paper folding part body 11 is located) of the paper folding part body 11, a cutting plane 112 is provided at the junction of the adjacent paper folding surfaces 111. Compared with the original three-pump paper folding structure, when the paper folding part body 11 is folded, the thickness of the fold line is reduced, and large-area folding displacement of the paper folding part 11 is easier to realize.

The main body 11 of the paper folding part can be made of one or more of Polydimethylsiloxane (PDMS), copolyester (ecoflex) or other elastic materials. The paper folding portion body 11 may be prepared by means of mold casting or 3D printing. The elastic material has higher compressibility and lower Young modulus, can obtain larger deformation under the action of stress, and finally induces larger capacitance change.

A first electrode 12 is provided on a fold paper surface 111 on the top surface of the fold paper body 11. The material of the first electrode may be a stretchable conductive material such as liquid metal, silver nanowire, carbon black, graphite, conductive rubber, or the like. For example, the first electrode may be directly coated on the paper folding surface 111 while the paper folding part body 11 is in a semi-cured state.

As shown in fig. 3, the first electrode 12 applied on the paper folding surface 111 may be divided into a plurality of

sub-electrodes

121, 122, 123, 124, 125, and the like, and each sub-electrode can form a capacitance change independent of the single second electrode 13. Under the action of an external load, the capacitance of each sub-electrode changes, and the distribution condition of the load can be reversely obtained according to the change value of each capacitance by combining a capacitance calculation formula (described later).

As shown in fig. 4, the carrier film 14 is provided on the bottom surface of the paper folding portion body 11, and the carrier film 14 may be connected to the cutting plane 112, for example. The material of the carrier film 14 may be the same as that of the paper folding section body 11. Illustratively, the thickness of the film 2 may be 0.05mm to 5mm, preferably 2 mm.

A second electrode 13 may be provided on a side of the carrier film 14 remote from the paper fold 11. Likewise, the second electrode 13 may be made of the same material as the first electrode 12. The second electrode 13 may be first applied to the carrier film 14, and when the paper folding portion body 11 is in a semi-cured state, the carrier film 14 and the second electrode 13 may be directly pasted together to the bottom surface of the paper folding portion 11.

As shown in fig. 5 and 6, taking a folding paper 111 as an example, the first electrode 12 thereon is also parallelogram-shaped. When not stressed, the acute angle in the first electrode 12 is α, the side length of the other side surface in the first electrode 12 is a, and the side length of the other side is b. The first electrode 12 and the other side surface have an angle θ, and the lowest point of the first electrode 12 is at a distance d from the second electrode 13. According to the formula, the relationship between the capacitance C and the deformation of the first electrode 12 is:

wherein epsilon₀Is the dielectric constant of the first electrode 12 and the second electrode 13.

For convenience of introduction, the present application introduces a coordinate system in the longitudinal direction X, the width direction Y, and the height direction Z. The paper folding portion body 11 has a length L, a width W, and a height H. Poisson's ratio in plane of paper folding part body 11

Out-of-plane Poisson's ratio

When the paper folding portion body 11 is pressed down in the height direction Z, Δ W (a change in width) and Δ L (a change in length) are both positive values, and Δ H (a change in height) is a negative value, that is, the in-plane poisson's ratio of the paper folding portion body 11 is a negative value, and the out-of-plane poisson's ratio is a positive value.

The first electrode 12 can change its position as the paper folding portion body 11 deforms, and the capacitance between the first electrode 12 and the second electrode 13 changes. Such in-plane negative poisson's ratio and out-of-plane positive poisson's ratio of the paper folding portion body 11 are characteristic of multiplying the variation of capacitance, and making the sensitivity of the capacitance sensor higher.

As shown in fig. 1, the lead-out portion 2 may be a wire lead-out structure connected to the paper folding portion 1. Exemplarily, the lead part 2 may include a plurality of lead bars 21 and a lead block 22. Each lead-out bar 21 corresponds to one sub-electrode of the first electrode 12 extending in the length direction X. And then the signals of the first electrode 12 and the second electrode 13 are gathered together through the leading-out block 22 and are led out uniformly.

The capacitance sensor is made of elastic materials, and has very large deformation under the action of normal load (the direction of the normal load is parallel to the height direction Z), so that the pressure sensor has very wide pressure measurement range and high sensitivity.

Further, the pressure sensor can be optimally designed. When the pressure sensor is subjected to a tangential load (for example, the direction of the tangential load is parallel to the width direction Y), the two sets of sub-electrodes of the first electrode 12 are deformed to different degrees, and the magnitude of the stress can be calculated by the capacitance difference between the two sets of sub-electrodes and the second electrode 13. The pressure sensor can detect normal load and tangential load.

While the foregoing is directed to the preferred embodiment of the present application, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the application.

Claims

1. A paper folding structure-based flexible capacitive pressure sensor is characterized by comprising:

the paper folding device comprises a paper folding part body (11), wherein the surface of the paper folding part body (11) is provided with a plurality of paper folding surfaces (111) which are mutually connected in a bending way, and when the paper folding part body (11) is pressed along the height direction (Z), the sizes of the paper folding part body (11) along the length direction (X) and the width direction (Y) are increased;

a first electrode (12), the first electrode (12) being provided on a paper folding surface (111) on one side of the paper folding portion body (11), the first electrode (12) including a plurality of sub-electrodes (121, 122, 123, 124, 125) spaced apart along the width direction (Y) and extending along the length direction (X);

a second electrode (13), the second electrode (13) being provided on the other side surface of the paper folding part body (11),

cutting planes (112) are arranged on the surface of one side and the surface of the other side of the paper folding part body (11) at the joint of the adjacent paper folding surfaces (111), the plurality of sub-electrodes are separated by the cutting planes (112) in the width direction (Y), each sub-electrode can form relatively independent capacitance change with the single second electrode (13),

when the paper folding part body (11) is subjected to a load parallel to the width direction (Y), the included angle between the paper folding surface (111) and the second electrode (13) is changed, and the deformation degrees of the two sub-electrodes separated by the cutting plane (112) are different.

2. The paper folding structure-based flexible capacitive pressure sensor according to claim 1, characterized in that a carrier film (14) is further arranged between the paper folding portion body (11) and the second electrode (13).

3. Flexible capacitive pressure sensor based on paper folding structure according to claim 2, characterized in that the carrying film (14) is of the same material as the paper folding body (11) and is of an elastic material.

4. The origami-based flexible capacitive pressure sensor according to claim 3, wherein said elastomeric material comprises polydimethylsiloxane and/or copolyester.

5. The origami-based flexible capacitive pressure sensor according to claim 1, wherein the first electrode (12) and the second electrode (13) are of the same material and are one of liquid metal, silver nanowires, carbon black, graphite, conductive rubber.

6. The paper folding structure-based flexible capacitive pressure sensor according to claim 1, characterized in that the paper folding structure-based flexible capacitive pressure sensor further comprises a lead-out part (2), wherein the lead-out part (2) is used for outputting information of the first electrode (12) and the second electrode (13).

7. The flexible capacitive pressure sensor based on a paper folding structure according to claim 1, wherein in an unstressed state, the paper folding surface (111) has an included angle with the other side surface of the paper folding portion body (11), and in a state where the paper folding portion body (11) is subjected to pressure along the height direction (Z), the included angle of the paper folding surface (111) with the other side surface becomes smaller, so that the size of the paper folding portion body (11) along the length direction (X) and the width direction (Y) increases.

8. The flexible capacitive pressure sensor based on the paper folding structure is characterized in that the leading-out part (2) comprises a leading-out block (22) and a plurality of leading-out strips (21), each leading-out strip (21) is connected with one sub-electrode, and the leading-out block (22) converges and leads out signals of the first electrode (12) and the second electrode (13).