CN111256884A - Flexible sensors that identify pressure and shear - Google Patents

Abstract

A flexible sensor that can identify pressure and shear includes a signal-sensitive layer and a microstructured layer. The signal sensitive layer includes a strain grid; the strain grid includes a pressure strain grid (2) and a plurality of shear strain grids (1). The flexible sensor comprises at least two groups of shear strain grids (1), and the two shear strain grids (1) of the same group are located on both sides of the pressure strain grid (2) along the radial direction of the circumference. The microstructure layer includes a pressure strain grid junction (4) and a shear strain grid junction (5); the microstructure (7) of the pressure strain grid junction (4) covers the pressure strain grid (2) in the radial direction of the circumference. The metal line segment, the microstructure (7) of the shear strain grid junction (5) has a portion extending radially beyond the metal line segment of the corresponding shear strain grid (1), a plurality of shear strain grid junctions (5) and The combination formed by the corresponding shear strain grid (1) is symmetrical about the center of the circumference.

Description

Flexible sensors that identify pressure and shear

technical field

The present invention relates to the technical field of sensors, and in particular, to a flexible sensor that can identify pressure and shear force.

Background technique

With the development of science and technology and the improvement of people's living standards, wearable devices for medical and health care have attracted more and more attention. Stress or strain sensors have a wide range of applications in health detection, smart screens, human-computer interaction, electronic skin and other fields. In recent years, a variety of flexible stress/strain sensors suitable for wearable devices have been developed, such as biocellulose-based strain sensors, silver nanowire sensors, and graphene flexible sensors.

The development trend of future-oriented smart wearable devices is to simulate human skin to detect complex mechanical signals. At present, most flexible sensors can only sense compressive stress or compressive strain, but cannot detect shear stress and distinguish the direction of shear stress.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-described state of the art. The purpose of the present invention is to provide a flexible sensor that can identify pressure and shear force, and the flexible sensor can identify pressure, as well as the magnitude and direction of shear force.

A flexible sensor capable of recognizing pressure and shear force is provided, which includes a substrate, a signal-sensitive layer and a microstructure layer, wherein the signal-sensitive layer includes a strain grid and is stacked on the upper surface of the substrate;

The strain grid includes a plurality of shear strain grids arranged in a circumferential direction and a pressure strain grid located at the center of the plurality of shear strain grids, each of the shear strain grid and the pressure strain grid having A plurality of metal line segments connected end to end to form a serpentine shape, the plurality of shear strain grids are grouped in two groups, the flexible sensor includes at least two groups of the shear force strain grids, two shear force grids in the same group The strain grids are located on both sides of the pressure strain grid along the radial direction of the circumference;

The microstructure layer includes a plurality of microstructures, and the microstructure layer includes a pressure strain grid joint portion and a shear strain grid joint portion;

The microstructure of the pressure strain grid junction covers the metal line segments of the pressure strain grid in the radial direction of the circumference, and the microstructure of the shear strain grid junction has a radial direction of the circumference. For the portion radially extending beyond the metal line segment of the corresponding shear strain grid, the combination formed by a plurality of the shear strain grid joint portions and the corresponding shear strain grid is symmetrical about the center of the circumference.

In at least one embodiment, the flexible sensor further includes a conductive network, which leads out both ends of the pressure strain grid and each of the shear strain grids to form a conductive loop.

In at least one embodiment, the conductive network includes connecting wires connecting each of the shear strain grids and the pressure strain grids together, and conducting wires, the connecting wires and the conducting wires being used in the An electrical circuit is formed between the strain grid and external electrical equipment.

In at least one embodiment, when the flexible sensor is subjected to pressure, the pressure strain grid produces a resistance change ΔR ₁ , and according to Equation (1-1), Equation (1-2) and Equation (1-3) Identify the pressure F _P experienced by the flexible sensor:

ΔR ₁ =K ₁ ε ₁ (1-1);

Wherein, E ₁ is the elastic modulus of the microstructure of the pressure strain grid, K ₁ is the strain sensitivity coefficient of the pressure strain grid, ε ₁ is the compressive strain of the pressure strain grid, and σ is the pressure compressive stress of the strain grid, d ₁ is the width of the microstructure of the compressive strain grid;

When the flexible sensor is subjected to shear force, the same set of shear strain grids are subjected to shear force component F _τ , and the shear strain grids located in the front and rear along the direction of the shear force component F _τ The resistance changes ΔR ₂₁ and ΔR ₂₂ are generated, respectively, the flexible sensor according to Equation (2-1), Equation (2-2), Equation (2-3), Equation (3-1), Equation (3-2) and Equation (3-3) identifies the shear force component F _τ :

For the shear strain grid forward in the direction of the shear component F _τ :

ΔR ₂₁ =K ₂₁ ε ₂₁ (2-1);

For the shear strain grid located behind in the direction of the shear component F _τ :

ΔR ₂₂ =K ₂₂ ε ₂₂ (3-1);

Wherein, E ₂₁ and E ₂₂ are the elastic moduli of the corresponding microstructures of the shear strain grid, K ₂₁ and K ₂₂ are the corresponding strain sensitivity coefficients of the shear strain grid, ε ₂₁ and ε ₂₂ are the compressive strains of the corresponding shear strain grids, σ ₂₁ and σ ₂₂ are the corresponding compressive stresses of the shear strain grids, η ₂₁ and η ₂₂ are the corresponding microstructures of the shear strain grids Compared with the position offset of the metal line segment of the corresponding shear strain grid, L ₂₁ and L ₂₂ are the heights of the corresponding microstructures of the shear strain grid, and d ₂₁ and d ₂₂ are the corresponding the width of the microstructure of the shear strain grid;

The shear force experienced by the flexible sensor is obtained by synthesizing the shear force component force F _τ identified by the shear force strain grids in different groups according to the quadrilateral rule.

In at least one embodiment, the flexible sensor includes two sets of the shear strain grids, the two sets of the shear strain grids being arranged orthogonally.

In at least one embodiment, the shear strain grid includes a plurality of arc-shaped metal line segments that are spaced apart and connected in the radial direction, and the metal segments are sequentially arranged from the outside to the inside along the radial direction. The length of the line segments gradually decreases so that the shear strain grid is fan-shaped.

In at least one embodiment, the microstructure of the shear strain grid junction is a cylinder and is arranged in a plurality of arcs concentric with the shear strain grid, or the shear strain grid junction The shape of the microstructure is an arc concentric with the shear strain grid,

A plurality of the microstructures are arranged at intervals on each of the metal wire segments of the shear strain grid.

In at least one embodiment, the shear strain grid is integrally formed by bending the metal wire multiple times in a serpentine shape.

In at least one embodiment, the metal wire segments of the pressure strain grid are located on a plurality of concentric circular trajectories and the pressure strain grid is disc-shaped.

In at least one embodiment, the microstructure of the pressure strain grid junction is a cylinder and is arranged in a plurality of rings concentric with the pressure strain grid, or the microstructure of the pressure strain grid junction The shape of the structure is a ring concentric with the pressure strain grid,

A plurality of the microstructures are arranged at intervals on each of the metal line segments of the pressure strain grid.

In at least one embodiment, in the radial direction of the circumference, the microstructure of the pressure strain grid junction just covers the metal wire segment of the pressure strain grid, or has all the parts beyond the pressure strain grid. part of the metal wire segment.

In at least one embodiment, the pressure strain grid includes a plurality of semicircular metal wire segments distributed on both sides of a diameter of the circumference to form two pressure strain grids Locally, the two pressure strain grids are connected locally at the center of the circumference.

In at least one embodiment, the microstructure layer further comprises a flexible substrate, the plurality of microstructures are carried on the flexible substrate, the microstructures are cantilever structures and the fixed ends thereof are disposed on the flexible substrate.

The following beneficial effects can be obtained through the above technical solution:

When the flexible sensor is subjected to shear force, the microstructure will bend, and the bending direction of the microstructure at the junction of the shear strain grids covering the two shear strain grids of each group is opposite, so that the two shear strains of each group The resistance changes of the grids are different, and then the shear force component of each group of shear strain grids can be obtained according to the formula. According to the parallelogram law, the shear force components acting along the arrangement directions of different groups of shear strain grids are synthesized, so that the flexible sensor can measure the shear force in any direction (including the magnitude and direction of the shear force).

Description of drawings

FIG. 1 is a schematic diagram of the main body portion of the flexible sensor capable of recognizing pressure and shear of the present invention.

FIG. 2 is an overall schematic diagram of a strain grid of a flexible sensor and a partial enlarged view thereof.

FIG. 3 is an overall schematic diagram of a microstructure layer of a flexible sensor and a partial enlarged view thereof.

FIG. 4 is a schematic diagram of a first embodiment in which the microstructure is combined with the metal line segments of the pressure strain grid, showing that the width of the microstructure is larger than the width of the metal line segments of the pressure strain grid.

Figure 5 is a schematic diagram of a second embodiment of a microstructure combined with a metal line segment of a pressure strain grid, showing that the width of the microstructure is equal to the width of the metal line segment of the pressure strain grid.

FIG. 6 is a schematic diagram of a first embodiment in which the metal line segments of two shear strain grids of the same group are combined with microstructures.

FIG. 7 is a schematic diagram of a second embodiment in which the metal line segments of two shear strain grids of the same group are combined with microstructures.

Description of reference numbers:

1 Shear strain grid, 11 Metal segment of shear strain grid, 2 Pressure strain grid, 21 Metal segment of pressure strain grid, 3 Conductive network, 31 Connecting wire, 32 Conductor, 33 Outgoing wire, 4 Pressure strain grid junction, 5. Shear strain gate junction, 6. Substrate, 7. Microstructure.

Detailed ways

Exemplary embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that these specific descriptions are only used to teach those skilled in the art how to implement the present invention, and are not used to exhaust all possible ways of the present invention, nor to limit the scope of the present invention.

As shown in FIG. 1 , FIG. 2 and FIG. 3 , the present disclosure provides a flexible sensor that can identify pressure and shear force. The pressure on the flexible sensor is perpendicular to the direction of the paper surface, and the shear force received by the flexible sensor is parallel to the direction of the paper surface. The flexible sensor is a sheet body, and the main body of the flexible sensor includes a substrate 6, a signal-sensitive layer and a microstructure layer, which are stacked and combined. As defined below, the side of the substrate 6 for combining the signal-sensitive layer and the microstructure layer is the "upper" side, and the opposite side is the "lower" side.

The signal sensitive layer is laminated on the upper surface of the substrate 6, and the microstructure layer is laminated on the upper surface of the signal sensitive layer. The substrate 6 may, for example, be made of a flexible material, such as a polymer film. The signal-sensitive layer can convert the force signal into an electrical signal, and the microstructure layer can be a polymer film with a human fingerprint-like structure including a plurality of microstructures 7 .

The signal sensitive layer includes a strain grid and a conductive network 3 , and the strain grid includes a pressure strain grid 2 and a plurality of (eg four) shear strain grids 1 . A plurality of shear strain grids 1 are arranged along the circumferential direction, and the pressure strain grids 2 are located at the center of the circumference. Specifically, the pressure strain grid 2 may be in the shape of a disc, and each shear strain grid 1 may be in the shape of a sector concentric with the pressure strain grid 2 .

The circumference enclosed by the multiple shear strain grids 1 and the pressure strain grid 2 have the same "radial direction", "circumferential direction" and "circle center", and the "radial direction", "circumferential direction" and "circle center" are all referred to below. A circle surrounded by a plurality of shear strain grids 1 and a pressure strain grid 2 are used as reference. The "width" of the microstructure 7 is referred to herein as the dimension of the microstructure 7 in the radial direction.

A plurality of shear strain grids 1 are arranged in pairs, and the signal sensitive layer includes at least two groups of shear strain grids 1 . In each set of shear strain grids 1, the arrangement direction of the two shear strain grids 1 passes through the center of the pressure strain grid 2, for example, the radial direction of the pressure strain grid 2, and the two shear strain grids 1 are related to the pressure The center of the strain grid 2 is symmetrical.

It should be understood that in the embodiment in which the pressure strain grid 2 does not have a center of circle, the arrangement direction of the two shear strain grids 1 passes through the center of the pressure strain grid 2 .

Both the pressure strain grid 2 and the shear strain grid 1 include a plurality of metal line segments arranged at intervals in the radial direction and extending in the circumferential direction. The shear strain grid 1 includes a plurality of arc-shaped metal line segments 11 arranged at intervals in the radial direction. The plurality of arc-shaped metal line segments 11 are connected end to end to form a serpentine shape, and the metal line segments 11 are sequentially arranged from the outside to the inside along the radial direction. The length gradually decreases so that the shear strain grid 1 is fan-shaped as a whole.

In other embodiments, the shear strain grid 1 may further include a plurality of linear metal line segments 11 arranged at intervals along the radial direction, and the plurality of linear metal line segments 11 are connected end to end to form a serpentine shape.

The shear strain grid 1 can be integrally formed by bending the metal wire in a serpentine shape multiple times. In this way, the shear strain grid 1 is smoother and easier to combine with the microstructure layer. Of course, the form of the shear strain grid 1 is not limited to this.

Of course, in other embodiments, the shear strain grid 1 may also be formed by connecting a plurality of metal wires in a serpentine shape.

The pressure strain grid 2 includes a plurality of semicircular metal wire segments 21, and the plurality of semicircular metal wire segments 21 are distributed on both sides of one diameter of the pressure strain grid 2 to form two pressure strain grid parts. In each pressure strain grid portion, a plurality of metal line segments 21 are connected end to end to form a serpentine shape, and two pressure strain grid portions are connected at the center of the pressure strain grid 2 . The partial semicircular metal line segments of the two pressure strain grids are approximately symmetrical with respect to the above-mentioned diameters, so that the metal line segments 21 of the pressure strain grid 2 are mainly located on a plurality of circular trajectories.

In other embodiments, the metal line segment 21 of the pressure strain grid 2 may be located on a helical trajectory centered on the center of the pressure strain grid 2 .

The conductive network 3 includes connecting wires 31 , a plurality of (eg six) wires 32 and a plurality of lead wires 33 . The connection line 31 may be in the shape of a circular arc, and the connection line 31 connects each of the shear strain grids 1 and the pressure strain grids 2 together. The connecting line 31 may connect the radially innermost side of each shear strain grid 1 and the radially outermost side of the pressure strain grid 2 . The connecting wires 31 and the wires 32 form an electrical circuit between the strain grid and external electrical equipment. The wires 32 are connected to the connecting wires 31 , the respective shear strain grids 1 and pressure strain grids 2 . The lead wires 33 are used to connect the wires 32 and external electrical equipment to transmit electrical signals.

Specifically, the radially outermost metal line segment 21 of one pressure strain grid part is connected to a wire 32, and the radially outermost metal line segment 21 of the other pressure strain grid part is connected to a connecting line 31, which is connected to A wire 32. The radially innermost metal wire segment 11 of each shear strain grid 1 is connected to the connecting wire 31 , and the radially outermost metal wire segment 11 of each shear strain grid 1 is connected to a wire 32 respectively.

In this way, the conductive network 3 outputs the force information (in the form of electrical signals) collected by the shear strain grid 1 and the pressure strain grid 2 respectively.

The microstructure layer includes a plurality of microstructures 7 and a flexible substrate, and a plurality of microstructures 7 and a flexible substrate can be integrally formed through a casting process. The microstructure 7 is a "cantilever" structure, and its fixed end is set on the flexible substrate. The size of the microstructures 7 is generally 5 micrometers to 500 micrometers, and a plurality of microstructures 7 are dispersed in the microstructure layer. Both the microstructures 7 and the flexible substrate may be formed from flexible materials. The microstructure 7 is, for example, a cylinder, specifically, a cubic cylinder or a cylinder.

The microstructure layer includes a plurality of microstructures 7 with a "cantilever" structure, which can realize local stress concentration and imitate the fingerprint structure of a human palm, so that the flexible sensor has high sensitivity.

In other embodiments, the microstructures 7 may also be elongated sheets, such as arc-shaped or semi-circular sheets, and the microstructure layer includes a plurality of sheets spaced along the radial direction. The "cantilever" structure is still formed with one end set on the flexible substrate as the fixed end.

The microstructure layer includes a pressure strain grid joint 4 and a shear strain grid joint 5, the pressure strain grid joint 4 covers the upper surface of the pressure strain grid 2, and the shear strain grid joint 5 may include a plurality of parts of a separate body. The upper surfaces of the shear strain grids 1 are respectively covered in a one-to-one correspondence.

The pressure strain grid junction 4 may have the same shape as that of the pressure strain grid 2, eg a disc shape. The microstructures 7 of the pressure strain grid junction 4 can be arranged into a plurality of rings concentric with the pressure strain grid 2 , and the rings formed by the microstructures 7 of the pressure strain grid junction 4 can cover the positions of the pressure strain grid 2 in one-to-one correspondence. Metal segment 21 on a circular trajectory. Corresponding to each metal line segment 21, a plurality of microstructures 7 spaced apart along the extending direction of the metal line segment 21 may be provided.

In other embodiments, the shape of the microstructure 7 of the pressure strain grid joint 4 may be an annular shape that is concentric with the pressure strain grid 2 , that is, the microstructure 7 is an annular body.

In other embodiments, the shape of the pressure strain grid joint portion 4 may be other shapes capable of covering the pressure strain grid 2 .

As shown in FIGS. 4 and 5 , the microstructure 7 of the pressure-strain grid joint 4 may just cover the metal line segment 21 of the pressure-strain grid 2 , or have a portion that extends radially beyond the metal line segment 21 of the pressure-strain grid 2 , such as microstructures. The radial dimension (width) of the structure 7 may be greater than or equal to the width of the metal line segment 21 of the pressure strain grid 2 . After the pressure acts on the pressure strain grid joint 4 , it can be completely collected and transmitted to the pressure strain grid 2 .

The shear strain grid joint 5 may have the same shape as that of the shear strain grid 1 , such as a fan shape, and the shear strain grid joint 5 may completely cover the shear strain grid 1 in the circumferential direction. The microstructures 7 of the shear strain grid joint 5 may be arranged into a plurality of arcs concentric with the shear strain grid 1 , and the lengths of the arcs arranged in turn from the outside to the inside in the radial direction gradually decrease. The arcs formed by the microstructures 7 of the shear strain grid joint 5 can cover the metal line segments 11 of the shear strain grid 1 in a one-to-one correspondence. Corresponding to each metal line segment 11, a plurality of microstructures 7 spaced apart along the extending direction of the metal line segment 11 may be provided.

In other embodiments, the shape of the microstructure 7 of the shear strain grid joint 5 may be an arc concentric with the shear strain grid 1 , that is, the microstructure 7 is an arc body.

In other embodiments, the shape of the shear strain grid joint 5 may be other shapes capable of covering the shear strain grid 1 .

The microstructures 7 of the shear strain grid junctions 5 have portions that extend radially beyond the metal line segments 11 of the corresponding shear strain grid 1 , ie the microstructures 7 of the shear strain grid junctions 5 radially cover the shear strain The metal line segment 11 of the grid 1 extends beyond the metal line segment 11 or is radially offset from the metal line segment 11 of the shear strain grid 1 . For the same shear strain grid 1 , the portions of the microstructures 7 of the multiple shear strain grid joint portions 5 beyond the metal line segments 11 of the corresponding shear strain grids 1 are the same. The combination formed by the plurality of shear strain grid joints 5 and the corresponding shear strain grids 1 is symmetrical with respect to the center of the pressure strain grid 2 .

As shown in FIG. 6 , in one embodiment, the microstructures 7 of the shear strain grid junctions 5 may radially cover the metal line segments 11 of the shear strain grid 1 and extend radially outward beyond the metal line segments 11 , ie shearing The radially inner edge of the microstructure 7 of the force-strain grid junction 5 is aligned with the radially inner edge of the metal line segment 11 of the shear-strain grid 1, and the radially outer edge of the microstructure 7 of the shear-strain grid junction 5 exceeds the shear The radially outer edge of the metal wire segment 11 of the force strain grid 1 .

In other embodiments, the microstructures 7 of the shear strain grid junction 5 may also radially cover the metal wire segment 11 of the shear strain grid 1 and extend radially inwardly over the metal wire segment 11 .

As shown in FIG. 7 , in another embodiment, the microstructures 7 of the shear strain grid junction 5 may be offset from the metal line segments 11 of the shear strain grid 1 radially inward, that is, the shear strain grid junction 5 The radially inner edge of the microstructure 7 exceeds the radially inner edge of the metal wire segment 11 of the shear strain grid 1 , and the radially outer edge of the metal wire segment 11 of the shear strain grid 1 exceeds the microstructure 7 of the shear strain grid junction 5 the radial outer edge.

In other embodiments, the microstructures 7 of the shear strain grid junctions 5 may be offset radially outward from the metal line segments 11 of the shear strain grid 1 .

When the flexible sensor is subjected to shearing force, the microstructures 7 will bend, and the bending directions of the microstructures 7 covering the shear strain grid junctions 5 of the two shear strain grids 1 of each group are opposite, so that the two The resistance changes of the shear strain grids 1 are different, and then the shear force component of each group of shear strain grids 1 can be obtained according to the formula (described in detail below). Then, according to the parallelogram law, the shear force components acting along the arrangement directions of different groups of shear strain grids 1 are synthesized, so that the flexible sensor can measure the shear force in any direction (including the magnitude and direction of the shear force).

The pressure strain grid 2 will produce a resistance change under the action of pressure, and the pressure F _P that the flexible sensor is subjected to can be obtained according to the relationship between the resistance change and the compressive strain, compressive stress and pressure.

The relationship between resistance change and compressive strain: ΔR ₁ =K ₁ ε ₁ (1-1);

The relationship between compressive strain and compressive stress:

The relationship between compressive stress and pressure:

Among them, E1 is the elastic modulus of the microstructure ₇ covering the pressure strain grid ₂ , K1 is the strain sensitivity coefficient of the pressure strain grid ₂ , ε1 is the compressive strain, σ is the compressive stress, and _ΔR1 is the pressure strain grid 2. The resistance changes, and d ₁ is the width of the microstructure 7 of the pressure strain grid 2 .

The resistance change ΔR ₁ can be measured. The elastic modulus E ₁ and the strain sensitivity coefficient K ₁ are determined according to the material. Combined with formulas (1-1) and (1-2), the compressive stress σ of the pressure strain grid 2 can be obtained. , bringing σ into formula (1-3) to obtain the magnitude of the pressure on the pressure strain grid 2, that is, the magnitude of the pressure on the flexible sensor.

Preferably, the two groups of shear strain grids 1 may be orthogonally arranged along the X axis and the Y axis, that is, the lines on which the two groups of shear strain grids 1 are located are orthogonal to each other.

The following takes a set of shear strain grids 1 set on the X axis as an example to introduce the calculation method of the shear force component of a set of shear strain grids 1. The shear force component of a set of shear strain grids 1 set on the Y axis is The calculation method of the shear force component is the same.

In a set of shear strain grids 1 arranged on the X-axis, two shear strain grids 1 are located on both sides of the origin of the X-axis, respectively. Assuming that the shear force component F _τ on the X axis of the shear force on the flexible sensor is along the positive X axis, the two shear strain grids 1 in the group are subjected to asymmetric (different) compressive stresses σ ₂₁ and σ ₂₂ .

The compressive stress σ ₂₁ received by the shear strain grid 1 located in the positive direction of the X axis along the direction of the shear force component F _τ (positive X axis) is:

The compressive stress σ ₂₂ received by the shear strain grid 1 located in the rear along the direction of the shear force component F _τ , that is, in the negative direction of the X axis is:

Among them, η ₂₁ and η ₂₂ are the positional offsets between the microstructure 7 of the corresponding shear strain grid 1 and the metal line segment 11 of the corresponding shear strain grid 1, that is, the centerline h of the microstructure 7 in the radial direction and the shear force distance m from the center line t of the metal line segment 11 of the strain grid 1 in the radial direction; F _p is the pressure on the flexible sensor, L ₂₁ and L ₂₂ are the heights of the microstructure 7 of the corresponding shear strain grid 1, d ₂₁ and d ₂₂ are the widths of the microstructures 7 of the corresponding shear strain grid 1 .

On the premise of knowing the compressive stresses σ ₂₁ and σ ₂₂ of a set of shear strain grids 1 on the X axis, a set of shear strains on the X axis can be determined according to formulas (2-3) and (3-3). The shear force component F _τ experienced by the force-strain grid 1 . For the shear force component F _τ of different groups of shear strain grids 1, the shear force experienced by the flexible sensor is synthesized according to the parallelogram law.

According to formulas (2-3) and (3-3), the pressure F _p on the flexible sensor can be determined again. When the F _p determined by formulas (2-3) and (3-3) is different from the 3) When the determined F _p is different, the accurate F _p can be obtained by taking the average value.

The following describes how to obtain the compressive stresses σ ₂₁ and σ ₂₂ of the shear strain grid 1 .

The shear strain grid 1 will generate a resistance change under the action of force, and the corresponding stress can be obtained according to the relationship between the resistance change and the strain and stress.

For shear strain grid 1 forward in the direction of the shear component F _τ :

The relationship between resistance change and compressive strain: ΔR ₂₁ =K ₂₁ ε ₂₁ (2-1);

The relationship between compressive strain and compressive stress:

For shear strain grid 1 located behind in the direction of said shear component F _τ :

The relationship between resistance change and compressive strain: ΔR ₂₂ =K ₂₂ ε ₂₂ (3-1);

The relationship between compressive strain and compressive stress:

Among them, E ₂₁ and E ₂₂ are the elastic moduli of the microstructure 7 of the corresponding shear strain grid 1, K ₂₁ and K ₂₂ are the strain sensitivity coefficients of the corresponding shear strain grid 1, ε ₂₁ and ε ₂₂ are the corresponding The compressive strain of the shear strain grid 1.

The resistance changes ΔR ₂₁ and ΔR ₂₂ can be measured, the elastic moduli E ₂₁ and E ₂₂ , and the strain sensitivity coefficients K ₂₁ and K ₂₂ are determined according to the material.

When the materials of the two shear strain grids 1 are the same, the strain sensitivity coefficients K ₂₁ and K ₂₂ are equal. When the materials of the microstructures 7 corresponding to the two shear strain grids 1 are the same, the elastic moduli E ₂₁ and E ₂₂ are equal. When the shapes of the microstructures 7 corresponding to the two shear strain grids 1 are the same, L ₂₁ and L ₂₂ are equal, and d ₂₁ and d ₂₂ are equal.

Taking the detection of skin surface stress as an example, the use process of the flexible sensor is introduced.

The skin of the sticking area is first cleaned, then the flexible sensor is applied to the skin surface, and then an external load is applied to the flexible sensor. The applied load first acts on the microstructured layer and creates a stress concentration in the microstructured layer, and the microstructured layer transmits the force to the signal sensitive layer. The signal-sensitive layer is strained under the action of external force, resulting in a change in resistance, so as to measure the shear force and pressure and display the indication.

The flexible sensor has the characteristics of low cost, high sensitivity, good repeatability, can identify compressive stress and shear stress, and can identify the magnitude and direction of shear force. The microstructure layer imitates the fingerprint of the human palm to help the flexible sensor identify different directions, Different types of stress have good application prospects in biological health detection, human-computer interaction, electronic skin and other fields.

It should be understood that the flexible material may be PDMS (polydimethylsiloxane) or the like.

It should be understood that the above-mentioned embodiments are only exemplary, and are not intended to limit the present invention. Those skilled in the art can make various modifications and changes to the above-described embodiments under the teachings of the present invention without departing from the scope of the present invention.

Claims (13)

1. A flexible sensor capable of identifying pressure and shear force comprises a substrate (6), and is characterized by further comprising a signal sensitive layer and a microstructure layer, wherein the signal sensitive layer comprises a strain gate and is laminated on the upper surface of the substrate (6);

the strain grids comprise a plurality of shear strain grids (1) arranged along the circumferential direction and pressure strain grids (2) located in the centers of the shear strain grids (1), each shear strain grid (1) and each pressure strain grid (2) are provided with a plurality of metal line segments which are connected end to form a snake shape, the shear strain grids (1) are arranged in pairs, the flexible sensor comprises at least two groups of shear strain grids (1), and two shear strain grids (1) in the same group are located on two sides of each pressure strain grid (2) along the radial direction of the circumference;

the microstructure layer comprises a plurality of microstructures (7), and the microstructure layer comprises a pressure strain grid combination part (4) and a shear strain grid combination part (5);

the microstructure (7) of the compressive strain grid combination part (4) covers the metal line segment of the compressive strain grid (2) in the radial direction of the circumference, the microstructure (7) of the shear strain grid combination part (5) is provided with a part exceeding the metal line segment of the corresponding shear strain grid (1) in the radial direction of the circumference, and a combination formed by the shear strain grid combination parts (5) and the corresponding shear strain grids (1) is symmetrical about the center of the circumference.

2. The flexible pressure and shear force identifiable sensor according to claim 1, further comprising a conductive network (3), wherein the conductive network (3) leads out both ends of the pressure strain grid (2) and each shear strain grid (1) for forming a conductive loop.

3. A flexible sensor capable of identifying pressure and shear force according to claim 2, wherein the conductive network (3) comprises a connection line (31) and a lead (32), the connection line (31) connects each shear strain grid (1) and the pressure strain grid (2) together, and the connection line (31) and the lead (32) are used for forming an electrical circuit between the strain grids and an external electrical device.

4. Flexible sensor capable of identifying pressure and shear force according to claim 1, characterized in that the pressure strain grid (2) generates a change in resistance Δ R when the flexible sensor is subjected to pressure₁And identifying the pressure F applied to the flexible sensor according to the formula (1-1), the formula (1-2) and the formula (1-3)_P：

ΔR₁＝K₁ε₁(1-1)；

Wherein E is₁Is the elastic modulus, K, of the microstructure (7) of the compressive strain gate (2)₁Is the strain sensitivity coefficient, epsilon, of the pressure strain grid (2)₁Is the compressive strain of the compressive strain gauge (2), σ is the compressive stress of the compressive strain gauge (2), d₁The width of the microstructure (7) being a compressive strain gate (2);

when the flexible sensor is subjected to shear force, the same group of shear strain grids (1) is subjected to shear force component F_τAlong the shear force component F_τThe shear strain grids (1) positioned in the front and the rear directions respectively generate resistance changes delta R₂₁And Δ R₂₂The flexible sensor identifies the shear force component F according to formula (2-1), formula (2-2), formula (2-3), formula (3-1), formula (3-2), and formula (3-3)_τ：

For the component force F along the shearing force_τThe shear strain grid (1) being located forward:

ΔR₂₁＝K₂₁ε₂₁(2-1)；

for the component force F along the shearing force_τThe shear strain grid (1) with a direction behind:

ΔR₂₂＝K₂₂ε₂₂(3-1)；

wherein E is₂₁And E₂₂The modulus of elasticity, K, of the microstructure (7) of the corresponding shear strain grid (1)₂₁And K₂₂For the corresponding strain sensitivity coefficient, epsilon, of the shear strain grid (1)₂₁And ε₂₂For corresponding compressive strain, σ, of the shear strain grid (1)₂₁And σ₂₂For the corresponding compressive stress of the shear strain grid (1), η₂₁And η₂₂Is as followsThe microstructure of the shear strain grid (1) is offset from the position of the corresponding metal line segment of the shear strain grid (1), L₂₁And L₂₂Is the height of the microstructure (7) of the corresponding shear strain grid (1), d₂₁And d₂₂Is the width of the microstructure (7) of the respective shear strain gate (1);

the shearing force borne by the flexible sensor is the shearing force component F identified by the shearing force strain grids (1) of different groups_τSynthesized according to the quadrilateral rule.

5. The identifiable pressure and shear flexible sensor according to any of claims 1-4, characterized in that the flexible sensor comprises two sets of the shear strain grids (1), the two sets of the shear strain grids (1) being arranged orthogonally.

6. The flexible pressure and shear force sensor as claimed in any one of claims 1 to 4, wherein the shear strain grid (1) comprises a plurality of arc-shaped metal wire segments arranged at intervals along the radial direction and connected into a whole, and the lengths of the metal wire segments arranged in sequence from the outside to the inside along the radial direction are gradually reduced so that the shear strain grid (1) is in a fan shape.

7. Flexible sensor capable of identifying pressure and shear force according to claim 6, characterized in that the microstructures (7) of the shear strain grid connection (5) are cylinders and are arranged in a plurality of arcs concentric with the shear strain grid (1), or the microstructures (7) of the shear strain grid connection (5) are in the shape of arcs concentric with the shear strain grid (1),

a plurality of microstructures (7) are arranged on each metal wire section of the shear strain grid (1) at intervals.

8. Flexible sensor of the kind that can identify pressure and shear forces according to any of claims 1-4, characterized in that the shear strain grid (1) is integrally formed by bending a metal wire multiple times in a serpentine shape.

9. Flexible sensor of identifiable pressure and shear force according to one of claims 1-4, characterized in that the metal wire sections of the pressure-strain grid (2) are located on a plurality of concentric circular tracks and the pressure-strain grid (2) is disc-shaped.

10. The pressure and shear identifiable flexible sensor according to claim 9, characterized in that the microstructures (7) of the compressive strain grating bond (4) are cylinders and are arranged in a plurality of rings concentric with the compressive strain grating (2), or the microstructures (7) of the compressive strain grating bond (4) are ring-shaped concentric with the compressive strain grating (2),

a plurality of microstructures (7) are arranged on each metal wire section of the compressive strain gate (2) at intervals.

11. Flexible sensor capable of identifying pressure and shear forces according to any of claims 1 to 4, characterized in that the microstructure (7) of the compressive strain gate bonding (4) covers the metal wire section of the compressive strain gate (2) exactly in the radial direction of the circumference or has a portion beyond the metal wire section of the compressive strain gate (2).

12. Flexible sensor of the kind that can identify pressure and shear forces according to any of claims 1-4, characterized in that the pressure-strain grid (2) comprises a plurality of semicircular wire segments distributed on both sides of one diameter of the circumference so as to form two pressure-strain grid parts that are connected at the center of the circumference.

13. The flexible pressure and shear force sensor of any one of claims 1 to 4, wherein the microstructure layer further comprises a flexible substrate, the plurality of microstructures (7) are carried on the flexible substrate, the microstructures (7) are cantilever structures and fixed ends thereof are provided on the flexible substrate.

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