Multi-dimensional flexible force sensor with multi-electrode cavity structure

Abstract

The invention relates to the technical field of three-dimensional force sensors, in particular to a multi-dimensional flexible force sensor with a multi-electrode cavity structure, which comprises a PDMS substrate, a cavity is formed in the center of the top surface of the PDMS substrate, and a PDMS contact layer is arranged on the top surface of the PDMS substrate; a groove is additionally formed in the middle area of a PDMS substrate, independent PVDF is designed at the bottom of the groove, electrode output potentials on the two sides of the middle PVDF have a linear mapping relation with normal force within a certain force range, coupling between the electrode output potentials and tangential force is small and can be neglected, and the coupling between the electrode output potentials and the tangential force is small and can be neglected. The output potential difference of the two opposite electrodes of the hollow-square-shaped PVDF has a linear mapping relation with the tangential force within a certain force range, the coupling between the output potential difference and the normal force is small and can be ignored, the direction of the force can be visually determined, the normal force and the tangential force can be distinguished on the electrical signal level, direction recognition and spatial decoupling of the force are achieved, and the detection accuracy is improved. The sensor can effectively distinguish normal force and tangential force, decoupling sensing of the force is achieved, and therefore the sensor has the excellent multi-axis force detection and decoupling capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of three-dimensional force sensors, and in particular to a multi-dimensional flexible force sensor with a multi-electrode cavity structure. Background Art

[0002] A three-dimensional force sensor is a device that can simultaneously measure the forces acting on an object in three mutually perpendicular directions (X, Y, and Z axes). It operates based on the principle of strain gauge force measurement and is widely used in industrial automation, robotics, electronic skin, aerospace, and other fields. It measures the change in resistance of a resistance strain gauge caused by the deformation of an elastic element, which is converted into a voltage signal output via a Wheatstone bridge circuit. It can simultaneously detect three-dimensional force components with coupling errors controlled within 1% FS. Electronic skin is a new type of intelligent material that combines flexible electronic technology and bionics, capable of simulating the sensory functions of human skin (such as touch, temperature, and pressure). In the field of medical aesthetics, it is also used to refer to certain wearable or implantable electronic devices used for skin monitoring, repair, or rejuvenation treatments.

[0003] Most of the existing three-dimensional force sensors have piezoelectric sensing layers in the same plane and are separated. When subjected to external force, the output voltage needs to undergo mathematical modeling or neural network algorithm. The nonlinear mapping relationship between output and input is fitted through signal processing to separate and reconstruct the force components. The corresponding force can only be obtained through the assistance of a neural network. However, this method has complex manufacturing processes and high preparation costs, and has certain limitations in practical applications. For this reason, a multi-dimensional flexible force sensor with a multi-electrode cavity structure is proposed. Summary of the Invention

[0004] In order to solve the technical problems existing in the above-mentioned prior art, the present invention provides a multi-dimensional flexible force sensor with a multi-electrode cavity structure.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a multi-dimensional flexible force sensor with a multi-electrode cavity structure, comprising a PDMS substrate, a cavity is opened at the center position of the top surface of the PDMS substrate, a PDMS contact layer is provided on the top surface of the PDMS substrate, the edge of the PDMS substrate is fixed by adhesion to the edge of the PDMS contact layer, a symmetrically distributed full electrode assembly is provided between the PDMS substrate and the PDMS contact layer, and a PDMS microcolumn is fixedly connected to the top surface of the PDMS contact layer above the cavity.

[0006] Preferably, the full electrode assembly includes a meandering PVDF film and a central PVDF film, the meandering PVDF film is fixed to the top surface of the PDMS substrate by PDMS adhesion, the central PVDF film is adhered and fixed inside the cavity, and electrode assemblies are arranged on the upper and lower surfaces of the meandering PVDF film and the central PVDF film.

[0007] Preferably, the electrode assembly comprises edge Ag positive electrodes, central Ag positive electrodes, edge Ag negative electrodes and central Ag negative electrodes, the edge Ag positive electrodes and the edge Ag negative electrodes are fixed in the middle of each section of the upper and lower surfaces of the meander-shaped PVDF film, and the central Ag positive electrodes and the central Ag negative electrodes are fixed on the upper and lower surfaces of the central PVDF film.

[0008] Preferably, the sum of the thicknesses of the central PVDF film, the central Ag positive electrode and the central Ag negative electrode is less than the thickness of the cavity, and the edges of the central PVDF film, the central Ag positive electrode and the central Ag negative electrode are in close contact with the edges of the inner wall of the cavity.

[0009] Preferably, a three-dimensional force sensing method of a multi-electrode cavity structure multi-dimensional flexible force sensor, the three-dimensional force sensing method specifically comprises the following steps:

[0010] (a) Set the XY coordinate axis with the PDMS substrate as the plane and the central Ag positive electrode and the central Ag negative electrode as the origin, and the four edge Ag positive electrodes and the edge Ag negative electrodes are respectively on the X-axis and the Y-axis, which are respectively the left electrode, the right electrode, the upper electrode and the lower electrode, and the PDMS micro column is on the Z-axis, and the closed loop formed by the positive electrode and the negative electrode and the lead wire generates an output potential, and the signal data output by the potential response output of the five Ag electrodes is read to determine the direction of the force;

[0011] (b) When the PDMS micro column is exposed on the surface of the electronic skin during use, when a normal force is applied to the PDMS micro column along the Z-axis, the force will act on the top surface of the PDMS micro column, the PDMS contact layer is deformed and penetrates into the cavity, and the central PVDF film, the central Ag positive electrode and the central Ag negative electrode are squeezed, the central Ag positive electrode and the central Ag negative electrode generate a potential difference, Uz is the intermediate potential, Uz is positive, indicating that the normal force is downward, the PDMS contact layer above the cavity has small bending stiffness and the boundary is fixed, so that the displacement of the boundary of the PDMS contact layer is small, resulting in obvious concave deformation of the cavity area, and the deformation amount is large, so that a higher sensitive sensing of the normal force can be generated, and the four peripheral meander-shaped PVDF films are symmetrical and the boundary is constrained, so that the two symmetrical potential changes are close to equal, and therefore the potential difference generated by the symmetrical electrodes on the X-axis and the Y-axis is zero;

[0012] (c) When a tangential force is applied to the PDMS micro-column along the X axis, the two symmetrical regions of the meandering PVDF film in the X axis direction will be deformed, one side is compressed and the other side is stretched, according to the piezoelectric effect, the compression causes the potential difference generated by the electrodes on both sides of the meandering PVDF film to be positive, and the stretching causes the potential difference generated by the electrodes on both sides of the meandering PVDF film to be negative, Ux = right electrode-left electrode, Ux is positive, indicating that the tangential force is in the positive direction of the X axis, Ux is negative, indicating that the tangential force is in the negative direction of the X axis, at this time the potential of the two edges Ag positive electrodes in the Y axis direction is close to zero, and the edge fixation of the PDMS contact layer suppresses the rotation freedom of the material, combined with the design of the cavity, the central PVDF film does not contact or slightly contacts the PDMS contact layer under the action of the tangential force, at this time the potential change of the central Ag positive electrode is very small, so that the potential change of the middle electrode is very small, Uz is close to zero;

[0013] (d) When a tangential force is applied to the PDMS micro-column along the Y axis, then the upper and lower edges of the Ag positive electrode in the Y axis generate a potential difference, Uy = upper electrode-lower electrode, Uy is positive, indicating that the tangential force is in the positive direction of the Y axis, Uy is negative, indicating that the tangential force is in the negative direction of the Y axis, while the potential of the two edge Ag positive electrodes in the X axis is close to zero, and the designed cavity (2) structure makes the central PVDF film still not contact or slightly contact the PDMS contact layer under the action of the tangential force;

[0014] (e) When a tangential force is applied to the PDMS micro-column along the first quadrant, the upper electrode and the right electrode are in a stretched state, and the lower electrode and the left electrode are in a compressed state, at this time Ux and Uy are both negative; When a tangential force is applied to the PDMS micro-column along the second quadrant, the upper electrode and the left electrode are in a stretched state, and the lower electrode and the right electrode are in a compressed state, at this time Ux is positive and Uy is negative; When a tangential force is applied to the PDMS micro-column along the third quadrant, the upper electrode and the right electrode are in a compressed state, and the lower electrode and the left electrode are in a stretched state, at this time Ux and Uy are both positive; When a tangential force is applied to the PDMS micro-column along the fourth quadrant, the upper electrode and the left electrode are in a compressed state, and the lower electrode and the right electrode are in a stretched state, at this time Ux is negative and Uy is positive.

[0015] The beneficial effects of the present application compared with the prior art are:

[0016] The application can intuitively determine the force direction, can distinguish the normal force and the tangential force in the electrical signal level, realizes the force direction identification and the space decoupling, and has excellent multi-axis force detection and decoupling capacity. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the application;

[0018] Figure 2 It is a schematic diagram of the overall structure of the application;

[0019] Figure 3 It is a schematic diagram of the overall structure of the application;

[0020] Figure 4 It is a schematic diagram of the overall structure of the application;

[0021] Figure 5 It is a schematic diagram of the overall structure of the application;

[0022] Figure 6 It is a schematic diagram of the overall structure of the application;

[0023] Figure 7 It is a schematic diagram of the overall structure of the application;

[0024] Figure 8 It is a schematic diagram of the overall structure of the application;

[0025] Figure 9 It is a schematic diagram of the overall structure of the application;

[0026] Figures in the drawing represent:

[0027] 1, PDMS substrate; 2, cavity; 3, meander-shaped PVDF film; 4, central PVDF film; 5, edge Ag positive electrode; 6, central Ag positive electrode; 7, PDMS contact layer; 8, PDMS microcolumn; 9, edge Ag negative electrode; 10, central Ag negative electrode. DETAILED DESCRIPTION

[0028] The above and other technical features and advantages of the present application will be further explained by the following description with reference to the accompanying drawings and embodiments, but the following embodiments are merely preferred embodiments of the present application, and are not all.

[0029] Embodiments:

[0030] As Figures 1-9 shown, the present application provides a multi-dimensional flexible force sensor of multi-electrode cavity structure, comprising a PDMS substrate 1, PDMS is a high polymer, the PDMS substrate 1 is fixed on the connecting part at the edge, a cavity 2 is provided at the center position of the top surface of the PDMS substrate 1, a PDMS contact layer 7 is provided on the top surface of the PDMS substrate 1, the edge of the PDMS substrate 1 is fixed by PDMS and the edge of the PDMS contact layer 7, and a full electrode assembly is arranged symmetrically between the PDMS substrate 1 and the PDMS contact layer 7, and the top surface of the PDMS contact layer 7 above the cavity 2 is fixedly connected with a PDMS micro column 8.

[0031] In this embodiment, the full electrode assembly comprises a meandering PVDF film 3 and a central PVDF film 4, the meandering PVDF film 3 is fixed by PDMS on the top surface of the PDMS substrate 1, PVDF is a highly non-reactive thermoplastic fluorine-containing polymer, and the central PVDF film 4 is fixedly connected inside the cavity 2, and the upper and lower surfaces of the meandering PVDF film 3 and the central PVDF film 4 are provided with electrode assemblies.

[0032] In this embodiment, the electrode assembly comprises edge Ag positive electrode 5, central Ag positive electrode 6, edge Ag negative electrode 9 and central Ag negative electrode 10, the edge Ag positive electrode 5 and the edge Ag negative electrode 9 are fixed in the middle of each section of the upper and lower surfaces of the meandering PVDF film 3, the central Ag positive electrode 6 and the central Ag negative electrode 10 are fixed on the upper and lower surfaces of the central PVDF film 4, the positive electrode on the upper surface of the edge Ag positive electrode 5 and the central Ag positive electrode 6 and the negative electrode on the lower surface form a closed loop through external wires, the PDMS substrate 1 is taken as a plane, the center of the PDMS substrate 1 is taken as the origin to set the XY coordinate axis, the four edge Ag positive electrodes 5 are respectively on the X axis and the Y axis, and the PDMS micro column 8 is the Z axis.

[0033] In this embodiment, the sum of the thicknesses of the central PVDF film 4, the central Ag positive electrode 6 and the central Ag negative electrode 10 is less than the thickness of the cavity 2, so that when a tangential force is applied to the PDMS micro column 8 along the XY axis, the PDMS micro column 8 is difficult to contact the central Ag positive electrode 6, and the edges of the central PVDF film 4 and the central Ag positive electrode 6 are in close contact with the inner wall edges of the cavity 2, when a normal force is applied to the PDMS micro column 8 along the Z axis, the central Ag positive electrode 6 can fully sense the deformation of the PDMS contact layer 7, so as to distinguish the normal force and the tangential force.

[0034] Working principle: as Figure 9 shown, in the perception, to establish with PDMS base 1 as plane, central Ag positive electrode 6 and central Ag negative electrode 10 as the origin, set up XY coordinate axis, four edge Ag positive electrode 5 and edge Ag negative electrode 9 are respectively on X axis and Y axis, respectively left electrode, right electrode, upper electrode and lower electrode, PDMS microcolumn 8 is on Z axis, the closed loop formed by the positive electrode and the negative electrode external wire generates output potential, and the signal data output by reading the potential response output of the five Ag electrodes judges the direction of force;

[0035] When using, PDMS microcolumn 8 is exposed on the surface of electronic skin, when the normal force is applied to PDMS microcolumn 8 along Z axis, the force will act on the top surface of PDMS microcolumn 8, which drives PDMS contact layer 7 to deform into cavity 2 and extrude central PVDF film 4, central Ag positive electrode 6 and central Ag negative electrode 10, central Ag positive electrode 6 and central Ag negative electrode 10 generate potential difference, Uz is the intermediate potential, Uz is positive, indicating that the normal force is downward, the PDMS contact layer 7 above cavity 2 itself has small bending stiffness and the boundary is fixed, so that the displacement of the boundary of PDMS contact layer 7 is small, which causes the obvious concave deformation of cavity 2 region, and the deformation amount is large, so that the normal force can be sensitively perceived, and the four peripheral PVDF films 3 are symmetrical and the boundary is constrained, so the potential difference generated by the symmetrical electrodes on X axis and Y axis is close to zero, as Figure 5 and Figure 6 shown, when the sinusoidal force of 5Hz is applied, the potential output of the middle level and the upper and lower electrodes;

[0036] When the tangential force is applied to PDMS microcolumn 8 along X axis, the two symmetrical edge regions of X axis will deform, one side is compressed and the other side is stretched, according to the piezoelectric effect, the potential difference generated by the electrodes on both sides of the compressed PVDF film 3 is positive, and the potential difference generated by the electrodes on both sides of the stretched PVDF film 3 is negative, thus forming the potential difference, Ux=right electrode-left electrode, Ux is positive, indicating that the tangential force is in the positive direction of X axis, Ux is negative, when the sinusoidal force of 5Hz is applied, as Figure 7The output potential trends of the left and right electrodes indicate that the tangential force is in the negative direction of the X-axis. At this time, the potential difference between the two edge Ag positive electrodes 5 in the Y-axis direction is close to zero. At the same time, the fixed edge of the PDMS contact layer 7 suppresses the rotational freedom of the material. In conjunction with the design of the cavity 2, the central PVDF film 4 remains out of contact with or slightly contacts the PDMS contact layer 7 under the action of the tangential force. At this time, the potential change of the central Ag positive electrode 6 is extremely small, thereby making the potential change of the middle electrode extremely small. Uz is close to zero, which plays a shielding role, so that the sensor can effectively distinguish between normal force and tangential force, realizing decoupled force perception;

[0037] When a tangential force is applied to the PDMS microcolumn 8 along the Y axis, a significant potential difference is generated between the upper and lower edges of the Ag positive electrode 5 on the Y axis, Uy = upper electrode - lower electrode. A positive value of Uy indicates that the tangential force is in the positive direction of the Y axis, and a negative value of Uy indicates that the tangential force is in the positive direction of the Y axis. When a 5 Hz sinusoidal force is applied, such as Figure 7 The output potential trends of the upper and lower electrodes indicate that the tangential force is in the negative direction of the Y axis, while the potentials of the two edge Ag positive electrodes 5 on the X axis are close to zero. The symmetrical structure enables the sensor to have directional selectivity for tangential forces in different directions. At the same time, the designed cavity (2) structure enables the central PVDF film 4 to remain in non-contact or slightly contact the PDMS contact layer 7 under the action of the tangential force.

[0038] When a tangential force is applied to the PDMS micropillar 8 along the first quadrant, the upper electrode and the right electrode are in a tensile state, while the lower electrode and the left electrode are in a compressed state. At this time, Ux and Uy are both negative;

[0039] When a tangential force is applied to the PDMS micropillar 8 along the second quadrant, the upper electrode and the left electrode are in a tensile state, while the lower electrode and the right electrode are in a compressed state. At this time, Ux is a positive value and Uy is a negative value;

[0040] When a tangential force is applied to the PDMS micropillar 8 along the third quadrant, the upper electrode and the right electrode are in compression, while the lower electrode and the left electrode are in tension. At this time, Ux and Uy are both positive.

[0041] When a tangential force is applied to the PDMS microcolumn 8 along the fourth quadrant, the upper electrode and the left electrode are in a compressed state, while the lower electrode and the right electrode are in a stretched state. At this time, Ux is a negative value and Uy is a positive value.

[0042] The above description is merely a preferred embodiment of the present invention and is intended to be illustrative rather than restrictive of the present invention. Those skilled in the art will appreciate that many changes, modifications, and even equivalents may be made to the present invention within the spirit and scope of the claims, all of which fall within the scope of protection of the present invention.

Claims

1. A multi-dimensional flexible force sensor with a multi-electrode cavity structure, characterized in that: The invention comprises a PDMS substrate (1), a cavity (2) is provided at the center of the top surface of the PDMS substrate (1), a PDMS contact layer (7) is provided on the top surface of the PDMS substrate (1), the edge of the PDMS substrate (1) is adhered and fixed to the edge of the PDMS contact layer (7) through PDMS, a symmetrically distributed full electrode assembly is provided between the PDMS substrate (1) and the PDMS contact layer (7), and a PDMS microcolumn (8) is fixedly connected to the top surface of the PDMS contact layer (7) above the cavity (2).

2. The multi-dimensional flexible force sensor with a multi-electrode cavity structure according to claim 1, characterized in that: The full electrode assembly comprises a circular PVDF film (3) and a central PVDF film (4); the circular PVDF film (3) is fixed to the top surface of the PDMS substrate (1) by PDMS adhesion; the central PVDF film (4) is fixed to the inside of the cavity (2); and electrode assemblies are provided on the upper and lower surfaces of the circular PVDF film (3) and the central PVDF film (4).

3. The multi-dimensional flexible force sensor with a multi-electrode cavity structure according to claim 2, characterized in that: The electrode assembly comprises an edge Ag positive electrode (5), a central Ag positive electrode (6), an edge Ag negative electrode (9) and a central Ag negative electrode (10); the edge Ag positive electrode (5) and the edge Ag negative electrode (9) are fixed in the middle of each section of the upper and lower surfaces of the circular PVDF film (3); and the central Ag positive electrode (6) and the central Ag negative electrode (10) are fixed on the upper and lower surfaces of the central PVDF film (4).

4. The multi-dimensional flexible force sensor with a multi-electrode cavity structure according to claim 3, characterized in that: The sum of the thicknesses of the central PVDF film (4), the central Ag positive electrode (6), and the central Ag negative electrode (10) is less than the thickness of the cavity (2), and the edges of the central PVDF film (4) and the central Ag positive electrode (6) are both in contact with the inner wall edge of the cavity (2).

5. The three-dimensional force sensing method of a multi-dimensional flexible force sensor with a multi-electrode cavity structure according to claim 4 is characterized in that: The three-dimensional force sensing method specifically includes the following steps: (a) The PDMS substrate (1) is used as a plane, and the central Ag positive electrode (6) and the central Ag negative electrode (10) are used as the origin to set the XY coordinate axis. The four edge Ag positive electrodes (5) and the edge Ag negative electrodes (9) are respectively on the X axis and the Y axis, which are the left electrode, the right electrode, the upper electrode and the lower electrode. The PDMS microcolumn (8) is on the Z axis. The positive electrode and the negative electrode are connected to the closed circuit formed by the external wires and generate an output potential. The potential response output signal data of the five Ag electrodes is read to determine the direction of the force. (b) When in use, the PDMS microcolumn (8) is exposed on the surface of the electronic skin. When a normal force is applied to the PDMS microcolumn (8) along the Z axis, the force acts on the top surface of the PDMS microcolumn (8), and the PDMS contact layer (7) is deformed and penetrates into the cavity (2) through the PDMS microcolumn (8), and squeezes the central PVDF film (4), the central Ag positive electrode (6) and the central Ag negative electrode (10). The central Ag positive electrode (6) and the central Ag negative electrode (10) generate a potential difference, and Uz is the intermediate potential. Uz is a positive value, indicating that the normal force is downward. The PDMS contact layer (7) above the cavity (2) has a small bending stiffness and a fixed boundary, so that the displacement of the boundary of the PDMS contact layer (7) is small, resulting in a significant concave deformation in the cavity (2) area and a large deformation amount, thereby being able to produce a high sensitivity to the normal force. Due to the symmetry and boundary constraints of the four peripheral shaped PVDF films (3), the two symmetrical potential changes are close to equal, so the potential difference generated by the symmetrical electrodes on the X-axis and Y-axis is zero; (c) When a tangential force is applied to the PDMS microcolumn (8) along the X-axis, the two symmetrical areas of the meandering PVDF film (3) on the left and right sides of the X-axis will deform, with one side being compressed and the other side being stretched. According to the piezoelectric effect, the potential difference generated by the electrodes on both sides of the meandering PVDF film (3) due to compression is positive, and the potential difference generated by the electrodes on both sides of the meandering PVDF film (3) due to stretching is negative, Ux = right electrode - left electrode, Ux is a positive value, indicating that the tangential force is in the positive direction of the X-axis, and Ux is a negative value, indicating that the tangential force is in the negative direction of the X-axis. At this time, the potential of the two edge Ag positive electrodes (5) in the Y-axis direction is close to zero, and at the same time, the fixed edge of the PDMS contact layer 7 suppresses the rotational freedom of the material. In conjunction with the design of the cavity (2), the central PVDF film (4) remains non-contacting or slightly contacting the PDMS contact layer (7) under the action of the tangential force. At this time, the potential change of the central Ag positive electrode (6) is extremely small, thereby making the potential change of the middle electrode extremely small, and Uz is close to zero; (d) When a tangential force is applied to the PDMS microcolumn (8) along the Y axis, a potential difference is generated between the upper and lower edge Ag positive electrodes (5) on the Y axis, Uy = upper electrode - lower electrode, Uy is a positive value, indicating that the tangential force is in the positive direction of the Y axis, and Uy is a negative value, indicating that the tangential force is in the negative direction of the Y axis, while the potential of the two edge Ag positive electrodes (5) on the X axis is close to zero. At the same time, the designed cavity (2) structure ensures that the central PVDF film (4) remains out of contact or slightly in contact with the PDMS contact layer (7) under the action of the tangential force; (e) When a tangential force is applied to the PDMS microcolumn (8) along the first quadrant, the upper electrode and the right electrode are in a tensile state, while the lower electrode and the left electrode are in a compressive state, and at this time Ux and Uy are both negative values; when a tangential force is applied to the PDMS microcolumn (8) along the second quadrant, the upper electrode and the left electrode are in a tensile state, while the lower electrode and the right electrode are in a compressive state, and at this time Ux is a positive value, and Uy is a negative value; when a tangential force is applied to the PDMS microcolumn (8) along the third quadrant, the upper electrode and the right electrode are in a compressive state, while the lower electrode and the left electrode are in a tensile state, and at this time Ux and Uy are both positive values; when a tangential force is applied to the PDMS microcolumn (8) along the fourth quadrant, the upper electrode and the left electrode are in a compressive state, while the lower electrode and the right electrode are in a tensile state, and at this time Ux is a negative value, and Uy is a positive value.

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