A piezoresistive flexible distributed three-dimensional tactile sensor based on a multi-layer structure

Abstract

The present invention discloses a piezoresistive flexible distributed three-dimensional tactile sensor based on a multi-layer structure. The force transmission hemispheres of the three-dimensional tactile sensor are arranged in an array at intervals on the force transmission hemisphere layer and receive external three-dimensional force; the two electrode sensing layers are stacked and arranged at intervals and are both provided with interval sensing points. Every four sensing points and one force transmission hemisphere constitute a sub-tactile sensor. The thin film separation layer separates the two electrode sensing layers, and the bottom layer is packaged for bottom packaging. The electrode layer of the present invention is made of a mixed material of carbon nanotubes and graphene, integrating the electrode conductive function and the piezoresistive sensing function, and has ultra-high sensitivity and excellent mechanical properties; the structural design of a sensor composed of every four sensing points and the force transmission hemisphere can realize multi-point three-dimensional force measurement within the contact area; by adjusting the thickness ratio of each electrode layer and the ratio of carbon nanotubes and graphene, the sensor can show different sensitivities within different force ranges, thereby realizing wide-range measurement.

Description

Technical Field

[0001] The present invention relates to a three-dimensional tactile sensor, and in particular to a piezoresistive flexible distributed three-dimensional tactile sensor based on a multi-layer structure. Background Art

[0002] Currently, most robotic arms are only capable of operating in specific work scenarios, performing grasping tasks for a limited number of cooperative objects. Their grasping success rate is significantly impacted when faced with non-cooperative objects of varying shapes and sizes. To meet the demands of grasping a wide range of objects in non-specific scenarios, robotic arms require strong adaptive grasping capabilities. When performing grasping tasks, robotic arms rely primarily on the pressure and friction generated by contact between their fingers and the object, inevitably squeezing the object. When the pressure applied by the robotic arm exceeds the threshold an object can withstand, it can cause irreversible deformation or even damage. Therefore, when grasping objects with specific pressure requirements, robotic arms must also be able to sense contact force. Tactile perception is essential for humanoid robots to be practical in these scenarios. Dexterous hands with tactile perception will play an irreplaceable role in the era of voice-enabled intelligence.

[0003] At present, research on tactile perception sensors has made certain progress, but they do not have the flexibility to conform to any surface, are insufficient in sensing tiny forces, and cannot meet the needs of scenarios in production and life that require precise force control. Summary of the Invention

[0004] To address the problems in the background art, the present invention provides a multi-layer piezoresistive flexible distributed three-dimensional tactile sensor. The present invention can solve the technical problems of existing sensors, such as difficulty in applying flexible distribution, measuring three-dimensional force, and having a narrow measurement range.

[0005] The technical solution adopted in the present invention is:

[0006] The piezoresistive flexible distributed three-dimensional tactile sensor based on a multi-layer structure of the present invention comprises:

[0007] The force-transmitting hemisphere layer is composed of a substrate and a plurality of force-transmitting hemispheres arranged in an array at intervals thereon, and is used to receive external three-dimensional forces.

[0008] Two electrode sensing layers are stacked and spaced at the bottom of the force-transmitting hemisphere layer and electrically connected to an external data collector via a number of wires. Both electrode sensing layers are provided with a number of spaced-apart sensing points. Every four sensing points in each of the two electrode sensing layers and a force-transmitting hemisphere on top constitute a sub-tactile sensor for receiving external local three-dimensional force.

[0009] A thin film separation layer, located between the two electrode sensing layers and used to separate the two electrode sensing layers;

[0010] The packaging bottom layer is used for the bottom layer packaging of the three-dimensional tactile sensor. The force transmission hemisphere layer, the top electrode sensing layer, the thin film separation layer, the bottom electrode sensing layer and the packaging bottom layer are stacked in sequence.

[0011] The force-transmitting hemispheres on the force-transmitting hemisphere layer are arranged in an n×n array, with the center-to-center distances being equal or different. Each hemisphere is located on the side of the substrate facing away from the top electrode sensing layer. The force-transmitting hemispheres transmit three-dimensional contact force to four sensing points. Each sensor can be considered a pressure-variable resistor to infer the external three-dimensional contact force. The shape and size of the three-dimensional tactile sensor can be arbitrarily designed according to actual application requirements and can be installed on a gripping device or on the skin surface.

[0012] The top electrode sensing layer includes a first row electrode layer and a first column electrode layer, and the bottom electrode sensing layer includes a second row electrode layer and a second column electrode layer. The first row electrode layer and the second row electrode layer each include i row electrode sheets, and the first column electrode layer and the second column electrode layer each include j column electrode sheets. The electrode sheets of each electrode layer are arranged in parallel with equal or non-equal spacing. The row electrode sheets in the row electrode layer and the column electrode sheets in the column electrode layer are stacked vertically with each other. Several rectangular overlapping areas of the row electrode sheets and the column electrode sheets are all used as a sensing point. The electrode sheets can be arranged on a plane or a curved surface to achieve flexible distribution, forming i*j sensing points; each row electrode sheet in the first row electrode layer is directly opposite to a row electrode sheet in the second row electrode layer at the bottom of itself, and the first Each column electrode sheet in the column electrode layer faces a column electrode sheet in the second column electrode layer at its bottom, and the bottom of each force transmission hemisphere in the force transmission hemisphere layer faces four sensing points in each electrode sensing layer. The distance between the row electrodes isolates different sensing points in the vertical direction; similarly, the distance between the column electrodes isolates different sensing points in the horizontal direction. Each electrode sheet has a wire running through it along its length. A column selection switch is used to output a preset driving voltage to the wires of each column electrode sheet in turn, and a row selection switch is used to select the wires of each row electrode sheet in turn to connect to an external data collector. The single-point resistance value of each sensing point is measured by the external data collector, and the magnitude and direction of the three-dimensional force are inferred from the respective resistance values.

[0013] The two longest sides of each two adjacent row electrode sheets that are farthest apart are tangent to the bottom circle of the force transmission hemisphere and the distance between them is equal to the diameter of the force transmission hemisphere. The two longest sides of each two adjacent column electrode sheets that are farthest apart are tangent to the bottom circle of the force transmission hemisphere and the distance between them is equal to the diameter of the force transmission hemisphere.

[0014] The thicknesses of the electrode layers are the same or different.

[0015] Each electrode layer is formed by 3D printing using a mixed material of carbon nanotubes and graphene.

[0016] When the electrode layer is made of a mixed material of carbon nanotubes with a mass fraction of 1% to 3% and graphene with a mass fraction of 0.7% to 2%, the thickness formed by 3D printing is 5 to 200 microns. At this time, the measured three-dimensional force pressure is 10 to 100 kPa, and the corresponding sensitivity is 10 -2 ~10 -3 (ΔR / (RPa)), ΔR is the change in resistance of the three-dimensional tactile sensor under pressure, and R is the initial resistance of the three-dimensional tactile sensor before pressure. When a mixed material with a mass fraction of 3% to 5% carbon nanotubes and a mass fraction of 2% to 5% graphene is used, the thickness of the 3D printed material is 200 to 1000 microns. At this time, the measured three-dimensional force pressure is 100 to 500 kPa, and the corresponding sensitivity is 10 -3 ~10 -4 (ΔR / (RPa)); When the electrode layers are made of carbon nanotubes and graphene mixed materials with different mass fractions, the combination of the two can achieve a wide range of measurements. At this time, the measured three-dimensional force pressure is between 10 and 500 kPa, and the corresponding sensitivity range is 10 -2 ~10 -4 (ΔR / (RPa)).

[0017] The beneficial effects of the present invention are:

[0018] 1. The electrode layer of the present invention is made of a mixed material of carbon nanotubes and graphene, integrating the electrode conductive function and the piezoresistive sensing function. The piezoresistive effect of the mixed material has ultra-high sensitivity, can detect tiny force changes, has excellent mechanical properties, and is suitable for installation on flexible curved surfaces.

[0019] 2. The multi-layer structure of the present invention can be formed into an array. Every four sensing points and a force-transmitting hemisphere together form a sensor structure design, so that the resistance value at the corresponding position in the force direction changes significantly. The size, direction and position of the three-dimensional force can be inferred based on the change in the resistance value of the four sensing points, thereby realizing multi-point three-dimensional force measurement within the contact area.

[0020] 3. The present invention can make the sensor show different sensitivities in different force ranges by adjusting the thickness ratio of each layer and the ratio of carbon nanotubes to graphene, thereby achieving a wide range of measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the three-dimensional tactile sensor of the present invention;

[0022] Figure 2A schematic diagram of a three-dimensional structure of an array of three-dimensional tactile sensors in an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the structure of a single tactile sensor in an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the principle of a single tactile sensor in an embodiment of the present invention;

[0025] In the figure: 1. force transmission hemisphere layer, 2. first row electrode layer, 3. first column electrode layer, 4. thin film separation layer, 5. second row electrode layer, 6. second column electrode layer, 7. packaging bottom layer. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 1 and Figure 2 As shown, the piezoresistive flexible distributed three-dimensional tactile sensor based on the multi-layer structure of the present invention includes: a force transmission hemisphere layer 1, two electrode sensing layers, a thin film separator layer 4 and an encapsulation bottom layer 7. The force transmission hemisphere layer 1 is composed of a substrate and a plurality of force transmission hemispheres arranged in an array at intervals thereon, and is used to receive external three-dimensional forces; two electrode sensing layers are stacked and spaced apart at the bottom of the force transmission hemisphere layer 1 and are electrically connected to an external data collector via a plurality of wires; both electrode sensing layers are provided with a plurality of spaced apart sensing points, and each of the four sensing points in each of the two electrode sensing layers and a force transmission hemisphere on top thereof constitutes a sub-tactile sensor and is used to receive external local three-dimensional forces; the thin film separator layer 4 is located between the two electrode sensing layers and is used to separate the two electrode sensing layers; the encapsulation bottom layer 7 is used for the bottom encapsulation of the three-dimensional tactile sensor, and the force transmission hemisphere layer 1, the top electrode sensing layer, the thin film separator layer 4, the bottom electrode sensing layer and the encapsulation bottom layer 7 are stacked in sequence. In specific implementation, the force transmission hemispheres on the force transmission hemisphere layer 1 are arranged in a 3×3 equally spaced array, the center distances of the force transmission hemispheres are the same, and the force transmission hemispheres are located on a side of the substrate away from the top electrode sensing layer.

[0028] The top electrode sensing layer includes a first row electrode layer 2 and a first column electrode layer 3, and the bottom electrode sensing layer includes a second row electrode layer 5 and a second column electrode layer 6. The first row electrode layer 2 and the second row electrode layer 5 each include six row electrode sheets, and the first column electrode layer 3 and the second column electrode layer 6 each include six column electrode sheets. The electrode sheets of each electrode layer 2, 3, 5, and 6 are arranged in parallel with equal intervals. The row electrode sheets in the row electrode layers 2 and 5 and the column electrode sheets in the column electrode layers 3 and 6 are stacked vertically with each other. Several rectangular overlapping areas of the row electrode sheets and the column electrode sheets are all used as a sensing point. The electrode sheets can be arranged on a plane or a curved surface to achieve flexible distribution and form 6*6 sensing points; each row electrode sheet in the first row electrode layer 2 is directly opposite to a row electrode sheet in the second row electrode layer 5 at the bottom of itself. Electrode sheet, each column electrode sheet in the first column electrode layer 3 faces a column electrode sheet in the second column electrode layer 6 at its bottom, the bottom of each force transmission hemisphere in the force transmission hemisphere layer 1 faces four sensing points in each electrode sensing layer, and the distance between the row electrodes is used to isolate different sensing points in the vertical direction; similarly, the distance between the column electrodes is used to isolate different sensing points in the horizontal direction; each electrode sheet has a wire running through it along its length, and a column selection switch is used to output a preset driving voltage to the wires of each column electrode sheet in turn, and a row selection switch is used to select the wires of each row electrode sheet in turn to connect to an external data collector, and the single-point resistance value of each sensing point is measured by the external data collector, and the magnitude and direction of the three-dimensional force are inferred by the respective resistance values. The two longest sides of every two adjacent row electrode sheets that are farthest apart are tangent to the bottom circle of the force transmission hemisphere and the distance between them is equal to the diameter of the force transmission hemisphere. The two longest sides of every two adjacent column electrode sheets that are farthest apart are tangent to the bottom circle of the force transmission hemisphere and the distance between them is equal to the diameter of the force transmission hemisphere.

[0029] like Figure 3 As shown in the figure, a single sub-tactile sensor is used. When a three-dimensional force acts on the force-transmitting hemisphere, the force-transmitting hemisphere transmits the three-dimensional contact force to four sensing points. Each sensor can be regarded as a pressure variable resistor to inversely solve the external three-dimensional contact force. Taking the coordinate system constructed in the figure as an example, the normal force along the Z axis and the two tangential forces along the X and Y axes can be obtained by analysis. Figure 4 As shown, the overlapping area of ​​the two electrode layers constitutes a sensing point, each sensing point is equivalent to a variable resistor, and every four sensing points and a force transmission hemisphere together constitute a sensor.

[0030] When the electrode layers 2, 3, 5, and 6 are made of a mixture of carbon nanotubes with a mass fraction of 1% to 3% and graphene with a mass fraction of 0.7% to 2%, the thickness formed by 3D printing is 5 to 200 microns. At this time, the measured three-dimensional force pressure is 10 to 100 kPa, and the corresponding sensitivity is 10 -2 ~10 -3(ΔR / (RPa)), ΔR is the change in resistance of the three-dimensional tactile sensor under pressure, and R is the initial resistance of the three-dimensional tactile sensor before pressure. When a mixed material with a mass fraction of 3% to 5% carbon nanotubes and a mass fraction of 2% to 5% graphene is used, the thickness of the 3D printed material is 200 to 1000 microns. At this time, the measured three-dimensional force pressure is 100 to 500 kPa, and the corresponding sensitivity is 10 -3 ~10 -4 (ΔR / (RPa)); When the electrode layers 2, 3, 5, and 6 are made of carbon nanotube and graphene mixed materials with different mass fractions, the combination of the two can achieve a wide range of measurement. At this time, the measured three-dimensional force pressure is between 10 and 500 kPa, and the corresponding sensitivity range is 10 -2 ~10 -4 (ΔR / (RPa)).

[0031] In practice, carbon nanotubes and graphene can be mixed with a polymer matrix, such as ABS, and a terpolymer of acrylonitrile (A), butadiene (B), and styrene (S), to prepare a nanocomposite material. One mixture consists of 2% carbon nanotubes, 1% graphene, and 97% ABS by mass; another comprises 4% carbon nanotubes, 5% graphene, and 91% ABS by mass. The carbon nanotube and graphene composite material is extruded in the form of filaments using FDM (Fused Deposition Modeling). The FDM process requires ensuring that the material's melt viscosity is suitable for printing while maintaining the properties of the carbon nanotubes and graphene. After printing, heat treatment or annealing is performed to improve the material's electrical conductivity and mechanical properties, which helps rearrange the carbon nanotubes and graphene and enhance their conductive network within the matrix. Finally, 3D printing results in electrode layers 2, 3, 5, and 6 of equal thickness.

[0032] Carbon nanotube and graphene hybrid materials are highly sensitive to mechanical stress, pressure, and touch. This sensitivity is due to their unique nanostructure, which causes a significant change in the material's internal resistance when subjected to external force. This high sensitivity enables them to detect even tiny changes in touch. The hybrid materials exhibit excellent mechanical properties and can be made very thin and flexible. This makes them ideal for integration into flexible and wearable devices, creating bendable and stretchable tactile sensors. The hybrid materials respond quickly to touch or pressure and quickly recover to their original state after the pressure is removed. This rapid response and recovery is crucial for real-time tactile detection. Carbon nanotube and graphene hybrid materials are highly sensitive to mechanical stress, pressure, and touch, offering ultra-high sensitivity but a narrow measurement range. By adjusting the thickness ratio of electrode layers 2, 3, 5, and 6, as well as the ratio of carbon nanotubes to graphene, the sensor's sensitivity can be tailored to different force ranges, enabling a wide range of measurements.

[0033] The shape and size of the three-dimensional tactile sensor can be arbitrarily designed according to actual application requirements and installed on the grasping device or skin surface.

[0034] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention's patent shall be determined by the claims.

Claims

1. A piezoresistive flexible distributed three-dimensional tactile sensor based on a multi-layer structure, characterized in that: include: The force-transmitting hemisphere layer (1) is composed of a substrate and a plurality of force-transmitting hemispheres arranged in an array at intervals thereon, and is used to receive external three-dimensional forces; Two electrode sensing layers are stacked and spaced apart at the bottom of the force transmission hemisphere layer (1) and are electrically connected to an external data collector via a plurality of wires; the two electrode sensing layers are each provided with a plurality of sensing points spaced apart, and each of the four sensing points in the two electrode sensing layers and a force transmission hemisphere on the top thereof constitute a sub-tactile sensor and are used to receive an external local three-dimensional force; A thin film separation layer (4), located between the two electrode sensing layers and used to separate the two electrode sensing layers; The packaging bottom layer (7) is used for the bottom layer packaging of the three-dimensional tactile sensor, wherein the force transmission hemispherical layer (1), the top electrode sensing layer, the thin film separation layer (4), the bottom electrode sensing layer and the packaging bottom layer (7) are sequentially stacked; The top electrode sensing layer includes a first row electrode layer (2) and a first column electrode layer (3), and the bottom electrode sensing layer includes a second row electrode layer (5) and a second column electrode layer (6). The first row electrode layer (2) and the second row electrode layer (5) each include i row electrode sheets, and the first column electrode layer (3) and the second column electrode layer (6) each include j column electrode sheets. The electrode sheets of each electrode layer (2, 3, 5, 6) are arranged in parallel with equal spacing or non-equal spacing. The row electrode sheets in the row electrode layers (2, 5) and the column electrode sheets in the column electrode layers (3, 6) are arranged vertically stacked on each other, and several rectangular overlapping areas of the row electrode sheets and the column electrode sheets are all used as a sensing point. Each row electrode sheet in the first row electrode layer (2) faces a row electrode sheet in the second row electrode layer (5) at its bottom, each column electrode sheet in the first column electrode layer (3) faces a column electrode sheet in the second column electrode layer (6) at its bottom, and the bottom of each force transmission hemisphere in the force transmission hemisphere layer (1) faces four sensing points in each electrode sensing layer; each electrode sheet is provided with a wire along its length direction, and a column selection switch is used to output a preset driving voltage to the wires of each column electrode sheet in turn, and a row selection switch is used to select the wires of each row electrode sheet in turn to connect to an external data collector, and the single-point resistance value of each sensing point is measured by the external data collector.

2. The multi-layer piezoresistive flexible distributed three-dimensional tactile sensor according to claim 1, characterized in that: The force transmission hemispheres on the force transmission hemisphere layer (1) are arranged in an n×n interval array, the center distances of the force transmission hemispheres are the same or different, and the force transmission hemispheres are located on a side of the substrate away from the top electrode sensing layer.

3. The multi-layer piezoresistive flexible distributed three-dimensional tactile sensor according to claim 1, characterized in that: The two longest sides of every two adjacent row electrode sheets that are farthest apart are tangent to the bottom circle of the force transmission hemisphere and the distance between them is equal to the diameter of the force transmission hemisphere. The two longest sides of every two adjacent column electrode sheets that are farthest apart are tangent to the bottom circle of the force transmission hemisphere and the distance between them is equal to the diameter of the force transmission hemisphere.

4. The multi-layer piezoresistive flexible distributed three-dimensional tactile sensor according to claim 1, characterized in that: The thicknesses of the electrode layers (2, 3, 5, 6) are the same or different.

5. The multi-layer piezoresistive flexible distributed three-dimensional tactile sensor according to claim 1, characterized in that: Each of the electrode layers (2, 3, 5, 6) is formed by 3D printing using a mixed material of carbon nanotubes and graphene.

6. The multi-layer piezoresistive flexible distributed three-dimensional tactile sensor according to claim 5, characterized in that: When the electrode layers (2, 3, 5, 6) are made of a mixture of carbon nanotubes with a mass fraction of 1% to 3% and graphene with a mass fraction of 0.7% to 2%, the thickness formed by 3D printing is 5 to 200 microns. At this time, the measured three-dimensional force pressure is 10 to 100 kPa, and the corresponding sensitivity is , is the change in resistance of the three-dimensional tactile sensor under pressure, is the initial resistance of the three-dimensional tactile sensor before pressure is applied; when a mixed material with a mass fraction of 3% to 5% carbon nanotubes and a mass fraction of 2% to 5% graphene is used, the thickness of the 3D printed material is 200 to 1000 microns. At this time, the measured three-dimensional force pressure is 100 to 500 kPa, and the corresponding sensitivity is When the electrode layers (2, 3, 5, 6) are made of carbon nanotube and graphene mixed materials with different mass fractions, the measured three-dimensional force pressure is between 10 and 500 kPa, and the corresponding sensitivity range is .

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