Piezoresistive flexible distribution three-dimensional tactile sensor based on multilayer structure

Abstract

The invention discloses a piezoresistive flexible distribution three-dimensional tactile sensor based on a multilayer structure. Force transmission hemispheres are arranged on a force transmission hemisphere layer of the three-dimensional tactile sensor in an array at intervals and receive external three-dimensional force; the two electrode sensing layers are arranged in a stacked and spaced mode and provided with spaced sensing points, every four sensing points and one force transmission hemisphere form a sub tactile sensor, the thin film separating layer separates the two electrode sensing layers, and the packaging bottom layer conducts bottom layer packaging. The electrode layer is prepared by mixing a carbon nanotube and graphene mixed material, an electrode conductive function and a piezoresistive sensing function are integrated, and the electrode has ultrahigh sensitivity and excellent mechanical performance; the structural design that every four sensing points and the force transmission hemisphere form a sensor is adopted, so that multi-point three-dimensional force measurement in a contact area can be realized; by adjusting the thickness ratio of each electrode layer and the ratio of the carbon nano tube to the graphene, the sensor can show different sensitivities in different force ranges, so that wide-range measurement is realized.

Description

Technical Field

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

[0002] At present, most manipulators can only work in a specific working scenario and carry out grasping tasks for some cooperative targets. When facing non-cooperative targets of different shapes and sizes, the grasping success rate of these manipulators will be greatly affected. In order to meet the requirements of grasping various types of objects in non-specific scenarios, manipulators need to have strong adaptive grasping capabilities. When performing grasping tasks, manipulators mainly rely on the pressure and friction generated when the fingers contact the grasped objects to grasp the objects. In this process, the grasped objects will inevitably be squeezed. When the pressure applied by the manipulator exceeds the threshold that the object can withstand, it will cause irreversible deformation or even damage to the object. Therefore, when grasping objects with special requirements for pressure, the manipulator should also have the ability to perceive contact force. If humanoid robots want to land in the scene, tactile perception is indispensable. Dexterous hands with tactile perception will play an irreplaceable role in the era of voice intelligence.

[0003] At present, the research on tactile perception sensors has made certain progress, but they do not have the flexibility to fit any surface arbitrarily, and 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] In order to solve the problems existing in the background technology, the present invention provides a piezoresistive flexible distributed three-dimensional tactile sensor based on a multi-layer structure. The present invention can solve the technical problems that the existing sensors are difficult to apply to flexible distribution, measure three-dimensional force and have a narrow measurement range.

[0005] The technical solution adopted by 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 for receiving external three-dimensional forces.

[0008] Two electrode sensing layers are stacked and spaced at the bottom of the force transmission hemisphere layer and electrically connected to an external data collector through a number of wires; the two electrode sensing layers are each provided with a number of sensing points spaced apart, and every four sensing points in each of the two electrode sensing layers and a force transmission hemisphere on the top constitute a sub-tactile sensor and are used to receive 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 hemispherical 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 transmission hemispheres on the force transmission hemisphere layer 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 surface of the substrate away from the top electrode sensing layer. The force transmission hemispheres transmit the three-dimensional contact force to four sensing points, and each sensor can be regarded as a pressure variable resistor to inversely resolve 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 installed on a gripping device or 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 meet the requirements of plane or curved surface arrangement to achieve flexible distribution and form 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. 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 from the vertical direction; similarly, the distance between the column electrodes isolates different sensing points from the horizontal direction. Each electrode sheet has a wire running through it 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, and the size and direction of the three-dimensional force are inferred from the respective resistance values.

[0013] The two longest sides of every two adjacent row electrode sheets 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 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 of 3% to 5% carbon nanotubes and 2% to 5% graphene is used, the thickness formed by 3D printing 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 flexible curved surface installation.

[0019] 2. The multilayer structure of the present invention can form an array, and every four sensing points and a force transmission hemisphere together form a sensor structure design, so that the resistance value of 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 and graphene, thereby achieving wide range measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a 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 is 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 comprises: a force transmission hemisphere layer 1, two electrode sensing layers, a thin film separation layer 4 and a packaging bottom layer 7, wherein 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 force; the two electrode sensing layers are stacked and spaced at the bottom of the force transmission hemisphere layer 1 and are electrically connected to an external data collector through a plurality of wires; the two electrode sensing layers are both provided with a plurality of sensing points arranged at intervals, 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 is used to receive external local three-dimensional force; the thin film separation layer 4 is located between the two electrode sensing layers and is 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, and the force transmission hemisphere 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 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 at 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 arranged vertically and stacked 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 meet the requirements of plane or curved surface arrangement 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 thereof. 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 from the vertical direction; similarly, the distance between the column electrodes is used to isolate different sensing points from the horizontal direction; each electrode sheet is penetrated by a wire along its own 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 with an external data collector, and the single-point resistance value of each sensing point is measured by the external data collector, and the size 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 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 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, it is a single sub-tactile sensor. When the three-dimensional force acts on the force transmission hemisphere, the force transmission 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 axis and the Y axis 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 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 of 3% to 5% carbon nanotubes and 2% to 5% graphene is used, the thickness formed by 3D printing 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 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)).

[0031] In specific implementation, carbon nanotubes and graphene can be mixed with a polymer matrix such as ABS, a terpolymer of three monomers of acrylonitrile (A), butadiene (B), and styrene (S) to prepare a nanocomposite material, one of which has a mixing ratio of 2% carbon nanotubes, 1% graphene, and 97% ABS; the other has a mixing ratio of 4% carbon nanotubes, 5% graphene, and 91% ABS; the carbon nanotube and graphene composite material is extruded in the form of filaments using the fused deposition modeling (FDM) technology, and the fused deposition modeling (FDM) process needs to ensure that the melt viscosity of the material is suitable for printing while maintaining the characteristics of the carbon nanotubes and graphene; after printing, heat treatment or annealing is performed to improve the conductivity and mechanical properties of the material, which helps to rearrange the carbon nanotubes and graphene and improve their conductive network in the matrix. Finally, 3D printing is performed to form electrode layers 2, 3, 5, and 6 of the same thickness.

[0032] Carbon nanotube and graphene hybrid materials are very sensitive to mechanical stress, pressure and touch. This sensitivity is due to their unique nanostructure, which causes a significant change in the resistance inside the material when subjected to external forces. This high sensitivity allows them to detect small tactile changes. The hybrid materials have excellent mechanical properties and can be made into very thin and flexible materials. This makes them very suitable for integration into flexible and wearable devices for making bendable and stretchable tactile sensors. The hybrid materials can respond quickly when touched or pressed, and quickly return to their original state after the pressure is removed. This fast response and recovery property is very important for real-time tactile detection. Carbon nanotube and graphene hybrid materials are very sensitive to mechanical stress, pressure and touch, and have ultra-high sensitivity, but the measurement range is relatively narrow. By adjusting the thickness ratio of each electrode layer 2, 3, 5, 6, and the ratio of carbon nanotubes and graphene, the sensor can show different sensitivities in different force ranges, thereby achieving 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 gripping device or skin surface.

[0034] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to 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 hemispherical layer (1) is composed of a substrate and a plurality of force-transmitting hemispherical layers arranged in an array at intervals thereon, and is used to receive external three-dimensional forces; Two electrode sensing layers are stacked and spaced 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 at intervals, 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 a 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.

2. The piezoresistive flexible distributed three-dimensional tactile sensor based on a multi-layer structure 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 surface of the substrate away from the top electrode sensing layer.

3. The piezoresistive flexible distributed three-dimensional tactile sensor based on a multi-layer structure according to claim 1, characterized in that: The top electrode sensing layer comprises a first row electrode layer (2) and a first column electrode layer (3), and the bottom electrode sensing layer comprises 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 comprise i row electrode sheets, the first column electrode layer (3) and the second column electrode layer (6) each comprise j column electrode sheets, the electrode sheets of each electrode layer (2, 3, 5, 6) are arranged in parallel with equal or unequal 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, and a plurality of rectangular overlapping areas of the row electrode sheets and the column electrode sheets are each regarded 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, 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.

4. The piezoresistive flexible distributed three-dimensional tactile sensor based on a multi-layer structure according to claim 3 is characterized in that: The two longest sides of every two adjacent row electrode sheets 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 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.

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

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

7. The piezoresistive flexible distributed three-dimensional tactile sensor based on a multi-layer structure according to claim 6, characterized in that: When the electrode layers (2, 3, 5, 6) are 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 of 3% to 5% carbon nanotubes and 2% to 5% graphene is used, the thickness formed by 3D printing 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, 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 10 -2 ~10 -4 (ΔR / (RPa)).

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