Soft grid magnetic sensor for tactile and non-tactile perception

Abstract

The invention relates to a soft mesh magnetic sensor for tactile and non-tactile perception. The sensor comprises a neodymium iron boron-organic silicon elastomer magnetic film, an aluminum foil, a PDMS elastomer, a TMR element and a printed circuit board, wherein the TMR element is welded on the printed circuit board, and the PDMS elastomer coats the TMR element and covers the PCB; the PDMS elastomer is covered with an aluminum foil, and a neodymium iron boron-organic silicon elastomer magnetic film is arranged on the aluminum foil; the PDMS elastomer is of a sandwich structure and is composed of an upper thin film, a lower thin film and a middle small cylinder array. The lower film is provided with a strip-shaped groove which is used for wrapping the TMR element. The soft grid magnetic sensor disclosed by the invention has the advantages of high sensitivity, high flexibility and strong multi-mode sensing capability.

Description

Technical Field

[0001] The present invention applies neodymium iron boron magnetic particles (Nd2Fe 14 B1), silicone elastomer (Ecoflex 00-30), single-electrode triboelectric nanogenerator, polydimethylsiloxane (PDMS), and tunnel magnetoresistance element TMR (Tunnel Magnetic Resistance) to the sensor field of a manipulator. The product is a grid-shaped magnetic sensor based on a neodymium iron boron-silicone elastomer magnetic film with tactile and non-tactile sensing functions. Background Art

[0002] As an important research direction in the fields of flexible electronics and intelligent sensing, flexible tactile sensors have made remarkable progress in materials, structural design, and applications. Its core goal is to simulate the tactile function of human skin, achieve high-sensitivity, fast-response, and stable detection of multi-physical quantities such as pressure, strain, and temperature, thereby promoting innovative applications in the fields of medical health monitoring, intelligent robots, wearable devices, and human-computer interaction. In terms of materials, the introduction of conductive polymers (such as PEDOT:PSS), nanomaterials (such as graphene, carbon nanotubes), and liquid metals (such as gallium-based alloys) has significantly improved the conductivity and flexibility of the sensors. At the same time, the application of elastic substrate materials such as PDMS and Ecoflex and hydrogels has further optimized the stretchability and biocompatibility of the devices. In terms of structural design, the introduction of bionic microstructures has enhanced the sensitivity of the sensors, while multi-modal integration technology enables them to synchronously detect signals such as pressure, temperature, and humidity.

[0003] In recent years, flexible sensing has received extensive attention in multiple fields such as artificial intelligence, electronic skin, biomedicine, and intelligent manufacturing. With the increasing complexity of the target object and the sensing process, new requirements have been put forward for flexible sensing systems. These requirements include ideal flexibility under normal conditions, compliance under mechanical loads, selective response during operation, and most importantly, the ability to integrate multiple sensing modes and accurately distinguish these modes in real time. Traditional dual-mode flexible sensing systems mainly rely on physical contact and signal tracking techniques, and the most common application is a flexible capacitive structure with pressure and distance detection capabilities. Therefore, breaking through the limitations of traditional technologies, developing a new system with tactile and non-tactile dual-mode sensing functions, and optimizing its comprehensive sensing performance have important scientific and practical values.

[0004] The patent (application number 202210958263.8) invents a contact / non-contact force-magnetic dual-mode sensing sensor based on a magnetostrictive film. The sensor consists of a sensitive layer, a conversion layer, and a matching conversion circuit and excitation power supply. The magnetostrictive film sensitive layer and the coil conversion layer are arranged vertically to form a planar flexible sensing structure. However, due to the generally low saturation magnetization intensity of magnetostrictive materials, this traditional magnetostrictive sensor has weak magnetic properties, low coercive force, and is easily demagnetized. In addition, due to the presence of the coil, a lot of energy loss (such as eddy current loss and hysteresis loss) will be generated. Summary of the Invention

[0005] The present invention aims to address the technical issues of current flexible tactile sensors, such as low sensitivity, poor anti-interference capabilities, and a single detectable physical quantity, by providing a soft grid magnetic sensor for tactile and non-tactile perception. The sensor's magnetic film is grid-shaped, capable of detecting minute magnetic field changes and suitable for high-precision measurements. The chain-like microstructure formed by the neodymium iron boron particles in the grid gaps has a greater impact on changes in the sensor's internal magnetic flux density under pressure. The addition of a triboelectric structure (aluminum foil) allows the electrical signal generated by the friction between the magnetic film and the foil to decouple the tactile and non-tactile modes, enabling more timely and accurate judgment of the two modes. The soft grid magnetic sensor of the present invention has the advantages of high sensitivity, high flexibility, and excellent multimodal sensing performance.

[0006] The technical solution of the present invention is:

[0007] A soft mesh tactile sensor for tactile and non-tactile sensing, the sensor comprising a NdFeB-silicone elastomer magnetic film, aluminum foil, PDMS elastomer, a TMR element, and a printed circuit board;

[0008] The TMR element is welded on the printed circuit board, and the PDMS elastomer covers the TMR element and covers the printed circuit board PCB; the PDMS elastomer is covered with aluminum foil, and the aluminum foil is covered with a NdFeB-silicone elastomer magnetic film;

[0009] The PDMS elastomer has a "sandwich" structure, consisting of two layers of film and a small cylindrical array in the middle. The lower film has a strip-shaped groove for covering the TMR element.

[0010] The TMR element is an X-axis tunnel magnetoresistive TMR2103, with a number of 2 to 4 elements, which are linearly and evenly distributed on the center line of the printed circuit board (PCB) surface;

[0011] The NdFeB-silicone elastomer magnetic film has triangular grooves distributed in an array on its surface; the number of the arrays on the NdFeB-silicone elastomer magnetic film is the same as the number of the arrays in the PDMS elastomer;

[0012] A wire is connected to the aluminum foil, and the other end of the wire is grounded;

[0013] The neodymium iron boron - silicone elastomer magnetic thin film is made by mixing neodymium iron boron particles and silicone elastomer prepolymer in a mass ratio of 3:1;

[0014] The PDMS elastomer is made by mixing PDMS main agent and curing agent in a mass ratio of 15:1;

[0015] In the described triangular groove array, the triangle is an equilateral triangle with a side length of 1.5 - 2 mm, a left - right spacing of 2 - 3 mm, an up - down spacing of 2 - 3 mm, and a depth of 1 - 2 mm;

[0016] The thicknesses of the upper and lower two layers of the PDMS elastomer film are 0.9 - 1.1 mm and 1.4 - 1.8 mm respectively; the height of the cylinders in the cylinder array is 1.8 - 2.2 mm, and the diameter is 1.8 - 2.2 mm;

[0017] The described array is a rectangular array of 3 - 7×3 - 7;

[0018] The overall length of the magnetic sensor is 18 - 25 mm, and the width is 18 - 22 mm;

[0019] The thickness of the magnetic thin film is 1.8 - 2.2 mm, and the thickness of the aluminum foil is 0.015 - 0.02 mm.

[0020] The substantial features of the present invention are:

[0021] In the current technology, the magnetic film is all in a planar structure, which will cause low flexibility in magnetic field regulation, slow dynamic response, and poor mechanical adaptability; the present invention adopts a grid - shaped magnetic film, which can detect tiny magnetic field changes and is suitable for high - precision measurement. Compared with the uniformly distributed neodymium iron boron particles, the chain - like micro - structure formed by the neodymium iron boron particles in the grid gaps has a greater impact on the change of the internal magnetic flux density of the sensor under pressure. The elastomer is composed of many small cylinders, which increases the space for elastic deformation and can detect deformation more accurately.

[0022] In terms of the material of the magnetic thin film, the current magnetostrictive thin film is changed to a neodymium iron boron thin film, and its characteristics of ultra - high magnetic performance, micro - nano process compatibility, and high - frequency response ability are utilized to achieve more sensitive detection of tactile and non - tactile signals, higher - frequency dynamic response, reduction of energy loss, and improvement of efficiency.

[0023] In addition, by adding a triboelectric structure (aluminum foil), the electrical signals generated by the friction between the magnetic film and the aluminum foil can be used to decouple the tactile mode and the non - tactile mode, and the two modes can be judged more timely and accurately.

[0024] The beneficial effects of the present invention are:

[0025] 1. The sensor consists of a neodymium iron boron - silicone elastomer magnetic thin film and a tunneling magnetoresistance (TMR) element. Among them, the magnetic thin film serves as the sensing part, combining the high magnetic properties of neodymium iron boron and the excellent flexibility of silicone elastomer; the TMR element serves as the detection part, featuring high sensitivity. The two work together to achieve precise detection of tactile signals. Figure 6 It can be seen the relationship between the pressure F applied to the grid - shaped tactile sensor and the output voltage U of the TMR. The output voltage of the TMR element shows a good linear relationship with the applied pressure within the range of 0 - 7N, and the output voltage can remain stable under a constant pressure. When the pressure is applied to about 8N, the output voltage curve starts to slow down. When the pressure reaches 18N, the maximum output voltage is 1216.1mV, and the maximum sensitivity is 126mV / N.

[0026] 2. In the non - tactile mode, Figure 7 It can be seen the relationship between the distance between the magnetic object and the sensor and the output voltage U of the TMR in the non - tactile mode of the sensor, and the difference in the output voltage waveforms is relatively obvious. The magnetic object starts to approach from a distance of 10 mm from the magnetic film. As the distance gets closer, the relative change in the output voltage becomes larger. There is a good correspondence between the relative change in the output voltage and the distance of the target object, and the stability and accuracy do not decrease, ensuring a reliable electrical output. In addition, within the range of 10 mm, the output signal and the distance are mainly linearly related, indicating good linearity.

[0027] 3. The tactile mode and the non - tactile mode can be distinguished according to the characteristics such as the amplitude, waveform, or direction of the electrical signal output on the aluminum foil. Figure 5 It can be seen that during the transition from the non - tactile mode to the tactile mode, the single - electrode triboelectric nanogenerator outputs a positive voltage signal. When the target object is in full contact with the magnetic thin film, the target object enters a stable state and the voltage signal disappears. When transitioning from the tactile mode to the non - tactile mode, a reverse voltage signal is generated. When the target object completely detaches from the surface of the magnetic thin film, the voltage signal disappears. This realizes the decoupling of the critical state between the two modes. The experimental results are as Figure 8 shown. When the target object contacts or moves away from the sensor, the output voltage curve generated by the internal single - electrode triboelectric nanogenerator becomes the mode - distinguishing signal. The signal is positive when in contact and negative when separated. In this way, the decoupling of the tactile mode and the non - tactile mode is achieved, and the two modes can be judged accurately and in a timely manner by observing the positive and negative of the output signal on the aluminum foil. The advantage of using a single - electrode triboelectric nanogenerator for mode decoupling is that when the target object contacts the magnetic film, it can generate an instantaneous voltage during the transition process.

[0028] 4. The present invention's silicone elastic substrate is made of a PDMS elastomer bonded to a printed circuit board. The small cylindrical design increases the space for elastic deformation, enabling more precise sensing of force changes compared to traditional elastomers. It also maintains the distance between the NdFeB-silicone elastomer magnetic film and the TMR, leaving sufficient space for the magnetic film to deform. The PDMS is cured directly around the TMR, providing a protective buffer while also securing the TMR at the optimal operating magnetic field strength, improving sensor sensitivity. This is compared to other TMR locations on the circuit board, where the strongest magnetic field intensity is not directly above the TMR. Consequently, the TMR detects less accurate magnetic field density changes and cannot effectively transmit signals.

[0029] 5. Compared with the previously disclosed patents, the grid structure can increase the flexibility and ductility of the magnetic film, and the deformation under the same pressure is more obvious. Compared with uniformly distributed NdFeB particles, the NdFeB particles in the grid gap have a greater impact on the change of the magnetic flux density inside the sensor under pressure, and are easier to detect small magnetic field changes than planar structures.

[0030] 6. The preparation process of the present invention is simple, low-cost, and does not require additional complex signal processing circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the overall structural assembly diagram of the soft grid magnetic sensor for dual-modal sensing;

[0032] Figure 2 This is a disassembled diagram of the various components of the dual-modal sensing soft grid magnetic sensor;

[0033] Figure 3 This is a three-dimensional image of the soft elastomer PDMS substrate of the soft grid magnetic sensor for dual-modal sensing;

[0034] Figure 4 This is a top view of the printed circuit board of the soft grid magnetic sensor for dual-modal sensing;

[0035] Figure 5 Schematic diagram of a single-electrode triboelectric nanogenerator in a soft-grid magnetic sensor for dual-modal sensing;

[0036] Figure 6 is the output voltage diagram of the dual-modal sensing soft grid magnetic sensor under pressure;

[0037] Figure 7 It is a graph of relative voltage changes at different distances between the magnetic object and the sensor;

[0038] Figure 8 is the modal discrimination signal diagram of the sensing system output by the single-electrode triboelectric nanogenerator;

[0039] Figure 9 It is the distribution diagram of the tensile force of the magnetic thin film under different ratios of neodymium iron boron particles and organosilicon elastomer prepolymer;

[0040] Among them, 1 - neodymium iron boron - organosilicon elastomer magnetic thin film, 2 - aluminum foil, 3 - PDMS elastomer, 4 - X - axis tunnel magnetoresistance TMR element, 5 - printed circuit board PCB, 6 - external circuit wire connected to the aluminum foil, 7 - groove inlaid with TMR. Specific implementation mode

[0041] The present invention designs a dual - mode flexible sensor based on the neodymium iron boron magnetoconductance effect, triboelectric effect and TMR tunnel magnetoresistance effect, which is composed of a double - layer sensing device and a testing device with a magnetic induction grid structure, and is composed of a magnetic thin film, aluminum foil, PDMS flexible substrate, TMR sensor array and signal processing circuit. The tactile mode includes perceiving physical contact or interaction with an object, while the non - tactile mode refers to perceiving an object or environment without direct physical contact. When there is no contact, the distance when a magnetic object approaches is detected by the change of the magnetic field. In the space magnetic field generated by the magnetic thin film, the magnetic field line density and distribution around the magnetic object change. When a magnetic object approaches the sensor, it will cause changes in the spatial distribution and magnitude of the magnetic flux density around the sensor. When an external force acts, the deformation of the thin film leads to the reconstruction of internal magnetic domains and changes in the surrounding magnetic field; the highly sensitive TMR element converts the magnetic field fluctuation into a magnetoresistance change through the tunnel magnetoresistance effect, and then outputs a corresponding voltage signal through a bridge circuit, and finally the signal is processed and visualized by a data acquisition system.

[0042] Based on the sliding morphology of the finger pad and the sensing mechanism of human skin, a multi-layered grid-shaped magnetic sensor was designed. This sensor senses and decouples tactile and non-tactile signals, achieving dual-mode signal monitoring on a single sensing platform. The top layer consists of a magnetized square grid film. The surface pattern of the film consists of neatly arranged triangles, forming a parallel grid structure with the same width from top to bottom. Compared to existing planar thin-film sensors, the grid-shaped film has a smaller contact area and is more easily deformed under low contact forces, resulting in higher sensitivity of the sensing unit. Furthermore, the grid-shaped film can detect minute magnetic field changes, making it suitable for high-precision measurements. Compared to uniformly distributed NdFeB particles, the chain-like microstructure formed by the NdFeB particles in the grid gaps has a greater impact on the changes in the sensor's internal magnetic flux density under pressure. Furthermore, the grid layout suppresses ambient noise, improving signal quality. Furthermore, the grid-shaped film shape reduces friction between the sensing unit and the contact surface during sliding, thereby reducing wear and testing costs, and extending the life of the tactile sensor unit. The middle layer is a square aluminum foil that serves as the electrode layer. It has a low elastic modulus, excellent bending and tensile properties, and fatigue resistance, giving the sensor unit strong stability and durability to withstand the downward pressure of the film. The third layer is a PDMS elastic substrate, consisting of two layers of PDMS film and a 5×5 cylindrical array. This increases the space for elastic deformation and can detect changes in tangential force. The bottom layer embeds a tunnel magnetoresistive (TMR) magnetic sensor element as a magnetic detection element. The tunnel magnetoresistive (TMR) element is soldered to a printed circuit board (PCB).

[0043] The magnetic film has dual functions: one is to sense external forces, and the other is to provide a stable bias magnetic field to ensure that the TMR element operates in the linear range. The PDMS flexible substrate is used to sense the surrounding stress and provide sufficient elastic deformation space, while buffering external mechanical forces. Aluminum foil is attached to the substrate of the magnetic film as an electrode layer to form a single-electrode triboelectric nanogenerator, such as Figure 5 As shown, at the moment an object contacts and separates from the magnetic film, the transfer of charge on the electrode surface causes an electrical signal to be generated in the external circuit. The characteristics of this electrical signal are exploited for dual-mode decoupling. When a tactile force is applied to an object and the magnetic film, positive and negative charges accumulate on the contact surface due to the different charge characteristics of positive and negative charges. Typically, positive charges accumulate on the magnetic contact object, while negative charges accumulate on the magnetic film. When the force is removed, the target object instantly separates from the magnetic film, and electrons transfer from the bottom aluminum electrode to the ground, generating a positive current signal in the external circuit of the single-electrode triboelectric nanogenerator. When the tactile force is applied again, electrons flow from the ground back to the bottom aluminum electrode, generating a reverse current.

[0044] The side length of the neodymium iron boron - silicone elastomer magnetic film part of the soft grid - shaped magnetic sensor of the present invention is 20 mm, and the thickness is 2 mm; the PDMS elastic substrate part is 20 mm long, 20 mm wide, and 4 mm high. The magnetic - sensitive direction of TMR2103 is the X - axis (the X - axis refers to the axis parallel to the height of the sensor), with a length of 3 mm, a width of 3 mm, and a height of 1.45 mm. The TMR element and the neodymium iron boron - silicone elastomer magnetic film are both placed parallel to the printed circuit board. When a magnetic object approaches the sensor, it will cause changes in the spatial distribution and magnitude of the magnetic flux density around the sensor. When the sensing unit is subjected to an extrusion force, the magnetic film undergoes elastic deformation and causes changes in the internal magnetic domains. TMR converts the detected magnetic field change into a change in internal magnetoresistance, and then the change in internal magnetoresistance is converted into a change in voltage through a bridge circuit and output. The detection position is directly above TMR2103.

[0045] The invention is further described in detail below. This embodiment is only a specific description of the invention and is not regarded as a limitation of the protection scope.

[0046] Embodiment 1

[0047] The overall structure assembly diagram of the soft grid - shaped magnetic sensor described in the present invention is as shown in Figure 1 and includes a neodymium iron boron - silicone elastomer magnetic film 1, an aluminum foil 2, a PDMS elastomer 3, a TMR element 4, and a printed circuit board PCB5;

[0048] The disassembly diagram of each part structure of the sensor is as shown in Figure 2 and shows that the TMR element 4 is soldered on the printed circuit board PCB5, the PDMS elastomer 3 covers the TMR element 4 and covers the printed circuit board PCB5; an aluminum foil 2 is covered on the PDMS elastomer 3, and the neodymium iron boron - silicone elastomer magnetic film 1 is on the aluminum foil 2;

[0049] The structure of the PDMS elastomer 3 is as shown in Figure 3 and is a "sandwich" structure, composed of upper and lower thin films and a small cylindrical array in the middle; the projection area is the same as that of the printed circuit board PCB5; the lower thin film has a strip - shaped groove for covering the TMR element 4; the array is a 5×5 square array;

[0050] The thicknesses of the upper and lower thin films of the PDMS elastomer 3 are 1 mm and 1.6 mm respectively; the height of the cylinders in the cylindrical array is 2 mm, and the diameter is 2 mm; the overall height of the PDMS elastomer 3 is 4.6 mm.

[0051] The PDMS elastomer 3 is made by mixing PDMS base agent and curing agent in a ratio of 15:1;

[0052] The TMR element 4 described above is the TMR2103 with X-axis tunneling magnetoresistance, and the number is 3, which are linearly and evenly distributed on the center line of the surface of the printed circuit board PCB5;

[0053] For the neodymium iron boron-silicone elastomer magnetic thin film 1 described above, there are triangular grooves with an array distribution of 5×5 on the surface; the array on the neodymium iron boron-silicone elastomer magnetic thin film 1 overlaps with the projection of the array in the PDMS elastomer 3, that is, the center lines of the small cylinders and the corresponding upper triangles overlap.

[0054] The neodymium iron boron-silicone elastomer magnetic thin film 1 described above is made by mixing neodymium iron boron particles and silicone elastomer prepolymer in a mass ratio of 3:1;

[0055] In the described triangular array, the triangles are equilateral triangles with a side length of 1.73 mm, a left-right spacing of 2.5 mm, an up-down spacing of 2.03 mm, and a depth of 2 mm; a parallel grid structure with the same width at the top and bottom is formed;

[0056] The silicone elastomer prepolymer described above is made by mixing the A agent and B agent of the Ecoflex 00-30 series of Smooth-On company in a ratio of 1:1;

[0057] The preparation method of the neodymium iron boron-silicone elastomer magnetic thin film 1 described above includes the following steps:

[0058] The silicone elastomer is made by mixing the A agent and B agent of the Ecoflex 00-30 series in a ratio of 1:1. Mix the silicone prepolymer and Nd2Fe 14 B1 magnetic particles in a mass ratio of 1:3, put them into a blender and stir for 120 minutes to prepare the neodymium iron boron-silicone prepolymer. Place it in a vacuum environment for 30 minutes to eliminate air bubbles. After eliminating air bubbles, pour it into a 3D printed resin mold and cure it in a nitrogen environment at 80 °C for 120 minutes for preliminary curing; then continue to cure it in a nitrogen environment at 120 °C for 60 minutes to completely remove the air bubbles in the composite film; finally, cool it at 25 °C for 60 minutes to completely cure the film. After curing, take it out of the mold to obtain the magnetic thin film. Put the obtained flexible film into a magnetizer for magnetization. In order to make the film decoupled, the film is magnetized in multiple poles along the horizontal center line to obtain the neodymium iron boron-silicone elastomer magnetic thin film. The magnetization is a well-known technology and can also be commissioned commercially.

[0059] The planar structure is a continuous two-dimensional entity that can resist deformation through a uniform stress distribution when subjected to external forces. The grid structure is composed of multiple nodes and rods connected together, and each node has multiple degrees of freedom (translation and rotation). Under the action of external forces, the node displacements will be transmitted and superimposed through the rods, resulting in an amplified overall deformation. The deformation of grid structures with different depths was simulated using the COMSOL model, and the optimal depth was determined to be 2 millimeters.

[0060] Array correspondence can reduce the interference between the grid and the cylindrical gap, and increase the deformation space both above and below. If the grid uses non-triangular units such as squares or hexagons, its geometric stability is poor. For example, square units are prone to diamond deformation (shear deformation) when subjected to force, while triangular units can effectively resist such deformation due to their natural geometric rigidity (triangle stability principle). The triangle is the only stable structure in geometry that does not require additional support, and its grooves can effectively disperse stress when bearing loads, reducing the risk of deformation. In contrast, the right angles of square grooves are prone to stress concentration, while circular grooves have weaker bending resistance.

[0061] The printed circuit board with TMR2103 soldered on it was laid flat, and the aluminum foil, magnetic film, PDMS elastic substrate and the bottom PCB were bonded using PDMS special glue to obtain a complete magnetic sensor; the aluminum foil was 0.015mm thick.

[0062] The X-axis TMR elements are connected to the acquisition card to detect the output on the center line. The wires connected to the aluminum foil are also connected to the acquisition card to output voltage signals. Figure 1 As shown in the figure, it is 20mm long, 20mm wide and 6mm high. When stress is applied downward directly above the TMR2103, the magnetic film and elastic substrate undergo elastic deformation downward. After the pressure is removed, they can quickly return to their original shape and no plastic deformation occurs within the force measurement range.

[0063] The printed circuit board substrate is made of resin; TMR2103 is soldered on the surface of the circuit board; the printed circuit board is 20 mm long and 20 mm wide and can be worn on a robotic finger as an intelligent finger pad to detect the pressure and real-time position of an object.

[0064] The top view of the printed circuit board of the tactile sensor is as follows Figure 4 As shown in the figure, TMR indicates the soldering position of TMR2103, where the VCC output terminal is connected to a 5V DC power supply to power the TMR, and the V+ and V- output terminals are connected to an acquisition card to collect the output voltage of the TMR.

[0065] The diameter of the NdFeB magnetic particles is 100-200 μm, and the chemical formula of the NdFeB magnetic particles is Nd2Fe 14 B1, that is, the atomic ratio of Nd, Fe, and B in a NdFeB molecule is 2:14:1.

[0066] Example 2

[0067] On the basis of the same method as in Example 1, the prepared NdFeB-silicone elastomer flexible film was magnetized horizontally and radially, and a magnetized film along the length direction and a magnetized film along the thickness direction were obtained after magnetization.

[0068] The obtained films magnetized along the thickness direction and the films magnetized along the center line were respectively adsorbed on the surface of a smooth magnet. A tensiometer was used to pull the two films obtained by different magnetization methods. The experimental results showed that the film magnetized along the center line could withstand a greater tensile force and had a higher magnetic field strength than the film magnetized only along the thickness direction. Therefore, it was determined that the magnetization method for fabricating the NdFeB-silicone elastomer magnetic film was magnetization along the center line.

[0069] COMSOL was used to simulate the two magnetization methods. The results showed that when magnetized along the thickness direction, the magnetic field was stronger at the boundary of the magnetic film and weaker in the middle of the magnetic film. When magnetized along the center line direction, the magnetic field was stronger at the center line of the magnetic film. Therefore, it was determined that the magnetization method for the magnetic film was magnetization along the center line.

[0070] Example 3

[0071] The static normal force characteristics of the dual-mode sensor were tested. The main purpose of this example was to determine the static force measurement range, input-output relationship, and sensitivity to static force of the sensor.

[0072] Construction of the experimental platform: The test platform included a digital display push-pull tensiometer (Eidelberg HP-30), a DC regulated power supply (HY3005B), a dynamic data acquisition card (DH8301), and a computer; as Figure 1 shown, the sensor was assembled and fixed on the base of the digital display push-pull tensiometer. The DC regulated power supply was used to supply power to the TMR element, and the output of the TMR element was connected to the data acquisition card.

[0073] Experimental process and results: The step size was set to 0.5 N. A normal force vertically downward was applied using the digital display push-pull tensiometer, with a maximum of 0 - 18 N. The external force was maintained for several seconds each time the external force was applied, and then the external force was removed. The output voltage of the TMR element 4 at the center of the sensor was as Figure 6 shown. The output voltage of the TMR element 4 showed a good linear relationship with the applied pressure in the range of 0 - 7 N. The output voltage could remain stable under a constant pressure and quickly returned to 0 after the external force was removed. The sensor had good static characteristics. When the pressure was applied to about 8 N, the output voltage curve began to flatten. When the pressure reached 18 N, the maximum output voltage was 1216.1 mV, and the maximum sensitivity was 126 mV / N.

[0074] Example 4

[0075] On the experimental platform built in Example 3, the relationship between the distance between the magnetic object and the magnetic film of the sensor when the magnetic object approached the sensor was tested. The main purpose of this example was to study the input-output correspondence of the grid-shaped magnetic sensor and the information mapping of distance perception. As Figure 1The assembled sensor is shown and fixed on the base of the digital display push-pull force gauge. A DC regulated power supply is used to supply power to the TMR element, and the output of the TMR element is connected to the data acquisition card. As Figure 7 shown, V0 and ΔV respectively represent the initial voltage when the target object approaches from a distance and the change in the output voltage of the sensor. The magnetic object starts to approach from a distance of 10 mm from the magnetic film. As the distance gets closer, the relative change in the output voltage becomes larger and larger. There is a good correspondence between the relative change in the output voltage and the distance of the target object, and the stability and accuracy do not decrease, ensuring a reliable electrical output. In addition, within the range of 10 mm, the output signal and the distance are mainly linearly related, indicating good linearity.

[0076] Example 5

[0077] On the experimental platform built in Example 3, the change in the voltage signal output on the aluminum foil during the process of the target object approaching, contacting, and then separating is tested. The main purpose of this example is to study the decoupling function of the electrical signal generated by the single-electrode triboelectric nanogenerator in the grid-shaped magnetic sensor. According to Figure 1 shown, the assembled sensor is fixed on the base of the digital display push-pull force gauge, and the external circuit wire connected to the aluminum foil is connected to the data acquisition card. As Figure 8 shown, when the target object contacts or moves away from the sensor, the output voltage curve generated by the internal single-electrode triboelectric nanogenerator becomes a mode discrimination signal. The signal is positive when contacting and negative when separating. In this way, the decoupling of the tactile mode and the non-tactile mode is realized, and the two modes can be judged accurately and in a timely manner by observing the positive and negative of the output signal on the aluminum foil.

[0078] The relative change in the output voltage of the TMR sensor can also roughly estimate the situation of dual-mode decoupling. However, the voltage change of the TMR sensor is mainly caused by the significant change in magnetic flux in the sensing layer. There is an intermediate transition process during the mode conversion, and the magnetic flux in the sensing layer does not change significantly. The advantage of using the single-electrode triboelectric nanogenerator for mode decoupling is that it can generate an instantaneous voltage during the transition process when the target object contacts the magnetic film. Therefore, combining the signal of the triboelectric nanogenerator can improve the accuracy and real-time decoupling of the signal.

[0079] Examples 6 - 8

[0080] During the preparation of the neodymium iron boron - silicone elastomer magnetic thin film, the mixing ratio of the neodymium iron boron magnetic particles and the silicone elastomer prepolymer is changed to 1:1, 2:1, and 4:1. The flexible thin films produced are all magnetized along the center line, and other production steps remain unchanged;

[0081] Alternating magnetization films with different mixing ratios are adsorbed on the surface of a smooth magnet, and a tensiometer is used to pull the alternating magnetization films with different ratios to obtain a distribution diagram of different ratios and the applied pulling force as shown in Figure 9 It can be seen from the figure. The experiment found that when the mixing ratio of neodymium iron boron magnetic particles and organosilicon elastomer prepolymer is 1:1, the magnetic field strength of the film is not high; when the mixing ratio of neodymium iron boron magnetic particles and organosilicon elastomer prepolymer is 4:1, the film begins to show rigidity and its flexibility deteriorates. Therefore, the optimal ratio for fabricating the neodymium iron boron-organosilicon elastomer magnetic film is determined to be 3:1.

[0082] As can be seen from the above embodiments, the dual-mode magnetic sensor of the present invention can be worn as an intelligent finger pad on a robotic finger for applications in tactile and non-tactile sensing. In the non-tactile mode, the distance when a magnetic object approaches is detected by the change in the magnetic field. In the spatial magnetic field generated by the magnetic film, the magnetic field line density and distribution around the magnetic object change. In the tactile mode, after the neodymium iron boron-organosilicon elastomer magnetic film is stressed and causes the soft grid-shaped magnetic sensor to deform, the deformation of the PDMS elastic substrate causes the relative position between the magnetic film and the TMR to change. At the same time, the relative position of the neodymium iron boron magnetic particles in the magnetic film changes. Both of these cause the magnetic field strength detected by the TMR to change. The change in the magnetic field will cause a change in the internal magnetoresistance of the TMR, and then the change in the internal magnetoresistance is converted into a change in voltage and output through a bridge circuit. At the same time, combined with a triboelectric nanogenerator, the tactile mode and the non-tactile mode can be distinguished according to the characteristics such as the amplitude, waveform or direction of the output electrical signal, realizing the decoupling of the two modes.

[0083] The software or protocols involved in the present invention are all well-known technologies.

[0084] Matters not covered in the present invention are well-known technologies.

Claims

1. A soft grid tactile sensor for tactile and non-tactile perception, characterized in that, The sensor includes a neodymium iron boron-silicone elastomer magnetic thin film, aluminum foil, PDMS elastomer, TMR element, and printed circuit board; Among them, the TMR element is soldered on the printed circuit board, the PDMS elastomer covers the TMR element and covers the printed circuit board (PCB), the aluminum foil is covered on the PDMS elastomer, and the neodymium iron boron-silicone elastomer magnetic thin film is on the aluminum foil; The PDMS elastomer has a "sandwich" structure and is composed of two upper and lower thin films and a small cylindrical array in the middle. The lower thin film has a strip-shaped groove for covering the TMR element; The TMR element is TMR2103 with X-axis tunneling magnetoresistance, and the number is 2 to 4, linearly and evenly distributed on the center line of the surface of the printed circuit board (PCB); The surface of the neodymium iron boron-silicone elastomer magnetic thin film has triangular grooves distributed in an array; the number of arrays on the neodymium iron boron-silicone elastomer magnetic thin film is the same as the number of arrays in the PDMS elastomer.

2. The soft grid tactile sensor for tactile and non-tactile perception according to claim 1, characterized in that, The neodymium iron boron-silicone elastomer magnetic thin film is made by mixing neodymium iron boron particles and silicone elastomer prepolymer in a mass ratio of 3:1; The PDMS elastomer is made by mixing PDMS base and curing agent in a mass ratio of 15:

1.

3. The soft grid tactile sensor for tactile and non-tactile perception according to claim 1, characterized in that, In the triangular groove array, the triangle is an equilateral triangle with a side length of 1.5 to 2 mm, a left-right spacing of 2 to 3 mm, an up-down spacing of 2 to 3 mm, and a depth of 1 to 2 mm; The thicknesses of the upper and lower thin films of the PDMS elastomer are 0.9 to 1.1 mm and 1.4 to 1.8 mm respectively; the height of the cylinders in the cylindrical array is 1.8 to 2.2 mm, and the diameter is 1.8 to 2.2 mm.

4. The soft grid tactile sensor for tactile and non-tactile perception according to claim 1, characterized in that, The array is a 3 to 7×3 to 7 rectangular array.

5. The soft grid tactile sensor for tactile and non-tactile perception according to claim 1, characterized in that, The overall length of the magnetic sensor is 18 to 25 mm, and the width is 18 to 22 mm.

6. The soft grid tactile sensor for tactile and non-tactile perception according to claim 1, characterized in that, The thickness of the magnetic thin film is 1.8 to 2.2 mm, and the thickness of the aluminum foil is 0.015 to 0.02 mm.

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