Resistance type whisker sensor and electronic skin

Abstract

The utility model provides a resistance type whisker sensor, an electronic skin and a preparation method thereof, the resistance type whisker sensor comprises a substrate layer, a liquid metal-carbon nano tube sensitive material layer and a packaging layer, the liquid metal-carbon nano tube sensitive material layer is packaged between the substrate layer and the packaging layer, the liquid metal-carbon nano tube sensitive material forms a conductive network, the conductive network is composed of liquid metal particles and carbon nano tubes generated by laser ablation, and the liquid metal particles are connected through the carbon nano tubes. In the nature, many organisms realize high-precision tactile detection by virtue of tentacles, for example, beards of animals such as cats and rats can sense tiny changes of the surrounding environment and recognize the shape, texture and vibration information of objects, and the high-sensitivity tactile sensing capability plays an important role in survival and environmental adaptation of the animals. The utility model provides the electronic whisker with high sensitivity, and provides the electronic skin based on the whisker sensor array.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of tactile sensing, in particular to a resistance type feeler sensor, electronic skin and its preparation method. TECHNICAL BACKGROUND

[0002] Electronic skin (E-Skin) is an intelligent sensing system that simulates the functions of human skin. Its core lies in realizing multi-modal information acquisition such as tactile perception, temperature detection, humidity measurement, and strain response of the environment through flexible electronic technology and sensor networks. This technology has broad application prospects in the fields of bionic robots, intelligent medical care, wearable devices, and human-computer interaction. With the advancement of artificial intelligence technology, robots play an increasingly important role in industrial manufacturing, medical rehabilitation, and social services. How to endow robots with human-like tactile perception ability has become one of the core issues in current research.

[0003] The utility model patent (publication number CN118654788, publication date 2024.09.17, application number 202411132284.X) discloses a piezoresistive flexible pressure feeler sensor. The utility model includes a circular base, a circular top cover, cilia, and a needle cone. The needle cone is fixed to the top of the circular base, and the top of the needle cone is inserted into the groove at the bottom of the circular top cover. The top center of the circular top cover is fixedly connected with a supporting cylinder. The cilia are inserted into and fixedly connected with the supporting cylinder. The diameter of the circular top cover is smaller than that of the circular base. A flexible film is connected between the circular top cover and the circular base. Multiple groups of sensitive grids are pasted on the flexible film and evenly arranged along the circumference of the flexible film. This patent has the following problems: the mechanical structure is complex. The receptors of the feeler sensor in this patent are located on the base, i.e., around the root of the feeler, and include multiple receptors. The structure is complex, and multiple sensors are needed to cooperate to identify the bending direction of the feeler. However, the receptors of the feeler sensor in this invention are located on the feeler, the structure is simple, and a single receptor can identify bending in two directions.

[0004] Invention patent (publication number CN119043530, publication date 2024.11.29, application number 202411175519.3) discloses a replaceable whisker frictional electrostatic sensor based on liquid metal, which comprises a sensor body and a whisker body. The upper end of the sensor body is provided with a protrusion, the middle part of the protrusion is provided with a plug-in interface, the lower end of the whisker body is provided with a metal block, the metal block is inserted into the plug-in interface, and the metal block and the plug-in interface are detachably connected. The inside of the whisker body is provided with liquid metal, and the lower part of the liquid metal is provided with a lead wire for transmitting signals, and the lead wire is electrically connected with the sensor body. The patent has the following problems: the receptor of the whisker sensor in the patent is based on the principle of frictional electrification. Although the whisker will generate an electric signal when it is bent, the electric signal will only be generated at the moment of bending. Even if the bending state is maintained, the electric signal will not be maintained, but will quickly decay to 0. Therefore, this type of sensor can only be used for dynamic measurement, and is not suitable for static measurement. The whisker sensor of the present invention is a resistance type sensor, and the electric signal is only related to the state of the whisker at that time. Therefore, it is suitable for both dynamic and static measurement.

[0005] Utility model patent (publication number CN222086917, publication date 2024.11.29, application number 202420520349.7) discloses a one-dimensional roll-shaped structure flexible strain sensor. The flexible strain sensor is prepared in the following way: preparation of liquid metal ink; printing liquid metal circuit on the base material according to the predetermined design pattern shape by using screen printing process to generate the conductive layer; cutting the base material printed with liquid metal circuit into a preset sensor size by using laser; hot pressing a layer of elastic protective film on the base material printed with liquid metal circuit to obtain a two-dimensional plane sensor; rolling up the two-dimensional plane sensor from one side of the long side to obtain a one-dimensional roll-shaped structure flexible strain sensor; adding a signal transmission interface to the flexible strain sensing structure to obtain a one-dimensional roll-shaped structure flexible strain sensor. The utility model has the following disadvantages: one-dimensional sensor, and the existing electronic skin touch sensing ability is single.

[0006] Currently, electronic skin is usually realized by printing / depositing a two-dimensional pressure sensor array on a flexible substrate, wherein the selection of sensor sensitive material directly determines the performance of the resistance skin. In recent years, researchers have developed various conductive materials with high sensitivity, flexibility and durability, such as carbon nanomaterials (graphene, carbon nanotubes, carbon black, etc.), liquid metals (such as EGaIn, Galinstan), metal nanomaterials (such as nano-silver wire, gold nanoparticles, etc.), conductive polymers (such as PEDOT:PSS, polyaniline, etc.) and MXene (Ti3C2T x). The application of these new materials significantly improves the sensitivity, response speed, mechanical durability, and flexible adaptability of resistive skin tactile perception. However, existing electronic skin technology based on two-dimensional sensor arrays still faces several key problems:

[0007] First, the existing electronic skin tactile perception ability is single: current electronic skin mainly uses pressure, capacitance, piezoresistance, etc. sensors to perceive normal pressure signals, and has limited detection capability for shear force, vibration, flow field changes, etc. information, making it difficult to achieve high-precision multi-modal perception. Second, the sensors in existing electronic skin have poor flexibility and compliance. Most electronic skin and sensors are made of rigid or semi-rigid materials, which lack flexibility and affect their application on complex curved surfaces, and are also difficult to adapt to dynamic interfaces. Third, the sensor array signal processing is complex: electronic skin systems usually need to integrate a large number of sensor units, resulting in large amounts of signal data, making it difficult to achieve real-time, low-power data processing and sensor fusion. Fourth, the scalability of the sensor is limited: traditional electronic skin sensors use two-dimensional layout and lack three-dimensional structural design, limiting their application in dynamic environments.

[0008] To address these challenges, a resistive tactile sensor and its electronic skin need to be developed. Unlike traditional flexible tactile sensors, the core advantage of bionic tactile sensor is flexible structure, rich perception mode, and strong environmental adaptability, which can provide more close-to-biological tactile detection capability. Practical new type content

[0009] The electronic skin based on tactile sensor array is proposed in the present utility model. In nature, many organisms rely on tactile hairs to achieve high-precision tactile detection, such as the whiskers of cats, mice, and other animals, which can perceive small changes in the surrounding environment and identify the shape, texture, and vibration information of objects. This high-sensitivity tactile perception capability plays a crucial role in the survival and environmental adaptation of animals. Inspired by this, bionic tactile sensors have gradually become an important research direction in the field of tactile perception in recent years. Compared with traditional flexible pressure sensors, tactile sensors can detect small contact forces, shear forces, wind field changes, etc. information, and have wider application potential.

[0010] Therefore, the purpose of the present utility model is to disclose a resistive tactile sensor,

[0011] Another purpose of the present utility model is to disclose an electronic skin of a resistive tactile sensor,

[0012] Still another purpose of the present utility model is to disclose a preparation method of an electronic skin of a resistive tactile sensor.

[0013] Specifically, the resistance type whisker sensor comprises a substrate layer, a liquid metal-carbon nanotube sensitive material layer and a packaging layer, wherein the liquid metal-carbon nanotube sensitive material layer is packaged between the substrate layer and the packaging layer, the liquid metal-carbon nanotube sensitive material forms a conductive network, the conductive network is composed of liquid metal particles and carbon nanotubes, the liquid metal particles are connected through the carbon nanotubes, and the carbon nanotubes form a conductive bridge between the liquid metal particles. The conductive network is mainly composed of two parts of liquid metal particles and carbon nanotubes. The liquid metal particles have excellent conductivity, while the carbon nanotubes have weak conductivity. The resistance of the conductive pattern mainly comes from the carbon nanotube part. Therefore, when the conductive network is stretched or compressed, the length of the carbon nanotube bridge will be correspondingly elongated or shortened, thereby causing the rapid increase or decrease of the resistance of the point network.

[0014] The liquid metal-carbon nanotube sensitive material layer is prepared by using liquid metal and polyacrylonitrile (PAN) as basic materials, preparing conductive ink through ultrasonic dispersion method, and constructing a conductive network by using laser ablation technology.

[0015] The substrate layer (11) is at least one of polyethylene terephthalate (PET) film or polyimide (PI) film, and the packaging layer (13) is at least one selected from polyurethane, polydimethylsiloxane or PET.

[0016] An electronic skin composed of a whisker sensor array comprises a plurality of the above-mentioned whisker sensors, and the plurality of whisker sensors are arranged in a certain direction and distance to be arranged on a soft substrate in an array arrangement mode to form a whisker sensor array. Specifically, the conductive joints of the whisker sensors are vertically inserted into and fixed on the soft substrate to form an array, and then the conductive joints of the sensor array are connected to a detection circuit in sequence through wires. Through analysis software, the whisker sensor can perceive normal pressure and identify the distribution of the pressure. The sensor array is connected into a data acquisition circuit in a row-column scanning mode, that is, the detection circuit is arranged in a row-column mode. When a row or a column is activated each time, the signals of the sensors at the intersection of the corresponding row and column will be read and processed. The signal reading and processing are realized through a Wheatstone bridge circuit.

[0017] Optionally, in the above-mentioned whisker sensor electronic skin, the soft substrate is at least one selected from a polydimethylsiloxane (PDMS) substrate, a thermoplastic elastomer substrate or a biodegradable plastic substrate.

[0018] Optionally, by arranging multiple whisker sensors into an array, each whisker sensor is at a different position in the array, and in particular, each whisker sensor is rotated at a different angle (e.g. 0°, 45°, 90°) with its vertical axis as the center, so that the sensor array has different response degrees to shear forces in different directions; in the array, the rotation angle of the whisker (e.g. 0°, 45°, 90°) is changed so that it can detect shear forces in different directions.

[0019] The preparation method of the resistance type whisker sensor comprises the following steps:

[0020] Step 1. Preparation of conductive ink: mixing polyacrylonitrile (PAN) and liquid metal in an ink solvent, and adding a surfactant to prevent particle agglomeration, ultrasonic treatment to convert the liquid metal into liquid metal micro-nanoparticles and uniformly mix with PAN particles to obtain a uniform and stable conductive ink;

[0021] Step 2. Patterning and laser ablation of whisker sensor: using patterning technology to print the above-prepared conductive ink on a rigid substrate, the printed pattern is in an elongated snake pattern with an aspect ratio greater than 5, and the printed pattern is placed in an oven at 80-150°C for drying, the dried pattern is non-conductive, and the dried pattern is ablated by laser to form a conductive pattern;

[0022] Step 3. Packaging of whisker sensor: using polyurethane, polydimethylsiloxane (PDMS) or polyethylene terephthalate (PET) to package the conductive pattern by spin coating, hot pressing, cold pressing or ultrasonic bonding method to complete the preparation of a single whisker sensor.

[0023] The preparation method of the whisker sensor electronic skin comprises vertically inserting and fixing a plurality of whisker sensors in a certain direction and distance on a soft substrate to form an array to form a whisker sensor electronic skin.

[0024] Optionally, in the above preparation method, the soft substrate is selected from at least one of a polydimethylsiloxane (PDMS) substrate, a thermoplastic elastomer substrate or a biodegradable plastic substrate.

[0025] Compared with the prior art, the utility model has the following beneficial effects:

[0026] 1. High sensitivity sensing: the whisker sensor of the utility model is based on liquid metal-carbon nanotube composite conductive material, since the carbon nanotube forms a bridge structure between the liquid metal particles, obvious resistance change can be caused when bending and deforming, so that it can detect micro contact force in the micro-newton (μN) range, and has obvious advantages in fine tactile perception, wind speed detection, vibration detection and the like. For liquid metal conductive materials without carbon nanotube bridge structure, there is no obvious resistance change when bending and deforming.

[0027] 2. Multi-modal information acquisition: In addition to normal force, the tactile sensor can also detect shear force, vibration frequency, fluid dynamics changes, etc., providing more comprehensive tactile feedback for robots and intelligent prostheses.

[0028] 3. Flexible and deformable: Compared with traditional rigid tactile sensors, the tactile sensor is made of flexible materials, which can adapt to complex surfaces and maintain good sensing ability even under large-scale bending or stretching.

[0029] 4. Strong scalability: The tactile sensor can be composed of an array to achieve large-area, distributed tactile sensing, and can be flexibly designed and adjusted according to application requirements.

[0030] These technical advantages make the electronic skin based on the tactile sensor one of the key technologies for future robot tactile sensing systems, and it is expected to be widely used in bionic robots, intelligent prostheses, wearable smart devices, etc. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a structural diagram of a single tactile sensor of the utility model;

[0032] Figure 2 It is a microcosmic change mechanism diagram of the liquid metal-carbon nanotube sensitive material in the tactile sensor of the utility model when deforming;

[0033] Figure 3 It is a different resistance change diagram obtained by bending the tactile sensor in different directions;

[0034] Figure 4 It is an array diagram composed of tactile sensors of the utility model;

[0035] Figure 5 It is an array diagram composed of 0° and 90° tactile sensors of the utility model. DETAILED DESCRIPTION

[0036] The utility model will be described in detail below in combination with the drawings through specific embodiments.

[0037] The principle of the utility model is based on liquid metal-carbon nanotube sensitive material, and a high-sensitivity electronic whisker is prepared by combining laser ablation technology, the electronic whisker is further arranged into an array to form a large-area electronic skin for sensing pressure distribution, and the turning of the whisker in the array is further adjusted for multi-modal mechanical sensing. Finally, a high-sensitivity tactile sensing network is constructed by the flexible whisker sensor, and multi-modal and intelligent sensing of environmental information is realized. The utility model not only helps to break through the bottleneck of the existing electronic skin technology, but also provides an innovative solution for intelligent robots, intelligent prostheses, flexible electronics and other fields.

[0038] As shown in Figure 1 and Figure 2 The resistance type whisker sensor 1 comprises a substrate layer 11, a liquid metal-carbon nanotube sensitive material layer 12 and a packaging layer 13. The sensor is provided with a wiring area 14 and a sensor sensitive band 15, and a conductive connector 16 is arranged at the root; one end of the conductive connector 16 is connected with the liquid metal-carbon nanotube sensitive material layer 12, and the other end is used for connecting a detection circuit. The liquid metal-carbon nanotube sensitive material layer 12 is packaged between the substrate layer 11 and the packaging layer 13, and the liquid metal-carbon nanotube sensitive material layer 12 forms a conductive network.

[0039] The liquid metal-carbon nanotube sensitive material layer 12 is a conductive network prepared by using liquid metal and polyacrylonitrile (PAN) as basic materials, preparing conductive ink by ultrasonic dispersion method and adopting laser ablation technology.

[0040] The liquid metal-carbon nanotube sensitive material layer 12 comprises liquid metal particles 121 and carbon nanotubes 122. In a microscopic state, the liquid metal particles 121 are not conductive due to the isolation of the oxide film, and a conductive network can be formed by introducing the carbon nanotubes 122 as conductive bridges to connect the liquid metal particles 121, the conductive bridges are the carbon nanotubes 122 converted from PAN, the carbon nanotubes 122 are connected with the liquid metal particles 121 at both ends, and the carbon nanotubes 122 form conductive bridges between the liquid metal particles 121. As shown in Figure 2As shown, the conductive network is mainly composed of two parts, liquid metal particles 121 and carbon nanotubes 122 generated by laser ablation, the liquid metal particles 121 are connected by the carbon nanotubes 122, and a stable conductive network is constructed, and the originally non-conductive pattern becomes conductive after the laser ablation due to the PAN being converted into carbon nanotubes 122. The liquid metal particle 121 part has excellent conductivity, and the carbon nanotube 122 part has weak conductivity, so the resistance of the conductive network of the liquid metal-carbon nanotube sensitive material layer 12 mainly comes from the carbon nanotube part, and the conductive pattern is in an elongated and serpentine shape, and the aspect ratio is greater than 5. Therefore, when the conductive network is stretched or compressed, the distance between the liquid metal particles at both ends of the carbon nanotube is elongated or shortened (the length of the carbon nanotube does not change, and the distance between the liquid metal particles changes), thereby causing the resistance of the point network to sharply increase or decrease.

[0041] The substrate layer 11 is a rigid material, and is selected from at least one of a polyethylene terephthalate (PET) film or a polyimide (PI) film;

[0042] The packaging layer 13 is a flexible material, and is selected from at least one of polyurethane, polydimethylsiloxane (PDMS), or polyethylene terephthalate (PET).

[0043] The single-resistance type whisker sensor 1 can be bent in two directions, left and right, and in space, the single-resistance type whisker sensor can identify two different directions of deformation. The single-resistance type whisker sensor is flat, and the liquid metal-carbon nanotube sensitive material is arranged between the substrate layer 11 and the packaging layer 13, the sensor is provided with a wiring area 14 and a sensor sensitive band 15, and a conductive connector 16 is arranged at the root, one end of the conductive connector 16 is connected with the liquid metal-carbon nanotube sensitive material layer 12, and the other end is used for connecting a detection circuit.

[0044] When the end of the whisker sensor touches an object, the whisker is bent. Figure 3 In order to bend the whisker sensor in different directions, different resistance change graphs are obtained. When the whisker sensor is bent to the packaging layer side (right bending, or Figure 2 bending up as shown in the figure), the conductive pattern is compressed, and the resistance is reduced; on a microscopic level, the distance between the liquid metal particles is reduced, and the length of the carbon nanotube bridge connecting adjacent liquid metal particles is shortened, as shown in Figure 2 Since the resistance of the conductive pattern mainly comes from the carbon nanotube, the compressed conductive pattern will have a significant resistance reduction. When the whisker sensor is bent to the substrate layer side (left bending, or Figure 2 bending down as shown in the figure), the conductive pattern is stretched, and the resistance is increased, as shown in Figure 3As shown in the figure; at the micro level, the distance between the liquid metal particles is reduced, and the length of the carbon nanotube bridge connecting adjacent liquid metal particles is lengthened, as shown in the figure Figure 2 As shown in the figure, the conductive pattern subjected to stretching has a significant increase in resistance. Compared with the conductive pattern without carbon nanotubes, the resistance of the conductive pattern hardly changes during the right and left bending processes.

[0045] As shown in the figure Figure 4 As shown in the figure, the electronic skin composed of the resistance type whisker sensor array of the utility model, including multiple resistance type whisker sensors 1, multiple resistance type whisker sensors 1 are arranged on the soft substrate 2 in a certain direction and distance to form a whisker sensor array;Specifically, the conductive joints of the multiple resistance type whisker sensors 1 are vertically inserted and fixed on the soft substrate 2 to form an array, and the conductive joints of the resistance type whisker sensor array are connected to the detection circuit in order through the wires, and the detection circuit is arranged in a row-column mode, and the signals of the sensors on the corresponding row-column intersection are read and processed when a row or a column is activated each time. Signal reading and processing are realized through a Wheatstone bridge circuit. Through the analysis software, the resistance type whisker sensor can perceive the normal pressure and identify the pressure distribution. The conductive joints of the sensor array are connected to the detection circuit, and the detection circuit and the analysis software belong to the prior art, which will not be described here.

[0046] The soft substrate is a low modulus elastomer substrate, preferably, the soft substrate is selected from at least one of a polydimethylsiloxane (PDMS) substrate, a biodegradable plastic substrate or a thermoplastic elastomer (such as a thermoplastic polyurethane elastomer TPU, a styrene-butadiene-styrene block copolymer SBS) substrate. The biodegradable plastic substrate, such as the ecoflex substrate, is a biodegradable plastic of BASF Company.

[0047] Preferably, by arranging multiple resistance type whisker sensors into an array, each resistance type whisker sensor is at a different position in the array, and specifically, each resistance type whisker sensor is rotated by different angles, such as 0°, 45° and 90°, with its vertical axis as the center, so that the sensor array has different response degrees to shear forces in different directions; in the array, the rotation angle of the whisker, such as 0°, 45° and 90°, is changed, so that it can detect shear forces in different directions.

[0048] In order to accurately analyze the pressure distribution, the shape and material of the contact object, and the direction and size of the shear force of the whisker sensor array, the utility model adopts a deep learning model mainly composed of CNN (convolutional neural network) + Transformer (time sequence feature modeling) for calculation.

[0049] Figure 4The array map of the utility model is composed of 0° whisker sensors, the direction of the arrangement of each whisker sensor 1 is consistent, each whisker sensor is arranged left and right, and each whisker sensor can rotate forward and backward and is used for detecting the movement of forward and backward movement.

[0050] Figure 5 The array map of the utility model is composed of 0° whisker sensors and 90° whisker sensors. As shown in the figure, a plurality of whisker sensors 1 are arranged at 0° and a plurality of whisker sensors 1' are arranged at 90°, and the array is composed of 0° whisker sensors and 90° whisker sensors.

[0051] In other embodiments, a plurality of 45° arranged whisker sensors can also be arranged, the interval of the 45° arranged sensors is 15mm, for example, the 90° arranged sensors in the above embodiment are replaced by 45° arranged whisker sensors. Figure 5

[0052] A preparation method of a resistance type whisker sensor, comprising the following steps

[0053] Step 1. Preparation of conductive ink

[0054] Polyacrylonitrile (PAN) and liquid metal are mixed in the ink solvent, and a surfactant is added to prevent particle agglomeration. The mixed solution is subjected to ultrasonic treatment by using a cell disruptor, so that the liquid metal is converted into liquid metal microparticles and uniformly mixed with the PAN particles, to obtain a uniform and stable conductive ink.

[0055] The mass fraction of the ink solvent is selected in the range of 10wt%-50wt%, and the ink solvent is selected from at least one of ethanol, butanol, methyl ethyl ketone, isobutyl ketone, ethylene glycol ethyl ether acetate and propylene glycol monomethyl ether.

[0056] The mass fraction of polyacrylonitrile (PAN) is 0.5wt%-5wt%. PAN is a precursor material, which is converted into carbon nanotubes (CNTs) in the ablation process, and is used to build a conductive bridge. The molecular weight range is 50,000-150,000g / mol, and the particle size is 20nm, 100nm, 5μm, 10μm or 50μm. PAN is added to the conductive ink so that PAN is converted into carbon nanotubes connecting the liquid metal particles in the step of laser ablation.

[0057] The mass fraction of the liquid metal is selected in the range of 40wt%-90wt%, and the liquid metal is selected from at least one of pure gallium (Ga), gallium-indium alloy (Ga-In), gallium-indium-tin alloy and gallium-zinc alloy.

[0058] The mass fraction of the surfactant is 0-5wt%, and the surfactant is selected from at least one of sodium dodecyl sulfate, polyoxyethylene alkyl phenol ether, polyvinyl pyrrolidone and sodium polyacrylate.​

[0059] Step 2. Patternization of whisker sensor and laser ablation

[0060] The conductive ink prepared above is printed on a rigid substrate layer using patternization techniques such as screen printing, inkjet printing, stenciling, etc. and dried to obtain a dried pattern. The substrate layer can be a polyethylene terephthalate (PET) film, a polyimide (PI) film, etc. In order to achieve the purpose of whisker, the printed pattern is in the form of an elongated snake, with an aspect ratio greater than 5. The printed pattern is dried in an oven at 80-150°C. The dried pattern is non-conductive.

[0061] The dried pattern is subjected to laser ablation to form a conductive pattern. The laser type can be a femtosecond laser (wavelength 500-1500 nm), a Nd:YAG laser (wavelength 1064 nm), and a CO2 laser (wavelength 10.6 µm). The laser power density (1-10 W / cm 2 ) is controlled, and the pattern is scanned at a speed of 1-20 mm / s. During the laser ablation of the pattern, the laser causes the liquid metal particles to break, and under the action of high temperature, the PAN is converted into carbon nanotubes connecting the liquid metal particles, thereby forming a conductive network composed of liquid metal-carbon nanotube sensitive material. The carbon nanotubes form a conductive bridge between the liquid metal particles, building a stable conductive network. The originally non-conductive pattern becomes conductive after laser ablation. The conductive network is mainly composed of two parts: liquid metal particles and carbon nanotubes. The liquid metal particle part has excellent conductivity, while the carbon nanotube part has relatively weak conductivity. Therefore, the resistance of the conductive pattern mainly comes from the carbon nanotube part. The laser ablation of the dried pattern is a special step of the present application. In this step, the PAN is converted into carbon nanotubes connecting the liquid metal particles.

[0062] Step 3. Packaging of whisker sensor

[0063] The conductive pattern is packaged using flexible materials such as polyurethane, polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), etc. by spin coating, hot pressing, cold pressing, ultrasonic bonding, etc. to complete the preparation of a single whisker sensor.

[0064] The thickness of the packaging layer needs to be less than the thickness of the substrate layer to ensure that the conductive pattern is not on the neutral plane when the whisker is bent under stress, thereby improving the signal response. When the end of the whisker sensor touches an object, the whisker will bend. Figure 3 The whisker sensor of the present application bends in different directions to obtain different resistance change graphs. When the whisker sensor bends to one side of the packaging layer (right bend, or Figure 2As shown in the upward bend, the conductive pattern is compressed, and the resistance decreases; at the microscopic level, compared to the undeformed state, the distance between the liquid metal particles decreases, and the length of the carbon nanotube bridges connecting adjacent liquid metal particles becomes shorter, such as... Figure 2 As shown, since the resistance of the conductive pattern mainly originates from carbon nanotubes, the resistance of the compressed conductive pattern decreases significantly. When the tentacle sensor bends towards the substrate (left bend, or...), the resistance decreases. Figure 2 As shown in the downward bend, the conductive pattern is stretched, and the resistance increases, as... Figure 3 As shown; at the microscopic level, compared to the undeformed state, the distance between liquid metal particles decreases, and the length of the carbon nanotube bridges connecting adjacent liquid metal particles increases, such as... Figure 2 As shown, the resistance of the stretched conductive pattern increases significantly. In contrast, the resistance of the conductive pattern remains almost unchanged during right and left bends, compared to the conductive pattern without carbon nanotubes.

[0065] Step 4. Arrange the tentacles sensor array to form an electronic skin:

[0066] Arranging tactile sensors into a matrix array creates a large-area electronic skin. This involves arranging multiple tactile sensors at specific directions and distances to form a tactile sensor array. Multiple tactile sensors can be vertically inserted onto a soft substrate, such as a polydimethylsiloxane (PDMS) substrate or an ecoflex substrate, to form the array. The conductive connectors of the sensor array are then connected to a detection circuit via wires in sequence. Through analysis software, the tactile sensors can sense normal pressure and identify its distribution. In addition, they can also sense vibration frequency, fluid dynamics changes, and other information. Different spacing and arrangement methods can optimize tactile resolution.

[0067] A single whisker sensor can bend in both left and right directions, and in space, a single whisker sensor can detect deformation in two different directions. To enable a whisker sensor array to detect shear forces in different directions, the sensor array is designed using the following method.

[0068] By arranging multiple tentacle sensors into an array, such as Figure 4 As shown, the touch sensors located at different positions in the array are then rotated by different angles (e.g., 0°, 45°, 90°) around the vertical axis, so that the sensor array has different degrees of response to shear forces in different directions, such as... Figure 5 As shown. In the array, the rotation angle of the tentacles is changed (e.g., 0°, 45°, 90°) to enable them to detect shear forces in different directions.

[0069] In order to accurately analyze the pressure distribution, the shape of the contact object, the material and the shear force direction and size of the whisker sensor array, the utility model adopts the deep learning model mainly composed of CNN (convolutional neural network) + Transformer (time sequence feature modeling) to solve.

[0070] Embodiment 1

[0071] Ethanol (10wt%) and methyl ethyl ketone (5wt%) are selected as the ink mixed solvent. Polyacrylonitrile (PAN) powder is weighed, and the mass fraction is 3wt%, and the particle size is 100 nanometers. Select liquid metal alloy (Ga-In-Sn), and the mass fraction is 80wt%. Add a surfactant (polyvinylpyrrolidone, 2wt%) to prevent particle agglomeration. PAN and liquid metal are added to the ink solvent, and stirred at room temperature for 30 minutes to form a uniform mixture. The mixture is treated with a cell disrupter (frequency 20kHz, time 5 minutes) to convert the liquid metal into micro-nanoparticles. After ultrasonic treatment, the liquid metal particles are uniformly distributed around the PAN particles, forming a stable conductive ink. The ink is printed on a polyurethane flexible substrate using screen printing to form a long strip pattern. The pattern is dried in an oven at 80 degrees Celsius for 10 minutes. Using a femtosecond laser, control the laser power density 1W / cm 2 ), and the printed pattern is scanned at a speed of 5mm / s. During the laser ablation of the pattern, the laser will cause the liquid metal particles to break, and under the action of high temperature, the PAN will be converted into carbon nanotubes, which will form conductive bridges between the liquid metal. The conductive pattern is encapsulated using a polyurethane film by a hot pressing method, and the thickness of the encapsulation layer is less than the thickness of the substrate to ensure that the signal changes significantly when bending. The sensor can respond to external stimuli such as touch and bending, and reflect the stress state of the sensor through resistance changes.

[0072] Embodiment 2:

[0073] Ethylene glycol ethyl ether acetate (10 wt%) was chosen as the ink solvent, and polyacrylonitrile (PAN) powder was weighed with a mass fraction of 5 wt%, and the particle size was selected as 300 nm. Liquid metal alloy (Ga-In) was selected with a mass fraction of 83 wt%. A surfactant, sodium polyacrylate, was added at 2 wt% to prevent particle agglomeration and increase the ink's printing wettability. PAN and liquid metal were added to the ink solvent, and the mixture was stirred at room temperature for 30 minutes to form a uniform mixture. A high-speed blender was used to stir the mixture (speed 10000 r / min for 20 minutes), which converted the liquid metal into microparticles and formed a stable conductive ink. The ink was printed on a PDMS flexible substrate using an inkjet printing method to form a serpentine pattern with an aspect ratio of 5. The pattern was dried in an oven at 80 degrees Celsius for 10 minutes. Using a Nd:YAG laser (wavelength 1064 nm), the laser power density was controlled at 2 W / cm 2 ), and the printed pattern was scanned at a speed of 20 mm / s. Under the action of the laser, the liquid metal particles were broken and connected with the carbon nanotube network formed by PAN to realize the conversion of electrical conductivity. The conductive pattern was encapsulated using PDMS by the spin coating method, and the thickness of the encapsulation layer was less than the thickness of the substrate to ensure that the signal change was obvious when bending.

[0074] Sensor array construction. A plurality of whisker sensors were vertically arranged on a PDMS flexible substrate to form an array. By changing the rotation angle of the whiskers at different positions of the array, 0° rotation angle whiskers and 90° rotation angle whiskers were obtained. The 0° whiskers were most sensitive to x-direction shear force, while having a smaller response to y-direction shear force. The 90° whiskers were most sensitive to y-direction shear force, while having a smaller response to x-direction shear force. The whisker sensor can simultaneously measure pressure (normal force) and shear force (horizontal force), and the resistance change of the whisker is not only related to the shear force, but also affected by the bending caused by the vertical pressure. The sensor array was connected to the data acquisition circuit by row-column scanning, i.e., the detection circuit was arranged in a row-column manner, and the signal of the sensor at the intersection of the corresponding row and column was read and processed when a row or a column was activated. Signal reading and processing were achieved through a Wheatstone bridge circuit. Finally, a deep learning model combining CNN and Transformer was used to analyze the signals of the whisker sensor array, and to accurately identify the shape, material, and pressure distribution of the contact object, as well as the size and direction of the shear force.

[0075] Unless otherwise defined, all technical and / or scientific terms used in the present application have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains. The materials, methods, and examples provided in the application are illustrative only and not intended to be limiting. Although the present application has been described in conjunction with specific embodiments thereof, it is to be understood that equivalent changes and modifications will be apparent to those skilled in the art once armed with the above description. Therefore, the intent is to cover all such changes and modifications that fall within the scope of the present application.

Claims

1. A resistive touch sensor, comprising a substrate layer (11), a liquid metal-carbon nanotube sensitive material layer (12), and an encapsulation layer (13), wherein the liquid metal-carbon nanotube sensitive material layer (12) forms a conductive network, the conductive network being composed of liquid metal particles (121) and carbon nanotubes (122), the liquid metal particles (121) being connected to each other via the carbon nanotubes (122), characterized in that, The liquid metal-carbon nanotube sensitive material layer (12) is encapsulated between the substrate layer (11) and the encapsulation layer (13).

2. The resistive touch sensor according to claim 1, characterized in that, The base layer (11) is a polyethylene terephthalate film or a polyimide film, and the encapsulation layer (13) is selected from polyurethane, polydimethylsiloxane, or polyethylene terephthalate.

3. A touch sensor electronic skin, characterized in that, It includes a plurality of resistive whisker sensors (1) according to any one of claims 1 to 2, wherein the plurality of resistive whisker sensors are arranged in an array on a soft substrate (2) to form a whisker sensor array.

4. The electronic skin with a touch sensor according to claim 3, characterized in that, The soft substrate is selected from one of the following: silicone substrate, polydimethylsiloxane substrate, thermoplastic elastomer substrate, or biodegradable plastic substrate.

5. The electronic skin with a touch sensor according to claim 3, characterized in that, Each touch sensor rotates at a different angle around its vertical axis.

6. The electronic skin with a touch sensor according to claim 5, characterized in that, The rotation angle is 0°, 45° or 90°.

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