Self-recognition and self-adjustment bionic flexible strain sensor based on root soft tissue of murine whisker receptor and preparation method of self-recognition and self-adjustment bionic flexible strain sensor

Abstract

The invention discloses a self-recognition and self-adjustment bionic flexible strain sensor based on root soft tissue of a mouse whisker receptor and a preparation method of the self-recognition and self-adjustment bionic flexible strain sensor, relates to the technical field of flexible sensors, and provides the self-recognition and self-adjustment bionic flexible strain sensor based on the root soft tissue of the mouse whisker receptor and the preparation method of the self-recognition and self-adjustment bionic flexible strain sensor based on the root soft tissue of the mouse whisker receptor. The sensor can perform self-sensing identification on the motion state of the sensor, and can adjust a sensing reference point (the minimum resistance value of the sensor) in real time according to the motion state, so that the real-time motion monitoring of a single device on a plurality of segments of motion states is realized; according to the invention, the real-time self-adaptive adjustment sensing function of the sensing domain of the tentacle receptor is realized by simulating the distribution mode of root soft tissue muscle fibers, collagen and sensing nerves of the mouse tentacle receptor, material characteristics and a collaborative cooperation mechanism; according to the self-recognition and self-adjustment bionic flexible strain sensor based on the root soft tissue of the rat whisker receptor and the preparation method of the self-recognition and self-adjustment bionic flexible strain sensor, a bionic means is adopted to enable a single sensor to have the functions of motion state self-recognition and sensing self-adjustment; and the requirement of real-time accurate monitoring of a single sensing device for multi-section movement of a mechanical equipment task execution assembly is met.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible sensors, and in particular to a self-identifying and self-regulating bionic flexible strain sensor based on the soft tissue at the root of a rodent whisker receptor and a preparation method thereof. Background Art

[0002] With the rapid increase in the diversity of high-end mechanical equipment tasks and the complexity of scenarios, the mechanical equipment actuators are developing in the direction of multi-degree-of-freedom, cross-scale, and refinement. Real-time and accurate monitoring of the motion state of mechanical equipment actuators is the key to ensuring the stability and reliability of mechanical equipment precision operations.

[0003] Traditional strain sensors are limited by the sensing mechanism and structural design principles, and a single device is difficult to meet the complex motion state monitoring needs that cover both large-scale mechanism motion and tiny structural deformation. Among them, flexible strain sensors have great application potential in large-scale motion monitoring due to their good ductility, but they are also limited by traditional sensing principles and design methods, and it is difficult to meet the monitoring needs of a single sensor device for multiple motions.

[0004] The current mainstream monitoring method for multi-stage motion is to build a sensor cluster through multiple sensors, combined with back-end algorithms for information processing, so as to realize the identification and monitoring of multi-stage motion states. Although this type of sensor cluster monitoring meets the needs of complex motion monitoring, it limits the overall degree of miniaturization and leads to a surge in back-end data processing. At the same time, in the process of multiple sensors working together, when a sensor device produces data inaccuracy or abnormal signal fluctuations due to environmental changes, electromagnetic interference or its own failure, the interaction of multiple sensors can easily cause the sensor system to misjudge and fail. Therefore, there is an urgent need for a new type of sensor device that meets the needs of real-time and accurate monitoring of multi-stage motion of mechanical equipment actuators. Summary of the invention

[0005] In order to solve the problems in the above-mentioned background technology, the present invention is a self-identifying and self-adjusting bionic flexible strain sensor based on the soft tissue at the root of the rodent whisker receptor and a preparation method thereof. The sensor can self-perceive and identify its own motion state, and adjust the perception reference point (minimum resistance of the sensor) in real time according to the motion state, thereby realizing real-time motion monitoring of multiple motion states by a single device.

[0006] A self-identifying and self-adjusting bionic flexible strain sensor based on the soft tissue at the root of the rodent whisker receptor, comprising a surface low resistance layer and an adaptive recognition function layer, wherein the adaptive recognition function layer is a substrate, as a main body, the adaptive recognition function layer comprises a multiple cross-linked network and a conductive network, the multiple cross-linked network and the conductive network together form a multiple network, the surface low resistance layer is a nano-scale conductive metal layer formed by magnetron sputtering coating, and the surface low resistance layer is arranged on the outer surface of one side of the adaptive recognition function layer; The multiple cross-linked networks inside the adaptive recognition functional layer have the characteristics of high strength and toughness, ensuring that the bionic flexible strain sensor has the ability to perform large-scale movement with the object being measured without being damaged. Secondly, the internal conductive network should be a non-uniform and non-continuous network, and the size of the internal conductive particles should be smaller than the pores in the multiple cross-linked networks, ensuring that the discontinuous conductive networks inside the adaptive recognition functional layer as the substrate are locked in the multiple cross-linked networks respectively.

[0007] A method for preparing a self-identifying and self-adjusting bionic flexible strain sensor based on the soft tissue at the root of a rodent whisker receptor comprises the following steps: Step 1: Use an organic solvent to dissolve the polymer materials used to prepare the adaptive recognition functional layer, and use an ultrasonic oscillator and a magnetic stirrer to make a suspension of the carbon black, carbon nanotubes, and graphene conductive particles used. After ensuring that each material is completely dissolved, mix them and further stir them to make them evenly mixed; Step 2: After all materials are fully mixed, the cross-linking agents of the polymers are added to the solution respectively, and the selected polymers are fully stirred under the conditions of polymerization reaction to allow the cross-linking agent to fully react with the polymers; Step 3: pour the reacted solution into the prepared barbell-shaped mold, use a vacuum oven to completely solidify the solution, and prepare barbell-shaped splines of uniform size and shape to facilitate subsequent performance testing, which will serve as the base adaptive recognition functional layer of the bionic flexible strain sensor; Step 4: sputter conductive nanoparticles such as gold and silver on one side of the barbell-shaped substrate adaptive recognition functional layer to form a surface low resistance layer, thereby completing the preparation of a bionic flexible strain sensor with self-recognition and self-regulation functions.

[0008] Beneficial effects of the present invention: The present invention realizes the real-time adaptive adjustment and perception function of the perception domain of the whisker receptor by imitating the distribution mode, material properties and synergistic cooperation mechanism of the soft tissue muscle fibers, collagen and sensory nerves at the base of the whisker receptor of mice, and completes a self-identifying and self-adjusting bionic flexible strain sensor based on the soft tissue at the base of the whisker receptor of mice and its preparation method. The bionics method is used to enable a single sensor device to have the functions of self-identification of motion state and self-adjustment of perception, meeting the needs of real-time and accurate monitoring of multi-stage motion of a single sensor device of a task execution component of mechanical equipment. The bionic flexible strain sensor achieves the balance of strength, toughness and ductility through the multiple polymer cross-linked network. At the same time, through the locking effect of the non-uniform non-continuous conductive network and the multiple polymer cross-linked network, the multi-stage difference change of the resistance of the bionic flexible strain sensor is realized, thereby having the functions of self-identification and self-adjustment of its own motion state. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is an overall schematic diagram of the present invention; Figure 2 It is a working principle diagram of the present invention; Figure 3 It is a schematic diagram of resistance change in the adaptive sensing and normal sensing processes of the present invention; Figure 4 This is the main response change phase of the adaptive process of the present invention. DETAILED DESCRIPTION

[0010] See also Figures 1 to 4 As shown, a self-identifying and self-adjusting bionic flexible strain sensor based on the soft tissue at the root of the rodent whisker receptor comprises a surface low resistance layer 2 and an adaptive recognition function layer 1, wherein the adaptive recognition function layer 1 is a substrate, as a main body, the adaptive recognition function layer 1 comprises a multiple cross-linked network 3 and a conductive network 4, the multiple cross-linked network 3 and the conductive network 4 together form a multiple network, the surface low resistance layer 2 is a nano-scale conductive metal layer formed by magnetron sputtering coating, and the surface low resistance layer 2 is arranged on the outer surface of one side of the adaptive recognition function layer 1; Specifically, the multiple cross-linked network 3 is made of polymers in a certain proportion, the conductive network 4 is made of conductive materials, and the metal in the surface low-resistance layer 2 has good conductivity, such as gold, silver, and copper; The multiple cross-linked network 3 inside the adaptive recognition functional layer 1 has the characteristics of high strength and toughness, ensuring that the bionic flexible strain sensor has the ability to perform large-scale movement with the measured object without damage. Secondly, the internal conductive network 4 should be a non-uniform and non-continuous network, and the size of the internal conductive particles should be smaller than the pores in the multiple cross-linked network 3, ensuring that the discontinuous conductive network 4 inside the adaptive recognition functional layer 1 as the substrate is locked in the multiple cross-linked network 3 respectively. This is the key to ensure that the bionic flexible strain sensor can achieve self-recognition and self-regulation of the motion state; Specifically, the multiple cross-linked network 3 inside the adaptive recognition functional layer 1 is an interpenetrating cross-linked network formed by two or more polymers; such as a physical interpenetrating cross-linked network formed by polyether polyurethane and silicone rubber, wherein polyether polyurethane has high strength, but pure polyether polyurethane has poor ductility and is difficult to meet the large-scale motion deformation requirements of the bionic flexible strain sensor; and silicone rubber itself is a material with good toughness and ductility, but its strength is poor. Although it meets the deformation requirements of the bionic flexible strain sensor, it is easy to be damaged, which seriously affects the service life of the bionic flexible strain sensor. By adjusting the blending ratio of polyether polyurethane and silicone rubber, a substrate adaptive recognition functional layer that meets both strength and toughness can be prepared; Specifically, the conductive network 4 in the adaptive recognition functional layer 1 is discontinuous, so that the conductivity of the adaptive recognition functional layer 1 is mainly determined by the tunneling effect between the intermediate network segments of the conductive network, and the distance between the conductive particles in the tunneling effect determines the size of its internal resistance, so that the substrate adaptive recognition functional layer produces a large resistance change during the overall deformation process of the bionic flexible strain sensor; Specifically, although the conductive network 4 in the adaptive recognition functional layer 1 is non-uniform, the conductive particles in the conductive network 4 are locked by the multiple cross-linked network 3, and will be rearranged as the multiple cross-linked network 3 is deformed (when the bionic flexible strain sensor is deformed, the multiple cross-linked network 3 will be stretched, so that the gaps in the multiple cross-linked network 3 are compressed, thereby forcing the conductive network 4 to rearrange as the gaps are compressed, which will cause a sharp decrease in resistance, which is opposite to the increase in resistance caused by the increase in the distance between the conductive particles during the deformation process. At the same time, this rearrangement requires the deformation state to be maintained for a certain period of time and will not affect the normal perception process). When the object to be measured produces large-scale motion and maintains the motion state for a period of time, the conductive network 4 in the adaptive recognition functional layer 1 is rearranged, and the total resistance value of the bionic flexible strain sensor changes, thereby achieving self-regulation; The surface low resistance layer 2 is a conductive metal film layer prepared by magnetron sputtering after the preparation of the adaptive identification functional layer 1 is completed. After the preparation of the surface low resistance layer 2 is completed, the bionic flexible strain sensor needs to be pre-stretched for the first time (stretched to the stretching limit of the bionic flexible strain sensor). At this time, a large number of microcracks will be generated on the surface of the conductive metal film, and then the bionic flexible strain sensor is restored to its original state. At this time, the cracks of the conductive metal film on the surface are closed. Due to the existence of these microcracks, the sensitivity of the prepared bionic flexible strain sensor is greatly improved, ensuring its perception accuracy of microstrain.

[0011] The present invention provides a method for preparing a self-identifying and self-adjusting bionic flexible strain sensor based on the soft tissue at the root of a rodent whisker receptor, the steps comprising: Step 1: Take out an appropriate amount of polyether polyurethane prepolymer and pour it into a 50 ml glass beaker, place it in an electric vacuum drying oven, set the temperature to 120°C, and heat it in a vacuum environment for 1 hour to remove excess water and bubbles in the polyurethane, then let it cool naturally to 60°C for use; Take 10 g of the heated polyether polyurethane prepolymer and mix it with 10 g of acetone-tetrahydrofuran solution in a ratio of 1:1, place it on a heated stirring table and stir it thoroughly until the polyether polyurethane prepolymer is completely dissolved; Take 10 g of epoxy resin silicone rubber and mix it with 20 g of tetrahydrofuran solution, place it on a stirring table and stir it thoroughly until it is completely dissolved; Weigh 0.3 g of carbon nanotubes and 3 g of carbon black, inject 10 g of acetone, stir for 5 min, and place them in an ultrasonic oscillation cleaning machine to form a uniform carbon nanotube-carbon black suspension; Step 2: Place the prepared polyether polyurethane prepolymer-acetone-tetrahydrofuran solution, epoxy resin silicone rubber-tetrahydrofuran solution and carbon nanotube-carbon black-acetone suspension on a heated stirring table and mix them thoroughly; Take a certain amount of white di-o-chlorodiphenylmethane particles (MOCA particles), place them in an electric vacuum drying oven, and heat them at 120°C for more than 20 min to make them enter a molten state and turn them into a light yellow transparent liquid; A sufficient amount of MOCA as a crosslinking agent for the polyether polyurethane prepolymer was injected at a ratio of 100:12.5 of polyether polyurethane prepolymer:MOCA, and a sufficient amount of silane coupling agent as a crosslinking agent for the epoxy resin silicone rubber was injected at a ratio of 100:2 of epoxy resin silicone rubber:silane coupling agent, and the solution was placed on a heated stirring table, heated and stirred at 50°C for 30 minutes to allow a full reaction to occur; Step 3: Pour the stirred solution into a pre-prepared mold, put it into an electric vacuum drying oven, and heat it at 50°C for more than 24 hours under a vacuum environment to form a flexible film with uniform texture; After ensuring that the solution is completely solidified into a film, the prepared multi-crosslinked network film is taken out and cut using a laser marking machine to divide it into barbell-shaped splines of equal size with a central rectangular area of ​​10 mm × 20 mm, thereby completing the preparation of the adaptive recognition functional layer 1; Step 4: Using a plasma coating apparatus (Q150 RS, Quorum Technology Co., Ltd, UK), a layer of silver nanoparticle sensitive functional layer was deposited on the adaptive recognition functional layer prepared in the above process. The deposition duration was set to 150 s and the deposition thickness was about 200 nm. On the basis of retaining the effective sensing size of 10 mm × 20 mm, an appropriate amount of conductive silver paste was evenly applied to both ends of the prepared sample, and conductive tape was attached as the wires of the self-identifying and self-adjusting bionic flexible strain sensor. It was placed on a heating table and allowed to stand at 70 °C for 4 h to ensure that the wires were firmly connected, thus completing the preparation of the self-identifying and self-adjusting bionic flexible strain sensor.

[0012] The above is only the best implementation scheme proposed by the present invention based on various considerations. Other schemes can be selected in many places. The specific situations are as follows: In addition to the polyether polyurethane and silicone rubber used in step one, other polymers capable of forming a cross-linked network may also be selected, such as urethane polymers, polyvinyl chloride, mold rubber, etc. Relatively speaking, the preparation process of the cross-linked network of polyether polyurethane and silicone rubber is simpler.

[0013] The ratio of each solution in step 2 will directly affect the mechanical properties of the prepared adaptive recognition functional layer, and should be adjusted accordingly according to the required mechanical properties.

[0014] In step three, the crosslinking agent and the ratio should be changed according to the polymer used.

[0015] In step 4, other nanoparticles with good conductivity, such as gold, can be sputtered. However, relatively speaking, silver has good conductivity and relatively low cost.

[0016] Bionic principle of the present invention: In addition to the ability to accurately perceive weak external vibration disturbances, the whisker receptors of mice can also make real-time adjustments based on the size of external disturbances to capture and perceive larger disturbance signals. The realization of this unique adaptive adjustment function mainly relies on the soft tissue located at the root of the whisker receptors. This soft tissue contains interwoven and mixed muscle fibers and collagen, which synergistically give this part of the tissue extremely high strength and toughness. At the same time, the sensory nerves of mice are wrapped in muscle fibers and collagen. When the external over-stimulation signal is too high, the muscle fibers become autonomously congested and tense, changing the stiffness of the receptor nerve site, increasing the perception threshold, and thus achieving self-regulation of perception.

[0017] This self-identifying and self-regulating bionic flexible strain sensor completes the mapping of the above-mentioned biological adaptive regulation principle of the soft tissue at the root of the mouse whisker receptor to the sub-identification and self-regulation mechanism of the sensor device. The essence of this self-identifying and self-regulating mechanism is that when the motion state of the measured object changes, the bionic flexible strain sensor will self-identify its own motion state. When it is determined that its own motion state has changed, the internal multiple cross-linked networks of the bionic flexible strain sensor will shrink due to the change in motion state, thereby forcing the internal locked conductive network to rearrange and produce a large-scale change in resistance. The macroscopic manifestation of this change is the self-identification and self-regulation function of the bionic flexible strain sensor, which enables this self-identifying and self-regulating bionic flexible strain sensor to meet the needs of real-time and accurate monitoring of multi-segment motion of a single sensor device of the actuator of mechanical equipment.

Claims

1. A self-identifying and self-adjusting biomimetic flexible strain sensor based on the soft tissue at the base of rodent vibrissae receptors, characterized by: The invention comprises a surface low resistance layer (2) and an adaptive recognition function layer (1), wherein the adaptive recognition function layer (1) is a substrate and serves as a main body. The adaptive recognition function layer (1) comprises a multiple cross-linked network (3) and a conductive network (4), wherein the multiple cross-linked network (3) and the conductive network (4) together form a multiple network. The surface low resistance layer (2) is a nano-scale conductive metal layer formed by magnetron sputtering coating. The surface low resistance layer (2) is provided on the outer surface of one side of the adaptive recognition function layer (1). The multiple cross-linked networks (3) inside the adaptive recognition functional layer (1) have the characteristics of high strength and strong toughness, ensuring that the bionic flexible strain sensor has the ability to move on a large scale with the object being measured without being damaged. Secondly, the internal conductive network (4) should be a non-uniform and non-continuous network, and the size of the internal conductive particles should be smaller than the pores in the multiple cross-linked networks (3), ensuring that the discontinuous conductive networks (4) inside the adaptive recognition functional layer (1) as the base are locked in the multiple cross-linked networks (3) respectively.

2. A method for preparing a self-identifying and self-adjusting biomimetic flexible strain sensor based on the soft tissue at the base of rodent vibrissae receptors, characterized by: The following steps are involved: Step 1: using an organic solvent to dissolve the polymer materials used to prepare the adaptive recognition functional layer (1), and using an ultrasonic oscillator and a magnetic stirrer to prepare a suspension of the carbon black, carbon nanotubes, and graphene conductive particles used, and after ensuring that all materials are completely dissolved, mixing them and further stirring them to make them uniform; Step 2: After all materials are fully mixed, add the crosslinking agent of each polymer to the solution respectively, and stir it fully under the conditions of polymerization reaction of the selected polymer to allow the crosslinking agent and the polymer to fully react; Step 3: Pour the reacted solution into the prepared barbell-shaped mold, and use a vacuum oven to completely solidify the solution to prepare barbell-shaped splines of uniform size and shape for subsequent performance testing, which will serve as the base adaptive recognition functional layer (1) of the bionic flexible strain sensor; Step 4: Sputtering conductive nanoparticles such as gold and silver on one side of the barbell-shaped substrate adaptive recognition functional layer (1) to form a surface low resistance layer (2), thereby completing the preparation of a bionic flexible strain sensor with self-recognition and self-regulation functions.

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