A printable electronic skin for high-precision detection of damage location and outer contour

Abstract

The present invention discloses a printable electronic skin for high-precision detection of damaged positions and outer contours, and relates to the field of surface damage monitoring technology. Compared with previous thin film damage detection technologies, the present invention solves the problem that existing thin film damage detection technologies cannot accurately locate damaged positions and accurately detect damaged outer contours and areas; the electrical signals of each intersection between the longitude and latitude are measured separately to quickly detect and judge damage events, and the intersections are also regulated by signal through diode rectification characteristics, the damaged position shape and damaged outer contour are evaluated, and the damaged area is calculated based on the generated damaged outer contour, which can greatly improve the accuracy of damage positioning and detection. Moreover, the electronic skin can be prepared by full solution printing technology, and can be in-situ superimposed layer by layer on the surface of the object to be measured according to the hierarchical structure. The direct in-situ construction method can directly reflect the damage on the surface of the object, improve the detection sensitivity of damage, and the preparation is also more convenient and quick.

Description

Technical Field

[0001] The present invention relates to the technical field of surface damage monitoring, and in particular to a printable electronic skin for high-precision detection of damage positions and outer contours. Background Art

[0002] In recent years, civil infrastructure, mechanical industrial equipment, etc. have been continuously deployed on a large scale, and the requirements put forward are also more stringent, such as corrosion, fatigue damage and impact damage of equipment or structures, long-term service in harsh environments, etc. Health monitoring of structures and equipment (especially surface damage or damage detection) is of great significance to their long-term, safe and reliable operation.

[0003] Surface damage monitoring is an important part of the health assessment of engineering structures. Currently, common surface damage detection technologies include: damage monitoring based on distributed fiber Bragg grating sensing, damage detection based on acoustic wave conduction, damage detection based on visual sensing, etc. Fiber Bragg grating sensing plays a huge role in the fields of telecommunications and data communications due to its advantages of fast speed, low loss, small size, strong anti-interference ability, and large information carrying capacity, but its disadvantages are also obvious. The optical fiber material is very fragile and very easy to be damaged, and it needs to be properly coated with other materials for protection. Secondly, fiber optic sensing technology requires the use of longer optical fiber cables, which are more complicated and cumbersome to install, especially in complex environments. Installation and debugging are more difficult. Thirdly, optical fiber sensors are easily affected by temperature. Since the refractive index of optical fiber materials changes with the temperature of the environment, the accuracy of optical devices is easily affected in environments with large temperature changes.

[0004] Ultrasonic conduction detection and visual sensing also have their technical disadvantages. For example, ultrasonic conduction is susceptible to signal interference, and the flatness and uniformity of the device surface will seriously affect the accuracy of its sensing signal. Visual sensing usually has a slow response speed. In addition, visual sensing is easily affected by the illumination of the incident light, and its application is limited in closed environments with poor lighting.

[0005] Compared with the above technologies, the flexible electronic skin sensing technology based on electrical parameter measurement has the advantages of stable and reliable signals, less external interference such as temperature, and low cost. More importantly, the flexible electronic skin can be processed over a large area, and has the unique advantages of being ultra-thin, light, low-cost, and conformally attached to three-dimensional curves or dynamic surfaces. After being attached to the surface of the structure, it is an ideal damage detection device and method. In addition, compared with other detection methods, flexible electronic skin can be manufactured on a large scale in a controlled manner using advanced printing technologies such as inkjet printing, screen printing, and 3D printing, and can also be manufactured in situ on the surface of various equipment by spraying or brushing. It is easy and quick to deploy, and can achieve reliable monitoring of structural surface damage events. It has good competitiveness and good application prospects.

[0006] Currently, most electronic skins used for surface damage detection build a conductive network, then collect the changes in the resistance values ​​of different wires in the conductive network, and finally infer and analyze the location and general outline of the damage event. There are many network structures that meet the requirements. Different structural forms have different requirements for wiring scale, data collection scale, and detection algorithm complexity. Common forms include direct network structure, ring network structure, combined network structure, etc.

[0007] The through detection network can realize surface detection and point detection. The detection is intuitive and convenient, and the logic is simple. In this network, the warp wires and weft wires are arranged vertically and horizontally, and these wires are isolated from each other. During the detection, the conductivity of each warp and weft wire is tested separately, such as transmitting an electrical signal from one end of each wire and detecting the received signal at the other end. When damage occurs, the warp and weft conductivity corresponding to the damaged area will be broken, and the current cannot pass through these wires, and the electrical signals at both ends of the corresponding warp and weft wires will not be measured. By detecting and analyzing the conduction and breakage of the warp and weft wires, the location and range of the damage can be evaluated. However, this method can only make an approximate estimate of the damage location and area, but it is difficult to accurately detect the damage pattern and precise area, especially when the shape of the damage location is non-rectangular. The evaluated location and shape are very different from the actual situation, and the overall positioning accuracy and area calculation accuracy are poor, which is subject to many limitations in practical applications.

[0008] The above technology can detect the location and contour of damage by detecting the conductivity of different wires. However, this technology can only detect the location and approximate range of the damage, and cannot detect the location, actual shape and precise area of ​​the damage. For example, when the shape of the damage is a slit, but the damage detected according to the conductivity of different wires is rectangular or square, it is far from the actual situation, especially when accurately describing the actual outer contour of the damage and calculating the actual damage area, the existing technology has significant deficiencies and cannot accurately locate and accurately evaluate the damage event. How to accurately, reliably and comprehensively detect and evaluate damage events, there is currently no relevant technical solution. In addition, the detection network construction method used by this technology is relatively cumbersome, especially when the surface area to be detected is large or the required detection accuracy is high (the number of wires increases), the layout of the wires will be very difficult.

[0009] In order to solve the above problems, the present invention proposes a printable electronic skin for high-precision detection of damaged positions and outer contours, so as to achieve high-precision detection of damaged positions, outer contours and areas, and use the unidirectional conduction characteristics of diodes to perform signal regulation on the longitude and latitude sensing network, so that each cross-sensing point of the longitude and latitude sensing network does not interfere with each other, thereby accurately detecting the damaged position, contour and area to a single damaged point and surrounding line segments, which can greatly improve the damage positioning and detection accuracy. A three-dimensional configuration of a longitude and latitude sensing network with electrode-insulating layer-electrode-diode layer stacked layer by layer is designed to prevent short circuits between longitude and latitude electrodes and facilitate the integration of the diode part. At the same time, the electronic skin can be constructed in situ on the same surface of a complex curved surface by full solution printing, realizing the integration of the device surface and the detection skin. Summary of the invention

[0010] The purpose of the present invention is to provide a printable electronic skin for high-precision detection of damage position and outer contour to solve the problems raised in the background technology:

[0011] The existing technology can only detect the location and approximate range of the damage, but cannot detect the damage location, actual shape and precise area. In addition, the detection network construction method adopted by the existing technology is relatively cumbersome, especially when the surface area to be detected is large or the required detection accuracy is high, the layout of the wires will be very difficult.

[0012] In order to achieve the above object, the present invention adopts the following technical solutions:

[0013] A printable electronic skin for high-precision detection of damaged positions and outer contours, wherein the electronic skin is prepared by printing directly on the surface of an object based on a full solution printing technology; the electronic skin comprises a flexible polymer substrate, a conductive warp and weft network, an insulating layer and a diode element; the conductive warp and weft network is prepared by adopting a three-dimensional planar configuration of electrode-insulating layer-electrode, and a side electrode is added to the electrode at each point of the conductive warp and weft network for the integration of a diode array; the electronic skin is provided with a flexible polymer substrate, a weft electrode and its side electrodes, an insulating layer, a warp electrode and its side electrodes and a diode array in sequence from bottom to top.

[0014] Preferably, each intersection of the conductive longitude and latitude network is integrated with a diode, so that signal detection between the points does not cause mutual interference.

[0015] Preferably, the specific preparation process of the electronic skin is as follows:

[0016] Step A: Printing a flexible polymer substrate layer on the surface of the object;

[0017] Step B: using a conductive paste to print the weft conductive electrodes by inkjet printing;

[0018] Step C: after drying, the insulating layer is printed on the points corresponding to the warp electrodes, and an insulating layer of a certain thickness is obtained after ultraviolet light curing;

[0019] Step D: Printing the insulation layer through several printing operations;

[0020] Step E: Use conductive paste to print warp conductive electrodes on the corresponding insulating layer to obtain the warp and weft electrode network part of the electronic skin.

[0021] Preferably, in the specific preparation process of the electronic skin, the diode element is constructed in situ at the intersection of the warp electrode and the weft electrode by a full solution printing process;

[0022] The diode is an organic diode or a Schottky diode; the organic diode comprises four layers: a bottom electrode, an N-type organic semiconductor layer, a P-type organic semiconductor layer and a top electrode; the Schottky diode comprises four layers: a bottom electrode, a polymer semiconductor layer, an insulating layer and a top electrode; the specific preparation steps of the diode are as follows:

[0023] Step 1: Print the bottom electrode on one of the side electrodes in the intersection of the warp and weft network electrodes, and sinter and solidify at 100-150°C;

[0024] Step 2: Print a second layer within a certain thickness range on the bottom electrode layer and sinter and solidify it at 100-150°C;

[0025] Step 3: Print the third layer and sinter and solidify at 100-150℃;

[0026] Step 4: Finally, the printed top electrode is connected to another side electrode at the intersection of the warp and weft network electrodes, and sintered and cured at 100-150°C;

[0027] Step 5: After the diode printing at each point is completed, an insulating protective layer is printed on the entire surface of the electronic skin.

[0028] A detection method for high-precision detection of damage position and outer contour of printable electronic skin comprises the following steps:

[0029] S1: Use the full solution printing process to construct a conductive warp-and-weft network with mutually insulated warp-and-weft electrodes and diodes at the intersections to form a damage detection electronic skin, and build an array scanning circuit;

[0030] S2: Using the rectification characteristics of the diode, the resistance or voltage signal of the circuits in the four directions at each intersection of the longitude and latitude sensing electrode network is collected, and the collected electrical signals are used to determine damage. If it is determined that no damage has occurred, S2 is continued to be executed. If it is determined that damage has occurred, S3 is transferred;

[0031] S3: Count the damage of each intersection, obtain the pattern of the damaged outer contour based on the damage shape contour judgment algorithm, and then calculate the damaged contour area based on the area estimation method.

[0032] Preferably, the array scanning circuit in S1 includes four multi-way analog switches, ADC, MCU and power supply module, wherein the MCU is connected to the address end and control end of the four multi-way analog switches to control the gating of the measurement path and measurement direction in the scanning circuit; the MCU is also connected to the address end of the four multi-way analog switches in the power supply module to control the gating of the output end of the power supply module; the ADC receives the analog signals transmitted by the four multi-way analog switches, converts them into digital signals and sends them to the MCU; the MCU transmits the data to the PC through serial port communication for further algorithm processing and image display.

[0033] Preferably, the step of performing damage judgment on each intersection of the longitude and latitude sensing electrode network based on the scanning circuit in S2 is as follows:

[0034] S2.1: The MCU controls the power supply module to provide a voltage signal to the input end of the first multi-way analog switch, the MCU controls the first multi-way analog switch and the second multi-way analog switch to be in working state, and controls the channels of the first multi-way analog switch and the second multi-way analog switch to scan the array circuit by inputting different level signals to the address end, the MCU controls the first multi-way analog switch and the fourth multi-way analog switch to be in working state, and repeats the above circuit scanning steps;

[0035] S2.2: The MCU controls the power supply module to provide a voltage signal to the input end of the third multi-way analog switch, and then controls the third multi-way analog switch and the second multi-way analog switch, and the third multi-way analog switch and the fourth multi-way analog switch to be in working state respectively, and repeats the above circuit scanning steps;

[0036] S2.3: The on / off status of the circuits in the four directions of each intersection is obtained, and the MCU transmits the data to the PC via serial communication for further algorithm processing and image display.

[0037] Preferably, in S1, the array circuit is scanned by scanning column by column, and the voltage signals are sequentially converted by the ADC into digital signals and sent to the MCU for storage and analysis.

[0038] Preferably, in S2.3, when the electrode grid is damaged, the signal data in the four directions of the test are sent to the PC to perform pattern detection and area calculation of the outer contour of the damaged position.

[0039] Preferably, the damage shape contour judgment algorithm in S3 is specifically as follows:

[0040] S3.1.1: Determine the grid line segments to be disconnected: If the circuits in the two directions adjacent to the intersection are both in an open circuit state, the common grid line segments in the two directions adjacent to the intersection are determined to be disconnected and marked as 0; if one of the circuits in the two directions adjacent to the intersection is in a connected state, the common grid line segments in the two directions adjacent to the intersection are determined to be not disconnected and marked as 1;

[0041] S3.1.2: Determine the specific disconnected grid line segment: If the line segment between two adjacent points is marked as 0, the line segment is determined to be in a disconnected state, and the midpoint of the two adjacent points is taken as the disconnection point;

[0042] S3.1.3: Execute S3.1.1 to S3.1.2 on the entire grid map, and generate a number of two-dimensional point groups consisting of cut points on the grid map, and connect the outer points of the two-dimensional point groups in sequence to form a damaged outer contour image.

[0043] Preferably, the area estimation method is as follows:

[0044] S3.2.1: Subdivide and approximate the outer contour image generated by the outer contour judgment algorithm to obtain a smooth outer contour image;

[0045] S3.2.2: Select a point inside the generated outer contour polygon, and then evenly select several points on the edge of the outer contour. Connect the selected points with the edge points of the outer contour polygon to form several triangles. Calculate the distance between the inner point and the edge points, and use Heron's formula to calculate the area of ​​each triangle and then sum up the areas to calculate the damaged area.

[0046] Compared with the prior art, the present invention provides a printable electronic skin for high-precision detection of damage position and outer contour, which has the following beneficial effects:

[0047] The present invention measures the electrical signals of each intersection point between the longitude and latitude lines to quickly detect and determine the damaged position, and constructs a diode at the intersection. It also accurately evaluates the damaged shape and damaged outer contour of the damaged point and the surrounding lines through the characteristics of diode rectification, and accurately calculates the damaged area according to the damaged outer contour generated by the computer, which can greatly improve the damage positioning and detection accuracy. In addition, the electronic skin can be prepared by full solution printing technology, and can be in-situ superimposed layer by layer on the surface of the object to be tested according to the structure of electrode-insulating layer-electrode-diode layer. The direct in-situ construction method can directly reflect the damage on the surface of the object, improve the detection sensitivity of the damage, and the preparation is more convenient and quick. The wiring of the electronic skin proposed by the present invention is relatively simple, the crosstalk between lines can be completely eliminated, the operation is convenient, the deployment difficulty and cost are low, and it has good potential applications in human-computer interaction interfaces, solar panels, and various mechanical equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The detection principle, the principle of the diode control circuit and the schematic diagram of the electronic skin mentioned in Example 1 of the present invention;

[0049] Figure 2 The in-situ construction strategy of the damage detection electronic skin on a complex curved surface and the large-area preparation process diagram of the organic diode mentioned in Example 1 of the present invention;

[0050] Figure 3 This is a flow chart of implementing the damage detection method mentioned in Embodiment 2 of the present invention;

[0051] Figure 4 This is a schematic diagram of the scanning circuit mentioned in Embodiment 2 of the present invention;

[0052] Figure 5 This is a schematic diagram of damage shape and outer contour judgment mentioned in Example 2 of the present invention;

[0053] Figure 6 This is a schematic diagram of the damage position and contour detection effect mentioned in Example 2 of the present invention. DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0055] The present invention measures the conductivity of the intersection points between the longitude and latitude lines to quickly detect and determine the damage location, and accurately evaluates the damage shape and outer contour of the damaged point and the surrounding lines through the characteristics of diode rectification, and accurately calculates the damaged area based on the damaged outer contour generated by the computer, which can greatly improve the damage location and detection accuracy. The electronic skin proposed by the present invention has relatively simple wiring, crosstalk between lines can be completely eliminated, easy to operate, and has low deployment difficulty and cost. It has good potential applications in human-computer interaction interfaces, solar panels, and various mechanical equipment. Specifically including the following contents.

[0056] Embodiment 1:

[0057] See also Figure 1-2The present invention discloses a printable electronic skin, comprising: a flexible polymer substrate (such as PET, PI, TPU, etc.), a conductive warp-weft network (such as a conductive carbon electrode, a silver electrode, a copper electrode, etc.), an insulating layer (such as UV insulating ink), and a diode element. The conductive warp-weft network adopts a "sandwich" structure of electrode-insulating layer-electrode. In this embodiment, the conductive warp-weft network is also patterned with electrodes, and a side electrode is added to the electrode at each point to facilitate the integration of the diode; the size of the insulating layer is slightly larger than the cross-section of the electrode. Figure 1 (a) The left side describes the basic principle of the detection method. By measuring the signal values ​​of the circuits corresponding to each other in the four directions of each intersection, the on-off status of the circuits near the intersection can be determined, thereby comprehensively judging the damage status of the intersection. Figure 1 (a) The right side describes the principle of eliminating mutual interference between intersections based on the unidirectional conductivity of diodes. One current flows to the test path of the point to be tested, and the other current and the dark gray current flow to the column electrode interference branch and the row electrode interference branch respectively. Due to the reverse cutoff characteristics of the diode, the current cannot pass through these interference branches, so only the branch of the diode to be tested can be turned on, and the final measured on-off state depends only on the point to be tested. If the diode is replaced with an ordinary conductor resistor, there is no diode on the other branches for rectification, resulting in direct connection of the line to generate bypass crosstalk, and the on-off state of the intersection cannot be accurately measured. Figure 1 (b) is an exploded diagram of the components of the electronic skin, which includes, from bottom to top, a substrate, a weft electrode and its side electrodes, an insulating layer, a warp electrode and its side electrodes, and a diode; Figure 1 (c) is a schematic diagram of the three-dimensional configuration at the intersection. The positive and negative poles of the diode represent the direction of forward conduction and reverse cutoff, and the contact area is increased by the side electrodes to improve the stability of the signal.

[0058] In order to make the electronic skin easy to attach to the curved surface and have a higher sensitivity for damage detection, the flexible polymer substrate should be bendable, thin and easy to break. PI (polyimide), PET (polyethylene terephthalate), TPU (thermoplastic polyurethane elastomer) and other materials with good flexibility can be selected, and the electronic skin can be prepared directly on the surface of the object through full solution printing technology; the conductive warp and weft network is one of the core parts of the electronic skin, and should have the characteristics of stable potential, good reproducibility and not easy to fall off the substrate. The optional conductive pastes include silver, graphene, copper, etc. These materials can be stably deposited on a variety of substrates and are not easy to fall off; the insulating layer is added to prevent direct contact between the warp electrodes and the weft electrodes, which may cause a short circuit at the intersection node; the diode adopts a jet-printed organic diode, and the diode element is constructed in situ between the warp electrodes and the weft electrodes through a full solution jet printing process.

[0059] Reference Figure 2The base part of the electronic skin is deposited on the substrate or the surface of the object by inkjet printing. Inkjet printing is a maskless technology for rapid prototyping. It deposits a small amount of polymer solution, small molecule dispersion or nanoparticle suspension on various surfaces and substrates to form a specific pattern. The preparation process of the base part of the electronic skin is as follows: Figure 2 As shown in (a), first, a flexible polymer base layer is printed on the surface of the object, and then a conductive paste (such as conductive carbon paste, silver paste, copper paste, etc.) is used to print the weft conductive electrodes by inkjet printing. After drying, an insulating layer (such as UV insulating ink) is printed on the corresponding points of the warp electrodes, and an insulating layer of a certain thickness is obtained after ultraviolet light curing. The insulating layer is printed multiple times. Finally, the warp conductive electrodes are printed on the corresponding insulating layer using a conductive paste to obtain the warp and weft electrode network part of the electronic skin.

[0060] Depending on the actual conditions of the environment and surface of the object to be tested, the diode part of the electronic skin can be welded or bonded with ordinary SMD diodes, or it can be prepared by direct printing, and the printing method is more convenient. Figure 2 As shown in (b), a typical organic diode is an organic diode based on the PN junction principle, which is prepared by contacting a p-type semiconductor material with an n-type semiconductor material. The p-type organic semiconductors that can be used include P3HT, oxidized PA (polyacetylene), PAN (polyacrylonitrile), polycyclic aromatic hydrocarbons, sexithiophene and its derivatives, phthalocyanine compounds, etc., and the n-type organic semiconductor materials include NTCDI (naphthalenetetracarboxylic diimide), reduced PA, lutetium phthalocyanine, single crystal dinaphthylene, etc. Figure 2 As shown in (c): First, a bottom electrode is printed on a side electrode at each intersection of the warp and weft network electrodes, sintered at 100-150°C, and after solidification, an N-type organic semiconductor within a certain thickness range is printed, and sintered and solidified at 100-150°C; then, the P-type semiconductor layer and the top electrode are printed layer by layer in sequence, the top electrode is connected to another side electrode, and the P-type semiconductor layer and the top electrode layer are sintered at 100-150°C; finally, after the diode printing at each point is completed, an insulating protective layer is printed on the overall surface of the electronic skin.

[0061] The other is a diode based on the Schottky barrier principle. The organic diode consists of two electrode layers and a polymer semiconductor layer and an insulator layer sandwiched between the two electrode layers. As long as the work functions of the top electrode material, the polymer semiconductor material, and the bottom electrode material are in a certain relationship, an ohmic contact that does not hinder the flow of charge and a Schottky contact that hinders the flow of charge under voltage bias can be formed respectively to achieve rectification characteristics. Among them, the materials that can be used for the semiconductor layer include PTAA (poly(triarylamine)), P3HT (poly(3-hexylthiophene)), P(NDI2OD-T2) (poly{[N,N′-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt5,5′-(2,2′-bithiophene)}), etc. The electrode layer can use metal electrodes (silver electrodes, copper electrodes, aluminum electrodes, etc.) and polymer electrodes (such as PEDOT:PSS ((3,4-ethylenedioxythiophene)-polystyrene sulfonic acid)). The insulator layer is an important part of the diode. The work function of the bottom electrode can be changed according to its thickness, so that it can be prepared using materials such as PMMA (polymethyl methacrylate), MMAcoMAA (poly(methyl methacrylate / methacrylic acid)), and PEI (polyethyleneimine). The preparation process is similar to that of an organic diode based on a PN junction.

[0062] Embodiment 2:

[0063] See also Figure 3-6 The present invention provides a detection method for high-precision detection of damage position and outer contour of printable electronic skin. The above method is implemented based on a scanning circuit, and the corresponding row and column lines are continuously selected by a multi-way analog switch to send the signal to the ADC. Figure 4 The scanning circuit includes four multi-channel analog switches, ADC, MCU and power supply module, wherein the MCU is connected to the address end and control end of the four multi-channel analog switches to control the gating of the measurement path and measurement direction in the circuit; the MCU is also connected to the address end of the analog switch in the power supply module to control the gating of the output end of the power supply module; the ADC receives the analog signal transmitted by the multi-channel analog switch and converts it into a digital signal and sends it to the MCU; the MCU transmits the data to the PC through serial communication for further algorithm processing and image display;

[0064] The signal acquisition process based on the scanning circuit is as follows:

[0065] S2.1: The MCU controls the power supply module to provide a voltage signal to the input end of the first multi-way analog switch, and the MCU controls the first multi-way analog switch and the second multi-way analog switch to be in working state, wherein the working voltages of the four multi-way analog switches are all provided by the internal power supply voltage of the MCU, and controls the channels of the first multi-way analog switch and the second multi-way analog switch to scan the array circuit by inputting different level signals to the address end, and the MCU controls the first multi-way analog switch and the fourth multi-way analog switch to be in working state, and repeats the above circuit scanning steps;

[0066] S2.2: The MCU controls the power supply module to provide a voltage signal to the input end of the third multi-way analog switch, and then controls the third multi-way analog switch and the second multi-way analog switch, and the third multi-way analog switch and the fourth multi-way analog switch to be in working state respectively, and repeats the above circuit scanning steps;

[0067] S2.3: The on / off status of the circuits in the four directions of each intersection is obtained, and the MCU transmits the data to the PC via serial communication for further algorithm processing and image display.

[0068] Reference Figure 5 , the coordinates of the four directions of the electrode grid are named an, bn, cn, dn (n = 1, 2, 3 ... 10). Figure 5 When the damage is shown in (a), the signal data in four directions is tested and sent to the PC. The damage shape contour judgment algorithm can be used to obtain the following Figure 5 (b) shows the damaged outer contour, and the contour area can be calculated by the area estimation method. If the signal value is only tested in one direction, since the test paths of the intersection points in the same column or row may overlap, it is very likely to cause misjudgment if the signal value is only passed in one direction. For example, for point (a4, b6), if only the signal at the (a4, b6) end is tested, it can be determined that the point is cut off. Similarly, in the column (a4, b4), if the signal value of the point below (a4, b4) is only measured in one direction, it will be misjudged. Therefore, it is necessary to test the signal values ​​in four directions to comprehensively determine the on-off state of the intersection.

[0069] The damaged shape and outer contour judgment algorithm is as follows:

[0070] S2.3.1.1: Determine the grid line segments to be disconnected. If the circuits in the two directions adjacent to the intersection are both open, the common grid line segments in these two directions are determined to be disconnected and marked as 0; if one of the circuits in the two directions adjacent to the intersection is connected, the common grid line segments in these two directions are determined to be connected and marked as 1. For example, for point (a4, b6), the circuit in the (a4, b6) direction of this point is measured to be open, indicating that the two lines in this direction are cut, but the specific line and position cannot be determined. The circuit in the adjacent (a4, b6) direction is also measured to be open, so we judge that the line upward from the common line in the two directions at the intersection is cut, but the specific position cannot be determined, so the (a4, d6)-(a4, d5) line segment is judged to be disconnected and marked as 0; in the circuits in the (a4, b6) direction and the (c4, b6) direction of this point, the circuit in the (c4, b6) direction is not open, so it is judged that the common line segment in the two directions is not cut, and the (a4, d6)-(a5, d6) line segment is marked as 1. By judging the two adjacent directions of the point in turn, we can finally conclude that the line segments around point (a4, b6) are marked as (1, 0, 1, 1) (counting clockwise from the left end). Similarly, we can obtain the quasi-on and off states of the four grid electrodes at all intersections on the (a4, c4) column.

[0071] S2.3.1.2: Determine the specific disconnected grid line segments. If the line segments between two adjacent points are marked as 0, the line segment is judged to be in a cut-off state, and the midpoint of the point is taken as the cut-off point, that is, the search is performed from both ends of the same line. If it is to be disconnected in both the front and rear directions, it is judged to be a cut-off point. For example, the line segments between point (a4, d2) and point (a4, d3), and between point (a4, d5) and point (a4, d6) can be judged to be in a cut-off state. The above analysis is performed on the entire grid map, and finally a two-dimensional point group consisting of several cut-off points is generated on the grid map.

[0072] S2.3.1.3: Connect the outer contour of the two-dimensional point group to generate Figure 5 The figure shown in (b) can reflect the location, outer contour and area of ​​the surface damage at this time.

[0073] The method of outer contour generation and area calculation is as follows: first, use the correlation algorithm to extract the outer contour formed by the two-dimensional point group, and connect them to form a damaged outer contour image; then use the correlation function to subdivide and approximate the generated outer contour image to obtain a smooth outer contour image; finally, the area of ​​the damaged outer contour figure is calculated, and the calculation algorithm is as follows: select a point in the generated outer contour polygon, and then evenly select several points on the edge of the outer contour, connect the selected points with the selected points in the outer contour to form a triangle, calculate the distance between the inner point and the edge points, and use Heron's formula to calculate the area and then sum them up to estimate the approximate area.

[0074] Reference Figure 6 , Figure 6 (a) shows the schematic diagram of the damaged outline of the electronic skin after being damaged by a knife during the experiment. Before the experiment, each electrode was tested to ensure that there was no short circuit or open circuit. First, the 20 electrodes were tested using the straight-through wire detection method, and the on / off status was recorded as 0 / 1 and saved as a 10×2 matrix. Finally, the computer generated the following Figure 6 (b) shows the detected contour, and the area is calculated to be 55.76; then the high-precision detection method of measuring the outer contour of the intersection is used to detect the on-off status of each of the 7×6 damaged points in four directions, and the on-off status is recorded as 0 / 1 and saved as a 42×4 matrix. The contour point group is generated by connecting the boundary points and smoothing them to generate the following Figure 6 (c) shows the detected contour with an area of ​​30.25.

[0075] By comparison, it can be seen that the image and area generated by the high-precision detection method for measuring the outer contour of the intersection point are more consistent with the actual damage pattern, and the detected damage area is also more accurate. The detection method of the straight-through wire can only roughly detect the location of the damage by detecting the cutting of the wire, while this high-precision detection method for measuring the outer contour of the intersection point can measure the cutting of the grid line at the intersection of each longitude and latitude electrode. It can not only detect the location of the damage, but also accurately determine the damage point to each grid, greatly improving the detection accuracy.

[0076] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A printable electronic skin for high-precision detection of damage position and outer contour, characterized in that: The electronic skin is prepared by printing the electronic skin directly on the surface of an object based on the full solution printing technology; the electronic skin includes a flexible polymer substrate, a conductive warp and weft network, an insulating layer and a diode element; The conductive warp and weft network is prepared by adopting a three-dimensional planar configuration of electrode-insulating layer-electrode. A side electrode is added to the electrode at each point of the conductive warp and weft network for the integration of the diode array. The electronic skin is provided with a flexible polymer substrate, a weft electrode and its side electrode, an insulating layer, a warp electrode and its side electrode, and a diode array in sequence from the bottom to the top. The electronic skin detection method comprises the following steps: S1: Use the full solution printing process to construct a conductive warp-and-weft network with mutually insulated warp-and-weft electrodes and diodes at the intersections to form a damage detection electronic skin, and build an array scanning circuit; The array scanning circuit includes four multi-way analog switches, an ADC, an MCU and a power supply module, wherein the MCU is connected to the address terminals and control terminals of the four multi-way analog switches to control the gating of the measurement path and the measurement direction in the scanning circuit; the MCU is also connected to the address terminals of the four multi-way analog switches in the power supply module to control the gating of the output terminal of the power supply module; the ADC receives the analog signals transmitted by the four multi-way analog switches, converts them into digital signals and sends them to the MCU; the MCU transmits the data to the PC through serial port communication for further algorithm processing and image display; S2: Using the rectification characteristics of the diode, the resistance or voltage signal of the circuits in the four directions at each intersection of the longitude and latitude sensing electrode network is collected, and the collected electrical signals are used to determine damage. If it is determined that no damage has occurred, S2 is continued to be executed. If it is determined that damage has occurred, S3 is transferred; S3: Count the damage of each intersection, obtain the pattern of the damaged outer contour based on the damage shape contour judgment algorithm, and then calculate the damaged contour area based on the area estimation method.

2. The printable electronic skin for high-precision detection of damage position and outer contour according to claim 1, characterized in that: The conductive longitude and latitude network utilizes the rectifying characteristics of diodes to prevent mutual interference in signal detection between intersections.

3. The printable electronic skin for high-precision detection of damage position and outer contour according to claim 2, characterized in that: The specific preparation process of the electronic skin is as follows: Step A: Printing a flexible polymer substrate layer on the surface of the object; Step B: using a conductive paste to print the weft conductive electrodes by inkjet printing; Step C: after drying, the insulating layer is printed on the points corresponding to the warp electrodes, and an insulating layer of a certain thickness is obtained after ultraviolet light curing; Step D: Printing the insulation layer through several printing operations; Step E: Use conductive paste to print warp conductive electrodes on the corresponding insulating layer to obtain the warp and weft electrode network part of the electronic skin.

4. The printable electronic skin for high-precision detection of damage position and outer contour according to claim 3, characterized in that: In the specific preparation process of the electronic skin, the diode element is constructed in situ at the intersection of the warp electrode and the weft electrode by a full solution printing process; The diode element adopts an organic diode or a Schottky diode; the organic diode comprises four layers: a bottom electrode, an N-type organic semiconductor layer, a P-type organic semiconductor layer and a top electrode; the Schottky diode comprises four layers: a bottom electrode, a polymer semiconductor layer, an insulating layer and a top electrode; the specific preparation steps of the diode element are as follows: Step 1: Print the bottom electrode on one of the side electrodes in the intersection of the warp and weft network electrodes, and sinter and solidify at 100-150°C; Step 2: Print a second layer within a certain thickness range on the bottom electrode layer and sinter and solidify it at 100-150°C; Step 3: Print the third layer and sinter and solidify at 100-150℃; Step 4: Finally, the printed top electrode is connected to another side electrode at the intersection of the warp and weft network electrodes, and sintered and cured at 100-150°C; Step 5: After the diode printing at each point is completed, an insulating protective layer is printed on the entire surface of the electronic skin.

5. The printable electronic skin for high-precision detection of damage position and outer contour according to claim 1, characterized in that: The steps of S2 for judging damage at each intersection of the longitude and latitude sensing electrode network based on the scanning circuit are as follows: S2.1: The MCU controls the power supply module to provide a voltage signal to the input end of the first multi-way analog switch, the MCU controls the first multi-way analog switch and the second multi-way analog switch to be in working state, and controls the channels of the first multi-way analog switch and the second multi-way analog switch to scan the array circuit by inputting different level signals to the address end, the MCU controls the first multi-way analog switch and the fourth multi-way analog switch to be in working state, and repeats the above circuit scanning steps; S2.2: The MCU controls the power supply module to provide a voltage signal to the input end of the third multi-way analog switch, and then controls the third multi-way analog switch and the second multi-way analog switch, and the third multi-way analog switch and the fourth multi-way analog switch to be in working state respectively, and repeats the above circuit scanning steps; S2.3: The on / off status of the circuits in the four directions of each intersection is obtained, and the MCU transmits the data to the PC via serial communication for further algorithm processing and image display.

6. The printable electronic skin for high-precision detection of damage position and outer contour according to claim 5, characterized in that: In S2.3, when the electrode grid is damaged, the signal data in the four directions of the test are sent to the PC to perform pattern detection and area calculation of the outer contour of the damaged position.

7. The printable electronic skin for high-precision detection of damage position and outer contour according to claim 1, characterized in that: The damage shape contour judgment algorithm described in S3 is as follows: S3.1.1: Determine the grid line segments to be disconnected: If the circuits in the two directions adjacent to the intersection are both in an open circuit state, the common grid line segments in the two directions adjacent to the intersection are determined to be disconnected and marked as 0; if one of the circuits in the two directions adjacent to the intersection is in a connected state, the common grid line segments in the two directions adjacent to the intersection are determined to be not disconnected and marked as 1; S3.1.2: Determine the specific disconnected grid line segment: If the line segment between two adjacent points is marked as 0, the line segment is determined to be in a disconnected state, and the midpoint of the two adjacent points is taken as the disconnection point; S3.1.3: Execute S3.1.1 to S3.1.2 for the entire grid map, and generate several two-dimensional point groups consisting of cut points on the grid map, and connect the outer points of the two-dimensional point groups in sequence to form a damaged outer contour image.

8. The printable electronic skin for high-precision detection of damage position and outer contour according to claim 1, characterized in that: The area estimation method described in S3 is as follows: S3.2.1: Subdivide and approximate the outer contour image generated by the outer contour judgment algorithm to obtain a smooth outer contour image; S3.2.2: Select a point inside the generated outer contour, then evenly select several points on the edge of the outer contour, connect the selected points with the selected points inside the outer contour to form several triangles, calculate the distance between the inner point and each point on the edge, and use Heron's formula to calculate the area of ​​each triangle and then sum the areas to calculate the damaged area.

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