CN111189493A - Flexible intelligent skin for multi-physical-field measurement, metamorphic structure and application thereof - Google Patents
Flexible intelligent skin for multi-physical-field measurement, metamorphic structure and application thereof Download PDFInfo
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Abstract
The invention belongs to the field of flexible electronic skin, and discloses a flexible intelligent skin for multi-physical-field measurement, a metamorphic structure and application thereof. The flexible intelligent skin sequentially comprises a first electrode, a dielectric layer, a second electrode, a piezoelectric layer and a third electrode from top to bottom, wherein the first electrode, the dielectric layer and the second electrode form a capacitance sensor, and the second electrode, the piezoelectric layer and the third electrode form a piezoelectric sensor; the second electrode comprises two resistors which are respectively a first resistor and a second resistor, the first resistor forms a resistor sensor, and the first resistor and the second resistor together form a capacitor sensor; the third electrode comprises two resistors with different thermoelectric coefficients, namely a third resistor and a fourth resistor, the third resistor forms a resistor sensor, and the third resistor and the fourth resistor form a thermocouple sensor together. The invention realizes the measurement of physical quantities such as pressure, temperature, strain, vibration, humidity, flow rate, health state and the like, has highly integrated functions and simplified structure.
Description
Technical Field
The invention belongs to the field of flexible electronic skin, and particularly relates to a flexible intelligent skin for multi-physical-field measurement, a metamorphic structure and application thereof.
Background
Flight parameters such as flight speed adjustment, attitude adjustment, maneuverability operation, environment perception and the like need to be acquired during wind tunnel test and attitude adjustment of the aircraft in the flight process in the design stage, and parameters such as a surface flow field, a wind pressure and wind resistance, temperature and humidity, vibration characteristics and the like need to be acquired in a complex airflow environment depending on real-time acquisition of flight pneumatic parameters of the surface of the aircraft. The existing mature punching method and intelligent coating method in the wind tunnel test have the disadvantages of high cost, complex measurement and relatively single measurement amount, and cannot simultaneously measure various pneumatic parameters on the surface of an aircraft. The research of the intelligent skin sensor at the present stage is also in a basic research stage of small-area and single sensing. Therefore, the multifunctional sensor can be conformally attached to the complex surface of the aircraft in a large area and can obtain the surface aerodynamic parameters, and the multifunctional sensor has very important significance for aircraft research.
Related proposals have been made in the prior art, for example, northwest industry institute of university and park daisie political team proposed a flexible light and handy skin, which utilized optical methods, hot-film methods, etc. to measure environmental parameters such as pressure and flow rate (fresh, leeway, marburg and, et al. MEMS micro pressure sensor for measuring air flow on the outer surface of skin [ J ] mechanical science and technology, 2005(3): 312. liuqiu, aster wei, warfarin, et al. micro flexible thermal sensor array application research [ J ] instrumental report, 2007,28(9): 1583. 1587.), which was very thin and flexible, and had high sensitivity and accuracy, but the measured physical quantities were relatively small, mainly concentrated on pressure, shear stress, flow rate, etc., and each physical quantity was measured separately. A super-stretching sensor network is prepared by a Qinghai Xinlin team of Xiamen university, and multiple functions can be integrated in a stacking mode to prepare a large-area multifunctional sensor network (Qing XP. distributed multifunctional sensor network for composite structural state sensing. proceedings of SPIE-The International society for Optical Engineering 2012,8345(2): 103). Moreover, the complexity of the sensor network is quite high, which greatly increases the difficulty of preparation and testing.
Aiming at the distributed measurement requirements of large-area surface and multiple physical quantities of an aircraft, the prior art can not meet the requirement of measuring multiple physical fields in an online and in-situ manner, or can not ensure the integration density of the sensor on the premise of ensuring multiple functions, so that the difficulty in preparing and testing the sensor network is greatly increased. Therefore, it is urgently needed to design and manufacture a sensor network which is applicable to the curved surface of an aircraft, can complete measurement of a plurality of physical quantities in situ, and has the advantages of simple preparation process, convenient test process, rich sensing functions, high device space utilization rate and high integration density.
Disclosure of Invention
Aiming at the defects or improvement requirements of the prior art, the invention provides a flexible intelligent skin for multi-physical-field measurement, a metamorphic structure and application thereof, and the electrodes of all layers are designed, so that each layer of electrode can be independently used as a sensor for application, and can also be matched with electrodes of other layers to form another sensor, the functions of a plurality of sensors are highly integrated, on one hand, the complicated work of switching the plurality of sensors in the measurement process is reduced, meanwhile, the number of pins of the sensors is also reduced, and the process is simplified.
To achieve the above object, according to one aspect of the present invention, a flexible smart skin for multi-physical-field measurement includes, in order from top to bottom, a first electrode, a dielectric layer, a second electrode, a piezoelectric layer, and a third electrode, wherein,
the first electrode, the dielectric layer and the second electrode form a capacitance sensor, the dielectric layer is a flexible insulating base material and is used for separating the first electrode from the second electrode; reflecting the change of the external environment by measuring the change of the capacitance between the first electrode and the second electrode;
the second electrode, the piezoelectric layer and the third electrode form a piezoelectric sensor, the piezoelectric layer is used for separating the second electrode from the third electrode, and when the flexible smart skin is subjected to pressure, the pressure is reflected by measuring the voltage between the second electrode and the third electrode;
the second electrode comprises two resistors, namely a first resistor and a second resistor, the first resistor is bent to form a sensitive grid structure, the length of the resistor is prolonged, the second resistor is distributed in parallel with the first resistor, pins A and F are arranged at two ends of the first resistor, a pin D is arranged at the tail end of the second resistor, the first resistor forms a resistor sensor, the change of the resistor is reflected by monitoring the resistor between the pins A and F, the first resistor and the second resistor together form a capacitor sensor, and the change of the capacitor is reflected by monitoring the capacitor between the pins A/F and D;
the third electrode comprises two resistors with different thermoelectric coefficients, namely a third resistor and a fourth resistor, the third resistor is of a sensitive grid structure, the fourth resistor is communicated with the third resistor and forms a thermocouple at a connecting point, pins B and E are arranged at two ends of the third resistor, a pin C is arranged at the tail end of the fourth resistor, the third resistor forms a resistor sensor, the change of the resistors is reflected by monitoring the resistance between the pins B and C, the third resistor and the fourth resistor together form a thermocouple sensor, and the change of the thermocouple is reflected by monitoring the thermocouple between the pins B/E and C.
Further preferably, the first electrode is preferably made of an electromagnetic wave absorbing material for absorbing electromagnetic waves.
Further preferably, the first resistor and the second resistor are made of the same material, and preferably have a strain sensitivity coefficient of more than 1.6, a resistivity of more than 0.25 [ mu ] omega-mm, and a temperature coefficient of resistance of less than 40 × 10-6The material between/DEG C has high sensitivity coefficient and keeps constant to make the first resistor sensitive to strain, the resistivity is high, the signal-to-noise ratio can be improved, the influence of lead resistance is reduced, the temperature coefficient of the resistor is small, the sensitivity of the first resistor to temperature can be reduced, and therefore the first resistor is guaranteed to have high sensitivity only to strain change.
Further preferably, the material of the third resistor preferably has a temperature coefficient of resistance greater than 3000 × 10-6The material of/° c and the material of the fourth resistor are preferably materials having a thermoelectric coefficient difference of more than 5 μ V/° c from the third resistor, so that the third resistor forms an RTD temperature sensor, and the third resistor and the fourth resistor form a thermocouple temperature sensor, thereby satisfying temperature measurements in different temperature ranges. Further preferably, the thickness of the flexible smart skin is preferably 20 μm to 30 μm.
Further preferably, the first electrode, the second electrode and the third electrode are obtained by obtaining a required shape through photoetching in sequence and then depositing metal through magnetron sputtering or evaporation.
Further preferably, an additional resistor is connected to the first resistor, so as to increase the area coverage of the third electrode.
According to yet another aspect of the present invention, there is provided a use of the multi-physics measuring flexible smart skin described above for measuring pressure, temperature, strain, vibration and humidity.
According to another aspect of the present invention, there is provided a multi-cell structure formed by the flexible smart skin for multi-physical field measurement, wherein the flexible smart skin is used as a single cell, and a plurality of single cell structures are oppositely arranged to form the multi-cell structure, the multi-cell structure is attached to the surface of an object to be measured, an alternating current is introduced between the second electrode and the third electrode in one of the single cells, voltages between the second electrode and the third electrode in other single cells are measured, and the surface quality of the object to be measured is reflected by different voltages in the single cells measured at different positions; or, the multi-cell structure is attached to the surface of the object to be measured, the resistance of the two ends of the third electrode B, E of the other single cell is measured through direct current in the third electrode of one single cell, and the flow rate of the air at the position of the single cell is obtained through calculation according to the resistance.
According to a further aspect of the present invention there is provided the use of a multicellular structure as described above for monitoring the health of an aircraft and the ambient air flow rate.
In general, the above technical solutions contemplated by the present invention can achieve the following advantageous effects compared to the prior art.
1. The invention provides a large-area conformal flexible intelligent skin, which is characterized in that a multimode intelligent and changeable cell sensor is provided, the geometric structure of the sensor cannot be changed, and the selection of electrodes with different functional structures is completed through the switching between topological logic circuits, so that the electrodes can work in different functional modes, the in-situ measurement requirement of one sensor for multiple physical quantities is met, the space utilization rate of the sensor is greatly improved, the integration density of the sensor is improved, and the high-density measurement requirement of the intelligent skin is met;
2. the flexible intelligent skin has multiple functions due to the structural design and material characteristics of each layer of electrode, can finish the measurement of corresponding single physical quantity, can finish the measurement of different physical quantities by combining different layers of electrodes for use, has other multiple functions, can finish the measurement of other physical quantities by only selecting the output pin of the intelligent metamorphic sensor through the corresponding topological logic circuit designed by the invention, can finish the measurement of different physical quantities by pasting one flexible intelligent skin, can finish the online in-situ measurement of physical quantities such as pressure, temperature, strain, vibration, humidity, flow rate and the like on the surface of an object to be measured at high density and large area, and can also finish the structural health monitoring of the surface of the object to be measured.
Drawings
FIG. 1 is a schematic diagram of an exploded structure of a single cell flexible smart skin constructed in accordance with a preferred embodiment of the present invention;
FIG. 2 is a schematic top view of a flexible smart skin constructed in accordance with a preferred embodiment of the present invention;
FIG. 3 is a schematic diagram of a first electrode constructed in accordance with a preferred embodiment of the invention;
FIG. 4 is a schematic diagram of a second electrode constructed in accordance with a preferred embodiment of the invention;
FIG. 5 is a schematic structural diagram of a third electrode constructed in accordance with a preferred embodiment of the present invention;
FIG. 6 is a schematic diagram of a topology logic circuit constructed in accordance with a preferred embodiment of the present invention;
fig. 7 is a schematic diagram of a multi-cell flexible smart skin assembly constructed in accordance with a preferred embodiment of the present invention.
The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:
1-first electrode, 2-dielectric layer, 3-second electrode, 4-piezoelectric layer, 5-third electrode, 6-additional resistance.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The main part of the flexible smart skin comprises five layers of structures in total, as shown in figure 1, a first electrode 1, a dielectric layer 2, a second electrode 3, a piezoelectric layer 4 and a third electrode 5 are sequentially arranged from top to bottom, the first electrode can be used as an electromagnetic wave absorption layer, the second electrode 3 can be used for measuring a strain and humidity sensing layer, and the third electrode 5 can be used for measuring temperature. The first electrode 1 is provided with a pin G, the second electrode 3 is provided with three pins A, D and F, the third electrode 5 is provided with three pins B, C and E, and each unit cell flexible smart skin has 7 pins. The thickness of the whole device is 20-30 mu m, the device has good flexibility, and the device is very suitable for being attached to the surface of a curved aircraft to perform in-situ measurement of multiple physical quantities.
As shown in fig. 3, the first electrode 1 is a metamaterial structure having an electromagnetic wave absorption function, for example, a cross-shaped, zigzag, circular structure, etc.; when the intelligent metamorphic sensor does not work, the first electrode 1 forms an LC oscillation circuit, so that electromagnetic waves in the external environment can be absorbed, and an object to be detected is in a stealth state
As shown in fig. 4, the second electrode 3 includes a first resistor of a metal strain gauge type sensitive grid structure, the material of which may be constantan, and a second resistor engaged with the first resistor, in the figure, the black area is the first resistor and an additional resistor, the first resistor and the additional resistor are placed in a matching manner, the additional resistor is filled in a gap of the sensitive grid structure formed by the first resistor and is communicated with the first resistor at a certain position, the gray grid area is the second resistor, the first resistor and the second resistor are arranged in parallel, and the first resistor and the second resistor are matched to form a planar capacitance sensor, which can be used for measuring the humidity on the surface of an aircraft, and the area coverage rate of the whole second electrode 2 is greatly increased by the sensitive grid structure; when the second electrode 3 is used alone, it can be used alone as a resistance sensor and a capacitance sensor, which can be used to measure the strain and humidity of the object to be measured, respectively, and when used to measure humidity, the dielectric constant of its capacitance is related to the humidity of the environment.
The first resistor is a sensitive grid foil type, namely A to F in the figure, and the material is constantan (Cu)55Ni45) The resistivity of constantan is relatively large, and the temperature coefficient of resistivity is relatively low, so that the influence of temperature is very small on the premise of accurately measuring strain, and each resistance strain unit Rx and three standard resistors R are interconnected to form a Wheatstone full-bridge circuit. If the power supply voltage of the bridge is Vcc, the voltage difference of the bridge arms is divided,
furthermore, in order to increase the area coverage rate of the whole second electrode, a second resistor is designed, the second resistor and the first resistor form a planar capacitance sensor, the plate-to-plate area of the capacitor is fixed, the plate-to-plate distance is only related to the dielectric constant between the plates of the capacitor, the dielectric constant is easily influenced by humidity in the environment, and therefore when the humidity changes, the capacitance of the parallel plate capacitor changes along with the change of the humidity, and the humidity of the surface of the aircraft can be measured.
As shown in fig. 5, the third electrode 5 comprises two resistors with significantly different thermoelectric coefficients, one of which is the third resistor of the sensing grid foil of the thermoresistive temperature sensor, the white meandering area of which is the third resistor, the material of which is selected to be platinum, in order to further increase the area coverage of the third electrode 5, another one is a fourth resistor connected to the platinum grid sensitive to temperature, the black area in the figure is the fourth resistor, in the enlarged view in fig. 5, indicated by the white dashed box, it can be seen that the third resistor communicates with a fourth resistor, optionally platinum rhodium, the two resistors cooperating to form a thermocouple sensor, the resistance temperature measuring device is used for measuring the temperature in a larger range, completing the measurement of the temperature in a larger range or increasing the robustness of the temperature measurement, making up the deficiency of the measuring range of the third resistance temperature, and the measurement results of the resistance temperature measuring device and the resistance temperature measuring device can be verified mutually in a low temperature range.
An additional resistor 6 is also connected to the fourth resistor, as shown in fig. 5, and serves to increase the area coverage of the third electrode.
In this embodiment, the third electrode is made of platinum with a relatively high temperature coefficient of resistance as a material of the temperature sensing layer, and the resistance temperature unit is configured as a foil type with a sensitive gate structure that is uniformly distributed along eight directions, such as pins B to E in the figure, so as to ensure accuracy in temperature measurement.
In addition, in order to increase the whole area coverage rate of the third electrode, a fourth resistor is connected with the third resistor, so that the whole duty ratio of the third electrode is increased from 42% to 88%, the electrical output performance of the third electrode is greatly improved, and the fourth resistor is made of platinum-rhodium alloy and forms a platinum-rhodium thermocouple sensor together with the third resistor made of platinum.
The platinum resistance temperature sensor has higher sensitivity and precision, but the measurement range is-50-150 ℃, while the precision of the thermocouple is lower, but the measurement range can reach 2000 ℃, and the measurement range can work at 0-350 ℃ due to the limitation of the substrate material. Therefore, in a low-temperature range, a platinum resistor temperature sensor mode is selected to improve the measurement accuracy, and a thermocouple temperature sensor mode can be selected to correct the measurement result of the platinum resistor; when the temperature sensor is in a high-temperature range, the measurement precision is not very high, and a thermocouple temperature sensor mode can be selected, so that the accuracy, the universality and the robustness of temperature measurement are improved through the conversion of the measurement mode.
Dielectric layer, insulating flexible substrate, optional materials are: PI (good temperature resistance), PDMS, etc., which separates the first and third electrodes so that they can form a capacitor;
a piezoelectric layer interposed between the second electrode 3 and the third electrode 5 such that the second electrode, the piezoelectric layer and the third electrode are integrally formed into a piezoelectric sensor, the piezoelectric layer being selected from piezoelectric materials having a large piezoelectric constant, for example: piezoelectric ceramics.
The electrodes of different layers of a single sensor can be used together to form a plurality of brand new sensing measurement modes, the acquisition pins are switched by gating of the topological logic circuit, a capacitance sensor can be formed by a first electrode-dielectric layer-second electrode structure, and the static pressure on the surface of the aircraft can be measured by measuring the capacitance change of the capacitance sensor; the structure of the second electrode 3, the piezoelectric layer and the third electrode 5 forms a piezoelectric sensor, when pressure is applied, positive and negative charges are drawn on the surface of the piezoelectric sensor, voltage is formed by derivation of acquisition equipment, the pressure on the surface of the piezoelectric sensor can be calculated by measuring the voltage between the second electrode 3 and the third electrode, and the piezoelectric sensor is high in frequency response, sensitivity and response speed and is very suitable for measuring high-frequency dynamic pressure or vibration signals on the surface of an aircraft.
A multilayer structure of a first electrode-a dielectric layer-a second electrode-a piezoelectric layer-a third electrode. For a multilayer structure sensor, the typical structure is an electrode-functional layer-electrode structure mode, the most basic function of the electrode is to guide the electrical output signal of the functional layer to an acquisition device for acquisition, and the material selection is generally matched with the structural parameters of the functional layer and the preparation process of the sensor. However, aiming at the design of the electrode, the upper layer electrode and the lower layer electrode not only have the function of simply transmitting electric signals, but also have the functions of sensing, electrical stimulation, sounding, heating, electromagnetic wave absorption and the like. Aiming at a multi-layer structure sensor of an electrode-functional layer-electrode, such as a piezoelectric sensor, a capacitance sensor and the like, one unit cell of the intelligent skin has more functions on the premise of not increasing the structural complexity and the preparation process difficulty of the sensor through the isomerization design of the upper and lower electrodes.
As shown in fig. 7, the flexible smart skin is used as one single cell, when a plurality of single cells form a multi-cell structure together, when the flexible smart skin is in the multi-cell structure, the single cell is used as an electric signal input to be used as a stimulus or an excitation to complete other experimental monitoring or measurement requirements, the requirement of the flexible smart skin on the electrode is that two pins are required to be reserved on a single-layer electrode, so that the output and the input of the electric signal can be facilitated, wherein the second electrode and the third electrode are both of sensitive grid structure foil type electrode designs, as shown in fig. 2, each single cell contains 7 pins, and the total number of the pins is 28 for the multi-cell structure containing 4 single cells. The second electrode and the third electrode are made of different materials to measure different physical quantities, for example, when constantan and platinum are respectively used, the strain and the temperature can be measured. When the second electrode and the third electrode are used as sensors respectively, two pins AF and BE of the first resistor of the second electrode and the third resistor of the third electrode are respectively connected with a lead-out wire, and the temperature or the strain at each unit can BE measured. The four unit cells of the multi-cell structure are arranged in different directions, and the first resistances of the second electrodes of the multi-cell structure are also arranged in different directions, so that the strains in different directions can be measured. When used as a pressure sensor, the second electrode, the piezoelectric layer and the third electrode are connected to form a port, and the two pins of the second electrode are connected to form a port, for example: by connecting the pin A, F as the port O and the pin B, E as the pin P, the output voltage between OP is measured, and the pressure at this point can be known. When one of the unit cells is used as a drive, a drive signal source is connected between two pins of the second electrode of one of the unit cells, for example: when a direct current is applied between the pins B1 and E1, the third electrode is converted into a heat generating source, and the resistance between the two pins of the third electrode of the other unit cell is measured, for example: the flow velocity at the position can be calculated by the resistance among the pins B2-E2, B3-E3 and B4-E4; when alternating current is introduced between the second electrode and the third electrode of one unit cell, the voltage between the second electrode and the third electrode of other unit cells is measured, and the quality states of the other unit cells including whether cracks and impact exist at the measuring position are reflected through the voltage, so that the method is widely applied to the structural health monitoring.
As shown in fig. 6, each cell smart skin has 7 ABCDEFG pins, and two multiplexing electronic switches S1 and S2 are respectively selected to control and switch the 7 pins, so that the output or input of any two pins can be realized. When the method is combined with the specific implementation case of the invention, a plurality of measurement functions are not used simultaneously, so that a bus sharing mode can be adopted, and the complexity of a topological logic circuit is greatly simplified. Therefore, at the other end of the circuit, the switches are S3, S4, S5, S6 and S7 double-pole switches which are respectively and correspondingly connected with five devices of resistance measurement, capacitance measurement, voltage measurement, direct current excitation and alternating current excitation, and thus the measurement of all 8 functions of the intelligent metamorphic sensor can be covered. The conversion between different measurement functions will be specifically described below in conjunction with the structure of each layer.
During measurement, a B pin is selected through a topological logic circuit switch S1, an E pin is selected through a switch S2, the sensor works in a platinum resistance temperature sensor mode, S3 is closed, S4-S7 are disconnected, a B, E pin is connected to resistance acquisition equipment such as an LCR (resistance-capacitance resistor) meter or a digital multimeter, the resistance value and the change of a resistance temperature unit are measured, a sensitivity coefficient value is obtained through a calibration experiment, the temperature change at the position can be converted, and therefore the temperature value at the position can be known. The resistance temperature unit is connected into the bridge, and the temperature value can be calculated by measuring the voltage change at the two ends of the bridge. The C pin is selected through the topology logic circuit switch S1, the B pin or the E pin is selected through the switch S2, the sensor works in a thermocouple temperature sensor mode, the switch S5 is closed, and the potential between electrodes B, C is measured, so that the temperature at the position can be known.
When the third electrodes are required to be used together as electrodes, the switch S1 is selected B, C, E at the same time. When a plurality of units are used in combination, the topological circuit switch S1 of the first unit selects the pin B1, the switch S2 selects the pin E1, the selective switch S6 is closed, the electrode is converted into a heat generating source, the topological circuit switch S1 of the second unit selects the pin B2, the switch S2 selects the pin E2, the selective switch S3 is closed, and the flow velocity at the position can be calculated by measuring the resistance at the position.
Through a topological logic circuit, when the switch S1 selects A, the switch S2 selects F, the switch S3 is closed, the resistance measuring device is connected, the second electrode works in a strain sensor mode, and the magnitude and the direction of the strain on the surface of the aircraft can be measured through the combined measurement of a plurality of sensors; when D is selected at S1, F is selected at S2, and switch S4 is closed, the second electrode is operated in the humidity sensor mode to measure the humidity of the aircraft surface. When the second electrodes are required to be used together as electrodes, the switch S1 is only required to be simultaneously selected A, D, F.
The first electrode-dielectric layer-second electrode structure forms a capacitance sensor, a switch S1 of the topological circuit selects A, D, F, a switch S2 selects a pin G, a selection switch S4 is closed, and static pressure of the surface of the aircraft can be measured by measuring capacitance change of the capacitance.
The second electrode, the piezoelectric layer and the third electrode form a pressure sensor, when the pressure sensor is pressed, charges proportional to the pressure are polarized on two surfaces of the piezoelectric layer and are led out through the electrodes to form a voltage. The upper surface of the second electrode is made of constantan materials, the lower surface of the second electrode is made of metal platinum and platinum-rhodium alloy, when the working mode of the intelligent metamorphic sensor is a pressure sensor, the second electrode 2 is used as a top electrode of the piezoelectric sensor, and polarization charges generated on the upper surface of the piezoelectric material are collected; the third electrode is used as a bottom electrode of the piezoelectric sensor and collects polarization charges generated on the lower surface of the piezoelectric material. When the intelligent skin pressure measuring device works, the scanning array gating circuit is used, the switch S1 selects the pin A, D, F to serve as the positive electrode of the piezoelectric sensor, the switch S2 selects the pin B, C, E to serve as the negative electrode of the piezoelectric sensor, the switch S5 is closed, and the dynamic pressure acting on the surface of the intelligent skin can be measured by measuring the output voltage between the two electrodes. Further, by analyzing the frequency spectrum and the phase diagram of the measured voltage curve, the vibration frequency of the aircraft surface can be derived. And the piezoelectric sensor has large impedance, high frequency response, quick response time and small influence of errors of environment, measuring lines and the like, and is very suitable for measuring the pressure field with rapid surface change of the aircraft. The four intelligent skins are combined for use, the switch S1 of the first unit cell selects pins A1, D1 and F1, the switch S2 selects pins B1, C1 and E1, the switch S7 is closed, the electrode structure is converted into a surface acoustic wave emission source, the switches S1 of the other three units select pins A, D, F (2-4), the switch S2 selects pins B, C, E (2-4), the switch S5 is closed, voltage output between the pins is measured, cracks and impact at the position can be measured, and the method has wide application in structural health monitoring.
In this embodiment, the specific process steps of the preparation process of the flexible smart skin are as follows:
s1, preparation of a sacrificial layer solution: preparing PZT precursor solution, and preparing the PZT precursor solution according to the molar concentration ratio of metal ions as Pb: zr: ti ═ 1.15: 0.52: weighing solutes of lead acetate trihydrate, zirconium nitrate pentahydrate and tetrabutyl titanate according to the proportion of 0.48, dissolving the solutes of lead acetate trihydrate, zirconium nitrate pentahydrate and tetrabutyl titanate in solvents such as ethylene glycol monomethyl ether and acetylacetone, forming a precursor solution of PZT through hydrolysis reaction and polymerization reaction, adjusting the pH value, fixing the volume to 0.4-0.6 mol/L, naturally cooling, standing, sealing, and aging for 40-80 hours under natural conditions to form a PZT precursor gel solution;
s2, preparation of a sacrificial layer: cleaning a sapphire substrate, spin-coating a PZT precursor solution on the sapphire substrate, curing at 120 ℃ for 2min for hardening, further heating at 300 ℃ for 10min to remove organic matters, repeatedly coating four layers in such a way to reach the expected thickness of the piezoelectric layer, and then performing high-temperature rapid annealing at 650 ℃ to form a perovskite phase as a PZT sacrificial layer;
s3, preparing a third electrode 5: preparing a self-similar interconnected electrode structure on the PZT sacrificial layer by a photoetching technology, depositing metal platinum by magnetron sputtering or evaporation, and removing photoresist to form a bottom platinum resistance temperature sensor electrode structure; photoetching and magnetron sputtering again to finish the deposition of the platinum-rhodium alloy so as to obtain a third electrode;
s4, preparing a piezoelectric layer: spin-coating a PZT precursor solution on the third electrode 5, repeating six coating steps similar to step S2, and performing high-temperature annealing to obtain a PZT functional layer;
s5, preparing a second electrode: preparing a self-similar interconnected electrode structure on the PZT sacrificial layer by a photoetching technology, depositing constantan of a metal electrode by magnetron sputtering or evaporation, removing photoresist, and preparing an upper self-similar interconnected electrode structure to obtain a second electrode;
s6, preparing a dielectric layer: spin coating PI solution, curing at 150 deg.C for 5min, and heating in oven at 220 deg.C for 3 hr for imidization to obtain dielectric layer.
S7, preparing a first electrode: and preparing an electromagnetic wave absorption metamaterial structure on the PI dielectric layer by photoetching and magnetron sputtering technologies so as to obtain a first electrode.
S8, utilizing a laser stripping technology and high-temperature pyrolysis to knock off the PZT sacrificial layer to realize nondestructive stripping of the intelligent metamorphic sensor, and preparing the flexible intelligent metamorphic sensor.
According to the invention, through the electrode design of the multi-mode intelligent metamorphic sensor, the electrodes of the sensor play different roles and can be used for completing different functions, the pins of the electrodes are connected to the logic topological circuit, and the connection mode between the electrodes of the sensor can be completed through the switching of the circuit, so that the sensor completes the conversion from some sensors to other sensors, and the in-situ measurement of multiple physical quantities such as the surface pressure distribution, the airflow flow rate, the temperature distribution, the stress strain, the vibration, the humidity, the structural health and the like of an aircraft can be realized. Thus, the measurement of 8 functions can be completed in situ and on line through one sensor, compared with the traditional wind tunnel measurement technology, the metamorphic intelligent skin has the advantages of large area, ultra-thin and multiple measurement functions, and can be used for in situ and on line detection of multiple physical parameters without influencing the flow field on the surface of an aircraft when being used in the field of aircraft; compared with the multifunctional sensors which are distributed side by side, the space density of the sensors is greatly increased, and the measurement accuracy is improved; with the sensor that piles up of multilayer, greatly reduced the quantity of lead wire, also reduced the degree of difficulty of processing preparation.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. The flexible intelligent skin for multi-physical-field measurement is characterized by sequentially comprising a first electrode (1), a dielectric layer (2), a second electrode (3), a piezoelectric layer (4) and a third electrode (5) from top to bottom, wherein,
the first electrode (1), the dielectric layer (2) and the second electrode (3) form a capacitance sensor, the dielectric layer is a flexible insulating base material and is used for separating the first electrode from the second electrode; reflecting the change of the external environment by measuring the change of the capacitance between the first electrode and the second electrode;
the second electrode (3), the piezoelectric layer (4) and the third electrode (5) form a piezoelectric sensor, the piezoelectric layer (4) is used for separating the second electrode (3) from the third electrode (5), and when the flexible smart skin is subjected to pressure, the magnitude of the pressure is reflected by measuring the magnitude of voltage between the second electrode and the third electrode;
the second electrode (3) comprises two resistors, namely a first resistor and a second resistor, the first resistor is bent to form a sensitive grid structure, the length of the resistor is prolonged, the second resistor is distributed in parallel with the first resistor, pins A and F are arranged at two ends of the first resistor, a pin D is arranged at the tail end of the second resistor, the first resistor forms a resistor sensor, the change of the resistor is reflected by monitoring the resistor between the pins A and F, the first resistor and the second resistor together form a capacitor sensor, and the change of the capacitor is reflected by monitoring the capacitor between the pins A, F and D;
the third electrode (5) comprises two resistors with different thermoelectric coefficients, namely a third resistor and a fourth resistor, the third resistor is of a sensitive grid structure, the fourth resistor is communicated with the third resistor and forms a thermocouple at a connecting point, pins B and E are arranged at two ends of the third resistor, a pin C is arranged at the tail end of the fourth resistor, the third resistor forms a resistor sensor, the change of the resistors is reflected by monitoring the resistance between the pins B and C, the third resistor and the fourth resistor form a thermocouple sensor together, and the change of the thermocouple is reflected by monitoring the thermoelectric potential between the pins B/E and C.
2. The flexible smart skin with multiple physical field measurement units as claimed in claim 1, wherein the first electrode is preferably made of electromagnetic wave absorbing material for absorbing electromagnetic waves.
3. The flexible smart skin for multi-physical-field measurement according to claim 1, wherein the first resistor and the second resistor are made of the same material, and preferably have a strain sensitivity coefficient greater than 1.6, a resistivity greater than 0.25 μ Ω -mm, and a temperature coefficient of resistance less than 40 x 10-6The material of/° C has high sensitivity coefficient and keeps constant to make the first resistor sensitive to strain, the resistivity is high, the signal-to-noise ratio can be improved, the influence of lead resistance is reduced, the temperature coefficient of the resistor is small, the sensitivity of the first resistor to temperature can be reduced, and therefore the first resistor is ensured to be only sensitive to strain changeHigh.
4. The flexible smart skin for multi-physical-field measurement according to claim 1, wherein the material of the third resistor preferably has a temperature coefficient of resistance greater than 3000 x 10-6The fourth resistor is preferably made of a material with thermoelectric potential higher than 5 μ V/DEG C for the third resistor, so that the third resistor forms an RTD temperature sensor, and the third resistor and the fourth resistor form a thermocouple temperature sensor to meet temperature measurement in different temperature ranges.
5. The flexible smart skin for multi-physical-field measurement according to claim 1, wherein the thickness of the flexible smart skin is preferably 20 μm to 30 μm.
6. The flexible smart skin for multi-physical-field measurement according to claim 1, wherein the first electrode, the second electrode and the third electrode are obtained by sequentially performing photolithography to obtain a desired shape, and then performing magnetron sputtering or evaporation to deposit metal.
7. The flexible smart skin for multi-physical-field measurements according to claim 1, wherein an additional resistor is further coupled to the first resistor to increase the area coverage of the third electrode.
8. Use of the multi-physics measuring flexible smart skin of any one of claims 1-7 to measure pressure, temperature, strain, vibration, and humidity.
9. The multi-cell structure formed by the flexible intelligent skin measured by the multi-physical field according to any one of claims 1 to 7, wherein the flexible intelligent skin is used as a single cell and is oppositely arranged through a plurality of single cell structures to form the multi-cell structure, the multi-cell structure is attached to the surface of an object to be measured, alternating current is introduced between a second electrode and a third electrode in one single cell, voltages between the second electrode and the third electrode in other single cells are measured, and the surface quality of the object to be measured is reflected through different voltages in the single cells measured at different positions; or, the multi-cell structure is attached to the surface of an object to be measured, the resistance at two ends of the third electrode of other single cells is measured through direct current in the third electrode of one single cell, and the flow rate of the air at the position of the single cell is obtained through calculation according to the resistance.
10. Use of a multicellular structure as defined in claim 9 to monitor the health of an aircraft and the ambient air flow rate.
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