Flexible packaged multi-modal sensor and method of manufacturing and use thereof

Abstract

The present application belongs to the technical field of flexible sensor, and discloses a flexible packaged multi-modal sensor and a preparation method and application thereof. The multi-modal sensor comprises a flexible substrate, a lower thermoelectric electrode, an intermediate patterned dielectric layer and an upper patterned electrode. The multi-modal sensor realizes the simultaneous measurement of four physical quantities, i.e. heat flow, temperature, flow rate and vibration, in voltage mode, resistance mode and charge mode through the combination of the components thereof. The lower electrode is embedded in the intermediate dielectric layer to form the cold end and the hot end of the heat flow density sensor, and the corresponding induced electromotive force is measured through the first lead and the second lead, i.e. the heat flow sensor; the upper patterned electrode forms a resistance sensor through the third lead and the fourth lead to realize the measurement of physical quantities such as temperature and flow rate; the piezoelectric part in the intermediate dielectric layer and the upper and lower electrodes form a sandwich piezoelectric sensor to express the pressure value outside the sensor through the first lead and the third lead.

Description

Technical Field

[0001] This invention belongs to the field of flexible sensor technology, and more specifically, relates to a flexible packaged multimodal sensor, its fabrication method, and its application. Background Technology

[0002] Monitoring aerodynamic parameters of aircraft surfaces is crucial for improving flight safety and efficiency. During flight, aircraft face complex aerodynamic challenges such as high / low temperature shocks, laminar flow separation, and boundary layer transitions, leading to ablation / wing icing, increased drag, stall, and dynamic instability, all of which increase safety risks. Hypersonic aircraft, in particular, generate strong shock waves at their noses during atmospheric flight. Under the influence of these shock waves, the surrounding air temperature can surge to several thousand degrees Celsius, generating enormous heat flux. Studying the flow field characteristics and their variations on aircraft surfaces is key to solving these problems. Currently, researchers have developed various measurement schemes for measuring aerodynamic loads such as temperature, pressure, and wall shear stress on aircraft surfaces, including temperature-sensitive paint, pressure-sensitive paint, and embedded and surface-mount sensors. For static pressure measurement, the commonly used method is to install sensors through pressure holes. This method is invasive; the pressure holes can damage the structure and affect the wall flow field characteristics, reducing sensor accuracy. Furthermore, it is difficult to achieve large-scale multi-parameter integrated measurement and still suffers from blind spots and the limitation of measuring only a single physical quantity.

[0003] Flexible electronic devices offer similar electronic functions to current electronic devices, capable of bending, twisting, stretching, and deforming on arbitrary surfaces. This enables innovative applications that are difficult to achieve with traditional microelectronics technology. However, single-function flexible sensors still have many shortcomings, such as relatively simple structural materials and the inability to measure multiple physical quantities. Even when multiple physical quantities are measured, they are often not in-situ measurements. Generally, in-situ data is needed to describe the real world, so in-situ measurement devices are necessary in some situations. The requirements for the functional diversity, high-density integration, high robustness, and in-situ sensing excitation of flexible sensor systems are becoming increasingly stringent. Traditional multimodal flexible sensors cannot meet the needs of real-time measurement of multiple physical parameters on complex curved surfaces. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a flexible packaged multimodal sensor, its preparation method and application, which aims to solve the problem that the existing flexible sensors cannot achieve co-position measurement of multiple physical parameters.

[0005] To achieve the above objectives, according to one aspect of the present invention, a flexible packaged multimodal sensor is provided. The multimodal sensor includes, from bottom to top, a flexible substrate, a lower thermopile electrode, an intermediate patterned dielectric layer, and an upper patterned electrode. The lower thermopile electrode is disposed on one surface of the flexible substrate and includes a lower platinum electrode and a lower gold electrode. The lower platinum electrode includes an annular platinum strip array with an opening, a first pin, and a second pin. Platinum strips at both ends of the platinum strip array are respectively connected to the first pin and the second pin. The lower gold electrode forms an intermittent gold strip array, and the gold strip array is stacked. The platinum strip array is connected to the tail of the platinum strip at the discontinuity; the platinum strips in the platinum strip array and the gold strips in the gold strip array are connected in pairs and connected in series to form a circuit; the intermediate patterned dielectric layer includes an intermediate thermal resistance layer and an intermediate piezoelectric layer, the intermediate piezoelectric layer is embedded in the middle of the intermediate thermal resistance layer and is disposed on the lower thermopile electrode; the lower thermopile electrode is located in the intermediate thermal resistance layer; the upper patterned electrode is provided with a third pin and a fourth pin, and it also includes an annular hot wire with an opening, the third pin and the fourth pin being respectively connected to the two ends of the hot wire.

[0006] Furthermore, the flexible substrate is made of polyimide, a flexible insulating material.

[0007] Furthermore, the lower platinum electrode includes a central disc located in the middle of the platinum metal strip array, and the two are concentrically arranged; the first pin is also connected to the central disc.

[0008] Furthermore, the intermediate thermal resistance layer covers the flexible substrate and the lower thermopile electrode; the material of the intermediate thermal resistance layer is photosensitive PI.

[0009] Furthermore, the intermediate thermal resistance layer includes an outer ring and an inner ring arranged concentrically, and the intermediate piezoelectric layer is disposed within the inner ring and is in the shape of a disc.

[0010] Furthermore, the material of the upper patterned electrode has a resistivity thermal sensitivity coefficient greater than 3000*10. -6 Materials at / ℃.

[0011] Furthermore, the potential coefficient difference between the lower platinum electrode and the lower gold electrode is greater than 5 uV / ℃.

[0012] Furthermore, the thickness of the multimodal sensor is 30µm to 50µm.

[0013] The present invention also provides a method for fabricating a flexible packaged multimodal sensor, the method being used to fabricate the flexible packaged multimodal sensor as described above.

[0014] The present invention also provides an application of the flexible packaged multimodal sensor described above in wind tunnel testing of aircraft.

[0015] In summary, compared with the prior art, the flexible packaged multimodal sensor, its fabrication method, and its application provided by this invention have the following advantages:

[0016] 1. The multimodal sensor achieves simultaneous measurement of four physical quantities—heat flux, temperature, flow rate, and vibration—through the combination of its components in three different acquisition modes: voltage mode, resistance mode, and charge mode. Specifically, the photosensitive PI portion of the intermediate dielectric layer is encapsulated on the surface of the lower electrode, forming the cold and hot ends of the heat flux density sensor. The temperature difference electromotive force is generated as the heat flux density changes, and the corresponding induced electromotive force is measured through the first and second pins, thus constituting the heat flux sensor. The upper patterned electrode forms a resistance sensor through the third and fourth pins, enabling the measurement of physical quantities such as temperature and flow rate, thus constituting the temperature sensor and the hot-film sensor. The piezoelectric portion in the intermediate dielectric layer, together with the upper and lower electrodes, forms a sandwich-type piezoelectric sensor, expressing the external pressure value through the first and third pins, thus constituting the vibration sensor.

[0017] 2. The lower platinum electrode, the lower gold electrode, and the intermediate thermal resistance layer can form a heat flow sensor as a module. The non-adjacent overlapping nodes of the lower thermopile electrodes covered by the intermediate thermal resistance layer constitute the cold end of the heat flow sensor, while the overlapping nodes of the lower thermopile electrodes not covered by the intermediate thermal resistance layer constitute the hot end of the heat flow sensor, thereby enabling the measurement of heat flow. The inner and outer rings of the intermediate thermal resistance layer respectively cover the non-adjacent overlapping nodes of the concentric radial metal array of the lower thermopile electrodes, serving as thermal resistance.

[0018] 3. The upper patterned electrode constitutes a hot-film sensor. A constant high voltage is applied between the two pins of the upper patterned electrode using a CVA circuit to generate Joule heating. When the ambient air flows, some of the Joule heat is carried away, the electrode temperature decreases, and the resistance changes. The CVA circuit can also convert the resistance signal across the sensor into a voltage signal and amplify it, improving the detection sensitivity. By measuring this voltage signal, changes in the ambient airflow velocity can be reflected. The upper patterned electrode also constitutes a temperature sensor, and the material used is a temperature-sensitive material, enabling ambient temperature measurement.

[0019] 4. The lower platinum electrode, the intermediate piezoelectric layer, and the upper patterned electrode form a piezoelectric sensor as a module. The intermediate thermal resistance layer prevents direct contact between the upper and lower electrodes, which transfer charge through the intermediate piezoelectric layer. This piezoelectric sensor measures parameters such as vibration and shock based on the positive piezoelectric effect. When no external pressure is applied, the internal electric dipoles are in equilibrium with the external environment, appearing macroscopically uncharged. When subjected to external pressure, the centers of positive and negative charges within the sensor further shift, resulting in polarization, and thus positive and negative charges are generated on the upper and lower surfaces.

[0020] 5. The thickness of the third pin and the fourth pin is basically the same as the thickness of the hot wire, but the hot wire is longer and has a smaller cross-sectional area, so that most of the resistance of the upper patterned electrode is concentrated on the middle hot wire. This is beneficial for the voltage to be concentrated in the functional area when high voltage is applied, thereby improving the sensitivity of flow velocity physical quantity measurement.

[0021] 6. The lower-layer thermopile electrode uses a Pt-Au alloy as the thermopile material primarily due to its excellent ductility and thermal stability. Compared to the more brittle Pt-PtRh thermopile, the Pt-Au system, through magnetron sputtering, maintains good plastic deformation capability while effectively mitigating stress accumulation during thermal cycling. The two metal materials exhibit better matching thermal expansion behaviors, avoiding interface cracking caused by thermal mismatch. Furthermore, their excellent cold working properties make it easier to fabricate dense electrode structures. This material combination significantly improves the reliability of the device under both mechanical and thermal stresses.

[0022] 7. The upper patterned electrode uses two different modes of sensing: temperature and hot film. It can switch the acquisition and sensing mode of the middle and lower heat flow sensors. When the upper electrode is switched to temperature sensing, the heat flow sensor acquires the input quantity of pure external environmental heat flow pulsation, and heat flow sensing is achieved through the different heat exchange between the cold end and the hot end and the outside world. When the upper electrode is switched to hot film sensing, the heat flow sensor acquires the input quantity of external environmental heat flow pulsation and Joule heat generated by the constant high voltage applied to both ends of the upper patterned electrode. The change in input quantity causes a certain transition between the cold end and the hot end of the thermopile. By controlling the input voltage at both ends of the hot film, the heat flow sensing can be enhanced to a certain extent.

[0023] 8. By using the lower platinum electrode to fully couple the two sensors, co-position measurement is achieved. Unlike other multifunctional sensors that require non-overlapping sensor patterns to measure multiple physical quantities, in this invention, the piezoelectric sensor and the thermocouple sensor are located in the same position, which can make more accurate measurements of physical quantities at a certain point. Attached Figure Description

[0024] Figure 1 This is a front view of the structure of a flexible packaged multimodal sensor provided in an embodiment of the present invention;

[0025] Figure 2 yes Figure 1 Exploded view of a flexible-packaged multimodal sensor;

[0026] Figure 3 (a), (b), (c), and (d) in the embodiments of the present invention are respectively schematic diagrams of the heat flow sensor structure, the lower platinum electrode structure, the lower gold electrode structure, and the middle PI thermal resistance layer structure provided in the embodiments of the present invention.

[0027] Figure 4 These are schematic diagrams of the piezoelectric sensor structure and the intermediate piezoelectric layer structure provided in embodiments of the present invention;

[0028] Figure 5 These are schematic diagrams of the temperature / thermal film sensor structure and the upper patterned electrode provided in this embodiment of the invention.

[0029] Figure 6 This is a schematic diagram of the application of the present invention when multiple sensors are combined and connected to form a smart skin.

[0030] Figure 7 This is a flowchart of a method for fabricating a flexible packaged multimodal sensor according to an embodiment of the present invention.

[0031] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-packaging substrate, 2-lower thermopile electrode, 2.1-lower platinum electrode, 2.2-lower gold electrode, 3-intermediate patterned dielectric layer, 3.1-intermediate thermal resistance layer, 3.2-intermediate piezoelectric layer, 4-upper patterned electrode, 5-multimodal sensor, 6-flexible smart skin, 7-wing model, 8-wind tunnel. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0033] This invention provides a flexible packaged multimodal sensor 5. Each electrode layer, due to its material and structural design, possesses multiple functions, enabling the measurement of a single physical quantity. Different electrode combinations can perform even more functions. Furthermore, integrating more sensors can accomplish the measurement of more complex physical quantities. This reduces the need for a greater number of functional layers and lead interfaces.

[0034] The multimodal sensor 5 has a combined layered structure, integrating a heat flow sensor, a temperature sensor, and a piezoelectric sensor. The multimodal sensor 5 can achieve simultaneous measurement of multiple physical quantities in both the external environment and its own structure, and provides real-time response and feedback in complex environments. Through pin connections, the multimodal sensor 5 achieves simultaneous measurement of four physical quantities—heat flow, temperature, flow rate, and vibration—in three different acquisition modes: voltage mode, resistance mode, and charge mode, thus improving the accuracy and real-time performance of the sensor in complex scenarios.

[0035] Please see Figure 1 and Figure 2 The multimodal sensor 5 includes, from bottom to top, an encapsulation substrate 1, a lower thermopile electrode 2, an intermediate patterned dielectric layer 3, and an upper patterned electrode 4. The encapsulation substrate 1 can be made of materials such as polyimide (PI), polyethylene terephthalate (PET), polyvinyl alcohol (PVA), polydimethylsiloxane (PDMS), or polyethylene naphthalate (PEN). Because polyimide has high temperature resistance (stable below 300 degrees Celsius), high mechanical strength (tensile strength 231 MPa), good chemical stability, and excellent electrical insulation, the encapsulation substrate 1 is preferably made of the flexible insulating material polyimide (PI). The encapsulation substrate 1 serves to support the lower thermopile electrode 2, the intermediate patterned dielectric layer 3, and the upper patterned electrode 4, and to isolate them from the external environment.

[0036] The lower thermopile electrode 2 is disposed on one surface of the encapsulation substrate 1, and includes a lower platinum electrode 2.1 and a lower gold electrode 2.2. The lower platinum electrode 2.1 forms an array of intermittent platinum metal strips, and the lower gold electrode 2.2 forms an array of intermittent gold metal strips. The gold metal strips are stacked at the discontinuities of the platinum metal strip array and connected to the tails of the platinum metal strips. The platinum metal strips in the platinum metal strip array and the gold metal strips in the gold metal strip array overlap each other and are connected in series to form a circuit. In another embodiment, the lower platinum electrode 2.1 and the lower gold electrode 2.2 can be replaced by a lower platinum electrode and a lower platinum-rhodium electrode.

[0037] The lower platinum electrode 2.1 includes a central disc, an open-ring-shaped array of platinum metal strips, a first pin, and a second pin. The central disc is located in the center of the platinum metal strip array, and the two are concentrically arranged. The platinum metal strip array has a concentric radial structure, with the platinum metal strips at both ends connected to the first pin and the second pin, respectively. The first pin is also connected to the central disc. The lower gold electrode 2.2 has a concentric radial gold metal strip array.

[0038] The intermediate patterned dielectric layer 3 includes an intermediate thermal resistance layer 3.1 and an intermediate piezoelectric layer 3.2. The intermediate piezoelectric layer 3.2 is embedded in the middle of the intermediate thermal resistance layer 3.1 and is disposed on the lower thermopile electrode 2. The intermediate thermal resistance layer 3.1 covers the packaging substrate 1 and the lower thermopile electrode 2. The lower thermopile electrode 2 is located within the intermediate thermal resistance layer 3.1, and its position corresponds to the position of the intermediate piezoelectric layer 3.2. The intermediate thermal resistance layer 3.1 is made of photosensitive PI, utilizing the insulating properties of the photosensitive PI to prevent charge propagation between the upper and lower electrodes.

[0039] Please see Figure 3 The intermediate thermal resistance layer 3.1 includes a concentric outer ring and an inner ring. The intermediate piezoelectric layer 3.2 is disposed within the inner ring and is disc-shaped. The outer ring is connected to a side structure. The lower platinum electrode 2.1, the lower gold electrode 2.2, and the intermediate thermal resistance layer 3.1 can form a heat flow sensor as a module. The non-adjacent overlapping nodes of the lower thermopile electrode 2 covered by the intermediate thermal resistance layer 3.1 constitute the cold end of the heat flow sensor, and the overlapping nodes of the lower thermopile electrode 2 not covered by the intermediate thermal resistance layer 3.1 constitute the hot end of the heat flow sensor, thereby realizing the measurement of heat flow. The inner and outer rings of the intermediate thermal resistance layer 3.1 respectively cover the non-adjacent overlapping nodes of the concentric radial metal array of the lower thermopile electrode 2, thus playing a role in thermal resistance.

[0040] The hot and cold ends of the heat flow sensor are constructed using the low thermal conductivity of the photosensitive PI sensor. When a heat flow impacts the sensor from the external environment, the hot end, not covered by the intermediate thermal resistance layer 3.1, can directly contact the external heat flow through the through-holes in the intermediate thermal resistance layer 3.1, resulting in a relatively high temperature. The heat flow is conducted to the cold end relatively slowly, thus the cold end temperature is relatively low. When there is a certain temperature difference between the hot and cold ends, a potential difference will be generated due to the Seebeck effect, as shown in the following equation:

[0041] ΔU=SΔT

[0042] Where S is the Seebeck coefficient, ΔU and ΔT are the potential difference and temperature difference between the hot and cold ends, respectively. The thermoelectric signal is amplified by connecting multiple hot and cold ends in series. The heat flux density is obtained using the heat flux density calculation formula.

[0043]

[0044] Where λ is the thermal conductivity and Δd is the distance between the cold end and the hot end.

[0045] The upper patterned electrode 4 is made of a material with good conductivity and serves as the upper electrode for the piezoelectric flexible sensor. It has a third and a fourth pin for conducting the potential signal generated by the sensor. The lower platinum electrode 2.1 is made of a material with good conductivity that can produce a Seebeck effect with the lower gold electrode 2.2, serving as a shared layer for both sensors. The intermediate piezoelectric layer 3.2 is made of a flexible material with a piezoelectric effect. When the complex curved surface is subjected to pressure, the flexible sensor attached to the curved surface is also subjected to pressure, causing the intermediate piezoelectric layer 3.2 to produce a piezoelectric effect. The magnitude of the pressure is reflected by measuring the electrical signal between the first pin, the third pin, or the second pin and the fourth pin.

[0046] The upper patterned electrode 4 includes an open annular hot wire and a piezoelectric electrode disposed in the middle of the hot wire. The third pin and the fourth pin are respectively connected to the two ends of the hot wire. The thickness of the third pin and the fourth pin is basically the same as the thickness of the hot wire, but the hot wire is longer and has a smaller cross-sectional area. This makes most of the resistance of the upper patterned electrode 4 concentrated on the middle hot wire, which is beneficial for concentrating the voltage in the functional area under high voltage loading, thereby improving the sensitivity of flow velocity measurement.

[0047] The upper patterned electrode 4 constitutes a hot-film sensor. A constant high voltage is applied between the two pins of the upper patterned electrode 4 using a CVA circuit to generate Joule heating. When the ambient air flows, some of the Joule heat is carried away, the electrode temperature decreases, and the resistance changes. The CVA circuit can also convert the resistance signal across the sensor into a voltage signal and amplify it, improving the detection sensitivity. By measuring this voltage signal, changes in the ambient airflow velocity can be reflected. The upper patterned electrode 4 also constitutes a temperature sensor. The upper patterned electrode 4 is made of a temperature-sensitive material, enabling the measurement of ambient temperature.

[0048] The lower platinum electrode 2.1 plays a dual role in the entire multilayer structure. On the one hand, it serves as the lower electrode of the piezoelectric sensor to conduct the electrical signal generated by the piezoelectric material; on the other hand, it serves as one electrode of the heat flow sensor to form a heat flow sensor. This arrangement enables complete coupling and truly achieves in-situ measurement.

[0049] The material of the upper patterned electrode 4 is preferably selected with a resistance thermal sensitivity coefficient greater than 3000*10. -6 The material is selected to ensure the sensitivity of the constructed temperature sensor. The potential coefficient difference between the lower platinum electrode 2.1 and the lower gold electrode 2.2 of the lower thermopile electrode 2 is greater than 5uV / ℃ to ensure the sensitivity of the constructed heat flow sensor.

[0050] Please see Figure 4The lower platinum electrode 2.1, the intermediate piezoelectric layer 3.2, and the upper patterned electrode 4 form a piezoelectric sensor as a module. The intermediate thermal resistance layer 3.1 prevents direct contact between the upper and lower electrodes, while the upper and lower electrodes transfer charge through the intermediate piezoelectric layer 3.2. This piezoelectric sensor measures parameters such as vibration and shock based on the positive piezoelectric effect. When there is no external pressure, the internal electric dipoles are in equilibrium with the external environment, macroscopically appearing uncharged. When subjected to external pressure, the centers of positive and negative charges inside further shift, resulting in polarization. Positive and negative charges are generated on the upper and lower surfaces, and the density of these charges is proportional to the magnitude of the external force, corresponding to the piezoelectric control equation:

[0051] S = s E T+d T E

[0052] D=dT+ε0ε rT E

[0053] Where S is the strain tensor, T is the stress tensor, E is the electric field, D is the electric displacement field, and the material parameter s E d is the stiffness matrix, d is the piezoelectric constant matrix, ε0 is the vacuum permittivity, and ε rT Let be the relative permittivity matrix under constant stress.

[0054] When the applied electric field E = 0 and the force is applied only in the z-axis direction, the charge change on both surfaces of the intermediate piezoelectric layer 3.2 in the z-axis direction is linearly related to the pressure:

[0055] σ3=d 33 T3

[0056] Please see Figure 5 The upper patterned electrode 4, when used as a standalone module, can form a hot-film sensor. The sensing unit of this sensor operates on the principle of platinum-based heat loss sensing. A high voltage is applied across the electrode to generate Joule heating. In the absence of fluid flow, the hot-film element maintains a stable temperature. However, when fluid flows through the hot film, convective heat transfer between the fluid and the hot-film element removes some heat, causing the element's temperature to drop. The heat loss of the hot-film element is directly proportional to the fluid velocity. The higher the fluid velocity, the more heat is removed, and the more significant the temperature drop. Therefore, by measuring the temperature change of the hot-film element, the fluid velocity can be indirectly measured. The upper patterned electrode 4, when used as a standalone module, can also form a temperature sensor. When the ambient temperature changes, the temperature of the hot wire changes, and the metal resistance also changes. The rate of change of resistance is linearly related to temperature.

[0057]

[0058] In the formula, R TR0 is the resistance of the metal at temperature T; R0 is the resistance of the metal at temperature T0; k is the temperature coefficient of the metal resistance. The ambient temperature can be obtained by measuring the metal resistance in real time.

[0059] In one embodiment, the intermediate patterned dielectric layer 3 is fabricated using a patterning process to prepare the intermediate thermal resistance layer 3.1 and the intermediate piezoelectric layer 3.2. The intermediate thermal resistance layer 3.1 is made of photosensitive PI material, whose thermal conductivity is much lower than that of the material used in the intermediate piezoelectric layer 3.2, thereby improving the sensitivity of the heat flow measurement of the lower electrode. The intermediate piezoelectric layer 3.2 is made of a mixture of piezoelectric powder and PI, and is integrated with other structures of the sensor by electro-spraying adhesive. The piezoelectric powder can be selected from inorganic piezoelectric powders such as lead zirconate titanate, barium titanate, and lead niobate, or organic piezoelectric powders such as polyvinylidene fluoride.

[0060] The thickness of the multimodal sensor 5 is preferably 30 μm to 50 μm. The thickness of the packaging substrate 1 is preferably 10 μm to 20 μm, the thickness of the lower platinum electrode 2.1 is preferably 70 nm to 100 nm, the thickness of the lower gold electrode 2.2 is preferably 120 nm to 150 nm, the thickness of the intermediate patterned dielectric layer 3 is preferably 20 μm to 30 μm, and the thickness of the upper patterned electrode 4 is preferably 70 nm to 100 nm.

[0061] Please see Figure 6The present invention also provides an application of a flexible smart skin 6 integrating multiple multimodal sensors 5. The process of an airfoil model 7 with the flexible smart skin 6 entering a wind tunnel 8 to sense the environmental parameters of the flow field and its own structural parameters is mainly divided into three stages: 1 entering the flow field, 2 changing the positive angle of attack, and 3 leaving the flow field. In stage 1, the wing model 7 enters the flow field at a 0° angle of attack. The third and fourth pins of the sensor are switched. Due to the high temperature of the incoming flow, the surface temperature of the wing model 7 rises sharply after entering the flow field. The resistivity of the metal in the temperature sensor, composed of the multimodal sensor 5 on the smart skin of the model surface, changes with temperature, causing the resistance to increase, thus achieving surface temperature measurement of the wing model 7. The first and second pins of the sensor are then switched. Due to the difference in temperature between the incoming flow and the surface of the wing model 7, as well as the thermal insulation of the thermal resistance layer of the heat flow sensor composed of the multimodal sensor 5, a temperature difference exists between the cold and hot ends of the heat flow module. The heat flow module generates a potential based on the magnitude of this temperature difference to measure the heat flow on the model surface. Finally, the first and third pins of the sensor are switched. Due to the high-density, high-frequency airflow load acting on the wing model 7, when the surface skin of the wing model 7 is subjected to the airflow load, the positive and negative charge centers inside the piezoelectric module shift, generating polarization. Positive and negative charges are thus generated on the upper and lower surfaces of the material. The generated charge density is proportional to the magnitude of the external force, achieving measurement of the magnitude and frequency of the external load. In stage 2, the wing model 7 changes from 0° angle of attack to positive angle of attack. The third and fourth pins of the sensor are switched. After the angle of attack changes, the smart skin faces the airflow. The metal resistivity of the temperature sensor composed of multimodal sensor 5 increases further with temperature, but the slope of change is different from the first change. The first and second pins of the sensor are switched. Since the smart skin faces the airflow, the temperature difference between the cold and hot ends of the heat flow module increases, resulting in a larger potential. The first and third pins of the sensor are switched. Since the smart skin faces the airflow, the surface skin of the wing model 7 is subjected to a larger airflow load, and polarization occurs again. The positive and negative charge centers inside the piezoelectric module shift, and positive and negative charges are generated on the upper and lower surfaces of the material. In stage 3, wing model 7 leaves the flow field at an angle of attack of 0°. Switching the third and fourth pins of the sensor, as the incoming flow disappears, the smart skin exchanges heat with the ambient temperature environment, and the temperature drops. The metal resistivity of the temperature module of the multimodal sensor 5 decreases with the temperature. Switching the first and second pins of the sensor, as the airflow disappears, there is a temperature gradient between the surface of wing model 7 and the external environment that is opposite to that in the previous two stages, causing the heat flow module to generate a negative potential. Switching the first and third pins of the sensor, as the airflow disappears, the positive and negative charge centers inside the piezoelectric module recover, and positive and negative charges are generated again on the upper and lower surfaces of the material.

[0062] The present invention also provides a method for fabricating the above-mentioned multimodal sensor 5, comprising the following steps:

[0063] S1 selects a glass sheet as a rigid substrate, spin-coates PMM first layer as a sacrificial layer on the rigid substrate, and then spin-coates two layers of PI flexible substrate on PMM first sacrificial layer. After spin-coating, it is placed in an oven and cured at 250 degrees Celsius for 3 hours.

[0064] S2 involves spin-coating photoresist onto the cured PI substrate. After selective coating, the resulting sample is placed on a photolithography machine for photolithography. After photolithography and development, Pt / Ti metal is sputtered using magnetron sputtering. The sputtered sample is then stripped of the photoresist to obtain the desired patterned lower platinum electrode 2.1. After the lower platinum electrode 2.1 is prepared, the sample is then subjected to secondary photolithography and magnetron sputtering according to the above steps to prepare the lower gold electrode 2.2.

[0065] S3 spin-coated photosensitive PI onto the sample after the lower electrode preparation was completed, then patterned by photolithography and development, and finally prepared the intermediate piezoelectric layer 3.2 by electro-spray printing.

[0066] S4 first spin-coates photoresist onto the intermediate structure. After selective coating, the sample is placed on a photolithography machine for photolithography. After photolithography and development, Pt / Ti metal is sputtered by magnetron sputtering. The sputtered sample is then stripped to obtain the desired patterned upper platinum electrode.

[0067] The S5 removes the sacrificial layer using laser ablation, peeling the multimodal flexible sensor off the rigid glass substrate.

[0068] In another embodiment, please refer to Figure 7 The method for fabricating the multimodal sensor 5 includes the following steps:

[0069] (a) Preparation of the underlying flexible polyimide encapsulation substrate

[0070] Select a glass sheet as a rigid substrate, clean it thoroughly, and spin-coat PMMA as a sacrificial layer onto the rigid substrate. Pre-cur it on a hot plate at 180°C for 5 minutes. Then spin-coat two layers of PI onto the PMMA sacrificial layer. After each spin-coating, pre-cur it on a hot plate at 120°C for 5 minutes. After spin-coating, place it in an oven for high-temperature annealing to eliminate internal stress and enhance the physical properties of the substrate.

[0071] (b) Fabrication of heteroelectrodes in the lower thermopile:

[0072] Step 1, photolithography: spin-coat photoresist onto the flexible substrate, pre-cur it on a hot plate at 95°C for 60 seconds after spin-coating, and then place it in a photolithography machine to perform photolithography using a mask.

[0073] Step 2, Development: Immerse the photolithographic glass slide in the developer for 60 seconds, and simultaneously place it in an ultrasonic cleaner and vibrate it. After the photoresist is removed, rinse it with 95% nitrogen gas to allow any remaining liquid to evaporate.

[0074] Step 3, magnetron sputtering: Place the developed sample in a vacuum of 1.0*10⁻⁶. -4 In a vacuum environment of Pa, Pt and titanium are used as metal targets, and argon gas with a purity of 99.99% (volume fraction) is introduced as the sputtering medium. A layer of titanium is sputtered under certain sputtering pressure and power to increase the adhesion of the substrate to the metal. Then, a layer of P is sputtered. After removing the adhesive, the lower platinum electrode 2.1 is obtained.

[0075] Step 4: Perform photolithography and magnetron sputtering again, and complete the gold deposition according to the process in Step 3 to obtain the lower gold electrode 2.2.

[0076] (c) Fabrication of the intermediate dielectric layer

[0077] The sample with the lower electrode prepared was spin-coated with photosensitive PI and pre-cured on a hot plate at 120°C for 3 minutes, followed by patterning by photolithography. Then, the intermediate dielectric layer piezoelectric portion was prepared by electro-spray printing, and finally placed in an oven for high-temperature annealing.

[0078] (d) Fabrication of the patterned top electrode

[0079] Step 1, photolithography: spin-coat photoresist onto the intermediate dielectric layer. After spin-coating, pre-cur it on a 95°C hot plate for 60 seconds, then place it in the photolithography machine and perform photolithography according to the mask.

[0080] Step 2, Development: Immerse the photolithographic glass slide in the developer for 60 seconds, and simultaneously place it in an ultrasonic cleaner and vibrate it. After the photoresist is removed, rinse it with 95% nitrogen gas to allow any remaining liquid to evaporate.

[0081] Step 3, magnetron sputtering: Place the developed sample in a vacuum of 1.0*10⁻⁶. -4 In a vacuum environment of Pa, Pt and titanium are used as metal targets, and argon gas with a purity of 99.99% (volume fraction) is introduced as the sputtering medium. A layer of titanium is sputtered under certain sputtering pressure and power to increase the adhesion of the substrate to the metal. Then, a layer of Pt is sputtered. After removing the adhesive, the electrode pattern of the top electrode is obtained.

[0082] (e) Laser peeling

[0083] The prepared sensor is placed in a laser ablation device, and the PMMA sacrificial layer is carbonized by laser irradiation due to the increase in temperature, thereby separating the sensor from the hard substrate.

[0084] This invention provides a high-frequency force, heat, and electrical multimodal sensor, offering a new solution for high-speed aircraft and other structures that require in-situ measurement of multiple physical parameters. The sensor is simple to manufacture, economical, small in size, and easy to wire.

[0085] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A flexible-packaged multimodal sensor, characterized in that: The multimodal sensor includes, from bottom to top, a flexible substrate, a lower thermopile electrode, an intermediate patterned dielectric layer, and an upper patterned electrode. The lower thermopile electrode is disposed on one surface of the flexible substrate and includes a lower platinum electrode and a lower gold electrode. The lower platinum electrode includes an array of annular platinum strips with openings, a first pin, and a second pin. Platinum strips at both ends of the platinum strip array are respectively connected to the first pin and the second pin. The lower gold electrode forms an array of discontinuous gold strips, which are stacked at the discontinuities of the platinum strip array and are connected to the platinum... The tails of the metal strips are connected; the platinum metal strips in the platinum metal strip array and the gold metal strips in the gold metal strip array are connected in pairs and connected in series to form a circuit; the intermediate patterned dielectric layer includes an intermediate thermal resistance layer and an intermediate piezoelectric layer, the intermediate piezoelectric layer is embedded in the middle of the intermediate thermal resistance layer and is disposed on the lower thermopile electrode; the lower thermopile electrode is located in the intermediate thermal resistance layer; the upper patterned electrode is provided with a third pin and a fourth pin, and it also includes an annular hot wire with an opening, the third pin and the fourth pin being respectively connected to the two ends of the hot wire.

2. The flexible packaged multimodal sensor as described in claim 1, characterized in that: The lower platinum electrode, the lower gold electrode, and the intermediate thermal resistance layer together form a heat flow sensor; the heat flow sensor's acquisition and sensing mode is switched by changing the mode of the upper patterned electrode; the upper patterned electrode forms a thermal film sensor; the intermediate thermal resistance layer serves as both the thermal resistance layer of the heat flow sensor and the heat insulation and sensitivity enhancement layer of the thermal film sensor.

3. The flexible packaged multimodal sensor as described in claim 2, characterized in that: The lower platinum electrode, the middle piezoelectric layer, and the upper patterned electrode together form a piezoelectric sensor; the lower platinum electrode also serves as the lower electrode of the piezoelectric sensor and an electrode of the heat flow sensor.

4. The flexible packaged multimodal sensor as described in claim 1, characterized in that: The intermediate thermal resistance layer covers the flexible substrate and the lower thermopile electrode; the material of the intermediate thermal resistance layer is photosensitive PI; the material of the flexible substrate is flexible insulating material polyimide.

5. The flexible packaged multimodal sensor as described in claim 1, characterized in that: The intermediate thermal resistance layer includes an outer ring and an inner ring arranged concentrically. The intermediate piezoelectric layer is disposed within the inner ring and is disc-shaped. The lower platinum electrode includes a central disc located in the middle of the platinum metal strip array and the two are arranged concentrically. The first pin is also connected to the central disc.

6. The flexible packaged multimodal sensor as described in claim 1, characterized in that: The material of the upper patterned electrode has a resistivity thermal sensitivity greater than 3000*10. -6 Materials at / ℃.

7. The flexible packaged multimodal sensor as described in claim 1, characterized in that: The potential coefficient difference between the lower platinum electrode and the lower gold electrode is greater than 5 uV / ℃; the lower platinum electrode and the lower gold electrode can be replaced by a lower platinum electrode and a lower platinum-rhodium electrode or a lower platinum electrode and a lower constantan electrode.

8. The flexible-encapsulated multimodal sensor according to any one of claims 1-7, characterized in that: The multimodal sensor consists of multiple functional modules arranged along the same axis. The thickness of the multimodal sensor along its own central axis is 30um to 50um, which enables multiple functional modules to measure in the same position.

9. A method for fabricating a flexible packaged multimodal sensor, characterized in that: The preparation method is used to prepare the flexible packaged multimodal sensor according to any one of claims 1-8.

10. The application of a flexible packaged multimodal sensor according to any one of claims 1-8 in wind tunnel testing of aircraft.

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