A nanowire-based wind speed tag and a wind speed detection method thereof

Abstract

This invention discloses a nanowire-based wind speed tag, comprising: a substrate; a suspended nanowire array, wherein the suspended nanowire array has multiple nanowires disposed above the substrate and fixed at both ends to the substrate, and a gap is formed between the middle portion of each nanowire and the surface of the substrate; at least some of the nanowires in the suspended nanowire array have different structural parameters, and the critical fracture wind speeds of the nanowires with different structural parameters under the action of a wind field are different; the wind speed is determined by the fracture state of each nanowire after the suspended nanowire array is exposed to a wind field.

Description

Technical Field

[0001] This invention relates to the field of nanodevices, and more particularly to a nanowire-based wind speed tag and a method for wind speed detection using the tag. This invention can be applied to scenarios requiring passive wind speed monitoring or post-event peak wind speed recording, such as aerospace, meteorological monitoring, building structural safety assessment, microfluidic chips, wind tunnel experiments, and extreme weather early warning. Background Technology

[0002] Accurate wind speed measurement is of great value in many engineering and technical fields, especially in microscale environmental flow field monitoring, post-disaster assessment (such as determining the peak value of local airflow overload), and passive / low power monitoring scenarios. The acquisition of wind speed or historical peak wind speed has special requirements, and the accurate acquisition of wind speed or historical peak wind speed is particularly critical.

[0003] Existing wind speed measurement technologies and sensors can be mainly classified into the following categories: Hot-wire anemometers measure flow rate by utilizing the relationship between the heat dissipation rate of a heating element in a fluid and the flow velocity. While they offer fast response and high sensitivity, these devices are highly sensitive to changes in ambient temperature and require continuous high-power supply, making them unsuitable for passive, long-term deployment, or power-constrained applications.

[0004] Ultrasonic and piezoresistive / piezoelectric anemometers: These sensors detect wind speed based on acoustic time difference or the elastic deformation of a microelectromechanical system (MEMS) cantilever beam. These sensors typically only provide real-time dynamic measurements; when sudden strong winds or hazardous air currents cause power outages or damage, the elastic reversibility of the deformation means the structure will elastically reset after the wind dissipates, making it impossible to retain a "post-hoc peak recording" of the wind speed.

[0005] Indicator / threshold type tracer tags: Many existing passive indicator tags rely on chemical discoloration, surface coating erosion, or large-size mechanically vulnerable structures. These tags generally suffer from low spatial resolution, inaccurate threshold response, and susceptibility to interference from environmental humidity and chemical corrosion, making it difficult to achieve high-density wind speed gradient calibration and accurate quantification at the micro-nano scale.

[0006] In recent years, with the development of micro / nano-fabrication technology, one-dimensional nanomaterials (such as metal nanowires, semiconductor nanowires, and carbon nanotubes) have been gradually explored for application in the field of micro-sensing due to their unique mechanical and electrical properties. However, existing wind speed sensors based on nanomaterials still focus mainly on the acquisition of real-time resistance / capacitance signals, failing to fully utilize the mechanical fracture and failure characteristics of nanowires under fluid-structure interaction (FSI) to construct passive recording tags.

[0007] Developing a wind speed tag that requires no power supply, has a compact structure, high spatial resolution, and can accurately reproduce wind speed thresholds / historical peak values ​​through visualization or easy reading by utilizing controllable mechanical response mechanisms at the micro-nano scale is a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0008] To address the shortcomings of existing wind speed sensors, such as high power dependence, inability to achieve passive post-event wind speed peak recording, low microscale spatial resolution, and complex structure, this invention provides a nanowire-based wind speed tag and its wind speed detection method. This invention utilizes the differentiated bending and fracture failure mechanisms of suspended nanowires with different structural parameters under the influence of wind field fluid resistance to achieve accurate measurement of wind speed and historical peak wind speed in a passive, zero-power, high-spatial-resolution manner with irreversible physical memory.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a nanowire-based wind speed tag, comprising: Base; A suspended nanowire array has multiple nanowires disposed above a substrate and fixed at both ends to the substrate, with a gap formed between the middle portion of each nanowire and the surface of the substrate; the multiple nanowires in the suspended nanowire array have a preset stiffness gradient; the stiffness gradient is constructed by changing at least one of the geometric dimensions, cross-sectional morphology, suspension height, or suspension span of each nanowire; nanowires with different stiffness gradients have different critical fracture wind velocities under the action of wind field fluid resistance, which is used to determine the wind speed or historical peak wind speed by the fracture state of the nanowires.

[0010] Preferably, at least one microgroove is formed on the substrate, and each nanowire spans the microgroove. The two ends of the nanowire are respectively fixed to the substrate on opposite sides of the microgroove. The gap is the space between the middle portion of each nanowire and the bottom surface of the microgroove, forming a suspended structure with fixed ends. The suspended gap between the middle portion of the nanowire and the bottom surface of the microgroove allows the nanowire to freely bend and deform under the influence of airflow.

[0011] Preferably, the structural parameters include nanowire geometric parameters, such as diameter; the suspended nanowire array has at least two different diameters of nanowires. The bending stiffness of the nanowire is proportional to the fourth power of its diameter, therefore even a small difference in diameter can produce a significant difference in the critical fracture wind speed.

[0012] Preferably, the structural parameters include the suspension span of the nanowires, which is the length of the free, suspended section of each nanowire not in contact with the substrate. Multiple microgrooves of different widths are formed on the substrate, and each nanowire spans over a microgroove of a different width to create different suspension spans. According to mechanical principles, the maximum bending stress of a double-ended fixed beam under uniform fluid load is proportional to the square of the suspension span. Therefore, the critical fracture wind speed of each nanowire can be precisely controlled by changing the width of the microgrooves. Simultaneously, the bending stress of the nanowires due to fluid resistance is also related to the cube of the suspension span, further enhancing the sensitivity of the span variation to the control of the critical fracture wind speed.

[0013] Preferably, the structural parameters include at least one of the suspension height of the nanowire and the cross-sectional morphology; the suspension height is the vertical distance from the axis of the nanowire to the bottom surface of the microgroove, and the suspension height is changed by adjusting the depth of the microgroove, thereby changing the fluid drag torque and shear stress distribution experienced by the nanowire in the boundary layer airflow; Preferably, the cross-sectional morphology is selected from one of a circular cross-section, a polygonal cross-section, and a flat strip cross-section. Nanowires with different cross-sectional morphologies have different moments of inertia, and the fluid drag coefficients experienced by different cross-sectional shapes in airflow are also different, thus affecting the magnitude of the fluid load experienced by the nanowires at the same wind speed.

[0014] Preferably, the substrate material is selected from one of metal, silicon, silicon oxide and polyimide; the nanowire material is at least one of metal nanowires (such as silver nanowires, gold nanowires, copper nanowires), semiconductor nanowires (such as silicon nanowires, zinc oxide nanowires), carbon nanotubes and polymer nanofibers.

[0015] Preferably, the device further includes an electrode array disposed on the substrate. The electrode array is disposed at the corresponding nanowire ends of each microgroove and forms a one-to-one detection path with the nanowire. One end electrode is an independent electrode, and the other end electrode is an independent electrode or connected to form a common electrode. The open or closed state of the detection path is used to determine whether the corresponding nanowire has broken. The electrode array can realize rapid electrical scanning of the nanowire breakage state, and can complete the automated reading without relying on equipment such as optical microscopes.

[0016] Preferably, there are multiple suspended nanowire arrays, which are arranged on the substrate in different directions. Each suspended nanowire array is used to sense the wind speed in the corresponding direction. The wind direction and wind speed are determined by comparing the number of fractures and the fracture threshold distribution in the nanowire arrays in different directions.

[0017] This invention also discloses a method for wind speed detection using the aforementioned wind speed tag, comprising the following steps: Calibration steps: Pre-determine or simulate the critical fracture wind speed corresponding to each of the nanowires with different structural parameters, and establish a calibration database that establishes the correspondence between the parameters or numbers of each nanowire and the critical fracture wind speed.

[0018] Wind field exposure step: Place the wind speed tag in the wind field to be tested, so that the airflow of the wind field acts on the suspended nanowire array. When the wind speed reaches or exceeds the critical fracture wind speed of any of the nanowires, the bending stress generated by the fluid resistance of the nanowire exceeds its fracture strength and it breaks.

[0019] Status reading steps: After the wind field exposure is completed, the fracture status of each nanowire is detected.

[0020] Wind speed determination steps: By comparing with the calibration database, the maximum critical fracture wind speed corresponding to the fractured nanowire is determined as the upper limit of the wind speed experienced by the wind field to be measured or the historical peak wind speed, and the minimum critical fracture wind speed in the unfractured nanowire is taken as the lower limit of the wind speed, thereby locking the wind speed range to be measured.

[0021] The state reading step uses optical microscope (OM) or scanning electron microscope (SEM) for morphological visualization observation and judgment, or uses electrical judgment by measuring the on / off electrical signals of the electrode array.

[0022] In the wind speed determination step, the maximum value of the critical fracture wind speed of each of the broken nanowires is determined as the lower limit of the wind speed experienced by the wind field to be measured or the historical peak wind speed, and the minimum value of the critical fracture wind speed of each of the unbroken nanowires is determined as the upper limit of the wind speed; when all nanowires are unbroken, the minimum value of the critical fracture wind speed of all nanowires is used as the upper limit of the wind speed to be measured.

[0023] The technical solution provided in this application has at least the following technical effects or advantages: 1. Passive Zero Power Consumption and Post-Disaster Memory Function: This invention is based on the mechanical fracture failure mechanism induced by fluid-structure interaction at the micro-nano scale, transforming wind speed information into an irreversible physical fracture mode. The tag itself does not require a power supply and can permanently save the peak wind speed record even after the wind field disappears or the system is powered off, providing reliable data for post-disaster assessment and greatly expanding the application scope of extreme environments, passive scenarios, and post-disaster assessment.

[0024] 2. Extremely high flexibility and precision in wind speed threshold control: The bending stiffness of the nanowires in this invention is extremely sensitive to their diameter and suspension span. By precisely controlling the geometry, morphology, and suspension parameters of the nanowires through micro / nano fabrication processes, a wide dynamic range and high-resolution gradient configuration can be achieved at the micrometer / nano scale, ranging from light winds (m / s) to strong winds (tens of m / s).

[0025] 3. Ultra-high spatial resolution and miniaturized integration: The overall size of the wind speed tag of this invention can be controlled in the range of micrometers to millimeters. The nanowire array occupies a very small area and has almost no interference with the flow field to be measured (low flow field intrusion). It is particularly suitable for sensing the micro-area wind speed distribution inside microfluidic chips, micro wind tunnels or complex microstructures.

[0026] 4. Flexible and convenient reading methods: This invention can be used for "image identification" through simple optical microscopy, or it can be combined with array electrodes to realize automated electrical on / off scanning, meeting the needs of different application scenarios for cost and detection efficiency. Attached Figure Description

[0027] Figure 1 This is a three-dimensional structural diagram of the wind speed label in the embodiment; Figure 2 This is a side view cross-section and a schematic diagram of the stress mechanism of a single suspended nanowire in the embodiment; Figure 3 This is a schematic diagram illustrating the step-by-step fracture process of suspended nanowire arrays with different stiffness gradients under different wind speeds in the embodiment. Figure 4 This is a schematic diagram of the wind speed tag continuity detection structure with integrated electrical detection electrodes in the embodiment; Figure 5 This is a schematic diagram of the nanowire array arrangement structure used for wind direction calibration and wind speed detection in the embodiment.

[0028] In the figure: 1. Array of silver nanowires with different diameters; 2. Substrate; 3. Metal electrode array; 4. First nanowire; 5. Second nanowire; 6. Third nanowire; 7. Axial tensile force; 8. Fluid resistance; 9. Suspension span; 10. Suspension height; 11. Array of nanowires with the same diameter; 12. Suspension span of the first microgroove; 13. Suspension span of the second microgroove; 14. Suspension span of the third microgroove; 15. Circuit testing tool; 16. Break; 17. Fourth nanowire; 18. Fifth nanowire. Detailed Implementation

[0029] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0030] Example 1: This example provides a passive wind speed tag based on nanowire diameter gradient for detecting the upper limit of wind speed and historical peak wind speed in a micro-area flow field. (See attached...) Figures 1-2 As shown, the wind speed tag in this embodiment includes a substrate 2, on the surface of which are processed rectangular microgrooves with a suspension height H = 2 μm. A set of parallel silver nanowire arrays 1 of different diameters are arranged above the microgrooves, with each long nanowire spanning multiple microgrooves. The two ends of each nanowire are fixed to the substrate step surface on both sides of the microgrooves, with the middle portion suspended, the suspension span 9 being 20 μm. To construct a stiffness gradient, this embodiment selects three different diameter silver nanowires, whose structural parameters and corresponding critical fracture wind velocities are as follows: First nanowire 4: diameter d1=50nm, corresponding to the smallest bending stiffness and a low critical fracture wind speed; Second nanowire 5: diameter d2=100nm, corresponding to medium bending stiffness; The third nanowire 6 has a diameter d3=150nm, corresponding to the highest bending stiffness and a relatively high critical fracture wind speed.

[0031] The specific manufacturing process steps for the wind speed tag in this embodiment are as follows: (1) Substrate cleaning and microgroove photolithography: A silicon wafer with a thickness of 500μm and a surface protective layer of 500nm thermally oxidized silicon dioxide (SiO2) was selected as substrate 2; the substrate was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water in sequence, and after drying, photoresist was spin-coated. The substrate was exposed and developed by ultraviolet photolithography using a mask to expose a parallel strip microgroove pattern with a width of 20μm.

[0032] (2) Microgroove depth etching: The substrate is vertically etched downward using reactive ion etching (RIE) to form a microgroove with a suspended height of 10 μm. After etching, the residual photoresist is removed and the substrate is cleaned.

[0033] (3) Selective assembly and transfer of nanowires: Silver nanowires are selectively and orientably assembled onto the corresponding microgrooves by means of probe or thin film transfer.

[0034] (4) End reinforcement and annealing: In the contact area where the nanowire spans the steps at both ends of the substrate, the fixed area at both ends of the nanowire is defined by photolithography, and 100nm of metal material is deposited by vapor deposition to prevent the nanowire from falling off or slipping from the substrate when the wind field impacts, and to ensure that the fracture failure only occurs in the suspended section; heat annealing at 150℃ for 15 minutes eliminates contact stress and enhances mechanical anchoring strength.

[0035] Example 2: Unlike Example 1, this example uses homogeneous array nanowires 11 of the same diameter (such as single-crystal silicon nanowires generated in the same batch, d=100nm). The suspension span L is controlled by designing stepped microgrooves of different widths on the substrate, thereby constructing the stiffness and stress response gradient.

[0036] Combination Figure 2 and Figure 3 According to the mechanical model, the nanowires on the microgrooves are fixed at both ends, providing axial tensile force to the nanowires. The critical fracture wind speed of a double-ended fixed beam under uniform fluid load is shown in Figure 7. With suspended span Inversely proportional ( ).

[0037] The first microgroove is set with a suspended span of 12 and L1 = 15 μm, which corresponds to a relatively high critical fracture wind speed (e.g., about 21 m / s). The second microgroove is set with a suspended span of 13 and L2 = 25 μm, corresponding to a moderate critical fracture wind speed (e.g., about 13 m / s). The third microgroove is set with a suspended span of 14 and L3 = 40 μm, which corresponds to a relatively low critical fracture wind speed (e.g., about 8 m / s).

[0038] The advantages of this embodiment are: it only requires the synthesis of nanowire materials of a single specification, which reduces the cost of material screening; and it can achieve extremely high-precision wind speed threshold gradient division simply by the precise patterning design of the microgroove width on the photolithography mask, which is very suitable for large-scale industrial micro-nano manufacturing.

[0039] Example 3: Combined with Appendix Figure 1 and Figure 4 This embodiment further integrates an electrical signal reading module based on the structure of Embodiment 1 to achieve rapid automated diagnosis without the need for an optical microscope.

[0040] (1) Structural Description: On the substrate surfaces on both sides of the microgroove, a metal electrode array 3 composed of titanium / gold (Ti / Au, 10nm / 80nm) is pre-deposited using photolithography and lift-off processes. The electrode array is respectively disposed at the corresponding nanowire ends of each microgroove, and forms a one-to-one detection path with the nanowire, wherein one end electrode can be connected to form a common electrode. During electrical detection, a probe or multimeter circuit testing tool 15 measures the continuity between each independent electrode and the common electrode.

[0041] (2) Detection mechanism: When not subjected to strong winds, the nanowires are intact, and the resistance between each electrode pair is in a normal low-resistance state (ohmic contact, the resistance is usually in the tens to hundreds of ohms); the wind speed to be measured exceeds the critical breakage wind speed of a certain nanowire (such as the first nanowire 4). At that time, the nanowire breaks to form a fracture 16; the fracture cuts off the corresponding detection path, causing the resistance between the electrodes to rise sharply to the open circuit state (megaohm level and above).

[0042] Example 4: This example provides a nanowire-based wind speed tag for wind direction calibration and wind speed detection in micro-area flow fields. (See attached image.) Figure 5 As shown: The wind speed tag in this embodiment has a total of 8 sampling units, which are arranged in a ring-shaped array around the same central axis, with an angle difference of 45° between adjacent units. The detection path lead-out electrodes of each of the 8 sampling units form an 8-bit binary signal output terminal. In use, the entire ring array is placed in the wind field to be measured. The incoming wind blows towards the array at a certain azimuth angle. The nanowires perpendicular to the wind direction will break first. Due to the influence of the angle, the remaining sampling units located on the sloping or leeward side will have fewer nanowires broken than the nanowire group on the windward side because the wind-receiving area is reduced and the wind pressure is lower than the breakage threshold. That is, the wind direction can be roughly obtained by the number of nanowires broken. Assuming that the direction of the fourth nanowire 17 and the fifth nanowire 18 is the windward side, a signal acquisition tool can be connected to the signal output terminal of each unit detection path. By acquiring the disconnection time of the electrical signals at both ends of the fourth nanowire 17 and the fifth nanowire 18, the wind direction can be determined as whether the wind is blowing from the fourth nanowire 17 to the fifth nanowire 18 or from the fifth nanowire 18 to the fourth nanowire 17. In other words, the specific wind direction can be obtained by the order of nanowire breakage. Finally, the specific wind speed can be obtained by calibrating the database corresponding to the nanowire breakage in that direction.

[0043] Example 5: This example provides a method for wind speed detection using the wind speed tag described above, including the following steps: (1) Calibration steps: Pre-determine or simulate the critical fracture wind speed corresponding to nanowires with different stiffness gradients using COMSOL, and establish a calibration database that corresponds one-to-one with the parameters or numbers of nanowires and the critical fracture wind speed. This includes, but is not limited to: the wind speed corresponding to the fracture of nanowires with different diameters under the same suspended length microgroove, such as the wind speed corresponding to 3m / s, 4m / s, 5m / s, etc. for nanowires with diameters of 50nm, 100nm, 150nm, etc. under a suspended length of 9μm; the wind speed corresponding to the fracture of nanowires with the same diameter under different suspended length microgrooves, such as the wind speed corresponding to 8m / s, 13m / s, 21m / s, etc. for nanowires with a diameter of 50nm under suspended lengths of 15μm, 25μm, 40μm. The finer the diameter and suspended length dimensions, the more accurate the results measured by the wind direction label. (2) Wind field exposure procedure: If the wind direction is known, place the wind speed tag in the wind field to be measured, so that the airflow of the wind field acts perpendicular to the suspended nanowire array. When the wind speed reaches or exceeds the critical fracture wind speed of any nanowire, the bending stress generated by the fluid resistance 8 of the nanowire exceeds its fracture strength and causes irreversible fracture. If the wind direction is unknown, use nanowire arrays arranged in different directions for measurement; (3) Status reading steps: After the wind field exposure ends, the fracture status of each nanowire is detected. The morphological observation can be performed by optical microscope or scanning electron microscope, or the electrical determination can be performed by measuring the on and off electrical signals of each detection path in the electrode array. (4) Wind speed determination steps: Based on the nanowire breakage status, the wind speed is obtained by referring to the calibrated database. For example, in a wind direction label with a suspended length of 9 μm, nanowires with diameters of 50 nm and 100 nm are broken, while nanowires with a diameter of 150 nm remain intact. According to the calibrated database, the wind speed is 4 m / s. For nanowire arrays distributed in different directions, the approximate wind direction is first determined by the number of nanowire breaks in different directions. Then, the specific wind direction is determined by the order in which the first and last nanowires of the same diameter break in that direction. Finally, the specific wind speed is obtained by referring to the calibrated database based on the nanowire breakage status in that direction.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A nanowire-based wind speed tag, characterized in that, include: Base; A suspended nanowire array, wherein the suspended nanowire array has multiple nanowires disposed above the substrate and fixed at both ends to the substrate, and a gap is formed between the middle portion of each nanowire and the surface of the substrate. At least some of the nanowires in the suspended nanowire array have different structural parameters, and the critical fracture wind speeds of the nanowires with different structural parameters under the action of a wind field are different. The suspended nanowire array determines the wind speed by the fracture state of each nanowire after exposure to a wind field.

2. The nanowire-based wind speed tag according to claim 1, characterized in that: At least one microgroove is formed on the substrate, and each nanowire is disposed across the microgroove. The gap is the space between the middle part of each nanowire and the bottom surface of the microgroove.

3. The nanowire-based wind speed tag according to claim 2, characterized in that: The structural parameters include the diameter of the nanowires; the suspended nanowire array has at least two different diameters of nanowires.

4. The nanowire-based wind speed tag according to claim 2, characterized in that: The structural parameters include the suspension span of the nanowires, which is the length of the free suspension segment of each nanowire that is not in contact with the substrate; the substrate has multiple microgrooves of different widths, and each nanowire is respectively straddling the microgrooves of different widths to form different suspension spans.

5. The nanowire-based wind speed tag according to claim 2, characterized in that: The structural parameters include at least one of the nanowire suspension height and cross-sectional morphology; the suspension height is the vertical distance from the axis of the nanowire to the bottom surface of the microgroove, and the suspension height is changed by adjusting the depth of the microgroove; the cross-sectional morphology is selected from one of a circular cross-section, a polygonal cross-section, and a flat strip cross-section.

6. The nanowire-based wind speed tag according to claim 1, characterized in that: The substrate is made of metal, silicon, silicon oxide, or polyimide; the nanowires are made of metal nanowires, semiconductor nanowires, carbon nanotubes, or polymer nanofibers.

7. The nanowire-based wind speed tag according to claim 1, characterized in that: It also includes an electrode array disposed on the substrate. The electrode array is disposed at the corresponding nanowire ends of each microgroove and forms a one-to-one detection path with the nanowire. One end electrode is an independent electrode, and the other end electrode is an independent electrode or connected to form a common electrode. The open or closed state of the detection path is used to determine whether the corresponding nanowire has broken.

8. The nanowire-based wind speed tag according to claim 1, characterized in that: The suspended nanowire array comprises multiple arrays arranged in different directions on the substrate. Each array is used to sense the wind speed in its corresponding direction. The wind direction and speed are determined by comparing the number of fractures and the fracture threshold distribution in the nanowire arrays of different directions.

9. A method for wind speed detection using a wind speed tag as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Calibration steps: Pre-determine or simulate the critical fracture wind speed corresponding to each of the nanowires with different structural parameters, and establish a calibration database of the correspondence between the parameters or numbers of each nanowire and the critical fracture wind speed; Wind field exposure step: Place the wind speed tag in the wind field to be tested, so that the wind field airflow acts on the suspended nanowire array. When the wind speed reaches or exceeds the critical fracture wind speed of any nanowire, the nanowire breaks. Status reading steps: After the wind field exposure ends, the fracture status is determined by morphological observation using an optical microscope or a scanning electron microscope, or by electrical determination by measuring the on / off electrical signals of each detection path in the electrode array; Wind speed determination steps: By comparing with the calibration database, and based on the critical fracture wind speeds of the broken and unbroken nanowires, the range of the wind speed to be measured or the historical peak wind speed is determined.

10. The wind speed detection method according to claim 9, characterized in that: In the wind speed determination step, the maximum value of the critical fracture wind speed of each of the broken nanowires is determined as the lower limit of wind speed or historical peak wind speed experienced by the wind field to be measured, and the minimum value of the critical fracture wind speed of each of the unbroken nanowires is determined as the upper limit of wind speed. When all nanowires are intact, the minimum critical fracture wind speed among all nanowires is used as the upper limit of the wind speed to be measured.

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