A leviton-based icing sensing device and system

Abstract

The application relates to the field of icing sensors, in particular to an icing sensor device and system based on Love waves, which comprises a silicide-containing protective layer (5), a PDMS micro-fluidic chip and a chip packaging enclosure; wherein the silicide-containing protective layer (5) is engraved on the waveguide layer (2) and is located between the input transducer (3) and the output transducer (4); the PDMS micro-fluidic chip is bonded with the silicide-containing protective layer (5) at the four peripheral edges of the PDMS micro-fluidic chip; the PDMS micro-fluidic chip is packaged by the chip packaging enclosure; and the PDMS micro-fluidic chip and the chip packaging enclosure jointly form a PDMS water storage cavity (6). The application is provided with the PDMS water storage cavity (6), water storage is realized, and electrode short circuit caused by water leakage is prevented; the photoetching technology is adopted to engrave the silicide-containing thin layer (5) on the transmission path, the PDMS water storage cavity (6) is bonded, and water leakage to the surrounding interdigital electrodes is prevented.

Description

Technical Field

[0001] This invention relates to the field of icing sensors, and more specifically to an icing sensor device and system based on Leff wave. Background Technology

[0002] Aircraft icing is a typical meteorological factor affecting flight safety and one of the main causes of aircraft crashes and accidents. Because icing sensors are crucial for safe flight, the issue of aircraft icing safety has been given considerable attention since their widespread application, leading to significant research and development of icing monitoring technologies. Research on icing detection technology abroad began in the 1950s, and by the mid-1980s, icing sensors had become standard equipment on various military and civilian aircraft in the United States. Currently, typical icing monitoring technologies mainly include fiber optics, magnetostriction, and piezoelectric films.

[0003] Fiber optic icing sensors detect icing based on the principle of ice reflection. However, relying on the intensity of light received by the receiver, they are inevitably affected by stray light from the environment, as well as fluctuations in light source power and fiber optic transmission loss, leading to inaccurate icing detection. Magnetostrictive icing sensors, utilizing the magnetostrictive effect, offer advantages such as high strength, reliability, practicality, and stable operation in complex environments, showing great promise. However, their installation location is external to the fuselage, nose, or other parts, and the probe can affect the flow field at the installation location or the overall aerodynamic performance of the aircraft. Furthermore, changes in ambient temperature affect the natural frequency of the vibrating tube and the resonant frequency of the circuitry, necessitating sensor temperature compensation technology. Piezoelectric diaphragm icing sensors, based on the piezoelectric effect, can be embedded in the fuselage or wing, offering convenient installation and good detection accuracy, but require an excitation signal and an additional temperature compensation module. Existing icing monitoring technologies face challenges in terms of sensitivity, anti-interference capability, reliability, size, and power consumption, making it difficult to meet the application requirements for ensuring flight safety of aircraft. Therefore, exploring new principles for icing monitoring and developing high-performance icing sensors that are fast, accurate, miniaturized, low-power, and anti-interference have become an inevitable requirement and development trend for maintaining aviation safety and protecting people's lives and property.

[0004] Surface acoustic wave (SAW) sensors are small in size and can perform wireless, passive measurements. Lough waves are shear-polarized surface guided waves that propagate in a layered structure. Specifically, a waveguide layer is coated on the surface of a piezoelectric substrate supporting horizontal shear-type SAW (SH-SAW) propagation, coupling the elastic wave excited within the substrate into the surface waveguide layer, effectively reducing sound wave attenuation. The basic principle of Lough wave icing sensing is to utilize the corresponding changes in SAW propagation velocity and sound attenuation caused by the physical effects of the mass load and other physical effects of the icing process on the Lough waves, thereby achieving real-time monitoring of the icing state and thickness. Compared to other icing monitoring technologies such as fiber optics, magnetostriction, and piezoelectric films, SAW technology features miniaturization, low power consumption, fast response, high sensitivity, and strong anti-interference capabilities. In particular, it can utilize the electromagnetic wave excitation principle to achieve "passive" sensor sensing and "wireless" transmission of the sensing signal, aligning with the development trend of icing monitoring in fields such as aviation and rail transportation.

[0005] Patent 201911075381.9 discloses a surface acoustic wave (SAW) icing sensor and its system based on a reflection delay line. The system includes a piezoelectric wafer substrate and, sequentially arranged from one end to the other on the upper surface of the piezoelectric wafer substrate, an interdigital transducer, a first reflector, a water storage device, a second reflector, and a third reflector. The system also includes a SAW icing sensor and a radio frequency (RF) readout module. Patent 201911075381.9 uses the interdigital transducer to generate SAW waves and then determines the icing state of the water storage device based on the reflected waves formed by the first, second, and third reflectors.

[0006] Patent 201811603907.1 discloses an icing sensor based on a surface acoustic wave (SAW) oscillator, comprising a SAW device and an oscillation circuit, an encapsulated shell, and a water-permeable membrane. The SAW device is externally encapsulated by the shell; the water-permeable membrane is disposed at the opening of the shell; the surface of the SAW oscillator is covered with a thin SiO2 protective layer; the SAW device outputs an electrical signal with varying oscillation frequency to the oscillation circuit, which detects sudden changes in the oscillation frequency of the electrical signal and outputs the oscillation frequency to achieve icing early warning and monitoring. It features high detection sensitivity, good temperature stability, and timely icing warning, making SAW technology relatively easy to implement. Water vapor ices on the surface of the SiO2 protective layer through the water-permeable membrane, causing the SAW device to output an electrical signal with varying oscillation frequency to the oscillation circuit, thereby monitoring icing.

[0007] However, the surface acoustic wave (SAW) icing technology used in patent 201911075381.9 is generally quite simple. It uses a single signal source to excite a SAW device to generate SAW waves, and the SAW device is directly exposed to the environment for icing monitoring. This results in severe interference from the external environment with the SAW signal, and the device is easily damaged, leading to problems such as lack of system integrity and insufficient device sealing. Patent 201811603907.1 discloses an icing sensor based on a SAW oscillator, but it does not encapsulate the icing sensor, resulting in poor sealing. Its disclosed technical solution involves allowing water vapor that permeates through a water-permeable membrane to freeze directly on a protective thin layer. Once the protective thin layer is damaged, water vapor, ice, or melted water will directly contact the SAW oscillator. Water leakage can cause inaccurate icing monitoring, electrode short circuits, or damage to the icing sensor. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing icing sensors, such as large size, poor real-time performance, difficulty in implementation, and poor sealing. This invention designs a new icing sensor based on Leffe wave propagation, which offers high detection sensitivity, good temperature stability, and excellent sealing, enabling timely early warning. The invention strengthens the bond between the PDMS water storage chamber and the sensor by etching a thin layer of silicon-containing compound onto the acoustic wave transmission path and bonding it to the silicon-containing compound layer. This allows the loaded water to be stored within the PDMS storage chamber, increasing the sensor's sealing and preventing damage caused by the loaded water. Furthermore, by integrating this sensor with a circuit, a monitoring system is designed, effectively solving the problems of poor stability, difficulty in implementation, low detection sensitivity, and slow detection speed inherent in current icing sensors. This invention proposes an icing sensor based on Leff waves, comprising: a piezoelectric substrate 1, a waveguide layer 2, an input transducer 3 and an output transducer 4, a metal encapsulation shell 7, and a water-permeable membrane 8. The icing sensor also includes: a silicide protective layer 5, a PDMS microfluidic chip, and a chip encapsulation enclosure.

[0009] The silicide protective layer 5 is fitted over the waveguide layer 2 and is located between the input transducer 3 and the output transducer 4; the silicide protective layer 5 is rectangular and has an opening in the middle;

[0010] The PDMS microfluidic chip is bonded to the silicon-containing protective layer 5 at its four edges; the PDMS microfluidic chip is encapsulated using the chip encapsulation barrier; the PDMS microfluidic chip and the chip encapsulation barrier together form a PDMS water storage cavity 6;

[0011] The chip packaging enclosure is a rectangular frame composed of vertical partitions. The lower edge of the chip packaging enclosure is bonded to the waveguide layer 2, and the upper edge of the chip packaging enclosure is connected to the packaging cap of the metal packaging shell 7.

[0012] The metal encapsulation tube 7 has an opening at the corresponding position of the PDMS water storage cavity 6; the water-permeable membrane 8 is disposed at the opening of the metal encapsulation tube 7.

[0013] As an improvement to the above-mentioned device, the icing sensor based on the Lep wave includes:

[0014] The input transducer 3 and the output transducer 4 are deposited on the piezoelectric substrate 1;

[0015] The waveguide layer 2 is deposited on the piezoelectric substrate 1, the input transducer 3, and the output transducer 4;

[0016] The metal encapsulation housing 7 is used to encapsulate the surface acoustic wave device;

[0017] The surface acoustic wave device includes: the piezoelectric substrate 1, the waveguide layer 2, the input transducer 3, the output transducer 4, the silicon-containing compound protective layer 5, and the PDMS water storage cavity 6.

[0018] The metal encapsulation tube 7 has an encapsulation cap on top.

[0019] As an improvement to the above-mentioned device, the piezoelectric substrate 1 is cut by rotating 42.75° around the Y direction and propagating 90° along the X direction; the material of the piezoelectric substrate 1 is: 36°YXLiTaO3, 41°YXLiTaO3, 64°YXLiTaO3 or ST-90°X quartz crystal.

[0020] As an improvement to the above-mentioned device, the waveguide layer 2 is made of SU-8, PMMA or SiO2 thin layer; the thickness of the waveguide layer 2 is 1-3%λ; where λ is the wavelength of the sound wave along the direction of sound wave propagation.

[0021] As an improvement to the aforementioned device, both the input transducer 3 and the output transducer 4 adopt an EWC / SPUDT structure to reduce the insertion loss of the Röpf wave-based icing sensor, lower the detection limit of the Röpf wave-based icing sensor, and provide stability. The EWC / SPUDT structure includes: a plurality of interdigital pairs 31 and a plurality of reflective electrodes 32; each interdigital pair includes two interdigital electrodes, the width of which is 1 / 8λ, and the spacing between the interdigital electrodes is 1 / 8λ; the width of the reflective electrode is 1 / 4λ; the reflective electrode... The thickness of the reflective electrode 32 and the interdigital electrode is 1%λ to 1.5%λ; the distance between the edge of the reflective electrode 32 and its corresponding interdigital pair 31 is 3 / 16λ; the materials of the interdigital electrode and the reflective electrode 32 include gold, aluminum, or a gold-aluminum alloy; the input transducer 3 also adopts a comb-like structure; the input transducer 3 is formed by periodically removing part of the interdigital electrode to form a comb-like structure; the comb-like structure includes several sets of comb tooth structure units; the spaces between the comb teeth are filled with a pseudo-finger electrode 33 with a width of 1 / 8λ and one end grounded, where λ is the wavelength of the sound wave along the direction of sound wave propagation.

[0022] As an improvement to the above-mentioned device, the silicon-containing compound thin layer 5 is rectangular, with a width H along the Y direction greater than the acoustic aperture and less than the width of the piezoelectric substrate 1; the distances from the outer edges of both sides of the silicon-containing compound thin layer 5 to the input transducer 3 and the output transducer 4 are 10λ respectively; a rectangular opening is provided in the center of the silicon-containing compound thin layer 5; the length from the edge of the rectangular opening to the edge of the silicon-containing compound thin layer 5 is 1% to 1.5%λ; the thickness of the silicon-containing compound thin layer 5 is 3%λ to 50%λ; where λ is the wavelength of the sound wave along the direction of sound wave propagation.

[0023] As an improvement to the above-mentioned device, the silicon-containing compound thin layer 5 is overlaid on the waveguide layer 2 by photolithography; the silicon-containing compound thin layer 5 is physically reversibly bonded to the PDMS water storage cavity 6 through Si-Si or Si-O bonds, or irreversible bonding is achieved by exposing the piezoelectric substrate 1, waveguide layer 2, silicon-containing compound thin layer 5 and PDMS water storage cavity 6 to oxygen plasma for bonding oxygen plasma treatment; the material of the silicon-containing compound thin layer 5 includes: SiO2, SiC or SiN, and the material of the silicon-containing compound thin layer 5 also includes: doped SiO2, SiC or SiN.

[0024] As an improvement to the above device, the width of the PDMS water storage cavity 6 along the x-direction is set to λ or an integer multiple of λ, and the width along the y-direction is set to be less than the width of the piezoelectric substrate 1; where λ is the wavelength of the sound wave along the direction of sound wave propagation.

[0025] As an improvement to the above-mentioned device, the permeable membrane 8 is an oxygen-barrier permeable membrane or a polyvinyl alcohol-chitosan blend composite permeable membrane.

[0026] As an improvement to the above device, λ is the wavelength of the sound wave along the direction of sound wave propagation, λ = v / f; where v is the propagation speed of the surface acoustic wave on the piezoelectric substrate 1, and f is the operating frequency of the icing sensor device based on the Leff wave, which is in the same frequency as the signal excitation source 9.

[0027] A system for an icing sensor based on a Leff wave, implemented based on an icing sensor based on a Leff wave as described in any one of claims 1-10, the system comprising:

[0028] Signal excitation source 9 is used to output a specific signal source;

[0029] Signal distributor 10 is used to input the specific signal source to the icing sensor based on the Leff wave;

[0030] Phase detector 11 is used to receive the electrical signal transmitted by the icing sensor of the Lefu wave; it is also used to perform phase detection between the specific signal source and the received electrical signal to obtain the phase difference and amplitude difference.

[0031] AD converter 12 is used to convert phase difference and amplitude difference into voltage signal;

[0032] Data acquisition unit 13 is used to acquire and record the voltage signal;

[0033] A display terminal is used to display the recorded voltage signal and the corresponding icing thickness.

[0034] The advantages of this invention are:

[0035] 1. The icing sensor based on the LEFF wave of the present invention improves the temperature stability of the device by depositing SU-8 with opposite temperature coefficient polarity on the surface of the piezoelectric substrate 1 with high voltage coefficient. SU-8 serves as waveguide layer 2 to excite LEFF waves and protect the input transducer 3 and the output transducer 4. By exciting LEFF waves and their propagation changes in the waveguide layer, the state changes of the waveguide layer 2 are sensitive, and icing can be monitored in real time.

[0036] 2. The icing sensor based on the Lefu wave of the present invention applies EWC / SPUDT and comb structure to the design, which can reduce the insertion loss of the device and obtain a single oscillation mode, thereby improving the detection limit and stability of the icing sensor.

[0037] 3. The present invention is based on the wave icing sensor device of Lefu. A PDMS water storage cavity 6 is provided between the output transducer (4) and the input transducer (3) to realize water storage and prevent water leakage from causing electrode short circuit.

[0038] 4. The Lefu wave icing sensor of the present invention uses photolithography to overlay a thin layer 5 of silicon compound on the transmission path, which facilitates bonding with the PDMS water storage cavity 6 to prevent water from leaking onto the surrounding interdigitated electrodes.

[0039] 5. The invented Lefubo icing sensor has a metal package and a water-permeable membrane that communicates with the outside world on the metal package. This ensures that the surface of the device is clean while maintaining the same temperature and humidity conditions as the external environment, thereby improving the accuracy of icing detection. Attached Figure Description

[0040] Figure 1 A schematic diagram of the principle structure of an icing sensor based on Lep wave provided for Embodiment 1 of the present invention;

[0041] Figure 2 A schematic diagram of the planar structure of the input transducer and output transducer of an icing sensor based on Leff wave provided for Embodiment 1 of the present invention;

[0042] Figure 3 This is a front view of the icing sensor device based on Lepton waves provided in Embodiment 1 of the present invention;

[0043] Figure 4(a) is a schematic diagram of silicon-containing compound thin-layer overlay of a Lefu wave icing sensor device provided in Embodiment 1 of the present invention;

[0044] Figure 4(b) is a schematic diagram of the PDMS water storage chamber of a Lefubo icing sensor device provided in Embodiment 1 of the present invention.

[0045] Attached Figure Labels

[0046] 1. Piezoelectric substrate 2. Waveguide layer 3. Input transducer

[0047] 4. Output transducer; 5. Silicon compound thin layer; 6. PDMS water storage chamber

[0048] 7. Metal encapsulation housing; 8. Water-permeable membrane; 9. Signal excitation source

[0049] 10. Signal distributor; 11. Phase detector; 12. AD converter

[0050] 13. Data acquisition unit; 14. Interdigitated pair; 15. Reflective electrode. Detailed Implementation

[0051] The technical solutions provided by the present invention will be further illustrated below with reference to the embodiments.

[0052] This invention proposes an icing sensor based on Leff waves, comprising: a piezoelectric substrate 1, a waveguide layer 2, an input transducer 3 and an output transducer 4, a metal encapsulation shell 7, and a water-permeable membrane 8. The icing sensor also includes: a silicide protective layer 5, a PDMS microfluidic chip, and a chip encapsulation enclosure.

[0053] The input transducer 3 and the output transducer 4 are deposited on the piezoelectric substrate 1;

[0054] The waveguide layer 2 is deposited on the piezoelectric substrate 1, the input transducer 3, and the output transducer 4; it is used to couple the elastic wave excited in the piezoelectric substrate 1 into the surface wave waveguide layer 2.

[0055] The metal encapsulation housing 7 is used to encapsulate the surface acoustic wave device;

[0056] The surface acoustic wave device includes: the piezoelectric substrate 1, the waveguide layer 2, the input transducer 3, the output transducer 4, the silicon-containing compound protective layer 5, and the PDMS water storage cavity 6.

[0057] The metal encapsulation tube 7 has an encapsulation cap on top.

[0058] The silicide protective layer 5 is fitted over the waveguide layer 2 and is located between the input transducer 3 and the output transducer 4; the silicide protective layer 5 is rectangular and has an opening in the middle;

[0059] The PDMS microfluidic chip is bonded to the silicon-containing protective layer 5 at its four edges; the PDMS microfluidic chip is encapsulated using the chip encapsulation barrier; the PDMS microfluidic chip and the chip encapsulation barrier together form a PDMS water storage cavity 6;

[0060] The chip packaging enclosure is a rectangular frame composed of vertical partitions. The lower edge of the chip packaging enclosure is bonded to the waveguide layer 2, and the upper edge of the chip packaging enclosure is connected to the packaging cap of the metal packaging shell 7.

[0061] The metal encapsulation tube 7 has an opening at the corresponding position of the PDMS water storage cavity 6; the water-permeable membrane 8 is disposed at the opening of the metal encapsulation tube 7; this allows the environment inside the PDMS water storage cavity 6 to be the same as the external environment in terms of temperature, humidity, and other conditions, so as to ensure accurate and smooth freezing.

[0062] The piezoelectric substrate 1 is cut by rotating 42.75° around the Y direction and propagating 90° along the X direction; the material of the piezoelectric substrate 1 is: 36°YXLiTaO3, 41°YXLiTaO3, 64°YXLiTaO3 or ST-90°X quartz crystal.

[0063] Waveguide layer 2 is made of SU-8, PMMA or SiO2 thin layer; the thickness of waveguide layer 2 is 1-3%λ; where λ is the wavelength of the sound wave along the direction of sound wave propagation.

[0064] Both the input transducer 3 and the output transducer 4 adopt an EWC / SPUDT structure to reduce the insertion loss of the icing sensor based on the Röhler wave, reduce the detection limit of the icing sensor based on the Röhler wave, and provide stability. The EWC / SPUDT structure includes: a plurality of interdigital pairs 31 and a plurality of reflective electrodes 32; each interdigital pair includes two interdigital electrodes, the width of the interdigital electrodes is 1 / 8λ, and the spacing between the interdigital electrodes is 1 / 8λ; the width of the reflective electrode is 1 / 4λ; the thickness of the reflective electrode 32 and the interdigital electrode is 1%λ to 1.5%λ; the distance between the reflective electrode 32 and the edge of its corresponding interdigital pair 31 is 3 / 16λ; the materials of the interdigital electrode and the reflective electrode 32 include: gold, aluminum, or a gold-aluminum alloy; where λ is the wavelength of the sound wave along the direction of sound wave propagation.

[0065] The input transducer 3 also adopts a comb-like structure; the input transducer 3 is periodically stripped of part of the interdigital electrodes to form a comb-like structure; the comb-like structure includes several sets of comb tooth structure units; the comb teeth are filled with dummy finger electrodes (33) with a width of 1 / 8λ and one end grounded to maintain the uniformity of the elastic wave propagation speed; where λ is the wavelength of the sound wave along the direction of sound wave propagation.

[0066] The silicon-containing compound thin layer 5 is rectangular, with a width H along the Y direction greater than the acoustic aperture and less than the width of the piezoelectric substrate 1; the distances from the outer edges of the silicon-containing compound thin layer 5 to the input transducer 3 and the output transducer 4 are 10λ respectively; a rectangular opening is provided in the center of the silicon-containing compound thin layer 5; the length from the edge of the rectangular opening to the edge of the silicon-containing compound thin layer 5 is 1% to 1.5%λ; the thickness of the silicon-containing compound thin layer 5 is 3%λ to 50%λ; where λ is the wavelength of the sound wave along the direction of sound wave propagation.

[0067] The silicon-containing compound thin layer 5 is overlaid on the waveguide layer 2 by photolithography. The silicon-containing compound thin layer 5 is physically reversibly bonded to the PDMS water storage cavity 6 through Si-Si or Si-O bonds, or irreversibly bonded by exposing the piezoelectric substrate 1, waveguide layer 2, silicon-containing compound thin layer 5 and PDMS water storage cavity 6 to oxygen plasma for bonding oxygen plasma treatment. The material of the silicon-containing compound thin layer 5 includes SiO2, SiC or SiN, and the material of the silicon-containing compound thin layer 5 also includes doped SiO2, SiC or SiN.

[0068] The PDMS water storage cavity 6 is disposed between the input transducer 3 and the output transducer 4; the PDMS water storage cavity includes a microfluidic chip designed with polydimethylsiloxane (PDMS) material; the PDMS water storage cavity 6 is bonded to the silicon compound protective layer 5 through the microfluidic chip to achieve water storage and to encapsulate the sensor, ensuring that no leakage occurs after water is loaded, while ensuring that the device surface is clean and avoiding interference from the external environment; the width of the PDMS water storage cavity 6 along the x-direction is set to λ or an integer multiple of λ, and the width along the y-direction is set to be less than the width of the piezoelectric substrate 1; where λ is the wavelength of the sound wave along the direction of sound wave propagation.

[0069] The pore size of the permeable membrane 8 is large enough to allow small water molecules to pass through; the permeable membrane 8 has permeation evaporation separation performance and water permeability performance; the permeable membrane 8 is a graphene oxide gas-barrier permeable membrane, a polyvinyl alcohol (PVA) permeable membrane, or a chitosan blend composite permeable membrane (CS / PSF).

[0070] λ is the wavelength of the sound wave along the direction of sound wave propagation, λ = v / f; where v is the propagation speed of the surface acoustic wave on the piezoelectric substrate 1, and f is the operating frequency of the icing sensor based on the Leff wave, which is in the same frequency as the signal excitation source 9.

[0071] To achieve another objective of the present invention, the present invention provides a system for an icing sensor based on a Leff wave, implemented based on the aforementioned icing sensor based on a Leff wave, the system comprising:

[0072] The signal excitation source 9 is used to output a specific signal source;

[0073] Signal distributor 10 is used to input the specific signal source to the icing sensor based on the Leff wave;

[0074] Phase detector 11 is used to receive the electrical signal transmitted by the icing sensor of the Lefu wave; it is also used to perform phase detection between the specific signal source and the received electrical signal to obtain the phase difference and amplitude difference.

[0075] AD converter 12 is used to convert phase difference and amplitude difference into voltage signal;

[0076] Data acquisition unit 13 is used to acquire and record the voltage signal;

[0077] A display terminal is used to display the recorded voltage signal and the corresponding icing thickness.

[0078] Example 1:

[0079] Figure 1 The present invention illustrates the specific structure and operation of an icing sensor device and system based on Lepton waves provided in Embodiment 1 of the present invention.

[0080] like Figure 1 As shown, an icing sensor based on Leff wave includes a piezoelectric substrate 1, an input transducer 3 and an output transducer 4 deposited on the piezoelectric substrate, an SU-8 waveguide layer 2 deposited on the piezoelectric substrate 1, the input transducer 3 and the output transducer 4, a silicon-containing compound thin layer 5 (a SiO2 thin layer is used in this embodiment) overlaid on the SU-8 waveguide layer 2, a PDMS water storage cavity 6 bonded to the SiO2 thin layer 5, a metal encapsulation shell 7, a water-permeable membrane 8, a signal excitation source 9, a signal distributor 10, a phase detector 11, an AD converter 12 and a data acquisition unit 13; wherein, the piezoelectric substrate 1 is a quartz piezoelectric substrate cut by rotating 42.75° around the Y direction and propagating 90° along the X direction. The input sensor 3 and the output sensor 4 adopt an electrode width control / unidirectional single-phase transducer (EWC / SPUDT) structure, using aluminum interdigitated electrodes and aluminum reflective electrodes 32, and the electrode film thickness is 1% to 1.5%λ.

[0081] Among them, the SU-8 thin film serves as the acoustic waveguide layer 2 and is used to protect the input sensor 3 and the output sensor 4. By using the waveguide layer to couple the elastic wave excited in the substrate to the surface wave waveguide layer, the attenuation of the acoustic wave can be reduced. The SU-8 thin film is extremely sensitive to surface load, which can effectively improve the detection sensitivity of the sensor.

[0082] The SiO2 thin layer 5 is overlaid on the acoustic wave transmission path by photolithography. Its width H can be greater than the acoustic aperture, but cannot exceed the width of the overall device dicing. The lengths L1 and L2 are 1% to 1.5%λ. The distance L between the SiO2 thin layer and the input and output transducers is 10λ.

[0083] The bottom of the PDMS water storage chamber 6 employs a microfluidic chip, located between the input transducer 3 and the output transducer 4. The microfluidic chip is designed using polydimethylsiloxane (PDMS) material and is bonded to a SiO2 thin layer 5 through plasma treatment. A chip encapsulation barrier is set around it, and the area above the barrier facilitates water storage and sensor encapsulation, ensuring no leakage after water is loaded. Its width along the x-direction is set to λ or an integer multiple of λ, and its width along the y-direction does not exceed the width of the scribe strip, where λ is the wavelength of the sound wave along the direction of sound wave propagation.

[0084] The permeable membrane 8 is connected to the outside world, allowing water molecules to pass through. Under certain temperature, humidity, and wind speed conditions, it can freeze in the PDMS water storage cavity. This can cause changes in the acoustic mode through waveguide effects, and the resulting response phase and amplitude can be used to achieve icing early warning. In addition, the increase in ice thickness will increase the mass load effect on SAW, thereby causing corresponding changes in phase and response amplitude. By processing the phase difference and amplitude difference, icing can be monitored.

[0085] The sensor employs a SU-8 / ST-90°X quartz LOFT acoustic waveguide structure. Since the LOFT wave icing sensor needs to be in contact with the liquid, and longitudinal or vertical shear waves will experience energy leakage during propagation in the liquid, while Rayleigh and Lamb waves will suffer severe attenuation, only horizontal shear waves can be utilized. LOFT waves are horizontal shear waves that can be absorbed by the piezoelectric waveguide layer, making them suitable for detecting different mass loads in water and ice.

[0086] A system based on Leff wave icing sensors, the system comprising:

[0087] The signal excitation source 9 is used to output a specific signal source;

[0088] The signal distributor 10 is used to input the specific signal source to the icing sensor based on the Leff wave.

[0089] The phase detector 11 is used to receive the electrical signal transmitted by the icing sensor of the Lefu wave; it is also used to perform phase detection between the specific signal source and the received electrical signal to obtain the phase difference and amplitude difference.

[0090] AD converter 12 is used to convert phase difference and amplitude difference into voltage signal;

[0091] Data acquisition unit 13 is used to acquire and record the voltage signal;

[0092] A display terminal is used to display the recorded voltage signal and the corresponding icing thickness.

[0093] The specific working process of the icing sensor system displayed on the terminal is as follows:

[0094] Step 1) Output a specific signal source through the signal excitation source 9;

[0095] Step 2) The specific signal source is input to the input transducer 3 through the signal distributor 10;

[0096] Step 3) The input transducer 3 converts the input specific signal source into a surface acoustic wave signal, which propagates on the surface of the piezoelectric substrate 1 to excite elastic waves within the piezoelectric substrate 1; the elastic waves within the piezoelectric substrate 1 are coupled to the waveguide layer 2 to excite Leff waves to propagate in the waveguide layer 2.

[0097] Step 4) Receive the Leff wave signal through the output transducer 4 and convert the Leff wave signal into an electrical signal;

[0098] Step 5) After a certain time delay, the output transducer 4 inputs the electrical signal to the phase detector 11; the magnitude of the delay time t depends on the phase velocity v of the surface acoustic wave of the substrate material and the distance L between the input transducer 3 and the output transducer 4, i.e. t = L / v;

[0099] Step 6) The phase detector 11 is used to compare the specific signal source with the electrical signal received from the output transducer 4 to obtain the phase difference and amplitude difference.

[0100] Step 7) The phase difference and amplitude difference are converted into voltage signals by the AD converter 12; the voltage signals are acquired and recorded by the data acquisition unit 13, and finally the voltage signal to be detected, i.e. the icing signal, and the corresponding icing thickness are displayed by the display terminal, where the thickness value h = kφ, k is a constant whose value is related to the selected piezoelectric substrate and waveguide layer material, and φ is the electrical signal output by the data acquisition unit 13.

[0101] like Figure 1 The icing sensor based on the Leff wave shown operates at a frequency of 200MHz. The input transducer 3 has a length of 198λ and is divided into four groups. Each group includes comb teeth and grounding dummy fingers 33 distributed between the comb teeth. The comb teeth have a length of 18λ, and the grounding dummy fingers have a length of 42λ. The output transducer 4 has a length of 60λ. The center distance between the input transducer 3 and the output transducer 4 is 160λ. A SU-8 thin film with a thickness of 1-3%λ is covered on the surfaces of the piezoelectric substrate 1, the input transducer 3, and the output transducer 4. A SiO2 protective layer is overlaid on the propagation path between the input transducer 3 and the output transducer 4 to facilitate bonding to the PDMS water storage cavity 6. The SiO2 protective layer has a width H of 4mm and lengths L1 and L2 of 0.1mm. The length, width, and height of the PDMS water storage cavity 6 are 3.5mm, 4mm, and 5mm, respectively. Thus, a novel icing sensor based on surface acoustic waves was obtained, and the area of ​​the prepared sample was 12mm × 5mm.

[0102] like Figure 1 The icing sensor based on a surface acoustic wave oscillator shown has an input transducer 3 with a comb-like structure. This means that a portion of the interdigitated fingers of the input transducer 3 is periodically removed, dividing it into several groups (ranging from 2 to 5 groups) called comb teeth. Each interdigitated finger pair 14 consists of two electrodes with a width of 1 / 8λ. The electrode width of the interdigitated finger pair is 1 / 8λ, and the edge spacing between the electrodes is 1 / 8λ. The width of the reflecting electrode is 1 / 4λ, and the distance between the reflecting electrode and the edge of the interdigitated finger pair is 3 / 16λ. The spaces between the comb teeth are filled with dummy finger electrodes 33, each with a width of 1 / 8λ and one end grounded. Here, λ is the wavelength along the direction of sound wave propagation, λ = v / f, v is the propagation speed of the surface acoustic wave on the piezoelectric substrate, and f is the oscillation frequency of the sensor.

[0103] The comb-like structure is mainly used to ensure that the surface acoustic wave device has only one phase period in the passband, thereby reducing device loss and achieving a single oscillation frequency to improve the stability of the corresponding circuit.

[0104] like Figure 2 As shown, the input transducer 3 consists of interdigital pairs 14 and reflective electrodes 15 distributed between the interdigital pairs. Each interdigital pair 14 comprises two electrodes with a width of 1 / 8λ, the electrode width of which is 1 / 8λ, and the edge spacing between the electrodes is 1 / 8λ. The reflective electrode has a width of 1 / 4λ, and the distance between the reflective electrode and the edge of the interdigital pair is 3 / 16λ. The spaces between the comb teeth are filled with dummy finger electrodes 33, each with a width of 1 / 8λ and one end grounded. Considering that the preferred embodiment of the icing sensor based on a surface acoustic wave oscillator provides an icing sensor using a quartz piezoelectric substrate cut by rotating 42.75° around the Y direction and propagating 90° along the X direction, all electrodes of the input transducer 3 are aluminum electrodes.

[0105] from Figure 3 As can be seen from the cross-sectional view of the icing sensor device involved in the embodiment of the present invention, it consists of a piezoelectric substrate 1, an input transducer 3 and an output transducer 4 deposited on the piezoelectric substrate, an SU-8 waveguide layer 2 deposited on the piezoelectric crystal 1, the input transducer 3 and the output transducer 4, a SiO2 protective layer overlaid on the SU-8 waveguide layer 2, a PDMS water storage cavity 6 bonded to the SiO2 protective layer 5, a metal encapsulation shell 7, and a water-permeable membrane 8.

[0106] As shown in Figure 4, the SiO2 protective layer of the icing sensor device involved in the embodiment of the present invention is shown in the top view and the cross-sectional view of the microfluidic chip and the water-permeable membrane. In Figure 4(a), the SiO2 thin layer is etched on the acoustic wave transmission path by photolithography. Its width H is greater than the acoustic aperture, but does not exceed the width of the overall device dicing. The lengths L1 and L2 are 1% to 1.5%λ, and the distance L from the input and output transducers is 10λ. In Figure 4(b), the microfluidic chip is designed with polydimethylsiloxane (PDMS) material. The PDMS water storage chamber 6 is bonded to the sensor through plasma treatment to achieve water storage. This can realize the encapsulation of the sensor device and ensure that no leakage occurs after water is loaded. The entire sensor device is metal-encapsulated by a metal encapsulation shell, and an opening is made at the top of the metal encapsulation shell. A water-permeable membrane with permeable evaporation separation properties with a pore size that can pass through small water molecules is covered, such as graphene oxide gas-barrier water-permeable membrane, polyvinyl alcohol (PVA) chitosan blend composite membrane (CS / PSF), etc.

[0107] The icing sensor based on Leff wave provided in this invention uses quartz as a piezoelectric substrate and SU-8 thin layer as an acoustic waveguide layer. A silicon-containing thin layer made of SiO2 is bonded to a PDMS water storage cavity with a microfluidic chip to prevent inaccurate icing monitoring, electrode short circuits, or damage to the icing sensor caused by water leakage. It utilizes the mass loading effect caused by ice deposition and changes in acoustic modes, combined with a phase detection circuit, to achieve real-time monitoring of icing and ice thickness. It has the advantages of high sealing, small size, high detection sensitivity, fast response speed, and low cost.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An icing sensor based on Lepton waves, comprising: The device comprises a piezoelectric substrate (1), a waveguide layer (2), an input transducer (3) and an output transducer (4), a metal encapsulation shell (7) and a water-permeable membrane (8), characterized in that the icing sensor based on the Leff wave further includes: a silicon compound protective layer (5), a PDMS microfluidic chip and a chip encapsulation enclosure; wherein, The silicon-containing compound protective layer (5) is engraved on top of the waveguide layer (2) and is located between the input transducer (3) and the output transducer (4); the silicon-containing compound protective layer (5) is rectangular and has an opening in the middle; The PDMS microfluidic chip is bonded to the silicon-containing compound protective layer (5) at its four edges; and the PDMS microfluidic chip is encapsulated using the chip encapsulation barrier; the PDMS microfluidic chip and the chip encapsulation barrier together form a PDMS water storage cavity (6); wherein, The chip packaging enclosure is a rectangular frame composed of vertical partitions. The lower edge of the chip packaging enclosure is bonded to the waveguide layer (2), and the upper edge of the chip packaging enclosure is connected to the packaging cap of the metal packaging shell (7). The metal encapsulation tube (7) has an opening at the corresponding position of the PDMS water storage cavity (6); the water-permeable membrane (8) is disposed at the opening of the metal encapsulation tube (7); The piezoelectric substrate (1) is cut by rotating 42.75° around the Y direction and propagating 90° along the X direction; the material of the piezoelectric substrate (1) is: 36°YXLiTaO3, 41°YXLiTaO3, 64°YXLiTaO3 or ST-90°X quartz crystal; The waveguide layer (2) is protected by SU-8, PMMA or SiO2; the thickness of the waveguide layer (2) is 1-3%λ; where λ is the wavelength of the sound wave along the direction of sound wave propagation, λ=v / f; where v is the propagation speed of the surface acoustic wave on the piezoelectric substrate (1), and f is the operating frequency of the icing sensor device based on the Leff wave, which is in the same frequency as the signal excitation source (9); The input transducer (3) and output transducer (4) both adopt the EWC / SPUDT structure to reduce the insertion loss of the icing sensor based on the Röp wave, reduce the detection limit of the icing sensor based on the Röp wave, and provide stability. The EWC / SPUDT structure includes: several interdigital pairs (31) and several reflective electrodes (32). Each interdigital pair includes two interdigital electrodes with a width of 1 / 8λ and a spacing of 1 / 8λ between them. The reflective electrode has a width of 1 / 4λ. The reflective electrode (32) and the interdigital electrode have a thickness of 1%λ to 1.5%λ. The distance between the reflective electrode (32) and the edge of its corresponding interdigital pair (31) is 3 / 16λ. The materials of the interdigital electrode and the reflective electrode (32) include: gold, aluminum, or a gold-aluminum alloy. The input transducer (3) also adopts a comb-like structure; the input transducer (3) is formed by periodically removing part of the interdigital electrodes to form a comb-like structure; the comb-like structure includes several sets of comb tooth structure units; the comb teeth are filled with a pseudo-finger electrode (33) with a width of 1 / 8λ and one end grounded, where λ is the wavelength of the sound wave along the direction of sound wave propagation, λ=v / f; where v is the propagation speed of the surface acoustic wave on the piezoelectric substrate (1), and f is the operating frequency of the icing sensor device based on the Leff wave, which is in the same frequency as the signal excitation source (9).

2. The icing sensor based on Lepton waves according to claim 1, characterized in that, The icing sensor based on Lep wave includes: The input transducer (3) and the output transducer (4) are deposited on the piezoelectric substrate (1); The waveguide layer (2) is deposited on the piezoelectric substrate (1), the input transducer (3) and the output transducer (4); The metal encapsulation shell (7) is used to encapsulate the surface acoustic wave device; The surface acoustic wave device includes: the piezoelectric substrate (1), the waveguide layer (2), the input transducer (3), the output transducer (4), the silicon compound protective layer (5), and the PDMS water storage cavity (6). The metal encapsulation tube (7) has an encapsulation cap on top.

3. The icing sensor based on Lepton waves according to claim 1, characterized in that, The silicon-containing compound protective layer (5) is rectangular, with a width H along the Y direction greater than the acoustic aperture and less than the width of the piezoelectric substrate (1); the distances from the outer edges of the silicon-containing compound protective layer (5) to the input transducer (3) and the output transducer (4) are 10λ respectively; a rectangular opening is provided in the center of the silicon-containing compound protective layer (5); the length from the edge of the rectangular opening to the edge of the silicon-containing compound protective layer (5) is 1%~1.5%λ; the thickness of the silicon-containing compound protective layer (5) is 3%λ~50%λ; where λ is the wavelength of the acoustic wave along the direction of acoustic wave propagation, λ=v / f; where v is the propagation speed of the surface acoustic wave on the piezoelectric substrate (1), and f is the operating frequency of the icing sensor device based on the Leff wave, which is in the same frequency as the signal excitation source (9).

4. The icing sensor based on Lepton waves according to claim 1, characterized in that, The silicon-containing compound protective layer (5) is overlaid on the waveguide layer (2) by photolithography; the silicon-containing compound protective layer (5) is physically reversibly bonded to the PDMS microfluidic chip of the PDMS water storage cavity (6) by Si-Si or Si-O bonds, or irreversible bonding is achieved by exposing the piezoelectric substrate (1), the waveguide layer (2), the silicon-containing compound protective layer (5) and the PDMS microfluidic chip of the PDMS water storage cavity (6) to oxygen plasma and performing oxygen plasma bonding treatment on the silicon-containing compound protective layer (5) and the PDMS microfluidic chip of the PDMS water storage cavity (6); The materials of the silicon compound protective layer (5) include: SiO2, SiC or SiN, and the materials of the silicon compound protective layer (5) also include: doped SiO2, SiC or SiN.

5. An icing sensor based on Leff wave according to claim 1, characterized in that, The width of the PDMS water storage cavity (6) along the x-direction is set to λ or an integer multiple of λ, and the width along the y-direction is set to be less than the width of the piezoelectric substrate (1); where λ is the wavelength of the sound wave along the direction of sound wave propagation, λ=v / f; where v is the propagation speed of the surface acoustic wave on the piezoelectric substrate (1), and f is the operating frequency of the icing sensor device based on the Leff wave, which is in the same frequency as the signal excitation source (9).

6. The icing sensor based on Lepton waves according to claim 1, characterized in that, The permeable membrane (8) is a graphene oxide gas-barrier permeable membrane or a polyvinyl alcohol chitosan blend composite permeable membrane.

7. A system for an icing sensor based on a Leff wave, implemented based on the icing sensor based on a Leff wave as described in any one of claims 1-6, characterized in that, The system includes: Signal excitation source (9) is used to output a specific signal source; A signal distributor (10) is used to input the specific signal source to the icing sensor device based on the Lep wave; The phase detector (11) is used to receive the electrical signal transmitted by the icing sensor of the Lefu wave; it is also used to perform phase detection between the specific signal source and the received electrical signal to obtain the phase difference and amplitude difference. An AD converter (12) is used to convert phase difference and amplitude difference into voltage signals; Data acquisition unit (13) is used to acquire and record the voltage signal; A display terminal is used to display the recorded voltage signal and the corresponding icing thickness.

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