Resonant Surface Acoustic Wave Wireless Passive Temperature / Humidity Sensor

Abstract

The present invention discloses a resonant surface acoustic wave wireless passive temperature / humidity sensor, which is integrated with a temperature sensor and a humidity sensor in parallel and coplanar, including a composite piezoelectric substrate layer, an interdigital transducer, a reflection grating array, and a surface piezoelectric waveguide layer. The reflection grating array forms a resonant cavity, and the temperature sensor and the humidity sensor have the same resonator structure and surface piezoelectric waveguide layer structure. A nano-humidity sensitive material is integrated above the surface piezoelectric waveguide layer of the humidity sensor. The present invention has been widely used in many fields because the surface acoustic wave passive wireless sensor has the advantages of non-contact, no power supply, anti-interference, good confidentiality, and low cost. By using temperature / humidity sensor arrays with different working frequency bands, the sensor array does not need to be connected by wires, can be distributed in different work locations, and is not restricted in application. It is particularly suitable for some occasions with complex and harsh application environments.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental parameter detection, and in particular relates to a high-precision sensor capable of detecting temperature and humidity. Background Art

[0002] Temperature and humidity are the two most closely related physical quantities that affect people's daily lives in the daily environment. They are also important physical quantities that need to be measured and controlled in scientific experiments and production activities. Temperature / humidity sensors are the most widely used sensors in daily life and industrial production. They can be applied to industrial and agricultural production, logistics transportation and management, health care, hospital drug storage and supervision, food quality monitoring, building structure quality monitoring and many other occasions. Take the storage management of drugs as an example. The drug storage conditions required by GSP certification must have classified storage of drugs and warehouses that meet the requirements for drug storage. The temperature of the normal temperature warehouse is 0-30℃, the temperature of the cool warehouse is not higher than 20℃, and the temperature of the cold storage is 2-10℃; the relative humidity of each warehouse should be maintained between 45 and 75%. When storing drugs, the storage temperature and humidity of the warehouse should be controlled according to the changes in seasons and climate, so as to ensure the quality of drug storage and follow the principles of efficiency, economy, convenience and safety.

[0003] At present, most temperature / humidity sensors used in industrial and agricultural production are sensors that combine thermistors and humidity-sensitive capacitors, which usually require wiring connections to achieve signal transmission and power supply. For temperature / humidity monitoring in closed and narrow spaces, the use of such sensors brings many inconveniences to cable configuration and maintenance and installation. For this reason, it is of great value and significance to develop a small, wireless passive temperature / humidity sensor that does not require the use of cables and power. Currently known wireless passive temperature / humidity sensors mainly include the following types:

[0004] MK Jain et al. developed a passive wireless temperature and humidity sensor based on the magnetoacoustic principle [Jain MK, Schmidt S, Ong KG, et al. Magnetoacoustic remote query temperature and humidity sensors. Smart Materials and Structures, 2000, 9 (4): 502-510.]. The magnetoacoustic sensor resonant frequency changes due to the change of Young's modulus of the magnetoelastic film with temperature and mass load (humidity is characterized by the amount of water molecules adsorbed by the aluminum oxide film). This sensor has the disadvantages of low sensitivity and high system cost.

[0005] CN201810399536.3 discloses a surface acoustic wave (SAW) temperature / humidity sensor. The temperature / humidity sensor converts surface acoustic waves and electromagnetic waves through an interdigital transducer arranged on a delay line, and calculates the temperature and humidity through the propagation time difference of the surface acoustic wave on the delay line. The delay line type SAW sensor has the disadvantages of short wireless transmission distance and high system cost.

[0006] CN201710886337.0 discloses an inductive cantilever beam wireless passive humidity sensor. The sensor uses the deformation of the inductive cantilever beam caused by temperature and humidity to change the resonant frequency of the inductor-capacitor (LC) resonant circuit. The main disadvantage of the LC type resonant sensor is the short wireless sensing distance.

[0007] Therefore, the development of low-cost, high-sensitivity and long-distance wireless sensing temperature / humidity sensors is of great significance for monitoring the temperature / humidity of industrial and agricultural production and residents' living environment. Summary of the invention

[0008] Aiming at the problem that the wireless passive temperature / humidity sensor in the prior art has short wireless transmission distance or low detection sensitivity, the present invention provides a resonant surface acoustic wave wireless passive temperature / humidity sensor, which has high sensitivity, long transmission distance and can measure temperature and humidity simultaneously.

[0009] The present invention is achieved through the following technical solutions:

[0010] The resonant surface acoustic wave wireless passive temperature / humidity sensor is characterized in that the system includes a temperature / humidity sensor, which is a temperature sensor and a humidity sensor integrated in parallel and coplanar, including a composite piezoelectric substrate layer, an interdigital transducer arranged on the composite piezoelectric substrate layer, a reflection grating array with equal spacing symmetrically distributed on the left and right sides of the interdigital transducer, and a surface piezoelectric waveguide layer arranged above the interdigital transducer, the reflection grating array forms a resonant cavity, the temperature sensor and the humidity sensor have the same resonator structure and surface piezoelectric waveguide layer structure, and a nano-humidity-sensitive material is integrated above the surface piezoelectric waveguide layer of the humidity sensor.

[0011] Preferably, the composite piezoelectric substrate layer consists of an IDT piezoelectric layer with a thickness of 100 nm to 10 μm and a substrate piezoelectric layer with a thickness of 200 μm to 500 μm.

[0012] Preferably, the piezoelectric layer of the interdigital transducer is made of any material selected from the group consisting of zinc oxide, aluminum nitride, lead zirconate titanate piezoelectric ceramics, and polyvinylidene fluoride, preferably zinc oxide; the base piezoelectric layer is made of any material selected from the group consisting of ST-90°x quartz, 37°y-90°x quartz, 41°yx-LiNbO3, and 36°yx-LiTaO3 that can generate shear acoustic surface waves.

[0013] Preferably, the IDT structure is a single metal IDT structure or a double metal IDT structure. For the double metal IDT structure, there is a gap between the two metal IDTs, and the reflective grating array is an open grating, a short grating and a mixed grating.

[0014] Preferably, a signal electrode and a ground electrode are provided at both ends of the IDT, the signal electrode is integrated with the antenna, and the ground electrode is connected to the ground wire and extends to surround the entire IDT structure and the reflective grid array.

[0015] Preferably, the surface piezoelectric waveguide layer has a thickness of 10-100 nm and is made of the same material as the piezoelectric layer of the interdigital transducer, or any one of silicon oxide, titanium oxide, silicon nitride and polymethyl methacrylate.

[0016] Preferably, the nano-humidity-sensitive material is prepared on the upper surface of the surface piezoelectric waveguide layer and is located above the interdigital transducer or above the interval between two interdigital transducers; the nano-humidity-sensitive material is a low-dimensional nanostructured material, and its structure is any one of nanodots, nanoparticles, nanowires, nanorods, nanocolumns, nanotubes, nanoflowers, nanosheets, nanobelts, nanosprings, and nanocages; the nano-humidity-sensitive material is selected from any one of inorganic oxides, polymer nano-humidity-sensitive materials, and carbon-based nanomaterials; the inorganic oxide is any one of Fe3O4, Fe2O3, Cr2O3, Al2O3, Sb2O3, TiO2, SnO2, ZnO, CuO, Cu2O, and ZrO2; the polymer nano-humidity-sensitive material is any one of polystyrene, polyimide, and silicone resin; the carbon-based nanomaterial is any one of fullerene, carbon nanotube, graphene, and graphene oxide.

[0017] Preferably, the sensor also includes a transceiver antenna, a conversion switch, a control unit, an excitation signal generator, a temperature / humidity reader, and a display unit. The transceiver antenna is controlled by the conversion switch to alternately transmit excitation electromagnetic signals and receive temperature / humidity sensing electromagnetic signals to the transceiver device. The frequency response bandwidth of the transceiver antenna covers the frequency response bandwidth of the temperature / humidity sensor; the excitation signal generator can generate multiple excitation electromagnetic signals with different center frequencies through the control unit; the temperature / humidity reader can process the received temperature / humidity sensing electromagnetic signals; and the display unit is used to display the measured temperature and humidity values.

[0018] The passive wireless sensor of the surface acoustic wave has been widely used in many fields because of its advantages of non-contact, no power supply, anti-interference, good confidentiality and low cost. By using temperature / humidity sensor arrays of different working frequency bands, the sensor array does not need lead connection, can be distributed in different working locations, and is not restricted in application. It is particularly suitable for some occasions with complex and harsh application environments, such as narrow spaces, rotating parts, high voltage and high electromagnetic field environments. The present invention proposes to use the IDT piezoelectric layer and the substrate piezoelectric layer to achieve a higher electromechanical coupling coefficient than a single piezoelectric substrate. Since the surface acoustic wave mode is the most sensitive working mode of all acoustic wave sensors. At the same time, the surface acoustic wave has the advantages of low propagation loss, low phase noise, low aging and low vibration sensitivity, and is particularly suitable for the application of surface acoustic wave temperature / humidity sensors. Therefore, the composite piezoelectric substrate of the present invention selects the substrate piezoelectric layer that can generate surface acoustic wave, so that the surface acoustic wave energy is concentrated in the surface piezoelectric waveguide layer for transmission. In order to reduce the scattering loss of surface acoustic waves caused by rough surface nano-humidity sensitive structural materials, the surface piezoelectric waveguide layer is designed to enhance the transmission of surface acoustic waves in the surface piezoelectric waveguide layer, thereby improving the interaction between surface acoustic waves and nano-humidity sensitive materials and the sensitivity of the sensor. The resonant surface acoustic wave wireless passive temperature / humidity sensor proposed by the present invention can simultaneously detect the temperature and humidity parameters of the environment. At the same time, the measured temperature parameters are also used to decouple the temperature-affected components in the humidity sensor. The composite piezoelectric surface acoustic wave wireless passive temperature / humidity sensor of the present invention is manufactured by MEMS micromachining method, and therefore has the advantages of integrated manufacturing, mass production, good consistency and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the structure of a ZnO / quartz composite piezoelectric surface acoustic wave wireless passive temperature / humidity sensor based on a single metal IDT structure according to Example 1 of the present invention;

[0020] Figure 2 for Figure 1 AA section view;

[0021] Figure 3 This is a manufacturing process flow chart of the ZnO / quartz composite piezoelectric surface acoustic wave wireless passive temperature / humidity sensor based on a single metal IDT structure of the present invention;

[0022] Figure 4 This is a schematic structural diagram of an AlN / 41°yx-LiNbO3 composite piezoelectric surface acoustic wave wireless passive temperature / humidity sensor based on a bimetallic IDT structure according to Example 2 of the present invention;

[0023] Figure 5 for Figure 4 AA section view;

[0024] Figure 6 This is a manufacturing process flow chart of the AlN / 41°yx-LiNbO3 composite piezoelectric surface acoustic wave wireless passive temperature / humidity sensor based on a bimetallic IDT structure of the present invention;

[0025] Figure 7 The present invention is a schematic diagram of a wireless transceiver device and working principle of a composite piezoelectric surface acoustic wave wireless passive temperature / humidity sensor.

[0026] In the figure: 1-1: base piezoelectric layer, 1-2: interdigital transducer piezoelectric layer, 1-3: interdigital transducer, 1-4: reflection grating array, 1-5: surface piezoelectric waveguide layer, 1-6: nano-humidity sensitive material, 1-7: signal electrode, 1-8: ground electrode, 2: transceiver antenna, 3: conversion switch, 4: control unit, 5: excitation signal generator, 6: temperature / humidity reader, 7: display unit. DETAILED DESCRIPTION

[0027] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, a detailed description is given below in conjunction with the accompanying drawings and specific embodiments.

[0028] The following embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

[0029] The resonant surface acoustic wave wireless passive temperature / humidity sensor of the present invention is a surface acoustic wave resonator, in which one or two metal interdigital transducers (IDTs) are prepared on a composite piezoelectric substrate, and a reflection grating array with equal spacing is symmetrically distributed on the left and right sides thereof to form a resonant cavity. The temperature sensor and the humidity sensor are integrated together in parallel and coplanar, and the two sensors have the same resonator structure and surface piezoelectric waveguide layer structure. Among them, a nano-humidity sensitive material is integrated on the surface piezoelectric waveguide layer of the humidity sensor. The composite piezoelectric substrate is composed of an IDT piezoelectric layer and a substrate piezoelectric layer, and the surface acoustic waves generated by the temperature sensor and the humidity sensor prepared by the composite piezoelectric substrate are surface acoustic shear waves. The piezoelectric waveguide layer is preferably made of the same material and structure as the IDT piezoelectric layer. The nano-humidity sensitive material is integrated on the surface piezoelectric waveguide layer and is located above the resonant cavity. The nano-humidity sensitive material has a large specific surface area and a hydrophilic surface, and has a high ability to adsorb water molecules in the air. The signal electrode of the temperature / humidity sensor can be integrated with an antenna to receive an excitation electromagnetic signal emitted by a remote wireless transceiver and to emit a temperature / humidity sensing electromagnetic signal. The temperature sensing electromagnetic signal is not only used for temperature measurement, but also used to decouple the temperature-affected component in the humidity sensing electromagnetic signal.

[0030] Furthermore, the composite piezoelectric substrate is composed of an IDT piezoelectric layer and a substrate piezoelectric layer. The IDT piezoelectric layer material can be zinc oxide (ZnO), aluminum nitride (AlN), lead zirconate titanate piezoelectric ceramics (PZT), polyvinylidene fluoride (PVDF), etc., preferably ZnO; the substrate piezoelectric layer material is a piezoelectric material that can generate surface acoustic shear waves, which can be ST-90°x quartz, 37°y-90°x quartz, 41°yx-LiNbO3, 36°yx-LiTaO3, etc. The thickness of the IDT piezoelectric layer material is 100nm~10μm; the thickness of the substrate piezoelectric layer is 200μm~500μm.

[0031] Furthermore, the metal IDT of the surface acoustic wave resonator is prepared on the IDT piezoelectric layer of the composite piezoelectric substrate. The surface acoustic wave resonator is divided into two types: a single metal IDT structure and a bimetallic IDT structure. For the bimetallic IDT structure, there is a spacing distance between the two metal IDTs. The metal IDT structure is symmetrically distributed with equally spaced reflective grating arrays on both sides, and the reflective grating array can be an open-circuit grating, a short-circuit grating, and a hybrid grating. There are signal electrodes and ground electrodes at both ends of the metal IDT. The signal electrode can be integrated with the antenna, and the ground electrode is connected to the ground wire and extends to surround the entire metal IDT structure and the reflective grating array.

[0032] Furthermore, the surface piezoelectric waveguide layer covers the surface of the surface acoustic wave resonator. In order to improve the quality factor of the surface acoustic wave resonator, the surface piezoelectric waveguide layer is preferably made of the same material as the IDT piezoelectric layer. The surface piezoelectric waveguide layer can also use a material different from the IDT piezoelectric layer, such as silicon oxide (SiO2), titanium oxide (TiO2), silicon nitride (Si x N y ), polymethyl methacrylate (PMMA), etc. The thickness of the surface piezoelectric waveguide layer is 10 to 100 nm.

[0033] Further, the nano-humidity-sensitive material is prepared on the upper surface of the surface piezoelectric waveguide layer and is located above the metal IDT or above the interval between two metal IDTs. The nano-humidity-sensitive material is a low-dimensional nanostructured material with a high ability to adsorb water molecules in the air. The low-dimensional nanostructure includes nanodots, nanoparticles, nanowires, nanorods (nanopillars), nanotubes, nanoflowers, nanosheets (nanobelts), nanosprings, nanocages, etc. The nano-humidity-sensitive material includes inorganic oxides (such as Fe3O4, Fe2O3, Cr2O3, Al2O3, Sb2O3, TiO2, SnO2, ZnO, CuO, Cu2O, ZrO2, etc.), polymer nano-humidity-sensitive materials (such as polystyrene, polyimide, silicone resin, etc.), carbon-based nanomaterials (such as fullerene, carbon nanotubes, graphene, graphene oxide, etc.), etc.

[0034] Furthermore, the operating frequency band of the resonant surface acoustic wave wireless passive temperature / humidity sensor can be changed by changing the size parameters of the metal IDT structure (such as the width and spacing of the metal fingers). A plurality of temperature sensors and humidity sensors with different operating frequency bands can form a wireless passive distributed sensing system.

[0035] Example 1

[0036] like Figure 1 and Figure 2 As shown, the temperature / humidity sensor is a ZnO / quartz composite piezoelectric surface acoustic wave wireless passive temperature / humidity sensor based on a single metal IDT structure, including using ST-90°x quartz as a base piezoelectric layer 1-1, ZnO as an interdigital transducer piezoelectric layer 1-2 and a surface piezoelectric waveguide layer 1-5, and ZnO nanorods as nano-humidity sensitive materials 1-6. The signal electrode of the temperature / humidity sensor can be integrated with an antenna to receive an excitation electromagnetic signal emitted by a remote wireless transceiver and to emit a temperature / humidity sensing electromagnetic signal. The temperature sensing electromagnetic signal is not only used for temperature measurement, but also used to decouple the temperature-affected component in the humidity sensing electromagnetic signal.

[0037] The specific manufacturing process steps are as follows: Figure 3 The process flow shown:

[0038] 1) Using single-polished ST-90°x quartz as the base piezoelectric layer 1-1;

[0039] 2) using magnetron sputtering technology, using Zn metal as a target, argon and oxygen as a mixed gas, a 300 nm thick c-axis oriented ZnO IDT piezoelectric layer 1-2 is deposited on ST-90°x quartz;

[0040] 3) Coat photoresist on the ZnO IDT piezoelectric layer and perform mask lithography. Form a mask structure by development. Deposit 300nm of aluminum metal using magnetron sputtering technology, and prepare metal IDT, reflective grid array, signal electrode and ground electrode by lift-off technology;

[0041] 4) using magnetron sputtering technology, using Zn metal as a target material, argon and oxygen as a mixed gas, depositing a 300 nm thick c-axis oriented ZnO surface piezoelectric waveguide layer 1-5 on the surface of the substrate prepared in the previous step;

[0042] 5) Prepare ZnO nano-pillar humidity-sensitive material on the ZnO surface piezoelectric waveguide layer by hydrothermal method. Place the substrate prepared in the previous step in a reaction kettle, pour in a mixed growth solution of 0.05 mol zinc nitrate, 0.05 mol hexamethylenetetramine, and 5% polyetherimide, and then keep it at a constant temperature of 95°C for 1 hour. After taking it out, wash the obtained ZnO nano-pillar nano-humidity-sensitive material 1-6 with deionized water.

[0043] Example 2

[0044] like Figure 4 and Figure 5 As shown, this embodiment is an AlN / 41°yx-LiNbO3 composite piezoelectric surface acoustic wave wireless passive temperature / humidity sensor based on a bimetallic interdigital transducer structure, including using 41°yx-LiNbO3 as a base piezoelectric layer 1-1, AlN as an interdigital transducer piezoelectric layer 1-2 and a surface piezoelectric waveguide layer 1-5, and graphene oxide as a nano-humidity sensitive material 1-6.

[0045] The specific manufacturing process steps are as follows: Figure 6 The process flow shown:

[0046] 1) Using single-throw 41°yx-LiNbO3 as the base piezoelectric layer 1-1;

[0047] 2) using magnetron sputtering technology, using Al metal as a target, argon and nitrogen as a mixed gas, a 50nm AlN buffer layer and a 250nm thick c-axis oriented AlN interdigital transducer piezoelectric layer 1-2 are deposited on 41°yx-LiNbO3;

[0048] 3) Coat photoresist on the AlN IDT piezoelectric layer and perform mask lithography. Form a mask structure by development. Deposit 300nm of aluminum metal using magnetron sputtering technology, and prepare metal IDT, reflective grid array, signal electrode and ground electrode through lift-off technology;

[0049] 4) using magnetron sputtering technology, using Al metal as a target material and argon and nitrogen as a mixed gas, a 300 nm thick c-axis oriented AlN surface piezoelectric waveguide layer is deposited on the surface of the substrate prepared in the previous step;

[0050] 5) Prepare graphene oxide on the piezoelectric waveguide layer on the AlN surface. Graphene oxide powder is mixed with ultrapure water or an organic liquid (such as ethanol, dimethylformamide, tetrahydrofuran, etc.) at a concentration of 0.1 mg / ml, and a graphene oxide dispersion is formed by vigorous stirring by ultrasound or high shear. The graphene oxide dispersion is then dripped onto the piezoelectric waveguide layer on the AlN surface and located in the area between the two metal IDTs. The device is kept at room temperature until the liquid evaporates, thereby forming a graphene oxide nano-humidity-sensitive material on the piezoelectric waveguide layer on the AlN surface.

[0051] Example 3

[0052] like Figure 7As shown, the wireless transceiver device and working principle diagram of the composite piezoelectric surface acoustic wave wireless passive temperature / humidity sensor of the present invention. The device includes a transceiver antenna, a conversion switch, a control unit, an excitation signal generator, a temperature / humidity reader, and a display unit. The excitation signal generator can alternately generate excitation electromagnetic signals with frequencies of f1 and f2 through the control unit, and transmit them through the transceiver antenna. The humidity sensor and the temperature sensor can receive the excitation electromagnetic signal and transmit the sensing electromagnetic signals f1+·f1 and f2+·f2 through their respective antennas. The conversion switch in the wireless transceiver device can realize the conversion between signal transmission and signal reception. The sensing electromagnetic signal received by the transceiver antenna is transmitted to the temperature / humidity reader for data processing. The temperature sensing electromagnetic signal is not only used for temperature measurement, but also used to decouple the temperature-affected component in the humidity sensing electromagnetic signal. The ambient temperature and humidity parameters finally obtained are digitally presented in the display unit.

Claims

1. Resonant surface acoustic wave wireless passive temperature / humidity sensor, characterized in that The temperature / humidity sensor is a temperature sensor and a humidity sensor integrated in parallel and coplanarly, comprising a composite piezoelectric substrate layer, an interdigital transducer (1-3) arranged on the composite piezoelectric substrate layer, a reflection grating array (1-4) symmetrically distributed on the left and right sides of the interdigital transducer (1-3) with equal spacing, and a surface piezoelectric waveguide layer (1-5) arranged above the interdigital transducer (1-3), wherein the reflection grating array (1-4) forms a resonant cavity, and the composite piezoelectric substrate layer is composed of an interdigital transducer piezoelectric layer (1-2) with a thickness of 100 nm to 10 mm and a surface piezoelectric waveguide layer (1-5) with a thickness of 200 nm to 30 mm. The invention relates to a temperature sensor and a humidity sensor, wherein the temperature sensor and the humidity sensor are composed of a base piezoelectric layer (1-1) with a thickness of 500 mm; the piezoelectric layer (1-2) of the interdigital transducer is made of any material selected from zinc oxide, aluminum nitride, lead zirconate titanate piezoelectric ceramics, and polyvinylidene fluoride; the base piezoelectric layer (1-1) is made of any material selected from ST-90°x quartz, 37°y-90°x quartz, 41°yx-LiNbO3, and 36°yx-LiTaO3 capable of generating surface acoustic shear waves; the temperature sensor and the humidity sensor have the same resonator structure and surface piezoelectric waveguide layer structure; a nano-humidity sensitive material (1-6) is integrated above the surface piezoelectric waveguide layer of the humidity sensor; the surface piezoelectric waveguide layer (1-5) has a thickness of 10-100 nm and is made of the same material as the piezoelectric layer of the interdigital transducer, or is made of any one of silicon oxide, titanium oxide, silicon nitride, and polymethyl methacrylate.

2. The resonant surface acoustic wave wireless passive temperature / humidity sensor according to claim 1, characterized in that The interdigital transducer (1-3) structure is a single metal interdigital transducer structure or a double metal interdigital transducer structure. For the double metal interdigital transducer structure, there is a gap between the two metal interdigital transducers. The reflection grid array (1-4) is an open grid, a short grid and a mixed grid.

3. The resonant surface acoustic wave wireless passive temperature / humidity sensor according to claim 1, characterized in that A signal electrode (1-7) and a ground electrode (1-8) are provided at both ends of the interdigital transducer (1-3); the signal electrode (1-7) is integrated with the antenna; the ground electrode (1-8) is connected to a ground wire and extends to surround the entire interdigital transducer structure and the reflection grid array.

4. The resonant surface acoustic wave wireless passive temperature / humidity sensor according to claim 1, characterized in that The nano-humidity-sensitive material (1-6) is prepared on the upper surface of the surface piezoelectric waveguide layer (1-5) and is located above the interdigital transducer (1-3) or above the gap between two interdigital transducers; the nano-humidity-sensitive material (1-6) is a low-dimensional nanostructured material, and its structure is any one of nanodots, nanoparticles, nanowires, nanorods, nanopillars, nanotubes, nanoflowers, nanosheets, nanobelts, nanosprings, and nanocages; the nano-humidity-sensitive material (1-6) is selected from any one of inorganic oxides, polymer nano-humidity-sensitive materials, and carbon-based nano-materials; the inorganic oxide is any one of Fe3O4, Fe2O3, Cr2O3, Al2O3, Sb2O3, TiO2, SnO2, ZnO, CuO, Cu2O, and ZrO2; the polymer nano-humidity-sensitive material is any one of polystyrene, polyimide, and silicone resin; the carbon-based nano-material is any one of fullerene, carbon nanotube, graphene, and graphene oxide.

5. The resonant surface acoustic wave wireless passive temperature / humidity sensor according to claim 1, characterized in that The sensor further comprises a transceiver antenna (2), a conversion switch (3), a control unit (4), an excitation signal generator (5), a temperature / humidity reader (6), and a display unit (7). The transceiver antenna (2) is controlled by the conversion switch (3) to alternately transmit an excitation electromagnetic signal and receive a temperature / humidity sensing electromagnetic signal to the transceiver device. The frequency response bandwidth of the transceiver antenna (2) covers the frequency response bandwidth of the temperature / humidity sensor. The excitation signal generator (5) can generate a plurality of excitation electromagnetic signals with different center frequencies through the control unit (4). The temperature / humidity reader (6) can process the received temperature / humidity sensing electromagnetic signal. The display unit (7) is used to display the measured temperature and humidity values.

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