Passive and chipless RFID multi-dimensional sensor, and preparation method and application thereof

Abstract

The application discloses a kind of passive chipless RFID multidimensional sensors and preparation method and application thereof, the preparation method of passive chipless RFID multidimensional sensor, comprising the following steps, S1: preparation passive chipless RFID antenna;S2: preparation humidity-sensitive material, photosensitive material and gas-sensitive material;S3: the humidity-sensitive material, photosensitive material and gas-sensitive material prepared in step S2 are respectively attached to the corresponding area of RFID antenna prepared in step S1, to obtain passive chipless RFID multidimensional sensor;S4: corresponding parameter of passive chipless RFID multidimensional sensor is measured and optimized.The application utilizes inkjet printing technology to obtain passive chipless RFID multidimensional sensor with ZnO / RGO humidity-sensitive layer, TiO2 / RGO light-sensitive layer and MoS2 / RGO gas-sensitive layer on the surface, which is implanted on food packaging, and data statistics can be realized through information sensing, without the need for manual scanning one by one, greatly saving manpower and resources.

Description

Technical Field

[0001] This invention relates to the field of food safety testing technology, and in particular to a passive, chipless RFID multidimensional sensor, its preparation method, and its application. Background Technology

[0002] Traditional food packaging barcodes are easily damaged and become unreadable after damage. Furthermore, barcodes can only identify the manufacturer and the product, not individual items, lacking traceability information about the food's origin and failing to verify the authenticity of the product. This exposes consumers to the risk of foodborne illnesses. Therefore, developing passive, chipless RFID sensor technology to replace barcodes in food packaging is essential. Summary of the Invention

[0003] To address the aforementioned problems, this invention aims to provide a passive, chipless RFID multidimensional sensor, its fabrication method, and its application. The invention utilizes inkjet printing technology to fabricate a passive, chipless RFID multidimensional sensor with a ZnO / RGO humidity-sensitive layer, a TiO2 / RGO light-sensitive layer, and a MoS2 / RGO gas-sensitive layer on its surface. When embedded in food packaging, data can be collected through information sensing, eliminating the need for manual scanning and significantly saving manpower and resources.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for fabricating a passive, chip-free RFID multi-dimensional sensor, characterized by comprising the following steps:

[0006] S1: Fabrication of a passive, chipless RFID antenna;

[0007] S2: Preparation of humidity-sensitive materials, photosensitizing materials, and gas-sensitive materials;

[0008] S3: The humidity-sensitive material, photosensitive material and gas-sensitive material prepared in step S2 are respectively attached to the corresponding areas of the RFID antenna prepared in step S1 to obtain a passive chipless RFID multi-dimensional sensor.

[0009] S4: Measure and optimize the parameters of the passive chipless RFID multi-dimensional sensor.

[0010] Furthermore, the specific operation of step S1 includes the following steps:

[0011] S101: Simulation design of RFID antenna using HFSS software;

[0012] S102: Using a PET flexible board as a substrate and nano-silver as ink, the RFID antenna designed in step S101 is printed on the substrate using inkjet printing technology.

[0013] S103: Use a constant temperature drying oven to dry the RFID antenna printed on the substrate. The drying temperature is 60℃ and the drying time is 30min.

[0014] S104: Apply zinc oxide solution to the RFID antenna using a microsyringe, then repeat step S103:

[0015] S105: Under normal temperature conditions, use a spin coater to apply a mixed solution of PVA and graphene to the gaps of the RFID antenna and the surface of the substrate.

[0016] S106: The RFID antenna coated with a mixture of PVA and graphene is dried using a constant temperature drying oven to form a thin film on the surface of the RFID antenna, thus obtaining a passive chipless RFID antenna.

[0017] Furthermore, the preparation of the mixed solution of PVA and graphene described in step S105 includes the following steps:

[0018] S1051: Precisely weigh 3g of PVA powder;

[0019] S1052: Add 150mL of deionized water to a beaker, with the water temperature not exceeding 30℃;

[0020] S1053: Use a stirrer to stir the deionized water in the beaker, while slowly adding PVA powder into the beaker in multiple even portions.

[0021] S1054: Continue stirring for 15-30 minutes, then heat the PVA solution in the beaker to 85°C and keep it warm until the PVA powder is completely dissolved;

[0022] S1055: Weigh 20 mg of graphene oxide powder and add it to the PVA solution obtained in step S1054 and stir thoroughly.

[0023] S1056: The temperature of the mixed solution in step S1055 is reduced to the required temperature, and the solution is filtered through a filter screen to remove impurities, thereby obtaining a mixed solution of PVA and graphene.

[0024] Furthermore, the humidity-sensitive material mentioned in step S2 is a ZnO / RGO humidity-sensitive material, and the preparation of the ZnO / RGO humidity-sensitive material includes the following steps:

[0025] Step 1: Weigh 1.487g of Zn(NO3)6H2O solid powder and 2.16g of hexamethylenetetramine solid powder, dissolve them in 100mL of deionized water, and sonicate them in an ultrasonic machine until the precipitate just disappears to obtain the precursor solution.

[0026] Step 2: Transfer the precursor solution to a high-pressure reactor with a polytetrafluoroethylene liner, maintain a filling degree of 80%, react at 95°C for 5 hours, then allow it to cool naturally to room temperature, filter and collect the white precipitate.

[0027] Step 3: Rinse the white precipitate repeatedly with deionized water to remove excess adsorbed ions, and then dry it in a 90℃ oven to obtain nano ZnO powder;

[0028] Step 4: Prepare RGO solution.

[0029] Furthermore, the photosensitive material mentioned in step S2 is a TiO2 / RGO photosensitive material, and the preparation of the TiO2 / RGO photosensitive material includes the following steps:

[0030] Step 1: Weigh 5g of tetrabutyl titanate and add it to a dry beaker containing 1mL of diethanolamine. Add 20mL of anhydrous ethanol to the beaker and stir until a colorless and transparent sol is formed.

[0031] Step 2: Transfer the colorless and transparent sol to a hydrothermal reactor lined with polytetrafluoroethylene, place it in an oven, heat at 180°C for 4 hours, and then remove the hydrothermal reactor and allow it to cool naturally to room temperature.

[0032] Step 3: Remove the product from the beaker, wash it with double-distilled water and anhydrous ethanol until neutral, and then dry it at 80°C to obtain nano TiO2 powder;

[0033] Step 4: Prepare RGO solution.

[0034] Furthermore, the gas-sensitive material mentioned in step S2 is a MoS2 / RGO gas-sensitive material, and the preparation of the MoS2 / RGO gas-sensitive material includes the following steps:

[0035] Step 1: Weigh 0.3g of ammonium molybdate powder and 0.2g of thiourea powder, put them into 40mL of deionized water, place the resulting mixture on a magnetic stirrer and stir thoroughly until all the solutes are dissolved to obtain a transparent solution;

[0036] Step 2: Pour the transparent solution obtained in Step 1 into a 50 mL reaction vessel, place the reaction vessel in an oven, and react at 180 °C for 24 hours; after the reaction is completed, turn off the oven and allow the reaction vessel to cool naturally to room temperature. Wash the black precipitate obtained from the reaction three times each with anhydrous ethanol and deionized water to remove residual reactants and obtain the MoS2 product.

[0037] Step 3: Clean the MoS2 product obtained in Step 2 and dry it at 60°C for 12 hours to obtain pure black nano MoS2 powder.

[0038] Step 4: Prepare RGO solution.

[0039] Furthermore, the preparation of the RGO solution includes the following steps:

[0040] Step 1: Weigh 50 mg of graphene oxide (GO), disperse it in 10 mL of deionized water, and sonicate for 1 h to obtain a GO dispersion.

[0041] Step 2: Add 40 mL of anhydrous ethanol to the GO dispersion for dilution, and sonicate to obtain 50 mL of GO dispersion with a concentration of 1 mg / mL.

[0042] Step 3: Weigh 0.27g of glucose and add it to 5mL of deionized water to obtain a 0.3mol / L glucose solution;

[0043] Step 4: Place the GO dispersion obtained in Step 2 into a water bath at 60°C and stir magnetically. Slowly add the glucose solution obtained in Step 3, and continue heating and stirring. Terminate the reaction after 1 hour and cool to room temperature to obtain the reduced graphene oxide solution, i.e., RGO solution.

[0044] Furthermore, the specific operation of step S3 includes the following steps:

[0045] S301: Prepare nano ZnO powder, nano TiO2 powder and nano MoS2 powder obtained in step S2 into nano ZnO solution, nano TiO2 solution and nano MoS2 solution with concentrations of 10 mol / L, 6 mol / L and 3 mol / L respectively.

[0046] S302: Place the passive chipless RFID antenna prepared in step S1 on a spin coater, and successively drop 5 mL of nano ZnO solution and 10 μL of RGO solution onto the corresponding positions of the passive chipless RFID antenna, setting the rotation speed to 3000 r / min;

[0047] S303: After spin coating, place the passive chipless RFID antenna in a drying oven at 60℃ for 30 min to form a ZnO / RGO humidity-sensitive layer on the surface of the passive chipless RFID antenna.

[0048] S304: Repeat steps S302 and S303 to spin-coat nano TiO2 solution and RGO solution, and nano MoS2 solution and RGO solution on the surface of the passive chipless RFID antenna, respectively. After spin-coating, dry the antenna to form a passive chipless RFID multi-dimensional sensor with a ZnO / RGO humidity-sensitive layer, a TiO2 / RGO light-sensitive layer and a MoS2 / RGO gas-sensitive layer on the surface of the passive chipless RFID antenna.

[0049] Furthermore, a passive chipless RFID multidimensional sensor was prepared using a method for preparing a passive chipless RFID multidimensional sensor.

[0050] Furthermore, the passive chipless RFID multidimensional sensor prepared using a method for preparing a passive chipless RFID multidimensional sensor is applied in smart food packaging.

[0051] The beneficial effects of this invention are:

[0052] 1. The method for fabricating the passive chipless RFID multi-dimensional sensor in this invention first utilizes inkjet printing technology to design a passive chipless RFID antenna. Then, ZnO / RGO humidity-sensitive material, TiO2 / RGO photosensitive material, and MoS2 / RGO gas-sensitive material are spin-coated onto corresponding positions of the antenna, completing the integration of the multi-dimensional sensor and the passive chipless RFID antenna. The resulting passive chipless RFID multi-dimensional sensor can transmit the parameter changes of the three sensitive materials to a handheld reader via radio frequency technology. It features a large contact area of ​​the sensitive materials, a fast change rate of dielectric constant, and the ability to collect various environmental information. Compared with traditional RFID tag sensors, it not only eliminates the IC chip but also allows for the simultaneous acquisition of multiple sensing information.

[0053] 2. In this invention, the passive chipless RFID multidimensional sensor uses a PVA and graphene mixed solution for spin coating on the surface of the passive chipless RFID antenna, which can form a thin film on the surface of the passive chipless RFID antenna. This film can protect the placement of the three sensitive materials from falling off, and can also be tightly bonded to the antenna, thereby increasing the sensitivity coefficient and service life of the multidimensional sensor.

[0054] 3. The passive chipless RFID multi-dimensional sensor in this invention can be applied to smart food packaging. By embedding the passive chipless RFID multi-dimensional sensor on the food packaging, data statistics of the food packaging environment can be realized through information sensing, eliminating the need for manual scanning one by one. Moreover, the passive chipless RFID multi-dimensional sensor does not require a separate power supply, which greatly saves manpower and material resources and facilitates processing and subsequent promotion. Attached Figure Description

[0055] Figure 1 This is a flowchart illustrating the fabrication method of the passive, chipless RFID multidimensional sensor of the present invention.

[0056] Figure 2 This is a SEM image of the nano-ZnO powder prepared in this invention.

[0057] Figure 3 This is a SEM image of the nano-TiO2 powder prepared in this invention.

[0058] Figure 4 This is a SEM image of the nano-MoS2 powder prepared in this invention.

[0059] Figure 5 This is a schematic diagram of the passive chipless RFID multi-dimensional sensor of the present invention.

[0060] Figure 6 This describes the sensing mechanism of the humidity-sensitive material (ZnO / RGO) of the present invention.

[0061] Figure 7 This describes the sensing mechanism of the photosensitive material (TiO2 / RGO) of the present invention.

[0062] Figure 8 This describes the sensing mechanism of the gas-sensitive material (MoS2 / RGO) of the present invention.

[0063] Figure 9 This is the LC resonant equivalent circuit diagram of the passive chipless RFID multi-dimensional sensor of the present invention.

[0064] Figure 10 This is a schematic diagram showing the affixing position of the passive chipless RFID multi-dimensional sensor in food packaging according to the present invention. Detailed Implementation

[0065] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0066] Example 1:

[0067] A method for fabricating a passive, chip-free RFID multidimensional sensor, as shown in the attached figure. Figure 1 As shown, it includes the following steps:

[0068] S1: Fabrication of a passive, chipless RFID antenna;

[0069] Specifically, S101: The RFID antenna was simulated and designed using HFSS software; the final RFID antenna with a frequency band of 916MHz was designed.

[0070] S102: Using a PET flexible board as a substrate and nano-silver as ink, the RFID antenna designed in step S101 is printed on the substrate using inkjet printing technology; the printing is repeated 10 times to make the antenna thickness reach 100μm.

[0071] S103: Use a constant temperature drying oven to dry the RFID antenna printed on the substrate. The drying temperature is 60℃ and the drying time is 30min.

[0072] S104: Apply zinc oxide solution to the RFID antenna using a microsyringe, then repeat step S103:

[0073] S105: Under normal temperature conditions, use a spin coater (set the rotation speed to 3000 r / min) to apply a mixed solution of PVA and graphene to the gaps of the RFID antenna and the surface of the substrate;

[0074] The preparation of the mixed solution of PVA and graphene includes the following steps:

[0075] S1051: Precisely weigh 3g of PVA powder;

[0076] S1052: Add 150mL of deionized water to a beaker, with the water temperature not exceeding 30℃;

[0077] S1053: Use a stirrer to stir the deionized water in the beaker, while slowly adding PVA powder into the beaker in multiple even portions.

[0078] S1054: Continue stirring for 15-30 minutes, then heat the PVA solution in the beaker to 85°C and keep it warm until the PVA powder is completely dissolved;

[0079] S1055: Weigh 20 mg of graphene oxide powder and add it to the PVA solution obtained in step S1054 and stir thoroughly.

[0080] S1056: The temperature of the mixed solution in step S1055 is reduced to the required temperature, and the solution is filtered through a filter screen to remove impurities, thereby obtaining a mixed solution of PVA and graphene.

[0081] S106: The RFID antenna coated with a mixture of PVA and graphene is dried using a constant temperature drying oven to form a thin film on the surface of the RFID antenna, thus obtaining a passive chipless RFID antenna.

[0082] After the passive chipless RFID antenna is prepared, a vector network analyzer is used to collect and simulate experimental data of the antenna and to calibrate it. The specific calibration method adopts the existing calibration method, which will not be described in detail in this invention.

[0083] Furthermore, S2: Prepare humidity-sensitive materials, photosensitizing materials, and gas-sensitive materials;

[0084] Specifically, the humidity-sensitive material is a ZnO / RGO humidity-sensitive material, the photosensitive material is a TiO2 / RGO photosensitive material, and the gas-sensitive material is a MoS2 / RGO gas-sensitive material;

[0085] The preparation of the ZnO / RGO humidity-sensitive material includes the following steps.

[0086] Step 1: Weigh 1.487g of Zn(NO3)6H2O solid powder and 2.16g of hexamethylenetetramine solid powder, dissolve them in 100mL of deionized water, and sonicate them in an ultrasonic machine for 5 minutes until the precipitate just disappears (pH≈10) to obtain the precursor solution.

[0087] Step 2: Transfer the precursor solution to a high-pressure reactor with a polytetrafluoroethylene liner, maintain a filling degree of 80%, react at 95°C for 5 hours, then allow it to cool naturally to room temperature, filter and collect the white precipitate.

[0088] Step 3: Rinse the white precipitate repeatedly with deionized water to remove excess adsorbed ions, and then dry it in a 90℃ oven to obtain nano ZnO powder;

[0089] Step 4: Prepare RGO solution.

[0090] The preparation of the TiO2 / RGO photosensitive material includes the following steps.

[0091] Step 1: Weigh 5g of tetrabutyl titanate ((CH3CH2O)4Ti) and add it to a dry small beaker (100mL or 50mL) containing 1mL of diethanolamine. Add 20mL of anhydrous ethanol to the beaker, stir to dissolve the tetrabutyl titanate, and continue stirring for 1 hour until a colorless and transparent sol is formed.

[0092] Step 2: Transfer the colorless and transparent sol to a hydrothermal reactor lined with polytetrafluoroethylene, place it in an oven, heat at 180°C for 4 hours, and then remove the hydrothermal reactor and allow it to cool naturally to room temperature.

[0093] Step 3: Remove the product from the beaker, wash it with double-distilled water and anhydrous ethanol until neutral, and then dry it at 80°C to obtain nano TiO2 powder;

[0094] Step 4: Prepare RGO solution.

[0095] The preparation of the MoS2 / RGO gas-sensitive material includes the following steps.

[0096] Step 1: Weigh 0.3g of ammonium molybdate powder and 0.2g of thiourea powder, put them into 40mL of deionized water, place the resulting mixture on a magnetic stirrer and stir thoroughly until all the solutes are dissolved to obtain a transparent solution;

[0097] Step 2: Pour the transparent solution obtained in Step 1 into a 50 mL reaction vessel, place the reaction vessel in an oven, and react at 180 °C for 24 hours; after the reaction is completed, turn off the oven and allow the reaction vessel to cool naturally to room temperature. Wash the black precipitate obtained from the reaction three times each with anhydrous ethanol and deionized water to remove residual reactants and obtain the MoS2 product.

[0098] Step 3: Clean the MoS2 product obtained in Step 2 and dry it at 60°C for 12 hours to obtain pure black nano MoS2 powder.

[0099] Step 4: Prepare RGO solution.

[0100] The preparation of the RGO solution includes the following steps:

[0101] Step 1: Weigh 50 mg of graphene oxide (GO), disperse it in 10 mL of deionized water, and sonicate for 1 h to obtain a GO dispersion.

[0102] Step 2: Add 40 mL of anhydrous ethanol to the GO dispersion for dilution, and sonicate to obtain 50 mL of GO dispersion with a concentration of 1 mg / mL.

[0103] Step 3: Weigh 0.27g of glucose and add it to 5mL of deionized water to obtain a 0.3mol / L glucose solution;

[0104] Step 4: Place the GO dispersion obtained in step S1052 into a water bath at 60°C and stir magnetically. Slowly add the glucose solution obtained in step S1053, and continue heating and stirring. Terminate the reaction after 1 hour and cool to room temperature to obtain the reduced graphene oxide solution, i.e., RGO solution.

[0105] It should be noted that after preparing nano-ZnO powder, nano-TiO2 powder, and nano-MoS2 powder, their corresponding properties need to be characterized. Existing characterization methods were used, and will not be elaborated here. The characterization results are as follows:

[0106] SEM images of nano ZnO powder are attached. Figure 2 As shown, attached Figure 2 In the image, the left image is a SEM image of a layer of nano-ZnO, and the right image is a SEM image of a layer of nano-ZnO. It can be observed that the combination of ZnO and RGO is more compact, which is more conducive to the absorption of humidity and improves sensitivity.

[0107] SEM images of nano-TiO2 powder are attached. Figure 3 As shown, attached Figure 3 In the image, the left image is a SEM image of a layer of nano-TiO2, and the right image is a SEM image of a layer of nano-TiO2. It can be observed that the combination of TiO2 and RGO is more compact, and the TiO2 distribution area is larger, which is beneficial to improving the sensitivity to light.

[0108] SEM images of nano MoS2 powder are attached. Figure 4 As shown, attached Figure 4In the image, the left image is a SEM image of a layer of nano-MoS2, and the right image is a SEM image of a layer of nano-MoS2. It can be observed that MoS2 and RGO are more closely attached, and there are obvious gaps between the spherical MoS2, which is conducive to the coating of CO2 molecules.

[0109] Furthermore, S3: The humidity-sensitive material, photosensitizing material, and gas-sensitive material prepared in step S2 are respectively attached to the corresponding areas of the RFID antenna prepared in step S1 to obtain a passive chipless RFID multi-dimensional sensor.

[0110] Specifically, S301: The nano ZnO powder, nano TiO2 powder and nano MoS2 powder obtained in step S2 are respectively prepared into nano ZnO solution, nano TiO2 solution and nano MoS2 solution of 10 mol / L, 6 mol / L and 3 mol / L.

[0111] S302: Place the passive chipless RFID antenna prepared in step S1 on a spin coater, and successively drop 5 mL of nano ZnO solution and 10 μL of RGO solution onto the corresponding positions of the passive chipless RFID antenna, setting the rotation speed to 3000 r / min;

[0112] S303: After spin coating, place the passive chipless RFID antenna in a drying oven at 60℃ for 30 min to form a ZnO / RGO humidity-sensitive layer on the surface of the passive chipless RFID antenna.

[0113] S304: Repeat steps S302 and S303 to spin-coat nano TiO2 solution and RGO solution, and nano MoS2 solution and RGO solution on the surface of the passive chipless RFID antenna, respectively. After spin-coating, dry the antenna to form a passive chipless RFID multi-dimensional sensor with a ZnO / RGO humidity-sensitive layer, a TiO2 / RGO light-sensitive layer and a MoS2 / RGO gas-sensitive layer on the surface of the passive chipless RFID antenna.

[0114] A detailed structural diagram of the passive chipless RFID multidimensional sensor prepared using the method described in this invention is attached. Figure 5 As shown, in the appendix Figure 5 In the diagram, light yellow represents a flexible polyimide substrate, blue represents a tag antenna printed with nano-silver ink, yellow-green represents a thin film formed from a PVA / G mixed solution, light blue represents a ZnO / RGO humidity-sensitive material, light purple represents a TiO2 / RGO photosensitive material, and light green represents a MoS2 / RGO gas-sensitive material.

[0115] S4: Measure and optimize the parameters of the passive, chipless RFID multi-dimensional sensor using the S1 port of a vector network analyzer. Specifically, connect the fabricated antenna to the S11 port of the vector network analyzer, measure its actual frequency and amplitude curves, and compare them with the simulation results. If the error is too large, the antenna needs to be remade. Optimizing the antenna fabrication process involves repeatedly printing and measuring with calipers during the antenna fabrication process to find a precise antenna that meets the requirements.

[0116] The working principle of the passive chipless RFID multi-dimensional sensor in this invention is as follows:

[0117] The sensing mechanism of the humidity-sensitive material (ZnO / RGO) in this invention is as follows: Figure 6 As shown, when in a natural environment, water molecules in the air bind to reduced graphene oxide via hydrogen atoms. Under the influence of an electric field, water molecules adhere to defects in the ZnO nanosheets, thus triggering electrolytic conduction. This leads to an increase in the relative permittivity of the humidity-sensitive material, indicating fluctuations in the corresponding capacitance and resonant frequency of the proposed sensor.

[0118] The sensing mechanism of the light-sensitive material (TiO2 / RGO) in this invention is as follows: Figure 7 As shown, when TiO2 attached to the RFID antenna is exposed to light in a natural environment, electrons in the valence band gain energy from photons and jump to the conduction band, resulting in a photocatalytic reaction. This leads to an increase in the relative permittivity of the photosensitive material, indicating fluctuations in the corresponding capacitance and resonant frequency of the sensor.

[0119] The sensing mechanism of the gas-sensitive material (MoS2 / RGO) in this invention is as follows: Figure 8 As shown, when in a natural environment, CO2 in the air binds to reduced graphene oxide via carbon atoms. Under the influence of an electric field, CO2 molecules adhere to defects in the MoS2 nanosheets, thus triggering electrolytic conduction. This leads to an increase in the relative permittivity of the gas-sensitive material, indicating fluctuations in the corresponding capacitance and resonant frequency of the proposed sensor.

[0120] When a passive, chipless RFID sensor receives an electromagnetic wave signal, the tag antenna and the sensitive material are equivalent to a resistor and a capacitor, respectively. The induced current forms an inductance in the tag antenna, generating resonance and thus forming an LC resonant circuit. The equivalent circuit is as follows: Figure 9 As shown.

[0121] In the equivalent circuit, the distance between the capacitors is d, the dielectric constant of the sensitive material is ε_r, and the charge is Q with charge density σ.

[0122] According to Gauss's law

[0123] The electric field strength is

[0124] The voltage between the capacitors is

[0125] Constructing equivalent capacitance

[0126] The resonant frequency is equal to The change in L is very small. In the humidity sensor, humidity causes a change in the dielectric constant of the sensitive material, which in turn causes a change in f0.

[0127] Example 2:

[0128] Example 2 is a passive chipless RFID multidimensional sensor prepared using the preparation method of the passive chipless RFID multidimensional sensor in Example 1.

[0129] This passive, chipless RFID multidimensional sensor can be applied to smart food packaging, specifically by attaching it to the inside of the food packaging bag, as shown in the attached image. Figure 10 As shown, by attaching passive, chip-free RFID multi-dimensional sensors inside food packaging bags, three environmental parameters—humidity, light intensity, and CO2 concentration—can be collected and determined more quickly and accurately. This allows for the assessment of whether the food storage environment is suitable and whether the food is spoiled, among other food safety issues. When used in conjunction with a handheld reader, it enables sales staff to instantly monitor food storage conditions and determine whether food needs to be removed from shelves or replaced.

[0130] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a passive and chipless RFID multi-dimensional sensor, characterized in that, It comprises the following steps, S1: preparing a passive chipless RFID antenna; S2: preparing a humidity-sensitive material, a light-sensitive material and a gas-sensitive material; The humidity-sensitive material is a ZnO / RGO humidity-sensitive material; the light-sensitive material is a TiO2 / RGO light-sensitive material; and the gas-sensitive material is a MoS2 / RGO gas-sensitive material; S3: attaching the humidity-sensitive material, the light-sensitive material and the gas-sensitive material prepared in step S2 to the corresponding areas of the RFID antenna prepared in step S1 respectively to obtain a passive chipless RFID multi-dimensional sensor; S4: measuring the corresponding parameters of the passive chipless RFID multi-dimensional sensor and optimizing them; The specific operation of step S1 comprises the following steps, S101: simulating and designing the RFID antenna by using HFSS software; S102: using a PET flexible plate as a substrate and nano-silver as ink, the RFID antenna designed in step S101 is printed on the substrate by using inkjet printing technology; S103: drying the RFID antenna printed on the substrate by using a constant-temperature drying box, the drying temperature is 60 DEG C, and the drying time is 30 min; S104: using a microsyringe to apply zinc oxide solution to the RFID antenna, and then repeating step S103: S105: under normal temperature conditions, using a spin coater to apply a mixed solution of PVA and graphene to the gap of the RFID antenna and the surface of the substrate; S106: drying the RFID antenna covered with the mixed solution of PVA and graphene by using a constant-temperature drying box, forming a thin film on the surface of the RFID antenna to obtain a passive chipless RFID antenna; The specific operation of step S3 comprises the following steps, S301: preparing the nano-ZnO powder, the nano-TiO2 powder and the nano-MoS2 powder prepared in step S2 into 10 mol / L, 6 mol / L and 3 mol / L nano-ZnO solution, nano-TiO2 solution and nano-MoS2 solution respectively; S302: placing the passive chipless RFID antenna prepared in step S1 on a spin coater, and then dropping and coating 5 mL of nano-ZnO solution and 10 μL of RGO solution to the corresponding positions of the passive chipless RFID antenna, and setting the rotation number to 3000 r / min; S303: after the spin coating, placing the passive chipless RFID antenna into a drying oven for drying at 60 DEG C for 30 min, and forming a ZnO / RGO humidity-sensitive layer on the surface of the passive chipless RFID antenna; S304: repeating steps S302 and S303, respectively, to spin coat the nano-TiO2 solution and the RGO solution, and the nano-MoS2 solution and the RGO solution on the surface of the passive chipless RFID antenna, and then drying after the spin coating, and finally forming a passive chipless RFID multi-dimensional sensor with a ZnO / RGO humidity-sensitive layer, a TiO2 / RGO light-sensitive layer and a MoS2 / RGO gas-sensitive layer on the surface of the passive chipless RFID antenna.

2. The method of claim 1, wherein the method further comprises: The preparation of the mixed solution of PVA and graphene in step S105 comprises the following steps, S1051: precisely weigh 3g of PVA powder; S1052: add 150mL of deionized water to the beaker, the water temperature is not more than 30℃; S1053: use the stirrer to stir the deionized water in the beaker, while slowly adding the PVA powder into the beaker in multiple times; S1054: continue to stir for 15~30min, then warm the PVA solution in the beaker to 85℃, and keep warm until the PVA powder is completely dissolved; S1055: weigh 20mg of graphene oxide powder, and add it to the PVA solution obtained in step S1054 and stir well; S1056: reduce the temperature of the mixed solution in step S1055 to the desired temperature, filter through a filter screen to remove impurities, and obtain a mixed solution of PVA and graphene.

3. The method of claim 1, wherein the method further comprises: The preparation of the ZnO / RGO humidity-sensitive material includes the following steps, Step 1: weigh 1.487g of Zn(NO3)6H2O solid powder and 2.16g of hexamethylenetetramine solid powder, dissolve them in 100mL of deionized water, and put them into an ultrasonic machine to ultrasonic until the generated precipitate just disappears, to obtain a precursor solution; Step 2: transfer the precursor solution into a high-pressure kettle with a polytetrafluoroethylene liner, keep the filling degree at 80%, react at 95℃ for 5h, then naturally cool to room temperature, and collect the white precipitate by suction filtration; Step 3: rinse the white precipitate with deionized water repeatedly to remove the adsorbed excess ions, and then dry it in a 90℃ oven to obtain nano ZnO powder; Step 4: prepare an RGO solution.

4. The method of claim 3, wherein the method further comprises: The preparation of the TiO2 / RGO photosensitive material includes the following steps, Step 1: weigh 5g of tetrabutyl titanate and add it to a dry beaker with 1mL of diethanolamine, add 20mL of anhydrous ethanol to the beaker, and stir until a colorless transparent sol is formed; Step 2: transfer the colorless transparent sol into a hydrothermal reactor lined with polytetrafluoroethylene, and place it in an oven, heat at 180℃ for 4h, and then take out the hydrothermal reactor and naturally cool it to room temperature; Step 3: take out the product from the beaker, wash it with double-distilled water and anhydrous ethanol respectively until it is neutral, and then dry it at 80℃ to obtain nano TiO2 powder; Step 4: prepare an RGO solution.

5. The method of claim 4, wherein the method further comprises: The preparation of the MoS2 / RGO gas-sensitive material includes the following steps, Step 1: weigh 0.3g of ammonium molybdate powder and 0.2g of thiourea powder, and put them into 40mL of deionized water, and then put the formed mixed solution on a magnetic stirrer for sufficient stirring until all the solutes are dissolved to obtain a transparent solution; Step 2: pour the transparent solution obtained in step 1 into a 50mL reaction kettle, and place the reaction kettle in an oven, react at 180℃ for 24h; after the reaction is completed, turn off the oven, and let the reaction kettle naturally cool to room temperature, and then wash the black precipitate obtained by reaction with anhydrous ethanol and deionized water respectively for three times to remove the residual reactants, and obtain MoS2 product; Step 3: clean the MoS2 product obtained in step 2, and dry it at 60℃ for 12h to obtain pure black nano MoS2 powder; Step 4: prepare an RGO solution.

6. The method of claim 5, wherein the method further comprises: The preparation operation of the RGO solution comprises the following steps, Step 1: 50 mg of graphene oxide GO is weighed and dispersed in 10 mL of deionized water to obtain a GO dispersion liquid by ultrasonic treatment for 1 h; Step 2: 40 mL of anhydrous ethanol is added to the GO dispersion liquid for dilution, and ultrasonic treatment is performed to obtain a GO dispersion liquid with a concentration of 1 mg / mL and a volume of 50 mL; Step 3: 0.27 g of glucose is weighed and added to 5 mL of deionized water to obtain a glucose solution with a concentration of 0.3 mol / L; Step 4: The GO dispersion liquid obtained in step 2 is placed in a water bath kettle at 60 DEG C and magnetically stirred, and the glucose solution obtained in step 3 is slowly added dropwise, and the reaction is terminated after continuous heating and stirring for 1 h, and the solution is cooled to room temperature to obtain a reduced graphene oxide solution, namely an RGO solution.

7. A passive chipless RFID multi-dimensional sensor prepared by the preparation method of the passive chipless RFID multi-dimensional sensor according to any one of claims 1-6.

8. Application of the passive chipless RFID multi-dimensional sensor prepared by the preparation method of the passive chipless RFID multi-dimensional sensor according to any one of claims 1-6 in intelligent food packaging.

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