A wearable sensor for detecting the growth state of plants

Abstract

The present invention discloses a wearable sensor for detecting the growth state of plants, which includes a flexible substrate layer, a polyimide layer located on the flexible substrate layer, a flexible electrode layer and a transparent conductive layer located on the polyimide layer, a flexible sensing device layer located on the flexible electrode layer, and a nanostructure layer located on the transparent conductive layer; the flexible electrode layer is a circular electrode, and the transparent conductive layer and the nanostructure layer are located in the middle of the circular electrode; by virtue of the adhesiveness of the flexible substrate layer of the wearable sensor, the sensor is attached to the surface of the plant. Due to the flexible wearable characteristics of the sensor, it can adapt to various irregular surfaces of the plant and can be attached to the surface of the plant leaf without damaging the plant itself. The wearable sensor of the present invention can achieve long-term and non-destructive detection. The present invention utilizes the surface Raman enhanced spectroscopy of the detector to achieve non-destructive detection of the pesticide content and alkaloids in the plant epidermis, thereby judging whether the plant may be suffering from diseases.

Description

Technical Field

[0001] The present invention relates to the field of flexible sensors, and particularly to a wearable sensor structure for detecting the growth state of plants, and its preparation and use methods. Background Art

[0002] There are approximately more than 300,000 species of plants, accounting for more than 80% of the total biological mass on Earth. Plants are not only the sources of food, medicine, industrial raw materials and energy, but also determine the environment and climate of the Earth. The growth state of plants directly reflects the health and survival ability of plants, and plays a decisive role in the health of plants. The growth state of plants is related to many factors, such as water, humidity, temperature, biological nutrients, pesticides, hormones in vivo, etc. Water is an important component of plant protoplasm and a key factor for plants to carry out photosynthesis, nutrient transport and transpiration. Water has a very significant impact on the growth state of plants. When the water loss of plants exceeds the water absorption, resulting in a decrease in tissue water content and the inability to carry out normal metabolism, plants will have problems such as weakened photosynthesis, abnormal hormone content, and damage to the protoplasm of cells. The detection of plant water can not only ensure the growth state of plants, but also avoid the existing irrigation methods, achieve precise irrigation of plants, and reduce water resource waste. Pesticides are crucial in the growth state of plants, which can effectively prevent, eliminate or control diseases, insects, weeds and other harmful organisms that endanger agriculture, protect the healthy growth of crops and improve the external and internal quality of crops. Detecting plant pesticides can avoid the impact on crop health due to the lack of pesticides in some plants, and at the same time reduce environmental pollution caused by excessive spraying of pesticides.

[0003] Traditional rigid sensors cannot deform, resulting in ineffective fitting with the plant surface. Long-term use of rigid sensors may have a certain impact on the growth of the plants themselves and may damage the plants themselves. Traditional detection of plant pesticides or hormones in vivo requires manual sampling, pretreatment of samples, and may also damage the plants themselves. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the above background art, and provide a wearable sensor for detecting the growth state of plants, which realizes in-situ, non-destructive and rapid detection of plant water through laser-induced graphene technology and graphene oxide as a humidity-sensitive material, so as to timely give early warnings of plant water shortage and drought. By using the design of the sensor structure to amplify the detection signal, non-destructive detection of the pesticide content and alkaloids on the plant epidermis can be achieved by using surface Raman enhanced spectroscopy.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A wearable sensor for detecting the growth state of plants, including a flexible substrate layer, characterized in that: it further includes a polyimide layer located on the flexible substrate layer, a flexible electrode layer and a transparent conductive layer located on the polyimide layer, a flexible sensing device layer located on the flexible electrode layer, and a nanostructure layer located on the transparent conductive layer; the flexible electrode layer is a circular electrode, and the transparent conductive layer and the nanostructure layer are located in the middle of the circular electrode.

[0007] Furthermore, the flexible substrate layer may include, but is not limited to, one or more of polyimide, polydimethylsiloxane, polyethylene terephthalate, polyester resin, and ultra-thin adhesive tape.

[0008] Furthermore, the transparent conductive layer and the nanostructure layer serve as a surface Raman enhancement spectroscopy substrate and are placed in the middle of the circular electrode.

[0009] Furthermore, the flexible electrode layer is a cross electrode structure.

[0010] Furthermore, the transparent conductive layer includes, but is not limited to, one or more of indium tin oxide, graphene, carbon nanotubes, and metal nanowires.

[0011] A preparation method of a wearable sensor for detecting the growth state of plants, the method comprising the following steps:

[0012] Step 1: Uniformly coat the polydimethylsiloxane PDMS mixed solution into an acrylic template and heat-cure it to obtain a flexible substrate layer.

[0013] Step 2: Affix the polyimide flatly on the cured polydimethylsiloxane to obtain a polyimide layer.

[0014] Step 3: Use laser-induced graphene technology to prepare cross electrodes on the polyimide as the flexible electrode layer.

[0015] Step 4: Drop-coat graphene oxide on the cross electrodes in Step 3 as the flexible sensing device layer.

[0016] Step 5: Evaporate indium tin oxide on the polyimide as a circular transparent conductive layer.

[0017] Step 6: Uniformly coat the nanoparticle solution on the surface of the transparent conductive layer and obtain a circular nanostructure layer after vacuum drying.

[0018] Furthermore, in the Step 1, the PDMS mixed solution is a mixture of a polydimethylsiloxane solution and a curing agent in a ratio of 10:1; the curing temperature is 60 °C, and the curing time is 1 h.

[0019] Furthermore, the preparation method of the flexible electrode layer 3 in the third step includes using CAD to draw a cross-electrode image, importing it into the engraving software LightBurn, inducing graphene with a laser on the engraving machine, with an engraving speed of 2300 mm / s, a maximum power of 22.5%, and a cycle number of 1.

[0020] Furthermore, the fifth step includes evaporating 200 nm of indium tin oxide on the polyimide as a transparent conductive layer.

[0021] A method for detecting the growth state of plants using the plant growth state detection wearable sensor described above, the method includes:

[0022] Attach the wearable sensor to the plant surface through the adhesiveness of the flexible substrate layer of the wearable sensor;

[0023] Connect the electrode pins of the flexible circular cross-electrodes of the wearable sensor through an LCR meter, read the capacitance reading of the LCR meter to obtain a capacitance value, and each capacitance value has a corresponding plant water content;

[0024] Place the plant with the attached sensor under a Raman spectrometer, use the microscope of the Raman spectrometer to focus on the Raman substrate of the sensor, and obtain Raman spectral signals;

[0025] Each Raman spectral signal feature corresponds to a compound, and determine the compounds contained in the plant based on the obtained Raman spectral signal features.

[0026] The beneficial effects of the present invention are:

[0027] 1. Traditional rigid sensors cannot be deformed, resulting in ineffective fitting with the plant surface. Long-term use of rigid sensors may have a certain impact on the growth of the plant itself and may damage the plant itself. The present invention attaches the wearable sensor to the plant surface through the adhesiveness of the flexible substrate layer of the wearable sensor. Due to the flexible wearable characteristics of the sensor of the present invention, it can thus adapt to various irregular surfaces of plants and can be attached to the surfaces of leaves and fruits and vegetables without damaging the plant itself. The wearable sensor of the present invention has excellent flexibility, ductility, and biocompatibility, and can achieve in-situ, long-term, and non-destructive detection.

[0028] 2. The wearable sensor prepared by the present invention can achieve rapid and stable moisture detection on the plant surface, can accurately measure the water content of the plant, and thus the growth state of the plant can be evaluated from the detection results and early warnings can be made for the water shortage and drought of the plant to a certain extent, realizing the detection of the growth state of the plant.

[0029] 3. For traditional detection of plant pesticides or endogenous hormones, manual sampling and pretreatment of samples are required, and it may also damage the plants themselves. The present invention utilizes surface-enhanced Raman spectroscopy on the detector surface to achieve non-destructive detection of pesticide content and alkaloids in the plant epidermis. In the wearable sensor of the present invention, a transparent conductive layer and a nanostructured layer are used as the surface-enhanced Raman spectroscopy substrate, and the type of compound is determined by the characteristics of the collected Raman spectral signals.

[0030] 4. Compared with ordinary spectral detection, the method of the present invention can amplify spectral signals using the nanostructured layer, greatly improving the detection sensitivity; it can detect the residual amount of plant pesticides, thereby determining whether the plant may be diseased.

[0031] 5. The present invention has the advantages of low manufacturing cost and simple manufacturing method, and can be subsequently applied to smart agriculture to achieve unmanned and intelligent monitoring of plants. Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of the wearable sensor for detecting the growth state of plants according to the present invention.

[0033] Figure 2 It is a schematic diagram of the flexible electrode according to the present invention.

[0034] Figure 3 It is the relationship between the capacitance value and humidity of sensors with different spacings.

[0035] Figure 4 It is the sensitivity response diagram of the sensor under different humidity environments according to the present invention.

[0036] Figure 5 It is the dynamic sensitivity response diagram of the transfer sensor under different humidities according to the present invention.

[0037] Figure 6 It is the enhancement effect of the SERS substrate under different film pressure values.

[0038] Figure 7 It is the Raman spectrogram for detecting thiram according to the present invention.

[0039] In the figure: 1. Flexible substrate layer; 2. Polyimide layer; 3. Flexible electrode layer; 4. Flexible sensing device layer; 5. Transparent conductive layer; 6. Nanostructured layer. Detailed Embodiments

[0040] In order to make the purpose, technical solutions and advantages of the invention clearer, the present invention will be further described below with reference to the accompanying drawings.

[0041] As Figure 1As shown in the figure, a wearable sensor for detecting the growth state of plants according to the present invention includes a flexible substrate layer 1, a polyimide layer 2, a flexible electrode layer 3, a flexible sensing device layer 4, a transparent conductive layer 5, and a nanostructure layer 6.

[0042] Among them, the flexible substrate layer 1 may include, but is not limited to, one or more of polyimide, polydimethylsiloxane, polyethylene terephthalate, polyester resin, and ultra-thin adhesive tape.

[0043] The thickness of the polyimide layer 2 can be selected as 35μm, 80μm, 100μm, 230μm, etc. The power and speed of inducing graphene are different for polyimides with different thicknesses.

[0044] The flexible electrode layer 3 can be prepared by methods such as transfer printing, screen printing, inkjet printing, laser cutting, laser direct writing, and photolithography. As Figure 2 shown in the figure, the flexible electrode layer 3 adopts an interdigitated electrode structure, and parallel interdigitated electrodes and circular electrodes can be selected.

[0045] The flexible sensing device layer 4 is used to detect the water vapor released by plant transpiration to measure the water content of plant leaves. When the plant has sufficient water content, transpiration will be strengthened; when the plant has insufficient water content, transpiration will be weakened. Its measurement principle is that graphene oxide, as a nanomaterial with a large specific surface area, has an affinity for water molecules. When the plant undergoes transpiration, water molecules will be released. After graphene oxide adsorbs these water molecules, the functional groups of graphene oxide can form hydrogen bonds with water molecules, thereby affecting the conductivity. Thus, the water content of the plant can be manifested by the change in capacitance. Further, the flexible sensing device layer 4 can be selected from graphene or graphene oxide.

[0046] The nanostructure layer 6 excites corresponding resonance peaks through the surface plasmon resonance effect, enhancing the interaction between the spectrum and the substance, and further improving the detection sensitivity of the spectrum.

[0047] The materials of the transparent conductive layer 5 include, but are not limited to, indium tin oxide, graphene, carbon nanotubes, metal nanowires, etc.

[0048] For the plant wearable sensor provided by the present invention, the flexible electrode layer 3 adopts a circular electrode, and the transparent conductive layer 5 and the nanostructure layer 6 are used as the surface Raman enhanced spectroscopy substrate and placed in the middle of the circle. The surface Raman enhanced spectroscopy substrate can adsorb more charged ions, improving the detection accuracy of the sensor.

[0049] A preparation method of a wearable sensor for detecting the growth state of plants provided by the present invention includes the following steps:

[0050] Step 1: Uniformly coat the polydimethylsiloxane (PDMS) mixed solution onto a self-made acrylic template and heat it for curing to obtain the flexible substrate layer 1.

[0051] Step 2: Attach the polyimide flatly onto the cured polydimethylsiloxane to obtain the polyimide layer 2.

[0052] Step 3: Use the laser-induced graphene technology to fabricate cross electrodes on the polyimide as the flexible electrode layer 3. As Figure 3 shown, sensors with spacings of 0.3 mm, 0.45 mm, and 0.6 mm were experimentally prepared. It can be seen from the figure that as the spacing decreases, the capacitance value increases, indicating that the sensitivity of the sensor is better.

[0053] Step 4: Drop-coat graphene oxide onto the cross electrodes in Step 3 as the flexible sensing device layer 4.

[0054] Step 5: Evaporate indium tin oxide on the polyimide as the circular transparent conductive layer 5.

[0055] Step 6: Transfer the nanoparticle solution onto the surface of the transparent conductive layer and vacuum dry it to obtain the circular nanostructure layer 6. The nanoparticles are obtained by the self-assembly method. The nanoparticle material is silver, and the optimal size is 45 nm. The process of transferring it to the transparent conductive layer 5 is completed using a syringe and an LB film instrument. The injection rate of the syringe is 0.4 mL / min, and the optimal film pressure value is 55 mN / m.

[0056] In the above Step 1, the PDMS mixed solution is a mixture of a polydimethylsiloxane solution and a curing agent in a ratio of 10:1; the curing temperature is 60 °C, and the curing time is 1 h. The curing agent can be tetramethylcyclotetrasiloxane.

[0057] The cured PDMS mixed solution has a certain viscosity. In Step 2, a thinner polyimide plate can be attached to the cured polydimethylsiloxane. If it is a thicker polyimide plate, tape can be additionally set to attach the polyimide plate to the cured polydimethylsiloxane.

[0058] In Step 3, use CAD to draw the required cross electrode image, import it into the engraving software LightBurn, and use the L6 engraving machine to induce graphene by laser. The engraving speed is 2300 mm / min, the maximum power is 22.5%, and the number of cycles is 1. As Figure 3As shown, according to the preparation method, the spacing between adjacent cross electrodes prepared in the experiment is 0.3 mm, 0.45 mm or 0.6 mm. The response curve of the cross electrode test sensor to humidity is prepared. It can be seen from the figure that as the spacing decreases, the capacitance value increases, indicating that the sensitivity of the sensor is better. The cross electrode with a spacing of 0.3 mm prepared has the highest sensitivity to humidity response.

[0059] In step 4, 1 mL of 0.5 mg / mL graphene oxide is the optimal solution volume and content.

[0060] The manufacturing method of the transparent conductive layer in step 5 includes but is not limited to methods such as sputtering deposition, evaporation coating, deposition, spin coating, and spraying.

[0061] In step 6, the nanoparticle solution is obtained by a self-assembly method. The nanoparticle material can be silver or gold, with a size of 10 - 80 nm. The process of transferring it to the transparent conductive layer 5 is completed using a syringe and an LB film instrument. The injection rate of the syringe is 0.4 mL / min, and the optimal film pressure value is 55 mN / m. The optimal film pressure value is determined through an experiment using crystal violet (CV) because the Raman scattering area of crystal violet is relatively large. As Figure 6 shown, in the experiment, crystal violet (CV) is used as a probe molecule for detecting the enhancement effect of the Raman substrate. SERS substrates with 40 mN / m, 45 mN / m, 50 mN / m, 55 mN / m, and 58 mN / m are prepared. From the experimental results, when the film pressure increases from 40 mN / m to 55 mN / m, the signal of the Raman spectrum gradually increases. This is because the larger the film pressure value, the smaller the gap between the nanoparticles, which is more conducive to generating surface plasmon resonance. However, when the film pressure exceeds 55 mN / m, the Raman intensity decreases instead because the structure is damaged. Therefore, the optimal film pressure value is 55 mN / m. Among them, the Raman shift (cm -1 ), Raman intensity (cps).

[0062] The present invention provides a method for detecting the growth state of plants: Based on the above-mentioned sensor, the sensor is attached to the surface of plant leaves, and the capacitance value of the sensor is measured by an LCR meter; the Raman spectrum signal is collected by a Raman spectrometer. A model is established based on the collected capacitance value, and the relationship between the water content of the plant and the transpiration of the plant is analyzed by comparison to judge the water state of the plant.

[0063] The information on the water content of the plant can be collected by attaching the fabricated wearable sensor to the plant leaves, such as Figure 4 and Figure 5As shown, an oscillation circuit is used to collect the capacitance changes generated by the sensor due to the influence of moisture. These capacitance changes will be configured in the signal acquisition module by connecting to the I / O port of the controller, writing a communication protocol to read the required data, converting the capacitance changes into digital signals, performing operations on the digital signals by the control module, and finally outputting the moisture content information to the display device to display the moisture content.

[0064] Figure 4 and Figure 5 In it, the RH is the relative humidity, which refers to the ratio of the actual water vapor pressure in the air to the saturated water vapor pressure at the current air temperature. It reflects the degree of the air from being saturated, represents the ratio of the absolute humidity in the air to the saturated absolute humidity at the same temperature and pressure, and is a percentage value, that is, it refers to the ratio of the mass of water vapor contained in a certain moist air to the mass of water vapor contained in the saturated air at the same temperature and pressure.

[0065] Figure 4 The capacitance change characteristics of the sensor in different relative humidity environments. Specifically, when the sensor is transferred from an environment with a relative humidity of 22% to an environment with a relative humidity of 94.3%, its capacitance value increases significantly, showing excellent humidity response ability. Under low humidity (22% RH) conditions, the capacitance value of the sensor remains at a low level of about 90 PF, while under high humidity (94.3% RH) conditions, the capacitance value rapidly increases to about 100,000 PF and remains stable within about 100 seconds to 400 seconds.

[0066] Figure 5 and Figure 3 are similar. When the sensor is transferred from a high humidity condition to a low humidity environment, the capacitance value gradually decreases.

[0067] Figure 4 and 5 clearly demonstrate the high sensitivity of the sensor to humidity changes and its fast response time, thus verifying the effectiveness and reliability of the sensor in humidity monitoring applications.

[0068] In the present invention, usually, the relationship between the capacitance value and the plant moisture content is determined in advance. The capacitance value of the sensor is measured by an LCR meter, and the corresponding plant moisture content at the capacitance value is measured by a humidity sensor, obtaining multiple capacitance values and the corresponding plant moisture contents. The multiple capacitance values and the corresponding plant moisture contents are stored in a computer as a database. In subsequent experiments, no humidity sensor is required. After measuring the capacitance value of the sensor by an LCR meter, the plant moisture content corresponding to the capacitance value can be output from the database, so as to realize continuous detection of plants by the sensor of the present invention.

[0069] In the present invention, the collected Raman spectral signals are smoothed and denoised, and the baseline is corrected. Then, the spectral signals are intercepted in a suitable band for feature extraction, and the extracted characteristic peak information is compared with the existing spectral library of the sample to be detected.

[0070] The above-mentioned Raman spectrum is a scattering spectrum and a kind of inelastic scattering phenomenon that occurs when light interacts with matter. The Raman spectrum is called the "fingerprint spectrum" because each molecule has its unique Raman spectrum. In the Raman spectrum, each Raman peak represents the wavelength position and intensity of the corresponding Raman scattered light, and each spectral peak corresponds to a specific molecular bond vibration. According to this principle, the types of molecules that make up the substance can be identified. After obtaining the characteristic peaks of the Raman signal, since each compound has corresponding characteristic peaks of the Raman signal, it is possible to determine what kind of compound it belongs to based on the obtained characteristic peaks of the Raman signal.

[0071] According to the method for detecting the growth state of plants provided by the present invention, the target compounds to be detected include: thiram, zineb, ammonium dithionite, ethanol, nicotine, etc. Example

[0072] The present invention provides a plant wearable sensor, and the specific manufacturing process includes the following steps:

[0073] 1. Fabrication of the flexible substrate layer;

[0074] Mix the polydimethylsiloxane solution and the curing agent in a ratio of 10:1, and use a glass rod to stir the mixed solution evenly until fine and uniform bubbles appear. Then, put the solution into a vacuum pump and evacuate until no bubbles emerge. Coat the mixed solution on a self-made acrylic plate, and place the coated acrylic plate in an oven at 60 °C for 1 hour. Take out the cured polydimethylsiloxane as the flexible substrate layer.

[0075] 2. Preparation of the flexible electrode;

[0076] Attach the polyimide flatly to the cured polydimethylsiloxane, import the required pattern into the laser engraving software, and then use an L6 type engraving machine. Set the focal length to 5 mm, the laser power to 22.5%, and the engraving speed to 2300 mm / min. Then, utilize the polyimide to absorb the incident photon energy and convert it into heat energy to break the C-N and C-O chemical bonds in the polyimide. During the final thermal decomposition and carbonization process of the polyimide, the gas is rapidly released, thereby generating graphene. At the same time, the patterning of graphene is also completed during the process of laser-induced graphene, and a flexible electrode based on laser-induced graphene is obtained.

[0077] 3. Preparation of the flexible sensing device;

[0078] Take graphene oxide with a concentration of 0.5 mg / mL, place it in a water bath ultrasonic machine and run it at a power of 100 W for 5 minutes, then evenly drop the graphene oxide evenly dispersed after ultrasound on the working area of the laser-induced graphene flexible electrode, place it on the workbench and let it stand. After natural drying, a graphene oxide film is obtained as a flexible sensing device.

[0079] 4. Preparation of transparent conductive layer;

[0080] 200 nm of indium tin oxide was evaporated on the polyimide as a transparent conductive layer.

[0081] 5. Fabrication of nanostructured layer;

[0082] First, 45 nm silver nanoparticles were synthesized: 0.1 mg / mL PEG-SH chloroform solution was prepared; the silver nanoparticle solution, PEG-SH chloroform solution, and methanol solution were fully mixed at a volume ratio of 1:1:1. The mixture was centrifuged at 8000 rpm for 15 min, the supernatant was discarded, and the precipitate was redissolved to one-third of the original volume with chloroform solution; centrifuged at 8000 rpm for 15 min, the supernatant was discarded, and the precipitate was redissolved to one-third of the original volume with chloroform solution; centrifuged at 8000 rpm for 15 min, the supernatant was discarded, and the precipitate was redissolved to one-tenth of the original volume with chloroform solution; then the concentration of silver nanoparticles was increased by centrifugation, and these high-concentration silver nanoparticle solutions were transferred to the surface of the transparent conductive layer using a syringe and the water surface tension was monitored using an LB film analyzer (by Figure 6 By comparison, the optimal tension is 55mN / m), and the nano-silver cubes are uniformly and completely transferred to the surface of the transparent conductive layer as a dense single molecular layer. Finally, they are dried in a vacuum drying oven at room temperature, so that the silver nano-particle cube layer forms a nano-structure layer on the surface of the transparent conductive layer. The nano-structure layer is the core of the sensor and is used to amplify the Raman signal.

[0083] Flexible electrodes such as Figure 2 As shown, the rings are crossed electrodes and the circle in the middle is the Raman substrate. Example

[0084] According to the plant wearable sensor provided by the present invention, the method for detecting the growth status of a plant includes:

[0085] 1. Using the stickiness of the flexible substrate layer of the wearable sensor, the sensors prepared above were attached to the surfaces of different samples, and watering and water-free treatments were performed, and pesticides were dripped on the samples;

[0086] 2. After a predetermined time, connect the electrode pins of the flexible ring cross electrode through the LCR meter and read the LCR meter capacitance reading. Perform multiple measurements to establish a model of the relationship between capacitance value and plant water status.

[0087] 3. Place the sample attached to the sensor under the Raman spectrometer, use the microscope of the Raman spectrometer to focus on the Raman substrate of the sensor, adjust the laser wavelength to 785nm (or 514nm, 532nm, 633nm, 780nm, 830nm), and adjust the laser energy and aperture to obtain a clear Raman spectrum signal.

[0088] 4. Sampling can be repeated multiple times according to the set sampling points of the Raman substrate.

[0089] 5. Intercept the collected Raman signal with a suitable wavelength and save the data in a computer; use Python / Matable software to train the model in the computer, eliminate the interference of the original data, and extract the characteristic peak information of the Raman signal.

[0090] 6. Compare with the Raman spectrum library of the sample to be tested, the collected Raman spectrum signal is the characteristic peak information of the target compound.

[0091] Raman spectroscopy is a technique commonly used to analyze molecular structural characteristics because its unique spectral lines can be used as a "fingerprint" to identify molecules. The characteristic peaks in this spectrum can reveal the bond types in chemical molecules. However, the signal of Raman spectroscopy is very weak, and metal nanostructures (such as gold and silver) are required to enhance the signal. The enhancement principle is that when light is irradiated on the surface of metal nanostructures such as gold and silver, surface plasma resonance will be induced. This phenomenon will generate a strong local electromagnetic field, which will significantly amplify the Raman scattering signals of molecules close to these metal nanostructures. This signal amplification greatly improves the sensitivity and selectivity of detection.

[0092] The samples of the present invention may be plant leaves, crops, fruits and vegetables.

[0093] According to the method for detecting the growth status of a plant provided by the present invention, the target compounds detected by surface Raman enhanced spectroscopy can be: thiram, zineb, mancozeb, ethanol, nicotine and the like. Example

[0094] Taking the plant wearable sensor made by the present invention to detect thiram as an example, the specific measurement process includes the following:

[0095] S1. Sample preparation: Tomato leaves are selected as samples. Tomatoes should be selected at a specific developmental stage to avoid experimental instability and ensure the presence of the markers to be tested. The sensor is attached to the surface of the tomato leaf.

[0096] S2. Dropwise coating of the sample to be measured: Take 5 μL of thiram solution and drop it on the Raman sensor substrate (the combination of 5 and 6). This can be repeated three times to obtain three reference sample points.

[0097] S3. Raman spectrum signal acquisition: Place the sample in a Raman spectrometer with a laser wavelength of 758 nm, a laser energy of 2 mW, and a slit of 50 μm; align the laser beam with the Raman sensor substrate and collect spectral data.

[0098] S4. Data processing: The collected Raman data contains interference information such as background, noise, and power fluctuations. Therefore, it is necessary to perform normalization, calibration, denoising, baseline correction, smoothing, etc. on the data to optimize the spectral data.

[0099] S5. Feature extraction: Analyze the processed spectral data, intercept the required wavelength band, and find the characteristic peaks related to thiram.

[0100] S6. Data comparison: Compare the obtained characteristic peak information with the known spectral information of thiram to judge the accuracy of the detection.

[0101] The detection result of thiram is as Figure 7 shown.

[0102] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

Claims

1. A preparation method of a wearable sensor for detecting the growth state of plants, characterized in that: The sensor comprises a flexible substrate layer (1), a polyimide layer (2) located on the flexible substrate layer (1), a flexible electrode layer (3) and a transparent conductive layer (5) located on the polyimide layer (2), a flexible sensing device layer (4) located on the flexible electrode layer (3), and a nanostructure layer (6) located on the transparent conductive layer (5); the flexible electrode layer (3) is a ring electrode, the transparent conductive layer (5) and the nanostructure layer (6) are arranged in the middle of the ring as a surface Raman enhanced spectroscopy substrate, and the surface Raman enhanced spectroscopy substrate is used to adsorb charged ions; The method for preparing the sensor comprises the following steps: Step 1: Spin-coat a polydimethylsiloxane (PDMS) mixed solution onto an acrylic template and heat and solidify the resultant flexible substrate layer (1); Step 2: attaching polyimide to the cured polydimethylsiloxane to obtain a polyimide layer (2); Step 3: Using laser induced graphene technology to prepare cross electrodes on polyimide as a flexible electrode layer (3); Step 4: drop-coating graphene oxide on the cross-electrodes in step 3 as a flexible sensing device layer (4); Step 5: sputtering indium tin oxide on the polyimide as a circular transparent conductive layer (5); Step 6: First, synthesize 45 nm silver nanoparticles and prepare a 0.1 mg / mL PEG-SH solution in chloroform. Fully mix the silver nanoparticle solution, PEG-SH solution in chloroform, and methanol solution at a volume ratio of 1:1:

1. Centrifuge the mixture at 8000 rpm for 15 min, discard the supernatant, and redissolve the precipitate to one third of the original volume with chloroform solution. Centrifuge at 8000 rpm for 15 min. min, discard the supernatant, and redissolve the precipitate with chloroform solution to one third of the original volume; centrifuge at 8000 rpm for 15 min, discard the supernatant, and redissolve the precipitate with chloroform solution to one tenth of the original volume; then increase the concentration of silver nanoparticles by centrifugation, transfer the silver nanoparticle solution with increased concentration to the surface of the transparent conductive layer using a syringe, and use an LB film analyzer to monitor the water surface tension, transfer the nanosilver block monomolecular layer to the surface of the transparent conductive layer, and finally dry it in a vacuum drying oven at room temperature to form a nanostructured layer on the surface of the transparent conductive layer.

2. The preparation method of a wearable sensor for detecting the growth state of plants according to claim 1, characterized in that: In the step 1, the flexible substrate layer (1) is polydimethylsiloxane, the PDMS mixed solution is spin-coated at a speed of 3000 rpm, a spin-coating time of 60 s, and a spin-coating thickness of 80 um; the curing temperature is 60° C., and the curing time is 1 h.

3. The preparation method of a wearable sensor for detecting the growth state of plants according to claim 1, wherein: The transparent conductive layer (5) and the nanostructure layer (6) serve as surface Raman enhanced spectroscopy substrates and are placed in the middle of the annular electrode.

4. The preparation method of a wearable sensor for detecting plant growth state according to claim 1, characterized in that: The flexible electrode layer (3) is a cross-electrode structure, and the transparent conductive layer (5) is indium tin oxide.

5. The preparation method of a wearable sensor for detecting the growth state of plants according to claim 1, characterized in that: The preparation method of the flexible electrode layer (3) in the third step includes using CAD to draw the cross-electrode image, importing it into the engraving software LightBurn, inducing graphene by laser using an engraving machine, with an engraving speed of 2300 mm / min, a maximum power of 22.5%, and a cycle number of 1. The distance between adjacent cross-electrodes prepared is 0.3 mm, 0.45 mm, or 0.6 mm.

6. The preparation method of a wearable sensor for detecting plant growth status according to claim 1, characterized in that: The fifth step includes sputtering indium tin oxide of 200 nm on the polyimide as the transparent conductive layer (5).

7. A method for detecting the growth state of plants using the sensor obtained by the method for preparing a wearable sensor for detecting the growth state of plants according to claim 1, characterized in that, The method includes: Attaching the wearable sensor to the plant surface through the adhesiveness of the flexible substrate layer of the wearable sensor; Connecting the electrode pins of the flexible circular cross-electrodes of the wearable sensor through an LCR meter, reading the capacitance reading of the LCR meter to obtain the capacitance value, and each capacitance value has a corresponding plant water content; Placing the plant attached with the sensor under a Raman spectrometer, using the microscope of the Raman spectrometer to focus on the Raman substrate of the sensor to obtain Raman spectral signals; Each Raman spectral signal feature corresponds to a compound, and the compounds contained in the plant are determined based on the obtained Raman spectral signal features.

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