Leaf sensor patch for monitoring plant physiology and preparation method and application method thereof

Abstract

The invention discloses a leaf sensor patch for monitoring plant physiology as well as a preparation method and an application method thereof, and belongs to the technical field of plant sensing. The blade sensor patch comprises a flexible substrate, a silver nanowire cross electrode and a sensor group; the sensor group comprises at least one resistance-type volatile organic compound sensor, at least one resistance-type blade temperature sensor, at least one capacitance-type blade surface humidity sensor and at least one capacitance-type environment humidity sensor; the silver nanowire cross electrode is embedded into the flexible PDMS substrate, the sensor group is integrated on the surface of the flexible PDMS substrate, and all sensors in the sensor group are connected with the silver nanowire cross electrode. Synchronous monitoring of volatile organic compounds of leaves, surface temperature / humidity and environment humidity is achieved, high sensitivity and selectivity are achieved, and the problem that an existing plant physiology monitoring sensor cannot synchronously monitor plant biochemical signals and biophysical signals can be effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of plant sensing technology, and relates to a leaf sensor patch for monitoring plant physiology, its preparation method and application method. Specifically, it designs a monitoring sensor patch that integrates the detection functions of volatile organic compounds, temperature and humidity. It monitors plant physiology by tracking the biochemical and biophysical signals of plants and their microenvironment, and is especially suitable for the early diagnosis of plant abiotic stress and pathogen infection. Background Technology

[0002] During plant growth, the biochemical and biophysical signals of the plant and its microenvironment are crucial for diagnosing its health status. Stomata on plant leaves are the main gateways for the exchange of various molecules, including water, oxygen, carbon dioxide, and volatile organic compounds. These stomata can be used to monitor and reflect the plant's biochemical and biophysical signals, further analyzing its physiological state, stress response, and environmental adaptability. Therefore, plant leaves are an important location for sensors to attach and monitor plant health. Traditional sensor applications place the sensor in the environment; however, a different approach involves mounting the sensor on the lower surface of the leaf, maximizing the plant's output signal.

[0003] Traditional plant health monitoring technologies, such as imaging, spectral analysis, and electrophysiological sensing, suffer from low sensitivity and poor specificity. Existing plant physiological monitoring sensors are mostly limited to detecting single biophysical signal parameters, such as temperature or humidity, lacking the ability to simultaneously monitor biochemical signals, such as VOCs. Some plant physiological monitoring sensors, such as the one disclosed in patent CN107926655A (an automatic cultivation device), feature an environmental detector with a temperature sensor, humidity sensor, VOC content detector, and light intensity detector, but do not disclose the specific structure of the sensors. Furthermore, current VOC sensors mostly use metal oxides (such as zinc oxide and titanium dioxide) and carbon nanotubes as the sensitive membrane materials for gas sensors, which suffer from reduced sensitivity under high temperature and humidity conditions and cannot coordinate with other sensors for monitoring under multiple conditions.

[0004] Therefore, there is a need for an integrated sensor that can stably monitor multiple physiological data of plants in terms of sensor materials, sensor layout, and sensor coordination, so as to monitor various biotic and abiotic stresses, detect pathogens early, prevent disease outbreaks, and promote plant growth. Summary of the Invention

[0005] The technical problem to be solved by this invention is that existing plant physiological monitoring sensors cannot simultaneously monitor the biochemical and biophysical signals of plants.

[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows: In a first aspect, the present invention provides a leaf sensor patch for monitoring plant physiology, comprising a flexible PDMS substrate, silver nanowire (AgNWs) cross electrodes, and a sensor group; wherein the sensor group includes at least one resistive volatile organic compound (VOCs) sensor, at least one resistive leaf temperature sensor, at least one capacitive leaf surface humidity sensor, and at least one capacitive ambient humidity sensor; in the leaf sensor patch, the AgNWs cross electrodes are embedded inside the flexible PDMS substrate, the sensor group is integrated on the surface of the flexible PDMS substrate, and all sensors in the sensor group are interconnected with the AgNWs cross electrodes.

[0007] The aforementioned resistive VOCs sensor includes a hybrid sensing layer and a hydrophobic sol-gel layer covering the hybrid sensing layer.

[0008] Furthermore, the aforementioned hybrid sensing layer consists of multi-walled carbon nanotubes (MWCNTs) and gold-coated silver nanowires (Au@AgNWs) with sulfur-containing halothiophene ligands modified on their surfaces.

[0009] Furthermore, the molar ratio of Au@AgNWs containing sulfur-containing halothiophene ligands to MWCNTs is 5:1.

[0010] Furthermore, the sulfur-containing halothiophene ligand includes at least one of fluorothiophene (FTP), chlorothiophene (CTP), bromothiophene (BTP), and iodine-polythiophene (ITP).

[0011] Furthermore, the hydrophobic sol-gel layer is composed of methyltrimethoxysilane (MTMS), tetramethyl orthosilicate (TMOS), methanol, and nano-pure water.

[0012] Furthermore, the molar ratio of methyltrimethoxysilane, tetramethyl orthosilicate, methanol, and nanopure water is 1:1:11:5.

[0013] The aforementioned resistive blade temperature sensor includes Au@AgNWs and a flexible PDMS protective layer covering Au@AgNWs.

[0014] Furthermore, the flexible substrate PDMS is prepared by mixing PDMS prepolymer and curing agent at a mass ratio of 20:1.

[0015] The aforementioned capacitive blade surface humidity sensor or capacitive ambient humidity sensor includes a Nafion film and a flexible PDMS protective layer covering the Nafion film.

[0016] Furthermore, the thickness of the Nafion film is 2 μm.

[0017] The shape of the blade sensor patch and the number of sensors in the sensor group are adaptively adjusted according to the blade morphology.

[0018] Secondly, the present invention provides a method for preparing the above-mentioned blade sensor patch, comprising the following steps: S1. Fix a mask with a cross electrode pattern onto the surface of a pretreated polyimide (PI) substrate, then spray with AgNWs, remove the mask, remove the residual solvent, and obtain a substrate with AgNWs cross electrodes. S2. Mix the PDMS prepolymer and curing agent at a mass ratio of 20:1, degas under vacuum, and slowly pour the mixture onto the substrate obtained in step S1 for step curing. After cooling to room temperature, peel off the PI substrate to obtain a flexible PDMS substrate with AgNWs cross electrodes embedded inside. S3. Using a porous PDMS mask to expose the electrode nodes, different sensing materials are then deposited on the electrode areas to obtain blade sensor patches: gold-coated silver nanowires are deposited on the electrode areas, dried, and covered with a flexible PDMS protective layer to obtain a resistive blade temperature sensor; Nafion films are deposited on different electrode areas, dried, and covered with a flexible PDMS protective layer to obtain a capacitive blade surface humidity sensor and a capacitive ambient humidity sensor; a hybrid sensing layer is deposited on the electrode areas, dried, and covered with a hydrophobic sol-gel layer to obtain a resistive volatile organic compound sensor.

[0019] Furthermore, in step S1 above, the pretreatment method for the polyimide substrate is as follows: the polyimide film with a thickness of 50~100μm is ultrasonically cleaned with acetone and isopropanol in sequence, dried with nitrogen, and then placed in a plasma cleaner for treatment.

[0020] Furthermore, in step S2 above, the stepped curing specifically involves: first, pre-curing at a low temperature of 40~50℃ for 1~2 hours, then performing a medium-temperature main curing at 80~100℃ for 1~2 hours, and finally performing a high-temperature post-curing at 120~150℃ for 0.5~1 hours.

[0021] Furthermore, in step S3 above, the hybrid sensing layer is obtained by mixing gold-coated silver nanowires with sulfur-containing halothiophene ligands on their surfaces with multi-walled carbon nanotubes, and the molar ratio of the gold-coated silver nanowires with sulfur-containing halothiophene ligands to the multi-walled carbon nanotubes is 5:1.

[0022] Furthermore, in step S3 above, the hydrophobic sol-gel layer is obtained by mixing methyltrimethoxysilane, tetramethyl orthosilicate, methanol and nano-pure water, with a molar ratio of methyltrimethoxysilane, tetramethyl orthosilicate, methanol and nano-pure water of 1:1:11:5.

[0023] Thirdly, the present invention provides a method for applying the above-mentioned leaf sensor patch, comprising the following steps: adjusting the shape of the leaf sensor patch and the number of sensors in the sensor group according to the leaf shape, and selecting the surface of the leaf with higher stomatal density as the attachment position of the leaf sensor patch; attaching the patch to the selected surface of the leaf, and making the resistive leaf temperature sensor in direct contact with the leaf surface; the resistive volatile organic compound sensor and the capacitive leaf surface humidity sensor facing the leaf; the capacitive ambient humidity sensor extending outward from the leaf edge and being fully exposed to the air; and connecting the leaf sensor patch to the data acquisition system through wires to monitor plant physiological signals.

[0024] The beneficial effects of this invention are: this invention achieves simultaneous monitoring of leaf volatile organic compounds, leaf surface temperature / humidity and ambient humidity through a flexible PDMS substrate, AgNWs cross electrodes and sensor group, with high sensitivity and selectivity. Attached Figure Description

[0025] Figure 1 This is a structural diagram of the leaf sensor patch for monitoring plant physiology according to the present invention; Figure 2 UV-Vis data for Au@AgNWs mixed with different amounts of FTP solution; Figure 3 UV-Vis data of Au@AgNWs coated with four ligands (FTP, CTP, BTP and ITP); Figure 4 The resistivity change rate of PDMS prepolymer and curing agent at different ratios under different temperature conditions; Figure 5 The capacitance change rate is given for different Nafion film thicknesses under different humidity conditions. Detailed Implementation

[0026] To make the technical problems, solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with the embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as understood by one of ordinary skill in the art.

[0027] I. Leaf sensor patch for monitoring plant physiology A leaf sensor patch for monitoring plant physiology includes a flexible PDMS substrate, AgNWs cross electrodes, and a sensor array. The sensor array includes at least one resistive VOCs sensor, at least one resistive leaf temperature sensor, at least one capacitive leaf surface humidity sensor, and at least one capacitive ambient humidity sensor. In the leaf sensor patch, the AgNWs cross electrodes are embedded within the flexible PDMS substrate, and the sensor array is integrated on the surface of the flexible PDMS substrate. All sensors in the sensor array are interconnected with the AgNWs cross electrodes. This invention utilizes the balance point between the elastic modulus and thermal expansion of the flexible PDMS substrate to balance its flexibility and heat resistance, allowing for a curved surface fit to the leaf and maximizing the plant's output signal. The use of AgNWs cross electrodes enables the integration of multiple sensor circuits on the flexible PDMS substrate, allowing for unified signal acquisition. The shape of the leaf sensor patch can vary according to the leaf shape, and the function and number of individual sensors can be varied depending on the monitoring indicators.

[0028] In one embodiment of the present invention, the leaf sensor patch for monitoring plant physiology comprises seven sensors, including four resistive VOCs sensors, one resistive leaf temperature sensor, one capacitive leaf surface humidity sensor, and one capacitive ambient humidity sensor. All seven individual sensors are integrated on a flexible PDMS substrate and interconnected with AgNWs cross electrodes. The leaf temperature sensor, leaf surface humidity sensor, and ambient humidity sensor are responsible for collecting basic temperature and humidity data, providing fundamental support for plant physiology monitoring. The four VOCs sensors accurately distinguish between different pollutant types such as formaldehyde, benzene, and alcohol through differences in response modes, improving identification accuracy. Even if one VOCs sensor fails, the remaining sensors can still maintain functional coverage and measurement redundancy, ensuring reliable long-term monitoring.

[0029] Preferably, the structure of the blade sensor patch is as follows: Figure 1 As shown, the resistive blade temperature sensor is in direct contact with the blade surface; the resistive VOCs sensor and the capacitive blade surface humidity sensor face the blade, while the capacitive ambient humidity sensor extends from the blade and is open to the environment. Active sensing materials (Au@AgNWs, MWCNTs, Nafion films, etc.) are bonded to patterned, interlaced electrodes made of AgNWs, which are embedded beneath the surface of a flexible PDMS substrate. This invention employs an innovative spatial layout, with the ambient humidity sensor "extending from the blade" to avoid interference from the blade's microenvironment. This structural design solves the problem of cross-interference in existing integrated sensors, and the number of sensors and the shape of the patches are adjustable (e.g., to adapt to different blade shapes), breaking through the traditional fixed template design.

[0030] 1. Resistive VOCs sensor In one embodiment of the present invention, the resistive VOCs sensor comprises a hybrid network (hybrid sensing layer) of Au@AgNWs and MWCNTs with surface-modified sulfur-containing halothiophene ligands, wherein the MWCNTs are embedded in a hydrophobic sol-gel composed of MTMS and TMOS, etc. The hybrid sensing layer is obtained by mixing gold-coated silver nanowires with surface-modified sulfur-containing halothiophene ligands with multi-walled carbon nanotubes, wherein the molar ratio of the gold-coated silver nanowires with sulfur-containing halothiophene ligands to the multi-walled carbon nanotubes is 5:1; the hydrophobic sol-gel layer is obtained by mixing methyltrimethoxysilane, tetramethyl orthosilicate, methanol and nanopure water, wherein the molar ratio of methyltrimethoxysilane, tetramethyl orthosilicate, methanol and nanopure water is 1:1:11:5. In this invention, through innovative material combination, the high humidity interference in the plant microenvironment is addressed. The high conductivity and stability of Au@AgNWs (antioxidant) are innovatively combined with the anti-interference properties of hydrophobic sol-gel to improve the sensitivity of VOCs sensors in humid and hot environments, as detailed below.

[0031] (1) Au@AgNWs is a one-dimensional nanomaterial with a core-shell structure, consisting of AgNWs as the core and an outer Au shell. This composite structure combines the high conductivity of silver, the high chemical stability of gold, and surface plasmon resonance characteristics, and is widely used in flexible electronics, catalysis, and biosensing. Compared with AgNWs, Au@AgNWs has a thin gold layer (about 30 nm) on its surface. Gold can form stronger Au-S bonds with thioligands, and the gold surface is more chemically inert, thus improving stability. At the same time, the Au-S bonds are oriented on the gold surface to form ordered monolayers (SAMs), which improve the selectivity and sensitivity of the sensing material. In this process, when VOC molecules are adsorbed onto the conductive material Au@AgNWs surface, charge transfer causes a change in resistance, thereby collecting information on volatile organic compounds during plant growth.

[0032] (2) MWCNTs have a high specific surface area (approximately 300 m²). 2 / g), in which the hollow tubular structure provides more active sites, forming a three-dimensional conductive framework to accelerate electron transport; after being combined with Au@AgNWs, the π-π conjugated structure of MWCNTs and the metal nanowires synergistically catalyze the VOC oxidation reaction, reducing the detection limit.

[0033] (3) In the hydrophobic sol-gel composed of MTMS and TMOS, the hydrophobic layer blocks the penetration of environmental water molecules, allowing small VOC molecules (such as aldehydes and ketones) to diffuse through the pores to the sensing layer, thereby blocking large molecular interferences (such as aerosol particles) and improving environmental stability; at the same time, it also plays a certain physical protection role, preventing sensor failure caused by physical wear (such as blade friction).

[0034] In one embodiment of the present invention, the Au@AgNWs used in the resistive VOCs sensor are Au@AgNWs surface-modified with sulfur-containing halogenated thiophene ligands. For the selection of the coating ligands, they can be flexibly replaced according to different monitoring indicators. Aldehyde emissions can be used as biomarkers for the health status of plants and are important indicators in the monitoring of plant volatile organic compounds for early disease diagnosis. Therefore, Au@AgNWs are coated with halogenated thiophene ligands (containing sulfur atoms): FTP, CTP, BTP, ITP, etc., which can selectively detect leaf aldehydes through reversible halogen bonds. The synthesis processes of the above four halogenated thiophene ligands are mature, and the halogen bonds have a strength gradient. The atomic radius and polarization ability of the halogen atoms increase in sequence (F < Cl < Br < I), which can selectively detect leaf aldehydes. They form reversible halogen bonds with the carbonyl oxygen atoms of leaf aldehydes, and the molecular adsorption caused by the halogen bonds leads to local electron density changes, manifested as changes in resistance or capacitance signals to achieve information transmission. Therefore, in the present invention, the sulfur-containing halogenated thiophene ligands include at least one of fluorothiophene, chlorothiophene, bromothiophene, and iodopolythiophene.

[0035] In one embodiment of the present invention, the performance of the above resistive VOCs sensor depends to a large extent on the number of ligands attached to the surface of the nanomaterials. Too low ligand concentration will result in insufficient coverage of the nanowire surface, which not only reduces the reactivity to VOC analytes but also cannot effectively prevent oxidation; while too high concentration is prone to cause aggregation of the Au@AgNWs solution, and the formed aggregates hinder the nanowire connection, increasing the sheet resistance and resistivity of the electrode, and may also lead to over-passivation and affect conductivity. If the resistance response is not obvious, that is, the sensitivity is low or it cannot be discriminated, the sensitivity of the resistance response can be optimized and the sensor performance can be optimized by optimizing the modification concentration and amount of ligands on the surface of Au@AgNWs, that is, adjusting the ligand concentration and changing the volume of the ligand solution to optimize the dosage of the ligand solution.

[0036] The ligand modification process of traditional sensors is relatively fixed, but the present invention optimizes and improves the coating ligand modification mechanism of Au@AgNWs. In one embodiment of the present invention, by dynamically regulating the ligand concentration and modification amount, the response performance of the sensor is effectively optimized: that is, the coated surface is characterized and analyzed by ultraviolet-visible (UVvis) spectroscopy, and then the surface ligand density is accurately optimized; at the same time, according to different monitoring indicators, the coating ligands are flexibly selected and replaced, so as to significantly improve the response adaptability of the sensor to various aldehyde VOCs, and make it show a more excellent detection effect when facing different aldehyde VOCs. The specific process is as follows: To determine the dosage of the ligand solution, the present invention selects a ligand solution concentration of 0.1 μM, and tests the ultraviolet-visible spectral data of different dosages of FTP coated on Au@AgNWs by changing the volume of the ligand solution (300, 500, and 1000 μL) ( Figure 2 ) As Figure 2 As shown, the absorption peak intensity of the 500 μL group was approximately 4 a.u., lower than that of the 300 μL group (approximately 6 a.u.), indicating a higher ligand density. The 1000 μL group had the lowest absorption peak intensity (approximately 2 a.u.), suggesting a possible ligand excess despite its high density. Simultaneously, the peak shape of the 500 μL group was relatively symmetrical (the more symmetrical the peak shape, the less obvious the broadening or redshift caused by aggregation, the better the stability), falling between the 300 μL group (broader peak shape, possibly indicating partial aggregation) and the 1000 μL group (excessively broad peak shape, possibly due to ligand excess leading to instability). No severe aggregation or abnormal peak shapes caused by ligand excess were observed. Therefore, the results indicate that a 500 μL solution is optimal, balancing ligand density and stability. Similarly, other VOC sensors were prepared using 500 μL solutions of 0.1 μM ITP, BTP, and CTP ligands. Each functionalization reaction was gently shaken at room temperature for 8 hours, after which the supernatant was collected, and its UV-Vis spectra (e.g., ...) were measured. Figure 3 As shown). By Figure 3 It is known that it also has better ligand density and stability. Therefore, in this invention, when preparing Au@AgNWs containing sulfur halothiophene ligands, the concentration of the ligand solution is 0.1 μM and the volume of the ligand solution is 500 μL.

[0037] 2. Resistive blade temperature sensor In one embodiment of the present invention, the resistive blade temperature sensor includes gold-coated silver nanowires and a flexible PDMS protective layer covering the gold-coated silver nanowires. The resistive blade temperature sensor uses Au@AgNWs as the sensing material, with the Au@AgNWs embedded in a flexible PDMS substrate.

[0038] In one embodiment of the present invention, the flexible PDMS substrate is prepared by mixing PDMS prepolymer and curing agent at a mass ratio of 20:1. Au@AgNWs form a three-dimensional conductive network. Due to the temperature sensitivity of Au@AgNWs, temperature changes lead to enhanced metal lattice vibrations and intensified electron scattering, resulting in a linear increase in resistance with increasing temperature, thus detecting temperature changes. However, the increase in temperature causes thermal expansion of the PDMS substrate, leading to microstructural deformation of the temperature sensor and altering the baseline value of the resistance or capacitance signal. To reduce the interference of this phenomenon on temperature monitoring, it is necessary to adjust the ratio of the PDMS elastic modulus prepolymer (main agent) to the curing agent to find a balance between the elastic modulus of PDMS and thermal expansion, i.e., to ensure sensor sensitivity (requiring a certain degree of flexibility) while suppressing thermal expansion interference (requiring high rigidity).

[0039] To investigate the effect of PDMS thermal expansion on temperature sensing, the resistivity change rate (e.g., ) was measured under different temperature conditions at varying ratios of prepolymer and curing agent (20:1, 15:1, 10:1, 5:1). Figure 4 As shown in the figure, an optimal mixing ratio was used to test the improvement of temperature sensor sensitivity. The results showed that PDMS with a high elastic modulus (e.g., a 5:1 ratio) has a lower coefficient of thermal expansion and less deformation under temperature changes. When the mixing ratio increased to 20:1, PDMS softened, its thermal expansion was greater, and it was more prone to substrate deformation due to temperature fluctuations, resulting in the largest resistivity change rate (ΔR / R0). While the temperature sensor sensitivity was slightly improved, its resistance temperature sensitivity was significantly affected. Therefore, in this invention, the flexible substrate PDMS is prepared by mixing PDMS prepolymer and curing agent at a mass ratio of 20:1.

[0040] 3. Capacitive blade surface humidity sensor and capacitive ambient humidity sensor In one embodiment of the present invention, the above-mentioned capacitive blade surface humidity sensor or capacitive ambient humidity sensor uses Nafion film as the active humidity sensing material and embeds the Nafion film on a flexible PDMS substrate.

[0041] In one embodiment of the present invention, the thickness of the Nafion membrane is 2 μm. Nafion is an ion exchange membrane with strong water absorption, and its humidity sensing mechanism is based on capacitance changes. The Nafion membrane is composed of a perfluorosulfonic acid polymer. The sulfonic acid groups (-SO3H) have strong hydrophilicity and can rapidly adsorb water molecules from the environment through hydrogen bonding. When Nafion absorbs water molecules, continuous ion channels are formed inside the membrane, and water molecules replace the air inside the membrane. + Increased ion mobility leads to a significant increase in the overall dielectric constant, which in turn alters the capacitance between electrodes.

[0042] To investigate the effect of Nafion film thickness on temperature sensing and optimize detection sensitivity by controlling the Nafion film thickness, the capacitance change rate (e.g., under different humidity conditions) of different Nafion film thicknesses was tested. Figure 5 (As shown). Capacitance formula: C = Ɛ r Ɛ 0 A / d; where, Ɛ r It is the dielectric constant. Ɛ 0 It is the vacuum permittivity. ALet d be the electrode area and d be the film thickness. Results show that controlling the Nafion film thickness can optimize detection sensitivity; as the film thickness increases, the ability to absorb water molecules increases, and the sensitivity also improves. However, when the thickness exceeds 5 μm, the film delaminates from the substrate due to a significant stiffness mismatch between the film and the substrate. Therefore, this invention selects a Nafion film thickness of 2 μm as the optimal thickness.

[0043] II. Preparation method of leaf sensor patch for monitoring plant physiology A method for fabricating leaf sensor patches for monitoring plant physiology involves spraying AgNWs onto a PI thin film (50-100 μm thick) substrate, and using a template mask to pattern and interconnect cross electrodes. After patterning, a PDMS solution is poured in to transfer the AgNWs from the PI to the PDMS. Once the PDMS has completely cured, the PI substrate is removed. Using the patterned AgNW substrate, the sensing material for each sensor is selectively deposited onto the cross electrodes; for example, Au@AgNWs are used for temperature sensors, Nafion for leaf surface humidity sensors and ambient humidity sensors, and functionalized Au@AgNW+MWCNTs for VOC sensors.

[0044] In one embodiment of the present invention, after imaging, a PDMS solution is poured in for stepwise curing to transfer AgNWs from PI onto PDMS. The stepwise curing is specifically as follows: (1) Initial low-temperature pre-curing (eliminating bubbles and preliminary cross-linking): Temperature: 40~50℃, Time: 1~2 hours; Function: Promotes the preliminary mixing and cross-linking of PDMS prepolymer and curing agent, avoids rapid reaction at high temperature leading to bubbles, and slows down the reaction rate in a low-temperature environment, allowing residual micro bubbles to escape from the surface in sufficient time. (2) Medium-temperature main curing (completing the main cross-linking reaction): Temperature: 80~100℃, Time: 1.5~2 hours; Function: Activates the cross-linking reaction and forms an elastic network structure. (3) High-temperature post-curing (enhancing stability and substrate adhesion): Temperature: 120~150℃, Time: 0.5~1 hour; Function: Eliminates internal stress and improves the mechanical strength and thermal stability of the material (PDMS working temperature can reach 200℃).

[0045] The following specific embodiments will be provided to explain the solution of the present invention. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0046] Example

[0047] I. Preparation of Reagents 1. The Au@AgNWs dispersion used in this embodiment is prepared by a modified polyol method and dispersed in deionized (DI) water to form the Au@AgNWs dispersion, specifically including the following steps.

[0048] (1) Preparation of solution A: Take 10 ml of 10 mg / ml AgNW aqueous solution, 70 ml of 5 wt% polyvinylpyrrolidone aqueous solution, 14 ml of 0.5 mol / L L-ascorbic acid aqueous solution, 14 ml of 0.5 mol / L sodium hydroxide solution, 3.5 ml of 0.1 mol / L sodium sulfite aqueous solution and 80 ml of deionized water and put them into a container. Stir and mix them evenly with a glass rod to obtain solution A for later use.

[0049] (2) Preparation of solution B: First, put 10 ml of 0.1 mol / L sodium sulfite aqueous solution, 3.5 ml of 0.5 mol / L sodium hydroxide aqueous solution and 100 ml of deionized water into a container and mix them evenly; then add 1.5 ml of 0.25 mol / L tetrachloroauric acid trihydrate (HAuCl4·3H2O) to the mixed solution, and gently stir with a glass rod to mix evenly to obtain solution B for later use.

[0050] (3) Solution B was then immediately and slowly poured into solution A, forming a light purple mixture with a metallic luster. The beaker containing the mixture was sealed and allowed to stand for 12 hours. After the reaction was complete, a light brown precipitate formed in the solution, and the remaining solution turned transparent black. The light brown solution was centrifuged at 1000 rpm for 1 minute, and then the black solution was carefully poured off, retaining the light brown precipitate (Au@AgNWs) at the bottom of the centrifuge tube. The precipitate was washed three times with 95% ethanol to remove residual ions and organic impurities. The precipitate was then redispersed in an appropriate amount of deionized water to obtain an Au@AgNWs dispersion for later use.

[0051] 2. Preparation of Au@AgNWs containing sulfur-containing halothiophene ligands: Au@AgNWs containing FTP, CTP, BTP and ITP were prepared by using 500 μL of 0.1 μM FTP, CTP, BTP and ITP solutions respectively, and were then prepared for use.

[0052] 3. Preparation of flexible PDMS: It is prepared by mixing PDMS prepolymer and curing agent at a mass ratio of 20:1.

[0053] 4. Preparation of the hybrid sensing layer of the resistive VOCs sensor: Au@AgNWs containing sulfur halothiophene ligands were mixed with MWCNTs at a molar ratio of 5:1 to prepare FTP, CTP, BTP and ITP sensors for later use.

[0054] 5. Preparation of hydrophobic sol-gel layer of resistive VOCs sensor: It is prepared by mixing MTMS, TMOS, methanol and nanopure water in a molar ratio of 1:1:11:5.

[0055] II. Preparation of leaf sensor patches for monitoring plant physiology, specifically including the following steps: 1. AgNWs spraying and patterned electrode preparation: The PI film was ultrasonically cleaned with acetone and isopropanol in sequence, dried with nitrogen, and then treated in a plasma cleaner to improve the surface hydrophilicity; a stainless steel mask was made using photolithography or laser cutting, and a cross electrode pattern was designed and fixed to the PI substrate surface by vacuum adsorption; the AgNWs dispersion was loaded into an aerosol spray gun and sprayed multiple times. After removing the mask, residual solvent was removed and conductivity was enhanced.

[0056] 2. PDMS Transfer and Substrate Peeling: Flexible PDMS is vacuum degassed and slowly poured onto an AgNWs patterned PI substrate for step-by-step curing. First, it is pre-cured at a low temperature of 40~50℃ for 1~2 hours, then cured at a medium temperature of 80~100℃ for 1~2 hours, and finally cured at a high temperature of 120~150℃ for 0.5~1 hours. After curing, it is cooled to room temperature, and the PDMS / AgNWs composite layer is slowly peeled off from the edge. The difference in interfacial energy between PDMS and PI is used to achieve non-destructive transfer.

[0057] 3. Cross-electrode functionalization: Using a porous PDMS mask (pore size matched to electrode sites), different sensor regions were exposed by microscopic alignment, and then different sensing materials were deposited on the electrode regions to obtain blade sensor patches: 2μm thick Nafion films were deposited on two different cross-electrode regions, dried, and covered with a PDMS protective layer to obtain a capacitive blade surface humidity sensor and a capacitive ambient humidity sensor; Au@AgNWs dispersion was drop-coated onto the cross-electrode regions, dried, and covered with a PDMS protective layer to obtain a resistive blade temperature sensor; a mixed sensing layer was precisely drop-added to four different VOC sensor regions using a micropipette, dried, and covered with a hydrophobic sol-gel layer by spraying to obtain a resistive VOCs sensor.

[0058] 4. Finally, the PDMS with AgNWs electrodes transferred on it is placed in anhydrous ethanol for ultrasonic cleaning to remove surface impurities, thus obtaining a leaf sensor patch for monitoring plant physiology.

[0059] A leaf sensor patch for monitoring plant physiology was fabricated, containing seven sensors: four resistive VOCs sensors (i.e., FTP, CTP, BTP, and ITP sensors), one resistive leaf temperature sensor, one capacitive leaf surface humidity sensor, and one capacitive ambient humidity sensor. All seven individual sensors are integrated on a flexible PDMS substrate and interconnected with AgNWs cross electrodes.

[0060] III. Application of Leaf Sensor Patches for Monitoring Plant Physiology The stomatal density on the front and back of the blade was observed and compared using a microscope. The surface with higher stomatal density was selected as the attachment site for the sensor patch to obtain better sensor performance. During installation, follow... Figure 1 The structure shown features a resistive blade temperature sensor in direct contact with the blade surface to ensure efficient heat transfer; a resistive VOCs sensor and a capacitive blade surface humidity sensor face the blade to accurately sense the microenvironment on the blade surface; and a capacitive ambient humidity sensor extends from the blade, open to the environment, to simultaneously monitor atmospheric humidity. Fine copper wire and conductive silver paste are used to securely interconnect the sensor electrodes with the data acquisition system, ensuring the stability and reliability of data transmission.

[0061] In this system, a leaf temperature sensor, a leaf surface humidity sensor, and an ambient humidity sensor together constitute the basic temperature and humidity monitoring unit, providing fundamental support for judging the physiological state of plants. Four resistive VOCs sensors form a gas sensing array, which, by virtue of the differences in their response modes, can accurately distinguish and identify different volatile organic compounds such as formaldehyde, benzene, and alcohol, significantly improving the analytical capability and measurement redundancy advantage in complex pollution environments: even if a single sensor fails, the remaining units can still work together to maintain the overall functional coverage and long-term monitoring reliability of the system.

[0062] Acetone or hexanal vapor was used to simulate ketone and aldehyde VOCs emitted by plants. The performance of a resistive VOCs sensor was tested by measuring the resistance under acetone or hexanal vapor exposure. The test results showed that the resistive VOCs sensor exhibited excellent chemielectric resistance response characteristics: its resistance value changed with the adsorption of VOC molecules on the surface of the MWCNTs sensitive layer. Under high concentrations of VOC exposure, a large number of adsorbed molecules could cause local conductive pathways in the MWCNTs network to be interrupted, leading to a significant increase in resistance. This resulted in excellent detection sensitivity and a distinguishable response curve, providing an effective means for early warning of plant stress.

Claims

1. A leaf sensor patch for monitoring plant physiology, characterized by: The blade sensor patch comprises a flexible PDMS substrate, a silver nanowire cross electrode and a sensor group; wherein the sensor group comprises at least one resistive volatile organic compound sensor, at least one resistive blade temperature sensor, at least one capacitive blade surface humidity sensor, and at least one capacitive ambient humidity sensor; In the blade sensor patch, the silver nanowire cross electrode is embedded in the inside of the flexible PDMS substrate, and the sensor group is integrated on the surface of the flexible PDMS substrate, and all sensors in the sensor group are interconnected with the silver nanowire cross electrode.

2. The leaf sensor patch for monitoring plant physiology of claim 1, wherein: The resistive volatile organic compound sensor comprises a mixed sensing layer and a hydrophobic sol-gel layer covering the mixed sensing layer; The mixed sensing layer is composed of multi-walled carbon nanotubes and gold-coated silver nanowires with sulfur-containing halogenated thiophene ligands on the surface, and the molar ratio of gold-coated silver nanowires with sulfur-containing halogenated thiophene ligands to multi-walled carbon nanotubes is 5:1; The sulfur-containing halogenated thiophene ligand comprises at least one of fluorothiophene, chlorothiophene, bromothiophene and iodothiophene; when preparing the gold-coated silver nanowires with sulfur-containing halogenated thiophene ligands, the concentration of the ligand solution is 0.1 μM, and the volume of the ligand solution is 500 μL; The hydrophobic sol-gel layer is composed of methyltrimethoxysilane, tetramethyl orthosilicate, methanol and nanometer pure water; the molar ratio of methyltrimethoxysilane, tetramethyl orthosilicate, methanol and nanometer pure water is 1:1:11:

5.

3. The leaf sensor patch for monitoring plant physiology of claim 1, wherein: The resistive blade temperature sensor comprises gold-coated silver nanowires and a flexible PDMS protective layer covering the gold-coated silver nanowires; The flexible substrate PDMS is prepared by mixing PDMS prepolymer and curing agent at a mass ratio of 20:

1.

4. The leaf sensor patch for monitoring plant physiology of claim 1, wherein: The capacitive blade surface humidity sensor comprises a Nafion film and a flexible PDMS protective layer covering the Nafion film; The thickness of the Nafion film is 2 μm.

5. The leaf sensor patch for monitoring plant physiology of claim 1, wherein: The capacitive ambient humidity sensor comprises a Nafion film and a flexible PDMS protective layer covering the Nafion film; The thickness of the Nafion film is 2 μm.

6. The leaf sensor patch for monitoring plant physiology of claim 1, wherein: The shape of the blade sensor patch and the number of sensors in the sensor group are self-adaptively adjusted according to the blade shape.

7. The method of making a blade sensor patch according to any one of claims 1 to 6, wherein, The method comprises the following steps: S1. Fix the mask plate with the cross electrode pattern on the surface of the pretreated polyimide substrate, then use silver nanowire spraying, remove the mask plate, and remove the residual solvent to obtain a substrate printed with a silver nanowire cross electrode; S2. Mix the PDMS prepolymer and the curing agent at a mass ratio of 20:1, vacuum degas, then slowly pour on the substrate obtained in step S1 for stepwise curing, cool to room temperature, and peel off the polyimide substrate to obtain a flexible PDMS substrate with silver nanowire cross electrodes embedded in the inside; S3. The electrode nodes are exposed using a porous PDMS mask, and then different sensing materials are deposited on the electrode regions respectively to obtain the leaf sensor patch: gold-coated silver nanowires are deposited on the electrode regions, and a flexible PDMS protective layer is covered after drying to obtain a resistance type leaf temperature sensor; Nafion films are deposited on different electrode regions respectively, and a flexible PDMS protective layer is covered after drying to obtain a capacitance type leaf surface humidity sensor and a capacitance type ambient humidity sensor; a mixed sensing layer is deposited on the electrode regions, and a hydrophobic sol-gel layer is covered after drying to obtain a resistance type volatile organic compound sensor.

8. The method of claim 7, wherein the leaf sensor patch is prepared by, At least one of the following is included: In step S1, the pretreatment method of the polyimide substrate is as follows: a polyimide film with a thickness of 50-100 μm is sequentially cleaned with acetone and isopropyl alcohol by ultrasonic cleaning, dried with nitrogen, and then placed in a plasma cleaning machine for treatment; In step S2, the stepwise curing is specifically as follows: first, low-temperature pre-curing at 40-50°C for 1-2 hours, then main curing at 80-100°C for 1-2 hours, and finally post-curing at 120-150°C for 0.5-1 hour.

9. The method of claim 7, wherein the blade sensor patch is prepared by, At least one of the following is included: In step S3, the thickness of the Nafion film is 2 μm; In step S3, the mixed sensing layer is obtained by mixing gold-coated silver nanowires modified with sulfur-containing halogenated thiophene ligands and multi-walled carbon nanotubes, and the molar ratio of the gold-coated silver nanowires modified with sulfur-containing halogenated thiophene ligands to the multi-walled carbon nanotubes is 5:1; In step S3, when the gold-coated silver nanowires modified with sulfur-containing halogenated thiophene ligands are prepared, the concentration of the ligand solution is 0.1 μM, and the volume of the ligand solution is 500 μL; In step S3, the hydrophobic sol-gel layer is obtained by mixing methyltrimethoxysilane, tetramethyl orthosilicate, methanol and nanometer pure water, and the molar ratio of methyltrimethoxysilane, tetramethyl orthosilicate, methanol and nanometer pure water is 1:1:11:

5.

10. Use of a blade sensor patch according to any one of claims 1 to 6, or a blade sensor patch prepared by the method according to any one of claims 7 to 9, characterized in that: The shape of the leaf sensor patch and the number of sensors in the sensor group are adjusted according to the shape of the leaf, and the surface with a higher stomatal density is selected as the attachment position of the leaf sensor patch; the patch is attached to the selected surface of the leaf, and the resistance type leaf temperature sensor is in direct contact with the leaf surface, the resistance type volatile organic compound sensor and the capacitance type leaf surface humidity sensor face the leaf, and the capacitance type ambient humidity sensor extends outward from the edge of the leaf and is completely exposed to the air; The leaf sensor patch and the data acquisition system are connected through wires to monitor the plant physiological signals.

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