A flexible wearable sensor for detecting net photosynthetic rate of plants and a preparation method and application thereof

Abstract

The application discloses a flexible wearable sensor for detecting net photosynthetic rate of plants and a preparation method and application thereof, and the sensor is composed of a fixing layer, a substrate layer, an electrode layer and a conductive layer, and stretchable net structures are formed at both ends of the substrate layer; the electrode layer is a concentric circle sensing electrode, so that a uniform radial alternating current field is generated, and the conductive layer is closely attached to the surface of the leaf to reduce the interface contact impedance. The detection system constructed by the sensor can effectively solve the technical problem that the net photosynthetic rate of plants cannot be monitored in a long-term, non-destructive, real-time and in-situ manner in the prior art according to the high correlation between the alternating impedance parameters of the plant leaves under a specific characteristic frequency and the ion exchange of the leaf cells, by in-situ collection of the impedance change of the leaves, and by combination of environmental parameters, to calculate the net photosynthetic rate.

Description

Technical Field

[0001] This invention relates to the field of plant physiological information detection technology, and more specifically, to a flexible wearable sensor system for detecting the net photosynthetic rate of plants. Based on flexible impedance analysis and distributed computing technology, this system enables in-situ, non-destructive, and long-term continuous monitoring of the net photosynthetic rate of plant leaves. Background Technology

[0002] Net photosynthetic rate (NPR) is a core physiological indicator for measuring a plant's photosynthetic capacity, assessing its growth status, light energy utilization efficiency, and tolerance to environmental stress. Accurate acquisition of NPR data is crucial for precision agriculture management, plant phenotyping, crop genetics and breeding, and global carbon cycle research.

[0003] Currently, NPR detection primarily relies on commercially available photosynthesis meters (such as the LI-COR LI-6400 / 6800 series) based on Infrared Gas Analyzer (IRGA). While these devices offer high measurement accuracy, traditional photosynthesis meters are bulky and power-consuming, making it difficult to conduct long-term, synchronous, continuous monitoring of a large number of plants in complex field environments, thus failing to meet the demands of high-throughput plant phenotypic analysis. Measurements require clamping leaves into closed or semi-closed leaf chambers, a process that significantly alters the leaf surface microenvironment (such as temperature, humidity, and airflow patterns), leading to changes in stomatal conductance and introducing measurement errors. Furthermore, the clamping force of the leaf chambers can cause physical damage to the leaves, preventing truly non-destructive, in-situ long-term monitoring.

[0004] In recent years, with the development of flexible electronics technology, researchers have begun to explore the application of flexible sensors in in-situ monitoring of physiological information on plant surfaces. However, existing research on flexible wearable sensors mainly focuses on monitoring single environmental parameters (such as temperature and humidity) or plant water content, lacking an integrated, multimodal sensing scheme that can directly link to key processes of photosynthesis (such as stomatal movement and changes in ion flow).

[0005] In summary, developing a flexible wearable system capable of long-term, non-destructive, and real-time monitoring of plant net photosynthetic rate is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In response to the needs of existing plant photosynthetic rate monitoring technologies in application scenarios such as continuous in-situ monitoring, flexible attachment, and multi-point deployment, this invention aims to provide a flexible wearable sensor system for detecting plant net photosynthetic rate, so as to solve the technical problem that existing technologies cannot perform long-term, non-destructive, real-time, and in-situ monitoring of plant net photosynthetic rate.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0008] A flexible wearable sensor for detecting net photosynthetic rate in plants, comprising:

[0009] A breathable fixing layer is provided for bonding and fixing to the test object;

[0010] A base layer is provided on the surface of the fixed layer, an electrode layer is provided in the middle region of the base layer, and a stretchable mesh structure is provided at both ends of the base layer;

[0011] The electrode layer is patterned into concentric circular sensing electrodes to generate a uniform radial alternating electric field. The two poles of the concentric circular sensing electrodes are connected to the contact pads at both ends through internal connecting leads, and are electrically connected to the external connecting wires.

[0012] A conductive layer is provided outside the electrode layer.

[0013] Furthermore, the substrate layer is selected from polydimethylsiloxane (PDMS) film.

[0014] Furthermore, multiple rows of staggered parallel slits are pre-cut at both ends of the PDMS film. When no external force is applied, these slits remain closed, maintaining the integrity of the film. When the sensor is subjected to axial or lateral tensile stress, these staggered slits will undergo out-of-plane and in-plane deformation and open rapidly, spontaneously evolving into a three-dimensional hexagonal honeycomb mesh.

[0015] Furthermore, the electrode layer is formed by screen printing using conductive silver paste.

[0016] Furthermore, the conductive layer is made of hydrogel.

[0017] A method for fabricating a flexible wearable sensor for detecting net photosynthetic rate in plants includes the following steps:

[0018] Step 1: Mix the PDMS prepolymer and curing agent in a certain proportion and degas under vacuum. Then spin-coat the mixture onto a flat glass substrate that has been cleaned and heat-cured under constant temperature conditions.

[0019] Step 2: Based on the pattern of concentric sensing electrodes and contact pads, a stainless steel wire mesh stencil is made. After oxygen plasma hydrophilic treatment of the PDMS surface, flexible conductive silver paste is screen-printed onto the surface of the substrate layer. Then, it is baked to form an integral electrode layer.

[0020] Step 3: For the PDMS film with electrodes, regular intersecting parallel slits are cut in the non-electrode regions at both ends of the substrate layer to obtain a stretchable mesh structure.

[0021] Step 4: Prepare a KCl-doped polyvinyl alcohol / polyacrylamide hydrogel precursor solution, and coat it onto the effective test area surface of the concentric circular sensing electrode using a mask printing method; crosslink the precursor by ultraviolet light irradiation to form a three-dimensional network semi-solid conductive layer.

[0022] Step 5: At the contact pads, use conductive silver paste to firmly connect the external connecting wires; finally, cover the back of the sensor except for the hydrogel test area and the honeycomb slit stretching areas at both ends with an attachment and fixing layer to complete the fabrication.

[0023] Furthermore, the PDMS prepolymer and curing agent are mixed at a mass ratio of 10:1.

[0024] Furthermore, a stretchable mesh structure was prepared using ultraviolet laser cold processing.

[0025] A system for detecting net photosynthetic rate in plants, comprising:

[0026] Flexible wearable sensors are attached to the surface of the test object to acquire impedance data;

[0027] A flexible system circuit connected to a flexible wearable sensor integrates an impedance detection module and a wireless communication module. The impedance detection module includes an excitation signal generation unit and a response signal extraction unit. The excitation signal generation unit comprises a microcontroller, a waveform generation module, and an excitation signal conditioning circuit connected in sequence, which inputs the generated excitation current to the concentric circle sensing electrodes. The response signal extraction unit comprises a transimpedance amplifier, an amplitude / phase detection circuit, an ADC sampling module, and a data packaging module connected in sequence, which outputs the impedance information detected by the concentric circle sensing electrodes. The wireless communication module communicates with an external mobile terminal.

[0028] The external mobile terminal acquires data through the Bluetooth data receiving module. After being filtered by the data preprocessing module, the data is combined with the real-time temperature and light intensity acquired by the environmental parameter acquisition module and input into the net photosynthetic rate conversion model, ultimately outputting the net photosynthetic rate value.

[0029] Furthermore, the flexible system circuitry utilizes a PI flexible substrate.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The substrate layer of this invention not only uses a low Young's modulus PDMS film, but also innovatively introduces a stretchable mesh structure based on the "honeycomb" principle at both ends. This structure, through a specific staggered parallel slit design, maintains the integrity of the membrane shape when not under stress, while opening to form a three-dimensional hexagonal honeycomb mesh when subjected to wind pulling or blade growth expansion. This structure can achieve ultra-large strain elongation with extremely low elastic resistance, effectively dissipating mechanical stress and avoiding stress concentration and material fracture problems caused by direct perforation, greatly improving the stability of long-term in-situ monitoring in the field.

[0032] 2. This invention adds a hydrogel conductive layer between the conductive silver paste electrode layer and the plant leaf. The hydrogel has excellent biocompatibility and water retention, and can closely adhere to the complex microscopic three-dimensional epidermal structure of the leaf surface, greatly reducing interfacial contact resistance and avoiding the heavy metal ion stress that may result from direct contact between metal materials and the leaf.

[0033] 3. This invention employs a concentric circle sensing electrode array. The concentric circle structure eliminates the electric field distortion caused by sharp edges, forming a more uniform and deeply penetrating edge-radiated electric field within the mesophyll tissue, thereby more accurately capturing intracellular and extracellular ion migration and membrane potential changes caused by photosynthesis.

[0034] 4. This invention uses materials with excellent biocompatibility. Long-term adhesion experiments have verified that it has no adverse effects on plant growth, and the electrode structure is stable, ensuring long-term stable operation of the system.

[0035] 5. This invention adopts a "sensor-end acquisition - mobile-end computing" architecture. The sensor end does not execute complex algorithms, which extends the device life and supports large-scale array deployment. Combined with the advanced TabFPN deep learning model, it significantly improves the detection accuracy of net photosynthetic rate. Attached Figure Description

[0036] Figure 1 A schematic diagram illustrating the overall testing and application scenarios of a flexible wearable sensor system for detecting net photosynthetic rate in plants, provided by this invention.

[0037] Figure 2 This is a schematic diagram of the cross-sectional layers of the flexible wearable sensor of the present invention;

[0038] Figure 3 This is a diagram of the flexible wearable sensor of the present invention in its unstretched state;

[0039] Figure 4 This is a partial enlarged view of the core region of the sensing electrode of the present invention;

[0040] Figure 5 This is a block diagram of the hardware circuit and software algorithm architecture of the system of the present invention;

[0041] Figure 6 A graph showing the relationship between the actual and predicted values ​​of the net photosynthetic rate prediction model established in this invention.

[0042] Figure 7 This is a graph showing the impedance amplitude stability of the system for continuous monitoring of plant leaves according to the present invention.

[0043] Legend:

[0044] 1. Plant leaf; 2. Flexible wearable sensor; 3. External connecting wires; 4. Flexible system circuit board; 5. External mobile terminal; 6. Fixing layer; 7. Substrate layer; 8. Electrode layer; 9. Conductive layer; 10. Stretchable mesh structure; 11. Contact pads; 12. Concentric sensing electrodes; 13. Internal connecting leads; 14. Impedance detection module; 15. Controller MCU; 16. Waveform generation module; 17. Excitation signal conditioning circuit; 18. Transimpedance amplifier; 19. Amplitude / phase detection circuit; 20. ADC sampling module; 21. Data packaging module; 22. Wireless communication module; 23. Bluetooth data receiving module; 24. Data preprocessing module; 25. Environmental parameter acquisition module; 26. Net photosynthetic rate conversion model; Detailed Implementation

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] A flexible wearable sensor for detecting net photosynthetic rate in plants, the structure of which is as follows: Figure 1 , 2 As shown in Figures 3 and 4. Figure 1 In a practical application scenario, using a pothos (Epipremnum aureum) as the test object, the flexible wearable sensor 2 was attached to the back of the pothos leaf 1.

[0047] like Figure 2 As shown, the four-layer core physical structure of the flexible wearable sensor 2 is as follows:

[0048] 1. Fixing layer 6 is breathable, allowing water vapor to pass through, and can adhere and fix to the leaf to be tested; in this embodiment, medical microporous breathable tape is used, whose surface is distributed with a large number of micron-sized pores, and its water vapor permeability is not less than 2000g / m³. 2 / 24h. This ensures normal exchange of carbon dioxide (CO2) and water vapor (H2O) between the stomata on the underside of the leaves of the pothos plant and the external environment, avoiding localized decreases in CO2 concentration or increases in humidity caused by covering, and eliminating the interference of the "leaf chamber effect" on the true value of net photosynthetic rate.

[0049] 2. The base layer 7 is located on one side of the fixing layer 6 and is made of polydimethylsiloxane (PDMS) film. PDMS has excellent flexibility, transparency and biocompatibility, and can achieve conformal adhesion to the plant leaf 1.

[0050] 3. Electrode layer 8: Attached to the surface of the base layer 7, it is printed with conductive silver paste through screen printing process and is responsible for transmitting the weak physiological electrical signals of the pothos leaves to the external circuit.

[0051] 4. Conductive layer 9: A layer of hydrogel is coated between the electrode layer 8 and the plant leaf 1. The hydrogel has excellent water retention and ionic conductivity, which can perfectly fill the three-dimensional micro-folds of the epidermis of the plant leaf 1 and significantly reduce the interfacial contact impedance between the silver paste electrode and the mesophyll tissue.

[0052] The graphical and innovative mechanical structure design of the flexible wearable sensor 2 is as follows: Figure 3 and Figure 4 As shown.

[0053] To address the challenges posed by wind swaying and the natural growth and expansion of leaves in the pothos plant (1) under field conditions, this invention incorporates a unique stretchable mesh structure (10) at both ends of the base layer (7). This structure draws inspiration from the mechanical expansion principle of a honeycomb: multiple rows of staggered parallel slits are pre-cut into the PDMS film (i.e., adjacent rows of slits are staggered by half a cycle). When no external force is applied, these slits remain closed, maintaining the integrity of the film. When the sensor is subjected to axial or lateral tensile stress, these staggered slits undergo out-of-plane and in-plane deformation and rapidly open, spontaneously evolving into a three-dimensional hexagonal honeycomb mesh. This unique honeycomb stretchable structure endows the sensor with extremely high stretchability, effectively dissipating mechanical strain energy and preventing displacement or tearing during the dynamic growth of the leaves.

[0054] In the central test area of ​​the sensor, the electrode layer 8 is patterned into concentric circle sensing electrodes 12. The concentric circle pattern can generate a uniform radial alternating electric field, which can effectively penetrate the cuticle of the pothos leaf. The two poles of the concentric circle sensing electrodes 12 are extended to the contact pads 11 at both ends through internal connecting leads 13, so as to form a stable electrical connection with the external connecting wires 3.

[0055] To further illustrate the feasibility of the present invention, a detailed fabrication process for the flexible wearable sensor 2 is provided. A method for fabricating a flexible wearable sensor for detecting the net photosynthetic rate of plants includes the following steps:

[0056] Step 1: Preparation of flexible substrate layer 7

[0057] The PDMS prepolymer and curing agent were mixed at a mass ratio of 10:1 and vacuum degassed before being spin-coated onto a cleaned, flat glass substrate. The spin-coating speed was controlled to precisely maintain the thickness between 50 μm and 100 μm, and the mixture was heat-cured at a constant temperature of 80°C for 2 hours.

[0058] Step 2: Screen printing of electrode layer 8

[0059] A stainless steel wire mesh stencil was fabricated based on the pattern of the concentric sensing electrodes 12 and contact pads 11. After a short-term oxygen plasma hydrophilic treatment of the PDMS surface, flexible conductive silver paste was screen-printed onto the surface of the substrate layer 7. Subsequently, it was placed in an oven and baked at 120°C for 30 minutes to sinter the silver paste to make it conductive, thus forming the electrode layer 8 in one piece.

[0060] Step 3: Laser cutting of the stretchable mesh structure 10 (honeycomb biomimetic processing)

[0061] The PDMS film with electrodes is placed flat on the UV laser cutting machine platform. The CAD processing trajectory of the "interlaced parallel slit" array is imported. Utilizing the cold processing characteristics of UV laser, regular interlaced slits are cut into the non-electrode areas at both ends of the substrate layer 7. These slits do not remove any solid material, thereby forming a stretchable mesh structure 10 based on the honeycomb unfolding principle.

[0062] Step 4: Coating and cross-linking of conductive layer 9

[0063] A KCl-doped polyvinyl alcohol / polyacrylamide (PVA / PAM) hydrogel precursor solution was prepared. It was precisely coated onto the surface of the effective testing area of ​​the concentric circular sensing electrode 12 using a mask printing method. The precursor was then cross-linked by ultraviolet light irradiation to form a three-dimensional network semi-solid conductive layer 9 with a thickness of approximately 20 μm.

[0064] Step 5: Encapsulation and wire connection

[0065] At the contact pad 11, conductive silver paste is used to firmly connect the external connecting wire 3. Finally, medical microporous breathable tape is applied as a fixing layer 6 to the back of the sensor, except for the hydrogel test area and the honeycomb slit stretching areas at both ends, to complete the fabrication.

[0066] A system for detecting net photosynthetic rate in plants was constructed based on the aforementioned flexible wearable sensor. The flexible wearable sensor 2 is connected to the flexible system circuit board 4 via an external connecting wire 3. The system circuit 4 is responsible for collecting signals and wirelessly transmitting the data to an external mobile terminal 5, such as a smartphone, via Bluetooth. The external mobile terminal 5 performs the inversion calculation and real-time visualization of the net photosynthetic rate. Its core innovation lies in the fact that an increased photosynthetic rate accelerates electron transfer, leading to the formation of a proton kinetic potential across the thylakoid membrane, causing ion transmembrane transport, increasing the intracellular ion concentration, and reducing leaf impedance. By utilizing the high correlation between the AC impedance parameter of plant leaves at a specific characteristic frequency (1kHz) and ion exchange in mesophyll cells, the net photosynthetic rate is calculated by in-situ collecting changes in leaf impedance and combining it with environmental parameters.

[0067] The distributed computing hardware links of this system are as follows: Figure 5 As shown:

[0068] The flexible system circuit 4 integrates an impedance detection module 14 and a wireless communication module 22 via surface mount technology (SMT). A microcontroller 15 controls a waveform generation module 16 to generate a 300mV, 1kHz sinusoidal AC voltage signal, which is applied to concentric sensing electrodes 12 via an excitation signal conditioning circuit 17. The weak response current flowing through the plant leaf tissue 1 is received by a transimpedance amplifier 18 and converted into a voltage signal. An amplitude / phase detection circuit 19 extracts the DC level reflecting the impedance magnitude and the digital value reflecting the time difference of the phase angle. An ADC sampling module 20 digitizes the magnitude and sends it to a data packaging module 21 for encapsulation. The data is transmitted in real-time via the wireless communication module 22 at a frequency of 2Hz. Because the flexible system circuit board 4 uses polyimide (PI) as a flexible substrate, its thickness is controlled between 12.5μm and 50μm to ensure the overall bendability of the circuit, allowing it to adapt to the complex curvature of leaves and stems, and maintaining the stability of the electrical connection even when subjected to external bending forces.

[0069] The external mobile terminal 5 acquires data through the Bluetooth data receiving module 23. After being filtered by the data preprocessing module 24, the data is combined with the real-time temperature and light intensity acquired by the environmental parameter acquisition module 25 and input into the net photosynthetic rate conversion model 26 (TabFPN model) deployed on the mobile phone. Finally, the net photosynthetic rate value is output.

[0070] To verify the accuracy and reliability of this invention, a series of comparative experiments were conducted. The sensor of this invention was attached to the underside of a pothos leaf, and the same leaf was simultaneously monitored using a LI-6800 portable photosynthesis meter (as a reference standard). Recordings were continuously conducted for 24 hours under natural photoperiod variations. Experimental data showed that at a frequency of 1 kHz, the trend of impedance modulus changes measured by the sensor was highly consistent with the trend of net photosynthetic rate changes measured by the LI-6800. Figure 6 As shown, a linear regression analysis was performed on the measured values ​​of impedance change rate and net photosynthetic rate, and the coefficient of determination (R²) was calculated. 2 The result reached 0.96, verifying that the sensor of this invention has good measurement consistency with commercial standard instruments.

[0071] The sensor was continuously attached to the surface of pothos leaves for 10 days to monitor the impedance signal. The results showed that, after eliminating the influence of environmental fluctuations, the baseline impedance value of the sensor remained stable, and no signal drift was observed due to electrode aging or interface degradation. Figure 7 As shown. After 10 days, the sensor was removed, and the area where the leaf was attached was observed. No visible tissue damage, yellowing, or necrosis was observed. The plant was then cultured for another week after the sensor was removed, and new leaves grew normally, indicating that the sensor system has no adverse effects on the long-term growth of the plant.

[0072] In summary, the flexible wearable sensor system provided in this embodiment has successfully achieved long-term, in-situ, non-destructive, and real-time monitoring of the net photosynthetic rate of pothos leaves, verifying the feasibility and superiority of its technical solution.

[0073] The above embodiments are only used to illustrate the design concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications made based on the principles and design ideas disclosed in the present invention are within the protection scope of the present invention.

Claims

1. A flexible wearable sensor for detecting net photosynthetic rate in plants, characterized in that, include: A breathable fixing layer (6) is provided for bonding and fixing to the test object; A base layer (7) is provided on the surface of the fixed layer (6), an electrode layer (8) is provided in the middle region of the base layer (7), and a stretchable mesh structure (10) is provided at both ends of the base layer (7). The electrode layer (8) is patterned into concentric circle sensing electrodes (12) to generate a uniform radial alternating electric field. The two poles of the concentric circle sensing electrodes (12) are extended to the contact pads (11) at both ends through internal connecting leads (13) and are electrically connected to the external connecting wires (3). A conductive layer (9) is provided outside the electrode layer (8).

2. The flexible wearable sensor for detecting net photosynthetic rate in plants according to claim 1, characterized in that, The substrate layer (7) is selected from polydimethylsiloxane (PDMS) film.

3. The flexible wearable sensor for detecting net photosynthetic rate in plants according to claim 1, characterized in that, Multiple rows of staggered parallel slits are pre-cut at both ends of the PDMS film. When no external force is applied, these slits remain closed, maintaining the integrity of the film. When the sensor is subjected to axial or lateral tensile stress, these staggered slits will undergo out-of-plane and in-plane deformation and open rapidly, spontaneously evolving into a three-dimensional hexagonal honeycomb mesh.

4. A flexible wearable sensor for detecting net photosynthetic rate in plants according to claim 1, characterized in that, The electrode layer (8) is printed using conductive silver paste through a screen printing process.

5. A flexible wearable sensor for detecting net photosynthetic rate in plants according to claim 1, characterized in that, The conductive layer (9) is made of hydrogel.

6. A method for fabricating a flexible wearable sensor for detecting net photosynthetic rate in plants, characterized in that, Includes the following steps: Step 1: Mix the PDMS prepolymer and curing agent in a certain proportion and degas under vacuum. Then spin-coat the mixture onto a flat glass substrate that has been cleaned and heat-cured under constant temperature conditions. Step 2: Based on the pattern of the concentric sensing electrode (12) and the contact pad (11), a stainless steel wire mesh is made. After the PDMS surface is treated with oxygen plasma hydrophilic treatment, flexible conductive silver paste is screen-printed onto the surface of the substrate layer (7) through the wire mesh. Then, baking (30) is performed to form an electrode layer (8) in one piece. Step 3: For the PDMS film with electrodes, regular intersecting parallel slits are cut in the non-electrode areas at both ends of the substrate layer (7) to obtain a stretchable mesh structure (10). Step 4: Prepare a KCl-doped polyvinyl alcohol / polyacrylamide hydrogel precursor solution and coat it onto the effective test area surface of the concentric circle sensing electrode (12) by mask printing. The precursor is cross-linked by ultraviolet light irradiation to form a three-dimensional network semi-solid conductive layer. Step 5: At the contact pad (11), use conductive silver paste to firmly connect the external connecting wire (3); finally, cover the back of the sensor except for the hydrogel test area and the honeycomb slit stretching area at both ends with the attachment fixing layer (6) to complete the preparation.

7. A method for fabricating a flexible wearable sensor for detecting net photosynthetic rate in plants according to claim 6, characterized in that, The PDMS prepolymer and curing agent are mixed at a mass ratio of 10:

1.

8. A method for fabricating a flexible wearable sensor for detecting net photosynthetic rate in plants according to claim 6, characterized in that, Stretchable mesh structures were prepared by ultraviolet laser cold processing (10).

9. A system for detecting net photosynthetic rate in plants, characterized in that, include: A flexible wearable sensor (2) is attached to the surface of the test object to obtain impedance data; A flexible system circuit (4) is connected to the flexible wearable sensor (2). The flexible system circuit (4) integrates an impedance detection module (14) and a wireless communication module (22). The impedance detection module (14) includes an excitation signal generation unit and a response signal extraction unit. The excitation signal generation unit includes a microcontroller (15), a waveform generation module (16), and an excitation signal conditioning circuit (17) connected in sequence, which input the generated excitation current to the concentric circle sensing electrode (12). The response signal extraction unit includes a transimpedance amplifier (18), an amplitude / phase detection circuit (19), an ADC sampling module (20), and a data packaging module (21) connected in sequence, which output the impedance information detected by the concentric circle sensing electrode (12). The wireless communication module (22) communicates with an external mobile terminal (5). The external mobile terminal (5) acquires data through the Bluetooth data receiving module (23), and after being filtered by the data preprocessing module (24), it is combined with the real-time temperature and light intensity acquired by the environmental parameter acquisition module (25) and input into the net photosynthetic rate conversion model (26) to finally output the net photosynthetic rate value.

10. A system for detecting net photosynthetic rate in plants according to claim 9, characterized in that, The flexible system circuit (4) uses a PI flexible substrate.

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