Plant growth monitoring sensor based on bionic structure and preparation method

Abstract

The invention discloses a plant growth monitoring sensor based on a bionic structure and a preparation method, and relates to the technical field of plant growth monitoring. The design inspiration of the sensor is derived from a micron-sized slit receptor of a scorpion, a bionic gradient V-shaped groove structure is adopted, the structure can provide high sensitivity through a deep V-shaped groove under small strain, meanwhile, through the design of a deep-shallow double-channel V-shaped groove, the sensitivity of the sensor is improved, and the sensitivity of the sensor is improved. High sensitivity and stability of the sensor can be guaranteed through the shallow V-shaped groove under large strain, balance between high sensitivity and wide working range is achieved through the double-channel design, the balance is difficult to achieve in an existing flexible sensor, ultrahigh sensitivity can be kept within the strain range of 0%-18%, the highest sensitivity coefficient can reach 199.98, and the sensor can be widely applied to the field of flexible sensors. Therefore, the sensor provided by the invention has the advantage of balance between high sensitivity and wide detection range.

Description

Technical Field

[0001] The present invention relates to the technical field of plant growth monitoring, and specifically to a plant growth monitoring sensor based on a bionic structure and a preparation method thereof. Background Art

[0002] In the field of plant growth monitoring, traditional monitoring methods include remote sensing technology, hyperspectral reflection, infrared thermal imaging, and unmanned aerial vehicle (UAV) image recognition. Remote sensing technology uses sensors on platforms such as satellites and airplanes to obtain electromagnetic wave information at a distance. Based on the differences in the reflection, absorption, and emission of electromagnetic waves by plants in different growth states, data is analyzed to identify plant species and judge health conditions, etc. Hyperspectral reflection technology obtains the reflection spectral data of plants in hundreds to thousands of continuous narrow bands, thereby accurately obtaining physiological information such as plant pigment content and leaf structure, and then inferring the growth status of plants. Infrared thermal imaging technology collects the infrared radiation on the surface of plants through an infrared thermal imager and converts it into a thermal image. According to the temperature distribution, transpiration and water conditions are evaluated to judge its health degree. UAV image recognition technology uses the high-resolution camera carried to obtain high-definition images from multiple angles, and uses image recognition algorithms to obtain information such as the number of plants, plant height, and leaf area for large-scale farmland monitoring.

[0003] With the development of flexible electronics technology, researchers have begun to try to use flexible electronics technology to make wearable sensors to achieve plant monitoring. For example, some researchers have developed and designed a wearable strain sensing system based on highly stretchable conjugated polymers for monitoring the growth rate of grass leaves and environmental responses, which has high sensitivity. Researchers have designed a stretchable multi-sensory wearable system that can monitor the growth direction of plants and environmental responses by integrating multi-parameter sensing capabilities (strain, temperature, humidity, stress distribution, etc.).

[0004] Traditional monitoring methods are easily affected by the environment, and there are problems such as complex data processing, limited image resolution, response delay, low accuracy, and insufficient resolution, making it difficult to deeply explore the internal physiological processes of plants, unable to accurately detect subtle changes, and unable to meet the requirements of real-time and accurate monitoring in precision agriculture.

[0005] Most of the existing flexible sensors can only improve sensitivity or expand the sensing range separately, and it is difficult to balance both, resulting in the inability to accurately monitor the dynamic growth process of plants in practical applications.

[0006] Therefore, a new solution needs to be proposed for the above problems. Summary of the Invention

[0007] The object of the present invention is to provide a plant growth monitoring sensor based on a bionic structure and a preparation method thereof, so as to obtain a wearable plant growth sensor based on a bionic gradient V-groove structure that is easy to prepare and can simultaneously achieve high sensitivity and a wide working range, and solve the technical problems proposed in the background art.

[0008] To achieve the above object, the present invention provides the following technical solution: A preparation method of a plant growth monitoring sensor based on a bionic structure, at least including the following steps:

[0009] S1: Use a commercial engraving machine to cut a bionic gradient V-groove pattern on a PET film. The bionic gradient V-grooves are distributed in an arc-shaped circumference, and the distance between the grooves is 0.5 mm;

[0010] S2: Template preparation. Prepare an epoxy resin solution, uniformly coat it on the cut PET film, put the PET coated with epoxy resin into a vacuum drying oven, and dry it at 60 °C for 3 hours to obtain a template;

[0011] S3: Prepare a PDMS film. Prepare a PDMS solution with a ratio of 10:1, coat it on the prepared template, place the template containing the PDMS solution in a vacuum drying oven, and dry it at 55 °C for 3 hours to obtain a PDMS film;

[0012] S4: Coating preparation. Attach the dried PDMS film to the substrate of a vacuum evaporation coating device, place it in the chamber of the device, put pure chromium particles in a tungsten boat, and add a small amount of silver particles in another tungsten boat;

[0013] S5: Evacuate. Close the vacuum chamber door, start the automatic vacuum pumping system, and keep running until the vacuum degree in the chamber drops below 1×10 -3 MPa;

[0014] S6: Evaporation coating. Set the evaporation current to 120 mA, start the evaporation coating process. Under vacuum conditions, first deposit a chromium layer. Observe it in real time through a film thickness monitor. When the thickness of the chromium layer reaches 10 nm, terminate the evaporation coating. Adjust the evaporation current to 80 mA, start the evaporation coating program again, continuously monitor the film thickness, and end the evaporation coating process when the thickness of the silver layer reaches 120 nm to complete the preparation.

[0015] Further, the epoxy resin solution is prepared by using epoxy resin and a curing agent in a ratio of 3:1.

[0016] Further, the PDMS solution is prepared by using a PDMS matrix and a crosslinking agent in a ratio of 10:1.

[0017] Further, the pure chromium particles used are 0.1 g, and the silver particles used are 0.8 g.

[0018] A new technical solution is further proposed:

[0019] The plant growth monitoring sensor based on the bionic structure is obtained by processing through the preparation method of the plant growth monitoring sensor based on the bionic structure, and the plant growth monitoring sensor based on the bionic structure is a flexible resistive sensor.

[0020] Further, the plant growth monitoring sensor based on the bionic structure includes a PDMS thin film substrate, a silver layer, and 24 groups of bionic gradient V-grooves;

[0021] When the sensor is affected by external stress, the distance between the conductive metal particles in the bionic gradient V-groove will change, and then the tunneling effect will occur, resulting in a corresponding change in the resistance value of the sensor, thereby generating ultra-high sensitivity;

[0022] The PDMS thin film substrate, as a flexible substrate, has good flexibility and biocompatibility;

[0023] The silver layer, as a conductive layer, is uniformly deposited on the surface of the PDMS thin film substrate by vacuum evaporation technology;

[0024] The 24 groups of bionic gradient V-grooves are arranged in an arc-shaped circumference, and each group of bionic gradient V-grooves includes a shallow V-groove and a deep V-groove;

[0025] The deep V-groove is used to detect small deformations. Because within the small strain range, the distance between the silver nanoparticles in the deep V-groove changes significantly, and then the tunneling effect caused causes a significant change in the resistance value of the sensor. As the strain increases, the internal deformation of the deep V-groove gradually increases when it is subjected to tensile force, and the distance between the conductive elements in the deep V-groove also gradually expands. And this distance expansion caused by deformation continues to develop, eventually exceeding the effective range of the tunneling effect, resulting in the sensor being unable to detect such changes, thus making the situation beyond the detection range of the sensor;

[0026] On the contrary, the shallow V-groove is used to detect large deformations. The V-groove is shallower. When there is a small deformation, the change in the distance between the nanoparticles in the V-groove is not obvious. As the strain increases significantly, the distance between the nanoparticles in the shallow V-groove changes significantly, and the tunneling effect caused causes a significant change in the resistance value of the sensor. Therefore, it plays a key role in large strain detection;

[0027] One deep and one shallow V-groove maintain good responses under small and large strains respectively, ensuring the stability and high sensitivity of the entire sensor within a wide strain range.

[0028] Further, the depth of the shallow V-shaped groove is 56.24 μm and the width is 115.74 μm; the depth of the deep V-shaped groove is 110.34 μm and the width is 162.43 μm.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. The design inspiration of the sensor of the present invention comes from the micron-scale slit receptors of scorpions, and a bionic gradient V-shaped groove structure is adopted. This structure can not only provide high sensitivity through the deep V-shaped groove under small strain, but also ensure the high sensitivity and stability of the sensor through the shallow V-shaped groove under large strain by designing a double-channel V-shaped groove with one deep and one shallow. Through this double-channel design, the balance between high sensitivity and wide working range is achieved, which is difficult to achieve in existing flexible sensors. It can maintain ultra-high sensitivity in the strain range of 0% - 18%, and the highest sensitivity coefficient can reach 199.98. Therefore, the sensor of the present invention has the advantage of the balance between high sensitivity and wide detection range. Traditional sensors usually can only choose between high sensitivity and wide detection range and it is difficult to take both into account. However, the present invention successfully solves this problem through the bionic gradient V-shaped groove structure, which enables the sensor to provide accurate monitoring under both small deformation and large deformation, greatly improving the performance and application range of the sensor.

[0031] 2. The present invention combines a simple secondary casting method and a vacuum evaporation technology. The preparation process is simple and the cost is low. Compared with the complex and high-cost preparation processes of traditional flexible sensors, the technology of the present invention breaks through the bottlenecks of cost and large-scale production, and can achieve large-scale production and low-cost application.

[0032] 3. The sensor of the present invention can maintain good stability under different environmental conditions, overcoming the problem that traditional plant monitoring methods are easily interfered in complex environments. This high environmental adaptability and stability make the sensor have strong operability in practical applications. Description of the Drawings

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0034] Figure 1 It is a schematic structural diagram of the sensor of the present invention;

[0035] Figure 2 It is a resistance response diagram of the sensor of the present invention under different strain states;

[0036] Figure 3 Resistance response diagram of the sensor of the present invention at different humidities;

[0037] Figure 4 Resistance response diagram of the sensor of the present invention at different temperatures;

[0038] Figure 5 Resistance response diagram of the sensor of the present invention when immersed in water and in a dry state;

[0039] Figure 6 24-hour growth curve of pineapple monitored by the sensor of the present invention.

[0040] In the figure: 1. PDMS film substrate; 2. Silver layer; 3. Shallow V-shaped groove; 4. Deep V-shaped groove. Detailed implementation manners

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0042] Embodiment 1:

[0043] This embodiment is used to disclose a preparation method of a plant growth monitoring sensor based on a bionic structure, which at least includes the following steps:

[0044] S1: Use a commercial engraving machine to cut a bionic gradient V-shaped groove pattern on a PET film. The bionic gradient V-shaped grooves are distributed in an arc-shaped circumference, and the distance between the grooves is 0.5 mm;

[0045] S2: Template preparation. Prepare an epoxy resin solution, uniformly coat it on the cut PET film, and place the PET coated with epoxy resin in a vacuum drying oven and dry it at 60 °C for 3 hours to obtain a template;

[0046] S3: Prepare a PDMS film. Prepare a PDMS solution with a ratio of 10:1, coat it on the prepared template, and place the template containing the PDMS solution in a vacuum drying oven and dry it at 55 °C for 3 hours to obtain a PDMS film;

[0047] S4: Coating preparation. Attach the dried PDMS film to the substrate of a vacuum evaporation coating device, and place it in the chamber of the device. Place pure chromium particles in a tungsten boat and add a small amount of silver particles to another tungsten boat;

[0048] S5: Evacuate. Close the vacuum chamber door, start the automatic vacuum pumping system, and keep running until the vacuum degree in the chamber drops below 1×10 -3 MPa;

[0049] S6: Evaporation coating. Set the evaporation current to 120 mA and start the evaporation coating process. Under vacuum conditions, first deposit a chromium layer. Observe it in real time through a film thickness monitor. When the thickness of the chromium layer reaches 10 nm, terminate the evaporation coating. Adjust the evaporation current to 80 mA and start the evaporation coating process again. Continuously monitor the film thickness. When the thickness of the silver layer reaches 120 nm, end the evaporation coating process to complete the preparation.

[0050] The epoxy resin solution is prepared by mixing epoxy resin and curing agent in a ratio of 3:1.

[0051] The PDMS solution is prepared by mixing a PDMS matrix and a crosslinking agent in a ratio of 10:1.

[0052] The amount of pure chromium particles used is 0.1 g, and the amount of silver particles used is 0.8 g.

[0053] The existing preparation process of flexible sensors is complex and costly, making it difficult to be applied on a large scale. In this embodiment, the sensor uses a simple secondary casting method and vacuum evaporation coating technology, with a simple preparation process and low cost. By cutting a PET film with a commercial engraving machine and then coating it with an epoxy resin solution as a template, large-scale preparation can be achieved. This low-cost preparation process enables the sensor to be widely used in large-scale farmland monitoring. The sensor can be deployed on each plant at low cost to achieve real-time monitoring of each plant, providing technical support for the popularization of precision agriculture.

[0054] Example Two:

[0055] Refer to Figure 1 , this embodiment is used to disclose a plant growth monitoring sensor based on a bionic structure;

[0056] The plant growth monitoring sensor based on a bionic structure is obtained by processing through the preparation method of the plant growth monitoring sensor based on a bionic structure, and the plant growth monitoring sensor based on a bionic structure is a flexible resistive sensor.

[0057] The plant growth monitoring sensor based on a bionic structure includes a PDMS thin film substrate 1, a silver layer 2, and 24 groups of bionic gradient V-shaped grooves;

[0058] The PDMS thin film substrate 1 serves as a flexible substrate, having good flexibility and biocompatibility;

[0059] The silver layer 2 serves as a conductive layer and is uniformly deposited on the surface of the PDMS thin film substrate 1 through vacuum evaporation coating technology;

[0060] The 24 groups of bionic gradient V-shaped grooves are arranged in an arc-shaped circumference. Each group of bionic gradient V-shaped grooves includes a shallow V-shaped groove 3 and a deep V-shaped groove 4;

[0061] The deep V-shaped groove 4 is used to detect small deformations, and the shallow V-shaped groove 3 is used to detect large deformations.

[0062] The depth of the shallow V-shaped groove (3) is 56.24 μm, and the width is 115.74 μm; the depth of the deep V-shaped groove (4) is 110.34 μm, and the width is 162.43 μm. It should be noted that different depth and width dimensions of the V-shaped groove will affect its performance.

[0063] In this embodiment, the sensing mechanism of the plant growth monitoring sensor based on the bionic structure is based on the tunneling effect and the change in the distance between conductive particles.

[0064] When the sensor is affected by external stress, the distance between the conductive metal particles in the bionic gradient V-shaped groove will change. This change will generate a tunneling effect, resulting in a corresponding change in the resistance value of the sensor, thereby generating extremely high sensitivity. Through the bionic gradient V-shaped groove design, at a smaller strain, the deep V-shaped groove 4 plays a dominant role because it causes a more obvious change in the distance between the silver particles. As the strain increases, the internal deformation of the deep V-shaped groove 4 gradually increases. Therefore, the distance between the conductive elements in the deep V-shaped groove 4 also gradually expands. And this distance expansion caused by deformation continues to develop, eventually exceeding the effective range of the tunneling effect, causing the sensor to be unable to detect such changes and exceeding its detection ability. On the contrary, the structural characteristics of the shallow V-shaped groove 3 are highlighted, and the particle spacing changes significantly, playing a key role in large strain detection and ensuring the stability and high sensitivity of the entire sensor within a wide strain range.

[0065] This dual-channel structure enables the sensor to maintain a sensitivity coefficient as high as 199.98 within a strain range of 0% to 14%, breaking through the dilemma that it is difficult to balance high sensitivity and wide detection range in existing sensors. This design enables the sensor to accurately capture the subtle and dynamic strain changes during the plant growth process, providing strong support for precisely monitoring the plant growth state.

[0066] To sum up:

[0067] Most existing flexible sensors can only improve sensitivity or expand the detection range separately, and it is difficult to achieve both at the same time. If the sensor only has high sensitivity and its detection range is narrow, it cannot cope with large strain changes during the plant growth process; on the contrary, if the sensor only has a relatively wide detection range but its sensitivity is low, it is difficult to capture the subtle changes in plant growth. Moreover, traditional plant monitoring methods (such as remote sensing technology, infrared thermal imaging, etc.) are easily affected by environmental factors (such as temperature, humidity, light, etc.), resulting in large fluctuations in monitoring data and making it difficult to work stably in the complex and changeable field environment.

[0068] The sensors of the present invention exhibit good stability under different environmental conditions (such as humidity, temperature, immersion in water, and dry state).

[0069] Refer to Figures 2 - 6 , through experimental tests, under different humidity (40% - 100%), temperature (-10°C to 70°C), and immersion in water conditions, the resistance change rate of the sensor is at a minimum value, indicating that it can maintain stable working performance under different environmental conditions. This environmental stability enables the sensor to work stably in complex field environments for a long time, ensuring the reliability of monitoring data. For example, in tropical regions with high temperature and high humidity, the sensor can still accurately monitor the growth rate of plants, providing reliable decision-making basis for farmers.

[0070] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A method for preparing a plant growth monitoring sensor based on a bionic structure, characterized in that: At least the following steps are included: S1: using a commercial engraving machine to cut a bionic gradient V-shaped groove pattern on a PET film, wherein the bionic gradient V-shaped grooves are distributed in an arc-shaped circle, and the spacing between the grooves is 0.5 mm; S2: Template preparation: prepare epoxy resin solution, evenly coat it on the cut PET film, put the epoxy resin coated PET into a vacuum drying oven, and dry it at 60°C for 3 hours to obtain a template; S3: preparing a PDMS film, preparing a 10:1 PDMS solution, coating it on the prepared template, placing the template containing the PDMS solution in a vacuum drying oven, and drying it at 55° C. for 3 hours to obtain a PDMS film; S4: coating preparation, attaching the dried PDMS film to the substrate of the vacuum evaporation coating device and placing it in the chamber of the device, placing pure chromium particles in a tungsten boat, and adding a small amount of silver particles in another tungsten boat; S5: Evacuate the chamber, close the vacuum chamber door, start the automatic vacuum system, and continue to operate until the vacuum degree in the chamber drops below 1×10 -3 MPa; S6: Evaporation, set the evaporation current to 120mA, start the evaporation process, first deposit the chromium layer under vacuum conditions, and observe in real time through the film thickness monitor. When the thickness of the chromium layer reaches 10nm, stop the evaporation, adjust the evaporation current to 80mA, start the evaporation program again, and continuously monitor the film thickness. When the thickness of the silver layer reaches 120nm, end the evaporation process and complete the preparation.

2. The method for preparing a plant growth monitoring sensor based on a bionic structure according to claim 1, characterized in that: The epoxy resin solution is prepared by mixing epoxy resin and curing agent in a ratio of 3:

1.

3. The method for preparing a plant growth monitoring sensor based on a bionic structure according to claim 1, characterized in that: The PDMS solution is prepared by mixing the PDMS matrix and the cross-linking agent in a ratio of 10:

1.

4. The method for preparing a plant growth monitoring sensor based on a bionic structure according to claim 1, characterized in that: The amount of the pure chromium particles used is 0.1 grams, and the amount of the silver particles used is 0.8 grams.

5. The plant growth monitoring sensor based on bionic structure according to claim 1, characterized in that: The plant growth monitoring sensor based on the bionic structure is obtained by the preparation method of the plant growth monitoring sensor based on the bionic structure according to claims 1 to 4, and the plant growth monitoring sensor based on the bionic structure is a flexible resistive sensor.

6. The plant growth monitoring sensor based on bionic structure according to claim 5 is characterized by: It comprises a PDMS film substrate (1), a silver layer (2) and 24 groups of bionic gradient V-shaped grooves; When the sensor is affected by external stress, the spacing between the conductive metal particles in the bionic gradient V-shaped groove will change, resulting in a tunneling effect, which causes the resistance value of the sensor to change accordingly, resulting in ultra-high sensitivity; The PDMS film substrate (1) is a flexible substrate having good flexibility and biocompatibility; The silver layer (2) is used as a conductive layer and is uniformly deposited on the surface of the PDMS thin film substrate (1) by vacuum evaporation technology; The 24 groups of bionic gradient V-shaped grooves are arranged in an arc-shaped circle, and each group of bionic gradient V-shaped grooves includes a shallow V-shaped groove (3) and a deep V-shaped groove (4); The deep V-shaped groove (4) is used to detect small deformations, because within a small strain range, the spacing between the nanosilver particles in the deep V-shaped groove (4) changes significantly, and the resulting tunneling effect causes the sensor resistance value to change significantly. As the strain increases, the deep V-shaped groove (4) gradually deforms when subjected to tension, and the distance between the conductive elements in the deep V-shaped groove (4) also gradually expands. This distance expansion caused by deformation continues to develop and eventually exceeds the effective range of the tunneling effect, causing the sensor to be unable to detect such changes, thereby causing the situation to exceed the sensor's detection range; On the contrary, the shallow V-groove (3) is used to detect large deformation. The V-groove is shallow. When the deformation is small, the distance between the nanoparticles in the V-groove does not change significantly. As the strain increases significantly, the distance between the nanoparticles in the shallow V-groove (3) changes significantly. The tunneling effect caused by the shallow V-groove causes a significant change in the resistance value of the sensor. Therefore, it plays a key role in large strain detection. One deep and one shallow V-groove maintain good response under small strain and large strain respectively, ensuring the stability and high sensitivity of the entire sensor in a wide strain range.

7. The plant growth monitoring sensor based on bionic structure according to claim 6 is characterized by: The shallow V-shaped groove (3) has a depth of 56.24 μm and a width of 115.74 μm; the deep V-shaped groove (4) has a depth of 110.34 μm and a width of 162.43 μm.

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