RFID tags and passive RFID tag sensors for plants

Abstract

To provide an RFID tag and a passive type RFID tag sensor for plant which can wirelessly measure a dynamic behavior of a plant being raised or a parameter regarding the temperature or a dry / wet state of the plant itself.SOLUTION: An RFID tag comprises: a conductor pattern 11 having an annular opening; an impedance matching part 10 having an IC chip 20 electrically connected to the conductor pattern 11 in the vicinity of the opening; an antenna part 12 which is made of a radiation conductor extending in a first direction and a second direction from the impedance matching part 10; and a plurality of hollow rings 30 having a through hole which are bonded to the antenna part 12. The hollow rings 30 are capable of holding a plant body 40, and the hollow rings 30 are constituted that the plant body 40 can move inside the rings.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to RFID tags and passive RFID tag sensors for plants. [Background technology]

[0002] In a plant factory where plants are cultivated in a closed space, a plant cultivation house, the light, temperature, humidity, and other conditions in the plant cultivation house have been conventionally controlled to create an atmosphere suitable for plant cultivation in order to promote good plant growth (see, for example, Patent Documents 1, 2, 3, and 4). In the plant factory, information on the environmental temperature, humidity, and the like is measured by various sensors installed in the plant factory and sent to a control unit, which controls the air conditioner and the fan that generates the air current so that the values ​​are suitable for plant growth.

[0003] In order to optimize plant growth in such closed spaces, information on the environment inside a plant cultivation greenhouse, such as the ambient temperature and humidity, has been used up until now, but this has not detected the dynamic behavior of plant growth or the wet / dry state of the plants themselves. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-231721 A [Patent Document 2] Patent No. 5841820 [Patent Document 3] Patent No. 6292698 [Patent Document 4] JP 2019-128703 A Summary of the Invention [Problem to be solved by the invention]

[0005] In plant cultivation in a closed-space plant factory, it is possible to control conditions such as temperature and humidity in the plant cultivation house almost uniformly, and in that case, it is possible to control an environment suitable for plant growth by managing the atmosphere in the plant cultivation house based on information such as environmental temperature and environmental humidity. In contrast, in the case of an open-space plant factory, conditions such as temperature and humidity are not uniform, and information such as environmental temperature and environmental humidity measured in the open space may not reflect the state of the plant itself. In order to detect the state of not only plant factories but also plants exposed to the natural environment in an open space, it is necessary to measure parameters related to the temperature and wet / dry state of the plant itself.

[0006] When sensing the condition of plants in such open spaces in the field, the issues that arise are the power supply and lead wires for the sensors, and the equipment to be installed for data acquisition, but there are often restrictions in fieldwork. For this reason, a wireless sensing method using passive sensors that do not require a power supply and that enable sensing in the field is needed.

[0007] The present invention has been made in consideration of these problems, and aims to provide an RFID tag and a passive RFID tag sensor for plants that can wirelessly measure parameters related to the dynamic behavior of plants during growth, as well as the temperature and wet / dry state of the plants themselves. [Means for solving the problem]

[0008] Plants grow by constantly changing the direction of bending and stretching in response to external stimuli such as gravity and light. There are two types of tropism: positive tropism, which moves towards the direction of the stimulus, and negative tropism, which moves away from the direction of the stimulus. Gravitropism is tropism caused by gravity, and plant stems exhibit negative gravitropism, bending in the opposite direction to gravity. Phototropism is tropism caused by light, and plant stems and leaves exhibit phototropism, bending towards the light.

[0009] In order to sense plants, a sensing method that does not disturb the dynamic behavior of plants is required. Lead wires for supplying power to the sensor and acquiring data are a constraint on the plant. For this reason, wireless sensing using a small, lightweight passive RFID tag sensor that operates with passive wireless power supply is an effective method.

[0010] The RFID tag of the first invention comprises a conductor pattern having a ring-shaped opening, an impedance matching section having an IC chip electrically connected to the conductor pattern near the opening, an antenna section consisting of a radiating conductor extending from the impedance matching section in a first direction and a second direction, and a plurality of hollow rings having through holes connected to the antenna section, and is characterized in that the RFID tag is capable of holding a plant body within the hollow rings and is configured to allow the plant body to move within the hollow rings.

[0011] The RFID tag of the second invention comprises an insulating film, a conductor pattern provided on the surface of the insulating film and having a ring-shaped opening, an impedance matching section having an IC chip electrically connected to the conductor pattern in the vicinity of the opening, and an antenna section extending from the impedance matching section in a first direction and a second direction and consisting of a plurality of radiating conductor pieces connected via the insulating film, and is configured so that when attached to a plant body, the plant body can move due to the expansion and contraction of the insulating film.

[0012] In the RFID tags according to the first and second aspects of the present invention, the width of the radiating conductor and each of the radiating conductor pieces is preferably 0.01 mm or more and 2 mm or less.

[0013] In the RFID tag according to the first aspect of the present invention, it is preferable that two or more of the hollow rings are coupled to the antenna portion.

[0014] In the RFID tag according to the second aspect of the present invention, the antenna portion preferably comprises four or more of the radiating conductor pieces connected together via the insulating film.

[0015] In the RFID tag according to the second aspect of the present invention, the insulating film preferably has a thickness of 0.01 μm or more and 1000 μm or less.

[0016] The passive RFID tag sensor for plants according to the first invention has an RFID tag according to the first invention, and is characterized in that it is capable of detecting the temperature of the plant body held in the hollow ring by a temperature code from the IC chip of the impedance matching unit, and / or is capable of detecting the wet / dry state of the plant body held in the hollow ring by a sensor code S from the IC chip of the impedance matching unit, and / or is capable of detecting the movement of the plant body held in the hollow ring by the RSSI value from the IC chip of the impedance matching unit.

[0017] A passive RFID tag sensor for plants according to the second invention is characterized in that it has an RFID tag according to the second invention, and is capable of detecting the temperature of the attached plant body by a temperature code from the IC chip of the impedance matching unit, and / or is capable of detecting the wet / dry state of the attached plant body by a sensor code S from the IC chip of the impedance matching unit, and / or is capable of detecting the movement of the attached plant body by an RSSI value from the IC chip of the impedance matching unit. Effect of the Invention

[0018] According to the present invention, it is possible to provide an RFID tag and a passive RFID tag sensor for plants that can wirelessly measure parameters related to the dynamic behavior of a plant during growth and the temperature and wet / dry state of the plant itself. [Brief description of the drawings]

[0019] [Figure 1] 1A is a plan view, FIG. 1B is a cross-sectional view, and FIG. 1C is a right end view of an RFID tag (shape A) according to a first embodiment of the present invention. [Diagram 2] 11A and 11B are a plan view and a cross-sectional view of an RFID tag (shape B) according to a second embodiment of the present invention. [Diagram 3] FIG. 1 is a perspective view showing a method for evaluating characteristics of an RFID tag in accordance with the first and second embodiments of the present invention. [Figure 4] 1A and 1B are perspective views showing the shape of a plant body equipped with an RFID tag (shape A) according to the first embodiment of the present invention, (a) before gravitropism, (b) an enlarged view before gravitropism, and (c) after gravitropism. [Diagram 5] 1 is a graph showing time changes in (a) vertical displacement and (b) displacement speed in gravitropism of a plant body equipped with an RFID tag (shape A) according to the first embodiment of the present invention. [Figure 6] 13 is a graph showing the time changes in (a) temperature, (b) sensor code S, (c) reader RSSI, and (d) on-chip RSSI during gravitropism of a plant body equipped with an RFID tag (shape A) according to embodiment 1 of the present invention. [Figure 7] FIG. 2 is a perspective view showing the shape of a plant body to which an RFID tag (shape A) in accordance with the first embodiment of the present invention is attached, (a) before dehydration and (b) after dehydration. [Figure 8] 1 is a graph showing (a) vertical displacement and (b) displacement speed over time during a dehydration process of a plant body equipped with an RFID tag (shape A) according to the first embodiment of the present invention. [Figure 9] 1 is a graph showing the change over time in the sensor code S during the dehydration process of a plant body equipped with an RFID tag (shape A) according to embodiment 1 of the present invention (a in the figure), and the change over time in the sensor code S of a bamboo skewer (non-living object) that is already in a dried state according to comparison example 2 (b in the figure). [Figure 10] 1 is a graph showing time changes in (a) horizontal displacement and (b) displacement speed in phototropism of a plant body to which an RFID tag (shape A) according to embodiment 1 of the present invention is attached. [Figure 11]13 is a graph showing the time changes in (a) temperature, (b) sensor code S, (c) reader RSSI, and (d) on-chip RSSI in phototropism of a plant body equipped with an RFID tag (shape A) according to embodiment 1 of the present invention. [Figure 12] 10 is a graph showing the relationship between tensile force and elongation of the RFID tag (shape B) according to the second embodiment of the present invention. [Figure 13] FIG. 11 is an oblique view showing the shapes of a plant body equipped with an RFID tag (shape B) according to embodiment 2 of the present invention, (a) before gravitropism (0 minutes), (b) during gravitropism (60 minutes after the onset of gravitropism), and (c) during gravitropism (120 minutes after the onset of gravitropism). [Figure 14] Graphs showing the time changes in (a) the difference between the plant temperature and the environmental temperature, (b) the sensor code S, (c) the reader RSSI, and (d) the on-chip RSSI in gravitropism of a plant body equipped with an RFID tag (shape B) according to embodiment 2 of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the same or common parts are denoted by the same reference numerals, and the description thereof will not be repeated. For ease of understanding, the scale of each part in the drawings may differ from the actual scale. Directions such as parallel, right angle, orthogonal, horizontal, vertical, up and down, left and right, and terms such as same and equal are allowed to have deviations to the extent that they do not impair the functions and effects of the embodiments. The X-axis direction, the Y-axis direction, and the Z-axis direction respectively represent directions parallel to the X-axis, the Y-axis, and the Z-axis. The X-axis direction, the Y-axis direction, and the Z-axis direction are mutually perpendicular.

[0021] The RFID tag of the embodiment of the present invention comprises an impedance matching unit having an IC chip, which are components of a UHF band RFID tag, and an antenna unit, and further the RFID tag has a structure that does not interfere with the dynamic behavior of a plant when attached to the plant. Next, each element of the RFID tag described above will be described in detail.

[0022] [RFID tag configuration] 1 shows a plan view and a cross-sectional view of an RFID tag (shape A) 101 according to a first embodiment of the present invention. The RFID tag (shape A) 101 includes an impedance matching section 10 in which an IC chip 20 is connected to a conductor pattern 11 having a ring-shaped opening, an antenna section 12 made of a radiation conductor extending in a first direction and a second direction from the impedance matching section 10, and a plurality of hollow rings 30 having through holes connected to the antenna section 12. A plant body can be held within the hollow ring 30, and the plant body can move within the hollow ring 30.

[0023] 1 shows six hollow rings 30, but the number, size, and width of the hollow rings 30 are not limited as long as they are adapted to the shape of the plant body to which the RFID tag 101 is attached. The shape of the hollow rings 30 does not need to be a perfect circle, and is not limited as long as it is adapted to the shape of the plant body to which the RFID tag 101 is attached, and various shapes including an ellipse and a polygon can be applied.

[0024] The hollow ring 30 shown in the RFID tag (shape A) 101 in Figure 1 has a closed ring-shaped structure, but is not limited to this as long as it can hold a plant within the hollow ring 30 and allow the plant body to move, and may be a hollow structure with a notch that can be opened, closed, or deformed for attachment to the plant body, or a hollow structure that is attached to the plant body and then glued together.

[0025] The shape of the opening of the conductor pattern 11 in FIG. 1 is a substantially quadrilateral having a pair of long sides parallel to the X-axis direction and a pair of short sides parallel to the Y-axis direction. However, the shape of the opening is not limited to the form in FIG. 1, and may be, for example, a substantially quadrilateral having a pair of short sides parallel to the X-axis direction and a pair of long sides parallel to the Y-axis direction. The substantially quadrilateral may include a perfect quadrilateral. "Substantially" means that the corners or sides are rounded. The quadrilateral may include a rectangle, a rhombus, a parallelogram, and a square. The shape of the opening may be a polygon other than a quadrilateral, a circle, or an ellipse.

[0026] As a structure that allows the plant body to move with an RFID tag attached thereto, the structure of an RFID tag (shape B) 102 according to a second embodiment of the present invention shown in Fig. 2 is also conceivable. The antenna section 12 of the RFID tag (shape B) 102 is made up of a plurality of radiating conductor pieces 13 connected via an insulating film 31, and the structure allows the plant body to move with the RFID tag (shape B) 102 attached thereto due to the expansion and contraction of the insulating film 31.

[0027] The material of the conductor pattern 11 and the antenna section 12 in Fig. 1 is not particularly limited, but may be formed from a conductor having electrical conductivity, for example, metal such as aluminum, copper, gold, platinum, silver, nickel, chromium, zinc, lead, tungsten, iron, etc. The material of the conductor pattern 11 and the antenna section 12 may be a metal oxide layer such as tin oxide or ITO (indium tin oxide), a conductive layer using metal nanowires such as gold, silver, or copper, and a conductive resin mixture or a conductive resin layer in which a metal powder or a conductive carbon material is mixed with a resin, formed on an insulating film 14, as shown in Fig. 1(b). The thickness of the conductor section of the conductor pattern 11 and the antenna section 12 is preferably 0.01 to 1000 µm, more preferably 1 to 100 µm, from the viewpoints of flexibility and strength.

[0028] The material of the insulating film 14 shown in FIG. 1(b) is not particularly limited, and examples thereof include resin substrates such as urethane-based elastomers, styrene-based elastomers, vinyl chloride-based elastomers, polyester-based elastomers, silicone-based elastomers, polyurethane (PU), polyethylene terephthalate (PET), polyimide (PI), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), fluorinated resin copolymers, triacetyl cellulose (TAC), polyethylene naphthalate (PEN), syndiotactic polystyrene, polyphenylene sulfide, polycarbonate, polyarylate, polysulfone, polyester sulfone, polyetherimide, cyclic polyolefins, brominated phenoxy resins, norbornene resins, cycloolefin polymers, cycloolefin copolymers, and polyacetal; and composite substrates such as paper substrates, paper phenol substrates, paper epoxy substrates, glass composite substrates, and glass epoxy substrates.

[0029] 3 is a conceptual diagram showing a method for measuring the characteristics of a UHF band RFID tag in accordance with the first and second embodiments of the present invention. The measuring device 70 has an RFID reader / writer 71 and an antenna 72 of the RFID reader / writer 71. The communication distance CL is measured as the distance between the surface of the antenna 72 and the IC chip 20 of the RFID tag 73 attached to the plant body 40. The plant body 40 is inserted into a sample tube bottle 74 filled with water through a small hole in a sample tube screw cap 75 having a small hole slightly larger than the diameter of the stem of the plant body 40, and is held by a hydroponic sponge 76 that surrounds the stem of the plant body 40 between the small hole of the sample tube screw cap 75 and the sample tube bottle 74 and is provided to prevent water leakage from the small hole of the sample tube screw cap 75.

[0030] The type of plant 40 to which the RFID tags 101 and 102 of the first and second embodiments of the present invention can be applied is not particularly limited, but here, the characteristics of the RFID tags 101 and 102 will be described using a pea seedling, which is a pea sprout.

[0031] [RFID tag (shape A); measurement of plant gravitropism] 4 is a schematic diagram showing the shape of the RFID tag (shape A) 101 according to the first embodiment of the present invention in a used state attached to a plant body 40, (a) before gravitropism, (b) an enlarged view before gravitropism, and (c) after gravitropism. The stem of the plant body 40 is held by the hollow ring 30 of the RFID tag (shape A) 101, and as shown in FIG. 4(b), the tip of the stem of the plant body 40 and one end of the antenna part 12 of the RFID tag (shape A) 101 are fixed by wrapping surgical tape 32 (thickness 8 μm). This allows the stem of the plant body 40 to move inside the hollow ring 30 as the plant body 40 bends and grows.

[0032] 4(a) becomes bent as shown in FIG. 4(c) due to negative gravitropism (bending in the direction opposite to gravity) and elongation growth. RFID tag (shape A) 101 can bend and move in accordance with the bending and elongation growth of plant 40, and transmits information from IC chip 20 installed near plant 40 to RFID reader / writer 71.

[0033] 5 is a graph showing the time change in vertical displacement and displacement speed in gravitropism of a plant 40 for the RFID tag (shape A) 101 according to the first embodiment of the present invention. Observation of gravitropism was carried out in a dark box installed in an air-conditioned room. The gravitropism of the stem of a plant (a pea seedling, a pea sprout) 40 was photographed by a time-lapse camera in the dark box, and the movement of the vicinity of the tip of the stem of the plant 40 in the image was subjected to trajectory analysis by motion analysis software to determine the time change in vertical displacement and displacement speed.

[0034] The vertical displacement in FIG. 5(a) shows an increasing tendency up to about 150 minutes, after which it decreases slightly but remains almost constant. This indicates that gravitropism of the plant body 40 is completed at about 150 minutes. The displacement velocity in FIG. 5(b) shows a peak at about 80 minutes, after which it decreases to a value close to 0. Here, the displacement velocity shown in FIG. 5(b) is a value including horizontal displacement in addition to vertical displacement.

[0035] 6 is a graph showing the time changes in (a) temperature, (b) sensor code S, (c) reader RSSI, and (d) on-chip RSSI obtained by the RFID tag (shape A) 101 during gravitropism of a plant 40 equipped with an RFID tag (shape A) 101 according to the first embodiment of the present invention. A certain type of IC chip (e.g., IC chip 20) has a temperature measurement function, and the temperature measured by the IC chip is transmitted to the RFID reader / writer 71 as a temperature code. The temperature in FIG. 6(a) was obtained from the temperature code, IC-specific parameters, and a conversion formula.

[0036] The sensor code S is a value related to the impedance of the RFID tag 101 observed by the UHF input. The impedance matching unit 10 of the RFID tag 101 forms a loop circuit consisting of the IC chip 20 and the conductor pattern 11 having a substantially quadrilateral opening, and adjusts the shape and size of the opening to control the imaginary part (reactance) of the complex impedance, thereby performing impedance matching in the input and output of signals between the antenna unit 12 and the IC chip 20. The impedance value of the impedance matching unit 10 varies depending on the surrounding environment, but some IC chips (IC chip 20) have a function of auto-tuning to an optimal impedance value for the IC to receive signals, and transmits a value related to the auto-tuning of the impedance to the RFID reader / writer 71 as the sensor code S.

[0037] The value of the sensor code S is approximately 250 when the impedance matching unit 10 of the RFID tag 101 is in free space (in air), and decreases when the impedance matching unit 10 comes into contact with a substance that contains a large amount of moisture and has a high dielectric constant, and becomes approximately 10 when it comes into contact with water droplets, etc.

[0038] The reader RSSI (Received Signal Strength Indicator) is a value related to the power that the RFID reader / writer 71 is receiving from the RFID tag 101, and the on-chip RSSI is a value related to the power that the RFID tag 101 is receiving from the RFID reader / writer 71. These values ​​become larger under conditions of impedance matching in which the internal impedance values ​​of the impedance matching section 10 and the IC chip 20 are equivalent. The greater the influence of water, which has a large dielectric constant, the more difficult it is to satisfy the impedance matching conditions, and the smaller the RSSI value becomes.

[0039] In Fig. 6(a), a decrease in temperature is shown in the time region up to about 150 minutes when gravitropism of the plant body 40 is completed. The dynamic behavior of gravitropism of a plant body is related to changes in turgor pressure of the plant tissue, and one of the driving forces is a change in the water flow rate in the plant tissue. During gravitropism, an increase in the water flow from the water-filled sample vial 74 to the plant body 40 causes a decrease in the temperature of the plant body 40 as shown in Fig. 6(a). In this way, by directly attaching the RFID tag 101 equipped with the IC chip 20 having a temperature sensing function to the plant body 40, it becomes possible to directly detect the temperature change of the plant body 40 itself.

[0040] In an open space, the surrounding environmental temperature may not reflect the temperature of the plant 40, and by being able to directly detect temperature changes in the plant 40 itself, it becomes possible to more accurately manage the growth of the plant 40.

[0041] In FIG. 6, as the temperature of the plant body 40 decreases, the sensor code S also decreases (see FIG. 6(b)). The decrease in the sensor code S means that more water with a large dielectric constant has been absorbed into the plant body 40, which coincides with the tendency for the water flow velocity to increase suggested by the temperature change within the vertical body 40. In this way, the sensor code S is a parameter that reflects the wet / dry state of the plant body 40.

[0042] 6, the reader RSSI, which is a value related to the power the RFID reader / writer 71 receives from the RFID tag 101, and the on-chip RSSI, which is a value related to the power the RFID tag 101 receives from the RFID reader / writer 71, also decrease with the gravitropism of the plant 40. The reader RSSI and on-chip RSSI values ​​decrease in the presence of water, which has a large dielectric constant. The decrease in the temperature of the plant 40 in FIG. 6(a) and the sensor code S in FIG. 6(b) suggest an increase in the water flow within the plant 40, and this behavior coincides with the decrease in the reader RSSI and on-chip RSSI.

[0043] [RFID tag (shape A); measuring bending of plant body due to dehydration] 7 is a schematic diagram showing the shapes of a plant body (a pea seedling, which is a pea sprout) 40 equipped with an RFID tag (shape A) 101 according to the first embodiment of the present invention before and after dehydration. The plant body 40 in a state where no water is supplied takes on a downwardly bent shape as shown in FIG. 7(b) after 60 minutes of dehydration.

[0044] Figure 8 shows the time changes in vertical displacement and displacement speed obtained by photographing the bending of the stem of plant body 40 due to dehydration with a time-lapse camera in a dark box and analyzing the trajectory of the movement near the tip of the stem of plant body 40 in the video using motion analysis software. As shown in Figure 8, a fast displacement occurs at the beginning of dehydration, and the change gradually becomes more gradual.

[0045] The change in the sensor code S observed by the IC chip 20 of the RFID tag 101 attached to the plant body 40 at this time is shown in the graph of FIG. 9a, which coincides with the tendency of the results of the displacement and displacement speed in FIG. 8. The value of the sensor code S was about 155 at the beginning of dehydration, and about 195 after 60 minutes. The value of the sensor code S becomes lower in an environment with a higher dielectric constant where water is present. The sensor code S of the bamboo skewer (non-living object) in a dry state used as a comparison sample at this time was constant as shown in the graph of FIG. 9b, and the value was about 214. In this way, the value of the sensor code S observed by the IC chip 20 of the RFID tag 101 attached to the plant body 40 can be used to detect the wet or dry state of the plant body 40.

[0046] [RFID tag (shape A); measurement of phototropism of plants] 10 is a graph showing the time change of horizontal displacement and displacement speed in the phototropism of the plant body 40 for the RFID tag (shape A) 101 according to the first embodiment of the present invention. The horizontal displacement of the plant body 40 due to the phototropism was observed by placing an LED light source directly to the side of the plant body 40 in a dark box. Continuous horizontal displacement occurred over a period of 100 minutes, and the displacement speed peaked around 60 minutes.

[0047] Fig. 11 is a graph showing the time changes in (a) temperature, (b) sensor code S, (c) reader RSSI, and (d) on-chip RSSI during phototropism of a plant 40 equipped with an RFID tag (shape A) 101 according to embodiment 1 of the present invention. The temperature of the plant 40 in Fig. 11(a) shows a continuous change similar to that of the horizontal displacement graph in Fig. 10, and the direction of the change is a decrease in temperature, suggesting that an increase in water flow to the plant 40 during tropism occurs, similar to that in the case of gravitropism.

[0048] In the sensor code S, the reader RSSI, and the on-chip RSSI, a rapid decrease occurs around 60 minutes when the displacement speed in Fig. 10(b) peaks. In the phototropism of the plant body 40, the transpiration of water from the tissue of the plant body 40 is more significant than in the case of gravitropism, and the effect of this is reflected in the changes in the sensor code S, the reader RSSI, and the on-chip RSSI.

[0049] [RFID tag (shape B); measurement of gravitropism of plants] 2 was attached to the plant body, and wireless sensing of gravitropism of the plant body (a bean seedling, which is a pea sprout) 40 was performed. The RFID tag (shape B) 102 includes an insulating film 31, an impedance matching section 10 in which an IC chip 20 is connected to a conductor pattern 11 having a ring-shaped opening, and an antenna section 12 extending in a first direction and a second direction from the impedance matching section 10. The antenna section 12 is made up of a plurality of radiating conductor pieces 13 connected via the insulating film 31, and is structured so that the plant body 40 to which the RFID tag (shape B) 102 is attached can move due to the expansion and contraction of the insulating film 31.

[0050] The material of the radiating conductor piece 13 is not particularly limited, but may be the same as the material of the conductor pattern 11 having an annular opening and the antenna portion 12 of the RFID tag (shape A) 101.

[0051] The material of the insulating film 31 is not particularly limited, and examples thereof include resin base materials such as urethane-based elastomers, styrene-based elastomers, vinyl chloride-based elastomers, polyester-based elastomers, silicone-based elastomers, polyurethane (PU), polyethylene terephthalate (PET), polyimide (PI), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), fluorinated resin copolymers, triacetyl cellulose (TAC), polyethylene naphthalate (PEN), syndiotactic polystyrene, polyphenylene sulfide, polycarbonate, polyarylate, polysulfone, polyester sulfone, polyetherimide, cyclic polyolefins, brominated phenoxy resins, norbornene resins, cycloolefin polymers, cycloolefin copolymers, and polyacetal; and composite base materials such as paper base materials, paper phenol base materials, paper epoxy base materials, glass composite base materials, and glass epoxy base materials. From the viewpoint of flexibility, resin or paper base material is preferable, and from the viewpoint of stretchability, polyurethane (PU) film or elastomer film is more preferable. The thickness of the insulating film 31 is preferably 1 μm or more and 1000 μm or less, and more preferably 8 μm or more and 100 μm or less.

[0052] Fig. 12 is a graph showing the relationship between tensile force and elongation of the RFID tag (shape B) 102 (radiating conductor piece 13: copper tape, width W1 = approximately 1 mm, thickness approximately 50 µm, insulating film: polyurethane film, thickness approximately 8 µm) shown in Fig. 2. The RFID tag (shape B) 102 shows an elongation of 1.0 mm or more at a tensile force of 0.02 N, and has a structure that makes it difficult for bending or inhibition of elongation growth of the plant body 40 to occur even when attached to the plant body 40.

[0053] 13 is a schematic diagram showing the shapes of a plant 40 to which an RFID tag (shape B) 102 according to the second embodiment of the present invention is attached (a) before gravitropism (0 minutes), (b) during gravitropism (60 minutes after the start of gravitropism), and (c) during gravitropism (120 minutes after the start of gravitropism). An adhesive was applied in spots to the radiating conductor piece 13 of the RFID tag (shape B) 102, and the RFID tag (shape B) 102 was attached to the plant 40 by directly attaching the RFID tag (shape B) 102 to the plant 40. At this time, one end of the RFID tag (shape B) 102 in the tip direction of the plant 40 was fixed to the plant 40 by wrapping a surgical tape 32 around it.

[0054] 13, even when an RFID tag (shape B) 102 consisting of small radiating conductor pieces 13 connected by an extremely thin polyurethane film was directly attached to a plant 40, the plant 40 exhibited gravitropism. This is because the RFID tag (shape B) 102 has a structure that allows it to stretch even with an extremely small force, as shown in FIG. 12, due to the elasticity of the extremely thin polyurethane film (thickness approximately 8 μm).

[0055] 14 is a graph showing the time changes of (a) the difference between the plant temperature and the environmental temperature, (b) the sensor code S, (c) the reader RSSI, and (d) the on-chip RSSI in gravitropism of a plant 40 equipped with an RFID tag (shape B) 102 according to the second embodiment of the present invention. The temperature of the plant 40 was lower than the surrounding environmental temperature, and gradually decreased in the time period up to about 100 minutes before gravitropism occurred.

[0056] As gravitropism of the plant body 40 progresses, the extremely thin polyurethane film connecting the radiating conductor pieces 13 stretches, increasing the distance between the radiating conductor pieces 13 functioning as antenna sections 12 and decreasing the received and transmitted signal strength, so that the reader RSSI and on-chip RSSI decrease with the gravitropism of the plant body 40.

[0057] As gravitropism of the plant body 40 progresses, the extremely thin polyurethane film connecting the radiating conductor pieces 13 stretches, and the ratio of the area of ​​the low impedance polyurethane film to the area of ​​the radiating conductor pieces 13 in the total area of ​​the antenna section 12 increases, resulting in an increase in the sensor code S, as shown in Figure 14b.

[0058] The present invention makes it possible to provide an RFID tag and a passive RFID tag sensor for plants for wirelessly sensing parameters related to the temperature and wet / dry state of the plant itself, as well as dynamic behavior such as the tropism and elongation growth of the plant during growth.

[0059] [Specific example] Next, specific examples of the embodiment of the present invention and comparative examples will be described. The present invention is not limited to these specific examples. The materials and devices used in the specific examples are as follows.

[0060] [material] (1) IC chip 20: manufactured by AXZON; Magnus-S3, size 1.6 BSC × 1.6 BSC, thickness 0.35 mm. (2) UHF band RFID tag: Avery Dennison Smartrac; Temperature Sensor Dogbone, IC chip: Axzon Magnus-S3, frequency band: UHF 860-960MHz, IC chip: IC chip 20 (Magnus-S3). (3) Aluminum-coated PET sheet: made by Kenis; thickness 0.05 mm. (4) Copper tape: manufactured by 3M; conductive single-sided copper foil tape Cu-35C, soft rolled copper foil, thickness approximately 0.035 mm, conductive particle dispersed acrylic adhesive. (5) Thin film dressing: manufactured by Nitto Denko Corporation; polyurethane film, Permilor Lite, thickness 8 μm. (6) Adhesive: Cemedine Co., Ltd.; BBX, elastic adhesive (7) Transparent tube: Sumitomo Electric Fine Polymer: Sumitube C4C, 4 mm (8) Elastic silver paste: NAMICS; XE181G (9) Sample tube: Maruemu; screw vial 30mL transparent, sample vial borosilicate glass, sample tube screw cap polypropylene (10) Hydroponic sponge: manufactured by uxcell; hydroponic sponge cylinder, size 25mmφ×20mm.

[0061] [Device] (11) UHF band RFID reader / writer: Takaya Corporation; UTR-S201, specific low-power radio station type, transmission frequency 916.8MHz~923.2MHz (18 channels), transmission output 10dBm (10mW)~24dBm (250mW), interface USB interface board TR3-IF-U1C. (12) UHF band external antenna (linearly polarized type): Manufactured by Takaya Co., Ltd.; UTR-UA1709-1. (13) Digital force gauge: manufactured by Imada Corporation; sensor replaceable display eZT. (14) Load cell for digital force gauge: Manufactured by IMADA Co., Ltd.; compression / tension dual-purpose load cell eDPU-2N, maximum load 2N. (15) Thermocouple thermometer: Graphtec; mini LOGGER GL240. (16) Temperature sensor: manufactured by RIKA ELECTRIC CO., LTD.; ST-51-100-C, K thermocouple. (17) Time lapse camera; Brinno; TLC200Pro. (18) White LED: Generic LED Co.; 3W, color temperature 4500K.

[0062] [software] (19) Software for UHF band RFID reader / writer: UTRRWManager Version 1.3.2, manufactured by Takaya Corporation. (20) Homemade software for UHF band RFID reader / writer: Using Takaya Corporation UTR communication protocol ver1.15 and serial port control module EasyComm, the RFID reader / writer was controlled and data was acquired from Microsoft Excel. The reader RSSI was acquired from the IC chip 20 (Magnus-S3) according to Takaya Corporation UTR communication protocol. The sensor code S was acquired from the IC chip 20 (Magnus-S3) according to the memory bank (RESERVED), word address (C), and other information published in the RFmicron document (AN002F40: Reading Magnus (registered trademark)-S Sensors). h ), and according to the information in Number of Bits (9). (21) Motion analysis software; Made by KINOVEA; Open source motion analysis software Kinovea, https: / / www.kinovea.org / . EXAMPLES

[0063] [Production of RFID tag (shape A) 101] The RFID tag (shape A) 101 shown in FIG. 1 was produced as follows. An aluminum-deposited PET sheet was cut into the shape of the plan view of shape A in Fig. 1 (L = 90 mm, LA1 = about 70 mm, LA2 = about 20 mm, LI = about 10 mm, W1 = about 1 mm). At this time, a notch was provided in the impedance matching section 10 of the conductor pattern 11 having an annular opening where the IC chip 20 was to be attached. The aluminum-deposited PET portion with the IC chip 20 attached was cut out into a rectangle from the UHF band RFID tag and attached so as to straddle the notch.

[0064] The protective film covering the surface of the conductor pattern 11 on which the IC chip 20 cut out from the UHF band RFID tag was attached was peeled off and removed, and silver paste was applied to the joint with the antenna part 12 to electrically connect it to the conductor pattern 11 having a ring-shaped opening.

[0065] Next, multiple transparent tubes (outer diameter D1 = approximately 4 mm, width L2 = approximately 2 mm) were attached to an antenna part 12 made of an aluminum-vapor-deposited PET sheet at intervals of approximately 30 mm using an elastic adhesive to form a hollow ring 30 having a through hole, thereby producing an RFID tag (shape A) 101 shown in Figure 1. EXAMPLES

[0066] [Production of RFID tag (shape B) 102] The RFID tag (shape B) 102 shown in FIG. 2 was produced as follows. An impedance matching section 10 equipped with an IC chip 20 and a conductive pattern 11 having an annular opening was cut out from a UHF band RFID tag (LI = approximately 15 mm), and the protective film covering the surface was peeled off and removed. The impedance matching section 10 was attached to the adhesive surface of an 8 μm thick polyurethane film.

[0067] Copper tape (L=80 mm, width W1=approximately 1 mm) was attached onto an 8 μm thick polyurethane film with an impedance matching section 10 attached, and the copper tape portion was cut at intervals of approximately 5 mm to create an antenna section 12 consisting of a radiating conductor piece 13 as shown in FIG. 2. Silver paste was applied to the joint of the radiating conductor piece 13 that contacted the impedance matching section 10, so that it was electrically connected to the conductor pattern 11 having a ring-shaped opening. Furthermore, an 8 μm thick polyurethane film was attached onto the copper tape, and cut into a rectangular shape (L=approximately 80 mm, LA1=approximately 50 mm, LA2=approximately 30 mm, W2=approximately 3 mm), and the protective film covering the surface opposite to the adhesive surface of the polyurethane film was peeled off and removed to create an RFID tag (shape B) 102 shown in FIG. 2. EXAMPLES

[0068] [Observation of plant gravitropism using RFID tag (shape A) 101] FIG. 3 shows a conceptual diagram of a measurement system used to evaluate the characteristics of an RFID tag. The measurement device 70 has an RFID reader / writer 71 and an antenna 72 of the RFID reader / writer 71. The distance between the surface of the antenna 72 and the IC chip 20 of the RFID tag 73 attached to the plant body 40 was set as the communication distance CL. One end of the plant body 40 (the stem of a bean seedling) was inserted into a sample tube bottle 74 filled with water through a small hole in a sample tube screw cap 75 having a small hole slightly larger than the diameter of the stem of the plant body 40. The stem of the plant body 40 was surrounded by a hydroponic cultivation sponge 76, which was attached to the inside of the sample tube screw cap 75, and the sample tube screw cap 75 was screwed into the sample tube bottle 74 to prevent water leakage from the small hole in the sample tube screw cap 75.

[0069] The plant body 40 (the stem of a pea seedling) was passed through the hollow ring 30 of the RFID tag (shape A) 101, and the RFID tag (shape A) 101 was attached to the plant body 40 so as to be in the state shown in FIG. 4(a), and the characteristics were evaluated. At this time, as shown in FIG. 4(b), one end of the RFID tag in the direction of the tip of the stem of the pea seedling was wrapped around the stem of the pea seedling with surgical tape 32 (thickness 8 μm) made of polyurethane film and fixed by adhesion. Since the stem of the plant can move in the hollow ring 30 in other parts of the RFID tag except for the part fixed to the tip, the inhibition of the growth elongation and bending of the plant due to the attachment of the RFID tag can be reduced as much as possible. FIG. 4(c) shows the shape of the stem of the pea seedling to which the RFID tag (shape A) 101 was attached after gravitropism (after 120 minutes). It is known that gravitropism of plants occurs in about 120 minutes.

[0070] 5 shows the time changes in vertical displacement and displacement speed in gravitropism of a plant body 40 (a pea seedling stem) equipped with an RFID tag (shape A) 101. The gravitropism of the pea seedling stem was photographed from the side with a time-lapse camera, and the motion analysis software Kinovea was used to perform trajectory analysis of the tip of the pea seedling stem to determine the time changes in vertical displacement and displacement speed.

[0071] Figure 6 shows the time changes in (a) temperature, (b) sensor code S, (c) reader RSSI, and (d) on-chip RSSI in the gravitropism of a plant 40 (a pea seedling stem) equipped with an RFID tag (shape A) 101. The communication distance CL was set to 28 cm. Comparing Figures 5 and 6, it can be seen that changes continued for about 150 minutes in both cases, and the degree of change was greatest around 80 minutes, showing good agreement.

[0072] Although a linearly polarized antenna was used as antenna 72, a circularly polarized antenna can also be used for communication with the RFID tag of the embodiment of the present invention. When a circularly polarized antenna is used, the communication distance is slightly shorter than when a linearly polarized antenna is used, but communication with the RFID tag becomes possible by irradiating radio waves from a wider angle.

[0073] [Comparative Example 1: RFID tag without hollow ring 30] When an RFID tag with a shape similar to that of RFID tag (shape A) 101 but without the hollow ring 30 was created and attached directly to a plant 40 (a pea seedling stem) with an adhesive, the plant 40 no longer exhibited gravitropism. This is because the RFID tag attached directly to the plant 40 does not have flexibility, and thus inhibits the growth, elongation, and bending of the plant. EXAMPLES

[0074] [Observation of the dehydration process of plants using RFID tag (shape A) 101] As in Example 3 above, an RFID tag (shape A) 101 was attached to a plant body 40 (the stem of a bean sprout) and attached to an empty sample tube 74 that was not filled with water, and an investigation was conducted into the change in the signal from the RFID tag (shape A) 101 during the dehydration process of the plant body 40.

[0075] Figure 7 shows the change in shape of the stem of a plant body 40 (a pea sprout) equipped with an RFID tag (shape A) 101 before and after dehydration. The stem of the pea sprout wilted due to dehydration and bent downward as shown in Figure 4(b). The dehydration process was photographed from the side with a time-lapse camera, and the trajectory of the tip of the pea sprout's stem was analyzed using the motion analysis software Kinovea to determine the change over time in vertical displacement and displacement speed, which are shown in Figure 8.

[0076] Graph a in Fig. 9 shows the change over time in the sensor code S during the dehydration process of a plant body 40 (a stem of a pea sprout) equipped with an RFID tag (shape A) 101. The communication distance CL was set to 28 cm. The value of the sensor code S is lower in environments with a higher dielectric constant where water is present, but graph a in Fig. 9 shows a gradual increase in the value of the sensor code S over time, which is similar to the tendency of the downward bending behavior of the plant body 40 due to wilting associated with dehydration (see Fig. 8(a)).

[0077] [Comparative Example 2: When RFID tag (shape A) 101 is attached to a non-living object] When an RFID tag (shape A) 101 was attached to a bamboo skewer (non-living object) that was already in a dry state, the change in the sensor code S over time was observed and was constant, as shown in the graph in FIG. 9b. EXAMPLES

[0078] [Observation of phototropism of plants using RFID tag (shape A) 101] The RFID tag (shape A) 101 was attached to the plant body 40 (the stem of the pea seedling) and white LED light was irradiated from the side to observe the change in parameters from the RFID tag (shape A) 101 during the phototropism process of the stem of the pea seedling. The plant body 40 (the stem of the pea seedling) to which the RFID tag (shape A) 101 was attached was attached to a sample tube bottle 74 filled with water, as in Example 3.

[0079] The behavior of a plant body 40 (a pea seedling stem) equipped with an RFID tag (shape A) 101 during phototropism was photographed from above with a time-lapse camera, and the trajectory of the tip of the pea seedling stem was analyzed using the motion analysis software Kinovea to determine the changes in horizontal displacement and displacement speed over time, which are shown in Figure 10.

[0080] Figure 11 shows the time changes in (a) temperature, (b) sensor code S, (c) reader RSSI, and (d) on-chip RSSI in the phototropism of a plant body 40 (a pea seedling stem) equipped with an RFID tag (shape A) 101. The communication distance CL was set to 23 cm. Comparing Figures 10 and 11, the largest changes were observed around 60 minutes in both cases, and the behaviors were consistent. EXAMPLES

[0081] [Characteristics evaluation of RFID tag (shape B) 102] Fig. 12 shows the relationship between the tensile force and elongation of the RFID tag (shape B) 102. The antenna part 12 of the RFID tag (shape B) 102, which is configured such that the radiating conductor pieces 13 are connected by an extremely thin polyurethane film, has a highly elastic structure that elongates by 1.0 mm or more when subjected to a tensile force of 0.02 N.

[0082] 13 shows the shapes of a plant 40 (a bean sprout stem) with an RFID tag (shape B) 102 attached thereto (a) before gravitropism (0 min), (b) during gravitropism (60 min after the onset of gravitropism), and (c) during gravitropism (120 min after the onset of gravitropism). An adhesive was applied in spots to the radiating conductor piece 13 of the RFID tag (shape B) 102, and the RFID tag (shape B) 102 was attached to the plant 40 by attaching the RFID tag (shape B) 102 to the plant 40. Because the RFID tag (shape B) 102 has a highly elastic structure, gravitropism occurred even when the RFID tag (shape B) 102 was directly attached to the plant 40.

[0083] FIG. 14 shows the time changes of (a) the difference between the plant temperature and the environmental temperature, (b) the sensor code S, (c) the reader RSSI, and (d) the on-chip RSSI in the gravitropism of a plant 40 (a pea sprout stem) equipped with an RFID tag (shape B) 102. The communication distance CL was set to 10 cm. A thermocouple thermometer was placed near the plant 40 equipped with an RFID tag (shape B) 102 to measure the surrounding environmental temperature and determine the difference between the plant temperature and the environmental temperature. Changes in each parameter from the RFID tag (shape B) 102 associated with the gravitropism of the plant 40 were observed. [Industrial Applicability]

[0084] In the present invention, a RFID tag and a passive RFID tag sensor for plants can be provided for wirelessly measuring the dynamic behavior of plants during growth and parameters related to the temperature and wet / dry state of the plants themselves using a sensor equipped with a small IC chip capable of measuring parameters related to temperature and wet / dry state, and can be suitably used for plant cultivation management in open space plant factories with distribution of temperature, humidity, etc. Also, the sensor can be suitably used for sensing the growth state of plants in fields where it is difficult to use a power source and lead wires for the sensor, and equipment installed for data acquisition.

[0085] Although the embodiments have been described above, the technology of the present invention is not limited to the above-described embodiments, and various modifications and improvements, such as combinations with or substitutions for part or all of other embodiments, are possible. [Explanation of symbols]

[0086] 10 Impedance matching section 11 Conductor Pattern 12 Antenna section 13 Radiating conductor strip 14 Insulating film 20 IC chip 30 Hollow Ring 31 Insulating film 32 Surgical Tape 40 Plants 70 Measuring Equipment 71 RFID Reader / Writer 72 (RFID reader / writer) antenna 73 RFID tags 74 Sample Vial 75 Sample Tube Screw Cap 76 Hydroponic Sponge 101, 102 RFID tags

Claims

1. a conductor pattern having an annular opening; an impedance matching section having an IC chip electrically connected to the conductor pattern in the vicinity of the opening; an antenna portion including a radiation conductor extending in a first direction and a second direction from the impedance matching portion; a plurality of hollow rings having through holes coupled to the antenna portion; The hollow ring is configured to be capable of holding a plant body and to allow the plant body to move within the hollow ring. The RFID tag is characterized by:

2. 2. The RFID tag according to claim 1, wherein the width of the radiation conductor is 0.01 mm or more and 2 mm or less.

3. 2. The RFID tag according to claim 1, wherein two or more of said hollow rings are coupled to said antenna portion.

4. The RFID tag according to claim 1, The temperature of the plant body held in the hollow ring can be detected by a temperature code from the IC chip of the impedance matching unit. A passive RFID tag sensor for plants.

5. The RFID tag according to claim 1, a sensor code S from the IC chip of the impedance matching unit is provided to be capable of detecting the wet or dry state of the plant body held in the hollow ring; A passive RFID tag sensor for plants.

6. The RFID tag according to claim 1, The impedance matching unit is provided so as to be capable of detecting the movement of the plant body held in the hollow ring based on the RSSI value from the IC chip of the impedance matching unit. A passive RFID tag sensor for plants.

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