A gravity-sensing UHF RFID step-sensing yarn and its preparation method

Abstract

The present application belongs to the field of flexible hybrid electronics, and relates to a gravity sensing UHF RFID step sensing yarn and a preparation method thereof. The sensing yarn comprises a first core yarn and one interconnecting body, the interconnecting body is composed of an RFID chip and two conductors, at least one of the conductors has a segmented structure; the segmented structure is composed of a conductive length segment and a gravity sensing tilt switch; the axial length of the conductive length segment has specific requirements; in the same segmented structure, when the number of gravity sensing tilt switches is greater than one, the farther the tilt switch is from the RFID chip, the greater the tilt threshold is. In preparation, the interconnecting body is first prepared and spirally wound on the first core yarn, and the first and second reverse insulating wires can be directly wound outside the whole of the first core yarn and the interconnecting body; or the whole can be first wound on a second core yarn, and then the reverse insulating wires are wound. The present application can realize step mutation of sensing signals, the jump point is only related to the tilt angle and position, has strong anti-interference ability, and does not need to be calibrated in advance.

Description

Technical Field

[0001] This invention belongs to the field of flexible hybrid electronics technology and relates to a gravity-sensing UHF RFID step-sensing yarn and its preparation method. Background Technology

[0002] Flexible hybrid electronic yarns possess excellent weavability, easily integrating into various fabric structures; they offer outstanding comfort, causing no extra burden or discomfort to the user; they are highly discreet, easily concealed within everyday items or clothing; and they boast powerful versatility, integrating multiple functional modules to meet the needs of different scenarios. Based on these advantages, they demonstrate extremely broad application prospects in numerous fields such as smart healthcare, motion monitoring, and virtual reality.

[0003] Among them, flexible hybrid electronic yarn based on ultra-high frequency radio frequency identification (UHF RFID) technology, namely UHF RFID sensing yarn, is gradually gaining attention due to its unique advantages. It features simple wiring, eliminating the need for complex wiring connections and greatly simplifying the system structure; its wireless and passive characteristics free it from the constraints of power cords, making it more flexible and convenient to use and reducing maintenance costs; at the same time, its relatively low cost facilitates large-scale promotion and application.

[0004] Currently, the antennas used in existing UHF RFID sensing yarns are mainly of two types: linear dipole antennas and normal-mode spiral antennas. Based on the gamma matching principle and impedance mismatch principle, related research has produced UHF RFID temperature sensing yarns with wireless temperature measurement capabilities through specific design. However, due to their linear structure, linear dipole antennas have significant drawbacks in practical use. They are prone to breakage under external forces or frequent use, resulting in poor mechanical stability of the sensing yarn and affecting its long-term stable operation.

[0005] To address the problem of poor mechanical stability of linear dipole antennas, patent application CN107122815A discloses a spiral processing method for linear dipole antennas, which discloses a sensing yarn based on a normal mode spiral antenna. This spiral design enhances the structural strength of the antenna, improves the fracture resistance of the sensing yarn, and significantly improves mechanical stability.

[0006] Patent application CN115644846A focuses on the field of respiratory monitoring, proposing a wireless passive RFID tag sensing yarn for respiratory monitoring. Its working principle involves interconnecting thermistor units on conductive fibers (normal-mode helical antennas). When a person breathes, the airflow changes the temperature of the thermistor units. This temperature change causes a continuous change in the resistance of the thermistor units, which in turn causes a change in the overall impedance of the antenna. This leads to a change in the matching degree between the antenna and the RFID tag chip, altering the power transmission coefficient. Ultimately, this is reflected in the change in the received signal strength (RSSI) of the reader. By monitoring and analyzing the changes in RSSI, human respiratory information can be reflected.

[0007] During respiratory monitoring, human respiration is a natural physiological process. During exhalation, the warm airflow continuously raises the temperature of the thermistor, while during inhalation, the cool airflow continuously lowers it. This temperature change is gradual and continuous, without abrupt changes. Due to the continuous temperature change, the impedance of the thermistor, the impedance and gain of the overall structure (i.e., the antenna) composed of the thermistor and conductive fibers, and the impedance matching degree between the RFID chip and the antenna do not change abruptly. Consequently, the RSSI of the sensing signal also does not change abruptly, resulting in a non-stepping signal. If the sensing results could exhibit a stepping signal, it would be of great significance in the field of respiratory monitoring. A stepping signal could indicate a sudden change in respiratory status, such as a sudden and drastic change in breathing, providing a faster and more direct reflection of respiratory system abnormalities and offering crucial information for medical intervention. However, current technology cannot achieve stepping signal monitoring, affecting the timely capture of sudden respiratory abnormalities and reducing the timeliness and accuracy of respiratory monitoring.

[0008] Patent application CN116999055A focuses on limb movement monitoring, proposing a wireless passive strain sensing yarn and its preparation method. When a human limb moves, the sensing yarn, which is coplanar with the limb, undergoes bending deformation, changing the electromagnetic radiation distribution of the conductive fibers in space, i.e., the antenna gain. The change in antenna gain leads to a change in the sensing signal, which is reflected by the change in RSSI on the reader.

[0009] Human limb movement is a continuous process. When the sensing yarn monitors limb movement, the bending and deformation occur gradually, without abrupt changes in yarn shape or antenna gain. Therefore, the RSSI of the sensing signal does not change abruptly, and the monitoring result is not a step-like signal. If the monitoring result were a step-like signal, it could indicate an instantaneous change in limb movement state, such as a sudden fall or violent limb twitching. A step-like signal could more clearly define the transition point in movement state, helping to accurately analyze limb movement patterns and judge unexpected situations. However, current technology cannot acquire step-like signals, limiting the accurate monitoring and analysis of instantaneous changes in limb movement and reducing the reliability and effectiveness of limb movement monitoring.

[0010] In summary, the existing UHF RFID sensing yarn does not produce step-up signals in respiratory and limb movement monitoring. This characteristic limits its application in more accurate and rapid response to abnormal situations and urgently needs further improvement and innovation. Summary of the Invention

[0011] The purpose of this invention is to solve the problems existing in the prior art and to provide a gravity-sensing UHF RFID step-sensing yarn and its preparation method.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0013] A gravity-sensing UHF RFID step-sensing yarn A includes a first core yarn and an interconnecting body spirally integrated on the surface of the first core yarn. The interconnecting body is formed by sequentially connecting conductor I, an RFID chip, and conductor II. Conductor I and conductor II are normal mode spiral antennas, and at least one of conductor I and conductor II has a segmented structure.

[0014] The segmented structure includes at least two conductive length segments, which are conductive fiber segments or conductive yarn segments. Adjacent conductive length segments are connected by gravity-sensing tilt switches. By instantaneously opening and closing the gravity-sensing tilt switches, abrupt changes in the axial length (i.e., the effective axial length of the antenna) of the part of each segmented structure that forms an electrical connection with the RFID chip can be achieved, thereby achieving abrupt changes in sensing performance.

[0015] The axial length of the conductive length segment is at least 1.2% of the maximum operating wavelength of the gravity-sensing UHF RFID step-sensing yarn A;

[0016] In the same segmented structure, when the number of gravity-sensing tilt switches is greater than 1, the farther the gravity-sensing tilt switch is from the RFID chip, the larger the tilt threshold.

[0017] As a preferred technical solution:

[0018] As described above, in a gravity-sensing UHF RFID step sensor yarn A, both conductor I and conductor II have segmented structures.

[0019] As described above, in a gravity-sensing UHF RFID step-change sensor A, the gravity-sensing tilt switch in conductor I and the gravity-sensing tilt switch in conductor II are symmetrically distributed with the RFID chip as the center of symmetry. Compared with the gravity-sensing tilt switch only on one side of the RFID chip, when the gravity-sensing tilt switch is symmetrically distributed, the effective axial length change of the antenna doubles at the instant the switch is closed, the change in impedance matching degree between the antenna and the RFID chip is more significant, and the step-change signal is more significant.

[0020] The present invention also provides a gravity-sensing UHF RFID step-sensing yarn B, which is basically the same as the gravity-sensing UHF RFID step-sensing yarn A described in any of the preceding claims, except that: it also includes a first insulating wire and a second insulating wire; the first insulating wire and the second insulating wire are both spirally wound on the surface of the whole composed of the first core yarn and the interconnecting body, and the spiral directions are opposite, which can reduce slippage.

[0021] The present invention also provides a gravity-sensing UHF RFID step-sensing yarn C, which is basically the same as the gravity-sensing UHF RFID step-sensing yarn A described in any of the preceding claims, except that it further includes a second core yarn, and the entire core yarn and interconnecting body are spirally wound around the surface of the second core yarn, which can improve the step-sensing effect.

[0022] The change in the effective axial length of the antenna before and after the gravity-sensing tilt switch in sensing yarn A is equal to the change in the effective axial length of the antenna before and after the gravity-sensing tilt switch in sensing yarn C is closed. Since sensing yarn C undergoes two spiral integrations, it offers two major advantages: First, the spiral length of the antenna per unit length in the second core yarn is longer, resulting in a greater change in the spiral length before and after the gravity-sensing tilt switch is closed. Second, because each spiral integration introduces a new inductance, meaning the inductance of the antenna per unit axial length is positively correlated with the number of spiral integrations, the change in inductance per unit axial length of the antenna before and after the gravity-sensing tilt switch is closed is greater when the antenna undergoes two spiral integrations. Both of these advantages lead to a greater degree of impedance matching variation and a more pronounced signal step-up effect.

[0023] The present invention also provides a gravity-sensing UHF RFID step-sensing yarn D, which is basically the same as the gravity-sensing UHF RFID step-sensing yarn C described above, except that it also includes a first insulating wire and a second insulating wire; the first insulating wire and the second insulating wire are both spirally wound on the surface of the whole composed of the second core yarn, the first core yarn and the interconnection, and the spiral directions are opposite, which can further reduce slippage.

[0024] The present invention also provides a method for preparing a gravity-sensing UHF RFID step-sensing yarn B as described above. First, a gravity-sensing tilt switch, conductive fiber (or conductive yarn) and RFID chip are interconnected to form an integral structure to prepare an interconnect body. Then, the interconnect body is spirally wound around the surface of the first core yarn. Next, the first insulating wire and the second insulating wire are spirally wound around the surface of the integral structure composed of the first core yarn and the interconnect body, and the spiral directions of the two are controlled to be opposite, thus obtaining the gravity-sensing UHF RFID step-sensing yarn B.

[0025] The present invention also provides a method for preparing a gravity-sensing UHF RFID step-sensing yarn D as described above. First, a gravity-sensing tilt switch, conductive fibers (or conductive yarns), and an RFID chip are interconnected to form an integral structure to prepare an interconnect body. Then, the interconnect body is spirally wound around the surface of a first core yarn. Next, the entire structure consisting of the first core yarn and the interconnect body is spirally wound around the surface of a second core yarn. Finally, a first insulating wire and a second insulating wire are spirally wound around the surface of the entire structure consisting of the second core yarn, the first core yarn, and the interconnect body, with the spiral directions of the two wires controlled to be opposite, thus obtaining the gravity-sensing UHF RFID step-sensing yarn D.

[0026] Invention principle:

[0027] In this invention, when the tilt of the sensing yarn does not exceed the tilt threshold of any gravity-sensing tilt switch, no electrical connection is actually formed between the conductive length segments in the same segmented structure. This results in a shorter axial length of the portion of the segmented structure that forms an electrical connection with the RFID chip. As the tilt of the sensing yarn gradually increases, successively exceeding the tilt thresholds of each gravity-sensing tilt switch with an increasing distance from the RFID chip, each gravity-sensing tilt switch closes sequentially. Each time a gravity-sensing tilt switch closes, the axial length of the portion of the segmented structure that forms an electrical connection with the RFID chip increases.

[0028] According to the literature (Structural Relationship and Application of Normal Mode Spiral Dipole Type UHF RFID Tag Yarn [D]. Donghua University, 2024.), the pitch of similar normal mode spiral dipole type UHF RFID tag yarn antennas is usually 0.5~1.5mm. For the end spiral section with a switch connected on one side and suspended on the other, in order to ensure that the number of spiral coils is not less than 2 turns and to avoid spiral structure decoupling and deformation and sensor performance instability, the theoretical minimum axial length calculated based on the maximum pitch is 3mm. Taking into account the process allowance for connection and fixing during the manufacturing process and the pitch manufacturing tolerance, the shortest axial length of the end conductive length section is taken as 4mm. This invention operates in the 902~928MHz UHF RFID general frequency band, and the corresponding maximum free space wavelength is about 333mm. Therefore, the ratio of the shortest axial length to the maximum operating wavelength is about 1.2% (4×100% / 333).

[0029] Because this invention controls "the axial length of the conductive length segment to be at least 1.2% of the maximum operating wavelength of the gravity-sensing UHF RFID step-sensing yarn", the increase is relatively large. This will cause abrupt changes in the antenna gain, antenna impedance, and impedance matching degree between the antenna and the RFID chip, resulting in abrupt changes in the sensing signal.

[0030] This invention can monitor and obtain step-change signals, and its principle is significantly different from existing technologies. For example, patent CN115644846A changes the antenna impedance by altering the impedance of the temperature-sensitive element, without changing the antenna's structural parameters. This invention changes the antenna impedance by changing the effective axial length of the antenna, thus changing the antenna's structural parameters. During monitoring, patent application CN116999055A changes the antenna's gain and structural shape (straightening and bending), while this invention changes the antenna's impedance in addition to its gain, without altering the antenna's structural shape.

[0031] Beneficial effects:

[0032] (1) The present invention changes the effective axial length of the antenna by closing and opening the gravity-sensing tilt switch, which causes the antenna gain, impedance and impedance matching degree between the antenna and the RFID chip to change abruptly, realizing the step change of the sensing signal, which can accurately capture the sudden state change of the monitored object and improve the timeliness, accuracy and reliability of monitoring.

[0033] (2) The present invention uses a normal mode spiral antenna as conductor I and conductor II, which retains the structural advantages of the normal mode spiral antenna, improves the mechanical stability and anti-breakage ability of the sensing yarn, and ensures the long-term stable operation of the sensing yarn.

[0034] (3) The switching point of the sensing signal of the present invention depends only on the tilt angle of the sensing yarn and is not affected by environmental factors. It does not need to be calibrated before use, thus improving the anti-interference ability of the sensing yarn.

[0035] (4) By setting a second core yarn, the sensing yarn is integrated through two spirals, which increases the change in the spiral length of the antenna before and after the gravity-sensing tilt switch is closed, as well as the change in the inductance of the antenna per unit axial length, thereby improving the degree of impedance matching and making the step-up effect of the sensing signal more obvious. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the gravity-sensing UHF RFID step-sensing yarn structure of Example 1. Figure 1 (a) is a schematic diagram of the structure wrapped with the first and second insulating wires. Figure 1 (b) is a structural diagram without the first and second insulating wires wrapped around it; where 1 is the first core yarn, 2 is the RFID chip, 3 is the gravity-sensing tilt switch I, 4 is the gravity-sensing tilt switch II, 5 is the first insulating wire, 6 is the second insulating wire, 7 is the conductive fiber segment a, 8 is the conductive fiber segment b, 9 is the conductive fiber segment c, and 10 is the conductive fiber segment d.

[0037] Figure 2This is a schematic diagram of the pitch S, helix radius r, and axial lengths l1~l4 in Example 1;

[0038] Figure 3 This is a schematic diagram of the gravity-sensing tilt switch I in Example 1. Figure 3 In the middle (a), the switch is in the open state. Figure 3 (b) shows the switch closed (the arrow in the figure indicates the positive direction of the angle); where 3-1 is a movable conductor and 3-2 is a terminal.

[0039] Figure 4 The curve of RSSI versus time under the periodic reciprocating motion of the gravity-sensing UHF RFID step sensor yarn in Example 1 is shown.

[0040] Figure 5 The impedance matching performance comparison curves of the normal mode spiral antenna before and after the gravity-sensing tilt switch is turned off are shown in Example 2.

[0041] Figure 6 The impedance matching performance comparison curves of the normal mode spiral antenna before and after the gravity-sensing tilt switch is disconnected are shown in Example 3.

[0042] Figure 7 The curves showing the impedance matching performance of the normal mode spiral antenna before and after the gravity-sensing tilt switch is turned off correspond to Example 4; where (a) is before the gravity-sensing tilt switch is turned off, and (b) is after the gravity-sensing tilt switch is turned off.

[0043] Figure 8 This is a schematic diagram of the gravity-sensing UHF RFID step-sensing yarn structure in Example 5. Figure 8 (a) is a schematic diagram of the structure wrapped with the first and second insulating wires. Figure 8 (b) is a schematic diagram of the structure without the first and second insulating wires; where 1 is the first core yarn, 2 is the RFID chip, 3 is the gravity-sensing tilt switch I, 4 is the gravity-sensing tilt switch II, 5 is the first insulating wire, 6 is the second insulating wire, 7 is conductive fiber segment a, 8 is conductive fiber segment b, 9 is conductive fiber segment c, 10 is conductive fiber segment d; 11 is gravity-sensing tilt switch III, 12 is gravity-sensing tilt switch IV; 13 is conductive fiber segment e, and 14 is conductive fiber segment f.

[0044] Figure 9 This is a schematic diagram of the axial lengths l1 to l6 in Example 5;

[0045] Figure 10 Example 5 shows the gravity-sensing UHF RFID step-sensing yarn under different inclination degrees. 11 Curve showing variation with frequency. Detailed Implementation

[0046] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0047] Example 1

[0048] A method for preparing a gravity-sensing UHF RFID step-sensing yarn, the specific steps of which are as follows:

[0049] (1) Preparation of materials;

[0050] First core yarn: cotton yarn (manufacturer: Anhui Hengyi Textile Technology Co., Ltd., brand name: DIYC14), diameter: 1.4mm;

[0051] Conductive fiber: fine copper wire, manufactured by Baoxin Copper Industry (Shenzhen) Co., Ltd., grade TW0045, diameter 0.09mm;

[0052] First and second insulated wires: both are spandex multifilament (manufacturer: Zhuji Manyue Chemical Fiber Factory, brand: PU1120, specification: 1120D).

[0053] RFID chip: Alien Higgs 3 radio frequency chip;

[0054] Anisotropic conductive adhesive: SONY, BP303;

[0055] Solder wire: Anrixin, 1mm diameter solder wire;

[0056] Flexible insulating adhesive: UV-cured polyurethane acrylate (prepared according to patent application CN116999055A);

[0057] Gravity-sensing tilt switch I: Structure as follows Figure 3 As shown, it includes a movable conductor 3-1 and a terminal 3-2, with a tilt threshold of 10°;

[0058] Gravity-sensing tilt switch II: Same as gravity-sensing tilt switch I;

[0059] (2) Fabrication of interconnects;

[0060] (2.1) Prepare a mold. The mold is made of polytetrafluoroethylene. The surface of the mold has one cuboid groove and two semi-cylindrical grooves. The two semi-cylindrical grooves are parallel to each other and pass through a pair of opposite vertices of the cuboid groove outline. The size of the cuboid groove is comparable to the size of the RFID chip, and the inner diameter of the two semi-cylindrical grooves is comparable to the diameter of the conductive fiber.

[0061] (2.2) Place the RFID chip into the rectangular groove and apply an appropriate amount of anisotropic conductive adhesive;

[0062] (2.3) Take two conductive fibers and place them into two semi-cylindrical grooves respectively. They are then hot-pressed to obtain an interconnect intermediate component. The two conductive fibers are located directly above the RF area and GND area of ​​the RFID chip, respectively. The hot-pressing temperature is 230℃, the hot-pressing time is 8s, the bonding pressure is 0.5N / Bump, and a tension of 0.4cN is applied on both sides of the encapsulation point of the two conductive fibers.

[0063] (2.4) Use a thin-blade cutter to trim away excess flexible packaging edges and conductive fiber ends on the interconnect intermediate components;

[0064] (2.5) Take 0.05 mL of flexible insulating adhesive and apply it to the assembly joint between the conductive fiber and the RFID chip. Cure it in a UV curing oven (Baoding Zhonghe Machinery Company, HWUV0133X-18, power: 1700W) for 15 seconds.

[0065] (2.6) Cut the conductive fibers on both sides of the RFID chip into two segments. The two segments on one side are denoted as conductive fiber segment a and conductive fiber segment b, and the two segments on the other side are denoted as conductive fiber segment c and conductive fiber segment d. At 250°C, use solder wire to weld gravity-sensing tilt switch I between conductive fiber segment a and conductive fiber segment b, and weld gravity-sensing tilt switch II between conductive fiber segment c and conductive fiber segment d to obtain the interconnect.

[0066] (3) Prepare gravity-sensing UHF RFID step-up sensing yarn;

[0067] The interconnect is spirally wound around the surface of the first core yarn, and then the first insulating wire and the second insulating wire are spirally wound around the surface of the whole composed of the first core yarn and the interconnect, and the spiral directions of the two are controlled to be opposite, thus obtaining the gravity-sensing UHF RFID step-sensing yarn.

[0068] like Figure 1 and Figure 2As shown, the final gravity-sensing UHF RFID step-sensing yarn includes one interconnect, a first core yarn 1, a first insulating wire 5, and a second insulating wire 6; the interconnect is spirally integrated on the surface of the first core yarn 1, with a pitch S of 1.5 mm and a spiral radius r of 0.62 mm; the interconnect is formed by sequentially connecting conductor I, RFID chip 2, and conductor II, and conductor I and conductor II are normal mode spiral antennas;

[0069] Conductor I has a segmented structure A, and conductor II has a segmented structure B. Segmented structure A consists of conductive fiber segment a 7, conductive fiber segment b 8, and gravity-sensing tilt switch I 3. Segmented structure B consists of conductive fiber segment c 9, conductive fiber segment d 10, and gravity-sensing tilt switch II 4. Conductive fiber segments a 7 and b 8 are connected by gravity-sensing tilt switch I 3, and conductive fiber segments c 9 and d 10 are connected by gravity-sensing tilt switch II 4. Gravity-sensing tilt switch I 3 in conductor I and gravity-sensing tilt switch II 4 in conductor II are symmetrically distributed with RFID chip 2 as the center of symmetry.

[0070] The axial length l1 of conductive fiber segment a 7 is 30 mm, the axial length l2 of conductive fiber segment b 8 is 20 mm, the axial length l3 of conductive fiber segment c 9 is 20 mm, and the axial length l4 of conductive fiber segment d 10 is 30 mm.

[0071] The first insulating wire 5 and the second insulating wire 6 are both spirally wound on the surface of the whole composed of the first core yarn 1 and the interconnecting body, and the spiral directions are opposite.

[0072] The working wavelength of the gravity-sensing UHF RFID step sensor yarn is 32.3-33.2cm.

[0073] The monitoring effect of the gravity-sensing UHF RFID step-sensing yarn prepared in this embodiment was characterized using a reader (E9012PLNF) and RSSI as a characteristic index. The horizontal distance between the reader and the gravity-sensing UHF RFID step-sensing yarn was 3m. In the initial state, the angle x between the core conductive contacts (terminals) of gravity-sensing tilt switches I and II and the ground was 15° (at this time, gravity-sensing tilt switches I and II were both in the closed state, such as...). Figure 3 As shown in (b), let it stand still for 25 seconds. Then, rotate the gravity-sensing UHF RFID step sensor yarn counterclockwise by 25° around its axis at a speed of 360° / s. The angle x between the core conductive contact (terminal) of gravity-sensing tilt switch I and gravity-sensing tilt switch II and the ground is -10° (at this time, gravity-sensing tilt switches I and II are both in the open state, such as...). Figure 3As shown in (a), remain still for 10 seconds; then rotate the gravity-sensing UHF RFID step sensor yarn 25° clockwise around its axis at a speed of 360° / s, and remain still for 10 seconds. Repeat this cycle for 100 seconds. The reader antenna has a transmit power of 1W, a gain of 12dBi, and a test frequency of 915.25MHz. Figure 4 It can be seen that as the periodic reciprocating motion proceeds, the sensor signal image appears as a step, and the frequency of signal abrupt changes corresponds to the frequency of the reciprocating motion.

[0074] Example 2

[0075] A method for preparing a gravity-sensing UHF RFID step-sensing yarn, the specific steps of which are as follows:

[0076] (1) Preparation of materials;

[0077] First core yarn: cotton yarn (manufacturer: Anhui Hengyi Textile Technology Co., Ltd., brand name: DIYC14), diameter: 1.4mm;

[0078] Conductive fiber: fine copper wire, manufactured by Baoxin Copper Industry (Shenzhen) Co., Ltd., grade TW0045, diameter 0.09mm;

[0079] First and second insulated wires: both are spandex multifilament (manufacturer: Zhuji Manyue Chemical Fiber Factory, brand: PU1120, specification: 1120D).

[0080] RFID chip: Alien Higgs 3 radio frequency chip;

[0081] Anisotropic conductive adhesive: SONY, BP303;

[0082] Solder wire: Anrixin, 1mm diameter solder wire;

[0083] Flexible insulating adhesive: UV-cured polyurethane acrylate (prepared according to patent application CN116999055A);

[0084] Gravity-sensitive tilt switch I: includes a movable conductor and a terminal block, with a tilt threshold of 10°;

[0085] Gravity-sensing tilt switch II: Same as gravity-sensing tilt switch I;

[0086] (2) Fabrication of interconnects;

[0087] (2.1) Prepare a mold. The mold is made of polytetrafluoroethylene. The surface of the mold has one cuboid groove and two semi-cylindrical grooves. The two semi-cylindrical grooves are parallel to each other and pass through a pair of opposite vertices of the cuboid groove outline. The size of the cuboid groove is comparable to the size of the RFID chip, and the inner diameter of the two semi-cylindrical grooves is comparable to the diameter of the conductive fiber.

[0088] (2.2) Place the RFID chip into the rectangular groove and apply an appropriate amount of anisotropic conductive adhesive;

[0089] (2.3) Take two conductive fibers and place them into two semi-cylindrical grooves respectively. They are then hot-pressed to obtain an interconnect intermediate component. The two conductive fibers are located directly above the RF area and GND area of ​​the RFID chip, respectively. The hot-pressing temperature is 230℃, the hot-pressing time is 8s, the bonding pressure is 0.5N / Bump, and a tension of 0.4cN is applied on both sides of the encapsulation point of the two conductive fibers.

[0090] (2.4) Use a thin-blade cutter to trim away excess flexible packaging edges and conductive fiber ends on the interconnect intermediate components;

[0091] (2.5) Take 0.06 mL of flexible insulating adhesive and apply it to the assembly joint between the conductive fiber and the RFID chip. Cure it in an ultraviolet curing oven (Baoding Zhonghe Machinery Company, HWUV0133X-18, power: 1700W) for 15 seconds.

[0092] (2.6) Cut the conductive fibers on both sides of the RFID chip into two segments. The two segments on one side are denoted as conductive fiber segment a and conductive fiber segment b, and the two segments on the other side are denoted as conductive fiber segment c and conductive fiber segment d. At 250°C, use solder wire to weld gravity-sensing tilt switch I between conductive fiber segment a and conductive fiber segment b, and weld gravity-sensing tilt switch II between conductive fiber segment c and conductive fiber segment d to obtain the interconnect.

[0093] (3) Prepare gravity-sensing UHF RFID step-up sensing yarn;

[0094] The interconnect is spirally wound around the surface of the first core yarn, and then the first insulating wire and the second insulating wire are spirally wound around the surface of the whole composed of the first core yarn and the interconnect, and the spiral directions of the two are controlled to be opposite, thus obtaining the gravity-sensing UHF RFID step-sensing yarn.

[0095] The final gravity-sensing UHF RFID step-sensing yarn includes one interconnect, a first core yarn, a first insulating wire, and a second insulating wire; the interconnect is spirally integrated on the surface of the first core yarn with a pitch of 1.5 mm and a spiral radius of 0.63 mm; the interconnect is composed of conductor I, an RFID chip, and conductor II connected in sequence, and conductor I and conductor II are normal mode spiral antennas;

[0096] Conductor I has a segmented structure A, and conductor II has a segmented structure B. Segmented structure A consists of conductive fiber segment a, conductive fiber segment b, and gravity-sensing tilt switch I. Segmented structure B consists of conductive fiber segment c, conductive fiber segment d, and gravity-sensing tilt switch II. Conductive fiber segment a and conductive fiber segment b are connected by gravity-sensing tilt switch I, and conductive fiber segment c and conductive fiber segment d are connected by gravity-sensing tilt switch II. Gravity-sensing tilt switch I in conductor I and gravity-sensing tilt switch II in conductor II are symmetrically distributed with the RFID chip as the center of symmetry.

[0097] The axial length of conductive fiber segment a is 30mm, the axial length of conductive fiber segment b is 19.5mm, the axial length of conductive fiber segment c is 19.5mm, and the axial length of conductive fiber segment d is 30mm.

[0098] Both the first and second insulating wires are spirally wound on the surface of the whole consisting of the first core yarn and the interconnecting body, and the spiral directions are opposite.

[0099] The working wavelength of the gravity-sensing UHF RFID step sensor yarn is 32.3-33.2cm.

[0100] To demonstrate the abrupt change in performance of the gravity-sensing UHF RFID step-sensing yarn before and after the gravity-sensing tilt switch is closed, a model of the gravity-sensing UHF RFID step-sensing yarn was established using the simulation software Ansys HFSS 2023 R1, and simulation calculations were performed. Model parameters were set according to the actual structural dimensions of the gravity-sensing UHF RFID step-sensing yarn. Referring to the actual conductivity of copper, the conductivity of the gravity-sensing UHF RFID step-sensing yarn was set to 5.8 × 10⁻⁶. 7 S / m; The gravity-sensing UHF RFID step sensor port adopts lumped port excitation, and the port impedance is set to the impedance conjugate matched with the RFID chip impedance, i.e., 27.38+j200.76Ω.

[0101] According to the literature (The influence of structure uniformity on resonant frequency of ultra-high frequency radio frequency identification tag thread With normalmode helix dipole antenna [J]. Journal of Industrial Textiles, 2022, 52:15280837221123592.), the influence of yarn dielectric properties on simulation accuracy is negligible. That is, the influence of the first core yarn, the first insulating wire, and the second insulating wire on the impedance and resonant frequency of the gravity-sensing UHF RFID step-sensing yarn is minimal and can be ignored. Therefore, they are omitted in the simulation model and are equivalent to air medium.

[0102] Furthermore, theoretically, parasitic effects exist between the tilt switch and the interconnect and packaging materials, which mainly depend on the supporting materials and processes used for interconnection. The interconnect and packaging materials used in this embodiment are commonly used materials for chip and conductive fiber packaging and interconnection. The parasitic effects introduced by the tilt switch through the interconnection with conductive fibers using this type of material are similar in magnitude to the parasitic effects produced by using the same material to achieve chip-conductive fiber interconnection. As can be seen from the literature (Wireless Temperature Sensing Yarn Based on UHF RFID Helix Dipole Hybrid Antenna [J]. IEEE Sensors Journal, 2023, 23: 20107-20115.) and (Structural Relationship and Application of Normal Mode Helical Dipole Type UHF RFID Tag Yarn [D]. Donghua University, 2024.), when using this type of material to complete the chip and conductive fiber interconnection and packaging, the resulting parasitic effects can be disregarded. This is because, without considering parasitic effects, the actual sample prepared after optimizing the sensing yarn structure parameters through simulation still possesses good sensing performance. However, if the parasitic effects introduced by this type of interconnect are significant, they will significantly degrade the RF sensing performance of the device, and the actual sample will fail to achieve the expected sensing effect. In summary, parasitic effects can be disregarded during the simulation stage.

[0103] Depend on Figure 5 It can be seen that the impedance of the gravity-sensing UHF RFID step sensor yarn changes abruptly before and after the gravity-sensing tilt switch I and gravity-sensing tilt switch II are opened. Simulation results show that the resonant frequency changes by approximately 1360MHz between the open and closed states of the switches.

[0104] Example 3

[0105] A method for preparing a gravity-sensing UHF RFID step-sensing yarn differs from Example 2 in that step (2.6) involves cutting the conductive fiber located on one side of the RFID chip into two segments, denoted as conductive fiber segment a and conductive fiber segment b, and welding the gravity-sensing tilt switch I between conductive fiber segment a and conductive fiber segment b using tin wire at 250°C. The resulting gravity-sensing UHF RFID step-sensing yarn does not have a segmented structure in its conductor II.

[0106] Depend on Figure 6 It can be seen that the impedance of the gravity-sensing UHF RFID step-sensing yarn changes abruptly before and after the gravity-sensing tilt switch I is opened. Simulation results show that the change in resonant frequency between the open and closed states of the switch is about 320MHz, which is less than the 1360MHz in Example 2, and the change in sensing performance is not obvious.

[0107] Example 4

[0108] A method for preparing a gravity-sensing UHF RFID step-sensing yarn, the specific steps of which are as follows:

[0109] (1) Preparation of materials;

[0110] First core yarn and second core yarn: cotton yarn (manufacturer: Anhui Hengyi Textile Technology Co., Ltd., brand name: DIYC14), diameter: 1.4mm;

[0111] Conductive fiber: fine copper wire, manufactured by Baoxin Copper Industry (Shenzhen) Co., Ltd., grade TW0045, diameter 0.09mm;

[0112] First and second insulated wires: both are spandex multifilament (manufacturer: Zhuji Manyue Chemical Fiber Factory, brand: PU1120, specification: 1120D).

[0113] RFID chip: Alien Higgs 3 radio frequency chip;

[0114] Anisotropic conductive adhesive: SONY, BP303;

[0115] Solder wire: Anrixin, 1mm diameter solder wire;

[0116] Flexible insulating adhesive: UV-cured polyurethane acrylate (prepared according to patent application CN116999055A);

[0117] Gravity-sensitive tilt switch I: includes a movable conductor and a terminal block, with a tilt threshold of 10°;

[0118] Gravity-sensing tilt switch II: Same as gravity-sensing tilt switch I;

[0119] (2) Fabrication of interconnects;

[0120] (2.1) Prepare a mold. The mold is made of polytetrafluoroethylene. The surface of the mold has one cuboid groove and two semi-cylindrical grooves. The two semi-cylindrical grooves are parallel to each other and pass through a pair of opposite vertices of the cuboid groove outline. The size of the cuboid groove is comparable to the size of the RFID chip, and the inner diameter of the two semi-cylindrical grooves is comparable to the diameter of the conductive fiber.

[0121] (2.2) Place the RFID chip into the rectangular groove and apply an appropriate amount of anisotropic conductive adhesive;

[0122] (2.3) Take two conductive fibers and place them into two semi-cylindrical grooves respectively. They are then hot-pressed to obtain an interconnect intermediate component. The two conductive fibers are located directly above the RF area and GND area of ​​the RFID chip, respectively. The hot-pressing temperature is 230℃, the hot-pressing time is 8s, the bonding pressure is 0.5N / Bump, and a tension of 0.4cN is applied on both sides of the encapsulation point of the two conductive fibers.

[0123] (2.4) Use a thin-blade cutter to trim away excess flexible packaging edges and conductive fiber ends on the interconnect intermediate components;

[0124] (2.5) Take 0.06 mL of flexible insulating adhesive and apply it to the assembly joint between the conductive fiber and the RFID chip. Cure it in an ultraviolet curing oven (Baoding Zhonghe Machinery Company, HWUV0133X-18, power: 1700W) for 15 seconds.

[0125] (2.6) Cut the conductive fibers on both sides of the RFID chip into two segments. The two segments on one side are denoted as conductive fiber segment a and conductive fiber segment b, and the two segments on the other side are denoted as conductive fiber segment c and conductive fiber segment d. At 250°C, use solder wire to weld gravity-sensing tilt switch I between conductive fiber segment a and conductive fiber segment b, and weld gravity-sensing tilt switch II between conductive fiber segment c and conductive fiber segment d to obtain the interconnect.

[0126] (3) Prepare gravity-sensing UHF RFID step-up sensing yarn;

[0127] The interconnect is spirally wound around the surface of the first core yarn, and then the whole consisting of the first core yarn and the interconnect is spirally wound around the surface of the second core yarn. Then the first insulating wire and the second insulating wire are spirally wound around the surface of the whole consisting of the second core yarn, the first core yarn and the interconnect, and the spiral directions of the two are controlled to be opposite, thus obtaining the gravity-sensing UHF RFID step-sensing yarn.

[0128] The final gravity-sensing UHF RFID step-sensing yarn includes one interconnect, a first core yarn, a second core yarn, a first insulating wire, and a second insulating wire. The interconnect is spirally integrated on the surface of the first core yarn with a pitch of 1.5 mm, a spiral radius of 0.63 mm, and an axial length of 99 mm. The integral spiral formed by the first core yarn and the interconnect is wound around the surface of the second core yarn with a pitch of 9.9 mm, a spiral radius of 0.925 mm, and an axial length of 85.357 mm. The interconnect is formed by sequentially connecting conductor I, an RFID chip, and conductor II. Conductors I and II are normal-mode spiral antennas.

[0129] Conductor I has a segmented structure A, and conductor II has a segmented structure B. Segmented structure A consists of conductive fiber segment a, conductive fiber segment b, and gravity-sensing tilt switch I. Segmented structure B consists of conductive fiber segment c, conductive fiber segment d, and gravity-sensing tilt switch II. Conductive fiber segment a and conductive fiber segment b are connected by gravity-sensing tilt switch I, and conductive fiber segment c and conductive fiber segment d are connected by gravity-sensing tilt switch II. Gravity-sensing tilt switch I in conductor I and gravity-sensing tilt switch II in conductor II are symmetrically distributed with the RFID chip as the center of symmetry.

[0130] The distance between the gravity-sensing tilt switch I and the RFID chip is 12.6785mm, and the distance between the gravity-sensing tilt switch II and the RFID chip is 12.6785mm.

[0131] When gravity-sensing tilt switch I and gravity-sensing tilt switch II are simultaneously disconnected, the total change in axial length of the gravity-sensing UHF RFID step sensor yarn is 60mm, and the axial length of conductor I and conductor II on both sides of the RFID chip is reduced by 30mm.

[0132] Both the first and second insulating wires are spirally wound on the surface of the whole consisting of the second core yarn, the first core yarn, and the interconnecting body, and the spiral directions are opposite.

[0133] The working wavelength of the gravity-sensing UHF RFID step sensor yarn is 32.3-33.2cm.

[0134] like Figure 7 Simulation results show that the resonant frequency changes by 2044MHz before and after the switch is turned off, which is greater than the 1360MHz change in Example 2.

[0135] Example 5

[0136] A method for preparing a gravity-sensing UHF RFID step-sensing yarn, the specific steps of which are as follows:

[0137] (1) Preparation of materials;

[0138] First core yarn: cotton yarn (manufacturer: Anhui Hengyi Textile Technology Co., Ltd., brand name: DIYC14), diameter: 1.4mm;

[0139] Conductive fiber: fine copper wire, manufactured by Baoxin Copper Industry (Shenzhen) Co., Ltd., grade TW0045, diameter 0.09mm;

[0140] First and second insulated wires: both are spandex multifilament (manufacturer: Zhuji Manyue Chemical Fiber Factory, brand: PU1120, specification: 1120D).

[0141] RFID chip: Alien Higgs 3 radio frequency chip;

[0142] Anisotropic conductive adhesive: SONY, BP303;

[0143] Solder wire: Anrixin, 1mm diameter solder wire;

[0144] Flexible insulating adhesive: UV-cured polyurethane acrylate (prepared according to patent application CN116999055A);

[0145] Gravity-sensitive tilt switch I: includes a movable conductor and a terminal block, with a tilt threshold of 10°;

[0146] Gravity-sensing tilt switch II: Same as gravity-sensing tilt switch I;

[0147] Gravity-sensitive tilt switch III: includes a movable conductor and terminals, with a tilt threshold of 30°;

[0148] Gravity-sensing tilt switch IV: Same as gravity-sensing tilt switch III;

[0149] (2) Fabrication of interconnects;

[0150] (2.1) Prepare a mold. The mold is made of polytetrafluoroethylene. The surface of the mold has one cuboid groove and two semi-cylindrical grooves. The two semi-cylindrical grooves are parallel to each other and pass through a pair of opposite vertices of the cuboid groove outline. The size of the cuboid groove is comparable to the size of the RFID chip, and the inner diameter of the two semi-cylindrical grooves is comparable to the diameter of the conductive fiber.

[0151] (2.2) Place the RFID chip into the rectangular groove and apply an appropriate amount of anisotropic conductive adhesive;

[0152] (2.3) Take two conductive fibers and place them into two semi-cylindrical grooves respectively. They are then hot-pressed to obtain an interconnect intermediate component. The two conductive fibers are located directly above the RF area and GND area of ​​the RFID chip, respectively. The hot-pressing temperature is 230℃, the hot-pressing time is 8s, the bonding pressure is 0.5N / Bump, and a tension of 0.4cN is applied on both sides of the encapsulation point of the two conductive fibers.

[0153] (2.4) Use a thin-blade cutter to trim away excess flexible packaging edges and conductive fiber ends on the interconnect intermediate components;

[0154] (2.5) Take 0.05 mL of flexible insulating adhesive and apply it to the assembly joint between the conductive fiber and the RFID chip. Cure it in a UV curing oven (Baoding Zhonghe Machinery Company, HWUV0133X-18, power: 1700W) for 15 seconds.

[0155] (2.6) Cut the conductive fibers on both sides of the RFID chip into three segments respectively. The three segments on one side are denoted as conductive fiber segment a, conductive fiber segment b, and conductive fiber segment e, and the three segments on the other side are denoted as conductive fiber segment c, conductive fiber segment d, and conductive fiber segment f. At 250°C, use solder wire to weld gravity-sensing tilt switch I between conductive fiber segment a and conductive fiber segment b, gravity-sensing tilt switch II between conductive fiber segment c and conductive fiber segment d, gravity-sensing tilt switch III between conductive fiber segment a and conductive fiber segment e, and gravity-sensing tilt switch IV between conductive fiber segment d and conductive fiber segment f to obtain the interconnect.

[0156] (3) Prepare gravity-sensing UHF RFID step-up sensing yarn;

[0157] The interconnect is spirally wound around the surface of the first core yarn, and then the first insulating wire and the second insulating wire are spirally wound around the surface of the whole composed of the first core yarn and the interconnect, and the spiral directions of the two are controlled to be opposite, thus obtaining the gravity-sensing UHF RFID step-sensing yarn.

[0158] like Figure 8 As shown, the final gravity-sensing UHF RFID step-sensing yarn includes one interconnect, a first core yarn 1, a first insulating wire 5, and a second insulating wire 6; the interconnect is spirally integrated on the surface of the first core yarn 1 with a pitch of 1 mm and a spiral radius of 0.62 mm; the interconnect is formed by sequentially connecting conductor I, RFID chip 2, and conductor II, and conductor I and conductor II are normal mode spiral antennas;

[0159] Conductor I has a segmented structure A, and conductor II has a segmented structure B. Segmented structure A consists of conductive fiber segment e 13, gravity-sensing tilt switch III 11, conductive fiber segment a 7, gravity-sensing tilt switch I 3, and conductive fiber segment b 8. Segmented structure B consists of conductive fiber segment c 9, gravity-sensing tilt switch II 4, conductive fiber segment d 10, gravity-sensing tilt switch IV 12, and conductive fiber segment f 14. Conductive fiber segments e 13 and a 7 are connected by gravity-sensing tilt switch III 11; conductive fiber segments a 7 and b 8 are connected by gravity-sensing tilt switch I 3; conductive fiber segments c 9 and d 10 are connected by gravity-sensing tilt switch II 4; and conductive fiber segments d 10 and f 14 are connected by gravity-sensing tilt switch IV 12. Gravity-sensing tilt switch I 3 in conductor I is connected to gravity-sensing tilt switch II 14 in conductor II. 4. The gravity-sensing tilt switch III 11 in conductor I and the gravity-sensing tilt switch IV 12 in conductor II are symmetrically distributed about the RFID chip 2.

[0160] like Figure 9 As shown, the axial length l5 of conductive fiber segment e 13 is 4 mm, the axial length l1 of conductive fiber segment a 7 is 16 mm, the axial length l2 of conductive fiber segment b 8 is 23 mm, the axial length l3 of conductive fiber segment c 9 is 23 mm, the axial length l4 of conductive fiber segment d 10 is 16 mm, and the axial length l6 of conductive fiber segment f 14 is 4 mm.

[0161] The first insulating wire 5 and the second insulating wire 6 are both spirally wound on the surface of the whole composed of the first core yarn 1 and the interconnecting body, and the spiral directions are opposite.

[0162] The working wavelength of the gravity-sensing UHF RFID step sensor yarn is 32.3-33.2cm.

[0163] The antenna geometric model of the gravity-sensing UHF RFID step-sensing yarn was established using the simulation software Ansys HFSS 2023 R1. The impedance matching between the antenna and the RFID chip was simulated when the tilt angle of the gravity-sensing tilt switch was 5°, 15°, and 45°. The radius 'a' of the helical conductive fiber conductor was 0.045 mm, and the conductivity was 5.8 × 10⁻⁶. 7S / m; Structural parameters: l5=4mm, l1=16mm, l2=23mm, l3=23mm, l4=16mm; l6=4mm; Antenna port excitation is set to lumped port excitation, and its impedance is conjugate with the RFID chip impedance, which is 27.38+j200.76Ω; Because the textile material has little impact on antenna performance, it is ignored here.

[0164] When the tilt angle is 5°, gravity-sensing tilt switch I, gravity-sensing tilt switch II, gravity-sensing tilt switch III, and gravity-sensing tilt switch IV are all in the off state. When the tilt angle is 15°, gravity-sensing tilt switch I and gravity-sensing tilt switch II are in the closed state, and gravity-sensing tilt switch III and gravity-sensing tilt switch IV are in the off state. When the tilt angle is 45°, gravity-sensing tilt switch I, gravity-sensing tilt switch II, gravity-sensing tilt switch III, and gravity-sensing tilt switch IV are all in the closed state.

[0165] from Figure 10 As can be seen, as the tilt angle of the gravity-sensing tilt switch gradually increases, the resonant frequency between the antenna and the RFID chip abruptly shifts to lower frequencies. Specifically, at the operating frequency of 902-927MHz, the impedance matching level abruptly improves. Since RSSI is positively correlated with impedance matching, the RSSI abruptly increases.

Claims

1. A gravity-sensing UHF RFID step-sensing yarn, comprising a first core yarn and an interconnecting element spirally integrated onto the surface of the first core yarn, the interconnecting element being composed of conductor I, an RFID chip, and conductor II sequentially connected, wherein conductor I and conductor II are normal-mode spiral antennas, characterized in that, At least one of conductor I and conductor II has a segmented structure; The segmented structure includes at least two conductive length segments, which are conductive fiber segments or conductive yarn segments, and adjacent two conductive length segments are connected by a gravity-sensing tilt switch. The axial length of the conductive length segment is at least 1.2% of the maximum operating wavelength of the gravity-sensing UHF RFID step-sensing yarn; In the same segmented structure, when the number of gravity-sensing tilt switches is greater than 1, the farther the gravity-sensing tilt switch is from the RFID chip, the larger the tilt threshold.

2. The gravity-sensing UHF RFID step-sensing yarn according to claim 1, characterized in that, Both conductor I and conductor II have segmented structures.

3. The gravity-sensing UHF RFID step-sensing yarn according to claim 2, characterized in that, The gravity-sensing tilt switch in conductor I and the gravity-sensing tilt switch in conductor II are symmetrically distributed with the RFID chip as the center of symmetry.

4. A gravity-sensing UHF RFID step-sensing yarn according to any one of claims 1 to 3, characterized in that, It also includes a first insulating wire and a second insulating wire; both the first insulating wire and the second insulating wire are spirally wound on the surface of the whole composed of the first core yarn and the interconnecting body, and the spiral directions are opposite.

5. A gravity-sensing UHF RFID step-sensing yarn according to any one of claims 1 to 3, characterized in that, It also includes a second core yarn, which is a whole spiral wound around the surface of the second core yarn consisting of the first core yarn and the interconnecting body.

6. The gravity-sensing UHF RFID step-sensing yarn according to claim 5, characterized in that, It also includes a first insulating wire and a second insulating wire; both the first insulating wire and the second insulating wire are spirally wound on the surface of the whole composed of the second core yarn, the first core yarn and the interconnection body, and the spiral directions are opposite.

7. A method for preparing a gravity-sensing UHF RFID step-sensing yarn as described in claim 4, characterized in that, First, an interconnect is prepared, then the interconnect is spirally wound around the surface of the first core yarn, and then the first insulating wire and the second insulating wire are spirally wound around the surface of the whole composed of the first core yarn and the interconnect, and the spiral directions of the two are controlled to be opposite, thus obtaining the gravity-sensing UHF RFID step-sensing yarn.

8. A method for preparing a gravity-sensing UHF RFID step-sensing yarn as described in claim 6, characterized in that, First, an interconnect is prepared. Then, the interconnect is spirally wound around the surface of the first core yarn. Next, the whole consisting of the first core yarn and the interconnect is spirally wound around the surface of the second core yarn. Then, the first insulating wire and the second insulating wire are spirally wound around the surface of the whole consisting of the second core yarn, the first core yarn and the interconnect, and the spiral directions of the two are controlled to be opposite, thus obtaining the gravity-sensing UHF RFID step-sensing yarn.

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