CN118313391B - Passive sensing tag fusing antenna and electrode and related product and device - Google Patents

Abstract

The present invention provides a passive sensing tag that integrates an antenna and an electrode, comprising a flexible substrate, a tag chip, an antenna and an electrode, wherein the tag chip, the antenna and the electrode are all arranged on the same surface of the flexible substrate, and the electrode comprises a first electrode and a second electrode and constitutes a capacitive sensor, and the coverage range of the capacitive sensor constitutes a detection area; the antenna is integrated into the first electrode and becomes a part of the first electrode; the tag chip comprises a radio frequency analog front end, a digital part, a memory, and a capacitive detection circuit; when the detection area is infiltrated by a liquid containing water, a capacitance value positively correlated with the infiltration state is generated between the first and second electrodes, which is used to realize a quantitative moisture detection function; the present invention also provides a smart diaper comprising a passive sensing tag, and an RFID excrement detection and identification system device comprising a smart diaper and a tag reader.

Description

A passive sensor tag integrating antenna and electrode and related products and devices

Technical Field

The present invention relates to a passive sensor tag, in particular to a capacitive passive sensor tag which integrates an antenna and an electrode and can realize quantitative moisture detection, and a related intelligent diaper and a detection system device.

Background Art

How to better apply passive sensor tags (RFID/radio frequency identification tags/electronic tags) to diapers and realize intelligent wireless moisture detection is a goal that people pursue. Diapers are disposable sanitary products that need to be replaced in time. If they are replaced too frequently, it will not only be troublesome but also wasteful; if they are changed too late, it will easily cause leakage and lead to skin diseases such as diaper rash. Therefore, people need a smart diaper product that can prompt replacement at the right time to meet relevant requirements.

In terms of the prior art, Chinese patent publications CN203894918U and CN104951723A respectively provide a urine wetness monitoring device based on radio frequency identification technology and an environmental variable state monitoring device and disposable consumables based on radio frequency identification technology, which put an RFID tag into a diaper and obtain the information of the RFID tag through an RFID reader. When the diaper is in a dry state, the tag sensitivity is high and the reader can read the tag information normally; when the diaper is in a wet state, the tag sensitivity decreases and the reader will not be able to read the tag information, thereby knowing the wet state of the diaper and providing a urine wetness prompt.

The main shortcomings of the above-mentioned prior art are that its reliability is easily affected by the reading distance, reading angle and interference of environmental signals, and it can only provide two state information, dry and wet, but cannot provide quantitative wet state (wetness degree) information. In addition, it cannot provide information on the saturation of diapers and distinguish between urination and defecation.

In order to provide information on the wetness of diapers, Chinese patent publication number CN114324502B provides a capacitive sensing film, and an electronic tag chip and an antenna are arranged on the sensing film. The electronic tag chip is electrically connected to the first and second detection electrodes and realizes a quantitative diaper wetness status detection function through electrolytic capacitance detection between the detection electrodes.

The antenna and detection electrode of the prior art are independent of each other, and are performed when there is no small loop antenna in the tag. In practical applications, electronic tags usually have a small loop antenna, which connects the left and right antennas to form a dipole half-wave antenna that is easy to achieve conjugate matching. However, when the small loop antenna exists, the tag chip of the prior art cannot be connected to the antenna and the two detection electrodes at the same time, because the small loop antenna will block the connection end of one of the poles.

In order to solve the problem of connecting the tag chip with the antenna and the two electrodes on the same plane in the presence of a small loop antenna, a new technical solution is needed.

Summary of the invention

The technical problem to be solved by the present invention is to integrate the antenna and the electrode together to form a small loop antenna through an integrated design, and to connect the tag chip, the antenna and the two electrodes on the same plane. In addition, the problem of digitizing the signal without a digital communication interface and ADC, and the problem of detecting the saturation of the diaper and distinguishing between urine and feces when the passive sensor tag is embedded in the diaper must be solved.

In order to solve the above technical problems, on the one hand, the present invention provides a passive sensing tag that integrates an antenna and an electrode, including a flexible substrate, a tag chip, an antenna and an electrode, wherein the tag chip, the antenna and the electrode are all arranged on the same surface of the flexible substrate, and the electrode includes a first electrode and a second electrode and constitutes a capacitive sensor, and the coverage range of the capacitive sensor constitutes a detection area; the antenna is integrated into the first electrode and becomes a part of the first electrode; the tag chip includes a radio frequency analog front end, a digital part, a memory, and a capacitive detection circuit; when the detection area is infiltrated by a liquid containing water, a capacitance value positively correlated with the infiltration state will be generated between the first and second electrodes, which is used to realize a quantitative moisture detection function.

The antenna includes a dipole antenna and a small loop antenna connected thereto or a coupled small loop coupled thereto. The small loop antenna or the coupled small loop is used to help the dipole antenna and the tag chip achieve conjugate matching.

The main body of the first electrode is connected to the antenna at a single point in the middle of the small loop antenna, so as to reduce the high-frequency signal coupling between the main body of the first electrode and the antenna.

The first electrode further includes a low-pass extension portion for increasing the coverage of the electrode without affecting the operation of the antenna.

Among them, the antenna includes a first antenna and a second antenna, which are respectively multiplexed with the first electrode and the second electrode to form a dual antenna, and the tag chip includes an analog switch matrix for realizing the switching of antenna mode and electrode mode; when in antenna mode, the dual antenna is connected to the dual-port Inlay antenna interface in the tag chip to form a 3D passive sensing tag.

Among them, the capacitance detection circuit includes a charging circuit, a discharging circuit and a counter, which are used to charge and discharge the capacitance between the first and second electrodes, and calculate the time from the start of charging to the voltage rising to a preset trigger threshold, and store the counter value at this time as a capacitance value related to the humidity level in the memory.

It also includes a waterproof protective layer, and the electrode, antenna and tag chip are all located in a waterproof interlayer composed of the waterproof protective layer and the flexible substrate. When the detection area is infiltrated by a liquid containing an electrolyte, the electrode will form an electrolytic capacitor together with the flexible substrate, the waterproof protective layer and the liquid, wherein the electrode constitutes the two poles of the electrolytic capacitor, the flexible substrate and the waterproof protective layer constitute the dielectric of the electrolytic capacitor, and the liquid constitutes the electrolyte of the electrolytic capacitor. The capacitance value of the electrolytic capacitor is positively correlated with the area of the liquid-infiltrated detection area.

Among them, it includes a flexible passive ultra-high frequency sensor tag; the flexible substrate includes a plastic film with a thickness between 5 microns and 0.5 mm; the antenna and electrode include an aluminum plating layer with a thickness between 20 nanometers and 0.1 mm; the waterproof protective layer includes a polymer material coating or a waterproof material composite layer with a thickness between 0.5 microns and 0.5 mm.

On the other hand, the present invention further provides a smart diaper, comprising a passive sensor tag and a disposable absorbent product, wherein the disposable absorbent product comprises a surface layer, an absorbent layer and a leakproof layer, and the passive sensor tag is arranged inside the disposable absorbent product.

Among them, the passive sensor tag is set between the surface layer and the absorption layer of the disposable absorbent product, with the side with higher detection sensitivity facing the surface layer, which is used to obtain the nature of the excrement and the saturation state of the disposable absorbent product by detecting the moisture of the surface layer and analyzing its change rules.

The passive sensor tag is arranged between the absorbent layer and the bottom film of the disposable absorbent article, wherein the side with higher detection sensitivity faces the absorbent layer, and is used to detect the moisture state of the absorbent layer.

Among them, the passive sensor tag is set between the front and crotch of the disposable absorbent product, wherein the tag chip and antenna are close to the front position and the electrode extends to the crotch position, which is used to detect the moisture of the crotch of the disposable absorbent product while avoiding liquid from infiltrating the antenna and affecting communication, and avoiding the electrode from being squeezed by the user's buttocks and affecting the detection accuracy.

On the other hand, the present invention also provides an RFID excrement detection and identification system device, including a tag reader and a smart diaper, wherein the tag reader is used to provide power to the passive sensor tag wirelessly and read the capacitance value related to the wet state of the disposable absorbent product from the passive sensor tag.

It also includes a computer, a smart phone or a status indication device, which is used to obtain capacitance value information from a tag reader, and analyze and determine the nature of the excrement and the saturation state of the disposable absorbent product according to the change pattern of the capacitance value, and provide status indication or prompts.

Wherein, analyzing and judging the nature of the excrement and the saturation state of the disposable absorbent article according to the variation law of the capacitance value includes:

When the capacitance value increases rapidly, it is judged that an excretion process is taking place;

When the capacitance value drops from the peak value, it is judged that the excretion process has ended;

When the capacitance value drops back quickly, it is judged that the excrement is urine and the disposable absorbent product is not saturated;

When the capacitance value falls back slowly, it is judged that the excrement is loose stool or the disposable absorbent product is close to saturation;

When the capacitance value drops rapidly at first and then slowly, the excrement is judged to be a mixture of urine and feces.

The beneficial effect of the present invention is that by using the same material and process to generate all antennas and electrodes of the passive sensor tag at one time, the integrated design and fusion of the antenna and the electrode are realized, which not only solves the problem of the generation of the small loop antenna and the connection between the tag chip and the two electrodes in the presence of the small loop antenna, but also simplifies the production process and reduces the production cost. In addition, low-cost and low-power capacitance signal digitization is realized by means of comparators and counters, and the saturation of the diaper and the distinction between urine and feces are realized by continuously monitoring the moisture level of the diaper surface layer.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

FIG1 is a system structure block diagram of a passive sensor tag that integrates an antenna and an electrode according to an embodiment of the present invention;

2A and 2B are schematic diagrams of the appearance structure of a passive sensor tag that integrates an antenna and an electrode according to an embodiment of the present invention;

3A and 3B are schematic diagrams of the appearance structure of a passive sensor tag in which an antenna and an electrode are integrated, wherein a main body of a first electrode and a small loop antenna are connected at a single point;

FIG4 is a schematic diagram of the appearance structure of a passive sensor tag in which an antenna and an electrode are integrated according to an embodiment of the present invention, in which the first electrode includes a low-pass extension portion;

FIG5 is a schematic structural diagram of a passive sensor tag that integrates an antenna and an electrode, including a coupling loop, according to an embodiment of the present invention;

FIG6 is a schematic diagram of the appearance structure of a passive sensor tag that integrates an antenna and an electrode and includes dual antennas according to an embodiment of the present invention;

7 is a schematic diagram of a cross-sectional structure of a passive sensor tag that integrates an antenna and an electrode and performs capacitance detection without a waterproof protective layer according to an embodiment of the present invention;

FIG8 is a schematic diagram/equivalent circuit diagram of a detectable capacitance value generated when the passive sensor tag shown in FIG7 is immersed in a liquid containing water/electrolyte;

FIG9 is a schematic cross-sectional structure diagram of a passive sensor tag that integrates an antenna and an electrode and performs capacitance detection in the presence of a waterproof protective layer according to an embodiment of the present invention;

FIG10 is a schematic diagram/equivalent circuit diagram of a detectable capacitance value generated when the passive sensor tag shown in FIG9 is immersed in a liquid containing water/electrolyte;

FIG11 is a schematic diagram of a cross-sectional structure of a passive sensor tag in which an antenna and an electrode are integrated and the antenna/electrode is exposed at the edge of the interlayer according to an embodiment of the present invention;

FIG12 is a schematic diagram/equivalent circuit diagram of a detectable capacitance value generated when the passive sensor tag shown in FIG11 is immersed in a liquid containing water/electrolyte;

13 is a block diagram of a system structure in which a tag chip of a passive sensor tag that integrates an antenna and an electrode includes an analog switch matrix and implements antenna and electrode multiplexing according to an embodiment of the present invention;

FIG14 is a block diagram of a capacitance detection circuit of a passive sensor tag that integrates an antenna and an electrode according to an embodiment of the present invention;

FIG15 is a schematic diagram of the layered structure of a smart diaper including a passive sensor tag and capable of detecting and distinguishing urination and defecation according to an embodiment of the present invention;

FIG. 16 is a block diagram of an RFID excrement detection and identification system device including a passive sensor tag and a disposable absorbent article according to an embodiment of the present invention.

DETAILED DESCRIPTION

The following descriptions of the embodiments are made with reference to the accompanying drawings to illustrate specific embodiments in which the present invention may be implemented. The directions and positions mentioned in the present invention, such as "upper", "lower", "front", "back", "left", "right", "inside", "outside", "top", "bottom", "side", "front", "front end", "rear end", "both ends", "both sides", etc., are only with reference to the directions or positions of the accompanying drawings. Therefore, the directions and positions used are used to illustrate and understand the present invention, but are not intended to limit the scope of protection of the present invention.

The present invention is further described below in conjunction with the accompanying drawings. Referring to Figure 1, this is a system structure block diagram of a passive sensor tag that integrates an antenna and an electrode according to an embodiment of the present invention. The passive sensor tag 10 of this embodiment, which can also be called an RFID tag, a radio frequency identification tag, an electronic tag, a sensor tag or simply a tag, includes a tag chip 20 (referred to as chip), a first electrode 41, and a second electrode 42, wherein the first and second electrodes together constitute a capacitive sensor 40 of an embodiment of the present invention and output a capacitance value that is positively correlated with the degree of moisture (wetting area), where the electrodes can also be referred to as detection electrodes or sensing electrodes. The capacitive sensor of an embodiment of the present invention is a moisture/humidity/moisture sensor (Wetness/Moisture Sensor) that detects the presence and amount of liquid containing water by means of capacitance. The more liquid, the greater the capacitance output, thereby achieving quantitative moisture detection.

The antenna 30 of the embodiment of the present invention is integrated with the first electrode 41, or the antenna 30 is contained in/fused in the first electrode 41 and constitutes a part of the first electrode 41. The tag chip 20 includes an antenna connection terminal 21, a radio frequency analog front end 22, a digital part 23, and a memory 24, which constitute a conventional RFID passive sensor tag. The embodiment of the present invention preferably uses an ultra-high frequency (UHF) passive sensor tag, because the passive sensor tag in this frequency band has low cost and long transmission distance, generally up to 3-10 meters, which can meet the needs of general application scenarios. If it is to be configured within a larger range, a higher-power tag reader can be used, or multiple readers can be configured according to the size of the site to achieve a wider range of coverage.

In order to realize capacitance detection, the tag chip 20 of the embodiment of the present invention further includes a capacitance connection terminal 25, a capacitance detection circuit 26 and a storage capacitor 27. The capacitance signal between the first and second electrodes is input through the capacitance connection terminal 25 (including two capacitance connection terminals C+ and C-) and sent to the capacitance detection circuit 26. The capacitance detection circuit 26 digitizes the analog signal, converts it into a quantized data and stores it in the memory 24 of the tag chip, so that the tag reader can read the data at any time.

In order to ensure sufficient electrical energy, the tag chip 20 of the embodiment of the present invention will also include an energy storage capacitor 27. When the reader is working, it will emit a wireless carrier signal of a certain power. The passive sensor tag 10 will receive these carrier signals through the antenna 30 and obtain energy supply from them. The excess energy will also be stored in the energy storage capacitor 27, so that additional electrical energy can be provided when necessary to complete some tasks with relatively high energy consumption, such as when the signal is returned to the reader and when the capacitance detection is performed.

Figures 2A and 2B are schematic diagrams of the appearance structure of a passive sensor tag that integrates an antenna and an electrode according to an embodiment of the present invention. The antenna of this embodiment includes two 1/4 wavelength antennas 30A and 30B and constitutes a half-wave oscillator antenna/dipole antenna, and the main body 41A of the first electrode connects the two 1/4 wavelength antennas 30A and 30B together and generates a small loop antenna 30C at the connection point. Therefore, the antenna of this embodiment can be called a half-wave dipole antenna with a small loop antenna. In this structure, the small loop antenna 30C is mainly used to help the dipole antenna and the tag chip achieve conjugate matching, and plays a role in improving the anti-static level of the tag, which is particularly important for the passive sensor tag of the embodiment of the present invention as a wearable device working in a humid environment.

The antenna of the embodiment of the present invention is composed of 30A, 30B and 30C, which can be marked as 30, which is included in/fused in the first electrode 41 and constitutes a part of the first electrode 41. In addition to the part fused with the antenna 30, the first electrode 41 also includes a main body 41A. That is to say, the first electrode 41 is composed of components 41A, 30A, 30B, and 30C, while the second electrode 42 exists independently and has no intersection with any unit of the antenna.

The first electrode 41 and the second electrode 42 together constitute the capacitive sensor 40 of the embodiment of the present invention. The tag chip 20 of the present embodiment includes four connection terminals, namely the connection terminals 301 and 302 of the antennas 30A and 30B, and the connection terminals 401 and 402 of the first and second electrodes 41 and 42. In practical applications, the connection terminal 401 of the first electrode 41 can be used as a ground terminal and connected to the capacitor connection terminal C- inside the tag chip 20, while the second electrode 42 is connected to the capacitor connection terminal C+ inside the tag chip 20. In addition, the connection terminal 401 can be removed and any one of the connection terminals 301 and 302 can be used to replace the connection terminal 401 and connect to the first electrode 41. For low frequency or direct current, these three connection terminals are of equal potential.

The main body 41A of the first electrode 41 and the second electrode 42 of this embodiment are both longer than the antenna 30. The longer the electrode, the larger the detection area. In the application, the length of the electrode can be selected according to actual needs, which is important for the application on diapers, because diapers have different models and specifications and need to be matched with sensor tags with different detection area ranges to achieve the best use effect.

The tag chip 20 of the embodiment shown in FIG2A is located in the middle of the tag, while the tag chip 20 of the embodiment shown in FIG2B is biased to one side (towards the right side in the figure). The advantage of the antenna being biased to one side is that when it is set inside a diaper, the antenna position can be set near the front part (waistband) of the diaper, which is usually not wetted by urine and will not be pressed by the user, which can reduce the impact on the operation of the sensor tag.

In view of the situation that the label may be soaked when wet, some anti-liquid measures can be taken when designing the label, so that the label can still work normally when soaked in urine. In addition, the dipole antenna shown in this embodiment is a straight design. In practical applications, a bending design and end loading can be used as needed to adjust the length of the antenna and improve the impedance matching between the antenna and the tag chip. In addition, non-half-wave dipole antennas and single-loop monopole antenna designs can also be used. These are existing technologies and can be used as needed, so I will not go into details.

3A and 3B are schematic diagrams of the appearance structure of a passive sensor tag that integrates an antenna and an electrode in an embodiment of the present invention, in which the main part 41A of the first electrode 41 and the small loop antenna 30C are connected at a single point through a connection point 31. The single point connection can reduce the coupling between the main part 41A of the first electrode and the small loop antenna 30C, thereby reducing the impact on the antenna. In order to further reduce the impact, a low-pass filter/inductor can be added at the connection point 31 to allow the low-frequency or DC capacitance signal of the main part 41A to pass through and filter the radio frequency signal, so that the main part 41A of the first electrode has almost no effect on the antenna.

The main body 41A of the first electrode of the embodiment shown in FIG3A is symmetrical with the second electrode 42, while the middle portion of the main body 41A of the first electrode of the embodiment shown in FIG3B is recessed, and the half-wave dipole antenna formed by the antennas 30A, 30B and 30C is embedded in the recessed portion, which appears to be asymmetrical with the second electrode 42 in appearance. However, for capacitance detection, the antenna is also a part of the electrode, that is, the first electrode 41 includes the main body 41A and the antennas 30A, 30B and 30C at the same time. For capacitance detection, the first electrode 41 is basically symmetrical with the second electrode 42 in electrical performance.

FIG4 is a schematic diagram of the appearance structure of the first electrode 41 of a passive sensor tag that integrates an antenna and an electrode according to an embodiment of the present invention, including a low-pass extension portion 41B. The antenna 30 of this embodiment completely overlaps with the main body 41A of the first electrode 41, so the length of the main body 41A is subject to the length of the antenna 30. In order to extend the first electrode 41, one end of the first electrode 41 of this embodiment includes a low-pass extension portion 41B, that is, the extension portion 41B is connected to the main body 41A through an inductor/low-pass filter L1, which can block radio frequency signals and allow low-frequency or DC capacitance signals to pass through, thereby achieving the purpose of extending the electrode. As for the second electrode 42, since it does not need to match the antenna, the length can be freely selected. In practical applications, the second electrode usually selects a length consistent with the first electrode 41 (including the main body 41A and the extension portion 41B).

The most commonly used antenna design for passive sensor tags is the half-wave dipole antenna, which is half-wave in length without bending (usually slightly shorter than half-wave to achieve impedance matching). In order to obtain different lengths, the embodiments of the present invention may also use some specific graphic designs to change its shape, such as using a bending design to reduce its length, or using electromagnetic wave offset or blocking methods to increase the length, etc. In addition, the antenna may also be designed according to different percentages of the wavelength, such as 1/4, 1.5 times, or 2.5 times the wavelength, and the specific design may be selected or adjusted according to actual requirements. In addition, the detection range may be increased by placing multiple passive sensor tags in diapers.

The passive sensor tag of the embodiment of the present invention is usually placed in the crotch position of the diaper, and the tag will be soaked when urine occurs. In order to protect the tag, a waterproof protective layer can be covered on the chip, antenna and electrode through non-contact coating, such as spray coating, or a waterproof material can be combined with it to form a protective layer to reduce the impact of urine on the tag. In addition, the tag used on the diaper is a wearable device, and the impact of the human body on the wireless communication of the tag needs to be considered. In practice, anti-liquid tag design measures are usually adopted to further reduce the impact of liquid and human body on the tag.

FIG5 is a schematic diagram of the appearance structure of a passive sensor tag that integrates antenna and electrode according to an embodiment of the present invention, including a coupling small loop. In the figure, there is no small loop antenna 30C directly connected to the dipole antenna 30A/30B. Instead, there is a coupling small loop 30D that is coupled to the dipole antenna 30A and 30B in a non-contact manner (inductive manner). Its function is similar to that of the small loop antenna 30C, and it can also be considered as a variation of the small loop antenna. In addition, the first electrode 41 of this embodiment is completely overlapped/fused with the dipole antenna composed of 30A and 30B. Therefore, the electrode of this embodiment will accommodate the antenna design. If the length of the electrode is to be increased, the embodiment shown in FIG4 can be referred to, and the extension of the electrode can be achieved by increasing the low-pass extension part.

FIG6 is a schematic diagram of the appearance structure of a passive sensor tag that fuses an antenna with an electrode, including dual antennas, according to an embodiment of the present invention. Unlike the antennas of the aforementioned other embodiments that only include one antenna and are only fused with the first electrode, this embodiment includes two dipole antennas that are fused with two electrodes respectively. Specifically, the first electrode 41 is fused with the first antenna 30 (composed of 30A, 30B, and 30C), the second electrode 42 is fused with the second antenna 30' (composed of 30A', 30B', and 30C'), and is connected to the tag chip 20 through the connection terminals 51-54.

In order to separate the antenna function from the electrode function, an analog switch matrix may be included in the tag chip 20. When the analog switch is switched to the antenna mode, the wireless signals of the first antenna 30 and the second antenna 30' may be input, and these two signals are connected to the dual-port Inlay antenna interface inside the tag chip 20 to form a 3D passive sensing tag; and when the analog switch is switched to the capacitance detection mode, the capacitance signals of the first electrode 41 and the second electrode 42 may be input and transmitted to the capacitance detection circuit 26 to realize the capacitance detection function between the first and second electrodes.

FIG7 is a schematic diagram of a cross-sectional structure of a passive sensor tag that integrates an antenna and an electrode in an embodiment of the present invention and performs capacitance detection without a waterproof protective layer, which is an A-A' section of FIG6. In this section, it can be seen that the first electrode 41, the second electrode 42 and the tag chip 20 are all arranged on the same surface of the flexible substrate 43, and the tag chip 20 is connected to the first and second electrodes 41 and 42 to achieve capacitance detection. Since this embodiment is intended to illustrate the capacitance detection function, the antenna is not marked and the antenna function is not explained.

The flexible substrate 43 of the embodiment of the present invention can be selected from soft and waterproof plastic films, such as polyester film (PET), biaxially oriented polypropylene film (BOPP), cast polypropylene film (CPP), polyethylene film (PE), polyimide film (PI), etc., and the thickness can be between 5-500 microns. The antenna and the electrode are both generated by the same material and process, for example, they can be generated by etching or evaporation of metals such as copper and aluminum, or printed with conductive inks such as carbon paste and silver paste. In practical applications, it is preferred that a vacuum evaporation process is used to generate a thin layer of metal aluminum film on the PET film at one time, with a thickness ranging from tens of nanometers to hundreds of nanometers, and then the required antenna and electrode patterns are generated by hollowing processes such as water washing and alkali washing or laser engraving processes. That is to say, the antenna and the electrode of the embodiment of the present invention are generated at one time using the same material and process, and are integrated and integrated with each other, which not only simplifies the process but also saves costs.

When the passive sensor tag shown in FIG7 is immersed in a liquid 16 containing water/electrolyte, a detectable capacitance value is generated between the first and second electrodes 41 and 42, and its schematic diagram/equivalent circuit diagram is shown in FIG8. Since there is no waterproof protective layer, the two electrodes of this embodiment are exposed and directly contact with the liquid and generate a double-layer capacitance C1 between the first electrode 41 and the second electrode 42.

According to the double-layer capacitance theory, when a liquid containing an electrolyte comes into contact with a solid electrode, a double-layer capacitance is generated at the contact interface between the solid electrode and the liquid (referred to as the liquid-solid interface or interface). When a DC voltage is applied between the two electrodes, the negative ions in the liquid accumulate on the positive electrode, while the positive ions in the liquid accumulate on the negative electrode. The positive and negative ions in the liquid and the opposite ions on the solid electrode form a layer of ionic dielectric, thereby generating a double-layer capacitance.

Since water is also an electrolyte (weak electrolyte), it will also generate a double-layer capacitor on the electrode. As for human excrement such as urine, it contains salt, which is a strong electrolyte and will enhance the electrolytic properties of water. The embodiment of the present invention regards the liquid containing water as a liquid containing an electrolyte (referred to as liquid). When the tag is infiltrated by the liquid, a double-layer capacitor C1 is generated between the first and second electrodes. Its size is positively correlated with the area of the two electrodes infiltrated by the liquid. By measuring the capacitance value of the double-layer capacitor C1, the area/degree of infiltration can be known.

FIG9 is a cross-sectional schematic diagram of a passive sensor tag that integrates antenna and electrode and performs capacitance detection in the presence of a waterproof protective layer according to an embodiment of the present invention. The tag of this embodiment includes a waterproof protective layer 44, which covers the first electrode 41, the second electrode 42, the antenna 30 (not shown in the figure) and the tag chip 20, so that these components are all within a waterproof interlayer 45 composed of a flexible substrate 43 and the waterproof protective layer 44, so that the liquid 16 cannot contact these components, which can make the tag work more stably.

Fig. 10 is a schematic diagram/equivalent circuit diagram of the detectable capacitance value generated when the passive sensor tag shown in Fig. 9 is immersed in a liquid containing water/electrolyte. Due to the presence of the waterproof protective layer 44, the liquid 16 cannot contact the electrode surface, so the double-layer capacitor C1 shown in Fig. 8 will not be generated, and instead, an electrolytic capacitor C2 will be generated.

When the tag is immersed in a liquid 16 containing an electrolyte, the first and second electrodes 41, 42 together with the flexible substrate 43, the waterproof protective layer 44 and the liquid 16 form an electrolytic capacitor C2, wherein the first and second electrodes 41, 42 constitute the two poles of the electrolytic capacitor C2, the flexible substrate 43 and the waterproof protective layer 44 constitute the dielectric of the electrolytic capacitor C2, the liquid 16 constitutes the electrolyte of the electrolytic capacitor C2, and the capacitance value of the electrolytic capacitor C2 is positively correlated with the area of the detection area infiltrated by the liquid 16, thereby achieving a stable and reliable quantitative moisture detection function.

In practical applications, the waterproof protective layer 44 is usually made of polymer materials and is formed by covering the antenna, electrode and tag chip by non-contact coating/spray coating. Its thickness can be set as needed, ranging from 0.5 microns to 0.5 mm. In addition, the antenna, electrode and tag chip can also be protected by a waterproof film and a flexible substrate.

Since the electrolytic capacitor C2 is produced by the liquid 16 adhering to the surface of the waterproof protective layer 44 and the flexible substrate 43, different thicknesses will result in different detection sensitivities. The thinner the thickness, the higher the detection sensitivity. Usually, the side with higher sensitivity is used as the main sensing surface, and it is directed toward the direction of key detection during use. For example, when the label is placed between the surface layer and the absorption layer of the diaper, the main sensing surface can be directed toward the surface layer, so that the moisture level of the surface layer can be focused on. Because the surface layer is a layer close to the skin, its moisture level is consistent with the real feeling of the human body. At the same time, it is also easier to detect feces and distinguish between feces and urine.

Figure 11 is a cross-sectional schematic diagram of a passive sensor tag that integrates an antenna and an electrode according to an embodiment of the present invention, in which the antenna/electrode is exposed at the edge of an interlayer 45. The main difference between it and Figure 9 is that the first and second electrodes 41 and 42 of this embodiment are exposed at the edge of the interlayer 45 through incisions and can contact the liquid. Since this design does not require leaving blank space at the edge of the interlayer, the label can be designed to be more compact, thereby saving costs.

Fig. 12 is a schematic diagram/equivalent circuit diagram of the detectable capacitance value generated when the passive sensor tag shown in Fig. 11 is immersed in a liquid containing water/electrolyte. Since the first and second electrodes 41 and 42 of this embodiment have both a portion protected by the waterproof protective layer 44 and a portion exposed at the edge of the interlayer 45, it can generate an electrolytic capacitor C2 through the waterproof protective layer 44 and a double electric layer capacitor C3 through the portion exposed at the edge of the interlayer.

The size of the electrolytic capacitor C2 is proportional to the area of the liquid covering the surface of the protective layer corresponding to the electrode and the surface of the flexible substrate, while the size of the double-layer capacitor C3 is proportional to the width of the electrode in contact with the liquid at the edge of the gap. Since the electrode of the embodiment of the present invention is very thin, for example, the thickness of the vacuum-evaporated aluminum is at the nanometer level, and the width of the electrode exposed at the edge of the sandwich and in contact with the liquid is also at the nanometer level, the double-layer capacitor C3 generated by the contact surface with the nanometer-level width will be much smaller than the capacitance value of the electrolytic capacitor C2 generated by the electrode with the millimeter-level width, so the double-layer capacitor C3 can be ignored, so the detection sensitivity of this embodiment is similar to that of the label without exposed electrodes shown in Figure 9.

Fig. 13 is a block diagram of a system structure of a tag chip of a passive sensor tag that integrates antenna and electrode, including an analog switch matrix and realizing antenna and electrode multiplexing, which is particularly suitable for the case of dual antennas as shown in Fig. 6. This embodiment includes an analog switch matrix 28, the left side of which is connected to four input terminals/connection terminals 51-54, and the right side is respectively connected to the antenna connection terminal 21 and the capacitor connection terminal 25.

The analog switch matrix 28 can select two of its inputs as antenna inputs and the other two as capacitor inputs. When the antenna function is selected, the capacitor function can also be shielded to avoid affecting the operation of the antenna. Similarly, when the capacitor function is selected, the antenna function can also be shielded to avoid affecting the detection of the capacitor.

FIG14 is a block diagram of a capacitance detection circuit of a passive sensor tag that integrates an antenna and an electrode according to an embodiment of the present invention. The capacitance C output between the two electrodes of this embodiment enters the capacitance detection circuit 26 through the capacitance connection terminal 25. Of the two capacitance connection terminals, the C-terminal is usually connected to the ground level, while the C+ terminal is connected to the capacitance detection circuit 26. The high-frequency filter circuit capacitor 261 in the capacitance detection circuit 26 can filter out the high-frequency components mixed in the capacitance signal.

The capacitance detection circuit 26 further includes a charging circuit 262, a discharging circuit 263, a reference voltage 264, a comparator 265, a counter 266 and a clock 267. The charging circuit 262 can be a resistor connected to a power supply terminal, or a constant current charging circuit, for charging the capacitor C. Before charging, the capacitor C must be discharged through the discharging circuit 263 so that the subsequent charging can start from zero voltage.

When charging starts, the counter 266 will be started synchronously to count the clock 267 to calculate the charging time. When the voltage across the capacitor C rises and exceeds the reference voltage 264 (a preset voltage trigger threshold), the comparator 265 will flip and stop the counter. At this time, the value of the counter is proportional to the size of the capacitor C, and it can be directly regarded as a capacitance value representing the degree of humidity.

In practical applications, buffers, inverters, Schmitt triggers, semiconductor switches, MOS tubes and other components can also be used to play the role of reference voltage 264 and comparator 265. When the voltage value across the capacitor exceeds the switching voltage or the trigger voltage, the output levels of these components will change, and the change in output level can be used to trigger the counter to store the count value into the memory, thereby realizing the required capacitance detection function.

The digital part 23 inside the tag chip can be used to control the entire capacitance detection process. For example, it can control the capacitance value to be detected once every second, and discharge the capacitor C after the detection is completed, and then charge the capacitor C again after 1 second; when the comparator is reversed, the digital part 23 will receive the corresponding signal, and then instruct the counter 266 to transfer the value to the memory 24 for storage, and then return the value to the reader when the reader queries.

FIG15 is a schematic diagram of the layered structure of a smart diaper including a passive sensor tag that can detect and distinguish urination and defecation according to an embodiment of the present invention. The smart diaper 60 includes a disposable absorbent article and a passive sensor tag 10 according to an embodiment of the present invention disposed inside the disposable absorbent article. The disposable absorbent article generally includes a surface layer (dry layer) 61, an absorbent layer (hygroscopic layer) 62, and a leakproof layer (bottom film) 65. The passive sensor tag 10 can be disposed on the surface layer of the disposable absorbent article, between the surface layer and the absorbent layer, inside the absorbent layer, or between the absorbent layer and the leakproof layer.

In the figure (this embodiment), the passive sensor tag 10 is set between the surface layer 61 and the absorption layer 62. At this time, the side with higher detection sensitivity can be facing the surface layer. Since the surface layer is in direct contact with the skin, the moisture detection of the surface layer can truly reflect the user's skin feeling. At the same time, the surface layer is the closest part of the diaper to excrement, and it is easier to detect feces.

If the passive sensor tag 10 is placed between the absorption layer and the anti-leakage layer, the side with higher detection sensitivity should face the absorption layer to detect the moisture state of the absorption layer. Placing the passive sensor tag 10 between the absorption layer and the anti-leakage layer is conducive to the downward penetration of urine, but the cost is that feces cannot be detected. At this time, the passive sensor tag 10 is mainly used for urine wetness detection and saturation detection of diapers.

In this embodiment, the passive sensor tag 10 adopts the design shown in Figure 2B in which the tag chip 20 is biased to one end. The figure shows that it is biased to the left end and is located in the front position 66 (abdomen position) of the disposable absorbent product. Here, the tag chip and the antenna can be prevented from being soaked by urine and affecting signal transmission; the electrode part extends to the crotch position 67 to detect the moisture state of the crotch; as for the rear position 68 (back position), there is no tag, which can prevent the user's back from pressing on the tag and affecting the tag operation.

16 is a block diagram of an RFID excrement detection and identification system device including a passive sensor tag and a disposable absorbent product according to an embodiment of the present invention, including a smart diaper 60 and a passive sensor tag 10 disposed inside the smart diaper, a tag reader 70 communicating with the passive sensor tag 10, and a computer, smart phone or other status display/indication device 80 connected to the tag reader 70 by wire or wireless, wherein the indication device may also be disposed inside the tag reader.

The tag reader 70 can not only read the capacitance value information related to the humidity level in the memory from the passive sensor tag 10 through wireless radio frequency (such as ultra-high frequency UHF), but also provide the passive sensor tag 10 with the power required for its operation through wireless radio frequency. As for the computer, smart phone or status indication device 80, in addition to obtaining the humidity level data/capacitance value information from the tag reader 70, it can also analyze and determine the nature of the excrement and the saturation state of the disposable absorbent product according to the change law of the capacitance value and provide related status indications; including:

When the capacitance value increases rapidly, it is judged that a discharge process is taking place;

When the capacitance value drops from the peak value, it is judged that the aforementioned excretion process has ended;

When the capacitance value drops back quickly, it is judged that the excrement is urine and the disposable absorbent product is not saturated;

When the capacitance value drops slowly, it is judged that the excrement is loose stool or the disposable absorbent product is close to saturation;

When the capacitance value drops rapidly at first and then slowly, it is determined that the excrement is a mixture of urine and feces.

The above disclosures are only some preferred embodiments of the present invention, and are described by taking moisture detection of disposable absorbent products as an example. This cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes and expansions of the scope of application made according to the claims of the present invention are still within the scope covered by the present invention.

Claims (15)

1. The passive sensing tag is characterized by comprising a flexible substrate, a tag chip, an antenna and an electrode, wherein the tag chip, the antenna and the electrode are arranged on the same surface of the flexible substrate, the electrode comprises a first electrode and a second electrode and forms a capacitance sensor, and the coverage area of the capacitance sensor forms a detection area; the antenna is fused inside the first electrode and becomes a part of the first electrode; the tag chip comprises a radio frequency analog front end, a digital part, a memory and a capacitance detection circuit; when the detection area is infiltrated by the liquid containing moisture, a capacitance value positively correlated with the infiltration state is generated between the first electrode and the second electrode, so as to realize the quantized moisture detection function.

2. A passive sensing tag according to claim 1, wherein the antenna comprises a dipole antenna and a loop antenna connected thereto or a coupling loop coupled thereto, the loop antenna or coupling loop being adapted to assist in conjugate matching of the dipole antenna to the tag chip.

3. A passive sensing tag according to claim 2, wherein the body portion of the first electrode is single point connected to the antenna at a location intermediate the small loop antenna for reducing high frequency signal coupling of the body portion of the first electrode to the antenna.

4. A passive sensing tag according to claim 3, wherein the first electrode further comprises a low pass extension for increasing the coverage of the electrode without affecting the operation of the antenna.

5. The passive sensing tag of claim 1, wherein the antenna comprises a first antenna and a second antenna and is multiplexed with the first electrode and the second electrode respectively to form a dual antenna, and the tag chip comprises an analog switch matrix for realizing switching between an antenna mode and an electrode mode; when the antenna is in the antenna mode, the dual antennas are connected with a dual-port Inlay type antenna interface in the tag chip to form a 3D passive sensing tag.

6. The passive sensor tag of claim 1, wherein the capacitance detection circuit comprises a charging circuit, a discharging circuit and a counter for charging and discharging the capacitance between the first and second electrodes, calculating a time from a start of charging to a rise of the voltage to a predetermined trigger threshold, and storing the counter value at the time as a capacitance value related to the degree of wetness in the memory.

7. The passive sensor tag of claim 1, further comprising a waterproof layer, wherein the electrode, antenna and tag chip are all located within a waterproof layer formed by the waterproof layer and the flexible substrate, wherein the electrode forms an electrolytic capacitor with the flexible substrate, waterproof layer and liquid when the detection area is wetted by the liquid containing electrolyte, wherein the electrode forms two poles of the electrolytic capacitor, the flexible substrate and waterproof layer form a dielectric of the electrolytic capacitor, the liquid forms an electrolyte of the electrolytic capacitor, and a capacitance value of the electrolytic capacitor is positively correlated with an area of the detection area wetted by the liquid.

8. A passive sensing tag incorporating an antenna and an electrode as claimed in claim 1, comprising a flexible passive ultra-high frequency sensing tag; the flexible substrate comprises a plastic film having a thickness of between 5 microns and 0.5 millimeters; the antenna and the electrode comprise aluminized layers with a thickness between 20 nanometers and 0.1 millimeter.

9. An intelligent paper diaper, characterized by comprising the passive sensing tag according to any one of claims 1 to 8 and a disposable absorbent article, wherein the disposable absorbent article comprises a surface layer, an absorbent layer and a leakage-proof layer, and the passive sensing tag is arranged in the disposable absorbent article.

10. The smart diaper of claim 9 wherein said passive sensor tag is disposed between a facing layer and an absorbent layer of said disposable absorbent article, wherein a side of said disposable absorbent article having a higher detection sensitivity is oriented toward said facing layer for obtaining the nature of the feces and the saturation status of said disposable absorbent article by detecting wetness of said facing layer and its change law analysis.

11. The smart diaper of claim 9 wherein the passive sensing label is disposed between an absorbent layer and a carrier film of the disposable absorbent article, wherein a side of the absorbent layer having a higher detection sensitivity is oriented to detect a wetness state of the absorbent layer.

12. The smart diaper of claim 9 wherein the passive sensing tag is disposed between the front and crotch portions of the disposable absorbent article, wherein the tag chip and antenna are positioned adjacent the front portion and the electrode extends to the crotch portion for detecting wetness of the crotch portion of the disposable absorbent article while avoiding liquids from wetting the antenna and affecting communication and avoiding the electrode from being squeezed by the user's buttocks and affecting accuracy of detection.

13. An RFID excreta detection and identification system device comprising a tag reader and the smart diaper of claim 9, wherein the tag reader is configured to wirelessly provide power to the passive sensing tag and to read a capacitance value associated with the wetness state of the disposable absorbent article from the passive sensing tag.

14. The RFID excreta detection and identification system device of claim 13, further comprising a computer, a smart phone, or a status indication device for acquiring the capacitance value from the tag reader, analyzing and judging the nature of the excreta and the saturation status of the disposable absorbent article according to the change rule of the capacitance value, and performing status indication or prompt.

15. The RFID excreta detection and identification system device of claim 14, wherein the analysis of the property of the excreta and the saturation state of the disposable absorbent article according to the change law of the capacitance value comprises:

Judging that a drainage process is occurring when the capacitance value is rapidly increased;

judging that the draining process is finished when the capacitance value falls back from a peak value;

Judging that the excrement is urine and the disposable absorbent article is unsaturated when the falling speed of the capacitance value is high;

judging that the excrement is loose stool or the disposable absorbent article is nearly saturated when the falling speed of the capacitance value is low;

And judging that the excrement is a mixture of urine and feces when the falling speed of the capacitance value is firstly high and then low.