Chronic wound pH monitoring method and system based on passive RFID

Abstract

The present application relates to a kind of chronic wound pH monitoring method and system based on passive RFID.For the problems such as weak response of sensing material, difficult integration and strong environmental interference, the sensing loop nested in the dipole antenna inside in the present scheme will be embedded in the porous microstructure PEDOT:PSS sensing material.By using the principle that the conductivity of sensing material increases with the increase of pH, and then enhancing the eddy current of sensing loop and regulating the equivalent inductance of sensing loop antenna, the accurate modulation of backscattering signal phase is realized.Combined with the space-time difference of double label and the frequency domain slope extraction algorithm, while ensuring the efficiency of far field communication, the pH sensing sensitivity and motion anti-interference ability are significantly improved.The system does not need battery, and the cost is low, which is suitable for long-term, real-time monitoring of chronic wound state.

Description

Technical Field

[0001] This invention relates to the fields of radio frequency identification (RFID) and flexible bioelectronic sensing technology, and in particular to a real-time, non-invasive, motion-interference-resistant method and system for monitoring pH in chronic wounds based on passive RFID technology. Background Technology

[0002] Chronic wounds, especially diabetic foot ulcers (DFUs), have become a serious challenge for healthcare systems worldwide. Due to their slow healing and high susceptibility to recurrent infections, continuous monitoring of physiological parameters is crucial for guiding clinical decisions, reducing amputation rates, and alleviating the financial burden on patients. Among numerous biomarkers, the pH value of the wound surface is widely recognized as one of the "gold standards" for assessing healing status: healthy skin is typically slightly acidic, while the pH value of chronic wounds often rises to alkaline (pH>8); as the wound heals, the pH value gradually decreases.

[0003] Currently, clinical monitoring of wound pH mainly relies on large laboratory equipment or disposable electrochemical sensors. However, laboratory analysis has significant time lag and cannot provide real-time alerts; while electrochemical sensors can monitor in real time, their high cost, complex wiring, and potential cytotoxicity of sensor electrodes limit their widespread application in home care settings.

[0004] In recent years, passive RFID technology based on the ultra-high frequency (UHF) backscattering principle has provided a highly promising technological approach for developing "smart dressings" due to its characteristics such as battery-free operation, low cost, ultra-thin flexibility, and contactless communication. Passive RFID technology based on the UHF backscattering principle is the core physical foundation for achieving remote, passive sensing. This technology typically operates in the 860MHz to 960MHz frequency band, and its basic working mechanism is based on the electromagnetic energy interaction between the reader and the passive tag. During monitoring, the RFID reader emits continuous radio frequency waves through its antenna. When the passive tag within the electromagnetic field captures this energy, its internal rectifier circuit converts the received radio frequency energy into DC power, thereby activating the tag chip. Unlike wireless communication devices that actively transmit signals, passive tags do not have the ability to autonomously transmit radio frequency signals. Instead, they use load modulation technology to "inject" the data or sensing information to be transmitted into the reflected wave.

[0005] Specifically, the tag chip modulates the antenna's reflection cross-section of incident electromagnetic waves by rapidly switching the impedance state of its internal antenna, thereby altering the impedance matching between the antenna and the chip. This modulated reflected signal is retransmitted back to the reader and is known as the backscattered signal. In the context of chronic wound pH monitoring, this backscatter-based architecture exhibits unique advantages. Since the tag requires no battery power, the sensing system can be designed to be extremely thin and flexible, easily integrated into wound dressings without imposing a physical burden on the patient. More importantly, the phase of the radio frequency signal is extremely sensitive to changes in the tag chip's input impedance. When the electrical properties of the pH sensing material integrated on the antenna change, this microscopic chemical change is directly translated into a macroscopic phase shift. By analyzing the phase characteristics of the backscattered signal at different frequencies, the system can achieve non-invasive telemetry of the wound's biochemical environment without contacting electronic components, providing an ideal technical path for building a long-term, continuous home rehabilitation monitoring system.

[0006] However, in the actual process of applying passive RFID technology to high-sensitivity physiological monitoring of chronic wounds, there are still a series of underlying technical obstacles that need to be addressed.

[0007] First, the cross-scale sensitivity adaptation problem between pH sensing materials and radio frequency signals is very prominent. Traditional pH sensing materials often have weak electrical responses under physiological conditions. When such small impedance changes are transmitted spatially through the backscattering mechanism of passive RFID, the signal characteristic shift caused at the reader end is easily overwhelmed by system thermal noise, resulting in the sensor lacking sufficient quantization accuracy and signal-to-noise ratio in the critical pH fluctuation range.

[0008] Secondly, achieving physical integration of sensors without compromising the impedance matching of RFID antennas is a significant challenge in flexible hardware design. Because pH sensing materials typically possess complex impedance characteristics, the integration process often alters the original current distribution and radiation modes of the antenna, leading to severe frequency drift or gain reduction. This not only limits the efficiency of the tag in harvesting energy from the radio frequency field but also compresses the effective communication distance of the system, meaning that improvements in sensitivity often come at the cost of sacrificing the stability and reliability of system communication.

[0009] Finally, phase aliasing under dynamic physiological conditions severely interferes with the robustness of monitoring. Because the backscattered phase of RFID is extremely sensitive to the spatial distance between the tag and the reader, in real-world wearable scenarios, fluctuations in a patient's breathing, muscle tremors, and even spatial displacement caused by walking can generate drastic phase fluctuations. These physical-dimensional motion noises are highly coupled in the time domain with the phase response caused by the chemical dimension, forming a complex nonlinear interference. This interference is often several times larger than the actual physiological signal, making it exceptionally difficult to accurately decouple a pure pH value from the chaotic original phase sequence. This has become a key technical hurdle hindering the transition of passive monitoring systems from controlled laboratory environments to complex clinical home applications. Summary of the Invention

[0010] In view of this, the present invention provides a chronic wound pH monitoring system (pHTag) based on passive RFID, which aims to solve the above problems through hardware and software co-design.

[0011] In a first aspect, this disclosure proposes a passive RFID for pH monitoring of chronic wounds. The RFID antenna of the passive chip RFID for pH monitoring of chronic wounds includes a dipole antenna for far-field communication and a sensing loop nested inside its center for near-field sensing. The feed end of the dipole antenna is connected to the RFID chip. The sensing loop is a closed inductor coil that interacts with the RFID chip through mutual inductance. An annular sensing gap is left in the central region of the sensing loop, and a porous microstructure PEDOT:PSS sensing material is embedded in the annular sensing gap.

[0012] In one embodiment of the above technical solution, the step of embedding a porous microstructure PEDOT:PSS sensing material includes: adding a biocompatible thickener to a PEDOT:PSS solution and forming a hydrogel with a porous microstructure by ultrasonic treatment; wherein the conductivity of the PEDOT:PSS solution is tuned to a range of 500 S / cm to 1000 S / cm; and embedding the porous microstructure hydrogel into an annular sensing gap.

[0013] In one embodiment of the above technical solution, the sensing loop is between 10mm and 15mm, the dipole antenna is length-optimized according to the 902MHz-928MHz frequency band, and the coupling distance between the sensing loop and the center input end of the dipole antenna is preset so that the impedance of the RFID antenna remains within the activation power threshold of the RFID chip within the pH value variation range.

[0014] In one embodiment of the above technical solution, the annular sensing gap ranges from 8.2 mm to 12 mm.

[0015] In one embodiment of the above technical solution, the distance between the sensing loop and the center input end of the dipole antenna is 2.8mm, so as to achieve a balance between the impedance modulation range and the minimum operating voltage of the RFID chip.

[0016] In one embodiment of the above technical solution, the biocompatible thickener is polyvinyl alcohol (PVA); preferably, the biocompatible thickener is added in the form of a 5% PVA solution by mass.

[0017] In one embodiment of the above technical solution, the sensing tag and the reference tag are located on a multilayer flexible substrate, with each layer having a thickness between 50μm and 125μm to accommodate the bending requirements of human skin and wound surfaces.

[0018] In one embodiment of the above technical solution, the embedding method includes 3D printing and drop coating.

[0019] Secondly, this disclosure proposes a method for pH monitoring of chronic wounds based on passive RFID. The steps include: applying a sensing tag to the surface of a dressing for the chronic wound, and attaching a reference tag to dry skin or a normal dressing adjacent to the wound. The RFID antenna of the sensing tag includes a dipole antenna for far-field communication and a sensing loop nested within its center for near-field sensing. The feed end of the dipole antenna is connected to an RFID chip. The sensing loop is a closed inductor coil that interacts with the RFID chip through mutual inductance. A ring-shaped sensing gap is left in the central region of the sensing loop, and a porous microstructured PEDOT:PSS sensing material is embedded in the ring-shaped sensing gap. The distance between the sensing tag and the reference tag should be maintained within the range of 2cm to 5cm to ensure the accuracy of the phase difference. The original phase data of the sensing tag and the reference tag at different frequencies are collected using an RFID reader. The phase difference is obtained based on a dual-tag differential algorithm, and then the differential phase slope is obtained. Based on a pre-defined pH calibration curve model To obtain the real-time pH value of the wound.

[0020] Thirdly, this disclosure proposes a chronic wound pH monitoring system based on passive RFID. The system includes: a passive chip-type RFID antenna, whose antenna comprises a dipole antenna for far-field communication and a sensing loop nested within its center for near-field sensing. The feed end of the dipole antenna is connected to the RFID chip. The sensing loop is a closed inductor coil that interacts with the RFID chip through mutual inductance. A ring-shaped sensing gap is left in the central region of the sensing loop, and a porous microstructured PEDOT:PSS sensing material is embedded in the ring-shaped sensing gap. A computing server is configured to process the raw phase data of the sensing tag and reference tag collected by the RFID reader, obtain the phase difference based on a dual-tag differential algorithm, and then obtain the differential phase slope. Based on a preset pH calibration curve model To obtain the real-time pH value of the wound.

[0021] The beneficial technical effects of this invention are as follows: The passive RFID for pH monitoring of chronic wounds designed in this disclosure embeds a porous microstructured PEDOT:PSS sensing material into a sensing loop nested within a dipole antenna. Utilizing the principle that the conductivity of the sensing material increases with increasing pH, thereby enhancing the eddy current in the sensing loop and modulating the equivalent inductance of the dipole antenna, a high linearity response to minute changes in pH is achieved. Combined with a dual-tag spatiotemporal difference and frequency domain slope extraction algorithm, phase fluctuations caused by changes in distance between the tag and reader are effectively offset, allowing patients to obtain accurate measurement results even during daily activities. The system requires no battery, and the sensing and reference tags are made of flexible substrates, making them comfortable to wear. It can capture changes in the wound environment in real time, providing data support for early clinical intervention and is suitable for long-term home-based chronic wound care. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. By reading the detailed description of the embodiments below, the advantages and benefits of the solutions will become clear to those skilled in the art. The accompanying drawings are only for illustrating preferred embodiments and are not intended to limit the present invention. In the accompanying drawings: Figure 1 This is a schematic diagram of a passive RFID structure for pH monitoring of chronic wounds in one embodiment.

[0023] Figure 2 This is a schematic diagram illustrating pH monitoring for foot wounds in one implementation method.

[0024] Figure 3 This is a schematic diagram of a passive RFID sensing tag structure for pH monitoring of chronic wounds in one embodiment. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and thoroughly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art should fall within the protection scope of the present invention.

[0026] See Figure 1 The passive RFID structure shown includes a sensing tag 100, a reference tag 200, an RFID reader 300, and a computing server 400.

[0027] For example, see Figure 2 Sensing tag 100 (pHTag) is affixed to the dressing of a patient's chronic wound (such as a diabetic foot ulcer) to directly sense the biochemical indicators of the wound exudate; reference tag 200 is affixed to dry skin or dressing near the wound to collect reference signals for environmental interference and motion noise. In a running system, RFID reader 300 communicates simultaneously with sensing tag 100 and reference tag 200 via an radio frequency link, and transmits the collected raw phase data to computing server 400 for processing in real time.

[0028] Both the sensing tag 100 and the reference tag 200 are based on ultra-high frequency (UHF) passive RFID technology and do not require battery power. The RFID reader 300 transmits radio frequency signals to activate the sensing tag and the reference tag and records the backscattered signals.

[0029] In the passive chip RFID of this application, such as Figure 3 The sensor tag 100 shown comprises four main parts: a flexible substrate 110, an RFID antenna 120, an RFID chip 130, and a pH sensing material 140. The RFID antenna 120 includes a dipole antenna and a sensing loop. The RFID chip 130 is electrically connected to the dipole antenna. The pH sensing material 140 is embedded in the gaps of the sensing loop. By adjusting the impedance of the sensing loop antenna through mutual inductance, a high linearity response to minute changes in pH value is achieved. An RFID reader collects the raw phase data of the sensor tag and a reference tag at different frequencies. The phase difference is obtained based on a dual-tag differential algorithm, and then the differential slope characteristic is obtained. This effectively offsets phase fluctuations caused by changes in distance between the tag and the reader, allowing patients to obtain accurate measurement results even during daily activities. The system requires no batteries, the tags are extremely low-cost and comfortable to wear, and they can capture real-time changes in the wound environment, providing data support for early clinical intervention and making them suitable for long-term home-based chronic wound care.

[0030] In one embodiment of the sensing tag 100, a multi-layer flexible structure design is adopted. The bottom layer is a flexible substrate 110 (such as PI polyimide or PET material) with a thickness between 50μm and 125μm to adapt to the bending requirements of human skin and wound surfaces. The RFID antenna 120 adopts a nested dual-function design, which includes a dipole antenna for far-field communication and a sensing loop for near-field sensing nested inside its center. The dipole antenna is optimized for the 902MHz-928MHz frequency band to ensure gain stability in the human tissue attachment environment. The sensing loop is a closed inductor coil with an annular sensing gap in its central region with an inner diameter of 8.2 mm and an outer diameter of 12 mm. The pH sensing material 140 (PEDOT:PSS porous hydrogel containing 5% PVA) is precisely embedded in the annular gap by 3D printing. The sensing loop is not directly connected to the dipole antenna or RFID chip through wires, but exchanges energy and signals through the near-field mutual inductance effect. When the magnetic field emitted by the reader passes through the sensing loop, the conductivity (σ) of the sensing material changes with the pH value of the wound exudate (for example, as pH increases, the increased conductivity enhances the eddy currents within the material, leading to a decrease in the equivalent inductance of the sensing loop), thereby altering the load impedance of the entire antenna system and enabling wireless pH reading. For instance, as pH increases, the ion mobility within the sensing material changes, and the conductivity increases accordingly (equivalent resistance decreases), thus enhancing the eddy currents in the sensing loop and reducing its equivalent inductance. According to the mutual inductance model, the load impedance of the sensing loop... It will be through the coupling coefficient Input impedance mapped to a dipole antenna The above formula is expressed as follows: , This is the original impedance of the dipole antenna. This is the operating angular frequency. This impedance change ultimately causes a phase shift in the backscattered signal, and the specific pH value of the wound exudate can be obtained using the phase shift data.

[0031] To achieve optimal coupling sensitivity, the diameter of the sensing loop can be optimized between 10mm and 15mm (preferably, an outer diameter of 16.8mm and an inner diameter of 12mm), and the distance between the sensing loop and the center input of the dipole antenna is precisely controlled at 2.8mm to achieve a balance between the impedance modulation range and the minimum operating voltage of the RFID chip 130. This layout ensures that changes in the conductivity of the sensing material can effectively modulate the impedance of the main antenna through near-field coupling, while keeping the return loss below -10dB, thus guaranteeing the communication distance and stability of the tag.

[0032] The aforementioned pH-sensing material 140 is a composite hydrogel formed by mixing a PEDOT:PSS aqueous dispersion with a 5% (w / w) polyvinyl alcohol (PVA) solution, followed by high-energy ultrasonic treatment and magnetic stirring. PEDOT:PSS serves as the sensing active ingredient, utilizing its conductivity sensitivity to pH to achieve signal modulation; PVA acts as a biocompatible thickener, used to construct a 3D porous microstructure that supports rapid ion migration. This porous microstructure not only significantly increases the material's specific surface area but also provides abundant channels for ion migration in the exudate, greatly enhancing proton accessibility, thus enabling the material's conductivity to exhibit a highly sensitive and linear response to pH changes.

[0033] The working principle of the aforementioned sensing tag 100 is as follows: When the pH value of the wound exudate changes, the conductivity of the pH sensing material 140 changes accordingly. Specifically, if the wound becomes infected, causing the pH value to rise (tending towards alkalinity), the conductivity of the sensing material increases accordingly, which strengthens the induced current (eddy current) intensity of the sensing loop under the radio frequency field. The enhanced eddy current suppresses the original magnetic field through the mutual inductance effect, resulting in a decrease in the equivalent inductance of the sensing loop antenna, thereby modulating the phase characteristics of the RFID signal. Conversely, when the wound heals, causing the pH value to decrease (tending towards weak acidity), the conductivity of the sensing material decreases, the eddy current intensity weakens, the equivalent inductance increases, and the signal phase shifts in the opposite direction.

[0034] By setting a preset pH threshold (e.g., pH > 8.0 is used as an infection warning), this system can achieve real-time, wireless monitoring of the condition of chronic wounds: a continuous increase in the phase offset indicates wound deterioration or infection, while a decrease in the offset and stabilization at a low level indicates that the wound is repairing itself towards an acidic healthy environment.

[0035] According to the principle of mutual inductance, the change in induced current in the sensing loop will generate a secondary magnetic field. This magnetic field will change the complex impedance of the antenna by adjusting the equivalent inductance of the dipole antenna in the RFID antenna 120, and will ultimately be reflected as the phase shift of the RFID backscatter signal.

[0036] For the acquired phase offset data, the processing server 400 uses a dual-tag time-frequency differential model to process the collected signals. The steps include: calculating the differential phase between the sensing tag and the reference tag. When wound exudate soaks into the tag, a significant abrupt change occurs within a very short time, allowing identification of the starting point of the monitored event. Since the phase offset is greatly affected by distance fluctuations, and the relationship between phase and distance is consistent across different frequencies, the differential slope feature can effectively counteract the interference from distance changes caused by human movement (such as breathing or walking) between the tag and the reader. Therefore, the slope of the differential phase as a function of frequency can be extracted. This serves as the basis for frequency domain pH quantization.

[0037] Example 1 Step 1: Prepare the sensing tag 100 (pHTag) and the reference tag 200. The sensing tag 100 uses a flexible substrate, with the pH sensing material 140 (porous microstructure PEDOT:PSS hydrogel) embedded in the sensing loop gap of the RFID chip 130 of the antenna. The reference tag 200 is a conventional passive RFID tag without sensing material. Apply the sensing tag 100 to the dressing surface of a chronic wound (such as a diabetic foot ulcer), and attach the reference tag 200 to dry skin or a normal dressing area next to the wound.

[0038] Step 2: Configure the RFID reader 300 and the computing server 400. The reader 300 operates in the ultra-high frequency (UHF) band (e.g., 902MHz-928MHz) using frequency hopping technology. The computing server 400 pre-stores a pH calibration curve model F, which describes the final differential phase slope (…). The mapping relationship between pH and standard pH values.

[0039] Step 3: Start data acquisition. The RFID reader 300 transmits radio frequency signals to activate the sensing tag 100 and the reference tag 200. The reader 300 utilizes the backscattering principle to simultaneously record the sensing tag and the reference tag at multiple frequency points (e.g., ...). The phase data under () are respectively denoted as and , For..., and transmit the data stream to the computing server 400 in real time.

[0040] Step 4, Time-domain event detection. The computing server 400 calculates the real-time differential phase between the phase data of the sensing tag and the reference tag:

[0041] When wound exudate begins to infiltrate the sensing material 140, the electrical properties of the sensing material undergo a sudden change. The system monitors the rate of change of the differential phase in real time through a sliding window. When the rate exceeds a preset threshold, it is automatically marked as the start time of the monitoring event. As the infiltration reaches saturation, the real-time differential phase curve tends to flatten. When the standard deviation of the real-time differential phase within a window is less than a set threshold and remains below that threshold for a certain period, the stable point of the data is marked. (i.e., the end time of a single measurement event).

[0042] Step 5: Frequency Domain Feature Extraction and Denoising. At a determined steady-state time... Then, the computing server 400 extracts all frequency points at that moment. The corresponding differential phase data. A linear fit is performed on the relationship between phase difference and frequency using the least squares method:

[0043] The differential phase slope was calculated. Furthermore, by sensing the slope corresponding to the label and the reference label... , The difference is calculated to obtain the final monitoring feature quantity. B is the differential phase intercept.

[0044] Step 6: Anti-motion interference handling. During monitoring, if the patient experiences limb tremors, displacement, or changes in the relative position between the body and the reader antenna due to breathing, the raw phase data will change with the distance between the tag and the reader antenna. The changes are drastic. Reference tag 200 captures multipath effects and background noise in the environment in real time, and in step 4, it is transmitted via differential phase. The operation treats this as "common-mode noise" and removes it. According to electromagnetic wave propagation theory, phase... ,frequency With transmission distance The relationship follows:

[0045] in, At the speed of light, This refers to the phase shift caused by device system delay. In step 5, this is achieved by adjusting multiple frequency points. differential phase Perform linear fitting, and extract the fitting slope. In mathematics, it equals right The derivative. Due to the distance term. It exhibits consistency across different frequency points, and the resulting linear phase shift occurs when differentiating (i.e., calculating the slope). During the process, it is transformed into a constant term or canceled out by the difference, thus resulting in the final characteristic quantity. Decoupling distance Interference.

[0046] The dual processing of removing environmental noise and extracting the frequency domain slope (eliminating distance interference) ensures that the system can stably and uniquely reflect the impedance modulation information caused by pH value changes, even in dynamic environments.

[0047] Step 7: pH value quantification output. The computing server 400 outputs the monitoring characteristic values ​​calculated in step 5. Substitute the pre-stored pH calibration curve model F:

[0048] The model is established through nonlinear regression or polynomial fitting, and the computing server 400 determines the health status of the wound based on the output pH value. If the pH value exceeds a preset safety threshold (e.g., pH>8.0, indicating a potential risk of infection), the computing server 400 issues an alert to medical staff or patients via a mobile terminal.

[0049] Step 8: Continuous monitoring. Repeat steps 3 to 7 to achieve 24-hour uninterrupted, passive real-time monitoring of the chronic wound environment and generate a pH change trend chart.

[0050] The above implementation can achieve a pH resolution of 0.1 units, which is sufficient to capture the subtle biochemical changes caused by early infection of chronic wounds. Through the dual-label time-frequency difference algorithm, the phase error caused by motion is reduced by more than 90%. When patients are performing daily activities (such as supine breathing and limb tremors), the pH monitoring error can still be controlled within ±0.25, so that patients can obtain accurate measurement results even in daily activities.

[0051] Furthermore, this solution employs a completely passive RFID design, requiring no batteries, with extremely low tag costs (approximately $0.10), and excellent biocompatibility. It can be directly integrated into flexible dressings, enabling continuous, real-time monitoring without removing the dressing. No complex wiring or large reading / writing equipment is needed; a single portable RFID reader can cover the monitoring area, reducing installation and maintenance complexity by over 90% compared to wired monitoring devices. Comfortable to wear, it can capture real-time changes in the wound environment, providing data support for early clinical intervention and is suitable for long-term home-based chronic wound care.

[0052] In summary, this disclosure provides a passive RFID for pH monitoring of chronic wounds. The passive chip-based RFID antenna for chronic wound pH monitoring includes a dipole antenna for far-field communication and a sensing loop nested within its center for near-field sensing. The feed end of the dipole antenna is connected to the RFID chip. The sensing loop is a closed inductor coil that interacts with the RFID chip through mutual inductance. A ring-shaped sensing gap is left in the central region of the sensing loop, and a porous microstructured PEDOT:PSS sensing material is embedded in this gap. The loop inductance is adjusted by changing the conductivity of the sensing material with the pH value of the wound exudate, thereby changing the antenna impedance and achieving sensing while ensuring communication efficiency. Using this passive RFID for wound monitoring can improve the accuracy of wound monitoring and the ability to resist motion interference, and it requires no battery, resulting in low cost.

[0053] This disclosure also provides a method for pH monitoring of chronic wounds based on passive RFID. A sensing tag is applied to the dressing surface of the chronic wound, and a reference tag is attached to dry skin or a normal dressing adjacent to the wound. The RFID antenna of the sensing tag includes a dipole antenna for far-field communication and a sensing loop nested within its center for near-field sensing. The feed end of the dipole antenna is connected to an RFID chip. The sensing loop is a closed inductor coil that interacts with the RFID chip through mutual inductance. A ring-shaped sensing gap is left in the central region of the sensing loop, and a porous microstructured PEDOT:PSS sensing material is embedded in the ring-shaped sensing gap. The original phase data of the sensing tag and the reference tag are collected using an RFID reader. The phase difference is obtained based on a dual-tag differential algorithm, and then the differential phase slope is obtained. Based on a pre-defined pH calibration curve model To obtain the real-time pH value of the wound.

[0054] This disclosure also provides a chronic wound pH monitoring system based on passive RFID. The system includes: a passive RFID antenna, whose antenna includes a dipole antenna for far-field communication and a sensing loop nested inside its center for near-field sensing. The feed end of the dipole antenna is connected to the RFID chip. The sensing loop is a closed inductor coil that interacts with the RFID chip through mutual inductance. An annular sensing gap is left in the central region of the sensing loop, and a porous microstructured PEDOT:PSS sensing material is embedded in the annular sensing gap. A computing server is configured to process the raw phase data of the sensing tag and reference tag collected by the RFID reader, obtain the phase difference based on a dual-tag differential algorithm, and then obtain the differential phase slope. Based on a preset pH calibration curve model To obtain the real-time pH value of the wound.

[0055] It should be noted that although specific embodiments of the present invention have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of the present invention. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of the present invention.

[0056] The examples of the embodiments of the present invention are intended to concisely illustrate the technical features of the embodiments of the present invention, so that those skilled in the art can intuitively understand the technical features of the embodiments of the present invention, and are not intended to be an improper limitation of the embodiments of the present invention.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A passive RFID for pH monitoring of chronic wounds, characterized in that, The passive chip-based RFID antenna for pH monitoring of chronic wounds includes a dipole antenna for far-field communication and a sensing loop nested in its center for near-field sensing. The feed end of the dipole antenna is connected to the RFID chip. The sensing loop is a closed inductor coil that interacts with the RFID chip through mutual inductance. A ring-shaped sensing gap is left in the central region of the sensing loop, and a porous microstructure PEDOT:PSS sensing material is embedded in the ring-shaped sensing gap.

2. The passive RFID according to claim 1, characterized in that, The steps involved in embedding the porous microstructure of the PEDOT:PSS sensing material include: A biocompatible thickener was added to a PEDOT:PSS solution, and a hydrogel with a porous microstructure was formed by ultrasonic treatment; wherein the conductivity of the PEDOT:PSS solution was tuned to a range of 500 S / cm to 1000 S / cm. A porous microstructured hydrogel is embedded within an annular sensing gap.

3. The passive RFID according to claim 1, characterized in that, The sensing loop is between 10mm and 15mm in length, and the dipole antenna is optimized for the 902MHz-928MHz frequency band. The coupling distance between the sensing loop and the center input of the dipole antenna is preset so that the impedance of the RFID antenna remains within the activation power threshold of the RFID chip within the pH value variation range.

4. The passive RFID according to claim 1, characterized in that, The annular sensing gap ranges from 8.2 mm to 12 mm.

5. The passive RFID according to claim 1, characterized in that, The distance between the sensing loop and the center input of the dipole antenna is 2.8 mm to achieve a balance between the impedance modulation range and the minimum operating voltage of the RFID chip.

6. The passive RFID according to claim 1, characterized in that, The biocompatible thickener is polyvinyl alcohol (PVA); preferably, the biocompatible thickener is added in the form of a 5% PVA solution by mass.

7. The passive RFID according to claim 1, characterized in that, The sensing tags and reference tags use multi-layer flexible substrates, with each layer ranging from 50μm to 125μm in thickness, to accommodate the bending requirements of human skin and wound surfaces.

8. The passive RFID according to claim 1, characterized in that, Embedding methods include 3D printing and drop coating.

9. A method for monitoring pH in chronic wounds based on passive RFID, characterized in that the steps include... include: The sensing tag is applied to the dressing surface of a chronic wound, and the reference tag is attached to the dry skin or normal dressing next to the wound. The RFID antenna of the sensing tag includes a dipole antenna for far-field communication and a sensing loop nested in its center for near-field sensing. The feed end of the dipole antenna is connected to the RFID chip. The sensing loop is a closed inductor coil that interacts with the RFID chip through mutual inductance. An annular sensing gap is left in the central area of ​​the sensing loop, and a porous microstructure PEDOT:PSS sensing material is embedded in the annular sensing gap. The distance between the sensing tag and the reference tag should be maintained within the range of 2cm to 5cm to ensure the accuracy of the phase difference; The raw phase data of sensing tags and reference tags at different frequencies are collected using an RFID reader. The phase difference is obtained based on a dual-tag differential algorithm, and then the differential phase slope is obtained. ; Based on a pre-set pH calibration curve model To obtain the real-time pH value of the wound.

10. A chronic wound pH monitoring system based on passive RFID, characterized in that, The system includes: The passive chip-based RFID antenna includes a dipole antenna for far-field communication and a sensing loop nested inside its center for near-field sensing. The feed end of the dipole antenna is connected to the RFID chip. The sensing loop is a closed inductor coil that interacts with the RFID chip through mutual inductance. The central region of the sensing loop has an annular sensing gap, in which a porous microstructure PEDOT:PSS sensing material is embedded. The processing server is configured to process the raw phase data collected by the RFID reader from the sensing tag and the reference tag, obtain the phase difference based on the dual-tag differential algorithm, and then obtain the differential phase slope. Based on a preset pH calibration curve model To obtain the real-time pH value of the wound.

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