Implantable biofilm wireless monitoring sensor and system based on agcl / ag impedance conversion

Abstract

The present application relates to the technical field of bioelectric signal monitoring, in particular to an implantable biological membrane wireless monitoring sensor and system based on AgCl / Ag impedance conversion, which comprises an anode integrated module, a cathode verification module, a frequency analysis module, a closed-loop control module and a packaging state evaluation module.In the present application, the implant closed-loop circuit current and biological membrane charge transfer resistance are directly collected to provide original interface information for subsequent analysis, the silver chloride resistivity change rate is detected, the silver / silver chloride antenna resonance frequency offset is synchronously measured, a high-sensitivity abnormality identification mechanism is constructed, the early interface instability or material degradation early warning capability is improved, the circuit phase angle and antenna Q value are extracted after identifying the abnormality, the frequency compensation coefficient is calculated by applying frequency domain least square fitting, the silver chloride / silver conversion rate is controlled, the wireless signal transmission is optimized, the packaging water vapor transmission rate and ion permeation flux are monitored, and the long-term reliability of the implanted device is ensured.

Description

Technical Field

[0001] This invention relates to the field of bioelectric signal monitoring technology, and in particular to an implantable wireless monitoring sensor and system for biomembranes based on AgCl / Ag impedance conversion. Background Technology

[0002] The field of bioelectric signal monitoring technology encompasses techniques for assessing health status and analyzing pathological conditions using electrical signals generated by the organism's own electrical properties or metabolic activities. It primarily involves technical branches such as monitoring the electrochemical behavior of biomembranes, biosensor design, electrochemical impedance spectroscopy analysis, and weak signal acquisition and processing. Application scenarios include implantable medical devices, in vitro diagnostic instruments, and real-time physiological parameter monitoring systems. The core technology in this field lies in obtaining impedance change information through the interfacial reaction between electrodes and biomembranes, combining this with signal conversion circuits to convert biochemical signals into quantifiable electrical signals, and achieving remote monitoring based on data transmission protocols. Technical challenges include electrode material stability, anti-interference capabilities for high-frequency weak signals, and long-term implantation biocompatibility.

[0003] The implantable wireless monitoring system for biomembranes based on AgCl / Ag impedance conversion uses silver chloride and silver electrodes as the biomembrane interface impedance sensing unit. A small-amplitude AC excitation signal is applied via a potentiostat to capture the changes in charge transfer impedance and solution resistance caused by variations in biomembrane ion concentration. The current signal is converted into a voltage signal using a transimpedance amplifier, and after filtering and analog-to-digital conversion, it is wirelessly transmitted to an external receiving terminal via a low-power radio frequency chip at a specific frequency band. Specific technical aspects of this system include the AgCl / Ag reference electrode fabrication process, the polarization control method of the three-electrode system in a body fluid environment, the rules for extracting frequency domain features of the impedance signal, and the wireless communication protocol adaptation mechanism.

[0004] Existing bioelectrical signal monitoring technologies struggle to effectively distinguish between physiological fluctuations in biomembranes and signal drift caused by electrode interface aging in long-term implantation applications. For example, during long-term operation of AgCl / Ag electrodes, uneven dissolution or conversion of AgCl can lead to reference potential drift, and its impedance baseline changes can easily be confused with real biological signals, reducing monitoring accuracy. Regarding the impact of high-frequency interference and dynamic changes in the implantation environment on wireless communication, existing technologies largely rely on passive filtering or fixed communication protocols, lacking proactive adaptation capabilities. For instance, tissue encapsulation or changes in body fluids can cause antenna detuning, reducing signal transmission quality; existing technologies typically cannot adjust matching network compensation in real time. Furthermore, there is insufficient real-time assessment mechanism for the integrity of implanted device packaging. Minor damage to the packaging can lead to fluid infiltration, affecting circuit stability; traditional monitoring methods often fail to detect this early, until significant device malfunction occurs, posing a long-term implantation risk. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and to propose an implantable wireless monitoring sensor and system for biomembranes based on AgCl / Ag impedance conversion.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: an implantable biomembrane wireless monitoring system based on AgCl / Ag impedance conversion includes:

[0007] The anode integrated module collects the closed-loop circuit current on the implant surface, as well as the charge transfer resistance of the biomembrane, and transmits it to the cathode verification module.

[0008] The cathode verification module detects the change rate of AgCl resistivity of the charge transfer resistance of the biofilm, measures the resonant frequency offset of the Ag / AgCl antenna, performs normalized proportional conversion to calculate the product, and generates an abnormal signal when the product exceeds the dielectric loss threshold, and transmits it to the frequency analysis module.

[0009] The frequency analysis module extracts the phase angle and antenna Q value data of the closed-loop circuit corresponding to the abnormal signal, calculates the frequency compensation coefficient caused by biomembrane metabolism by combining the frequency domain least squares fitting algorithm, and transmits it to the closed-loop control module.

[0010] The closed-loop control module, based on the frequency compensation coefficient, controls the AgCl / Ag conversion rate and the Ag cathode DC bias voltage through the cathode polarization voltage output by the potentiostat, generates a dynamic adjustment result of the cathode polarization voltage, and transmits it to the packaging status evaluation module.

[0011] The packaging status assessment module uses humidity and pressure sensors to acquire water vapor transmission rate and ion permeation flux after dynamic adjustment of the cathode polarization voltage, eliminating impedance fluctuations caused by water vapor transmission and ion permeation, and obtaining monitoring results of the packaging status.

[0012] As a further aspect of the present invention, the closed-loop circuit current value and biomembrane charge transfer resistance include current response signal amplitude, charge transport path parameters, and electrode interface reaction impedance; the abnormal signal includes resistivity change rate and frequency offset product, encapsulation control trigger command, and abnormal signal trigger condition; the frequency compensation coefficient specifically includes phase angle, antenna Q value, and frequency domain fitting residual; the dynamic adjustment result of cathode polarization voltage includes polarization voltage adjustment value, AgCl / Ag conversion rate control value, and Smith chart matching point coordinates; and the monitoring result of encapsulation status includes water vapor permeability and ion permeation flux.

[0013] As a further aspect of the present invention, the anode integration module includes:

[0014] Anode embedding submodule: embeds carbon cloth bioanode into the implant surface, detects implant surface morphology features, extracts surface curvature distribution based on optical scanning data, matches the pore structure of carbon cloth anode, measures contact resistance using four-point probe method, and generates contact area parameters by combining the fitting curve of surface roughness and contact resistance.

[0015] Current acquisition submodule: Acquires the current response signal of the carbon cloth anode, divides the original signal into frequency bands according to the mapping relationship between the contact area parameters and the current acquired by the closed-loop circuit, and uses wavelet transform to extract the frequency components related to the biofilm impedance to generate the closed-loop current value.

[0016] The resistance conversion submodule inputs the closed-loop current value and the real-time monitored biomembrane polarization voltage into the equivalent circuit model, solves the real and imaginary parts of the charge transfer impedance through an iterative method, and reconstructs the double-layer capacitance compensation coefficient based on the correlation between impedance phase angle and frequency, thereby generating the biomembrane charge transfer resistance value and the corrected closed-loop circuit current value.

[0017] The double-layer capacitance compensation coefficient is calculated by using a constant phase angle element model to obtain the compensated double-layer capacitance value based on the pseudo-capacitor parameters, angular frequency, and phase angle correction index. This value is used to correct the influence of the non-ideal characteristics of the double-layer capacitance on the imaginary part of the impedance.

[0018] The equivalent circuit model is a network composed of circuit elements connected in series and parallel to represent the physical processes of solution resistance, charge transfer resistance, and double-layer capacitance, and it is used to fit and analyze the impedance data measured in experiments.

[0019] As a further aspect of the present invention, the cathode verification module includes:

[0020] Resistivity detection submodule: detects the AgCl component of the charge transfer resistance of the biofilm, selects four equally spaced probe contacts on the electrode surface, applies a constant current and measures the voltage between the contacts, calculates the area resistivity according to the four-probe method, extracts resistivity data for three consecutive sampling cycles, calculates the average value of the difference between adjacent cycles, and generates the resistivity change rate.

[0021] Frequency offset submodule: Sets the start and cutoff frequencies of the sweep frequency signal output by the vector network analyzer according to the resistivity change rate, transmits a sinusoidal excitation signal to the Ag / AgCl antenna, collects the amplitude and phase data of the reflection coefficient, extracts the center frequency corresponding to the resonance point, calculates the deviation from the initial calibration frequency, and generates the resonance frequency offset.

[0022] Anomaly Detection Submodule: Calculates the product of the resistivity change rate and the resonant frequency offset, maps the product to a preset dielectric loss factor threshold range through normalization, compares the mapped value with the upper and lower limits of the dielectric loss threshold range, and generates an anomaly signal.

[0023] The dielectric loss threshold is a critical reference value set by referring to the standard dielectric loss range of the target material at a preset operating frequency and temperature, and combining it with the minimum acceptable standard for signal integrity or energy efficiency of the implanted biosensor.

[0024] As a further aspect of the present invention, the resistivity change rate is calculated, and the resistivity data of the sampling period is processed using the formula:

[0025] ;

[0026] in It is the rate of change of resistivity. Represents reference temperature The initial resistivity below, Represents the temperature coefficient of resistance. Represents the current ambient temperature. Represents the reference temperature. Represents the current change sensitivity factor. Current change rate over time interval Integrals within.

[0027] As a further aspect of the present invention, the frequency analysis module includes:

[0028] Signal Feature Submodule: Based on the abnormal signal, the voltage and current waveform data of the closed-loop circuit are collected, the time difference between the voltage peak and the current trough is measured using an inverting amplifier, the phase angle difference between the two is calculated, and the ratio of the half-power bandwidth of the antenna resonant peak to the center frequency is measured using an impedance analyzer to generate the phase angle deviation value and the Q value fluctuation.

[0029] Least square fitting algorithm submodule: Call the phase angle deviation value and the Q value fluctuation, select discrete data points of the real and imaginary parts of the impedance in the frequency domain, construct a linear fitting objective function with frequency as the independent variable, fit the first slope parameter a and the first intercept b to the real part data using the least squares method, fit the second slope parameter c and the second intercept d to the imaginary part data, and generate metabolic frequency compensation coefficients.

[0030] Coefficient transfer submodule: After converting the metabolic frequency compensation coefficient into a binary data frame, it is used to coordinate the polarization voltage control logic of the potentiostat to generate frequency compensation coefficients for biofilm monitoring.

[0031] The closed-loop control module directly calls the stored frequency compensation coefficients through a potentiostat and impedance matching circuit to achieve synergistic optimization of the AgCl / Ag electrochemical reaction rate and the antenna impedance matching state.

[0032] The storage address for storing the frequency compensation coefficient refers to the specific physical storage location allocated to the frequency compensation coefficient in the internal register or non-volatile memory of the closed-loop control module.

[0033] As a further aspect of the present invention, the frequency compensation value after quantization is calculated, and a binary data frame conversion operation is performed based on the frequency compensation value after quantization, using the formula:

[0034] ;

[0035] in, It is the frequency compensation value after quantization. The sign function represents the sign of K. Represents the maximum allowable frequency compensation coefficient. N represents the number of bits in the quantized data. The analog frequency compensation coefficient to be quantized The base-2 logarithmic function is used to compress the data range, enabling the SPI data frame to correspond to the adjustment of the antenna impedance matching network and optimize the Smith chart matching point position. The floor function represents the floor function.

[0036] As a further aspect of the present invention, the closed-loop control module includes:

[0037] Voltage regulation submodule: Calls the frequency compensation coefficient, sets the initial step size of the potentiostat output voltage as the reference step size, monitors the differential value of the AgCl / Ag electrode reaction current over time, calculates the difference between the differential value of the current and the dielectric loss threshold, uses the difference as the step size adjustment factor, linearly scales the voltage step size amplitude, and generates the polarization voltage regulation coefficient.

[0038] Bias control submodule: Calls the polarization voltage adjustment coefficient, measures the real and imaginary components of the impedance of the Ag cathode under DC bias voltage, substitutes the real and imaginary components into the Smith chart coordinate system, calculates the difference in ohmic loss and capacitive reactance between the current coordinate point and the reference point, adjusts the bias voltage output amplitude according to the difference, and generates the bias voltage correction amount.

[0039] Smith chart matching submodule: calls the polarization voltage adjustment coefficient and the bias voltage correction amount, extracts the magnitude phase coordinates of the Smith chart coordinate system, calculates the Euclidean geometric distance between the real-time coordinates and the target matching point, updates the impedance matching network parameters based on the distance inverse proportional function, and generates the dynamic adjustment result of the cathode polarization voltage.

[0040] As a further aspect of the present invention, the packaging state evaluation module includes:

[0041] Sensor data acquisition submodule: detects the water vapor transmission rate output by the humidity sensor, acquires the ion permeation flux output by the pressure sensor, and uses a sliding window mean filter to eliminate sensor baseline drift and impedance fluctuations caused by water vapor transmission and ion permeation for the parameters after dynamic adjustment of the cathode polarization voltage, generating dynamically corrected water vapor transmission rate and ion permeation flux.

[0042] The parameter fusion analysis submodule calls the water vapor permeability and ion permeation flux, adjusts the parameters based on the polarization voltage output by the potentiostat, and maps the three to the 0-1 range using a linear normalization method. Combining the dielectric loss threshold and the preset encapsulation air permeability benchmark value, the indicators of air permeability and ion barrier capability are calculated through linear combination to generate parameter fusion coefficients characterizing the air permeability of the encapsulation material.

[0043] Packaging status determination submodule: compares the parameter fusion coefficient with the preset packaging stability threshold range point by point, marks those exceeding the threshold as packaging instability, and marks those not exceeding the threshold as packaging stability, generating the monitoring result of packaging status;

[0044] The preset encapsulation stability threshold is set based on measured data of water vapor transmission rate of the encapsulation material, fluctuation range of Ag / AgCl electrode polarization voltage, and dynamic interpolation compensation mechanism of body fluid temperature and ion concentration.

[0045] As a further aspect of the present invention, an implantable biofilm wireless monitoring sensor based on AgCl / Ag impedance conversion includes a memory and a processor. The memory stores a computer program and data received by an Ag / AgCl antenna and a potentiostat. When the processor executes the computer program, it realizes an implantable biofilm wireless monitoring system based on AgCl / Ag impedance conversion.

[0046] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0047] In this invention, the closed-loop circuit current of the implant and the charge transfer resistance of the biomembrane are directly collected to provide raw interface information for subsequent analysis. The rate of change of the silver chloride resistivity of this resistance is detected, and the resonant frequency offset of the silver / silver chloride antenna is simultaneously measured. The normalized product of these two measurements is compared with the dielectric loss threshold to construct a highly sensitive anomaly identification mechanism, improving the early warning capability for early interface instability or material degradation. After anomaly identification, the circuit phase angle and antenna Q-value data are extracted, and frequency compensation coefficients caused by biomembrane metabolism are calculated using frequency domain least squares fitting. This coefficient guides the output cathode polarization voltage of the potentiostat to control the silver chloride / silver conversion rate and maintain the stability of the sensing interface; simultaneously, the DC bias of the silver cathode is adjusted, the matching point of the antenna Smith chart is reconstructed, and wireless signal transmission is optimized. This dual-channel closed-loop control ensures optimized sensor operation in complex physiological environments. Combining humidity and pressure sensors to monitor the water vapor permeation rate and ion permeation flux of the encapsulation, and outputting the encapsulation permeation rate results, ensures the long-term reliability of the implanted device. Attached Figure Description

[0048] Figure 1 This is a system flowchart of the present invention;

[0049] Figure 2 This is a system block diagram of the present invention. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0051] In the description of this invention, it should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, in the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0052] Example 1

[0053] Please see Figure 1 This invention provides a technical solution: an implantable biomembrane wireless monitoring system based on AgCl / Ag impedance conversion, comprising:

[0054] The anode integrated module collects the closed-loop circuit current on the implant surface, as well as the charge transfer resistance of the biomembrane, and transmits it to the cathode verification module.

[0055] The cathode verification module detects the change rate of AgCl resistivity in the charge transfer resistance of the biofilm, measures the resonant frequency offset of the Ag / AgCl antenna, performs normalized proportional conversion to calculate the product, and generates an abnormal signal when the product exceeds the dielectric loss threshold, which is then transmitted to the frequency analysis module.

[0056] The frequency analysis module extracts the phase angle and antenna Q value data of the closed-loop circuit corresponding to the abnormal signal, calculates the frequency compensation coefficient caused by biomembrane metabolism by combining the frequency domain least squares fitting algorithm, and transmits it to the closed-loop control module.

[0057] The closed-loop control module, based on the frequency compensation coefficient, controls the AgCl / Ag conversion rate and the Ag cathode DC bias voltage through the cathode polarization voltage output by the potentiostat, generates dynamic adjustment results of the cathode polarization voltage, and transmits them to the package status evaluation module.

[0058] The packaging status assessment module uses humidity and pressure sensors to acquire water vapor transmission rate and ion permeation flux after dynamic adjustment of cathode polarization voltage, eliminating impedance fluctuations caused by water vapor transmission and ion permeation, and obtaining monitoring results of packaging status.

[0059] The closed-loop circuit current value and biomembrane charge transfer resistance include current response signal amplitude, charge transport path parameters, and electrode interface reaction impedance. Abnormal signals include the product of resistivity change rate and frequency offset, encapsulation control trigger command, and detection of over-limit events. The frequency compensation coefficient specifically includes phase angle, antenna Q value, and frequency domain fitting residual. The dynamic adjustment results of cathode polarization voltage include polarization voltage adjustment value, AgCl / Ag conversion rate control value, and Smith chart matching point coordinates. The monitoring results of encapsulation status include water vapor permeability and ion permeation flux.

[0060] Please see Figure 2 The anode integrated module includes:

[0061] Anode embedding submodule: embeds carbon cloth bioanode into the implant surface, detects implant surface morphology features, extracts surface curvature distribution based on optical scanning data, matches the pore structure of carbon cloth anode, measures contact resistance using four-point probe method, and generates contact area parameters by combining the fitting curve of surface roughness and contact resistance.

[0062] Optical scanning was performed on the implant surface to obtain surface height data, and the surface of the titanium alloy joint prosthesis was scanned. The region, obtained by A height matrix composed of sampling points is used. The radius of curvature is calculated by comparing the height of each point with that of its neighboring points. At point The height measured at is The average height of the surrounding 8 neighboring points is radius of curvature Based on the curvature distribution, the pore matching region is selected when... The area was identified as a candidate region for micropores. Pore size statistics were performed on the carbon cloth anode; the equivalent diameter of 50 random pores was measured in the scanning electron microscope image, and the statistical mean was [value missing]. The standard deviation is The radius of curvature of the implant surface is less than... The proportion of the area in the region ( ) and the proportion of carbon cloth pore area ( Compare and calculate the matching coefficient. ,when Contact resistance measurement is performed at that time. In the four-point probe method, the probe spacing is set to... Apply A constant current was used to measure the voltage difference. The contact resistance is calculated as follows: Surface roughness Substitute into a cubic polynomial to fit the curve Calculate the contact area parameters: .

[0063] Table 1 Surface Feature Parameters

[0064]

[0065] As shown in Table 1, when the radius of curvature is less than At that time, the contact resistance was less than Threshold.

[0066] Current acquisition submodule: Acquires the current response signal of the carbon cloth anode, divides the original signal into frequency bands according to the mapping relationship between the contact area parameter and the current acquired by the closed-loop circuit, and uses wavelet transform to extract the frequency components related to the biofilm impedance to generate the closed-loop current value.

[0067] Setting the sampling frequency in the closed-loop circuit The current waveform was continuously acquired for 100 cycles. The contact area parameters were then analyzed. With the original current Substitute into the linear relationship: A Fast Fourier Transform (FFT) is performed on the calibrated signal to identify key frequency components. The amplitude detected within the range is of Quantity, in The amplitude detected within the range is of Components. Based on experimental data of biomembrane impedance characteristic frequencies (frequency band: Set the bandpass filter cutoff frequency to and .right The components are subjected to 6-level db4 wavelet decomposition to extract the level 3 detail coefficients. Calculate the biomembrane-related current components ,in The frequency normalization coefficient represents the ratio of the biomembrane-related current component to the fundamental frequency component. Superimposed to generate closed-loop current values. .

[0068] The resistance conversion submodule inputs the closed-loop current value and the real-time monitored biomembrane polarization voltage into the equivalent circuit model, solves the real and imaginary parts of the charge transfer impedance through an iterative method, and reconstructs the double-layer capacitance compensation coefficient based on the correlation between impedance phase angle and frequency, generating the biomembrane charge transfer resistance value and the corrected closed-loop circuit current value.

[0069] The double-layer capacitance compensation coefficient is calculated by using a constant phase angle element model to calculate the pseudo-capacitor parameters, angular frequency, and phase angle correction index to obtain the compensated double-layer capacitance value, which is used to correct the influence of the non-ideal characteristics of the double-layer capacitance on the imaginary part of the impedance.

[0070] The equivalent circuit model is a network composed of circuit elements connected in series and parallel to represent the physical processes of solution resistance, charge transfer resistance and double-layer capacitance. It is used to fit and analyze the impedance data measured in experiments.

[0071] Set the initial parameters of the equivalent circuit: solution resistance Charge transfer resistance Double-layer capacitor Polarization voltage and closed-loop current Substitute into the impedance formula: ,in The phase angle correction index, It is the total impedance. Solution resistance, It is a charge transfer resistor. Double-layer capacitor, setting the iteration step size At frequency Calculate the imaginary part of the initial impedance: , Describe the imaginary part of the complex number z, and the measured imaginary part. The error is calculated by comparison. .Adjustment Value from Gradually increase to Time error reduced to ,Sure The double-layer capacitance compensation coefficient was calculated using a constant phase angle element (CPE) model. Based on electrochemical impedance spectroscopy measurement data, pseudo-capacitance parameters were obtained through curve fitting. and phase angle correction index The reference angular frequency is selected as Substitute the values ​​into the formula to calculate the compensated double-layer capacitance: The effect of the non-ideal characteristics of the double-layer capacitance on the imaginary part of the impedance is corrected by using the calculated compensated double-layer capacitance value, and the corrected charge transfer resistance and closed-loop current value are obtained.

[0072] Please see Figure 2 The cathode verification module includes:

[0073] Resistivity detection submodule: detects the AgCl component of charge transfer resistance in biofilms, selects four equally spaced probe contacts on the electrode surface, applies a constant current and measures the voltage between the contacts, calculates the area resistivity according to the four-probe method, extracts resistivity data for three consecutive sampling cycles, calculates the average value of the difference between adjacent cycles, and generates the resistivity change rate.

[0074] Four equally spaced probe contacts were placed on the electrode surface, with the probe spacing calibrated to 2 mm. A constant current of 10 mA was applied, and the voltage drop between the inner probes was measured three times, yielding values ​​of 24.5 mV, 24.8 mV, and 24.3 mV respectively. The average value of 24.5 mV was taken, and the initial resistivity was calculated. Over three consecutive sampling periods, the ambient temperature increased from 25 degrees Celsius to 27 degrees Celsius, and the current linearly increased from 10 mA to 11 mA. Calculate the current derivative. Change in integral current Substitute into the formula ,in It is dynamic resistivity. Represents reference temperature The initial resistivity below, Represents the temperature coefficient of resistance. Represents the current ambient temperature. Represents the reference temperature. Represents the current change sensitivity factor. Current change rate over time interval The integral within the timeframe, and the current change sensitivity factor β, are determined experimentally based on the rate of current change under different temperature conditions. The linear relationship between resistivity change and resistivity change was obtained by measuring the rate of change of electrode current under constant voltage and different temperatures (increasing in 2°C increments within the 20°C to 30°C range); the corresponding resistivity change values ​​were measured, and a linear relationship curve between resistivity change and current change rate was plotted; linear regression was performed on the measured data to obtain the slope of the linear fitting equation, which is the quantified value of the current change sensitivity factor β. The resistivity of the multi-cycle was calculated to be 0.0778, 0.0789, and 0.0800 ohm·cm, respectively. The difference between adjacent cycles was calculated to be 0.0008, 0.0011, and 0.0011, and the mean value was calculated to be 0.0010 ohm·cm.

[0075] Table 2 Resistivity Measurement Data

[0076]

[0077] As shown in Table 2, the average resistivity change rate is 0.0010 ohm·cm, which is lower than the preset threshold of 0.002 ohm·cm. This result is used to trigger the frequency offset submodule.

[0078] Frequency offset submodule: Sets the start and cutoff frequencies of the sweep frequency signal output by the vector network analyzer according to the resistivity change rate, transmits a sinusoidal excitation signal to the Ag / AgCl antenna, collects the amplitude and phase data of the reflection coefficient, extracts the center frequency corresponding to the resonant point, calculates the deviation from the initial calibration frequency, and generates the resonant frequency offset.

[0079] Based on the average resistivity change rate of 0.0010 ohm·cm, set the scaling factor. Calculate the frequency offset The vector network analyzer outputs a sweep frequency signal, starting frequency. Cutoff frequency A sine wave with a transmission frequency of 2.40 GHz and a power of -10 dBm was transmitted, and the reflection coefficient was collected. The resonant frequency corresponding to a phase of -90 degrees is extracted to be 2.3998 GHz, which deviates from the calculated initial calibration frequency of 2.4000 GHz. The resonant frequency offset is 0.0002 GHz.

[0080] Anomaly Detection Submodule: Calculates the product of resistivity change rate and resonant frequency offset, maps the product to a preset dielectric loss factor threshold range through normalization, compares the mapped value with the upper and lower limits of the dielectric loss threshold range, and generates an anomaly signal.

[0081] The dielectric loss threshold is a critical reference value set by referring to the standard dielectric loss range of the target material at a preset operating frequency and temperature, and combining it with the minimum acceptable standard for signal integrity or energy efficiency of implantable biosensors.

[0082] Calculate the product of the resistivity change rate of 0.0010 ohm·cm and the frequency offset of -0.0002 GHz. Set the lower limit of the normalization interval Upper limit The dielectric loss factor threshold is mapped to a range of 0.02 to 0.10. The minimum acceptable standard is determined based on biosensor signal integrity testing experiments. The absolute value of the product of resistivity change rate and frequency offset, 0.00005 Ω·GHz·m, is used as the threshold for monitoring biomembrane impedance anomalies to ensure the accuracy and reliability of anomaly signal detection. The dielectric loss factor threshold is calculated by multiplying the resistivity change rate and resonant frequency offset, mapping it to a standardized range, and then calculating the normalized value. The value of 0.166 is compared with the preset dielectric loss thresholds of 0.02 to 0.10. The value of 0.166 exceeds the upper limit of the threshold, and an abnormal signal is generated.

[0083] Please see Figure 2 The frequency analysis module includes:

[0084] Signal Characterization Submodule: Based on abnormal signals, it collects voltage and current waveform data of the closed-loop circuit, uses an inverting amplifier to measure the time difference between voltage peaks and current troughs, calculates the phase angle difference between the two, and uses an impedance analyzer to measure the ratio of the antenna resonant peak half-power bandwidth to the center frequency, generating phase angle deviation and Q value fluctuation.

[0085] Based on closed-loop circuit voltage waveform data (Sampling interval) ) and current waveform data Locating the peak time of voltage waves With current trough Calculate the time difference According to the center frequency Calculate the phase angle difference The half-power bandwidth of the resonance peak was measured using an impedance analyzer. Calculate the Q-value fluctuation. Generate phase angle deviation value With Q-value fluctuation .

[0086] Least square fitting algorithm submodule: Call the phase angle deviation value and Q value fluctuation, select discrete data points of the real and imaginary parts of impedance in the frequency domain, construct a linear fitting objective function with frequency as independent variable, fit the first slope parameter a and the first intercept b to the real part data using the least squares method, fit the second slope parameter c and the second intercept d to the imaginary part data, and generate metabolic frequency compensation coefficients.

[0087] Call phase angle deviation value With Q-value fluctuation The least squares fitting algorithm submodule selects discrete data points for the real and imaginary parts of the impedance using a weighted method of phase angle deviation and Q-value fluctuation in the frequency domain, and constructs linear fitting objective functions with frequency as the independent variable. Using the least squares method, it calculates the slope parameter a and intercept parameter b for the real part, and the slope parameter c and intercept parameter d for the imaginary part, and utilizes the weighting relationship... Ensure data quality and reliability in the frequency domain Internal selection of real part of impedance data and imaginary part data Construct a real part linear fitting objective function Calculate the slope ,intercept slope of imaginary part fitting ,intercept Generate metabolic frequency compensation coefficient .

[0088] Coefficient transfer submodule: After converting the metabolic frequency compensation coefficient into a binary data frame, it is used to coordinate the polarization voltage control logic of the potentiostat to generate the frequency compensation coefficient for biofilm monitoring.

[0089] The closed-loop control module directly calls the stored frequency compensation coefficients through a potentiostat and impedance matching circuit to achieve synergistic optimization of the AgCl / Ag electrochemical reaction rate and the antenna impedance matching state.

[0090] The storage address of the frequency compensation coefficient refers to the specific physical storage location allocated to the frequency compensation coefficient in the internal register or non-volatile memory of the closed-loop control module.

[0091] Will According to the formula: It is the frequency compensation value after quantization. The sign function represents the sign of K. Represents the maximum allowable frequency compensation coefficient. N represents the number of bits in the quantized data. The analog frequency compensation coefficient to be quantized `<logarithm>` represents a base-2 logarithmic function used to compress the data range, ensuring that the SPI data frame corresponds to adjustments in the antenna impedance matching network and optimizing the Smith chart matching point position. `floor` represents a floor function. Logarithmic compression term: merging results Generate an SPI data frame 0x51E (hexadecimal), add an odd parity bit, write it to address 0x2000F004, and generate the frequency compensation coefficient.

[0092] Please see Figure 2 The closed-loop control module includes:

[0093] Voltage regulation submodule: Calls the frequency compensation coefficient, sets the initial step size of the potentiostat output voltage as the reference step size, monitors the differential value of the AgCl / Ag electrode reaction current over time, calculates the difference between the differential value of the current and the dielectric loss threshold, uses the difference as the step size adjustment factor, linearly scales the voltage step size amplitude, and generates the polarization voltage regulation coefficient.

[0094] Call frequency compensation coefficient Set the baseline step size ,exist Inner Interval sampling current data Calculate the differential value of the current. Take the standard deviation of the most recent 5 differential values. Combined with material sensitivity factor Set dielectric loss threshold Calculate the difference Step size adjustment factor Scaling voltage step size ,when Time limit is Generate polarization voltage regulation coefficient .

[0095] Bias control submodule: Calls the polarization voltage adjustment coefficient, measures the real and imaginary components of the impedance of the Ag cathode under DC bias voltage, substitutes the real and imaginary components into the Smith chart coordinate system, calculates the difference in ohmic loss and capacitive reactance between the current coordinate point and the reference point, adjusts the bias voltage output amplitude according to the difference, and generates the bias voltage correction amount.

[0096] Apply DC bias voltage Measure the real part of the impedance imaginary part In the Smith chart coordinate system, the reference point is Calculate the difference in ohmic loss. Capacitive difference Set adjustment weight , Bias voltage correction Limit the range of corrections Output bias voltage correction amount .

[0097] Smith chart matching submodule: calls the polarization voltage adjustment coefficient and bias voltage correction amount, extracts the magnitude phase coordinates of the Smith chart coordinate system, calculates the Euclidean geometric distance between the real-time coordinates and the target matching point, updates the impedance matching network parameters based on the distance inverse proportional function, and generates the dynamic adjustment result of the cathode polarization voltage;

[0098] Based on closed-loop dynamic adjustment logic, the target matching point is initialized as follows: Real-time measurement of the current impedance coordinates is Calculate Euclidean distance Set an inverse proportional coefficient Generate impedance matching network parameter update amount Adjust the real impedance to The imaginary impedance is Adjusted impedance As a new measured point, the Euclidean distance to the target point is recalculated. ,when At that time, the target matching point is dynamically updated. Repeat the steps, and adjust the impedance a second time. Euclidean distance is reduced to ,satisfy The convergence condition is used to generate the dynamic adjustment result of the cathode polarization voltage. .

[0099] Table 3 Closed-Loop Dynamic Adjustment Data Table

[0100]

[0101] As shown in Table 3, the Euclidean distance is reduced from [value missing] through three iterations. Down to This enables dynamic reconstruction of matching points in the Smith chart.

[0102] Please see Figure 2 The encapsulation status assessment module includes:

[0103] Sensor data acquisition submodule: detects water vapor transmission rate output by humidity sensor, acquires ion permeation flux output by pressure sensor, and uses sliding window mean filtering to eliminate sensor baseline drift and impedance fluctuations caused by water vapor transmission and ion permeation for parameters after dynamic adjustment of cathode polarization voltage, generating dynamically corrected water vapor transmission rate and ion permeation flux.

[0104] The water vapor transmission rate monitoring device consists of a humidity sensor (model HIH-4000), a constant temperature chamber (temperature control accuracy ±0.5°C), and a 16-bit ADC data acquisition module. The ion permeation flux monitoring device includes a pressure sensor (range 0-10 kPa, accuracy ±0.1%) and electrochemical detection (three-electrode system). The calibration method is as follows: at a constant temperature of 25°C, a standard saturated salt solution (MgCl2·6H2O, humidity 32.8%RH) is injected into the chamber, and the output value of the humidity sensor is recorded. Adjust the ADC gain to ensure the measured error is ≤±1%. Ion permeation flux calibration was performed using a 0.1M NaCl solution with a constant voltage of 0.5V applied, and the steady-state current was measured. Converted to flux ( After correcting the sensor slope coefficient to an error ≤ ±2%, and completing the calibration, set the sliding window length. Data collection The average of the first 5 data points is calculated as follows: The mean of the 6th data point after the window is slid is The data after full sequence filtering is calculated sequentially as follows: Simultaneously collect ion permeation flux data after calibration. Filtered sequence When the difference between the means of adjacent windows exceeds or When baseline drift elimination is complete, the corrected water vapor transmission rate is generated. With ion permeation flux .

[0105] The parameter fusion analysis submodule calls water vapor transmission rate and ion permeation flux, adjusts parameters based on the polarization voltage output by the potentiostat, and maps the three to the 0-1 range using a linear normalization method. Combining the dielectric loss threshold and the preset encapsulation air permeability benchmark value, the module calculates the indicators of air permeability and ion barrier capability through linear combination, and generates parameter fusion coefficients characterizing the air permeability of the encapsulation material.

[0106] Set water vapor transmission rate range Ion permeation flux range Polarization voltage adjustment parameter range For the corrected water vapor transmission rate Normalization ion permeation flux Normalization Polarization voltage parameters Normalization Combined with dielectric loss threshold Compared with the packaging air permeability benchmark value Calculate the air permeability index Ion barrier index fusion coefficient ,when Time correction Generate parameter fusion coefficients.

[0107] Packaging status determination submodule: compares the parameter fusion coefficient with the preset packaging stability threshold range point by point, marks those exceeding the threshold as packaging instability, and marks those not exceeding the threshold as packaging stability, generating the monitoring result of packaging status;

[0108] The preset encapsulation stability threshold is set by the measured data of water vapor transmission rate of the encapsulation material, the fluctuation range of Ag / AgCl electrode polarization voltage, and the dynamic interpolation compensation mechanism of body fluid temperature and ion concentration.

[0109] Preset package stability threshold range A cubic spline interpolation method was used with a dynamic interpolation compensation mechanism, with water vapor transmission rate measured at points (0.2, 0.5, 0.8 g·m⁻¹). - ²·day - ¹) and the liquid temperature-ion concentration measurement points (20℃-0.1 mol / L, 25℃-0.15 mol / L, 30℃-0.2 mol / L) are used as interpolation nodes to construct a continuous and smooth interpolation curve, ensuring accurate prediction of the encapsulation stability threshold and stability of the monitoring results during the compensation process. The parameter fusion coefficient is taken. Comparison Marked as encapsulation instability, if the fusion coefficient of another set of data is Comparison Mark as stable encapsulation and generate monitoring results.

[0110] Table 4 Packaging Status Judgment Table

[0111]

[0112] As shown in Table 4, the comparison between the coefficient and the threshold range directly determines the packaging state classification.

[0113] An implantable wireless biofilm monitoring sensor based on AgCl / Ag impedance conversion includes a memory and a processor. The memory stores a computer program and data received by an Ag / AgCl antenna and a potentiostat. When the processor executes the computer program, it realizes an implantable wireless biofilm monitoring system based on AgCl / Ag impedance conversion.

[0114] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. An implantable biomembrane wireless monitoring system based on AgCl / Ag impedance conversion, characterized in that, The system includes: The anode integrated module collects the closed-loop circuit current on the implant surface, as well as the charge transfer resistance of the biomembrane, and transmits it to the cathode verification module. The cathode verification module detects the AgCl resistivity change rate of the biofilm charge transfer resistance, measures the resonant frequency offset of the Ag / AgCl antenna, calculates the product of the resistivity change rate and the resonant frequency offset, maps the product to a preset dielectric loss factor threshold range through normalization, compares the mapped value with the upper and lower limits of the dielectric loss threshold range, generates an abnormal signal, and transmits it to the frequency analysis module. The frequency analysis module extracts the phase angle and antenna Q value data of the closed-loop circuit corresponding to the abnormal signal, calculates the frequency compensation coefficient caused by biomembrane metabolism by combining the frequency domain least squares fitting algorithm, and transmits it to the closed-loop control module. The closed-loop control module, based on the frequency compensation coefficient, controls the AgCl / Ag conversion rate and the Ag cathode DC bias voltage through the cathode polarization voltage output by the potentiostat, generates a dynamic adjustment result of the cathode polarization voltage, and transmits it to the packaging status evaluation module. The dynamic adjustment results of the cathode polarization voltage include the polarization voltage adjustment value, the AgCl / Ag conversion rate control value, and the coordinates of the Smith chart matching point. The packaging status assessment module uses humidity and pressure sensors to acquire water vapor transmission rate and ion permeation flux after dynamic adjustment of the cathode polarization voltage, eliminating impedance fluctuations caused by water vapor transmission and ion permeation, and obtaining monitoring results of the packaging status.

2. The implantable biomembrane wireless monitoring system based on AgCl / Ag impedance conversion according to claim 1, characterized in that, The closed-loop circuit current value and biomembrane charge transfer resistance include current response signal amplitude, charge transport path parameters, and electrode interface reaction impedance. The abnormal signals include the product of resistivity change rate and frequency offset, encapsulation control trigger command, and abnormal signal trigger conditions. The frequency compensation coefficient specifically includes phase angle, antenna Q value, and frequency domain fitting residual. The monitoring results of the encapsulation status include water vapor permeability and ion permeation flux.

3. The implantable biomembrane wireless monitoring system based on AgCl / Ag impedance conversion according to claim 1, characterized in that, The anode integration module includes: Anode embedding submodule: embeds carbon cloth bioanode into the implant surface, detects implant surface morphology features, extracts surface curvature distribution based on optical scanning data, matches the pore structure of carbon cloth anode, measures contact resistance using four-point probe method, and generates contact area parameters by combining the fitting curve of surface roughness and contact resistance. Current acquisition submodule: Acquires the current response signal of the carbon cloth anode, divides the original signal into frequency bands according to the mapping relationship between the contact area parameters and the current acquired by the closed-loop circuit, and uses wavelet transform to extract the frequency components related to the biofilm impedance to generate the closed-loop current value. The resistance conversion submodule inputs the closed-loop current value and the real-time monitored biomembrane polarization voltage into the equivalent circuit model, solves the real and imaginary parts of the charge transfer impedance through an iterative method, and reconstructs the double-layer capacitance compensation coefficient based on the correlation between impedance phase angle and frequency, thereby generating the biomembrane charge transfer resistance value and the corrected closed-loop circuit current value. The double-layer capacitance compensation coefficient is calculated by using a constant phase angle element model to obtain the compensated double-layer capacitance value based on the pseudo-capacitor parameters, angular frequency, and phase angle correction index. This value is used to correct the influence of the non-ideal characteristics of the double-layer capacitance on the imaginary part of the impedance. The equivalent circuit model is a network composed of circuit elements connected in series and parallel to represent the physical processes of solution resistance, charge transfer resistance, and double-layer capacitance, and it is used to fit and analyze the impedance data measured in experiments.

4. The implantable biomembrane wireless monitoring system based on AgCl / Ag impedance conversion according to claim 1, characterized in that, The cathode verification module includes: Resistivity detection submodule: detects the AgCl component of the charge transfer resistance of the biofilm, selects four equally spaced probe contacts on the electrode surface, applies a constant current and measures the voltage between the contacts, calculates the area resistivity according to the four-probe method, extracts resistivity data for three consecutive sampling cycles, calculates the average value of the difference between adjacent cycles, and generates the resistivity change rate. Frequency offset submodule: Sets the start and cutoff frequencies of the sweep frequency signal output by the vector network analyzer according to the resistivity change rate, transmits a sinusoidal excitation signal to the Ag / AgCl antenna, collects the amplitude and phase data of the reflection coefficient, extracts the center frequency corresponding to the resonance point, calculates the deviation from the initial calibration frequency, and generates the resonance frequency offset. Anomaly Detection Submodule: Calculates the product of the resistivity change rate and the resonant frequency offset, maps the product to a preset dielectric loss factor threshold range through normalization, compares the mapped value with the upper and lower limits of the dielectric loss threshold range, and generates an anomaly signal. The dielectric loss threshold is a critical reference value set by referring to the standard dielectric loss range of the target material at a preset operating frequency and temperature, and combining it with the minimum acceptable standard for signal integrity or energy efficiency of the implanted biosensor.

5. The implantable biomembrane wireless monitoring system based on AgCl / Ag impedance conversion according to claim 4, characterized in that, The resistivity change rate is calculated by processing the resistivity data from the sampling period using the following formula: ； in It is the rate of change of resistivity. Represents reference temperature The initial resistivity below, Represents the temperature coefficient of resistance. Represents the current ambient temperature. Represents the reference temperature. Represents the current change sensitivity factor. Current change rate over time interval Integrals within.

6. The implantable biomembrane wireless monitoring system based on AgCl / Ag impedance conversion according to claim 1, characterized in that, The frequency analysis module includes: Signal Feature Submodule: Based on the abnormal signal, the voltage and current waveform data of the closed-loop circuit are collected, the time difference between the voltage peak and the current trough is measured using an inverting amplifier, the phase angle difference between the two is calculated, and the ratio of the half-power bandwidth of the antenna resonant peak to the center frequency is measured using an impedance analyzer to generate the phase angle deviation value and the Q value fluctuation. Least square fitting algorithm submodule: Call the phase angle deviation value and the Q value fluctuation, select discrete data points of the real and imaginary parts of the impedance in the frequency domain, construct a linear fitting objective function with frequency as the independent variable, fit the first slope parameter a and the first intercept b to the real part data using the least squares method, fit the second slope parameter c and the second intercept d to the imaginary part data, and generate metabolic frequency compensation coefficients. Coefficient transfer submodule: After converting the metabolic frequency compensation coefficient into a binary data frame, it is used to coordinate the polarization voltage control logic of the potentiostat to generate frequency compensation coefficients for biofilm monitoring. The closed-loop control module achieves synergistic optimization of the AgCl / Ag electrochemical reaction rate and the antenna impedance matching state by directly calling the stored frequency compensation coefficients. The storage address for storing the frequency compensation coefficient refers to the specific physical storage location allocated to the frequency compensation coefficient in the internal register or non-volatile memory of the closed-loop control module.

7. The implantable biomembrane wireless monitoring system based on AgCl / Ag impedance conversion according to claim 6, characterized in that, Calculate the frequency compensation value after quantization, and then perform binary data frame conversion based on the quantized frequency compensation value, using the following formula: ； in, It is the frequency compensation value after quantization. The sign function represents the sign of K. Represents the maximum allowable frequency compensation coefficient. N represents the number of bits in the quantized data. The analog frequency compensation coefficient to be quantized The base-2 logarithmic function is used to compress the data range, enabling the SPI data frame to correspond to the adjustment of the antenna impedance matching network and optimize the Smith chart matching point position. The floor function represents the floor function.

8. The implantable biomembrane wireless monitoring system based on AgCl / Ag impedance conversion according to claim 1, characterized in that, The closed-loop control module includes: Voltage regulation submodule: Calls the frequency compensation coefficient, sets the initial step size of the potentiostat output voltage as the reference step size, monitors the differential value of the AgCl / Ag electrode reaction current over time, calculates the difference between the differential value of the current and the dielectric loss threshold, uses the difference as the step size adjustment factor, linearly scales the voltage step size amplitude, and generates the polarization voltage regulation coefficient. Bias control submodule: Calls the polarization voltage adjustment coefficient, measures the real and imaginary components of the impedance of the Ag cathode under DC bias voltage, substitutes the real and imaginary components into the Smith chart coordinate system, calculates the difference in ohmic loss and capacitive reactance between the current coordinate point and the reference point, adjusts the bias voltage output amplitude according to the difference, and generates the bias voltage correction amount. Smith chart matching submodule: calls the polarization voltage adjustment coefficient and the bias voltage correction amount, extracts the magnitude phase coordinates of the Smith chart coordinate system, calculates the Euclidean geometric distance between the real-time coordinates and the target matching point, updates the impedance matching network parameters based on the distance inverse proportional function, and generates the dynamic adjustment result of the cathode polarization voltage.

9. The implantable biomembrane wireless monitoring system based on AgCl / Ag impedance conversion according to claim 1, characterized in that, The packaging status evaluation module includes: Sensor data acquisition submodule: detects the water vapor transmission rate output by the humidity sensor, acquires the ion permeation flux output by the pressure sensor, and uses a sliding window mean filter to eliminate sensor baseline drift and impedance fluctuations caused by water vapor transmission and ion permeation for the parameters after dynamic adjustment of the cathode polarization voltage, generating dynamically corrected water vapor transmission rate and ion permeation flux. The parameter fusion analysis submodule calls the water vapor permeability and ion permeation flux, adjusts the parameters based on the polarization voltage output by the potentiostat, and maps the three to the 0-1 range using a linear normalization method. Combining the dielectric loss threshold and the preset encapsulation air permeability benchmark value, the indicators of air permeability and ion barrier capability are calculated through linear combination to generate parameter fusion coefficients characterizing the air permeability of the encapsulation material. Packaging status determination submodule: compares the parameter fusion coefficient with the preset packaging stability threshold range point by point, marks those exceeding the threshold as packaging instability, and marks those not exceeding the threshold as packaging stability, generating the monitoring result of packaging status; The preset encapsulation stability threshold is set based on measured data of water vapor transmission rate of the encapsulation material, fluctuation range of Ag / AgCl electrode polarization voltage, and dynamic interpolation compensation mechanism of body fluid temperature and ion concentration.

10. An implantable wireless monitoring sensor for biomembranes based on AgCl / Ag impedance conversion, comprising a memory and a processor, characterized in that, The memory stores a computer program and data received by the Ag / AgCl antenna and potentiostat. When the processor executes the computer program, it implements the implantable biomembrane wireless monitoring system based on AgCl / Ag impedance conversion as described in any one of claims 1-9.

Images