Implanted biological membrane wireless monitoring sensor and system based on AgCl / Ag impedance conversion

Abstract

The invention relates to the technical field of bioelectricity signal monitoring, in particular to an implantable biofilm wireless monitoring sensor and system based on AgCl / Ag impedance conversion, and the system comprises an anode integration module, a cathode verification module, a frequency analysis module, a closed-loop regulation and control module and a packaging state evaluation module. According to the method, by directly collecting the current of the closed-loop circuit of the implant and the charge transfer resistance of the biological membrane, original interface information is provided for subsequent analysis, the change rate of the resistivity of the silver chloride is detected, the resonant frequency deviation of the silver / silver chloride antenna is synchronously measured, a high-sensitivity anomaly recognition mechanism is constructed, and the early-warning capability of interface instability or material degradation in the early stage is improved; extracting a circuit phase angle and an antenna Q value after abnormity identification, calculating a frequency compensation coefficient by applying frequency domain least square fitting, controlling a silver chloride / silver conversion rate, optimizing wireless signal transmission, monitoring a packaged water vapor transmission rate and an ion permeation flux, and ensuring long-term reliability of implanted equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bioelectric signal monitoring, and in particular to an implantable biofilm wireless monitoring sensor and system based on AgCl / Ag impedance conversion. BACKGROUND

[0002] The technical field of bioelectric signal monitoring includes technologies for evaluating health status and analyzing pathology using electrical signals generated by the electrical properties or metabolic activities of living organisms. It mainly involves biofilm electrochemical behavior monitoring, biosensor design, electrochemical impedance spectroscopy analysis, weak signal acquisition and processing, and other technical branches. Application scenarios include implantable medical devices, in-vitro diagnostic instruments, real-time physiological parameter monitoring systems, etc. The core technology in this field is to obtain impedance change information through the interface reaction between the electrode and the biofilm, convert the biochemistry signal into quantifiable electrical signal based on signal conversion circuit, and realize remote monitoring based on data transmission protocol. The technical difficulties include electrode material stability, high-frequency weak signal anti-interference ability, long-term implantation biocompatibility, etc.

[0003] Among them, the implantable biofilm wireless monitoring system based on AgCl / Ag impedance conversion refers to using silver chloride and silver electrodes as biofilm interface impedance sensing units, applying a small amplitude alternating excitation signal through a constant potential instrument, capturing the impedance change caused by the change of biofilm ion concentration, and using a transimpedance amplifier to convert the current signal into a voltage signal. After filtering and analog-to-digital conversion, it is wirelessly transmitted to the external receiving terminal at a specific frequency band through a low-power radio frequency chip. The specific technical matters of this system include AgCl / Ag reference electrode preparation process, polarization control method of three-electrode system in body fluid environment, impedance signal frequency domain feature extraction rule, and wireless communication protocol adaptation mechanism.

[0004] In the long-term implantation application of existing bioelectric signal monitoring technology, it is difficult to effectively distinguish the signal drift caused by physiological fluctuations of biofilm and electrode interface aging. For example, in the long-term work of AgCl / Ag electrode, AgCl dissolution or uneven transformation may cause reference potential drift, and the impedance baseline change is easy to be confused with the real bio signal, reducing the monitoring accuracy. In the face of high-frequency interference and the influence of dynamic changes of implantation environment on wireless communication, existing technologies mostly rely on passive filtering or fixed communication protocol, and lack of active adaptation ability. For example, tissue wrapping or body fluid changes can cause antenna detuning, reducing signal transmission quality, and existing technologies usually cannot adjust the matching network compensation in real time. In addition, there is a lack of real-time evaluation mechanism for the integrity of the implanted device package. Small damage to the package may cause body fluid to seep in and affect the stability of the circuit, and traditional monitoring methods usually cannot detect early, until the device function is significantly abnormal, posing a risk for long-term implantation. SUMMARY

[0005] The implantable biofilm wireless monitoring sensor and system based on AgCl / Ag impedance conversion are proposed to solve the problems in the prior art.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical scheme: an implantable biofilm wireless monitoring system based on AgCl / Ag impedance conversion comprises:

[0007] The anode integrated module collects the closed loop circuit current on the surface of the implant and the biofilm charge transfer resistance and transmits to the cathode verification module;

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

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

[0010] The closed loop control module controls the AgCl / Ag conversion rate and the Ag cathode direct current bias voltage based on the frequency compensation coefficient through the cathode polarization voltage output by the potentiostat, generates a cathode polarization voltage dynamic adjustment result, and transmits to the packaging state evaluation module;

[0011] The packaging state evaluation module obtains the water vapor transmission rate and ion permeation flux after the cathode polarization voltage dynamic adjustment through the humidity and pressure sensor, eliminates the impedance fluctuation caused by water vapor transmission and ion permeation, and obtains the monitoring result of the packaging state.

[0012] As a further scheme of the present application, the closed loop circuit current value and biofilm charge transfer resistance include current response signal amplitude, charge transmission path parameter, and electrode interface reaction impedance, the abnormal signal includes resistance change rate and frequency offset product, packaging control trigger instruction, and abnormal signal trigger condition, the frequency compensation coefficient specifically is phase angle, antenna Q value, and frequency domain fitting residual, and the cathode polarization voltage dynamic adjustment result includes polarization voltage adjustment value, AgCl / Ag conversion rate control value, and Smith chart matching point coordinate, and the monitoring result of the packaging state includes water vapor transmission rate and ion permeation flux.

[0013] As a further scheme of the present application, the anode integrated module comprises:

[0014] Anode embedding submodule: embedding carbon cloth bioanode into the surface of the implant, detecting the surface morphology characteristics of the implant, extracting the surface curvature distribution based on optical scanning data, matching the pore structure of the carbon cloth anode, measuring the contact resistance by the four-point probe method, combining the fitting curve of the surface roughness and the contact resistance to generate the contact area parameter;

[0015] Current acquisition submodule: acquiring the current response signal of the carbon cloth anode, according to the mapping relationship between the contact area parameter and the current collected by the closed loop circuit, dividing the original signal into frequency bands, extracting the frequency component associated with the biofilm impedance by wavelet transform, and generating the closed loop current value;

[0016] Resistance conversion submodule: inputting the closed loop current value and the real-time monitored biofilm polarization voltage into the equivalent circuit model, solving the real part and the imaginary part of the charge transfer impedance by the iteration method, reconstructing the double-layer capacitance compensation coefficient based on the correlation between the impedance phase angle and the frequency, generating the biofilm charge transfer resistance value and the corrected closed loop circuit current value;

[0017] The double-layer capacitance compensation coefficient is calculated by the constant phase angle element model 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.

[0018] The equivalent circuit model is composed of a network of circuit elements connected in series and parallel, which represents the physical processes of solution resistance, charge transfer resistance and double-layer capacitance, and is fitted with the impedance data measured by analysis experiment.

[0019] As a further scheme of the present application, the cathode verification module comprises:

[0020] Resistivity detection submodule: detecting the AgCl component of the biofilm charge transfer resistance, selecting four equally spaced probe contacts on the electrode surface, applying a constant current and measuring the voltage between the contacts, calculating the area resistivity according to the four-probe method, extracting the resistivity data of the consecutive three sampling periods, calculating the average value of the difference between adjacent periods, and generating the resistance change rate;

[0021] Frequency offset submodule: setting the start and end frequencies of the output sweep signal of the vector network analyzer according to the resistance change rate, transmitting a sinusoidal excitation signal to the Ag / AgCl antenna, collecting the reflection coefficient amplitude and phase data, extracting the center frequency corresponding to the resonance point, calculating the deviation from the initial calibration frequency, and generating the resonance frequency offset;

[0022] Abnormality determination submodule: calculating the product of the resistance change rate and the resonance frequency offset, mapping the product to the preset dielectric loss factor threshold interval by normalization, comparing the mapping value with the upper and lower limits of the dielectric loss threshold interval, and generating an abnormal 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 the minimum acceptable standard of signal integrity or energy efficiency of the implantable biosensor.

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

[0025] ;

[0026] Wherein is the resistance change rate, represents the initial resistivity at the reference temperature , represents the resistance temperature coefficient, represents the current change sensitive factor, represents the current environmental temperature, represents the reference temperature, represents the current change sensitive factor, the integral of the current change rate in the time interval .

[0027] As a further scheme of the present application, the frequency analysis module comprises:

[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 value of the two is calculated, the ratio of the half-power bandwidth to the center frequency of the antenna resonance peak is measured using an impedance analyzer, and the phase angle deviation value and the Q value fluctuation are generated;

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

[0030] Coefficient transfer submodule: after the metabolic frequency compensation coefficient is converted into binary data frame, it is used to coordinate the polarization voltage control logic of the potentiostat, and a frequency compensation coefficient for biological membrane monitoring is generated.

[0031] The closed loop control end directly calls the stored frequency compensation coefficient through the potentiostat and the impedance matching circuit, realizes the coordinated optimization of the AgCl / Ag electrochemical reaction rate and the antenna impedance matching state;

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

[0033] As a further scheme of the present application, the frequency compensation value after quantization processing is calculated, and the conversion operation of the binary data frame is performed according to the frequency compensation value after quantization processing, using the formula:

[0034]

[0035] wherein, is the frequency compensation value after quantization processing, is the sign function, indicating the sign of K represents the maximum value of the allowed frequency compensation coefficient, and N represents the number of data bits of quantization represents the analog frequency compensation coefficient to be quantized represents the logarithm function with base 2, which is used to compress the data range, so that the SPI data frame can correspond to the adjustment of the antenna impedance matching network, and optimize the Smith chart matching point position, and floor represents the floor function.

[0036] As a further scheme of the present application, the closed-loop control module comprises:

[0037] The voltage regulation sub-module calls the frequency compensation coefficient, sets the initial step length of the potentiostat output voltage to the reference step length, monitors the differential value of the AgCl / Ag electrode reaction current with time, calculates the difference between the current differential value and the dielectric loss threshold value, takes the difference as a step adjustment factor, linearly scales the voltage step length amplitude, and generates a polarization voltage adjustment coefficient;

[0038] The bias control sub-module calls the polarization voltage adjustment coefficient, measures the impedance real part and imaginary part of the Ag cathode under the direct current bias voltage, substitutes the real part and imaginary part into the Smith chart coordinate system, calculates the ohmic loss difference and capacitive reactance difference between the current coordinate point and the reference point, adjusts the output amplitude of the bias voltage according to the difference, and generates a bias voltage correction amount;

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

[0040] As a further scheme of the present application, the packaging state evaluation module comprises:

[0041] The 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 adopts sliding window mean filtering to eliminate the sensor baseline drift according to the parameters adjusted dynamically according to the cathode polarization voltage, eliminate the impedance fluctuation caused by water vapor transmission and ion permeation, and generate the dynamically corrected water vapor transmission rate and ion permeation flux.

[0042] The parameter fusion analysis submodule calls the water vapor transmission rate and ion permeation flux, adjusts the parameters based on the polarization voltage output by the potentiostat, adopts linear normalization method to map the three to the 0-1 interval, combines the dielectric loss threshold and the preset packaging air permeability reference value, calculates the indicators of air permeability and ion barrier ability through linear combination, and generates the parameter fusion coefficient representing the air permeability of the packaging material.

[0043] The packaging state determination submodule compares the parameter fusion coefficient with the preset packaging stability threshold interval point by point, marks the packaging instability when the parameter fusion coefficient exceeds the threshold, and marks the packaging stability when the parameter fusion coefficient does not exceed the threshold, and generates the monitoring result of the packaging state.

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

[0045] As a further scheme of the application, the implantable biological membrane wireless monitoring sensor based on AgCl / Ag impedance conversion comprises a memory and a processor, characterized in that the memory stores a computer program and data received by the Ag / AgCl antenna and the potentiostat, and the processor executes the computer program to realize the implantable biological membrane wireless monitoring system based on AgCl / Ag impedance conversion.

[0046] Compared with the prior art, the application has the following advantages and positive effects:

[0047] In the present application, the original interface information is provided for subsequent analysis by directly collecting the implant closed-loop circuit current and the biological membrane charge transfer resistance. The silver chloride resistivity change rate of the resistance is detected, the silver / silver chloride antenna resonance frequency offset is synchronously measured, the normalized product of the two is compared with the dielectric loss threshold, a high-sensitivity abnormality identification mechanism is constructed, and the early warning ability for early interface instability or material degradation is improved. After identifying the abnormality, the circuit phase angle and antenna Q value data are extracted, and the frequency compensation coefficient caused by the biological membrane metabolism is calculated by applying the frequency domain least square fitting. The coefficient guides the potentiostat to output the cathode polarization voltage, controls the silver chloride / silver conversion rate, and maintains the stability of the sensing interface; at the same time, the silver cathode direct current bias is adjusted, the antenna Smith chart matching point is reconstructed, and the wireless signal transmission is optimized. The double-channel closed-loop regulation ensures the optimal operation of the sensor in the complex physiological environment. The humidity and pressure sensors are combined to monitor the packaging water vapor transmission rate and ion permeation flux, and the packaging transmission rate result is output to ensure the long-term reliability of the implanted device. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 The system flowchart of the present application is shown in Figure

[0049] Figure 2 The system block diagram of the present application is shown in Figure DETAILED DESCRIPTION

[0050] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0051] In the description of the present application, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, in the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0052] Example 1

[0053] Referring to Figure 1 The present application provides a technical scheme: an implantable biological membrane wireless monitoring system based on AgCl / Ag impedance conversion includes:

[0054] The anode integrated module collects the closed-loop circuit current on the surface of the implant and the biological membrane charge transfer resistance 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 biofilm charge transfer resistance include current response signal amplitude, charge transport path parameters, electrode interface reaction impedance, abnormal signals include resistance change rate and frequency offset product, encapsulation control trigger command, detection of over-limit events, frequency compensation coefficient specifically phase angle, antenna Q value, frequency domain fitting residual, cathode polarization voltage dynamic adjustment results include polarization voltage adjustment value, AgCl / Ag conversion rate control value, Smith chart matching point coordinates, and encapsulation status monitoring results 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 smaller than that of the implant. 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] Region number Radius of curvature (mm) Pore size (pm) Contact resistance (Ω-cm2) 1 0.03 142 0.28 2 0.07 155 0.35 3 0.04 138 0.31

[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 angular frequency. It is the imaginary unit. 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 resistance 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] Time (sec) Temperature (°C) Current (mA) Resistivity (ohm-cm) Resistance change rate (ohm-cm) 1 26 10.5 0.0778 0.0008 2 27 11.0 0.0789 0.0011 3 28 11.5 0.0800 0.0011

[0077] As shown in Table 2, the average resistance 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 resistance 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 rate of change of resistance 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 the resistance 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.

[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 rate of change of resistance (0.0010 ohm·cm) and the frequency offset (-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 the resistance change rate and the 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 resistance change rate and the 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 , It is the frequency domain The average value, It is the objective function The average value, intercept slope of the 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 terminal directly calls the stored frequency compensation coefficient 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 refers to the specific physical storage location in the internal register or non-volatile memory of the closed-loop control terminal that is allocated to the frequency compensation coefficient.

[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, extracts the magnitude and 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 the 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] Iteration number Target point coordinate (Ω) Measured point coordinate (Ω) Euclidean distance 1 50,15050,150 52,15852,158 8.258.25 2 49.58,148.3249.58,148.32 49.58,148.3249.58,148.32 1.731.73 3 49.58,148.3249.58,148.32 49.07,146.2649.07,146.26 0.850.85

[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 dynamic interpolation compensation mechanism using cubic spline interpolation was employed. The interpolation nodes were the water vapor transmission rate measurement points (0.2, 0.5, 0.8 g·m⁻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). This constructed a continuous and smooth interpolation curve, ensuring accurate prediction of the encapsulation stability threshold and the stability of the monitoring results during the compensation process. The parameter fusion coefficient was then used. 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] Test group Parameter fusion coefficient Determination result 1 0.0 Package instability 2 0.75 Package stability

[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 biofilm wireless monitoring system based on AgCl / Ag impedance conversion, characterized in that, The system comprises: an anode integrated module, which collects closed-loop circuit current of an implant surface and biofilm charge transfer resistance and transmits to a cathode verification module; the cathode verification module, which detects AgCl resistivity change rate of the biofilm charge transfer resistance, measures Ag / AgCl antenna resonance frequency offset, performs normalized proportional conversion calculation product, generates an abnormal signal when the product exceeds dielectric loss threshold, and transmits to a frequency analysis module; the frequency analysis module, which extracts closed-loop circuit phase angle and antenna Q value data corresponding to the abnormal signal, calculates frequency compensation coefficient caused by biofilm metabolism by combining frequency domain least square fitting algorithm, and transmits to a closed-loop control module; the closed-loop control module, which controls AgCl / Ag conversion rate and Ag cathode direct current bias voltage based on the frequency compensation coefficient through cathode polarization voltage output by a constant potential instrument, generates cathode polarization voltage dynamic adjustment result, and transmits to a packaging state evaluation module; the packaging state evaluation module, which obtains water vapor transmission rate and ion permeation flux after dynamic adjustment of the cathode polarization voltage through humidity and pressure sensors, eliminates impedance fluctuation caused by water vapor transmission and ion permeation, and obtains monitoring result of the packaging state.

2. The implantable biofilm wireless monitoring system based on AgCl / Ag impedance conversion of claim 1, wherein, The closed-loop circuit current value and biofilm charge transfer resistance include current response signal amplitude, charge transmission path parameter and electrode interface reaction impedance, the abnormal signal includes resistance change rate and frequency offset product, packaging control trigger instruction and abnormal signal trigger condition, the frequency compensation coefficient specifically is phase angle, antenna Q value and frequency domain fitting residual, and the cathode polarization voltage dynamic adjustment result includes polarization voltage adjustment value, AgCl / Ag conversion rate control value and Smith chart matching point coordinate, and the monitoring result of the packaging state includes water vapor transmission rate and ion permeation flux. 3.The implantable biofilm wireless monitoring system based on AgCl / Ag impedance conversion of claim 1, wherein, The anode integrated module comprises: an anode embedding sub-module, which embeds a carbon cloth bio-anode into an implant surface, detects implant surface morphology characteristics, extracts surface curvature distribution based on optical scanning data, matches pore structure of the carbon cloth anode, measures contact resistance by a four-point probe method, combines fitting curve of surface roughness and contact resistance, and generates contact area parameter; a current collection sub-module, which collects current response signal of the carbon cloth anode, performs frequency band division on original signal according to mapping relationship between the contact area parameter and current collected by the closed-loop circuit, extracts frequency component associated with biofilm impedance by wavelet transform, and generates closed-loop current value; a resistance conversion sub-module, which inputs an equivalent circuit model to the closed-loop current value and real-time monitored biofilm polarization voltage, solves real part and imaginary part of charge transfer impedance by an iteration method, reconstructs double-layer capacitance compensation coefficient based on correlation between impedance phase angle and frequency, generates biofilm charge transfer resistance value and corrected closed-loop circuit current value, and transmits to the cathode verification module; The double-layer capacitance compensation coefficient is calculated by a constant phase angle element model on pseudo-capacitance parameter, angular frequency and phase angle correction index to obtain compensated double-layer capacitance value, which is used to correct influence of non-ideal characteristics of the double-layer capacitance on the impedance imaginary part. The equivalent circuit model is composed of a network of circuit elements in series and parallel representing physical processes of solution resistance, charge transfer resistance and double layer capacitance, which is fitted with the impedance data measured in the analytical experiment.

4. The implantable biofilm wireless monitoring system based on AgCl / Ag impedance conversion of claim 1, wherein, The cathode verification module comprises: The resistivity detection submodule detects the AgCl component of the biofilm charge transfer resistance, selects four equidistant 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 the resistivity data of the consecutive three sampling periods, calculates the average value of the difference between adjacent periods, and generates the resistance change rate; The frequency offset submodule sets the start and end frequencies of the output sweep signal of the vector network analyzer according to the resistance 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; The abnormality determination submodule calculates the product of the resistance change rate and the resonance frequency offset, maps the product to the preset dielectric loss factor threshold interval through normalization, compares the mapped value with the upper and lower limits of the dielectric loss threshold interval, and generates an abnormal 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 the minimum acceptable standard for signal integrity or energy efficiency of the implantable biosensor.

5. The implantable biofilm wireless monitoring system based on AgCl / Ag impedance conversion of claim 4, wherein, Calculate the resistance change rate, process the resistivity data of the sampling period, and use the formula: ； in It is the rate of change of resistance. 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 biofilm wireless monitoring system based on AgCl / Ag impedance conversion of claim 1, wherein, The frequency analysis module comprises: The signal feature submodule collects the voltage and current waveform data of the closed-loop circuit based on the abnormal signal, measures the time difference between the voltage peak and the current valley using an inverting amplifier, calculates the phase angle difference value, measures the ratio of the half-power bandwidth to the center frequency of the antenna resonance peak using an impedance analyzer, and generates the phase angle deviation value and the Q value fluctuation; The least squares fitting algorithm submodule calls the phase angle deviation value and the Q value fluctuation, selects discrete data points of the real and imaginary parts of the impedance in the frequency domain, constructs a linear fitting target function with frequency as the independent variable, fits the first slope parameter a and the first intercept b to the real part data by the least squares method, and fits the second slope parameter c and the second intercept d to the imaginary part data, to generate a metabolic frequency compensation coefficient; The coefficient transfer submodule converts the metabolic frequency compensation coefficient after binary data frame conversion to be used for coordinating the polarization voltage control logic of the potentiostat, and generates a frequency compensation coefficient for biofilm monitoring; The closed-loop control end directly calls the stored frequency compensation coefficient through the potentiostat and impedance matching circuit, to realize the coordinated optimization of the AgCl / Ag electrochemical reaction rate and the antenna impedance matching state; The storage address points to a specific physical storage location in the internal register or non-volatile memory of the closed-loop control end allocated to the frequency compensation coefficient.

7. The implantable biofilm wireless monitoring system based on AgCl / Ag impedance conversion of claim 6, wherein, Calculate the quantized frequency compensation value, perform binary data frame conversion according to the quantized frequency compensation value, and use the formula: ； wherein, is the quantized frequency compensation value, is the sign function, representing the sign of K represents the maximum allowed frequency compensation coefficient, N represents the number of quantized data bits represents the analog frequency compensation coefficient to be quantized represents the logarithm function with base 2, used to compress the data range, so that the SPI data frame can correspond to the adjustment of the antenna impedance matching network, and optimize the Smith chart matching point position, floor represents the floor function.

8. The implantable biofilm wireless monitoring system based on AgCl / Ag impedance conversion of claim 1, wherein, The closed-loop control module comprises: The voltage regulation sub-module: calls the frequency compensation coefficient, sets the initial step length of the potentiostat output voltage as the reference step length, monitors the differential value of the AgCl / Ag electrode reaction current with time, calculates the difference between the current differential value and the dielectric loss threshold, takes the difference as the step adjustment factor, linearly scales the voltage step length amplitude, and generates the polarization voltage adjustment coefficient; The bias control sub-module: calls the polarization voltage adjustment coefficient, measures the impedance real and imaginary parts of the Ag cathode under the direct current bias voltage, substitutes the real and imaginary parts into the Smith chart coordinate system, calculates the ohmic loss difference and the capacitive reactance difference 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; The circle diagram matching sub-module: calls the polarization voltage adjustment coefficient and the bias voltage correction amount, extracts the modulus and 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 cathode polarization voltage dynamic adjustment result. 9.The implantable biofilm wireless monitoring system based on AgCl / Ag impedance conversion of claim 1, wherein, The encapsulation state evaluation module includes: The sensor data acquisition sub-module: detects the water vapor transmission rate output by the humidity sensor, collects the ion permeation flux output by the pressure sensor, and uses the sliding window mean filtering to eliminate the sensor baseline drift for the parameters adjusted by the cathode polarization voltage, eliminates the impedance fluctuations caused by water vapor transmission and ion permeation, and generates the dynamically corrected water vapor transmission rate and ion permeation flux; The parameter fusion analysis sub-module: calls the water vapor transmission rate and ion permeation flux, based on the polarization voltage adjustment parameters output by the potentiostat, uses linear normalization method to map them to the 0-1 interval, combines the dielectric loss threshold and the preset encapsulation gas permeability reference value, calculates the indicators of gas permeability and ion barrier ability through linear combination, and generates the parameter fusion coefficient representing the gas permeability of the encapsulation material; The encapsulation state determination sub-module: compares the parameter fusion coefficient with the preset encapsulation stability threshold interval point by point, marks the values exceeding the threshold as encapsulation instability, and marks the values not exceeding the threshold as encapsulation stability, and generates the monitoring result of the encapsulation state; The preset encapsulation stability threshold is set through the water vapor transmission rate measured data of the encapsulation material, the polarization voltage fluctuation range of the Ag / AgCl electrode, and the dynamic interpolation compensation mechanism of the body fluid temperature and ion concentration.

10. An implantable biofilm wireless monitoring sensor based on AgCl / Ag impedance conversion, comprising a memory and a processor, characterized in that, The memory stores computer programs and data received by the Ag / AgCl antenna and the potentiostat, and the processor executes the computer programs to realize the implantable biological membrane wireless monitoring system based on the AgCl / Ag impedance conversion of any one of claims 1-9.

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