Biosensor Drift Compensation via Admittance Measurement
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Solution Overview
Problem
Current continuous glucose monitoring systems face challenges in reliably detecting in-vivo drift of biosensors, which affects the accuracy of analyte value determination, and require frequent recalibrations, especially due to changes in membrane properties during in-vivo operation.
Innovation Solution
A method involving an electronics unit that measures raw current and in-vivo current response at different operating points to determine sensitivity-to-admittance relations, allowing for compensation of in-vivo sensitivity drift and monitoring of biosensor failsafe operations, thereby reducing the need for frequent calibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If continuous glucose monitoring is performed using transcutaneous or subcutaneous biosensors, then glucose concentration can be determined continuously in interstitial tissue, but in-vivo drift of the biosensor occurs due to changes in membrane properties, affecting measurement accuracy
Solution Approach 1:
The system performs repeated sensitivity-to-admittance measurements during in-vivo operation and uses the detected drift to compensate sensitivity values. This feedback mechanism continuously corrects measurement accuracy based on real-time biosensor state changes, resolving the contradiction between continuous monitoring duration and measurement precision.
Solution Approach 2:
The system changes the operating conditions by applying potential steps at different operating points (different voltages) to measure sensitivity-to-admittance relations. By varying these parameters and detecting how they change over time, the system can compensate for membrane property changes and maintain accurate glucose measurements throughout the continuous monitoring period.
2Measurement precision
If sensitivity drift compensation is performed frequently to maintain accuracy, then measurement precision improves, but the complexity of the electronics unit and calibration requirements increase
Solution Approach 1:
The electronics unit is designed to perform multiple functions: it measures both the raw current for glucose determination and the sensitivity-to-admittance relation for drift detection using the same hardware components. By making the electronics unit multi-functional, the system achieves accurate drift compensation without proportionally increasing device complexity.
Solution Approach 2:
The biosensor system performs self-diagnosis by automatically measuring its own sensitivity-to-admittance relation and detecting its drift state without external intervention. This self-service capability allows the system to maintain accuracy through automatic compensation rather than requiring complex external calibration equipment or procedures.
3Ease of operation
If in-vivo drift is not detected and compensated, then device operation is simple, but the reliability of analyte value determination deteriorates over time
Solution Approach 1:
The system replaces complex mechanical calibration procedures with electrical measurements of sensitivity-to-admittance relations. By using electrical potential steps and current measurements instead of mechanical adjustment or manual calibration, the system maintains ease of operation while significantly improving reliability through automatic drift detection and compensation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables reliable and recurrent detection of in-vivo biosensor drift, improving analyte value accuracy and reducing the number of required calibrations by utilizing sensitivity-to-admittance relations and potential step measurements.
Implementation Method 1
the working electrode includes an enzyme for providing a reaction with the analyte
Implementation Method 2
the biosensor is adapted for electrochemically determining at least one value of an analyte
Implementation Method 3
the membrane has an electrical resistance
Implementation Method 4
the working electrode has an electrical capacitance
Data Source
Figure 1~2A
Figure 2B
Figure 3A~3C
AI summary
A method for detecting in-vivo properties of a biosensor (110) is disclosed. Herein the biosensor (110) is, in interoperation with an electronics unit (202), adapted for electrochemically determining at least one value of an analyte (136) in a sample of a body fluid (140), wherein the biosensor (110) comprises at least one working electrode (120), wherein the working electrode (120) is covered by a membrane (132) and includes an enzyme (134) for providing a reaction with the analyte (136), wherein the membrane (132) has an electrical resistance and the working electrode (120) has an electrical capacitance. Further, the electronics unit (202) is adapted for measuring a raw current and a current response indicative of an admittance of the biosensor (110). Herein, the method comprises the steps of: a)providing a sensitivity-to-admittance relation of the biosensor (110); b) measuring a raw current in the biosensor (110); c) measuring an in-vivo current response indicative of the in-vivo admittance of the biosensor (110), wherein the in-vivo current response is measured at at least one first operating point (156) and at at least one second operating point (158), wherein the first operating point (156) is selected for providing a first characteristic value being related to the electrical resistance of the membrane (132), and wherein the second operating point (158) is selected for providing a second characteristic value being related to the electrical capacitance of the working electrode (120); d) determining an analyte (136) value in a sample of a body fluid (140) by using the raw current and compensating an in-vivo sensitivity drift in the biosensor(110) by correcting the measured value for the raw current by determining an actual value of the sensitivity by using the first characteristic value, whereby the sensitivity-to- admittance relation as provided during step a) is taken into account;and e)monitoring a fail safe operation of the biosensor (110) based on the first characteristic value and/or the second characteristic value. The method and a system (200) comprising a biosensor (100) and an electronics unit (202) may, primarily, be used for a long-term monitoring of an analyte (136) concentration in a body fluid (140), in particular for long-term monitoring of a glucose level,in the field of home care as well as in the filed of professional care.The present method may, especially, allow reducing a number of calibration procedures and, moreover, be capable of relying on a factory calibration of the biosensor (110).