Finite State Machine Calibration for Analyte Sensors
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Solution Overview
Problem
Existing in vivo analyte monitoring systems, such as glucose sensors, face challenges in accurately measuring analyte concentrations due to manufacturing variability and limited oxygen diffusion through hydrophilic membranes, leading to inconsistent calibration coefficients and reduced accuracy.
Innovation Solution
A body-worn analyte monitoring system with a processor and sensor interface that employs a finite state machine to select and apply calibration coefficients based on current system states and longitudinal inputs from the analyte sensor, enabling real-time calibration and improved accuracy in measuring analytes like glucose and lactate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a hydrophilic polymer membrane is used to allow glucose diffusion, then glucose measurement accuracy is improved, but oxygen diffusion is severely limited
Solution Approach 1:
The patent changes the membrane material parameter from hydrophilic to hydrophobic (or uses a hybrid membrane with both hydrophilic and hydrophobic regions). This parameter change allows the membrane to be permeable to both glucose and oxygen simultaneously, resolving the contradiction between glucose diffusion and oxygen availability. The hydrophobic membrane or hybrid structure enables oxygen to pass through while maintaining glucose selectivity, ensuring sufficient oxygen reaches the electrode for accurate glucose measurement.
2Ease of manufacture
If calibration coefficients are determined based on sensor design alone, then manufacturing process is simplified, but manufacturing variability causes inconsistent calibration
Solution Approach 1:
The patent applies preliminary action by pre-determining calibration coefficients during the manufacturing process for each individual sensor based on its specific design parameters and measured performance characteristics. These calibration coefficients are then stored in memory associated with each sensor before deployment. This preliminary calibration action ensures that each sensor has an accurate, sensor-specific calibration coefficient that accounts for manufacturing variability, while the overall process remains efficient through automation.
Solution Approach 2:
The patent implements feedback by measuring the actual performance of each sensor during manufacturing and using this feedback information to determine appropriate calibration coefficients for that specific sensor. The calibration process incorporates feedback from electrical measurements and performance tests to adjust and optimize the calibration coefficients, ensuring consistency and accuracy despite manufacturing variability.
3Productivity
If oxygen concentration is insufficient at the working electrode, then the system operates, but glucose measurement becomes proportional to oxygen concentration rather than glucose concentration
Solution Approach 1:
The patent changes the membrane permeability parameter to allow sufficient oxygen diffusion to the electrode surface. By using a hydrophobic membrane or hybrid membrane structure, the system maintains high oxygen permeability while preserving glucose selectivity. This parameter change ensures that oxygen concentration at the electrode remains sufficient for the enzymatic reaction, preventing the measurement from becoming oxygen-limited and ensuring accurate glucose concentration measurement.
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
The system provides continuous, real-time, and accurate in-vivo monitoring of analytes by dynamically adjusting calibration coefficients, reducing the impact of manufacturing variability and ensuring proportional glucose measurement even with limited oxygen availability.
Implementation Method 1
the electrode surface is coated with an enzyme which is then further coated with a polymer membrane
Implementation Method 2
the glucose sensor works by using the enzyme to catalyze a reaction between glucose and oxygen resulting in hydrogen peroxide that is oxidized at a working electrode
Implementation Method 3
the polymer membrane is hydrophilic which allows glucose to easily diffuse through the membrane layer
Data Source
AI summary
In one embodiment an analyte monitoring system is disclosed. The system includes a body worn device having a housing that contains a processor, a memory, a power supply and a sensor interface. The system further includes an analyte sensor that is coupled to the sensor interface. The analyte sensor has a proximal portion contained within the housing that is interfaced with the sensor interface. The analyte sensor also has a distal portion configured to be inserted into a host when positioned outside the housing. The system also includes a finite state machine that selects from possible sensor calibration coefficients based on a current state of the analyte monitoring system, an initial input, and longitudinal inputs received from the analyte sensor. Wherein the processor generates calibrated sensor values based on the selected calibration coefficients and longitudinal inputs from the analyte sensor.