Self-Calibrating Ion-Selective Electrodes Using Differential Voltage
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Solution Overview
Problem
Ion-selective electrodes (ISEs) used in Point of Care (POC), wearable, and implantable applications face challenges in maintaining accuracy due to varying ambient temperatures, requiring frequent calibration and external temperature sensing arrangements that increase power consumption and complexity.
Innovation Solution
A self-calibration method and system where ISEs serve as their own temperature-sensing units, calibrating against a reference electrode in a solution with varying temperatures, allowing for precise measurement of analyte concentration without external temperature sensors, using the voltage difference between ISEs to determine temperature and correct for temperature-induced errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external temperature sensors and calibration systems are added to ISEs, then temperature compensation accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The ISE is designed to perform dual functions: (1) its primary function of measuring analyte concentration, and (2) a secondary function of sensing temperature. By making the ISE itself temperature-sensitive and using its voltage response to both analyte concentration and temperature, the system eliminates the need for separate temperature sensors while achieving accurate temperature compensation.
Solution Approach 2:
The patent combines the temperature sensing function with the ISE measurement function into a single integrated system. Instead of having separate temperature sensors and ISEs, the method merges these functions by using the ISE's inherent temperature sensitivity and processing its voltage response to extract both temperature and concentration information.
2Measurement precision
If external temperature sensors and batteries are added to ISEs, then temperature compensation capability is improved, but ease of operation and maintenance worsen due to frequent battery replacement
Solution Approach 1:
The ISE system performs self-temperature-compensation using its own voltage response characteristics. The ISE inherently responds to both analyte concentration and temperature, and the system uses this self-generated signal to calculate and compensate for temperature effects, eliminating the need for external powered temperature sensors and batteries.
Solution Approach 2:
The ISE serves multiple functions without additional power requirements: it measures analyte concentration, senses temperature variations, and provides the data needed for temperature compensation, all while maintaining battery-free operation.
3Device complexity
If fixed temperature approximation is used in ISE measurements, then device complexity is reduced, but measurement precision deteriorates under varying temperature conditions
Solution Approach 1:
The system uses feedback from the ISE's own voltage response to continuously monitor and compensate for temperature effects. By measuring the voltage at different times when temperature varies, the system calculates the temperature coefficient and applies real-time compensation to maintain accurate concentration measurements despite temperature fluctuations.
Solution Approach 2:
Instead of using a fixed temperature approximation, the system dynamically adapts to changing temperature conditions by continuously measuring voltage responses, calculating temperature coefficients, and adjusting compensation parameters in real-time to maintain measurement accuracy.
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 accurate measurement of pH and nitrate concentrations within 0.3% and 5% of true values under varying conditions, reducing measurement errors and maintaining battery-free operation, validated through controlled experiments and field studies.
Implementation Method 1
a potentiometric ISE converts target ionic activity into a measurable voltage based on a well-known Nernst principle
Implementation Method 2
measuring voltage across a first of the at least two calibrated ISEs and the RE (Vi), measuring voltage across a second of the at least two calibrated ISEs and the RE (Vi+1), determining Vi−Vi+1, and determining the one or more field parameters
Data Source
AI summary
A method of temperature self-calibrating ion-selective electrodes (ISEs) is disclosed which includes calibrating at least two ISEs against a reference electrode (RE) in a calibration solution with a predetermined concentration as the temperature of the calibration solution varies according to a known schedule, wherein the calibration of the at least two ISEs includes determining calibration parameters of each of the at least two ISEs with respect to the RE, placing the at least two calibrated ISEs and the RE into a field solution for determining one or more field parameters of the field solution, measuring voltage across a first of the at least two calibrated ISEs and the RE (Vi), measuring voltage across a second of the at least two calibrated ISEs and the RE (Vi+1), determining Vi−Vi+1, and determining the one or more field parameters.