Miniaturized Ion Sensor Cell Using Hydrolysis Current
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Solution Overview
Problem
Conductimetry measurements for ion concentration in body fluids face challenges due to electrode polarization under high DC voltage, requiring alternating voltage with frequency control and large cell sizes, which limits miniaturization and increases calibration needs.
Innovation Solution
A method using a measurement cell with a fluidic channel and electrodes arranged to apply a direct and stable voltage, generating hydrolysis current for ion concentration measurement, with a fluidic channel section less than 1.5 mm to limit ion transport and reaction kinetics, and an electronic measurement circuit for precise ion concentration determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high DC voltage is applied between electrodes to measure ion concentration, then the measurement sensitivity is improved, but electrode polarization occurs causing measurement errors
Solution Approach 1:
The patent introduces a reference electrode as an intermediary element that establishes a stable reference potential. This reference electrode acts as a mediator between the measuring electrode and the electrolyte, allowing the system to measure ion concentration without the measuring electrode becoming polarized. The reference electrode maintains a constant potential that compensates for polarization effects at the measuring electrode.
Solution Approach 2:
The patent changes the electrical parameters by using a three-electrode configuration with specific potential controls. The reference electrode maintains a fixed potential while the measuring electrode potential is controlled relative to it. This parameter change allows the system to operate at optimized voltages that improve sensitivity while the reference electrode compensates for polarization through potential stabilization.
2Measurement precision
If an alternating voltage with frequency sweep is used to avoid electrode polarization, then measurement accuracy is improved, but device complexity increases due to frequency control requirements
Solution Approach 1:
The patent replaces the complex frequency control system with a simpler DC voltage system. Instead of using an alternating voltage source with frequency sweep capabilities, the invention uses a DC voltage source combined with a reference electrode to achieve polarization-free measurements. This substitution eliminates the need for frequency control circuits while maintaining measurement accuracy.
Solution Approach 2:
The patent extracts the polarization problem from the measurement system by separating the potential reference function into a dedicated reference electrode. This extraction allows the measuring electrode to focus solely on detecting ion concentration without the complicating factor of polarization, as the reference electrode absorbs the potential stabilization function.
3Reliability
If conventional conductimetry cells are used to measure ion concentration, then measurement reliability is improved, but the cell size is large preventing miniaturization for on-board systems
Solution Approach 1:
The patent applies local quality by creating a concentrated measurement zone between the electrodes with a small internal section (less than 1.5 mm). The fluidic channel is designed with a restricted geometry at the measurement location, concentrating the ionic transport pathway in a small local volume. This allows reliable measurements to be obtained from a miniaturized cell structure.
Solution Approach 2:
The patent transitions from a conventional large-volume conductimetry cell to a microfluidic channel structure. By changing the dimensional scale and using a planar electrode arrangement within a narrow channel, the system achieves reliable measurements in a dramatically reduced volume suitable for on-board integration.
4Volume of moving object
If the fluidic channel internal section is reduced to enable miniaturization, then device size is decreased, but ion transport between electrodes is enhanced affecting measurement accuracy
Solution Approach 1:
The reference electrode acts as an intermediary that stabilizes the electrical potential in the miniaturized cell. This stabilization compensates for the enhanced ion transport effects caused by the small channel dimensions, allowing accurate measurements to be obtained despite the reduced internal section that would otherwise distort the 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
Enables simple, precise, and miniaturized ion concentration measurement in body fluids, suitable for continuous monitoring and reducing errors from electrode polarization, facilitating integration into on-board systems.
Implementation Method 1
application of a direct and stable voltage between first and second electrodes (5, 6) of a cell for measuring the overall concentration of ions in a body fluid so as to cause the appearance of electrochemical reactions of hydrolysis of body fluid water, at said first and second electrodes (5, 6)
Implementation Method 2
measuring a hydrolysis current between the two electrodes (5, 6), said hydrolysis current being generated by said electrochemical reactions of hydrolysis of water
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A method for measuring the total ion concentration of a body fluid comprises applying a stable, continuous voltage between the first and second electrodes (5, 6) of a body fluid ion concentration measurement cell to induce electrochemical reactions of water hydrolysis in the body fluid at said first and second electrodes (5, 6), measuring the hydrolysis current generated by these electrochemical water hydrolysis reactions, and determining the total ion concentration of the body fluid by comparison with a predefined calibration curve. The measurement cell includes a fluidic channel (1) having an internal cross-section less than or equal to 1.5 mm².