Silver/Silver Chloride Sensor Element with Tailored AgCl Density
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Solution Overview
Problem
Existing medical electrodes suffer from baseline drift due to imbalanced AgCl and Ag levels, leading to electrode failure and waste of valuable silver, especially in long-term use, and there is a need for a design that optimizes AgCl surface density and surface area to extend wear time without excessive silver consumption.
Innovation Solution
A medical electrode with a tailored effective AgCl area density and surface area, determined by the equation ρ A,AgCl = C ⋅ t app ⋅ 1 / A sensor, to ensure stable biopotential signals and minimize silver waste, where ρ A,AgCl is the effective AgCl area density, C is a constant, t app is the wear time, and A sensor is the surface area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If excessive amounts of silver are used in the sensor element, then reliable biopotential signals can be obtained over long wear times, but valuable silver is wasted and costs increase
Solution Approach 1:
The patent applies parameter changes by precisely controlling the AgCl area density (ρA,AgCl) and sensor layer surface area (Asensor) to match the specific application time requirements. Instead of using excessive silver universally, the invention tailors these parameters to provide just enough AgCl for the required wear duration, thereby maintaining signal reliability while minimizing silver consumption and waste.
Solution Approach 2:
The invention introduces dynamics by making the sensor design adaptable to different application times. The AgCl area density and surface area are dynamically adjusted based on the specific wear time requirement (tapp), allowing the same electrode design methodology to serve both short-term and long-term applications with optimized silver content for each scenario.
2Duration of action of stationary object
If the sensor element is designed for long-term use, then wear time is extended, but baseline drift occurs due to imbalanced AgCl and Ag levels
Solution Approach 1:
The patent resolves this contradiction by changing the critical parameter of AgCl area density (ρA,AgCl) to ensure sufficient AgCl is available throughout the intended wear time. The equation ρA,AgCl = C · tapp · 1/Asensor directly links the required AgCl density to the application time, preventing baseline drift by maintaining proper AgCl levels even for extended wear periods.
Solution Approach 2:
The invention applies preliminary action by pre-calculating and incorporating the exact amount of AgCl needed for the desired wear time into the sensor design. This preliminary determination of AgCl requirements ensures that the electrode is properly prepared before use, preventing baseline drift from occurring during the actual wear period.
3Duration of action of stationary object
If the sensor layer surface area is increased, then more AgCl is available to extend wear time, but the amount of silver consumed increases
Solution Approach 1:
The patent applies parameter changes by optimizing the relationship between AgCl area density (ρA,AgCl) and sensor surface area (Asensor) through the equation ρA,AgCl = C · tapp · 1/Asensor. This allows designers to balance these two parameters according to specific needs - increasing surface area only when necessary for the required wear time, rather than universally increasing silver content.
Solution Approach 2:
The invention applies local quality by concentrating the AgCl exactly where it is needed - at the sensor surface in contact with the electrolyte gel. By controlling the AgCl area density at the surface rather than uniformly distributing silver throughout the entire sensor structure, the design achieves extended wear time with minimal total silver content.
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 solution allows for high-quality, stable biopotential signals over specified wear times by optimizing AgCl surface density and area, reducing silver waste and preventing baseline drift, applicable to ECG, EMG, and EEG applications.
Implementation Method 1
The electrochemical reaction occurring at the sensor surface may be described as: Ag + Cl- ↔ AgCl + e-
Implementation Method 2
an ion conductive layer, which is in contact with the skin side of a sensor layer in the sensor element
Data Source
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Figure 2b
AI summary
The present disclosure relates to a medical electrode for biopotential monitoring and/or recording of biopotential signals when attached to the skin of a human or animal. The medical electrode comprises a sensor element and an ion conductive layer, which is in contact with the skin side of a sensor layer in the sensor element. The sensor layer comprises silver (Ag) and silver chloride (AgCI) and has a tailored effective AgCl area density, which depends on the electrode wear time and surface area of the sensor layer.