Porous Electrophysiology Electrodes for Impedance Reduction
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Solution Overview
Problem
Electrophysiology catheters with smaller measurement electrodes face increased impedance issues due to dimensional dependence of volumetric resistance and limited ionic AC current caused by reduced surface area, which affects electroanatomical mapping during medical procedures.
Innovation Solution
The development of electrophysiology catheters with porous electrodes formed by creating a substrate of a noble metal and an alloy of another noble and less noble metal, where the alloy is de-alloyed to form a porous matrix, increasing the microscopic surface area and reducing impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the dimensions of measurement electrodes are decreased, then the catheter can access smaller anatomical structures, but the impedance increases due to higher volumetric resistance and reduced surface area
Solution Approach 1:
The patent applies porous materials by forming a porous surface layer on the electrode through dealloying of an alloy containing noble and less noble metals. The porous structure increases the microscopic surface area by 20-40 times compared to the macroscopic surface area, thereby reducing impedance while maintaining the small macroscopic dimensions needed for accessing small anatomical structures.
Solution Approach 2:
The patent uses composite materials by creating an alloy structure consisting of noble metal and less noble metal, then selectively removing the less noble metal through dealloying. This creates a composite porous structure where the noble metal forms the porous framework, combining the benefits of high nobility with increased surface area.
2Reliability
If material is added to increase electrode surface area, then impedance decreases, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies parameter changes by altering the chemical composition and microstructure of the electrode surface through dealloying. By changing the alloy composition parameters and controlling the dealloying process parameters, the microscopic surface area is increased 20-40 times without adding significant material mass, thereby reducing impedance while keeping the manufacturing process relatively simple.
Solution Approach 2:
The patent applies the extraction principle by selectively removing the less noble metal from the alloy through dealloying. This extraction process creates the porous structure by taking out the less noble metal components, leaving behind the noble metal framework with increased surface area, avoiding the need to add complex coating materials.
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 porous electrodes achieve a 20 to 40 times increase in microscopic surface area, improving biosignal fidelity and reducing impedance, thereby enhancing the accuracy and effectiveness of electroanatomical mapping and ablation procedures.
Implementation Method 1
De-alloying the alloy can include electrochemically dissolving the less noble metal from the alloy
Implementation Method 2
de-alloying the alloy to form a porous matrix consisting essentially of the second more noble metal
Data Source
Figure 1
Figure 2
Figure 3A~4
AI summary
An electrophysiology catheter includes a catheter body and at least one porous electrode. The porous electrode is formed by forming a substrate of a first more noble metal and forming an alloy on the substrate. The alloy includes a second more noble metal and a less noble metal. The alloy is de-alloyed to form a porous matrix consisting essentially of the second more noble metal. The more noble metals can be gold, copper, and/or platinum, while the less noble metal can be silver, zinc, and/or lead.