Implantable Electrode Construction Using Cold-Worked Tantalum Core
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Solution Overview
Problem
Existing implantable medical electrical leads face challenges in achieving a thin, cost-effective electrode construction with a stable and corrosion-resistant surface, as the encroachment of the tantalum core into the platinum-iridium cladding zone requires increased nominal cladding thickness, which contradicts the goal of reducing the electrode profile and increasing cost savings.
Innovation Solution
A tantalum core overlaid with a platinum-iridium cladding, where the surface quality of the tantalum core is improved through cold working or sintered and grain-stabilized processes to minimize encroachment into the cladding zone, allowing for a reduced nominal cladding thickness while maintaining a stable and corrosion-resistant surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the tantalum core surface is not properly prepared, then the manufacturing process is simpler, but the encroachment into the cladding zone increases requiring thicker cladding
Solution Approach 1:
The patent applies preliminary action by performing cold working processes (peening or swaging) on the tantalum core surface before the Pt-Ir cladding is applied. This pre-treatment creates a smoother surface that reduces encroachment into the cladding zone, allowing for thinner nominal cladding thickness while maintaining adequate minimum cladding thickness for corrosion protection.
Solution Approach 2:
The patent changes the physical parameters of the tantalum core through cold working processes that alter the surface morphology and grain structure. By modifying parameters such as surface roughness and grain size through controlled deformation, the encroachment into the cladding zone is reduced, enabling thinner overall electrode construction.
2Length of moving object
If the nominal cladding thickness is reduced to decrease electrode profile, then the electrode diameter is smaller, but the encroachment of Ta core into cladding zone requires increased nominal thickness
Solution Approach 1:
The cold working process is performed in advance to prepare the tantalum core surface, creating a smoother profile that reduces the encroachment into the cladding zone. This preliminary surface preparation enables the use of thinner nominal cladding thickness while ensuring that the minimum cladding thickness remains adequate for corrosion protection.
Solution Approach 2:
The patent applies local quality by differentiating between nominal cladding thickness and minimum cladding thickness. The cold working process improves the local surface quality of the tantalum core, allowing the nominal thickness to be reduced while maintaining the critical minimum thickness required for bio-stability and corrosion resistance at the electrode-tissue interface.
3Manufacturing precision
If cold working process is applied to improve tantalum core surface, then the encroachment into cladding zone is reduced, but the manufacturing complexity increases
Solution Approach 1:
The cold working process (peening or swaging) is applied as a preliminary step before cladding to improve the tantalum core surface quality. This early intervention prevents encroachment issues that would otherwise require thicker cladding, and the process is integrated into the existing manufacturing workflow to minimize additional complexity.
Solution Approach 2:
The patent employs conventional cold working processes that use relatively simple, cost-effective equipment compared to alternative surface treatment methods. The processes are well-established in the industry and can be performed using standard machinery, making them cost-effective despite adding a manufacturing step.
4Reliability
If Pt-Ir cladding thickness is increased to compensate for Ta core encroachment, then the corrosion resistance is maintained, but the electrode profile and cost increase
Solution Approach 1:
By performing cold working on the tantalum core before cladding, the patent reduces the encroachment into the cladding zone. This allows for a reduction in the nominal Pt-Ir cladding thickness while maintaining adequate minimum thickness for corrosion resistance, thereby reducing the quantity of expensive Pt-Ir material required.
Solution Approach 2:
The patent changes the surface parameters of the tantalum core through cold working, which reduces the encroachment volume into the cladding zone. This parameter change enables a reduction in the nominal cladding thickness specification while maintaining the critical minimum thickness required for corrosion protection, thus reducing material quantity.
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 a thinner, more cost-effective electrode construction with improved surface quality and reduced profile, facilitating smaller diameter coils and enhanced bio-compatibility without compromising the electrode's performance.
Implementation Method 1
The surface of the Ta core may be modified, to improve a surface quality thereof, by a cold working process, such as peening or swaging
Implementation Method 2
a Pt-Ir cladding directly overlaying the core and forming an exposed outer surface of the electrode
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
An implantable electrode for electrical stimulation of a body, for example, being a component of an implantable medical electrical lead, is preferably in the form of a coiled conductor wire, wherein the wire is formed by a tantalum (Ta) core directly overlaid with a platinum-iridium (Pt-Ir) cladding. When a maximum thickness of the Pt-Ir cladding defines a cladded zone between an outer, exposed surface of the electrode and the Ta core, a surface of the Ta core encroaches into the cladded zone by no more than approximately 50 micro-inches. The tantalum core may be cold worked to improve surface quality or formed from a sintered and, preferably, grain stabilized tantalum.