Selective Parylene Coating for Pacemaker Electrodes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for partially coating porous layers with parylene suffer from reproducibility issues and damage to the underlying porous film during mask removal, leading to inconsistent electrical properties in stimulation electrodes.
Innovation Solution
A full-surface parylene coating is applied and removed using a plasma method with controlled parameters to maintain a defined film thickness, ensuring precise and reproducible partial coating without damaging the porous layer, allowing for high capacitance and biocompatibility in stimulation electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If masks are applied and later removed to create partial coating, then partial coating is achieved, but the parylene film bleeds during mask removal and the porous film is damaged
Solution Approach 1:
The patent applies a preliminary full-surface parylene coating before any removal process. This preliminary coating ensures complete coverage first, then allows controlled removal in specific areas. The preliminary action of full coating prevents the bleeding issue during mask removal because there is no mask to remove - the definition is achieved through selective removal of the previously deposited uniform layer.
Solution Approach 2:
Instead of the conventional approach of applying mask first then coating (which causes bleeding during mask removal), the patent inverts the sequence: it applies full coating first, then removes material selectively. This inversion eliminates the mask removal bleeding problem and protects the underlying porous film from damage associated with mask application and removal processes.
2Manufacturing precision
If parylene film is removed after full-surface coating, then partial coating is achieved, but the porous layer underneath is damaged and capacitance is reduced
Solution Approach 1:
The patent carefully controls the parameters of the removal process, including plasma power, gas flow rates, and etch time, to achieve selective removal of parylene without damaging the porous film. By optimizing these parameters, the removal process becomes gentle enough to preserve the porous film's capacitance while still achieving the desired partial coating definition.
Solution Approach 2:
The patent replaces mechanical mask removal methods with plasma-based selective removal. Instead of physically removing masks that may tear or damage the porous film, a plasma process is used to chemically etch away the parylene in defined areas. This substitution of mechanical with chemical/physical field-based removal protects the porous film's integrity and maintains its capacitance.
3Manufacturing precision
If masks are used for partial coating, then coating pattern is defined, but the mask or its removal damages the porous film
Solution Approach 1:
The patent extracts the masking step entirely from the process. Instead of applying and removing masks, the method uses direct selective deposition or selective removal techniques where the pattern is defined by the deposition/etching process itself rather than by a temporary mask. This extraction eliminates the source of damage to the porous film while maintaining pattern definition capability.
Solution Approach 2:
The patent introduces a parylene intermediate layer that is deposited uniformly first, then selectively removed. This intermediate layer serves as a sacrificial material that protects the porous film during the patterning process. The intermediary parylene layer can be removed cleanly without damaging the porous film, unlike masks that may physically damage the substrate during application or removal.
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 method achieves a reproducible partial parylene coating on stimulation electrodes with a capacitance of over 15 μF/cm² and a dielectric breakdown voltage of >100 V, maintaining the integrity of the porous film and enabling effective insulation for biocompatible materials like Ir, TiN, or Pt.
Implementation Method 1
A gas-phase polymerization of parylene is suitable for achieving a uniform coating
Implementation Method 2
A parylene coating made uniformly in this way can be removed, in turn, by a plasma method whose parameters are oriented to the film thickness
Data Source
AI summary
A stimulation electrode is produced having a porous film layer and being partially coated with an insulating parylene (polyparaxylylene) film, whose insulating film has a dielectric breakdown voltage of greater than 100 V. Parylene is deposited on the entire surface of a porous film coating and then partially removed again by plasma. After the partial removal of the parylene, this porous film still has a capacitance of greater than 15 mF/cm2 in a physiological NaCl solution at a frequency of 0.1 Hz. For the stimulation electrode, the transition from the insulating film to the porous film is formed so that the film thickness of the parylene film decreases continuously. In this way, a stimulation electrode having a porous film layer and being partially coated with an insulating parylene film is provided, whose electrode on the non-insulating parylene film-coated surface has a capacitance of greater than 15 mF/cm2 in a physiological NaCl solution at a frequency of 0.1 Hz and whose insulating film advantageously has a dielectric breakdown voltage of greater than 100 V.