Predicting Corrosion Delamination Failure in Active Implantable Medical Devices: Analytical Model and Validation...

Area of Science:

• Biomaterials Science
• Materials Science
• Medical Device Engineering

Background:

• Active implantable medical devices (AIMDs) are susceptible to failure due to the ingress of body fluids.
• Delamination at the interface between exposed electrodes/conductive pathways and the implant interior is a primary failure mode.
• Existing testing methods lack clearly defined three-phase boundaries (body fluid-metal-polymer).

Purpose of the Study:

• To develop a simple method for fabricating reliable test specimens with defined boundaries for AIMD interface analysis.
• To investigate the mechanisms of delamination at the metal-polymer interface relevant to AIMDs.
• To establish a mathematical model to describe the observed delamination processes.

Main Methods:

• Fabrication of test specimens using silicone rubber and a metal surface (copper used as a model for platinum).
• Observation and analysis of corrosion-triggered delamination processes.
• Development of a mathematical model coupling a Stefan-model with volume diffusion to describe experimental data.

Main Results:

• A novel, corrosion-triggered delamination process was observed and characterized.
• Two superimposed processes were identified: diffusion-limited chemical reactions undermining adhesion and influx of ions/body fluid components migrating through the polymer.
• The mathematical model accurately reproduced experimental data, demonstrating good agreement.

Conclusions:

• The developed method provides reliable test specimens with defined boundaries for studying AIMD interface failures.
• The identified dual delamination mechanism, including ion migration through the encapsulating polymer, offers new insights into AIMD degradation.
• The validated mathematical model can be generalized for further analysis and prediction of AIMD material performance.