Quantifying Moisture Penetration in Encapsulated Devices by Heavy Water Mass Spectrometry: A Standard Moisture Leak...

Area of Science:

• Biomedical Engineering
• Materials Science
• Analytical Chemistry

Background:

• Moisture ingress into biomedical implants causes corrosion, necessitating device replacement and further surgery.
• Current moisture leak detection methods lack sufficient sensitivity and a standard for comparison with helium leak rates.
• Helium leak detection, while sensitive, has an uncertain correlation with actual moisture ingress due to complex flow dynamics.

Purpose of the Study:

• To develop a practical, calibrated moisture leak standard traceable to fundamental units.
• To compare calibrated moisture leak rates with helium leak rates in biomedical test structures.
• To investigate the driving forces behind moisture penetration in encapsulated devices.

Main Methods:

• Fabrication of a calibrated moisture leak standard using poly(ether-ether-ketone) (PEEK).
• Calibration of heavy water mass spectrometry using the PEEK standard.
• Measurement of molar moisture leak rates and helium leak rates in manufactured biomedical test structures.

Main Results:

• Calibrated moisture leak rates were found to exceed helium leak rates in most tested biomedical encapsulations.
• This discrepancy was particularly pronounced for both very small and very large leak sizes.
• Theoretical analysis identified LaPlace pressure as the primary driver for enhanced moisture flow.

Conclusions:

• The developed PEEK-based standard enables accurate calibration of moisture leak rates for biomedical devices.
• The findings indicate that current helium testing limits may not adequately predict moisture ingress.
• A reduction in the compliance limit for helium testing in biomedical devices by one order of magnitude is recommended.