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U.S. Department of Health and Human Services

About FDA

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Research Project: Hermeticity

Medical device applications of Polyparaxylylene (PPX) traditionally include coatings to improve lubricity, adhesion, or abrasion resistance. Recent applications have emerged that include drug encapsulation for long term delivery and the development of robust, flexible, moisture barriers for active implantable electronic devices (AIMDs). Since AIMDs require a hermetic seal between the electronic components and the moist environment inside of the human body, understanding the interplay between polymer structure, physical properties, manufacturing, and water transport becomes critical in evaluating next generation AIMDs to ensure reliability, safety, and efficacy.

Time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy has emerged as a powerful evaluative tool for studying the transport of liquids and small molecules in polymeric materials. The FTIR-ATR provides molecular-level contrast between diffusant(s) (e.g., water, drug surrogates) and the polymer – allowing for a more complete understanding of transport processes. Both diffusion and polymer relaxations are measured simultaneously, in real time, when the polymer is exposed to a macroscopic concentration gradient. In conjunction with in situ temperature-dependent X-ray scattering to probe the polymer structure, we are achieving a new level of rigor in the characterizing the structure-processing-transport relationships in polymer coatings.