E. Guyer, Exponent Failure Analysis Associates, Menlo Park, CA; M. Lane, Emory & Henry College, Emory, VA
Advances in thin-film coating technologies are enabling rapid innovation in medical devices. New coating technologies and thin-film structures used for implantable medical devices serve many critical roles ranging from protection of corrosion prone materials or drug delivery from nanoporous layers, to delivery of an electrical signal directly from an integrated circuit (IC). Reliability of these coatings is of the utmost importance since their performance can in some cases be critical to a patient's life. The human body is an extremely harsh environment, particularly during the immunological response phase, and the success of current and next generation implantable micro/nanoelectronic devices depends to a large extent on understanding how to increase coating adhesion and decrease susceptibility to the body's inherently harsh environment. This article provides a summary of the basic principles of adhesion and cohesion, time dependent failure of coatings in harsh chemical environments such as the human body, the methods for measuring these properties, analytical techniques for assessing failure paths and guidance for mitigating these failures.
Summary: The long-term reliability of protective and active coatings on medical devices is critical to ensure safe patient care. The first portion of this talk is focused on understanding how film and interface chemistry, mechanical properties, mode mixity and interface morphology can be manipulated to increase adhesion. The second portion of the talk addresses the deleterious effects of environment on adhesion and cohesion of thin-films. Specifically, the effect of the the immunological response chemistry (e.g. low pH and peroxide radicals) is discussed in terms of slow crack growth in thin-films.
