In the comprehensive review titled “Non-hermetic packaging of biomedical microsystems from a materials perspective: A review” on Wiley Online Library,
The integrity of encapsulation techniques for long-term implantable biomedical microdevices is paramount, ensuring their safe and consistent operation in chronic applications. Traditional methods employing titanium or ceramic enclosures face scalability challenges, incompatibility with microfabrication processes, and limitations in miniaturization. To address these concerns, a multitude of polymeric materials, including polyimide, parylene, liquid crystal polymer (LCP), and polydimethylsiloxane (PDMS), have been identified for encapsulation. These materials, although not as hermetic as traditional counterparts, exhibit promising potential, particularly for devices fabricated on polymeric substrates.
This review delves into the encapsulation performance of emerging polymeric materials, with a specific emphasis on their long-term functionality and the quantification of their expected lifetimes.
Traditionally, implantable electronic devices have relied on hermetic encapsulation using materials like glass, metal, or ceramics to safeguard against the in vivo environment. However, risk of electrochemical corrosion on metallic surfaces due to various ions, amino acids, proteins, and dissolved oxygen is a valid concern. Hermeticity, defined as the ability to resist foreign gases and liquids from penetrating the encapsulation, is a hallmark of hermetic packages. Such materials, with negligible gas and moisture permeability, have been successfully employed for chronic applications in notable devices like cochlear implants and cardiac pacemakers.
Nevertheless, as the electronics shrink in size and a desire for flexibility on polymer substrates arises, the traditional rigid packaging approaches face limitations. The use of conventional hermetic packages results in devices that occupy larger volumes than desired and restrict mechanical flexibility.
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