Non‐hermetic packaging of biomedical microsystems from a materials perspective: A review

Abstract

Traditionally, implantable electronic devices have used metal-based hermetic encapsulation to protect the internal components from damage by the aggressive in vivo environment. Concurrently, hermetic encapsulation protects the surrounding tissue from harmful substances that might be leached from the packaged components (Bazaka & Jacob, 2012). In some cases, however, there is risk of electrochemical corrosion on the metallic surfaces because of the presence of various ions, amino acids, proteins and dissolved oxygen (Eliaz, 2019). Hermeticity is defined as the ability of sealed packages to resist foreign gases and liquids from penetrating the seal or encapsulating material (Madduri, Sammakia, Infantolino, & Chaparala, 2008). Hermetic packages are conventionally made from glass, metal or ceramic materials whereby the gas and moisture permeability through the material is negligible (Madduri et al., 2008; Schuettler, Schatz, Ordonez, & Stieglitz, 2011). Hermetic materials have been successfully used to package devices for chronic applications, some of the most notable being cochlear implants and cardiac pacemakers (Kirsten, Wetterling, Uhlemann, Wolter, & Zigler, 2013). Titanium is the most commonly used metal for hermetic encapsulation because of its biocompatibility, low permeability for ions and moisture, mechanical durability and the ability to create viable hermetic seals by laser welding (Amanat, James, & McKenzie, 2010). Ceramics have also been used for implants for wireless devices to address issues related to attenuation of electromagnetic transmission by metallic packaging (El Khatib, Pothier, Crunteanu, & Blondy, 2007; Schubring & Fujita, 2007; Shen & Maharbiz, 2019). Driven by the increased functionality and scalability offered by innovations in application-specific integrated circuits (ASICs) and the desire to create highly miniaturized devices on flexible polymer substrates, significant efforts have been made in creating miniaturized implants by integrating the majority of components on a single chip. As the

Soft Devices for High-Resolution Neuro-Stimulation: The Interplay Between Low-Rigidity and Resolution

“…Doped nanocrystalline diamond channels within polycrystalline diamond insulation were also suggested as a possible solution (100). More detailed discussion of the types of hermetic sealing methods, the challenges and advances as well as non-hermetic packaging can be found in (9,(101)(102)(103)(104).…”

“…We use examples based on our own work experience to highlight workable solutions to some of the challenges we present in this paper. Many other aspects (such as low power ASIC design, energy transfer approaches and wireless communication) are not discussed as they go beyond the scope of this paper (6)(7)(8)(9).…”

Ultrasound‐Powered Implants: A Critical Review of Piezoelectric Material Selection and Applications

“…For devices implanted in the human body, a layer of encapsulating material must be included to seal in any active electrical components and prevent aggravated host immune response. Reviews on this topic have been published, [ 144,145 ] but to summarize: viable encapsulation materials need to be biocompatible, must last the duration of the implant lifespan, and should scale to small sizes. Traditional implants have sought to use bio‐inert materials like titanium or ceramics.…”

The Safety of Micro-Implants for the Brain

“…Additionally, neural tissue interaction with the implant material over time could cause neurotoxicity or other damage ( Gulino et al, 2019 ). Historically, implant casings have been metallic ( Chong et al, 2020 ). Borosilicate glass encapsulation is an attractive alternative to metallic enclosures due to its excellent material properties, biocompatibility and recent advancements in micro-machining ( Mund and Leib, 2004 ; Ginggen et al, 2008 ; Hansen et al, 2009 ; Leib et al, 2009 ).…”