Structural analysis of explanted microelectrode arrays

Abstract

Structural analysis of explanted and Utah microelectrode arrays (MEA) was performed using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) to determine the impact of prolonged exposure to the IN VIVO environment. The MEAs, one designed for recording and one designed for stimulation, had been implanted in the pre-and postcentral gyri, respectively, of a rhesus macaque for 362 days, prior to explantation. Possible processing, handling or implantation damage was observed on individual electrodes on each MEA. Metal degradation/delamination was observed on the stimulating MEA while residual carbon-based matter on the electrode sites and small fissures in the insulation were observed on the recording MEA. The electrode area of the recording MEA had a 5.0x range and the stimulating MEA had a 7.6x range, which did not appear to be related to long-term exposure to tissue.

Mechanical failure modes of chronically implanted planar silicon-based neural probes for laminar recording

“…Good SU and MU activity were recorded on many of these recording sites. Regardless of the electrode type used, insulation failure remains a common form of material electrode failure [39, 40, 77]. …”

“…In contrast, simple designs such as microwires and bed of needle arrays that are conformally coated with a single layer of polymer insulation may bypasses this polymer-polymer delamination failure. Nevertheless, these devices also suffer from conductor-polymer delamination and insulation cracks near the recording tip [20, 39, 40]. …”

“…microwire arrays and bulk silicon micromachined Utah-arrays) [18, 37], and thin-film microfabricated planar arrays [38]. Several studies have characterized the material failure mechanism of microwire- and Utah- arrays [20, 39, 40]. Failure modes include corrosion, cracking, bending of recording sites, and delamination or cracking of the insulating polymer materials, such as parylene-C [20, 39, 40].…”

“…Several studies have characterized the material failure mechanism of microwire- and Utah- arrays [20, 39, 40]. Failure modes include corrosion, cracking, bending of recording sites, and delamination or cracking of the insulating polymer materials, such as parylene-C [20, 39, 40]. However, limited investigation has been reported on the mechanical failure modes of thin film planar silicon arrays.…”

Neuroadhesive L1 coating attenuates acute microglial attachment to neural electrodes as revealed by live two-photon microscopy

“…Material failures largely result from corrosion and delamination of the electrode sites [19–25], cracks in the electrical traces [26–28], and delamination of insulation materials [18,25,28–30], all of which are exacerbated by perpetual strain caused by tissue micromotion during movement [28,31,32]. Biological failure modes of neural interfaces result from multiple sources that ultimately lead to meningeal cell invasion and fibrous encapsulation [14,33], insulting glial scar encapsulation, and neural degeneration [34,35].…”