Ultra-nanocrystalline diamond electrodes: optimization towards neural stimulation applications

Abstract

Diamond is well known to possess many favourable qualities for implantation into living tissue including biocompatibility, biostability, and for some applications hardness. However, conducting diamond has not, to date, been exploited in neural stimulation electrodes due to very low electrochemical double layer capacitance values that have been previously reported. Here we present electrochemical characterization of ultra-nanocrystalline diamond electrodes grown in the presence of nitrogen (N-UNCD) that exhibit charge injection capacity values as high as 163 µC cm(-2) indicating that N-UNCD is a viable material for microelectrode fabrication. Furthermore, we show that the maximum charge injection of N-UNCD can be increased by tailoring growth conditions and by subsequent electrochemical activation. For applications requiring yet higher charge injection, we show that N-UNCD electrodes can be readily metalized with platinum or iridium, further increasing charge injection capacity. Using such materials an implantable neural stimulation device fabricated from a single piece of bio-permanent material becomes feasible. This has significant advantages in terms of the physical stability and hermeticity of a long-term bionic implant.

Carbon-based smart nanomaterials in biomedicine and neuroengineering

“…The use of ND as a platform material for neural interfaces [131] has been studied both in vivo [132], ex vivo [133] and in vitro [128]. For these applications, boron doping of ND [134–135] has often been considered to bestow ND metallic properties, thus enabling superior S/N performances in the detection of neuronal activity and a wider electrochemical window for electrical stimulation.…”

Large charge-storage-capacity iridium/ruthenium oxide coatings as promising material for neural stimulating electrodes

“…Fig. 5(b) is an example of analysis applied to the Ir 0.8 eRu 0.2 -oxide coating [56,69,70]. The corresponding current vs. scan dependence shows good linearity (Fig.…”

Biocompatible ultrananocrystalline diamond coatings for implantable medical devices

“…(2) one of the lowest coeffi cients of friction (0.02-0.04) 1 13 ) or B atoms substitution for C atoms in the diamond lattice (B-UNCD) 1 to provide electrons into the conduction band, yielding electrical conductivity; 14 (5) extreme resistance to chemical attack by body fl uids, as demonstrated by an UNCD-coated Si microchip implanted inside rabbit eyes as the main component of an artifi cial retina with the aim to restore partial sight to people blinded by genetically induced degeneration of photoreceptors; 9 and (6) the use of UNCD fi lms as scaffolds for effi cient stem cell growth and differentiation for tissue engineering 15 (this characteristic may enable enhanced grafting of UNCD-coated dental and other implants via bone cell growth onto the UNCD surface of the implant).…”