title: In vitro and in vivo evaluation of ultrananocrystalline diamond for coating of implantable retinal microchips.
abstract: In this work, ultrananocrystalline diamond (UNCD) thin films were evaluated for use as hermetic and bioinert coatings for a retinal microchip. These films were deposited on highly conductive Si substrates at different temperatures (from 400 to 800 degrees C), using microwave plasma enhanced chemical vapor deposition with argon-rich Ar/CH4 gas mixtures and different relative amounts of hydrogen (0-20%). Scanning electron microscopy studies showed that all the films are dense and continuous. Results of cyclic voltammetry test revealed that when there was <2% of hydrogen in the plasma, the film obtained renders the surface electrochemically inactive, with very low leakage currents ( approximately 4 x 10(-7) A/cm2 at +/-5 V). In addition, in vivo tests of the UNCD-coated Si samples were performed by implanting them in the eyes of rabbits for 4-6 months within the eye physiological environment. According to all these results, it was concluded that UNCD is a promising candidate for use as the encapsulating coatings for implantable retinal microelectronic devices.
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Xingcheng
authors.initials: X
authors.lastname: Xiao
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.forename: Chao
authors.initials: C
authors.lastname: Liu
authors.forename: John A
authors.initials: JA
authors.lastname: Carlisle
authors.forename: Brian
authors.initials: B
authors.lastname: Mech
authors.forename: Robert
authors.initials: R
authors.lastname: Greenberg
authors.forename: Dilek
authors.initials: D
authors.lastname: Guven
authors.forename: Ricardo
authors.initials: R
authors.lastname: Freda
authors.forename: Mark S
authors.initials: MS
authors.lastname: Humayun
authors.forename: James
authors.initials: J
authors.lastname: Weiland
authors.forename: Orlando
authors.initials: O
authors.lastname: Auciello
mesh_terms: D000818:Animals; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D018130:Diamond; D004582:Electronics, Medical; D020007:Implants, Experimental; D008855:Microscopy, Electron, Scanning; D049329:Nanostructures; D019736:Prostheses and Implants; D011817:Rabbits; D012160:Retina; D012825:Silicon; D013499:Surface Properties
chemical_list: D020099:Coated Materials, Biocompatible; D018130:Diamond; D012825:Silicon