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ELECTRODEPOSITION OF PLATINUM-IRIDIUM COATINGS AND NANOWIRES FOR NEUROSTIMULATING APPLICATIONS: FABRICATION, CHARACTERIZATION AND IN-VIVO RETINAL STIMULATION/RECORDING EIS STUDIES OF HEXAVALENT AND TRIVALENT CHROMIUM BASED MILITARY COATING SYSTEMS by Artin Petrossians A Dissertation Presented to the FACULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (MATERIALS SCIENCE) May 2012 Copyright 2012 Artin Petrossians
|Title||Electrodeposition of platinum-iridium coatings and nanowires for neurostimulating applications: fabrication, characterization and in-vivo retinal stimulation/recording EIS studies of hexavalent and trivalent chromium based military coating systems|
|Degree||Doctor of Philosophy|
|Degree program||Materials Science|
|School||Viterbi School of Engineering|
|Advisor (committee chair)||Mansfeld, Florian|
|Advisor (committee member)||
Weiland, James D.
Goo, Edward K.
Nutt, Steven R.
Humayun, Mark S.
|Abstract||The studies presented in this thesis are composed of two different projects demonstrated in two different parts. The first part of this thesis represents an electrochemical approach to possible improvements of the interface between an implantable device and biological tissue. The second part of this thesis represents electrochemical impedance spectroscopy (EIS) studies on the corrosion resistance behavior of different types of polymer coated Al2024 alloys. ❧ In the first part of this thesis, a broad range of investigations on the development of an efficient and reproducible electrochemical deposition method for fabrication of thin-film platinum-iridium alloys were performed. The developed method for production of dense films was then modified to produce very high surface area coatings with ultra-low electrochemical impedance characteristics. The high-surface area platinum-iridium coating was applied on microelectrode arrays for chronic in-vitro stimulation. ❧ Using the same method of producing dense films, platinum-iridium nanowires were fabricated using Anodized Aluminum Oxide (AAO) templates for hermetic packaging applications to be used in implantable microelectronics. The implantable microelectronics will be used to perform data reception and transmission management, power recovery, digital processing and analog output of stimulus current. ❧ Finally, in-vivo electrical stimulation tests were performed on an animal retina using high surface-area platinum-iridium coated single microelectrodes to verify the charge transfer characteristics of the coatings. ❧ In the second part of this thesis, three different sets of samples with different combinations of pretreatments, primers with the same type of topcoat were tested in 0.5 N NaCl for period of 30 days. The surface changes measured by EIS as a function of time were then analyzed. The analysis of the fit parameters of the impedance spectra showed that the different primers had the most effect on the corrosion protection properties of the coatings in which the primers with hexavalent chromium ions (Cr⁶⁺) provided better corrosion protection compared to primers with trivalent chromium ions (Cr³⁺). ❧ After 30 days of the exposure of the samples in 0.5 N NaCl, one sample from each set of samples was scribed and exposed to 0.5 N NaCl for 3 days. Analysis of the impedance spectra revealed that the samples with chromium conversion coating pretreatment and hexavalent chromium primer showed “self-healing” characteristics and provided better corrosion protection on the scribed areas compared to the scribed samples with trivalent chromium pretreatment and non-hexavalent chromium primer.|
|Keyword||electrodeposition; platinum-iridium; thin film; implantable; microelectrodes|
|Part of collection||University of Southern California dissertations and theses|
|Publisher (of the original version)||University of Southern California|
|Place of publication (of the original version)||Los Angeles, California|
|Publisher (of the digital version)||University of Southern California. Libraries|
|Provenance||Electronically uploaded by the author|
|Legacy record ID||usctheses-m|
|Contributing entity||University of Southern California|
|Physical access||The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright. The original signature page accompanying the original submission of the work to the USC Libraries is retained by the USC Libraries and a copy of it may be obtained by authorized requesters contacting the repository e-mail address given.|
|Repository name||University of Southern California Digital Library|
|Repository address||USC Digital Library, University of Southern California, University Park Campus MC 7002, 106 University Village, Los Angeles, California 90089-7002, USA|
|Contributing entity||University of Southern California|
|Full text||ELECTRODEPOSITION OF PLATINUM-IRIDIUM COATINGS AND NANOWIRES FOR NEUROSTIMULATING APPLICATIONS: FABRICATION, CHARACTERIZATION AND IN-VIVO RETINAL STIMULATION/RECORDING EIS STUDIES OF HEXAVALENT AND TRIVALENT CHROMIUM BASED MILITARY COATING SYSTEMS by Artin Petrossians A Dissertation Presented to the FACULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (MATERIALS SCIENCE) May 2012 Copyright 2012 Artin Petrossians|