BME Seminar: Stuart F. Cogan
Monday, March 25, 202412:00 -12:50 pm
Stuart F. Cogan, ScD
Professor of Bioengineering
The University of Texas at Dallas
"Structure and Electrochemical Characterization of Neural Stimulation Electrode Coatings"
Keating 103
Zoom link | Password: BearDown
Hosts: Dr. Mario Romero-Ortega and Dr. Shang Song
(Instructor permission required for enrolled students to attend via Zoom)
Persons with a disability may request a reasonable accommodation by contacting the Disability Resource Center at 621-3268 (V/TTY).
Abstract: Ultra-small penetrating electrode arrays with cross-sectional dimensions on the order of a cell soma or smaller appear to avoid a significant deleterious foreign body response in brain. In the absence of a foreign body response, electrode sites are closer to viable neural processes than with conventional penetrating microelectrode arrays. The apposition of electrode and neural target has the potential to provide higher spatial selectivity for recording and stimulation than is possible with conventional microelectrodes. A consequence of reducing the dimensions of electrode sites on these ultra-small arrays is the large increase in required charge-injection capacity of the electrodes. Here, we examine the connection between structure and the neural stimulation properties of prototypical high charge-injection capacity electrode coatings. The coatings studied included “mixed-conductor” metal oxide coatings of sputtered iridium oxide (SIROF) and ruthenium oxide (RuOx), which inject charge by faradaic processes, as well as purely capacitive charge-injection coatings of titanium nitride (TiN). The morphology of the oxide-based coatings was modified by selection of sputtering parameters and film thickness and their charge-injection properties characterized by cyclic voltammetry (CV), impedance spectroscopy, and voltage transients during current pulsing. We also investigated the addition of titanium to RuOx films by a co-sputtering process. The titanium enhances mechanical stability, as measured through film hardness, but at the expense of reduced charge-injection capacity. As an alternative to inorganic oxide or nitride coatings, an intrinsically conductive polymer coating of poly(ethylenedioxythiophene) doped with polystyrene sulphonate (PEDOT-PSS) was also investigated. Our initial studies suggest the PEDOT-PSS has a limited electrochemical potential range of stability and exhibits mixed failure modes that involve an intrinsic loss of charge storage capacity on CV cycling as well as delamination from underlying metal contacts during pulsing. Comments are made on the selection of charge-injection coatings for clinical devices and the importance or relevance of often-quoted charge-storage capacities and charge-injection capacities for assessing clinical
suitability.
Bio: Dr. Cogan is a professor of bioengineering at The University of Texas at Dallas, where he conducts research on neural stimulation and recording with an emphasis on thin-film electrodes, materials, and devices. His current research focuses on the development of multielectrode arrays based on amorphous silicon carbide and the application of ultra-microelectrodes as neural interfaces to the brain and peripheral nerve. Prior to joining UT Dallas, Dr. Cogan was vice president and director of advanced materials research at EIC Laboratories. Dr. Cogan received a BSc degree in mechanical engineering and a MS degree in materials science from Duke University in 1975 and 1977, respectively. He obtained a ScD from the Massachusetts Institute of Technology (MIT) in 1979.