title: Long-Term Stable Adhesion for Conducting Polymers in Biomedical Applications: IrOx and Nanostructured Platinum Solve the Chronic Challenge.
abstract: Conducting polymers (CPs) have frequently been described as outstanding coating materials for neural microelectrodes, providing significantly reduced impedance or higher charge injection compared to pure metals. Usability has until now, however, been limited by poor adhesion of polymers like poly(3,4-ethylenedioxythiophene) (PEDOT) to metallic substrates, ultimately precluding long-term applications. The aim of this study was to overcome this weakness of CPs by introducing two novel adhesion improvement strategies that can easily be integrated with standard microelectrode fabrication processes. Iridium Oxide (IrOx) demonstrated exceptional stability for PEDOT coatings, resulting in polymer survival over 10 000 redox cycles and 110 days under accelerated aging conditions at 60 °C. Nanostructured Pt was furthermore introduced as a purely mechanical adhesion promoter providing 10-fold adhesion improvement compared to smooth Pt substrates by simply altering the morphology of Pt. This layer can be realized in a very simple process that is compatible with any electrode design, turning nanostructured Pt into a universal adhesion layer for CP coatings. By the introduction of these adhesion-promoting strategies, the weakness of CP-based neural probes can ultimately be eliminated and true long-term stable use of PEDOT on neural probes will be possible in future electrode generations.
authors.affiliation: BrainLinks-BrainTools Center & Department of Microsystems Engineering (IMTEK), University of Freiburg , Georges-Koehler-Allee 102, 79110 Freiburg, Germany.
authors.forename: Christian
authors.identifier: 0000-0002-7961-7411
authors.initials: C
authors.lastname: Boehler
authors.affiliation: BrainLinks-BrainTools Center & Department of Microsystems Engineering (IMTEK), University of Freiburg , Georges-Koehler-Allee 102, 79110 Freiburg, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Oberueber
authors.affiliation: Institute for Applied Materials (IAM) and Karlsruhe Nano Micro Facility (KNMF), Karlsruhe Institute of Technology (KIT) , Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Schlabach
authors.affiliation: BrainLinks-BrainTools Center & Department of Microsystems Engineering (IMTEK), University of Freiburg , Georges-Koehler-Allee 102, 79110 Freiburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Stieglitz
authors.affiliation: BrainLinks-BrainTools Center & Department of Microsystems Engineering (IMTEK), University of Freiburg , Georges-Koehler-Allee 102, 79110 Freiburg, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Asplund
mesh_terms: D019086:Bridged Bicyclo Compounds, Heterocyclic; D006801:Humans; D008839:Microelectrodes; D049329:Nanostructures; D010984:Platinum; D011108:Polymers
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D011108:Polymers; C121383:poly(3,4-ethylene dioxythiophene); D010984:Platinum
keywords: adhesion promotion; conducting polymers; electrodes; long-term stability; nanostructured platinum; neural implant