title: Significant enhancement of PEDOT thin film adhesion to inorganic solid substrates with EDOT-acid.
abstract: With its high conductivity, tunable surface morphology, relatively soft mechanical response, high chemical stability, and excellent biocompatibility, poly(3,4-ethylenedioxythiophene) (PEDOT) has become a promising coating material for a variety of electronic biomedical devices. However, the relatively poor adhesion of PEDOT to inorganic metallic and semiconducting substrates still poses challenges for long-term applications. Here, we report that 2,3-dihydrothieno(3,4-b)(1,4)dioxine-2-carboxylic acid (EDOT-acid) significantly improves the adhesion between PEDOT thin films and inorganic solid electrodes. EDOT-acid molecules were chemically bonded onto activated oxide substrates via the chemisorption of the carboxylic groups. PEDOT was then polymerized onto the EDOT-acid modified substrates, forming covalently bonded coatings. The adsorption of EDOT-acid onto the electrode surfaces was characterized by cyclic voltammetry (CV), contact angle measurements, atomic force microscopy, and X-ray photoelectron spectroscopy. The electrical properties of the subsequently coated PEDOT films were studied by electrochemical impedance spectroscopy and CV. An aggressive ultrasonication test confirmed the significantly improved adhesion and mechanical stability of the PEDOT films on electrodes with EDOT-acid treatment over those without treatment.
authors.affiliation: †Department of Materials Science and Engineering, The University of Delaware, Newark, Delaware 19716, United States.
authors.forename: Bin
authors.initials: B
authors.lastname: Wei
authors.affiliation: †Department of Materials Science and Engineering, The University of Delaware, Newark, Delaware 19716, United States.
authors.forename: Jinglin
authors.initials: J
authors.lastname: Liu
authors.affiliation: †Department of Materials Science and Engineering, The University of Delaware, Newark, Delaware 19716, United States.
authors.forename: Liangqi
authors.initials: L
authors.lastname: Ouyang
authors.affiliation: †Department of Materials Science and Engineering, The University of Delaware, Newark, Delaware 19716, United States.
authors.forename: Chin-Chen
authors.initials: CC
authors.lastname: Kuo
authors.affiliation: †Department of Materials Science and Engineering, The University of Delaware, Newark, Delaware 19716, United States.|‡Department of Biomedical Engineering, The University of Delaware, Newark, Delaware 19716, United States.
authors.forename: David C
authors.initials: DC
authors.lastname: Martin
mesh_terms: D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry*; D004566:Electrodes; D056951:Photoelectron Spectroscopy; D058105:Polymerization; D011108:Polymers / Q000737:chemistry*
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D011108:Polymers; C121383:poly(3,4-ethylene dioxythiophene)
keywords: EDOT-acid; PEDOT; adhesion; conjugated polymers; neural electrode