Electrochemical characterization of nanostructured Ag:TiN thin films produced by glancing angle deposition on polyurethane substrates for bio-electrode applications

Flexible polyurethane substrates were coated with Ag:TiN thin films (N/Ti atomic ratio = 0.7; 10 at% Ag), with different column inclinations (alpha = 0 degrees, 40 degrees and 80 degrees) and architectures (columnar, zigzag with 2 and 4 periods), using the Glancing Angle Deposition (GLAD) technique. The coatings were characterized in order to assess the best thin film architecture to suit the bio-potential electrode applications. An abrupt increase of porosity of the samples was perceivable with increasing et angles (particularly from 40 to 80). Hence, the sputtered films could be divided into dense (Ag:TiN 0 degrees and Ag:TiN 40 degrees) and porous (Ag:TiN 80 degrees, Ag:TiN 80 degrees 2Z and Ag:TiN 80 degrees 4Z) samples. The electrochemical behaviour of the samples was consistently linked to the porosity differences, which was accompanied by an increase of the surface Ag content. Furthermore, the porous samples exhibited lower impedances (similar to 10(4) Omega cm(2) at 2 MHz), as well as electrochemical noise and drift rate values similar to those of the commercial Ag/AgCl electrodes. Hence, the porous Ag:TiN 80 degrees, Ag:TiN 80 degrees 2Z and Ag:TiN 80 degrees 4Z porous Ag:TiN GLAD coatings seem to be the most promising architectures for the envisaged bio-potential electrode applications. (C) 2016 Elsevier B.V. All rights reserved.