RESEARCH ARTICLE A Multimodal, SU-8 - Platinum - Polyimide Microelectrode Array for Chronic In Vivo Neurophysiology Gergely Márton 1,2,3 *, Gábor Orbán 4 , Marcell Kiss 2,4 , Richárd Fiáth 1,5 , Anita Pongrácz 2 , István Ulbert 1,5 1 Institute of Cognitive Neuroscience and Psychology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, building Q2, H-1117, Budapest, Hungary, 2 Department of Microtechnology, Institute for Technical Physics and Materials Science, Centre for Energy Research, Hungarian Academy of Sciences, Konkoly Thege M. út. 29–33, H-1121, Budapest, Hungary, 3 School of Ph. D. Studies, Semmelweis University, Ü llői út 26, H – 1085, Budapest, Hungary, 4 Department of Electron Devices, Budapest University of Technology and Economics, Magyar tudósok körútja 2, building Q, H-1117, Budapest, Hungary, 5 Faculty of Information Technology and Bionics, Pázmány Péter Catholic University, Práter utca 50/a, H-1083, Budapest, Hungary * marton.gergely@ttk.mta.hu Abstract Utilization of polymers as insulator and bulk materials of microelectrode arrays (MEAs) makes the realization of flexible, biocompatible sensors possible, which are suitable for vari- ous neurophysiological experiments such as in vivo detection of local field potential changes on the surface of the neocortex or unit activities within the brain tissue. In this paper the microfabrication of a novel, all-flexible, polymer-based MEA is presented. The device consists of a three dimensional sensor configuration with an implantable depth elec- trode array and brain surface electrodes, allowing the recording of electrocorticographic (ECoG) signals with laminar ones, simultaneously. In vivo recordings were performed in anesthetized rat brain to test the functionality of the device under both acute and chronic conditions. The ECoG electrodes recorded slow-wave thalamocortical oscillations, while the implanted component provided high quality depth recordings. The implants remained viable for detecting action potentials of individual neurons for at least 15 weeks. Introduction In the last few decades, the range of experimental neuroscience methods has been extremely widened by various technological advances. A remarkable segment of this progress was fueled by the utilization of microelectromechanical systems (MEMS) technology for the fabrication of high density microelectrode arrays (MEAs). Following the appearance of the first silicon-based micromachined neural implants [1], such devices evolved rapidly and today a great variety of precisely and reproducibly fabricated MEAs are available, which make the recording of poten- tial changes in the extracellular space with high spatial density possible [2–5]. PLOS ONE | DOI:10.1371/journal.pone.0145307 December 18, 2015 1 / 16 OPEN ACCESS Citation: Márton G, Orbán G, Kiss M, Fiáth R, Pongrácz A, Ulbert I (2015) A Multimodal, SU-8 - Platinum - Polyimide Microelectrode Array for Chronic In Vivo Neurophysiology. PLoS ONE 10(12): e0145307. doi:10.1371/journal.pone.0145307 Editor: Liset Menendez de la Prida, Consejo Superior de Investigaciones Cientificas - Instituto Cajal, SPAIN Received: September 9, 2015 Accepted: December 2, 2015 Published: December 18, 2015 Copyright: © 2015 Márton et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: This work was funded by the Bolyai János Grant of the HAS and KTIA NAP 13-2-2015-0004 to Anita Pongrácz, and OTKA K81354, KTIA_13_NAP- A-IV/1-2-3-6, ANR-TÉT Multisca, TAMOP-4.2.1.B-11/ 2/KMR-2011-0002, EU FP7 Grant No. 600925 NeuroSeeker grants to István Ulbert. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.