  Citation: Astanei, D.; Burlica, R.; Cretu, D.-E.; Olariu, M.; Stoica, I.; Beniuga, O. Treatment of Polymeric Films Used for Printed Electronic Circuits Using Ambient Air DBD Non-Thermal Plasma. Materials 2022, 15, 1919. https://doi.org/ 10.3390/ma15051919 Academic Editors: Stefano Caporali and Emanuele Galvanetto Received: 28 January 2022 Accepted: 3 March 2022 Published: 4 March 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). materials Article Treatment of Polymeric Films Used for Printed Electronic Circuits Using Ambient Air DBD Non-Thermal Plasma Dragos Astanei 1 , Radu Burlica 1, * , Daniel-Eusebiu Cretu 1 , Marius Olariu 1,2 , Iuliana Stoica 3 and Oana Beniuga 1 1 Faculty of Electrical Engineering, “Gheorghe Asachi” Technical University of Iasi, 700050 Ia¸ si, Romania; dragos.astanei@tuiasi.ro (D.A.); daniel-eusebiu.cretu@academic.tuiasi.ro (D.-E.C.); marius.olariu@prosupport-consulting.ro (M.O.); oana.beniuga@tuiasi.ro (O.B.) 2 S.C. Prosupport Consulting S.R.L., 707410 Valea Lupului, Romania 3 Department of Physical Chemistry of Polymers, Petru Poni Institute of Macromolecular Chemistry, 700487 Ia¸ si, Romania; stoica_iuliana@icmpp.ro * Correspondence: radu.burlica@tuiasi.ro; Tel.: +40-723232530 Abstract: This study aims to present the properties of the polymeric films after being subjected to DBD plasma treatment in atmospheric conditions. Three different commercial films of polyester (Xerox Inkjet transparencies and Autostat CUS5 Clear film) and polycarbonate (Lexan™ 8010 MC) have been considered for the tests. The surface wettability has been evaluated based on static water contact angle (WCA) for different treatment times varying between 0.2 s and 30 s, the results revealing a maximum WCA decrease compared to a pristine of up to 50% for Xerox films, 75% for Autostat and 70% for Lexan. The persistence of the hydrophilic effect induced by the plasma treatment has also been verified for up to 72 h of storage after treatment, the results indicating a degradation of the treatment effects starting with the first hours after the treatment. The WCA stabilizes to a value inferior to the one corresponding to pristine in the first 24 h after plasma treatment. The adhesion forces, as well as preliminary surface morphology evaluations have been determined for the considered films using atomic force microscopy (AFM). The adhesion forces are increased together with the prolongation of the plasma treatment application time, varying from initial values of 165 nN, 58 nN and 204 nN to around 390 nN, 160 nN and 375 nN for Xerox, Autostat and Lexan films, respectively, after 5 s of DBD treatment. For the considered materials, the results revealed that the plasma treatment determines morphological changes of the surfaces indicating an increase in surface roughness. Keywords: air DBD plasma; polymer films treatment; adhesion; surface wettability 1. Introduction Polymer films have been frequently used in many modern industrial applications owing to their high performance. In the area of printed electronics, polymeric materials such as polycarbonate (PC), polyethylene terephthalate (PET) and other films are used as a substrate material for the manufacture of organic light-emitting diodes, sensor applications and organic solar cells [1,2] due to their outstanding flexibility, transparency, fold resistance, tensile strength and chemical and corrosion resistance, low weight and lower cost [3]. The manufacture of printed flexible electronics often requires changing the surface of the polymer to improve adhesion or wetting [4,5]. In this regard, although low-pressure plasma can be used, it was found that atmospheric plasma treatment is more convenient, relatively simple and economical in terms of technology without any vacuum systems suitable for this task [6–8]. By using an atmospheric pressure reactor, microscopic structures could be more easily formed on the film substrates through in-line or roll-to-roll processing [9]. Non-thermal plasma has been considered a climate-friendly, sustainable and reliable treatment technology to change the surface of polymers and has a couple of benefits as Materials 2022, 15, 1919. https://doi.org/10.3390/ma15051919 https://www.mdpi.com/journal/materials