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2019-12-03 - Colloque/Présentation - communication orale - Anglais - page(s)

Thiry Damien , Vinx Nathan , Leclère Philippe , Damman Pascal , Tessier Pierre-Yves, Snyders Rony , "The Wrinkling Concept Applied to Plasma Polymers: an Innovative Approach for the Fabrication of Flexible Electrodes" in 2019 MRS Fall Meeting, Boston, Etats-Unis

  • Codes CREF : Chimie des surfaces et des interfaces (DI1327)
  • Unités de recherche UMONS : Chimie des interactions plasma-surface (S882)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux)
  • Centres UMONS : Centre d’Innovation et de Recherche en Matériaux Polymères (CIRMAP)

Abstract(s) :

(Anglais) Following the current development of strategies for the fabrication of structured surfaces, we present in this work an innovative approach for the synthesis of thin films with tunable morphology. Our method is based on the controlled generation of surfaces instabilities in bilayer systems formed by a mechanically responsive plasma polymer films (PPF) synthesized by the Plasma Enhanced Chemical Vapor Deposition (PECVD) method in combination with stiffer coatings. As a case study, PPF were grown from propanethiol on silicon or flexible polyethylene terephthalate (PET) substrates. AFM data (i.e. peak force quantitative nanomechanical property mapping, scratching experiment) reveals that the nature of the PPF is dramatically affected by the substrate temperature (Ts): from a high viscous liquid (η ~ 106 Pa.s.) to a viscoelastic (E ~ 0,1 GPa) and finally to a stiffer elastic solid (E ~ 0,9 GPa) material when increasing Ts from 10°C to 45°C. This evolution in the mechanical properties is correlated with a pronounced increase in the cross-linking degree of PPF evaluated by ToF-SIMS measurements, combined with a statistical treatment of the data. This trend is ascribed to an increae with Ts in the flux of energy brought to the growing film by positive ions and normalised with respect to the total amount of matter deposited. In order to inducing a morphological reorganization of the material, we have deposited a Al thin film (50 nm) by the magnetron sputtering technique on the top of a mechanically responsive PPF. The mismatch between the mechanical properties between both layers results in the spontaneous formation of a wrinkled surface. By tuning the thickness as well as the mechanical properties of the PPF layers, the height (i.e. from 0.4 to 5.2 µm) and the width (i.e. from 0.6 µm to 6.5 µm) of the nano/micro wrinkles can be easily tailored in a wide range offering a great flexibility in term of surface engineering. The same methodology was applied on flexible PET substrates. To evaluate the potential of the Al-based wrinkled/PET material as a flexible thin-film electrode, the mechanical stability of the electrode is explored under severe and repeated positive deformations. For this purpose, applying a strain of 1%, the electrodes are bent up for 10,000 times. The electrical resistance, measured after each bending cycle, shows a relatively stable behavior (the resistance increase only by 15 %). In contrast, for a flat Al thin film directly deposited on flexible PET, the electrical resistance dramatically increases by 12,000 % after 500 cycles indicating failure of the electrode. Our results reveal the attractiveness of our method for the fabrication of micro/nano pattern with tuneable dimensions with potential applications in flexible electronics.