Direct Patterning of Ionic Polymers with E-Beam Lithography
- PDF / 609,078 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 97 Downloads / 263 Views
Direct Patterning of Ionic Polymers with E-Beam Lithography Annina M. Steinbach1, Stefan Jenisch1, Parisa Bakhtiarpour2, Masoud Amirkhani2, Steffen Strehle1 1 Institute of Electron Devices and Circuits, Ulm University, Albert-Einstein-Allee 45, 89069 Ulm, Germany 2 Institute of Experimental Physics, Ulm University, Albert-Einstein-Allee 11, 89069 Ulm, Germany ABSTRACT Controlling the bending properties of ionic polymer-metal composites may immediately affect their implementation in robotics and medicine. In the present work, we propose a direct patterning method for the ionic polymer Nafion using conventional electron-beam writing. In a proof-of-concept study, we show that patterns of arbitrary geometry and sizes between 1 μm and 50 μm can be engraved into the polymer surface without using resists. Pattern depth can be deliberately controlled by adjusting the exposure dose. The patterns were stable even after prolonged immersion in ionic solution. The presented technique therefore opens up the possibility to create unique electrode geometries and to investigate independently the effect of pattern size, density, depth as well as geometry on ionic polymer-metal composite bending. INTRODUCTION Ionic polymer-metal composites (IPMCs) combine actuating and sensing ability as well as biocompatibility [1,2] and are therefore highly promising materials for applications in soft robotics and medicine [3]. The basis for the functional composite material are ionic polymers such as Nafion that are in close contact with electrode coatings on either side of the polymer membrane. To ensure this close contact between the two components of the IPMC, in most cases, electroless plating is used. During electroless plating the polymer is impregnated with metal ions, which are reduced afterwards to produce metal particles inside the polymer [4]. This process yields well working composites but the distribution of the metal particles cannot be controlled accurately. Additionally, in the case of using IPMCs as actuator and sensor simultaneously [5], actuator and sensor parts have to be separated by a shield in between them. This necessitates patterning the electrode structures with accuracy during the fabrication process. To find a strategy that will support accurate control over electrode structure, we investigated the direct patterning of the ionic polymer Nafion by an electron-beam (e-beam). The underlying concept is comparable to resist-based e-beam lithography, locally disintegrating the chemical structure of the ionic polymer by electron bombardment to make these areas soluble in a developer [6]. This ablating process produces holes and trenches increasing the interface between polymer and electrodes and thus potentially metal adhesion and reliability. In combination with a resist-based lift-off procedure [7] or adequate polishing, metal patterns similar to a damascene process could be realized [8,9]. In that case, the metal is buried in the surface and will touch the polymer on three sides. The major advantage of our lithography
45
Data Loading...
