Printable Electronics: Patterning of Conductive Materials for Novel Applications
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Printable Electronics: Patterning of Conductive Materials for Novel Applications Anupama Karwa2, Yu Xia2, Daniel M. Clark3, Thomas W. Smith2, Bruce E. Kahn1, 2* Rochester Institute of Technology, Rochester, NY, 14623 1) Imaging and Photographic Technology 2) Center for Materials Science and Engineering 3) Printing Applications Lab ABSTRACT
RFID tags in order to make them economically and commercially viable. Most commercial conductive inks designed for the various printing processes (like lithography, flexography, gravure, screen printing, inkjet printing etc.) are formulated using conducting metal particles as the conducting phase while resins are used as the binders and vehicles. Almost all inks that are formulated contain pigments as a major component. [2-3], [6]. Certain formulations also contain polymers as additives that perform a variety of functions such as binding, vehicles, viscosity regulators etc. The use of a conducting polymer to formulate conducting inks suitable for high volume printing processes would eliminate the need of using of metal conductors as well as external additives. The ink formulations could be modified to achieve properties suitable for the particular printing conditions, substrates and applications.
The convergence of materials science, printing, and electronics promises to offer low cost and high volume production of devices such as transistors, RFID tags, wearable electronics and other novel applications. Although a number of “soft lithographic” techniques have been used to make these devices, they are slow and have a limited production volume [5], [14-15]. Here high volume printing processes like rotary letterpress, flexography and offset lithography have been investigated for patterning conductive materials [1]. The synthesis and development of conducting inks using electrically functional polymers has been studied. The feasibility of using such inks in high volume printing processes has been studied. An attempt has been made to print conductive interdigitated electrodes using these inks to obtain uniform coating properties and appropriate electrical characteristics. Various process parameters like type of substrate, inking time and speed, printing pressure, printing force and ink formulation have been investigated.
1) High Volume 2) Inexpensive 3) Additive 4) Less waste 5) Variety of substrates (including flexible substrates)
INTRODUCTION
Ink formulations
Conductive inks are gaining a rapid commercial importance due to the development of the new RFID technology. Printing has proved to be the appropriate method for large-scale production of such
Aniline, thiophene, pyrrole (or other conjugated monomers) can be polymerized in a continuous phase made up of a group of ionomeric and ionophoric block copolymers. The product can be obtained in the form of environmentally stable films, dispersions or
Advantages of Printing
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Figure 1. Repeat units of some conductive polymers The challenge here was to obtain a continuous phase conducting structure in the form of
