Integrated Polypyrrole Flexible Conductors for Biochips and MEMS Applications

Integrated polypyrrole, a conductive polymer, interconnects on polymeric substrates were microfabricated for flexible sensors and actuators applications. It allows manufacturing of moving polymeric microcomponents suitable, for example, for micro-optical-electromechanical (MOEMS) systems or implanted sensors. This generic technology allows producing “all polymer” components where the polymers serve as both the structural and the actuating materials. In this paper we present two possible novel architectures that integrate polypyrrole conductors with other structural polymers: (a) polypyrrole embedded into flexible polydimethylsiloxane (PDMS) matrix forming high aspect ratio electrodes and (b) polypyrrole deposited on planar structures. Self-aligned polypyrrole electropolymerization was developed and demonstrated for conducting polymer lines on either gold or copper seed layers. The electropolymerization process, using cyclic voltammetry from an electrolyte containing the monomer, is described, as well as the devices’ characteristics. Finally, we discuss the effect of integrating conducting polymers with metal seed layer, thus enhancing the device durability and reliability. 1. Introduction Polymeric materials, both insulators and conductors, offer several interesting characteristics useful for MEMS applications. They are especially attractive for applications in which conventional materials such as silicon, glass, and most metals are too stiff. Using polymers with a lower Young’s modulus will allow the development of microsensors, optical components, microfluidics and actuators with reduced stiffness [1–3], allowing larger deformations under lower driving forces. They are also characterized by several advantageous properties [4] such as high elasticity, variety of 3D structure formations, and potentially low cost for mass production. Polymers are attractive candidates for bio-sensors and implanted devices since many of the polymers are biocompatible and can be chemically functionalized by modifying the devices surface. Polymers are especially attractive for microactuators since their reduced stiffness allows low operating voltages and less power consumption. We can classify the polymers based on their electrical properties: conductors, insulators, and semiconductor-like polymers. Most of the polymers are insulators, and there are many available structural polymers with microfabrication compatibility and Young’s modulus that can exceed 1？GPa (e.g., polyimide) or below 1？MPa (e.g., PDMS). A special class of polymers, the conjugated organic polymers, is