PEDOT:PSS microwave structures : fabrication, electromagnetic properties and applications

Electronic waste has become an environmental concern with the advent of the Internet of Things (IoT) and the new generation of wireless technologies due to the substantial increase in the manufacturing of metal based electronic components. The trend towards smaller and more powerful devices requires materials that offer both high performance and environmental sustainability, highlighting Intrinsically Conductive Polymers (ICPs) as key candidates for future technological advancements. Among different ICPs, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) stands out as a candidate due to its unique physical and electrical properties. Despite the progress made in PEDOT:PSS microwave structures, the detailed microwave behavior of this material and its interaction with electromagnetic waves have remained unexplored. This thesis delves into the electromagnetic properties of PEDOT:PSS-based structures within the microwave regime, investigating factors that influence their microwave responses, and evaluating their performances in different applications. This research is structured into two primary streams: wired and wireless microwave structures. In the first stream, the study examines the electromagnetic properties of PEDOT:PSS microstrip lines with variable thicknesses from 2 μm to 16 μm, and PEDOT:PSS patch resonators doped with various concentrations of dimethyl sulfoxide (DMSO) from 0 wt.% to 8 wt.%. The experimental setup involves measuring the microwave response of these structures across different frequency bands and validating the results with simulations in various software. The findings reveal that the thickness of the PEDOT:PSS layer significantly impacts the propagation efficiency of microwave signals, and the dopant concentration influences the material’s sensitivity to relative humidity changes. In the second stream, the study investigates the absorbing capabilities of multilayer PEDOT:PSS thin films and explores the use of PEDOT:PSS patterned surfaces for sensing applications. The research demonstrates that multilayer structures with varying distances from the electromagnetic source and different layer arrangements exhibit distinct reflection responses. Additionally, the PEDOT:PSS patch resonator array shows promising results as a microwave-absorbing surface and a sensitive element for humidity detection. The split ring resonator composed of DMSO-doped PEDOT:PSS and silver nanowires effectively distinguishes between different standard liquids based on their complex permittivity and can be implemented as a flexible structure for a wide range of non-intrusive sensing applications. This comprehensive study advances the understanding of PEDOT:PSS’s behavior in the microwave regime and underscores its suitability and tunability for various microwave applications.