Exploring PEDOT:PSS interaction with hazardous gas molecules in microwave regime using organic microwave resonators

Organic electronics have offered an interdisciplinary solution for the development of modern electronics that are flexible, affordable, easy to implement, and eco-friendly. This paper outlines the design and implementation of an organic microwave resonator (OMR) where the conventional metallic trace was replaced by an intrinsically conducting polymer: poly (3,4 ethylenedioxythiophene):poly(styrene sulfonate), known as PEDOT:PSS. Owing to this conducting polymer's reversible doping/dedoping properties in reaction with electron-donating gases, the proposed organic resonator was implemented to monitor ammonia gas, as a proof of concept. PEDOT:PSS patterned in a split-ring configuration operates in the C-band (i.e., 4 GHz to 8 GHz) with a resonant frequency of 4.93 GHz and resonant amplitude of-23.74 dB. The large active surface area stemming from the entire ring resonator made of PEDOT:PSS yielded excellent detection sensitivity (9.4 mdB/ppm) and repeatability (<5% variation) to enable the detection of low concentrations of ammonia gas (limit of detection of 1.3 ppm). Moreover, the device demonstrated high selectivity to ammonia gas with negligible sensitivity (<0.1 dB) observed to 1000 ppm of various interferant gases (acetone, ethanol, isopropyl alcohol, and methanol). This study demonstrates the significant potential of organic microwave resonators for the development of the next generation of low-cost, printable, and passive microwave resonators that can be made wearable and flexible for a wide variety of applications.