Inkjet-Printing With Micrometer Resolution on Paper for Flexible RF Applications

Geometry is a critical factor in radio frequency design that directly affects the performance and efficiency of RF components and systems. The characteristic impedance and the propagation constant of transmission lines are affected by the conductor width, spacing, and the dielectric properties. In addition, performance metrics such as insertion loss and bandwidth of microwave filters are also affected by the geometric configuration of resonant elements. This article explores the use of a noncommercial inkjet printer prototype to fabricate high-frequency devices with microscale precision, achieving high-resolution gaps, uniform spacing as small as $9~\mu $ m, conductor widths of $50~\mu $ m, and a filter that operates at frequencies up to 50 GHz. The chosen substrate is paper as a sustainable, environmentally friendly, and flexible platform that offers adaptability for RF applications in dynamic environments. The design, fabrication, and measurements of coplanar waveguides (CPWs) transmission lines and passband filter operating at a central frequency of 25 GHz are presented. The printed CPWs demonstrate attenuation of 0.5 dB/mm at 10 GHz and 1.1 dB/mm at 50 GHz. The fabricated bandpass filter achieves an insertion loss of −5 dB in the bandpass. The performance of the printed filters was studied with respect to the printing and annealing conditions, and it was compared to equivalent filter designs printed on a PET substrate.