Fabrication of a non-wettable wearable textile-based metamaterial microwave absorber

Abstract

In this article, a textile-based metamaterial with broadband microwave absorption was developed using a screen printing technique. The metamaterial has over 90% absorption from 7.39 GHz to 18 GHz. The metamaterial consists of a top layer of the printed structure of commercial conductive inks on various kinds of clothes, which is separated from a conductive ground plane with flexible dielectric foam of 3.2 mm thickness. The metamaterial absorber was simulated using ANSYS HFSS software for various thicknesses of the printed ink. It was observed that the absorption band varies with variation in printed thickness, and the optimized printed thickness was found to be about 50 µm. With the increase in printed thickness, the absorption shifts from broadband to narrow band. To achieve the optimum thickness in fabrication, statistically designed experiments were conducted to study the variation of printed thickness and width with different kinds of clothes and substrates (FR4, plain weave cotton cloth, and twill weave cotton cloth), mesh number of the screen (50–110) and the number of passes (1–3). Substrate material and the number of passes were found to be the most significant factors that affect the printed width resolution and thickness. Rigid copper foil and printed cloth could both be used as the ground plane. A complete, flexible absorber was fabricated using printed cloth as the ground plane. The microwave response (absorption) of all the fabricated absorbers was measured and found to be in agreement (more than 90%) with the simulation. Further, the fabricated absorber on the cloth substrate was also made hydrophobic by treating it with polydimethylsiloxane.