Fabrication and characterization of resistive double square loop arrays for ultra-wide bandwidth microwave absorption

Ji-Young Jeong,Hyeonjin Park,Eun-Chae Jeon,Jonghwa Shin,Je-Ryung Lee,Doo-Sun Choi,Joonkyo Jung,Tae-Jin Je,Jun Sae Han

doi:10.1038/s41598-021-91868-y

Abstract

Microwave absorbers using conductive ink are generally fabricated by printing an array pattern on a substrate to generate electromagnetic fields. However, screen printing processes are difficult to vary the sheet resistance values for different regions of the pattern on the same layer, because the printing process deposits materials at the same height over the entire surface of substrate. In this study, a promising manufacturing process was suggested for engraved resistive double square loop arrays with ultra-wide bandwidth microwave. The developed manufacturing process consists of a micro-end-milling, inking, and planing processes. A 144-number of double square loop array was precisely machined on a polymethyl methacrylate workpiece with the micro-end-milling process. After engraving array structures, the machined surface was completely covered with the developed conductive carbon ink with a sheet resistance of 15 Ω/sq. It was cured at room temperature. Excluding the ink that filled the machined double square loop array, overflowed ink was removed with the planing process to achieve full filled and isolated resistive array patterns. The fabricated microwave absorber showed a small radar cross-section with reflectance less than − 10 dB in the frequency band range of 8.0–14.6 GHz.

Highlights

Microwave absorbers using conductive ink are generally fabricated by printing an array pattern on a substrate to generate electromagnetic fields
Light and thin absorbers that can strongly absorb microwave without using heavy ferrite materials are in demand. Such needs have resulted in various research on ‘electromagnetic metamaterial absorbers’
Electromagnetic metamaterials can possess unique electromagnetic attributes that can be explained with unusual values of effective material parameters such as magnetic permeability and electric permittivity

Summary

Introduction

Microwave absorbers using conductive ink are generally fabricated by printing an array pattern on a substrate to generate electromagnetic fields. The lumped resistor inclusions in some of the proposed metamaterial absorber designs are not ideal in terms of fabrication cost and durability To solve these problems, many studied metamaterials using a polymeric conductive material including carbon or graphite with periodic patterns as a circuit and specific sheet resistance instead of using materials having lumped r esistances[14,17,18,19,20]. Printing processes are promising candidates for low-cost fabrication of microwave metamaterials, it is difficult to adjust the sheet resistance value for different parts of a pattern in a finely-controlled fashion. Rheology properties of inks have much less effects on final shapes of patterns because inks only fill engraved patterns

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