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Open AccessArticle

Microwave Metamaterial Absorber for Non-Destructive Sensing Applications of Grain

by Yin Zhang 1,2, Junming Zhao 2, Jie Cao 1,* and Bo Mao 1
1
Collaborative Innovation Center for Modern Grain Circulation and Safety, School of Information Engineering, Nanjing University of Finance and Economics, Nanjing 210046, China
2
Department of Electronic Engineering, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China
*
Author to whom correspondence should be addressed.
Sensors 2018, 18(6), 1912; https://doi.org/10.3390/s18061912
Received: 3 May 2018 / Revised: 1 June 2018 / Accepted: 10 June 2018 / Published: 12 June 2018
(This article belongs to the Special Issue Antenna Technologies for Microwave Sensors)
In this work, we propose a metamaterial absorber at microwave frequencies with significant sensitivity and non-destructive sensing capability for grain samples. This absorber is composed of cross-resonators periodically arranged on an ultrathin substrate, a sensing layer filled with grain samples, and a metal ground. The cross-resonator array is fabricated using the printed circuit board process on an FR-4 board. The performance of the proposed metamaterial is demonstrated with both full-wave simulation and measurement results, and the working mechanism is revealed through multi-reflection interference theory. It can serve as a non-contact sensor for food quality control such as adulteration, variety, etc. by detecting shifts in the resonant frequencies. As a direct application, it is shown that the resonant frequency displays a significant blue shift from 7.11 GHz to 7.52 GHz when the mass fraction of stale rice in the mixture of fresh and stale rice is changed from 0% to 100%. In addition, the absorber shows a distinct difference in the resonant absorption frequency for different varieties of grain, which also makes it a candidate for a grain classification sensor. The presented scheme could open up opportunities for microwave metamaterial absorbers to be applied as efficient sensors in the non-destructive evaluation of agricultural and food product quality. View Full-Text
Keywords: metamaterial absorber; resonant frequency; sensing; effective permittivity; grain; non-destructive evaluation metamaterial absorber; resonant frequency; sensing; effective permittivity; grain; non-destructive evaluation
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MDPI and ACS Style

Zhang, Y.; Zhao, J.; Cao, J.; Mao, B. Microwave Metamaterial Absorber for Non-Destructive Sensing Applications of Grain. Sensors 2018, 18, 1912.

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