Collaborative Innovation Center for Modern Grain Circulation and Safety, School of Information Engineering, Nanjing University of Finance and Economics, Nanjing 210046, China.
Department of Electronic Engineering, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China.
Sensors (Basel). 2018 Jun 12;18(6):1912. doi: 10.3390/s18061912.
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.
在这项工作中，我们提出了一种在微波频率下具有显著灵敏度和无损传感能力的超材料吸收体，用于谷物样品。该吸收体由周期性排列在超薄基底上的十字谐振器、填充有谷物样品的传感层和金属地组成。十字谐振器阵列使用 FR-4 板上的印刷电路板工艺制造。通过全波仿真和测量结果验证了所提出的超材料的性能，并通过多次反射干涉理论揭示了其工作机制。它可以通过检测谐振频率的偏移来作为食品质量控制（如掺假、品种等）的非接触式传感器。作为一个直接的应用，当新鲜和陈旧大米混合物中陈旧大米的质量分数从 0%变化到 100%时，其谐振频率从 7.11GHz 明显蓝移到 7.52GHz。此外，吸收体对不同品种的谷物表现出明显不同的谐振吸收频率，这也使其成为谷物分类传感器的候选者。所提出的方案为微波超材料吸收体作为农业和食品质量无损评估的高效传感器的应用开辟了机会。
