Electromagnetic Metamaterial Absorbers for Soil Property Evaluation

In this paper, we proposed a sensor probe utilizing an electromagnetic metamaterial absorber. This device comprises a tri-layer structure with periodically arranged copper split-ring resonators, a resin layer, and a magnesium layer, forming a complete electromagnetic wave absorber. Magnesium in contact with the soil dissolves in response to soil properties, and wireless measurement of the reflected response due to dissolution enables measurement of soil properties. Simulation and reflection measurement results revealed that this device can absorb 70% of incident electromagnetic waves. Furthermore, we examined the relationship between the reflection spectrum and the polarization direction, as well as the correlation between the time of device placement on soil and the reflection spectrum. The results showed that the device exhibited a low dependency on polarization direction and underwent significant changes in the reflection spectrum with the dissolution of magnesium. Therefore, this device shows a promising potential for a practical application in soil property evaluation.