Biodegradable Cuboid Isotropic Metamaterial for Wireless Soil Monitoring

Advanced sensing technologies such as remote sensing and sensor networks, important for enhancing land use through soil condition monitoring, are facing issues including high machine learning costs, limited measurement point density, and environmental impact. This study introduces a remote sensing method that offers both direct and wide-area sensing of soil properties using a dispersible, biodegradable cuboid-shaped isotropic metamaterial equipped with a water-soluble Mg-based resonance antenna structure. The symmetrical metal patterns ensure isotropic reflectance within the 1.2-3.6-GHz range, enabling robust sensing even when the metamaterial is dispersed randomly on the soil. The degradation of the Mg antenna in the soil presents a significant reflection reduction from 80% to 20% at a 2.4-GHz resonant frequency on the soil, promoting the feasibility of combination with a simple wireless measurement system. Integration with functional coatings that dissolve in response to specific soil substances such as pH-sensitive hydroxyapatite leads to the development of biodegradable soil remote monitoring sensors, offering precise, sustainable land management.