Fully Biodegradable Wireless Soil Urea Sensor Using Metamaterial Perfect Absorber for Robust Measurements

This paper presents a fully biodegradable wireless sensor for measurements of soil urea over a large area. The sensor consists of an alginate hydrogel with immobilized urease enzyme and a metamaterial perfect absorber. Our sensor has the capability to detect the urea concentration in soil wirelessly. In this paper, we succeeded in wirelessly and robustly detecting the soil urea by measuring time-transient changes of electromagnetic responses from the biodegradable soil urea sensors placed on the urea-containing soils. This proposed sensor would enable continuous but also robust measurements for soil urea monitoring over a large area.