Metal Halide-Based Microelectrode Sensors for Accurate Determination of Soil Moisture

Soil moisture monitoring is critical to agricultural production and water resource management, yet existing sensors often exhibit limitations in accuracy, cost-effectiveness, and long-term stability. This study aimed to develop a high-performance capacitive soil moisture sensor to address these issues. We selected eco-friendly lead-free K2CuBr3 as the hygroscopic material and optimized the interdigital electrode (IE) structure via theoretical analysis and finite element simulation. The sensors were fabricated using micro-electro-mechanical system (MEMS) technology, and their performance was systematically evaluated with real soil samples. The results demonstrated that K2CuBr3 substantially enhanced the sensor sensitivity. The optimal sensor exhibited a measurement error of approximately 5% over the soil moisture range of 0–42.5%, a relative standard deviation (RSD) of less than 2%, and good stability. This low-cost, lead-free MEMS capacitive sensor, based on K2CuBr3, offers high accuracy and excellent stability. It resolves key drawbacks of traditional sensors and offers a reliable solution for in situ real-time soil moisture monitoring, with broad prospects in smart agriculture.