A Self-Sustaining Regenerative Amplifier Sensor Using Perfect Metamaterial Absorber for Liquid Concentration Prediction

This paper presents a self-powered microwave sensing platform for precise methanol concentration detection in water. The system features a high-efficiency perfect metamaterial absorber (PMA) that converts ambient electromagnetic energy into DC via a dual-stage rectifier, powering an active split-ring-resonator (SRR) sensor. The PMA harvester, optimized with lumped inductors and series capacitors, achieves over 98% absorption efficiency, resulting in stable performance across different angles and polarizations. Operating at 2.4 GHz, the sensor effectively detects methanol concentrations ranging from 0% to 100%. Sensor data is analyzed using an LSTM model for liquid concentration prediction, providing robustness in noisy environments with measurement anomalies. This approach achieves a 98% accuracy rate in predicting methanol concentrations. The compact, energy-efficient system is well-suited for remote monitoring in the food, beverage, and chemical industries, advancing self-powered microwave sensing technology for reliable material characterization.