Portable microwave sensor system for real-time detection of microplastics in seawater

With the rapid development of the global plastic industry, microplastic pollution has become an increasingly serious environmental concern. However, standardized technologies for convenient, accurate, and real-time microplastic detection are limited. To address this challenge, a microwave resonant sensor with a complete microplastic detection system equipped with a Bluetooth module for remote real-time monitoring of microplastic concentrations was developed. Microplastic concentrations were measured in deionized water containing polyvinyl chloride powder (particle size: 6.5 ± 1 μm), simulated artificial seawater, and real seawater samples. The integration of the microfluidic system mitigated the interference caused by the complex seawater matrix, thereby ensuring stable and reliable microwave-based detection of microplastic concentrations. The system demonstrated high repeatability for predicting the concentration of microplastics in seawater samples. The proposed method demonstrated a recognition rate of over 96% with a tolerance of ±0.01 mg/mL, while maintaining a minimum detection limit of 48.72 ng/mL. To improve the prediction accuracy, a convolutional neural network algorithm was employed to predict microplastic concentrations based on the test results, with the predicted and actual concentrations being highly consistent. Finally, a compact and portable seawater microplastic monitoring system was developed by integrating the microwave sensor with Bluetooth and embedded systems, enabling real-time microplastic concentration monitoring in marine environments.