Portable surface acoustic wave sensor systems for microplastic detection in beverages

Abstract The escalating global plastic production (~ 390 million tons in 2022) and subsequent environmental release of microplastics necessitate urgent advancements in real-time detection technologies. While optical methods (Raman spectroscopy, FTIR) dominate current microplastic analysis, their reliance on bulky instrumentation limits field applications. This study presents a portable surface acoustic wave (SAW) sensor system for real-time microplastic detection in beverages. A biocompatible aluminum interdigital transducer (IDT) array (40 pairs, 30 μm gap) was fabricated on piezoelectric substrates (InGaN and PMN-PT), with SU-8 passivation selectively exposing sensing regions to minimize liquid-phase interference. Material characterization confirmed substrate crystallinity and composition, revealing InGaN’s superior sensitivity, estimated to be ~ 0.168 MHz/(mg/mL) than the PMN-PT-based device. The integrated system employs an InGaN-based oscillator circuit resonating at 39.06 MHz, enabling standalone operation without external signal generators. A threshold-driven LED interface (red/green for ≥ / < 0.25 mg) provides intuitive readouts, while universal printed circuit board (PCB) integration ensures portability. This work demonstrates a scalable platform for on-site microplastic monitoring, addressing critical gaps in consumer safety and environmental health.