Technology

Nile Red staining uses a fluorescent dye that binds to hydrophobic materials, causing microplastics to glow under specific lighting. Although effective in controlled lab settings, it requires chemical reagents, multi‑step preparation, filtration, drying, and fluorescence microscopy. Organic matter like algae and oils also fluoresce, creating false positives. The method is slow, messy, and impossible to automate into a compact device, which makes it unsuitable for rapid or community‑based environmental monitoring.

FTIR spectroscopy identifies microplastics by measuring how particles absorb infrared light, producing a chemical “fingerprint” for each polymer. While highly accurate, FTIR instruments are large, expensive, and extremely sensitive to humidity, vibration, and sample contamination. They require clean, dry, isolated particles placed on specialized substrates, meaning they cannot analyze microplastics directly in water. These limitations prevent FTIR from being used in real‑time or field‑deployable sensing systems.

LDIR uses a quantum cascade laser to rapidly scan filtered samples and automatically identify microplastics by size and polymer type. It is faster and more automated than traditional FTIR, but it still depends on pristine, lab‑prepared samples and delicate optical components. LDIR systems cost hundreds of thousands of dollars, require stable environmental conditions, and cannot operate in wet or flowing water environments. Their size, power demands, and maintenance needs make them impractical for widespread monitoring or portable detection.