Microplastics are a rapidly emerging contaminant in water sources. California is in the process of standardizing testing methods for monitoring microplastics in drinking water (Bill SB1422-Safe Drinking Water Act). Existing technologies require filtration, tinting of the plastics via fluorescent dye, and manual examination under an FTIR or Raman spectrometer, and cannot accurately measure particles under 50 um. 

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In contrast to traditional bright field and dark field microscopes, NEREID uses a 532 nm laser to illuminate solid particles in the water. A digital microscope records videos of illuminated particles, and an image processing algorithm in Python analyzes particle characteristics, including particle size and count distributions. NEREID can measure the shape and size of particles bigger than 10 um and detect particles as small as 5 nm in under 10 seconds. 

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To distinguish microplastics from other debris in water, a 405 nm UV laser is used with a series of color filter lenses to study particle fluorescence emissions. Different solid particle contaminants may be characterized via this optical method. Further testing using a spectrometer is needed to distinguish microplastics from other debris. 

NEREID is integrated with the Raspberry Pi to bring the cost to under $60. This optical solution is useful for environmental, medical, and consumer applications.