Due to the immense number of chemicals that may occur in drinking water, it is not practical to regularly quantify every contaminant of concern at every tap using standard methods for water analysis. A low cost method capable of rapid fingerprinting of a water sample as a whole and quickly documenting changes in water quality would be immensely valuable. Experiments were conducted to characterize the fingerprints left by various water samples that were dried under conditions that harness coffee ring effect. The coffee ring effect is capable of providing nano-scale separation of particles in concentric rings at the drop edge of a water sample, while soluble species deposit in intricate crystal patterns across the center of the residue. The unique residue patterns that were left by an array of water solutions were photographed, chemical maps collected, and the resulting fingerprints were analyzed using principal component analysis (PCA) of the image files and PCA on feature measurements within each fingerprint. Trends between water fingerprints and water chemistry were identified. The coffee ring effect and the nucleation and growth of crystals from dissolved salts in drying tap water samples are sensitive to miniscule changes in water chemistry; thus, the phenomena are ideal for tap water fingerprinting.

Imaging the coffee ring effect for tap water fingerprinting

2019 Fall National Meeting

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