The coffee ring effect can be observed in many particle suspension systems. This is where the constituents of a pinned sessile drop are deposited preferentially around the circumference of a stain left after the liquid has evaporated. This phenomena has been shown to be highly dependent on the initial particle concentration and contact angle of the suspension. The effect is also seen in the dried deposits of whole blood. As low red cell concentration is a symptom of some types of anaemia, drying blood samples on a range of surfaces and visually comparing the patterns formed is proposed to be a new rapid, low-cost diagnostic tool.<br/><br/>In the first part of this presentation the effect of the independent variables affecting coffee ring formation with blood is demonstrated experimentally. In the second, a fluid mechanics model of the process is presented.<br/><br/>During blood drop drying, two phases are present: a central fluid region and a deformable porous outer region where the particles (red blood cells) have consolidated. As drying continues this inner region shrinks and the outer region grows. A numerical model was developed to predict the evolution and final height profile in thin droplets containing flexible particles. The model is based on coupling lubrication theory assuming infinite vertical diffusion in the centre region, with a Darcy’s law continuum model in the outer region.

Modelling patterns in dried blood drops for diagnostics

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.