Understanding how the rheological behavior of biological fluids is related to health

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PI: Schultz, WilliamProposal Number: 1604903This proposal is based upon the hypothesis that health is reflected by changes in biological fluids, most important and accessible of which is saliva, and these changes affect the rheological properties of biofluids. This hypothesis further stipulates that rheological characterization of saliva, and quantification of its properties, can provide information about a person's health. Saliva rheology is similar to that of water, making measuring non-Newtonian properties difficult. Capillary Break-up Rheometry (CBR) is commonly used to determine extensional parameters of such fluids. It is proposed to re-examine CBR foundations with differential one-dimensional models to eliminate the large correction factors required when measuring the radius-thinning rate at the filament midpoint. Unlike previous methods, new analysis recognizes curvature gradients that drive the flow and therefore the free surface profile evolution is required to accurately determine extensional properties. This analysis is consistent with filament evolution all the way through beads-on-a-string formation that they have been observed in Newtonian and preliminary saliva demonstrations. Next the spatially-varying surface tension in Newtonian analysis is used to study the role of surfactants in filament dynamics as well as the more prominent extensional viscoelastic properties of long-chained molecules (such as mucins) or by surfactants (such as in soap films) that could be interpreted as stickiness. Unlike saliva viscoelasticity, the role of surface activity in saliva filament formation and its implications on health diagnosis have not yet been considered. Characterizing saliva rheological properties could guide the development of more effective saliva substitutes, stimulants, and hydrating liquids for xerostomia or dysphagia. The co-PIs will collaborate with U. Ghana Biomedical Engineering Department to study dysphagia problems prevalent in local populations. Techniques developed through this project can help to characterize other biological and industrial fluids. There are also plans to engage in activities to promote women in engineering including educational outreach to over 200 4th through 6th grade girls through the University of Michigan FEMMES program and involving undergraduate women in research.