CAREER: Interrogating dense anisotropic colloidal suspensions with SMR-TIRM

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Nanometer to micrometer scale "colloidal" particles are found in consumer products, coatings, and nature. For example, paints, inks, and lubricants contain particles of this size that are designed to be well-dispersed in a liquid. However, particles may deposit or aggregate in ways that diminish performance. It is difficult to predict these unfavorable processes for particles that are non-spherical or have non-uniform surface chemistry. The principal investigator will develop and apply an experimental technique to reveal the physical and chemical forces controlling the deposition or aggregation of these complex particles. The results should transform our understanding of advanced coatings, multiphase materials, and biofilm adhesion. In addition, the PI will form teams of high school, undergraduate, and graduate students to explore the world of consumer products, textiles, cosmetics, and food through an experiential summer program. The program consists of laboratory and in-class experiences that will culminate in the development of a college-level course, teaching tools, and case studies to be disseminated throughout Ohio. This CAREER award integrates research and educational objectives to transform our understanding of how anisotropic colloidal particles interact with interfaces for the processing of coatings, production of multiphase materials, and understanding of synthetic and biological active colloids. The research objective of this work is to measure conservative and non-conservative surface interactions for dense suspensions of colloids with anisotropy in both shape and surface chemistry. The current bottleneck to completing this work is that existing surface interaction measurement techniques are either not suitable for such systems or are not sufficiently sensitive. The PI will develop a tool called Scattering Morphology Resolved Total Internal Reflection Microscopy (SMR-TIRM). SMR-TIRM works by utilizing fluctuations in the morphology of evanescent wave scattering from a colloidal particle, rather than the integrated intensity fluctuations. The PI will use SMR-TIRM to quantify the nature of symmetry breaking in driven colloids and the dependence of surface interactions on crowding of anisotropic particles near rigid and non-rigid interfaces. This research will provide crucial information for how anisotropic colloidal particles interact with surfaces. The education objective is to build an experiential program that integrates university activities with those at an on-campus STEM high school, which is part of the Cleveland Metropolitan School District. The theme of the program will be applications of Colloid and Interface Science in the design of chemical products. The program will consist of a college-level course in Chemical Product Design, a project based experiential learning program for high school students, and a research experience fostering multi-level project teams of high school students, undergraduates, and graduate students housed in the new shared Soft Materials Lab at Cleveland State University.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.