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Rinse and Repeat : Turning liquids into soft adhesives

Gerald Fuller Chemical Engineering, Stanford University

This paper describes “rinsing flows” wherein a jet of one fluid ablates a layer of a second, miscible liquid that coats a solid substrate. This process is common to everyday experience and to many industrial processes, particularly cleaning operations. This flow arrangement is accompanied by a classic, “hydraulic jump” phenomenon but the stratification of two liquids, with differing rheologies, leads to qualitatively new results. Of particular interest to one of the applications of this process (the cleaning of colloidal particles from solid, planar substrates) is the case when the liquid coating the substrate (the one being rinsed off) possesses a large elongational viscosity. Data are offered that demonstrate that fluids with large, strain thickening extensional viscosities very effectively “pluck” adsorbed colloidal particles from planar surfaces.