Stability of the Interface Between Two Immiscible Liquids in a Model Eye Subject to Saccadic Motion.

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Wang, Ru 
Tsai, Jheng-Han 
Snead, Martin P 
Alexander, Philip 
Wilson, D Ian 

The interface between silicone oil and saline layers in a three-dimensional model of the eye chamber was studied under different eye-like saccadic motions in order to determine the stability of the interface and propensity for emulsification in the bulk. The effect of level of fill, saccade amplitude, angular velocity, latency time, and orientation were investigated experimentally in spherical flasks with internal diameters 10, 28, and 40 mm, as well as a 28 mm diameter flask with an indent replicating the lens or the presence of a buckle. The deformation of the interface was quantified in terms of the change in its length in two-dimensional images. The deformation increased with Weber number, We, and was roughly proportional to We for We > 1. The presence of the lens gave rise to higher deformation near this feature. In all cases emulsification was not observed in either bulk fluid. The velocity profile in the spherical configuration was mapped using particle imaging velocimetry and is compared with an analytical solution and a short computational fluid dynamics simulation study. These confirm that the saccadic motion induces flow near the wall in the saline layer and significantly further into the chamber in the silicone oil. Surfactants soluble in the aqueous and oil phases reduced the interfacial tension, increasing deformation but did not lead to emulsification in the bulk.

emulsion, eye, interface stability, saccadic motion, two-phase flow, vitreous chamber, Hydrodynamics, Rheology, Saccades, Silicone Oils, Surface Tension
Journal Title
J Biomech Eng
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ASME International
W.D. Armstrong Fund, University of Cambridge, PhD scholarship, R. Wang Cambridge Taiwan Trust, PhD scholarship, J.-H. Tsai
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