The oscillations of free-falling drops with size range from pl to μl have been used to measure the transient shear viscosity and the dynamic surface tension of shear-thinning fluids on the timescale of 10−5–10−2 s. The method is first validated with Newtonian fluids. For a given surface tension, the lower and upper limits for accurate measurement of the viscosity are determined as a function of drop size. The dynamic properties of two types of shear-thinning fluids with varying viscoelasticity are reported: aqueous suspensions of the antifungal drug griseofulvin and of the organic light-emitting diode material poly(3,4-ethylenedioxythiophene): polystyrene-sulphonate. In both cases, the free-falling drop retains the high-shear viscosity.
Determination of dynamic surface tension and viscosity of non-Newtonian fluids from drop oscillations
Current address: Department of Creative IT Engineering, Pohang University of Science and Technology, Pohang, South Korea.
Lisong Yang, Bethany K. Kazmierski, Stephen D. Hoath, Sungjune Jung, Wen-Kai Hsiao, Yiwei Wang, Arganthaël Berson, Oliver Harlen, Nik Kapur, Colin D. Bain; Determination of dynamic surface tension and viscosity of non-Newtonian fluids from drop oscillations. Physics of Fluids 1 November 2014; 26 (11): 113103. https://doi.org/10.1063/1.4901823
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