Effect of Operating Conditions on the Sessile Drop Oscillation of PEO Solutions in the Capillary Thinning Process

In this study, we investigate the sessile drop oscillation of aqueous PEO solutions after the transition from visco-capillary to elasto-capillary regime in the capillary thinning process of low-viscosity elastic fluids. Among various factors that affect oscillation, we focus on the effect of operating conditions that induce capillary thinning. The lifting velocity to lift the upper plate and the plate diameter to load the sample are selectively controlled. The generated oscillation is quantitatively analyzed in terms of oscillation frequency and decay ratio. The oscillation frequency and oscillation decay ratio are found to be independent of the lifting velocity. The oscillation frequency of all samples is about 140 Hz independent of the lifting velocity, and the decay ratio is not affected by the lifting velocity. On the contrary, the plate diameter affects the oscillation. The oscillation frequency increases to 210 Hz and the decay ratio shows a larger value (close to one) when a smaller plate is used. This study opens a way to improve the measurement of extensional properties which suffers from oscillation.