Fingering Flow Pattern of a Liquid Film on a Rotating Substrate.

Togashi, Shigenori; Ohta, Takashi; Azuma, Hitoshi

doi:10.1252/jcej.34.1402

Cited by 4 publications

(3 citation statements)

References 11 publications

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“…The growth of the compactness ratio changed in three ways as a result of a higher rotation rate and lower flow rate. First, the critical radius decreased, consistent with the quantitative relationship presented by Togashi et al 22 Second, the rate of growth of the compactness ratio after the critical radius was reached increased. Third, the previous two concurrent effects resulted in a higher peak compactness ratio.…”

Section: Evolution Of the Compactness Ratiosupporting

confidence: 87%

“…As centrifugal force increases, rivulets form earlier, as observed in both this study and previous studies. 12,13,22 As a result, rivulets begin to grow earlier as well. Additionally, the increase in the gradient of the centrifugal force with radius causes rivulets to extend beyond the lagging edge of the spreading front more quickly at higher rotation rates.…”

Section: Comparing the Effects Of Rotation Rate Flow Rate And Surfamentioning

confidence: 99%

“…Togashi et al showed that during the spreading of aqueous glycerol solutions supplied by an impinging jet, the critical radius at which rivulets emerged increased roughly as the flow rate to the one-third power. 22 Others considered the case of an impinging jet that dispensed a fixed volume of liquid at a constant rate. They found that spreading is initially dominated by the impinging jet, but later resembles droplet spreading.…”

Section: Introductionmentioning

confidence: 99%

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Evolution of rivulets during spreading of an impinging water jet on a rotating, precoated substrate

et al. 2019

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The spreading of a liquid film across a rotating surface is inherently unstable due to the centrifugal force, which causes the formation of rivulets along the spreading front. This instability produces a rich diversity of spreading patterns and is important to control for the optimization of spin-coating and spin-rinsing of silicon wafers during the fabrication of microelectronics. The present work is an experimental investigation of the evolution of rivulets arising from this instability during the spreading of an impinging water jet across a rotating substrate that is precoated with a thin, aqueous film. To characterize these rivulets, we developed a high-speed imaging apparatus and image-processing software that traces the spreading front over time. We show how the morphology of the spreading front is qualitatively affected by varying the Reynolds number of the impinging jet, the ratio of centrifugal to Coriolis forces, and the type of liquid used to precoat the substrate. For quantitative analysis of rivulets, we measured the "compactness ratio" of the spreading front, which quantifies deviation from a circular spreading front. We used the compactness ratio to demonstrate that rivulets are suppressed most strongly at low rotation rates, at high flow rates, and on substrates precoated with water, although with notable exceptions.

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Section: Evolution Of the Compactness Ratiosupporting

confidence: 87%

Section: Comparing the Effects Of Rotation Rate Flow Rate And Surfamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evolution of rivulets during spreading of an impinging water jet on a rotating, precoated substrate

et al. 2019

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Spreading and fingering in a yield-stress fluid during spin coating

2009

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International audienceWe study the deformation, spreading, and fingering of small droplets of a yield-stress fluid subjected to a centrifugal force on a rotating substrate. At low rotation rates and for small enough droplets, the droplets deform elastically but retain their essentially circular contact line. For large enough droplet volumes and rotation speeds, however, one or more fingers eventually form and grow at the edge of the drop. This fingering is qualitatively different from the contact line instability observed in other fluids, and appears to be a localized phenomenon that occurs when the stress at some point on the perimeter of the drop exceeds the yield stress

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Spreading and fingering in spin coating

et al. 2007

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We study the spreading and fingering of drops of silicone oil on a rotating substrate for a range of rotation speeds and drop volumes. The spreading of the drop prior to the onset of fingering is found to follow the theoretically predicted time dependence, but with a large shift in time scale. For the full range of experimental parameters studied, the contact line becomes unstable and fingers develop when the radius of the drop becomes sufficiently large. We study the growth of perturbations around the perimeter of the drop and find the growth rate of the most unstable mode to agree well with the predictions of lubrication theory. The number of fingers which form around the perimeter of the drop is found to be a function of both rotation speed and drop volume, and is also in excellent agreement with theoretical predictions.

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Fingering Flow Pattern of a Liquid Film on a Rotating Substrate.

Cited by 4 publications

References 11 publications

Evolution of rivulets during spreading of an impinging water jet on a rotating, precoated substrate

Evolution of rivulets during spreading of an impinging water jet on a rotating, precoated substrate

Spreading and fingering in a yield-stress fluid during spin coating

Spreading and fingering in spin coating

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