A viscous switch for liquid-liquid dewetting

Edwards, Andrew M., Ledesma Aguilar, Rodrigo, Newton, Michael I., Brown, C. V. and McHale, Glen (2020) A viscous switch for liquid-liquid dewetting. Communications Physics, 3 (1). p. 21. ISSN 2399-3650

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Abstract

The spontaneous dewetting of a liquid film from a solid surface occurs in many important processes, such as printing and microscale patterning. Experience suggests that dewetting occurs faster on surfaces of higher film repellency. Here we show how, unexpectedly, a surrounding viscous phase can switch the overall dewetting speed so that films retract slower with increasing surface repellency. We present experiments and a hydrodynamic theory covering five decades of the viscosity ratio between the film and surrounding phase. The timescale of dewetting is controlled by the geometry of the liquid-liquid interface close to the contact line and the viscosity ratio. At small viscosity ratio, dewetting is slower on low film-repellency surfaces due to a high dissipation at the edge of the receding film. This situation is reversed at high viscosity ratios, leading to aslower dewetting on high film-repellency surfaces due to the increased dissipation of the advancing surrounding phase.

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