Evaporation-driven dewetting of a liquid film

We study the dynamics of evaporating ethanol films deposited by a receding liquid meniscus. The films are surrounded by pure vapor in a capillary heated above the saturation temperature. We observe the substrate dewetting with the dewetting ridge in spite of the complete wetting at equilibrium. The dewetting is caused by a high contact angle (similar to 30 degrees) induced by evaporation. The obtained values agree with a theory proposed earlier. The film shape ismeasured with both grid deflection technique and interferometry. The phenomenon is convenient to observe inside a capillary with an axial thermal gradient. When the capillary is closed at one end and open at another to a constant pressure reservoir, the meniscus oscillations are known to appear spontaneously. Such a system is the simplest version of an industrial device called a pulsating heat pipe. The effect is general and can be used in any system to control the wetting properties.