The life cycle of individual boiling bubbles: Insights from beyond optical imaging

With a high-speed camera, we have investigated the dynamics of individual vapor bubbles boiling on a laser-heated surface.~ Their sizes and shapes as they grow and depart from a surface are correlated with simultaneous thermal imaging measurements of the boiling surface using thermoreflectance-based microscopy to measure temperatures of individual stochastic events.~ Analysis of both the thermal profiles and the bubble shapes suggests the presence of an evaporating liquid microlayer under the developing bubble.~ Tuning surface and heating properties, we control the shapes of bubbles, ranging from regular periodic growth and departure to stochastic bubbles which exhibit rapid cavitation-like expansion and collapse.~ Unlike typical cavitation bubbles which collapse and form jets pointed towards the surface, jets from bubbles observed during boiling were observed to be directed away from the surface.~ By tuning the wettability of the substrate, we will report on how wettability affects the strength and direction of these jets.