Host: The Japan Society of Vacuum and Surface Science
A laser spot on the FeSi2 thin film was used as a heat resistant and localized heat source with flexible size and power. The local heating of the degassed water led to the generation of a water vapor microbubble, which showed self-oscillation at 0.1-0.7 MHz under continuous heating. The bubble oscillation frequency showed the maximum value when the absorbed power density reaches 1 mW/μm2, regardless of the laser spot size. This value is close to the critical heat flux for highly subcooled boiling of water. Thus, the maximum bubble oscillation frequency indicates that there was the transition from nucleate boiling to local film boiling. The variation of the bubble oscillation frequency was studied by numerical analysis to investigate the bubble oscillation mechanism. Our results are useful for understanding and enhancing the flow generated around the water vapor bubble, and the design of microscale cooling devices.
