Microscale bubble evolution on microheater during microsecond-pulse heating process

Transient heating of liquids on a microheater surface is commonly encountered in thermal inkjet printing, laser medicinal treatment, and various microelectromechanical systems. Unlike the quasi-steady-state pool boiling, the physical process described above is usually accompanied by local soaring fluid temperatures and violent explosive boiling. Here, the subcooled pool boiling of water upon a platinum (Pt) thin-film microheater (1,000 × 1,000 μm) subjected to microsecond-pulse heating is investigated. For the cases at q_ave = 58.9, 68.8, and 79.4 MW m⁻², the temperature-response curves exhibit a single-peak mode, single peak-and-valley mode, and double-peak mode, respectively, which are strongly related to the formation and collapse of the vapor film. For the cases with higher initial liquid temperature, boiling incipience occurs earlier and is followed by a faster vapor film formation. As the heat flux increases, the sensitivity of boiling incipience and vapor film formation to the initial liquid temperature obviously decreases.