Effect of Surface Wettability on Fast Transient Microboiling Behavior
O C. Thomas, Richard E. Cavicchi, Michael J. Tarlov
Microboiling events associated with the fast transient heating of a micrometer-scale metallic thin film heater immersed in water have been studied. The effect of surface properties on the microboiling transients was examined by modifying heater surfaces with hydrophobic and hydrophilic alkanethiol self-assembled monolayers (SAMs). The microheaters are thin films of platinum or gold-plated platinum that are approximately tens of micrometers in width and hundreds in length. The micro-heaters are immersed in water and rapidly heated with short (108 K/sec), superheating occurs and nucleation temperatures as high as 296 C have been measured in water. The surface of gold-plated heaters were coated with a series of hydrophilic [HO(CH2)6SH, HO(CH2)11SH, HO(CH2)16SH] and hydrophobic [CH3(CH2)7SH, CH3(CH2)11SH, and CH3(CH2)15SH] SAMs. Dramatic differences are observed in the temperature-time transients of hydrophilic versus hydrophobic SAM-coated microheaters. Microheaters modified with hydrophobic SAMs exhibit lower boiling nucleation temperatures, more pronounced inflection points, and higher average temperatures during microboiling. These differences can be rationalized by considering simple models of surface wetting and surface vapor bubble formation. The evolution of temperature vs. time waveforms with successive pulses indicates that the monolayers remain significantly intact on the heater surface even after a schedule of 1000 heating events.
, Cavicchi, R.
and Tarlov, M.
Effect of Surface Wettability on Fast Transient Microboiling Behavior, Langmuir, [online], https://doi.org/10.1021/La030147e
(Accessed December 11, 2023)