A collaborative team from the Laboratory for Thermal Technology (LTT) and colleagues from KU Leuven (Belgium) has obtained novel insights into how surface tension influences the formation, growth, and detachment of vapor bubbles in the nucleate boiling regime. The results of this research have been published in the journal Applied Thermal Engineering (IF = 6.9).
Figure 1: (a,b) Artificial conical cavity and (c ) visualization of bubble nucleation and growth.
Efficient heat removal is paramount for modern high-power, miniaturized electronic devices, where conventional cooling methods often fall short, prompting the use of phase-change cooling. While nucleate boiling dramatically enhances heat transfer, the precise mechanisms governing individual bubble nucleation and departure remain elusive. Crucially, the isolated effect of surface tension at a single, well-defined nucleation site has never before been probed experimentally.
Previous experiments relied on arrays of cavities or varying fluid properties, making it impossible to decouple surface-tension effects from interactions between neighboring bubbles or other fluid parameters. As a result, predictions of bubble dynamics often diverged substantially from real-world observations.
By laser-texturing a single, high-aspect-ratio conical microcavity and systematically tuning water’s surface tension with trace surfactant, this collaboration delivers novel insights into the dual role of surface tension on bubble life cycles. Using femtosecond laser pulses, researchers engineered 100 μm-thick titanium foils with a narrow conical indentation, which was capable of nucleating single vapor bubbles under controlled heat flux conditions. Surface tension was systematically lowered using Dynol 800, leaving all other fluid properties unchanged. High-speed side-view video paired with infrared thermography tracked bubble growth rates, detachment diameters, and local surface temperatures across hundreds of cycles. The results reveal a non-monotonic dependence: a moderate decrease in surface tension accelerates bubble growth and reduces detachment size, but further reduction reverses these trends by altering thermal-boundary-layer dynamics.
These insights lay the groundwork for designing advanced boiling surfaces that precisely tune boiling behavior, potentially revolutionizing thermal management of high-power-density electronics.
Cover image created using AI.