Xiaoxiao Xu

Boiling of dielectric liquids is limited by a trade-off between efficient nucleation and interfacial instabilities that trigger premature critical heat flux (CHF). In this Letter, we show that the dynamics of bubble coalescence and liquid-film drainage in HFE (Hydrofluoroether)-7100 can be tuned by coupling surface structuring with fluid composition. Micro-grooved surfaces enhance the heat transfer coefficient (HTC) by increasing nucleation-site density, but hydrodynamic instabilities restrict gains in CHF. Introducing a small fraction of high surface-tension lubricant alters interfacial stresses: the oil accumulates at the gas–liquid interface, generates Marangoni convection into thinning films, and suppresses coalescence. This stabilizes bubble dynamics, concentrates energy fluctuations at low frequencies, and delays CHF. When 1 wt. % oil is combined with 100 μm-pitch grooves, HTC is enhanced by 64.9% relative to a flat surface, while CHF is significantly extended. These results highlight the fundamental role of Marangoni-driven interfacial flows in retarding film rupture in boiling and demonstrate a hybrid pathway to overcome the HTC–CHF trade-off in dielectric boiling.