Effect of gold nanoparticles on the dynamics of gas bubbles.

The effect of gold nanoparticles on the formation of gas bubbles on top of a stainless steel tube is investigated in this work. Unlike other observations of bubble dynamics under evaporation or boiling conditions, which are caused by the surface modification due to particle sedimentation, this work reveals a unique phenomenon of enhanced pinning of the triple line and improved wetting by nanoparticles suspended in the liquid phase. Detailed characteristics related to bubble growth inside pure water and gold nanofluids, including the dynamics of the triple line, the variation of instantaneous contact angle, bubble height, and bubble volume expansion rate, are analyzed. The shape of the bubble is found to be in good agreement with predictions of the Young-Laplace equation by using experimental captured radius of contact line and bubble height as the two known inputs. The variation of surface tensions and the resultant force balance at the triple line are believed to be responsible for the modified dynamics of the triple line and subsequent bubble formation.