Effect of Nanoparticles on the Spreading of Bubble Triple Line on Top of a Stainless Steel Substrate Nozzle

The purpose of this study is to investigate the effect of gold nanofluid on the formation of gas bubbles on top of a stainless steel substrate plate nozzle. The experiment reveals a unique phenomenon of enhanced pinning of the triple line of gold nanofluids for bubbles forming on the substrate plate, i.e the gold nanoparticles are found to prevent the spreading of the triple line during the bubble formation. Different to the liquid droplet measurement, the bubble contact angle is found to be slightly larger for formation of bubbles inside gold nanofluids. It is also observed that bubbles develop earlier inside the nanofluids with reduced bubble departure volume and increased bubble formation frequency. The shape of the bubble is found to be in good agreement with predictions of the Laplace-Young equation under the low gas flow rates inside water. Such a good agreement is also observed for bubbles forming inside nanofluids except a few characteristic points. The variation of solid surface tensions and the resultant force balances at the triple line are believed to be responsible for the modified dynamics of the triple line inside gold nanofluids and subsequent bubble formation.