Experimental study of the detachment behavior of bubbles of different sizes from a hydrophobic surface immersed in a liquid pool using direct current electrowetting actuation

The unexpected presence of microbubbles in microfluidic systems typically results in performance degradation owing to their ability to obstruct fluidic pathways, causing pressure fluctuations or shear force variations. To develop or enhance undesired bubble-removal strategies, a solid understanding of the fundamental physics governing the bubble-removal processes is essential. In this context, the present study aims to thoroughly investigate the detachment dynamics of different-sized bubbles, ranging in volume from 3 to 75 μL, from a hydrophobic surface fully submerged in a liquid pool while being subjected to direct current electrowetting (DC EW) actuation. From systematic experimental data on the temporal variations in the base radius of retracting bubbles of different volumes subjected to varying DC EW actuations, empirical relationships between detachment process characteristics (e.g., threshold voltage for bubble detachment and detaching time) and physical factors (e.g., bubble volume and applied voltage) can be determined. These relationships are compared with predictions derived from scaling analysis. The findings will provide valuable insight into the elimination of unwanted bubbles in microfluidic systems for biomedical applications and the rapid removal of bubbles to improve heat transfer rates in pool boiling for thermal management applications, including heat exchangers and cooling systems.