Abstract
Understanding the process of bubble detachment and motion along microchannel walls, driven by liquid flow, is crucial for elucidating bubble dynamics and realizing diverse applications within the realm of microfluidics. This paper uses the phase-field method to perform a comprehensive numerical study on the conversion of surface gas bubbles into bulk bubbles at the lower wall of a microfluidic channel. The study identifies several key factors that have a coupled impact on the 'surface-bulk' conversion, including wall wettability, Reynolds number, and the initial contact angle/volume of the surface bubbles (with contact angle and volume positively correlated at a fixed base radius). Specifically, higher Reynolds numbers, smaller initial bubble contact angles, and more hydrophilic channel walls facilitate the detachment of surface bubbles from the channel wall. However, at high Reynolds numbers, bubbles on superhydrophilic surfaces may be split, causing fluctuations or longer conversion time. Conversely, as wall hydrophobicity increases, surface bubbles remain attached.