The Limits to Bubble Capture through Porous Aerophilic Membranes

Hydrophobic membranes are a common tool used to capture unwanted bubbles in applications ranging from microfluidics to anti-foaming. In these, rapid bubble capture on the order of milliseconds is required as longer bubble capture times will lead to bottlenecks. For example, in microfluidics a larger channel would be required to capture sufficient gas fluxes ; while in the anti-foaming case, foaming will not be prevented if the sparging rate exceeds to bubble capture rate. Hence, in this work we seek out the mechanisms behind transport of a bubble in contact with a hydrophobic membrane. For this, we fabricated super-hydrophobic membranes with with variable dimensions. Through altering physical parameters of the membrane, we have identified three different limiting regimes of bubble capture through a membrane. With the use of scaling laws, we can predict the transition between regimes. At the high end, bubble capture times under 1ms have been recorded for a 3.5mm diameter bubble. This work elucidates the limiting factors behind bubble transport through a membrane, and its results can be translated to applications where bubble capture is required.