The Limits to Bubble Capture Through High Permeability Membranes*

The ability to efficiently capture and transport bubbles can have an impact on an array of industries, such as biomanufacturing, electrochemical gas evolving systems, methane capture, and others. Hydrophobic membranes are a common tool used to capture unwanted bubbles. Here, rapid bubble capture on the order of tens of milliseconds is required as longer bubble capture times will lead to bottlenecks. In this work we seek out the mechanisms behind transport of bubbles through hydrophobic membranes of different permeabilities. For this, we designed and fabricated a silicon membrane platform. 

Through bubble evacuation experiments on our membrane platform, we have uncovered three different distinct regimes limiting the bubble evacuation through an aerophilic membrane. Through the use of scaling laws, we can predict the transition between these regimes. These results are then combined on a design map. This design map allows for prediction of the evacuation time of a bubble through a membrane, given a certain set of experimental conditions including radius, a set of viscosities, and a membrane permeability.

At the high end, bubble capture times under 1ms have been recorded for a 3.5mm diameter bubble. As far as the authors are aware, no faster time has been recorded in literature as of July 2023. This work elucidates the limiting factors behind bubble transport through a membrane. Our work can directly be used by anyone requiring bubble evacuation through a membrane driven by Laplace pressure, regardless of the properties of the medium, the bubble, the surface tension, or the membrane. Hence its results can be directly translated to applications where bubble capture is required.