Little pockets of gas create aerophilic surfaces

In many industrial processes, materials need to avoid full contact with a liquid. Maintaining gas on the material’s surface while submerged in a fluid can be difficult because the gas can be absorbed by its surroundings.

Certain engineered materials can bypass this and maintain a thin layer of gas, making them aerophilic. Expanding the scope of these materials, Nemir et al. developed microscale-textured surfaces that can act aerophilic when the pockets between the textured structures are continuously replenished with gas.

They demonstrated that continuous replenishment allows the gas to remain pinned to the textured surface and, in cases where the surrounding liquid absorbs the gas, prevents it from running out. The gas flow rate must be tuned so the pockets are oriented convex-out, which ensures they are thermodynamically stable.

“When the aerophilic surface is replenished at an optimal flow rate, the gas-liquid interface remains pinned in this convex-out state,” said author Sami Khan. “Without replenishment, the surrounding fluid gradually dissolves the trapped gas, causing the liquid to flood the cavities, thus requiring substantially more energy to displace the liquid and restore the aerophilic state.”

Though the group’s tests used carbon dioxide, their approach works with any gas-liquid combination. In practical applications, this could work through a mechanism that directly distributes the gas into the material.

“This concept can be extended to other applications, such as electrochemical carbon dioxide conversion and aeration systems in the food industry, by adjusting the gas-liquid combination, flow rate, and aerophilic surface geometry accordingly,” said Khan. “In each case, the replenishment ensures that the gas-liquid interface is always maintained, allowing the system to operate efficiently over long durations without the mass-transfer limitations seen in conventional gas-liquid headspace configurations.”

Source: “Mass transfer enhancement in continually replenished aerophilic surfaces,” by Omar Nemir, Rawad Refai, Ralph Rodrigues, Campbell Tiffin, Natasia Fisher, Lorenzo Yao-Bate, and Sami Khan, Applied Physics Letters (2025). The article can be accessed at https://doi.org/10.1063/5.0283693 .