Biomimetic “Lungs” for gas exchange in metal-air battery electrolytes.

Screen capture of 3d printed tree structure to show evaporation depositing dye in the “branches” of a biomimetic tree.

A recent article in Nature ( https://www.nature.com/articles/s41586-021-03603-2 ) explores creating lattice frameworks to transport liquids through micro-fluidic structures. Like plants, this allows for having fluids do things like cooling the structure, or transpiration-style evaporation. Supplemental video is available at https://www.youtube.com/watch?v=pdKn0UgcfXg

The scientists explored a number of ideas, including “selective flow” where structures could be metalized based on how the lattice was 3D printed, bio-reactors where air interface could assist in processing methane into other products, and cooling based on evaporation. The 3D printing allowed them to create many different configurations quickly, from mimicking a tree, to creating flow patterns in what appears to be a 3D lattice.

This gas/liquid interface structure is very similar to how a number of animals breathe, and immediately made me think that it could be applied to a circulated electrolyte system, almost an inverse of the tree shown. Let’s look at an example of iron salts that might mimic animal haemoglobin. “Spent” Fe2+ salts could be circulated into the cellular fluidic “lung” from one side, where it interacts with atmospheric oxygen to oxidize to Fe3+ salts. Using hydrophobic coatings on the intervening spaces would reinforce…