We talked several months ago about the 3D fractal patterns in the vertebrate *lung* which enables *incoming blood*, *outgoing blood* and air to interact. The problem with lungs is that they have to expand and contract to bring in new air and expel old air. So perhaps we need *four* interacting fractals: * incoming fluid (blood ?) * outgoing fluid (blood ?) * incoming gas (air/oxygen ?) * outgoing gas (air/CO2/whatever ?) So here's the problem: Is there a * fractal pattern that is * 3D printable * that can be made out of a 3D printable material (plastic, metal) * that can be built out of small number of 3D "tiles" (or whatever they're called in 3D) * that can be put together (perhaps with glue) * With an input plenum for air, an output plenum for air, an input plenum for fluid, an output plenum for fluid The idea is to bring the air & fluid together in microscopic lowest level fractal "tubing" (probably not circular, but perhaps) where the gas & fluid can "react". An artificial lung might be one application, but there's lots of applications where gasses & liquids need to come into intimate contact.