Francois Audouy did some preliminary work on the AmnioTank, but as seemed often to be the case on Avatar I was brought in to detail and finish. All elaboration was based on the functional requirements of the tank as it nourished and protected the growing avatar bodies on their interstellar voyage. A lot of research into med tech had already been done in the art department and I supplemented this with my own, esp. relating to hyperbaric chambers, dialysis systems, chassis for heavy equipment, etc.. More info in this io9 article.