Just some advice from what i've learned (not a total solution as i'm sure there's other ways). Basically i got this from using the Melatonin Nanobot Artifacts crafted in the emporium. The Mk I nanobots give 25% health back at the end of each turn and the Mk II give 50% health at the end of each turn. I equipped them in the barracks on all 3 fighters every time they ran out. The achievement popped whilst i was equipping in the barracks and not whilst fighting. Other things may or may not work, but all i ever use is the Mk II Melatonin Nanobot Artifacts which last 3 turns and thus i always saved my crafting materials for this. Like everything else they're not always available to craft so craft lots when you can. Nanotech Fiber is the only hard to come by ingredient.