The robots handle the saliva with care. They group scores of tiny, rubber-capped test tubes into orderly racks and position them under plunging needles. An articulated arm moves some of them from one automated track to another, and all of them eventually get loaded into a small, box-shaped device whose sole job is to vigorously shake things. This separates patients' DNA from their spit. Everything that this huddle of roughly 200 robotic components is doing is about extracting valuable genetic signals from raw physiological noise.