Used to test the chemicals released by chewing (apples, in this case), the mouth sounds like an easy enough body part to duplicated, but there were actually multiple complications. A chewing rotation had to be programmed to fill in the role of the tongue (lest saliva not spread properly and big apple chunks avoid mashing), and scientists had to adjust their measurement techniques to account for the fact that humans tend to swallow saliva without swallowing their food, which the robotic mouth cannot do at this time.

While the technology is promising for testing foods that might be considered harmless until chewed, we know that one day our pet robot will eat the last Entenmann's donut. And on that day, the war will begin. [ACS Publications via io9]

Is your breath kicking? [Coolest-Gadgets]