Researchers at the Massachusetts Institute of Technology (MIT), U.S., have built an ingestible sensor equipped with genetically engineered bacteria that can diagnose bleeding in the stomach or other gastrointestinal problems. This “bacteria-on-a-chip” approach combines sensors made from living cells with ultra-low-power electronics that convert the bacterial response into a wireless signal. In turn, this can be read by a smartphone. To make these bacteria more useful for real-world applications, the MIT team decided to combine them with an electronic chip that could translate the bacterial response into a wireless signal. The researchers tested the ingestible sensor in pigs and showed that it could correctly determine whether any blood was present in the stomach.