Specifically, the EPFL team has developed a gelatinous actuator, the component of robots that make them move. And rather than rely on a mechanical motor or external power source, these actuators use liquids and air that react to chemicals. Each segmented actuator is roughly 4 cm in length and, as you can see in the image above, curl to one side when activated. This allows a single actuator to crawl -- inchworm-style -- through the digestive tract or, working in tandem, create a crude gripper. These actuators can also be paired with small digestible batteries, cameras and sensor equipment, all of which is already available, to create a truly edible robot.
The gelatin actuator is still in the early stages of its development and won't be getting swallowed anytime soon. However, the EPFL team is working with chefs from the École hôtelière de Lausanne to develop different edible substances which can be roboticized.