While there are many useful questions to ask when encountering a new robot, “can I eat it” is generally not one of them. I say ‘generally,’ because edible robots are actually a thing—and not just edible in the sense that you can technically swallow them and suffer both the benefits and consequences, but ingestible, where you can take a big bite out of the robot, chew it up, and swallow it.
Yum.
But so far these ingestible robots have included a very please-don’t-ingest-this asterisk: the motor and battery, which are definitely toxic and probably don’t taste all that good. The problem has been that soft, ingestible actuators run on gas pressure, requiring pumps and valves to function, neither of which are easy to make without plastic and metal. But in a new paper, researchers from Dario Floreano’s Laboratory of Intelligent Systems at EPFL in Switzerland have demonstrated ingestible versions of both of batteries and actuators, resulting in what is, as far as I know, the first entirely ingestible robot capable of controlled actuation.
EPFL
Let’s start with the battery on this lil’ guy. In a broad sense, a battery is just a system for storing and releasing energy. In the case of this particular robot, the battery is made of gelatin and wax. It stores chemical energy in chambers containing liquid citric acid and baking soda, both of which you can safely eat. The citric acid is kept separate from the baking soda by a membrane, and enough pressure on the chamber containing the acid will puncture that membrane, allowing the acid to slowly drip onto the baking soda. This activates the battery and begins to generate CO 2 gas, along with sodium citrate (common in all kinds of foods, from cheese to sour candy) as a byproduct.
EPFL
The CO2 gas travels through gelatin tubing into the actuator, which is of a fairly common soft robotic design that uses interconnected gas chambers on top of a slightly stiffer base that bends when pressurized. Pressurizing the actuator gets you one single actuation, but to make the actuator wiggle (wiggling being an absolutely necessary skill for any robot), the gas has to be cyclically released. The key to doing this is the other major innovation here: an ingestible valve.
EPFL
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