Harvard roboticists have engineered a folding robot that can move without batteries. The origami robots, which are about the size of a quarter, could have biomedical applications. Imagine "robots that you could swallow and then … control their motions for diagnostic procedures, biopsies, drug delivery," says study author Robert Wood from Harvard University.

How it works: Wirelessly induced electrical currents are delivered to the robot's "muscles" — mechanical actuators — to activate them. The robot can change shape — including returning to its original configuration — when heated with electrical current because of the specialized metal alloy coils in its joints. The combination of the two features allows the researchers to fold and unfold the robots parts independent of each other, or together, creating complex movements. For example, this technology could get a ship in a bottle to move its sail without any connection.

What's new: The complexity of movement is what sets these robots apart, says Harvard's Mustafa Boyvat, another author on the study. "We can remotely select which folds to actuate and control the time to do that with ability to repeat." Existing designs typically require wires or electronics on board the robot, which can make them heavier and unsafe to swallow. Roboticists at MIT created an origami robot controlled by magnets but it can fold only once.

What's next: "Go smaller," says Boyvat, who plans to work with doctors on the next iterations of the robots. They're small, but not small enough to swallow yet, and there are, unsurprisingly, a host of concerns about ingesting machines.