An advancement in soft robotics by Harvard-affiliated researchers allows these flexible robots to react faster than ever and jump more than a foot in the air.

The study’s critical innovation was the incorporation of an internal gas combustion engine for the robot’s motion, according to Adam A. Stokes, one of the authors of the study. Gas combustion, as opposed to previously used gas compression, enables motion at a much faster pace. Now soft robots jump within four milliseconds of initiation.

“Jumping is a side effect of exploring combustion as a propulsion and power source for soft robots,” said the study’s lead author Robert F. Shepherd, a former postdoctoral researcher at Harvard and now an assistant professor at Cornell.

The three-legged robots are made of compressible material, such as silicone, that can return to its shape. Each leg contains an internal chamber that wires inject with explosive gases. In an emailed statement to The Crimson, Stokes compared the technology to the “spark plug in a car engine.” Upon gas combustion, the volume of the robot changes, exerting a force against the ground and causing the jump.

This study, funded by the Defense Advanced Research Projects Agency, is the latest installment in the Whitesides Research Group’s work in soft robotics. In 2011, a team of researchers under George M. Whitesides ’60 first developed a robot to imitate the motion of a squid.

Made using 3D printers, soft robots are cheaper and more easily manufactured than hard robots. This lower price and ability to avoid obstacles will potentially make them more useful than hard robots for search and rescue missions, Shepherd said.

Still, despite the large potential for soft robots, Harvard research associate and study author Jabulani R. Barber said that scientists “aren’t trying to replace hard robots.”

Instead, Shepherd said that soft-robots have the ability to complement hard robots.

“Soft robots are important because they will eventually allow robots to be used in places where hard robots can’t, perhaps in internal surgery,” Shepherd said.

Current and future developments in soft robotics are focused on “trying out new materials and designs for crawling, jumping, gripping, color changing, and ‘looking’” Stokes wrote.