As our skies increasingly crowd with buzzing, hovering, flitting drones, spare a thought for the humble hopping robot.
Hopping, a popular form of locomotion in the insect and amphibian worlds, is nearly two orders of magnitude more energy-efficient than flying. Unlike a mosquito that must constantly expend energy to stay aloft, a flea only works out when it jumps. Those cost savings could also pay off in the world of robotics: A group of small, simple hopping robots could explore a location much more cheaply than flying drones. These robots could find gas leaks in an oil refinery, monitor water and fertilizer usage on a farm, or even explore other planets.
With this in mind, engineers at the University of Washington have created DirectHop, a roughly 1-gram robot that can perform multiple hops in sequence and jump high enough to clear a standard stair step. The robot uses a tiny electric motor and three folding legs to launch itself to a specified jump height with single centimeter accuracy. After it lands, DirectHop can twitch to right itself and then ready for another jump.
The prototype, which fits in the palm of a hand, represents multiple steps on the path to an autonomous hopping robot that can traverse a variety of environments.
“In my mind, the three hardest challenges for hopping robots are the ability to vary jump length, self-right and reload for multiple hops,” said senior author Sawyer Fuller , a UW associate professor of mechanical engineering. “DirectHop clears all three of those hurdles with a totally new design, and we’re well on our way to tackling other challenges like onboard power, steering and navigation.”
Fuller and his team will present DirectHop on Sept 30th at the International Conference on Intelligent Robots and Systems. The paper is available here .
Most hopping robots are modeled after insects like fleas that are literally spring-loaded. Fleas compress and then release parts of their exoskeletons to launch themselves to distances 50 times their own height . Robots that utilize springs and latches à la fleas can also travel impressive distances, but they have no easy way to calibrate jump distance — discharging a spring is an “all or nothing” action, said Fuller. What’s more, springs and latches are complex bits of machinery that are difficult to build and operate at small scales.
DirectHop’s solution to those problems is ditching the spring entirely.
“We found that a very small electric motor can accelerate fast enough to power a jump directly, the way a frog’s leg muscles directly power its hop,” said lead author Hanquan (John) Wang , a UW graduate research assistant in mechanical engineering. “We also discovered that by adjusting the current going to the motor, we could make the robot jump specific distances.”
The robot itself consists of a tiny electric motor attached to a tower by a length of fishing line. When the motor accelerates, it spools the line quickly and hoists itself up the tower, pulling the rest of the robot into the air. As the motor rises, three hinged legs extend to keep the motor aligned with the robot’s foot.
Since the robot tends to tumble in the air, the researchers included a roll cage to support it when it lands on its side. From there, the team was able to right it 90% of the time by sending the motor back down the tower, which shifts the robot’s center of gravity and causes it to roll back onto its foot, readying it for another jump.
The design was inspired by box turtles, which can roll themselves upright using a similarly-shaped shell.
The current prototype has some notable limitations. Power is supplied via wires, and it has no way to steer or orient itself beyond random twitching. Wang and Fuller, however, are working on solutions: onboard solar cells and a battery for power, a vibration motor to spin the robot in place, tiny retractable feet to adjust hop angle, and an onboard camera and electronics to navigate.
“One of our goals is fully autonomous stair climbing,” Fuller said. “A camera looks at the stair, the processor figures out how high the robot has to jump, it steers itself into position, jumps, self-rights, steers again and repeats. It uses a combination of simple sensors and actions to perform a complex task.”
Wang thinks it’s reasonable to imagine producing a fully featured DirectHop bot for about $10 since the individual components are so small and cheap. At that price, the bots could be extremely useful as a semidisposable complement to larger, more capable, more expensive robots.
“We could dispatch 100 or even 1,000 of these robots into the field,” Wang said. “If some are lost or disabled, it’s not really a failure. The team of them can complete the task.”
Yash Talwekar, a UW research assistant in mechanical engineering, is a co-author.
This research was funded by the National Science Foundation.
For more information, contact Fuller at minster@uw.edu or Wang at hw328@uw.edu .
DirectHop: A Direct-Drive Insect-Sized Robot that can Control Jump Height and Self-Right
30-Sep-2026