DirectHop: a one-gram robot that uses a motor to control precise hops

DirectHop is a prototype hopping robot developed at the University of Washington. It weighs about one gram, fits in the palm of a hand, and demonstrates a different approach to small‑scale mobility by using a direct electric motor to control jumping rather than passive elastic elements like springs.

DirectHop launches itself using three folding legs driven by a tiny electric motor. The motor sets the launch parameters so the robot can choose a target jump height with single‑centimeter accuracy. After landing, the robot can twitch to right itself and prepare for another jump, allowing repeated hops without external intervention.

• Mass: approximately 1 gram.
• Actuation: a tiny electric motor drives three folding legs.
• Jump control: the robot can set jump height with roughly centimeter precision.
• Mobility: it can clear a standard stair step and perform multiple sequential hops.
• Recovery: after landing, DirectHop can twitch to right itself and ready for the next jump.

Hopping is an efficient way to cover uneven terrain for small machines. The reporting around DirectHop notes that hopping can be nearly two orders of magnitude more energy‑efficient than sustaining flight. For centimeter‑scale and gram‑scale robots, those energy savings matter: batteries and power budgets are extremely limited, and simpler mechanical designs can reduce overall system complexity.

DirectHop's capabilities suggest specific niches where tiny hoppers could be preferable to small drones or wheeled robots:

• Interior inspection in cluttered or confined spaces where rotors are unsafe or impractical.
• Distributed sensing where many inexpensive, energy‑efficient agents survey an area rather than a single flying robot.
• Agricultural or industrial monitoring tasks that need brief hops to traverse obstacles or steps.
• Planetary or remote exploration concepts where many low‑mass, low‑power devices could complement larger rover systems.

Next steps and practical constraints

DirectHop demonstrates that active motor control can replace passive springs for precise, repeatable hopping at the gram scale. Its centimeter‑level jump control, self‑righting recovery, and ability to clear typical step heights point to practical research directions for low‑mass, energy‑efficient mobile robots that operate where flying systems are costly or unsafe.