Subgram Hopper
An insect-scale continuous hopping robot powered by soft actuators

Passive leg

The robot features a passive, spring-loaded leg that stores energy during ground contact. With an efficiency exceeding 84%, the leg significantly reduces power for locomotion.

Continuous hopping

Continuous hopping—where energy is stored and reused for the next jump—is a rare phenomenon in nature and has now been demonstrated for the first time in sub-gram robots.

Overcome obstacle

The robot can accurately follow a predefined trajectory and reach lateral speeds of up to 30 cm/s. It can also dynamically adjust its jump height to leap over tall obstacles.

Less power & more payload

The hopper reduces power consumption by 64% and supports a payload 10 times greater than flying, opening up possibilities for onboard batteries, power electronics, and sensors.

Multi-terrains adaptability

The mechanical design enables the hopper to traverse a wide range of terrains—including soil, ice, wood, grass, glass, and even wet glass—without changing its control parameters. On slippery surfaces like wet glass, the robot only needs to reduce its landing angle. Thanks to its high-frequency jumping—reaching up to 8.4 Hz in this study—it can maintain high speeds even on challenging terrain.

Inclined surface hopping

As long as the robot's leg maintains traction, it can hop across inclined surfaces—even when the surface is rotating.

Agile maneuver

Thanks to its reduced moment of inertia, the hopper is capable of performing a somersault between two consecutive jumps.

Unconventional terrain

The hopper’s ultra-lightweight design enables it to effortlessly jump onto a floating lotus on the water’s surface—something that is especially challenging for larger, heavier robots at the gram or kilogram scale.

Collaboration across scales

The jumper's small weight allows it to hop onto another flying robot without significantly disrupting its stability. This opens the door for cross-platform collaboration between heterogeneous robotic systems.

Lightweight controller for fast and power-efficient hopping

The controller for this jumper uses an empirical mapping between the landing angle and takeoff velocity. This approach keeps the control system lightweight and paves the way for future onboard implementation. To maximize efficiency, the robot activates thrust only during a brief “powered ascent” phase. For the rest of the motion, it passively follows a ballistic trajectory—either in free fall or ascent—making the system extremely power efficient.

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Subgram HopperAn insect-scale continuous hopping robot powered by soft actuators