DirectHop: a 1-gram robot that controls jump height with centimeter accuracy

# What DirectHop is DirectHop is a palm-sized hopping robot developed at the University of Washington. It weighs about 1 gram and can perform repeated hops, control how high it jumps with centimeter-level precision, and right itself after landing.

# How it moves Instead of the spring-and-latch mechanism used by many small hopping robots (modeled after fleas), DirectHop uses a tiny electric motor that directly accelerates the robot. The motor spools fishing line to pull the robot up a short tower, launching the body into the air. As the motor lifts, three hinged legs deploy to align the motor with the robot's foot and stabilize the takeoff.

Controlling jump height is done by varying the current to the motor. Adjusting motor current changes acceleration and thus the launch energy, allowing precise control over jump distance instead of an all-or-nothing spring release.

# Recovering and repeating hops DirectHop tends to tumble in the air, so the team added a roll cage to protect the body on impact. To recover, the robot sends the motor back down the tower, shifting the center of gravity and causing the robot to roll upright onto its foot. This self-righting maneuver succeeds about 90% of the time in the prototype, enabling multiple hops in sequence.

# Current capabilities and limits The prototype can clear a standard stair step and perform multiple sequential hops. It is tethered for power and lacks deliberate steering or precise orientation control. Righting is mechanical and relies on the motor-driven center-of-gravity shift plus passive geometry rather than active reorientation during flight.

# Planned improvements The research team is working on adding onboard power via a battery and solar cells, a vibration motor to allow controlled spinning for orientation, retractable feet to adjust hop angle, and onboard camera and electronics for navigation. Those additions aim to enable autonomous tasks like stair climbing where the robot measures a step, chooses a jump height, steers into position, jumps, self-rights, and repeats.

# Potential applications and cost model Hopping uses far less energy than flying, which makes small hopping robots attractive for distributed, low-cost deployments. The researchers suggest a fully featured DirectHop could be produced for about $10 per unit because components are small and inexpensive. With that cost structure, teams of many robots could be dispatched for tasks where losing some units is acceptable, such as environmental sensing, agricultural monitoring, infrastructure inspection, or planetary exploration.

# Why this matters DirectHop demonstrates a different approach to miniature hopping mobility: using a direct-drive motor for controllable launch energy and a simple mechanical sequence for recovery. That approach removes the complexity of tiny springs and latches and opens a path to affordable, repeating hopping robots that could complement flying drones or larger ground robots for certain field tasks.