Monolithic 3D Printing Creates Gas-Powered Robots with Soft Actuators

Researchers at the Bioinspired Robotics Laboratory, University of California San Diego, have developed robots that can be printed from a single piece of material in a single pass. These robots can walk without electronics, powered only by a compressed gas cartridge.

The researchers used a desktop 3D printer and commercial printing supplies. Each robot costs around $20 to manufacture, making the design both affordable and durable.

“This is a completely different way of looking at building machines,” said Michael Tolley, a Professor and Study Senior Author at the UC San Diego Department of Mechanical and Aerospace Engineering.

These robots could be used in environments where electronics are not viable, such as space exploration, disaster relief, or scientific missions in radiation-heavy areas.

After laboratory testing, the researchers showed that the robots could operate continuously for up to three days when connected to a constant air or gas source. They also demonstrated that the robots could walk untethered outdoors across various terrains, including sand and turf, and could even operate underwater.

The objective was to create robots that could walk directly out of the printer, powered by soft, flexible materials and a compressed gas cartridge.

These robots are not manufactured with any of the traditional, rigid components researchers typically use.

Michael Tolley, Professor and Study Senior Author, Department of Mechanical and Aerospace Engineering, University of California San Diego

Instead, the robots are made from simple 3D-printing filaments.

The most challenging task was developing a design that would integrate both a control system and artificial muscles into a single print using the same soft material. To create an electronics-free gripper, the team, led by Postdoctoral Scholar Yichen Zhai in Tolley's research group at the UC San Diego Jacobs School of Engineering, modified a 3D printing method they had previously used. Their work led to the creation of a six-legged robot.

“We have taken a giant leap forward with a robot that walks entirely on its own,” Zhai said.

Like the mechanism that powers a locomotive's steam engine, the team developed a pneumatic oscillating circuit to control the repetitive motions of soft actuators to move the robots.

By alternating between two sets of three legs and applying air pressure at the appropriate times, the circuit regulates the movement of the six legs. This allows the robot to walk in a straight line, with its legs able to move in four directions: up, down, forward, and backward.

The next steps involve using recyclable or biodegradable materials and finding a way to store compressed gas inside the robots. Additionally, the researchers are exploring how to add manipulators like grippers to the robots.

Through their California Research Alliance (CARA), Tolley's lab collaborated with BASF to test various soft materials for use with standard 3D printers. While the robots were successfully printed using off-the-shelf materials, some of the high-end materials tested are not yet commercially available.

In collaboration with BASF and with funding from the National Science Foundation, the research team completed the 3D-printed walking robot in 2022, presenting it at the Gordon Research Conference on Robotics before its publication.

The robot developed by UC San Diego and BASF researchers takes a walk out of the lab. Video Credit: University of California, San Diego

Journal Reference:

Zhai, Y., et al. (2025) Monolithic Desktop Digital Fabrication of Autonomous Walking Robots. Advanced Intelligent Systems. doi.org/10.1002/aisy.202400876.