Steerable Micro-Bots Are Ready to Explore

Humanoid robots are stealing most of the headlines with their acrobatics and ever-increasing sophistication, but they may not prove to be the most useful types of robots in the future. Replicating what we can do is very valuable, of course, but what about all of the things that we could never do? Imagine a robot that could crawl through a person’s veins to provide noninvasive medical treatments, or one that could slither through a jet engine to make sure it is ready for its next flight, for instance.

But despite the value that such a robot could provide, nothing capable of these tasks has been developed — at least nothing that would be practical for real-world use, anyway. These robots not only need to be tiny, but they also need to be agile and flexible. That combination of traits has proven to be too challenging to build into a robot using the technologies available today.

That may change in the near future, however. A group of engineers at the University of California, San Diego has created a novel robotic skin just a few millimeters in width that can slither through extremely tight spaces. The addition of a clever control mechanism allows this system to be steered, and it can make turns of more than 100 degrees to wiggle its way through even very complex structures.

The team used their artificial skin to create soft vine robots that can move and steer without rigid components. The robots grow by turning themselves inside out from the tip — similar to how a sock unrolls — allowing them to extend without dragging their bodies across surrounding surfaces. This unique form of movement minimizes friction and makes them ideal for navigating delicate environments such as arteries or fragile machinery.

Until now, however, steering these soft vine robots has been a major obstacle. Conventional designs could grow forward but had limited ability to bend or maneuver through winding paths. To overcome this, the team integrated a series of ultra-thin actuators made from liquid crystal elastomer (LCE) into the robot’s skin. These materials contract when heated, providing powerful yet flexible motion at a small scale.

Each LCE actuator is paired with a flexible heater that raises its temperature using a small electrical current. When one side of the robot’s body heats up and contracts, it bends in that direction. By embedding multiple pairs of heaters and actuators around the circumference and along the length of the robot, the researchers can steer it in multiple directions, achieving complex curvatures and turns.

The robot’s motion is controlled through a combination of internal air pressure and actuator temperature. Adjusting the pressure changes the robot’s stiffness; higher pressure keeps it straight and rigid, while lower pressure allows more bending. Meanwhile, controlling the actuator temperature fine-tunes the degree of curvature. The team found that combining both factors in a hybrid control scheme provided the best precision and responsiveness.

In laboratory tests, the researchers built vine robots between 3 and 7 millimeters in diameter and about 25 centimeters in length. Despite their small size, these robots could make sharp turns exceeding 100 degrees and squeeze through gaps half their own diameter. One robot even navigated a model of the human aorta and connecting arteries, demonstrating its potential for future medical procedures. Another explored the interior of a jet engine model, showing promise for use in industrial inspections where traditional tools cannot reach.

Future work will focus on miniaturizing the system even further and enabling remote or autonomous control. With these enhancements, these tiny, steerable vine robots could soon explore environments once thought virtually inaccessible.