Researchers build a crawling biohybrid robot

Combining the tissues from a sea slug with a flexible 3D printed body, researchers at Case Western Reserve University have created a crawling “biohybrid” robot.

A sea slug’s buccal I2 muscle powers this biohybrid robot as it crawls like a sea turtle. The body and arms are made from a 3-D printed polymer. Photo courtesy of Victoria Webster.

The team believes the potential for this application is endless. Biohybrid robots could be released in swarms and collaborate in locating dangerous leaks in situations that would render other methods ineffective.

“We’re building a living machine – a biohybrid robot that’s not completely organic – yet,” said Victoria Webster, a PhD student who is leading the research.

Webster worked with Roger Quinn, the Arthur P. Armington Professor of Engineering and director of Case Western Reserve’s Biologically Inspired Robotics Laboratory; Hillel Chiel, a biology professor who has studied the California sea slug for decades; Ozan Akkus, professor of mechanical and aerospace engineering and director of the CWRU Tissue Fabrication and Mechanobiology Lab; Umut Gurkan, head of the CWRU Biomanufacturing and Microfabrication Laboratory, undergraduate researchers Emma L. Hawley and Jill M. Patel and recent master’s graduate Katherine J. Chapin.

The biohybrid robot is just under 2 inches long. Movement is controlled by an external electrical field and provided by a muscle from the slug’s mouth. However, future iterations of the device will include ganglia, bundles of neurons and nerves that normally conduct signals to the muscle as the slug feeds, as an organic controller.

By combining materials from the California sea slug, Aplysia californica, with three-dimensional printed parts, “we’re creating a robot that can manage different tasks than an animal or a purely man-made robot could,” said Quinn.

The sea slug is a perfect specimen for this application because it is highly adaptable and can withstand substantial changes in temperature, salinity and depth changes.

For the searching tasks, “we want the robots to be compliant, to interact with the environment,” Webster said. “One of the problems with traditional robotics, especially on the small scale, is that actuators – the units that provide movement – tend to be rigid.”

Muscle cells are compliant and carry their own fuel source – nutrients in the surrounding around. Because they’re soft, they’re safer for operations than nuts-and-bolts actuators and have a much higher power-to-weight ratio, Webster adds.

The team used the entire I2 muscle from the mouth area as it provided the optimal structure and form.

In their first robots, the buccal muscle is connected to the robots printed polymer arms and body. The robot moves when the buccal muscle contracts and releases, swinging the arms back and forth. In early testing, the bot pulled itself about 0.4 centimeters per minute.

The team is preparing to test organic versions as well as new geometries for the body, designed to produce more efficient movement.

www.case.edu