Case Western Reserve University Scientists Create “Biohybrid” Robots from Sea Slug Muscles and 3D Printed Parts

If I were to mention cyborg sea slugs, you’d likely assume I was about to tell you about the latest midnight horror film festival I went to, and you’d be justified in that response – but you’d be wrong. The “biohybrid” robots, created by researchers at Cleveland’s Case Western Reserve University by combining sea slug parts with 3D printed components, are very real, but don’t worry, they’re not the products of a mad scientist intent on zombifying the masses. In fact, they have the potential to do a lot of good for humans and the environment.

Robots are becoming more and more advanced, but they still have their limitations, so a research group led by PhD student Victoria Webster has developed biohybrids, machines that combine the adaptability and durability of living tissue with the controllability of a robot. The small machines, in their current form, crawl with a movement similar to that of sea turtles on a beach, and in the future, swarms of them could be released into bodies of water to search out the source of toxic leaks or even to find the black boxes from crashed planes.

Each biohybrid robot is constructed from flexible 3D printed components whose movement is generated by a muscle taken from the mouth of the California sea slug. The muscle is controlled by an external electrical field, but future iterations, according to the researchers, will be organically controlled by ganglia, which are bundles of nerves and neurons that normally transmit signals to the mouth muscle as the slug feeds. Collagen from the slug’s skin will also be tested as an organic scaffold for the robot.

Why sea slugs? Well, they’re exceptionally durable creatures, for one thing. Unlike mammals or birds, for instance, sea slugs can handle dramatic changes in temperature, water salinity, and other conditions that the Pacific Ocean’s tides throw at them. And while the idea that sea slugs could be superior to robots may never have crossed your mind, living muscle cells carry numerous advantages: they have their own built-in fuel source in the nutrients surrounding them, they’re compliant, and they’re soft, which, according to Webster, makes them safer and more efficient with a higher power-to-weight ratio.

“(For searching purposes,) 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.”

Originally, the researchers tried using muscle cells, but found that the entire I2 muscle from the mouth area, aka the buccal mass, was already the ideal shape and structure for the functions they wanted to create. The buccal muscle has two armlike appendanges that, when the muscle contracts and releases, move the 3D printed polymer robot forward. In early tests, the biohybrid, which is just under two inches long, was able to pull itself forward at a rate of about 0.4 centimeters per minute.

The team expects the robot’s movement to improve, and become more complex, once they integrate the sea slug’s ganglia into the machine. Using either chemical or electrical stimuli to signal the nerves to contract the muscle, they hope to be able to train the robot to move forward in response to one signal and backward in response to another.

Victoria Webster

“With the ganglia, the muscle is capable of much more complex movement, compared to using a manmade control, and it’s capable of learning,” said Webster.

The researchers’ ultimate goal is to create a fully organic robot; such a creature would be inexpensive to create and also biodegradable so there would be no worry about pollution if it were lost in the ocean or in some other remote location. Ozan Akkus, professor of mechanical and aerospace engineering and director of the CWRU Tissue Fabrication and Mechanobiology Lab, worked with his lab to create an organic scaffold for the robot by gelling collagen from the slug’s skin and using electrical currents to align and compact the collagen threads together. The result was a flexible, strong and lightweight scaffold that takes the team a step closer to a completely organic creation.

The researchers will also be testing different geometries for the robots in the hopes of producing more efficient movement. Webster will be discussing her research at the Living Machines 2016 conference, which is currently taking place in Edinburgh, Scotland. Additional members of the research team include Roger D. Quinn, the Arthur P. Armington Professor of Engineering and director of Case Western Reserve’s Biologically Inspired Robotics Laboratory; biology professor Hillel J. Chiel; 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. You can access the full study here. Discuss further in the 3D Printed Biohybrid Robots forum over at 3DPB.com.