In the future, the scientists say, swarms of biohybrid robots could be released for such tasks as locating the source of a toxic leak underwater, or search the ocean floor for black box flight data recorders, a process that takes too long for current, battery powered robots.
By combining materials from a California sea slug with three-dimensional printed parts, “we’re creating a robot that can manage different tasks than an animal or a purely manmade robot could,” said Roger Quinn, Professor of Engineering and director of Case Western Reserve's Biologically Inspired Robotics Laboratory.
The researchers chose the sea slug because the animal is durable down to its cells, withstanding substantial changes in temperature, salinity and more. Compared to mammal and bird muscles, which require strictly controlled environments to operate, the slug's proved much more adaptable.
For the searching tasks, “we want the robots to be compliant, to interact with the environment,” said Victoria Webster, a PhD student who is leading the research. “One of the problems with traditional robotics, especially on the small scale, is that actuators tend to be rigid.”
Muscle cells are compliant and also carry their own fuel source. Because they're soft, they're safer for operations than nuts-and-bolts actuators and have a much higher power-to-weight ratio, Webster said.
In their first robots, the buccal 12 muscle, which naturally has two ‘arms’, is connected to the robot’s 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 robot pulled itself about 0.4cm per minute.
To control movement, the scientists are turning to the animal's own ganglia. They can use either chemical or electrical stimuli to induce the nerves to contract the muscle.
“With the ganglia, the muscle is capable of much more complex movement, compared to using a manmade control, and it's capable of learning,” Webster said.
The team hopes to train the ganglia to move the robot forward in response to one signal and backward in response to a second.
With the goal of making a completely organic robot, the researchers gelled collagen from the slug's skin and also used electrical currents to align and compact collagen threads together, to build a lightweight, flexible, yet strong scaffold.
The team is preparing to test organic versions as well as new geometries for the body, designed to produce more efficient movement.
The researchers add that completely organic robots will likely be inexpensive and won’t pollute the location they operate in with metals and battery chemicals if they can’t be recovered. Instead, they will likely be eaten or biodegrade.