The researchers used the slug’s muscle cells to enable the robot’s movement. The muscle cells also provide their own fuel source via nutrients in the surrounding substance.
Because muscle cells are soft, they are safer to use than traditional actuators. Furthermore, muscle cells have a significantly greater power-to-weight ratio. Initial efforts used individual sea slug muscle cells, but this progressed to using the entire I2 muscle from the mouth area.
Hillel Chiel, a biology professor who has spent decades studying the California sea slug explained that, “The [I2] muscle already had the optimal structure and form to provide the function and strength needed.”
The slug moves like a turtle on the beach, and its movement is achieved via an external electrical field.
In early versions of the robot, the buccal muscle, which has two “arms”, connected to the robot’s printed polymer arms and body. Contraction and release of the buccal muscle caused the robot to move via the back and forth swinging of these arms.
With this method, the robot moved at approximately 0.4 centimetres per minute. The next stage of development will use ganglia from the California sea slug, which would enable the use of either chemical or electrical stimuli to actually control the robot’s movement.
“When we integrate the mucles with its natural biological structure, it’s hundreds to thousands of times better,” said Ozan Akkus, professor of mechanical and aerospace engineering and director of the CWRU Tissue Fabrication and Mechanobiology Lab.
Moving Biorobotics Forward
In the future, ganglia—bundles of neurons and nerves that conduct signals to the muscles—will be used to actually control the robot’s movement. The result is a more lifelike, internal control mechanism for the biohybrid robot.
Roger Quinn, a professor of engineering and director of Case Western Reserve’s Biologically Inspired Robotics Laboratory explained the team’s motivation for constructing the biohybrid: “We’re creating a robot that can manage different tasks than an animal or a purely manmade robot could”.
Potential applications include locating the source of a toxic leak in underwater environments or as a tool in oceanographic exploration. Due to the projected inexpensiveness of the product as well as its environmentally-friendly degradation, recovery would not be a high priority.
For more on biohybrid robotics, this biohybrid ray is a leap forward in robotic bioengineering.