'Cyborg' robot built with sea slug muscle, 3D printed parts

 Scientists have built "biohybrid" robots by combining tissues from a sea slug with flexible 3D printed components, an advance that could lead to swarms of cyborgs that can detect toxic leaks in a pond or search the ocean floor for a black box flight data recorder.

A muscle from the slug's mouth provides the movement, which is currently controlled by an external electrical field.

The researchers also manipulated collagen from the slug's skin to build an organic scaffold to be tested in new versions of the robot.

In the future, swarms of biohybrid robots could be released for such tasks as locating the source of a toxic leak in a pond that would send animals fleeing, scientists said.

They could search the ocean floor for a black box flight data recorder, a potentially long process that may leave current robots stilled with dead batteries.

"We're building a living machine - a biohybrid robot that's not completely organic," said Victoria Webster, a PhD student at Case Western Reserve University who led the study.

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 Roger Quinn, professor at Case Western Reserve University.

The researchers chose the sea slug because the animal is durable down to its cells, withstanding substantial changes in temperature, salinity and more as Pacific Ocean tides shift its environment between deep water and shallow pools.

Compared to mammal and bird muscles, which require strictly controlled environments to operate, the slug's are much more adaptable.

"One of the problems with traditional robotics, especially on the small scale, is that actuators—the units that provide movement—tend to be rigid," Webster said.

Muscle cells are compliant and also carry their own fuel source - nutrients in the medium around them.

Since they are soft, they are 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 muscle, which naturally has two "arms", 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 centimetres 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 man-made control, and it's capable of learning," Webster said.

The team hopes to train ganglia to move the robot forward in response to one signal and backward in response to another.