Worms, slugs inspire robotic devices

Drawing on an understanding of how slugs, leeches and earthworms traverse their environments and grasp objects, a team of Case Western Reserve University biologists and engineers has developed two flexible robotic devices that could make invasive medical procedures such as colonoscopies safer for patients and easier for doctors to administer.

The researchers from Case’s departments of biology, mechanical and aerospace engineering and electrical engineering and computer science have obtained a patent for a new endoscopic device and a provisional patent for a gripping device that may have industrial as well as medical uses. “We have taken our understanding of biology to use it as an inspiration for novel robotic devices,” said Hillel Chiel, Case professor of biology and principal investigator on the project. “By taking nature seriously, we have created novel, flexible and adaptive devices that will be useful for a variety of applications.”

The endoscopic device, constructed of three muscle-like actuators made of latex bladders and surrounded by nylon mesh, looks like a nine-inch long hollow worm. The actuator segments, inflating and contracting in sequence, propel the device forward, mimicking the undulating movement of slugs and worms. “This device can literally worm its way into complicated places or into curving tubing such as the colon,” Chiel explained.

The current prototype can be added to existing medical endoscopes. Eventually, the device may be miniaturized and equipped with sensors that enable it to work autonomously and self propelling. According to Chiel, the research team will also be working to make the device more flexible, imitating the reflex responses of slugs and worms to changes in their environment. As a result of these refinements, the new device could reduce discomfort and the risk of injury among patients undergoing invasive medical tests, and thereby increase compliance with doctors’ orders to have such tests performed.

The second device, a biologically inspired “gripper,” mimics the way hungry California sea slugs in Chiel’s lab grasp seaweed in its many highly slippery forms. The prototype consists of a four-inch, ball-like device, surrounded by muscle-like actuators in the form of tubes or rings. One of these tubes contains a mouth that opens and closes. The ball pushes forward, opens its mouth and grasps at the object before it.

This device could meet an industrial need for grippers that can pick up soft objects without destroying them. Building grippers to pick up soft materials has been very hard,” Chiel explained. “Most gripper devices are fairly rigid and designed to work effectively with things that have a fixed orientation or a certain texture or toughness.”

Chiel also noted that if the gripping device were miniaturized and equipped with sensors, it could have medical applications as well. Such a device, for example, might eat its way through occluded blood vessels.

Animal behavior and robots

For nearly two decades and with support from the National Science Foundation, Chiel has studied the detailed movements of soft-tissue animals like the California sea slug, chronicling their behavior on film and with MRI imaging..

“My focus has been basic science,” Chiel explained. “If we can understand how nature controls adaptive behavior through its neural and biomechanical mechanisms, it will have spinoffs in novel devices. But it will also help us understand behavior in more complicated systems like human beings.”

Taking Chiel’s findings about animal motion, Roger Quinn, director of the Biorobotics Laboratory in the engineering school, and Randy Beer, Case professor of electrical engineering and computer science, designed the robotic devices. Elizabeth Mangan, a graduate student in mechanical engineering, built them. A second graduate student in mechanical engineering, Gregory Sutton, also contributed to the “Gripper” project.

The two new devices join other inventions–including several generations of insect-like robots that imitate cockroach behavior–created by researchers from the College of Arts and Sciences and the Case School of Engineering.