Learning to Crawl

A team of researchers at Case Western Reserve University has created a robotic device that moves much like a slug or earthworm – and it could ultimately become the ideal tool to help doctors perform colonoscopies.

By studying how invertebrates such as the California sea slug traverse their environment, Dr. Hillel Chiel, professor of biology at Case Western Reserve in Cleveland, and a group of biologists and engineers were able to create a flexible robot that resembles a worm or slug, imitating the movements of those creatures. Chiel says his initial interest in understanding and replicating these simple biological systems was driven by “pure curiosity.” But applications for practical uses – particularly colonoscopies – quickly emerged.

Building on several years of work studying the movements and behavior of soft-tissue animals, Chiel’s team has constructed an endoscopic device made up of three muscle-like latex actuators – mechanisms that help the robot move in its environment – covered in nylon mesh. The device resembles a nine-inch hollow worm with a small camera inside it. Right now, it’s about a half-inch wide, but the team hopes to miniaturize it further.

By inflating and contracting the mechanism, using a self-managing movable seal system that the researchers had to create, the actuator segments move the robotic “worm” forward – the same way its biological counterpart scrunches its body to propel itself. Doctors will use a joystick, initially connected by wire to the device, to control the direction in which it travels, says Chiel.

Chiel admits that worms aren’t an obvious inspiration for engineering a new technique for performing a colon cancer screening. But its developers believe their device could be an advance in the field, allowing the diagnostic camera to move more easily through the long and twisted pathways of the large intestine, which would help doctors spot signs of cancer or bleeding more easily. 

“This device can literally ‘worm’ its way into complicated places or curved tubing such as the colon,” says Chiel in a press release.

Working with Olympus Medical Devices, the medical systems unit of camera maker Olympus, Chiel’s team has built a prototype – it has yet to be tested on a human being – that can be fitted like a sleeve over a medical endoscope, so that it moves the camera through a colon autonomously.

Currently, patients need to be anaesthetized before receiving a colonoscopy, in which a long tube-like instrument with a camera is inserted into the rectum and up through the colon. As unpleasant as it sounds, the procedure is necessary to spot colorectal forms of cancer. The disease strikes more than 145,000 Americans each year, and more than 56,000 of them are expected to die in 2005, according to the American Cancer Society.

On May 19, The New England Journal of Medicine reported that the less-invasive sigmoidoscopy, in which only the lower part of the colon is examined (as opposed to the entire colon in a colonoscopy), was found to miss a majority of advanced colorectal lesions in women. By creating a colonoscope that could perform the same task more easily and with less discomfort, they hope that more people might be willing to have the screening procedure, and catch a potentially life-threatening disease early on.

Dr. M. Anthony Lewis is president and CEO of Iguana Robotics, an Urbana, Illinois, company that makes biologically inspired robots such as “Marilyn,” a biomorphic humanoid robot used to study the neuro-control of movement. He believes that innovations like the “slug” colonoscope prove how engineers can take inspiration from the natural world.

“Traditional robotic mechanisms designed by mechanical engineers are very good at handling hard, manmade objects, but not soft tissue,” Lewis says. This work is an “example of how ideas from biology can contribute to innovations in technology.”

For his part, Chiel has been studying the behavior and movement of soft-tissue animals like the sea slug for nearly 20 years, with the motivating idea that “if we can understand how nature controls adaptive behavior through its neural and biomechanical mechanisms, it will have spin-offs in novel devices.” 

As Lewis points out, the robotic device Chiel and his team created isn’t just inspired by soft-tissue animals – it’s actually made up of softer and more pliable materials, like nylon and latex, rather than hard, heavy, inflexible metals. Creating a robot that replicates the “coordination [people] take completely for granted is a very difficult thing,” Chiel says.

With that in mind, Case Western graduate student in mechanical engineering Liz Mangan had a challenging task in building the robotic device that Chiel and his colleagues Roger Quinn, director of the university’s Biorobotics Laboratory, and Randy Beer, professor of electrical engineering and computer science, designed in 2000.

Mangan, who now holds a Master’s degree, was an undergraduate specializing in biomechanics when she began working on the project in February 2001. The biggest challenge, she says, was building a working model of their device out of off-the-shelf parts. It meant a lot of improvising. For instance, Mangan built her own bearings for one part of the device, and used the fingertips of plastic gloves for seals on another. She finished the first working prototype in August 2001, and not long afterward, the university applied for a patent, which was issued in July 2004.

Perhaps the biggest challenge she faced, Mangan admits, is one that “we haven’t really solved” yet. Earthworms have tiny hairs on their bodies that help grip surfaces when they move. Unable to replicate that ultra-delicate feature in their artificial version, Mangan says her robotic device still needs to contact a surface in at least two places.

Dr. Ron Fearing, a professor of electrical engineering and computer science at the University of California at Berkeley, believes that more researchers are beginning to realize that nature is “doing things in a very clever way – but not in the way engineers have typically designed systems.” 

He says the Case Western work typifies a shift in robotics, where more engineers will copy biological systems to create “anthropomorphic robots” made of softer and lighter materials that operate like a living creature.

The Berkeley Robotics Laboratory, for instance, is creating “biomemetic” machines, which can imitate the movement of insects or frogs. And researchers at the California Institute of Technology helped develop a biomorphic robot for NASA, called BIROD, designed to distribute power throughout its “body,” similar to how human bodies work, rather than a centralized power system.

“Engineering is starting to take inspiration from biology as we come across challenges that machines can’t solve,” Mangan says.