Harvard researchers are exploring new and clever ways of designing nature-inspired robots. Inspired by arthropod insects and spiders, Arthrobots are semi-soft walking robots constructed from drinking straws.
Unlike soft robots, Arthrobots don’t have the same air chambers that expand and contract to generate clumsy movement. These robots are far more rigid and nimble, and researchers hope someday Arthrobots could be used in real-world scenarios like (wait for it) disaster response.
“If you look around the world, there are a lot of things, like spiders and insects, that are very agile,” said George Whitesides, a professor at Harvard. “They can move rapidly, climb on various items, and are able to do things that large, hard robots can’t do because of their weight and form factor. They are among the most versatile organisms on the planet.”
Whitesides and Alex Nemiroski, a former postdoctoral fellow at the Whitesides Research Group, developed a simple joint made from the average drinking straw.
“This all started with an observation that George made, that polypropylene tubes have an excellent strength-to-weight ratio. That opened the door to creating something that has more structural support than purely soft robots have,” he said. “That was the building block, and then we took inspiration from arthropods to figure out how to make a joint and how to use the tubes as an exoskeleton. From there it was a question of how far can your imagination go? Once you have a Lego brick, what kind of castle can you build with it?”
A notch was cut into the straws, allowing them to bend. Whitesides and Nemiroski inserted plastic tubing that, when inflated, would expand and cause the joint to extend. Rubber tendons were added to bend the joint back into position when the tubing deflated.
Coupling a few of these clever joints together and the team of scientists was able to build a number of insectoid robots. Creatures from inchworms to ants to spiders.
“With every new level of systems complexity, we would have to go back to the original joint and make modifications to make it capable of exerting more force or to be able to support the weight of larger robots,” Nemiroski said. “Eventually, when we graduated to six- or eight-legged arthrobots, making them walk became a challenge from a programming perspective. For example, we looked at the way ants and spiders sequence the motion of their limbs and then tried to figure out whether aspects of these motions were applicable to what we were doing or whether we’d need to develop our own type of walking tailored to these specific types of joints.”
Robots with few joints were controlled by hand using a syringe, but with more joints, the team used an Arduino microcontroller to handle the pumps and valves.
“We put together a microcontroller run by Arduino that uses valves and a central compressor,” he said. “That allowed us the freedom to evolve their gait rapidly.”