Harvard team designs soft robotic mechanism modeled from biology

The chameleon's catapulting tongue and the bloodworm's burrowing proboscis inspired the creation of a soft touch robotic mechanism that can manipulate delicate objects without damaging them.

By mimicking the natural movements of the chameleon and the bloodworm, a team of researchers at Harvard University's Department of Chemistry and Chemical Biology designed a hybrid soft mechanism that can grip, catch, and convey fragile or irregularly shaped objects. The system is simple, without the need for compressed air or high voltages that other soft gripping mechanisms require.

Their work appears in Cell Reports Physical Science, Sept. 22.

The three soft mechanisms--gripping, catching, and conveying--all make use of a toroidal hydrostat. This is a soft-polymer donut-shaped container filled with water. It's similar to a children's toy, called a water wiggly, which is commercially sold and often filled with colored beads. 

"This unique elasto-fluid object can invert around, encapsulate and grip irregularly shaped objects within an elastomeric membrane under a uniform hydrostatic pressure," the researchers write.

"Moreover, the inherent rubber elasticity of the toroidal hydrostat can be leveraged to store mechanical energy and drive a catapult mechanism for rapidly catching objects. Finally, the toroidal topology of the hydrostat enables a novel feed-through transportation mechanism that represents a hybrid between biological peristalsis and a man-made conveyer belt."

Looking to nature for solutions

Senior author of the paper, professor George Whitesides, discussed the advantages of observing nature to find for solutions to problems. 

"Looking at nature to be stimulated by ideas that have been tested through evolution and seeing if you can replicate them and extend them in other areas is a very good thing to do, a very profitable area for research," he said. "There are all sorts of interesting applications of systems that have already been worked out in biology that can be adapted to other purposes as well. So much of science is that way. You do it because you're interested, because you'd like to make something happen, because there's an idea that there's a least a demonstration of it, because it just might be a lot of fun to do it."

"You're trying to build something that replicates a mouth or a throat, or a gut, or a bell or how a squid squirts out as it's moving through water," he added.

Whitesides said the research team has a "fair amount of autonomy" in what it does within a given scope of a project. The process is "curiosity-driven," he stressed.

How the chameleon's tongue and the bloodworm's proboscis work is known to scientists, but the mechanical mechanism "really hasn't been used in soft robotics," he said. "We thought we'd see what we could do with that."

"The real innovation" in the development of the toroidal hydrostat was due to the first author of the paper, who saw in the science museum in Boston an example of a system which was doing something with a soft mechanism which duplicated this kind of action," he added/ "It's really a question of keeping one's eyes open and looking at clever work done by other people, other engineers in the world."

Future uses for soft robotics

A soft robotic system could be used to handle foods, where businesses would want to move things, such as tomatoes or strawberries, without "putting fingerprints on them," Whitesides said. "You might handle food, or fruit, anything soft" that might get bruised by something with a hard tip.

A soft robotic system could pick up a soft item without "any particular pressure points. In any circumstance where you might want to transport something from point A to point B, as in for example, in harvesting, you might do a good job by working with peristaltic as opposed to a pick-and-drop kind of mechanism," he added. 

As for the next steps with the soft robotics, Whitesides said researchers are seeking someone who would try some of their robotics with a product like fruit to "see if this actually solves the problem, or does it create some other problem of another sort."

"The ideal way of doing it is to find some group that has an engineer that would like to contribute to this," he said. "Because engineers have a way of solving problems by taking an existing idea and making it work better and better and better, until it works better than you might ever think." 

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S.E. Root, Bio-inspired design of soft mechanisms using a toroidal hydrostat, Cell Reports Physical Science, Sept. 22.

https://doi.org/10.1016/j.xcrp.2021.100572