Carnivorous plants have long fascinated humans with their blood-sucking capabilities. The Venus flytrap is even smart enough to pause before snapping shut, ensuring that whatever falls in isn't a fluke. Now, this intelligent flesh-eating plant is the inspiration for a new biomimetic robot made from an artificial muscle material.
"We are trying to learn more from nature to be able to improve the performance of these muscles," said Mohsen Shahinpoor, a professor of mechanical engineering at the University of Maine who created the robotic Venus flytrap. He recently described his biting bot in the academic journal Bioinspiration & Biomimetics.
Shahinpoor says he's amazed by the way real Venus flytraps contain sensory cells at the base of their necks that can generate an electric charge. After counting for several beats, the plant's traps, called lobes, close rapidly. The plant secretes sap to dissolve its prey, absorbs the nutrients and anything left dries up and blows away in the wind.
To make a tiny robotic Venus flytrap, Shahinpoor used a material he invented years ago called ionic polymeric metal composites or IPMCs. This soft nanomaterial is frequently used by roboticists to mimic muscle function because adding voltage causes the ions inside it to redistribute, bending the surface. Plus, the material works when wet.
"We can use a material that is its own sensor and its own actuator, as a robot," Shahinpoor said.
He took two small sheets of the special nanomaterial to approximate Venus flytrap lobes and integrated the pair into a spine made from a copper roll. For the trigger hairs, he attached tiny strips of IPMC strips. Touching the trigger hairs activates a solid-state relay and a small dynamic voltage generator causes the lobes to close quickly.
The robot actually works. To test it, Shahinpoor flicked the trigger hairs several times with a long stick and, after a pre-programmed pause, the small Venus flytrap robot ensnared it. While Shahinpoor doesn't want to get into the gruesome details, he said the robot also successfully closed around a hapless fly.
"Although it's not eating flies at all, theoretically speaking it can lure prey into its area and just capture it," he said. Next, the engineer says he wants to gain a better understanding of how the real Venus flytrap's lobes close so quickly, and use those results to come up with better materials that mimic the mechanism.
This kind of capability has potential for numerous applications, primarily medical ones. Patients suffering from facial paralysis require the use of many tiny muscles, Shahinpoor said, and such soft robotic material could one day be implanted in the face to help. Similarly, people with eye and heart diseases could benefit from high-performing muscle-like material.
Kwang Kim is a mechanical engineering professor at the University of Nevada, Reno, who has worked with the material Shahinpoor invented. Kim and associate professor Kam Leang used a special IPMC pattern to design an artificial fin to help tiny robots move better underwater.
"If you wanted to make a Venus flytrap using other available materials, I'm not quite sure what kind of options that engineers have," Kim said. "This is very unique." With the trapping mechanism Shahinpoor added, the material becomes more interesting, he added. "I think it's a great concept."
Robotic Venus flytraps have made it to the marketplace, although they've tended to be snapping and burping novelty toys instead of scientific breakthroughs. Shahinpoor laughs when asked if his robot could be used to catch bugs on a large scale, and responds that he's not planning on commercializing it.
"People would rather use those electronic zappers in their back yard," he said.