A hypnotist may have made your uncle Stuart cluck like a chicken, but a physicist and a chemical engineer can make an inanimate blob of goo creep like a snail, inch along like an inchworm, or slither like a snake. The biomimetic booger might help explain all types of limbless locomotion.
CREDIT: M. CHAUDHURY
Creeping, inching, and slithering might be different manifestations of the same basic interaction between body and surface, says physicist Lakshminarayanan Mahadevan of Harvard University. To explore that idea, he and Manoj Chaudhury of Lehigh University in Bethlehem, Pennsylvania, made a slug of polymer gel move across a rubberized plate of glass just by shaking the plate. They sliced the plate at an angle to make scales that would only let the blob slide one way. When the scales were parallel like railroad ties, the blob slid like a snail when the plate shook back and forth, they report in the 6 January issue of the Proceedings of the National Academy of Sciences. When the plate shook up and down at the same time, the blob bowed repeatedly to advance like an inchworm. And when the slices weren't parallel but fanned out, first to the right, then to the left, the blob spontaneously slithered across the jiggling glass like a snake.
The experiment "suggests that you don't need to redesign an organism all over to change its manner of motion," says Joseph Keller, a mathematician at Stanford University. "It may just be a matter of changing a parameter or two."
