Meniscus is no Mole Hill to the Small

CAMBRIDGE, Mass., Sept. 29 -- Walking on water is no problem for some bugs. Getting out can be another story.

An obstacle that's nearly invisible to humans can be a life-or-death challenge for a creature the size of, say, a speck of dust. Two researchers are studying this dilemma, with an eye toward applying it to nanotechnology.

Many water-walking insects can't climb menisci using their traditional means of propulsion. (Credit: David Hu and John Bush, Massachusetts Institute of Technology/Nicolle Rager Fuller, National Science Foundation)

Water-walking insects that can't climb a "meniscus" -- the crescent-shaped and barely visible slope literally at water's edge -- must summon the energy to surf the interface between liquid and solid in ponds and other wet places in order to escape predators or reproduce.

Menisci are all around us -- for example, the slight upward curve of water in a glass where it meets the side.

"But we don't notice them because they're so small, only a few millimeters in height," said mathematician David Hu of the Massachusetts Institute of Technology. For insects, he said, those slopes are like frictionless, slippery mountains.

Hu and coworker John Bush have done the math to explain how nearly weightless insects find the traction to ascend a wall of water several times their height. Such obstacles may surround a leaf floating in a stream or a stone on the riverbank.

According to Bush, the study, which was funded by the National Science Foundation, may be of interest to nanotechnology researchers, "because they, too, are concerned with problems at very small scales."

For more information, visit: www.mit.edu