Small particles suspended in a liquid are constantly buffeted by collisions with other molecules, causing them to jiggle erratically in a manner known as Brownian motion. The phenomenon-first observed by botanist Robert Brown in 1824 and later described theoretically by Albert Einstein-is ubiquitous in nature, an inevitable consequence of thermal energy in the environment. Now, University of Chicago biochemist R. Dean Astumian claims that by applying external forces and employing various tricks, we can "bias" these otherwise random meanderings and "get things to move more one way than the other," thus laying the groundwork for potentially useful devices.

Select from the choices above to read the entire article.