Wrinkle, wrinkle, little polymer.Scientists have developed a cheap and easy way to create specific patterns of tiny wrinkles on the surface of a flexible and commonly used polymer--a technique that could be used to fabricate an assortment of microdevices.
Polydimethylsiloxane (PDMS (Product Data Management System) See PDM. ), the soft polymer that's the main ingredient in Silly Putty Silly Putty
synthetic clay; uses ranging from bouncing balls to false mustaches. [Am. Hist.: Sann, 165]
See : Fads , also comes in transparent, pliable sheets in which some of the material's long-chain molecules are chemically crosslinked, says John W. Hutchinson John W. Hutchinson is a renowned scholar in the field of applied mechanics, and has made seminal contributions to the mechanics of structures and mechanics of materials. He is a recipient of the Timoshenko Medal. , a mechanical engineer at Harvard University Harvard University, mainly at Cambridge, Mass., including Harvard College, the oldest American college. Harvard College
Harvard College, originally for men, was founded in 1636 with a grant from the General Court of the Massachusetts Bay Colony. . He and his colleagues found that when they irradiated a 3-millimeter-thick sheet of PDMS with a beam of gallium ions, the material became a wrinkled, glasslike skin about 25 nanometers thick.
Bombardment by about 10 trillion ions per square centimeter formed mostly straight lines spaced about 460 nm apart. At exposures above 70 trillion ions/[cm.sup.2], smaller wrinkles formed atop these lines, the researchers report in the Jan. 23 Proceedings of the National Academy of Sciences The Proceedings of the National Academy of Sciences of the United States of America, usually referred to as PNAS, is the official journal of the United States National Academy of Sciences. . Various combinations of repeated exposures generated similar yet distinct patterns of ridges.
Because wrinkled areas of PDMS sheets repel water more readily than unwrinkled areas do, zapping the material with gallium could create tiny channels that might steer various chemicals within 'lab-on-a-chip' devices, says Hutchinson. Other possible applications include the manufacture of optical filters and sensors, the researchers suggest.