Fine print: New technique allows fast printing of microscopic e...( A new technique for printing extraor...)

A new technique for printing extraordinarily thin lines quickly over wide areas could lead to larger, less expensive and more versatile electronic displays as well new medical devices, sensors and other technologies.

Solving a fundamental and long-standing quandary, chemical engineers at Princeton developed a method for shooting stable jets of electrically charged liquids from a wide nozzle. The technique, which produced lines just 100 nanometers wide (about one ten-thousandth of a millimeter), offers at least 10 times better resolution than ink-jet printing and far more speed and ease than conventional nanotechnology.

It is a liquid delivery system on a micro scale, said Ilhan Aksay, professor of chemical engineering. And it becomes a true writing technology.

Aksay and graduate student Sibel Korkut published the results Jan. 25 in Physical Review Letters. The paper also includes as a co-author Dudley Saville, a chemical engineering professor who initiated the project but died in 2006. The research was funded by grants from the Army Research Office, the National Science Foundation and NASA.

Developing a deep understanding of the fundamental physics behind the process rather than building highly specialized equipment, the researchers were able to use a nozzle that is half a millimeter wide, or 5,000 times wider than the lines it produced.

The key to the process is something called an electrohydrodynamic (EHD) jet -- a stream of liquid forced from a nozzle by a very strong electric field. Such jets were first investigated in 1917 and are now commonly used in a variety of industrial processes. However, one of the main features of EHD jets is that the stream of liquid becomes unstable soon after it leaves the nozzle and either whips around uncontrollably or breaks up into fine liquid drops. Engineers have used these effects to their advantage in spinning fibers and in industrial electrospray painting
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