Northwestern University researchers have developed a new technique for rapidly prototyping nanoscale devices and structures that are so inexpensive the ‘print head’ can be thrown away when done. Hard-tip, soft-spring lithography (HSL) rolls into one method the best of scanning-probe lithography, high resolution, and the best of polymer pen lithography with low cost and easy implementation. To demonstrate the method's capabilities, the researchers duplicated the pyramid on the U.S. one-dollar bill and the surrounding words approximately 19,000 times at 855 million dots per square inch. Each image consists of 6,982 dots. This exercise highlights the sub-50-nanometer resolution and the scalability of the method. “Hard-tip, soft-spring lithography is to scanning-probe lithography what the disposable razor is to the razor industry. This is a major step forward in the realization of desktop fabrication that will allow researchers in academia and industry to create and study nanostructure prototypes on the fly,” said Chad A. Mirkin, director of Northwestern's International Institute for Nanotechnology. Scanning probe lithographies typically rely on the use of cantilevers as the printing device components. Cantilevers are microscopic levers with tips, typically used to deposit materials on surfaces in a printing experiment. They are fragile, expensive, cumbersome and difficult to implement in an array-based experiment. Hard-tip, soft-spring lithography uses a soft polymer backing that supports sharp silicon tips as its ‘print head’. The spring polymer backing allows all of the tips to come in contact with the surface in a uniform manner and eliminates the need to use cantilevers. Essentially, hard tips are floating on soft polymeric springs, allowing either materials or energy to be delivered to a surface.
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