January 26, 2011





Nature - Hard-tip, soft-spring lithography
The pyramid on the dollar made only tens of microns across

Schematic illustration of an HSL tip array supported by a transparent, soft backing layer that provides mechanical flexibility to each tip. b, Experimental procedure to fabricate the tip arrays: 50-μm-thick (100)Si wafers with thermally

Nanofabrication strategies are becoming increasingly expensive and equipment-intensive, and consequently less accessible to researchers. As an alternative, scanning probe lithography has become a popular means of preparing nanoscale structures, in part owing to its relatively low cost and high resolution, and a registration accuracy that exceeds most existing technologies. However, increasing the throughput of cantilever-based scanning probe systems while maintaining their resolution and registration advantages has from the outset been a significant challenge. Even with impressive recent advances in cantilever array design, such arrays tend to be highly specialized for a given application, expensive, and often difficult to implement. It is therefore difficult to imagine commercially viable production methods based on scanning probe systems that rely on conventional cantilevers. Here we describe a low-cost and scalable cantilever-free tip-based nanopatterning method that uses an array of hard silicon tips mounted onto an elastomeric backing. This method—which we term hard-tip, soft-spring lithography—overcomes the throughput problems of cantilever-based scanning probe systems and the resolution limits imposed by the use of elastomeric stamps and tips: it is capable of delivering materials or energy to a surface to create arbitrary patterns of features with sub-50-nm resolution over centimetre-scale areas. We argue that hard-tip, soft-spring lithography is a versatile nanolithography strategy that should be widely adopted by academic and industrial researchers for rapid prototyping applications.


Hard-tip, soft-spring lithography is to scanning-probe lithography what the disposable razor is to the razor industry,” said Chad A. Mirkin, the paper’s senior author. “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.”





“Scaling cantilever-based architectures at low cost is not trivial and often leads to devices that are difficult to operate and limited with respect to the scope of application,” Mirkin said.

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.




“Eventually we should be able to build arrays with millions of pens, where each pen is independently actuated,” Mirkin said.

8 pages of supplemental material


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