----- Forwarded message from Alejandro Dubrovsky <[log in to unmask]> -----
From: Alejandro Dubrovsky <[log in to unmask]>
Date: Wed, 27 Apr 2005 19:40:59 +1000
To: transhumantech <[log in to unmask]>
Subject: [>Htech] scienceblog: on-board "ink" storage dip pen nanolithography
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(
http://www.scienceblog.com/cms/node/7685
)
Fountain pen writes on the nanoscale
The first practical fountain pen was invented in 1884 by Lewis Waterman.
Although pens with self-contained ink reservoirs had existed for more
than a hundred years before his invention, they suffered from ink leaks
and other troubles. Waterman solved these problems by inventing the
capillary feed which produced even ink flow. Now fountain pen history is
repeating itself in the tiny world of nanoscale writing.
Researchers at Northwestern University have demonstrated writing at the
sub-100 nanometer molecular scale in fountain-pen fashion. They
developed a novel atomic force microscope (AFM) probe chip with an
integrated microfluidic system for capillary feeding of molecular ink.
Their results are published online by Small, a new journal dedicated to
breakthroughs in nanoscience and engineering
(http://dx.doi.org/10.1002/smll.200500027).
Dip-pen nanolithography (DPN) has been well-known for its capability of
high-resolution direct writing as a bottom-up nanofabrication technique.
The DPN technique exploits controlled deposition of molecules from an
AFM tip to a surface. However, the need of replenishing ink whenever
exhausted has been a limiting feature. Various attempts have been
reported to overcome such a drawback, but none of them reached molecular
patterns with features smaller than 100 nanometers.
The Nanofountain Probe (NFP) developed by Horacio D. Espinosa, professor
of mechanical engineering, and his colleagues employs a volcano-like
dispensing tip and capillary fed solutions to enable sub-100 nanometer
molecular writing. The NFP was microfabricated on a chip to be mounted
on commercially available AFMs. The device consists of an on-chip
reservoir, microchannels and a volcano-like dispensing tip. The
microchannels are embedded in the AFM cantilevers of the chip and the
volcano dispensing tip has an annular aperture to guide ink dispensing.
The ink on the reservoir is driven through the microchannel via
capillary action to reach the dispensing tip. At present, the smallest
feature width achieved with the device is 40 nanometers.
The standard microfabrication techniques used for the NFP chip -- an
important feature of this development -- provides scalability to
massively parallel arrays of probes and reservoirs for high throughput
patterning with multiple molecular inks.
"The writing capability of such NFP arrays with chemical and bimolecular
inks in fountain-pen mode is unique," said Espinosa. "We believe the
technology will likely lead to many high-impact applications in the
field of nanosensors, biotechnology and pharmaceuticals."
In addition to Espinosa, other authors on the Small paper are graduate
student Keun-Ho Kim and research assistant professor of mechanical
engineering Nicolaie A. Moldovan, both from Northwestern.
>From Northwestern University
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