From: Eliezer S. Yudkowsky (sentience@pobox.com)
Date: Fri Oct 15 1999 - 08:17:20 MDT
Not drextech - they're still painting in 2D, rather than using atomic
positioning in 3D - but progress. Not that I'm in favor of
nanotechnological progress, you understand, but I see in all these STM
advances the possibility of building (if not, exactly, manufacturing) at
least one 10^17 ops/sec computer, even if it takes a dedicated pen and a
couple of years. With any luck, all I'll need is one.
http://www.eurekalert.org/releases/nwun-ncp101299.html
Northwestern chemists plot the next step in nanotechnology
EVANSTON, Ill. --- In a paper to be published in the Oct. 15 issue of
the journal Science, researchers at Northwestern University demonstrate
a new technology that may be used to miniaturize electronic circuits,
put thousands of different medical sensors on an area much tinier than
the head of a pin and develop an understanding of the intrinsic behavior
of ultrasmall structures -- ones comprised of a small collection of
molecules patterned on a solid substrate.
By miniaturizing existing writing and printing techniques, such as the
4,000-year-old quill pen, a research team led by Chad Mirkin, Charles E.
and Emma H. Morrison Professor of Chemistry and director of
Northwestern's Center for Nanotechnology, has paved the way for such possibilities.
In their paper, the researchers detail how they have transformed their
world's smallest pen (Science, Jan. 29, 1999) into the world's smallest
plotter, a device capable of drawing multiple lines of molecules -- each
line only 15 nanometers or 30 molecules wide -- with such precision that
only five nanometers, or about 200 billionths of an inch, separate each
line. By contrast, a human hair is about 10,000 nanometers wide.
"Our dip-pen nanolithography, or what we call the world's smallest pen,
allowed us to draw tiny lines with a single 'ink' or type of molecule,"
Mirkin said. "Now, with the nano-plotter, we can place multiple 'inks,'
or different kinds of molecules, side by side with such accuracy that we
can retain the chemical purity of each line. Solving the problem of
nanostructure registration has taken us to a whole new level. In a
sense, we have transitioned dip-pen nanolithography from a single ink
process to a four-color printing type of process -- on a nanometer scale."
It is the nano-plotter's accuracy of registration when building
nanostructures of different organic molecules that could dramatically
impact molecule-based electronics, molecular diagnostics and catalysis,
in addition to leading to new applications not yet imagined in nanotechnology.
Dip-pen nanolithography (DPN), which is described in the Jan. 29, 1999,
issue of Science and is the basis for Mirkin's nano-plotter, turns a
common laboratory instrument called an atomic force microscope (AFM )
into a writing instrument. First, an oily "ink" of octadecanethiol (ODT)
is applied uniformly to the AFM's tip. When the tip is brought into
contact with a thin sheet of gold "paper," the ODT molecules are
transferred to the gold's surface via a tiny water droplet that forms
naturally at the tip. Using this technique, the researchers can draw
fine lines one molecule high and a few dozen molecules wide.
The nano-plotter, the subject of the Oct. 15 paper, multiplies this
technique, laying down a series of molecular lines with precision never
seen before.
The researchers first demonstrated DPN's registration prowess by putting
down dots of 16-mercaptohexadecanoic acid (MHA), each 15 nanometers in
diameter, on a surface of gold using an inked AFM tip. (MHA was selected
because of its reactive properties with gold.) The same tip then images
or "reads?" the pattern of dots and sends the dots' coordinates to the
system's computer. Using this information, the computer calculates
coordinates for a new pattern of dots, which it ships back to the AFM's
tip. The inked tip then sets down the new pattern of MHA dots with such
accuracy that only five nanometers of space stand between the second set
of dots and the originals.
"While the registration using this technique was exceptional, there was
one problem," Mirkin said. "Because we imaged the dots with the same
inked AFM tip with which we drew them, there was a chance that, during
the imaging process, we had scattered a few molecules where they
shouldn't be," Mirkin said. "That could be unacceptable for electronic
purposes and many other applications as it compromises the chemical
integrity of the nanostructures, especially where multiple inks are used."
Mirkin and his team developed a solution to this problem that has not
been matched by any currently available nanofabrication method. It
required a straightforward but significant modification of the first
experiment. Using DPN, they first drew cross-hair larger scale alignment
marks with an MHA ink on either side of the area of gold to be patterned
and imaged. Next, three parallel lines using the same MHA ink were set
down at a precalculated position with respect to the alignment marks.
The AFM tip was then replaced with a tip coated with ODT. The tip
located the alignment marks and then, using precalculated coordinates
based on the marks, drew three 50 nanometer ODT lines, each one exactly
70 nanometers to the left of an MHA line from the initial pattern. At
that point, the entire area was imaged with an ink-free tip.
"Because the patterned lines are imaged only at the end of the process,
cross-contamination of ink or molecules is prevented," Mirkin explained.
"And that is one of the keys to this technology." What's more, Mirkin's
multiple ink plotter can be automated, it uses a relatively inexpensive
tool (an atomic force microscope) that is common in the laboratories of
companies and universities, and it works under normal atmospheric conditions.
"This technology should become a real workhorse for the
nanotechnologist," Mirkin said. "It will soon be possible to pattern one
master plate with thousands of different organic nanostructures, each
structure designed to react with a certain disease agent, for example.
That's what is exciting about this -- no other method exists to do this
on such a small scale."
While the microfabrication of electronic circuits and other products
currently use solid-state or inorganic materials, innovations such as
the nano-plotter will direct future technologies toward the use of
organic and even biological materials. "Nature gives us a limited number
of materials," Mirkin noted, "but, in the lab, there are an infinite
number of organic molecules a chemist can make. And, by designing
molecules carefully, one can use them as inks in DPN to custom design
nanostructures for addressing critical issues in nanoscale science and
technology. For example, the conductivity, thermal stability, and
chemical reactivity of a circuit drawn via DPN could all be controlled
through choice of inks used to generate such structures."
In the case of biomolecules like DNA, it will be possible to generate
ultrahigh density arrays that could be quite useful in the genomics and
medical diagnostics industries. Such arrays are currently generated via
techniques with much lower resolution than DPN.
--
sentience@pobox.com Eliezer S. Yudkowsky
http://pobox.com/~sentience/tmol-faq/meaningoflife.html
Running on BeOS Typing in Dvorak Programming with Patterns
Voting for Libertarians Heading for Singularity There Is A Better Way
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