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The C-R-Newsletter
C-R-Newsletter #62:
March 31, 2008
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Every month is full of activity for CRN. To follow the latest happenings on a daily basis, be sure to check our Responsible Nanotechnology weblog.
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Powerful Nanoscale Computer Created
A potentially powerful new form of
nanoscale computing has
been developed by scientists in Japan. BBC News
describes the
development as a "tiny chemical 'brain' which could one day act as a remote
control for swarms of nano-machines." The innovative device is made of
duroquinone, a compound
composed of carbon, hydrogen, and oxygen, which suggests that it might become a
key component of an early-generation nanofactory.
MSNBC has an excellent
article online about the new computing technique and also offers an
interesting video to
illustrate it.
More Enabling Technologies
CRN has been tracking numerous examples of
enabling technologies
that may help pave the way for molecular manufacturing.
Over the last several weeks, these are some of the most interesting that we’ve
found:
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Using DNA nanotechnology to build three-dimensional crystals |
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Visions of the Future
A new three-part TV series
from the BBC features leading theoretical physicist and futurist Dr Michio Kaku
exploring the cutting edge of science. In part three of the series, Kaku says:
“Amazingly, we can now manipulate individual atoms. We can pick them up, move them around, and even play with them. Today we can manipulate individual atoms, but this is just the beginning of a journey -- a journey which will ultimately give us the power to manipulate the very stuff of our universe: matter itself. We are on the brink of a revolution which will give us control -- exquisite control -- of our physical world.”
Part three covers, among other things, bloodstream nanobots,
space elevators, invisibility, teleportation, and military nanobots. A good deal
of time is also spent presenting the concept of a desktop nanofactory.
You can watch all
three
parts online.
Empowering Hope
CRN’s latest
monthly column for the popular Nanotechnology Now web portal is by
our Director of Impacts Analysis, Jamais
Cascio. His article is titled "Super-Empowered Hopeful Individuals." Here is
the abstract:
Most discussions of the benefits of molecular manufacturing tend to focus either on broad social advances or individual desires that such a transformative technology may be able to satisfy. These are surely useful ways of thinking about a nanotech-enabled world. But what if this model misses another category, one that may be less noticeable precisely because we pay so much attention to its opposite?
We hope you'll read
all our
columns, offer feedback, and tell others about them too.
Disruptive Nanotechnology
A California newspaper, Palo Alto Weekly, has a cover story on
nanotechnology. It's a long article that covers both current work in nanoscale
technologies and the more futuristic possibilities of molecular manufacturing.
CRN executive director Mike Treder was interviewed for the piece and quoted
extensively in it. You can read the whole article
online.
Religion & Nanotech
In February, the University of Wisconsin-Madison released the results of a study
on religion and nanotechnology. A
press release about their findings deals with the question: “Is
nanotechnology morally acceptable?”
The article generated significant coverage online, including
numerous comments at
CRN’s blog.
New Nano TV Show
"Nanotechnology: The
Power of Small" is coming to U.S. public television stations in April 2008.
The program, produced by the Fred Friendly Seminars and sponsored by the
National Science Foundation, comprises three episodes:
PRIVACY - Watching You Watching Me
HEALTH - Forever Young
ENVIRONMENT - Clean, Green, and Unseen
CRN’s Mike Treder was asked by the makers of the program to preview it and give
them a reaction. Afterwards,
he wrote:
Imagine yourself sitting in an audience at a university symposium and watching a large and diverse panel of experts from science, business, and activist groups debate the merits of advanced nanotechnology. That's exactly the experience you'll have in viewing this program. Unlike many so-called science specials on TV these days, "The Power of Small" takes its subject seriously and treats its audience as intelligent, discriminating adults. Thankfully, there are no flashy graphics, no distracting camera tricks or special effects; just smart, thoughtful people led by a capable moderator discussing provocative issues. Overall, I was quite impressed.
Debating CRN's Scope
Although we call ourselves the Center for Responsible Nanotechnology, we've
confined our focus to a specific, powerful application of advanced
nanotechnology known as molecular manufacturing.
However, not everyone believes that CRN should continue concentrating only on
molecular manufacturing and its implications. We’ve recently had a
good long discussion on our blog about whether, how, and why CRN should
consider expanding our scope. Please let us know if you have anything to add!
Archiving Nanotech Interviews
Sander Olson is one of the original developers of the NanoApex and
NanoMagazine websites. Over the years, Sander has conducted numerous
conversations with notable figures working in or commenting on the field of
nanotechnology. Since the acquisition of his sites in 2005 by the International
Small Technology Network, many of Sander's interviews have not been available on
the web.
To correct this, CRN created a page on our
main website as an archive of his interviews. In recent weeks, we’ve added
Sander’s in-depth talks with Jeff Chinn, Hugo DeGaris, Jack Dunietz, Glenn
Fishbine, J. Storrs Hall, Jeffrey Harrow, Gary Mezo, Jagdish Narayan, and James
Talton.
Guest Science Essay: Atomic Force Microscopy
By Michael Berger, editor-in-chief of Nanowerk
(This article was
originally published on March 10, 2008, at Nanowerk.com and is reprinted
here by permission.)
Whenever you read an article about nano this or nano that, chances are you come
across a large number of confusing three-letter acronyms - AFM, SFM, SEM, TEM,
SPM, FIB, CNT and so on. It seems scientists earn extra kudos when they come up
with a new three-letter combination. One of the most important acronyms in
nanotechnology is AFM - Atomic Force Microscopy. This instrument has become the
most widely used tool for imaging, measuring and manipulating matter at the
nanoscale and in turn has inspired a variety of other scanning probe techniques.
Originally the AFM was used to image the topography of surfaces, but by
modifying the tip it is possible to measure other quantities (for example,
electric and magnetic properties, chemical potentials, friction and so on), and
also to perform various types of spectroscopy and analysis. Today we take a look
at one of the instruments that has it all made possible. So far, over 20,000 AFM-related
papers have been published; over 500 patents were issued related to various
forms of scanning probe microscopes (SPM); several dozen companies are involved
in manufacturing SPM and related instruments, with an annual worldwide turnover
of $250–300 million, and approx. 10,000 commercial systems sold (not counting a
significant number of
home-built systems).
To put the AFM in its context: The reason why nanosciences and nanotechnologies
have taken off with such amazing force over the past 20 years is because our
ongoing quest for miniaturization has resulted in tools such as the AFM
(invented in 1986) or its precursor, the scanning tunneling microscope (STM;
invented in 1982. IBM has a website with a gallery of STM images
here).
Combined with refined processes such as electron beam lithography, this allowed
scientists to deliberately manipulate and manufacture nanostructures, something
that wasn't possible before.
These engineered nanomaterials, either by way of a top-down approach (a bulk
material is reduced in size to nanoscale particles) or a bottom-up approach
(larger structures are built or grown atom by atom or molecule by molecule), go
beyond just a further step in miniaturization. They have broken a physical
barrier beyond, or rather: below, which the standard laws of physics are
replaced by what is called "quantum effects". Any material reduced to the
nanoscale can suddenly show very different properties than to what it shows on a
macro- and larger scale. For instance, opaque substances become transparent
(copper); inert materials become catalysts (platinum); stable materials turn
combustible (aluminum); solids turn into liquids at room temperature (gold);
insulators become conductors (silicon).
A second important aspect of the nanoscale is that the smaller nanoparticles get
the larger their relative surface area becomes. The larger the relative surface
area, the more reactive a particle becomes with regard to other substances. The
fascination with nanotechnology stems from these unique quantum and surface
phenomena that matter exhibits at the nanoscale, enabling novel applications and
interesting materials.
But without the AFM, all this wouldn't be happening.
The term microscope in the name is actually a misnomer because it implies
looking, while in fact the information is gathered by feeling the surface with a
mechanical probe. The operation principle of an AFM is based on three key
elements:
1) an atomically sharp tip (the "probe"), placed at the end of a flexible
cantilever beam, that is brought into physical contact with the surface of a
sample. The cantilever beam deflects in proportion to the force of interaction;
2) a piezoelectric transducer to facilitate positioning and scanning the probe
in three dimensions over the sample with very precise movements; and
3) a feedback system to detect the interaction of the probe with the sample.
Scanning across the surface, the sharp tip follows the bumps and grooves formed
by the atoms on the surface. By monitoring the deflections of the flexible
cantilever beam one can generate a topography of the surface.
This principle has been the basis for one of the most important nanoscience
tools and allowed the visualization of nanoscale objects where conventional
optics cannot resolve them due to the wave nature of light.
A recently published article in the Encyclopedia of Life Sciences,
written by Martijn de Jager and John van Noort, both from the University of
Leiden in the Netherlands, gives an excellent overview of
Atomic Force Microscopy
and its applications in life sciences. Below we are summarizing some of the key
information from this article.
The AFM can be operated in a number of modes, depending on the application but
four modes are most commonly used for AFM imaging: contact mode (or constant
height mode), where the deflection of the cantilever is directly used as a
measure for the height of the tip and the normal force applied to the sample
scales directly with its height. In constant force mode, the normal force the
cantilever deflection under scanning reflects repulsive forces acting upon the
tip, and at sufficiently small scanning velocities the force feedback can reduce
the normal force. Tapping mode (or noncontact mode), where the tip is vibrated
(oscillating at its resonance frequency) perpendicular to the specimen plane to
avoid gouging the specimen as the tip is scanned laterally and the lateral
forces are reduced. In a fourth mode of scanning, the force–distance mode, the
tip is brought to the sample at frequencies far below the resonance frequency of
the cantilever while at the same time the deflection is recorded. This allows
one to measure the local interaction as a function of the tip-sample distance.
As de Jager and van Noort write in their article, large numbers of various
biological samples, including cells, cell compartments and biomolecules, have
been studied with AFM. "In some of these studies, AFM is used as a plain imaging
tool to investigate the topography of immobilized and/or fixed samples,
complementing existing methods such as electron microscopy, with the advantage
that sample preparation is generally more straightforward. For other
experiments, the use of AFM is a prerequisite to look at nonfixed materials and
even their dynamics in aqueous environment. Besides its imaging capabilities AFM
is becoming increasingly important as a nanomanipulation tool. The
single-molecule analysis of interaction forces, elasticity and tertiary protein
structure in intact biological materials is uniquely possible using AFM."
Introducing this vast body of research is beyond the scope of any article. Let's
just take a look at two examples illustrated in the paper:
Imaging Cells
"AFM imaging of living cells provides a direct measurement of cell morphology
with nanometer resolution in three dimensions. Because of its noninvasive nature
and the absence of fixation and staining, even dynamic processes like exocytosis,
infection by virus particles and budding of enveloped viruses have been
successfully visualized in successive scans. Owing to the high elasticity of the
cell membrane, the tip can deeply indent the cell without disrupting the
membrane. Making use of this effect, even submembraneous structures such as
cytoskeletal elements or organelles like transport vesicles can be revealed.
However, due to the elasticity of the cell the contact area between the tip and
the sample increases with increasing applied force. The elastic modulus of
living cells varies between 10 and 100 kPa, which results in a tip sample
contact area of 50–100nm in the softest region of the cell. Therefore, the
(sub-) nanometer resolution that is routinely achieved on more rigid samples
cannot be achieved on membranes of intact cells."
Structure, Function and Interaction of Single DNA and Protein Molecules
"Besides the analysis of cells and cell membranes, AFM-based methods to study
purified single molecules like proteins, deoxyribonucleic acid (DNA) and
ribonucleic acid (RNA) have developed rapidly in the past decade. Unique details
on the mechanism and function of DNA- and RNA metabolizing proteins can directly
be obtained by quantification of the number, position, volume and shape of
protein molecules on their substrate. Like other single molecule techniques all
individual instances of the entire population of structures are revealed, also
showing rare but important species. Further insights in the mechanism of a
reaction can be obtained from image analysis by measuring parameters such as
protein-induced DNA bending, wrapping and looping. Besides topography imaging,
force spectroscopy has been successful in unraveling tertiary structure in
proteins, RNA and other polymers."
Although it already is an essential tool for structural analysis and
manipulation of complex macromolecules and living cells, it is to be expected
that AFM-based applications will be further extended in the future. Technical
developments will advance the AFM system itself, by improvement of resolution,
image rate, sensitivity and functionality. A combination with complementary
techniques will fill in some limitations of AFM.
To fully exploit the potential of AFM to study functional biomolecules and their
interactions, de Jager and van Noort say that video microscopy would be needed
to capture dynamic events. "Currently, the scan rate is limited by the
mechanical response of the cantilever and the piezo. Smaller cantilevers will
result in higher resonance frequencies, allowing faster scanning rates. By
reducing the size of the cantilevers one order of magnitude, the frame rate can
be reduced from typically a minute down to video rate, allowing the study of a
significantly larger range of biomolecular processes."
The two researchers expect the most important developments for the tip itself.
"Image resolution in all modes is dependent on tip geometry. The reduction of
tip size, increase of its aspect ratio and its resistance to wear as a result of
scanning will have a considerable impact on all AFM applications."
For instance, researchers at Harvard and Stanford universities have developed a
specially designed
AFM
cantilever tip, the torsional harmonic cantilever (THC), which offers orders
of magnitude improvements in temporal resolution, spatial resolution,
indentation and mechanical loading compared to conventional tools.
With high operating speed, increased force sensitivity and excellent lateral
resolution, this tool facilitates practical mapping of nanomechanical
properties.
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