Printing Nano Building Blocks

A unique printing method could lead to precise nanofabrication

Researchers from IBM's [profile] Zurich Research Lab have devised a way to print particles as small as 60 nanometers in diameter with single-particle resolution. The technique lets researchers arrange tiny particles of various materials into well-defined structures on a surface--a step necessary for the mass production of devices such as nanowire transistors, biomedical sensors, and flexible, ultrasmall lenses capable of bending light.

"This is a very precise and efficient technique for taking nanoparticles with interesting properties and arranging them in an orderly fashion onto a surface," says Tobias Kraus, a researcher on the IBM nano-patterning team. The group details its findings in a paper published in the journal Nature Nanotechnology.

To create an imprint, the IBM team first makes a template with grooves or holes only tens of nanometers deep and shaped in a desired pattern. Then the researchers move a liquid suspension containing nanoparticles over the template; the particles fill the shallow grooves or holes.

Researchers from IBM's Zurich Research Lab have devised a way to print particles as small as 60 nanometers in diameter with single-particle resolution. The technique lets researchers arrange tiny particles of various materials into well-defined structures on a surface--a step necessary for the mass production of devices such as nanowire transistors, biomedical sensors, and flexible, ultrasmall lenses capable of bending light.

"This is a very precise and efficient technique for taking nanoparticles with interesting properties and arranging them in an orderly fashion onto a surface," says Tobias Kraus, a researcher on the IBM nano-patterning team. The group details its findings in a paper published in the journal Nature Nanotechnology.

To create an imprint, the IBM team first makes a template with grooves or holes only tens of nanometers deep and shaped in a desired pattern. Then the researchers move a liquid suspension containing nanoparticles over the template; the particles fill the shallow grooves or holes.

After the liquid dries, the team takes the template and presses it onto a substrate that has been prepared with a strong adhesive on its surface. The key step in the process is to ensure a difference in the strength of adhesives on the two surfaces: since the particles adhere better to a polymer layer on the substrate, they don't stick to the original template once it's removed. The result is a printed structure composed of single nanoparticles on the substrate.

Other researchers have previously shown that nanoparticles suspended in a liquid can be guided into patterns on a substrate. But, says Stephen Chou, head of the NanoStructure Laboratory at Princeton University, this is the first time he's seen someone devise a way to print the structures onto the surface of another substrate with great precision. "The novelty here is that they're able to print these particles onto another substrate," Chou says.

"The authors describe a very clever way to use nanoparticles as 'inks' in a soft lithographic printing process," says John Rogers, a professor of engineering at the University of Illinois, Urbana Champaign. Rogers's own team has also recently devised a novel nanoscale printing technique. (See "Nanoscale Inkjet Printing.") Along with other recent research in the area, he says, these techniques represent a new and powerful direction in nano printing.

The IBM team demonstrated the precision and versatility of the method by printing a nanoscale version of Robert Fludd's 17th-century image of the sun. The image is composed of 20,000 gold particles, each of them only 60 nanometers in diameter.

Before any useful applications result from the research, Kraus says that his team will have to devise a way of increasing the long-range accuracy of the method--that is, a way to make sure that each particle along a long line is exactly where the researchers want it to be. They will also have to develop strategies for particles smaller than the 60-nanometer size. For IBM's method to get below that size, the researchers will have to find the right balance between the depth of the grooves on their templates and the size of the particle. If the particle is too small and the depth too great, the particle will sit in the well and never adhere in the transfer.

Still, Kraus says, the IBM fabrication process applies to a wide range of materials--they include metals, polymers, and semiconductors--and is very reliable.

Cyborg Suits Strut the Catwalk

BOSTON -- It's been 10 years since Alex "Sandy" Pentland's graduate students began strolling around the MIT campus looking like cyborgs, straining under the weight of bulky "wearable" computers and heavy-duty eyeglasses with built-in displays.

Now Pentland is taking a lighter approach to the problem of melding man and machine, collaborating with haute couture designers such as Jean Paul Gaultier on cyborg-inspired fashions built from so-called smart fabrics.

Designs incorporating computer chips and sensors could monitor the wearer's health, or extend their social network, Pentland said here recently at a futuristic fashion show presented by the Materials Research Society, or MRS, where he cited Star Trek as a major inspiration.

"It's worth it to start thinking about Star Trek and this cyborg stuff, because that's where we're headed," said Pentland, who directs MIT Media Lab's Human Dynamics Group and is widely regarded as a pioneer in the field of wearable computing.

The MRS show last week did not exactly take the audience where no man has gone before. But the models did show off some of the more-commercial bets the clothing industry is placing on high-tech wearable gear.

BO-busting jackets and MP3-playing ski suits strutted their stuff in a show heavy on polyester with nanoparticle coatings, and light on the kinds of "smart clothing" that contain sensors and computers Pentland was promoting.

Nanoparticle coatings are already becoming so popular -- and nanotechnology such a buzzword in the textiles business -- that one organization at the MRS, the Hohenstein Institutes, introduced a quality label that would certify consumers that a particular garment contains nanotechnology.

The German company Tex A Med exhibited silver nanoparticle-coated underwear, which offers relief from a form of chronic dermatitis and some allergies.

Other companies are developing "self-cleaning" suits whose surfaces are designed to mimic the texture of the lotus leaf, or a fly's hairy wings, which deflect dirt and water.

Pentland encouraged scientists to look beyond the new coatings to the applications possible with wearable sensors and computers -- heart-rate monitoring systems and cognitive aids that could help memory-impaired people remember faces and complete day-to-day tasks.

But he conceded that more elaborate and "social" wearable technologies, including those that change color and shape in response to human touch and movement, are a few years away.

 One of the first tricks in Penn and Teller's Las Vegas show begins when
Teller—the short, quiet one—strolls onstage with a lit cigarette, inhales,
drops it to the floor, and stamps it out. Then he takes another cigarette
from his suit pocket and lights it.
No magic there, right? But then Teller pivots so the audience can see him
from the other side. He goes through the same set of motions, except this
time everything is different: Much of what just transpired, the audience
now perceives, was a charade, a carefully orchestrated stack of lies. He
doesn't stamp out the first cigarette—he palms it, then puts it in his
ear. There is no second cigarette; it's a pencil stub. The smoke from the
first butt is real, but the lighter used on the pencil is actually a
flashlight. Yet the illusion is executed so perfectly that every step
looks real, even when you're shown that it is not.

 Penn and Teller demonstrate the seven basic principles of magic.
The trick is called Looks Simple, and the point is that even a puff on a
cigarette, closely examined, can disintegrate into smoke and mirrors.
"People take reality for granted," Teller says shortly before stepping
onstage. "Reality seems so simple. We just open our eyes and there it is.
But that doesn't mean it is simple."
For Teller (that's his full legal name), magic is more than entertainment.
He wants his tricks to reveal the everyday fraud of perception so that
people become aware of the tension between what is and what seems to be.
Our brains don't see everything—the world is too big, too full of stimuli.
So the brain takes shortcuts, constructing a picture of reality with
relatively simple algorithms for what things are supposed to look like.
Magicians capitalize on those rules. "Every time you perform a magic
trick, you're engaging in experimental psychology," Teller says. "If the
audience asks, 'How the hell did he do that?' then the experiment was
successful. I've exploited the efficiencies of your mind."
Now that on-the-job experimentation has taken an academic turn. A couple
of years ago, Teller joined a coterie of illusionists and tricksters
recruited by Stephen Macknik and Susana Martinez-Conde, researchers at the
Barrow Neurological Institute in Phoenix, Arizona, to look at the
neuroscience of magic. Last summer, that work culminated in an article for
the journal Nature Reviews Neuroscience called "Attention and Awareness in
Stage Magic." Teller was one of the coauthors, and its publication was a
signal event in a field some researchers are calling magicology, the
mining of stage illusions for insights into brain function.
"Tricks work only because magicians know, at an intuitive level, how we
look at the world," says Macknik, lead author of the paper. "Even when we
know we're going to be tricked, we still can't see it, which suggests that
magicians are fooling the mind at a very deep level." By
reverse-engineering these deceptions, Macknik hopes to illuminate the
mental loopholes that make us see a woman get sawed in half or a rabbit
appear out of thin air even when we know such stuff is impossible.
"Magicians were taking advantage of these cognitive illusions long before
any scientist identified them," Martinez-Conde says.

Last year, a team at Duke announced a beta cloaking material whose special
nano-properties make it "invisible" to microwaves. Today, however,
researchers in Stuttgart have got something even better — a "metamaterial"
that can cloak objects in the visible light spectrum. Made of gold
nano-mesh, the material has a negative refraction index for visible light
— that means it doesn't reflect light, and could give the illusion of
blending into the background.

The way humans perceive the world is through their senses that use certain
rules by which they navigate. For instance, the use of perspective,
stereopsis, occlusion, shading and sfumato are all listed in Scientific
American Mind's article A Perspective on 3-D Visual Illusions as rules
that "create a 3D formation about our world". The human brain and nervous
system sees this 3-dimensional world on 2-dimensional eye retinas. Thus,
rules are used to constantly interpret between the 2-D world and the 3-D
world.(1)
One example proving this inference between the 3-dimensional and the
2-dimensional is the visual illusion of the Leaning Tower of Pisa. When
two images of the receding tower are placed next to one another, the tower
to the right seems to lean at a greater angle than the image to the left.
This is because the human eyes want to see the tower image to the right as
parallel to the tower image to the left. This cannot happen because both
images are receding; the brain reconfigures the images to diverge. In
other words, the brain reconstructs a third dimension.(1)
Illusions like the Tower of Pisa illusion give us proof that our brains
use rules to navigate the world. When 3-D is placed on 2-D this often
tricks the mind into "seeing" differently. So, what does this mean for
architecture? How is the 2-D within architectural design evolving? Why is
the use of surface so important? What new illusions might we uncover in
the future as the use of surface in architecture continues to advance?
Since early times, 2-D surface has been used to create illusions and
representations of our 3-D world. At times, our eyes navigate 2-D surface
using 3-D navigation rules. This is most evident when we see perspective
drawings on a canvas or building surface. Artists and architects alike
make the most of our visual sensory system to use surface to create space.
Within architecture, for example, the use of perspective on actual
building surface can greatly modify spatial character.
Now, with the digital revolution, architectural space can be manipulated
evermore by using surface. Architects are going beyond merely painting or
applying a surface coating or facing. Architectural surface can literally
become space that our eyes move through. With digital media, motion can
also be applied to such surfaces, giving space more depths and varying
dynamic movements. On very thin screens, humans are now able to navigate
3-D virtual space. At the same time, since this is virtual space –
designers may challenge the rules that we humans have come to understand
in the real world. (Rules of physics like gravity, friction and inertia
can be altered to create certain environmental constructs.)
Nanotechnology is also changing the way architects and designers think of
surface. As materials are constructed at the atomic and molecular level,
nanotechnology has the power to alter material behavior. Such materials
may be used to construct architecture and may transform the way occupants
expect materials to perform. As materials become stronger, lighter and
cleaner, surface applications will fundamentally change. Just imagine a
surface that is perceived as strong and durable as opposed to vulnerable
and delicate. The possibilities are immense.
Surfaces are becoming increasingly transient. As we advance further into
the future, smart materials will continue to advance and alter the way
building materials function. Now, we have glass that can change
transparencies and sensors that can actuate LED surface lighting. In
effect, the notion of "surface" is changing, and our perception of what we
think 2-D space can do is expanding. We have come a long way from
discovering the rules of perspective; yet, we are just beginning to
understand the brain, its systems and the illusions that define them.
Still, it is with the advancement of "surface" that 3-dimensional space
continues to evolve – a direct influence from the human sensory system and
how it navigates the world