The document discusses techniques for constructing pictures and galleries using carbon nanotubes. Carbon nanotubes are grown on substrates in specific patterns to form intricate structures, such as President Obama's face, that are barely visible to the naked eye. Scanning electron microscopes are used to image the nanotube structures. The techniques allow for self-assembly of nanotubes into complex shapes that can represent logos, symbols, or other images at the micro- and nanoscales.

1. Abstract
Now a days the nanotechnology has wide range of
applications in the field of science and technology.As
though the nano particles involved are very small in size
they have a big future because of many of their
properties. The carbon nanotubes ,extended tubes of
rolled graphite sheets can be grown. By growing these
tubes under suitable conditions, pictures like Obama’s
face and galleries can be constructed.
This paper is about construction
of pictures and galleries by using carbon nanotubes
with some techniques. These techniques, nanobliss are
now media for art, science , architecture and for
promoting popular awareness and education about
nano materials and related technologies.
Introduction:
The Nanobliss is a gallery of visualizations of small-scale
structures of carbon nanotubes and silicon, created
by John Hart and collaborators. Nanobliss artifacts are
small intricate structures that are fabricated from organic
and inorganic materials such as carbon and silicon. The
structures range in size from far invisible to nearly
visible to the naked eye. Techniques of materials
science, chemistry, micro-fabrication, self-assembly,
mechanical shaping, scanning electron microscopy,
optical photography, and digital image processing are
used to create the structures and images shown here.
Nanobliss is largely based on technologies for
synthesis of carbon nanotube structures, which were
developed by John Hart through his research at the
Massachusetts Institute of Technology. Microscopic
faces of President-elect Barack Obama were made using
nanotechnology, and imaged using a scanning electron
microscope. Each face consists of millions of vertically-aligned
carbon nanotubes, grown by a high temperature
chemical reaction.
Carbon nanotubes(CNT):
Carbon nanotubes (CNTs) are cylindrical molecules of
carbon atoms, where the carbon atoms are arranged in a
hexagonal lattice as in graphite (Figure 1). Because
carbon-carbon bonds are very stable and strong, and
because CNTs are seamless and have a very small
diameter (1-100 nanometers, or 0.00000004-0.000004
inches), CNTs have exceptional properties. High-quality
CNTs have several times the strength of steel piano wire
at one-fourth the density, at least five times the thermal
conductivity of copper, and very high electrical
conductivity and current-carrying capacity. These
properties have generated broad interest in CNTs, for
potential applications such as next-generation
electronics where individual CNTs are transistors, to
advanced composites where trillions of CNTs work
together to form the structure of an airplane wing. For
example, a fully-loaded 747 (~400 tons) could hang
from a 5 millimeter (1/4 inch) diameter rope made from
continuous parallel CNTs!
Fig:1The structure of a CNT: a seamless cylinder of
carbon atoms arranged in a hexagonal lattice. The
schematic at left is of a single-wall CNT, and the
schematic at right is of a multi-wall CNT.
CNTs are made by the high-temperature process of
chemical vapor deposition (CVD). A carbon-containing
gas is converted in to CNTs using small catalyst
particles which act like "seeds" for growth; wherever a
catalyst particle is placed, a CNT starts growing when
the catalyst is heated to the necessary reaction
temperature and the carbon gas is introduced.
Fig:2.Schematic of growth of a CNT from a metal
catalyst nanoparticle on a substrate.
Fabrication Techniques
For Nanobliss, CNTs are grown on substrates
such as silicon wafers: first, the catalyst is arranged on
the surface of the wafer, and then the carbon source is

2. introduced to grow the nanotubes by placing the
catalyst-coated substrate in a sealed reaction chamber.
When a relatively high density of catalyst particles is
placed on the substrate, the CNTs align with each other
and grow perpendicular to and upward from the
substrate, to form a CNT "forest". By controlling the
density of the catalyst particles as well as the reaction
temperature and chemistry, we can grow these CNT
forests to millimeter heights [2].
A hierarchy of length scales is involved
(Figure 3). At the molecular (nanometer) scale, carbon
atoms organize at a catalyst particle to produce a single
CNT. The individual graphitic walls of each CNT are
visible using a transmission electron microscope (TEM),
as each CNT is approximately 10 nanometers in
diameter. At the micrometer scale, the CNTs are self-organized
to form the forest in which the CNTs are
roughly parallel and aligned; this is seen using a
scanning electron microscope (SEM). At the millimeter
scale, the microscopic shape of the forest, in this case
the sidewall, is seen to stretch to a height of millimeters,
and is again imaged using a scanning electron
microscope.
At the centimer scale, we see an optical photograph of a
thick CNT forest on a substrate, resting on a human
fingertip. There are approximately 20 billion CNTs on
this substrate, and each CNT has an aspect ratio
(length/diameter) of approximately 400,000:1.
Fig:3Ascending hierarchy of length scales in assembly
of a CNT forest (click on image to enlarge): (1) TEM
image showing concentric layers of a multi-wall CNT;
(2) SEM image showing alignment among CNTs in
sidewall of a forest; (3) SEM image of sidewall of a 2
mm tall forest; (4) optical image of forest on a silicon
substrate (approximately 1 cm x 1 cm) resting on a
human fingertip.
Chemical, mechanical, and thermal assembly processes
convolve to realize the CNT structures which are
imaged for the Nanobliss galleries. In the simplest case,
the catalyst is deposited in a uniform layer, and a forest
of CNTs (as shown in Figure 3) which entirely covers
the top surface of the substrate. In particular cases,
differential growth rates across large numbers of CNTs
cause the CNTs to bend or wrinkle. Mechanical friction
among the growing CNTs can cause groups of CNTs to
break away from the forest or to grow taller than
neighboring groups. Additional complexity is added by
patterning the catalyst, such as by photolithography, so
CNTs grow only in certain areas on the substrate. This
produces arrays of microstructures and complex shapes
(Figure 4). By introducing spatial and temporal
gradients in the reaction conditions or by spatially
varying the size of the patterns, the shapes can be
influenced to grow to different heights or to lean in
particular directions.
The gallery of self-organized and
patterned architectures exemplifies these techniques. In
the gallery of logos and popular impressions, structures
are engineered to represent exemplary logos and other
advertising symbols. In principle, any two-dimensional
drawing can be replicated in a three-dimensional CNT
structure by patterning the catalyst.
Figure 4. Fabricating a CNT microstructure (click on
images to enlarge): (left) by patterning of the catalyst on
the substrate; (right) "molding" CNTs into three-dimensional
structures by applying mechanical pressure
and confinement during growth
A further technique uses mechanical pressure
to define the shapes of the CNT structures; in research,
we discovered that CNT growth can output a significant
force, and therefore forces can be used to affect the
growth process [3]. For example, confining the CNTs
inside a mold causes growth to take the shape of the
mold (Figure 4). In comparison to patterning of the

3. catalyst which defines a two-dimensional template for
growth, using a mold defines a three-dimensional
template [4]. Pressing on the CNTs also causes them to
bend, and by controlling the applied pressure we can
cause the CNTs within a forest to be "wavy" rather than
aligned. Examples are in the gallery of mechanically-shaped
structures.
This page describes just a few of many
current and possible fabrication techniques for
Nanobliss. The catalyst particles can be organized using
polymer chemistry to precisely control the density of
CNTs on a Substrate [5]. We can watch growth by
placing the substrate on a locally-heated platform in an
open-view reaction chamber [6]. By resistively-heating
a silicon platform beyond its melting temperature,
followed by sudden re-solidification, we create
intricately branched silicon structures.
Imaging
Because the CNT and silicon structures are
electrically conductive, they can be imaged using a
conventional scanning electron microscope (SEM).
Compared to optical imaging where interaction of light
with the subject (sample) forms the image, in electron
microscopy interaction of electrons with the sample
forms the image. Local charging of the sample, along
with the intensity of the electron beam and the position
of the detector, create apparent lighting and shadowing
effects in the electron microscope image. Further, an
SEM can resolve features much smaller than the
wavelength of light, and has a relatively large depth of
focus.
Nanobama:
The nanobama structures are made of
carbon nanotubes, and the pictures were taken using
optical and electron microscopes. CNTs are grown by a
high-temperature chemical reaction, using patterns of
nanoscale metal catalyst particles arranged in the shapes
of the faces, text, and flags that you see in the images.
Each face contains millions of parallel nanotubes,
standing vertically on the substrate like a forest of trees.
The nanobamas are made as follows, and as
shown in the diagram below:
(1) convert an image (original by Shepard Fairey) of
Barack Obama to a line drawing
(2) shrink the drawing and print it onto a glass plate
(mask), using a laser system
(3) shine ultraviolet light through the mask, and onto a
thin layer of polymer on a silicon wafer, thereby
patterning the polymer by photolithography
(4) Coat the wafer with a thin layer of catalyst
nanoparticle "seeds" for nanotube growth
(5) Remove the remaining polymer, leaving the catalyst
seeds in the shapes of the nanobamas
(6) grow the CNTs from the catalyst patterns, by placing
the wafer in a high-temperature furnace and filling the
furnace with a carbon-containing gas
(7) take pictures of the structures, which are barely
visible to the naked eye, using electron and optical
microscope.
The images can be digitally-enhanced, such as by
adding colors and highlighting using Adobe Photoshop,
as shown in the gallery of colorized images.
When the desired field of view exceeds the field of view
of the electron microscope (typically a few millimeters),

4. several frames can be "stitched" together to effectively
create a wide-field electron image. This technique was
demonstrated using Microsoft Expression Graphic
Designer, in collaboration with Michael Cohen at
Microsoft Research and Felice Frankel at MIT. More
examples of the stitching technique are in the gallery of
stitched images.
Figure5. Images of "Seed of Life" pattern of carbon
nanotube structures grown on a silicon substrate: (left)
digitally-stitched raw SEM image; (right) optical
photograph.
Some nanobliss pictures:
SEM images of the rabbit heads are in the logos and
impressions section of Nanobliss.
Uses:
1 .The visualizations and the underlying fabrication
techniques are new media for art, science, and
architecture; and for promoting popular awareness
and education about nanomaterials and related
technologies.
2. In museum/gallery exhibitions and laboratory
experiments, and advertising and informational
in scientific and popular literature.
Conclusions:
The construction of the different pictures
by using carbon nano tubes is discussed in the above
paper .It makes the fun sometimes .The technology to
construct these galleries is awesome.
References:
www.google.com
www.flickr.com
www.nanobama.com