Passive Assembly of Carbon Nanotubes Principal Investigator: Nick McGruer Center for High Rate Nanom

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Passive Assembly of Carbon NanotubesPrincipal
Investigator Nick McGruer - Center for High Rate
Nanomanufacturing, Northeastern UniversityRET
Participants Amie Milkowski Malden High School
(author) Richard Bernard Jr. TechBoston
AcademyLaboratory Support Michael Swanwick
Scanning Electron Microscope The Northeastern
University Research Experience for Teachers (RET)
provided me with priceless exposure to a graduate
level research lab, the George J. Kostas Center
for High Rate Nanomanufacturing and
Nanofabrication (CHN). Through this opportunity
I was able to become significantly well trained
at using a Scanning Electron Microscope (SEM) to
image carbon nanotubes. This is a complicated
instrument with which I might otherwise never
have receive hands-on experience.

Methods
Introduction
Carbon nanotubes (CNTS) belong to the same
structural family of fullerenes as buckyballs.
They consist of hexagonally bonded carbon atoms
and based on their configurations may be either
semi conducting or metallic. As a result of
their incredibly small size, only a few
nanometers in diameter, CNTs have the
possibilities in a wide range of research areas.
See the diagram below of possible applications.
Carbon nanotubes are so incredibly
small that Van Der Waals intermolecular forces
dictate their behavior, in so much as their
adhesion to other surfaces. On such a small
scale gravity becomes a negligible force.
Consequently CNTs have the ability to adhere
strongly to certain surfaces, some more than
others, depending on the strength of the
intermolecular forces that exist between the CNTs
and the desired substrate. At the George
J. Kostas Center for High Rate Nanomanufacturing
and Nanofabrication, many researchers are working
towards assembling circuits using nanoscale
components, specifically carbon nanotubes. Most
commonly researchers utilize electrophoresis to
deposit carbon nanotubes into trenches etched in
a photo resist, such as PMMA, by optical or
e-beam lithography. These trenches expose the
substrate beneath the photo resist, possibly
gold, silicon, or silicon dioxide. Applying an
electric field to a solution of CNTs via
electrophoresis induces the deposition of the
CNTs into these trenches. According to
researchers at the Kostas Center, little work has
been done studying the deposition of CNTs on to a
substrate without the aid of electrophoresis.
Therefore an experiment was designed to
characterize the deposition of CNTs onto three
different substrates.

• Samples are prepared by placing a 10.0µL droplet
  of a solution containing CNTs onto three
  different substrates substrates.
• Substrates used Polymethylmethacrylate (PMMA) on
  Gold, Silicon, and Silicon Dioxide.
• For each type substrate used, four different
  samples were created by allowing a droplet of CNT
  solution to remain on each sample for varying
  lengths of time before rinsing in distilled
  water.
• Droplets were left on the first sample for 10s,
  on the second for 1min, on the third for 10min,
  and on the fourth until the droplet of CNT
  solution evaporated without rinsing.
• The samples produced correspond with the matrix
  to the right

Substrate Time Droplet On Substrate
Learning to use the SEM effectively was a
daunting task. There was so much theoretical
information to read and practical experience to
gain. The whole process was rather overwhelming
and some of the theoretical knowledge required
for operating and properly tuning the microscope
was far outside of my knowledge base.
Approximately three weeks into the RET experience
I was able to begin producing some what clear
images with the SEM. The most difficult skill to
learn in the practical use of the instrument was
identifying what on the scope need to be tuned
focus, aperture, or stigmation. However, with
the patient instruction of Michael Swanwick, a
member of the CHN research group, I was able to
image carbon nanotubes.
Simulation of Carbon Nanotubes being deposited
into trenches in photoresist.1
Back in the Classroom After participating,
Northeastern University Research Experience for
Teachers I am confident that nanotechnology must
have a place in my science classroom. Many high
school students are simply not aware of all the
different possibilities and avenues science and
engineering offer. Utilizing the inquiry
method, nanotechnology and scientific curiosity
can be fostered in the classroom. Allowing
students to create, observe, play/experiment
with, investigate and research polymers is a
tangible way to bring nanotechology into the
classroom. Polymers are macromolecules which can
be treated as distinct entities on the nanoscale.
This lesson proposal is designed to target
eleventh and twelfth grade chemistry students
with a working knowledge of laboratory safety,
chemical bonding, structural formulas, physical
properties, and classification. In the first
phase, lab stations should be set up so that
students can enter and combine two unknowns to
make a third unknown (slime)! Allow students
time to make observations and then construct a
KWL as a class. Encourage students to debate
whether their creation is a solid or a liquid.
Next students are tasked to develop the best toy.
Working in pairs or small groups in the lab,
allow them to experiment by combining different
ratios of the two reagents used previously to
make slime with different consistencies. Require
them to quantify their results, (viscosity,
bouncibility). Let the students design their own
criteria and guide their own toy development.
Each group may consider different properties
ideal for their toy. Upon completion of this
phase introduce the concepts of polymerization,
non-Newtonian fluids and cross-linking to
students. Students should now understand that
not all polymers are slimy. Present them with
several different materials, wood, cotton,
Styrofoam, plastic bottles, rubber, silly putty.
and allow them to explore, hypothesize, and
research which are polymers. As a form of
assessment allow each student, or pair of
students, to research a different polymer and
create an informational web page using a program
such as Dream Weaver.
References and Acknowledgements

• Center for High Rate Nanomanufacturing Overview
  Slide Show http//www.nano.neu.edu/nsec
• Young, R.J., Lovell, P.A. Introduction to
  Polymers. Second Edition. CRC, 2000.
• Postek, Michael T. Scanning Electron Microscope
  A Students Handbook. Ladd Research Industries,
  1980.
• Laws, Graham. Scanning Electron Microscopy and
  X-Ray Microanalysis. Wiley, 1987.
• Many thanks to Nick McGruer, Michael Swanwick,
  Claire Duggan, and Matthew Corcoran for their
  support.

Research Experiences for Teachers at Northeastern
UniversityClaire Duggan, Program Director