Liming Dai talks with
ScienceWatch.com and answers a few questions about
this month's Fast Breaking Paper in the field of Materials
Science. The author has also sent along images of
their work.
Article Title: Gecko-foot-mimetic aligned
single-walled carbon nanotube dry adhesives with unique
electrical and thermal properties
Authors: Qu, L;Dai,
L
Journal: ADVAN MATER
Volume: 19
Issue: 22
Page: 3844-+
Year: NOV 19 2007
* Univ Dayton, Sch Engn, Dept Chem & Mat Sci, Dayton,
OH 45469 USA.
* Univ Dayton, Sch Engn, Dept Chem & Mat Sci, Dayton,
OH 45469 USA.
Why do you think your paper is highly
cited?
In our paper, we demonstrated that vertically-aligned single-walled carbon
nanotube arrays can be used for a successful synthetic approach to mimic
gecko foot-hairs to develop advanced dry adhesives with fairly reversible
semiconducting behaviors under load and provide an excellent thermal
resistance, due to the unique thermal and electric properties intrinsically
associated with single-walled carbon nanotubes.
Such multifunctional aligned single-walled carbon nanotube dry adhesives
are about three times stickier than natural gecko feet and will offer
options for many novel applications of carbon nanotubes. Many researchers
are looking into novel applications for carbon nanotubes and
multifunctionalities for gecko-foot-mimetic dry adhesives. Our paper
provides a unique combination which should lead to new directions in both
fields.
Does it describe a new discovery, methodology, or
synthesis of knowledge?
Understanding that sample purity and quality are important in order to
ensure strong adhesion for carbon nanotube dry adhesive, we used a combined
method of plasma-enhanced chemical vapor deposition and fast heating for
the syntheses of vertically-aligned single-walled carbon nanotube arrays
with a high purity and graphitization degree.
The small nanotube diameter, together with a pure p -p conjugated carbon
surface, allowed vertically-aligned single-walled carbon nanotube arrays to
have an intimate contact and an enhanced adhesion force along the substrate
surface in respect to their multiwalled counterparts previously studied as
gecko-foot-mimetic dry adhesives.
Would you summarize the significance of your paper in
layman's terms?
The secret behind the gecko's ability to scurry up walls and cling to
ceilings lies in the forest of microscopic hairs on the underside of its
foot. Under a microscope, vertically-aligned carbon nanotubes look a lot
like the tiny, sticky hairs on the gecko's feet. This finding has prompted
several research groups to develop gecko-foot-mimetic dry adhesives based
on vertically-aligned multiwalled carbon nanotubes.
In our research, we used tailor-made vertically-aligned single-walled
carbon nanotube arrays to mimic gecko feet. Better than the natural gecko
foot and its multiwalled counterpart, this new single-walled carbon
nanotube dry adhesive is nearly three times stickier than natural gecko
feet, with additional thermal and electrical management capabilities.
This discovery could lead to various applications, ranging from low-tech
fridge magnets to holding together electronics or even holding together the
parts of an airplane. For instance, rather than soldering components into
electronic devices, these parts could be easily held together by using the
new adhesive.
Computers and laptops could also be made to disperse heat from their
circuits without the need for additional heat sinkers. As a dry adhesive,
carbon nanotube material would also have many uses in space, where there's
a vacuum and traditional kinds of adhesives dry out. They can also be used
to create wall/rock climbing robots, super-grip tires, and to provide rapid
repairs for various systems.
How did you become involved in this research, and were
there any problems along the way?
My group has been working on the growth and microfabrication of
vertically-aligned carbon nanotubes for a long time. Although the formation
of an aligned/micropatterned multiwalled carbon nanotube array has been
known about for some years, the synthesis of a vertically-aligned
single-walled carbon nanotube array is a fairly recent development.
Soon after the first paper on the growth of vertically-aligned
single-walled carbon nanotubes from Sumio Iijima's group at the Japan
Science and Technology Agency (JST/SORST) appeared in 2004, we, along with
several other groups, successfully produced vertically-aligned
single-walled carbon nanotube arrays. The use of our high-quality
vertically-aligned single-walled carbon nanotube arrays to mimic the gecko
foot-hairs turned out to be very successful with the first set of adhesion
data obtained in early 2006.
Where do you see your research leading in the
future?
"The secret behind the gecko's
ability to scurry up walls and cling to
ceilings lies in the forest of microscopic
hairs on the underside of its
foot."
Further research on functionalization of these carbon nanotube "gecko feet"
should lead to a wide range of multifunctional smart (e.g.,
photo-sensitive, temperature-responsive, or optoelectronically active) dry
adhesives, attractive for diverse potential applications. The possibilities
for practical uses of these vertically-aligned single-walled carbon
nanotube dry adhesives has not yet been fully exploited, largely because it
is still a challenge to synthesize high-quality vertically-aligned
single-walled carbon nanotube arrays on a large-scale and in a
cost-effective manner.
Overcoming this challenge should facilitate the research and development of
vertically-aligned single-walled carbon nanotube dry adhesives with
enhanced multifunctional performance. This, in turn, would then allow for a
large-scale preparation of vertically-aligned single-walled carbon nanotube
dry adhesives that could be repeatedly used in a variety of practical
applications.
Do you foresee any social or political implications for
your research?
Our results indicated that only 150 pieces of these small single-walled
carbon nanotube arrays, each one measuring only 4×4 square
millimeters, with a total contact area of about 5×5 square
centimeters, which is much smaller than the palm of your hand, would be
needed to collectively hold a person weighing about 70 kg.
Apart from their potential applications as dry adhesives in electronics and
aerospace vehicles, therefore, these vertically-aligned carbon nanotubes
might find possible uses for climbing robots just like Spider-Man.
Continued research efforts in this exciting field should affect the lives
of everyone and, in the longer term, also influence many industrial sectors
around the world.
Liming Dai
Wright Brothers Institute Endowed Chair
Professor of Nanomaterials
Department of Chemical and Materials Engineering
School of Engineering
University of Dayton
Dayton, Ohio, USA Web