Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > UT Dallas, Brazilian Researchers Discover Remarkable New Properties for Nanotube Sheets

Figure 1: Atomic force micrograph of multi-walled carbon nanotubes in buckypaper. Each of these nanotubes is 10,000 times thinner than a human hair.
Figure 1: Atomic force micrograph of multi-walled carbon nanotubes in buckypaper. Each of these nanotubes is 10,000 times thinner than a human hair.

Abstract:
Strange, Useful Properties Obtained by Nanoscale Self Assembly are Reported in the April 25 Issue of Prestigious Scientific Journal

UT Dallas, Brazilian Researchers Discover Remarkable New Properties for Nanotube Sheets

Dallas, TX | Posted on April 24th, 2008

A team of nanotechnologists at The University of Texas at Dallas, along with Brazilian collaborators, have discovered that sheets of carbon nanotubes can produce bizarre mechanical properties when stretched or uniformly compressed. These unexpected but highly useful properties could be used for such applications as making composites, artificial muscles, gaskets or sensors.

The team's findings are reported in the April 25 issue of the journal Science.

When most materials are pulled in one direction, they get thinner in the other direction, similar to how a rubber band behaves when it is stretched. However, specially designed carbon nanotube sheets, dubbed "buckypaper,‰ can increase in width when stretched. The buckypaper can also increase in both length and width when uniformly compressed.

Ordinary materials contract laterally when stretched ˜ a phenomenon that can be quantified by Poisson's ratio, which is the ratio of the percent lateral contraction to the percent applied stretch.

In probability theory and statistics, the Poisson distribution is a discrete probability distribution that expresses the probability of a number of events occurring in a fixed period of time if these events occur with a known average rate and independently of the time since the last event. The Poisson distribution can also be used for the number of events in other specified intervals such as distance, area or volume. The distribution was discovered by Siméon-Denis Poisson (1781ˆ1840) and published, together with his probability theory, in 1838.

Without realizing it, people have been using Poisson's ratio for more than 2,000 years ˜ in the form of wine bottle corks. Corks have a near-zero but positive Poisson's ratio, which makes them difficult to insert but easy to remove. The opposite would be true if the cork had a negative Poisson's ratio.

Without realizing it, people have been using Poisson's ratio for more than 2,000 years ˜ in the form of wine bottle corks. Corks have a near-zero but positive Poisson's ratio, which makes them difficult to insert but easy to remove. The opposite would be true if the cork had a negative Poisson's ratio.

Dr. Ray H. Baughman, Robert A. Welch Professor of Chemistry and director of UT Dallas' NanoTech Institute and his colleagues created their nanotube sheets, or buckypaper, by using ancient methods for making ordinary writing paper ˜ by drying a fiber slurry. The slurry has a mixture of carbon single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs). The researchers found that increasing the amount of MWNTs in the paper produced a sharp transition from a positive Poisson's ratio of about 0.06 to a much larger magnitude negative value of about -0.20.

As described by the team in Science, this transition can be understood by relating the deformation modes of the nanotube sheets to those of a collapsible wine rack. If two neighboring nanotube layers are coupled like the struts in a compressible wine rack, Poisson's ratio is positive and the rack becomes narrower when stretched. In contrast, if the rack is blocked so that it can no longer be collapsed but the struts are stretchable, increases in strut length produce a negative Poisson's ratio.

"This abrupt switching of the sign of Poisson's ratio is so surprising and the structure of the nanotube sheets is so complicated that we initially believed that quantitative explanation was impossible using state-of-art theoretical capabilities,‰ said Baughman, the article's corresponding author. "Distant daily teaming with our Brazilian colleagues through the Internet enabled us to jointly extract essential features from a structure that was much too complex for complete analysis, leading to our successful wine-rack-like model.‰

Baughman and his team subsequently found that the nanotube sheets containing both single-walled and multi-walled nanotubes had a 1.6 times higher strength-to-weight ratio, 1.4 times higher modulus-to-weight ratio and a 2.4 times higher toughness than sheets made of SWNTs or MWNTs alone.

According to Baughman, the implications of the discovery that properties can be enhanced by mixing nanotube types can likely be extended from nanotube sheets to other nanotube arrays, like the twisted nanotube yarns Baughman and colleagues invented in 2005.

Similarly, the ability to tune Poisson's ratio could be exploited for designing sheet-derived composites, artificial muscles, gaskets, stress and strain sensors and chemical sensors.

A thick nanotube sheet could also be made to wrap around a concave, convex, or saddle shaped surface depending on the sign of Poisson's ratio ˜ something that could come in useful for forming shaped composites.

By choosing the ratio of SWNTs and MWNTs, the Poisson ratio can be adjusted to zero, which is useful for designing cantilevers for sensing that do not distort in width during bending. Tensile sensors can provide a sensitivity that is proportional to the volume change produced by stretch, and this volume change can be increased by the team's discovery of the tunability of Poisson's ratio.

The breakthroughs resulted from the diverse expertise of the article's co-authors, who come from around the world: Dr. Lee Hall and Dr. Ray Baughman from the U.S., Dr. Vitor Coluci, Dr. Douglas Galvão, and Dr. Sócrates Dantas from Brazil, Dr. Mikhail Kozlov from the Ukraine and Dr. Mei Zhang from China. Hall, the first author on the article, made his contributions to the discovery as part of his Ph.D. under the direction of Baughman. Lee and Baughman previously co-authored a paper in Science about fuel-powered artificial muscles.

The team's research was funded by the National Science Foundation, the Air Force Office of Scientific Research, Lintec Corporation and the Brazilian agencies FAPESP and CNPq.

To obtain a copy of the Science article, please contact the journal at 202-326-6440 or . A supplemental information file and figures describing applications evaluations that go beyond the scope of the Science article can also be found at .

####

About University of Texas at Dallas
The University of Texas at Dallas, located at the convergence of Richardson, Plano and Dallas in the heart of the complex of major multinational technology corporations known as the Telecom Corridor, enrolls more than 14,500 students. The school's freshman class traditionally stands at the forefront of Texas state universities in terms of average SAT scores. The University offers a broad assortment of bachelor's, master's and doctoral degree programs.

For more information, please click here

Contacts:
Jenni Huffenberger
UT Dallas
(972) 883-4431

Copyright © University of Texas at Dallas

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

A new product to help combat mouldy walls, thanks to technology developed at the ICN2 December 14th, 2017

Sandia researchers make solid ground toward better lithium-ion battery interfaces: Reducing the traffic jam in batteries December 13th, 2017

Perking up and crimping the 'bristles' of polyelectrolyte brushes December 13th, 2017

Columbia engineers create artificial graphene in a nanofabricated semiconductor structure: Researchers are the first to observe the electronic structure of graphene in an engineered semiconductor; finding could lead to progress in advanced optoelectronics and data processing December 13th, 2017

Self Assembly

Physicists gain new insights into nanosystems with spherical confinement: Enormous potential for the targeted delivery of pharmaceutical agents and the creation of tailored nanoparticles July 27th, 2017

Oddball enzyme provides easy path to synthetic biomaterials May 17th, 2017

Nanotubes that build themselves April 14th, 2017

Nanocages for gold particles: what is happening inside? March 16th, 2017

Nanotubes/Buckyballs/Fullerenes/Nanorods

Scientists make transparent materials absorb light December 1st, 2017

Researchers advance technique to detect ovarian cancer: Rice, MD Anderson use fluorescent carbon nanotube probes to achieve first in vivo success November 30th, 2017

NanoSummit in Luxembourg: single wall carbon nanotubes have entered our lives as we approach a nanoaugmented future November 23rd, 2017

Fine felted nanotubes : Research team of Kiel University develops new composite material made of carbon nanotubes November 22nd, 2017

Sensors

Leti to Demo Wristband with Embedded Sensors to Diagnose Sleep Apnea: APNEAband, Which Will Be Demonstrated at CES 2018, Also Monitors Mountain Sickness, Dehydration, Dialysis Treatment Response and Epileptic Seizures December 12th, 2017

Leti Develops World’s First Micro-Coolers for CERN Particle Detectors: Leti Design, Fabrication and Packaging Expertise Extends to Very Large Scientific Instruments December 11th, 2017

Graphene oxide making any material suitable to create biosensors: Scientists from Tomsk Polytechnic University have developed a new tool for biomedical research focused on single-cell investigation November 27th, 2017

The stacked color sensor: True colors meet minimization November 16th, 2017

Discoveries

Sandia researchers make solid ground toward better lithium-ion battery interfaces: Reducing the traffic jam in batteries December 13th, 2017

Perking up and crimping the 'bristles' of polyelectrolyte brushes December 13th, 2017

Columbia engineers create artificial graphene in a nanofabricated semiconductor structure: Researchers are the first to observe the electronic structure of graphene in an engineered semiconductor; finding could lead to progress in advanced optoelectronics and data processing December 13th, 2017

Untangling DNA: Researchers filter the entropy out of nanopore measurements December 8th, 2017

Announcements

A new product to help combat mouldy walls, thanks to technology developed at the ICN2 December 14th, 2017

Sandia researchers make solid ground toward better lithium-ion battery interfaces: Reducing the traffic jam in batteries December 13th, 2017

Perking up and crimping the 'bristles' of polyelectrolyte brushes December 13th, 2017

Columbia engineers create artificial graphene in a nanofabricated semiconductor structure: Researchers are the first to observe the electronic structure of graphene in an engineered semiconductor; finding could lead to progress in advanced optoelectronics and data processing December 13th, 2017

Research partnerships

Perking up and crimping the 'bristles' of polyelectrolyte brushes December 13th, 2017

Wheat gets boost from purified nanotubes: Rice University toxicity study shows plant growth enhanced by -- but only by -- purified nanotubes December 6th, 2017

Copper will replace toxic palladium and expensive platinum in the synthesis of medications: The effectiveness of copper nanoparticles as a catalyst has been proven December 5th, 2017

Researchers advance technique to detect ovarian cancer: Rice, MD Anderson use fluorescent carbon nanotube probes to achieve first in vivo success November 30th, 2017

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project