Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Nanotubes laid out in stripes

02.06.2014

New technologies can be realized with thin layers of carbon nanotubes. Würzburg researchers have examined a technique that creates such layers, gaining fresh insights.

A number of technical innovations of recent times involve the use of thin layers of carbon nanotubes. In 2013, for instance, scientists from Stanford University (USA) presented the prototype of a computer whose electronic components are based not on silicon but on carbon nanotubes. And nanotubes are already being used in part in smartphone displays – as a more cost-effective alternative to conventional indium tin oxides.


Carbon nanotubes are deposited from a liquid onto a surface in regular stripes. Würzburg researchers have characterized this process more precisely.

(Graphic: Tobias Hertel)

Thin layers of carbon nanotubes can be generated using various methods. “It is very important to be able to control the production of the layers precisely in order to achieve the desired structures and properties,” says Professor Tobias Hertel from the University of Würzburg. His team at the Institute of Physical and Theoretical Chemistry has now gained new insights into this. These are presented in the journal “ACS Nano” published by the American Chemical Society (ACS).

Horizontal deposition of nanotubes

The team led by Tobias Hertel has examined the technique of horizontal deposition. In this, the nanotubes from an evaporating liquid are deposited onto a surface. “This technique uses the self-organization phenomena of the nanotubes,” explains the professor, “it enables, for example, the creation of extremely thin layers in which all nanotubes are arranged in the same orientation.”

Using this technique, layers can also be produced in which the nanotubes are organized into regular stripe patterns with dimensions in the micrometer range. “This effect is very similar to the formation of coffee deposits and is therefore also occasionally referred to as the coffee stain phenomenon,” says Hertel. The layers that are created like this are ideal for making nanotube-based transistors. But there was no clear idea before of how the regular stripes are formed and how this process can be controlled. Thanks to the research by the Würzburg scientists, this has now changed.

Smooth motion produces stripe pattern

Researchers previously assumed that the evaporating liquid moves jerkily over the surface to be coated and that every jolt causes a stripe of nanotubes to be left behind at its edge – “in the same way as a stuttering car tire on asphalt brings a car to a shuddering halt,” says Hertel by way of a comparison.

However, his team has now shown that the edge of the liquid moves over the surface at an ever slower pace in a smooth not jerky manner and then picks up speed again. Since this happens periodically, regular stripe patterns are produced.

Glass plates accelerate the process

The researchers have also discovered how to speed up this process considerably: “If we feed the liquid from which the layers are deposited between two glass plates that are only a hair's breadth apart, the stripe patterns form up to a hundred times faster.” Responsibility for this lies with the evaporation at the boundary between liquid and substrate, which can take place at any speed in theory – an effect that can only be felt at the micrometer level.

Professor Hertel has posted a video on YouTube. This shows in slow motion how a stripe pattern consisting of carbon nanotubes is created step by step using the technique of horizontal deposition: http://www.youtube.com/watch?v=KBHswRKdQXQ

Future research

The next experiments, according to Professor Hertel, will focus on controlling the layer formation better and accelerating it further. “If we want to make this process truly useful, we still have a whole lot of work ahead of us. In particular, we need to push back the limits of what is possible in terms of the speed at which these layers are created.”

Contact
Prof. Dr. Tobias Hertel, Institute of Physical and Theoretical Chemistry, University of Würzburg, T +49 (0)931 31-86300, tobias.hertel@uni-wuerzburg.de

“Dynamical Contact-Line Pinning and Zipping during Carbon Nanotube Coffee Stain Formation”, Han Li, Tilman C. Hain, Andreas Muzha, Friedrich Schöppler, Tobias Hertel. ACS Nano, published online on May 14, 2014, DOI: 10.1021/nn501957y

Robert Emmerich | Julius-Maximilians-Universität Würzburg

Further reports about: ACS Nano Nanotubes coffee created deposited effect formation glass layers patterns stripe technique transistors

More articles from Materials Sciences:

nachricht Phagraphene, a 'relative' of graphene, discovered
03.09.2015 | Moscow Institute of Physics and Technology

nachricht For 2-D boron, it's all about that base
03.09.2015 | Rice University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fraunhofer ISE Develops Highly Compact Inverter for Uninterruptible Power Supplies

Silicon Carbide Components Enable Efficiency of 98.7 percent

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE have developed a highly compact and efficient inverter for use in uninterruptible power...

Im Focus: How wind sculpted Earth's largest dust deposit

China's Loess Plateau was formed by wind alternately depositing dust or removing dust over the last 2.6 million years, according to a new report from University of Arizona geoscientists. The study is the first to explain how the steep-fronted plateau formed.

China's Loess Plateau was formed by wind alternately depositing dust or removing dust over the last 2.6 million years, according to a new report from...

Im Focus: An engineered surface unsticks sticky water droplets

The leaves of the lotus flower, and other natural surfaces that repel water and dirt, have been the model for many types of engineered liquid-repelling surfaces. As slippery as these surfaces are, however, tiny water droplets still stick to them. Now, Penn State researchers have developed nano/micro-textured, highly slippery surfaces able to outperform these naturally inspired coatings, particularly when the water is a vapor or tiny droplets.

Enhancing the mobility of liquid droplets on rough surfaces could improve condensation heat transfer for power-plant heat exchangers, create more efficient...

Im Focus: Increasingly severe disturbances weaken world's temperate forests

Longer, more severe, and hotter droughts and a myriad of other threats, including diseases and more extensive and severe wildfires, are threatening to transform some of the world's temperate forests, a new study published in Science has found. Without informed management, some forests could convert to shrublands or grasslands within the coming decades.

"While we have been trying to manage for resilience of 20th century conditions, we realize now that we must prepare for transformations and attempt to ease...

Im Focus: OU astrophysicist and collaborators find supermassive black holes in quasar nearest Earth

A University of Oklahoma astrophysicist and his Chinese collaborator have found two supermassive black holes in Markarian 231, the nearest quasar to Earth, using observations from NASA's Hubble Space Telescope.

The discovery of two supermassive black holes--one larger one and a second, smaller one--are evidence of a binary black hole and suggests that supermassive...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Together - Work - Experience

03.09.2015 | Event News

Networking conference in Heidelberg for outstanding mathematicians and computer scientists

20.08.2015 | Event News

Scientists meet in Münster for the world’s largest Chitin und Chitosan Conference

20.08.2015 | Event News

 
Latest News

Lighter with Laser Welding

03.09.2015 | Process Engineering

For 2-D boron, it's all about that base

03.09.2015 | Materials Sciences

Phagraphene, a 'relative' of graphene, discovered

03.09.2015 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>