Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Nanotubes laid out in stripes


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:

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.”

Prof. Dr. Tobias Hertel, Institute of Physical and Theoretical Chemistry, University of Würzburg, T +49 (0)931 31-86300,

“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 The route to high temperature superconductivity goes through the flat land
23.11.2015 | Aalto University

nachricht Quantum spin could create unstoppable, one-dimensional electron waves
19.11.2015 | DOE/Brookhaven National Laboratory

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Innovative Photovoltaics – from the Lab to the Façade

Fraunhofer ISE Demonstrates New Cell and Module Technologies on its Outer Building Façade

The Fraunhofer Institute for Solar Energy Systems ISE has installed 70 photovoltaic modules on the outer façade of one of its lab buildings. The modules were...

Im Focus: Lactate for Brain Energy

Nerve cells cover their high energy demand with glucose and lactate. Scientists of the University of Zurich now provide new support for this. They show for the first time in the intact mouse brain evidence for an exchange of lactate between different brain cells. With this study they were able to confirm a 20-year old hypothesis.

In comparison to other organs, the human brain has the highest energy requirements. The supply of energy for nerve cells and the particular role of lactic acid...

Im Focus: Laser process simulation available as app for first time

In laser material processing, the simulation of processes has made great strides over the past few years. Today, the software can predict relatively well what will happen on the workpiece. Unfortunately, it is also highly complex and requires a lot of computing time. Thanks to clever simplification, experts from Fraunhofer ILT are now able to offer the first-ever simulation software that calculates processes in real time and also runs on tablet computers and smartphones. The fast software enables users to do without expensive experiments and to find optimum process parameters even more effectively.

Before now, the reliable simulation of laser processes was a job for experts. Armed with sophisticated software packages and after many hours on computer...

Im Focus: Quantum Simulation: A Better Understanding of Magnetism

Heidelberg physicists use ultracold atoms to imitate the behaviour of electrons in a solid

Researchers at Heidelberg University have devised a new way to study the phenomenon of magnetism. Using ultracold atoms at near absolute zero, they prepared a...

Im Focus: Climate Change: Warm water is mixing up life in the Arctic

AWI researchers’ unique 15-year observation series reveals how sensitive marine ecosystems in polar regions are to change

The warming of arctic waters in the wake of climate change is likely to produce radical changes in the marine habitats of the High North. This is indicated by...

All Focus news of the innovation-report >>>



Event News

Fraunhofer’s Urban Futures Conference: 2 days in the city of the future

25.11.2015 | Event News

Gluten oder nicht Gluten? Überempfindlichkeit auf Weizen kann unterschiedliche Ursachen haben

17.11.2015 | Event News

Art Collection Deutsche Börse zeigt Ausstellung „Traces of Disorder“

21.10.2015 | Event News

Latest News

Harnessing a peptide holds promise for increasing crop yields without more fertilizer

25.11.2015 | Agricultural and Forestry Science

Earth's magnetic field is not about to flip

25.11.2015 | Earth Sciences

Tracking down the 'missing' carbon from the Martian atmosphere

25.11.2015 | Physics and Astronomy

More VideoLinks >>>